Physics Commons^™

Vibrational Properties Of Ferroelectric Β-Vinylidene Fluoride Polymers And Oligomers, Serge M. Nakhmanson, Rafal Korlacki, J. Travis Johnston, Stephen Ducharme, Zhongxin Ge, James M. Takacs

Stephen Ducharme Publications

We utilize a plane-wave density-functional theory approach to investigate the vibrational properties of the all-trans ferroelectric phase of poly(vinylidene fluoride) (β-PVDF) showing that its stable state corresponds to the Ama2 structure with ordered dihedral tilting of the VDF monomers along the polymer chains. We then combine our theoretical analysis with IR spectroscopy to examine vibrations in oligomer crystals that are structurally related to the β-PVDF phase. We demonstrate that these materials—which can be grown in a highly crystalline form—exhibit IR activity similar to that of β-PVDF, making them an attractive choice for the studies of electroactive phenomena and phase transitions …

Why Ferroelectric Polyvinylidene Fluoride Is Special, Matt Poulsen, Stephen Ducharme

Stephen Ducharme Publications

Ferroelectric polymers entail a number of constraints, which together limit the useful compositional variations. These constraints include the following: a stable molecular dipole moment, compact crystal structure, conformational flexibility, and minimal steric hindrance. They are well satisfied by the prototype ferroelectric polymer, polyvinylidene fluoride, and yet almost every other conceivable molecular structure is limited by comparison.

Probing Equilibrium By Nonequilibrium Dynamics: Aging In Co/Cr Superlattices, Tathagata Mukherjee, M. Pleimling, Christian Binek

Christian Binek Publications

Magnetization relaxation is investigated in a structurally ordered magnetic Co/Cr superlattice. Tailored nanoscale periodicity creates mesoscopic spatial magnetic correlations with slow relaxation dynamics when quenching the system into a nonequilibrium state. Magnetization transients are measured after exposing the heterostructure to a magnetic set field for various waiting times. Scaling analysis reveals an asymptotic powerlaw behavior in accordance with a full aging scenario. The temperature dependence of the relaxation exponent shows pronounced anomalies at the equilibrium phase transitions of the antiferromagnetic superstructure and the ferromagnetic to paramagnetic transition of the Co layers. The latter leaves only weak fingerprints in the equilibrium …

Ab Initio Calculations And Ellipsometry Measurements Of The Optical Properties Of The Layered Semiconductor In4Se3, L. Makinistian, E. A. Albanesi, N. V. Gonzalez Lemus, A. G. Petukhov, D. Schmidt, Eva Schubert, M. Schubert, Yaroslav B. Losovyj, P. Galiy, Peter A. Dowben

Peter Dowben Publications

In this work, we present a thorough study of the optical properties of the layered orthorhombic compound In₄Se₃. The dielectric function—real and imaginary parts, the complex refraction index, the reflectivity, the absorption coefficient, and the conductivity of In₄Se₃ were calculated with the inclusion of the spin-orbit interaction, using an ab initio FP-LAPW method based on DFT. Also, generalized ellipsometry was employed for more precise measurement of the anisotropic dielectric functions for polarization along crystal a, b, and c axes of orthorhombic absorbing In₄Se₃ single crystals cut approximately parallel to …

The Local Structure Of Transition Metal Doped Semiconducting Boron Carbides, Jing Liu, Guangfu Luo, Wai-Ning Mei, Orhan Kizilkaya, Eric D. Shepherd, Jennifer I. Brand, Peter A. Dowben

Peter Dowben Publications

Transition metal doped boron carbides produced by plasma enhanced chemical vapour deposition of orthocarborane (closo-1,2-C₂B₁₀H₁₂) and 3d metal metallocenes were investigated by performing K-edge extended x-ray absorption fine structure and x-ray absorption near edge structure measurements. The 3d transition metal atom occupies one of the icosahedral boron or carbon atomic sites within the icosahedral cage. Good agreement was obtained between experiment and models for Mn, Fe and Co doping, based on the model structures of two adjoined vertex sharing carborane cages, each containing a transition metal. The local spin configurations of all …

