Elementary reaction rate measurements at high temperatures by tunable-laser flash-absorption (open access)

Elementary reaction rate measurements at high temperatures by tunable-laser flash-absorption

The major objective of this program is to measure thermal rate coefficients and branching ratios of elementary reactions. To perform these measurements, we have constructed an ultrahigh-purity shock tube to generate temperatures between 1000 and 5500 K. The tunable-laser flash-absorption technique is used to measure the rate of change of the concentration of species which absorb below 50,000 cm{sup {minus}1} e.g.: OH, CH, and CH{sub 3}. This technique is being extended into the vacuum-ultraviolet spectral region where we can measure atomic species e.g.: H, D, C, O, and N; and diatomic species e.g.: O{sub 2}, CO, and OH.
Date: March 20, 1992
Creator: Hessler, J.P.
System: The UNT Digital Library
Real time loss detection for SNM in process (open access)

Real time loss detection for SNM in process

This paper discusses the basis of a design for real time special nuclear material (SNM) loss detectors. The design utilizes process measurements and signal processing techniques to produce a timely estimate of material loss. A state estimator is employed as the primary signal processing algorithm. Material loss is indicated by changes in the states or process innovations (residuals). The design philosophy is discussed in the context of these changes.
Date: March 20, 1980
Creator: Candy, J. V.; Dunn, D. R. & Gavel, D. T.
System: The UNT Digital Library
Vibrational Spectroscopy and X-ray Diffraction of Cd(OH)2 to 28GPa at 300 K (open access)

Vibrational Spectroscopy and X-ray Diffraction of Cd(OH)2 to 28GPa at 300 K

We report Raman and infrared absorption spectroscopy alongwith X-ray diffraction for brucite-type beta-Cd(OH)2 to 28 GPa at 300 K.The OH-stretching modes soften with pressure and disappear at 21 GPa withtheir widths increasing rapidly above 5 GPa, consistent with a gradualdisordering of the H sublattice at 5 20 GPa similar to that previouslyobserved for Co(OH)2.Asymmetry in the peak shapes of the OH-stretchingmodes suggests the existence of diverse disordered sitesfor H atoms inCd(OH)2 under pressure. Above 15 GPa, the A1g(T) lattice mode showsnon-linear behavior and softens to 21 GPa, at which pressure significantchanges are observed: new Raman modes appear, two Raman-active latticemodes and the OH-stretching modes of the low-pressure phase disappears,and the positions of some X-ray diffraction lines change abruptly withthe appearance of weak new diffraction features. These observationssuggest that amorphization of the H sublattice is accompanied by acrystalline-to-crystalline transition at 21 GPa in Cd(OH)2, which has notbeen previously observed in the brucite-type hydroxides. The Ramanspectra of the high-pressure phase of Cd(OH)2 is similar to those of thehigh-pressure phase of single-crystal Ca(OH)2 of which structure has beententatively assigned to the Sr(OH)2 type.
Date: March 20, 2006
Creator: Shim, Sang-Heon; Rekhi, Sandeep; Martin, Michael C. & Jeanloz,Raymond
System: The UNT Digital Library
MICROFLUIDIC MIXERS FOR THE INVESTIGATION OF PROTEIN FOLDING USING SYNCHROTRON RADIATION CIRCULAR DICHROISM SPECTROSCOPY (open access)

MICROFLUIDIC MIXERS FOR THE INVESTIGATION OF PROTEIN FOLDING USING SYNCHROTRON RADIATION CIRCULAR DICHROISM SPECTROSCOPY

The purpose of this study is to design, fabricate and optimize microfluidic mixers to investigate the kinetics of protein secondary structure formation with Synchrotron Radiation Circular Dichroism (SRCD) spectroscopy. The mixers are designed to rapidly initiate protein folding reaction through the dilution of denaturant. The devices are fabricated out of fused silica, so that they are transparent in the UV. We present characterization of mixing in the fabricated devices, as well as the initial SRCD data on proteins inside the mixers.
Date: March 20, 2006
Creator: Kane, A; Hertzog, D; Baumgartel, P; Lengefeld, J; Horsley, D; Schuler, B et al.
System: The UNT Digital Library
TRITIUM MOVEMENT AND ACCUMULATION IN THE NGNP SYSTEM INTERFACE AND HYDROGEN PLANT (open access)

