Vol 12, No 4 (2018)

Data on rates and enthalpies of the reactions of quadricyclane (4) and diadamantylidene (5) with N-phenylmaleimide (1), 4-phenyl-1,2,4-triazoline-3,5-dione (2), and tetracyanoethylene (3) are obtained for the first time. Reagent 2 with the N=N reaction center is found to be six orders of magnitude more active than its structural analog 1. A strong π-acceptor 3 is 370 times more active than reagent 2 in the reaction with a strong π-donor substrate 4 but is less active than reagent 2 in many [4π + 2π], [2π + 2π + 2π], and [2π + 2π] cycloaddition reactions, and, especially, in ene reactions. The possible causes of the strong difference and variable activity of compounds 1–3 with C=C and N=N bonds are discussed.

Composite materials made of ultrahigh-molecular-weight polyethylene (UHMWPE) and boron have been synthesized using polymerization filling (polymerization in situ), varying the boron content in a wide range from, 10 to 75 vol %. The behavior of synthesized composites during deformation under compression depending on the degree of filling has been studied, and it has been determined that composites with a boron content of about 45 vol % have the maximum value for Young’s modulus, and increases in stress values at offset yield strength under compression is observed up to the filler content of 52 vol %. Based on the analysis of the stress–strain curves under compression, it can be asserted that, even at high degrees of filling, UHMWPE–boron composites retain plastic deformation.

Using X-ray phase analysis and impedance monitoring, it was shown that for a nanolayered structure, softened glass (V₂O₅ · GeO₂) can take an imprint from AgI lattice and retain it while being cooled to temperatures below Tg.

Ab initio calculations of the adiabatic potential curves and matrix elements of radial nonadiabatic coupling of the N₂ molecule for the states related to dissociation limits I–V were performed. The most important spectral characteristics of the adiabatic states agreed well with the available experimental and theoretical data. The diabatic states were constructed. The diabatic quantum defects and radial matrix elements of the configuration interaction of the dissociative and Rydberg configurations whose states converge to the ground state \(X^{2}\Sigma{_g^+}\) and the first electronically excited state A²Π_u of the \(\rm{N_2^+}\) ion were calculated. The possibility of using the results for calculating the cross sections and rate constants of dissociative recombination and associative ionization within the framework of the multichannel quantum defect theory was discussed.

In Earth and environmental chemistry magnetic isotopes are the universal means to identify reaction mechanisms. Mass-independent fractionation of isotopes as a signature of mechanism occurs by two ways: first, via magnetic isotope effect (MIE), which is controlled by magnetic, or hyperfine, coupling between unpaired electrons and magnetic nuclei in paramagnetic species (in radicals, particularly), and, second, via nuclear volume effect (NVE), which is induced by the difference in volumes of isotopic nuclei. MIE is the dependence of the reaction rates on the nuclear magnetic moment of reactants and fractionates magnetic and nonmagnetic isotopes; NVE fractionates isotopes with different nuclear volumes. Both effects, MIE and NVE, are supposed to coexist in condensed phases. Decisive test for their differentiation is illustrated by example of radical pairs with mercury nuclei: if isotope fractionation is controlled by MIE, the ratio Δ²⁰¹Hg/Δ¹⁹⁹Hg is expected to be in the limits 1.05–1.25 for isotopic enrichment and 0.80–0.92 for impoverishment. If isotope fractionation is controlled by NVE, this ratio is estimated to be in the range 0.50–0.62. In contrast to MIE-induced two-directional fractionation, which is controlled by direction of coherent spin conversion of radical pair (triplet–singlet or vice versa), the NVE induces one-directional, universal isotope fractionation, almost independent on the reaction mechanism.

The optical properties of the films of new nanosized of ZnO: SiO₂ materials with intense ultraviolet luminescence (UVL) with a maximum at 362 nm were studied. When human serum albumin (HSA) is applied on the surface of films, an effective fluorescent energy transfer occurs, which is manifested in an increase in the intensity of ultraviolet luminescence of ZnO: SiO₂. The increase in integrated UVL intensity is inversely proportional to HSA concentration; it has 9.2–12.6 times (with a decrease in the HSA concentration from 10^–8 to 10^–12 M) the UVL intensity of purified ZnO: SiO₂ film. The dependence of the UVL intensity on the HSA concentration is close to linear. Compared to the intensity at a concentration of 10–8 M, the gain is 8, 19, 31, and 36% for protein concentrations in the solution applied to the surface of ZnO: SiO₂ of 10^–9, 10^–10, 10^–11, and 10^–12 M, respectively. These supramolecular systems can be used to create biosensors and to simulate the physicochemical processes of photosynthesis. In the former case, the linear dependence of fluorescence on concentration is a significant advantage.

