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排序方式: 共有468条查询结果,搜索用时 15 毫秒
1.
2.
Balakrishnan S. Anju Neeraja R. Nair Dr. Subrata Kundu 《Angewandte Chemie (International ed. in English)》2023,62(48):e202311523
Nitrite (NO2−) and nitric oxide (NO) interconversion is crucial for maintaining optimum NO flux in mammalian physiology. Herein we demonstrate that [ L 2CuII(nitrite)]+ moieties (in 2 a and 2 b ; where, L = Me2PzPy and Me2PzQu ) with distorted octahedral geometry undergo facile reduction to provide tetrahedral [ L 2CuI]+ (in 3 a and 3 b ) and NO in the presence of biologically relevant reductants, such as 4-methoxy-2,6-di-tert-butylphenol (4-MeO-2,6-DTBP, a tyrosine model) and N-benzyl-1,4-dihydronicotinamide (BNAH, a NAD(P)H model). Interestingly, the reaction of excess NO gas with [ L 2CuII(MeCN)2]2+ (in 1 a ) provides a putative {CuNO}10 species, which is effective in mediating the nitrosation of various nucleophiles, such as thiol and amine. Generation of the transient {CuNO}10 species in wet acetonitrile leads to NO2− as assessed by Griess assay and 14N/15N-FTIR analyses. A detailed study reveals that the bidirectional NOx-reactivity, namely, nitrite reductase (NIR) and NO oxidase (NOO), at a common CuII site, is governed by the geometric-preference-driven facile CuII/CuI redox process. Of broader interest, this study not only highlights potential strategies for the design of copper-based catalysts for nitrite reduction, but also strengthens the previous postulates regarding the involvement of red copper proteins in denitrification. 相似文献
3.
S. Madhusudana Rao A.R. Balakrishnan 《International Journal of Heat and Fluid Flow》1998,19(6):661-671
The flow boiling phenomenon over a heated tube restricted by an interference sleeve, which is a passive enhancement technique, has been analysed using a semi-empirical approach. The liquid boiled was water flowing through an annular cross-section. A model developed earlier for the case of pool boiling over porous surfaces has been adapted after modification to pool boiling with interference surfaces using equivalent geometrical parameters and a modified permeability factor. This was further extended to saturated flow boiling situation using an additive mechanism. The single phase heat transfer coefficient required for the additive mechanism is obtained from an experimental correlation developed in the present study. The suppression factors evaluated for the eight sleeve geometries used in the present investigation are expressed in terms of the single phase Reynolds number and the Martinelli parameter. Very good agreement was observed between the model predictions and experimental data validating the mechanisms postulated. Further, a purely empirical correlation based on the present experimental data has been proposed to estimate the two-phase heat transfer coefficient. While the empirical correlation shows a better fit with the experimental data, the additive model has a physical basis. 相似文献
4.
Abstract The kinetics of phase-transfer-agent-assisted free-radical polymerization of methyl methacrylate using K2S2O8 as the water-soluble initiator and triethylbenzylammonium chloride (TEBA) as the phase-transfer catalyst (PTC) was investigated in toluene-water biphase media at 60°C. The effect of varying [MMA], [K2S2O8], [TEBA], [H+], the ionic strength of the medium, and the temperature on the rate of polymerization (R p) was studied. R p was found to be proportional to [MMA]2, [K2S2O8]1, and [TEBA]0.5. Based on the kinetic results, a mechanism involving initiation of polymerization by phase-transferred S2O8 2- and termination by Q+ (quaternary ammonium ion) is proposed. 相似文献
5.
Birnbaum and Saunders introduced a two‐parameter lifetime distribution to model the fatigue life of a metal, subject to cyclic stress. Since then, extensive work has been done on this model providing different interpretations, constructions, generalizations, inferential methods, and extensions to bivariate, multivariate, and matrix‐variate cases. More than 200 papers and one research monograph have already appeared describing all these aspects and developments. In this paper, we provide a detailed review of all these developments and, at the same time, indicate several open problems that could be considered for further research. 相似文献
6.
