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Articles 1 - 29 of 29
Full-Text Articles in Physics
3he Spin-Dependent Cross Sections And Sum Rules, K. Slifer, M. Amarian, L. Auerbach, T. Averett, J. Berthot, P. Bertin, B. Bertozzi, K. Mccormick, F. Sabatié, L. Todor
3he Spin-Dependent Cross Sections And Sum Rules, K. Slifer, M. Amarian, L. Auerbach, T. Averett, J. Berthot, P. Bertin, B. Bertozzi, K. Mccormick, F. Sabatié, L. Todor
Physics Faculty Publications
We present a measurement of the spin-dependent cross sections for the 3→He(→e,e′)X reaction in the quasielastic and resonance regions at a four-momentum transfer 0.1≤Q2≤0.9 GeV2. The spin-structure functions have been extracted and used to evaluate the nuclear Burkhardt-Cottingham and extended Gerasimov-Drell-Hearn sum rules for the first time. The data are also compared to an impulse approximation calculation and an exact three-body Faddeev calculation in the quasielastic region.
Reflection High-Energy Electron Diffraction Studies Of Indium Phosphide (100) And Growth On Indium And Indium Nitride On Silicon (100), Mohamed Abd-Elsattar Hafez
Reflection High-Energy Electron Diffraction Studies Of Indium Phosphide (100) And Growth On Indium And Indium Nitride On Silicon (100), Mohamed Abd-Elsattar Hafez
Electrical & Computer Engineering Theses & Dissertations
Study of the effects of atomic hydrogen exposure on structure and morphology of semiconductor surfaces is important for fundamental properties and applications. In this dissertation, the electron yield of a hydrogen-cleaned indium phosphide (InP) surface was measured and correlated to the development of the surface morphology, which was monitored by in situ reflection high-energy electron diffraction (RHEED). Atomic hydrogen treatment produced a clean, well-ordered, and (2x4)-reconstructed InP(100) surface. The quantum efficiency, after activation to negative electron affinity, and the secondary electron emission were shown to increase with hydrogen cleaning time. RHEED patterns of low-index InP(100) surface were modified by the …
Investigation Of (E, 2e) Collisions And Related Phenomena, Jason Manuel Martinez
Investigation Of (E, 2e) Collisions And Related Phenomena, Jason Manuel Martinez
Physics Theses & Dissertations
In this thesis I investigate (e, 2e) processes, or electron impact ionization, using several theoretical methods. I first examine the problem using the Born approximations, particularly the Distorted Wave Born Approximation (DWBA), focusing on the underlying processes that dominate for ionization of the 2p state of Argon and Magnesium. I investigate as well the ionization of helium and hydrogen and use the simplicity of the approximation to probe the incident particle effects on the Helium cross section. In both cases the results are compared with experiment. I also produce cross section results for ions near threshold, a regime that …
Investigation Of Loading Of Pulsed And Continuous-Wave Optical Dipole Force Traps, M. Shiddiq, E. M. Ahmed, M. D. Havey, C. I. Sukenik
Investigation Of Loading Of Pulsed And Continuous-Wave Optical Dipole Force Traps, M. Shiddiq, E. M. Ahmed, M. D. Havey, C. I. Sukenik
Physics Faculty Publications
We have investigated the behavior of an optical dipole force trap realized using a mode-locked Nd:YAG laser and have compared performance to a continuous-wave (cw) trap built using the same laser but running in a cw mode. The traps are used to confine ultracold 85Rb atoms which are loaded from a magneto-optical trap (MOT). In most respects, the two traps behave similarly over a wide range of laser parameters provided that the average potential well depth is the same; however, there is a notable difference in the dipole trap loading efficiency dependence on the detuning of the MOT trap laser …
Extended Tuning Of An Injection-Locked Diode Laser, M. K. Shaffer, G. Ranjit, C. I. Sukenik
Extended Tuning Of An Injection-Locked Diode Laser, M. K. Shaffer, G. Ranjit, C. I. Sukenik
Physics Faculty Publications
We have investigated the application of an electronic feedback technique recently reported by Repasky, et.al. [Appl. Opt. 45, 9013 (2006)] to an injection-locked semiconductor diode laser. We find that without electronic feedback, the injection-locked slave laser will only follow the master for less than 1 GHz, but once the electronic feedback is applied, the slave laser is capable of following for more than 20 GHz, corresponding to the full scan range of the master laser.
