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Environmental Degradation of Materials for Nuclear Waste Repositories Engineered Barriers (open access)

Environmental Degradation of Materials for Nuclear Waste Repositories Engineered Barriers

Several countries are considering geological repositories for the storage of nuclear waste. Most of the environments for these repositories will be reducing in nature, except for the repository in the US, which is going to be oxidizing. For the reducing repositories, alloys such as carbon steel, copper, stainless steels and titanium are being evaluated. For the repository in the US, some of the most corrosion resistant commercially available alloys are being investigated. This paper presents a summary of the behavior of the different materials under consideration for the repositories and the current understanding of the degradation modes of the proposed alloys in ground water environments from the point of view of general corrosion, localized corrosion and environmentally assisted cracking.
Date: December 24, 2006
Creator: Rebak, R B
System: The UNT Digital Library
Comparison of the Acceptability of Various Oil Shale Processes (open access)

Comparison of the Acceptability of Various Oil Shale Processes

None
Date: November 24, 2006
Creator: Burnham, A K & McConaghy, J R
System: The UNT Digital Library
T. D. Lee: Relativistic Heavy Ion Collisions and the Riken Brookhaven Center. (open access)

T. D. Lee: Relativistic Heavy Ion Collisions and the Riken Brookhaven Center.

This paper presents the history of Professor T. D. Lee's seminal work on the theory of relativistic heavy ion collisions, and the founding and development of the Riken Brookhaven Center. A number of anecdotes are given about Prof. Lee, and his strong positive effect on his colleagues, particularly young physicists.
Date: November 24, 2006
Creator: McLerran, L. & Samios, N.
System: The UNT Digital Library
Accelerator Physics Code Web Repository (open access)

Accelerator Physics Code Web Repository

In the framework of the CARE HHH European Network, we have developed a web-based dynamic accelerator-physics code repository. We describe the design, structure and contents of this repository, illustrate its usage, and discuss our future plans, with emphasis on code benchmarking.
Date: October 24, 2006
Creator: Zimmermann, F.; Basset, R.; Bellodi, G.; Benedetto, E.; Dorda, U.; Giovannozzi, M. et al.
System: The UNT Digital Library
Coulomb Excitation of the 242mAm Isomer (open access)

Coulomb Excitation of the 242mAm Isomer

The {sup 242m}Am isomer, a well-known candidate for photo-depopulation research, has been studied in this first ever Coulomb excitation of a nearly pure ({approx} 98%) isomer target. Thirty new states, including a new rotational band built on a K{sup {pi}} = 6{sup -} state have been identified. Strong K-mixing results in nearly equal populations of the K{sup {pi}} = 5{sup -} and 6{sup -} states. Newly identified states have been assigned to the K{sup {pi}} = 3{sup -} rotational band, the lowest states of which are known to decay into the ground-state band. Implications regarding K-mixing and Coulomb excitation paths to the ground state are discussed.
Date: October 24, 2006
Creator: Hayes, A. B.; Cline, D.; Moody, K. J.; Wu, C. Y.; Becker, J. A.; Carpenter, M. P. et al.
System: The UNT Digital Library
The First Estimate of BR(\bar B to X_s\gamma) at O(\alpha_s^2) (open access)

The First Estimate of BR(\bar B to X_s\gamma) at O(\alpha_s^2)

Combining our results for various {Omicron}({alpha}{sub s}{sup 2}) corrections to the weak radiative B-meson decay, we are able to present the first estimate of the branching ratio at the next-to-next-to-leading order in QCD. We find {Beta}({bar B} {yields} X{sub s}{gamma}) = (3.15 {+-} 0.23) x 10{sup -4} for E{sub {gamma}} > 1.6 GeV in the {bar B}-meson rest frame. The four types of uncertainties: non-perturbative (5%), parametric (3%), higher-order (3%) and m{sub c}-interpolation ambiguity (3%) have been added in quadrature to obtain the total error.
Date: October 24, 2006
Creator: Misiak, M.; Asatrian, H. M.; Bieri, K.; Czakon, M.; Czarnecki, A.; Ewerth, T. et al.
System: The UNT Digital Library
Flux Compactification (open access)

