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Analysis Of Variable Vhe Gamma-Ray Emission From The Hard Spectrum Blazar 1es 1218+304, Asif Imran 2010 Iowa State University

Analysis Of Variable Vhe Gamma-Ray Emission From The Hard Spectrum Blazar 1es 1218+304, Asif Imran

Graduate Theses and Dissertations

This thesis is a study of the very high energy gamma-ray emission from the hard spectrum blazar 1ES 1218+304. The data were collected during the 2008/09 observing season by the VERITAS observatory, an array of four atmospheric Cherenkov telescopes in Southern Arizona. This work describes the development of a set of analysis tools suitable for the extraction of the energy spectra of astrophysical objects. Initially, the tools are applied to the Crab nebula data to optimize and calibrate the analysis. Afterwards, the analysis is applied to the high energy observations of the blazar 1ES 1218+304. We report ...


Structure, Function, And Regulation Of Multidrug Export Proteins Among The Rnd Superfamily In Gram-Negative Bacteria, Mathew David Routh 2010 Iowa State University

Structure, Function, And Regulation Of Multidrug Export Proteins Among The Rnd Superfamily In Gram-Negative Bacteria, Mathew David Routh

Graduate Theses and Dissertations

Multidrug binding proteins are able to recognize structurally unrelated compounds. These proteins play a crucial role as drug resistant export proteins in both eukaryotic and prokaryotic cells. Furthermore, multidrug binding proteins exist that regulate transcription of multidrug transporters and play an important role in responding to incoming toxins. To study the function of multidrug binding proteins and exporters, AcrD of Escherichia coli (E. coli), CmeR of Campylobacter jejuni, and AcrR of E. coli were chosen as models. AcrD, a multidrug efflux pump, functions to rid the bacterial cell of incoming hydrophilic substrates by harboring a diverse ligand binding cavity capable ...


Neutron Scattering Study Of Charge-Ordering In R1/3Sr2/3Feo3(R=La, Pr, Nd, Sm, And Y), Jie Ma 2010 Iowa State University

Neutron Scattering Study Of Charge-Ordering In R1/3Sr2/3Feo3(R=La, Pr, Nd, Sm, And Y), Jie Ma

Graduate Theses and Dissertations

The series of compounds R1/3Sr2/3FeO3 (R = La, Pr, Nd, and Sm) undergo a Verwey transition along with an antiferromagnetic ordering of Fe spins as well as a slight structural distortion below the Verwey transition temperature, TV. The charge disproportionation occurs via 3Fe3.67+=>2Fe3++Fe5+. The driving force of the charge ordering was determined from the magnetic and phonon spectra measured using inelastic neutron scattering. The data indicate a dominant role of the magnetic energy behind the charge ordering of Fe ions in La1/3Sr2/3 ...


Contribution To Individual Blazar Spectrum From The Cascade Of Very-High Energy Gamma Rays, Ke Fang 2010 Iowa State University

Contribution To Individual Blazar Spectrum From The Cascade Of Very-High Energy Gamma Rays, Ke Fang

Graduate Theses and Dissertations

As Very High Energy (VHE) photons travel through the extragalactic background light (EBL), they will interact and generate electron and positron pairs via pair production. The newly produced electrons and positrons will Inverse-Compton scatter the background soft photons to secondary gamma-rays in the process of electromagnetic cascading. The intensity of a cosmological population emitting at VHEs will be attenuated at the highest energies due to absorption and enhanced at lower energies by the resulting cascade. We calculate the cascade radiation created by VHE photons produced by blazars and investigate the effects of cascades on the observed intensity of individual blazars ...


