3,706 Matching Results

Results open in a new window/tab.

Strategic Domain: Reconquest Romanesque Along the Duero in Soria, Spain (open access)

Strategic Domain: Reconquest Romanesque Along the Duero in Soria, Spain

This article uses a mapping project to examine the relationship between a small set of chapels in close proximity to defensive fortresses along the upper Duero in the region of Soria.
Date: 2007
Creator: Abel, Mickey S.
System: The UNT Digital Library
Phase Equilibria in High Energy Density PVDF-Based Polymers (open access)

Phase Equilibria in High Energy Density PVDF-Based Polymers

Article on phase equilibria in high energy density PVDF-based polymers.
Date: July 27, 2007
Creator: Ranjan, Vivek; Yu, Liping; Buongiorno Nardelli, Marco & Bernholc, Jerry
System: The UNT Digital Library

Older Poor Parents who Lost an Adult Child to AIDS in Togo, West Africa: A Qualitative Study

Access: Use of this item is restricted to the UNT Community
Article on a qualitative study exploring older poor parents who lost an adult child to AIDS in Togo, West Africa.
Date: January 2007
Creator: Moore, Ami R.
System: The UNT Digital Library
Consequences of Empowered CNA Teams in Nursing Home Settings: A Longitudinal Assessment (open access)

Consequences of Empowered CNA Teams in Nursing Home Settings: A Longitudinal Assessment

Article on a longitudinal assessment and the consequences of empowered CAN teams in nursing home settings.
Date: 2007
Creator: Yeatts, Dale E., 1952- & Cready, Cynthia M.
System: The UNT Digital Library
Fluctuation-Dissipation Theorem for Event-Dominated Processes (open access)

Fluctuation-Dissipation Theorem for Event-Dominated Processes

Article discussing the fluctuation-dissipation theorem for event-dominated processes.
Date: July 6, 2007
Creator: Allegrini, Paolo; Bologna, Mauro; Grigolini, Paolo & West, Bruce J.
System: The UNT Digital Library
Brain, Music, and Non-Poisson Renewal Processes (open access)

Brain, Music, and Non-Poisson Renewal Processes

Article discussing research that shows both music composition and brain function, as revealed by the electroencephalogram (EEG) analysis, are renewal non-Poisson processes living in the nonergodic dominion.
Date: June 21, 2007
Creator: Bianco, Simone; Ignaccolo, Massimiliano; Rider, Mark S.; Ross, Mary J.; Winsor, Phil & Grigolini, Paolo
System: The UNT Digital Library
An IRE-Like AGC Kinase Gene, MtIRE, Has Unique Expression in the Invasion Zone of Developing Root Nodules in Medicago truncatula (open access)

An IRE-Like AGC Kinase Gene, MtIRE, Has Unique Expression in the Invasion Zone of Developing Root Nodules in Medicago truncatula

This article discusses AGC kinase genes. The authors report here the isolation and characterization of the first AGC kinase gene identified in Medicago truncatula, MtIRE.
Date: June 2007
Creator: Pislariu, Catalina I. & Dickstein, Rebecca
System: The UNT Digital Library
Image-Based Modeling Reveals Dynamic Redistribution of DNA Damageinto Nuclear Sub-Domains (open access)

Image-Based Modeling Reveals Dynamic Redistribution of DNA Damageinto Nuclear Sub-Domains

Several proteins involved in the response to DNA doublestrand breaks (DSB) f orm microscopically visible nuclear domains, orfoci, after exposure to ionizing radiation. Radiation-induced foci (RIF)are believed to be located where DNA damage occurs. To test thisassumption, we analyzed the spatial distribution of 53BP1, phosphorylatedATM, and gammaH2AX RIF in cells irradiated with high linear energytransfer (LET) radiation and low LET. Since energy is randomly depositedalong high-LET particle paths, RIF along these paths should also berandomly distributed. The probability to induce DSB can be derived fromDNA fragment data measured experimentally by pulsed-field gelelectrophoresis. We used this probability in Monte Carlo simulations topredict DSB locations in synthetic nuclei geometrically described by acomplete set of human chromosomes, taking into account microscope opticsfrom real experiments. As expected, simulations produced DNA-weightedrandom (Poisson) distributions. In contrast, the distributions of RIFobtained as early as 5 min after exposure to high LET (1 GeV/amu Fe) werenon-random. This deviation from the expected DNA-weighted random patterncan be further characterized by "relative DNA image measurements." Thisnovel imaging approach shows that RIF were located preferentially at theinterface between high and low DNA density regions, and were morefrequent than predicted in regions with lower DNA density. The samepreferential nuclear location was also measured …
Date: August 3, 2007
Creator: Costes Sylvain V.; Ponomarev, Artem; Chen, James L.; Nguyen, David; Cucinotta, Francis A. & Barcellos-Hoff, Mary Helen
System: The UNT Digital Library
Environmental Challenges for the Nuclear Diagnostics on the NIF and LMJ (open access)

