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511.
A microwave-assisted extraction technique was developed to optimize the extraction of phenolic compounds from grape seeds. The microwave power (300-150W) and time of extraction (20-200s) were varied during the optimization process. The polyphenol content of the resulting extracts were measured as mg of tannic acid equivalent per gram of crude extract (mg TAE/g of crude extract), using a Folin-Ciocalteau reagent. In general, neither the time nor the power had a significant effect on the overall % yield (average of 13.5%) and on the polyphenol content (392 mg TAE/g of crude extract) of the extracts. However, when the solvent polarity was changed by the addition of 10% water, the yield increased to 15.2% and the polyphenol content increased to 429 mg TAE/g of crude extract. 相似文献
512.
W. Semmler P. Raghavan M. Senba R. S. Raghavan 《Zeitschrift für Physik B Condensed Matter》1981,45(1):29-37
The quadrupole interaction constants of69GeT1 and113SnSn were measured by means of the perturbed angular distribution technique as a function of temperature in the range of 80KT508 K and 80KT480 K, respectively. Isomeric states in69Ge and113Sn were populated by the heavy ion reactions56Fe(16O, 2p n) and100Mo(16O, 3n) and recoil implanted into polycrystalline Tl- and single crystalline Sn-backings. In the case of113SnSn, where the quadrupole coupling is weak, a special single crystal geometry was employed to enhance the sensitivity of the measurement. Within the limits of the errors the temperature dependence for both systems follows the empirical T1.5-dependence. While a strong temperature dependence comparable to InIn is observed for69GeT1, that for113SnSn is weaker than expected. The strength of the temperature dependence for113SnSn does not agree with the predictions of a lattice vibration model proposed recently for the temperature dependence of the quadrupole interaction.Supported in part by NSFAssociate of the Graduate Faculty of Rutgers University 相似文献
513.
S. Banerjee S. N. Ganguli P. K. Malhotra R. Raghavan K. Sudhakar 《Zeitschrift fur Physik C Particles and Fields》1979,3(1):1-8
We present a study of the inclusive production ofK *(892) and ∑t+-(1385)+cc at 3.6 GeV/c from \(\bar p\) p interactions. The sensitivity of the exposure is 35.4 events/μb. Longitudinal and transverse momentum distributions are presented. The indirect production ofK s 0 from parentK * and that of Λ's from parent Σ(1385) are studied. The shape of thex distribution of Λ's for \(p\xrightarrow{{\bar p}}\Lambda \) are calculated from \(p\xrightarrow{p}\Lambda \) and \(p\xrightarrow{{\pi ^ - }}\Lambda \) and compared with the experimental distributions. The difference of antiparticle production cross-section ofK s 0 in the central region is compared with the expectation from Mueller-Regge formalism. 相似文献
514.
Jason E. Imbriglio Daniel DiRocco Subharekha Raghavan Richard G. Ball Nancy Tsou Ralph T. Mosley James R. Tata Steven L. Colletti 《Tetrahedron letters》2008,49(33):4897-4900
The optimization of a palladium-catalyzed amidation reaction providing a new class of amino acid-tetrahydroanthranilic acid derivatives has been achieved. The scope of the reaction and preliminary conformational analysis of the resulting series of molecules is discussed. 相似文献
515.
516.
Everta Keren Govindarajan Sundararajan 《Journal of polymer science. Part A, Polymer chemistry》2007,45(16):3599-3610
The 2‐[benzyl‐(2‐hydroxy‐2‐phenylethyl)‐amino]‐1‐phenylethanol ligand (1‐H2) prepared as a diastereomeric mixture or in racemic and meso forms, from known procedure, has been disodiated and complexed with ZrCl4. The precatalysts (mix‐1‐ZrCl2, rac‐1‐ZrCl2, and meso‐1‐ZrCl2) were used in combination with methylaluminoxane and found to be active for the polymerization of 1‐hexene and 1‐octene. The high molecular weight polyhexenes (PHs) and polyoctenes (POs) thus obtained were isotactic in nature and showed a negligible amount of end groups arising from the chain termination reactions. In PHs and POs, there was linear correlation in the modified Arrhenius plot (the natural logarithm of the number‐average molecular weight vs. the reciprocal of the temperature), indicating the presence of a single active species. The enantiomerically pure titanium precatalyst ((R,R)‐1‐TiCl2), when employed for the polymerization of 1‐hexene, was found to be active and the modified Arrhenius plot showed linear dependence demonstrating presence of a single active species. The analogous titanium precatalysts (mix‐1‐TiCl2, rac‐1‐TiCl2, and meso‐1‐TiCl2) obtained from known procedures were also found to be active for the polymerization of 1‐octene. The rac‐1‐TiCl2 precatalyst demonstrated a sigmoidal behavior in the modified Arrhenius plot for the POs and the mix‐1‐TiCl2 precatalyst showed an exponential type of behavior. The obtained POs seemed to have small amounts of chain termination via β‐hydride elimination alone. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3599–3610, 2007 相似文献
517.
