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Full-Text Articles in Physics

Confined Fluid Analyzed With Near-Field Acoustic Detection, Rodolfo Fernandez Rodriguez, Theodore Brockman, J. Bai, Andres H. La Rosa Dec 2018

Confined Fluid Analyzed With Near-Field Acoustic Detection, Rodolfo Fernandez Rodriguez, Theodore Brockman, J. Bai, Andres H. La Rosa

Physics Faculty Publications and Presentations

Measurement of the damping and elastic interactions between two solids interfaces (one being the apex of a tapered probe that is attached to one tine of a quartz tuning fork while the other is a flat substrate) under relative lateral oscillatory motion are reported. The solid boundaries are separated by a nanometer sized gap, and emphasis is placed on the role played by the mesoscopic fluid trapped in between. The measurements were implemented using two new acoustic techniques that have been integrated into a tuning fork based scanning probe microscope; the whole metrology system offers sub-nanometer precision for controlling the ...


Combining Atomic Force Microscopy And Shear-Force Acoustic Near-Field Microscopy To Characterize Confined Mesoscopic Fluids, Monte Allen Kozell, Theodore Brockman, Andres H. La Rosa Dec 2018

Combining Atomic Force Microscopy And Shear-Force Acoustic Near-Field Microscopy To Characterize Confined Mesoscopic Fluids, Monte Allen Kozell, Theodore Brockman, Andres H. La Rosa

Physics Faculty Publications and Presentations

An atomic force microscopy (AFM) cantilever is integrated into to a quartz tuning fork (QTF) to probe the viscoelastic properties of mesoscopic fluid layers confined between two solid surfaces under shear. Two procedures to fabricate the AFM/QTF probe are described herein. In the first, a nano-manipulator is used to transport a commercially available afm cantilever from its chip holder to the edge of a QTF tine. In the second, an afm cantilever is fabricated at the edge of the QTF tine itself. In both cases we exploit the capabilities of a dual-beam system (focused ion beam/scanning electron microscope ...


Finite Element Method Analysis Of Whispering Gallery Acoustic Sensing, T. Le, H. Tran, Rodolfo Fernandez Rodriguez, C.J. Solano Salinas, Nima Laal, R. Bringas, J. Quispe, F. Segundo, Andres H. La Rosa Dec 2018

Finite Element Method Analysis Of Whispering Gallery Acoustic Sensing, T. Le, H. Tran, Rodolfo Fernandez Rodriguez, C.J. Solano Salinas, Nima Laal, R. Bringas, J. Quispe, F. Segundo, Andres H. La Rosa

Physics Faculty Publications and Presentations

Whispering Gallery Acoustic Sensing (WGAS) has recently been introduced as a sensing feedback mechanism to control the probe-sample separation distance in scanning probe microscopy that uses a quartz tuning fork as a sensor (QTF-SPM). WGAS exploits the SPM supporting frame as a resonant acoustic cavity to monitor the nanometer-sized amplitude of the QTF oscillations. Optimal WGAS sensitivity depends on attaining an exact match between the cavity's frequency peak response and the TF resonance frequency. However, two aspects play against this objective: i) the unpredictable variability of the TF resonance frequency (upon attaching a SPM-probe to one of its tines ...


High-Performance Self-Powered Uv Detector Based On Sno2-Tio2 Nanomace Arrays, Duo Chen, Lin Wei, Lingpan Meng, Yanxue Chen, Yufeng Tian, Shishen Yan, Liangmo Mei, Jun Jiao Dec 2018

High-Performance Self-Powered Uv Detector Based On Sno2-Tio2 Nanomace Arrays, Duo Chen, Lin Wei, Lingpan Meng, Yanxue Chen, Yufeng Tian, Shishen Yan, Liangmo Mei, Jun Jiao

Physics Faculty Publications and Presentations

Photoelectrochemical cell-typed self-powered UV detectors have attracted intensive research interest due to their low cost, simple fabrication process, and fast response. In this paper, SnO2-TiO2 nanomace arrays composed of SnO2 nanotube trunk and TiO2 nanobranches were prepared using soft chemical methods, and an environment-friendly self-powered UV photodetector using this nanostructure as the photoanode was assembled. Due to the synergistic effect of greatly accelerated electron-hole separation, enhanced surface area, and reduced charge recombination provided by SnO2-TiO2 nanomace array, the nanostructured detector displays an excellent performance over that based on bare SnO2 arrays. The impact of the growing time of TiO2 branches ...


