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Full-Text Articles in Physics

Electromagnetic Reciprocity In The Presence Of Topological Insulators, Huai-Yi Xie, P. T. Leung Sep 2020

Electromagnetic Reciprocity In The Presence Of Topological Insulators, Huai-Yi Xie, P. T. Leung

Physics Faculty Publications and Presentations

Electromagnetic reciprocity is studied in the presence of topological insulators (TI) with application of axion electrodynamics for harmonic electromagnetic fields. The corresponding generalized Lorentz and Feld-Tai type lemmas are derived in terms of the axion coupling parameter, and their correlation to the conditional symmetry in source-observer coordinates for the various Green dyadics is established subjected to different types of boundary conditions. Possible application of the results to the probing of the topological magneto-electric effects from TI is discussed.


A New Look At The Quantum Liouville Theorem, P. T. Leung, G. I. Ni Aug 2020

A New Look At The Quantum Liouville Theorem, P. T. Leung, G. I. Ni

Physics Faculty Publications and Presentations

We clarify certain confusions in the literature of the density operator in quantum mechanics, and demonstrate that the quantum Liouville theorem has the same form in both the Schrodinger and the Heisenberg pictures. Our starting point is to treat the density operator as an observable which has its specific time dependence in each of the two pictures. It is further shown that such a formulation will provide the exact correspondence between classical and quantum statistical mechanics with the Liouville theorem being interpreted as a conservation law, which is derivable from the equation of motion only in the quantum case.


Kinetic Exclusion Assay Of Biomolecules By Aptamer Capture, Mark H. Smith, Daniel Fologea Jun 2020

Kinetic Exclusion Assay Of Biomolecules By Aptamer Capture, Mark H. Smith, Daniel Fologea

Physics Faculty Publications and Presentations

DNA aptamers are short nucleotide oligomers selected to bind a target ligand with affinity and specificity rivaling that of antibodies. These remarkable features recommend aptamers as candidates for analytical and therapeutic applications that traditionally use antibodies as biorecognition elements. Numerous traditional and emerging analytical techniques have been proposed and successfully implemented to utilize aptamers for sensing purposes. In this work, we exploited the analytical capabilities offered by the kinetic exclusion assay technology to measure the affinity of fluorescent aptamers for their thrombin target and quantify the concentration of analyte in solution. Standard binding curves constructed by using equilibrated mixtures of ...


Temporary Membrane Permeabilization Via The Pore-Forming Toxin Lysenin, Nisha Shrestha, Christopher A. Thomas, Devon Richtsmeier, Andrew Bogard, Rebecca Hermann, Malyk Walker, Gamid Abatchev, Raquel J. Brown, Daniel Fologea May 2020

Temporary Membrane Permeabilization Via The Pore-Forming Toxin Lysenin, Nisha Shrestha, Christopher A. Thomas, Devon Richtsmeier, Andrew Bogard, Rebecca Hermann, Malyk Walker, Gamid Abatchev, Raquel J. Brown, Daniel Fologea

Physics Faculty Publications and Presentations

Pore-forming toxins are alluring tools for delivering biologically-active, impermeable cargoes to intracellular environments by introducing large conductance pathways into cell membranes. However, the lack of regulation often leads to the dissipation of electrical and chemical gradients, which might significantly affect the viability of cells under scrutiny. To mitigate these problems, we explored the use of lysenin channels to reversibly control the barrier function of natural and artificial lipid membrane systems by controlling the lysenin’s transport properties. We employed artificial membranes and electrophysiology measurements in order to identify the influence of labels and media on the lysenin channel’s conductance ...


Analytical Results For The Three-Body Radiative Attachment Rate Coefficient, With Application To The Positive Antihydrogen Ion H¯+, Jack C. Straton Apr 2020

Analytical Results For The Three-Body Radiative Attachment Rate Coefficient, With Application To The Positive Antihydrogen Ion H¯+, Jack C. Straton

Physics Faculty Publications and Presentations

To overcome the numerical difficulties inherent in the Maxwell–Boltzmann integral of the velocity-weighted cross section that gives the radiative attachment rate coefficient αRA for producing the negative hydrogen ion H or its antimatter equivalent, the positive antihydrogen ion H¯+ , we found the analytic form for this integral. This procedure is useful for temperatures below 700 K, the region for which the production of H¯+ has potential use as an intermediate stage in the cooling of antihydrogen to ultra-cold (sub-mK) temperatures for spectroscopic studies and probing the gravitational interaction of the anti-atom. Our results, utilizing a 50-term explicitly correlated exponential ...


