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Physics Faculty Publications

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Articles 631 - 660 of 1942

Full-Text Articles in Physical Sciences and Mathematics

Polyglutamine Aggregates Impair Lipid Membrane Integrity And Enhance Lipid Membrane Rigidity, Chian Sing Ho, Nawal K. Khadka, Fengyu She, Jianfeng Cai, Jianjun Pan Apr 2016

Polyglutamine Aggregates Impair Lipid Membrane Integrity And Enhance Lipid Membrane Rigidity, Chian Sing Ho, Nawal K. Khadka, Fengyu She, Jianfeng Cai, Jianjun Pan

Physics Faculty Publications

Lipid membranes are suggested as the primary target of amyloid aggregates. We study aggregates formed by a polyglutamine (polyQ) peptide, and their disruptive effect on lipid membranes. Using solution atomic force microscopy (AFM), we observe polyQ oligomers coexisting with short fibrils, which have a twisted morphology that likely corresponds to two intertwined oligomer strings. Fourier transform infrared spectroscopy reveals that the content of β-sheet enriched aggregates increases with incubation time. Using fluorescence microscopy, we find that exposure to polyQ aggregates results in deflated morphology of giant unilamellar vesicles. PolyQ aggregates induced membrane disruption is further substantiated by time-dependent calcein leakage …

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Signal Enhanced Holographic Fluorescence Microscopy With Guide-Star Reconstruction, Changwon Jang, David C. Clark, Jonghyun Kim, Byoungho Lee, Myung K. Kim Mar 2016

Signal Enhanced Holographic Fluorescence Microscopy With Guide-Star Reconstruction, Changwon Jang, David C. Clark, Jonghyun Kim, Byoungho Lee, Myung K. Kim

Physics Faculty Publications

We propose a signal enhanced guide-star reconstruction method for holographic fluorescence microscopy. In the late 00’s, incoherent digital holography started to be vigorously studied by several groups to overcome the limitations of conventional digital holography. The basic concept of incoherent digital holography is to acquire the complex hologram from incoherent light by utilizing temporal coherency of a spatially incoherent light source. The advent of incoherent digital holography opened new possibility of holographic fluorescence microscopy (HFM), which was difficult to achieve with conventional digital holography. However there has been an important issue of low and noisy signal in HFM which slows …

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Anions Govern Cell Volume: A Case Study Of Relative Astrocytic And Neuronal Swelling In Spreading Depolarization, Niklas Hübel, Ghanim Ullah Mar 2016

Anions Govern Cell Volume: A Case Study Of Relative Astrocytic And Neuronal Swelling In Spreading Depolarization, Niklas Hübel, Ghanim Ullah

Physics Faculty Publications

Cell volume changes are ubiquitous in normal and pathological activity of the brain. Nevertheless, we know little about the dynamics of cell and tissue swelling, and the differential changes in the volumes of neurons and glia during pathological states such as spreading depolarizations (SD) under ischemic and non–ischemic conditions, and epileptic seizures. By combining the Hodgkin–Huxley type spiking dynamics, dynamic ion concentrations, and simultaneous neuronal and astroglial volume changes into a comprehensive model, we elucidate why glial cells swell more than neurons in SD and the special case of anoxic depolarization (AD), and explore the relative contributions of the two …

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Interface‐Coupled Bifeo3/Bimno3 Superlattices With Magnetic Transition Temperature Up To 410 K, Eun-Mi Choi, Josée E. Kliebeuker, Thomas Fix, Jie Xiong, Christy J. Kinane, Dario Arena, Sean Langridge, Aiping Chen, Zhenxing Bi, Joon Hwan Lee, Quanix Jia, Mark G. Blamire, Judith L. Macmanus-Driscoll Mar 2016

Interface‐Coupled Bifeo3/Bimno3 Superlattices With Magnetic Transition Temperature Up To 410 K, Eun-Mi Choi, Josée E. Kliebeuker, Thomas Fix, Jie Xiong, Christy J. Kinane, Dario Arena, Sean Langridge, Aiping Chen, Zhenxing Bi, Joon Hwan Lee, Quanix Jia, Mark G. Blamire, Judith L. Macmanus-Driscoll

Physics Faculty Publications

Enhanced magnetic transition temperatures are demonstrated in 50 nm thick (001)‐oriented (BiFeO3)m/(BiMnO3)m (BFO/BMO) superlattices (SL). Highly strained ultra‐short SLs showed a magnetic transition, TC2, up to ≈410 K as a result of ferrimagnetic interaction between BFO/BMO. All SL showed a new ferromagnetic transtion, TC1, of ≈150 K coming from Fe4+‐Fe4+ interaction explained by electron transfer/leakage from Fe3+ to Mn3+.

