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Spatial Coherence of Synchrotron Radiation (open access)

Spatial Coherence of Synchrotron Radiation

Synchrotron Radiation (SR) has been widely used since the 80's as a tool for many applications of UV, soft X rays and hard X rays in condensed matter physics, chemistry and biology. The evolution of SR sources towards higher brightness has led to the design of low-emittance electron storage rings (emittance is the product of beam size and divergence), and the development of special source magnetic structures, as undulators. This means that more and more photons are available on a narrow bandwidth and on a small collimated beam; in other words there is the possibility of getting a high power in a coherent beam. In most applications, a monochromator is used, and the temporal coherence of the light is given by the monochromator bandwidth. With smaller and smaller sources, even without the use of collimators, the spatial coherence of the light has become appreciable, first in the UV and soft X ray range, and then also with hard X rays. This has made possible new or improved experiments in interferometry, microscopy, holography, correlation spectroscopy, etc. In view of these recent possibilities and applications, it is useful to review some basic concepts about spatial coherence of SR, and its measurement and …
Date: October 30, 2003
Creator: Marchesini, S & Coisson, R
System: The UNT Digital Library
Boron Addition to Model Austenitic Steels and void Nucleation (open access)

Boron Addition to Model Austenitic Steels and void Nucleation

Fe-15Cr-16Ni, -0.25Ti, -500appmB, and -0.25Ti-500appmB have been irradiated in FFTF/MOTA over a wide range of dose rate which covers more than two orders difference in magnitude, within the very limited temperature range of 387-444 C. The effects of dose rate and boron addition on swelling are examined. Lower dose rates increase the swelling by shortening the incubation dose for swelling. Addition of boron does not significantly change the swelling nor the dose rate dependence of swelling for both the ternary and Ti-modified alloy. The helium pressure of cavities is found to be much smaller than the surface tension at every irradiation condition including the lowest dose and dose rate, helium generated by boron transmutant does not play any role in cavity formation in this experiment. Cavities form without helium. The difference in cavity morphology by boron addition is most likely caused by formation of borides and by lithium.
Date: October 30, 2003
Creator: Okita, T; Wolfer, W G; Garner, F A & Sekimura, N
System: The UNT Digital Library
Studies of Electron Transport and Isochoric Heating and Their Applicability to Fast Ignition (open access)

Studies of Electron Transport and Isochoric Heating and Their Applicability to Fast Ignition

Experimental measurements of electron transport and isochoric heating in 100 J, 1 ps laser irradiation of solid A1 targets are presented. Modeling with a hybrid PIC code is compared with the data and good agreement is obtained using a heuristic model for the electron injection. The relevance for fast ignition is discussed.
Date: October 30, 2003
Creator: Key, M. H.; Amiranoff, F.; Andersen, C.; Batani, D.; Baton, S. D.; Cowan, T. et al.
System: The UNT Digital Library
Carcinogens formed when Meat is Cooked (open access)

Carcinogens formed when Meat is Cooked

Diet has been associated with varying cancer rates in human populations for many years, yet the causes of the observed variation in cancer patterns have not been adequately explained (Wynder et al. 1977). Along with the effect of diet on human cancer incidence is the strong evidence that mutations are the initiating events in the cancer process (Vogelstein et al. 1992). Foods, when heated, are a good source of genotoxic carcinogens that very likely are a cause for some of these events(Doll et al. 1981). These carcinogens fall into two chemical classes: heterocyclic aromatic amines (HAA) and polycyclic aromatic hydrocarbons (PAH). There is ample evidence that many of these compounds are complete carcinogens in rodents(El-Bayoumy et al. 1995; Ohgaki et al. 1991). Heterocyclic aromatic amines are among the most potent mutagenic substances ever tested in the Ames/Salmonella mutagenicity test (Wakabayashi et al. 1992). Both classes of carcinogen cause tumors in rodents at multiple sites, (El-Bayoumy et al. 1995; Ohgaki et al. 1991) many of which are common tumor sites in people on a Western diet. An HAA, PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine), and a PAH, B[a]P (benzo[a]pyrene), of comparable carcinogenic potency caused mammary gland tumors in a feeding study in female rats (El-Bayoumy …
Date: May 30, 2003
Creator: Felton, J S; Salmon, C P & Knize, M G
System: The UNT Digital Library
Incorporation of Chemical Reactions into Building-scale Flow (open access)

