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91.
The problem concerning the explosion of a cord charge in the ground, with a hard upper layer, is considered in pulse formulation. A numerical solution is obtained and profiles are given for the throwout craters for several values of thickness of the layer and emplacement depth of the charge, in two limiting cases: when the resistance of the lower ground is negligibly small in comparison with the resistance of the layer and when the resistance of the ground and layer are quite close in magnitude.Translated from Zhurnal Prikladnoi Mekhanika i Tekhnicheskoi Fiziki, No. 2, pp. 143–146, March–April, 1973. 相似文献
92.
I. V. Solodin F. D. Polyak A. V. Eremeev I. A. Vosekalna É. É. Liepin'sh I. I. Chervin R. G. Kostyanovskii 《Chemistry of Heterocyclic Compounds》1985,21(10):1110-1113
Individual diastereomers of aziridine-2-carboxylic acid esters that contain R- and S-valine and R- and S-hexafluorovaline fragments were isolated by high-performance liquid chromatogrpahy (HPLC). The absolute configurations of both asymmetric centers of the diastereomeric esters were determined on the basis of the parameters of the PMR spectra (AB) and circular dichroism (the sign of the cotton effect at 200–220 nm).Communication 44 from the series Asymmetric unbridged nitrogen. See [1] for communication 43.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1355–1358, October, 1985. 相似文献
93.
V. I. Mikhailov L. E. Polyak V. M. Kanevskii 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(3):342-347
Surface processes in CdTe molecular-beam epitaxy were studied using in situ mass spectrometry. Modulated molecular Cd and Te2 beams were used for measuring kinetic parameters. The experiments were performed at crystal temperatures of 600–730 K. The results were processed within a model in which condensation and evaporation occur through adsorption and desorption stages. The desorption rate was 2–10 s?1 for Te2 and more than 30 s?1 for Cd. The CdTe evaporation activation energy and desorption energies were determined as E ev = 1.1 eV, E d (Cd) = 1.0 eV, and E d (Te) = 0.6 eV. The adsorbate coverage was estimated as n(Cd) < 0.01 and n(Te) = 0.1–1 Te. 相似文献
94.
V. I. Mikhailov A. V. Butashin V. M. Kanevsky L. E. Polyak E. V. Rakova A. E. Moslemov V. B. Kvartalov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2011,5(3):595-600
The effect of thermal treatment of (0001) sapphire substrates on the structure of cadmium telluride films grown by molecular
beam epitaxy was investigated. The growth process was carried out on a laboratory facility equipped with a mass spectrometer
and electron diffractometer. It was established that no annealing or annealing in vacuum (P < 0.13 Pa) results in the growth of polycrystalline CdTe films. Epitaxial CdTe films with a cubic structure of the sphalerite
type oriented with the (111) plane parallel to the substrate grow on the substrates annealed in air at T > 1000°C. Electron diffraction patterns showed that they have a mosaic structure and contain twins with the 〈111〉 twinning
axis. Atomic-force microscopic images revealed CdTe crystallites with lateral sizes of ∼50 nm arranged along the steps on
the sapphire substrate surface. These results allowed the conclusion to be drawn that the growth of CdTe on sapphire substrates
can occur by the formation of the three-dimensional nucleation centers according to the Volmer-Weber mechanism. 相似文献
95.
Gómez H Polyak I Thiel W Lluch JM Masgrau L 《Journal of the American Chemical Society》2012,134(10):4743-4752
Glycosyltransferases (GTs) catalyze the highly specific biosynthesis of glycosidic bonds and, as such, are important both as drug targets and for biotechnological purposes. Despite their broad interest, fundamental questions about their reaction mechanism remain to be answered, especially for those GTs that transfer the sugar with net retention of the configuration at the anomeric carbon (retaining glycosyltransferases, ret-GTs). In the present work, we focus on the reaction catalyzed by lipopolysaccharyl-α-1,4-galactosyltransferase C (LgtC) from Neisseria meningitides. We study and compare the different proposed mechanisms (S(N)i, S(N)i-like, and double displacement mechanism via a covalent glycosyl-enzyme intermediate, CGE) by using density functional theory (DFT) and quantum mechanics/molecular mechanics (QM/MM) calculations on the full enzyme. We characterize a dissociative single-displacement (S(N)i) mechanism consistent with the experimental data, in which the acceptor substrate attacks on the side of the UDP leaving group that acts as a catalytic base. We identify several key interactions that help this front-side attack by stabilizing the transition state. Among them, Gln189, the putative nucleophile in a double displacement mechanism, is shown to favor the charge development at the anomeric center by about 2 kcal/mol, compatible with experimental mutagenesis data. We predict that using 3-deoxylactose as acceptor would result in a reduction of k(cat) to 0.6-3% of that for the unmodified substrates. The reactions of the Q189A and Q189E mutants have also been investigated. For Q189E, there is a change in mechanism since a CGE can be formed which, however, is not able to evolve to products. The current findings are discussed in the light of the available experimental data and compared with those for other ret-GTs. 相似文献
96.
