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421.
422.
We present here a study of the electronic and optical properties of rutile (TiO2). An investigation into the energy, pressure and temperature dependence of neff and ε∞ eff is presented. Using the calculated values of neff and ε∞ effs, we evaluate the Penn gap. The Penn gap thus obtained is shown to be in good agreement with the reflectivity data and also with the value obtained from band structure. In addition, we also show that essentially the Varshni formula explains the temperature dependence of the energy gap for rutile fairly well. 相似文献
423.
Berge's strong perfect-graph conjecture states that a graph is perfect iff it has neither C2n+1 nor , n ≥ 2 as an induced subgraph. In this note we establish the validity of this conjecture for (K4?e)-free graphs. 相似文献
424.
Copper(II) Schiff base complexes derived from furan-2-carboxaldehyde, 2-furylmethyl ketone, thiophene-2-carboxaldehyde and methyl-2-thienyl ketone with semicarbazide and thiosemicarbazide have been prepared and characterized by analytical, i.r., electronic, e.s.r. and c.v. spectral data. The electronic spectral d–d band position varies from 744–415nm in pyridine and 872–371nm in DMF. E.s.r. g
values lie between 2.1439 and 2.3149 at LNT. All complexes undergo quasi-reversible one-electron electrochemical reduction (CuIII/CuII) in the 0.42–0.52V potential range. The electron transfer is much faster in thiosemicarbazone complexes compared to semicarbazone complexes. All these copper(II) complexes showed increased nuclease activity in presence of oxidant. 相似文献
425.
We introduce a computable estimator of block entanglement entropy for many-body spin systems admitting total singlet ground states. Building on a simple geometrical interpretation of entanglement entropy of the so-called valence bond states, this estimator is defined as the average number of common singlets to two subsystems of spins. We show that our estimator possesses the characteristic scaling properties of the block entanglement entropy in critical and noncritical one-dimensional Heisenberg systems. We invoke this new measure to examine entanglement scaling in the two-dimensional Heisenberg model on a square lattice revealing an "area law" for the gapped phase and a logarithmic correction to this law in the gapless phase. 相似文献
426.
We present an experimentally realizable stabilized charge pumping scheme in a linear array of Cooper-pair boxes. The system design intrinsically protects the pumping mechanism from severe errors, especially current reversal and spontaneous charge excitation. The quantum Zeno effect is implemented to further diminish pumping errors. The characteristics of this scheme are considered from the perspective of improving the current standard. Such an improvement bears relevance to the closure of the so-called measurement triangle (see [D. Averin, Nature (London) 434, 285 (2005)). 相似文献
427.
Nikam Keval Chandrakant Kumar Ravinder Jilte Ravindra 《Journal of Thermal Analysis and Calorimetry》2021,146(3):1121-1131
Journal of Thermal Analysis and Calorimetry - Photocatalytically active titania thin films and powders were prepared via sol–gel route from TiCl4 precursor. Organic polymer hydroxypropyl... 相似文献
428.
Paik Y Yang C Metaferia B Tang S Bane S Ravindra R Shanker N Alcaraz AA Johnson SA Schaefer J O'Connor RD Cegelski L Snyder JP Kingston DG 《Journal of the American Chemical Society》2007,129(2):361-370
The important anticancer drug Taxol (paclitaxel, PTX) owes its unique activity to its ability to bind to tubulin in a stoichiometric ratio and promote its assembly into microtubules. The conformation of the microtubule-bound drug has been the focus of numerous research efforts, since the inability of polymerized tubulin to form crystals precludes structure proof by X-ray crystallography. Likewise, although the alpha,beta-tubulin dimer structure has been solved by electron crystallography, the 3.7 A resolution is too low to permit direct determination of either ligand conformation or binding pose. In this article, we present experimental results from 2H{19F} REDOR NMR that provide direct confirmation that paclitaxel adopts a T-shaped conformation when it is bound to tubulin. 相似文献
429.
Aggarwal VK Binanzer M de Ceglie MC Gallanti M Glasspoole BW Kendrick SJ Sonawane RP Vázquez-Romero A Webster MP 《Organic letters》2011,13(6):1490-1493
Tertiary allyl- or crotylsilanes have been prepared in high er and dr via the lithiation-borylation reaction of alkyl carbamates with silaboronates. Using a related strategy, quaternary allylsilanes could be accessed in similarly high er. 相似文献
430.
Acid-base catalyzed glycosyl donor and then glycosyl acceptor activation with phenylboron difluoride or diphenylboron fluoride permits hydrogen bond mediated intramolecular S(N)2-type glycosidation in generally high anomeric selectivity. 相似文献