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Elastic and transport properties in polycrystals of crackedgrains: Cross-property relations and microstructure
Some arguments of Bristow (1960) concerning the effects of cracks on elastic and transport (i.e., electrical or thermal conduction) properties of cold-worked metals are reexamined. The discussion is posed in terms of a modern understanding of bounds and estimates for physical properties of polycrystals--in contrast to Bristow's approach using simple mixture theory. One type of specialized result emphasized here is the cross-property estimates and bounds that can be obtained using the methods presented. Our results ultimately agree with those of Bristow, i.e., confirming that microcracking is not likely to be the main cause of the observed elastic behavior of cold-worked metals. However, it also becomes clear that the mixture theory approach to the analysis is too simple and that crack-crack interactions are necessary for proper quantitative study of Bristow's problem.
Date:
October 2, 2007
Creator:
Berryman, J.G.
System:
The UNT Digital Library
DiMES Studies of Temperature Dependence of Carbon Erosion and Re-Deposition in the DIII-D Divertor
A strong effect of a moderately elevated surface temperature on net carbon deposition and deuterium co-deposition in the DIII-D divertor was observed under detached conditions. A DiMES sample with a gap 2 mm wide and 18 mm deep was exposed to lower-single-null (LSN) L-mode plasmas first at room temperature, and then at 200 C. At the elevated temperature, deuterium co-deposition in the gap was reduced by an order of magnitude. At the plasma-facing surface of the heated sample net carbon erosion was measured at a rate of 3 nm/s, whereas without heating net deposition is normally observed under detachment. In a related experiment three sets of molybdenum mirrors recessed 2 cm below the divertor floor were exposed to identical LSN ELMy H-mode discharges. The first set of mirrors exposed at ambient temperature exhibited net carbon deposition at a rate of up to 3.7 nm/s and suffered a significant drop in reflectivity. In contrast, two other mirror sets exposed at elevated temperatures between 90 C and 175 C exhibited virtually no carbon deposition.
Date:
October 2, 2006
Creator:
Rudakov, D.; Jacob, W.; Krieger, K.; Litnovsky, A.; Philipps, V.; West, W. et al.
System:
The UNT Digital Library
Introduction to Electroweak Symmetry Breaking
The Standard Model (SM) is the backbone of elementary particle physics-not only does it provide a consistent framework for studying the interactions of quark and leptons, but it also gives predictions which have been extensively tested experimentally. In these notes, I review the electroweak sector of the Standard Model, discuss the calculation of electroweak radiative corrections to observables, and summarize the status of SM Higgs boson searches. Despite the impressive experimental successes, however, the electroweak theory is not completely satisfactory and the mechanism of electroweak symmetry breaking is untested. I will discuss the logic behind the oft-repeated statement: 'There must be new physics at the TeV scale'. These lectures reflect my strongly held belief that upcoming results from the LHC will fundamentally change our understanding of electroweak symmetry breaking. In these lectures, I review the status of the electroweak sector of the Standard Model, with an emphasis on the importance of radiative corrections and searches for the Standard Model Higgs boson. A discussion of the special role of the TeV energy scale in electroweak physics is included.
Date:
October 2, 2008
Creator:
Dawson,S.
System:
The UNT Digital Library
Measurement of Transverse Single-Spin Asymmetries for Di-JetProduction in Proton-Proton Collisions at sqrt s = 200 GeV
We report the first measurement of the opening angledistribution between pairs of jets produced in high-energy collisions oftransversely polarized protons. The measurement probes (Sivers)correlations between the transverse spin orientation of a proton and thetransverse momentum directions of its partons. With both beams polarized,the wide pseudorapidity (-1 leq eta leq +2) coverage for jets permitsseparation of Sivers functions for the valence and sea regions. Theresulting asymmetries are all consistent with zero and considerablysmaller than Sivers effects observed in semi-inclusive deep inelasticscattering (SIDIS). We discuss theoretical attempts to reconcile the newresults with the sizable transverse spin effects seen in SIDIS andforward hadron production in pp collisions.
Date:
October 2, 2007
Creator:
Abelev, B. I.; Adams, J.; Aggarwal, M. M.; Ahammed, Z.; Amonett, J.; Anderson, B. D. et al.