Flux Compactification

We review recent work in which compactifications of string and M theory are constructed in which all scalar fields (moduli) are massive, and supersymmetry is broken with a small positive cosmological constant, features needed to reproduce real world physics. We explain how this work implies that there is a ''landscape'' of string/M theory vacua, perhaps containing many candidates for describing real world physics, and present the arguments for and against this idea. We discuss statistical surveys of the landscape, and the prospects for testable consequences of this picture, such as observable effects of moduli, constraints on early cosmology, and predictions for the scale of supersymmetry breaking.
Date: October 24, 2006
Creator: Douglas, Michael R. & Kachru, Shamit
System: The UNT Digital Library
Gauge/gravity Duality and MetastableDynamical Supersymmetry Breaking (open access)

Gauge/gravity Duality and MetastableDynamical Supersymmetry Breaking

We engineer a class of quiver gauge theories with several interesting features by studying D-branes at a simple Calabi-Yau singularity. At weak 't Hooft coupling we argue using field theory techniques that these theories admit both supersymmetric vacua and meta-stable non-supersymmetric vacua, though the arguments indicating the existence of the supersymmetry breaking states are not decisive. At strong 't Hooft coupling we find simple candidate gravity dual descriptions for both sets of vacua.
Date: October 24, 2006
Creator: Argurio, Riccardo; Bertolini, Matteo; Franco, Sebastian & Kachru, Shamit
System: The UNT Digital Library
Most of rare missense alleles in humans are deleterious:implications for evolution of complex disease and associationstudies (open access)

Most of rare missense alleles in humans are deleterious:implications for evolution of complex disease and associationstudies

The accumulation of mildly deleterious missense mutations inindividual human genomes has been proposed to be a genetic basis forcomplex diseases. The plausibility of this hypothesis depends onquantitative estimates of the prevalence of mildly deleterious de novomutations and polymorphic variants in humans and on the intensity ofselective pressure against them. We combined analysis of mutationscausing human Mendelian diseases, human-chimpanzee divergence andsystematic data on human SNPs and found that about 20 percent of newmissense mutations in humans result in a loss of function, while about 27percent are effectively neutral. Thus, more than half of new missensemutations have mildly deleterious effects. These mutations give rise tomany low frequency deleterious allelic variants in the human populationas evident from a new dataset of 37 genes sequenced in over 1,500individual human chromosomes. Surprisingly, up to 70 percent of lowfrequency missense alleles are mildly deleterious and associated with aheterozygous fitness loss in the range 0.001-0.003. Thus, the low allelefrequency of an amino acid variant can by itself serve as a predictor ofits functional significance. Several recent studies have reported asignificant excess of rare missense variants in disease populationscompared to controls in candidate genes or pathways. These studies wouldbe unlikely to work if most rare variants were neutral …
Date: October 24, 2006
Creator: Kryukov, Gregory V.; Pennacchio, Len A. & Sunyaev, Shamil R.
System: The UNT Digital Library
Quantifying the Diffusion of a Fluid through Membranes by RemoteDetection MRI (open access)

Quantifying the Diffusion of a Fluid through Membranes by RemoteDetection MRI

We present a method to measure self-diffusion acrossmembranes without the need for concentration or pressure gradients.Hyperpolarized xenon in combination with remote detection of NMR allowsthe measurement of membrane permeation, even in the gas phase. Theresulting images allow quantification of the amount of fluid diffusedthrough the membrane, and represent an alternative, potentially moreprecise way of measuring a membrane diffusion coefficient. The use ofremote detection of NMR allows for non-invasive signal encoding coupledto sensitive detection, making this approach ideal for the study ofdiffusion in intact devices such as fuel cells or separationsystems.
Date: October 24, 2006
Creator: Telkki, Ville-Veikko; Hilty, Christian; Garcia, Sandra; Harel,Elad & Pines, Alexander
System: The UNT Digital Library
Single Transverse-Spin Asymmetries at Large-x (open access)

Single Transverse-Spin Asymmetries at Large-x

The large-x behavior of the transverse-momentum dependent quark distributions is analyzed in the factorization-inspired perturbative QCD framework, particularly for the naive time-reversal-odd quark Sivers function which is responsible for the single transverse-spin asymmetries in various semi-inclusive hard processes. By examining the dominant hard gluon exchange Feynman diagrams, and using the resulting power counting rule, we find that the Sivers function has power behavior (1-x){sup 4} at x {yields} 1, which is one power of (1-x) suppressed relative to the unpolarized quark distribution. These power-counting results provide important guidelines for the parameterization of quark distributions and quark-gluon correlations.
Date: October 24, 2006
Creator: Brodsky, Stanley J. & Yuan, Feng
System: The UNT Digital Library
Stringy Instantons and Quiver Gauge Theories (open access)

