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Mechanical and charge transport properties of alkanethiol self-assembled monolayers on Au (111) surface: The Role of Molecular Tilt

Description: The relationship between charge transport and mechanical properties of alkanethiol self-assembled monolayers (SAM) on Au(111) films has been investigated using an atomic force microscope with a conductive tip. Molecular tilts induced by the pressure applied by the tip cause stepwise increases in film conductivity. A decay constant {beta} = 0.57 {+-} 0.03 {angstrom}{sup -1} was found for the current passing through the film as a function of tip-substrate separation due to this molecular tilt. Th… more
Date: November 12, 2007
Creator: Mulleregan, Alice; Qi, Yabing; Ratera, Imma; Park, Jeong Y.; Ashby, Paul D.; Quek, Su Ying et al.
Partner: UNT Libraries Government Documents Department
open access

Compact Proton Accelerator for Cancer Therapy

Description: An investigation is being made into the feasibility of making a compact proton dielectric wall (DWA) accelerator for medical radiation treatment based on the high gradient insulation (HGI) technology. A small plasma device is used for the proton source. Using only electric focusing fields for transporting and focusing the beam on the patient, the compact DWA proton accelerator m system can deliver wide and independent variable ranges of beam currents, energies and spot sizes.
Date: June 12, 2007
Creator: Chen, Y. & Paul, A. C.
Partner: UNT Libraries Government Documents Department
open access

Void Coalescence Processes Quantified Through Atomistic and Multiscale Simulation

Description: Simulation of ductile fracture at the atomic scale reveals many aspects of the fracture process including specific mechanisms associated with void nucleation and growth as a precursor to fracture and the plastic deformation of the material surrounding the voids and cracks. Recently we have studied void coalescence in ductile metals using large-scale atomistic and continuum simulations. Here we review that work and present some related investigations. The atomistic simulations involve three-dime… more
Date: January 12, 2007
Creator: Rudd, R E; Seppala, E T; Dupuy, L M & Belak, J
Partner: UNT Libraries Government Documents Department
open access

Communication Requirements and Interconnect Optimization forHigh-End Scientific Applications

Description: The path towards realizing peta-scale computing isincreasingly dependent on building supercomputers with unprecedentednumbers of processors. To prevent the interconnect from dominating theoverall cost of these ultra-scale systems, there is a critical need forhigh-performance network solutions whose costs scale linearly with systemsize. This work makes several unique contributions towards attaining thatgoal. First, we conduct one of the broadest studies to date of high-endapplication communicati… more
Date: November 12, 2007
Creator: Kamil, Shoaib; Oliker, Leonid; Pinar, Ali & Shalf, John
Partner: UNT Libraries Government Documents Department
open access

Aligned vertical fractures, HTI reservoir symmetry, and Thomsenseismic anisotropy parameters for polar media

Description: Sayers and Kachanov (1991) defined crack-influence parameters that are shown to be directly related to Thomsen (1986) weak-anisotropy seismic parameters for fractured reservoirs when the crack/fracture density is small enough. These results are then applied to the problem of seismic wave propagation in polar (i.e., non-isotropic) reservoirs having HTI seismic wave symmetry due to the presence of aligned vertical fractures and resulting in azimuthal seismic wave symmetry at the earth's surface. … more
Date: December 12, 2007
Creator: Berryman, James G.
Partner: UNT Libraries Government Documents Department
open access

Precise predictions for B -> Xs l+ l- in the large q2 region

Description: The inclusive B -> Xs l+ l- decay rate in the large q2 region (q2> m_psi'2) receives significant nonperturbative corrections. The resulting uncertainties can be drastically reduced by normalizing the rate to the B -> Xu l nu rate with the same q2 cut, which allows for much improved tests of short distance physics. We calculate this ratio, including the order 1/m_b3 nonperturbative corrections and the analytically known NNLO perturbative corrections. Since in the large q2 region an … more
Date: July 12, 2007
Creator: Ligeti, Zoltan; Ligeti, Zoltan & Tackmann, Frank J.
Partner: UNT Libraries Government Documents Department
open access

Search for lepton flavor violating decays tau to l \omega (l = e, mu)

