Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

University of Texas Rio Grande Valley

Discipline
Keyword
Publication Year
Publication
Publication Type

Articles 2101 - 2130 of 2419

Full-Text Articles in Physical Sciences and Mathematics

Antimicrobial Activity Of Eugenol Derivatives, George Eyambe, Luis Canales, Bimal K. Banik Jan 2011

Antimicrobial Activity Of Eugenol Derivatives, George Eyambe, Luis Canales, Bimal K. Banik

Chemistry Faculty Publications and Presentations

The antibacterial properties of the clove plant are due to the presence of eugenol, an aromatic phenolic compound. Eugenol was isolated from clove by stem distillation. The alkene group in eugenol was epoxidized resulting in the synthesis of epoxide-eugenol. The heterocyclic ring in epoxide was cleaved to a bromoalcohol derivative. The compounds synthesized epoxideeugenol, bromo alcohol and euginol were tested for antimicrobial activity against Staphylococcus aureus (ATCC 25923). Epoxide-eugenol was found to be the most effective antimicrobial agent among the three compounds tested.

Go to article

Dow Chemical Vs. ‘Coercive Utopians’: Constructing The Contested Ground Of Science And Government Regulation In 1970s America, Amy M. Hay Jan 2011

Dow Chemical Vs. ‘Coercive Utopians’: Constructing The Contested Ground Of Science And Government Regulation In 1970s America, Amy M. Hay

History Faculty Publications and Presentations

In 1979, the Dow Chemical Company published an excerpt from a speech by H. Peter Metzger that announced an emerging conflict in American ideals and public policy. He stated that a new kind of individual inhabited Washington, people from the counterculture who were “coercive utopians” because they sought to achieve their agenda through covert actions and hoped to end the American free market economy. Following the 1962 publication of Rachel Carson’s Silent Spring and the subsequent banning of DDT in 1972, Dow and other chemical manufacturers fought to keep the regulatory climate favorable to industry. Dow found itself defending the …

Go to article

Unidirectional Invisibility Induced By Pt-Symmetric Periodic Structures, Zin Lin, Hamidreza Ramezani Jan 2011

Unidirectional Invisibility Induced By Pt-Symmetric Periodic Structures, Zin Lin, Hamidreza Ramezani

Physics and Astronomy Faculty Publications and Presentations

Parity-time (PT) symmetric periodic structures, near the spontaneous PT-symmetry breaking point, can act as unidirectional invisible media. In this regime, the reflection from one end is diminished while it is enhanced from the other. Furthermore, the transmission coefficient and phase are indistinguishable from those expected in the absence of a grating. The phenomenon is robust even in the presence of Kerr nonlinearities, and it can also effectively suppress optical bistabilities.

Go to article

Microwave-Induced Bismuth Nitrate-Catalyzed Expeditious Enamination Of Β-Dicarbonyl Compounds Under Solvent-Free Conditions, Debasish Bandyopadhyay, Bimal K. Banik Jan 2011

Microwave-Induced Bismuth Nitrate-Catalyzed Expeditious Enamination Of Β-Dicarbonyl Compounds Under Solvent-Free Conditions, Debasish Bandyopadhyay, Bimal K. Banik

Chemistry Faculty Publications and Presentations

Bismuth nitrate-catalyzed, automated microwave-assisted expeditious synthesis of β- enaminones and β-enaminoesters has been carried out in an efficient manner under solvent-free condition. The reaction is general for primary, secondary (cyclic, heterocyclic and acyclic), benzylic as well as aromatic amines.

Go to article

Magnetization Precession And Domainwall Structure In Cobalt-Ruthenium-Cobalt Trilayers, Zhen Li, Ralph Skomski, Sy-Hwang Liou, Steven Michalski, Mircea Chipara, Roger D. Kirby Jan 2011

Magnetization Precession And Domainwall Structure In Cobalt-Ruthenium-Cobalt Trilayers, Zhen Li, Ralph Skomski, Sy-Hwang Liou, Steven Michalski, Mircea Chipara, Roger D. Kirby

