FN Thomson Reuters Web of Science™ VR 1.0 PT J AU Corbett, DR Burnett, WC Cable, PH Clark, SB AF Corbett, DR Burnett, WC Cable, PH Clark, SB TI Radon tracing of groundwater input into Par Pond, Savannah River Site SO JOURNAL OF HYDROLOGY AB The groundwater contribution into Par Pond, a former cooling reservoir for two nuclear reactors located on the Department of Energy's Savannah River Site (South Carolina), was estimated using a standard hydrologic budget as well as one augmented by a natural tracer approach. We determined a geochemical budget for Rn-222, normally found at much higher concentrations in groundwater than surface waters, to assist in constraining the hydrologic estimates. The radon budget accounted for all quantifiable surface sources and sinks including the flux across the sediment-water interface which was determined by application of an advection-diffusion model. All hydrologic parameters and radon concentrations were monitored seasonally from February 1994 to August 1995. Using the water balance approach alone, the average groundwater discharge entering the lake was estimated to have an upper limit of approximately 0.95 +/- 0.13 m(3) s(-1). The groundwater contribution obtained using the combined hydrologic/Rn-222 approach ranged from 0.17 to 0.76 m(3) s(-1) with a best estimate of 0.35 +/- 0.16 m(3) s(-1). Lake profiles show enhanced Rn-222 concentrations in some areas indicating that groundwater enters Par Pond mostly through a small region in the northern portion of the lake, probably via small seeps or springs. Estimates show that groundwater plays a significant role in the overall water budget of the lake, accounting for 10%-33% of the total estimated inflow from all measured sources. Our results show that supplementing a standard hydrological water balance with radon budget considerations helps to constrain estimated groundwater flow into surface reservoirs. (C) 1997 Elsevier Science B.V. SN 0022-1694 EI 1879-2707 PD DEC 31 PY 1997 VL 203 IS 1-4 BP 209 EP 227 DI 10.1016/S0022-1694(97)00103-0 UT WOS:000072028400018 ER PT J AU Wang, JH Kenseth, JR Jones, VW Green, JBD McDermott, MT Porter, MD AF Wang, JH Kenseth, JR Jones, VW Green, JBD McDermott, MT Porter, MD TI SFM tip-assisted hydrolysis of a dithiobis(succinimidoundecanoate) monolayer chemisorbed on a Au(111) surface SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB This paper reports on the use of a scanning force microscope (SFM) for the tip-assisted base hydrolysis of an ester-terminated alkanethiolate monolayer on Au(111). We have found that contact imaging accelerates the base hydrolysis of a dithiobis(succinimido undecanoate) monolayer relative to the surrounding unimaged area. It is proposed that (1) the mechanical disruption by the SFM probe tip of the steric barrier imposed by the neighboring adsorbates facilitates access of hydroxide ions to the buried acyl carbons in the adlayer, and (2) the surface area hydrolytically transformed by this disruption can be controlled by the SFM imaging conditions, Findings in support of our conclusions are presented, and potential implications to nanotechnology are briefly discussed. OI McDermott, Mark/0000-0001-8372-0158 SN 0002-7863 PD DEC 31 PY 1997 VL 119 IS 52 BP 12796 EP 12799 DI 10.1021/ja9715051 UT WOS:000071393800011 ER PT J AU Kleinke, H Franzen, HF AF Kleinke, H Franzen, HF TI Novel quaternary metal-rich phosphides: Stabilization by differential fractional site occupancies and polar intermetallic bonding SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB The new phosphide Hf5Nb5Ni3P5 has been prepared by are-melting of a pressed stoichiometric mixture of HfP, Nb, and Ni. Single crystals suitable for the structure determination were obtained after annealing in an induction furnace at 1350 degrees C. Hf5Nb5Ni3P5 crystallizes in the hexagonal space group (No. 189). The early transition metal atoms Hf and Nb are found on three crystallographically different sites, with refined occupancies of 100% Hf for the M1, 59.5(4)% Hf and 40.5(4)% Nb for the M2, and 13.1(6)% Hf and 86.9(6)% Nb for the M3 site. Small variations of the Hf to Nb ratio are possible, occurring with significantly different lattice parameters. The early transition elements form a three-dimensional framework with numerous M-M (M = Hf, Nb) interactions, including Ni and P in its trigonal prismatic voids. The differential fractional site occupancies can be understood on the basis of the different preferences of Hf and Nb to form M-M, M-Ni, and M-P bonds. The metallic character is confirmed by the Pauli paramagnetism experimentally obtained. SN 0002-7863 PD DEC 31 PY 1997 VL 119 IS 52 BP 12824 EP 12830 DI 10.1021/ja9718681 UT WOS:000071393800014 ER PT J AU Kuhn, M Spaeth, C Pintaske, R Peter, S Richter, F Anders, A AF Kuhn, M Spaeth, C Pintaske, R Peter, S Richter, F Anders, A TI The effect of additional ion/plasma assistance in CNx-film deposition based on a filtered cathodic arc SO THIN SOLID FILMS AB The crucial parameters in CNx-film deposition are the nature of carbon and nitrogen species and their kinetic energy. The filtered cathodic are produces a highly ionised carbon plasma, containing mainly C+ ions. In a standard reactive process, deposition is performed in a reactive gas atmosphere, and there is only little control of the degree of ionisation and kinetic energy of the gas species. Therefore, three types of ion or plasma sources have been used for additional nitrogen bombardment during the deposition of CNx-films: a two-grid Kaufman ion source, a gridless Kaufman source and a hollow anode plasma source. Characterisation of the different types of nitrogen plasma or ion beams was carried out by means of energy resolved mass spectroscopy and electric probe measurements. The films have been analysed for their chemical composition, microstructure and mechanical properties. High energy ion bombardment from the two-grid Kaufman ion source yields films with relatively high nitrogen content (up to 30 at.%) but rather poor mechanical properties. Using the nitrogen beams from the two other sources CNx-films with lower N-content but enhanced mechanical properties have been found. (C) 1997 Elsevier Science S.A. RI Anders, Andre/B-8580-2009 OI Anders, Andre/0000-0002-5313-6505 SN 0040-6090 PD DEC 31 PY 1997 VL 311 IS 1-2 BP 151 EP 156 DI 10.1016/S0040-6090(97)00470-7 UT WOS:000072708600025 ER PT J AU Vaidya, B Watson, SW Coldiron, SJ Porter, MD AF Vaidya, B Watson, SW Coldiron, SJ Porter, MD TI Reduction of chloride ion interference in chemical oxygen demand (COD) determinations using bismuth-based adsorbents SO ANALYTICA CHIMICA ACTA AB An efficient method for the reduction of chloride interference in the determination of chemical oxygen demand (GOD) without the use of Hg(II) as a masking agent is described. Chloride ion is removed as hydrochloric acid gas from acidified sample solutions at 150 degrees C in a closed reaction tube and captured by a bismuth-based adsorbent suspended above the heated solution. The effects of adsorbent composition, sulfuric acid concentration, reflux time, chloride concentration, and Ag(I) catalyst on the efficiency of the removal of chloride ion and the COD determination are discussed. The viability of the approach is demonstrated using st wastewater sample. (C) 1997 Elsevier Science B.V. SN 0003-2670 PD DEC 30 PY 1997 VL 357 IS 1-2 BP 167 EP 175 DI 10.1016/S0003-2670(97)00541-2 UT WOS:000071301800023 ER PT J AU Michalakes, J Skalin, R AF Michalakes, J Skalin, R TI Parallel computing in regional weather modeling SO PARALLEL COMPUTING SN 0167-8191 PD DEC 30 PY 1997 VL 23 IS 14 BP 2133 EP 2133 DI 10.1016/S0167-8191(97)80583-2 UT WOS:000071605300001 ER PT J AU Baillie, C Michalakes, J Skalin, R AF Baillie, C Michalakes, J Skalin, R TI Regional weather modeling on parallel computers SO PARALLEL COMPUTING AB This special issue on 'regional weather models' complements the October 1995 special issue on 'climate and weather modeling' which focused on global models, In this introduction we review the similarities and differences between regional and global atmospheric models. Next, the structure of regional models is described and we consider how the basic algorithms applied in these models influence the parallelization strategy, Finally, we give a brief overview of the eight articles in this issue and discuss some remaining challenges in the area of adapting regional weather models to parallel computers. (C) 1997 Elsevier Science B.V. SN 0167-8191 PD DEC 30 PY 1997 VL 23 IS 14 BP 2135 EP 2142 DI 10.1016/S0167-8191(97)00104-X UT WOS:000071605300002 ER PT J AU Michalakes, J AF Michalakes, J TI MM90: A scalable parallel implementation of the Penn State NCAR mesoscale model (MM5) SO PARALLEL COMPUTING AB This paper describes MM90, a parallel regional weather model based on the Penn State/NCAR MM5. Parallelization of finite differencing, horizontal interpolation, and nesting on distributed-memory (message passing) computers is handled transparently using the RSL library package. Fortran90 modules, derived data types, dynamic memory allocation, pointers, and recursion are used, making the code modular, flexible, extensible, and run-time configurable. The model can dynamically sense and correct load imbalances. The paper provides performance, scaling, and load-balancing data collected on the IBM SP2 computers at Argonne National Laboratory and NASA Ames Laboratory. Future work will address the impact of parallel modifications on existing modeling software; an approach using commercially available source translation software is described. (C) 1997 Published by Elsevier Science B.V. SN 0167-8191 PD DEC 30 PY 1997 VL 23 IS 14 BP 2173 EP 2186 DI 10.1016/S0167-8191(97)00107-5 UT WOS:000071605300005 ER PT J AU Friedmann, TA Sullivan, JP Knapp, JA Tallant, DR Follstaedt, DM Medlin, DL Mirkarimi, PB AF Friedmann, TA Sullivan, JP Knapp, JA Tallant, DR Follstaedt, DM Medlin, DL Mirkarimi, PB TI Thick stress-free amorphous-tetrahedral carbon films with hardness near that of diamond SO APPLIED PHYSICS LETTERS AB We have developed a process for making thick, stress-free, amorphous-tetrahedrally bonded carbon (a-tC) films with hardness and stiffness near that of diamond. Using pulsed-laser deposition, thin a-tC films (0.1-0.2 mu m) were deposited at room temperature. The intrinsic stress in these films (6-8 GPa) was relieved by a short (2 min) anneal at 600 degrees C. Raman and electron energy-loss spectra from single-layer annealed specimens show only subtle changes from as-grown films. Subsequent deposition and annealing steps were used to build up thick layers. Films up to 1.2 mu m thick have been grown that are adherent to the substrate and have low residual compressive stress (<0.2 GPa). The values of hardness and modulus determined directly from an Oliver-Pharr analysis of nanoindentation experimental data were 80.2 and 552 GPa, respectively. We used finite-element modeling of the experimental nanoindentation curves to separate the "intrinsic" film response from the measured substrate/film response. We found a hardness of 88 GPa and Young's modulus of 1100 GPa. From these fits, a lower bound on the compressive yield stress of diamond (similar to 100 GPa) was determined. (C) 1997 American Institute of Physics. [S0003-6951(97)00852-8]. SN 0003-6951 EI 1077-3118 PD DEC 29 PY 1997 VL 71 IS 26 BP 3820 EP 3822 DI 10.1063/1.120515 UT WOS:000071184700025 ER PT J AU Kim, TJ Holloway, PH Kenik, EA AF Kim, TJ Holloway, PH Kenik, EA TI Ge concentration in regrown GaAs for ohmic contacts SO APPLIED PHYSICS LETTERS AB Dissociation and solid phase epitaxial regrowth of GaAs in Ti/Ge/Ni/GaAs were investigated using the transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS) of x-rays with spatial resolution approaching 2 nm. A ternary Ni2.4GaAs phase, similar to 130 nm thick, was formed by 300 degrees C in situ anneals of 65 nm Ni film on GaAs. After this in situ anneal, films of 30 nm Ge and 20 nm Ti were deposited in sequence. The EDS analysis showed that Ni2.4GaAs transformed into Ni-As and Ni-Ga binaries after annealing at 500 degrees C for 5 min, while similar to 30 nm of GaAs regrew by solid phase epitaxial regrowth from decomposition of the binary phases. High spatial resolution microanalysis allowed detection of similar to 1 X 10(20) cm(-3) Ge in the regrown GaAs. This confirms that Ge is incorporated into GaAs during regrowth for ohmic contact formation. (C) 1997 American Institute of Physics. [S0003-6951(97)00452-X]. SN 0003-6951 PD DEC 29 PY 1997 VL 71 IS 26 BP 3835 EP 3837 DI 10.1063/1.120519 UT WOS:000071184700030 ER PT J AU Gossmann, HJ Haynes, TE Stolk, PA Jacobson, DC Gilmer, GH Poate, JM Luftman, HS Mogi, TK Thompson, MO AF Gossmann, HJ Haynes, TE Stolk, PA Jacobson, DC Gilmer, GH Poate, JM Luftman, HS Mogi, TK Thompson, MO TI The interstitial fraction of diffusivity of common dopants in Si SO APPLIED PHYSICS LETTERS AB The relative contributions of interstitials and vacancies to diffusion of a dopant A in silicon are specified by the interstitial fraction of diffusivity, f(A). Accurate knowledge of f is required for predictive simulations of Si processing during which the point defect population is perturbed, such as transient enhanced diffusion, While experimental determination of f(A) is traditionally based on an underdetermined system of equations, we show here that it is actually possible to derive expressions that give meaningful bounds on f(A) without any further assumptions but that of local equilibrium, By employing a pair of dopants under the same point-defect perturbance, and by utilizing perturbances very far from equilibrium, w e obtain experimentally f(Sb)less than or equal to 0.012 and f(B) greater than or equal to 0.98 at temperatures of similar to 800 degrees C, which are the strictest bounds reported to date, Our results are in agreement with a theoretical expectation that a substitutional dopant in Si should either be a pure vacancy, or a pure interstitial(cy) diffuser. (C) 1997 Americaan Institute of Physics. [S0003-6951(97)03152-5]. RI Haynes, Tony/P-8932-2015; OI Haynes, Tony/0000-0003-2871-4745; Thompson, Michael/0000-0002-4933-009X SN 0003-6951 PD DEC 29 PY 1997 VL 71 IS 26 BP 3862 EP 3864 DI 10.1063/1.120527 UT WOS:000071184700039 ER PT J AU Shah, MM Campbell, JA AF Shah, MM Campbell, JA TI Transformation of nitrobenzene by ferredoxin NADP oxidoreductase from spinach leaves SO BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS AB Nitrobenzene was reduced in a solution containing ferredoxin NADP oxidoreductase (FNR) from spinach leaves and NADPH generating system. The product of nitrobenzene was identified as phenylhydroxylamine (PHA) on 1:1 basis. (C) 1997 Academic Press. SN 0006-291X PD DEC 29 PY 1997 VL 241 IS 3 BP 794 EP 796 DI 10.1006/bbrc.1997.7860 UT WOS:000071259500033 PM 9434788 ER PT J AU Lochter, A Galosy, S Muschler, J Freedman, N Werb, Z Bissell, MJ AF Lochter, A Galosy, S Muschler, J Freedman, N Werb, Z Bissell, MJ TI Matrix metalloproteinase stromelysin-1 triggers a cascade of molecular alterations that leads to stable epithelial-to-mesenchymal conversion and a premalignant phenotype in mammary epithelial cells SO JOURNAL OF CELL BIOLOGY AB Matrix metalloproteinases (MMPs) regulate ductal morphogenesis, apoptosis, and neoplastic progression in mammary epithelial cells. To elucidate the direct effects of MMPs on mammary epithelium, we generated functionally normal cells expressing an inducible autoactivating stromelysin-1 (SL-1) transgene. Induction of SL-1 expression resulted in cleavage of E-cadherin, and triggered progressive phenotypic conversion characterized by disappearance of E-cadherin and catenins from cell-cell contacts, downregulation of cytokeratins, upregulation of vimentin, induction of keratinocyte growth factor expression and activation, and upregulation of endogenous MMPs. Cells expressing SL-1 were unable to undergo lactogenic differentiation and became invasive. Once initiated, this phenotypic conversion was essentially stable, and progressed even in the absence of continued SL-1 expression. These observations demonstrate that inappropriate expression of SL-1 initiates a cascade of events that may represent a coordinated program leading to loss of the differentiated epithelial phenotype and gain of some characteristics of tumor cells. Our data provide novel insights into how MMPs function in development and neoplastic conversion. RI Freedman, Neal/B-9741-2015 OI Freedman, Neal/0000-0003-0074-1098 SN 0021-9525 PD DEC 29 PY 1997 VL 139 IS 7 BP 1861 EP 1872 DI 10.1083/jcb.139.7.1861 UT WOS:000071266100023 PM 9412478 ER PT J AU Gentzler, M Reimer, JA AF Gentzler, M Reimer, JA TI H-1 NMR relaxation study of chain motions and solid-state ordering in stiff, random copolymers SO MACROMOLECULES AB Fully-aromatic, thermotropic, liquid crystalline random copolyesters of 4-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA) were studied at elevated temperatures with H-1 NMR. Proton T-1 measurements provide high-frequency characterization of the glass transition. Proton rotating frame relaxation time (T-1 rho) measurements near room temperature are sensitive to HBA rotational motions; these motions are expected when there is monomer length-scale chain conformational disorder. In melt-quenched samples, this disorder is spatially homogeneous (i.e., the material solidifies without crystallization). Annealing below the nominal solidification temperature (T-s) results only in a slight, uniform lessening of this disorder. For samples annealed above T-s, proton T-1 rho measurements show a spatially distinct component in which monomeric rotational motions are suppressed. Spin-diffusion experiments indicate this component has a mean thickness of 10 +/- 2 nm. H-1-C-13 (cross polarization-magic-angle spinning) CP-MAS measurements indicate that these ordered regions are enriched in HBA. The fraction and HNA content of the "cocrystallites" decrease at higher annealing temperatures. We discuss a new conceptual model of solid ordering in highly sequence-frustrated, stiff HBA/HNA copolyesters that is consistent with these and previously reported data. SN 0024-9297 PD DEC 29 PY 1997 VL 30 IS 26 BP 8365 EP 8374 DI 10.1021/ma961109n UT WOS:000071476900036 ER PT J AU Li, Z Qu, S Rafailovich, MH Sokolov, J Tolan, M Turner, MS Wang, J Schwarz, SA Lorenz, H Kotthaus, JP AF Li, Z Qu, S Rafailovich, MH Sokolov, J Tolan, M Turner, MS Wang, J Schwarz, SA Lorenz, H Kotthaus, JP TI Confinement of block copolymers on patterned surfaces SO MACROMOLECULES AB Smectic ordered films of the copolymer PS-P2VP were studied on periodic silicon surfaces (surface gratings). The modulation of the film surface with respect to that of the underlying substrate was found to be either in phase (conformal) or-surprisingly-out of phase (anticonformal). The critical height of the surface grating which is defined by the transition from conformal behavior to the anticonformal conformation of the films was found to be proportional to the lamellar height of the diblock copolymers. This has been quantitatively understood within a mean field theory as a result of balancing the deformation and interfacial energies. Furthermore, diblock copolymer films propagate the substrate roughness by significantly larger distances than observed for amorphous homopolymers. RI Kotthaus, Jorg/A-7674-2010; Cavendish, TCM/C-9489-2009; Turner, Matthew/D-1121-2011 SN 0024-9297 PD DEC 29 PY 1997 VL 30 IS 26 BP 8410 EP 8419 DI 10.1021/ma9615009 UT WOS:000071476900041 ER PT J AU Rey, SJ AF Rey, SJ TI Classical and quantum aspects of BPS black holes in N=2, D=4 heterotic string compactifications SO NUCLEAR PHYSICS B AB We study classical and quantum aspects of D = 4, N = 2 BPS black holes for T-2 compactification of D = 6,N = 1 heterotic string vacua, We extend dynamical relaxation phenomena of moduli fields to a background consisting of a BPS soliton or a black hole and provide a simpler but. more general derivation of the Ferrara-Kallosh extremized black hole mass and entropy, We study quantum effects to the BPS black hole mass spectra and to their dynamical relaxation, We show that, despite non-renormalizability of string effective supergravity, the quantum effect modifies BPS mass spectra only through coupling constant and :moduli field renormalizations, Based on target-space duality, we establish a perturbative non-renormalization theorem and obtain the exact BPS black hole mass and entropy in terms of the renormalized string loop-counting parameter and renormalized moduli fields, We show that a similar conclusion holds, in the large T-2 limit, for leading non-perturbative correction. We finally discuss implications to type-I and type-IIA Calabi-Yau black holes. (C) 1997 Elsevier Science B.V. OI Rey, Soo-Jong/0000-0002-2589-7331 SN 0550-3213 PD DEC 29 PY 1997 VL 508 IS 3 BP 569 EP 608 DI 10.1016/S0550-3213(97)00606-8 UT WOS:A1997YL29800003 ER PT J AU Atwood, D Soni, A AF Atwood, D Soni, A TI Seeking nonstandard phases via direct CP violation in b -> sg* processes SO PHYSICAL REVIEW LETTERS AB Attributing the recent CLEO discovery of B --> eta' + X-s to originate (primarily) from the fragmentation of an off-shell gluon (g*) via b --> s + g*, g* --> g + eta', we emphasize that many such states (X-g) should materialize. Indeed the hadronic fragments (X-g) of g* are closely related to those seen in J/psi --> gamma(phi, omega) + X-g. A particular final state of considerable interest is X-g = K+K-. Signals from such states in B decays may be combined to provide a very sensitive search for CP violating phase(s) from nonstandard physics. The method should work even if the contribution of these source(s) to the rates is rather small (similar to 10%). [S0031-9007(97)04883-7]. SN 0031-9007 PD DEC 29 PY 1997 VL 79 IS 26 BP 5206 EP 5209 DI 10.1103/PhysRevLett.79.5206 UT WOS:000071200000005 ER PT J AU Reinhold, CO Burgdorfer, J Frey, MT Dunning, FB AF Reinhold, CO Burgdorfer, J Frey, MT Dunning, FB TI Dynamical stabilization of the periodically kicked Rydberg atom SO PHYSICAL REVIEW LETTERS AB Measurements in which K(np) Rydberg atoms with n similar to 388 are subject to a train of up to 50 half-cycle pulses are reported and reveal a peak in the atomic survival probability for pulse repetition frequencies near the classical orbital frequency. Classical calculations show that this behavior is associated with dynamical stabilization and the periodic orbits in phase space around which stable islands form are identified. This work provides the first direct evidence for dynamical stabilization of a periodically kicked Rydberg atom. [S0031-9007(97)04891-6]. OI Reinhold, Carlos/0000-0003-0100-4962 SN 0031-9007 PD DEC 29 PY 1997 VL 79 IS 26 BP 5226 EP 5229 DI 10.1103/PhysRevLett.79.5226 UT WOS:000071200000010 ER PT J AU Melnichenko, YB Anisimov, MA Povodyrev, AA Wignall, GD Sengers, JV van Hook, WA AF Melnichenko, YB Anisimov, MA Povodyrev, AA Wignall, GD Sengers, JV van Hook, WA TI Sharp crossover of the susceptibility in polymer solutions near the critical demixing point SO PHYSICAL REVIEW LETTERS AB We have observed a sharp and nonmonotonic crossover of the susceptibility (osmotic compressibility) from mean-field to Ising critical behavior in semidilute solutions of polystyrene in deuterocyclohexane as the temperature decreases from-the Theta region down to the critical temperature of the phase separation. We describe this crossover in terms of a competition between the long-range but finite intramolecular correlations of monomers in the polymer chain and the diverging correlation length of concentration fluctuations. OI Wignall, George/0000-0002-3876-3244 SN 0031-9007 PD DEC 29 PY 1997 VL 79 IS 26 BP 5266 EP 5269 DI 10.1103/PhysRevLett.79.5266 UT WOS:000071200000020 ER PT J AU Melik-Alaverdian, V Bonesteel, NE Ortiz, G AF Melik-Alaverdian, V Bonesteel, NE Ortiz, G TI Quantum Hall fluids on the Haldane sphere: A diffusion Monte Carlo study SO PHYSICAL REVIEW LETTERS AB A generalized diffusion Monte Carlo method for solving the many-body Schrodinger equation on curved manifolds is introduced and used to perform a "fixed-phase" simulation of the fractional quantum Hall effect on the Haldane sphere. This new method is used to study the effect of Landau level mixing on the nu = 1/3 energy gap and the relative stability of spin-polarized and spin-reversed quasielectron excitations. SN 0031-9007 PD DEC 29 PY 1997 VL 79 IS 26 BP 5286 EP 5289 DI 10.1103/PhysRevLett.79.5286 UT WOS:000071200000025 ER PT J AU Balakrishnan, R Blumenfeld, R AF Balakrishnan, R Blumenfeld, R TI On the twist excitations in a classical anisotropic antiferromagnetic chain SO PHYSICS LETTERS A AB In a recent Erratum [M. Daniel and R. Amuda, Phys. Lett. A 224 (1997) 389] the authors have explained that an algebraic error in their earlier analysis [Phys. Lett. A 191 (1994) 46] of a nonlinear evolution equation for a certain anisotropic antiferromagnetic chain in a magnetic field invalidates the twist solution obtained by them for any finite anisotropy. Using a transformed variable and a different analysis of that evolution equation in the presence of a field, we obtain a pi/2-traveling twist solution for a finite anisotropy and a pi-twist for negligible anisotropies. (C) 1997 Elsevier Science B.V. SN 0375-9601 PD DEC 29 PY 1997 VL 237 IS 1-2 BP 69 EP 72 DI 10.1016/S0375-9601(97)00685-3 UT WOS:000071327900014 ER PT J AU Zender, CS Bush, B Pope, SK Bucholtz, A Collins, WD Kiehl, JT Valero, FPJ Vitko, J AF Zender, CS Bush, B Pope, SK Bucholtz, A Collins, WD Kiehl, JT Valero, FPJ Vitko, J TI Atmospheric absorption during the Atmospheric Radiation Measurement (ARM) Enhanced Shortwave Experiment (ARESE) SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES AB The objectives of the Atmospheric Radiation Measurement (ARM) Enhanced Shortwave Experiment (ARESE) are to directly measure clear and cloudy sky shortwave atmospheric absorption and to quantify any absorption found in excess of model predictions. We undertake detailed model comparisons to near-infrared and total solar flux time series observed by surface and airborne radiometric instruments during the ARESE campaign. Model clear-sky absorption biases generally fall within the range of uncertainty generated by sample size, and assumptions of aerosol properties and surface albedo. Direct measurements by stacked aircraft on the overcast day of October 30, 1995, confirm the detection of enhanced cloud shortwave absorption during ARESE. The detection is substantiated by, and consistent with, three independent measures of cloudy sky absorption estimated in previous studies: cloud forcing ratio, insolation forcing ratio, and albedo/transmission slope. A significant portion of the enhanced absorption occurs at visible wavelengths. Collocated measurements of liquid water path (LWP) suggest the magnitude of the enhanced absorption increases with LWP. RI Zender, Charles/D-4485-2012; Collins, William/J-3147-2014 OI Zender, Charles/0000-0003-0129-8024; Collins, William/0000-0002-4463-9848 SN 2169-897X PD DEC 27 PY 1997 VL 102 IS D25 BP 29901 EP 29915 DI 10.1029/97JD01781 UT WOS:000071277300013 ER PT J AU Valero, FPJ Cess, RD Zhang, MH Pope, SK Bucholtz, A Bush, B Vitko, J AF Valero, FPJ Cess, RD Zhang, MH Pope, SK Bucholtz, A Bush, B Vitko, J TI Absorption of solar radiation by the cloudy atmosphere: Interpretations of collocated aircraft measurements SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES AB As part of the Atmospheric Radiation Measurement (ARM) Enhanced Shortwave Experiment (ARESE), we have obtained and analyzed measurements made from collocated aircraft of the absorption of solar radiation within the atmospheric column between the two aircraft. The measurements were taken during October 1995 at the ARM site in Oklahoma. Relative to a theoretical radiative transfer model, we find no evidence for excess solar absorption in the clear atmosphere and significant evidence for its existence in the cloudy atmosphere. This excess cloud solar absorption appears to occur in both visible (0.224-0.68 mu m) and near-infrared (0.68-3.30 mu m) spectral regions, although not at 0.5 mu m for the visible contribution, and it is shown to be true absorption rather than an artifact of sampling errors caused by measuring three-dimensional clouds. SN 2169-897X PD DEC 27 PY 1997 VL 102 IS D25 BP 29917 EP 29927 DI 10.1029/97JD01782 UT WOS:000071277300014 ER PT J AU Halthore, RN Schwartz, SE Michalsky, JJ Anderson, GP Ferrare, RA Holben, BN Ten Brink, HM AF Halthore, RN Schwartz, SE Michalsky, JJ Anderson, GP Ferrare, RA Holben, BN Ten Brink, HM TI Comparison of model estimated and measured direct-normal solar irradiance SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES AB Direct-normal solar irradiance (DNSI), the energy in the solar spectrum incident in unit time at the Earth's surface on a unit area perpendicular to the direction to the Sun, depends only on atmospheric extinction of solar energy without regard to the details of the extinction, whether absorption or scattering. Here we report a set of closure experiments performed in north central Oklahoma in April 1996 under cloud-free conditions, wherein measured atmospheric composition and aerosol optical thickness are input to a radiative transfer model, MODTRAN 3, to estimate DNSI, which is then compared with measured values obtained with normal incidence pyrheliometers and absolute cavity radiometers. Uncertainty in aerosol optical thickness (AOT) dominates the uncertainty in DNSI calculation. AOT measured by an independently calibrated Sun photometer and a rotating shadow-band radiometer agree to within the uncertainties of each measurement. For 36 independent comparisons the agreement between measured and model-estimated values of DNSI falls within the combined uncertainties in the measurement (0.3-0.7%) and model calculation (1.8%), albeit with a slight average model underestimate (-0.18 +/- 0.94)%; for a DNSI of 839 W m(-2) this corresponds to -1.5 +/- 7.9 W m(-2). The agreement is nearly independent of air mass and water-vapor path abundance. These results thus establish the accuracy of the current knowledge of the solar spectrum, its integrated power, and the atmospheric extinction as a function of wavelength as represented in MODTRAN 3. An important consequence is that atmospheric absorption of short-wave energy is accurately parametrized in the model to within the above uncertainties. RI Schwartz, Stephen/C-2729-2008 OI Schwartz, Stephen/0000-0001-6288-310X SN 2169-897X EI 2169-8996 PD DEC 27 PY 1997 VL 102 IS D25 BP 29991 EP 30002 DI 10.1029/97JD02628 UT WOS:000071277300019 ER PT J AU Novakov, T Hegg, DA Hobbs, PV AF Novakov, T Hegg, DA Hobbs, PV TI Airborne measurements of carbonaceous aerosols on the East Coast of the United States SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES AB In this paper we report results of aircraft measurements of mass concentrations of carbonaceous aerosols, total aerosol mass, and simultaneously determined light scattering and absorption coefficients onshore and offshore of the eastern coast of the United States. We describe the sampling and analytical methodology used to derive spatially resolved aerosol carbon concentrations and discuss these in the context of other concurrently collected data. The carbon mass was, on average, 50% of the total dry aerosol mass. The carbon mass fraction tended to increase with altitude, suggesting that ground-based measurements can significantly underestimate the importance of carbon species in the column aerosol mass budget. The aerosol carbon mass was significantly correlated with aerosol light absorption, suggesting that the black and organic carbon components have, at least in part, common combustion sources. A regression of the light absorption coefficient onto carbon mass suggests that similar to 10% of the carbon mass is in the form of black (light-absorbing) carbon. SN 2169-897X PD DEC 27 PY 1997 VL 102 IS D25 BP 30023 EP 30030 DI 10.1029/97JD02793 UT WOS:000071277300022 ER PT J AU Kuhns, H Davidson, C Dibb, J Stearns, C Bergin, M Jaffrezo, JL AF Kuhns, H Davidson, C Dibb, J Stearns, C Bergin, M Jaffrezo, JL TI Temporal and spatial variability of snow accumulation in central Greenland SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES AB Snow accumulation records from central Greenland are explored to improve the understanding of the accumulation signal in Greenland ice core records. Results from a "forest" of 100 bamboo poles and automated accumulation monitors in the vicinity df Summit as well as shallow cores collected in the Summit and Crete areas are presented. Based on these accumulation data, a regression has been calculated to quantify the signal-to-noise variance ratio of ice core accumulation signals on a variety of temporal (1 week to 2 years) and spatial (20 m to 200 km) scales. Results are consistent with data obtained from year-round automated accumulation measurements deployed at Summit which suggest that it is impossible to obtain regional snow accumulation data with seasonal resolution using four accumulation monitors positioned over a length scale of similar to 30 km. Given this understanding of the temporal and spatial dependence of noise in the ice core accumulation signal, the accumulation records from 17 shallow cores are revisited. Each core spans the time period from 1964 to 1983. By combining the accumulation records, the regional snow accumulation record has been obtained for this period. The results show that 9 of the 20 years can be identified as having an accumulation different from the 20 year mean with 99% confidence. The signal-to-noise variance ratio for the average accumulation signal sampled at annual intervals is 5.8 +/- 0.5. The averaged accumulation time series may be useful to climate modelers attempting to validate their models with accurate regional hydrologic data sets. RI Kuhns, Hampden/C-3563-2008 SN 2169-897X PD DEC 27 PY 1997 VL 102 IS D25 BP 30059 EP 30068 DI 10.1029/97JD02760 UT WOS:000071277300025 ER PT J AU Jones, PD Osborn, TJ Wigley, TML Kelly, PM Santer, BD AF Jones, PD Osborn, TJ Wigley, TML Kelly, PM Santer, BD TI Comparisons between the microwave sounding unit temperature record and the surface temperature record from 1979 to 1996: Real differences or potential discontinuities? SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES AB This paper reports a detailed comparison at the global, hemispheric, three 60 degrees-latitude zone, and grid-box scale between lower tropospheric temperatures from the microwave sounding units (MSU2R) on board NOAA polar orbiting satellites and surface temperatures. The comparisons reveal differences in the course of temperature trends over the 1979-1996 period in the two sets of time series. The surface data warms relative to MSU2R by 0.19 degrees C per decade over this period, with much of the change occurring as a jump in the difference series, particularly during 1991 but also in 1981. The differences either reflect problems in one or both of the surface or MSU2R records or, if both records are correct, a significant change in lapse rates in the lower part of the atmosphere on a global scale particularly since mid-1991. Although MSU2R data agree well with radiosonde data on global and hemispheric scales over 1979-1996, surface and radiosonde data agree almost exactly when their trends are compared over 1958-1993 and 1965-1996. The differences in the two data sets are discussed in terms of possible natural causes and data homogeneities. RI Wigley, Tom/B-4705-2008; Jones, Philip/C-8718-2009; Santer, Benjamin/F-9781-2011; Osborn, Timothy/E-9740-2011 OI Jones, Philip/0000-0001-5032-5493; Osborn, Timothy/0000-0001-8425-6799 SN 2169-897X PD DEC 27 PY 1997 VL 102 IS D25 BP 30135 EP 30145 DI 10.1029/97JD02432 UT WOS:000071277300031 ER PT J AU Zhang, D Shen, YR Somorjai, GA AF Zhang, D Shen, YR Somorjai, GA TI Studies of surface structures and compositions of polyethylene and polypropylene by IR plus visible sum frequency vibrational spectroscopy SO CHEMICAL PHYSICS LETTERS AB IR + visible sum-frequency generation (SFG) was used to obtain surface vibrational spectra of polyethylene and polypropylene. It was found that low density and ultrahigh-molecular-weight polyethylene have different surface structures. The latter has a surface mainly composed of orderly packed gauche conformers while the former has a surface with a more random distribution of polymer chains. The SFG spectra also show thar surface structures of atactic and isotactic polypropylenes are different. Segregation of additives at surfaces of industrial polyethylene and polypropylene, that cannot be detected by IR and Raman spectroscopies, can be readily observed by SFG. (C) 1997 Elsevier Science B.V. SN 0009-2614 PD DEC 26 PY 1997 VL 281 IS 4-6 BP 394 EP 400 DI 10.1016/S0009-2614(97)01311-0 UT WOS:000072254400025 ER PT J AU Dobosy, RJ Crawford, TL MacPherson, JI Desjardins, RL Kelly, RD Oncley, SP Lenschow, DH AF Dobosy, RJ Crawford, TL MacPherson, JI Desjardins, RL Kelly, RD Oncley, SP Lenschow, DH TI Intercomparison among four flux aircraft at BOREAS in 1994 SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES AB Four airplanes measured fluxes of momentum, heat, water vapor, and carbon dioxide in 1994, during the intensive field campaigns of the Boreal Ecosystem-Atmosphere Study (BOREAS): the NOAA/ATDD Long-EZ, the NRC Twin Otter, the University of Wyoming King Air, and the NCAR Electra. This paper presents the results of wing-towing formation flights comparing the flux measurements from these airplanes. Comparisons of the spectra of wind components, air temperature, water vapor concentration, and carbon dioxide concentration along with the cospectra of these quantities with vertical velocity showed numerous instructive differences. However, among the three airplanes using established techniques, the fluxes and variances of these quantities generally did not differ by more than one would expect, given the separation of the airplanes. Statistics computed from the Long-EZ data, based on a still evolving application of the Global Positioning System, often differed more strongly. RI Dobosy, Ronald/C-3303-2016; OI Dobosy, Ronald/0000-0001-8399-8774; LENSCHOW, DONALD/0000-0003-4353-0098 SN 2169-897X EI 2169-8996 PD DEC 26 PY 1997 VL 102 IS D24 BP 29101 EP 29111 DI 10.1029/97JD01174 UT WOS:000071384900031 ER PT J AU Markham, BL Schafer, JS Holben, BN Halthore, RN AF Markham, BL Schafer, JS Holben, BN Halthore, RN TI Atmospheric aerosol and water vapor characteristics over north central Canada during BOREAS SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES AB A network of five automated and two handheld solar radiometers was operated during the 1993-1996 Boreal Ecosystem-Atmosphere Study (BOREAS) in northern Saskatchewan and Manitoba, Canada, in order to characterize the atmospheric aerosol properties. Direct solar measurements were used to measure atmospheric transmission and infer aerosol optical thickness and water vapor column abundance. Near-Sun sky radiance measurements (solar aureole) were used to estimate the aerosol size distribution. Aerosol conditions were heavily influenced by the presence or absence of forest fires. In 1996, when few fires occurred, conditions were uniform across the region with median aerosol optical thickness (AOT) at 500 nm of 0.12 and 90th percentile values of 0.27 for the May-October period. During the 1994 and 1995 seasons, numerous fires occurred in the vicinity of the sites. The median AOT values were comparable with the 1996 values, though the 90th percentile values were larger, in general measuring 0.85 (southern 1994 season was 0.43). Median column water vapor measurements for the same 7 month period were in the range from 1.32 to 1.58 cm at both sites, with 1995 being the driest year of observation. Winter median values of AOT and water vapor were typically 0.09 and 0.34 cm, respectively. Size distributions derived from solar almucantar measurements show the predominance of small particles during smoke episodes when compared to that for background conditions. Spectral dependence of the AOT as characterized by the wavelength exponent, alpha, asymptotes at 1.8 for high optical depths for a 7 month season of cloud-screened data at the northern young jack pine site. This observed wavelength exponent for boreal biomass burning conditions is within the range of values found during the burning season in a study in Brazil. RI Schafer, Joel/A-3978-2010; Markham, Brian/M-4842-2013 OI Markham, Brian/0000-0002-9612-8169 SN 2169-897X EI 2169-8996 PD DEC 26 PY 1997 VL 102 IS D24 BP 29737 EP 29745 DI 10.1029/97JD00241 UT WOS:000071384900084 ER PT J AU Trahanovsky, WS Miller, DL Wang, YL AF Trahanovsky, WS Miller, DL Wang, YL TI Oligomerization of the thiophene-based p-quinodimethanes 2,5-dimethylene-2,5-dihydrothiophene and 2-ethylidene-5-methylene-2,5-dihydrothiophene SO JOURNAL OF ORGANIC CHEMISTRY AB Flash vacuum pyrolysis (FVP) of (5-methyl-2-thiophene-yl)methyl benzoate (8) produces in ca. 75% yield 2,5-dimethylene-2,3-dihydrothiophene, S-monomer (3). S-Monomer 3 is relatively stable dissolved in carbon disulfide-chloroform at -78 degrees C. The structure of 3 is confirmed by its spectral properties. When a 0.17 M solution of S-monomer 3 was allowed to warm to room temperature, SS-dimer 5 ([2,2](2,5)thiophenophane, 14.7%), SSS-trimer 7 ([2,2,2](2,5)thiophenophane, 44.3%), and polymer were produced. A small amount (<1%) of an SSSS-tetramer was detected by GC/MS. The mechanism proposed for the formation of these oligomers involves the combination of two molecules of 3 to give an intermediate diradical (11) that can close to form dimer 5 or react with additional molecules of 3 to form the higher oligomers. Evidence for the trapping of diradical 11 by 2,5-dimethylene-2,5-dihydrofuran (O-monomer 2) was obtained. Co-oligomerization of S-monomer 3 and O-monomer 2 gave four compounds containing the thiophene moiety: OS-dimer 16, SS-dimer 5, OSS-trimer 17, and SSS-trimer 7. Some OO-dimer 4 was produced but no 000-trimer 6 was observed and only a trace of OOS-trimer 18 was detected. Additional support for the diradical mechanism was obtained from the study of the oligomerization of the methyl derivatives of 3,2-ethylidene-5-methylene-2,5-dihydrothiophene (10, E and Z isomers), prepared by the FVP of (5-ethyl-2-thiophene-yl)methyl benzoate (9). Oligomerization of 10 gave several dimers and trimers including two acyclic dimers that are accounted for by intramolecular disproportionation. SN 0022-3263 PD DEC 26 PY 1997 VL 62 IS 26 BP 8980 EP 8986 DI 10.1021/jo961528i UT WOS:000071410200010 ER PT J AU Serebrov, AP Mityukhlyaev, VA Zakharov, AA Bowles, T Greene, G Sromicki, J AF Serebrov, AP Mityukhlyaev, VA Zakharov, AA Bowles, T Greene, G Sromicki, J TI Solid deuterium source of ultracold neutrons based on a pulsed spallation source SO JETP LETTERS AB A new type of source of ultracold neutrons (UCNs) is proposed. The source operates on the basis of a pulsed spallation source. Solid deuterium makes it possible to obtain UCN density 10(4) neutrons/cm(3) as a result of high gain at low temperatures and the possibility of withstanding high pulsed heat loads as a result of the high specific heat of solid deuterium. (C) 1997 American Institute of Physics. [S0021-3640(97)00424-6]. RI Mityukhlyaev, Vitaly/B-2824-2014; Serebrov, Anatoly/A-6771-2014 OI Serebrov, Anatoly/0000-0002-6734-038X SN 0021-3640 PD DEC 25 PY 1997 VL 66 IS 12 BP 802 EP 808 DI 10.1134/1.567601 UT WOS:000071928300004 ER PT J AU Mondy, LA Tetlow, N Graham, AL Abbott, J Brenner, H AF Mondy, LA Tetlow, N Graham, AL Abbott, J Brenner, H TI The pressure drop created by a ball settling in a quiescent suspension of comparably sized spheres SO JOURNAL OF FLUID MECHANICS AB Measurements are reported of the pressure differences Delta P existing at large distances above and below a ball settling along the axis of a circular cylinder filled with an otherwise quiescent viscous Newtonian liquid in which identical particles, comparable in size to the settling ball, are suspended. The suspensions ranged in solids volume fraction phi from 0.30 to 0.50 and consisted of 0.635 cm diameter spheres density-matched to the suspending oil. The settling balls varied in diameter from 0.1318 to 1.27 cm, resulting in particle Reynolds numbers always less than about 0.4 based upon ball diameter and the effective viscosity of the suspension. For the moderately concentrated suspension (phi = 0.30), the product of Delta P with the cross-sectional area A of the containing cylinder was observed to be equal to twice the drag force D on the settling sphere, in accord with theory. In the more concentrated suspension (phi = 0.50) this product was found to be slightly, but significantly, less than twice the drag on the settling sphere. It is speculated that this lower pressure drop may result from the presence of one or more of the following phenomena: (i) migration of the falling ball off the cylinder axis; (ii) apparent slip of the suspension at the cylinder wall; (iii) blunting of the otherwise Poiseuillian parabolic velocity profile, the latter phenomenon being known to occur during the creeping flow of concentrated suspensions through circular tubes. Incidental to the suspension experiments, for a homogeneous fluid we verify the classical theoretical formula for the off-axis pressure drop when the sphere settles at a non-concentric position in the cylinder. SN 0022-1120 PD DEC 25 PY 1997 VL 353 BP 31 EP 44 DI 10.1017/S0022112097007209 UT WOS:000071380700002 ER PT J AU Wigmosta, MS Burges, SJ AF Wigmosta, MS Burges, SJ TI An adaptive modeling and monitoring approach to describe the hydrologic behavior of small catchments SO JOURNAL OF HYDROLOGY AB An adaptive combination of field mapping, simple hydrologic monitoring, and hydrologic modeling was used to describe the hydrologic behavior of two zero-order catchments: one undeveloped forest, the other suburban. Field mapping was used to delineate hydrologic process zones and provide guidance for the location of monitoring stations. Hydrologic monitoring included continuous streamflow and precipitation, as well as limited piezometer information. The hydrologic model was developed in conjunction with the measurement program to assure that the level of model detail was consistent with the level of field measurements used for model input and testing, At the start of the work it was anticipated that saturation overland flow would drive peak discharge in the forested catchment and Horton overland Bow from impervious surfaces would dominate storm runoff in the suburban catchment, Instead, subsurface flow was found to dominate both annual and peak discharge in the forested site, and discharge from lawns and other pervious areas accounted for roughly 60% of annual and storm runoff from the suburban catchment, The adaptive combination of modeling and measurements was essential to elucidate the various components of Row production and flow paths in these catchments. (C) 1997 Elsevier Science B.V. SN 0022-1694 PD DEC 25 PY 1997 VL 202 IS 1-4 BP 48 EP 77 DI 10.1016/S0022-1694(97)00057-7 UT WOS:000071644800004 ER PT J AU Devlin, M LaFosse, DR Lerma, F Sarantites, DG Baktash, C Birriel, I Jin, HQ Lee, IY Macchiavelli, AO Rudolph, D Saladin, JX Sylvan, GN Tabor, SL Winchell, DF Wood, VQ Yu, CH AF Devlin, M LaFosse, DR Lerma, F Sarantites, DG Baktash, C Birriel, I Jin, HQ Lee, IY Macchiavelli, AO Rudolph, D Saladin, JX Sylvan, GN Tabor, SL Winchell, DF Wood, VQ Yu, CH TI Superdeformed bands in Sr-80 and the evolution of deformation in Sr isotopes SO PHYSICS LETTERS B AB Four superdeformed bands are reported in Sr-80, extending known superdeformation in the Sr-38 series down to N = 42. The characteristics of these bands are discussed. Residual Doppler shifts were measured and average transition quadrupole moments (Q(t)) inferred for these new bands, These Q(t) values are compared to Q(t) values obtained for previously identified superdeformed bands in Sr81-83. The low Q(t) of 2.7(-0.6)(+0.7) eb obtained for the yrast band in Sr-80 indicates a reduction in the deformation of yrast superdeformed bands in the series Sr80-83 with decreasing N, and possibly the onset of triaxiality in superdeformed shapes. (C) 1997 Elsevier Science B.V. RI Rudolph, Dirk/D-4259-2009; Devlin, Matthew/B-5089-2013 OI Rudolph, Dirk/0000-0003-1199-3055; Devlin, Matthew/0000-0002-6948-2154 SN 0370-2693 PD DEC 25 PY 1997 VL 415 IS 4 BP 328 EP 334 DI 10.1016/S0370-2693(97)01289-6 UT WOS:000071349200004 ER PT J AU Sundaram, UM Zhang, HH Hedman, B Hodgson, KO Solomon, EI AF Sundaram, UM Zhang, HH Hedman, B Hodgson, KO Solomon, EI TI Spectroscopic investigation of peroxide binding to the trinuclear copper cluster site in laccase: Correlation with the peroxy-level intermediate and relevance to catalysis SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB Laccase is a multicopper oxidase which contains four coppers, one type 1, one type 2, and a coupled binuclear type 3 pair, the type 2 and type 3 copper centers together forming a trinuclear copper cluster. The type I mercury derivative of laccase (T1Hg Lc) has the type 1 center substituted with a redox-inactive Hg2+ ion and an intact trinuclear copper cluster. Reaction of H2O2 with fully oxidized T1Hg Le produces a peroxide adduct which has now been studied in detail. Peroxide is shown to bind to the trinuclear cluster with low affinity, producing spectral and geometric features similar to the intermediate formed in the reduction of O-2 to H2O which had been shown to have the type 2 copper reduced, the type 3 pair oxidized and antiferromagnetically coupled, and two coppers bridged at a distance of 3.4 Angstrom. The peroxide adduct and the intermediate have similar geometric and electronic features with the type 2 oxidized in the adduct. This center is paramagnetic and has been studied in detail. Peroxide binds to the type 2 center. EPR and ligand field (NiR MCD) coupled with CT (absorption and MCD) data demonstrate that peroxide binds to the type 2 Cu which goes from being 3-coordinate in the resting protein to 4-coordinate in the peroxide adduct. Peroxide also binds to the type 3 site from a comparison of ligand field absorption and CD and the presence of more than one intense O-2(2-) --> Cu(II) band in the CT absorption spectrum. A bridging interaction between coppers at 3.4 Angstrom is seen from the EXAFS data. Possible geometric structures for the peroxide adduct and intermediate are proposed, with the electronic structural difference between the adduct and the intermediate being related to the type 2 copper being reduced in the latter. This study (i) firmly establishes the role of the type 2 in catalysis, (ii) demonstrates a type 2/type 3 bridging mode of binding that promote further 2e(-) reduction of peroxide to water, and (iii) provides further support for a peroxide-level intermediate in the catalytic cycle of the multicopper oxidases which involve two 2e(-) steps in the reduction of O-2 to H2O. SN 0002-7863 PD DEC 24 PY 1997 VL 119 IS 51 BP 12525 EP 12540 DI 10.1021/ja972039i UT WOS:000071272500012 ER PT J AU Shin, IJ Ting, AY Schultz, PG AF Shin, IJ Ting, AY Schultz, PG TI Analysis of backbone hydrogen bonding in a beta-turn of staphylococcal nuclease SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY SN 0002-7863 PD DEC 24 PY 1997 VL 119 IS 51 BP 12667 EP 12668 DI 10.1021/ja972820q UT WOS:000071272500031 ER PT J AU Bridgewater, JS Lee, B Bernhard, S Schoonover, JR Ford, PC AF Bridgewater, JS Lee, B Bernhard, S Schoonover, JR Ford, PC TI Time-resolved infrared spectral studies of photochemically induced oxidative addition of benzene to trans-RhCl(CO)(PMe3)(2) SO ORGANOMETALLICS AB Time-resolved infrared and time-resolved optical spectroscopy were used to examine the pathway(s) by which 355 nm photolysis of the rhodium(I) species trans-RhCl(CO)(PMe3)(2) (1) in benzene leads to the C-H oxidative-addition product (Ph)(H)RhCl(CO)(PMe3)(2) (2). True reaction pathways to the formation of 2 were found. One of these was the "prompt" formation (<150 ns) of 2, the apparent result of a direct reaction of the electronic excited state of the four-coordinate species 1 with the C6H6 solvent. The second route was more a convoluted stepwise process, involving CO photodissociation to give the "tricoordinate" intermediate RhCl(PMe3)(2) followed by benzene oxidative addition then CO addition to give 2. RI Bernhard, Stefan/A-9389-2008; Ford, Peter/D-1826-2011 OI Ford, Peter/0000-0002-5509-9912 SN 0276-7333 PD DEC 23 PY 1997 VL 16 IS 26 BP 5592 EP 5594 DI 10.1021/om970679o UT WOS:000071423300002 ER PT J AU Miedaner, A Noll, BC DuBois, DL AF Miedaner, A Noll, BC DuBois, DL TI Synthesis and characterization of palladium and nickel complexes with positively charged triphosphine ligands and their use as electrochemical CO2-reduction catalysts SO ORGANOMETALLICS AB The synthesis and characterization of [M(Bu(3)P(+)etpE)Br](BF4)(2) (where M = Ni or Pd and Bu(3)P(+)etpE = [(Bu3PCH2CH2)P(CH2CH2PEt2)(2)](+)) and [M(etpPBu(3)(+))Br]Br(BF4)(4) (where M = Ni or Pd and etpPBu(3)(+) = {PhP[CH2CH2P(CH2CH2PBu3)(2)](2)}(4+)) are described. The structure of [Ni(etpPBu(3)(+))Br]Br(BF4)(4) has been determined by X-ray diffraction. Treatment of [Pd(Bu(3)P(+)etPE)Br](BF4)(2) with AgBF4 in acetonitrile produced [Pd(Bu(3)P(+)etpE)(CH3CN)](BF4)(3). The latter compound has also been characterized by single-crystal X-ray diffraction action methods. Electrochemical studies indicate that this compound and its closely related methyl analog, [Pd(Me(3)P(+)etpE)(CH3CN)](BF4)(3), are catalysts for the electrochemical reduction of CO2 to CO in acidic dimethylformamide solutions. Kinetic and mechanistic studies of this catalytic reaction are reported. SN 0276-7333 PD DEC 23 PY 1997 VL 16 IS 26 BP 5779 EP 5791 DI 10.1021/om970519c UT WOS:000071423300034 ER PT J AU Goodson, BM Song, YQ Taylor, RE Schepkin, VD Brennan, KM Chingas, GC Budinger, TF Navon, G Pines, A AF Goodson, BM Song, YQ Taylor, RE Schepkin, VD Brennan, KM Chingas, GC Budinger, TF Navon, G Pines, A TI In vivo NMR and MRI using injection delivery of laser-polarized xenon SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA AB Because xenon NMR is highly sensitive to the local environment, laser-polarized xenon could be a unique probe of living tissues. Realization of clinical and medical science applications beyond lung airspace imaging requires methods of efficient delivery of laser-polarized xenon to tissues, because of the short spin-lattice relaxation times and relatively low concentrations of xenon attainable in the body. Preliminary results from the application of a polarized xenon injection technique for in vivo Xe-129 NMR/MRI are extrapolated along with a simple model of xenon transit to show that the peak local concentration of polarized xenon delivered to tissues by injection may exceed that delivered by respiration by severalfold. RI Schepkin, Victor/A-1245-2007 SN 0027-8424 PD DEC 23 PY 1997 VL 94 IS 26 BP 14725 EP 14729 DI 10.1073/pnas.94.26.14725 UT WOS:000071182800090 PM 9405680 ER PT J AU Pinnaduwage, LA Ding, WX McCorkle, DL AF Pinnaduwage, LA Ding, WX McCorkle, DL TI Enhanced electron attachment to highly excited molecules using a plasma mixing scheme SO APPLIED PHYSICS LETTERS AB We present preliminary results on a glow discharge-based technique to populate highly excited states of molecules using a novel excitation transfer process, and to efficiently produce negative ions via electron attachment to those excited states. (C) 1997 American Institute of Physics. [S0003-6951(97)03851-5]. SN 0003-6951 PD DEC 22 PY 1997 VL 71 IS 25 BP 3634 EP 3636 DI 10.1063/1.120464 UT WOS:000071151400012 ER PT J AU Benaissa, M Gonsalves, KE Rangarajan, SP AF Benaissa, M Gonsalves, KE Rangarajan, SP TI AlGaN nanoparticle/polymer composite: Synthesis, optical, and structural characterization SO APPLIED PHYSICS LETTERS AB The aluminum gallium nitride (AlGaN) alloy is uniquely suited for fabricating optoelectronic devices in the ultraviolet and visible bands of the spectrum. Its synthesis in a nanometer scale may potentially open the way for applications such as tunable optoelectronic devices. Presently, results concerning the synthesis and microstructural and optical characterization of nanometer-sized AlGaN imbedded in a poly-methylmethacrylate (PMMA) matrix are reported. Our optical measurement showed that the AlGaN/PMMA nanoparticle/polymer composite efficiently emits in the violet-blue region, while the microstructural characterization confirms the formation of defect-free zinc blende AlGaN nanoparticles. (C) 1997 American Institute of Physics. [S0003-6951(97)02551-5]. SN 0003-6951 PD DEC 22 PY 1997 VL 71 IS 25 BP 3685 EP 3687 DI 10.1063/1.120481 UT WOS:000071151400029 ER PT J AU Huang, Y Merkle, KL Lee, LP Teepe, M Char, K AF Huang, Y Merkle, KL Lee, LP Teepe, M Char, K TI Microstructural origin of 1/f noise in high T-c bicrystal SQUID magnetometers SO APPLIED PHYSICS LETTERS AB The origin of noise in YBa2Cu3O7-x (YBCO) bicrystal SQUID magnetometers on SrTiO3 substrates is investigated by comparing the microstructure of actual low-noise and high-noise devices. The most obvious difference in the microstructure is the presence of a-axis oriented particles in the high-noise devices, whereas the low-noise devices consist exclusively of c-axis oriented YBCO films. The growth of the a-axis particles in the YBCO films induces many defects, including amorphous regions, distortion in c-axis lattice planes and extra a-c interfaces. The quality of the junction boundary is also degraded by the a-axis particles. The existence of these defects are expected to affect the superconducting current and the motion of the magnetic flux in the films and hence generate extra noise in the devices. (C) 1997 American Institute of Physics. [S0003-6951(97)00151-4]. SN 0003-6951 PD DEC 22 PY 1997 VL 71 IS 25 BP 3703 EP 3705 DI 10.1063/1.120487 UT WOS:000071151400035 ER PT J AU Koretsky, GM Knickelbein, MB AF Koretsky, GM Knickelbein, MB TI The reactions of silver clusters with ethylene and ethylene oxide: Infrared and photoionization studies of Agn(C2H4)(m), Ag-n(C2H4O)(m) and their deuterated analogs SO JOURNAL OF CHEMICAL PHYSICS AB Ethylene and ethylene oxide react readily with silver clusters at 70 K to form the addition complexes, Ag-n(C2H4), and Ag-n(C2H4O)(m), respectively. The infrared photodissociation spectra of Ag-n(C2H4)(m) and Ag-n(C2D4)(m) (n = 3-7) recorded in the 9-11 mu m region show several characteristic vibrational bands of ethylene lying near their gas phase frequencies. Photoionization spectroscopy studies reveal that the ionization potentials (IPs) of the complexes decrease monotonically with adsorption of additional ethylene molecules. Together, these results imply that as on macroscopic Silver surfaces, ethylene adsorbs molecularly to small silver clusters, with a net donation of electron density into the underlying cluster. Similarly, silver cluster-ethylene oxide complexes display IPs that decrease with increasing adsorbate coverage. The infrared depletion spectra of Ag-n(C2D4O)(m) complexes reveal a single feature at 949 cm(-1), assigned to the nu(4)(a(1)) fundamental of C2D4O. These results verify that ethylene oxide adsorbs molecularly to silver clusters, with the oxygen atom oriented toward the silver cluster. (C) 1997 American Institute of Physics. SN 0021-9606 PD DEC 22 PY 1997 VL 107 IS 24 BP 10555 EP 10566 DI 10.1063/1.474219 UT WOS:000071071800022 ER PT J AU Taatjes, CA AF Taatjes, CA TI Association and isotopic exchange reactions of CH(CD) [X-2 Pi]+CO (vol 106, pg 1786, 1997) SO JOURNAL OF CHEMICAL PHYSICS SN 0021-9606 PD DEC 22 PY 1997 VL 107 IS 24 BP 10829 EP 10829 DI 10.1063/1.475311 UT WOS:000071071800056 ER PT J AU Chou, A Kallosh, R Rahmfeld, J Rey, SJ Shmakova, M Wong, WK AF Chou, A Kallosh, R Rahmfeld, J Rey, SJ Shmakova, M Wong, WK TI Critical points and phase transitions in 5d compactifications of M-theory SO NUCLEAR PHYSICS B AB We study critical points of the BPS mass Z, the BPS string tension Z(m), the black hole potential V and the gauged central charge potential P for M-theory compactified on Calabi-Yau three-folds, We first show that the stabilization equations for Z (determining the black hole entropy) take an extremely simple form in five dimensions as opposed to four dimensions. The stabilization equations for Z(m) are also very simple and determine the size of the infinite adS(3)throat of the string. The black hole potential in general exhibits two classes of critical points: supersymmetric critical points which coincide with those of the central charge and non-supersymmetric critical points. We then generalize the discussion to the entire extended Kahler cone encompassing topologically different but birationally equivalent Calabi-Yau three-folds that are connected via flop transitions, We examine behavior of the four potentials to probe the nature of these phase transitions. We find that V and P are continuous but not smooth across the flop transition, while Z and its first two derivatives, as well as Z(m) and its first derivative, are continuous. This in turn implies that supersymmetric stabilization of Z and Z(m) for a given configuration takes place in at most one point throughout the entire extended Kahler cone, The corresponding black holes (or string states) interpolate between different Calabi-Yau three-folds. At the boundaries of the extended Kahler cone we observe that electric states become massless and/or magnetic strings become tensionless. (C) 1997 Elsevier Science B.V. SN 0550-3213 PD DEC 22 PY 1997 VL 508 IS 1-2 BP 147 EP 180 DI 10.1016/S0550-3213(97)00528-2 UT WOS:A1997YL09400007 ER PT J AU Hielscher, AH Eick, AA Mourant, JR Shen, D Freyer, JP Bigio, IJ AF Hielscher, Andreas H. Eick, Angelia A. Mourant, Judith R. Shen, Dan Freyer, James P. Bigio, Irving J. TI Diffuse backscattering Mueller matrices of highly scattering media SO OPTICS EXPRESS AB We report on the development of a method that records spatially dependent intensity patterns of polarized light that is diffusely backscattered from highly scattering media. It is demonstrated that these intensity patterns can be used to differentiate turbid media, such as polystyrene-sphere and biological-cell suspensions. Our technique employs polarized light from a He-Ne laser (lambda = 543 nm), which is focused onto the surface of the scattering medium. A surface area of approximately 4x4 cm centered on the light input point is imaged through polarization-analysis optics onto a CCD camera. One can observe a large variety of intensity patterns by varying the polarization state of the incident laser light and changing the analyzer configuration to detect different polarization components of the backscattered light. Introducing the Mueller-matrix concept for diffusely backscattered light, a framework is provided to select a subset of measurements that comprehensively describe the optical properties of backscattering media. (C) 1997 Optical Society of America SN 1094-4087 PD DEC 22 PY 1997 VL 1 IS 13 BP 441 EP 453 UT WOS:000208802600007 PM 19377568 ER PT J AU Pacheco, JM Schone, WD AF Pacheco, JM Schone, WD TI Shape phase transitions in the absorption spectra of atomic clusters SO PHYSICAL REVIEW LETTERS AB A quantum-mechanical framework for calculating the photoabsorption cross section of atomic clusters, which explicitly includes the thermal motion of the ions, is proposed. We compute the photoabsorption cross section of Na-8 for ionic temperatures below and above melting. At equilibrium the line shape of Na-8 is dominated by two peaks separated by 200 meV. This structure is found to survive up to T = 100 K. With increasing temperatures, the cross section undergoes a shape phase transition such that, at T = 300 K, the double-peak structure has changed into a broad and asymmetric line shape dominated by a single peak, providing an excellent fit to the available experimental data. RI Pacheco, Jorge/B-6116-2008 OI Pacheco, Jorge/0000-0002-2579-8499 SN 0031-9007 PD DEC 22 PY 1997 VL 79 IS 25 BP 4986 EP 4989 DI 10.1103/PhysRevLett.79.4986 UT WOS:000071096100012 ER PT J AU Pasternak, MP Taylor, RD Jeanloz, R Li, X Nguyen, JH McCammon, CA AF Pasternak, MP Taylor, RD Jeanloz, R Li, X Nguyen, JH McCammon, CA TI High pressure collapse of magnetism in Fe0.94O: Mossbauer spectroscopy beyond 100 GPa SO PHYSICAL REVIEW LETTERS AB First studies of Mossbauer spectroscopy to pressures above 100 GPa are reported. The magnetic state of Fe0.94O was investigated to 120 GPa at T less than or equal to 300 K. At 300 K a diamagnetic low-spin (LS) state of Fe2+ is detected at 90 GPa: its abundance increases with P. The gap between the T-5(2g) high-spin ground state and the (1)A(1g) LS excited state decreases with increasing P and at 120 GPa the LS species, first observed at 70 K, is fully converted at similar to 450 K. The magnetic collapse of Fe1-xO is an isochoric, second-order transition resulting front a gradual increase in the crystal-field with increasing pressure. RI McCammon, Catherine/B-4983-2010 OI McCammon, Catherine/0000-0001-5680-9106 SN 0031-9007 PD DEC 22 PY 1997 VL 79 IS 25 BP 5046 EP 5049 DI 10.1103/PhysRevLett.79.5046 UT WOS:000071096100027 ER PT J AU Schumann, FO Willis, RF Goodman, KG Tobin, JG AF Schumann, FO Willis, RF Goodman, KG Tobin, JG TI Magnetic instability of ultrathin fcc FexNi1-x films SO PHYSICAL REVIEW LETTERS AB The "invar effect" in Fe3Nit-x alloys occurs when the Fe content approaches 65%. At this point, the magnetization falls to zero, and a martensitic structural transformation from a fee to a bce lattice occurs. This paper addresses the question: "What happens if the structural transformation is suppressed in an ultrathin alloy film?" We present results to this effect, showing the variation of the magnetization with changing composition in ultrathin film grown on Cu(100). We find a new low-spin, ferromagnetic phase of matter, which is a sensitive function of the atomic volume. RI Schumann, Frank /K-9364-2014; Tobin, James/O-6953-2015 SN 0031-9007 PD DEC 22 PY 1997 VL 79 IS 25 BP 5166 EP 5169 DI 10.1103/PhysRevLett.79.5166 UT WOS:000071096100057 ER PT J AU Cruz-Pacheco, G Luce, BP AF Cruz-Pacheco, G Luce, BP TI On the relationship of periodic wavetrains and solitary waves of complex Ginzburg-Landau type equations SO PHYSICS LETTERS A AB The relationship between periodic wavetrains and solitary waves in complex Ginzburg-Landau type equations, such as those that model optical fiber amplifiers, is studied in the nonlinear Schrodinger limit with a Melnikov method. An important example, the cubic complex Ginzburg-Landau equation, is studied in detail. For this equation it is found that in the NLS limit particular families of periodic wavetrains all deform asymptotically to a single, persisting, stationary, nonlinear Schrodinger soliton as their periods tend to infinity. (C) 1997 Published by Elsevier Science B.V. SN 0375-9601 PD DEC 22 PY 1997 VL 236 IS 5-6 BP 391 EP 402 DI 10.1016/S0375-9601(97)00785-8 UT WOS:000071179800004 ER PT J AU Wright, JL Zhu, JH AF Wright, JL Zhu, JH TI Environmental embrittlement of an ordered Ni-Mo alloy SO SCRIPTA MATERIALIA SN 1359-6462 PD DEC 22 PY 1997 VL 38 IS 2 BP 253 EP 257 DI 10.1016/S1359-6462(97)00436-3 UT WOS:000071537400011 ER PT J AU Takasugi, T Liu, CT Lee, EH Heatherly, L George, EP AF Takasugi, T Liu, CT Lee, EH Heatherly, L George, EP TI Effect of quenching temperature on grain boundary chemistry and mechanical properties of Ni-3(Si,Ti) SO SCRIPTA MATERIALIA RI George, Easo/L-5434-2014; OI Liu, Chain Tsuan/0000-0001-7888-9725 SN 1359-6462 PD DEC 22 PY 1997 VL 38 IS 2 BP 287 EP 292 DI 10.1016/S1359-6462(97)00484-3 UT WOS:000071537400016 ER PT J AU Chen, MW Lin, DL Liu, CT AF Chen, MW Lin, DL Liu, CT TI Influence of strain rate on fracture mode of a polycrystalline Ni3Al SO SCRIPTA MATERIALIA RI Chen, Mingwei/A-4855-2010; OI Chen, Mingwei/0000-0002-2850-8872; Liu, Chain Tsuan/0000-0001-7888-9725 SN 1359-6462 PD DEC 22 PY 1997 VL 38 IS 2 BP 293 EP 297 DI 10.1016/S1359-6462(97)00445-4 UT WOS:000071537400017 ER PT J AU Routbort, JL Goretta, KC de Arellano-Lopez, AR Wolfenstine, J AF Routbort, JL Goretta, KC de Arellano-Lopez, AR Wolfenstine, J TI Creep of Ce0.9Gd0.1O1.95 SO SCRIPTA MATERIALIA OI R. de Arellano Lopez, Antonio/0000-0002-7443-0244 SN 1359-6462 PD DEC 22 PY 1997 VL 38 IS 2 BP 315 EP 320 DI 10.1016/S1359-6462(97)00452-1 UT WOS:000071537400020 ER PT J AU Whittum, DH AF Whittum, DH TI Beam break-up with tune chirp for an arbitrary wakefield SO JOURNAL OF PHYSICS A-MATHEMATICAL AND GENERAL AB The asymptotic form of the beam break-up instability is computed up to qundrature for an arbitrary wakefield, in the presence of a linear variation in betatron tune from head to tail along the beam. For illustration, the result is applied to a broadband impedance (resistive wall) and a narrow band impedance (single resonator) and benchmarked against simulation, for parameters of interest in induction linacs. SN 0305-4470 PD DEC 21 PY 1997 VL 30 IS 24 BP 8751 EP 8760 DI 10.1088/0305-4470/30/24/033 UT WOS:000071486100033 ER PT J AU Fischel, LB Newman, J Theodorou, DN AF Fischel, LB Newman, J Theodorou, DN TI Segment density of a block copolymer chain tethered at both ends SO JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS AB The exact solution for the end-to-end distance distribution of unperturbed block copolymer molecules and its inverse-langevin, sine-series, and Gaussian mathematical approximations are derived from the formal integral solution to the problem of random flights. Using the Markov property of random flights, these end-to-end distance distributions combine to give segment densities of perturbed block copolymer molecules, where the perturbation manifests itself as a geometric constraint on specific segments, called tethering. Computations for the case of a singly or doubly tethered diblock copolymer molecule, symmetric with respect to the number of bonds, having short bonds and long bonds, elucidate differences between the above mathematical approximations and three homopolymer approximations, and between the segment types. The Gaussian approximation is best and easiest for several reasons, giving only a few per cent error for chains of more than 40 bonds. Among the homopolymer approximations, the one that preserves the contour length and the mean-square end-to-end distance of the copolymer molecule yields the best agreement, within a few per cent, with the copolymer distribution. For the doubly tethered case, segments that are close, along the contour, to the tethered ends display a maximum probability density about an order of magnitude greater and a full width at half maximum about an order of magnitude smaller than segments that are far, along the contour, from the tethered ends. When the distributions are averaged over all segments of a block, the maxima of the distributions for the two segment types are within a few bond lengths of each other and are located near the tethered end of the segments connected by short bonds. The distribution for the segments connected by short bonds is highly peaked and localized, but the distribution for the segments connected by long bonds has a moderate maximum and a broad plateau of segment density extending to the other tethered end. The different segment types have maxima and full widths at half maximum that differ by about an order of magnitude from each other. The scaling of the distributions with contour length suggests that the reduced distributions are within a few per cent of each other for chains greater than 40 bonds, and the Gaussian approximation is within a few per cent of the exact solution above this length. Tabulation of the reduced distributions in the form of four-dimensional histograms, with only a moderate number of intervals in each dimension, appears promising for use in computer simulations of physical properties in the condensed phase. RI Newman, John/B-8650-2008; OI Newman, John/0000-0002-9267-4525; Theodorou, Doros/0000-0002-4763-9739 SN 0956-5000 PD DEC 21 PY 1997 VL 93 IS 24 BP 4355 EP 4370 DI 10.1039/a705898e UT WOS:000071068400019 ER PT J AU Pisharody, M Job, PK Magill, S Proudfoot, J Stanek, R AF Pisharody, M Job, PK Magill, S Proudfoot, J Stanek, R TI Measurement of gas bremsstrahlung from electron storage rings SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB Bremsstrahlung is produced in electron storage rings when the particle beam interacts with the storage ring components or with the residual gas molecules in the storage ring vacuum, The interaction of the particle beam with the gas molecules occurs continuously during storage ring operation, At straight sections of a storage ring, the gas bremsstrahlung contribution from each interaction adds up to produce a narrow monodirectional photon beam that travels down the beamlines. At the Advanced Photon Source (APS), where the stood electron beam energy is 7 GeV, gas bremsstrahlung generated in the straight sections of the insertion device beamlines, which is a total of 15.38 m in effective length, can be significant. This paper presents the results of the bremsstrahlung spectrum and energy measurements from the insertion device beamlines of the APS using a hermetic lead glass calorimeter, The calorimeter consists of 25 lead glass blocks, each 6.3 cm x 6.3 cm x 35 cm, stacked into a 5 x 5 array. Phototubes connected to the lead glass blocks collected the signals. The calorimeter is calibrated using the maximum energy of the observed bremsstrahlung spectrum. The total energy radiated and the bremsstrahlung spectrum There measured as a function of the storage ring beam current: for both electrons and positrons of 7 GeV energy. Vacuum in the straight section was continuously monitored, and measurements to determine the nature of the residual gas inside the storage ring were performed. The measured bremsstrahlung spectra are fitted to a function that shows an approximate l/E behavior, The gas bremsstrahlung rate from the APS undulator beamline straight path of 15.38 m is measured as 60.0 +/- 2.0 GeV/s/nT/mA. Significant contribution of bremsstrahlung from sources other than the residual gas molecules is observed. The maximum bremsstrahlung energy measured in a beamline during the experiment is 369.0 +/- 22.0 GeV/s/nT/mA. SN 0168-9002 PD DEC 21 PY 1997 VL 401 IS 2-3 BP 442 EP 462 DI 10.1016/S0168-9002(97)01035-8 UT WOS:000071039500027 ER PT J AU Widmayer, CC Milam, D deSzoeke, SP AF Widmayer, CC Milam, D deSzoeke, SP TI Nonlinear formation of holographic images of obscurations in laser beams SO APPLIED OPTICS AB Computer models are used to simulate the nonlinear formation of images of obscurations in laser beams. The predictions of the model are found to be in good agreement with measurements conducted in the nonlinear regime corresponding to a typical solid-state laser operation. In this regime, peak-to-mean fluence ratios large enough to induce damage in optical components are observed. The amplitude of the images and their location along the propagation axis are accurately predicted by the simulations. This indicates that the model is a reliable design tool for specifying component staging and optical specifications to avoid optical damage by this mechanism. (C) 1997 Optical Society of America. SN 0003-6935 PD DEC 20 PY 1997 VL 36 IS 36 BP 9342 EP 9347 DI 10.1364/AO.36.009342 UT WOS:A1997YL30200002 PM 18264492 ER PT J AU Alcock, C Allen, WH Allsman, RA Alves, D Axelrod, TS Banks, TS Beaulieu, SF Becker, AC Becker, RH Bennett, DP Bond, IA Carter, BS Cook, KH Dodd, RJ Freeman, KC Gregg, MD Griest, K Hearnshaw, JB Heller, A Honda, M Jugaku, J Kabe, S Kaspi, S Kilmartin, PM Kitamura, A Kovo, O Lehner, MJ Love, TE Maoz, D Marshall, SL Matsubara, Y Minniti, D Miyamoto, M Morse, JA Muraki, Y Nakamura, T Peterson, BA Phillips, MM Pratt, MR Quinn, PJ Reid, IN Reid, M Reiss, D Retter, A Rodgers, AW Sargent, WLW Sato, H Sekiguchi, M Stetson, PB Stubbs, CW Sullivan, DJ Sutherland, W Tomaney, A Vandehei, T Watase, Y Welch, DL Yanagisawa, T Yoshizawa, H Yock, PCM AF Alcock, C Allen, WH Allsman, RA Alves, D Axelrod, TS Banks, TS Beaulieu, SF Becker, AC Becker, RH Bennett, DP Bond, IA Carter, BS Cook, KH Dodd, RJ Freeman, KC Gregg, MD Griest, K Hearnshaw, JB Heller, A Honda, M Jugaku, J Kabe, S Kaspi, S Kilmartin, PM Kitamura, A Kovo, O Lehner, MJ Love, TE Maoz, D Marshall, SL Matsubara, Y Minniti, D Miyamoto, M Morse, JA Muraki, Y Nakamura, T Peterson, BA Phillips, MM Pratt, MR Quinn, PJ Reid, IN Reid, M Reiss, D Retter, A Rodgers, AW Sargent, WLW Sato, H Sekiguchi, M Stetson, PB Stubbs, CW Sullivan, DJ Sutherland, W Tomaney, A Vandehei, T Watase, Y Welch, DL Yanagisawa, T Yoshizawa, H Yock, PCM CA MACHO Collaboration GMAN Collanoration TI Macho alert 95-30: First real-time observation of extended source effects in gravitational microlensing SO ASTROPHYSICAL JOURNAL AB We present analysis of MACHO Alert 95-30, a dramatic gravitational microlensing event toward the Galactic bulge whose peak magnification departs significantly from the standard point-source microlensing model. Alert 95-30 was Observed in real time by the Global Microlensing Alert Network (GMAN), which obtained densely sampled photometric and spectroscopic data throughout the event. We interpret the light-curve "fine structure" as indicating transit of the lens across the extended face of the source star. This signifies resolution of a star several kiloparsecs distant. We find a lens angular impact parameter theta(min)/theta(source) = 0.715 +/- 0.003. This information, along with the radius and distance of the source, provides an additional constraint on the lensing system. Spectroscopic and photometric data indicate the source is a M4 III star of radius 61 +/- 12 R., located on the far side of the bulge at similar to 9 kpc. We derive a lens angular velocity, relative to the source, of 21.5 +/- 2.9 km s(-1) kpc(-1), where the error is dominated by uncertainty in the angular size of the source star. Likelihood analysis yields a median lens mass of 0.67(-0.46)(+2.53) M., located with 80% probability in the Galactic bulge at a distance of 6.93(-2.25)(+1.56) kpc. If the lens is a main-sequence star, we can include constraints on the lens luminosity. This modifies our estimates to M-lens = 0.53(-0.35)(+0.52) M. and D-lens = 6.57(-2.25)(+0.99) kpc. Spectra taken during the event show that the absorption-line equivalent widths of H alpha and the TiO bands near 6700 Angstrom vary, as predicted for microlensing of an extended source. This is most likely due to center-to-limb variation in the stellar spectral lines. The observed spectral changes further support our microlensing interpretation. These data demonstrate the feasibility of using microlensing limb crossings as a tool to probe stellar atmospheres directly. RI Stubbs, Christopher/C-2829-2012; Quinn, Peter/B-3638-2013 OI Stubbs, Christopher/0000-0003-0347-1724; SN 0004-637X EI 1538-4357 PD DEC 20 PY 1997 VL 491 IS 2 BP 436 EP 450 DI 10.1086/304974 PN 1 UT WOS:000071152600002 ER PT J AU Seifert, H Teegarden, BJ Cline, TL Gehrels, N Zand, JJMI Palmer, DM Ramaty, R Hurley, K Madden, NW Pehl, R AF Seifert, H Teegarden, BJ Cline, TL Gehrels, N Zand, JJMI Palmer, DM Ramaty, R Hurley, K Madden, NW Pehl, R TI Transient gamma-ray spectrometer observation of the bright gamma-ray burst GRB 950822 SO ASTROPHYSICAL JOURNAL AB The Transient Gamma-Ray Spectrometer (TGRS) on the Wind satellite is designed to perform spectroscopy of bright gamma-ray bursts in the similar to 20-8000 keV energy range, having a resolution 5-30 times better than that of earlier generation detectors. GRB 950822 was the brightest burst observed by TGRS in its first year of operation, with a peak flux (1024 ms) of similar to 78.3 photons cm(-2) s(-1) and a fluence (50-300 keV) of similar to 1.4 x 10(-4) ergs cm(-2); therefore, the GRB data in this paper represent the first high-resolution spectroscopy ever performed on a burst of this brightness. The continuum spectrum of GRB 950822 has the classical gamma-ray burst shape and exhibits typical evolution from hard to soft over the course of the burst. We found no evidence of line features or any other spectral fine structure with significance greater than 3.5 sigma in our data. RI Gehrels, Neil/D-2971-2012 SN 0004-637X PD DEC 20 PY 1997 VL 491 IS 2 BP 697 EP 703 DI 10.1086/304991 PN 1 UT WOS:000071152600022 ER PT J AU Guzik, JA Swenson, FJ AF Guzik, JA Swenson, FJ TI Seismological comparisons of solar models with element diffusion using the MHD, OPAL, and SIREFF equations of state SO ASTROPHYSICAL JOURNAL AB We compare the thermodynamic and helioseismic properties of solar models evolved using three different equation of state (EOS) treatments: the Mihalas, Dappen & Hummer EOS tables (MHD); the latest Rogers, Swenson, & Iglesias EOS tables (OPAL), and a new analytical EOS (SIREFF) developed by Swenson et al. All of the models include diffusive settling of helium and heavier elements. The models use updated OPAL opacity tables based on the 1993 Grevesse & Noels solar element mixture, incorporating 21 elements instead of the 14 elements used for earlier tables. The properties of solar models that are evolved with the SIREFF EOS agree closely with those of models evolved using the OPAL or MHD tables. However, unlike the MHD or OPAL EOS tables, the SIREFF in-line EOS can readily account for variations in overall Z abundance and the element mixture resulting from nuclear processing and diffusive element settling. Accounting for Z abundance variations in the EOS has a small, but nonnegligible, effect on model properties (e.g., pressure or squared sound speed), as much as 0.2% at the solar center and in the convection zone). The OPAL and SIREFF equations of state include electron exchange, which produces models requiring a slightly higher initial helium abundance, and increases the convection zone depth compared to models using the MHD EOS. However, the updated OPAL opacities are as much as 5% lower near the convection zone base, resulting in a small decrease in convection zone depth. The calculated low-degree nonadiabatic frequencies for all of the models agree with the observed frequencies to within a few microhertz (0.1%). The SIREFF analytical calibrations are intended to work over a wide range of interior conditions found in stellar models of mass greater than 0.25 M-. and evolutionary states from pre-main-sequence through the asymptotic giant branch (AGB). It is significant that the SIREFF EOS produces solar models that both measure up to the stringent requirements imposed by solar oscillation observations and inferences, and are more versatile than EOS tables. SN 0004-637X PD DEC 20 PY 1997 VL 491 IS 2 BP 967 EP 979 DI 10.1086/304988 PN 1 UT WOS:000071152600045 ER PT J AU Kotamarthi, VR Rodriguez, JM Sze, ND Kondo, Y Pueschel, R Ferry, G Bradshaw, J Sandholm, S Gregory, G Davis, D Liu, S AF Kotamarthi, VR Rodriguez, JM Sze, ND Kondo, Y Pueschel, R Ferry, G Bradshaw, J Sandholm, S Gregory, G Davis, D Liu, S TI Evidence of heterogeneous chemistry on sulfate aerosols in stratospherically influenced air masses sampled during PEM-West B SO JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES AB Signatures of the N2O5 hydrolysis by sulfate aerosols have been previously documented, primarily from balloon and remote-sensing platforms, by measurements of nitrogen species aboard the NASA ER-2 flying at an altitude of approximately 20 km and some ER-2 and DC-8 measurements near the tropopause during stratospheric campaigns. This study documents such signatures in the NOX/NOY ratios derived from DC-8 measurements during Pacific Exploratory Measurements in the Western Pacific Ocean (PEM-West B) in stratospherically influenced air masses sampled during a level leg at an altitude of 10.7 km in flight 17 out of Japan. Despite the very low abundance of total bromine, we also show that heterogeneous hydrolysis of BrNO3 on sulphate aerosols can catalytically convert NOX and liquid H2O into HNO3 and OH and thereby lower the calculated equilibrium NOx/NOy by about 20 to 35% in these air masses, bringing closer agreement with the nitrogen partitioning deduced from measurements. However, the NOx/NO ratios calculated from a model including heterogeneous chemistry were a factor of 3 smaller than ratios derived from data for a segment of this flight leg when DC-8 measurements indicated a stronger tropospheric influence. We also modeled the equilibrium partitioning of nitrogen species for all upper tropospheric air masses encountered by the DC-8; since NOy in the troposphere may contain nonnegligible contributions from long-lived nitrates (such as peroxyacetylnitrate), we have compared instead modeled and measured NOx/HNO3. The calculated equilibrium NOx/HNO3 ratios using only gas-phase chemistry are on the average smaller than those deduced from measurements in upper tropospheric air masses; inclusion of N2O5 hydrolysis reduces these ratios by an additional 20%, thus worsening the discrepancy. These results suggest a rapid transition from "denoxified" conditions in the lower stratosphere to "renoxified" conditions in the upper troposphere. This transition could be due to intrinsically different chemistry in the troposphere. Alternatively, rapid transport in the troposphere could keep the NOx and HNO3 away from chemical equilibrium. Detailed analysis of current and future tropospheric data could shed light on this issue. RI Kondo, Yutaka/D-1459-2012; Rodriguez, Jose/G-3751-2013; OI Rodriguez, Jose/0000-0002-1902-4649; Kotamarthi, Veerabhadra Rao/0000-0002-2612-7590 SN 2169-897X PD DEC 20 PY 1997 VL 102 IS D23 BP 28425 EP 28436 DI 10.1029/97JD02511 UT WOS:000071162700033 ER PT J AU Kofke, DA Cummings, PT AF Kofke, DA Cummings, PT TI Quantitative comparison and optimization of methods for evaluating the chemical potential by molecular simulation SO MOLECULAR PHYSICS AB The precision of several methods for computing the chemical potential by molecular simulation is investigated. The study does not apply molecular simulation to the analysis but instead works with models of the simulation process. These models enable the variance of the chemical potential to be computed accurately and very quickly and thereby permits the methods (free-energy perturbation, expanded ensembles, thermodynamic integration, and histogram-distribution methods) to be optimized and compared over a range of densities. The study focuses exclusively on the hard-sphere model. This model is simple and well characterized; yet it exhibits the essential features that make the chemical potential calculation difficult; arguments are presented to support the broader applicability of the study. The severe asymmetry of particle insertion against particle deletion is highlighted, and it is shown that any staged free-energy perturbation method with a 'deletion' component is highly prone to systematic error. More generally this implies that such methods should always be staged in the direction of decreasing entropy. Other findings show that uniform sampling is not optimal for umbrella-sampling and expanded-ensemble applications, although it remains a good rule of thumb for tuning these approaches. Among the techniques we study, optimally staged insertion and the distribution-histogram methods are the most efficient and precise. The latter is effective only when used in an interpolative fashion, and we identify it as the most likely route to further progress in the field. RI Kofke, David/E-8102-2011; Cummings, Peter/B-8762-2013 OI Kofke, David/0000-0002-2530-8816; Cummings, Peter/0000-0002-9766-2216 SN 0026-8976 EI 1362-3028 PD DEC 20 PY 1997 VL 92 IS 6 BP 973 EP 996 DI 10.1080/002689797169600 UT WOS:000071069600003 ER PT J AU Tyson, TA Federici, JF Chew, D Bishop, AR Furenlid, L Savin, W Wilber, W AF Tyson, TA Federici, JF Chew, D Bishop, AR Furenlid, L Savin, W Wilber, W TI Local structural and electronic changes accompanying photodoping in YBa2Cu3O6-x SO PHYSICA C AB Polarized X-ray absorption measurements reveal that photodoping of oxygen deficient YBa2Cu3O6+x (YBCO) produces a local axial distortion of the CuOx chains. The broad normal state axial Cu(1)-O(4) bond distribution becomes two well-defined peaks in the photodoped state and suggest local ordering. XANES measurements reveal a transfer of hole density into the CuO2 planes. These results support a common structure-related transport enhancement mechanism in chemically doped and photodoped high temperature superconductor systems. (C) 1997 Elsevier Science B.V. SN 0921-4534 PD DEC 20 PY 1997 VL 292 IS 3-4 BP 163 EP 170 DI 10.1016/S0921-4534(97)01757-7 UT WOS:000071404800001 ER PT J AU Chmaissem, O Guptasarma, P Welp, U Hinks, DG Jorgensen, JD AF Chmaissem, O Guptasarma, P Welp, U Hinks, DG Jorgensen, JD TI Effect of Re substitution on the defect structure, and superconducting Properties of (Hg1-xRex)Ba2Can-1CunO2n+2+delta (n = 2, 3, 4) SO PHYSICA C AB We have investigated the structure, and superconducting properties of a series of Re substituted HgBa2Can-1CunO2n+2+delta (n = 2, 3, 4) samples by neutron powder diffraction, AC susceptibility, and magnetization measurements. Re atoms substitute at the Hg site and alter the defect structure of the host layer by pulling in four new oxygen atoms at (xx0) to form an octahedron around Re. Re substitution makes it easier to synthesize the different members of the series; in particular (Hg,Re)-1234 which forms readily with Re concentrations x greater than or equal to 0.2. T-c values of the as-prepared samples are 108, 132, and 122 K for the n = 2, 3 and 4 members, respectively. Magnetization measurements show a small enhancement of H-irr with increasing Re-content at low temperatures. No significant enhancement at higher temperatures (T > 70 K) is observed. (C) 1997 Elsevier Science B.V. SN 0921-4534 PD DEC 20 PY 1997 VL 292 IS 3-4 BP 305 EP 314 DI 10.1016/S0921-4534(97)01746-2 UT WOS:000071404800021 ER PT J AU Goldbach, A Iton, LE Saboungi, ML AF Goldbach, A Iton, LE Saboungi, ML TI On the formation of isolated Se-8 rings in zeolites SO CHEMICAL PHYSICS LETTERS AB Even at sub-stoichiometric Se loading into the supercages of Sr-Y zeolite, significant concentrations of Se-8 rings form in addition to the open chain structures. This material provides an excellent medium for the investigation of the vibrational and UV/VIS absorption spectra of isolated Se-8 molecules under well-defined conditions. The potential of these nanostructured composite materials has not yet been fully exploited, and a complete understanding of the molecular structure of such encapsulates is prerequisite for tailoring new materials for optoelectronic purposes. (C) 1997 Elsevier Science B.V. RI Saboungi, Marie-Louise/C-5920-2013 OI Saboungi, Marie-Louise/0000-0002-0607-4815 SN 0009-2614 PD DEC 19 PY 1997 VL 281 IS 1-3 BP 69 EP 73 DI 10.1016/S0009-2614(97)01083-X UT WOS:000071256600010 ER