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2010 MICROBIAL STRESS RESPONSE GORDON RESEARCH CONFERENCE, JULY 18-23, 2010 (open access)

2010 MICROBIAL STRESS RESPONSE GORDON RESEARCH CONFERENCE, JULY 18-23, 2010

The 2010 Gordon Research Conference on Microbial Stress Responses provides an open and exciting forum for the exchange of scientific discoveries on the remarkable mechanisms used by microbes to survive in nearly every niche on the planet. Understanding these stress responses is critical for our ability to control microbial survival, whether in the context of biotechnology, ecology, or pathogenesis. From its inception in 1994, this conference has traditionally employed a very broad definition of stress in microbial systems. Sessions will cover the major steps of stress responses from signal sensing to transcriptional regulation to the effectors that mediate responses. A wide range of stresses will be represented. Some examples include (but are not limited to) oxidative stress, protein quality control, antibiotic-induced stress and survival, envelope stress, DNA damage, and nutritional stress. The 2010 meeting will also focus on the role of stress responses in microbial communities, applied and environmental microbiology, and microbial development. This conference brings together researchers from both the biological and physical sciences investigating stress responses in medically- and environmentally relevant microbes, as well as model organisms, using cutting-edge techniques. Computational, systems-level, and biophysical approaches to exploring stress responsive circuits will be integrated throughout the sessions alongside the …
Date: July 23, 2011
Creator: Ades, Sarah
System: The UNT Digital Library
Gravitomagnetism in Quantum Mechanics (open access)

Gravitomagnetism in Quantum Mechanics

None
Date: November 23, 2011
Creator: Adler, Ronald J.; /Stanford U., HEPL; Chen, Pisin & /Taiwan, Natl. Taiwan U. /KIPAC, Menlo Park
System: The UNT Digital Library
EVALUATION OF POTENTIAL ELUANTS FOR NON-ACID ELUTION OF CESIUM FROM SPHERICAL RESORCINOL-FORMALDEHYDE RESIN (open access)

EVALUATION OF POTENTIAL ELUANTS FOR NON-ACID ELUTION OF CESIUM FROM SPHERICAL RESORCINOL-FORMALDEHYDE RESIN

Ion Exchange column loading and elution of cesium from spherical resorcinol-formaldehyde resin have been conducted for two potential non-acid eluants -(NH{sub 4}){sub 2}CO{sub 3} and CH{sub 3}COONH{sub 4}. The results revealed encouraging cesium elution performance. 100% elution was achieved in at most 22 hours ({approx}28 bed volumes) of elution. Elution performance was fairly high at 6 hours ({approx}8 bed volumes) of elution for some of the eluants and also practically comparable to the benchmark acid eluant (HNO{sub 3}). Hence, it is quite possible 100% percent elution will be closer to the 6th hour than the 22nd hour. Elution is generally enhanced by increasing the concentration and pH of the eluants, and combining the eluants.
Date: October 23, 2011
Creator: Adu-Wusu, K.; Nash, C. & Pennebaker, F.
System: The UNT Digital Library
Beam Polarization at the ILC: the Physics Impact and the Accelerator Solutions (open access)

Beam Polarization at the ILC: the Physics Impact and the Accelerator Solutions

In this contribution accelerator solutions for polarized beams and their impact on physics measurements are discussed. Focus are physics requirements for precision polarimetry near the interaction point and their realization with polarized sources. Based on the ILC baseline programme as described in the Reference Design Report (RDR), recent developments are discussed and evaluated taking into account physics runs at beam energies between 100 GeV and 250 GeV, as well as calibration runs on the Z-pole and options as the 1TeV upgrade and GigaZ. The studies, talks and discussions presented at this conference demonstrated that beam polarization and its measurement are crucial for the physics success of any future linear collider. To achieve the required precision it is absolutely decisive to employ multiple devices for testing and controlling the systematic uncertainties of each polarimeter. The polarimetry methods for the ILC are complementary: with the upstream polarimeter the measurements are performed in a clean environment, they are fast and allow to monitor time-dependent variations of polarization. The polarimeter downstream the IP will measure the disrupted beam resulting in high background and much lower statistics, but it allows access to the depolarization at the IP. Cross checks between the polarimeter results give redundancy …
Date: November 23, 2011
Creator: Aurand, B.; Bailey, I.; Bartels, C.; Brachmann, A.; Clarke, J.; Hartin, A. et al.
System: The UNT Digital Library
Radiative B Decays (open access)

