Accuracy of Determining Reverberation Parameters during Recovery of a Signal with Reverberation Distortions in the Case of Discrete Delays

We discuss the accuracy of determining reverberation parameters, which is required to recover a signal with reverberation distortions. It is shown that if the signal with distortions is digitized under conditions of the sampling theorem, then it is insufficient to determine the delay time of the retarded signal with an accuracy of the sampling interval. We present an iterative algorithm for determining the reverberation parameters with sufficient accuracy.     

Effect of laser erosion on the copper and zinc concentrations in the surface layer of brass

A REMMA 102 scanning electron microscope equipped with semiconductor and wave spectrometers is applied to measure the copper and zinc concentrations in the surface layers of an M161 brass sample and the same sample subjected to a focused laser radiation. The results are compared with the results obtained with an MS3101 laser mass spectrometer having a laser-plasma ion source. The laser-assisted erosion of the surface layer in the brass is shown to significantly change the copper and zinc concentrations. It is found that, when the craters produced by laser pulses on the initial surface do not overlap, the copper and zinc contents in the laser-induced plasma correspond to their contents in the sample.     

Mesoporous Titanium-containing Silicas. Synthesis and geometrical characteristics

Mesoporous titanium-containing silicas with TiO₂ contents from 1 up to 70 mol% were prepared. The obtained samples have been characterized by the powder X-ray diffraction data, the diffuse reflectance infrared Fourier transform method, and nitrogen adsorption at 77 K. Specific surface area, total pore volume, distribution pore volume on pore sizes were determined from nitrogen adsorption isotherm for synthesized titanosilicas. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mechanism and kinetics of the hydrogenation of CO with the formation of paraffins and olefins on an iron catalyst

A kinetic model is proposed for the hydrogenation of CO on a Fe/Al₂O₃ catalyst, based on a mechanism of parallel formation of paraffins and olefins. The model satisfactorily describes the experimental data on the dependence of the total rate of conversion of CO to hydrocarbons and the selectivity with respect to paraffins on the composition of the reaction mixture. It was shown that in the case of olefins the successive steps of their hydrogenation, which make a substantial contribution to the distribution of reaction products, must be taken into consideration.L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Nauki Prospekt, Kiev 252039, Ukraine. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. 2, pp. 118–123, March–April, 1996. Original article submitted May 22, 1995.     

Effect of the nature of the metal oxide on selective transformation of methane under unsteady conditions in the absence of oxidant in the gaseous phase

The catalytic transformation of methane into higher hydrocarbons was studied under unsteady conditions on oxides of various metals (Pb, Fe, Nb, Ti, Cd, Mo, Mg, Zn, Zr, Bi, Mn), and also on Sr-, La-, Y-, and Mn-containing oxides of perovskite structure. It is shown that the effectiveness of the catalysts not only depends on their chemical composition, but also is determined to a considerable degree by the specific surface of the oxides. L. V. Pisarzhevskii Institute of Physical Chemistry, Academy of Sciences of Ukraine, 252039 Kiev, Prosp. Nauki, 31, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 2, pp. 91–95, March–April, 1997.     

Polysaccharides of brown algae VIII. A study of pelvecyan and sargassan by methylation

Conclusions It has been shown by the methylation method that pelvecyan and sargassan are polysaccharides of similar structures with a high degree of branching of the carbohydrate chains. Fucose, xylose, and galactose are located at the nonreducing ends of their molecules, and mannose and galactose form points of branching of the carbohydrate chains of these polysaccharides.The positions of the bonds between the monosaccharide residues in pelvecyan and sargassan have been determined.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 142–145, March–April, 1974.     

Reaction of pentachloropyridine N-oxide with potassium hydrogen sulfide

Depending on the conditions, the reaction of pentachloropyridine N-oxide with potassium hydrogen sulfide leads to the N-oxide of the potassium salt of 3,4,5,6-tetrachloropyridin-2-thiol or the dipotassium salt of 3,4,5-trichloropyridine-2,6-dithiol, which are converted by the action of dimethyl sulfate into the corresponding methylthio derivatives. Oxidation of the latter has given sulfones. It has been shown that for these sulfones,reactions with nucleophilic reagents take place at the methylsulfonyl group and not at the chlorine atoms.     

Investigation of the mechanism of methane formation in the fischer-tropsch synthesis on a Co/SiO2·ZrIV catalyst

Methane is formed in the Fischer-Tropsch synthesis under real conditions both through intermediates leading to chain propagation and by hydrogenation of surface carbon. L. V. Pisarzhevskii Institute of Physical Chemistry, National Academy of Sciences of Ukraine, Prospekt Nauki 31, 252039 Kiev, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, No. 1, pp. 41–43, January–February, 1996.     

Mechanism and kinetics of the hydrogenation of CO to saturated hydrocarbons and alcohols on supported bimetallic catalysts containing rhodium

The mechanism of the simultaneous formation of methane, ethane, propane, methanol, ethanol, and propanol from carbon monoxide and hydrogen over supported bimetallic catalyst, Rh-M/Al₂O₃, has been established on the basis of kinetic and adsorption data. The experimental data are described quantitatively by kinetic and thermodynamic parameters calculated using the kinetic model.L. V. Pisarzhevskii Institute of Physical Chemistry, Ukraine National Academy of Sciences, Ukraine, 252039 Kiev, Nauki Prosp. 31. D. V. Sokol'skii Institute of Organic Catalysis and Electrochemistry, Kazakhstan National Academy of Sciences, Kazakhstan, 480110 Alma Ata, D. Kunaev Street, 142. Translated from Teoreticheskeskaya i Éksperimental'naya Khimiya, Vol. 32, No. 2, pp. 97–101, March–April, 1996. Original article submitted May 23, 1995.