68 Matching Results

Search Results

Results: 1 - 24 next
open access

On the Virial Theorem for Interstellar Medium

Description: An attempt has been made to derive a version of the virial integral that would describe average properties of the interstellar medium (ISM). It is suggested to eliminate the (large) contribution of stellar matter by introducing 'exclusion zones' surrounding stars. Such an approach leads to the appearance of several types of additional surface integrals in the general expression. Their contribution depends on the rate of energy and matter exchange between the stars and ISM. If this exchange is w… more
Date: September 24, 2007
Creator: Ryutov, D.
Partner: UNT Libraries Government Documents Department
open access

Entropy of near-extremal black holes in AdS5

Description: We construct the microstates of near-extremal black holes in AdS_5 x S5 as gases of defects distributed in heavy BPS operators in the dual SU(N) Yang-Mills theory. These defects describe open strings on spherical D3-branes in the S5, and we show that they dominate the entropy by directly enumerating them and comparing the results with a partition sum calculation. We display new decoupling limits in which the field theory of the lightest open strings on the D-branes becomes dual to a near-horizo… more
Date: July 24, 2007
Creator: Simon, Joan; Balasubramanian, Vijay; de Boer, Jan; Jejjala, Vishnu & Simon, Joan
Partner: UNT Libraries Government Documents Department
open access

Deinococcus geothermalis: The Pool of Extreme Radiation Resistance Genes Shrinks

Description: Bacteria of the genus Deinococcus are extremely resistant to ionizing radiation (IR), ultraviolet light (UV) and desiccation. The mesophile Deinococcus radiodurans was the first member of this group whose genome was completely sequenced. Analysis of the genome sequence of D. radiodurans, however, failed to identify unique DNA repair systems. To further delineate the genes underlying the resistance phenotypes, we report the whole-genome sequence of a second Deinococcus species, the thermophile D… more
Date: July 24, 2007
Creator: Makarova, Kira S.; Omelchenko, Marina V.; Gaidamakova, Elena K.; Matrosova, Vera Y.; Vasilenko, Alexander; Zhai, Min et al.
Partner: UNT Libraries Government Documents Department
open access

Where Water is Oxidized to Dioxygen: Structure of the Photosynthetic Mn4Ca Cluster from X-ray Spectroscopy

Description: Light-driven oxidation of water to dioxygen in plants, algae and cyanobacteria iscatalyzed within photosystem II (PS II) by a Mn4Ca cluster. Although the cluster has been studied by many different methods, the structure and the mechanism have remained elusive. X-ray absorption and emission spectroscopy and EXAFS studies have been particularly useful in probing the electronic and geometric structure, and the mechanism of the water oxidation reaction. Recent progress, reviewed here, includes pola… more
Date: October 24, 2007
Creator: Yano, Junko; Yano, Junko & Yachandra, Vittal K.
Partner: UNT Libraries Government Documents Department
open access

A High Repetition Rate VUV-Soft X-Ray FEL Concept

Description: We report on design studies for a seeded FEL light source that is responsive to the scientific needs of the future. The FEL process increases radiation flux by several orders of magnitude above existing incoherent sources, and offers the additional enhancements attainable by optical manipulations of the electron beam: control of the temporal duration and bandwidth of the coherent output, reduced gain length in the FEL, utilization of harmonics to attain shorter wavelengths, and precise synchron… more
Date: June 24, 2007
Creator: Corlett, J.; Byrd, J.; Fawley, W. M.; Gullans, M.; Li, D.; Lidia, S. M. et al.
Partner: UNT Libraries Government Documents Department
open access

Does complex absorption behavior leading to conditioning and damage in KDP/DKDP reflect the electronic structure of initiators?

Description: Currently, most of our thinking about the defects responsible for initiating laser damage considers them as featureless absorbers. However, an increasing body of evidence, particularly involving multi-wavelength irradiation, suggests electronic structure of damage initiators is important in determining both initiation and conditioning behaviors in KDP. The effective absorption coefficient of energy under multi-wavelength irradiation cannot be accounted for by a structureless absorber, but is co… more
Date: October 24, 2007
Creator: Feit, M D; DeMange, P P; Negres, R A; Rubenchik, A M & Demos, S G
Partner: UNT Libraries Government Documents Department
open access

Energy dependence of jet transport parameter and parton saturationin quark-gluon plasma

Description: We study the evolution and saturation of the gluondistribution function in the quark-gluon plasma as probed by apropagating parton and its effect on the computation of jet quenching ortransport parameter $\hat q $. For thermal partons, the saturation scale$Q2_s$ is found to be proportional to the Debye screening mass $\mu_D2$.For hard probes, evolution at small $x=Q2_s/6ET$ leads to jet energydependence of hat q. We study this dependence for both a conformal gaugetheory in weak and strong coupl… more
Date: June 24, 2007
Creator: Casalderrey-Solana, Jorge & Wang, Xin-Nian
Partner: UNT Libraries Government Documents Department
open access

Testing Large CICC in Short Sample Configuration and Predicting Their Performance in Large Magnets

