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171.
For a nearest-neighbor Ising model on a square lattice all cluster configurations with 17 or fewer spins are identified. In neglect of cluster-cluster interactions, critical sizes and barriers to nucleation are obtained as functions of temperature and magnetic field for two alternative definitions of a "critical cluster." 相似文献
172.
Model for heat conduction in nanofluids 总被引:1,自引:0,他引:1
Kumar DH Patel HE Kumar VR Sundararajan T Pradeep T Das SK 《Physical review letters》2004,93(14):144301
A comprehensive model has been proposed to account for the large enhancement of thermal conductivity in nanofluids and its strong temperature dependence, which the classical Maxwellian theory has been unable to explain. The dependence of thermal conductivity on particle size, concentration, and temperature has been taken care of simultaneously in our treatment. While the geometrical effect of an increase in surface area with a decrease in particle size, rationalized using a stationary particle model, accounts for the conductivity enhancement, a moving particle model developed from the Stokes-Einstein formula explains the temperature effect. Predictions from the combined model agree with the experimentally observed values of conductivity enhancement of nanofluids. 相似文献
173.
T.?LeeEmail author W.G.?Bessler C.?Schulz M.?Patel J.B.?Jeffries R.K.?Hanson 《Applied physics. B, Lasers and optics》2004,79(4):427-430
UV planar laser-induced fluorescence (PLIF) images of hot carbon dioxide (CO2) are obtained in a laminar flame (CH4/air) at high pressure (20 bar) with excitation wavelengths at 239.34 nm and 242.14 nm. Excitation wavelengths are chosen to minimize the contribution of nitric oxide and molecular oxygen LIF signals. Spectrally resolved single point measurements are used for correction of the remaining oxygen LIF interference. The continuum LIF signal from electronically excited CO2 is detected in a broad (280–400 nm) emission region. The UV PLIF of hot CO2 has the potential for application to a wide variety of diagnostic needs in high-pressure flames, combustors, and engines. PACS 42.62.Fi; 42.30.Va; 07.25+k; 39.30+w 相似文献
174.
Fernandez Ocaña M Neubert H Przyborowska A Parker R Bramley P Halket J Patel R 《The Analyst》2004,129(2):111-115
The epidemic of bovine spongiform encephalopathy (BSE) is thought to have resulted from feeding scrapie-infected sheep to cattle. This has led to a ban of feeding animals with "processed animal protein"(PAP). We report a novel approach for the mass spectrometric detection of PAP contamination in animal feedstuffs by detecting gelatine, a derivative of the major animal protein collagen. A method was developed to hydrolyse gelatine standards with hydrochloric acid, followed by detection of the derived hydrolytic peptides at m/z 828, 915, 957 and 1044 by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) and liquid chromatography electrospray ionisation mass spectrometry (LC-ESI-MS-MS). The marker peptides can be detected at concentrations of 100 ng ml(-1) gelatine in water with MALDI. The procedure was adapted to obtain a suitable peptide map of gelatine extracted from spiked feed. The ratio of signal area of the gelatine-derived peptide at m/z 1044 to the internal standard at m/z 556 is shown to relate to the total amount of gelatine present in the sample. 相似文献
175.
Spolenak R Brown WL Tamura N MacDowell AA Celestre RS Padmore HA Valek B Bravman JC Marieb T Fujimoto H Batterman BW Patel JR 《Physical review letters》2003,90(9):096102
Grain-to-grain interactions dominate the plasticity of Al thin films and establish effective length scales smaller than the grain size. We have measured large strain distributions and their changes under plastic strain in 1.5-microm-thick Al 0.5% Cu films using a 0.8-microm-diameter white x-ray probe at the Advanced Light Source. Strain distributions arise not only from the distribution of grain sizes and orientation, but also from the differences in grain shape and from stress environment. Multiple active glide plane domains have been found within single grains. Large grains behave like multiple smaller grains even before a dislocation substructure can evolve. 相似文献
176.
177.
Singh J Kronenthal DR Schwinden M Godfrey JD Fox R Vawter EJ Zhang B Kissick TP Patel B Mneimne O Humora M Papaioannou CG Szymanski W Wong MK Chen CK Heikes JE DiMarco JD Qiu J Deshpande RP Gougoutas JZ Mueller RH 《Organic letters》2003,5(17):3155-3158
[reaction: see text] An efficient asymmetric synthesis of the vasopeptidase inhibitor BMS-189921 was accomplished. Two short enantioselective syntheses of the common key intermediate (S)-alpha-aminoazepinone 6b were developed. Olefin 3 was converted to 6b via asymmetric hydrogenation. Alternatively, enyne 12 was converted to racemic alpha-aminoazepinone 15b, which was transformed to 6b by a practical dynamic resolution. 相似文献
178.
Kylstra NJ Worthington RA Patel A Knight PL Vazquez De Aldana JR Roso L 《Physical review letters》2000,85(9):1835-1838
An analysis of the influence of the magnetic field of an intense, high-frequency laser pulse on the stabilization of an atomic system is presented. We demonstrate that at relatively modest intensities the magnetic field can significantly alter the dynamics of the system. In particular, a breakdown of stabilization occurs, thereby restricting the intensity regime in which the atom is relatively stable against ionization. Counterpropagating pulses do not negate the detrimental effects of the magnetic field. We compare our quantum mechanical results with classical Monte Carlo simulations. 相似文献
179.
Nishant N. Patel K. B. Joshi 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(1):19-23
Using empirical pseudopotential method Γ-L crossover is found for
the Ga0.74Al0.26Sb. The conduction band minimum is observed to
switch at the (0.87, 0, 0) point for Ga0.51Al0.49Sb which shifts to
the X point for Ga0.21Al0.79Sb and remains at X leading finally to
indirect band gap in AlSb. Band structure calculations for a large number of
alloys are performed and bowing parameters bX and bL are proposed
for the EX and EL respectively. Our findings may serve as
directive to select the materials in a range of composition to examine the
bowing parameters and thereby effective mass experimentally for the
GaxAl1-xSb alloys. 相似文献
180.
Nayan Patel Mehmet Krta Vaidya Sankaran Suresh Menon 《Proceedings of the Combustion Institute》2007,31(2):2327-2334
Large-eddy simulation (LES) of a liquid-fueled lean-direct injection (LDI) combustor is carried out by resolving the entire inlet flow path through the swirl vanes and the combustor. A localized dynamic subgrid closure is combined with a subgrid mixing and combustion model so that no adjustable parameters are required for both non-reacting and reacting LES. Time-averaged velocity predictions compare well with the measured data. The unsteady flow features that play a major role in spray dispersion, fuel–air mixing and flame stabilization are identified from the simulation data. It is shown that the vortex breakdown bubble (VBB) is smaller with more intense reverse flow when there is heat release. The swirling shear layer plays a major role in spray dispersion and the VBB provides an efficient flameholding mechanism to stabilize the flame. 相似文献