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Articles 661 - 680 of 680
Full-Text Articles in Physical Sciences and Mathematics
Polymer Depletion Effects Near Mesoscopic Particles, Andreas Hanke, E. Eisenriegler, S. Dietrich
Polymer Depletion Effects Near Mesoscopic Particles, Andreas Hanke, E. Eisenriegler, S. Dietrich
Physics and Astronomy Faculty Publications and Presentations
The behavior of mesoscopic particles dissolved in a dilute solution of long, flexible, and nonadsorbing polymer chains is studied by field-theoretic methods. For spherical and cylindrical particles the solvation free energy for immersing a single particle in the solution is calculated explicitly. Important features are qualitatively different for self-avoiding polymer chains as compared with ideal chains. The results corroborate the validity of the Helfrich-type curvature expansion for general particle shapes and allow for quantitative experimental tests. For the effective interactions between a small sphere and a wall, between a thin rod and a wall, and between two small spheres, quantitative …
Detecting An Association Between Gamma Ray And Gravitational Wave Bursts, Lee Samuel Finn, Soumya Mohanty, Joseph D. Romano
Detecting An Association Between Gamma Ray And Gravitational Wave Bursts, Lee Samuel Finn, Soumya Mohanty, Joseph D. Romano
Physics and Astronomy Faculty Publications and Presentations
If γ-ray bursts (GRBs) are accompanied by gravitational wave bursts (GWBs) the correlated output of two gravitational wave detectors evaluated in the moments just prior to a GRB will differ from that evaluated at other times. We can test for this difference without prior knowledge of either the GWB wave form or the detector noise spectrum. With a model for the GRB source population and GWB spectrum we can put a limit on the in-band rms GWB signal amplitude. Laser-Interferometer Gravitational Wave Observatory I detector observations coincident with 1000 GRB observations could lead us to exclude with 95% confidence associated …
Critical Adsorption On Curved Objects, Andreas Hanke, S. Dietrich
Critical Adsorption On Curved Objects, Andreas Hanke, S. Dietrich
Physics and Astronomy Faculty Publications and Presentations
A systematic field-theoretical description of critical adsorption on curved objects such as spherical or rodlike colloidal particles immersed in a fluid near criticality is presented. The temperature dependence of the corresponding order parameter profiles and of the excess adsorption are calculated explicitly. Critical adsorption on elongated rods is substantially more pronounced than on spherical particles. It turns out that, within the context of critical phenomena in confined geometries, critical adsorption on a microscopically thin ‘‘needle’’ represents a distinct universality class of its own. Under favorable conditions the results are relevant for the flocculation of colloidal particles.
Apex: Cross-Platform Analysis Program For Exafs, N. Dimakis, Grant Bunker
Apex: Cross-Platform Analysis Program For Exafs, N. Dimakis, Grant Bunker
Physics and Astronomy Faculty Publications and Presentations
We have developed version 1.0 of a freely available (including source code) suite of basic X-Ray Absorption Fine Structure (XAFS) data analysis programs for data reduction and single scattering analysis. This package is based on the University of Washington (UW/NRL) Fortran 77 programs that are available on the International XAFS Society (IXS) database, complemented by a graphical TCL/TK scripting language based user interface which runs virtually unchanged between platforms, using the native look and feel of the corresponding platform. The package has been tested on MacOS 8.1, Linux, IRIX, Windows95 and NT. Particular emphasis is placed on simplicity, reliability, and …
Radio Pulse Properties Of The Millisecond Pulsar Psr J0437-4715. I. Observations At 20 Centimeters, F. A. Jenet, S. B. Anderson, V. M. Kaspi, T. A. Prince, S. C. Unwin
Radio Pulse Properties Of The Millisecond Pulsar Psr J0437-4715. I. Observations At 20 Centimeters, F. A. Jenet, S. B. Anderson, V. M. Kaspi, T. A. Prince, S. C. Unwin
Physics and Astronomy Faculty Publications and Presentations
We present a total of 48 minutes of observations of the nearby, bright millisecond pulsar PSR J0437-4715 taken at the Parkes Observatory in Australia. The data were obtained at a central radio frequency of 1380 MHz using a high-speed tape recorder that permitted coherent Nyquist sampling of 50 MHz of bandwidth in each of two polarizations. Using the high time resolution available from this voltage recording technique, we have studied a variety of single-pulse properties, many for the first time in a millisecond pulsar. We show that individual pulses are broad band, have pulse widths ranging from ∼ 10 (∼ …
Critical Casimir Forces Between Spherical Particles In Fluids, Andreas Hanke, F. Schlesener, E. Eisenriegler, S. Dietrich
Critical Casimir Forces Between Spherical Particles In Fluids, Andreas Hanke, F. Schlesener, E. Eisenriegler, S. Dietrich
Physics and Astronomy Faculty Publications and Presentations
Long-ranged correlations in a fluid close to its critical point Tc cause distinct forces between immersed colloidal particles and the container walls. We calculate such a force and its temperature dependence for the generic case of a spherical particle located at a distance D from a planar wall and find that the force attains a maximum at a temperature Tmax(D) above Tc, which facilitates quantitative experimental tests. The corresponding effective pair interaction between the colloidal particles themselves, potentially leading to aggregation, is also discussed.
