Resource Type

1,483 Matching Results

Results open in a new window/tab.

CORROSION OF LEAD SHIELDING IN NUCLEAR MATERIALS PACKAGES (open access)

CORROSION OF LEAD SHIELDING IN NUCLEAR MATERIALS PACKAGES

Inspection of United States-Department of Energy (US-DOE) model 9975 nuclear materials shipping package revealed corrosion of the lead shielding induced by off-gas constituents from organic components in the package. Experiments were performed to determine the corrosion rate of lead when exposed to off-gas or degradation products of these organic materials. The results showed that the room temperature vulcanizing (RTV) sealant was the most corrosive organic species followed by the polyvinyl acetate (PVAc) glue. The fiberboard material induced corrosion to a much lesser extent than the PVAc glue and RTV, and only in the presence of condensed water. The results indicated faster corrosion at temperatures higher than ambient and with condensed water as expected. A corrosion rate of 0.05 mm/year measured for coupons exposed to the most aggressive conditions was recommended as a conservative estimate for use in package performance calculations.
Date: November 16, 2007
Creator: Subramanian, K & Kerry Dunn, K
System: The UNT Digital Library
Design and testing of a control strategy for a large naturallyventilated office building (open access)

Design and testing of a control strategy for a large naturallyventilated office building

The design for the new Federal Building for San Franciscoincludes an office tower that is to be naturally ventilated. Each flooris designed to be cross-ventilated, through upper windows that arecontrolled by the building management system (BMS). Users have controlover lower windows, which can be as much as 50 percent of the totalopenable area. There are significant differences in the performance andthe control of the windward and leeward sides of the building, andseparate monitoring and control strategies are determined for each side.The performance and control of the building has been designed and testedusing a modified version of EnergyPlus. Results from studies withEnergyPlus and CFD are used in designing the control strategy. EnergyPluswas extended to model a simplified version of the airflow patterndetermined using CFD. Wind-driven cross-ventilation produces a main jetthrough the upper openings of the building, across the ceiling from thewindward to the leeward side. Below this jet, the occupied regions aresubject to a recirculating air flow. Results show that temperatureswithin the building are predicted to be satisfactory, provided a suitablecontrol strategy is implemented uses night cooling in periods of hotweather. The control strategy has 10 window opening modes. EnergyPlus wasextended to simulate the effects of these modes, and to assess …
Date: March 16, 2004
Creator: Carrilho da Graca, Guilherme; Linden, Paul F. & Haves, Philip
System: The UNT Digital Library
New experimental measurements of electron clouds in ion beams with large tune depression (open access)

New experimental measurements of electron clouds in ion beams with large tune depression

We study electron clouds in high perveance beams (K = 8E-4) with a large tune depression of 0.2 (defined as the ratio of a single particle oscillation response to the applied focusing fields, with and without space charge). These 1 MeV, 180 mA, K+ beams have a beam potential of +2 kV when electron clouds are minimized. Simulation results are discussed in a companion paper [J-L. Vay, this Conference]. We have developed the first diagnostics that quantitatively measure the accumulation of electrons in a beam [1]. This, together with measurements of electron sources, will enable the electron particle balance to be measured, and electron-trapping efficiencies determined. We, along with colleagues from GSI and CERN, have also measured the scaling of gas desorption with beam energy and dE/dx [2]. Experiments where the heavy-ion beam is transported with solenoid magnetic fields, rather than with quadrupole magnetic or electrostatic fields, are being initiated. We will discuss initial results from experiments using electrode sets (in the middle and at the ends of magnets) to either expel or to trap electrons within the magnets. We observe electron oscillations in the last quadrupole magnet when we flood the beam with electrons from an end wall. These …
Date: March 16, 2006
Creator: Molvik, A W; Covo, M K; Cohen, R H; Friedman, A; Bieniosek, F M; Leister, C M et al.
System: The UNT Digital Library
Status And Prospects of the BaBar SVT (open access)

