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The energy dependence of the total charm cross section

Description: We discuss the energy dependence of the total charm cross section and some of its theoretical uncertainties including the quark mass, scale choice and the parton densities. We compare the next-to-leading order calculation of the total cross section with results obtained using PYTHIA.
Date: October 18, 2007
Creator: Vogt, R
Partner: UNT Libraries Government Documents Department
open access

Pump and probe damage testing for investigation of transient material modifications associated with laser damage in optical materials

Description: Laser-induced breakdown in the bulk of transparent dielectric materials is associated with the generation of extreme localized conditions of temperatures and pressures. In this work, we perform pump and probe damage testing experiments to investigate the evolution of transient absorption by the host material arising from modifications following confined laser energy deposition in fused silica and DKDP materials. Specifically, we measure the size of the damage sites observed in the region of spa… more
Date: October 18, 2007
Creator: Negres, R A; Feit, M D; DeMange, P; Bude, J D & Demos, S G
Partner: UNT Libraries Government Documents Department
open access

A High-Order Finite-Volume Algorithm for Fokker-Planck Collisions in Magnetized Plasmas

Description: A high-order finite volume algorithm is developed for the Fokker-Planck Operator (FPO) describing Coulomb collisions in strongly magnetized plasmas. The algorithm is based on a general fourth-order reconstruction scheme for an unstructured grid in the velocity space spanned by parallel velocity and magnetic moment. The method provides density conservation and high-order-accurate evaluation of the FPO independent of the choice of the velocity coordinates. As an example, a linearized FPO in const… more
Date: April 18, 2007
Creator: Xiong, Z; Cohen, R H; Rognlien, T D & Xu, X Q
Partner: UNT Libraries Government Documents Department
open access

Modeling Incoherent Electron Cloud Effects

Description: Incoherent electron effects could seriously limit the beam lifetime in proton or ion storage rings, such as LHC, SPS, or RHIC, or blow up the vertical emittance of positron beams, e.g., at the B factories or in linear-collider damping rings. Different approaches to modeling these effects each have their own merits and drawbacks. We describe several simulation codes which simplify the descriptions of the beam-electron interaction and of the accelerator structure in various different ways, and pr… more
Date: June 18, 2007
Creator: Vay, Jean-Luc; Benedetto, E.; Fischer, W.; Franchetti, G.; Ohmi, K.; Schulte, D. et al.
Partner: UNT Libraries Government Documents Department
open access

Temperature dependence of protein hydration hydrodynamics by molecular dynamics simulations.

Description: The dynamics of water molecules near the protein surface are different from those of bulk water and influence the structure and dynamics of the protein itself. To elucidate the temperature dependence hydration dynamics of water molecules, we present results from the molecular dynamic simulation of the water molecules surrounding two proteins (Carboxypeptidase inhibitor and Ovomucoid) at seven different temperatures (T=273 to 303 K, in increments of 5 K). Translational diffusion coefficients of … more
Date: July 18, 2007
Creator: Lau, E Y & Krishnan, V V
Partner: UNT Libraries Government Documents Department
open access

Dielectric Wall Accelerator Technology

Description: The dielectric wall accelerator (DWA) is a compact pulsed power device where the pulse forming lines, switching, and vacuum wall are integrated into a single compact geometry. For this effort, we initiated a extensive compact pulsed power development program and have pursued the study of switching (gas, oil, laser induced surface flashover and photoconductive), dielectrics (ceramics and nanoparticle composites), pulse forming line topologies (asymmetric and symmetric Blumleins and zero integral… more
Date: October 18, 2007
Creator: Sampayan, S.; Caporaso, G.; Chen, Y.; Harris, J.; Hawkins, S.; Holmes, C. et al.
Partner: UNT Libraries Government Documents Department
open access