Mahalingam Vanjinathan A. Raghavan A. Sultan Nasar 《Journal of polymer science. Part A, Polymer chemistry》2007,45(14):2959-2977
3,5‐bis(4‐aminophenoxy)phenyl phenylcarbamate—a novel AB2‐type blocked isocyanate monomer and 3,5‐bis{ethyleneoxy(4‐aminophenoxy)}phenyl carbonyl azide—a novel AB2‐type azide monomer were synthesized in high yield. Step‐growth polymerization of these monomers were found to give a first example of hyperbranched poly (aryl‐ether‐urea) and poly(aryl‐alkyl‐ether‐urea). Molecular weights (Mw) of the polymer were found to vary from 1,858 to 52,432 depending upon the monomer and experimental conditions used. The polydispersity indexes were relatively narrow due to the controlled regeneration of isocyanate functional groups for the polymerization reaction. The degree of branching (DB) was determined using 1H‐NMR spectroscopy and the values ranged from 87 to 54%. All the polymers underwent two‐stage decomposition and were stable up to 300 °C. Functionalized end‐capping of poly(aryl‐ether‐urea) using phenylchloroformate and di‐t‐butyl dicarbonate (Boc)2O changed the thermal properties and solubility of the polymers. Copolymerization of AB2‐type blocked isocyante monomer with functionally similar AB monomer were also carried out. The molecular weights of copolymers were found to be in the order of 6 × 105 with narrow dispersity. It was found that the Tg's of poly(aryl‐alkyl‐ether‐urea)s were significantly less (46–49 °C) compared to poly(aryl‐ether‐urea)s. Moreover the former showed melting transition at 154 °C, which was not observed in the latter case. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2959–2977, 2007 相似文献
518.
519.
Assignment games with stable core 总被引:1,自引:0,他引:1
We prove that the core of an assignment game (a two-sided matching game with transferable utility as introduced by Shapley
and Shubik, 1972) is stable (i.e., it is the unique von Neumann-Morgenstern solution) if and only if there is a matching between
the two types of players such that the corresponding entries in the underlying matrix are all row and column maximums. We
identify other easily verifiable matrix properties and show their equivalence to various known sufficient conditions for core-stability.
By these matrix characterizations we found that on the class of assignment games, largeness of the core, extendability and
exactness of the game are all equivalent conditions, and strictly imply the stability of the core. In turn, convexity and
subconvexity are equivalent, and strictly imply all aformentioned conditions.
Final version: April 1, 2001 相似文献
520.
Arun Singh Chouhan Naga Prathibha Jasti Shreyash Hadke Srinivasan Raghavan Sushobhan Avasthi 《Current Applied Physics》2017,17(10):1335-1340
Spin coated perovskite thin films are known to have an issue of pinholes & poor morphology control which lead to poor device-to-device repeatability, that is an impediment to scale-up. In this work, Methylamine vapor annealing process is demonstrated which consistently leads to high-quality perovskite thin-films with an average grain-size of 10–15 μm. The improvement in film morphology enables improvement in effective carrier recombination lifetime, from 21 μs in as-deposited films to 54 μs in vapor-annealed films. The annealed films with large-grains are also more stable in ambient conditions. Devices made on annealed perovskite films are very consistent, with a standard deviation of only 0.7%. Methylamine vapor annealing process is a promising method of depositing large-grain CH3NH3PbI3 films with high recombination lifetime and the devices with improved performance. 相似文献