Radiative B Decays

I discuss recent results in radiative B decays from the Belle and BaBar collaborations. I report new measurements of the decay rate and CP asymmetries in b {yields} s{gamma} and b {yields} d{gamma} decays, and measurements of the photon spectrum in b {yields} s{gamma}. Radiative penguin decays are flavour changing neutral currents which do not occur at tree level in the standard model (SM), but must proceed via one loop or higher order diagrams. These transitions are therefore suppressed in the SM, but offer access to poorlyknown SM parameters and are also a sensitive probe of new physics. In the SM, the rate is dominated by the top quark contribution to the loop, but non-SM particles could also contribute with a size comparable to leading SM contributions. The new physics effects are potentially large which makes them theoretically very interesting, but due to their small branching fractions they are typically experimentally challenging.
Date: November 23, 2011
Creator: Bard, D.
System: The UNT Digital Library
Development of Cdznte Radiation Detectors (open access)

Development of Cdznte Radiation Detectors

Cadmium Zinc Telluride (CdZnTe or CZT) is a very attractive material for room-temperature semiconductor detectors because of its wide band-gap and high atomic number. Despite these advantages, CZT still presents some material limitations and poor hole mobility. In the past decade most of the developing CZT detectors focused on designing different electrode configurations, mainly to minimize the deleterious effect due to the poor hole mobility. A few different electrode geometries were designed and fabricated, such as pixelated anodes and Frisch-grid detectors developed at Brookhaven National Lab (BNL). However, crystal defects in CZT materials still limit the yield of detector-grade crystals, and, in general, dominate the detector's performance. In the past few years, our group's research extended to characterizing the CZT materials at the micro-scale, and to correlating crystal defects with the detector's performance. We built a set of unique tools for this purpose, including infrared (IR) transmission microscopy, X-ray micro-scale mapping using synchrotron light source, X-ray transmission- and reflection-topography, current deep level transient spectroscopy (I-DLTS), and photoluminescence measurements. Our most recent work on CZT detectors was directed towards detailing various crystal defects, studying the internal electrical field, and delineating the effects of thermal annealing on improving the material properties. In …
Date: October 23, 2011
Creator: Bolotnikov, A.; Camarda, G.; Hossain, A.; Kim, K. H.; Yang, G.; Gul, R. et al.
System: The UNT Digital Library
DAFNE Status Report (open access)

DAFNE Status Report

DAFNE, the Frascati {Phi}-factory, is providing an increasing peak and integrated luminosity for the KLOE experiment. Such improvements, together with a background reduction in the KLOE detector, have been obtained after continuous machine studies. An increase of the single bunch luminosity has been achieved essentially by the reduction of the effects of machine non-linearities. The integrated luminosity was improved by the capability of topping up the beam currents while keeping the KLOE detector on, together with an increase of the stored currents.
Date: November 23, 2011
Creator: Boscolo, M.; Alesini, D.; Benedetti, G.; Bertolucci, S.; Biscari, C.; Boni, R. et al.
System: The UNT Digital Library
Sensitivity of CUORE to Neutrinoless Double-Beta Decay (open access)

Sensitivity of CUORE to Neutrinoless Double-Beta Decay

In this paper, we study the sensitivity of CUORE, a bolometric double-beta decay experiment under construction at the Laboratori Nazionali del Gran Sasso in Italy. Two approaches to the computation of experimental sensitivity are discussed and compared, and the formulas and parameters used in the sensitivity estimates are provided. Assuming a background rate of 10{sup -2} cts/(keV kg y), we find that, after 5 years of live time, CUORE will have a 1#27;{sigma} sensitivity to the neutrinoless double-beta decay half-life of {caret T{sup 0{nu}}{sub 1/2}}(1{sigma}#27;) = 1.6x#2;10{sup 26} y and thus a potential to probe the effective Majorana neutrino mass down to 41-95 meV; the sensitivity at 1.64{sigma}#27;, which corresponds to 90% C.L., will be {caret T{sup 0{nu}}{sub 1/2}(1.64{sigma}#27;}) = 9.5x10{sup 25} y. This range is compared with the claim of observation of neutrinoless double-beta decay in {sup 76}Ge and the preferred range in the neutrino mass parameter space from oscillation results.
Date: November 23, 2011
Creator: CUORE; Alessandria, F.; Andreotti, E.; Ardito, R.; Arnaboldi, C.; Avignone, F. T. III et al.
System: The UNT Digital Library
A Next Generation Light Source Facility at LBNL (open access)