Double Parton Interactions In Γ = 3 Jet Events In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We have used a sample of γ + 3 jets events collected by the D0 experiment with an integrated luminosity of about 1 fb^-1 to determine the fraction of events with double parton scattering (f_DP) in a single pp collision at √s = 1.96 TeV. The DP fraction and effective cross section (τ_eff ), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in p_T) jet transverse momentum p^jet2_T within the range 15 ≤ p^jet2_T ≤ …

Search For Higgs Boson Production In Dilepton And Missing Energy Final States With 5.4 Fb-1 Of Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

A search for the standard model Higgs boson is presented using events with two charged leptons and large missing transverse energy selected from 5.4 fb^-1 of integrated luminosity in pp collisions at √s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron collider. No significant excess of events above background predictions is found, and observed (expected) upper limits at 95% confidence level on the rate of Higgs boson production are derived that are a factor of 1.55 (1.36) above the predicted standard model cross section at m_H = 165 GeV.

Combination Of Tevatron Searches For The Standard Model Higgs Boson In The W+W- Decay Mode, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We combine searches by the CDF and D0 Collaborations for a Higgs boson decaying to W⁺W^-. The data correspond to an integrated total luminosity of 4.8 (CDF) and 5.4 (D0) fb^-1 of pp collisions at √s = 1.96 TeV at the Fermilab Tevatron collider. No excess is observed above background expectation, and resulting limits on Higgs boson production exclude a standard model Higgs boson in the mass range 162–166 GeV at the 95% C.L.

Studies Of Aspect Angle Dependence Of Plasma Turbulence At Haarp, Nargis Adham

Master's Theses and Doctoral Dissertations

We report the results from a recent series of campaigns employing the HAARP HF transmitter to generate and study strong Langmuir turbulence (SLT) in the interaction region of overdense ionospheric plasma. Diagnostics included the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the Super DARN-Kodiak HF radar, and HF receivers to record stimulated electromagnetic emissions (SEE). Short pulse, low duty cycle experiments demonstrate control and suppression of artificial field-aligned irregularities (AFAI). This allows the isolation of ponderomotive plasma turbulence effects. Plasma line spectra exhibit a marked dependence on the aspect angle of the HF pump beam and the pointing of …

Internal Magnetic Structure Of Magnetite Nanoparticles At Low Temperature, Kathryn L. Krycka, Julie A. Borchers, R.A. Booth, C.R. Hogg, Yumi Ijiri, W.C. Chen, S.M. Watson, M. Laver, T.R. Gentile, S. Harris

Faculty & Staff Scholarship

Small-angle neutron scattering with polarization analysis reveals that Fe3O4 nanoparticles with 90 Å diameters have ferrimagnetic moments significantly reduced from that of bulk Fe3O4 at 10 K, nominal saturation. Combined with previous results for an equivalent applied field at 200 K, a core-disordered shell picture of a spatially reduced ferrimagnetic core emerges, even well below the bulk blocking temperature. Zero-field cooling suggests that this magnetic morphology may be intrinsic to the nanoparticle, rather than field induced, at 10 K.

A Case Study On \Sigma \Lambda Conversion In P-Shell Hypernuclei, Masroor Bukhari

Turkish Journal of Physics

The important process of \Sigma-\Lambda conversion is presented and discussed in this report and a case example has been presented reviewing some cross sections and decay widths calculated for the process in a p-shell hypernucleus in recent studies.

Influence Of The Nitrogen Concentration On The Electrical Characteristic Of Hydrogenated Amorphous Silicon Nitride (A-Sin_X:H) Based Schottky Diodes, İlker Ay, Hüseyi̇n Tolunay

Turkish Journal of Physics

In this study, the Schottky diode characteristic of hydrogenated amorphous silicon nitride (a-SiN_x:H) samples containing various amounts of nitrogen have been investigated via both I-V and C-V measurements. From forward bias I-V measurements in the dark, the barrier height of samples (\phi_{B0}), ideality factor (\eta ), modified Richardson constant (A^\ast) and series resistances (R_s) have been obtained as the function of temperature for different nitrogen content. In addition, forward and reverse bias current ratios (I_f/I_r) at V~=~1 volt have been investigated as the function of temperature for different nitrogen content. Light sensitivity of the samples has also been investigated under …

