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STRANGENESS PRODUCTION AS A FUNCTION OF SYSTEM SIZE AND ENERGY OF RHIC. (open access)

STRANGENESS PRODUCTION AS A FUNCTION OF SYSTEM SIZE AND ENERGY OF RHIC.

In this paper we report on strangeness measurements in p+p, Au+Au and Cu+Cu collisions at different energies in the STAR detector at RHIC. We will focus on two momentum regions in particular: Firstly we look at strangeness enhancement in A+A collisions with respect to p+p. These yields are dominated by low transverse momentum. We compare the enhancements from Au+Au and Cu+Cu data at {radical}s{sub NN} = 200 GeV with Pb+Pb data at {radical}s{sub NN} = 17.2 GeV and find that the enhancement does not scale with N{sub part} as expected, but rather scales with N{sub part}{sup 1/3}, where N{sub part} represents the number of participants; We then examine {Lambda}/K{sub S}{sup 0} ratios at intermediate transverse momentum in both Au+Au and Cu+Cu data where we find a greater enhancement in Cu+Cu compared to Au+Au data when we compare integrated ratios between 1.5 < p{sub T} < 3.5 GeV/c.
Date: July 19, 2007
Creator: LAMONT,M.
System: The UNT Digital Library
New cubic phase of lithium nitride to 200 GPa (open access)

New cubic phase of lithium nitride to 200 GPa

We present a new cubic ({gamma}) Li{sub 3}N phase discovered above 40({+-}5) GPa. Structure and electronic bands are examined at high pressure with synchrotron x-ray diffraction and inelastic x-ray scattering in a diamond anvil cell, and also with first-principles calculations. We observe a dramatic band-gap widening and volume collapse at the phase transition. {gamma}-Li{sub 3}N remains extremely stable and ionic to 200 GPa, with predicted metallization near 8 TPa. The high structural stability, wide band-gap and simple electronic structure of {gamma}-Li{sub 3}N are analogous to that of such lower valence closed-shell solids as NaCl, MgO and Ne, meriting its use as a low-Z internal pressure standard.
Date: July 19, 2005
Creator: Lazicki, A.; Maddox, B.; Evans, W.; Yoo, C. S.; McMahan, A. K.; Pickett, W. E. et al.
System: The UNT Digital Library
Epigenetic reversion of breast carcinoma phenotype is accompanied by DNA sequestration (open access)

Epigenetic reversion of breast carcinoma phenotype is accompanied by DNA sequestration

The importance of microenvironment and context in regulation of tissue-specific genes is finally well established. DNA exposure to, or sequestration from, nucleases can be used to detect differences in higher order chromatin structure in intact cells without disturbing cellular or tissue architecture. To investigate the relationship between chromatin organization and tumor phenotype, we utilized an established 3-D assay where normal and malignant human breast cells can be easily distinguished by the morphology of the structures they make (acinus-like vs tumor-like, respectively). We show that these phenotypes can be distinguished also by sensitivity to AluI digestion where the malignant cells are resistant to digestion relative to non-malignant cells. Reversion of the T4-2 breast cancer cells by either cAMP analogs, or a phospatidylinositol 3-kinase (P13K) inhibitor not only reverted the phenotype, but also the chromatin sensitivity to AluI. By using different cAMP-analogs, we show that the cAMP-induced phenotypic reversion, polarization, and shift in DNA organization act through a cAMP-dependent-protein-kinase A-coupled signaling pathway. Importantly, inhibitory antibody to fibronectin also reverted the malignant phenotype, polarized the acini, and changed chromatin sequestration. These experiments show not only that modifying the tumor microenvironment can alter the organization of tumor cells but also that architecture of the …
Date: July 19, 2006
Creator: Sandal, Tone; Valyi-Nagy, Klara; Spencer, Virginia A.; Folberg,Robert; Bissell, Mina J. & Maniotis, Andrew J.
System: The UNT Digital Library
History and Evolution of Control Banding: A Review (open access)

History and Evolution of Control Banding: A Review

Control Banding (CB) strategies offer simplified solutions for controlling worker exposures to constituents often encountered in the workplace. The original CB model was developed within the pharmaceutical industry; however, the modern movement involves models developed for non-experts to input hazard and exposure potential information for bulk chemical processes, receiving control advice as a result. The CB approach utilizes these models for the dissemination of qualitative and semi-quantitative risk assessment tools being developed to complement the traditional industrial hygiene model of air sampling and analysis. It is being applied and tested in small and medium size enterprises (SMEs) within developed countries and industrially developing countries; however, large enterprises (LEs) have also incorporated these strategies within chemical safety programs. Existing research of the components of the most available CB model, the Control of Substances Hazardous to Health (COSHH) Essentials, has shown that exposure bands do not always provide adequate margins of safety, that there is a high rate of under-control errors, that it works better with dusts than with vapors, that there is an inherent inaccuracy in estimating variability, and that when taken together the outcomes of this model may lead to potentially inappropriate workplace confidence in chemical exposure reduction in some …
Date: July 19, 2006
Creator: Zalk, D. & Nelson, D.
System: The UNT Digital Library
Performance and scaling of locally-structured grid methods forpartial differential equations (open access)

