Oligomer and Polymer Formation in Hexamethylcyclotrisiloxane (D<Subscript>3</Subscript>) – Hydrosilane Systems Under Catalysis by tris(pentafluorophenyl)borane

Summary Reactions of hexamethylcyclotrisiloxane, D₃, with 1,1,3,3-tetramethyldisiloxane, ^HMM^H, 1,1,1,3,3-pentamethyldisiloxane, ^HMM, phenyldimethylsilane and phenylmethylsilane catalyzed by tris(pentafluorophenyl)borane were studied. These reactions lead to ring opening of D₃ by the SiH reactant producing open chain oligomers with hydrosilane functionality at one or both chain ends. The reactivity of the hydrosilanes toward D₃ decreases in the series: PhMeSiH₂ > ^HMM^H > PhMe₂SiH > ^HMM. Competitive self-oligomerization of ^HMM^H and ^HMM also occurs. Primary products of these processes are able to enter into reactions with the SiH and D₃ reactants; some also undergo cyclization. Thus, consecutive and competitive processes lead to a series of various oligohomologues. Gas chromatography in conjunction with chemical ionization mass spectroscopy permitted identification of structure and determination of the basic directions of these oligomerization processes. Polysiloxanes of higher molecular weight may be also formed in some of these systems. The reactions, which occur in the systems studied, are rationalized on the basis of the mechanism involving the hydride transfer from silicon to trivalent boron. This includes the transient formation of tertiary trisilyloxonium borate which decomposes by the hydride transfer to one of the silicon atoms of the trisilyloxonium center. Footnote: This paper is dedicated to Professor Ian Manners in recognition of his significant contributions to the field of organometallic polymers.     

Driving as a human: a track learning based adaptable architecture for a car racing controller

We present the evolution and current state of the Mr. Racer car racing controller that excelled at the corresponding TORCS competitions of the last years. Although several heuristics and black-box optimization methods are employed, the basic idea of the controller architecture has been to take over many of the mechanisms human racing drivers apply. They learn the track geometry, plan ahead, and wherever necessary, adapt their plans to the current circumstances quickly. Mr. Racer consists of several modules that have partly been adapted and optimized separately, where the final tuning is usually done with respect to a certain racing track during the warmup phase of the TORCS competitions. We also undertake an experimental evaluation that investigates how the controller profits from adding some of the modules to a basic configuration and which modules are most important for reaching the best possible performance.     

HamleDT: Harmonized multi-language dependency treebank

We present HamleDT—a HArmonized Multi-LanguagE Dependency Treebank. HamleDT is a compilation of existing dependency treebanks (or dependency conversions of other treebanks), transformed so that they all conform to the same annotation style. In the present article, we provide a thorough investigation and discussion of a number of phenomena that are comparable across languages, though their annotation in treebanks often differs. We claim that transformation procedures can be designed to automatically identify most such phenomena and convert them to a unified annotation style. This unification is beneficial both to comparative corpus linguistics and to machine learning of syntactic parsing.     

Drying-induced stresses in elastic and viscoelastic saturated materials

The paper presents a theoretical analysis of stresses generated during convective drying of kaolin, based on elastic and viscoelastic models. The equations of these models were solved analytically for a cylindrically shaped sample; the distribution and evolution of the radial and circumferential stresses are illustrated in diagrams. The acoustic emission method was used in experimental tests for identification on line of the time period during which the stresses reach their maximal values. A better correlation has been found between the experimental tests and the theoretical predictions obtained on the basis of the viscoelastic model.     

