67 Matching Results

Results open in a new window/tab.

Gene by Disease Interaction on Orbitofrontal Gray Matter in Cocaine Addiction (open access)

Gene by Disease Interaction on Orbitofrontal Gray Matter in Cocaine Addiction

Chronic cocaine use has been associated with structural deficits in brain regions having dopamine receptive neurons. However, the concomitant use of other drugs and common genetic variability in monoamine regulation present additional structural variability. We therefore examined variations in gray matter volume (GMV) as a function of lifetime drug use and the monoamine oxidase A (MAOA) genotype in cocaine use disorders (CUD) and healthy controls.
Date: December 5, 2010
Creator: Alia-Klein, N.; Alia-Klein, N.; Parvaz, M. A.; Woicik, P. A.; Konova, A.; Maloney, T. et al.
System: The UNT Digital Library
Calculation of the substitutional fraction of ion-implanted He in an Fe target (open access)

Calculation of the substitutional fraction of ion-implanted He in an Fe target

None
Date: November 5, 2010
Creator: Erhart, P. & Marian, J.
System: The UNT Digital Library
Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol (open access)

Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol

A detailed understanding of the sources, transformations, and fates of organic species in the environment is crucial because of the central roles that organics play in human health, biogeochemical cycles, and Earth's climate. However, such an understanding is hindered by the immense chemical complexity of environmental mixtures of organics; for example, atmospheric organic aerosol consists of at least thousands of individual compounds, all of which likely evolve chemically over their atmospheric lifetimes. Here we demonstrate the utility of describing organic aerosol (and other complex organic mixtures) in terms of average carbon oxidation state (OSC), a quantity that always increases with oxidation, and is readily measured using state-of-the-art analytical techniques. Field and laboratory measurements of OSC , using several such techniques, constrain the chemical properties of the organics and demonstrate that the formation and evolution of organic aerosol involves simultaneous changes to both carbon oxidation state and carbon number (nC).
Date: November 5, 2010
Creator: Technology, Massachusetts Institute of; Kroll, Jesse H.; Donahue, Neil M.; Jimenez, Jose L.; Kessler, Sean H.; Canagaratna, Manjula R. et al.
System: The UNT Digital Library
Imaging the early material response associated with exit surface damage in fused silica (open access)

Imaging the early material response associated with exit surface damage in fused silica

The processes involved at the onset of damage initiation on the surface of fused silica have been a topic of extensive discussion and thought for more than four decades. Limited experimental results have helped develop models covering specific aspects of the process. In this work we present the results of an experimental study aiming at imaging the material response from the onset of the observation of material modification during exposure to the laser pulse through the time point at which material ejection begins. The system involves damage initiation using a 355 nm pulse, 7.8 ns FWHM in duration and imaging of the affected material volume with spatial resolution on the order of 1 {micro}m using as strobe light a 150 ps laser pulse that is appropriately timed with respect to the pump pulse. The observations reveal that the onset of material modification is associated with regions of increased absorption, i.e., formation of an electronic excitation, leading to a reduction in the probe transmission to only a few percent within a time interval of about 1 ns. This area is subsequently rapidly expanding with a speed of about 1.2 {micro}m/ns and is accompanied by the formation and propagation of radial cracks. …
Date: November 5, 2010
Creator: Demos, S G; Raman, R N & Negres, R A
System: The UNT Digital Library
Quantitative Visualization of ChIP-chip Data by Using Linked Views (open access)

