Variable VHE gamma-ray emission from Markarian 501 (open access)

Variable VHE gamma-ray emission from Markarian 501

The blazar Markarian 501 (Mrk 501) was observed at energies above 100 GeV with the MAGIC telescope from May through July 2005. The high sensitivity of the instrument enabled the determination of the flux and spectrum of the source on a night-by-night basis. Throughout our observational campaign, the flux from Mrk 501 was found to vary by an order of magnitude, and to be correlated with spectral changes. Intra-night flux variability with flux-doubling times down to 2 minutes was also observed. The strength of variability increased with the energy of the {gamma}-ray photons. The energy spectra were found to harden significantly with increasing flux, and a spectral peak clearly showed up during very active states. The position of the spectral peak seems to be correlated with the source luminosity.
Date: February 6, 2007
Creator: Albert, Jordi
System: The UNT Digital Library
Measurement of CP Asymmetry in B0 to Ks pi0 pi0 Decays (open access)

Measurement of CP Asymmetry in B0 to Ks pi0 pi0 Decays

We present a measurement of the time-dependent CP asymmetry for the neutral B-meson decay into the CP = +1 final state K{sub S}{sup 0}{pi}{sup 0}{pi}{sup 0}, with K{sub S}{sup 0} {yields} {pi}{sup +}{pi}{sup -}. We use a sample of approximately 227 million B-meson pairs recorded at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II B-Factory at SLAC. From an unbinned maximum likelihood fit we extract the mixing-induced CP-violation parameter S = 0.72 {+-} 0.71 {+-} 0.08 and the direct CP-violation parameter C = 0.23 {+-} 0.52 {+-} 0.13, where the first uncertainty is statistical and the second systematic.
Date: February 6, 2007
Creator: Aubert, B.
System: The UNT Digital Library
The Fermilab data storage infrastructure (open access)

The Fermilab data storage infrastructure

Fermilab, in collaboration with the DESY laboratory in Hamburg, Germany, has created a petabyte scale data storage infrastructure to meet the requirements of experiments to store and access large data sets. The Fermilab data storage infrastructure consists of the following major storage and data transfer components: Enstore mass storage system, DCache distributed data cache, ftp and Grid ftp for primarily external data transfers. This infrastructure provides a data throughput sufficient for transferring data from experiments' data acquisition systems. It also allows access to data in the Grid framework.
Date: February 6, 2003
Creator: Bakken, Jon A.; Berman, Eileen; Huang, Chih-Hao; Moibenko, Alexander; Petravick, Donald & Zalokar, Michael
System: The UNT Digital Library
Influence of the Sb dopant distribution on far infrared photoconductivity in Ge:Sb blocked impurity band detectors (open access)

Influence of the Sb dopant distribution on far infrared photoconductivity in Ge:Sb blocked impurity band detectors

Extended long wavelength response to {approx}200 {micro}m (50 cm{sup -1}) has been observed in Ge:Sb Blocked Impurity Band (BIB) detectors with N{sub D} {approx} 1 x 10{sup 16} cm{sup -3}. The cut-off wavelength increases from 150 {micro}m (65 cm{sup -1}) to 200 {micro}m (50 cm{sup -1}) with increasing bias. The responsivity at long wavelengths was lower than expected. This can be explained by considering the observed Sb diffusion profile in a transition region between the blocking layer and active layer. BIB modeling is presented which indicates that this Sb concentration profile increases the electric field in the transition region and reduces the field in the blocking layer. The depletion region consists partially of the transition region between the active and blocking layer, which could contribute to the reduced long wavelength response. The field spike at the interface is the likely cause of breakdown at a lower bias than expected.
Date: February 6, 2002
Creator: Bandaru, Jordana; Beeman, Jeffrey W.; Haller, Eugene E.; Samperi, Stacy & Haegel, Nancy M.
System: The UNT Digital Library
Feasibility Evaluation and Retrofit Plan for Cold Crucible Induction Melter Deployment in the Defense Waste Processing Facility at Savannah River Site 8118 (open access)

Feasibility Evaluation and Retrofit Plan for Cold Crucible Induction Melter Deployment in the Defense Waste Processing Facility at Savannah River Site 8118

