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Bound Nucleon Form Factors, Quark-Hadron Duality, and the Nuclear EMC Effect (open access)

Bound Nucleon Form Factors, Quark-Hadron Duality, and the Nuclear EMC Effect

We discuss the electromagnetic form factors, axial form factors, and structure functions of a nucleon bound in the quark-meson coupling (QMC) model. Free space nucleon form factors are calculated using the improved cloudy bag model (ICBM). After describing finite nuclei and nuclear matter in the quark-based (EMC) model, the in-medium modification of the bound nucleon form factors is calculated in the same model. Finally, the bound nucleon structure function, F2, is extracted using the calculated in-medium electromagnetic form factors and Bloom-Gilman (quark-hadron) duality.
Date: September 13, 2002
Creator: Tsushima, K.; Lu, D. H.; Melnitchouk, W.; Saito, K. & Thomas, A. W.
System: The UNT Digital Library
First prototype undulator for the LCLS project - mechanical design and prototype lessons. (open access)

First prototype undulator for the LCLS project - mechanical design and prototype lessons.

The design of a new hybrid-type undulator with a fixed gap of 6 mm, a period of 30 mm, and a length of 3.4 m is presented. The undulator line, consisting of 33 such units, is a critical part of the LCLS project, which is one step toward the design of a fourth-generation synchrotron radiation source. Magnetic tolerance of all 33 undulators, as well as the corresponding mechanical uniformity, is a major challenge. A ridged C-shape design with a titanium housing of 12 inch diameter was chosen to provide easy access to the gap area for magnetic measuring and tuning. Lessons learned while working with this prototype are critical for successful project execution. Assembly and tests results, as well as possible design changes, are presented.
Date: August 13, 2002
Creator: Trakhtenberg, E.; Tcheskidov, V.; Erdmann, M.; Vasserman, I.; Vinokurov, N.; Makarov, O. et al.
System: The UNT Digital Library
Reply to the Comment on : ''What is the Entanglement Length in a Polymer Melt?'' (open access)

Reply to the Comment on : ''What is the Entanglement Length in a Polymer Melt?''

None
Date: November 13, 2000
Creator: Putz, M.; Kremer, K. & Grest, Gary S.
System: The UNT Digital Library
TECHNOLOGY ROADMAPPING FOR IAEA SEALS. (open access)

TECHNOLOGY ROADMAPPING FOR IAEA SEALS.

In the fall of 2002, the U.S. Support Program (USSP) initiated an effort to define a strategy or ''roadmap'' for future seals technologies and to develop a generalized process for planning safeguards equipment development, which includes seals and other safeguards equipment. The underlying objectives of the USSP include becoming more proactive than reactive in addressing safeguards equipment needs, helping the IAEA to maintain an inventory of cost-effective, reliable, and effective safeguards equipment, establishing a long-term planning horizon, and securing IAEA ownership in the process of effective requirements definition and timely transitioning of new or improved systems for IAEA use. At an initial workshop, seals, their functions, performance issues, and future embodiments were discussed in the following order: adhesive seals, metal seals, passive and active loop seals, ultrasonic seals, tamper indicating enclosures (including sample containers, equipment enclosures, and conduits). Suggested improvements to these technologies focused largely on a few themes: (1) The seals must be applied quickly, easily, and correctly; (2) Seals and their associated equipment should not unduly add bulk or weight to the inspectors load; (3) Rapid, in-situ verifiability of seals is desirable; and (4) Seal systems for high risk or high value applications should have two-way, remote communications. …
Date: July 13, 2003
Creator: Hoffheins, Barbara; Annese, Cynthia; Goodman, Mark; O'Connor, Willian; Gushue, Stephen & Pepper, Susan
System: The UNT Digital Library
Real-time data reorganizer for the D0 central fiber tracker trigger system at Fermilab (open access)

Real-time data reorganizer for the D0 central fiber tracker trigger system at Fermilab

