Catalytic Properties of Acid Solutions and the Structure of Acid–Base Complexes with Strong Hydrogen Bonds

The catalytic action of acid solutions involves an equilibrium step in the formation of a reactive complex of reactant molecules with catalyst entities. The relative concentrations of these complexes are determined by using thermodynamic parameters (acidity functions and activities of catalyst components). Data on the structure of complexes with strong H-bonds can be obtained from the vibrational spectra of these species. These data are required for establishing the mechanisms of catalytic reactions and for predicting the catalytic properties of acid solutions containing these complexes.     

Detection and synthesis of a synergist of the sex pheromone of the cotton bollworm

The synergisic properties of docosa-5Z, 17Z-diene — one of the by-products of the synthesis of the synthetic cotton bollworm pheromone — have been revealed.A. S. Sadykov Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax 627071. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 130–132, January–February, 1994.     

A Study of Amorphous Precursors for PbZrO3-PbTiO3 Based Ceramic Materials

Amorphous precursors for PbZrO₃ and PbTiO₃ ceramics were prepared from lead acetate and the transition metaln-propoxide inn-propanol orn-butoxide inn-butanol and hydrolysed with an excess of water. According to GLC and TGA/EGA analyses, the type of alkoxide group influences distinctly the structure of heterometallic precursors, i.e., oxo or acetate bridging, and the amounts of hydroxyl and organic groups bound to the metal network. The local environments of metal atoms in the amorphous precursors were also studied by EXAFS. The analysis reveals that in Pb−Zr precursors alkoxide groups modify the coordination spheres of the zirconium atoms. Conversely, local environments of both lead and titanium atoms within the analysed range of 3.4 A depend weakly on the type of alkoxide used.     

Synthesis of the first stable carborane containing simple enol

A carborane-containing stable simple enol — 1-2-isopropyl-o-carboran-I-yl)-1-phenyl2-mesityl-2-lrydroxyctlrylcne — has been synthesized. This enol does not isomerize to the starting ketone or keto-enol mixture even after prolonged heating in benzene in the presence of CF₃COOH.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1561–1563, June, 1996.     

Kinetics of Hydroperoxide Epoxidation of 1-Octene in the Presence of MoB2

We have studied the kinetics of the process of epoxidation of 1-octene by tert-butyl hydroperoxide in the presence of molybdenum boride MoB₂. We have studied the effect of the concentrations of starting materials and reaction products on the process. We suggest a kinetic scheme and we calculate the kinetic parameters of the process.     

Beryllium diffusion across GaAs/(Al,Ga)As heterojunctions and GaAs/AlAs superlattices during MBE growth

Beryllium diffusion during MBE growth of (Al, Ga)As layers, (Al, Ga)As/GaAs heterojunctions and GaAs/AlAs superlattices has been studied by electrochemical C-V and secondary ion mass spectrometry (SIMS) concentration profiling, in conjunction with transmission electron microscopy. Diffusion times were comparatively short since they were limited to part of the growth sequence, so non-equilibrium effects had a significant influence. The results are consistent with an interstitial-substitutional mechanism in which lattice site incorporation becomes more difficult with increasing band gap enthalpy. Incorporation involves a kick-out reaction which leads to the observed disordering of the superlattices.     

Simulating the diffraction pattern in the focal plane of a lens-axicon system

Laser beam concentration into a narrow ring with a lens and axicon is considered, as there are applications in working surfaces, cutting wafers and slices, and in welding or soldering tubes to heat-exchanger plates. A model is constructed and a working formula is derived for the diffraction pattern in the focal plane of such a system when the axicon is illuminated by a plane wave. For large h/, where h is axicon height and is wavelength, a formula is obtained that passes asymptotically into the approximate Belanger and Rioux ones.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 36–41, December, 1987.     

Electron emission from Al,Pt, Ag,and Au surfaces under the action of resonant photons with λ=2537 and 1850 Å

An original variant of an electronic device is described, which can be used for gamma-process selection under ionized gas conditions. The device is based on a Hanley and Schaffernicht electron gun. Selection of photons and metastable atoms is performed by a quartz tube located in axial symmetry with the primary electron gun. The desired signal is measured from the flow of secondary electrons emitted from Al, Pt, Ag, and Au surfaces under the action of resonant photons radiated from the levels Hg(6³P₁) and Hg(6¹P₁). For =2537 Å the following values were obtained for _ph 9.1, 3.8, 1.1, 0.25. Analogous values of _ph for =1850 Å were equal to 45.5, 10.8, 6.5, 3.2. The _ph values are in units of 10^–4.Translated from Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 68–74, December, 1987.     

Self-activated luminescence of zinc sulfide

The nature of the luminescence of zinc sulfide in the spectral range (360), 380–420 nm (SAL) at 80K is analyzed. It is shown that the appearance of SAL radiation is accompanied by additional absorption in the region (350) 365–370 nm at 80K. The low-temperature spectra of sphalerite, exposed to different radiation and subjected to different treatment, are studied. The multiband luminescence of the isoelectronic sulfur impurity in ZnO deposits in the region 383–640 nm is discussed. It is concluded that SAL luminescence is attributable to the localization of excitons in ZnS on clusters, whose formation precedes the precipitation of the ZnO·S phase. The formation of oxygen clusters and deposits on dislocations in ZnS is studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 60–66, February, 1987.