Physics Commons^™

What Brown Saw And You Can Too, Philip Pearle, Brian Collett, Kenneth Bart, David Bilderback, Dara Newman, D. Scott Samuels

Biological Sciences Faculty Publications

A discussion of Robert Brown’s original observations of particles ejected by pollen of the plant Clarkia pulchella undergoing what is now called Brownian motion is given. We consider the nature of those particles and how he misinterpreted the Airy disk of the smallest particles to be universal organic building blocks. Relevant qualitative and quantitative investigations with a modern microscope and with a “homemade” single lens microscope similar to Brown’s are presented.

In Silico Modeling Of Ph-Optimum Of Protein-Protein Binding, Rooplekha C. Mitra, Zhe Zhang, Emil Alexov

Publications

Protein-protein association is a pH-dependent process and thus the binding affinity depends on the local pH. In vivo the association occurs in a particular cellular compartment, where the individual monomers are supposed to meet and form a complex. Since the monomers and the complex exist in the same micro environment, it is plausible that they coevolved toward its properties, in particular, toward the characteristic subcellular pH. Here we show that the pH at which the monomers are most stable (pH-optimum) or the pH at which stability is almost pH-independent (pH-flat) of monomers are correlated with the pH-optimum of maximal affinity …

Large Group Delay In A Microwave Metamaterial Analog Of Electromagnetically Induced Transparency, Lei Zhang, Philippe Tassin, Thomas Koschny, Cihan Kurter, Steven M. Anlage, C. M. Soukoulis

Physics Faculty Research & Creative Works

We report on our experimental work concerning a planar metamaterial exhibiting classical electromagnetically induced transparency (EIT). Using a structure with two mirrored split-ring resonators as the dark element and a cut wire as the radiative element, we demonstrate that an EIT-like resonance can be achieved without breaking the symmetry of the structure. The mirror symmetry of the metamaterial's structural element results in a selection rule inhibiting magnetic dipole radiation for the dark element, and the increased quality factor leads to low absorption (<10%) and large group index (of the order of 30).

Direct Observation Of Spin-Polarized Surface States In The Parent Compound Of A Topological Insulator Using Spin- And Angle-Resolved Photoemission Spectroscopy In A Mott-Polarimetry Mode, David Hsieh, Lewis Andrew Wray, Dong Qian, Yuqi Xia, Jan Hugo Dil, Fabian Meier, Luc Patthey, Jurg Osterwalder, Gustav Bihlmayer, Yew San Hor, Robert Joseph Cava, Md Zahid Hasan

Physics Faculty Research & Creative Works

We report high-resolution spin-resolved photoemission spectroscopy (spin-ARPES) measurements on the parent compound Sb of the recently discovered three-dimensional topological insulator Bi_1-xSb_x (Hsieh et al 2008 Nature 452 970, Hsieh et al 2009 Science 323 919). By modulating the incident photon energy, we are able to map both the bulk and the (111) surface band structure, from which we directly demonstrate that the surface bands are spin polarized by the spin-orbit interaction and connect the bulk valence and conduction bands in a topologically non-trivial way. A unique asymmetric Dirac surface state gives rise to a k-splitting of its …

Reaction Dynamics In Double Ionization Of Helium By Electron Impact, Marcelo F. Ciappina, Michael Schulz, Tom Kirchner

Physics Faculty Research & Creative Works

We present theoretical fully differential cross sections (FDCS) for double ionization of helium by 500 eV and 2 keV electron impact. Contributions from various reaction mechanisms to the FDCS were calculated separately and compared to experimental data. Our theoretical methods are based on the first Born approximation. Higher-order effects are incorporated using the Monte Carlo event generator technique. Earlier, we successfully applied this approach to double ionization by ion impact, and in the work reported here it is extended to electron impact. We demonstrate that at 500 eV impact energy, double ionization is dominated by higher-order mechanisms. Even at 2 …

Could Alice Find The Elusive Higgs?, Tyler Williams

Physics

The Higgs boson is the theoretical mechanism for creating the mass of particles.  Although it has never been seen, the CERN Large Hadron Collider (LHC) is the most likely place for it to be created in the laboratory.  The ALICE (A Large Ion Collider Experiment) detector is focused on the study of heavy ion collisions at the LHC and was not designed to find the Higgs boson; however, there is a chance it could be detected there. Although the luminosity (collision rate) for PbPb collisions is much lower than that for pp collisions, PbPb collisions have a higher probability to …