PT J AU Goldston, RJ AF Goldston, RJ TI Fusion alternatives SO SCIENCE SN 0036-8075 PD DEC 19 PY 1997 VL 278 IS 5346 BP 2032 EP 2033 UT WOS:A1997YM23500008 ER PT J AU Moir, RW AF Moir, RW TI Fusion alternatives SO SCIENCE SN 0036-8075 PD DEC 19 PY 1997 VL 278 IS 5346 BP 2033 EP 2033 UT WOS:A1997YM23500009 ER PT J AU Baldwin, DP Zamzow, DS AF Baldwin, DP Zamzow, DS TI Limits of detection for an AOTF-FFP spectrometer in ICP atomic emission spectroscopy SO TALANTA AB Limits of detection for a number of elements both in air and in argon inductively coupled plasma atomic emission spectroscopy (ICPAES) have been determined using a high-resolution interferometric spectrometer (HiRIS) that consists of an acousto-optic tunable filter, a fiber-optic Fabry-Perot interferometer, and a photon-counting PMT detector. Detection limits using the HiRIS are comparable to those determined using a 1.5 m focal-length grating spectrometer, which has resolution similar to that of the HiRIS. Differences between the two spectrometer systems and the two plasma systems are discussed. The portability and versatility of the HiRIS make it a useful alternative For field or on-line measurements using ICPAES. The high-resolution capabilities allow the HiRIS to replace large grating spectrometers for resolution of isotopic and complex spectra. (C) 1997 Elsevier Science B.V. SN 0039-9140 PD DEC 19 PY 1997 VL 45 IS 2 BP 229 EP 235 DI 10.1016/S0039-9140(97)00143-4 UT WOS:A1997YG86300001 PM 18966997 ER PT J AU Cormier, RA Gregg, BA AF Cormier, RA Gregg, BA TI Self-organization in thin films of liquid crystalline perylene diimides SO JOURNAL OF PHYSICAL CHEMISTRY B AB A family of Liquid crystalline organic semiconductors based on perylene-3,4,9,10-tetracarboxyldiimide is introduced. The thermal transitions, self-organizing behavior, and change in photophysical properties upon self-organization of one member of the family are described. Red, polycrystalline thin films of spin-coated N,N'-bis[3-[1,3-bis[2-(2-methoxyethoxy)ethoxy]-2-propoxy]propyl] perylene-3,4,9,10-tetracarboxyldiimide spontaneously form a highly crystalline black phase after about 24 h. The quantum yield for fluorescence from the black phase is enhanced 7-fold, and the width (fwhm) of the emission band is decreased by more than a factor of 2, with respect to the red phase. The self-organization process appears to decrease spontaneously both the energetic disorder and the density of exciton quenching sites in the film. SN 1089-5647 PD DEC 18 PY 1997 VL 101 IS 51 BP 11004 EP 11006 DI 10.1021/jp9732064 UT WOS:000071255300006 ER PT J AU Girndt, A Jahnke, F Koch, SW Chow, WW AF Girndt, A Jahnke, F Koch, SW Chow, WW TI Microscopic gain theory for group III nitride semiconductor quantum wells SO MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY AB The gain/absorption properties of III-V nitride quantum well systems are computed microscopically using multi-band semiconductor Bloch equations. Lineshape and dephasing are treated at the level of quantum kinetic theory in second Born approximation in the Markovian limit. The compositional and structural properties of the quantum wells are modelled using k.p theory. Numerical results are presented for the example of several InGaN/AlGaN structures. (C) 1997 Elsevier Science S.A. SN 0921-5107 PD DEC 18 PY 1997 VL 50 IS 1-3 BP 174 EP 179 DI 10.1016/S0921-5107(97)00158-X UT WOS:000071974800036 ER PT J AU de Angelis, G Fahlander, C Gadea, A Farnea, E Gelletly, W Aprahamian, A Bazzacco, D Becker, F Bizzeti, PG Bizzeti-Sona, A Brandolini, F de Acuna, D De Poli, M Eberth, J Foltescu, D Lenzi, SM Lunardi, S Martinez, T Napoli, DR Pavan, P Petrache, CM Alvarez, CR Rudolph, D Rubio, B Satula, W Skoda, S Spolaore, P Thomas, HG Ur, CA Wyss, R AF de Angelis, G Fahlander, C Gadea, A Farnea, E Gelletly, W Aprahamian, A Bazzacco, D Becker, F Bizzeti, PG Bizzeti-Sona, A Brandolini, F de Acuna, D De Poli, M Eberth, J Foltescu, D Lenzi, SM Lunardi, S Martinez, T Napoli, DR Pavan, P Petrache, CM Alvarez, CR Rudolph, D Rubio, B Satula, W Skoda, S Spolaore, P Thomas, HG Ur, CA Wyss, R TI Delayed g(9/2)(2) alignment in the N=Z nucleus Kr-72 SO PHYSICS LETTERS B AB The structure of Kr-72 has been investigated at GASP through the Ca-40(Ca-40,2 alpha) reaction at a beam energy of 160 MeV using the 4 pi ISIS Si-ball for reaction channel selection. The level scheme has been extended up to an excitation energy of approximate to 8.5 MeV. The spins and parities of the observed levels are assigned tentatively. The observed band shows the predicted change from oblate to prolate shape. The four quasi-particle g(9/2) alignment is found to be significantly delayed in rotational frequency with respect to the heavier Kr isotopes. Such a delay contradicts the predictions of standard mean-field calculations and may reflect either additional correlations in the T = 0 pairing channel or coupling to vibrational degrees of freedom or both. (C) 1997 Elsevier Science B.V. RI Rudolph, Dirk/D-4259-2009; Petrache, Costel/E-9867-2012; Lenzi, Silvia/I-6750-2012; Martinez, Trinitario/K-6785-2014; Rubio, Berta/M-1060-2014; Gadea, Andres/L-8529-2014; Napoli, Daniel R./D-9863-2012 OI Rudolph, Dirk/0000-0003-1199-3055; Petrache, Costel/0000-0001-8419-1390; Martinez, Trinitario/0000-0002-0683-5506; Rubio, Berta/0000-0002-9149-4151; Gadea, Andres/0000-0002-4233-1970; Napoli, Daniel R./0000-0002-8154-6958 SN 0370-2693 PD DEC 18 PY 1997 VL 415 IS 3 BP 217 EP 222 DI 10.1016/S0370-2693(97)01217-3 UT WOS:000071329000002 ER PT J AU Abele, A Adomeit, J Amsler, C Baker, CA Barnett, BM Batty, CJ Benayoun, M Berdoz, A Beuchert, K Bischoff, S Blum, P Braune, K Bugg, DV Case, T Cramer, O Crede, V Crowe, KM Degener, T Djaoshvili, N von Dombrowski, S Doser, M Dunnweber, W Ehmanns, A Engelhardt, D Faessler, MA Felix, C Giarritta, P Haddock, RP Heinsius, FH Heinzelmann, M Herz, M Hessey, NP Hidas, P Hodd, C Holtzhaussen, C Jamnik, D Kalinowsky, H Kammle, B Kammel, P Kisiel, J Klempt, E Koch, H Kolo, C Kunze, M Kurilla, U Lakata, M Landua, R Matthay, H McCrady, R Meier, J Meyer, CA Montanet, L Ouared, R Ould-Saada, F Peters, K Pick, B Pietra, C Pinder, CN Ratajcak, M Regenfus, C Reissmann, J Resag, S Roethel, W Schmidt, P Scott, I Seibert, R Spanier, S Stock, H Strassburger, C Strohbusch, U Suffert, M Thoma, U Tischhauser, M Volcker, C Wallis, S Walther, D Wiedner, U Zou, BS Zupancic, C AF Abele, A Adomeit, J Amsler, C Baker, CA Barnett, BM Batty, CJ Benayoun, M Berdoz, A Beuchert, K Bischoff, S Blum, P Braune, K Bugg, DV Case, T Cramer, O Crede, V Crowe, KM Degener, T Djaoshvili, N von Dombrowski, S Doser, M Dunnweber, W Ehmanns, A Engelhardt, D Faessler, MA Felix, C Giarritta, P Haddock, RP Heinsius, FH Heinzelmann, M Herz, M Hessey, NP Hidas, P Hodd, C Holtzhaussen, C Jamnik, D Kalinowsky, H Kammle, B Kammel, P Kisiel, J Klempt, E Koch, H Kolo, C Kunze, M Kurilla, U Lakata, M Landua, R Matthay, H McCrady, R Meier, J Meyer, CA Montanet, L Ouared, R Ould-Saada, F Peters, K Pick, B Pietra, C Pinder, CN Ratajcak, M Regenfus, C Reissmann, J Resag, S Roethel, W Schmidt, P Scott, I Seibert, R Spanier, S Stock, H Strassburger, C Strohbusch, U Suffert, M Thoma, U Tischhauser, M Volcker, C Wallis, S Walther, D Wiedner, U Zou, BS Zupancic, C CA Crystal Barrel Collaboration TI Antiproton-proton annihilation at rest into Kappa(L)Kappa(S)pi(0)pi(0) SO PHYSICS LETTERS B AB The annihilation channel (p) over bar p --> KLKS pi(0) pi(0) was studied with the Crystal Barrel detector at LEAR. This final state with negative C-parity is dominated by the strange resonances K*(892), K-1(1270), K-0*(1400) and K-0*(1430). In addition, a J(PC) = 1(+-) state is seen in the K*K decay mode. This state could be the isoscalar, axialvector h(1)' seen here with a mass of m = (1440 +/- 60)MeV/c(2) and a width of Gamma=(170 +/- 80)MeV/c(2). (C) 1997 Published by Elsevier Science B.V. OI Heinsius, Fritz-Herbert/0000-0002-9545-5117 SN 0370-2693 PD DEC 18 PY 1997 VL 415 IS 3 BP 280 EP 288 DI 10.1016/S0370-2693(97)01268-9 UT WOS:000071329000010 ER PT J AU Abele, A Adomeit, J Amsler, C Baker, CA Barnett, BM Batty, CJ Benayoun, M Berdoz, A Beuchert, K Bischoff, S Blum, P Braune, K Bugg, DV Case, T Cramer, O Crede, V Crowe, KM Degener, T Djaoshvili, N von Dombrowski, S Doser, M Dunnweber, W Ehmanns, A Engelhardt, D Faessler, MA Giarritta, P Haddock, RP Heinsius, FH Heinzelmann, M Herz, M Hessey, NP Hidas, P Hodd, C Holtzhaussen, C Jamnik, D Kalinowsky, H Kammle, B Kammel, P Kisiel, J Klempt, E Koch, H Kolo, C Kunze, M Kurilla, U Lakata, M Landua, R Matthay, H McCrady, R Meier, J Meyer, CA Montanet, L Ouared, R Ould-Saada, F Peters, K Pick, B Pietra, C Pinder, CN Ratajcak, M Regenfus, C Reissmann, J Resag, S Roethel, W Schmidt, P Scott, I Seibert, R Spanier, S Stock, H Strassburger, C Strohbusch, U Suffert, M Thoma, U Tischhauser, M Volcker, C Wallis, S Walther, D Wiedner, U Zou, BS Zupancic, C AF Abele, A Adomeit, J Amsler, C Baker, CA Barnett, BM Batty, CJ Benayoun, M Berdoz, A Beuchert, K Bischoff, S Blum, P Braune, K Bugg, DV Case, T Cramer, O Crede, V Crowe, KM Degener, T Djaoshvili, N von Dombrowski, S Doser, M Dunnweber, W Ehmanns, A Engelhardt, D Faessler, MA Giarritta, P Haddock, RP Heinsius, FH Heinzelmann, M Herz, M Hessey, NP Hidas, P Hodd, C Holtzhaussen, C Jamnik, D Kalinowsky, H Kammle, B Kammel, P Kisiel, J Klempt, E Koch, H Kolo, C Kunze, M Kurilla, U Lakata, M Landua, R Matthay, H McCrady, R Meier, J Meyer, CA Montanet, L Ouared, R Ould-Saada, F Peters, K Pick, B Pietra, C Pinder, CN Ratajcak, M Regenfus, C Reissmann, J Resag, S Roethel, W Schmidt, P Scott, I Seibert, R Spanier, S Stock, H Strassburger, C Strohbusch, U Suffert, M Thoma, U Tischhauser, M Volcker, C Wallis, S Walther, D Wiedner, U Zou, BS Zupancic, C CA Crystal Barrel Collaboration TI Antiproton-proton annihilation at rest into Kappa(O)(L)Kappa(+/-)pi(-/+)pi(O) - manifestations of isospin interference SO PHYSICS LETTERS B AB The decay (p) over bar p (at rest) --> K(L)(o)K(+/-)pi(+/-)pi(o), studied on a sample of more than 14000 events, is found to proceed dominantly via two-body channels containing resonances with open strangeness. Contributions from K-1(1270)(K) over bar and K-1(1400)(K) over bar, branching into the successive K-1-decay modes, and from K*(K) over bar*, K*((K) over bar pi)(S) and (K pi)(S)((K) over bar pi)(S) are extracted by means of a partial-wave analysis which accounts well for the data and also allows a search for weak contributions from other (K pi pi) and from(K (K) over bar pi) resonances. Striking asymmetries between the charged and the neutral kaonic resonances give evidence for interfering isospin 0 and 1 annihilation amplitudes. (C) 1997 Published by Elsevier Science B.V. SN 0370-2693 PD DEC 18 PY 1997 VL 415 IS 3 BP 289 EP 298 DI 10.1016/S0370-2693(97)01267-7 UT WOS:000071329000011 ER PT J AU Acciarri, M Adriani, O Aguilar-Benitez, M Ahlen, S Alcaraz, J Alemanni, G Allaby, J Aloisio, A Alverson, G Alviggi, MG Ambrosi, G Anderhub, H Andreev, VP Angelescu, T Anselmo, F Arefiev, A Azemoon, T Aziz, T Bagnaia, P Baksay, L Banerjee, S Banerjee, S Banicz, K Barczyk, A Barillere, R Barone, L Bartalini, P Baschirotto, A Basile, M Battiston, R Bay, A Becattini, F Becker, U Behner, F Berdugo, J Berges, P Bertucci, B Betev, BL Bhattacharya, S Biasini, M Biland, A Bilei, GM Blaising, JJ Blyth, SC Bobbink, GJ Bock, R Bohm, A Boldizsar, L Borgia, B Bourilkov, D Bourquin, M Braccini, S Branson, JG Brigljevic, V Brock, IC Buffini, A Buijs, A Burger, JD Burger, WJ Busenitz, J Button, A Cai, XD Campanelli, M Capell, M Romeo, GC Carlino, G Cartacci, AM Casaus, J Castellini, G Cavallari, F Cavallo, N Cecchi, C Cerrada, M Cesaroni, F Chamizo, M Chang, YH Chaturvedi, UK Chekanov, SV Chemarin, M Chen, A Chen, G Chen, GM Chen, HF Chen, HS Chereau, X Chiefari, G Chien, CY Cifarelli, L Cindolo, F Civinini, C Clare, I Clare, R Cohn, HO Coignet, G Colijn, AP Colino, N Commichau, V Costantini, S Cotorobai, F de la Cruz, B Csilling, A Dai, TS D'Alessandro, R de Asmundis, R Degre, A Deiters, K della Volpe, D Denes, P DeNotaristefani, F DiBitonto, D Diemoz, M van Dierendonck, D Di Lodovico, F Dionisi, C Dittmar, M Dominguez, A Doria, A Dova, MT Duchesneau, D Duinker, P Duran, I Dutta, S Easo, S Efremenko, Y El Mamouni, H Engler, A Eppling, FJ Erne, FC Ernenwein, JP Extermann, P Fabre, M Faccini, R Falciano, S Favara, A Fay, J Fedin, O Felcini, M Fenyi, B Ferguson, T Ferroni, F Fesefeldt, H Fiandrini, E Field, JH Filthaut, F Fisher, PH Fisk, I Forconi, G Fredj, L Freudenreich, K Furetta, C Galaktionov, Y Ganguli, SN Garcia-Abia, P Gau, SS Gentile, S Gheordanescu, N Giagu, S Goldfarb, S Goldstein, J Gong, ZF Gougas, A Gratta, G Gruenewald, MW Gupta, VK Gurtu, A Gutay, LJ Hartmann, B Hasan, A Hatzifotiadou, D Hebbeker, T Herve, A van Hoek, WC Hofer, H Hong, SJ Hoorani, H Hou, SR Hu, G Innocente, V Jenkes, K Jin, BN Jones, LW de Jong, P Josa-Mutuberria, I Kasser, A Khan, RA Kamrad, D Kamyshkov, Y Kapustinsky, JS Karyotakis, Y Kaur, M Kienzle-Focacci, MN Kim, D Kim, DH Kim, JK Kim, SC Kim, YG Kinnison, WW Kirkby, A Kirkby, D Kirkby, J Kiss, D Kittel, W Klimentov, A Konig, AC Kopp, A Korolko, I Koutsenko, V Kraemer, RW Krenz, W Kunin, A de Guevara, PL Laktineh, I Landi, G Lapoint, C Lassila-Perini, K Laurikainen, P Lebeau, M Lebedev, A Lebrun, P Lecomte, P Lecoq, P Le Coultre, P Le Goff, JM Leiste, R Leonardi, E Levtchenko, P Li, C Lin, CH Lin, WT Linde, FL Lista, L Liu, ZA Lohmann, W Longo, E Lu, W Lu, YS Lubelsmeyer, K Luci, C Luckey, D Luminari, L Lustermann, W Ma, WG Maity, M Majumder, G Malgeri, L Malinin, A Mana, C Mangeol, D Mangla, S Marchesini, P Marin, A Martin, JP Marzano, F Massaro, GGG McNally, D McNeil, RR Mele, S Merola, L Meschini, M Metzger, WJ von der Mey, M Mi, Y Mihul, A van Mil, AJW Mirabelli, G Mnich, J Molnar, P Monteleoni, B Moore, R Morganti, S Moulik, T Mount, R Muller, S Muheim, F Muijs, AJM Nahn, S Napolitano, M Nessi-Tedaldi, F Newman, H Niessen, T Nippe, A Nisati, A Nowak, H Oh, YD Opitz, H Organtini, G Ostonen, R Palomares, C Pandoulas, D Paoletti, S Paolucci, P Park, HK Park, IH Pascale, G Passaleva, G Patricelli, S Paul, T Pauluzzi, M Paus, C Pauss, F Peach, D Pei, YJ Pensotti, S Perret-Gallix, D Petersen, B Petrak, S Pevsner, A Piccolo, D Pieri, M Pinto, JC Piroue, PA Pistolesi, E Plyaskin, V Pohl, M Pojidaev, V Postema, H Produit, N Prokofiev, D Rahal-Callot, G Raja, N Rancoita, PG Rattaggi, M Raven, G Razis, P Read, K Ren, D Rescigno, M Reucroft, S van Rhee, T Riemann, S Riles, K Robohm, A Rodin, J Roe, BP Romero, L Rosier-Lees, S Rosselet, P van Rossum, W Roth, S Rubio, JA Ruschmeier, D Rykaczewski, H Salicio, J Sanchez, E Sanders, MP Sarakinos, ME Sarkar, S Sassowsky, M Schafer, C Schegelsky, V Schmidt-Kaerst, S Schmitz, D Schmitz, P Scholz, N Schopper, H Schotanus, DJ Schwenke, J Schwering, G Sciacca, C Sciarrino, D Servoli, L Shevchenko, S Shivarov, N Shoutko, V Shukla, J Shumilov, E Shvorob, A Siedenburg, T Son, D Sopczak, A Smith, B Spillantini, P Steuer, M Stickland, DP Stone, A Stone, H Stoyanov, B Straessner, A Strauch, K Sudhakar, K Sultanov, G Sun, LZ Susinno, GF Suter, H Swain, JD Tang, XW Tauscher, L Taylor, L Ting, SCC Ting, SM Tonutti, M Tonwar, SC Toth, J Tully, C Tuchscherer, H Tung, KL Uchida, Y Ulbricht, J Uwer, U Valente, E Van de Walle, RT Vesztergombi, G Vetlitsky, I Viertel, G Vivargent, M Volkert, R Vogel, H Vogt, H Vorobiev, I Vorobyov, AA Vorvolakos, A Wadhwa, M Wallraff, W Wang, JC Wang, XL Wang, ZM Weber, A Wittgenstein, F Wu, SX Wynhoff, S Xu, J Xu, ZZ Yang, BZ Yang, CG Yao, XY Ye, JB Yeh, SC You, JM Zalite, A Zalite, Y Zemp, P Zeng, Y Zhang, Z Zhang, ZP Zhou, B Zhu, GY Zhu, RY Zichichi, A Ziegler, F AF Acciarri, M Adriani, O Aguilar-Benitez, M Ahlen, S Alcaraz, J Alemanni, G Allaby, J Aloisio, A Alverson, G Alviggi, MG Ambrosi, G Anderhub, H Andreev, VP Angelescu, T Anselmo, F Arefiev, A Azemoon, T Aziz, T Bagnaia, P Baksay, L Banerjee, S Banerjee, S Banicz, K Barczyk, A Barillere, R Barone, L Bartalini, P Baschirotto, A Basile, M Battiston, R Bay, A Becattini, F Becker, U Behner, F Berdugo, J Berges, P Bertucci, B Betev, BL Bhattacharya, S Biasini, M Biland, A Bilei, GM Blaising, JJ Blyth, SC Bobbink, GJ Bock, R Bohm, A Boldizsar, L Borgia, B Bourilkov, D Bourquin, M Braccini, S Branson, JG Brigljevic, V Brock, IC Buffini, A Buijs, A Burger, JD Burger, WJ Busenitz, J Button, A Cai, XD Campanelli, M Capell, M Romeo, GC Carlino, G Cartacci, AM Casaus, J Castellini, G Cavallari, F Cavallo, N Cecchi, C Cerrada, M Cesaroni, F Chamizo, M Chang, YH Chaturvedi, UK Chekanov, SV Chemarin, M Chen, A Chen, G Chen, GM Chen, HF Chen, HS Chereau, X Chiefari, G Chien, CY Cifarelli, L Cindolo, F Civinini, C Clare, I Clare, R Cohn, HO Coignet, G Colijn, AP Colino, N Commichau, V Costantini, S Cotorobai, F de la Cruz, B Csilling, A Dai, TS D'Alessandro, R de Asmundis, R Degre, A Deiters, K della Volpe, D Denes, P DeNotaristefani, F DiBitonto, D Diemoz, M van Dierendonck, D Di Lodovico, F Dionisi, C Dittmar, M Dominguez, A Doria, A Dova, MT Duchesneau, D Duinker, P Duran, I Dutta, S Easo, S Efremenko, Y El Mamouni, H Engler, A Eppling, FJ Erne, FC Ernenwein, JP Extermann, P Fabre, M Faccini, R Falciano, S Favara, A Fay, J Fedin, O Felcini, M Fenyi, B Ferguson, T Ferroni, F Fesefeldt, H Fiandrini, E Field, JH Filthaut, F Fisher, PH Fisk, I Forconi, G Fredj, L Freudenreich, K Furetta, C Galaktionov, Y Ganguli, SN Garcia-Abia, P Gau, SS Gentile, S Gheordanescu, N Giagu, S Goldfarb, S Goldstein, J Gong, ZF Gougas, A Gratta, G Gruenewald, MW Gupta, VK Gurtu, A Gutay, LJ Hartmann, B Hasan, A Hatzifotiadou, D Hebbeker, T Herve, A van Hoek, WC Hofer, H Hong, SJ Hoorani, H Hou, SR Hu, G Innocente, V Jenkes, K Jin, BN Jones, LW de Jong, P Josa-Mutuberria, I Kasser, A Khan, RA Kamrad, D Kamyshkov, Y Kapustinsky, JS Karyotakis, Y Kaur, M Kienzle-Focacci, MN Kim, D Kim, DH Kim, JK Kim, SC Kim, YG Kinnison, WW Kirkby, A Kirkby, D Kirkby, J Kiss, D Kittel, W Klimentov, A Konig, AC Kopp, A Korolko, I Koutsenko, V Kraemer, RW Krenz, W Kunin, A de Guevara, PL Laktineh, I Landi, G Lapoint, C Lassila-Perini, K Laurikainen, P Lebeau, M Lebedev, A Lebrun, P Lecomte, P Lecoq, P Le Coultre, P Le Goff, JM Leiste, R Leonardi, E Levtchenko, P Li, C Lin, CH Lin, WT Linde, FL Lista, L Liu, ZA Lohmann, W Longo, E Lu, W Lu, YS Lubelsmeyer, K Luci, C Luckey, D Luminari, L Lustermann, W Ma, WG Maity, M Majumder, G Malgeri, L Malinin, A Mana, C Mangeol, D Mangla, S Marchesini, P Marin, A Martin, JP Marzano, F Massaro, GGG McNally, D McNeil, RR Mele, S Merola, L Meschini, M Metzger, WJ von der Mey, M Mi, Y Mihul, A van Mil, AJW Mirabelli, G Mnich, J Molnar, P Monteleoni, B Moore, R Morganti, S Moulik, T Mount, R Muller, S Muheim, F Muijs, AJM Nahn, S Napolitano, M Nessi-Tedaldi, F Newman, H Niessen, T Nippe, A Nisati, A Nowak, H Oh, YD Opitz, H Organtini, G Ostonen, R Palomares, C Pandoulas, D Paoletti, S Paolucci, P Park, HK Park, IH Pascale, G Passaleva, G Patricelli, S Paul, T Pauluzzi, M Paus, C Pauss, F Peach, D Pei, YJ Pensotti, S Perret-Gallix, D Petersen, B Petrak, S Pevsner, A Piccolo, D Pieri, M Pinto, JC Piroue, PA Pistolesi, E Plyaskin, V Pohl, M Pojidaev, V Postema, H Produit, N Prokofiev, D Rahal-Callot, G Raja, N Rancoita, PG Rattaggi, M Raven, G Razis, P Read, K Ren, D Rescigno, M Reucroft, S van Rhee, T Riemann, S Riles, K Robohm, A Rodin, J Roe, BP Romero, L Rosier-Lees, S Rosselet, P van Rossum, W Roth, S Rubio, JA Ruschmeier, D Rykaczewski, H Salicio, J Sanchez, E Sanders, MP Sarakinos, ME Sarkar, S Sassowsky, M Schafer, C Schegelsky, V Schmidt-Kaerst, S Schmitz, D Schmitz, P Scholz, N Schopper, H Schotanus, DJ Schwenke, J Schwering, G Sciacca, C Sciarrino, D Servoli, L Shevchenko, S Shivarov, N Shoutko, V Shukla, J Shumilov, E Shvorob, A Siedenburg, T Son, D Sopczak, A Smith, B Spillantini, P Steuer, M Stickland, DP Stone, A Stone, H Stoyanov, B Straessner, A Strauch, K Sudhakar, K Sultanov, G Sun, LZ Susinno, GF Suter, H Swain, JD Tang, XW Tauscher, L Taylor, L Ting, SCC Ting, SM Tonutti, M Tonwar, SC Toth, J Tully, C Tuchscherer, H Tung, KL Uchida, Y Ulbricht, J Uwer, U Valente, E Van de Walle, RT Vesztergombi, G Vetlitsky, I Viertel, G Vivargent, M Volkert, R Vogel, H Vogt, H Vorobiev, I Vorobyov, AA Vorvolakos, A Wadhwa, M Wallraff, W Wang, JC Wang, XL Wang, ZM Weber, A Wittgenstein, F Wu, SX Wynhoff, S Xu, J Xu, ZZ Yang, BZ Yang, CG Yao, XY Ye, JB Yeh, SC You, JM Zalite, A Zalite, Y Zemp, P Zeng, Y Zhang, Z Zhang, ZP Zhou, B Zhu, GY Zhu, RY Zichichi, A Ziegler, F TI Single and multi-photon events with missing energy in e(+)e(-) collisions at 161 GeV gamma(gamma) cross section as well as upper limits on new physics processes. (C) 1997 Published by Elsevier Science B.V. RI Sanchez, Eusebio/H-5228-2015; Duran, Ignacio/H-7254-2015; Rancoita, Pier Giorgio/J-9896-2015; Hoorani, Hafeez/D-1791-2013; Palomares, Carmen/H-7783-2015; Fedin, Oleg/H-6753-2016; Roth, Stefan/J-2757-2016; Kamyshkov, Yuri/J-7999-2016; Di Lodovico, Francesca/L-9109-2016; Berdugo, Javier/A-2858-2015; Fiandrini, Emanuele/C-4549-2008; D'Alessandro, Raffaello/F-5897-2015; Lista, Luca/C-5719-2008; Kirkby, Jasper/A-4973-2012; Servoli, Leonello/E-6766-2012; bertucci, bruna/J-5237-2012; Cavallo, Nicola/F-8913-2012; Cerrada, Marcos/J-6934-2014; Josa, Isabel/K-5184-2014; de la Cruz, Begona/K-7552-2014; Vogel, Helmut/N-8882-2014; Ferguson, Thomas/O-3444-2014 OI Sanchez, Eusebio/0000-0002-9646-8198; Rancoita, Pier Giorgio/0000-0002-1990-4283; Palomares, Carmen/0000-0003-4374-9065; Roth, Stefan/0000-0003-3616-2223; Kamyshkov, Yuri/0000-0002-3789-7152; Di Lodovico, Francesca/0000-0003-3952-2175; Castellini, Guido/0000-0002-0177-0643; Berdugo, Javier/0000-0002-7911-8532; D'Alessandro, Raffaello/0000-0001-7997-0306; Kirkby, Jasper/0000-0003-2341-9069; Servoli, Leonello/0000-0003-1725-9185; Cerrada, Marcos/0000-0003-0112-1691; Vogel, Helmut/0000-0002-6109-3023; Ferguson, Thomas/0000-0001-5822-3731 SN 0370-2693 EI 1873-2445 PD DEC 18 PY 1997 VL 415 IS 3 BP 299 EP 310 DI 10.1016/S0370-2693(97)01296-3 UT WOS:000071329000012 ER PT J AU Sanchez-Herencia, AJ Moya, JS Tomsia, AP AF Sanchez-Herencia, AJ Moya, JS Tomsia, AP TI Microstructural design in alumina-alumina/zirconia layered composites SO SCRIPTA MATERIALIA RI Sanchez-Herencia, Antonio Javier/D-1518-2011; Moya, Jose/I-5841-2013; Sanchez-Herencia, Antonio Javier/I-2110-2015; OI Sanchez-Herencia, Antonio Javier/0000-0002-9982-4127; Sanchez-Herencia, Antonio Javier/0000-0003-2874-6640; Sanchez-Herencia, Antonio Javier/0000-0002-2104-1691 SN 1359-6462 PD DEC 18 PY 1997 VL 38 IS 1 BP 1 EP 5 DI 10.1016/S1359-6462(97)00443-0 UT WOS:000071234700001 ER PT J AU Castaing, J Mitchell, TE Rodriguez, AD AF Castaing, J Mitchell, TE Rodriguez, AD TI Evolution of specimen shape for uniaxial compression of single crystals SO SCRIPTA MATERIALIA SN 1359-6462 PD DEC 18 PY 1997 VL 38 IS 1 BP 45 EP 51 DI 10.1016/S1359-6462(97)00437-5 UT WOS:000071234700008 ER PT J AU Henning, RW Corbett, JD AF Henning, RW Corbett, JD TI Cs8Ga11, a new isolated cluster in a binary gallium compound. A family of valence analogues A(8)Tr(11)X: A = Cs, Rb; Tr = Ga, In, Tl; X = Cl, Br, I SO INORGANIC CHEMISTRY AB Fusion of the elements, and alkali-metal halide when appropriate, in stoichiometric amounts in Ta containers followed by slow cooling results in high yields of the title compounds. X-ray structures refined for rhombohedral Cs8Ga11 (R (3) over bar c, Z = 6, a = 9.9962(5) Angstrom, c = 50.839(6) Angstrom) and Cs8Ga11Cl (R (3) over bar (3) over bar c, Z = 6, a = 10.0111(7) Angstrom, c 50.504(6) Angstrom) reveal isolated clusters of pentacapped, trigonal prismatic gallium anions, Ga-11(7-), the former compound being isostructural with K8In11 and A(8)Tl(11) (A = K, Rb, Cs). The clusters are arranged in pseudo-ccp layers separated by double layers of cesium atoms. The halide in Cs8Ga11Cl is bound in a preformed cavity within the cesium double layers where it is surrounded by eight cations. Of the nine examples reported for A(8)Tr(11)X, three chlorides occur in systems in which the binary A(8)Tr(11) do not form, Rb-Ga, Rb-In, and Cs-In. These halides are the first examples of Tr-11(7-) compounds that are valence phases and do not contain an extra alkali-metal cation and electron. Magnetic susceptibility data indicate an apparently localized electron in paramagnetic Cs-8-Ga-11 and diamagnetism for Cs8Ga11Cl. SN 0020-1669 PD DEC 17 PY 1997 VL 36 IS 26 BP 6045 EP 6049 DI 10.1021/ic970904u UT WOS:000071112900011 ER PT J AU Bau, R Schreiber, A Metzenthin, T Lu, RS Lutz, F Klooster, WT Koetzle, TF Seim, H Kleber, HP Brewer, F Englard, S AF Bau, R Schreiber, A Metzenthin, T Lu, RS Lutz, F Klooster, WT Koetzle, TF Seim, H Kleber, HP Brewer, F Englard, S TI Neutron diffraction structure of (2R,3R)-L-(-)-[2-D]carnitine tetrachloroaurate, [(CH3)(3)N-CH2-CHOH-CHD-COOH](+)[AuCl4](-): Determination of the absolute stereochemistry of the crotonobetaine-to-carnitine transformation catalyzed by L-carnitine dehydratase from Escherichia coli SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB Single-crystal neutron diffraction has been used to determine the stereochemical course of the hydration of trans-crotonobetaine to L-(-)-carnitine by the enzyme L-carnitine dehydratase. Firstly, an X-ray analysis of the undeuterated carnitinium salt [(CH3)(3)N-CH2-CH(OH)-CH2-COOH](+)[AuCl4](-) confirmed that the absolute configuration at the C-3 position of L-(-)-carnitine (the CHOH group) is indeed R. This was accomplished using the gold atom as an anomalously-scattering source. Then stereospecifically deuterated L-(-)-[2-D] carnitine was prepared by the hydration of trans-crotonobetaine in D2O using purified L-carnitine dehydratase from Escherichia coli. The subsequent neutron analysis of deuterated [(CH3)(3)N-CH2-CH(OH)-CH2-COOH](+)[AuCl4](-) revealed that the CHD group at position C-2 also had the absolute R configuration, thus establishing that the addition of D2O across the C=C double bond of trans-crotonobetaine proceeds by a stereospecific syn pathway. In Contrast, all other hydration-dehydration reactions examined thus far show that, when the proton added or abstracted is bonded to a carbon atom that is adjacent to a carboxylate group, the absolute stereochemistry of the resulting transformation is anti. Crystallographic details for [(CH3)(3)N-CH2-CH(OH)-CHD-COOH](+)[AuCl4](-) are as follows: space group P2(1)2(1)2(1) (orthorhombic), a = 10.855(2), b = 11.678(3), c = 22.776(6) Angstrom; Z = 8; final agreement factor for the neutron analysis at 15 K: R(F-0) = 0.097 based on 1140 reflections with I > 3 sigma(I). SN 0002-7863 PD DEC 17 PY 1997 VL 119 IS 50 BP 12055 EP 12060 DI 10.1021/ja972105g UT WOS:000071146000004 ER PT J AU Chen, LF Cotton, FA Klooster, WT Koetzle, TF AF Chen, LF Cotton, FA Klooster, WT Koetzle, TF TI Characterization and reactions of [PPh4](3)[Zr6Cl18H5] and its deprotonation products SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB The octahedral hexazirconium cluster compound [PPh4](3)[Zr6Cl18H5] has been structurally characterized by both neutron and X-ray single-crystal diffraction studies. The compound [PPh4](3)[Zr6Cl18H5]. 3CH(2)Cl(2) crystallizes in the triclinic space group PT with unit cell parameters of a = 15.993(3), b = 22.237(3), and c = 14.670(4) Angstrom, alpha = 95.31(1), beta = 112.07(2), and gamma = 82.06(2)degrees, V = 4784(2) Angstrom(3), and Z = 2 at ambient temperature and a = 15.780(6), b = 21.96(3), and c 14.521(7) Angstrom, alpha = 94.96(8), beta = 111.59(4), and gamma = 81.72(5)degrees, V = 4627(11) Angstrom(3), and Z = 2 at T = 15 K. The hydrogen atoms in the cluster anion, [Zr6Cl18H5](3-), were found to be distributed at the centers of the eight triangular faces of the Zr-6 octahedron from neutron diffraction data. The occupancy parameters of the sites range from 0.32 to 0.92 with a total of 5.3(1) hydrogen atoms per cluster, close to the value from H-1 NMR measurement (5.0). The average Zr-H distance is 1.96(4) Angstrom. A variable temperature H-1 NMR study indicated that the cluster hydrogen atoms undergo rapid movement at room temperature. One of the five hydrogen atoms in the cluster [Zr6Cl18H5](3-) was readily removed as a proton with primary linear amines with formation of the corresponding ammonium cations, while the cluster anion, [Zr6Cl18H5](3-), was thus converted into a new cluster anion, [Zr6Cl18H4](4-). The feasibility of such a deprotonation reactions is controlled by the size of both the Lewis base and the cavity available on the Zr-3 triangular faces of the Zr-6 clusters, and also by the basicity of the deprotonating reagents. Two products, [PPh4](4)[Zr6Cl18H4]. 4CH(2)Cl(2) and [H3NEt](4)[Zr6Cl18H4]. 4MeCN from the deprotonation reactions were characterized by X-ray crystallography. SN 0002-7863 PD DEC 17 PY 1997 VL 119 IS 50 BP 12175 EP 12183 DI 10.1021/ja972835o UT WOS:000071146000020 ER PT J AU Xu, T Kob, N Drago, RS Nicholas, JB Haw, JF AF Xu, T Kob, N Drago, RS Nicholas, JB Haw, JF TI A solid acid catalyst at the threshold of superacid strength: NMR, calorimetry, and density functional theory studies of silica-supported aluminum chloride SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB Solid state NMR, calorimetry, and density functional theory (DPT) all provide a consistent interpretation of the acidity of the solid acid catalyst (SG)(n)AlCl2 which is prepared by reacting aluminum chloride with conditioned silica gel. These studies firmly establish that the acid sites are Bronsted in nature and that their strength is significantly greater than those in zeolites. Proton NMR results, including experiments exploiting H-1-Al-27 dipolar couplings, demonstrate that the Bronsted acid sites have an isotropic H-1 chemical shift of 5.7 ppm and a concentration of 0.58 mmol/g. The strongest sites on this solid acid, present at 0.03 mmol/g, have -Delta H-av, values of 52 kcal/mol for reaction with pyridine. A value of 44 kcal/mol is maintained for incremental addition of pyridine up to 0.1 mmol/g. In comparison, -Delta H-av for the strongest sites in zeolite HZSM-5 is only 42 kcal/mol. N-15 magic angle spinning (MAS) NMR studies of adsorbed pyridine and P-31 MAS NMR of trimethylphosphine confirm the Bronsted nature of these acid sites. The C-13 isotropic chemical shift of acetone-2-C-13 on (SG)(n)AlCl2 (245 ppm) is identical to that measured in 100% H2SO4. C-13 in situ NMR studies of ethylene and propene oligomerization show that the activity of (SG)(n)AlCl2 is far greater than that of zeolites. Cyclopentenyl carbenium ions are formed in significant yields in those reactions as well as during skeletal isomerization and cracking of cyclohexane at 433 K on (SG)(n)AlCl2. Local DFT calculations at the SVWN/DZVP2 level were used to provide predictions of the structure and energetics of the catalyst. The acidity (defined as the deprotonation energy corrected for zero-point and thermal contributions) obtained from these calculations ranges from 275.5 to 293.4 kcal/mol. Two of the three (SG)(n)AlCl2 models considered are more strongly acidic than a HZSM-5 cluster model treated at the same level of theory. The aggregate evidence from this study strongly supports classification of (SG)(n)AlCl2 as a catalyst with a Bronsted acid strength on the threshold of superacidity. SN 0002-7863 PD DEC 17 PY 1997 VL 119 IS 50 BP 12231 EP 12239 DI 10.1021/ja970850n UT WOS:000071146000026 ER PT J AU Zhu, WJ Hor, PH Jacobson, AJ Crisci, G Albright, TA Wang, SH Vogt, T AF Zhu, WJ Hor, PH Jacobson, AJ Crisci, G Albright, TA Wang, SH Vogt, T TI A(2)Cu(2)CoO(2)S(2) (A = Sr, Ba), a novel example of a square-planar CoO2 layer SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY RI Vogt, Thomas /A-1562-2011 OI Vogt, Thomas /0000-0002-4731-2787 SN 0002-7863 PD DEC 17 PY 1997 VL 119 IS 50 BP 12398 EP 12399 DI 10.1021/ja972542v UT WOS:000071146000062 ER PT J AU Mazzanti, M Marchon, JC Shang, MY Scheidt, WR Jia, SL Shelnutt, JA AF Mazzanti, M Marchon, JC Shang, MY Scheidt, WR Jia, SL Shelnutt, JA TI A pyridine-sensitive venus flytrap porphyrin SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY RI Shelnutt, John/A-9987-2009 OI Shelnutt, John/0000-0001-7368-582X SN 0002-7863 PD DEC 17 PY 1997 VL 119 IS 50 BP 12400 EP 12401 DI 10.1021/ja972947f UT WOS:000071146000063 ER PT J AU Rabinovich, D Schimek, GL Pennington, WT Nielsen, JB Abney, KD AF Rabinovich, D Schimek, GL Pennington, WT Nielsen, JB Abney, KD TI Dibromobis(eta(5)-pentamethylcyclopentadienyl)thorium(IV) SO ACTA CRYSTALLOGRAPHICA SECTION C-CRYSTAL STRUCTURE COMMUNICATIONS AB The title compound, [ThBr2(eta(5)-C10H15)(2)] or Cp-2*ThBr2 [Cp* = eta(5)-C-5(CH3)(5)], presents a pseudo-tetrahedral 'bent-metallocene' geometry in the solid state, with the Th atom binding to two pentamethylcyclopentadienyl ligands and two bromide ligands. The Th-Br bond length is 2.800(2)Angstrom, whereas the Th-C distances are in the range 2.77(1)-2.782(9) Angstrom. SN 0108-2701 PD DEC 15 PY 1997 VL 53 BP 1794 EP 1797 DI 10.1107/S0108270197010056 PN 12 UT WOS:000071310800030 ER PT J AU Dearth, MA Asano, KG Hart, KJ Buchanan, MV Goeringer, DE McLuckey, SA AF Dearth, MA Asano, KG Hart, KJ Buchanan, MV Goeringer, DE McLuckey, SA TI Nitric oxide chemical ionization ion trap mass spectrometry for the determination of automotive exhaust constituents SO ANALYTICAL CHEMISTRY AB Nitric oxide chemical ionization in a glow discharge ionization source coupled with a quadrupole ion trap mass spectrometer has been evaluated for application to automotive exhaust measurements. Emphasis was placed on the determination of hydrocarbons at parts-per-million to parts-per-billion levels. Nitric oxide chemical ionization was found to yield diagnostic ions for alkanes, alkenes, and arenes, whereas water chemical ionization failed to provide diagnostic ions for the alkanes, The ability to measure a variety of hydrocarbons present at roughly 15 ppb at measurement rates of 3 Hz was demonstrated. All of the ions with potential to serve as parent ions in a tandem mass spectrometry experiment were found to yield parent-to-product conversion efficiencies greater than 75%. The flexibility afforded to the ion trap by the use of tailored waveforms applied to the endcaps allows parallel monitoring schemes to be devised that provide many of the advantages of tandem mass spectrometry without a major loss in measurement rate. A large loss in measurement rate would ordinarily result from the use of conventional tandem mass spectrometry experiments carried out in series for a large number of targeted components. RI McLuckey, Scott/B-2203-2009; Asano, Keiji/L-3164-2016 OI McLuckey, Scott/0000-0002-1648-5570; Asano, Keiji/0000-0003-2254-3586 SN 0003-2700 PD DEC 15 PY 1997 VL 69 IS 24 BP 5121 EP 5129 DI 10.1021/ac970841x UT WOS:A1997YL29900026 ER PT J AU Kelly, JA Reddy, KR Lee, CS AF Kelly, JA Reddy, KR Lee, CS TI Mechanistic studies of postcapillary affinity detection for capillary zone electrophoresis based on the biotin-streptavidin system SO ANALYTICAL CHEMISTRY AB Postcapillary affinity detection is developed to analyze structurally related compounds following capillary zone electrophoresis separation. In this work, biotin and biotin derivatives are resolved by capillary zone electrophoresis and selectively identified on the basis of their cross-reactivity with streptavidin-fluorescein isothiocyanate, added via a postcapillary reactor. Direct sensing of the affinity reaction is achieved bq monitoring the resulting fluorescence enhancement of streptavidin-fluorescein isothiocyanate upon biotin binding. The effects of postcapillary reactor parameters, including capillary gap distance, dilution ratio, and reaction distance, on peak area and peak efficiency of the biotin-streptavidin complex are investigated. A reaction kinetic model is presented for evaluating the dynamic range and detection limits of postcapillary affinity detection as a function of streptavidin concentration in the postcapillary reactor. The detection limit for postcapillary affinity detection of biotin is on the order of 3 nM, or 4 fg. SN 0003-2700 PD DEC 15 PY 1997 VL 69 IS 24 BP 5152 EP 5158 DI 10.1021/ac9705879 UT WOS:A1997YL29900031 ER PT J AU Kutter, JP Jacobson, SC Ramsey, JM AF Kutter, JP Jacobson, SC Ramsey, JM TI Integrated microchip device with electrokinetically controlled solvent mixing for isocratic and gradient elution in micellar electrokinetic chromatography SO ANALYTICAL CHEMISTRY AB A monolithic micromachined device is presented which allows on-chip adjustments of the content of organic modifier in the run buffer for fast, efficient MEKC separations. Isocratic and gradient conditions are controlled by proper setting of voltages applied to the buffer reservoirs of the microchip. The precision of this control is tested for gradients of various shapes (linear, concave, convex) by mixing pure buffer and buffer doped with a fluorescent dye. The effect of isocratic and gradient solvent changes on the MEKC separation of a mixture of coumarin dyes is demonstrated using methanol and acetonitrile as modifiers. Separations were carried out using a column length of 25 mm and a field strength of 660 V/cm with high resolution. Analysis times were as short as 33 s for methanol and under 22 s for acetonitrile. Gradients with both modifiers were executed within 10 s. Of the two modifiers, acetonitrile proved to have a more pronounced impact on the elution pattern of the test mixture. Only slight band broadening is observed for gradient runs as compared to isocratic runs using methanol. On the other hand, in the case of acetonitrile gradients, some of the peaks exhibit a focusing effect (as observed in HPLC gradients), yielding up to 100 000 plates. RI Kutter, Jorg/E-3256-2010 OI Kutter, Jorg/0000-0003-1065-1985 SN 0003-2700 PD DEC 15 PY 1997 VL 69 IS 24 BP 5165 EP 5171 DI 10.1021/ac970723+ UT WOS:A1997YL29900033 ER PT J AU Gruverman, A Tokumoto, H Prakash, AS Aggarwal, S Yang, B Wuttig, M Ramesh, R Auciello, O Venkatesan, T AF Gruverman, A Tokumoto, H Prakash, AS Aggarwal, S Yang, B Wuttig, M Ramesh, R Auciello, O Venkatesan, T TI Nanoscale imaging of domain dynamics and retention in ferroelectric thin films SO APPLIED PHYSICS LETTERS AB We report results on the direct observation of the microscopic origins of backswitching in ferroelectric thin films. The piezoelectric response generated in the film by a biased atomic force microscope tip was used to obtain static and dynamic piezoelectric images of individual grains in a polycrystalline material. We demonstrate that polarization reversal occurs under no external field (i.e., loss of remanent polarization) via a dispersive continuous-time random walk process, identified by a stretched exponential decay of the remanent polarization. (C) 1997 American Institute of Physics. [S0003-6951(97)00550-0]. RI Wuttig, Manfred/A-8763-2012; Venkatesan, Thirumalai/E-1667-2013; Gruverman, alexei/P-3537-2014 OI Gruverman, alexei/0000-0003-0492-2750 SN 0003-6951 PD DEC 15 PY 1997 VL 71 IS 24 BP 3492 EP 3494 DI 10.1063/1.120369 UT WOS:A1997YL27300010 ER PT J AU Ahuja, R Johansson, B Wills, JM Eriksson, O AF Ahuja, R Johansson, B Wills, JM Eriksson, O TI On the semiconducting state and structural properties of YH3 from first principles theory SO APPLIED PHYSICS LETTERS AB With the use of first principles theory we confirm the semiconducting ground state of the technologically interesting YH3 compound. Thus, unlike previously published theories, we demonstrate that density functional theory in the local density approximation reproduces the existence of a band gap. We also show that the HoD3 structure is the stable structure at ambient conditions, in agreement with experiment. In addition, we predict that moderate applied pressure will drive YH3 into the cubic structure. (C) 1997 American Institute of Physics. [S0003-6951(97)02050-0]. RI Eriksson, Olle/E-3265-2014 OI Eriksson, Olle/0000-0001-5111-1374 SN 0003-6951 PD DEC 15 PY 1997 VL 71 IS 24 BP 3498 EP 3500 DI 10.1063/1.120371 UT WOS:A1997YL27300012 ER PT J AU Thompson, C Foster, CM Eastman, JA Stephenson, GB AF Thompson, C Foster, CM Eastman, JA Stephenson, GB TI Observation of the polarization of domains in ferroelectric thin films using x-ray interference SO APPLIED PHYSICS LETTERS AB We report that the sign of the polarization of an epitaxial ferroelectric film can be determined from the interference between the x-ray scattering from the film and the substrate. X-ray scattering measurements of a 10 nm epitaxial PbTiO3 film grown by metal-organic chemical vapor deposition on a SrTiO3 substrate are presented. The scattering profile near the 001 peaks of the film and substrate shows clear evidence of the interference effects. Analysis indicates that this film is a single domain of specific polarity. (C) 1997 American Institute of Physics. [S0003-6951(97)03650-4]. RI Eastman, Jeffrey/E-4380-2011; OI Eastman, Jeff/0000-0002-0847-4265; Thompson, Carol/0000-0003-3832-4855 SN 0003-6951 PD DEC 15 PY 1997 VL 71 IS 24 BP 3516 EP 3518 DI 10.1063/1.120377 UT WOS:A1997YL27300018 ER PT J AU Campbell, IH Kress, JD Martin, RL Smith, DL Barashkov, NN Ferraris, JP AF Campbell, IH Kress, JD Martin, RL Smith, DL Barashkov, NN Ferraris, JP TI Controlling charge injection in organic electronic devices using self-assembled monolayers SO APPLIED PHYSICS LETTERS AB We demonstrate control and improvement of charge injection in organic electronic devices by utilizing self-assembled monolayers (SAMs) to manipulate the Schottky energy barrier between a metal electrode and the organic electronic material. Hole injection from Cu electrodes into the electroluminescent-conjugated polymer poly[2-methoxy,5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] was varied by using two conjugated-thiol based SAMs. The chemically modified electrodes were incorporated in organic diode structures and changes in the metal/polymer Schottky energy barriers and current-voltage characteristics were measured. Decreasing (increasing) the Schottky energy barrier improves (degrades) charge injection into the polymer. (C) 1997 American Institute of Physics. [S0003-6951(97)01 150-9]. SN 0003-6951 PD DEC 15 PY 1997 VL 71 IS 24 BP 3528 EP 3530 DI 10.1063/1.120381 UT WOS:A1997YL27300022 ER PT J AU Wu, H Kramer, MJ Dennis, KW McCallum, RW AF Wu, H Kramer, MJ Dennis, KW McCallum, RW TI Mechanism for flux pinning in NdBa2Cu3O7-delta melt-textured in low oxygen partial pressure SO APPLIED PHYSICS LETTERS AB When NdBa2Cu3O7-delta> (Nd123) is melt-textured in low oxygen partial pressure (PO2) and subsequently annealed in oxygen to produce the superconducting phase, there is a considerable enhancement of flux pinning compared to Y123. This enhancement is accompanied by a precipitation mechanism due to a change of the solubility limits of Nd1+xBa2-xCu3O7-delta between the high temperature low PO2 conditions used in melt-textured growth and the low temperature oxygen annealing. Transmission electron microscopy reveals a coherent intermediate precipitate structure with a composition of BaCuO2 and a high density of dislocations. We believe these defects are responsible for the strong flux pinning in this material. (C) 1997 American Institute of Physics. [S0003-6951(97)00250-7]. SN 0003-6951 PD DEC 15 PY 1997 VL 71 IS 24 BP 3572 EP 3574 DI 10.1063/1.120395 UT WOS:A1997YL27300037 ER PT J AU DeNardo, GL Kukis, DL DeNardo, SJ Shen, S Mausner, LF O'Donnell, RT Lamborn, KR Meyers, FJ Srivastava, SC Miers, LA AF DeNardo, GL Kukis, DL DeNardo, SJ Shen, S Mausner, LF O'Donnell, RT Lamborn, KR Meyers, FJ Srivastava, SC Miers, LA TI Enhancement of Cu-67-2IT-BAT-LYM-1 therapy in mice with human Burkitt's lymphoma (Raji) using interleukin-2 SO CANCER CT 6th Conference on Radioimmunodetection and Radioimmunotherapy of Cancer CY OCT 10-12, 1996 CL PRINCETON, NEW JERSEY SP NIH NCI, Ctr Molec Med & Immunol, Garden State Canc Ctr AB BACKGROUND. Lymphomas have been shown to be responsive to I-131 immunoconjugates in studies conducted in mice and patients. We have observed that copper 67 (Cu-67)-labeled Lym-1 remains in lymphomatous tissue longer than I-131-Lym-1 and, consequently, results in higher absorbed radiation doses to tumors. In addition, recombinant interleukin-2 (rIL-2) has been reported to increase tumor uptake of radiolabeled antibody. Therefore, we examined the efficacy of Cu-67-labeled Lym-1 and the ability of rIL-2 to enhance this efficacy in athymic mice implanted with Raji xenografts. METHODS. 6[p-(bromoacetamido) benzyl]-1,4,8,11-tetraazacyclotetradecane-N,N', N ",N'''-tetraacetic acid (BAT) was conjugated to Lym-1 via 2-iminothiolane (2IT) to prepare 2IT-BAT-Lym-1, which was labeled with Cu-67. Mice with Raji xenografts were treated with 335-500 mu Ci (12.4-18.0 MBq) of Cu-67-2IT-BAT-Lym-1 with or without 48,000-144,000 IU of rIL-2 once or were treated b.i.d, for 5 days beginning simultaneously with Cu-67-2IT-BAT-Lym-1. Mouse weight, blood counts, and mortality were monitored to assess toxicity, and tumor size was measured to assess efficacy. In addition, groups of mice were sacrificed to assess the biodistribution of Cu-67-2IT- BAT-Lym-1 with and without rIL-2. RESULTS. In mice treated with 335 mu Ci of Cu-67-2IT-BAT-Lym-1 alone, 28% of tumors were cured. When 48,000 IU of rIL-2 were added, 50% were cured. The overall response rate was 50% for both regimens. In mice treated with 400 mu Ci of Cu-67- 2IT-BAT-Lym-1 alone, 42% responded, all of which were cured. When 38,000 IU of rIL-2 were added, 77% of tumors responded, and 38% were cured. Larger or multiple doses of rIL-2 did not result in additional therapeutic enhancement. The tumor uptake and radiation dose after Cu-67-2IT-BAT-Lym-1 were about two times greater when a single dose of rIL-2 was added: This may be the basis for enhanced therapeutic efficacy. Mortality was not altered for 335 mu Ci or 400 mu Ci doses of Cu-67-2IT-BAT-Lym-1 by rIL-2 nor were other toxicity parameters. Mortality was increased at 500 mu Ci by the addition of rIL-2. CONCLUSIONS. Cu-67-2IT-BAT-Lym-1 provided a therapeutic and frequently curative dose of radiation to tumored mice at tolerated doses. The therapeutic effectiveness of Cu-67-2IT-BAT-Lym-1 may have been enhanced by rIL-2. (C) 1997 American Cancer Society. SN 0008-543X PD DEC 15 PY 1997 VL 80 IS 12 SU S BP 2576 EP 2582 DI 10.1002/(SICI)1097-0142(19971215)80:12+<2576::AID-CNCR33>3.0.CO;2-7 UT WOS:000071035600033 PM 9406712 ER PT J AU Limoli, CL Kaplan, MI Corcoran, J Meyers, M Boothman, DA Morgan, WF AF Limoli, CL Kaplan, MI Corcoran, J Meyers, M Boothman, DA Morgan, WF TI Chromosomal instability and its relationship to other end points of genomic instability SO CANCER RESEARCH AB Chromosomal destabilization is one end point of the more general phenomenon of genomic instability. We previously established that chromosomal instability can manifest in clones derived from single progenitor cells several generations after X-irradiation. To understand the potential relationship between chromosomal destabilization and the other end points of genomic instability, we generated a series of chromosomally stable and unstable clones by exposure to X-rays, All clones were derived from the human-hamster hybrid line GM10115, which contains a single copy of human chromosome 4 in a background of 20-24 hamster chromosomes, These clones were then subjected to a series of assays to determine whether chromosomal instability is associated with a general "mutator phenotype" and whether it modulates other end points of genomic instability, Thus, we analyzed clones for sister chromatid exchange, delayed reproductive cell death, delayed mutation, mismatch repair, and delayed gene amplification, Statistical analyses performed on each group of chromosomally stable and unstable clones indicated that, although individual clones within each group were significantly different from unirradiated clones for many of the end points, there was no significant correlation between chromosomal instability and sister chromatid exchange, delayed mutation, and mismatch repair, Delayed gene amplification was found to be marginally correlated to chromosomal instability (P < 0.1), and delayed reproductive cell death (the persistent reduction in plating efficiency after irradiation) was found to be significantly correlated (P < 0.05). These correlations may be explained by chromosomal destabilization, which can mediate gene amplification and can result in cellular lethality. These data implicate multiple molecular and genetic pathways leading to different manifestations of genomic instability in GM10115 cells surviving exposure to DNA-damaging agents. SN 0008-5472 PD DEC 15 PY 1997 VL 57 IS 24 BP 5557 EP 5563 UT WOS:000070948600023 PM 9407967 ER PT J AU Murdoch, P Benzley, S Blacker, T Mitchell, SA AF Murdoch, P Benzley, S Blacker, T Mitchell, SA TI The spatial twist continuum: A connectivity based method for representing all-hexahedral finite element meshes SO FINITE ELEMENTS IN ANALYSIS AND DESIGN AB This paper introduces the spatial twist continuum (STC), a powerful extension of the dual of a hexahedral mesh. The STC captures the global connectivity constraints inherent in hexahedral meshing. We begin by describing the two-dimensional analog of the representation for quadrilateral meshes: The STC of a quadrilateral mesh is an arrangement of curves called chords. Chords pass through opposite quadrilateral edges and intersect at quadrilateral centroids. The power of the STC is displayed in the three-dimensional representation, where continuous surfaces called twist planes pass through layers of hexahedra. Pairs of twist planes intersect to form chords that pass through opposite faces of hexahedra. Triples of twist planes orthogonally intersect at the centroids of hexahedra. The continuity of the twist planes and chords, and how twist planes and chords twist through space, are the basis of the spatial twist continuum. (C) 1997 Elsevier Science B.V. SN 0168-874X PD DEC 15 PY 1997 VL 28 IS 2 BP 137 EP 149 DI 10.1016/S0168-874X(97)81956-7 UT WOS:000071025300004 ER PT J AU Albala, JS Thelen, MP Prange, C Fan, WF Christensen, M Thompson, LH Lennon, GG AF Albala, JS Thelen, MP Prange, C Fan, WF Christensen, M Thompson, LH Lennon, GG TI Identification of a novel human RAD51 homolog, RAD51B SO GENOMICS AB The highly conserved Saccharomyces cerevisiae RAD51 protein functions in both mitotic and meiotic homologous recombination and in double-strand break repair. Screening of the public cDNA sequence database for RAD51-like genes led to the identification of a partial sequence from a breast tissue library present in the I.M.A.G.E. (Integrated Molecular Analysis of Genes and their Expression) collection. An extended 1764-bp cDNA clone encoding an open reading frame of 350 amino acids was isolated. This clone showed significant amino acid identity with other human RAD51 homologs. The new homolog, named RAD51B, was mapped to human chromosome 14q23-q24.2 using a panel of human-hamster somatic cell hybrids and fluorescence in situ hybridization. Northern blot analysis demonstrated that RAD51B mRNA is widely expressed and most abundant in tissues active in recombination. Functions associated with known RAD51 homologs suggest a role for RAD51B in meiotic recombination and/or recombinational repair. (C) 1997 Academic Press. RI Thelen, Michael/C-6834-2008; Thelen, Michael/G-2032-2014 OI Thelen, Michael/0000-0002-2479-5480; Thelen, Michael/0000-0002-2479-5480 SN 0888-7543 PD DEC 15 PY 1997 VL 46 IS 3 BP 476 EP 479 DI 10.1006/geno.1997.5062 UT WOS:000071455600020 PM 9441753 ER PT J AU Boslough, MBE Gladstone, GR AF Boslough, MBE Gladstone, GR TI An impact plume model for atmospheric holes in the FUV dayglow SO GEOPHYSICAL RESEARCH LETTERS AB A transient decrease in FUV dayglow emission from a similar to 10(3) km(2) region of Earth's upper atmosphere is one expected outcome of the collision of a stony meteoroid as small as 50 cm in diameter. Computational models of the entry of projectiles between 210 and 21,000 kg predict the ejection of low-density plumes of air from the stratosphere and mesosphere at velocities of up to 5 km/s. The plumes reach an altitude of over 1000 km, displacing the atomic O-rich thermosphere, and replacing it with photoelectron-and O-poor air from beneath 80 km. The FUV dayglow is normally dominated by O emissions so the plume appears as a dark spot when viewed from above. FUV dayglow holes are reported at rates similar to 10(4)-10(6) larger than the impact flux of objects in the sie range modeled here, suggesting either 1) the observed rate is greatly overestimated, 2) there is an additional mechanism, or 3) much smaller impactors (which we have not modeled) can also generate FUV darkening plumes. SN 0094-8276 PD DEC 15 PY 1997 VL 24 IS 24 BP 3117 EP 3120 DI 10.1029/97GL53303 UT WOS:000071222700004 ER PT J AU Zuelsdorf, RS Strangeway, RJ Russell, CT Casler, C Christian, HJ Franz, RC AF Zuelsdorf, RS Strangeway, RJ Russell, CT Casler, C Christian, HJ Franz, RC TI Trans-ionospheric pulse pairs (TIPPs): Their geographic distributions and seasonal variations SO GEOPHYSICAL RESEARCH LETTERS AB Since November 1993 the Blackbeard instrument aboard the ALEXIS satellite has detected pairs of pulses in the VHF band, known as Trans-Ionospheric Pulse Pairs (TIPPs). These pulses exhibit dispersion consistent with a source of sub-ionospheric origin. As of January 1997 over 850 TIPPs have been detected. The source of these emissions still remains a mystery, although it is believed that TIPPs are in some way related to thunderstorms as such storms provide a strong sub-ionospheric source and produce radiation in the same frequencies observed by Blackbeard. In an attempt to establish this connection we compare the geographic occurrence of TIPPs to that of lightning flashes observed from space by the Optical Transient Detector (OTD) on the Microlab-1 spacecraft. TIPP data run from 2 November 1993 to 19 November 1996. OTD data run from 1 May 1995 to 30 November 1996. The geographical occurrence of TIPPs and that of lightning flashes is strongly correlated. TIPPs occur less frequently during the winter months and their region of production moves southward in the North American sector similar in behavior to lightning activity. OI Russell, Christopher/0000-0003-1639-8298 SN 0094-8276 PD DEC 15 PY 1997 VL 24 IS 24 BP 3165 EP 3168 DI 10.1029/97GL02949 UT WOS:000071222700016 ER PT J AU Jorgensen, AM Spence, HE Henderson, MG Reeves, GD Sugiura, M Kamei, T AF Jorgensen, AM Spence, HE Henderson, MG Reeves, GD Sugiura, M Kamei, T TI Global energetic neutral atom (ENA) measurements and their association with the Dst index SO GEOPHYSICAL RESEARCH LETTERS AB We present a new global magnetospheric index that measures the intensity of the Earth's ring current through energetic neutral atoms (ENAs). We have named it the Global Energetic Neutral Index (GENI), and it is derived from ENA measurements obtained by the Imaging Proton Spectrometer (IFS), part of the Comprehensive Energetic Particle and Pitch Angle Distribution (CEPPAD) experiment on the POLAR satellite. GENI provides a simple orbit-independent global sum of ENAs measured with IFS. Actual ENA measurements for the same magnetospheric state look different when seen from different points in the POLAR orbit. In addition, the instrument is sensitive to weak ion populations in the polar cap, as well as cosmic rays. We have devised a method for removing the effects of cosmic rays and weak ion fluxes, in order to produce an image of "pure" ENA counts. We then devised a method of normalizing the ENA measurements to remove the orbital bias effect. The normalized data were then used to produce the GENI. We show, both experimentally and theoretically the approximate proportionality between the GENI and the Dst index. In addition we discuss possible implications of this relation. Owing to the high sensitivity of IFS to ENAs, we can use these data to explore the ENA/Dst relationship not only during all phases of moderate geomagnetic storms, but also during quiescent ring current periods. RI Spence, Harlan/A-1942-2011; Reeves, Geoffrey/E-8101-2011; Henderson, Michael/A-3948-2011; OI Reeves, Geoffrey/0000-0002-7985-8098; Henderson, Michael/0000-0003-4975-9029; Spence, Harlan/0000-0002-2526-2205 SN 0094-8276 PD DEC 15 PY 1997 VL 24 IS 24 BP 3173 EP 3176 DI 10.1029/97GL03095 UT WOS:000071222700018 ER PT J AU D'Anna, G Benoit, W Vinokur, VM AF D'Anna, G Benoit, W Vinokur, VM TI Internal friction and dislocation collective pinning in disordered quenched solid solutions SO JOURNAL OF APPLIED PHYSICS AB We introduce the collective pinning of dislocations in disordered quenched solid solutions and calculate the macroscopic mechanical response to a small de or ac applied stress. This work is a generalization of the Granato-Lucke string model, able to describe self-consistently short and long range dislocation motion. Under de applied stress the long distance dislocation creep has at the microscopic level avalanche features, which result in a macroscopic nonlinear "glassy" velocity-stress characteristic. Under ac conditions the model predicts, in addition to the anelastic internal friction relaxation in the high frequency regime, a linear internal friction background which remains amplitude-independent down to a crossover frequency to a strongly nonlinear internal friction regime. (C) 1997 American Institute of Physics. SN 0021-8979 PD DEC 15 PY 1997 VL 82 IS 12 BP 5983 EP 5990 DI 10.1063/1.366463 UT WOS:000071043400013 ER PT J AU Falkenstein, Z Coogan, JJ AF Falkenstein, Z Coogan, JJ TI Photoresist etching with dielectric barrier discharges in oxygen SO JOURNAL OF APPLIED PHYSICS AB This article presents results on the surface etching of a Novolak-type polymer (Shipley, SPR2) on Si wafers using dielectric barrier discharges in oxygen at high pressures and room temperature. The etching depth is measured by mechanical profilometry as a function of gap spacing and gas pressure. Figures of merit are generated allowing comparison with conventional plasma surface treatment, as etch rate per power density coupled onto the sample surface (nm J(-1) cm(2)), or coupled into the gas volume (nm J(-1) cm(3)). Energy-density specific etch rates were measured as a function of the gap spacing (d) and the total oxygen gas pressure (p), as well as a function of the product of pd in the gas pressure range of 50-1500 mbar and of the gap spacing range of 1-20 mm. At a constant gap spacing and pressure, the removal rate is a linear function of the applied power density. The highest achieved etching rate per surface energy density is 2.2 nm J(-1) cm(2) at 730 mbar and 1 mm (0.2 nm J(-1) cm(3)) and the highest etching rate per volumetric energy density is 0.85 nm J(-1) cm(3) at 290 mbar and 7 mm (0.87 nm J(-1) cm(2)). The surface of the etched photoresist is characterized using mechanical profilometry and scanning electron microscopy. The results obtained in this work suggest that dielectric barrier discharges can be an efficient, alternative plasma source for general surface processing, because they can provide nonthermal discharges also near atmospheric pressures and thereby eliminate the need of costly vacuum systems. (C) 1997 American Institute of Physics. SN 0021-8979 PD DEC 15 PY 1997 VL 82 IS 12 BP 6273 EP 6280 DI 10.1063/1.366514 UT WOS:000071043400058 ER PT J AU Davids, PS Campbell, IH Smith, DL AF Davids, PS Campbell, IH Smith, DL TI Device model for single carrier organic diodes SO JOURNAL OF APPLIED PHYSICS AB We present a unified device model for single layer organic light emitting diodes (LEDs) which includes charge injection, transport, and space charge effects in the organic material. The model can describe both injection limited and space charge limited current flow and the transition between them. We specifically considered cases in which the energy barrier to injection of electrons is much larger than that for holes so that holes dominate the current flow in the device. Charge injection into the organic material occurs by thermionic emission and by tunneling. For Schottky energy barriers less than about 0.3-0.4 eV, for typical organic LED device parameters, the current flow is space charge limited and the electric field in the structure is highly nonuniform. For larger energy barriers the current flow is injection limited. In the injection limited regime, the net injected charge is relatively small, the electric field is nearly uniform, and space charge effects are not important. At smaller bias in the injection limited regime, thermionic emission is-the dominant injection mechanism. For this case the thermionic emission injection current and a backward flowing interface recombination current, which is the time reversed process of thermionic emission, combine to establish a quasi-equilibrium carrier density. The quasi-equilibrium density is bias dependent because of image force lowering of the injection barrier. The net device current is determined by the drift of these carriers in the nearly constant electric field. The net device current is much smaller than either the thermionic emission or interface recombination current which nearly cancel. At higher bias, injection is dominated by tunneling. The bias at which tunneling exceeds thermionic emission depends on the size of the Schottky energy barrier. When tunneling is the dominant injection mechanism, a combination of tunneling injection current and the backflowing interface recombination current combine to establish the carrier density. We compare the model results with experimental measurements on devices fabricated using the electroluminescent conjugated polymer poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] which by changing the contacts can show either injection limited behavior or space charge limited behavior. (C) 1997 American Institute of Physics. RI Davids, Paul/D-1550-2010 SN 0021-8979 PD DEC 15 PY 1997 VL 82 IS 12 BP 6319 EP 6325 DI 10.1063/1.366522 UT WOS:000071043400065 ER PT J AU Litorja, M Ruscic, B AF Litorja, M Ruscic, B TI Evidence of rotational autoionization in the threshold region of the photoionization spectrum of CH3 SO JOURNAL OF CHEMICAL PHYSICS AB The photoionization spectrum of the threshold region of CH3 equilibrated at room temperature has been recorded and compared to the zero electron kinetic energy (ZEKE) spectrum of Blush et al. [J. Chem, Phys, 98, 3557 (1993)]. The ionization onset region is at similar to 70 cm(-1) higher energy than previous high-temperature photoionization work [Chupka and Lifshitz, J. Chem, Phys. 48, 1109 (1967)], but still similar to 34 cm(-1) lower than that implied by invoking only direct ionization. The residual discrepancy can be accounted for by including fully allowed quadrupole-induced and partially allowed dipole-induced rotational autoionization, thus making the observed onset completely congruous with the ZEKE ionization potential. In addition, the fragment appearance potential of CH3+ from CH4 was redetermined by accurate fitting as AP(0)(CH3+/CH4) = 14.322+/-0.003 eV. With the very precise ZEKE ionization potential, this yields the best current value for the bond dissociation energy in methane, D-0(H-CH3)=4.484+/-0.003 eV =103.40+/-0.07 kcal/mol (104.96+/-0.07 kcal/mol at 298 K). (C) 1997 American Institute of Physics. [S0021-9606(97)03247-9]. RI Ruscic, Branko/A-8716-2008 OI Ruscic, Branko/0000-0002-4372-6990 SN 0021-9606 PD DEC 15 PY 1997 VL 107 IS 23 BP 9852 EP 9856 DI 10.1063/1.475282 UT WOS:A1997YK98200016 ER PT J AU Baer, R HeadGordon, M AF Baer, R HeadGordon, M TI Chebyshev expansion methods for electronic structure calculations on large molecular systems SO JOURNAL OF CHEMICAL PHYSICS AB The Chebyshev polynomial expansion of the one electron density matrix (DM) in electronic structure calculations is studied, extended in several ways, and benchmark demonstrations are applied to large saturated hydrocarbon systems,using a tight-binding method. We describe a flexible tree code for the sparse numerical algebra. We present an efficient method to locate the chemical potential. A reverse summation of the expansion is found to significantly improve numerical speed. We also discuss the use of Chebyshev expansions as analytical tools to estimate the range and sparsity of the DM and the overlap matrix. Using these analytical estimates, a comparison with other linear scaling algorithms and their applicability to various systems is considered. (C) 1997 American Institute of Physics. [S0021-9606(97)03947-0]. SN 0021-9606 EI 1089-7690 PD DEC 15 PY 1997 VL 107 IS 23 BP 10003 EP 10013 DI 10.1063/1.474158 UT WOS:A1997YK98200035 ER PT J AU Challacombe, M White, C HeadGordon, M AF Challacombe, M White, C HeadGordon, M TI Periodic boundary conditions and the fast multipole method SO JOURNAL OF CHEMICAL PHYSICS AB The seminal work of Nijboer and De Wette [Physica 23, 309 (1957)] enables the calculation of lattice sums of spherical harmonics, but has long been overlooked. In this article, their central result is recast in a simplified form suitable for modern multipole algorithms that employ the solid harmonics. This formulation makes possible the imposition of periodic boundary conditions within modern versions of the fast multipole method, and other fast N-body methods. The distinction between the extrinsic values obtained with the lattice sums M of the multipole interaction tensors, and the intrinsic values associated with Taylor's expansion of the Ewald formulas, is made. The central constants, M, are computed to 32 digit accuracy using extended precision arithmetic. Timings and corresponding errors obtained with a periodic version of the fast multipole method are presented for particle numbers spanning [10(3),10(6)], and a range of expansion orders. A qualitative comparison is made between the present implementation, other periodic versions of the fast multipole method, and fast Ewald methods. (C) 1997 American Institute of Physics. [S0021-9606(97)02947-4]. RI White, Christopher/B-7390-2009 SN 0021-9606 PD DEC 15 PY 1997 VL 107 IS 23 BP 10131 EP 10140 DI 10.1063/1.474150 UT WOS:A1997YK98200048 ER PT J AU Gupta, SA Cochran, HD Cummings, PT AF Gupta, SA Cochran, HD Cummings, PT TI Shear behavior of squalane and tetracosane under extreme confinement .1. Model, simulation method, and interfacial slip SO JOURNAL OF CHEMICAL PHYSICS AB In this three part study, nonequilibrium molecular dynamics simulation of the rheology of confined films is used to explore the microscopic properties and response of model lubricants under shear. The rheological behavior of two alkanes that differ in molecular structural complexity is examined: tetracosane (C24H50), which is a linear alkane, and squalane (C30H62), which has six symmetrically placed methyl branches along a 24 carbon backbone. The model lubricants are confined between model walls that have short chains tethered to them, thus screening the wall details. Shear flow is generated by moving the walls at constant velocity, and various properties are calculated after attainment of steady state, Heat generated by viscous dissipation is removed by thermostatting the first two atoms of the tethered molecules at 300 K, which allows a temperature profile to develop across the width of the lubricant layer, This paper details the molecular model and simulation method, and examines interfacial slip al the interface between the tethered chains and the fluid alkane, The effects of various parameters on the slip behavior are presented. Two subsequent papers respectively address the structural features of these liquid alkanes under shear flow: and compare the viscosities from independent calculations of the bulk and confined fluids. (C) 1997 American Institute of Physics. [S0021-9606(97)50847-6]. RI Cummings, Peter/B-8762-2013 OI Cummings, Peter/0000-0002-9766-2216 SN 0021-9606 PD DEC 15 PY 1997 VL 107 IS 23 BP 10316 EP 10326 DI 10.1063/1.474171 UT WOS:A1997YK98200067 ER PT J AU Gupta, SA Cochran, HD Cummings, PT AF Gupta, SA Cochran, HD Cummings, PT TI Shear behavior of squalane and tetracosane under extreme confinement .2. Confined film structure SO JOURNAL OF CHEMICAL PHYSICS AB This paper focuses on the structural characteristics of confined squalane and tetracosane under shear flow conditions. Nonequilibrium molecular dynamics simulation is used to explore the rheology of these model lubricants. A preceding paper describes the molecular model and the simulation method, and examines interfacial slip. The lubricants are confined between model walls that have short chains tethered to them, thus screening the wall details. In this paper we examine the density profiles and chain conformations of the alkanes under shear flow conditions. Our results indicate a profound influence of the walls on the fluid structure. In particular, when the wall spacing is close to an integral multiple of the molecular diameter, tetracosane shows the formation of distinct layers with the molecules being in a fully extended state. This behavior is not observed for squalane. Under shear flow conditions the molecules tend to orient parallel to the walls, as would be expected, with a greater degree of orientation (a) close to the walls, (b) at the positions of local density maxima, and(c) at higher strain rates. (C) 1997 American Institute of Physics. [S0021-9606(97)50947-0]. RI Cummings, Peter/B-8762-2013 OI Cummings, Peter/0000-0002-9766-2216 SN 0021-9606 PD DEC 15 PY 1997 VL 107 IS 23 BP 10327 EP 10334 DI 10.1063/1.474172 UT WOS:A1997YK98200068 ER PT J AU Gupta, SA Cochran, HD Cummings, PT AF Gupta, SA Cochran, HD Cummings, PT TI Shear behavior of squalane and tetracosane under extreme confinement .3. Effect of confinement on viscosity SO JOURNAL OF CHEMICAL PHYSICS AB This study uses nonequilibrium molecular dynamics simulation to explore the rheology of confined liquid alkanes. Two alkanes that differ in molecular structural complexity are examined: tetracosane (C24H50), which is a linear alkane, and squalane (C30H62), which has six symmetrically placed methyl branches along a 24 carbon backbone. These model lubricants are confined between model walls that have short chains tethered to them, thus screening the wall details. This paper, the third of a three part series, compares the viscosities of the confined fluids to those of the bulk fluids. The alkanes are described by a well-documented potential model that has been shown to reproduce bulk experimental viscosity and phase equilibria measurements. Details of the simulation method, and structural information can be found in the preceding two papers of this series. The measured strain rates in these simulations range between 10(8) and 10(11) s(-1), which is typical of a number of practical applications. The confined fluids undergo extensive shear thinning, showing a power-law behavior. Comparison of results for the confined fluid to those for the bulk fluid reveal that, for the conditions examined, there is no difference between the bulk and confined viscosities for these alkanes. This observation is in contrast to experimental results at much lower strain rates (10-10(5) s(-1)), which indicate the viscosities of the confined fluid to be much larger than the bulk viscosities. In making the comparison, we have carefully accounted for slip at the wall and have performed simulations of the bulk fluid at the same conditions of strain rate, temperature, and pressure as for the corresponding confined fluid. The viscosity is found to be independent of the wall spacing. The calculated power-law exponents are similar to experimentally observed values. We also note that the exponent increases with increasing density of the fluid. (C) 1997 American Institute of Physics. [S0021-9606(97)51047-6]. RI Cummings, Peter/B-8762-2013 OI Cummings, Peter/0000-0002-9766-2216 SN 0021-9606 PD DEC 15 PY 1997 VL 107 IS 23 BP 10335 EP 10343 DI 10.1063/1.474173 UT WOS:A1997YK98200069 ER PT J AU Kearl, PM AF Kearl, PM TI Observations of particle movement in a monitoring well using the colloidal borescope SO JOURNAL OF HYDROLOGY AB The colloidal borescope consists of a set of lenses and miniature video cameras capable of observing natural particles in monitoring wells. Based on field observations of these particles, it appears possible to measure in situ groundwater velocity in a well bore. Field observations have shown that directional measurements using the colloidal borescope are generally in good agreement with expected flow directions. However, the magnitude of Bow velocity is higher compared with values based on conventional test methods. High relative Bow velocities, even after correction factors have been applied to compensate for well bore effects, are believed to be due to preferential Bow zones in the surrounding aquifer. Low flow zones exhibit swirling multidirectional flow that does not allow for a linear velocity measurement. Consequently, groundwater Bow velocities measured by the colloidal borescope in heterogeneous aquifers will be biased toward the maximum velocity values present in the aquifer. A series of laboratory experiments was conducted to assess the reliability of the instrument. Based on this work, a seepage velocity correction factor (<(alpha)over bar>) of 1-4 was found for quantifying groundwater seepage velocity in the adjacent aquifer from observations in a well bore. Laboratory measurements also indicate that preferential flow in the surrounding aquifer dominates flow in the well. Results of this work suggest the possibility of quantifying higher-flow velocities associated with preferential flow zones in the subsurface. (C) 1997 Elsevier Science B.V. SN 0022-1694 PD DEC 15 PY 1997 VL 200 IS 1-4 BP 323 EP 344 DI 10.1016/S0022-1694(97)00026-7 UT WOS:000071050300019 ER PT J AU Wofsy, C Torigoe, C Kent, UM Metzger, H Goldstein, B AF Wofsy, C Torigoe, C Kent, UM Metzger, H Goldstein, B TI Exploiting the difference between intrinsic and extrinsic kinases: Implications for regulation of signaling by immunoreceptors SO JOURNAL OF IMMUNOLOGY AB When receptors must interact with an extrinsic kinase to initiate signaling, the kinase can play a regulatory role that is not available to intrinsic receptor kinases. Whether control is exercised at this level depends critically on the amount of kinase available to the receptors and on the potential for redistribution of the kinase during signaling. This study demonstrates that the high affinity receptor for IgE (Fc epsilon RI) on rat basophilic leukemia cells is regulated by its initiating kinase. We present a mathematical model that allows for the reversible recruitment of extrinsic kinases to phosphorylated immunoreceptor tyrosine-based activation motifs. By comparing model predictions to experimental time courses of phosphorylation, we infer that Lyn is limiting, that redistribution occurs after receptors are aggregated, and that the redistribution makes the relationship between tyrosine phosphorylation and receptor aggregation nonlinear. SN 0022-1767 PD DEC 15 PY 1997 VL 159 IS 12 BP 5984 EP 5992 UT WOS:000071914900029 PM 9550396 ER PT J AU Streckert, HH Norton, KP Katz, JD Freim, JO AF Streckert, HH Norton, KP Katz, JD Freim, JO TI Microwave densification of electrophoretically infiltrated silicon carbide composite SO JOURNAL OF MATERIALS SCIENCE AB A new method to fabricate SiC composites by microwave heating SiC preforms is described. Preforms were produced by electrophoretically infiltrating SiC fibre (Nicalon) preforms with SiC powder. Samples were heated to 1600 degrees C in a matter of minutes and held at temperature for 5 min to minimize fibre degradation. To achieve densification, heated preforms required the application of a uniform load. Bulk densities increased from similar to 0.8 gcm(-3) for the as-infiltrated preforms to over 1.9 gcm(-3) for microwave-heated samples with a small applied load of similar to 13 kPa. Microstructural analysis revealed the presence of some pores and cracks in the matrix; however, large areas of dense SiC matrix material are apparent. SN 0022-2461 PD DEC 15 PY 1997 VL 32 IS 24 BP 6429 EP 6433 DI 10.1023/A:1018634521493 UT WOS:A1997YK05700003 ER PT J AU Yang, N Guthrie, SE Ho, S Lavernia, EJ AF Yang, N Guthrie, SE Ho, S Lavernia, EJ TI Solidification behaviour of Pd-Rh droplets during spray atomization SO JOURNAL OF MATERIALS SCIENCE AB Solidification microstructure in spray-atomized Pd-10 wt % Rh powders using high-pressure gas atomization was studied. The solidification cooling rate and the solidification front velocity were investigated using a transient heat-transfer finite element method. Two different atomization gases, nitrogen and helium, were considered in the modelling studies. On the basis of the results obtained, it was found that gas atomization using helium gas led to solidification cooling rates and solidification front velocities which were two times higher than those obtained using nitrogen gas. Moreover, the cooling rate and the solidification front velocity increased with decreasing powder size for both types of atomization gas. The numerically estimated solidification front velocity using finite element analysis for nitrogen gas atomization was found to be smaller than the analytically determined absolute stability velocity that is required to promote a segregation-free microstructure. This was noted to be consistent with the segregated microstructure that was experimentally observed in nitrogen gas atomized powders. In the case of helium gas atomization, however, the increased cooling rate and solidification front velocity are anticipated to promote the formation of a segregation-free microstructure in the gas-atomized powders. SN 0022-2461 PD DEC 15 PY 1997 VL 32 IS 24 BP 6589 EP 6594 DI 10.1023/A:1018631815558 UT WOS:A1997YK05700026 ER PT J AU Shield, JE Campbell, JA Sordelet, DJ AF Shield, JE Campbell, JA Sordelet, DJ TI Mechanical properties of Al-Cu-Fe-based quasicrystalline coatings SO JOURNAL OF MATERIALS SCIENCE LETTERS SN 0261-8028 PD DEC 15 PY 1997 VL 16 IS 24 BP 2019 EP 2021 DI 10.1023/A:1018544313643 UT WOS:000071148600016 ER PT J AU Hasse, RD Severson, MW Szczesniak, MM Chalasinski, G Cieplak, P Kendall, RA Cybulski, SM AF Hasse, RD Severson, MW Szczesniak, MM Chalasinski, G Cieplak, P Kendall, RA Cybulski, SM TI Ar-C2H2: a challenging system for ab initio calculations SO JOURNAL OF MOLECULAR STRUCTURE AB The Ar-HCCH interaction is investigated by the supermolecular Moller-Plesset perturbation theory and coupled-cluster theory in conjunction with the perturbation theory of intermolecular forces. The interaction energy in this cluster is dissected into the fundamental components such as exchange, induction, and dispersion, and the anisotropy of the overall surface is analysed in terms of the angular behaviors of these components. The shape of the PES of Ar-HCCH is very sensitive to the level of ab initio theory. The coupled-cluster approach which included the single, double, and approximate triple excitations combined with the aug-cc-pvtz basis set supplemented by bond functions was necessary to obtain the best estimates of D-e (within +/- 5% error) for two minima: the global one for a skew T-configuration (118 cm(-1)), and a secondary one for the collinear arrangement (115 cm(-1)). The PES generated at a lower level of calculation was used in diffusion quantum Monte Carlo (DMC) calculations of the ground and first excited bending vibrational state of the cluster. The expectation values of the coordinates and rotational constants are provided for the ground state. DMC calculations are relatively unsensitive to the details of the PES. The nature and decomposition of three-body interactions in the related cluster Ar-2-HCCH were also investigated. (C) 1997 Elsevier Science B.V. SN 0022-2860 PD DEC 15 PY 1997 VL 437 SI SI BP 387 EP 400 DI 10.1016/S0022-2860(97)00132-4 UT WOS:000071435500036 ER PT J AU Dandoloff, R Saxena, A AF Dandoloff, R Saxena, A TI Interaction induced deformation of two coupled XY spin chains SO JOURNAL OF PHYSICS-CONDENSED MATTER AB We study two coupled XY spin chains in the continuum limit with ferromagnetic interaction both along and between the chains. We find 2 pi twist soliton solutions for the difference in orientation angle of the spins along the chains. If we allow the chains to be elastic, they will deform (move apart) in the region of the soliton in order to reduce magnetic energy. The extent of deformation is a result of a balance between the gain in magnetic energy and elastic energy cost. We also generalize these results to the case of a soliton lattice. SN 0953-8984 PD DEC 15 PY 1997 VL 9 IS 50 BP L667 EP L670 DI 10.1088/0953-8984/9/50/004 UT WOS:000071070100004 ER PT J AU Fu, Q Liou, KN Cribb, MC Charlock, TP Grossman, A AF Fu, Q Liou, KN Cribb, MC Charlock, TP Grossman, A TI Multiple scattering parameterization in thermal infrared radiative transfer SO JOURNAL OF THE ATMOSPHERIC SCIENCES AB A systematic formulation of various radiative transfer parameterizations is presented, including the absorption approximation (AA), delta-two-stream approximation (D2S), delta-four-stream approximation (D4S), and delta-two- and four-stream combination approximation (D2/4S), in a consistent manner for thermal infrared flux calculations. The D2/4S scheme uses a source function from the delta-two-stream approximation and evaluates intensities in the four-stream directions. A wide range of accuracy checks for monochromatic emissivity of a homogeneous layer and broadband heating rates and fluxes in nonhomogeneous atmospheres is performed with respect to the "exact" results computed from the delta-128-stream scheme for radiative transfer. The computer time required for the calculations using different radiative transfer parameterizations is compared. The results pertaining to the accuracy and efficiency of various radiative transfer approximations can be utilized to decide which approximate method is most appropriate for a particular application. In view of its overall high accuracy and computational economy, it is recommended that the D2/4S scheme is well suited for GCM and climate modeling applications. RI Cribb, Maureen/K-1341-2013 OI Cribb, Maureen/0000-0002-9745-3676 SN 0022-4928 PD DEC 15 PY 1997 VL 54 IS 24 BP 2799 EP 2812 DI 10.1175/1520-0469(1997)054<2799:MSPITI>2.0.CO;2 UT WOS:000071211200002 ER PT J AU Govindasamy, B Garner, ST AF Govindasamy, B Garner, ST TI The equilibration of short baroclinic waves SO JOURNAL OF THE ATMOSPHERIC SCIENCES AB The life cycles of short baroclinic waves are investigated with the intention of completing a simple classification of nonlinear equilibration scenarios. Shea waves become important in moist environments as latent heating reduces the scale of maximum baroclinic instability. Long-wave life cycles (wavenumber 6) were previously found to depend on details of the low-level momentum fluxes established during the earliest stages of development. These fluxes also serve as a focal point for the present study. For a realistic, zonally symmetric jet on the sphere, the normal mode life cycle of a short wave (wavenumber 8) under both dry and moist conditions is described. Latent heating intensifies the low pressure system and frontal zones but does not alter the broader details of the life cycle. The normal modes have predominantly equatorward momentum fluxes, in contrast to the mainly poleward momentum fluxes of long waves. The short waves are more meridionally confined. The equatorward momentum fluxes direct the waves toward cyclonic breaking. The feedback with the zonal mean wind, the so-called barotropic governor, is less effective than in the standard long-wave life cycle, which ends in anticyclonic breaking. However, in contrast to long-wave life cycles that are "engineered" to produce equatorward momentum fluxes, relatively little potential vorticity and surface temperature anomaly roil up into isolated vortices. Therefore, the short wave undergoes protracted barotropic decay leading to complete zonalization. Short waves also have a brief period of baroclinic decay due to cold advection over the surface cyclones. Eliassen-Palm cross sections for the short-wave life cycles show the usual combination of upward and meridional propagation of wave activity. However, the meridional propagation is mainly toward the pole and there is a consequent zonal-mean deceleration at high latitudes. These details are included in the proposed classification of equilibration scenarios. SN 0022-4928 PD DEC 15 PY 1997 VL 54 IS 24 BP 2850 EP 2871 DI 10.1175/1520-0469(1997)054<2850:TEOSBW>2.0.CO;2 UT WOS:000071211200005 ER PT J AU Liu, Y Russell, TP Samant, MG Stohr, J Brown, HR Cossy-Favre, A Diaz, J AF Liu, Y Russell, TP Samant, MG Stohr, J Brown, HR Cossy-Favre, A Diaz, J TI Surface relaxations in polymers SO MACROMOLECULES AB Near-edge X-ray absorption line structure, NEXAFS, spectroscopy was used to investigate the relaxations of polystyrene, a typical amorphous polymer, near a free surface after the imposition of a small deformation. Using synchrotron radiation, the NEXAFS dichroic ratio was determined for both the Auger and total electron yield processes as a function of temperature to determine the orientation of the polymer in the first 1 and 10 nm from the free surface, respectively. Complete relaxation of the polymer was not seen for temperatures less than the bulk glass transition temperature. No evidence of enhanced mobility at the free surface was found. A planar relaxation of the polymer was found in, the first nanometer from the free surface, whereas in the first 10 nm, the dominant relaxation was normal to the surface. RI Diaz, Javier/F-2381-2016 SN 0024-9297 PD DEC 15 PY 1997 VL 30 IS 25 BP 7768 EP 7771 DI 10.1021/ma970869a UT WOS:000071057600018 ER PT J AU Mirkarimi, PB McCarty, KF Medlin, DL AF Mirkarimi, PB McCarty, KF Medlin, DL TI Review of advances in cubic boron nitride film synthesis SO MATERIALS SCIENCE & ENGINEERING R-REPORTS AB Cubic boron nitride (cBN) has a number of highly desirable mechanical, thermal, electrical, and optical properties. Because of this, there has been an extensive worldwide effort to synthesize thin films of cBN. Film synthesis is difficult in that without significant levels of ion bombardment during growth, only sp2-bonded BN forms, not sp3-bonded cBN. Recently there has been considerable progress in improving the deposition techniques and cBN film quality. In addition, progress has been made in understanding how energetic deposition conditions can lead to cBN formation. However, unanswered questions remain and process improvements are still needed. In this paper we critically and comprehensively review recent developments in cBN film synthesis and characterization. First, the structures and stability of the BN phases and characterization techniques are described. Next, the key experimental parameters controlling cBN film formation and synthesis techniques are discussed. Following a review of microstructure, the proposed mechanisms of cBN formation and the observed mechanical and electrical properties of cBN films are analyzed. We conclude by highlighting the current impediments to the practical realization of cBN-film technology. (C) 1997 Published by Elsevier Science S.A. RI McCarty, Kevin/F-9368-2012 OI McCarty, Kevin/0000-0002-8601-079X SN 0927-796X PD DEC 15 PY 1997 VL 21 IS 2 BP 47 EP 100 DI 10.1016/S0927-796X(97)00009-0 UT WOS:000071716500001 ER PT J AU Moser, MJ Holley, WR Chatterjee, A Mian, IS AF Moser, MJ Holley, WR Chatterjee, A Mian, IS TI The proofreading domain of Escherichia coli DNA polymerase I and other DNA and/or RNA exonuclease domains SO NUCLEIC ACIDS RESEARCH AB Prior sequence analysis studies have suggested that bacterial ribonuclease (RNase) Ds comprise a complete domain that is found also in Homo sapiens polymyositis-scleroderma overlap syndrome 100 kDa autoantigen and Werner syndrome protein. This RNase D 3'-->5' exoribonuclease domain was predicted to have a structure and mechanism of action similar to the 3'-->5' exodeoxyibonuclease (proofreading) domain of DNA polymerases. Here, hidden Markov model (HMM) and phylogenetic studies have been used to identify and characterise other sequences that may possess this exonuclease domain. Results indicate that it is also present in the RNase T family; Borrelia burgdorferi P93 protein, an immunodominant antigen in Lyme disease; bacteriophage T4 dexA and Escherichia coli exonuclease I, processive 3'-->5' exodeoxyribonucleases that degrade single-stranded DNA; Bacillus subtilis dinG, a probable helicase involved in DNA repair and possibly replication, and peptide synthase 1; Saccharomyces cerevisiae Pab1p-dependent poly(A) nuclease PAN2 subunit, required for shortening mRNA poly(A) tails; Caenorhabditis elegans and Mus musculus CAF1, transcription factor CCR4-associated factor 1; Xenopus laevis XPMC2, prevention of mitotic catastrophe in fission yeast; Drosophila melanogaster egalitarian, oocyte specification and axis determination, and exuperantia, establishment of oocyte polarity; H.sapiens HEM45, expressed in tumour cell lines and uterus and regulated by oestrogen; and 31 open reading frames including one in Methanococcus jannaschii. Examination of a multiple sequence alignment and two three-dimensional structures of proofreading domains has allowed definition of the core sequence, structural and functional elements of this exonuclease domain. SN 0305-1048 EI 1362-4962 PD DEC 15 PY 1997 VL 25 IS 24 BP 5110 EP 5118 DI 10.1093/nar/25.24.5110 UT WOS:000071498400036 PM 9396823 ER PT J AU Lambert, MA Rodrigue, GH Hewett, DW AF Lambert, MA Rodrigue, GH Hewett, DW TI A parallel DSDADI method for solution of the steady state diffusion equation SO PARALLEL COMPUTING AB A parallel diagonally scaled dynamic alternating-direction-implicit (DSDADI) method is shown to be an effective algorithm for solving the 2D and 3D steady-state diffusion equation on large uniform Cartesian grids. Empirical evidence from the parallel solution of large gridsize problems suggests that the computational work done by DSDADI to converge over an N-d grid with continuous diffusivity is of lower order than O(Nd+alpha) for any fixed alpha > 0. This is in contrast to the method of diagonally scaled conjugate gradients (DSCG), for which the computational work necessary for convergence is O(Nd+1). Furthermore, the combination of diagonal scaling, spatial domain decomposition (SDD), and distributed tridiagonal system solution gives the DSDADI algorithm reasonable scalability on distributed-memory multiprocessors such as the GRAY T3D. Finally, an approximate parallel tridiagonal system solver with diminished interprocessor communication exhibits additional utility for DSDADI. (C) 1997 Published by Elsevier Science B.V. SN 0167-8191 PD DEC 15 PY 1997 VL 23 IS 13 BP 2041 EP 2065 DI 10.1016/S0167-8191(97)00065-3 UT WOS:000071402700010 ER PT J AU Marinescu, DC Quinn, JJ Sitko, P Yi, KS AF Marinescu, DC Quinn, JJ Sitko, P Yi, KS TI Composite fermions and the half-filled state SO PHYSICAL REVIEW B AB Under appropriate conditions electron-hole symmetry should apply to a partially filled Landau level of a two-dimensional