Cold crucible induction melters (CCIM) have been proposed as an alternative technology for waste glass melting at the Defense Waste Processing Facility (DWPF) at Savannah River Site (SRS) as well as for other waste vitrification facilities. Proponents of this technology cite high temperature operation, high tolerance for noble metals and aluminum, high waste loading, high throughput capacity, and low equipment cost as the advantages over existing Joule Heated Melter (JHM) technology. The CCIM uses induction heating to maintain molten glass at high temperature. A water-cooled helical induction coil is connected to an AC current supply, typically operating at frequencies from 100 KHz to 5 MHz. The oscillating magnetic field generated by the oscillating current flow through the coil induces eddy currents in conductive materials within the coil. Those oscillating eddy currents, in turn, generate heat in the material. In the CCIM, the induction coil surrounds a 'Cold Crucible' which is formed by metal tubes, typically copper or stainless steel. The tubes are constructed such that the magnetic field does not couple with the crucible. Therefore, the field generated by the induction coil couples primarily with the conductive medium (hot glass) within. The crucible tubes are water cooled to maintain their …
Date: February 6, 2008
Creator: Barnes, Allan B.; Iverson, Daniel C.; Adkins, Brannen J. & Tchemitcheff, Eric
System: The UNT Digital Library
Crystal level simulations using Eulerian finite element methods (open access)

Crystal level simulations using Eulerian finite element methods

Over the last several years, significant progress has been made in the use of crystal level material models in simulations of forming operations. However, in Lagrangian finite element approaches simulation capabilities are limited in many cases by mesh distortion associated with deformation heterogeneity. Contexts in which such large distortions arise include: bulk deformation to strains approaching or exceeding unity, especially in highly anisotropic or multiphase materials; shear band formation and intersection of shear bands; and indentation with sharp indenters. Investigators have in the past used Eulerian finite element methods with material response determined from crystal aggregates to study steady state forming processes. However, Eulerian and Arbitrary Lagrangian-Eulerian (ALE) finite element methods have not been widely utilized for simulation of transient deformation processes at the crystal level. The advection schemes used in Eulerian and ALE codes control mesh distortion and allow for simulation of much larger total deformations. We will discuss material state representation issues related to advection and will present results from ALE simulations.
Date: February 6, 2004
Creator: Becker, R; Barton, N R & Benson, D J
System: The UNT Digital Library
Simulations of shock-induced mixing& combustion of an acetylene cloud in a chamber (open access)

Simulations of shock-induced mixing& combustion of an acetylene cloud in a chamber

In this paper we present numerical simulations of the interaction of a blast wave with an acetylene bubble in a closed chamber. We model the system using the inviscid Euler equations for a mixture of ideal gases. The formulation specifies the thermodynamic behavior of the system using a Chemkin interface and includes the capability to model combustion as the ambient air mixes with the acetylene. The simulations are performed using a three-dimensional adaptive mesh refinement algorithm based on a second-order Godunov integration scheme. Simulations are compared with experimental measurements for the same configuration.
Date: February 6, 2001
Creator: Bell, J B; Day, M S; Beckner, V E; Kuhl, A L; Neuwald, P & Reichenbach, H
System: The UNT Digital Library
Seismic Waves in Rocks with Fluids and Fractures (open access)

Seismic Waves in Rocks with Fluids and Fractures

Seismic wave propagation through the earth is often strongly affected by the presence of fractures. When these fractures are filled with fluids (oil, gas, water, CO{sub 2}, etc.), the type and state of the fluid (liquid or gas) can make a large difference in the response of the seismic waves. This paper will summarize some early work of the author on methods of deconstructing the effects of fractures, and any fluids within these fractures, on seismic wave propagation as observed in reflection seismic data. Methods to be explored here include Thomsen's anisotropy parameters for wave moveout (since fractures often induce elastic anisotropy), and some very convenient fracture parameters introduced by Sayers and Kachanov that permit a relatively simple deconstruction of the elastic behavior in terms of fracture parameters (whenever this is appropriate).
Date: February 6, 2006
Creator: Berger, E. L.
System: The UNT Digital Library
Flat space physics from holography (open access)

Flat space physics from holography

We point out that aspects of quantum mechanics can be derived from the holographic principle, using only a perturbative limit of classical general relativity. In flat space, the covariant entropy bound reduces to the Bekenstein bound. The latter does not contain Newton's constant and cannot operate via gravitational backreaction. Instead, it is protected by--and in this sense, predicts--the Heisenberg uncertainty principle.
Date: February 6, 2004
Creator: Bousso, Raphael
System: The UNT Digital Library
Xenon N4,500 Auger spectrum - a useful calibration source (open access)

