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[After a Fashion, January 2005] (open access)

[After a Fashion, January 2005]

Article about the Golden Globe Awards, Erin Elmore, and the author's receipt of the Media Correspondent Award from Philanthropy World magazine.
Date: January 2005
Creator: Moser, Stephen MacMillan
System: The UNT Digital Library
The Weak lensing bispectrum (open access)

The Weak lensing bispectrum

Weak gravitational lensing of background galaxies offers an excellent opportunity to study the intervening distribution of matter. While much attention to date has focused on the two-point function of the cosmic shear, the three-point function, the bispectrum, also contains very useful cosmological information. Here, we compute three corrections to the bispectrum which are nominally of the same order as the leading term. We show that the corrections are small, so they can be ignored when analyzing present surveys. However, they will eventually have to be included for accurate parameter estimates from future surveys.
Date: January 1, 2005
Creator: Dodelson, Scott & Zhang, Pengjie
System: The UNT Digital Library
POLARIZED HYDROGEN JET TARGET FOR MEASUREMENT OF RHIC PROTON BEAM POLARIZATION. (open access)

POLARIZED HYDROGEN JET TARGET FOR MEASUREMENT OF RHIC PROTON BEAM POLARIZATION.

The performance and unique features of the RHIC polarized jet target and our solutions to the important design constraints imposed on the jet by the RHIC environment are described. The target polarization and thickness were measured to be 0.924 {+-} 2% and 1.3 {+-} 0.2 x 10{sup 12} atoms/cm{sup 2} respectively.
Date: January 28, 2005
Creator: Makdisi, Y.; Wise, T.; Chapman, M.; Graham, D.; Kponou, A.; Mahler, G. et al.
System: The UNT Digital Library
Unveiling neutrino mixing and leptonic CP violation (open access)

Unveiling neutrino mixing and leptonic CP violation

We review the present understanding of neutrino masses and mixings, discussing what are the unknowns in the three family oscillation scenario. Despite the anticipated success coming from the planned long baseline neutrino experiments in unraveling the leptonic mixing sector, there are two important unknowns which may remain obscure: the mixing angle {theta}{sub 13} and the CP-phase {delta}. The measurement of these two parameters has led us to consider the combination of superbeams and neutrino factories as the key to unveil the neutrino oscillation picture.
Date: January 1, 2005
Creator: Mena, Olga
System: The UNT Digital Library
High-Latitude Molecular Clouds as (Gamma)-ray Sources for GLAST (open access)

High-Latitude Molecular Clouds as (Gamma)-ray Sources for GLAST

For about two decades, a population of relative small and nearby molecular clouds has been known to exist at high Galactic latitudes. Lying more than 10{sup o} from the Galactic plane, these clouds have typical distances of {approx}150 pc, angular sizes of {approx}1{sup o}, and masses of order tens of solar masses. These objects are passive sources of high-energy {gamma}-rays through cosmic ray-gas interactions. Using a new wide-angle CO survey of the northern sky, we show that typical high-latitude clouds are not bright enough in {gamma}-rays to have been detected by EGRET, but that of order 100 of them will be detectable by the Large Area Telescope (LAT) on GLAST. Thus, we predict a new steady population of {gamma}-ray sources at high Galactic latitudes, perhaps the most numerous after active galactic nuclei.
Date: January 5, 2005
Creator: Torres, D F; Dame, T M & Digel, S W
System: The UNT Digital Library
469nm Fiber Laser Source (open access)