Measurement Of High-Q2 Charged Current Deep Inelastic Scattering Cross Sections With A Longitudinally Polarised Positron Beam At Hera, H. Abramowicz, I. Abt, L. Adamczyk, M. Adamus, R. Aggarwal, S. Antonelli, P. Antonioli, A. Antonov, M. Arneodo, V. Aushev, Y. Aushev, O. Bachynska, A. Bamberger, A. N. Barakbaev, G. Barbagli, G. Bari, F. Barreiro, D. Bartsch, M. Basile, O. Behnke, J. Behr, U. Behrens, L. Bellagamba, A. Bertolin, S. Bhadra, M. Bindi, C. Blohm, V. Bokhonov, T. Bołd, E. G. Boos, K. Borras, Margarita C. K. Mattingly

Faculty Publications

Measurements of the cross sections for charged current deep inelastic scattering in e+p collisions with a longitudinally polarised positron beam are presented. The measurements are based on a data sample with an integrated luminosity of 132 pb-1 collected with the ZEUS detector at HERA at a centre-of-mass energy of 318 GeV. The total cross section is presented at positive and negative values of the longitudinal polarisation of the positron beams. The single-differential cross-sections dσ/dQ2, dσ/dx and dσ/dy are presented for Q2>200 GeV2. The reduced cross-section σ̃ is presented in the kinematic range 200

Scattering Matrix Elements For The Nonadiabatic Collision B (2PJₐ) + H2 (1Σ+G, Ν, Ј) ↔ B (2PJ’ₐ) + H2 (1Σ+G, Ν’, J’), Luke A. Barger

Theses and Dissertations

Scattering matrix elements are calculated for the nonadiabatic inelastic collision B (²P_jₐ) + H₂ (¹Σ⁺_g, ν, ј) ↔ B (²P_j’ₐ) + H₂ (¹Σ⁺_g, ν’, j’). This calculation utilizes the effective potential energy surfaces for this collision generated by Garvin along with a correction to the asymptotic H₂ potential. Wavepackets are propagated on these surfaces using a split-operator propagator. This propagation yields correlation functions between reactant and product Møller states which are used to calculate the scattering …

Coercivity And Exchange Bias Of Mn0.25ti1.1s2 In The Cluster-Glass State, P. M. Shand, T. Rash, M. Streicher, T. E. Kidd, K. R. Boyle, Laura Strauss

Faculty Work

Magnetic measurements have been carried out on the Mn-intercalated transition-metal dichalcogenide Mn_0.25Ti_1+yS₂. The material, which contained a concentration y≈0.1 of excess intercalated Ti, exhibited paramagnetic behavior at high temperatures with an effective moment per Mn ion of µ_eff=6.07 ± 0.23 µ_B, which shows that the system comprises localized Mn²⁺ moments. A Curie-Weiss temperature Θ_CW=-26 ± 1 K indicated that antiferromagnetic interactions were dominant. Deviation from Curie-Weiss behavior below 100 K signaled the formation of antiferromagnetically correlated clusters. Bifurcation of the zero-fieldcooled and field-cooled magnetizations below 20 K …

A System For Measuring Radiation Induced Chemical Products In Atmospheric Gases Using Optical Detection Methods, Tyler Webster Reese

Master's Theses

This research is a part of an effort to characterize the chemical products generated by radiation interacting with atmosphere. One method of detecting ionizing radiation is to monitor the radiation induced products in the atmosphere around the source. This project explored the potential for using Cavity Ringdown Spectroscopy to evaluate the presence of chemical products generated by the air-radiation interaction near an alpha radiation source. In particular, measurements of ozone concentration within a controlled atmosphere chamber as affected by radiation exposure were obtained.

The first portion of this thesis provides brief reviews of ionizing radiation and ozone formation as well …

On A Couple-Stress Fluid Heated From Below In Hydromagnetics, Vivek Kumar, Sudhir Kumar

Applications and Applied Mathematics: An International Journal (AAM)

The combined effect of dust particles, magnetic field and rotation on a couple-stress fluid heated from below is considered. For the case of stationary convection, dust particles are found to have a destabilizing effect on the system, whereas the rotation is found to have stabilizing effect on the system. Couple-stress and magnetic field are found to have both stabilizing and destabilizing effects under certain conditions. The oscillatory modes are introduced due to the presence of magnetic field and rotation in the system. The results are presented through graphs in each case.

