NNDC PERSPECTIVE ON NUCLEAR REACTION DATABASES AND ORELA. (open access)

NNDC PERSPECTIVE ON NUCLEAR REACTION DATABASES AND ORELA.

We discuss perspective of the National Nuclear Data Center on nuclear reaction databases, focusing on contributions from the ORELA machine over more than 3 decades. We conclude that ORELA had profound impact on nuclear reaction databases, in particular CSISRS and ENDF. In addition, ORELA contributed considerable amount of data included in the recent Atlas of Neutron Resonances, along with data of critical importance for nuclear reaction model calculations by codes such as EMPIRE.
Date: July 14, 2005
Creator: OBLOZINSKY, P.
System: The UNT Digital Library
Detonation Reaction Zones in Condensed Explosives (open access)

Detonation Reaction Zones in Condensed Explosives

Experimental measurements using nanosecond time resolved embedded gauges and laser interferometric techniques, combined with Non-Equilibrium Zeldovich--von Neumann--Doring (NEZND) theory and Ignition and Growth reactive flow hydrodynamic modeling, have revealed the average pressure/particle velocity states attained in reaction zones of self-sustaining detonation waves in several solid and liquid explosives. The time durations of these reaction zone processes is discussed for explosives based on pentaerythritol tetranitrate (PETN), nitromethane, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), triaminitrinitrobenzene(TATB) and trinitrotoluene (TNT).
Date: July 14, 2005
Creator: Tarver, Craig M.
System: The UNT Digital Library
Microlensing Optical Depth towards the Galactic Bulge Using Clump Giants from the MACHO Survey (open access)

Microlensing Optical Depth towards the Galactic Bulge Using Clump Giants from the MACHO Survey

Using 7 years of MACHO survey data, we present a new determination of the optical depth to microlensing towards the Galactic bulge. We select the sample of 62 microlensing events (60 unique) on clump giant sources and perform a detailed efficiency analysis. We use only the clump giant sources because these are bright bulge stars and are not as strongly affected by blending as other events. Using a subsample of 42 clump events concentrated in an area of 4.5 deg{sup 2} with 739000 clump giant stars, we find {tau} = 2.17{sub -0.38}{sup +0.47} x 10{sup -6} at (l,b) = (1{sup o}.50, -2{sup o}.68), somewhat smaller than found in most previous MACHO studies, but in excellent agreement with recent theoretical predictions. We also present the optical depth in each of the 19 fields in which we detected events, and find limits on optical depth for fields with no events. The errors in optical depth in individual fields are dominated by Poisson noise. We measure optical depth gradients of (1.06 {+-} 0.71) x 10{sup -6}deg{sup -1} and (0.29 {+-} 0.43) x 10{sup -6}deg{sup -1} in the galactic latitude b and longitude l directions, respectively. Finally, we discuss the possibility of anomalous duration …
Date: July 14, 2005
Creator: Popowski, P.; Griest, K.; Thomas, C. L.; Cook, K. H.; Bennett, D. P.; Becker, A. C. et al.
System: The UNT Digital Library
Galactic Bulge Microlensing Events from the MACHO Collaboration (open access)

Galactic Bulge Microlensing Events from the MACHO Collaboration

None
Date: July 14, 2005
Creator: Thomas, C. L.; Griest, K.; Popowski, P.; Cook, K. H.; Drake, A. J.; Minniti, D. et al.
System: The UNT Digital Library
Whole-genome analyses of the speciation events in the pathogenic Brucellae (open access)

Whole-genome analyses of the speciation events in the pathogenic Brucellae

Despite their high DNA identity and a proposal to group classical Brucella species as biovars of B. melitensis, the commonly recognized Brucella species can be distinguished by distinct biochemical and fatty acid characters as well as by a marked host range (e.g. B. suis for swine, B. melitensis for sheep and goats, B. abortus for cattle). Here we present the genome of B. abortus 2308, the virulent prototype biovar 1 strain, and its comparison to the two other human pathogenic Brucellae species and to the B. abortus field isolate 9-941. The global distribution of pseudogenes, deletions and insertions support previous indications that B. abortus and B. melitensis share a common ancestor that diverged from B. suis. With the exception of a dozen genes, the genetic complement of both B. abortus strains is identical, whereas the three species differ in gene content and pseudogenes. The pattern of species-specific gene inactivations affecting transcriptional regulators and outer membrane proteins suggest that these inactivations may play an important role in the establishment of host-specificity and may have been a primary driver of speciation in the Brucellae. Despite being non-motile, the Brucellae contain flagellum gene clusters and display species-specific flagellar gene inactivations, which lead to …
Date: July 14, 2005
Creator: Chain, P,; Comerci, D.; Tolmasky, M.; Larimer, F.; Malfatti, S.; Vergez, L. et al.
System: The UNT Digital Library
HST imaging of MEGA Microlensing Candidates in M31 (open access)