Dust Devils On Titan, Brian Jackson, Ralph D. Lorenz, Jason W. Barnes, Michelle Szurgot Mar 2020

Dust Devils On Titan, Brian Jackson, Ralph D. Lorenz, Jason W. Barnes, Michelle Szurgot

Physics Faculty Publications and Presentations

Conditions on Saturn's moon Titan suggest that dust devils, which are convective, dust‐laden plumes, may be active. Although the exact nature of dust on Titan is unclear, previous observations confirm an active aeolian cycle, and dust devils may play an important role in Titan's aeolian cycle, possibly contributing to regional transport of dust and even production of sand grains. The Dragonfly mission to Titan will document dust devil and convective vortex activity and thereby provide a new window into these features, and our analysis shows that associated winds are likely to be modest and pose no hazard ...


Conceptual Change By Fiat?, Dewey I. Dykstra Mar 2020

Conceptual Change By Fiat?, Dewey I. Dykstra

Physics Faculty Publications and Presentations

What Murphy and Gash are attempting to do is to solve a significant problem some students have being successful in school, one that is not often addressed in any significant way. The language used to describe the lessons has some significant departures from radical constructivism. It is, no doubt, beneficial that the students in the study may have developed improvements in self-image, but, as seen in other work, the application of radical constructivism to develop and extend the work started in the study could result in more and more lasting improvements.


On The Relationship Between Dust Devil Radii And Heights, Brian Jackson Mar 2020

On The Relationship Between Dust Devil Radii And Heights, Brian Jackson

Physics Faculty Publications and Presentations

The influence of dust devils on the martian atmosphere depends on their capacity to loft dust, which depends on their wind profiles and footprint on the martian surface, i.e., on their radii, 𝑅. Previous work suggests the wind profile depends on a devil’s thermodynamic efficiency, which scales with its height, ℎ. However, the precise mechanisms that set a dust devil’s radius have remained unclear. Combining previous work with simple assumptions about angular momentum conservation in dust devils predicts that 𝑅 ∝ ℎ1∕2, and a model fit to observed radii and heights from a survey of martian ...


Polarization In The Production Of The Antihydrogen Ion, Casey A. Yazejian, Jack C. Straton Jan 2020

Polarization In The Production Of The Antihydrogen Ion, Casey A. Yazejian, Jack C. Straton

Physics Faculty Publications and Presentations

We provide estimates of both the cross section and rate coefficient for the radiative attachment of a second positron to create the H̅+ ion, H̅(1s)+e+→H̅+(1s2 1Se)+ℏω, for which the polarization of the initial state H̅(1s) is taken into account. We show how to analytically integrate the resulting six-dimensional, three-body integrals for wave functions composed of explicitly correlated exponentials, a result that may be extended to Hylleraas wave functions. We extend Bhatia’s polarization results for the equivalent matter problem down to the low temperatures required for the Gravitational ...


Reducing A Class Of Two-Dimensional Integrals To One-Dimension With An Application To Gaussian Transforms, Jack C. Straton Jan 2020

Reducing A Class Of Two-Dimensional Integrals To One-Dimension With An Application To Gaussian Transforms, Jack C. Straton

Physics Faculty Publications and Presentations

Quantum theory is awash in multidimensional integrals that contain exponentials in the integration variables, their inverses, and inverse polynomials of those variables. The present paper introduces a means to reduce pairs of such integrals to one dimension when the integrand contains powers multiplied by an arbitrary function of xy/ (x + y) multiplying various combinations of exponentials. In some cases these exponentials arise directly from transition-amplitudes involving products of plane waves, hydrogenic wave functions, and Yukawa and/or Coulomb potentials. In other cases these exponentials arise from Gaussian transforms of such functions.


