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ENCAPSULATION OF PALLADIUM IN POROUS WALL HOLLOW GLASS MICROSPHERES (open access)

ENCAPSULATION OF PALLADIUM IN POROUS WALL HOLLOW GLASS MICROSPHERES

A new encapsulation method was investigated in an attempt to develop an improved palladium packing material for hydrogen isotope separation. Porous wall hollow glass microspheres (PWHGMs) were produced by using a flame former, heat treating and acid leaching. The PWHGMs were then filled with palladium salt using a soak-and-dry process. The palladium salt was reduced at high temperature to leave palladium inside the microspheres.
Date: April 9, 2008
Creator: Heung, L.; George Wicks, G. & Ray Schumacher, R.
System: The UNT Digital Library
New Results on Leptonic B Meson Decays at BaBar (open access)

New Results on Leptonic B Meson Decays at BaBar

The authors present selected new results on leptonic B meson decays from the BABAR experiment: searches for the decays B{sup 0} {yields} {ell}{sup +}{ell}{sup -}, B{sup +} {yields} {ell}{sup +}{nu} and B{sup 0} {yields} {ell}{sup +}{tau}{sup -}, and B {yields} K{nu}{bar {nu}}, where {ell} = e or {mu}. They observe no evidence for these decays and set upper limits on their branching fractions.
Date: June 9, 2008
Creator: Kim, Hojeong
System: The UNT Digital Library
SYNTHESIS OF THE FULLY PROTECTED PHOSPHORAMIDITE OF THE BENZENE-DNA ADDUCT, N2- (4-HYDROXYPHENYL)-2'-DEOXYGUANOSINE AND INCORPORATION OF THE LATER INTO DNA OLIGOMERS (open access)

SYNTHESIS OF THE FULLY PROTECTED PHOSPHORAMIDITE OF THE BENZENE-DNA ADDUCT, N2- (4-HYDROXYPHENYL)-2'-DEOXYGUANOSINE AND INCORPORATION OF THE LATER INTO DNA OLIGOMERS

N2-(4-Hydroxyphenyl)-2'-deoxyguanosine-5'-O-DMT-3'-phosphoramidite has been synthesized and used to incorporate the N2-(4-hydroxyphenyl)-2'-dG (N2-4-HOPh-dG) into DNA, using solid-state synthesis technology. The key step to obtaining the xenonucleoside is a palladium (Xantphos-chelated) catalyzed N2-arylation (Buchwald-Hartwig reaction) of a fully protected 2'-deoxyguanosine derivative by 4-isobutyryloxybromobenzene. The reaction proceeded in good yield and the adduct was converted to the required 5'-O-DMT-3'-O-phosphoramidite by standard methods. The latter was used to synthesize oligodeoxynucleotides in which the N2-4-HOPh-dG adduct was incorporated site-specifically. The oligomers were purified by reverse-phase HPLC. Enzymatic hydrolysis and HPLC analysis confirmed the presence of this adduct in the oligomers.
Date: June 9, 2008
Creator: Chenna, Ahmed; Gupta, Ramesh C.; Bonala, Radha R.; Johnson, Francis & Huang, Bo
System: The UNT Digital Library
Structure and Reactions of Carbon and Hydrogen on Ru(0001): A Scanning Tunneling Microscopy Study (open access)

Structure and Reactions of Carbon and Hydrogen on Ru(0001): A Scanning Tunneling Microscopy Study

The interaction between carbon and hydrogen atoms on a Ru(0001) surface was studied using scanning tunneling microscopy (STM), Density Functional Theory (DFT) and STM image calculations. Formation of CH species by reaction between adsorbed H and C was observed to occur readily at 100 K. When the coverage of H increased new complexes of the form CH+nH (n = 1, 2 and 3) were observed. These complexes, never observed before, might be precursors for further hydrogenation reactions. DFT analysis reveals that a considerable energy barrier exists for the CH+H {yields} CH{sub 2} reaction.
Date: September 9, 2008
Creator: Shimizu, Tomoko K.; Mugarza, Aitor; Cerda, Jorge & Salmeron, Miquel
System: The UNT Digital Library
Silver ion mediated shape control of platinum nanoparticles: Removal of silver by selective etching leads to increased catalytic activity (open access)

