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Full-Text Articles in Physics

Ucna/Ucna+, Robert Pattie Aug 2019

Ucna/Ucna+, Robert Pattie

Robert W. Pattie Jr.

The neutron provides a simple yet dynamic nuclear system to study the Standard Model of Particle Physics. The process of transforming a neutron into a proton, an electron, and an anti-neutrino contains a wealth of information in the decay rate and the kinematics of the emitted particles. Precision measurements of angular correlations in neutron β-decay can lend insight to the structure of the weak interaction and probe for physics beyond the Standard Model. The UCNA experiment at the Los Alamos Neutron Science Center is the only experiment to use ultracold neutrons to perform such a measurement, determining the β-asymmetry parameter ...


Temperaments And Learning Styles Vs. Academic Performance Of First-Semester Physics Students, Shel Randall Jul 2018

Temperaments And Learning Styles Vs. Academic Performance Of First-Semester Physics Students, Shel Randall

Shel Randall

Purpose: The purpose of this retrospective quantitative correlational study was to determine the relationship of student temperament (as measured by the online Jung Typology Test) and learning styles (as measured by the Felder-Soloman Index of Learning Styles) to academic performance of first-semester physics students while enrolled in a Sierra Community College Physics Department course during the 2014 – 2016 school years
Methodology: This is a retrospective quantitative correlational study of the relationship between student personality information self-reported by survey and student performance as measured by semester grades. The historical survey data consists of results from two online assessments: the JTT (measuring ...


Comparing Experts And Novices In Solving Electrical Circuit Problems With The Help Of Eye-Tracking, David Rosengrant, Colin Thomson, Taha Mzoughi Jul 2017

Comparing Experts And Novices In Solving Electrical Circuit Problems With The Help Of Eye-Tracking, David Rosengrant, Colin Thomson, Taha Mzoughi

David Rosengrant

In order to help introductory physics students understand and learn to solve problems with circuits, we must first understand how they differ from experts. This preliminary study focuses on problem-solving dealing with electrical circuits. We investigate difficulties novices have with circuits and compare their work with those of experts. We incorporate the use of an eye-tracker to investigate any possible differences or similarities on how experts and novices solve electrical circuit problems. Our results show similarities in gaze patterns among all subjects on the components of the circuit. We further found that experts would look back at the circuit while ...


Pre-Service Physics Teachers And Physics Education Research, David Rosengrant Jul 2017

Pre-Service Physics Teachers And Physics Education Research, David Rosengrant

David Rosengrant

Training pre-service teachers requires, among other things, content knowledge, pedagogical skills and pedagogical content knowledge. Teacher preparation programs have little, if any spare time to add more courses/activities to their program. However, I argue in this paper that we, as educators, must enhance the amount of physics education research in our pre-service physics teacher training programs. In this study, I analyze the results of two different types of exposure to physics education research (PER) from two different groups of pre-service physics teachers in our masters of arts and teaching program. The preliminary results show, for example that the PER ...


A Simple Electric Field Probe In A Gauss's Law Laboratory, Daniel O. Ludwigsen, Gregory N. Hassold May 2017

A Simple Electric Field Probe In A Gauss's Law Laboratory, Daniel O. Ludwigsen, Gregory N. Hassold

Gregory Hassold

Early in our calculus-based introductory course, students are introduced to electric fields and sometimes struggle with the abstraction of a vector field. They have less familiarity with the phenomena associated with electric fields, and the connection between phenomena and mathematical formalism is weaker. Our very next topic is Gauss's law.


Vector Acoustic Intensity Around A Tuning Fork, Daniel A. Russell, Justin Junell, Daniel O. Ludwigsen May 2017

Vector Acoustic Intensity Around A Tuning Fork, Daniel A. Russell, Justin Junell, Daniel O. Ludwigsen

Daniel Ludwigsen

The acoustic intensity vector field around a tuning fork is investigated. Theory for a longitudinal quadrupole source predicts a well-defined transition between near-field and far-field, with significant circulation of sound energy in the near-field. Vector components of the time-averaged intensity were measured using a two-microphone intensity probe and found to agree well with predictions from theory. The vector intensity map is interpreted, and shown to provide useful information about the near-field of an acoustic source.


