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Internet Use in Latin America

Description: This paper explores the development of Internet use in Latin America by exploring the macro- and micro-social expectations and actualities of Internet use.
Date: December 2011
Creator: Salzman, Ryan & Albarran, Alan B.
Partner: UNT College of Visual Arts + Design
open access

Virtualization Based Secure Execution And Testing Framework

Description: Article discussing the use of a virtualization software to build a Virtualization Based Secure Execution and Testing Framework for testing hardware secure architectures.
Date: December 2011
Creator: Kotikela, Srujan Das; Nimgaonkar, Satyajeet & Gomathisankaran, Mahadevan
Partner: UNT College of Engineering
open access

Toward TW-Level, Hard X-Ray Pulses at LCLS

Description: Coherent diffraction imaging of complex molecules such as proteins requires a large number (e.g., {approx} 10{sup 13}/pulse) of hard X-ray photons within a time scale of {approx} 10 fs or less. This corresponds to a peak power of {approx} 1 TW, much larger than that currently generated by LCLS or other proposed X-ray free electron lasers (FELs). We study the feasibility of producing such pulses using a LCLS-like, low charge electron beam, as will be possible in the LCLS-II upgrade project, empl… more
Date: December 13, 2011
Creator: Fawley, W. M.; Frisch, J.; Huang, Z.; Jiao, Y.; Nuhn, H. D.; Pellegrini, C. et al.
Partner: UNT Libraries Government Documents Department
open access

A Hierarchical Control Architecture for a PEBB-Based ILC Marx Modulator

Description: The idea of building power conversion systems around Power Electronic Building Blocks (PEBBs) was initiated by the U.S. Office of Naval Research in the mid 1990s. A PEBB-based design approach is advantageous in terms of power density, modularity, reliability, and serviceability. It is obvious that this approach has much appeal for pulsed power conversion including the International Linear Collider (ILC) klystron modulator application. A hierarchical control architecture has the inherent capabil… more
Date: December 15, 2011
Creator: Macken, K.; Burkhart, C.; Larsen, R.; Nguyen, M. N. & Olsen, J.
Partner: UNT Libraries Government Documents Department
open access

Search for 14.4-KeV Solar Axions Emitted in the M1-Transition of Fe-57 Nuclei with CAST

Description: We have searched for 14.4 keV solar axions or more general axion-like particles (ALPs), that may be emitted in the M1 nuclear transition of 57Fe, by using the axion-to-photon conversion in the CERN Axion Solar Telescope (CAST) with evacuated magnet bores (Phase I). From the absence of excess of the monoenergetic X-rays when the magnet was pointing to the Sun, we set model-independent constraints on the coupling constants of pseudoscalar particles that couple to two photons and to a nucleon g{su… more
Date: December 2, 2011
Creator: Andriamonje, S.; Aune, S.; Autiero, D.; Barth, K.; Belov, A.; Beltran, B. et al.
Partner: UNT Libraries Government Documents Department
open access

The nature of the lightest scalar meson, its N_c behaviour and semi-local duality

Description: One-loop unitarized Chiral Perturbation Theory (UChPT) calculations, suggest a different N{sub c} behaviour for the {sigma} or f{sub 0}(600) and {rho}(770) mesons: while the {rho} meson becomes narrower with N{sub c}, as expected for a {bar q}q meson, the f{sub 0}(600) contribution to the total cross section below 1 GeV becomes less and less important. Here we review our recent work where we have shown, by means of finite energy sum rules, that a different N{sub c} behavior for these resonances… more
Date: December 1, 2011
Creator: JR Pelaez, MR Pennington, J Ruiz de Elvira, DJ Wilson
Partner: UNT Libraries Government Documents Department
open access

Femtosecond X-ray Pulse Temporal Characterization in Free-Electron Lasers Using a Transverse Deflector

