Physical Sciences and Mathematics Commons^™

A Model For The Hysteresis Observed In Gating Of Lysenin Channels, Eric Krueger, Radwan Al Faouri, Daniel Fologea, Ralph Henry, David Straub, Greg J. Salamo

Physics Faculty Publications and Presentations

The pore-forming toxin lysenin self-inserts to form conductance channels in natural and artificial lipid membranes containing sphingomyelin. The inserted channels exhibit voltage regulation and hysteresis of the macroscopic current during the application of positive periodic voltage stimuli. We explored the bi-stable behavior of lysenin channels and present a theoretical approach for the mechanism of the hysteresis to explain its static and dynamic components. This investigation develops a model to incorporate the role of charge accumulation on the bilayer lipid membrane in influencing the channel conduction state. Our model is supported by experimental results and also provides insight into the temperature …

Evolution Of Magnetism In The Single-Crystal Honeycomb Iridates (Na1−XLiX)2Iro3, Gang Cao, Tongfei Qi, L. Li, Jsaminka Terzic, Vincent Shian Cao, Shujuan Yuan, M. Tovar, Ganpathy Murthy, Ribhu K. Kaul

Physics and Astronomy Faculty Publications

We report the successful synthesis of single crystals of the layered iridate (Na_1−xLi_x)₂IrO₃, 0 ≤ x ≤ 0.9, and a thorough study of its structural, magnetic, thermal, and transport properties. This compound allows a controlled interpolation between Na₂IrO₃ and Li₂IrO₃, while maintaining the quantum magnetism of the honeycomb Ir⁴⁺ planes. The measured phase diagram demonstrates a suppression of the Néel temperature T_N at an intermediate x, indicating that the magnetic orders in Na₂IrO₃ and Li₂IrO_{3 …}

Planar Anchoring Strength And Pitch Measurements In Achiral And Chiral Chromonic Liquid Crystals Using 90-Degree Twist Cells, Christine K. Mcginn , '16, Laura I. Laderman , '15, N. Zimmermann, H.-S. Kitzerow, Peter J. Collings

Physics & Astronomy Faculty Works

Chromonic liquid crystals are formed by molecules that spontaneously assemble into anisotropic structures in water. The ordering unit is therefore a molecular assembly instead of a molecule as in thermotropic liquid crystals. Although it has been known for a long time that certain dyes, drugs, and nucleic acids form chromonic liquid crystals, only recently has enough knowledge been gained on how to control their alignment so that studies of their fundamental liquid crystal properties can be performed. In this article, a simple method for producing planar alignment of the nematic phase in chromonic liquid crystals is described, and this in …

On The Orientation Dependence Of The Casimir Force, Christopher David Markle

All Theses and Dissertations (ETDs)

In the 83 years of its development, Casimir force theory has seen many advances.

However, there still exists a need for more comprehensive approaches, particularly to complex geometries. To this end we have developed an approach to the Casimir force and demonstrated its use in predicting the Casimir force present in many cases such as the case of a single hollow sphere, finite size parallel plates, and anisotropic conductors.

Within the field of Casimir force experimentation, many predicted characteristics have not yet been demonstrated. To that end, we are performing an experiment designed to investigate the orientational dependence of the …

Timing And Spectroscopy Requirements For A Plastic Scintillating Fiber Bundle Time-Of-Flight Neutron Spectrometer, Paul A. Clement

Theses and Dissertations

The design parameters of a Time-of-Flight (TOF) neutron spectrometer composed of BCF-12 plastic scintillating fibers were investigated. A GEANT4 transport model was developed for analyzing the interaction of 2.5 MeV neutrons with a 14 x 14 BCF-12 fiber bundle. The bundle simulation demonstrated that 0.359% of all neutrons incident on the bundle will double scatter. The timing and data collection e efficiencies of a Tektronix DPO7104 series digital oscilloscope were examined to determine the signal processing requirements for future fiber bundle measurements. The minimum detectable neutron energy was computed by taking into account the bundle scintillation e efficiency, light collection …

Table Of Contents, Michele Harmon

Journal of the South Carolina Academy of Science

No abstract provided.