A Simple Electric Field Probe In A Gauss's Law Laboratory, Daniel O. Ludwigsen, Gregory N. Hassold May 2017

A Simple Electric Field Probe In A Gauss's Law Laboratory, Daniel O. Ludwigsen, Gregory N. Hassold

Daniel Ludwigsen

Early in our calculus-based introductory course, students are introduced to electric fields and sometimes struggle with the abstraction of a vector field. They have less familiarity with the phenomena associated with electric fields, and the connection between phenomena and mathematical formalism is weaker. Our very next topic is Gauss's law.


Supersymmetry And The Tunneling Problem In An Asymmetric Double Well, Asim Gangopadhyaya, Prasanta Panigrahi, Uday Sukhatne Dec 2015

Supersymmetry And The Tunneling Problem In An Asymmetric Double Well, Asim Gangopadhyaya, Prasanta Panigrahi, Uday Sukhatne

Asim Gangopadhyaya

The techniques of supersymmetric quantum mechanics are applied to the calculation of the energy difference between the ground state and the first excited state of an asymmetric double well. This splitting, originating from the tunneling effect, is computed via a systematic, rapidly converging perturbation expansion. Perturbative calculations to any order can be easily carried out using a logarithmic perturbation theory. Our approach yield substantially better results than alternative widely used semiclassical analyses.


Identifying Productive Resources In Secondary School Students' Discourse About Energy, Benedikt Walter Harrer Aug 2015

Identifying Productive Resources In Secondary School Students' Discourse About Energy, Benedikt Walter Harrer

Benedikt W. Harrer

A growing program of research in science education acknowledges the beginnings of disciplinary reasoning in students’ ideas and seeks to inform instruction that responds productively to these disciplinary progenitors in the moment to foster their development into sophisticated scientific practice. This dissertation examines secondary school students’ ideas about energy for progenitors of disciplinary knowledge and practice. Previously, researchers argued that students’ ideas about energy were constrained by stable and coherent conceptual structures that conflicted with an assumed unified scientific conception and therefore needed to be replaced. These researchers did not attend to the productive elements in students’ ideas about energy ...


Basic Astronomy Labs, Terry L. Smith, Michael D. Reynolds, Jay S. Huebner Jul 2014

Basic Astronomy Labs, Terry L. Smith, Michael D. Reynolds, Jay S. Huebner

Jay S Huebner

Providing the tools and know-how to apply the principles of astronomy first-hand, these 43 laboratory exercises each contain an introduction that clearly shows budding astronomers why the particular topic of that lab is of interest and relevant to astronomy. About one-third of the exercises are devoted solely to observation, and no mathematics is required beyond simple high school algebra and trigonometry.Organizes exercises into six major topics—sky, optics and spectroscopy, celestial mechanics, solar system, stellar properties, and exploration and other topics—providing clear outlines of what is involved in the exercise, its purpose, and what procedures and apparatus are ...


Introduction To Physics Ii: Laboratory Manual, Robert Coakley May 2014

Introduction To Physics Ii: Laboratory Manual, Robert Coakley

Robert Coakley

No abstract provided.


Measurement Of The Half-Life Of The T=1/2 Mirror Decay Of Ne-19 And Its Implication On Physics Beyond The Standard Model, Leah J. Broussard, Henning O. Back, Mitzi S. Boswell, A. S. Crowell, Peter Dendooven, G. S. Giri, Calvin R. Howell, M. F. Kidd, Klaus Jungmann, Wilbert L. Kruithof, A. Mol, Cornelis J. G. Onderwater, Robert W. Pattie Jr., Praveen D. Shidling, M. Sohani, D. J. Van Der Hoek, A. Rogachevskiy, Emil Traykov, Oscar O. Versolato, Lorenz Willmann, Hans W. Wilschut, Andrew T. Young May 2014

