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Articles 2251 - 2280 of 2944

Full-Text Articles in Astrophysics and Astronomy

A Search For Low-Amplitude Variability Among Population I Main Sequence Stars, Michael Benjamin Rose Jul 2006

A Search For Low-Amplitude Variability Among Population I Main Sequence Stars, Michael Benjamin Rose

Theses and Dissertations

The detection of variable stars in open clusters is an essential component of testing stellar structure and evolution theories. The ability to detect low-amplitude variability among cluster members is directly related to the quality of the photometric results. Point Spread Function (PSF) fitting is the best method available for measuring accurate magnitudes within crowded fields of stars, while high-precision differential photometry is the preferred technique for removing the effects of atmospheric extinction and variable seeing. In the search for new variable stars among hundreds or thousands of stars, the Robust Median Statistic (RoMS) is proven more effective for finding low-amplitude …

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Physical Conditions In Orion's Veil. Ii. A Multicomponent Study Of The Line Of Sight Toward The Trapezium, N. P. Abel, Gary J. Ferland, C. R. O'Dell, G. Shaw, Thomas H. Troland Jun 2006

Physical Conditions In Orion's Veil. Ii. A Multicomponent Study Of The Line Of Sight Toward The Trapezium, N. P. Abel, Gary J. Ferland, C. R. O'Dell, G. Shaw, Thomas H. Troland

Physics and Astronomy Faculty Publications

Orion's Veil is an absorbing screen that lies along the line of sight to the Orion H II region. It consists of two or more layers of gas that must lie within a few parsecs of the Trapezium cluster. Our previous work considered the Veil as a whole and found that the magnetic field dominates the energetics of the gas in at least one component. Here we use high-resolution STIS UV spectra that resolve the two velocity components in absorption and determine the conditions in each. We derive a volume hydrogen density, 21 cm spin temperature, turbulent velocity, and kinetic …

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Mechanisms Of The Wurtzite To Rock Salt Phase Transitions In Galium Nitride, Jesse Z. Gunter Jun 2006

Mechanisms Of The Wurtzite To Rock Salt Phase Transitions In Galium Nitride, Jesse Z. Gunter

Theses and Dissertations

We studied the wurtzite to rock salt phase transition in gallium nitride ( GaN ). Using the mapping algorithm of COMSUBS we found 435 possible mechanisms for this transition. We then used FIREBALL to do density functional theory calculations and found enthalpy barrier heights for the transition pathway. We used this to determine the mechanisms that are the most favorable for GaN. The most favorable mechanisms for GaN are those that break no bonds during the phase transition. The bond-preserving mechanisms involve bilayer sliding of (010) hexagonal plane in the plus or minus [100] hexagonal direction.

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[Accepted Article Manuscript Version (Postprint)] Testing The Inverse-Compton Catastrophe Scenario In The Intra-Day Variable Blazar S5 0716+71. I. Simultaneous Broadband Observations During November 2003, Bruce Wilking, L. Ostorero, S Wagner, J. Gracia, E. Ferrero, T Krichbaum, S. Britzen, A. Witzel, K. Nilsson, M. Villata, U. Bach, D. Barnaby, S. Bernhart, M Carini, C Chen, W. Chen, S. Ciprini, S. Crapanzano, V. Doroshenko, N Efimova, D. Emmanoulopoulos, L. Fuhrmann, K Gabanyi, A. Giltinan, V. Hagen-Thorn, M. Hauser, J. Heidt, A Hojaev, T. Hovatta, F. Hroch, M. Ibrahimov, V. Impellizzeri, R Ivanidze, D. Kachel, A. Kraus, O. Kurtanidze, A. Lähteenmäki, L. Lanteri, V. Larionov, Z Lin, E. Lindfors, F. Munz, M. Nikolashvili, G. Nucciarelli, A. O’Connor, J. Ohlert, M. Pasanen, C. Pullen, C. Raiteri, T Rector, R. Robb, L. Sigua, A. Sillanpää, L. Sixtova, N. Smith, P. Strub, S. Takahashi, L. Takalo, C. Tapken, J. Tartar, M. Tornikoski, G. Tosti, M. Tröller, R. Walters, W. Wills, I. Agudo, H. Aller, M. Aller, E. Angelakis, J. Klare, E. Körding, R Strom, H. Teräsranta, H. Ungerechts, B. Vila-Vilaró Jun 2006