Quantitative Visualization of ChIP-chip Data by Using Linked Views

Most analyses of ChIP-chip in vivo DNA binding have focused on qualitative descriptions of whether genomic regions are bound or not. There is increasing evidence, however, that factors bind in a highly overlapping manner to the same genomic regions and that it is quantitative differences in occupancy on these commonly bound regions that are the critical determinants of the different biological specificity of factors. As a result, it is critical to have a tool to facilitate the quantitative visualization of differences between transcription factors and the genomic regions they bind to understand each factor's unique roles in the network. We have developed a framework which combines several visualizations via brushing-and-linking to allow the user to interactively analyze and explore in vivo DNA binding data of multiple transcription factors. We describe these visualization types and also provide a discussion of biological examples in this paper.
Date: November 5, 2010
Creator: Huang, Min-Yu; Weber, Gunther; Li, Xiao-Yong; Biggin, Mark & Hamann, Bernd
System: The UNT Digital Library
REGULATORY STRATEGIES TO MINIMIZE GENERATION OF REGULATED WASTES FROM CLEANUP, CONTINUED USE OR DECOMMISSIONING OF NUCLEAR FACILITIES CONTAMINATED WITH POLYCHLORINATED BIPHENYLS (PCBS) - 11198 (open access)

REGULATORY STRATEGIES TO MINIMIZE GENERATION OF REGULATED WASTES FROM CLEANUP, CONTINUED USE OR DECOMMISSIONING OF NUCLEAR FACILITIES CONTAMINATED WITH POLYCHLORINATED BIPHENYLS (PCBS) - 11198

Disposal costs for liquid PCB radioactive waste are among the highest of any category of regulated waste. The high cost is driven by the fact that disposal options are extremely limited. Toxic Substances Control Act (TSCA) regulations require most liquids with PCBs at concentration of {ge} 50 parts-per-million to be disposed by incineration or equivalent destructive treatment. Disposal fees can be as high as $200 per gallon. This figure does not include packaging and the cost to transport the waste to the disposal facility, or the waste generator's labor costs for managing the waste prior to shipment. Minimizing the generation of liquid radioactive PCB waste is therefore a significant waste management challenge. PCB spill cleanups often generate large volumes of waste. That is because the removal of PCBs typically requires the liberal use of industrial solvents followed by a thorough rinsing process. In a nuclear facility, the cleanup process may be complicated by the presence of radiation and other occupational hazards. Building design and construction features, e.g., the presence of open grating or trenches, may also complicate cleanup. In addition to the technical challenges associated with spill cleanup, selection of the appropriate regulatory requirements and approach may be challenging. The …
Date: November 5, 2010
Creator: Lowry, N.
System: The UNT Digital Library
Fighting Fire with Fire: Superlattice Cooling of Silicon Hotspots to Reduce Global Cooling Requirements (open access)

Fighting Fire with Fire: Superlattice Cooling of Silicon Hotspots to Reduce Global Cooling Requirements

The running costs of data centers are dominated by the need to dissipate heat generated by thousands of server machines. Higher temperatures are undesirable as they lead to premature silicon wear-out; in fact, mean time to failure has been shown to decrease exponentially with temperature (Black's law). Although other server components also generate heat, microprocessors still dominate in most server configurations and are also the most vulnerable to wearout as the feature sizes shrink. Even as processor complexity and technology scaling have increased the average energy density inside a processor to maximally tolerable levels, modern microprocessors make extensive use of hardware structures such as the load-store queue and other CAM-based units, and the peak temperatures on chip can be much worse than even the average temperature of the chip. In recent studies, it has been shown that hot-spots inside a processor can generate {approx} 800W/cm{sup 2} heat flux whereas the average heat flux is only 10-50W/cm{sup 2}, and due to this disparity in heat generation, the temperature in hot spots may be up to 30 C more than average chip temperature. The key problem processor hot-spots create is that in order to prevent some critical hardware structures from wearing out …
Date: October 5, 2010
Creator: Biswas, S; Tiwari, M; Sherwood, T; Theogarajan, L & Chong, F T
System: The UNT Digital Library
NSC109268 potentiates cisplatin-induced cell death in a p53-independent manner (open access)

NSC109268 potentiates cisplatin-induced cell death in a p53-independent manner

This article's study endeavors to determine if p53 is responsible for cisplatin sensitization by NSC109268. Results have implications for sensitivity of ovarian cancer cells to cisplatin independent of p53.
Date: October 5, 2010
Creator: Shankar, Eswar; Basu, Chandreyi; Adkins, Brett; Siede, Wolfram & Basu, Alakananda
System: The UNT Digital Library
Multiple Syntrophic Interactions in a Terephthalate-Degrading Methanogenic Consortium (open access)

