Time-resolved THz studies of carrier dynamics in semiconductors, superconductors, and strongly-correlated electron materials (open access)

Time-resolved THz studies of carrier dynamics in semiconductors, superconductors, and strongly-correlated electron materials

Perhaps the most important aspect of contemporary condensed matter physics involves understanding strong Coulomb interactions between the large number of electrons in a solid. Electronic correlations lead to the emergence of new system properties, such as metal-insulator transitions, superconductivity, magneto-resistance, Bose-Einstein condensation, the formation of excitonic gases, or the integer and fractional Quantum Hall effects. The discovery of high-Tc superconductivity in particular was a watershed event, leading to dramatic experimental and theoretical advances in the field of correlated-electron systems. Such materials often exhibit competition between the charge, lattice, spin, and orbital degrees of freedom, whose cause-effect relationships are difficult to ascertain. Experimental insight into the properties of solids is traditionally obtained by time-averaged probes, which measure e.g., linear optical spectra, electrical conduction properties, or the occupied band structure in thermal equilibrium. Many novel physical properties arise from excitations out of the ground state into energetically higher states by thermal, optical, or electrical means. This leads to fundamental interactions between the system's constituents, such as electron-phonon and electron-electron interactions, which occur on ultrafast timescales. While these interactions underlie the physical properties of solids, they are often only indirectly inferred from time-averaged measurements. Time-resolved spectroscopy, consequently, is playing an ever increasing role …
Date: November 14, 2006
Creator: Kaindl, Robert A. & Averitt, Richard D.
Object Type: Book
System: The UNT Digital Library
GASP: A Performance Analysis Tool Interface for Global AddressSpace Programming Models, Version 1.5 (open access)

GASP: A Performance Analysis Tool Interface for Global AddressSpace Programming Models, Version 1.5

Due to the wide range of compilers and the lack of astandardized performance tool interface, writers of performance toolsface many challenges when incorporating support for global address space(GAS) programming models such as Unified Parallel C (UPC), Titanium, andCo-Array Fortran (CAF). This document presents a Global Address SpacePerformance tool interface (GASP) that is flexible enough to be adaptedinto current global address space compiler and runtime infrastructureswith little effort, while allowing performance analysis tools to gathermuch information about the performance of global address spaceprograms.
Date: September 14, 2006
Creator: Leko, Adam; Bonachea, Dan; Su, Hung-Hsun; George, Alan D.; Sherburne, Hans & George, Alan D.
Object Type: Report
System: The UNT Digital Library
New results on the resistivity structure of Merapi Volcano(Indonesia), derived from 3D restricted inversion of long-offsettransient electromagnetic data (open access)

New results on the resistivity structure of Merapi Volcano(Indonesia), derived from 3D restricted inversion of long-offsettransient electromagnetic data

Three long-offset transient electromagnetic (LOTEM) surveyswerecarried out at the active volcano Merapi in Central Java (Indonesia)during the years 1998, 2000, and 2001. The measurements focused on thegeneral resistivity structure of the volcanic edifice at depths of 0.5-2km and the further investigation of a southside anomaly. The measurementswere insufficient for a full 3D inversion scheme, which could enable theimaging of finely discretized resistivity distributions. Therefore, astable, damped least-squares joint-inversion approach is used to optimize3D models with a limited number of parameters. The mode ls feature therealistic simulation of topography, a layered background structure, andadditional coarse 3D blocks representing conductivity anomalies.Twenty-eight LOTEM transients, comprising both horizontal and verticalcomponents of the magnetic induction time derivative, were analyzed. Inview of the few unknowns, we were able to achieve reasonable data fits.The inversion results indicate an upwelling conductor below the summit,suggesting hydrothermal activity in the central volcanic complex. Ashallow conductor due to a magma-filled chamber, at depths down to 1 kmbelow the summit, suggested by earlier seismic studies, is not indicatedby the inversion results. In conjunction with an anomalous-density model,derived from arecent gravity study, our inversion results provideinformation about the southern geological structure resulting from amajor sector collapse during the Middle Merapi period. The density …
Date: June 14, 2006
Creator: Commer, Michael; Helwig, Stefan, L.; Hordt, Andreas; Scholl,Carsten & Tezkan, Bulent
Object Type: Article
System: The UNT Digital Library
TRANSITION TEMPERATURE IN QCD WITH PHYSICAL LIGHT AND STRANGE QUARK MASSES. (open access)

TRANSITION TEMPERATURE IN QCD WITH PHYSICAL LIGHT AND STRANGE QUARK MASSES.

