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91.
Ab initio calculations reveal that all-metal antiaromatic molecules like Al4M4 (M = Li, Na and K) can be stabilized in half sandwich (Al4M4)Fe(CO)3 and full sandwich (Al4M4)2Ni complexes. The formation of the full sandwich complex [(Al4M4)2Ni] from its organometallic precursor depends on the stability of the organic-inorganic hybrid (C4H4)Ni(Al4Li4). 相似文献
92.
Manas Chakrabarty Ratna Mukherjee Sulakshana Karmakar Yoshihiro Harigaya 《Monatshefte für Chemie / Chemical Monthly》2007,138(12):1279-1282
Summary. 2-Substituted and 1,2-disubstited benzimidazoles were prepared efficiently from o-phenylenediamines and aryl aldehydes using p-toluenesulphonic acid (5 mol%)-on-silica gel as a cheap and environmentally benign catalyst. 相似文献
93.
Ayan Mukherjee Sarah Taragin Hagit Aviv Ilana Perelshtein Malachi Noked 《Advanced functional materials》2020,30(38)
Owing to high energy density and economic viability, rechargeable Mg batteries are considered alternatives to lithium ion batteries. However besides the chevrel phase, none of the conventional inorganic cathode materials demonstrate reversible intercalation/deintercalation of Mg+2 ions in an anhydrous electrolyte system. The lack of high voltage and high capacity cathode frustrates the realization of Mg batteries. Previous studies indicate that vanadium pentoxide (V2O5) has the potential to reversibly insert/extract Mg ions. However, many attempts to utilize V2O5 demonstrate limited electrochemical response, due to hindered Mg ion mobility in solid. Here, monodispersed spherical V2O5 with a hierarchical architecture is rationally designed, through a facile and scalable approach. The V2O5 spheres exhibit initial discharge capacity of 225 mA h g?1 which stabilizes at ≈190 mA h g?1 at 10 mA g?1, much higher than previous reports. The V2O5 spheres exhibit specific discharge capacity of 55 mA h g?1 at moderate current rate (50 mA g?1) with negligible fading after 50 cycles (≈5%) and 100 cycle (≈13%), while it retains ≈95% columbic efficiency after 100 cycles demonstrating excellent stability during Mg+2 ion intercalation/deintercalation. Most interestingly, exact phase and morphology are completely retained even after repeated Mg+2 ion intercalation/deintercalation at different current rates, demonstrating pronounced electrochemical activity in an anhydrous magnesium electrolyte. 相似文献
94.
Nemai C. Karmakar 《International Journal of Electronics》2013,100(1):65-77
With the advent of planar photonic bandgap (PBG) materials different topologies of PBG structures have been proposed to improve the bandpass and band rejection performances of microwave signals. Conventional circular patterned PBGs have constraints in the broadband performance due to the high ripple heights in S-parameters. In this paper, we suggest two novel configurations with non-uniform dimensions of circular patterned PBG to improve the stopband bandwidth and the ripples. The dimensions of the circles are varied proportionally to the Binomial and Shebyshev polynomial distributions. The S-parameter performances with respect to frequencies have been presented. It is seen that Shebyshev distribution produce excellent performances by suppressing ripples and generating sharp cut-offs. 相似文献
95.
Numerical modelling of a direct current non-transferred thermal plasma torch for optimal performance
A laminar steady-state 2D axisymmetric model of a direct current (DC) thermal plasma torch using a magneto-hydrodynamic approach has been developed. The model takes into account the entire torch system comprising the plasma gas injection, the inner region of the torch, and the jet exiting into the ambient environment. Numerical results are obtained for two different power inputs chosen from published experimental data. The temperature predictions at the torch exit are found in good agreement with experimental results. Velocity analysis of the plasma jet has been presented and the impact of electromagnetic force on jet velocity is analysed. The Lorentz force arising due to the coupling of fluid motion and electromagnetic forces shoots up the jet velocity to significantly high values near the cathode tip. Temperature and velocity profiles are in good agreement with the characteristics of a long laminar plasma jet. An operating value of heat transfer coefficient (h) has been suggested for optimal torch operation, thus ensuring a low anode erosion rate and acceptable thermal efficiency. The argon torch has the maximum temperature and longest jet length among the plasma gases considered. 相似文献
96.
Parnajyoti Karmakar Subhasis Mallick Biplab K. Bera Arup Mandal Subala Mondal Sudip K. Mukhopadhyay Alak K. Ghosh 《Transition Metal Chemistry》2010,35(8):911-916
The kinetics of the interaction of glycine-l-leucine (Glyleu) with cis-[Pt(cis-dach)(OH2)2]2+ (dach = 1,2-diaminocyclohexane) has been studied spectrophotometrically as a function of [cis-[Pt(cis-dach)(OH2)2]2+], [Glyleu] and temperature at pH 4.0, where the complex exists predominantly as the diaqua species and Glyleu as a zwitterion.