TRITIUM MOVEMENT AND ACCUMULATION IN THE NGNP SYSTEM INTERFACE AND HYDROGEN PLANT

Tritium movement and accumulation in the Next Generation Nuclear Plant (NGNP) employing either a high-temperature electrolysis (HTE) process or a thermochemical water-splitting Sulfur-Iodine (SI) process to produce hydrogen is estimated by a numerical code, THYTAN, as a function of design, operational and material parameters. Estimated tritium concentrations in the hydrogen product and in the process chemicals of the hydrogen plant using the HTE process are slightly higher than the limit in drinking water defined by the U.S. Environmental Protection Agency (EPA) and in effluent at the boundary of an unrestricted area defined by the U.S. Nuclear Regulatory Commission (NRC), respectively. Estimated tritium concentrations in the NGNP using the SI hydrogen production process are significantly higher, and are largely affected by undetermined parameters (i.e., tritium permeability of heat exchanger materials, hydrogen concentration in the helium energy transport fluids, equilibrium constant of the tritium isotope exchange reaction between HT and H{sub 2}SO{sub 4}). These parameters should be measured or estimated in the near future, as should the tritium generation and release rate from the NGNP nuclear reactor core. Decreasing the tritium permeation rate between the primary and secondary heat transport circuits is an effective measure to decrease the tritium concentrations in the …
Date: March 20, 2008
Creator: Sherman, S
System: The UNT Digital Library
Real time assessment of RF cardiac tissue ablation with optical spectroscopy (open access)

Real time assessment of RF cardiac tissue ablation with optical spectroscopy

An optical spectroscopy approach is demonstrated allowing for critical parameters during RF ablation of cardiac tissue to be evaluated in real time. The method is based on incorporating in a typical ablation catheter transmitting and receiving fibers that terminate at the tip of the catheter. By analyzing the spectral characteristics of the NIR diffusely reflected light, information is obtained on such parameters as, catheter-tissue proximity, lesion formation, depth of penetration of the lesion, formation of char during the ablation, formation of coagulum around the ablation site, differentiation of ablated from healthy tissue, and recognition of micro-bubble formation in the tissue.
Date: March 20, 2008
Creator: Demos, S G & Sharareh, S
System: The UNT Digital Library
Probabilistic aspects of meteorological and ozone regional ensemble forecasts (open access)

Probabilistic aspects of meteorological and ozone regional ensemble forecasts

This study investigates whether probabilistic ozone forecasts from an ensemble can be made with skill; i.e., high verification resolution and reliability. Twenty-eight ozone forecasts were generated over the Lower Fraser Valley, British Columbia, Canada, for the 5-day period 11-15 August 2004, and compared with 1-hour averaged measurements of ozone concentrations at five stations. The forecasts were obtained by driving the CMAQ model with four meteorological forecasts and seven emission scenarios: a control run, {+-} 50% NO{sub x}, {+-} 50% VOC, and {+-} 50% NO{sub x} combined with VOC. Probabilistic forecast quality is verified using relative operating characteristic curves, Talagrand diagrams, and a new reliability index. Results show that both meteorology and emission perturbations are needed to have a skillful probabilistic forecast system--the meteorology perturbation is important to capture the ozone temporal and spatial distribution, and the emission perturbation is needed to span the range of ozone-concentration magnitudes. Emission perturbations are more important than meteorology perturbations for capturing the likelihood of high ozone concentrations. Perturbations involving NO{sub x} resulted in a more skillful probabilistic forecast for the episode analyzed, and therefore the 50% perturbation values appears to span much of the emission uncertainty for this case. All of the ensembles analyzed …
Date: March 20, 2006
Creator: Monache, L D; Hacker, J; Zhou, Y; Deng, X & Stull, R
System: The UNT Digital Library
Temperature response of 129Xe depolarization transfer and its application for ultra-sensitive NMR detection (open access)