Description: We propose a novel method to characterize the temporal duration and shape of femtosecond x-ray pulses in a free-electron laser (FEL) by measuring the time-resolved electron-beam energy loss and energy spread induced by the FEL process, with a transverse radio-frequency deflector located after the undulator. Its merits are simplicity, high resolution, wide diagnostic range, and non-invasive to user operation. When the system is applied to the Linac Coherent Light Source, the first hard x-ray fre… more
Date: December 13, 2011
Creator: Ding, Y.; Behrens, C.; Emma, P.; Frisch, J.; Huang, Z.; Loos, H. et al.
Partner: UNT Libraries Government Documents Department
open access

Search for universal extra dimensions in ppbar collisions

Description: We present a search for Kaluza-Klein (KK) particles predicted by models with universal extra dimensions (UED) using a data set corresponding to an integrated luminosity of 7.3 fb{sup -1}, collected by the D0 detector at a p{bar p} center of mass energy of 1.96 TeV. The decay chain of KK particles can lead to a final state with two muons of the same charge. This signature is used to set a lower limit on the compactification scale of R{sup -1} > 260 GeV in a minimal UED model.
Date: December 1, 2011
Creator: Abazov, Victor Mukhamedovich; /Dubna, JINR; Abbott, Braden Keim; U., /Oklahoma; Acharya, Bannanje Sripath; Inst., /Tata et al.
Partner: UNT Libraries Government Documents Department
open access

Theory of Microwave Instability and Coherent Synchrotron Radiation in Electron Storage Rings

Description: Bursting of coherent synchrotron radiation has been observed and in fact used to generate THz radiation in many electron storage rings. In order to understand and control the bursting, we return to the study of the microwave instability. In this paper, we will report on the theoretical understanding, including recent developments, of the microwave instability in electron storage rings. The historical progress of the theories will be surveyed, starting from the dispersion relation of coasting be… more
Date: December 9, 2011
Creator: Cai, Y.
Partner: UNT Libraries Government Documents Department
open access

Suzaku And Multi-Wavelength Observations of OJ 287 During the Periodic Optical Outburst in 2007

Description: Suzaku observations of the blazar OJ 287 were performed in 2007 April 10-13 and November 7-9. They correspond to a quiescent and a flaring state, respectively. The X-ray spectra of the source can be well described with single power-law models in both exposures. The derived X-ray photon index and the flux density at 1 keV were found to be {Lambda} = 1.65 {+-} 0.02 and S{sub 1keV} = 215 {+-} 5 nJy, in the quiescent state. In the flaring state, the source exhibited a harder X-ray spectrum ({Lambda… more
Date: December 1, 2011
Creator: Seta, Hiromi; Isobe, N.; Tashiro, Makoto S.; Yaji, Yuichi; Arai, Akira; Fukuhara, Masayuki et al.
Partner: UNT Libraries Government Documents Department
open access

ALPHA SPECTROMETRIC EVALUATION OF SRM-995 AS A POTENTIAL URANIUM/THORIUM DOUBLE TRACER SYSTEM FOR AGE-DATING URANIUM MATERIALS

Description: Uranium-233 (t{sub 1/2} {approx} 1.59E5 years) is an artificial, fissile isotope of uranium that has significant importance in nuclear forensics. The isotope provides a unique signature in determining the origin and provenance of uranium-bearing materials and is valuable as a mass spectrometric tracer. Alpha spectrometry was employed in the critical evaluation of a {sup 233}U standard reference material (SRM-995) as a dual tracer system based on the in-growth of {sup 229}Th (t{sub 1/2} {approx}… more
Date: December 6, 2011
Creator: Beals, D.
Partner: UNT Libraries Government Documents Department
open access

Constructing Amplitudes from Their Soft Limits

Description: The existence of universal soft limits for gauge-theory and gravity amplitudes has been known for a long time. The properties of the soft limits have been exploited in numerous ways; in particular for relating an n-point amplitude to an (n-1)-point amplitude by removing a soft particle. Recently, a procedure called inverse soft was developed by which 'soft' particles can be systematically added to an amplitude to construct a higher-point amplitude for generic kinematics. We review this procedur… more
Date: December 9, 2011
Creator: Boucher-Veronneau, Camille & Larkoski, Andrew J.
Partner: UNT Libraries Government Documents Department
open access