Measurement Of Single Transverse Spin Asymmetry Via Single Hadrons And Di-Hadron Correlations In The 200gev P + P Collision In The Phenix Experiment At Rhic, Feng Wei 2010 Iowa State University

Measurement Of Single Transverse Spin Asymmetry Via Single Hadrons And Di-Hadron Correlations In The 200gev P + P Collision In The Phenix Experiment At Rhic, Feng Wei

Graduate Theses and Dissertations

The spin structure of the proton has been revealed to be extremely complex. The proton spin is composed of the spins and the orbital angular momenta of quarks and gluons in the proton. The first results from polarized deep inelastic scattering (pDIS) experiments in the late 1980s and early 1990s revealed that quarks do not carry a significant fraction of the proton's spin. The recent global analysis on gluon spin including RHIC results showed that gluons have a very small contribution on the spin of proton. Therefore, it is extremely important for physicists understanding the contribution from the orbital ...


Reducing The Losses Of Optical Metamterials, Anan Fang 2010 Iowa State University

Reducing The Losses Of Optical Metamterials, Anan Fang

Graduate Theses and Dissertations

The field of metamaterials is driven by fascinating and far-reaching theoretical visions,

such as perfect lenses, invisibility cloaking, and enhanced optical nonlinearities. However,

losses have become the major obstacle towards real world applications in the optical regime.

Reducing the losses of optical metamaterials becomes necessary and extremely important.

In this thesis, two approaches are taken to reduce the losses. One is to construct an

indefinite medium. Indefinite media are materials where not all the principal components of the permittivity and permeability tensors have the same sign. They do not need the resonances to achieve negative permittivity. So, the losses can ...


Characterization And Correction Of Dark Current In Compact Consumer Cameras, Justin Charles Dunlap, Erik Bodegom, Ralf Widenhorn 2010 Portland State University

Characterization And Correction Of Dark Current In Compact Consumer Cameras, Justin Charles Dunlap, Erik Bodegom, Ralf Widenhorn

Physics Faculty Publications and Presentations

A study of dark current in digital imagers within consumer grade digital cameras is presented. Dark current is shown to vary with temperature, exposure time, and ISO setting. Further, dark current is shown to increase in successive images during a series of images. Consumer cameras are often designed to be as compact as possible and therefore the digital imagers within the camera frame are prone to heat generated by nearby elements within the camera body. It is the scope of this work to characterize the dark current in such cameras and to show that the dark current, in part due ...


Symmetry In The Dissociative Recombination Of Polyatomic Ions And In Ultra-Cold Few Body Collisions, Nicolas Douguet 2010 University of Central Florida

Symmetry In The Dissociative Recombination Of Polyatomic Ions And In Ultra-Cold Few Body Collisions, Nicolas Douguet

Electronic Theses and Dissertations

We discuss the role of symmetries in the dissociative recombinations (DR) of three polyatomic ions, namely the linear HCO+ (formyl) ion and the two highly symmetric H+3 and H3O+ (hydronium) molecular ions. Regarding the HCO+ ion, we apply a quantum mechanical treatment using the Multi-channel Quantum Defect Theory (MQDT) formalism to describe the ion-electron scattering process. Our study takes into account the Renner-Teller effect in order to model the non Born-Oppenheimer vibronic coupling in linear polyatomic ions. The coupling has shown to represent the main mechanism responsible for electronic capturing in highly excited Rydberg states associated with excited vibrational ...


Comparison Of Flight And Ground Tests Of Environmental Degradation Of Misse-6 Suspecs Materials, JR Dennison, John Prebola, Amberly Evans, Danielle Fullmer, Joshua L. Hodges, Dustin H. Crider, Daniel S. Crews 2010 Utah State Univesity

Comparison Of Flight And Ground Tests Of Environmental Degradation Of Misse-6 Suspecs Materials, Jr Dennison, John Prebola, Amberly Evans, Danielle Fullmer, Joshua L. Hodges, Dustin H. Crider, Daniel S. Crews

Conference Proceedings

The effects of prolonged exposure to the LEO space environment and charge-enhanced contamination on optical, thermal, and electron emission and transport properties of common spacecraft materials have been investigated by comparing pre- and post-flight characterization measurements. The State of Utah Space Environment and Contamination Study (SUSpECS) deployed in March 2008 on board the Materials International Space Station Experiment (MISSE-6) payload, was exposed for ~18 months on the exterior of the International Space Station (ISS), and was retrieved in September 2009. A total of 165 samples were mounted on three separate SUSpECS panels on the ram and wake sides on the ...


