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1.
Mithu VS Paul S Kurur ND Madhu PK 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,209(2):359-363
We compare in this communication several heteronuclear dipolar decoupling sequences in solid-state nuclear magnetic resonance experiments under a magic-angle spinning frequency of 60 kHz. The decoupling radiofrequency field amplitudes considered are 190 and 10 kHz. No substantial difference was found among the sequences considered here in performance barring the difference in the optimisation protocol of the various schemes, an aspect that favours the use of swept-frequency two pulse phase modulation (SW(f)-TPPM). 相似文献
2.
Baidya T Gayen A Hegde MS Ravishankar N Dupont L 《The journal of physical chemistry. B》2006,110(11):5262-5272
Nanocrystalline Ce(1)(-)(x)Ti(x)O(2) (0 < or = x < or = 0.4) and Ce(1-)(x)(-)(y)Ti(x)Pt(y)O(2)(-)(delta) (x = 0.15, y = 0.01, 0.02) solid solutions crystallizing in fluorite structure have been prepared by a single step solution combustion method. Temperature programmed reduction and XPS study of Ce(1)(-)(x)Ti(x)O(2) (x = 0.0-04) show complete reduction of Ti(4+) to Ti(3+) and reduction of approximately 20% Ce(4+) to Ce(3+) state compared to 8% Ce(4+) to Ce(3+) in the case of pure CeO(2) below 675 degrees C. The substitution of Ti ions in CeO(2) enhances the reducibility of CeO(2). Ce(0.84)Ti(0.15)Pt(0.01)O(2)(-)(delta) crystallizes in fluorite structure and Pt is ionically substituted with 2+ and 4+ oxidation states. The H/Pt atomic ratio at 30 degrees C over Ce(0.84)Ti(0.15)Pt(0.01)O(2)(-)(delta) is 5 and that over Ce(0.99)Pt(0.01)O(2)(-)(delta) is 4 against just 0.078 for 8 nm Pt metal particles. Carbon monoxide and hydrocarbon oxidation activity are much higher over Ce(1-)(x)(-)(y)Ti(x)Pt(y)O(2) (x = 0.15, y = 0.01, 0.02) compared to Ce(1)(-)(x)Pt(x)O(2) (x = 0.01, 0.02). Synergistic involvement of Pt(2+)/Pt degrees and Ti(4+)/Ti(3+) redox couples in addition to Ce(4+)/Ce(3+) due to the overlap of Pt(5d), Ti(3d), and Ce(4f) bands near E(F) is shown to be responsible for improved redox property and higher catalytic activity. 相似文献
3.
Fluorite-type Ce0.5Zr0.5O2 and Ce0.5Hf0.5O2 have been synthesized by a solution combustion route, and their oxygen release and reduction have been investigated up to 850 degrees C. On reduction, the zirconium system forms two pyrochlore phases, Ce2Zr2O7 (pyrochlore-I) and Ce2Zr2O6.2 (pyrochlore-II), while the hafnium system forms only a disordered fluorite phase with the composition Ce0.5Hf0.5O1.77, under the same experimental conditions. The crystal structures of the reduction products have been characterized by powder X-ray diffraction and Rietveld refinement, and their electronic structures have been investigated by photoelectron spectroscopy and electrical conductivity measurements. Pyrochlore-I (a = 10.6727(4) A) is a semiconductor, while pyrochlore-II (a = 10.6463(8) A) is a good conductor (with a nearly temperature independent resistivity of approximately 2.5 ohm.cm in the 400-1000 K range). X-ray photoelectron spectroscopy (XPS) shows an admixture of Ce(5d,6s) with Zr(4d) and O(2p) and a significant density of states near EF in the highly reduced pyrochlore-II phase. The changes have been rationalized in terms of a qualitative energy band scheme that brings out the special role of zirconium vis-à-vis hafnium in the reduction/oxygen release properties of Ce0.5Zr0.5O2 and Ce0.5Hf0.5O2. 相似文献
4.
C.?M.?de?Silva R.?Baidya M.?Khashehchi I.?MarusicEmail author 《Experiments in fluids》2012,52(2):425-440
Simulations of tomographic particle image velocimetry (Tomo-PIV) are performed using direct numerical simulation data of a
channel flow at Reynolds number of Re
τ = 934, to investigate the influence of experimental parameters such as camera position, seeding density, interrogation volume
size and spatial resolution. The simulations employ camera modelling, a Mie scattering illumination model, lens distortion
effects and calibration to realistically model a tomographic experiment. Results are presented for camera position and orientation
in three-dimensional space, to obtain an optimal reconstruction quality. Furthermore, a quantitative analysis is performed
on the accuracy of first and second order flow statistics, at various voxel sizes normalised using the viscous inner length
scale. This enables the result to be used as a general reference for wall-bounded turbulent experiments. In addition, a ratio
relating seeding density and the interrogation volume size is proposed to obtain an optimal reference value that remains constant.