Status And Prospects of the BaBar SVT

The BABAR Silicon Vertex Tracker (SVT) has been efficiently operated for five years since the start of data taking in 1999. It has met design requirements and no degradation in its performance has been observed thus far. However, because of higher than expected background levels, and anticipated further increases in luminosity and dose rates, we have done a thorough study to assess the viability of operating the SVT until the end of the decade.
Date: May 16, 2006
Creator: Re, V.; Bruinsma, M.; Curry, S.; Kirkby, D.; Berryhill, J.; Burke, S. et al.
System: The UNT Digital Library
The Community Climate System Model Project from an Interagency Perspective (open access)

The Community Climate System Model Project from an Interagency Perspective

In 2007, the Intergovernmental Panel on Climate Change (IPCC) will publish its Fourth Assessment Report of the Scientific Basis of Climate Change (AR4). A significant portion of the AR4 will be the analysis of coupled general circulation model (GCM) simulations of the climate of the past century as well as scenarios of future climates under prescribed emission scenarios. Modeling groups worldwide have contributed to AR4, including three from the U.S., the Community Climate System Model (CCSM) project, the National Aeronautics and Space Administration (NASA) Goddard Institute for Space Sciences, and the National Oceanic and Atmospheric Administration (NOAA) Geophysical Fluid Dynamics Laboratory (GFDL). This collection of model results is providing a wealth of new information that will be used to examine the state of climate science, the potential impacts from climate changes, and the policy consequences that they imply. Our focus here is on the CCSM project. Although it is centered at the National Center for Atmospheric Research (NCAR), the CCSM version 3 (CCSM3) was designed, developed, and applied in a uniquely distributed fashion with participation by many institutions. This model has produced some of the most scientifically complete and highest resolution simulations of climate change to date, thanks to the …
Date: June 16, 2005
Creator: Bader, D C; Bamzai, A; Fein, J; Patrinos, A & Leinen, M
System: The UNT Digital Library
A reservoir management plan (open access)

A reservoir management plan

There are numerous documented cases of extraction of fluids from the ground causing surface subsidence. The cases include groundwater, oil and gas, as well as geothermal fluid withdrawal. A recent comprehensive review of all types of man-induced land subsidence was published by the Geological Survey of America. At the early stages of a geothermal power development project it is standard practice in most countries for an environmental impact report to be required. The possibility of geothermal subsidence has to be addressed, and usually it falls on the geophysicists and/or geologists to make some predictions. The advice given is vital for planning the power plant location and the borefield pipe and drain layout. It is not so much the vertical settlement that occurs with subsidence but the accompanying horizontal ground strains that can do the most damage to any man-made structure.
Date: June 16, 1989
Creator: Allis, R.G.
System: The UNT Digital Library
Symmetry reduction of (delta)-plutonium: an electronic-structure effect (open access)

Symmetry reduction of (delta)-plutonium: an electronic-structure effect

Using first-principles density-functional theory calculations, we show that the anomalously large anisotropy of {sigma}-plutonium is a consequence of greatly varying bond-strengths between the 12 nearest neighbors. Employing the calculated bond strengths, we expand the tenants of classical crystallography by incorporating anisotropy of chemical bonds, which yields a structure with the monoclinic space group Cm for {delta}-plutonium rather than face-centered cubic Fm{bar 3}m. The reduced space group for {delta}-plutonium enlightens why the ground state of the metal is monoclinic, why distortions of the metal are viable, and has considerable implications for the behavior of the material as it ages. These results illustrate how an expansion of classical crystallography that accounts for anisotropic electronic structure can explain complicated materials in a novel way.
Date: November 16, 2005
Creator: Moore, K; Soderlind, P; Schwartz, A & Laughlin, D
System: The UNT Digital Library
EVALUATION OF RADIONUCLIDE ACCUMULATION IN SOIL DUE TO LONG-TERM IRRIGATION (open access)