A custom digital data Mixer system has been designed to reorganize, in real time, the data produced by the Fermilab D0 Scintillating Fiber Detector. The data is used for the Level 1 and Level 2 trigger generation. The Mixer System receives the data from the front-end digitization electronics over 320 Low Voltage Differential Signaling (LVDS) links running at 371 MHz. The input data is de-serialized down to 53 MHz by the LVDS receivers, clock/frame re-synchronized and multiplexed in Field Programmable Gate Arrays (FPGAs). The data is then reserialized at 371 MHz by LVDS transmitters over 320 LVDS output links and sent to the electronics responsible for Level 1 and Level 2 trigger decisions. The Mixer System processes 311 Gigabits per second of data with an input to output delay of 200 nanoseconds.
Date: December 13, 2002
Creator: Stefano Marco Rapisarda, Jamieson T Olsen and Neal George Wilcer
System: The UNT Digital Library
Adapting SAM for CDF (open access)

Adapting SAM for CDF

The CDF and D0 experiments probe the high-energy frontier and as they do so have accumulated hundreds of Terabytes of data on the way to petabytes of data over the next two years. The experiments have made a commitment to use the developing Grid based on the SAM system to handle these data. The D0 SAM has been extended for use in CDF as common patterns of design emerged to meet the similar requirements of these experiments. The process by which the merger was achieved is explained with particular emphasis on lessons learned concerning the database design patterns plus realization of the use cases.
Date: October 13, 2003
Creator: Bonham, D.; Garzoglio, G.; Herber, R.; Kowalkowski, J.; Litvintsev, D.; Lueking, L. et al.
System: The UNT Digital Library
Summary and highlights of the 14th Topical Conference on Hadron Collider Physics (HCP2002) (open access)

Summary and highlights of the 14th Topical Conference on Hadron Collider Physics (HCP2002)

First of all, I would like to thank the scientific committee, the conference organizers, the University of Karlsruhe and the Institute for Experimental Nuclear Physics, all of the speakers, and the conference secretariat, for making this an extremely well-organized and uniformly high-quality meeting. I would also like to thank all of the speakers who provided me with material for my talk before and during the conference. There is obviously no point in these proceedings in attempting to repeat all of the material from the individual contributions; by definition, these are all available earlier in this volume. In the written version, therefore, I will try to give a high level overview of the current state of hadron collider physics and to highlight the connections between the many presentations at this conference.
Date: November 13, 2002
Creator: Womersley, John
System: The UNT Digital Library
Electrical characterization of irradiated prototype silicon pixel sensors for BTeV (open access)

Electrical characterization of irradiated prototype silicon pixel sensors for BTeV

The pixel detector in the BteV experiment at the Tevatron (Fermi Laboratory) is an important detector component for high-resolution tracking and vertex identification. For this task the hybrid pixel detector has to work in a very harsh radiation environment with up to 10{sup 14} minimum ionizing particles/cm{sup 2}/year. Radiation hardness of prototype n{sup +}/n/p{sup +} silicon pixel sensors has been investigated. We present Electrical characterization curves for irradiated prototype n{sup +}/n/p{sup +} sensors, intended for use in the BTeV experiment. We tested pixel sensors from various vendors and with two pixel isolation techniques: p-stop and p-spray. Results are based on irradiation with 200 MeV protons up to 6 x 10{sup 14} protons/cm{sup 2}.
Date: November 13, 2002
Creator: al., Maria Rita Coluccia et
System: The UNT Digital Library
Density Distributions in TATB Prepared by Various Methods (open access)

Density Distributions in TATB Prepared by Various Methods

The density distribution of two legacy types of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) particles were compared with TATB synthesized by new routes and recrystallized in several different solvents using a density gradient technique. Legacy wet (WA) and dry aminated (DA) TATB crystalline aggregates gave average densities of 1.9157 and 1.9163 g/cc, respectively. Since the theoretical maximum density (TMD) for a perfect crystal is 1.937 g/cc, legacy TATB crystals averaged 99% of TMD or about 1% voids. TATB synthesized from phloroglucinol (P) had comparable particle size to legacy TATBs, but significantly lower density, 1.8340 g/cc. TATB synthesized from 3,5 dibromoanisole (BA) was very difficult to measure because it contained extremely fine particles, but had an average density of 1.8043 g/cc over a very broad range. Density distributions of TATB recrystallized from dimethylsulfoxide (DMSO), sulfolane, and an 80/20 mixture of DMSO with the ionic liquid 1-ethyl-3-methyl- imidazolium acetate (EMImOAc), with some exceptions, gave average densities comparable or better than the legacy TATBs.
Date: May 13, 2008
Creator: Hoffman, D. M. & Fontes, A. T.
System: The UNT Digital Library
Fracture Resistant Properties of Aermet Steels (open access)

