Synthesis of the acetate of (±)-2,6-dimethylhepta-1,5-dien-3-ol — The racemic form of the sex pheromone of Pseudococcus comstocki

4-Methylpent-3-enal has been synthesized by the dehydration of trans-2-(1-hydroxy-1-methylethyl)-1-methoxycyclopropane, and this has been brought into reaction with propen-2-ylmagnesium bromide. Acetylation of the carbinol so formed gave the acetate of (±)-2,6-dimethylhepta-1,5-diene-3-ol — the racemic form of the sex pheromone of the Comstock mealybug.Scientific-Research Institute of Physicochemical Problems, V. I. Lenin Belorussian University, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 747–748, September–October, 1988.     

Heat-stimulated currents in semi-insulating gallium arsenide

The energy spectrum of charge carrier traps of semi-insulating n-type gallium arsenide has been investigated by the method of heat-stimulated currents and the parameters characterizing these traps have been estimated. Trap acceptor levels with energies 0.37, 0.41 and 0.17, 0.28, 0.32, 0.34, 0.38, 0.40 eV have been found for samples with the specific resistivity 2.7 · 10⁷ and 1.6 · 10⁸ · cm, respectively. The results obtained are well explained within the framework of the theory of a compensated semiconductor.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 11, pp. 22–26, November, 1971.The authors are grateful to A. P. Vyatkin, V. G. Voevodin, and E. V. Kozeev for kindly providing the gallium arsenide crystals and stimulating the research.     

Kinetic model for binary homogeneous nucleation in the H2O-H2SO4 system: comparison with experiments and classical theory of nucleation

A kinetic model to predict nucleation rates in the sulfuric acid-water system is presented. It allows calculating steady-state nucleation rates and the corresponding time lag, using a direct solution of a system of kinetic equations that describe the populations of sub- and near-critical clusters. This kinetic model takes into account cluster-cluster collisions and decay of clusters into smaller clusters. The model results are compared with some predictions obtained with the classical nucleation theory (CNT) and also with available measurement data obtained in smog chambers or flow tubes. It is shown that in the case of slow nucleation processes, the kinetic model and the CNT as used by Shugard et al. [J. Chem. Phys. 75, 5298 (1974)] give the same results. However, in the case of intensive nucleation, a large part of the nucleation flux is due to cluster-cluster collisions and the CNT underestimates the nucleation rates.     

Magnetic field effects on formaldehyde-d2 Predissociation and photochemical reactions of SO2 with pentane in the gas phase

The magnetic field and pressure effects in the photolysis of deuteroformaldehyde and sulfur dioxide in the near ultra-violet reagion have been investigated. A two-level model is proposed to interpret the results obtained.     

Investigation of the Li (e,e′p) reaction at 1200 MeV

The reaction ⁶Li (e, e′p)⁵He has been investigated with a resolution good enough to distinguish the effects of the s- and p-shells of the ⁶Li nucleus. The reaction cross section has been measured as a function of the missing energy from −15 to +30 MeV. The proton angular distribution has been measured at missing energies of 4 and 20 MeV. The comparison of the data with calculations within the framework of the plane-wave impulse approximation gives the harmonic oscillator parameters q_p = 50 ± 5 MeV/c,q_s = 108 ± 9 MeV/c.