Enhancing Final Image Contrast In Off-Axis Digital Holography Using Residual Fringes, Manuel Bedrossian, Kent Wallace, Eugene Serabyn, Chris Lindensmith, Jay Nadeau Jan 2020

Enhancing Final Image Contrast In Off-Axis Digital Holography Using Residual Fringes, Manuel Bedrossian, Kent Wallace, Eugene Serabyn, Chris Lindensmith, Jay Nadeau

Physics Faculty Publications and Presentations

We show that background fringe-pattern subtraction is a useful technique for removing static noise from off-axis holographic reconstructions and can enhance image contrast in volumetric reconstructions by an order of magnitude in the case for instruments with relatively stable fringes. We demonstrate the fundamental principle of this technique and introduce some practical considerations that must be made when implementing this scheme, such as quantifying fringe stability. This work also shows an experimental verification of the background fringe subtraction scheme using various biological samples.


Characterization Of Retinol Stabilized In Phosphatidylcholine Vesicles With And Without Antioxidants, Yekaterina G. Chmykh, Jay Nadeau Jan 2020

Characterization Of Retinol Stabilized In Phosphatidylcholine Vesicles With And Without Antioxidants, Yekaterina G. Chmykh, Jay Nadeau

Physics Faculty Publications and Presentations

Retinol stability has been reported to be improved by encapsulation in liposomes, both with and without cholesterol. However, this improvement is limited because of lipid peroxidation. In this study, we compare the stability of retinol in phosphatidylcholine liposomes under ultraviolet (UV) light or standard room air, with and without the addition of antioxidants. Both butylated hydroxytoluene (BHT) and a proprietary mix (StoppOx) improved the shelf stability from vesicles, including within the aqueous layer. Fluorescence lifetimes were equally heterogeneous. Under UV irradiation, StoppOx protected retinol for significantly longer than BHT and via different mechanisms. This suggests that natural antioxidants work well ...


Topological Magnetoelectric Effect As Probed By Nanoshell Plasmonic Modes, Railing Chang, Huai Yi Xie, Ya-Chih Wang, Hai-Pang Chiang, P.T. Leung Dec 2019

Topological Magnetoelectric Effect As Probed By Nanoshell Plasmonic Modes, Railing Chang, Huai Yi Xie, Ya-Chih Wang, Hai-Pang Chiang, P.T. Leung

Physics Faculty Publications and Presentations

Axion electrodynamics is applied to study the response of a plasmonic nanoshell with a core made of topological insulator (TI) materials. The electric polarizability of such a system is calculated in the long wavelength limit via the introduction of two scalar potentials satisfying the various appropriate boundary conditions. Our focus is on the topological magneto-electric effect (TME) as manifested in the coupled plasmonic resonances of the nanoshell. It is found that for a TI with broken time-reversal symmetry, such TME will lead to observable red-shifts in the coupled plasmonic modes, with more significant manifestation of such shifts for the bonding ...


Adapting Realtime Physics For Distance Learning With The Iolab, Erik Bodegom, Erik Jensen, David Sokoloff Sep 2019

Adapting Realtime Physics For Distance Learning With The Iolab, Erik Bodegom, Erik Jensen, David Sokoloff

Physics Faculty Publications and Presentations

The IOLab is a versatile and inexpensive data acquisition device in a cart that can roll on its three wheels. It has numerous sensors for a variety of physical quantities. We adapted RealTime Physics, Module 1: Mechanics active learning labs for use with the IOLab. We tested these labs both on campus and with distance learners at Portland State University and Chemeketa Community College for three years, consistently obtaining significant conceptual learning gains on the Force and Motion Conceptual Evaluation (FMCE). Student attitudes towards the labs, the device, and distance learning—as measured by post-course evaluations—were generally very positive.


An Effective Electric Dipole Model For Voltage-Induced Gating Mechanism Of Lysenin, Eric Krueger, Daniel Fologea Aug 2019

An Effective Electric Dipole Model For Voltage-Induced Gating Mechanism Of Lysenin, Eric Krueger, Daniel Fologea

Physics Faculty Publications and Presentations

Lysenin is a pore-forming toxin, which self-inserts open channels into sphingomyelin containing membranes and is known to be voltage regulated. The mechanistic details of its voltage gating mechanism, however, remains elusive despite much recent efforts. Here, we have employed a novel combination of experimental and computational techniques to examine a model for voltage gating, that is based on the existence of an “effective electric dipole” inspired by recent reported structures of lysenin. We support this mechanism by the observations that (i) the charge-reversal and neutralization substitutions in lysenin result in changing its electrical gating properties by modifying the strength of ...


