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Full-Text Articles in Physical Sciences and Mathematics

Structure And Water Permeability Of Fully Hydrated Diphytanoylpc., Stephanie Tristram-Nagle, Dong Joo Kim, Nadia Akhunzada, Norbert Kucerka, John Mathai, John Katsaras, Mark Zeidel, John Nagle Aug 2014

Structure And Water Permeability Of Fully Hydrated Diphytanoylpc., Stephanie Tristram-Nagle, Dong Joo Kim, Nadia Akhunzada, Norbert Kucerka, John Mathai, John Katsaras, Mark Zeidel, John Nagle

Prof. Stephanie Tristram-Nagle Ph.D.

Diphytanoylphosphatidylcholine (DPhyPC) is a branched chain lipid often used for model membrane studies, including peptide/lipid interactions, ion channels and lipid rafts. This work reports results of volume measurements, water permeability measurements P(f), X-ray scattering from oriented samples, and X-ray and neutron scattering from unilamellar vesicles at T=30 degrees C. We measured the volume/lipid V(L)=1426+/-1A(3). The area/lipid was found to be 80.5+/-1.5A(2) when both X-ray and neutron data were combined with the SDP model analysis (Kucerka, N., Nagle, J.F., Sachs, J.N., Feller, S.E., Pencer, J., Jackson, A., Katsaras, J., 2008. Lipid bilayer structure determined by the simultaneous analysis of neutron and …


The Search For Quantum Critical Scaling In A Classical System, Jagat Lamsal, John Gaddy, Marcus Petrovic, Wouter Montfrooij, Thomas Vojta Jan 2009

The Search For Quantum Critical Scaling In A Classical System, Jagat Lamsal, John Gaddy, Marcus Petrovic, Wouter Montfrooij, Thomas Vojta

Physics Faculty Research & Creative Works

Order-disorder phase transitions in magnetic metals that occur at zero temperature have been studied in great detail. Theorists have advanced scenarios for these quantum critical systems in which the unusual response can be seen to evolve from a competition between ordering and disordering tendencies, driven by quantum fluctuations. Unfortunately, there is a potential disconnect between the real systems that are being studied experimentally, and the idealized systems that theoretical scenarios are based upon. Here we discuss how disorder introduces a change in morphology from a three-dimensional system to a collection of magnetic clusters, and we present neutron scattering data on …


Phase Transitions In Lafeaso: Structural, Magnetic, Elastic, And Transport Properties, Heat Capacity And Mössbauer Spectra, Michael A. Mcguire, Andrew D. Christianson, Athena S. Sefat, Brian C. Sales, Mark D. Lumsden, Rongying Jin, Edward Andrew Payzant, David G. Mandrus, Yanbing Luan, Veerle M. Keppens, Vijayalaksmi Varadarajan, Joseph W. Brill, Raphäel P. Hermann, M. T. Sougrati, Fernande Grandjean, Gary J. Long Sep 2008

Phase Transitions In Lafeaso: Structural, Magnetic, Elastic, And Transport Properties, Heat Capacity And Mössbauer Spectra, Michael A. Mcguire, Andrew D. Christianson, Athena S. Sefat, Brian C. Sales, Mark D. Lumsden, Rongying Jin, Edward Andrew Payzant, David G. Mandrus, Yanbing Luan, Veerle M. Keppens, Vijayalaksmi Varadarajan, Joseph W. Brill, Raphäel P. Hermann, M. T. Sougrati, Fernande Grandjean, Gary J. Long

Chemistry Faculty Research & Creative Works

We present results from a detailed experimental investigation of LaFeAsO, the parent material in the series of “FeAs” based oxypnictide superconductors. Upon cooling, this material undergoes a tetragonal-orthorhombic crystallographic phase transition at ~160 K followed closely by an antiferromagnetic ordering near 145 K. Analysis of these phase transitions using temperature dependent powder x-ray and neutron-diffraction measurements is presented. A magnetic moment of ~0.35µB per iron is derived from Mössbauer spectra in the low-temperature phase. Evidence of the structural transition is observed at temperatures well above the transition temperature (up to near 200 K) in the diffraction data as well …