Environmental Challenges for the Nuclear Diagnostics on the NIF and LMJ

The National Ignition Facility (NIF) and Laser Mega Joule (LMJ) facilities are currently under construction in the United States and France. Ignited targets at these facilities are anticipated to produce up to 1019 deuterium-tritium fusion neutrons. This will provide unprecedented opportunities and challenges for the use of nuclear diagnostics in inertial confinement fusion experiments. The NIF and LMJ nuclear diagnostics will work in a harsh radiation environment that includes neutron, hard x-ray, and gamma backgrounds, neutron induced signals in coaxial cables, and electromagnetic pulse (EMP) generated signals. Recent results of different background measurements on OMEGA laser facility will be reported. Based on these results, specific design concepts have been identified to mitigate much of the radiation and EMP-induced backgrounds. An overview of the background mitigation techniques in the NIF nuclear diagnostics conceptual designs will be presented.
Date: June 27, 2007
Creator: al., K. Miller et
System: The UNT Digital Library
Horizontal gene transfer and the evolution of transcriptionalregulation in Escherichia coli (open access)

Horizontal gene transfer and the evolution of transcriptionalregulation in Escherichia coli

Background: Most bacterial genes were acquired by horizontalgene transfer from other bacteria instead of being inherited bycontinuous vertical descent from an ancient ancestor}. To understand howthe regulation of these {acquired} genes evolved, we examined theevolutionary histories of transcription factors and of regulatoryinteractions from the model bacterium Escherichia coli K12. Results:Although most transcription factors have paralogs, these usually arose byhorizontal gene transfer rather than by duplication within the E. colilineage, as previously believed. In general, most neighbor regulators --regulators that are adjacent to genes that they regulate -- were acquiredby horizontal gene transfer, while most global regulators evolvedvertically within the gamma-Proteobacteria. Neighbor regulators wereoften acquired together with the adjacent operon that they regulate, sothe proximity might be maintained by repeated transfers (like "selfishoperons"). Many of the as-yet-uncharacterized (putative) regulators havealso been acquired together with adjacent genes, so we predict that theseare neighbor regulators as well. When we analyzed the histories ofregulatory interactions, we found that the evolution of regulation byduplication was rare, and surprisingly, many of the regulatoryinteractions that are shared between paralogs result from convergentevolution. Another surprise was that horizontally transferred genes aremore likely than other genes to be regulated by multiple regulators, andmost of this complex regulation probably evolved …
Date: December 20, 2007
Creator: Price, Morgan N.; Dehal, Paramvir S. & Arkin, Adam P.
System: The UNT Digital Library
Mechanical and charge transport properties of alkanethiol self-assembled monolayers on Au (111) surface: The Role of Molecular Tilt (open access)

Mechanical and charge transport properties of alkanethiol self-assembled monolayers on Au (111) surface: The Role of Molecular Tilt

The relationship between charge transport and mechanical properties of alkanethiol self-assembled monolayers (SAM) on Au(111) films has been investigated using an atomic force microscope with a conductive tip. Molecular tilts induced by the pressure applied by the tip cause stepwise increases in film conductivity. A decay constant {beta} = 0.57 {+-} 0.03 {angstrom}{sup -1} was found for the current passing through the film as a function of tip-substrate separation due to this molecular tilt. This is significantly smaller than the value of {approx} 1 {angstrom}{sup -1} found when the separation is changed by changing the length of the alkanethiol molecules. Calculations indicate that for isolated dithiol molecules S-bonded to hollow sites, the junction conductance does not vary significantly as a function of molecular tilt. The impact of S-Au bonding on SAM conductance is discussed.
Date: November 12, 2007
Creator: Mulleregan, Alice; Qi, Yabing; Ratera, Imma; Park, Jeong Y.; Ashby, Paul D.; Quek, Su Ying et al.
System: The UNT Digital Library
R. Bruce Merrifield and Solid-Phase Peptide Synthesis: A Historical Assessment (open access)

