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Investigation of Sodium Distribution in Phosphate Glasses Using Spin-Echo {sup 23}Na NMR (open access)

Investigation of Sodium Distribution in Phosphate Glasses Using Spin-Echo {sup 23}Na NMR

The spatial arrangement of sodium cations for a series of sodium phosphate glasses, xNa{sub 2}O(100-x)P{sub 2}O{sub 5} (x<55), were investigated using {sup 23}Na spin-echo NMR spectroscopy. The spin-echo decay rate is a function of the Na-Na homonuclear dipolar coupling and is related to the spatial proximity of neighboring Na nuclei. The spin-echo decay rate in these sodium phosphate glasses increases non-linearly with higher sodium number density, and thus provides a measure of the Na-Na extended range order. The results of these {sup 23}Na NMR experiments are discussed within the context of several structural models, including a decimated crystal lattice model, cubic dilation lattice model, a hard sphere (HS) random distribution model and a pair-wise cluster hard sphere model. While the experimental {sup 23}Na spin-echo M{sub 2} are described adequately by both the decimated lattice and the random HS model, it is demonstrated that the slight non-linear behavior of M{sub 2} as a function of sodium number density is more correctly described by the random distribution in the HS model. At low sodium number densities the experimental M{sub 2} is inconsistent with models incorporating Na-Na clustering. The ability to distinguish between Na-Na clusters and non-clustered distributions becomes more difficult at higher …
Date: September 16, 1999
Creator: ALAM, TODD M.; BOYLE, TIMOTHY J.; BROW, RICHARD K.; CLICK, CAROL C.; CONZONE, SAM; McLAUGHLIN, JAY et al.
System: The UNT Digital Library
HIGH-INTENSITY, HIGH CHARGE-STATE HEAVY ION SOURCES (open access)

HIGH-INTENSITY, HIGH CHARGE-STATE HEAVY ION SOURCES

There are many accelerator applications for high intensity heavy ion sources, with recent needs including dc beams for RIA, and pulsed beams for injection into synchrotrons such as RHIC and LHC. The present status of sources producing high currents of high charge state heavy ions is reviewed. These sources include ECR, EBIS, and Laser ion sources. Benefits and limitations for these type sources are described. Possible future improvements in these sources are also mentioned.
Date: August 16, 2004
Creator: ALESSI,J. G.
System: The UNT Digital Library
FUTURE PLANS AT BNL: RHIC-II AND eRHIC. (open access)

FUTURE PLANS AT BNL: RHIC-II AND eRHIC.

The development of future facilities relevant to the study of deep inelastic scattering at BNL is described.
Date: April 16, 2007
Creator: ARONSON,S.
System: The UNT Digital Library
Data Torturing and the Misuse of Statistical Tools (open access)

Data Torturing and the Misuse of Statistical Tools

Statistical concepts, methods, and tools are often used in the implementation of statistical thinking. Unfortunately, statistical tools are all too often misused by not applying them in the context of statistical thinking that focuses on processes, variation, and data. The consequences of this misuse may be ''data torturing'' or going beyond reasonable interpretation of the facts due to a misunderstanding of the processes creating the data or the misinterpretation of variability in the data. In the hope of averting future misuse and data torturing, examples are provided where the application of common statistical tools, in the absence of statistical thinking, provides deceptive results by not adequately representing the underlying process and variability. For each of the examples, a discussion is provided on how applying the concepts of statistical thinking may have prevented the data torturing. The lessons learned from these examples will provide an increased awareness of the potential for many statistical methods to mislead and a better understanding of how statistical thinking broadens and increases the effectiveness of statistical tools.
Date: August 16, 1999
Creator: Abate, Marcey L.
System: The UNT Digital Library
Growth and Fabrication of GaN/AlGaN Heterojunction Bipolar Transistor (open access)

