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Magnetism Of Core-Shell Ti:Tio Nanoparticles, Xiaohui Wei, Ralph Skomski, Balamurugan Balasubramanian, David J. Sellmyer 2010 University of Nebraska-Lincoln

Magnetism Of Core-Shell Ti:Tio Nanoparticles, Xiaohui Wei, Ralph Skomski, Balamurugan Balasubramanian, David J. Sellmyer

Ralph Skomski Publications

Ti nanoparticles were produced using a cluster-deposition method. Ti:TiO core-shell structures were fabricated by partially oxidizing the surface of the Ti nanoparticles produced by a cluster-deposition system via multistep annealing at 250 °C in oxygen. X-ray diffraction and transmission-electron microscopy studies reveal an increase in the thickness of the TiO shell with increasing annealing time. The magnetic moment and the coercivity of the core-shell nanoparticles increase with the TiO shell thickness, which is consistent with homogenous bulk defects in TiO. The core-shell nanoparticles display an abnormal hysteresis loop, which probably reflects a combination of antiferromagnetic exchange and magnetocrystalline anisotropy.


Magnetic Anisotropy In Itinerant Magnets, Ralph Skomski, Arti Kashyap, A. Solanki, Axel Enders, David J. Sellmyer 2010 University of Nebraska-Lincoln

Magnetic Anisotropy In Itinerant Magnets, Ralph Skomski, Arti Kashyap, A. Solanki, Axel Enders, David J. Sellmyer

Ralph Skomski Publications

The structural dependence of the magnetocrystalline anisotropy of itinerant permanent magnets (or nanostructures of iron-series 3d elements) is investigated by model and tight-binding calculations. Magnetic nanostructures yield strong oscillations of the anisotropy as a function of the number of d electrons per atom, which can be tuned by alloying. While interatomic hopping is usually more important in metals than crystal-field interactions, we find substantial crystal-field corrections for some configurations, especially for the atomic square. Finally, we compare our results with Néel model.


Entropy Localization In Magnetic Compounds And Thin-Film Nanostructures, Ralph Skomski, Christian Binek, Steven A. Michalski, Tathagata Mukherjee, Axel Enders, David J. Sellmyer 2010 University of Nebraska-Lincoln

Entropy Localization In Magnetic Compounds And Thin-Film Nanostructures, Ralph Skomski, Christian Binek, Steven A. Michalski, Tathagata Mukherjee, Axel Enders, David J. Sellmyer

Ralph Skomski Publications

The effect of nanostructuring on the magnetic entropy of materials for room-temperature magnetic cooling is investigated by model calculations. The materials are structurally inhomogeneous with a large number of nonequivalent crystallographic sites. In the mean-field Heisenberg model, the entropy density is a unique function of the local magnetization so that the coupled set of nonlinear mean-field equations yields not only the magnetization but also the entropy density. Since most of the entropy is localized near grain boundaries, nanomagnetic cooling requires small feature sizes. Magnetic anisotropy is a substantial complication, even on a mean-field level, but the corresponding corrections are often ...


Magnetic Antiphase Domains In Co/Ru/Co Trilayers, Zhen Li, Ralph Skomski, Steven A. Michalski, Lanping Yue, Roger D. Kirby 2010 University of Nebraska-Lincoln

Magnetic Antiphase Domains In Co/Ru/Co Trilayers, Zhen Li, Ralph Skomski, Steven A. Michalski, Lanping Yue, Roger D. Kirby

Ralph Skomski Publications

Ultrathin Co/Ru/Co trilayers are investigated experimentally by magnetization curves and magnetic-force microscopy (MFM). Emphasis is on the domain-wall fine structure of antiphase domain walls in the films. The trilayers are produced by sputtering and consist of two Co layers of equal thickness (5 nm), exchange-coupled through a Ru layer of variable thickness. The sign and magnitude of the interlayer exchange are tuned by the thickness of the Ru interlayer. The exchange and its distribution are investigated by measurements of the static magnetization curves. For a Ru thickness of 0.4 nm, the exchange is predominantly antiferromagnetic and the ...


Alignment And Orientation Of Diatomic Molecules Induced By Polarized Electron Impact, Jack W. Maseberg, Timothy J. Gay 2010 University of Nebraska at Lincoln

Alignment And Orientation Of Diatomic Molecules Induced By Polarized Electron Impact, Jack W. Maseberg, Timothy J. Gay

Timothy J. Gay Publications

We report measurements of linear and circular fluorescence polarizations for molecular transitions in H2, D2, and N2 induced by spin-polarized electron impact. Circular polarizations resulting from some Fulcher-α transitions in H2 and D2 are found to be significant, while the null results from nitrogen’s second positive system are consistent with an earlier measurement by the Münster group. We compare this nitrogen data to that from our previous study of nitrogen’s first negative system. Emphasis is placed on understanding the mechanisms that cause the values of circular polarization from N2 to be relatively ...