Star-Formation in Low Radio Luminosity AGN from the Sloan Digital Sky Survey

Description: We investigate faint radio emission from low- to high-luminosity Active Galactic Nuclei (AGN) selected from the Sloan Digital Sky Survey (SDSS). Their radio properties are inferred by coadding large ensembles of radio image cut-outs from the FIRST survey, as almost all of the sources are individually undetected. We correlate the median radio flux densities against a range of other sample properties, including median values for redshift, [O III] luminosity, emission line ratios, and the strength… more
Date: April 18, 2007
Creator: de Vries, W. H.; Hodge, J. A.; Becker, R. H.; White, R. L. & Helfand, D. J.
Partner: UNT Libraries Government Documents Department
open access

Enhancing Price Response Programs through Auto-DR: California's 2007 Implementation Experience

Description: This paper describes automated demand response (Auto-DR) activities, an innovative effort in California to ensure that DR programs produce effective and sustainable impacts. Through the application of automation and communication technologies coupled with well-designed incentives and DR programs such as Critical Peak Pricing (CPP) and Demand Bidding (DBP), Auto-DR is opening up the opportunity for many different types of buildings to effectively participate in DR programs. We present the result… more
Date: December 18, 2007
Creator: Kiliccote, Sila; Wikler, Greg; Chiu, Albert; Piette, Mary Ann; Kiliccote, Sila; Hennage, Dan et al.
Partner: UNT Libraries Government Documents Department
open access

Bi3+ Luminescence in ABiO2Cl (A = Sr, Ba) and BaBiO2Br

Description: Trivalent bismuth luminescence is reported in three Sillenbismuth oxyhalide phases, SrBiO2Cl, BaBiO2Cl, and BaBiO2Br. Thesecompounds exhibit Bi 6s6->6 s2 emission under UV and X-ray radiation.At room temperature, BaBiO2Cl shows the most intense light emission, withspectral and decay properties similar to those found in Bi4Ge3O12 (BGO).At low temperatures, each phase show an increase in the photoluminescenceintensities and a narrowing of the emission peaks. In contrast to thetemperature dependen… more
Date: January 18, 2007
Creator: Porter-Chapman, Yetta D.; Bourret-Courchesne, Edith E. & Derenzo,Stephen E.
Partner: UNT Libraries Government Documents Department
open access

Simulation of Comet Impact and Survivability of Organic Compounds

Description: Comets have long been proposed as a potential means for the transport of complex organic compounds to early Earth. For this to be a viable mechanism, a significant fraction of organic compounds must survive the high temperatures due to impact. We have undertaken three-dimensional numerical simulations to track the thermodynamic state of a comet during oblique impacts. The comet was modeled as a 1-km water-ice sphere impacting a basalt plane at 11.2 km/s; impact angles of 15{sup o} (from horizon… more
Date: July 18, 2007
Creator: Liu, B T; Lomov, I N; Blank, J G & Antoun, T H
Partner: UNT Libraries Government Documents Department
open access

Magnetohydrodynamic Simulations of Disk GalaxyFormation: the Magnetization of The Cold and Warm Medium

Description: Using magnetohydrodynamic (MHD) adaptive mesh refinement simulations, we study the formation and early evolution of disk galaxies with a magnetized interstellar medium. For a 10{sup 10} M{sub {circle_dot}} halo with initial NFW dark matter and gas profiles, we impose a uniform 10{sup -9} G magnetic field and follow its collapse, disk formation and evolution up to 1 Gyr. Comparing to a purely hydrodynamic simulation with the same initial condition, we find that a protogalactic field of this stre… more
Date: December 18, 2007
Creator: Wang, Peng; Abel, Tom & /KIPAC, Menlo Park /Santa Barbara, KITP
Partner: UNT Libraries Government Documents Department
open access

STATUS OF THE INTERNATIONAL MUON IONIZATION COOLING EXPERIMENT(MICE)

Description: An international experiment to demonstrate muon ionization cooling is scheduled for beam at Rutherford Appleton Laboratory (RAL) in 2007. The experiment comprises one cell of the Study II cooling channel [1], along with upstream and downstream detectors to identify individual muons and measure their initial and final 6D phase-space parameters to a precision of 0.1%. Magnetic design of the beam line and cooling channel are complete and portions are under construction. The experiment will be desc… more
Date: July 18, 2007
Creator: Zisman, Michael S.
Partner: UNT Libraries Government Documents Department
open access

