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231.
MHD free convection flow of visco-elastic fluid past an infinite vertical porous plate 总被引:2,自引:0,他引:2
This work provides a comprehensive theoretical analysis of a two-dimensional unsteady free convection flow of an incompressible,
visco-elastic fluid past an infinite vertical porous plate. Solutions for the zero order perturbation velocity profile, the
first order perturbation velocity and temperature profiles in closed form are obtained with the help of Laplace transform
technique. The numerical solutions are carried out for the Prandtl number 0.1, 0.72, 1.0, 1.5 and 2.0 which are appropriate
for different types of liquid metals and for different values of magnetic field parameter, M.
Received on 1 September 1999 相似文献
232.
Carlee A. Montgomery Islam Jameel Fabio Cuzzucoli Tristan Chidley Prof. Dr. W. Scott Hopkins Prof. Dr. Graham K. Murphy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(71):e202202029
The first systematic evaluation of the electrostatic potential energy maps of iodonium ylides was conducted. We determined that they possess two σ-holes of differing electron deficiencies, with the more electropositive σ-hole located opposite the dative I−C bond to the β-dicarbonyl motif, and the lesser electropositive σ-hole located opposite the iodoarene C−I bond. We also conducted the first systematic evaluation of carboxylic acids, phenols and thiophenols in the O/S-alkylation reaction of iodonium ylides. While carboxylic acids and thiophenols were found to be generally viable, only phenols possessing electron-withdrawing substituents were effective. This high-yielding and highly chemoselective reaction is believed to involve halogen-bond activation of heteroatoms, and nicely complements existing diazo-based methods for alkylation of acidic functional groups. 相似文献
233.
Md Fokhrul Islam Yiing C. Yap Feng Li Rosanne M. Guijt Michael C. Breadmore 《Electrophoresis》2020,41(23):2007-2014
A three-dimensional-printed microfluidic device made of a thermoplastic material was used to study the creation of molecular filters by controlled dielectric breakdown. The device was made from acrylonitrile butadiene styrene by a fused deposition modeling three-dimensional printer and consisted of two V-shaped sample compartments separated by 750 µm of extruded plastic gap. Nanofractures were formed in the thin piece of acrylonitrile butadiene styrene by controlled dielectric breakdown by application voltage of 15–20 kV with the voltage terminated when reaching a defined current threshold. Variation of the size of the nanofractures was achieved by both variation of the current threshold and by variation of the ionic strength of the electrolyte used for breakdown. Electrophoretic transport of two proteins, R-phycoerythrin (RPE; <10 nm in size) and fluorescamine-labeled BSA (f-BSA; 2–4 nm), was used to monitor the size and transport properties of the nanofractures. Using 1 mM phosphate buffer, both RPE and f-BSA passed through the nanofractures when the current threshold was set to 25 µA. However, when the threshold was lowered to 10 µA or lower, RPE was restricted from moving through the nanofractures. When we increased the electrolyte concentration during breakdown from 1 to 10 mM phosphate buffer, BSA passed but RPE was blocked when the threshold was equal to, or lower than, 25 µA. This demonstrates that nanofracture size (pore area) is directly related to the breakdown current threshold but inversely related to the concentration of the electrolyte used for the breakdown process. 相似文献
234.
The Mott law for the dc hopping conductivity for amorphous semiconductors is derived from the rate equation formalism by using the methodology of Butcher and Hayden. This formula is then fitted to the experimental data for a-Si, a-Ge, partially compensated heavily doped n-type Ge and polymer PPIB at 640 atmospheric pressures. It is found that the “simplified Butcher formula” approximately fits the experimental data for a-Si and a-Ge. The values of the density of states at the Fermi level calculated from the expression for the prefactor of this formula are much more reasonable values than those obtained from the original Mott formula. The origin of this significant improvement is found to lie not in improved approximations but in the choice of the values of the characteristics frequency R0. 相似文献
235.