The substitution reaction shows two consecutive steps: the first is the ligand-assisted anation and the second is the chelation
step. The activation parameters for both the steps were evaluated using Eyring’s equation. The low ∆H1≠ (51.9 ± 2.8 kJmol−1) and large negative value of ∆S1≠ (−152 ± 8 JK−1mol−1) as well as ∆H2≠ (54.4 ± 1.7 kJmol−1) and ∆S2≠ (−162 ± 5 JK−1mol−1) indicate an associative mode of activation for both the aqua ligand substitution processes. 相似文献
97.
Biplab K. Bera Subhasis Mallick Arup Mandal Parnajyoti Karmakar Asok K. Datta Alak K. Ghosh 《Transition Metal Chemistry》2010,35(5):541-547
The kinetics of the aqua ligand substitution from hydroxopentaaquarhodium(III) ion, [Rh(H2O)5(OH)]2+, by l-Arginine has been studied spectrophotometrically as a function of Arginine concentration, and temperature, at pH 4.3. The
reaction proceeds via a rapid outer sphere association complex formation step followed by two consecutive steps. The first
of these involves ligand-assisted anation, while the second involves chelation as the second aqua ligand is displaced. The
association equilibrium constant for the outer sphere complex formation has been evaluated together with the rate constants
for the two subsequent steps. The activation parameters for both steps have been evaluated using Eyring’s equation. Thermodynamic
parameters calculated from the temperature dependence of the outer sphere association equilibrium constants are also consistent
with an associative mode of activation. The product of the reaction has been characterized by conductivity measurement and
IR spectroscopic analysis. 相似文献
98.
Tandra?Das Biplab?K.?Bera Subhasis?Mallick Parnajyoti?Karmakar Arup?Mandal Subala?Mondal Gauri?S.?De Alak?K.?Ghosh 《Transition Metal Chemistry》2010,35(7):885-890
The interaction of thiosemicarbazide with the title complex has been studied spectrophotometrically in aqueous medium as a
function of [complex], [thiosemicarbazide], pH and temperature at constant ionic strength. At pH 7.4, the reaction shows two
distinct paths; both of which are [thiosemicarbazide] dependent. A parallel reaction scheme fits well with the experimental
findings. An associative interchange mechanism is proposed for both the paths; the activation parameters calculated from Eyring
plots are ΔH1≠ = 14.2 ± 0.8 kJ mol−1, ΔS1≠ = −241 ± 2 JK−1 mol−1, ΔH2≠ = 30.8 ± 1.4 kJ mol−1 and ΔS2≠ = −236 ± 4 JK−1 mol−1. From the temperature dependence of the outer sphere association complex equilibrium constants, the thermodynamic parameters
calculated are ΔH1° = 34.25 ± 1.9 kJ mol−1, ΔS1° = 146 ± 6 J K−1 mol−1 and ΔH2° = 9.4 ± 1.1 kJ mol−1, ΔS2° = 71 ± 3 JK−1 mol−1, which gives a negative ΔG° at all temperatures studied, supporting the spontaneous formation of an outer sphere association
complex. 相似文献
99.
Mantosh K. Sinha Ofer Reany Dr. Galit Parvari Ananta Karmakar Dr. Ehud Keinan Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(30):9056-9067
4‐Aminobipyridine derivatives form strong inclusion complexes with cucurbit[6]uril, exhibiting remarkably large enhancements in fluorescence intensity and quantum yields. The remarkable complexation‐induced pKa shift (ΔpKa=3.3) highlights the strong charge–dipole interaction upon binding. The reversible binding phenomenon can be used for the design of switchable beacons that can be incorporated into cascades of binding networks. This concept is demonstrated herein by three different applications: 1) a switchable fluorescent beacon for chemical sensing of transition metals and other ligands; 2) direct measurement of binding constants between cucurbit[6]uril and various nonfluorescent guest molecules; and 3) quantitative monitoring of biocatalytic reactions and determination of their kinetic parameters. The latter application is illustrated by the hydrolysis of an amide catalyzed by penicillin G acylase and by the elimination reaction of a β‐cabamoyloxy ketone catalyzed by aldolase antibody 38C2. 相似文献
100.
M. B. Das S. Karmakar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(3):339-341
Lifetimes of eight levels belonging to the 5p46d configuration of
singly ionized xenon have been measured by high frequency deflection
technique with a delayed coincidence single photon counting arrangement. The
results have been compared with other experimental and theoretical values.
The lifetimes of the 6d 2F3/2 and 6d 4F3/2 levels have
been measured for the first time. 相似文献