Plasma-Chemical Conversion of Lower Alkanes with Stimulated Condensation of Incomplete Oxidation Products

Oxidative conversion of a mixture of natural gas and oxygen in a barrier-discharge plasma-chemical reaction was investigated experimentally. The process was conducted at atmospheric pressure and room temperature. The discharge was initiated by high-voltage pulses of 50–100 s duration at a repetition frequency of up to 2 kHz. The principal feature of the process was that in the plasma-chemical reactor conditions were created which stimulated the condensation of the products of incomplete oxidation of methane that resulted in the formation of aerosol even from nonsaturated vapor. The removal of intermediate reagents from the gaseous phases into the aerosol prevented them from further oxidation. Depending on the experimental conditions, the mass percentage of the components of the condensate formed varied within the following limits: formic acid from 20 to 40%, methanol from 8 to 15%, methylformate from 4 to 8%, and water from 40 to 60%. The conversion process has been realized on a laboratory setup of average power up to 1 kW. In the single-pass mode, a 57% degree of conversion of the mixture has been achieved. The energy value of the condensate is 15–20 kWh/kg.     

A novel mathematical mechanism of the critical endpoint generation

We develop a novel model of the QCD matter critical endpoint by matching the deconfinement phase transition curve with the nil line of the bag surface tension coefficient. As a result, this leads to a new structure of the leading singularities of isobaric partition, and in contrast to all previous studies of such models, the deconfined phase in our approach is defined not by an essential singularity of the isobaric partition function but its simple pole. As an unexpected result, we find out that the first order phase transition in this model is the surface tension induced transition. The sufficient conditions of its existence are analyzed and the possible physical consequences are discussed.     

Acoustic and NMR investigations of melting and crystallization of indium–gallium alloys in pores of synthetic opal matrices

The paper presents the results of studying the crystallization and melting processes of Ga–In eutectic alloys, which are embedded in opal matrices, using acoustic and NMR methods. The indium concentrations in the alloys were 4, 6, 9, and 15 at %. Measurements were performed upon cooling from room temperature to complete crystallization of the alloys and subsequent heating. It is revealed how the size effects and alloy composition influence the formation of phases with α- and β-Ga structures and on changes in the melting-temperature ranges. A difference was observed between the results obtained using acoustic and NMR methods, which was attributed to different temperature measurement conditions.     

Influence of the fractality of opal matrices on melting and crystallization of decane in pores

In this paper we present the results of studies on melting and crystallization of decane embedded in the pores of opal matrices filled with chemically pure hexadecane. In this studies measured the ultrasonic velocity by the pulse-interference method at frequencies of about 7 MHz in the temperature range 170–290 K.     

Experimental search for gamma-ray bursts from evaporating primordial black holes

The energy spectra and temporal characteristics of high-energy gamma-ray bursts from evaporating primordial black holes have been calculated using various evaporation models. The currently existing theoretical uncertainties in the shape of the evaporated photon spectrum are discussed. The data from the Andyrchy and Carpet-2 arrays of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) obtained in the mode of detection of a single cosmic-ray component are used to search for cosmic gamma-ray bursts with a primary photon energy of about 8 GeV. New upper limits have been obtained for the number density of evaporating black holes in a local region of space with a characteristic size of ～10^?3 pc for various evaporation models.     

Structure of cobalt nanoparticles as studied by X-ray absorption spectroscopy

Ab initio modeling is used to analyze the specific near-edge features of the X-ray absorption K spectra of ∼3-nm cobalt nanoparticles. It is established that the observed differences between the spectra of the nanoparticles and those of bulk cobalt samples are due to contribution from atoms of the nanoparticles’ surface layer, the local environment of which is considerably different from that of atoms in the bulk of the nanoparticle. It is also established that the local environment of cobalt atoms in the nanoparticle bulk corresponds to the FCC structure of bulk metal, and the fraction of such atoms is found to be 65 ± 5%.     

Omega, J/psi, and psi(') production in nuclear collisions and quark-gluon-plasma hadronization

The transverse mass spectra of Omega, J/psi, and psi' in Pb+Pb collisions at 158A GeV are studied within a hydrodynamical model of the quark-gluon-plasma expansion and hadronization. The model reproduces the existing data with the common hadronization parameters: temperature T = T(H) congruent with 170 MeV and average collective transverse velocity v(T) congruent with 0.2.     

Amplification of ultrasound by transverse electric current in semiconductors with hot electrons

The possibility of amplification of ultrasound by the transverse electric current (i.e. when the drift of electrons in the direction of sound is absent) in a transverse magnetic field is shown for a semiconductor where the alternating heating of electrons by the sound wave is essential. The physical explanation of this phenomenon is given on the basis of concept of the motion of electron bunches created by the sound wave under the action of crossed electric and magnetic fields.     

The complement: a solution to liquid drop finite size effects in phase transitions

The effects of the finite size of a liquid drop undergoing a phase transition are described in terms of the complement, the largest (but mesoscopic) drop representing the liquid in equilibrium with the vapor. Vapor cluster concentrations, pressure, and density from fixed mean density lattice gas (Ising) calculations are explained in terms of the complement generalization of Fisher's model. Accounting for this finite size effect is important for extracting the infinite nuclear matter phase diagram from experimental data.