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41.
When a finite quantum system, say a fluorescent molecule is attached to a bulk surface and excited by a short laser pulse, the decay dynamics of the system is modulated by the surface and the signal is enhanced due to the bulk surface. We have considered the decay dynamics of a model of displaced distorted molecule whose excited potential surface is coupled to a continuum and then this first continuum is in turn coupled to a second continuum. In the short time scale there is a coherent exchange of energy between the system molecule and the first continuum states. In the long time scale the energy of the whole system plus first continuum drains out to the final continuum states. A dendrimer nanocomposite with the gold surface shows an enhanced light emission. This can be qualitatively understood from the model we proposed here. We have numerically studied the various potential parameters of the molecule which can affect the signal. When the potential surfaces are flat, the band structure of the first continuum states along with its initial excitation has some nontrivial effect on the profile of the radiative decay. 相似文献
42.
In this paper, we consider the stochastic fluid-flow model of a single node in a high-speed telecommunication network handling multi-class traffic. The node has multiple buffers, one for each class of traffic. The contents of these buffers are multiplexed onto a single output channel using one of the service scheduling policies: the Timed Round Robin Policy or the Static Priority Service Policy. The Quality of Service requirements for each class are based on cell loss probabilities. Using effective bandwidth methodologies and the recently developed bounds for semi-Markov modulated traffic, we solve call admission control problems for the two service scheduling policies at this node. We compare the performance of the effective bandwidth methodologies and the SMP bounds technique. We also numerically compare the performance of the two service scheduling policies. 相似文献
43.
The response to drying and storage at -20 degrees C or in liquid nitrogen was studied in seeds of the freshwater aquatic plant Najas flexilis. The seeds of this species show some desiccation sensitivity, although post-harvest storage in water at 16 degrees C resulted in improvements in desiccation tolerance. There was 63% germination of seeds dried to 9.5% moisture content (30% RH) following this maturation period. Optimum moisture contents for seeds stored at -20 degrees C for 3 months and in liquid nitrogen for 1 week were ~11% and ~15%, respectively. 相似文献
44.
Gautam Rajesh Kumar Seth Debabrata 《Journal of Thermal Analysis and Calorimetry》2020,140(6):2633-2640
Journal of Thermal Analysis and Calorimetry - We have reported the thermal conductivities of three deep eutectic solvents (DESs). We have used choline chloride, N,N-diethyl ethanol ammonium... 相似文献
45.
46.
Sodium cleaves elemental tellurium, TeX, quantitatively to Te2– 2 and Te2- in anhydrous tetrahydrofuran in the presence of catalytic amounts of naphthalene. Subsequent addition of alkylating agent affords dialkyl tellurides and dialkyl ditellurides in excellent yields. 相似文献
47.
A new alternative system for the oxidation of secondary alcohols to ketones with DMSO/N2H4.H2O/I2/H2O/CH3CN in hydrated media has been developed. The system also selectively oxidizes the secondary alcoholic groups to the corresponding ketones in the presence of primary alcoholic groups present within the same molecule in moderate to very good yields at reflux temperature. 相似文献
48.
The analytically derived predictions of a recently developed theory on phase conjugate four wave mixing (FWM) in two-level atoms [Phys. Rev. A 60, 1672 (1999)], which interprets many of the signal features as a consequence of quantum interference between the probability amplitudes for photon emission from relevant dressed states, is compared to the results that one obtains from a non-perturbative, numerical calculation of the density matrix equations. The results delineate the regimes and assumptions under which the perturbative results are valid, and it is shown that despite the simplifying assumptions that are invoked for the dressed state theory, many of its predictions are in qualitative agreement with the exact, numerical results. 相似文献
49.
Dr. Mostakim SK Dr. Soumitra Barman Shounik Paul Ratnadip De Dr. S. S. Sreejith Dr. Helge Reinsch Dr. Maciej Grzywa Dr. Norbert Stock Prof. Dr. Dirk Volkmer Dr. Shyam Biswas Prof. Dr. Soumyajit Roy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(12):4098-4107
A Zr-based metal-organic framework has been synthesized and employed as a catalyst for photochemical carbon dioxide reduction coupled with water oxidation. The catalyst shows significant carbon dioxide reduction property with concomitant water oxidation. The catalyst has broad visible light as well as UV light absorption property, which is further confirmed from electronic absorption spectroscopy. Formic acid was the only reduced product from carbon dioxide with a turn-over frequency (TOF) of 0.69 h−1 in addition to oxygen, which was produced with a TOF of 0.54 h−1. No external photosensitizer is used and the ligand itself acts as the light harvester. The efficient and selective photochemical carbon dioxide reduction to formic acid with concomitant water oxidation using Zr-based MOF as catalyst is thus demonstrated here. 相似文献
50.
D. Gautam 《Tetrahedron letters》2010,51(32):4199-4201
A stereoselective approach for the synthesis of (+)-(1R,2S,5S,7R)-2-hydroxy-exo-brevicomin from l-ascorbic acid has been described. The key steps are highly stereoselective nucleophilic addition reaction on aldehyde 8 and also a single pot transformation of 15 to (+)-(1R,2S,5S,7R)-2-hydroxy-exo-brevicomin. The later tandem reaction which involves the hydrogenation of double bond, debenzylation, MOM deprotection and bicyclic ketal formation was carried under Pd/C, H2 followed by acid treatment. 相似文献