Determining The 7li(N,Gamma) Cross Section Via Coulomb Dissociation Of 8li, R. Izsak, A. Horvath, A. Kiss, Z. Seres, A. Galonsky, C. A. Bertulani, Zs Fueloep, T. Baumann, D. Bazin, K. Ieki, C. Bordeanu, N. Carlin, M. Csanád, F. Deák, Paul A. Deyoung, N. Frank, T. Fukuchi, A. Gade, D. Galaviz, C. R. Hoffman, W. A. Peters, H. Schelin, M. Thoennessen, G. I. Veres

Faculty Publications

The applicability of Coulomb dissociation reactions to determine the cross section for the inverse neutron capture reaction was explored using the reaction Li-8(gamma,n)Li-7. A 69.5 MeV/nucleon Li-8 beam was incident on a Pb target, and the outgoing neutron and Li-7 nucleus were measured in coincidence. The deduced (n,gamma) excitation function is consistent with data for the direct capture reaction Li-7(n,gamma) Li-8 and with low-energy effective field theory calculations.

Ultra-Low Temperature Measurements Of London Penetration Depth In Iron Selenide Telluride Superconductors, Andrei Diaconu

University of New Orleans Theses and Dissertations

The newly discovered iron based superconductors have captivated the attention of the scientific community due to the unusual mechanism behind their superconductivity and their promise as the next generation high temperature superconductors. After a century of superconductor research, the physical mechanism behind high temperature superconductivity is still not understood. These new materials bring renewed hope in elucidating the pairing mechanism responsible with high temperature superconductors and achieving the ultimate goal of the field, room temperature superconductivity. Consequently, a deeper understanding of the intriguing properties of iron based materials is essential.

A great deal about the pairing mechanism of Cooper electron …

Molecular Hydrogen Regulated Star Formation In Cosmological Smoothed Particle Hydrodynamics Simulations, Robert Thompson, Kentaro Nagamine, Jason Jaacks, Jun-Hwan Choi

Physics and Astronomy Faculty Publications

Some observations have shown that star formation (SF) correlates tightly with the presence of molecular hydrogen (H₂); therefore, it is important to investigate its implication on galaxy formation in a cosmological context. In the present work, we implement a sub-grid model (hereafter H₂-SF model) that tracks the H₂ mass fraction within our cosmological smoothed particle hydrodynamics code GADGET-3 by using an equilibrium analytic model of Krumholz et al. This model allows us to regulate the SF in our simulation by the local abundance of H₂ rather than the total cold gas density, which naturally …

Dose Dependent Effects Of Caffeine On Cognitive Performance And Neuronal Activation, Stephan Albrecht, Helen Morris, Michelle Vieyra

Journal of the South Carolina Academy of Science

Many students assume that the more caffeine you drink, the better your cognitive performance. Over-consumption of caffeine has many negative effects, so if there are no dose related cognitive benefits to large amounts of caffeine, then college students should limit their intake. This study looked at whether ingesting a medium dose (200 mg) versus a lower dose (100 mg) of caffeine improved short term memory as measured by Flanker and n-back tests, compared to a control group. In addition, we looked at whether larger doses of caffeine produced a difference in neuronal activation during these tests as measured by functional …

An Improved Fibonacci Inequality, Cameron T. Cooper, Fidele F. Ngwane, Wei-Kai Lai

Journal of the South Carolina Academy of Science

Fibonacci numbers and Fibonacci sequences play a key role in many areas of mathematics and other sciences. Many inequalities satisfied by Fibonacci sequences have been established. In this paper we prove a new Fibonacci inequality using Candido's identity.

Fourier Analysis Of Phase Resetting Curves Of Neural Oscillators, Robert A. Raidt, Sorinel A. Oprisan

Journal of the South Carolina Academy of Science

We investigated the impact of changes in biologically relevant control parameters, such as the shape of an external perturbation or the conductance values of an individual model neuron, on the shape of the phase resetting curve (PRC) of that neuron. For that purpose, PRCs were generated for groups of Morris-Lecar (ML) model neurons with different conductance values but similar firing periods (within 0.005ms) using external rectangular, triangular, or trapezoidal perturbations of varying areas. These PRCs were numerically described and analyzed as a series of coefficient values using a Fourier Discrete Sine Transform (DST). We found that changes in the shape …

Energy Of Electrons In A Nanowire Subject To Spin-Orbit Interaction, Ryan Brennan Fcrh '11, Sheehan Ahmed Fcrh '11, Antonios Balassis, Vassilios Fessatidis