Photoassociative Spectroscopy Of Ultracold Metastable Argon And Study Of Dual Species Trap Loss In A Rubidium-Metastable Argon Mot, Michael K. Shaffer
Photoassociative Spectroscopy Of Ultracold Metastable Argon And Study Of Dual Species Trap Loss In A Rubidium-Metastable Argon Mot, Michael K. Shaffer
Physics Theses & Dissertations
This dissertation presents the findings of two experimental investigations in ultracold atomic and molecular physics: The study of the dual species trap loss in a rubidium - metastable argon magneto-optical trap and the photoassociative spectroscopy of ultracold metastable argon. The interspecies trap loss rate coefficients have been measured for ultracold collisions between 85Rb and 40Ar* in a dual-species magneto-optical trap (MOT) and the two rates have been found to be approximately equal over the range of intensities studied with values of β'Rb–Ar* = 3.0 ± 1.3 × 10-11 cm3/s and β'Ar*–Rb = 1.9 …
Quantifying Vertical Mixing In Estuaries, W. Rockwell Geyer, Malcolm E. Scully, David K. Ralston
Quantifying Vertical Mixing In Estuaries, W. Rockwell Geyer, Malcolm E. Scully, David K. Ralston
CCPO Publications
Estuarine turbulence is notable in that both the dissipation rate and the buoyancy frequency extend to much higher values than in other natural environments. The high dissipation rates lead to a distinct inertial subrange in the velocity and scalar spectra, which can be exploited for quantifying the turbulence quantities. However, high buoyancy frequencies lead to small Ozmidov scales, which require high sampling rates and small spatial aperture to resolve the turbulent fluxes. A set of observations in a highly stratified estuary demonstrate the effectiveness of a vessel-mounted turbulence array for resolving turbulent processes, and for relating the turbulence to the …
Cold Atmospheric Pressure Air Plasma Jet For Medical Applications, Juergen Friedrich Kolb, A.-A H. Mohamed, R. O. Price, R. J. Swanson, A. Bowman, R. L. Chiavarini, Michael W. Stacey
Cold Atmospheric Pressure Air Plasma Jet For Medical Applications, Juergen Friedrich Kolb, A.-A H. Mohamed, R. O. Price, R. J. Swanson, A. Bowman, R. L. Chiavarini, Michael W. Stacey
Bioelectrics Publications
By flowing atmospheric pressure air through a direct current powered microhollow cathode discharge, we were able to generate a 2 cm long plasma jet. With increasing flow rate, the flow becomes turbulent and temperatures of the jet are reduced to values close to room temperature. Utilizing the jet, yeast grown on agar can be eradicated with a treatment of only a few seconds. Conversely, animal studies show no skin damage even with exposures ten times longer than needed for pathogen extermination. This cold plasma jet provides an effective mode of treatment for yeast infections of the skin.