Description: It is well known that large Nb3Sn Cable-in-Conduit Conductors (CICC) do not always completely utilize current carrying capacity of the strands they are made of. The modern state of theory is not accurate enough to eliminate CICC full scale testing. Measuring properties of large CICC is not a simple task due to variety of parameters that need to be controlled, like temperature, exposure of all the strands to the peak magnetic field, mass flow and particular nonuniform current distribution. The p… more
Date: August 24, 2007
Creator: Martovetsky, N. N.
Partner: UNT Libraries Government Documents Department
open access

Parton Distributions and Spin-Orbital Correlations

Description: In this talk, I summarize a recent study showing that the large-x parton distributions contain important information on the quark orbital angular momentum of nucleon. This contribution could explain the conflict between the experimental data and the theory predictions for the polarized quark distributions. Future experiments at JLab shall provide further test for our predictions.
Date: September 24, 2007
Creator: Yuan, Feng
Partner: UNT Libraries Government Documents Department
open access

Scalable High Performance Message Passing over InfiniBand for Open MPI

Description: InfiniBand (IB) is a popular network technology for modern high-performance computing systems. MPI implementations traditionally support IB using a reliable, connection-oriented (RC) transport. However, per-process resource usage that grows linearly with the number of processes, makes this approach prohibitive for large-scale systems. IB provides an alternative in the form of a connectionless unreliable datagram transport (UD), which allows for near-constant resource usage and initialization ov… more
Date: October 24, 2007
Creator: Friedley, A.; Hoefler, T.; Leininger, M. L. & Lumsdaine, A.
Partner: UNT Libraries Government Documents Department
open access

Examples of the Zeroth Theorem of the History of Science

Description: The zeroth theorem of the history of science, enunciated byE. P. Fischer, states that a discovery (rule,regularity, insight) namedafter someone (often) did not originate with that person. I present fiveexamples from physics: the Lorentz condition partial muAmu = 0 definingthe Lorentz gauge of the electromagnetic potentials; the Dirac deltafunction, delta(x); the Schumann resonances of the earth-ionospherecavity; the Weizsacker-Williams method of virtual quanta; the BMTequation of spin dynamics.… more
Date: August 24, 2007
Creator: Jackson, J.D.
Partner: UNT Libraries Government Documents Department
open access

Gouy Interferometry: Properties of Multicomponent System Omega Graphs

Description: We consider the properties of {Omega} graphs ({Omega} vs f(z)) obtained from Gouy interferometry on multicomponent systems with constant diffusion coefficients. We show that they must have (a) either a maximum or else a minimum between f(z)=0 and f(z)=1 and (b) an inflection point between the f(z) value at the extremum and f(z)=1. Consequently, an {Omega} graph cannot have both positive and negative {Omega} values.
Date: January 24, 2007
Creator: Miller, D. G.
Partner: UNT Libraries Government Documents Department
open access

Mineral dissolution kinetics at the pore scale

Description: Mineral dissolution rates in the field have been reported to be orders of magnitude slower than those measured in the laboratory, an unresolved discrepancy that severely limits our ability to develop scientifically defensible predictive or even interpretive models for many geochemical processes in the earth and environmental sciences. One suggestion links this discrepancy to the role of physical and chemical heterogeneities typically found in subsurface soils and aquifers in producing scale-dep… more
Date: May 24, 2007
Creator: Li, L.; Steefel, C.I. & Yang, L.
Partner: UNT Libraries Government Documents Department
open access

Genome-wide experimental determination of barriers to horizontal gene transfer

Description: Horizontal gene transfer, in which genetic material is transferred from the genome of one organism to another, has been investigated in microbial species mainly through computational sequence analyses. To address the lack of experimental data, we studied the attempted movement of 246,045 genes from 79 prokaryotic genomes into E. coli and identified genes that consistently fail to transfer. We studied the mechanisms underlying transfer inhibition by placing coding regions from different species … more
Date: September 24, 2007
Creator: Rubin, Edward; Sorek, Rotem; Zhu, Yiwen; Creevey, Christopher J.; Francino, M. Pilar; Bork, Peer et al.
Partner: UNT Libraries Government Documents Department
open access

The Next Generation Air Particle Detectors for the United States Navy

Description: Design and testing of the United States Navy’s next generation air particle detector (NGAPD) is presently underway. The NGAPD is intended for use in nuclear applications for the United States Navy and is being designed to detect airborne Co-60 with a reduction in false alarms and improved ease of use. Features being developed include gamma compensation, low maintenance, commercial off-the-shelf electronics, and spectrum simulation for quality assurance and functional testing applications. By su… more
Date: June 24, 2007
Creator: Hayes, Robert & Marianno, Craig
Partner: UNT Libraries Government Documents Department
open access

CANCELLED EMT and back again: does cellular plasticity fuel neoplastic progression?