The Fordham Undergraduate Research Journal

The Hamiltonian for a particle subject to spin-orbit interaction is more complicated than that of a free particle, containing terms corresponding to the electric dipole and Thomas precession processes. For a thin quantum wire in the x-y plane, a non-zero electric field perpendicular to the plane of the wire gives rise to yet another process of spin-orbit interaction called the Rashba spin-orbit interaction. The contribution of this Rashba mechanism is dictated by a parameter α which is proportional to the perpendicular electric field. Additionally, a strong potential well within the x-y plane may be associated with an electric field, which …

Automated Annotation Of Functional Imaging Experiments Via Multi-Label Classification, Matthew D. Turner, Chayan Chakrabarti, Thomas B. Jones, Jiawei F. Xu, Peter T. Fox, George F. Luger, Angela Laird, Jessica A. Turner

Department of Physics

Identifying the experimental methods in human neuroimaging papers is important for grouping meaningfully similar experiments for meta-analyses. Currently, this can only be done by human readers. We present the performance of common machine learning (text mining) methods applied to the problem of automatically classifying or labeling this literature. Labeling terms are from the Cognitive Paradigm Ontology (CogPO), the text corpora are abstracts of published functional neuroimaging papers, and the methods use the performance of a human expert as training data. We aim to replicate the expert's annotation of multiple labels per abstract identifying the experimental stimuli, cognitive paradigms, response types, …

Weak Interaction Studies Ith 6He, A. Knecht, Z. T. Alexander, Y. Bagdasarova, T. M. Cope, B. G. Delbridge, X. Fléchard, A. García, R. Hong, E. Liénard, P. Mueller, O. Naviliat-Cuncic, A. S.C. Palmer, R. G.H. Robertson, D. W. Storm, H. E. Swanson, S. Utsuno, F. Wauters, William Williams, C. Wrede, D. W. Zumwalt

Physics: Faculty Publications

The 6He nucleus is an ideal candidate to study the weak interaction. To this end we have built a high-intensity source of 6He delivering ∼1010 atoms/s to experiments. Taking full advantage of that available intensity we have performed a high-precision measurement of the 6He half-life that directly probes the axial part of the nuclear Hamiltonian. Currently, we are preparing a measurement of the beta-neutrino angular correlation in 6He beta decay that will allow to search for new physics beyond the Standard Model in the form of tensor currents. © 2013 AIP Publishing LLC.

Direct Coupling Of Photonic Modes And Surface Plasmon Polaritons Observed In 2-Photon Peem, Robert Campbell Word, Joseph Fitzgerald, Rolf Könenkamp

Physics Faculty Publications and Presentations

We report the direct microscopic observation of optical energy transfer from guided photonic modes in an indium tin oxide (ITO) thin film to surface plasmon polaritons (SPP) at the surfaces of a single crystalline gold platelet. The photonic and SPP modes appear as an interference pattern in the photoelectron emission yield across the surface of the specimen. We explore the momentum match between the photonic and SPP modes in terms of simple waveguide theory and the three-layer slab model for bound SPP modes of thin metal films. We show that because the gold is thin (30- 40 nm), two SPP …

Impact Of Alkaline Doping And Reducing Conditions On Lafeo3, Geoffrey L. Beausoleil Ii

Geoffrey L Beausoleil II

Efficient and reliable materials for gas separation, syngas production, and hybrid nuclear power plants must be capable of reliably operating at a high-temperature range of 700-1000°C and under exposure to highly oxidizing and reducing conditions. Candidate materials for these applications include alkaline metal doped lanthanum ferrite.

In the first study, the impact of A site substitution by different alkaline metals on lanthanum ferrite (LMF, M=Ca, Sr, and Ba) was investigated. The study focused on thermal expansion near the Néel transition temperature and a magneto-elastic contribution to thermal expansion was identified for each sample. Iron oxidation, Fe3+ to Fe4+, was identified …

Physics 2710 – Example Exam Iii, David Peak

Exams

No abstract provided.