Growth and Fabrication of GaN/AlGaN Heterojunction Bipolar Transistor

A GaN/AlGaN heterojunction bipolar transistor structure with Mg doping in the base and Si Doping in the emitter and collector regions was grown by Metal Organic Chemical Vapor Deposition in c-axis Al(2)O(3). Secondary Ion Mass Spectrometry measurements showed no increase in the O concentration (2-3x10(18) cm(-3)) in the AlGaN emitter and fairly low levels of C (~4-5x10(17) cm (-3)) throughout the structure. Due to the non-ohmic behavior of the base contact at room temperature, the current gain of large area (~90 um diameter) devices was <3. Increasing the device operating temperature led to higher ionization fractions of the mg acceptors in the base, and current gains of ~10 were obtained at 300 degree C.
Date: March 16, 1999
Creator: Abernathy, C. R.; Baca, A. G.; Cao, X. A.; Cho, H.; Dang, G. T.; Donovan, S. M. et al.
System: The UNT Digital Library
Corrosion of structural materials by lead-based reactor coolants. (open access)

Corrosion of structural materials by lead-based reactor coolants.

Advanced nuclear reactor design has, in recent years, focused increasingly on the use of heavy-liquid-metal coolants, such as lead and lead-bismuth eutectic. Similarly, programs on accelerator-based transmutation systems have also considered the use of such coolants. Russian experience with heavy-metal coolants for nuclear reactors has lent credence to the validity of this approach. Of significant concern is the compatibility of structural materials with these coolants. We have used a thermal convection-based test method to allow exposure of candidate materials to molten lead and lead-bismuth flowing under a temperature gradient. The gradient was deemed essential in evaluating the behavior of the test materials in that should preferential dissolution of components of the test material occur we would expect dissolution in the hotter regions and deposition in the colder regions, thus promoting material transport. Results from the interactions of a Si-rich mild steel alloy, AISI S5, and a ferritic-martensitic stainless steel, HT-9, with the molten lead-bismuth are presented.
Date: November 16, 2000
Creator: Abraham, D. P.; Leibowitz, L.; Maroni, V. A.; McDeavitt, S. M. & Raraz, A. G.
System: The UNT Digital Library
Partition of Neutral Molecules and Ions from Water to o-Nitrophenyl Octyl Ether and of Neutral Molecules from the Gas Phase to o-Nitrophenyl Octyl Ether (open access)

Partition of Neutral Molecules and Ions from Water to o-Nitrophenyl Octyl Ether and of Neutral Molecules from the Gas Phase to o-Nitrophenyl Octyl Ether

This article sets out an equation for partition of 87 neutral molecules from water to o-nitrophenyl octyl ether, NPOE, an equation for partition of the 87 neutral molecules and 21 ionic species from water to NPOE, and an equation for partition of 87 neutral molecules from the gas phase to NPOE.
Date: February 16, 2018
Creator: Abraham, M. H. (Michael H.); Acree, William E. (William Eugene) & Liu, Xiangli
System: The UNT Digital Library
Multidimensional solitons in fiber arrays (open access)

Multidimensional solitons in fiber arrays

We demonstrate that nonlinear optical fiber arrays can support stable soliton-like pulses with finite energy. The bound state that we have found is localized both in time and in a spatial domain in the direction perpendicular to the pulse propagation. We have proved the boundedness of the Hamiltonian function for the array. Finally, numerical studies support our analytical conclusions.
Date: August 16, 1993
Creator: Aceves, A. B.; De Angelis, C.; Rubenchik, A. M. & Turitsyn, S. K.
System: The UNT Digital Library
Computer modeling in the design and evaluation of electric and hybrid vehicles (open access)

Computer modeling in the design and evaluation of electric and hybrid vehicles

This demonstration project uses modern simulation techniques to illustrate the important technologies and design variables that an auto-designer would consider in production a high efficiency, low emissions vehicle. Simulation and modeling techniques use the idea of capturing the relationships between real components of the systems with mathematical equations. These equations are then solved on a computer to simulate the behavior or performance of the system under various conditions. In the current demonstration project, we focus on many variations of a hydrogen-powered vehicle.
Date: August 16, 1996
Creator: Aceves, S. M.; Smith, J. R. & Johnson, N. L.
System: The UNT Digital Library
Waste form development and characterization in pyrometallurgical treatment of spent nuclear fuel. (open access)

Waste form development and characterization in pyrometallurgical treatment of spent nuclear fuel.