Reproducible Increased Mg Incorporation And Large Hole Concentration In Gan Using Metal Modulated Epitaxy, Shawn D. Burnham, Gon Namkoong, David C. Look, Bruce Clafin, W. Alan Doolittle
Reproducible Increased Mg Incorporation And Large Hole Concentration In Gan Using Metal Modulated Epitaxy, Shawn D. Burnham, Gon Namkoong, David C. Look, Bruce Clafin, W. Alan Doolittle
Electrical & Computer Engineering Faculty Publications
The metal modulated epitaxy (MME) growth technique is reported as a reliable approach to obtain reproducible large hole concentrations in Mg-doped GaN grown by plasma-assisted molecular-beam epitaxy on c-plane sapphire substrates. An extremely Ga-rich flux was used, and modulated with the Mg source according to the MME growth technique. The shutter modulation approach of the MME technique allows optimal Mg surface coverage to build between MME cycles and Mg to incorporate at efficient levels in GaN films. The maximum sustained concentration of Mg obtained in GaN films using the MME technique was above 7 × 1020 cm-3 …
Dedication To Pierre Lallemand On The Occasion Of His Retirement, Dominque D'Humieres, Manfred Krafczyk, Li-Shi Luo, Robert Rubinstein
Dedication To Pierre Lallemand On The Occasion Of His Retirement, Dominque D'Humieres, Manfred Krafczyk, Li-Shi Luo, Robert Rubinstein
Mathematics & Statistics Faculty Publications
The fourth international conference for mesoscopic methods in engineering and science (http://www.icmmes. org), held in Munich, Germany, 16–20 July 2007, was closed with a celebration honouring Dr Pierre Lallemand on the occasion of his retirement from the Centre National de la Recherche Scientifique (CNRS) after more than 40 years of service.
Ratios Of 15N/12C And 4He/12C Inclusive Electroproduction Cross Sections In The Nucleon Resonance Region, P. E. Bosted, R. Fersch, G. Adams, M. Amaryan, S. Anefalos, M. Anghinolfi, G. Asryan, H. Avakian, H. Badasaryan, N. Baillie, M. Bektasoglu, S. Bültmann, S. L. Careccia, G. E. Dodge, K. V. Dharmawardane, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, N. Kalantarians, A. Klein, S. E. Kuhn, J. Lachniet, R. A. Niyazov, L. M. Qin, F. Sabatié, S. Tkachenko, L. B. Weinstein, J. Zhang, Clas Collaboration
Ratios Of 15N/12C And 4He/12C Inclusive Electroproduction Cross Sections In The Nucleon Resonance Region, P. E. Bosted, R. Fersch, G. Adams, M. Amaryan, S. Anefalos, M. Anghinolfi, G. Asryan, H. Avakian, H. Badasaryan, N. Baillie, M. Bektasoglu, S. Bültmann, S. L. Careccia, G. E. Dodge, K. V. Dharmawardane, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde-Wright, N. Kalantarians, A. Klein, S. E. Kuhn, J. Lachniet, R. A. Niyazov, L. M. Qin, F. Sabatié, S. Tkachenko, L. B. Weinstein, J. Zhang, Clas Collaboration
Physics Faculty Publications
The (W,Q2) dependence of the ratio of inclusive electron scattering cross sections for 15N/12C was determined in the kinematic ranges 0.8 < W < 2 GeV and 0.2 < Q2 < 1 GeV2 using 2.285 GeV electrons and the CLAS detector at Jefferson Lab. The ratios exhibit only slight resonance structure, in agreement with a simple phenomenological model and an extrapolation of deep-inelastic scattering ratios to low Q2. Ratios of 4He/12C using 1.6 to 2.5 GeV electrons were measured with very high statistical precision and were used to correct for He in the N and C targets. …
Next-To-Leading Order Evolution Of Color Dipoles, Ian Balitsky, Giovanni A. Chirilli
Next-To-Leading Order Evolution Of Color Dipoles, Ian Balitsky, Giovanni A. Chirilli
Physics Faculty Publications
The small-x deep inelastic scattering in the saturation region is governed by the nonlinear evolution of Wilson-line operators. In the leading logarithmic approximation it is given by the Balitsky-Kovchegov equation for the evolution of color dipoles. In the next-to-leading order the Balitsky-Kovchegov equation gets contributions from quark and gluon loops as well as from the tree gluon diagrams with quadratic and cubic nonlinearities. We calculate the gluon contribution to the small-x evolution of Wilson lines (the quark part was obtained earlier).