Stringy Instantons and Quiver Gauge Theories

We explore contributions to the 4D effective superpotential which arise from Euclidean D3 branes (''instantons'') that intersect space-filling D-branes. These effects can perturb the effective field theory on the space-filling branes by nontrivial operators composed of charged matter fields, changing the vacuum structure in a qualitative way in some examples. Our considerations are exemplified throughout by a careful study of a fractional brane configuration on a del Pezzo surface.
Date: October 24, 2006
Creator: Florea, Bogdan; Kachru, Shamit; McGreevy, John & Saulina, Natalia
System: The UNT Digital Library
Study of Charm Baryons with the BaBar Experiment (open access)

Study of Charm Baryons with the BaBar Experiment

The authors report on several studies of charm baryon production and decays by the BABAR collaboration. They confirm previous observations of the {Xi}'{sub c}{sup 0/+}, {Xi}{sub c}(2980){sup +} and {Xi}{sub c}(3077){sup +} baryons, measure branching ratios for Cabibbo-suppressed {Lambda}{sub c}{sup +} decays and use baryon decays to study the properties of the light-quark baryons, {Omega}{sup -} and {Xi}(1690){sup 0}.
Date: October 24, 2006
Creator: Petersen, Brian Aa.
System: The UNT Digital Library
Study of Collective Beam Instabilities using a Correleation-moment Analysis (open access)

Study of Collective Beam Instabilities using a Correleation-moment Analysis

A general formalism for treating simultaneously the transverse coupled bunch and transverse coupled mode instabilities is presented. In this approach, the equations of motion of a coupled multi-bunch beam are expanded to yield a system of equations involving correlation-moments of the transverse and longitudinal motions. After a proper truncation, the system of equations is closed and can be solved. This approach allows us to formulate within one framework several known instability mechanisms including the single bunch mode coupling instability, the coupled bunch instability, the mode coupling instability, and the coupled mode coupled bunch instability as particular cases.
Date: October 24, 2006
Creator: Heifets, S. A. & Chao, A. W.
System: The UNT Digital Library
Ultrafast Time-Resolved Electron Diffraction with Megavolt Electron Beams (open access)

Ultrafast Time-Resolved Electron Diffraction with Megavolt Electron Beams

An rf photocathode electron gun is used as an electron source for ultrafast time-resolved pump-probe electron diffraction. We observed single-shot diffraction patterns from a 160 nm Al foil using the 5.4 MeV electron beam from the Gun Test Facility at the Stanford Linear Accelerator. Excellent agreement with simulations suggests that single-shot diffraction experiments with a time resolution approaching 100 fs are possible.
Date: October 24, 2006
Creator: Hastings, J. B.; Rudakov, F. M.; Dowell, D. H.; Schmerge, J. F.; Cardoza, J. D.; Castro, J. M. et al.
System: The UNT Digital Library
3-D Hydrodynamic Modeling in a Geospatial Framework (open access)

3-D Hydrodynamic Modeling in a Geospatial Framework

3-D hydrodynamic models are used by the Savannah River National Laboratory (SRNL) to simulate the transport of thermal and radionuclide discharges in coastal estuary systems. Development of such models requires accurate bathymetry, coastline, and boundary condition data in conjunction with the ability to rapidly discretize model domains and interpolate the required geospatial data onto the domain. To facilitate rapid and accurate hydrodynamic model development, SRNL has developed a pre- and post-processor application in a geospatial framework to automate the creation of models using existing data. This automated capability allows development of very detailed models to maximize exploitation of available surface water radionuclide sample data and thermal imagery.
Date: August 24, 2006
Creator: Bollinger, J.; Alfred Garrett, A.; Larry Koffman, L. & David Hayes, D
System: The UNT Digital Library
Extending the cereus group genomics to putative food-borne pathogens of different toxicity (open access)

Extending the cereus group genomics to putative food-borne pathogens of different toxicity

