A fast contour descriptor algorithm for supernova imageclassification (open access)

A fast contour descriptor algorithm for supernova imageclassification

We describe a fast contour descriptor algorithm and its application to a distributed supernova detection system (the Nearby Supernova Factory) that processes 600,000 candidate objects in 80 GB of image data per night. Our shape-detection algorithm reduced the number of false positives generated by the supernova search pipeline by 41% while producing no measurable impact on running time. Fourier descriptors are an established method of numerically describing the shapes of object contours, but transform-based techniques are ordinarily avoided in this type of application due to their computational cost. We devised a fast contour descriptor implementation for supernova candidates that meets the tight processing budget of the application. Using the lowest-order descriptors (F{sub 1} and F{sub -1}) and the total variance in the contour, we obtain one feature representing the eccentricity of the object and another denoting its irregularity. Because the number of Fourier terms to be calculated is fixed and small, the algorithm runs in linear time, rather than the O(n log n) time of an FFT. Constraints on object size allow further optimizations so that the total cost of producing the required contour descriptors is about 4n addition/subtraction operations, where n is the length of the contour.
Date: July 16, 2006
Creator: Aragon, Cecilia R. & Aragon, David Bradburn
Object Type: Article
System: The UNT Digital Library
Development of ITER 15 MA ELMy H-mode Inductive Scenario (open access)

Development of ITER 15 MA ELMy H-mode Inductive Scenario

The poloidal field (PF) coil system on ITER, which provides both feedforward and feedback control of plasma position, shape, and current, is a critical element for achieving mission performance. Analysis of PF capabilities has focused on the 15 MA Q = 10 scenario with a 300-500 s flattop burn phase. The operating space available for the 15 MA ELMy H-mode plasma discharges in ITER and upgrades to the PF coils or associated systems to establish confidence that ITER mission objectives can be reached have been identified. Time dependent self-consistent free-boundary calculations were performed to examine the impact of plasma variability, discharge programming, and plasma disturbances. Based on these calculations a new reference scenario was developed based upon a large bore initial plasma, early divertor transition, low level heating in L-mode, and a late H-mode onset. Equilibrium analyses for this scenario indicate that the original PF coil limitations do not allow low li (<0.8) operation or lower flux states, and the flattop burn durations were predicted to be less than the desired 400 s. This finding motivates the expansion of the operating space, considering several upgrade options to the PF coils. Analysis was also carried out to examine the feedback current …
Date: October 16, 2008
Creator: Kessel, C. E.; Campbell, D.; Gribov, Y.; Saibene, G.; Ambrosino, G.; Casper, T. et al.
Object Type: Article
System: The UNT Digital Library
An Analysis of the DER Adoption Climate in Japan UsingOptimization Results for Prototype Buildings with U.S. Comparisons (open access)

An Analysis of the DER Adoption Climate in Japan UsingOptimization Results for Prototype Buildings with U.S. Comparisons

This research demonstrates economically optimal distributedenergy resource (DER) system choice using the DER choice and operationsoptimization program, the Distributed Energy Resources Customer AdoptionModel (DER-CAM). DER-CAM finds the optimal combination of installedequipment given prevailing utility tariffs and fuel prices, siteelectrical and thermal loads (including absorption cooling), and a menuof available equipment. It provides a global optimization, albeitidealized, that shows how site useful energy loads can be served atminimum cost. Five prototype Japanese commercial buildings are examinedand DER-CAM is applied to select the economically optimal DER system foreach. Based on the optimization results, energy and emission reductionsare evaluated. Significant decreases in fuel consumption, carbonemissions, and energy costs were seen in the DER-CAM results. Savingswere most noticeable in the prototype sports facility, followed by thehospital, hotel, and office building. Results show that DER with combinedheat and power equipment is a promising efficiency and carbon mitigationstrategy, but that precise system design is necessary. Furthermore, aJapan-U.S. comparison study of policy, technology, and utility tariffsrelevant to DER installation is presented.
Date: June 16, 2006
Creator: Zhou, Nan; Marnay, Chris; Firestone, Ryan; Gao, Weijun & Nishida,Masaru
Object Type: Article
System: The UNT Digital Library
2006 Oak Ridge National Laboratory Annual Illness and Injury Surveillance Report (open access)