Description: A search for lepton flavor violating decays of a {tau} to a lighter-mass charged lepton and an {omega} vector meson is performed using 384.1 fb{sup -1} of e{sup +}e{sup -} annihilation data collected with the BABAR detector at the Stanford Linear Accelerator Center PEP-II storage ring. No signal is found, and the upper limits on the branching ratios are determined to be {beta}({tau}{sup {+-}} {yields} e{sup {+-}}{omega}) < 1.1 x 10{sup -7} and {beta}({tau}{sup {+-}} {yields} {mu}{sup {+-}}{o… more
Date: November 12, 2007
Creator: Collaboration, The BABAR & Aubert, B.
Partner: UNT Libraries Government Documents Department
open access

Effects of d-electrons in pseudopotential screened-exchange density functional calculations

Description: We report a theoretical study on the role of shallow d states in the screened-exchange local density approximation (sX-LDA) band structure of binary semiconductor systems.We found that inaccurate pseudo-wavefunctions can lead to 1) an overestimation of the screened-exchange interaction betweenthe localized d states and the delocalized higher energy s and p states and 2) an underestimation of the screened-exchange interaction between the d states. The resulting sX-LDA band structures have substa… more
Date: September 12, 2007
Creator: Lee, Byounghak; Canning, Andrew & Wang, Lin-Wang
Partner: UNT Libraries Government Documents Department
open access

ATLAS Inner Detector Event Data Model

Description: The data model for event reconstruction (EDM) in the Inner Detector of the ATLAS experiment is presented. Different data classes represent evolving stages in the reconstruction data flow, and specific derived classes exist for the sub-detectors. The Inner Detector EDM also extends the data model for common tracking in ATLAS and is integrated into the modular design of the ATLAS high-level trigger and off-line software.
Date: December 12, 2007
Creator: ATLAS; Akesson, F.; Costa, M. J.; Dobos, D.; Elsing, M.; Fleischmann, S. et al.
Partner: UNT Libraries Government Documents Department
open access

Simulation and Analysis of Microwave Transmission through an Electron Cloud, a Comparison of Results

Description: Simulation studies for transmission of microwaves through electron cloudes show good agreement with analytic results. The elctron cloud produces a shift in phase of the microwave. Experimental observation of this phenomena would lead to a useful diagnostic tool for acessing the local density of electron clouds in an accelerator. These experiments are being carried out at the CERN SPS and the PEP-II LER at SLAC and is proposed to be done at the Fermilab maininjector. In this study, a brief analy… more
Date: March 12, 2007
Creator: Sonnad, Kiran; Sonnad, Kiran; Furman, Miguel; Veitzer, Seth; Stoltz, Peter & Cary, John
Partner: UNT Libraries Government Documents Department
open access

Monte Carlo without chains

Description: A sampling method for spin systems is presented. The spin lattice is written as the union of a nested sequence of sublattices, all but the last with conditionally independent spins, which are sampled in succession using their marginals. The marginals are computed concurrently by a fast algorithm; errors in the evaluation of the marginals are offset by weights. There are no Markov chains and each sample is independent of the previous ones; the cost of a sample is proportional to the number of sp… more
Date: December 12, 2007
Creator: Chorin, Alexandre J.
Partner: UNT Libraries Government Documents Department
open access

High-resolution detection system for time-of-flight electron spectrometry

Description: One of the key components of a time-of-flight (TOF) spectrometer is the detection system. In addition to high timing resolution, accurate two-dimensional imaging substantially broadensthe areas of applications of TOF spectrometers; for example, add a new dimension to angle-resolved photoemission spectroscopy (ARPES). In this paper we report on the recent developments of a high spatial (<50 mm) and timing (<130 ps) resolution imaging system capable of selective detection of electrons, ions… more
Date: August 12, 2007
Creator: Hussain, Zahid; Tremsin, A.S.; Lebedev, G.V.; Siegmund, O.H.W.; Vallerga, J.V.; McPhate, J.B. et al.
Partner: UNT Libraries Government Documents Department
open access

New inflation vs. chaotic inflation, higher degree potentials and the reconstruction program in light of WMAP3