Physics and Astronomy Faculty Publications and Presentations

The magnetization dynamics of Co(5 nm)/Ru/Co(5 nm) trilayers with Ru thicknesses from 0.3–0.6 nm is experimentally and theoretically investigated. The coupling between the Co layers is antiferromagnetic (AFM) and yields a stable AFM domain structure with frozen domain walls. Comparing high-resolution magnetic force microscopy (MFM) and pump-probe measurements, we analyze the behavior of the films for different field-strength regimes. For moderate magnetic fields, pump-probe measurements provide dynamic characterization of the coupled precessional modes in the GHz range. The dynamics at small fields is realized by the pinning of AFM domain walls at inhomogeneities. The MFM images yield a domain-wall width …

Go to article

Sythesis Of Glucose Peracetate Via Bismuth Nitrate-Induced Reaction, Jose Lerma, Bimal K. Banik Jan 2011

Sythesis Of Glucose Peracetate Via Bismuth Nitrate-Induced Reaction, Jose Lerma, Bimal K. Banik

Chemistry Faculty Publications and Presentations

Simple synthesis peracetylated glucose has been achieved starting from glucose and acetic anhydride in the absence of solvent via bismuth nitrate-catalyzed reaction. This method does not need large excess of acetic anhydride.

Go to article

Microwave-Induced Bismuth Nitrate-Catalyzed Electrophilic Substitution Of Indole With Keto Ester Under Slovent-Free Conditions, Sonya Rivera, Laura Iglesias, Debasish Bandyopadhyay, Bimal K. Banik Jan 2011

Microwave-Induced Bismuth Nitrate-Catalyzed Electrophilic Substitution Of Indole With Keto Ester Under Slovent-Free Conditions, Sonya Rivera, Laura Iglesias, Debasish Bandyopadhyay, Bimal K. Banik

Chemistry Faculty Publications and Presentations

Microwave-induced preparation of bis(indollyl)methane derivative has been developed through a bismuth nitrate-catalyzed reaction of indole with diethylketomalonate under solventfree conditions.

Go to article

Microwave-Induced Bismuth Nitrate-Catalyzed Electrophilic Substitution Of 7-Aza Indole With Activated Carbonyl Compound Under Solvent-Free Conditions, Sonya Rivera, Debasish Bandyopadhyay, Bimal K. Banik Jan 2011

Microwave-Induced Bismuth Nitrate-Catalyzed Electrophilic Substitution Of 7-Aza Indole With Activated Carbonyl Compound Under Solvent-Free Conditions, Sonya Rivera, Debasish Bandyopadhyay, Bimal K. Banik

Chemistry Faculty Publications and Presentations

An expeditious microwave-induced synthetic method for the preparation of bis(azaindollyl)methane derivative has been developed through a bismuth nitrate-catalyzed reaction of 7-azaindole with diethylketomalonate under solvent-free conditions.

Go to article

Microwave-Induced Stereoselectivity Of Β-Lactam Formation: Effects Of Solvents, Debasish Bandyopadhyay, Marco Yanez, Bimal K. Banik Jan 2011

Microwave-Induced Stereoselectivity Of Β-Lactam Formation: Effects Of Solvents, Debasish Bandyopadhyay, Marco Yanez, Bimal K. Banik

Chemistry Faculty Publications and Presentations

Synthesis of 3, 4-disubstituted 2-azetidinones has been achieved following Staudinger reaction under microwave-induced conditions. The stereoselectivity of β-lactam formation depends on the nature of the solvents used in the reaction.

Go to article

Phosphoric Acid Catalyzed Aza-Michael Reaction In Water: An Ecofriendly Procedure, Debasish Bandyopadhyay, Stephanie Maldonado, Bimal K. Banik Jan 2011

Phosphoric Acid Catalyzed Aza-Michael Reaction In Water: An Ecofriendly Procedure, Debasish Bandyopadhyay, Stephanie Maldonado, Bimal K. Banik

Chemistry Faculty Publications and Presentations

Phosphoric acid catalyzed aza-Michael reaction in water has been carried out in an efficient manner at room temperature. The reaction is general for primary, secondary (cyclic, heterocyclic and acyclic), benzylic as well as aromatic amines. No bis-addition was observed for primary amines.