Measurement Of The Half-Life Of The T=1/2 Mirror Decay Of Ne-19 And Its Implication On Physics Beyond The Standard Model, Leah J. Broussard, Henning O. Back, Mitzi S. Boswell, A. S. Crowell, Peter Dendooven, G. S. Giri, Calvin R. Howell, M. F. Kidd, Klaus Jungmann, Wilbert L. Kruithof, A. Mol, Cornelis J. G. Onderwater, Robert W. Pattie Jr., Praveen D. Shidling, M. Sohani, D. J. Van Der Hoek, A. Rogachevskiy, Emil Traykov, Oscar O. Versolato, Lorenz Willmann, Hans W. Wilschut, Andrew T. Young

Robert W. Pattie Jr.

The 1 2 þ → 1 2 þ superallowed mixed mirror decay of 19Ne to 19F is excellently suited for high precision studies of the weak interaction. However, there is some disagreement on the value of the half-life. In a new measurement we have determined this quantity to be T1=2 ¼ 17.2832 #1; 0.0051ðstatÞ #1; 0.0066ðsystÞ s, which differs from the previous world average by 3 standard deviations. The impact of this measurement on limits for physics beyond the standard model such as the presence of tensor currents is discussed.


Titanium Oxide Nanotubes: Synthesis, Properties And Applications For Solar Energy Harvesting, Eugen Panaitescu Dec 2013

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 ...


An Experimental Set-Up For In Situ Hall Measurements Under High-Energy Electron Irradiation For Wide-Bandgap Materials, Cevdet Coşkun, David Look, Gary Farlow, Zhaoqiang Fang Apr 2013

An Experimental Set-Up For In Situ Hall Measurements Under High-Energy Electron Irradiation For Wide-Bandgap Materials, Cevdet Coşkun, David Look, Gary Farlow, Zhaoqiang Fang

Gary C. Farlow

A dc Hall-effect apparatus, based on conventional van der Pauw specimen geometry, has been developed for in situ measurements under van de Graaff electron irradiation (0.7-2.2 MeV). An associated cryostat permits ambient temperatures of 95-300 K. A key element is a flat permanent magnet of field strength 3.55 kG. Initial test measurements have been performed on wide-bandgap semiconductor materials, including an HVPE-grown AlGaN/GaN heterostructure field-effect transistor structure.


Vapor-Phase Growth Of High-Quality Zno Micro- And Nano-Structures, Monica Morales, David Look, Gary Farlow, Bruce Claflin Apr 2013

Vapor-Phase Growth Of High-Quality Zno Micro- And Nano-Structures, Monica Morales, David Look, Gary Farlow, Bruce Claflin

Gary C. Farlow

Micro- and nano-structures of ZnO have been grown on substrates from flowing carrier gases in a tube furnace. We have investigated how variations in the carrier gas composition, gas flow rate and the position of the substrate control the formation and the morphology of the nanostructures. The source material was pure zinc powder evaporated in the temperature range 500ºC to 650ºC in flowing Ar plus oxygen at atmospheric pressure. It was found that precise control of the gas composition, gas flow rate, and growth time was necessary for reliable deposition. It was also found that zinc powder must be washed ...


Radiation Hardness Of Zno At Low Temperatures, Cevdet Coşkun, David Look, Gary Farlow, J. Sizelove Apr 2013

Radiation Hardness Of Zno At Low Temperatures, Cevdet Coşkun, David Look, Gary Farlow, J. Sizelove

Gary C. Farlow

In situ Hall-effect measurements have been carried out on vapour-phase-grown, n-type ZnO irradiated with 1.0 and 1.5 MeV electrons in the [000-1] direction. The electrical properties change very little during irradiation at temperatures as low as 130 K, the lowest temperature presently attainable under 1 MeV, 0.3 muA cm(-2) irradiation. It is concluded that long-term damage in ZnO is limited by defect annihilations that are rapid on the time scale of the experiment (min), even at 130 K.


