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1/2 Sintering of Mullite-Containing Materials: I. Effect of Composition (open access)

1/2 Sintering of Mullite-Containing Materials: I. Effect of Composition

Sintering behavior of mullite-containing powders was studied over a range of chemical compositions (Al{sub 2}O{sub 3}/SiO{sub 2} ratio). Densification measurements were made for both liquid phase-containing and solid state systems. Small amounts of liquid phase were observed to have a significant effect on densification rate. A linear relationship was obtained between the percent of theoretical density and the logarithm of time for compositions in the range 73-75 wt% Al{sub 2}O{sub 3}. Currently available models for intermediate stage sintering kinetics were considered to be inadequate for these systems. Grain boundary transport 0r diffusion appeared to be the primary mechanism of densification.
Date: December 1, 1981
Creator: Sacks, Michael D. & Pask, Joseph A.
System: The UNT Digital Library
1-D Van der Waals Foams Heated by Ion Beam Energy Deposition (open access)

1-D Van der Waals Foams Heated by Ion Beam Energy Deposition

One dimensional simulations of various initial average density aluminum foams (modeled as slabs of solid metal separated by low density regions) heated by volumetric energy deposition are conducted with a Lagrangian hydrodynamics code using a van der Waals equation of tate (EOS). The resulting behavior is studied to facilitate the design of future warm dense matter (WDM) experiments at LBNL. In the simulations the energy deposition ranges from 10 to 30 kJ/g and from 0.075 to 4.0 ns total pulse length, resulting in temperatures from approximately 1 o 4 eV. We study peak pressures and temperatures in the foams, expansion velocity, and the phase evolution. Five relevant time scales in the problem are identified. Additionally, we present a method for characterizing the level of inhomogeneity in a foam target as it is heated and the time it takes for a foam to homogenize.
Date: December 23, 2009
Creator: Zylstra, A. B.; Barnard, J. J. & More, R. M.
System: The UNT Digital Library
1 MeV electron irradiation of solid Xe nanoclusters in Al : an in-situ HRTEM study. (open access)

1 MeV electron irradiation of solid Xe nanoclusters in Al : an in-situ HRTEM study.

Thin film samples of a simple embedded nanocluster system consisting of solid Xe precipitates in Al have been subjected to 1 MeV electron irradiation in a high-voltage electron microscope. High-resolution images have been recorded on videotape in order to monitor the changes to the system resulting from the passage of electrons through the film. Inspection of the video recordings (in some cases frame-by-frame) reveals that complex, rapid processes occur under the electron beam. These include, movement of small clusters, coalescence of neighboring clusters, shape changes, the apparent melting and resolidification of the Xe, and the creation and annealing of extended defects within the Xe lattice. A tentative interpretation of some of the observations is presented in terms of the electron-induced displacement processes at the surface of the clusters.
Date: December 5, 1997
Creator: Donnelly, S. E.; Furuya, K.; Song, M.; Birtcher, R. C. & Allen, C. W.
System: The UNT Digital Library
2-D Finite Element Cable and Box IEMP Analysis (open access)

2-D Finite Element Cable and Box IEMP Analysis

A 2-D finite element code has been developed for the solution of arbitrary geometry cable SGEMP and box IEMP problems. The quasi- static electric field equations with radiation- induced charge deposition and radiation-induced conductivity y are numerically solved on a triangular mesh. Multiple regions of different dielectric materials and multiple conductors are permitted.
Date: December 17, 1998
Creator: Scivner, G.J. & Turner, C.D.
System: The UNT Digital Library
3-D field computations for accelerator magnets using finite element and integral codes (open access)

3-D field computations for accelerator magnets using finite element and integral codes

Two dimensional (2-D) computation has been an accepted part of the design of accelerator magnets since the 1960`s, but three-dimensional (3-D) computations are still not fully trusted. This paper describes the successes and limitations of 3-D computations, as applied to accelerator magnets for the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). Both the finite element code TOSCA and the edge element volume integral code CORAL have been used in these computations. The ends of the dipole bending magnet for the injector synchrotron were designed using TOSCA; comparisons with measurements are described. Computation of other APS magnets are also described.
Date: December 1, 1992
Creator: Turner, L. R.; Kim, S. H.; Kim, K. & Kettunen, L.
System: The UNT Digital Library
A 3-D numerical study of pinhole diffraction to predict the accuracy of EUV point diffraction interferometry (open access)

A 3-D numerical study of pinhole diffraction to predict the accuracy of EUV point diffraction interferometry