Concomitants Of Upper Record Statistics For Bivariate Pseudo–Weibull Distribution, Muhammad Ahsanullah, Saman Shahbaz, Muhammad Qaiser Shahbaz, Muhammad Mohsin

Applications and Applied Mathematics: An International Journal (AAM)

In this paper the Bivariate Pseudo–Weibull distribution has been defined as a compound distribution of two random variables to model the failure rate of component reliability. The distribution of r–th concomitant and joint distribution of r–th and s–th concomitant of record statistics of the resulting distribution have been derived. Single and product moments alongside the correlation coefficient have also been obtained. Recurrence relation for the single moments has also been obtained for the resulting distributions.

Particulate Suspension Blood Flow Through A Stenosed Catheterized Artery, V. P. Srivastava, Rochana Vishnoi, Poonam Sinha

Applications and Applied Mathematics: An International Journal (AAM)

The flow of blood through a narrow catheterized artery with an overlapping stenosis has been investigated. To account for the presence of red cells, blood has been represented by a macroscopic two-phase model (i.e., a suspension of erythrocytes in plasma). The expression for the flow characteristics-the flow rate, the impedance (resistance to flow), the wall shear stress in the stenotic region, the shear stresses at the stenosis two throats and at critical height of the stenosis, has been derived. It is found that the impedance increases with the catheter size, with the hematocrit and also with the stenosis size (height …

Finite Element Analysis In Porous Media For Incompressible Flow Of Contamination From Nuclear Waste, Abbas Al-Bayati, Saad A. Manaa, Ekhlass S. Ahmed

Applications and Applied Mathematics: An International Journal (AAM)

A non-linear parabolic system is used to describe incompressible nuclear waste disposal contamination in porous media, in which both molecular diffusion and dispersion are considered. The Galerkin method is applied for the pressure equation. For the brine, radionuclide and heat, a kind of partial upwind finite element scheme is constructed. Examples are included to demonstrate certain aspects of the theory and illustrate the capabilities of the kind of partial upwind finite element approach.

New To Ols For Monitoring Gamma Camera Uniformity, Brad K. Lofton

Dissertations and Theses (Open Access)

Detector uniformity is a fundamental performance characteristic of all modern gamma camera systems, and ensuring a stable, uniform detector response is critical for maintaining clinical images that are free of artifact. For these reasons, the assessment of detector uniformity is one of the most common activities associated with a successful clinical quality assurance program in gamma camera imaging. The evaluation of this parameter, however, is often unclear because it is highly dependent upon acquisition conditions, reviewer expertise, and the application of somewhat arbitrary limits that do not characterize the spatial location of the non-uniformities. Furthermore, as the goal of any …

Two-Layered Pulsatile Blood Flow In A Stenosed Artery With Body Acceleration And Slip At Wall, Devajyoti Biswas, Uday Shankar Chakraborty

Applications and Applied Mathematics: An International Journal (AAM)

Pulsatile flow of blood through an artery in presence of a mild stenosis has been investigated in this paper assuming the body fluid blood as a two-fluid model with the suspension of all the erythrocytes in the core region as Bingham Plastic and the peripheral region of plasma as a Newtonian fluid. This model has been used to study the influence of body acceleration, non- Newtonian nature of blood and a velocity slip at wall, in blood flow through stenosed arteries. By employing a perturbation analysis, analytic expressions for the velocity profile, Plug-core radius, flow rate, wall shear stress and …

Bound For The Complex Growth Rate In Thermosolutal Convection Coupled With Cross-Diffusions, Hari Mohan Sharma

Applications and Applied Mathematics: An International Journal (AAM)

Thermosolutal convection problem of the Veronis’ type coupled with cross–diffusion is considered in the present paper. A semi -circle theorem that prescribes upper limit for the complex growth rate of oscillatory motions of neutral or growing amplitude in such a manner that it naturally culminates in sufficient conditions precluding the non- existence of such motions is derived. Further, results for thermosolutal convection problems with or without the individual consideration of Dufour and Soret effects follow as a consequence.