System:
The UNT Digital Library
Telomere dysfunction and cell survival: Roles for distinct TIN2-containing complexes
Telomeres are maintained by three DNA binding proteins (TRF1, TRF2 and POT1), and several associated factors. One factor, TIN2, binds TRF1 and TRF2 directly and POT1 indirectly. Along with two other proteins, TPP1 and hRap1, these form a soluble complex that may be the core telomere maintenance complex. It is not clear whether sub-complexes also exist in vivo. We provide evidence for two TIN2 sub-complexes with distinct functions in human cells. We isolated these two TIN2 sub-complexes from nuclear lysates of unperturbed cells and cells expressing TIN2 mutants TIN2-13, TIN2-15C, which cannot bind TRF2 or TRF1, respectively. In cells with wild-type p53 function, TIN2-15C was more potent than TIN2-13 in causing telomere uncapping and eventual growth arrest. In cells lacking p53 function, TIN2-15C was more potent than TIN2-13 in causing telomere dysfunction and cell death. Our findings suggest that distinct TIN2 complexes exist, and that TIN2-15C-sensitive subcomplexes are particularly important for cell survival in the absence of functional p53.
Date:
October 2, 2007
Creator:
Kim, Sahn-ho; Davalos, Albert R.; Heo, Seok-Jin; Rodier, Francis; Zou, Ying; Beausejour, Christian et al.
System:
The UNT Digital Library
Toward a Mesoscale Model for the Dynamics of Polymer Solutions
To model entire microfluidic systems containing solvated polymers we argue that it is necessary to have a numerical stability constraint governed only by the advective CFL condition. Advancements in the treatment of Kramers bead-rod polymer models are presented to enable tightly-coupled fluid-particle algorithms in the context of system-level modeling.
Date:
October 2, 2006
Creator:
Miller, G H & Trebotich, D
System:
The UNT Digital Library
Compton scattering measurements from dense plasmas
Compton scattering has been developed for accurate measurements of densities and temperatures in dense plasmas. One future challenge is the application of this technique to characterize compressed matter on the National Ignition Facility where hydrogen and beryllium will approach extremely dense states of matter of up to 1000 g/cc. In this regime, the density, compressibility, and capsule fuel adiabat may be directly measured from the Compton scattered spectrum of a high-energy x-ray line source. Specifically, the scattered spectra directly reflect the electron velocity distribution. In non-degenerate plasmas, the width provides an accurate measure of the electron temperatures, while in partially Fermi degenerate systems that occur in laser-compressed matter it provides the Fermi energy and hence the electron density. Both of these regimes have been accessed in experiments at the Omega laser by employing isochorically heated solid-density beryllium and moderately compressed beryllium foil targets. In the latter experiment, compressions by a factor of 3 at pressures of 40 Mbar have been measured in excellent agreement with radiation hydrodynamic modeling.
Date:
October 2, 2007
Creator:
Glenzer, S. H.; Neumayer, P.; Doeppner, T.; Landen, L.; Lee, R. W.; Wallace, R. et al.
System:
The UNT Digital Library
MAXIMA-1: A Measurement of the Cosmic Microwave Background Anisotropy on Angular Scales of 10' to 5 Degrees
We present a map and an angular power spectrum of the anisotropy of the cosmic microwave background (CMB) from the first flight of MAXIMA. MAXIMA is a balloon-borne experiment with an array of 16 bolometric photometers operated at 100 mK. MAXIMA observed a 124 deg region of the sky with 10' resolution at frequencies of 150, 240 and 410 GHz. The data were calibrated using in-flight measurements of the CMB dipole anisotropy. A map of the CMB anisotropy was produced from three 150 and one 240 GHz photometer without need for foreground subtractions. Analysis of this CMB map yields a power spectrum for the CMB anisotropy over the range 36 {le} {ell} {le} 785. The spectrum shows a peak with an amplitude of 78 {+-} 6 {mu}K at {ell} {approx_equal} 220 and an amplitude varying between {approx} 40 {mu}K and {approx} 50 {mu}K for 400 {approx}< {ell} {approx}< 785.