469nm Fiber Laser Source

We have demonstrated 466mW of 469nm light from a frequency doubled continuous wave fiber laser. The system consisted of a 938nm single frequency laser diode master oscillator, which was amplified in two stages to 5 Watts using cladding pumped Nd{sup 3+} fiber amplifiers and then frequency doubled in a single pass through periodically poled KTP. The 3cm long PPKTP crystal was made by Raicol Crystals Ltd. with a period of 5.9 {micro}m and had a phase match temperature of 47 degrees Centigrade. The beam was focused to a 1/e{sup 2} diameter in the crystal of 29 {micro}m. Overall conversion efficiency was 11% and the results agreed well with standard models. Our 938nm fiber amplifier design minimizes amplified spontaneous emission at 1088nm by employing an optimized core to cladding size ratio. This design allows the 3-level transition to operate at high inversion, thus making it competitive with the 1088nm 4-level transition. We have also carefully chosen the fiber coil diameter to help suppress propagation of wavelengths longer than 938 nm. At 2 Watts, the 938nm laser had an M{sup 2} of 1.1 and good polarization (correctable with a quarter and half wave plate to >10:1).
Date: January 20, 2005
Creator: Drobshoff, A; Dawson, J W; Pennington, D M; Payne, S A & Beach, R
System: The UNT Digital Library
Water at a hydrophilic solid surface probed by ab-initio molecular dynamics: inhomogeneous thin layers of dense fluid (open access)

Water at a hydrophilic solid surface probed by ab-initio molecular dynamics: inhomogeneous thin layers of dense fluid

We present a microscopic model of the interface between liquid water and a hydrophilic, solid surface, as obtained from ab-initio molecular dynamics simulations. In particular, we focused on the (100)surface of cubic SiC, a leading candidate semiconductor for bio-compatible devices. Our results show that, in the liquid in contact with the clean substrate, molecular dissociation occurs in a manner unexpectedly similar to that observed in the gas phase. After full hydroxylation takes place, the formation of a thin ({approx}3 {angstrom})interfacial layer is observed, which has higher density than bulk water and forms stable hydrogen bonds with the substrate. The liquid does not uniformly wet the surface, rather molecules preferably bind along directions parallel to the Si dimer rows. Our calculations also predict that one dimensional confinement between two hydrophilic surfaces at about 1.3 nm distance does not affect the structural and electronic properties of the whole water sample.
Date: January 28, 2005
Creator: Cicero, G; Grossman, J; Galli, G & Catellani, A
System: The UNT Digital Library
Emittance dilution and halo creation during the first milliseconds after injection at the Fermilab Booster (open access)

Emittance dilution and halo creation during the first milliseconds after injection at the Fermilab Booster

During the past year, the Fermilab Booster has been pushed to record intensities in order to satisfy the needs of the Tevatron collider and neutrino programs. This high intensity makes the study of space-charge effects and halo formation highly relevant to optimizing Booster performance. We present measurements of beam width evolution, halo formation, and coherent tune shifts, emphasizing the experimental techniques used and the calibration of the measuring devices. We also use simulations utilizing the 3D space-charge code Synergia to study the physical origins of these effects.
Date: January 1, 2005
Creator: Spentzouris, Panagiotis & Amundson, J.
System: The UNT Digital Library
Star Formation in High Pressure, High Energy Density Environments: Laboratory Experiments of ISM Dust Analogs (open access)

Star Formation in High Pressure, High Energy Density Environments: Laboratory Experiments of ISM Dust Analogs

Dust grains control the chemistry and cooling, and thus the gravitational collapse of interstellar clouds. Energetic particles, shocks and ionizing radiation can have a profound influence on the structure, lifetime and chemical reactivity of the dust, and therefore on the star formation efficiency. This would be especially important in forming galaxies, which exhibit powerful starburst (supernovae) and AGN (active galactic nucleus) activity. How dust properties are affected in such environments may be crucial for a proper understanding of galaxy formation and evolution. The authors present the results of experiments at LLNL which show that irradiation of the interstellar medium (ISM) dust analog forsterite (Mg{sub 2}SiO{sub 4}) with swift heavy ions (10 MeV Xe) and a large electronic energy deposition amorphizes its crystalline structure, without changing its chemical composition. From the data they predict that silicate grains in the ISM, even in dense and cold giant molecular clouds, can be amorphized by heavy cosmic rays (CR's). This might provide an explanation for the observed absence of crystalline dust in the ISM clouds of the Milky Way galaxy. This processing of dust by CR's would be even more important in forming galaxies and galaxies with active black holes.
Date: January 5, 2005
Creator: van Breugel, W; Bajt, S; Bradley, J; Bringa, E; Dai, Z; Felter, T et al.
System: The UNT Digital Library
Asymptotic Freedom in the Diffusive Regime of Neutron Transport (open access)