Multiple Syntrophic Interactions in a Terephthalate-Degrading Methanogenic Consortium

Terephthalate (TA) is one of the top 50 chemicals produced worldwide. Its production results in a TA-containing wastewater that is treated by anaerobic processes through a poorly understood methanogenic syntrophy. Using metagenomics, we characterized the methanogenic consortium tinside a hyper-mesophilic (i.e., between mesophilic and thermophilic), TA-degrading bioreactor. We identified genes belonging to dominant Pelotomaculum species presumably involved in TA degradation through decarboxylation, dearomatization, and modified ?-oxidation to H{sub 2}/CO{sub 2} and acetate. These intermediates are converted to CH{sub 4}/CO{sub 2} by three novel hyper-mesophilic methanogens. Additional secondary syntrophic interactions were predicted in Thermotogae, Syntrophus and candidate phyla OP5 and WWE1 populations. The OP5 encodes genes capable of anaerobic autotrophic butyrate production and Thermotogae, Syntrophus and WWE1 have the genetic potential to oxidize butyrate to COsub 2}/H{sub 2} and acetate. These observations suggest that the TA-degrading consortium consists of additional syntrophic interactions beyond the standard H{sub 2}-producing syntroph ? methanogen partnership that may serve to improve community stability.
Date: August 5, 2010
Creator: Lykidis, Athanasios; Chen, Chia-Lung; Tringe, Susannah G.; McHardy, Alice C.; Copeland, Alex 5; Kyrpides, Nikos C. et al.
System: The UNT Digital Library
Azimuthal Charged-Particle Correlations and Possible Local Strong Parity Violation (open access)

Azimuthal Charged-Particle Correlations and Possible Local Strong Parity Violation

Parity-odd domains, corresponding to non-trivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the system's orbital momentum axis. We investigate a three particle azimuthal correlator which is a {Rho} even observable, but directly sensitive to the charge separation effect. We report measurements of charged hadrons near center-of-mass rapidity with this observable in Au+Au and Cu+Cu collisions at {radical}s{sub NN} = 200 GeV using the STAR detector. A signal consistent with several expectations from the theory is detected. We discuss possible contributions from other effects that are not related to parity violation.
Date: July 5, 2010
Creator: STAR Collaboration
System: The UNT Digital Library
Center of mass energy and system-size dependence of photon production at forward rapidity at RHIC (open access)

Center of mass energy and system-size dependence of photon production at forward rapidity at RHIC

We present the multiplicity and pseudorapidity distributions of photons produced in Au+Au and Cu+Cu collisions at {radical}s{sub NN} = 62.4 and 200 GeV. The photons are measured in the region -3.7 < {eta} < -2.3 using the photon multiplicity detector in the STAR experiment at RHIC. The number of photons produced per average number of participating nucleon pairs increases with the beam energy and is independent of the collision centrality. For collisions with similar average numbers of participating nucleons the photon multiplicities are observed to be similar for Au+Au and Cu+Cu collisions at a given beam energy. The ratios of the number of charged particles to photons in the measured pseudorapidity range are found to be 1.4 {+-} 0.1 and 1.2 {+-} 0.1 for {radical}s{sub NN} = 62.4 GeV and 200 GeV, respectively. The energy dependence of this ratio could reflect varying contributions from baryons to charged particles, while mesons are the dominant contributors to photon production in the given kinematic region. The photon pseudorapidity distributions normalized by average number of participating nucleon pairs, when plotted as a function of {eta} - ybeam, are found to follow a longitudinal scaling independent of centrality and colliding ion species at both beam …
Date: July 5, 2010
Creator: STAR Collaboration
System: The UNT Digital Library
Charged and strange hadron elliptic flow in Cu+Cu collisions at sqrt sNN = 62.4 and 200 GeV (open access)