Fracture Resistant Properties of Aermet Steels

None
Date: November 13, 2000
Creator: Chhabildas, Lalit C.; Reinhart, William D.; Kipp, Marlin E.; Thornhill , Tom F. III; Reedal, D. R.; Wilson, L. T. et al.
System: The UNT Digital Library
A Fusion Reactor Design with a Liquid First Wall and Divertor (open access)

A Fusion Reactor Design with a Liquid First Wall and Divertor

Within the magnetic fusion energy program in the US, a program called APEX is investigating the use of free flowing liquid surfaces to form the inner surface of the chamber around the plasma. As part of this work, the APEX Team has investigated several possible design implementations and developed a specific engineering concept for a fusion reactor with liquid walls. Our approach has been to utilize an already established design for a future fusion reactor, the ARIES-RS, for the basic chamber geometry and magnetic configuration and to replace the chamber technology in this design with liquid wall technology for a first wall and divertor and a blanket with adequate tritium breeding. This paper gives an overview of one design with a molten salt (a mixture of lithium, beryllium and sodium fluorides) forming the liquid surfaces and a ferritic steel for the structural material of the blanket. The design point is a reactor with 3840MW of fusion power of which 767MW is in the form of energetic particles (alpha power) and 3073MW is in the form of neutrons. The alpha plus auxiliary power total 909MW of which 430MW is radiated from the core mostly onto the first wall and the balance …
Date: November 13, 2003
Creator: Nygren, R E; Rognlien, T D; Rensink, M E; Smolentsev, S S; Youssef, M E; Sawan, M Z et al.
System: The UNT Digital Library
Contamination due to memory effects in filtered vacuum arc plasma deposition systems (open access)

Contamination due to memory effects in filtered vacuum arc plasma deposition systems

Thin film synthesis by filtered vacuum arc plasma deposition is a widely used technique with a number of important emerging technological applications. A characteristic feature of the method is that during the deposition process not only is the substrate coated by the plasma, but the plasma gun itself and the magnetic field coil and/or vacuum vessel section constituting the macroparticle filter are also coated to some extent. If then the plasma gun cathode is changed to a new element, there can be a contamination of the subsequent film deposition by sputtering from various parts of the system of the previous coating species. We have experimentally explored this effect and compared our results with theoretical estimates of sputtering from the SRIM (Stopping and Range of Ions in Matter) code. We find film contamination of order 10-4 - 10-3, and the memory of the prior history of the deposition hardware can be relatively long-lasting.
Date: August 13, 2002
Creator: Martins, D. R.; Salvadori, M. C.; Verdonck, P. & Brown, I. G.
System: The UNT Digital Library
The Melting Curve and High-Pressure Chemistry of Formic Acid to 8 GPa and 600 K (open access)

The Melting Curve and High-Pressure Chemistry of Formic Acid to 8 GPa and 600 K

We have determined the melting temperature of formic acid (HCOOH) to 8.5 GPa using infrared absorption spectroscopy, Raman spectroscopy and visual observation of samples in a resistively heated diamond-anvil cell. The experimentally determined melting curve compares favorably with a two-phase thermodynamic model. Decomposition reactions were observed above the melting temperature up to a pressure of 6.5 GPa, where principal products were CO{sub 2}, H{sub 2}O and CO. At pressures above 6.5 GPa, decomposition led to solid-like reaction products. Infrared and Raman spectra of these recovered products indicate that pressure affects the nature of carbon-carbon bonding.
Date: April 13, 2005
Creator: Montgomery, W.; Zaug, J. M.; Howard, W. M.; Goncharov, A. F.; Crowhurst, J. C. & Jeanloz, R.
System: The UNT Digital Library
[Overview of the instructional unit guidelines online article] (open access)