A 3-D electromagnetic field simulation is used to model the propagation of extreme ultraviolet (EUV), 13-nm, light through sub-1500 {Angstrom} dia pinholes in a highly absorptive medium. Deviations of the diffracted wavefront phase from an ideal sphere are studied within 0.1 numerical aperture, to predict the accuracy of EUV point diffraction interferometersused in at-wavelength testing of nearly diffraction-limited EUV optical systems. Aberration magnitudes are studied for various 3-D pinhole models, including cylindrical and conical pinhole bores.
Date: December 1, 1995
Creator: Goldberg, K.A.; Tejnil, E. & Bokor, J.
System: The UNT Digital Library
3-D subsurface modeling within the framework of an environmental restoration information system: Prototype results using earthvision (open access)

3-D subsurface modeling within the framework of an environmental restoration information system: Prototype results using earthvision

As a result of the DOE Oak Ridge Reservation (DOE-ORR) placement on the EPA Superfund National Priorities List in December of 1989, all remedial activities, including characterization, remedial alternatives selection, and implementation of remedial measures, must meet the combined requirements of RCRA, CERCLA, and NEPA. The Environmental Restoration Program, therefore, was established with the mission of eliminating or reducing to prescribed safe levels the risks to the environment or to human health and safety posed by inactive and surplus DOE-ORR managed sites and facilities that have been contaminated by radioactive and surplus DOE-ORR managed sites and facilities that have been contaminated by radioactive, hazardous, or mixed wastes. In accordance with an established Federal Facilities Agreement (FFA), waste sites and facilities across the DOE-ORR have been inventoried, prioritized, and are being systematically investigated and remediated under the direction of Environmental Restoration. EarthVision, a product of Dynamic Graphics, Inc., that provides three-dimensional (3-D) modeling and visualization, was exercised within the framework of an environmental restoration (ER) decision support system. The goal of the prototype was to investigate framework integration issues including compatibility and value to decision making. This paper describes the ER program, study site, and information system framework; selected EarthVision results …
Date: December 31, 1994
Creator: Goeltz, R. T. & Zondlo, T. F.
System: The UNT Digital Library
3-Nitropropionic Acid is a Suicide Inhibitor of MitochondrialRespiration that, Upon Oxidation by Complex II, Forms a Covalent AdductWith a Catalytic Base Arginine in the Active Site of the Enzyme (open access)

3-Nitropropionic Acid is a Suicide Inhibitor of MitochondrialRespiration that, Upon Oxidation by Complex II, Forms a Covalent AdductWith a Catalytic Base Arginine in the Active Site of the Enzyme

We report three new structures of mitochondrial respiratory Complex II (succinate ubiquinone oxidoreductase, E.C. 1.3.5.1) at up to 2.1 {angstrom} resolution, with various inhibitors. The structures define the conformation of the bound inhibitors and suggest the residues involved in substrate binding and catalysis at the dicarboxylate site. In particular they support the role of Arg297 as a general base catalyst accepting a proton in the dehydrogenation of succinate. The dicarboxylate ligand in oxaloacetate-containing crystals appears to be the same as that reported for Shewanella flavocytochrome c treated with fumarate. The plant and fungal toxin 3-nitropropionic acid, an irreversible inactivator of succinate dehydrogenase, forms a covalent adduct with the side chain of Arg297. The modification eliminates a trypsin cleavage site in the flavoprotein, and tandem mass spectroscopic analysis of the new fragment shows the mass of Arg 297 to be increased by 83 Da and to have potential of losing 44 Da, consistent with decarboxylation, during fragmentation.
Date: December 1, 2005
Creator: Huang, Li-shar; Sun, Gang; Cobessi, David; Wang, Andy C.; Shen,John T.; Tung, Eric Y. et al.
System: The UNT Digital Library
4-D XRD for strain in many grains using triangulation (open access)

4-D XRD for strain in many grains using triangulation

Determination of the strains in a polycrystalline materialusing 4-D XRD reveals sub-grain and grain-to-grain behavior as a functionof stress. Here 4-D XRD involves an experimental procedure usingpolychromatic micro-beam X-radiation (micro-Laue) to characterizepolycrystalline materials in spatial location as well as with increasingstress. The in-situ tensile loading experiment measured strain in a modelaluminum-sapphire metal matrix composite using the Advanced Light Source,Beam-line 7.3.3. Micro-Laue resolves individual grains in thepolycrystalline matrix. Results obtained from a list of grains sorted bycrystallographic orientation depict the strain states within and amongindividual grains. Locating the grain positions in the planeperpendicular to the incident beam is trivial. However, determining theexact location of grains within a 3-D space is challenging. Determiningthe depth of the grains within the matrix (along the beam direction)involved a triangulation method tracing individual rays that producespots on the CCD back to the point of origin. Triangulation wasexperimentally implemented by simulating a 3-D detector capturingmultiple diffraction images while increasing the camera to sampledistance. Hence by observing the intersection of rays from multiple spotsbelonging to the corresponding grain, depth is calculated. Depthresolution is a function of the number of images collected, grain to beamsize ratio, and the pixel resolution of the CCD. The 4DXRD methodprovides grain morphologies, strain …
Date: December 31, 2006
Creator: Bale, Hrishikesh A.; Hanan, Jay C. & Tamura, Nobumichi
System: The UNT Digital Library
5. international workshop on the identification of transcribed sequences (open access)

