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991.
We study finite difference schemes to approximate the first initial-boundary value problem for linear second order parabolic equations and obtain some convergence rate estimates. When difference schemes are constructed for such problems, in the process of obtaining convergence rate estimates compatible with smoothness of the solution, various authors assume that the solution of the problem can be extended to the exterior of the domain of integration, preserving the Sobolev class. Our investigations show that this restriction can be removed if, instead of using the exact initial condition, we use certain approximations of the initial conditions. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
992.
Influence of electron‐beam (e‐beam) irradiation on multi‐walled (MW) and single‐walled (SW) carbon nanotube films grown by microwave chemical vapor deposition technique is investigated. These films were subjected to an e‐beam energy of 50 keV from a scanning electron microscope for 2.5, 5.5, 8.0, and 15 h, and to 100 and 200 keV from a transmission electron microscope for a few minutes to ∼2 h continuously. Such conditions resemble an increased temperature and pressure regime enabling a degree of structural fluidity. To assess structural modifications, they were analyzed prior to and after irradiation using resonance Raman spectroscopy (RRS) in addition to in situ monitoring by electron microscopy. The experiments showed that with extended exposures, both types of nanotubes displayed various local structural instabilities including pinching, graphitization/amorphization, and formation of an intramolecular junction (IMJ) within the area of electron beam focus possibly through amorphous carbon aggregates. RRS revealed that irradiation generated defects in the lattice as quantified through (1) variation of the intensity of radial breathing mode (RBM), (2) intensity ratio of D to G band (ID/IG), and (3) positions of the D and G bands and their harmonics (D* and G*) and combination bands (D + G). The increase in the defect‐induced D band intensity, quenching of RBM intensity, and only a slight increase in G band intensity are some of the implications. The MW nanotubes tend to reach a state of saturation for prolonged exposures, while the SW ones transform from a semiconducting to a quasi‐metallic character. Softening of the q = 0 selection rule is suggested as a possible reason to explain these results. Furthermore, these studies provide a contrasting comparison between MW and SW nanotubes. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
993.
A short‐range force constant model has been applied to investigate the Raman and the infrared wavenumbers in R2BaNiO5 (R = Y, Gd) in their orthorhombic phase of space group Immm. Calculations of zone‐center phonons are made with seven stretching and four bending force constants. The force constants are evaluated by fitting nine Raman and two infrared modes. Two Raman modes are reassigned on the basis of group theoretical calculations. The calculated Raman and infrared modes show good agreement with the observed values. The infrared values are assigned for the first time in these oxides. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
994.
Guohua Chen Malancha Gupta Kelvin Chan Karen K. Gleason 《Macromolecular rapid communications》2007,28(23):2205-2209
Furan ring‐functionalized solid surfaces are achieved by the initiated chemical vapor deposition (iCVD) method, a solvent‐free process to form films under mild conditions. The polymerization of furfuryl methacrylate monomer is initiated by a resistively heated filament wire. The functionality of the furan group in the iCVD film enabled Diels–Alder chemistry with 4‐phenyl‐1,2,3‐triazolin‐3,5‐dione (N‐PTD).
995.
A. K. Gupta Bowling Green State University USA D. G. Kabe Sf. Mary''''s University USA 《数学物理学报(B辑英文版)》2001,21(2):221-223
1 IntroductionWe are given k independent Wishart densities of the p x p random symmetric positivedefinite matrices G1, G2,' t Gkwhere Ri denotes the population correlation matrir, and K as a generic letter denotes thenormalizing constants of density functions in this paper. The squared multiple correlationcoefficient of the i-th population is pf = r:Riz1.)ri, whereand a likelihood ratio test for testing the hypothesisis desired.Now Wilks (l932, l946) provides certain procedures and guidel… 相似文献
996.
