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Articles 1 - 9 of 9
Full-Text Articles in Physics
Isostructural Metal-Insulator Transition In Vo2, J. W. Spinuzzi, D. A. Tenne
Isostructural Metal-Insulator Transition In Vo2, J. W. Spinuzzi, D. A. Tenne
Physics Faculty Publications and Presentations
The metal-insulator transition in correlated materials is usually coupled to a symmetry-lowering structural phase transition. This coupling not only complicates the understanding of the basic mechanism of this phenomenon but also limits the speed and endurance of prospective electronic devices. Here, we design and demonstrate an isostructural, purely electronically-driven metal-insulator transition in epitaxial heterostructures of an archetypal correlated material vanadium dioxide. A combination of thin-film synthesis, structural and electrical characterizations, and theoretical modeling reveals that an interface interaction suppresses the electronic correlations without changing the crystal structure in this otherwise correlated insulator. It stabilizes a non-equilibrium metallic phase, and leads …
Tip-Enhanced Stimulated Raman Scattering With Ultra-High-Aspect-Ratio Tips And Confocal Polarization Raman Spectroscopy For Evaluation Of Sidewalls In Type Ii Superlattices Fpas, D. A. Tenne
Physics Faculty Publications and Presentations
Actoprobe team had developed custom Tip Enhancement Raman Spectroscopy System (TERS) with specially developed Ultra High Aspect Ratio probes for AFM and TERS measurements for small pixel infrared FPA sidewall characterization. Using this system, we report on stimulated Raman scattering observed in a standard tip-enhanced Raman spectroscopy (TERS) experiment on GaSb materials excited by 637-nm pump laser light. We explain our results by TERS-inherent mechanisms of enormous local field enhancement and by the special design and geometry of the ultra- high-aspect-ratio tips that enabled conditions for stimulated Raman scattering in the sample with greatly enhanced resonance Raman gain when aided …
A Timelapse Camera Dataset And Markov Model Of Dust Devil Activity At Eldorado Playa, Nevada, Usa, Ralph D. Lorenz, Brian K. Jackson, Peter D. Lanagan
A Timelapse Camera Dataset And Markov Model Of Dust Devil Activity At Eldorado Playa, Nevada, Usa, Ralph D. Lorenz, Brian K. Jackson, Peter D. Lanagan
Physics Faculty Publications and Presentations
We report a May-June 2015 survey of dust devil activity on a Nevada desert playa using an inexpensive digital timelapse camera. We discuss techniques for exploiting the large volume of data (∼32,700 images, made publicly-available) generated in these observations, similar to imaging from Mars landers and rovers, noting the diurnal image filesize variations as a useful quick-look metric of weather conditions. We present results from a semi-automated image classification: this classification is available to other workers, for example for benchmarking automated procedures. The acquisition of images at 1/min for some 36 days permits study of the diurnal variation of dust …
Insights Into The Voltage Regulation Mechanism Of The Pore-Forming Toxin Lysenin, Sheenah Lynn Bryant, Tyler Clark, Christopher Alex Thomas, Kaitlyn Summer Ware, Andrew Bogard, Colleen Calzacorta, Daniel Prather, Daniel Fologea
Insights Into The Voltage Regulation Mechanism Of The Pore-Forming Toxin Lysenin, Sheenah Lynn Bryant, Tyler Clark, Christopher Alex Thomas, Kaitlyn Summer Ware, Andrew Bogard, Colleen Calzacorta, Daniel Prather, Daniel Fologea
Physics Faculty Publications and Presentations
Lysenin, a pore forming toxin (PFT) extracted from Eisenia fetida, inserts voltage-regulated channels into artificial lipid membranes containing sphingomyelin. The voltage-induced gating leads to a strong static hysteresis in conductance, which endows lysenin with molecular memory capabilities. To explain this history-dependent behavior, we hypothesized a gating mechanism that implies the movement of a voltage domain sensor from an aqueous environment into the hydrophobic core of the membrane under the influence of an external electric field. In this work, we employed electrophysiology approaches to investigate the effects of ionic screening elicited by metal cations on the voltage-induced gating and hysteresis …
Experimental And Sensitivity Analysis Of Dmasp Cantilever Vibration Behavior Based On Mcs Theory In The Moist Environment, M. H. Korayem, Byung I. Kim, A. H. Korayem
Experimental And Sensitivity Analysis Of Dmasp Cantilever Vibration Behavior Based On Mcs Theory In The Moist Environment, M. H. Korayem, Byung I. Kim, A. H. Korayem