A three step synthesis of novel ‘multi-site’ water soluble phase transfer catalyst viz., α,α′-bis(triethyl ammonium methylene chloride) β-phenyl ethene and its utility in various organic biphase reactions are described. 相似文献
7.
Yandan Yang Hon Keung Tony Ng Narayanaswamy Balakrishnan 《Computational Statistics》2016,31(2):609-641
Statistical estimation of the model parameters of component lifetime distribution based on system lifetime data with known system structure is discussed here. We propose the use of stochastic expectation-maximization (SEM) algorithm for obtaining the maximum likelihood estimates of model parameters based on complete and censored system lifetimes. Different ways of implementing the SEM algorithm are also studied. We have shown that the proposed methods are feasible and are easy to implement for various families of component lifetime distributions. The proposed methodologies are then illustrated with two popular lifetime models—the Weibull and Birnbaum-Saunders distributions. Monte Carlo simulation is then used to compare the performance of the proposed methods with the corresponding estimation by direct maximization. Finally, two illustrative examples are presented along with some concluding remarks. 相似文献
8.
Benoit Roberge Serge Jandl Agung A. Nugroho Thomas T. M. Palstra Le D. Tung Geetha Balakrishnan 《Journal of Raman spectroscopy : JRS》2015,46(11):1157-1160
The coexistence at low temperature in YVO3 and LaVO3 of two competing phases with defined orbital and spin orientations is studied by Raman spectroscopy. The temperature evolution of the phonons indicates that phase coexistence, due to strain in YVO3 and fluctuations in LaVO3, is not restricted to small R ionic radius in RVO3 compounds. Also, a typical temperature at 50 K is inferred from the temperature dependence of the intensities in LaVO3. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
9.
Sadhasivam Velu Sankar Balakrishnan Elamathi Ganesan Mariyappan Mathappan Siva Ayyanar 《Research on Chemical Intermediates》2020,46(1):681-700
Research on Chemical Intermediates - This work is described as an environmental friendly approach for Cu(OAc)2 entrapped on ethylene glycol-modified melamine–formaldehyde-based polymeric... 相似文献
10.
The single- and multi-mode Richtmyer–Meshkov instabilities (RMI) with reshock are numerically analyzed in two- and three-dimensional
domains. Four different types of air/SF
6 interface shapes are investigated in a shock tube configuration, and the predicted post-reshock growth rates are compared
with available empirical models of Mikaelian’s (Physica D 36(3):343–347, 1989) and Charakhch’an’s (J Appl Mech Tech Phys 41(1):23–31, 2000). The simulation of 3D multi-mode RMI shows good agreement with a past experimental study, but other interface types (2D
single-mode, 2D multi-mode and 3D single-mode) result in different growth rates after reshock. Parametric studies are therefore
performed to investigate the sensitivities of the post-reshock growth rates to model the empirical parameters. For single-mode
RMI configurations, the interface shape is found to be only a weak function of the post-reshock growth rate, as also predicted
by previous reshock models. The post-reshock growth rate shows a linear correlation to the velocity jump due to reshock; however,
it is only about a half of the prediction of Charakhch’an’s model even though the growth before reshock compares well with
pre-reshock models. The 3D single-mode post-reshock RMI growth rate is nearly 1.6 times larger than the 2D single-mode RMI.
The parametric studies of multi-mode RMI show two distinctly different growth rates depending on the mixing conditions at
reshock. If the interface remains sharp at the time of reshock, the post-reshock growth rate is as large as the single-mode
cases. However, if the interface is mixed due to non-linear interactions of bubbles and spikes, the growth rates becomes slow
and independent of the interface shapes. Overall, this study provides new insights into the flow features of reshocked RMI
for different initial perturbation types. 相似文献