Photocurrent And Surface Recombination Mechanisms In The In_Xga_{1-X}N\Slashgan Different-Sized Quantum Dot Solar Cells, Hossein Movla, Foozieh Sohrabi, Jafar Fathi, Hassan Babaei, Arash Nikniazi, Khadije Khalili, Nima Es'haghi Gorji

Turkish Journal of Physics

We present a p-i-n structured solar cell with stacked layers of In_xGa_{1-x}N Quantum Dots (QDs) with different indium composition. The photocurrent and surface recombination processes are investigated in the i-region. We have shown that the QDs in the i-region can play the role of both generation or recombination centers. The photocurrent has been calculated by self-consistent method to solve continuity equation of charge carriers in the layers of the i-region. By changing the Indium composition in In_xGa_{1-x}N QDs, the band gap of QDs varies and therefore provides a considerable overlapping with solar spectrum. Proposed SC with different-sized QDs and different …

Structure And Optical Properties Of Cuals_2 Thin Films Prepared Via Chemical Bath Deposition, Tariq Alwan, Mushtak Jabbar

Turkish Journal of Physics

CuAlS_2 thin films of thicknesses 118 \pm 5 nm were deposited on glass substrates using chemical bath deposition technique. The details of the preparation method are well described. The method is relatively simple and is easily controlled and sufficient to produce large area and good adherence to the substrate films. Effect of annealing temperature T_a on the structure, and optical properties of CuAlS_2 films were investigated. The structures of the films were studied by X-ray diffraction and FTIR spectrophotometer. The optical properties of the films were ascertained by UV-VIS spectrophotometer (wavelengths ranging between 300 and 900 nm). The optical transmittance …

Weak Shear Study Of Galaxy Clusters By Simulated Gravitational Lensing, David Coss

Doctoral Dissertations

"Gravitational lensing has been simulated for numerical galaxy clusters in order to characterize the effects of substructure and shape variations of dark matter halos on the weak lensing properties of clusters. In order to analyze realistic galaxy clusters, 6 high-resolution Adaptive Refinement Tree N-body simulations of clusters with hydrodynamics are used, in addition to a simulation of one group undergoing a merger. For each cluster, the three-dimensional particle distribution is projected perpendicular to three orthogonal lines of sight, providing 21 projected mass density maps. The clusters have representative concentration and mass values for clusters in the concordance cosmology. Two gravitational …

A Study Of The Growth And Structure Of Chromium And Iron Oxide Films On Pd(001) Using X-Ray Photoelectron Diffraction And Low Energy Electron Diffraction, Tina Dhekial-Phukan

Doctoral Dissertations

"In this study, attempts were made to grow well-ordered chromium- and iron-oxide films on a Pd(001) surface, and two sample preparation techniques, the multilayer and the sequential growth techniques, were used to grow these transition metal oxide films. The study is a part of a larger project that aims to look into the interaction between metal substrates and the overlayers grown on them. Previous studies of oxide films on Ag(001) resulted in the growth of 4-fold and 3-fold symmetry oxide structures from the multilayer and sequential growth techniques respectively. The present investigation's goal was to study how the growth of …

Particle Swarm Optimization And Gravitational Wave Data Analysis: Performance On A Binary Inspiral Testbed, Yan Wang, Soumya Mohanty

Physics & Astronomy Faculty Publications

The detection and estimation of gravitational wave signals belonging to a parameterized family of waveforms requires, in general, the numerical maximization of a data-dependent function of the signal parameters. Because of noise in the data, the function to be maximized is often highly multimodal with numerous local maxima. Searching for the global maximum then becomes computationally expensive, which in turn can limit the scientific scope of the search. Stochastic optimization is one possible approach to reducing computational costs in such applications. We report results from a first investigation of the particle swarm optimization method in this context. The method is …

Search For Gravitational Waves From Compact Binary Coalescence In Ligo And Virgo Data From S5 And Vsr1, J. Abadie, B. P. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Volker Quetschke, Malik Rakhmanov, Joseph D. Romano