Asymptotic Freedom in the Diffusive Regime of Neutron Transport

The accuracy of a numerical method for solving the neutron transport equation is limited by the smallest mean free path in the problem. Since problems in the asymptotic diffusive regimes have vanishingly small mean free paths, it seems hopeless, given a limited amount of computer memory, that an accurate solution can be obtained for these problems. However we found that the accuracy of a numerical method improves as the scattering ratio increases with the total cross section and the grid spacing held fixed for problems that are in the asymptotic diffusive regime. This phenomenon is independent of the numerical method and can be explained on physical grounds. The numerical results by the Diamond Difference Method are given to show this phenomenon.
Date: January 25, 2005
Creator: Chang, B.
System: The UNT Digital Library
Facile Synthesis of a Crystalline, High-Surface Area SnO2 Aerogel (open access)

Facile Synthesis of a Crystalline, High-Surface Area SnO2 Aerogel

We report the preparation of a novel monolithic SnO{sub 2} aerogel using a straightforward sol-gel technique. TEM and XRD analysis show that the as-prepared material is comprised of interconnected, randomly oriented crystalline (rutile) SnO{sub 2} nanoparticles {approx}3-5 nm in size. As a result, the low-density SnO{sub 2} monolith ({approx}97% porous) exhibits a very high surface area of 383 m{sup 2}/g. /XANES spectroscopy at the Sn M{sub 4,5} edge reveals that the electronic structure of the SnO{sub 2} aerogel is similar to that of tetragonal SnO rather than SnO{sub 2} or {beta}-Sn, and that the undercoordinated surface atoms in the material introduce additional Sn-related electronic states close to the conduction band minimum.
Date: January 3, 2005
Creator: Baumann, T. F.; Kucheyev, S. O.; Gash, A. E. & Satcher, J. H. Jr.
System: The UNT Digital Library
Measurement of the Analyzing Power in PP Elastic Scattering in the Peak CNI Region at RHIC (open access)

Measurement of the Analyzing Power in PP Elastic Scattering in the Peak CNI Region at RHIC

The analyzing power A{sub N} for pp elastic scattering is expected to reach a peak value of 0.045 in the Coulomb Nuclear Interference (CNI) region at a momentum transfer -t of 0.003 (GeV/c){sup 2}. During the 2004 RHIC Run, we completed a measurement of A{sub N} in the CNI region by detecting the recoil protons from pp elastic scattering using a polarized atomic hydrogen gas jet target and the 100 GeV RHIC proton beam. We report the first measurements of the A{sub N} absolute value and shape in the -t range from 0.0015 to 0.010 (GeV/c){sup 2} with a precision better than 0.005 for each A{sub N} data point. The recoil protons were detected with two arrays of Si detectors. The absolute target polarization as monitored by a Breit-Rabi polarimeter was stable at 0.924 {+-} 0.018. This result allows us to further investigate the spin dependence of elastic pp scattering in the very low -t region.
Date: January 28, 2005
Creator: Makdisi, Y.; Okada, H.; Alekseev, I. G.; Bravar, A.; Bunce, G. & AL, ET
System: The UNT Digital Library
Cross Sections for (Gamma)-Ray Production in the 191ir (N,Xn(Gamma)) Reactions (open access)