Electrometallurgical treatment is a compact, inexpensive method that is being developed at Argonne National Laboratory to deal with spent nuclear fuel, primarily metallic and oxide fuels. In this method, metallic nuclear fuel constituents are electrorefined in a molten salt to separate uranium from the rest of the spent fuel. Oxide and other fuels are subjected to appropriate head end steps to convert them to metallic form prior to electrorefining. The treatment process generates two kinds of high-level waste--a metallic and a ceramic waste. Isolation of these wastes has been developed as an integral part of the process. The wastes arise directly from the electrorefiner, and waste streams do not contain large quantities of solvent or other process fluids. Consequently, waste volumes are small and waste isolation processes can be compact and rapid. This paper briefly summarizes waste isolation processes then describes development and characterization of the two waste forms in more detail.
Date: April 16, 1998
Creator: Ackerman, J.
System: The UNT Digital Library
Search for Dark Matter Satellites Using the FERMI-LAT (open access)

Search for Dark Matter Satellites Using the FERMI-LAT

Numerical simulations based on the {Lambda}CDM model of cosmology predict a large number of as yet unobserved Galactic dark matter satellites. We report the results of a Large Area Telescope (LAT) search for these satellites via the {gamma}-ray emission expected from the annihilation of weakly interacting massive particle (WIMP) dark matter. Some dark matter satellites are expected to have hard {gamma}-ray spectra, finite angular extents, and a lack of counterparts at other wavelengths. We sought to identify LAT sources with these characteristics, focusing on {gamma}-ray spectra consistent with WIMP annihilation through the b{bar b} channel. We found no viable dark matter satellite candidates using one year of data, and we present a framework for interpreting this result in the context of numerical simulations to constrain the velocity-averaged annihilation cross section for a conventional 100 GeV WIMP annihilating through the b{bar b} channel.
Date: August 16, 2012
Creator: Ackermann, M.; Albert, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D. et al.
System: The UNT Digital Library
Comments Concerning “Solubility and Dissolution Thermodynamic Properties of 1,6-Bis[3-(3,5-Di-Tert-Butyl-4-Hydroxyphenyl) Propionamido]Hexane in Pure Solvents and Binary Solvent Mixtures” (open access)

Comments Concerning “Solubility and Dissolution Thermodynamic Properties of 1,6-Bis[3-(3,5-Di-Tert-Butyl-4-Hydroxyphenyl) Propionamido]Hexane in Pure Solvents and Binary Solvent Mixtures”

This article comments on mathematical errors pertaining to published equation coefficients for the modified Apelblat and for the polynomial equation based on the Combined Jouyban-Acree and modified Apelblat models.
Date: February 16, 2018
Creator: Acree, William E. (William Eugene)
System: The UNT Digital Library
Using Water-Solvent Systems To Estimate In Vivo Blood-Tissue Partition Coefficients (open access)

Using Water-Solvent Systems To Estimate In Vivo Blood-Tissue Partition Coefficients

This article discusses water-solvent systems for estimating in vivo blood-tissue partition coefficients.
Date: October 16, 2015
Creator: Acree, William E. (William Eugene); Derricott, Caitlin E.; Knight, Emily A. & Lang, Andrew S. I. D.
System: The UNT Digital Library
Pion, kaon, proton and anti-proton transverse momentum distributions from p+p and d+Au collisions at sqrt(sNN) = 200 GeV (open access)

Pion, kaon, proton and anti-proton transverse momentum distributions from p+p and d+Au collisions at sqrt(sNN) = 200 GeV