[Overview of the instructional unit guidelines online article]

An online article that is an overview of the instructional unit guidelines for the National Arts Education Consortium.
Date: September 13, 2000
Creator: unknown
System: The UNT Digital Library
Capital night for movies and shakers (open access)

Capital night for movies and shakers

Article about the Texas Film Hall of Fame Awards dinner and other celebrations in the Houston, Texas area in March of 2006.
Date: March 13, 2006
Creator: Hodge, Shelby
System: The UNT Digital Library
[Society Section: Houston Chronicle] (open access)

[Society Section: Houston Chronicle]

Articles in the Society section of Houston Chronicle containing information about various events in the Houston, Texas area.
Date: March 13, 2006
Creator: Hodge, Shelby
System: The UNT Digital Library
The Injection Laser System on the National Ignition Facility (open access)

The Injection Laser System on the National Ignition Facility

The National Ignition Facility (NIF) is currently the largest and most energetic laser system in the world. The main amplifiers are driven by the Injection Laser System comprised of the master oscillators, optical preamplifiers, temporal pulse shaping and spatial beam formatting elements and injection diagnostics. Starting with two fiber oscillators separated by up to a few angstroms, the pulse is phase modulated to suppress SBS and enhance spatial smoothing, amplified, split into 48 individual fibers, and then temporally shaped by an arbitrary waveform generator. Residual amplitude modulation induced in the preamplifiers from the phase modulation is also precompensated in the fiber portion of the system before it is injected into the 48 pre-amplifier modules (PAMs). Each of the PAMs amplifies the light from the 1 nJ fiber injection up to the multi-joule level in two stages. Between the two stages the pre-pulse is suppressed by 60 dB and the beam is spatially formatted to a square aperture with precompensation for the nonuniform gain profile of the main laser. The input sensor package is used to align the output of each PAM to the main laser and acquire energy, power, and spatial profiles for all shots. The beam transport sections split …
Date: December 13, 2006
Creator: Bowers, Mark; Burkhart, Scott; Cohen, Simon; Erbert, Gaylen; Heebner, John; Hermann, Mark et al.
System: The UNT Digital Library
Application of a Dynamic Stress Theory to Pike Leaks (open access)

Application of a Dynamic Stress Theory to Pike Leaks

This report talks about Application of a Dynamic Stress Theory to Pike Leaks
Date: March 13, 2006
Creator: Leishear, Robert A.
System: The UNT Digital Library
Oxidative Dna Damage Background Estimated by a System Model of Base Excision Repair (open access)

Oxidative Dna Damage Background Estimated by a System Model of Base Excision Repair

Human DNA can be damaged by natural metabolism through free radical production. It has been suggested that the equilibrium between innate damage and cellular DNA repair results in an oxidative DNA damage background that potentially contributes to disease and aging. Efforts to quantitatively characterize the human oxidative DNA damage background level based on measuring 8-oxoguanine lesions as a biomarker have led to estimates varying over 3-4 orders of magnitude, depending on the method of measurement. We applied a previously developed and validated quantitative pathway model of human DNA base excision repair, integrating experimentally determined endogenous damage rates and model parameters from multiple sources. Our estimates of at most 100 8-oxoguanine lesions per cell are consistent with the low end of data from biochemical and cell biology experiments, a result robust to model limitations and parameter variation. Our results show the power of quantitative system modeling to interpret composite experimental data and make biologically and physiologically relevant predictions for complex human DNA repair pathway mechanisms and capacity.
Date: May 13, 2004
Creator: Sokhansanj, B. A. & Wilson, D. M., III
System: The UNT Digital Library
MOS-Gated Thyristors (MCTs) for Repetitive High Power Switching (open access)