The Combined Effect Of Chemical Reaction, Radiation, Mhd On Mixed Convection Heat And Mass Transfer Along A Vertical Moving Surface, Navneet Joshi, Manoj Kumar

Applications and Applied Mathematics: An International Journal (AAM)

This paper discusses the effect of Chemical reaction, Radiation and MHD on laminar mixed convection boundary layer flow and heat and mass transfer on continuously moving vertical surface. The fluid viscosity is assumed to vary as an inverse linear function of temperature and local similarity solutions are obtained for the boundary layer equations subject to isothermally moving vertical surface with uniform speed. The system of non-linear partial differential equations developed in the process is finally transformed into a set of ordinary differential equations with the help of similarity transformations involved in the problem. This set of equations is for different …

Solutions Of Nonlinear Second Order Multi-Point Boundary Value Problems By Homotopy Perturbation Method, S. Das, Sunil Kumar, O. P. Singh

Applications and Applied Mathematics: An International Journal (AAM)

In this paper, we present an algorithm for the numerical solution of the second order multi- point boundary value problem with suitable multi boundary conditions. The algorithm is based on the homotopy perturbation approach and the solutions are calculated in the form of a rapid convergent series. It is observed that the method gives more realistic series solutions that converge very rapidly in physical problems. Illustrative numerical examples are provided to demonstrate the efficiency and simplicity of the proposed method in solving this type of multipoint boundary value problems.

Inner-Shell Photodetachment Of Transition Metal Negative Ions, Ileana Dumitriu

Dissertations

This thesis focuses on the study of inner-shell photodetachment of transition metal negative ions, specifically Fe¯ and Ru¯. Experimental investigations have been performed with the aim of gaining new insights into the physics of negative atomic ions and providing valuable absolute cross section data for astrophysics. The experiments were performed using the X-ray radiation from the Advanced Light Source, Lawrence Berkeley National Laboratory, and the merged-beam technique for photoion spectroscopy.

Negative ions are a special class of atomic systems very different from neutral atoms and positive ions. The fundamental physics of the interaction of transition metal negative ions with photons …

Spatial Light Dilution As A Technique For Conversion Of Solar Energy To Algal Biomass, Daniel J. Dye

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A photobioreactor has been designed and developed to efficiently utilize solar irradiance through spatial dilution of sunlight. The concept of spatial light dilution is simple: incident sunlight is spread over a large surface area, thus reducing the photon flux density of the light. The implementation of this technique, however, is difficult. The reactor described within uses a new approach to spatial light dilution, utilizing recently-developed optical components to diffuse concentrated sunlight inside an algae culture. Preliminary productivity tests indicate a 2-3 fold increase in productivity per unit aperture (sunlight collection area) over a control reactor with direct-sunlight. Aperture productivity of …

Statistical Analysis Of The Usu Lidar Data Set With Reference To Mesospheric Solar Response And Cooling Rate Calculation, With Analysis Of Statistical Issues Affecting The Regression Coefficients, Troy Alden Wynn

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Though the least squares technique has many advantages, its possible limitations as applied in the atmospheric sciences have not yet been fully explored in the literature. The assumption that the atmosphere responds either in phase or out of phase to the solar input is ubiquitous. However, our analysis found this assumption to be incorrect. If not properly addressed, the possible consequences are bias in the linear trend coefficient and attenuation of the solar response coefficient.

Using USU Rayleigh lidar temperature data, we found a significant phase offset to the solar input in the temperatures that varies ±5 years depending on …

Comparison Of H-Alpha And H-Beta Temperature Indices In The Hyades And Coma Star Clusters And Selected H-Beta Standard Stars, Miriam Anne West

Theses and Dissertations

Using the Dominion Astrophysical Observatory's 1.2-m McKellar Telescope, we have obtained spectra on 81 stars from the Hyades Cluster, the Coma Cluster, and selected H-beta standard stars. These spectra cover from 4500 Å to 6900 Å which includes both the H-β and H-α absorption lines. The H-β absorption line has a long history of being used as a temperature index and more recently, calibration of an H-α index has been established for photometric observations. Through spectrophotometric comparison of temperature indices from the H-α and H-β absorption lines we find the expected strong correlation between photometric indices based on the strength …

Measurement System For High Pressure Characterizations Of Materials, Matthew K. Jacobsen