Silver ion mediated shape control of platinum nanoparticles: Removal of silver by selective etching leads to increased catalytic activity

A procedure has been developed for the selective etching of Ag from Pt nanoparticles of well-defined shape, resulting in the formation of elementally-pure Pt cubes, cuboctahedra, or octahedra, with a largest vertex-to-vertex distance of {approx}9.5 nm from Ag-modified Pt nanoparticles. A nitric acid etching process was applied Pt nanoparticles supported on mesoporous silica, as well as nanoparticles dispersed in aqueous solution. The characterization of the silica-supported particles by XRD, TEM, and N{sub 2} adsorption measurements demonstrated that the structure of the nanoparticles and the mesoporous support remained conserved during etching in concentrated nitric acid. Both elemental analysis and ethylene hydrogenation indicated etching of Ag is only effective when [HNO{sub 3}] {ge} 7 M; below this concentration, the removal of Ag is only {approx}10%. Ethylene hydrogenation activity increased by four orders of magnitude after the etching of Pt octahedra that contained the highest fraction of silver. High-resolution transmission electron microscopy of the unsupported particles after etching demonstrated that etching does not alter the surface structure of the Pt nanoparticles. High [HNO{sub 3}] led to the decomposition of the capping agent, polyvinylpyrollidone (PVP); infrared spectroscopy confirmed that many decomposition products were present on the surface during etching, including carbon monoxide.
Date: January 9, 2008
Creator: Grass, Michael E.; Yue, Yao; Habas, Susan E.; Rioux, Robert M.; Teall, Chelsea I. & Somorjai, G.A.
System: The UNT Digital Library
The US Support program to IAEA Safeguards - 2008 (open access)

The US Support program to IAEA Safeguards - 2008

The U.S. Support Program to IAEA Safeguards (USSP) was established in 1977 to provide technical assistance to the IAEA Department of Safeguards. Since that time the U.S. Department of State has provided funding of over $200 million and over 900 tasks have been completed by USSP contractors on behalf of the KEA. The USSP is directed by a U.S. interagency subcommittee known as the Subgroup on Safeguards Technical Support (SSTS) and is managed by the International Safeguards Project Office (ISPO) at Brookhaven National Laboratory. In recent years, the SSTS and ISPO have identified priorities to guide the process of determining which IAEA requests are aligned with US. policy and will be funded. The USSP priorities are reviewed and updated prior to the USSP Annual Review Meeting which is hosted by the International Atomic Energy Agency (IAEA) each spring in Vienna, Austria. This paper will report on the 2008 USSP priorities and be an introduction for a session which will consist of four papers on USSP priorities and four other papers related to USSP activities.
Date: June 9, 2008
Creator: Pepper,S.
System: The UNT Digital Library
EFFECTIVE DOSIMETRIC HALF LIFE OF CESIUM 137 SOIL CONTAMINATION (open access)

EFFECTIVE DOSIMETRIC HALF LIFE OF CESIUM 137 SOIL CONTAMINATION

In the early 1960s, an area of privately-owned swamp adjacent to the US Department of Energy's Savannah River Site (SRS), known as Creek Plantation, was contaminated by site operations. Studies conducted in 1974 estimated that approximately 925 GBq of {sup 137}Cs was deposited in the swamp. Subsequently, a series of surveys--composed of 52 monitoring locations--was initiated to characterize and trend the contaminated environment. The annual, potential, maximum doses to a hypothetical hunter were estimated by conservatively using the maximum {sup 137}Cs concentrations measured in the soil. The purpose of this report is to calculate an 'effective dosimetric' half-life for {sup 137}Cs in soil (based on the maximum concentrations) and compare it to the effective environmental half-life (based on the geometric mean concentrations).
Date: January 9, 2008
Creator: Jannik, T; P Fledderman, P & Michael Paller, M
System: The UNT Digital Library
X-ray streak camera temporal resolution improvement using a longitudinal time-dependent field (open access)