Advances On Elic Design Studies, S. A. Bogacz, P. Chevtsov, Ya. Derbenev, P. Evtushenko, G. Krafft, A. Hutton, R. Li, L. Merminga, J. Musson, B. Yunn, Y. Zhang, H. Sayed
Advances On Elic Design Studies, S. A. Bogacz, P. Chevtsov, Ya. Derbenev, P. Evtushenko, G. Krafft, A. Hutton, R. Li, L. Merminga, J. Musson, B. Yunn, Y. Zhang, H. Sayed
Physics Faculty Publications
An electron-ion collider of a center-of-mass energy up to 90 GeV at luminosity up to 1035 cm-2s-1 with both beams highly polarized is essential for exploring the new QCD frontier of strong color fields in nuclear and precisely imaging the sea-quarks and gluons in the nucleon. A conceptual design of a ring-ring collider based on CEBAF (ELIC) with energies up to 9 GeV for electrons/positrons and up to 225 GeV for protons and 100 GeV/u for ions has been proposed to fulfill the science desire and to serve as the next step for CEBAF after the …
Light Vector Mesons In The Nuclear Medium, M. H. Wood, M. J. Amaryan, H. Bagdasaryan, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, H. G. Juengst, N. Kalantarians, A. Klein, K. V. Klimenko, S. E. Kuhn, J. Lachniet, M. R. Niroula, R. A. Niyazov, S. Tkachenko, L. B. Weinstein, J. Zhang, Clas Collaboration
Light Vector Mesons In The Nuclear Medium, M. H. Wood, M. J. Amaryan, H. Bagdasaryan, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, H. G. Juengst, N. Kalantarians, A. Klein, K. V. Klimenko, S. E. Kuhn, J. Lachniet, M. R. Niroula, R. A. Niyazov, S. Tkachenko, L. B. Weinstein, J. Zhang, Clas Collaboration
Physics Faculty Publications
The light vector mesons (ρ,ω, and ϕ) were produced in deuterium, carbon, titanium, and iron targets in a search for possible in-medium modifications to the properties of the ρ meson at normal nuclear densities and zero temperature. The vector mesons were detected with the CEBAF Large Acceptance Spectrometer (CLAS) via their decays to e+e−. The rare leptonic decay was chosen to reduce final-state interactions. A combinatorial background was subtracted from the invariant mass spectra using a well-established event-mixing technique. The ρ-meson mass spectrum was extracted after the ω and ϕ signals were removed in a nearly model-independent way. Comparisons …
First Measurement Of Target And Double Spin Asymmetries For Ep → Epπ° In The Nucleon Resonance Region Above The Δ (1232), Clas Collaborative, M. J. Amaryan, H. Bagdasaryan, S. Bültmann, G. E. Dodge, N. Guler, N. Kalantarians, A. Klein, S. E. Kuhn, S. Tkachenko, L. B. Weinstein, J. Zhang
First Measurement Of Target And Double Spin Asymmetries For Ep → Epπ° In The Nucleon Resonance Region Above The Δ (1232), Clas Collaborative, M. J. Amaryan, H. Bagdasaryan, S. Bültmann, G. E. Dodge, N. Guler, N. Kalantarians, A. Klein, S. E. Kuhn, S. Tkachenko, L. B. Weinstein, J. Zhang