Xenon N4,500 Auger spectrum - a useful calibration source

In the xenon N4,5OO Auger spectrum there are 19 prominent lines ranging from 8 to 36 eV that provide a convenient set of standards for calibrating electron spectrometers. Combining optical data with recent measurements of this spectrum gives energies for these lines that are absolutely accurate to 11 meV. For most lines the relative accuracy is better than 1 meV; for a few it is about 3 meV. The spin-orbit splitting of the xenon 4d lines is measured to be 1979.0 +- 0.5meV.
Date: February 6, 2002
Creator: Carroll, T.X.; Bozek, J.D.; Kukk, E.; Myrseth, V.; Saethre, L.J.; Thomas, T.D. et al.
System: The UNT Digital Library
2009 Plant Lipids: Structure, Metabolism & Function Gordon Research Conference - February 1- 6 ,2009 (open access)

2009 Plant Lipids: Structure, Metabolism & Function Gordon Research Conference - February 1- 6 ,2009

The Gordon Research Conference on 'Plant Lipids: Structure, Metabolism and Function' has been instituted to accelerate research productivity in the field of plant lipids. This conference will facilitate wide dissemination of research breakthroughs, support recruitment of young scientists to the field of plant lipid metabolism and encourage broad participation of the plant lipid community in guiding future directions for research in plant lipids. This conference will build upon the strengths of the successful, previous biannual meetings of the National Plant Lipid Cooperative (www.plantlipids.org) that began in 1993, but will reflect a broader scope of topics to include the biochemistry, cell biology, metabolic regulation, and signaling functions of plant acyl lipids. Most importantly, this conference also will serve as a physical focal point for the interaction of the plant lipid research community. Applications to attend this conference will be open to all researchers interested in plant lipids and will provide a venue for the presentation of the latest research results, networking opportunities for young scientists, and a forum for the development and exchange of useful lipid resources and new ideas. By bringing together senior- and junior-level scientists involved in plant lipid metabolism, a broad range of insights will be shared and …
Date: February 6, 2009
Creator: Chapman, Kent D.
System: The UNT Digital Library
Spallation neutron source and other high intensity froton sources (open access)

Spallation neutron source and other high intensity froton sources

This lecture is an introduction to the design of a spallation neutron source and other high intensity proton sources. It discusses two different approaches: linac-based and synchrotron-based. The requirements and design concepts of each approach are presented. The advantages and disadvantages are compared. A brief review of existing machines and those under construction and proposed is also given. An R&D program is included in an appendix.
Date: February 6, 2003
Creator: Chou, Weiren
System: The UNT Digital Library
Fabrication and Test Results of a Nb3Sn Superconducting Racetrack Dipole Magnet (open access)

Fabrication and Test Results of a Nb3Sn Superconducting Racetrack Dipole Magnet

A 'proof-of-principle' Nb{sub 3}Sn superconducting dual-bore dipole magnet was built from racetrack coils, as a first step in a program to develop an economical, 15 Tesla, accelerator-quality magnet. The mechanical design and magnet fabrication procedures are discussed. No training was required to achieve temperature-dependent plateau currents, despite several thermal cycles that involved partial magnet disassembly and substantial pre-load variations. Subsequent magnets are expected to approach 15 Tesla with substantially improved conductor.
Date: February 6, 2000
Creator: Chow, K.; Dietderich, D. R.; Gourlay, S. A.; Gupta, R.; Harnden, W.; Lietzke, A. F. et al.
System: The UNT Digital Library
ISS-flation (open access)

ISS-flation

Inflation may occur while rolling into the metastable supersymmetry-breaking vacuum of massive supersymmetric QCD. We explore the range of parameters in which slow-roll inflation and long-lived metastable supersymmetry breaking may be simultaneously realized. The end of slow-roll inflation in this context coincides with the spontaneous breaking of a global symmetry, which may give rise to significant curvature perturbations via inhomogeneous preheating. Such spontaneous symmetry breaking at the end of inflation may give rise to observable non-gaussianities, distinguishing this scenario from more conventional models of supersymmetric hybrid inflation.
Date: February 6, 2008
Creator: Craig, Nathaniel J. & /SLAC /Stanford U., ITP
System: The UNT Digital Library
MSW Effects in Vacuum Oscillations (open access)

