The cyclodimerisation of 3-methyl-2-butenenitrile

3-Methyl-2-butenenitrile (1) cyclodimerised on treatment with lithium diisopropylamide in dimethoxyethane at temperatures between ?78°C and 0°C to 3-amino-4-cyano-1,5,5-trimethyl-1,3-cyclohexadiene (2) the structure of which was established by acid hydrolysis to the known 4-cyano-1,5,5-trimethyl-1-cyclohexene-3-one (3).     

Conical parametric scattering of a single extraordinary beam in BaTiO3 crystal

In this paper, the parametric scattering of a single extraordinary polarized beam of laser in BaTiO₃ photorefractive crystal has been investigated experimentally and theoretically. The resulting pattern consists of beam fanning, isotropic ring, and anisotropic one. Among all parts of scattering pattern, isotropic ring has not been studied as much as beam fanning and anisotropic ring, and there still are some differences in reports about it. Therefore, the study has mainly focused on this part. In this experimental configuration, isotropic ring is just visible in positive angles although the other parts of parametric scattering pattern can be visible from behind and in front of the crystal. In addition to steady state pattern in forward and backward directions, its transient behavior with the rotation of crystal has been studied. The results of experiments have been analyzed carefully, and their theoretical explanations have been presented based on the standard theory of parametric scattering in photorefractive crystals. It has been shown that this configuration corresponds to the so called parametric B-process scattering.     

Quantum dynamics of formation of an unstable field state in the process of intracavity third-harmonic generation

The dynamics of the Wigner functions and quantum entropy of the fundamental and third-harmonic modes is studied for the process of intracavity third-harmonic generation. It is shown that quantum dynamics of the system strongly depends on the coupling coefficient of the interacting modes. The dynamics of the transition of the system from a stable to an unstable state is investigated.     

Adhesion-induced DNA naturation

DNA adsorption and naturation is modeled via two interacting flexible homopolymers coupled to a solid surface. DNA denatures if the entropy gain for unbinding the two strands overcomes the loss of binding energy. When adsorbed to a surface, the entropy gain is smaller than in the bulk, leading to a stronger binding and, upon neglecting self-avoidance, absence of a denatured phase. Now consider conditions where the binding potentials are too weak for naturation, and the surface potential too weak to adsorb single strands. In a variational approach it is shown that their combined action may lead to a naturated adsorbed phase. Conditions for the absence of naturation and adsorption are derived too. The phase diagram is constructed qualitatively.     

Self-chemical ionization of diethylzinc

The self-chemical ionization of diethylzinc is examined by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and semiempirical molecular orbital calculations. Electron impact of diethylzinc neutral produces the radical cation, C(4)H(15)Zn(+) (m/z x 122), which reacts further with the neutral (C(2)H(5))(2)Zn to give the following product ions: Zn(+) (m/z x 64), C(2)H(5)Zn(+) (m/z x 93), C(4)H(9)Zn(+) (m/z x 121), C(4)H(11)Zn(2)(+) (m/z x 187), and C(6)H(15)Zn(2)(+) (m/z x 215). To determine the structure and pathways for production of these ions, monoisotopic (12)C(4)H(15)(64)Zn(+), (64)Zn(+) and (12)C(2)H(5)(64)Zn(+) were individually isolated and reacted with the neutral background. We also performed semiempirical molecular orbital calculations (ZINDO/1). The molecular orbital calculations and experimental data are consistent in predicting that the ethyl group on the diethylzinc cation carries the positive charge. Copyright 1999 John Wiley & Sons, Ltd.     

Dielectric permittivity superlattice formation

A dielectric medium consisting of roughly polarized molecules has been treated as a 3D disordered spin system (spin glass). Having in view the study of the statistical properties of this system on a micrometer scale and nanosecond time scale of a standing electromagnetic wave, a microscopic approach has been developed. Using the Birkhoff ergodic hypothesis, the initial 3D spin problem is reduced to two conditionally separate 1D problems along the external electromagnetic field propagation. The first problem describes a disordered N-particle quantum system with relaxation in the framework of a Langevin-Schrödinger (L-Sch)-type equation, while the second one describes a steric disordered spin-chain system. The statistical properties of both systems were investigated in detail. Based on these constructions, the coefficient of polarizability related to the collective orientational effects was calculated. The Clausius-Mossotti relation for the dielectric constant was generalized. Taking into account the generalized Clausius-Mossotti relation, a generalized equation for the dielectric permittivity function has been found. A simple formula was derived for the dielectric permittivity function in the X-ray frequency range, which can be larger than unity on the micrometer scale and nanosecond time scale.     

Orientation relaxation in H8 nematic and its solution in a nonmesogenic solvent under a magnetic field

The time dependences of the ultrasound absorption coefficient in the H8 nematic and its solution in a nonmesogenic solvent (benzene) under a pulsating magnetic field and varying thermodynamic parameters of state (p, T) are studied. The ratio of the rotational viscosity to the diamagnetic susceptibility (γ₁/Δχ), the activation energy for different pressures, and the activation volume are found.     

Radiation of a charged particle in a random stack of plates

Radiation from a charged particle moving in a system of randomly spaced plates is considered. It is shown that the dominant radiation mechanism is diffusion. The total intensity of radiation is investigated, and its quadratic dependence on particle energy is noted in the optical region. A comparison with Cherenkov radiation is carried out. Zh. éksp. Teor. Fiz. 114, 91–99 (July 1998) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

怀孕期头发中一些元素含量的变化趋势

用同步辐射激发X射线荧光分析,对11个产妇怀孕期间头发内一些元素含量的变化趋势进行了测量,在各自对比的基础上,得到了一些结果。