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University of South Florida

Physics Faculty Publications

Articles 1 - 15 of 15

Full-Text Articles in Physical Sciences and Mathematics

Dielectric Analysis Of Aqueous Poly(L-Glutamic Acid) And Poly-L-(Glutamic Acid4, Tyrosine1) Solutions At High Frequencies From Capacitance Measurements, Jorge Monreal, Tatiana Eggers, Manh-Huong Phan Dec 2016

Dielectric Analysis Of Aqueous Poly(L-Glutamic Acid) And Poly-L-(Glutamic Acid4, Tyrosine1) Solutions At High Frequencies From Capacitance Measurements, Jorge Monreal, Tatiana Eggers, Manh-Huong Phan

Physics Faculty Publications

A new parallel-plate capacitor fixture has been designed and successfully used to measure dielectric loss of polyelectrolyte solutions with volumes as low as droplets of 13–26 μL. It is particularly useful when studying polypeptides that are either high-cost or can be synthesized only in limited quantities. The ease with which the fixture can be used to obtain preliminary dielectric loss data yields savings in time and cost. In this study capacitance measurements were performed in a wide range of frequencies between 1 and 800 MHz using an Agilent 4191RF Impedance Analyzer. Accuracy of measurements was carefully examined through a comparison …

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Exchange Bias Effects In Iron Oxide-Based Nanoparticle Systems, Manh-Huong Phan, Javier Alsonso, Hafsa Khurshid, Paula Lampen-Kelley, Sayan Chandra, Kristen Stojak Repa, Zohreh Nemati, Raja Das, Óscar Iglesias, Hariharan Srikanth Nov 2016

Exchange Bias Effects In Iron Oxide-Based Nanoparticle Systems, Manh-Huong Phan, Javier Alsonso, Hafsa Khurshid, Paula Lampen-Kelley, Sayan Chandra, Kristen Stojak Repa, Zohreh Nemati, Raja Das, Óscar Iglesias, Hariharan Srikanth

Physics Faculty Publications

The exploration of exchange bias (EB) on the nanoscale provides a novel approach to improving the anisotropic properties of magnetic nanoparticles for prospective applications in nanospintronics and nanomedicine. However, the physical origin of EB is not fully understood. Recent advances in chemical synthesis provide a unique opportunity to explore EB in a variety of iron oxide-based nanostructures ranging from core/shell to hollow and hybrid composite nanoparticles. Experimental and atomistic Monte Carlo studies have shed light on the roles of interface and surface spins in these nanosystems. This review paper aims to provide a thorough understanding of the EB and related …

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Binary Alkali-Metal Silicon Clathrates By Spark Plasma Sintering: Preparation And Characterization, Igor Veremchuk, Matt Beekman, Iryna Antonyshyn, Walter Schnelle, Michael Baitinger, George S. Nolas, Yuri Grin Jul 2016

Binary Alkali-Metal Silicon Clathrates By Spark Plasma Sintering: Preparation And Characterization, Igor Veremchuk, Matt Beekman, Iryna Antonyshyn, Walter Schnelle, Michael Baitinger, George S. Nolas, Yuri Grin

Physics Faculty Publications

The binary intermetallic clathrates K8-xSi46 (x = 0.4; 1.2), Rb6.2Si46, Rb11.5Si136 and Cs7.8Si136 were prepared from M4Si4 (M = K, Rb, Cs) precursors by spark-plasma route (SPS) and structurally characterized by Rietveld refinement of PXRD data. The clathrate-II phase Rb11.5Si136 was synthesized for the first time. Partial crystallographic site occupancy of the alkali metals, particularly for the smaller Si20 dodecahedra, was found in all compounds. SPS preparation of Na24Si136 with different SPS current polarities …

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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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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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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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Validation Of An Improved Helical Diode Array And Dose Reconstruction Software Using Tg‐244 Datasets And Stringent Dose Comparison Criteria, Saeed Ahmed, Benjamin Nelms, Jakub Kozelka, Geoffrey Zhang, Eduardo Moros, Vladimir Feygelman Jan 2016

Validation Of An Improved Helical Diode Array And Dose Reconstruction Software Using Tg‐244 Datasets And Stringent Dose Comparison Criteria, Saeed Ahmed, Benjamin Nelms, Jakub Kozelka, Geoffrey Zhang, Eduardo Moros, Vladimir Feygelman

Physics Faculty Publications

The original helical ArcCHECK (AC) diode array and associated software for 3D measurement‐guided dose reconstruction were characterized and validated; however, recent design changes to the AC required that the subject be revisited. The most important AC change starting in 2014 was a significant reduction in the overresponse of diodes to scattered radiation outside of the direct beam, accomplished by reducing the amount of high‐Z materials adjacent to the diodes. This change improved the diode measurement accuracy, but in the process invalidated the dose reconstruction models that were assembled based on measured data acquired with the older version of the AC. …

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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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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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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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Tio2-Based Nanomaterials For Advanced Environmental And Energy-Related Applications, Xujie Lü, Baoyu Xia, Yefeng Yang, Hao Tang Jan 2016

Tio2-Based Nanomaterials For Advanced Environmental And Energy-Related Applications, Xujie Lü, Baoyu Xia, Yefeng Yang, Hao Tang

Physics Faculty Publications

No abstract provided.

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Correction: A Novel Approach For Detection And Quantification Of Magnetic Nanomarkers Using A Spin Valve Gmr-Integrated Microfluidic Sensor, J. Devkota, G. Kokkinis, T. Berris, M. Jamalieh, S. Cardoso, F. Cardoso, Hariharan Srikanth, Manh-Huong Phan, I. Giouroudi May 2015

Correction: A Novel Approach For Detection And Quantification Of Magnetic Nanomarkers Using A Spin Valve Gmr-Integrated Microfluidic Sensor, J. Devkota, G. Kokkinis, T. Berris, M. Jamalieh, S. Cardoso, F. Cardoso, Hariharan Srikanth, Manh-Huong Phan, I. Giouroudi

Physics Faculty Publications

We demonstrate the application of a spin valve giant magneto-resistance (GMR) integrated microfluidic sensor for the detection and quantification of superparamagnetic nanomarkers. A microfluidic channel containing the magnetic fluid, micro-conductors (MCs) for collection of magnetic markers and a spin valve GMR sensor for detecting the presence of magnetic stray field were integrated into a single chip and employed for detection of various concentrations of Nanomag-D beads of 250 nm diameter. The results show that the sensor is capable of detecting concentrations as low as 500 pg μl−1 of Nanomag-D beads and quantifying them in a linear scale over a …

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