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91.
The Liesegang phenomenon is interpreted as a moving boundary problem. The existing time law, spacing law, and width law are revisited and reformulated on the basis of the new scenario. A better understanding of the basic facts associated with pattern formation is made possible with the new concept. The phenomenon is explained on the basis of colloidal kinetics. Diffusion coefficients of the outer electrolyte in the gel for various experiments in the literature are calculated. The diffusion coefficients so calculated range from 1.792-5.996᎒-10 m2 s-1. It is suggested that such values confirm the fast colloidal dynamics during the process of periodic precipitation pattern formation. 相似文献
92.
Joseph C. Varghese G. Ittyachen M. A. 《Journal of Thermal Analysis and Calorimetry》1998,52(2):517-522
Neodymium praseodymium oxalate decahydrate crystals were grown using silica gel technique by the controlled reaction of rare
earth nitrates with oxalic acid. The grown crystal were characterized using X-ray powder diffraction and thermogravimetric
analysis. The thermal decomposition process of the crystals is in good agreement with the proposed crystal structure.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
93.
Jobi Kodiyan Varghese Dong Sik Park Jong Yeob Jeon Bun Yeoul Lee 《Journal of polymer science. Part A, Polymer chemistry》2013,51(22):4811-4818
Simple mixing of H3Co(CN)6 and ZnCl2 in methanol resulted in precipitates of [ZnCl]+2[HCo(CN)6]2?, constituting a new type of double metal cyanide (DMC) catalyst exhibiting a high performance in carbon dioxide (CO2)/propylene oxide (PO) copolymerization. High‐molecular‐weight poly(propylene carbonate‐co‐propylene oxide)s [poly(PC‐co‐PO)s] (Mn~40,000) were consistently obtained with high carbonate fractions (~60 mol %) and a high selectivity (>95%) with the new type of DMC catalyst. Conventional preparation of the DMC catalyst using K3Co(CN)6 and ZnCl2 required removing KCl through thorough washing and resulted in lower carbonate fractions (10–40 mol %), which depended on the washing conditions. Feeding hydrophobic diols such as 1,10‐decanediol as chain transfer agent preserved the high carbonate fraction (~60%) and enabled precise control of the molecular weight, including preparation of a low‐molecular‐weight poly(PC‐co‐PO)‐diol (Mn ~2000), which was a flowing viscous liquid with a low Tg (?30 °C) suitable for polyurethane applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4811–4818 相似文献
94.
Seema Jaggi Cini Varghese Eldho Varghese V.K. Sharma 《Statistics & probability letters》2010,80(7-8):706-710
Generalized incomplete Trojan-type designs are defined to be row–column designs in which each cell, corresponding to the intersection of row and column, contains more than one treatment and the rows are incomplete. A method of constructing generalized incomplete Trojan-type design has been developed and some properties of this class of designs are discussed. 相似文献
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The effect of phase‐pure cristobalite (a high temperature crystalline polymorph of silica) on the adhesive characteristics of hydroxyl terminated polydimethylsiloxane (PDMS) was studied. The potential advantages of PDMS/cristobalite composite system as an adhesive for aerospace applications are also discussed. A PDMS/cristobalite composite adhesive system containing different filler contents (0–46 volume percentage, vol%) was prepared. The filler material, phase‐pure cristobalite, was synthesized by the pyrolysis of fused silica at 1400°C. The mechanical, rheological, and thermal characteristics of the composites were studied. A high yield stress (0.151 Pa), shear‐thinning index (1.051), and fast recovery rate were observed for ~34 vol% cristobalite loading, which indicate that PDMS retains its excellent adhesive and flow characteristics even at high filler loading with enhanced mechanical characteristics. Thermal analysis shows the onset of degradation of PDMS shifts to higher temperatures, 372–438°C and 317–417°C in nitrogen and air atmosphere respectively, which shows excellent thermal stability. The residual component yields after thermal degradation of PDMS/cristobalite composite system in nitrogen and air atmosphere show different degradation mechanisms. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
100.
C.J. Antony M. Junaid Bushiri Hema Tresa Varghese C. Yohannan Panicker Michel Fleck 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,73(5):942-945
Raman and FTIR spectra of guanidinium zinc sulphate [C(NH2)3]2Zn(SO4)2 are recorded and the spectral bands assignment is carried out in terms of the fundamental modes of vibration of the guanidinium cations and sulphate anions. The analysis of the spectrum reveals distorted SO42− tetrahedra with distinct S–O bonds. The distortion of the sulphate tetrahedra is attributed to Zn–O–S–O–Zn bridging in the structure as well as hydrogen bonding. The CN3 group is planar which is expressed in the twofold symmetry along the C–N (1) vector. Spectral studies also reveal the presence of hydrogen bonds in the sample. The vibrational frequencies of [C(NH2)3]2 and HC(NH2)3 are computed using Gaussian 03 with HF/6-31G* as basis set. 相似文献