Triruthenium dodecacarbonyl/triphenylphosphine catalyzed dehydrogenation of primary and secondary alcohols

Dehydrogenation of alcohols into aldehydes and ketones by Ru₃(CO)₁₂/PPh₃ based homogeneous catalysis has been investigated as an alternative for the classical Oppenauer oxidation. Several catalytic systems have been screened in the Oppenauer-like oxidation of alcohols. A systematic study of various combinations of Ru₃(CO)₁₂, mono- and bidentate ligands and hydride acceptors was performed to enable dehydrogenation of primary alcohols to stop at the aldehyde stage. Among many H-acceptors screened, diphenylacetylene (tolane) proved the most suitable judged from its smooth reduction. Electron rich and deficient analogues of tolane have been synthesized and, based on competition experiments between these H-acceptors, a tentative catalytic cycle for the Ru₃(CO)₁₂/PPh₃-catalyzed dehydrogenations has been proposed.     

Gaussian Approximations in the Stochastic Theory of Spontaneous Ignition of Coal Particles

Stochastic models of the process of spontaneous ignition of coal particles are distinguished by a pronounced nonlinearity due to the Arrhenius approximation for the constant of the reaction rate and by a complex structure of the stochastic component (noise). We present models describing the dynamics of the distribution of this quantity. The models obtained consist of nonlinear ordinary differential equations, which are solved by numerical methods with the use of computer technologies.     

Influence of Conditions of Zinc Selenide Oxidation with Atmospheric Oxygen on the Composition of Volatile Products

The qualitative and quantitative composition of volatile products of zinc selenide oxidation with atmospheric oxygen was determined. The influence of the process conditions on quantitative composition of the volatile products was studied.     

Micromechanisms and Mechanics of Damage and Fracture in Thin Film/Substrate Systems

The purpose of this paper is to review the mechanisms and available theoretical methods for modeling the strength and failure of thin film/substrate systems     

Surface roughness investigation of semi-conductor wafers

Conventionally, surface roughness is predominantly determined through the use of stylus instruments. However, there are certain limitations involved in the method, particularly when a test specimen, such as a silicon wafer, has a smooth mirror-like surface. Hence, it is necessary to explore alternative non-contact techniques. Light scattering has recently been gaining popularity as an optical technique to provide prompt and precise inspection of surface roughness. In this paper, the total integrated scattering (TIS) model is modified to retrieve parameters on surface micro-topography through light scattering. The applicability of the proposed modified TIS model is studied and compared with an atomic force microscope. Experimental results obtained show that the proposed technique is highly accurate for measuring surface roughness in the nanometer range.     

Study of ferroelectric switching by domain-wall induced light scattering

Measurements of 90°-scattering of weak laser light are used to investigate pulsed domain switching in ferroelectrics. The studies were performed on strontium-barium niobate (SBN) single crystals. A good agreement of the switching parameters estimated from the optical measurements with those obtained by means of conventional electrical methods proves the validity of the optical method for switching studies. Due to the limited scattering volume in all three spatial dimensions, the method facilitates local probing of the switching within the crystal bulk. In particular, local specialities of the domain density can be detected. Furthermore, the excellent time resolution inherent in optical probing techniques allows for a comprehensive study of the dynamics.     

Tandem silylformylation-allyl(crotyl)silylation: a new approach to polyketide synthesis

Tandem intramolecular silylformylation-allyl(crotyl)silylation reactions have been developed that allow the highly efficient synthesis of polyketide fragments. The substrates are subjected to Rh(I)-catalyzed silylformylation to afford β-(diallyl)silyl aldehydes which undergo spontaneous uncatalyzed allylsilylation. This unusual spontaneous allylsilylation reaction is driven by strain release Lewis acidity, which arises from the ∼95° O-Si-C bond angle in the oxasilacyclopentane product of the silylformylation reaction. The methodology has been developed both for alkene and alkyne substrates, may be used to establish as many as three stereocenters, and has been shown to be amenable to use in an iterative fashion.