Incorporation of Chemical Reactions into Building-scale Flow

Many hazardous atmospheric releases involve chemical reactions that occur within a few kilometers of the source. Reactions with commonly occurring atmospheric compounds such as the OH radical, can transform and potentially neutralize original release compounds. Especially in these cases, accurately resolving flow around nearby structures and over surrounding topography can be critical to correctly predicting material dispersion, and thus, the extent of any hazard. Accurate prediction of material dispersion around complex geometries near the source of an atmospheric release requires high-resolution computation. Further complications arise if the compounds released undergo chemical reactions which could alter the extent of the main plume. The reaction products form dispersion patterns separate from, and often more complicated than, the original plume. Directions for future work include expanding the library of chemical reaction mechanisms, adding capabilities for aqueous and heterogeneous reactions, and integrating this model within larger-scale models. We plan that the larger-scale models will provide meteorological and chemical boundary conditions, and that this model could provide a source term in larger-scale models, both for momentum and for dispersed compounds.
Date: October 30, 2003
Creator: Humphreys, T D; Jayaweera, T M & Lee, R L
System: The UNT Digital Library
Current Drive and Pressure Profile Modifications with Electron Cyclotron Power in DIII-D Quiescent Double Barrier Experiments (open access)

Current Drive and Pressure Profile Modifications with Electron Cyclotron Power in DIII-D Quiescent Double Barrier Experiments

None
Date: June 30, 2003
Creator: Casper, T. A.; Burrell, K. H.; Doyle, E. J.; Gohil, P.; Greenfield, C. M.; Groebner, R. J. et al.
System: The UNT Digital Library
Scene-based Wave-front Sensing for Remote Imaging (open access)

Scene-based Wave-front Sensing for Remote Imaging

Scene-based wave-front sensing (SBWFS) is a technique that allows an arbitrary scene to be used for wave-front sensing with adaptive optics (AO) instead of the normal point source. This makes AO feasible in a wide range of interesting scenarios. This paper first presents the basic concepts and properties of SBWFS. Then it discusses that application of this technique with AO to remote imaging. For the specific case of correction of a lightweight optic. End-to-end simulation results establish that in this case, SBWFS can perform as well as point-source AO. Design considerations such as noise propagation, number of subapertures and tracking changing image content are analyzed.
Date: July 30, 2003
Creator: Poyneer, L A; LaFortune, K & Chan, C
System: The UNT Digital Library
Statistical Study of SCM Simulations Using Continuous Forcing Data Derived from NWP Products with the ARM Data Constraints (open access)

Statistical Study of SCM Simulations Using Continuous Forcing Data Derived from NWP Products with the ARM Data Constraints

Statistical study of Single Column Model (SCM) results has been recently advocated by the ARM cloud parameterization and modeling working group. This is partly due to the sensitivity nature of Single Column Models (SCMs) to uncertainties in the initial conditions and the specified large-scale forcing. In addition, given the limitation of SCM framework (e.g. the lack of effective internal feedback between the SCM and the specified forcing) and the inevitable error in the initial conditions and the large-scale forcing, it might not be realistic to expect that SCMs can correctly capture every individual synoptic event. Statistical studies can help smooth out those random errors related to uncertainties in the initial conditions and the specified large-scale forcing so that one can focus on those physically important systematic errors from SCM simulations. Noted that, for climate simulations, it is more important for a given physical parameterization to successfully simulate statistics right for the process that is being parameterized. This study conducts a statistical study of SCM simulations by using the ARM recently developed continuous forcing data for the year 2000. The NCAR CCM3 SCM is used in this study. The long-term continuous forcing data were developed from the NOAA mesoscale model RUC …
Date: June 30, 2003
Creator: Xie, S.; Cederwall, R.; Zhang, M. & Yio, J. J.
System: The UNT Digital Library
Measurement of the Branching Fraction for B- --->D0 K*- (open access)

