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121.
Viqar Uddin Ahmad Atta-ur-Rahman Tahir Rasheed Habib-ur-Rehman Abdul Qasim Khan 《Tetrahedron》1987,43(24)
A novel alkaloid, cohirsine (1) was isolated from
. Its structure has been investigated by extensive NMR studies including 2D NMR experiments. Its stereochemistry has been determined by 2D NOESY and NOE difference measurements. 相似文献
122.
Soluble in organic solvent polyaniline (PANI) was prepared using DBSA as a functional dopant. Miscibility was maximized for
PMMA with hydroquinone. Transmission electron micrographs showed lowest level of phase separation. Thermal studies by differential
scanning calorimetry show some peak shifts which indicate the miscibility of two polymers. The formations of new bonds are
also confirmed by Fourier transformation infrared spectroscopy. Electroconductivity increased with increase of content of
doped PAN1, showing percolation threshold at 3 wt %. 相似文献
123.
Anwar Usman Ibrahim Abdul Razak Suchada Chantrapromma Hoong-Kun Fun Jayanta Kumar Ray Sujit Das Adhikari Bishnu Pada Datta 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(12):1441-1442
In the title compound, C20H20FNO5S, the pyrrolidine ring adopts an envelope conformation. The fluorophenyl and thiophene rings are individually planar. The molecular and crystal structures are stabilized by intra- and intermolecular C—H⋯O interactions. 相似文献
124.
125.
Muhammad Saleem Naseem Akhter Muhammad Shaiq Ali Mamona Nazir Naheed Riaz Muhammad Moazzam Muhammad Arshad Abdul Jabbar 《Magnetic resonance in chemistry : MRC》2009,47(3):263-265
Chromatographic analysis of the alcoholic extract from Salsola imbricata yielded two new secondary metabolites, salisomide (1) and salisoflavan (2). Their structures were established with the help of spectroscopic techniques including COSY, HMQC and HMBC NMR experiments. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
126.
In the present paper our aim is to establish convergence and Voronovskaja-type theorems for first derivatives of generalized
Baskakov operators for functions of one and two variables in exponential and polynomial weight spaces.
相似文献
127.
Abdul G. Al Lafi James N. Hay David J. Parker 《Journal of Polymer Science.Polymer Physics》2008,46(11):1094-1103
Amorphous poly(ether‐ether‐ketone) (PEEK) progressively crosslinks on irradiation with 11.0 MeV protons, and this has a marked effect on the extent of crystallinity that subsequently develops and on the kinetics of the high temperature isothermal crystallization. The extent of crystallinity with time was analyzed using the Avrami equation, and the temperature dependence of the rate constants was analyzed in terms of nucleation theory. While irradiation inhibits the overall rates of crystallization by the reduction in the mobility of the chain segments as observed by the progressive increase in the glass transition temperature, it also alters the fold surface free energy. The observed melting points were consistent with depression of the equilibrium melting point by the crosslinks produced by irradiation. These two effects alone are sufficient to account for the inhibition of crystallization on irradiation of PEEK by protons. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1094–1103, 2008 相似文献
128.
K.A. Kurnia F. Harris C.D. Wilfred M.I. Abdul Mutalib T. Murugesan 《The Journal of chemical thermodynamics》2009,41(10):1069-1073
Solubility of CO2 in six hydroxyl ammonium ionic liquids 2-hydroxyethanaminium acetate [hea], bis(2-hydroxyethyl)ammonium acetate [bheaa], 2-hydroxy-N-(2-hydroxyethyl)-N-methylethanaminium acetate [hhemea], 2-hydroxyethanaminium lactate [hel], bis(2-hydroxyethyl)ammonium lactate [bheal], 2-hydroxy-N-(2-hydroxyethyl)-N-methylethanaminium lactate [hhemel] at temperatures (298.15, 313.15, and 328.16) K and pressures ranging from (100 to 1600) kPa was determined. From the experimental solubility data, the Henry’s constant of CO2 for each hydroxyl ammonium ionic liquids was estimated and reported as a function of temperature. Furthermore, enthalpy and entropy of absorption were obtained from estimated Henry’s constant. The results showed that the solubility increase with increasing pressure and decrease with increasing temperature and the solubility of CO2 in these six hydroxyl ammonium ionic liquids was in sequence: [hea] > [bheaa] > [hel] > [bheal] > [hhemel] > [hhemea]. 相似文献
129.
Abdul Rehman Khan Johnson MathewKhawla Al-Shayji Majed Sari 《European Polymer Journal》2002,38(5):1013-1023
The synthesis of copolyesteramides using para-acetamido benzoic acid (PABA) and polyethylene terephthalate (PET) by melt polymerization has been studied in detail. The performance of three transesterification catalysts are assessed for three different initial compositions, PABA 60 mol%/PET 40%, PABA 50 mol%/PET 50% and PABA 40 mol%/PET 60%. The polycondensations are found to obey second order kinetics, irrespective of whether the reaction was catalysed or not. The mechanism of initial stage polymerization kinetics of the copolymers has been fully explained.It is suggested that acetic acid is evolved only by the homopolymerization of PABA and that the insertion of a monomer of homopolymer of PABA into PET does not yield any acetic acid. A set of differential equations containing three different rate constants, k1 for homopolymerization of PABA, k2 for PET reaction with dimer of PABA and k3 for PABA reaction with copolymer of PABA and PET has been developed and numerically solved, to study the initial stage kinetics. The computed values of acetic acid are compared with the experimentally collected amount and the three rate constants are optimized using a differential algebraic optimization technique. The present model represents the data with an acceptable accuracy with an average % error of less than 5% between experimental and computed values for the entire experimental range. The correlation coefficient values range between 0.988 and 0.999.Differential scanning analysis of the copolyestermides indicates that 40 mol% PABA and 60% PET had the highest enthalpy values of the order of 18 kJ/mol. It is found that within the copolyesteramide series the degree of crystallinity increased with the increase of PET contents in the feed mixture to the batch reactor. 相似文献
130.
P.D. Lokhande Abdul Raheem S.T. Sabale A.R. Chabukswar S.C. Jagdale 《Tetrahedron letters》2007,48(39):6890-6892
The reaction of substituted salicyaldehydes with hydrazine hydrochloride under different conditions gave the corresponding 1-H indazoles. However, the reaction of benzaldehydes with hydrazine hydrate under the same conditions yielded only hydrazones. 相似文献