Physics Commons^™

Staircase Band Gap Si 1-XGeX/Si Photodectectors, Zhiyun Lo, Ruolian Jiang, Youdou Zheng, Lan Zang, Zhizhong Chen, Shunming Zhu, Xuemei Cheng, Xiabing Liu

Physics Faculty Research and Scholarship

We fabricated Si _1-xGe_x/Si photodetectors by using a staircase band gap Si _1-xGe_x/Si structure. These devices exhibit a high optical response with a peak responsive wavelength at 0.96 μm and a responsivity of 27.8 A/W at -5 V bias. Excellent electrical characteristics evidenced by good diode rectification are also demonstrated. The dark current density is 0.1 pA/μm² at V bias, and the breakdown voltage is -27 V. The high response is explained as the result of a staircase band gap by theoretical analysis.

Spontaneous Evolution Of Rydberg Atoms Into An Ultracold Plasma, M. P. Robinson, B. Laburthe Tolra, Michael W. Noel, T. F. Gallagher, P. Pillet

Physics Faculty Research and Scholarship

We have observed the spontaneous evolution of a dense sample of Rydberg atoms into an ultracold plasma, in spite of the fact that each of the atoms may initially be bound by up to 100 cm21. When the atoms are initially bound by 70 cm21, this evolution occurs when most of the atoms are translationally cold, ,1 mK, but a small fraction, 􏰟1%, is at room temperature. Ionizing collisions between hot and cold Rydberg atoms and blackbody photoionization produce an essentially stationary cloud of cold ions, which traps electrons produced later. The trapped electrons rapidly collisionally ionize the remaining cold …

Applications Of The Atomic Force Microscope Within The Fields Of Haematology And Cytogenetics, Margaret O'Reilly-Crowley

Theses

Atomic force microscopy [AFM] has become a rapidly developing interdisciplinary field of research in recent years. The technique, including instrumentation and specimen preparation methods, is now more sophisticated and its application has increased dramatically. The key advantage of AFM is in providing three-dimensional images of samples imaged. Both size and shape of samples imaged can be obtained allowing their subsequent quantification. Red blood cells [RBCs] and chromosomes were imaged in this work. A brief overview of the current status of biomedical AFM, has been presented in the review.

Measurement of mean cell volume [MCV] of immobilised red blood cells with …

Robust Test For Detecting Nonstationarity In Data From Gravitational Wave Detectors, Soumya Mohanty

Physics & Astronomy Faculty Publications

It is difficult to choose detection thresholds for tests of nonstationarity that assume a priori a noise model if the data are statistically uncharacterized to begin with. This is a potentially serious problem when an automated analysis is required, as would be the case for the huge data sets that large interferometric gravitational wave detectors will produce. A solution is proposed in the form of a robust time-frequency test for detecting nonstationarity whose threshold for a specified false alarm rate is almost independent of the statistical nature of the ambient stationary noise. The efficiency of this test in detecting bursts …

Renormalons As Dilation Modes In The Functional Space, A. Babansky, I. Balitsky

Physics Faculty Publications

There are two possible sources of the factorial large-order behavior of a typical perturbative series. First, the number of different Feynman diagrams may be large; second, there may be abnormally large diagrams known as renormalons. It is well known that the large combinatorial number of diagrams is described by instanton-type solutions of the classical equations. We demonstrate that, from the functional-integral viewpoint, the renormalons do not correspond to a particular configuration but manifest themselves as dilatation modes in the functional space.

Experimental Investigation Of Long-Lived "Zeke" Rydberg States In Ultracold Argon, Gambhir Ranjit

Physics Theses & Dissertations

There is considerable interest in the dynamics of ultracold plasmas and ultracold Rydberg gases. Ultracold plasmas are typically formed by photo-excitation of ultracold atoms to an energy region near (both above and below) an ionization threshold. Excitation to bound, highly-excited Rydberg states can lead to formation of a plasma via several processes, including collisions between Rydberg atoms. Three-body recombination in an ultracold plasma can also result in the production of ultracold Rydberg atoms. Understanding the dynamics of ultracold Rydberg gases is therefore important for understanding the dynamics of ultracold plasmas. In this dissertation, we have investigated the formation and survival …

Virtual Compton Scattering In The Nucleon Resonance Region, Luminita Anca Todor

Physics Theses & Dissertations

This thesis is a study of virtual Compton scattering reaction in which a virtual photon is elastically scattered off a proton γv p → γp. The p( e,e′p)γ reaction was measured in the nucleon resonance region for the first time in the experiment E93-050 in Hall A at Thomas Jefferson National Accelerator Facility. To lowest order in ^αQED, this reaction is a coherent superposition of radiation from the incident or scattered electron in elastic ep scattering (Bethe-Heitler) and exclusive production of a photon on the proton, by absorption of a virtual photon …

Prompt Atmospheric Neutrinos And Muons: Nlo Versus Lo Qcd Predictions, Gabriele U. Varieschi

Physics Faculty Works

No abstract provided.

