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61.
Sulphonated styrene-divinylbenzene resins with various cross-linking have been synthesized and the dehydration of 2-butanol
has been studied on these acid catalysts. The pore structure of the resin controls the rate of dehydration. Thecis totrans ratio of the 2-butene formed indicate that the resin catalysts behave like aqueous solution of acids, i.e.dissociated protons
are responsible for catalysis. 相似文献
62.
Assuming confinement and chiral symmetry breaking, we have calculated constituent quark masses from phenomenological q potentials by using a BCS-like gap equation. 相似文献
63.
Alexander McKillop Alan Henderson Partha S. Ray Carmen Avendano Encarnacion G. Molinero 《Tetrahedron letters》1982,23(33):3357-3360
Ethyl carboethoxyformimidate is shown to be a versatile reagent for the synthesis of a variety of mono- and bicyclic heterocyclic systems. 相似文献
64.
Separation of lignosulfonate from its aqueous solution using supported liquid membrane 总被引:2,自引:1,他引:1
Kabita Chakrabarty Prabirkumar Saha Aloke Kumar Ghoshal 《Journal of membrane science》2009,340(1-2):84-91
This paper presents an experimental and theoretical study on facilitated transport of lignosulfonate (LS) through a flat sheet supported liquid membrane using trioctylamine (TOA) as carrier and dichloroethane as diluent. The studies were carried out with various support materials and operating conditions (viz. carrier concentration, strip phase concentration, salt concentration, etc.) and their effects on the transport of LS. The results were analyzed to identify a suitable combination of support and operating condition that would yield best performance of the supported liquid membrane (SLM) in terms of fast and efficient transport of LS. The stability of the SLM was assessed in terms of loss of liquid from the pores of membrane support. The SLM is found to be stable till 10 h. Co-transport mechanism has been adopted in this work by using NaOH as the strip phase. It was observed that extraction of LS is increased with increase in concentration of NaOH up to a limiting value of 0.5 M NaOH. Difference of salt concentration between feed and strip phase considerably affect the separation process. The diffusional resistances of organic membrane (Δorg) and aqueous solution (Δaq) calculated from the permeation model, which is again a combination of three unique mechanisms viz., diffusion through a feed aqueous layer, a fast interfacial chemical reaction, and diffusion of carrier–complex through the organic membrane, are found to be 609.9 and 176.6 s cm−1, respectively. The values of the diffusion coefficient in the membrane (Dorg) and in the bulk organic phase (Dcomplex) are 1.67×10−9 and 6.68 × 10−8 m2s−1, respectively. The extraction of LS is about 90%. Nearly 43% of LS can be recovered at optimum condition. 相似文献
65.
Pui David Y.H. Biswas Pratim Fissan Heinz Schoonman Joop 《Journal of nanoparticle research》2000,2(4):425-426
Journal of Nanoparticle Research - 相似文献
66.
Partha Niyogi Stephen Smale Shmuel Weinberger 《Discrete and Computational Geometry》2008,39(1-3):419-441
Recently there has been a lot of interest in geometrically motivated approaches to data analysis in high-dimensional spaces.
We consider the case where data are drawn from sampling a probability distribution that has support on or near a submanifold
of Euclidean space. We show how to “learn” the homology of the submanifold with high confidence. We discuss an algorithm to
do this and provide learning-theoretic complexity bounds. Our bounds are obtained in terms of a condition number that limits
the curvature and nearness to self-intersection of the submanifold. We are also able to treat the situation where the data
are “noisy” and lie near rather than on the submanifold in question.
The main results of this paper were first presented at a conference in honor of John Franks and Clark Robinson at Northwestern
University in April 2003. These results were formally written as Technical Report No. TR-2004-08, Department of Computer Science,
University of Chicago. 相似文献
67.
Alok Chakrabarty Pradipta Purkayastha Nitin Chattopadhyay 《Journal of photochemistry and photobiology. A, Chemistry》2008,198(2-3):256-261
The cis-skew to trans-planar photoisomerization of benzil in the photoexcited state was studied by laser-induced optoacoustic spectroscopy (LIOAS) in a series of normal alkane solvents at room temperature. The structural volume change due to the photoisomerization process has been estimated and compared with the same calculated from the optimized skew and trans structures. The magnitude of the structural volume change is estimated to be 22.9 ± 1.2 mL/mol. This study reveals that an expansion in volume occurs during the photoinduced isomerization process. In non-polar alkane solvents, the estimated volume change has been argued to be free from electrostrictional contribution. 相似文献
68.
Papia Chowdhury Tirtha Pratim Adhikary Sankar Chakravorti 《Journal of luminescence》2008,128(7):1113-1120
In this paper, an interesting transformation of the emission of anionic conformer of 2-benzoyl bezimidazole in ionic and non-ionic micelles is reported. Deprotonation is hindered in cationic and non-ionic micelles owing to probe molecule's passage deep inside positive ion-rich Stern-layer in contrast with anionic micelle. The orientation of probe molecule in the two ionic micelles, as determined from the spectral properties is opposite in nature. Micellar environment shields the formation of mono- and di-cationic species at very low pH. Three decay times of the probe in different time domains were attributed to three possible anionic species and they are modified differently in ionic and neutral micelles. Quantum chemical calculations also predict the existence of three different possible anionic species. 相似文献
69.
This paper presents a new interpretation of a digital circle in terms of the distribution of square numbers in discrete intervals. The number-theoretic analysis that leads to many important properties of a digital circle succinctly captures the original perspectives of digital calculus and digital geometry for its visualization and characterization. To demonstrate the capability and efficacy of the proposed method, two simple algorithms for the construction of digital circles, based on simple number-theoretic concepts, have been reported. Both the algorithms require only a few primitive operations and are completely devoid of any floating-point computation. To speed up the computation, especially for circular arcs of high radii, a hybridized version of these two algorithms has been given. Experimental results have been furnished to elucidate the analytical power and algorithmic efficiency of the proposed approach. It has been also shown, how and why, for sufficiently high radius, the number-theoretic technique can expedite a circle construction algorithm. 相似文献
70.
Vivekanandan Kannan Pradeep Narayanaswamy Deepak Gadamsetty Partha Hazra Anand Khedkar Harish Iyer 《Rapid communications in mass spectrometry : RCM》2009,23(7):1035-1042
Glycoforms of glargine expressed in Pichia pastoris were isolated by high‐performance liquid chromatography and analyzed by a series of chemical and mass spectrometric methods for the identification of various glycoforms, glycosylation position, nature and structure of glycans. Reduction and alkylation, peptide mapping techniques were used to decipher the amino acid site at which glycosylation had taken place. Chemical methods were coupled with mass spectrometry techniques such as electrospray ionization and matrix‐assisted laser desorption/ionization for identification of the glycosylation site. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献