Photoelectron Properties and Organic Molecules Photodegradation Activity of Titania Nanotubes with CuxO Nanoparticles Heat Treated in Air and Argon

Titania is very famous photocatalyst for decomposition of organic pollutants. Its photocatalytic properties significantly depend on the morphology and chemical composition of the samples. Herein, the TiO₂ nanotubes/Cu_xO nanoheterostructures have been synthesized and the effect of heat treatment performed in molecular atmospheres of air and argon on their photoelectrochemical and photocatalytic properties has been studied. The prepared samples have a higher reaction rate constant compared to TiO₂ nanotubes in the decomposition reaction of methylene blue molecules. It is established that in argon treated nanoheterostructures, the copper oxide is present in two phases, CuO and Cu₂O, while in air treated ones there is only CuO. In the TiO₂ nanotubes/Cu_xO samples, Cu²⁺ ions and molecular O₂⁻ radicals were detected while in TiO₂ nanotubes only carbon dangling bond defects are present. The dynamics of O₂⁻ radicals under illumination are discussed. It was shown that the TiO₂ nanotubes do not exhibit photocatalytic activity under visible light. The mechanism of the photocatalytic reaction on the surface of the TiO₂ nanotubes/Cu_xO samples was proposed. It is assumed that a photocatalytic decomposition of organic molecules under visible light at the surface of the nanoheterostructures under investigation is realized mainly by the reaction of these molecules with photogenerated O₂⁻ radicals. The results obtained are completely original and indicate the high promise of the prepared photocatalysts.     

Synthesis and properties of nanosilicon stabilized by butyl and perfluorobutyl ligands

Nanocrystalline silicon stabilized by butyl and perfluorobutyl ligands that form improper surface states of silicon nanocrystals were synthesized. The presence of perfluorobutyl ligands on the surface of silicon nanocrystals was proved by IR spectroscopy. Nanocrystals with perfluorobutyl ligands form aggregates, which decreases the efficiency of photoluminescence. The nanocrystals with butyl ligands have smaller size but their photoluminescence can be clearly recorded.     

Lyapunov functionals of constant signs in the stability problem for a functional-differential equation of neutral type

We present a generalization of the Lyapunov functional method and use it to study the stability of nonautonomous functional-differential equations of neutral type with finite delay. This generalization is based on constructing the limit equations and the limit functionals.     

Capital Asset Pricing Model (CAPM) with drawdown measure

The notion of drawdown is central to active portfolio management. Conditional Drawdown-at-Risk (CDaR) is defined as the average of a specified percentage of the largest drawdowns over an investment horizon and includes maximum and average drawdowns as particular cases. The necessary optimality conditions for a portfolio optimization problem with CDaR yield the capital asset pricing model (CAPM) stated in both single and multiple sample-path settings. The drawdown beta in the CAPM has a simple interpretation and is evaluated for hedge fund indices from the HFRX database in the single sample-path setting. Drawdown alpha is introduced similarly to the alpha in the classical CAPM and is evaluated for the same hedge fund indices. Both drawdown beta and drawdown alpha are used to prioritize hedge fund strategies and to identify instruments for hedging against market drawdowns.     

Statistical synthesis of multiantenna ultrawideband radiometric complexes

An optimum signal processing algorithm of radiometric imaging has been synthesized for the first time using multiantenna ultrawideband (UWB) radiometric complexes (RMCs). Radiometric images (RMI) are interpreted physically as intensity depending on the angular coordinates or the spectral radio brightness averaged in the operation frequency band. In accordance with the synthesized algorithm, a structural scheme of ultrawideband radiometric complexes has been developed. An analytical expression for the ambiguity function of radiometric complexes has been obtained. The ambiguity function is modeled in the case of processing narrowband and ultrawideband radiometric signals. As follows from the analysis of the results, new elements of the theory of optimum processing of UWB radiometric signals with the involvement of multielement antenna systems are an important tool in creating highly accurate, biologically and ecologically safe complexes for studying various media and objects.     

Synthesis of acetylenic carbinols of the 2,2,6,6-tetramethylpiperidine series

Conclusions A convenient method was proposed for the preparation of acetylenic carbinols of the 2,2,6,6-tetramethyl-piperidine series by the ethynylation of 2,2,6,6-tetramethyl-4-oxopiperidine in liquid ammonia in the presence of alcoholic alkali.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1680–1681, July, 1978.