[Accepted Article Manuscript Version (Postprint)] Testing The Inverse-Compton Catastrophe Scenario In The Intra-Day Variable Blazar S5 0716+71. I. Simultaneous Broadband Observations During November 2003, Bruce Wilking, L. Ostorero, S Wagner, J. Gracia, E. Ferrero, T Krichbaum, S. Britzen, A. Witzel, K. Nilsson, M. Villata, U. Bach, D. Barnaby, S. Bernhart, M Carini, C Chen, W. Chen, S. Ciprini, S. Crapanzano, V. Doroshenko, N Efimova, D. Emmanoulopoulos, L. Fuhrmann, K Gabanyi, A. Giltinan, V. Hagen-Thorn, M. Hauser, J. Heidt, A Hojaev, T. Hovatta, F. Hroch, M. Ibrahimov, V. Impellizzeri, R Ivanidze, D. Kachel, A. Kraus, O. Kurtanidze, A. Lähteenmäki, L. Lanteri, V. Larionov, Z Lin, E. Lindfors, F. Munz, M. Nikolashvili, G. Nucciarelli, A. O’Connor, J. Ohlert, M. Pasanen, C. Pullen, C. Raiteri, T Rector, R. Robb, L. Sigua, A. Sillanpää, L. Sixtova, N. Smith, P. Strub, S. Takahashi, L. Takalo, C. Tapken, J. Tartar, M. Tornikoski, G. Tosti, M. Tröller, R. Walters, W. Wills, I. Agudo, H. Aller, M. Aller, E. Angelakis, J. Klare, E. Körding, R Strom, H. Teräsranta, H. Ungerechts, B. Vila-Vilaró

Physics Faculty Works

Context. Some intra-day variable, compact extra-galactic radio sources show brightness temperatures severely exceeding 1012 K, the limit set by catastrophic inverse-Compton (IC) cooling in sources of incoherent synchrotron radiation. The violation of the IC limit, actually possible under non-stationary conditions, would lead to IC avalanches in the soft-γ-ray energy band during transient periods.Aims. For the first time, broadband signatures of possible IC catastrophes were searched for in a prototypical source, S5 0716+71.Methods. A multifrequency observing campaign targetting S5 0716+71 was carried out during November 06-20, 2003. The observations, organized under the framework of the European Network for the Investigation of …

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Development And Comparison Of Highly Directional Loudspeakers, Gordon Robert Dix May 2006

Development And Comparison Of Highly Directional Loudspeakers, Gordon Robert Dix

Theses and Dissertations

Highly directive loudspeakers have long been important tools for sound system designers, experimental acousticians, and many other professionals in the audio industry. They allow sound engineers to more easily manipulate the radiation pattern of their loudspeakers to accommodate the purpose of the venue. Many commercially available products, while exhibiting good directivity at mid and high frequencies, generally lack control in the low frequency range. A new method for controlling the radiation pattern of a loudspeaker at low frequencies has been developed and modeled extensively. Prototypes have been built and tested in an anechoic chamber. Results from computer modeling and experimental …

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Direct Observation Of Laser Filamentation In High-Order Harmonic Generation, John Charles Painter May 2006

Direct Observation Of Laser Filamentation In High-Order Harmonic Generation, John Charles Painter

Theses and Dissertations

We investigate the spatial evolution of an intense laser pulse as it generates high-order harmonics in a long gas cell, filled with 80 torr of helium. A thin foil separates the gas-filled region of the cell from a subsequent evacuated region. The exit plane of the gas cell can be scanned along the laser axis so that the evolution of the laser throughout the focus can be observed (full scanning range of 9 cm). We constructed an apparatus that images the laser radial energy profile as it exits the cell. The high harmonics, odd orders ranging from 45 to 91, …