Charged and strange hadron elliptic flow in Cu+Cu collisions at sqrt sNN = 62.4 and 200 GeV

We present the results of an elliptic flow, v{sub 2}, analysis of Cu+Cu collisions recorded with the STAR detector at RHIC at {radical}s{sub NN} = 62.4 and 200 GeV. Elliptic flow as a function of transverse momentum, v{sub 2}(p{sub T}), is reported for different collision centralities for charged hadrons h{sup {+-}}, and strangeness containing hadrons K{sub S}{sup 0}, {Lambda}, {Xi}, {phi} in the midrapidity region |{eta}| < 1.0. Significant reduction in systematic uncertainty of the measurement due to non-flow effects has been achieved by correlating particles at midrapidity, |{eta}| < 1.0, with those at forward rapidity, 2.5 < |{eta}| < 4.0. We also present azimuthal correlations in p+p collisions at {radical}s = 200 GeV to help estimating non-flow effects. To study the system-size dependence of elliptic flow, we present a detailed comparison with previously published results from Au+Au collisions at {radical}s{sub NN} = 200 GeV. We observe that v{sub 2}(p{sub T}) of strange hadrons has similar scaling properties as were first observed in Au+Au collisions, i.e.: (i) at low transverse momenta, p{sub T} < 2 GeV/c, v{sub 2} scales with transverse kinetic energy, m{sub T} - m, and (ii) at intermediate p{sub T}, 2 < p{sub T} < 4 GeV/c, …
Date: July 5, 2010
Creator: STAR Collaboration
System: The UNT Digital Library
Full multiple scattering analysis of XANES at the Cd L3 and O K edges in CdO films combined with a soft-x-ray emission investigation (open access)

Full multiple scattering analysis of XANES at the Cd L3 and O K edges in CdO films combined with a soft-x-ray emission investigation

X-ray absorption near edge structure (XANES) at the cadmium L3 and oxygen K edges for CdO thin films grown by pulsed laser deposition method, is interpreted within the real-space multiple scattering formalism, FEFF code. The features in the experimental spectra are well reproduced by calculations for a cluster of about six and ten coordination shells around the absorber for L3 edge of Cd and K edge of O, respectively. The calculated projected electronic density of states is found to be in good agreement with unoccupied electronic states in experimental data and allows to conclude that the orbital character of the lowest energy of the conductive band is Cd-5s-O-2p. The charge transfer has been quantified and not purely ionic bonding has been found. Combined XANES and resonant inelastic x-ray scattering measurements allow us to determine the direct and indirect band gap of investigated CdO films to be {approx}2.4-eV and {approx}0.9-eV, respectively.
Date: July 5, 2010
Creator: Demchenko, I. N.; Denlinger, J. D.; Chernyshova, M.; Yu, K. M.; Speaks, D. T.; Olalde-Velasco, P. et al.
System: The UNT Digital Library
Growth of Long Range Forward-Backward Multiplicity Correlations with Centrality in Au+Au Collisions at sqrt sNN = 200 GeV (open access)

Growth of Long Range Forward-Backward Multiplicity Correlations with Centrality in Au+Au Collisions at sqrt sNN = 200 GeV

Forward-backward multiplicity correlation strengths have been measured with the STAR detector for Au+Au and p+p collisions at {radical}s{sub NN} = 200 GeV. Strong short and long range correlations (LRC) are seen in central Au+Au collisions. The magnitude of these correlations decrease with decreasing centrality until only short range correlations are observed in peripheral Au+Au collisions. Both the Dual Parton Model (DPM) and the Color Glass Condensate (CGC) predict the existence of the long range correlations. In the DPM the fluctuation in the number of elementary (parton) inelastic collisions produces the LRC. In the CGC longitudinal color flux tubes generate the LRC. The data is in qualitative agreement with the predictions from the DPM and indicates the presence of multiple parton interactions.
Date: July 5, 2010
Creator: STAR Collaboration
System: The UNT Digital Library
Identified high-pT spectra in Cu+Cu collisions at sqrt sNN=200 GeV (open access)