2006 Oak Ridge National Laboratory Annual Illness and Injury Surveillance Report

The U.S. Department of Energy’s (DOE) commitment to assuring the health and safety of its workers includes the conduct of illness and injury surveillance activities that provide an early warning system to detect health problems among workers. The Illness and Injury Surveillance Program monitors illnesses and health conditions that result in an absence, occupational injuries and illnesses, and disabilities and deaths among current workers.
Date: May 16, 2008
Creator: United States. Department of Energy. Office of Health, Safety, and Security.
Object Type: Report
System: The UNT Digital Library
NERSC Cyber Security Challenges That Require DOE Development andSupport (open access)

NERSC Cyber Security Challenges That Require DOE Development andSupport

Traditional security approaches do not adequately addressall the requirements of open, scientific computing facilities. Many ofthe methods used for more restricted environments, including almost allcorporate/commercial systems, do not meet the needs of today's science.Use of only the available "state of the practice" commercial methods willhave adverse impact on the ability of DOE to accomplish its sciencegoals, and impacts the productivity of the DOE Science community. Inparticular, NERSC and other high performance computing (HPC) centers havespecial security challenges that are unlikely to be met unless DOE fundsdevelopment and support of reliable and effective tools designed to meetthe cyber security needs of High Performance Science. The securitychallenges facing NERSC can be collected into three basic problem sets:network performance and dynamics, application complexity and diversity,and a complex user community that can have transient affiliations withactual institutions. To address these problems, NERSC proposes thefollowing four general solutions: auditing user and system activityacross sites; firewall port configuration in real time;cross-site/virtual organization identity management and access control;and detecting security issues in application middleware. Solutions arealsoproposed for three general long term issues: data volume,application complexity, and information integration.
Date: January 16, 2007
Creator: Draney, Brent; Campbell, Scott & Walter, Howard
Object Type: Report
System: The UNT Digital Library
MULTISCALE MODELING OF POLYMER NANOCOMPOSITES (open access)

MULTISCALE MODELING OF POLYMER NANOCOMPOSITES

Polymer Nanocomposites are an important class of nanomaterials with potential applications including but not limited to structural and cushion materials, electromagnetic and heat shields, conducting plastics, sensors, and catalysts for various chemical and bio processes. Success in most such applications hinges on molecular-level control of structure and assembly, and a deep understanding of how the overall morphology of various components and the interfaces between them affect the composite properties at the macroscale. The length and time-scales associated with such assemblies are prohibitively large for a full atomistic modeling. Instead we adopt a multiscale methodology in which atomic-level interactions between different components of a composite are incorporated into a coarse-grained simulation of the mesoscale morphology, which is then represented on a numerical grid and the macroscopic properties computed using a finite-elements method.
Date: July 16, 2007
Creator: Maiti, A
Object Type: Article
System: The UNT Digital Library
Solution Verification Linked to Model Validation, Reliability, and Confidence (open access)

Solution Verification Linked to Model Validation, Reliability, and Confidence

The concepts of Verification and Validation (V&V) can be oversimplified in a succinct manner by saying that 'verification is doing things right' and 'validation is doing the right thing'. In the world of the Finite Element Method (FEM) and computational analysis, it is sometimes said that 'verification means solving the equations right' and 'validation means solving the right equations'. In other words, if one intends to give an answer to the equation '2+2=', then one must run the resulting code to assure that the answer '4' results. However, if the nature of the physics or engineering problem being addressed with this code is multiplicative rather than additive, then even though Verification may succeed (2+2=4 etc), Validation may fail because the equations coded are not those needed to address the real world (multiplicative) problem. We have previously provided a 4-step 'ABCD' quantitative implementation for a quantitative V&V process: (A) Plan the analyses and validation testing that may be needed along the way. Assure that the code[s] chosen have sufficient documentation of software quality and Code Verification (i.e., does 2+2=4?). Perform some calibration analyses and calibration based sensitivity studies (these are not validated sensitivities but are useful for planning purposes). Outline the …
Date: June 16, 2004
Creator: Logan, R W & Nitta, C K
Object Type: Report
System: The UNT Digital Library
Radiochemical Analyses of the Filter Cake, Granular Activated Carbon, and Treated Ground Water from the DTSC Stringfellow Superfund Site Pretreatment Plant (open access)