EVALUATION OF RADIONUCLIDE ACCUMULATION IN SOIL DUE TO LONG-TERM IRRIGATION

Radionuclide accumulation in soil due to long-term irrigation is an important part of the model for predicting radiation dose in a long period of time. The model usually assumes an equilibrium condition in soil with a constant irrigation rate, so that radionuclide concentration in soil does not change with time and can be analytically solved. This method is currently being used for the dose assessment in the Yucca Mountain project, which requires evaluating radiation dose for a period of 10,000 years. There are several issues associated with the method: (1) time required for the equilibrium condition, (2) validity of constant irrigation rate, (3) agricultural land use for a long period of time, and (4) variation of a radionuclide concentration in water. These issues are evaluated using a numerical method with a simple model built in the GoldSim software. Some key radionuclides, Tc-99, Np-237, Pu-239, and Am-241 are selected as representative radionuclides. The results indicate that the equilibrium model is acceptable except for a radionuclide that requires long time to accumulate in soil and that its concentration in water changes dramatically with time (i.e. a sharp peak). Then the calculated dose for that radionuclide could be overestimated using the current equilibrium …
Date: April 16, 2006
Creator: Wu, De Wesley
System: The UNT Digital Library
Electronics for Satellite Experiments (open access)

Electronics for Satellite Experiments

The tracking detector for the LAT science instrument on the GLAST mission is an example of a large-scale particle detection system built primarily by particle physicists for space flight within the context of a NASA program. The design and fabrication model in most ways reflected practice and experience from particle physics, but the quality assurance aspects were guided by NASA. Similarly, most of the electronics in the LAT as a whole were designed and built by staff at a particle physics lab. This paper reports on many of the challenges and lessons learned in the experience of designing and building the tracking detector and general LAT electronics for use in the NASA GLAST mission.
Date: May 16, 2006
Creator: Johnson, Robert P. & /UC, Santa Cruz
System: The UNT Digital Library
Measurement of the Branching Fractions of the Rare Decays B0 to Ds(*)+pi-,B0 to Ds(*)+rho-, and B0 to Ds(*)-K(*)+ (open access)

Measurement of the Branching Fractions of the Rare Decays B0 to Ds(*)+pi-,B0 to Ds(*)+rho-, and B0 to Ds(*)-K(*)+

The authors report the measurement of the branching fractions of the rare decays B{sup 0} {yields} D{sub s}{sup (*)+} {pi}{sup -}, B{sup 0} {yields} D{sub s}{sup (*)+} {rho}{sup -}, and B{sup 0} {yields} D{sub s}{sup (*)-} K{sup (*)+} in a sample of 381 x 10{sup 6} {Upsilon}(4S) decays into B{bar B} pairs collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} storage ring. They present evidence for the decay B{sup 0} {yields} D{sub s}{sup -} K*{sup +} and the vector-vector decays B{sup 0} {yields} D{sub s}{sup *+} {rho}{sup -} and B{sup 0} {yields} D{sub s}{sup *-} K{sup *+}, as well as the first measurement of the vector meson polarization in these decays. They also determine the ratios of the CM-suppressed to CKM-favored amplitudes r(D{sup (*)}{pi}) and r(D{sup (*)}{rho}) in decays B{sup 0} {yields} D{sup (*)}{sup {+-}}{pi}{sup {-+}} and B{sup 0} {yields} D{sup (*)}{sup {+-}}{rho}{sup {-+}}, and comment on the prospects for measuring the Cp observable sin(2{beta} + {gamma}).
Date: April 16, 2008
Creator: Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
System: The UNT Digital Library
Binary Pseudo-random Grating Standard for Calibration of Surface Profilometers (open access)