5. international workshop on the identification of transcribed sequences

This workshop was held November 5--8, 1995 in Les Embiez, France. The purpose of this conference was to provide a multidisciplinary forum for exchange of state-of-the-art information on mapping the human genome. Attention is focused on the following topics: transcriptional maps; functional analysis; techniques; model organisms; and tissue specific libraries and genes. Abstracts are included of the papers that were presented.
Date: December 31, 1995
Creator: unknown
System: The UNT Digital Library
The 8.4 MW Modulator/Regulator Power Systems for the Electron Cyclotron Heating Facility Upgrade at DIII-D (open access)

The 8.4 MW Modulator/Regulator Power Systems for the Electron Cyclotron Heating Facility Upgrade at DIII-D

Over the next three years the DIII-D National Fusion Facility at General Atomics will upgrade its electron cyclotron heating (ECH) capability from the present 3 MW at 110 GHz to 10 MW of injected microwave power. There will be ten gyrotron tubes supplied by five 8.4 MW modulator/regulator (M/R) power systems. The project has gained considerable leverage from the acquisition of surplus hardware from the MFTF program that was conducted at LLNL in the early 1980s. One of these systems had been refurbished and converted for use as an ECH power supply earlier. The experience gained and the lessons learned from operating that system have proved valuable in guiding the engineering of the new systems. This paper provides an overview of the power system design and a report on the present status of the project.
Date: December 1999
Creator: Pronko, S. G. E. & Baggest, D. S.
System: The UNT Digital Library
8. annual national conference of black physics students -- A summary report (open access)

8. annual national conference of black physics students -- A summary report

The primary goals of the conference were to: (1) Develop a peer/mentor network within the African-American physics community; (2) Inform African-American students in physics of the various academic and professional opportunities; and (3) Bring important academic, economic and political issues and developments in the field to the attention of the students. The conference program was designed to fulfill these goals and optimize the students` exposure to physics as a professional and its real-life applications in both industry and academia.
Date: December 31, 1994
Creator: Valk, H.S.
System: The UNT Digital Library
9. international mouse genome conference (open access)

9. international mouse genome conference

This conference was held November 12--16, 1995 in Ann Arbor, Michigan. The purpose of this conference was to provide a multidisciplinary forum for exchange of state-of-the-art information on genetic mapping in mice. This report contains abstracts of presentations, focusing on the following areas: mutation identification; comparative mapping; informatics and complex traits; mutagenesis; gene identification and new technology; and genetic and physical mapping.
Date: December 31, 1995
Creator: unknown
System: The UNT Digital Library
9 M.y. record of southern Nevada climate from Yucca Mountain secondary minerals (open access)

9 M.y. record of southern Nevada climate from Yucca Mountain secondary minerals

Yucca Mountain, Nevada, is presently the object of intense study as a potential permanent repository for the Nation`s high-level radioactive wastes. The mountain consists of a thick sequence of volcanic tuffs within which the depth to water table ranges from 500 to 700 meters below the land surface. This thick unsaturated zone (UZ), which would host the projected repository, coupled with the present day arid to semi-arid climate, is considered a favorable attribute of the site. Evaluation of the site includes defining the relation between climate variability, as the input function or driver of site- and regional-scale ground-water flow, and the possible future transport and release of radionuclides to the accessible environment. Secondary calcite and opal have been deposited in the UZ by meteoric waters that infiltrated through overlying soils and percolated through the tuffs. The oxygen isotopic composition ({delta}{sup 18}O values) of these minerals reflect contemporaneous meteoric waters and the {delta}{sup 13}C values reflect soil organic matter, and hence the resident plant community, at the time of infiltration. Recent U/Pb age determinations of opal in these occurrences, coupled with the {delta}{sup 13}C values of associated calcite, allow broadbrush reconstructions of climate patterns during the past 9 M.y.
Date: December 1998
Creator: Whelan, Joseph F. & Moscati, Richard J.
System: The UNT Digital Library
A 10-GeV, 5-MW proton source for a muon-muon collider (open access)