electron gas. This suggests that the application of Jain's composite fermion (CF) picture to either electrons or holes should lead to equivalent results. Surprisingly, for a system of N-e electrons on a Haldane sphere, this is not true for three values of the Landau level degeneracy 2S + 1. When N-e - 1 less than or equal to S less than or equal to N-e. the sum of the electron filling factor nu and the hole filling factor ILL, as determined from Jain's picture, is smaller than unity. Because of this, use of the relation nu = 1 - mu can lead to "twin" or "alias" states having different values of nu for the same N-e and 2S+1. One example is the "half-filled" state. It is determined by requiring the effective (mean-held) flux 2S* "seen" by one CF to vanish. Different results are obtained when S-e* = S-e - (N-e - 1) and S-h* = S - (N-h - 1) are set equal to zero. The same problem arises in the CF hierarchy picture when the number of quasielectrons n(QE) is related to the effective flux 2S* by 2(n(QE) - 1)less than or equal to 2S*less than or equal to 2n(QE). SN 1098-0121 PD DEC 15 PY 1997 VL 56 IS 23 BP 14941 EP 14943 DI 10.1103/PhysRevB.56.14941 UT WOS:000071043700019 ER PT J AU Sales, BC Mandrus, D Chakoumakos, BC Keppens, V Thompson, JR AF Sales, BC Mandrus, D Chakoumakos, BC Keppens, V Thompson, JR TI Filled skutterudite antimonides: Electron crystals and phonon glasses SO PHYSICAL REVIEW B AB Crystallographic data, electrical and thermal transport measurements, and magnetic susceptibility values are reported for several compounds and alloys with the filled skutterudite structure, R1-yFe4-xCoxSb12 (R = La, Ce. or Th: 0 < y < 1; x = 0, 1). Room-temperature velocity of sound data is also reported. These materials are of interest because of their potential in thermoelectric power generation and refrigeration applications. The trans port properties of both filled and unfilled skutterudite compound's are analyzed using standard semiconductor transport models. Filled skutterudite antimonides appear to be a good approximation of an idealized solid with the good electrical transport properties of a crystal but the poor heat conduction characteristics of a glass. The incoherent rattling of the weakly bound rare-earth atoms in these materials lowers the thermal conductivity at room temperature to values comparable to that of vitreous silica. Relative to the analogous unfilled compounds, the filled skutterudites exhibit larger effective masses and smaller mobilities. Good overall electrical transport is maintained, however, as evidenced by values for the figure of merit (ZT) greater than 1 at elevated temperatures (700 - 1000 K). Above room temperature, there is very little difference in the electrical and thermal transport behavior between the La and Ce filled compounds. The effects of the hybridization caused by the proximity of the Ce 4f level to the Fermi energy, however, are evident at temperatures below 300 K. RI Mandrus, David/H-3090-2014; Chakoumakos, Bryan/A-5601-2016 OI Chakoumakos, Bryan/0000-0002-7870-6543 SN 1098-0121 PD DEC 15 PY 1997 VL 56 IS 23 BP 15081 EP 15089 DI 10.1103/PhysRevB.56.15081 UT WOS:000071043700038 ER PT J AU Lidorikis, E Busch, K Li, QM Chan, CT Soukoulis, CM AF Lidorikis, E Busch, K Li, QM Chan, CT Soukoulis, CM TI Optical nonlinear response of a single nonlinear dielectric layer sandwiched between two linear dielectric structures SO PHYSICAL REVIEW B AB We consider the general problem of electromagnetic wave propagation through a one-dimensional system consisting of a nonlinear medium sandwiched between two linear structures. Special emphasis is given to systems where the latter comprise Bragg reflectors. We obtain an exact expression for the nonlinear response of such dielectric superlattices when the nonlinear impurity is very thin, or in the delta-function limit. We find that both the switching-up and switching-down intensities of the bistable response can be made very low, when the frequency of the incident wave matches that of the impurity mode of the structure. Numerical results for a nonlinear layer of finite width display qualitatively similar behavior, thus confirming the usefulness of the simpler delta-function model. In addition, an analytical solution for the resonance states of an infinitely extended finite-width superlattice with a finite-width nonlinear impurity is presented. RI Soukoulis, Costas/A-5295-2008 SN 1098-0121 PD DEC 15 PY 1997 VL 56 IS 23 BP 15090 EP 15099 DI 10.1103/PhysRevB.56.15090 UT WOS:000071043700039 ER PT J AU Fan, XD Wang, HL Hou, HQ Hammons, BE AF Fan, XD Wang, HL Hou, HQ Hammons, BE TI Laser emission from semiconductor microcavities: Transition from nonperturbative to perturbative regimes SO PHYSICAL REVIEW B AB We have demonstrated laser emission at densities below the saturation exciton density in a semiconductor microcavity by tuning the cavity resonance to the low-energy side of the inhomogeneously broadened exciton distribution. Laser emission in this regime arises from population inversion of localized excitons at the low-energy tail of the inhomogeneous distribution. Distinct spectral line shapes of laser emission and especially a large and abrupt change in the lasing threshold are observed when the composite system undergoes a transition from the nonperturbative to the perturbative regimes. The abrupt threshold change is attributed to ionization of excitons occurring in the transition region. RI Wang, Hailin/A-2362-2011 SN 1098-0121 PD DEC 15 PY 1997 VL 56 IS 23 BP 15256 EP 15260 DI 10.1103/PhysRevB.56.15256 UT WOS:000071043700061 ER PT J AU Kim, C Shen, ZX Motoyama, N Eisaki, H Uchida, S Tohyama, T Maekawa, S AF Kim, C Shen, ZX Motoyama, N Eisaki, H Uchida, S Tohyama, T Maekawa, S TI Separation of spin and charge excitations in one-dimensional SrCuO2 SO PHYSICAL REVIEW B AB In this paper we expand on our earlier results [Phys. Rev. Lett. 77, 4054 (1996)] on angle-resolved photoemission studies on one-dimensional SrCuO2 that reveal a behavior of a hole in Cu-O chain. The results cannot be explained within the conventional band theory, but require a picture in which the spin and charge degrees of freedom for a single electron are separated. Instead of a single branch as predicted in band theory, E versus k relationship can be explained by underlying spinon and holon excitations scaled by hopping energy t and exchange energy J, respectively, indicating separated spin and charge excitations. This is an experimental observation of direct consequence of the spin-charge separation driven by electron correlations that was first predicted thirty years ago. It also shows spinon and holons are real particles with definite energy-momentum dispersions. SN 0163-1829 PD DEC 15 PY 1997 VL 56 IS 24 BP 15589 EP 15595 DI 10.1103/PhysRevB.56.15589 UT WOS:000071251000020 ER PT J AU Cerda, J Van Hove, MA Sautet, P Salmeron, M AF Cerda, J Van Hove, MA Sautet, P Salmeron, M TI Efficient method for the simulation of STM images. I. Generalized Green-function formalism SO PHYSICAL REVIEW B AB We present a theoretical formalism specially suited for the simulation of scanning tunneling microscopy (STM) images. The method allows for a realistic description of the STM system, taking fully into account its three-dimensional nature. Bias effects may also be considered since the theory is not restricted to the low-bias limit. The starting point is the previously applied Landauer-Buttiker formula, which expresses the current at the STM junction as a sum of transmission coefficients linking eigenstates at each electrode. The transmission coefficients are directly obtained from the scattering matrix which is, in our approach evaluated through Green-function techniques; in particular, we employ the surface Green-function matching (SGFM) method to find the Green function at the interface, and explicitly derive simple expressions for the current. Additionally, the formalism goes beyond the elastic-scattering limit by considering inelastic effects via an optical potential. We also present a method to analyze the current in terms of contributions arising from individual atomic orbital interactions and their interference with other interactions. To this end, the SGFM method is replaced by a first-order expansion of the interface Green function. [S0163-1829(47)04648-1]. RI Van Hove, Michel/A-9862-2008; Cerda, Jorge/F-4043-2010; Sautet, Philippe/G-3710-2014 OI Van Hove, Michel/0000-0002-8898-6921; Cerda, Jorge/0000-0001-6176-0191; Sautet, Philippe/0000-0002-8444-3348 SN 0163-1829 PD DEC 15 PY 1997 VL 56 IS 24 BP 15885 EP 15899 DI 10.1103/PhysRevB.56.15885 UT WOS:000071251000053 ER PT J AU Cerda, J Yoon, A Van Hove, MA Sautet, P Salmeron, M Somorjai, GA AF Cerda, J Yoon, A Van Hove, MA Sautet, P Salmeron, M Somorjai, GA TI Efficient method for the simulation of STM images. II. Application to clean Rh(111) and Rh(111)+c(4x2)-2S SO PHYSICAL REVIEW B AB We apply our recently developed Green-function formalism for the simulation of scanning tunneling microscopy (STM) images to the clean Rh(111) and the Rh(111) + c(4 X 2)-2S systems. The former represents a test case in order to study the adequacy of the extended Huckel theory (EHT) as an approximation to the Hamiltonian matrix elements of the entire system. It Is shown that, via a suitable parametrization of the atomic-orbital basis set, the EHT-provides a reasonable description of the electronic structure of the sample and the tip, together with the interactions at the STM interface. When the same parametrization scheme is applied to the Rh(111) + c(4 X 2)-2S system, we find a good agreement with the experimental images by considering a Pt tip with its apex terminated in a Pt or S atom. More specifically, the two inequivalent maxima per unit cell that appear in the images are unambiguously assigned to a S atom adsorbed at the hcp site (brightest maximum) and to another S atom at the fcc site. Furthermore, the simulations for each tip termination can be associated to two different types of experimental images which could be acquired in a reproducible way. At the same time, and after a detailed study on the relevance of most of the parameters involved in the calculation, some general criteria for the estimation of their value, prior to the STM calculation, are established. Finally, an analysis of the tunneling current on the Rh(111) system allows us to identify the Rh-d(z2) orbitals at the surface as the main states responsible for the atomic resolution. It is also found that the most relevant probing orbitals at the tip apex are those with axial symmetry along the surface normal; for the S ended tip, it is the S-p(z) orbital which dominates by far the current, whereas, for the Pt-ended tip, first the Pt-s and next the -d(z2) provide the major contributions. The better resolution obtained with the former tip is a consequence of the different levels of localization of these probing orbitals. A similar analysis applied to the Rh(111) + c(4 X 2)-2S system explains the tip-dependent features in the simulated images, again through the higher localization of the tip S-p(z) orbital with respect to the Pt-s orbital, and the simultaneous interaction of these states with the p(z) orbitals of the S atoms at the surface. The inequivalence between the two S maxima in the unit cell, on the other hand, arises as a consequence of a better coupling of the substrate to the S-p(z) orbitals when the adsorbate is at the hcp site than when it is at the fcc site. [S0163-1829(97)04948-5]. RI Van Hove, Michel/A-9862-2008; Cerda, Jorge/F-4043-2010; Sautet, Philippe/G-3710-2014 OI Van Hove, Michel/0000-0002-8898-6921; Cerda, Jorge/0000-0001-6176-0191; Sautet, Philippe/0000-0002-8444-3348 SN 0163-1829 PD DEC 15 PY 1997 VL 56 IS 24 BP 15900 EP 15918 DI 10.1103/PhysRevB.56.15900 UT WOS:000071251000054 ER PT J AU Phillips, JM Larese, JZ AF Phillips, JM Larese, JZ TI Microscopic structure and transitions in xenon multilayer films SO PHYSICAL REVIEW B AB We report a computer simulation analysis of the growth and structural transitions in the first few layers of an adsorbing film. Recent high-resolution adsorption isotherms, heat capacity, and diffraction experiments show remarkable detail in the growth of microscopically thin films. The sharpness of adsorption isotherm steps or the magnitude of their derivative is a measure of the changes in the compressibility of the film during layering. Our computed isothermal compressibilities scale consistently with the corresponding steps in experiments. By these direct observations of equilibrium structures, our study shows these transitions are due to the details of the two-dimensional phase diagram of the top few layers of the film. [S0163-1829(97)01748-7]. SN 0163-1829 PD DEC 15 PY 1997 VL 56 IS 24 BP 15938 EP 15946 DI 10.1103/PhysRevB.56.15938 UT WOS:000071251000057 ER PT J AU Moler, EJ Kellar, SA Hussain, Z Chen, YF Shirley, DA Huff, WRA Huang, ZQ AF Moler, EJ Kellar, SA Hussain, Z Chen, YF Shirley, DA Huff, WRA Huang, ZQ TI Direct evidence for the nature of core-level photoemission satellites using angle-resolved photoemission extended fine structure SO PHYSICAL REVIEW B AB Photoemission satellites from several systems have been found to exhibit exactly the same angle-resolved photoemission extended fine structure (ARPEFS) as found in the main peaks, when referred to the equivalent photoelectron wave number k for their own photoelectrons. This provides a direct and powerful method for experimentally determining the angular momentum parameters and the intrinsic/extrinsic nature of core-level photoemission satellites. We present ARPEFS satellite data for nitrogen 1s line in c(2 X 2) N-2/Ni(100), the nickel 3p line in clean nickel (111), the carbon 1s lines in (root 3 X root 3)R30 CO/Cu(111) and p2mg(2 X 1)CO/Ni(110), and the cobalt 1s line in p(1 X 1) Co/Cu(100). For the last two cases the "satellite" structure is actually the low-energy tail of a Doniach-Sunjic line shape. The satellite peaks and the tails of the Doniach-Sunjic line shapes exhibit ARPEFS curves that in all cases except one indicate angular-momentum parameters identical to the main peak and an Intrinsic nature. [S0163-1829(97)03648-5]. SN 0163-1829 PD DEC 15 PY 1997 VL 56 IS 24 BP 16016 EP 16020 DI 10.1103/PhysRevB.56.16016 UT WOS:000071251000066 ER PT J AU Kim, JN Wang, LW Zunger, A AF Kim, JN Wang, LW Zunger, A TI Prediction of charge separation in GaAs/AlAs cylindrical nanostructures SO PHYSICAL REVIEW B AB It is known that in a sequence of flat, type-I (GaAs)(m)/(AlAs)(n)/(GaAs)(p)/(AlAs)(q) ... multiple quantum wells (MQWs), the wave functions of both the valence-band maximum and the conduction-band minimum are localized on the widest well. Thus, electron-hole charge separation is not possible. On the other hand, for short-period superlattices (type II), the electron and hole are localized on different materials (electron on AlAs and hole on GaAs) and different band-structure valleys (hole at Gamma and electron at X). Using a plane-wave pseudopotential direct-diagonalization approach, we predict that electron-hole charge separation on different layers of the same material (GaAs) and same valley (Gamma) is possible in curved (but not in flat) geometries. This is predicted for a set of concentric, nested cylinders of GaAs and AlAs (Russian Doll). Since the flat multiple-quantum-well structure and the Russian Doll structure with the same layer thicknesses have the same band offset diagram, the difference in behavior is not due to the potential. Rather, it reflects different interband coupling and kinetic energy confinement induced by the curvature, present in the nested-cylinder geometry but absent in the MQW. This identifies a geometric degree of freedom (curvature) that can be used to tailor electronic properties of nanostructures. RI Zunger, Alex/A-6733-2013 SN 0163-1829 PD DEC 15 PY 1997 VL 56 IS 24 BP R15541 EP R15544 UT WOS:000071251000009 ER PT J AU Bruenn, SW Mezzacappa, A AF Bruenn, SW Mezzacappa, A TI Ion screening effects and stellar collapse SO PHYSICAL REVIEW D AB During the collapse of a massive star's stellar core Coulomb effects maintain the ions in a highly correlated state. This has an important consequence: Neutrino-nucleus elastic scattering, which dominates the neutrino opacity, is substantially reduced for low-energy neutrinos. This results from phase interference effects that occur when the neutrino wavelength becomes larger than the interion spacing, and is analogous to a crystal becoming transparent to x rays when the change in wave number from scattering is smaller than the reciprocal lattice spacing. This reduction in the neutrino-nucleus elastic scattering cross section, referred to as "ion screening," has been calculated most recently by Horowitz. Using his correction, we investigate its effect on stellar core collapse. Our numerical results show that nu(e) downscattering with electrons is sufficiently rapid to fill the low-energy neutrino window created by ion screening, but the window width is insufficient for ion screening to have a significant effect on core deleptonization. Zn particular, inclusion of ion screening lowers the trapped lepton fraction by only 0.015 in both our 15M. and a 25M. models. We confirm this with an analytic model that elucidates ion screening's essential effect. For the sake of comparison, we also investigate the effect on core deleptonization of turning neutrino-nucleus elastic scattering off completely, and of turning off all semileptonic neutral-current neutrino scattering. These latter neutrino opacity modifications have substantially greater effects on core deleptonization than the ion-screening correction. [S0556-2821(97)06922-1]. RI Mezzacappa, Anthony/B-3163-2017 OI Mezzacappa, Anthony/0000-0001-9816-9741 SN 0556-2821 PD DEC 15 PY 1997 VL 56 IS 12 BP 7529 EP 7547 DI 10.1103/PhysRevD.56.7529 UT WOS:000071043600006 ER PT J AU Green, AM Liddle, AR Riotto, A AF Green, AM Liddle, AR Riotto, A TI Primordial black hole constraints in cosmologies with early matter domination SO PHYSICAL REVIEW D AB Moduli fields. a natural prediction of any supergravity and superstring-inspired supersymmetry theory. may lead to a prolonged period of matter domination in the early universe. This can be observationally viable provided the moduli decay early enough to avoid harming nucleosynthesis. If primordial black holes form, they would be expected to do so before or during this matter-dominated era. We examine the extent to which the standard primordial black hole constraints are weakened in such a cosmology. Permitted mass fractions of black holes at formation are of order 10(-8), rather than the usual 10(-20) or so. If the black holes form from density perturbations with a power-law spectrum, its spectral index is limited to n less than or similar to 1.3, rather than the n less than or similar to 1.25 obtained in the standard cosmology. [S0556-2821(97)03424-3]. OI Green, Anne/0000-0002-7135-1671 SN 0556-2821 PD DEC 15 PY 1997 VL 56 IS 12 BP 7559 EP 7565 DI 10.1103/PhysRevD.56.7559 UT WOS:000071043600008 ER PT J AU Adler, S Atiya, MS Chiang, IH Frank, JS Haggerty, JS Kycia, TF Li, KK Littenberg, LS Sambamurti, A Stevens, A Strand, RC Witzig, C Louis, WC Akerib, DS Ardebili, M Convery, M Ito, MM Marlow, DR McPherson, R Meyers, PD Selen, MA Shoemaker, FC Smith, AJS Blackmore, EW Bryman, DA Felawka, L Konaka, A Kuno, Y Macdonald, JA Numao, T Padley, P Poutissou, JM Poutissou, R Roy, J Turcot, AS Kitching, P Nakano, T Rozon, M Soluk, R AF Adler, S Atiya, MS Chiang, IH Frank, JS Haggerty, JS Kycia, TF Li, KK Littenberg, LS Sambamurti, A Stevens, A Strand, RC Witzig, C Louis, WC Akerib, DS Ardebili, M Convery, M Ito, MM Marlow, DR McPherson, R Meyers, PD Selen, MA Shoemaker, FC Smith, AJS Blackmore, EW Bryman, DA Felawka, L Konaka, A Kuno, Y Macdonald, JA Numao, T Padley, P Poutissou, JM Poutissou, R Roy, J Turcot, AS Kitching, P Nakano, T Rozon, M Soluk, R TI Observation of the decay K+->pi(+)mu(+)mu(-) SO PHYSICAL REVIEW LETTERS AB We have observed the rare decay K+ --> pi(+)mu(+)mu(-) and measured the branching ratio Gamma(K+ --> pi(+)mu(+)mu(-))/T(K+ --> all) = [5.0 +/- 0.4-(stat) +/- 0.7(syst) +/- 0.6(th)] x 10(-8). We compare this result with predictions from chiral perturbation theory and estimates based on the decay K+ --> pi(+)e(+)e(-). RI Marlow, Daniel/C-9132-2014; OI Littenberg, Laurence/0000-0001-8373-7179 SN 0031-9007 PD DEC 15 PY 1997 VL 79 IS 24 BP 4756 EP 4759 DI 10.1103/PhysRevLett.79.4756 UT WOS:A1997YL24400010 ER PT J AU Abe, F Akimoto, H Akopian, A Albrow, MG Amendolia, SR Amidei, D Antos, J Aota, S Apollinari, G Arisawa, T Asakawa, T Ashmanskas, W Atac, M Azfar, F AzziBacchetta, P Bacchetta, N Badgett, W Bagdasarov, S Bailey, MW Bao, J deBarbaro, P BarbaroGaltieri, A Barnes, VE Barnett, BA Barone, M Barzi, E Bauer, G Baumann, T Bedeschi, F Behrends, S Belforte, S Bellettini, G Bellinger, J Benjamin, D Benlloch, J Bensinger, J Benton, D Beretvas, A Berge, JP Berryhill, J Bertolucci, S Bettelli, S Bevensee, B Bhatti, A Biery, K Binkley, M Bisello, D Blair, RE Blocker, C Blusk, S Bodek, A Bokhari, W Bolla, G Bolognesi, V Bonushkin, Y Bortoletto, D Boudreau, J Breccia, L Bromberg, C Bruner, N BuckleyGeer, E Budd, HS Burkett, K Busetto, G ByonWagner, A Byrum, KL Campagnari, C Campbell, M Caner, A Carithers, W Carlsmith, D Cassada, J Castro, A Cauz, D Cen, Y Cerri, A Cervelli, F Chang, PS Chang, PT Chao, HY Chapman, J Cheng, MT Chertok, M Chiarelli, G Chikamatsu, T Chiou, CN Christofek, L Cihangir, S Clark, AG Cobal, M Cocca, E Contreras, M Conway, J Cooper, J Cordelli, M Couyoumtzelis, C Crane, D CroninHennessy, D Culbertson, R Daniels, T DeJongh, F Delchamps, S DellAgnello, S DellOrso, M Demina, R Demortier, L Deninno, M Derwent, PF Devlin, T Dittmann, JR Donati, S Done, J Dorigo, T Dunn, A Eddy, N Einsweiler, K Elias, JE Ely, R Engels, E Errede, D Errede, S Fan, Q Feild, G Feng, Z Ferretti, C Fiori, I Flaugher, B Foster, GW Franklin, M Frautschi, M Freeman, J Friedman, J Frisch, H Fukui, Y Funaki, S Galeotti, S Gallinaro, M Ganel, O GarciaSciveres, M Garfinkel, AF Gay, C Geer, S Gerdes, DW Giannetti, P Giokaris, N Giromini, P Giusti, G Gladney, L Gold, M Gonzalez, F Gordon, A Goshaw, AT Gotra, Y Goulianos, K Grassmann, H Groer, L GrossoPilcher, C Guillian, G Guimaraes, J Guo, RS Haber, C Hafen, E Hahn, SR Hamilton, R Handler, R Hans, RM Happacher, F Hara, K Hardman, AD Harral, B Harris, RM Hauger, SA Hauser, J Hawk, C Hayashi, E Heinrich, J Hinrichsen, B Hoffman, KD Hohlmann, M Holck, R Hollebeek, R Holloway, L Hong, S Houk, G Hu, P Huffman, BT Hughes, R Huston, J Huth, J Hylen, J Ikeda, H Incagli, M Incandela, J Introzzi, G Iwai, J Iwata, Y Jensen, H Joshi, U Kadel, RW Kajfasz, E Kambara, H Kamon, T Kaneko, T Karr, K Kasha, H Kato, Y Keaffaber, TA Kelley, K Kennedy, RD Kephart, R Kesten, P Kestenbaum, D Keutelian, H Keyvan, F Kharadia, B Kim, BJ Kim, DH Kim, HS Kim, SB Kim, SH Kim, YK Kirsch, L Koehn, P Kongeter, A Kondo, K Konigsberg, J Kopp, S Kordas, K Korytov, A Koska, W Kovacs, E Kowald, W Krasberg, M Kroll, J Kruse, M Kuhlmann, SE Kuns, E Kuwabara, T Laasanen, AT Lami, S Lammel, S Lamoureux, JI Lancaster, M Lanzoni, M Latino, G LeCompte, T Leone, S Lewis, JD Limon, P Lindgren, M Liss, TM Liu, JB Liu, YC Lockyer, N Long, O Loomis, C Loreti, M Lu, J Lucchesi, D Lukens, P Lusin, S Lys, J Maeshima, K Maghakian, A Maksimovic, P Mangano, M Mariotti, M Marriner, JP Martin, A Matthews, JAJ Mattingly, R Mazzanti, P McIntyre, P Melese, P Menzione, A Meschi, E Metzler, S Miao, C Miao, T Michail, G Miller, R MInato, H Miscetti, S Mishina, M Mitsushio, H Miyamoto, T Miyashita, S Moggi, N Morita, Y Mukherjee, A Muller, T Murat, P Murgia, S Nakada, H Nakano, I Nelson, C Neuberger, D NewmanHolmes, C Ngan, CYP Ninomiya, M Nodulman, L Oh, SH Ohl, KE Ohmoto, T Ohsugi, T Oishi, R Okabe, M Okusawa, T Oliveira, R Olsen, J Pagliarone, C Paoletti, R Papadimitriou, V Pappas, SP Parashar, N Park, S Parri, A Patrick, J Pauletta, G Paulini, M Perazzo, A Pescara, L Peters, MD Phillips, TJ Piacentino, G Pillai, M Pitts, KT Plunkett, R Pondrom, L Proudfoot, J Ptohos, F Punzi, G Ragan, K Reher, D Ribon, A Rimondi, F Ristori, L Robertson, WJ Rodrigo, T Rolli, S Romano, J Rosenson, L Roser, R Saab, T Sakumoto, WK Saltzberg, D Sansoni, A Santi, L Sato, H Schlabach, P Schmidt, EE Schmidt, MP Scott, A Scribano, A Segler, S Seidel, S Seiya, Y Semeria, F Sganos, G Shah, T Shapiro, MD Shaw, NM Shen, Q Shepard, PF Shimojima, M Shochet, M Siegrist, J Sill, A Sinervo, P Singh, P Sliwa, K Smith, C Snider, FD Song, T Spalding, J Speer, T Sphicas, P Spinella, F Spiropulu, M Spiegel, L Stanco, L Steele, J Stefanini, A Strait, J Strohmer, R Stuart, D Sullivan, G Sumorok, K Suzuki, J Takada, T Takahashi, T Takano, T Takikawa, K Tamura, N Tannenbaum, B Tartarelli, F Taylor, W Teng, PK Teramoto, Y Tether, S Theriot, D Thomas, TL Thun, R ThurmanKeup, R Timko, M Tipton, P Titov, A Tkaczyk, S Toback, D Tollefson, K Tollestrup, A Toyoda, H Trischuk, W deTroconiz, JF Truitt, S Tseng, J Turini, N Uchida, T Uemura, N Ukegawa, F Unal, G Valls, J vandenBrink, SC Vejcik, S Velev, G Vidal, R Vilar, R Vondracek, M Vucinic, D Wagner, RG Wagner, RL Wahl, J Wallace, NB Walsh, AM Wang, C Wang, CH Wang, J Wang, MJ Wang, QF Warburton, A Watts, T Webb, R Wei, C Wei, H Wenzel, H Wester, WC Wicklund, AB Wicklund, E Wilkinson, R Williams, HH Wilson, P Winer, BL Winn, D Wolinski, D Wolinski, J Worm, S Wu, X Wyss, J Yagil, A Yao, W Yasuoka, K Ye, Y Yeh, GP Yeh, P Yin, M Yoh, J Yosef, C Yoshida, T Yovanovitch, D Yu, I Yu, L Yun, JC Zanetti, A Zetti, F Zhang, L Zhang, W Zucchelli, S AF Abe, F Akimoto, H Akopian, A Albrow, MG Amendolia, SR Amidei, D Antos, J Aota, S Apollinari, G Arisawa, T Asakawa, T Ashmanskas, W Atac, M Azfar, F AzziBacchetta, P Bacchetta, N Badgett, W Bagdasarov, S Bailey, MW Bao, J deBarbaro, P BarbaroGaltieri, A Barnes, VE Barnett, BA Barone, M Barzi, E Bauer, G Baumann, T Bedeschi, F Behrends, S Belforte, S Bellettini, G Bellinger, J Benjamin, D Benlloch, J Bensinger, J Benton, D Beretvas, A Berge, JP Berryhill, J Bertolucci, S Bettelli, S Bevensee, B Bhatti, A Biery, K Binkley, M Bisello, D Blair, RE Blocker, C Blusk, S Bodek, A Bokhari, W Bolla, G Bolognesi, V Bonushkin, Y Bortoletto, D Boudreau, J Breccia, L Bromberg, C Bruner, N BuckleyGeer, E Budd, HS Burkett, K Busetto, G ByonWagner, A Byrum, KL Campagnari, C Campbell, M Caner, A Carithers, W Carlsmith, D Cassada, J Castro, A Cauz, D Cen, Y Cerri, A Cervelli, F Chang, PS Chang, PT Chao, HY Chapman, J Cheng, MT Chertok, M Chiarelli, G Chikamatsu, T Chiou, CN Christofek, L Cihangir, S Clark, AG Cobal, M Cocca, E Contreras, M Conway, J Cooper, J Cordelli, M Couyoumtzelis, C Crane, D CroninHennessy, D Culbertson, R Daniels, T DeJongh, F Delchamps, S DellAgnello, S DellOrso, M Demina, R Demortier, L Deninno, M Derwent, PF Devlin, T Dittmann, JR Donati, S Done, J Dorigo, T Dunn, A Eddy, N Einsweiler, K Elias, JE Ely, R Engels, E Errede, D Errede, S Fan, Q Feild, G Feng, Z Ferretti, C Fiori, I Flaugher, B Foster, GW Franklin, M Frautschi, M Freeman, J Friedman, J Frisch, H Fukui, Y Funaki, S Galeotti, S Gallinaro, M Ganel, O GarciaSciveres, M Garfinkel, AF Gay, C Geer, S Gerdes, DW Giannetti, P Giokaris, N Giromini, P Giusti, G Gladney, L Gold, M Gonzalez, F Gordon, A Goshaw, AT Gotra, Y Goulianos, K Grassmann, H Groer, L GrossoPilcher, C Guillian, G Guimaraes, J Guo, RS Haber, C Hafen, E Hahn, SR Hamilton, R Handler, R Hans, RM Happacher, F Hara, K Hardman, AD Harral, B Harris, RM Hauger, SA Hauser, J Hawk, C Hayashi, E Heinrich, J Hinrichsen, B Hoffman, KD Hohlmann, M Holck, R Hollebeek, R Holloway, L Hong, S Houk, G Hu, P Huffman, BT Hughes, R Huston, J Huth, J Hylen, J Ikeda, H Incagli, M Incandela, J Introzzi, G Iwai, J Iwata, Y Jensen, H Joshi, U Kadel, RW Kajfasz, E Kambara, H Kamon, T Kaneko, T Karr, K Kasha, H Kato, Y Keaffaber, TA Kelley, K Kennedy, RD Kephart, R Kesten, P Kestenbaum, D Keutelian, H Keyvan, F Kharadia, B Kim, BJ Kim, DH Kim, HS Kim, SB Kim, SH Kim, YK Kirsch, L Koehn, P Kongeter, A Kondo, K Konigsberg, J Kopp, S Kordas, K Korytov, A Koska, W Kovacs, E Kowald, W Krasberg, M Kroll, J Kruse, M Kuhlmann, SE Kuns, E Kuwabara, T Laasanen, AT Lami, S Lammel, S Lamoureux, JI Lancaster, M Lanzoni, M Latino, G LeCompte, T Leone, S Lewis, JD Limon, P Lindgren, M Liss, TM Liu, JB Liu, YC Lockyer, N Long, O Loomis, C Loreti, M Lu, J Lucchesi, D Lukens, P Lusin, S Lys, J Maeshima, K Maghakian, A Maksimovic, P Mangano, M Mariotti, M Marriner, JP Martin, A Matthews, JAJ Mattingly, R Mazzanti, P McIntyre, P Melese, P Menzione, A Meschi, E Metzler, S Miao, C Miao, T Michail, G Miller, R MInato, H Miscetti, S Mishina, M Mitsushio, H Miyamoto, T Miyashita, S Moggi, N Morita, Y Mukherjee, A Muller, T Murat, P Murgia, S Nakada, H Nakano, I Nelson, C Neuberger, D NewmanHolmes, C Ngan, CYP Ninomiya, M Nodulman, L Oh, SH Ohl, KE Ohmoto, T Ohsugi, T Oishi, R Okabe, M Okusawa, T Oliveira, R Olsen, J Pagliarone, C Paoletti, R Papadimitriou, V Pappas, SP Parashar, N Park, S Parri, A Patrick, J Pauletta, G Paulini, M Perazzo, A Pescara, L Peters, MD Phillips, TJ Piacentino, G Pillai, M Pitts, KT Plunkett, R Pondrom, L Proudfoot, J Ptohos, F Punzi, G Ragan, K Reher, D Ribon, A Rimondi, F Ristori, L Robertson, WJ Rodrigo, T Rolli, S Romano, J Rosenson, L Roser, R Saab, T Sakumoto, WK Saltzberg, D Sansoni, A Santi, L Sato, H Schlabach, P Schmidt, EE Schmidt, MP Scott, A Scribano, A Segler, S Seidel, S Seiya, Y Semeria, F Sganos, G Shah, T Shapiro, MD Shaw, NM Shen, Q Shepard, PF Shimojima, M Shochet, M Siegrist, J Sill, A Sinervo, P Singh, P Sliwa, K Smith, C Snider, FD Song, T Spalding, J Speer, T Sphicas, P Spinella, F Spiropulu, M Spiegel, L Stanco, L Steele, J Stefanini, A Strait, J Strohmer, R Stuart, D Sullivan, G Sumorok, K Suzuki, J Takada, T Takahashi, T Takano, T Takikawa, K Tamura, N Tannenbaum, B Tartarelli, F Taylor, W Teng, PK Teramoto, Y Tether, S Theriot, D Thomas, TL Thun, R ThurmanKeup, R Timko, M Tipton, P Titov, A Tkaczyk, S Toback, D Tollefson, K Tollestrup, A Toyoda, H Trischuk, W deTroconiz, JF Truitt, S Tseng, J Turini, N Uchida, T Uemura, N Ukegawa, F Unal, G Valls, J vandenBrink, SC Vejcik, S Velev, G Vidal, R Vilar, R Vondracek, M Vucinic, D Wagner, RG Wagner, RL Wahl, J Wallace, NB Walsh, AM Wang, C Wang, CH Wang, J Wang, MJ Wang, QF Warburton, A Watts, T Webb, R Wei, C Wei, H Wenzel, H Wester, WC Wicklund, AB Wicklund, E Wilkinson, R Williams, HH Wilson, P Winer, BL Winn, D Wolinski, D Wolinski, J Worm, S Wu, X Wyss, J Yagil, A Yao, W Yasuoka, K Ye, Y Yeh, GP Yeh, P Yin, M Yoh, J Yosef, C Yoshida, T Yovanovitch, D Yu, I Yu, L Yun, JC Zanetti, A Zetti, F Zhang, L Zhang, W Zucchelli, S TI Properties of jets in W boson events from 1.8 TeV (p)over-bar-p collisions SO PHYSICAL REVIEW LETTERS AB We present a study of events with W bosons and hadronic jets produced in (p) over bar p collisions at a center of mass energy of 1.8 TeV. The data consist of 51400 W+/--->e(+/-)v decay candidates from 108 pb(-1) of integrated luminosity collected using the CDF detector at the Fermilab Tevatron Collider. Cross sections and jet production properties have been measured for W+ greater than or equal to 1 to greater than or equal to 4 jet events. The data are compared to predictions of leading-order QCD matrix element calculations with added gluon radiation and simulated parton fragmentation. RI Lancaster, Mark/C-1693-2008; Vucinic, Dejan/C-2406-2008; Azzi, Patrizia/H-5404-2012; Punzi, Giovanni/J-4947-2012; Chiarelli, Giorgio/E-8953-2012; Warburton, Andreas/N-8028-2013; Kim, Soo-Bong/B-7061-2014; Paulini, Manfred/N-7794-2014; Introzzi, Gianluca/K-2497-2015; OI Azzi, Patrizia/0000-0002-3129-828X; Punzi, Giovanni/0000-0002-8346-9052; Chiarelli, Giorgio/0000-0001-9851-4816; Warburton, Andreas/0000-0002-2298-7315; Paulini, Manfred/0000-0002-6714-5787; Introzzi, Gianluca/0000-0002-1314-2580; Gallinaro, Michele/0000-0003-1261-2277; Turini, Nicola/0000-0002-9395-5230 SN 0031-9007 PD DEC 15 PY 1997 VL 79 IS 24 BP 4760 EP 4765 DI 10.1103/PhysRevLett.79.4760 UT WOS:A1997YL24400011 ER PT J AU Voloshin, S Lednicky, R Panitkin, S Xu, N AF Voloshin, S Lednicky, R Panitkin, S Xu, N TI Relative space-time asymmetries in pion and nucleon production in noncentral nucleus-nucleus collisions at high energies SO PHYSICAL REVIEW LETTERS AB We propose the use of ratios of the pion-proton correlation functions evaluated under different conditions to study the relative space-time asymmetries in pion and proton emission (pion and nucleon source relative shifts) in high energy heavy ion collisions. We address the question of the noncentral collisions, where the sources can be shifted spatially relative to each other both in the longitudinal and in the transverse directions in the reaction plane. We use the RQMD event generator to illustrate the effect and the technique. RI Voloshin, Sergei/I-4122-2013; Lednicky, Richard/K-4164-2013 SN 0031-9007 PD DEC 15 PY 1997 VL 79 IS 24 BP 4766 EP 4769 DI 10.1103/PhysRevLett.79.4766 UT WOS:A1997YL24400012 ER PT J AU Chmaissem, O Jorgensen, JD Kondo, S Johnston, DC AF Chmaissem, O Jorgensen, JD Kondo, S Johnston, DC TI Structure and thermal expansion of LiV2O4: Correlation between structure and heavy fermion behavior SO PHYSICAL REVIEW LETTERS AB The structural properties ol the heavy fermion (HF) transition metal oxide LiV2O4 have been studied as a function of temperature T from 4 to 295 K. Upon cooling from 295 K the lattice parameter a contracts gradually to become nearly constant between 65 and 20 K and then decreases again below 20 K. The downturn in a(T) below 20 K correlates with the crossover from local moment to HF behavior. The thermal expansion is found to depend predominantly on the interatomic Li-O bonds while V-O bond lengths change only slightly. The electronic Gruneisen parameter at 7 K is inferred to be large (similar to 25), similar to low:T values of some f-electron HF compounds. SN 0031-9007 PD DEC 15 PY 1997 VL 79 IS 24 BP 4866 EP 4869 DI 10.1103/PhysRevLett.79.4866 UT WOS:A1997YL24400037 ER PT J AU Bonca, J Trugman, SA AF Bonca, J Trugman, SA TI Inelastic quantum transport SO PHYSICAL REVIEW LETTERS AB We solve a Schrodinger equation for inelastic quantum transport that retains full quantum coherence, in contrast to previous rate or Boltzmann equation approaches. The model Hamiltonian is the zero temperature 1D Holstein model for an electron coupled to optical phonons (polaron), in a strong electric field. The Hilbert space glows exponentially with electron position, forming a nonstandard Bethe lattice. We calculate nonperturbatively the transport current, electron-phonon correlations. and quantum diffusion. This system is a toy model for the constantly branching ''wave function of the universe.''. SN 0031-9007 PD DEC 15 PY 1997 VL 79 IS 24 BP 4874 EP 4877 DI 10.1103/PhysRevLett.79.4874 UT WOS:A1997YL24400039 ER PT J AU Munkholm, A Brennan, S Comin, F Ortega, L AF Munkholm, A Brennan, S Comin, F Ortega, L TI Observation of a distributed epitaxial oxide in thermally grown SiO2 on Si(001) - Reply SO PHYSICAL REVIEW LETTERS SN 0031-9007 PD DEC 15 PY 1997 VL 79 IS 24 BP 4933 EP 4933 DI 10.1103/PhysRevLett.79.4933 UT WOS:A1997YL24400056 ER PT J AU Kendziora, C Martin, MC Forro, L Mandrus, D Mihaly, L AF Kendziora, C Martin, MC Forro, L Mandrus, D Mihaly, L TI Optical conductivity of high T-c superconductors: From underdoped to overdoped - Comment SO PHYSICAL REVIEW LETTERS RI Mandrus, David/H-3090-2014 SN 0031-9007 PD DEC 15 PY 1997 VL 79 IS 24 BP 4935 EP 4935 DI 10.1103/PhysRevLett.79.4935 UT WOS:A1997YL24400058 ER PT J AU Wong, KL Bretz, NL Hahm, TS Synakowski, E AF Wong, KL Bretz, NL Hahm, TS Synakowski, E TI Short wavelength fluctuations and electron heat conductivity in enhanced reversed shear plasmas SO PHYSICS LETTERS A AB Short wavelength fluctuations with k similar to omega(pe)/c and k rho i similar to 5 are detected by microwave scattering in TFTR plasmas with reversed magnetic shear. They propagate in the ion diamagnetic drift direction with a frequency below the ion diamagnetic drift frequency in the frame of reference where E-r = 0. The variation of the fluctuation amplitude in the plasma core correlates with the variation of the local electron heat conductivity, suggesting that these fluctuations may be the cause of anomalous electron heat transport in these plasmas. (C) 1997 Elsevier Science B.V. SN 0375-9601 PD DEC 15 PY 1997 VL 236 IS 4 BP 339 EP 344 DI 10.1016/S0375-9601(97)00806-2 UT WOS:000071015500014 ER PT J AU Perkins, LJ AF Perkins, LJ TI Shape-enhanced fusion: increasing the reactivity for some advanced fusion fuels SO PHYSICS LETTERS A AB We show that an order of magnitude enhancement of the fusion cross section is possible for some advanced fusion fuels involving deformed nuclei providing the reacting nuclei fuse ina directed orientation. This process is a manifestation of Coulomb barrier reduction and we identify some candidate advanced fusion fuels which could exploit this phenomenon including p-B-11, p-Li-7 and p-B-10. (C) 1997 Elsevier Science B.V. SN 0375-9601 PD DEC 15 PY 1997 VL 236 IS 4 BP 345 EP 350 DI 10.1016/S0375-9601(97)00756-1 UT WOS:000071015500015 ER PT J AU Ciocco, MV Cugini, AV Wildman, DJ Erinc, JB Staymates, WJ AF Ciocco, MV Cugini, AV Wildman, DJ Erinc, JB Staymates, WJ TI Rheology of coal/waste coprocessing mixtures SO POWDER TECHNOLOGY CT 1995 Meeting of the International-Freight-Pipeline-Society CY SEP, 1995 CL PITTSBURGH, PA SP Int Freight Pipeline Soc AB The economical recycling of waste materials to produce liquid fuel feedstocks is being investigated. Particular emphasis at the Pittsburgh Energy Technology Center (PETC) has been given to coal/waste coprocessing. Coal/waste coprocessing represents the conversion, into fuels and higher value products, of coal with a combination of any or all of the following: plastics, rubber, heavy oil, waste oil and paper. This study focuses on the rheology of various mixtures of coal, plastics, rubber and oil in order to facilitate their pumping in coal/waste coprocessing continuous units. The rheological properties of these mixtures determine their pumpability and the feed system requirements for the slurries. The viscosities of coal/waste mixtures were measured at various temperatures and shear rates. It was noted that these mixtures had non-Newtonian flow properties, hence their viscosities were a strong function of shear rate. The relative amounts of coal, plastics (and plastics type), rubber and oil were varied in order to evaluate their effect on apparent viscosity. A bench-scale continuous unit was used to evaluate the pumpability of slurries that represent mixtures that may be used in coal/waste coprocessing. (C) 1997 Elsevier Science S.A. SN 0032-5910 PD DEC 15 PY 1997 VL 94 IS 3 BP 207 EP 210 DI 10.1016/S0032-5910(97)03295-6 UT WOS:A1997YK11700005 ER PT J AU Khaleel, MA Smith, MT Pitman, SG AF Khaleel, MA Smith, MT Pitman, SG TI The effect of strain rate history on the ductility in superplastic AA-5083 SO SCRIPTA MATERIALIA OI khaleel, mohammad/0000-0001-7048-0749 SN 1359-6462 PD DEC 15 PY 1997 VL 37 IS 12 BP 1909 EP 1915 DI 10.1016/S1359-6462(97)00381-3 UT WOS:A1997YJ07000012 ER PT J AU Hoyt, JJ AF Hoyt, JJ TI A mean field description of the kinetics of precipitate free zone formation SO SCRIPTA MATERIALIA RI LAI, JING/F-6526-2010 SN 1359-6462 PD DEC 15 PY 1997 VL 37 IS 12 BP 2033 EP 2039 DI 10.1016/S1359-6462(97)00369-2 UT WOS:A1997YJ07000030 ER PT J AU Rawers, JC Krabbe, RA Wittenberger, JD AF Rawers, JC Krabbe, RA Wittenberger, JD TI Hot-extrusion of attrition milled, iron alloy powders SO SCRIPTA MATERIALIA SN 1359-6462 PD DEC 15 PY 1997 VL 37 IS 12 BP 2053 EP 2059 DI 10.1016/S1359-6462(97)00397-7 UT WOS:A1997YJ07000033 ER PT J AU Wang, HY Foote, RS Jacobson, SC Schneibel, JH Ramsey, JM AF Wang, HY Foote, RS Jacobson, SC Schneibel, JH Ramsey, JM TI Low temperature bonding for microfabrication of chemical analysis devices SO SENSORS AND ACTUATORS B-CHEMICAL AB A low temperature bonding process was developed for the fabrication of microchip devices for liquid and heterogeneous phase chemical analysis, Photolithographically etched microchannels on glass substrates were closed by bonding a glass cover plate using a spin-on sodium silicate layer as an adhesive. Good channel sealing was achieved by curing at 90 degrees C for 1 h or room temperature overnight. The fluidic performance of the device was evaluated by monitoring the electroosmotic flow on the chip. The results compared well with those obtained from devices made by high temperature direct bonding of the substrate and cover plate. The dielectric and mechanical strength for bonds, created using the low and high temperature methods, were compared. A dielectric strength of 400 kV cm(-1) was obtained for the sodium silicate bonding and 1100 kV cm(-1) for the high temperature bonding. Mechanical strength measurements gave a surface energy value of approximate to 2.7 J m(-2) for sodium silicate bonding, compared to 6.5 J m(-2) for direct bonding. The mechanical strength of glass bonds obtained with sodium silicate at low temperature was comparable to that reported for the sodium silicate bonding of silicon wafers at >200 degrees C or by conventional direct bonding of oxidized silicon at 1400 degrees C. The low temperature bonding performance is adequate for microfabricated fluidic devices that employ electrokinetic transport phenomena. The reduced temperature of the bonding process will allow chemical surface modification prior to bonding. (C) 1997 Elsevier Science S.A. All rights reserved. SN 0925-4005 PD DEC 15 PY 1997 VL 45 IS 3 BP 199 EP 207 DI 10.1016/S0925-4005(97)00294-3 UT WOS:000072641900004 ER PT J AU Bodenhofer, K Hierlemann, A Schlunk, R Gopel, W AF Bodenhofer, K Hierlemann, A Schlunk, R Gopel, W TI New method of vaporizing volatile organics for gas SO SENSORS AND ACTUATORS B-CHEMICAL AB A new vaporizer for organic volatiles is presented. The essential features include the possibility to vaporize only very small analyte quantities and the release of the analyte gases at extremely constant concentrations such providing excellent reproducibility and small contributions to the overall experimental noise by fluctuating analyte concentration. Since the organic liquids are sorbed into a ceramic material, there does not occur any aerosol formation, and the sublimation of 'frozen' liquids (e.g. benzene) is possible. The released analyte concentrations can be calculated using the common Antoine-equation. The new vaporizer additionally allows the determination of unknown saturation vapor pressures of organic volatiles. (C) 1997 Elsevier Science S.A. All rights reserved. RI Hierlemann, Andreas/A-7046-2008 OI Hierlemann, Andreas/0000-0002-3838-2468 SN 0925-4005 PD DEC 15 PY 1997 VL 45 IS 3 BP 259 EP 264 DI 10.1016/S0925-4005(97)00319-5 UT WOS:000072641900013 ER PT J AU Ehlich, R Knospe, O Schmidt, R AF Ehlich, R Knospe, O Schmidt, R TI Molecular dynamics studies of inelastic scattering and fragmentation in collisions of C-60 with rare-gas atoms SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS AB Collisions of C-60 with neon and helium atoms were studied using molecular dynamics with empirical two-and three-body forces. Inelastic scattering including the capture of the rare-gas atom and fragmentation were analysed at collision energies in the centre-of-mass system between 1 and 200 eV with sufficient statistics for the microscopic calculation of differential cross sections on an absolute scale. The angular distributions are characterized by enlarged average deflections of the rare-gas atom due to the C-60 surface corrugation at low collision energies (similar to 10 eV) and shooting through the C-60 at high collision energies (similar to 200 eV). The kinetic-energy spectra of the scattered rare-gas atoms indicate the extreme inelasticity of C-60 in collisions. Good agreement between calculated and measured kinetic-energy spectra from C-60(5 keV) + He collisions was found. In particular, the position of the inelastic peak at the low-energy end of the spectrum was reproduced perfectly. Cross sections for the formation of Rg@C-60 compounds were calculated in order to provide a measure for the fine tuning of potential parameters. The calculated mass spectra of the primary fragments at 200 eV collision energy exhibit a bimodal distribution with a few fission-like events in Ne + C-60 collisions. Double differential cross sections for the kinetic energy of cluster fragments formed as a direct result of the impact demonstrate the non-thermal character of this direct fragmentation of C-60 at high collision energies. SN 0953-4075 PD DEC 14 PY 1997 VL 30 IS 23 BP 5429 EP 5449 DI 10.1088/0953-4075/30/23/011 UT WOS:000071070000011 ER PT J AU Colvin, ME Seidl, ET Nielsen, IMB Le Bui, L Hatch, FT AF Colvin, ME Seidl, ET Nielsen, IMB Le Bui, L Hatch, FT TI Deprotonation and hydride shifts in nitrenium and iminium forms of aminoimidazole-azaarene mutagens SO CHEMICO-BIOLOGICAL INTERACTIONS AB The mutagenicity of many 2-aminoimidazole-azaarenes (AIA) is thought to be mediated by the nitrenium form of the exocyclic amine. This hypothesis is supported by the numerous correlations found between calculated and experimentally-measured chemical properties for the nitreniums and the mutagenic potencies of the nitreniums and their parent amines. One factor favoring high mutagenic potency is the presence of a methyl substituent in the 1- or 3-imidazole position. In this paper, we investigate both the deprotonation of the imidazole ring nitrogens in non-N-methylated AIA mutagens and the plausibility of a chemical pathway involving a 1-4 hydride shift to form an iminium ion, thereby stabilizing the cationic N-methyl substituted AIA mutagens. It has been widely noted that factors that stabilize the nitrenium moiety lead to significantly higher mutagenic potency; hence, the transformation of the nitrenium to a more stable species might be expected to increase the potency, provided that it does not eliminate the electrophilic reactivity of the compound. Using ab initio quantum chemistry and polarizable continuum solvation models, we find that the imidazole ring nitrogens of the nitrenium ions are extremely acidic. This suggests that upon formation of the exocyclic nitrenium these sites will deprotonate to form a neutral imine. We have also studied the 1-4 hydride shift from an imidazole ring methyl to the exocyclic nitrenium to form an iminium. We predict that for AIA mutagens with just two fused rings the resulting iminium species are more stable in the gas phase than the corresponding nitreniums, For mutagens with larger conjugated systems, the nitrenium is stabilized by resonance and is more stable than the corresponding iminium. In the aqueous phase, however, the Iminium form is predicted to be more stable than the nitreniums for all poly-cyclic compounds studied. Although equilibrium calculations favor the iminium form, these have been experimentally shown to be short-lived and their actual concentration will depend on the complex kinetics of AIA mutagen metabolism. The quantum chemical results also show a strong correlation between the relative iminium-nitrenium energy difference and the charge on the exocyclic nitrogen. (C) 1997 Elsevier Science Ireland Ltd. SN 0009-2797 PD DEC 12 PY 1997 VL 108 IS 1-2 BP 39 EP 66 DI 10.1016/S0009-2797(97)00094-X UT WOS:000071649600004 PM 9463520 ER PT J AU Zhao, JK Trewhella, J Corbin, J Francis, S Mitchell, R Brushia, R Walsh, D AF Zhao, JK Trewhella, J Corbin, J Francis, S Mitchell, R Brushia, R Walsh, D TI Progressive cyclic nucleotide-induced conformational changes in the cGMP-dependent protein kinase studied by small angle X-ray scattering in solution SO JOURNAL OF BIOLOGICAL CHEMISTRY AB Small angle scattering data from bovine lung type I alpha cGRSP-dependent protein kinase (PKG) in the absence of cGMP show the protein to have a highly asymmetric structure with a radius of gyration (R-g) of 45 Angstrom and a maximum linear dimension (d(max)) of 165 Angstrom. The addition of cGMP induces a marked conformational change in PKG. The R-g and d(max) increase 25-30%, and the protein's mass moves further away from the center of mass; this results in an even more asymmetric structure, Fourier transform infrared spectroscopy data suggest that the conformational change induced by cGMP binding is primarily due to a topographical movement of the structural domains of PKG rather than to secondary structural changes within one or more of the individual domains. Each monomer of the dimeric PKG contains one high and one low affinity cGMP-binding site. A prominent increase in the asymmetry of PKG occurs with binding to high affinity cGMP-binding sites alone, but the full domain movements require the binding to both sets of sites, These conformational changes occurring in PKG with the progressive binding of cGMP to both sets of cGMP-binding sites correlate with past data, which have indicated that cGMP binding to both sets of sites is required for the fall activation of the enzyme, These results provide the first quantitative measurement of the overall PKG structure, as well as an assessment of the structural events that accompany the activation of a protein kinase upon binding a small molecular weight ligand. RI Zhao, Jinkui/B-7872-2013; OI Zhao, Jinkui/0000-0002-7756-1952; Trewhella, Jill/0000-0002-8555-6766 SN 0021-9258 EI 1083-351X PD DEC 12 PY 1997 VL 272 IS 50 BP 31929 EP 31936 DI 10.1074/jbc.272.50.31929 UT WOS:A1997YL41900101 PM 9395542 ER PT J AU Bishop, JB Witt, KL Sloane, RA AF Bishop, JB Witt, KL Sloane, RA TI Genetic toxicities of human teratogens SO MUTATION RESEARCH-FUNDAMENTAL AND MOLECULAR MECHANISMS OF MUTAGENESIS AB Birth defects cause a myriad of societal problems and place tremendous anguish on the affected individual and his or her family, Current estimates categorize about 3% of all newborn infants as having some form of birth defect or congenital anomaly. As more precise means of detecting subtle anomalies become available this estimate, no doubt, will increase, Even though birth defects have been observed in newborns throughout history, our knowledge about the causes and mechanisms through which these defects are manifested is limited. For example, it has been estimated that around 20% of all birth defects are due to gene mutations, 5-10% to chromosomal abnormalities, and another 5-10% to exposure to a known teratogenic agent or maternal factor [D.A. Beckman, R.L, Brent, Mechanisms of teratogenesis, Ann. Rev. Pharmacol. Toxicol, 24 (1984) 483-500; K. Nelson, L.B. Holmes, Malformations due to presumed spontaneous mutations in newborn infants, N. Engl. J. Med. 320 (1989) 19-23.]. Together, these percentages account for only 30-40%, leaving the etiology of more than half of all human birth defects unexplained. It has been speculated that environmental factors account for no more than one-tenth of all congenital anomalies [D.A. Beekman, R.L. Brent, Mechanisms of teratogenesis, Ann. Rev. Pharmacol. Toxicol. 24 (1984) 383-500], Furthermore, since 'there is no evidence in humans that the exposure of an individual to any mutagen measurably increases the risk of congenital anomalies in his or her offspring' [J.F. Crow, C. Denniston, Mutation in human populations, Adv. Human Genet. 14 (1985) 59121; J.M. Friedman, J.E. Polifka, Teratogenic Effects of Drugs: A Resource for Clinicians (TERIS), The John Hopkins University Press, Baltimore, 1994], the mutagenic activity of environmental agents and drugs as a factor in teratogenesis has been given very little attention, Epigenetic activity has also been given only limited consideration as a mechanism for teratogenesis. As new molecular methods are developed for assessing processes associated with teratogenesis, especially those with a genetic or an epigenetic basis, additional environmental factors may be identified. These are especially important because they are potentially preventable. This paper examines the relationships between chemicals identified as human teratogens (agents that cause birth defects) and their mutagenic activity as evaluated in one or more of the established short-term bioassays currently used to measure such damage. Those agents lacking mutagenic activity but with published evidence that they may otherwise alter the expressions or regulate interactions of the genetic material, i.e. exhibit epigenetic activity, have likewise been identified. The information used in making these comparisons comes from the published literature as well as from unpublished data of the U.S. National Toxicology Program (NTP). (C) 1997 Elsevier Science B.V. SN 0027-5107 PD DEC 12 PY 1997 VL 396 IS 1-2 SI SI BP 9 EP 43 DI 10.1016/S0027-5107(97)00173-5 UT WOS:000071205500002 PM 9434858 ER PT J AU DeBiase, AE Taylor, BE AF DeBiase, AE Taylor, BE TI Aglaodiaptomus atomicus, a new species (Crustacea : Copepoda : Calanoida : Diaptomidae) from freshwater wetland ponds in South Carolina, USA, and a redescription of A-saskatchewanensis (Wilson 1958) SO PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON AB A new calanoid copepod, Aglaodiaptomus atomicus, is described from freshwater wetland ponds in Aiken County, South Carolina, U.S.A. It is common in Aiken and Barnwell Counties. It has been collected from shallow, acidic wetland ponds, most of which dry periodically. Aglaodiaptomus atomicus resembles A. saskatchewanensis, which is redescribed from Saskatchewan, Canada, and Louisiana, U. S. A. The male of A. atomicus differs from all of its congeners by possessing a distinctively large distolateral process on the right leg 5, exopod 1. The female differs from its closest congener, A. saskatchewanensis, in possessing nearly symmetrical thoracic wings. In A. saskatchewanensis, the wings are distinctly asymmetrical. SN 0006-324X EI 1943-6327 PD DEC 12 PY 1997 VL 110 IS 4 BP 569 EP 580 UT WOS:000071014700009 ER PT J AU Eiceman, GA Preston, D Tiano, G Rodriguez, J Parmeter, JE AF Eiceman, GA Preston, D Tiano, G Rodriguez, J Parmeter, JE TI Quantitative calibration of vapor levels of TNT, RDX, and PETN using a diffusion generator with gravimetry and ion mobility spectrometry SO TALANTA AB A prototype generator for creating a continuous stream of explosive vapor was referenced quantitatively both to a standard weight from the National Institute of Standards and Technology (NIST) and to the response of an ion mobility spectrometer. Vapors from solid explosive, in a precision bore glass tube at constant temperature, diffuse into an inert gas flow. Mass output rates were determined by (1) sample temperature, and (2) sample tube dimensions (length and cross-sectional area). A reference to NIST was achieved gravimetrically though a microbalance calibrated with a reference weight; mass output rates were obtained for 2,4,6-trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX) and pentaerythritol tetranitrate (PETN) at three or more oven temperatures between 79 degrees C and 150 degrees C. The mass output rate was stable over hundreds of hours of continuous operation and the output was adjustable from a few picograms per second to several nanograms per second through variation of the oven temperature. An independent calibration of the vapor generator for TNT at 79 degrees C using an ion mobility spectrometer matched exactly the gravimetric-based findings. In most instances, measured mass output rates compared favorably with theoretically calculated mass output rates, with discrepancies in a few cases resulting primarily from uncertainties in terms (vapor pressures and diffusion coefficients) used to perform the calculations. Agreement is generally not good for PETN, where molecular decomposition contributed to higher than expected measured mass outputs. (C) 1997 Elsevier Science B.V. SN 0039-9140 PD DEC 12 PY 1997 VL 45 IS 1 BP 57 EP 74 DI 10.1016/S0039-9140(97)00107-0 UT WOS:A1997YG72000008 PM 18966981 ER PT J AU Yonker, CR Wallen, SL Palmer, BJ Garrett, BC AF Yonker, CR Wallen, SL Palmer, BJ Garrett, BC TI Effects of pressure and temperature on the dynamics of liquid tert-butyl alcohol SO JOURNAL OF PHYSICAL CHEMISTRY A AB The solution structure of tert-butyl alcohol was investigated as a function of pressure and temperature using high-resolution nuclear magnetic resonance (NMR) spectroscopy. Simulations of the solution structure were undertaken using molecular dynamics and a simple phenomenological model describing clustering in liquid tert-butyl alcohol, Chemical shifts, relaxation times (T-1), and line widths (fwhm) of the CH3 and OH groups were monitored over a pressure and temperature range up to similar to 1.0 kbar and from 297 to 423 K, respectively. Simulations demonstrated a cyclic tetramer as the dominant structure in the liquid, with pressure having negligible effects on the overall liquid structure. Temperature shifted the structural distribution and increased the mole fraction of short linear chains in liquid tert-butyl alcohol. The rotational correlation time determined from the spin-lattice relaxation time, T-1, and its pressure dependence is consistent with a cyclic structure for liquid tert-butyl alcohol that is stable as a function of pressure. This is in contrast to earlier studies of methanol in which pressure was determined to decrease hydrogen bonding and linear chain structures were predominant in the liquid. RI Garrett, Bruce/F-8516-2011 SN 1089-5639 PD DEC 11 PY 1997 VL 101 IS 50 BP 9564 EP 9570 DI 10.1021/jp972154f UT WOS:A1997YL46500002 ER PT J AU Wallen, SL Palmer, BJ Pfund, DM Fulton, JL Newville, M Ma, YJ Stern, EA AF Wallen, SL Palmer, BJ Pfund, DM Fulton, JL Newville, M Ma, YJ Stern, EA TI Hydration of bromide ion in supercritical water: An X-ray absorption fine structure and molecular dynamics study SO JOURNAL OF PHYSICAL CHEMISTRY A AB X-ray absorption fine structure (XAFS) measurements and molecular dynamics simulations(MD) are used to explore the extent of Br-ion hydration in supercritical water solutions. The structure of the first hydration shell under ambient conditions is compared to that in the supercritical region spanning a temperature range from 25 to 475 degrees C and pressures from 1 to 650 bar. The RbBr salt concentration was varied from 0.02 to 1.5 molal. The wide range of conditions studied allowed a detailed examination of the effect of temperature, density, and concentration on the extent of ion hydration under supercritical conditions. The present results provide important new insights into factors affecting ion hydration in supercritical water. Changing the density of the supercritical solution by a factor of 1.5 causes only minor changes in the extent of ion hydration at 425 degrees C, whereas a pronounced dehydration occurs as the temperature is increased from 25 to 475 degrees C, Specifically, the number of water molecules in the first hydration shell is reduced from 7.1(+/-1.5) under ambient conditions to 2.8(+/-0.4) under the supercritical conditions of 425 degrees C and 413 bar. Over a concentration range of almost two orders-of-magnitude, there is little change in the extent of hydration. MD simulations of this system are used to generate XAFS spectra that are directly compared to the experimental results. Analysis of the MD-simulated XAFS spectra verified the data reduction technique used for the high temperature conditions, There is qualitative agreement between the simulation and experiment with respect to the number of nearest neighbor waters, the nearest-neighbor distances, the degree of disorder in the first shell, and the trends of these parameters with increasing temperature. It is, however, evident that refinements in the water-bromine intermolecular potentials are required to fully capture the observed behavior under supercritical conditions. SN 1089-5639 PD DEC 11 PY 1997 VL 101 IS 50 BP 9632 EP 9640 DI 10.1021/jp971361c UT WOS:A1997YL46500010 ER PT J AU Chen, LX Rajh, T Wang, ZY Thurnauer, MC AF Chen, LX Rajh, T Wang, ZY Thurnauer, MC TI XAFS studies of surface structures of TiO2 nanoparticles and photocatalytic reduction of metal ions SO JOURNAL OF PHYSICAL CHEMISTRY B AB To probe the origin of the unique functions of titanium dioxide (TiO2) nanoparticles observed in photocatalytic reactions, structures of Ti atom sites in titanium dioxide (TiO2) nanoparticles with different sizes were studied by Ti K-edge XAFS (X-ray absorption fine structure). Compared to the bulk TiO2 structure, a shorter Ti-O distance from surface TiO2 resulting from Ti-OH bonding was observed. The XAFS spectra also revealed an increasing disorder of the lattice with decreasing sizes of the nanoparticles based on a coordination number decrease for the third-shell O atoms as well as changes in relative intensities of preedge peaks A(1), A(2), and A(3). However, the Ti sites largely remain octahedral even in the 30 Angstrom diameter particles. These results imply that The increasing number of surface Ti sites as well as possible corner defects in small nanoparticles may be the main cause of ?he unique surface chemistry exhibited by nanoparticles of TiO2. XAFS was also used in monitoring-the photoreduction reaction products of Cu2+ and Hg2+ on TiO2 nanoparticle surfaces, with or without surface adsorbers, alanine (Ala) and thiolactic acid (TLA). Ala dramatically enhanced photoreduction of Cu2+ on TiO2 nanoparticle surfaces, whereas thiolactic acid did not affect or even hindered Hg2+ photoreduction. Although both surface adsorbers chelated with the metal ions in the absence of TiO2 nanoparticles, this chelation was drastically changed in the Cu-Ala complex but was largely retained in the Hg-TLA complex when TiO2 was present. This may correlate with the different effects of the adsorbers on the photoreduction of the metal. Our experimental results suggest that a proper balance between the affinities of the adsorber to the metal ions and to the surface Ti atoms of TiO2 may be one of the keys in selecting a surface adsorber for enhanced photoreduction efficiency. SN 1089-5647 PD DEC 11 PY 1997 VL 101 IS 50 BP 10688 EP 10697 DI 10.1021/jp971930g UT WOS:A1997YL46600013 ER PT J AU Chaturvedi, S Rodriguez, JA Hrbek, J AF Chaturvedi, S Rodriguez, JA Hrbek, J TI Reaction of S-2 with ZnO and Cu/ZnO surfaces: Photoemission and molecular orbital studies SO JOURNAL OF PHYSICAL CHEMISTRY B AB The adsorption of S-2 on ZnO and Cu/ZnO has been investigated using synchrotron-based high-resolution photoemission spectroscopy. On dosing a clean ZnO surface with S-2 at 300 K, the molecule dissociates, The S is associated first with Zn and at medium coverages with Zn-O sites. When the sulfur coverage is increased to theta( )= 0.5 ML, evidence is found for sulfur bound purely to the O sites of ZnO. The sulfur species associated with O and the Zn-O sires are unstable at temperatures above 500 K. Possible reaction pathways for the dissociation of S-2 on ZnO(0001)-Zn and Zn(1010) surfaces were studied using ab initio SCF calculations. At low sulfur coverages, an adsorption complex in which S-2 is bridge bonded to two adjacent Zn atoms (Zn-S-S-Zn) is probably the precursor state for the dissociation for the molecule, It is possible to gel much higher coverages of sulfur on ZnO (0.7 ML) than on Al2O3 (0.1 ML) at similar S-2 exposures. This, in conjunction with results previously reported for H2S adsorption on Cr2O3 and Cr3O4, indicates that the reactivity of metal oxides toward sulfur is inversely proportional to the size of their band gap. Oxides with a large band gap (e.g., Al2O3, similar to 9.0 eV) are less susceptible to sulfur adsorption than oxides with a small band gap (e.g., ZnO, similar to 3.4 eV), The presence of Cu atoms on both metal oxides enhances their respective reactivities reward S-2. Upon dosing Cu/ZnO with S-2 at 300 K, sulfur prefers to attack supported Cu followed by reaction with the Zn sites of the oxide, and at large sulfur coverages the adsorbate bonds simultaneously to metal and oxygen sites on the surface. The sulfur bonded to both the metal and oxygen sites on the surface is relatively weakly bound and desorbs by 500 K. The Cu <-> S interactions are strong and lead to the formation of copper sulfides that exhibit a distinctive band structure and decompose at temperatures above 700 K. RI Hrbek, Jan/I-1020-2013 SN 1520-6106 PD DEC 11 PY 1997 VL 101 IS 50 BP 10860 EP 10869 DI 10.1021/jp972653g UT WOS:A1997YL46600037 ER PT J AU Gidalevitz, D Mindyuk, OY Heiney, PA Ocko, BM Henderson, P Ringsdorf, H Boden, N Bushby, RJ Martin, PS Strzalka, J McCauley, JP Smith, AB AF Gidalevitz, D Mindyuk, OY Heiney, PA Ocko, BM Henderson, P Ringsdorf, H Boden, N Bushby, RJ Martin, PS Strzalka, J McCauley, JP Smith, AB TI Structure of discotic liquid crystalline compounds at the air-water interface SO JOURNAL OF PHYSICAL CHEMISTRY B AB We have used grazing incidence X-ray diffraction and X-ray specular reflectivity to study the behavior of platelike hexaalkoxytriphenylene derivatives at the air-water interface. The data are consistent with a two-dimensional columnar mesophase, wherein the molecules are arranged ''edge-on'' to the water surface, with intercolumnar spacings of 13-19 Angstrom. We propose a molecular conformation in which hydrophobic tails lie parallel to the water surface so as to allow the hydrophilic oxygen atoms to directly contact the water surface. In equimolar mixtures of two disubstituted amphiphilic isomers of a triphenylene derivative, we see direct evidence for structural self-organization and intercolumnar order. We also present indirect evidence for orientational self-organization in symmetrically substituted triphenylene derivatives. RI Gidalevitz, David/D-6717-2012 SN 1089-5647 PD DEC 11 PY 1997 VL 101 IS 50 BP 10870 EP 10875 DI 10.1021/jp972678f UT WOS:A1997YL46600038 ER PT J AU Field, EH Johnson, PA Beresnev, IA Zeng, YH AF Field, EH Johnson, PA Beresnev, IA Zeng, YH TI Nonlinear ground-motion amplification by sediments during the 1994 Northridge earthquake SO NATURE AB It has been known since at least 1898 (ref. 1) that sediments can amplify earthquake ground motion relative to bedrock. For the weak ground motion accompanying small earthquakes, the amplification due to sediments is well understood in terms of linear elasticity (Hooke's law)(2), but there has been a long-standing debate regarding the amplification associated with the strong ground motion produced by large earthquakes. The view of geotechnical engineers, based largely on laboratory studies, is that Hooke's law breaks down at larger strains causing a reduced (nonlinear) amplification. Seismologists, on the other hand, have tended to remain sceptical of this nonlinear effect, mainly because the relatively few strong-motion observations seemed to be consistent with linear elasticity, Although some recent earthquake studies have demonstrated nonlinear behaviour under certain circumstances(3,4), the significance of nonlinearity for the type of stiff-soil sites found in the greater Los Angeles region remains unresolved(5). Here we report that ground-motion amplification due to sediments for the main shock of the 1994 Northridge earthquake was up to a factor of two less than the amplification observed for its aftershocks, These observations imply significant nonlinearity in such amplification, and bring into question the use of measurements of weak ground motion to predict the strong ground motion at sedimentary sites. SN 0028-0836 PD DEC 11 PY 1997 VL 390 IS 6660 BP 599 EP 602 DI 10.1038/37586 UT WOS:A1997YK85300046 ER PT J AU Acharya, BS Baldin, B Banerjee, S Beri, SB Bhatnagar, V Bhattacharjee, M Brandt, A Brock, R Butler, JM Chopra, S Cummings, M Denisov, D Diehl, HT Dugad, SR Duggan, P Fahey, S Flattum, E Fortner, M Glebov, V Solis, JLG Green, DR Green, J Grossman, N Gupta, A Haggerty, H Hansen, S Hatcher, R Hedin, D HernandezMontoya, R Hu, T Igarashi, S Ito, AS Jerger, SA Johns, K Kalmani, SD Kohli, JM Krishnaswamy, MR Markeloff, R Marshall, T McMahon, T Miller, D Mondal, NK Nagaraj, P Narasimham, VS Narayanan, A Nicola, M Nila, M Parua, N Pope, BG Quintas, PZ Rao, MVS Reddy, LV Regan, T Rockwell, T Satyanarayana, B Shankar, HC Singh, JB Sood, PM Taketani, A Vishwanath, PR Wilcox, J Wood, DR Yamada, R Yasuda, T Chang, S Johari, H Smart, W Fuess, S Ahn, S Carvalho, W Neto, JD AF Acharya, BS Baldin, B Banerjee, S Beri, SB Bhatnagar, V Bhattacharjee, M Brandt, A Brock, R Butler, JM Chopra, S Cummings, M Denisov, D Diehl, HT Dugad, SR Duggan, P Fahey, S Flattum, E Fortner, M Glebov, V Solis, JLG Green, DR Green, J Grossman, N Gupta, A Haggerty, H Hansen, S Hatcher, R Hedin, D HernandezMontoya, R Hu, T Igarashi, S Ito, AS Jerger, SA Johns, K Kalmani, SD Kohli, JM Krishnaswamy, MR Markeloff, R Marshall, T McMahon, T Miller, D Mondal, NK Nagaraj, P Narasimham, VS Narayanan, A Nicola, M Nila, M Parua, N Pope, BG Quintas, PZ Rao, MVS Reddy, LV Regan, T Rockwell, T Satyanarayana, B Shankar, HC Singh, JB Sood, PM Taketani, A Vishwanath, PR Wilcox, J Wood, DR Yamada, R Yasuda, T Chang, S Johari, H Smart, W Fuess, S Ahn, S Carvalho, W Neto, JD TI Scintillation counters for the DO muon upgrade SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB We present the results of an upgrade to the DO muon system. Scintillating counters have been added to the existing central DO muon system to provide rejection for cosmic-ray muons and out-of-time background, and to provide additional fast-timing information for muons in an upgraded Tevatron. Performance and results from the 1994-1996 Tevatron run are presented. RI Bheesette, Satyanarayana/A-1360-2013; Taketani, Atsushi/E-1803-2017; de Mello Neto, Joao/C-5822-2013 OI Taketani, Atsushi/0000-0002-4776-2315; de Mello Neto, Joao/0000-0002-3234-6634 SN 0168-9002 PD DEC 11 PY 1997 VL 401 IS 1 BP 45 EP 62 DI 10.1016/S0168-9002(97)01020-6 UT WOS:A1997YL03300003 ER PT J AU Bamberger, A Boterenbrood, H Bulmahn, J Carlin, R Cunitz, H Dawson, J deKamps, M Hain, W Hanna, D Hauschildt, J Klanner, R Kotz, U Kruse, A Lim, JN Morandin, M Ng, JST Okrasinski, JR Parsons, J Pitacco, G Repond, J Ritz, S Rohde, M Schlereth, J Schott, W Talaga, R Tiecke, H Verkerke, W Whitmore, JJ AF Bamberger, A Boterenbrood, H Bulmahn, J Carlin, R Cunitz, H Dawson, J deKamps, M Hain, W Hanna, D Hauschildt, J Klanner, R Kotz, U Kruse, A Lim, JN Morandin, M Ng, JST Okrasinski, JR Parsons, J Pitacco, G Repond, J Ritz, S Rohde, M Schlereth, J Schott, W Talaga, R Tiecke, H Verkerke, W Whitmore, JJ TI The small angle rear tracking detector of ZEUS SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB The design, construction, installation, and performance of the small angle rear tracking detector of the ZEUS experiment are described. The results on electron position measurement, electron energy correction, and background reduction at the first-level trigger are presented. The impact on the measurement of the proton structure function is discussed. RI Morandin, Mauro/A-3308-2016 OI Morandin, Mauro/0000-0003-4708-4240 SN 0168-9002 PD DEC 11 PY 1997 VL 401 IS 1 BP 63 EP 80 DI 10.1016/S0168-9002(97)01029-2 UT WOS:A1997YL03300004 ER PT J AU Cho, HS Hong, WS Kadyk, J PerezMendez, V Kim, JG Vujic, J AF Cho, HS Hong, WS Kadyk, J PerezMendez, V Kim, JG Vujic, J TI Performance of microstrip gas chambers with conductive surface coating of doped amorphous silicon carbide (a-Si:C:H) SO NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT AB A new technique involves the use of doped amorphous silicon carbide (a-Si:C:H) as a conductive surface coating in the fabrication of microstrip gas chambers, to eliminate the effect of charge accumulation on the substrate surface. The performance of these detectors made in this way has been tested, measuring gas gains with respect to several operating parameters such as time, anode voltage (V-a), backplane voltage (V-b); and drift voltage (V-d). Doped a-Si:C:H film is a conductive surface coating that works well, and is an attractive alternative to other surface treatments of the substrate, because its resistivity can be easily controlled over a wide range by doping, it has a naturally good radiation hardness, and large areas can be coated at relatively low cost. SN 0168-9002 PD DEC 11 PY 1997 VL 401 IS 1 BP 81 EP 88 DI 10.1016/S0168-9002(97)00934-0 UT WOS:A1997YL03300005 ER PT J AU Lipkin, HJ AF Lipkin, HJ TI Penguins, trees and final state interactions in B decays in broken SU3 SO PHYSICS LETTERS B AB The availability of data on B-s decays to strange quasi-two-body final states, either with or without charmonium opens new possibilities for understanding different contributions of weak diagrams and in particular the relative contributions of tree and penguin diagrams. Corresponding B-d and B-s decays to charge conjugate final states are equal in the SU(3) symmetry limit and the dominant SU(3) breaking mechanism is given by ratios of CKM matrix elements. Final State Interactions effects should be small, because strong interactions conserve C and should tend to cancel in ratios between charge conjugate states. Particularly interesting implications of decays into final states containing eta and eta' are discussed. (C) 1997 Published by Elsevier Science B.V. SN 0370-2693 PD DEC 11 PY 1997 VL 415 IS 2 BP 186 EP 192 DI 10.1016/S0370-2693(97)01262-8 UT WOS:000071132900013 ER PT J AU Page, PR AF Page, PR TI Implications of a J(PC) exotic SO PHYSICS LETTERS B AB Recent experimental data from BNL on the isovector J(PC) = 1(-+) exotic at 1.6 GeV in rho pi indicate the existence of a non-quarkonium state consistent with lattice gauge theory predictions. We discuss how further experiments can strengthen this conclusion. We show that the rho pi, eta'pi and eta pi couplings of this state qualitatively support the hypothesis that it is a hybrid meson, although other interpretations cannot be eliminated. (C) 1997 Elsevier Science B.V. RI Page, Philip/L-1885-2015 OI Page, Philip/0000-0002-2201-6703 SN 0370-2693 EI 1873-2445 PD DEC 11 PY 1997 VL 415 IS 2 BP 205 EP 210 DI 10.1016/S0370-2693(97)01232-X UT WOS:000071132900016 ER PT J AU Jannuzi, BT Yanny, B Impey, C AF Jannuzi, BT Yanny, B Impey, C TI Hubble Space Telescope imaging of the host galaxies of three X-ray-selected BL Lacertae objects SO ASTROPHYSICAL JOURNAL AB Hubble Space Telescope (HST) WFPC-2 I-band (F814W) images of three X-ray-selected BL Lacertae objects (MS 1221.8+2452, MS 1407.9+5954, and MS 2143.4+0704) reveal that each of these BL Lac objects is well centered in an extended nebulosity that is consistent in brightness and morphology with light from an elliptical galaxy at their previously reported redshifts. Each of the detected host galaxies have radial surface-brightness profiles that are well fitted by a de Vaucouleurs law with effective radii of between 3 and 12 kpc (H-0 = 50 km s(-1) Mpc(-1), q(0) = 0). The absolute magnitudes of the host galaxies fall in the range of luminosities determined for other BL Lacertae object host galaxies, -24.7 < M-I < -23.5. In addition to allowing the measurement of the host galaxy magnitudes and radial surface brightness profiles, the HST images allow a search for substructure in the host galaxies and for the presence of close companion galaxies at spatial resolutions not yet achievable from the ground. While no evidence was found for any ''bars'' or spiral arms, ''boxy'' isophotes are present in the host galaxy of at least one of the three objects observed as part of this study (MS 2143.4+0704). The apparent magnitudes and image properties of the companions of the BL Lac objects are cataloged as part of this work. The three BL Lac objects appear to occur in diverse environments, from relative isolation (MS 1221.8 + 2452) to, possibly, a rich group of galaxies (MS 1407.9 + 5954). SN 0004-637X PD DEC 10 PY 1997 VL 491 IS 1 BP 146 EP & DI 10.1086/304944 PN 1 UT WOS:A1997YL50700014 ER PT J AU Alcock, C Allsman, RA Alves, D Axelrod, TS Becker, AC Bennett, DP Cook, KH Freeman, KC Griest, K Keane, MJ Lehner, MJ Marshall, SL Minniti, D Peterson, BA Pratt, MR Quinn, PJ Rodgers, AW Stubbs, CW Sutherland, W Tomaney, AB Vandehei, T Welch, D AF Alcock, C Allsman, RA Alves, D Axelrod, TS Becker, AC Bennett, DP Cook, KH Freeman, KC Griest, K Keane, MJ Lehner, MJ Marshall, SL Minniti, D Peterson, BA Pratt, MR Quinn, PJ Rodgers, AW Stubbs, CW Sutherland, W Tomaney, AB Vandehei, T Welch, D TI First detection of a gravitational microlensing candidate toward the small magellanic cloud SO ASTROPHYSICAL JOURNAL AB We report the first discovery of a gravitational microlensing candidate toward a new population of source stars, the Small Magellanic Cloud (SMC). The candidate event's light curve shows no variation for 3 yr before an upward excursion lasting similar to 217 days that peaks around 1997 January 11 at a magnification of similar to 2.1. Microlensing events toward the Large Magellanic Cloud and the Galactic bulge have allowed important conclusions to be reached on the stellar and dark matter content of the Milky Way. The SMC gives a new line of sight through the Milky Way and is expected to prove useful in determining the flattening of the Galactic halo. RI Stubbs, Christopher/C-2829-2012; Quinn, Peter/B-3638-2013; OI Stubbs, Christopher/0000-0003-0347-1724; Lehner, Matthew/0000-0003-4077-0985 SN 0004-637X PD DEC 10 PY 1997 VL 491 IS 1 BP L11 EP L13 DI 10.1086/311053 PN 2 UT WOS:A1997YL50900003 ER PT J AU Matsubara, T Suto, Y Szapudi, I AF Matsubara, T Suto, Y Szapudi, I TI Light-cone effect on higher order clustering in redshift surveys SO ASTROPHYSICAL JOURNAL AB We have evaluated a systematic effect on counts-in-cells analysis of deep, wide-field galaxy catalogs induced by the evolution of clustering within the survey volume. A multiplicative correction factor is explicitly presented, which can be applied after the higher order correlation functions have been extracted in the usual way, without taking into account the evolution. The general theory of this effect combined with the Ansatz describing the nonlinear evolution of clustering in simulations enables us to estimate the magnitude of the correction factor in different cosmologies. In a series of numerical calculations assuming an array of cold dark matter models, it is found that, as long as galaxies are unbiased tracers of underlying density field, the effect is relatively small (similar or equal to 10%) for the shallow surveys (z < 0.2), while it becomes significant (of order unity) in deep surveys (z similar or equal to 1). Depending on the scales of interest, the required correction is comparable to or smaller than the expected errors of ongoing wide-field galaxy surveys such as the Sloan Digital Sky Survey and the 2 Degree Field Survey. Therefore, at present, the effect has to be taken into account for high-precision measurements at very small scales only, while in future deep surveys it amounts to a significant correction. SN 0004-637X EI 1538-4357 PD DEC 10 PY 1997 VL 491 IS 1 BP L1 EP L5 DI 10.1086/311051 PN 2 UT WOS:A1997YL50900001 ER PT J AU Tkachov, FV AF Tkachov, FV TI Measuring multijet structure of hadronic energy flow - Or, what is a jet? SO INTERNATIONAL JOURNAL OF MODERN PHYSICS A AB Ambiguities of jet algorithms are reinterpreted as instability wrt small variations of input. Optimal stability occurs for observables possessing property of calorimetric continuity (C-continuity) predetermined by kinematical structure of calorimetric detectors. The so-called G-correlators form a basic class of such observables and fit naturally into QFT framework, allowing systematic theoretical studies. A few rules generate other C-continuous observables. The resulting G-algebra correctly quantifies any feature of multijet structure such as the "number of jets" and mass spectra of "multijet substates." The new observables are physically equivalent to traditional ones but can be computed from final states bypassing jet algorithms which reemerge as a tool of approximate computation of C-observables from data with all ambiguities under analytical control and an optimal recombination criterion minimizing approximation errors. SN 0217-751X PD DEC 10 PY 1997 VL 12 IS 30 BP 5411 EP 5529 DI 10.1142/S0217751X97002899 UT WOS:000071062100004 ER PT J AU Gronbech-Jensen, N Hummer, G Beardmore, KM AF Gronbech-Jensen, N Hummer, G Beardmore, KM TI Lekner summation of Coulomb interactions in partially periodic systems SO MOLECULAR PHYSICS AB We present Lekner summations of long-range interactions in three-dimensional media, which are periodic in one or two dimensions. While the basic summation techniques are well known from Lekner's original work, we emhasize a simple method for correctly evaluating the self-energies of particles in a partially periodic lattice. RI Hummer, Gerhard/A-2546-2013 OI Hummer, Gerhard/0000-0001-7768-746X SN 0026-8976 PD DEC 10 PY 1997 VL 92 IS 5 BP 941 EP 945 DI 10.1080/002689797169871 UT WOS:000071011100014 ER PT J AU Zhang, JD Plummer, EW AF Zhang, JD Plummer, EW TI Surface lattice dynamics of La0.65Ca0.35MnO3 across the Curie temperature SO SURFACE SCIENCE AB We report a temperature-dependent study of the surface optical phonons of La0.65Ca0.35MnO3 films using high-resolution electron-energy-loss spectroscopy. Three surface modes have been observed and correspond to the bulk modes which are associated with the internal vibrations of the MnO6 octahedron, However, analogous to the high-T-c superconducting cuperates, the surface phonons have higher energies than the bulk modes, indicating that the surface and the bulk have significantly different lattice dynamics. The small energy dispersion and large linewidth reflect a short phonon life time. The strong temperature dependence of the linewidth corresponds to coupled-random dynamic lattice distortions. A 2-4 meV shift in the phonon energy across the Curie temperature is associated with a static lattice distortion related to the magnetic phase transition. The temperature dependence of the surface phonon modes are compared with the current understanding of the bulk lattice dynamics, above and below the critical temperature for the structural, electronic, and magnetic phase transitions in the "colossal" magnetoresistance materials. (C) 1997 Elsevier Science B.V. SN 0039-6028 PD DEC 10 PY 1997 VL 393 IS 1-3 BP 64 EP 71 DI 10.1016/S0039-6028(97)00559-1 UT WOS:000071333200016 ER PT J AU Kelchner, CL DePristo, AE AF Kelchner, CL DePristo, AE TI Molecular dynamics simulations of multilayer homoepitaxial thin film growth in the diffusion-limited regime SO SURFACE SCIENCE AB Molecular dynamics (MD) simulations permit multiple-layer thin film growth to be studied in detail, using reliable interatomic potentials for fee metals from corrected effective medium theory. Results are presented for the homoepitaxial deposition of 50 monolayers on Pd(001) and Cu(001) near 0 K. We find that atoms in overhang sites are stable due to the absence of diffusion at very low temperature and the short time scale of MD simulations. This stability leads to interesting features in the film which may be observable in STM or other experiments near 0 EC. The growth behavior of the thin him changes after deposition of the first 5-10 monolayers: more overhanging atoms are present, the surface is rougher, and multiple-layer events begin to occur. The formation of large voids in the film and the mechanism of multi-atom rearrangement events which decrease the surface roughness are discussed. Several simulation parameters have been varied (e.g. deposition rate, system size, random aiming points of the deposited atoms) to study their effects on the results. There is no clear difference between Pd and Cu thin film growth near 0 K. (C) 1997 Elsevier Science B.V. SN 0039-6028 PD DEC 10 PY 1997 VL 393 IS 1-3 BP 72 EP 84 DI 10.1016/S0039-6028(97)00560-8 UT WOS:000071333200017 ER PT J AU Kiely, JD Yeh, T Bonnell, DA AF Kiely, JD Yeh, T Bonnell, DA TI Evidence for the segregation of sulfur to Ni-alumina interfaces SO SURFACE SCIENCE AB The S enrichment of Ni-sapphire interfaces in the temperature range 500-800 degrees C was measured with Auger electron spectroscopy. Atomic force microscopy was used to confirm that S segregated to the interface rather than to interface voids or grain boundaries. The effects of atomic defects such as dislocations on S segregation was not determined. Maximum segregation occurred at 700 degrees C, similar to that to Ni grain boundaries. (C) 1997 Elsevier Science B.V. SN 0039-6028 PD DEC 10 PY 1997 VL 393 IS 1-3 BP L126 EP L130 DI 10.1016/S0039-6028(97)00786-3 UT WOS:000071333200010 ER PT J AU Pai, WW Zhang, ZY Zhang, JD Wendelken, JF AF Pai, WW Zhang, ZY Zhang, JD Wendelken, JF TI Direct visualization in manipulation of stable molecular radicals at room temperature SO SURFACE SCIENCE AB We present a novel approach for room-temperature molecular manipulation which exploits the reduced thermal mobility of chemisorbed molecular radicals, with cyclopentadienyl, C5H5, on Ag(100) as an example. Several novel manipulation modes are demonstrated, all achieved at room temperature. Most notably, the dynamics of the radicals can be directly visualized during manipulation, revealing their preferred direction of motion to be perpendicular to the tip displacement. Additionally, individual radicals can be selectively desorbed intact. These findings point to the feasibility of controlling surface chemistry and molecular engineering down to the fundamental ligand level. (C) 1997 Elsevier Science B.V. SN 0039-6028 PD DEC 10 PY 1997 VL 393 IS 1-3 BP L106 EP L112 DI 10.1016/S0039-6028(97)00712-7 UT WOS:000071333200007 ER PT J AU Tilinin, IS Van Hove, MA Salmeron, M AF Tilinin, IS Van Hove, MA Salmeron, M TI Quantum oscillations in surface-tip transfer of adatoms on AFM/STM with a dissipative environment SO SURFACE SCIENCE AB The influence of a dissipative environment on quantum coherence in surface-tip adatom transfer in AFM/STM is studied within an adiabatic approach. taking into account the slow motion of the tip with respect to an adsorption site. It is shown that coherent tunneling is the dominant mechanism of adatom transfer at temperatures below 10 K for insulators and semiconductors, and below 0.1 K for metals. The negative influence of electron and phonon polaron effects, which manifests itself in the destruction of coherence, may be noticeably compensated by potential fluctuations due to atom vibrations. As a result, the renormalized coherent tunneling amplitude may be even greater than the ground energy level splitting in the absence of a dissipative environment. Prospective pratical applications of the quantum coherence in adatom transfer are discussed. (C) 1997 Elsevier Science B.V. RI Van Hove, Michel/A-9862-2008 OI Van Hove, Michel/0000-0002-8898-6921 SN 0039-6028 PD DEC 10 PY 1997 VL 393 IS 1-3 BP L88 EP L92 DI 10.1016/S0039-6028(97)00706-1 UT WOS:000071333200004 ER PT J AU Skarpelos, P Morris, JW AF Skarpelos, P Morris, JW TI The effect of surface morphology on friction during forming of electrogalvanized sheet steel SO WEAR AB In the automotive industry, the surface morphology of sheet steel is controlled to improve both paint finish and formability. Formability, in turn, is influenced by the friction between the sheet and stamping tools, which the industry commonly measures with the 'drawbead simulator' (DBS) test. This investigation evaluated the use of various surface parameters as predictors of the frictional properties of electrogalvanized (EG) steel sheet as measured in the DBS test. The surfaces of a set of commercial EG steel sheets were measured using a profilometer and tested for friction in a DBS machine. The results were compared to various statistical measures of the sheet surfaces. The best of the simple measures proved to be a combination of two parameters: the arithmetic average roughness (R-a) and the mean wavelength of the roughness, as determined from the Fourier power spectrum. Surfaces with higher R-a were more likely to have lower friction in the DBS tests. But low friction can be obtained with lower values of the R-a if the roughness is concentrated at the shorter wavelengths (below 500 mu m) Surfaces with roughness distributed in the shorter wavelengths have the additional benefit of being easily painted to a high quality finish. (C) 1997 Elsevier Science S.A. SN 0043-1648 PD DEC 10 PY 1997 VL 212 IS 2 BP 165 EP 172 DI 10.1016/S0043-1648(97)00174-9 UT WOS:000071272800003 ER PT J AU Bell, CE Poon, PH Schumaker, VN Eisenberg, D AF Bell, CE Poon, PH Schumaker, VN Eisenberg, D TI Oligomerization of a 45 kilodalton fragment of diphtheria toxin at pH 5.0 to a molecule of 20-24 subunits SO BIOCHEMISTRY AB Diphtheria toxin (DT) is a 58 kDa protein, secreted by lysogenic strains of Corynebacterium diphtheriae, that causes the disease diphtheria in humans. The catalytic (C) domain of DT kills host cells by gaining entry into the cytoplasm and inhibiting protein synthesis. The translocation of the C domain across the endosomal membrane and into the cytoplasm of a host cell is mediated by the translocation (T) domain of DT. This process is triggered by acidification from pH similar to 7 to pH similar to 5 within the endosome. Here we show that crm45 (cross-reacting material of 45 kDa), a 45 kDa deletion mutant of DT which contains the C and T domains but lacks the C-terminal receptor-binding (R) domain, undergoes a transition from a monomer to a large oligomer upon acidification from pH 7.0 to pH 5.0. Dynamic light scattering analysis of crm45 at pH 5.0 results in a polydispersity value of only 8-17%, suggesting that the oligomer is uniformly sized. Using analytical ultracentrifugation, measurements of the sedimentation rate and diffusion coefficient of crm45 at pH 5.0 result in a molecular mass determination of 890 +/- 40 kDa (20 +/- 1 subunits) for the oligomer. Equilibrium sedimentation data on crm45 at pH 5.0 are best fit by a single species with a mass of 1000 +/- 50 kDa (24 +/- 1 subunits). These results reveal the pH-dependent formation of a uniformly sized, 20-24 subunit oligomer of the C and T domains of DT, in solution. Because the oligomer of crm45 forms at the pH of the acidified endosome, it could be relevant to the translocation of the C domain of DT across the endosomal membrane and into the cytoplasm of host cells, The possible relevance of this oligomer of crm45 to the membrane translocation of the C domain of DT correlates with earlier kinetic studies of DT intoxication of Vero cells, which inferred the transfer of similar to 20 C domains of DT to the cytoplasm of host cells, in a single event. SN 0006-2960 PD DEC 9 PY 1997 VL 36 IS 49 BP 15201 EP 15207 DI 10.1021/bi971301x UT WOS:A1997YL10500019 PM 9398247 ER PT J AU Hang, B Rothwell, DG Sagi, J Hickson, ID Singer, B AF Hang, B Rothwell, DG Sagi, J Hickson, ID Singer, B TI Evidence for a common active site for cleavage of an AP site and the benzene-derived exocyclic adduct, 3,N-4-benzetheno-dC, in the major human AP endonuclease SO BIOCHEMISTRY AB We have previously reported that the 3,N-4-benzetheno-dC (p-BQ-dC) endonuclease activity found in HeLa cells is