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Physics

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2015

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Articles 31 - 60 of 100

Full-Text Articles in Physical Sciences and Mathematics

Mathematical Modeling Of Two-Dimensional Unsteady Flow In Growing Tumor, N. Gracia, D. N. Riahi, R. Roy Jun 2015

Mathematical Modeling Of Two-Dimensional Unsteady Flow In Growing Tumor, N. Gracia, D. N. Riahi, R. Roy

Applications and Applied Mathematics: An International Journal (AAM)

We investigate the problem of unsteady fluid flow in growing solid tumors. We develop a mathematical model for a growing tumor whose boundary is taken as a sphere, and the unsteady fluid flow within the tumor is assumed to be two dimensional with respect to the radial distance and the latitudinal angle in spherical coordinates. The expressions for the time, radial and latitudinal variations of the flow velocity, pressure, and the two investigated drug concentrations within the tumor were determined analytically. We calculated these quantities in the tumor as well as in a corresponding normal tissue. We find, in particular, …

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Mathematical Model: Comparative Study Of Thermal Effects Of Laser In Corneal Refractive Surgeries, Gokul Kc, Dil B. Gurung, Pushpa R. Adhikary Jun 2015

Mathematical Model: Comparative Study Of Thermal Effects Of Laser In Corneal Refractive Surgeries, Gokul Kc, Dil B. Gurung, Pushpa R. Adhikary

Applications and Applied Mathematics: An International Journal (AAM)

Lasers have been widely used in ophthalmology. Refractive errors are some of the most common ophthalmic abnormalities worldwide. Laser refractive surgery was developed to correct refractive errors myopia, hyperopia and astigmatism. Two types of laser surgical techniques: lamellar and thermal are available to reshape the corneal curvature. Ultraviolet (UV) emitting argon fluoride (ArF) excimer laser is used to sculpt cornea in lamellar procedures, whereas, infrared (IR) emitting holmium yttrium aluminum garnet (Ho: YAG) laser is used to shrink cornea in thermal procedure. Tissue heating is common in all types of laser surgical techniques. Hence, in this paper, a finite element …

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Unsteady Boundary Layer Flow Of Thermophoretic Mhd Nanofluid Past A Stretching Sheet With Space And Time Dependent Internal Heat Source/Sink, N. Sandeep, C. Sulochana, C. S. K. Raju, M. J. Babu, V. Sugunamma Jun 2015

Unsteady Boundary Layer Flow Of Thermophoretic Mhd Nanofluid Past A Stretching Sheet With Space And Time Dependent Internal Heat Source/Sink, N. Sandeep, C. Sulochana, C. S. K. Raju, M. J. Babu, V. Sugunamma

Applications and Applied Mathematics: An International Journal (AAM)

In this study we analyze the boundary layer flow of a thermophoretic magnetohydrodynamic dissipative nanofluid over an unsteady stretching sheet in a porous medium with space and time dependent internal heat source/sink. The governing equations are transformed to ordinary differential equations by using similarity transformation. Numerical solutions of these equations are obtained by using the Shooting Technique. The effects of non-dimensional governing parameters on the velocity, temperature, concentration profiles, friction factor, Nusselt and Sherwood numbers are discussed and presented through graphs and tables. Accuracy of the results compared with the existing ones. Excellent agreement is found with earlier studies.

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Effects Of Temperature On The Crystal Structure Of Lithium-Lanthanum Zirconate, Mir Iqbal May 2015

Effects Of Temperature On The Crystal Structure Of Lithium-Lanthanum Zirconate, Mir Iqbal

DePaul Discoveries

ABSTRACT Lithium-lanthanum zirconate (LLZ) can potentially be used as a solid electrolyte in lithium-metal batteries. Li-metal batteries offer superior charge capacities and higher energy densi-ties compared to currently used Li-ion batteries. Lithium is highly reactive, which can be dangerous in consumer electronics, but a layer of LLZ electrolyte inserted alongside the Li-metal electrode greatly stabilizes its reactivity. The cubic phase structure of LLZ (Li7La3Zr2O12) has the highest conductivity of its crystalline phases, making it the most promising crystal form of LLZ for this application. Samples of LLZ were doped with different amounts …