We present results from a calculation of the transition temperature in QCD with two light (up, down) and one heavier (strange) quark mass as well as for QCD with three degenerate quark masses. Furthermore, we discuss first results from an ongoing calculation of the QCD equation of state with almost realistic light and strange quark masses.
Date: November 14, 2006
Creator: KARSCH, F.
Object Type: Article
System: The UNT Digital Library
Probing Structure Property Relationships in Complex Engineering Silicones by 1H NMR (open access)

Probing Structure Property Relationships in Complex Engineering Silicones by 1H NMR

It is generally accepted that the properties of polymeric materials are controlled by the network structure and the reactions by which they have been constructed. These properties include the bulk moduli at creation, but also the properties as a function of age during use. In order to interpret mechanical properties and predict the time dependent changes in these properties, detailed knowledge of the effect of structural changes must be obtained. The degree and type of crosslinking, the molecular weight between crosslinks, the number of elastically ineffective chains (loops, dangling chain ends, sol-fraction) must be characterized. A number of theoretical and experimental efforts have been reported in the last few years on model networks prepared by endlinking reactions and the relationships of those structures with the ultimate mechanical properties. A range of experimental methods have been used to investigate structure including rheometric, scattering, infrared, {sup 29}Si MAS and CPMAS, {sup 1}H relaxation measurements, and recently {sup 1}H multiple quantum methods. Characterization of the growth of multiple quantum coherences have recently been shown to provide detailed insight into silicone network structure by the ability to selective probe the individual components of the polymer network, such as the polymer-filler interface or network chains. …
Date: July 14, 2006
Creator: Chinn, S. C.; Gjersing, E. L.; Maxwell, R. S.; Eastwood, E.; Bowen, D. & Stephens, T.
Object Type: Article
System: The UNT Digital Library
Chapter 4: Geological Carbon Sequestration (open access)

Chapter 4: Geological Carbon Sequestration

Carbon sequestration is the long term isolation of carbon dioxide from the atmosphere through physical, chemical, biological, or engineered processes. The largest potential reservoirs for storing carbon are the deep oceans and geological reservoirs in the earth's upper crust. This chapter focuses on geological sequestration because it appears to be the most promising large-scale approach for the 2050 timeframe. It does not discuss ocean or terrestrial sequestration. In order to achieve substantial GHG reductions, geological storage needs to be deployed at a large scale. For example, 1 Gt C/yr (3.6 Gt CO{sub 2}/yr) abatement, requires carbon capture and storage (CCS) from 600 large pulverized coal plants ({approx}1000 MW each) or 3600 injection projects at the scale of Statoil's Sleipner project. At present, global carbon emissions from coal approximate 2.5 Gt C. However, given reasonable economic and demand growth projections in a business-as-usual context, global coal emissions could account for 9 Gt C. These volumes highlight the need to develop rapidly an understanding of typical crustal response to such large projects, and the magnitude of the effort prompts certain concerns regarding implementation, efficiency, and risk of the enterprise. The key questions of subsurface engineering and surface safety associated with carbon sequestration …
Date: June 14, 2006
Creator: Friedmann, J. & Herzog, H.
Object Type: Book
System: The UNT Digital Library
Query-Driven Network Flow Data Analysis and Visualization (open access)

Query-Driven Network Flow Data Analysis and Visualization

This document is the final report for a WFO agreement between LBNL and the National Visualization and Analytics Center at PNNL. The document lists project milestones, their completion date, research results and findings. In brief, the project focuses on testing the hypothesis that the duty cycle in scientific discovery can be reduced by combining visual analytics interfaces, novel visualization techniques and scientific data management technology.
Date: June 14, 2006
Creator: Bethel, E. Wes
Object Type: Report
System: The UNT Digital Library
A Strategy for Interpretation of Microearthquake Tomography Results in the Salton Sea Geothermal Field Based upon Rock Physics Interpretations of State 2-14 Borehole Logs (open access)