Temperature response of 129Xe depolarization transfer and its application for ultra-sensitive NMR detection

Temporary trapping of atomic xenon in functionalized cryptophane cages makes the high sensitivity of hyperpolarized (hp) 129Xe available for highly specific NMR detection of biomolecules like proteins in solution. Here, we study the signal transfer onto a reservoir of unbound hp xenon by gating the residence time of the nuclei in the cage through the temperature-dependent exchange rate. Temperature changes were detectable immediately as an altered reservoir signal and yielded a sensitivity of 0.6 K. The temperature response is adjustable with lower concentrations of caged xenon providing more sensitivity at higher temperatures and allows ultra-sensitive detection of such molecular cages at 310 K. Functionalized cryptophane could be detected at concentrations as low as 10nM which corresponds to a 4000-fold sensitivity enhancement compared to conventional detection. This sensitivity makes hp-NMR capable of detecting such constructs in concentrations far belowthe detection limit by UV-visible light absorbance.
Date: March 20, 2008
Creator: Schroeder, Leif; Schroder, Leif; Meldrum, Tyler; Smith, Monica; Lowery, Thomas J.; Wemmer, David E. et al.
System: The UNT Digital Library
Reconstruction from Uniformly Attenuated SPECT Projection Data Using the DBH Method (open access)

Reconstruction from Uniformly Attenuated SPECT Projection Data Using the DBH Method

An algorithm was developed for the two-dimensional (2D) reconstruction of truncated and non-truncated uniformly attenuated data acquired from single photon emission computed tomography (SPECT). The algorithm is able to reconstruct data from half-scan (180o) and short-scan (180?+fan angle) acquisitions for parallel- and fan-beam geometries, respectively, as well as data from full-scan (360o) acquisitions. The algorithm is a derivative, backprojection, and Hilbert transform (DBH) method, which involves the backprojection of differentiated projection data followed by an inversion of the finite weighted Hilbert transform. The kernel of the inverse weighted Hilbert transform is solved numerically using matrix inversion. Numerical simulations confirm that the DBH method provides accurate reconstructions from half-scan and short-scan data, even when there is truncation. However, as the attenuation increases, finer data sampling is required.
Date: March 20, 2008
Creator: Huang, Qiu; You, Jiangsheng; Zeng, Gengsheng L. & Gullberg, Grant T.
System: The UNT Digital Library
A Kalman-filter bias correction of ozone deterministic, ensemble-averaged, and probabilistic forecasts (open access)

A Kalman-filter bias correction of ozone deterministic, ensemble-averaged, and probabilistic forecasts

Kalman filtering (KF) is used to postprocess numerical-model output to estimate systematic errors in surface ozone forecasts. It is implemented with a recursive algorithm that updates its estimate of future ozone-concentration bias by using past forecasts and observations. KF performance is tested for three types of ozone forecasts: deterministic, ensemble-averaged, and probabilistic forecasts. Eight photochemical models were run for 56 days during summer 2004 over northeastern USA and southern Canada as part of the International Consortium for Atmospheric Research on Transport and Transformation New England Air Quality (AQ) Study. The raw and KF-corrected predictions are compared with ozone measurements from the Aerometric Information Retrieval Now data set, which includes roughly 360 surface stations. The completeness of the data set allowed a thorough sensitivity test of key KF parameters. It is found that the KF improves forecasts of ozone-concentration magnitude and the ability to predict rare events, both for deterministic and ensemble-averaged forecasts. It also improves the ability to predict the daily maximum ozone concentration, and reduces the time lag between the forecast and observed maxima. For this case study, KF considerably improves the predictive skill of probabilistic forecasts of ozone concentration greater than thresholds of 10 to 50 ppbv, but …
Date: March 20, 2006
Creator: Monache, L D; Grell, G A; McKeen, S; Wilczak, J; Pagowski, M O; Peckham, S et al.
System: The UNT Digital Library
Cable Damage Detection Using Time Domain Reflectometry and Model-Based Algorithms (open access)

Cable Damage Detection Using Time Domain Reflectometry and Model-Based Algorithms