Radiochemical Analyses of the Filter Cake, Granular Activated Carbon, and Treated Ground Water from the DTSC Stringfellow Superfund Site Pretreatment Plant

The Department of Toxic Substance Control (DTSC) requested that Lawrence Livermore National Laboratory (LLNL) evaluate the treatment process currently employed at the Department's Stringfellow Superfund Site Pretreatment Plant (PTP) site to determine if wastes originating from the site were properly managed with regards to their radioactivity. In order to evaluate the current management strategy, LLNL suggested that DTSC characterize the effluents from the waste treatment system for radionuclide content. A sampling plan was developed; samples were collected and analyzed for radioactive constituents. Following is brief summary of those results and what implications for waste characterization may be made. (1) The sampling and analysis provides strong evidence that the radionuclides present are Naturally Occurring Radioactive Material (NORM). (2) The greatest source of radioactivity in the samples was naturally occurring uranium. The sample results indicate that the uranium concentration in the filter cake is higher than the Granular Activated Carbon (GAC) samples. (11 -14 and 2-6 ppm respectively). (3) No radiologic background for geologic materials has been established for the Stringfellow site, and comprehensive testing of the process stream has not been conducted. Without site-specific testing of geologic materials and waste process streams, it is not possible to conclude if filter cake …
Date: September 16, 2005
Creator: Esser, B K; McConachie, W; Fischer, R; Sutton, M & Szechenyi, S
Object Type: Report
System: The UNT Digital Library
Dynamics of Adipocyte Turnover in Humans (open access)

Dynamics of Adipocyte Turnover in Humans

Obesity is increasing in an epidemic fashion in most countries and constitutes a public health problem by enhancing the risk for cardiovascular disease and metabolic disorders such as type 2 diabetes. Owing to the increase in obesity, life expectancy may start to decrease in developed countries for the first time in recent history. The factors determining fat mass in adult humans are not fully understood, but increased lipid storage in already developed fat cells is thought to be most important. We show that adipocyte number is a major determinant for the fat mass in adults. However, the number of fat cells stays constant in adulthood in lean and obese and even under extreme conditions, indicating that the number of adipocytes is set during childhood and adolescence. To establish the dynamics within the stable population of adipocytes in adults, we have measured adipocyte turnover by analyzing the integration of {sup 14}C derived from nuclear bomb tests in genomic DNA. Approximately 10% of fat cells are renewed annually at all adult ages and levels of body mass index. Neither adipocyte death nor generation rate is altered in obesity, suggesting a tight regulation of fat cell number that is independent of metabolic profile …
Date: July 16, 2007
Creator: Spalding, K; Arner, E; Westermark, P; Bernard, S; Buchholz, B; Bergmann, O et al.
Object Type: Article
System: The UNT Digital Library
The L_X-M relation of Clusters of Galaxies (open access)

The L_X-M relation of Clusters of Galaxies

We present a new measurement of the scaling relation between X-ray luminosity and total mass for 17,000 galaxy clusters in the maxBCG cluster sample. Stacking sub-samples within fixed ranges of optical richness, N200, we measure the mean 0.1-2.4 keV X-ray luminosity, <L{sub X}>, from the ROSAT All-Sky Survey. The mean mass, <M{sub 200}>, is measured from weak gravitational lensing of SDSS background galaxies (Johnston et al. 2007). For 9 {le} N{sub 200} < 200, the data are well fit by a power-law, <L{sub X}>/10{sup 42} h{sup -2} ergs{sup -1} = (12.6{sub -1.3}{sup +1.4}(stat) {+-} 1.6 (sys)) (<M{sub 200}>/10{sup 14} h{sup -1} M{sub {circle_dot}}){sup 1.65{+-}0.13}. The slope agrees to within 10% with previous estimates based on X-ray selected catalogs, implying that the covariance in L{sub X} and N{sub 200} at fixed halo mass is not large. The luminosity intercept is 30%, or 2{sigma}, lower than determined from the X-ray flux-limited sample of Reiprich & Boehringer (2002), assuming hydrostatic equilibrium. This slight difference could arise from a combination of Malmquist bias and/or systematic error in hydrostatic mass estimates, both of which are expected. The intercept agrees with that derived by Stanek et al. (2006) using a model for the statistical correspondence between …
Date: May 16, 2008
Creator: Rykoff, E. S.; Evrard, A. E.; McKay, T. A.; Becker, M. R.; Johnston, D. E.; Koester, B. P. et al.
Object Type: Report
System: The UNT Digital Library
Relative Biological Effectiveness of HZE Fe Ions for Induction of Micro-Nuclei at Low Doses (open access)