A Strategy for Interpretation of Microearthquake Tomography Results in the Salton Sea Geothermal Field Based upon Rock Physics Interpretations of State 2-14 Borehole Logs

We devise a strategy for analysis of Vp and Vs microearthquake tomography results in the Salton Sea geothermal field to identify important features of the geothermal reservoir. We first interpret rock properties in State 2-14 borehole based upon logged core through the reservoir. Then, we interpret seismic recordings in the well (Daley et al., 1988) to develop the strategy. We hypothesize that mapping Poisson's ratio has two applications for the Salton Sea geothermal reservoir: (1) to map the top of the reservoir, and (2) as a diagnostic for permeable zones. Poisson's ratio can be obtained from Vp and Vs. In the State 2-14 borehole, Poisson's ratio calculated from large scale averages ({approx} 150 m) shows a monotonic decrease with depth to about 1300 m, at which point it increases with depth. Our model is that the monotonic decrease is due to compaction, and the increase below 1300 m is due to the rocks being hydrothermally altered. We hypothesize we can map the depth to alteration by identifying the transition from decreasing to increasing values; and thus, map the top of the reservoir, which is associated with a known increase in sulfite, chlorite, and epidote alteration that may be indicative of …
Date: June 14, 2006
Creator: Bonner, B.; Hutchings, L. & Kasameyer, P.
Object Type: Article
System: The UNT Digital Library
Radiation Damage Effects on the Magnetic Properties of Pu(1-x)Am(x) (x=0.224) (open access)

Radiation Damage Effects on the Magnetic Properties of Pu(1-x)Am(x) (x=0.224)

Pu(Am) is stable in the fcc {delta}-phase from a few atomic percent to nearly 80 atomic percent Am, expanding the average interatomic separation as the alloy concentration of Am increases. Both Pu and Am spontaneously decay by {alpha}-emission creating self-damage in the lattice in the form of vacancy-interstitial pairs and their aggregates. At sufficiently low temperatures, the damage is frozen in place, but can be removed by thermal annealing at sufficiently high temperatures, effectively resetting the system to an undamaged condition. The magnetic susceptibility and magnetization are observed to increase systematically as a function of accumulated damage in the fcc {delta}-Pu{sub 1-x}Am{sub x} (x=0.224). Some results of these observations are reported here.
Date: December 14, 2006
Creator: McCall, S K; Fluss, M J; Chung, B W; McElfresh, M W & Haire, R G
Object Type: Article
System: The UNT Digital Library
Technical WOrk Plan for: Construction Effects Monitoring (open access)

Technical WOrk Plan for: Construction Effects Monitoring

This document is the technical work plan (TWP) for performing the Construction Effects Monitoring (CEM) activity, which is one of 20 testing and monitoring activities included in Performance Confirmation Plan (BSC 2004 [DIRS 172452]). Collectively, the 20 activities make up the Performance Confirmation Program described in the plan. Each of the other 19 activities will have a separate TWP. This plan, though titled Construction Effects Monitoring, in accordance with the Performance Confirmation Plan, also includes testing that may be performed in addition to monitoring, if required. Performance confirmation is required by regulation 10 CFR Part 63 [DIRS 173273], and was started during site characterization (consistent with the regulation) and will continue until permanent closure of the repository (10 CFR 63.13 1 (b) [DIRS 173273]). This CEM activity has two primary goals: (1) to collect, analyze, and report on repository rock properties data for the purpose of confirming geotechnical and design parameters used in repository design, and (2) to provide information intended to confirm that the ability to retrieve waste from the repository has been preserved. It will be necessary for information from this CEM activity to be evaluated in combination with that obtained from other Performance Confirmation Program activities to …
Date: September 14, 2006
Creator: Goodin, S.
Object Type: Report
System: The UNT Digital Library
Cross-Roll Flow Forming of ODS Alloy Heat Exchanger Tubes For Hoop Creep Enhancement, Quarterly Technical Progress Report: January-March 2006 (open access)

Cross-Roll Flow Forming of ODS Alloy Heat Exchanger Tubes For Hoop Creep Enhancement, Quarterly Technical Progress Report: January-March 2006