Go to article

Separating Ne From Some Nonuniform Nondeterministic Complexity Classes, Bin Fu, Ansheng Li, Liyu Zhang Jan 2011

Separating Ne From Some Nonuniform Nondeterministic Complexity Classes, Bin Fu, Ansheng Li, Liyu Zhang

Computer Science Faculty Publications and Presentations

We investigate the question whether NE can be separated from the reduction closures of tally sets, sparse sets and NP. We show that (1) NE 6 ⊆ RNP no(1) −T (TALLY); (2)NE 6 ⊆ RSN m (SPARSE); and (3) NE 6 ⊆ PNP nk −T /nk for all k ≥ 1. Result (3) extends a previous result by Mocas to nonuniform reductions. We also investigate how different an NE-hard set is from an NP-set. We show that for any NP subset A of a many-one-hard set H for NE, there exists another NP subset A′ of H such that A′ …

Go to article

Directional Limits On Persistent Gravitational Waves Using Ligo S5 Science Data, J. Abadie, B. P. Abbott, Matthew Benacquista, Teviet Creighton, R. Grosso, J. Li, Soma Mukherjee, Soumya Mohanty, Malik Rakhmanov, Volker Quetschke, Robert Stone, Joseph D. Romano, B. Vaishnav Jan 2011

Directional Limits On Persistent Gravitational Waves Using Ligo S5 Science Data, J. Abadie, B. P. Abbott, Matthew Benacquista, Teviet Creighton, R. Grosso, J. Li, Soma Mukherjee, Soumya Mohanty, Malik Rakhmanov, Volker Quetschke, Robert Stone, Joseph D. Romano, B. Vaishnav

Physics and Astronomy Faculty Publications and Presentations

The gravitational-wave (GW) sky may include nearby pointlike sources as well as stochastic backgrounds. We perform two directional searches for persistent GWs using data from the LIGO S5 science run: one optimized for pointlike sources and one for arbitrary extended sources. Finding no evidence to support the detection of GWs, we present 90% confidence level (C.L.) upper-limit maps of GW strain power with typical values between 2−20×10−50  strain2 Hz−1 and 5−35×10−49  strain2 Hz−1 sr−1 for pointlike and extended sources, respectively. The latter result is the first of its kind. We also set 90% C.L. limits on the narrow-band root-mean-square GW …

Go to article

Magnetization Precession And Domain-Wall Structure In Cobalt-Ruthenium-Cobalt Trilayers, Zhen Li, Ralph Skomski, Sy-Hwang Liou, Steven Michalski, Mircea Chipara, Roger D. Kirby Jan 2011

Magnetization Precession And Domain-Wall Structure In Cobalt-Ruthenium-Cobalt Trilayers, Zhen Li, Ralph Skomski, Sy-Hwang Liou, Steven Michalski, Mircea Chipara, Roger D. Kirby

Physics and Astronomy Faculty Publications and Presentations

The magnetization dynamics of Co(5 nm)/Ru/Co(5 nm) trilayers with Ru thicknesses from 0.3–0.6 nm is experimentally and theoretically investigated. The coupling between the Co layers is antiferromagnetic (AFM) and yields a stable AFM domain structure with frozen domain walls. Comparing high-resolution magnetic force microscopy (MFM) and pump-probe measurements, we analyze the behavior of the films for different field-strength regimes. For moderate magnetic fields, pump-probe measurements provide dynamic characterization of the coupled precessional modes in the GHz range. The dynamics at small fields is realized by the pinning of AFM domain walls at inhomogeneities. The MFM images yield a domain-wall width …

Go to article

Teaching Introductory Undergraduate Physics Using Commercial Video Games, Soumya D. Mohanty, Sergio Cantu Jan 2011

Teaching Introductory Undergraduate Physics Using Commercial Video Games, Soumya D. Mohanty, Sergio Cantu

Physics and Astronomy Faculty Publications and Presentations

Commercial video games are increasingly using sophisticated physics simulations to create a more immersive experience for players. This also makes them a powerful tool for engaging students in learning physics. We provide some examples to show how commercial off-the-shelf games can be used to teach specific topics in introductory undergraduate physics. The examples are selected from a course taught predominantly through the medium of commercial video games.