Performance and scaling of locally-structured grid methods forpartial differential equations

In this paper, we discuss some of the issues in obtaining high performance for block-structured adaptive mesh refinement software for partial differential equations. We show examples in which AMR scales to thousands of processors. We also discuss a number of metrics for performance and scalability that can provide a basis for understanding the advantages and disadvantages of this approach.
Date: July 19, 2007
Creator: Colella, Phillip; Bell, John; Keen, Noel; Ligocki, Terry; Lijewski, Michael & Van Straalen, Brian
System: The UNT Digital Library
Seismic design and development for fast reactors: a design-application perspective with directions for improvement (open access)

Seismic design and development for fast reactors: a design-application perspective with directions for improvement

Applications of seismic design criteria and qualification methods to the US breeder reactor projects have developed new findings, improvements in design methods, and identified areas for further development. Discussions are presented regarding site free field motion, soil-structure interaction, equipment response spectra, piping, snubbers and support design analyses, dynamic decoupling, seismic qualification testing, and protection of Seismic Category I components from Non-Category I equipment failures.
Date: July 19, 1979
Creator: Severud, L. K.
System: The UNT Digital Library
Microwave kinoform for magnetic fusion (open access)

Microwave kinoform for magnetic fusion

A microwave kinoform that modifies both the phase and polarization of an incident wavefront has been designed. This kinoform for the TMX-U magnetic fusion experiment has been fabricated and tested. The design procedure, method of fabrication, and experimental test results are discussed.
Date: July 19, 1983
Creator: Gallagher, N.C. Jr. & Sweeney, D.W.
System: The UNT Digital Library
Core-level spectroscopy of thin oxides and oxynitrides (open access)

Core-level spectroscopy of thin oxides and oxynitrides

Several spectroscopic methods are discussed that use core levels, such as photoelectron spectroscopy and absorption spectroscopy with photoelectron or fluorescence detection. Measurements are presented on the desorption of a chemical oxide and the growth of oxynitrides with N{sub 2}0 on Si(100). The stoichiometry is found to change strongly with thickness, from a nitrogen-terminated Si surface to a nearly-pure oxide in the outer region of 40--60 {Angstrom} films. Using a third generation synchrotron beam line a sensitivity of better than a tenth of a monolayer is achieved by a simple photocurrent measurement.
Date: July 19, 1994
Creator: Himpsel, F. J.; Akatsu, H. & Carlisle, J. A.
System: The UNT Digital Library
Long Period Variables in the LMC: Results from MACHO and 2Mass (open access)

Long Period Variables in the LMC: Results from MACHO and 2Mass

We use the eight year light curve database from the MACHO (MAssive Compact Halo Objects) project together with infrared colors and magnitudes from 2MASS (the Two Micron All Sky Survey) to identify a sample of 22,000 long period variables in the Large Magellanic Cloud (referred to hereafter as LMC LPVs). A period luminosity diagram of these stars reveals six well defined sequences, in substantial agreement with previous analyses of samples from OGLE (Optical Gravitational Lensing Experiment). In our analysis we identify analogues to galactic LPVs in the LMC LPV sample. We find that carbon dominated AGB stars populate only two of the sequences, one of which includes the Mira variables. The high luminosity end of the same two sequences are also the location of the only stars with J K{sub s} > 2, indicating that they are enshrouded in dust. The unknown mechanism that produces the variability of the last sequence--those stars with long secondary periods--produces different morphology in the period luminosity diagram than what is seen in the first four sequences, which are thought to be caused by pulsation. In particular, the last sequence extends to lower luminosity RGB stars and the luminosity function does not peak among the …
Date: July 19, 2004
Creator: Fraser, O J; Cook, K H; Keller, S C & Hawley, S L
System: The UNT Digital Library
Fiber Lasers X: Technology, Systems and Aplications (open access)

Fiber Lasers X: Technology, Systems and Aplications

None
Date: July 19, 2012
Creator: Drachenberg, D
System: The UNT Digital Library
Soft ionization of thermally evaporated hypergolic ionic liquid aerosols (open access)