Tania Konry Shyam Sundhar Bale Abhinav Bhushan Keyue Shen Erkin Seker Boris Polyak Martin Yarmush 《Mikrochimica acta》2012,176(3-4):251-269
There is a growing need for diagnostic technologies that provide laboratories with solutions that improve quality, enhance laboratory system productivity, and provide accurate detection of a broad range of infectious diseases and cancers. Recent advances in micro- and nanoscience and engineering, in particular in the areas of particles and microfluidic technologies, have advanced the “lab-on-a-chip” concept towards the development of a new generation of point-of-care diagnostic devices that could significantly enhance test sensitivity and speed. In this review, we will discuss many of the recent advances in microfluidics and particle technologies with an eye towards merging these two technologies for application in medical diagnostics. Although the potential diagnostic applications are virtually unlimited, the most important applications are foreseen in the areas of biomarker research, cancer diagnosis, and detection of infectious microorganisms. Figure
There is a growing need for diagnostic technologies that provide laboratories with solutions that improve quality, enhance laboratory system productivity, and provide accurate detection of a broad range of infectious diseases and cancers. In this review, we will discuss many of the recent advances in microfluidics and particle technologies with an eye towards merging these two technologies for application in medical diagnostics such as microfluidic device to monitor molecular secretions in real-time as demonstrated in this figure. 相似文献
97.
The problem of finding the eigenvector corresponding to the largest eigenvalue of a stochastic matrix has numerous applications
in ranking search results, multi-agent, consensus, networked control and data mining. The power method is a typical tool for
its solution. However randomized methods could be competitors vs standard ones; they require much less calculations for one
iteration and are well tailored for distributed computations. We propose a new randomized algorithm and provide upper bound
for its rate of convergence which is O(lnN/n), where N is the dimension and n is the number of iterations. The bound looks promising because lnN is not large even for very high dimensions. The algorithm is based on the mirror-descent method for convex stochastic optimization.
Applications to PageRank problem are discussed.
Published in Russian in Doklady Akademii Nauk, 2009, Vol. 426, No. 6, pp. 734–737.
Presented by Academician S.N. Vasil’ev February 9, 2009
The article was translated by the authors. 相似文献
98.
Roman A. Polyak 《Mathematical Programming》2009,120(1):125-145
We introduce the regularized Newton method (rnm) for unconstrained convex optimization. For any convex function, with a bounded
optimal set, the rnm generates a sequence that converges to the optimal set from any starting point. Moreover the rnm requires
neither strong convexity nor smoothness properties in the entire space. If the function is strongly convex and smooth enough
in the neighborhood of the solution then the rnm sequence converges to the unique solution with asymptotic quadratic rate.
We characterized the neighborhood of the solution where the quadratic rate occurs. 相似文献
99.
Multi-Input Multi-Output Ellipsoidal State Bounding 总被引:7,自引:0,他引:7
Ellipsoidal state outer bounding has been considered in the literature since the late sixties. As in the Kalman filtering, two basic steps are alternated: a prediction phase, based on the approximation of the sum of ellipsoids, and a correction phase, involving the approximation of the intersection of ellipsoids. The present paper considers the general case where K ellipsoids are involved at each step. Two measures of the size of an ellipsoid are employed to characterize uncertainty, namely, its volume and the sum of the squares of its semiaxes. In the case of multi-input multi-output state bounding, the algorithms presented lead to less pessimistic ellipsoids than the usual approaches incorporating ellipsoids one by one. 相似文献