Binary Pseudo-random Grating Standard for Calibration of Surface Profilometers

We suggest and describe the use of a binary pseudo-random (BPR) grating as a standard test surface for measurement of the modulation transfer function (MTF) of interferometric microscopes. Knowledge of the MTF of a microscope is absolutely necessary to convert the measured height distribution of a surface undergoing metrology into an accurate power spectral density (PSD) distribution. For an'ideal' microscope with an MTF function independent of spatial frequency out to the Nyquist frequency of the detector array with zero response at higher spatial frequencies, a BPR grating would produce a flat 1D PSD spectrum, independent of spatial frequency. For a'real' instrument, the MTF is found as the square root of the ratio of the PSD spectrum measured with the BPR grating to the'ideal,' spatial frequency independent, PSD spectrum. We present the results from a measurement of the MTF of MicromapTM-570 interferometric microscope demonstrating a high efficiency for the calibration method.
Date: January 16, 2008
Creator: Yashchuk, Valeriy; Yashchuk, Valeriy V.; McKinney, Wayne R. & Takacs, Peter Z.
System: The UNT Digital Library
Search for New Physics Beyond the Standard Model at BaBar (open access)

Search for New Physics Beyond the Standard Model at BaBar

A review of selected recent BaBar results are presented that illustrate the ability of the experiment to search for physics beyond the standard model. The decays B {yields} {tau}{nu} and B {yields} s{gamma} provide constraints on the mass of a charged Higgs. Searches for Lepton Flavour Violation could provide a clear signal for beyond the standard model physics. Babar does not observe any signal for New Physics with the current dataset.
Date: April 16, 2008
Creator: Barrett, Matthew & U., /Brunel
System: The UNT Digital Library
Scale Matters: An Action Plan for Realizing Sector-Wide"Zero-Energy" Performance Goals in Commercial Buildings (open access)

Scale Matters: An Action Plan for Realizing Sector-Wide"Zero-Energy" Performance Goals in Commercial Buildings

It is widely accepted that if the United States is to reduce greenhouse gas emissions it must aggressively address energy end use in the building sector. While there have been some notable but modest successes with mandatory and voluntary programs, there have also been puzzling failures to achieve expected savings. Collectively, these programs have not yet reached the majority of the building stock, nor have they yet routinely produced very large savings in individual buildings. Several trends that have the potential to change this are noteworthy: (1) the growing market interest in 'green buildings' and 'sustainable design', (2) the major professional societies (e.g. AIA, ASHRAE) have more aggressively adopted significant improvements in energy efficiency as strategic goals, e.g. targeting 'zero energy', carbon-neutral buildings by 2030. While this vision is widely accepted as desirable, unless there are significant changes to the way buildings are routinely designed, delivered and operated, zero energy buildings will remain a niche phenomenon rather than a sector-wide reality. Toward that end, a public/private coalition including the Alliance to Save Energy, LBNL, AIA, ASHRAE, USGBC and the World Business Council for Sustainable Development (WBCSD) are developing an 'action plan' for moving the U.S. commercial building sector towards zero …
Date: June 16, 2008
Creator: Selkowitz, Stephen; Selkowitz, Stephen; Granderson, Jessica; Haves, Philip; Mathew, Paul & Harris, Jeff
System: The UNT Digital Library
Merger Histories of Galaxy Halos and Implications for Disk Survival (open access)

Merger Histories of Galaxy Halos and Implications for Disk Survival

The authors study the merger histories of galaxy dark matter halos using a high resolution {Lambda}CDM N-body simulation. The merger trees follow {approx} 17,000 halos with masses M{sub 0} = (10{sup 11} - 10{sup 13})h{sup -1}M{sub {circle_dot}} at z = 0 and track accretion events involving objects as small as m {approx_equal} 10{sup 10} h{sup -1}M{sub {circle_dot}}. They find that mass assembly is remarkably self-similar in m/M{sub 0}, and dominated by mergers that are {approx}10% of the final halo mass. While very large mergers, m {approx}> 0.4 M{sub 0}, are quite rare, sizeable accretion events, m {approx} 0.1 M{sub 0}, are common. Over the last {approx} 10 Gyr, an overwhelming majority ({approx} 95%) of Milky Way-sized halos with M{sub 0} = 10{sup 12} h{sup -1}M{sub {circle_dot}} have accreted at least one object with greater total mass than the Milky Way disk (m > 5 x 10{sup 10} h{sup -1}M{sub {circle_dot}}), and approximately 70% have accreted an object with more than twice that mass (m > 10{sup 11} h{sup -1}M{sub {circle_dot}}). The results raise serious concerns about the survival of thin-disk dominated galaxies within the current paradigm for galaxy formation in a {Lambda}CDM universe. in order to achieve a {approx} 70% …
Date: May 16, 2008
Creator: Stewart, Kyle R.; Bullock, James S.; Wechsler, Risa H.; Maller, Ariyeh H. & Zentner, Andrew R.
System: The UNT Digital Library
Making Amines Strong Bases: Thermodynamic Stabilization ofProtonated Guests in a Highly-Charged Supramolecular Host (open access)