Physics Faculty Publications and Presentations
A Micro-cantilever (MC) and a probe are two main components of the atomic force microscope (AFM). The dimensions of these components are in micro scales while their oscillation amplitude is on a nanometer scale. The present study intended to not only increase the accuracy of the simulation with regard to geometric discontinuities based on the Timoshenko Beam Model using the modified couple stress (MCS) theory but also increase the accuracy of the prediction of a system behavior by considering the effect hysteresis effect into the system vibration equations based on Bouc-Wen Model. Due to the lack of the experimental results …
Spherical Radiative Transfer In C++ (Srtc++): A Parallel Monte-Carlo Radiative Transfer Model For Titan, Brian K. Jackson
Spherical Radiative Transfer In C++ (Srtc++): A Parallel Monte-Carlo Radiative Transfer Model For Titan, Brian K. Jackson
Physics Faculty Publications and Presentations
We present a new computer program, SRTC++, to solve spatial problems associated with explorations of Saturn’s moon Titan. The program implements a three-dimensional structure well-suited to addressing shortcomings arising from plane-parallel radiative transfer approaches. SRTC++’s design uses parallel processing in an object-oriented, compiled computer language (C++) leading to a flexible and fast architecture. We validate SRTC++ using analytical results, semianalytical radiative transfer expressions, and an existing Titan plane-parallel model. SRTC++ complements existing approaches, addressing spatial problems like near-limb and near-terminator geometries, non-Lambertian surface phase functions (including specular reflections), and surface albedo nonuniformity.
Quantum Dot Growth On (111) And (110) Surfaces Using Tensile-Strained Self-Assembly, Paul J. Simmonds
Quantum Dot Growth On (111) And (110) Surfaces Using Tensile-Strained Self-Assembly, Paul J. Simmonds
Physics Faculty Publications and Presentations
The self-assembly of epitaxial quantum dots on (001) surfaces, driven by compressive strain, is a widely used tool in semiconductor optoelectronics. In contrast, the growth of quantum dots on (111) and (110) surfaces has historically been a significant challenge. In most cases the strain relaxes rapidly via dislocation nucleation and glide before quantum dots can form. In this paper, we discuss a method for the reliable and controllable self-assembly of quantum dots on both (111) and (110) surfaces, where tensile strain is now the driving force. By showing that tensile-strained self-assembly is applicable to several material systems, we demonstrate the …
Using An Instrumented Drone To Probe Dust Devils On Oregon’S Alvord Desert, Brian Jackson, Ralph Lorenz, Karan Davis, Brock Lipple
Using An Instrumented Drone To Probe Dust Devils On Oregon’S Alvord Desert, Brian Jackson, Ralph Lorenz, Karan Davis, Brock Lipple
Physics Faculty Publications and Presentations
Dust devils are low-pressure, small (many to tens of meters) convective vortices powered by surface heating and rendered visible by lofted dust. Dust devils occur ubiquitously on Mars, where they may dominate the supply of atmospheric dust, and since dust contributes significantly to Mars’ atmospheric heat budget, dust devils probably play an important role in its climate. The dust-lifting capacity of a devil likely depends sensitively on its structure, particularly the wind and pressure profiles, but the exact dependencies are poorly constrained. Thus, the exact contribution to Mars’ atmosphere remains unresolved. Analog studies of terrestrial devils have provided some insights …
A Framework For Relating The Structures And Recovery Statistics In Pressure Time-Series Surveys For Dust Devils, Brian Jackson, Ralph Lorenz, Karan Davis
A Framework For Relating The Structures And Recovery Statistics In Pressure Time-Series Surveys For Dust Devils, Brian Jackson, Ralph Lorenz, Karan Davis
Physics Faculty Publications and Presentations
Dust devils are likely the dominant source of dust for the martian atmosphere, but the amount and frequency of dust-lifting depend on the statistical distribution of dust devil parameters. Dust devils exhibit pressure perturbations and, if they pass near a barometric sensor, they may register as a discernible dip in a pressure time-series. Leveraging this fact, several surveys using barometric sensors on landed spacecraft have revealed dust devil structures and occurrence rates. However powerful they are, though, such surveys suffer from non-trivial biases that skew the inferred dust devil properties. For example, such surveys are most sensitive to dust devils …