The Fourier Spectrum Of A Singing Wine Glass, Reuben Leatherman, Justin Charles Dunlap, Ralf Widenhorn Aug 2019

The Fourier Spectrum Of A Singing Wine Glass, Reuben Leatherman, Justin Charles Dunlap, Ralf Widenhorn

Physics Faculty Publications and Presentations

The phenomenon of the singing wineglass is familiar to many. Most people have run a finger along the rim of a wine glass with the right speed and pressure to get it to whistle a tone or perhaps heard a glass harmonica being played. However, have you ever noticed and wondered why the vibrations caused by a finger on a glass produce a pulsating sound, rather than a steady, constant-amplitude vibration? Further exploration reveals that the sound and pulsations of a wine glass vary depending on the way the wine glass is stimulated. In this paper, we investigate and model ...


Multiwavelength Digital Holographic Imaging And Phase Unwrapping Of Protozoa Using Custom Fiji Plug-Ins, David Cohoe, Iulia Hanczarek, J. Kent Wallace, Jay Nadeau Jul 2019

Multiwavelength Digital Holographic Imaging And Phase Unwrapping Of Protozoa Using Custom Fiji Plug-Ins, David Cohoe, Iulia Hanczarek, J. Kent Wallace, Jay Nadeau

Physics Faculty Publications and Presentations

Multiwavelength digital holographic microscopy (DHM) has been used to improve phase reconstructions of digital holograms by reducing 2p phase ambiguities. However, most samples used as test images have been solid or adhered to a surface, making it easy to determine focal planes and correct for chromatic aberration. In this study we apply 3-wavelength off-axis DHM to swimming protozoa containing distinct spectral features such as chlorophyll and carotenoids. We reconstruct the holograms into amplitude and phase images using the angular spectrum method. Methods for noise subtraction, chromatic aberration correction, and image registration are presented for both amplitude and phase. Approaches to ...


Single-Molecule Imaging Reveals The Interplay Between Transcription Factors, Nucleosomes, And Transcriptional Bursting, Matthew L. Ferguson Jun 2019

Single-Molecule Imaging Reveals The Interplay Between Transcription Factors, Nucleosomes, And Transcriptional Bursting, Matthew L. Ferguson

Physics Faculty Publications and Presentations

Transcription factors show rapid and reversible binding to chromatin in living cells, and transcription occurs in sporadic bursts, but how these phenomena are related is unknown. Using a combination of in vitro and in vivo single-molecule imaging approaches, we directly correlated binding of the Gal4 transcription factor with the transcriptional bursting kinetics of the Gal4 target genes GAL3 and GAL10 in living yeast cells. We find that Gal4 dwell time sets the transcriptional burst size. Gal4 dwell time depends on the affinity of the binding site and is reduced by orders of magnitude by nucleosomes. Using a novel imaging platform ...


Variability In The Atmosphere Of The Hot Jupiter Kepler-76b, Brian Jackson, Elisabeth Adams, Wesley Sandidge, Steven Kreyche, Jennifer Briggs Jun 2019

Variability In The Atmosphere Of The Hot Jupiter Kepler-76b, Brian Jackson, Elisabeth Adams, Wesley Sandidge, Steven Kreyche, Jennifer Briggs

Physics Faculty Publications and Presentations

No abstract provided.


On Classification Approaches For Crystallographic Symmetries Of Noisy 2d Periodic Patterns, Peter Moeck May 2019

On Classification Approaches For Crystallographic Symmetries Of Noisy 2d Periodic Patterns, Peter Moeck

Physics Faculty Publications and Presentations

The existing types of classification approaches for the crystallographic symmetries of patterns that are more or less periodic in two dimensions (2D) are reviewed. Their relative performance is evaluated in a qualitative manner. Pseudo-symmetries of different kinds are discussed as they present severe challenges to most classification approaches when noise levels are moderate to high. The author’s information theory based approaches utilize digital images and geometric Akaike Information Criteria. They perform well in the presence of pseudo-symmetries and turn out to be the only ones that allow for fully objective (completely researcher independent) and generalized noise level dependent classifications ...