Physics Faculty Publications
The exclusive channel polarized proton(polarized e,e' p)π0 was studied in the first and second nucleon resonance regions in the Q2 range from 0.187 to 0.770 GeV2 at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). Longitudinal target and beam-target asymmetries were extracted over a large range of center-of-mass angles of the π0 and compared to the unitary isobar model MAID, the dynamic model by Sato and Lee, and the dynamic model DMT. A strong sensitivity to individual models was observed, in particular for the target asymmetry and in the higher invariant mass region. This data …
Electroproduction Of ɸ(1020) Mesons At 1.4 ≤ Q² ≤ 3.8 Gev² Measured With The Clas Spectrometer, Clas Collaboration, M. J. Amaryan, H. Bagdasaryan, M. Bektasoglu, S. Bültmann, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, C. E. Hyde-Wright, H. G. Jungst, N. Kalantarians, A. Klien, A. V. Klimenko, S. E. Kuhn, R. A. Niyazov, T. Tkachenko, L. B. Weinstein, J. Zhang
Electroproduction Of ɸ(1020) Mesons At 1.4 ≤ Q² ≤ 3.8 Gev² Measured With The Clas Spectrometer, Clas Collaboration, M. J. Amaryan, H. Bagdasaryan, M. Bektasoglu, S. Bültmann, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, C. E. Hyde-Wright, H. G. Jungst, N. Kalantarians, A. Klien, A. V. Klimenko, S. E. Kuhn, R. A. Niyazov, T. Tkachenko, L. B. Weinstein, J. Zhang
Physics Faculty Publications
Electroproduction of exclusive ϕ vector mesons has been studied with the CLAS detector in the kinematic range 1.4 ⩽ Q2 ⩽ 3.8 GeV2 ,0.0 ⩽ t′ ⩽3.6 GeV2 , and 2.0 ⩽ W ⩽ 3.0 GeV. The scaling exponent for the total cross section as 1/(Q2 +M2ϕ)n was determined to be n = 2.49 ± 0.33. The slope of the four-momentum transfer t′ distribution is bϕ = 0.98 ± 0.17 GeV-2 . Under the assumption of s -channel helicity conservation, we determine the ratio of longitudinal to transverse cross sections …
Experimental Study Of Isovector Spin Sum Rules, A. Deur, P. Bosted, V. Burkert, D. Crabb, V. Dharmawardane, G. E. Dodge, T. A. Forest, K. A. Griffioen, S. E. Kuhn, R. Minehart, Y. Prok
Experimental Study Of Isovector Spin Sum Rules, A. Deur, P. Bosted, V. Burkert, D. Crabb, V. Dharmawardane, G. E. Dodge, T. A. Forest, K. A. Griffioen, S. E. Kuhn, R. Minehart, Y. Prok
Physics Faculty Publications
We present the Bjorken integral extracted from Jefferson Lab experiment EG1b for 0.05< Q2 2. The integral is fit to extract the twist-4 element f p−n2 which appears to be relatively large and negative. Systematic studies of this higher twist analysis establish its legitimacy at Q2 around 1 GeV2. We also performed an isospin decomposition of the generalized forward spin polarizability γ0. Although its isovector part provides a reliable test of the calculation techniques of chiral perturbation theory, our data disagree with the calculations.