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Joint Ligo And Tama300 Search For Gravitational Waves From Inspiralling Neutron Star Binaries, B. P. Abbott, R. Abbott, W. G. Anderson, Mario C. Diaz, Wm. R. Johnston, Soma Mukherjee, Cristina V. Torres May 2006

Joint Ligo And Tama300 Search For Gravitational Waves From Inspiralling Neutron Star Binaries, B. P. Abbott, R. Abbott, W. G. Anderson, Mario C. Diaz, Wm. R. Johnston, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We search for coincident gravitational wave signals from inspiralling neutron star binaries using LIGO and TAMA300 data taken during early 2003. Using a simple trigger exchange method, we perform an intercollaboration coincidence search during times when TAMA300 and only one of the LIGO sites were operational. We find no evidence of any gravitational wave signals. We place an observational upper limit on the rate of binary neutron star coalescence with component masses between 1 and 3M⊙ of 49 per year per Milky Way equivalent galaxy at a 90% confidence level. The methods developed during this search will find application in …

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The Shape Of Dark Matter Haloes: Dependence On Mass, Redshift, Radius And Formation, Ricardo Flores, Brandon Allgood, Joel Primack, Andrey Kravtsov, Risa Wechsler, Andreas Faltenbacher, James Bullock Apr 2006

The Shape Of Dark Matter Haloes: Dependence On Mass, Redshift, Radius And Formation, Ricardo Flores, Brandon Allgood, Joel Primack, Andrey Kravtsov, Risa Wechsler, Andreas Faltenbacher, James Bullock

Physics Faculty Works

Using six high-resolution dissipationless simulations with a varying box size in a flat Lambda cold dark matter (ΛCDM) universe, we study the mass and redshift dependence of dark matter halo shapes for Mvir= 9.0 × 1011− 2.0 × 1014h−1 M⊙, over the redshift range z= 0–3, and for two values of σ8= 0.75 and 0.9. Remarkably, we find that the redshift, mass and σ8 dependence of the mean smallest-to-largest axis ratio of haloes is well described by the simple power-law relation 〈s〉= (0.54 ± 0.02)(Mvir/M*)−0.050±0.003, where s is measured at 0.3Rvir, and the z and σ8 dependences are governed by …

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Compositional Stability Of Fept Nanoparticles On Sio2/Si During Annealing, Richard R. Vanfleet, B. Yao, R. V. Petrova, K. R. Coffey Apr 2006

Compositional Stability Of Fept Nanoparticles On Sio2/Si During Annealing, Richard R. Vanfleet, B. Yao, R. V. Petrova, K. R. Coffey

Faculty Publications

The loss of Fe due to oxidation or diffusion into the substrate can prevent the successful preparation of well-ordered, stoichiometric, FePt nanoparticles. In this work we report the composition changes during annealing observed for small (<10 nm) FePt nanoparticles on thermally grown SiO2 layers on Si wafer substrates. Additionally, we describe the use of a controlled reducing gas mixture, Ar+H2+H2O, to reduce the loss of Fe.

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Post-Outburst Infrared Spectra Of V1647 Ori, The Illuminating Star Of Mcneil's Nebula, Erika Gibb, T Rettig, S Brittain, D Wasikowski, Theodore Simon, William Vacca, Michael Cushing Apr 2006

Post-Outburst Infrared Spectra Of V1647 Ori, The Illuminating Star Of Mcneil's Nebula, Erika Gibb, T Rettig, S Brittain, D Wasikowski, Theodore Simon, William Vacca, Michael Cushing

Physics Faculty Works

V1647 Ori is a low-mass star in the L1630 star-forming region that underwent an outburst in late 2003 and early 2004. We present postoutburst infrared spectra obtained with NIRSPEC (Keck II) and SpeX (IRTF) and compare these to spectra taken during the outburst. The results show that the temperature of the hot CO formed in the inner part of the disk has declined by ~800 K, while the water and CO ice and low-J CO gas features remained unchanged, consistent with previous assertions that the latter, low-temperature features arise in the foreground cloud. The P Cygni profiles of the Paschen …