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Intermittency On Simultaneous Observations Of Riometer At Several Antarctic Locations, E. M. Ovalle, A. J. Foppiano, M. V. Stepanova, Allan T. Weatherwax Mar 2016

Intermittency On Simultaneous Observations Of Riometer At Several Antarctic Locations, E. M. Ovalle, A. J. Foppiano, M. V. Stepanova, Allan T. Weatherwax

Physics Faculty Publications

It is well known that auroral radio wave absorption, as measured by riometers, consists of periods of relative quiescence which are interrupted by short bursts of activity. Such patterns in activity are observed in systems ranging from the stock market to turbulence, i.e. they exhibit intermittency. In the case of the auroral absorption it has also been found that intermittency strongly depends on the magnetic local time, being largest in the night-time sector. This can be interpreted as indicating that the precipitating particles responsible of the absorption exhibit intermittency, especially near the substorm eye, where the level of turbulence increases. …

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Impaired Mitochondrial Function Due To Familial Alzheimers Disease-Causing Presenilins Mutants Via Calcium Disruptions, Patrick T. Toglia, King-Ho Cheung, Don-On Daniel Mak, Ghamim Ullah Feb 2016

Impaired Mitochondrial Function Due To Familial Alzheimers Disease-Causing Presenilins Mutants Via Calcium Disruptions, Patrick T. Toglia, King-Ho Cheung, Don-On Daniel Mak, Ghamim Ullah

Physics Faculty Publications

Muatans in presenilins (PS1 or PS2) is the major cause of Familial Alzheimer's disease (FAD). FAD causing PS mutants affect intracellular Ca2+ ([Ca2+]i) homeostasis by enhancing the gating of inositol trisphosphate (IP3) receptor (IP3R) Ca2+ release channels on the endoplasmic reticulum (ER), leading to exaggerated Ca2+ release into the cytoplasm (Cheung et al., Neuron 2008:871, Sci. Signal 2010:ra22). Using experimental IP3R-mediated Ca2+ release data, in conjunction with a computational model of cell bioenergetics (Cortassa et al., Biophys. J. 2003:2734, 2004:2067), we explore how the differences in …

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Non-Parametric Reconstruction Of An Inflaton Potential From Einstein–Cartan–Sciama–Kibble Gravity With Particle Production, Shantanu Desai, Nikodem Poplawski Feb 2016

Non-Parametric Reconstruction Of An Inflaton Potential From Einstein–Cartan–Sciama–Kibble Gravity With Particle Production, Shantanu Desai, Nikodem Poplawski

Physics Faculty Publications

The coupling between spin and torsion in the Einstein–Cartan–Sciama–Kibble theory of gravity generates gravitational repulsion at very high densities, which prevents a singularity in a black hole and may create there a new universe. We show that quantum particle production in such a universe near the last bounce, which represents the Big Bang, gives the dynamics that solves the horizon, flatness, and homogeneity problems in cosmology. For a particular range of the particle production coefficient, we obtain a nearly constant Hubble parameter that gives an exponential expansion of the universe with more than 60 e -folds, which lasts about ∼10 …

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Ultrafast Saturation Of Electronic-Resonance-Enhanced Coherent Anti-Stokes Raman Scattering And Comparison For Pulse Durations In The Nanosecond To Femtosecond Regime, Anil K. Patnaik, Sukesh Roy, James R. Gord Feb 2016

Ultrafast Saturation Of Electronic-Resonance-Enhanced Coherent Anti-Stokes Raman Scattering And Comparison For Pulse Durations In The Nanosecond To Femtosecond Regime, Anil K. Patnaik, Sukesh Roy, James R. Gord

Physics Faculty Publications

The saturation threshold of a probe pulse in an ultrafast electronic-resonance-enhanced (ERE) coherent anti-Stokes Raman spectroscopy (CARS) configuration is calculated. We demonstrate that while the underdamping condition is a sufficient condition for saturation of ERE-CARS with the long-pulse excitations, a transient gain must be achieved to saturate the ERE-CARS signal for the ultrafast probe regime. We identify that the area under the probe pulse can be used as a definitive parameter to determine the criterion for a saturation threshold for ultrafast ERE-CARS. From a simplified analytical solution and a detailed numerical calculation based on density-matrix equations, the saturation threshold of …