None
Date: April 14, 2006
Creator: Kad, Bimal K.
Object Type: Report
System: The UNT Digital Library
The effects of surface damage on RF cavity operation (open access)

The effects of surface damage on RF cavity operation

We describe a model of damage in rf cavities and show how this damage can limit cavity operation. We first present a review of mechanisms that may or may not affect the ultimate fields that can be obtained in rf cavities, assuming that mechanical stress explains the triggers of rf breakdown events. We present a method of quantifying the surface damage caused by breakdown events in terms of the spectrum of field enhancement factors, Beta, for asperities on the surface. We then model an equilibrium that can develop between damage and conditioning effects, and show how this equilibrium can determine cavity performance and show experimental evidence for this mechanism. We define three functions that quantify damage, and explain how the parameters that determine this performance can be factored out and measured. We then show how this model can quantitatively explain the dependence of cavity performance on material, frequency, pulse length, gas, power supply and other factors. The examples given in this paper are derived from a variety of incomplete data sets, so we outline an experimental program that should improve these predictions, provide mechanisms for comparing data from different facilities, and fill in many gaps in the existing data.
Date: April 14, 2006
Creator: Hassanein, A.; Insepov, Z.; Norem, J.; Moretti, A.; Qian, Z.; Bross, A. et al.
Object Type: Article
System: The UNT Digital Library
The Peculiar SN 2005hk: Do Some Type Ia Supernovae Explode As Deflagrations? (open access)

The Peculiar SN 2005hk: Do Some Type Ia Supernovae Explode As Deflagrations?

We present extensive u{prime}g{prime}r{prime}i{prime} BV RIY JHK{sub s} photometry and optical spectroscopy of SN 2005hk. These data reveal that SN 2005hk was nearly identical in its observed properties to SN 2002cx, which has been called 'the most peculiar known type Ia supernova'. Both supernovae exhibited high ionization SN 1991T-like pre-maximum spectra, yet low peak luminosities like SN 1991bg. The spectra reveal that SN 2005hk, like SN 2002cx, exhibited expansion velocities that were roughly half those of typical type Ia supernovae. The R and I light curves of both supernovae were also peculiar in not displaying the secondary maximum observed for normal type Ia supernovae. Our Y JH photometry of SN 2005hk reveals the same peculiarity in the near-infrared. By combining our optical and near-infrared photometry of SN 2005hk with published ultraviolet light curves obtained with the Swift satellite, we are able to construct a bolometric light curve from {approx} 10 days before to {approx}60 days after B maximum. The shape and unusually low peak luminosity of this light curve, plus the low expansion velocities and absence of a secondary maximum at red and near-infrared wavelengths, are all in reasonable agreement with model calculations of a 3D deflagration which produces {approx} …
Date: November 14, 2006
Creator: Phillips, M. M.; Li, W.; Frieman, J. A.; Blinnikov, S. I.; DePoy, D.; Prieto, J. L. et al.
Object Type: Article
System: The UNT Digital Library
BaBar: Rare Charmless B Decays (open access)

BaBar: Rare Charmless B Decays

Three two body and two resonance decays of the B mesons have been measured using data from the BABAR detector: B{sup 0} {yields} {pi}{sup {+-}}, K{sup {-+}}, K{sup +}K{sup -}, K{sub S}{sup 0}{pi}{sup +}{pi}{sup -} and B{sup 0} {yields} a{sub 1}{sup +}(1260){pi}{sup -}. The branching ratio and that of some intermediate resonances are presented along with the Cp asymmetry of the decay B{sup 0} {yields} K*{sup +}{pi}{sup -}.
Date: April 14, 2006
Creator: Hutchcroft, D.
Object Type: Article
System: The UNT Digital Library
NEUTRON ACTIVATION ANALYSIS APPLICATIONS AT THE SAVANNAH RIVER SITE USING AN ISOTOPIC NEUTRON SOURCE (open access)