A Next Generation Light Source Facility at LBNL

The Next Generation Light Source (NGLS) is a design concept, under development at LBNL, for a multibeamline soft x-ray FEL array powered by a ~;;2 GeV superconducting linear accelerator, operating with a 1 MHz bunch repetition rate. The CW superconducting linear accelerator is supplied by a high-brightness, highrepetition- rate photocathode electron gun. Electron bunches are distributed from the linac to the array of independently configurable FEL beamlines with nominal bunch rates up to 100 kHz in each FEL, and with even pulse spacing. Individual FELs may be configured for EEHG, HGHG, SASE, or oscillator mode of operation, and will produce high peak and average brightness x-rays with a flexible pulse format, with pulse durations ranging from sub-femtoseconds to hundreds of femtoseconds.
Date: March 23, 2011
Creator: Corlett, J. N.; Austin, B.; Baptiste, K. M.; Byrd, J. M.; Denes, P.; Donahue, R. et al.
System: The UNT Digital Library
Compact Cdznte-Based Gamma Camera for Prostate Cancer Imaging (open access)

Compact Cdznte-Based Gamma Camera for Prostate Cancer Imaging

In this paper, we discuss the design of a compact gamma camera for high-resolution prostate cancer imaging using Cadmium Zinc Telluride (CdZnTe or CZT) radiation detectors. Prostate cancer is a common disease in men. Nowadays, a blood test measuring the level of prostate specific antigen (PSA) is widely used for screening for the disease in males over 50, followed by (ultrasound) imaging-guided biopsy. However, PSA tests have a high false-positive rate and ultrasound-guided biopsy has a high likelihood of missing small cancerous tissues. Commercial methods of nuclear medical imaging, e.g. PET and SPECT, can functionally image the organs, and potentially find cancer tissues at early stages, but their applications in diagnosing prostate cancer has been limited by the smallness of the prostate gland and the long working distance between the organ and the detectors comprising these imaging systems. CZT is a semiconductor material with wide band-gap and relatively high electron mobility, and thus can operate at room temperature without additional cooling. CZT detectors are photon-electron direct-conversion devices, thus offering high energy-resolution in detecting gamma rays, enabling energy-resolved imaging, and reducing the background of Compton-scattering events. In addition, CZT material has high stopping power for gamma rays; for medical imaging, a …
Date: October 23, 2011
Creator: Cui, Y.; Lall, T.; Tsui, B.; Yu, J.; Mahler, G.; Bolotnikov, A. et al.
System: The UNT Digital Library
Liquid-Water Uptake and Removal in PEM Fuel-Cell Components (open access)

Liquid-Water Uptake and Removal in PEM Fuel-Cell Components

Management of liquid water is critical for optimal fuel-cell operation, especially at low temperatures. It is therefore important to understand the wetting properties and water holdup of the various fuel-cell layers. While the gas-diffusion layer is relatively hydrophobic and exhibits a strong intermediate wettability, the catalyst layer is predominantly hydrophilic. In addition, the water content of the ionomer in the catalyst layer is lower than that of the bulk membrane, and is affected by platinum surfaces. Liquid-water removal occurs through droplets on the surface of the gas-diffusion layer. In order to predict droplet instability and detachment, a force balance is used. While the pressure or drag force on the droplet can be derived, the adhesion or surface-tension force requires measurement using a sliding-angle approach. It is shown that droplets produced by forcing water through the gas-diffusion layer rather than placing them on top of it show much stronger adhesion forces owing to the contact to the subsurface water.
Date: September 23, 2011
Creator: Das, Prodip K.; Gunterman, Haluna P.; Kwong, Anthony & Weber, Adam Z.
System: The UNT Digital Library
Ekpyrosis and inflationary dynamics in heavy ion collisions: the role of quantum fluctuations (open access)

Ekpyrosis and inflationary dynamics in heavy ion collisions: the role of quantum fluctuations

We summarize recent significant progress in the development of a first-principles formalism to describe the formation and evolution of matter in very high energy heavy ion collisions. The key role of quantum fluctuations both before and after a collision is emphasized. Systematic computations are now feasible to address early time isotropization, flow, parton energy loss and the Chiral Magnetic Effect.
Date: May 23, 2011
Creator: Dusling, K.; Venugopalan, R. & Gelis, F.
System: The UNT Digital Library
Two-dimensional Imaging Velocity Interferometry: Technique and Data Analysis (open access)