Description: The cosmic microwave background power spectra are studied for different families of single field new and chaotic inflation models in the effective field theory approach to inflation. We implement a systematic expansion in 1/N(e), where N(e)~;;50 is the number of e-folds before the end of inflation. We study the dependence of the observables (n(s), r and dn(s)/dlnk) on the degree of the potential (2n) and confront them to the WMAP3 and large scale structure data: This shows in general that fourt… more
Date: February 12, 2007
Creator: Ho, Chiu Man; Boyanovsky, D.; de Vega, H.J.; Ho, C.M. & Sanchez, N.G.
Partner: UNT Libraries Government Documents Department
open access

Circumnuclear Star Clusters in the Galaxy Merger NGC 6240, Observed with Keck Adaptive Optics and HST

Description: We discuss images of the central {approx} 10 kpc (in projection) of the galaxy merger NGC 6240 at H and K{prime} bands, taken with the NIRC2 narrow camera on Keck II using natural guide star adaptive optics. We detect 28 star clusters in the NIRC2 images, of which only 7 can be seen in the similar-spatial-resolution, archival WFPC2 Planetary Camera data at either B or I bands. Combining the NIRC2 narrow camera pointings with wider NICMOS NIC2 images taken with the F110W, F160W, and F222M filter… more
Date: February 12, 2007
Creator: Pollack, L K; Max, C E & Schneider, G
Partner: UNT Libraries Government Documents Department
open access

The Redshift Dependence of Gamma-Ray Absorption in the Environments of Strong-Line AGNs

Description: The case of {gamma}-ray absorption due to photon-photon pair production of jet photons in the external photon environments, such as the accretion disk and the broad-line region radiation fields, of {gamma}-ray--loud active galactic nuclei (AGNs) that exhibit strong emission lines is considered. I demonstrate that this 'local opacity,' if detected, will almost unavoidably be redshift-dependent in the sub-TeV range. This introduces nonnegligible biases and complicates approaches for studying the … more
Date: November 12, 2007
Creator: Reimer, A. & /Stanford U., HEPL /KIPAC, Menlo Park
Partner: UNT Libraries Government Documents Department
open access

High-energy Picosecond Laser Pulse Recirculation for Compton Scattering

Description: Frequency upconversion of laser-generated photons by inverse Compton scattering for applications such as nuclear spectroscopy and gamma-gamma collider concepts on the future ILC would benefit from an increase of average source brightness. The primary obstacle to higher average brightness is the relatively small Thomson scattering cross section. It has been proposed that this limitation can be partially overcome by use of laser pulse recirculation. The traditional approach to laser recirculation… more
Date: June 12, 2007
Creator: Jovanovic, I; Anderson, S G; Betts, S M; Brown, C; Gibson, D J; Hartemann, F V et al.
Partner: UNT Libraries Government Documents Department
open access

Noninvariance of Space and Time Scale Ranges under a Lorentz Transformation and the Implications for the Numerical Study of Relativistic Systems

Description: We present an analysis which shows that the ranges of space and time scales spanned by a system are not invariant under the Lorentz transformation. This implies the existence of a frame of reference which minimizes an aggregate measure of the range of space and time scales. Such a frame is derived for example cases: free electron laser, laser-plasma accelerator, and particle beam interacting with electron clouds. Implications for experimental, theoretical and numerical studies are discussed. Th… more
Date: November 12, 2007
Creator: Vay, J. L. & Vay, J. L.
Partner: UNT Libraries Government Documents Department
open access

Acid Catalysis in Basic Solution: A Supramolecular Host PromotesOrthoformate Hydrolysis

Description: Though many enzymes can promote chemical reactions by tuning substrate properties purely through the electrostatic environment of a docking cavity, this strategy has proven challenging to mimic in synthetic host-guest systems. Here we report a highly-charged, water soluble, metal-ligand assembly with a hydrophobic interior cavity that thermodynamically stabilizes protonated substrates and consequently catalyzes the normally acidic hydrolysis of orthoformates in basic solution, with rate acceler… more
Date: December 12, 2007
Creator: Pluth, Michael D.; Bergman, Robert G. & Raymond, Kenneth N.
Partner: UNT Libraries Government Documents Department
open access