X-ray streak camera temporal resolution improvement using a longitudinal time-dependent field

X-ray streak cameras (XSC) have been known to be one of the fastest detectors forultrafast X-ray science. A number of applications in material science, biochemistry, accelerator physics, require sub-picosecond resolution to study new phenomena. Inthis paper, we report on a new method which can potentially improve the temporal resolution of a streak camera down to 100 femtoseconds. This method uses a time-dependent acceleration field to lengthen the photoelectron bunch, significantlyimproving the time resolution as well as reducing the time dispersion caused byinitial energy spread and the effects fromthe space charge forces. A computer simulation of an XSC using this method shows significant improvement in the resolution.
Date: May 9, 2008
Creator: Qiang, Ji; Qiang, J.; Byrd, J.M.; Feng, J. & Huang, G.
System: The UNT Digital Library
Ion Exclusion by Sub 2-nm Carbon Nanotube Pores (open access)

Ion Exclusion by Sub 2-nm Carbon Nanotube Pores

Carbon nanotubes offer an outstanding platform for studying molecular transport at nanoscale, and have become promising materials for nanofluidics and membrane technology due to their unique combination of physical, chemical, mechanical, and electronic properties. In particular, both simulations and experiments have proved that fluid flow through carbon nanotubes of nanometer size diameter is exceptionally fast compared to what continuum hydrodynamic theories would predict when applied on this length scale, and also, compared to conventional membranes with pores of similar size, such as zeolites. For a variety of applications such as separation technology, molecular sensing, drug delivery, and biomimetics, selectivity is required together with fast flow. In particular, for water desalination, coupling the enhancement of the water flux with selective ion transport could drastically reduce the cost of brackish and seawater desalting. In this work, we study the ion selectivity of membranes made of aligned double-walled carbon nanotubes with sub-2 nm diameter. Negatively charged groups are introduced at the opening of the carbon nanotubes by oxygen plasma treatment. Reverse osmosis experiments coupled with capillary electrophoresis analysis of permeate and feed show significant anion and cation rejection. Ion exclusion declines by increasing ionic strength (concentration) of the feed and by lowering solution …
Date: April 9, 2008
Creator: Fornasiero, F; Park, H G; Holt, J K; Stadermann, M; Grigoropoulos, C P; Noy, A et al.
System: The UNT Digital Library
Probing the spin polarization of current by soft x-ray imaging of current-induced magnetic vortex dynamics (open access)

Probing the spin polarization of current by soft x-ray imaging of current-induced magnetic vortex dynamics

Time-resolved soft X-ray transmission microscopy is applied to image the current-induced resonant dynamics of the magnetic vortex core realized in a micron-sized Permalloy disk. The high spatial resolution better than 25 nm enables us to observe the resonant motion of the vortex core. The result also provides the spin polarization of the current to be 0.67 {+-} 0.16 for Permalloy by fitting the experimental results with an analytical model in the framework of the spin-transfer torque.
Date: December 9, 2008
Creator: Kasai, Shinya; Fischer, Peter; Im, Mi-Young; Yamada, Keisuke; Nakatani, Yoshinobu; Kobayashi, Kensuke et al.
System: The UNT Digital Library
TRACE ELEMENT ANALYSES OF URANIUM MATERIALS (open access)