Two-dimensional Imaging Velocity Interferometry: Technique and Data Analysis

We describe the data analysis procedures for an emerging interferometric technique for measuring motion across a two-dimensional image at a moment in time, i.e. a snapshot 2d-VISAR. Velocity interferometers (VISAR) measuring target motion to high precision have been an important diagnostic in shockwave physics for many years Until recently, this diagnostic has been limited to measuring motion at points or lines across a target. We introduce an emerging interferometric technique for measuring motion across a two-dimensional image, which could be called a snapshot 2d-VISAR. If a sufficiently fast movie camera technology existed, it could be placed behind a traditional VISAR optical system and record a 2d image vs time. But since that technology is not yet available, we use a CCD detector to record a single 2d image, with the pulsed nature of the illumination providing the time resolution. Consequently, since we are using pulsed illumination having a coherence length shorter than the VISAR interferometer delay ({approx}0.1 ns), we must use the white light velocimetry configuration to produce fringes with significant visibility. In this scheme, two interferometers (illuminating, detecting) having nearly identical delays are used in series, with one before the target and one after. This produces fringes with at …
Date: March 23, 2011
Creator: Erskine, D. J.; Smith, R. F.; Bolme, C.; Celliers, P. & Collins, G.
System: The UNT Digital Library
Multipacting Analysis for the Half-Wave Spoke Resonator Crab Cavity for LHC (open access)

Multipacting Analysis for the Half-Wave Spoke Resonator Crab Cavity for LHC

A compact 400-MHz half-wave spoke resonator (HWSR) superconducting crab cavity is being developed for the LHC upgrade. The cavity shape and the LOM/HOM couplers for such a design have been optimized to meet the space and beam dynamics requirements, and satisfactory RF parameters have been obtained. As it is known that multipacting is an issue of concern in a superconducting cavity which may limit the achievable gradient. Thus it is important in the cavity RF design to eliminate the potential MP conditions to save time and cost of cavity development. In this paper, we present the multipacting analysis for the HWSR crab cavity using the Track3P code developed at SLAC, and to discuss means to mitigate potential multipacting barriers. Track3P was used to analyze potential MP in the cavity and the LOM, HOM and FPC couplers. No resonances were found in the LOM couplers and the coaxial beam pipe. Resonant trajectories were identified on various locations in cavity, HOM and FPC couplers. Most of the resonances are not at the peak SEY of Nb. Run-away resonances were identified in broader areas on the cavity end plate and in the HOM coupler. The enhancement counter for run-away resonances does not show …
Date: June 23, 2011
Creator: Ge, Lixin & Li, Zenghai
System: The UNT Digital Library
Accurate Alignment of Plasma Channels Based on Laser Centroid Oscillations (open access)

Accurate Alignment of Plasma Channels Based on Laser Centroid Oscillations

A technique has been developed to accurately align a laser beam through a plasma channel by minimizing the shift in laser centroid and angle at the channel outptut. If only the shift in centroid or angle is measured, then accurate alignment is provided by minimizing laser centroid motion at the channel exit as the channel properties are scanned. The improvement in alignment accuracy provided by this technique is important for minimizing electron beam pointing errors in laser plasma accelerators.
Date: March 23, 2011
Creator: Gonsalves, Anthony; Nakamura, Kei; Lin, Chen; Osterhoff, Jens; Shiraishi, Satomi; Schroeder, Carl et al.
System: The UNT Digital Library
GLAST Prospects for Swift-Era Afterglows (open access)

GLAST Prospects for Swift-Era Afterglows

We calculate the GeV spectra of gamma-ray burst afterglows produced by inverse Compton scattering of these objects sub-MeV emission. We improve on earlier treatments by using refined afterglow parameters and new model developments motivated by recent Swift observations. We present time-dependent GeV spectra for standard, constant-parameter models, as well as for models with energy injection and with time-varying parameters, for a range of burst parameters. We evaluate the limiting redshift to which such afterglows can be detected by the GLAST Large Area Telescope, as well as by AGILE.
Date: November 23, 2011
Creator: Gou, L.J.; /Penn State U., Astron. Astrophys.; Meszaros, P. & U., /Penn State
System: The UNT Digital Library
Unique Challenges Accompany Thick-Shell CdSe/nCdS (n > 10) Nanocrystal Synthesis (open access)