MSW Effects in Vacuum Oscillations

We point out that for solar neutrino oscillations with the mass-squared difference of Delta m^2 ~;; 10^-10 - 10^-9 eV^2, traditionally known as"vacuum oscillation'' range, the solar matter effects are non-negligible, particularly for the low energy pp neutrinos. One consequence of this is that the values of the mixing angle theta and pi/2-theta are not equivalent, leading to the need to consider the entire physical range of the mixing angle 0<=theta<=pi/2 when determining the allowed values of the neutrino oscillation parameters.
Date: February 6, 2000
Creator: Friedland, Alexander
System: The UNT Digital Library
Effects of Boundary Conditions and Flow on the Kink Instability in a Cylindrical Plasma Column (open access)

Effects of Boundary Conditions and Flow on the Kink Instability in a Cylindrical Plasma Column

An experimental investigation of the kink instability is presented in a linear plasma column where one end is line-tied to the plasma source, and the other end is not line-tied and therefore free to slide over the surface of the end-plate. This latter boundary condition is a result of plasma sheath resistance that insulates, at least partially, the plasma from the end-plate. The helical m = 1 kink mode is observed to grow when the plasma current exceeds a threshold and, close to the criticality, is characterized by an axial mode structure with maximum displacement at the free axial boundary. Azimuthal rotation of the mode is observed such that the helically kinked column always screws into the free axial boundary. The kink mode structure, rotation frequency and instability threshold are accurately reproduced by a recent kink theory [D. D. Ryutov, et al., Phys. Plasmas 13, 032105 (2006)], which includes axial plasma flow and one end of the plasma column that is free to move due to a perfect non-line-tying boundary condition which is experimentally verified. A brief review of the kink theory and its predictions for the boundary conditions relevant in the present experiments are presented.
Date: February 6, 2007
Creator: Furno, I.; Intrator, T. P.; Lapenta, G.; Dorf, L. & Ryutov, D. D.
System: The UNT Digital Library
Phase transitions in neutron stars (open access)

Phase transitions in neutron stars

None
Date: February 6, 2004
Creator: Glendenning, Norman K.
System: The UNT Digital Library
Coral Radiocarbon Records of Indian Ocean Water Mass Mixing and Wind-Induced Upwelling Along the Coast of Sumatra, Indonesia (open access)

Coral Radiocarbon Records of Indian Ocean Water Mass Mixing and Wind-Induced Upwelling Along the Coast of Sumatra, Indonesia

Radiocarbon ({sup 14}C) in the skeletal aragonite of annually banded corals track radiocarbon concentrations in dissolved inorganic carbon (DIC) in surface seawater. As a result of nuclear weapons testing in the 1950s, oceanic uptake of excess {sup 14}C in the atmosphere has increased the contrast between surface and deep ocean {sup 14}C concentrations. We present accelerator mass spectrometric (AMS) measurements of radiocarbon isotope ({Delta}{sup 14}C) in Porites corals from the Mentawai Islands, Sumatra (0 S, 98 E) and Watamu, Kenya (3 S, 39 E) to document the temporal and spatial evolution of the {sup 14}C gradient in the tropical Indian Ocean. The rise in {Delta}{sup 14}C in the Sumatra coral, in response to the maximum in nuclear weapons testing, is delayed by 2-3 years relative to the rise in coral {Delta}{sup 14}C from the coast of Kenya. Kenya coral {Delta}{sup 14}C values rise quickly because surface waters are in prolonged contact with the atmosphere. In contrast, wind-induced upwelling and rapid mixing along the coast of Sumatra entrains {sup 14}C-depleted water from the subsurface, which dilutes the effect of the uptake of bomb-laden {sup 14}C by the surface-ocean. Bimonthly AMS {Delta}{sup 14}C measurements on the Mentawai coral reveal mainly interannual variability …
Date: February 6, 2004
Creator: Guilderson, T. P.; Grumet, N. S.; Abram, N. J.; Beck, J. W.; Dunbar, R. B.; Gagan, M. K. et al.
System: The UNT Digital Library
Speech Articulator and User Gesture Measurements Using Micropower, Interferometric EM-Sensors (open access)

Speech Articulator and User Gesture Measurements Using Micropower, Interferometric EM-Sensors