Description: Epithelial-mesenchymal transition (EMT) is a cellular transdifferentiation program that facilitates organ morphogenesis and tissue remodeling in physiological processes such as embryonic development and wound healing. However, a similar phenotypic conversion is also detected in fibrotic diseases and neoplasia, in which it is associated with disease progression. EMT in cancer epithelial cells often appears to be an incomplete and bi-directional process. Here we discuss the phenomenon of EMT as i… more
Date: February 24, 2007
Creator: Turley, Eva A.; Veiseh, Mandana; Radisky, Derek C. & Bissell, MinaJ.
Partner: UNT Libraries Government Documents Department
open access

Structural re-alignment in an immunologic surface region of ricin A chain

Description: We compared structure alignments generated by several protein structure comparison programs to determine whether existing methods would satisfactorily align residues at a highly conserved position within an immunogenic loop in ribosome inactivating proteins (RIPs). Using default settings, structure alignments generated by several programs (CE, DaliLite, FATCAT, LGA, MAMMOTH, MATRAS, SHEBA, SSM) failed to align the respective conserved residues, although LGA reported correct residue-residue (R-R… more
Date: July 24, 2007
Creator: Zemla, A T & Zhou, C E
Partner: UNT Libraries Government Documents Department
open access

Overview of Modeling and Simulations of Plutonium Aging

Description: Computer-aided materials research is now an integral part of science and technology. It becomes particularly valuable when comprehensive experimental investigations and materials testing are too costly, hazardous, or of excessive duration; then, theoretical and computational studies can supplement and enhance the information gained from limited experimental data. Such is the case for improving our fundamental understanding of the properties of aging plutonium in the nuclear weapons stockpile. T… more
Date: April 24, 2007
Creator: Schwartz, A J & Wolfer, W G
Partner: UNT Libraries Government Documents Department
open access

In-Situ observation of wet oxidation kinetics on Si (100) via ambient pressure x-ray photoemission spectroscopy

Description: The initial stages of wet thermal oxidation of Si(100)-(2x1) have been investigated by in-situ ambient pressure x-ray photoemission spectroscopy (APXPS), including chemical-state resolution via Si 2p core-level spectra. Real-time growth rates of silicon dioxide have been monitored at 100 mTorr of water vapor. This pressure is considerably higher than in any prior study using XPS. Substrate temperatures have been varied between 250 and 500 C. Above a temperature of {approx} 400 C, two distinct r… more
Date: August 24, 2007
Creator: Hussain, Zahid; Rossi, Massimiliano; Mun, Bongjin S.; Enta, Yoshiharu; Fadley, Charles S.; Lee, Ki-Suk et al.
Partner: UNT Libraries Government Documents Department
open access

Searching for plasmas with anomalous dispersion in the soft X-ray regime

Description: Over the last decade the electron density of plasmas has been measured using X-ray laser interferometers in the 14 to 47 nm wavelength regime. With the same formula used in decades of experiments with optical interferometers, the data analysis assumes the index of refraction is due only to the free electrons, which makes the index less than one. Over the last several years, interferometer experiments in C, Al, Ag, and Sn plasmas have observed plasmas with index of refraction greater than one at… more
Date: August 24, 2007
Creator: Nilsen, J; Johnson, W R & Cheng, K T
Partner: UNT Libraries Government Documents Department
open access

A Cell-Based Approach for the Biosynthesis/Screening of Cyclic Peptide Libraries against Bacterial Toxins

Description: Available methods for developing and screening small drug-like molecules able to knockout toxins or pathogenic microorganisms have some limitations. In order to be useful, these new methods must provide high-throughput analysis and identify specific binders in a short period of time. To meet this need, we are developing an approach that uses living cells to generate libraries of small biomolecules, which are then screened inside the cell for activity. Our group is using this new, combined appro… more
Date: October 24, 2007
Creator: Camarero, J. A.; Kimura, R.; Woo, Y.; Cantor, J. & Steenblock, E.
Partner: UNT Libraries Government Documents Department
open access

Progress in Finite Temperature Lattice Qcd.

Description: I review recent progress in finite temperature lattice calculations, including the determination of the transition temperature, equation of state, screening of static quarks and meson spectral functions.
Date: June 24, 2007
Creator: Petreczky, P.
Partner: UNT Libraries Government Documents Department
open access

Identify Dynamic Network Modules with Temporal and Spatial Constraints

Description: Despite the rapid accumulation of systems-level biological data, understanding the dynamic nature of cellular activity remains a difficult task. The reason is that most biological data are static, or only correspond to snapshots of cellular activity. In this study, we explicitly attempt to detangle the temporal complexity of biological networks by using compilations of time-series gene expression profiling data.We define a dynamic network module to be a set of proteins satisfying two conditions… more
Date: September 24, 2007
Creator: Jin, R.; McCallen, S.; Liu, C.; Almaas, E. & Zhou, X. J.
Partner: UNT Libraries Government Documents Department
open access

Measuring the Interestingness of News Articles

Description: An explosive growth of online news has taken place. Users are inundated with thousands of news articles, only some of which are interesting. A system to filter out uninteresting articles would aid users that need to read and analyze many articles daily, such as financial analysts and government officials. The most obvious approach for reducing the amount of information overload is to learn keywords of interest for a user (Carreira et al., 2004). Although filtering articles based on keywords rem… more
Date: September 24, 2007
Creator: Pon, R K; Cardenas, A F & Buttler, D J
Partner: UNT Libraries Government Documents Department
Back to Top of Screen