Deep Centers In Conductive And Semi-Insulating Gan, Z-Q. Fang, Gary Farlow, Bruce Claflin, Look Apr 2013

Deep Centers In Conductive And Semi-Insulating Gan, Z-Q. Fang, Gary Farlow, Bruce Claflin, Look

Gary C. Farlow

Unintentionally doped conductive and carbon doped semi-insulating GaN films have been characterized by deep level transient spectroscopy, thermally stimulated current spectroscopy, and photoluminescence (PL). Based on correlations with dislocation density, point defects created by electron irradiation, and deep PL bands, the major traps in GaN can be tentatively associated with N vacancies, Ga vacancies, and N interstitials.


Defect Studies In Electron-Irradiated Zno And Gan, David Look, F. Tuomisto, Gary Farlow Apr 2013

Defect Studies In Electron-Irradiated Zno And Gan, David Look, F. Tuomisto, Gary Farlow

Gary C. Farlow

We present experimental results obtained with positron annihilation spectroscopy in room-temperature electron-irradiated n-type ZnO and GaN. The cation vacancies act as important compensating centers in 2 MeV electron-irradiated samples, even though their introduction rates are different by 2 orders of magnitude. In addition, negatively charged non-open volume defects that also compensate the n-type conductivity are produced together with the cation vacancies at similar introduction rates. The low introduction rates of compensating defects in ZnO demonstrate the radiation hardness of the material. Isochronal thermal annealings were performed to study the dynamics of the irradiation-induced defects. In 2 MeV electron-irradiated ZnO, all ...


Effects Of Electron Irradiation On Deep Centers In High-Purity Semi-Insulating 6h-Sic, Z-Q. Fang, Bruce Claflin, Look, Gary Farlow Apr 2013

Effects Of Electron Irradiation On Deep Centers In High-Purity Semi-Insulating 6h-Sic, Z-Q. Fang, Bruce Claflin, Look, Gary Farlow

Gary C. Farlow

Many point-defect-related centers have been investigated in electron-irradiated 6H-SiC by deep-level transient spectroscopy (DLTS). Most of them are believed to be related to vacancies. Our DLTS studies on deep centers produced by electron-irradiation (EI) in conductive epi-6H-SiC are in agreement with the literature data. However, for semi-insulating SiC, DLTS cannot be used for trap studies so we have applied thermally stimulated current (TSC) spectroscopy. At least nine TSC traps have been observed in high-purity/semi-insulating (HPSI) 6H-SiC. To understand the nature of these centers, 1-MeV EI and postirradiation annealing at 600 degrees C were applied to the sample. The TSC ...


Electrical And Optical Properties Of Defects And Impurities In Zno, David Look, Cevdet Coşkun, Bruce Claflin, Gary Farlow Apr 2013

Electrical And Optical Properties Of Defects And Impurities In Zno, David Look, Cevdet Coşkun, Bruce Claflin, Gary Farlow

Gary C. Farlow

Advancements in ZnO device applications have fostered much interest in the electrical and optical activities of various defects and impurities in the material. Although it has long been known that Group III dopants, such as Al, make efficient donors, the roles of other impurities, such as H and N, are only recently being elucidated. The same is true of the simplest point defects, such as Zn and O vacancies and interstitials. Theoretical work has been essential in identifying and understanding various defects and impurities. For example, theory has shown that H is always a donor (not amphoteric), that the O ...


Neutron Interferometric Method To Provide Improved Constraints On Non-Newtonian Gravity At The Nanometer Scale, Geoffrey Greene, Vladimir Gudkov Apr 2013

Neutron Interferometric Method To Provide Improved Constraints On Non-Newtonian Gravity At The Nanometer Scale, Geoffrey Greene, Vladimir Gudkov

Geoffrey Greene

In recent years, an energetic experimental program has set quite stringent limits on a possible “non-1/r2” dependence on gravity at short length scales. This effort has been largely driven by the predictions of theories based on compactification of extra spatial dimensions. It is characteristic of many such theories that the strength and length scales of such anomalous gravity are not clearly determined from first principles. As a result, it is productive to extend the current limits the range and strength of such hypothetical interactions. As a heavy, neutral, and (almost) stable particle, the neutron provides an ideal probe for ...


