6,515 research outputs found
Increases in the Irreversibility Field and the Upper Critical Field of Bulk MgB2 by ZrB2 Addition
In a study of the influence of ZrB2 additions on the irreversibility field,
Birr and the upper critical field Bc2, bulk samples with 7.5 at. % ZrB2
additions were made by a powder milling and compaction technique. These samples
were then heated to 700-900C for 0.5 hours. Resistive transitions were measured
at 4.2 K and Birr and Bc2 values were determined. An increase in Bc2 from 20.5
T to 28.6 T and enhancement of Birr from 16 T to 24 T were observed in the ZrB2
doped sample as compared to the binary sample at 4.2 K. Critical field
increases similar to those found with SiC doping were seen at 4.2 K. At higher
temperatures, increases in Birr were also determined by M-H loop extrapolation
and closure. Values of Birr which were enhanced with ZrB2 doping (as compared
to the binary) were seen at temperatures up to 34 K, with Birr values larger
than those for SiC doped samples at higher temperatures. The transition
temperature, Tc, was then measured using DC susceptibility and a 2.5 K drop of
the midpoint of Tc was observed. The critical current density was determined
using magnetic measurements and was found to increase at all temperatures
between 4.2 K and 35 K with ZrB2 doping.Comment: 15 pages, 5 figs, 1 tabl
Hydrodynamic origin of diffusion in nanopores
We study the transport of a subcritical Lennard-Jones fluid in a cylindrical nanopore, using a combination of equilibrium and nonequilibrium as well as dual control volume grand canonical molecular dynamics methods. We show that all three techniques yield the same value of the transport coefficient for diffusely reflecting pore walls, even in the presence of viscous transport. We also demonstrate that the classical Knudsen mechanism is not manifested, and that a combination of viscous flow and momentum exchange at the pore wall governs the transport over a wide range of densities
Strange Quarks Nuggets in Space: Charges in Seven Settings
We have computed the charge that develops on an SQN in space as a result of
balance between the rates of ionization by ambient gammas and capture of
ambient electrons. We have also computed the times for achieving that
equilibrium and binding energy of the least bound SQN electrons. We have done
this for seven different settings. We sketch the calculations here and give
their results in the Figure and Table II; details are in the Physical Review
D.79.023513 (2009).Comment: Six pages, one figure. To appear in proceedings of the 2008 UCLA
coference on dark matter and dark energ
Integrated processing of peanut for the separation of major constituents
Bench-scale experiments were carried out on the processing of peanut by a new method. The decuticled kernels were pasted, and the paste was subjected to the Skipin process to recover approximately 30% oil; the residual paste was made into a dispersion at 10.0 pH and clarified to get a carbohydrate meal (15.7% moisture-free); the clarified dispersion was centrifuged to obtain another 12% fat and the remaining dispersion was acidified to get the protein (21.9% moisture-free). Fifteen batches of 100-1b. (45.4 kg.) each have been processed, and the reproducibility of the yields has been ascertained. The scope for increasing the oil yield and for improving protein quality is discussed
Extremal extensions of entanglement witnesses: Unearthing new bound entangled states
In this paper, we discuss extremal extensions of entanglement witnesses based
on Choi's map. The constructions are based on a generalization of the Choi map
due to Osaka, from which we construct entanglement witnesses. These extremal
extensions are powerful in terms of their capacity to detect entanglement of
positive under partial transpose (PPT) entangled states and lead to unearthing
of entanglement of new PPT states. We also use the Cholesky-like decomposition
to construct entangled states which are revealed by these extremal entanglement
witnesses.Comment: 8 pages 6 figures revtex4-
Gravitational Lensing Bound On The Average Redshift Of Gamma Ray Bursts In Models With Evolving Lenses
Identification of gravitationally lensed Gamma Ray Bursts (GRBs) in the BATSE
4B catalog can be used to constrain the average redshift of the GRBs.
In this paper we investigate the effect of evolving lenses on the of
GRBs in different cosmological models of universe. The cosmological parameters
$\Omega$ and $\Lambda$ have an effect on the of GRBs. The other factor
which can change the of GRBs is higher in evolving model of galaxies as compared to
non-evolving models of galaxies.Comment: 23 pages,one plain LaTeX file with three postscript figures This is
modified version with recent BATSE efficiency parameter and with the latest F
paramete
Modeling mixture transport at the nanoscale: Departure from existing paradigms
We present a novel theory of mixture transport in nanopores, which represents wall effects via a species-specific friction coefficient determined by its low density diffusion coefficient. Onsager coefficients from the theory are in good agreement with those from molecular dynamics simulation, when the nonuniformity of the density distribution is included. It is found that the commonly used assumption of a uniform density in the momentum balance is in serious error, as is also the traditional use of a mixture center of mass based frame of reference
Synthesis, Characterization and Quantification of Simvastatin Metabolites and Impurities
Simvastatin is used in treatment of hypercholesterolemia because it regulates cholesterol synthesis as a result of its β-hydroxy acid acting as an inhibitor of 3-hydroxy-methylglutaryl coenzyme A (HMG-CoA). The present communication deals with synthesis, characterization and development of accurate, precise and sensitive Reverse Phase High Performance Liquid Chromatography (RP-HPLC) method for simultaneous estimation of simvastatin and its synthetic impurities. The impurities methyl ether and β-hydroxy acid of simvastatin were synthesized in the laboratory and characterized by MS, NMR and FT-IR spectroscopy. The separation of simvastatin and its impurities was carried out on an isocratic JASCO RP-HPLC system using KYA TECH HIQ SIL C18 column (150 × 4.6 mm internal diameter, particle size 5 μm) operating at ambient temperature using acetonitrile:water (80:20 v/v) with 0.1% orthophosphoric acid as mobile phase. The method developed for HPLC analysis of three impurities along with simvastatin was validated using ICH Q2B (R1) guidelines and it complied with these guidelines. The results of analysis were found to be in the range of 98.14% to 101.89% for all analytes with acceptable accuracy and precision. The method can be used for detection and quantification of synthetic impurities in bulk or formulations of simvastatin
Bit Plane Coding Based Steganography Technique for JPEG2000 Images and Videos
In this paper, a Bit Plane Coding (BPC) based steganography technique for JPEG2000 images and Motion JPEG2000 video is proposed. Embedding in this technique is performed in the lowest significant bit planes of the wavelet coefficients of a cover image. In JPEG2000 standard, the number of bit planes of wavelet coefficients to be used in encoding is dependent on the compression rate and are used in Tier-2 process of JPEG2000. In the proposed technique, Tier-1 and Tier-2 processes of JPEG2000 and Motion JPEG2000 are executed twice on the encoder side to collect the information about the lowest bit planes of all code blocks of a cover image, which is utilized in embedding and transmitted to the decoder. After embedding secret data, Optimal Pixel Adjustment Process (OPAP) is applied on stego images to enhance its visual quality. Experimental results show that proposed technique provides large embedding capacity and better visual quality of stego images than existing steganography techniques for JPEG2000 compressed images and videos. Extracted secret image is similar to the original secret image
Wall mediated transport in confined spaces: Exact theory for low density
We present a theory for the transport of molecules adsorbed in slit and cylindrical nanopores at low density, considering the axial momentum gain of molecules oscillating between diffuse wall reflections. Good agreement with molecular dynamics simulations is obtained over a wide range of pore sizes, including the regime of single-file diffusion where fluid-fluid interactions are shown to have a negligible effect on the collective transport coefficient. We show that dispersive fluid-wall interactions considerably attenuate transport compared to classical hard sphere theory
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