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31.
Lipase B from Candida antarctica was used to catalyze the condensation polymerization of 1,3-bis(3-carboxypropyl)tetramethyldisiloxane with three different alkanediols (1,4-butanediol, 1,6-hexanediol and 1,8-octanediol) in the bulk and under reduced pressure. The effect of temperature, vacuum, enzyme activity and enzyme concentration on the reaction kinetics was investigated. Progress of the reactions was monitored using Fourier Transform Infrared Spectroscopy (FTIR) and Gel Permeation Chromatography (GPC) by analyzing the samples collected at selected time intervals. In all the three polyesterification reactions that were investigated herein, the rate of product formation increased when the temperature was increased from 50 to 90 °C. An increase in the applied vacuum from 50 to 300 mm Hg (vacuum gauge pressure) was found to have little or no effect on the rate of product formation during the first stage of the reaction (24 h). However, the molecular weight of the polymer increased during the latter half of the reaction, apparently due to a shift from reaction control to diffusion control in the increasingly viscous system. The activity of the enzyme and chain-length of the alkanediols were found to be critical for the reactions investigated. Furthermore, the activity of the recovered lipase using THF and toluene was reduced to below 50%, apparently due to the enzyme leaching out from the immobilized acrylic resin. 相似文献
32.
Cation‐ and Anion‐Substituted Potassium Manganese Phosphate,KMnP3O9: Luminescence and Photocatalytic Studies 下载免费PDF全文
Sudhakar Reddy Chandiri Ravi Gundeboina Sreenu Kurra Ravinder Guje Malathi Maligi Vithal Muga 《Photochemistry and photobiology》2017,93(2):569-578
Phosphates as multifunctional materials were of vital importance in the environmental and energy fields. In the present work, a new cyclophosphate, potassium manganese phosphate (KMnP3O9) (hereafter KMPO), was prepared by solid state method. Cations (Ag+ and Cu2+) and anion (N3?) were substituted into KMPO lattice via ion‐exchange and solid state methods, respectively. The as‐prepared materials were characterized by powder X–ray diffraction, SEM–EDS and UV–visible diffuse reflectance spectra. Rietveld refinement was carried out for parent material. All the prepared materials were found to crystallize in the hexagonal lattice and isomorphous with KCoP3O9. The nitrogen content in N3?‐substituted KMPO was estimated by EDS and O‐N‐H analysis. The bandgap energy of the cation‐ and anion‐substituted samples was lower compared to that of pristine KMPO. Gouy method was employed to determine the magnetic susceptibility of KMPO. The photoluminescence property of Mn2+ in all the samples was studied, and the color coordinates were calculated using CIE 1931 chromaticity. The photocatalytic activity of visible light active material, N3?‐substituted KMPO, was examined against the degradation of methylene blue and methyl violet at ambient conditions. 相似文献
33.
T. Goverdhan Reddy P. Yadagiri Reddy V. Raghavendra Reddy Ajay Gupta K. Rama Reddy 《Hyperfine Interactions》2005,160(1-4):253-260
Electrical conductivity with and without magnetic field, d.c. magnetization and 151Eu Mössbauer studies were carried out in La0.38Eu0.29Ca0.33MnO3 perovskite manganite system. An insulating ground state is found throughout the temperature range with charge ordered (CO) state emerging at T CO ~ 140 K, where as an external magnetic field of 6 T induces metal-insulator transition at ~120 K. D.C. magnetization measurements show the antiferromagnetic (AFM) transition occurring at T N ≈ 48 K. The temperature dependent 151Eu Mössbauer measurements showed that the substituted Eu replaces La3+ in the 3+ charge state and a small magnetic moment gets induced at the Eu nucleus at low temperatures. The anomalous variation of the f- factor with temperature occurring around T N and T CO corroborates the occurrence of antiferromagnetic (AFM) and charge ordering (CO) transition, respectively. 相似文献
34.
Praveen Kumar Mupparapu Narasimha Swamy Thirukovela Sadanandam Gullapelli Mohan Kurra Srinivas Gali Namratha Vaddiraju 《Journal of heterocyclic chemistry》2021,58(6):1379-1387
In this study, a series of novel geminal bis 1,2,3-triazoles linked to 2H-furo[2,3-d][1,3]thiazine-2,4,5(1H,6H)-trione ( 3a-3m ) were prepared in one pot starting from 5-Acetyl-4-Hydroxy-1,3-thiazine-2,6-dione ( 1 ) to 6,6-diazido-2H-furo[2,3-d][1,3]thiazine-2,4,5(1H,6H)-trione ( 2 ) followed by Cu(I)-catalyzed azide-alkyne cycloaddition. The synthesized compounds were further explored for in vitro cytotoxic activity against PC3, A549, MCF-7, and HeLa cell lines and results revealed that the five compounds 3c , 3d , 3g , 3l , and 3m have displayed comparable in vitro cytotoxic activity with the standard drug Etoposide. 相似文献
35.