Making Amines Strong Bases: Thermodynamic Stabilization ofProtonated Guests in a Highly-Charged Supramolecular Host

A highly-charged, cavity-containing supramolecular assembly formed by metal-ligand interactions acts as a host to dramatically shift the effective basicity of encapsulated protonated amine guests. The scope of encapsulated protonated amine and phosphine guests shows size selectivity consistent with a constrained binding environment. Protonation of the encapsulated guests is confirmed by {sup 31}P NMR studies, mass spectrometry studies, and the pH dependence of guest encapsulation. Rates of guest self-exchange were measured using the Selective Inversion Recovery method and were found to correlate with the size rather than the basicity of the guests. The activation parameters for guest self-exchange are consistent with the established mechanism for guest exchange. The binding constants of the protonated amines are then used to calculate the effective basicity of the encapsulated amines. Depending on the nature of the guest, shifts in the effective basicities of the encapsulated amines of up to 4.5 pK{sub a} units are observed, signifying a substantial stabilization of the protonated form of the guest molecule and effectively making phosphines and amines strong bases.
Date: April 16, 2007
Creator: Pluth, Michael D.; Bergman, Robert G. & Raymond, Kenneth N.
System: The UNT Digital Library
The Beta-Neutrino Correlation in Sodium-21 and Other Nuclei (open access)

The Beta-Neutrino Correlation in Sodium-21 and Other Nuclei

We have measured the mbox beta - nu correlation coefficient,a_beta nu, in 21Na using a laser-trapped sample. We measure the energyspectrum of the recoil nuclei by measuring their time-of-flight incoincidence with the atomic electrons shaken off in beta decay. Highdetectionefficiency of these low-energy electrons allows good countingstatistics, even with low trap density, which suppresses thephotoassociation of molecular sodium, which can cause a large systematicerror. Our measurement, with a 1 percent fractional uncertainty, agreeswith the Standard Model prediction but disagrees with our previousmeasurement which was susceptible to error introduced by molecularsodium. We summarize precise measurements of a_ beta nu and theirconsequences for searches for Beyond Standard Model scalar and tensorcurrent couplings.
Date: January 16, 2008
Creator: Vetter, Paul A.; Abo-Shaeer, Jamil; Freedman, Stuart J. & Maruyama, Reina
System: The UNT Digital Library
A Summary of Recent Experimental Research on Ion Energy and Charge States of Pulsed Vacuum Arcs (open access)

A Summary of Recent Experimental Research on Ion Energy and Charge States of Pulsed Vacuum Arcs

The paper reviews the results of vacuum arc experimental investigations made collaboratively by research groups from Berkeley and Tomsk over the last two years, i.e. since the last ISDEIV in 2006. Vacuum arc plasma of various metals was produced in pulses of a few hundred microseconds duration, and the research focussed on three topics: (i) the energy distribution functions for different ion charge states, (ii) the temporal development of the ion charge state distribution, and (iii) the evolution of the mean directed ion velocities during plasma expansion. A combined quadruple mass-to-charge and energy ana-lyzer (EQP by HIDEN Ltd) and a time-of-flight spectrometer were employed. Cross-checking data by those complimen-tary techniques helped to avoid possible pitfalls in interpre-tation. It was found that the ion energy distribution func-tions in the plasma were independent of the ion charge state, which implies that the energy distribution on a substrate are not equal to due to acceleration in the substrate's sheath. In pulsed arc mode, the individual ion charge states fractions showed changes leading to a decrease of the mean charge state toward a steady-state value. This decrease can be re-duced by lower arc current, higher pulse repetition rate and reduced length of the discharge …
Date: June 16, 2008
Creator: Oks, Efim M.; Yushkov, Georgy Yu. & Anders, Andre
System: The UNT Digital Library
Electronic structure of cobalt nanocrystals suspended inliquid (open access)