MOS-Gated Thyristors (MCTs) for Repetitive High Power Switching

Certain applications for pulse power require narrow, high current pulses for their implementation. This work was performed to determine if MCTS (MOS Controlled Thyristors) could be used for these applications. The MCTS were tested as discharge switches in a low inductance circuit delivering 1 {micro}s pulses at currents between roughly 3 kA and 11 kA, single shot and repetitively at 1, 10 and 50 Hz. Although up to 9000 switching events could be obtained, all the devices failed at some combination of current and repetition rate. Failure was attributed to temperature increases caused by average power dissipated in the thyristor during the switching sequence. A simulation was performed to confirm that the temperature rise was sufficient to account for failure. Considerable heat sinking, and perhaps a better thermal package, would be required before the MCT could be considered for pulse power applications.
Date: January 13, 2000
Creator: Bayne, S. B.; Portnoy, W. M.; Rohwein, G. J. & Hefner, A. R.
System: The UNT Digital Library
The Use of Thyristors for Repetitive Narrow Pulse, High Power Switching (open access)

The Use of Thyristors for Repetitive Narrow Pulse, High Power Switching

Inverter type thyristors were switched repetitively to failure with 1 {micro}s pulses at repetition rates of 10, 50 and 100 pps and at peak currents up to 12 kA. Millions of pulses could be obtained before failure if the peak current were held at around 6 kA.
Date: January 13, 2000
Creator: Bayne, S. B.; Portnoy, W. M. & Rohwein, G. J.
System: The UNT Digital Library
Theory of Nanocluster Size Distributions from Ion Beam Synthesis (open access)

Theory of Nanocluster Size Distributions from Ion Beam Synthesis

Ion beam synthesis of nanoclusters is studied via both kinetic Monte Carlo simulations and the self-consistent mean-field solution to a set of coupled rate equations. Both approaches predict the existence of a steady state shape for the cluster size distribution that depends only on a characteristic length determined by the ratio of the effective diffusion coefficient to the ion flux. The average cluster size in the steady state regime is determined by the implanted species/matrix interface energy.
Date: June 13, 2008
Creator: Yuan, C. W.; Yi, D. O.; Sharp, I. D.; Shin, S. J.; Liao, C. Y.; Guzman, J. et al.
System: The UNT Digital Library
Effect of pressure on the luminescence emissions in CuGaSe2 (open access)

Effect of pressure on the luminescence emissions in CuGaSe2

We present the results of a pressure-dependent photoluminescence (PL) study on CuGaSe{sub 2} films grown on GaAs substrate by metalorganic vapor phase epitaxy. The low-temperature PL spectra of the CuGaSe{sub 2} samples measured at atmospheric pressure are dominated by one near band-edge exciton luminescence line and two strong and relatively broad emissions associated with donor acceptor pairs (DAP). All the observed luminescence emission lines shift toward higher energy with increasing pressure at almost the same rate. The nearly identical pressure coefficients of the two DAP emissions as compared to that of the exciton emission confirm the suggestion that the recombination processes associated with the DAPs involve one shallow donor and two different acceptor species with different binding energies and related to two different native defects.
Date: July 13, 2004
Creator: Shan, W.; Walukiewicz, W.; Wu, J.; Yu, K. M.; Ager, J. W., III; Siebentritt, S. et al.
System: The UNT Digital Library
Pressure-dependent photoluminescence study of ZnO nanowires (open access)

Pressure-dependent photoluminescence study of ZnO nanowires

The pressure dependence of the photoluminescence (PL) transition associated with the fundamental band gap of ZnO nanowires has been studied at pressures up to 15 GPa. ZnO nanowires are found to have a higher structural phase transition pressure around 12 GPa as compared to 9.0 GPa for bulk ZnO. The pressure-induced energy shift of the near band-edge luminescence emission yields a linear pressure coefficient of 29.6 meV/GPa with a small sublinear term of -0.43 meV/GPa{sup 2}. An effective hydrostatic deformation potential -3.97 eV for the direct band gap of the ZnO nanowires is derived from the result.
Date: September 13, 2004
Creator: Shan, W.; Walukiewicz, W.; Ager, J. W., III; Yu, K. M.; Zhang, Y.; Mao, S. S. et al.
System: The UNT Digital Library