Quantum Dot Based Mode-Locked Semiconductor Lasers And Applications, Jimyung Kim 2010 University of Central Florida

Quantum Dot Based Mode-Locked Semiconductor Lasers And Applications, Jimyung Kim

Electronic Theses and Dissertations

In this dissertation, self-assembled InAs/InGaAs quantum dot Fabry-Perot lasers and mode-locked lasers are investigated. The mode-locked lasers investigated include monolithic and curved two-section devices, and colliding pulse mode-locked diode lasers. Ridge waveguide semiconductor lasers have been designed and fabricated by wet etching processes. Electroluminescence of the quantum dot lasers is studied. Cavity length dependent lasing via ground state and/or excited state transitions is observed from quantum dot lasers and the optical gain from both transitions is measured. Stable optical pulse trains via ground and excited state transitions are generated using a grating coupled external cavity with a curved ...


Electro-Optical And All-Optical Switching In Multimode Interference Waveguides Incorporating Semiconductor Nanostructures, Nathan Bickel 2010 University of Central Florida

Electro-Optical And All-Optical Switching In Multimode Interference Waveguides Incorporating Semiconductor Nanostructures, Nathan Bickel

Electronic Theses and Dissertations

The application of epitaxially grown, III-V semiconductor-based nanostructures to the development of electro-optical and all-optical switches is investigated through the fabrication and testing of integrated photonic devices designed using multimode interference (MMI) waveguides. The properties and limitations of the materials are explored with respect to the operation of those devices through electrical carrier injection and optical pumping. MMI waveguide geometry was employed as it offered advantages such as a very compact device footprint, low polarization sensitivity, large bandwidth and relaxed fabrication tolerances when compared with conventional single-mode waveguide formats. The first portion of this dissertation focuses on the characterization of ...


Study Of The Numerical Modeling Of The Temperature Dependence Of The Dark Current In Charge Coupled Devices, Ralf Widenhorn, Ionel Tunaru, Erik Bodegom, Dan A. Iordache 2010 Portland State University

Study Of The Numerical Modeling Of The Temperature Dependence Of The Dark Current In Charge Coupled Devices, Ralf Widenhorn, Ionel Tunaru, Erik Bodegom, Dan A. Iordache

Physics Faculty Publications and Presentations

As it is well known, the classical works of the Dark Current Spectroscopy method allow - using some not too accurate theoretical relations, but huge numbers of dark current values for thousands of pixels - the evaluation of a reduced number of basic impurities parameters. Unlike these works, this paper tries to obtain--by means of some better approximations of the Shockley-Read-Hall (SRH) model--more information about the studied impurities, as well as the study of the compatibility of the used theoretical model SRH relative to the experimental data. In this manner, both the compatibility SRH model with the studied experimental data was checked ...


Zero Field Magnetic Phase Transitions And Anomalous Low Temperature Upturn In Resistivity Of Single Crystalline Α-Tmalb4, N. H. Sung, Andreas Kreyssig, H. Kim, Makariy A. Tanatar, J. S. Rhyee, B. Y. Kang, M. G. Kim, J. Y. Kim, Paul C. Canfield, Ruslan Prozorov, Alan I. Goldman, B. K. Cho 2010 Gwangju Institute of Science and Technology

Zero Field Magnetic Phase Transitions And Anomalous Low Temperature Upturn In Resistivity Of Single Crystalline Α-Tmalb4, N. H. Sung, Andreas Kreyssig, H. Kim, Makariy A. Tanatar, J. S. Rhyee, B. Y. Kang, M. G. Kim, J. Y. Kim, Paul C. Canfield, Ruslan Prozorov, Alan I. Goldman, B. K. Cho