Cross Sections for (Gamma)-Ray Production in the 191ir (N,Xn(Gamma)) Reactions

Discrete {gamma}-ray spectra have been measured for nuclei populated in {sup 191}Ir(n{sub 4}xn{gamma}) with x{<=}11, as a function of incident neutron energy using neutrons from the 'white' neutron source at the Los Alamos Neutron Science Center's WNR facility. The energy of the neutrons was determined using the time-of-flight technique. The data were taken using the GEANIE spectrometer. The cross sections for emission of 202 {gamma} rays of {sup 181-191}Ir were determined for neutron energies 0.2 MeV < E{sub n} < 300 MeV. Comparison with model calculations, using the GNASH reaction model, and with GEANIE results from the similar {sup 193}Ir(n{sub 4}xn{gamma}) reactions is made.
Date: January 11, 2005
Creator: Fotiades, N.; Nelson, R. O.; Devlin, M.; Chadwick, M. B.; Talou, P.; Becker, J. A. et al.
System: The UNT Digital Library
The Development of a Detailed Chemical Kinetic Mechanism for Diisobutylene and Comparison to Shock Tube Ignition Times (open access)

The Development of a Detailed Chemical Kinetic Mechanism for Diisobutylene and Comparison to Shock Tube Ignition Times

There is much demand for chemical kinetic models to represent practical fuels such as gasoline, diesel and aviation fuel. These blended fuels contain hundreds of components whose identity and amounts are often unknown. A chemical kinetic mechanism that would represent the oxidation of all these species with accompanying chemical reactions is intractable with current computational capabilities, chemical knowledge and manpower resources. The use of surrogate fuels is an approach to make the development of chemical kinetic mechanisms for practical fuels tractable. A surrogate fuel model consists of a small number of fuel components that can be used to represent the practical fuel and still predict desired characteristics of the practical fuel. These desired fuel characteristics may include ignition behavior, burning velocity, fuel viscosity, fuel vaporization, and fuel emissions (carbon monoxide, hydrocarbons, soot and nitric oxides). Gasoline consists of many different classes of hydrocarbons including n-alkanes, alkenes, iso-alkanes, cycloalkanes, cycloalkenes, and aromatics. One approach is to use a fuel surrogate that has a single component from each class of hydrocarbon in gasoline so that the unique molecular structure of each class is represented. This approach may lead to reliable predictions of many of the combustion properties of the practical fuel. In …
Date: January 21, 2005
Creator: Metcalfe, W; Curran, H J; Simmie, J M; Pitz, W J & Westbrook, C K
System: The UNT Digital Library
The SDSS u-band Galaxy Survey: Luminosity functions and evolution (open access)

The SDSS u-band Galaxy Survey: Luminosity functions and evolution

We construct and analyze a u-band selected galaxy sample from the SDSS Southern Survey, which covers 275 deg{sup 2}. The sample includes 43223 galaxies with spectroscopic redshifts in the range 0.005 < z < 0.3 and with 14.5 < u < 20.5. The S/N in the u-band Petrosian aperture is improved by coadding multiple epochs of imaging data and by including sky-subtraction corrections. Luminosity functions for the near-UV {sup 0.1}u band ({lambda} {approx} 322 {+-} 26 nm) are determined in redshift slices of width 0.02, which show a highly significant evolution in M* of -0.8 {+-} 0.1 mag between z = 0 and 0.3; with M* - 5 log h{sub 70} = -18.84 {+-} 0.05 (AB mag), log {phi}* = -2.06 {+-} 0.03 (h{sub 70}{sup 3} Mpc{sup -3}) and log {rho}{sub L} = 19.11 {+-} 0.02 (h{sub 70} W Hz{sup -1}Mpc{sup -3}) at z = 0.1. The faint-end slope determined for z < 0.06 is given by {alpha} = -1.05 {+-} 0.08. This is in agreement with recent determinations from GALEX at shorter wavelengths. Comparing our z < 0.3 luminosity density measurements with 0.2 < z < 1.2 from COMBO-17, we find that the 280-nm density evolves as {rho}{sub L} …
Date: January 1, 2005
Creator: Baldry, Ivan K.; Glazebrook, K.; Budavari, T.; Eisenstein, D. J.; Annis, J.; Bahcall, N. A. et al.
System: The UNT Digital Library
THE BNL SUPER NEUTRINO BEAM PROJECT. (open access)

THE BNL SUPER NEUTRINO BEAM PROJECT.