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Spatially Resolved Mid-Infrared Spectroscopy Of Ngc 1068: The Nature And Distribution Of The Nuclear Material, R. E. Mason, T. R. Geballe, C. Packham, N. A. Levenson, Moshe Elitzur, R. S. Fisher, E. Perlman Apr 2006

Spatially Resolved Mid-Infrared Spectroscopy Of Ngc 1068: The Nature And Distribution Of The Nuclear Material, R. E. Mason, T. R. Geballe, C. Packham, N. A. Levenson, Moshe Elitzur, R. S. Fisher, E. Perlman

Physics and Astronomy Faculty Publications

We present spatially resolved, near-diffraction-limited 10 μm spectra of the nucleus of the Seyfert 2 galaxy NGC 1068, obtained with Michelle, the mid-IR imager and spectrometer on the 8.1 m Gemini North Telescope. The spectra cover the nucleus and the central 6.0” × 0.4” of the ionization cones at a spatial resolution of approximately 0.4” (≈30 pc). The spectra extracted in 0.4” steps along the slit reveal striking variations in continuum slope, silicate feature profile and depth, and fine-structure line fluxes on subarcsecond scales, illustrating in unprecedented detail the complexity of the circumnuclear regions of NGC 1068 at mid-IR …

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The Structure Of Flux Transfer Events Recovered From Cluster Data, H Hasegawa, B U. Ö Sonnerup, C J. Owen, B Klecker, G Paschmann, A Balogh, H Re`Me Mar 2006

The Structure Of Flux Transfer Events Recovered From Cluster Data, H Hasegawa, B U. Ö Sonnerup, C J. Owen, B Klecker, G Paschmann, A Balogh, H Re`Me

Dartmouth Scholarship

The structure and formation mechanism of a to- tal of five Flux Transfer Events (FTEs), encountered on the equatorward side of the northern cusp by the Cluster space- craft, with separation of ∼5000 km, are studied by apply- ing the Grad-Shafranov (GS) reconstruction technique to the events. The technique generates a magnetic field/plasma map of the FTE cross section, using combined magnetic field and plasma data from all four spacecraft, under the assump- tion that the structure is two-dimensional (2-D) and time- independent. The reconstructed FTEs consist of one or more magnetic flux ropes embedded in the magnetopause, suggest- ing …

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The Violation Of Bell's Inequality In A Deterministic But Nonlocal Model, Stephanie Allred Magleby Mar 2006

The Violation Of Bell's Inequality In A Deterministic But Nonlocal Model, Stephanie Allred Magleby

Theses and Dissertations

This thesis investigates the violation of Bell's Inequality through the use of nonlocal measurement schemes as encapsulated in a quasi-deterministic toy model. This toy model, called the Q Box, is reminiscent of Mermin's Box in that it describes a system that appears to be deterministic yet produces the statistics of a quantum type system. [1] The workings of the Q Box are detailed both as a thought experiment and as a computer simulation. Nonlocal measurement protocols similar to those which generate a violation of Bell's Inequality in the Q Box are also applied to Mermin's Box, with comparable results. [1] …

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Physical Conditions In The Interstellar Medium Toward Hd 185418, Gargi Shaw, Gary J. Ferland, R. Srianand, N. P. Abel Mar 2006

Physical Conditions In The Interstellar Medium Toward Hd 185418, Gargi Shaw, Gary J. Ferland, R. Srianand, N. P. Abel

Physics and Astronomy Faculty Publications

We have developed a complete model of the hydrogen molecule as part of the spectral simulation code Cloudy. Our goal is to apply this to spectra of high-redshift star-forming regions where H2 absorption is seen, but where few other details are known, to understand its implication for star formation. The microphysics of H2 is intricate, and it is important to validate these numerical simulations in better understood environments. This paper studies a well-defined line of sight through the Galactic interstellar medium (ISM) as a test of the microphysics and methods we use. We present a self-consistent calculation of …