State-Resolved Dynamics of the CN(B2Sigma+) and CH(A2Delta)Excited Products Resulting from the VUV Photodissociation of CH3CN

Description: Fourier transform visible spectroscopy, in conjunction withVUV photons produced by a synchrotron, is employed to investigate thephotodissociation of CH3CN. Emission is observed from both theCN(B2Sigma+ - X2Sigma+) and CH(A2Delta - X2PI) transitions; only theformer is observed in spectra recorded at 10.2 and 11.5 eV, whereas bothare detected in the 16 eV spectrum. The rotational and vibrationaltemperatures of both the CN(B2Sigma+) and CH(A2Delta) radical productsare derived using a combination o… more
Date: January 18, 2007
Creator: Howle, Chris R.; Arrowsmith, Alan N.; Chikan, Viktor & Leone,Stephen R.
Partner: UNT Libraries Government Documents Department
open access

Significant Lifetime and Background Improvements in PEP-II by Reducing the 3rd Order Chromaticity in LER with Orbit Bumps

Description: Orbit bumps in sextupoles are routinely used for tuning the luminosity in the PEP-II B-Factory. Anti-symmetric bumps at a pair of identical sextupoles separated by -I section generate the net dispersion, while symmetric horizontal bumps induce a tune shift and beta beat. By combining two of these symmetric bumps with opposite signs, where the second pair is 90{sup o} away, the tune shift cancels and the beta beat doubles. In the low energy ring (LER), there are four -I sextupole pairs per arc, … more
Date: December 18, 2007
Creator: Decker, F. J.; Nosochkov, Y.; Sullivan, M. & Yocky, G.
Partner: UNT Libraries Government Documents Department
open access

Geometric Gyrokinetic Theory for Edge Plasma

Description: It turns out that gyrokinetic theory can be geometrically formulated as special cases of a geometrically generalized Vlasov-Maxwell system. It is proposed that the phase space of the spacetime is a 7-dimensional fiber bundle P over the 4-dimensional spacetime M, and that a Poincare-Cartan-Einstein 1-form {gamma} on the 7-dimensional phase space determines particles worldlines in the phase space. Through Liouville 6-form {Omega} and fiber integral, the 1-form {gamma} also uniquely defines a geom… more
Date: January 18, 2007
Creator: Qin, H; Cohen, R H; Nevins, W M & Xu, X Q
Partner: UNT Libraries Government Documents Department
open access

Electron-Cloud Build-Up: Summary

Description: I present a summary of topics relevant to the electron-cloud build-up and dissipation that were presented at the International Workshop on Electron-Cloud Effects 'ECLOUD 07' (Daegu, S. Korea, April 9-12, 2007). This summary is not meant to be a comprehensive review of the talks. Rather, I focus on those developments that I found, in my personal opinion, especially interesting. The contributions, all excellent, are posted in http://chep.knu.ac.kr/ecloud07/.
Date: June 18, 2007
Creator: Furman, M. A.
Partner: UNT Libraries Government Documents Department
open access

Nucleosynthesis in O-Ne-Mg Supernovae

Description: We have studied detailed nucleosynthesis in the shocked surface layers of an oxygen-neon-magnesium core collapse supernova with an eye to determining whether the conditions are suitable for r-process nucleosynthesis. We find no such conditions in an unmodified model, but do find overproduction of N=50 nuclei (previously seen in early neutron-rich neutrino winds) in amounts that, if ejected, would pose serious problems for Galactic chemical evolution.
Date: December 18, 2007
Creator: Hoffman, R D; Janka, H & Muller, B
Partner: UNT Libraries Government Documents Department
open access

Fiberoptics-Based Instrumentation for Storage Ring BeamDiagnostics

Description: In several cases, coupling synchrotron light into opticalfibers can substantially facilitate the use of beam diagnosticinstrumentation, that measures longitudinal beam properties by detectingsynchrotron radiation. It has been discussed in [1]with some detail, howfiberoptics can bring the light at relatively large distances from theaccelerator, where a variety of devices can be used to measure beamproperties and parameters. Light carried on a fiber can be easilyswitched between instruments so th… more
Date: April 18, 2007
Creator: Byrd, John M.; De Santis, Stefano & Yin, Yan
Partner: UNT Libraries Government Documents Department
open access

Response to ?A Madden-Julian Oscillation Event Realistically Simulated by a Global Cloud-Resolving Model?