A 10-GeV, 5-MW proton source for a muon-muon collider

The performance parameters of a proton source which produces the required flux of muons for a 2-TeV on 2-TeV muon collider are: a beam energy of 10 GeV, a repetition rate of 30 Hz, two bunches per pulse with 5 x 10{sup 13} protons per bunch, and an rms bunch length of 3 nsec (1). Aside from the bunch length requirement, these parameters are identical to those of a 5-MW proton source for a spallation neutron source based on a 10-GeV rapid cycling synchrotron (RCS) (2). The 10-GeV synchrotron uses a 2-GeV accelerator system as its injector, and the 2-GeV RCS is an extension of a feasibility study for a I-MW spallation source described elsewhere (3--9). A study for the 5-MW spallation source was performed for ANL site-specific geometrical requirements. Details are presented for a site-independent proton source suitable for the muon collider utilizing the results of the 5-MW spallation source study.
Date: December 31, 1995
Creator: Cho, Y.; Chae, Y.-C. & Crosbie, E.
System: The UNT Digital Library
A 10-GeV, 5-MW proton source for a pulsed spallation source (open access)

A 10-GeV, 5-MW proton source for a pulsed spallation source

A feasibility study for a pulsed spallation source based on a 5-MW, 10-GeV rapid proton synchrotron (RCS) is in progress. The integrated concept and performance parameters of the facility are discussed. The 10-GeV synchrotron uses as its injector the 2-GeV accelerator system of a 1-MW source described elsewhere. The 1-MW source accelerator system consists of a 400-MeV H{sup {minus}} linac with 2.5 MeV energy spread in the 75% chopped (25% removed) beam and a 30-Hz RCS that accelerates the 400-MeV beam to 2 GeV. The time averaged current of the accelerator system is 0.5 mA, equivalent to 1.04 {times} 10{sup 14} protons per pulse. The 10-GeV RCS accepts the 2 GeV beam and accelerates it to 10 GeV. Beam transfer from the 2-GeV synchrotron to the 10-GeV machine u highly efficient bunch-to-bucket injection, so that the transfer can be made without beam loss. The synchrotron lattice uses FODO cells of 90{degrees} phase advance. Dispersion-free straight sections are obtained using a missing magnet scheme. The synchrotron magnets are powered by dual-frequency resonant circuits. The magnets are excited at a 20-Hz rate and de-excited at 60-Hz. resulting in an effective 30-Hz rate. A key feature of the design of this accelerator system …
Date: December 31, 1995
Creator: Cho, Y.; Chae, Y.C. & Crosbie, E.
System: The UNT Digital Library
10-GW CO₂ laser system at the Brookhaven Accelerator Test Facility (open access)

10-GW CO₂ laser system at the Brookhaven Accelerator Test Facility

Design and performance of a high peak-power CO{sub 2} laser system to produce subnanosecond IR pulses for electron acceleration experiment are presented. We discuss theoretical aspects of the picosecond laser pulse propagation in a molecular amplifier and a design approach towards compact Terawatt CO{sub 2} laser systems.
Date: December 31, 1993
Creator: Pogorelsky, I.; Fischer, J. & Fisher, A. S.
System: The UNT Digital Library
10. international mouse genome conference (open access)

10. international mouse genome conference

Ten years after hosting the First International Mammalian Genome Conference in Paris in 1986, Dr. Jean-Louis Guenet presided over the Tenth Conference at the Pasteur Institute, October 7--10, 1996. The 1986 conference was a satellite to the Human Gene Mapping Workshop and had approximately 50 attendees. The 1996 meeting was attended by 300 scientists from around the world. In the interim, the number of mapped loci in the mouse increased from 1,000 to over 20,000. This report contains a listing of the program and its participants, and two articles that review the meeting and the role of the laboratory mouse in the Human Genome project. More than 200 papers were presented at the conference covering the following topics: International mouse chromosome committee meetings; Mutant generation and identification; Physical and genetic maps; New technology and resources; Chromatin structure and gene regulation; Rate and hamster genetic maps; Informatics and databases; and Quantitative trait analysis.
Date: December 31, 1996
Creator: Meisler, M. H.
System: The UNT Digital Library
A 12-channel VMEbus-based pulse-height analysis module (open access)

A 12-channel VMEbus-based pulse-height analysis module

The author describes a 12-channel VMEbus-based pulse-height analysis board that was designed for use in a high-rate, multidetector, gamma-ray imaging system. This module was designed to minimize dead-time losses and to allow all key parameters to be software controlled. Gamma-ray detectors are connected directly to this module, eliminating the need for additional electronics.
Date: December 1, 1993
Creator: Arnone, G. J.
System: The UNT Digital Library
A 14.6 Arcsecond Quasar Lens Split by a Massive Dark Matter Halo (open access)