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Accurate Evolutions Of Orbiting Black-Hole Binaries Without Excision, M. Campanelli, C. O. Lousto, P. Marronetti, Z. Zlochower Mar 2006

Accurate Evolutions Of Orbiting Black-Hole Binaries Without Excision, M. Campanelli, C. O. Lousto, P. Marronetti, Z. Zlochower

Physics & Astronomy Faculty Publications

We present a new algorithm for evolving orbiting black-hole binaries that does not require excision or a corotating shift. Our algorithm is based on a novel technique to handle the singular puncture conformal factor. This system, based on the Baumgarte-Shapiro-Shibata-Nakamura formulation of Einstein’s equations, when used with a ‘‘precollapsed’’ initial lapse, is nonsingular at the start of the evolution and remains nonsingular and stable provided that a good choice is made for the gauge. As a test case, we use this technique to fully evolve orbiting black-hole binaries from near the innermost stable circular orbit regime. We show fourth-order convergence …

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Compact Solid-State Laser Source For 1s-2s Spectroscopy In Atomic Hydrogen, Scott D. Bergeson, N. Kolachevsky, J. Alnis, T. W. Hansch Feb 2006

Compact Solid-State Laser Source For 1s-2s Spectroscopy In Atomic Hydrogen, Scott D. Bergeson, N. Kolachevsky, J. Alnis, T. W. Hansch

Faculty Publications

We demonstrate a compact solid-state laser source for high-resolution two-photon spectroscopy of the 1S-2S transition in atomic hydrogen. The source emits up to 20 mW at 243 nm and consists of a 972 nm diode laser, a tapered amplifier, and two doubling stages. The diode laser is actively stabilized to a high-finesse cavity. We compare the new source to the stable 486 nm dye laser used in previous experiments and record 1S-2S spectra using both systems. With the solid-state laser system, we demonstrate a resolution of the hydrogen spectrometer of 6×10^11, which is promising for a number of high-precision measurements …

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Finding The Radial Parallel Temperature Profile In A Non-Neutral Plasma Using Equilibrium Calculations On Experimental Data, Grant W. Hart, Bryan G. Peterson Feb 2006

Finding The Radial Parallel Temperature Profile In A Non-Neutral Plasma Using Equilibrium Calculations On Experimental Data, Grant W. Hart, Bryan G. Peterson

Faculty Publications

In 1992, Eggleston et al. [D. L. Eggleston et al., Phys. Fluids B 4, 3432 (1992)] reported on a technique for measuring the radial temperature profile in a pure-electron plasma confined in a Malmberg-Penning trap by partially dumping the plasma onto a charge collector at the end of the trap. For short plasmas and short confining rings, the assumptions in their paper are violated and a more general calculation is needed. This paper presents a variation of the standard equilibrium calculation to find the temperature profile of a pure-electron plasma. Eggleston's shortcut "evaporation" temperature method is found to require a …

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Evolution Of Stellar Bars In Live Axisymmetric Halos: Recurrent Buckling And Secular Growth, Inma Martinez-Valpuesta, Isaac Shlosman, Clayton Heller Jan 2006

Evolution Of Stellar Bars In Live Axisymmetric Halos: Recurrent Buckling And Secular Growth, Inma Martinez-Valpuesta, Isaac Shlosman, Clayton Heller

Physics & Astronomy: Faculty Publications

Evolution of stellar bars in disk galaxies is accompanied by dynamical instabilities and secular changes. Following the vertical buckling instability, the bars are known to weaken dramatically and develop a pronounced boxy/ peanut shape when observed edge-on. Using high-resolution N-body simulations of stellar disks embedded in live axisymmetric dark matter halos, we have investigated the long-term changes in the bar morphology, specifically the evolution of the bar size, its vertical structure, and the exchange of angular momentum. We find that following the initial buckling, the bar resumes its growth from deep inside the corotation radius and follows the ultraharmonic resonance …

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A Cosmic Milestone: Constraints From Metal-Poor Halo Stars On The Cosmological Reionization Epoch, Aparna Venkatesan Jan 2006