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Analysis Of Spin Polarization In Half-Metallic Heusler Alloys, Alexandra Mcnichol Boldin May 2015

Analysis Of Spin Polarization In Half-Metallic Heusler Alloys, Alexandra Mcnichol Boldin

Macalester Journal of Physics and Astronomy

Half-metals have recently gained great interest in the field of spintronics because their 100% spin polarization may make them an ideal current source for spintronic devices. This project examines four Heusler Alloys of the form Co2FexMn1−xSi that are expected to be half-metallic. Two magnetic properties of these alloys were examined, the Anisotropic Magnetoresistance (AMR) and the Anomalous Hall Effect (AHE). These properties have the potential to be used as simple and fast ways to identify materials as half-metallic or non-half-metallic. The results of these measurements were also used to examine the spin …

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Modelling Transient Terahertz Magneto-Spectroscopy Measurements Of P-Type Cvd Graphene Leading To A Negative Photoconductivity., Rhyan Foo Kune May 2015

Modelling Transient Terahertz Magneto-Spectroscopy Measurements Of P-Type Cvd Graphene Leading To A Negative Photoconductivity., Rhyan Foo Kune

Macalester Journal of Physics and Astronomy

Ultrafast Terahertz (THz) Magneto-Spectroscopy (UTMS) measurements were performed on p-type CVD graphene sample to investigate the intrinsic carrier dynamics of the material. We investigated static and time-resolved THz transmission measurements, in which the sample was photo-excited by a near infrared (NIR) pump pulse, in order to study its behavior in a magnetic field. In these measurements the free carriers were probed to independently measure the carrier density and scattering rate in this film. We observed, in our graphene sample, an increase in transmission related to a negative photoconductivity (decrease in conductivity after photoexcitation) consistent with previous research. This decrease is …

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Ultrafast Photoconductivity Measurements Of A Thermoelectric Nanocomposite: Tellurium Nanowire/Pedot:Pss, Brittany A. Ehmann May 2015

Ultrafast Photoconductivity Measurements Of A Thermoelectric Nanocomposite: Tellurium Nanowire/Pedot:Pss, Brittany A. Ehmann

Macalester Journal of Physics and Astronomy

This project explores the conductivity properties of a novel thermoelectric hybrid material (Tellurium nanowires in a conducting polymer PEDOT:PSS) using both static and time-resolved conductivity measurements. We find that the effect of the conducting polymer PEDOT is weak and that the observed differences in conductivity measurements between the hybrid and non-hybrid material are most likely caused by the different sizes of the nanowires.

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Mid-Ir Excitation Of Graphene, Andrew R. Banman, James Heyman May 2015

Mid-Ir Excitation Of Graphene, Andrew R. Banman, James Heyman

Macalester Journal of Physics and Astronomy

In this research we investigate how the conductivity of graphene changes in response to mid-infrared photoexcitation. Our p-type sample was formed through chemical vapor deposition. Pump/probe methodology produced the time-resolved Terahertz transmission, from which the photoconductivity was calculated. We probed the sample with energies above and below the Fermi energy, which was determined by Fourier transform infrared spectroscopy. Our results support a model in which heating of the electron gas, leading to high carrier scattering rates, is responsible for a decrease in conductivity. We observe this negative photoconductivity at all pump energies, allowing us to rule out the possibility of …

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The Role Of Cold Gas In Low-Level Supermassive Black Hole Activity, Erik D. Alfvin May 2015

The Role Of Cold Gas In Low-Level Supermassive Black Hole Activity, Erik D. Alfvin