R. Bruce Merrifield and Solid-Phase Peptide Synthesis: A Historical Assessment

Bruce Merrifield, trained as a biochemist, had to address three major challenges related to the development and acceptance of solid-phase peptide synthesis (SPPS). The challenges were (1) to reduce the concept of peptide synthesis on a insoluble support to practice, (2) overcome the resistance of synthetic chemists to this novel approach, and (3) establish that a biochemist had the scientific credentials to effect the proposed revolutionary change in chemical synthesis. How these challenges were met is discussed in this article.
Date: December 4, 2007
Creator: Mitchell, A R
System: The UNT Digital Library
Operation of a Free-Electron Laser from the Extreme Ultraviolet to the Water Window (open access)

Operation of a Free-Electron Laser from the Extreme Ultraviolet to the Water Window

We report results on the performance of a free-electron laser operating at a wavelength of 13.7 nm where unprecedented peak and average powers for a coherent extreme-ultraviolet radiation source have been measured. In the saturation regime, the peak energy approached 170 {micro}J for individual pulses, and the average energy per pulse reached 70 {micro}J. The pulse duration was in the region of 10 fs, and peak powers of 10 GW were achieved. At a pulse repetition frequency of 700 pulses per second, the average extreme-ultraviolet power reached 20mW. The output beam also contained a significant contribution from odd harmonics of approximately 0.6% and 0.03% for the 3rd (4.6 nm) and the 5th (2.75 nm) harmonics, respectively. At 2.75 nm the 5th harmonic of the radiation reaches deep into the water window, a wavelength range that is crucially important for the investigation of biological samples.
Date: December 17, 2007
Creator: Ackermann, W.; Asova, G.; Ayvazyan, V.; Azima, A.; Baboi, N.; Bahr, J. et al.
System: The UNT Digital Library
X-ray spectroscopic study of the charge state and local orderingof room-temperature ferromagnetic Mn oped ZnO (open access)

X-ray spectroscopic study of the charge state and local orderingof room-temperature ferromagnetic Mn oped ZnO

The charge state and local ordering of Mn doped into a pulsed laser deposited single-phase thin film of ZnO are investigated by using X-ray absorption spectroscopy at the O K-, Mn K- and L-edges, and X-ray emission spectroscopy at the O K- and Mn L-edge. This film is found to be ferromagnetic at room temperature. EXAFS measurement shows that Mn{sup 2+} replaces Zn site in tetrahedral symmetry, and there is no evidence for either metallic Mn or MnO in the film. Upon Mn doping, the top of O 2p valence band extends into the bandgap indicating additional charge carries being created.
Date: August 7, 2007
Creator: Guo, J.-H.; Gupta, Amita; Sharma, Parmanand; Rao, K.V.; Marcus,M.A.; Dong, C.L. et al.
System: The UNT Digital Library
Plan for Using Solar-Powered Jack Pumps to Sample Groundwater at the Nevada Test Site (open access)

Plan for Using Solar-Powered Jack Pumps to Sample Groundwater at the Nevada Test Site

Groundwater is sampled from 39 monitoring wells on the Nevada Test Site (NTS) as part of the Routine Radiological Environmental Monitoring Program. Many of these wells were not designed or constructed for long-term groundwater monitoring. Some have extensive completion zones and others have obstructions such as pumps and tubing. The high-volume submersible pumps in some wells are unsuitable for long-term monitoring and result in large volumes of water that may have to be contained and characterized before subsequent disposition. The configuration of most wells requires sampling stagnant well water with a wireline bailer. Although bailer sampling allows for the collection of depth-discrete samples, the collected samples may not be representative of local groundwater because no well purging is done. Low-maintenance, solar-powered jack pumps will be deployed in nine of these onsite monitoring wells to improve sample quality. These pumps provide the lift capacity to produce groundwater from the deep aquifers encountered in the arid environment of the NTS. The water depths in these wells range from 700 to 2,340 ft below ground surface. The considerable labor and electrical power requirements of electric submersible pumps are eliminated once these pumps are installed. Access tubing will be installed concurrent with the installation …
Date: May 3, 2007
Creator: David Hudson, Charles Lohrstorfer, Bruce Hurley
System: The UNT Digital Library
Book Review Geostatistical Analysis of Compositional Data (open access)

