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941.
942.
943.
Mössbauer and magnetic investigations were carried out on a series of Li-Zn-Ti ferrites with compositional formula Li035?+?0.5t Zn03Ti t Fe2.35???1.5t O4. Mössbauer spectra were taken at room temperature and analysed to yield information on hyperfine properties like isomer shift, quadrupole splitting and nuclear magnetic fields. Magnetic properties like Curie temperature and saturation magnetization have also been studied. The magnetic properties were observed to fall with increased values of ‘t’. The results obtained and the mechanisms involved are discussed. 相似文献
944.
The reaction of α,β-chalcone ditosylates with various reagents such as phenylhydrazine hydrochloride, semicarbazide hydrochloride and thiosemicarbazide in suitable conditions leads to 1,2-aryl shift, thereby providing a novel route for the synthesis of 1,4,5-trisubstituted pyrazoles. 相似文献
945.
An efficient new method for the silylation of p‐nitrobenzyl‐2‐diazoacetoacetate using hexamethyl disilane and iodine is presented. 相似文献
946.
M. Dhandapani L. Thyagu P. Arun Prakash G. Amirthaganesan M. A. Kandhaswamy V. Srinivasan 《Crystal Research and Technology》2006,41(4):328-331
Potassium magnesium sulphate hexahydrate (picromerite) was synthesized and single crystals were obtained from saturated aqueous solution by slow evaporation method at room temperature. The crystals were bright, colourless and transparent having well defined external faces. The grown crystals were characterized through Fourier Transform Infrared (FTIR) spectral studies and thermal analysis. The FTIR data were used to assign the characteristic vibrational frequencies of the various chemical bonds in the compound. The compound crystallizes in monoclinic lattice with the space group P21/c. The thermogravimetry (TG) indicates the removal of only two water molecules around 100 °C. A suitable decomposition pattern was formulated based on the percentage weight losses observed in TG of the compound. The results of differential thermal analysis (DTA) conform to the results of TGA. Differential scanning calorimetry (DSC) analysis carried out at high temperature suggests that the occurrence of two phase transitions in the crystal between 140 and 180 °C. When the crystal was cooled below the room temperature up to –170 °C, no thermal anomaly was observed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
947.
Asymptotics for Wavelet Based Estimates of Piecewise Smooth Regression for Stationary Time Series 总被引:3,自引:1,他引:2
Young K. Truong Prakash N. Patil 《Annals of the Institute of Statistical Mathematics》2001,53(1):159-178
Wavelet methods are used to estimate density and (auto-) regression functions that are possibly discontinuous. For stationary time series that satisfy appropriate mixing conditions, we derive mean integrated squared errors (MISEs) of wavelet-based estimators. In contrast to the case for kernel methods, the MISEs of wavelet-based estimators are not affected by the presence of discontinuities in the curves. Applications of this approach to problems of identification of nonlinear time series models are discussed. 相似文献
948.
Vibha Saxena Vinay Shirodkar Rajiv Prakash 《Applied biochemistry and biotechnology》2001,96(1-3):63-69
A device has been developed for the measurement of copper(II) ions (Cu++) in aqueous medium. The device reported here is an electrochemical transistor that consists of two platinum electrodes separated
by 100-μm spacing and bridged with an anodically grown polycarbazole film. The undoped polycarbazole film is observed to be
highly selective for the Cu(II) ions. In a completed device, the conductivity of the polycarbazole film changes on addition
of Cu (II)ions. This change in conductivity is attributed to the conformational changes in the polymer phase on occupation
of the Cu(II) ions, without affecting electron/proton transfer. The device turns on by adding 2.5×10−6
M Cu(II) ions and reaches a saturation region above a concentration of 10−4
M Cu(II) ions. In this concentration range, the plot of I
D
vs log[Cu(II)] is linear. The selectivity of the device for other metal ions such as Cu(I), Co(II), Fe(II), Fe(III), Zn(II),
and Pb(II) is also studied. 相似文献
949.
J. Muthukumaran A. Parthiban H. Surya Prakash Rao R. Krishna 《Journal of chemical crystallography》2011,41(12):1927-1934
Abstract
4H-chromenes are among the essential groups of biologically important compounds used as synthetic ligands for drug designing and discovery process. In this study, we have presented the single-crystal structure analysis of racemic 4H-chromene derivative namely N-methyl-3-nitro-4-(nitromethyl)-4H-chromen-2-amine. The optical rotation measurement data is supporting that the title compound is racemic in nature. The compound was crystallized in monoclinic crystal system in the non-centrosymmetric space group P21 with unit cell parameters a = 5.1041 (3), b = 7.7519 (4), c = 14.7974 (8), α = 90°, β = 97.088 (5)° and γ = 90°. The nitro group of title compound is disordered over two orientations (N3A/O4A/O5A & N3B/O4B/O5B) with the refined site-occupancy ratio of 0.626(6)/0.374(6). The structure was solved by direct methods using the program SHELXS-97 and refined by SHELXL-97 with the full-matrix least square procedure to a final R-value of 0.0429 and Goodness of Fit (GooF) of 0.982. The molecules in the unit cell are stabilized by N–H···O and C–H···O types of hydrogen bonds. The intermolecular hydrogen bonds are forming C (6) motifs, which is observed to contribute the crystal packing stability. Moreover, the intramolecular hydrogen bonds are forming S (6) motif essential to stabilize the molecular structure of title compound. 相似文献950.