BNL plans to create a very long base line super neutrino beam facility by upgrading the AGS from the current 0.14 MW to 1.0 MW and beyond. The proposed facility consists of three major components. First is a 1.5 GeV superconducting linac to replace the booster as injector for the AGS, second is the performance upgrade of the AGS itself for higher intensity and repetition rate, and finally is the target and horn system for the neutrino production. The major contribution for the higher power is from the increase of the repetition rate of the AGS from 0.3 Hz to 2.5 Hz, with moderate increase from the intensity. The accelerator design considerations to achieve high intensity and low losses for the new linac and the AGS will be presented. The target and horn design for high power operation and easy maintenance will also be covered.
Date: January 26, 2005
Creator: Raparia, D.
System: The UNT Digital Library
Flow Around a Complex Building: Experimental and Large-Eddy Simulation Comparisons (open access)

Flow Around a Complex Building: Experimental and Large-Eddy Simulation Comparisons

None
Date: January 13, 2005
Creator: Calhoun, R.; Gouveia, F.; Shinn, J.; Chan, S.; Stevens, D.; Lee, R. et al.
System: The UNT Digital Library
Towards SiC Surface Functionalization: An Ab Initio Study (open access)

Towards SiC Surface Functionalization: An Ab Initio Study

We present a microscopic model of the interaction and adsorption mechanism of simple organic molecules on SiC surfaces as obtained from ab initio molecular dynamics simulations. Our results open the way to functionalization of silicon carbide, a leading candidate material for bio-compatible devices.
Date: January 28, 2005
Creator: Cicero, G & Catellani, A
System: The UNT Digital Library
How to Determine The Precession of the Inner Accretion Disk in Cygnus X-1 (open access)

How to Determine The Precession of the Inner Accretion Disk in Cygnus X-1

We show that changes in the orientation of the inner accretion disk of Cygnus X-1 affect the shape of the broad Fe K{alpha} emission line emitted from this object, in such a way that eV-level spectral resolution observations (such as those that will be carried out by the ASTRO-E2 satellite) can be used to analyze the dynamics of the disk. We here present a new diagnosis tool, supported by numerical simulations, by which short observations of Cygnus X-1, separated in time, can determine whether its accretion disk actually processes, and if so, determine its period and precession angle. Knowing the precession parameters of Cygnus X-1 would result in a clarification of the origin of such precession, distinguishing between tidal and spin-spin coupling. This approach could also be used for similar studies in other microquasar systems.
Date: January 5, 2005
Creator: Torres, D F; Romero, G E; Barcons, X & Lu, Y
System: The UNT Digital Library
New Approaches for Collaborative Sharing of Chemical Model Data and Analysis Tools (open access)

New Approaches for Collaborative Sharing of Chemical Model Data and Analysis Tools

The urgent need for high-efficiency, low-emission energy utilization technologies for transportation, power generation, and manufacturing processes presents difficult challenges to the combustion research community. The required predictive understanding requires systematic knowledge across the full range of physical scales involved in combustion processes--from the properties and interactions of individual molecules to the dynamics and products of turbulent multi-phase reacting flows. Innovative experimental techniques and computational approaches are revolutionizing the rate at which chemical science research can produce the new information necessary to advance our combustion knowledge. But the increased volume and complexity of this information often makes it even more difficult to derive the systems-level knowledge we need. Combustion researchers have responded by forming interdisciplinary communities intent on sharing information and coordinating research priorities. Such efforts face many barriers, however, including lack of data accessibility and interoperability, missing metadata and pedigree information, efficient approaches for sharing data and analysis tools, and the challenges of working together across geography, disciplines, and a very diverse spectrum of applications and funding. This challenge is especially difficult for those developing, sharing and/or using detailed chemical models of combustion to treat the oxidation of practical fuels. This is a very complex problem, and the development of …
Date: January 19, 2005
Creator: Schuchardt, K; Oluwole, O; Pitz, W; Rahn, L A; Green, Jr., W H; Leahy, D et al.
System: The UNT Digital Library
Beam-beam simulations of hadron colliders (open access)