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Scaling Law For Electrocaloric Temperature Change In Antiferroelectrics, Sergey Lisenkov, B. K. Mani, E. Glazkova, C. W. Miller, Inna Ponomareva Jan 2016

Scaling Law For Electrocaloric Temperature Change In Antiferroelectrics, Sergey Lisenkov, B. K. Mani, E. Glazkova, C. W. Miller, Inna Ponomareva

Physics Faculty Publications

A combination of theoretical and first-principles computational methods, along with experimental evidence from the literature, were used to predict the existence of a scaling law for the electrocaloric temperature change in antiferroelectric materials. We show that the temperature change scales quadratically with electric field, allowing a simple transformation to collapse the set of ΔT(E) onto a single curve. This offers a unique method that can be used to predict electrocaloric behavior beyond the limits of present measurement ranges or in regions where data are not yet available.

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Analysis Of Solar Photovoltaic And Wind Power Potential In Afghanistan, Ahmad Murtaza Ershad, Robert J. Brecha, Kevin P. Hallinan Jan 2016

Analysis Of Solar Photovoltaic And Wind Power Potential In Afghanistan, Ahmad Murtaza Ershad, Robert J. Brecha, Kevin P. Hallinan

Physics Faculty Publications

Afghanistan has a need for increased access to energy to enable development. In this paper we analyze the potential for large-scale grid-connected solar photovoltaic (PV) and wind power plants in two of Afghanistan's most populous provinces (Balkh and Herat) to meet a large fraction of growing electricity demand. The results presented here represent the first quantitative analysis of potential capacity factors and energy yields of power plants in the country using measured wind speed and typical solar radiation data. Variability of resources is also investigated by comparing temporal profiles with those of electricity demand, using residual load duration curves to …

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Mechanisms Of Small Molecule-Dna Interactions Probed By Single-Molecule Force Spectroscopy, Ali A. Almaqwashi, Thayaparan Paramanathan, Ioulia Rouzina, Mark C. Williams Jan 2016

Mechanisms Of Small Molecule-Dna Interactions Probed By Single-Molecule Force Spectroscopy, Ali A. Almaqwashi, Thayaparan Paramanathan, Ioulia Rouzina, Mark C. Williams

Physics Faculty Publications

There is a wide range of applications for non-covalent DNA binding ligands, and optimization of such interactions requires detailed understanding of the binding mechanisms. One important class of these ligands is that of intercalators, which bind DNA by inserting aromatic moieties between adjacent DNA base pairs. Characterizing the dynamic and equilibrium aspects of DNA-intercalator complex assembly may allow optimization of DNA binding for specific functions. Single-molecule force spectroscopy studies have recently revealed new details about the molecular mechanisms governing DNA intercalation. These studies can provide the binding kinetics and affinity as well as determining the magnitude of the double helix …

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Biophysical Measurements Of Cells, Microtubules, And Dna With An Atomic Force Microscope, Luka M. Devenica, Clay Contee, Raysa Cabrejo, Matthew Kurek, Edward F. Deveney, Ashley R. Carter Jan 2016

Biophysical Measurements Of Cells, Microtubules, And Dna With An Atomic Force Microscope, Luka M. Devenica, Clay Contee, Raysa Cabrejo, Matthew Kurek, Edward F. Deveney, Ashley R. Carter

Physics Faculty Publications

Atomic force microscopes (AFMs) are ubiquitous in research laboratories and have recently been priced for use in teaching laboratories. Here, we review several AFM platforms and describe various biophysical experiments that could be done in the teaching laboratory using these instruments. In particular, we focus on experiments that image biological materials (cells, microtubules, and DNA) and quantify biophysical parameters including membrane tension, persistence length, contour length, and the drag force.