Date:
October 2, 2000
Creator:
Ade, P.; Balbi, A.; Bock, J.; Borrill, J.; Boscaleri, A.; deBernardis, P. et al.
System:
The UNT Digital Library
The Genetically Remote Pathogenic Strain NVH391-98 of the Bacillus cereus Group Represents the Cluster of Thermophilic Strains
Bacteria of the Bacillus cereus group are known to cause food poisoning. A rare phylogenetically remote strain, NVH391-98, was recently characterized to encode a particularly efficient cytotoxin K presumably responsible for food poisoning. This pathogenic strain and its close relatives can be phenotypically distinguished from other strains of the B. cereus group by the inability to grow at temperatures below 17 degrees C and by the ability to grow at temperatures from 48 to 53 degrees C. A temperate phage, phBC391A2, residing in the genome of NVH391-98 allows us to distinguish the three known members of this thermophilic strain cluster.
Date:
October 2, 2007
Creator:
Auger, Sandrine; Galleron, Nathalie; Bidnenko, Elena; Ehrlich, S. Dusko; Lapidus, Alla & Sorokin, Alexei
System:
The UNT Digital Library
Java Tool Framework for Automation of Hardware Commissioning and Maintenance Procedures
The National Ignition Facility (NIF) is a 192-beam laser system designed to study high energy density physics. Each beam line contains a variety of line replaceable units (LRUs) that contain optics, stepping motors, sensors and other devices to control and diagnose the laser. During commissioning and subsequent maintenance of the laser, LRUs undergo a qualification process using the Integrated Computer Control System (ICCS) to verify and calibrate the equipment. The commissioning processes are both repetitive and tedious when we use remote manual computer controls, making them ideal candidates for software automation. Maintenance and Commissioning Tool (MCT) software was developed to improve the efficiency of the qualification process. The tools are implemented in Java, leveraging ICCS services and CORBA to communicate with the control devices. The framework provides easy-to-use mechanisms for handling configuration data, task execution, task progress reporting, and generation of commissioning test reports. The tool framework design and application examples will be discussed.
Date:
October 2, 2007
Creator:
Ho, J. C.; Fisher, J. M.; Gordon, J. B.; Lagin, L. J. & West, S. L.
System:
The UNT Digital Library
Olivine-FeS Partial-Melt
The figure shows Fe-S-filled melt channels in olivine created at high temperature and pressure. The 3D image was obtained on Beamline 8.3.2 at the Advanced Light Source, Lawrence Berkeley Laboratory, with a spatial resolution of better than two microns (bar is 10 microns). Permeability of Fe-S melts in olivine at high temperatures and pressures provides an important constraint on models of planetary core formation. Permeability must be inferred from empirical relationships based on microstructure. To date, estimates of permeability have varied by more than five orders of magnitude. To provide more accurate constraints, we used high-resolution synchrotron radiation computed tomography to image the three-dimensional network of melt-containing pores in an olivine matrix, and calculated the permeability directly by solving the equations of Stokes flow through the actual pore network using a lattice-Boltzmann approach. These calculations provide an independent constraint on models of planetary core formation.
Date:
October 2, 2006
Creator:
Roberts, J.; Siebert, J.; Ryerson, F. J. & Kinney, J.
System:
The UNT Digital Library
RHIC Performance with polarized protons in run-6
In this study, an array of vibration measurements at the undisturbed NSLS II site has been performed in order to establish the 'green-field' vibration environment and its spectral characteristics. The interaction of the green-field vibration environment with the NSLS II accelerator structure and the quantification of the storage ring vibration, both in terms of amplitude and spectral content have been assessed through a state-of-the-art wave propagation and scattering analysis. This paper focuses on the wave propagation and scattering aspect as well as on the filtering effects of accelerator structural parameters.
Date:
October 2, 2006
Creator:
Ptitsyn, V.; Ahrens, L.; Bai, M.; Beebe-Wang, J.; Blaskiewicz, M.; Bravar, S. et al.