Sound Propagation, Reflection, And Its Relevance To Ultrasound Imaging, Thomas Allen, Alex Chally, Bradley Moser, Ralf Widenhorn Mar 2019

Sound Propagation, Reflection, And Its Relevance To Ultrasound Imaging, Thomas Allen, Alex Chally, Bradley Moser, Ralf Widenhorn

Physics Faculty Publications and Presentations

The labs presented here build on a simple speed of sound activity and models medical ultrasound imaging by demonstrating how multiple reflections propagate in a closed system. A short sound pulse is emitted into a pipe that is closed at one end and contains one or more partially reflecting surfaces within the pipe. The variety of reflections and transmissions that occur can be measured with a microphone at the pipe entrance.


Viscosities, Diffusion Coefficients, And Mixing Times Of Intrinsic Fluorescent Organic Molecules In Brown Limonene Secondary Organic Aerosol And Tests Of The Stokes–Einstein Equation, Dagny A. Ullmann, Mallory L. Hinks, Adrian M. Maclean, Christopher Butenhoff, James W. Grayson, Kelley Barsanti, Jose L. Jimenez, Sergey A. Nizkorodov, Saeid Kamal, Allan K. Bertram Feb 2019

Viscosities, Diffusion Coefficients, And Mixing Times Of Intrinsic Fluorescent Organic Molecules In Brown Limonene Secondary Organic Aerosol And Tests Of The Stokes–Einstein Equation, Dagny A. Ullmann, Mallory L. Hinks, Adrian M. Maclean, Christopher Butenhoff, James W. Grayson, Kelley Barsanti, Jose L. Jimenez, Sergey A. Nizkorodov, Saeid Kamal, Allan K. Bertram

Physics Faculty Publications and Presentations

Viscosities and diffusion rates of organics within secondary organic aerosol (SOA) remain uncertain. Using the bead-mobility technique, we measured viscosities as a function of water activity (aw) of SOA generated by the ozonolysis of limonene followed by browning by exposure to NH3 (referred to as brown limonene SOA or brown LSOA). These measurements together with viscosity measurements reported in the literature show that the viscosity of brown LSOA increases by 3–5 orders of magnitude as the aw decreases from 0.9 to approximately 0.05. In addition, we measured diffusion coefficients of intrinsic fluorescent organic molecules within ...


Photoemission Electron Microscopy To Characterize Slow Light In A Photonic Crystal Line Defect, Theodore Stedmark, Rolf Könenkamp Jan 2019

Photoemission Electron Microscopy To Characterize Slow Light In A Photonic Crystal Line Defect, Theodore Stedmark, Rolf Könenkamp

Physics Faculty Publications and Presentations

Using femtosecond nonlinear photoemission electron microscopy (PEEM) we provide a detailed characterization of slow light in a small-size asymmetric photonic crystal structure. We show that PEEM is capable of providing a unique description of the light propagation in such structures by direct imaging of the guided mode. This noninvasive characterization technique allows modal properties such as effective index, phase velocities, and group velocities to be determined. Combining experimental results with finite element method simulation calculations, we study slow light phenomena in a photonic crystal defect mode, and we produce a comprehensive picture of the mechanisms behind it. Our results illustrate ...


Imaging Technologies And Strategies For Detection Of Extant Extraterrestrial Microorganisms, Jay Nadeau, Manuel Bedrossian, Chris Lindensmith Jan 2019

Imaging Technologies And Strategies For Detection Of Extant Extraterrestrial Microorganisms, Jay Nadeau, Manuel Bedrossian, Chris Lindensmith

Physics Faculty Publications and Presentations

There is no reductionist definition of life, so the way organisms look, behave, and move is the most definitive way to identify extraterrestrial life. Life elsewhere in the Solar System is likely to be microbial, but no microscope capable of imaging prokaryotic life has ever flown on a lander mission to a habitable planet. Nonetheless, high-resolution microscopes have been developed that are appropriate for planetary exploration. Traditional light microscopy, interferometric microscopy, light-field microscopy, scanning probe microscopy, and electron microscopy are all possible techniques for the detection of extant micro-organisms on Mars and the moons of Jupiter and Saturn. This article ...


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 ...


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 ...


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 ...


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 ...


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 ...


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 ...