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71.
We have studied the thermodynamic properties and microscopic structures of HgNa liquid alloy at 673 K on the basis of regular associated solution model. The concentrations of ApB type complex in a regular associated solution of Hg and Na have been determined. We have then used the concentration of complex to calculate the free energy of mixing, enthalpy of mixing, entropy of mixing, activity, concentration fluctuations in long wavelength limit SCC(0) and the Warren-Cowley short-range parameter α1. The analysis suggests that heterocoordination leading to the formation of complex Hg4Na is likely to exist in the liquid and is of a strongly interacting nature. The theoretical analysis reveals that the pairwise interaction energies between the species depend considerably on temperature and the alloy is more ordered towards Hg-rich region. 相似文献
72.
73.
Park IW Yoo J Kim B Adhikari S Kim SK Yeon Y Haynes CJ Sutton JL Tong CC Lynch VM Sessler JL Gale PA Lee CH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(9):2514-2523
A ditopic ion-pair receptor (1), which has tunable cation- and anion-binding sites, has been synthesized and characterized. Spectroscopic analyses provide support for the conclusion that receptor 1 binds fluoride and chloride anions strongly and forms stable 1:1 complexes ([1·F](-) and [1·Cl](-)) with appropriately chosen salts of these anions in acetonitrile. When the anion complexes of 1 were treated with alkali metal ions (Li(+), Na(+), K(+), Cs(+), as their perchlorate salts), ion-dependent interactions were observed that were found to depend on both the choice of added cation and the initially complexed anion. In the case of [1·F](-), no appreciable interaction with the K(+) ion was seen. On the other hand, when this complex was treated with Li(+) or Na(+) ions, decomplexation of the bound fluoride anion was observed. In contrast to what was seen with Li(+), Na(+), K(+), treating [1·F](-) with Cs(+) ions gave rise to a stable, host-separated ion-pair complex, [F·1·Cs], which contains the Cs(+) ion bound in the cup-like portion of the calix[4]pyrrole. Different complexation behavior was seen in the case of the chloride complex, [1·Cl](-). Here, no appreciable interaction was observed with Na(+) or K(+). In contrast, treating with Li(+) produces a tight ion-pair complex, [1·Li·Cl], in which the cation is bound to the crown moiety. In analogy to what was seen for [1·F](-), treatment of [1·Cl](-) with Cs(+) ions gives rise to a host-separated ion-pair complex, [Cl·1·Cs], in which the cation is bound to the cup of the calix[4]pyrrole. As inferred from liposomal model membrane transport studies, system 1 can act as an effective carrier for several chloride anion salts of Group 1 cations, operating through both symport (chloride+cation co-transport) and antiport (nitrate-for-chloride exchange) mechanisms. This transport behavior stands in contrast to what is seen for simple octamethylcalix[4]pyrrole, which acts as an effective carrier for cesium chloride but does not operates through a nitrate-for-chloride anion exchange mechanism. 相似文献
74.
75.
Lokendra Kumar Balvinder Singh Dilip Kumar Adhikari Joydeep Mukherjee Debashish Ghosh 《Applied biochemistry and biotechnology》2012,166(7):1723-1735
Purification and characterization of halotolerant, thermostable alkaline l-glutaminase from a Bacillus sp. LKG-01 (MTCC 10401), isolated from Gangotri region of Uttarakhand Himalaya, is being reported in this paper. Enzyme has
been purified 49-fold from cell-free extract with 25% recovery (specific activity 584.2 U/mg protein) by (NH4)2SO4 precipitation followed by anion exchange chromatography and gel filtration. Enzyme has a molecular weight of 66 kDa. l-Glutaminase is most active at pH 11.0 and stable in the pH range 8.0–11.0. Temperature optimum is 70 °C and is completely
stable after 3 h pre-incubation at 50 °C. Enzyme reflects more enhanced activity with 1–20% (w/v) NaCl, which is further reduced to 80% when NaCl concentration was increased up to 25%. l-Glutaminase is almost active with K+, Zn2+, and Ni2+ ions and K
m and V
max values of 240 μM and 277.77 ± 1.1 U/mg proteins, respectively. Higher specific activity, purification fold, better halo-tolerance,
and thermostability would make this enzyme more attractive for food fermentation with respect to other soil microbe derived
l-glutaminase reported so far. 相似文献
76.