Identified high-pT spectra in Cu+Cu collisions at sqrt sNN=200 GeV

We report new results on identified (anti)proton and charged pion spectra at large transverse momenta (3 < p{sub T} < 10 GeV/c) from Cu+Cu collisions at {radical}s{sub NN} = 200 GeV using the STAR detector at the Relativistic Heavy Ion Collider (RHIC). This study explores the system size dependence of two novel features observed at RHIC with heavy ions: the hadron suppression at high-p{sub T} and the anomalous baryon to meson enhancement at intermediate transverse momenta. Both phenomena could be attributed to the creation of a new form of QCD matter. The results presented here bridge the system size gap between the available pp and Au+Au data, and allow the detailed exploration for the on-set of the novel features. Comparative analysis of all available 200 GeV data indicates that the system size is a major factor determining both the magnitude of the hadron spectra suppression at large transverse momenta and the relative baryon to meson enhancement.
Date: July 5, 2010
Creator: STAR Collaboration
System: The UNT Digital Library
Identified particle production, azimuthal anisotropy, and interferometry measurements in Au+Au collisions at sqrt sNN = 9.2 GeV (open access)

Identified particle production, azimuthal anisotropy, and interferometry measurements in Au+Au collisions at sqrt sNN = 9.2 GeV

We present the first measurements of identified hadron production, azimuthal anisotropy, and pion interferometry from Au+Au collisions below the nominal injection energy at the Relativistic Heavy-Ion Collider (RHIC) facility. The data were collected using the large acceptance STAR detector at {radical}s{sub NN} = 9.2 GeV from a test run of the collider in the year 2008. Midrapidity results on multiplicity density (dN/dy) in rapidity (y), average transverse momentum (<p{sub T}>), particle ratios, elliptic flow, and HBT radii are consistent with the corresponding results at similar {radical}s{sub NN} from fixed target experiments. Directed flow measurements are presented for both midrapidity and forward rapidity regions. Furthermore the collision centrality dependence of identified particle dN/dy, <p{sub T}>, and particle ratios are discussed. These results also demonstrate that the capabilities of the STAR detector, although optimized for {radical}s{sub NN} = 200 GeV, are suitable for the proposed QCD critical point search and exploration of the QCD phase diagram at RHIC.
Date: July 5, 2010
Creator: STAR Collaboration
System: The UNT Digital Library
Long range rapidity correlations and jet production in high energy nuclear collisions (open access)

Long range rapidity correlations and jet production in high energy nuclear collisions

The STAR Collaboration at RHIC presents a systematic study of high transverse momentum charged di-hadron correlations at small azimuthal pair separation {Delta}{phi}, in d+Au and central Au+Au collisions at {radical}s{sub NN} = 200 GeV. Significant correlated yield for pairs with large longitudinal separation {Delta}{eta} is observed in central Au+Au, in contrast to d+Au collisions. The associated yield distribution in {Delta}{eta} x {delta}{phi} can be decomposed into a narrow jet-like peak at small angular separation which has a similar shape to that found in d+Au collisions, and a component which is narrow in {Delta}{phi} and depends only weakly on {Delta}{eta}, the 'ridge'. Using two systematically independent analyses, finite ridge yield is found to persist for trigger p{sub t} > 6 GeV/c, indicating that it is correlated with jet production. The transverse momentum spectrum of hadrons comprising the ridge is found to be similar to that of bulk particle production in the measured range (2 < p{sub t} < 4 GeV/c).
Date: July 5, 2010
Creator: STAR Collaboration
System: The UNT Digital Library
Longitudinal Spin Transfer to Lambda and Lambda bar Hyperons in Polarized Proton-Proton Collisions at sqrt s = 200 GeV (open access)

