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2008

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Articles 61 - 90 of 801

Full-Text Articles in Physics

Turbulent Dispersion In Cloudy Boundary Layers, Remco A. Verzijlbergh, Harmen J.J. Jonker, Thijs Heus, J. Vilà-Guerau De Arellano Nov 2008

Turbulent Dispersion In Cloudy Boundary Layers, Remco A. Verzijlbergh, Harmen J.J. Jonker, Thijs Heus, J. Vilà-Guerau De Arellano

Physics Faculty Publications

Compared to dry boundary layers, dispersion in cloud-topped boundary layers has received less attention. In this LES based numerical study we investigate the dispersion of a passive tracer in the form of Lagrangian particles for four kinds of atmospheric boundary layers: 1) a dry convective boundary layer (for reference), 2) a "smoke" cloud boundary layer in which the turbulence is driven by radiative cooling, 3) a stratocumulus topped boundary layer and 4) a shallow cumulus topped boundary layer. We show that the dispersion characteristics of the smoke cloud boundary layer as well as the stratocumulus situation can be well understood …

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Abrupt Transition From A Free, Repulsive To A Condensed, Attractive Dna Phase, Induced By Multivalent Polyamine Cations, Xiangyun Qiu, Kurt Andresen, Jessica S. Lamb, Lisa W. Kwok, Lois Pollack Nov 2008

Abrupt Transition From A Free, Repulsive To A Condensed, Attractive Dna Phase, Induced By Multivalent Polyamine Cations, Xiangyun Qiu, Kurt Andresen, Jessica S. Lamb, Lisa W. Kwok, Lois Pollack

Physics and Astronomy Faculty Publications

We have investigated the energetics of DNA condensation by multivalent polyamine cations. Solution small angle x-ray scattering was used to monitor interactions between short 25 base pair dsDNA strands in the free supernatant DNA phase that coexists with the condensed DNA phase. Interestingly, when tetravalent spermine is used, significant inter-DNA repulsion is observed in the free phase, in contrast with the presumed inter-DNA attraction in the coexisting condensed phase. DNA condensation thus appears to be a discrete, first-order-like, transition from a repulsive gaseous to an attractive condensed solid phase, in accord with the reported all-or-none condensation of giant DNA. We …

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Morphology Of The Dayside Ionosphere Of Venus: Implications For Ion Outflows, Jane L. Fox Nov 2008

Morphology Of The Dayside Ionosphere Of Venus: Implications For Ion Outflows, Jane L. Fox

Physics Faculty Publications

The nightside ionosphere of Venus is formed mostly by day-to-night transport of ions below the ionopause, with a small contribution from precipitation of energetic electrons from the wake. This nightward flux of ions should result in dayside ionospheres that are characterized by smaller electron density scale heights at high altitudes than those that are characteristic of diffusive equilibrium. In order to determine both the maximum possible values of the upward fluxes and the upward fluxes implied by comparison of our computed ion and electron density profiles to measurements, we have constructed more than 60 models of the high solar activity …

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Nonlinear Magneto-Optic Polarization Rotation With Intense Laser Fields, Paul S. Hsu, Anil K. Patnaik, George R. Welch Nov 2008

Nonlinear Magneto-Optic Polarization Rotation With Intense Laser Fields, Paul S. Hsu, Anil K. Patnaik, George R. Welch

Physics Faculty Publications

We have studied the nonlinear Faraday effect with intense linear polarized light in an optically thick atomic rubidium vapor. We demonstrate that the polarization rotation rate (rotation angle per unit magnetic field, in the limit of low field) has a maximum value as the intensity and density are increased. We also show that the optimal sensitivity of an optical magnetometer based on this system reaches a saturation value as the intensity and density are increased.