Physics & Astronomy Faculty Publications

We report the results of the first search for gravitational waves from compact binary coalescence using data from the Laser Interferometer Gravitational-Wave Observatory and Virgo detectors. Five months of data were collected during the Laser Interferometer Gravitational-Wave Observatory’s S5 and Virgo’s VSR1 science runs. The search focused on signals from binary mergers with a total mass between 2 and 35M⊙. No gravitational waves are identified. The cumulative 90%-confidence upper limits on the rate of compact binary coalescence are calculated for nonspinning binary neutron stars, black hole-neutron star systems, and binary black holes to be 8.7×10−3  yr−1 L−110, 2.2×10−3  yr−1 L−110, …

Spectroscopic Analysis Of Tungsten Oxide Thin Films For Sensor Applications, Jose Luis Enriquez Carrejo

Open Access Theses & Dissertations

The objective of this study is targeted toward improving the quality of pure tungsten oxide (WO3) for application to the detection of poisoning gases, especially of H2S. While pure WO3 is a recognized candidate for gas sensing, its characteristics are strongly dependent on the conditions and methods used in its deposition.

Samples of WO3 thin films analyzed in this work were grown on silicon and sapphire substrates using RF magnetron sputtering at a number of different substrate temperatures and Ar:O2 pressure ratios. The properties of the samples were investigated spectroscopically with the goal of determining how variations in the above …

An Ab-Initio Study Of The Elastic Properties Of Important Group Iv Diborides At High Temperatures, Manny Gonzales

Open Access Theses & Dissertations

Presented is an ab-initio Molecular Dynamics (MD) study, employing the Density Functional Theory (DFT), of the lattice parameter, thermal expansion coefficients and elastic constants of ZrB₂, TiB₂ and HfB₂ as a function of temperature. The MD trajectories provide the equilibrium lattice parameters at finite temperatures, and the gradient of the energy from these equilibrium solutions is then used to calculate the components of the stiffness tensor. The results for ZrB₂ are shown to agree well with reported experimental results for the lattice parameters and elastic constants as a function of temperature.

Spectroscopic Study Of The Inhibition Of Calcium Oxalate Calculi By Larrea Tridentata, Luis Alonso Pinales

Open Access Theses & Dissertations

The causes of urolithiasis include such influences as diet, metabolic disorders, and genetic factors which have been documented as sources that aggravate urinary calculi depositions and aggregations, and, implicitly, as causes of urolithiasis. This study endeavors to detail the scientific mechanisms involved in calcium oxalate calculi formation, and, more importantly, their inhibition under growth conditions imposed by the traditional medicinal approach using the herbal extract, Larrea tridentata. The calculi were synthesized without and with Larrea tridentata infusion by employing the single diffusion gel technique. A visible decrease in calcium oxalate crystal growth with increasing amounts of Larrea tridentata herbal infusion …

Far-Field Optical Nanoscopy Based On Continuous Wave Laser Stimulated Emission Depletion, C. Kuang, Wei Zhao, Guiren Wang

Faculty Publications

Stimulated emission depletion (STED) microscopy is one of the breakthrough technologies that belong to far-field optical microscopy and can achieve nanoscale spatial resolution. We demonstrate a far-field optical nanoscopy based on continuous wave lasers with different wavelengths, i.e., violet and green lasers for excitation and STED, respectively. Fluorescent dyes Coumarin 102 and Atto 390 are used for validating the depletion efficiency. Fluorescent nanoparticles are selected for characterizing the spatial resolution of the STED system. Linear scanning of the laser beams of the STED system along one line of a microscope slide, which is coated with the nanoparticles, indicates that a …

Parameters Of Reform And Unifification In Modern Japanese, R. Holzlöhner, S. M. Rochester, D. Bonaccini Calia, D. Budker, James M. Higbie, W. Hackenberg

Faculty Journal Articles

No abstract provided.

Classical Thermodynamics Of Particles In Harmonic Traps, Martin K. Ligare

Faculty Journal Articles

No abstract provided.