A Low-Voltage Retarding-Field Mott Polarimeter For Photocathode Characterization, J.L. McCarter, M.L. Stutzman, K.W. Trantham, Timothy G. Anderson, A.M. Cook, Timothy J. Gay 2010 Thomas Jefferson National Accelerator Facility

A Low-Voltage Retarding-Field Mott Polarimeter For Photocathode Characterization, J.L. Mccarter, M.L. Stutzman, K.W. Trantham, Timothy G. Anderson, A.M. Cook, Timothy J. Gay

Timothy J. Gay Publications

Nuclear physics experiments at Thomas Jefferson National Accelerator Facility’s CEBAF rely on high polarization electron beams. We describe a recently commissioned system for prequalifying and studying photocathodes for CEBAF with a load-locked, low-voltage polarized electron source coupled to a compact retarding-field Mott polarimeter. The polarimeter uses simplified electrode structures and operates from 5 to 30 kV. The effective Sherman function for this device has been calibrated by comparison with the CEBAF 5 MeV Mott polarimeter. For elastic scattering from a thick gold target at 20 keV, the effective Sherman function is 0.201(5). Its maximum efficiency at 20 ...


Electron-Spin-Reversal Phenomenon In Optically Pumped Rubidium, E. B. Norrgard, D. Tupa, J. M. Dreiling, Timothy J. Gay 2010 University of Nebraska - Lincoln

Electron-Spin-Reversal Phenomenon In Optically Pumped Rubidium, E. B. Norrgard, D. Tupa, J. M. Dreiling, Timothy J. Gay

Timothy J. Gay Publications

We have studied the optical pumping of mixtures of Rb vapor and N2 buffer gas by laser light tuned to the D1 transition having a spectral width of ∼500 MHz. The Rb densities are of the order of 1013 cm−3, while the buffer-gas pressures range from 0.1 to 10 torr. As the frequency of the right-hand circularly polarized laser is varied across the D1 absorption profile, the electron spin polarization of the Rb is found to take on negative values for small negative values of pump detuning from the absorption profile center. This occurs for ...


Semiclassical Complex-Time Method For Tunneling Ionization: Molecular Suppression And Orientational Dependence, Gordon A. Gallup, Ilya I. Fabrikant 2010 University of Nebraska-Lincoln

Semiclassical Complex-Time Method For Tunneling Ionization: Molecular Suppression And Orientational Dependence, Gordon A. Gallup, Ilya I. Fabrikant

Gordon Gallup Publications

We apply a previously developed semiclassical complex time method to the calculation of tunneling ionization of several diatomic molecules and CO2.We investigate the presence or absence of the molecular suppression effect by calculating ionization rates of N2 versus Ar, O2 versus Xe, F2 versus Ar, and CO versus Kr. Comparisons with other theories, including the molecular-orbital-Ammosov-Delone-Krainov (MO-ADK) model and the strong-field approximation, are given. We also analyze the dependence of the ionization rate on the angle θF between the molecular axis and the field direction. The theoretical results agree quite well with experiment for ...


Use Biomedical Laboratories In Physics To Develop Student Reasoning, Robert G. Fuller 2010 Uinv. of Nebraska Lincoln

Use Biomedical Laboratories In Physics To Develop Student Reasoning, Robert G. Fuller

Robert G. Fuller Publications and Presentations

The results of the “intrinsic motivation for learning” work by Thomas Malone (1) can be combined with the “development of reasoning” work by Robert Karplus (2) to create introductory physics laboratories that feature biomedical applications of physics. This presentation will discuss the attributes of the work of Malone and Karplus and illustrate how they can work together to construct physics laboratories that encourage the development of reasoning by students as well as intrigue them with biomedical applications. A concrete example will be given in a six-week module “How Do We See Color?” that was developed as part of the Humanized ...