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Kinetic And Spectroscopic Analysis Of The Catalytic Role Of H79 In The Methionine Aminopeptidase From Escherichia Coli, Sarah J. Watterson, Sanghamitra Mitra, Sabina I. Swierczek, Brian Bennett, Richard C. Holz Nov 2008

Kinetic And Spectroscopic Analysis Of The Catalytic Role Of H79 In The Methionine Aminopeptidase From Escherichia Coli, Sarah J. Watterson, Sanghamitra Mitra, Sabina I. Swierczek, Brian Bennett, Richard C. Holz

Physics Faculty Research and Publications

To gain insight into the role of the strictly conserved histidine residue, H79, in the reaction mechanism of the methionyl aminopeptidase from Escherichia coli (EcMetAP-I), the H79A mutated enzyme was prepared. Co(II)-loaded H79A exhibits an overall >7000-fold decrease in specific activity. The almost complete loss of activity is primarily due to a >6000-fold decrease in kcat. Interestingly, the Km value obtained for Co(II)-loaded H79A was approximately half the value observed for wild-type (WT) EcMetAP-I. Consequently, kcat/Km values decreased only 3000-fold. On the other hand, the observed specific activity of Mn(II)-loaded …

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Trapping And Characterization Of A Reaction Intermediate In Carbapenem Hydrolysis By B. Cereus Metallo-Β-Lactamase, Mariana F. Tioni, Leticia L. Llarrull, Andrés A. Poeylaut-Palena, Marcelo A. Martí, Miguel Saggu, Gopal R. Periyannan, Ernesto G. Mata, Brian Bennett, Daniel H. Murgida, Alejandro J. Vila Nov 2008

Trapping And Characterization Of A Reaction Intermediate In Carbapenem Hydrolysis By B. Cereus Metallo-Β-Lactamase, Mariana F. Tioni, Leticia L. Llarrull, Andrés A. Poeylaut-Palena, Marcelo A. Martí, Miguel Saggu, Gopal R. Periyannan, Ernesto G. Mata, Brian Bennett, Daniel H. Murgida, Alejandro J. Vila

Physics Faculty Research and Publications

Metallo-β-lactamases hydrolyze most β-lactam antibiotics. The lack of a successful inhibitor for them is related to the previous failure to characterize a reaction intermediate with a clinically useful substrate. Stopped-flow experiments together with rapid freeze−quench EPR and Raman spectroscopies were used to characterize the reaction of Co(II)−BcII with imipenem. These studies show that Co(II)−BcII is able to hydrolyze imipenem in both the mono- and dinuclear forms. In contrast to the situation met for penicillin, the species that accumulates during turnover is an enzyme−intermediate adduct in which the β-lactam bond has already been cleaved. This intermediate is a metal-bound anionic species …

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Laser Channeling Of Bethe-Heitler Pairs, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel Nov 2008

Laser Channeling Of Bethe-Heitler Pairs, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel

Physics Faculty Research & Creative Works

Electron-positron pair creation is analyzed for an arrangement involving three external fields: a high-frequency gamma photon, the Coulomb field of a nucleus, and a strong laser wave. The frequency of the incoming gamma photon is assumed to be larger than the threshold for pair production in the absence of a laser, and the peak electric field of the laser is assumed to be much weaker than Schwinger's critical field. The total number of pairs produced is found to be essentially unchanged by the laser field, while the differential cross section is drastically modified. We show that the laser can channel …

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Visualizing A Fourth Dimension: Hypercubic Resistor Networks, Andrew J. Nelson '08 Nov 2008

Visualizing A Fourth Dimension: Hypercubic Resistor Networks, Andrew J. Nelson '08

Honors Projects

A booming field in physics research today is the search for extra dimensions. This is something that has been thought about and discussed in both the scientific and non-scientific world for a long time. Many physicists are currently attempting to answer the question: "is our world really four dimensional?" The purpose of this research, however, is not to answer that question. The purpose of this work is to help reveal four-dimensional artifacts in our perceived three-dimensional world in order to help a student, even a non-physicist, to understand and visualize how the extra spatial dimensionality, if present, might reveal itself …