Prompt Atmospheric Neutrinos And Muons: Dependence On The Gluon Distribution Function, Gabriele U. Varieschi

Physics Faculty Works

No abstract provided.

Perturbative Quantum Chromodynamics Predictions For Very High Energy Atmospheric Neutrinos And Muons, Gabriele U. Varieschi

Physics Faculty Works

We compare the leading and next-to-leading order Quantum Chromodynamics predictions for the flux of atmospheric muons and neutrinos from decays of charmed particles. We then compute this flux for different Partonic Distribution Functions (PDF's) and different extrapolations of these at small partonic momentum fraction x. We find that the predicted fluxes vary up to almost two orders of magnitude at the largest energies studied, depending on the chosen extrapolation of the PDF's. We show that the spectral index of the atmospheric leptonic fluxes depends linearly on the slope of the gluon distribution function at very small x. Finally, we analyze …

X-Ray Emission Following Low-Energy Charge Exchange Collisions Of Highly Charged Ions, P. Beiersdorfer, Ronald E. Olson, G. V. Brown, H. Chen, C. L. Harris, P. A. Neill, L. Schweikhard, S. B. Utter, K. Widmann

Physics Faculty Research & Creative Works

K-shell x-ray emission following low-energy charge exchange collisions (≤11 eV/amu) has been measured for ten bare and hydrogenic ions up to U⁹¹⁺. The data resolve capture into angular momentum states with ℓ=1 and provide a stringent test of theory. The assumption of Stark mixing of angular momentum states is inappropriate at such energies. Results from detailed calculations give a better description of the data, but significant discrepancies are noted. The measurements show that the hardness ratio of charge-exchange induced K-shell x-ray emission represents a diagnostic of the dynamics of ion-atom interactions in situations where the energy is below …

Greenhouse Gases And Other Airborne Pollutants From Household Stoves In China: A Database For Emission Factors, J. Zhang, K. R. Smith, Y. Ma, S. Ye, F. Jiang, W. Qi, P. Liu, M. A. K. Khalil, R. A. Rasmussen, S. A. Thorneloe

Physics Faculty Publications and Presentations

Emissions from household stoves, especially those using solid fuels, can contribute significantly to greenhouse gas (GHG) inventories and have adverse health impacts. Few data are available on emissions from the numerous types of cookstoves used in developing countries. We have systematically measured emissions from 56 fuel/stove combinations in India and China, a large fraction of the combinations in use world-wide. A database was generated containing emission factors of direct and indirect GHGs and other airborne pollutants such as CO2, CO, CH4, TNMHC, N2O, SO2, NOx, TSP, etc. In this paper, we report on the 28 fuel/stove combinations tested …

Molecular Interaction Between Nitric Oxide And Ryanodine Receptors Of Skeletal And Cardiac Sarcoplasmic Reticulum, Guy Salama, Elizaveta V. Menshikova, Jonathan J. Abramson

Physics Faculty Publications and Presentations

In striated muscle, the sarcoplasmic reticulum (SR) is the major storage compartment of intracellular Ca2+ that controls cytosolic free Ca2+ (Cai) and developed force by sequestering and releasing Ca2+ during each contraction. Ca2+ release from the SR occurs through high-conductance Ca2+ release channels or ryanodine receptors (RyR), which are regulated by various signaling processes. Over the last 15 years, there has been a growing consensus that critical sulfhydryl sites on RyRs can be oxidized and reduced, respectively, to open and close the release channels. The pharmacological actions of various classes of sulfhydryl reagents have demonstrated the existence of hyperreactive thiols …

The Canonical Thermodynamic Formalism: Chaotic States Of Spin And Gauge Systems, Nerses Ananikian

Turkish Journal of Physics

The three-site antiferromagnetic Ising, $Q$-state Potts $(Q

Noncommutativity In String Theory And Large Extra Dimensions, Farhad Ardalan

Turkish Journal of Physics

Noncommutativity of space coordinates of string theory are reviewed and are related to the large extra dimension solution of the hierarchy problem.