Very low power, GHz frequency, ''radar-like'' sensors can measure a variety of motions produced by a human user of machine interface devices. These data can be obtained ''at a distance'' and can measure ''hidden'' structures. Measurements range from acoustic induced, 10-micron amplitude vibrations of vocal tract tissues, to few centimeter human speech articulator motions, to meter-class motions of the head, hands, or entire body. These EM sensors measure ''fringe motions'' as reflected EM waves are mixed with a local (homodyne) reference wave. These data, when processed using models of the system being measured, provide real time states of interface positions or other targets vs. time. An example is speech articulator positions vs. time in the user's body. This information appears to be useful for a surprisingly wide range of applications ranging from speech coding synthesis and recognition, speaker or object identification, noise cancellation, hand or head motions for cursor direction, and other applications.
Date: February 6, 2001
Creator: Holzrichter, J F & Ng, L C
System: The UNT Digital Library
Chemical and electronic characterization of cobalt in Lanthanumperovskites. Effects of Strontium substitution (open access)

Chemical and electronic characterization of cobalt in Lanthanumperovskites. Effects of Strontium substitution

Two different cobaltites, LaCoO{sub 3} and La{sub 0.5}Sr{sub 0.5}CoO{sub 3-{delta}}, have been prepared and characterized by means of high energy Co K-edge and low energy O K-edge X-ray absorption spectroscopy (XAS). The partial substitution of La(III) by Sr(II) species induces important changes in the reactivity and electronic state of the perovskite, while little or no changes can be detected in the formal oxidation state of cobalt atoms. The presence of strontium cations induces two main effects in the chemical and electronic behavior of the perovskite. The charge balance with Sr(II) species is reached by the formation of oxygen vacancies throughout the network, which increases the reactivity of the perovskite, now more reducible than the original LaCoO{sub 3} perovskite. O K-edge XAS experiments indicate that the Sr(II) species cause d electrons of cobalt cations to change from low to high spin configuration. Our data allow us to propose that this change in spin multiplicity is induced by the bigger size of Sr(II) cations, which aligns the Co-O-Co atoms, and favors the overlapping of {pi}-symmetry cobalt and oxygen orbitals, reducing the splitting energy of e{sub g} and t{sub 2g} levels.
Date: February 6, 2009
Creator: Hueso, Jose L.; Holgado, Juan P.; Pereniguez, Rosa; Mun, Simon; Salmeron, Miquel & Caballero, Alfonso
System: The UNT Digital Library
W charge asymmetry measurement in CDF Run2 (open access)

W charge asymmetry measurement in CDF Run2

We present the status of the forward-backward charge asymmetry measurement for W boson production using early Run 2 data collected with the Collider Detector at Fermilab (CDF). Tracking for forward electrons is a critical component of this measurement, and we describe a new technique which combines the position and energy measurements from the calorimeter with position measurements in the silicon detector to provide tracking and charge determination for electron candidates. The performance of this algorithm is described and the sensitivity for the W charge asymmetry measurement with Run 2 data is quantified.
Date: February 6, 2003
Creator: Issever, C.
System: The UNT Digital Library
Field Quality And Magnetic Center Stability Achieved in a Variable Permanent Magnet Quadrupole for the ILC (open access)

Field Quality And Magnetic Center Stability Achieved in a Variable Permanent Magnet Quadrupole for the ILC

A superstrong permanent magnet quadrupole (PMQ) is one of the candidates for the final focus lens for the International Linear Collider (ILC). Our prototype PMQ can produce variable strengths from 3.5T to 24.2T in 1.4T steps. The magnetic center of the PMQ must not move more than a few microns during a 20% strength change to enable a Beam-Based Alignment (BBA) process to work. Our PMQ can be mechanically adjusted to suppress the center movement from more than 30{micro}m to less than 10{micro}m during strength changes.
Date: February 6, 2006
Creator: Iwashita, Y.; Mihara, T.; Kumada, M. & Spencer, C.
System: The UNT Digital Library
High Electron Mobility InN (open access)

High Electron Mobility InN

None
Date: February 6, 2007
Creator: Jones, R. E.; Li, S. X.; Haller, E. E.; van Genuchten, H. C. M.; Yu, K. M.; Ager, J. W., III et al.
System: The UNT Digital Library
A C++ Framework for Conducting High-Speed, Long-Term Particle Tracking Simulations (open access)

A C++ Framework for Conducting High-Speed, Long-Term Particle Tracking Simulations

For the purpose of conducting parallel, long-term tracking studies of storage rings such as the ones described in [3], [4], maximum execution speed is essential. We describe an approach involving metaprogramming techniques in C++ which results in execution speeds rivaling hand-optimized assembler code for a particular tracking lattice while retaining the generality and flexibility of an all-purpose tracking code.
Date: February 6, 2006
Creator: Kabel, A. C.
System: The UNT Digital Library