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121.
Magnetite particles of different diameters were synthesized by chemical co-precipitation technique and the same are dispersed
in dodecane to prepare a magnetic fluid. The results of X-ray diffraction, magnetization measurements, ac susceptibility and
viscosity measurements are analyzed and discussed in the text. 相似文献
122.
123.
R. K. Upadhyay 《Chromatographia》1978,11(4):197-201
Summary Twenty four new anils derived from thiophen glyoxal have been resolved and estimated quantitatively on thinlayers of silica
gel with starch as binder. RF and spectroscopic correlations were used in the identification of isomers. Owing to their fast colours, no locating agent
was needed. 相似文献
124.
Uzra Diwan Virendra Kumar Rakesh K. Mishra Nishant Kumar Rana Biplob Koch Manish Kumar Singh K.K. Upadhyay 《Analytica chimica acta》2016
The present study deals with the photophysical property of a pyrene-benzthiazolium conjugate R1, as a strong intramolecular charge transfer (ICT) probe exhibiting long wavelength emission in the red region. Unlike traditional planar polyaromatic hydrocarbons whose aggregation generally quenches the light emission, the pyrene based R1 was found to display aggregation-induced emission (AIE) property along with simultaneous increase in its quantum yield upon increasing the water content of the medium. The R1 exhibits high specificity towards HSO3−/SO32− by interrupting its own ICT producing there upon a large ratiometric blue shift of ∼220 nm in its emission spectrum. The lowest detection limit for the above measurement was found to be 8.90 × 10−8 M. The fluorescent detection of HSO3− was also demonstrated excellently by test paper strip and silica coated TLC plate incorporating R1. The live cell imaging of HSO3─ through R1 in HeLa cells was studied using fluorescence microscopic studies. The particle size and morphological features of R1 and R1-HSO3− aggregates in aqueous solution were characterized by DLS along with SEM analysis. 相似文献
125.
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
126.
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
127.
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
128.
Archana Srivastava S. N. Tiwari A. N. Upadhyay M. Zulfequar Shamshad A. Khan 《Journal of Thermal Analysis and Calorimetry》2017,129(3):1435-1444
Present research work describes the crystallization kinetics and structural studies in Se85In15?xZnx chalcogenide glasses. Bulk alloys of Se85In15?xZnx were synthesized by melt-quenching procedure. High resolution X-ray diffraction (HRXRD) was used to confirm the amorphous nature of synthesized samples. Non-isothermal differential scanning calorimetry (DSC) measurements were performed at 5, 10, 15, 20 and 25 K min?1 heating rates to study kinetics of crystallization in Se85In15?xZnx. Various crystallization parameters such as glass transition (T g), onset crystalline (T c), peak crystallization (T p) and melting temperature (T m) were calculated from DSC curves. The activation energies of structural relaxation (ΔE t) and crystallization (ΔE c) were determined by using Kissinger, Moynihan and Ozawa approaches. ΔE t is found to be the lowest for Se85In6Zn9 sample which shows this sample has the highest probability of escape to a state of lower configurational energy and has greater stability. Thermal stability of various compositions was studied and found to vary with Zn content. Further, HRXRD and field emission scanning electron microscope were used for the study of first phase transformation in Se85In15?xZnx samples. 相似文献
129.
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
130.
Upadhyay RV Parekh K Mehta RV 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,187(2):314-319
Electron spin resonance (ESR) spectra of magnetic fluids involving polydispersed Zn(0.5)Fe(0. 5)Fe(2)O(4) (FZ5) and Zn(0.7)Fe(0. 3)Fe(2)O(4) (FZ7) nanomagnetic particles are scanned from 4.2 to 300K. The FZ7 fluid exhibits certain distinct features below 40K which are different from FZ5 fluid. These include (i) an isotropic shift in resonance field in zero-field-cooled ESR study, (ii) deviation of resonance field from sin(2)theta behavior (where theta is the angle between axis of the particle and field) in field cooled (FC) sample and (iii) abrupt increase in anisotropy field for FC sample. The results are analyzed in light of the core-shell model for nanomagnetic particles. 相似文献