Description: I agree with the authors that forecasting the Madden-Julian Oscillation (MJO) in a high resolution global model is important for numerous reasons, including improved weather forecast skill beyond 10 days, and resolving small scale features embedded in the MJO that coarse resolution ({approx}100-300km horizontal grid spacing) climate models do not (e.g., tropical cyclones). Unfortunately, the authors promote the (incorrect) overall impression that coarse resolution climate models cannot simulate… more
Date: December 18, 2007
Creator: Sperber, K R
Partner: UNT Libraries Government Documents Department
open access

Comparing Patterns of Natural Selection Across Species Using Selective Signatures

Description: Comparing gene expression profiles over many different conditions has led to insights that were not obvious from single experiments. In the same way, comparing patterns of natural selection across a set of ecologically distinct species may extend what can be learned from individual genome-wide surveys. Toward this end, we show how variation in protein evolutionary rates, after correcting for genome-wide effects such as mutation rate and demographic factors, can be used to estimate the level and… more
Date: December 18, 2007
Creator: Alm, Eric J.; Shapiro, B. Jesse & Alm, Eric J.
Partner: UNT Libraries Government Documents Department
open access

Rh(I)-Catalyzed Arylation of Heterocycles via C-H Bond Activation: Expanded Scope Through Mechanistic Insight

Description: A practical, functional group tolerant method for the Rh-catalyzed direct arylation of a variety of pharmaceutically important azoles with aryl bromides is described. Many of the successful azole and aryl bromide coupling partners are not compatible with methods for the direct arylation of heterocycles using Pd(0) or Cu(I) catalysts. The readily prepared, low molecular weight ligand, Z-1-tert-butyl-2,3,6,7-tetrahydrophosphepine, which coordinates to Rh in a bidentate P-olefin fashion to provide… more
Date: July 18, 2007
Creator: Lewis, Jared; Berman, Ashley; Bergman, Robert & Ellman, Jonathan
Partner: UNT Libraries Government Documents Department
open access

An alternative NMSSM phenomenology with manifest perturbative unification

Description: Can supersymmetric models with a moderate stop mass be made consistent with the negative Higgs boson searches at LEP, while keeping perturbative unification manifest? The NMSSM achieves this rather easily, but only if extra matter multiplets filling complete SU(5) representations are present at intermediate energies. As a concrete example which makes use of this feature, we give an analytic description of the phenomenology of a constrained NMSSM close to a Peccei-Quinn symmetry point. The relat… more
Date: December 18, 2007
Creator: Hall, Lawrence; Barbieri, Riccardo; Pappadopulo, Duccio; Rychkov, Vyacheslav S.; Hall, Lawrence J. & Papaioannou, Anastasios Y.
Partner: UNT Libraries Government Documents Department
open access

Mechanical and electronic-structure properties of compressed CdSetetrapod nanocrystals

Description: The coupling of mechanical and optical properties insemiconductor nanostructures can potentially lead to new types ofdevices. This work describes our theoretical examination of themechanical properties of CdSe tetrapods under directional forces, such asmay be induced by AFM tips. In addition to studying the general behaviorof the mechanical properties under modifications of geometry,nanocrystal-substrate interaction, and dimensional scaling, ourcalculations indicate that mechanical deformations… more
Date: January 18, 2007
Creator: Schrier, Joshua; Lee, Byounghak & Wang, Lin-Wang
Partner: UNT Libraries Government Documents Department
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