Go to article

The Behavior Of Nanothermite Reaction Based On Bi2o3/Al, L. Wang, D. Luss, Karen S. Martirosyan Jan 2011

The Behavior Of Nanothermite Reaction Based On Bi2o3/Al, L. Wang, D. Luss, Karen S. Martirosyan

Physics and Astronomy Faculty Publications and Presentations

We studied the impact of aluminum particle size and the thickness of surrounding alumina layer on the dynamic pressure discharge of nanothermite reactions in the Bi2O3/Al system. A pressure discharge from 9 to 13 MPa was generated using as-synthesized Bi2O3 nano-particles produced by combustion synthesis and Al nanoparticles with size from 3 μm to 100 nm. The maximum reaction temperature was measured to be ∼2700 °C. The estimated activation energy of the reaction was 45 kJ/mol. A very large (several orders of magnitude) difference existed between the rate of the pressure pulse release by nanothermite reactions and by thermite …

Go to article

Characterizations Of Exponential Distribution Via Conditional Expectations Of Record Values, George Yanev Jan 2011

Characterizations Of Exponential Distribution Via Conditional Expectations Of Record Values, George Yanev

School of Mathematical and Statistical Sciences Faculty Publications and Presentations

We prove that the exponential distribution is the only one which satisfies a regression identity. This identity involves conditional expectation of the sample mean of record values given two record values outside of the sample.

Go to article

Due Diligence And Demographic Disparities: Effects Of The Planning Of U.S.- Mexico Border Fence On Marginalized Populations, J. Gaines Wilson, Jude A. Benavides, Karen Engle, Denise Gilman, Anthony Reisinger, Jessica Spangler, Joe Lemen Dec 2010

Due Diligence And Demographic Disparities: Effects Of The Planning Of U.S.- Mexico Border Fence On Marginalized Populations, J. Gaines Wilson, Jude A. Benavides, Karen Engle, Denise Gilman, Anthony Reisinger, Jessica Spangler, Joe Lemen

School of Earth, Environmental, and Marine Sciences Faculty Publications and Presentations

In the buildup to the construction the U.S.-Mexico border fence by the United States Department of Homeland Security (USDHS), much attention was drawn to security, drug enforcement, and immigration issues. However, there was little quantitative analysis regarding which populations were most likely to be affected by the proposed fence. Using a geographic information system, we classified census blocks in Cameron County, Texas into one of two categories: either ‘fence’ or ‘gap’. A total of 14 demographic factors were tested for disparities between those living in gap areas and those living in areas exposed to the fence. Twelve of fourteen factors …

Go to article

Double Compact Objects As Low-Frequency Gravitational Wave Sources, Krzysztof Belczynski, Matthew Benacquista, Tomasz Bulik Dec 2010

Double Compact Objects As Low-Frequency Gravitational Wave Sources, Krzysztof Belczynski, Matthew Benacquista, Tomasz Bulik

Physics and Astronomy Faculty Publications and Presentations

We study the Galactic field population of double compact objects (DCOs; NS-NS, BH-NS, BH-BH binaries) to investigate the number (if any) of these systems that can potentially be detected with the Laser Interferometer Space Antenna (LISA) at low gravitational wave frequencies. We calculate the Galactic numbers and physical properties of these binaries and show their relative contributions from the disk, bulge, and halo. Although the Galaxy hosts ∼10 5 DCO binaries emitting low-frequency gravitational waves, only a handful of these objects in the disk will be detectable with LISA, but none from the halo or bulge. This is because the …

Go to article

Equation Of State Of A Dense And Magnetized Fermion System, Efrain J. Ferrer, Vivian De La Incera, Jason P. Keith, Israel Portillo, Paul L. Springsteen Dec 2010

Equation Of State Of A Dense And Magnetized Fermion System, Efrain J. Ferrer, Vivian De La Incera, Jason P. Keith, Israel Portillo, Paul L. Springsteen

Physics and Astronomy Faculty Publications and Presentations

The equation of state of a system of fermions in a uniform magnetic field is obtained in terms of the thermodynamic quantities of the theory by using functional methods. It is shown that the breaking of the O(3) rotational symmetry by the magnetic field results in a pressure anisotropy, which leads to the distinction between longitudinal- and transverse-to-the-field pressures. A criterion to find the threshold field at which the asymmetric regime becomes significant is discussed. This threshold magnetic field is shown to be the same as the one required for the pure field contribution to the energy and pressures to …

