Unusual transfoemation of trimethylsilyl ester of 5-chloromethyl-2-isoxazoline-3-carboxylic acid

Conclusions The silylation of 5-chloromethyl-2-isoxazoline-3-carboxylic acid with the usual silylating agents leads to the corresponding trimethylsilyl ester, which when heated is converted to 4-chloro-3-trimethylsiloxybutyronitrile.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2818–2819, December, 1981.     

Asymmetry of formation of π+-mesons by linearly polarized photons in the region of the first pion-nucleon resonance

This article presents measurements of the asymmetry of formation of ⁺ mesons on a proton by linearly polarized photons in the energy region from 220 to 320 MeV and for pion emission angles 90–135° in the c.m.s. Aphenomenological analysis is carried out on the basis of 25 measured values of the asymmetry and the data of other laboratories. As a result of the analysis, five independent values are obtained for the multipole amplitude functions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 94–101, May, 1978.     

Hydrogenation of carbon monoxide catalysts prepared by pyrolysis of Co2(CO)8 on various oxide supports

Catalysts prepared by pyrolysis of Co₂(CO)₈ on oxide supports have been studied in the hydrogenation of CO. It is shown that MgO and -Al₂O₃-based catalysts are less active than those supported on SiO₂, TiO₂ and ZrO₂. The application of -Al₂O₃ as a support increases the relative yield of light hydrocarbons.

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, Co₂(CO)₈ , CO. , MgO -Al₂O₃ SiO₂, TiO₂ ZrO₂. -Al₂O₃ .

     

The Interaction of O2, NO,and N2O with Surface Defects of Dispersed Titanium Dioxide

A combined study of intrinsic structural defects in reduced TiO₂ was performed using mass spectrometry, optical diffuse-reflectance spectroscopy, and UV photoelectron spectroscopy (UPS). It was found that the reduction of TiO₂ resulted in the appearance of absorption in the region 0.50 h 3.50 eV (400 2500 nm), which is formed by absorption due to free electrons (a continuum at h 1.50 eV), local centers—Ti³⁺ ions (a band at 2.00 eV), and oxygen vacancies (bands at 1.17, 2.81, and 2.55 eV). The spectrum of induced occupied electronic states in the forbidden gap and the position of oxygen vacancy levels with respect to the Fermi level were determined by UPS. The absorption of reduced TiO₂ was stable on the sample to T = 800 K in a vacuum; however, it weakened in contact with O₂, NO, and N₂O molecules beginning at T = 300 K (surface sites) and T 400 K (subsurface sites) as a result of filling oxygen vacancies with atomic oxygen in the course of dissociative adsorption. The adsorption complexes formed by the interaction of O₂, NO, and N₂O with defects were analyzed by temperature-programmed desorption. The distribution of sites over the energies of oxygen binding was found with the use of a nonuniform surface model, and specific oxygen adsorption species were revealed. It was found that the irradiation of TiO₂ activates the formation and decay of sites and results in the formation of specific O₂ and N₂O adsorption species.     

Derivatives of the closo-dodecaborate anion and their application in medicine

The paper presents a comparative analysis of the possibilities and characteristic features of the application of various polyhedral boron compounds, viz., the closo-decaborate anion [B₁₀H₁₀]^2–, the closo-dodecaborate anion [B₁₂H₁₂]^2–, the carba-closo-dodecaborate anion [CB₁₁H₁₂]^–, carboranes C₂B₁₀H₁₂, and the bis(dicarbollide) complexes [M(C₂B₉H₁₁)₂]^– (M = Fe, Co, or Ni), in boron neutron capture therapy (BNCT) for cancer. The requirements on compounds used in BNCT are formulated and the advantages of the application of the closo-dodecaborate anion are considered. The data on the synthesis of various derivatives of the closo-dodecaborate anion, which either already found use in BNCT or are most promising in this field, are summarized. The possibilities of the application of agents derived from the closo-dodecaborate anion in medical diagnostics are discussed.     

Optical “memory” centers on an adsorption silicon surface

The charging of an illuminated silicon surface discovered by Abkevich [1] is of considerable interest for a number of practical applications (for example, semiconductor photography [2] and gas analysis). The present paper gives the results of investigations aimed at establishing the possibility of controlling the optical charge memory on the silicon surface by adsorption methods.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 92–96, January, 1981.We thank V. F. Kiselev for discussing the work and for helpful comments.     

Photoinjection phenomena in a silicon-silcon dioxide system

Silicon-silicon dioxide structures obtained by thermal, anodic, and chemical oxidation of silicon are studied by the photocharge and photoinjection current methods. It is shown that the extent of the fluctuation state tails" near the edges of the SiO₂ forbidden zone is small (0.2 eV). The threshold for negative photocharging of anodic oxide traps is found to decrease with increase in oxide thickness, a fact related to the existence of a nonstoichiometric transition layer between the silicon and silicon dioxide. The effect of hydration and dehydration on negative optical charge of oxide traps is studied, and it is shown that the basis of electron traps is formed by the most hydrated and deformed SiO₄H_n tetrahedra. The possibility of creating electron and hole traps in the oxide layer by doping with metal ions from a solution is demonstrated. It is found that the corresponding defects are also adsorption centers for water molecules by a coordination mechanism.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 3–7, July, 1981.In conclusion, the authors thank V. F. Kiselev for his interest in the study and valuable remarks.     

Physical and chemical properties of silicon carbonitride nanocrystalline films

Nanocrystalline transparent films SiC_xN_y were obtained by plasma-enhanced chemical deposition within the temperature range 473–1173 K from low pressure gas phase from a mixture of hexamethyldisilazane vapor, ammonia, and helium. Physical chemical properties of the films obtained were studied by IR and Raman spectroscopy, ellipsometry, X-ray photoelectron spectroscopy, scanning electron microscopy, high resolution transmission electron spectroscopy and synchrotron radiation powder diffaction. Voltage-capacity and voltage-current measurements were also made. The dependence of chemical and phase composition of the films on deposition conditions was determined, and the formation of approximately 2 nm sized spherical nanocrystals within the films was established. The nanocrystals are formed by a phase similar to usual α-Si₃N₄, with silicon atoms partially substituted by carbon ones.     

Graph Methodology and Principles of Linear Nonequilibrium Thermodynamics in the Theory of Flow-Injection Analysis

It is shown that chemical, configurational, and informational properties of flow-injection systems can be interrelated with the use of the methodology of the graph theory. The main equation of the theory is derived using a mathematical expression of the transition paths from the analyte to the detection of a product of the analytical reaction. Examples of specific developments are discussed for redox reactions, ligand exchange reactions, and heterogeneous exchange reactions, with due regard to, the hidden peculiarities of their chemical mechanisms that are essential for flow analysis and also for on-line preconcentration by coprecipitation. It is also shown that the conditions obtained in a flow system correspond to the basic postulates of linear nonequilibrium thermodynamics, which provides a basis for a new approach to the theory of flow analysis. An example of a complexation reaction was used for discussing the possibility that a linear interrelation exists between flows and forces in a flow system, which corresponds to the Onsager reciprocal relation.