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Iterative Monte Carlo Analysis Of Spin-Dependent Parton Distributions, Nobuo Sato, W. Melnitchouk, S. E. Kuhn, J. J. Ethier, A. Accardi, Jefferson Lab Angular Momentum Collaboration Jan 2016

Iterative Monte Carlo Analysis Of Spin-Dependent Parton Distributions, Nobuo Sato, W. Melnitchouk, S. E. Kuhn, J. J. Ethier, A. Accardi, Jefferson Lab Angular Momentum Collaboration

Physics Faculty Publications

We present a comprehensive new global QCD analysis of polarized inclusive deep-inelastic scattering, including the latest high-precision data on longitudinal and transverse polarization asymmetries from Jefferson Lab and elsewhere. The analysis is performed using a new iterative Monte Carlo fitting technique which generates stable fits to polarized parton distribution functions (PDFs) with statistically rigorous uncertainties. Inclusion of the Jefferson Lab data leads to a reduction in the PDF errors for the valence and sea quarks, as well as in the gluon polarization uncertainty at x ≳ 0.1 . The study also provides the first determination of the flavor-separated twist-3 PDFs …

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High-Fidelity Simulations Of Long-Term Beam-Beam Dynamics On Gpus, B. Terzić, K. Arumugam, M. Aturban, C. Cotnoir, A. Godunov, D. Ranjan, M. Stefani, M. Zubair, F. Lin, V. Morozov, Y. Roblin, H. Zhang Jan 2016

High-Fidelity Simulations Of Long-Term Beam-Beam Dynamics On Gpus, B. Terzić, K. Arumugam, M. Aturban, C. Cotnoir, A. Godunov, D. Ranjan, M. Stefani, M. Zubair, F. Lin, V. Morozov, Y. Roblin, H. Zhang

Physics Faculty Publications

Future machines such as the Electron Ion Collider (MEIC), linac-ring machines (eRHIC) or LHeC are particularly sensitive to beam-beam effects. This is the limiting factor for long-term stability and high luminosity reach. The complexity of the non-linear dynamics makes it challenging to perform such simulations typically requiring millions of turns. Until recently, most of the methods have involved using linear approximations and/or tracking for a limited number of turns. We have developed a framework which exploits a massively parallel Graphical Processing Units (GPU) architecture to allow for tracking millions of turns in a sympletic way up to an arbitrary order. …

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Rapidity Factorization And Evolution Of Gluon Tmds, Ian Balitsky Jan 2016

Rapidity Factorization And Evolution Of Gluon Tmds, Ian Balitsky

Physics Faculty Publications

I discuss how the rapidity evolution of gluon transverse momentum dependent distribution changes from nonlinear evolution at small x « 1 to linear evolution at moderate x ∼ 1.

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Hadron Resonaces From Qcd, Jozef J. Dudek Jan 2016

Hadron Resonaces From Qcd, Jozef J. Dudek

Physics Faculty Publications

I describe how hadron-hadron scattering amplitudes are related to the eigenstates of QCD in a finite cubic volume. The discrete spectrum of such eigenstates can be determined from correlation functions computed using lattice QCD, and the corresponding scattering amplitudes extracted. I review results from the Hadron Spectrum Collaboration who have used these finite volume methods to study ππ elastic scattering, including the ρ resonance, as well as coupled-channel πK, ηK scattering. The very recent extension to the case where an external current acts is also presented, considering the reaction πγ* → ππ, from which the unstable ρ …

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Connecting Physical Resonant Amplitudes And Lattice Qcd, Daniel R. Bolton, Raúl A. Briceño, David J. Wilson Jan 2016

Connecting Physical Resonant Amplitudes And Lattice Qcd, Daniel R. Bolton, Raúl A. Briceño, David J. Wilson

Physics Faculty Publications

We present a determination of the isovector, P-wave π π scattering phase shift obtained by extrapolating recent lattice QCD results from the Hadron Spectrum Collaboration using mπ = 236 MeV. The finite volume spectra are described using extensions of Ltischer's method to determine the infinite volume Unitarized Chiral Perturbation Theory scattering amplitude. We exploit the pion mass dependence of this effective theory to obtain the scattering amplitude at mπ = 140 MeV. The scattering phase shift is found to agree with experiment up to center of mass energies of 1.2 GeV. The analytic continuation of the scattering amplitude …

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First Measurement Of The Helicity Asymmetry E In Ƞ Photoproduction On The Proton, I. Senderovich, B.T. Morrison, M. Dugger, B.G. Ritchie, E. Pasyuk, R. Tucker, J. Brock, C. Carlin, C.D. Keith, D. G. Meekins, Y. Prok Jan 2016

First Measurement Of The Helicity Asymmetry E In Ƞ Photoproduction On The Proton, I. Senderovich, B.T. Morrison, M. Dugger, B.G. Ritchie, E. Pasyuk, R. Tucker, J. Brock, C. Carlin, C.D. Keith, D. G. Meekins, Y. Prok

