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[en] The state of the art of the chemistry of hypercoordinate silicon compounds is analyzed. Published data on the current top-priority approaches to the preparative synthesis of these compounds and on their properties, structures and reactivity are summarized and generalized. Relying on the results obtained by modern physicochemical methods, the possible mechanisms of stereodynamic processes occurring in the coordination units of hypercoordinate silicon complexes are discussed. The bibliography includes 157 references
[en] The methods of synthesis and reactions of organosilicon and organogermanium peroxides are surveyed. The emphasis is placed on the studies reported in the last two decades, because in this period, the use of singlet oxygen and the Isayama–Mukaiyama reaction for the synthesis of organosilicon peroxides started. The use of these compounds in the development of antiparasitic agents is considered. The bibliography includes 220 references.
[en] X-ray spectrometry has been, since the last two or three decades, the traditional procedure for the chemical analysis of refractories, due to its high degree of accuracy and speed to produce analytical results. An interesting alternative to X-ray fluorescence is provided by the Inductively Coupled Plasma Spectrometry technique, for those laboratories where wet chemistry facilities are already available or process control is not required at high speed, or investiment costs have to be low. This paper presents results obtained by plasma spectroscopy for the analysis of silico - aluminous refractories, showing calibration curves, precion and detection limits. Considerations and comparisons with X-ray fluorescence are also made. (author)
[pt]O presente trabalho procura apresentar um tecnica instrumental, a espectrometria de plasma acoplado indutivamente (ICP), de desenvolvimento relativamente recente porem ja largamente empregado na analise de minerais e metais, mostrando os resultados obtidos para refratarios silico-aluminosos e discutindo suas vantagens e desvantagens em relacao aos metodos anteriormente mencionados. (autor)
[en] To research the recombination processes spectral and time dependences of lateral photoconductivity nanoheterostructures Si/Ge with SiGe nanoislands, obtained by molecular beam epitaxy were studied. Photoconductivity at T<190 K, in the spectral region where Si is transparent, is conditioned due to transitions involving localized states nanoislands SiGe. It is shown that when the temperature was decreased the most significant is the decrease in the photoconductivity of the fundamental absorption of nanoislands
[en] The history and state of the art of research on silylium ions are summarised. Achievements of the last two decades in the preparation of silylium ions as individual species in solutions and crystals and as intermediates in reactions of organosilicon compounds are considered. Attention is focused on ion-molecular reactions of silylium ions with nucleophilic reagents in the gas and condensed phases.