System:
The UNT Digital Library
Multiscale modeling of MEMS dynamics and failure
This work studies multiscale phenomena in silicon micro-resonators which comprise the mechanical components of next-generation Micro-Electro-Mechanical Systems (MEMS). Unlike their larger relatives, the behavior of these sub-micron MEMS is not described well by conventional continuum models and finite elements, but it is determined appreciably by the interplay between physics at the Angstrom, nanometer and micron scales. As device sizes are reduced below the micron scale, atomistic processes cause systematic deviations from the behavior predicted by conventional continuum elastic theory. [1] These processes cause anomalous surface effects in the resonator frequency and quality factor-even for single crystal devices with clean surfaces due to thermal fluctuations. The simulation of these atomistic effects is a challenging problem due to the large number of atoms involved and due to the fact that they are finite temperature phenomena. Our simulations include up to two million atoms in the device itself, and hundreds of millions more are in the proximal regions of the substrate. A direct, atomistic simulation of the motion of this many atoms is prohibitive, and it would be inefficient. The micron-scale processes in the substrate are well described by finite elements, and an atomistic simulation is not required. On the other hand, atomistic …
Date:
October 2, 2000
Creator:
Rudd, R E
System:
The UNT Digital Library
Proceedings of the 23rd Seismic Research Symposium: Worldwide Monitoring of Nuclear Explosions
These proceedings contain papers prepared for the 23rd Seismic Research Review: Worldwide Monitoring of Nuclear Explosions, held 2-5 October, 2001 in Jackson Hole, Wyoming. These papers represent the combined research related to ground-based nuclear explosion monitoring funded by the National Nuclear Security Administration (NNSA), Defense Threat Reduction Agency (DTRA), Air Force Technical Applications Center (AFTAC), the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), and other invited sponsors. The scientific objectives of the research are to improve the United States capability to detect, locate, and identify nuclear explosions. The purpose of the meeting is to provide the sponsoring agencies, as well as potential users, an opportunity to review research accomplished during the preceding year and to discuss areas of investigation for the coming year. For the researchers, it provides a forum for the exchange of scientific information toward achieving program goals, and an opportunity to discuss results and future plans. Paper topics include: seismic regionalization and calibration; detection and location of sources; wave propagation from source to receiver; the nature of seismic sources, including mining practices; hydroacoustic, infrasound, and radionuclide methods; on-site inspection; and data processing.
Date:
October 2, 2001
Creator:
Warren, N. Jill & Chavez, Francesca C.
System:
The UNT Digital Library
Femtosecond THz Studies of Intra-Excitonic Transitions
Few-cycle THz pulses are employed to resonantly access the internal fine structure of photogenerated excitons in semiconductors, on the femtosecond time scale. This technique allows us to gain novel insight into many-body effects of excitons and reveal key quantum optical processes. We discuss experiments that monitor the density-dependent re?normalization of the binding energy of a high-density exciton gas in GaAs/AlGaAs quantum wells close to the Mott transition. In a dilute ensemble of 3p excitons in Cu2O, stimulated THz emission from internal transitions to the energetically lower 2s state is observed at a photon energy of 6.6 meV, with a cross section of 10-14 cm2. Simultaneous interband excitation of both exciton levels drives quantum beats, which cause efficient THz emission at the difference frequency. By extending this principle to various other exciton resonances, we develop a novel way of mapping the fine structure by two-dimensional THz emission spectroscopy.
Date:
October 2, 2007
Creator:
Huber, Rupert; Schmid, Ben A.; Kaindl, Robert A. & Chemla, Daniel S.
System:
The UNT Digital Library
Proton Decay and the Planck Scale
Even without grand unification, proton decay can be a powerful probe of physics at the highest energy scales. Supersymmetric theories with conserved R-parity contain Planck-suppressed dimension 5 operators that give important contributions tonucleon decay. These operators are likely controlled by flavor physics, which means current and near future proton decay experiments might yield clues about the fermion mass spectrum. I present a thorough analysis of nucleon partial lifetimes in supersymmetric one-flavon Froggatt-Nielsen models with a single U(1)_X family symmetry which is responsible for the fermionic mass spectrum as well as forbidding R-parity violating interactions. Many of the models naturally lead to nucleon decay near present limits without any reference to grand unification.