The oscillatory wake potential for a slowly moving or static test dust particulate in a finite temperature, collisionless
and unmagnetized dusty plasma with a continuous flow of ions and dust particles has been studied. The collective resonant
interaction of the moving test particle with the low-frequency and low-phase-velocity dust-acoustic mode is the origin of
the periodic attractive force between the like polarity particulates along and perpendicular to the streaming ions and dust
grains resulting into dust-Coulomb crystal formation. This wake potential can explain the three-dimensional dust-Coulomb crystal
formation in the laboratory conditions. 相似文献
236.
Spectrophotometric Determination of Prochlorperazine Maleate in Pure and Pharmaceutical Preparations
Tehseen Aman Zeeshan Majeed Asrar Ahmad Kazi Islam Ullah Khan 《Mikrochimica acta》2002,138(1-2):13-17
Prochlorperazine maleate reacts with 1-naphthylamine and sodium nitrite, after heating for 110 s at 80 °C to give an orange
red colour having maximum absorbance at 460 nm. The reaction is selective for prochlorperazine maleate with 0.01 mg/mL as
visual limit of quantitation and provides a basis for a new spectrophotometric determination. The colour reaction obeys Beer’s
law from 0.01 mg/10 mL to 0.33 mg/10 mL of prochlorperazine maleate and the relative standard deviation is 0.68%. The quantitative
assessment of tolerable amounts of other drugs is also studied.
Received September 22, 2000. Revision June 19, 2001 相似文献
237.
Sartaj Tabassum Nahid Nishat Farukh Arjmand Lutfullah Khwaja Salahuddin Siddiqi 《Transition Metal Chemistry》1996,21(2):97-100
Summary Benzoylacetic acid (1 mol) interacts with ethylenediamine or with propanediamine (2 mol) to yield new N4 macrocycles 1,5,8,12-tetraazacyclotetradeca-2,4,9,11-tetraphenyl-3, 10-dicarboxylic-4,11-diacetic acid- 1,8-diene (L1) and 1,5,9,13-tetraazacyclohexadeca-2,4,10,12-tetraphenyl-3, 11-dicarboxylic-4,12-diacetic acid-1,9-diene (L2), respectively. These macrocycles have been successfully complexed with CrIII, FeIII, MnII, CoII, NiII, CuII and ZnII. The complexes of the divalent metal ions are non-electrolytes, while those of FeIII and CrIII are 1:1 electrolytes in DMSO. On the basis of ligand field spectra and magnetic moments an octahedral geometry has been proposed for all the complexes. 相似文献
238.
Islam Md Rafiqul 《Tetrahedron letters》2004,45(32):6187-6190
A series of 1,2,4-dichalcogenazoles were synthesized by the reaction of 6H-1,3,5-oxachalcogenazines with elemental chalcogen through the plausible pathway involving in situ generation of 1,3-chalcogenaza-1,3-butadienes and the subsequent reaction with chalcogen species. Synthetic utilities of 1,2,4-dichalcogenazoles were also explored. 相似文献
239.
240.
Waseeq Ahmad Siddiqui Saeed Ahmad Islam Ullah Khan Hamid Latif Siddiqui Masood Parvez 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(5):o286-o289
The structures of 2‐[N‐(2‐chlorophenyl)carbamoyl]benzenesulfonamide and 2‐[N‐(4‐chlorophenyl)carbamoyl]benzenesulfonamide, both C13H11ClN2O3S, are stabilized by extensive intra‐ and intermolecular hydrogen bonds. In both structures, sulfonamide groups are hydrogen bonded via the N and O atoms and form chains of molecules. The carbamoyl groups are also hydrogen bonded, involving the O and N atoms, further strengthening the polymeric chains running along the c and a axes in the 2‐ and 4‐chloro derivatives, respectively. Carbamoylsulfonamide derivatives are novel compounds with a great potential for medicinal applications. 相似文献