This can be used to determine the required seeding density concentration for a certain interrogation volume size. 相似文献
5.
The imidazoles 1a-g add to the CC-double bond of the iminium ion 2 with rate constants as predicted by the equation log k = s(N)(N + E). Unfavourable proton shifts from the imidazolium unit to the enamine fragment in the adduct 3 account for the failure of imidazoles to take part in iminium-activated aza-Michael additions to enals. 相似文献
6.
Priyadip Das Amal Kumar Mandal Nellore Bhanu Chandar Mithu Baidya Harshad B. Bhatt Bishwajit Ganguly Dr. Sudip K. Ghosh Dr. Amitava Das 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(48):15382-15393
In this work, we have rationally designed and synthesized two new reagents ( L1 and L2 ), each bearing a pendant aldehyde functionality. This aldehyde group can take part in cyclization reactions with β‐ or γ‐amino thiols to yield the corresponding thiazolidine and thiazinane derivatives, respectively. The intramolecular charge‐transfer (ICT) bands of these thiazolidine and thiazinane derivatives are distinctly different from those of the molecular probes ( L1 and L2 ). Such changes could serve as a potential platform for using L1 and L2 as new colorimetric/fluorogenic as well as ratiometric sensors for cysteine (Cys) and homocysteine (Hcy) under physiological conditions. Both reagents proved to be specific towards Cys and Hcy even in the presence of various amino acids, glucose, and DNA. Importantly, these two chemodosimetric reagents could be used for the quantitative detection of Cys present in blood plasma by using a pre‐column HPLC technique. Such examples are not common in contemporary literature. MTT assay studies have revealed that these probes have low cytotoxicity. Confocal laser scanning micrographs of cells demonstrated that these probes could penetrate cell membranes and could be used to detect intracellular Cys/Hcy present within living cells. Thus, the results presented in this article not only demonstrate the efficiency and specificity of two ratiometric chemodosimeter molecules for the quantitative detection of Cys and Hcy, but also provide a strategy for developing reagents for analysis of these vital amino acids in biological samples. 相似文献
7.
Jun-Bo Chen Dr. Cen Zhou Ru-Qiang Lu Dr. Xin-Chang Wang Hang Qu Dr. Mithu Saha Hao-Liang Liu Prof. Hui Zhang Prof. Xiao-Yu Cao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(5):1293-1299
Triindolo-truxene, a C3-symmetric molecule with a large π-conjugated plane, has six methylene carbon atoms and three aromatic carbon atoms that can be facilely functionalized. Herein, butyl, carbonyl, cyano, and/or malononitrile groups were introduced at six methylene carbon atoms (6-, 14-, 22- or 8-, 16-, 24-positions) and/or three aromatic carbon atoms (2-, 10-, and 18-positions) of triindolo-truxene to produce eight derivatives. Their photophysical properties, electrochemical properties, and molecular assembly can be effectively modulated by substituents and substitution patterns. Incorporation of electron-deficient groups led to redshifts in both the absorption and emission of these derivatives and also lowered their HOMO and LUMO levels. Different substitution patterns resulted in the different intramolecular donor–acceptor interactions. Electron-deficient substituents at the methylene carbon atoms in the 6-, 14-, and 22-positions led to intramolecular charge transfer from the fluorene arms to the truxene core, whereas the corresponding substitutions at the methylene carbon atoms in the 8-, 16-, and 24-positions resulted in intramolecular charge transfer from the truxene core to the fluorene arms. The molecular packing in single crystals and molecular aggregation in solution are also influenced by the substituents and substitution patterns. This work provides a straightforward strategy to alter the properties of triindolo-truxene. 相似文献
8.
Poonia Nisha Lal Kashmiri Kumar Ashwani Kumar Anil Sahu Srikanta Baidya Anurag T. K. Kumar Rajnish 《Molecular diversity》2022,26(5):2375-2391
Molecular Diversity - Some urea-thiazole/benzothiazole hybrids with a triazole linker were synthesized via Cu(I)-catalysed click reaction. After successfully analysed by various spectral techniques... 相似文献
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10.
Sibaji Nandi Mullah Muhaiminul Islam Mithu Saha Sivaprasad Mitra Snehadrinarayan Khatua 《合成通讯》2016,46(17):1461-1476
An efficient, one-pot, solvent-free, regioselective synthesis of functionalized [1,6]-naphthyridines was explored by a heterogeneous catalyst via a three-component multicomponent reaction (MCR). KF/basic alumina–catalyzed double heteroannulation of aryl alkyl ketones, malononitrile, and alkyl amines generates the compounds with high appendage diversity combinatorially via Knoevenagel condensation followed by Michael addition and cyclization pathway. Short reaction time, high yield, simple reaction technique, and recoverability and reusability of the catalyst without compromising the yield and purity of the compounds are the salient features of this methodology. Additionally, these compounds exhibit promising photophysical properties. 相似文献