Beam-beam simulations of hadron colliders

None
Date: January 1, 2005
Creator: Sen, Tanaji
System: The UNT Digital Library
Intracavity, adaptive correction of a high-average-power, solid-state, heat-capacity laser (open access)

Intracavity, adaptive correction of a high-average-power, solid-state, heat-capacity laser

The Solid-State, Heat-Capacity Laser (SSHCL) program at Lawrence Livermore National Laboratory is a multigeneration laser development effort scalable to the megawatt power levels. Wavefront quality is a driving metric of its performance. A deformable mirror with over 100 degrees of freedom situated within the cavity is used to correct both the static and dynamic aberrations sensed with a Shack-Hartmann wavefront sensor. The laser geometry is an unstable, confocal resonator with a clear aperture of 10 cm x 10 cm. It operates in a pulsed mode at a high repetition rate (up to 200 Hz) with a correction being applied before each pulse. Wavefront information is gathered in real-time from a low-power pick-off of the high-power beam. It is combined with historical trends of aberration growth to calculate a correction that is both feedback and feed-forward driven. The overall system design, measurement techniques and correction algorithms are discussed. Experimental results are presented.
Date: January 5, 2005
Creator: LaFortune, K N; Hurd, R L; Brase, J M & Yamamoto, R M
System: The UNT Digital Library
autokonf - A Configuration Script Generator Implemented in Perl (open access)

autokonf - A Configuration Script Generator Implemented in Perl

This paper discusses configuration scripts in general and the scripting language issues involved. A brief description of GNU autoconf is provided along with a contrasting overview of autokonf, a configuration script generator implemented in Perl, whose macros are implemented in Perl, generating a configuration script in Perl. It is very portable, easily extensible, and readily mastered.
Date: January 12, 2005
Creator: Reus, J F
System: The UNT Digital Library
Ultra-thick, low-stress nanostructured diamond films (open access)

Ultra-thick, low-stress nanostructured diamond films

We describe a hot-filament chemical vapor deposition process for growing freestanding nanostructured diamond films, {approx}80 {micro}m thick, with residual tensile stress levels {le} 90 MPa. We characterize the film microstructure, mechanical properties, chemical bond distribution, and elemental composition. Results show that our films are nanostructured with columnar grain diameters of {le} 150 nm and a highly variable grain length along the growth direction of {approx}50-1500 nm. These films have a rms surface roughness of {le} 200 nm for a 300 x 400 {micro}m{sup 2} scan, which is about one order of magnitude lower than the roughness of typical microcrystalline diamond films of comparable thickness. Soft x-ray absorption near-edge structure (XANES) spectroscopy indicates a large percentage of sp{sup 3} bonding in the films,consistent with a high hardness of 66 GPa. Nanoindentation and XANES results are also consistent with a high phase and elemental purity of the films, directly measured by x-ray and electron diffraction, Rutherford backscattering spectrometry, and elastic recoil detection analysis. Cross-sectional transmission electron microscopy reveals a large density of planar defects within the grains, suggesting a high rate of secondary nucleation during film growth. These films represent a new class of smooth, ultra-thick nanostructured diamond.
Date: January 13, 2005
Creator: Kucheyev, S O; Biener, J; Tringe, J W & Wang, Y M
System: The UNT Digital Library