Macalester Journal of Physics and Astronomy

The nature of the relationship between low-level supermassive black hole activity and galactic cold gas, if any, is currently unclear. It has been hypothesized that feedback may heat or expel gas and quench star formation; alternatively, central black holes may feed at higher rates (either directly or as a secondary effect from stellar winds) in gas-rich galaxies. We use a combination of radio data from the on-going ALFALFA survey and from the literature, along with archival X-ray flux measurements from the Chandra X-ray observatory, to investigate this potential relationship. We construct a sample of 136 late-type galaxies, with MB < −18 out to 50 Mpc, that have both HI masses and sensitive X-ray coverage. Of these, 76 host a nuclear X-ray source, a 56% detection fraction. There is a highly significant correlation between LX and Mstar with a slope of 1.5±0.2, and a tentative correlation (significant at the 2.5σ level) between LX and MHI. However, a joint fit to LX as a function of both Mstar and MHI finds no significant dependence on MHI, and similarly the residuals of LX − LX(Mstar) show no trend with MHI. We conclude that the galaxy-wide cold gas content in these spirals does not strongly influence their low-level supermassive black hole activity.

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Dual Species Magneto-Optical Trap, Daniel Woodbury, Scott Bergeson May 2015

Dual Species Magneto-Optical Trap, Daniel Woodbury, Scott Bergeson

Journal of Undergraduate Research

In the last several decades, laser cooling has become the primary tool for atomic research and, in our lab, has facilitated the study of ultracold plasma. Using a novel laser cooling setup, we created a vacuum chamber and related hardware for a dual species magneto-optical trap (MOT). The design of the MOT will allow us to improve trapping efficiency and atom density in our plasma, better understand laser cooling and trapping of calcium and ytterbium, and probe their interactions in ultracold hetero-nuclear plasma.

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Section Abstracts: Astronomy, Mathematics And Physics With Material Science May 2015

Section Abstracts: Astronomy, Mathematics And Physics With Material Science

Virginia Journal of Science

Abstracts of the Astronomy, Mathematics, and Physics with Material Science Section for the 93rd Annual Meeting of the Virginia Academy of Science, May 21-23, 2015, James Madison University, Richmond, Virginia

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Metal Cnt-M, New Materials And New Approaches To Microfabrication, Richard Vanfleet Apr 2015

Metal Cnt-M, New Materials And New Approaches To Microfabrication, Richard Vanfleet

Journal of Undergraduate Research

This Mentored Environment Grant (MEG) proposed to explore Carbon Nanotube Templated Microfabrication (CNT-M) approaches that used metal as the infiltration material. We proposed to focus on two specific metal systems; traditionally electrodeposited metals such as nickel and high atomic number metals like tungsten which in many cases cannot be electroplated. Our two objectives were:

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The Rise Of Carbon Nanoscience In South Carolina, Apparao M. Rao Apr 2015

The Rise Of Carbon Nanoscience In South Carolina, Apparao M. Rao

Journal of the South Carolina Academy of Science

No abstract provided.

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On The Influence Of Ionic Strength On Radium And Strontium Sorption To Sandy Loam Soils, Brian A. Powell, Todd Miller, Daniel I. Kaplan Apr 2015

On The Influence Of Ionic Strength On Radium And Strontium Sorption To Sandy Loam Soils, Brian A. Powell, Todd Miller, Daniel I. Kaplan

Journal of the South Carolina Academy of Science

Models which can estimate environmental transport of radioactive contaminants in natural and engineered systems are required to 1) deploy effective remediation strategies for contaminated sites, 2) design waste repositories for future waste streams, and 3) ensure protection of human and environmental health in all cases. These models require accurate transport parameters in order to correctly predict how these contaminants will move in the subsurface. This work aimed to determine more accurately the distribution coefficients for radium and strontium sorption to Savannah River Site (SRS) soils. Radium and strontium sorption to the soils was found to be highly dependent upon ionic …

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Towards The Perfect Optical Fiber, John Ballato Apr 2015