Relative Biological Effectiveness of HZE Fe Ions for Induction of Micro-Nuclei at Low Doses

Dose-response curves for induction of micro-nuclei (MN) was measured in Chinese hamster V79 and xrs6 (Ku80-) cells and in human mammary epithelial MCF10A cells in the dose range of 0.05-1 Gy. The Chinese Hamster cells were exposed to 1 GeV/u Fe ions, 600 MeV/u Fe ions, and 300 MeV/u Fe ions (LETs of 151, 176 and 235 keV/{micro}m respectively) as well as with 320 kVp X-rays as reference. Second-order polynomials were fitted to the induction curves and the initial slopes (the alpha values) were used to calculate RBE. For the repair proficient V79 cells the RBE at these low doses increased with LET. The values obtained were 3.1 (LET=151 keV/{micro}m), 4.3 (LET = 176 keV/{micro}m) and 5.7 (LET = 235 keV/{micro}m), while the RBE was close to 1 for the repair deficient xrs6 cells regardless of LET. For the MCF10A cells the RBE was determined for 1 GeV/u Fe ions and found to be 5.4, slightly higher than for V79 cells. To test the effect of shielding, the 1 GeV/u Fe ion beam was intercepted by various thickness of high-density polyethylene plastic absorbers, which resulted in energy loss and fragmentation. It was found that the MN yield for V79 cells …
Date: January 16, 2007
Creator: Groesser, Torsten; Chun, Eugene & Rydberg, Bjorn
Object Type: Article
System: The UNT Digital Library
B Counting at BaBar (open access)

B Counting at BaBar

In this thesis we examine the method of counting B{bar B} events produced in the BABAR experiment. The original method was proposed in 2000, but improvements to track reconstruction and our understanding of the detector since that date make it appropriate to revisit the B Counting method. We propose a new set of cuts designed to minimize the sensitivity to time-varying backgrounds. We find the new method counts B{bar B} events with an associated systematic uncertainty of {+-} 0.6%.
Date: December 16, 2008
Creator: McGregor, Grant Duncan
Object Type: Report
System: The UNT Digital Library
Multidimensional Conservation Laws and Low Regularity Solutions (open access)

Multidimensional Conservation Laws and Low Regularity Solutions

This is the concluding report for the project, a continuation of research by Keyfitz and co-workers on multidimensional conservation laws, and applications of nonhyperbolic conservation laws in the two-fluid model for multiphase flow. The multidimensional research project was started with Suncica Canic, at the University of Houston and with Eun Heui Kim, now at California State University Long Beach. Two postdoctoral researchers, Katarina Jegdic and Allen Tesdall, also worked on this research. Jegdic's research was supported (for a total of one year) by this grant. Work on nonhyperbolic models for two-phase flows is being pursued jointly with Michael Sever, Hebrew University. Background for the project is contained in earlier reports. Note that in 2006, the project received a one-year no-cost extension that will end in September, 2007. A new proposal, for continuation of the research and for new projects, will be submitted in the Fall of 2007, with funding requested to begin in the summer of 2008. The reason for the 'funding gap' is Keyfitz's four-year stint as Director of the Fields Institute in Toronto, Canada. The research has continued, but has been supported by Canadian grant funds, as seems appropriate during this period.
Date: June 16, 2007
Creator: Keyfitz, Barbara Lee
Object Type: Report
System: The UNT Digital Library
Furnace Blower Electricity: National and Regional Savings Potential (open access)

