Liquid-crystal 2-aroylaminopyridines

A number of 2-aroylaminopyridines that have mesogenic properties were synthesized. The relationship between the mesogenic character and the structure was traced on the basis of data from x-ray diffraction analysis and IR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1079–1082, August, 1992.     

Measured lifetimes of states in 197Au and a critical comparison with the weak-coupling core-excitation model

The lifetimes of five excited states in ¹⁹⁷Au up to an excitation energy of 885 keV were measured by the recoil-distance method (RDM). These levels were populated by Coulomb excitation using both 90 MeV ²⁰Ne and 120 MeV ³⁵Cl ion beams. The experimentally determined spectroscopy of the low-lying levels $\text{3}\text{2}{}^{\mathrm{+}}$ (ground state) and $\text{1}\text{2}{}^{\mathrm{+}}$, $\text{3}\text{2}{}_2{}^{\mathrm{+}}$, $\text{5}\text{2}{}^{\mathrm{+}}$, and $\text{7}\text{2}{}^{\mathrm{+}}$ at 77.3, 268.8, 278.9, and 547.5 keV excitation energy, respectively, has been critically compared with the detailed predictions of the de-Shalit weak-coupling core-excitation model. When the model is taken to represent the case of a $\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ proton hole coupled to a ¹⁹⁸Hg core, the model parameters obtained are in accord with the criteria implicit for weak core coupling and, at the same time, are in remarkably good agreement with virtually all measured E2 and M1 transition rates.     

Investigation of electronic structure in chlorine-substituted methanes

The electronic structure, dipole moments, and nuclear magnetic resonance and nuclear quadrupole resonance constants of the CH₄, CCl₄, CHCl₃, CH₂Cl₂, and CH₃Cl molecules were calculated by the Parr-Pariser-Pople (PPP) and Wolfsberg-Helmholz (WH) methods, with self-consistency of the charges on the atoms. Conclusions were reached on the applicability limits of these methods. The calculated values were compared with experimental data.     

Level structure and lifetimes of low-excitation states in 63Cu

The lifetimes of 9 states in ⁶³Cu up to an excitation energy of 2092 keV have been determined by means of the Doppler-shift attenuation method using the ${}^{60}\text{Ni}\text{(α,}\text{p}\text{γ)}$ reaction. A search was made for a suitable set of M1 and E2 single-particle matrix elements for use with shell-model eigenstates throughout the Ni, Cu and Zn isotopes. The theoretical predictions for the level spectroscopy and electromagnetic transitions and static moments in ⁶³Cu are in satisfactory agreement with the experimental findings.     

Stability of the combustion process in elastic combustion chambers

High-frequency instability phenomena in rigid combustion chambers have been studied theoretically in [1–3]. This phenomenon is attributed to the interaction between the combustion processes and combustion-product fluctuations in the chamber. One of the possible mechanisms of formation of high-frequency instability is examined in [3], where the combustion rate is represented in the form of a retarded pressure functional. In this case, the problem is reduced to studying the stability of a certain distributed self-oscillating time-lag system.If the oscillation frequencies of the combustion products are comparable to the natural vibrations of the shell which forms the combustion chamber, then it is natural to expect that the elasticity of the chamber walls will affect the combustion process. Coupled effects of acoustoelastic instability can arise, in whose development the vibrations of the chamber wall play a substantial role. These effects are particularly undesirable from the point of view of the vibrational stability of combustion chambers.In this paper, a theory of high-frequency instability of stationary combustion is developed with allowance for elastic deformations of the combustion chamber walls. The theory is based on the mechanism of vibrational combustion [1–3], according to which the combustion front is assumed to the concentrated, while the velocity jump at the front is expressed through a retarded pressure functional. It is assumed that the combustion product flow is one-dimensional and isentropic and that the chamber is cylindrical. The deformations of the chamber are described via the moment theory of shells. The existence is revealed of additional instability regions produced by the interaction between the elastic vibrations of the chamber walls and the acoustic oscillations of the combustion products. The influence of the relation between the elastic and acoustic frequencies and of the structural damping factor in the combustion chamber walls on the stability of the stationary combustion process is examined. The problem discussed is treated as a mathematical model for more complex asymmetric problems in which the elastic and acoustic frequencies can be of the same order.     

Effect of the condition of synthesis on the composition and structure of copper(II) complexes with benzimidazole

The composition and structure of copper(II) benzimidazole complexes obtained by the reaction of CuCl₂ with benzimidazole (BIm) were determined. At pH 4.5–5.5, depending on the reactant ratio, dimeric compounds with the composition Cu(BIm)₄Cl₂ · 2H₂O and Cu(BIm)₂Cl₂ · H₂O are formed. They are converted to monomers at about 200°C. At pH > 8, irrespective of the reactant ratio, the polymer (Cu(OH)L)n is formed. The complexation of copper(II) with benzimidazole in water and aqueous dioxane was studied by potentiometry, and the stability constants of the complex compounds and their dependence on the solvent composition were determined.     

The effect of microdamage on fatigue-crack growth

The theory of fatigue-crack growth, based on a synthesis of fracture mechanics and continuum mechanics of microdamage accumulation, is applied to the problem of crack growth under cyclic loading, taking into account the plastic deformations in the tip zones. The model of a thin plastic zone, which is a region of considerable plastic deformations at the crack tip, is supplemented by taking into account the effect of microdamage on the value of the specific fracture work and the limit stresses in the tip zone. Governing equations which describe fatigue-crack growth taking these factors into account are derived. The effect of the material characteristics and the load parameters on the growth rate and the distribution of microdamage in the tip zone and on its extensions is investigated by a computational experiment. Particular attention is given to the initial stage when crack growth may occur abruptly and the growth rate depends substantially on the initial conditions