The Decomposition Of Yba₂Cu₃O₇₋Δ Doped Into Ba₂Yruo₆, H. A. Blackstead, William B. Yelon, M. Kornecki, M. P. Smylie, P. J. Mcginn, Jinbo Yang, Qingsheng Cai, William Joseph James Feb 2008

The Decomposition Of Yba₂Cu₃O₇₋Δ Doped Into Ba₂Yruo₆, H. A. Blackstead, William B. Yelon, M. Kornecki, M. P. Smylie, P. J. Mcginn, Jinbo Yang, Qingsheng Cai, William Joseph James

Physics Faculty Research & Creative Works

One of the persistent criticisms of claims for observation of superconductivity in Ba2YRu1−uCuuO6 (O6) is that the diamagnetism is actually due to the decomposition of the material into YBa2Cu3O7−delta and other phases. We report a series of experiments in which YBa2Cu3O7−delta is doped into Ba2YRuO6 and carried through a series of sintering steps which were followed by magnetization, neutron diffraction, and scanning electron microscopy/microprobe measurements. It was found that the dopant YBa2Cu3O7−delta decomposed and failed to reform with cooling. It is concluded that the O6 phase is the stable high-temperature phase. The Cu released from the Y123 decomposition doped the …


Crystal And Electronic Structures Of The Complex Hydride Li₄Bn₃H₁₀, Jinbo Yang, X. J. Wang, Qingsheng Cai, William B. Yelon, William Joseph James Aug 2007

Crystal And Electronic Structures Of The Complex Hydride Li₄Bn₃H₁₀, Jinbo Yang, X. J. Wang, Qingsheng Cai, William B. Yelon, William Joseph James

Physics Faculty Research & Creative Works

The crystal structure of Li4BN3H10 was investigated using powder neutron diffraction with high sensitivity. The compound crystallizes in the cubic space group 213 with lattice parameters a=10.645 19(52) Å with an ordered arrangement of [NH2]−1 and [BH4]−1 anions in a molar ratio of 3:1. The bond lengths between the nearest nitrogen and hydrogen atoms are 1.04(4) and 1.14(4) Å. The bond angle between H(1)-N-H(2) is about 126(6)°, while those between H(3)-B-H(3) and H(3)-B-H(4) are about 109(6)°-110(7)°. There are three different Li sites surrounded by [NH2]−1 and [BH4]−1 anions in distorted tetrahedral configurations. The Li(3)-B and Li(3)-N bond distances are about …


Structure, Magnetic, And Transport Properties Of Ti-Substituted La₀.₇Sr₀.₃Mno₃, M. S. Kim, Jinbo Yang, Qingsheng Cai, X.-D. Zhou, William Joseph James, William B. Yelon, D. Buddhikot, Satish K. Malik, Paul Ernest Parris Jan 2005

Structure, Magnetic, And Transport Properties Of Ti-Substituted La₀.₇Sr₀.₃Mno₃, M. S. Kim, Jinbo Yang, Qingsheng Cai, X.-D. Zhou, William Joseph James, William B. Yelon, D. Buddhikot, Satish K. Malik, Paul Ernest Parris

Materials Science and Engineering Faculty Research & Creative Works

Ti-substituted perovskites La0.7Sr0.3Mn1-xTixO3 with 0 ≤ x ≤ 0.20, were investigated by neutron diffraction, magnetization, electric resistivity, and magnetoresistance (MR) measurements. All samples show a rhombohedral structure (space group R3c) from 10 K to room temperature. At room temperature, the cell parameters a,c and the unit cell volume increase with increasing Ti content. However, at 10 K, the cell parameter a has a maximum value for x = 0.10, and decreases for x > 0.10, while the unit cell volume remains nearly constant for x > 0.10. The average (Mn,Ti)-O bond length increases …


The Effect Of Cu-Doping On The Magnetic And Transport Properties Of La₀.₇Sr₀.₃Mno₃, M. S. Kim, Jinbo Yang, Qingsheng Cai, X.-D. Zhou, William B. Yelon, Paul Ernest Parris, William Joseph James Jan 2005

The Effect Of Cu-Doping On The Magnetic And Transport Properties Of La₀.₇Sr₀.₃Mno₃, M. S. Kim, Jinbo Yang, Qingsheng Cai, X.-D. Zhou, William B. Yelon, Paul Ernest Parris, William Joseph James