None
Date: March 20, 2008
Creator: Clark, G A
System: The UNT Digital Library
K-corrections and spectral templates of Type Ia supernovae (open access)

K-corrections and spectral templates of Type Ia supernovae

With the advent of large dedicated Type Ia supernova (SN Ia) surveys, K-corrections of SNe Ia and their uncertainties have become especially important in the determination of cosmological parameters. While K-corrections are largely driven by SN Ia broadband colors, it is shown here that the diversity in spectral features of SNe Ia can also be important. For an individual observation, the statistical errors from the inhomogeneity in spectral features range from 0.01 (where the observed and rest-frame filters are aligned) to 0.04 (where the observed and rest-frame filters are misaligned). To minimize the systematic errors caused by an assumed SN Ia spectral energy distribution (SED), we outline a prescription for deriving a mean spectral template time series that incorporates a large and heterogeneous sample of observed spectra. We then remove the effects of broadband colors and measure the remaining uncertainties in the K-corrections associated with the diversity in spectral features. Finally, we present a template spectroscopic sequence near maximum light for further improvement on the K-correction estimate. A library of ~;;600 observed spectra of ~;;100 SNe Ia from heterogeneous sources is used for the analysis.
Date: March 20, 2007
Creator: Nugent, Peter E.; Hsiao, E. Y.; Conley, A.; Howell, D. A.; Sullivan, M.; Pritchet, C. J. et al.
System: The UNT Digital Library
Relevance of international research facilities to international stability (open access)

Relevance of international research facilities to international stability

International Facilities have played an important play in expanding and keeping open a dialogue between east and west. The advent of glasnost has dramatically reduced inhibitions on communications and opened new opportunities for international facilities to facilitate the understanding and appreciation of common goals and common threats. This is accomplished through frank discussions in which real problems are identified and assessed while fictitious ones are laid to rest.
Date: March 20, 1989
Creator: Rosen, L.
System: The UNT Digital Library
Acceleration of polarized protons in AHF (Advanced Hadron Facility) (open access)

Acceleration of polarized protons in AHF (Advanced Hadron Facility)

In this paper an analysis of the depolarization expected during acceleration from 0.8 to 45.0 GeV kinetic energy in the Advanced Hadron Facility (AHF) accelerators is performed.
Date: March 20, 1987
Creator: Colton, E. P.
System: The UNT Digital Library
Safeguards research at Lawrence Livermore Laboratory (open access)

Safeguards research at Lawrence Livermore Laboratory

The LLL safeguards research program includes inspection methods, facility assessment methodologies, value-impact analysis, vulnerability analysis of accounting systems, compliance with regulations, process monitoring, etc. Each of those projects is described as are their goals and progress. (DLC)
Date: March 20, 1980
Creator: Dunn, D. R.; Huebel, J. G. & Poggio, A. J.
System: The UNT Digital Library
Impact of a reduced nuclear weapons stockpile on strategic stability (open access)

Impact of a reduced nuclear weapons stockpile on strategic stability

This presentation is to discuss the impact of a reduced nuclear weapons stockpile on the strategic stability. Methodologies used to study strategic stability issues include what are basically strategic-force exchange models. These models are used to simulate a massive nuclear exchange in which one side attacks and the other side retaliates. These models have been of interest to the Strategic Defense Initiative (SDI) program. Researchers have been looking at issues concerning the stability of the transition period, during which some defenses have been deployed and during which deterrence and war-fighting capability reply partly on defense and partly on offense. Also, more recently, with interest in the Strategic Arms Reduction Treaty (START) and force reductions beyond START, the same calculation engines have been used to examine the impact of reduced forces on strategic stability. For both the SDI and the START reduction cases, exchange models are able to address only a rather narrow class of strategic stability issues. Other broader stability questions that are unrelated to nuclear weapons or that relate to nuclear weapons but are not addressed by the calculational tools which are not included in this discussion. 6 refs., 1 fig., 1 tab. (BN)
Date: March 20, 1991
Creator: Chrzanowski, P.
System: The UNT Digital Library
Formation of negative hydrogen ions in surface and volume processes (open access)