Physics Faculty Publications

Results are presented for the first measurement of the double-polarization helicity asymmetry E for the ƞ photoproduction reaction ɣp -> ηp. Data were obtained using the FROzen Spin Target (FROST) with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of center-of-mass energy W from threshold to 2.15 GeV and a large range in center-of-mass polar angle. As an initial application of these data, the results have been incorporated into the Jülich-Bonn model to examine the case for the existence of a narrow N* resonance between 1.66 and 1.70 GeV. The addition of these data to the …

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Improved Sensitivity Mems Cantilever Sensor For Terahertz Photoacoustic Spectroscopy, Ronald A. Coutu Jr., Ivan Medvedev, Douglas T. Petkie Jan 2016

Improved Sensitivity Mems Cantilever Sensor For Terahertz Photoacoustic Spectroscopy, Ronald A. Coutu Jr., Ivan Medvedev, Douglas T. Petkie

Physics Faculty Publications

In this paper, a microelectromechanical system (MEMS) cantilever sensor was designed, modeled and fabricated to measure the terahertz (THz) radiation induced photoacoustic (PA) response of gases under low vacuum conditions. This work vastly improves cantilever sensitivity over previous efforts, by reducing internal beam stresses, minimizing out of plane beam curvature and optimizing beam damping. In addition, fabrication yield was improved by approximately 50% by filleting the cantilever’s anchor and free end to help reduce high stress areas that occurred during device fabrication and processing. All of the cantilever sensors were fabricated using silicon-on-insulator (SOI) wafers and tested in a custom …

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Magnetic And Magneto-Transport Studies Of Substrate Effect On The Martensitic Transformation In A Nimnin Shape Memory Alloy, Andrei Sokolov, Eugene Kirianov, Albina Zlenko, Abdiel Quetz, Anil Aryal, Sudip Pandey, Igor Dubenko, Shane Stadler, Naushad Ali, Nabil Al-Aqtash, Renat Sabirianov Jan 2016

Magnetic And Magneto-Transport Studies Of Substrate Effect On The Martensitic Transformation In A Nimnin Shape Memory Alloy, Andrei Sokolov, Eugene Kirianov, Albina Zlenko, Abdiel Quetz, Anil Aryal, Sudip Pandey, Igor Dubenko, Shane Stadler, Naushad Ali, Nabil Al-Aqtash, Renat Sabirianov

Physics Faculty Publications

The effect of substrates on the magnetic and transport properties of Ni2Mn1.5In0.5 ultra-thin films were studied theoretically and experimentally. High quality 8-nm films were grown by laser-assisted molecular beam epitaxy deposition. Magneto-transport measurements revealed that the films undergo electronic structure transformation similar to those of bulk materials at the martensitic transformation. The temperature of the transformation depends strongly on lattice parameters of the substrate. To explain this behavior, we performed DFT calculations on the system and found that different substrates change the relative stability of the ferromagnetic (FM) austenite and ferrimagnetic (FiM) martensite states. We conclude that the energy difference …

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On The Probability Summation Model For Laser-Damage Thresholds, Clifton D. Clark, Gavin D. Buffington Jan 2016

On The Probability Summation Model For Laser-Damage Thresholds, Clifton D. Clark, Gavin D. Buffington

Physics Faculty Publications

This paper explores the probability summation model in an attempt to provide insight to the model’s utility and ultimately its validity. The model is a statistical description of multiple-pulse (MP) damage trends. It computes the probability of n pulses causing damage from knowledge of the single-pulse dose–response curve. Recently, the model has been used to make a connection between the observed n−1∕4 trends in MP damage thresholds for short pulses (<10 >μs) and experimental uncertainties, suggesting that the observed trend is an artifact of experimental methods. We will consider the correct application of the model in this case. We also …

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Thin Insb Layers With Metallic Gratings: A Novel Platform For Spectrally-Selective Thz Plasmonic Sensing, Shuai Lin, Khagendra Bhattarai, Jiangfeng Zhou, Diyar Talbayev Jan 2016

Thin Insb Layers With Metallic Gratings: A Novel Platform For Spectrally-Selective Thz Plasmonic Sensing, Shuai Lin, Khagendra Bhattarai, Jiangfeng Zhou, Diyar Talbayev