Furnace Blower Electricity: National and Regional Savings Potential

Currently, total electricity consumption of furnaces is unregulated, tested at laboratory conditions using the DOE test procedure, and is reported in the GAMA directory as varying from 76 kWh/year to 1,953 kWh/year. Furnace blowers account for about 80percent of the total furnace electricity consumption and are primarily used to distribute warm air throughout the home during furnace operation as well as distribute cold air during air conditioning operation. Yet the furnace test procedure does not provide a means to calculate the electricity consumption during cooling operation or standby, which account for a large fraction of the total electricity consumption. Furthermore, blower electricity consumption is strongly affected by static pressure. Field data shows that static pressure in the house distribution ducts varies widely and that the static pressure used in the test procedure as well as the calculated fan power is not representative of actual field installations. Therefore, accurate determination of the blower electricity consumption is important to address electricity consumption of furnaces and air conditioners. This paper compares the potential regional and national energy savings of two-stage brushless permanent magnet (BPM) blower motors (the blower design option with the most potential savings that is currently available in the market) to …
Date: May 16, 2008
Creator: Center, Florida Solar Energy; Franco, Victor; Franco, Victor; Lutz, Jim; Lekov, Alex & Gu, Lixing
Object Type: Article
System: The UNT Digital Library
CFD Analysis for the Applicability of the Natural Convection Shutdown Heat Removal Test Facility (NSTF) for the Simulation of the Vhtr Rccs. Topical Report. (open access)

CFD Analysis for the Applicability of the Natural Convection Shutdown Heat Removal Test Facility (NSTF) for the Simulation of the Vhtr Rccs. Topical Report.

The Very High Temperature gas cooled reactor (VHTR) is one of the GEN IV reactor concepts that have been proposed for thermochemical hydrogen production and other process-heat applications like coal gasification. The USDOE has selected the VHTR for further research and development, aiming to demonstrate emissions-free electricity and hydrogen production at a future time. One of the major safety advantages of the VHTR is the potential for passive decay heat removal by natural circulation of air in a Reactor Cavity Cooling System (RCCS). The air-side of the RCCS is very similar to the Reactor Vessel Auxiliary Cooling System (RVACS) that has been proposed for the PRISM reactor design. The design and safety analysis of the RVACS have been based on extensive analytical and experimental work performed at ANL. The Natural Convective Shutdown Heat Removal Test Facility (NSTF) at ANL that simulates at full scale the air-side of the RVACS was built to provide experimental support for the design and analysis of the PRISM RVACS system. The objective of this work is to demonstrate that the NSTF facility can be used to generate RCCS experimental data: to validate CFD and systems codes for the analysis of the RCCS; and to support …
Date: May 16, 2007
Creator: Tzanos, C. P.
Object Type: Report
System: The UNT Digital Library
Long-Term Modeling of Solar Energy: Analysis of Concentrating Solar Power (CSP) and PV Technologies (open access)

Long-Term Modeling of Solar Energy: Analysis of Concentrating Solar Power (CSP) and PV Technologies

This report presents an overview of research conducted on solar energy technologies and their implementation in the ObjECTS framework. The topics covered include financing assumptions and selected issues related to the integration of concentrating thermal solar power (CSP) and photovoltaics PV technologies into the electric grid. A review of methodologies for calculating the levelized energy cost of capital-intensive technologies is presented, along with sensitivity tests illustrating how the cost of a solar plant would vary depending on financing assumptions. An analysis of the integration of a hybrid concentrating thermal solar power (CSP) system into the electric system is conducted. Finally a failure statistics analysis for PV plants illustrates the central role of solar irradiance uncertainty in determining PV grid integration characteristics.
Date: August 16, 2007
Creator: Zhang, Yabei & Smith, Steven J.
Object Type: Report
System: The UNT Digital Library
Estimates of Optimal Backward Perturbations for Linear LeastSquares Problems (open access)

Estimates of Optimal Backward Perturbations for Linear LeastSquares Problems

Numerical tests are used to validate a practical estimatefor the optimal backward errors of linear least squares problems. Thissolves a thirty-year-old problem suggested by Stewart andWilkinson.
Date: July 16, 2007
Creator: Grcar, Joseph F.; Saunders, M.A. & Su, Zheng
Object Type: Article
System: The UNT Digital Library
HOM and LOM Coupler Optimizations for the ILC Crab Cavity (open access)

HOM and LOM Coupler Optimizations for the ILC Crab Cavity

None
Date: July 16, 2007
Creator: Xiao, L.; Ko, K.; Li, Z.; Ng, C.; Schussman, G.; Seryi, A. et al.
Object Type: Article
System: The UNT Digital Library
On the non-invariance of space and time scale ranges under Lorentztransformation, and its implications for the study of relativisticinteractions (open access)

