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Search Results: 1 - 10 of 286642 matches for " W. R. Branford "
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MALTS: A tool to simulate Lorentz Transmission Electron Microscopy from micromagnetic simulations
S. K. Walton,K. Zeissler,W. R. Branford,S. Felton
Physics , 2012,
Abstract: Here we describe the development of the MALTS software which is a generalised tool that simulates Lorentz Transmission Electron Microscopy (LTEM) contrast of thin magnetic nanostructures. Complex magnetic nanostructures typically have multiple stable domain structures. MALTS works in conjunction with the open access micromagnetic software Object Oriented Micromagnetic Framework or MuMax. Magnetically stable trial magnetisation states of the object of interest are input into MALTS and simulated LTEM images are output. MALTS computes the magnetic and electric phases accrued by the transmitted electrons via the Aharonov-Bohm expressions. Transfer and envelope functions are used to simulate the progression of the electron wave through the microscope lenses. The final contrast image due to these effects is determined by Fourier Optics. Similar approaches have been used previously for simulations of specific cases of LTEM contrast. The novelty here is the integration with micromagnetic codes via a simple user interface enabling the computation of the contrast from any structure. The output from MALTS is in good agreement with both experimental data and published LTEM simulations. A widely-available generalized code for the analysis of Lorentz contrast addresses is a much needed step towards the use of LTEM as a standardized laboratory technique.
Structural, magnetic and transport properties of thin films of the Heusler alloy Co2MnSi
L. J. Singh,Z. H. Barber,Y. Miyoshi,Y. Bugoslavsky,W. R. Branford,L. F. Cohen
Physics , 2003, DOI: 10.1063/1.1690868
Abstract: Thin films of Co2MnSi have been grown on a-plane sapphire substrates from three elemental targets by dc magnetron co-sputtering. These films are single phase, have a strong (110) texture and a saturation magnetization of 4.95 uB/formula unit at 10 K. Films grown at the highest substrate temperature of 715 K showed the lowest resistivity (47 uOhm cm at 4.2 K) and the lowest coercivity (18 Oe). The spin polarization of the transport current was found to be of the order of 54% as determined by point contact Andreev reflection spectroscopy. A decrease in saturation magnetization with decreasing film thickness and different transport behaviour in thinner films indicate a graded disorder in these films grown on non-lattice matched substrates.
High field magneto-transport in high mobility gated InSb/InAlSb quantum well heterostructures
A. M. Gilbertson,W. R. Branford,M. Fearn,L. Buckle,P. D. Buckle,T. Ashley,L. F. Cohen
Physics , 2009, DOI: 10.1103/PhysRevB.79.235333
Abstract: We present high field magneto-transport data from a range of 30nm wide InSb/InAlSb quantum wells. The low temperature carrier mobility of the samples studied ranged from 18.4 to 39.5 m2V-1s-1 with carrier densities between 1.5x1015 and 3.28x1015 m-2. Room temperature mobilities are reported in excess of 6 m2V-1s-1. It is found that the Landau level broadening decreases with carrier density and beating patterns are observed in the magnetoresistance with non-zero node amplitudes in samples with the narrowest broadening despite the presence of a large g-factor. The beating is attributed to Rashba splitting phenomenon and Rashba coupling parameters are extracted from the difference in spin populations for a range of samples and gate biases. The influence of Landau level broadening and spin-dependent scattering rates on the observation of beating in the Shubnikov-de Haas oscillations is investigated by simulations of the magnetoconductance. Data with non-zero beat node amplitudes are accompanied by asymmetric peaks in the Fourier transform, which are successfully reproduced by introducing a spin-dependent broadening in the simulations. It is found that the low-energy (majority) spin up state suffers more scattering than the high-energy (minority) spin down state and that the absence of beating patterns in the majority of (lower density) samples can be attributed to the same effect when the magnitude of the level broadening is large.
CVD of CrO2: towards a lower temperature deposition process
P. M. Sousa,S. A. Dias,A. J. Silvestre,O. Conde,B. Morris,K. A. Yates,W. R. Branford,L. F. Cohen
Physics , 2007, DOI: 10.1002/cvde.200604233
Abstract: We report on the synthesis of highly oriented a-axis CrO2 films onto (0001) sapphire by atmospheric pressure CVD from CrO3 precursor, at growth temperatures down to 330 degree Celsius, i.e. close to 70 degrees lower than in published data for the same chemical system. The films keep the high quality magnetic behaviour as those deposited at higher temperature, which can be looked as a promising result in view of their use with thermally sensitive materials, e.g. narrow band gap semiconductors.