Instrumentation-Level Improvements In Shear-Force Near-Field Acoustic Microscopy, J. Bai, P. Devulapalli, Theodore Brockman, Andres H. La Rosa Dec 2018

Instrumentation-Level Improvements In Shear-Force Near-Field Acoustic Microscopy, J. Bai, P. Devulapalli, Theodore Brockman, Andres H. La Rosa

Physics Faculty Publications and Presentations

The recently introduced Shear-force Near-field Acoustic Microscopy (SANM) brings a new sensing mechanism to the scanning probe microscopy family. SANM's ability to simultaneously monitor, in real time, several physical sample's responses presents some challenges for ensuring optimal operation; namely, avoid "cross-talk" among the multiple signals, address the compensation of thermal drift to ensure reproducibility of the measurements, and measuring the typical low-level signals obtained from nanometer-sized tested regions. Here, several improvements relevant to SANM, but valid for SPM in general, are addressed. i) The probe's coarse approach is performed via stepper motors, which are controlled either by ...


Probe Damage Evaluation In Frequency-Modulation Shear-Force Acoustic Near-Field Microscopy, Theodore Brockman, Rodolfo Fernandez Rodriguez, J. Bai, Monte Allen Kozell, Andres H. La Rosa Dec 2018

Probe Damage Evaluation In Frequency-Modulation Shear-Force Acoustic Near-Field Microscopy, Theodore Brockman, Rodolfo Fernandez Rodriguez, J. Bai, Monte Allen Kozell, Andres H. La Rosa

Physics Faculty Publications and Presentations

Shear-force acoustic near-field microscopy (SANM) and Whispering Gallery Acoustic Sensing have recently been introduced as a tandem system to characterize the viscoelastic response of fluids confined between two solid-boundaries in relative oscillatory lateral motion. SANM uses a) a laterally oscillating tapered probe (attached to a quartz tuning fork QTF) as one of the trapping boundaries, and b) an acoustic sensor (attached to the other flat-substrate boundary) that independently monitors the fluid’s acoustic emission. On the other and, WGAS is another technique that uses an acoustic transducer (attached to the frame holding the probe) to monitor the probe’s lateral ...


Isostructural Metal-Insulator Transition In Vo2, J. W. Spinuzzi, D. A. Tenne Nov 2018

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 Sep 2018

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 ...


Supercanonical Probability Distributions, John D. Ramshaw Aug 2018

Supercanonical Probability Distributions, John D. Ramshaw

Physics Faculty Publications and Presentations

The canonical probability distribution describes a system in thermal equilibrium with an infinite heat bath. When the bath is finite the distribution is modified. These modifications can be derived by truncating a Taylor-series expansion of the entropy of the heat bath, but their form depends on the expansion parameter chosen. We consider two such expansions, which yield supercanonical (i.e., higher-order canonical) distributions of exponential and power-law form. The latter is identical in form to the "Tsallis distribution," which is therefore a valid asymptotic approximation for an arbitrary finite heat bath, but bears no intrinsic relation to Tsallis entropy.


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 Aug 2018

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 in ...


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 Jul 2018

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 ...


Steady States And Transport Processes In Urban Ozone Balances, M. A. K. Khalil Jul 2018

Steady States And Transport Processes In Urban Ozone Balances, M. A. K. Khalil

Physics Faculty Publications and Presentations

Core chemical theory is combined with transport processes and local emissions to study the validity of commonly made assumptions regarding steady states to interpret urban and regional ozone data. It is shown that photo-stationary states of NO and NO2 cannot exist in urban areas or polluted regions in addition to the lack of such a state for ozone. Calculations in published papers, which make the assumption of a photo-stationary state for NO and NO2, or ozone, are likely to be inaccurate by unacceptable amounts. The Leighton Ratio is re-interpreted to show how it incorporates both the peroxy radical and transport ...


Enhanced Terahertz Emission From Quantum Dot By Graphene-Coated Nanoparticle, Edin Sijercic, P. T. Leung Jul 2018

Enhanced Terahertz Emission From Quantum Dot By Graphene-Coated Nanoparticle, Edin Sijercic, P. T. Leung

Physics Faculty Publications and Presentations

The terahertz (THz) emission from quantum dots in close proximity to graphene-coated nanoparticles is studied via phenomenological modeling with particular interest in the possibility of enhancement for such emission via the excitation of the graphene plasmons. It is shown that depending on various factors such as the damping factor and the Fermi level of the graphene, as well as the size and core material of the coated particle, such plasmonic-enhanced THz emission is indeed possible. This thus opens up a new pathway to provide intense THz sources for future applications.