Formation of negative hydrogen ions in surface and volume processes

The backscattering of energetic hydrogen particles, 1-1000 eV, from alkali metal surfaces provides for a relatively large yield of negative hydrogen ions. These yields are enhanced by particle reflection from surfaces consisting of partial alkali coatings over high-Z transition-metal substrates. The theoretical data supporting these observations are reviewed. The parameters leading to optimum reflection yields are summarized. In the volume of a hydrogen discharge with electron temperatures of about one electron volt, negative ions are formed by dissociative attachment to vibrationally excited molecules. The vibrational distribution is determined by e-V collisions between low energy electrons and vibrationally excited molecules, E-V singlet electron excitation processes caused by high energy (100 eV) electrons colliding with ground state molecules exciting to electronic states followed by radiative decay to higher vibrational levels, and V-T collisions between molecules resulting in transfer of vibrational excitation to translational energy. The role of these different processes as they bear on the vibrational distribution is discussed. The possibility of a volume-surface interaction leading to a high volume density of negative ions is considered.
Date: March 20, 1981
Creator: Hiskes, J.R.
System: The UNT Digital Library
Operation of the 8-T, 1-m-diameter test facility at Lawrence Livermore National Laboratory (open access)

Operation of the 8-T, 1-m-diameter test facility at Lawrence Livermore National Laboratory

The High-Field Test Facility (HFTF) being built at Lawrence Livermore National Laboratory (LLNL) consists of a set of four Nb-Ti coils, inside of which there is a pair of multifilamentary Nb/sub 3/Sn coils. The outer coils are designed to generate 8 T in the 1-m bore; the Nb/sub 3/Sn coils will boost this to 12 T in a 40-cm bore. This paper describes the first operation of the complete set of Nb-Ti coils and describes and gives results from the data acquisition and analysis system that was used during the test.
Date: March 20, 1981
Creator: Zbasnik, J. P.; Cornish, D. N.; Scanlan, R. M.; Leber, R. L.; Chaplin, M. R.; Rosdahl, A. R. et al.
System: The UNT Digital Library
New Constraints on Isospin-Violating Dark Matter (open access)

New Constraints on Isospin-Violating Dark Matter

None
Date: March 20, 2013
Creator: Kumar, Jason; U., /Hawaii; Sanford, David; /UC, Irvine; Strigari, Louis E. & /KIPAC, Menlo Park /Stanford U., Phys. Dept.
System: The UNT Digital Library
W+n-Jet Predictions With MC@NLO in Sherpa (open access)

W+n-Jet Predictions With MC@NLO in Sherpa

Results for the production of W-bosons in conjunction with up to three jets including parton shower corrections are presented and compared to recent LHC data. These results consistently incorporate the full next-to leading order QCD corrections through the MC{at}NLO method, as implemented in the SHERPA event generator, with the virtual corrections obtained from the BLACKHAT library.
Date: March 20, 2012
Creator: Hoeche, Stefan; Krauss, Frank; Schonherr, Marek & Siegert, Frank
System: The UNT Digital Library
Study of CP violation in Dalitz-plot analyses of B0 to K K-KS, B to K K-K , and B to KSKSK (open access)

Study of CP violation in Dalitz-plot analyses of B0 to K K-KS, B to K K-K , and B to KSKSK