Longitudinal Spin Transfer to Lambda and Lambda bar Hyperons in Polarized Proton-Proton Collisions at sqrt s = 200 GeV

The longitudinal spin transfer, D{sub LL}, from high energy polarized protons to {Lambda} and {bar {Lambda}} hypersons has been measured for the first time in proton-proton collisions at {radical}s = 200 GeV with the STAR detector at RHIC. The measurements cover pseudorapidity, {eta}, in the range |{eta}| < 1.2 and transverse momenta, p{sub T}, up to 4 GeV/c. The longitudinal spin transfer is found to be D{sub LL} = -0.03{+-}0.13(stat){+-}0.04(syst) for inclusive {Lambda} and D{sub LL} = -0.12{+-}0.08(stat){+-}0.03(syst) for inclusive {bar {Lambda}} hyperons with <{eta}> = 0.5 and <p{sub T}> = 3.7 GeV/c. The dependence on {eta} and p{sub T} is presented.
Date: July 5, 2010
Creator: STAR Collaboration
System: The UNT Digital Library
Observation of an Antimatter Hypernucleus (open access)

Observation of an Antimatter Hypernucleus

Nuclear collisions recreate conditions in the universe microseconds after the Big Bang. Only a very small fraction of the emitted fragments are light nuclei, but these states are of fundamental interest. We report the observation of antihypertritons - composed of an antiproton, antineutron, and antilambda hyperon - produced by colliding gold nuclei at high energy. Our analysis yields 70 {+-} 17 antihypertritons ({sub {bar {Lambda}}}{sup 3}{bar H}) and 157 {+-} 30 hypertritons ({sub {Lambda}}{sup 3}H). The measured yields of {sub {Lambda}}{sup 3}H ({sub {bar {Lambda}}}{sup 3}{bar H}) and {sup 3}He ({sup 3}{ovr He}) are similar, suggesting an equilibrium in coordinate and momentum space populations of up, down, and strange quarks and antiquarks, unlike the pattern observed at lower collision energies. The production and properties of antinuclei, and nuclei containing strange quarks, have implications spanning nuclear/particle physics, astrophysics, and cosmology.
Date: July 5, 2010
Creator: STAR Collaboration
System: The UNT Digital Library
Observation of charge-dependent azimuthal correlations and possible local strong parity violation in heavy-ion collisions (open access)

Observation of charge-dependent azimuthal correlations and possible local strong parity violation in heavy-ion collisions

Parity-odd domains, corresponding to non-trivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the orbital momentum of the system created in non-central collisions. To study this effect, we investigate a three particle mixed harmonics azimuthal correlator which is a {Rho}-even observable, but directly sensitive to the charge separation effect. We report measurements of this observable using the STAR detector in Au+Au and Cu+Cu collisions at {radical}s{sub NN} = 200 and 62 GeV. The results are presented as a function of collision centrality, particle separation in rapidity, and particle transverse momentum. A signal consistent with several of the theoretical expectations is detected in all four data sets. We compare our results to the predictions of existing event generators, and discuss in detail possible contributions from other effects that are not related to parity violation.
Date: July 5, 2010
Creator: STAR Collaboration
System: The UNT Digital Library
Observation of pi+pi-pi+pi- photoproduction in ultraperipheral heavy-ion collisions at sqrt sNN = 200 GeV at the STAR detector (open access)

Observation of pi+pi-pi+pi- photoproduction in ultraperipheral heavy-ion collisions at sqrt sNN = 200 GeV at the STAR detector