Towards The Perfect Optical Fiber, John Ballato

Journal of the South Carolina Academy of Science

Optical fibers are being used in an ever more diverse array of applications today. Many of these modern applications are in high-power and, particularly, high power-per-unit-bandwidth systems where optical nonlinearities historically have not limited overall performance. Today, however, nominally weak effects, such as stimulated Brillouin scattering (SBS), are restricting continued scaling to higher optical powers. To address these limitations, the optical fiber industry has focused on fiber geometry-related solutions such as large mode area (LMA) designs. However, since all linear and nonlinear optical phenomena are fundamentally materials-based in origin, this paper identifies material solutions to present and future performance limitations …

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Magnetic Memory In Exchange Bias Films, Clarke Safsten, Karine Chenel Apr 2015

Magnetic Memory In Exchange Bias Films, Clarke Safsten, Karine Chenel

Journal of Undergraduate Research

My project for which I received an ORCA grant has advanced considerably. I work with Dr. Chesnel studying magnetic thin films. These films consist of layered ferromagnetic and antiferromagnetic materials. In previous experiments, Dr. Chesnel has determined that these types of films exhibit a property called magnetic memory. My project is to determine if the magnetic memory persists, and to what degree, in various circumstances. My project is divided into three primary pieces: experiment, computation, and conclusion.

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Transiting Exo-Planets Indirect Detection Of Planets Orbiting Other Stars, Brian Shaw, Denise Stephens Apr 2015

Transiting Exo-Planets Indirect Detection Of Planets Orbiting Other Stars, Brian Shaw, Denise Stephens

Journal of Undergraduate Research

Introduction Over the past year I have been looking at pictures filled with dots and running them through computers. On the surface that doesn’t seem quite exciting but once one understands what is happening between the pixels, the humdrum atmosphere disappears. Each of those dots represent an actual star in our galaxy. And by analyzing the pixels, I can determine properties of these stars. The Orson Pratt Observatory atop the Eyring Science Center on BYU campus has been collection data of potential transits provided by the KELT-North Project. I have been taking that data and reducing it to the point …

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“Ultra Cold” Room Temperature Plasma, Stephen Rupper, Dr. Scott Bergeson Apr 2015

“Ultra Cold” Room Temperature Plasma, Stephen Rupper, Dr. Scott Bergeson

Journal of Undergraduate Research

Many scientists throughout the world are currently doing research on ultra cold neutral plasmas (UCNP). These plasmas are difficult to make and require quite a sophisticated setup. A method that we employ in our lab requires multiple laser pulses to be timed perfectly and aligned precisely in order to ionize the atoms. It also requires the use of a magneto optical trap, which traps the atoms before they are ionized. This setup is very time consuming to build and maintain but we have a mathematical model for it. Since the current methods of creating ultra cold plasmas are hard to …

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Determining Thin Film Roughness With Euv Reflection, Cody Petrie, Steven Turley Apr 2015

Determining Thin Film Roughness With Euv Reflection, Cody Petrie, Steven Turley

Journal of Undergraduate Research

Introduction: Reflection of extreme ultraviolet (EUV) light is made difficult by a number of factors. First, most materials have a large, imaginary part of the index of refraction for EUV light, causing absorption. As a result, our experiment is done under vacuum. Second, since the wavelength of EUV light (1-100 nm) is smaller than visible light, it is scattered more strongly than visible light. To overcome this obstacle we need to make our reflecting surfaces smoother. To be able to do this we need a good probe for surface roughness on the scale of EUV wavelengths. Currently the best method …

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Wavelength Detection From Filtered Photodiodes, Nils Otterstrom, Dallin Durfee Apr 2015