R.W. Burchfield. The New Fowler's Modern English Usage
Bill Branford
Lexikos , 2012, DOI: 10.5788/8-1-961
Abstract: Review of R.W. Burchfield. The New Fowler's Modern English Usage Resensie van R.W. Burchfield. The New Fowler's Modern English Usage
Solid dispersions in the form of electrospun core-sheath nanofibers
Yu DG, Zhu LM, Branford-White CJ, Yang JH, Wang X, Li Y, Qian W
International Journal of Nanomedicine , 2011, DOI: http://dx.doi.org/10.2147/IJN.S27468
Abstract: lid dispersions in the form of electrospun core-sheath nanofibers Original Research (4087) Total Article Views Authors: Yu DG, Zhu LM, Branford-White CJ, Yang JH, Wang X, Li Y, Qian W Published Date December 2011 Volume 2011:6 Pages 3271 - 3280 DOI: http://dx.doi.org/10.2147/IJN.S27468 Deng-GuangYu1, Li-Min Zhu2, Christopher J Branford-White3, Jun-He Yang1, Xia Wang1, Ying Li1, Wei Qian1 1School of Materials Science and Engineering, University of Shanghai for Science and Technology; 2College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, People's Republic of China; 3Faculty of Life Sciences, London Metropolitan University, London, United Kingdom Background: The objective of this investigation was to develop a new type of solid dispersion in the form of core-sheath nanofibers using coaxial electrospinning for poorly water-soluble drugs. Different functional ingredients can be placed in various parts of core-sheath nanofibers to improve synergistically the dissolution and permeation properties of encapsulated drugs and to enable drugs to exert their actions. Methods: Using acyclovir as a model drug, polyvinylpyrrolidone as the hydrophilic filament-forming polymer matrix, sodium dodecyl sulfate as a transmembrane enhancer, and sucralose as a sweetener, core-sheath nanofibers were successfully prepared, with the sheath part consisting of polyvinylpyrrolidone, sodium dodecyl sulfate, and sucralose, and the core part composed of polyvinylpyrrolidone and acyclovir. Results: The core-sheath nanofibers had an average diameter of 410 ± 94 nm with a uniform structure and smooth surface. Differential scanning calorimetry and x-ray diffraction results demonstrated that acyclovir, sodium dodecyl sulfate, and sucralose were well distributed in the polyvinylpyrrolidone matrix in an amorphous state due to favoring of second-order interactions. In vitro dissolution and permeation studies showed that the core-sheath nanofiber solid dispersions could rapidly release acyclovir within one minute, with an over six-fold increased permeation rate across the sublingual mucosa compared with that of crude acyclovir particles. Conclusion: The study reported here provides an example of the systematic design, preparation, characterization, and application of a novel type of solid dispersion consisting of multiple components and structural characteristics.
Radiative pi0 photoproduction on protons in the Delta+(1232) region
S. Schumann,B. Boillat,E. J. Downie,P. Aguar-Bartolomé,J. Ahrens,J. R. M. Annand,H. J. Arends,R. Beck,V. Bekrenev,A. Braghieri,D. Branford,W. J. Briscoe,J. W. Brudvik,S. Cherepnya,R. Codling,P. Drexler,L. V. Fil'kov,D. I. Glazier,R. Gregor,E. Heid,D. Hornidge,O. Jahn,V. L. Kashevarov,R. Kondratiev,M. Korolija,M. Kotulla,D. Krambrich,B. Krusche,M. Lang,V. Lisin,K. Livingston,S. Lugert,I. J. D. MacGregor,D. M. Manley,M. Martinez-Fabregate,J. C. McGeorge,D. Mekterovic,V. Metag,B. M. K. Nefkens,A. Nikolaev,R. Novotny,M. Ostrick,R. O. Owens,P. Pedroni,A. Polonski,S. N. Prakhov,J. W. Price,G. Rosner,M. Rost,T. Rostomyan,D. Sober,A. Starostin,I. Supek,C. M. Tarbert,A. Thomas,M. Unverzagt,Th. Walcher,D. P. Watts,F. Zehr
Physics , 2010, DOI: 10.1140/epja/i2010-10925-y
Abstract: The reaction gamma p -> p pi0 gamma' has been measured with the Crystal Ball / TAPS detectors using the energy-tagged photon beam at the electron accelerator facility MAMI-B. Energy and angular differential cross sections for the emitted photon gamma' and angular differential cross sections for the pi0 have been determined with high statistics in the energy range of the Delta+(1232) resonance. Cross sections and the ratio of the cross section to the non-radiative process gamma p -> p pi0 are compared to theoretical reaction models, having the anomalous magnetic moment kappa_Delta+ as free parameter. As the shape of the experimental distributions is not reproduced in detail by the model calculations, currently no extraction of kappa_Delta+ is feasible.