A Cosmic Milestone: Constraints From Metal-Poor Halo Stars On The Cosmological Reionization Epoch, Aparna Venkatesan

Physics and Astronomy

Theoretical studies and current observations of the high-redshift intergalactic medium (IGM) indicate that at least two cosmic transitions occur by the time the universe reaches gas metallicities of about 10-3 Z☉. One is the cosmological reionization of the IGM, and the second is the transition from a primordial to present-day mode of star formation. We quantify this relation through new calculations of the ionizing radiation produced in association with the elements carbon, oxygen, and silicon observed in Galactic metal-poor halo stars, which are likely second-generation objects formed in the wake of primordial supernovae. We demonstrate that sufficient …

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The Radiative Transport Of Dust In Primordial Galaxies And Second-Generation Star Formation, Aparna Venkatesan, Biman B. Nath, J Shull Jan 2006

The Radiative Transport Of Dust In Primordial Galaxies And Second-Generation Star Formation, Aparna Venkatesan, Biman B. Nath, J Shull

Physics and Astronomy

We investigate the radiativetransport of dust inprimordial galaxies in thepresence of the UVradiation field from thefirst metal-free stars. Wefind that dust createdin the first supernova(SN) explosions can bedriven through the interiorof the SN remnantto accumulate in theSN shells, where second-generationstars may form fromcompressed cooling gas. Thisscenario requires metal-free starsto form continuously overtimescales of up to10 Myr, consistent withrecent estimates. Silicate andgraphite grains, as wellas iron-bearing magnetites, aretransported to the shellsfor reasonable parameter assumptions,but their relative yieldsfrom primordial SNe isan important factor inthe resulting abundance ratios.We compare the resultsof segregated grain transportwith the current nucleosyntheticdata on extremely metal-poorGalactic halo stars. Fossilsignatures …

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Estimating Hydrodynamic Quantities In The Presence Of Microscopic Fluctuations, Alejandro Garcia Jan 2006

Estimating Hydrodynamic Quantities In The Presence Of Microscopic Fluctuations, Alejandro Garcia

Faculty Publications

This paper discusses the evaluation of hydrodynamic variables in the presence of spontaneous fluctuations, such as in molecular simulations of fluid flows. The principal point is that hydrodynamic variables such as fluid velocity and temperature must be defined in terms of mechanical variables such as momentum and energy density). Because these relations are nonlinear and because fluctuations of mechanical variables are correlated, care must be taken to avoid introducing a bias when evaluating means, variances, and correlations of hydrodynamic variables. The unbiased estimates are formulated; some alternative, incorrect approaches are presented as cautionary warnings. The expressions are verified by numerical …

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The Lazarus Project. Ii. Spacelike Extraction With The Quasi-Kinnersley Tetrad, Manuela Campanelli, Bernard Kelly, Carlos O. Lousto Jan 2006

The Lazarus Project. Ii. Spacelike Extraction With The Quasi-Kinnersley Tetrad, Manuela Campanelli, Bernard Kelly, Carlos O. Lousto

Physics & Astronomy Faculty Publications

The Lazarus project was designed to make the most of limited 3D binary black-hole simulations, through the identification of perturbations at late times, and subsequent evolution of the Weyl scalar Ψ4 via the Teukolsky formulation. Here we report on new developments, employing the concept of the “quasi-Kinnersley” (transverse) frame, valid in the full nonlinear regime, to analyze late-time numerical space-times that should differ only slightly from Kerr. This allows us to extract the essential information about the background Kerr solution, and through this, to identify the radiation present. We explicitly test this procedure with full-numerical evolutions of Bowen-York data for …

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Near-Infrared And The Inner Regions Of Protoplanetary Disks, Dejan Vinković, Željko Ivezić, Tomislav Jurkić, Moshe Elitzur Jan 2006

Near-Infrared And The Inner Regions Of Protoplanetary Disks, Dejan Vinković, Željko Ivezić, Tomislav Jurkić, Moshe Elitzur