Identified mid-rapidity particle spectra of {pi}{sup {+-}}, K{sup {+-}}, and p({bar p}) from 200 GeV p+p and d+Au collisions are reported. A time-of-flight detector based on multi-gap resistive plate chamber technology is used for particle identification. The particle-species dependence of the Cronin effect is observed to be significantly smaller than that at lower energies. The ratio of the nuclear modification factor (R{sub dAu}) between (p+ {bar p}) and charged hadrons (h) in the transverse momentum range 1.2 &lt; p{sub T} &lt; 3.0 GeV/c is measured to be 1.19 {+-} 0.05(stat) {+-} 0.03(syst) in minimum-bias collisions and shows little centrality dependence. The yield ratio of (p + {bar p})/h in minimum-bias d+Au collisions is found to be a factor of 2 lower than that in Au+Au collisions, indicating that the Cronin effect alone is not enough to account for the relative baryon enhancement observed in heavy ion collisions at RHIC.
Date: September 16, 2003
Creator: Adams, J.; Adler, C.; Aggarwal, M. M.; Ahammed, Z.; Amonett, J.; Anderson, B. D. et al.
System: The UNT Digital Library
International Symposium on Systems and Human Science - SSR2005 (open access)

International Symposium on Systems and Human Science - SSR2005

None
Date: March 16, 2005
Creator: Addison, K J
System: The UNT Digital Library
First Results From the Electron Hose Instability Studies in FACET (open access)

First Results From the Electron Hose Instability Studies in FACET

None
Date: October 16, 2013
Creator: Adli, E.; Corde, S.; England, R. J.; Frederico, J.; Gessner, S. J.; Li, S. et al.
System: The UNT Digital Library
Securing collaborative environments (open access)

Securing collaborative environments

The diverse set of organizations and software components involved in a typical collaboratory make providing a seamless security solution difficult. In addition, the users need support for a broad range of frequency and locations for access to the collaboratory. A collaboratory security solution needs to be robust enough to ensure that valid participants are not denied access because of its failure. There are many tools that can be applied to the task of securing collaborative environments and these include public key infrastructure, secure sockets layer, Kerberos, virtual and real private networks, grid security infrastructure, and username/password. A combination of these mechanisms can provide effective secure collaboration capabilities. In this paper, we discuss the requirements of typical collaboratories and some proposals for applying various security mechanisms to collaborative environments.
Date: May 16, 2002
Creator: Agarwal, Deborah; Jackson, Keith & Thompson, Mary
System: The UNT Digital Library
The Impact of COVID-19 Shocks on Business and GDP of Global Economy (open access)

The Impact of COVID-19 Shocks on Business and GDP of Global Economy

Article examines the relationship between COVID-19 shocks and GDP loss of different countries worldwide based on the seven scenarios of the epidemiological DSGE/CGE model. Their results reveal that the most significant GDP loss is associated with Japan, Germany, and the US, respectively, which are industrialized countries with the most prominent automobile manufacturers.
Date: November 16, 2022
Creator: Ahangar, Reza Gharoie & Kim, Myungsup
System: The UNT Digital Library
Study of the high-j states in {sup 249}Cm. (open access)

Study of the high-j states in {sup 249}Cm.

The authors have performed the reaction {sup 248}Cm({sup 4}He, {sup 3}He) using 98.5-MeV alpha particles from the IUCF cyclotron to populate high-j states in {sup 249}Cm. A tentative assignment of the K{sub 17/2} component of the 1/2{sup +}[880] Nilsson state has been made.
Date: July 16, 1998
Creator: Ahmad, I.
System: The UNT Digital Library
Large-Signal Injection-Level Spectroscopy of Impurities in Silicon (open access)

Large-Signal Injection-Level Spectroscopy of Impurities in Silicon

Deep level defects in silicon are identified by measuring the recombination lifetime as a function of the injection level. The basic models for recombination at deep and shallow centers is developed. The defect used for the theoretical model is the well-known interstitial Fe ion in silicon. Data are presented on silicon samples ranging in defect content from intentionally Fe-doped samples to an ultra-pure float-zone grown sample. These data are analyzed in terms of the injection-level spectroscopy model.
Date: October 16, 1998
Creator: Ahrenkiel, R. K. & Johnston, S. W.
System: The UNT Digital Library
Recombination Lifetime of InxGa1-xAs Alloys Used in Thermophotovoltaic Converters (open access)