On the non-invariance of space and time scale ranges under Lorentztransformation, and its implications for the study of relativisticinteractions

We present an analysis which shows that the ranges of space and time scales spanned by a system are not invariant under the Lorentz transformation. This implies the existence of a frame of reference which minimizes an aggregate measure of the range of space and time scales. Such a frame is derived for example cases: free electron laser, laser-plasma accelerator, and particle beam interacting with electron clouds. Implications for experimental, theoretical and numerical studies are discussed. The most immediate relevance is the reduction by orders of magnitude in computer simulation run times for such systems.
Date: January 16, 2007
Creator: Vay, J. L.
Object Type: Article
System: The UNT Digital Library
Effect of Titanium Substitution on the Compatiblity of Electrodeswith Pyrrolidinium-Based Ionic Liquid Electrolytes (open access)

Effect of Titanium Substitution on the Compatiblity of Electrodeswith Pyrrolidinium-Based Ionic Liquid Electrolytes

The quest for the development of rechargeable lithium-metal batteries has attracted vigorous worldwide research efforts because this system offers the highest theoretical specific energy [1]. For this to be achieved, the repetitive deposition and stripping of lithium must be close to fully reversible. Thus, alternative electrolytes have been investigated, such as the room-temperature ionic liquid (RTILs). Lithium can be cycled with a high degree of reversibility with efficiencies exceeding 99% using systems based on N-methyl N-alkyl pyrrolidinium (P{sub 1X}{sup +}) combined with the TFSI anion [2]. More recent efforts have been directed towards systems based on P{sub 1X}{sup +} cations with the FSI anion and appear to be even more promising [3,4]. In this work, we discuss to what extent RTILs based on P{sub 1X}{sup +} cations with TFSI or FSI anions can be used as electrolytes for rechargeable Li batteries. In particular, their physical and chemical properties are thoroughly discussed so as to explain the difference observed in their electrochemical behavior. Although these two systems seem to be stable against lithium, their compatibilities with cathode materials require full assessment as well. Thus, various manganese oxide cathodes are investigated in this study. Strategies to minimize cathode dissolution are also debated, …
Date: May 16, 2007
Creator: Saint, Juliette A.; Shin, Joon-Ho; Best, Adam; Hollenkamp,Anthony; Kerr, John & Doeff, Marca M.
Object Type: Article
System: The UNT Digital Library
The Assembly of Galaxy Clusters (open access)

The Assembly of Galaxy Clusters

We study the formation of fifty-three galaxy cluster-size dark matter halos (M = 10{sup 14.0-14.76} M{sub {circle_dot}}) formed within a pair of cosmological {Lambda}CDM N-body simulations, and track the accretion histories of cluster subhalos with masses large enough to host {approx} 0.1L{sub *} galaxies. By associating subhalos with cluster galaxies, we find the majority of galaxies in clusters experience no 'pre-processing' in the group environment prior to their accretion into the cluster. On average, {approx} 70% of cluster galaxies fall into the cluster potential directly from the field, with no luminous companions in their host halos at the time of accretion; and less than {approx} 12% are accreted as members of groups with five or more galaxies. Moreover, we find that cluster galaxies are significantly less likely to have experienced a merger in the recent past ({approx}< 6 Gyr) than a field halo of the same mass. These results suggest that local, cluster processes like ram-pressure stripping, galaxy harassment, or strangulation play the dominant role in explaining the difference between cluster and field populations at a fixed stellar mass; and that pre-evolution or past merging in the group environment is of secondary importance for setting cluster galaxy properties for most …
Date: May 16, 2008
Creator: Berrier, Joel C.; Stewart, Kyle R.; Bullock, James S.; Purcell, Chris W.; Barton, Elizabeth J. & Wechsler, Risa H.
Object Type: Article
System: The UNT Digital Library
A Study of Factorization and a Measurement of CP Violation (open access)