Physics and Astronomy Faculty Publications

We examine the “puffed-up inner disk” model proposed by Dullemond, Dominik, & Natta for explaining the near-IR excess radiation from Herbig Ae/Be stars. Detailed model computations show that the observed near-IR excess requires more hot dust than is contained in the puffed-up disk rim. The rim can produce the observed near-IR excess only if its dust has perfectly gray opacity, but such dust is in conflict with the observed 10 μm spectral feature. We find that a compact (~10 AU), tenuous (τV ≲ 0.4), dusty halo around the disk inner regions contains enough dust to readily explain …

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Growth And Thermal Properties Of Sr W O 4 Single Crystal, J. D. Fan, H. J. Wang, M. H. Jiang, Robert I. Boughton, D. G. Ran, S. Q. Sun, H. R. Xia Jan 2006

Growth And Thermal Properties Of Sr W O 4 Single Crystal, J. D. Fan, H. J. Wang, M. H. Jiang, Robert I. Boughton, D. G. Ran, S. Q. Sun, H. R. Xia

Physics and Astronomy Faculty Publications

A strontium tungstate SrWO4 single crystal with dimensions of 25 40 mm2 has been grown by the Czochralski method using an iridium crucible. X-ray powder diffraction results show that as grown the SrWO4 crystal belongs to the tetragonal system in the scheelite structure. The effective segregation coefficients of elemental W and Sr in the crystal growth are measured by x-ray fluorescence, and the respective values are close to 1. The thermal properties of the SrWO4 crystal were systemically studied by measuring the thermal expansion, specific heat, and thermal diffusion coefficient. These results show that the crystal possesses a large anisotropic …

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Constraints On The Nucleon Strange Form Factors At Q2 ∼ 0.1 Gev2, K. A. Aniol, D. S. Armstrong, T. Averett, H. Benaoum, P. Y. Bertin, E. Burtin, J. Cahoon, G. D. Cates, C. C. Chang, Y.-C. Chao, D. Deepa, H. Ibrahim Jan 2006

Constraints On The Nucleon Strange Form Factors At Q2 ∼ 0.1 Gev2, K. A. Aniol, D. S. Armstrong, T. Averett, H. Benaoum, P. Y. Bertin, E. Burtin, J. Cahoon, G. D. Cates, C. C. Chang, Y.-C. Chao, D. Deepa, H. Ibrahim

Mechanical & Aerospace Engineering Faculty Publications

We report the most precise measurement to date of a parity-violating asymmetry in elastic electron–proton scattering. The measurement was carried out with a beam energy of 3.03 GeV and a scattering angle (θlab) = 6.0○ , with the result A PV = ( − 1.14 ± 0.24 ( stat ) ± 0.06 ( syst ) ) × 10−6 . From this we extract, at Q2 = 0.099 GeV2 , the strange form factor combination GsE + 0.080 GsM = 0.030 ± 0.025 ( stat ) ± 0.006 ( syst ) ± …

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Measurement Of The X- And Q2 -Dependence Of The Asymmetry A1 On The Nucleon, K. V. Dharmawardane, S. E. Kuhn, P. Bosted, Y. Prok, G. Adams, P. Ambrozewicz, M. Anghinolfi, G. Asryan, H. Avakian, H. Bagdasaryan, M. Bektasoglu, S. Bültmann, S. L. Careccia, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, H. G. Juengst, A. Klein, J. Lachniet, M. R. Niroula, R. A. Niyazov, L. M. Qin, F. Sabatié, S. Tkachenko, L. B. Weinstein, J. Zhang Jan 2006

Measurement Of The X- And Q2 -Dependence Of The Asymmetry A1 On The Nucleon, K. V. Dharmawardane, S. E. Kuhn, P. Bosted, Y. Prok, G. Adams, P. Ambrozewicz, M. Anghinolfi, G. Asryan, H. Avakian, H. Bagdasaryan, M. Bektasoglu, S. Bültmann, S. L. Careccia, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, H. G. Juengst, A. Klein, J. Lachniet, M. R. Niroula, R. A. Niyazov, L. M. Qin, F. Sabatié, S. Tkachenko, L. B. Weinstein, J. Zhang