Steady States Of Dynamically Coupled Two-Species Systems, Muntasi̇r Barma, Sri̇ram Ramaswamy

Turkish Journal of Physics

We study the steady states of two stochastic lattice models with two species of particles, where the local mobility of one species depends on the spatial distribution of the other. The eigenvalues of a $2\times 2$ matrix of couplings can develop imaginary parts, and the question arises whether this implies an instability to a macroscopically different steady state. In the first model, where the mobility depends on the local density of the other species, we show that the system undergoes macroscopic phase separation. In the second model, where the mobility depends on the second derivative of the density of the …

Skyrmions From Harmonic Maps, Wojtek Zakrzewski

Turkish Journal of Physics

We describe some relations between solitonic solutions of various models in different dimensions. We present some examples and then concentrate on some of our recent work (performed in collaboration with Ioannidou and Piette) \cite{IPZ} \cite{us2} which shows how some harmonic maps from $S^2$ to $CP^{N-1}$ can be used to find nontrivial spherically symmetric static solutions of the $SU(N)$ Skyrme model in 3 dimensions and to generate some of its low energy field configurations.

The Effect Of Potassium Doping On Resistive Transitions And Transport Critical Current Of Bulk Ybco High-Tc Superconductors, S. Çelebi̇, A. Öztürk, İ. Karaca, U. Kölemen

Turkish Journal of Physics

We report on observations of the effect of potassium in YBCO (123) high temperature superconductors with nominal composition Y\( _{1-0,2x} \) Ba\( _{2-0.2x} \) K\( _{x} \) Cu\( _{3} \) O\( _{y} \). The electrical resistivity measurements show that the critical temperature T$_{c} \) (R=0) shifted slightly to lower temparature due to the K doping process. This process also decreases the transport critical current density and the activation energy for thermally activated flux flow. The magnetic field dependence of \( j_{c} \) was measured at 77 K after zero field cooling (ZFC) when the applied magnetic field is impressed (ZFCV) …

Optical Properties Of Zns Thin Films, M. Y. Nadeem, Waqas Ahmed

Turkish Journal of Physics

Zinc sulfide (ZnS) thin films of different thickness were deposited on Corning 7059 glass substrate at room temperature and high vacuum using resistive heating technique. The film properties investigated include their absorbance / transmittance / reflectance spectra, band gap, refractive index, extinction coefficient, optical conductivity, complex dielectric constant and thickness. The films were found to exhibit high transmittance (60-99\%), low absorbance and low reflectance in the visible / near infrared region up to 1100 nm. However, the absorbance of the films was found to be high in the ultra violet region with peak around 360 nm. The thickness (using quartz …

Characterization Of Phenanthrene Single Crystals, M. Tariq Bhatti, Anwar Manzoor Rana, Mazhar Ali, Gul N. Shahid, M. Saleh

Turkish Journal of Physics

Single crystals of phenanthrene were successfully grown from melt using Bridgeman Crystal Growth System Type 365. The starting material was purified by sublimation and zone refining techniques in specially designed crystal growth tubes. Phenanthrene single crystals grow with the plane of maximum growth corresponding to the ab-crystallographic plane, and cleave readily in this plane. The optical absorption spectra of phenanthrene single crystals and phenanthrene crystals dissolved in benzene, alcohol and acetone solutions were studied in the wavelength range (200 - 400 nm). The optical excitations i.e., \( \pi - \pi^{*} \) transitions, are attributed to the weak and strong optical …

Critical Adsorption On Defects In Ising Magnets And Binary Alloys, Andreas Hanke

Physics & Astronomy Faculty Publications

Long-range correlations in a magnet close to its critical point or in a binary alloy close to a continuous order-disorder transition can substantially enhance the effect of local perturbations. It is demonstrated using a position-space renormalization procedure that quasi-one-dimensional defects which break the symmetry of the order parameter have pronounced effects: They cause long-range critical adsorption profiles and give rise to new universal critical exponents, which are identified and calculated using field-theoretical methods.