Expanding The Substantial Interactome Of Nemo Using Protein Microarrays., Beau J. Fenner, Michael Scannell, Jochen H M Prehn 2010 Royal College of Surgeons in Ireland

Expanding The Substantial Interactome Of Nemo Using Protein Microarrays., Beau J. Fenner, Michael Scannell, Jochen H M Prehn

Physiology and Medical Physics Articles

Signal transduction by the NF-kappaB pathway is a key regulator of a host of cellular responses to extracellular and intracellular messages. The NEMO adaptor protein lies at the top of this pathway and serves as a molecular conduit, connecting signals transmitted from upstream sensors to the downstream NF-kappaB transcription factor and subsequent gene activation. The position of NEMO within this pathway makes it an attractive target from which to search for new proteins that link NF-kappaB signaling to additional pathways and upstream effectors. In this work, we have used protein microarrays to identify novel NEMO interactors. A total of 112 ...


Interionic Energy Transfer In Y3Al5O12: Ce3+, Pr3+ Phosphor, Lei Wang, Xia Zhang, Zhendong Hao, Yongshi Luo, Jiahua Zhang, Xiao-Jun Wang 2010 Chinese Academy of Sciences

Interionic Energy Transfer In Y3Al5O12: Ce3+, Pr3+ Phosphor, Lei Wang, Xia Zhang, Zhendong Hao, Yongshi Luo, Jiahua Zhang, Xiao-Jun Wang

Physics Faculty Publications

We present an investigation of dynamical processes of nonradiative energy transfer (ET)between Ce3+ and Pr3+ , and between Pr3+ ions in Y3Al5O12:Ce3+ , Pr3+ phosphor.Photoluminescence spectroscopy and fluorescence decay patterns are studied as a function ofPr3+ and Ce3+ concentrations. The analysis based on Inokuti–Hirayama model indicates that the ET from the lowest 5d state of Ce3+ to the D12 state of Pr3+ , and the quenching of theD12 state through a cross relaxation involving Pr3+ ions in the ground state are both governed by electric dipole–dipole interaction. An increase in the Ce3+–Pr3+ ET rate followed by the ...


Electro-Optic And Magneto-Dielectric Properties Of Multifunctional Nitride And Oxide Materials, Ambesh Dixit 2010 Wayne State University

Electro-Optic And Magneto-Dielectric Properties Of Multifunctional Nitride And Oxide Materials, Ambesh Dixit

Wayne State University Dissertations

ABSTRACT

Materials that simultaneously exhibit different physical properties provide a rich area of research leading to the development of new devices. For example, materials having a strong coupling between charge and spin degrees of freedom are essential to realizing a new class of devices referred to generally as spintronics. However, these multifunctional systems pose new scientific challenges in understanding the origin and mechanisms for cross-control of different functionalities. The core of this Ph.D. dissertation deals with multifunctional nitride and oxide compound semiconductors as well as multiferroic magnetic oxide systems by investigating structural, optical, electrical, magnetic, magnetodielectric and magnetoelectric properties ...


A Search For The Sm Higgs Boson In The Process Zhllbb In 4.1/Fb Of Cdf Ii Data, Shalhout Zaki Shalhout 2010 Wayne State University

A Search For The Sm Higgs Boson In The Process Zhllbb In 4.1/Fb Of Cdf Ii Data, Shalhout Zaki Shalhout

Wayne State University Dissertations

This dissertation presents a search for the standard model (SM) Higgs boson in the associated production process ZH → l+l- bb using 4.1fb-1 of Tevatron collision data collected with the CDF II detector.

To increase the sensitivity to a ZH signal over previous CDF searches, we implement new electron and expanded b-jet identification algorithms.

We utilize neural network classifiers enhanced with matrix element probabilities, a b-jet identifying neural network, and multivariate jet energy corrections to maximize the separation of signal from SM backgrounds.

We employ three neural network classifiers separately optimized for each of our three b-tag categories ...


Proximity And Thickness Estimation Of Aluminum 3003 Alloy Metal Sheets Using Multi-Frequency Eddy Current Sensor, Sunil S. Kamanalu 2010 Wright State University

Proximity And Thickness Estimation Of Aluminum 3003 Alloy Metal Sheets Using Multi-Frequency Eddy Current Sensor, Sunil S. Kamanalu

Browse all Theses and Dissertations

The research work is focused on conducting a feasibility study on a new "non-contact" single probe dual coil inductive sensor for sensing the proximity and thickness of Aluminum (Al) 3003 alloy metal sheets, which is a non-magnetic metal. A bulk of the research and development work has already been done in the area of non-destructive testing (NDT) using eddy current technology targeted to various applications like corrosion detection, material thickness, material conductivity, etc. The research work presented in this thesis uses the prior research and development work completed in NDT as a platform for conducting this study to estimate proximity ...