TRACE ELEMENT ANALYSES OF URANIUM MATERIALS

The Savannah River National Laboratory (SRNL) has developed an analytical method to measure many trace elements in a variety of uranium materials at the high part-per-billion (ppb) to low part-per-million (ppm) levels using matrix removal and analysis by quadrapole ICP-MS. Over 35 elements were measured in uranium oxides, acetate, ore and metal. Replicate analyses of samples did provide precise results however none of the materials was certified for trace element content thus no measure of the accuracy could be made. The DOE New Brunswick Laboratory (NBL) does provide a Certified Reference Material (CRM) that has provisional values for a series of trace elements. The NBL CRM were purchased and analyzed to determine the accuracy of the method for the analysis of trace elements in uranium oxide. These results are presented and discussed in the following paper.
Date: June 9, 2008
Creator: Beals, D & Charles Shick, C
System: The UNT Digital Library
Evidence for X(3872) --> Psi(2S) gamma in B+/- --> X(3872) K+/- Decays, and a Study of B --> ccbar gamma K (open access)

Evidence for X(3872) --> Psi(2S) gamma in B+/- --> X(3872) K+/- Decays, and a Study of B --> ccbar gamma K

In a search for B {yields} c{bar c}{gamma} K decays with the BABAR detector, where c{bar c} includes J/{psi} and {psi}(2S), and K includes K{sup {+-}}, K{sub S}{sup 0} and K*(892), they find evidence for X(3872) {yields} J/{psi}{gamma} and X(3872) {yields} {psi}(2S){gamma} with 3.6{sigma} and 3.5{sigma} significance, respectively. They measure the product of branching fractions {Beta}(B{sup {+-}} {yields} X (3872)K{sup {+-}}) {center_dot} {Beta}(X(3872) {yields} J/{psi}{gamma}) = (2.8 {+-} 0.8(stat.) {+-} 0.2(syst.)) x 10{sup -6} and {Beta}(B{sup {+-}} {yields} X(3872)K{sup {+-}}) {center_dot} {Beta}(X(3872) {yields} {psi}(2S){gamma}) = (9.9 {+-} 2.9(stat.) {+-} 0.6(syst.)) x 10{sup -6}.
Date: September 9, 2008
Creator: Fulsom, B
System: The UNT Digital Library
Hydrocarbon-free resonance transition 795-nm rubidium laser (open access)

Hydrocarbon-free resonance transition 795-nm rubidium laser

An optical resonance transition rubidium laser (5{sup 2}P{sub 1/2} {yields} 5{sup 2}S{sub 1/2}) is demonstrated with a hydrocarbon-free buffer gas. Prior demonstrations of alkali resonance transition lasers have used ethane as either the buffer gas or a buffer gas component to promote rapid fine-structure mixing. However, our experience suggests that the alkali vapor reacts with the ethane producing carbon as one of the reaction products. This degrades long term laser reliability. Our recent experimental results with a 'clean' helium-only buffer gas system pumped by a Ti:sapphire laser demonstrate all the advantages of the original alkali laser system, but without the reliability issues associated with the use of ethane.
Date: January 9, 2008
Creator: Wu, S Q; Soules, T F; Page, R H; Mitchell, S C; Kanz, V K & Beach, R J
System: The UNT Digital Library
Measurement of the CKM Angle Gamma in B0 to Anti-D0 (D0) K*0 With a Dalitz Analysis of D0 to K(S) Pi+ Pi- (open access)

Measurement of the CKM Angle Gamma in B0 to Anti-D0 (D0) K*0 With a Dalitz Analysis of D0 to K(S) Pi+ Pi-

The authors present a measurement of the angle {gamma} of the Unitarity Triangle with a Dalitz analysis of neutral D decays to K{sub S}{pi}{sup +}{pi}{sup -} from the processes B{sup 0} {yields} {bar D}{sup 0}(D{sup 0})K*{sup 0} ({bar B}{sup 0} {yields} D{sup 0}({bar D}{sup 0}){bar K}*{sup 0}) with K*{sup 0} {yields} K{sup +}{pi}{sup -} ({bar K}*{sup 0} {yields} K{sup -} {pi}{sup +}). Using a sample of 371 x 10{sup 6} B{bar B} pairs collected with the BABAR detector at PEP II, they measure the angle {gamma} as a function of r{sub S}, the magnitude of the average ratio between b {yields} u and b {yields} c amplitudes. Combining this result with the available information on r{sub S}, they obtain {gamma} = (162 {+-} 56){sup o} or (342 {+-} 56){sup o} and r{sub S} < 0.55 at 95% probability.
Date: June 9, 2008
Creator: Aubert, Bernard; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prudent, X. et al.
System: The UNT Digital Library
TOF Electron Energy Analyzer for Spin and Angular Resolved Photoemission Spectroscopy (open access)