Unique Challenges Accompany Thick-Shell CdSe/nCdS (n > 10) Nanocrystal Synthesis

Thick-shell CdSe/nCdS (n {ge} 10) nanocrystals were recently reported that show remarkably suppressed fluorescence intermittency or 'blinking' at the single-particle level as well as slow rates of Auger decay. Unfortunately, whereas CdSe/nCdS nanocrystal synthesis is well-developed up to n {le} 6 CdS monolayers (MLs), reproducible syntheses for n {ge} 10 MLs are less understood. Known procedures sometimes result in homogeneous CdS nucleation instead of heterogeneous, epitaxial CdS nucleation on CdSe, leading to broad and multimodal particle size distributions. Critically, obtained core/shell sizes are often below those desired. This article describes synthetic conditions specific to thick-shell growth (n {ge} 10 and n {ge} 20 MLs) on both small (sub2 nm) and large (>4.5 nm) CdSe cores. We find added secondary amine and low concentration of CdSe cores and molecular precursors give desired core/shell sizes. Amine-induced, partial etching of CdSe cores results in apparent shell-thicknesses slightly beyond those desired, especially for very-thick shells (n {ge} 20 MLs). Thermal ripening and fast precursor injection lead to undesired homogeneous CdS nucleation and incomplete shell growth. Core/shells derived from small CdSe (1.9 nm) have longer PL lifetimes and more pronounced blinking at single-particle level compared with those derived from large CdSe (4.7 nm). We expect …
Date: December 23, 2011
Creator: Guo, Yijun; Marchuk, Kyle; Sampat, Siddharth; Abraham, Rachel; Fang, Ning; Malko, Anton V. et al.
System: The UNT Digital Library
Research and Development of H Ion Source and LEBT for a Kaon-neutrino Factory (open access)

Research and Development of H Ion Source and LEBT for a Kaon-neutrino Factory

A baseline H{sup -} ion source and low energy beam transport system (LEBT) have been identified for Project X. The filament-discharge H{sup -} ion source has been fabricated by D-Pace, Inc. and is now in operation at LBNL. The source is capable of delivering over 10mA of H{sup -} beam in cw operation with normalized 4rms emittances less than 0.7 {pi} mm mrad. A two-solenoid magnetic lens LEBT system has been design. The design has been validated with simulations of beam transport for 5 mA 30 keV H- beams using various simulation codes.
Date: November 23, 2011
Creator: Ji, Q.; Staples, J.; Schenkel, T. & Li, D.
System: The UNT Digital Library
A Model for Tow Impregnation and Consolidation for Partially Impregnated Thermoset Prepregs (open access)

A Model for Tow Impregnation and Consolidation for Partially Impregnated Thermoset Prepregs

The formation and transport of voids in composite materials remains a key research area in composite manufacturing science. Knowledge of how voids, resin, and fiber reinforcement propagate throughout a composite material continuum from green state to cured state during an automated tape layup process is key to minimizing defects induced by void-initiated stress concentrations under applied loads for a wide variety of composite applications. This paper focuses on modeling resin flow in a deforming fiber tow during an automated process of partially impregnated thermoset prepreg composite material tapes. In this work, a tow unit cell based model has been presented that determines the consolidation and impregnation of a thermoset prepreg tape under an input pressure profile. A parametric study has been performed to characterize the behavior of varying tow speed and compaction forces on the degree of consolidation. Results indicate that increased tow consolidation is achieved with slower tow speeds and higher compaction forces although the relationship is not linear. The overall modeling of this project is motivated to address optimization of the 'green state' composite properties and processing parameters to reduce or eliminate 'cured state' defects, such as porosity and de-lamination. This work is partially funded by the Department …
Date: May 23, 2011
Creator: Jr, John J. Gangloff; Sinha, Shatil & Advani, Suresh G.
System: The UNT Digital Library
A Model for Tow Impregnation and Consolidation for Partially Impregnated Thermoset Prepregs (open access)

A Model for Tow Impregnation and Consolidation for Partially Impregnated Thermoset Prepregs

The formation and transport of voids in composite materials remains a key research area in composite manufacturing science. Knowledge of how voids, resin, and fiber reinforcement propagate throughout a composite material continuum from green state to cured state during an automated tape layup process is key to minimizing defects induced by void-initiated stress concentrations under applied loads for a wide variety of composite applications. This paper focuses on modeling resin flow in a deforming fiber tow during an automated process of partially impregnated thermoset prepreg composite material tapes. In this work, a tow unit cell based model has been presented that determines the consolidation and impregnation of a thermoset prepreg tape under an input pressure profile. A parametric study has been performed to characterize the behavior of varying tow speed and compaction forces on the degree of consolidation. Results indicate that increased tow consolidation is achieved with slower tow speeds and higher compaction forces although the relationship is not linear. The overall modeling of this project is motivated to address optimization of the 'green state' composite properties and processing parameters to reduce or eliminate 'cured state' defects, such as porosity and de-lamination. This work is partially funded by the Department …
Date: May 23, 2011
Creator: Jr, John J. Gangloff; Sinha, Shatil & Advani, Suresh G.
System: The UNT Digital Library
Hidden magnetic configuration in epitaxial La1-rSrzMnO3 films (open access)