We present a measurement of {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -} photonuclear production in ultra-peripheral Au-Au collisions at {radical}s{sub NN} = 200 GeV from the STAR experiment. The {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -} final states are observed at low transverse momentum and are accompanied by mutual nuclear excitation of the beam particles. The strong enhancement of the production cross section at low transverse momentum is consistent with coherent photoproduction. The {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -} invariant mass spectrum of the coherent events exhibits a broad peak around 1540 {+-} 40 MeV/c{sup 2} with a width of 570 {+-} 60 MeV/c{sup 2}, in agreement with the photoproduction data for the {rho}{sup 0}(1700). We do not observe a corresponding peak in the {pi}{sup +}{pi}{sup -} final state and measure an upper limit for the ratio of the branching fractions of the {rho}{sup 0}(1700) to {pi}{sup +}{pi}{sup -} and {pi}{sup +}{pi}{sup -}{pi}{sup +}{pi}{sup -} of 2.5% at 90% confidence level. The ratio of {rho}{sup 0}(1700) and {rho}{sup 0}(770) coherent production cross sections is measured to be 13.4 {+-} 0.8{sub stat.} {+-} 4.4{sub syst.}%.
Date: July 5, 2010
Creator: STAR Collaboration
System: The UNT Digital Library
Systemsize dependence of associated yields in hadron-triggered jets (open access)

Systemsize dependence of associated yields in hadron-triggered jets

We present results on the system size dependence of high transverse momentum di-hadron correlations at {radical}s{sub NN} = 200 GeV as measured by STAR at RHIC. Measurements in d+Au, Cu+Cu and Au+Au collisions reveal similar jet-like correlation yields at small angular separation ({Delta}{phi} {approx} 0, {Delta}{eta} {approx} 0) for all systems and centralities. Previous measurements have shown that the away-side yield is suppressed in heavy-ion collisions. We present measurements of the away-side suppression as a function of transverse momentum and centrality in Cu+Cu and Au+Au collisions. The suppression is found to be similar in Cu+Cu and Au+Au collisions at a similar number of participants. The results are compared to theoretical calculations based on the parton quenching model and the modified fragmentation model. The observed differences between data and theory indicate that the correlated yields presented here will provide important constraints on medium density profile and energy loss model parameters.
Date: July 5, 2010
Creator: STAR Collaboration
System: The UNT Digital Library
Bacterial Microcompartments (open access)

Bacterial Microcompartments

Bacterialmicrocompartments (BMCs) are organelles composed entirely of protein. They promote specific metabolic processes by encapsulatingand colocalizing enzymes with their substrates and cofactors, by protecting vulnerable enzymes in a defined microenvironment, and bysequestering toxic or volatile intermediates. Prototypes of the BMCsare the carboxysomes of autotrophic bacteria. However, structures of similarpolyhedral shape are being discovered in an ever-increasing number of heterotrophic bacteria, where they participate in the utilization ofspecialty carbon and energy sources.Comparative genomics reveals that the potential for this type of compartmentalization is widespread acrossbacterial phyla and suggests that genetic modules encoding BMCs are frequently laterally transferred among bacteria. The diverse functionsof these BMCs suggest that they contribute to metabolic innovation in bacteria in a broad range of environments.
Date: June 5, 2010
Creator: Kerfeld, Cheryl A.; Heinhorst, Sabine & Cannon, Gordon C.
System: The UNT Digital Library
Simulations of a stretching bar using a plasticity model from the shear transformation zone theory (open access)

Simulations of a stretching bar using a plasticity model from the shear transformation zone theory

An Eulerian simulation is developed to study an elastoplastic model of amorphous materials that is based upon the shear transformation zone theory developed by Langer and coworkers. In this theory, plastic deformation is controlled by an effective temperature that measures the amount of configurational disorder in the material. The simulation is used to model ductile fracture in a stretching bar that initially contains a small notch, and the effects of many of the model parameters are examined. The simulation tracks the shape of the bar using the level set method. Within the bar, a finite difference discretization is employed that makes use of the essentially non-oscillatory (ENO) scheme. The system of equations is moderately stiff due to the presence of large elastic constants, and one of the key numerical challenges is to accurately track the level set and construct extrapolated field values for use in boundary conditions. A new approach to field extrapolation is discussed that is second order accurate and requires a constant amount of work per gridpoint.
Date: June 5, 2010
Creator: Rycroft, Chris H. & Gibou, Frederic
System: The UNT Digital Library