Recombination Lifetime of InxGa1-xAs Alloys Used in Thermophotovoltaic Converters

The family of ternary compounds of composition InxGa1-xAs are of considerable interest for thermophotovoltaic energy converters. The recombination lifetimes of the various compositions are critical to the successful application of these materials as efficient converters. Here we will describe experimental results on the composition. In0.53Ga0.47 that is lattice-matched to InP. We will also describe lifetime results on the compositions In0.68Ga0.32As, with bandgap of 0.60 eV to compositions In0.78Ga0.22As with a bandgap of 0.50 eV. Double heterostructure confinement devices have been made over a range of both n- and p-type doping. These results are preliminary, but the goal is to obtain the radiative and Auger recombination coefficients for the alloys in this composition range.
Date: February 16, 1999
Creator: Ahrenkiel, R. K.; Ellingson, R.; Johnston, S.; Webb, J.; Carapella, J. & Wanlass, M.
System: The UNT Digital Library
Setup and Performance of the Rhic Injector Accelerators for the 2005 Run With Copper Ions. (open access)

Setup and Performance of the Rhic Injector Accelerators for the 2005 Run With Copper Ions.

Copper ions for the 2005 run [1] of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) are accelerated in the Tandem, Booster and AGS prior to injection into RHIC. The setup and performance of these accelerators with copper are reviewed in this paper.
Date: May 16, 2005
Creator: Ahrens, L.; Alessi, J. & Gardner, C. J.
System: The UNT Digital Library
The Luminosity Function of Fermi-detected Flat-Spectrum Radio Quasars (open access)

The Luminosity Function of Fermi-detected Flat-Spectrum Radio Quasars

Fermi has provided the largest sample of {gamma}-ray selected blazars to date. In this work we use a complete sample of FSRQs detected during the first year of operation to determine the luminosity function (LF) and its evolution with cosmic time. The number density of FSRQs grows dramatically up to redshift {approx}0.5-2.0 and declines thereafter. The redshift of the peak in the density is luminosity dependent, with more luminous sources peaking at earlier times; thus the LF of {gamma}-ray FSRQs follows a luminosity-dependent density evolution similarly to that of radio-quiet AGN. Also using data from the Swift Burst Alert Telescope we derive the average spectral energy distribution of FSRQs in the 10 keV-100GeV band and show that there is no correlation of the peak {gamma}-ray luminosity with {gamma}-ray peak frequency. The coupling of the SED and LF allows us to predict that the contribution of FSRQs to the Fermi isotropic {gamma}-ray background is 9.3{sub -1.0}{sup +1.6}% ({+-}3% systematic uncertainty) in the 0.1-100GeV band. Finally we determine the LF of unbeamed FSRQs, finding that FSRQs have an average Lorentz factor of {gamma} = 11.7{sub -2.2}{sup +3.3}, that most are seen within 5{sup o} of the jet axis, and that they represent …
Date: April 16, 2012
Creator: Ajello, M.; Shaw, M. S.; Romani, R. W.; Dermer, C. D.; Costamante, L.; King, O. G. et al.
System: The UNT Digital Library
Three-Body Breakup Dynamics in Dissociative Recombination (open access)

Three-Body Breakup Dynamics in Dissociative Recombination

Using the CRYRing Facility in Stockholm Coupled with an MCP-CCD detector, and a differential stopping foil, we have determined dynamic parameters in the three-body dissociative recombination of H<sub>2</sub>O<sup>+</sup>. These include the distribution between the O(<sup>3</sup>P) and O(<sup>1</sup>D) channels, the distribution of H atom recoil energies in the O(<sup>3</sup>P) channel and the distribution of angles between the two departing H atoms.
Date: June 16, 1999
Creator: Al-Khalili, A.; Datz, S.; Derkatch, A.; Larsson, M.; Rosén, S.; Shi, W. et al.
System: The UNT Digital Library