Measurement Of Deeply Virtual Compton Scattering Beam-Spin Asymmetries, Clas Collaboration, H. Bagdasaryan, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, C. E. Hyde, H. G. Juengst, N. Kalantarians, A. Klein, A. V. Klimenko, S. E. Kuhn, J. Lachniet, S. Tkachenko, L. B. Weinstein, J. Zhang
Measurement Of Deeply Virtual Compton Scattering Beam-Spin Asymmetries, Clas Collaboration, H. Bagdasaryan, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, C. E. Hyde, H. G. Juengst, N. Kalantarians, A. Klein, A. V. Klimenko, S. E. Kuhn, J. Lachniet, S. Tkachenko, L. B. Weinstein, J. Zhang
Physics Faculty Publications
The beam-spin asymmetries in the hard exclusive electroproduction of photons on the proton (→ep→epγ ) were measured over a wide kinematic range and with high statistical accuracy. These asymmetries result from the interference of the Bethe-Heitler process and of deeply virtual Compton scattering. Over the whole kinematic range (xB from 0.11 to 0.58, Q2 from 1 to 4.8 GeV2, −t from 0.09 to 1.8 GeV2), the azimuthal dependence of the asymmetries is compatible with expectations from leading-twist dominance, A ≃ asinϕ/(1+ccosϕ). This extensive set of data can thus be used to …
Measurement Of Ep→Epπᵒ Beam Spin Asymmetries Above The Resonance Region, Clas Collaborative, M. J. Amaryan, H. Bagdasaryan, S. Bültmann, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, N. Kalantarians, A. Klien, A. V. Klimenko, S. E. Kuhn, M. R. Niroula, S. Tkachenko, L. B. Weinstein, J. Zhang
Measurement Of Ep→Epπᵒ Beam Spin Asymmetries Above The Resonance Region, Clas Collaborative, M. J. Amaryan, H. Bagdasaryan, S. Bültmann, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, N. Kalantarians, A. Klien, A. V. Klimenko, S. E. Kuhn, M. R. Niroula, S. Tkachenko, L. B. Weinstein, J. Zhang
Physics Faculty Publications
The beam spin asymmetry (BSA) in the exclusive reaction →ep→epπ0 was measured with the CEBAF 5.77 GeV polarized electron beam and Large Acceptance Spectrometer (CLAS). The xB,Q2,t , and ϕ dependences of the π0 BSA are presented in the deep inelastic regime. The asymmetries are fitted with a sinϕ function and their amplitudes are extracted. Overall, they are of the order of 0.04–0.11 and roughly independent of t . This is the signature of a nonzero longitudinal-transverse interference. The implications concerning the applicability of a formalism based on generalized parton distributions, as well as …
Cross Sections And Beam Asymmetries For E ⃗ P → Enπ+ In The Nucleon Resonance Region For 1.7 ⩽ Q2 ⩽ 4.5 Gev2, M. J. Amaryan, H. Bagdasaryan, S. Bültmann, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, N. Kalantarians, A. Klein, A. V. Klimenko, S. E. Kuhn, J. Lachniet, R. A. Niyazov, F. Sabatié, S. Tkachenko, L. B. Weinstein, J. Zhang, Et Al., The Clas Collaboration
Cross Sections And Beam Asymmetries For E ⃗ P → Enπ+ In The Nucleon Resonance Region For 1.7 ⩽ Q2 ⩽ 4.5 Gev2, M. J. Amaryan, H. Bagdasaryan, S. Bültmann, K. V. Dharmawardane, G. E. Dodge, G. Gavalian, N. Guler, C. E. Hyde-Wright, N. Kalantarians, A. Klein, A. V. Klimenko, S. E. Kuhn, J. Lachniet, R. A. Niyazov, F. Sabatié, S. Tkachenko, L. B. Weinstein, J. Zhang, Et Al., The Clas Collaboration
Physics Faculty Publications
The exclusive electroproduction process e ⃗ p → e'nπ+ was measured in the range of the photon virtuality Q2 =1.7-4.5 GeV2, and the invariant mass range for the n π+ system of W=1.15-1.7 GeV using the CEBAF Large Acceptance Spectrometer. For the first time, these kinematics are probed in exclusive π+ production from protons with nearly full coverage in the azimuthal and polar angles of the nπ+ center-of-mass system. The nπ+ channel has particular sensitivity to the isospin 1/2 excited nucleon states, and together with the pπ0 final state will serve …
Studies Of Breakdown In A Pressurized Rf Cavity, M. Bastaninejad, A. A. Elmustafa, C. M. Ankenbrandt, A. Moretti, M. Popovic, K. Yonehara, D. M. Kaplan, M. Alsharo'a, P. M. Hanlet, R. P. Johnson, M. Kuchnir, D. Newsham, D. V. Rose, C. Thoma, D. R. Welch
Studies Of Breakdown In A Pressurized Rf Cavity, M. Bastaninejad, A. A. Elmustafa, C. M. Ankenbrandt, A. Moretti, M. Popovic, K. Yonehara, D. M. Kaplan, M. Alsharo'a, P. M. Hanlet, R. P. Johnson, M. Kuchnir, D. Newsham, D. V. Rose, C. Thoma, D. R. Welch
Mechanical & Aerospace Engineering Faculty Publications
Microscopic images of the surfaces of metallic electrodes used in high-pressure gas-filled 805 MHz RF cavity experiments [1] have been used to investigate the mechanism of RF breakdown [2]. The images show evidence for melting and boiling in small regions of ∼10 micron diameter on tungsten, molybdenum, and beryllium electrode surfaces. In these experiments, the dense hydrogen gas in the cavity prevents electrons or ions from being accelerated to high enough energy to participate in the breakdown process so that the only important variables are the fields and the metallic surfaces. The distributions of breakdown remnants on the electrode surfaces …
Nlo Evolution Of Color Dipole, Ian Balitsky, Giovanni A. Chirilli
Nlo Evolution Of Color Dipole, Ian Balitsky, Giovanni A. Chirilli
Physics Faculty Publications
No abstract provided.