Hidden magnetic configuration in epitaxial La1-rSrzMnO3 films

We present an unreported magnetic configuration in epitaxial La{sub 1-x}Sr{sub x}MnO{sub 3} (x {approx} 0.3) (LSMO) films grown on strontium titanate (STO). X-ray magnetic circular dichroism indicates that the remanent magnetic state of thick LSMO films is opposite to the direction of applied magnetic field. Spectroscopic and scattering measurements reveal that the average Mn valence varies from mixed Mn{sup 3+}/Mn{sup 4+} to an enriched Mn{sup 3+} region near the STO interface, resulting in a compressive lattice along a, b-axis and a possible electronic reconstruction in the Mn e{sub g} orbital (d{sub 3z{sup 2}-r{sup 2}}). This reconstruction may provide a mechanism for coupling the Mn{sup 3+} moments antiferromagnetically along the surface normal direction, and in turn may lead to the observed reversed magnetic configuration.
Date: May 23, 2011
Creator: Kao, Chi-Chang
System: The UNT Digital Library
A PROTOTYPE FOUR INCH SHORT HYDRIDE (FISH) BED AS A REPLACEMENT TRITIUM STORAGE BED (open access)

A PROTOTYPE FOUR INCH SHORT HYDRIDE (FISH) BED AS A REPLACEMENT TRITIUM STORAGE BED

The Savannah River Site (SRS) tritium facilities have used 1st generation (Gen1) metal hydride storage bed assemblies with process vessels (PVs) fabricated from 3 inch nominal pipe size (NPS) pipe to hold up to 12.6 kg of LaNi{sub 4.25}Al{sub 0.75} metal hydride for tritium gas absorption, storage, and desorption for over 15 years. The 2nd generation (Gen2) of the bed design used the same NPS for the PV, but the added internal components produced a bed nominally 1.2 m long, and presented a significant challenge for heater cartridge replacement in a footprint limited glove-box. A prototype 3rd generation (Gen3) metal hydride storage bed has been designed and fabricated as a replacement candidate for the Gen2 storage bed. The prototype Gen3 bed uses a PV pipe diameter of 4 inch NPS so the bed length can be reduced below 0.7 m to facilitate heater cartridge replacement. For the Gen3 prototype bed, modeling results show increased absorption rates when using hydrides with lower absorption pressures. To improve absorption performance compared to the Gen2 beds, a LaNi{sub 4.15}Al{sub 0.85} material was procured and processed to obtain the desired pressure-composition-temperature (PCT) properties. Other bed design improvements are also presented.
Date: February 23, 2011
Creator: Klein, J.; Estochen, E.; Shanahan, K. & Heung, L.
System: The UNT Digital Library
The Ultraviolet-To-Mid-Infrared Spectral Energy Distribution of Weak Emission Line Quasars (open access)

The Ultraviolet-To-Mid-Infrared Spectral Energy Distribution of Weak Emission Line Quasars

This article presents Spitzer Space Telescope photometry of 18 Sloan Digital Sky Survey quasars which have weak or undetectable high-ionization emission lines in their rest-frame ultraviolet spectra.
Date: September 23, 2011
Creator: Lane, Ryan A.; Shemmer, Ohad; Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Anderson, Scott F.; Brandt, William Nielsen et al.
System: The UNT Digital Library
Top Quark Amplitudes with an Anomolous Magnetic Moment (open access)

Top Quark Amplitudes with an Anomolous Magnetic Moment

The anomalous magnetic moment of the top quark may be measured during the first run of the LHC at 7 TeV. For these measurements, it will be useful to have available tree amplitudes with t{bar t} and arbitrarily many photons and gluons, including both QED and color anomalous magnetic moments. In this paper, we present a method for computing these amplitudes using the Britto-Cachazo-Feng-Witten recursion formula. Because we deal with an effective theory with higher-dimension couplings, there are roadblocks to a direct computation with the Britto-Cachazo-Feng-Witten method. We evade these by using an auxiliary scalar theory to compute a subset of the amplitudes.
Date: June 23, 2011
Creator: Larkoski, Andrew J. & Peskin, Michael E.
System: The UNT Digital Library