Wavelength Detection From Filtered Photodiodes, Nils Otterstrom, Dallin Durfee

Journal of Undergraduate Research

Introduction Physics laboratories all over the world depend on accurate wavelength meters to tune their lasers to desired optical frequencies. Our ion interferometry lab, for example, relies heavily on the precision of these instruments to laser cool beams of strontium ions and then split and recombine their wave functions. Unfortunately, some these devices can be extremely expensive and very cumbersome to use. A frequency comb wavelength detector, although remarkably accurate, can cost around $100,000 dollars. In our lab we employ a Michelson-Morley interferometer based wavelength meter, which costs around $8,000 dollars. Despite its relatively high accuracy, the device is extremely …

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Porous Cantilevers As Chemical Sensors, Steven Noyce, Robert Davis Apr 2015

Porous Cantilevers As Chemical Sensors, Steven Noyce, Robert Davis

Journal of Undergraduate Research

Resonant cantilevers, or small vibrating beams, are used to detect small concentrations of chemicals. As molecules or atoms of the substance to be sensed adhere to the vibrating beam, the resonant frequency changes as a result of the change in mass. These sensors are built on the microscale to allow for mass parallelization. An array of cantilevers could each be coated with a different adhesion layer, making each beam sensitive to a unique substance. These sensors have previously been made of solid materials, but because the sensitivity is proportional to the surface area of the resonator, a porous cantilever could …

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Chaotic Scattering In General Relativity, Taylor Hugh Morgan, David Neilsen Apr 2015

Chaotic Scattering In General Relativity, Taylor Hugh Morgan, David Neilsen

Journal of Undergraduate Research

I. Introduction Our research is on the gravitational three-body problem where there are three star-like objects with the only acting force on the objects being gravity. Since the discovery of gravity, many physicists and mathematicians have looked for an analytic solution to the three-body problem including Poincare, Euler, Lagrange, and Jacobi. We now know that there is in fact no analytic solution to this problem. Due to the advent of high performance computing we have discovered much about the chaotic nature1 of this problem and its sensitivity to initial perturbations. For our research we have extended the scope of the …

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Determining Surface Roughness Using Extreme Ultraviolet Light, Joshua Marx, Steve Turley Apr 2015

Determining Surface Roughness Using Extreme Ultraviolet Light, Joshua Marx, Steve Turley

Journal of Undergraduate Research

Extreme ultraviolet (XUV) light is light with wavelengths between one and 60 nanometers. The shorter wavelengths of light in this range are on the same order of magnitude as atomic dimensions. Currently, XUV optics have many uses and even more potential applications in a variety of fields, such as photolithography, plasma diagnostics, and astrophysics.

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The Impact Of Imperfect Information On Network Attack, A. Melchionna, Jesus Caloca, S. Squires, T. Antonsen, E. Ott, M. Girvan Apr 2015

The Impact Of Imperfect Information On Network Attack, A. Melchionna, Jesus Caloca, S. Squires, T. Antonsen, E. Ott, M. Girvan

McNair Scholars Research Journal

This paper explores the effectiveness of network attack when the attacker has imperfect information about the network. For Erdös-Rényi networks, we observe that dynamical importance and betweenness centrality-based attacks are surprisingly robust to the presence of a moderate amount of imperfect information and are more effective compared with simpler degree-based attacks even at moderate levels of network information error. In contrast, for scale-free networks the effectiveness of attack is much less degraded by a moderate level of information error. Furthermore, in the Erdös-Rényi case the effectiveness of network attack is much more degraded by missing links as compared with the …

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Novel Magnetic And Optical Properties Of Sn1-XZnXO2 Nanoparticles, Nevil Franco Apr 2015

Novel Magnetic And Optical Properties Of Sn1-XZnXO2 Nanoparticles, Nevil Franco

McNair Scholars Research Journal

In this work, we report on the effects of doping SnO2 nanoparticles with Zn2+ ions. A series of ~2- 3nm sized Sn1- xZnxO2 crystallite samples with 0 ≤ x ≤ 0.18 were synthesized using a forced hydrolysis method. Increasing dopant concentration caused systematic changes in the crystallite size, oxidation state of Sn, visible emission and band gap of SnO2 nanoparticles. X-ray Diffraction (XRD) studies confirmed the SnO2 phase purity and the absence of any impurity phases. Magnetic measurements at room temperature showed a weak ferromagnetic behavior characterized by an open hysteresis …