Electroexcitation Of The Roper Resonance For 1.7 < Q² < 4.5gev² In Ep → Enπ+, Clas Collaboration, M. J. Amaryan, M. Bektasoglu, S. Bültmann, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde, A. Klein, S. E. Kuhn, L. M. Qin, L. B. Weinstein, J. Yun, J. Zhang
Electroexcitation Of The Roper Resonance For 1.7 < Q² < 4.5gev² In Ep → Enπ+, Clas Collaboration, M. J. Amaryan, M. Bektasoglu, S. Bültmann, S. L. Careccia, K. V. Dharmawardane, G. E. Dodge, T. A. Forest, G. Gavalian, N. Guler, C. E. Hyde, A. Klein, S. E. Kuhn, L. M. Qin, L. B. Weinstein, J. Yun, J. Zhang
Physics Faculty Publications
The helicity amplitudes of the electroexcitation of the Roper resonance are extracted for 1.7 < Q2 < 4.5 GeV2 from recent high precision JLab-CLAS cross section and longitudinally polarized beam asymmetry data for π+ electroproduction on protons at W=1.15-1.69 GeV. The analysis is made using two approaches, dispersion relations and a unitary isobar model, which give consistent Q2 behavior of the helicity amplitudes for the gamma*p -> N (1440)P11 transition. It is found that the transverse helicity amplitude A 1/2, which is large and negative at Q2=0, becomes large and positive at Q2 similar or equal …
Electron Density And Temperature Measurement Of An Atmospheric Pressure Plasma By Millimeter Wave Interferometer, Xinpei Lu, Mounir Laroussi
Electron Density And Temperature Measurement Of An Atmospheric Pressure Plasma By Millimeter Wave Interferometer, Xinpei Lu, Mounir Laroussi
Electrical & Computer Engineering Faculty Publications
In this paper, a 105 GHz millimeter wave interferometer system is used to measure the electron density and temperature of an atmospheric pressure helium plasma driven by submicrosecond pulses. The peak electron density and electron-neutral collision frequency reach 8 X 1012 cm-3 and 2.1 X 1012 s-1, respectively. According to the electron-helium collision cross section and the measured electron-neutral collision frequency, the electron temperature of the plasma is estimated to reach a peak value of about 8.7 eV.