Spherical Radiative Transfer In C++ (Srtc++): A Parallel Monte-Carlo Radiative Transfer Model For Titan, Brian K. Jackson Jun 2018

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.


Towards Generalized Noise-Level Dependent Crystallographic Symmetry Classifications Of More Or Less Periodic Crystal Patterns, Peter Moeck Apr 2018

Towards Generalized Noise-Level Dependent Crystallographic Symmetry Classifications Of More Or Less Periodic Crystal Patterns, Peter Moeck

Physics Faculty Publications and Presentations

Geometric Akaike Information Criteria (G-AICs) for generalized noise-level dependent crystallographic symmetry classifications of two-dimensional (2D) images that are more or less periodic in either two or one dimensions as well as Akaike weights for multi-model inferences and predictions are reviewed. Such novel classifications do not refer to a single crystallographic symmetry class exclusively in a qualitative and definitive way. Instead, they are quantitative, spread over a range of crystallographic symmetry classes, and provide opportunities for inferences from all classes (within the range) simultaneously. The novel classifications are based on information theory and depend only on information that has been extracted ...


Interlaboratory Comparison Of Δ13c And Δd Measurements Of Atmospheric Ch4 For Combined Use Of Data Sets From Different Laboratories, Taku Umezawa, Carl Brenninkmeijer, Thomas Röckmann, Carina Van Der Veen, Stanley C. Tyler, Ryo Fujita, Shinji Morimoto, Shuji Aoki, Todd Sowers, Jochen Schmitt, Michael Bock, Jonas Beck, Hubertus Fischer, Sylvia E. Michel, Bruce H. Vaughn, John B. Miller, James W.C. White, Gordon Brailsford, Hinrich Schaefer, Peter Sperlich, Willi A. Brand, Michael Rothe, Thomas Blunier, David Lowry, Rebecca E. Fisher, Euan G. Nisbet, Andrew L. Rice, Peter Bergamaschi, Cordelia Veidt, Ingeborg Levin Mar 2018

Interlaboratory Comparison Of Δ13c And Δd Measurements Of Atmospheric Ch4 For Combined Use Of Data Sets From Different Laboratories, Taku Umezawa, Carl Brenninkmeijer, Thomas Röckmann, Carina Van Der Veen, Stanley C. Tyler, Ryo Fujita, Shinji Morimoto, Shuji Aoki, Todd Sowers, Jochen Schmitt, Michael Bock, Jonas Beck, Hubertus Fischer, Sylvia E. Michel, Bruce H. Vaughn, John B. Miller, James W.C. White, Gordon Brailsford, Hinrich Schaefer, Peter Sperlich, Willi A. Brand, Michael Rothe, Thomas Blunier, David Lowry, Rebecca E. Fisher, Euan G. Nisbet, Andrew L. Rice, Peter Bergamaschi, Cordelia Veidt, Ingeborg Levin

Physics Faculty Publications and Presentations

We report results from a worldwide interlaboratory comparison of samples among laboratories that measure (or measured) stable carbon and hydrogen isotope ratios of atmospheric CH413C-CH4 and δD-CH4). The offsets among the laboratories are larger than the measurement reproducibility of individual laboratories. To disentangle plausible measurement offsets, we evaluated and critically assessed a large number of intercomparison results, some of which have been documented previously in the literature. The results indicate significant offsets of δ13C-CH4 and δD- CH4 measurements among data sets reported from different laboratories; the differences among laboratories at ...


A Virtual Lock-In Amplifier, Spectrum Analyzer, Impedance Meter And Semiconductor Analyzer Implemented On An Sr7265 Hardware Target, Jianghua Bai, John L. Freeouf, Andres H. La Rosa Mar 2018

A Virtual Lock-In Amplifier, Spectrum Analyzer, Impedance Meter And Semiconductor Analyzer Implemented On An Sr7265 Hardware Target, Jianghua Bai, John L. Freeouf, Andres H. La Rosa

Physics Faculty Publications and Presentations

Lock-in amplifiers are used to detect and measure very small AC signals down to the range of nVs. Accurate measurements may be made even when the small signals are buried by noise sources thousands of times larger. With the digital signal processing (DSP) technology involved in modern instrumentation, a lock-in amplifier is more versatile than sensing and recover small signals. Combining the virtual instrumentation technology, we reorganize the functional blocks of a programmable lock-in amplifier and build it as a virtual spectrum analyzer, virtual impedance meter, virtual network analyzer, virtual semiconductor parameter analyzer, signal generator, etc. A 4 layer model ...