We perform amplitude analyses of the decays B{sup 0} {yields} K{sup +}K{sup -}K{sub s}{sup 0}, B{sup +} {yields} K{sup +}K{sup -}K{sup +}, and B{sup +} {yields}, and measure CP-violating parameters and partial branching fractions. The results are based on a data sample of approximately 470 x 10{sup 6} B{bar B} decays, collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the SLAC National Accelerator Laboratory. For B{sup +} {yields} K{sup +}K{sup -}K{sup +}, we find a direct CP asymmetry in B{sup +} {yields} {phi}(1020)K{sup +} of A{sub CP} = (12.8 {+-} 4.4 {+-} 1.3)%, which differs from zero by 2.8{sigma}. For B{sup 0} {yields} K{sup +}K{sup -}K{sub s}{sup 0}, we measure the CP-violating phase {beta}{sub eff} ({phi}(1020)K{sub s}{sup 0}) = (21 {+-} 6 {+-} 2){sup o}. For B{sup +} {yields} K{sub s}{sup 0}K{sub s}{sup 0}K{sup +}, we measure an overall direct CP asymmetry of A{sub CP} = (4{sub -5}{sup +4} {+-} 2)%. We also perform an angular-moment analysis of the three channels, and determine that the f{sub X}(1500) state can be described well by the sum of the resonances f{sub 0}(1500), f{prime}{sub 2}(1525), and f{sub 0}(1710).
Date: March 20, 2012
Creator: Lees, J.P.
System: The UNT Digital Library
Hiding a Heavy Higgs Boson at the 7 TeV LHC (open access)

Hiding a Heavy Higgs Boson at the 7 TeV LHC

A heavy Standard Model Higgs boson is not only disfavored by electroweak precision observables but is also excluded by direct searches at the 7 TeV LHC for a wide range of masses. Here, we examine scenarios where a heavy Higgs boson can be made consistent with both the indirect constraints and the direct null searches by adding only one new particle beyond the Standard Model. This new particle should be a weak multiplet in order to have additional contributions to the oblique parameters. If it is a color singlet, we find that a heavy Higgs with an intermediate mass of 200-300 GeV can decay into the new states, suppressing the branching ratios for the standard model modes, and thus hiding a heavy Higgs at the LHC. If the new particle is also charged under QCD, the Higgs production cross section from gluon fusion can be reduced significantly due to the new colored particle one-loop contribution. Current collider constraints on the new particles allow for viable parameter space to exist in order to hide a heavy Higgs boson. We categorize the general signatures of these new particles, identify favored regions of their parameter space and point out that discovering or excluding …
Date: March 20, 2012
Creator: Bai, Yang; Fan, JiJi & Hewett, JoAnne L.
System: The UNT Digital Library
Dark Matter Profiles and Annihilation in Dwarf Spheroidal Galaxies: Prospectives for Present and Future Gamma-Ray Observatories - I. the Classical DSphs (open access)

Dark Matter Profiles and Annihilation in Dwarf Spheroidal Galaxies: Prospectives for Present and Future Gamma-Ray Observatories - I. the Classical DSphs

None
Date: March 20, 2013
Creator: Charbonnier, A.; /Paris U., VI-VII; Combet, C.; U., /Leicester; Daniel, M.; U., /Durham et al.
System: The UNT Digital Library
Expansion of the Genomic Encyclopedia of Bacteria and Archaea (open access)

Expansion of the Genomic Encyclopedia of Bacteria and Archaea

To date the vast majority of bacterial and archaeal genomes sequenced are of rather limited phylogenetic diversity as they were chosen based on their physiology and/ or medical importance. The Genomic Encyclopedia of Bacteria and Archaea (GEBA) project (Wu et al. 2009) is aimed to systematically filling the gaps of the tree of life with phylogenetically diverse reference genomes. However more than 99percent of microorganisms elude current culturing attempts, severely limiting the ability to recover complete or even partial genomes of these largely mysterious species. These limitations gave rise to the GEBA uncultured project. Here we propose to use single cell genomics to massively expand the Genomic Encyclopedia of Bacteria and Archaea by targeting 80 single cell representatives of uncultured candidate phyla which have no or very few cultured representatives. Generating these reference genomes of uncultured microbes will dramatically increase the discovery rate of novel protein families and biological functions, shed light on the numerous underrepresented phyla that likely play important roles in the environment, and will assist in improving the reconstruction of the evolutionary history of Bacteria and Archaea. Moreover, these data will improve our ability to interpret metagenomics sequence data from diverse environments, which will be of tremendous …
Date: March 20, 2011
Creator: Rinke, Christian; Sczyrba, Alex; Malfatti, Stephanie; Lee, Janye; Cheng, Jan-Fang; Stepanauskas, Ramunas et al.
System: The UNT Digital Library