Characterizing Scientific Production And Consumption In Physics, Qian Zhang, Nicola Perra, Bruno Gonçalves, Fabio Ciulla, Alessandro Vespignani Mar 2013

Characterizing Scientific Production And Consumption In Physics, Qian Zhang, Nicola Perra, Bruno Gonçalves, Fabio Ciulla, Alessandro Vespignani

Alessandro Vespignani

We analyze the entire publication database of the American Physical Society generating longitudinal (50 years) citation networks geolocalized at the level of single urban areas. We define the knowledge diffusion proxy, and scientific production ranking algorithms to capture the spatiotemporal dynamics of Physics knowledge worldwide. By using the knowledge diffusion proxy we identify the key cities in the production and consumption of knowledge in Physics as a function of time. The results from the scientific production ranking algorithm allow us to characterize the top cities for scholarly research in Physics. Although we focus on a single dataset concerning a specific ...


A Short Introduction To Numerical Linked-Cluster Expansions, Baoming Tang, Ehsan Khatami, Marcos Rigol Feb 2013

A Short Introduction To Numerical Linked-Cluster Expansions, Baoming Tang, Ehsan Khatami, Marcos Rigol

Ehsan Khatami

We provide a pedagogical introduction to numerical linked-cluster expansions (NLCEs). We sketch the algorithm for generic Hamiltonians that only connect nearest-neighbor sites in a finite cluster with open boundary conditions. We then compare results for a specific model, the Heisenberg model, in each order of the NLCE with the ones for the finite cluster calculated directly by means of full exact diagonalization. We discuss how to reduce the computational cost of the NLCE calculations by taking into account symmetries and topologies of the linked clusters. Finally, we generalize the algorithm to the thermodynamic limit, and discuss several numerical resummation techniques ...


Evidence For Native-Defect Donors In N-Type Zno, David C. Look, Gary C. Farlow, Pakpoom Reunchan, Sukit Limpijumnong, S. B. Zhang, K. Nordlund Oct 2012

Evidence For Native-Defect Donors In N-Type Zno, David C. Look, Gary C. Farlow, Pakpoom Reunchan, Sukit Limpijumnong, S. B. Zhang, K. Nordlund

Gary C. Farlow

Recent theory has found that native defects such as the O vacancy VO and Zn interstitial ZnI have high formation energies in n-type ZnO and, thus, are not important donors, especially in comparison to impurities such as H. In contrast, we use both theory and experiment to show that, under N ambient, the complex ZnI-NO is a stronger candidate than H or any other known impurity for a 30 meV donor commonly found in bulk ZnO grown from the vapor phase. Since the Zn vacancy is also the dominant acceptor in such material, we must conclude that native defects are ...


Introduction And Recovery Of Ga And N Sublattice Defects In Electron-Irradiated Gan, F. Tuomisto, V. Ranki, David C. Look, Gary C. Farlow Oct 2012

Introduction And Recovery Of Ga And N Sublattice Defects In Electron-Irradiated Gan, F. Tuomisto, V. Ranki, David C. Look, Gary C. Farlow

Gary C. Farlow

We have used positron annihilation spectroscopy to study the introduction and recovery of point defects introduced by 0.45 and 2 MeV electron irradiation at room temperature in n-type GaN. Isochronal annealings were performed up to 1220 K. We observe vacancy defects with specific lifetime of τV=190±15 ps that we tentatively identify as N vacancies or related complexes in the neutral charge state in the samples irradiated with 0.45 MeV electrons. The N vacancies are produced at a rate ΣN0.45≃0.25 cm−1. The irradiation with 2 MeV electrons produces negatively charged Ga vacancies and ...


Silicon Crystallite Formation In Ion-Implanted Quartz, U. B. Ramabadran, H. E. Jackson, Gary C. Farlow Oct 2012

Silicon Crystallite Formation In Ion-Implanted Quartz, U. B. Ramabadran, H. E. Jackson, Gary C. Farlow

Gary C. Farlow

Rapid thermally annealed silicon‐implanted x‐cut α‐quartz samples have been examined by Rutherford backscattering and Raman microprobe spectroscopy. The data indicate that the silicon has diffused at 1200 °C to form a buried layer of crystallites of size 1–10 μm. The crystallites are preferentially oriented and under substantial stress.