Measurement of the Branching Fraction for B- --->D0 K*-

The authors present a measurement of the branching fraction for the decay B{sup -} {yields} D{sup 0} K{sup *-} using a sample of approximately 86 million B{bar B} pairs collected by the BABAR detector from e{sup +}e{sup -} collisions near the {Upsilon}(4S) resonance. The D{sup 0} is detected through its decays to K{sup -}{pi}{sup +}, K{sup -}{pi}{sup +}{pi}{sup 0} and K{sup -} {pi}{sup +}{pi}{sup -}{pi}{sup +}, and the K{sup *-} through its decay to K{sub S}{sup 0} {pi}{sup -}. They measure the branching fraction to be {Beta}(B{sup -} {yields} D{sup 0}K{sup *-}) = (6.3 {+-} 0.7(stat.){+-}0.5(syst.)) x 10{sup -4}.
Date: December 30, 2003
Creator: Lange, D J; Wright, D M; Simani, M C & Cheng, C H
System: The UNT Digital Library
A Multi-Resolution Data Structure for Two-Dimensional Morse Functions (open access)

A Multi-Resolution Data Structure for Two-Dimensional Morse Functions

The efficient construction of simplified models is a central problem in the field of visualization. We combine topological and geometric methods to construct a multi-resolution data structure for functions over two-dimensional domains. Starting with the Morse-Smale complex we build a hierarchy by progressively canceling critical points in pairs. The data structure supports mesh traversal operations similar to traditional multi-resolution representations.
Date: July 30, 2003
Creator: Bremer, P-T; Edelsbrunner, H; Hamann, B & Pascucci, V
System: The UNT Digital Library
Possible problems in ENDF/B-VI.r8 (open access)

Possible problems in ENDF/B-VI.r8

This document lists the problems that we encountered in processing ENDF/B-VI.r8 that we suspect are problems with ENDF/B-VI.r8 itself. It also contains a comparison of linear interpolation methods. Finally, this documents proposes an alternative to the current scheme of reporting problems to the ENDF community.
Date: October 30, 2003
Creator: Brown, David & Hedstrom, Gerry
System: The UNT Digital Library
Prospects for Investigating Unusual Nuclear Reaction Environments Using the National Ignition Facility (open access)

Prospects for Investigating Unusual Nuclear Reaction Environments Using the National Ignition Facility

The standard capsule design1 and other laser plasma targets at the National Ignition Facility offer the possibility of generating and studying thermal rates for significant astrophysical fusion reactions such as {sup 3}He({sup 3}He,2p){alpha}, {sup 7}Be(p,{gamma})B, and {sup 15}N(p,{alpha}){sup 12}C. At present the ''S'' factors for these reactions are determined either by extrapolation from higher energy scattering data or by underground laboratory, low event rate experiments such as at LUNA on un-ionized atoms with concomitantly large screening corrections. The ability to directly generate astrophysical fusion reactions in thermonuclear plasmas will be complemented by new, ab initio, ''no frozen core'' detailed shell model predictions for such light ion reactions. In addition, the expected fluence of neutrons from the main D + T {yields} {alpha} burn reaction, is high enough to drive 10-20% of seeded spectator nuclei into excited states via (n,n') reactions. Furthermore, the {approx}2% ''minority'' D + D {yields} {sup 3}He + n can drive reactions pertinent to the r, s, and p process nucleosynthesis of heavy elements, including branches that pass through excited states with t > 10 ps, that can be studied using particle spectroscopy and radiochemistry. Additionally, for the first time, it will be possible to measure the …
Date: September 30, 2003
Creator: Libby, S. B.; Tabak, M.; Hoffman, R. D.; Stoyer, M. A.; Haan, S. W.; Hatchett, S. P. et al.
System: The UNT Digital Library
Transport in a Microfluidic Catalytic Reactor (open access)

Transport in a Microfluidic Catalytic Reactor

A study of the heat and mass transfer, flow, and thermodynamics of the reacting flow in a catalytic microreactor is presented. Methanol reforming is utilized in the fuel processing system driving a micro-scale proton exchange membrane fuel cell. Understanding the flow and thermal transport phenomena as well as the reaction mechanisms is essential for improving the efficiency of the reforming process as well as the quality of the processed fuel. Numerical studies have been carried out to characterize the transport in a silicon microfabricated reactor system. On the basis of these results, optimized conditions for fuel processing are determined.
Date: April 30, 2003
Creator: Park, Hyun Gyu; Chung, Jaewon; Grigoropoulos, Costas P.; Greif, Ralph; Havstad, Mark & Morse, Jeffrey D.
System: The UNT Digital Library
Progress in Horizontal and Slant-Path Imaging Speckle Imaging (open access)

