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991.
Godin OA 《The Journal of the Acoustical Society of America》2007,121(2):EL96-E102
The fluctuation-dissipation theorem is used to show how acoustic Green's functions corresponding to sound propagation in opposite directions between any two given points can be extracted from time series of thermal noise recorded at these points. The result applies to arbitrarily inhomogeneous, moving or motionless fluids with time-independent parameters, and demonstrates that the two-point correlation function of thermal noise contains as much information about the environment as can be obtained acoustically by placing transceivers at the two points. 相似文献
992.
Chun‐I Lee Wei‐Chun Shih Jia Zhou Joseph H. Reibenspies Oleg V. Ozerov 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(47):14209-14213
A two‐step reaction to convert terminal alkynes into triborylalkenes is reported. In the first step, the terminal alkyne and pinacolborane (HBpin) are converted into an alkynylboronate, which is catalyzed by an iridium complex supported by a SiNN pincer ligand. In the second step, treatment of the reaction mixture with CO generates a new catalyst which mediates dehydrogenative diboration of alkynylboronate with pinacolborane. The mechanism of the diboration remains unclear but it does not proceed via intermediacy of hydroboration products or via B2pin2. 相似文献
993.
994.
Unexpected Chemistry from the Reaction of Naphthyl and Acetylene at Combustion‐Like Temperatures
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Dr. Dorian S. N. Parker Prof. Dr. Ralf. I. Kaiser Dr. Biswajit Bandyopadhyay Dr. Oleg Kostko Dr. Tyler P. Troy Dr. Musahid Ahmed 《Angewandte Chemie (International ed. in English)》2015,54(18):5421-5424
The hydrogen abstraction/acetylene addition (HACA) mechanism has long been viewed as a key route to aromatic ring growth of polycyclic aromatic hydrocarbons (PAHs) in combustion systems. However, doubt has been drawn on the ubiquity of the mechanism by recent electronic structure calculations which predict that the HACA mechanism starting from the naphthyl radical preferentially forms acenaphthylene, thereby blocking cyclization to a third six‐membered ring. Here, by probing the products formed in the reaction of 1‐ and 2‐naphthyl radicals in excess acetylene under combustion‐like conditions with the help of photoionization mass spectrometry, we provide experimental evidence that this reaction produces 1‐ and 2‐ethynylnaphthalenes (C12H8), acenaphthylene (C12H8) and diethynylnaphthalenes (C14H8). Importantly, neither phenanthrene nor anthracene (C14H10) was found, which indicates that the HACA mechanism does not lead to cyclization of the third aromatic ring as expected but rather undergoes ethynyl substitution reactions instead. 相似文献
995.
Synthesis of Triborylalkenes from Terminal Alkynes by Iridium‐Catalyzed Tandem CH Borylation and Diboration
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Dr. Chun‐I Lee Wei‐Chun Shih Prof. Jia Zhou Dr. Joseph H. Reibenspies Prof. Oleg V. Ozerov 《Angewandte Chemie (International ed. in English)》2015,54(47):14003-14007
A two‐step reaction to convert terminal alkynes into triborylalkenes is reported. In the first step, the terminal alkyne and pinacolborane (HBpin) are converted into an alkynylboronate, which is catalyzed by an iridium complex supported by a SiNN pincer ligand. In the second step, treatment of the reaction mixture with CO generates a new catalyst which mediates dehydrogenative diboration of alkynylboronate with pinacolborane. The mechanism of the diboration remains unclear but it does not proceed via intermediacy of hydroboration products or via B2pin2. 相似文献
996.