Soft ionization of thermally evaporated hypergolic ionic liquid aerosols

Isolated ion pairs of a conventional ionic liquid, 1-Ethyl-3-Methyl-Imidazolium Bis(trifluoromethylsulfonyl)imide ([Emim+][Tf2N?]), and a reactive hypergolic ionic liquid, 1-Butyl-3-Methyl-Imidazolium Dicyanamide ([Bmim+][Dca?]), are generated by vaporizing ionic liquid submicron aerosol particles for the first time; the vaporized species are investigated by dissociative ionization with tunable vacuum ultraviolet (VUV) light, exhibiting clear intact cations, Emim+ and Bmim+, presumably originating from intact ion pairs. Mass spectra of ion pair vapor from an effusive source of the hypergolic ionic liquid show substantial reactive decomposition due to the internal energy of the molecules emanating from the source. Photoionization efficiency curves in the near threshold ionization region of isolated ion pairs of [Emim+][Tf2N?]ionic liquid vapor are compared for an aerosol source and an effusive source, revealing changes in the appearance energy due to the amount of internal energy in the ion pairs. The aerosol source has a shift to higher threshold energy (~;;0.3 eV), attributed to reduced internal energy of the isolated ion pairs. The method of ionic liquid submicron aerosol particle vaporization, for reactive ionic liquids such as hypergolic species, is a convenient, thermally ?cooler? source of isolated intact ion pairs in the gas phase compared to effusive sources.
Date: July 19, 2011
Creator: Koh, Christine J.; Liu, Chen-Lin; Harmon, Christopher W.; Strasser, Daniel; Golan, Amir; Kostko, Oleg et al.
System: The UNT Digital Library
SYNTHESIS AND CHARACTERIZATION OF SMART FUNCTIONAL COATINGS BY CHEMICAL SOLUTION DEPOSITION METHODS (open access)

SYNTHESIS AND CHARACTERIZATION OF SMART FUNCTIONAL COATINGS BY CHEMICAL SOLUTION DEPOSITION METHODS

New coating technology enables the fabrication of low cost structural health monitoring (SHM) and tamper indication devices that can be employed to strengthen national and international safeguards objectives. In particular, such innovations could serve the safeguards community by improving both the timeliness of detection and confidence in verification and monitoring. This work investigates the synthesis of functional surface coatings using chemical solutions deposition methods. Chemical solution deposition has recently received attention in the materials research community due to its unique advantages such as low temperature processing, high homogeneity of final products and the ability to fabricate materials with controlled surface properties and pore structures. The synthesis of functional coatings aimed at modifying the materials conductivity and optical properties was investigated by the incorporation of transition element (e.g. Cr{sup +3}) and rare earth (e.g. Er{sup +3}) serving as dopants in a polymer or gel matrix. The structural and morphological investigation of the as-deposited films was carried out using UV/Vis and photoluminescence (PL) spectroscopy. The as deposited coating was further investigated by scanning electron microscopy and energy dispersive x-ray microscopy.
Date: July 19, 2011
Creator: Mendez-Torres, A.
System: The UNT Digital Library
Colliding Laser Pulses for Laser-Plasma Accelerator Injection Control (open access)

Colliding Laser Pulses for Laser-Plasma Accelerator Injection Control

Decoupling injection from acceleration is a key challenge to achieve compact, reliable, tunable laser-plasma accelerators (LPA). In colliding pulse injection the beat between multiple laser pulses can be used to control energy, energy spread, and emittance of the electron beam by injecting electrons in momentum and phase into the accelerating phase of the wake trailing the driver laser pulse. At LBNL, using automated control of spatiotemporal overlap of laser pulses, two-pulse experiments showed stable operation and reproducibility over hours of operation. Arrival time of the colliding beam was scanned, and the measured timing window and density of optimal operation agree with simulations. The accelerator length was mapped by scanning the collision point.
Date: July 19, 2011
Creator: Plateau, Guillaume; Geddes, Cameron; Matlis, Nicholas; Cormier-Michel, Estelle; Mittelberger, Daniel; Nakamura, Kei et al.
System: The UNT Digital Library
Complete Calculation of Evaluated Maxwellian-Averaged Cross Sections and Their Uncertainties for S-Process Nucleosynthesis (open access)

Complete Calculation of Evaluated Maxwellian-Averaged Cross Sections and Their Uncertainties for S-Process Nucleosynthesis