Book Review Geostatistical Analysis of Compositional Data

Compositional data are represented as vector variables with individual vector components ranging between zero and a positive maximum value representing a constant sum constraint, usually unity (or 100 percent). The earth sciences are flooded with spatial distributions of compositional data, such as concentrations of major ion constituents in natural waters (e.g. mole, mass, or volume fractions), mineral percentages, ore grades, or proportions of mutually exclusive categories (e.g. a water-oil-rock system). While geostatistical techniques have become popular in earth science applications since the 1970s, very little attention has been paid to the unique mathematical properties of geostatistical formulations involving compositional variables. The book 'Geostatistical Analysis of Compositional Data' by Vera Pawlowsky-Glahn and Ricardo Olea (Oxford University Press, 2004), unlike any previous book on geostatistics, directly confronts the mathematical difficulties inherent to applying geostatistics to compositional variables. The book righteously justifies itself with prodigious referencing to previous work addressing nonsensical ranges of estimated values and error, spurious correlation, and singular cross-covariance matrices.
Date: March 26, 2007
Creator: Carle, S F
System: The UNT Digital Library
Electron cooling rates characterization at Fermilab's Recycler (open access)

Electron cooling rates characterization at Fermilab's Recycler

A 0.1 A, 4.3 MeV DC electron beam is routinely used to cool 8 GeV antiprotons in Fermilab's Recycler storage ring [1]. The primary function of the electron cooler is to increase the longitudinal phase-space density of the antiprotons for storing and preparing high-density bunches for injection into the Tevatron. The longitudinal cooling rate is found to significantly depend on the transverse emittance of the antiproton beam. The paper presents the measured rates and compares them with calculations based on drag force data.
Date: June 1, 2007
Creator: Prost, Lionel R. & Shemyakin, A.
System: The UNT Digital Library
New experimental capabilities and theoretical insights of high pressure compression waves (open access)

New experimental capabilities and theoretical insights of high pressure compression waves

Currently there are three platforms that offer quasi-isentropic compression or ramp-wave compression (RWC): light-gas gun, magnetic flux (Z-pinch), and laser. We focus here on the light-gas gun technique and on some current theoretical insights from experimental data. A gradient impedance through the length of the impactor provides the pressure pulse upon impactor to the subject material. Applications and results are given concerning high-pressure strength and liquid to solid, phase transition of water plus its associated phase fraction history. We also introduce the Korteweg-deVries-Burgers equation as a means to understand the evolution these RWC waves that propagate through the thickness of the subject material. This equation has the necessary competition between non-linear, dispersion, and dissipation processes, which is shown through observed structures that are manifested in the experimental particle velocity histories. Such methodology points towards a possible quantifiable dissipation, through which RWC experiments may be analyzed.
Date: July 20, 2007
Creator: Orlikowski, D.; Nguyen, J.; Patterson, J. R.; Minich, R.; Martin, L. P. & Holmes, N.
System: The UNT Digital Library
Progress with Tevatron Electron Lenses (open access)

Progress with Tevatron Electron Lenses

None
Date: September 13, 2007
Creator: Kamerdzhiev, V.; Alexahin, Y.; Kuznetsov, G. F.; Shiltsev, V. D. & Zhang, X.
System: The UNT Digital Library
Direct Assay of Filter Media following DEOX Testing (open access)

Direct Assay of Filter Media following DEOX Testing

The direct assay of filter media by gamma spectrometry following DEOX testing has distinct advantages over analytical chemistry. Prior to using gamma spectrometry for the quantification of cesium (Cs-137), a calibration must be established with known sources since gamma spectrometry yields relative results. Quantitative analytical chemistry, in particular ICP-MS, has been performed on the filter media for comparison to the gamma spectrometry data. The correlation of gamma spectrometry to ICP-MS data is presented to justify the continued use of gamma spectrometry for filter media.
Date: September 1, 2007
Creator: Lind, R. P.; Giglio, J. J.; Cummings, D. G.; Huntley, M. W.; Morgan, C. D.; Bateman, K. J. et al.
System: The UNT Digital Library
Theory and Fluid Simulations of Boundary Plasma Fluctuations (open access)