Anastasia M. Alekseeva Ilya V. Tertov Andrey V. Mironov Ivan V. Mikheev Oleg A. Drozhzhin Emiliya V. Zharikova Marina G. Rozova Evgeny V. Antipov 《无机化学与普通化学杂志》2020,646(14):1260-1266
New sodium vanadium(III) hydrogenphosphate hydrate NaV(HPO4)2(H2O)0.5 and sodium vanadium(III) hydrogenphosphate β-NaV(HPO4)2 were prepared in mild hydrothermal conditions. The crystal structures of NaV(HPO4)2(H2O)0.5 [space group Cc, Z = 4, a = 8.46174(19) Å, b = 9.52583(19) Å, c = 8.69376(15) Å, β = 110.9553(11) °, V = 654.41(2) Å3] and β-NaV(HPO4)2 [space group C2/c, Z = 4, a = 7.8681(3) Å, b = 9.8451(3) Å, c = 8.5180(2) Å, β = 107.626(2) °, V = 628.85(3) Å3] were solved and refined from X-ray powder diffraction data. Both compounds were used as precursors in a new route for the preparation of attractive cathode material β-NaVP2O7. The formation of the structure motive providing fast sodium ion diffusion at the first synthesis stage and its further conservation upon stepwise dehydration was revealed. The oversized Na+-embedding channels are stabilized by site-coordinated water in NaV(HPO4)2(H2O)0.5 structure. The topology resemblance and difference in known sodium vanadium(III) complex phosphates are discussed. 相似文献
997.
Mikhail Kamenskii Oleg Makarenkov Paolo Nistri 《Journal of Dynamics and Differential Equations》2011,23(3):425-435
The goal of this paper is to present a new method to prove bifurcation of a branch of asymptotically stable periodic solutions of a T-periodically perturbed autonomous system from a T-periodic limit cycle of the autonomous unperturbed system. The method is based on a linear scaling of the state variables to convert, under suitable conditions, the singular Poincaré map (with two singularity conditions) associated to the perturbed autonomous system into an equivalent non-singular equation to which the classical implicit function theorem applies directly. As a result we obtain the existence of a unique branch of T-periodic solutions (usually found for bifurcations of co-dimension 2) as well as a relevant property of the spectrum of their derivatives. Finally, by a suitable representation formula of the classical Malkin bifurcation function, we show that our conditions are equivalent to the existence of a non-degenerate simple zero of the Malkin function. The novelty of the method is that it permits to solve the problem without explicit reduction of the dimension of the state space as it is usually done in the literature by the Lyapunov–Schmidt method. 相似文献
998.
We derive a new estimate of the size of finite sets of points in metric spaces with few distances. The following applications are considered:
- •
- we improve the Ray-Chaudhuri-Wilson bound of the size of uniform intersecting families of subsets;
- •
- we refine the bound of Delsarte-Goethals-Seidel on the maximum size of spherical sets with few distances;
- •
- we prove a new bound on codes with few distances in the Hamming space, improving an earlier result of Delsarte.
999.
Oleg Velichko 《Applied Mathematical Modelling》2011,35(3):1134-1141
The stress-mediated diffusion of nonequilibrium point defects into the bulk of a semiconductor is investigated by computer simulation. It is assumed that the point defects are generated on the surface of a semiconductor and that in the course of diffusion they pass through the local region of elastic stresses because the average length of defect migration is greater than the thickness and depth of the strained layer. Within the strained layer, point defect segregation or heavy defect depletion occurs if defect drift under stresses is directed in or out of the layer, respectively. The calculations also show that, in contrast to the case of local defect sink, the local region of elastic stresses practically does not change the distribution of defects beyond this region if there is no generation/absorption of point defects within the strained layer. 相似文献
1000.
The diffusion of two-dimensional adatom-islands (up to 100 atoms) on Cu(111) has been studied, using the self-learning kinetic Monte Carlo method (Trushin et?al 2005 Phys. Rev. B 72 115401). A variety of multiple-?and single-atom processes are revealed in the simulations, and the size dependences of the diffusion coefficients and effective diffusion barriers are calculated for each. From the tabulated frequencies of events found in the simulation, we show a crossover from diffusion due to the collective motion of the island to a regime in which the island diffuses through periphery-dominated mass transport. This crossover occurs for island sizes between 13 and 19 atoms. For islands containing 19-100 atoms the scaling exponent is 1.5, which is in good agreement with previous work. The diffusion of islands containing 2-13 atoms can be explained primarily on the basis of a linear increase of the barrier for the collective motion with the size of the island. 相似文献