A mathematical model of the physicochemical processes that occur under low-frequency mechanical action on bimolecular reaction kinetics with consideration for the association of reagents is presented. As a result of the mathematical simulation, special features of the kinetics and stability of the reaction modes were established. It was shown that, in a structured liquid, a formally simple reaction occurs as a complex process with the appearance of bistability regimes, the formation of a temporal dissipative structure, and the complex structure of intermediate concentration oscillations. The possibility of controlling transitions from stable to unstable reaction conditions and vice versa under changes in the external action amplitude was demonstrated.

This paper analyzes detonation processes in an explosive laser device, in particular the indirect radiation of an explosive material. A hydrodynamic approach is applied to the numerical analysis, the results of which are in good agreement with experimental data.

The negative ion mass spectrum of an aqueous solution of completely neutralized monochloroacetic acid (MCAA) was measured by a mass-spectrometric method of electrolyte solution electrospray in a vacuum. It was found that the negative ions of the MCAA acid residue, which were formed on the dissociation of MCAA molecules in water, decomposed under the electrospray. The efficiency of disintegration depends on the isotope of chlorine in the MCAA molecule.

Magnetic isotope effect controls enzymatic DNA synthesis and strongly, by 2–3 times, suppresses catalytic activity of polymerases and increases even more strongly, by 20–50 times, the mortality of cancer cells. Catalyzing ions ²⁵Mg²⁺, ⁴³Ca²⁺, and ⁶⁷Zn²⁺ carrying magnetic nuclei are shown to efficiently kill cancer cells. The advantage of these ions for practical medicine is that being injected in blood they are captured selectively and almost exclusively by cancer cells inducing their death. The healthy cells capture these ions much less efficiently (perhaps due to the lower penetrability of their membranes) and are not vulnerable to these ions in comparison with cancer cells. Of course, penetrability of cells is identical for magnetic and nonmagnetic ions, but only the former kill cancer cells.

The rheological properties of aqueous solutions of a sodium salt of carboxymethyl cellulose are studied. The occurrence of a region of unstructured semidilute solutions in which the entanglement network is absent is found. The introduction of both opposite and like-charged micelles of the lyophobic sol into a semidilute polymer solution leads to its structuring due to the appearance of an additional network because of polymer adsorption on the surface of the sol. As a result of the network formation a decrease in the interval between the crossover and the formation concentration of the entanglement network and also an increase in the viscosity of the semidilute solution are observed.

The structural characteristics, valence states, and distribution of cerium ions between the components in In₂O₃–CeO₂ and SnO₂–CeO₂ nanocomposites fabricated using the impregnation method were studied. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) were used to show that, during impregnation, cerium ions are not included into In₂O₃ crystals and are disposed only on their surface in the form of nano-sized crystallites or amorphous clusters. On the other side, under the contact of CeO₂ clusters with a surface of SnO₂ matrix crystals, cerium ions penetrate into the surface layer of these crystals. In contrast to an In₂O₃–CeO₂ system, where the addition of CeO₂ does not affect the conduction activation energy, where cerium oxide is added to SnO₂, the observed increase in the resistance of a SnO₂–CeO₂ composite is accompanied by a sufficient increase in activation energy. These data and the XPS spectra confirm the modification of the surface layers of conductive SnO₂ crystals as, a result of the penetration of cerium ions into these layers.

Based on the chemical model of coal, slit micropores with different pore sizes are established and structures are optimized in the software of materials studio. As the temperature rises, absolute adsorption capacities of H₂O are slightly affected, while absolute adsorption capacities of CO₂ and CH₄ gradually decrease. As the fugacity rises, excess adsorption curves of CO₂ experience increase-decrease-gentle three stages, while the curves of CH₄ gradually decrease. With the increase of pore size, adsorption capacities of H₂O increase, while adsorption capacities of CO₂ and CH₄ gradually decrease. H₂O firstly adsorbs on the oxygen-containing functional group, so the walls of pore are the preferential area for H₂O, while CO₂ and CH₄ choose to adsorb on–C–C–, therefore the walls are the primary area for CO₂ and CH₄. Strong potential in micropores and hydrogen bond among water molecules will promote the water adsorption, while the adsorptions of CO₂ and CH₄ are only induced by the Van der Waals interaction, but the difference between adsorption density and bulk density of CO₂ and CH₄ decides the change of excess adsorption capacity.