Determination of the Dalitz plot parameter alpha for the decay eta->3pi^0 with the Crystal Ball at MAMI-B
M. Unverzagt,P. Aguar-Bartolome,J. Ahrens,J. R. M. Annand,H. J. Arends,R. Beck,V. Bekrenev,B. Boillat,A. Braghieri,D. Branford,W. J. Briscoe,J. W. Brudvik,S. Cherepnya,R. Codling,E. J. Downie,L. V. Filkov,D. I. Glazier,R. Gregor,E. Heid,D. Hornidge,O. Jahn,V. L. Kashevarov,R. Kondratiev,M. Korolija,M. Kotulla,D. Krambrich,B. Krusche,M. Lang,V. Lisin,K. Livingston,S. Lugert,I. J. D. MacGregor,D. M. Manley,M. Martinez-Fabregate,J. C. McGeorge,D. Mekterovic,V. Metag,B. M. K. Nefkens,A. Nikolaev,R. Novotny,R. O. Owens,P. Pedroni,A. Polonski,S. N. Prakhov,J. W. Price,G. Rosner,M. Rost,T. Rostomyan,S. Schumann,D. Sober,A. Starostin,I. Supek,C. M. Tarbert,A. Thomas,Th. Walcher,D. P. Watts,F. Zehr
Statistics , 2008, DOI: 10.1140/epja/i2008-10710-7
Abstract: A precise measurement of the Dalitz plot parameter, alpha, for the eta->3pi^0 decay is presented. The experiment was performed with the Crystal Ball and TAPS large acceptance photon detectors at the tagged photon beam facility of the MAMI-B electron accelerator in Mainz. High statistics of 1.8*10^6 eta->3pi^0 events were obtained, giving the result alpha = -0.032 +/- 0.002(stat) +/- 0.002(syst).
Determination of the η mass with the Crystal Ball at MAMI-B
A. Nikolaev,P. Aguar-Bartolomé,J. Ahrens,J. R. M. Annand,H. J. Arends,R. Beck,V. Bekrenev,B. Boillat,A. Braghieri,D. Branford,W. J. Briscoe,J. W. Brudvik,S. Cherepnya,R. Codling,M. Dehn,E. J. Downie,L. V. Fil'kov,D. I. Glazier,R. Gregor,E. Heid,D. Hornidge,O. Jahn,A. Jankowiak,K. -H. Kaiser,V. L. Kashevarov,R. Kondratiev,M. Korolija,M. Kotulla,D. Krambrich,B. Krusche,M. Lang,V. Lisin,K. Livingston,U. Ludwig-Mertin,S. Lugert,I. J. D. MacGregor,D. M. Manley,M. Martinez-Fabregate,J. C. McGeorge,D. Mekterovic,V. Metag,B. M. K. Nefkens,R. Novotny,R. O. Owens,P. Pedroni,A. Polonski,S. N. Prakhov,J. W. Price,A. Reiter,G. Rosner,M. Rost,T. Rostomyan,S. Schumann,D. Sober,A. Starostin,I. Supek,C. M. Tarbert,A. Thomas,M. Unverzagt,Th. Walcher,D. P. Watts,F. Zehr
Statistics , 2012,
Abstract: A new precise determination of the {\eta} meson mass is presented. It is based on a measurement of the threshold for the {\gamma}p -> p{\eta} reaction using the tagger focal-plane microscope detector at the MAMI-B facility in Mainz. The tagger microscope has a higher energy resolution than the standard tagging spectrometer and, hence, allowed an improvement in the accuracy compared to the previous {\eta} mass measurement at MAMI-B. The result m{\eta} = (547.851 +- 0.031 stat. +- 0.062 syst.) MeV agrees very well with the precise values of the NA48, KLOE and CLEO collaborations and deviates by about 5{\sigma} from the smaller, but also very precise value obtained by the GEM collaboration at COSY.
Size Dependent Competition in Centric Diatoms as a Function of Nitrogen and Silicon Availability  [PDF]
Paul D. van Ruth, Jian G. Qin, Alan J. Branford
Open Journal of Marine Science (OJMS) , 2012, DOI: 10.4236/ojms.2012.21005
Abstract: Size dependent competition was examined in two marine centric diatoms, Coscinodiscus sp. and Thalassiosira rotula at various, and Si concentrations. The growth responses for both species to nutrient levels were evaluated using two forms of nitrogen (NH4 and NO3) and silicon in both monoculture and mixed culture conditions. Under single species culture, the impact of Si did not depend on N forms for both diatoms. The increase of NH4-N enhanced the growth of Coscinodiscus, but did not affect T. rotula. When NO3-N was the nitrogen source, cell densities of both species were significantly enhanced by increasing Si concentrations, but only T. rotula density was affected by increasing N concentration. When Coscinodiscus sp. and T. rotula grew in the same culture, Coscinodiscus sp. dominated in both N forms. The scale of the dominance of Coscinodiscus sp. over T. rotula increased with decreasing N and Si concentrations. In the competition experiment, when was the N source, both Coscinodiscus sp. and T. rotula were signifi- cantly affected by changes in N concentration, but only T. rotula was affected by Si. When NO3 was the N source, neither Coscinodiscus sp. nor T. rotula was affected by Si, but T. rotula was enhanced by N levels. Regardless the N form, the impact of Si on neither Coscinodiscus sp. nor T. rotula depended on N concentration. Our results indicate that large diatom species have a competitive advantage over small species, and both large and small species were sensitive to NH4-N limitation, but the small species was more sensitive to NO3-N limitation than the large species.
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