Effects Of Electron-Irradiation On Electrical Properties Of Algan/Gan Schottky Barrier Diodes, Z-Q. Fang, Gary Farlow, B. Claflin, David Look, D. Green Oct 2012

Effects Of Electron-Irradiation On Electrical Properties Of Algan/Gan Schottky Barrier Diodes, Z-Q. Fang, Gary Farlow, B. Claflin, David Look, D. Green

Gary C. Farlow

Effects of 1 MeV electron-irradiation at room temperature on the electrical properties of AlGaN/GaN heterostructures, including leakage currents, threshold voltages, and electron traps, have been investigated using Schottky barrier diodes (SBDs) fabricated on the AlGaN. The SBDs, before and after the irradiation with a dose of 5×1015 cm−2, were characterized by temperature dependent current-voltage and capacitance-voltage measurements and deep level transient spectroscopy. It is found that the irradiation causes (i) significant increase in leakage currents, dominated by tunneling conduction, at both reverse and low-forward biases; (ii) a clear negative shift in threshold voltage in the pinch-off region ...


Electron Irradiation Induced Deep Centers In Hydrothermally Grown Zno, Z-Q. Fang, B. Claflin, David Look, Gary Farlow Oct 2012

Electron Irradiation Induced Deep Centers In Hydrothermally Grown Zno, Z-Q. Fang, B. Claflin, David Look, Gary Farlow

Gary C. Farlow

An n-type hydrothermally grown ZnO sample becomes semi-insulating (ρ~108 Ω cm) after 1-MeV electron-irradiation. Deep traps produced by the irradiation were studied by thermally stimulated current spectroscopy. The dominant trap in the as-grown sample has an activation energy of 0.24 eV and is possibly related to LiZn acceptors. However, the electron irradiation introduces a new trap with an activation energy of 0.15 eV, and other traps of energy 0.30 and 0.80 eV, respectively. From a comparison of these results with positron annihilation experiments and density functional theory, we conclude that the 0.15-eV trap may ...


Introduction And Recovery Of Point Defects In Electron-Irradiated Zno, F. Tuomisto, K. Saarinen, David C. Look, Gary C. Farlow Oct 2012

Introduction And Recovery Of Point Defects In Electron-Irradiated Zno, F. Tuomisto, K. Saarinen, David C. Look, Gary C. Farlow

Gary C. Farlow

We have used positron annihilation spectroscopy to study the introduction and recovery of point defects in electron-irradiated n -type ZnO. The irradiation ( Eel=2MeV , fluence 6×1017cm-2 ) was performed at room temperature, and isochronal annealings were performed from 300 to 600 K. In addition, monochromatic illumination of the samples during low-temperature positron measurements was used in identification of the defects. We distinguish two kinds of vacancy defects: the Zn and O vacancies, which are either isolated or belong to defect complexes. In addition, we observe negative-ion-type defects, which are attributed to O interstitials or O antisites. The Zn vacancies and ...


On The Nitrogen Vacancy In Gan, David Look, Gary Farlow, P. Drevinsky, D. Bliss, J. Sizelove Oct 2012

On The Nitrogen Vacancy In Gan, David Look, Gary Farlow, P. Drevinsky, D. Bliss, J. Sizelove

Gary C. Farlow

The dominant electrically active defect produced by 0.42 MeV electron irradiation in GaN is a 70 meV donor. Since only N-sublattice displacements can be produced at this energy, and since theory predicts that the N interstitial is a deep acceptor in n-type GaN, we argue that the 70 meV donor is most likely the isolated N vacancy. The background shallow donors, in the 24–26 meV range, actually decrease in concentration, probably due to interactions with mobile N interstitials that are produced by the irradiation. Thus, the recent assignment of a photoluminescence (PL) line as an exciton bound to ...