The main problems in the remote passive location of positions on the Earth’s surface are reviewed in detail. The first is related to the source of incoherent microwave radiation represented by a layer of two-temperature nonequilibrium ionospheric plasma at an altitude of ca. 80–110 km, which is located below a low Earth-orbiting satellite and formed under the influence of solar activity. As a result, the satellite receives direct radiation from this layer as well as reflected radiation from the Earth’s surface. The next problem is the attenuation of the intensity of the incident radiation as a result of the scattering of radio waves by charged aerosol layers located below the luminous layer. Aerosol particles are affected by solar and cosmic radiation and electronic and ionic attacks, due to which they become charged. Aerosol particles directly take part in the formation of a complete balance of charges in the atmosphere and are an effective catalyst for many physicochemical processes in neutral gaseous media. The processes related to the formation of aerosol particles, the kinetics of formation of their charge, and the processes of their interaction with incoherent microwave radiation are considered. This gives rise to the need to develop a fundamentally new scheme of passive location. Three possible versions of the arrangement of measurements are analyzed. In the first version, a complete set of measurements is implemented when the receiving equipment is simultaneously installed on the Earth, an aircraft, and a low Earth-orbiting satellite; in the second version, the receiving equipment is simultaneously installed on an aircraft and a satellite; in the third version, only on one satellite. The separation of the contributions of direct and reflected incoherent radiation received by the satellite can be achieved only using a special mathematical approach to the information processing (wavelet analysis), which has been under actively development in recent years. We fully show its broad possibilities for solving geophysical problems and discuss the problems of the calibration of the measuring equipment, which are associated with taking into account the superposition of two types of radiation coming to a satellite and with variation of the main parameters (concentration, flux density, and temperature of electrons) of the nonequilibrium two-temperature plasma in time.

Plasma-chemical processes in the lower ionosphere at altitudes of 90–100 km are studied. The background concentrations of the main charged particles and the temperatures of electrons under normal conditions are determined, based on numerical simulation. The plasma composition of air at these altitudes is analyzed.

The paper presents the results of modeling ionospheric parameters using the Global Self-Consistent Model of the Thermosphere, Ionosphere, and Protonosphere (GSM TIP) of the Earth. Numerical experiments have been performed for three variants of the solar EUV spectrum data: the Nusinov model, EUVAC, and generalized solar flux measurements (SOLID). The calculations have been carried out on March 22, 2009 (F_10.7 ~ 68) and March 22, 2014 (F_10.7 ~ 154). The maximum ionization rate and, correspondingly, the critical frequency of the F2 layer have been obtained using the Nusinov model for low and high solar activities. The lowest ionization rates and values of foF2 have been obtained using the EUVAC model. Simulations with the SOLID spectrum show the better agreement of foF2 with the empirical model IRI-2007 at the maximum solar activity. At the same time, at the minimum solar activity, all models of the spectrum provide an underestimation of the values of the critical frequency of the F2 layer.

The maximum electron density of the F2 layer N_mF2 relative to the solar activity level is studied. The optimal period for averaging the solar activity index F_10.7 is found, which gives on average the lowest error and the highest correlation coefficient (in space and in time) for describing the linear dependence of N_mF2 vs. F_10.7. This result depends substantially on the duration of N_mF2 data storage selected.

In this paper, we consider the unresolved problems of chemistry of the middle atmosphere related to the atmospheric lifetime of the O_x family and its O₃, O(³P), and O(¹D) components, as well as problems associated with the odd oxygen loss in the O_x, HO_x, NO_x, ClO_x, and BrO_x catalytic cycles. We showed that modern interpretations of the odd oxygen concept do not allow obtaining reliable data on the atmospheric lifetime of an odd oxygen family and its components, which is of fundamental importance for the chemistry of the middle atmosphere. Existing methods for determining the rate of ozone depletion in the above cycles are also shown not to have taken into account the chain nature of atmospheric ozone destruction, which leads to significant errors in the results of calculations made using them. We provide the algorithm for a correct estimate of the atmospheric lifetime of the O_x family, as well as an algorithm for calculating the rate of ozone depletion in the O_x, HO_x, NO_x, ClO_x, and BrO_x cycles, which is also used to calculate the atmospheric lifetime of the O_x family.