NEUTRON ACTIVATION ANALYSIS APPLICATIONS AT THE SAVANNAH RIVER SITE USING AN ISOTOPIC NEUTRON SOURCE

NAA using {sup 252}Cf is used to address important areas of applied interest at SRS. Sensitivity needs for many of the applications are not severe; analyses are accomplished using a 21 mg {sup 252}Cf NAA facility. Because NAA allows analysis of bulk samples, it offers strong advantages for samples in difficult-to-digest matrices when its sensitivity is sufficient. Following radiochemical separation with stable carrier addition, chemical yields for a number methods are determined by neutron activation of the stable carrier. In some of the cases where no suitable stable carriers exist, the source has been used to generate radioactive tracers to yield separations.
Date: August 14, 2006
Creator: Diprete, D; C Diprete, C & Raymond Sigg, R
Object Type: Article
System: The UNT Digital Library
Niobium Oxide-Metal Based Seals for High Temperature Applications (open access)

Niobium Oxide-Metal Based Seals for High Temperature Applications

The present final report describes technical progress made in regards to evaluating niobium oxide/alumina as a high temperature seal material. Fabrication and characterization of specimens comprising niobium oxide and alumina composites of various compositions was performed. The goal was to identify regions where a glass formed. There were no experimental conditions where a glassy phase was unequivocally identified. However, the results led to the formation of an interesting class of fibrous composites which may have applications where high compliance and high toughness are needed. It is clear that vapor phase sintering is an active mass transport mechanism in Nb{sub 2}O{sub 5}-Al{sub 2}O{sub 3} composites (Figure 1), and it may be possible to design porous materials by utilizing vapor phase sintering. The compositions evaluated in the present work are 52, 60, 73, 82 and 95 mol. % Nb{sub 2}O{sub 5} with the remainder Al{sub 2}O{sub 3}. These were chosen so that some eutectic composition was present during cooling, in an attempt to encourage glass formation. However, the presence of large, elongated crystals, both in the slow cool and the quench experiments indicates that the driving force for crystallization is very high. Several joints were formed between high purity alumina with two …
Date: August 14, 2006
Creator: Reimanis, Ivar
Object Type: Report
System: The UNT Digital Library
DOE ECPI AWARD DE-FG02-05ER25689 FINAL TECHNICAL REPORT (open access)

DOE ECPI AWARD DE-FG02-05ER25689 FINAL TECHNICAL REPORT

None
Date: November 14, 2006
Creator: Nikolopoulos, Dimitris S.
Object Type: Report
System: The UNT Digital Library
The Radiation Dose Measurement System for the BaBar Electromagnetic Calorimeter (open access)

The Radiation Dose Measurement System for the BaBar Electromagnetic Calorimeter

An array of 116 p-channel radiation sensitive MOSFET transistors (RadFETs) has been operational for the past 6 years at the BaBar experiment at the PEP-II asymmetric B-Factory at the Stanford Linear Accelerator Center (SLAC). This system maps the integrated dose absorbed by different regions of the Electromagnetic Calorimeter (EMC) during the running of the experiment. We report on the design and implementation of the system and finally, the performance of the monitoring system during the last 6 years of BaBar data-taking.
Date: August 14, 2006
Creator: Khan, A.; U., /Brunel; Meyer, W.T.; U., /Iowa State; Stelzer, J.; /Stanford U., Phys. Dept. et al.
Object Type: Article
System: The UNT Digital Library
Large-scale turnover of functional transcription factor bindingsites in Drosophila (open access)

Large-scale turnover of functional transcription factor bindingsites in Drosophila

The gain and loss of functional transcription-factor bindingsites has been proposed as a major source of evolutionary change incis-regulatory DNA and gene expression. We have developed an evolutionarymodel to study binding site turnover that uses multiple sequencealignments to assess the evolutionary constraint on individual bindingsites, and to map gain and loss events along a phylogenetic tree. Weapply this model to study the evolutionary dynamics of binding sites ofthe Drosophila melanogaster transcription factor Zeste, using genome-widein vivo (ChIP-chip) binding data to identify functional Zeste bindingsites, and the genome sequences of D. melanogaster, D. simulans, D.erecta and D. yakuba to study their evolution. We estimate that more than5 percent of functional Zeste binding sites in D. melanogaster weregained along the D. melanogaster lineage or lost along one of the otherlineages. We find that Zeste bound regions have a reduced rate of bindingsite loss and an increased rate of binding site gain relative to flankingsequences. Finally, we show that binding site gains and losses areasymmetrically distributed with respect to D. melanogaster, consistentwith lineage-specific acquisition and loss of Zeste-responsive regulatoryelements.
Date: July 14, 2006
Creator: Moses, Alan M.; Pollard, Daniel A.; Nix, David A.; Iyer, VenkyN.; Li, Xiao-Yong; Biggin, Mark D. et al.
Object Type: Article
System: The UNT Digital Library
Fiber Laser Replacement for Short Pulse Ti:Sapphire Oscillators -- Scalable Mode Locking to Record Pulse Energies (open access)