a novel function of the major human AP endonuclease (HAP1) [Hang et al. (1996) Proc. Natl. Acad. Sci. U.S.A. 93, 13737-13741]. In this study, we compare the enzymatic and biochemical properties of the enzyme toward p-BQ-dC and an AP site in a defined oligonucleotide. A comparative analysis of the specificity constants (K-cat/K-m) for p-BQ-dC and an AP site indicates that the AP site is the preferred substrate. The enzyme does not cleave other structurally related exocyclic adducts and modified nucleosides such as 1,N-6-etheno-dA, 3,N-4-etheno-dC, 1,N-2-etheno-dG, 1,N-2-propano-dG, 8-oxo-dG, and thymine glycol. The p-BQ-dC activity requires a double-stranded DNA substrate and is affected by the base in the opposite strand, with maximal activity for a p-BQ-dC.G pair and minimal activity for a p-BQ-dC.C pair. The p-BQ-dC activity also requires Mg2+, Mn2+, or Zn2+ with optimal concentration spectra similar to those for the AP function. The optimal pH ranges for these two functions are also similar to each other (5.5-6.5). Six mutant HAP1 proteins containing single amino acid substitutions were assayed in parallel for comparison of their activities toward p-BQ-dC and the AP site. These mutants either concomitantly lost (N212A, D210N) or had reduced (D219A, E96A,and N212Q) or unchanged (H116N) p-BQ-dC and AP activities. This parallelism strongly supports the hypothesis that cleavage of p-BQ-dC requires the same catalytic active site as that proposed for the AP function. This dual activity toward two structurally unrelated substrates, an AP site and a bulky exocyclic adduct, has implications for substrate recognition. The AP site and p-BQ-dC cause different changes in the local conformation around the lesion as it is visualized by molecular modeling. SN 0006-2960 PD DEC 9 PY 1997 VL 36 IS 49 BP 15411 EP 15418 DI 10.1021/bi971367s UT WOS:A1997YL10500043 PM 9398271 ER PT J AU Frantz, CE Smith, H Eades, DM Grosovsky, AJ Eastmond, DA AF Frantz, CE Smith, H Eades, DM Grosovsky, AJ Eastmond, DA TI Bimolane: in vitro inhibitor of human topoisomerase II SO CANCER LETTERS AB Bimolane is a member of the bis(2,6-dioxopiperazine) class of drugs and has been widely used in China as an antineoplastic agent and for the treatment of psoriasis. Recent case reports indicate that bimolane is leukemogenic and is thought to exert its effects through the inhibition of topoisomerase II. However, there are no data showing the inhibition of topoisomerase II by this agent. In this report bimolane was shown to inhibit the activity of human topoisomerase II in vitro at concentrations of 100 mu M and higher when pBR322 was used as the DNA substrate, whereas inhibition was seen at 1.5 mM when using kDNA as a substrate. The results of enzyme and DNA titration assays indicate that inhibition of topoisomerase II by bimolane occurred through interactions with DNA, similar to the mechanism seen with the epipodophyllotoxin-type inhibitors. These results provide evidence that bimolane is an inhibitor of topoisomerase II in vitro. (C) 1997 Elsevier Science Ireland Ltd. SN 0304-3835 PD DEC 9 PY 1997 VL 120 IS 2 BP 135 EP 140 DI 10.1016/S0304-3835(97)00303-0 UT WOS:A1997YH95200002 PM 9461029 ER PT J AU Thomas, RB Beckman, DW Thompson, K Buhlmann, KA Gibbons, JW Moll, DL AF Thomas, RB Beckman, DW Thompson, K Buhlmann, KA Gibbons, JW Moll, DL TI Estimation of age for Trachemys scripta and Deirochelys reticularia by counting annual growth layers in claws SO COPEIA SN 0045-8511 EI 1938-5110 PD DEC 9 PY 1997 IS 4 BP 842 EP 845 DI 10.2307/1447303 UT WOS:000071052900019 ER PT J AU Weeks, SC Meffe, GK AF Weeks, SC Meffe, GK TI "Grandfather effects" on offspring size in the eastern mosquitofish, Gambusia holbrooki SO COPEIA SN 0045-8511 PD DEC 9 PY 1997 IS 4 BP 869 EP 874 UT WOS:000071052900024 ER PT J AU Puius, YA Zhao, Y Sullivan, M Lawrence, DS Almo, SC Zhang, ZY AF Puius, YA Zhao, Y Sullivan, M Lawrence, DS Almo, SC Zhang, ZY TI Identification of a second aryl phosphate-binding site in protein-tyrosine phosphatase 1B: A paradigm for inhibitor design SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA AB The structure of the catalytically inactive mutant (C215S) of the human protein-tyrosine phosphatase 1B (PTP1B) has been solved to high resolution in two complexes. In the first, crystals were grown in the presence of bis-(para-phosphophenyl) methane (BPPM), a synthetic high-affinity low-molecular weight nonpeptidic substrate (K-m = 16 mu M), and the structure was refined to an R-factor of 18.2% at 1.9 Angstrom resolution. In the second, crystals were grown in a saturating concentration of phosphotyrosine (pTyr), and the structure was refined to an R-factor of 18.1% at 1.85 Angstrom. Difference fourier maps showed the BPPM binds PTP1B in two mutually exclusive modes, one in which it occupies the canonical pTyr-binding site (the active site), and another in which a phosphophenyl moiety interacts with a set of residues not previously observed to bind aryl phosphates. The identification of a second pTyr module at the same site in the PTP1B/C215S-pTyr complex confirms that these residues constitute a low-affinity noncatalytic aryl phosphate-binding site. Identification of a second aryl phosphate binding site adjacent to the active site provides a paradigm for the design of tight-binding, highly specific PTP1B inhibitors that can span both the active site and the adjacent noncatalytic site. The design can be achieved by tethering together two small ligands that are individually targeted to the active site and the proximal noncatalytic site. SN 0027-8424 PD DEC 9 PY 1997 VL 94 IS 25 BP 13420 EP 13425 DI 10.1073/pnas.94.25.13420 UT WOS:A1997YK82500013 PM 9391040 ER PT J AU Reich, PB Walters, MB Ellsworth, DS AF Reich, PB Walters, MB Ellsworth, DS TI From tropics to tundra: Global convergence in plant functioning SO PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA AB Despite striking differences in climate, soils, and evolutionary history among diverse biomes ranging from tropical and temperate forests to alpine tundra and desert, me found similar interspecific relationships among leaf structure and function and plant growth in all biomes. Our results thus demonstrate convergent evolution and global generality in plant functioning, despite the enormous diversity of plant species and biomes, For 280 plant species from two global data sets, me found that potential carbon gain (photosynthesis) and carbon loss (respiration) increase in similar proportion with decreasing leaf life-span, increasing leaf nitrogen concentration, and increasing leaf surface area-to-mass ratio, Productivity of individual plants and of leaves in vegetation canopies also changes in constant proportion to leaf life-span and surface area-to-mass ratio, These global plant functional relationships have significant implications for global scale modeling of vegetation-atmosphere CO2 exchange. OI Ellsworth, David/0000-0002-9699-2272 SN 0027-8424 PD DEC 9 PY 1997 VL 94 IS 25 BP 13730 EP 13734 DI 10.1073/pnas.94.25.13730 UT WOS:A1997YK82500067 PM 9391094 ER PT J AU Anders, S Diaz, J Ager, JW Lo, RY Bogy, DB AF Anders, S Diaz, J Ager, JW Lo, RY Bogy, DB TI Thermal stability of amorphous hard carbon films produced by cathodic arc deposition SO APPLIED PHYSICS LETTERS AB The thermal stability of amorphous hard carbon films produced by cathodic are deposition was studied by near edge x-ray absorption fine structure (NEXAFS) spectroscopy, Raman spectroscopy, and nanoindentation evaluation. Pure carbon films of up to 85% sp(3) content were deposited using a pulsed biasing technique and annealed in ultrahigh vacuum up to 850 degrees C. NEXAFS spectra show no change in the film properties up to 700 degrees C, and a modification of the spectra for 800 and 850 degrees C, which indicate graphitization. Raman spectra show only a very slight change up to 850 degrees C. The nanoindentation data show no change in hardness and elastic modulus with annealing up to 850 degrees C. The study demonstrates the high thermal stability of the films. The difference in the NEXAFS and the Raman and nanoindentation results can be attributed to the surface sensitivity of NEXAFS in comparison to the more bulk sensitivity of Raman spectroscopy and nanoindentation. (C) 1997 American Institute of Physics. RI Diaz, Javier/F-2381-2016; Raoux, Simone/G-3920-2016; OI Ager, Joel/0000-0001-9334-9751 SN 0003-6951 EI 1077-3118 PD DEC 8 PY 1997 VL 71 IS 23 BP 3367 EP 3369 DI 10.1063/1.120339 UT WOS:A1997YK52500016 ER PT J AU Fu, HX Wang, LW Zunger, A AF Fu, HX Wang, LW Zunger, A TI Comparison of the k center dot p and the direct diagonalization approaches for describing the electronic structure of quantum dots SO APPLIED PHYSICS LETTERS AB It is shown that the standard (decoupled) 6x6 k.p effective-mass approach for semiconductor quantum dots overestimates significantly the hole and electron confinement energies, and, for dots made of materials with small spin-orbit coupling (e.g., phosphides, sulphides) produces a reverse order of s- and p-like valence states. By contrasting the electronic structures of dots as obtained by a direct diagonalization (multiband) pseudopotential approach and by its k.p approximation, we are able to trace the systematic errors of k.p in dots to the k.p errors in the underlying bulk solids. This suggests a ''diagnostic tool'' and a strategy for improving the k.p. (C) 1997 American Institute of Physics. RI Zunger, Alex/A-6733-2013 SN 0003-6951 PD DEC 8 PY 1997 VL 71 IS 23 BP 3433 EP 3435 DI 10.1063/1.120421 UT WOS:A1997YK52500038 ER PT J AU Gao, N Ponomarev, IY Xiao, QF Gibson, WM Carpenter, DA AF Gao, N Ponomarev, IY Xiao, QF Gibson, WM Carpenter, DA TI Enhancement of microbeam x-ray fluorescence analysis using monolithic polycapillary focusing optics SO APPLIED PHYSICS LETTERS AB A monolithic polycapillary focusing optic was tested in the microbeam x-ray fluorescence system at the Oak Ridge Center for Manufacturing Technology. The optic was designed to cover a wide energy range from 4 keV to 20 keV. The focal spot size of the output beam at 17.4 keV (Mo K alpha) was measured to be 21 mu m full width of half maximum. An average beam intensity of 1.5 x 10(5) photon/s/mu m(2) was obtained at the focus for Mo K alpha line using a 12 W microfocus x-ray source, This intensity is about 2400 times over that of a direct beam at 100 mm away from the x-ray source. The small, intense x-ray beam obtained was used to analyze and map the compositions of different elements in industrial samples. (C) 1997 American Institute of Physics. SN 0003-6951 PD DEC 8 PY 1997 VL 71 IS 23 BP 3441 EP 3443 DI 10.1063/1.120360 UT WOS:A1997YK52500041 ER PT J AU Lake, B Cowley, RA Tennant, DA AF Lake, B Cowley, RA Tennant, DA TI A dimer theory of the magnetic excitations in the ordered phase of the alternating-chain compound CuWO4 SO JOURNAL OF PHYSICS-CONDENSED MATTER AB A theory is developed to model the excitations in a dimerized, spin-1/2 system with a magnetically ordered ground state and where the dimer exchange constant is antiferromagnetic. This method starts by considering the energy levels of a single dimer in the effective, staggered magnetic field due to the mean-field ordering of the surrounding dimers. Pseudo-boson operators are introduced which create and annihilate these excitations, and the Hamiltonian of the magnetic system can be rewritten in terms of these operators and then diagonalized to yield one doubly degenerate transverse mode and a longitudinal singlet mode for each non-equivalent dimer in the magnetic unit cell. The dimer theory has been used to model the measured dispersion relations in the antiferromagnetically ordered phase of the alternating-chain compound CuWO4. It provides a good fit to the data and is as successful as spin-wave theory in accounting for the transverse excitations although with different values of the exchange constants. In addition the transition temperature and the size of the reduced moment at T = 0 K calculated in the dimer theory are closer to the experimental values of CuWO4 than those calculated by spin-wave theory. An important difference between these two models lies in their predictions of the longitudinal excitations: whereas in spin-wave theory these are regarded as two-magnon events resulting in a continuum of scattering, in the dimer theory one well defined mode is expected. An experimental measurement bf the longitudinal excitations should distinguish between these models. RI Tennant, David/Q-2497-2015; OI Tennant, David/0000-0002-9575-3368; Lake, Bella/0000-0003-0034-0964 SN 0953-8984 PD DEC 8 PY 1997 VL 9 IS 49 BP 10951 EP 10975 DI 10.1088/0953-8984/9/49/014 UT WOS:000071050500014 ER PT J AU Agashe, K Graesser, M AF Agashe, K Graesser, M TI Improving the fine tuning in models of low energy gauge mediated supersymmetry breaking SO NUCLEAR PHYSICS B AB The fine tuning in models of low energy gauge mediated supersymmetry breaking required to obtain the correct Z mass is quantified. To alleviate the fine tuning problem, a model with split (5 + (5) over bar) messenger fields is presented. This model has additional triplets in the low energy theory which get a mass of O(500) GeV from a coupling to a singlet. The improvement in fine tuning is quantified and the spectrum in this model is discussed. The same model with the above singlet coupled to the Higgs doublers to generate the mu term is also discussed. A Grand Unified version of the model is constructed and a known doublet-triplet splitting mechanism is used to split the messenger (5 + (5) over bar)'s A complete model is presented and some phenomenological constraints are discussed. (C) 1997 Elsevier Science B.V. SN 0550-3213 PD DEC 8 PY 1997 VL 507 IS 1-2 BP 3 EP 34 DI 10.1016/S0550-3213(97)00569-5 UT WOS:A1997YJ67400001 ER PT J AU Berends, FA Giele, WT AF Berends, FA Giele, WT TI On the construction of scattering amplitudes for spinning massless particles SO NUCLEAR PHYSICS B AB In this paper the general form of scattering amplitudes for massless particles with equal spins s (ss --> ss) or unequal spins (s(a)s(b) --> s(a)s(b)) are derived. The imposed conditions are that the amplitudes should have the lowest possible dimension, have propagators of dimension m(-2), and obey gauge invariance, It is shown that the number of momenta required for amplitudes involving particles with s > 2 is higher than the number implied by 3-vertices for higher spin particles derived in the literature. Therefore, the dimension of the coupling constants following from the latter 3-vertices has a smaller power of an inverse mass than our results imply. Consequently, the 3-vertices in the literature cannot be the first interaction terms of a gauge-invariant theory. When no spins s > 2 are present in the process the known QCD, QED or (super) gravity amplitudes are obtained from the above general amplitudes. (C) 1997 Elsevier Science B.V. SN 0550-3213 PD DEC 8 PY 1997 VL 507 IS 1-2 BP 157 EP 174 DI 10.1016/S0550-3213(97)00560-9 UT WOS:A1997YJ67400006 ER PT J AU Jessop, CP Lingel, K Marsiske, H Perl, ML Schaffner, SF Ugolini, D Wang, R Zhou, X Coan, TE Fadeyev, V Korolkov, I Maravin, Y Narsky, I Shelkov, V Staeck, J Stroynowski, R Volobouev, I Ye, J Artuso, M Efimov, A Frasconi, F Gao, M Goldberg, M He, D Kopp, S Moneti, GC Mountain, R Mukhin, Y Schuh, S Skwarnicki, T Stone, S Viehhauser, G Xing, X Bartelt, J Csorna, SE Jain, V Marka, S Freyberger, A Godang, R Kinoshita, K Lai, IC Pomianowski, P Schrenk, S Bonvicini, G Cinabro, D Greene, R Perera, LP Barish, B Chadha, M Chan, S Eigen, G Miller, JS OGrady, C Schmidtler, M Urheim, J Weinstein, AJ Wurthwein, F Asner, DM Bliss, DW Brower, WS Masek, G Paar, HP Sharma, V Gronberg, J Kutschke, R Lange, DJ Menary, S Morrison, RJ Nelson, HN Nelson, TK Qiao, C Richman, JD Roberts, D Ryd, A Witherell, MS Balest, R Behrens, BH Cho, K Ford, WT Park, H Rankin, P Roy, J Smith, JG Alexander, JP Bebek, C Berger, BE Berkelman, K Bloom, K Cassel, DG Cho, HA Coffman, DM Crowcroft, DS Dickson, M Drell, PS Ecklund, KM Ehrlich, R Elia, R Foland, AD Gaidarev, P Gittelman, B Gray, SW Hartill, DL Heltsley, BK Hopman, PI Kandaswamy, J Katayama, N Kim, PC Kreinick, DL Lee, T Liu, Y Ludwig, GS Masui, J Mevissen, J Mistry, NB Ng, CR Nordberg, E Ogg, M Patterson, JR Peterson, D Riley, D Soffer, A Ward, C Athanas, M Avery, P Jones, CD Lohner, M Prescott, C Yang, S Yelton, J Zheng, J Brandenburg, G Briere, RA Gao, YS Kim, DYJ Wilson, R Yamamoto, H Browder, TE Li, F Li, Y Rodriguez, JL Bergfeld, T Eisenstein, BI Ernst, J Gladding, GE Gollin, GD Hans, RM Johnson, E Karliner, I Marsh, MA Palmer, M Selen, M Thaler, JJ Edwards, KW Bellerive, A Janicek, R MacFarlane, DB McLean, KW Patel, PM Sadoff, AJ Ammar, R Baringer, P Bean, A Besson, D Coppage, D Darling, C Davis, R Hancock, N Kotov, S Kravchenko, I Kwak, N Anderson, S Kubota, Y Lattery, M ONeill, JJ Patton, S Poling, R Riehle, T Savinov, V Smith, A Alam, MS Athar, SB Ling, Z Mahmood, AH Severini, H Timm, S Wappler, F Anastassov, A Blinov, S Duboscq, JE Fisher, KD Fujino, D Fulton, R Gan, KK Hart, T Honscheid, K Kagan, H Kass, R Lee, J Spencer, MB Sung, M Undrus, A Wanke, R Wolf, A Zoeller, MM Nemati, B Richichi, SJ Ross, WR Skubic, P Wood, M Bishai, M Fast, J Gerndt, E Hinson, JW Menon, N Miller, DH Shibata, EI Shipsey, IPJ Yurko, M Gibbons, L Johnson, SD Kwon, Y Roberts, S Thorndike, EH AF Jessop, CP Lingel, K Marsiske, H Perl, ML Schaffner, SF Ugolini, D Wang, R Zhou, X Coan, TE Fadeyev, V Korolkov, I Maravin, Y Narsky, I Shelkov, V Staeck, J Stroynowski, R Volobouev, I Ye, J Artuso, M Efimov, A Frasconi, F Gao, M Goldberg, M He, D Kopp, S Moneti, GC Mountain, R Mukhin, Y Schuh, S Skwarnicki, T Stone, S Viehhauser, G Xing, X Bartelt, J Csorna, SE Jain, V Marka, S Freyberger, A Godang, R Kinoshita, K Lai, IC Pomianowski, P Schrenk, S Bonvicini, G Cinabro, D Greene, R Perera, LP Barish, B Chadha, M Chan, S Eigen, G Miller, JS OGrady, C Schmidtler, M Urheim, J Weinstein, AJ Wurthwein, F Asner, DM Bliss, DW Brower, WS Masek, G Paar, HP Sharma, V Gronberg, J Kutschke, R Lange, DJ Menary, S Morrison, RJ Nelson, HN Nelson, TK Qiao, C Richman, JD Roberts, D Ryd, A Witherell, MS Balest, R Behrens, BH Cho, K Ford, WT Park, H Rankin, P Roy, J Smith, JG Alexander, JP Bebek, C Berger, BE Berkelman, K Bloom, K Cassel, DG Cho, HA Coffman, DM Crowcroft, DS Dickson, M Drell, PS Ecklund, KM Ehrlich, R Elia, R Foland, AD Gaidarev, P Gittelman, B Gray, SW Hartill, DL Heltsley, BK Hopman, PI Kandaswamy, J Katayama, N Kim, PC Kreinick, DL Lee, T Liu, Y Ludwig, GS Masui, J Mevissen, J Mistry, NB Ng, CR Nordberg, E Ogg, M Patterson, JR Peterson, D Riley, D Soffer, A Ward, C Athanas, M Avery, P Jones, CD Lohner, M Prescott, C Yang, S Yelton, J Zheng, J Brandenburg, G Briere, RA Gao, YS Kim, DYJ Wilson, R Yamamoto, H Browder, TE Li, F Li, Y Rodriguez, JL Bergfeld, T Eisenstein, BI Ernst, J Gladding, GE Gollin, GD Hans, RM Johnson, E Karliner, I Marsh, MA Palmer, M Selen, M Thaler, JJ Edwards, KW Bellerive, A Janicek, R MacFarlane, DB McLean, KW Patel, PM Sadoff, AJ Ammar, R Baringer, P Bean, A Besson, D Coppage, D Darling, C Davis, R Hancock, N Kotov, S Kravchenko, I Kwak, N Anderson, S Kubota, Y Lattery, M ONeill, JJ Patton, S Poling, R Riehle, T Savinov, V Smith, A Alam, MS Athar, SB Ling, Z Mahmood, AH Severini, H Timm, S Wappler, F Anastassov, A Blinov, S Duboscq, JE Fisher, KD Fujino, D Fulton, R Gan, KK Hart, T Honscheid, K Kagan, H Kass, R Lee, J Spencer, MB Sung, M Undrus, A Wanke, R Wolf, A Zoeller, MM Nemati, B Richichi, SJ Ross, WR Skubic, P Wood, M Bishai, M Fast, J Gerndt, E Hinson, JW Menon, N Miller, DH Shibata, EI Shipsey, IPJ Yurko, M Gibbons, L Johnson, SD Kwon, Y Roberts, S Thorndike, EH TI Measurement of the decay amplitudes and branching fractions of B->J/psi K-* and B->J/psi K decays SO PHYSICAL REVIEW LETTERS AB Using data taken with the CLEO II detector at the Cornell Electron Storage Ring, we present the first full angular analysis in the color-suppressed modes B-0 --> J/psi K*(0) and B+ --> J/psi K*(+). This leads to a complete determination of the decay amplitudes of these modes including the longitudinal polarization Gamma(L)/Gamma = 0.52 +/- 0.07 +/- 0.04 and the P wave component \P\(2) = 0.16 +/- 0.08 +/- 0.04. In addition, we update the branching fractions for B --> J/psi K and B --> J/psi K*. RI Schaffner, Stephen/D-1189-2011; Briere, Roy/N-7819-2014; Frasconi, Franco/K-1068-2016 OI Briere, Roy/0000-0001-5229-1039; Frasconi, Franco/0000-0003-4204-6587 SN 0031-9007 PD DEC 8 PY 1997 VL 79 IS 23 BP 4533 EP 4537 DI 10.1103/PhysRevLett.79.4533 UT WOS:A1997YK36500005 ER PT J AU Jayanthi, CS Tang, M Wu, SY Cocks, JA Yip, S AF Jayanthi, CS Tang, M Wu, SY Cocks, JA Yip, S TI Local analysis of structural instability in stressed lattices: Crack nucleation in a covalent solid SO PHYSICAL REVIEW LETTERS AB For the local analysis of structural instability, a site-dependent measure of local contribution to a global mode is introduced which is decomposed into contributions from individual interatomic bonds. Since this measure incorporates both spatial and dynamical information, the method provides insight into the temporal evolution of the lattice instability. Using this method to study lattice decohesion under pure dilation, we find the crack nucleation process to consist of the onset of instabilities at several distinct sites, followed by coalescence of local instabilities which triggers the bond rupturing along a plane. SN 0031-9007 PD DEC 8 PY 1997 VL 79 IS 23 BP 4601 EP 4604 DI 10.1103/PhysRevLett.79.4601 UT WOS:A1997YK36500022 ER PT J AU Delin, A Fast, L Johansson, B Wills, JM Eriksson, O AF Delin, A Fast, L Johansson, B Wills, JM Eriksson, O TI Method for calculating valence stability in lanthanide systems SO PHYSICAL REVIEW LETTERS AB We demonstrate that from a state-of-the-art total energy method combined with information on atomic excitation energies, it is possible to calculate the energy difference between the divalent and trivalent states in lanthanide systems with an error less than 0.15 eV. This is shown by comparing theory with well documented experimental data for the lanthanide metals. In addition, we reproduce the intricate valence stability of selected Sm and Tm chalcogenides. Theory is thus shown to be able to address, without experimental input from the solid, important questions concerning intermediate valence. RI Eriksson, Olle/E-3265-2014; Delin, Anna/P-2100-2014 OI Eriksson, Olle/0000-0001-5111-1374; Delin, Anna/0000-0001-7788-6127 SN 0031-9007 EI 1079-7114 PD DEC 8 PY 1997 VL 79 IS 23 BP 4637 EP 4640 DI 10.1103/PhysRevLett.79.4637 UT WOS:A1997YK36500031 ER PT J AU McNeill, JD Lingle, RL Ge, NH Wong, CM Jordan, RE Harris, CB AF McNeill, JD Lingle, RL Ge, NH Wong, CM Jordan, RE Harris, CB TI Dynamics and spatial distribution of electrons in quantum wells at interfaces determined by femtosecond photoemission spectroscopy SO PHYSICAL REVIEW LETTERS AB The dynamics of excited electrons in insulator quantum well states on a metal substrate were determined by femtosecond two-photon photoemission for the first time. Lifetimes are reported for the first three excited states for 1-6 atomic layers of Xe on Ag(lll). As the image states evolve into quantum well states with increasing coverage, the lifetimes undergo an oscillation as the layer boundary crosses each node of the wave function. The lifetime data are modeled by extending the two-band nearly free-electron approximation to account for the presence of a dielectric layer. The lifetimes are shown to depend on the spatial distribution of the interfacial electron. RI McNeill, Jason/E-5389-2011 SN 0031-9007 EI 1079-7114 PD DEC 8 PY 1997 VL 79 IS 23 BP 4645 EP 4648 DI 10.1103/PhysRevLett.79.4645 UT WOS:A1997YK36500033 ER PT J AU Shenoy, SR Subrahmanyam, V Bishop, AR AF Shenoy, SR Subrahmanyam, V Bishop, AR TI Quantum paraelectric model for layered superconductors SO PHYSICAL REVIEW LETTERS AB We consider a Hubbard-model (H) layer of charged-carrier fraction x much less than 1, and an rms buckling angle s much less than 1, that is elastically and electrically coupled to anharmonic (oxygen) dipoles in a ferroelectric Bilz-model (B) layer. We find that (a) the B-layer dipoles are driven to a paraelectric phase by H-layer zero-point fluctuations; (b) the c-axis (dipolar, optical) and H-layer (acoustic) modes are mixed by s to form omega(+/-)(q) modes; and (c) the mode exchange, enhanced by a (omega(+)(2) - omega(-)(2))(-1) similar to s(-1) resonant denominator, produces dynamical local carrier pairing and 2D Anderson-Morel d(x2-y2)-type superconductivity, with peaks or plateaus in T-c(x). SN 0031-9007 PD DEC 8 PY 1997 VL 79 IS 23 BP 4657 EP 4660 DI 10.1103/PhysRevLett.79.4657 UT WOS:A1997YK36500036 ER PT J AU Solterbeck, C Schattke, W ZahlmannNowitzki, JW Gawlik, KU Kipp, L Skibowski, M Fadley, CS VanHove, MA AF Solterbeck, C Schattke, W ZahlmannNowitzki, JW Gawlik, KU Kipp, L Skibowski, M Fadley, CS VanHove, MA TI Energetic and spatial bonding properties from angular distributions of ultraviolet photoelectrons: Application to the GaAs(110) surface SO PHYSICAL REVIEW LETTERS AB Angle-resolved ultraviolet photoemission spectra are interpreted by combining the energetics and spatial properties of the contributing states. One-step calculations are in excellent agreement with new azimuthal experimental data for GaAs(110). Strong variations caused by the dispersion of the surface bands permit an accurate mapping of the electronic structure. The delocalization of the valence states is discussed analogous to photoelectron diffraction. The spatial origin of the electrons is determined, and found to be strongly energy dependent, with uv excitation probing the bonding region. RI Van Hove, Michel/A-9862-2008 OI Van Hove, Michel/0000-0002-8898-6921 SN 0031-9007 PD DEC 8 PY 1997 VL 79 IS 23 BP 4681 EP 4684 DI 10.1103/PhysRevLett.79.4681 UT WOS:A1997YK36500042 ER PT J AU Gailey, PC Neiman, A Collins, JJ Moss, F AF Gailey, PC Neiman, A Collins, JJ Moss, F TI Stochastic resonance in ensembles of nondynamical elements: The role of internal noise SO PHYSICAL REVIEW LETTERS AB While many examples of noise-induced signal enhancement have been reported, the role of internal noise has received little attention. Here we study aperiodic stochastic resonance in parallel arrays of nondynamical elements with internal noise. Ensembles of both threshold and threshold-free elements are studied, and the model is applied to two-state ion channels. In finite systems where the input signal controls the probability of discrete events, we demonstrate that the internal noise is modulated by both the applied signal and the external noise. We also show that the internal noise plays a constructive role in information transfer through such systems via an increase in external noise. RI Neiman, Alexander/G-2196-2010 OI Neiman, Alexander/0000-0002-0906-9894 SN 0031-9007 PD DEC 8 PY 1997 VL 79 IS 23 BP 4701 EP 4704 DI 10.1103/PhysRevLett.79.4701 UT WOS:A1997YK36500047 ER PT J AU Tyrlik, SK Tomasik, P Anderegg, JW Baczkowicz, M AF Tyrlik, SK Tomasik, P Anderegg, JW Baczkowicz, M TI Titanium (IV) starch complexes SO CARBOHYDRATE POLYMERS AB Potato and maize starch was titanated with titanium (IV) ethoxide. In both cases titanium was bound via the valence bond to the oxygen atom of the glucose unit 6-CH2OH group, with insignificant coordination to other oxygen atoms present in these units, and the titanium reagent was partly complexed with starch. The amount of titanium bound to starch in both cases was dependent on the starch variety and not on the starch/titanium (IV) ethoxide ratio in the reaction. After the reaction potato and maize starch contained 37.5 and 42.0% of titanium, respectively. Titanium (IV) potato and maize 'starchates' fully decomposed and lost complexed titanium (IV) ethoxide at 470 and 450 degrees C, respectively. Titanium (IV) oxide powder formed the residue in each case. (C) 1997 Published by Elsevier Science Ltd. All rights reserved. SN 0144-8617 PD DEC 5 PY 1997 VL 34 IS 1-2 BP 1 EP 7 DI 10.1016/S0144-8617(97)00102-1 UT WOS:000071392600001 ER PT J AU Ortiz, JV Rohlfing, CM AF Ortiz, JV Rohlfing, CM TI An ab initio study of geometries, polarizabilities, and rotation barriers of polyphenylsilane oligomers SO CHEMICAL PHYSICS LETTERS AB MP2 optimizations with the 6-31G* basis set have been performed on Si-3(C6H5)(2)H-6 and Si-3(C6H5)(3)H-5. The resulting structural information has been employed in determinations of rotation barriers and static polarizabilities at the HF/3-21G* level. Potential energy profiles for rotation about the central Si-Si bond have been obtained for two structural isomers of Si-4(C6H5)(4)H-6. Trends in polarizabilities for isotactic and syndiotactic oligomers from N=4 to N=8 have been extrapolated to the infinite polymer limit and the results are consistent with calculations where N=10. Helical structures have been considered through calculations on the N=8 chain with varying dihedral angles in the Si backbone. (C) 1997 Elsevier Science B.V. SN 0009-2614 PD DEC 5 PY 1997 VL 280 IS 3-4 BP 239 EP 243 DI 10.1016/S0009-2614(97)01108-1 UT WOS:000071131200012 ER PT J AU Su, XC Shen, YR Somorjai, GA AF Su, XC Shen, YR Somorjai, GA TI The surface chemistry of 1,3-cyclohexadiene and 1,4-cyclohexadiene on Pt(111) studied by surface vibrational spectroscopy with sum frequency generation SO CHEMICAL PHYSICS LETTERS AB The structure and reactions of 1,3-cyclohexadiene and 1,4-cyclohexadiene on Pt(111) has been studied by sum frequency generation at a pressure of 10(-10)-1 Torr. It was found that 1,4-cyclohexadiene adsorbs flat on the surface at low temperature and dehydrogenates to adsorbed benzene at about 300 K. 1,3-Cyclohexadiene undergoes a rearrangement to 1,3-cyclohexadiene through a 3-5 hydrogen shift which competes with the dehydrogenation reaction pathway at low temperature (< 290 K) and dehydrogenates to benzene at higher temperature. This competing reaction behavior has also been observed at 1 Torr pressure of 1,3-cyclohexadiene on Pt(111) at 285 K. (C) 1997 Elsevier Science B.V. SN 0009-2614 PD DEC 5 PY 1997 VL 280 IS 3-4 BP 302 EP 307 UT WOS:000071131200021 ER PT J AU Boettger, JC AF Boettger, JC TI Scalar-Relativistic LCGTO DFT calculations for atoms using the Douglas-Kroll transformation SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY CT 37th Annual Sanibel Symposium CY MAR 01-07, 1997 CL UNIV FLORIDA, PONCE DE LEON CONF CTR, ST AUGUSTINE, FL SP Univ Florida HO UNIV FLORIDA, PONCE DE LEON CONF CTR AB Haberlen and Rosch (HR) demonstrated [Chem. Phys. Lett. 199, 491 (1992)] the feasibility of performing scalar-relativistic, density functional theory (DFT) linear combination of Gaussian-tg pe orbitals-fitting function (LCGTO-FF) calculations on clusters of atoms using an ''incomplete'' Douglas-Kroll transformation. Some of the approximations used in their multiatom calculations have not yet been fully explored for isolated atoms, especially the neglect of matrix elements involving vector products of the momentum and the use of fitting functions. In this investigation, scalar-relativistic LCGTO calculations (without fitting functions) were carried out at four levels of approximation, including that employed by IIR, for four atoms: Ce, Au, Pb, and Pu. The results of these calculations suggest that the HR approximation should be applicable to atoms through the light actinides, so long as spin-orbit effects are unimportant. A comparison of very large basis-set results with results obtained using ordinary-size basis sets indicates that the valence (bonding) states from scalar-relativistic LCGTO-FF calculations should be no more sensitive to the orbital basis-set size than are their nonrelativistic counterparts. (C) 1997 John Wiley & Sons, Inc. SN 0020-7608 PD DEC 5 PY 1997 VL 65 IS 5 BP 565 EP 574 DI 10.1002/(SICI)1097-461X(1997)65:5<565::AID-QUA21>3.0.CO;2-0 UT WOS:A1997YG65000021 ER PT J AU Lehman, W Vibert, P Craig, R AF Lehman, W Vibert, P Craig, R TI Visualization of caldesmon on smooth muscle thin filaments SO JOURNAL OF MOLECULAR BIOLOGY AB Caldesmon, a narrow, elongated actin-binding protein, is found in both nonmuscle and smooth muscle cells. It inhibits actomyosin ATPase and filament severing in vitro, and is thus a putative regulatory protein. To elucidate its function, we have used electron microscopy and three-dimensional image reconstruction to reveal the location of caldesmon on isolated smooth muscle thin filaments. Caldesmon density was clearly delineated in reconstructions and found to occur peripherally, on the extreme outer edge of actin subdomains-l and 2, without making obvious contacts with tropomyosin strands on the inner domains of actin. When the reconstructions were fitted to the atomic model of F-actin, caldesmon appeared to cover potentially weak sites of myosin interaction with actin, while, together with tropomyosin, it flanked strong sites of myosin interaction, without covering them. These interactions are unlike those of troponin-tropomyosin and therefore inhibition of actomyosin ATPase by caldesmon-tropomyosin and by troponin-tropomyosin cannot occur in the same way. The location of caldesmon would allow it to compete with a number of cellular actin-binding proteins, including tl rose known to sever or sequester actin. (C) 1997 Academic Press Limited. SN 0022-2836 PD DEC 5 PY 1997 VL 274 IS 3 BP 310 EP 317 DI 10.1006/jmbi.1997.1422 UT WOS:000070972200003 PM 9405141 ER PT J AU Shelby, MD Tice, RR Witt, KL AF Shelby, MD Tice, RR Witt, KL TI 17-beta-estradiol fails to induce micronuclei in the bone marrow cells of rodents SO MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS SN 1383-5718 PD DEC 5 PY 1997 VL 395 IS 1 BP 89 EP 90 DI 10.1016/S1383-5718(97)00148-4 UT WOS:000071412100009 PM 9465917 ER PT J AU North, SW Marr, AJ Furlan, A Hall, GE AF North, SW Marr, AJ Furlan, A Hall, GE TI Nonintuitive asymmetry in the three-body photodissociation of CH3COCN SO JOURNAL OF PHYSICAL CHEMISTRY A AB Pathways, energetics, and mechanisms of the 193 nm photodissociation of acetyl cyanide (CH3COCN) have been investigated using high-resolution transient frequency modulation (FM) spectroscopy and photofragment translational spectroscopy. Vibrational and rotational state distributions of CN fragments measured by FM spectroscopy are in goad agreement with previous work, The quantum yield of CN is found to be 0.9 +/- 0.2. State-dependent translational energy distributions are nonstatistical. The laboratory-frame anisotropy of both velocity and angular momentum of CN fragments is vanishingly small, yet significant v.j correlations are observed, indicating a preference for the CN angular momentum to be perpendicular to the recoil velocity, Photofragment translational spectroscopy provided independent confirmation of kinetic energy distributions and fragmentation pathways. The combined measurements are consistent with the strong preference for primary CN elimination over CH3 elimination despite a large difference in C-C bond strengths. The primary acetyl radicals undergo virtually complete secondary dissociation. RI North, Simon/G-5054-2012; Hall, Gregory/D-4883-2013 OI North, Simon/0000-0002-0795-796X; Hall, Gregory/0000-0002-8534-9783 SN 1089-5639 PD DEC 4 PY 1997 VL 101 IS 49 BP 9224 EP 9232 DI 10.1021/jp972293x UT WOS:A1997YL17400006 ER PT J AU Dixon, DA Feller, D Peterson, KA AF Dixon, DA Feller, D Peterson, KA TI Accurate calculations of the electron affinity and ionization potential of the methyl radical SO JOURNAL OF PHYSICAL CHEMISTRY A AB The electron affinity and ionization potential for the CH3 radical have been calculated at high levels of ab initio molecular orbital theory. The best values are obtained by extrapolating CCSD(T)/aug-cc-pVxZ values where x = D, T, Q to the complete basis set limit. Zero-point energies were calculated at the CCSD(T)/aug-cc-pVTZ level and scaled to appropriate experimental values. The calculated values are EA(CH3) = 1.64 +/- 0.3 kcal/mol as compared to the experimental value of 1.84 +/- 0.69 kcal/mol and IP(CH3) = 9.837 +/- 0.01 eV as compared to the experimental value of 9.843 +/- 0.001 eV. The theoretical values included estimates of relativistic and core/valence correlation effects. SN 1089-5639 PD DEC 4 PY 1997 VL 101 IS 49 BP 9405 EP 9409 DI 10.1021/jp970964l UT WOS:A1997YL17400031 ER PT J AU Ho, P Colvin, ME Melius, CF AF Ho, P Colvin, ME Melius, CF TI Theoretical study of the thermochemistry of molecules in the Si-B-H-Cl system SO JOURNAL OF PHYSICAL CHEMISTRY A AB A self-consistent set of thermochemical parameters for about 100 molecules in the Si-B-H-Cl system is obtained using a combination of ab initio electronic structure calculations and empirical corrections (the BAC-MP4 method). The species include stable and radical species as well as a few transition states. Trends in calculated heats of formation, bond dissociation enthalpies, and heats of reaction for various molecular decomposition channels are discussed, Silylboranes are most Likely to decompose via the elimination of I-H, HCl, or silylenes, The presence of the B atom reduces the energy required for the 1,1 elimination of H-2 from the Si atom, relative to the analogous reaction in disilane. SN 1089-5639 PD DEC 4 PY 1997 VL 101 IS 49 BP 9470 EP 9488 DI 10.1021/jp971947z UT WOS:A1997YL17400041 ER PT J AU Omberg, KM Schoonover, JR Meyer, TJ AF Omberg, KM Schoonover, JR Meyer, TJ TI Electronic distribution in the metal-to-ligand charge transfer (MLCT) excited states of [(4,4'-(X)(2)bpy)(CO)(3)Re-I(4,4'-bpy)Re-I(CO)(3)(4,4'-(X)(2)bpy)](2+) (X = H, CH3). Application of time-resolved infrared and resonance Raman spectroscopies SO JOURNAL OF PHYSICAL CHEMISTRY A AB Ground- and excited-state resonance Raman and infrared spectra (354.7 nm excitation, in acetonitrile at 298 K) have been measured for [(4,4'-(X)(2)bpy>(Co)(3)Re-I(4,4'-bpy)Re-I(CO)(3)(4,4'-(X)(2)bpy)](2+)(bpy is 2,2'-bipyridine; 4,4'-bpy is 4,4'-bipyridine; X = H, CH3). The lowest lying excited states in these molecules are metal-to-ligand charge transfer (MLCT) in character. The spectra provide answers to two questions: Is the acceptor ligand for the excited electron 4,4'-bpy or 4,4'-(X)(2)bpy? Are there localized (Re-II-Re-I) or delocalized (Re-1.5-Re-1.5 5) sites in the mixed-valence excited states formed by MLCT excitation? Application of time-resolved resonance Raman (TR3) spectroscopy demonstrates that 4,4'-bpy is the acceptor in the lowest lying MLCT excited state(s) of [(dmb)(CO)(3)Re(4,4'-bpy)Re(CO)(3)(dmb)](2+)* (dmb = 4,4'-(CH3)(2)bpy) and that there is an equilibrium between 4,4'-bpy and bpy as acceptor in [(bpy)(CO)(3)Re(4,4'-bpy)Re(CO)(3)(bpy)](2+*). For both complexes, the appearance of two sets of overlapping v(CO) bands in the excited state by time-resolved infrared (TRIR) measurements is consistent with the localized description, Re-II-Re-I. RI Omberg, Kristin/I-5972-2013 SN 1089-5639 PD DEC 4 PY 1997 VL 101 IS 49 BP 9531 EP 9536 DI 10.1021/jp972522f UT WOS:A1997YL17400048 ER PT J AU Chang, TM Dang, LX AF Chang, TM Dang, LX TI Ion solvation in polarizable chloroform: A molecular dynamics study SO JOURNAL OF PHYSICAL CHEMISTRY B AB The structural, thermodynamic, and dynamical properties of the alkali-metal cations and the halide anions in liquid chloroform are investigated using molecular dynamics simulation techniques, From the atomic radiat distribution analysis, the chloroform molecules are found to form well-defined solvation shells around the alkali-metal cations and the halide anions. The size of the solvation cage and the coordination number both increase with increasing ion size. In liquid chloroform, all these ions are shown to induce a strong orientational order in the surrounding chloroform molecules as evidenced by the angular distribution functions. We found that the mean electric potentials induced by the chloroform molecules shifted to smaller magnitudes With increasing ion size. Because of the greater electric polarizabilities of the larger ions, the average induced dipole moments were enhanced with increasing ion size. The diffusion coefficients of the alkali-metal cations and the halide anions in liquid chloroform are estimated from the mean-square displacements and the velocity autocorrelation functions. Generally, the diffusion constants of the cations are larger than those of the anions, For the cations, the diffusion constants are of similar magnitudes and do nor depend on the ion size. However, the diffusion coefficients of the halide anions show a strong dependence on the ion size, The motion of the first coordination shell chloroform molecules is examined via their velocity autocorrelation functions. These correlation functions behave very similarly, suggesting that the motion of the first solvation shell is not governed by the sizes or the charges of these ions, In addition, the residence time autocorrelation functions of the first solvation shell are evaluated. As expected, the residence time decreases as the ion size increases. SN 1089-5647 PD DEC 4 PY 1997 VL 101 IS 49 BP 10518 EP 10526 DI 10.1021/jp972101y UT WOS:A1997YK29100049 ER PT J AU Csaki, C Skiba, W AF Csaki, C Skiba, W TI Duality in Sp and SO gauge groups from M theory SO PHYSICS LETTERS B AB We describe fivebrane configurations in M theory whose 4-d spacetime contains N = 1 supersymmetric Sp or SO gauge fields and fundamentals of these groups. We show how field-theory dualities for Sp and SO groups can be derived using these fivebrane configurations in M theory. (C) 1997 Elsevier Science B.V. SN 0370-2693 PD DEC 4 PY 1997 VL 415 IS 1 BP 31 EP 38 DI 10.1016/S0370-2693(97)01222-7 UT WOS:000071094500005 ER PT J AU Grossman, Y Kayser, B Nir, Y AF Grossman, Y Kayser, B Nir, Y TI The role of the vacuum insertion approximation in calculating CP asymmetries in B decays SO PHYSICS LETTERS B AB CP asymmetries in B decays into final CP eigenstates are in many cases theoretically clean. In particular, they do not depend on the values of hadronic parameters. The sign of the asymmetries, however, does depend on the sign of the B-B parameter. Furthermore, the information from epsilon(K) that all angles of the unitarity triangles lie in the range {O, pi} depends on the sign of the B-K parameter. Consequently, in the (unlikely) case that the vacuum insertion approximation is such a poor approximation that either B-B or B-K is negative, the sign of CP asymmetries in neutral B decays will be opposite to the standard predictions. Various subtleties concerning the role of K-(K) over bar mixing in the case of final states with a single K-S or K-L, such as the B --> psi K-S decay, are clarified. (C) 1997 Elsevier Science B.V. SN 0370-2693 PD DEC 4 PY 1997 VL 415 IS 1 BP 90 EP 96 DI 10.1016/S0370-2693(97)01223-9 UT WOS:000071094500013 ER PT J AU Andrews, MA Cook, GK Shriver, ZH AF Andrews, MA Cook, GK Shriver, ZH TI Thermodynamics of inter- and intramolecular hydrogen bonding in (disphosphine)platinum(II) diolate complexes and its role in carbohydrate complexation regioselectivity SO INORGANIC CHEMISTRY AB Thermodynamic data are reported for intermolecular hydrogen-bonding association of 1 and 2 equiv of phenol with [1,3 -bis(diphenylphosphino)propane] (phenylethane-1,2-diolato) platinum(II) ((dppp)Pt(Ped)) in dichloromethane solution: Delta H-1 degrees = -7.0 +/- 0.1 kcal/mol, Delta H-2 degrees = -7.7 +/- 0.4 kcal/mol, Delta S-1 degrees = -11.3 +/- 0.4 eu, and Delta S-2 degrees -17.8 +/- 1.2 eu. For comparison, the thermodynamics for hydrogen bonding of phenol to triphenylphosphine oxide in dichloromethane were also determined: Delta H degrees = -5.1 +/- 0.3 kcal/mol; Delta S degrees = -8.8 +/- 1.0 eu. Competitive coordination exchange reactions have been used to determine the apparent intramolecular hydrogen bond strengths in (dppp)Pt(1,2-O,O'-glycerolate) and (dppp)Pt(1,2-O,O'-butane-1,2,4-triolate) in both dichloromethane (Delta G(313) = -2.05 +/- 0.05 and -2.52 +/- 0.06 kcal/mol. respectively) and pyridine (Delta G(313) = -0.62 +/- 0.03 and -0.82 +/- 0.03 kcal/mol, respectively). Based on these findings, the role of hydrogen-bonding interactions in determining the regioselectivities of complexation of carbohydrates to diphosphine Pt(II) is discussed. SN 0020-1669 EI 1520-510X PD DEC 3 PY 1997 VL 36 IS 25 BP 5832 EP 5844 DI 10.1021/ic970860p UT WOS:A1997YK96400028 ER PT J AU English, DS Das, K Ashby, KD Park, J Petrich, JW Castner, EW AF English, DS Das, K Ashby, KD Park, J Petrich, JW Castner, EW TI Confirmation of excited-state proton transfer and ground-state heterogeneity in hypericin by fluorescence upconversion SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB Fluorescence upconversion measurements of hypericin and its methylated analog, O-hexamethoxyhypericin, which possesses no labile protons, confirm excited-state proton (or hydrogen atom) transfer as the primary photophysical event in hypericin. The presence of a rising component in the time-resolved fluorescence of hypericin and the absence of such a component for the hexamethoxy analog are consistent with our assignment of excited-state proton or atom transfer as the primary photophysical process in the light-activated antiviral compound, hypericin. The results using the fluorescence upconversion technique, which detects only emission from the excited state, are in good agreement with our previous transient absorbance measurements. The results are also consistent with a heterogeneous ground state of hypericin. RI English, Douglas/B-9382-2009; Petrich, Jacob/L-1005-2015 SN 0002-7863 PD DEC 3 PY 1997 VL 119 IS 48 BP 11585 EP 11590 DI 10.1021/ja9721071 UT WOS:A1997YK50200004 ER PT J AU Manna, J Kuehl, CJ Whiteford, JA Stang, PJ Muddiman, DC Hofstadler, SA Smith, RD AF Manna, J Kuehl, CJ Whiteford, JA Stang, PJ Muddiman, DC Hofstadler, SA Smith, RD TI Nanoscale tectonics: Self-assembly, characterization, and chemistry of a novel class of organoplatinum square macrocycles SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY AB Six nanoscale molecular squares are reported. They are prepared in essentially quantitative yields via spontaneous self-assembly of preprogrammed 90 degrees angular units with diverse bimetallic linear linkers. Characterization was accomplished with multinuclear NMR and, in two cases, via ESI-FTICR mass spectral data. The size of these novel metallomacrocycles range from 3.6 nm (diagonal) and 2.6 nm (side) for the smallest to 4.7 nm (diagonal) and 3.4 nm (side) for the largest as estimated by extensible systematic force field calculations. The molecular squares incorporating alkynyl units as corners are able to complex four Ag+ ions via the pi-tweezer effect. RI Smith, Richard/J-3664-2012 OI Smith, Richard/0000-0002-2381-2349 SN 0002-7863 PD DEC 3 PY 1997 VL 119 IS 48 BP 11611 EP 11619 DI 10.1021/ja972668s UT WOS:A1997YK50200008 ER PT J AU Haake, M Pines, A Reimer, JA Seydoux, R AF Haake, M Pines, A Reimer, JA Seydoux, R TI Surface-enhanced NMR using continuous-flow laser-polarized xenon SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY SN 0002-7863 PD DEC 3 PY 1997 VL 119 IS 48 BP 11711 EP 11712 DI 10.1021/ja9713587 UT WOS:A1997YK50200029 ER PT J AU Gilmanshin, R Williams, S Callender, RH Woodruff, WH Dyer, RB AF Gilmanshin, R Williams, S Callender, RH Woodruff, WH Dyer, RB TI Fast events in protein folding: Relaxation dynamics and structure of the I form of apomyoglobin SO BIOCHEMISTRY AB The fast relaxation dynamics of the acid destabilized I form of apomyoglobin (pH* 3, 0.15 M NaCl: apoMb-I) following a laser-induced temperature-jump have been probed using time-resolved infrared spectroscopy. Only a fast, single exponential phase is observed (bleach centered at v = 1633 cm(-1) and transient absorbance at 1666 cm(-1)) with relaxation times of 38 ns at 30 degrees C and 36 ns at 57 degrees C; no additional slow (microsecond) phase is observed as previously found in the native form of apomyoglobin, Folding times of approximately 66 ns are derived from the observed rates based on a simple two-state model. The equilibrium melting of the 1633 cm(-1) component shows noncooperative linear behavior over the temperature range studied (10-60 degrees C). The low amide I' frequency, the fast relaxation dynamics, and the noncooperative melting behavior are characteristic of isolated solvated helix. The analysis of the amide-I' band reveals another major component at 1650 cm(-1) assigned to native-like structure stabilized by tertiary contacts involving the AGH core, which does not show dynamic or static melting under our conditions. ApoMb-I has generally been taken to be a ''molten globule'' species, The present results indicate a heterogeneous structure consisting of separate regions of native-like unit(s), solvated helices, and disordered coil, excluding a homogeneous molten globule as a model for apoMb-I. From the current studies and other results, a detailed model of the folding of apomyoglobin is presented. SN 0006-2960 PD DEC 2 PY 1997 VL 36 IS 48 BP 15006 EP 15012 DI 10.1021/bi970634r UT WOS:A1997YJ70900048 PM 9398226 ER PT J AU Cleri, F Wolf, D Yip, S Phillpot, SR AF Cleri, F Wolf, D Yip, S Phillpot, SR TI Atomistic simulation of dislocation nucleation and motion from a crack tip SO ACTA MATERIALIA AB A recently developed fully atomistic technique for fracture simulations is applied to the study of dislocation emission From a crack tip in an elastically anisotropic f.c.c. crystal. The detailed atomic-scale mechanisms of dislocation nucleation and motion are investigated as a function of the external load. Analysis of the atomic configurations around the crack tip demonstrates an intimate coupling of the nucleating dislocation with a step formed at the crack surface. Displacement and stress fields around both nucleating and moving dislocations are compared to the predictions of the Peierls-Nabarro continuum-elastic model by Rice. The size of a nucleating (''incipient'') dislocation is found to be larger than that of a fully-formed dislocation. Also, we elucidate the reasons why the value of the unstable-stacking energy estimated by means of the rigid-block sliding concept, a feature common to several continuum-elastic models, overestimates the activation energy for dislocation nucleation. We conclude that the concept of unstable-stacking energy should be replaced by the true energy barrier for dislocation nucleation, incorporating the full inhomogeneity of the displacement held. (C) 1997 Acta Metallurgica Inc. RI Phillpot, Simon/J-9117-2012; OI Phillpot, Simon/0000-0002-7774-6535 SN 1359-6454 PD DEC PY 1997 VL 45 IS 12 BP 4993 EP 5003 DI 10.1016/S1359-6454(97)00214-0 UT WOS:A1997YJ67000013 ER PT J AU Bahr, DF Hoehn, JW Moody, NR Gerberich, WW AF Bahr, DF Hoehn, JW Moody, NR Gerberich, WW TI Adhesion and acoustic emission analysis of failures in nitride films with 14 metal interlayer SO ACTA MATERIALIA AB Interfacial fracture has been induced between a tantalum nitride film with an aluminum inter layer on a sapphire substrate using nanoindentation. To identify failures for which a model calculation is valid a commercial acoustic emission sensor has been used to study the details of the failure event. The interfacial fracture energy of the system with an aluminum interlayer under the loading conditions at the crack tip is approximately 8 J/m(2). Within narrow bounds, this toughness value is reproducible using three different theoretical approaches. The acoustic emission signal is used to determine a lower bound interfacial crack velocity of 5 m/s. The majority of the failure occurs at the aluminum-sapphire interface, suggesting that the Fracture energy and crack velocity determined are related to the toughness of this interface and not the nitride-aluminum interface. RI Bahr, David/A-6521-2012 OI Bahr, David/0000-0003-2893-967X SN 1359-6454 PD DEC PY 1997 VL 45 IS 12 BP 5163 EP 5175 DI 10.1016/S1359-6454(97)00180-8 UT WOS:A1997YJ67000029 ER PT J AU Yost, FG Rye, RR Mann, JA AF Yost, FG Rye, RR Mann, JA TI Solder wetting kinetics in narrow V-grooves SO ACTA MATERIALIA AB Experiments are performed to observe capillary flow in grooves cut into copper surfaces. Flow kinetics of two liquids, 1-heptanol and eutectic Sn-Pb solder, are modeled with modified Washburn kinetics and compared to flow data. It is shown that both liquids flow parabolically in narrow V-grooves, and the data scale as predicted by the modified Washburn model. The early portions of the flow kinetics are characterized by curvature in the length vs time relationship which is not accounted for in the modified Washburn model. This effect is interpreted in terms of a dynamic contact angle. It is concluded that under conditions of rapid flow, solder spreading can be understood as a simple fluid flow process. Slower kinetics, e.g. solder droplet spreading on flat surfaces, may be affected by subsidiary chemical processes such as reaction. (C) 1997 Acta Metallurgica Inc. SN 1359-6454 PD DEC PY 1997 VL 45 IS 12 BP 5337 EP 5345 DI 10.1016/S1359-6454(97)00205-X UT WOS:A1997YJ67000045 ER PT J AU Bjorken, JD AF Bjorken, JD TI Disoriented chiral condensate: Theory and phenomenology SO ACTA PHYSICA POLONICA B CT XXXVII Cracow-School-of-Theoretical-Physics on Dynamics of Strong Interactions CY MAY 30-JUN 10, 1997 CL ZAKOPANE, POLAND SP Jagellonian Univ, Inst Phys, H Niewodniczanski Inst Nucl Phys, Peco Nis European Community Programme, Polish State Comm Sci Res AB The basic ideas underlying the production dynamics and search techniques for disoriented chiral condensate are described. SN 0587-4254 PD DEC PY 1997 VL 28 IS 12 BP 2773 EP 2791 UT WOS:000072416400012 ER PT J AU Walecka, JD AF Walecka, JD TI Electron scattering and nuclear structure SO ACTA PHYSICA POLONICA B CT XXXVII Cracow-School-of-Theoretical-Physics on Dynamics of Strong Interactions CY MAY 30-JUN 10, 1997 CL ZAKOPANE, POLAND SP Jagellonian Univ, Inst Phys, H Niewodniczanski Inst Nucl Phys, Peco Nis European Community Programme, Polish State Comm Sci Res AB These lectures are divided into two parts. First, an elementary introduction to elelctron scattering is presented, starting with the scattering of a non-relativistic lepton from a charge distribution, the extending to a relativistic Dirac electron, and finally including the quantum dynamics of the target. The relation to gamma decay is discussed. The analysis is repeated in a covariant manner and target structure functions defined. The parity violating: asymmetry in the scattering of longitudinally polarized electrons arising from the exchange of a Z is calculated. The structure functions are evaluated for deep-inelastic scattering: in the quark-parton model where they exhibit Bjorken scaling. The asymmetry arising from scattering polarized nucleons on polarized nucleons is calculated in this model, as is the parity-violating asymmetry. The second part of the lecture series presents an overview of the current status of electron scattering, including a description of CEBAF. This latter material already appears in the published literature. SN 0587-4254 PD DEC PY 1997 VL 28 IS 12 BP 2897 EP 2917 UT WOS:000072416400017 ER PT J AU Moore, JD Cui, ST Cummings, PT Cochran, HD AF Moore, JD Cui, ST Cummings, PT Cochran, HD TI Lubricant characterization by molecular simulation SO AICHE JOURNAL RI Moore, Jonathan/B-8201-2009; Cummings, Peter/B-8762-2013 OI Cummings, Peter/0000-0002-9766-2216 SN 0001-1541 PD DEC PY 1997 VL 43 IS 12 BP 3260 EP 3263 DI 10.1002/aic.690431215 UT WOS:A1997YL14600014 ER PT J AU Asjo, B Barin, F Biberfeld, G Bradac, J Buve, A Dielly, S Fontanet, A Gurtler, L vanderGroen, G Hoelscher, M HolmHansen, C Hu, D JordanHarder, B Kaleebu, P Kaptue, L Korber, B Levin, A Lukashov, V Lyamuya, E Mboup, S McCutchan, FE Jackson, HM Mhalu, F Mkwera, H Msobi, N Mullins, J Mwakagile, D Nandi, J Nkengasong, J Nukulila, T Osmanov, S Peeters, M Pletschette, M Scarlatti, G Shao, J Shao, YM Sonnenburg, FV Sutherland, D Tennagashaw, M Urassa, W deVincenzi, I Weber, J Williamson, C Wolf, H AF Asjo, B Barin, F Biberfeld, G Bradac, J Buve, A Dielly, S Fontanet, A Gurtler, L vanderGroen, G Hoelscher, M HolmHansen, C Hu, D JordanHarder, B Kaleebu, P Kaptue, L Korber, B Levin, A Lukashov, V Lyamuya, E Mboup, S McCutchan, FE Jackson, HM Mhalu, F Mkwera, H Msobi, N Mullins, J Mwakagile, D Nandi, J Nkengasong, J Nukulila, T Osmanov, S Peeters, M Pletschette, M Scarlatti, G Shao, J Shao, YM Sonnenburg, FV Sutherland, D Tennagashaw, M Urassa, W deVincenzi, I Weber, J Williamson, C Wolf, H TI HIV-1 subtypes: implications for epidemiology, pathogenicity, vaccines and diagnostics - Workshop report from the European Commission (DG XII, INCO-DC) and the Joint United Nations Programme on HIV/AIDS SO AIDS AB Forty-three AIDS scientists from Europe, Africa, the United States, Canada, India and China met in Dar es Salaam, Tanzania to discuss the implications of the global variation of HIV (list of participants included in Appendix). This meeting followed an earlier meeting of the Joint United Nations Programme on HIV/AIDS, held in 1996 in Berlin, Germany [1], in which HIV genetic variability was considered in relation to transmissibility. During the Tanzania meeting, available data pertaining to the biological consequences of HIV genetic variation and its ramifications with regard to epidemiology, diagnostics, classification, and vaccine design were systematically reviewed. There was consensus that classification based on genetically defined subtypes provides an important framework for making advances on understanding viral biology and immunology, and for vaccine development. In addition, other groupings of viruses based on immunological and biological characteristics would be also valuable and help to further refine our understanding of the implications of variability. Key elements of the discussion are summarized here in the context of a review of the current literature. RI Hoelscher, Michael/D-3436-2012; OI Korber, Bette/0000-0002-2026-5757 SN 0269-9370 PD DEC PY 1997 VL 11 IS 15 BP 17 EP 36 UT WOS:A1997YH35800025 ER PT J AU Weinberg, AM AF Weinberg, AM TI Scientific millenarianism SO AMERICAN CERAMIC SOCIETY BULLETIN CT 99th Annual Meeting of the American-Ceramic-Society CY MAY 04-07, 1997 CL CINCINNATI, OHIO SP Amer Ceram Soc SN 0002-7812 PD DEC PY 1997 VL 76 IS 12 BP 57 EP 60 UT WOS:000071053400005 ER PT J AU Jones, RH Allen, BP Sharitz, RR AF Jones, RH Allen, BP Sharitz, RR TI Why do early-emerging tree seedlings have survival advantages?: A test using Acer rubrum (Aceraceae) SO AMERICAN JOURNAL OF BOTANY AB In forest understories, tree seedlings that germinate and emerge early in the growing season have significant survival advantages. We hypothesized that (a) early emergence is related to seed size and half-sib family, and (b) increased survival is due to reduced competition for resources. To test these hypotheses, we collected seeds of Acer rubrum from four half-sib families and planted them in the understory of a South Carolina floodplain forest. In one experiment, date of emergence was not related to seed size or half-sib family. However, our method of seed collection may have underestimated variability among half-sib families. In a second experiment, seeds were spread onto 20 understory plots, half of which were trenched to reduce root competition with overstory trees. One-year survival and biomass were greater for early-than for later-emerging cohorts. Trenching changed biomass distribution among aboveground parts and may have increased total biomass, but had essentially no impact on survival or root mass. Variation in plot flooding resulted in large differences in timing of emergence, survival, and biomass. For Acer rubrum, the survival advantage accorded by early emergence may be more related to flooding, light conditions, and genetic heterogeneity than to seed size or avoidance of root competition. SN 0002-9122 PD DEC PY 1997 VL 84 IS 12 BP 1714 EP 1718 DI 10.2307/2446470 UT WOS:000071234000011 PM 21708576 ER PT J AU Mendola, P Buck, GM Sever, LE Zielezny, M Vena, JE AF Mendola, P Buck, GM Sever, LE Zielezny, M Vena, JE TI Consumption of PCB-contaminated freshwater fish and shortened menstrual cycle length SO AMERICAN JOURNAL OF EPIDEMIOLOGY AB Highly contaminated Lake Ontario sport fish represent an important human dietary exposure to polychlorinated biphenyls (PCBs) and other toxic contaminants that may disrupt endocrine pathways. New York State Angler Cohort women interviewed by telephone in 1993 provided menstrual cycle length (n = 2,223). Fish consumption at cohort enrollment in 1991 was categorized by duration and frequency and was used to calculate a PCB exposure index, Multiple regression analyses identified significant cycle length reductions with consumption of more than one fish meal per month (1.11 days) and moderate/high estimated PCB index (-1.03 days). Women who consumed contaminated fish for 7 years or more also had shorter cycles (-0.63 days). OI Mendola, Pauline/0000-0001-5330-2844; Buck Louis, Germaine/0000-0002-1774-4490 SN 0002-9262 EI 1476-6256 PD DEC 1 PY 1997 VL 146 IS 11 BP 955 EP 960 UT WOS:A1997YJ90400009 PM 9400337 ER PT J AU Brame, EG Ferraro, JR Swan, E AF Brame, EG Ferraro, JR Swan, E TI Status of the Chemical Instrument Museum SO AMERICAN LABORATORY AB The Chemical Instrument Museum houses a display of instruments that played a significant role in the advancement of chemical science. This institution plays an important role in the educational and cultural development of the scientific community and deserves our support. SN 0044-7749 PD DEC PY 1997 VL 29 IS 24 BP 58 EP + UT WOS:000071274800014 ER PT J AU Wei, J Lee, CS AF Wei, J Lee, CS TI Polyacrylamide gel electrophoresis coupled with matrix-assisted laser desorption/ionization mass spectrometry for tRNA mutant analysis SO ANALYTICAL CHEMISTRY AB In analogy to two-dimensional analysis, the mobility shift in native polyacrylamide gel electrophoresis (PAGE) due to a nucleotide substitution of a single-stranded transfer ribonucleic acid (tRNA) fragment serves as the first dimension for tRNA mutation analysis. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), as the second dimension, allows precise determination of the mass of the tRNA fragments resolved by native PAGE. Off-line combination of native PAGE with MALDI-MS is demonstrated for high-resolution analysis of tRNA(val) and its mutants, including a three-nucleotide deletion and 12 single-base substitutions, Three approaches, including direct extraction of tRNAs from gel into buffer solution, dissolution of membrane in the matrix solution, and direct desorption of tRNAs from the membrane, are studied for coupling native PAGE with MALDI-MS. The membrane dissolution method is simple, and the resulting mixture is amenable to MALDI-MS analysis. In the membrane dissolution method, as little as 1 mu g or 40 pmol of tRNA sample is loaded on a native gel, separated, capillary eluted onto a nitrocellulose membrane, and recovered using the matrix solution of 2,4,6-trihydroxyacetophenone in acetone. SN 0003-2700 PD DEC 1 PY 1997 VL 69 IS 23 BP 4899 EP 4904 DI 10.1021/ac970725u UT WOS:A1997YJ91300029 PM 9454509 ER PT J AU Alvarado, JS Silzer, J Lemley, F Erickson, MD AF Alvarado, JS Silzer, J Lemley, F Erickson, MD TI Separation of polychlorinated biphenyls by fast gas chromatography SO ANALYTICAL COMMUNICATIONS AB The separation of commercially available polychlorinated biphenyls (PCBs) by fast gas chromatography (fast GC) has been studied. Aroclor 1254 was separated by using two column types: DB-1 and SPB-608. The fast GC used a split-splitless injector to introduce the sample, followed by a cold trap at -90 degrees C to focus the sample. Rapid heating was used to introduce the sample into the short chromatographic column to decrease band broadening. Hydrogen was the carrier gas at velocities of 100 to 125 cm s(-1). Analyses were performed by using an electron capture detector (ECD). Separation was achieved with both columns in less than 6 min, With the greatly shortened run times, reproducibility can be tested quickly and consequently with low cost. SN 1359-7337 PD DEC PY 1997 VL 34 IS 12 BP 381 EP 383 DI 10.1039/a706975h UT WOS:000071068700002 ER PT J AU Pern, FJ AF Pern, FJ TI Ethylene-vinyl acetate (EVA) encapsulants for photovoltaic modules: Degradation and discoloration mechanisms and formulation modifications for improved photostability SO ANGEWANDTE MAKROMOLEKULARE CHEMIE CT 19th Annual International Conference on Advances in the Stabilization and Degradation of Polymers CY JUN 09-11, 1997 CL LUZERN, SWITZERLAND AB Long-term photothermal stability is needed for the polymeric encapsulants made of ethylene-vinyl acetate (EVA) copolymer used in crystalline-silicon (c-Si) based photovoltaic (PV) modules. Severe browning of EVA was observed in late 1980s on Carrisa Plains PV arrays installed with reflecting mirrors and resulted in large losses of the power output. The EVA browning crisis prompted NREL scientists in 1990 to investigate the problems and search for solutions. The key degradation mechanisms and discoloration factors were investigated by using a variety of film samples, including field-degraded EVA samples and two commercial EVA formulations, regular-cure A9918 and fast-cure 15295, that were laminated, cured, and subjected to accelerated environmental exposures. Chemical, thermogravimetric, absorption/transmission, colorimetric, and fluorescence analyses were employed to characterize the EVA samples. Current-voltage (I-V) measurements were used to determine the electrical performance characteristics of solar cells. The results show that photothermal degradation is greater than thermal degradation and that the EVA A9918 discolors earlier and faster than EVA 15295. The UV absorber, Cyasorb UV 531,((TM)) in commercial formulations decomposes photochemically and its decomposition rate is directly related to the temporal evolution of discoloring polyenic chromophores. In general, the loss rate of the UV absorber and the progress of EVA discoloration from light yellow to brown follow a sigmoidal pattern. Physically, W-filtering glass superstrates that remove UV less than or equal to 350 nm effectively reduce the discoloration rate of both commercial EVA formulations. Chemically, the EVA discoloration rate is affected by a number of factors, but more strongly by the formulation additives and curing conditions, in which additives and curing-generated chromophores and their concentrations show a synergistic discoloring effect. Photobleaching reactions are responsible for the non-discolored but degraded EVA because of oxidative destruction of the curing-generated chromophores in the presence of oxygen. By using specifically selected stabilizers and curing agents in the new formulations, a large reduction in the chromophore generation by curing has been achieved and resulted in significant improvement of the photostability against discoloration. SN 0003-3146 PD DEC PY 1997 VL 252 BP 195 EP 216 DI 10.1002/apmc.1997.052520114 UT WOS:000071167400015 ER PT J AU Shenton, LR Bowman, KO AF Shenton, LR Bowman, KO TI Replenishment-depletion urn in equilibrium SO ANNALS OF THE INSTITUTE OF STATISTICAL MATHEMATICS AB An urn has balls of colors C-1 and C-2. It is replenished (R) by balls of both colors and then depleted by (D) the same number; this constitutes a cycle. When R = D, the system is closed and equilibrium will be reached after many cycles. The ultimate distribution is found only when the replenishment is the same for each color. Asymptotic normal and asymptotic binomial distributions arise when the parameters reach extreme values. For the multicolor urn an expression is given for the correlation between the number of balls of any two colors. SN 0020-3157 PD DEC PY 1997 VL 49 IS 4 BP 749 EP 760 DI 10.1023/A:1003278628791 UT WOS:000071601200010 ER PT J AU Kadam, KL Schmidt, SL AF Kadam, KL Schmidt, SL TI Evaluation of Candida acidothermophilum in ethanol production from lignocellulosic biomass SO APPLIED MICROBIOLOGY AND BIOTECHNOLOGY AB A Saccharomyces-cerevisiae-based simultaneous saccharification and fermentation (SSF) of lignocellulosic biomass is limited to an operating temperature of about 37 degrees C, and even a small increase in temperature can have a deleterious effect. This points to a need for a more thermotolerant yeast. To this end, S. cerevisiae D(5)A and a thermotolerant yeast, Candida acidothermophilum, were tested at 37 degrees C, 40 degrees C, and 42 degrees C using dilute-acid-pretreated poplar as substrate. At 40 degrees C, C. acidothermophilum produced 80% of the theoretical ethanol yield, which was higher than the yield from S. cerevisiae DSA at either 37 degrees C or 40 degrees C. At 42 degrees C, C. acidothermophilum showed a slight drop in performance. On the basis of preliminary estimates, SSF with C. acidothermophilum at 40 degrees C can reduce cellulase costs by about 16%. Proportionately greater savings can be realized at higher temperatures if such a high-temperature SSF is feasible. This demonstrates the advantage of using thermophilic or thermotolerant yeasts. SN 0175-7598 PD DEC PY 1997 VL 48 IS 6 BP 709 EP 713 UT WOS:000071324100006 PM 9457800 ER PT J AU Hyman, JM Shashkov, M AF Hyman, JM Shashkov, M TI Adjoint operators for the natural discretizations of the divergence, gradient and curl on logically rectangular grids SO APPLIED NUMERICAL MATHEMATICS AB We use the support-operator method to derive new discrete approximations of the divergence, gradient, and curl using discrete analogs of the integral identities satisfied by the differential operators. These new discrete operators are adjoint to the previously derived natural discrete operators defined using 'natural' coordinate-invariant definitions, such as Gauss' theorem for the divergence. The natural operators cannot be combined to construct discrete analogs of the second-order operators div grad, grad div, and curl curl because of incompatibilities in domains and in the ranges of values for the operators. The same is true for the adjoint operators, However, the adjoint operators have complementary domains and ranges of values and the combined set of natural and adjoint operators allow a consistent formulation for ail the compound discrete operators. We also prove that the operators satisfy discrete analogs of the major theorems of vector analysis relating the differential operators, including div (A) over right arrow = 0 if and only if (A) over right arrow = curl (B) over right arrow; curl (A) over right arrow = 0 if and only if (A) over right arrow = grad phi. (C) 1997 Elsevier Science B.V. SN 0168-9274 PD DEC PY 1997 VL 25 IS 4 BP 413 EP 442 DI 10.1016/S0168-9274(97)00097-4 UT WOS:A1997YJ72500006 ER PT J AU Altkorn, R Koev, I VanDuyne, RP Litorja, M AF Altkorn, R Koev, I VanDuyne, RP Litorja, M TI Low-loss liquid-core optical fiber for low-refractive-index liquids: fabrication, characterization, and application in Raman spectroscopy SO APPLIED OPTICS AB We describe a liquid-core optical fiber based on capillary tubing of Teflon AF 2400, which is a clear, amorphous fluoropolymer having a refractive index of 1.29. When filled with virtually any transparent liquid, the fiber is capable of transmitting Light by total internal reflection. Loss below 3 dB/m is demonstrated throughout much of the visible region for a 250-mu m-i.d. fiber filled with water. The utility of this device in enhancing the intensity of Raman spectra of core liquids is demonstrated. (C) 1997 Optical Society of America. SN 0003-6935 PD DEC 1 PY 1997 VL 36 IS 34 BP 8992 EP 8998 DI 10.1364/AO.36.008992 UT WOS:A1997YJ89900023 PM 18264455 ER PT J AU London, RA Glinsky, ME Zimmerman, GB Bailey, DS Eder, DC Jacques, SL AF London, RA Glinsky, ME Zimmerman, GB Bailey, DS Eder, DC Jacques, SL TI Laser-tissue interaction modeling with LATIS SO APPLIED OPTICS AB The role of modeling in designing new treatment protocols and instruments is discussed. A computer program for modeling laser-tissue interaction named LATIS is described. Interactions are divided into the processes of laser propagation, thermal effects, material effects, and hydrodynamics. Full coupling of the processes is taken into consideration. Applications in photothermal and photomechanical laser-tissue interactions are briefly discussed. A detailed description is given of a particular application of LATIS to study the effects of dynamic optical properties on dosimetry in photothermal therapy. Optical properties are functions of tissue damage, as determined by previous measurements. Results are presented for the time variation of the light distribution and damage within the tissue as the optical properties of the tissue are altered. It is found that proper accounting of dynamical optical properties is important for accurate dosimetry modeling. (C) 1997 Optical Society of America. SN 0003-6935 PD DEC 1 PY 1997 VL 36 IS 34 BP 9068 EP 9074 DI 10.1364/AO.36.009068 UT WOS:A1997YJ89900034 PM 18264466 ER PT J AU Perry, DL Thompson, AC Russo, RE Mao, XL Chapman, KL AF Perry, DL Thompson, AC Russo, RE Mao, XL Chapman, KL TI Characterization of quaternary metal oxide films by synchrotron X-ray fluorescence microprobe SO APPLIED SPECTROSCOPY AB A synchrotron X-ray fluorescence microprobe has been used to study the composition and microstructure of pulsed-laser ablation-deposited films of calcium-nickel-potassium oxides that have applications in heterogeneous catalysis. The films, whose individual metal oxide components have widely varying boiling points and thus prevent a solid-phase synthesis with the use of standard thermal techniques, represent a new quaternary metal oxide phase containing the three elements. Experimental conditions for preparing the films are given. The X-ray fluorescence microprobe data are discussed with respect to both the distribution of the three metals in the films at the micrometer lateral spatial resolution level and the presence of trace amounts of metals that were introduced into the films as contaminants in targets made of the parent three-metal oxide. SN 0003-7028 PD DEC PY 1997 VL 51 IS 12 BP 1781 EP 1783 DI 10.1366/0003702971939749 UT WOS:000071475300004 ER PT J AU Hahn, DW Flower, WL Hencken, KR AF Hahn, DW Flower, WL Hencken, KR TI Discrete particle detection and metal emissions monitoring using laser-induced breakdown spectroscopy SO APPLIED SPECTROSCOPY AB The unique conditions for the application of laser-induced breakdown spectroscopy (LIBS) as a metal emissions monitoring technology have been discussed. Because of the discrete, particulate nature of effluent metals, the utilization of LIBS is considered in part as a statistical sampling problem involving the finite laser-induced plasma volume, as well as the concentration and size distribution of the target metal species. Particle sampling rates are evaluated and Monte Carlo simulations are presented for relevant LIES parameters and wastestream conditions. For low metal effluent levels and submicrometer-sized particles, a LIBS-based technique mag become sample limited. An approach based on random LIBS sampling and the conditional analysis of the resulting data is proposed as a means to enhance the LIBS sensitivity in actual wastestreams. Monte Carlo simulations and experimental results from a pyrolytic waste processing facility are presented, which demonstrate that a significant enhancement of LIBS performance, greater than an order of magnitude, may be realized by taking advantage of the discrete particulate nature of metals. SN 0003-7028 PD DEC PY 1997 VL 51 IS 12 BP 1836 EP 1844 DI 10.1366/0003702971939659 UT WOS:000071475300013 ER PT J AU Bakac, A Burrows, HD AF Bakac, A Burrows, HD TI Uranyl ion: A convenient standard for transient molar absorption coefficient measurements SO APPLIED SPECTROSCOPY OI Burrows, Hugh/0000-0003-3127-2298 SN 0003-7028 PD DEC PY 1997 VL 51 IS 12 BP 1916 EP 1917 DI 10.1366/0003702971939767 UT WOS:000071475300023 ER PT J AU Kim, YJ Gao, Y Chambers, SA AF Kim, YJ Gao, Y Chambers, SA TI Core-level X-ray photoelectron spectra and X-ray photoelectron diffraction of RuO2(110) grown by molecular beam epitaxy on TiO2(110) SO APPLIED SURFACE SCIENCE AB We have measured Ru 3d, 4s, 4p and O Is high-resolution core-level X-ray photoelectron spectra, along with Ru 3d and O Is scanned-angle X-ray photoelectron diffraction angular distributions, for RuO2(110). The surfaces were prepared by oxygen-plasma-assisted molecular beam epitaxial growth of RuO2 on TiO2(110). XPS spectral interpretation and the nature of the XPD scans strongly suggest that the complex line shapes are due to final-state screening effects, rather than the presence of Ru in oxidation states other than +4. (C) 1997 Elsevier Science B.V. SN 0169-4332 PD DEC PY 1997 VL 120 IS 3-4 BP 250 EP 260 DI 10.1016/S0169-4332(97)00233-X UT WOS:000071323000009 ER PT J AU Louie, TM Ni, SS Xun, LY Mohn, WW AF Louie, TM Ni, SS Xun, LY Mohn, WW TI Purification, characterization and gene sequence analysis of a novel cytochrome c co-induced with reductive dechlorination activity in Desulfomonile tiedjei DCB-1 SO ARCHIVES OF MICROBIOLOGY AB The sulfate-reducing bacterium, Desulfomonile tiedjei DCB-1, conserves energy for growth from reductive dechlorination of 3-chlorobenzoate via halorespiration. To understand this respiratory process better, we examined electron carriers from different cellular compartments of D. tiedjei. A 50-kDa cytochrome from the membrane fraction was found to be co-induced with dechlorination activity. This inducible cytochrome was extracted from the membrane fractions by Tris-HCl buffer containing ammonium sulfate at 35% saturation and was purified to electrophoretic homogeneity by phenyl superose, Mono Q, and hydroxyapatite chromatography. The purified cytochrome had a high-spin absorption spectrum. In a pH titration experiment, the absorption spectrum of the inducible cytochrome shifted to low spin at pH 13.2. The midpoint potential of the inducible cytochrome at pH 7.0 was -342 mV. The NH2-terminal amino acid sequence of the inducible cytochrome was determined and was used to obtain inverse PCR products containing the sequence of the gene encoding the inducible cytochrome. The ORF was 1398 bp and coded for a protein of 52.6 kDa. Two c-type heme-binding domains were identified in the COOH-terminal half of the protein. A putative signal peptide of 26 residues was found at the NH2-terminal end. The protein sequence was not found to have substantial sequence similarity to any other sequence in GenBank. We conclude that this is a c-type cytochrome substantially different from previously characterized c-type cytochromes. SN 0302-8933 PD DEC PY 1997 VL 168 IS 6 BP 520 EP 527 DI 10.1007/s002030050530 UT WOS:000071002800011 PM 9385144 ER PT J AU Allen-Gil, SM Landers, DH Wade, TL Sericano, JL Lasorsa, BK Crecelius, EA Curtis, LR AF Allen-Gil, SM Landers, DH Wade, TL Sericano, JL Lasorsa, BK Crecelius, EA Curtis, LR TI Heavy metal, organochlorine pesticide and polychlorinated biphenyl contamination in Arctic ground squirrels (Spermophilus parryi) in northern Alaska SO ARCTIC AB Heavy metal and organochlorine (OC) concentrations, including organochlorine pesticides and polychlorinated biphenyl congeners (PCBs), were determined in arctic ground squirrels; (Spermophilus, parryi!) from three sites in the Brooks Range of northern Alaska in 1991-93. Heavy metals were present in most squirrel livers collected, with concentrations of trace elements (As, Cd, Hg, Ni, and Pb) averaging below 1 mu g/g wet weight. Hexachlorobenzene (HCB), p,p'-DDE, gamma hexachlorocyclohexane (gamma-HCH), trans-nonachlor, and PCBs 138, 153, and 170 were the most frequently detected OCs in fat and liver. Average concentrations of individual OC analytes were below 20 ng/g wet weight in liver and below 15 ng/g wet weight in fat. Rank correlations indicate that concentrations of heavy metals and of OCs accumulate in concert with one another (As, Cd, Cu, and Zn; PCBs 138, 170, and 180). Although heavy metal and OC concentrations are low relative to other areas and other arctic species, the occurrence of these compounds illustrates the global pervasiveness of persistent organic compounds and the potential for bioaccumulation in the terrestrial arctic food web. RI Wade, Terry/A-4012-2012 SN 0004-0843 PD DEC PY 1997 VL 50 IS 4 BP 323 EP 333 UT WOS:000071487900005 ER PT J AU Stanford, SA Elston, R Eisenhardt, PR Spinrad, H Stern, D Dey, A AF Stanford, SA Elston, R Eisenhardt, PR Spinrad, H Stern, D Dey, A TI An IR-selected galaxy cluster at z=1.27 SO ASTRONOMICAL JOURNAL AB We report the discovery of a galaxy cluster at z=1.27. CIG J0848+4453 was found in a near-IR field survey as a high density region of objects with very red J-K colors. Optical spectroscopy of a limited number of 24 less than or similar to R less than or similar to 25 objects in the area shows that 6 galaxies within a 90 arcsec (0.49h(100)(-1), Mpc, q(0) = 0.1) diameter region lie at z = 1.273+/-0.002. Most of these 6 member galaxies have broad-band colors consistent with the expected spectral energy distribution of a passively-evolving elliptical galaxy formed at high redshift, An additional 2 galaxies located similar to 2 arcmin from the cluster center are also at z = 1.27. Using all 8 of these spectroscopic members, we estimate the velocity dispersion sigma=700+/-180 km s(-1), which in similar to that of Abell richness class R = 1 clusters in the present epoch. A deep ROSAT/PSPC observation detects X-ray emission at the 4.5 sigma level coincident with the nominal cluster center. Assuming that the X-ray flux is emitted by hot gas trapped in rbe potential well of a collapsed system (no AGN are known to exist in the area), the resulting X-ray luminosity in the rest frame 0.1-2.4 keV band of L-x = 1.5 X 10(44) ergs s(-1) suggests the presence of a moderately massive system, CIG J0848+4453 is the highest redshift cluster found in a held survey. (C) 1997 American Astronomical Society. [S0004-6256(97)02112-2]. SN 0004-6256 PD DEC PY 1997 VL 114 IS 6 BP 2232 EP + DI 10.1086/118643 UT WOS:A1997YL19100004 ER PT J AU Skinner, CJ Meixner, M Barlow, MJ Collison, AJ Justtanont, K Blanco, P Pina, R Ball, JR Keto, E Arens, JF Jernigan, JG AF Skinner, CJ Meixner, M Barlow, MJ Collison, AJ Justtanont, K Blanco, P Pina, R Ball, JR Keto, E Arens, JF Jernigan, JG TI The remarkable asymmetric outflow from the Cygnus Egg Nebula SO ASTRONOMY & ASTROPHYSICS AB We present ground based continuum images in the infrared, from 1.2 to 19 mu m, and an H-2 2.122 mu m line emission image of the post-AGE star AFGL2688, the Cygnus Egg Nebula. We show that the standard model of this source, comprising a fast wind focussed by a dense, equatorial, dusty torus into a bipolar flow at position angle 15 degrees and close to the plane of the sky, cannot explain the combination of kinematic information from previous studies and morphological information in our own observations. Nor are the images consistent with a classical bipolar flow, since the apex of the two lobes observed in scattered light in the visible and near-IR are offset in R.A. with respect to one another. We suggest a model which is physically similar, but substantially different geometrically, in which there is a bipolar flow at a position angle closer to 60 degrees, rather than 15 degrees, still collimated by a dense, equatorial, dusty torus, but the opening angle of the cones out of which the Fast bipolar flow is directed is closer to 90 degrees, rather than 20 degrees or so as previously suggested. The bipolar flow axis is inclined by about 20-30 degrees, rather than in the plane of the sky as in previous models. The dust distribution in the nebula has to be extremely clumpy, and there is evidence that large scale mass loss from the progenitor AGE star occurred in discrete phases, recurring on a timescale of similar to 750 years. This model implies a much lower velocity for the 'fast' bipolar outflow than does the standard model, which is consistent with very recent Nobeyama Millimetre Array images in (CO)-C-13 emission. In support of our new model, we present a full radiative transfer model for the source, in axial symmetry, which reveals that the final phase of heavy mass loss included a superwind phase which lasted about two hundred years and removed about 0.7 M. from the envelope of the progenitor AGE star. Our results imply that the progenitor star must have been a relatively high mass AGB star. Our radiative transfer model also demonstrates convincingly that, in contrast with previous models, the core of the nebula has to be exceptionally optically thick, with an optical depth greater than unity even at 10 mu m. RI Barlow, Michael/A-5638-2009; OI Barlow, Michael/0000-0002-3875-1171; /0000-0003-1689-9201 SN 0004-6361 PD DEC PY 1997 VL 328 IS 1 BP 290 EP 310 UT WOS:A1997YJ08200033 ER PT J AU Dey, A vanBreugel, W Vacca, WD Antonucci, R AF Dey, A vanBreugel, W Vacca, WD Antonucci, R TI Triggered star formation in a massive galaxy at z=3.8: 4C 41.17 SO ASTROPHYSICAL JOURNAL AB We present deep spectropolarimetric observations obtained with the W. M. Keck Telescope of the very high redshift (z = 3.79786 +/- 0.0024) radio galaxy 4C 41.17. We find that the bright, spatially extended rest-frame UV continuum emission from this galaxy, which is aligned with the radio axis, is unpolarized (P-2 sigma < 2.4%). This implies that scattered AGN light, which is generally the dominant contributor to the rest-frame UV emission in z similar to 1 radio galaxies, is unlikely to be a major component of the UV flux from 4C 41.17. The resulting total light spectrum shows absorption lines and P Cygni-like features that are similar to those detected in the spectra of the recently discovered population of star forming galaxies at slightly lower (z similar to 2-3) redshifts. It may be possible for a galactic outflow to contribute partially to the absorption line profiles of the low ionization species; however, it is unlikely that the high-velocity wings of the high ionization line's are dominated by a galactic wind since the outflow mass implied by the absorption line strengths is very large. The detection of the S V lambda 1502 stellar photospheric absorption line, the shape of the blue wing of the Si rv profile, the unpolarized continuum emission, the inability of any AGN-related processes to account for the UV continuum flux, and the overall similarity of the UV continuum spectra of 4C 41.17 and the nearby star-forming region NGC 1741B1 strongly suggest that the UV light from 4C 41.17 is dominated by young, hot stars. If all of the UV emission is due to starlight from a young population, the implied star formation rate is roughly 140-1100 h(50)(-2) M. yr(-1). The deep spectroscopy presented here combined with the morphology of the system at radio and optical wavelengths and the possibly comparable ages for the radio source structure and the UV stellar population suggest that star formation in 4C 41.17 was triggered by the expansion of the radio source into the ambient medium. Our current observations are consistent with the hypothesis that 4C 41.17 is undergoing its major epoch of star formation at z similar to 4, and that by z similar to 1 it will have evolved to have spectral and morphological properties similar to those observed in known z similar to 1 powerful radio galaxies. SN 0004-637X EI 1538-4357 PD DEC 1 PY 1997 VL 490 IS 2 BP 698 EP + DI 10.1086/304911 PN 1 UT WOS:A1997YJ45400020 ER PT J AU Chiesa, G Bielicki, JK Parolini, C Colombo, N Milia, M Vignati, L Franceschini, G Forte, TM Rubin, EM Sirtori, CR AF Chiesa, G Bielicki, JK Parolini, C Colombo, N Milia, M Vignati, L Franceschini, G Forte, TM Rubin, EM Sirtori, CR TI Lipid metabolism in mice expressing human apolipoprotein A-I-Milano SO ATHEROSCLEROSIS RI Sirtori, Cesare/F-4658-2012; Parolini, Cinzia/G-8984-2012; Chiesa, Giulia/G-8987-2012 OI Parolini, Cinzia/0000-0002-5699-0918; Chiesa, Giulia/0000-0001-5553-1210 SN 0021-9150 PD DEC PY 1997 VL 135 SU 1 BP S9 EP S9 DI 10.1016/S0021-9150(97)89978-9 UT WOS:000071445900031 ER PT J AU Shannon, JD AF Shannon, JD TI Scales of sulfur concentrations and deposition from the perspective of the receptor SO ATMOSPHERIC ENVIRONMENT AB Median source-receptor separation distances and atmospheric transport times for atmospheric [SO2] and [SO42-] and wet and dry deposition of S are calculated from the perspective of the receptor. The temporal and spatial separations are weighted according to the relative contribution of the source to the total atmospheric concentration or deposition at the receptor as calculated with the Advanced Statistical Trajectory Regional Air Pollution (ASTRAP) model; thus, the scales are functions not just of climatological conditions and processes of atmospheric chemistry (as resolved and treated by the regional model) but also of the emission distribution. Calculations are made for a grid of receptor points covering the United States, Canada, and northern Mexico. The minimum spatial and temporal scale lengths occur in the principal emission region, the Ohio Valley, and near isolated western sources; maximum scale lengths occur in remote regions without significant local emissions. The spatial scale of [SO42-] is typically almost twice as large as that of [SO2] or dry deposition of S in the eastern United States, and the spatial scale of wet deposition of S is slightly greater than that for [SO42-]. The temporal scales of [SO42-] and wet deposition of S are two to three times those of [SO2] and dry deposition of S in the eastern United States. Weighted-mean spatial separations are larger than median separations by roughly 25% except in areas remote from sources where they are about equal. Over most of the region scales for wet deposition of S are shortest in summer and longest in winter. (C) 1997 Elsevier Science Ltd. SN 1352-2310 PD DEC PY 1997 VL 31 IS 23 BP 3933 EP 3939 DI 10.1016/S1352-2310(97)00242-2 UT WOS:A1997XZ76000008 ER PT J AU Leung, JW Yu, AS AF Leung, JW Yu, AS TI Hepatolithiasis and biliary parasites SO BAILLIERES CLINICAL GASTROENTEROLOGY AB Hepatolithiasis, or the presence of intrahepatic stones, is prevalent in East Asia and is characterized by the finding of stones within the intrahepatic bile ducts proximal to the confluence of the right and left hepatic ducts. Bile stasis and bacterial infection have been incriminated as the major aetiopathogenic factors. Clinical features include recurrent pyogenic cholangitis, multiple liver abscesses, secondary biliary cirrhosis and cholangiocarcinoma. The goals of management include accurate localization of pathologies, control of biliary sepsis and the elimination of stones and stasis. Ultrasonography, computed tomography and direct cholangiography complement each other in defining the stones, strictures and degree of liver damage. Non-operative biliary decompression by endoscopy and interventional radiology is effective in controlling the infection, but surgery remains the mainstay for the treatment of stones and strictures. Intra-operative ultrasound and flexible choledochoscopy, combined with percutaneous transhepatic cholangioscopy and intraductal lithotripsy, facilitate stone removal. Balloon dilatation and biliary stenting serve to open the bile duct strictures. The creation of a hepaticocutaneous jejunostomy after conventional surgery allows atraumatic access to the biliary system for the removal of recurrent stones. The management of biliary parasites begins with conservative measures, including analgesics and anti-helminthic therapy. In refractory cases or patients with acute cholangitis, endoscopic biliary drainage and the extraction of worms may be necessary. Improvement in sanitation plays a crucial role in the epidemiological control of these biliary diseases. SN 0950-3528 PD DEC PY 1997 VL 11 IS 4 BP 681 EP 706 DI 10.1016/S0950-3528(97)90016-6 UT WOS:000072017500005 PM 9512805 ER PT J AU Napolitano, GE Pollero, RJ Gayoso, AM MacDonald, BA Thompson, RJ AF Napolitano, GE Pollero, RJ Gayoso, AM MacDonald, BA Thompson, RJ TI Fatty acids as trophic markers of phytoplankton blooms in the Bahia Blanca estuary (Buenos Aires, Argentina) and in Trinity Bay (Newfoundland, Canada) SO BIOCHEMICAL SYSTEMATICS AND ECOLOGY AB The fatty acid compositions of phytoplankton and major primary consumers were analyzed during the development of seasonal algal blooms in the Bahia Blanca estuary, situated on the southern coast of the province of Buenos Aires (Argentina), and Trinity Bay. at Sunnyside, on the eastern coast of Newfoundland (Canada). Primary consumers in the Bahia Blanca estuary were zooplankton dominated by the calanoid copepod Acartia tonsa. At Sunnyside, the primary consumers were the sea scallop Placopecten magellanicus. an ecological and economical important benthic bivalve. The study shows that in spite of obvious differences between the two environments and the analytical approaches employed in each case, the analyses of fatty acid biomarkers can provide relevant ecological information. The fatty acid composition of the lipids of Bahia Blanca phytoplankton (high concentrations of the fatty acids 14:0. 