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排序方式: 共有133条查询结果,搜索用时 31 毫秒
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2.
S. A. Kotlyar G. L. Kamalov R. L. Savranskaya A. V. Bogatskii 《Chemistry of Heterocyclic Compounds》1981,17(2):120-123
It is shown that the reactivities of cyclic formals in the case of bromination with dioxane dibromide increase in the order 1,3-dioxepane > 1,3-dioxalane 1,3-dioxane, which is explained not only by steric factors but also by the ease of cleavage of the C4-O3 bond of the dioxacyclane ring. The bromination of cyclic acetals takes place through prior enolization of the cyclic acetal with subsequent electrophilic addition of bromine to the double bond.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 176–179, February, 1981. 相似文献
3.
Yu. B. Zelechonok L. P. Ivanova V. V. Zorin S. A. Kotlyar S. S. Zlotskii D. L. Rakhmankulov 《Chemistry of Heterocyclic Compounds》1988,24(1):64-65
Homolytic alkylation of protonated quinoxaline with 18-crown-6, initiated by the system pivalic acid-iron(II) sulfate at 20–25C, gives (quinoxalin-2-yl)-18-crown-6 in 85% yield. Under analogous conditions, the reaction with quinoline affords two isomers: (quinolin-4-yl)-18-crown-6 and (quinolin-2-yl)-18-crown-6, in yields of 20 and 30% respectively.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 75–76, January, 1988. 相似文献
4.
V. A. Tertykh S. S. Kotlyar V. V. Yanishpolskii K. B. Yatsimirskii T. N. Yakubovich Yu. I. Bratushko 《Reaction Kinetics and Catalysis Letters》1987,33(2):411-416
Porphyrin immobilized on silica and its complex with cobalt have been prepared and identified. Oxidation kinetics is described by the Michaelis-Menten equation.
- . - --.相似文献
5.
R. R. Reznik K. P. Kotlyar I. V. Il’kiv I. P. Soshnikov S. A. Kukushkin A. V. Osipov E. V. Nikitina G. E. Cirlin 《Physics of the Solid State》2016,58(10):1952-1955
The potential to grow filamentary GaN nanocrystals by molecular beam epitaxy on a silicon substrate with a nanosized buffer layer of silicon carbide has been demonstrated. Morphological and optical properties of the obtained system have been studied. It has been shown that the intensity of the photoluminescence spectrum peak of such structures is higher than that of the best filamentary GaN nanocrystals without the buffer silicon carbide layer by a factor of more than two. 相似文献
6.
N. I. Solin L. N. Romashev S. V. Naumov A. A. Saranin A. V. Zotov D. A. Olyanich V. G. Kotlyar O. A. Utas 《Technical Physics》2016,61(2):233-239
We consider methods for controlling magnetoresistive parameters of magnetic metal superlattices, manganites, and magnetic semiconductors. By reducing the thickness of ferromagnetic layers in superlattices (e.g., Fe layers in Fe/Cr superlattices), it is possible to form superparamagnetic clustered–layered nanostructures with a magnetoresistance weakly depending on the direction of the external magnetic field, which is very important for applications of such type of materials. Producing Mn vacancies and additionally annealing lanthanum manganites in the oxygen atmosphere, it is possible to increase their magnetoresistance by more than four orders of magnitude. By changing the thickness of p–n junction in the structure of ferromagnetic semiconductors, their magnetoresistance can be increased by 2–3 orders of magnitude. 相似文献
7.
Shapir E Yi J Cohen H Kotlyar AB Cuniberti G Porath D 《The journal of physical chemistry. B》2005,109(30):14270-14274
DNA has been at the center of an imaging effort since the invention of the scanning tunneling microscope (STM). In some of the STM imaging reports the molecules appeared with negative contrast, i.e., "submerged" under the metal background and darker. We demonstrate the phenomenon of contrast inversion in DNA STM imaging by controlled and spontaneous contrast inversions and by the dependence of the DNA apparent height with respect to the surface on the imaging bias voltage. Using these characterizations, we formulate a model explaining the above phenomenon by resonant tunneling through virtual states in the vacuum between the STM tip and the DNA molecule. 相似文献
8.
We investigate, by numerically calculating the charge stiffness, the effects of random diagonal disorder and electron-electron interaction on the nature of the ground state in the 2D Hubbard model through the finite-size exact diagonalization technique. By comparing with the corresponding 1D Hubbard model results and by using heuristic arguments we conclude that it is unlikely that there is a 2D metal-insulator quantum phase transition, although the effect of interaction in some range of parameters is to substantially enhance the noninteracting charge stiffness. 相似文献
9.
The two-dimensional problem of the electrochemical dimensional machining of a metal is investigated within the framework of
the model of an ideal stationary process, which makes it possible to use the analogy with the problems of fluid flows with
free surfaces. In the problem considered the cathode (machining tool) takes the form of two parallel semi-infinite rectangular
electrodes. The blank (anode) is a half-plane whose boundary is perpendicular to the cathodes. Depending on the relationship
between the physical and geometrical parameters of the problem, on the machined part (anode) a projection symmetrical about
the center line between the cathodes may be formed. Additional mechanical machining of the part is then required. In order
to exclude such solutions, a condition is obtained for the mathematical parameters which determine the solution of the problem
in the auxiliary complex plane. General and particular limiting cases are considered. For the cases considered the calculation
results are presented in the form of plots of the shape of the part machined. 相似文献
10.
A.A. Saranin A.V. Zotov V.G. Kotlyar O.A. Utas M. Katayama K. Oura 《Surface science》2005,574(1):99-109
Formation of the beryllium (Be) submonolayers on the Si(1 1 1)7 × 7 surface has been studied using scanning tunneling microscopy. It has been found that Be interaction with Si(1 1 1) at 500-700 °C results in a self-assembly formation of the four various types of the highly-ordered nanostructure arrays. The nanostructure arrays develop on top of the “soft” silicide layer, which period and orientation alter with the nanostructure growth: the shorter the nanostructure period, the larger the rotation angle. The main structural parameters of the silicide layer and nanostructure arrays have been established. 相似文献