Progress in Horizontal and Slant-Path Imaging Speckle Imaging

The difficulty in terrestrial imaging over long horizontal or slant paths is that atmospheric aberrations and distortions reduce the resolution and contrast in images recorded at high resolution. This paper will describe the problem of horizontal-path imaging, briefly cover various methods for imaging over horizontal paths and then describe the speckle imaging method actively being pursued at LLNL. We will review some closer range (1-3 km range) imagery of people we have already published, as well as show new results of vehicles we have obtained over longer slant-range paths greater than 20 km.
Date: January 30, 2003
Creator: Carrano, C J
System: The UNT Digital Library
Impact of Neutrino Oscillation Measurements on Theory (open access)

Impact of Neutrino Oscillation Measurements on Theory

Neutrino oscillation data had been a big surprise to theorists, and indeed they have ongoing impact on theory. I review what the impact has been, and what measurements will have critical impact on theory in the future.
Date: November 30, 2003
Creator: Murayama, Hitoshi
System: The UNT Digital Library
Comparative genomic analysis as a tool for biologicaldiscovery (open access)

Comparative genomic analysis as a tool for biologicaldiscovery

Biology is a discipline rooted in comparisons. Comparative physiology has assembled a detailed catalogue of the biological similarities and differences between species, revealing insights into how life has adapted to fill a wide-range of environmental niches. For example, the oxygen and carbon dioxide carrying capacity of vertebrate has evolved to provide strong advantages for species respiring at sea level, at high elevation or within water. Comparative- anatomy, -biochemistry, -pharmacology, -immunology and -cell biology have provided the fundamental paradigms from which each discipline has grown.
Date: March 30, 2003
Creator: Nobrega, Marcelo A. & Pennacchio, Len A.
System: The UNT Digital Library
Insights from Human/Mouse genome comparisons (open access)

Insights from Human/Mouse genome comparisons

Large-scale public genomic sequencing efforts have provided a wealth of vertebrate sequence data poised to provide insights into mammalian biology. These include deep genomic sequence coverage of human, mouse, rat, zebrafish, and two pufferfish (Fugu rubripes and Tetraodon nigroviridis) (Aparicio et al. 2002; Lander et al. 2001; Venter et al. 2001; Waterston et al. 2002). In addition, a high-priority has been placed on determining the genomic sequence of chimpanzee, dog, cow, frog, and chicken (Boguski 2002). While only recently available, whole genome sequence data have provided the unique opportunity to globally compare complete genome contents. Furthermore, the shared evolutionary ancestry of vertebrate species has allowed the development of comparative genomic approaches to identify ancient conserved sequences with functionality. Accordingly, this review focuses on the initial comparison of available mammalian genomes and describes various insights derived from such analysis.
Date: March 30, 2003
Creator: Pennacchio, Len A.
System: The UNT Digital Library
High current heavy ion beams in the electrostatic plasmalens (open access)

High current heavy ion beams in the electrostatic plasmalens

We describe applications of the electrostatic plasma lens for manipulating and focusing moderate energy, high current, broad, heavy ion beams. Use of a plasma lens in this way has been successfully demonstrated in a series of experiments carried out collaboratively between IP NASU (Kiev) and LBNL (Berkeley) in recent years. Here we briefly review the plasma lens fundamentals, peculiarities of focusing heavy ion beams, and summarize some recent developments (experiments, computer simulations, theory). We show that there is a very narrow range of low magnetic field for which the optical properties of the lens improve markedly. This opens up some attractive possibilities for the development of a new-generation compact lens based on permanent magnets. Preliminary experimental results obtained at Kiev and Berkeley on the operation of a permanent magnet plasma lens for manipulating wide aperture high-current heavy ion beams are presented and summarized.
Date: September 30, 2003
Creator: Goncharov, A.A. & Brown, I.G.
System: The UNT Digital Library
An evaluation of the active fracture concept with modelingunsaturated flow and transport in a fractured meter-sized block ofrock (open access)