16:1 omega 7, 16:4 omega 1, and 20:5 omega 3) reflected the presence of diatoms as a major component throughout the bloom. Patty acid markers of the post-bloom phytoplankton in Bahia Blanca indicated a decline of phytoplankton biomass, and a relatively high input of detritus and terrestrial plant materials to the particulate organic matter of the estuary. Linoleic acid (18:2 omega 6), a typical "terrestrial" fatty acid, was conspicuous in the lipids of the post bloom particulate matter of the Bahia Blanca estuary; 18:2 omega 2 was subsequently incorporated into zooplankton lipids. Diatom markers were also prominent in the lipids of pre-bloom and bloom phytoplankton at Sunnyside: post-bloom phytoplankton showed higher proportions of 18:0, 18:1 omega 9, and 18:4 omega 3, characteristic and often major fatty acids of dinoflagellates. The fatty acids of the digestive gland of P. magellanicus reflected the fatty acid composition of the phytoplankton, whereas those of the adductor muscle were practically unaffected by the composition of the food. This organ-specific response of an animal to the fatty acid composition of the diet is examined in terms of different applications of the fatty acid marker concept. (C) 1997 Elsevier Science Ltd. SN 0305-1978 PD DEC PY 1997 VL 25 IS 8 BP 739 EP 755 DI 10.1016/S0305-1978(97)00053-7 UT WOS:000071158500004 ER PT J AU Conry, MJ AF Conry, MJ TI Effect of fertiliser N on the grain yield and quality of spring malting barley grown of five contrasting soils in Ireland SO BIOLOGY AND ENVIRONMENT-PROCEEDINGS OF THE ROYAL IRISH ACADEMY AB Twenty experiments were carried out in the south-east of Ireland on five intensively cultivated soils with low residual soil N (Index 1) over a four-year period (1990-3). Small increments of fertiliser N (12.5kg/ha), ranging from 75kg/ha to 175kg/ha (maximum 137.5kg/ha in 1990), were applied to the cultivar Blenheim in an effort to assess accurately the amount of N that could be applied to optimise the yield and quality ex-farm of spring-sown malting barley on different soils. Increasing increments of fertiliser N, up to a certain level, increased grain yield, but the response varied with season and to a lesser extent with site. There was a gradual and significant increase in grain N with increasing increments of fertiliser N in all experiments, but there were large seasonal and site differences in the concentrations of grain N recorded. Increasing increments of N also increased the amount of screenings. Optimum yields of acceptable malting quality (< 17.5g N/kg and < 80g/kg screenings) were obtained, on average, by applying 125kg, 112.5kg, 125kg, 100kg and 75kg N/ha, respectively, to the Light gravelly soils at Oak Park, the medium-light sandstone soils at Whitegate, the medium-textured Ferns soils (Clonroche Series), the medium-heavy Knockbeg soils (Knockbeg Series) and the heavy Mulhuddart soils (Dunboyne Series), except in 1990 when grain N was seasonally high. SN 0791-7945 PD DEC PY 1997 VL 97B IS 3 BP 185 EP 196 UT WOS:000074192500002 ER PT J AU Duffy, KJ Ford, RM Cummings, PT AF Duffy, KJ Ford, RM Cummings, PT TI Residence time calculation for chemotactic bacteria within porous media SO BIOPHYSICAL JOURNAL AB Local chemical gradients can have a significant impact on bacterial population distributions within subsurface environments by evoking chemotactic responses. These local gradients may be created by consumption of a slowly diffusing nutrient, generation of a local food source from cell lysis, or dissolution of nonaqueous phase liquids trapped within the interstices of a soil matrix. We used a random walk simulation algorithm to study the effect of a local microscopic gradient on the swimming behavior of bacteria in a porous medium. The model porous medium was constructed using molecular dynamics simulations applied to a fluid of equal-sized spheres. The chemoattractant gradient was approximated with spherical symmetry, and the parameters for the swimming behavior of soil bacterium Pseudomonas putida were based on literature values. Two different mechanisms for bacterial chemotaxis, one in which the bacteria responded to both positive and negative gradients, and the other in which they responded only to positive gradients, were compared. The results of the computer simulations showed that chemotaxis can increase migration through a porous medium in response to microscopic-scale gradients. The simulation results also suggested that a more significant role of chemotaxis may be to increase the residence time of the bacteria in the vicinity of an attractant source. RI Cummings, Peter/B-8762-2013 OI Cummings, Peter/0000-0002-9766-2216 SN 0006-3495 PD DEC PY 1997 VL 73 IS 6 BP 2930 EP 2936 UT WOS:A1997YJ67300007 PM 9414207 ER PT J AU Kuehner, DE Heyer, C Ramsch, C Fornefeld, UM Blanch, HW Prausnitz, JM AF Kuehner, DE Heyer, C Ramsch, C Fornefeld, UM Blanch, HW Prausnitz, JM TI Interactions of lysozyme in concentrated electrolyte solutions from dynamic light-scattering measurements SO BIOPHYSICAL JOURNAL AB The diffusion of hen egg-white lysozyme has been studied by dynamic light scattering in aqueous solutions of ammonium sulfate as a function of protein concentration to 30 g/liter. Experiments were conducted under the following conditions: pH 4-7 and ionic strength 0.05-5.0 M. Diffusivity data for ionic strengths up to 0.5 M were interpreted in the context of a two-body interaction model for monomers. From this analysis, two potential-of-mean-force parameters, the effective monomer charge, and the Hamaker constant were obtained. At higher ionic strength, the data were analyzed using a model that describes the diffusion coefficient of a polydisperse system of interacting protein aggregates in terms of an isodesmic, indefinite aggregation equilibrium constant. Data analysis incorporated multicomponent virial and hydrodynamic effects. The resulting equilibrium constants indicate that lysozyme does not aggregate significantly as ionic strength increases, even at salt concentrations near the point of salting-out precipitation. SN 0006-3495 PD DEC PY 1997 VL 73 IS 6 BP 3211 EP 3224 UT WOS:A1997YJ67300032 PM 9414232 ER PT J AU Turner, MG Dale, VH Everham, EH AF Turner, MG Dale, VH Everham, EH TI Fires, hurricanes, and volcanoes: Comparing large disturbances SO BIOSCIENCE RI Dale, Virginia/B-6023-2009; Turner, Monica/B-2099-2010 SN 0006-3568 PD DEC PY 1997 VL 47 IS 11 BP 758 EP 768 DI 10.2307/1313098 UT WOS:A1997YH05400011 ER PT J AU Christara, CC Smith, B AF Christara, CC Smith, B TI Multigrid and multilevel methods for quadratic spline collocation SO BIT AB Multigrid methods are developed and analyzed for quadratic spline collocation equations arising from the discretization of one-dimensional second-order differential equations. The rate of convergence of the two-grid method integrated with a damped Richardson relaxation scheme as smoother is shown to be faster than 1/2, independently of the step-size. The additive multilevel versions of the algorithms are also analyzed. The development of quadratic spline collocation multigrid methods is extended to two-dimensional elliptic partial differential equations. Multigrid methods for quadratic spline collocation methods are not straightforward: because the basis functions used with quadratic spline collocation are not nodal basis functions, the design of efficient restriction and extension operators is nontrivial. Experimental results, with V-cycle and full multigrid, indicate that suitably chosen multigrid iteration is a very efficient solver for the quadratic spline collocation equations. SN 0006-3835 PD DEC PY 1997 VL 37 IS 4 BP 781 EP 803 DI 10.1007/BF02510352 UT WOS:000071148200002 ER PT J AU Morris, GM Coderre, JA Micca, PL Fisher, CD Capala, J Hopewell, JW AF Morris, GM Coderre, JA Micca, PL Fisher, CD Capala, J Hopewell, JW TI Central nervous system tolerance to boron neutron capture therapy with p-boronophenylalanine SO BRITISH JOURNAL OF CANCER AB A rat spinal cord model was used to evaluate the effects of boron neutron capture irradiation on the central nervous system (CNS), using a range of doses of the boron delivery agent p-boronophenylalanine (BPA). Three doses of BPA 700, 1000 and 1600 mg kg(-1) were used to establish the biodistribution of boron-10 (B-10) in blood, spinal cord and brain over a 3-h period after intraperitoneal (ip) administration. At the lowest dose of BPA used, blood B-10 levels remained relatively stable over the 3-h sampling period. With the two higher doses of BPA, blood B-10 concentrations were greatest at 1 h after BPA administration, and thereafter exhibited a biphasic clearance profile. The largest decline in blood B-10 levels occurred between 1 and 2 h after ip injection and was most pronounced (approximately 45%) in the highest BPA dose group. Considered overall, B-10 concentrations were marginally lower in the spinal cord than in the brain. Levels of B-10 in both of these organs showed a slow but progressive increase with time after administration of BPA. The B-10 concentration ratio for blood relative to CNS tissue increased with BPA dosage and reached a peak value of approximately 10:1 in the highest BPA dose group, at 1 h after ip injection,However, at 3 h after injection the B-10 concentration ratios had decreased to approximately 3:1 in all of the BPA dose groups. After irradiation with thermal neutrons in combination with BPA at blood B-10 concentrations of approximately 42 and approximately 93 mu g g(-1), myelopathy developed after latent intervals of 20.0 +/- 0.6 and 20.0 +/- 1.2 weeks respectively. ED50 values (+/- s.e.) for the incidence of myelopathy were calculated from probit fitted curves, and were 17.5 +/- 0.7 and 25.0 +/- 0.6 Gy after irradiation with thermal neutrons at blood B-10 levels of approximately 42 and approximately 93 mu g g(-1) respectively. The compound biological effectiveness (CBE) factor values, estimated from these data, were 0.67 +/- 0.23 and 0.48 +/- 0.18 respectively. This compared with a previous estimate of 0.88 +/- 0.14 at a blood B-10 concentration of approximately 19 mu g g(-1). It was concluded that the value of the CBE factor was not influenced by the level of log in the blood, but by the blood:CNS B-10 concentration ratio. In effect, the CBE factor decreases as the concentration ratio increases. Simulations using boron neutron capture therapy (BNCT) treatment planning software indicate a significant therapeutic advantage could be obtained in moving to higher BPA doses than those in current clinical use. SN 0007-0920 PD DEC PY 1997 VL 76 IS 12 BP 1623 EP 1629 DI 10.1038/bjc.1997.607 UT WOS:000071048400016 PM 9413952 ER PT J AU Post, MJ Fairall, CW Snider, JB Han, Y White, AB Ecklund, WL Weickmann, KM Quinn, PK Cooper, DI Sekelsky, SM McIntosh, RE Minnett, P Knuteson, RO AF Post, MJ Fairall, CW Snider, JB Han, Y White, AB Ecklund, WL Weickmann, KM Quinn, PK Cooper, DI Sekelsky, SM McIntosh, RE Minnett, P Knuteson, RO TI The Combined Sensor Program: An air-sea science mission in the Central and Western Pacific Ocean SO BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY AB Twelve national research organizations joined forces on a 30-day, 6800 n mi survey of the Central and Tropical Western Pacific on NOAA's Research Vessel Discoverer. The Combined Sensor Program (CSP), which began in American Samoa on 14 March 1996, visited Manus Island, Papua New Guinea, and ended in Hawaii on 13 April, used a unique combination of in situ, satellite, and remote sensors to better understand relationships between atmospheric and oceanic variables that affect radiative balance in this climatically important region. Besides continuously measuring both short-wave and longwave radiative fluxes, CSP instruments also measured most other factors affecting the radiative balance, including profiles of clouds (lidar and radar), aerosols (in situ and lidar), moisture (balloons, lidar, and radiometers), and sea surface temperature (thermometers and Fourier Transform Infrared Radiometers). Surface fluxes of heat, momentum, and moisture were also measured continuously. The Department of Energy's Atmospheric Radiation Measurement Program used the mission to validate similar measurements made at their CART site on Manus Island and to investigate the effect (if any) of large nearby landmasses on the island-based measurements. RI White, Allen/A-7946-2009; Han, Yong/F-5590-2010; Quinn, Patricia/R-1493-2016 OI Han, Yong/0000-0002-0183-7270; Quinn, Patricia/0000-0003-0337-4895 SN 0003-0007 PD DEC PY 1997 VL 78 IS 12 BP 2797 EP 2815 DI 10.1175/1520-0477(1997)078<2797:TCSPAA>2.0.CO;2 UT WOS:000072304100005 ER PT J AU Nadeau, RM McEvilly, TV AF Nadeau, RM McEvilly, TV TI Seismological studies at Parkfield V: Characteristic microearthquake sequences as fault-zone drilling targets SO BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA AB Studies at very high resolution of microearthquakes at Parkfield, California, since 1987 reveal a systematic organization in space and time, dominated by clustering of nearly identical, regularly occurring microearthquakes (characteristic events) on 10 to 20-m-wide patches within the fault zone. More than half of the 4000 + events in our 1987 to 1996 catalog exhibit this trait. In general, recurrence intervals (0.5 to 2 yr) scale with the magnitude of the repeating events for the on-scale range (Mw 0.2 to 1.3) in this study. The similar waveforms, superimposed locations, quasi-periodic recurrence, and uniform size of these characteristic events permit relative hypocenter location accuracy of meters and predictable occurrence times within windows of a few months. Clustered characteristic events occur at depths as shallow as about 3 km, and these are feasible targets for deep scientific drilling and observation at the focus of a subsequent small earthquake within an active plate-boundary fault zone. At Parkfield, the achievable location accuracy to which a hypocenter can be specified as well as the predictability of its occurrence time appear to be uniquely favorable for in situ fault-zone measurements. SN 0037-1106 PD DEC PY 1997 VL 87 IS 6 BP 1463 EP 1472 UT WOS:000071550700007 ER PT J AU Anant, KS Dowla, FU AF Anant, KS Dowla, FU TI Wavelet transform methods for phase identification in three-component seismograms SO BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA AB We apply the wavelet transform to seismic signals for the purpose of automatically identifying the P and S phase arrivals of seismic events, In this article, an algorithm is presented that locates these arrivals in single-station three-component short-period seismograms using polarization and amplitude information contained in the wavelet transform coefficients of the signals. The main idea is that strong features of the seismic signal appear in the wavelet coefficients across several scales, The first step iu the algorithm is the wavelet decomposition of each component of a three-component short-period seismogram, The resulting multi-scalar representation is used to construct "locator" functions that identify the P and S arrivals. The P locator function is constructed, by using polarization information across scales, and the S locator function is constructed using transverse over radial amplitude information across scales. These functions prove to be very effective at identifying the important P and S arrivals in the test data. The results are compared with arrival times picked by an analyst. SN 0037-1106 PD DEC PY 1997 VL 87 IS 6 BP 1598 EP 1612 UT WOS:000071550700017 ER PT J AU Rodgers, AJ Lay, T Walter, WR Mayeda, KM AF Rodgers, AJ Lay, T Walter, WR Mayeda, KM TI A comparison of regional-phase amplitude ratio measurement techniques SO BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA AB We compare several procedures for measuring regional-phase amplitude ratios commonly used in discrimination studies. Amplitude measurements are made on both raw velocity-proportional broadband seismograms and instrument-deconvolved displacement seismograms in the time and frequency domains. Pn/Lg and Pg/Lg ratios are measured on vertical-component waveforms for regional earthquakes observed at the Global Seismic Network (GSN) station ABKT (Alibek, Turkmenistan). Time-domain amplitude measurements are made on narrow-band filtered waveforms using signal energy measures given by the absolute mean, rms, and envelope mean, and peak measures given by the absolute maximum and envelope maximum. Frequency-domain measurements are made by computing the log(10)-mean amplitude within a narrow band from the broadband spectrum of each windowed phase. Time-domain amplitude ratios for raw velocity and instrument-deconvolved displacement seismograms are very similar (linear correlations greater than or equal to 0.97), indicating that the instrument response does not affect the time-domain amplitude ratio measurements for the broadband GSN data at the frequencies studied (0.75 to 9.0 Hz). Time-domain amplitude ratios made using the energy or peak measures are well correlated among themselves (linear correlations greater than or equal to 0.97). However, the energy and peak measures are slightly less well correlated with each other (linear correlations between 0.87 and 0.99). For the time-domain measures, the correlations generally degrade, and the scatter increases for the higher-frequency bands. Time-and frequency-domain measurements are well correlated for the lowest-frequency band (0.75 to 1.5 Hz). However, as the frequency band increases, the correlations decrease and the slopes deviate from 1.0. Time-domain amplitude ratios (for both Pn/Lg and Pg/Lg) are consistently larger than the frequency-domain amplitude ratios. Investigation of the frequency spectra of broadband and narrow-band filtered phases revealed that significant energy from outside the passband, particularly from lower frequencies, possibly biases the time-domain measurements. Log averaging the spectral amplitudes in a given passband before forming the amplitude ratios does not bias the measurements to the low end of passband. Better agreement between time-and frequency-domain measurements is found when linear averaging of the spectrum is used. These observations suggest that with care, time-and frequency-domain measures can be made to agree. We suggest that log-averaged frequency measures look promising for discriminant measures because (1) frequency-domain measurements offer complete control of the frequencies that contribute to the measurement, and (2) log averaging of the spectra does not overweigh spectral amplitudes associated with lower frequencies within the passband. However, because we consider only earthquake data, we cannot evaluate the discrimination performance of the various measurement techniques. RI Rodgers, Arthur/E-2443-2011; Walter, William/C-2351-2013 OI Walter, William/0000-0002-0331-0616 SN 0037-1106 PD DEC PY 1997 VL 87 IS 6 BP 1613 EP 1621 UT WOS:000071550700018 ER PT J AU Creek, MR Mani, C Vogel, JS Turteltaub, KW AF Creek, MR Mani, C Vogel, JS Turteltaub, KW TI Tissue distribution and macromolecular binding of extremely low doses of [C-14]-benzene in B6C3F1 mice SO CARCINOGENESIS AB The tissue distribution and macromolecular binding of benzene was studied over a dose range spanning nine-orders of magnitude to determine the nature of the dose-response and to establish benzene's internal dosimetry at doses encompassing human environmental exposures, [C-14]-Benzene was administered to B6C3F1 male mice at doses ranging between 700 pg/kg and 500 mg/kg body wt. Tissues, DNA and protein were analyzed for [C-14]-benzene content between 0 and 48 h post-exposure (625 Ng/kg and 5 mu g/kg dose) by accelerator mass spectrometry (AMS). [C-14]-Benzene levels were highest in the liver and peaked within 0.5 h of exposure, Liver DNA adduct levels peaked at 0.5 h, in contrast to bone marrow DNA adduct levels, which peaked at 12-24 h, Dose-response assessments at 1 h showed that adducts and tissue available doses increased linearly with administered dose up to doses of 16 mg/kg body wt. Tissue available doses and liver protein adducts plateau above the 16 mg/kg dose, Furthermore, a larger percentage of the available dose in bone marrow bound to DNA relative to liver, Protein adduct levels were 9- to 43-fold greater than DNA adduct levels. These data show that benzene is bioavailable at human-relevant doses and that DNA and protein adduct formation is linear with dose over a dose range spanning eight orders of magnitude, Finally, these data show that the dose of bioactive metabolites is greater to the bone marrow than the liver and suggests that protein adducts may contribute to benzene's hematoxicity. SN 0143-3334 PD DEC PY 1997 VL 18 IS 12 BP 2421 EP 2427 DI 10.1093/carcin/18.12.2421 UT WOS:000071425200019 PM 9450490 ER PT J AU Liu, SC Murley, JS Woloschak, G Grdina, DJ AF Liu, SC Murley, JS Woloschak, G Grdina, DJ TI Repression of c-myc gene expression by the thiol and disulfide forms of the cytoprotector amifostine SO CARCINOGENESIS AB The clinically approved cytoprotector amifostine, designated WR-2721, [S-2-(3-aminopropylamino)ethylphosphorothioic acid], protects against both radiation and drug-induced mutagenesis in animal systems, These effects extend over a wide concentration range making amifostine a strong candidate for evaluation as a possible cancer chemopreventive agent, To better identify and develop potential intermediate biomarkers for chemoprevention at the molecular level we applied the technique of differential display RT-PCR to assess the effects of both the thiol (SK), i.e. WR1065 and the disulfide (SS), i.e. WR-33278, metabolites of amifostine on gene expression in CHO-AAS cells, Cells were exposed to either 40 mu M or 4 mM of each agent for 30 min, and subsequent changes in gene expression were identified and contrasted to that found in corresponding untreated control cells, One band that showed a differential response was sequenced and was found to have 78% homology with a segment of the human pHL-1 cDNA clone contained in GenBank, This clone contains a COX III mitochondrial DNA insert and two exons of human c-myc, Northern blot analyses were performed by using the cloned human c-myc exon 1 probe to confirm whether c-myc gene expression was affected, Repression of c-myc expression was observed under all of the conditions evaluated, An exposure of cells to 40 CIM of the disulfide form of amifostine was the most effective in repressing c-myc, i.e. 27% of control level, A concentration of 4 mM of the disulfide form reduced gene expression to 45% of the control level, while the thiol form was less effective, with 4 mM and 40 mu M concentrations reducing c-myc gene expression to 65% and 56% of control levels, respectively. RI Woloschak, Gayle/A-3799-2017 OI Woloschak, Gayle/0000-0001-9209-8954 SN 0143-3334 PD DEC PY 1997 VL 18 IS 12 BP 2457 EP 2459 DI 10.1093/carcin/18.12.2457 UT WOS:000071425200025 PM 9450496 ER PT J AU Allan, ML AF Allan, ML TI Rheology of latex-modified grouts SO CEMENT AND CONCRETE RESEARCH AB The rheology of grouts containing latex was investigated. The two latex additives used were carboxylated styrene-butadiene and acrylic. The influences of superplasticizer, fly ash, and blast furnace slag on the rheology of latex-modified grouts were addressed. Shear stress-shear rate curves were determined for a variety of mix proportions. The time-dependent behaviour of selected grouts was also studied. It was determined that the yield stress and apparent viscosity are influenced by latex content and that the grouts are shear thinning at low water/cement ratios. Latex imparts stability and thixotropy in grouts. Partial replacement of cement with either fly ash or slag diminishes the effect of latex on theology. (C) 1997 Elsevier Science Ltd. RI Berndt, Marita/D-1901-2014 OI Berndt, Marita/0000-0002-6622-0597 SN 0008-8846 PD DEC PY 1997 VL 27 IS 12 BP 1875 EP 1884 DI 10.1016/S0008-8846(97)00205-6 UT WOS:000071255200012 ER PT J AU In, V Spano, ML Neff, JD Ditto, WL Daw, CS Edwards, KD Nguyen, K AF In, V Spano, ML Neff, JD Ditto, WL Daw, CS Edwards, KD Nguyen, K TI Maintenance of chaos in a computational model of a thermal pulse combustor SO CHAOS AB The dynamics of a thermal pulse combustor model are examined. it is found that, as a parameter related to the fuel flow rate is varied, the combustor will undergo a transition from periodic pulsing to chaotic pulsing to a chaotic transient leading to flameout. Results from the numerical model are compared to those obtained from a laboratory-scale thermal pulse combustor. Finally the technique of maintenance (or anticontrol) of chaos is successfully applied to the model, with the result that the operation of the combustor can be continued well into the flameout regime. (C) 1997 American Institute of Physics. RI Spano, Mark/B-6883-2011; OI Ditto, William/0000-0002-7416-8012 SN 1054-1500 PD DEC PY 1997 VL 7 IS 4 BP 605 EP 613 DI 10.1063/1.166260 UT WOS:000071084000010 ER PT J AU Zhong, GM Guiochon, G AF Zhong, GM Guiochon, G TI Simulated moving bed chromatography. Comparison between the behaviors under linear and nonlinear conditions SO CHEMICAL ENGINEERING SCIENCE AB The influence of the feed concentration on the progressive changes in concentration profiles along the simulated moving bed (SMB) columns and in the concentration histories at the SMB outlets during the transition of the SMB operation toward steady state is Studied. This investigation is concerned with what happens when the isotherms of the two components of the feed in the phase system have competitive Langmuir behavior and the feed concentration is raised froth the linear to the nonlinear range. In order to achieve a clear comparison between the SMB behaviors in the nonlinear and the linear case, the flow rates in all the sections of the SMB are kept constant, at the same value of these operation parameters as selected in the linear case. Transition concentration profiles to the steady state were examined as functions of the degree of nonlinear behavior, i.e. for different values of the reduced concentrations of the feed components, b(i)' = b(i)C(i). The profiles obtained in the linear and nonlinear case are compared to illustrate the nonlinear effects. Square-wave oscillations of the plateau concentrations of the extract in column II and the raffinate in column IV, due to the cyclical nature of the SMB operation, have been reported previously in the linear case. This phenomenon is discussed in the nonlinear case and the influence of the switching time is illustrated. (C) 1997 Elsevier Science Ltd. SN 0009-2509 PD DEC PY 1997 VL 52 IS 23 BP 4403 EP 4418 DI 10.1016/S0009-2509(97)00179-6 UT WOS:000071294400013 ER PT J AU Nakagawa, M Altobelli, SA Caprihan, A Fukushima, E AF Nakagawa, M Altobelli, SA Caprihan, A Fukushima, E TI NMRI study: axial migration of radially segregated core of granular mixtures in a horizontal rotating cylinder SO CHEMICAL ENGINEERING SCIENCE OI Fukushima, Eiichi/0000-0003-1670-5884 SN 0009-2509 PD DEC PY 1997 VL 52 IS 23 BP 4423 EP 4428 DI 10.1016/S0009-2509(97)00181-4 UT WOS:000071294400015 ER PT J AU Nellis, WJ AF Nellis, WJ TI Metallic hydrogen at high pressures and temperatures in Jupiter SO CHEMISTRY-A EUROPEAN JOURNAL AB Electrical conductivities of hydrogen were measured recently at 93-180 GPa (0.93-1.8 Mbar), 0.28-0.36 mol cm(-3), and 2000-4000 K. Shock temperatures were measured up to values of 5200 K at 0.83 Mbar. The conductivities indicate a continuous transition from a semiconducting to metallic fluid at 140 GPa and 3000 K. The results indicate that hydrogen becomes metallic much closer to the surface of Jupiter than thought previously and that Jupiter has no core-mantle boundary. SN 0947-6539 PD DEC PY 1997 VL 3 IS 12 BP 1921 EP 1924 DI 10.1002/chem.19970031205 UT WOS:A1997YK81800002 ER PT J AU Boyle, TJ Alam, TM Dimos, D Moore, GJ Buchheit, CD Al-Shareef, HN Mechenbier, ER Bear, BR Ziller, JW AF Boyle, TJ Alam, TM Dimos, D Moore, GJ Buchheit, CD Al-Shareef, HN Mechenbier, ER Bear, BR Ziller, JW TI Niobium(V) alkoxides. Synthesis, structure, and characterization of [Nb(mu-OCH2CH3)(OCH2C(CH3)(3))(4)](2), {[H3CC(CH2O)(CH2-mu-O)(C(O)(2))]Nb-2(mu-O)(OCH2CH3)(5)}(2), and {[H3CC(CH2O)(2)(CH2-mu-O)]Nb(OCH2CH3)(2)}(2) for production of mixed metal oxide thin films SO CHEMISTRY OF MATERIALS AB We have synthesized and isolated a number of unique niobium alkoxide compounds and introduced them into novel solution processes for the production of lead magnesium niobate oxide (PMN) and niobium-doped lead zirconate titanate oxide (PNZT) materials. A more sterically demanding analogue to Nb(OEt)(5) (Et = CH2CH3) was isolated as [Nb(mu-OEt)-(ONp)(4)](2) (1, Np = CH2C(CH3)(3) )by alcoholysis exchange. 1 crystallized in an edge-shared bioctahedral dinuclear arrangement with the smaller ligands acting as the bridging moieties. Multidentate ligands such as bis(hydroxymethyl)propionic acid (BHMP-H-3) and tris(hydroxymethyl)ethane (THME-H-3) were independently reacted with Nb(OEt)(5) to reduce the number of terminal ligands, yielding [(mu-BHMP)Nb-2(mu-O)(OEt)(5)](2) (2) and [(mu-THME)-Nb(OEt)(2)](2) (3) respectively. For 2, two unsymmetrical "(EtO)(2)Nb(mu-O)Nb(OEt)(3)" units are bridged by two tetradentate BHMP ligands. The THME moiety of 3 acts as a chelating, unidentate-bridging ligand forming a symmetrical dinuclear species, wherein each Nb atom possesses two terminal ethoxides. The synthesis, characterization, structural aspects, and solution properties of 1-3 are reported. The resulting morphological and electrical changes in the properties of the resulting electroceramic PMN and PNZT films due to the incorporation of these Nh alkoxides are also reported. SN 0897-4756 PD DEC PY 1997 VL 9 IS 12 BP 3187 EP 3198 DI 10.1021/cm970506p UT WOS:000071386900080 ER PT J AU Cheng, IF Muftikian, R Fernando, Q Korte, N AF Cheng, IF Muftikian, R Fernando, Q Korte, N TI Reduction of nitrate to ammonia by zero-valent iron SO CHEMOSPHERE AB The reduction of nitrate to ammonia occurs with nearly complete conversion at room temperature and pressure under aerobic conditions in the presence of iron and either HCl or a pH buffer. A 50.0 mL solution of 12.5 millimolar nitrate is rapidly reduced to ammonia when exposed to 4.00 g of 325 mesh iron at pH 5.0, 0.05 M sodium acetate/acetic acid. The pseudo-first order rate constant was 0.053 min(-1). Under conditions of pH 6.0 buffer, (i.e. 0.1 M 4-morpholineethanesulfonic acid adjusted to pH 6.0) and pH 7.0 buffer (0.1 M 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid adjusted to pH 7.0), the rate constants were 0.0408 min(-1) and 0.0143 min(-1), respectively. In unbuffered solutions there was no loss in nitrate and no production of ammonia. A more concentrated nitrate solution (100 mL of 1.0 M sodium nitrate) was also reduced to ammonia in the presence of 2.5 M HCl with the slow addition of 50.0 g of 325 mesh iron. (C) 1997 Elsevier Science Ltd. SN 0045-6535 PD DEC PY 1997 VL 35 IS 11 BP 2689 EP 2695 DI 10.1016/S0045-6535(97)00275-0 UT WOS:A1997YF73700020 ER PT J AU Ahluwalia, DV AF Ahluwalia, DV TI Three quantum aspects of gravity SO CHINESE JOURNAL OF PHYSICS CT Meeting in Honour of Dr Ta-You Wus Birthday CY AUG 11-15, 1997 CL TAIPEI, TAIWAN SP Academia Sin, Inst Phys, Natl Sci Council R O C, Nat Sci Div, Phys Res Promot Ctr, Phys Soc Republic China AB It is argued that (a) In the quantum realm test-particle masses have non-trivial observability which induces a non-geometric element in gravity, (b) Any theory of quantum gravity, on fundamental grounds, must contain an element of non-locality that makes position measurements non-commutative, and (c) The classical notion of free fall does not readily generalize to the quantum regime. SN 0577-9073 PD DEC PY 1997 VL 35 IS 6 BP 804 EP 808 PN 2 UT WOS:000071227600012 ER PT J AU Peng, JC Garvey, GT AF Peng, JC Garvey, GT TI Drell-Yan process and the sea quark distributions SO CHINESE JOURNAL OF PHYSICS CT Meeting in Honour of Dr Ta-You Wus Birthday CY AUG 11-15, 1997 CL TAIPEI, TAIWAN SP Academia Sin, Inst Phys, Natl Sci Council R O C, Nat Sci Div, Phys Res Promot Ctr, Phys Soc Republic China SN 0577-9073 PD DEC PY 1997 VL 35 IS 6 BP 832 EP 835 PN 2 UT WOS:000071227600015 ER PT J AU Wong, CY AF Wong, CY TI Heavy quarkonium production and propagation in nuclei SO CHINESE JOURNAL OF PHYSICS CT Meeting in Honour of Dr Ta-You Wus Birthday CY AUG 11-15, 1997 CL TAIPEI, TAIWAN SP Academia Sin, Inst Phys, Natl Sci Council R O C, Nat Sci Div, Phys Res Promot Ctr, Phys Soc Republic China AB We describe a precursor in heavy quarkonium production in terms of a coherent admixture of states of different color, spin, and angular momentum quantum numbers, and obtain the production amplitudes for different quarkonium bound states by projecting out this precursor state onto these bound states. The precursor is absorbed in its passage through a nucleus in a pA reaction, and the total cross section between this precursor with a nucleon can be calculated with the two-gluon model of the Pomeron. Such a description of coherent precursors and their subsequent interactions with nucleons can explain many salient features of J/psi and psi' production in pA collisions. SN 0577-9073 PD DEC PY 1997 VL 35 IS 6 BP 857 EP 865 PN 2 UT WOS:000071227600019 ER PT J AU Miller, WA AF Miller, WA TI The Hilbert action in Regge calculus SO CLASSICAL AND QUANTUM GRAVITY AB The Hilbert action is derived for a simplicial geometry. I recover the usual Regge calculus action by way of a decomposition of the simplicial geometry into four-dimensional cells defined by the simplicial (Delaunay) lattice as well as its dual (Voronoi)lattice. Within the simplicial geometry, the Riemann scalar curvature, the proper 4-volume, and hence, the Regge action is shown to be exact, in the sense that the definition of the action does not require one to introduce an averaging procedure or a sequence of continuum metrics which were common in all previous derivations. It appears that the unity of these two dual lattice geometries is a salient feature of Regge calculus. SN 0264-9381 PD DEC PY 1997 VL 14 IS 12 BP L199 EP L204 DI 10.1088/0264-9381/14/12/004 UT WOS:000071058700003 ER PT J AU Carey, JW Bish, DL AF Carey, JW Bish, DL TI Calorimetric measurement of the enthalpy of hydration of clinoptilolite SO CLAYS AND CLAY MINERALS AB The enthalpy of hydration of natural clinoptilolite was determined by isothermal immersion calorimetry on Ca-, Na-and K-exchanged clinoptilolite (Fish Creek Mountains, Nevada). Heats of immersion of clinoptilolite were determined at initial H(2)O contents ranging from theta = 0.02 to 0.85 (where a is the ratio [H(2)O content]/[maximum H(2)O content]). The heat of immersion (liquid H(2)O reference state) of Ca-clinoptilolite ranged from -7.5 (theta = 0.87) to -25.7 kJ/mol-H(2)O (theta = 0.19); values for Na-clinoptilolite: ranged from -6.3 (theta = 0.85) to -21.8 kJ/mol-H(2)O (theta = 0.11). and values for K-clinoptilolite ranged from -7.7 (theta = 0.80) to -24.6 kJ/mol-H(2)O (theta = 0.02). Linear regression of the calorimetric data provided the following values for the complete heat of immersion (from theta = 0): Ca-clinoptilolite, -30.3 +/- 2.0; Na-clinoptilolite, -23.4 +/- 0.6; and K-clinoptilolite, -22.4 +/- 0.8 kJ/mol-H(2)O. The heat of immersion measurements were compared with the enthalpy of hydration results of Carey and Bish (1996) determined in a thermogravimetric study of the same samples. The hear of immersion data are similar but of smaller magnitude than the values of enthalpy of hydration and are believed to be more accurate because they represent direct measurements of this thermodynamic property. The effect of dehydration of clinoptilolite on the thermal evolution of the potential high-level radioactive waste repository at Yucca Mountain was considered by comparing the amount of energy consumed by clinoptilolite dehydration with the amount of energy necessary to heat rocks lacking hydrous minerals. The extra energy consumed on heating clinoptilolite from 25 to 200 degrees C ranges between 70 and 80% in excess of that required for nondehydrating materials (that is, clinoptilolite acts as a heat sink). These results indicate that accurate thermohydrologic modeling of rock units at Yucca Mountain should consider the thermal effect of dehydration/hydration processes in clinoptilolite and other hydrous minerals, in addition to the water produced/adsorbed during heating/cooling. RI Carey, James/B-4421-2011 SN 0009-8604 PD DEC PY 1997 VL 45 IS 6 BP 826 EP 833 DI 10.1346/CCMN.1997.0450606 UT WOS:000071710200006 ER PT J AU Ashurst, WT AF Ashurst, WT TI Darrieus-Landau instability, growing cycloids and expanding flame acceleration SO COMBUSTION THEORY AND MODELLING AB A premixed flame, propagating away from a point ignition source into an unlimited domain displays an increasing flame speed after the flame size has grown beyond a transition radius. Experiments by Gostintsev et al are described by the relation R = R-1 + At-3/2,, where,, t is the time from ignition and A = a(sigma)S-L(2)/root kappa:, where S-L is the flame burning velocity and kappa is the thermal diffusivity; The non-dimensional function a(sigma) is determined from the experimental results to be equal to 0.002 sigma(2), where sigma is the density ratio across the flame. In the present work, two-dimensional Lagrangian simulations of flame propagation also display a radial growth with a 3/2 power-law behaviour. This is a potential Bow model-no vorticity is included. Hence, the Darrieus-Landau hydrodynamic instability by itself can generate flame acceleration. The numerical results are summarized by the relation R = R-1 + (tau(2)/40)L(S(L)t/L)(3/2), where L is a reference length and tau is the volume production ratio, tau = sigma -: 1. Equating the zone of velocity jump in the numerical scheme with the temperature jump in hydrocarbon flames allows a definition of an effective thermal diffusivity in the numerical work as kappa(N) = 0.0081S(L)L. With this relation, the radial growth is given as R = RI + 0.0023 tau(2)S(L)(2)t(3/2)/root kappa(N), in good agreement with the experimental result and the numerical results of Filyand et al. SN 1364-7830 PD DEC PY 1997 VL 1 IS 4 BP 405 EP 428 DI 10.1088/1364-7830/1/4/004 UT WOS:000071597900004 ER PT J AU Macal, CM Hurter, AP AF Macal, CM Hurter, AP TI Dependence of bilevel mathematical programs on irrelevant constraints SO COMPUTERS & OPERATIONS RESEARCH AB For standard, single-level mathematical programs, any optimal solution remains optimal when an inactive (i.e., irrelevant) constraint is added to the problem, a property termed independence of irrelevant constraints (IIC). In general, bilevel mathematical programs do not possess the IIC property. This paper presents necessary and sufficient conditions for the IIC property to hold for a bilevel program. A straightforward test is described that concludes whether or not a bilevel program is IIC. (C) 1997 Elsevier Science Ltd. SN 0305-0548 PD DEC PY 1997 VL 24 IS 12 BP 1129 EP 1140 DI 10.1016/S0305-0548(97)00025-7 UT WOS:A1997YC36000004 ER PT J AU Flagg, CN Wallace, D Kolber, Z AF Flagg, CN Wallace, D Kolber, Z TI Cold anticyclonic eddies formed from cold pool water in the southern Middle Atlantic Bight SO CONTINENTAL SHELF RESEARCH AB AVHRR satellite imagery of the southern Mid-Atlantic Eight during May 1993 revealed a large area of cold water over the shelf break and slope that appeared to spin up into a series of southward propagating anticyclonic eddies. The eddies had diameters of 35-45 km at the surface and moved southward at about 20 cm/sec. A radial TOYO CTD (to 50m) and ADCP velocity (to 400m) transect was conducted across the southern-most of these eddies. The upper 50 meters had minimum temperatures of less than 7 degrees C and salinities of about 33 pss, characteristics similar to cold pool waters usually found over the continental shelf. ADCP velocity data from one of-the eddies revealed anticyclonic flow extending to a depth of about 250m. The transport of cold pool water by the eddies was estimated to be 0.1 to 0.2 Sv which is of the same order as the annual mean alongshore transport of shelf water in this region. The origin of the deeper water within the eddy is unlikely to be the continental shelf because the shelf break is less than 100 m. The depth and velocity profiles along the TOYO transect were consistent with the constant potential vorticity eddy model of Flierl (1979) although the source of the eddy kinetic energy is uncertain. The cause for the exodus of cold pool water from the shelf, which extended northward to at least 38 degrees N, is unclear but must involve the establishment of an alongshore baroclinic pressure gradient against the usual southwestward shelf flow. It is possible that the intrusion of Gulf Stream waters onto the shelf near Cape Hatteras was a precursor of this off-shelf transport. The southern-most eddy was marked by high biological productivity and very high oxygen supersaturation. The phytoplankton bloom detected within the exported cold pool water, located over the continental slope, suggests a mechanism whereby production fueled by nutrients derived from the shelf can be locally exported into deep water. (C) 1998 Elsevier Science Ltd. All rights reserved. SN 0278-4343 PD DEC PY 1997 VL 17 IS 15 BP 1839 EP + UT WOS:000073397500002 ER PT J AU Kolman, DG Ford, DK Butt, DP Nelson, TO AF Kolman, DG Ford, DK Butt, DP Nelson, TO TI Corrosion of 304 stainless steel exposed to nitric acid-chloride environments SO CORROSION SCIENCE AB In an effort to examine the combined effect of HNO3, NaCl, and temperature on the general corrosion behavior of 304 stainless steel (SS), electrochemical studies were performed. The corrosion response of 304 SS was bifurcated: materials were either continuously passive following immersion or spontaneously passivated following a period of active dissolution. Active dissolution was autocatalytic, with the corrosion rate increasing exponentially with time and potential. The period of active corrosion terminated following spontaneous passivation, resulting in a corrosion rate decrease of up to five orders of magnitude. The length of the active corrosion period was strongly dependent on the solution volume-to-surface area ratio. This finding, coupled with other results, suggested that spontaneous passivation arises solely from solution chemistry as opposed to changes in surface oxide composition. Increasing NaCl concentrations promoted pitting, active dissolution upon initial immersion, a smaller potential range for passivity, longer active corrosion periods, larger active anodic charge densities preceding spontaneous passivation, and larger corrosion current and peak current densities. In contrast, intermediate HNO3 concentrations promoted active dissolution, with continuous passivity noted at HNO3 concentration extremes. During active corrosion, increased HNO3 concentrations increased the anodic charge density, corrosion current density, and peak current density. The time required for spontaneous passivation was greatest at intermediate HNO3 concentrations. Susceptibility to pitting was also greatest at intermediate HNO, concentrations: the pit initiation and repassivation potentials decreased with increasing HNO3 concentration until the HNO3 concentration exceeded a critical concentration beyond which susceptibility to pitting was entirely eliminated. Increasing solution temperature increased the susceptibility to both pitting and active dissolution. RI Butt, Darryl/B-7480-2008 OI Butt, Darryl/0000-0003-4501-8864 SN 0010-938X PD DEC PY 1997 VL 39 IS 12 BP 2067 EP 2093 DI 10.1016/S0010-938X(97)00092-9 UT WOS:000071493100003 ER PT J AU Cole, DR Riciputi, LR Wesolowski, DJ Paterson, BA Fortier, SM AF Cole, DR Riciputi, LR Wesolowski, DJ Paterson, BA Fortier, SM TI Studies of corrosion in power plant boiler tubes by measurement of oxygen isotopes and trace elements using secondary-ion mass spectrometry SO CORROSION SCIENCE AB Recent advances in secondary ionization mass spectrometry (SIMS) techniques allow the resolution of differences in the natural abundances of the isotopes of O-18 and O-16, and their ratio in both conducting and insulating materials. These techniques have been used in this study to measure the oxygen isotope signatures and their spatial distribution in corrosion products formed during high-temperature oxidation of steel boiler tubes from fossil-fuel power plants. The data obtained in this study are interpreted in terms of oxygen isotope fractionation between the available oxygen reservoirs and oxides formed on or within the metal. Results are presented for three different corrosion scenarios: steamside/fireside corrosion, aqueous phosphate corrosion and corrosion due to H-2 damage. Constant, but isotopically depleted values observed in magnetites formed during steamside corrosion and H-2 damage are indicative of interaction with locally derived meteoric water (which constitutes the boiler feed water). In contrast, isotope distributions in maricite (NaFePO4) suggest equilibrium fractionation between this phase and precursor magnetite. Oxygen isotope patterns in fireside magnetites exhibit a complex zoning that requires at least two isotopically distinct species with significantly different transport rates. Published by Elsevier Science Ltd. SN 0010-938X PD DEC PY 1997 VL 39 IS 12 BP 2215 EP 2232 DI 10.1016/S0010-938X(97)00104-2 UT WOS:000071493100011 ER PT J AU Olson, JR Swift, GW AF Olson, JR Swift, GW TI Acoustic streaming in pulse tube refrigerators: tapered pulse tubes SO CRYOGENICS AB Acoustic streaming is investigated in tapered tubes with axially varying temperature, in the boundary layer limit. By appropriately shaping the tube, the streaming can be eliminated. Experimental data demonstrate that an orifice pulse tube refrigerator with a conical pulse tube whose cone angle eliminates streaming has more cooling power than one with either a cylindrical pulse tube or a conical pulse tube with twice the optimum cone angle. (C) 1998 Elsevier Science Ltd. SN 0011-2275 PD DEC PY 1997 VL 37 IS 12 BP 769 EP 776 DI 10.1016/S0011-2275(97)00037-4 UT WOS:000072357900001 ER PT J AU Stolorz, P Musick, R AF Stolorz, P Musick, R TI Special issue: Scalable high performance computing for KDD SO DATA MINING AND KNOWLEDGE DISCOVERY SN 1384-5810 PD DEC PY 1997 VL 1 IS 4 BP 339 EP 341 DI 10.1023/A:1009799201038 UT WOS:000072406600001 ER PT J AU Berns, DH Cappelli, MA Shuh, DK AF Berns, DH Cappelli, MA Shuh, DK TI Near-edge X-ray absorption fine structure spectroscopy of arcjet-deposited cubic boron nitride SO DIAMOND AND RELATED MATERIALS AB Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy was employed to help determine the structure of boron nitride films grown by bias-enhanced chemical vapor deposition in a low-density supersonic arcjet flow. BN films containing 0-90% cubic boron nitride were analyzed by NEXAFS and compared with c-BN and h-BN reference spectra. The mainly cubic films have been shown previously to be nanocrystalline, which leads to the inability to obtain structural information from Raman scattering spectra. However, with NEXAFS, the nanocrystalline nature of the films does not strongly affect the structural interpretation. It is shown that films deposited with a bias of -75 V are primarily sp(3) bonded. This high sp(3) bonding character agrees with previous measurements based on infrared transmission and reflectance spectroscopy, as well as X-ray photoelectron spectroscopy. (C) 1997 Elsevier Science S.A. SN 0925-9635 PD DEC PY 1997 VL 6 IS 12 BP 1883 EP 1886 DI 10.1016/S0925-9635(97)00156-8 UT WOS:A1997YG13600021 ER PT J AU Boehler, R Ross, M AF Boehler, R Ross, M TI Melting curve of aluminum in a diamond cell to 0.8 Mbar: implications for iron SO EARTH AND PLANETARY SCIENCE LETTERS AB The melting curve of aluminum was measured in a laser-heated diamond cell up to a pressure of 0.8 Mbar in order to test the agreement between this technique and shock wave measurements, which has been lacking in the case for iron. At this pressure, which is over an order of magnitude higher than in previous experiments [1,2], the melting temperature is 3800 K, comparable to that measured for iron at 2 Mbar [3]. The present results for aluminum extrapolate smoothly to the previous melting measurements in a multi-anvil apparatus to 60 kbar and to the calculated shock melting point of 4750 K at 1.25 Mbar. They are also in excellent agreement with theoretical calculations. A review of the shock data reported for Al, Ta and Mo, close-packed metals, in which a break in the sound velocity-pressure curve is used to determine the melting pressure, shows that the change in velocity at melting is about 10% for all three metals. In the case of iron, the sound velocity data have been used to infer two transitions: a solid-solid transition at 2.0 Mbar and melting at 2.4 Mbar, each of these transitions having about a 5% change in sound velocity. It is unlikely that a phase transition between close-packed cubic structures will have a 5% velocity change, the same as is found in the melting transition. We therefore suggest that for iron there exists only a single transition, starting at 2.0 Mbar,a region of incomplete shock melting between 2 and 2.4 Mbar, and a total change in sound velocity of about 10%, which is closer to the value of the other metals studied. This interpretation introduces a very good agreement between the shock melting results of Brown and McQueen [4] and diamond cell measurements for iron [3] which has up to now been lacking. (C) 1997 Elsevier Science B.V. SN 0012-821X PD DEC PY 1997 VL 153 IS 3-4 BP 223 EP 227 DI 10.1016/S0012-821X(97)00188-X UT WOS:000071467400007 ER PT J AU Tan, HD Yeung, ES AF Tan, HD Yeung, ES TI Characterization of dye-induced mobility shifts affecting DNA sequencing in poly(ethylene oxide) sieving matrix SO ELECTROPHORESIS AB The influence of three classes of fluorescence labels including dipyrromethene-boron difluoride (BODIPY), energy transfer (ET) and conventional fluorescein and rhodamine (ABI), on DNA sequencing has been examined with laser-induced fluorescence detection and poly(ethylene oxide)-filled capillary electrophoresis. DNA sequencing fragments were generated by dye-labeled primer cycle-sequencing reactions in a hot-air thermal cycler. A parameter, relative-induced shift, was introduced to quantify the uniformity of electrophoretic mobilities of these fragments. BODIPY was found to have the smallest, but nonzero, effect for dye-induced nonuniformity. Although ET dyes provided the highest sensitivity due to their unique spectroscopic properties, they were found to lack photostability compared to BODIPY and ABI dyes. Characterization also brings out some important tips for selecting the suitable dye set for the two-channel ratio-based DNA base-calling method. SN 0173-0835 PD DEC PY 1997 VL 18 IS 15 BP 2893 EP 2900 DI 10.1002/elps.1150181529 UT WOS:000071948300028 PM 9504827 ER PT J AU Kim, YS Yeung, ES AF Kim, YS Yeung, ES TI DNA sequencing with pulsed-field capillary electrophoresis in poly(ethylene oxide) matrix SO ELECTROPHORESIS AB DNA sequencing by using pulsed-field capillary electrophoresis in a linear polymer matrix was performed in this work. The effects of waveform, frequency, modulation depth and heating were investigated. The separation performance for Sanger DNA fragments up to 1000 bp using a pulsed field was compared to isoelectric and isorheic conditions. A separation mechanism in the flexible poly(ethylene oxide) (PEG) gel was also suggested. We found that temperature change generated by either a pulsed field or ultrasound during DNA sequencing can have a deleterious effect on the separation efficiency. SN 0173-0835 PD DEC PY 1997 VL 18 IS 15 BP 2901 EP 2908 DI 10.1002/elps.1150181530 UT WOS:000071948300029 PM 9504828 ER PT J AU Dichtl, B Stevens, A Tollervey, D AF Dichtl, B Stevens, A Tollervey, D TI Lithium toxicity in yeast is due to the inhibition of RNA processing enzymes SO EMBO JOURNAL AB Hal2p is an enzyme that converts pAp (adenosine 3',5' bisphosphate), a product of sulfate assimilation, into 5' AMP and P-i. Overexpression of Hal2p confers lithium resistance in yeast, and its activity is inhibited by submillimolar amounts of Li+ in vitro. Here we report that pAp accumulation in HAL2 mutants inhibits the 5'-->3' exoribonucleases Xrn1p and Rat1p. Li+ treatment of a wild-type yeast strain also inhibits the exonucleases, as a result of pAp accumulation due to inhibition of Hal2p; 5' processing of the 5.8S rRNA and snoRNAs, degradation of pre-rRNA spacer fragments and mRNA turnover are inhibited, Lithium also inhibits the activity of RNase MRP by a mechanism which is not mediated by pAp, A mutation in the RNase MRP RNA confers Li+ hypersensitivity and is synthetically lethal with mutations in either HAL2 or XRN1. We propose that Li+ toxicity in yeast is due to synthetic lethality evoked between Xrn1p and RNase MRP. Similar mechanisms may contribute to the effects of Li+ on development and in human neurobiology. SN 0261-4189 EI 1460-2075 PD DEC 1 PY 1997 VL 16 IS 23 BP 7184 EP 7195 DI 10.1093/emboj/16.23.7184 UT WOS:000071055100027 PM 9384595 ER PT J AU Difiglio, C AF Difiglio, C TI Using advanced technologies to reduce motor vehicle greenhouse gas emissions SO ENERGY POLICY AB This paper quantifies the potential reduction in US greenhouse gas emissions that could be achieved by using advanced-technology motor vehicles and low-emission bio-fuels. These two approaches are compared to a variety of other approaches to reduce transportation sector emissions. It is concluded that only strong fiscal measures can produce emission reductions as large as are available from advanced-technology vehicles and low-emission fuels. A technology strategy is offered that should make the benefits of these technologies likely to occur should the US enter into a binding agreement to limit US greenhouse gas emissions. Various policy scenarios that could result from such an agreement are presented with the result that the technology strategy to produce advanced-technology vehicles and bio-fuels remains the most viable and cost-effective approach to control the future growth of transportation-sector greenhouse gas emissions. (C) 1997 Elsevier Science Ltd. All rights reserved. SN 0301-4215 PD DEC PY 1997 VL 25 IS 14-15 BP 1173 EP 1178 DI 10.1016/S0301-4215(97)00109-2 UT WOS:000071371000008 ER PT J AU Plotkin, SE Greene, D AF Plotkin, SE Greene, D TI Prospects for improving the fuel economy of light-duty vehicles SO ENERGY POLICY AB US efforts to reduce light-duty vehicle fuel use have focused primarily on policies aimed directly at vehicle fuel economy not use, eg fuel economy standards and research on efficiency technology, Although economists have traditionally favored fuel taxes as a more efficient policy tool, the US political system seems allergic to higher taxes, This paper explores the potential effectiveness of higher gasoline taxes vs, more stringent fuel economy standards, focusing particularly on the fuel price sensitivity of gasoline demand and the technical prospects for improved fuel economy, We conclude that the evidence supports a long-run price elasticity of about -0.4, ie gasoline demand is relatively insensitive to the fuel price, despite early econometric analyses projecting high fuel price elasticities of demand, We also conclude that there are substantial technical prospects for improving fuel economy although the current marketplace has little interest in such prospects. (C) 1997 Elsevier Science Ltd. All rights reserved. SN 0301-4215 PD DEC PY 1997 VL 25 IS 14-15 BP 1179 EP 1188 DI 10.1016/S0301-4215(97)00110-9 UT WOS:000071371000009 ER PT J AU Schlueter, EM Zimmerman, RW Witherspoon, PA Cook, NGW AF Schlueter, EM Zimmerman, RW Witherspoon, PA Cook, NGW TI The fractal dimension of pores in sedimentary rocks and its influence on permeability SO ENGINEERING GEOLOGY AB Perimeter-area power-law relationship of pores in five sedimentary rocks are estimated from scanning electron micrographs of thin sections. These relationships for the pores of four sandstones were found to lie between 1.43 and 1.49, while that of an Indiana limestone was found to be 1.67. We show how the perimeter-area power-law relationship of pores, along with a pore-size distribution, can be used to estimate the hydraulic permeability. A discussion is given of how the fractal dimension of the pore perimeter derived by Mandelbrot for islands whose boundaries are fractal: P=epsilon(D)A(D/2), where epsilon is some constant that depends on the length of the measuring grid size and D is the fractal dimension of the pore perimeter, influences permeability. (C) 1997 Elsevier Science B.V. OI Zimmerman, Robert/0000-0001-6674-3403 SN 0013-7952 PD DEC 1 PY 1997 VL 48 IS 3-4 BP 199 EP 215 DI 10.1016/S0013-7952(97)00043-4 UT WOS:000071855500004 ER PT J AU Suter, GW AF Suter, GW TI Integration of human health and ecological risk assessment SO ENVIRONMENTAL HEALTH PERSPECTIVES SN 0091-6765 PD DEC PY 1997 VL 105 IS 12 BP 1282 EP 1283 DI 10.2307/3433736 UT WOS:000072819500001 PM 9405324 ER PT J AU Stabin, MG AF Stabin, MG TI Health concerns related to radiation exposure of the female nuclear medicine patient SO ENVIRONMENTAL HEALTH PERSPECTIVES CT International Conference on Radiation and Health CY NOV 07-11, 1996 CL BEER SHEVA, ISRAEL SP Ben Gurion Univ Negev, Soroka Med Ctr, WHO, Int Assoc Radiat Res, US DOE, Israel Atom Energy Commiss, Elscint Ltd, Israel Canc Soc, Soreq Nucl Res Ctr, Israel Min Labor & Social Affairs, Comm Res & Prevent Occupat Safety & Hlth AB The female nuclear medicine patient is of special Concern in evaluating radiation dose and risk in nuclear medicine. The female's overall body size and organ sizes generally are smaller than those of her male counterpart (thus her radiation doses will be higher, given the same amounts of administered activity-and similar biokinetics); female gonads are inside the body instead of outside and are near several organs often important as source organs in internal dosimetry (urinary bladder, liver, kidneys, intestines); risk of breast cancer is significantly higher among females than males; and in the case of pregnancy, exposure to radiation of the embryo/fetus and the nursing infant are of special concern in such an analysis. All these concerns are addressed in this study through a comparative study of radiation doses for males and females over a large number (similar to 60) of nuclear medicine studies and through a study of what is known about radiation dosimetry in pregnancy and breast feeding. It was found that women's critical organ doses and effective doses (as defined by the international Commission on Radiological Protection 60 [ICRP 60]) are about 25% higher than those for men across ail these studies. Women's gonad doses, however, may be as much as 10 to 30 times higher than those in men, although 2- to 3-fold differences are common. Many radiopharmaceuticals are administered to women of childbearing age; however, little is known about how much activity crosses the placenta and about the biokinetics in the fetus should it occur. Nonetheless, dose estimates are provided at four stages of pregnancy (early, 3-month, 6-month, and 9-month gestation) for a large number of radiopharmaceuticals, whether or not quantitative estimates of placental crossover can be made. Many radiopharmaceuticals are also excreted in breast milk of nursing mothers. Breast feeding interruption schedules are suggested through analysis of the observed kinetics of these pharmaceuticals and an assumed dose limit of 1 mSv (effective dose equivalent) to the infant. SN 0091-6765 PD DEC PY 1997 VL 105 SU 6 BP 1403 EP 1409 DI 10.2307/3433640 UT WOS:000075404000005 PM 9467052 ER PT J AU Lucas, JN AF Lucas, JN TI Chromosome translocations: A biomarker for retrospective biodosimetry SO ENVIRONMENTAL HEALTH PERSPECTIVES CT International Conference on Radiation and Health CY NOV 07-11, 1996 CL BEER SHEVA, ISRAEL SP Ben Gurion Univ Negev, Soroka Med Ctr, WHO, Int Assoc Radiat Res, US DOE, Israel Atom Energy Commiss, Elscint Ltd, Israel Canc Soc, Soreq Nucl Res Ctr, Israel Min Labor & Social Affairs, Comm Res & Prevent Occupat Safety & Hlth AB We discuss here the results from our studies demonstrating that simple translocations detected by chromosome painting can be used to reconstruct radiation doses for workers exposed within the dose limits and for individuals with past exposure. To be useful, a biomarker for exposure and risk assessment should employ an end point that is highly quantitative, stable over time, and relevant to human risk. Recent advances in chromosome staining using fluorescence in situ hybridization facilitate fast and reliable measurement of simple translocations, a type of DNA damage linked both to prior clastogenic exposure and to risk. In contrast to other biomarkers available, the frequency of simple translocations in individuals exposed to whole-body radiation is stable over rime postexposure, has little interindividual variability, and can be measured accurately at low frequencies. SN 0091-6765 PD DEC PY 1997 VL 105 SU 6 BP 1433 EP 1436 DI 10.2307/3433645 UT WOS:000075404000010 PM 9467057 ER PT J AU Neta, R AF Neta, R TI Modulation with cytokines of radiation injury: Suggested mechanisms of action SO ENVIRONMENTAL HEALTH PERSPECTIVES CT International Conference on Radiation and Health CY NOV 07-11, 1996 CL BEER SHEVA, ISRAEL SP Ben Gurion Univ Negev, Soroka Med Ctr, WHO, Int Assoc Radiat Res, US DOE, Israel Atom Energy Commiss, Elscint Ltd, Israel Canc Soc, Soreq Nucl Res Ctr, Israel Min Labor & Social Affairs, Comm Res & Prevent Occupat Safety & Hlth AB Cytokines, hormonelike proteins, produced by stimulated cells and tissues, were found to protect mice against lethal hematopoietic failure caused by ionizing radiation. Radioprotection was achieved by pretreatment with interleukin-1 (IL-1), tumor necrosis factor (TNF), IL-12, or stem cell factor (SCF) at 18 to 24 hr before irradiation. Pretreatment with antibodies to these cytokines rendered the mice more susceptible to radiation lethality, indicating that these cytokines play a role in innate resistance to radiation. In contrast, treatment with tumor growth factor beta (TGF-beta), a cytokine that inhibits cycling of primitive hematopoietic progenitors, sensitized mice to radiation lethality. The schedule of IL-1 administration was critical to its radioprotective effect. Evidence was obtained that this may be based on the induction of additional cytokines by IL-1. The radioprotective effects of cytokines can be based on induction of cycling of primitive progenitor cells (IL-1, SCF), prevention of apoptosis (SCF), and induction of scavenging proteins and enzymes (IL-1, TNF) that reduce oxidative damage. In contrast, radiosensitizing effects may be due to inhibition of progenitor cycling (TGF-beta) or enhanced progenitor cell apoptosis (TGF-beta). Thus, the insights gained from such studies at the whole-animal level promise a better understanding of the membrane and intracellular events associated with radiation damage and repair of such damage. SN 0091-6765 PD DEC PY 1997 VL 105 SU 6 BP 1463 EP 1465 DI 10.2307/3433652 UT WOS:000075404000017 PM 9467064 ER PT J AU Weiss, JF AF Weiss, JF TI Pharmacologic approaches to protection against radiation-induced lethality and other damage SO ENVIRONMENTAL HEALTH PERSPECTIVES CT International Conference on Radiation and Health CY NOV 07-11, 1996 CL BEER SHEVA, ISRAEL SP Ben Gurion Univ Negev, Soroka Med Ctr, WHO, Int Assoc Radiat Res, US DOE, Israel Atom Energy Commiss, Elscint Ltd, Israel Canc Soc, Soreq Nucl Res Ctr, Israel Min Labor & Social Affairs, Comm Res & Prevent Occupat Safety & Hlth AB Studies on mechanisms of radioprotection are leading to a more rational use of protectors for different applications. In considering the feasibility of radioprotectors that act through various mechanisms, it is necessary to distinguish the application needed, e.g., protection against accidental external or internal exposures, acute high-close radiation injury or low doses over a long period, high-LET radiation exposures during space flight, and protection of normal tissues of cancer patients who are undergoing therapy. Protectors generally are classified as either sulfhydryl compounds, other antioxidants, or receptor-mediated agents (e.g., bioactive lipids, cytokines, and growth factors). This review focuses on comparative radioprotection and toxicity studies in mice using the most effective phosphorothioate agents designated as WR-compounds and other classes of protectors. The superiority of phosphorothioates (WR-2721, WR-151327) as radioprotectors appears to be related to their high affinity for DNA and the similarity in structure of phosphorothioate metabolites to polyamines, and their effects on processes related to DNA structure and synthesis. Drug tolerance levels are available from clinical trials using WR-2721 (amifostine) and provide a basis for discussions of the disadvantages of phosphorothioate administration outside a clinical setting. In this regard, arguments are presented against the current use of WR-2721 by Department of Energy personnel for planned radiation exposures during emergencies. Future research may demonstrate however, that pharmacologic agents could be useful in accident scenarios, especially when used in combination with therapeutic measures. Assessment of potential prophylactic measures should consider compatibility with therapeutic measures currently in use or ones that might be available in the future for the treatment of radiation injuries. These include antiemetics, purified stem cells, granulocyte colony-stimulating factor, and other cytokines. Their potential usefulness against radiation-induced mutagenesis of pre and postexposure administration of phosphorothioates and other classes of protectors should be corroborated in humans. SN 0091-6765 PD DEC PY 1997 VL 105 SU 6 BP 1473 EP 1478 DI 10.2307/3433654 UT WOS:000075404000019 PM 9467066 ER PT J AU Lee, DD Walker, JF Taylor, PA Hendrickson, DW AF Lee, DD Walker, JF Taylor, PA Hendrickson, DW TI Cesium-removal flow studies using ion exchange SO ENVIRONMENTAL PROGRESS AB The development, selection, and implementation of technologies to be used in removing cesium from radioactive liquid wastes in preparation for their final disposition is discussed. The methodology involved testing several proposed sorbents in ion-exchange columns using actual liquid wastes from underground storage tanks at U.S. Department of Energy sites. The sorbents initially tested included resorcinol-formaldehyde resin (RF), CS-100 resin, SuperLig 644C resin, 3M WEB with embedded SuperLig 644, granular potassium cobalt hexacyanoferrate, and granular crystalline silicotitanates (CSTs). The results of the bench-scale testing were used to select the sorbents for the full-scale Cesium Removal Demonstration Project (CsRD). This project will treat up to 25,000 gal of radioactive supernatant stored in the Melton Valley Storage Tanks (MVSTs) at Oak Ridge National Laboratory (ORNL). The demonstration system is modular in design and will process supernatant at flows up to 5 gal/min through 12-in.-diam columns. Following the demonstration the system will be used for routine processing of tank waste at ORNL. To show their applicability to wastes at other sites, RF and CST sorbents were tested in a bench-scale column using a diluted Hanford supernatant liquor (double-shell slurry feed) from tank 241-AW-101. The results are compared with those from tests of MVST supernatant. SN 0278-4491 PD WIN PY 1997 VL 16 IS 4 BP 251 EP 262 DI 10.1002/ep.3300160413 UT WOS:000073593900006 ER PT J AU Shi, Y Wang, H Chang, SG AF Shi, Y Wang, H Chang, SG TI Kinetics of NO absorption in aqueous iron (II)thiochelate solutions SO ENVIRONMENTAL PROGRESS AB Ferrous thiochelate solutions were used to absorb NO from flue gas. The absorption rates were studied as a function of pH with a double-stirred reactor at 50 degrees C. The rate constants of five ferrous thiochelates: Fe2+ (dimercaptosuccinate)(2), Fe2+ (dithioloxalate)(2), Fe2+ (aminoethanethiol)(2), Fe2+(cysteine)(2), Fe2+(penicillamine)(2), reacted with NO at pH 5.5 and pH 7.0, have been determined. The implications of the kinetic data on the use of these iron thiochelate additives in wet flue gas desulfurization scrubbers: limestone,lime, and sodium, for simultaneous SO2 and NOx removal is discussed. SN 0278-4491 PD WIN PY 1997 VL 16 IS 4 BP 301 EP 306 DI 10.1002/ep.3300160420 UT WOS:000073593900013 ER PT J AU Madden, TH Datye, AK Fulton, M Prairie, MR Majumdar, SA Stange, BM AF Madden, TH Datye, AK Fulton, M Prairie, MR Majumdar, SA Stange, BM TI Oxidation of metal-EDTA complexes by TiO2 photocatalysis SO ENVIRONMENTAL SCIENCE & TECHNOLOGY AB Ethylenediaminetetraacetic acid (EDTA), a common industrial agent for complexing metal ions in water, frequently inhibits conventional metals-removal technologies used in water treatment. This study investigated the use of TiO2 photocatalysis for the aqueous-phase oxidation of EDTA and several metal complexes of EDTA. Reactions were performed at 0.1 wt % loading of Degussa P-25 TiO2, a solute concentration of 0.8 mM and at a constant pH. The different metal-EDTA complexes exhibited widely different photocatalytic oxidation rates under equivalent conditions of pH = 4 +/- 0.1 in an aerobic system: Cu(II)-EDTA > Pb(II)-EDTA much greater than EDTA > Ni(II)-EDTA approximate to Cd(II)-EDTA approximate to Zn(II)-EDTA >>> Cr(III)-EDTA. Photoefficiency based on the Cu(II)-EDTA initial rate is nearly 60%. The rates of total organic carbon (TOC) removal and formaldehyde generation during photocatalytic EDTA oxidation indicate similarities to electrochemical oxidations of EDTA. Several means were explored to enhance the oxidation of NI(II)-EDTA, whose behavior was taken to represent that of the slowly oxidizing complexes. Continuous addition of H2O2 solution during the photocatalytic treatment increased the oxidation rate for NI(II)-EDTA as did the presence of homogeneous Cu2+. The presence of Cu2+ led to rapid ligand exchange transforming the Ni(II)-EDTA into Cu(II)-EDTA, which is easily oxidized. OI Datye, Abhaya/0000-0002-7126-8659 SN 0013-936X PD DEC PY 1997 VL 31 IS 12 BP 3475 EP 3481 DI 10.1021/es970226a UT WOS:A1997YJ88200043 ER PT J AU Shi, Z Sigman, ME Ghosh, MM Dabestani, R AF Shi, Z Sigman, ME Ghosh, MM Dabestani, R TI Photolysis of 2-chlorophenol dissolved in surfactant solutions SO ENVIRONMENTAL SCIENCE & TECHNOLOGY AB The photochemical degradation and dechlorination of 2-chlorophenol (2CP) (0.1 g/L) dissolved in surfactant solutions has been studied. The initial degradation and dechlorination of 2CP followed apparent first-order kinetics in nearly all the test solutions. The quantum yields of 2CP degradation and dechlorination were enhanced in th a presence of nonionic surfactant Brij 35 and anionic surfactant sodium dodecyl sulfate (SDS). A larger enhancement was observed at surfactant concentrations greater than the critical micelle concentration (cmc) and was attributed to partitioning of 2CP into the micelles. Furthermore, the study of 2CP photolysis in hexane, methanol, and dimethoxyethane suggested that the surfactant can serve as a hydrogen atom source in promoting 2CP degradation. Two 2CP phototransformation pathways in surfactant solutions were identified. The electronically excited anionic form of 2CP led to cyclopentadienecarboxylic acid formation through a ring contraction via the Wolff rearrangement. Electronic excitation of the undissociated form of 2CP led to the formation of catechol via a nucleophilic displacement of chloride in the presence of water. Phenol also observed as a photoproduct in non-nucleophilic solvents that can act as hydrogen atom donors. Phenol was also demonstrated to sensitize the 2CP transformation to phenol in micellar media. SN 0013-936X PD DEC PY 1997 VL 31 IS 12 BP 3581 EP 3587 DI 10.1021/es9703279 UT WOS:A1997YJ88200058 ER PT J AU Gunderson, CA Kostuk, JM Gibbs, MH Napolitano, GE Wicker, LF Richmond, JE Stewart, AJ AF Gunderson, CA Kostuk, JM Gibbs, MH Napolitano, GE Wicker, LF Richmond, JE Stewart, AJ TI Multispecies toxicity assessment of compost produced in bioremediation of an explosives-contaminated sediment SO ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY AB A multispecies terrestrial test system was used to assess the environmental effectiveness of composting for bioremediation of explosives-contaminated soils. The assessment involved comparing biological responses, from the individual to the community level, in remediated and reference composts. A 6-month greenhouse study incorporated two soil invertebrate species, three plant species and an associated symbiont, and the naturally occurring complement of soil microorganisms. Measured parameters included growth and reproduction of earthworms and isopods; soil mire diversity; soil lipid class composition as an indicator of soil microbial community structure; plant growth, photosynthesis, and reproduction; and root nodulation and symbiotic N-2 fixation. Additional short-term toxicity rests of seed germination and earthworm survival were performed to supplement the mesocosm data. Compost prepared from the explosives-contaminated soil inhibited several aspects of plant growth and physiology, but few adverse effects on soil invertebrates were detected. An initial lag in earthworm and isopod reproduction occurred in the reference compost, reflecting some inherent compost differences not associated with contamination, and highlighting the importance and the difficulty of finding appropriate reference soils for assessing hazardous waste sites or remediation technologies. Nonetheless, the results from this study suggested some nonlethal effects from the contaminated-soil compost, primarily to plants. The mesocosm methodology used in this study can bridge the gap between traditional short-term toxicity testing and longer term field assessments, and provide information on ecological effects by explicitly including measurements of multiple species across several levels of ecological organization. OI stewart, arthur/0000-0003-1968-5997 SN 0730-7268 PD DEC PY 1997 VL 16 IS 12 BP 2529 EP 2537 DI 10.1897/1551-5028(1997)016<2529:MTAOCP>2.3.CO;2 UT WOS:A1997YH37700014 ER PT J AU Spengler, SJ AF Spengler, SJ TI Emerging technologies from the human genome project for understanding susceptibility and risk SO ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY CT 3rd Annual NHEERL Symposium on Susceptibility and Risk Assessment CY SEP 24-27, 1996 CL DURHAM, NORTH CAROLINA SP NHEERL AB The new technologies from the Human Genome Program provide exceptional opportunities for surveying and measuring human exposure, as well as determining susceptibility on an individual-by-individual basis. These new technologies will soon enable rapid screening of populations at risk, as well as the broader public, for a variety of genes known to be associated with increased risk. These include specific oncogenes, tumor suppressor genes and DNA repair enzymes. Use of these technologies also presents a number of ethical issues, both in screening and in use of the information about individuals. Overall, the use of rapid genotyping technologies will introduce a specificity and possible group identifiers that will present new challenges to the determination of risk within the EPA mandate. (C) 1997 Elsevier Science B.V. SN 1382-6689 PD DEC PY 1997 VL 4 IS 3-4 BP 235 EP 238 DI 10.1016/S1382-6689(97)10016-3 UT WOS:000071826600007 PM 21781826 ER PT J AU Widdicombe, JH Bastacky, SJ Wu, DXY Lee, CY AF Widdicombe, JH Bastacky, SJ Wu, DXY Lee, CY TI Regulation of depth and composition of airway surface liquid SO EUROPEAN RESPIRATORY JOURNAL AB The depth and composition of human airway surface liquid (ASL) may depend on secretion from airway glands, ion transport across the surface epithelium, goblet cell discharge, transepithelial gradients in hydrostatic pressure, and surface tension, Published values for the frequency of airway glands and for the secretory rates of individual glands suggest that total gland secretion in human trachea can amount to similar to 60 mu L.cm(-2).h(-1). Volume absorption directly measured across cultures of surface epithelium from human trachea is similar to 5 mu L.cm(-2).h(-1). These flows should alter the depth of ASL at +10 and -1 mu m.min(-1). We have looked for I changes in ASL depth of this magnitude using low-temperature scanning electron microscopy (LT-SEM) of rapidly frozen specimens of bovine trachea, Stimulation of gland secretion with methacholine led to an initial increase in depth of similar to 25 mu m.min(-1) followed by a decline at similar to 15 mu m.min(-1). Whereas the initial increase in depth was probably due to transient gland secretion, the later decline reflected active absorption of liquid across the surface epithelium, Finally, we present preliminary data shelving that LT-SEM can be combined with X-ray microanalysis to determine the elemental composition of ASL. SN 0903-1936 PD DEC PY 1997 VL 10 IS 12 BP 2892 EP 2897 DI 10.1183/09031936.97.10122892 UT WOS:000071854700038 PM 9493680 ER PT J AU Cui, ST Cummings, PT Cochran, HD AF Cui, ST Cummings, PT Cochran, HD TI Configurational bias Gibbs ensemble Monte Carlo simulation of vapor-liquid equilibria of linear and short-branched alkanes SO FLUID PHASE EQUILIBRIA AB We report Gibbs ensemble Monte Carlo simulations of the linear alkane, n-nonane, and its branched isomer, branched 2,6-dimethylheptane; n-eicosane, and its branched isomer 2,6,11,15-tetramethylhexadecane; and an isomer of triacontane, 2,6,10,15,19,23-hexamethyltetracosane (squalane), using the configurational-bias technique to determine the vapor-liquid phase equilibria of these systems. For linear alkanes, quantitative agreement is obtained between simulation and experiment for both critical temperature and density. For short-branched alkanes for which there are experimental data available, the calculated vapor-liquid phase equilibria compare well with experiments, The critical density for branched alkanes studied here from the simulation is in quantitative agreement with experiment, while the critical temperature from simulation is slightly lower. Examination of the vapor-liquid phase equilibria for the applicability of the law of corresponding states shows very minor differences between a linear alkane and its short-branched isomers. In attempting to evaluate the accuracy of the current intermolecular potential model for the equation of state for the branched alkane molecules, we also performed molecular dynamics simulations. The combination of the Gibbs-ensemble and molecular dynamics results suggest that the potential model developed by Siepmann et al. gives reasonable agreement with experiment. (C) 1997 Elsevier Science B.V. RI Cummings, Peter/B-8762-2013 OI Cummings, Peter/0000-0002-9766-2216 SN 0378-3812 PD DEC PY 1997 VL 141 IS 1-2 BP 45 EP 61 DI 10.1016/S0378-3812(97)00209-4 UT WOS:000071655900004 ER PT J AU Mio, C Jayachandran, KN Prausnitz, JM AF Mio, C Jayachandran, KN Prausnitz, JM TI Vapor-liquid equilibria for binary solutions of some comb polymers based on poly(styrene-co-maleic anhydride) in acetone, methanol and cyclohexane SO FLUID PHASE EQUILIBRIA AB Vapor-liquid equilibria have been measured for comb and linear polymers using a gravimetric-sorption method in the temperature range 50-70 degrees C. Polymers were poly(styrene-co-maleic anhydride) with alkyl side chains of different length (C5, C12, C22) and poly(styrene-co-maleic anhydride) and poly(maleic anhydride). Solvents were acetone, methanol and cyclohexane. Due to different chemical structures, the phase behavior of the comb polymer solutions strongly depends on the ratio backbone/side chains. Freed's lattice-cluster theory gives a good representation of the data. (C) 1997 Elsevier Science B.V. SN 0378-3812 PD DEC PY 1997 VL 141 IS 1-2 BP 165 EP 178 DI 10.1016/S0378-3812(97)00177-5 UT WOS:000071655900011 ER PT J AU Burakovsky, L Horwitz, LP Schieve, WC AF Burakovsky, L Horwitz, LP Schieve, WC TI Mass-proper time uncertainty relation in a manifestly covariant relativistic statistical mechanics SO FOUNDATIONS OF PHYSICS LETTERS AB We prove the uncertainty relation T(Delta V)Delta m greater than or equal to 2 pi h/c(2), which is realized on a statistical mechanical level for an ensemble of events in (1 + D)-dimensional spacetime with motion parameterized by an invariant "proper time" tau, where T-Delta V is the average passage interval in tau for the events which pass through a small (typical) (1+ D)-volume Delta V, and Delta m is the dispersion of mass around its on-shell value in such an ensemble. We show that a linear mass spectrum is a completely general property of a (1 + D)-dimensional off-shell theory. SN 0894-9875 PD DEC PY 1997 VL 10 IS 6 BP 503 EP 516 DI 10.1023/A:1022473701046 UT WOS:000071381200001 ER PT J AU Bishop, JB Morris, RW Seely, JC Hughes, LA Cain, KT Generoso, WM AF Bishop, JB Morris, RW Seely, JC Hughes, LA Cain, KT Generoso, WM TI Alterations in the reproductive patterns of female mice exposed to xenobiotics SO FUNDAMENTAL AND APPLIED TOXICOLOGY AB Chemicals, by virtue of their varied interactions with biological molecules, are expected to differ in the way they may alter female reproduction. Reproductive toxicity may reflect effects either on the female germ cells or on various maternal processes such as ovulation, implantation, pregnancy, and parturition. In either case, the ultimate manifestation of chemical toxicity on female reproduction is a decrease in the number of normal young born. Very little information is available on the effects of chemicals that are nonhormonal in nature on the long-term ability of treated females to produce offspring. This report presents the results of long-term female total reproductive capacity (TRC) tests on 29 chemicals, including pharmaceuticals, pesticides, and alkylating and industrial agents. For each chemical, the minimum test involved an evaluation of the maximum tolerated dose administered as a single intraperitoneal injection. Females were single-pair mated with an untreated male for most of the female's reproductive life span (a minimum of 347 days posttreatment) and scored for the number of live births produced during this period. Confirmatory dominant lethal experiments or histological examinations for numbers of small follicles were carried out when mutagenic effects or cytotoxicity, respectively, were suspected as the basis for reduced fertility. Of the 29 chemicals studied, 17 had reproductive effects which may be grouped into one of three classes: (1) those that reduced the total number of young and litters per female, (2) those that reduced the total number of young but not of litters, and (3) those that had no significant effect on the total number of young produced but reduced the size of the first and/or second litters. The TRC provides a capacity for detecting a range of toxic insults upon female reproduction. Many of the chemicals were indeed shown to affect the reproductive performance of females through mutagenic and/or cytotoxic effects on follicles. In some cases, however, no causative mechanism could be identified for the observed reduction in reproductive performance. Nevertheless, with this report the number of chemicals tested by this TRC procedure has been quadrupled and the categories of chemicals tested have been substantially broadened. (C) 1997 Society of Toxicology. SN 0272-0590 PD DEC PY 1997 VL 40 IS 2 BP 191 EP 204 DI 10.1006/faat.1997.2379 UT WOS:000071561100004 PM 9441715 ER PT J AU Najmabadi, F Bathke, CG Billone, MC Blanchard, JP Bromberg, L Chin, E Cole, FR Crowell, JA Ehst, DA El-Guebaly, LA Herring, JS Hua, TQ Jardin, SC Kessel, CE Khater, H Lee, VD Malang, S Mau, TK Miller, RL Mogahed, EA Petrie, TW Reis, EE Schultz, J Sidorov, M Steiner, D Sviatoslavsky, IN Sze, DK Thayer, R Tillack, MS Titus, P Wagner, LM Wang, XR Wong, CPC AF Najmabadi, F Bathke, CG Billone, MC Blanchard, JP Bromberg, L Chin, E Cole, FR Crowell, JA Ehst, DA El-Guebaly, LA Herring, JS Hua, TQ Jardin, SC Kessel, CE Khater, H Lee, VD Malang, S Mau, TK Miller, RL Mogahed, EA Petrie, TW Reis, EE Schultz, J Sidorov, M Steiner, D Sviatoslavsky, IN Sze, DK Thayer, R Tillack, MS Titus, P Wagner, LM Wang, XR Wong, CPC TI Overview of the ARIES-RS reversed-shear tokamak power plant study SO FUSION ENGINEERING AND DESIGN AB The ARIES-RS tokamak is a conceptual, D-T-burning 1000 MWe power plant. As with earlier ARIES design studies, the final design of ARIES-RS was obtained in a self-consistent manner using the best available physics and engineering models. Detailed analyses of individual systems together with system interfaces and interactions were incorporated into the ARIES systems code in order to assure self-consistency and to optimize towards the lowest cost system. The ARIES-RS design operates with a reversed-shear plasma and employs a moderate aspect ratio (A = 4.0). The plasma current is relatively low (I(p) = 11.32 MA) and bootstrap current fraction is high (f(BC) = 0.88). Consequently, the auxiliary power required for RF current drive is relatively low(similar to 80 MW). At the same time, the average toroidal beta is high (beta = 5%), providing power densities near practical engineering limits (the peak neutron wall loading is 5.7 MW m(-2)). The toroidal-field (TF) coil system is designed with relatively 'conventional' materials (Nb(3)Sn and NbTi conductor with 316SS structures), and is operated at a design limit of similar to 16 T at the coil in order to optimize the design point. The ARIES-RS design uses a self-cooled lithium blanket with vanadium alloy as the structural material. The V-alloy has low activation, low afterheat, high temperature capability and can handle high heat flux. A self-cooled liquid lithium blanket is simple, and with the development of an insulating coating, has low operating pressure. Also, this blanket gives excellent neutronics performance. Detailed analysis has been performed to minimize the cost and maximize the performance of the blanket and shield. One of the distinctive features of this design is the integration of the first wall, blanket, parts of the shield, divertor and stability shells into an integral unit within each sector, The maintenance scheme consists of horizontal removal of entire sectors. Prior to the initiation of the ARIES-RS study, a set of top-level requirements and goals for fusion demonstration and commercial power plants was evolved in collaboration with representatives from US electric utilities and from industry. The degree to which ARIES-RS reached these requirements and goals and the necessary trade-offs are described and the high-leverage areas and key R&D items are presented. (C) 1997 Elsevier Science S.A. RI Jardin, Stephen/E-9392-2010 SN 0920-3796 PD DEC PY 1997 VL 38 IS 1-2 BP 3 EP 25 DI 10.1016/S0920-3796(97)00110-5 UT WOS:000071738300002 ER PT J AU Jardin, SC Kessel, CE Bathke, CG Ehst, DA Mau, TK Najmabadi, F Petrie, TW AF Jardin, SC Kessel, CE Bathke, CG Ehst, DA Mau, TK Najmabadi, F Petrie, TW TI Physics basis for a reversed shear tokamak power plant SO FUSION ENGINEERING AND DESIGN AB The reversed shear plasma configuration is examined as the basis for a tokamak fusion power plant. Analysis of plasma equilibrium and ideal MHD stability, bootstrap current and current drive, plasma vertical stability and position control, divertor physics and plasma power balance are used to determine the operating point parameters that maximize fusion power density and minimize the recirculating power fraction. The final plasma configuration for the ARIES-RS power plant obtains beta of 4.96%, plasma driven current fraction of 91%, plasma current of 11.3 MA, toroidal field of 8.0 T and major and minor radius of 5.5 and 1.4 m. The current drive system utilizes fast wave, lower hybrid and high frequency fast wave current drive to obtain maximum current profile flexibility, requiring less than or equal to 80 MW of power. A divertor solution is found which employs neon impurity injection to enhance the radiation in the scrape-off layer (SOL) and divertor and results in a combined particle and heat load in the divertor of less than or equal to 6 MW m(-2). The plasma is driven with a Q of 25 and is at a thermally stable operating point. The plasma is assumed to be in an ELMy H-mode, with low amplitude and high frequency ELMs. (C) 1997 Elsevier Science S.A. All rights reserved. RI Jardin, Stephen/E-9392-2010 SN 0920-3796 PD DEC PY 1997 VL 38 IS 1-2 BP 27 EP 57 DI 10.1016/S0920-3796(97)00111-7 UT WOS:000071738300003 ER PT J AU Bathke, CG AF Bathke, CG TI Systems analysis in support of the selection of the ARIES-RS design point SO FUSION