A 14.6 Arcsecond Quasar Lens Split by a Massive Dark Matter Halo

Gravitational lensing is a powerful tool to study the distribution of dark matter in the universe. The cold dark matter model of structure formation predicts the existence of quasars gravitationally lensed by concentrations of dark matter so massive that the quasar images would be split by over 7 inches. However, numerous searches for large-separation lensed quasars have been unsuccessful; all of the roughly 70 lensed quasars known to date, such as Q0957+561, have smaller splittings, and can be explained in terms of galaxy scale concentrations of baryonic matter that have undergone dissipative collapse. Here they report the discovery of the first large-separation lensed quasar, SDSS J1004+4112, with a maximum separation of 14.62 inches; at this separation, the lensing object must be dominated by dark matter. While gravitationally lensed galaxies of even large separation are known, large-separation quasars are more useful cosmological probes because of the simplicity of the resulting lens systems. The discovery in their current quasar sample is fully consistent with the theoretical expectations based on the cold dark matter model.
Date: December 4, 2003
Creator: Inada, N.; Oguri, M.; Pindor, B.; Hennawi, J.; Chiu, K.; Zheng, W. et al.
System: The UNT Digital Library
15. International Conference on Plant Growth Substances: Program -- Abstracts (open access)

15. International Conference on Plant Growth Substances: Program -- Abstracts

Since the 14th Conference in Amsterdam in 1991, progress in plant hormone research and developmental plant biology has been truly astonishing. The five ``classical`` plant hormones, auxin, gibberellin, cytokinin, ethylene, and abscisic acid, have been joined by a number of new signal molecules, e.g., systemin, jasmonic acid, salicylic acid, whose biosynthesis and functions are being understood in ever greater detail. Molecular genetics has opened new vistas in an understanding of transduction pathways that regulate developmental processes in response to hormonal and environmental signals. The program of the 15th Conference includes accounts of this progress and brings together scientists whose work focuses on physiological, biochemical, and chemical aspects of plant growth regulation. This volume contains the abstracts of papers presented at this conference.
Date: December 31, 1995
Creator: unknown
System: The UNT Digital Library
17 USC 108(h): The “Last Twenty Years” Exception (open access)

17 USC 108(h): The “Last Twenty Years” Exception

This document is part of a series of white papers on various copyright issues. One statute, 17 USC § 108, provides a number of exceptions specifically for libraries. In addition to fair use, there are a variety of other exceptions built into the copyright law that don’t get as much attention.This paper specifically addresses one of 108’s lesser-used provisions and the value it may hold for libraries and archives: 108(h).
Date: December 2017
Creator: Wolfson, Stephen M.
System: The UNT Digital Library
19-electron intermediates in the Ligand Substitution of CpW(CO)3with a Lewis Base (open access)

19-electron intermediates in the Ligand Substitution of CpW(CO)3with a Lewis Base

Odd electron species are important intermediates in organometallic chemistry, participating in a variety of catalytic and electron-transfer reactions which produce stable even-electron products. While electron deficient 17-electron (17e) radicals have been well characterized, the possible existence of short-lived 19-electron (19e) radicals has been a subject of continuing investigation. 19e radicals have been postulated as intermediates in the photochemical ligand substitution and disproportionation reactions of organometallic dimers containing a single metal-metal bond, yet the reactions of these intermediates on diffusion-limited time scales (ns-{micro}s) have never been directly observed. This study resolves the 19e dynamics in the ligand substitution of 17e radicals CpW(CO){sub 3}{sup {sm_bullet}} (Cp = C{sub 5}H{sub 5}) with the Lewis base P(OMe){sub 3}, providing the first complete description 19e reactivity.
Date: December 14, 2005
Creator: Cahoon, James F.; Kling, Matthias F.; Sawyer, Karma R.; Frei,Heinz & Harris, Charles B.
System: The UNT Digital Library
24-th Order high temperature expansion for the 3-d Ising model (open access)

24-th Order high temperature expansion for the 3-d Ising model

The authors present the series for the free energy and their estimate for the critical exponent {alpha}, as computed by a recursive bookkeeping algorithm on the CM5. They begin with a discussion of the algorithm to compute the High-Temperature expansion on finite 3-D Ising lattices.
Date: December 1, 1994
Creator: Glaessner, U.; Schilling, K.; Bhanot, G. & Creutz, M.
System: The UNT Digital Library