Jun Tang Tyler S. Mathis Narendra Kurra Asia Sarycheva Xu Xiao Mohamed N. Hedhili Qiu Jiang Husam N. Alshareef Baomin Xu Feng Pan Yury Gogotsi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(49):18013-18019
MXenes are a class of two‐dimensional (2D) transition metal carbides, nitrides and carbonitrides that have shown promise for high‐rate pseudocapacitive energy storage. However, the effects that irreversible oxidation have on the surface chemistry and electrochemical properties of MXenes are still not understood. Here we report on a controlled anodic oxidation method which improves the rate performance of titanium carbide MXene (Ti3C2Tx, Tx refers to ‐F, =O, ‐Cl and ‐OH) electrodes in acidic electrolytes. The capacitance retention at 2000 mV s?1 (with respect to the lowest scan rate of 5 mV s?1) increases gradually from 38 % to 66 % by tuning the degree of anodic oxidation. At the same time, a loss in the redox behavior of Ti3C2Tx is evident at high anodic potentials after oxidation. Several analysis methods are employed to reveal changes in the structure and surface chemistry while simultaneously introducing defects, without compromising electrochemically active sites, are key factors for improving the rate performance of Ti3C2Tx. This study demonstrates improvement of the electrochemical performance of MXene electrodes by performing a controlled anodic oxidation. 相似文献
36.
Mesram Manoj Kumar Dr. Parikibanda Venkataramana Prof. Parikibanda Yadagiri Swamy Dr. Yadaiah Chityala 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(70):17713-17721
A new route to synthesis of various mono-N-substituted hydrazines and hydrazides by involving in a new C−N bond formation by using N-amino-1,8-naphthalimide as a regenerated precursor was invented. Aniline and phenylhydrazines are reproduced upon reacting these individually with 1,8-naphthalic anhydride followed by hydrazinolysis. The practicality and simplicity of this C−N dihalo alkanes; developed a synthon for bond formation protocol was exemplified to various hydrazines and hydrazides. N-amino-1,8-naphthalimide is suitable synthon for transformation for selective formation of mono-substituted hydrazine and hydrazide derivatives. Those are selective mono - amidation of hydrazine with acid halides; mono-N-substituted hydrazones from aldehydes; synthesis of N-aminoazacycloalkanes from acetohydrazide scaffold and inserted to hydroxy derivatives; distinct synthesis of N,N-dibenzylhydrazines and N-benzylhydrazines from benzyl halides; synthesis of N-amino-amino acids from α-halo esters. Ecofriendly reagent N-amino-1,8-naphthalimide was regenerated with good yields by the hydrazinolysis in all procedures. 相似文献
37.
T. Satyanarayana Raju M. Ravikumar K. Vijay Kumar K. S. V. Raghavachary M. Satish Varma Ch. Surya Naga Malleswara Rao P. Yadagiri Swamy 《Chromatographia》2009,69(1-2):97-102
A simple, inexpensive and rapid isocratic LC method has been developed for the quantative determination of Rimonabant, an anti-obesity drug. The method can also be employed for the determination of Rimonabant and its impurities in the bulk drug. Degradation studies were performed on the bulk drug by heating to 60 °C, exposure to UV light at 254 nm, acid (0.5 N hydrochloric acid), base (0.5 N sodium hydroxide) and aqueous hydrolysis and oxidation with 3.0% v/v hydrogen peroxide. Considerable degradation was observed under oxidation conditions. Good resolution between the peaks corresponding to impurities produced during synthesis, degradation products and the analyte was achieved on a Phenomenex Gemini C18 LC column using a mobile phase consisting of a mixture of aqueous potassium dihydrogen phosphate (pH 3.0) and acetonitrile. The degradation samples were assayed against the reference standard of Rimonabant and the mass balance in each case was close to 99.5%. Validation of the method was carried out as per ICH requirements. 相似文献
38.
B. Sreenivasa Reddy M. Sreenath Reddy Ch. Gopal Reddy P. Yadagiri Reddy K. Rama Reddy 《Radiation measurements》2003,36(1-6):503-506
Radon/thoron levels are estimated in Khammam district as a part of “Radon/thoron mapping” program in Andhra Pradesh, India. About 100 dwellings were chosen at random covering most parts of Khammam district. Twin chamber cup dosimeters consisting of solid-state nuclear track detectors (SSNTDs, LR-115, Type-II) were used to evaluate the radiation levels at quarterly intervals for a period of one calendar year. The average radon and thoron concentrations were found to be 39.1±13.3 and 19.4±14.9 Bq/m3, respectively. Seasonal variations of radon/thoron levels were also studied. Variations of radon/thoron concentration levels with different types of dwellings have been studied. In the bare flooring dwellings thoron levels were found to be highest in comparison to concrete, limestone and marble floorings. 相似文献
39.
Various substituted benzimidazoles and imidazolo[4,5-b] pyridines 5a-c have been prepared by condensation of appropriate diamines and aldehydes in nitrobenzene. This method has been utilized to synthesize compounds 5f-h, which are analogues of the DNA binding fluorochrome Hoechst 33258. 相似文献
40.
A.V.Rama Rao E.Rajarathnam Reddy G.V.M. Sharma P. Yadagiri J.S. Yadav 《Tetrahedron letters》1985,26(4):465-468
Described herein is a convenient synthesis of coriolic acid () and dimorphecolic acid (), the two natural ionophores derived respectively from bovine heart mitochondria and also shown to be self defensive substances in rice plant against rice blast disease. 相似文献