Physics Faculty Publications

We present a computational study of terahertz optical properties of a grating-coupled plasmonic structure based on micrometer-thin InSb layers. We find two strong absorption resonances that we interpret as standing surface plasmon modes and investigate their dispersion relations, dependence on InSb thickness, and the spatial distribution of the electric field. The observed surface plasmon modes are well described by a simple theory of the air/InSb/air tri-layer. The plasmonic response of the grating/InSb structure is highly sensitive to the dielectric environment and the presence of an analyte (e.g., lactose) at the InSb interface, which is promising for terahertz plasmonic sensor applications. …

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Cooling Achieved By Rotating An Anisotropic Superconductor In A Constant Magnetic Field: An New Perspective, Manh-Huong Phan, David Mandrus Jan 2016

Cooling Achieved By Rotating An Anisotropic Superconductor In A Constant Magnetic Field: An New Perspective, Manh-Huong Phan, David Mandrus

Physics Faculty Publications

A new type of rotary coolers based on the temperature change (ΔTrot) of an anisotropic superconductor when rotated in a constant magnetic field is proposed. We show that at low temperature the Sommerfeld coefficient γ(B,Θ) of a single crystalline superconductor, such as MgB2 and NbS2, sensitively depends on the applied magnetic field (B) and the orientation of the crystal axis (Θ), which is related to the electronic entropy (SE) and temperature (T) via the expression: SE=γT. A simple rotation of the crystal from one …

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Mimicking Of Pulse Shape-Dependent Learning Rules With A Quantum Dot Memristor, P. Maier, F. Hartmann, Mariama Rebello Sousa Dias, M. Emmerling, C. Schneider, L. K. Castelano, M. Kamp, G. E. Marques, V. Lopez-Richard, S. Höfling Jan 2016

Mimicking Of Pulse Shape-Dependent Learning Rules With A Quantum Dot Memristor, P. Maier, F. Hartmann, Mariama Rebello Sousa Dias, M. Emmerling, C. Schneider, L. K. Castelano, M. Kamp, G. E. Marques, V. Lopez-Richard, S. Höfling

Physics Faculty Publications

We present the realization of four different learning rules with a quantum dot memristor by tuning the shape, the magnitude, the polarity and the timing of voltage pulses. The memristor displays a large maximum to minimum conductance ratio of about 57 000 at zero bias voltage. The high and low conductances correspond to different amounts of electrons localized in quantum dots, which can be successively raised or lowered by the timing and shapes of incoming voltage pulses. Modifications of the pulse shapes allow altering the conductance change in dependence on the time difference. Hence, we are able to mimic different …

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Light Sensitive Memristor With Bi-Directional And Wavelength-Dependent Conductance Control, P. Maier, F. Hartmann, Mariama Rebello Sousa Dias, M. Emmerling, C. Schneider, L. K. Castelano, M. Kamp, G. E. Marques, V. Lopez-Richard, L. Worschech, S. Höfling Jan 2016

Light Sensitive Memristor With Bi-Directional And Wavelength-Dependent Conductance Control, P. Maier, F. Hartmann, Mariama Rebello Sousa Dias, M. Emmerling, C. Schneider, L. K. Castelano, M. Kamp, G. E. Marques, V. Lopez-Richard, L. Worschech, S. Höfling

Physics Faculty Publications

We report the optical control of localized charge on positioned quantum dots in an electro-photosensitive memristor. Interband absorption processes in the quantum dot barrier matrix lead to photogenerated electron-hole-pairs that, depending on the applied bias voltage, charge or discharge the quantum dots and hence decrease or increase the conductance. Wavelength-dependent conductance control is observed by illumination with red and infrared light, which leads to charging via interband and discharging via intraband absorption. The presented memristor enables optical conductance control and may thus be considered for sensory applications in artificial neural networks as light-sensitive synapses or optically tunable memories.