Physics Faculty Research & Creative Works

The effects of Cu-doping on the structural, magnetic, and transport properties of La0.7Sr0.3Mn1xCuxO3 (0<=x<=0.20) have been studied using neutron diffraction, magnetization, and magnetoresistance (MR) measurements. All samples show the rhombohedral structure with the R[overline 3]c space-group from 10 K to room temperature (RT). Neutron diffraction data suggest that some of the Cu ions have a Cu3+ state in these compounds. The substitution of Mn by Cu affects the MnO bond length and Mn-O-Mn bond angle resulting from the minimization of the distortion of the MnO6 octahedron. Resistivity measurements show that a metal to insulator transition occurs for the x>=0.15 samples. The x=0.15 sample shows the highest MR([approximate]80%), which might result from the co-existence of Cu3-Cu2+ and the dilution effect of Cu-doping on the double exchange interaction


A Magnetic And Mössbauer Spectral Study Of The Spin Reorientation In Ndfe₁₁Ti And Ndfe₁₁Th, Cristina Piquer, Fernande Grandjean, Olivier Isnard, Viorel Pop, Gary J. Long Jun 2004

A Magnetic And Mössbauer Spectral Study Of The Spin Reorientation In Ndfe₁₁Ti And Ndfe₁₁Th, Cristina Piquer, Fernande Grandjean, Olivier Isnard, Viorel Pop, Gary J. Long

Chemistry Faculty Research & Creative Works

The influence of hydrogenation on the spin reorientation in the presence of neodymium was investigated in NdFe11Ti and NdFe11TH. The magnetic properties of these compounds were determined by utilizing ac magnetic susceptibility, thermomagnetic, and iron-57 Mössbauer spectral analysis. It was found that the these compounds had two advantages as hard magnetic materials such as: a high iron content yielding high magnetization and a high Curie temperature. The investigation results show that these compounds undergo a spin-reorientation transition at ~185 K and at 100± K, from an axial magnetic phase at high temperature to a basal magnetic …


Electrical And Magnetotransport Properties Of Canted Antiferromagnet Dy₅Si₂Ge₂, R. Nirmala, V. Sankaranarayanan, K. Sethupathi, Zili Chu, William B. Yelon, V. Prasad, A. V. Morozkin, Satish K. Malik, S. V. Subramanyam Jan 2002

Electrical And Magnetotransport Properties Of Canted Antiferromagnet Dy₅Si₂Ge₂, R. Nirmala, V. Sankaranarayanan, K. Sethupathi, Zili Chu, William B. Yelon, V. Prasad, A. V. Morozkin, Satish K. Malik, S. V. Subramanyam

Physics Faculty Research & Creative Works

Summary form only given. Since the giant magnetocaloric effect is encountered in a ferromagnetic Gd5Si2Ge2 alloy near room temperature it is considered as a suitable material for magnetic refrigerator applications. Also a commensurate structural transition occurs at the magnetic transition temperature and there is a good correlation between the crystal structure and magnetic properties. Such observations have triggered numerous experimental studies on similar rare earth alloys and compounds. We have synthesized its Dy- analogue, namely, Dy5Si2Ge2 and have characterized it by means of room temperature X-ray diffraction, ac magnetic susceptibility (15 K - 300 K), electrical resistivity (at zero field …


A High Energy X-Ray And Neutron Scattering Study Of Iron Phosphate Glasses Containing Uranium, Mevlüt Karabulut, G. K. Marasinghe, C. S. Ray, Y. S. Badyal, M.-L. Saboungi, S. Shastri, D. Haeffner, George Daniel Waddill, D. E. Day Mar 2000

A High Energy X-Ray And Neutron Scattering Study Of Iron Phosphate Glasses Containing Uranium, Mevlüt Karabulut, G. K. Marasinghe, C. S. Ray, Y. S. Badyal, M.-L. Saboungi, S. Shastri, D. Haeffner, George Daniel Waddill, D. E. Day