Go to article

Spectral Reflectance As An Indicator Of Foliar Concentrations Of Arsenic In Common Sunflower (Helianthus Annuus), Yuridia Patricia Peralta De Gandy Dec 2010

Spectral Reflectance As An Indicator Of Foliar Concentrations Of Arsenic In Common Sunflower (Helianthus Annuus), Yuridia Patricia Peralta De Gandy

Theses and Dissertations - UTB/UTPA

Studies were conducted to investigate the use of spectral reflectance by foliage of common sunflower as a potential indicator of arsenic contamination of soil. Germination method was developed for sunflower seeds, and cohorts of sunflower seedlings in hydroponic tanks were established. The cohorts were exposed to 0 ppm, 5 ppm, 7.5 ppm, and 10 ppm treatments of As (V) and reflectance measurements of foliage were collected using a spectroradiometer during two experiments.Results demonstrated the feasibility of using spectral reflectance by foliage of common sunflower as a potential indicator of arsenic contamination. In both experiments, arsenic concentrations in leaf tissues were …

Go to article

A Highly Efficient Bismuth Salts-Catalyzed Route For The Synthesis Of Alpha-Aminophosphonates, Antara Banik, Sahil Batta, Debasish Bandyopadhyay, Bimal K. Banik Nov 2010

A Highly Efficient Bismuth Salts-Catalyzed Route For The Synthesis Of Alpha-Aminophosphonates, Antara Banik, Sahil Batta, Debasish Bandyopadhyay, Bimal K. Banik

Chemistry Faculty Publications and Presentations

A convenient synthesis of different types of α-amino phosphonates via one-pot solvent-free three component reactions of aldehydes, amines and phosphites catalyzed by bismuth salts has been investigated. Bismuth triflate is found to be the most effective catalyst for this reaction.

Go to article

Importance Of Electronic Relaxation For Inter-Coulombic Decay In Aqueous Systems, Craig P. Schwartz, Shervin Fatehi, Richard J. Saykally, David Prendergast Nov 2010

Importance Of Electronic Relaxation For Inter-Coulombic Decay In Aqueous Systems, Craig P. Schwartz, Shervin Fatehi, Richard J. Saykally, David Prendergast

Chemistry Faculty Publications and Presentations

Inspired by recent photoelectron spectroscopy experiments on hydroxide solutions, we have examined the conditions necessary for enhanced (and, in the case of solutions, detectable) inter-Coulombic decay (ICD)—Auger emission from an atomic site other than that originally excited. We present general guidelines, based on energetic and spatial overlap of molecular orbitals, for this enhancement of inter-Coulombic decay-based energy transfer in solutions. These guidelines indicate that this decay process should be exhibited by broad classes of biomolecules and suggest a design criterion for targeted radiooncology protocols. Our findings show that photoelectron spectroscopy cannot resolve the current hydroxide coordination controversy.

Go to article

Detecting Massive Gravitons Using Pulsar Timing Arrays, Kejia Lee, F. A. Jenet, Richard H. Price, Norbert Wex, Michael Kramer Oct 2010

Detecting Massive Gravitons Using Pulsar Timing Arrays, Kejia Lee, F. A. Jenet, Richard H. Price, Norbert Wex, Michael Kramer

Physics and Astronomy Faculty Publications and Presentations

At the limit of weak static fields, general relativity becomes Newtonian gravity with a potential field that falls off as inverse distance rather than a theory of Yukawa-type fields with a finite range. General relativity also predicts that the speed of disturbances of its waves is c, the vacuum light speed, and is non-dispersive. For these reasons, the graviton, the boson for general relativity, can be considered to be massless. Massive gravitons, however, are features of some alternatives to general relativity. This has motivated experiments and observations that, so far, have been consistent with the zero-mass graviton of general relativity, …