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Science In A Nutshell: Studying The Use Of Humor In Science Writing, Meredith Gold, Gus Hart Mar 2015

Science In A Nutshell: Studying The Use Of Humor In Science Writing, Meredith Gold, Gus Hart

Journal of Undergraduate Research

Introduction The purpose of this study was to expand upon a previous and successful unofficial study that I did in high school, testing the effectiveness of humor in instructional science writing. Despite the fact that various extenuating circumstances (including multiple cases of prolonged illness) hindered measurable data collection, the first main question asked by the study was answered: It is even possible to write a physics textbook in the style of humor essays? To this, my project responds with a resounding yes. I wrote and began editing the full first draft of my first humorous physics textbook, coming in at …

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Relating Quantum Dynamics And Entanglement, John Gardiner, Jean-Francois Van Huele Mar 2015

Relating Quantum Dynamics And Entanglement, John Gardiner, Jean-Francois Van Huele

Journal of Undergraduate Research

Introduction Entanglement is a quantum phenomenon that is important to many applications including quantum computing and cryptography. The way that a quantum system changes in time is encoded in a mathematical object called the Hamiltonian of the system. The goal of this project was to better understand the relation between the quantum dynamics of a system, as described by the Hamiltonian, and the entanglements that arise in the system, with the bigger goal of better understanding how entanglement changes in time. To this end I studied computer simulations of simple quantum systems to observe how certain features of the Hamiltonian …

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Pharm: An Environment For Physical Acoustics Research And Mentoring, Kent L. Gee, Tracianne B. Neilsen Mar 2015

Pharm: An Environment For Physical Acoustics Research And Mentoring, Kent L. Gee, Tracianne B. Neilsen

Journal of Undergraduate Research

PHARM (PHysical Acoustics Research and Mentoring) has been operating partially with support from a MEG grant. The primary purpose of this mentoring environment is to provide undergraduates in Physics and Applied Physics opportunities to gain experience in fundamental areas of physical acoustics. It has also included students in Mechanical and Electrical Engineering and Mathematics. Within the acoustics community, “physical acoustics” refers to a number of subfields (e.g., outdoor sound propagation, aeroacoustics, and nonlinear acoustics). A large number of students have been able to participate in projects related to these areas. Many of these projects have been and are being documented …

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Magnetic Order And Fluctuation Dynamics Of Self-Assembled Magnetite Fe3o4 Nanoparticles, Karine Chesnel Mar 2015

Magnetic Order And Fluctuation Dynamics Of Self-Assembled Magnetite Fe3o4 Nanoparticles, Karine Chesnel

Journal of Undergraduate Research

The research plan described in the proposal (section 2.1) was well implemented during the period 2013-2014. Most of the steps listed in the plan were completed thanks to the fund: (1) nanoparticle preparation (2) structural characterization (3) magnetic characterization (4) particle deposition and self-assembling (5) net magnetization of the film measured via XMCD; we are still working on the last steps (6) magnetic order between particles measured via XRMS and (7) dynamical measurements, measured via CXRMS. The fund was especially useful to go and carry out a couple of synchrotron experiments at SSRL, SLAC at Stanford, to complete steps (5-7). …

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Sound Reduction In Protheses For Developing Countries, Ashlie Burton, Lawrence Rees Mar 2015

Sound Reduction In Protheses For Developing Countries, Ashlie Burton, Lawrence Rees

Journal of Undergraduate Research

Introduction 2ft Prosthetics has been making below-the-knee prostheses for developing countries since 2010. While these feet have been helpful, improvements should be made to the design. One of the common complaints about the PVC foot was the amount of noise created during gait. The purpose of this project was to research different sound reduction designs for the PVC prosthesis. Initially two designs were drafted, out of the two, one was built and tested.

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