Ab Initio Single- And Multiple-Scattering Exafs Debye-Waller Factors: Raman And Infrared Data, N. Dimakis, Grant Bunker
Ab Initio Single- And Multiple-Scattering Exafs Debye-Waller Factors: Raman And Infrared Data, N. Dimakis, Grant Bunker
Physics and Astronomy Faculty Publications and Presentations
The extended x-ray-absorption fine structure (EXAFS) Debye-Waller factor is an essential term appearing in the EXAFS equation that accounts for the molecular structural and thermal disorder of a sample. Single- and multiple-scattering Debye-Waller factors must be known accurately to obtain quantitative agreement between theory and experiment. Since the total number of fitting parameters that can be varied is limited in general, data cannot support fitting of all relevant multiple-scattering Debye-Waller factors. Calculation of the Debye-Waller factors is typically done using the correlated Debye approximation, where a single parameter (Debye temperature) is varied. However, this procedure cannot account in general for …
A Data Analysis Approach For Detecting Gravitational Waves From Psr 0437-4715, Soumya Mohanty, I. S. Heng, David Blair, S. Dhurandhar, M. Tovar, E. Ivanov
A Data Analysis Approach For Detecting Gravitational Waves From Psr 0437-4715, Soumya Mohanty, I. S. Heng, David Blair, S. Dhurandhar, M. Tovar, E. Ivanov
Physics and Astronomy Faculty Publications and Presentations
A search for gravitational waves from the millisecond pulsar PSR 0437-4715 has been initiated using the bar detector NIOBE which is located at the University of Western Australia. We present a detailed report on the data analysis algorithm, called phase plane rotation, which will be used in this search. A discussion of the actual implementation of the algorithm is presented. The data analysis algorithm mentioned above has the advantage that it requires minimal changes to the already-existing data acquisition facility of NIOBE but, at the same time, it is as efficient as optimal filtering in detecting a signal. This …
Searching For Periodic Sources With Ligo, Patrick R. Brady, Teviet Creighton, Curt Cutler, Bernard F. Schutz
Searching For Periodic Sources With Ligo, Patrick R. Brady, Teviet Creighton, Curt Cutler, Bernard F. Schutz
Physics and Astronomy Faculty Publications and Presentations
We investigate the computational requirements for all-sky, all-frequency searches for gravitational waves from spinning neutron stars, using archived data from interferometric gravitational wave detectors such as LIGO. These sources are expected to be weak, so the optimal strategy involves coherent accumulaton of signal-to-noise using Fourier transforms of long stretches of data (months to years). Earth-motion-induced Doppler shifts, and intrinsic pulsar spindown, will reduce the narrow-band signal-to-noise by spreading power across many frequency bins; therefore, it is necessary to correct for these effects before performing the Fourier transform. The corrections can be implemented by a parametrized model, in which one does …
Three Types Of Gamma-Ray Bursts, Soma Mukherjee, Eric D. Feigelson, Gutti Jogesh Babu, Flonn Murtagh, Chris Fralev, Adrian Raftery
Three Types Of Gamma-Ray Bursts, Soma Mukherjee, Eric D. Feigelson, Gutti Jogesh Babu, Flonn Murtagh, Chris Fralev, Adrian Raftery
Physics and Astronomy Faculty Publications and Presentations
A multivariate analysis of gamma-ray burst (GRB) bulk properties is presented to discriminate between distinct classes of GRBs. Several variables representing burst duration, fluence, and spectral hardness are considered. Two multivariate clustering procedures are used on a sample of 797 bursts from the Third BATSE Catalog, a nonparametric average linkage hierarchical agglomerative clustering procedure validated with Wilks' Λ* and other multivariate analysis of variance tests and a parametric maximum likelihood model-based clustering procedure assuming multinormal populations calculated with the Expectation-Maximization algorithm and validated with the Bayesian Information Criterion. The two methods yield very similar results. The BATSE GRB population consists …
Hierarchical Search Strategy For The Detection Of Gravitational Waves From Coalescing Binaries: Extension To Post-Newtonian Waveforms, Soumya Mohanty