Present contribution represents a significant improvement of our previous calculation of Maxwellian-averaged cross sections and astrophysical reaction rates. Addition of newly-evaluated neutron reaction libraries, such as ROSFOND and Low-Fidelity Covariance Project, and improvements in data processing techniques allowed us to extend it for entire range of sprocess nuclei, calculate Maxwellian-averaged cross section uncertainties for the first time, and provide additional insights on all currently available neutron-induced reaction data. Nuclear reaction calculations using ENDF libraries and current Java technologies will be discussed and new results will be presented.
Date: July 19, 2010
Creator: Pritychenko, B.
System: The UNT Digital Library
Suppressing Thermal Energy Drift In The LLNL Flash X-Ray Accelerator Using Linear Disk Resistor Stacks (open access)

Suppressing Thermal Energy Drift In The LLNL Flash X-Ray Accelerator Using Linear Disk Resistor Stacks

This paper addresses thermal drift in sodium thiosulfate liquid resistors and their replacement with linear disk resistors from HVR Advanced Power Components. Sodium thiosulfate resistors in the FXR induction linear accelerator application have a temperature coefficient of {approx}1.8%/C. The FXR Marx banks send an 8kJ pulse through eight 524 cm{sup 3} liquid resistors at a repetition rate of up to 1 every 45 seconds. Every pulse increases the temperature of the solution by {approx}0.4 C which produces a 0.7% change in resistance. The typical cooling rate is {approx}0.4 C per minute which results in {approx}0.1% energy drop per pulse during continuous pulsed operations. A radiographic accelerator is extraordinarily sensitive to energy variations. Changes in beam energy produce movement in beam transport, changes in spot size, and large dose variations. If self-heating were the only problem, we could predict the increase in input voltage required to compensate for the energy loss. However, there are other variables that influence the temperature of the resistors such as focus magnet heating, changes in room temperature, changes in cooling water, where the cell is located, etc. Additionally not all of the resistors have equivalent cooling rates and as many as 32 resistors are driven from …
Date: July 19, 2011
Creator: Kreitzer, B R; Houck, T L & Luchterhand, O C
System: The UNT Digital Library
X-ray Emission from Electron Betatron Motion in a Laser-Plasma Accelerator (open access)

X-ray Emission from Electron Betatron Motion in a Laser-Plasma Accelerator

Single-shot x-ray spectra from electron bunches produced by a laser-plasma wakefield accelerator (LPA) were measured using a photon-counting single-shot pixelated Silicon-based detector [3], providing for the first time direct spectra without assumptions required by filter based techniques. In addition, the electron bunch source size was measured by imaging a wire target, demonstrating few micron source size and stability. X-rays are generated when trapped electrons oscillate in the focusing field of the wake trailing the driver laser pulse. In addition to improving understanding of bunch emittance and wake structure, this provides a broadband, synchronized femtosecond source of keV x-rays. Electron bunch spectra and divergence were measured simultaneously and preliminary analysis shows correlation between x-ray andelectron spectra. Bremsstrahlung background was managed using shielding and magnetic diversion.
Date: July 19, 2011
Creator: Plateau, Guillaume; Geddes, Cameron; Thorn, Daniel; Matlis, Nicholas; Mittelberger, Daniel; Stoehlker, T et al.
System: The UNT Digital Library
MODELING GAS TRANSPORT AND REACTIONS IN POLYDIMETHYSILOXANE (open access)

MODELING GAS TRANSPORT AND REACTIONS IN POLYDIMETHYSILOXANE

None
Date: July 19, 2012
Creator: Lu, C; Sun, Y; Harley, S J & Glascoe, E A
System: The UNT Digital Library
A Radiating Shock Evaluated Using Implicit Monte Carlo Diffusion (open access)

A Radiating Shock Evaluated Using Implicit Monte Carlo Diffusion

None
Date: July 19, 2012
Creator: Cleveland, M. & Gentile, N. A.
System: The UNT Digital Library
Steam Oxidation at High Pressure (open access)

Steam Oxidation at High Pressure

A first high pressure test was completed: 293 hr at 267 bar and 670{degrees}C; A parallel 1 bar test was done for comparison; Mass gains were higher for all alloys at 267 bar than at 1 bar; Longer term exposures, over a range of temperatures and pressures, are planned to provide information as to the commercial implications of pressure effects; The planned tests are at a higher combination of temperatures and pressures than in the existing literature. A comparison was made with longer-term literature data: The short term exposures are largely consistent with the longer-term corrosion literature; Ferritic steels--no consistent pressure effect; Austenitic steels--fine grain alloys less able to maintain protective chromia scale as pressure increases; Ni-base alloys--more mass gains above 105 bar than below. Not based on many data points.
Date: July 19, 2013
Creator: Holcomb, Gordon R. & Carney, Casey
System: The UNT Digital Library
2011 Status of the Automatic Alignment System for the National Ignition Facility (open access)