Date:
October 2, 2004
Creator:
Larson, Daniel T.
System:
The UNT Digital Library
Using dissolved noble gas and isotopic tracers to evaluate the vulnerability of groundwater resources in a small, high elevation catchment to predicted climate changes
We use noble gas concentrations and multiple isotopic tracers in groundwater and stream water in a small high elevation catchment to provide a snapshot of temperature, altitude, and physical processes at the time of recharge; and to determine subsurface residence times of different groundwater components. They identify three sources that contribute to groundwater flow: (1) seasonal groundwater recharge with short travel times, (2) water from bedrock aquifers that have elevated radiogenic {sup 4}He, and (3) upwelling of deep fluids that have 'mantle' helium and hydrothermal carbon isotope signatures. Although a bimodal distribution in apparent groundwater age indicates that groundwater storage times range from less than a year to several decades, water that recharges seasonally is the largest likely contributor to stream baseflow. Under climate change scnearios with earlier snowmelt, the groundwater that moves through the alluvial aquifer seasonally will be depleted earlier, providing less baseflow and possible extreme low flows in the creek during summer and fall. Dissolved noble gas measurements indciate recharge temperatures are 5 to 11 degrees higher than would be expected for direct influx of snowmelt, and that excess air concentrations are lower than would be expected for recharge through bedrock fractures. Instead, recharge likely occurs over …
Date:
October 2, 2009
Creator:
Singleton, M. J. & Moran, J. E.
System:
The UNT Digital Library
SINGLE-TRANSVERSE SPIN ASYMMETRIES
We give a brief overview of some of the recent results on single-transverse spin asymmetries, highlighting in particular progress in theoretical understanding.
Date:
October 2, 2006
Creator:
VOGELSANG, W.
System:
The UNT Digital Library
ACCELERATING POLARIZED PROTONS TO HIGH ENERGY.
The Relativistic Heavy Ion Collider (RHIC) is designed to provide collisions of high energy polarized protons for the quest of understanding the proton spin structure. Polarized proton collisions at a beam energy of 100 GeV have been achieved in RHIC since 2001. Recently, polarized proton beam was accelerated to 250 GeV in RHIC for the first time. Unlike accelerating unpolarized protons, the challenge for achieving high energy polarized protons is to fight the various mechanisms in an accelerator that can lead to partial or total polarization loss due to the interaction of the spin vector with the magnetic fields. We report on the progress of the RHIC polarized proton program. We also present the strategies of how to preserve the polarization through the entire acceleration chain, i.e. a 200 MeV linear accelerator, the Booster, the AGS and RHIC.
Date:
October 2, 2006
Creator:
Bai, M.; Ahrens, L.; Alekseev, I. G.; Alessi, J.; Beebe-Wang, J.; Blaskiewicz, M. et al.
System:
The UNT Digital Library
Laurentide Ice Sheet meltwater and abrupt climate change during the last glaciation
A leading hypothesis to explain abrupt climate change during the last glacial cycle calls on fluctuations in the margin of the North American Laurentide Ice Sheet (LIS), which may have routed freshwater between the Gulf of Mexico (GOM) and North Atlantic, affecting North Atlantic Deep Water (NADW) variability and regional climate. Paired measurements of {delta}O and Mg/Ca of foraminiferal calcite from GOM sediments reveal five episodes of LIS meltwater input from 28-45 thousand years ago (ka) that do not match the millennial-scale Dansgaard-Oeschger (D/O) warmings recorded in Greenland ice. We suggest that summer melting of the LIS may occur during Antarctic warming and likely contributed to sea-level variability during Marine Isotope Stage 3 (MIS 3).