ENGINEERING AND DESIGN AB Systems analysis has been instrumental in the determination of the ARIES-RS reference design point through the evaluation of design options and the economic optimization of design variables. The ARIES-RS reference design point is described as modeled by the ARIES systems code. Parametric sensitivities about the ARIES-RS reference design point are presented that illustrate the economic impact of various design choices considered within the ARIES-RS design study. (C) 1997 Elsevier Science S.A. SN 0920-3796 PD DEC PY 1997 VL 38 IS 1-2 BP 59 EP 86 DI 10.1016/S0920-3796(97)00112-9 UT WOS:000071738300004 ER PT J AU Wong, CPC Chin, E Petrie, TW Reis, EE Tillack, M Wang, X Sviatoslavsky, I Malang, S Sze, DK AF Wong, CPC Chin, E Petrie, TW Reis, EE Tillack, M Wang, X Sviatoslavsky, I Malang, S Sze, DK TI ARIES-RS divertor system selection and analysis SO FUSION ENGINEERING AND DESIGN AB The ARIES-RS divertor system is selected and analyzed. A radiative divertor approach using Ne as the radiator is chosen to reduce the maximum heat flux to < 6 MW m(-2). A 2 mm W layer is used to withstand surface erosion allowing a design life close to 3 full-power-years. This W coating on the V-alloy structure is castellated to meet structural design limits. A detailed description of the calculated heat flux distribution, thermal-hydraulics, structural analysis, fabrication methods and vacuum system design are presented. An innovative design using adjustable bolts is utilized to support the divertor plates, withstand disruption loads and allow adjustment of alignment between plates. With the exception of the concentration of Ne at the divertor, it is found that this divertor system design can satisfy all the design criteria and most of the functional requirements specified by the project. (C) 1997 Elsevier Science S.A. SN 0920-3796 PD DEC PY 1997 VL 38 IS 1-2 BP 115 EP 137 DI 10.1016/S0920-3796(97)00117-8 UT WOS:000071738300006 ER PT J AU Frattolillo, A Migliori, S Combs, SK Milora, SL AF Frattolillo, A Migliori, S Combs, SK Milora, SL TI Development of a two-stage pneumatic repeating pellet injector for the refueling of long-pulse magnetic confinement fusion devices SO FUSION TECHNOLOGY AB Next-step fusion devices, like the International Ther monuclear Experimental Reactor (ITER), and future fusion power plants will require a flexible plasma fueling system, including both gas puffing and high-and low-speed pellet injection. To sustain core plasma density, relatively large pellets penetrating beyond the separatrix will have to be provided at a repetition rate of similar to 1 Hz for very long pulse operation. In the context of a cooperative agreement between the U.S. Department of Energy and the Euratom-ENEA Association, Oak Ridge National Laboratory (ORNL) has collaborated with ENEA Frascati to demonstrate the feasibility of a high-speed (2 to 3 km/s) repeating (similar to 1-Hz) pneumatic pellet injector for long-pulse operation. A test facility was assembled at ORNL that combined a Frascati repeating two-stage light-gas gun and an existing ORNL deuterium extruder equipped with a pellet chambering mechanism/gun barrel assembly. It was operated in the course of three joint experimental campaigns between September 1993 and May 1995. The results of the first two campaigns appear in an earlier paper: Here, the results are reported of the third campaign, during which the original objectives of the collaboration were met. Both performance and reliability of the system were improved, with the facility's being capable of delivering sequences of 2.7-mm deuterium pellets at a repetition rate of I Hz and velocities up to 2.5 km/s. The test facility was also briefly operated with neon pellets to explore the potential to produce fast "killer" pellets. Speeds of 1.7 km/s were easily achieved using a piston mass of 43 g. Higher speeds should be achievable with a system specifically designed for neon or other high-Z gases. SN 0748-1896 PD DEC PY 1997 VL 32 IS 4 BP 601 EP 609 UT WOS:000070993000007 ER PT J AU Ahluwalia, DV AF Ahluwalia, DV TI On a new non-geometric element in gravity SO GENERAL RELATIVITY AND GRAVITATION AB In this essay a generalized notion of flavor-oscillation clocks is introduced. The generalization contains the element that various superimposed mass eigenstates may have different relative orientation of the component of their spin with respect to the rotational axis of the gravitational source. It is found that these quantum mechanical clocks do not always redshift identically when moved from the gravitational environment of a non-rotating source to the field of a rotating source. The non-geometric contributions to the redshifts may be interpreted as quantum mechanically induced fluctuations over a geometric structure of space-time. SN 0001-7701 PD DEC PY 1997 VL 29 IS 12 BP 1491 EP 1501 DI 10.1023/A:1018874111373 UT WOS:A1997YJ02100001 ER PT J AU Carver, EA Stubbs, L AF Carver, EA Stubbs, L TI Zooming in on the human-mouse comparative map: Genome conservation re-examined on a high-resolution scale SO GENOME RESEARCH AB Over the past decade, conservation of genetic linkage groups has been shown in mammals and used to great advantage, fueling significant exchanges of gene mapping and functional information especially between the genomes of humans and mice. As human physical maps increase in resolution from chromosome bands to nucleotide sequence, comparative alignments of mouse and human regions have revealed striking similarities and surprising differences between the genomes of these two best-mapped mammalian species. Whereas, at present, very few mouse and human regions have been compared on the physical level, existing studies provide intriguing insights to genome evolution, including the observation of recent duplications and deletions of genes that may play significant roles in defining some of the biological differences between the two species. Although high-resolution conserved marker-based maps are currently available only for human and mouse, a variety of new methods and resources are speeding the development of comparative maps of additional organisms. These advances mark the first step toward establishment of the human genome as a reference map for vertebrate species, providing evolutionary and functional annotation to human sequence and vast new resources for genetic analysis of a variety of commercially, medically, and ecologically important animal models. OI Stubbs, Lisa/0000-0002-9556-1972 SN 1054-9803 PD DEC PY 1997 VL 7 IS 12 BP 1123 EP 1137 UT WOS:000071263100004 PM 9414318 ER PT J AU BouygeMoreau, I Rondeau, G AvetLoiseau, H Andre, MT Bezieau, S Cherel, M Saleun, S Cadoret, E Shaikh, T DeAngelis, MM Arcot, S Batzer, M Moisan, JP Devilder, MC AF BouygeMoreau, I Rondeau, G AvetLoiseau, H Andre, MT Bezieau, S Cherel, M Saleun, S Cadoret, E Shaikh, T DeAngelis, MM Arcot, S Batzer, M Moisan, JP Devilder, MC TI Construction of a 780-kb PAC, BAC, and cosmid contig encompassing the minimal critical deletion involved in B cell chronic lymphocytic leukemia at 13q14.3 SO GENOMICS AB A putative tumor suppressor gene involved in B cell chronic lymphocytic leukemia (B-CLL) was mapped to human chromosome 13q14.3 close to the genetic markers D13S25 and D13S319. We constructed a 780-kb-long contig composed of cosmids, bacterial artificial chromosomes, and bacteriophage P1-derived artificial chromosomes that provides essential information and tools for the positional cloning of this gene. The contig contains both flanking markers as well as several additional genetic markers, three ESTs, and one potential CpG island. In addition, using one B-CLL patient, we characterized a small internal deleted region of 550 kb. Comparing this deletion with other recently published deletions narrows the minimally deleted area to less than 100 kb in our physical map. This deletion core region should contain all or part of the disrupted in B cell malignancies tumor suppressor gene. (C) 1997 Academic Press. RI DeAngelis, e/J-7863-2015; Devilder, Marie Claire/L-2940-2015; Cherel, Michel/F-8298-2013; Bezieau, stephane/G-5621-2015 OI Bezieau, stephane/0000-0003-0095-1319 SN 0888-7543 PD DEC 1 PY 1997 VL 46 IS 2 BP 183 EP 190 DI 10.1006/geno.1997.5008 UT WOS:A1997YL01600003 PM 9417905 ER PT J AU Fan, WF Christensen, M Eichler, E Zhang, XX Lennon, G AF Fan, WF Christensen, M Eichler, E Zhang, XX Lennon, G TI Cloning, sequencing, gene organization, and localization of the human ribosomal protein RPL23A gene SO GENOMICS AB The intron-containing gene for human ribosomal protein RPL23A has been cloned, sequenced, and localized, The gene is approximately 4.0 kb in length and contains five exons and four introns. All splice sites exactly match the AG/GT consensus rule. The transcript is about 0.6 kb and is detected in all tissues examined. In adult tissues, the RPL23A transcript is dramatically more abundant in pancreas, skeletal muscle, and heart, while much less abundant in kidney, brain, placenta, lung, and liver. A full-length cDNA clone of 576 nt was identified, and the nucleotide sequence was found to match the exon sequence precisely, The open reading frame encodes a polypeptide of 156 amino acids, which is absolutely conserved with the rat RPL23A protein. In the 5' flanking region of the gene, a canonical TATA sequence and a defined CAAT box were found for the first time in a mammalian ribosomal protein gene. The intron-containing RPL23A gene was mapped to cytogenetic band 17q11 by fluorescence in situ hybridization. (C) 1997 Academic Press. SN 0888-7543 PD DEC 1 PY 1997 VL 46 IS 2 BP 234 EP 239 DI 10.1006/geno.1997.5038 UT WOS:A1997YL01600008 PM 9417910 ER PT J AU Gu, ZY Lal, D Liu, TS Guo, ZT Southon, J Caffee, MW AF Gu, ZY Lal, D Liu, TS Guo, ZT Southon, J Caffee, MW TI Weathering histories of Chinese loess deposits based on uranium and thorium series nuclides and cosmogenic Be-10 SO GEOCHIMICA ET COSMOCHIMICA ACTA AB The long, continuous deposition of dust in the Chinese loess plateau (Liu et al., 1985; Kukia and An, 1989; Ding et al., 1991a) offers an unique opportunity to study the nature of soil weathering in a wide range of climatic conditions. In this paper we report on measurements of concentrations of U-and Th-series nuclides and of major cations in 150 loess and paleosol samples from five sites, going back 2.5 Ma. Using the results for Be-10 concentrations in these soils (Gu et al., 1996), we determined the absolute amounts of water added to several soil units and obtained: (1) first-order leaching constants for U and several cations and (2) the compositions of the soils contributing to the dust-source regions and of the dust at deposition. Further, based on analyses of Th-230 in soils deposited in the past ca. 140 ka, we determined when the soils weathered in the source regions. We conclude that most of the weathering in the dust-source regions may have occurred during the interglacials. Copyright (C) 1997 Elsevier Science Ltd. RI Guo, Zhengtang/B-6854-2008; Caffee, Marc/K-7025-2015 OI Guo, Zhengtang/0000-0003-2259-9715; Caffee, Marc/0000-0002-6846-8967 SN 0016-7037 PD DEC PY 1997 VL 61 IS 24 BP 5221 EP 5231 DI 10.1016/S0016-7037(97)00313-X UT WOS:000071287900005 ER PT J AU Nishimura, T Fehler, M Baldridge, WS Roberts, P Steck, L AF Nishimura, T Fehler, M Baldridge, WS Roberts, P Steck, L TI Heterogeneous structure around the Jemez volcanic field, New Mexico, USA, as inferred from the envelope inversion of active-experiment seismic data SO GEOPHYSICAL JOURNAL INTERNATIONAL AB We analyse active-experiment seismic data obtained by the 1993 Jemez Tomography Experiment (JTEX) programme to elucidate the heterogeneous structure of the Jemez volcanic held, which is located at the boundary between the Colorado Plateau and the Rio Grande Rift. Using a single isotropic scattering assumption, we first calculate the envelope Green's functions for the upper and lower crust and the uppermost mantle. By fitting the theoretical envelopes with the observed three-component data, we estimate depth-dependent features of the scattering coefficients around Valles Caldera. We estimate the ratios of scattering coefficients, rather than scattering coefficients themselves, because of the uncertainty of the seismic efficiency of the explosive sources and knowledge of absolute site-amplification factors. The strongest scattering coefficients are observed at a shallow depth beneath the Valles Caldera. This is considered to be related to the complex structure caused by two episodes of caldera formation and the ensuing resurgent uplift in the caldera, etc. The depth-dependent characters of the scattering coefficients for the Colorado Plateau and the Rio Grande Rift are similar to each other: a transparent upper crust and a heterogeneous lower crust (small and large scattering coefficients, respectively). However, the scattering coefficients beneath the Rio Grande Rift are several times larger than those beneath the Colorado Plateau. Depths of the lower crust and the Moho boundary beneath the Rio Grande Rift are shallower than those of the Colorado Plateau. From their geological settings and other geophysical results around the region, we infer that the larger scattering coefficients of the rift are associated with rift formation and volcanic activity, such as magma ascent from the upper mantle to the crust. SN 0956-540X PD DEC PY 1997 VL 131 IS 3 BP 667 EP 681 DI 10.1111/j.1365-246X.1997.tb06605.x UT WOS:000071263800021 ER PT J AU Forsyth, RJ Balogh, A Smith, EJ Gosling, JT AF Forsyth, RJ Balogh, A Smith, EJ Gosling, JT TI Ulysses observations of the northward extension of the heliospheric current sheet SO GEOPHYSICAL RESEARCH LETTERS AB After passing through the northern polar regions of the heliosphere during the summer of 1995, the Ulysses spacecraft has been gradually returning towards lower equatorial latitudes, reaching 30 degrees N in August 1996 at about which time low speed solar wind from the streamer belt was once again observed. This paper reports on the Ulysses magnetic field observations, beginning from this time, concentrating on encounters with the heliospheric current sheet. These encounters restarted at a latitude of 25.5 degrees N, a higher latitude than might be expected at solar activity minimum. We show that this early reappearance was due to a northward deflection of the current sheet caused by a long-lived active region at the corresponding heliographic longitude in the photosphere. SN 0094-8276 PD DEC 1 PY 1997 VL 24 IS 23 BP 3101 EP 3104 DI 10.1029/97GL03099 UT WOS:A1997YJ98100040 ER PT J AU Piepel, G Redgate, T Masuga, P AF Piepel, G Redgate, T Masuga, P TI Comparison of mixture models and free energy of hydration models for waste glass releases SO GLASS TECHNOLOGY AB Mixture and free energy of hydration (FEH) approaches for modelling elemental releases fi om high level nuclear waste glass as functions of glass composition are compared. The FEH model is shown to be a restricted version of the first-order mixture (FOM) model. The performance of the two approaches in modelling elemental release as a function of glass composition is compared for three data sets. Least squares regression was used to fit both model types to each data set. The resulting FEH and FOM model coefficients and goodness-of-fit statistics are compared The FOM model fits release in each data set much better than the FEH model. Comparing FOM coefficients across the data sets shows that the effect of a glass component on release can depend on the level and range of the component and on the levels of other glass components. The FEH approach has a limited ability to represent such behaviour for different glass composition regions due to its reliance on assumed constant effects of each component. The mixture approach, on the other hand, determines from the data the effects of glass components on release. It also can account for higher order (i.e. curvilinear or interactive) effects of components. Thus, the mixture approach has more flexibility for approximating the relationships between glass composition and release for various glass composition regions. SN 0017-1050 PD DEC PY 1997 VL 38 IS 6 BP 210 EP 215 UT WOS:000071789000005 ER PT J AU Liang, LY Korte, N Goodlaxson, JD Clausen, J Fernando, Q Muftikian, R AF Liang, LY Korte, N Goodlaxson, JD Clausen, J Fernando, Q Muftikian, R TI Byproduct formation during the reduction of TCE by zero-valence iron and palladized iron SO GROUND WATER MONITORING AND REMEDIATION AB Trichloroethene (TCE) was reduced with zero-valence iron and palladized iron in zero-head-space extractors. Progress of the reaction in these batch studies was monitored with purge-and-trap gas chromatography and a flame ionization detector. When a 5 ppm initial concentration of TCE reacts with zero-valence iron, approximately 140 ppb of vinyl chloride persists for as long as 73 days. The concentration of vinyl chloride (approximately 10 ppb) remaining with palladized iron is approximately an order of magnitude less than when zero-valence iron is the reductant. These data suggest that volatile byproducts may be underrepresented in other published data regarding reduction with zero-valence metals. These results also demonstrate that the reduction of TCE with palladized iron (0.05 percent palladium) is more than an order of magnitude faster than with zero-valence iron. With a 5:1 solution-to-solid ratio the TCE half-life with zero-valence iron is 7.41 hours, but is only 0.59 hours with the palladized iron. RI Liang, Liyuan/O-7213-2014 OI Liang, Liyuan/0000-0003-1338-0324 SN 1069-3629 PD WIN PY 1997 VL 17 IS 1 BP 122 EP 127 DI 10.1111/j.1745-6592.1997.tb01191.x UT WOS:A1997WJ75100011 ER PT J AU Cossairt, JD Grossman, NL Marshall, ET AF Cossairt, JD Grossman, NL Marshall, ET TI Assessment of dose equivalent due to neutrinos SO HEALTH PHYSICS AB Neutrinos are present in the natural environment and are also produced by particle accelerators. A recent hypothesis has also been proposed that asserts that ionizing radiation due to neutrinos from certain astronomical events may have led to the extinction of some biological species. Thus, it is of interest to be able to estimate the dose equivalent due to these weakly interacting particles. Presented here are methods for estimating the dose equivalent due to neutrinos over a broad domain of energy, examples of such calculations, and an assessment of the postulated role of neutrinos in biological extinctions. It is concluded that the dose equivalent due to neutrinos from natural sources and from present-day accelerators is inconsequential and the postulated role of neutrinos in biological extinctions is highly improbable. SN 0017-9078 EI 1538-5159 PD DEC PY 1997 VL 73 IS 6 BP 894 EP 898 DI 10.1097/00004032-199712000-00002 UT WOS:A1997YG12800010 PM 9373066 ER PT J AU Strenge, DL AF Strenge, DL TI A general algorithm for radioactive decay with branching and loss from a medium SO HEALTH PHYSICS AB Many areas in the field of health physics require evaluation of the change of radionuclide quantity in a medium with time. A general solution to first-order compartmental models is presented in this paper for application to systems consisting of one physical medium that contains any number of radionuclide decay chain members, The general analytical solution to the problem is first described mathematically and then extended to four applications: 1) evaluation of the quantity of radionuclides as a function of time, 2) evaluation of the time integral of the quantity during a time period, 3) evaluation of the amount in a medium as a function of time following deposition at a constant rate, and 4) evaluation of the time integral of the amount in a medium after deposition at a constant rate for a time. The solution can be applied to any system involving constant physical transfers from the medium and radioactive chain decay with branching in the medium. The general solution is presented for quantities expressed in units of atoms and activity, Unlike many earlier mathematical solutions, this solution includes chain decay with branching explicitly in the equations. SN 0017-9078 EI 1538-5159 PD DEC PY 1997 VL 73 IS 6 BP 953 EP 957 DI 10.1097/00004032-199712000-00010 UT WOS:A1997YG12800018 PM 9373074 ER PT J AU Seol, SY Cha, YS Minkowycz, WJ AF Seol, SY Cha, YS Minkowycz, WJ TI Thermal analysis of composite superconductors subjected to time-dependent disturbances SO HEAT AND MASS TRANSFER AB A one-dimensional heat conduction equation with time-and temperature-dependent heat sources was employed to study the steady-state and transient response of a composite superconductor subjected to a thermal disturbance. An integral formulation was used to solve the steady-state problem of current redistribution and heat generation. The results of the integral formulation are compared with those of an analytical solution. The two solutions agree with each other except when the analytical solution fails as the temperature in the superconductor begins to exceed the critical temperature. Transient solutions were obtained by the finite-difference technique and the results are compared with a known analytical solution. Results of numerical calculations of the transient response of a composite superconductor subjected to an initial pulsed disturbance are presented. It is demonstrated that the superconductor can switch between the superconducting and the current-sharing state. The transient response and the stability of the composite conductor depend on the magnitude and duration of the disturbance, the dimensionless temperature theta*, and the dimensionless parameter phi. SN 0042-9929 PD DEC PY 1997 VL 33 IS 3 BP 177 EP 184 DI 10.1007/s002310050176 UT WOS:000073141200001 ER PT J AU Lam, NP Neumann, AU Perelson, AS Layden, TJ AF Lam, NP Neumann, AU Perelson, AS Layden, TJ TI Hepatitis C: Viral kinetics - Reply SO HEPATOLOGY SN 0270-9139 PD DEC PY 1997 VL 26 IS 6 BP 1692 EP 1693 UT WOS:A1997YK77200055 ER PT J AU Thornton, MJ Fritz, JS Klampfl, CW AF Thornton, MJ Fritz, JS Klampfl, CW TI Separation of native amino acids at low pH by capillary electrophoresis SO HRC-JOURNAL OF HIGH RESOLUTION CHROMATOGRAPHY AB Amino acids are cations at low pH and can be readily separated by capillary electrophoresis provided an alkanesulfonic acid is added to the electrolyte carrier. Formation of a positive net charge on the bare fused-silica surface at low pH was confirmed by measurement of an anodic electroosmotic flow. The addition of ethanesulfonic acid or octanesulfonic acid to the electrolyte carrier causes a reversal of the EOF. A mechanism is proposed in which the alkanesulfonic acid adsorbs to the positively-charged capillary wall through electrostatic attraction. Adsorption of a second molecule of alkanesulfonate by hydrophobic attraction to the carbon chain forms a negatively-charged coating on the capillary wall. The alkanesulfonate also imparts selectivity to the system by participation in ion-pairing interactions with the native amino acids to improve resolution. The CE separation of a mixture of the twenty common amino acids at pH 2.8 with direct absorbance detection at 185 mm resulted in 17 amino acid peaks in 20 minutes with a 30 kV applied voltage. The effect of several variables was studied including electrolyte carriers containing different alkanesulfonic acids, the influence of pH, applied voltage, and concentration of electrolyte carrier. OI Klampfl, Christian/0000-0001-9139-4022 SN 0935-6304 PD DEC PY 1997 VL 20 IS 12 BP 647 EP 652 UT WOS:000071191600005 ER PT J AU Thornton, MJ Fritz, JS AF Thornton, MJ Fritz, JS TI Separation of metal cations in acidic solution by capillary electrophoresis with direct and indirect UV detection SO HRC-JOURNAL OF HIGH RESOLUTION CHROMATOGRAPHY AB Methods for the detection of metal cations under acidic conditions, near pH 2, in capillary electrophoresis (CE) were investigated, Conditions for direct UV detection of UV absorbing metal cations such as Cr3+, Cu2+, Fe3+, UO22+, VO2+, and VO2+ were established with aqueous HCl or HClO4 as the electrolyte carrier, The speciation of vanadium(IV) and vanadium(V) at pH 2.3 by CE was achieved with direct detection at 185 nm, With the strong absorbance at 185 nm, no complexation was needed to detect the metal cations, An indirect UV detection scheme for acidic conditions was also investigated. Several background carrier electrolytes (BCES) were studied including 4-methylbenzylamine nicotinamide, pyridazine, guanidine, 3-picoline, and chromium(III) to determine their effectiveness under very acidic conditions, The effect of ionic surfactants and the nonionic surfactant, Triton X-100, on the peak heights and N values was also studied. SN 0935-6304 PD DEC PY 1997 VL 20 IS 12 BP 653 EP 656 UT WOS:000071191600006 ER PT J AU Forsythe, C AF Forsythe, C TI Human factors in agile manufacturing: A brief overview with emphasis on communications and information infrastructure SO HUMAN FACTORS AND ERGONOMICS IN MANUFACTURING AB Agile manufacturing has been promoted as a national strategy for improving industrial competitiveness. Agility refers to the capability to very rapidly go from a set of unique customer requirements to a quality, finished product. An appreciation of the human factors inherent to agile product development is pivotal to the successful integration of agility-enabling technologies, as well as the coordination of personnel working within a concurrent engineering environment. This article briefly summarizes human factors contributions to: (1) development of agile business practices; (2) design of enabling technologies; and (3) management of the introduction and fielding of new technologies and business practices. More detailed discussion is offered for human factors related to the communications and information infrastructure essential to an organization making the transition from traditional to agile product development. (C) 1997 John Wiley & Sons, Inc. SN 1090-8471 PD WIN PY 1997 VL 7 IS 1 BP 3 EP 10 UT WOS:A1997WL06400002 ER PT J AU Nemtchinov, IV Svetsov, VV Kosarev, IB Golub, AP Popova, OP Shuvalov, VV Spalding, RE Jacobs, C Tagliaferri, E AF Nemtchinov, IV Svetsov, VV Kosarev, IB Golub, AP Popova, OP Shuvalov, VV Spalding, RE Jacobs, C Tagliaferri, E TI Assessment of kinetic energy of meteoroids detected by satellite-based light sensors SO ICARUS AB Radiation energies of bright flashes caused by disintegration of large meteoroids in the atmosphere have been measured using optical sensors on board geostationary satellites. Light curves versus time are available for some of the events. We have worked out several numerical techniques to derive the kinetic energy of the meteoroids that produced the hashes. Spectral opacities of vapor of various types of meteoroids were calculated for a wide range of possible temperatures and densities. Coefficients of conversion of kinetic energy to radiation energy were computed for chondritic and iron meteoroids 10 cm to 10 m in size using radiation-hydrodynamics numerical simulations. Luminous efficiency increases with body size and initial velocity, Some analytical approximations are presented for average conversion coefficients for irons and H-chondrites. A mean value of this coefficient for large meteoroids (1-10 m in size) is about 5-10%. The theory was tested by analyzing the light curves of several events in detail. Kinetic energies of impactors and energy-frequency distribution of 51 bolides, detected during 22 months of systematic observations in 1994-1996, are determined using theoretical values of luminous efficiencies and heat-transfer coefficients, The number of impacts in the energy range from 0.25 to 4 kt TNT is 25 per year and per total surface of the Earth. The energy-frequency distribution is in a rather good agreement with that derived from acoustic observations and the lunar crater record, Acoustic systems have registered one 1 Mt event in 12 years of observation. Optical systems have not detected such an event as yet due to a shorter time of observation. The probability of a 1 Mt impact was estimated by extrapolation of the observational data. (C) 1997 Academic Press. RI Popova, Olga/K-1885-2012 SN 0019-1035 PD DEC PY 1997 VL 130 IS 2 BP 259 EP 274 DI 10.1006/icar.1997.5821 UT WOS:000072037700003 ER PT J AU Gibbard, SG Levy, EH Morfill, GE AF Gibbard, SG Levy, EH Morfill, GE TI On the possibility of lightning in the protosolar nebula SO ICARUS AB Chondrules constitute a significant fraction of primitive meteorites. Their thermal history includes rapid melting followed by cooling on timescales of minutes to hours. The mechanism underlying such extreme, short-lived thermal excursions away from the prevailing, much milder nebular equilibrium conditions has eluded understanding for many decades. Among the prime candidate mechanisms long thought to provide a possible explanation of chondrule formation is lightning-large-scale electrostatic discharges-in the protoplanetary nebula. In this paper, we explore the possible occurrence of such electrostatic discharges in the protoplanetary nebula powered by precipitation or other processes analogous to that believed to cause lightning on Earth and other planets. Our analysis incorporates charge separation in collisions of water-ice or other solid particles, and includes a self-consistent nebular electrical conductivity determined by a balance between production of free electrons and ions and loss to grain surfaces. We find that development of a large-scale electric field strong enough to produce discharges does not occur under conditions characteristic of protostellar nebulae. This is mainly a result of the fact that the high electrical conductivity of the environment and the relatively low density of solid particles combine to yield a situation in which the large scale electric fields, as well as the electric charges segregated on the particles are short circuited by the highly mobile electrons and ions. We also consider the possibility of lightning in altered nebula environments with higher than canonical dust density, such as a dust subdisk. (C) 1997 Academic Press. SN 0019-1035 PD DEC PY 1997 VL 130 IS 2 BP 517 EP 533 DI 10.1006/icar.1997.5846 UT WOS:000072037700022 ER PT J AU Floyd, S Jacobson, V Liu, CG McCanne, S Zhang, LX AF Floyd, S Jacobson, V Liu, CG McCanne, S Zhang, LX TI A reliable multicast framework for light-weight sessions and application level framing SO IEEE-ACM TRANSACTIONS ON NETWORKING AB This paper describes Scalable Reliable Multicast (SRM), a reliable multicast framework for light-weight sessions and application level framing, The algorithms of this framework are efficient, robust, and scale web to both very large networks and very large sessions, The SRM framework has been prototyped in wb, a distributed whiteboard application, which has been used on a global scale with sessions ranging from a few to a few hundred participants, The paper describes the principles that have guided the SRM design, including the IP multicast group delivery model, an end-to-end, receiver-based model of reliability, and the application level framing protocol model, As with unicast communications, the performance of a reliable multicast delivery algorithm depends on the underlying topology and operational environment, We investigate that dependence via analysis and simulation, and demonstrate an adaptive algorithm that uses the results of previous loss recovery events to adapt the control parameters used for future loss recovery, With the adaptive algorithm, our reliable multicast delivery algorithm provides good performance over a wide range of underlying topologies. SN 1063-6692 PD DEC PY 1997 VL 5 IS 6 BP 784 EP 803 DI 10.1109/90.650139 UT WOS:000071721400004 ER PT J AU Vawter, GA Sullivan, CT Wendt, JR Smith, RE Hou, HQ Flem, JF AF Vawter, GA Sullivan, CT Wendt, JR Smith, RE Hou, HQ Flem, JF TI Tapered rib adiabatic following fiber couplers in etched GaAs materials for monolithic spot-size transformation SO IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS AB Design details and demonstration data are presented for an (Al,Ga)As monolithic tapered rib waveguide achieving modal spot-size transformation. The tapered rib adiabatic following fiber coupler structure (TRAFFIC) achieves two-dimensional (2-D) expansion of the output optical mode of single-transverse-mode semiconductor waveguide modulators and lasers using a one-dimensional (1-D) taper between noncritical initial and final taper widths which are compatible,vith optical lithographic techniques, Measurements are presented of total mode expansion losses between similar to 1.5-2.0 dB and semiconductor to single-mode-fiber waveguide coupling losses of similar to 0.5-1.0 dB for doped pin optical-modulator-type waveguides using the TRAFFiC waveguide, A semiconductor laser with a TRAFFiC tapered-rib mode-expansion section and measured coupling loss between the laser output and single-mode fiber of only 0.9 dB is described, Finally, a TRAFFiC spot-size transformer for undoped waveguide modulators with total mode expansion losses of 1.84 dB and excellent modal behavior at 1.32-mu m wavelength is presented, The TRAFFiC structure is particularly well suited for integration with both active and passive etched rib waveguide devices, Fabrication is relatively simple, requiring only patterning and etching of the tapered waveguide and uniform-width outer mesa waveguide without any epitaxial regrowth. SN 1077-260X PD DEC PY 1997 VL 3 IS 6 BP 1361 EP 1371 DI 10.1109/2944.658790 UT WOS:000072123700007 ER PT J AU Schone, H Carson, RF Paxton, AH Taylor, EW AF Schone, H Carson, RF Paxton, AH Taylor, EW TI AlGaAs vertical-cavity surface-emitting laser responses to 4.5-MeV proton irradiation SO IEEE PHOTONICS TECHNOLOGY LETTERS AB We have irradiated single-and multimode AlGaAs vertical-cavity surface-emitting laser (VCSEL) arrays operating at a nominal wavelength of 780 nn with 4.5-MeV protons and doses ranging from 10 to 30 Mrad in the active region, We observed a peak power reduction of about 2% per Mrad in the 14-mu m aperture, multimode VCSEL's, Single-mode VCSEL's having an aperture of 6 mu m exhibited a smaller peak power reduction of 0.4%-1% per Mrad. A slight shift in the current threshold was observed only for the multimode VCSEL's at dose levels above 10 Mrad, First results indicate a reduced VCSEL peak laser power output that is dominated by a temperature shift caused by the radiation induced increase in resistive heating, In contrast, the power reduction in edge-emitting lasers is dominated by the enhanced radiation induced nonradiative recombination rate. The VCSEL irradiation was performed with a focused ion micro beam that was rastered over the device surface, ensuring a very uniform exposure of a single device in the array. SN 1041-1135 PD DEC PY 1997 VL 9 IS 12 BP 1552 EP 1554 DI 10.1109/68.643257 UT WOS:A1997YH17000002 ER PT J AU Pu, R Hayes, EM Jurrat, R Wilmsen, CW Choquette, KD Hou, HQ Geib, KM AF Pu, R Hayes, EM Jurrat, R Wilmsen, CW Choquette, KD Hou, HQ Geib, KM TI VCSEL's bonded directly to foundry fabricated GaAs smart pixel arrays SO IEEE PHOTONICS TECHNOLOGY LETTERS AB This letter reports the hip-chip bonding of an 8 x 8 array of free standing VCSEL's to a foundry fabricated GaAs metal-semiconductor field-effect transistor (MESFET) smart pixel array, The VCSEL's have oxide defined apertures and are co-planar bonded directly to smart pixels which perform the selection function of a data filter, The V-tb and series resistance of the VCSEL's were on average approximately 2.1 V and 250 Omega, respectively, which indicates that good electrical contact was obtainable with this process, The I-th ranged between 2-4 mA, with a corresponding output power of between 400 mu W and >1.0 mW depending on aperture size. SN 1041-1135 PD DEC PY 1997 VL 9 IS 12 BP 1622 EP 1624 DI 10.1109/68.643289 UT WOS:A1997YH17000026 ER PT J AU Vawter, GA Mar, A Hietala, V Zolper, J Hohimer, J AF Vawter, GA Mar, A Hietala, V Zolper, J Hohimer, J TI All optical millimeter-wave electrical signal generation using an integrated mode-locked semiconductor ring laser and photodiode SO IEEE PHOTONICS TECHNOLOGY LETTERS AB The first monolithic photonic integrated circuit for all-optical generation of millimeter (mm)-wave electrical signals is reported, The design integrates a mode-locked semiconductor ring diode laser, an optical amplifier, and a high-speed photodetector into a single optical integrated circuit. Signal generation is demonstrated at frequencies of 30, 60, and 90 GHz. SN 1041-1135 PD DEC PY 1997 VL 9 IS 12 BP 1634 EP 1636 DI 10.1109/68.643294 UT WOS:A1997YH17000030 ER PT J AU Sargis, PD Henderer, BD Lowry, ME AF Sargis, PD Henderer, BD Lowry, ME TI 10-Gb/s subcarrier multiplexed transmission over 490 km of ordinary single-mode fiber without dispersion compensation SO IEEE PHOTONICS TECHNOLOGY LETTERS AB This letter describes the results of a field trial in which four 2.5-Gb/s data channels were transmitted around the San Francisco Bay over ordinary telephone company fiber at 1550 nm with negligible dispersion penalty using subcarrier multiplexing (SCM). Using off-the-shelf microwave components and a lithium niobate external modulator having a modulation bandwidth of around 20 GHz, we were able to multiplex four tightly spaced high-speed data channels at a single wavelength, At the receiving end, we optically demultiplexed the data using optical filters and OC-48 clock recovery receivers. SN 1041-1135 PD DEC PY 1997 VL 9 IS 12 BP 1658 EP 1660 DI 10.1109/68.643303 UT WOS:A1997YH17000038 ER PT J AU Reagor, D Fan, Y Mombourquette, C Jia, QX Stolarczyk, L AF Reagor, D Fan, Y Mombourquette, C Jia, QX Stolarczyk, L TI A high-temperature superconducting receiver for low-frequency radio waves SO IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY AB We have developed a receiver for low-frequency radio waves using high-temperature superconducting quantum interference devices (SQUID's). The primary application of such a receiver is to communicate in underground areas where the overburden results in significant losses at the usual radio frequencies. The receiver constructed consists of a SQUID, a small dewar, control electronics, and a battery pack, The SQUID was fabricated in our laboratory using an edge junction technology, discussed in previous publications, For this work we increased the effective area by including a standard galvanically coupled pickup loop, We have investigated background noise spectra and found that the low noise boor of the SQUID's can be fully utilized in the receiver, provided that the signals be encoded with a bandwidth narrower than the 60 Hz spacing between powerline harmonics, The most significant advantage of SQUID's for this application is that they allow the compact construction of three-axis receivers that are necessary to overcome a dominant source of vibrational or motional noise. RI Jia, Q. X./C-5194-2008 SN 1051-8223 PD DEC PY 1997 VL 7 IS 4 BP 3845 EP 3849 DI 10.1109/77.659437 UT WOS:A1997YJ84600006 ER PT J AU Peterfreund, N Guez, A AF Peterfreund, N Guez, A TI Structure-based neural network learning SO IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS AB We present a new learning algorithm for the structure of recurrent neural networks. It is shown that any m linearly independent n-dimensional vectors can be stored in at most (n + m - 2)-dimensional symmetric network. A storage procedure which satisfy this bound is presented. We propose a new learning procedure for the domain of attraction which preserves both the equilibrium set and the stability property of the original system. It is shown that previously learned attraction regions remain invariant under the proposed learning rule. Our emphasis throughout this brief is on the design of associative memories and classifiers. SN 1549-8328 EI 1558-0806 PD DEC PY 1997 VL 44 IS 12 BP 1143 EP 1149 DI 10.1109/81.645155 UT WOS:000071164500005 ER PT J AU Vianco, PT Stephens, JJ Rejent, JA AF Vianco, PT Stephens, JJ Rejent, JA TI Intermetallic compound layer development during the solid state thermal aging of 63Sn-37Pb solder Au-Pt-Pd thick film couples SO IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING TECHNOLOGY PART A AB A study was performed which examined the solid stale, intermetallic compound layer growth kinetics between 63Sn-37Pb solder and a 76Au-21Pt-3Pd (wt.%) thick film conductor on 96% alumina substrates. A linear, multivariable regression analysis was used to assess the experimental data according to the following empirical relationship: x - x(o) = At-n exp(-Delta H/RT). A time exponent of n = 0.78 +/- 0.08 was observed, suggesting that a combination of bulk diffusion and interface reaction mechanisms were responsible for layer growth, The apparent activation energy, Delta H, was 106 +/- 8 kJ/mol, Parallel aging experiments were performed on diffusion couples fabricated between 63Sn-37Pb solder and bulk alloy stock having the same Au-Pt-Pd composition as the thick film, Similar growth kinetic parameters were computed, Intermetallic compound layer growth was accelerated under thermal cycling and thermal shock conditions due to residual stresses generated by the thermal expansion mismatch between the solder and the ceramic substrate. SN 1070-9886 PD DEC PY 1997 VL 20 IS 4 BP 478 EP 490 DI 10.1109/95.650938 UT WOS:000071415600013 ER PT J AU Warren, WL Fleetwood, DM Schwank, JR Shaneyfelt, MR Draper, BL Winokur, PS Knoll, MG Vanheusden, K Devine, RAB Archer, LB Wallace, RM AF Warren, WL Fleetwood, DM Schwank, JR Shaneyfelt, MR Draper, BL Winokur, PS Knoll, MG Vanheusden, K Devine, RAB Archer, LB Wallace, RM TI Protonic nonvolatile field effect transistor memories in Si/SiO2/Si structures SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB A low-voltage, radiation-tolerant, nonvolatile field effect transistor (NVFET) memory involving proton motion in SiO2 is illustrated in both bulk Si and silicon-on-insulator devices. Wt: discuss a mechanism by which the protons are created in the oxide layer by a. forming gas anneal. At low temperature (T < 250 degrees C), the H+ is largely "imprisoned" in the buried SiO2 layer; i.e., the ions are sandwiched between the two encapsulating Si layers. The Si layers can be: either c-Si or poly-Si, thus the: technology is compatible with standard Si processing. The protons can be reliably and controllably drifted from one interface to another without any noticeable degradation in the signal past 10(6) cycles. Under an unbiased condition, the net proton density is not significantly affected by radiation up to at least 100 krad (SiO2). Last, we compare many of the properties of the NVFET to commercial flash nonvolatile memories. RI Wallace, Robert/A-5283-2008 OI Wallace, Robert/0000-0001-5566-4806 SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 1789 EP 1798 DI 10.1109/23.658944 PN 1 UT WOS:000071062800005 ER PT J AU Chavez, JR Karna, SP Vanheusden, K Brothers, CP Pugh, RD Singaraju, BK Warren, WL Devine, RAB AF Chavez, JR Karna, SP Vanheusden, K Brothers, CP Pugh, RD Singaraju, BK Warren, WL Devine, RAB TI Microscopic structure of the E '(delta) center in amorphous SiO2: A first principles quantum mechanical investigation SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB We report the first ab initio quantum mechanical investigation of the structure of the E'(delta) center in amorphous SiO2 (a-SiO2). Our calculations suggest that the unpaired electron is shared by only two Si atoms, irrespective of the Si cluster size. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 1799 EP 1803 DI 10.1109/23.658945 PN 1 UT WOS:000071062800006 ER PT J AU Fleetwood, DM Johnson, MJ Meisenheimer, TL Winokur, PS Warren, WL Witczak, SC AF Fleetwood, DM Johnson, MJ Meisenheimer, TL Winokur, PS Warren, WL Witczak, SC TI 1/f noise, hydrogen transport, and latent interface-trap buildup in irradiated MOS devices SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, CO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB A large, delayed increase is observed in the postirradiation 1/f noise of Oki pMOS transistors prior to the onset of latent interface-trap buildup. Both effects are evidently due to similar thermally activated processes involving hydrogen. The increased noise through irradiation and anneal is found to be caused not only by the generation of defects at or near the Si/SiO2 interface, but also by an apparent transition from buried to surface channel conduction. This is evidently triggered by the passivation of dopants in the Si by hydrogen transport during irradiation and anneal. Switched bias annealing confirms many of these effects are reversible. Three types of hydrogen transport are identified in MOS oxides: dispersive transport leading to "two-stage" interface-trap buildup, retarded transport leading to latent interface-trap buildup, and blockaded transport leading to proton confinement in SiO2. The nature of the transport appears to correlate with O vacancy density and the temperature at which hydrogen is incorporated into the SiO2. Implications are discussed for enhanced bipolar low dose rate response, the sensitivity of pMOS dosimeters, and protonic nonvolatile memory elements. SN 0018-9499 EI 1558-1578 PD DEC PY 1997 VL 44 IS 6 BP 1810 EP 1817 DI 10.1109/23.658947 PN 1 UT WOS:000071062800008 ER PT J AU Fleetwood, DM AF Fleetwood, DM TI Revised model of thermally stimulated current in MOS capacitors SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB It is shown analytically and experimentally that, when significant densities of positive and/or negative charge are trapped in the bulk of the oxide, standard thermally stimulated current (TSC) measurements at negative gate bias may not provide accurate estimates of MOS oxide-trap charge densities. Combining TSC measurements at negative bias with capacitance-voltage (C-V) measurements allows useful, self-consistent estimates of trapped electron densities in the oxide to be obtained. However, unless one can determine whether most of the trapped electrons lie in the bulk of the oxide or in border traps, unambiguous estimates of trapped positive charge densities cannot be obtained with negative or positive bias TSC, with or without C-V measurements. Implications are discussed for charge trapping in radiation-hardened thermal oxides, SIMOX buried oxides, and bipolar base oxides. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 1826 EP 1833 DI 10.1109/23.658949 PN 1 UT WOS:000071062800010 ER PT J AU Paxton, AH Carson, RF Schone, H Taylor, EW Choquette, KD Hou, HQ Lear, KL Warren, ME AF Paxton, AH Carson, RF Schone, H Taylor, EW Choquette, KD Hou, HQ Lear, KL Warren, ME TI Damage from proton irradiation of vertical-cavity surface-emitting lasers SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB Damage resulting from irradiating oxide-confined vertical-cavity surface-emitting lasers became significant (threshold shift approximate to 20%, peak power degradation approximate to 20%) at fluence levels approaching 1 x 10(13) protons/cm(2). The threshold current shifted to higher values, and the peak light output power decreased. Forward-current annealing led to partial recovery of the performance of two of the three lasers for which annealing was attempted. Recent results[1-3] on proton-implanted devices are summarized in a table. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 1893 EP 1897 DI 10.1109/23.658958 PN 1 UT WOS:000071062800019 ER PT J AU Wu, A Schrimpf, RD Barnaby, HJ Fleetwood, DM Pease, RL Kosier, SL AF Wu, A Schrimpf, RD Barnaby, HJ Fleetwood, DM Pease, RL Kosier, SL TI Radiation-induced gain degradation in lateral PNP BJTs with lightly and heavily doped emitters SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB Radiation-induced gain degradation is compared in two types of lateral PNP bipolar devices that are identical except for the emitter doping. The devices with heavily-doped emitters (1x10(20) cm(-3)) degrade less than the devices with lightly-doped emitters (1x10(18) cm(-3)). Both device types are sensitive to interface-trap formation in the oxide above the emitter-base junction and the neutral base region. In addition, the devices with lightly-doped emitters experience spreading of the depletion region into the emitter, increasing their sensitivity to total-dose irradiation. The gain degradation in both device types is due to a combination of increased base current and decreased collector current. The radiation-induced decrease in collector current is more significant for devices from this technology than for other devices studied previously. Increased gain degradation is observed in heavily-doped devices irradiated at low dose rates, but the enhanced degradation appears to be due to time-dependent effects rather than true dose-rate effects. The lightly-doped devices do not exhibit a clear dose-rate trend and the gain of these devices improves during post-irradiation annealing. RI Schrimpf, Ronald/L-5549-2013 OI Schrimpf, Ronald/0000-0001-7419-2701 SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 1914 EP 1921 DI 10.1109/23.658962 PN 1 UT WOS:000071062800022 ER PT J AU Pease, RL Cohn, LM Fleetwood, DM Gehlhausen, MA Turflinger, TL Brown, DB Johnston, AH AF Pease, RL Cohn, LM Fleetwood, DM Gehlhausen, MA Turflinger, TL Brown, DB Johnston, AH TI A proposed hardness assurance test methodology for bipolar linear circuits and devices in a space ionizing radiation environment SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB A hardness assurance test approach has been developed for bipolar linear circuits and devices in space. It consists of an initial test for dose rate sensitivity and a characterization test method to develop the conditions for a lot acceptance test at high dose rate. For parts with adequate design margin and/or well behaved parts a generic elevated temperature irradiation test is proposed. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 1981 EP 1988 DI 10.1109/23.658976 PN 1 UT WOS:000071062800030 ER PT J AU Witczak, SC Schrimpf, RD Fleetwood, DM Galloway, KF Lacoe, RC Mayer, DC Puhl, JM Pease, RL Suehle, JS AF Witczak, SC Schrimpf, RD Fleetwood, DM Galloway, KF Lacoe, RC Mayer, DC Puhl, JM Pease, RL Suehle, JS TI Hardness assurance testing of bipolar junction transistors at elevated irradiation temperatures SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB The effect of dose rate on radiation-induced current gain degradation was quantified for radiation-hardened poly-Si emitter npn bipolar transistors over the range of 0.005 to 294 rad(Si)/s. Degradation increases sharply with decreasing dose rate and saturates near 0.005 rad(Si)/s. The amount of degradation enhancement at low dose rates decreases monotonically with total dose. In addition, the effect of ambient temperature on radiation-induced gain degradation at 294 rad(Si)/s was investigated over the range of 25 to 240 degrees C. Degradation is enhanced with increasing temperature while simultaneously being moderated by in situ annealing, such that, for a given total dose, an optimum irradiation temperature for maximum degradation results. The optimum irradiation temperature decreases logarithmically with total dose and, for a given dose, is smaller than optimum temperatures reported previously for pnp devices. High dose rate irradiation at elevated temperatures is less effective at simulating low dose rate degradation for the npn transistor than for the pnp transistors. However, additional degradation of the npn device at elevated temperatures is easily obtained using overtest. Differences in the radiation responses of the device types are attributed to the relative effects of oxide trapped charge on gain degradation. High dose rate irradiation near 125 degrees C is found to be suitable for the hardness assurance testing of these devices provided a design margin of at least two is employed. RI Schrimpf, Ronald/L-5549-2013 OI Schrimpf, Ronald/0000-0001-7419-2701 SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 1989 EP 2000 DI 10.1109/23.658978 PN 1 UT WOS:000071062800031 ER PT J AU Shaneyfelt, MR Winokur, PS Fleetwood, DM Hash, GL Schwank, JR Sexton, FW Pease, RL AF Shaneyfelt, MR Winokur, PS Fleetwood, DM Hash, GL Schwank, JR Sexton, FW Pease, RL TI Impact of aging on radiation hardness SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB Identifying aging effects that impact radiation hardness of microelectronics is becoming increasingly important as military weapon systems are kept in the stockpile for times beyond their originally intended use period. In this work, burn-in effects are used to demonstrate the potential impact of thermally-activated aging effects on integrated circuit radiation hardness. Static random access memories (SRAMs) from three different commercial technologies were irradiated with different pre-irradiation stress conditions. A reduction in the total dose functional failure level was observed for SRAMs from two of the technologies subjected to preirradiation elevated temperature stresses. This is the first time the burn-in effect has been shown to degrade the radiation-induced functional failure level of an IC. SRAM data also show no indication that the burn-in effect will saturate, at least for the conditions examined in this work. These data indicate that long-term aging can result in more device degradation than is accounted for by present hardness assurance test guidelines, potentially causing device and/or system failure during the aging period. While only a few technologies have been examined to date, we suspect other technologies may exhibit similar long-term aging effects. A technique for including aging effects within a hardness assurance test program is outlined. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 2040 EP 2047 DI 10.1109/23.658987 PN 1 UT WOS:000071062800038 ER PT J AU Simons, M Pease, RL Fleetwood, DM Schwank, JR Krzesniak, MF AF Simons, M Pease, RL Fleetwood, DM Schwank, JR Krzesniak, MF TI Dose enhancement in a room cobalt-60 source SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB A room Co-60 source was characterized using thermoluminescent dosimeters (TLDs) and pMOS RADFETs. Measurements were made over a range of dose rates between 0.8 and 100 mrad(Si)/s. Dose enhancement (DE) was measured using RADFETs with and without gold-flashed kovar lids. DE factors ranged from 1.05 to 2.35. A method was developed to predict dose enhancement as a function of position and test configuration. This method involves separation of direct and scattered gamma dose rate contributions. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 2052 EP 2057 DI 10.1109/23.658990 PN 1 UT WOS:000071062800040 ER PT J AU Turinetti, JR Critchfield, KL Chavez, JR Kemp, WT Bellem, RD Beutler, DE AF Turinetti, JR Critchfield, KL Chavez, JR Kemp, WT Bellem, RD Beutler, DE TI Determination of low energy (< 160 keV) X-ray spectra and verification of transport calculations through silicon SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB X-ray spectroscopy discrepancies at measured energies below 50 keV are shown through ITS detector response calculations to be caused by germanium K edge escape peak losses. Accounting for this detector response, CEPXS/ONELD transport calculations through silicon agree well with measurements. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 2065 EP 2070 DI 10.1109/23.659017 PN 1 UT WOS:000071062800042 ER PT J AU Griffin, PJ Williams, JG AF Griffin, PJ Williams, JG TI Least squares analysis of fission neutron standard fields SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB A least squares analysis of fission neutron standard fields has been performed using the latest measurements and dosimetry cross sections for activation foils, fission chambers, and helium accumulation monitors. Discrepant nuclear data are identified and adjusted spectra for the U-235 thermal fission field is presented. Comments are made on the consistency of the nuclear data for the Cf-252 spontaneous fission neutron environment. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 2071 EP 2078 DI 10.1109/23.659018 PN 1 UT WOS:000071062800043 ER PT J AU Griffin, PJ Luera, TF Sexton, FW Cooper, PJ Karr, SG Hash, GL Fuller, E AF Griffin, PJ Luera, TF Sexton, FW Cooper, PJ Karr, SG Hash, GL Fuller, E TI Role of thermal and fission neutrons in reactor neutron-induced upsets in commercial SRAMs SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB Reactor neutron environments can be used to test/screen the sensitivity of unhardened commercial SRAMs to low-LET neutron-induced upset. Tests indicate both thermal/epithermal (< 1 keV) and fast neutrons can cause upsets in unhardened parts, Measured upset rates in reactor environments can be used to estimate the upset rates from thermal and fast portions of arbitrary neutron spectra. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 2079 EP 2086 DI 10.1109/23.659019 PN 1 UT WOS:000071062800044 ER PT J AU Vanheusden, K Devine, RAB Schwank, JR Fleetwood, DM Polcawich, RG Warren, WL Karna, SP Pugh, RD AF Vanheusden, K Devine, RAB Schwank, JR Fleetwood, DM Polcawich, RG Warren, WL Karna, SP Pugh, RD TI Irradiation response of mobile protons in buried SiO2 films SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB We have performed current-voltage, capacitance-voltage and electron-paramagnetic-resonance (EPR) characterization of silicon-on-insulator (SOI) samples, subjected to a wide variety of irradiation and anneal treatments. By comparing transport properties and interfacial reaction mechanisms, we provide evidence for an intrinsic difference in the response of mobile protons in these oxides, depending on whether they are generated by irradiation or by H-2 annealing. A radiation effects study of SOI buried oxides containing annealing induced mobile protons is presented to gain insight into the mechanisms behind these fundamental differences. Electrical characterization shows that, for these devices, the initial interface trap and mobile proton densities are largely unaffected by the irradiation. However, if the irradiation is carried out in the presence of positive bias applied to the top Si, the protons become trapped in shallow levels. These proton traps are activated by the irradiation and are located near the oxide/substrate interface. These results may lead to improved radiation hardness of buried oxides for nonvolatile memory and other applications. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 2087 EP 2094 DI 10.1109/23.659021 PN 1 UT WOS:000071062800045 ER PT J AU Dodd, PE Shaneyfelt, MR Sexton, FW AF Dodd, PE Shaneyfelt, MR Sexton, FW TI Charge collection and SEU from angled ion strikes SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB Charge collection and SEU from angled ion strikes are studied using three-dimensional simulation. The physics of charge collection in unloaded diodes and transistors is explored, as is the angular dependence of upset threshold in CMOS SRAMs. The simulation results are compared to analytical models for charge collection. Modeling fundamental transport in SRAMs, the true effective LET relationship is computed and used to analyze experimental heavy-ion data. Impacts on SEU test methodology are discussed. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 2256 EP 2265 DI 10.1109/23.659044 PN 1 UT WOS:000071062800067 ER PT J AU Sexton, FW Fleetwood, DM Shaneyfelt, MR Dodd, PE Hash, GL AF Sexton, FW Fleetwood, DM Shaneyfelt, MR Dodd, PE Hash, GL TI Single event gate rupture in thin gate oxides SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB The dependence of single event gate rupture (SEGR) critical field on oxide thickness is examined for gate oxides from 6 to 18 nm. Capacitor data are compared to SEGR data from full integrated circuits. A 1/E-CR dependence is found for critical field to rupture as a function of ion linear energy transfer (LET), consistent with earlier work for power MOSFETS with oxide thicknesses from 30 to 150 nm. More importantly, critical field to rupture increases with decreasing oxide thickness, consistent with increasing oxide breakdown field prior to heavy-ion exposure. This suggests that SEGR need not be a limiting factor as future technologies scale into the deep submicron region. However, there is a great deal of uncertainty in how voltage may scale with decreasing oxide thickness, and SEGR may continue to be a concern for devices that operate at electric fields significantly higher than 5 MV/cm. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 2345 EP 2352 DI 10.1109/23.659060 PN 1 UT WOS:000071062800079 ER PT J AU Normand, E Wert, JL Oberg, DL Majewski, PP Voss, P Wender, SA AF Normand, E Wert, JL Oberg, DL Majewski, PP Voss, P Wender, SA TI Neutron-induced single event burnout in high voltage electronics SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 34th Annual IEEE International Nuclear and Space Radiation Effects Conference (NSREC 97) CY JUL 21-25, 1997 CL SNOWMASS VILLAGE, COLORADO SP IEEE NPSS, Def Special Weapons Agcy, Sandia Nat Labs, Philips Lab, JPL, NASA, Goddard AB Energetic neutrons with an atmospheric neutron spectrum, which were demonstrated to induce single event burnout in power MOSFETs, have been Shown to induce burnout in high voltage (>3000V) electronics when operated at voltages as low as 50% of rated voltage. The laboratory failure rates correlate well with field failure rates measured in Europe. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 2358 EP 2366 DI 10.1109/23.659062 PN 1 UT WOS:000071062800081 ER PT J AU Reutter, BW Klein, GJ Huesman, RH AF Reutter, BW Klein, GJ Huesman, RH TI Automated 3-D segmentation of respiratory-gated PET transmission images SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE CT 1996 Medical Imaging Conference (MIC) / Nuclear Science Symposium (NSS) CY NOV 05-09, 1996 CL ANAHEIM, CALIFORNIA SP Inst Elect & Electr Engineers AB As a preliminary step toward performing respiration compensated attenuation correction of respiratory-gated cardiac PET data, we acquired and automatically segmented respiratory-gated transmission data for a dog breathing on its own under gas anesthesia. Transmission data were acquired for 20 min on a CTI/Siemens ECAT EXACT HR (47-slice) scanner Two respiratory gates were obtained using data from a pneumatic bellows placed around the dog's chest. For each respiratory gate, torso and lung surfaces were segmented automatically using a differential 3-D image edge detection algorithm. Three-dimensional visualizations showed that during inspiration the heart translated about 4 mm transversely and the diaphragm translated about 9 mm inferiorly. The observed respiratory motion of the canine heart and diaphragm suggests that respiration compensated attenuation correction may be necessary for accurate quantitation. of high-resolution respiratory-gated human cardiac PET data. Our automated image segmentation results suggest that respiration compensated segmented attenuation correction may be possible using respiratory-gated transmission data obtained with as little as 3 min of acquisition time per gate. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 2473 EP 2476 DI 10.1109/23.656454 PN 2 UT WOS:000071063000014 ER PT J AU Funsten, HO Suszcynsky, DM Ritzau, SM Korde, R AF Funsten, HO Suszcynsky, DM Ritzau, SM Korde, R TI Response of 100% internal quantum efficiency silicon photodiodes to 200 eV-40 keV electrons SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE AB Electron irradiation of 100% internal quantum efficiency silicon photodiodes having a thin (60 Angstrom) SiO2 dead layer results in measured responsivities ranging from 0.056 A/W at an incident electron energy E-0 = 0.2 keV to 0.24 A/W at E-0 = 40 keV, By comparing the data to a Monte Carlo simulation of electron interactions with the photodiode over an energy range of 1-40 keV, we derive an average electron-hole pair creation energy of 3.71 eV, in close agreement with other studies. Analysis of electron energy lost to processes that do not contribute to electron-hole pair creation shows that the energy lost in the SiO2 dead layer is dominant for E-0 < 1.5 keV, whereas the energy removed by backscattered electrons is dominant for E-0 > 1.5 keV, At E-0 = 300 eV, the Monte Carlo simulation results show that the electron projected range is significantly less than the dead layer thickness even though the measured response is 0.082 A/W, indicating that electron-hole pairs generated in the oxide dead layer are collected by the junction. RI Funsten, Herbert/A-5702-2015 OI Funsten, Herbert/0000-0002-6817-1039 SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 2561 EP 2565 DI 10.1109/23.650863 PN 3 UT WOS:000071063200004 ER PT J AU Schieber, M Hermon, H James, RB Lund, J Antolak, A Morse, D Kolesnikov, NN Ivanov, YN Goorsky, MS Van Scyoc, JM Yoon, H Toney, J Schlesinger, TE Doty, FP Cozzatti, JPD AF Schieber, M Hermon, H James, RB Lund, J Antolak, A Morse, D Kolesnikov, NN Ivanov, YN Goorsky, MS Van Scyoc, JM Yoon, H Toney, J Schlesinger, TE Doty, FP Cozzatti, JPD TI Mapping high-pressure Bridgman Cd0.8Zn0.2Te SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE AB Single crystals of Cd0.8Zn0.2Te grown at the institute of Solid State Physics, Chernogolovka, Russia, by the high-pressure vertical Bridgman method (HPVB) were mapped using X-ray fluorescence (XRF), X-ray diffraction (XRD), photoluminescence (PL), and leakage current measurements, Most of the Russian samples which we refer to as p-type CZT were more uniform in Zn composition than U.S. commercially produced material. The Russian material had a poorer crystallinity and, in the best case, could only count nuclear radiation, Differences in the material properties between Russian (p-type) and U.S. (n-type) material will be described. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 2566 EP 2570 DI 10.1109/23.650864 PN 3 UT WOS:000071063200005 ER PT J AU Schieber, M Zuck, A Braiman, M Nissenbaum, J Turchetta, R Dulinski, W Husson, D Riester, JL AF Schieber, M Zuck, A Braiman, M Nissenbaum, J Turchetta, R Dulinski, W Husson, D Riester, JL TI Novel mercuric iodide polycrystalline nuclear particle counters SO IEEE TRANSACTIONS ON NUCLEAR SCIENCE AB Polycrystalline mercuric iodide nuclear radiation detectors have been produced in a novel technology, Unlike the normal single-crystal technology, there is no intrinsic limit to the surface on which these detectors can be produced, Detectors with areas up to about 1.5 cm(2), thicknesses from 30 to 600 mu m, and with single electrodes as well as microstrip and pixel contacts have been fabricated and successfully tested with photons in the range of 40-660 keV, beta particle's emitted from a Sr-Y source, and high energy (100 GeV) muons, Results on both charge collection and counting efficiency are reported as well as some very preliminary imaging results, The experimental results on charge collection have been compared with simulation, and a combined mu tau product 10(-7) cm(2)/V for electrons has been estimated. SN 0018-9499 PD DEC PY 1997 VL 44 IS 6 BP 2571 EP 2575 DI 10.1109/23.650865 PN 3 UT WOS:000071063200006 ER PT J AU Brown, IG Oks, EM AF Brown, IG Oks, EM TI Vacuum arc ion sources - A brief historical review SO IEEE TRANSACTIONS ON PLASMA SCIENCE AB The production of energetic metal ion beams by vacuum are ion sources is a subfield of ion beam science and technology that has experienced rapid growth and a great deal of research activity in the last decade or so, Interest in this kind of ion source derives from the high current of metal ions that can be produced-these are the defining and keg properties of the source, and they open up areas of application that have not previously been readily accessible, Here we present a concise history of this field of activity. The background, history, and recent research and development are discussed. RI Oks, Efim/A-9409-2014 OI Oks, Efim/0000-0002-9323-0686 SN 0093-3813 PD DEC PY 1997 VL 25 IS 6 BP 1222 EP 1228 DI 10.1109/27.650897 UT WOS:000071615900005 ER PT J AU Carreras, BA AF Carreras, BA TI Progress in anomalous transport research in toroidal magnetic confinement devices SO IEEE TRANSACTIONS ON PLASMA SCIENCE AB Transport is the outstanding physics issue in the quest for fusion by magnetic confinement, In spite of the intrinsic difficulty, a great deal of progress has been made in the past 25 years, Experiments have gone from being dominated by high anomalous losses, of the order of Bohm diffusion losses, to operation with no anomalous transport, This success is due to a combination of improved experimental infrastructure and the high degree of knowledge on how to control plasma discharges, Both have made it possible to access enhanced confinement regimes and to unravel new effects in confinement physics, Although there is not yet a complete understanding of the dynamical methanisms underlying the anomalous transport process, there is some understanding of important components such as the ion transport loss mechanism at the plasma Core and of the main mechanism for turbulence suppression in the enhanced confinement regimes. SN 0093-3813 EI 1939-9375 PD DEC PY 1997 VL 25 IS 6 BP 1281 EP 1321 DI 10.1109/27.650902 UT WOS:000071615900009 ER PT J AU Mehlhorn, TA AF Mehlhorn, TA TI Intense ion beams for inertial confinement fusion SO IEEE TRANSACTIONS ON PLASMA SCIENCE AB Intense beams of light and heavy ions are being studied as inertial confinement fusion (ICF) drivers for high yield and energy, Heavy and light ions have common interests in beam transport, targets, and alternative accelerators. Self-pinched transport is being jointly studied, This article reviews the development of intense ion beams for ICF, Light-ion drivers are highlighted because they are compact, modular, efficient and low cost, Issues facing light ions are: 1) decreasing beam divergence; 2) increasing beam brightness; and 3) demonstrating self-pinched transport, Applied-B ion diodes are favored because of efficiency, beam brightness, perceived scalability, achievable focal intensity, and multistage capability, A light-ion concept addressing these issues uses: 1) an injector divergence of less than or equal to 24 mrad at 9 MeV; 2) two-stage acceleration to reduce divergence to less than or equal to 12 mrad at 35 MeV; and 3) self-pinched transport accepting divergences up to 12 mrad. Substantial progress in ion-driven target physics and repetitive ion diode technology is also presented, Z-pinch drivers are being pursued as the shortest pulsed power path to target physics experiments and high-yield fusion, However, light ions remain the pulsed power ICF driver of choice for high-yield fusion energy applications that require driver standoff and repetitive operation. SN 0093-3813 PD DEC PY 1997 VL 25 IS 6 BP 1336 EP 1356 DI 10.1109/27.650904 UT WOS:000071615900011 ER PT J AU Lindemuth, IR Ekdahl, CA Fowler, CM Reinovsky, RE Younger, SM Chernyshev, VK Mokhov, VN Pavlovskii, AI AF Lindemuth, IR Ekdahl, CA Fowler, CM Reinovsky, RE Younger, SM Chernyshev, VK Mokhov, VN Pavlovskii, AI TI US/Russian collaboration in high-energy-density physics using high-explosive pulsed power: Ultrahigh current experiments, ultrahigh magnetic field applications, and progress toward controlled thermonuclear fusion SO IEEE TRANSACTIONS ON PLASMA SCIENCE AB A collaboration has been established between the All-Russian Scientific Research Institute of Experimental Physics (VNIIEF) and the Los Alamos National Laboratory (LANL), the two institutes which designed the first nuclear weapons for their respective countries, In 1992, when emerging governmental policy in the United States and Russia began to encourage "lab-to-lab" interactions, the two institutes quickly recognized a common interest in the technology and applications of magnetic flux compression, the technique for converting the chemical energy released by high-explosives into intense electrical pulses and intensely concentrated magnetic energy, In a period of just over three years, the two institutes have performed more than fifteen joint experiments covering research areas ranging from basic pulsed power technology to solid-state physics to controlled thermonuclear fusion, Using magnetic flux compression generators, electrical currents ranging from 20 to 100 MA were delivered to loads of interest in high-energy-density physics, A 20-MA pulse was delivered to an imploding liner load with a 10-90% rise time of 0.7 mu s. A new, high-energy concept for soft X-ray generation was tested at 65 MA. More than 20 MJ of implosion kinetic energy was delivered to a condensed matter imploding liner by a 100-MA current pulse. Magnetic flux compressors were used to determine the upper critical field of a high-temperature superconductor and to create pressure high enough that the transition from single particle behavior to quasimolecular behavior was observed in solid argon, A major step was taken toward the achievement of controlled thermonuclear fusion by a relatively unexplored approach known in Russia as MAGO (MAGnitnoye Obzhatiye, or "magnetic compression") and in the United States as MTF (Magnetized Target Fusion), Many of the characteristics of a target plasma that produced 10(13) fusion neutrons have been evaluated, Computational models of the target plasma suggest that the plasma is suitable for subsequent compression to fusion conditions by an imploding pusher. SN 0093-3813 PD DEC PY 1997 VL 25 IS 6 BP 1357 EP 1372 DI 10.1109/27.650905 UT WOS:000071615900012 ER PT J AU Mehr, R Perelson, AS FridkisHareli, M Globerson, A AF Mehr, R Perelson, AS FridkisHareli, M Globerson, A TI Regulatory feedback pathways in the thymus SO IMMUNOLOGY TODAY AB The idea that thymocytopoiesis may be subject to feedback regulation by mature lymphocytes is proposed on the basis of recent data from in vitro experimental models. Analysis of the data using mathematical models, presented here by Ramit Mehr and colleagues, suggests possible feedback control mechanisms in T-cell development. SN 0167-5699 PD DEC PY 1997 VL 18 IS 12 BP 581 EP 585 DI 10.1016/S0167-5699(97)01150-X UT WOS:A1997YL03800008 PM 9425736 ER PT J AU Siriwardane, RV Woodruff, S AF Siriwardane, RV Woodruff, S TI In situ Fourier transform infrared characterization of sulfur species resulting from the reaction of water vapor and oxygen with zinc sulfide SO INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB Steam is utilized as a diluent in the regeneration of zinc-based hot gas desulfurization sorbents used in fuel gas cleanup. Therefore, the effect of water vapor on the interaction of zinc sulfide (ZnS) with oxygen at 823, 873, and 923 K was studied using Fourier transform infrared (FTIR) spectroscopy. When ZnS at 823 K was exposed to oxygen, sulfate (SO42-) was the most prominent species observed at oxygen pressures greater than 5 x 10(-2) Torr while sulfite (SO32-) was the major species observed during the water vapor exposures. When ZnS at 823 K was exposed to an equimolar mixture of water vapor and oxygen, sulfite and sulfate were the most prominent products but the intensity of the sulfite peak was more than that of the sulfate. The sulfur species formed during the water vapor and oxygen exposures at both 873 and 923 K were similar to those at 823 K, but the relative intensities of the peaks corresponding to these sulfur species were different. At all three temperatures, the presence of water vapor enhanced the formation of sulfite, which can be decomposed more readily than sulfate. Thus, it is hypothesized that it would be desirable to have water vapor present during the regeneration of ZnS to form ZnO. SN 0888-5885 PD DEC PY 1997 VL 36 IS 12 BP 5277 EP 5281 DI 10.1021/ie970343e UT WOS:A1997YJ88100029 ER PT J AU Gu, D Nguyen, L Philip, CV Huckman, ME Anthony, RG Miller, JE Trudell, DE AF Gu, D Nguyen, L Philip, CV Huckman, ME Anthony, RG Miller, JE Trudell, DE TI Cs+ ion exchange kinetics in complex electrolyte solutions using hydrous crystalline silicotitanates SO INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB TAM-5 is a hydrous crystalline sodium silicotitanate inorganic ion exchanger with a high selectivity for Cs+. The kinetics of Cs+-Na+ ion exchange using TAM-5 in multicomponent electrolyte solutions were determined using batch experiments. For the powder, which is composed of crystals, a single-phase, homogeneous model fit the data best. For the granules, which were prepared from the powder, a two-phase, heterogeneous model resulted in an excellent fit of the data. Macropore and crystal diffusivities were determined by fitting the model to experimental data collected on the powder and the granules. Intracrystalline diffusivities were concentration dependent and were on the order of 10(-19) m(2)/s. Macropore diffusivities were on the order of 10(-10) m(2)/s. Resistance to diffusion in the macropores was not significant for granules with diameters less than 15 mu m. A two-phase, homogeneous model, where liquid within the pores is in equilibrium with the solid, was also evaluated for the granules. Surprisingly, for the granules, an excellent fit of the data was obtained; however, the effective macropore diffusivity was 1.1 x 10(-11) m(2)/s, an order of magnitude smaller than the macropore diffusivity found using the two-phase, heterogeneous model. RI Miller, James/C-1128-2011 OI Miller, James/0000-0001-6811-6948 SN 0888-5885 PD DEC PY 1997 VL 36 IS 12 BP 5377 EP 5383 DI 10.1021/ie960338v UT WOS:A1997YJ88100042 ER PT J AU Cotton, FA Haefner, SC Sattelberger, AP AF Cotton, FA Haefner, SC Sattelberger, AP TI Metal-metal multiply-bonded complexes of technetium .6. A mu eta(1)eta(2)-CH3CN complex prepared via reductive cleavage of the electron-rich Tc Tc triple bond in decakis-acetonitrile ditechnetium tetrafluoroborate SO INORGANICA CHIMICA ACTA AB Chemical reduction of the dinuclear cation [Tc-2(CH3CN)(10)](4+) in acetonitrile results in scission of the metal-metal triple bond to produce two Tc(CH3CN)(5) fragments linked together via a mu,eta(1),eta-acetonitrile ligand. The Tc(I)-Tc(II) mixed-valent compound [Tc-2(mu,eta(1),eta(2)-CH3CN) (CH3CN)(CH3CN)(10)][BF4](3) (1) was isolated as a red-brown solid in 70% yield using cobaltocene as a reductant. Lower yields (53%) were obtained when the reduction was carried out with zinc. The crystal structure of 1.0.83 CH3CN reveals that the Tc atoms are separated by a distance of 4.04(2) Angstrom consistent with the complete lack of any metal-metal bonding, Compound 1 has been fully characterized by a variety of spectroscopic techniques including H-1 NMR, UV-Vis and IR spectroscopies as well as cyclic voltammetry. Crystal data at -60 degrees C for 1.0.83CH(3)CN: triclinic space group P (No. 2), a = 12.658(4), b = 16.513(4), c = 19.495(6) Angstrom, alpha = 90.21(2), beta = 99.33(3), gamma = 90.18(3)degrees, V = 4020(2) Angstrom(3), Z = 4. (C) 1997 Elsevier Science S.A. SN 0020-1693 PD DEC 1 PY 1997 VL 266 IS 1 BP 55 EP 63 DI 10.1016/S0020-1693(97)05533-3 UT WOS:A1997YJ32700009 ER PT J AU Liu, CT Stringer, J Mundy, JN Horton, LL Angelini, P AF Liu, CT Stringer, J Mundy, JN Horton, LL Angelini, P TI Ordered intermetallic alloys: an assessment SO INTERMETALLICS AB The paper summarizes our present understanding, as established at a recent workshop, of two classes of intermetallic alloys: nickel and iron aluminides, which are currently used by industries; and advanced intermetallic alloys including silicides and Laves-phase alloys, which have a great potential to be developed as new high-temperature structural materials for future industrial use. The workshop emphasized close interaction and co-operation between basic research, applied research, and industrial development, and stressed discussion of critical scientific and technological issues. The current status of these intermetallic alloys was assessed, and the directions for future research and development, as well as emerging opportunities, were identified. The information presented in the text is summarized from the presentations at the workshop, and so no references are given to the published literature. However, an extensive bibliography is appended, in which further details may be found. (C) 1997 Elsevier Science Limited. OI Liu, Chain Tsuan/0000-0001-7888-9725 SN 0966-9795 PD DEC PY 1997 VL 5 IS 8 BP 579 EP 596 DI 10.1016/S0966-9795(97)00045-9 UT WOS:A1997YL57100001 ER PT J AU Pike, LM Chang, YA Liu, CT AF Pike, LM Chang, YA Liu, CT TI Solid-solution hardening and softening by Fe additions to NiAl SO INTERMETALLICS AB Solid-solution hardening in the case of a ternary alloy addition to a B2 compound with the triple defect structure has been investigated. The fact that the ternary element may occupy either of two sublattices or may affect the concentration of other types of point defects present in the material makes this a very interesting problem to consider. Ni-rich (40 at% Al), stoichiometric (50 at% Al), and Al-rich (52 at% Al) alloys were doped with up to 12 at% Fe. Lattice parameter, bulk density and hardness measurements were performed on samples quenched from 1000 degrees C. It was found that solid-solution softening actually occurs in the Ni-rich alloys, while hardening was observed in the stoichiometric and Al-rich alloys. The vacancy concentration was determined from the experimental data, and the site occupancies of the Fe atoms were estimated from a thermodynamic model. Through careful consideration of all point defect concentrations the solid-solution hardening and softening behaviors could be effectively rationalized. (C) 1997 Elsevier Science Limited. OI Liu, Chain Tsuan/0000-0001-7888-9725 SN 0966-9795 PD DEC PY 1997 VL 5 IS 8 BP 601 EP 608 DI 10.1016/S0966-9795(97)00040-X UT WOS:A1997YL57100003 ER PT J AU Cleghorn, SJC Ren, X Springer, TE Wilson, MS Zawodzinski, C Zawodzinski, TA Gottesfeld, S AF Cleghorn, SJC Ren, X Springer, TE Wilson, MS Zawodzinski, C Zawodzinski, TA Gottesfeld, S TI PEM fuel cells for transportation and stationary power generation applications SO INTERNATIONAL JOURNAL OF HYDROGEN ENERGY AB We describe recent activities at Los Alamos National Laboratory devoted to polymer electrolyte fuel cells in the contexts of stationary power generation and transportation applications. A low cost/high performance hydrogen or reformate/air stack technology is being developed based on ultra-low platinum loadings and non-machined, inexpensive elements for flow-fields and bipolar plates. On-board methanol reforming is compared to the option of direct methanol fuel cells in light of recent significant power density increases demonstrated in the latter. (C) 1997 International Association for Hydrogen Energy. RI ren, xiaoming/F-3953-2011 SN 0360-3199 PD DEC PY 1997 VL 22 IS 12 BP 1137 EP 1144 DI 10.1016/S0360-3199(97)00016-5 UT WOS:000071111700005 ER PT J AU Golovlev, VV Allman, SL Garrett, WR Taranenko, NI Chen, CH AF Golovlev, VV Allman, SL Garrett, WR Taranenko, NI Chen, CH TI Laser-induced acoustic desorption SO INTERNATIONAL JOURNAL OF MASS SPECTROMETRY AB The basic principles and experimental results of laser-induced acoustic desorption (LIAD) are reported in this work. LIAD was successfully used to desorb biomolecules in a mass spectrometer. LIAD holds some promise to eliminate many key factors which contribute to poor mass resolution in MALDI. Thus, it has potential for improvement in resolution of biomolecular mass analysis. (C) 1997 Elsevier Science B.V. RI Allman, Steve/A-9121-2011 OI Allman, Steve/0000-0001-6538-7048 SN 1387-3806 PD DEC PY 1997 VL 169 BP 69 EP 78 DI 10.1016/S0168-1176(97)00209-7 UT WOS:000072160400008 ER PT J AU Gronbech-Jensen, N AF Gronbech-Jensen, N TI Lekner summation of long range interactions in periodic systems SO INTERNATIONAL JOURNAL OF MODERN PHYSICS C AB We present a complete set of practical expressions for fast and accurate evaluation of Coulomb interactions, forces and energies, in any rectangular periodic medium. This analysis also includes explicit expressions for energy constants and self-energies of charged particles in periodic lattices. Energy constants and self-energies are further evaluated for logarithmic interactions in two-dimensional rectangular systems with periodic boundary conditions. The expressions are optimized for computational speed and tested by direct numerical implementation. SN 0129-1831 PD DEC PY 1997 VL 8 IS 6 BP 1287 EP 1297 DI 10.1142/S0129183197001144 UT WOS:000072313900010 ER PT J AU Serot, BD Walecka, JD AF Serot, BD Walecka, JD TI Recent progress in quantum hadrodynamics SO INTERNATIONAL JOURNAL OF MODERN PHYSICS E-NUCLEAR PHYSICS AB Quantum hadrodynamics (QHD) is a framework for describing the nuclear many-body problem as a relativistic system of baryons and mesons. Motivation is given for the utility of such an approach and for the importance of basing it on a local, Lorentz-invariant lagrangian density. Calculations of nuclear matter and finite nuclei in both renormalizable and nonrenormalizable, effective QHD models are discussed. Connections are made between the effective and renormalizable models, as well as between relativistic mean-field theory and more sophisticated treatments. Recent work in QHD involving nuclear structure, electroweak interactions in nuclei, relativistic transport theory, nuclear matter under extreme conditions, and the evaluation of loop diagrams is reviewed. SN 0218-3013 EI 1793-6608 PD DEC PY 1997 VL 6 IS 4 BP 515 EP 631 DI 10.1142/S0218301397000299 UT WOS:000071795300001 ER PT J AU Livingston, GK Jensen, RH Silberstein, EB Hinnefeld, JD Pratt, G Bigbee, WL Langlois, RG Grant, SG Shukla, R AF Livingston, GK Jensen, RH Silberstein, EB Hinnefeld, JD Pratt, G Bigbee, WL Langlois, RG Grant, SG Shukla, R TI Radiobiological evaluation of immigrants from the vicinity of Chernobyl SO INTERNATIONAL JOURNAL OF RADIATION BIOLOGY AB Eighty individuals (55 adults and 25 children) who were residents of four cities (Kiev, Mozyr, Gomel and Bobrujsk) located 100-200 km from Chernobyl at the time of the accident in 1986 were tested after immigrating to the US from 1989-1991. A whole-body counter was employed to quantitate radiocesium content. In addition, two biological measures of radiation effects, namely, chromosomal integrity using the micronucleus assay and somatic mutation analysis of erythrocytes at the glycophorin A (GPA) locus, were applied to this group. Radiocesium activity in the body rang ed from 0 to 56.8 Bq/kg with a mean and standard deviation of 5.0 +/- 8.2 and a median value of 2.0 Bq/kg. Mean radiocesium content by groups was highest in adult males (9.0 +/- 11.7; range 0.21-56.8 Bq/kg) followed by adult females (3.3 +/- 4.5; range 0-21.3 Bq/kg), male children (3.0 +/- 5.7; range 0-20.2 Bq/kg) and lowest in female children (1.6 +/- 3.5; range 0-12.7 Bq/kg). Individuals with the highest radiocesium content in each group belonged to one family that lived in Mozyr (100 km from Chernobyl) until emigrating in 1989. The frequency of lymphocyte micronuclei and erythrocyte GPA allele-loss (O/N) somatic mutations were both significantly correlated with radiocesium content (r=0.57, p=0.002; r=0.75, p=0.002, respectively). The micronucleus frequency also correlated with the estimated internal absorbed dose from radiocesium in a subset of 20 immigrants for whom this calculation was possible (r=0.71, p=0.0005). Altogether, the biomonitoring data indicate that some subjects had radiation doses sufficient to produce gene and chromosomal mutations in blood cells, although these effects cannot be attributed solely to radiocesium exposure. RI Grant, Stephen/D-6984-2014 OI Grant, Stephen/0000-0002-9236-0913 SN 0955-3002 PD DEC PY 1997 VL 72 IS 6 BP 703 EP 713 UT WOS:A1997YL22000009 PM 9416793 ER PT J AU Woloschak, GE AF Woloschak, GE TI Different pathways for radiation-induced apoptosis SO INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS RI Woloschak, Gayle/A-3799-2017 OI Woloschak, Gayle/0000-0001-9209-8954 SN 0360-3016 PD DEC 1 PY 1997 VL 39 IS 5 BP 951 EP 952 DI 10.1016/S0360-3016(97)00357-X UT WOS:A1997YG83800001 PM 9392530 ER PT J AU Castro, JR Char, DH Petti, PL Daftari, IK Quivey, JM Singh, RP Blakely, EA Phillips, TL AF Castro, JR Char, DH Petti, PL Daftari, IK Quivey, JM Singh, RP Blakely, EA Phillips, TL TI 15 years experience with helium ion radiotherapy for uveal melanoma SO INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS AB Purpose: To review the long-term experience of helium ion therapy as a therapeutic alternative to enucleation for uveal melanoma, particularly with respect to survival, local control, and morbidity. Methods and Materials: 347 patients with uveal melanoma were treated with heluim ion RT from 1978-1992. A nonrandomized dose-searching study was undertaken, with doses progressively reduced from 80 GyE in five fractions to 48 GyE in four fractions, given in 3-15 days, mean of 7 days. Results: Local control was achieved in 96% of patients, with no difference in the rate of local control being seen at 80, 70, 60, or 50 GyE in five fractions. At the lowest dose level of 48 GyE in four fractions, the local control rate fell to 87%. Fifteen of 347 patients (4%) had local regrowth in the eye requiring enucleation (12 patients), laser (1 patient) or reirradiation (2 patients). The time of appearance of local regrowth ranged from 4 months to 5 years posttreatment, with 85% occurring within 3 years. Of the 347 patients, 208 are alive as of May 1, 1997. The median follow up of all patients is 8.5 years, range 1-17 years. Kaplan-Maier (K-M) survival is 80% at 5 years, 76% at 10 years, and 72% at 15 years posttreatment. Patients with tumors not involving the ciliary body have a 15-year K-M survival of 80%. The results for patients whose tumors involved the ciliary body are poor, with a 15-year K-M survival of 43%. Seventy-five percent of patients with tumors at least 3.0 mm from the fovea and optic nerve, and initial ultrasound height less than 6.0 mm, retained vision of 20/200 or better posttreatment. Patients with tumors larger than 6 mm in thickness, or with tumors lying close to the optic nerve or fovea, have a reduced chance of retaining useful vision. The enucleation rate is 19%, 3% for local failure and 16% because of complications of the helium RT, particularly neovascular glaucoma, which occurred in 35% of patients. Conclusions: Local control and retention of the eye are excellent. Complications of therapy reduce vision and eye preservation. Twenty-four percent of patients manifested distant metastases 6 to 146 months posttreatment, mean of 43 months, median of 36 months. Late-appearing distant metastases do not appear to be caused by persistent tumor in the eye. The risk of metastases is high for patients with tumors greater than 7 mm in initial ultrasound height (37%), anterior tumors involving the ciliary body (47%), and in those with local failure (53%). Patients with tumors not involving the ciliary body and initial dimensions less than 10 mm had only an 8% chance of death from melanoma. A search for effective adjuvant therapy is needed for patients at high risk of metastases (large tumors, ciliary body involved, local regrowth in eye). (C) 1997 Elsevier Science Inc. SN 0360-3016 PD DEC 1 PY 1997 VL 39 IS 5 BP 989 EP 996 DI 10.1016/S0360-3016(97)00494-X UT WOS:A1997YG83800007 PM 9392536 ER PT J AU Daftari, IK Char, DH Verhey, LJ Castro, JR Petti, PL Meecham, WJ Kroll, S Blakely, EA AF Daftari, IK Char, DH Verhey, LJ Castro, JR Petti, PL Meecham, WJ Kroll, S Blakely, EA TI Anterior segment sparing to reduce charged particle radiotherapy complications in uveal melanoma SO INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS AB Purpose: The purpose of this investigation is to delineate the risk factors in the development of neovascular glaucoma (NVG) after helium-ion irradiation of uveal melanoma patients and to propose treatment technique that may reduce this risk, Methods and Materials: 347 uveal melanoma patients were treated with helium-ions using a single-port treatment technique. Using univariate and multivariate statistics, the NVG complication rate was analyzed according to the percent of anterior chamber in the radiation field, tumor size, tumor location, sex, age, dose, and other risk factors, Several University of California San Francisco-Lawrence Berkeley National Laboratory (LBNL) patients in each size category (medium, large, and extralarge) were retrospectively replanned using two ports instead of a single port, By using appropriate polar and azimuthal gaze angles or by treating patients with two ports, the maximum dose to the anterior segment of the eye can often be reduced, Although a larger volume of anterior chamber may receive a lower dose by using two ports than a single port treatment, We hypothesize that this could reduce the level of complications that result from the irradiation of the anterior chamber of the eye, Dose-volume histograms were calculated for the lens, and compared for the single and two-port techniques, Results: NVG developed in 121 (35%) patients, The risk of NVG peaked between 1 and 2.5 years posttreatment. By univariate and multivariate analysis, the percent of lens in the field was strongly correlated with the development of NVG, Other contributing factors were tumor height, history of diabetes, and vitreous hemorrhage. Dose-volume histogram analysis of single-port vs, two-port techniques demonstrate that for some patients in the medium and large category tumor groups, a significant decrease in dose to the structures in the anterior segment of the eye could have been achieved with the use of two ports, Conclusion: The development of NVG after helium-ion irradiation is correlated to the amount of lens, anterior chamber in the treatment field, tumor height, proximity to the fovea, history of diabetes, and the development of vitreous hemorrhage. Although the influence of the higher LET deposition of helium-ions is unclear, this study suggests that by reducing the dose to the anterior segment of the eye may reduce the NVG complications, Based on this retrospective analysis of LBNL patients, we have implemented techniques to reduce the amount of the anterior segment receiving a high dose in our new series of patients treated with protons using the cyclotron at the UC Davis Crocker Nuclear Laboratory (CNL). (C) 1997 Elsevier Science Inc. SN 0360-3016 PD DEC 1 PY 1997 VL 39 IS 5 BP 997 EP 1010 DI 10.1016/S0360-3016(97)00557-9 UT WOS:A1997YG83800008 PM 9392537 ER PT J AU May, AMB Pinder, JE Kroh, GC AF May, AMB Pinder, JE Kroh, GC TI A comparison of Landsat Thematic Mapper and SPOT multi-spectral imagery for the classification of shrub and meadow vegetation in northern California, USA SO INTERNATIONAL JOURNAL OF REMOTE SENSING AB The relative effectiveness of Landsat Thematic Mapper (TM) and SPOT multi-spectral data were compared for mapping shrub and meadow vegetation in northern California. Shrub vegetation included evergreen chaparral and deciduous willows and alders. Meadow vegetation included grass-dominated meadows on wet soils and forb-dominated meadows on drier sites. Despite differences in growth forms and species compositions, there was considerable similarity in spectral signatures among vegetation types. Because of greater spectral resolution, TM data were more effective than SPOT data in separating shrubs from meadows, but neither TM nor SPOT data were effective at separating meadow types. SN 0143-1161 PD DEC PY 1997 VL 18 IS 18 BP 3719 EP 3728 DI 10.1080/014311697216577 UT WOS:000070957300003 ER PT J AU Bower, KM Zyvoloski, G AF Bower, KM Zyvoloski, G TI A numerical model for thermo-hydro-mechanical coupling in fractured rock SO INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES AB Coupled thermo-hydro-mechanical codes with the ability to model fractured materials are used for predicting groundwater flow behavior in fractured aquifers containing thermal sources. The potential applications of such a code include the analysis of groundwater behavior within a geothermal reservoir. The capability of modeling hydro-thermo systems with a dual porosity, fracture flow model has been previously developed in the finite element code, FEHM. FEHM has been modified to include stress coupling with the dual porosity feature. FEHM has been further developed to couple the dependence of fracture hydraulic conductivity on effective stress within two-dimensional, saturated aquifers containing fracture systems. The cubic law for flow between parallel plates was used to model fracture permeability. The Barton-Bandis relation was used to determine the fracture aperture within the cubic law. The code used a Newton-Raphson iteration to implicitly solve for six unknowns at each node. Results from a model of heat flow from a reservoir to the moving fluid in a single fracture compared well with analytic results. Results of a model showing the increase in fracture flow due to a single fracture opening under fluid pressure compared well with analytic results. A hot dry rock, geothermal reservoir was modeled with realistic time steps indicating that the modified FEHM code does successfully model coupled flow problems with no convergence problems. (C) 1998 Elsevier Science Ltd. SN 0148-9062 PD DEC PY 1997 VL 34 IS 8 BP 1201 EP 1211 DI 10.1016/S0148-9062(97)00308-2 UT WOS:000072042700005 ER PT J AU Talesnick, ML Haimson, BC Lee, MY AF Talesnick, ML Haimson, BC Lee, MY TI Development of radial strains in hollow cylinders of rock subjected to radial compression SO INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES SN 0148-9062 PD DEC PY 1997 VL 34 IS 8 BP 1229 EP 1236 UT WOS:000072042700007 ER PT J AU Witten, A Won, IJ Norton, SJ AF Witten, A Won, IJ Norton, SJ TI Subsurface imaging with broadband electromagnetic induction SO INVERSE PROBLEMS AB Diffraction tomography (DT) is a quantitative technique for high-resolution subsurface imaging. In general, DT algorithms are used for subsurface imaging with propagating waves. In this study an imaging algorithm is developed and tested for use with broadband electromagnetic induction for a so-called 'multimonostatic' measurement geometry; a primary and secondary coil are coincident and move in unison over a uniformly spaced grid, on or above the ground surface. The algorithm is formulated in three dimensions and tested on simulated data for inhomogeneities that are both two and three dimensional. The algorithm is also applied, in two dimensions, to data acquired over a pair of parallel tunnels. One important finding is that good images can be reconstructed when the frequency band is limited to the case where all skin depths are greater than the depth of inhomogeneities. SN 0266-5611 PD DEC PY 1997 VL 13 IS 6 BP 1621 EP 1639 DI 10.1088/0266-5611/13/6/014 UT WOS:000071064000014 ER PT J AU O'Sullivan, E AF O'Sullivan, E TI Responses of sugar-beet cultivars to the control of rust (Uromyces betae) SO IRISH JOURNAL OF AGRICULTURAL AND FOOD RESEARCH AB The responses of six sugar-beet cultivars to fungicidal control of rust (Uromyces betae) were assessed in field experiments from 1990 to 1994. The cultivars included in these experiments were Monofeb, Rex and Accord from 1990 to 1994 and Fenyx, Celt and Proma from 1992 to 1994. Cultivars differed in susceptibility to rust, Monofeb and Rex having the highest levels of disease in all 5 years. The most consistent effect of controlling rust was increased sugar concentration in the roots. Increases in root weight and in sugar extractability were also recorded. Root weight, root sugar concentration and sugar extractability increases varied from 0 to 6.1 t / ha, 0 to 1.3 g / 100 g root and 0 to 1.8 g / 100 g total sugar, respectively. The magnitude and significance of these responses varied with cultivar and season. The most severe rust epidemics occurred in 1990 and 1992 and there were significant effects from controlling the disease in all cultivars. The least severe epidemic occurred in 1993 and effects of control were significant only in the more susceptible cultivars (Monofeb and Rex). The rust epidemics of 1991 and 1994 were moderate when compared with those of 1990 and 1992. There were significant effects from controlling rust in two of the three cultivars (Monofeb and Rex) in 1991 and in all cultivars except Proma in 1994. SN 0791-6833 PD DEC PY 1997 VL 36 IS 2 BP 175 EP 184 UT WOS:000072318400004 ER PT J AU Hacker, B AF Hacker, B TI National military establishments and the advancement of science and technology: Studies in twentieth-century history. SO ISIS SN 0021-1753 PD DEC PY 1997 VL 88 IS 4 BP 740 EP 741 DI 10.1086/383907 UT WOS:000072300900062 ER PT J AU Van Hove, MA Fadley, CS AF Van Hove, MA Fadley, CS TI Photoelectron diffraction theory applied to circular dichroism and spin-polarized photoelectron emission SO JOURNAL DE PHYSIQUE IV CT Colloquium on Surfaces and Interfaces of Advanced Materials CY OCT 02-04, 1996 CL MONTREAL, CANADA SP Entretiens Jacques Cartier, Lyon, Ecole Polytech Montreal, Univ Laval, Quebec, Univ Montreal, CERPIC, Quebec RI Van Hove, Michel/A-9862-2008 OI Van Hove, Michel/0000-0002-8898-6921 SN 1155-4339 PD DEC PY 1997 VL 7 IS C6 BP 65 EP 74 DI 10.1051/jp4:1997606 UT WOS:000072782500007 ER PT J AU Minnich, MG Houk, RS Woodin, MA Christiani, DC AF Minnich, MG Houk, RS Woodin, MA Christiani, DC TI Method to screen urine samples for vanadium by inductively coupled plasma mass spectrometry with cryogenic desolvation SO JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY AB The determination of vanadium by inductively coupled plasma mass spectrometry is complicated by ClO+ ions from chlorine matrices. Cryogenic desolvation reduces the amount of chloride reaching the plasma by condensing it as hydrogen chloride and reduces the amount of oxide formation by removing water vapor. Urine samples are-screened for vanadium at the 12 ppb level using scandium-as an internal standard. The V+ and Sc+ signals are affected by the matrix in the same way, so the V+/Sc+ signal ratio corrects for signal suppression by the matrix, as well as drift. Cryogenic desolvation also removes ArCl+, which should facilitate measurement of arsenic and selenium. SN 0267-9477 PD DEC PY 1997 VL 12 IS 12 BP 1345 EP 1350 DI 10.1039/a700172j UT WOS:000071161700001 ER PT J AU Schraad, MW Triantafyllidis, N AF Schraad, MW Triantafyllidis, N TI Scale effects in media with periodic and nearly periodic microstructures, part II: Failure mechanisms SO JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME AB Using the nonlinearly elastic planar lattice model presented in Part I, the influence of scale (i.e., the size of the representative volume, relative to the size of the unit cell) on the onset of failure in periodic and nearly periodic media is investigated. For this study, the concept of a microfailure surface is introduced-this surface being defined as the locus of first instability points found along radial load paths through macroscopic strain space. The influence of specimen size and microstructural imperfections (both geometric and constitutive) on these failure surfaces is investigated. The microfailure surface determined for the infinite model with perfectly periodic microstructure, is found to be a lower bound for the failure surfaces of perfectly periodic, finite models, and an upper bound for the failure surfaces of finite models with microstructural imperfections. The concept of a macrofailure surface is also introduced-this surface being defined as the locus of points corresponding to the loss of ellipticity in the macroscopic (homogenized) moduli of the model. The macrofailure surface is easier to construct than the microfailure surface, because it only requires calculation of the macroscopic properties for the unit cell, at each loading state along the principal equilibrium path. The relation between these two failure surfaces is explored in detail, with attention focused on their regions of coincidence, which are of particular interest due to the possible development of macroscopically localized failure modes. SN 0021-8936 PD DEC PY 1997 VL 64 IS 4 BP 763 EP 771 DI 10.1115/1.2788980 UT WOS:000071478100005 ER PT J AU Warren, WE Kraynik, AM AF Warren, WE Kraynik, AM TI Linear elastic behavior of a low-density Kelvin foam with open cells SO JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME AB A micromechanical analysis for the linear elastic behavior of a low-density foam with open cells is presented, The foam structure is based on the geometry of a Kelvin soap froth with pat faces. 