The crystal and molecular structures of the alkaloid Royline {(1α,6β,14α, 16β)-20-ethyl-4-hydroxymethyl)-1,6,14,16-tetramethoxyaconitane-7,8-diol} with a water molecule has been determined by X-ray diffraction analysis. The compound crystallizes in the space group P21 with the unit cell parameters a = 10.985(1) Å, b = 7.898(1) Å, c = 14.956(1) Å, β = 102.96(1)°, V = 1264.52 Å3, Z = 2, λMoK α = 0.71073 Å, and R = 0.033 for 2067 observed reflections. Rings A, B, and C adopt a chair conformation, ring D is a half-boat, ring E is a half-chair, and ring F is in an envelope conformation with C(14) at the flap. Molecules are linked together in the crystal by hydrogen bonds. 相似文献
997.
Rajnikant V. K. Gupta E. H. Khan S. Shafi S. Hashmi Shafiullah B. Varghese Dinesh 《Crystallography Reports》2001,46(6):963-966
The crystal structure of cholest-4-ene-3,6-dione (C27H44O2) has been determined by X-ray diffraction methods. The compound crystallizes in the monoclinic crystal system (space group P21) with the unit cell parameters a = 10.503(4) Å, b = 8.059(1) Å, c = 14.649(1) Å, β = 105.4(2)°, and Z = 2. The structure has been refined to an R value of 0.035 for 2252 observed reflections. Ring A of the steroid nucleus exists in a sofa conformation, while rings B and C adopt a chair conformation. The five-membered ring D exhibits a half-chair conformation. The molecules in the unit cell are linked together by the C-H?O hydrogen bonds. 相似文献
998.
When a laser source is used to illuminate a transmission hologram, the zero order beam is not utilised and is just wasted. The paper describes a new technique for economical utilisation of laser light by recycling the transmitted light to reconstruct a number of holograms simultaneously for viewing by a large number of observers. There is no danger to viewer who is exposed to the undiffracted laser beams transmitted through the hologram. The paper also discusses the diffraction efficiency requirement of successive hologram and the limit of number of holograms in the scheme. 相似文献
999.
Dibyalochan Mohanty Ameeduzzafar Zafar Mohammed Jafar Atul Kumar Upadhyay Mohammad Akiful Haque Jeetendra Kumar Gupta Vasudha Bakshi Mohammed M. Ghoneim Sultan Alshehri Mohammed Asadullah Jahangir Mohammed Javed Ansari 《Molecules (Basel, Switzerland)》2022,27(9)
Objective: The present study aimed to develop and optimize esomeprazole loaded proniosomes (EZL-PNs) to improve bioavailability and therapeutic efficacy. Method: EZL-PNs formulation was developed by slurry method and optimized by 33 box-Bhekhen statistical design software. Span 60 (surfactant), cholesterol, EZL concentration were taken as independent variables and their effects were evaluated on vesicle size (nm), entrapment efficiency (%, EE) and drug release (%, DR). Furthermore, optimized EZL-PNs (EZL-PNs-opt) formulation was evaluated for ex vivo permeation, pharmacokinetic and ulcer protection activity. Result: The EZL-PNs-opt formulation showed 616 ± 13.21 nm of vesicle size, and 81.21 ± 2.35% of EE. EZL-PNs-opt exhibited negative zeta potential and spherical confirmed scanning electron microscopy. EZL-PNs-opt showed sustained release of EZL (95.07 ± 2.10% in 12 h) than pure EZL dispersion. The ex-vivo gut permeation result exhibited a significantly (p < 0.05) enhanced flux than pure EZL. The in vivo results revealed 4.02-fold enhancement in bioavailability and 61.65% protection in ulcer than pure EZL dispersion (43.82%). Conclusion: Our findings revealed that EZL-PNs formulation could be an alternative delivery system of EZL to enhance oral bioavailability and antiulcer activity. 相似文献
1000.
V.P. Rama Kishore Putta Raghuram Gujjarappa Nagaraju Vodnala Richa Gupta Prasad P. Pujar Chandi C. Malakar 《Tetrahedron letters》2018,59(10):904-908
The first organocatalytic approach towards synthesis of rarely explored 1,2,4-selenadiazole and thiadiazole scaffolds have been devised using corresponding carboxamides as substrates. The transformations were realized using two distinct conditions in the presence of catalytic vitamin B3 or thiourea under aerobic conditions. Developed methods overcome the associated limitations of previous reported approaches and the desired products were obtained in high yields and selectivity without the formation of toxic side-products. 相似文献