An evaluation of the active fracture concept with modelingunsaturated flow and transport in a fractured meter-sized block ofrock

Numerical simulation is an effective and economical tool for optimally designing laboratory experiments and deriving practical experimental conditions. We executed a detailed numerical simulation study to examine the active fracture concept (AFC, Liu et al., 1998) using a cubic meter-sized block model. The numerical simulations for this study were performed by applying various experimental conditions, including different bottom flow boundaries, varying injection rates, and different fracture-matrix interaction (by increasing absolute matrix permeability at the fracture matrix boundary) for a larger fracture interaction under transient or balanced-state flow regimes. Two conceptual block models were developed based on different numerical approaches: a two-dimensional discrete-fracture-network model (DFNM) and a one-dimensional dual continuum model (DCM). The DFNM was used as a surrogate for a natural block to produce synthetic breakthrough curves of water and tracer concentration under transient or balanced-state conditions. The DCM is the approach typically used for the Yucca Mountain Project because of its computational efficiency. The AFC was incorporated into the DCM to capture heterogeneous flow patterns that occur in unsaturated fractured rocks. The simulation results from the DCM were compared with the results from the DFNM to determine whether the DCM could predict the water flow and tracer transport observed …
Date: May 30, 2003
Creator: Seol, Yongkoo; Kneafsey, Timothy J. & Ito, Kazumasa
System: The UNT Digital Library
Electron microscopy of biological macromolecules: Bridging the gapbetween what physics allows and what we currently can get (open access)

Electron microscopy of biological macromolecules: Bridging the gapbetween what physics allows and what we currently can get

The resolution achieved in low-dose electron microscopy of biological macromolecules is significantly worse than what can be obtained on the same microscopes with more robust specimens. When two-dimensional crystals are used, it is also apparent that the high-resolution image contrast is much less than what it could be if the images were perfect. Since specimen charging is one factor that might limit the contrast and resolution achieved with biological specimens, we have investigated the use of holey support films that have been coated with a metallic film before depositing specimens onto a thin carbon film that is suspended over the holes. Monolayer crystals of paraffin (C44H90) are used as a test specimen for this work because of the relative ease in imaging Bragg spacings at {approx}0.4 nm resolution, the relative ease of measuring the contrast in these images, and the similar degree of radiation sensitivity of these crystals when compared to biological macromolecules. A metallic coating on the surrounding support film does, indeed, produce a significant improvement in the high-resolution contrast for a small fraction of the images. The majority of images show little obvious improvement, however, and even the coated area of the support film continues to show a …
Date: April 30, 2003
Creator: Typke, Dieter; Downing, Kenneth H. & Glaeser, Robert M.
System: The UNT Digital Library
A new generation Nb3Sn wire, and the prospects for its use inparticle accelerators (open access)

A new generation Nb3Sn wire, and the prospects for its use inparticle accelerators

The US DOE has initiated a Conductor Development Program aimed at demonstrating a high current density, cost effective Nb3Sn conductor for use in accelerator magnets. The first goal, an increase in current density by 50%, has been achieved in a practical conductor. The program is focused at present on achieving the second goal of reduced losses. The different approaches for achieving these goals will be discussed, and the status will be presented. Magnet technology R&D has been proceeding in parallel with the conductor development efforts, and these two technologies are reaching the level required for the next step--introduction into operating accelerator magnets. An obvious point for introducing this technology is the LHC interaction region magnets, which require large apertures and high fields (or high field gradients). By upgrading the interaction region magnets, machine performance can be enhanced significantly without replacing the arc magnets, which represent most of the cost of an accelerator. Design requirements generated by recent studies and workshops will be reviewed, and a roadmap for the development of the next-generation interaction region magnets will be presented.
Date: September 30, 2003
Creator: Scanlan, R. M.; Dietderich, D. R. & Gourlay, S. A.
System: The UNT Digital Library
Specificity of anion-binding in the substrate-pocket ofbacteriorhodopsin (open access)