Optical Performance Of Grazing Incidence X-Ray / Euv Telescopes For Space Science Applications, Patrick Louis Thompson

Retrospective Theses and Dissertations

The science and technology of X-rays has only been part of human achievement for the past 100 years, while the study of image formation in general has endured for as long as 1000 years. The ability to conceive, design, and fabricate X-ray imagers, moreover, has existed for only the past 70 years, and X-ray astronomical telescopes have been in use for a mere 35 years. Considering that aplanatic, normal incidence telescope designs required more than 400 years to perfect, it is most interesting to note that the development of ‘aplanatic’ grazing incidence telescopes has taken only about 40 years. In …

Welcoming Address: "Mathematical Concepts In Politics", Erdal İnönü

Turkish Journal of Physics

No abstract provided.

Generalized 2d Yang-Mills Theories: Large-N Limit And Phase Structure, Masoud Alimohammadi

Turkish Journal of Physics

After review the 2D Yang--Mills theories (YM$_2$) and its large--$N$ behaviour, the Generalized 2D Yang--Mills theories (gYM$_2$) and their partition functions on a general two--dimensional Riemann surface are discussed.The large--$N$ behaviour of these models is studied in weak regime, and in strong regime, we restrict ourselves to $\phi^4$ gYM$_2$. We show that this model has a third order phase transition, similar to ordinary YM$_2$ theory.

Analysis On The 2-Dim Quantum Poincare Group At Roots Of Unity, Haji Ahmedov

Turkish Journal of Physics

2--Dim quantum Poincar\'e Group $E_q(1,1)$ at roots of unity, its dual $U_q(e(1,1))$ and some of its homogeneous spaces are introduced. Invariant integrals on $E_q(1,1)$ and its invariant discrete subgroup $E(1,1\mid p)$ are constructed. $*$--Representations of the quantum algebra $U_q(e(1,1))$ constructed in the homogeneous space $SO(1,1\mid p)$ are integrated to the pseudo--unitary representations of $E_q(1,1)$ by means of the universal $T$--matrix. $U_q(e(1,1))$ is realized on the quantum plane $E_q^{(1,1)}$ and the eigenfunctions of the complete set of observables are obtained in the angular momentum and momentum basis. The matrix elements of the pseudo--unitary irreducible representations are given in terms of the …

Quark And Lepton Masses From Fundamental Algebra With Exact Color Symmetry, Engi̇n Arik, Meti̇n Arik, Ufuk Kayserilioglu, M. Burcin Unlu

Turkish Journal of Physics

We propose a deformed algebra of creation and annihilation operators relating quark-lepton states. A diagonal mass operator with three parameters together with the three deformation parameters of the algebra gives a reasonable fit to observed quark-lepton masses.

On Fermi - Bose Symmetry In Conformal Field Theory, A. Belavin

Turkish Journal of Physics

The minimal models of CFT possess a few algebraic structures. Besides the Virasoro Algebra which is an explicit symmetry of these models they have also Quantum Group structure and Fermi-Bose duality. We discuss the relationship between these things.

Monopole Equations On R^8: The Energy Integral, Ayşe Hümeyra Bi̇lge, Teki̇n Dereli̇, Şahi̇n Koçak

Turkish Journal of Physics

We discuss the Seiberg-Witten theory in four dimensions and possible generalizations to eight dimensions. We propose an action which is minimized by a set of monopole equations, previously obtained as a generalization of Seiberg-Witten theory to eight manifolds with Spin(7) holonomy.

Kerr Spinning Particle, A. Burinskii

Turkish Journal of Physics

We give a brief review of the problems connected with the model of spinning particle based on the Kerr geometry. We consider peculiarities of the Kerr rotating black hole solution in gravity, supergravity and low energy string theory. A non-trivial supergeneralization of the Kerr-Newman solution to broken N=2 supergravity is considered. \par The problem of source of the Kerr geometry is discussed, and we consider some arguments in favor of the supersymmetric Fermi-ball model for the Kerr source based on the Witten $U(1)\times U(\tilde 1)$ field model for superconducting strings.

Global Results In Space Of Inter-Monomer Interactions For Hp Lattice Model, M. R. Ejtehadi̇, V. Shahrezaei̇, N. Hamedani̇

Turkish Journal of Physics

Using the ground state candidates for Hydrophobic-Polar lattice model on a two dimensional square lattice, we exactly enumerate the native states of proteins with length up to 20 for a wide range of energy parameters. We find the reduced set of contact maps, ground state candidates, perfectly stable sequences and designability of configurations.