Atmospheric and Wake Turbulence Impacts on Wind Turbine Fatigue Loading: Preprint

Description: Large-eddy simulations of atmospheric boundary layers under various stability and surface roughness conditions are performed to investigate the turbulence impact on wind turbines. In particular, the aeroelastic responses of the turbines are studied to characterize the fatigue loading of the turbulence present in the boundary layer and in the wake of the turbines. Two utility-scale 5 MW turbines that are separated by seven rotor diameters are placed in a 3 km by 3 km by 1 km domain. They are sub… more
Date: December 1, 2011
Creator: Lee, S.; Churchfield, M.; Moriarty, P.; Jonkman, J. & Michalakes, J.
Partner: UNT Libraries Government Documents Department
open access

Excited State Effects in Nucleon Matrix Element Calculations

Description: We perform a high-statistics precision calculation of nucleon matrix elements using an open sink method allowing us to explore a wide range of sink-source time separations. In this way the influence of excited states of nucleon matrix elements can be studied. As particular examples we present results for the nucleon axial charge g{sub A} and for the first moment of the isovector unpolarized parton distribution x{sub u-d}. In addition, we report on preliminary results using the generalized eigen… more
Date: December 1, 2011
Creator: Constantia Alexandrou, Martha Constantinou, Simon Dinter, Vincent Drach, Karl Jansen, Theodoros Leontiou, Dru B Renner
Partner: UNT Libraries Government Documents Department
open access

A Proposal for Study of Structure and Dynamics of Energy/Matter Based on Production of Gamma-Ray at SLAC Facility

Description: The success of this proposal will open new areas of Chemistry with antimatter: (1) new chemical dynamics; (2) exclusive production of parent ions by energy-tuning the positrons; (3) formation of antimatter compounds; (4) nano- and microscopic imaging of molecules, cells, and tumors (5) multi-positron systems and their thermodynamics and chemical kinetics. Also with o-Ps and p-Ps physics including speculations of dark mater (PAMELA & ATIC reported excesses in the e{sup +}e{sup -} cosmic rays).
Date: December 13, 2011
Creator: Decker, F. -J.; Krasnykh, Anatoly; Perelstein, M. & Shramenko, B.
Partner: UNT Libraries Government Documents Department
open access

Modeling of 10 GeV-1 TeV laser-plasma accelerators using Lorentz booster simulations

Description: Modeling of laser-plasma wakefield accelerators in an optimal frame of reference [J.-L. Vay, Phys. Rev. Lett. 98 130405 (2007)] allows direct and e#14;fficient full-scale modeling of deeply depleted and beam loaded laser-plasma stages of 10 GeV-1 TeV (parameters not computationally accessible otherwise). This verifies the scaling of plasma accelerators to very high energies and accurately models the laser evolution and the accelerated electron beam transverse dynamics and energy spread. Over 4,… more
Date: December 1, 2011
Creator: Vay, J. L.; Geddes, C. G. R.; Esarey, E.; Esarey, E.; Leemans, W. P.; Cormier-Michel, E. et al.
Partner: UNT Libraries Government Documents Department
open access

The Search for Exotic Mesons in gamma p -> pi+pi+pi-n with CLAS at Jefferson Lab

Description: The {pi}{sub 1}(1600), a J{sup PC} = 1{sup {-+}} exotic meson has been observed by experiments using pion beams. Theorists predict that photon beams could produce gluonic hybrid mesons, of which the {pi}{sub 1}(1600) is a candidate, at enhanced levels relative to pion beams. The g12 rungroup at Jefferson Lab's CEBAF Large Acceptance Spectrometer (CLAS) has recently acquired a large photoproduction dataset, using a liquid hydrogen target and tagged photons from a 5.71 GeV electron beam. A partia… more
Date: December 1, 2011
Creator: Bookwalter, Craig
Partner: UNT Libraries Government Documents Department
open access