TOF Electron Energy Analyzer for Spin and Angular Resolved Photoemission Spectroscopy

Current pulsed laser and synchrotron x-ray sources provide new opportunities for Time-Of- Flight (TOF) based photoemission spectroscopy to increase photoelectron energy resolution and efficiency compared to current standard techniques. The principals of photoelectron timing front formation, temporal aberration minimization, and optimization of electron beam transmission are presented. We have developed these concepts into a high resolution Electron Optical Scheme (EOS) of a TOF Electron Energy Analyzer (TOF-EEA) for photoemission spectroscopy. The EOS of the analyzer includes an electrostatic objective lens, three columns of transport lenses and a 90 degree energy band pass filter (BPF). The analyzer has two modes of operation: Spectrometer Mode (SM) with straight passage of electrons through the EOS undeflected by the BPF, allowing the entire spectrum to be measured, and Monochromator Mode (MM) in which the BPF defines a certain energy window inside the scope of the electron energy spectrum.
Date: July 9, 2008
Creator: Lebedev, Gennadi; Jozwiak, Chris; Andresen, Nord; Lanzara, Alessandra & Hussain, Zahid
System: The UNT Digital Library
Logarithmically enhanced corrections to the decayrate and forward backward asymmetry in \bar B to \ell^+ \ell^- (open access)

Logarithmically enhanced corrections to the decayrate and forward backward asymmetry in \bar B to \ell^+ \ell^-

We study logarithmically enhanced electromagnetic corrections to the decay rate in the high dilepton invariant mass region as well as corrections to the forward backward asymmetry (FBA) of the inclusive rare decay {bar B} {yields} X{sub s}{ell}{sup +}{ell}{sup -}. As expected, the relative effect of these corrections in the high dilepton mass region is around -8% for the muonic final state and therefore much larger than in the low dilepton mass region. We also present a complete phenomenological analysis, to improved NNLO accuracy, of the dilepton mass spectrum and the FBA integrated in the low dilepton mass region, including a new approach to the zero of the FBA. The latter represents one of the most precise predictions in flavor physics with a theoretical uncertainty of order 5%. We find (q{sub 0}{sup 2}){mu}{mu} = (3.50 {+-} 0.12)GeV{sup 2}. For the high dilepton invariant mass region, we have {Beta}({bar B} {yields} X{sub s}{mu}{mu}){sub high} = (2.40{sub -0.62}{sup +0.69}) x 10{sup -7}. The dominant uncertainty is due to the 1/m{sub b} corrections and can be significantly reduced in the future. For the low dilepton invariant mass region, we confirm previous results up to small corrections.
Date: January 9, 2008
Creator: Huber, Tobias; Hurth, Tobias & Lunghi, Enrico
System: The UNT Digital Library
Experimental and Kinetic Modeling Study of Extinction and Ignition of Methyl Decanoate in Laminar Nonpremixed Flows (open access)

Experimental and Kinetic Modeling Study of Extinction and Ignition of Methyl Decanoate in Laminar Nonpremixed Flows

