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81.
The influence of the capillary condensation of reactants on the poisoning of Pt/SiO2 catalysts by thiophene is studied experimentally for p-xylene hydrogenation at T = 60 and 80°C. The poisoning kinetics is independent of a catalyst and its rate decreases with a decrease in temperature. Poisoning during capillary condensation is 1.5–6 times slower than that in the gas phase, depending on the fraction of surface platinum in the pores filled with a liquid. The poisoning of the catalyst active sites in the pores filled with a liquid requires less sulfur at the same deactivation degree. The number of sulfur atoms per one platinum atom necessary for the complete poisoning of platinum in the gas phase is higher than that in the case of capillary condensation by a factor of 1.4–1.5.  相似文献   
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85.
The first and second protonations of annelated azoloazines have been investigated quantitatively in aqueous solution. Compounds investigated were pyrazolo[1,5-a]pyrimidine (pKBH 0.03±0.02, pKBH 2+ –7.87±0.30), 1,2,4-triazolo[4,3-b]-1,2,4-triazine (pKBH + –0.04±0.02, pKBH 2+ –8.00±0.10), 1,2,4-triazolo[1,5-a]pyrimidine (pKBH + 0.21±0.03, pKBH 2+ –9.00±0.09) and its 6R derivatives (R=NO2, Br, Cl). The annelated azoloazines studied are weaker bases than their unannelated analogs. According to quantum chemical calculations (AM1), protonation of these heterocycles may occur both at the azole and the azine fragments of the molecule.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 816–824, June, 2000.  相似文献   
86.
A fluctuation mechanism of origin of the deformation of a charged liquid surface, which explains the experimental facts, is proposed. The Hamilton equations that describe the dynamics of an inviscid fluid with electrically charged free surface are formulated. Solutions of these equations, which describe the evolution of the free surface, are found. The spectra of the surface disturbances are investigated.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.3, pp. 117–124, May–June, 1992.  相似文献   
87.
We show that the open unit ball of the space of operators from a finite-dimensional Hilbert space into a separable Hilbert space (we call it “operator ball”) has a restricted form of normal structure if we endow it with a hyperbolic metric (which is an analogue of the standard hyperbolic metric on the unit disc in the complex plane). We use this result to get a fixed point theorem for groups of biholomorphic automorphisms of the operator ball. The fixed point theorem is used to show that a bounded representation in a separable Hilbert space which has an invariant indefinite quadratic form with finitely many negative squares is unitarizable (equivalent to a unitary representation). We apply this result to find dual pairs of invariant subspaces in Pontryagin spaces. In Appendix A we present results of Itai Shafrir about hyperbolic metrics on the operator ball.  相似文献   
88.
Let μ be a finite nonnegative Borel measure. The classical Lévy–Raikov–Marcinkiewicz theorem states that if its Fourier transform μ? can be analytically continued to some complex half-neighborhood of the origin containing an interval (0,iR) then μ? admits analytic continuation into the strip {t:0<It<R}. We extend this result to general classes of measures and distributions, assuming non-negativity only on some ray and allowing temperate growth on the whole line. To cite this article: I. Ostrovskii, A. Ulanovskii, C. R. Acad. Sci. Paris, Ser. I 336 (2003).  相似文献   
89.
Capillary condensation was found to accompany gasphase catalytic reactions, in particular motor fuel hydrotreatment. Reaction conditions appear to differ significantly in large pores (filled with gas) and small ones (filled with liquid). Regarding capillary condensation we explain the strange dependences observed in this study or described in the literature. We have simulated jet fuel dearomatization taking into account capillary condensation as well.  相似文献   
90.
The protonation constants for the first and second stages (pKBH+, pKBH2+) of a series of 1,2,4-triazines with a phenyl substituent at various positions in the ring were determined in aqueous solution by a spectrophotometric method. The values of the basicity constants characterizing the first protonation of the heterocycles investigated was in the range of acidity of the medium of pH 3.5 to H 0 -2, and the second from H 0 -7.3 to H 0 -8.7. The position of the phenyl substituent proved to have a significant effect on the size of pKBH+. According to the results of ab initio calculations using HF/6-31G** for the heterocycles investigated the 1H+ form is thermodynamically most stable among the monocations, with the exception of 6-phenyl-1,2,4-triazine for which the existence of the monocation in the 1H+ and 2H+ forms are equally probable. In the case of the dications of all the triazines the 2,4-H,H2+ tautomer is the most preferred. The aromaticity of the 1,2,4-triazine ring is changed insignificantly on mono- and diprotonation.  相似文献   
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