A Study of Factorization and a Measurement of CP Violation

We report on a study of the decay {bar B}{sup 0} {yields} D*{sup +} {omega}{pi}{sup -} with the BABAR detector at the PEP-II B-factory at the Stanford Linear Accelerator Center. Based on a sample of 232 million B{sup 0}{bar B}{sup 0} decays collected between 1999 and 2004, we measure the branching fraction {Beta}({bar B}{sup 0} {yields} D*{sup +} {omega}{pi}{sup -}) = (2.88 {+-} 0.21(stat.) {+-} 0.31(syst.)) x 10{sup -3}. We study the invariant mass spectrum of the {omega}{pi}{sup -} system in this decay. This spectrum is in good agreement with expectations based on factorization and the measured spectrum in {tau}{sup -} {yields} {omega}{pi}{sup -} {nu}{sub {tau}}. We also measure the polarization of the D*{sup +} as a function of the {omega}{pi}{sup -} mass. In the mass region 1.1 to 1.9 GeV we measure the fraction of longitudinal polarization of the D*{sup +} to be {Lambda}{sub L}/{Lambda} = 0.654 {+-} 0.042(stat.) {+-} 0.016(syst.). This is in agreement with the expectations from heavy-quark effective theory and factorization assuming that the decay proceeds as {bar B}{sup 0} {yields} D*{sup +} {rho}(1450){sup -}, {rho}(1450){sup -} {yields} {omega}{pi}{sup -}. Furthermore, we present the results on the time-dependent CP asymmetry in neutral B meson decays to …
Date: January 16, 2008
Creator: Dahmes, Bryan
Object Type: Thesis or Dissertation
System: The UNT Digital Library
ARPES study of the evolution of band structure and charge density wave properties in RTe3 ( R=Y , La, Ce, Sm, Gd, Tb, and Dy) (open access)

ARPES study of the evolution of band structure and charge density wave properties in RTe3 ( R=Y , La, Ce, Sm, Gd, Tb, and Dy)

We present a detailed angle-resolved photoemission spectroscopy (ARPES) investigation of the RTe3 family, which sets this system as an ideal"textbook" example for the formation of a nesting driven charge density wave (CDW). This family indeed exhibits the full range of phenomena that can be associated to CDWinstabilities, from the opening of large gaps on the best nested parts of Fermi surface (up to 0.4 eV), to the existence of residual metallic pockets. ARPES is the best suited technique to characterize these features, thanks to its unique ability to resolve the electronic structure in k space. An additional advantage of RTe3 is that theband structure can be very accurately described by a simple two dimensional tight-binding (TB) model, which allows one to understand and easily reproduce many characteristics of the CDW. In this paper, we first establish the main features of the electronic structure by comparing our ARPES measurements with the linear muffin-tinorbital band calculations. We use this to define the validity and limits of the TB model. We then present a complete description of the CDW properties and of their strong evolution as a function of R. Using simple models, we are able to reproduce perfectly the evolution of gaps …
Date: January 16, 2008
Creator: Hussain, Zahid; Brouet, Veronique; Yang, Wanli; Zhou, Xingjiang; Hussain, Zahid; Moore, R. G. et al.
Object Type: Article
System: The UNT Digital Library
Giant Dipole Resonance in the hot and thermalized 132Ce nucleus: damping of collective modes at finite temperature (open access)

Giant Dipole Resonance in the hot and thermalized 132Ce nucleus: damping of collective modes at finite temperature

The {gamma} decay of the Giant Dipole Resonance in the {sup 132}Ce compound nucleus with temperature up to {approx} 4 MeV has been measured. The symmetric {sup 64}Ni + {sup 68}Zn at E{sub beam} = 300, 400, 500 MeV and the asymmetric reaction {sup 16}O + {sup 116}Sn at E{sub beam} = 130, 250 MeV have been investigated. Light charged particles and {gamma} rays have been detected in coincidence with the recoiling compound system. In the case of the mass symmetric {sup 64}Ni induced reaction the {gamma} and charged particle spectral shapes are found to be consistent with the emission from a fully equilibrated compound nuclei and the GDR parameters are extracted from the data using a statistical model analysis. The GDR width is found to increase almost linear with temperature. This increase is rather well reproduced within a model which includes both the thermal fluctuation of the nuclear shape and the lifetime of the compound nucleus.
Date: June 16, 2006
Creator: Wieland, O.; Bracco, A.; Camera, F.; Benzoni, G.; Blasi, N.; Brambilla, S. et al.
Object Type: Article
System: The UNT Digital Library