Modeling The Noble Metal/Tio2 (110) Interface With Hybrid Dft Functionals: A Periodic Electrostatic Embedded Cluster Model Study, Salai Cheettu Ammal, Andreas Heyden

Faculty Publications

The interaction of Aun and Ptn (n=2,3) clusters with the stoichiometric and partially reduced rutile TiO2 (110) surfaces has been investigated using periodic slab and periodic electrostatic embedded cluster models. Compared to Au clusters, Pt clusters interact strongly with both stoichiometric and reduced TiO2 (110) surfaces and are able to enhance the reducibility of the TiO2 (110) surface, i.e., reduce the oxygen vacancy formation energy. The focus of this study is the effect of Hartree–Fock exchange on the description of the strength of chemical bonds at the interface of Au/Pt clusters and the TiO2 (110) surface. Hartree–Fock exchange helps describing …

Dynamic Path Bifurcation For The Beckmann Reaction: Observation And Implication, H. Yamataka, M. Sato, H. Hasegawa, Salai Cheettu Ammal

Faculty Publications

The reaction of oximes to amides, known as the Beckmann rearrangement, may undergo fragmentation to form carbocations + nitriles instead of amides when the cations have reasonable stability. The reactions of oxime derivatives of 1-substituted-phenyl-2-propanones and 3-substituted-phenyl-2-butanones in aqueous solvents gave both rearrangement and fragmentation products, the ratio of which was dependent on substituents. Transition state (TS) optimizations and intrinsic reaction coordinate (IRC) calculations for the reaction of 1-phenyl-2-propanone oximes showed that there is a single TS for each substituted compound. The IRC path from the TS either led to a rearrangement product or a fragmentation product depending on the …

Unidirectional Nonlinear Pt-Symmetric Optical Structures, Hamidreza Ramezani, Tsampikos Kottos

Physics & Astronomy Faculty Publications

We show that nonlinear optical structures involving a balanced gain-loss profile can act as unidirectional optical valves. This is made possible by exploiting the interplay between the fundamental symmetries of parity (P) and time (T), with optical nonlinear effects. This unidirectional dynamics is specifically demonstrated for the case of an integrable PT-symmetric nonlinear system.

All-Sky Search For Gravitational-Wave Bursts In The First Joint Ligo-Geo-Virgo Run, J. Abadie, B. P. Abbott, Matthew Benacquista, Teviet Creighton, Mario C. Diaz, Soumya Mohanty, Soma Mukherjee, Malik Rakhmanov, Joseph D. Romano, Robert Stone

Physics & Astronomy Faculty Publications

We present results from an all-sky search for unmodeled gravitational-wave bursts in the data collected by the LIGO, GEO 600 and Virgo detectors between November 2006 and October 2007. The search is performed by three different analysis algorithms over the frequency band 50–6000 Hz. Data are analyzed for times with at least two of the four LIGO-Virgo detectors in coincident operation, with a total live time of 266 days. No events produced by the search algorithms survive the selection cuts. We set a frequentist upper limit on the rate of gravitational-wave bursts impinging on our network of detectors. When combined …

Investigating The Use Of Ranking Tasks To Improve Student Conceptual Understanding In An Introductory High School Physics Course, Matthew Joseph Harding

Dissertations and Theses @ UNI

The focus of this study was to determine whether the use of Ranking Tasks during study of physics could improve conceptual understanding for introductory high school physics students. The effectiveness of the treatment was evaluated by analyzing student performance on the Force Concept Inventory, and the Physics Class Attitudes Survey. As enrollment in introductory physics courses increases, and the variety of students studying physics broadens, instructors will be increasingly tasked with finding new instructional strategies that can benefit these student populations. Results of this study indicate promise for the implementation of Ranking Tasks for identifying student conceptual understanding in Newtonian …

Study Of The Numerical Modeling Of The Temperature Dependence Of The Dark Current In Charge Coupled Devices, Ralf Widenhorn, Ionel Tunaru, Erik Bodegom, Dan A. Iordache

Physics Faculty Publications and Presentations

As it is well known, the classical works of the Dark Current Spectroscopy method allow - using some not too accurate theoretical relations, but huge numbers of dark current values for thousands of pixels - the evaluation of a reduced number of basic impurities parameters. Unlike these works, this paper tries to obtain--by means of some better approximations of the Shockley-Read-Hall (SRH) model--more information about the studied impurities, as well as the study of the compatibility of the used theoretical model SRH relative to the experimental data. In this manner, both the compatibility SRH model with the studied experimental data …