Ames Laboratory Publications

In this study, pure α-TmAlB4 (YCrB4structure)single crystals were grown with no β-TmAlB4 (ThMoB4structure) intergrowth, and zero magnetic fieldtransitions were confirmed through specific heat capacity, magnetization, and electric resistivity measurements. The anomalous magnetic transition was found at approximately 6.2 K with long range antiferromagnetictransition at 5.6 K. The difference in field dependence between these two transitions indicates that they do not share a common magnetic origin. In addition, we investigated electrical resistivity down to 20 mK, and found upturn behavior at around 0.8 K. The low temperature upturn anomaly in resistivity was not found for other compounds ...


Upper Limits On A Possible Gluon Mass, Shmuel Nussinov, Robert Shrock 2010 Chapman University

Upper Limits On A Possible Gluon Mass, Shmuel Nussinov, Robert Shrock

Mathematics, Physics, and Computer Science Faculty Articles and Research

We analyze upper limits on a possible gluon mass, mg. We first discuss various ways to modify quantum chromodynamics to include m(g) not equal 0, including a bare mass, a Higgs mechanism, and dynamical breaking of color SU(3)(c). From an examination of experimental data, we infer an upper limit m(g) < O(1) MeV. As part of our analysis, we show that a claim, hitherto unrefuted in the literature, of a much stronger upper limit on m(g), is invalid. We discuss subtleties in interpreting gluon mass limits in view of the fact that at scales below Lambda(QCD), quantum chromodynamics is strongly coupled, perturbation theory is not reliable, and the physics is not accurately described in terms of the Lagrangian degrees of freedom, including gluons. We also point out a fundamental difference in the behavior of quantum chromodynamics with a nonzero gluon mass and a weakly coupled gauge theory with a gauge boson mass.


Periodic Step Arrays On The Aperiodic I-Al-Pd-Mn Quasicrystal Surface At High Temperature, Y. Sato, Barış Ünal, Thomas A. Lograsso, Patricia A. Thiel, A. K. Schmid, T. Duden, N. C. Bartelt, K. F. McCarty 2010 University of California, Davis

Periodic Step Arrays On The Aperiodic I-Al-Pd-Mn Quasicrystal Surface At High Temperature, Y. Sato, Barış Ünal, Thomas A. Lograsso, Patricia A. Thiel, A. K. Schmid, T. Duden, N. C. Bartelt, K. F. Mccarty

Chemistry Publications

We have observed the configuration and motion of surface steps on the aperiodic icosahedral (i-) Al-Pd-Mn quasicrystal using low-energy electron microscopy and scanning tunneling microscopy. As the quasicrystal is cooled from high temperature, bulk vacancies migrate to the surface causing the surface to be etched. Surprisingly, this etching occurs by two types of steps with different heights moving in different directions with different velocities. The steady-state surface morphology is a uniformly spaced rhomboidal step network. This network requires that the layer stacking near the surface deviates from the bulk quasicrystal stacking.


Dynamic Path Bifurcation For The Beckmann Reaction: Observation And Implication, H. Yamataka, M. Sato, H. Hasegawa, Salai Cheettu Ammal 2010 University of South Carolina - Columbia

Dynamic Path Bifurcation For The Beckmann Reaction: Observation And Implication, H. Yamataka, M. Sato, H. Hasegawa, Salai Cheettu Ammal

Faculty Publications

The reaction of oximes to amides, known as the Beckmann rearrangement, may undergo fragmentation to form carbocations + nitriles instead of amides when the cations have reasonable stability. The reactions of oxime derivatives of 1-substituted-phenyl-2-propanones and 3-substituted-phenyl-2-butanones in aqueous solvents gave both rearrangement and fragmentation products, the ratio of which was dependent on substituents. Transition state (TS) optimizations and intrinsic reaction coordinate (IRC) calculations for the reaction of 1-phenyl-2-propanone oximes showed that there is a single TS for each substituted compound. The IRC path from the TS either led to a rearrangement product or a fragmentation product depending on the substituent ...