Materials Science and Engineering Faculty Research & Creative Works

The atomic structure of iron phosphate glasses containing uranium has been studied by complementary neutron and x-ray scattering techniques. by combining x-ray and neutron structure factors, detailed information about different pair interactions has been obtained. Most of the basic structural features such as coordination numbers and O-O and P-O distances in uranium containing glasses are the same as those in the base glass of batch composition 40Fe2O3-60P2O5 (mol %). However, the Fe-O distances change slightly with the addition of uranium. The observed structural parameters support a structural model in which the waste elements occupy voids in the Fe-O-P network, hence, …


Neutron Diffraction And Magnetic Studies Of Nd₂Fe₁₇₋ₓtₓ (T=Si, Mn) Alloys, William B. Yelon, Z. Hu, Mingxing Chen, H. Luo, F. Pourarian, Peter C. Ezekwenna, G. K. Marasinghe, K. H. J. Buschow, D. P. Middleton, William Joseph James Jan 1996

Neutron Diffraction And Magnetic Studies Of Nd₂Fe₁₇₋ₓtₓ (T=Si, Mn) Alloys, William B. Yelon, Z. Hu, Mingxing Chen, H. Luo, F. Pourarian, Peter C. Ezekwenna, G. K. Marasinghe, K. H. J. Buschow, D. P. Middleton, William Joseph James

Physics Faculty Research & Creative Works

We have carried out neutron and magnetic studies on Nd2Fe17-xTx (T=Si, Mn) alloys. the unit cell of the compounds contracts with both Si and Mn substitution. Si atoms avoid the 6c site, prefer the 18h site strongly, fill the 9d site steadily and fill the 18f site only at relatively high Si concentration. Mn atoms avoid the 9d sites but prefer the 6c site strongly, while the 18f site and 18h site fill slowly. the Si site occupancies appear to be dominated by the crystal environment while the Mn site occupancies are dominated by steric …


Neutron Diffraction Studies Of Erni₅₋ₓcoₓ (X=0.68, 1.68, 2.26) Alloys, Z. Zu, William B. Yelon, G. K. Marasinghe, William Joseph James Jan 1995

Neutron Diffraction Studies Of Erni₅₋ₓcoₓ (X=0.68, 1.68, 2.26) Alloys, Z. Zu, William B. Yelon, G. K. Marasinghe, William Joseph James

Physics Faculty Research & Creative Works

ErNi5-xCox alloys were prepared by RF induction melting and analyzed using neutron powder diffraction. Rietveld analysis neutron diffraction data indicates the unit cell volume increases with Co content while the a and c lattice parameters show different dependencies on the composition. the Co atoms show higher affinity for the 3g sites than for the 2c sites. the Co sublattice tends to couple antiferromagnetically to the Er sublattice. the easy magnetization direction is along the c axis.


Neutron Investigations Of Novel Magnetic Phases, William B. Yelon Jan 1995

Neutron Investigations Of Novel Magnetic Phases, William B. Yelon

Physics Faculty Research & Creative Works

Recent years have seen a renewed search for Fe based permanent magnets, spurred by the discovery of Nd2Fe14B and interstitially modified rare-earth iron binaries. The insights derived from those compounds have suggested a number of routes to the development of such systems, including selective site substitution and combinations of site substitution and interstitial modification. Neutron diffraction is an essential component of this work, since it provides systematic information about the location of substitutional and interstitial atoms, and about the effects these changes have on the magnetic interactions in the systems of interest


Layer-By-Layer Growth Of Solid Argon Films On Graphite As Studied By Neutron Diffraction, J. Z. Larese, Q. M. Zhang, L. Passell, J. M. Hastings, John R. Dennison, H. Taub Sep 1989

Layer-By-Layer Growth Of Solid Argon Films On Graphite As Studied By Neutron Diffraction, J. Z. Larese, Q. M. Zhang, L. Passell, J. M. Hastings, John R. Dennison, H. Taub

All Physics Faculty Publications

The layer-by-layer growth of solid argon films on graphite at T=10 K is studied using elastic neutron diffraction. The growth is characterized by individual layers with commensurate in-plane lattice constants. As the coverage is increased beyond two layers, evidence of the coexistence of ABC and ABA stacking is apparent, with the ABC sequence dominating as the film thickens. A continuous decrease in the Debye-Waller factor also occurs as the film thickness grows, indicating a crossover from two-dimensional to three-dimensional behavior. As the coverage is increased beyond about four nominal layers, there is evidence of bulk crystallite formation. The diffraction results …