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Revisiting Unitarity Corrections For Electromagnetic Processes In Collisions Of Relativistic Nuclei, Ulrich D. Jentschura, Kai Hencken, Valery G. Serbo Nov 2008

Revisiting Unitarity Corrections For Electromagnetic Processes In Collisions Of Relativistic Nuclei, Ulrich D. Jentschura, Kai Hencken, Valery G. Serbo

Physics Faculty Research & Creative Works

Unitarity corrections to several electromagnetic processes in collisions of relativistic heavy nuclei are considered. They are due to the unitarity requirement for the S-matrix and correspond to the exchange of a light-by-light scattering block between colliding nuclei. We obtain improved results for the corrections to e+ e- and μ+ μ- pair production as well as new results for unitarity corrections to the production of photons via virtual Compton and virtual Delbrück scattering. These corrections can be numerically large; e.g., the μ+ μ- pair production cross section is reduced by about 50% and nuclear bremsstrahlung …

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Structure Property Relationships In Organic Conjugated Systems, Luke O'Neill Nov 2008

Structure Property Relationships In Organic Conjugated Systems, Luke O'Neill

Doctoral

A series of pi(п) conjugated oligomers containing 1 to 6 monomer units were studied by absorption and photoluminescence spectroscopies. The results are discussed and examined with regard to the variation of the optical properties with the increase of effective conjugation length. It was found that there was a linear relationship between the positioning of the absorption and photoluminescence maxima plotted against inverse conjugation length. The relationships are in good agreement with the simple particle in a box method, one of the earliest descriptions of the properties of one-dimensional organic molecules. Variations in the infinite chain limit band gap for a …

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New (E,2e) Studies Of Atomic And Molecular Targets, E. M. Staicu-Casagrande, A. Naja, A. Lahmam-Bennani, A. S. Kheifets, Don H. Madison, B. Joulakian Nov 2008

New (E,2e) Studies Of Atomic And Molecular Targets, E. M. Staicu-Casagrande, A. Naja, A. Lahmam-Bennani, A. S. Kheifets, Don H. Madison, B. Joulakian

Physics Faculty Research & Creative Works

We report new coplanar (e,2e) measurements characterised by large energy transfer and close to minimum momentum transfer from the projectile to the target. Ionisation of the two-electron targets He and H2 is investigated under these particular kinematics. The experimental data are compared with the predictions of the most elaborate theoretical models. The obtained good agreement motivated us to extend our research to the case of more complex targets such as Ar. Comparison with the most elaborate models in the case of multi-electron targets is excellent. Destructive and constructive interference effects in the case of H2 are observed and …

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Search For Gravitational-Wave Bursts From Soft Gamma Repeaters, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, K. Hayama, Soma Mukherjee, Soumya Mohanty, Joseph D. Romano, Robert Stone Nov 2008

Search For Gravitational-Wave Bursts From Soft Gamma Repeaters, B. P. Abbott, R. Abbott, Mario C. Diaz, R. Grosso, K. Hayama, Soma Mukherjee, Soumya Mohanty, Joseph D. Romano, Robert Stone

Physics & Astronomy Faculty Publications

We present a LIGO search for short-duration gravitational waves (GWs) associated with soft gamma ray repeater (SGR) bursts. This is the first search sensitive to neutron star f modes, usually considered the most efficient GW emitting modes. We find no evidence of GWs associated with any SGR burst in a sample consisting of the 27 Dec. 2004 giant flare from SGR 1806−20 and 190 lesser events from SGR 1806−20 and SGR 1900+14. The unprecedented sensitivity of the detectors allows us to set the most stringent limits on transient GW amplitudes published to date. We find upper limit estimates on the …

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Dynamical Pattern Formation During Growth Of A Dual-Species Bose-Einstein Condensate, Shai Ronen, John L. Bohn, Laura Elisa Halmo, Mark Edwards Nov 2008

Dynamical Pattern Formation During Growth Of A Dual-Species Bose-Einstein Condensate, Shai Ronen, John L. Bohn, Laura Elisa Halmo, Mark Edwards