HST imaging of MEGA Microlensing Candidates in M31

We investigate HST/ACS and WFPC2 images at the positions of five candidate microlensing events from a large survey of variability in M31 (MEGA). Three closely match unresolved sources, and two produce only flux upper limits. All are confined to regions of the color-magnitude diagram where stellar variability is unlikely to be easily confused with microlensing. Red variable stars cannot explain these events (although background supernova are possible for two). If these lenses arise in M31's halo, they are due to masses 0.08 < m/M{sub {circle_dot}} < 0.85 (95% certainty, for a {delta}-function mass distribution), brown dwarfs for disk/disk, and stellar masses for disk/bulge ''self-lensing''.
Date: July 14, 2005
Creator: Cseresnjes, Patrick; Crotts, Arlin P.S.; de Jong, Jelte T.A.; Bergier, Alex; Baltz, Edward A.; Gyuk, Geza et al.
System: The UNT Digital Library
Machos in M31? Absence of Evidence but not Evidence of Absence (open access)

Machos in M31? Absence of Evidence but not Evidence of Absence

We present results of a microlensing survey toward the Andromeda Galaxy (M31) carried out during four observing seasons at the Isaac Newton Telescope (INT). This survey is part of the larger microlensing survey toward M31 performed by the Microlensing Exploration of the Galaxy and Andromeda (MEGA) collaboration. Using a fully automated search algorithm, we indentify 14 candidate microlensing events, three of which are reported here for the first time. Observations obtained at the Mayall telescope are combined with the INT data to produce composite light curves for these candidates. The results from the survey are compared with theoretical predictions for the number and distribution of events. These predictions are based on a Monte Carlo calculation of the detection efficiency and disk-bulge-halo models for M31. The models provide the full phase-space distribution functions (DFs) for the lens and source populations and are motivated by dynamical and observational considerations. They include differential extinction and span a wide range of parameter space characterized primarily by the mass-to-light ratios for the disk and bulge. For most models, the observed event rate is consistent with the rate predicted for self-lensing--a MACHO halo fraction of 30% or higher can be ruled at the 95% confidence level. …
Date: July 14, 2005
Creator: de Jong, Jelte T.A.; Widrow, Lawrence M.; Cseresnjes, Patrick; Kuijken, Konrad; Crotts, Arlin P.S.; Bergier, Alexander et al.
System: The UNT Digital Library
Comparison of the complete genome sequences of Pseudomonas syringae pv. syringae B728a and pv. tomato DC3000 (open access)

Comparison of the complete genome sequences of Pseudomonas syringae pv. syringae B728a and pv. tomato DC3000

The complete genomic sequence of Pseudomonas syringae pathovar syringae B728a (Pss B728a), has been determined and is compared with that of Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). The two pathovars of this economically important species of plant pathogenic bacteria differ in host range and other interactions with plants, with Pss having a more pronounced epiphytic stage of growth and higher abiotic stress tolerance and Pst DC3000 having a more pronounced apoplastic growth habitat. The Pss B728a genome (6.1 megabases) contains a circular chromosome and no plasmid, whereas the Pst DC3000 genome is 6.5 mbp in size, composed of a circular chromosome and two plasmids. While a high degree of similarity exists between the two sequenced Pseudomonads, 976 protein-encoding genes are unique to Pss B728a when compared to Pst DC3000, including large genomic islands likely to contribute to virulence and host specificity. Over 375 repetitive extragenic palindromic sequences (REPs) unique to Pss B728a when compared to Pst DC3000 are widely distributed throughout the chromosome except in 14 genomic islands, which generally had lower GC content than the genome as a whole. Content of the genomic islands vary, with one containing a prophage and another the plasmid pKLC102 of P. aeruginosa …
Date: July 14, 2005
Creator: Feil, H; Feil, W S; Chain, P; Larimer, F; DiBartolo, G; Copeland, A et al.
System: The UNT Digital Library
Source and Propagation Characteristics of Explosive and Other Seismic Sources (open access)