Go to article

Ultra-Compact Dwarfs In The Core Of The Coma Cluster, Juan P. Madrid, Alister W. Graham, William E. Harris, Paul Goudfrooij, Duncan A. Forbes, David Carter, John P. Blakeslee, Lee R. Spitler, Henry C. Ferguson Oct 2010

Ultra-Compact Dwarfs In The Core Of The Coma Cluster, Juan P. Madrid, Alister W. Graham, William E. Harris, Paul Goudfrooij, Duncan A. Forbes, David Carter, John P. Blakeslee, Lee R. Spitler, Henry C. Ferguson

Physics and Astronomy Faculty Publications and Presentations

We have discovered both a red and a blue subpopulation of ultra-compact dwarf (UCD) galaxy candidates in the Coma galaxy cluster. We analyzed deep F475W (Sloan g) and F814W (I) Hubble Space Telescope images obtained with the Advanced Camera for Surveys Wide Field Channel as part of the Coma Cluster Treasury Survey and have fitted the light profiles of similar to 5000 point-like sources in the vicinity of NGC 4874, one of the two central dominant galaxies of the Coma Cluster. Although almost all of these sources are globular clusters that remain unresolved, we found that 52 objects have effective …

Go to article

First Search For Gravitational Waves From The Youngest Known Neutron Star, J. Abadie, B. P. Abbott, R. Abbott, M. Abernathy, C. Adams, R. Adhikari, P. Ajith, B. Allen, G. Allen, E. Amador Ceron, R. S. Amin, S. B. Anderson, W. G. Anderson, M. A. Arain, M. Araya, M. Aronsson, Y. Aso, S. Aston, D. E. Atkinson, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, S. Ballmer, D. Barker, S. Barnum, B. Barr, P. Barriga, L. Barsotti, M. A. Barton Oct 2010

First Search For Gravitational Waves From The Youngest Known Neutron Star, J. Abadie, B. P. Abbott, R. Abbott, M. Abernathy, C. Adams, R. Adhikari, P. Ajith, B. Allen, G. Allen, E. Amador Ceron, R. S. Amin, S. B. Anderson, W. G. Anderson, M. A. Arain, M. Araya, M. Aronsson, Y. Aso, S. Aston, D. E. Atkinson, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, S. Ballmer, D. Barker, S. Barnum, B. Barr, P. Barriga, L. Barsotti, M. A. Barton

Physics and Astronomy Faculty Publications and Presentations

We present a search for periodic gravitational waves from the neutron star in the supernova remnant Cassiopeia A. The search coherently analyzes data in a 12 day interval taken from the fifth science run of the Laser Interferometer Gravitational-Wave Observatory. It searches gravitational-wave frequencies from 100 to 300 Hz and covers a wide range of first and second frequency derivatives appropriate for the age of the remnant and for different spin-down mechanisms. No gravitational-wave signal was detected. Within the range of search frequencies, we set 95% confidence upper limits of (0.7-1.2) × 10 -24 on the intrinsic gravitational-wave strain, (0.4-4) …

Go to article

Dissipation Scales And Anomalous Sinks In Steady Two-Dimensional Turbulence, Eleftherios Gkioulekas Oct 2010

Dissipation Scales And Anomalous Sinks In Steady Two-Dimensional Turbulence, Eleftherios Gkioulekas

School of Mathematical and Statistical Sciences Faculty Publications and Presentations

In previous papers I have argued that the fusion rules hypothesis, which was originally introduced by L’vov and Procaccia in the context of the problem of three-dimensional turbulence, can be used to gain a deeper insight in understanding the enstrophy cascade and inverse energy cascade of two-dimensional turbulence. In the present paper, we show that the fusion rules hypothesis, combined with nonperturbative locality, itself a consequence of the fusion rules hypothesis, dictates the location of the boundary separating the inertial range from the dissipation range. In so doing, the hypothesis that there may be an anomalous enstrophy sink …

Go to article

Molecular Mechanisms Of Persistence Of Mutualistic Bacteria Photorhabdus In The Entomopathogenic Nematode Host, Ruisheng An, Parwinder Grewal Oct 2010

Molecular Mechanisms Of Persistence Of Mutualistic Bacteria Photorhabdus In The Entomopathogenic Nematode Host, Ruisheng An, Parwinder Grewal