Mid-Latiude Rayleigh-Mie-Raman Lidar For Observations From 15 To 120 Km, Vincent B. Wickwar, Leda Sox, Joshua P. Herron, Matthew T. Emerick

Posters

Rayleigh lidar opened a portion of the atmosphere, from 30 to 90 km, to ground-based observations. Rayleigh-scatter observations were made at the Atmospheric Lidar Observatory (ALO) at Utah State University (USU) from 1993–2004 between 45 and 90 km. The lidar consisted of a 0.44-m diameter mirror, a frequency-doubled Nd:YAG laser opera'ng at 532-nm at 30- Hz at either 18- or 24-W, giving power- aperture products (PAPs) of 2.7- or 3.6- Wm2, respec'vely, and one detector channel. An example of what was accomplished with this system is shown as part of Fig. 1. The temperature climatology was based on ~5000 hours …

Rheology Of Solutions Of Polyisophrene And Polyisoprene-Carbon Nanotube Composites, Ruiping Ge

Electronic Thesis and Dissertation Repository

The addition of a small amount of carbon nanotubes to a polymer matrix can result in large changes in its mechanical properties. In this work, we study the rheological behavior of solutions of polyisoprene (PI) in chloroform and suspensions of multi-walled carbon nanotubes (MWCNT) and single-walled carbon nanotubes (SWCNT) in these PI solutions using shear rheometry.

We perform rheological measurements to study the viscoelastic properties of solutions of trans-PI in chloroform for polymer concentrations ranging from 1.0 wt% to 10.0 wt%. Oscillatory strain sweep tests show a concentration-and-frequency independent critical strain of that defines the limit of the linear viscoelastic …

Atomic Data For S Ii—Toward Better Diagnostics Of Chemical Evolution In High-Redshift Galaxies, Romas Kisielius, Varsha P. Kulkarni, Gary J. Ferland, Pavel Bogdanovich, Matt L. Lykins

Physics and Astronomy Faculty Publications

Absorption-line spectroscopy is a powerful tool used to estimate element abundances in both the nearby and distant universe. The accuracy of the abundances thus derived is naturally limited by the accuracy of the atomic data assumed for the spectral lines. We have recently started a project to perform new extensive atomic data calculations used for optical/UV spectral lines in the plasma modeling code Cloudy using state of the art quantal calculations. Here, we demonstrate our approach by focussing on S II, an ion used to estimate metallicities for Milky Way interstellar clouds as well as distant damped Lyman-alpha (DLA) and …

Sensitivity Curves For Searches For Gravitational-Wave Backgrounds, E. H. Thrane, Joseph D. Romano

Physics and Astronomy Faculty Publications and Presentations

We propose a graphical representation of detector sensitivity curves for stochastic gravitational-wave backgrounds that takes into account the increase in sensitivity that comes from integrating over frequency in addition to integrating over time. This method is valid for backgrounds that have a power-law spectrum in the analysis band. We call these graphs “power-law integrated curves.” For simplicity, we consider cross-correlation searches for unpolarized and isotropic stochastic backgrounds using two or more detectors. We apply our method to construct power-law integrated sensitivity curves for second-generation ground-based detectors such as Advanced LIGO, space-based detectors such as LISA and the Big Bang Observer, …

Development And Validation Of An Automated Directivity Acquisition System Used In The Acquisition, Processing, And Presentation Of The Acoustic Far-Field Directivity Of Musical Instruments In An Anechoic Space, Nicholas J. Eyring

Theses and Dissertations

A high spatial resolution acoustic directivity acquisition system (ADAS) has been developed to acquire anechoic measurements of the far field radiation of musical instruments that are either remote controlled or played by musicians. Building upon work performed by the BYU Acoustic Research Group in the characterization of loudspeaker directivity, one can rotate a musical instrument with sequential azimuthal angle increments under a fixed semicircular array of microphones while recording repeated notes or sequences of notes. This results in highly detailed and instructive directivity data presented in the form of high-resolution balloon plots. The directivity data and corresponding balloon plots may …

Can Bohmian Mechanics Be Made Relativistic?, Detlef Dürr, Sheldon Goldstein, Travis Norsen, Ward Struyve, Nino Zaghì

Physics: Faculty Publications

In relativistic space-time, Bohmian theories can be formulated by introducing a privileged foliation of space-time. The introduction of such a foliation – as extra absolute space-time structure – would seem to imply a clear violation of Lorentz invariance, and thus a conflict with fundamental relativity. Here, we consider the possibility that, instead of positing it as extra structure, the required foliation could be covariantly determined by the wave function. We argue that this allows for the formulation of Bohmian theories that seem to qualify as fundamentally Lorentz invariant. We conclude with some discussion of whether or not they might also …

Potential For Measurement Of Mesospheric Ozone Density From Overdense Meteor Trains With A Monostatic Meteor Radar, Reynold E. Sukara