Electronic structure of cobalt nanocrystals suspended inliquid

The electronic structure of cobalt nanocrystals suspended in liquid as a function of size has been investigated using in-situ x-ray absorption and emission spectroscopy. A sharp absorption peak associated with the ligand molecules is found that increases in intensity upon reducing the nanocrystal size. X-ray Raman features due to d-d and to charge-transfer excitations of ligand molecules are identified. The study reveals the local symmetry of the surface of {var_epsilon}-Co phase nanocrystals, which originates from a dynamic interaction between Co nanocrystals and surfactant + solvent molecules.
Date: July 16, 2007
Creator: Liu, Hongjian; Guo, Jinghua; Yin, Yadong; Augustsson, Andreas; Dong, Chungli; Nordgren, Joseph et al.
System: The UNT Digital Library
Relativistic Dark Matter at the Galactic Center (open access)

Relativistic Dark Matter at the Galactic Center

In a large region of the supersymmetry parameter space, the annihilation cross section for neutralino dark matter is strongly dependent on the relative velocity of the incoming particles. We explore the consequences of this velocity dependence in the context of indirect detection of dark matter from the galactic center. We find that the increase in the annihilation cross section at high velocities leads to a flattening of the halo density profile near the galactic center and an enhancement of the annihilation signal.
Date: November 16, 2007
Creator: Amin, Mustafa A.; /Stanford U., Phys. Dept. /KIPAC, Menlo Park & Wizansky, Tommer
System: The UNT Digital Library
Measurement of the beta-neutrino correlation of sodium-21 usingshakeoff electrons (open access)

Measurement of the beta-neutrino correlation of sodium-21 usingshakeoff electrons

The beta-neutrino correlation coefficient, a_beta nu, ismeasured in 21Na by detecting the time-of-flight of the recoil nucleusdetected in coincidence with the atomic electrons shaken off in betadecay. The sample of 21Na is confined in a magneto-optic trap. Highdetection efficiency allows low trap density, which suppresses thephotoassociation of molecular sodium, which can cause a large systematicerror. Suppressing the fraction of trapped atoms in the excited stateusing a dark trap also reduces the photoassociation process, and datataken with this technique are consistent. The main remaining systematicuncertainties come from the measurement of the position and size of theatom trap, and the subtraction of background. We find mbox a_betanu=0.5502(60), in agreement with the Standard Model prediction of mboxa_beta nu=0.553(2), and disagreeing with a previous measurement which wassusceptible to an error introduced by the presence of molecularsodium.
Date: January 16, 2007
Creator: Vetter, Paul A.; Abo-Shaeer, Jamil R.; Freedman, Stuart J. & Maruyama, Reina
System: The UNT Digital Library
A Shape Memory Polymer Dialysis Needle Adapter for the Reduction of Hemodynamic Stress within Arteriovenous Grafts (open access)

A Shape Memory Polymer Dialysis Needle Adapter for the Reduction of Hemodynamic Stress within Arteriovenous Grafts