Hierarchical Search Strategy For The Detection Of Gravitational Waves From Coalescing Binaries: Extension To Post-Newtonian Waveforms, Soumya Mohanty
Physics and Astronomy Faculty Publications and Presentations
The detection of gravitational waves from coalescing compact binaries would be a computationally intensive process if a single bank of template wave forms (one step search) is used. In an earlier paper we presented a detection strategy, called a two step search, that utilizes a hierarchy of template banks. It was shown that in the simple case of a family of Newtonian signals, an on-line two step search was ≃8 times faster than an on-line one step search (for the initial LIGO). In this paper we extend the two step search to the more realistic case of …
Magnetic Field Decay In Single Radio Pulsars: A Statistical Study, Soma Mukherjee, Ajit Kembhavi
Magnetic Field Decay In Single Radio Pulsars: A Statistical Study, Soma Mukherjee, Ajit Kembhavi
Physics and Astronomy Faculty Publications and Presentations
We report on an extensive statistical study of single radio pulsar properties, which we undertook to estimate the decay timescale of pulsar magnetic fields. We synthesized a population of pulsars using assumed theoretical distributions of age, initial magnetic field, period of rotation, position, luminosity, and dispersion measure, taking into account the new distance model for pulsars as well as new velocity estimates. We also took into account the selection effects that characterize pulsar observations. We compared the simulated population with the observed single pulsar population using one- and two-dimensional Kolmogorov-Smirnov tests to obtain a lower bound of ∼160 Myr on …
Large-Amplitude Solitary Waves In Finite Temperature Dusty Plasma, R. Roychoudhury, S. Mukherjee
Large-Amplitude Solitary Waves In Finite Temperature Dusty Plasma, R. Roychoudhury, S. Mukherjee
Physics and Astronomy Faculty Publications and Presentations
Large-amplitude solitary waves in dusty plasma are investigated, taking into account the dusty particle temperature. It is shown that finite dusty temperature restricts the region for the existence of solitary waves.
Macrophage-Mediated 15-Lipoxygenase Expression Protects Against Atherosclerosis Development, Jianhe Shen, Ed Herderick, J. Fredrick Cornhill, Eva Zsigmond, Han Seob Kim, Hartmut Kühn, Natalia V. Guevara, Lawrence Chan
Macrophage-Mediated 15-Lipoxygenase Expression Protects Against Atherosclerosis Development, Jianhe Shen, Ed Herderick, J. Fredrick Cornhill, Eva Zsigmond, Han Seob Kim, Hartmut Kühn, Natalia V. Guevara, Lawrence Chan
Physics and Astronomy Faculty Publications and Presentations
Oxidative modification of LDL increases its atherogenicity, and 15- lipoxygenase (15-LO) has been implicated in the process. To address this issue, we generated transgenic rabbits that expressed 15-LO in a macrophage- specific manner and studied their susceptibility to atherosclerosis development when they were fed a high-fat, high-cholesterol (HFHC) diet (Teklad 0533 rabbit diet 7009 with 10% corn oil and 0.25% cholesterol) for 13.5 wk. Transgenic and nontransgenic rabbits developed similar degrees of hypercholesterolemia and had similar levels of triglyceride, VLDL, LDL, and HDL. Quantitative morphometric analysis of the aortic atherosclerosis indicated that the transgenic animals (n = 19) had significantly …
Polymers Interacting With Spherical And Rodlike Particles, E. Eisenriegler, Andreas Hanke, S. Dietrich
Polymers Interacting With Spherical And Rodlike Particles, E. Eisenriegler, Andreas Hanke, S. Dietrich
Physics and Astronomy Faculty Publications and Presentations
The interaction of a long flexible polymer chain with mesoscopic particles of spherical or elongated cylindrical shape is investigated by field-theoretic methods using the polymer-magnet analogy. In the case that these particles are immersed in a dilute polymer solution and exhibit purely repulsive surfaces we study density profiles for monomers and chain ends near such a particle, the change of configurational entropy by immersing a particle into the solution, and the depletion interaction between a particle and a distant planar wall. Both ideal chains and chains with an excluded-volume interaction are considered. We also analyze particle surfaces with a short-ranged …