Methyl decanoate is a large methyl ester that can be used as a surrogate for biodiesel. In this experimental and computational study, the combustion of methyl decanoate is investigated in nonpremixed, nonuniform flows. Experiments are performed employing the counterflow configuration with a fuel stream made up of vaporized methyl decanoate and nitrogen, and an oxidizer stream of air. The mass fraction of fuel in the fuel stream is measured as a function of the strain rate at extinction, and critical conditions of ignition are measured in terms of the temperature of the oxidizer stream as a function of the strain rate. It is not possible to use a fully detailed mechanism for methyl decanoate to simulate the counterflow flames because the number of species and reactions is too large to employ with current flame codes and computer resources. Therefore a skeletal mechanism was deduced from a detailed mechanism of 8555 elementary reactions and 3036 species using 'directed relation graph' method. This skeletal mechanism has only 713 elementary reactions and 125 species. Critical conditions of ignition were calculated using this skeletal mechanism and are found to agree well with experimental data. The predicted strain rate at extinction is found to be …
Date: January 9, 2008
Creator: Seshadri, K; Lu, T; Herbinet, O; Humer, S; Niemann, U; Pitz, W J et al.
System: The UNT Digital Library
Measurement of the B -> Omega l Nu and B -> Eta l Nu Branching Fractions Using Neutrino Reconstruction (open access)

Measurement of the B -> Omega l Nu and B -> Eta l Nu Branching Fractions Using Neutrino Reconstruction

The authors present a study of the charmless semileptonic B-meson decays B{sup +} {yields} {omega}{ell}{sup +}{nu} and B{sup +} {yields} {eta}{ell}{sup +}{nu}. The analysis is based on 383 million B{bar B} pairs recorded at the {Upsilon}(4S) resonance with the BABAR detector. The {omega} mesons are reconstructed in the channel {omega} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup 0} and the {eta} mesons in the channels {eta} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup 0} and {eta} {yields} {gamma}{gamma}. They measure the branching fractions {Beta}(B{sup +} {yields} {omega}{ell}{sup +}{nu}) = (1.14 {+-} 0.16{sub stat} {+-} 0.08{sub syst}) x 10{sup -4} and {Beta}(B{sup +} {yields} {eta}{ell}{sup +}{nu}) = (0.31 {+-} 0.06{sub stat} {+-} 0.08{sub syst}) x 10{sup -4}.
Date: September 9, 2008
Creator: Aubert, Bernard; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
System: The UNT Digital Library
Observation of the Bottomonium Ground State, eta_b, at BaBar (open access)

Observation of the Bottomonium Ground State, eta_b, at BaBar

The authors present the first observation of the bottomonium ground state {eta}{sub b}(1S) in the photon energy spectrum using a sample of (109 {+-} 1) million of {Upsilon}(3S) events recorded at the {Upsilon}(3S) energy with the BaBar detector at the PEP-II B factory at SLAC. A peak at E{sub {gamma}} = 921.2{sub -2.8}{sup +2.1}(stat) {+-} 2.4(syst) MeV observed with a significance of 10 standard deviations in the photon energy spectrum is interpreted as being due to the radiative transition {Upsilon}(3S) {yields} {gamma} {eta}{sub b}(1S). This photon energy corresponds to an {eta}{sub b}(1S) mass of 9388.9{sub -2.3}{sup +3.1}(stat) {+-} 2.7(syst) MeV/c{sup 2}. The hyperfine {Upsilon}(1S)-{eta}{sub b}(1S) mass splitting is 71.4{sub -3.1}{sup +2.3}(stat) {+-} 2.7(syst) MeV/c{sup 2}. The branching fraction for this radiative {Upsilon}(3S) decay is obtained as (4.8 {+-} 0.5(stat) {+-} 1.2(syst)) x 10{sup -4}.
Date: September 9, 2008
Creator: Grenier, Philippe & Collaboration, for the BABAR
System: The UNT Digital Library
IMPLEMENTING CHANGES TO AN APPROVED AND IN-USE DOCUMENTED SAFETY ANALYSIS (open access)

IMPLEMENTING CHANGES TO AN APPROVED AND IN-USE DOCUMENTED SAFETY ANALYSIS

None
Date: April 9, 2008
Creator: JP, KING
System: The UNT Digital Library
Field driven ferromagnetic phase nucleation and propagation from the domain boundaries in antiferromagnetically coupled perpendicular anisotropy films (open access)