Theory and Fluid Simulations of Boundary Plasma Fluctuations

Theoretical and computational investigations are presented of boundary plasma microturbulence that take into account important effects of the geometry of diverted tokamaks--in particular, the effect of x-point magnetic shear and the termination of field lines on divertor plates. We first generalize our previous 'heuristic boundary condition' which describes, in a lumped model, the closure of currents in the vicinity of the x-point region to encompass three current-closure mechanisms. We then use this boundary condition to derive the dispersion relation for low-beta flute-like modes in the divertor-leg region under the combined drives of curvature, sheath impedance, and divertor tilt effects. The results indicate the possibility of strongly growing instabilities, driven by sheath boundary conditions, and localized in either the private or common flux region of the divertor leg depending on the radial tilt of divertor plates. We re-visit the issue of x-point effects on blobs, examining the transition from blobs terminated by x-point shear to blobs that extend over both the main SOL and divertor legs. We find that, for a main-SOL blob, this transition occurs without a free-acceleration period as previously thought, with x-point termination conditions applying until the blob has expanded to reach the divertor plate. We also derive …
Date: January 9, 2007
Creator: Cohen, R. H.; LaBombard, B.; LoDestro, L. L.; Rognlien, T. D.; Ryutov, D. D.; Terry, J. L. et al.
System: The UNT Digital Library
Coherent neutrino-nucleus scattering and the MINERvA experiment (open access)

Coherent neutrino-nucleus scattering and the MINERvA experiment

In this paper we describe the capabilities of the MINERvA experiment for the measurement of neutrino-nucleus coherent scattering.
Date: January 1, 2007
Creator: Gallagher, H.; U., /Tufts; Harris, Deborah & /Fermilab
System: The UNT Digital Library
Assessing Recharge and Geological Model Uncertainty at the Climax Mine Area of the Nevada Test Site (open access)

Assessing Recharge and Geological Model Uncertainty at the Climax Mine Area of the Nevada Test Site

Hydrologic analyses are commonly based on a single conceptual-mathematical model. Yet hydrologic environments are open and complex, rendering them prone to multiple interpretations and mathematical descriptions. Considering conceptual model uncertainty is a critical process in hydrologic uncertainty assessment. This study assesses recharge and geologic model uncertainty for the Climax mine area of the Nevada Test Site, Nevada. Five alternative recharge models have been independently developed for Nevada and the Death Valley area of California. These models are (1) the Maxey-Eakin model, (2 and 3) a distributed parameter watershed model with and without a runon-runoff component, and (4 and 5) a chloride mass-balance model with two zero-recharge masks, one for alluvium and one for both alluvium and elevation. Similarly, five geological models have been developed based on different interpretations of available geologic information. One of them was developed by the U.S. Geological Survey for the Death Valley Regional Flow System (DVRFS) model; the other four were developed by Bechtel Nevada for the Yucca Flat Corrective Action Unit (CAU). The Climax mine area is in the northern part of the Yucca Flat CAU, which is within the DVRFS. A total of 25 conceptual models are thus formulated based on the five recharge …
Date: November 8, 2007
Creator: Ye, M.; Pohlmann, K.; Chapman, J. & Pohll, G.
System: The UNT Digital Library
New Equalizers for Antiproton Stochastic Cooling at Fermilab (open access)

New Equalizers for Antiproton Stochastic Cooling at Fermilab

In the continuous effort to improve antiproton stacking rate, a new type of equalizers has been developed and installed in antiproton accumulator. The R&D of these new equalizers is described in this paper. Equalizers are used in Fermilab antiproton stochastic cooling to compensate frequency response of the cooling system. Usually both amplitude and phase compensations are needed. However in most cases it is difficult to achieve a satisfactory compensation for both because of their interdependence. To make it more difficult is that in some cases large compensations (10 to 20 db of amplitude compensation or more than 100 degree of phase compensation) are needed near the low or high ends of a frequency band. Recently a new compensation scheme of equalizers is proposed for Fermilab antiproton accumulator. This scheme originated from the requirement to maximize the system performance resulting in a request for the phase of the cooling system transfer function to be extremely flat. For this kind of phase correction, a new type of equalizers has been developed.
Date: September 13, 2007
Creator: Lebedev, V. A.; Pasquinelli, R. J. & Sun, D.
System: The UNT Digital Library