Physics & Astronomy: Faculty Publications

We simulate the growth of a dual species Bose-Einstein condensate using a Gross-Pitaevskii equation with an additional gain term giving rise to the growth. Such growth occurs during simultaneous evaporative cooling of a mixture of two gases. The ground state of a dual condensate is normally either a miscible mixture, or an immiscible phase with two spatially separated components. In a cigar trap the ground state typically consists of one component in the center, and the other component flanking it. Our simulations show that when the condensates are formed in a cigar trap and the mixture is phase separated, then …

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Precise Measurement Of The Top-Quark Mass From Lepton + Jets Events, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration Oct 2008

Precise Measurement Of The Top-Quark Mass From Lepton + Jets Events, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration

Kenneth Bloom Publications

We measure the mass of the top quark using top-quark pair candidate events in the lepton + jets channel from data corresponding to 1 fb-1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron collider. We use a likelihood technique that reduces the jet energy scale uncertainty by combining an in situ jet energy calibration with the independent constraint on the jet energy scale (JES) from the calibration derived using photon þ jets and dijet samples. We find the mass of the top quark to be 171.5 ± 1.8(stat) + JES) ± 1.1(syst) GeV.

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Measurement Of The Polarization Of The Ү(1S) And Ү(2S) States In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Oct 2008

Measurement Of The Polarization Of The Ү(1S) And Ү(2S) States In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We present a study of the polarization of the Ү(1S) and Ү(2S) states using a 1.3 fb-1 data sample collected by the D0 experiment in 2002–2006 during run II of the Fermilab Tevatron Collider. We measure the polarization parameter α = (σT - 2σL), where σT and σL are the transversely and longitudinally polarized components of the production cross section, as a function of the transverse momentum (pTҮ) for the Ү(1S) and Ү(2S). Significant pTҮ-dependent longitudinal polarization is observed …

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Plurality Of Principal Angles For A Given Pseudo-Brewster Angle When Polarized Light Is Reflected At A Dielectric-Conductor Interface, R. M.A. Azzam, A. Alsamman Oct 2008

Plurality Of Principal Angles For A Given Pseudo-Brewster Angle When Polarized Light Is Reflected At A Dielectric-Conductor Interface, R. M.A. Azzam, A. Alsamman

Electrical Engineering Faculty Publications

The pseudo-Brewster angle ϕpB of minimum reflectance for p-polarized light and the principal angle ϕ¯ at which incident linearly polarized light of the proper azimuth is reflected circularly polarized are considered as functions of the complex relative dielectric function ε of a dielectric–conductor interface over the entire complex ε plane. In particular, the spread of ϕ¯for a given ϕpB is determined, and the maximum difference (ϕ¯−ϕpB)max is obtained as a function of ϕpB . The maximum difference (ϕ¯−ϕpB)max approaches 45° and 0 in the limit as ϕpB→0 and 90°, respectively. ForϕpB<22.666° , multiple principal angles ϕ¯i , i=1,2,3 , appear for each ε in a subdomain of fractional optical constants. …

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Usu’S Rayleigh-Scatter Lidar, Vincent B. Wickwar Oct 2008

Usu’S Rayleigh-Scatter Lidar, Vincent B. Wickwar

Presentations

No abstract provided.

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Extreme-Ultraviolet Polarimeter Utilizing Laser-Generated High-Order Harmonics, Nicole Brimhall, Matthew Turner, Nicholas Herrick, David D. Allred, R. Steven Turley, Michael Ware, Justin Peatross Oct 2008

Extreme-Ultraviolet Polarimeter Utilizing Laser-Generated High-Order Harmonics, Nicole Brimhall, Matthew Turner, Nicholas Herrick, David D. Allred, R. Steven Turley, Michael Ware, Justin Peatross