A deployable, shape memory polymer adapter is investigated for reducing the hemodynamic stress caused by a dialysis needle flow within an arteriovenous graft. Computational fluid dynamics simulations of dialysis sessions with and without the adapter demonstrate that the adapter provides a significant decrease in the wall shear stress. In vitro flow visualization measurements are made within a graft model following delivery and actuation of a prototype shape memory polymer adapter. Vascular access complications resulting from arteriovenous (AV) graft failures account for over $1 billion per year in the health care costs of dialysis patients in the U.S.[1] The primary mode of failure of arteriovenous fistulas (AVF's) and polytetrafluoroethylene (PTFE) grafts is the development of intimal hyperplasia (IH) and the subsequent formation of stenotic lesions, resulting in a graft flow decline. The hemodynamic stresses arising within AVF's and PTFE grafts play an important role in the pathogenesis of IH. Studies have shown that vascular damage can occur in regions where there is flow separation, oscillation, or extreme values of wall shear stress (WSS).[2] Nevaril et al.[3] show that exposure of red blood cells to WSS's on the order of 1500 dynes/cm2 can result in hemolysis. Hemodynamic stress from dialysis needle flow …
Date: August 16, 2006
Creator: Ortega, J M; Small, W; Wilson, T S; Benett, W; Loge, J & Maitland, D J
System: The UNT Digital Library
Feasibility of Diffraction Radiation for a Non-invasive Diagnostics of the SLAC Electron Beam (open access)

Feasibility of Diffraction Radiation for a Non-invasive Diagnostics of the SLAC Electron Beam

The development of the non-invasive bunch size diagnostics based on the diffraction radiation is now in progress in frame of TPU-KEK-SLAC collaboration. The experimental test of a transverse beam size measurement was performed successful on the KEK-ATF extracted electron beam. However many difficulties emerge if we going from the one GeV electron energy to the several tenth GeV electron beams. The extremely high Lorenz-factor value gives rise to the some problems, such as large contribution of a radiation from an accelerator construction elements in submillimeter wavelength region, extremely pre-wave zone effect even in the optical range, exceeding of the electron beam divergence over the diffraction radiation cone, and so on. More over, the sensitivity of the method based on the optical diffraction radiation from flat slit target decrease catastrophic when an electron energy increase up to several tenth GeV. We suggest the new method based on the phase shift on the slit target, consisting on the two semi-planes which are turned at a some angle one to other (crossed target technique) and present here the results of experimental test of this technique. Also we discuss the origins of indicated difficulties and suggest the ways of these problems solution.
Date: May 16, 2006
Creator: Naumenko, G.; Potylitsyn, A.; U., /Tomsk Polytechnic; Araki, S.; Aryshev, A.; Hayano, H. et al.
System: The UNT Digital Library
Unraveling the Fanconi anaemia-DNA repair connection through DNA helicase and translocase activities (open access)

Unraveling the Fanconi anaemia-DNA repair connection through DNA helicase and translocase activities

How the Fanconi anaemia (FA) chromosome stability pathway functions to cope with interstrand crosslinks and other DNA lesions has been elusive, even after FANCD1 proved to be BRCA2, a partner of Rad51 in homologous recombination. The identification and characterization of two new Fanconi proteins having helicase motifs, FANCM and FANCJ/BRIP1/BACH1, implicates the FANC nuclear core complex as a participant in recognizing or processing damaged DNA, and the BRIP1 helicase as acting independently of this complex.
Date: August 16, 2005
Creator: Thompson, L H
System: The UNT Digital Library
Elastic constants and volume changes associated with two high-pressure rhombohedral phase transformations in vanadium (open access)

Elastic constants and volume changes associated with two high-pressure rhombohedral phase transformations in vanadium

We present results from ab-initio electronic-structure calculations of mechanical properties of the rhombohedral phase of vanadium reported in recent experiments (R Ia), and other predicted high-pressure phases (R Ib and bcc), focusing on properties relevant to dynamic experiments. We find that of the three transitions the largest volume collapse (1.3%) is for the R Ia to R Ib transition. Calculations of the single crystal and polycrystal elastic constants reveal a remarkably small discontinuity across the phase transitions even at zero temperature where the transitions are first order.
Date: October 16, 2007
Creator: Lee, B; Rudd, R E; Klepeis, J E & Becker, R
System: The UNT Digital Library