Fiber Laser Replacement for Short Pulse Ti:Sapphire Oscillators -- Scalable Mode Locking to Record Pulse Energies

We have investigated fiber-based lasers that mode-lock via three nonlinear mechanisms: pulse evolution, bend loss, and tunneling. Experiments with nonlinear pulse evolution proved especially promising; we report here a fiber laser that produces 25 nJ, sub-200 fs pulses, an energy that is 60% higher than previous reports. Experiments with nonlinear bend loss were inconclusive; though bend-loss data show that the effect exits, we were not able to use the phenomenon to lock a laser. New models suggest that nonlinear tunneling could provide an alternate path.
Date: February 14, 2006
Creator: Dawson, J W; Messerly, M J & An, J
Object Type: Report
System: The UNT Digital Library
Effective Conveyer Belt Inspection for Improved Mining Productivity (open access)

Effective Conveyer Belt Inspection for Improved Mining Productivity

This document details progress on the project ''Effective Conveyor Belt Inspection for Improved Mining Productivity'' during the period from May 15, 2006 to November 14, 2006. Progress during this period includes significant advances in development of a Smart Camera based prototype system for on-site mechanical splice detection, and continued deployment of both the mechanical splice detection system and the vulcanized splice detection system in area coal mines.
Date: November 14, 2006
Creator: LaRose, David
Object Type: Report
System: The UNT Digital Library
Grid Application for the BaBar Experiment (open access)

Grid Application for the BaBar Experiment

This paper discusses the use of e-Science Grid in providing computational resources for modern international High Energy Physics (HEP) experiments. We investigate the suitability of the current generation of Grid software to provide the necessary resources to perform large-scale simulation of the experiment and analysis of data in the context of multinational collaboration.
Date: August 14, 2006
Creator: Khan, A.; U., /Brunel; Wilson, F. & /Rutherford
Object Type: Article
System: The UNT Digital Library
PROCEEDINGS OF RIKEN BNL RESEARCH CENTER WORKSHOP ENTITLED: "PARTON ORBITAL ANGULAR MOMENTUM" VOLUME 81. (open access)

PROCEEDINGS OF RIKEN BNL RESEARCH CENTER WORKSHOP ENTITLED: "PARTON ORBITAL ANGULAR MOMENTUM" VOLUME 81.

None
Date: June 14, 2006
Creator: BUNCE, G.; FIELDS, D. & VOGELSANG, W.
Object Type: Article
System: The UNT Digital Library
REACTIVITY OF RESORCINOL FORMALDEHYDE RESIN WITH NITRIC ACID (open access)

REACTIVITY OF RESORCINOL FORMALDEHYDE RESIN WITH NITRIC ACID

Solid-state infrared spectroscopy, differential scanning calorimetry, and elemental analysis have been used to evaluate the reactivity of resorcinol formaldehyde resin with nitric acid and characterize the solid product. Two distinct reactions were identified within the temperature range 25-55 C. The first reaction is primarily associated with resin nitration, while the second involves bulk oxidation and degradation of the polymer network leading to dissolution and off-gassing. Reaction was confirmed with nitric acid concentrations as low as 3 M at 25 C applied temperature and 0.625 M at 66 C. Although a nitrated resin product can be isolated under appropriate experimental conditions, calorimetry testing indicates no significant hazard associated with handling the dry material.
Date: June 14, 2006
Creator: King, W; Fernando Fondeur, F; Bill Wilmarth, B; Myra Pettis, M & Shirley Mccollum, S
Object Type: Article
System: The UNT Digital Library