Faculty Publications

We describe an extreme-ultraviolet (EUV) polarimeter that employs laser-generated high-order harmonics as the light source. The polarimeter is designed to characterize materials and thin films for use with EUV light. Laser high harmonics are highly directional with easily rotatable linear polarization, not typically available with other EUV sources. The harmonics have good wavelength coverage, potentially spanning the entire EUV from a few to a hundred nanometers. Our instrument is configured to measure reflectances from 14 to 30 nm and has ~180 spectral resolution (lambda/delta lambda). The reflection from a sample surface can be measured over a continuous range of incident …

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Exploration Of A Physical Picture For The Qcd Scalar Channel, Joseph Schechter, Amir H. Fariborz, Renata Jora Oct 2008

Exploration Of A Physical Picture For The Qcd Scalar Channel, Joseph Schechter, Amir H. Fariborz, Renata Jora

Physics - All Scholarship

A generalized linear sigma model is employed to study the quark structure of low lying scalar as well as pseudoscalar states. The model allows the possible mixing of quark anti-quark states with others made of two quarks and two antiquarks but no a priori assumption is made about the quark contents of the predicted physical states. Effects of SU(3) symmetry breaking are included. The lighter conventional pseudoscalars turn out to be primarily of two quark type whereas the lighter scalars have very large four quark admixtures.

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Observation Of Zz Production In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration Oct 2008

Observation Of Zz Production In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration

Kenneth Bloom Publications

We present an observation for ZZ → ℓ+ ℓ-ℓ‘+ℓ‘- (ℓ, ℓ‘ = e or μ ) production in pp collisions at a center-of-mass energy of √s = 1.96 TeV. Using 1.7 fb-1 of data collected by the D0 experiment at the Fermilab Tevatron Collider, we observe three candidate events with an expected background of 0.14+0.03 -0.02 events. The significance of this observation is 5.3 standard deviations. The combination of D0 results in this channel, as well as in ZZ → ℓ+ ℓ-vv, yields a significance of 5.7 …

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Observation Of Zz Production In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration Oct 2008

Observation Of Zz Production In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration

Kenneth Bloom Publications

We present an observation for ZZ → ℓ+ ℓ-ℓ‘+ℓ‘- (ℓ, ℓ‘ = e or μ ) production in pp collisions at a center-of-mass energy of √s = 1.96 TeV. Using 1.7 fb-1 of data collected by the D0 experiment at the Fermilab Tevatron Collider, we observe three candidate events with an expected background of 0.14+0.03 -0.02 events. The significance of this observation is 5.3 standard deviations. The combination of D0 results in this channel, as well as in ZZ → ℓ+ ℓ-vv, yields a significance of 5.7 …

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Quenching Of The Exchange Bias Training In Fe/Cr2o3/Fe Trilayer, Sarbeswar Sahoo, Christian Binek Oct 2008

Quenching Of The Exchange Bias Training In Fe/Cr2o3/Fe Trilayer, Sarbeswar Sahoo, Christian Binek

Christian Binek Publications

Exchange bias (EB) and its associated training effects are studied in an epitaxial Fe(10 nm)/Cr2O3(2.7 nm)/Fe(10 nm) trilayer heterostructure grown by molecular beam epitaxy. The EB decreases linearly with increasing temperature from T = 5 K to T = 50 K. It changes sign and becomes positive within 50 K < T < 200 K, finally changing back to regular EB for T<200K up to the highest measured temperature of T = 395 K. Remarkably, the latter is far above the bulk Néel temperature TN = 307 K. EB training effects occur only at 5 K < T < 50 K. We show that this training can be quenched by subjecting the system to DC magnetic field, µ0HDC <= 7 T. The applied field most likely induces a temperature dependent spin-flop transition. Upon its removal the antiferromagnetic Cr2O3 pinning layer evolves uniformly into its quasi-equilibrium spin configuration thus leading to quasi-equilibrium EB.