Date:
October 2, 2005
Creator:
Hill, H W; Flower, B P; Quinn, T M; Hollander, D J & Guilderson, T P
System:
The UNT Digital Library
ENDF/B-VII.0: Next Generation Evaluated Nuclear Data Library for Nuclear Science and Technology
We describe the next generation general purpose Evaluated Nuclear Data File, ENDF/B-VII.0, of recommended nuclear data for advanced nuclear science and technology applications. The library, released by the U.S. Cross Section Evaluation Working Group (CSEWG) in December 2006, contains data primarily for reactions with incident neutrons, protons, and photons on almost 400 isotopes. The new evaluations are based on both experimental data and nuclear reaction theory predictions. The principal advances over the previous ENDF/B-VI library are the following: (1) New cross sections for U, Pu, Th, Np and Am actinide isotopes, with improved performance in integral validation criticality and neutron transmission benchmark tests; (2) More precise standard cross sections for neutron reactions on H, {sup 6}Li, {sup 10}B, Au and for {sup 235,238}U fission, developed by a collaboration with the IAEA and the OECD/NEA Working Party on Evaluation Cooperation (WPEC); (3) Improved thermal neutron scattering; (4) An extensive set of neutron cross sections on fission products developed through a WPEC collaboration; (5) A large suite of photonuclear reactions; (6) Extension of many neutron- and proton-induced reactions up to an energy of 150 MeV; (7) Many new light nucleus neutron and proton reactions; (8) Post-fission beta-delayed photon decay spectra; (9) New …
Date:
October 2, 2006
Creator:
Chadwick, M. B.; Oblozinsky, P.; Herman, M.; Greene, N. M.; McKnight, R. D.; Smith, D. L. et al.
System:
The UNT Digital Library
Comment on "Radiocarbon Calibration Curve Spanning 0 to 50,000 Years B.P. Based on Paired 230Th/234U/238U and 14C Dates on Pristine Corals" by R.G. Fairbanks, R. A. Mortlock, T.-C. Chiu, L. Cao, A. Kaplan, T. P. Guilderson, T. W. Fairbanks, A. L. Bloom, P
Radiocarbon calibration curves are essential for converting radiocarbon dated chronologies to the calendar timescale. Prior to the 1980's numerous differently derived calibration curves based on radiocarbon ages of known age material were in use, resulting in ''apples and oranges'' comparisons between various records (Klein et al., 1982), further complicated by until then unappreciated inter-laboratory variations (International Study Group, 1982). The solution was to produce an internationally-agreed calibration curve based on carefully screened data with updates at 4-6 year intervals (Klein et al., 1982; Stuiver and Reimer, 1986; Stuiver and Reimer, 1993; Stuiver et al., 1998). The IntCal working group has continued this tradition with the active participation of researchers who produced the records that were considered for incorporation into the current, internationally-ratified calibration curves, IntCal04, SHCal04, and Marine04, for Northern Hemisphere terrestrial, Southern Hemisphere terrestrial, and marine samples, respectively (Reimer et al., 2004; Hughen et al., 2004; McCormac et al., 2004). Fairbanks et al. (2005), accompanied by a more technical paper, Chiu et al. (2005), and an introductory comment, Adkins (2005), recently published a ''calibration curve spanning 0-50,000 years''. Fairbanks et al. (2005) and Chiu et al. (2005) have made a significant contribution to the database on which the IntCal04 …
Date:
October 2, 2005
Creator:
Reimer, P. J.; Baillie, M. L.; Bard, E.; Beck, J. W.; Blackwell, P. G.; Buck, C. E. et al.
System:
The UNT Digital Library
THRESHOLD RESUMMATION EFFECTS IN THE POLARIZED DRELL-YAN MECHANISM.
We present theoretical predictions for the cross sections and spin asymmetries in dilepton pair production in transversely polarized pp and {bar p}p collisions. We use the available fixed-order corrections as well as the all-order resummation of threshold logarithms for the pair mass and rapidity distributions. Numerical results for pp collisions at {radical}s = 10 GeV at J-PARC and for {bar p}p collisions at {radical}s = 14.5 GeV at GSI-PAX are given.
Date:
October 2, 2006
Creator:
YOKOYA, H. & VOGELSANG, W.
System:
The UNT Digital Library
Measurements of the CKM Angle Gamma at BaBar
We present a short review of the measurements of the CKM angle {gamma} performed by the BABAR experiment. We focus on methods using charged B decays, which give a direct access to {gamma} and provide the best constraints so far.
Date:
October 2, 2007
Creator:
Latour, Emmanuel & Polytechnique, /Ecole
System:
The UNT Digital Library