Conversion of synthesis gas into alcohols on supported cobalt-molybdenum sulfide catalysts promoted with potassium

The use of transition metal sulfides as catalysts for the synthesis of alcohols can solve the problem of catalyst resistance to sulfur. Catalysts based on molybdenum sulfide of different compositions (promoted with Co and K) were synthesized with the use of various supports (aluminum oxide, aluminum oxide modified with silicon oxide, Sibunit, and titanium silicate) and tested in the reactions of alcohol synthesis and the hydrofining of a mixture of thiophene with n-1-hexene. The dependence of catalyst activity in the synthesis of alcohols on support pore size was demonstrated. It was found that an increase in the potassium content of the active phase of a catalyst increased its activity in the synthesis of alcohols and decreased it in hydrodesulfurization and hydrogenation reactions. Transmission electron microscopy data made it possible to quantitatively evaluate the effect of a potassium additive on the morphology of the active phase; the hypothesis that potassium was intercalated between the layers of molybdenum sulfide was proposed.     

Manifestation of hydrogen bonds in raman spectra of potassium pentaborate

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 3, pp. 397–404, September, 1991.     

Palladium(II)-catalysed H/D allylic exchange in alkenes: An intermediacy of palladium(IV)?

Evidence is presented that the dimeric π-allylic species [(η³-allyl)PdCl]₂ is not intermediate in the Li₂Pd₂Cl₆-catalysed allylic H/D exchange in alkenes. Neither H/D exchange in α-methylstyrene, nor enrichment of [(η³-2-PhC₃H₄)PdCl]₂, was observed when the latter complex was incubated at 100°C in D₃CCOOD either in the presence or in the absence of PhC(CH₃)?CH₂, respectively. The kinetics of H/D exchange in α-methylstyrene catalysed by Li₂Pd₂Cl₆ were studied in some detail. The exchange proceeds at highest rates when reduction of palladium(II) takes place and is much slower in the presence of 1,4-benzoquinone as a palladium reoxidant. The exchange rate is directly proportional to the alkene and catalyst concentrations and independent of the reoxidant concentration. It is suggested that the palladium(II)-catalysed exchange involves an intermediate hydrid-allyl species where palladium has a formal oxidation state of IV.     

Effect of the Earth's gravitational field on the detection of gravitational waves

We consider the laboratory detection of high-frequency gravitational waves in theories of gravitation based on a pseudo-Euclidean space-time. We analyze the effects due to the Earth's gravitational field on the propagation velocities of gravitational and electromagnetic waves in these theories. Experiments to test the predictions of this class of theories are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, 93–98, November, 1987.Finally, the authors thank A. A. Logunov for interest in the work.     

Population of the higher-lying vibrational levels of the nitrogen B3π state in a glow discharge

The absolute populations of the higher-lying vibrational levels of the B³ state of the nitrogen molecule in a glow discharge have been determined for pressures from 0.1 to 1.0 torr and current densities from 80 to 200 mA/cm². The absolute concentrations of molecules at levels v = 5, 6, ..., 12 under these conditions are of the order of 10⁹–10¹¹ cm^–3. The most probable processes leading to a population of the B³ state are thought to be direct electronic impact, cascade transitions, and collisions of normal molecules with molecules in the singlet state.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 2, pp. 57–63, February, 1971.     

Dynamical dielectric susceptibility of ferroelectric thin films and multilayers

The thickness dependence of the real and imaginary parts of the dynamical dielectric susceptibility is investigated phenomenologically for a multilayer structure consisting of alternating ferroelectric and paraelectric layers. It is shown that the frequency dependence of the linear dielectric response can be closely approximated by that of a damped harmonic oscillator, with the static susceptibility, relaxation time, and soft-mode frequency depending on the layer thickness and temperature. When the layer thickness and temperature are equal to their critical values corresponding to the onset of a size-driven ferroelectric phase transition, the static susceptibility and the relaxation time become anomalously large and then decrease with further increasing layer thickness. A spectrum of natural polarization oscillations is predicted to exist with thickness-dependent frequencies. This spectrum includes a soft-mode frequency which vanishes at the critical thickness and at the critical temperature. The frequency spectrum lies below the soft-mode frequency of a thick film (in which the gradient of polarization is negligible). The calculations are compared with experimentally measured dispersion of the dielectric response of a PbTiO₃-Pb_0.72La_0.28TiO₃ multilayer structure. The agreement between the theory and experiment is found to be good.     

Theoretical basis of the iterative process of the joint assessment of difficulties in tasks and levels of training students

In this paper, we study the iterative process of the joint numerical assessment of levels of training students and difficulties in tasks of diagnostic tools using the dichotomous response matrix A of size N × M with allowance for the contribution of tasks of different difficulty to the assessments obtained. It is shown that not for any matrix A there exist infinite iterative sequences, and in the case of their existence, they do not always converge. A wide range of sufficient conditions for their convergence have been obtained, which are based on the following: (1) the matrix A contains at least three different columns; (2) if one places the columns of the matrix A in non-decreasing order of column sums, then for any position of the vertical dividing line between the columns there exists a row, which has at least one unity to the left of the line and at least one zero to the right of the line. It is established that the response matrix A obtained as a result of testing reliability satisfies these two conditions. The properties of such matrices have been studied. In particular, the equivalence of the above-mentioned conditions of primitiveness of the square matrix B of order M with the entries \({b_{ij}} = \sum\limits_{\ell = 1}^N {(1 - {a_{\ell i}}){a_{\ell i}}} \) has been proved. Using the matrix analysis, we have proved that the primitiveness of the matrix B ensures the convergence of iterative sequences, as well as independence of their limits of the choice of the initial approximation. We have estimated the rate of convergence of these sequences and found their limits.