Hierarchical Search Strategy For The Detection Of Gravitational Waves From Coalescing Binaries, Soumya Mohanty, S. Dhurandhar
Hierarchical Search Strategy For The Detection Of Gravitational Waves From Coalescing Binaries, Soumya Mohanty, S. Dhurandhar
Physics and Astronomy Faculty Publications and Presentations
The detection of gravitational waves from coalescing compact binaries would be a computationally intensive process if a single bank of template wave forms (i.e., a one-step search) is used. We present, in this paper, a method which leads to a large reduction in the computational power required as compared to a one-step search. This method is a hierarchical search strategy involving two template banks. We show that the computational power required by such a two-step search, for an on-line detection of the one-parameter family of Newtonian signals, is 18 of that required when an on-line one-step search is used. This …
A Survey For Millisecond Pulsars, P. S. Ray, S. E. Thorsett, F. A. Jenet, M. H. Van Kerkwuk, S. R. Kulkarni, T. A. Prince, J. S. Sandhu, D. J. Nice
A Survey For Millisecond Pulsars, P. S. Ray, S. E. Thorsett, F. A. Jenet, M. H. Van Kerkwuk, S. R. Kulkarni, T. A. Prince, J. S. Sandhu, D. J. Nice
Physics and Astronomy Faculty Publications and Presentations
We have searched 960 square degrees of sky for radio pulsars, using the 305 m telescope at Arecibo, Puerto Rico. The 430 MHz survey reached a limiting sensitivity for slow pulsars of 0.7 mJy using a dual-polarization, 32 channel filter bank over 8 MHz of bandwidth. We have detected one new millisecond pulsar, 11 new slow pulsars, one previously known millisecond pulsar, and eight previously known slow pulsars. The new millisecond pulsar, PSR J2033 + 17, with a period of 5.9 ms, has been found to be in a binary system. The Keplerian circular orbital solution has a period of …
Density Of States Of A Damped Quantum Oscillator, Andreas Hanke, W. Zwerger
Density Of States Of A Damped Quantum Oscillator, Andreas Hanke, W. Zwerger
Physics and Astronomy Faculty Publications and Presentations
We calculate the density of states of a damped quantum-mechanical harmonic oscillator which is described by a Caldeira-Leggett type model with Ohmic dissipation and a Drude-like cutoff. From the exact expression for the associated partition function, we derive the asymptotic behavior of the density of states using Tauberian theorems. An effective algorithm to evaluate the density of states is presented and examples are given. It is pointed out that the calculated density of states is an experimentally accessible quantity.
Dilaton Black Holes With Electric Charge, Malik Rakhmanov
Dilaton Black Holes With Electric Charge, Malik Rakhmanov
Physics and Astronomy Faculty Publications and Presentations
New static spherically symmetric solutions of the Einstein-Maxwell gravity with the dilaton field are found. The solutions correspond to black holes and naked singularities. In addition to mass and electric charge these solutions are labeled by a new parameter, the dilaton charge of the black hole. Depending on the values of electric and dilaton charges there are different types of solutions. The solutions exhibit a new type of a symmetry. Namely one solution transforms into another when the mass and the dilaton charge are interchanged. We also found that there is a finite interval of values of electric charge for …
Second-Order Parametrized-Post-Newtonian Lagrangian, Matthew J. Benacquista
Second-Order Parametrized-Post-Newtonian Lagrangian, Matthew J. Benacquista
Physics and Astronomy Faculty Publications and Presentations
A many-body Lagrangian to second post-Newtonian order using an extension of the parametrized-post-Newtonian (PPN) formalism is introduced and the properties of new parameters are explored. A parametrized gauge transformation is developed to permit comparison with theories of gravity in a variety of different coordinate systems. A procedure to impose Lorentz invariance on a general second-order post-Newtonian Lagrangian is developed. The Lagrangian is then constrained to possess Lorentz invariance and a "Lorentz-invariant" gauge is introduced. The constrained Lagrangian is found to be described by ten new second-order PPN parameters. When the Lagrangian is further constrained to describe theories of gravity for …