Lines of Development of Seismic Prospecting in the 20th Century

The theory and practice of seismic prospecting are discussed. The period of its development is subdivided into two parts: the classical period up to the 70s years of the twentieth century and the modern technological period. Bibliography: 4 titles.     

Unusual dimerization of 1-ethyl-1,2,4-triazinium salts into 4a,4b,9,10-tetrahydro-1,3,6,8,8a,10a-hexaazaphenanthrenes

1- Ethyl-3-alkylthio-5-phenyl-l,2,4-triazinium tetrafluoroborates were found to undergo an unusual dimerization on treatment with triethylamine in methanol or ethanol solution. A mechanism for the formation of 4a,4b,9,10-tetrahydro-l,3,6,8,8a,l0a-hexaazaphenanthrenes is proposed.     

Determination of ionol in oils in the presence of low-molecular-weight phenols using reversed-phase HPLC

A procedure was developed for extracting phenol-type antioxidants from oils. The extraction system consisted of isopropanol, 25% NH₃, water, and ammonium sulfate as a salting-out agent. The optimum conditions were found for determining ionol in the presence of phenol and alkylphenols in the isopropanol extract using reversed-phase HPLC with an UV-detector. The time of analysis was 55 min. The detection limits in oils (taking into account extraction preconcentration) were 0.0005 mg/L for phenol, 0.0006 mg/L for cresols, and 0.015 mg/L for ionol.     

Synthesis of monosubstituted 1,2,4,5-tetrazines – 3-amino-1,2,4,5-tetrazines

Chemistry of Heterocyclic Compounds - The substitution of pyrazolyl moiety in 3-(3,5-dimethyl-1H-pyrazol-1-yl)-1,2,4,5-tetrazine with N-nucleophiles provided a series of highnitrogen tetrazine...     

Dependences of the osmotic coefficients of aqueous calcium chloride solutions on concentration at different temperatures

A model that considers the contributions from hydration, ion association, and electrostatic interactions to the nonideality of 2?1 electrolyte solutions is substantiated. The parameters of the model’s equations are the mean ion hydration number, the spread of the distribution of hydrated ion stoichiometric coefficients in the standard state, and the number of association. The model is successfully used to describe literature experimental data on the concentration dependence of osmotic coefficients of aqueous CaCl₂ solutions at temperatures ranging from 0 to 100°C. The modeling of the above systems shows that as the temperature rises, the hydration number falls slightly, the distribution of the hydration number broadens, and the ion paring of the salt rises by the first degree.     

Nuclear rainbow in the elastic scattering of <Superscript>16</Superscript>O nuclei on carbon isotopes

An investigation of refractive effects in heavy-ion scattering is continued. For the elastic scattering of ¹⁶O nuclei on a ¹³C target at E(¹⁶O) = 132 MeV, the differential cross sections are measured for the first time in addition to previous measurements for targets from the carbon isotopes ¹²C and ¹⁴C. Airy structures that are similar for all isotopes and which have close cross sections are observed and are found to be consistent with the energy systematics of Airy minima that were obtained previously. The volume integrals of the real and imaginary parts of the optical potentials found in the present study are nearly identical for all of the isotopes considered here and are also in good agreement with the systematics obtained previously.     

Periodic solutions of the quasilinear beam vibration equation with homogeneous boundary conditions

We prove the existence of infinitely many time-periodic solutions of the quasilinear beam vibration equation with homogeneous boundary conditions for the case in which the nonlinear term has power-law growth. We also prove the existence of at least one periodic solution provided that the nonlinear term satisfies the resonance-free condition.     

Some Aspects of the Effective Detection of Ammonium Nitrate-Based Explosives by Pulsed NQR Method

The nuclear quadrupole resonance (NQR) method has been applied to ammonium nitrate (AN)-based explosives, ANFO and REOGEL+, to find an optimized multi-pulse technique for effective detection. The relaxation parameters and signal intensities for nitrogen-14 lines of these substances were measured. The experimental results of applying the proposed multi-pulse technique in these samples are presented and convincingly demonstrate a path toward efficient detection. A detection using sequences of this character could be achieved over real-world scan volumes for screening of goods. It was proven that the cross-polarization technique can significantly enhance the NQR signal for AN-based explosives.     

Periodic solutions of a quasilinear wave equation

We study the properties of wave operators satisfying the periodicity condition with respect to time and homogeneous boundary conditions of the third kind and of Dirichlet type. We prove the existence of a nontrivial periodic (in time) sine-Gordon solution with homogeneous boundary conditions of the third kind and of Dirichlet type. We obtain theorems on the existence of periodic solutions of a quasilinear wave equation with variable (in x) coefficients and a boundary condition of the third kind.