Biocompatible organic acids and citrate-stabilized gold nanoparticles were interacted with nisin to generate robust antimicrobial agents, which display archetypical nisin activity even at elevated pH. 相似文献
77.
Eigenvalue problems play an important role in the dynamic analysis of engineering systems modeled using the theory of linear structural mechanics. When uncertainties are considered, the eigenvalue problem becomes a random eigenvalue problem. In this paper the density of the eigenvalues of a discretized continuous system with uncertainty is discussed by considering the model where the system matrices are the Wishart random matrices. An analytical expression involving the Stieltjes transform is derived for the density of the eigenvalues when the dimension of the corresponding random matrix becomes asymptotically large. The mean matrices and the dispersion parameters associated with the mass and stiffness matrices are necessary to obtain the density of the eigenvalues in the frameworks of the proposed approach. The applicability of a simple eigenvalue density function, known as the Marenko–Pastur (MP) density, is investigated. The analytical results are demonstrated by numerical examples involving a plate and the tail boom of a helicopter with uncertain properties. The new results are validated using an experiment on a vibrating plate with randomly attached spring–mass oscillators where 100 nominally identical samples are physically created and individually tested within a laboratory framework. 相似文献
78.
Anita Das Debasis Mukhopadhyay Satrajit Adhikari Michael Baer 《International journal of quantum chemistry》2012,112(13):2561-2570
The approach to calculate improved, two‐state, adiabatic‐to‐diabatic transformation angles (also known as mixing angles), presented before (see Das et al., J Chem Phys 2010, 133, 084107), was used here while studying the F + H2 system. However, this study is characterized by two new features: (a) it is the first of its kind in which is studied the interplay between Renner–Teller (RT) and Jahn–Teller (JT) nonadiabatic coupling terms (NACT); (b) it is the first of its kind in which is reported the effect of an upper singular RT‐NACT on a lower two‐state (JT) mixing angle. The fact that the upper NACT is singular (it is shown to be a quasi‐Dirac δ‐function) enables a semi‐analytical solution for this perturbed mixing angle. The present treatment, performed for the F + H2 system, revealed the existence of a novel parameter, η, the Jahn–Renner coupling parameter (JRCP), which yields, in an unambiguous way, the right intensity of the RT coupling (as resembled, in this case, by the quasi‐Dirac δ‐function) responsible for the fact that the final end‐of‐the contour angle (identified with the Berry phase) is properly quantized. This study implies that the numerical value of this parameter is a pure number (independent of the molecular system): η = $ 2\sqrt 2 /\pi $ (= 0.9003) and that there is a good possibility that this value is a novel characteristic molecular constant for a certain class of tri‐atomic systems. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
79.
Reactions of various halogenated peroxyl radicals with guanine, uric acid, xanthine, hypoxanthine and ascorbic acid in a quaternary microemulsion consisting of sodium lauryl sulfate/water/1-pentanol/cyclohexane have been studied using the technique of pulse radiolysis. For all purine derivatives and ascorbic acid, formation of the respective radical cations have been observed. Variation in biomolecular rate constant values for the reactions of peroxyl radicals with the above-mentioned compounds has been discussed in terms of diffusion of radicals. 相似文献
80.
S. D. Adhikari R. Balasubramanian F. Pappalardi P. Rath 《Proceedings Mathematical Sciences》2008,118(2):183-188
For an abelian group G, the Davenport constant D(G) is defined to be the smallest natural number k such that any sequence of k elements in G has a nonempty subsequence whose sum is zero (the identity element). Motivated by some recent developments around the notion
of Davenport constant with weights, we study them in some basic cases. We also define a new combinatorial invariant related
to (ℤ/nℤ)
d
, more in the spirit of some constants considered by Harborth and others and obtain its exact value in the case of (ℤ/nℤ)2 where n is an odd integer. 相似文献