Field driven ferromagnetic phase nucleation and propagation from the domain boundaries in antiferromagnetically coupled perpendicular anisotropy films

We investigate the reversal process in antiferromagnetically coupled [Co/Pt]{sub X-1}/{l_brace}Co/Ru/[Co/Pt]{sub X-1}{r_brace}{sub 16} multilayer films by combining magnetometry and Magnetic soft X-ray Transmission Microscopy (MXTM). After out-of-plane demagnetization, a stable one dimensional ferromagnetic (FM) stripe domain phase (tiger-tail phase) for a thick stack sample (X=7 is obtained), while metastable sharp antiferromagnetic (AF) domain walls are observed in the remanent state for a thinner stack sample (X=6). When applying an external magnetic field the sharp domain walls of the thinner stack sample transform at a certain threshold field into the FM stripe domain wall phase. We present magnetic energy calculations that reveal the underlying energetics driving the overall reversal mechanisms.
Date: December 9, 2008
Creator: Hauet, Thomas; Gunther, Christian M.; Hovorka, Ondrej; Berger, Andreas; Im, Mi-Young; Fischer, Peter et al.
System: The UNT Digital Library
CHARACTERIZATION OF DETECTOR GRADE CDZNTE MATERIAL FROM REDLEN TECHNOLOGIES (open access)

CHARACTERIZATION OF DETECTOR GRADE CDZNTE MATERIAL FROM REDLEN TECHNOLOGIES

CdZnTe (or CZT) crystals can be used in a variety of detector-type applications. This large band gap material shows great promise for use as a gamma radiation spectrometer. Historically, the performance of CZT has typically been adversely affected by point defects, structural and compositional heterogeneities within the crystals, such as twinning, pipes, grain boundaries (polycrystallinity) and secondary phases (SP). The synthesis of CZT material has improved greatly with the primary performance limitation being attributed to mainly SP. In this presentation, we describe the extensive characterization of detector grade material that has been treated with post growth annealing to remove the SPs. Some of the analytical methods used in this study included polarized, cross polarized and transmission IR imaging, I-V curves measurements, synchrotron X-ray topography and electron microscopy.
Date: July 9, 2008
Creator: Duff, M
System: The UNT Digital Library
Multiscale integration schemes for jump-diffusion systems (open access)

Multiscale integration schemes for jump-diffusion systems

We study a two-time-scale system of jump-diffusion stochastic differential equations. We analyze a class of multiscale integration methods for these systems, which, in the spirit of [1], consist of a hybridization between a standard solver for the slow components and short runs for the fast dynamics, which are used to estimate the effect that the fast components have on the slow ones. We obtain explicit bounds for the discrepancy between the results of the multiscale integration method and the slow components of the original system.
Date: December 9, 2008
Creator: Givon, D. & Kevrekidis, I.G.
System: The UNT Digital Library
Scratch Forensics (open access)

Scratch Forensics

Scratches on optical components which are formed during fabrication, cleaning, handling and end-use, are widespread and almost always detrimental. The impact of scratches on the end-use of the optic includes increased optical scatter, reduced system performance, and reduced strength. In the case of optics used in high intensity laser applications, prevention of scratches is paramount because they are closely associated with laser damage. Evaluation of the characteristics (dimensions, location on optic, shape, and orientation) of a scratch can serve a powerful tool to identify the cause of the scratch and lead to mitigations to prevent their reoccurrence. It is likely that opticians have used such techniques for hundreds of years. In recent years, by applying techniques of fracture mechanics and tribology, several new semi-quantitative rules-of-thumb have been developed allowing one to estimate the size and shape of the scratch inducing asperity or rogue particle, the load on the particle, the depth of the fractures in the scratch, and properties of material housing the rogue particle. The following discussion reviews some these techniques, which as a whole, we refer to as 'Scratch Forsenics'.
Date: July 9, 2008
Creator: Suratwala, T I; Miller, P E; Feit, M D & Menapace, J A
System: The UNT Digital Library