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First-Principles Definition And Measurement Of Planetary Electromagnetic-Energy Budget, Michael I. Mishchenko, James A. Lock, Andrew A. Lacis, Larry D. Travis, Brian Cairns Jan 2016

First-Principles Definition And Measurement Of Planetary Electromagnetic-Energy Budget, Michael I. Mishchenko, James A. Lock, Andrew A. Lacis, Larry D. Travis, Brian Cairns

Physics Faculty Publications

The imperative to quantify the Earths electromagnetic-energy budget with an extremely high accuracy has been widely recognized but has never been formulated in the framework of fundamental physics. In this paper we give a first-principles definition of the planetary electromagnetic-energy budget using the Poynting- vector formalism and discuss how it can, in principle, be measured. Our derivation is based on an absolute minimum of theoretical assumptions, is free of outdated notions of phenomenological radiometry, and naturally leads to the conceptual formulation of an instrument called the double hemispherical cavity radiometer (DHCR). The practical measurement of the planetary energy budget would …

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Charge-Induced Fluctuation Forces In Graphitic Nanostructures, D. Drosdoff, Igor V. Bondarev, Allan Wisdom, Rudolf Podogrnik, Lilia M. Woods Jan 2016

Charge-Induced Fluctuation Forces In Graphitic Nanostructures, D. Drosdoff, Igor V. Bondarev, Allan Wisdom, Rudolf Podogrnik, Lilia M. Woods

Physics Faculty Publications

Charge fluctuations in nanocircuits with capacitor components are shown to give rise to a novel type of long-ranged interaction, which coexist with the regular Casimir–van der Waals force. The developed theory distinguishes between thermal and quantum mechanical effects, and it is applied to capacitors involving graphene nanostructures. The charge fluctuations mechanism is captured via the capacitance of the system with geometrical and quantum mechanical components. The dependence on the distance separation, temperature, size, and response properties of the system shows that this type of force can have a comparable and even dominant effect to the Casimir interaction. Our results strongly …

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Combining Harmonic Generation And Laser Chirping To Achieve High Spectral Density In Compton Sources, Balša Terzić, Cody Reeves, Geoffrey A. Krafft Jan 2016

Combining Harmonic Generation And Laser Chirping To Achieve High Spectral Density In Compton Sources, Balša Terzić, Cody Reeves, Geoffrey A. Krafft

Physics Faculty Publications

Recently various laser-chirping schemes have been investigated with the goal of reducing or eliminating ponderomotive line broadening in Compton or Thomson scattering occurring at high laser intensities. As a next level of detail in the spectrum calculations, we have calculated the line smoothing and broadening expected due to incident beam energy spread within a one-dimensional plane wave model for the incident laser pulse, both for compensated (chirped) and unchirped cases. The scattered compensated distributions are treatable analytically within three models for the envelope of the incident laser pulses: Gaussian, Lorentzian, or hyperbolic secant. We use the new results to demonstrate …

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Comment On "Controlling The Spectral Shape Of Nonlinear Thomson Scattering With Proper Laser Chirping", Balša Terzić, Geoffrey A. Krafft Jan 2016

Comment On "Controlling The Spectral Shape Of Nonlinear Thomson Scattering With Proper Laser Chirping", Balša Terzić, Geoffrey A. Krafft

Physics Faculty Publications

Rykovanov, Geddes, Schroeder, Esarey and Leemans [Phys. Rev. Accel. Beams 19, 030701 (2016); hereafter RGSEL] have recently reported on the analytic derivation for the laser pulse frequency modulation (chirping) which controls spectrum broadening for high laser pulse intensities. We demonstrate here that their results are the same as the exact solutions reported in Terzic, Deitrick, Hofler and Krafft [Phys. Rev. Lett. 112, 074801 (2014); hereafter TDHK]. While the two papers deal with circularly and linearly polarized laser pulses, respectively, the difference in expressions for the two is just the usual factor of 1/2 present from going from circular to linear …

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Electroexcitation Of The Δ+ (1232) At Low Momentum Transfer, A. Blomberg, D. Anez, N. Sparveris, A. J. Sarty, M. Paolone, S. Gilad, D. Higinbotham, Z. Ahmed, H. Albataineh, K. Allada Jan 2016

Electroexcitation Of The Δ+ (1232) At Low Momentum Transfer, A. Blomberg, D. Anez, N. Sparveris, A. J. Sarty, M. Paolone, S. Gilad, D. Higinbotham, Z. Ahmed, H. Albataineh, K. Allada

Physics Faculty Publications

We report on new p(e, e' p)π°. measurements at the Δ+(1232) resonance at the low momentum transfer region, where the mesonic cloud dynamics is predicted to be dominant and rapidly changing, offering a test bed for chiral effective field theory calculations. The new data explore the Q2 dependence of the resonant quadrupole amplitudes and for the first time indicate that the Electric and the Coulomb quadrupole amplitudes converge as Q2 -> 0. The measurements of the Coulomb quadrupole amplitude have been extended to the lowest momentum transfer ever reached, and suggest that more than half of …

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