Source and Propagation Characteristics of Explosive and Other Seismic Sources

Understanding of the source and propagation characteristics of seismic events of different types including earthquakes, explosions and mining-induced events is essential for successful discrimination of nuclear explosions. We are compiling a data set of mining related seismic events in east Eurasia. Natural earthquake data in the same region are also collected for comparison study between mining related events and earthquakes. The ground-truth data set will provide a unique and valuable resource for monitoring research. We will utilize the data set to investigate the source and propagation characteristics of seismic sources of different types including mine blasts, tremors, collapses and earthquakes. We will use various seismological techniques including spectral analysis, and waveform modeling to conduct the investigation. The research will improve our understanding of the S-wave excitation and propagation characteristics of chemical explosions and other source types.
Date: July 14, 2005
Creator: Ni, X.; Chan, W.; Wagner, R.; Walter, W. R. & Matzel, E. M.
System: The UNT Digital Library
Safety Software Guide Perspectives for the Design of New Nuclear Facilities (U) (open access)

Safety Software Guide Perspectives for the Design of New Nuclear Facilities (U)

In June of this year, the Department of Energy (DOE) issued directives DOE O 414.1C and DOE G 414.1-4 to improve quality assurance programs, processes, and procedures among its safety contractors. Specifically, guidance entitled, ''Safety Software Guide for use with 10 CFR 830 Subpart A, Quality Assurance Requirements, and DOE O 414.1C, Quality Assurance, DOE G 414.1-4'', provides information and acceptable methods to comply with safety software quality assurance (SQA) requirements. The guidance provides a roadmap for meeting DOE O 414.1C, ''Quality Assurance'', and the quality assurance program (QAP) requirements of Title 10 Code of Federal Regulations (CFR) 830, Subpart A, Quality Assurance, for DOE nuclear facilities and software application activities. [1, 2] The order and guide are part of a comprehensive implementation plan that addresses issues and concerns documented in Defense Nuclear Facilities Safety Board (DNFSB) Recommendation 2002-1. [3] Safety SQA requirements for DOE as well as National Nuclear Security Administration contractors are necessary to implement effective quality assurance (QA) processes and achieve safe nuclear facility operations. DOE G 414.1-4 was developed to provide guidance on establishing and implementing effective QA processes tied specifically to nuclear facility safety software applications. The Guide includes software application practices covered by appropriate …
Date: July 14, 2005
Creator: O'Kula, Kevin R. & Sparkman, Debra
System: The UNT Digital Library
Statistical Hot Spot Model for Explosive Detonation (open access)

Statistical Hot Spot Model for Explosive Detonation

The Non-local Thermodynamic Equilibrium Statistical Hot Spot Model (NLTE SHS), a new model for explosive detonation, is described. In this model, the formation, ignition, propagation, and extinction of hot spots is explicitly modeled. The equation of state of the explosive mixture is treated with a non-local equilibrium thermodynamic assumption. A methodology for developing the parameters for the model is discussed, and applied to the detonation velocity diameter effect. Examination of these results indicates where future improvements to the model can be made.
Date: July 14, 2005
Creator: Nichols, A. L., III
System: The UNT Digital Library
Optimization of Carbon Coatings on LiFePO4 (open access)

Optimization of Carbon Coatings on LiFePO4

The electrochemical performance of LiFePO{sub 4} in lithium cells is strongly dependent on the structure (disordered/graphene or D/G ratio) of the in situ carbon produced during synthesis from carbon-containing precursors. Addition of pyromellitic acid (PA) prior to final calcination results in lower D/G ratios, yielding a higher-rate material. Further, improvements in electrochemical performance are realized when graphitization catalysts such as ferrocene are also added during LiFePO{sub 4} preparation, although overall carbon content is still less than 2 wt.%.
Date: July 14, 2005
Creator: Doeff, Marca M.; Wilcox, James D.; Kostecki, Robert & Lau, Grace
System: The UNT Digital Library