Preliminary Analysis and Simulation Results of Microwave Transmission Through an Electron Cloud

Description: The electromagnetic particle-in-cell (PIC) code VORPAL is being used to simulate the interaction of microwave radiation through an electron cloud. The results so far showgood agreement with theory for simple cases. The study has been motivated by previous experimental work on this problem at the CERN SPS [1], experiments at the PEP-II Low Energy Ring (LER) at SLAC [4], and proposed experiments at the Fermilab Main Injector (MI). With experimental observation of quantities such as amplitude, pha… more
Date: January 12, 2007
Creator: Sonnad, Kiran; Sonnad, Kiran; Furman, Miguel; Veitzer, Seth; Stoltz, Peter & Cary, John
Partner: UNT Libraries Government Documents Department
open access

ANOLE Portable Radiation Detection System Field Test and Evaluation Campaign

Description: Handheld, backpack, and mobile sensors are elements of the Global Nuclear Detection System for the interdiction and control of illicit radiological and nuclear materials. They are used by the U.S. Department of Homeland Security (DHS) and other government agencies and organizations in various roles for border protection, law enforcement, and nonproliferation monitoring. In order to systematically document the operational performance of the common commercial off-the-shelf portable radiation dete… more
Date: July 12, 2007
Creator: Hodge, Chris A.
Partner: UNT Libraries Government Documents Department
open access

Proceedings of the Plutonium Futures ? The Science 2006 Conference

Description: Plutonium Futures--The Science 2006 provided opportunities to examine present knowledge of the chemical and physical properties of plutonium and other actinides in complex media and materials; to discuss the current and emerging science (chemistry, physics, materials science, nuclear science, and environmental effects) of plutonium and actinides relevant to enhancing global nuclear security; and to exchange ideas. This international conference also provided a forum for illustrating and enhancin… more
Date: July 12, 2007
Creator: Fluss, M; Hobart, D; Allan, P & Jarvinen, G
Partner: UNT Libraries Government Documents Department
open access

Variable High Order Multiblock Overlapping Grid Methods for Mixed Steady and Unsteady Multiscale Viscous Flows

Description: Flows containing steady or nearly steady strong shocks in parts of the flow field, and unsteady turbulence with shocklets on other parts of the flow field are difficult to capture accurately and efficiently employing the same numerical scheme even under the multiblock grid or adaptive grid refinement framework. On one hand, sixth-order or higher shock-capturing methods are appropriate for unsteady turbulence with shocklets. On the other hand, lower order shock-capturing methods are more effecti… more
Date: December 12, 2007
Creator: Sjogreen, B & Yee, H C
Partner: UNT Libraries Government Documents Department
open access

DEPARTMENT OF ENERGY SOIL AND GROUNDWATER SCIENCE AND TECHNOLOGY NEEDS, PLANS AND INITIATIVES

Description: This paper presents the process used by the Department of Energy (DOE) Environmental Management (EM) Program to collect and prioritize DOE soil and groundwater site science and technology needs, develop and document strategic plans within the EM Engineering and Technology Roadmap, and establish specific program and project initiatives for inclusion in the EM Multi-Year Program Plan. The paper also presents brief summaries of the goals and objectives for the established soil and groundwater init… more
Date: December 12, 2007
Creator: Aylward, B; V. ADAMS, V; G. M. CHAMBERLAIN, G & T. L. STEWART, T
Partner: UNT Libraries Government Documents Department
open access

Synchronization in complex networks

Description: Synchronization processes in populations of locally interacting elements are in the focus of intense research in physical, biological, chemical, technological and social systems. The many efforts devoted to understand synchronization phenomena in natural systems take now advantage of the recent theory of complex networks. In this review, we report the advances in the comprehension of synchronization phenomena when oscillating elements are constrained to interact in a complex network topology. W… more
Date: December 12, 2007
Creator: Arenas, A.; Diaz-Guilera, A.; Moreno, Y.; Zhou, C. & Kurths, J.
Partner: UNT Libraries Government Documents Department
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