School of Earth, Environmental, and Marine Sciences Faculty Publications and Presentations

Symbioses between microbes and animals are ubiquitous, yet little is known about the intricate mechanisms maintaining such associations. In an emerging mutualistic model system, insect-pathogenic bacteria Photorhabdus and their insect-parasitic nematode partner Heterorhabditis, we found that the bacteria undergo major transcriptional reshaping in the nematode intestine. Besides general starvation mechanisms, the bacteria induce cellular acidification to slow down growth, switch to pentose phosphate pathway to overcome oxidative stress and nutrition limitation, and shed motility but develop biofilm to persist in the nematode intestine until being released into the insect hemolymph. These findings demonstrate how the symbiotic bacteria reduce their …

Go to article

The Sensitivity Of The Parkes Pulsar Timing Array To Individual Sources Of Gravitational Waves, D. R.B. Yardley, G. B. Hobbs, F. A. Jenet, J. P.W. Verbiest, Z. L. Wen, R. N. Manchester, W. A. Coles, W. Van Straten, M. Bailes, N. D.R. Bhat, S. Burke-Spolaor, D. J. Champion, A. W. Hotan, J. M. Sarkissian Sep 2010

The Sensitivity Of The Parkes Pulsar Timing Array To Individual Sources Of Gravitational Waves, D. R.B. Yardley, G. B. Hobbs, F. A. Jenet, J. P.W. Verbiest, Z. L. Wen, R. N. Manchester, W. A. Coles, W. Van Straten, M. Bailes, N. D.R. Bhat, S. Burke-Spolaor, D. J. Champion, A. W. Hotan, J. M. Sarkissian

Physics and Astronomy Faculty Publications and Presentations

We present the sensitivity of the Parkes Pulsar Timing Array to gravitational waves (GWs) emitted by individual supermassive black hole binary systems in the early phases of coalescing at the cores of merged galaxies. Our analysis includes a detailed study of the effects of fitting a pulsar timing model to non-white timing residuals. Pulsar timing is sensitive at nanoHertz frequencies and hence complementary to Laser Interferometer Gravitational-Wave Observatory and Laser Interferometer Space Antenna. We place a sky-averaged constraint on the merger rate of nearby (z < 0.6) black hole binaries in the early phases of coalescence with a chirp mass of 1010 M⊙ of less than one merger every 7 yr. The prospects for future GW astronomy of this type with the proposed Square Kilometre Array telescope are discussed. © 2010 The Authors. Journal compilation © 2010 RAS.

Go to article

Compact Binaries In Star Clusters - I. Black Hole Binaries Inside Globular Clusters, J. M.B. Downing, M. J. Benacquista, M. Giersz, R. Spurzem Sep 2010

Compact Binaries In Star Clusters - I. Black Hole Binaries Inside Globular Clusters, J. M.B. Downing, M. J. Benacquista, M. Giersz, R. Spurzem

Physics and Astronomy Faculty Publications and Presentations

We study the compact binary population in star clusters, focusing on binaries containing black holes, using a self-consistent Monte Carlo treatment of dynamics and full stellar evolution. We find that the black holes experience strong mass segregation and become centrally concentrated. In the core the black holes interact strongly with each other and black hole-black hole binaries are formed very efficiently. The strong interactions, however, also destroy or eject the black hole-black hole binaries. We find no black hole-black hole mergers within our simulations but produce many hard escapers that will merge in the Galactic field within a Hubble time. …

Go to article

Identification Of Parameters And The Distribution Of The Maximum And The Minimum, Lijuan Bi Aug 2010

Identification Of Parameters And The Distribution Of The Maximum And The Minimum, Lijuan Bi

Theses and Dissertations - UTB/UTPA

In problems of competing risks, where an individual may be subject to m causes of death and X(i) is the lifetime of an individual exposed to the ith cause, the X(i)s are not observable but only is their minimum, and inference is needed on the X(i) based on their minimum. The same is the case with a m-component system, where the components are connected in series, and we are interested in inference on the lifetimes of the individual components. These examples motivate problems on parameter identification by the distribution of the minimum. Similarly, the example of a m-component system where …

Go to article

First Prev Next Last