UNLV Theses, Dissertations, Professional Papers, and Capstones

Thermoelectric materials have long been investigated for possible use as power sources. This application was recently put to use in the Voyager space program, powering the deep space probes. Despite the usefulness of these materials, the use of pressure to investigate the material properties has only recently become interesting. As such, the work in this document was to developing a system for concurrently measuring the necessary properties. This system is capable of measuring the electrical resistivity, thermal conductivity, and Seebeck coefficient in the pressure range from 0 - 10 GPa. The results for zinc, almandine garnet, and nickel are presented …

Speciation And Spectroscopy Of The Uranyl And Tetravalent Plutonium Nitrate Systems: Fundamental Studies And Applications To Used Fuel Reprocessing, Nicholas A. Smith

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation explores the use of UV-Visible spectroscopy and Time Resolved Laser Induced Fluorescence spectroscopy as near real time process monitors of uranium and plutonium concentrations in aqueous reprocessing trains. The molar absorptivities and linear ranges of these metals were investigated under total nitrate and acid concentrations similar to those found in current reprocessing systems. Concurrent to this, a new multiple wavelength monitor was derived that is capable of determining the total nitrate concentration spectroscopically. This method uses the uranium absorbance spectrum to calculate the nitrate concentration in solution. When used as part of an Advanced Safeguard suite, this technique …

Chemical And Electronic Structure Of Surfaces And Interfaces In Compound Semiconductors, Sujitra Pookpanratana

UNLV Theses, Dissertations, Professional Papers, and Capstones

The interface formation between two different materials is important in applications for optoelectronic devices. Often, the success or performance of these devices is dependent on the formation of these heterojunctions. In this work, the surface and interfaces in such materials for optoelectronic devices are investigated by a suite of X-ray analytical techniques including X-ray photoelectron (XPS), X-ray excited Auger electron (XAES), and X-ray emission (XES) spectroscopies to provide novel insight.

For the group III-nitrides (e.g., AlxGa1-xN) used in many light emitting devices, a significant challenge exists to form an Ohmic contact. The electron affinities and band gaps of GaN and …

Momentum-Space Engineering Of Gaseous Bose-Einstein Condensates, Mark Edwards, Brandon Benton, Jeffrey Heward, Charles W. Clark

Physics & Astronomy: Faculty Publications

We show how the momentum distribution of gaseous Bose-Einstein condensates can be shaped by applying a sequence of standing-wave laser pulses. We present a theory, whose validity was demonstrated in an earlier experiment [L. Denget al., Phys. Rev. Lett. 83, 5407 (1999)], of the effect of a two-pulse sequence on the condensate wavefunction in momentum space. We generalize the previous result to the case of N pulses of arbitrary intensity separated by arbitrary intervals and show how these parameters can be engineered to produce a desired final momentum distribution. We find that several momentum distributions, important in …

Apertureless Near-Field/Far-Field Cw Two-Photon Microscope For Biological And Material Imaging And Spectroscopic Applications, Derek Brant Nowak, Andrew James Lawrence, Erik J. Sánchez

Physics Faculty Publications and Presentations

We present the development of a versatile spectroscopic imaging tool to allow for imaging with single-molecule sensitivity and high spatial resolution. The microscope allows for near-field and subdiffraction-limited far-field imaging by integrating a shear-force microscope on top of a custom inverted microscope design. The instrument has the ability to image in ambient conditions with optical resolutions on the order of tens of nanometers in the near field. A single low-cost computer controls the microscope with a field programmable gate array data acquisition card. High spatial resolution imaging is achieved with an inexpensive CW multiphoton excitation source, using an apertureless probe …

Liquid Helium Refill Shifts At The Cryogenic Underground Observatory For Rare Events, Robin L. Reil

Physics

No abstract provided.

Proton Capture Reactions And Network Calculations On 46Ti, 64Zn, 114Sn And 116Sn Relevant To The Rp-Process, Ravin S. T. Kodikara

Dissertations

The rp-process makes an important contribution to the stellar nucleosynthesis by producing many of the light proton rich nuclei. Successive proton captures on seed nuclei followed by occasional β-decays and electron captures are the key features of this mechanism. For a detailed rp-process analysis, proton capture cross sections and reaction rates are essential. However, the lack of experimental data forces the researcher to largely depend on statistical model predictions.

This dissertation research is an attempt to investigate the proton captures of four particular nuclides; ⁴⁶Ti, ⁶⁴Zn, ¹¹⁴Sn and ¹¹⁶Sn. At Western Michigan University Van de Graaff …