Respiratory-Gated Imrt Quality Assurance With Motion In Two Dimensions, Michael Todd Massie 2010 Wright State University

Respiratory-Gated Imrt Quality Assurance With Motion In Two Dimensions, Michael Todd Massie

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Intensity modulated radiation therapy (IMRT) plans can be further customized to each patient with the use of a four-dimensional (4D) respiratorygated computed tomography (CT), with time being the fourth dimension. The 4D respiratory-gated CT allows for the internal margin (IM), the expansion of the tumor volume that accounts for physiologic motions, to be addressed in the treatment planning process and no longer assumes that the treatments will be delivered to a fixed or rigid patient anatomy. Delivering the IMRT plan with a gated technique limits the treatment to a duty cycle when the target motion is at a minimum.

The ...


Experimental Comparison Of Acr And Icamrl Magnetic Resonance Imaging Accreditation Protocols, Brock Andrew Prater 2010 Wright State University

Experimental Comparison Of Acr And Icamrl Magnetic Resonance Imaging Accreditation Protocols, Brock Andrew Prater

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Two primary accrediting bodies exist for magnetic resonance imaging systems: the American College of Radiology (ACR) and the Intersocietal Commission for the Accreditation of Magnetic Resonance Laboratories (ICAMRL), each of which defines specific standards for specific image quality criteria at which MRI images must be produced. An MRI clinic that wishes to show a commitment to image quality may do so by becoming accredited by one of these organizations of their choosing. The limits of these image criteria were compared to demonstrate the standards of each accrediting body. Images were produced that fell well within the standards of both accrediting ...


Temperature And Frequency Dependent Conduction Mechanisms Within Bulk Carbon Nanotube Materials, John Simmons Bulmer 2010 Wright State University

Temperature And Frequency Dependent Conduction Mechanisms Within Bulk Carbon Nanotube Materials, John Simmons Bulmer

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The resistance of three types of bulk carbon nanotube (CNT) materials (floating catalyst CNT yarn, forest grown CNT yarn, and super acid spun CNT fiber) was measured from room temperature to 900 C. Fitting the curves to established conduction equations for disordered materials, competing conduction mechanisms pertaining to the material could be determined. Floating catalyst CNT yarn displayed both semiconductive and metallic isotropic behavior with a resistance minimum, similar to the behavior of crystalline graphite. It was found that, at room temperature, the semiconducting contribution-most likely junctions between CNTs-accounted for 99.99% of the overall resistance. The resistance of forest ...


Ostwald Ripening Of Iron (Fe) Catalyst Nanoparticles On Aluminum Oxide Surfaces (Al2O3) For The Growth Of Carbon Nanotubes, Roberto I. Acosta 2010 Wright State University

Ostwald Ripening Of Iron (Fe) Catalyst Nanoparticles On Aluminum Oxide Surfaces (Al2O3) For The Growth Of Carbon Nanotubes, Roberto I. Acosta

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Theoretical models have proposed that the nucleation and growth mechanism of carbon nanotubes (CNTs) has been affected by the catalytic activity of transition metals. The catalyst behavior during growth has been mainly associated as the responsible mechanism for the termination of CNT growth. Although several hypotheses have been developed to explain this mechanism, is still today an unresolved phenomenon. It was recently shown that the Ostwald ripening of iron (Fe) nanoparticles played a dominant role in the termination of CNT growth. The Ostwald ripening mechanism was further investigated as a function of thermal annealing in Hydrogen (H2) for iron ...


Dosimetric Effects Near Implanted Vascular Access Ports Under External Electron Beam Radiation, David Coll Segarra 2010 Wright State University

Dosimetric Effects Near Implanted Vascular Access Ports Under External Electron Beam Radiation, David Coll Segarra

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Previous studies on dosimetry show important effects for metal vascular access ports for x-rays and electron beams and moderate to no effects for plastic ports for x-ray beams when ports are in the path of the beam. No previous studies exist regarding the effects of electron beams on vascular access ports other than for those made of metal although it has been suggested that electron beam attenuation through non-metal ports may be possible.

Measurements of relative ionization through the device and adjacent to the device anteriorly and laterally were taken. A clinical particle accelerator delivered typical clinical electron beams of ...


Using Solar Energy, Peter Talmage 2010 University of Massachusetts Amherst

Using Solar Energy, Peter Talmage

Science and Engineering Saturday Seminars

• Best energy source for the environment • It’s getting more economical every day • Easy to maintain • Cuts down on foreign oil imports


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