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Sensitivity Of Pdr Calculations To Microphysical Details, N. P. Abel, P. A. M. Van Hoof, G. Shaw, Gary J. Ferland, T. Elwert Oct 2008

Sensitivity Of Pdr Calculations To Microphysical Details, N. P. Abel, P. A. M. Van Hoof, G. Shaw, Gary J. Ferland, T. Elwert

Physics and Astronomy Faculty Publications

Our understanding of physical processes in photodissociation regions or photon-dominated regions (PDRs) largely depends on the ability of spectral synthesis codes to reproduce the observed infrared emission-line spectrum. In this paper, we explore the sensitivity of a single PDR model to microphysical details. Our calculations use the Cloudy spectral synthesis code, recently modified to include a wealth of PDR physical processes. We show how the chemical/thermal structure of a PDR, along with the calculated spectrum, changes when the treatment of physical processes such as grain physics and atomic/molecular rates are varied. We find a significant variation in the intensities of …

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Seasonal Variations Of Semidiurnal Tidalperturbations In Mesopause Region Temperature And Zonal And Meridional Winds Above Fort Collins, Colorado(40.6°N, 105.1°W), Tao Yuan, H. Schmidt, C. Y. She, D. A. Krueger, S. Reising Oct 2008

Seasonal Variations Of Semidiurnal Tidalperturbations In Mesopause Region Temperature And Zonal And Meridional Winds Above Fort Collins, Colorado(40.6°N, 105.1°W), Tao Yuan, H. Schmidt, C. Y. She, D. A. Krueger, S. Reising

All Physics Faculty Publications

On the basis of Colorado State University (CSU) Na lidar observations over full diurnal cycles from May 2002 to April 2006, a harmonic analysis was performed to extract semidiurnal perturbations in mesopause region temperature and zonal and meridional winds over Fort Collins, Colorado (40.6°N, 105.1°W). The observed monthly results are in good agreement with MF radar tidal climatology for Urbana, Illinois, and with predictions of the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), sampled at the CSU Na lidar coordinates. The observed semidiurnal tidal period perturbation within the mesopause region is found to be dominated by propagating modes …

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Neutralino Dark Matter From Indirect Detection Revisited, Scott Watson, Phill Grajek, Gordon Kane, Daniel J. Phalen, Aaron Pierce Oct 2008

Neutralino Dark Matter From Indirect Detection Revisited, Scott Watson, Phill Grajek, Gordon Kane, Daniel J. Phalen, Aaron Pierce

Physics - All Scholarship

We revisit indirect detection possibilities for neutralino dark matter, emphasizing the complementary roles of different approaches. While thermally produced dark matter often requires large astrophysical "boost factors" to observe antimatter signals, the physically motivated alternative of non-thermal dark matter can naturally provide interesting signals, for example from light wino or Higgsino dark matter. After a brief review of cosmic ray propagation, we discuss signals for positrons, antiprotons, synchrotron radiation and gamma rays from wino annihilation in the galactic halo, and examine their phenomenology. For pure wino dark matter relevant to the LHC, PAMELA and GLAST should report signals.

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Challenges In Radiative Transfer Modeling - W3 Irs5, Lent C. Johnson Iv Oct 2008

Challenges In Radiative Transfer Modeling - W3 Irs5, Lent C. Johnson Iv

Undergraduate Research Symposium (UGRS)

By modeling the spectral energy distribution (SED) of the W3 IRS5 high-mass star formation region and matching this model to observed data, we can constrain the physical parameters of the basic system geometry and cloud mass distribution. From these parameters, we hope to add to the understanding of high-mass star formation processes. In particular, we hope to determine if the geometries associated with lowmass star formation carry over into the high-mass regime.

