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91.
We prove that there exists a finite universal Korovkin set with respect to positive spectral contraction operators for a Segal
algebra on a locally compact abelian groupG if and only ifĜ is finite dimensional separable metrizable space. 相似文献
92.
dc conductivity as a function of temperature has been measured for as-evaporated and annealed films of amorphous Si, grown by the vacuum evaporation technique. The experimental data suggest that conduction in the higher temperature range (~175–300 K) is by the thermally activated holes in the localized states near the valence band edge while conduction in the lower temperature range (~77–175 K) is found to be thermally assisted tunnelling in the localized states near the Fermi level. The activation energy for both the processes is found to increase with an increase in the annealing temperature. The average hopping distance, calculated for conduction near the Fermi level, is also found to increase with an increase in the annealing temperature. 相似文献
93.
A microwave-assisted, environmentally friendly, high-yielding, time-saving synthesis of medicinally important 3-substituted isocoumarins was carried out in a single step by direct condensation of homophthalic acid with aryol and acyl chlorides under solvent-free conditions without any solid support. The synthesised isocoumarins were structurally characterised by microanalysis, 1H NMR, EI, IR and UV. 相似文献
94.
The degradation of lignocellulosic wastes such as paddy straw, sorghum stalk, and banana pseudostem was investigated during solid-state fermentation by edible mushrooms Pleurotus eous and Lentinus connotus. Biological efficiency of 55-65% was observed in paddy straw followed by sorghum stalk (45%) and banana pseudostem (33%) for both fungal species. The activity of extracellular enzymes, namely cellulase, polyphenol oxidase, and laccase, together with the content of cellulose, lignin, and phenols, was studied in spent substrates on seventh, 17th, and 27th days of spawning, and these values were used as indicators of the extent of lignocellulosic degradation by mushroom. Both the mushroom species proved to be efficient degraders of lignocellulosic biomass of paddy straw and sorghum stalk, and the extent of cellulose degradation was 63-72% of dry weight (d.w.), and lignin degradation was 23-30% of the d.w. In banana pseudostem, the extent of the degradation was observed to be only 15-22% of the d.w. for both lignin and cellulose. Preferential removal of cellulose during initial growth period and delayed degradation of lignin were observed in all three substrates. This is associated with decrease in activity of cellulase and polyphenol oxidase and increase in laccase activity with spawn aging in spent substrates. Thus, bioconversion of lignocellulosic biomass by P. eous and L. connotus offers a promising way to convert low-quality biomass into an improved human food. 相似文献
95.
Dr. Nilofar Baral Soniya Rani Pinku Saikia Dr. Pradip Maity 《European journal of organic chemistry》2023,26(4):e202201238
Organophosphites are nucleophilic in nature and can act as a good leaving group owing to the stability of the phosphite anion. This dual reactivity makes them good candidates for nucleophilic organocatalysis. However, phosphites were introduced only in 2004 as the umpolung catalyst for acylsilane substrates utilizing sequential Brook rearrangements. Very recently, phosphites have been reported to catalyze aza-rearrangements and radical reactions. In this review, we discuss the reactivity parameters to understand its lack of use, as well as the potential for catalysis. 相似文献
96.
We obtain the expressions for sectional curvature, holomorphic sectional curvature and holomorphic bisectional curvature of a GCR-lightlike submanifold of an indefinite nearly K ¨ahler manifold and obtain characterization theorems for holo-morphic sectional and holomorphic bisectional curvature. We also establish a condi-tion for a GCR-lightlike submanifold of an indefinite complex space form to be a null holomorphically flat. 相似文献
97.
Biosourced carboxymethyl cellulose polymer electrolytes have been studied for potential application in electrochemical devices. The carboxymethyl cellulose was obtained by reacting cellulose derived from kenaf fibre with monochloroacetic acid. Films of the biosourced polymer electrolytes were prepared by solution-casting technique using ammonium acetate salt and (1-butyl)trimethyl ammonium bis(trifluoromethylsulfonyl)imide ionic liquid as charge carrier contributor and plasticizer, respectively. The shift of peak of carboxyl stretching in the Fourier transform infrared spectra confirmed the interactions between the host biosourced polymer with the ionic liquid. Scanning electron microscopy indicated that the incorporation of ionic liquid changed the morphology of the electrolyte films. The room temperature conductivity determined using impedance spectroscopic technique for the film without ionic liquid was 6.31 × 10?4 S cm?1 while the highest conductivity of 2.18 × 10?3 S cm?1 was achieved by the film integrated with 20 wt% (1-butyl)trimethylammonium bis(trifluoromethanesulfonyl) imide. This proved that the incorporation of ionic liquid into the salted system improved the conductivity. The improvement in conductivity was due to an increase in ion mobility. The results of linear sweep voltammetry showed that the electrolyte was electrochemically stable up to 3.07 V. 相似文献
98.
Anas S John J Sajisha VS John J Rajan R Suresh E Radhakrishnan KV 《Organic & biomolecular chemistry》2007,5(24):4010-4019
A novel reactivity of organoboronic acids with bicyclic hydrazines leading to the stereoselective formation of trans-vicinal disubstituted cyclopentenes in good to excellent yield is discussed. The reaction of cyclopentadiene and fulvene derived azabicyclic alkenes with organoboronic acids afforded the trans-3,4-disubstituted cyclopentenes and alkylidene cyclopentenes in good to excellent yields. The products, having a broad range of substituents, are important intermediates in the synthesis of a number of pharmaceutically important molecules. 相似文献
99.
Lobana Tarlok S. Paul Seema Hundal Geeta Obrai Sangeeta 《Transition Metal Chemistry》1999,24(2):202-205
Reaction of 1-hydroxypyridine-2-thione (HpyOS) in CHCl3 with Ag2CO3 suspended in CHCl3 under magnetic stirring followed by addition of PPh3 yields a product of stoichiometry: Ag(pyOS)(PPh3). The compound adopts a dimeric structure [Ag(pyOS)(PPh3)]2 (1) where each Ag atom acquires a distorted tetrahedral geometry by co-ordinating to one oxygen, two sulphur and one phosphorus atoms. The Ag2S2 core forms a parallelogram [Ag—S 2.507(1), 2.822(1)Å] with Ag—S—Ag and S—Ag—S angles of 74.8(1) and 105.2(1)°, respectively. 相似文献
100.
Anilinolysis of O‐butyl phenyl phosphonochloridothioate in acetonitrile: Synthesis,characterization, kinetic study,and reaction mechanism
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This paper describes a simple optimized method for the synthesis of O‐butyl phenyl phosphonochloridothioate ( 4 ) under mild conditions. The target compounds were characterized by 1H‐nuclear magnetic resonance (NMR), 13C‐NMR, and 31P‐NMR spectroscopy, as well as mass spectroscopy. The apparent structure of 4 was confirmed by optimization using the B3LYP/6‐311 + G(d,p) level in the Gaussian 09 program in acetonitrile. The nucleophilic substitution reactions of 4 with X‐anilines (XC6H4NH2) and deuterated X‐anilines (XC6H4ND2) were investigated kinetically in acetonitrile at 55.0°C. The free energy relationship with X in the anilines looked biphasic concave upwards with a break region between X = H and X = 3‐MeO, giving large negative ρX and small positive βX values. The deuterium kinetic isotope effects were secondary inverse (kH/kD < 1: 0.789‐0.995) and the magnitudes, (kH/kD), increased when the nucleophiles were changed from weakly basic to strongly basic anilines. A concerted SN2 mechanism is proposed on the basis of the selectivity parameters and the variation trend of the deuterium kinetic isotope effects with X. 相似文献