High oleic acid oil suppresses lung tumorigenesis in mice through the modulation of extracellular signal-regulated kinase cascade

This study was undertaken to estimate the effect of dietary high oleic acid oil (OA) on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in mice. Diet containing 10% oil was fed to mice through experimental periods. On day 30 after NNK injection (100 mg/kg body weight, i.p.), the treatment increased the level of prostaglandin E₂ (PGE₂) as well as proliferating cell nuclear antigen, a marker of cell proliferation in a high linoleic acid oil (LA)-fed group but not in an OA-fed group. The NNK treatment also induced the activation of an extracellular signal-regulated kinase (Erk) cascade (Erk, Mek and Raf-1) in an LA-fed group. On the other hand, OA feeding abolished the NNK-induced activation of the Erk cascade. In conjugation with these events, OA feeding reduced lung tumor incidence and tumor multiplicity (percentage of mice with tumors) in mice compared with LA feeding at the 20th experimental week. These results suggest that OA suppresses lung tumorigenesis and that this suppression is correlated with the inhibition of PGE₂ production and inactivation of the Erk cascade.     

Modification of zeolite surfaces by Grignard reagent

New microporous hybrid organic/inorganic materials were obtained by modification of zeolites using chlorination of their surface, followed by treatment with a Grignard reagent. Loading of butyl groups and retained crystallinity of ZSM-5 type zeolites was higher than for zeolites Y. In contrast to zeolites Y, the lattice parameters of zeolites ZSM-5 increased after surface modification. The obtained hybrid materials on the basis of high-silica zeolites possess a high degree of crystallinity at increased hydrophobicity.     

Stretching and deformation vibrations of CH2, C(CH3) and O(CH3) groups of poly(methyl methacrylate)

Infrared and Raman spectra of atactic PMMA and infrared spectra of stereoregular PMMA and of its four deuterated derivatives

, were measured. They were used to assign the bands of stretching and deformation vibrations of CH₂, CCH₃ and OCH₃ groups in the infrared and Raman spectra and to discuss the effect of stereoregularity on these bands in the infrared spectra.     

Methods to determine solubility parameters of polymers at high temperature using inverse gas chromatography

Experimental values of Flory–Huggins parameters, χ, between polymers and probes, are frequently used to determine the solubility parameters of the polymers by the method of DiPaola–Baranyi and Guillet. The solubility parameters of probes were usually estimated by using heat of vaporization. When χ is measured at a temperature near the critical temperature of the probes and used to determine the solubility parameter of polymers, the departure of enthalpy of the probe vapor from the ideal gas state should be considered. This study discussed the method to make the correction and its effect on the determination solubility parameter of polymers. Without correction in the vapor phase enthalpy, the solubility parameters of the probes and polymer tend to be underestimated and the error increases when the critical temperature is approaching. Analytical expressions for the effect of correction on the solubility parameter of probes and parameters of polymers were derived. By use of probes with a range of solubility parameters on both sides of the solubility parameter of polymers, the correlation between parameters of polymers was shown to be reduced. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1547–1555, 2004     

Flow modelling within non-homogeneous packings: The structural macro-correlations

The pressure drop and the fluid velocity profiles were investigated experimentally and numerically in the model packings of complex geometry. The numerical estimations were performed by means of the hybrid method involving the use of structural macro-correlations. In this paper it has been demonstrated on several examples that the structural macro-correlations allow to predict the macro-scale flow behaviour in non-homogeneous packings. Finally, the recent mechanistic approaches to flow modelling in packed tubes of low tube-to-particle diameter ratio have been discussed.     

High-pressure catalytic and thermal cracking of polyethylene

The thermal cracking and catalytic cracking processes of low-density polyethylene were studied in a closed autoclave. The compositions of gaseous and liquid products were analysed by means of GC/FID and GS/MS chromatographic methods. The fractional composition of liquid products was found by distillation. Increased temperature of PE depolymerisation process increases the production of gaseous products and low-boiling liquid compounds; more aromatic hydrocarbons are formed instead of alkenes. When a lower temperature and longer time are adopted for the process to reach the assumed conversion, more straight chained hydrocarbons are produced. The acidic aluminosilicate catalyst yields more low-boiling liquid fractions, more isoalkanes and more aromatics. The neutral alumina is favourable for the production of alkenes and vacuum gas oil fraction in comparison to a non-catalytic process. The Ni–Mo/Al₂O₃ catalyst is efficient in hydrogenation of depolymerisation products. The reaction products contain only saturated compounds then and no aromatics are formed.