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131.
Copolymerization of racemic propylene oxide with carbon dioxide is investigated in the presence of economically inexpensive and effective achiral salophenCo(III)X [salophen = N,N'-bis(3,5-di-tert-butylsalicylidene)-phenylenediimine, X = pentaflorobenzoate] catalyst and tetrabutyl ammonium bromide as co-catalyst. Effects of different variables like monomer to catalyst ratio, catalyst/co-catalyst ratio, temperature, pressure of CO2 on molecular weight, yield and selectivity of poly(propylene carbonate) [PPC] have been investigated. The maximum Mw of 25.8 g/mol has been obtained at 15 bar and 50°C. All the samples were found to have excellent polydispersity near to 1. 相似文献
132.
Upadhyay SP Pissurlenkar RR Coutinho EC Karnik AV 《The Journal of organic chemistry》2007,72(15):5709-5714
A furo-fused BINOL based chiral crown was developed as an enantioselective chiral sensor for phenylethylamine and ethyl ester of valine. Fusion of furan to BINOL has resulted in a highly stereo-discriminating backbone for the chiral crown developed. This chiral crown exhibited a fluorescence enhancement difference of 2.97 times between two enantiomers of phenylethylamine and 2.55 times between two enantiomers of ethyl ester of valine. The ratio of association constants for two diastereomeric complexes of two enantiomers of phenylethylamine was found to be 11.30, and the ratio for two enantiomers of ethyl ester of valine was 7.02. 相似文献
133.
An efficient and economical method was developed for synthesis of 3 alkynyl-3-hydroxyindolin-2-ones by addition of iodoalkynes to isatins using zinc dust. 相似文献
134.
Surface properties of a Melinex 800 PET polymer material modified by an atmospheric-pressure air dielectric barrier discharge (DBD) have been studied using X-ray photoelectron microscopy (XPS) and contact angle measurement. The results show that the material surface treated by the DBD was modified significantly in chemical composition, with the highly oxidised carbon species increasing as the surface processing proceeds. The surface hydrophilicity was dramatically improved after the treatment, with the surface contact angle reduced from 81.8° for the as-supplied sample to lower than 50° after treatment. Post-treatment recovery effect is found after the treated samples were stored in air for a long period of time, with the ultimate contact angles, as measured, being stabilised in the range 58-69° after the storage, varying with the DBD-treatment power density. A great amount of the C-O type bonding formed during the DBD treatment was found to be converted into the CO type during post-treatment storage. A possible mechanism for this bond conversion has been suggested. 相似文献
135.
R.R. Upadhyay K. Miki O.A. Ezekoye J. Marschall 《Experimental Thermal and Fluid Science》2011,35(8):1588-1599
In this paper, a stochastic system based Bayesian approach is applied to estimate different model parameters and hence quantify the uncertainty of a graphite nitridation experiment. The Bayesian approach is robust due to its ability to characterize modeling uncertainties associated with the underlying system and is rigorous due to its exclusive foundation on the axioms of probability theory. We choose an experiment by Zhang et al. [1] whose main objective is to measure the reaction efficiency for the active nitridation of graphite by atomic nitrogen. To obtain the primary physical quantity of interest, we need to model and estimate the uncertainty of a number of other physical processes associated with the experimental setup. We use the Bayesian method to obtain posterior probability distributions of all the parameters relevant to the experiment while taking into account uncertainties in the inputs and the modeling errors. We use a recently developed stochastic simulation algorithm which allows for efficient sampling in the high-dimensional parameter space. We show that the predicted reaction efficiency of the graphite nitridation and its uncertainty is ∼3.1 ± 1.0 × 10−3 that is slightly larger than the ones deterministically obtained by Zhang et al. [1]. 相似文献
136.
Mishra RK Upadhyay KK Shukla S Mishra R 《Chemical communications (Cambridge, England)》2012,48(35):4238-4240
We report herein the first small molecule based self-assembled fluorescent trinuclear Zn(II) supramolecular cylindrical motif as a structural and functional model of the active site of P1 nuclease. The DNA binding of the same was investigated through UV-Vis, fluorescence and circular dichroism studies. 相似文献
137.
Edmund J Keliher Thomas Reiner Greg M Thurber Rabi Upadhyay Ralph Weissleder 《ChemistryOpen》2012,1(4):177-183
A number of exendin derivatives have been developed to target glucagon-like peptide 1 (GLP-1) receptors on beta cells in vivo. Modifications of exendin analogues have been shown to have significant effects on pharmacokinetics and, as such, have been used to develop a variety of therapeutic compounds. Here, we show that an exendin-4, modified at position 12 with a cysteine conjugated to a tetrazine, can be labeled with 18F-trans-cyclooctene and converted into a PET imaging agent at high yields and with good selectivity. The agent accumulates in beta cells in vivo and has sufficiently high accumulation in mouse models of insulinomas to enable in vivo imaging. 相似文献
138.
We present a new ecological model, which displays “edge of chaos” (EoC) in parameter space. This suggests that ecological systems are not chaotic, instead, their dynamics can be characterized as short-term recurrent chaos. The system’s dynamics is unpredictable and admits bursts of short-term predictability. We also provide results, which suggest that fully developed chaos will rarely be observed in natural systems. 相似文献
139.
Pradeep Dewangan D. P. Bisen Nameeta Brahme Raunak Kumar Tamrakar Shweta Sharma Kanchan Upadhyay 《Optical and Quantum Electronics》2018,50(10):367
Sr3MgSi2O8:Dy3+ Nano-rods were synthesized by using solid state reaction method. The structural properties, morphology and band structure properties of the phosphor was studied. The structural properties were examined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Bonding behaviour of the phosphor was also determined by recording the FTIR spectra of the phosphor. Band structure i.e. band gap of the phosphor was determined by recording the absorption spectrum. The absorption spectrum was recorded for the sample and the band gap was determined by using Tauc plot. Band gap of the phosphor was found around 5.4 eV. 相似文献
140.
Nonlinear Dynamics - The firing activities of multiple timescale dynamics for single neurons can be treated with fractional-order derivative. It has been shown in previous studies (theoretical and... 相似文献