Specificity of anion-binding in the substrate-pocket ofbacteriorhodopsin

The structure of the D85S mutant of bacteriorhodopsin with a nitrate anion bound in the Schiff-base binding site, and the structure of the anion-free protein have been obtained in the same crystal form. Together with the previously solved structures of this anion pump, in both the anion-free state and bromide-bound state, these new structures provide insight into how this mutant of bacteriorhodopsin is able to bind a variety of different anions in the same binding pocket. The structural analysis reveals that the main structural change that accommodates different anions is the repositioning of the polar side-chain of S85. On the basis of these x-ray crystal structures, the prediction is then made that the D85S/D212N double mutant might bind similar anions and do so over a broader pH range than does the single mutant. Experimental comparison of the dissociation constants, K{sub d}, for a variety of anions confirms this prediction and demonstrates, in addition, that the binding affinity is dramatically improved by the D212N substitution.
Date: August 30, 2003
Creator: Facciotti, Marc T.; Cheung, Vincent S.; Lunde, Christopher S.; Rouhani, Shahab; Baliga, Nitin S. & Glaeser, Robert M.
System: The UNT Digital Library
Twenty-second Fungal Genetics Conference - Asilomar, 2003 (open access)

Twenty-second Fungal Genetics Conference - Asilomar, 2003

The purpose of the Twenty Second Fungal Genetics Conference is to bring together scientists and students who are interested in genetic approaches to studying the biology of filamentous fungi. It is intended to stimulate thinking and discussion in an atmosphere that supports interactions between scientists at different levels and in different disciplines. Topics range from the basic to the applied. Filamentous fungi impact human affairs in many ways. In the environment they are the most important agents of decay and nutrient turnover. They are used extensively in the food industry for the production of food enzymes such as pectinase and food additives such as citric acid. They are used in the production of fermented foods such as alcoholic drinks, bread, cheese, and soy sauce. More than a dozen species of mushrooms are used as foods directly. Many of our most important antibiotics, such as penicillin, cyclosporin, and lovastatin, come from fungi. Fungi also have many negative impacts on human health and economics. Fungi are serious pathogens in immuno-compromised patients. Fungi are the single largest group of plant pathogens and thus a serious limit on crop productivity throughout the world. Many fungi are allergenic, and mold contamination of residences and commercial …
Date: June 30, 2003
Creator: Walton, Jonathan D.
System: The UNT Digital Library
Apolipoprotein AIF gene variant S347 is associated with increased risk of coronary heart disease and lower apolipoprotein AIV plasma concentrations (open access)

Apolipoprotein AIF gene variant S347 is associated with increased risk of coronary heart disease and lower apolipoprotein AIV plasma concentrations

The impact of common variants in the apolipoprotein gene cluster (APOC3-A4-A5) on prospective CHD risk was examined in healthy UK men. Of the 2808 men followed over nine years, 187 had a clinically defined CHD event. Examination of 9 single nucleotide polymorphisms (SNPs) in this group revealed that homozygotes for APOA4 S347 had significantly increased risk of CHD [Hazard ratio (HR) of 2.07 (95%CI 1.04-4.12)] while men homozygous for APOC3 1100T were protected (HR 0.28 (95%CI 0.09-0.87)). In stepwise multiple regression analysis, after entering all the variants and adjusting for established risk factors APOA4 T347S alone remained in the model. Using nine-SNP haplotype analysis, highest risk-estimate haplotypes carried APOA4 S347 and rare alleles of the two flanking intergenic markers. The protective effect of APOC31100T could be explained by negative linkage disequilibrium with these alleles. To determine the association of APOA4 T347S with apoAIVlevels, the relationship was examined in over 1600 healthy young European men and women. S347 homozygotes had significantly lower apoAIV plasma levels (13.48 + 0.6mg/dl) compared to carriers of the T347 allele (14.85 + 0.12 mg/dl) (p=0.025). These results demonstrate that genetic variation in and around APOA4, independent of effects of TG, is associated with risk of CHD …
Date: January 30, 2003
Creator: Wong, Wai-man R.; Hawe, Emma; Li, Lai K.; Miller, George J.; Nicaud, Viviane; Pennacchio, Len A. et al.
System: The UNT Digital Library