Sublethal And Killing Effects Of Atmospheric-Pressure, Nonthermal Plasma On Eukaryotic Microalgae In Aqueous Media, Ying Zhong Tang, Xin Pei Lu, Mounir Laroussi, Fred C. Dobbs
Sublethal And Killing Effects Of Atmospheric-Pressure, Nonthermal Plasma On Eukaryotic Microalgae In Aqueous Media, Ying Zhong Tang, Xin Pei Lu, Mounir Laroussi, Fred C. Dobbs
OES Faculty Publications
In-depth studies on the interaction of nonthermal plasmas with microorganisms usually focus on bacteria; only little attention has been given to their effects on more complex eukaryotic cells. We report here nonthermal plasma's effects on cell motility, viability staining, and morphology of eukaryotic microalgae, with three marine dinoflagellates and a marine diatom as major targets. The effects on motility and viability staining depended on the time of exposure to plasma and the species of microalgae. We observed a strong pH decrease in aqueous samples (marine and freshwater algal cultures, their culture media, and deionized water) after exposure to plasma, and …
Nonthermal Laser-Induced Formation Of Crystalline Ge Quantum Dots On Si(100), M. S. Hegazy, H. E. Elsayed-Ali
Nonthermal Laser-Induced Formation Of Crystalline Ge Quantum Dots On Si(100), M. S. Hegazy, H. E. Elsayed-Ali
Electrical & Computer Engineering Faculty Publications
The effects of laser-induced electronic excitations on the self-assembly of Ge quantum dots on Si (100) - (2×1) grown by pulsed laser deposition are studied. Electronic excitations due to laser irradiation of the Si substrate and the Ge film during growth are shown to decrease the roughness of films grown at a substrate temperature of ∼120 °C. At this temperature, the grown films are nonepitaxial. Electronic excitation results in the formation of an epitaxial wetting layer and crystalline Ge quantum dots at ∼260 °C, a temperature at which no crystalline quantum dots form without excitation under the same deposition conditions. …
Activation Energy Of Surface Diffusion And Terrace Width Dynamics During The Growth Of In (4×3) On Si (100) - (2×1) By Femtosecond Pulsed Laser Deposition, M. A. Hafez, H. E. Elsayed-Ali
Activation Energy Of Surface Diffusion And Terrace Width Dynamics During The Growth Of In (4×3) On Si (100) - (2×1) By Femtosecond Pulsed Laser Deposition, M. A. Hafez, H. E. Elsayed-Ali
Electrical & Computer Engineering Faculty Publications
The nucleation and growth of indium on a vicinal Si (100) - (2×1) surface at high temperature by femtosecond pulsed laser deposition was investigated by in situ reflection high energy electron diffraction (RHEED). RHEED intensity relaxation was observed for the first ∼2 ML during the growth of In (4×3) by step flow. From the temperature dependence of the rate of relaxation, an activation energy of 1.4±0.2 eV of surface diffusion was determined. The results indicate that indium small clusters diffused to terrace step edges with a diffusion frequency constant of (1.0±0.1) × 1011 s-1. The RHEED specular …
Plasma Medicine, Mounir Laroussi, Alexander Fridman
Plasma Medicine, Mounir Laroussi, Alexander Fridman
Electrical & Computer Engineering Faculty Publications
Recent demonstrations of plasma technology in the treatment of living cells, tissues, and organs are creating a newfield at the intersection of plasma science and technology with biology and medicine - Plasma Medicine.
Hypersonic Boundary Layer Receptivity To Acoustic Disturbances Over Cones, Kursat Kara
Hypersonic Boundary Layer Receptivity To Acoustic Disturbances Over Cones, Kursat Kara
Mechanical & Aerospace Engineering Theses & Dissertations
The receptivity mechanisms of hypersonic boundary layers to free stream acoustic disturbances are studied using both linear stability theory (LST) and direct numerical simulations (DNS). A computational code is developed for numerical simulation of steady and unsteady hypersonic flow over cones by combining a fifth-order weighted essentially non-oscillatory (WENO) scheme with third-order total-variation-diminishing (TVD) Runge-Kutta method. Hypersonic boundary layer receptivity to free-stream acoustic disturbances in slow and fast modes over 5-degree, half-angle blunt cones and wedges are numerically investigated. The free-stream Mach number is 6.0, and the unit Reynolds number is 7.8×106/ft. Both the steady and unsteady solutions are obtained …