Modeling The Noble Metal/Tio2 (110) Interface With Hybrid Dft Functionals: A Periodic Electrostatic Embedded Cluster Model Study, Salai Cheettu Ammal, Andreas Heyden 2010 University of South Carolina - Columbia

Modeling The Noble Metal/Tio2 (110) Interface With Hybrid Dft Functionals: A Periodic Electrostatic Embedded Cluster Model Study, Salai Cheettu Ammal, Andreas Heyden

Faculty Publications

The interaction of Aun and Ptn (n=2,3) clusters with the stoichiometric and partially reduced rutile TiO2 (110) surfaces has been investigated using periodic slab and periodic electrostatic embedded cluster models. Compared to Au clusters, Pt clusters interact strongly with both stoichiometric and reduced TiO2 (110) surfaces and are able to enhance the reducibility of the TiO2 (110) surface, i.e., reduce the oxygen vacancy formation energy. The focus of this study is the effect of Hartree–Fock exchange on the description of the strength of chemical bonds at the interface of Au/Pt clusters and the TiO2 (110 ...


Quantum Trajectory Dynamics In Imaginary Time With The Momentum-Dependent Quantum Potential, Sophya V. Garashchuk 2010 University of South Carolina - Columbia

Quantum Trajectory Dynamics In Imaginary Time With The Momentum-Dependent Quantum Potential, Sophya V. Garashchuk

Faculty Publications

The quantum trajectory dynamics is extended to the wave function evolution in imaginary time. For a nodelesswave function a simple exponential form leads to the classical-like equations of motion of trajectories, representing the wave function, in the presence of the momentum-dependent quantum potential in addition to the external potential. For a Gaussian wave function this quantum potential is a time-dependent constant, generating zero quantum force yet contributing to the total energy. For anharmonic potentials the momentum-dependent quantum potential is cheaply estimated from the global Least-squares Fit to the trajectory momenta in the Taylor basis. Wave functions with nodes are described ...


Plasma Treatment Of Bulk Niobium Surface For Superconducting Rf Cavities: Optimization Of The Experimental Conditions On Flat Samples, M. Rašković, J. Upadhyay, L. Vuskovic, S. Popovic, A.-M. Valente-Feliciano, L. Phillips 2010 Old Dominion University

Plasma Treatment Of Bulk Niobium Surface For Superconducting Rf Cavities: Optimization Of The Experimental Conditions On Flat Samples, M. Rašković, J. Upadhyay, L. Vuskovic, S. Popovic, A.-M. Valente-Feliciano, L. Phillips

Physics Faculty Publications

Accelerator performance, in particular the average accelerating field and the cavity quality factor, depends on the physical and chemical characteristics of the superconducting radio-frequency (SRF) cavity surface. Plasma based surface modification provides an excellent opportunity to eliminate nonsuperconductive pollutants in the penetration depth region and to remove the mechanically damaged surface layer, which improves the surface roughness. Here we show that the plasma treatment of bulk niobium (Nb) presents an alternative surface preparation method to the commonly used buffered chemical polishing and electropolishing methods. We have optimized the experimental conditions in the microwave glow discharge system and their influence on ...


Conventions, Definitions, Identities, And Other Useful Formulae, Robert A. McNees IV 2010 Loyola University Chicago

Conventions, Definitions, Identities, And Other Useful Formulae, Robert A. Mcnees Iv

Physics: Faculty Publications and Other Works

As the name suggests, these notes contain a summary of important conventions, definitions, identities, and various formulas that I often refer to. They may prove useful for researchers working in General Relativity, Supergravity, String Theory, Cosmology, and related areas.


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