Medium Effects in Parton Distributions

Description: A defining experiment of high-energy physics in the 1980s was that of the EMC collaboration where it was first observed that parton distributions in nuclei are non-trivially related to those in the proton. This result implies that the presence of the nuclear medium plays an important role and an understanding of this from QCD has been an important goal ever since Here we investigate analogous, but technically simpler, effects in QCD and examine how the lowest moment of the pion parton distribut… more
Date: December 1, 2011
Creator: William Detmold, Huey-Wen Lin
Partner: UNT Libraries Government Documents Department
open access

An improved method for extracting matrix elements from lattice three-point functions

Description: The extraction of matrix elements from baryon three-point functions is complicated by the fact that the signal-to-noise drops rapidly as a function of time. Using a previously discussed method to improve the signal-to-noise for lattice two-point functions, we use this technique to do so for lattice three-point functions, using electromagnetic form factors for the nucleon and Delta as an example.
Date: December 1, 2011
Creator: C. Aubin, K. Orginos
Partner: UNT Libraries Government Documents Department
open access

Search for signatures of extra dimensions in the diphoton mass spectrum at the Large Hadron Collider

Description: A search for signatures of extra dimensions in the diphoton invariant-mass spectrum has been performed with the CMS detector at the LHC. No excess of events above the standard model expectation is observed using a data sample collected in proton-proton collisions at {radical}s = 7 TeV corresponding to an integrated luminosity of 2.2 fb{sup -1}. In the context of the large-extra-dimensions model, lower limits are set on the effective Planck scale in the range of 2.3-3.8 TeV at the 95% confidence… more
Date: December 1, 2011
Creator: Chatrchyan, Serguei; Khachatryan, Vardan; Sirunyan, Albert M.; Tumasyan, Armen; Adam, Wolfgang; Bergauer, Thomas et al.
Partner: UNT Libraries Government Documents Department
open access

Process-dependent transverse momentum distributions from lattice QCD

Description: Certain single-spin asymmetries in semi-inclusive DIS (SIDIS) and the Drell-Yan process (DY) can be explained by transverse momentum dependent parton distribution functions (TMDs) that are predicted to differ in sign for SIDIS and DY. On the lattice, we can use non-local operators with U-shaped Wilson lines to study these TMDs, in particular the Sivers- and the Boer-Mulders function. We discuss the method, its limitations and preliminary results from an exploratory calculation using lattices ge… more
Date: December 1, 2011
Creator: Musch, Bernhard
Partner: UNT Libraries Government Documents Department
open access

Optimization for Single-Spike X-Ray FELs at LCLS with a Low Charge Beam

Description: The Linac Coherent Light Source is an x-ray free-electron laser at the SLAC National Accelerator Laboratory, which is operating at x-ray wavelengths of 20-1.2 Angstrom with peak brightness nearly ten orders of magnitude beyond conventional synchrotron radiation sources. At the low charge operation mode (20 pC), the x-ray pulse length can be <10 fs. In this paper we report our numerical optimization and simulations to produce even shorter x-ray pulses by optimizing the machine and undulator s… more
Date: December 14, 2011
Creator: Wang, L.; Ding, Y. & Huang, Z.
Partner: UNT Libraries Government Documents Department
open access

Quark Contributions to Nucleon Momentum and Spin from Domain Wall fermion calculations

Description: We report contributions to the nucleon spin and momentum from light quarks calculated using dynamical domain wall fermions with pion masses down to 300 MeV and fine lattice spacing a=0.084 fm. Albeit without disconnected diagrams, we observe that spin and orbital angular momenta of both u and d quarks are opposite, almost canceling in the case of the d quark, which agrees with previous calculations using a mixed quark action. We also present the full momentum dependence of n=2 generalized form … more
Date: December 1, 2011
Creator: S. N. Syritsyn, J. R. Green, J. W. Negele, A. V. Pochinsky, M. Engelhardt, Ph. Hagler, B. Musch, W. Schroers
Partner: UNT Libraries Government Documents Department
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