Physics Faculty Publications

We report results for the virtual photon asymmetry A1 on the nucleon from new Jefferson Lab measurements. The experiment, which used the CEBAF Large Acceptance Spectrometer and longitudinally polarized proton (15NH3) and deuteron (15ND3) targets, collected data with a longitudinally polarized electron beam at energies between 1.6 GeV and 5.7 GeV. In the present Letter, we concentrate on our results for A1 ( x , Q2 ) and the related ratio g1 / F1 ( x , Q2 ) in the resonance and the deep inelastic …

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Search For Gravitational Waves From Binary Black Hole Inspirals In Ligo Data, B. P. Abbott, R. Abbott, W. G. Anderson, Mario C. Diaz, Wm. R. Johnston, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres Jan 2006

Search For Gravitational Waves From Binary Black Hole Inspirals In Ligo Data, B. P. Abbott, R. Abbott, W. G. Anderson, Mario C. Diaz, Wm. R. Johnston, Soumya Mohanty, Soma Mukherjee, Cristina V. Torres

Physics & Astronomy Faculty Publications

We report on a search for gravitational waves from binary black hole inspirals in the data from the second science run of the LIGO interferometers. The search focused on binary systems with component masses between 3 and 20M⊙. Optimally oriented binaries with distances up to 1 Mpc could be detected with efficiency of at least 90%. We found no events that could be identified as gravitational waves in the 385.6 hours of data that we searched.

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Electrical Pulse Formation During High Temperature Reaction Between Ni And Al, Mona Setoodeh, Karen S. Martirosyan, Dan Luss Jan 2006

Electrical Pulse Formation During High Temperature Reaction Between Ni And Al, Mona Setoodeh, Karen S. Martirosyan, Dan Luss

Physics & Astronomy Faculty Publications

An electric voltage pulse (duration of about 2ms) with an amplitude of up to 0.6V was generated during the reaction between nickel and aluminum powders by a high temperature moving reaction front. The electrical signal formed during the initial stages of the combustion was annihilated before the moving front attained its maximum temperature. The voltage amplitude and combustion temperature depended on the particle size of the reactants as well as the Al to Ni ratio in the reactant mixture, and their largest values were attained for a mixture containing 27–31.5wt% Al. The combustion temperature increased when smaller Al particles were …

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Hydrodynamic Description Of The Adiabatic Piston, Alejandro Garcia, M. M. Mansour Jan 2006

Hydrodynamic Description Of The Adiabatic Piston, Alejandro Garcia, M. M. Mansour

Faculty Publications

A closed macroscopic equation for the motion of the two-dimensional adiabatic piston is derived from standard hydrodynamics. It predicts a damped oscillatory motion of the piston towards a final rest position, which depends on the initial state. In the limit of large piston mass, the solution of this equation is in quantitative agreement with the results obtained from both hard disk molecular dynamics and hydrodynamics. The explicit forms of the basic characteristics of the piston’s dynamics, such as the period of oscillations and the relaxation time, are derived. The limitations of the theory’s validity, in terms of the main system …

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Ferromagnetic Resonance Investigations On Ga0.965mn0.035as Film, S. Balascuta, X. Liu, D. V. Baxter, J. Carini, T. Wojtowicz, Y. Sasaki, J. Furdyna, Mircea Chipara Jan 2006

Ferromagnetic Resonance Investigations On Ga0.965mn0.035as Film, S. Balascuta, X. Liu, D. V. Baxter, J. Carini, T. Wojtowicz, Y. Sasaki, J. Furdyna, Mircea Chipara

Physics & Astronomy Faculty Publications

Ferromagnetic resonance studies of the temperature dependence of magnetic anisotropies in a Ga0.965Mn0.035As film between 5 and 40K are reported. The in-plane and out-of-the-plane angular dependences of the resonance field were analyzed within the Landau-Lifshitz-Gilbert approach. The second- and fourth-order magnetic anisotropy energies were derived. The temperature dependence of magnetization and of magnetic anisotropy were studied by superconducting quantum interference device and ferromagnetic resonance.

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