The cereus group represents sporulating soil bacteriacontaining pathogenic strains which may cause diarrheic or emetic foodpoisoning outbreaks. Multiple locus sequence typing revealed a presencein natural samples of these bacteria of about thirty clonal complexes.Application of genomic methods to this group was however biased due tothe major interest for representatives closely related to B. anthracis.Albeit the most important food-borne pathogens were not yet defined,existing dataindicate that they are scattered all over the phylogenetictree. The preliminary analysis of the sequences of three genomesdiscussed in this paper narrows down the gaps in our knowledge of thecereus group. The strain NVH391-98 is a rare but particularly severefood-borne pathogen. Sequencing revealed that the strain must be arepresentative of a novel bacterial species, for which the name Bacilluscytotoxis is proposed. This strain has a reduced genome size compared toother cereus group strains. Genome analysis revealed absence of sigma Bfactor and the presence of genes encoding diarrheic Nhe toxin, notdetected earlier. The strain B. cereus F837/76 represents a clonalcomplex close to that of B. anthracis. Including F837/76, three such B.cereus strains had been sequenced. Alignment of genomes suggests that B.anthracis is their common ancestor. Since such strains often emerge fromclinical cases, they merit a special attention. The …
Date: August 24, 2006
Creator: Lapidus, Alla; Goltsman, Eugene; Auger, Sandrine; Galleron, Nathalie; Segurens, Beatrice; Dossat, Carole et al.
System: The UNT Digital Library
Discovery of a z = 6.1 Radio-Loud Quasar in the NDWFS (open access)

Discovery of a z = 6.1 Radio-Loud Quasar in the NDWFS

From examination of only 4 deg{sup 2} of sky in the NOAO Deep Wide-Field Survey (NDWFS) region, we have identified the first radio-loud quasar at a redshift z > 6. The object, FIRST J1427385+331241, was discovered by matching the FLAMEX IR survey to FIRST survey radio sources with NDWFS counterparts. One candidate z > 6 quasar was found, and spectroscopy with the Keck II telescope confirmed its identification, yielding a redshift z = 6.12. The object is a Broad Absorption Line (BAL) quasar with an optical luminosity of M{sub B} {approx} -26.9 and a radio-to-optical flux ratio {approx} 60. Two Mg II absorptions systems are present at redshifts of z = 2.18 and z = 2.20. We briefly discuss the implications of this discovery for the high-redshift quasar population.
Date: July 24, 2006
Creator: McGreer, I D; Becker, R H; Helfand, D J & White, R L
System: The UNT Digital Library
Experiment and theory in interplay on high-Z few-electron ion spectra from foil-excited ion beams and electron beam ion traps (open access)

Experiment and theory in interplay on high-Z few-electron ion spectra from foil-excited ion beams and electron beam ion traps

None
Date: July 24, 2006
Creator: Trabert, E; Beiersdorfer, P; Pinnington, E H; Utter, S B; Vilkas, M J & Ishikawa, Y
System: The UNT Digital Library
SOIL VAPOR EXTRACTION SYSTEM DESIGN: A CASE STUDY COMPARING VACUUM AND POREGAS VELOCITY CUTOFF CRITERIA (open access)

SOIL VAPOR EXTRACTION SYSTEM DESIGN: A CASE STUDY COMPARING VACUUM AND POREGAS VELOCITY CUTOFF CRITERIA

Soil vapor extraction (SVE) systems are typically designed based on the results of a vadose zone pumping test (transient or steady state) using a pressure criteria to establish the zone of influence (ZOI). A common problem associated with pressure based SVE design is overestimating the ZOI of the extraction well. The vacuum criteria commonly used to establish the boundary of the ZOI results in large areas with very low pore velocities and thus long cleanup times. As a result, design strategies based upon critical pore gas velocity (CPGV) have increased in popularity. The CPGV is used in an effort to loosely incorporate the effects of mass transfer limitations into the design of SVE systems. Critical pore gas velocity designs use a minimum pore gas velocity rather than minimum vacuum to identify the extent of the treatment zone of an SVE system. The CPGV is typically much larger than the pore gas velocity at the perimeter of vacuum based (ZOI) designs resulting in shorter cleanup times. In this paper, we report the results of testing performed at the Savannah River Site (SRS) to determine the influence of a vapor extraction well based upon both a pressure and pore gas velocity design …
Date: July 24, 2006
Creator: Dixon, Kenneth L. & Nichols, Ralph L.
System: The UNT Digital Library
Genomic analysis of the symbiotic marine crenarchaeon, Cenarchaeumsymbiosum (open access)