2011 Status of the Automatic Alignment System for the National Ignition Facility

Automated alignment for the National Ignition Facility (NIF) is accomplished using a large-scale parallel control system that directs 192 laser beams along the 300-m optical path. The beams are then focused down to a 50-micron spot in the middle of the target chamber. The entire process is completed in less than 50 minutes. The alignment system commands 9,000 stepping motors for highly accurate adjustment of mirrors and other optics. 41 control loops per beamline perform parallel processing services running on a LINUX cluster to analyze high-resolution images of the beams and their references. This paper describes the status the NIF automatic alignment system and the challenges encountered as NIF development has transitioned from building the laser, to becoming a research project supporting a 24 hour, 7 day laser facility. NIF is now a continuously operated system where performance monitoring is increasingly more critical for operation, maintenance, and commissioning tasks. Equipment wear and the effects of high energy neutrons from fusion experiments are issues which alter alignment efficiency and accuracy. New sensors needing automatic alignment assistance are common. System modifications to improve efficiency and accuracy are prevalent. Handling these evolving alignment and maintenance needs while minimizing the impact on NIF experiment …
Date: July 19, 2011
Creator: Wilhelmsen, K.; Awwal, A.; Burkhart, S.; McGuigan, D.; Kamm, V. M.; Leach, R. et al.
System: The UNT Digital Library
PRECISE CHARGE MEASUREMENT FOR LASER PLASMA ACCELERATORS (open access)

PRECISE CHARGE MEASUREMENT FOR LASER PLASMA ACCELERATORS

Cross-calibrations of charge diagnostics are conducted to verify their validity for measuring electron beams produced by laser plasma accelerators (LPAs). Employed diagnostics are a scintillating screen, activation based measurement, and integrating current transformer. The diagnostics agreed within {+-}8 %, showing that they can provide accurate charge measurements for LPAs provided they are used properly.
Date: July 19, 2011
Creator: Nakamura, Kei; Gonsalves, Anthony; Lin, Chen; Sokollik, Thomas; Shiraishi, Satomi; Tilborg, Jeroen van et al.
System: The UNT Digital Library
Simple Common Plane contact detection algorithm for FE/FD methods (open access)

Simple Common Plane contact detection algorithm for FE/FD methods

Common-plane (CP) algorithm is widely used in Discrete Element Method (DEM) to model contact forces between interacting particles or blocks. A new simple contact detection algorithm is proposed to model contacts in FE/FD methods which is similar to the CP algorithm. The CP is defined as a plane separating interacting faces of FE/FD mesh instead of blocks or particles in the original CP method. The method does not require iterations. It is very robust and easy to implement both in 2D and 3D case.
Date: July 19, 2006
Creator: Vorobiev, O
System: The UNT Digital Library
Study of the Electron Beam Dynamics in the Fermi @ Elettra Linac (open access)

Study of the Electron Beam Dynamics in the Fermi @ Elettra Linac

A study of the electron beam dynamics in the linac is conducted for the FERMI free electron laser (FEL) founded for construction at the Sincrotrone Trieste.
Date: July 19, 2006
Creator: Cornacchia, M.; Craievich, P.; Di Mitri, S.; Pogorelov, I.; Qiang, J.; Venturini, M. et al.
System: The UNT Digital Library
Characterization of the PEP-II Colliding-Beam Phase Space by the Boost Method (open access)

Characterization of the PEP-II Colliding-Beam Phase Space by the Boost Method

We present a novel approach to characterize the colliding-beam phase space at the interaction point of the energy-asymmetric PEP-II B-Factory. The method exploits the fact that the transverse-boost distribution of e{sup +}e{sup -} {yields} {mu}{sup +}{mu}{sup -} events reconstructed in the BABAR detector reflects that of the colliding electrons and positrons. The mean boost direction, when combined with the measured orientation of the luminous ellipsoid, determines the e{sup +}-e{sup -} crossing angles. The average angular spread of the transverse boost vector provides an accurate measure of the angular divergence of the incoming high-energy beam, confirming the presence of a sizeable dynamic-{beta} effect. The longitudinal and transverse dependence of the boost angular spread also allow to extract from the continuously-monitored distributions detailed information about the emittances and IP {beta}-functions of both beams during high-luminosity operation.
Date: July 19, 2006
Creator: Weaver, M.; Kozanecki, W. & Viaud, B.
System: The UNT Digital Library