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Onset Of Tt0 Suppression Studied In Cu + Cu Collisions At Square Root Of Snn = 22:4, 62.4, And 200 Gev, Andrew Marshall Adare, Sergey V. Afanasiev, Christine A. Aidala, N. N. Ajitanand, Yasuyuki Akiba, Gyöngyi Baksay, László A. Baksay, Marcus Hohlmann, S. Rembeczki, Klaus Dehmelt Oct 2008

Onset Of Tt0 Suppression Studied In Cu + Cu Collisions At Square Root Of Snn = 22:4, 62.4, And 200 Gev, Andrew Marshall Adare, Sergey V. Afanasiev, Christine A. Aidala, N. N. Ajitanand, Yasuyuki Akiba, Gyöngyi Baksay, László A. Baksay, Marcus Hohlmann, S. Rembeczki, Klaus Dehmelt

Aerospace, Physics, and Space Science Faculty Publications

Neutral pion transverse momentum (pT) spectra at midrapidity (jyj & 0:35) were measured in Cu þ Cu collisions at ffiffiffiffiffiffiffiffi sNN p ¼ 22:4, 62.4, and 200 GeV. Relative to 0 yields in p þ p collisions scaled by the number of inelastic nucleon-nucleon collisions (Ncoll) the 0 yields for pT * 2 GeV=c in central Cu þ Cu collisions are suppressed at 62.4 and 200 GeV whereas an enhancement is observed at 22.4 GeV. A comparison with a jet-quenching model suggests that final state parton energy loss dominates in central Cu þ Cu collisions at 62.4 and 200 GeV, …

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Enrichment Of Surface-Active Compounds In Coalescing Cloud Drops, Ilya Taraniuk, Alexander Kostinski, Yinon Rudich Oct 2008

Enrichment Of Surface-Active Compounds In Coalescing Cloud Drops, Ilya Taraniuk, Alexander Kostinski, Yinon Rudich

Department of Physics Publications

Surfactants often found in tropospheric aerosols, can affect the onset and development of clouds. Due to high dilution during droplet growth, the effects of surfactants on cloud microphysical processes have been mostly neglected. However, while cloud growth by coalescence conserves the combined volume of all cloud droplets, it reduces the combined surface area. This could lead to enrichment of water‐insoluble surfactants (WIS) and to reduced surface tension of droplets forming in warm processes. Measurements of individual raindrops reveal the presence of water insoluble surfactants. Our field and laboratory studies as well as simple theoretical arguments suggest that by causing varying …

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Photoelectron Spectroscopy And Theoretical Studies Of [Com(Pyrene)N]− (M=1,2 And N=1,2) Complexes, Anil K. Kandalam, Puru Jena, Xiang Li, Soren N. Eustis, Kit H. Bowen Oct 2008

Photoelectron Spectroscopy And Theoretical Studies Of [Com(Pyrene)N]− (M=1,2 And N=1,2) Complexes, Anil K. Kandalam, Puru Jena, Xiang Li, Soren N. Eustis, Kit H. Bowen

Physics & Engineering Faculty Publications

No abstract provided.

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Beauty Photoproduction Using Decays Into Electrons At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, F. Cindolo, M. Corradi, G. Iacobucci, A. Margotti, R. Nania, A. Polini, S. Antonelli, M. Basile, M. Bindi, L. Cifarelli, A. Contin, S. De Pasquale, G. Sartorelli, A. Zichichi, D. Bartsch, I. Brock, H. Hartmann Oct 2008

Beauty Photoproduction Using Decays Into Electrons At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, F. Cindolo, M. Corradi, G. Iacobucci, A. Margotti, R. Nania, A. Polini, S. Antonelli, M. Basile, M. Bindi, L. Cifarelli, A. Contin, S. De Pasquale, G. Sartorelli, A. Zichichi, D. Bartsch, I. Brock, H. Hartmann

Faculty Publications

Photoproduction of beauty quarks in events with two jets and an electron associated with one of the jets has been studied with the ZEUS detector at HERA using an integrated luminosity of 120pb-1. The fractions of events containing b quarks, and also of events containing c quarks, were extracted from a likelihood fit using variables sensitive to electron identification as well as to semileptonic decays. Total and differential cross sections for beauty and charm production were measured and compared with next-to-leading-order QCD calculations and MonteCarlo models. © 2008 The American Physical Society.

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