14-sided polyhedral cells contain six squares and eight hexagons. Four struts meet at every joint in the perfectly ordered, spatially periodic, open-cell structure. All of the struts and joints have identical shape. Strut-level force-displacement relations are expressed by compliances for stretching, bending, and twisting. We consider arbitrary homogeneous deformations of the foam and present analytic results for the force, moment, and displacement at each strut midpoint and the rotation at each joint. The effective stress-strain relations for the foam, which has cubic symmetry, are represented by three elastic constants, a bulk modulus, and two shear moduli, that depend on the strut compliances. When these compliances are evaluated for specific strut geometries, the shear moduli are nearly equal and therefore the elastic response is nearly isotropic. The variational results of Hashin and Shtrikman are used to calculate the effective isotropic shear modulus of a polycrystal that contain grains of Kelvin foam. SN 0021-8936 PD DEC PY 1997 VL 64 IS 4 BP 787 EP 794 DI 10.1115/1.2788983 UT WOS:000071478100008 ER PT J AU Garnich, MR Hansen, AC AF Garnich, MR Hansen, AC TI A multicontinuum approach to structural analysis of linear viscoelastic composite materials SO JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME AB A "multicontinuum" approach to structural analyses of composites is described. A continuum field is defined to represent each constituent material along with the traditional continuum field associated with the composite. Finite element micromechanics is used to establish relationships between composite and constituent field variables. These relationships uncouple the micromechanics from structural solutions and render an efficient means of extracting constituent information during the course of a finite element structural analysis. Equations are developed for the case of a linear elastic reinforcing material embedded in a linear viscoelastic matrix and verified by comparison with results of finite element micromechanics. SN 0021-8936 PD DEC PY 1997 VL 64 IS 4 BP 795 EP 803 DI 10.1115/1.2788984 UT WOS:000071478100009 ER PT J AU Liu, WK Uras, RA Chen, Y AF Liu, WK Uras, RA Chen, Y TI Enrichment of the finite element method with the reproducing kernel particle method SO JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME AB The reproducing kernel particle method (RKPM) has attractive properties in handling high gradients, concentrated forces, and large deformations where other widely implemented methodologies fail. In the present work, a multiple field computational procedure is devised to enrich the finite element method with RKPM, and RKPM with analytical functions. The formulation includes an interaction term that accounts for any overlap between the fields, and increases the accuracy of the computational solutions in a coarse mesh or particle grid. By replacing finite element method shape functions at selected nodes with higher-order RKPM window functions, RKPM p-enrichment is obtained. Similarly, by adding RKPM window functions into a finite element method mesh, RKPM hp-enrichment is achieved analogous to adaptive refinement. The fundamental concepts of the multiresolution analysis are used to devise an adaptivity procedure. RI Liu, Wing/B-7599-2009 SN 0021-8936 PD DEC PY 1997 VL 64 IS 4 BP 861 EP 870 DI 10.1115/1.2788993 UT WOS:000071478100018 ER PT J AU Buckley, RL Kurzeja, RJ AF Buckley, RL Kurzeja, RJ TI An observational and numerical study of the nocturnal sea breeze. Part I: Structure and circulation SO JOURNAL OF APPLIED METEOROLOGY AB Characteristics of inland-penetrating nocturnal sea breezes at the Savannah River Site (SRS) in South Carolina are discussed. Derailed observations from an area tower network during the Stable Boundary Layer Experiment (STABLE) indicate passage of marine air through SRS on three different nights. Large-scale winds are directed onshore for the first two nights, resulting in similar boundary layer structure and stability on these nights, while synoptic winds on the third night are offshore, leading to stronger convergence and wedging of the marine air under the inland air mass. The Regional Atmospheric Modeling System (RAMS) is used to simulate conditions for the final two nights. General features of the sea breeze are captured by the model, including wind shifts, moisture increases, turbulence structure differences between the two nights, and the formation of Kelvin-Helmholtz billows along the interface of marine and return airflow. SN 0894-8763 PD DEC PY 1997 VL 36 IS 12 BP 1577 EP 1598 DI 10.1175/1520-0450(1997)036<1577:AOANSO>2.0.CO;2 UT WOS:000072306300001 ER PT J AU Buckley, RL Kurzeja, RJ AF Buckley, RL Kurzeja, RJ TI An observational and numerical study of the nocturnal sea breeze. Part II: Chemical transport SO JOURNAL OF APPLIED METEOROLOGY AB Chemical transport at the Savannah River Site (SRS) in South Carolina during nocturnal sea-breeze passage is examined using simulations from a three-dimensional mesoscale dynamic model [(RAMS) Regional Atmospheric Modeling System] and a Lagrangian particle dispersion model (LPDM) and supplemental surface measurements of sulfur hexafluoride (SF6) obtained during a 1988 held campaign. Plume dispersion and regional transport were characterized by nights with onshore and offshore synoptic winds. For onshore winds, the sea breeze lifts, redirects, and broadens an initially narrow plume but maintains its general structure. Regional calculations reveal particle translations exceeding 100 km under these conditions. On the other hand, with offshore synoptic winds, frontal passage leads to stronger lifting, turbulence, and vertical shearing that fragments the plume. In addition, complicated recirculation of pollutants is possible and may increase chemical concentrations in areas near the source. Observed and model plumes were shown to depend strongly on vertical, horizontal, and temporal wind shear, and vertical motion. These features were simulated by the RAMS and LPDM models but are not possible with Gaussian models. Turbulence and topography also had important effects on plume characteristics but were simulated adequately only in the frontal region. Deficiencies in the model simulation were attributed mainly to insufficient vertical resolution and inadequate resolution of surface features. SN 0894-8763 PD DEC PY 1997 VL 36 IS 12 BP 1599 EP 1619 DI 10.1175/1520-0450(1997)036<1599:AOANSO>2.0.CO;2 UT WOS:000072306300002 ER PT J AU Dwight, D Rao, MV Holland, OW Kelner, G Chi, PH Kretchmer, J Ghezzo, M AF Dwight, D Rao, MV Holland, OW Kelner, G Chi, PH Kretchmer, J Ghezzo, M TI Nitrogen and aluminum implantation in high resistivity silicon carbide SO JOURNAL OF APPLIED PHYSICS AB In this article, the results on N and Al implantations into undoped high-resistance and vanadium doped semi-insulating bulk 6H-SiC are reported for the first time. The N implants were performed at 700 degrees C and the Al implants at 800 degrees C to create n- and p-type layers, respectively. For comparison, implants were performed into epitaxial layers at the above temperatures and, for N, also at room temperature. The implanted/annealed material was characterized by van der Pauw Hall, secondary ion mass spectrometry, and Rutherford backscattering (RES) measurements. After annealing, the room temperature N implantation gave similar electrical and RES results as the 700 degrees C implantation for a total implant dose of 8x10(14) cm(-2) which corresponds to a volume concentration of 2x10(19) cm(-3). The Al implant redistributed in the bulk crystals during annealing, resulting in a shoulder formation at the tail of the implant profile. Lower implant activation was obtained in V-doped material compared to the undoped bulk and epitaxial layers, but the results were promising enough to use implantation technology for making planar high frequency devices in the bulk V-doped substrates, especially as the quality of the substrates continue to improve. (C) 1997 American Institute of Physics. SN 0021-8979 PD DEC 1 PY 1997 VL 82 IS 11 BP 5327 EP 5333 DI 10.1063/1.366299 UT WOS:A1997YH59000008 ER PT J AU Schlamp, MC Peng, XG Alivisatos, AP AF Schlamp, MC Peng, XG Alivisatos, AP TI Improved efficiencies in light emitting diodes made with CdSe(CdS) core/shell type nanocrystals and a semiconducting polymer SO JOURNAL OF APPLIED PHYSICS AB We report experiments on bilayer light emitting diodes made with organically capped CdSe(CdS) core/shell type semiconductor nanocrystals and an electroluminescent (EL) semiconducting polymer [poly(p-phenylenevinylene) or PPV]. The devices emit from red to green with external quantum efficiencies of up to 0.22% at brightnesses of 600 cd/m(2) and current densities of 1 A/cm(2). They have operating voltages as low as 4 V and lifetimes under constant current flow of hundreds of hours. Most of these numbers are significant improvements over similar devices made with CdSe nanocrystals. The devices show either nanocrystal-only EL or a combination of nanocrystal and PPV EL, depending on nanocrystal layer thickness. The nanocrystal EL is dependent on nanocrystal size. Some devices show a voltage dependent spectral output. The spectral output is consistent with a field dependent electron range in the nanocrystal layer limited by carrier trapping. (C) 1997 American Institute of Physics. RI Alivisatos , Paul /N-8863-2015; peng, xiaogang/R-6184-2016 OI Alivisatos , Paul /0000-0001-6895-9048; peng, xiaogang/0000-0002-5606-8472 SN 0021-8979 PD DEC 1 PY 1997 VL 82 IS 11 BP 5837 EP 5842 DI 10.1063/1.366452 UT WOS:A1997YH59000081 ER PT J AU Elston, R Colt, J Abernethy, S Maslen, W AF Elston, R Colt, J Abernethy, S Maslen, W TI Gas bubble reabsorption in Chinook salmon: Pressurization effects SO JOURNAL OF AQUATIC ANIMAL HEALTH AB Gas bubble disease (GBD) can cause substantial morbidity and mortality of salmonids and other fishes residing in gas supersaturated water. The monitoring program for examining the prevalence of GBD in the Columbia and Snake rivers is only based on fish collected in the smelt bypass systems; fish that pass through the turbines, nagivation locks, adult fish ladders, or spillways are not sampled. The current monitoring program may underestimate the prevalence and severity of GBD because the high hydrostatic pressures experienced by the smelts as they pass through the smelt bypass system may cause rapid reabsorption of any gas bubbles that had formed upstream of the dam. A pressurization of 5 min to 30.5 m of head resulted in a substantial reduction in clinical signs of GBD in the fins, lateral lines, and gills of yearling spring chinook salmon Oncorhynchus tshawytscha. Clinical signs of GBD were lost most rapidly in gills, followed by the lateral line. The rate of bubble loss was much less for the primarily extravascular bubbles found in the fins. The gas transfer potential of pressure and length of exposure to pressure (pressure-time history) must be considered for smelts exposed to the bypass system. If the gas transfer poten tial of pressure-time history for in-river salmonids is similar to the 5-min pressurization treatment, the current smelt monitoring program aimed at evaluating the prevalence and severity of GBD, may be under-estimating the impact of GBD in the Snake and Columbia rivers. This work demonstrates that gas bubble reabsorption could be occurring in salmonid smelts examined at fish passage facilities and that further work is needed to quantify the extent and magnitude of bubble reabsorption at such facilities. SN 0899-7659 PD DEC PY 1997 VL 9 IS 4 BP 317 EP 321 DI 10.1577/1548-8667(1997)009<0317:GBRICS>2.3.CO;2 UT WOS:000072781600012 ER PT J AU Goldman, MV Newman, DL Drake, RP Afeyan, BB AF Goldman, MV Newman, DL Drake, RP Afeyan, BB TI Theory of convective saturation of Langmuir waves during ionospheric modification of a barium cloud SO JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS CT IV Suzdal URSI Symposium on Artificial Modification of the Ionosphere CY AUG 15-20, 1994 CL UPPSALA, SWEDEN AB In recent experiments (Djuth, F. T., Sulzer, M. P., Elder, J. H. and Groves, K. M. (1995) Journal of Geophysical Research, 100, 17,347), a parametric decay instability was excited by an ordinary-wave HF pump during an ionospheric chemical release from a rocket over Arecibo, PR, which created an artificial 'barium ionosphere,' with peak plasma frequency above the pump frequency, and a density gradient with a (short) 5 km scale length. Simultaneous incoherent scattering measurements revealed a strong initial asymmetry in the amplitudes of almost vertically upgoing versus downgoing measured plasma waves. We can account for this asymmetry in terms of linear convective saturation of parametrically unstable plasma waves propagating over a range of altitudes along geometric optics ray paths. Qualitative features of the frequency spectrum of the measured downgoing wave are in agreement with this model, although the theoretically predicted spectrum is narrower than observed. The observed altitude localization of the enhanced spectrum to a few range cells is consistent with the theory. (C) 1997 Elsevier Science Ltd. RI Drake, R Paul/I-9218-2012 OI Drake, R Paul/0000-0002-5450-9844 SN 1364-6826 PD DEC PY 1997 VL 59 IS 18 BP 2335 EP 2350 DI 10.1016/S1364-6826(96)00127-7 UT WOS:000071705700010 ER PT J AU McCune, W AF McCune, W TI Solution of the Robbins problem SO JOURNAL OF AUTOMATED REASONING AB In this article we show that the three equations known as commutativity, associativity, and the Robbins equation are a basis for the variety of Boolean algebras. The problem was posed by Herbert Robbins in the 1930s. The proof was found automatically by EQP, a theorem-proving program for equational logic. We present the proof and the search strategies that enabled the program to find the proof. SN 0168-7433 PD DEC PY 1997 VL 19 IS 3 BP 263 EP 276 DI 10.1023/A:1005843212881 UT WOS:A1997YG81200001 ER PT J AU George, GN AF George, GN TI X-ray absorption spectroscopy of molybdenum enzymes SO JOURNAL OF BIOLOGICAL INORGANIC CHEMISTRY AB One of the major goals of bioinorganic chemistry is a quantitative understanding of the structure-function relationships of metalloproteins. X-ray absorption spectroscopy (XAS) is one of the few experimental techniques that can provide structural details on active sites under almost any experimental condition. In the last few years, the field of molybdenum enzymes has been revolutionized by several protein crystal structures (see [1, 2] and references therein). Protein crystallography provides detailed information on protein folding and on the inter-relationship of various redox-active sites within the molecule. Unfortunately, the precise metrical details of the molybdenum site which are required for an adequate understanding of structure-function relationships can be lacking. This commentary will provide some perspective on the usefulness and limitations of X-ray absorption spectroscopy in providing an accurate picture of the active site of molybdenum enzymes. RI George, Graham/E-3290-2013 SN 0949-8257 PD DEC PY 1997 VL 2 IS 6 BP 790 EP 796 DI 10.1007/s007750050197 UT WOS:000071271700015 ER PT J AU Aylor, AW Lobree, LJ Reimer, JA Bell, AT AF Aylor, AW Lobree, LJ Reimer, JA Bell, AT TI Investigations of the dispersion of Pd in H-ZSM-5 SO JOURNAL OF CATALYSIS AB The state of Pd dispersion in Pd-H-ZSM-5 was investigated by means of infrared spectroscopy and temperature-programmed desorption spectroscopy, using CO and NO as probe molecules. Following oxidation in O-2 at 773 K of a freshly prepared, low-loaded sample (Pd/Al = 0.048), most of the Pd is found to be present as isolated cations, viz. Pdn+ (n = 1-3). CO reduction at 773 K leads to the formation of Pd particles that fill the local pore space of the zeolite and are inaccessible to CO. Following CO reduction, oxidation in O-2 for 2 or 8 h at 773 K only partially redisperses the Pd. During treatment of a reduced sample in 5000 ppm NO for 60 min at 673 K, N2O and N-2 are produced in an amount sufficient to oxidize all the Pd to PdO. Characterization of the state of Pd dispersion after NO pretreatment shows that all of the Pd has been redispersed as cations. Reoxidation of the reduced sample in NO is accompanied by a decrease in the infrared band due to Bronsted acid groups in an amount nearly equivalent to 2H(+)/Pd. Subsequent reduction of the sample regenerates the Bronsted acid band intensity. These observations suggest that isolated Pd cations may reside as Z(-)H(+)(PdO)H(+)Z(-) in association with pairs of Al sites in the zeolite that are next-nearest neighbors. Following oxidation in O-2 at 773 K, a high-loaded sample of Pd-H-ZSM-5 (Pd/Al = 0.48) is found to have nearly the same concentration of highly dispersed Pd cations as the low-loaded sample, with the balance of the Pd in this case being present as small particles of PdO. Treatment of a reduced, high-loaded sample of Pd-H-ZSM-5 in NO at 773 K redisperses all of the Pd in structures that are proposed to be Z(-)H(+)[(PdO)(NO)]H(+)Z(-) and Z(-)H(+)[(PdO)(NO)]. However, upon removal of the adsorbed NO by treatment in O-2 at 773 R, the Z(-)K(+)[(PdO)(NO)] species revert to PdO, but the Z(-)H(+)[(PdO)(NO)]H(+)Z species remain stable as Z(-)H(+)(PdO)H(+)Z(-). The present results suggest that maintenance of Pd in a high state of dispersion as isolated Pdn+ cations in the presence of O-2 at elevated temperatures requires pairs of next-nearest-neighbor Al sites in the zeolite. (C) 1997 Academic Press. OI Bell, Alexis/0000-0002-5738-4645 SN 0021-9517 PD DEC PY 1997 VL 172 IS 2 BP 453 EP 462 DI 10.1006/jcat.1997.1893 UT WOS:000071256700019 ER PT J AU Isfort, RJ Cody, DB Stuard, SB Randall, CJ Miller, C Ridder, GM Doersen, CJ Richards, WG Yoder, BK Wilkinson, JE Woychik, RP AF Isfort, RJ Cody, DB Stuard, SB Randall, CJ Miller, C Ridder, GM Doersen, CJ Richards, WG Yoder, BK Wilkinson, JE Woychik, RP TI The combination of epidermal growth factor and transforming growth factor-beta induces novel phenotypic changes in mouse liver stem cell lines SO JOURNAL OF CELL SCIENCE AB Mouse liver stem cell (oval cell) lines were investigated in order to determine the role which two families of growth and differentiation factors (GDFs), epidermal growth factor (EGF) family and transforming growth factor beta (TGF-beta) family, play in liver regeneration. EGF family members, including EGF, amphiregulin, betacellulin, heparin-binding epidermal growth factor, and TGF-alpha, were mitogenic for oval cell lines while TGF-beta family members, including TGF-beta 1, TGF-beta 2 and TGF-beta 3, inhibited mitogenesis and induced apoptosis in oval cell lines, Surprisingly, the combination of EGF family members and TGF-beta family members resulted in neither proliferation nor apoptosis but instead in a novel cellular response, cellular scattering in tissue culture and morphological differentiation in Matrigel, Analysis of the signal transduction pathways activated by exposure of oval cell lines to either EGF, EGF + TGF-beta, or TGF-beta indicated that novel combinations of intracellular signals result following stimulation of the cells with the combination of EGF + TGF beta. These data reveal that the dynamics of synergistic GDF action following tissue injury and regeneration results in a new level of complexity not obvious from the study of individual GDFs. SN 0021-9533 PD DEC PY 1997 VL 110 BP 3117 EP 3129 PN 24 UT WOS:000071273500013 PM 9365282 ER PT J AU Bein, K Husain, M Ware, JA Mucenski, ML Rosenberg, RD Simons, M AF Bein, K Husain, M Ware, JA Mucenski, ML Rosenberg, RD Simons, M TI C-myb function in fibroblasts SO JOURNAL OF CELLULAR PHYSIOLOGY AB The protooncogene c-myb is a nuclear transcription factor that shares significant sequence homology with two other myb family members, A-myb and B-myb. Recent studies have suggested that c-myb is involved in regulation of the cell cycle via control of intracellular calcium [Ca2+](i) concentration. Given the limited cell type expression of the c-myb gene, we set out to investigate whether myb-dependent cell cycle regulation occurs in cells not known to express the c-myb protein. NIH 3T3 fibroblasts were stably transfected with an inducible c-myb dominant negative construct composed of a myb DNA binding domain linked to the Drosophila engrailed transcription suppresser (pGREMEn) and a full-length murine c-myb cDNA sequence. Induced expression of the dominant negative construct was associated with a G(1) cell cycle arrest and a failure to increase late G(1) intracellular calcium levels. Similar expression studies in mouse embryonic fibroblasts derived from the c-myb knockout mouse have demonstrated lower baseline [Ca2+](i) levels than in normal mice fibroblasts that were not further lowered by MEn expression. We conclude that regulation of calcium homeostasis and cell cycle progression via myb-dependent transcription may play an important role in cells not possessing delectable levels of c-myb protein. (C) 1997 Wiley-iiss, inc. OI Husain, Mansoor/0000-0002-3740-6739; Simons, Michael/0000-0003-0348-7734 SN 0021-9541 PD DEC PY 1997 VL 173 IS 3 BP 319 EP 326 DI 10.1002/(SICI)1097-4652(199712)173:3<319::AID-JCP3>3.0.CO;2-Q UT WOS:A1997YE61900003 PM 9369944 ER PT J AU Hodgkinson, P Pines, A AF Hodgkinson, P Pines, A TI Cross-polarization efficiency in INS systems using adiabatic RF sweeps SO JOURNAL OF CHEMICAL PHYSICS AB The theory describing nuclear magnetic resonance cross-polarization using adiabatic sweeps of the rf spin-lock fields through the Hartmann-Hahn matching condition is extended to small homonuclear coupled systems of the type INS. In particular, the connection is made between such experiments and the associated theoretical limits on polarization transfer-the ''unitary bounds'' - demonstrating that these techniques can achieve the maximum transfer of polarization from the I spins to the S spins, subject to the constraint of angular momentum conservation imposed by spin-locking, Factors such as permutation symmetry of the spins, imperfect adiabaticity of individual crossings and fast sample spinning are shown to have no fundamental impact on the validity on these results. (C) 1997 American Institute of Physics. RI Hodgkinson, Paul/G-2867-2012 OI Hodgkinson, Paul/0000-0003-0327-3349 SN 0021-9606 EI 1089-7690 PD DEC 1 PY 1997 VL 107 IS 21 BP 8742 EP 8751 DI 10.1063/1.475167 UT WOS:A1997YJ46400002 ER PT J AU Nellis, WJ Holmes, NC Mitchell, AC Hamilton, DC Nicol, M AF Nellis, WJ Holmes, NC Mitchell, AC Hamilton, DC Nicol, M TI Equation of state and electrical conductivity of ''synthetic Uranus,'' a mixture of water, ammonia, and isopropanol, at shock pressure up to 200 GPa (2 Mbar) SO JOURNAL OF CHEMICAL PHYSICS AB Equation-of-state, temperature, and electrical-conductivity data were measured for a solution of water, ammonia, and isopropanol at shock pressures up to 200 GPa. The chemical composition is similar to that of the fluid mixture thought to be the major constituent of the giant planets Uranus and Neptune. (C) 1997 American Institute of Physics. SN 0021-9606 PD DEC 1 PY 1997 VL 107 IS 21 BP 9096 EP 9100 DI 10.1063/1.475200 UT WOS:A1997YJ46400037 ER PT J AU Rodriguez, JA Chaturvedi, S Kuhn, M vanEk, J Diebold, U Robbert, PS Geisler, H Ventrice, CA AF Rodriguez, JA Chaturvedi, S Kuhn, M vanEk, J Diebold, U Robbert, PS Geisler, H Ventrice, CA TI H2S adsorption on chromium, chromia, and gold/chromia surfaces: Photoemission studies SO JOURNAL OF CHEMICAL PHYSICS AB The reaction of H2S with chromium, chromia, and Au/chromia films grown on a Pt(111) crystal has been investigated using synchrotron-based high-resolution photoemission spectroscopy. At 300 K, H2S completely decomposes on polycrystalline chromium producing a chemisorbed layer of S that attenuates the Cr 3d valence features, No evidence was found for the formation of CrSx species. The dissociation of H2S on Cr3O4 and Cr2O3 films al room temperature produces a decrease of 0.3-0.8 eV in the work function of the surface and significant binding-energy shifts (0.2-0.6 eV) in the Cr 3p core levels and Cr 3d features in the valence region. The rate of dissociation of H2S increases following the sequence: Cr2O3 H2S(5a(1),2b(1)) bonding interactions and facilitates the decomposition of the molecule. (C) 1997 American Institute of Physics. RI Diebold, Ulrike/A-3681-2010 OI Diebold, Ulrike/0000-0003-0319-5256 SN 0021-9606 PD DEC 1 PY 1997 VL 107 IS 21 BP 9146 EP 9156 DI 10.1063/1.475319 UT WOS:A1997YJ46400044 ER PT J AU Hummer, G Pratt, LR Garcia, AE AF Hummer, G Pratt, LR Garcia, AE TI Ion sizes and finite-size corrections for ionic-solvation free energies SO JOURNAL OF CHEMICAL PHYSICS AB Free energies of ionic solvation calculated from computer simulations exhibit a strong system size dependence. We perform a finite-size analysis based on a dielectric-continuum model with periodic boundary conditions. That analysis results in an estimate of the Born ion size. Remarkably, the finite-size correction applies to systems with only eight water molecules hydrating a sodium ion and results in an estimate of the Born radius of sodium that agrees with the experimental value. (C) 1997 American Institute of Physics. RI Pratt, Lawrence/H-7955-2012; Hummer, Gerhard/A-2546-2013 OI Pratt, Lawrence/0000-0003-2351-7451; Hummer, Gerhard/0000-0001-7768-746X SN 0021-9606 PD DEC 1 PY 1997 VL 107 IS 21 BP 9275 EP 9277 DI 10.1063/1.475219 UT WOS:A1997YJ46400058 ER PT J AU Collins, WD Wang, JY Kiehl, JT Zhang, GJ Cooper, DI Eichinger, WE AF Collins, WD Wang, JY Kiehl, JT Zhang, GJ Cooper, DI Eichinger, WE TI Comparison of tropical ocean-atmosphere fluxes with the NCAR community climate model CCM3 SO JOURNAL OF CLIMATE AB The properties of the marine boundary layer produced by the National Center for Atmospheric Research (NCAR) Community Climate Model version 3 (CCM3) are compared with observations from two experiments in the central and western equatorial Pacific. The main objective of the comparison is determining the accuracy of the ocean-atmosphere fluxes calculated by the model. The vertical thermodynamic structure and the surface fluxes calculated by the CCM3 have been validated against data from the Central Equatorial Pacific Experiment (CEPEX) and the Tropical Ocean Global Atmosphere-Tropical Atmosphere Ocean (TOGA-TAO) buoy array. The mean latent heat flux for the TOGA-TAO array is 92 W m(-2), and the model estimate of latent flux is 109 W m(-2). The bias of 17 W m(-2) is considerably smaller than the overestimation of the Bur by the previous version of the CCM. The improvement in the latent heat flux is due to a reduction in the surface winds caused by nonlocal effects of a new convective parameterization. The agreement between the mean sensible heat flux for the TOGA-TAO array and the model estimate has also been improved in the new version of the model. The current version of the CCM overestimates the sensible heat flux by 3.4 W m(-2). The atmospheric temperature and water vapor mixing ratio from the lowest model layer are within 0.3 K and 0.4 g kg(-1) of measurements obtained from radiosondes. The mean model value of the boundary layer height is within 13 m of the average height derived from a Raman lidar on board a ship in the CEPEX domain. There is some evidence that the biases in the model can be reduced further by modifying the bulk formulation of the surface fluxes. RI Collins, William/J-3147-2014 OI Collins, William/0000-0002-4463-9848 SN 0894-8755 PD DEC PY 1997 VL 10 IS 12 BP 3047 EP 3058 DI 10.1175/1520-0442(1997)010<3047:COTOAF>2.0.CO;2 UT WOS:000071532800005 ER PT J AU Ghan, SJ Liljegren, JC Shaw, WJ Hubbe, JH Doran, JC AF Ghan, SJ Liljegren, JC Shaw, WJ Hubbe, JH Doran, JC TI Influence of subgrid variability on surface hydrology SO JOURNAL OF CLIMATE AB A 6.25-km resolution dataset of meteorology, vegetation type, and soil type for a domain covering a typical global climate model grid cell is used to drive a land surface physics model for a period of 6 months. Additional simulations are performed driving the land surface physics model by spatially averaged meteorology, spatially averaged vegetation characteristics, spatially averaged soil properties, and spatially averaged meteorology, vegetation characteristics, and soil properties. By comparing the simulated water balance for the whole domain for each simulation, the relative influence of subgrid variability in meteorology, vegetation, and soil are assessed. Subgrid variability in summertime precipitation is found to have the largest effect on the surface hydrology, with a nearly twofold increase on surface runoff and a 15% increase in evapotranspiration. Subgrid variations in vegetation and soil properties also increase surface runoff and reduce evapotranspiration, so that surface runoff is 2.75 times as great with subgrid variability than without and evapotranspiration is 19% higher with subgrid variability than without. RI Ghan, Steven/H-4301-2011 OI Ghan, Steven/0000-0001-8355-8699 SN 0894-8755 PD DEC PY 1997 VL 10 IS 12 BP 3157 EP 3166 DI 10.1175/1520-0442(1997)010<3157:IOSVOS>2.0.CO;2 UT WOS:000071532800011 ER PT J AU Weesner, FJ Bleam, WF AF Weesner, FJ Bleam, WF TI X-ray absorption and EPR spectroscopic characterization of adsorbed copper(II) complexes at the boehmite (AlOOH) surface SO JOURNAL OF COLLOID AND INTERFACE SCIENCE AB The chemical environment of Cu(II) adsorbed to the boehmite (AlOOH) surface at pH 6.5 is examined by electron paramagnetic resonance and X-ray absorption spectroscopy, Adsorbed Cu(II) is always coordinated by four oxygens in an axially symmetric Ligand field when adsorbed under our experimental conditions, The Cu-O bond distance is approximately 1.94 Angstrom. An oriented, inner-sphere Cu(II) surface complex is observed at low surface loading (<0.,2 mu mol/M-2). A second population of Cu(OH)(N) (H2O)(X)((2-N)+) outer-sphere complexes is proposed at higher surface loadings to explain X-ray absorption fine structure results, Cu(II) strongly resists any tendency to form a surface precipitate on boehmite at pH 6.5, The presence of specifically adsorbing anions had little effect on the local chemical environment of adsorbed Cu(II), (C) 1997 Academic Press. SN 0021-9797 PD DEC 1 PY 1997 VL 196 IS 1 BP 79 EP 86 DI 10.1006/jcis.1997.5190 UT WOS:000071509900009 ER PT J AU Boehm, RC Kress, JD Martin, RL Hay, PJ AF Boehm, RC Kress, JD Martin, RL Hay, PJ TI A theoretical study of bond energies in model Si-H-Cl molecules using density functional approaches for representing Si surface chemistry SO JOURNAL OF COMPUTATIONAL CHEMISTRY AB The reliability of density functional theory (DFT) methods for calculating Si-H, Si-Cl, and Si-Si bond energies is examined in reactions involving molecules and small clusters representing various surface sites appropriate for Si surface chemistry. Results are presented for systematic studies using a valence double-zeta polarization basis for both all-electron calculations and valence-electron calculations employing effective core potentials (ECPs). All-electron DFT results are comparable to much more demanding MP4, G2, and MC-SCF-CI calculations for computed bond energies. Whereas the use of ECPs introduces systematic energy differences of ca. 3-5 kcal/mol compared to AE results, depending on the type of bond involved, the use of ECPs for carrying out calculations on larger dusters is discussed where AE calculations become more computationally demanding. The convergence of Si bond energies as a function of replacing hydrogens with silyl. groups is examined. In constructing models to describe etching processes involving Cl species on Si surfaces, the need for incorporating differences in thermochemistries for one-, two-, and three-coordinate Si surface sites is emphasized. Comparisons of semiempirical approaches for thermochemistries of Si-containing species find these methods somewhat less reliable for obtaining reliable bond energies compared to computationally more demanding DFT and ab initio correlated models. (C) 1997 John Wiley & Sons, Inc. SN 0192-8651 PD DEC PY 1997 VL 18 IS 16 BP 2075 EP 2085 UT WOS:A1997YJ29600011 ER PT J AU Hewett, DW AF Hewett, DW TI The embedded curved boundary method for orthogonal simulation meshes SO JOURNAL OF COMPUTATIONAL PHYSICS AB A method for incorporating piecewise-linear approximations to curved boundaries is developed for codes using orthogonal meshes. The resulting method retains much of the fidelity of adaptive triangle meshes in 2D while retaining essentially all of the speed of traditional methods relying on banded matrix solutions. We find this technique useful for situations lying between the crude but fast stairstep approximation and the elegant but slower adaptive mesh techniques. This method provides a practical approach to problems such as space charge emission while retaining the simplicity and run time advantage of orthogonal-mesh-based codes. Examples from space-charge-limited flow between curved electrodes are given. (C) 1997 Academic Press. SN 0021-9991 PD DEC PY 1997 VL 138 IS 2 BP 585 EP 616 DI 10.1006/jcph.1997.5835 UT WOS:000072215600014 ER PT J AU Hou, SL Shan, XW Zou, QS Doolen, GD Soll, WE AF Hou, SL Shan, XW Zou, QS Doolen, GD Soll, WE TI Evaluation of two lattice Boltzmann models for multiphase flows SO JOURNAL OF COMPUTATIONAL PHYSICS AB Two lattice Boltzmann models for multiphase flows, the immiscible fluid model proposed by Rothman and Keller (R-K) and the multicomponent nonideal gas lattice Boltzmann model by Shan and Chen (S-C), are studied numerically to compare their abilities to simulate the physics of multiphase flows. The test problem is the simulation of a static bubble. Isotropy, strength of surface tension, thickness of the interface, spurious currents, Laplace's law, and steadiness of the bubble are examined. The results show that the S-C model is a major improvement over the R-K model. (C) 1997 Academic Press. RI Shan, Xiaowen/H-2836-2013 OI Shan, Xiaowen/0000-0002-6350-9248 SN 0021-9991 PD DEC PY 1997 VL 138 IS 2 BP 695 EP 713 DI 10.1006/jcph.1997.5839 UT WOS:000072215600018 ER PT J AU Minion, ML Brown, DL AF Minion, ML Brown, DL TI Performance of under-resolved two-dimensional incompressible flow simulations, II SO JOURNAL OF COMPUTATIONAL PHYSICS AB This paper presents a study of the behavior of several difference approximations for the incompressible Navier-Stokes equations as a function of the computational mesh resolution. In particular, the under-resolved case is considered, The methods considered include a Godunov projection method, a primitive variable ENO method, an upwind vorticity stream-function method, centered difference methods of both a pressure-Poisson and vorticity streamfunction formulation, and a pseudospectral method. It is demonstrated that all these methods produce spurious, nonphysical vortices of the type described by Brown and Minion for a Godunov projection method (J. Comput. Phys. 121, 1995) when the flow is sufficiently under-resolved. The occurrence of these artifacts appears to be due to a nonlinear effect in which the truncation error of the difference method initiates a vortex instability in the computed flow. The implications of this study for adaptive mesh refinement strategies are also discussed. (C) 1997 Academic Press. RI Minion, Michael/B-2235-2008 SN 0021-9991 PD DEC PY 1997 VL 138 IS 2 BP 734 EP 765 DI 10.1006/jcph.1997.5843 UT WOS:000072215600020 ER PT J AU Fabietti, LM Trivedi, R AF Fabietti, LM Trivedi, R TI Development of interface morphologies in the tert butyl alcohol-water system SO JOURNAL OF CRYSTAL GROWTH AB The process of interface pattern formation in a complex crystal structure is examined through directional solidification experiments in the tert butyl alcohol (TEA) - water system. The transition from a planar interface to cellular and needle morphologies with increasing velocity is examined. The anisotropic effects in the complex crystal structure have been shown to exhibit new features that have not been observed previously. The anisotropy effects have been found to preclude cell elimination and cell creation by the tip splitting processes, so that the wavelength of the cellular pattern is determined by the initial wavelength of perturbation on a planar interface. At higher velocities, a cellular structure is found to transform to a needle structure with highly faceted sides which stabilize the interface against sidebranch instability. The tip region of the needle morphology also exhibits a unique structure that resembles a fingernail, whose formation is governed by the anisotropic properties of the advancing interface. In this complex crystal structure, the growing planes are not symmetrical and the growth occurs preferentially only along specific orientations of the advancing interface which give rise to a fingernail morphology. The scaling law for the primary spacing and the variation of interface temperature with velocity have been found to show a behavior analogous to that for isotropic materials. SN 0022-0248 PD DEC PY 1997 VL 182 IS 1-2 BP 185 EP 197 DI 10.1016/S0022-0248(97)00321-7 UT WOS:A1997YJ71800024 ER PT J AU De Yoreo, JJ Land, TA Rashkovich, LN Onischenko, TA Lee, JD Monovskii, OV Zaitseva, NP AF De Yoreo, JJ Land, TA Rashkovich, LN Onischenko, TA Lee, JD Monovskii, OV Zaitseva, NP TI The effect of dislocation cores on growth hillock vicinality and normal growth rates of KDP {1 0 1} surfaces SO JOURNAL OF CRYSTAL GROWTH AB We present results from atomic force microscopy measurements on KDP {101} faces which show that over the range of supersaturations, 3% less than or equal to sigma less than or equal to 30%, the terrace widths on vicinal growth hillocks formed by dislocations are nearly independent of both supersaturation and dislocation structure, in contradiction to the predictions of simple BCF models. The data also show that, for Burgers vectors in excess of one unit step height, the dislocations generate hollow cores in accordance with theoretical predictions. Both analytical and numerical analyses are presented, which show that a model that takes into account the effect of these cores on the period of step rotation predicts a dependence of slope on supersaturation and Burgers vector, which is in good agreement with the experimental results. These calculations also show that the effect of the core perimeter on the step transit lime dominates the effect of reduced step velocity due to stresses near the core. Consequently, a simple analytical expression can be used to describe the slope even in the case of anistropic step kinetics. Finally, the results are used to explain the reproducible character of macroscopic growth rates and to rescale data on growth rate as a function of temperature and supersturation onto a single curve. SN 0022-0248 PD DEC PY 1997 VL 182 IS 3-4 BP 442 EP 460 DI 10.1016/S0022-0248(97)00358-8 UT WOS:000071041500026 ER PT J AU Rieke, PC AF Rieke, PC TI Application of Van Oss-Chaudhury-Good theory of wettability to interpretation of interfacial free energies of heterogeneous nucleation SO JOURNAL OF CRYSTAL GROWTH AB The Van Oss-Chaudhury-Good (VCG) theory of wettability is used to understand the role of hydrophilic and hydrophobic interfacial forces in promoting heterogeneous nucleation from solution-phase precipitation processes. The interfacial free energy of nucleation for heterogeneous processes is simply related to the relative nucleus-solvent and nucleus-surface areas and their individual interfacial free energies. VCG theory is used to extend this relationship to the individual surface free energies of the isolated phases. Surface free energies obtained from, for example, surface tension measurements and surface probe contact-angle measurements provide independent measure of the needed quantities. We use classical nucleation theory and VCG theory to connect the two types of experiments and allow prediction of how various types of surfaces may induce the heterogeneous nucleation in various solvents. A variety of examples are discussed that illuminate the important surface properties relevant to heterogeneous nucleation. This approach allows a rational design of surfaces to either promote or inhibit precipitate formation. SN 0022-0248 PD DEC PY 1997 VL 182 IS 3-4 BP 472 EP 484 DI 10.1016/S0022-0248(97)00357-6 UT WOS:000071041500029 ER PT J AU Tu, JF Lankalapalli, KN Gartner, M Leong, KH AF Tu, JF Lankalapalli, KN Gartner, M Leong, KH TI On-line estimation of laser weld penetration SO JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME AB High-power CO2 laser welding has been widely used in the industry because of its high productivity and excellent weld quality. In order to tap the potential of this process completely, it is important to have on-line weld quality inspection methods to improve the process productivity and reliability by achieving 100 percent weld inspection. Weld penetration is one of the most important factors critical to the quality of a laser weld. However, it is very difficult to directly measure the extent of penetration without sectioning the workpiece. In th is paper a model-based penetration depth estimation technique suitable for the production environment is developed The proposed model relates the temperature measured on the bottom surface of the workpiece, weld bead width, laser beam power and welding speed to penetration depth. The closed-loop depth estimator combines the model and a model-error compensator to compensate for the uncertainty in the measurement of the laser power and absorptivity. Other effects considered are the averaging due to the finite size of the sensor delay based on the sensor location and the process and sensor dynamics. Several bend-on-plate and butt welds were made on low carbon steel plates to validate the static process models and the depth estimation scheme. Temperatures on the bottom surface of the workpiece during welding were measured using infrared thermocouples. The welds were sectioned longitudinally to obtain the penetration profile. The penetration profiles estimated by the depth estimator matched satisfactorily with the measured penetration profiles. The results validate the capability of the proposed depth estimator to estimate penetration depth and its ability to trace the dynamic changes in penetration depth. SN 0022-0434 PD DEC PY 1997 VL 119 IS 4 BP 791 EP 801 DI 10.1115/1.2802392 UT WOS:000071079500024 ER PT J AU Parker, GG Eisler, GR Robinett, RD Feddema, JT AF Parker, GG Eisler, GR Robinett, RD Feddema, JT TI Optimal trajectories for flexible-link manipulator slewing using recursive quadratic programming: Experimental verification SO JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME AB Experimental verification of minimum time, straight-line tracking using a two-link planar flexible robot is presented Previously reported minimum-time angle histories are precompensated to account for joint servo-actuator dynamics. Using the precompensated joint commands, the optimal joint angles are tracked with such fidelity that the tip tracking error is less than 1.8 percent of the tip travel distance. SN 0022-0434 PD DEC PY 1997 VL 119 IS 4 BP 833 EP 836 DI 10.1115/1.2802400 UT WOS:000071079500032 ER PT J AU Tilinin, IS Jablonski, A Zemek, J Hucek, S AF Tilinin, IS Jablonski, A Zemek, J Hucek, S TI Escape probability of signal photoelectrons from non-crystalline solids: influence of anisotropy of photoemission SO JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA AB The escape probability of photoelectrons as a function of depth of origin has been studied experimentally, analytically and by the Monte Carlo (MS) technique. The depth distribution function (DDF) describing the probability for an electron emitted at a certain depth to leave a surface without being scattered inelastically has been obtained by solving a kinetic equation in the transport approximation. The analytically derived DDF is a universal function of the ratio of the inealstic to the transport mean free paths and the asymmetry parameter. In the directions of minima of the angular distribution, this function is no longer exponential, but it may be essentially nonmonotonic, reaching its maximum value at the depth comparable with the inelastic mean free path. The maximum value of the DDF exceeds its surface value by about 50% for the asymmetry parameter being equal to 2 in the emission directions close to that of X-ray propagation. Under the same conditions, the mean escape depth of electrons may be several times larger than the value predicted by the usual XPS formalism. Such behaviour of the escape probability is explained by elastic scattering of photoelectrons. The solution to the kinetic equation for a uniform target is generalized for a sample with an arbitrary depth profile and depth-dependent elastic and inelastic scattering cross-sections under the condition of the ratio of the inelastic to the transport mean free paths being independent of depth. Analytical formulas for the photoelectron yield from overlayer/substrate structure have been derived and studied in detail. The analytical predictions are compared with the experimental and Monte Carlo simulation data obtained for aluminium oxide/aluminium specimen. A satisfactory agreement is observed between the experimental and theoretical results. (C) 1997 Elsevier Science B.V. (C) 1997 Elsevier Science B.V. RI Zemek, Josef/G-6203-2014 SN 0368-2048 PD DEC PY 1997 VL 87 IS 2 BP 127 EP 140 DI 10.1016/S0368-2048(97)00086-8 UT WOS:000071230800004 ER PT J AU Kinoshita, CM Turn, SQ Overend, RP Bain, RL AF Kinoshita, CM Turn, SQ Overend, RP Bain, RL TI Power generation potential of biomass gasification systems SO JOURNAL OF ENERGY ENGINEERING-ASCE AB Biomass has the potential to contribute a significant portion of the electricity consumed in industrialized nations and a major share of the power mix in developing countries. In addition to providing an alternative to fossil-fuel-based energy and creating new markets for agriculture, a renewable resource like biomass used in a sustainable fashion facilitates closure of the carbon cycle. To realize these benefits, particularly in the shadow of uncertainties cast by deregulation and recent changes in federal energy and agricultural policies, biomass power systems must be competitive with incumbent power-generation technologies in terms of generation efficiency and overall cost. Anticipated performance and cost of biomass-based integrated gasification, combined-cycle power systems are discussed. The electric power that can be generated worldwide using existing biomass resources (primarily crop residues and wastes) and the potential amount that could be generated from crops grown specifically for electricity generation are projected. Technical and economic obstacles that must be overcome before advanced biomass-power systems based on aeroderivative turbines or fuel cells can become fully commercial are identified. Research, development, and demonstration efforts under way or being planned to overcome those obstacles are described; developments in a major biomass gasification demonstration project taking place in Hawaii under the auspices of the U.S. Department of Energy and the State of Hawaii are detailed. OI Overend, Ralph/0000-0002-5442-0890 SN 0733-9402 PD DEC PY 1997 VL 123 IS 3 BP 88 EP 99 DI 10.1061/(ASCE)0733-9402(1997)123:3(88) UT WOS:A1997YG70500002 ER PT J AU Abraham, MM Annamalai, K Claridge, DE AF Abraham, MM Annamalai, K Claridge, DE TI Optimization of the storage process for a cool thermal storage system SO JOURNAL OF ENERGY RESOURCES TECHNOLOGY-TRANSACTIONS OF THE ASME CT AIAA Thermophysics / ASME Heat Transfer Conference CY JUN 19-23, 1994 CL COLORADO SPRINGS, COLORADO SP AIAA, Amer Soc Mech Engineers AB The storage process for a static-water ice-on-coil cool thermal storage system is difficult to model analytically based on the dynamic behavior of ice production. Systems that utilize a vapor compression cycle, with the tank acting as an evaporator, further complicate an analytical model due to the two-phase heat transfer throughout the storage tank. This analysis presents a simplified model of the storage process for a static-water ice-on-coil storage tank acting as an evaporator in a vapor-compression cycle. Specifically, the storage process is optimized by minimizing the amount of compressor work required to freeze water at 0 degrees C. Optimization variables are refrigerant evaporating temperatures and tank heat exchanger sizing. The dynamics of ice production and two-phase heat transfer are simplified by assuming the overall hear transfer coefficient remains constant throughout the storage process. An average value for the overall hear transfer coefficient may be substituted and still provide useful results. A second law analysis utilizing the irreversibility developed during cool storage is also presented, The model is then used in side-by-side comparisons of compressor work, tank heat exchanger efficiency, and irreversibility as functions of evaporating temperature, for several heat exchanger sizes. SN 0195-0738 PD DEC PY 1997 VL 119 IS 4 BP 236 EP 241 DI 10.1115/1.2794996 UT WOS:000071322400004 ER PT J AU Wang, SB Cowan, JH Rose, KA Houde, ED AF Wang, SB Cowan, JH Rose, KA Houde, ED TI Individual-based modelling of recruitment variability and biomass production of bay anchovy in mid-Chesapeake Bay SO JOURNAL OF FISH BIOLOGY CT Fisheries-Society-of-the-British-Isles Annual Symposium on Ichthyoplankton Ecology CY JUL 08-11, 1997 CL GALWAY, IRELAND SP Fisheries Soc Brit Isles AB Production of bay anchovy Anchovy mitchilli is highest in the larval and juvenile stages. The interplay between vital rates, stage durations, prey resources, and anchovy abundance ultimately determines the relative magnitude of recruitment (which in the model varies by about three-fold) and of stage-specific production. Changes in adult seasonal spawning patterns that increase the number of larval survivors result in only a slight increase in overall production due to density-dependent decreases in growth rates of later life stages. Bay anchovy in the mid-Chesapeake Bay may reach a compensatory threshold during late summer-autumn as fish growth is affected by competition for food resources. Density dependence in the population is evident in the relationships between spawner-recruit, size-recruit, and production of larval or juvenile to young-of-the-year life stages. Density-dependent growth acts differentially upon the early life stage that exceeds the compensatory threshold in any given year, due either to environmental variability or population size, or both. This could explain partially the relatively low recruitment variability observed for this anchovy. (C) 1997 The Fisheries Society of the British Isles. RI Houde, Edward/D-8498-2012; Wang, Shyh-Bin/C-6141-2017 SN 0022-1112 PD DEC PY 1997 VL 51 SU A BP 101 EP 120 DI 10.1111/j.1095-8649.1997.tb06095.x UT WOS:000071446100006 ER PT J AU Prager, S Abdou, M Baldwin, D Briggs, R Neilson, GH Simonen, T AF Prager, S Abdou, M Baldwin, D Briggs, R Neilson, GH Simonen, T TI Report from the planning workshop for the fusion energy sciences program SO JOURNAL OF FUSION ENERGY RI Abdou, Mohamed/F-4691-2013 SN 0164-0313 PD DEC PY 1997 VL 16 IS 4 BP 299 EP 305 DI 10.1023/A:1021890318808 UT WOS:000071368100001 ER PT J AU Perkins, LJ AF Perkins, LJ TI Complexity and availability for fusion power plants: The potential advantages of inertial fusion energy SO JOURNAL OF FUSION ENERGY AB Probably the single largest advantage of the inertial route to fusion energy (IFE) is the perception that its power plant embodiments could achieve acceptable capacity factors. This is a result of its relative simplicity, the decoupling of the driver and reactor chamber, and the potential to employ thick liquid walls. We examine these issues in terms of the complexity, reliability, maintainability and, therefore, availability of both magnetic and inertial fusion power plants and compare these factors with corresponding scheduled and unscheduled outage data from present day fission experience. We stress that, given the simple nature of a fission core, the vast majority of unplanned outages in fission plants are due to failures outside the reactor vessel itself. Given we must be prepared for similar outages in the analogous plant external to a fusion power core, this puts severe demands on the reliability required of the fusion core itself. We indicate that such requirements can probably be met for IFE plants. We recommend that this advantage be promoted by performing a quantitative reliability and availability study for a representative IFE power plant and suggest that databases are probably adequate for this task. SN 0164-0313 PD DEC PY 1997 VL 16 IS 4 BP 307 EP 316 DI 10.1023/A:1021842402879 UT WOS:000071368100002 ER PT J AU Peerenboom, JP Hanson, ME Huddleston, JR Wolsko, TD AF Peerenboom, JP Hanson, ME Huddleston, JR Wolsko, TD TI Economic impacts on the United States of siting decisions for the International Thermonuclear Experimental Reactor SO JOURNAL OF FUSION ENERGY AB This paper presents the results of a study that examines and compares the probable short-term economic impacts of the International Thermonuclear Experimental Reactor (ITER) on the United States (U.S.) if (1) ITER were to be sited in the U.S., or (2) ITER were to be sited in one of the other countries that, along with the U.S., is currently participating in the ITER program. Life-cycle costs associated with ITER construction, operation, and decommissioning are analyzed to assess their economic impact. A number of possible U.S. host and U.S. non-host technology and cost-sharing arrangements with the other ITER Parties are examined, although cost-sharing arrangements and the process by which the Parties will select a host country and an ITER site remain open issues. Both national and local/regional economic impacts, as measured by gross domestic product, regional output, employment, net exports, and income, are considered. These impacts represent a portion of the complex, interrelated set of economic considerations that characterize U.S. host and U.S. non-host participation in ITER. A number of other potentially important economic and noneconomic considerations are discussed qualitatively. SN 0164-0313 PD DEC PY 1997 VL 16 IS 4 BP 317 EP 360 DI 10.1023/A:1021894419717 UT WOS:000071368100003 ER PT J AU Feldman, WC Habbal, SR Hoogeveen, G Wang, YM AF Feldman, WC Habbal, SR Hoogeveen, G Wang, YM TI Experimental constraints on pulsed and steady state models of the solar wind near the Sun SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS AB Ulysses observations of the high-latitude solar wind were combined with Spartan 201 observations of the corona to investigate the nature and extent of uncertainties in our knowledge of solar wind structure near the Sun. In addition to uncertainties stemming from the propagation of errors in density profiles inferred from coronagraph observations [see, e.g., Lallement et al., 1986], an assessment of the consequences of choosing different analysis assumptions reveals very large, fundamental uncertainties in our knowledge of even the basics of coronal structure near the Sun. In the spirit of demonstrating the nature and extent of these uncertainties we develop just one of a generic class of explicitly time-dependent and filamentary models of the corona that is consistent with the Ulysses and Spartan 201 data. This model provides a natural explanation for the radial profiles of both the axial ratios and apparent radial speeds of density irregularities measured at radial distances less than 10 R-S using the interplanetary scintillation technique. SN 0148-0227 PD DEC 1 PY 1997 VL 102 IS A12 BP 26905 EP 26918 DI 10.1029/97JA02436 UT WOS:A1997YJ88800003 ER PT J AU Lapenta, G Brackbill, JU AF Lapenta, G Brackbill, JU TI A kinetic theory for the drift-kink instability SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS AB We have developed a linear two-dimensional kinetic theory, which is motivated by recent results for the drift-kink instability. The theory predicts plasma instability for large values of ion-electron temperature ratios. T-i/T-e, moderate drift speeds, and large ion-electron mass ratios, m(i)/m(e), corresponding to conditions in the near-Earth region of the magnetotail neutral sheet. The growth rate predicted by the theory is in good agreement with nonlinear plasma simulations (but the mode structure is not), including linear growth rates obtained with an implicit, electromagnetic simulation with realistic ion-electron mass ratio. OI Lapenta, Giovanni/0000-0002-3123-4024 SN 0148-0227 PD DEC 1 PY 1997 VL 102 IS A12 BP 27099 EP 27108 DI 10.1029/97JA02140 UT WOS:A1997YJ88800016 ER PT J AU Gary, SP Wang, J Winske, D Fuselier, SA AF Gary, SP Wang, J Winske, D Fuselier, SA TI Proton temperature anisotropy upper bound SO JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS AB The electromagnetic proton cyclotron instability and the mirror instability are driven by the proton temperature anisotropy T-perpendicular to p/T-parallel to p > 1, where perpendicular to and parallel to denote directions relative to the background magnetic field. Linear theory and one-dimensional hybrid simulations imply that the former mode grows more rapidly over 0.05 less than or equal to beta(parallel to p) less than or equal to 5 and that wave-particle scattering by its enhanced fluctuations imposes an upper bound on the temperature anisotropy of the form T-perpendicular to p/T-parallel to p - 1 = S-p/beta(parallel to p)alpha(p) where beta(parallel to p) = 8 pi n(p)T(parallel to p)/B-o(2) and B-o is the background magnetic field. Here S-p and alpha(p) are fitting parameters, and 0.4 less than or similar to alpha(p) less than or similar to 0.5. This paper describes results from more general two-dimensional hybrid simulations, which permit both instabilities to grow simultaneously. These simulations confirm the one-dimensional results on the initial domain 0.05 less than or equal to beta(parallel to p) similar or equal to 5; enhanced fluctuations display the properties of the proton cyclotron instability and alpha(p) similar or equal to 0.4. On this domain the two-dimensional simulations also yield an upper bound for the fluctuating field energy density of the form \delta B\(2)/B-o(2) = Sigma k\delta B-k\(2)/B-o(2) = S-B beta(parallel to p)(alpha B) with fitting parameter 0.5 less than or similar to alpha(B) less than or similar to 1. The simulations on the initial domain 10 less than or equal to beta(parallel to p) less than or equal to 100 show spectral characteristics of both instabilities and exhibit a more stringent bound on the proton anisotropy, in agreement with observations in the terrestrial magnetosheath. PD DEC 1 PY 1997 VL 102 IS A12 BP 27159 EP 27169 DI 10.1029/97JA01726 UT WOS:A1997YJ88800022 ER PT J AU Falk, JE LopezCardona, E AF Falk, JE LopezCardona, E TI The surgical separation of sets SO JOURNAL OF GLOBAL OPTIMIZATION AB Given a pair of finite disjoint sets A and B in R-n, a fundamental problem with many important applications is to efficiently determine a hyperplane H(omega, lambda) which separates these sets when they are separable, or 'nearly' separates them when they are not. We seek a hyperplane which minimizes a natural error measure in the latter case, and so will 'surgically' separate the sets. When the sets are separable in a strong sense, we show that the problem is a convex program with a unique solution, which has been investigated by others. Using the KKT conditions, we improve on an existing algorithm. When the sets are not separable, the problem is nonconvex, generally with proper local solutions, and we solve an equivalent problem by Branch and found. Numerical results are presented. SN 0925-5001 PD DEC PY 1997 VL 11 IS 4 BP 433 EP 462 DI 10.1023/A:1008284015704 UT WOS:A1997YF22800006 ER PT J AU Schmidt, DM George, JS Penttila, SI Caprihan, A Fukushima, E AF Schmidt, DM George, JS Penttila, SI Caprihan, A Fukushima, E TI Diffusion imaging with hyperpolarized He-3 gas SO JOURNAL OF MAGNETIC RESONANCE AB We used MRI of hyperpolarized He-3 to demonstrate some novel aspects of gas diffusion, Two different techniques were used, First, a slice was burned into a one-dimensional image by inverting the spins in the slice and diffusion was studied by measuring the magnetization as it filled the depleted slice. A diffusion coefficient was determined by the fit of these data, Second, one-dimensional diffusion images were made using a Stejskal-Tanner PGSE method, This was done with and without a temperature gradient present, showing that the effect of temperature can be dynamically monitored by such diffusion images. (C) 1997 Academic Press. OI Fukushima, Eiichi/0000-0003-1670-5884 SN 1090-7807 PD DEC PY 1997 VL 129 IS 2 BP 184 EP 187 DI 10.1006/jmre.1997.1258 UT WOS:000071805300010 ER PT J AU Yang, JP Silks, L Wu, RL Isern, N Unkefer, C Kennedy, MA AF Yang, JP Silks, L Wu, RL Isern, N Unkefer, C Kennedy, MA TI Improvements for measuring H-1-H-1 coupling constants in DNA via new Stripe-COSY and superstripe-COSY pulse sequences combined with a novel strategy of selective deuteration SO JOURNAL OF MAGNETIC RESONANCE AB Three bond proton-proton vicinal coupling constants are of potential value for analyzing sugar conformations in DNA. However, self-cancellation in antiphase cross peaks and modulation of peak splittings by transverse cross relaxation can alter the apparent coupling constants such that they do not accurately reflect the sugar conformations, Transverse cross relaxation is most effective between strongly coupled geminal proton pairs. Here we report the use of stereospecific deuteration at the H2 " position in the A5 and A6 residues in the 12 base pair DNA sequence [d(CGCGAATTCGCG)2] as a means of investigating the effect of transverse cross relaxation on P.E.COSY type cross peaks, Deuteration of the H2 " proton is expected to reduce the transverse cross relaxation rate by the square of ratio of the proton to deuteron gyromagnetic ratios, i.e., by a factor of 42. Additionally, a striking eight-to ninefold increase in the signal intensity was observed for cross peaks involving the remaining H2' proton resulting from diminished dipolar relaxation, Further improvements in signal-to-noise ratio were realized by collecting P.E.COSY spectra in strips, using an experiment referred to as stripe-COSY, employing selective excitation pulses which reduced the number of required t(1) increments by a factor of four, A final improvement was achieved by employing selective time-shared homonuclear decoupling during the acquisition period, in an experiment referred to as superstripe-COSY, to collapse splittings due to passive couplings. Collectively, these approaches provide P.E.COSY-type spectra with two to three orders of magnitude increased sensitivity per unit time and that are relatively free from artifacts. (C) 1997 Academic Press. RI Isern, Nancy/J-8016-2013; OI Isern, Nancy/0000-0001-9571-8864 SN 1090-7807 PD DEC PY 1997 VL 129 IS 2 BP 212 EP 218 DI 10.1006/jmre.1997.1261 UT WOS:000071805300014 PM 9441887 ER PT J AU Lewis, LH Panchanathan, V Wang, JY AF Lewis, LH Panchanathan, V Wang, JY TI Technical magnetic properties of melt-spun (Nd1-xPrx)(2)Fe14B at low temperature SO JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS AB The spin-reorientation temperatures T-s and technical magnetic properties (coercivity H-ei and energy product (BH)(max)) of isotropic and aligned compacts of the pseudoternary melt-spun compound (Nd1-xPrx)Fe14B (0 less than or equal to x less than or equal to 0.52) have been studied as a function of temperature for 10 K less than or equal to T less than or equal to 150 K. Results measured on thermomechanically processed ('die-upset') samples are included for comparative purposes. Lattice parameters were measured with transmission synchrotron X-ray diffraction to verify the nominal compositions, and grain size determined by peak-broadening confirmed that these materials are nanoscaled. The spin-reorientation temperatures decrease with increasing x and are Found to be significantly lower than their bulk-literature counterparts. Both the coercivity and the energy product of the isotropic compacts decrease with increasing temperature; no anomaly in either property is found at T-s. The relative decrease in a technical magnetic property from its value at 10 K becomes smaller with increased Pr-content. The substitution of only a few atomic percent of Pr for Nd causes the coercivity to decrease sharply from its Pr-free value; the coercivity gradually recovers as increasing amounts of Pr art substituted into the lattice. (C) 1997 Elsevier Science B.V. All rights reserved. SN 0304-8853 PD DEC PY 1997 VL 176 IS 2-3 BP 288 EP 296 DI 10.1016/S0304-8853(97)00648-3 UT WOS:000071396800028 ER PT J AU Anderson, TS Magruder, RH Kinser, DL Wittig, JE Zuhr, RA Thomas, DK AF Anderson, TS Magruder, RH Kinser, DL Wittig, JE Zuhr, RA Thomas, DK TI Ag:Sb and Sb:Ag implantations into high purity silica SO JOURNAL OF MATERIALS RESEARCH AB Silica composites containing nanometer dimension colloids have been fabricated by implantation of Ag ions followed by Sb ions, and by implantation of Sb ions followed by Ag ions.; Doses for the sequential element implantations were in ratios of 9:3 Ag:Sb and 3:9 Sb:Ag with the total dose held constant al 12 x 10(16) ions/cm(2), Energies of implantation were 305 keV for the Ag ions and 320 keV for the Sb ions, Single element colloids were also fabricated by implantation of Ag or Sb using the same nominal dose and implantation energy of the sequential implantations. Approximately spherical particles were formed in all implanted samples, Microstructures of the nanoclusters in the various samples were markedly different, Selected area diffraction techniques revealed that alloyed phases of Ag-Sb were formed in same of the sequential implantations. The microstructure and the optical response of the nanocluster glass composites were found Co be strongly dependent upon the order of the ion species implanted. The optical spectra of the 3:9 Sb:Ag sample displays two resonance peaks indicative of a Ag resonance peak and a resonance peak of an alloyed phase o Ag-Sb, Optical spectra for the 9:3 AE:Sb sample displays two broad absorption peaks indicative of coated particles. SN 0884-2914 PD DEC PY 1997 VL 12 IS 12 BP 3316 EP 3321 DI 10.1557/JMR.1997.0436 UT WOS:A1997YJ23800021 ER PT J AU Macnaughton, SJ Jenkins, TL Wimpee, MH Cormier, MR White, DC AF Macnaughton, SJ Jenkins, TL Wimpee, MH Cormier, MR White, DC TI Rapid extraction of lipid biomarkers from pure culture and environmental samples using pressurized accelerated hot solvent extraction SO JOURNAL OF MICROBIOLOGICAL METHODS AB Lipid biomarker analysis is a quantitative and sensitive method for the in situ analysis of microbial communities in environmental samples (e.g. soil, water, air). The one-phase modified Bligh and Dyer solvent extraction is a commonly used method for obtaining phospholipid fatty acid biomarkers used in such community analysis. This method, however, is relatively labor intensive and slow, often taking up to 24 h for the initial extraction. Using a pressurized hot solvent extractor, we have been able to extract lipid biomarkers from selected vegetative and/or sporulated biomass (Escherichia coli, Staphylococcus aureus, Mycobacterium fortuitum, Bacillus subtilis, Saccharomyces cerevisiae and Aspergillus niger) as well as from environmental samples collected from water, soil and air. Depending on sample type, the automated extraction procedure took similar to 35-45 min per sample. Compared to the modified Bligh and Dyer extraction, phospholipid fatty acid lipid yields obtained using the pressurized hot solvent extraction were not significantly different for the vegetative biomass or water and soil samples (P>0.05), but were significantly higher for the spores and the airborne biomass (P<0.05 for both sample types). The advantage of using accelerated hot solvent extraction is that by increasing the speed and decreasing the labor involved, pressurized hot solvent extraction should enable the rapid and improved extraction of lipids from large numbers of environmental samples providing data essential for total microbial community analysis. (C) 1997 Elsevier Science B.V. SN 0167-7012 PD DEC PY 1997 VL 31 IS 1-2 BP 19 EP 27 DI 10.1016/S0167-7012(97)00081-X UT WOS:000071687000003 ER PT J AU Santos, A De Solorzano, CO Vaquero, JJ Pena, JM Malpica, N Del Pozo, F AF Santos, A De Solorzano, CO Vaquero, JJ Pena, JM Malpica, N Del Pozo, F TI Evaluation of autofocus functions in molecular cytogenetic analysis SO JOURNAL OF MICROSCOPY-OXFORD AB This work describes a systematic evaluation of several autofocus functions used for analytical fluorescent image cytometry studies of counterstained nuclei. Focusing is the first step in the automatic fluorescence in situ hybridization analysis of cells. Thirteen functions have been evaluated using qualitative and quantitative procedures, For the last of these procedures a figure-of-merit (FOM) is defined and proposed. This new FOM takes into account five important features of the focusing function. Our results show that functions based on correlation measures have the best performance for this type of image. RI Ortiz de Solorzano, Carlos/G-3278-2010; Vaquero, Juan Jose/D-3033-2009; Santos, Andres/C-4012-2009; DEL POZO GUERRERO, FRANCISCO/H-6668-2015; Malpica, Norberto/I-2090-2015 OI Ortiz de Solorzano, Carlos/0000-0001-8720-0205; Vaquero, Juan Jose/0000-0001-9200-361X; Santos, Andres/0000-0001-7423-9135; DEL POZO GUERRERO, FRANCISCO/0000-0001-9919-9125; Malpica, Norberto/0000-0003-4618-7459 SN 0022-2720 PD DEC PY 1997 VL 188 BP 264 EP 272 DI 10.1046/j.1365-2818.1997.2630819.x PN 3 UT WOS:000071375100008 PM 9450330 ER PT J AU Arvestad, L Bruno, WJ AF Arvestad, L Bruno, WJ TI Estimation of reversible substitution matrices from multiple pairs of sequences SO JOURNAL OF MOLECULAR EVOLUTION AB We present a method for estimating the most general reversible substitution matrix corresponding to a given collection of pairwise aligned DNA sequences. This matrix can then be used to calculate evolutionary distances between pairs of sequences in the collection. If only two sequences are considered, our method is equivalent to that of Lanave et al. (1984). The main novelty of our approach is in combining data from different sequence pairs. We describe a weighting method for pairs of taxa related by a known tree that results in uniform weights for all branches. Our method for estimating the rate matrix results in fast execution times, even on large data sets, and does not require knowledge of the phylogenetic relationships among sequences. In a test case on a primate pseudogene, the matrix we arrived at resembles one obtained using maximum likelihood, and the resulting distance measure is shown to have better linearity than is obtained in a less general model. RI Arvestad, Lars/F-9892-2011; OI Arvestad, Lars/0000-0001-5341-1733 SN 0022-2844 PD DEC PY 1997 VL 45 IS 6 BP 696 EP 703 DI 10.1007/PL00006274 UT WOS:000071307200014 PM 9419247 ER PT J AU Northrup, FJ Bethardy, GA Macdonald, RG AF Northrup, FJ Bethardy, GA Macdonald, RG TI Infrared absorption spectroscopy of HNC in the region 2.6 to 3.1 mu m SO JOURNAL OF MOLECULAR SPECTROSCOPY AB The HNC molecule was generated by the reaction of translationally hot H atoms with either CICN or BrCN. The energetically rich HNC products were probed by time-resolved infrared laser absorption spectroscopy. This allowed for the spectroscopic analysis of 16 vibrational bands in the wavelength region 2.6 to 3.1 mu m and the identification of 8 new bands for HNC. The dependence of G(nu), B-nu, and D-nu was fit to appropriate polynomials in the vibrational quantum numbers and l. No bands were identified in which the bend, nu(2), and CN stretch, nu(3), were simultaneously excited so that the spectroscopic constants depending on the interaction between these two vibrations could not be experimentally measured. Nevertheless, the observations of this work allow for an almost complete experimental determination of the quadratic spectroscopic constants of this simple but important molecule. (C) 1997 Academic Press. SN 0022-2852 PD DEC PY 1997 VL 186 IS 2 BP 349 EP 362 DI 10.1006/jmsp.1997.7464 UT WOS:000071803300015 ER PT J AU Marasinghe, GK Karabulut, M Ray, CS Day, DE Shumsky, MG Yelon, WB Booth, CH Allen, PG Shuh, DK AF Marasinghe, GK Karabulut, M Ray, CS Day, DE Shumsky, MG Yelon, WB Booth, CH Allen, PG Shuh, DK TI Structural features of iron phosphate glasses SO JOURNAL OF NON-CRYSTALLINE SOLIDS CT 14th University Conference on Glass Science CY JUN 17-20, 1997 CL LEHIGH UNIV, BETHLEHEM, PENNSYLVANIA SP Corning Inc, Amer Ceram Soc, Lehigh Valley Chapter, Lehigh Univ, Dept Mat Sci & Engn, Lehigh Univ, Mat Res Ctr, Natl Sci Fdn, Amer Ceram Soc HO LEHIGH UNIV AB The structures and valence states of iron ions in several iron phosphate glasses with batch compositions similar to 40Fe(2)O(3)-60P(2)O(5) (mol%) have been investigated using Mossbauer spectroscopy, X-ray absorption fine-structure spectroscopy (XAFS), X-ray photoelectron spectroscopy (XPS), differential thermal (DTA) and thermo-gravimetric (TGA) analysis and X-ray and neutron diffraction. Mossbauer spectra show that a redox equilibria corresponding to an Fe(II)/[Fe(II) + Fe(III)] ratio of 0.2-0.4 is reached under processing conditions described in this paper. Even though the valence state of iron ions in the glass appears to be insensitive to the oxygen content in the melting atmosphere, the Fe(II) content can be increased within the observed range of redox equilibria by increasing the partial pressure of a reducing gas in the melting atmosphere. Large amounts of Fe(II), Fe(II)/[Fe(II) + Fe(III)] greater than or equal to 0.4, appear to be detrimental to the glass-forming ability of the iron phosphate melts. The local structure of the iron phosphate glasses appears to be related to the short range structure of crystalline Fe-3(P2O7)(2) which consists of a network of (Fe3O12)(-16) clusters. These clusters consist of one iron(II) ion and two iron(III) ions in sixfold coordination with near-neighbor oxygen ions. The (Fe3O12)(-16) clusters are interconnected via (P2O7)(-4) groups. Compared to other phosphate glasses, the proposed structure for iron phosphate glasses contain a smaller number of P-O-P bonds, a feature which is believed to be responsible for the unusually good chemical durability of iron phosphate glasses. (C) 1997 Elsevier Science B.V. RI Booth, Corwin/A-7877-2008 SN 0022-3093 PD DEC PY 1997 VL 222 BP 144 EP 152 DI 10.1016/S0022-3093(97)90107-1 UT WOS:000071341000018 ER PT J AU Magruder, RH Weeks, RA Zuhr, RA Hensley, DK AF Magruder, RH Weeks, RA Zuhr, RA Hensley, DK TI Effects of MeV implanted boron on the optical properties of silica SO JOURNAL OF NON-CRYSTALLINE SOLIDS CT 14th University Conference on Glass Science CY JUN 17-20, 1997 CL LEHIGH UNIV, BETHLEHEM, PENNSYLVANIA SP Corning Inc, Amer Ceram Soc, Lehigh Valley Chapter, Lehigh Univ, Dept Mat Sci & Engn, Lehigh Univ, Mat Res Ctr, Natl Sci Fdn, Amer Ceram Soc HO LEHIGH UNIV AB Silica was implanted with B ions at 4 MeV with nominal doses of 0.1, 0.3, and 1.0 x 10(16) ions/cm(2). The optical absorption was measured from 2.7 to 6.2 eV. Bands at 5.85 and 5 eV are observed in the absorption spectra. The magnitude of the absorption increases with increasing dose. However the magnitude of the increase in absorption is not linear with dose with the lowest dose the most efficient on a per ion basis in creating defects which produce these two bands. The 1.0 x 10(16) sample was exposed to 5-eV KrF excimer irradiation with a fluence of 150 mJ/cm(2) per pulse for pulse totals of 1.5, 15 and 30 J/cm(2). Bleaching of the 5- and 5.85-eV bands is observed and is attributed to the bleaching of defects at 5, 5.5 and 5.85 eV. (C) 1997 Elsevier Science B.V. RI Hensley, Dale/A-6282-2016 OI Hensley, Dale/0000-0001-8763-7765 SN 0022-3093 PD DEC PY 1997 VL 222 BP 243 EP 249 UT WOS:000071341000031 ER PT J AU Sidebottom, DL Hruschka, MA Potter, BG Brow, RK AF Sidebottom, DL Hruschka, MA Potter, BG Brow, RK TI Structure and optical properties of rare earth-doped zinc oxyhalide tellurite glasses SO JOURNAL OF NON-CRYSTALLINE SOLIDS CT 14th University Conference on Glass Science CY JUN 17-20, 1997 CL LEHIGH UNIV, BETHLEHEM, PENNSYLVANIA SP Corning Inc, Amer Ceram Soc, Lehigh Valley Chapter, Lehigh Univ, Dept Mat Sci & Engn, Lehigh Univ, Mat Res Ctr, Natl Sci Fdn, Amer Ceram Soc HO LEHIGH UNIV AB Zinc tellurite glasses appear to be excellent candidates for hosting rare earth ions since they provide a low phonon energy environment to minimize non-radiative losses as well as possessing good chemical durability and optical properties. The optical behavior of the rare earth ion can be manipulated by modifying its local environment in the glass host. We report measurements of the emission lifetime, optical absorption, and vibrational density of states of the glass system (ZnO)(x)(ZnF2)(y)(TeO2)(1-x-y) doped (0.1 mol%) with a series of rare earths. Phonon sideband spectroscopy has been successfully employed to probe vibrational structure in the immediate vicinity of the rare earth ion. We observe a significant increase in the emission lifetime (from similar to 150 mu s to 250 mu s) of Nd3+ with