Genomic analysis of the symbiotic marine crenarchaeon, Cenarchaeumsymbiosum

Crenarchaea are ubiquitous and abundant microbial constituents of soils, sediments, lakes and ocean waters, yet relatively little is known about their fundamental evolutionary, ecological, and physiological properties. To better describe the ubiquitous nonthermophilic Crenarchaea, we analyzed the genome sequence of one representative, the uncultivated sponge symbiont, Cenarchaeum symbiosum. C. symbiosum genotypes coinhabiting the same host partitioned into two dominant populations, corresponding to previously described a- and b-type ribosomal RNA variants. Although synthetic, overlapping a- and b-type ribotypes harbored significant genetic variability. A single tiling path comprising the dominant a-type genotype was assembled, and used to explore the biological properties of C. symbiosum and its planktonic relatives. Out of a total of 2,066 predicted open reading frames, 36% were more highly conserved with other Archaea. The remainder partitioned between bacteria (18%), eukaryotes (1.5%) and viruses (0.1%). A total of 525 open reading frames were more highly conserved with sequences derived from marine environmental genomic surveys, most probably representing orthologous genes found in free-living planktonic Crenarchaea. The remaining genes partitioned between functional RNAs (2.4%), and hypotheticals (42%) with limited homology to known functional genes. The latter category likely contains genes specifically involved in mediated archaeal-sponge symbiosis. Phylogenetic analyses placed C. symbiosum as …
Date: June 24, 2006
Creator: Hallam, Steven J.; Konstantinidis, Konstantinos T.; Brochier, Celine; Putnam, Nik; Schleper, Christa; Watanabe, Yoh-ichi et al.
System: The UNT Digital Library
Modeling Complex Biological Flows in Multi-Scale Systems using the APDEC Framework (open access)

Modeling Complex Biological Flows in Multi-Scale Systems using the APDEC Framework

We have developed advanced numerical algorithms to model biological fluids in multiscale flow environments using the software framework developed under the SciDAC APDEC ISIC. The foundation of our computational effort is an approach for modeling DNA-laden fluids as ''bead-rod'' polymers whose dynamics are fully coupled to an incompressible viscous solvent. The method is capable of modeling short range forces and interactions between particles using soft potentials and rigid constraints. Our methods are based on higher-order finite difference methods in complex geometry with adaptivity, leveraging algorithms and solvers in the APDEC Framework. Our Cartesian grid embedded boundary approach to incompressible viscous flow in irregular geometries has also been interfaced to a fast and accurate level-sets method within the APDEC Framework for extracting surfaces from volume renderings of medical image data and used to simulate cardio-vascular and pulmonary flows in critical anatomies.
Date: June 24, 2006
Creator: Trebotich, D
System: The UNT Digital Library
High-Throughput Plasmid cDNA Library Screening (open access)

High-Throughput Plasmid cDNA Library Screening

Libraries of cDNA clones are valuable resources foranalysing the expression, structure, and regulation of genes, as well asfor studying protein functions and interactions. Full-length cDNA clonesprovide information about intron and exon structures, splice junctionsand 5'- and 3'-untranslated regions (UTRs). Open reading frames (ORFs)derived from cDNA clones can be used to generate constructs allowingexpression of native proteins and N- or C-terminally tagged proteins.Thus, obtaining full-length cDNA clones and sequences for most or allgenes in an organism is critical for understanding genome functions.Expressed sequence tag (EST) sequencing samples cDNA libraries at random,which is most useful at the beginning of large-scale screening projects.However, as projects progress towards completion, the probability ofidentifying unique cDNAs via EST sequencing diminishes, resulting in poorrecovery of rare transcripts. We describe an adapted, high-throughputprotocol intended for recovery of specific, full-length clones fromplasmid cDNA libraries in five days.
Date: May 24, 2006
Creator: Wan, Kenneth H.; Yu, Charles; George, Reed A.; Carlson, JosephW.; Hoskins, Roger A.; Svirskas, Robert et al.
System: The UNT Digital Library
Hydrogen-Deuerium Exchange between TpRu(PMe3)(L)X (L = PMe3 and X = OH, OPh, Me, Ph, or NHPh; L = NCMe and X = Ph) and Deuterated Arene Solvents: Evidence for Metal-Mediated Processes (open access)

Hydrogen-Deuerium Exchange between TpRu(PMe3)(L)X (L = PMe3 and X = OH, OPh, Me, Ph, or NHPh; L = NCMe and X = Ph) and Deuterated Arene Solvents: Evidence for Metal-Mediated Processes

This article discusses evidence for metal-mediated processes.
Date: May 24, 2006
Creator: Feng, Yuee; Lail, Marty; Foley, Nicholas A.; Gunnoe, T. Brent; Barakat, Khaldoon A.; Cundari, Thomas R., 1964- et al.
System: The UNT Digital Library