Implementing An Spm Controller With Labview, Jianghua Bai, John L. Freeouf, Andres H. La Rosa Mar 2018

Implementing An Spm Controller With Labview, Jianghua Bai, John L. Freeouf, Andres H. La Rosa

Physics Faculty Publications and Presentations

The purpose of this article is to reduce the barrier of developing a house-made scanning probe microscope(SPM). Here in this paper,we cover all the details of programming an SPM controller with LabVIEW. The main controller has three major sequential portions. They are system initialization portion,scan control and image display portion and system shutdown portion. The most complicated and essential part of the main controller is the scan control and image display portion, which is achieved with various parallel tasks. These tasks are scan area and image size adjusting module, Y-axis scan control module, Xaxis scan and image ...


Quantum Dot Growth On (111) And (110) Surfaces Using Tensile-Strained Self-Assembly, Paul J. Simmonds Feb 2018

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 ...


A Machine Learning Algorithm For Identifying And Tracking Bacteria In Three Dimensions Using Digital Holographic Microscopy, Manuel Bedrossian, Marwan El-Kholy, Daniel Neamati, Jay Nadeau Feb 2018

A Machine Learning Algorithm For Identifying And Tracking Bacteria In Three Dimensions Using Digital Holographic Microscopy, Manuel Bedrossian, Marwan El-Kholy, Daniel Neamati, Jay Nadeau

Physics Faculty Publications and Presentations

Digital Holographic Microscopy (DHM) is an emerging technique for three-dimensional imaging of microorganisms due to its high throughput and large depth of field relative to traditional microscopy techniques. While it has shown substantial success for use with eukaryotes, it has proven challenging for bacterial imaging because of low contrast and sources of noise intrinsic to the method (e.g. laser speckle). This paper describes a custom written MATLAB routine using machine-learning algorithms to obtain three-dimensional trajectories of live, lab-grown bacteria as they move within an essentially unrestrained environment with more than 90% precision. A fully annotated version of the software ...


Scheme For The Protective Measurement Of A Single Photon Using A Tunable Quantum Zeno Effect, Maximilian Schlosshauer Jan 2018

Scheme For The Protective Measurement Of A Single Photon Using A Tunable Quantum Zeno Effect, Maximilian Schlosshauer

Physics Faculty Publications and Presentations

This paper presents a proof-of-principle scheme for the protective measurement of a single photon. In this scheme, the photon is looped arbitrarily many times through an optical stage that implements a weak measurement of a polarization observable followed by a strong measurement protecting the state. The ability of this scheme to realize a large number of such interaction{protection steps means that the uncertainty in the measurement result can be drastically reduced while maintaining a sufficient probability for the photon to survive the measurement.


Using An Instrumented Drone To Probe Dust Devils On Oregon’S Alvord Desert, Brian Jackson, Ralph Lorenz, Karan Davis, Brock Lipple Jan 2018

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 ...


Ozone Balances In Urban Saudi Arabia, M. A. K. Khalil, Christopher L. Butenhoff, R.M. Harrison Jan 2018

Ozone Balances In Urban Saudi Arabia, M. A. K. Khalil, Christopher L. Butenhoff, R.M. Harrison

Physics Faculty Publications and Presentations

Net ozone production rates averaging 130 ppb/h lasting 3–5 h are calculated for five cities of urban Saudi Arabia where hourly ozone and NO2 measurements were taken for a whole year. Concentrations of ozone in the cities are not unusually high at ~40 ppb during the peak 4 h, but are 50–60 ppb at altitude throughout the day. A mass balance of ozone reveals that the locations represented by the sites export ozone during the peak production periods before mid-day at average rates comparable to the net production, but later a substantial import of ozone is required ...


Accurate Lattice Parameters From 2d-Periodic Images For Subsequent Bravais Lattice Type Assignments, Peter Moeck, Paul R. Destefano Jan 2018

Accurate Lattice Parameters From 2d-Periodic Images For Subsequent Bravais Lattice Type Assignments, Peter Moeck, Paul R. Destefano

Physics Faculty Publications and Presentations

Three different algorithms, as implemented in three different computer programs, were put to the task of extracting direct space lattice parameters from four sets of synthetic images that were per design more or less periodic in two dimensions (2D). One of the test images in each set was per design free of noise and, therefore, genuinely 2D periodic so that it adhered perfectly to the constraints of a Bravais lattice type, Laue class, and plane symmetry group. Gaussian noise with a mean of zero and standard deviations of 10 and 50% of the maximal pixel intensity was added to the ...