increasing fluorine substitution. (C) 1997 Elsevier Science B.V. SN 0022-3093 PD DEC PY 1997 VL 222 BP 282 EP 289 DI 10.1016/S0022-3093(97)90125-3 UT WOS:000071341000036 ER PT J AU Sidebottom, DL Green, PF Brow, RK AF Sidebottom, DL Green, PF Brow, RK TI Structural correlations in the ac conductivity of ion-containing glasses SO JOURNAL OF NON-CRYSTALLINE SOLIDS CT 14th University Conference on Glass Science CY JUN 17-20, 1997 CL LEHIGH UNIV, BETHLEHEM, PENNSYLVANIA SP Corning Inc, Amer Ceram Soc, Lehigh Valley Chapter, Lehigh Univ, Dept Mat Sci & Engn, Lehigh Univ, Mat Res Ctr, Natl Sci Fdn, Amer Ceram Soc HO LEHIGH UNIV AB The power law dispersion of the conductivity in most ion-containing oxide glasses appears to be universal. This universality indicates that no correspondence exists between the degree of non-Debye behavior and the microscopic structure of a glass host. Despite its universal frequency dependence, we demonstrate how the ac conductivity defines a special length scale, L, that represents average diffusional displacement of an ion per activated jump and which can be correlated to properties of the glass host. We compare this length scale to the inter-ionic spacing and demonstrate how both increase with decreasing ion concentration. Although there is much evidence for universality, we suggest that the conductivity exponent may in fact be influenced by the 'dimensionality' of the conduction process. (C) 1997 Elsevier Science B.V. SN 0022-3093 PD DEC PY 1997 VL 222 BP 354 EP 360 DI 10.1016/S0022-3093(97)00406-7 UT WOS:000071341000047 ER PT J AU Brow, RK Tallant, DR AF Brow, RK Tallant, DR TI Structural design of sealing glasses SO JOURNAL OF NON-CRYSTALLINE SOLIDS CT 14th University Conference on Glass Science CY JUN 17-20, 1997 CL LEHIGH UNIV, BETHLEHEM, PA SP Corning Inc, Amer Ceram Soc, Lehigh Valley Chapter, Lehigh Univ, Dept Mat Sci & Engn, Lehigh Univ, Mat Res Ctr, Natl Sci Fdn, Amer Ceram Soc HO LEHIGH UNIV AB Requirements for enhanced component performance and reliability have led to the development of novel glass compositions for a variety of hermetic sealing applications. The development of technologically useful glss compositions was based on an understanding of the relationships between the molecular-level glass structure and important physical properties. The properties of the alkaline earth aluminoborate glasses for lithium batteries are sensitive to changes in B-and Al-coordination number, characterized by solid state nuclear magnetic resonance (NMR) spectroscopy. In general, the most useful compositions have structures that are dominated by tetrahedral Band Al-sites. Mixed alkali aluminophosphate glasses were developed for aluminum electrical connectors. The properties of sodium aluminophosphate glasses depend on the O/P ratio and significant property changes (e.g. maxima in T-g and refractive index) occur when O/P exceeds the pyrophosphate limit at 3.5. Associated with these property changes is a decrease in the average Al-coordination number, from six to four, at O/P > 3.5. Raman spectroscopy provides additional information about the aluminophosphate network. Finally, zinc borophosphate glasses are developed for seals in flat panel displays. Boron-11 NMR shows that tetrahedral barons are preferred in xB(2)O(3)(1-x)(PO3)(2) and in yB(2)O(3)(1-y)Zn2P2O7 glasses for x < 0.4 and y < 0.2. Raman spectroscopy reveals the concomitant evolution from a phosphate to a borophosphate network with increasing x and y. (C) 1997 Elsevier Science B.V. SN 0022-3093 EI 1873-4812 PD DEC PY 1997 VL 222 BP 396 EP 406 DI 10.1016/S0022-3093(97)00382-7 UT WOS:000071341000053 ER PT J AU Saliger, R Bock, V Petricevic, R Tillotson, T Geis, S Fricke, J AF Saliger, R Bock, V Petricevic, R Tillotson, T Geis, S Fricke, J TI Carbon aerogels from dilute catalysis of resorcinol with formaldehyde SO JOURNAL OF NON-CRYSTALLINE SOLIDS AB Aqueous polycondensation of resorcinol with formaldehyde leads to organic gels the structure of which can be controlled by the reaction parameters. The amount of catalyst controls the size of the particles constituting the gel network. We could show that for very low catalyst concentrations in a high dilution of reactants, the particle growth can be further enhanced if the reaction temperature is kept low, and the gel time is prolonged. The resultant structure is largely affected by this treatment, producing particles with sizes of about 2 mu m and average pore sizes of up to 7 mu m Due to these coarse structures it is possible to dry these RF gels subcritically with very little shrinkage. The structure has been studied by nitrogen sorption, small angle X-ray scattering and acoustic sound propagation. The change of the elastic modulus caused by pyrolysis at around 1000 degrees C has been investigated. Mechanical properties of carbon aerogels are correlated with their electrical properties. The derived carbon aerogels have large specific surface areas, very little mesopore volume however, micron-sized macropores. (C) 1997 Elsevier Science B.V. SN 0022-3093 PD DEC PY 1997 VL 221 IS 2-3 BP 144 EP 150 DI 10.1016/S0022-3093(97)00411-0 UT WOS:000071297700004 ER PT J AU Lowdermilk, WH AF Lowdermilk, WH TI Inertial confinement fusion program at lawrence livermore national laboratory: The National Ignition Facility, inertial fusion energy, 100-1000 TW lasers, and the fast igniter concept SO JOURNAL OF NONLINEAR OPTICAL PHYSICS & MATERIALS AB The ultimate goal of worldwide research in inertial confinement fusion (ICF) is to develop fusion as an inexhaustible, economic, environmentally safe source of electric power. Following nearly thirty years of laboratory and underground fusion experiments, the next step toward this goal is to demonstrate ignition and propagating burn of fusion fuel in the laboratory. The National Ignition Facility (NIF) Project is being constructed at Lawrence Livermore National Laboratory (LLNL) for just this purpose. NIF Will use advanced Nd-glass laser technology to deliver 1.8 MJ of 0.35 mu m laser light in a shaped pulse, several nanoseconds in duration, achieving a peak power of 500 TW. A national community of U.S. laboratories is participating in this project, now in its final design phase. France and the United Kingdom are collaborating on development of required technology under bilateral agreements with the US. This paper presents key aspects of the laser design, and descriptions of principal laser and optical components. Follow-on development of lasers to meet the demands of an inertial fusion energy (IFE) power plant is reviewed. In parallel with the NIF Project and IFE developments, work is proceeding on ultrashort pulse lasers with peak power in the range of 100-1000 TW. A beamline on the Nova laser at LLNL recently delivered nearly 600 J of 1 mu m light in a 0.5 ps duration pulse, for a peak power in excess of a petawatt (10(15) W). This beamline, with advanced adaptive optics, will be capable of focused intensities in excess of 10(21) W/cm(2). Its primary purpose will be to test technological and scientific aspects of an alternate ignition concept, called the "Fast Igniter", that has the potential to produce higher fusion gain than conventional ICF. SN 0218-1991 PD DEC PY 1997 VL 6 IS 4 BP 507 EP 533 UT WOS:000072013800012 ER PT J AU Totemeier, TC Mariani, RD AF Totemeier, TC Mariani, RD TI Morphologies of uranium and uranium-zirconium electrodeposits SO JOURNAL OF NUCLEAR MATERIALS AB Uranium and uranium-zirconium electrodeposits produced in the Fuel Cycle Facility at Argonne National Laboratory-West were examined using standard metallurgical techniques. Substantial differences in the morphologies of the two types of deposits were observed. Samples from pure uranium deposits were comprised of chains of uranium crystals with a characteristic rhomboidal shape, while the morphologies of samples from deposits containing zirconium in excess of approximately 0.5 wt% showed more polycrystalline features. Zirconium was found to be present as a second, zirconium metal phase at or very near the uranium-zirconium dendrite surfaces. Higher collection efficiencies and total deposit weights were observed for the uranium-zirconium deposits; this performance increase is likely a result of better mechanical properties exhibited by the uranium-zirconium dendrite morphology. (C) 1997 Elsevier Science B.V. SN 0022-3115 PD DEC PY 1997 VL 250 IS 2-3 BP 131 EP 146 DI 10.1016/S0022-3115(97)00288-2 UT WOS:000071346300007 ER PT J AU Weber, WJ Ewing, RC Meldrum, A AF Weber, WJ Ewing, RC Meldrum, A TI The kinetics of alpha-decay-induced amorphization in zircon and apatite containing weapons-grade plutonium or other actinides SO JOURNAL OF NUCLEAR MATERIALS AB Zircon and apatite form as actinide host phases in several high-level waste forms and have been proposed as host phases for the disposition of excess weapons-grade Pu and other actinides. Additionally, closely-related structure types appear as actinide-bearing phases among the corrosion products of spent nuclear fuel and high-level waste glasses. Self-radiation damage from alpha-decay of the incorporated Pu or other actinides can affect the durability and performance of these actinide-bearing phases. For both zircon and apatite, these effects can be modeled as functions of storage time and repository temperature and validated by comparison with data from natural occurrences. Natural zircons and apatites, with ages up to 4 billion years, provide abundant evidence for their long-term durability because of their wide spread use in geochronology and fission-track dating. Detailed studies of natural zircons and apatites, Pu-238-containing zircon, a Cm-244-containing silicate apatite, and ion-irradiated zircon, natural apatite and synthetic silicate apatites provide a unique basis for the analysis of alpha-decay effects over broad time scales. Models for alpha-decay effects in zircon and apatite are developed that show alpha-decay of Pu and other actinides will lead to a crystalline-to-amorphous transformation in zircon, but not in apatite, under conditions typical of a repository, such as the Yucca Mountain site. (C) 1997 Elsevier Science B.V. RI Weber, William/A-4177-2008 OI Weber, William/0000-0002-9017-7365 SN 0022-3115 EI 1873-4820 PD DEC PY 1997 VL 250 IS 2-3 BP 147 EP 155 DI 10.1016/S0022-3115(97)00271-7 UT WOS:000071346300008 ER PT J AU Pareige, P Russell, KF Stoller, RE Miller, MK AF Pareige, P Russell, KF Stoller, RE Miller, MK TI Influence of long-term thermal aging on the microstructural evolution of nuclear reactor pressure vessel materials: an atom probe study SO JOURNAL OF NUCLEAR MATERIALS AB Atom probe field ion microscopy (APFIM) investigations of the microstructure of unaged (as-fabricated) and long-term thermally-aged (similar to 100 000 h at 280 degrees C) surveillance materials from commercial reactor pressure vessel steels were performed. This combination of materials and conditions permitted the investigation of potential thermal aging effects. This microstructural study focused on the quantification of the compositions of the matrix and carbides. The APFIM results indicate that there was no significant microstructural evolution after a long-term thermal exposure in weld, plate and forging materials. The matrix depletion of copper that was observed in weld materials was consistent with the copper concentration in the matrix after the stress relief heat treatment. The composition of cementite carbides aged for 100 000 h were compared to the Thermocalc (TM) prediction. The APFIM comparisons of materials under these conditions are consistent with the measured change in mechanical properties such as the Charpy transition temperature. (C) 1997 Elsevier Science B.V. RI Stoller, Roger/H-4454-2011; PAREIGE, Philippe/A-2588-2013 SN 0022-3115 PD DEC PY 1997 VL 250 IS 2-3 BP 176 EP 183 DI 10.1016/S0022-3115(97)00264-X UT WOS:000071346300012 ER PT J AU Huang, HC Ghoniem, N AF Huang, HC Ghoniem, N TI A swelling model for stoichiometric SiC at temperatures below 1000 degrees C under neutron irradiation SO JOURNAL OF NUCLEAR MATERIALS AB A simple phenomenological model for the saturation swelling below 1000 degrees C of neutron-irradiated silicon carbide (SiC) is presented in this paper. Under fast neutron irradiation, SiC is known to undergo volumetric expansion (swelling) which quickly saturates at a fast fluence of approximately 10(25) n/m(2) for irradiation temperatures below 1000 degrees C. A previous model due to Balarin attributes swelling to lattice dilation as a result of single point defects. We show in this paper that the experimentally observed linear temperature dependence of saturation swelling can be explained in terms of the formation and growth of small interstitial clusters, resulting directly from collision cascades initiated by energetic neutrons. These loops grow by absorption of mobile carbon interstitials and their composition is subject to stoichiometry constraints, requiring absorption of slower silicon interstitials. Because of cascade re-solution events, the density of loops decreases sharply with temperature as a result of overlap of cascades with larger size loops at higher temperatures. The average radius of these loops increases with temperature. Volumetric swelling is shown to obey a linear temperature dependence as a consequence of the strong decrease in density and the simultaneous increase in average radius, and to saturate with fluence. The model is shown to be consistent with experimental observations. In the temperature range below 500-600 degrees C, swelling seems to be dominated by single point defects, or defect clusters containing only a few atoms, in accordance with the explanation offered by Balarin. (C) 1997 Elsevier Science B.V. RI Huang, Hanchen/A-9323-2008; Ghoniem, Nasr/A-9799-2008 SN 0022-3115 PD DEC PY 1997 VL 250 IS 2-3 BP 192 EP 199 DI 10.1016/S0022-3115(97)00269-9 UT WOS:000071346300014 ER PT J AU Schneibel, JH Haines, JR Snead, LL Bloom, EE AF Schneibel, JH Haines, JR Snead, LL Bloom, EE TI Solid state bonding of beryllium to copper and vanadium using transition layers SO JOURNAL OF NUCLEAR MATERIALS AB Beryllium is a material under consideration for divertor surfaces in the international thermonuclear experimental reactor (ITER). Since Be itself is not a suitable structural material for constructing the divertor, it needs to be bonded to other materials with sufficiently high thermal conductivity, which at the same time satisfy structural requirements such as adequate strength and fracture toughness. Bonding of Be to other materials is usually accompanied by (a) mismatches in thermal expansion and/or (b) metallurgical incompatibilities. In an attempt to minimize the thermal expansion mismatch we employed Fe or Ni transition layers for the bonding of Be to a copper alloy by hot isostatic pressing. To alleviate the thermodynamic incompatibility between Be and most other metals, thin Ag foil (130 mu m) was used as a reaction barrier. Other experiments involved bonding Be (via an Ag reaction barrier) to a V-5Cr-5Ti (wt%) alloy. An Al-Be transition layer for bonding Be to a copper alloy was also explored. The microstructures of the interfaces were examined by optical and scanning electron microscopy. Shear tests carried out with Cu/Fe/Ag/Be and V/Ag/Be specimens indicated average room temperature shear strengths of 52 and 78 MPa, respectively. Fracture occurred usually at the Ag/Be interfaces, which were therefore the weakest link in the bonded specimens. (C) 1997 Elsevier Science B.V. SN 0022-3115 PD DEC PY 1997 VL 250 IS 2-3 BP 216 EP 222 DI 10.1016/S0022-3115(97)00254-7 UT WOS:000071346300016 ER PT J AU Miller, MK Russell, KF AF Miller, MK Russell, KF TI Atom probe characterization of copper solubility in the Midland weld after neutron irradiation and thermal annealing SO JOURNAL OF NUCLEAR MATERIALS AB An atom probe field ion microscopy characterization has been performed to determine the copper matrix concentration in a submerged are beltline weld of the Midland Unit 1 pressurized water reactor after 4 conditions: unirradiated, unirradiated and annealed for 168 h at 454 degrees C, neutron-irradiated in a test reactor to a fluence of 1.1 x 10(23) n m(-2) (E > 1 MeV) at a temperature of 288 degrees C, and neutron-irradiated and annealed for 168 h at 454 degrees C. Atom probe analysis of the unirradiated material revealed a substantial depletion of the copper in the matrix to 0.119 +/- 0.007 at% Cu from the bulk value of between 0.18 and 0.28 at% Cu. Annealing the unirradiated material produced intragranular copper-enriched precipitates and reduced the matrix copper level by similar to 25% to 0.088 +/- 0.012 at% Cu. Neutron irradiation also produced copper-enriched precipitates and reduced the matrix copper level by almost 50% over the stress relieved material to 0.058 +/- 0.008 at% Cu. Annealing the neutron-irradiated material reduced the matrix copper level further to 0.050 +/- 0.010+/-at% Cu. These results indicate that the annealing treatment coarsens the copper-enriched precipitates produced during neutron irradiation with a slight decrease in the matrix copper content. (C) 1997 Elsevier Science B.V. SN 0022-3115 PD DEC PY 1997 VL 250 IS 2-3 BP 223 EP 228 DI 10.1016/S0022-3115(97)00251-1 UT WOS:000071346300017 ER PT J AU Stabin, MG Kooij, PPM Bakker, WH Inoue, T Endo, K Coveney, J de Jong, R Minegishi, A AF Stabin, MG Kooij, PPM Bakker, WH Inoue, T Endo, K Coveney, J de Jong, R Minegishi, A TI Radiation dosimetry for indium-111-pentetreotide SO JOURNAL OF NUCLEAR MEDICINE AB We present radiation dose estimates for In-111-pentetreotide, Methods: Kinetic data were gathered in 10 subjects at two different sites. A compartmental model was used to fit the data, including retention, in three major organs and excretion. Results: The data were consistent for the subjects at both sites. The organ receiving the highest dose was the kidneys (0.52 mGy/MBq); the effective dose equivalent was 0.1 mSv/MBq, and the effective dose was 0.073 mSv/MBq. Conclusion: The results of this study provide the basis for evaluation of radiation safety of this drug. SN 0161-5505 PD DEC PY 1997 VL 38 IS 12 BP 1919 EP 1922 UT WOS:000071252800026 PM 9430470 ER PT J AU Faulkner, JS Wang, Y Stocks, GM AF Faulkner, JS Wang, Y Stocks, GM TI Coulomb energies in disordered alloys and improvements on the coherent potential approximation SO JOURNAL OF PHASE EQUILIBRIA CT TMS Annual Meeting CY FEB 12-16, 1995 CL LAS VEGAS, NV AB Order-N calculations of the electronic states of models of random substitutional Cu-Zn alloys have been carried out. By analyzing the results, new general features that are characteristic of the Coulomb energies of alloys have been discovered. This article shows how they compare with other models of alloys that have been discussed in the literature. The most important consequence of these calculations is the new insight that they give into the nature of the Coulomb energy in the density functional theory. RI Stocks, George Malcollm/Q-1251-2016 OI Stocks, George Malcollm/0000-0002-9013-260X SN 1054-9714 PD DEC PY 1997 VL 18 IS 6 BP 499 EP 508 DI 10.1007/BF02665803 UT WOS:A1997YK25400003 ER PT J AU Wang, CZ Ho, KM AF Wang, CZ Ho, KM TI Material simulations with tight-binding molecular dynamics SO JOURNAL OF PHASE EQUILIBRIA CT TMS Annual Meeting CY FEB 12-16, 1995 CL LAS VEGAS, NV AB Tight-binding molecular-dynamics has recently emerged as a useful method for atomistic simulation study of realistic materials. The method incorporates electronic structure calculation into molecular dynamics through an empirical tight-binding Hamiltonian and bridges the gap between ab initio molecular dynamics and simulations using empirical classical potentials. This article reviews some achievements and discusses some recent developments in materials simulations with tight-binding molecular dynamics. SN 1054-9714 PD DEC PY 1997 VL 18 IS 6 BP 516 EP 529 DI 10.1007/BF02665805 UT WOS:A1997YK25400005 ER PT J AU Chu, F Mitchell, TE Chen, SP Sob, M Siegl, R Pope, DP AF Chu, F Mitchell, TE Chen, SP Sob, M Siegl, R Pope, DP TI Phase stability and elasticity of C15 transition-metal intermetallic compounds SO JOURNAL OF PHASE EQUILIBRIA CT TMS Annual Meeting CY FEB 12-16, 1995 CL LAS VEGAS, NV AB First-principles quantum mechanical calculations based on the local-density-functional theory have been performed to study the electronic, physical, and metallurgical properties of C15 intermetallics MV2 (M = Zr, Hf, or Ta), The elastic constants of C15 HfV2 + Nb were measured by the resonant ultrasound spectroscopy technique, The phase stability of C15 HfV2 + Nb was studied by specific heat measurements and by TEM in a low-temperature specimen holder, The total energies and their lattice volume dependence were used to obtain the equilibrium lattice constants and bulk modulus, The band structures at the X-point near the Fermi level were employed to understand the anomalous temperature dependence of the shear modulus of the C15 intermetallics. It was found that the double degeneracy with a linear dispersion relation of electronic levels at the X-point near the Fermi surface is mainly responsible for the C15 anomalous elasticity. The density of states at the Fermi level, N(E-F), and the Fermi surface geometry were obtained to understand the low-temperature phase instability of C15 HfV2 and ZrV2 and the stability of C15 TaV2, It is proposed that the large N(E-F) and Fermi surface nesting are the physical reasons for the structural instability of the C15 HfV2 and ZrV2 at low temperatures, The relationship between the anomalous elasticity and structural instability of C15 HfV2 and ZrV2 are also discussed. RI Sob, Mojmir/D-1936-2012; Sob, Mojmir/G-6865-2011 SN 1054-9714 PD DEC PY 1997 VL 18 IS 6 BP 536 EP 543 DI 10.1007/BF02665807 UT WOS:A1997YK25400007 ER PT J AU Siegl, R Vitek, V Luzzi, DE Yan, M AF Siegl, R Vitek, V Luzzi, DE Yan, M TI Phase stability and grain boundary structure in the Cu-Bi system SO JOURNAL OF PHASE EQUILIBRIA CT TMS Annual Meeting CY FEB 12-16, 1995 CL LAS VEGAS, NV AB Cu-Bi system is a model system for studies of interfacial phenomena, such as segregation and segregation induced faceting, In previous studies it was found that there is a strong preference for Sigma = 3{111} - {111} type facets, and their atomic structure was successfully resolved by combining high-resolution electron microscopy and computer simulation using Finnis-Sinclair type interatomic potential, The resolved grain-boundary structure was examined using ab initio full-potential linear muffin-tin orbital method by calculating formation enthalpies of several (hypothetical) Cu-Bi compounds under pressure, It was found that there is no driving force for the ordered alloy formed at the boundary to grow into a three-dimensional phase and thus specific interfacial phases are formed in this system, The range of applicability of Finnis-Sinclair potential used in the previous studies was also investigated by comparison with ab initio calculations, and it was shown that the potential is entirely appropriate when Cu concentration is higher than about 66 at.%. In those cases the Cu-Bi system exhibits metallic behavior. SN 1054-9714 PD DEC PY 1997 VL 18 IS 6 BP 562 EP 566 DI 10.1007/BF02665812 UT WOS:A1997YK25400012 ER PT J AU Althoff, JD Johnson, DD AF Althoff, JD Johnson, DD TI The electronic origins of atomic short-range order in disordered fcc Cu-Ni-Zn ternary alloys SO JOURNAL OF PHASE EQUILIBRIA CT TMS Annual Meeting CY FEB 12-16, 1995 CL LAS VEGAS, NV AB Ternary alloys constitute an important and interesting laboratory for studying electronically driven ordering in alloys because (in contrast to binary alloys) the composition and electron-per-atom ratio (e/a) may be varied independently. Using their recently developed first-principles theory of atomic short-range order (ASRO) in alloys with an arbitrary number of components, the authors discuss ASRO in the ternary Cu-Ni-Zn system, Fermi-surface nesting is found to drive the ordering tendencies of the fee portion of the phase diagram, yielding ASRO whose dominant wave vector varies with e/a in a predictable manner, The authors' concentration-fluctuation theory yields both the wave vector and polarization of the concentration wave, necessary to fully specify the ASRO in an alloy of more than two components. OI Johnson, Duane/0000-0003-0794-7283 SN 1054-9714 PD DEC PY 1997 VL 18 IS 6 BP 567 EP 572 DI 10.1007/BF02665813 UT WOS:A1997YK25400013 ER PT J AU Wang, Y Stocks, GM Nicholson, DMC Shelton, WA Szotek, Z Temmerman, WM AF Wang, Y Stocks, GM Nicholson, DMC Shelton, WA Szotek, Z Temmerman, WM TI The local environmental effects on the magnetism of short-range clustered CuNi alloys SO JOURNAL OF PHASE EQUILIBRIA CT TMS Annual Meeting CY FEB 12-16, 1995 CL LAS VEGAS, NV AB The locally self-consistent multiple-scattering method has been applied to spin-polarized LDA calculations for ferromagnetic Cu0.2Ni0.8 alloys. The sample used to simulate the alloys involved up to 256 atoms per cell and was constructed to be short-range clustering with the experimentally measured short-range order parameters, The magnetic cross section for neutron scattering was also calculated and compared with the neutron scattering data, The magnetic moments of Ni atoms were found to be sensitive to local atomic configurations. RI Stocks, George Malcollm/Q-1251-2016 OI Stocks, George Malcollm/0000-0002-9013-260X SN 1054-9714 PD DEC PY 1997 VL 18 IS 6 BP 588 EP 592 DI 10.1007/BF02665816 UT WOS:A1997YK25400016 ER PT J AU Johnson, DD Althoff, JD Pinski, FJ Staunton, JB Ling, MF AF Johnson, DD Althoff, JD Pinski, FJ Staunton, JB Ling, MF TI Ordering tendencies in alloys and their microscopic origins from a first-principles theory of concentration waves SO JOURNAL OF PHASE EQUILIBRIA CT TMS Annual Meeting CY FEB 12-16, 1995 CL LAS VEGAS, NV AB Compositional, displacement, and magnetic pair-correlation functions in alloys are measured directly by diffuse scattering techniques. A first-principles theory of short-range order in high-temperature, disordered alloys has been developed and implemented that determines these correlation functions from the underlying local-density-functional electronic structure. Features in diffuse scattering experiments may be directly related to their electronic origins. Such a capability is not only important for interpreting experimental results but for understanding the microscopic origin of the system-dependent short-range order. Example applications are discussed in the Cu-Ni-Zn and Cu-Pt alloys, with emphasis on the importance of van-Rove states (i.e., the electronic states that give rise to van Rove singularities in the density of states). As a contrast, the origins for the magnetic and chemical short-range order in paramagnetic Cu-rich, Cu-Mn alloys, which are considered prototypical spin-glass systems, are also briefly discussed. OI Johnson, Duane/0000-0003-0794-7283 SN 1054-9714 PD DEC PY 1997 VL 18 IS 6 BP 598 EP 607 DI 10.1007/BF02665818 UT WOS:A1997YK25400018 ER PT J AU Chen, G Holsa, J Peterson, JR AF Chen, G Holsa, J Peterson, JR TI A luminescence study of single-crystal EuPO4 at high pressure SO JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS AB The pressure dependence of the luminescence from the D-5(0) --> F-7(0.2) transitions in the Eu3+ ion in single-crystal EuPO4 has been investigated to about 20 GPa using a diamond anvil cell. Based on the level energies derived from the luminescence spectra recorded from the same crystal specimen, the parameterization of the free ion and crystal field effects was carried out with good results, as indicated by the low RMS deviations obtained. The lifetime of the D-5(0) level was also measured as a function of pressure via monitoring a peak in the D-5(0) --> F-7(1) transition manifold. Abrupt changes in the Eu3+ ion luminescence spectra and lifetime were observed between 6 and 8 GPa, while the general spectral pattern remained the same over the entire pressure range investigated. Calculated crystal field parameters also displayed a discontinuity between 6 and 8 GPa. These facts indicate that the site symmetry of the Eu3+ ion in EuPO4 is not changed by the application of pressure to about 20 GPa, but the strength of the crystal field probably changes significantly between 6 and 8 GPa. These observations are consistent with the crystal undergoing an isostructural volume collapse between 6 and 8 GPa. The ambient-pressure phase, which exhibits the monazite-type monoclinic structure, is retained to at least 20 GPa. (C) 1997 Elsevier Science Ltd. All rights reserved. SN 0022-3697 PD DEC PY 1997 VL 58 IS 12 BP 2031 EP 2037 DI 10.1016/S0022-3697(97)00133-9 UT WOS:000071464400007 ER PT J AU Odyniec, G AF Odyniec, G CA NA49 Collaboration TI Xi(Omega) production in Pb+Pb collisions at 158 GeV c(-1) SO JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS CT International Symposium on Strangeness in Quark Matter CY APR 14-18, 1997 CL SANTORINI, GREECE SP Intracom SA AB Using the NA49 main TPC, the central production of (Xi + <(Xi)over bar>) hyperons has been measured in CERN SPS Pb-Pb collisions at 158 GeV c(-1). The preliminary (Xi + <(Xi)over bar>)/(Lambda + <()over bar>) ratio, studied at 2.0 < y < 2.6 and I < p(T) < 3 GeV c(-1), equals similar to(13 +/- 4)% (systematic error only). It is compatible, within errors, with the previously obtained ratios for central S + S [1], S + W [2], and S + Au [3] collisions. The fit to the transverse momentum distribution resulted in an inverse slope parameter T of 297 MeV. At this level of statistics we do not see any noticeable enhancement of hyperon production with the increased volume (and, possibly, degree of equilibration) of the system from S + S to Pb + Pb. This result is unexpected and counterintuitive, and should be further investigated. If confirmed, it will have a significant impact on our understanding of mechanisms leading to the enhanced strangeness production in heavy-ion collisions. SN 0954-3899 PD DEC PY 1997 VL 23 IS 12 BP 1827 EP 1835 UT WOS:000071070500005 ER PT J AU Best, D AF Best, D CA E895 Collaboration TI First results on Lambda production between 2 and 8 A GeV from E895 SO JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS CT International Symposium on Strangeness in Quark Matter CY APR 14-18, 1997 CL SANTORINI, GREECE SP Intracom SA AB The E895 experiment has recorded high statistics data using 2, 4, 6 and 8 A GeV Au beams impinging on a Au target. We report preliminary results on Lambda production at 6 and 8 A GeV based on the analysis of a small fraction of the recorded data. SN 0954-3899 PD DEC PY 1997 VL 23 IS 12 BP 1873 EP 1879 UT WOS:000071070500011 ER PT J AU Vogt, R AF Vogt, R TI Strange effects on charm at RHIC: initial charm suppression and thermal charm enhancement SO JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS CT International Symposium on Strangeness in Quark Matter CY APR 14-18, 1997 CL SANTORINI, GREECE SP Intracom SA AB Calculations of charm production in the initial nucleon-nucleon interactions at RHIC suggested that charm decays would dominate all other dilepton sources. We report here on two new calculations that could affect this conclusion. The first, a study on the in-medium energy loss of fast partons, suppresses the dilepton yield from charm decays. The second suggests that the thermal charm signature could be enhanced if the quarks and gluons acquire an effective mass in the plasma. SN 0954-3899 PD DEC PY 1997 VL 23 IS 12 BP 1989 EP 2000 DI 10.1088/0954-3899/23/12/024 UT WOS:000071070500024 ER PT J AU Glendenning, NK AF Glendenning, NK TI Strangeness in compact stars and signal of deconfinement SO JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS CT International Symposium on Strangeness in Quark Matter CY APR 14-18, 1997 CL SANTORINI, GREECE SP Intracom SA AB Phase transitions in compact stars are discussed including hyperonization, deconfinement and crystalline phases. Reasons why kaon condensation is unlikely are reviewed. Particular emphasis is placed on the evolution of internal structure with spin-down of pulsars. A signature of a first-order phase transition in the timing structure of pulsars, which is strong and easy to measure, is identified. SN 0954-3899 PD DEC PY 1997 VL 23 IS 12 BP 2013 EP 2027 DI 10.1088/0954-3899/23/12/026 UT WOS:000071070500026 ER PT J AU Schaffner-Bielich, J Greiner, C Stocker, H Vischer, AP AF Schaffner-Bielich, J Greiner, C Stocker, H Vischer, AP TI Properties of exotic matter for heavy-ion searches SO JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS CT International Symposium on Strangeness in Quark Matter CY APR 14-18, 1997 CL SANTORINI, GREECE SP Intracom SA AB We examine the properties of both forms of strange matter, small lumps of strange quark matter (strangelets) and of strange hadronic matter (metastable exotic multihypernuclear objects (MEMOs)) and their relevance for present and future heavy-ion searches. The strong and weak decays are discussed separately to distinguish between long-and short-lived candidates where the former ones are detectable in present heavy-ion experiments while the latter ones are present in future heavy-ion experiments, respectively. We find some long-lived strangelet candidates which are highly negatively charged with a mass-to-charge ratio like a anti deuteron (M/Z approximate to -2) but masses of A = 10-16. We also predict many short-lived candidates, both in quark and hadronic form, which can be highly charged. Purely hyperonic nuclei such as the Xi alpha (2 Xi(0)2 Xi(-)) are bound and have a negative charge while carrying a positive baryon number. We also demonstrate that multiply charmed exotics (charmlets) might be bound and can be produced at future heavy-ion colliders. RI Stoecker, Horst/D-6173-2013 OI Stoecker, Horst/0000-0002-3282-3664 SN 0954-3899 PD DEC PY 1997 VL 23 IS 12 BP 2107 EP 2115 DI 10.1088/0954-3899/23/12/036 UT WOS:000071070500036 ER PT J AU Annis, BK Wignall, GD Hopkins, AR Rasmussen, PG Basheer, RA AF Annis, BK Wignall, GD Hopkins, AR Rasmussen, PG Basheer, RA TI Structural investigation of polyaniline/Nylon 6 blends by small-angle neutron scattering and small-and wide-angle X-ray scattering SO JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS AB The structure of blends of Nylon 6 with deuterated polyaniline emeraldine base (D-PANI-EB) and fully doped D-PANI salts (D-PANI-ES) formed from camphorsulfonic acid(CSA), methanesulfonic acid (MSA), or dodecyl benzenesulfonic acid (DBSA) were investigated by small-angle neutron (SANS) and X-ray scattering. The blends were formed from hexafluoro-2-propanol solutions and had volume fractions of 0.038, 0.20, and 0.40 for D-PANI/CSA, 0.20 and 0.40 for D-PANI/MSA, 0.24 and 0.44 for D-PANI/DBSA, and 0.07, 0.14, and 0.31 for D-PANI-EB. The SANS results are compared with a number of standard models for two-phase systems. No evidence was found for significant molecular mixing. In some cases the inverse power law model is in reasonable agreement with observations, and in the case of the lowest concentration of D-PANI/CSA there is an indication of mass fractal structure. This was not found at the higher concentrations. The results establish that the blends with the smaller more polar dopants CSA and MSA behave similarly and are unlike either the D-PANI/DBSA blends or those with D-PANI-EB. There is evidence that the simple picture of two pure phases is inadequate for these materials. With the exception of the D-PANI/DBSA blend which has a relatively low scattering contrast, the results indicate that the lower limit of volume fraction for application of SANS is a few percent D-PANI-ES in Nylon 6. X-ray scattering was used to demonstrate the presence of Nylon 6 lamellae and residual peaks attributable to the pure components. (C) 1997 John Wiley & Sons, Inc. SN 0887-6266 PD DEC PY 1997 VL 35 IS 17 BP 2765 EP 2774 UT WOS:A1997YJ05200001 ER PT J AU Burnett, WC Corbett, DR Schultz, M Horwitz, EP Chiarizia, R Dietz, M Thakkar, A Fern, M AF Burnett, WC Corbett, DR Schultz, M Horwitz, EP Chiarizia, R Dietz, M Thakkar, A Fern, M TI Pre-concentration of actinide elements from soils and large volume water samples using extraction chromatography SO JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY CT 6th International Conference on Low-Level Measurements of Actinides and Long-Lived Radionuclides in Biological and Environmental Samples CY SEP 09-13, 1996 CL COGEMA-LA HAGUE, CHERBOURG, FRANCE SP COGEMA, La Hague, France HO COGEMA-LA HAGUE AB ?he analysis of environmental samples for low levels of U, Pu, Am and other actinide elements is often hampered by sample dependent problems involving the composition and/or mineralogy of specific samples. While relatively small samples (1-2 g of soil or 1-21 of water) are required to reach the extremely low detection limits occasionally mandated for environmental monitoring. One approach to avoid the troublesome and often inexplicable problems collectively referred to as "matrix effects" is to pre-concentrate actinides into a common form that would then behave uniformly and predictably during a subsequent separation scheme. Recently, a new extraction chromatographic resin based on diphosphonate chemistry was developed at Argonne National Laboratory. This resin commercialized as Eichrom's Actinide Resin, exhibits extremely high affinity for actinide elements even in the presence of high concentrations of salts. We have measured the uptake of actinides by the Dipex(R) extractant from natural waters and natural matrix soil standards. Water samples have been analyzed for gross alpha-activities and gave results that compared favorably to the traditional approach. In addition, we have obtained good recoveries and excellent separations for soil samples as judged by resolution on the alpha-spectra and the complete absence of interfering energies. SN 0236-5731 PD DEC PY 1997 VL 226 IS 1-2 BP 121 EP 127 DI 10.1007/BF02063635 UT WOS:000072260900020 ER PT J AU Sanquist, TF Raby, M Forsythe, A Carvalhais, AB AF Sanquist, TF Raby, M Forsythe, A Carvalhais, AB TI Work hours, sleep patterns and fatigue among merchant marine personnel SO JOURNAL OF SLEEP RESEARCH AB A field study of work and sleep patterns among commercial merchant marine personnel is reported. Data collected over a 10-30-d period from 141 subjects aboard eight ships included information concerning work-rest schedules, sleep timing, alertness on the job and critical fatigue. The data indicate that watchstanders on the 4-on, 8-off schedule show considerable disruption in their sleep. The average sleep duration for all mariners is 6.6 h; watchstanders obtain their sleep in fragmented periods that are frequently less than 5 h in duration. Analysis of critical fatigue shows an incidence of 1-24% across personnel and measures. Of particular concern are the watchstanders on the 04.00-08.00 schedule, who sleep less than 4 h per 24-h period 22% of the time. Potential countermeasures, including changes in scheduling and staffing are proposed. SN 0962-1105 PD DEC PY 1997 VL 6 IS 4 BP 245 EP 251 DI 10.1111/j.1365-2869.1997.00245.x UT WOS:000071940500005 PM 9493524 ER PT J AU Piepel, G Redgate, T AF Piepel, G Redgate, T TI Mixture experiment techniques for reducing the number of components applied for modeling waste glass sodium release SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY AB Statistical mixture experiment techniques were applied to a waste glass data set to investigate the effects of the glass components on Product Consistency Test (PCT) sodium release (NR) and to develop a model for PCT NR as a function of the component proportions. The mixture experiment techniques indicate that the waste glass system can be reduced from nine to four components for purposes of modeling PCT NR. Empirical mixture models containing four first-order terms and one or two second-order terms fit the data quite well, and can be used to predict the NR of any glass composition in the model domain. The mixture experiment techniques produce a better model in less time than required by another approach. SN 0002-7820 PD DEC PY 1997 VL 80 IS 12 BP 3038 EP 3044 UT WOS:000071152200009 ER PT J AU Petrovic, JJ Pena, MI Reimanis, IE Sandlin, MS Conzone, SD Kung, HH Butt, DP AF Petrovic, JJ Pena, MI Reimanis, IE Sandlin, MS Conzone, SD Kung, HH Butt, DP TI Mechanical behavior of MoSi2 reinforced-Si3N4 matrix composites SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY AB The mechanical behavior of MoSi2 reinforced-Si3N4 matrix composites was investigated as a function of MoSi2 phase content, MoSi2 phase size, and amount of MgO densification aid for the Si3N4 phase. Coarse-phase MoSi2Si3N4 composites exhibited higher room-temperature fracture toughness than fine-phase composites, reaching values >8 MPa.m(1/2). Composite fracture toughness levels increased at elevated temperature, Fine-phase composites were stronger and more creep resistant than coarse phase composites. Room-temperature strengths >1000 MPa and impression creep rates of similar to 10(-8) s(-1) at 1200 degrees C were observed, Increased MgO levels generally were deleterious to MoSi2-Si3N4 mechanical properties, Internal stresses due to MoSi2 and Si3N4 thermal expansion coefficient mismatch appeared to contribute to fracture toughening in MoSi2-Si3N4 composites. RI Butt, Darryl/B-7480-2008 OI Butt, Darryl/0000-0003-4501-8864 SN 0002-7820 PD DEC PY 1997 VL 80 IS 12 BP 3070 EP 3076 UT WOS:000071152200013 ER PT J AU Al-Shareef, HN Dimos, D AF Al-Shareef, HN Dimos, D TI Leakage and reliability characteristics of lead zirconate titanate thin-film capacitors SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY AB Resistance degradation in lead zirconate titanate (Pb(Zr,Ti)O-3, PZT) thin-film capacitors has been studied as a function of applied voltage, temperature, and film composition, The mean time-to-failure (lifetime, or t(f)) of the capacitors shows a power-law dependence on voltage of the t(f) proportional to V-n (n approximate to 4-5). The capacitor lifetime also exhibits a temperature dependence of the form t(f) proportional to exp[E-a(kT)], with an activation energy of 0.6-1.0 eV. The steady-state leakage current in these samples seems to be bulk controlled, The voltage V, temperature T, and polarity dependence of the leakage current collectively suggest a leakage-current mechanism that is most similar to a Frenkel-Poole process, The t(f) value and the leakage current of niobium-doped PZT films are superior to those of undoped PZT films, This result can be explained on the basis of the point-defect chemistry of the PZT system, Finally, the results indicate that the niobium-doped PZT films meet essential t(f) requirements for decoupling-capacitor applications. RI Alshareef, Husam Niman/A-2000-2015 OI Alshareef, Husam Niman/0000-0001-5029-2142 SN 0002-7820 PD DEC PY 1997 VL 80 IS 12 BP 3127 EP 3132 UT WOS:000071152200019 ER PT J AU Bamberger, CE Specht, ED Anovitz, LM AF Bamberger, CE Specht, ED Anovitz, LM TI Crystalline copper phosphates: Synthesis and thermal stability SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY AB The syntheses of Cu(PO3)(2), Cu2P2O7, Cu4P2O9, Cu5P2O10, Cu-3(PO4)(2), and Cu2PO4 were accomplished by several new solid-state routes. Attempts to synthesize CuPO3 were unsuccessful, and it is suspected that this compound, which is reported in the literature, may not exist. The thermal stabilities of Cu(PO3)(2), Cu2P2O7 and Cu-3(PO4)(2) were examined, and their decomposition was concluded to be strongly dependent on slow kinetics. RI Specht, Eliot/A-5654-2009; Anovitz, Lawrence/P-3144-2016 OI Specht, Eliot/0000-0002-3191-2163; Anovitz, Lawrence/0000-0002-2609-8750 SN 0002-7820 PD DEC PY 1997 VL 80 IS 12 BP 3133 EP 3138 UT WOS:000071152200020 ER PT J AU Lara-Curzio, E AF Lara-Curzio, E TI Stress-rupture of Nicalon/SiC continuous fiber ceramic composites in air at 950 degrees C SO JOURNAL OF THE AMERICAN CERAMIC SOCIETY AB The stress-rupture behavior of plain-weave CG-Nicalon/enhanced SiC was studied in air at 950 degrees C. It was found that this material exhibits delayed failure and that the lives of specimens subjected to constant stress levels of 80, 100, and 120 MPa were 21.6, 9.6, and 2.7 h, respectively. The strain histories of these tests revealed a continuous increase of the specimen compliance and accelerated deformation prior to failure. It is shown that both the shape of the strain vs time curves and the time dependence of the loss of strength can be explained using a simple model based on the oxidation-induced stress-rupture of the reinforcing fiber bundles. SN 0002-7820 PD DEC PY 1997 VL 80 IS 12 BP 3268 EP 3272 UT WOS:000071152200045 ER PT J AU Gelman, A Bois, FY AF Gelman, A Bois, FY TI Analysis of nonrandomly censored ordered categorical longitudinal data from analgesic trials - Comment SO JOURNAL OF THE AMERICAN STATISTICAL ASSOCIATION RI Bois, Frederic/E-9241-2012 OI Bois, Frederic/0000-0002-4154-0391 SN 0162-1459 PD DEC PY 1997 VL 92 IS 440 BP 1248 EP 1250 UT WOS:000071132200004 ER PT J AU Darling, R Newman, J AF Darling, R Newman, J TI Modeling a porous intercalation electrode with two characteristic particle sizes SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB A mathematical model of a complete cell containing a porous intercalation electrode with two characteristic particle sizes is presented. Galvanostatic cycling and relaxation phenomena on open-circuit are compared to a cell with a single particle size. Electrodes with a particle-size distribution show modestly inferior capacity-rate behavior in all cases considered in this work. The cycling results exhibit a mismatch in the states-of-charge of the surfaces of the different particle sizes located at the same position in the electrode. The magnitude of this mismatch correlates with the slope of the open-circuit potential vs. state-of-charge curve of the intercalation material. The relaxation on open circuit is substantially faster when the particles are uniformly sized. Asymptotic solutions were developed to aid in the description of the open-circuit behavior in the cases with nonuniform particle sizes. The particle-size distribution has a more pronounced influence on the open-circuit results than on the galvanostatic results. RI Newman, John/B-8650-2008 OI Newman, John/0000-0002-9267-4525 SN 0013-4651 PD DEC PY 1997 VL 144 IS 12 BP 4201 EP 4208 DI 10.1149/1.1838166 UT WOS:A1997YL46800026 ER PT J AU Feldberg, SW Reilly, JJ AF Feldberg, SW Reilly, JJ TI Phenomenological treatment of hydrogen transport in a metal/metal hydride system .1. Steady-state systems SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB Steady-state H-atom transport across a metal foil of uniform thickness is described using the phenomenological transport equation and the gradient of chemical potential deduced from the operative pressure-composition isotherm. The approach follows from that described by Wicke and Brodowsky(1) and leads directly to a description of the steady-state flux and the concentration profile of H-atoms across a metal/metal hydride foil of uniform thickness. As a demonstration we fabricate a simple chemical potential-composition isotherm which mimics the salient features of any of a number of experimentally observed isotherms, including (and especially) those describing two-phase systems, and which allows straightforward mathematical manipulation. We then show how the shape of the isotherm defines the steady-state flux of H-atoms across a metal/metal hydride foil of uniform thickness and defines the steady-state distribution of H-atoms across the foil, as well as the loading of H-atoms in the foil. SN 0013-4651 PD DEC PY 1997 VL 144 IS 12 BP 4260 EP 4265 DI 10.1149/1.1838175 UT WOS:A1997YL46800035 ER PT J AU Miller, JM Dunn, B Tran, TD Pekala, RW AF Miller, JM Dunn, B Tran, TD Pekala, RW TI Deposition of ruthenium nanoparticles on carbon aerogels for high energy density supercapacitor electrodes SO JOURNAL OF THE ELECTROCHEMICAL SOCIETY AB The preparation and characterization of high surface area ruthenium/carbon aerogel composite electrodes for use in electrochemical capacitors is reported. These new materials have been prepared by the chemical vapor impregnation of ruthenium into carbon aerogels to produce a uniform distribution of adherent approximate to 20 Angstrom nanoparticles on the aerogel surface. The electrochemically oxidized ruthenium particles contribute a pseudocapacitance to the electrode and dramatically improve the energy storage characteristics of the aerogel. These composites have demonstrated specific capacitances in excess of 200 F/g, in comparison to 95 F/g for the untreated aerogel. SN 0013-4651 PD DEC PY 1997 VL 144 IS 12 BP L309 EP L311 DI 10.1149/1.1838142 UT WOS:A1997YL46800002 ER PT J AU Page, E Praul, C Siminovitch, M AF Page, E Praul, C Siminovitch, M TI Comparative candlepower distribution analysis for compact fluorescent table lamp systems SO JOURNAL OF THE ILLUMINATING ENGINEERING SOCIETY AB The residential lighting sector represents a significant opportunity for energy conservation due to the almost exclusive use of inefficient incandescent sources. Compact fluorescent lamps (CFLs) have the potential to transform this market by using one-fourth as much power as an incandescent to provide the same amount of light. While technical advances such as triphosphors and electronic ballasts have addressed issues of color rendition, flicker, and hum, CFLs still face significant market barriers, particularly their perceived brightness level in traditional fixture applications. When operated in fixtures originally designed for A-lamps, CFLs with equal total lumen packages can appear dimmer due to differences in their light distributions. One such fixture, the common table lamp, is typically operated for more than 3 hrs/day, and thus represents a significant opportunity for energy savings. The authors conducted a series of goniophotometric candela distribution studies of table lamps with the initial objective of matching with CFLs the light distribution of the consumer-accepted A-lamp. While goniophotometric testing was done on numerous CFL and incandescent sources, this paper focuses on three typical sources that have very different distributions. Our photometric studies indicate that horizontally oriented CFLs may produce a more desirable distribution than either A-lamps or vertically oriented CFLs by minimizing shade losses and thus maximizing the amount of useful light leaving the fixture. Optimizing fixture geometry and lamp position can significantly increase the efficiency of these CFL fixtures. Ongoing research with the fixture industry seeks to identify and develop efficient source-fixture configurations. SN 0099-4480 PD WIN PY 1997 VL 26 IS 1 BP 3 EP & UT WOS:A1997XA02600001 ER PT J AU Packer, M AF Packer, M TI The application of light emitting diodes to traffic signals - Discussion SO JOURNAL OF THE ILLUMINATING ENGINEERING SOCIETY SN 0099-4480 PD WIN PY 1997 VL 26 IS 1 BP 24 EP 24 UT WOS:A1997XA02600014 ER PT J AU Navvab, M Siminovitch, M Love, J AF Navvab, M Siminovitch, M Love, J TI Variability of daylight in luminous environments SO JOURNAL OF THE ILLUMINATING ENGINEERING SOCIETY AB This paper reports on the measurements of physical parameters for evaluating the variability of daylight in interior spaces. Luminance and contrast are primary variables on visual performance. The spectral variation in the luminous environment affects pupil size, which can affect visual performance. The variability of daylight affects the :luminance and illuminance levels. These variations in illumination levels are measured in a full-scale office space. The photopic and scotopic spectral content of the ambient illumination on task as well as space surfaces are determined. The results are combined with calculated luminous efficacy of daylight to determine the relative power level for equal pupil size, amplitude, spectral, seasonal and time variation of daylight. Variability is also determined. The effective pupil lumen is applied as an index to show the variability of daylight in the interior luminous environment. SN 0099-4480 PD WIN PY 1997 VL 26 IS 1 BP 101 EP + UT WOS:A1997XA02600050 ER PT J AU Siminovitch, MJ AF Siminovitch, MJ TI Documenting the effects of luminaire venting on CFL downlight performance - Discussion SO JOURNAL OF THE ILLUMINATING ENGINEERING SOCIETY SN 0099-4480 PD WIN PY 1997 VL 26 IS 1 BP 123 EP 123 UT WOS:A1997XA02600052 ER PT J AU Berman, S AF Berman, S TI Evaluating light source efficacy under mesopic conditions using reaction times - Discussion SO JOURNAL OF THE ILLUMINATING ENGINEERING SOCIETY SN 0099-4480 PD WIN PY 1997 VL 26 IS 1 BP 135 EP 137 UT WOS:A1997XA02600057 ER PT J AU DiBartolomeo, DL Lee, ES Rubinstein, FM Selkowitz, SE AF DiBartolomeo, DL Lee, ES Rubinstein, FM Selkowitz, SE TI Developing a dynamic envelope/lighting control system with field measurements SO JOURNAL OF THE ILLUMINATING ENGINEERING SOCIETY AB The feasibility of an intelligent venetian blind/lighting control system was tested in a 1:3 scale model outdoors under variable sun and sky conditions. The control algorithm, direct sun block, and meeting the design workplane illuminance level, was implemented using commercially available and custom designed blind and lighting systems hardware. While blocking direct sunlight, the blinds were properly controlled to maintain the design workplane illuminance within a tolerance of -10 percent, +25 percent when there was sufficient daylight. When daylight levels alone were inadequate, the electric lighting control system maintained the design workplane illuminance. The electric lighting could be turned off if a user-specified time period at minimum power was exceeded. Lighting energy savings of 51-71 percent (southwest) and 37-75 percent (south) were attained for the period from 8:00 to 17:00 on clear sunny days, compared to a fixed, partially closed blind with the same lighting system. Practical details for implementation and commissioning are discussed. The impact of control variations such as profile angle, time step interval, and control area on energy demand is investigated. SN 0099-4480 PD WIN PY 1997 VL 26 IS 1 BP 146 EP & UT WOS:A1997XA02600063 ER PT J AU Butcher, T Lee, SW Celebi, Y Litzke, W AF Butcher, T Lee, SW Celebi, Y Litzke, W TI Fouling of heat-transfer surfaces in oil-fired boilers for domestic heating SO JOURNAL OF THE INSTITUTE OF ENERGY AB Domestic-heating boilers fired with distillate oil are subject to fouling of the convective section gas-side surfaces, and this fouling leads to a reduction in efficiency and to increased maintenance requirements. A rapid test to enable the composition of fouling deposits and the rates of fouling to be studied has been developed and used at two laboratory sites. It involves special fouling surfaces which can be removed for deposit analysis. Fouling rates are shown to be directly related to the sulphur content of the fuel. Also, operation with reduced excess air in these boilers can lessen fouling rates by reducing the conversion of fuel sulphur to sulphuric acid. Results are compared with those from tests on full-size boilers. SN 0144-2600 PD DEC PY 1997 VL 70 IS 485 BP 151 EP 159 UT WOS:000071698200004 ER PT J AU Hayashi, Y Golder, DG Jones, PW AF Hayashi, Y Golder, DG Jones, PW TI Tropical gravity waves and superclusters simulated by high-horizontal-resolution SKYHI general circulation models SO JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN AB Tropical gravity waves and superclusters simulated by 40-level GFDL SKYHI general circulation model experiments with higher horizontal resolutions (0.6 degrees longitude x 0.72 degrees latitude) and (1.0 degrees x 1.2 degrees) are compared with those simulated by a lower-resolution (3.0 degrees x 3.6 degrees) experiment. Results indicated that simulated precipitational heating appears to excite tropical gravity waves. At higher resolutions, precipitation is more confined in space and time, resulting in a broader wavenumber-frequency spectral distribution. Grid-scale precipitation, which is thought to mimic the precipitation associated with cloud clusters, is organized into larger-scale superclusters. The westward propagation of cloud clusters and eastward propagation of superclusters can be more clearly seen in the high-resolution experiments. The high-resolution (0.6 degrees x 0.72 degrees) model indicates that the lower-stratospheric gravity-wave momentum flux is dominated by high-frequency components having periods shorter than one day. This flux doubles as the resolution is increased from (3.0 degrees x 3.6 degrees) to (0.6 degrees x 0.72 degrees). It is speculated that a further increase in both the horizontal and vertical resolutions could substantially enhance the gravity-wave momentum flux convergence, thus forcing a stronger quasi-biennial oscillation. SN 0026-1165 EI 2186-9057 PD DEC PY 1997 VL 75 IS 6 BP 1125 EP 1139 UT WOS:000072527200009 ER PT J AU Whitten, WB Barnes, MD Ramsey, JM AF Whitten, WB Barnes, MD Ramsey, JM TI Propagation of short optical pulses in a dielectric sphere SO JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS AB Propagation of optical pulses in the whispering-gallery modes of a dielectric sphere is described. The pulse duration is assumed to be small compared with the round-trip transit time so that individual pulses can be resolved. Modal dispersion is calculated from an asymptotic expression for the frequency dependence of the propagation. The possibility of soliton propagation at certain wavelengths is discussed. (C) 1997 Optical Society of America [S0740-3224(97)00912-0]. SN 0740-3224 PD DEC PY 1997 VL 14 IS 12 BP 3424 EP 3429 DI 10.1364/JOSAB.14.003424 UT WOS:000071110200018 ER PT J AU Garrett, B Glaser, B AF Garrett, B Glaser, B TI China's pragmatic posture toward the Korean peninsula SO KOREAN JOURNAL OF DEFENSE ANALYSIS AB Most Chinese officials and experts approach analysis of the Korean peninsula from a pragmatic, national-interest perspective with little regard for ideological or historical ties to North Korea. They have become increasingly concerned about the deteriorating economic situation and the possibility of political struggle in the North. The Chinese nevertheless maintain that the North Koreans can endure extreme hardship and predict that the regime will muddle through, at least for the next few years. Chinese experts are convinced that a major conflict on the Korean peninsula is highly unlikely, The primary basis for this judgment is China's assessment of the balance of power on the peninsula. The Chinese judge that North Korea would not commit suicide by attacking the South when neither Russia nor China would support it and the adversary has overall superiority. Nor do they expect South Korea and the United States to attack the North. The Chinese also are optimistic that the process of reunification will be gradual and peaceful based on a soft landing in the North and accommodation between Pyongyang and Seoul. In the long run, most Chinese experts forecast, Korea will be reunified under the dominance of the South as the inevitable consequence of South Korea's advantages in comprehensive national power, especially in economic and political strength. Some Chinese hardliners may prefer that China press for removal of US forces from Korea after reunification, but the Chinese government probably will not want to risk tension over the issue in its bilateral relations with the new Korean state or with the United States if a unified Korea decides to maintain the alliance and requests continued stationing of some American forces on the peninsula. Nor will Beijing want to risk exacerbating fears in the region of Chinese hegemonism by seeking to pressure the Koreans to ask the US to leave. Moreover, some Chinese experts may argue in favor of tacit approval of continued presence of US forces in Korea as a stabilizer vis-a-vis the Korean-Japanese animosity that could escalate after reunification. Beijing does not appear to have a long-term strategy to achieve strategic goals on the Korean peninsula beyond preserving amicable ties with the North and further developing relations with the South, especially economic. China's Korea policy appears to be concentrated on short-term, tactical issues and Beijing's posture seems primarily defensive. The Chinese seem more concerned about protecting their national interests and maintaining their influence on the peninsula in the face of potentially dramatic changes than they are about positioning themselves to gain dominance in post-reunification Korea. They do not expect to be able to supplant the United States as the outside power with the greatest influence on a united Korea and are content, at least for now, to let the US take the initiative in trying to manage the volatile situation on the peninsula. Beijing is unlikely to adopt a more proactive approach toward the situation in Korea unless forced to do so by events or changing circumstances. In the meantime, it can be expected to continue to take steps to ensure the economic survival of North Korea. China is not likely to engage in heroic efforts to save a moribund regime, however, especially if it begins a process of political self-annihilation. SN 1016-3271 PD WIN PY 1997 VL 9 IS 2 BP 63 EP + UT WOS:000168676200004 ER PT J AU Brzezinski, MA Phillips, DR Chavez, FP Friederich, GE Dugdale, RC AF Brzezinski, MA Phillips, DR Chavez, FP Friederich, GE Dugdale, RC TI Silica production in the Monterey, California, upwelling system SO LIMNOLOGY AND OCEANOGRAPHY AB Silica cycling was examined during a major upwelling event in Monterey Bay, California. Strong upwelling-favorable winds blew for 6 d with speeds up to 15 m s(-1) just prior to the study. A survey of the region near the end of the wind event showed newly upwelled water at the north end of the bay, with silicic acid concentrations up to 29.8 mu M. Silicic acid concentrations decreased to a minimum of 15 mu M along the upwelling plume. Biogenic silica concentrations in the upwelling plume were generally between 2 and 5 mu mol Si liter(-1). Specific rates of biogenic silica production were <0.2 d(-1) in the freshly upwelled waters and increased to >1.0 d(-1) downplume. Kinetic experiments indicated that silicic acid concentrations throughout the upwelling plume supported maximal rates of silica production. Silica production rates were similar to 1 mu mol Si liter(-1) d(-1) at the upwelling source, increasing to 7 mu mol liter(-1) d(-1) downplume. The upwelling event was followed by several days of calm winds, creating ideal conditions for a phytoplankton bloom. integrated biogenic silica concentrations between the surface and the 0.1% light depth during the calm period ranged from 56 to 566 mmol Si m(-2), with 8 of 11 stations exhibiting concentrations >100 mmol Si m(-2). Specific production rates of biogenic silica were generally >1 d(-1), with production rates between 10 and 30 mu mol Si liter(-1) d(-1). integrated silica production rates averaged 205 mmol Si m(-2) d(-1) (range 13-1,140 mmol m(-2) d(-1)), which is four times greater than the average rate observed for other coastal upwelling systems. The maximum value observed (1,140 mmol m(-2) d(-1)) is nearly four times greater than levels ever observed before in the sea. The high silica production rates seemed to result from an inefficient silicate pump. On average: 72% of the biogenic silica produced in the upwelling plume was retained in the surface waters, resulting in biogenic silica concentrations of 6.7-13.7 mu mol Si liter(-1) at stations where integrated production rates were >200 mmol Si m(-2) d(-1). Ambient silicic acid concentrations in these same waters were generally >8 mu M. Kinetic studies showed that these silicic acid concentrations supported nearly maximal rates of silica production. Substrate limitation of silica production became readily detectable at 5 mu M Si(OH)(4). By that time, 80 to >90% of the silicic acid and similar to 90% of the nitrate in the upwelled waters had been consumed, indicating that substrate limitation of silica production played only a minor role in controlling the magnitude of both net silica production and new production by diatoms. SN 0024-3590 PD DEC PY 1997 VL 42 IS 8 BP 1694 EP 1705 UT WOS:000073407700005 ER PT J AU Neill, C Johnson, KM Lewis, E Wallace, DWR AF Neill, C Johnson, KM Lewis, E Wallace, DWR TI Accurate headspace analysis of fCO(2) in discrete water samples using batch equilibration SO LIMNOLOGY AND OCEANOGRAPHY AB A high-accuracy, batch-equilibration, static-headspace technique for the determination of the fugacity of CO2 (fCO(2)) in discrete water samples is described. The technique was designed for monitoring small changes of CO2 in the ocean and has accuracy and precision (<1% for water samples) comparable to that of the best techniques available. The method uses several novel approaches to maximize accuracy, requires only a small water sample (60 ml), and is very rapid (similar to 2 min per analysis). Precision of the calculated total alkalinity, based on the measured fCO(2) and C-T, is comparable to or better than is generally attained using potentiometric titration. Compared with C-T and total alkalinity measurements, the small sample volume and rapid analysis time makes it practical to perform analysis of multiple replicates in order to improve confidence in the result. The method is readily applicable to experimental studies such as incubations as well as to time-series measurements of in situ biological metabolism. Because the analysis employs gas chromatography, the technique can be adapted to measure simultaneously a suite of gases dissolved in seawater. SN 0024-3590 PD DEC PY 1997 VL 42 IS 8 BP 1774 EP 1783 UT WOS:000073407700013 ER PT J AU Kim, J Park, YS Chung, JH Stubbs, L AF Kim, J Park, YS Chung, JH Stubbs, L TI The gene encoding sepiapterin reductase is located in central mouse Chromosome 6 SO MAMMALIAN GENOME RI Park, Young Shik/E-7317-2017 OI Park, Young Shik/0000-0002-8808-4530 SN 0938-8990 PD DEC PY 1997 VL 8 IS 12 BP 942 EP 942 DI 10.1007/s003359900631 UT WOS:A1997YH38100015 PM 9383299 ER PT J AU Rawn, CJ Makovec, D Golic, L Samardzija, Z Kolar, D AF Rawn, CJ Makovec, D Golic, L Samardzija, Z Kolar, D TI New crystal structure in the BaO-Ce2O3-TiO2 system SO MATERIALS RESEARCH BULLETIN AB A new structure located in the TiO2-rich corner of the BaO-Ce2O3-TiO2 system crystallizes with an orthorhombic unit cell, space group Pnma, and with lattice parameters a = 27.88(1), b = 7.745(2), and c = 17.350(4) Angstrom. Refinement on F resulted in R1 = 6.46% for 3868 F-0 > 4 sigma. The structure is made up of a network of corner-sharing TiO6 octahedra creating rhombic (perovskite-like) and pentagonal channels. In this new structure, there are eight unique rhombic positions (occupied chiefly by Ce atoms), four unique pentagonal positions (occupied chiefly by Ba atoms), and eight unique Ti positions. Full occupation of the sites would correspond to the formula Ba16Ce32Ti64O192; however, refinement of the site occupancies of the Ce and Ba atoms suggests some substitution of the cations and vacancies. Electron probe wavelength dispersive spectroscopic microanalysis averaged from twenty measurements on three crystals' results in 4.68 +/- 0.11 at% Ba, 9.63 +/- 0.30 at% Ce, and 18.57 +/- 0.35 at% Ti. (C) 1997 Elsevier Science Ltd. SN 0025-5408 PD DEC PY 1997 VL 32 IS 12 BP 1657 EP 1672 DI 10.1016/S0025-5408(97)00164-5 UT WOS:000071056500008 ER PT J AU Paranthaman, M Shoup, SS Beach, DB Williams, RK Specht, ED AF Paranthaman, M Shoup, SS Beach, DB Williams, RK Specht, ED TI Epitaxial growth of BaZrO3 films on single crystal oxide substrates using sol-gel alkoxide precursors SO MATERIALS RESEARCH BULLETIN AB Epitaxial BaZrO3 (barium zirconium oxide) films were grown on single crystal substrates. A BaZrO3 precursor solution was prepared by sol-gel synthesis using an all-alkoxide route. The barium precursors were prepared by reacting barium metal with 2-methoxyethanol, and zirconium precursors were prepared by exchanging ligands between zirconium n-propoxide and 2-methoxyethanol. The resulting BaZrO3 precursor solution was partially hydrolyzed and spin-coated on sapphire (100), SrTiO3 (strontium titanium oxide) (100), and LaAlO3 (lanthanum aluminum oxide) (100) substrates. The films were post-annealed in oxygen at 800 degrees C for 2 min in a rapid thermal annealer. The coating and the annealing procedures were repeated three times to obtain the desired thickness, 300 nm. X-ray diffraction studies showed the presence of a single (100) cube texture for BaZrO3 films on SrTiO3 and LaAlO3 substrates. The BaZrO3 films grown on sapphire had a random texture. The BaZrO3 films grown on SrTiO3 substrates had a sharp texture compared to that on LaAlO3 substrates. This may be due to the relatively smaller lattice mismatch between SrTiO3 and BaZrO3. (C) 1997 Elsevier Science Ltd. RI Specht, Eliot/A-5654-2009; Paranthaman, Mariappan/N-3866-2015 OI Specht, Eliot/0000-0002-3191-2163; Paranthaman, Mariappan/0000-0003-3009-8531 SN 0025-5408 PD DEC PY 1997 VL 32 IS 12 BP 1697 EP 1704 DI 10.1016/S0025-5408(97)00159-1 UT WOS:000071056500012 ER PT J AU Misra, A Wu, ZL Kush, MT Gibala, R AF Misra, A Wu, ZL Kush, MT Gibala, R TI Microstructures and mechanical properties of directionally solidified NiAl-Mo and NiAl-Mo(Re) eutectic alloys SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA AB The room temperature fracture toughness of a directionally-solidified (DS) NiAl-9 at.%Mo eutectic alloy was evaluated. It was found that the toughness of NiAl-refractory metal eutectic composites may be limited by the low ductility of the reinforcing bcc metal phase at room temperature and weak interfaces. The effects of the residual interstitial impurities and solid-solution-strengthening of Mo fibers by Ni and Al which partition to the fibers from the matrix on the mechanical properties were identified. The potential of rhenium (Re) addition, which is known to solid-solution soften and lower the ductile-to-brittle transition temperature of various bcc metals, to enhance the ductility and toughness of DS NiAl-9Mo eutectic alloy was also investigated. Re partitioned to the bcc metal phase and formed a substitutional solid solution. The interface morphology was changed from a faceted to a non-faceted one. Re alloying caused softening of the Mo fibers: and as a result the NiAl-Mo(Re) alloys were softer in compression and had similar to 20% higher fracture toughness values as compared to the transverse orientation toughness of NiAl-9Mo alloy. The toughness of the NiAl-Mo(Re) alloys was lower than the longitudinal orientation toughness of the NiAl-9Mo alloy due to the poor alignment of the Mo(Re) phase with the growth direction. Processing conditions were successfully changed to produce plane front solidification resulting in completely eutectic microstructures with the fibers well-aligned with the growth direction in the NiAl-9Mo alloy; similar effort is needed for NiAl-Mo(Re) alloys to achieve higher toughness in the longitudinal orientation. The toughening mechanisms operative in these alloys are discussed. (C) 1997 Elsevier Science S.A. RI Misra, Amit/H-1087-2012 SN 0921-5093 PD DEC PY 1997 VL 240 BP 75 EP 87 DI 10.1016/S0921-5093(97)00563-7 UT WOS:000071868000010 ER PT J AU Nieh, TG Wadsworth, J AF Nieh, TG Wadsworth, J TI Microstructural characteristics and deformation properties in superplastic intermetallics SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA AB Superplasticity in intermetallic alloys is reviewed. Intermetallics which have been demonstrated to be superplastic include nickel-based (Ni3Al, Ni3Si), iron-based (Fe3Al, FeAl), and titanium-based (Ti3Al, TiAl) alloys. Superplasticity has been recorded in both quasi-single-phase and two-phase intermetallic alloys. The microstructural characteristics and deformation properties of superplastic intermetallics are in many ways similar to those observed in conventional superplastic metal alloys. In the present paper, some of the unusual microstructural features pertinent to superplastic intermetallics are described. Two interesting features are especially highlighted: intermetallics can exhibit superplastic properties in a relatively coarse-grained condition (>100 mu m); and intermetallics with a metastable, inhomogeneous microstructure can exhibit superplasticity at low temperatures. Examples are given for both cases. In addition, the superplastic deformation mechanisms as well as microstructural characteristics in different intermetallics are discussed. (C) 1997 Elsevier Science S.A. RI Nieh, Tai-Gang/G-5912-2011 OI Nieh, Tai-Gang/0000-0002-2814-3746 SN 0921-5093 PD DEC PY 1997 VL 240 BP 88 EP 96 DI 10.1016/S0921-5093(97)00564-9 UT WOS:000071868000011 ER PT J AU Kad, BK Horton, JA AF Kad, BK Horton, JA TI Discrepancies between microscopic (TEM) and macroscopic (texture) observations in high temperature deformation of FeAl an Fe3Al-based alloys SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA AB Macroscopic texture measurements of Fe,Al-based alloys deformed at 925 less than or similar to T less than or equal to 1325 K in the B2 structure regime by rolling, forging and extrusion, at deformation rates of 10(-4)-10(1) s(-1), agree well with the numerically predicted textures for the (111){110} + (110){112} slip system activation [1,2], for each of these deformation histories. These results appear to be in disagreement with prior transmission electron microscopy (TEM) observations, that overwhelmingly support the activation of (100){011} and (100){001} slip systems at high temperature [3-7]. To reconcile this discrepancy, we revisit the issue of TEM observations within the framework of a deformation experiment in the Gleeble(TM) apparatus, where the high temperature deformation substructure is 'quenched-in' by imposing cooling rates of about 10(3) K.sec(-1). Thus the incidence of thermally induced dislocation reorganization is minimized. TEM examinations reveal that the 'quenched-in' dislocation substructure is indeed dominated by (111) dislocations and not (100) dislocations. (C) 1997 Elsevier Science S.A. SN 0921-5093 PD DEC PY 1997 VL 240 BP 118 EP 125 UT WOS:000071868000015 ER PT J AU He, Y Schwarz, RB Darling, T Hundley, M Whang, SH Wang, ZM AF He, Y Schwarz, RB Darling, T Hundley, M Whang, SH Wang, ZM TI Elastic constants and thermal expansion of single crystal gamma-TiAl from 300 to 750 K SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA AB The six independent elastic constants of a gamma-TiAl (Ti44Al56) single crystal have been measured for the first time from room temperature to 750 K using a resonant ultrasound spectroscopy technique. The values of C-12 and C-13 are virtually temperature independent, whereas C-11, C-33, C-44, and C-66 decrease between 6 and 9% from 300 to 750 K, The two independent linear thermal expansion coefficients alpha(1) (along [100] direction) and alpha(2) (along [001] direction) of single crystal gamma-TiAl have been measured from 4 to 750 K using two different apparatus. The elastic constants have been corrected for the effect of thermal expansion, and the corrected C-ij have been used to calculate the Young's and shear moduli along various crystal directions. The elastic constants and moduli values have also been extrapolated to 1273 K. Finally, the elastic anisotropy has also been calculated as a function of temperature. (C) 1997 Elsevier Science S.A. SN 0921-5093 PD DEC PY 1997 VL 240 BP 157 EP 163 DI 10.1016/S0921-5093(97)00575-3 UT WOS:000071868000021 ER PT J AU Larson, DJ Liu, CT Miller, MK AF Larson, DJ Liu, CT Miller, MK TI Microstructural characterization of segregation and precipitation in alpha(2)+gamma titanium aluminides SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA AB Atom probe field ion microscopy investigations of alpha(2) + gamma TiAl alloys doped with B and W indicate that a significant proportion of the boron is concentrated in boride precipitates and the tungsten segregates to both gamma/gamma and alpha(2)/gamma interfaces. The solubility of boron in the gamma and alpha(2) matrix phases was found to be 0.011 +/- 0.005 at.% B and 0.003 +/- 0.005 at.% B, respectively. The solubility of tungsten in the gamma and alpha(2) matrix phases was found to be 0.16 +/- 0.02 at.% W and 0.33 +/- 0.06 at.% W, respectively. Several borides including TiB2, TiB as well as a (Ti,Cr)(2)B phase were detected. No appreciable evidence of boron segregation to gamma/gamma or alpha(2)/gamma interfaces was observed. The interfacial coverage of tungsten at alpha(2)/gamma and gamma/gamma interfaces was estimated to be similar to 1 - 5%. Chromium was also found to segregate to certain gamma/gamma interfaces. The observation of partitioning and interfacial segregation supports the previous result that tungsten additions stabilize the a, lamellae against growth and coarsening. There is no experimental evidence that boron significantly affects the rates of growth and coarsening of the lamellar structure in alpha(2) + gamma TiAl alloys due to interfacial segregation; however, boron additions dramatically affect the initial lamellar spacing, possibly through a modification of the gamma phase nucleation site density. (C) 1997 Elsevier Science S.A. SN 0921-5093 PD DEC PY 1997 VL 240 BP 220 EP 228 DI 10.1016/S0921-5093(97)00585-6 UT WOS:000071868000031 ER PT J AU Schneibel, JH Specht, ED Munroe, PR AF Schneibel, JH Specht, ED Munroe, PR TI On the strength of nickel-containing B2 iron aluminides SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CA AB When some of the iron in the B2 iron aluminide Fe-45 at.% Al is replaced by nickel, several important changes occur. Nickel dramatically slows down the removal of quenched-in thermal vacancies during annealing. Also, nickel additions render the hardening due to thermal vacancies less effective than that in binary iron aluminides. Both of these effects may be linked to the formation of nickel-vacancy complexes. Nickel additions also cause substantial solid solution strengthening, and possible reasons for this result are discussed. Our findings are supported by vacancy concentration determinations, by yield strength measurements, and by transmission electron microscope observations. (C) 1997 Elsevier Science S.A. RI Specht, Eliot/A-5654-2009; Munroe, Paul/I-9313-2016 OI Specht, Eliot/0000-0002-3191-2163; Munroe, Paul/0000-0002-5091-2513 SN 0921-5093 EI 1873-4936 PD DEC PY 1997 VL 240 BP 245 EP 250 DI 10.1016/S0921-5093(97)00588-1 UT WOS:000071868000034 ER PT J AU Thoma, DJ Chu, F Peralta, P Kotula, PG Chen, KC Mitchell, TE AF Thoma, DJ Chu, F Peralta, P Kotula, PG Chen, KC Mitchell, TE TI Elastic and mechanical properties of Nb(Cr, V)(2) C15 Laves phases SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA AB The effect of vanadium alloying additions to NbCr2 has been studied; focusing on the phase stability, defect structures, elastic properties, and mechanical behavior of these C15 Laves phases. First, the ternary Nb-Cr-V phase diagram is presented. The C15 phase field of NbCr2 is significantly extended by V alloying along the constant niobium isoplethal section, suggesting that V atoms substitute primarily on Cr sites rather than Nb sites. Next, the elastic properties of the C15 Nb(Cr, V)(2) Laves phases were examined using resonant ultrasound spectroscopy. The vanadium alloyed Laves phase alloys have slightly higher shear modulus values and lower Poisson's ratios than binary NbCr2. Finally, the mechanical properties of the C15 phases were investigated by indentation tests at different temperatures. Increasing the vanadium content modestly increases the strength but slightly decreases the fracture toughness and increases the brittle-to-ductile transition temperature in the alloys. The correlations between the phase stability, defect structures, elastic properties, and mechanical response of the C15 phases are discussed using a combination of atomic size arguments and electronic structure analyses. From these interpretations, an alloying strategy for improving the mechanical properties in C15 NbCr2 is proposed. (C) 1997 Elsevier Science S.A. RI Kotula, Paul/A-7657-2011 OI Kotula, Paul/0000-0002-7521-2759 SN 0921-5093 PD DEC PY 1997 VL 240 BP 251 EP 259 DI 10.1016/S0921-5093(97)00589-3 UT WOS:000071868000035 ER PT J AU Zhu, JH Liaw, PK Liu, CT AF Zhu, JH Liaw, PK Liu, CT TI Effect of electron concentration on the phase stability of NbCr2-based Laves phase alloys SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA AB The phase stability in NbCr2-based transition-metal Laves phases was investigated, using data from binary X-Cr, Nb-X, and ternary Nb-Cr-X phase diagrams. It was shown that when the atomic size ratios are kept identical, the average electron concentration factor, eia, is the dominating factor in controlling the phase stability of NbCr2-based transition-metal Laves phases. The eia ratios for different Laves polytypes were determined as follows: with e/a < 5.76, the C15 structure is stabilized; at an ela range of 5.88-7.53, the C14 structure is stabilized; with e/a > 7.65, the C15 structure is stabilized again. A further increase in the electron concentration factor (e/a > 8) leads to the disordering of the alloy. (C) 1997 Elsevier Science S.A. OI Liu, Chain Tsuan/0000-0001-7888-9725 SN 0921-5093 PD DEC PY 1997 VL 240 BP 260 EP 264 DI 10.1016/S0921-5093(97)00590-X UT WOS:000071868000036 ER PT J AU Wang, JG Zhang, LC Chen, GL Ye, HQ Nieh, TG AF Wang, JG Zhang, LC Chen, GL Ye, HQ Nieh, TG TI Deformation-induced gamma <->alpha phase transformation in a hot-forged Ti-45Al-10Nb alloy SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA AB Deformation-induced gamma --> alpha(2) and alpha(2) --> gamma phase transformations in a hot-forged Ti-45Al-10Nb alloy have been investigated by using high-resolution transmission electron microscopy (HREM). The gamma --> alpha(2) transformation is an interface-related process, which involves the emission of the interfacial superdislocations from the misoriented semi-coherent alpha(2)/gamma interface. These superdislocations further react with each other or with the moving dislocations in gamma phase and results in the formation of alpha(2) phase. On the other hand, the deformation-induced alpha(2) --> gamma phase transformation nucleates either at the alpha(2)/gamma interfaces or at the stacking faults on the basal plane of alpha(2) phase. The growth of gamma plate is accomplished by the moving of a/6 < <10(1)over bar 0> > Shockley partials on alternate basal plane (0001)(alpha 2). The interfaces as well as the crystallographic orientation relationship between the as-cast or deformation-induced alpha(2) and gamma phase have been analyzed. The mechanisms for the deformation-induced gamma --> alpha(2) and alpha(2)-gamma phase transformations were also discussed. (C) 1997 Elsevier Science S.A. RI Nieh, Tai-Gang/G-5912-2011 OI Nieh, Tai-Gang/0000-0002-2814-3746 SN 0921-5093 PD DEC PY 1997 VL 240 BP 287 EP 292 UT WOS:000071868000041 ER PT J AU Chen, MW Lin, DL Xia, YM Liu, CT AF Chen, MW Lin, DL Xia, YM Liu, CT TI Strain rate sensitivity of ductility and fracture behaviors in a Fe-28Al alloy SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA AB The mechanical properties of Fe-28Al under a strain rate ranging from 10(-4) to 1300 s(-1) were tested in air and water at room temperature. The ductility, yield stress and ultimate stress of Fe-28Al are sensitive to the strain rate and gradually increase with strain rate in all test ranges. The fracture surface observations indicated that the fracture mode of Fe-28Al varies from complete transgranular fracture to a mixture of transgranular cleavage and intergranular fracture with strain rate increasing from 10(-4) to 1300 s(-1). It is proved that environmental embrittlement is a main factor controlling the ductility of Fe-28Al, even at high strain rate, and grain boundaries play different roles in the ductility of Fe-28Al at low and high strain rate. (C) 1997 Elsevier Science S.A. OI Liu, Chain Tsuan/0000-0001-7888-9725 SN 0921-5093 PD DEC PY 1997 VL 240 BP 317 EP 323 DI 10.1016/S0921-5093(97)00702-8 UT WOS:000071868000045 ER PT J AU Kang, BSJ Yao, Q Li, Z Liu, CT AF Kang, BSJ Yao, Q Li, Z Liu, CT TI Investigation on environmental assisted fracture behavior of iron aluminides using moire interferometry SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA AB Comparative crack growth tests of Fe-28%Al iron aluminide alloys (all with basic composition of Fe-28Al-5Cr at.%, with micro-alloying additives of Zr, C or B) under air, oxygen, or water environments were conducted using moire interferometry. Test results showed that the alloys are susceptible to room-temperature hydrogen embrittlement in both B2 and DO3 conditions, and FA-187 and FA-189 are intrinsically more brittle than FA-186. (C) 1997 Elsevier Science S.A. OI Liu, Chain Tsuan/0000-0001-7888-9725 SN 0921-5093 PD DEC PY 1997 VL 240 BP 344 EP 352 DI 10.1016/S0921-5093(97)00602-3 UT WOS:000071868000049 ER PT J AU Heatherly, L George, EP Liu, CT Yamaguchi, M AF Heatherly, L George, EP Liu, CT Yamaguchi, M TI A study of the cleavage fracture behavior of PST TiAl alloys SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CA AB Samples of two polysynthetically twinned (PST) TiAl alloys (Ti-49at.%Al and Ti-49at.%Al-0.6at.%Cr) were fractured in different environments at room temperature and the fracture surfaces were analyzed using scanning Auger and scanning electron microscopy. These techniques were employed to determine the fracture mode and the chemical composition of the fracture surfaces of the TiAl alloys. Our study clearly indicates that all of the fracture surfaces exposed by bend testing were alpha(2), except when fracture occurred across the lamellae. No chromium enrichment was observed on any of the surfaces exposed during the fracture. From these observations, it was concluded that the fracture mode for these materials is cleavage through the alpha(2)-phase. (C) 1997 Elsevier Science S.A. RI George, Easo/L-5434-2014; OI Liu, Chain Tsuan/0000-0001-7888-9725 SN 0921-5093 EI 1873-4936 PD DEC PY 1997 VL 240 BP 404 EP 409 DI 10.1016/S0921-5093(97)00610-2 UT WOS:000071868000057 ER PT J AU Hsiung, LM Nieh, TG AF Hsiung, LM Nieh, TG TI The evolution of deformation substructure in a creep deformed fully-lamellar TiAl alloy SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA AB The evolution of deformation substructure in a powder metallurgy (P/M) TIAl alloy creep deformed at 760 degrees C has been examined using transmission electron microscopy. Since the multiplication of lattice dislocations within gamma lamellae becomes limited as a result of a refined fully-lamellar (FL) microstructure (i.e. refined lamellar spacing) within the PIM TiAl alloy, the deformation of the alloy at the primary creep stage is mainly accommodated by soft lamellar grains through the movement of interfacial dislocations in the gamma-alpha(2) and gamma-gamma interfaces. The mobility of interfacial dislocations is primarily impeded by grain boundaries, interface ledges and dislocation barriers formed by the impingement of lattice dislocations to the lamellar interfaces. When the alloy is deformed into the secondary creep stage, the density of interfacial dislocations increases and deformation twins nucleate and grow from the lamellar interfaces. It is suggested that deformation twinning in FL-TiAl results from a stress-relief process due to the pile-up of interfacial dislocations during deformation. The alloy becomes more resistant to creep deformation as a result of the deformation twinning because the deformation twins further restrict the dislocation motion within the gamma lamellae, and the formation of sessile dislocations at the intersections between the deformation twins and the gamma or alpha(2) lamellae provides effective barriers for the movement of interfacial dislocations. (C) 1997 Elsevier Science S.A. RI Nieh, Tai-Gang/G-5912-2011 OI Nieh, Tai-Gang/0000-0002-2814-3746 SN 0921-5093 PD DEC PY 1997 VL 240 BP 438 EP 444 DI 10.1016/S0921-5093(97)00614-X UT WOS:000071868000061 ER PT J AU Zhu, P Li, JCM Liu, CT AF Zhu, P Li, JCM Liu, CT TI Combustion reaction in multilayered nickel and aluminum foils SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA AB Ni/Al (3/1) multilayer reaction piles were heated in a vacuum furnace and the temperature (100 readings per s for a precision of 0.2 degrees C) of the reaction pile was measured continuously during the combustion reaction. The ignition temperature (at which the combustion starts) is almost the same independent of heating rate and the thickness of the foils. This temperature corresponds to the melting of Al which triggers the reaction. For thin Ni foils, less than 25 mu m thick, the maximum temperature shows a plateau with time, close to the adiabatic reaction temperature or the eutectic temperature close to Ni3Al. For thicker Ni foils, the maximum temperature decreases with the increase of foil thickness and the combustion is incomplete. The reaction time between the ignition temperature and the maximum temperature (or the beginning of the plateau temperature) increases from 8 s for a 12.5 mu m Ni foil to 125 s for a 150 mu m Ni foil and the relation is almost linear. For Ni foils less than 25 mu m thick, the final microstructure is homogeneous with a grain size approximately equal to the combined initial Ni and Al foil thicknesses, In the range used, 1-100 degrees C min(-1), the heating rate has very little effect on the combustion reaction. From the temperature-time profile and microstructure analysis, there are evidences of melting of Al, decomposition of Al3Ni and Al3Ni2, and the formation of NiAl and Ni3Al. (C) 1997 Elsevier Science S.A. OI Liu, Chain Tsuan/0000-0001-7888-9725 SN 0921-5093 PD DEC PY 1997 VL 240 BP 532 EP 539 DI 10.1016/S0921-5093(97)00627-8 UT WOS:000071868000074 ER PT J AU Sikka, VK Santella, ML Orth, JE AF Sikka, VK Santella, ML Orth, JE TI Processing and operating experience of Ni3Al-based intermetallic alloy IC-221M SO MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING CT 4th Conference on High Temperature Intermetallics CY APR 27-MAY 01, 1997 CL SAN DIEGO, CALIFORNIA AB The cast Ni3Al-based intermetallic alloy IC-221M is the most advanced in its commercial applications. This paper presents progress made for this alloy in the areas of: (1) composition optimization; (2) melting process development; (3) casting process; (4) mechanical properties; (5) welding process, weld repairs, and thermal aging response; and (6) applications. This paper also reviews the operating experience with several of the components. The projection for future growth in the applications of nickel aluminide is also discussed. (C) 1997 Elsevier Science S.A. SN 0921-5093 PD DEC PY 1997 VL 240 BP 564 EP 569 DI 10.1016/S0921-5093(97)00631-X UT WOS:000071868000078 ER EF