Electronic Thesis and Dissertation Repository

Thermally ablating meteoroids, colliding with the Earth’s atmosphere, leave a high temperature trail containing extremely energetic metallic ions and electrons. A well recognized, but unresolved, anomaly associated with ambipolar diffusion of meteor trains, which is more dominant in overdense meteors, takes place in the initial post-adiabatic train expansion. In this work, a newly proposed mechanism explaining this anomaly involves hyperthermal chemical reactions is presented. Data from the SKiYMET meteor radar system, deployed at latitudinally dispersed locations, were used to determine ozone density in the upper atmosphere by analyzing diffusion of overdense meteor trains. The results obtained in this study are …

Titanium Oxide Nanotubes: Synthesis, Properties And Applications For Solar Energy Harvesting, Eugen Panaitescu

Eugen Panaitescu

Titanium oxide (titania) nanotubes, although relatively recently discovered (less than 15 years ago), have already shown great promise regarding solar energy harvesting applications, exhibiting very good photocatalytic and photovoltaic properties. An alternative anodization route for production of titania nanotubes at the surface of a titanium foil using chloride ions as catalyst instead of the routinely used highly toxic fluorides, is presented in this work. Moreover, the fabrication parameters are extensively studied, thus providing both an insight into the synthesis mechanism and hints towards possible process optimization routes. Although not forming uniformly over the sample surface and lacking long range ordering, …

Structure And Dynamics Of Self-Assembling Colloidal Monolayers In Oscillating Magnetic Fields, Alison E. Patteson (Koser), Nathan C. Keim, Paulo E. Arratia

Physics - All Scholarship

Many fascinating phenomena such as large-scale collective flows, enhanced fluid mixing, and pattern formation have been observed in so-called active fluids, which are composed of particles that can absorb energy and dissipate it into the fluid medium. For active particles immersed in liquids, fluid-mediated viscous stresses can play an important role on the emergence of collective behavior. Here, we experimentally investigate their role in the dynamics of self-assembling magnetically driven colloidal particles which can rapidly form organized hexagonal structures. We find that viscous stresses reduce hexagonal ordering, generate smaller clusters, and significantly decrease the rate of cluster formation, all while …

Optical Spectroscopic Studies Of Two Star Forming Regions, Kristen Leilani Erickson

Dissertations

The ρ Ophiuchi and Serpens molecular clouds are sites of low mass star formation. The goals of this study were to identify young stellar objects (YSOs) and estimate ages and masses in order to infer an initial mass function (IMF), investigate disk evolution, and determine the star-forming history. Optical spectroscopic surveys of an unbiased sample of candidate young stars have been completed. Optical images taken in different photometric bands were used to create color-magnitude diagrams from which sources were selected for spectroscopic observation. In combination with published data, 135 association members in ρ Ophiuchi and 63 association members plus 16 …

Photoacoustic And Nephelometric Spectroscopy Of Aerosol Optical Properties With A Supercontinuum Light Source, Neha Sharma, I. J. Arnold, H. Moosmüller, W. P. Arnott, C. Mazzoleni

Michigan Tech Publications

A novel multi-wavelength photoacousticnephelometer spectrometer (SC-PNS) has been developed for the optical characterization of atmospheric aerosol particles. This instrument integrates a white light supercontinuum laser with photoacoustic and nephelometric spectroscopy to measure aerosol absorption and scattering coefficients at five wavelength bands (centered at 417, 475, 542, 607, and 675 nm). These wavelength bands are selected from the continuous spectrum of the laser (ranging from 400-2200 nm) using a set of optical interference filters. Absorption and scattering measurements on laboratory-generated aerosol samples were performed sequentially at each wavelength band. To test the instrument we measured the wavelength dependence of absorption and …

Capillary Channel Flow Experiments Aboard The International Space Station, Michael Conrath, P. J. Canfield, P. M. Bronowicki, Michael E. Dreyer, Mark M. Weislogel, A. Grah

Mechanical and Materials Engineering Faculty Publications and Presentations

In the near-weightless environment of orbiting spacecraft capillary forces dominate interfacial flow phenomena over unearthly large length scales. In current experiments aboard the International Space Station, partially open channels are being investigated to determine critical flow rate-limiting conditions above which the free surface collapses ingesting bubbles. Without the natural passive phase separating qualities of buoyancy, such ingested bubbles can in turn wreak havoc on the fluid transport systems of spacecraft. The flow channels under investigation represent geometric families of conduits with applications to liquid propellant acquisition, thermal fluids circulation, and water processing for life support. Present and near future experiments …