Autoxidation of Hydrocarbons: From Chemistry to Catalysis

This contribution summarizes our recent efforts to unravel the radical chemistry of autoxidations. Abstraction of the weakly bonded αH-atom of the primary hydroperoxide product by chain carrying peroxyl radicals is identified as the source of major end products such as alcohol and ketone/aldehyde. In the case of cyclohexane autoxidation, this reaction is even responsible for the majority of ring-opened by-products. In a second part, different approaches to autoxidation catalysis are discussed, ranging from transition metal ion catalysis to organocatalysis with immobilized N-hydroxyphthalimide.     

Taste recognition threshold concentrations of styrene in oil-in-water emulsions and yoghurts

Taste recognition threshold concentrations (TRTC) of styrene were determined in samples of oil-in-water emulsions (30–300 g kg^?1 oil) and yoghurts (1–30 g kg^?1 fat), spiked with styrene. The observed TRTC increased linearly with increasing fat content and ranged from 0–3 to 2–1 mg kg^?1 for the emulsions and from 36 to 171 g kg^?1 for the yoghurts. Styrene equilibrium partition coefficients between emulsions and their respective vapour phases were determined. The concentrations of styrene in the continuous aqueous phase of the emulsions and yoghurts were calculated at the TRTC. The styrene concentrations in the continuous phase had constant values of about 15 g kg^?1 indicating that perception of styrene for oil-in–water emulsions is determined by the aqueous phase of the emulsion. The concentrations of styrene in the vapor phases above the emulsions and yoghurts were also calculated and were found to be constant at the TRTC. This relationship probably resulted from the equilibrium of distribution of styrene between the respective phases. Commercial yoghurt packed in polystyrene beakers contained styrene levels in the range 2–11 g kg^?1, much lower then the TRTC reported.     

Water uptake of water-borne paint resin films as studied by impedance spectroscopy and gravimetry

Impedance spectroscopy and gravimetry were employed to characterize alkyd-acrylate and styrene-acrylate water-borne resin film properties during wetting-through (i.e. during water uptake).     

Cross-property connections for copper–graphite composites

Copper–graphite composite materials in the range of 0–10 vol% of carbon phase were prepared from the mixture of copper and graphite powders by hot isostatic pressing. The microstructure, mechanical (tensile strength, elongation to fracture) and physical (electrical and thermal conductivity) properties of composite samples were investigated, and the cross-property connections were calculated. It was shown that electrical and thermal conductivity cross-property (Lorenz number) is almost constant and increases only slightly (no more than 10 % increase was observed). This implies that in the investigated composition range the Lorenz number of a copper–graphite composite system behaves according to Franz–Wiedemann law for pure metals at constant temperature. On the contrary, the conductivity to tensile strength cross-property connections showed significant linear increase (over 200 % in the investigated composition range) for both electrical conductivity and thermal conductivity of composite materials. The cross-property connections of conductivity to the elongation to fracture exhibit a nonlinear dependence on the volume fraction of graphite.     

Slow and fast diffusion effects in image processing

A mathematical model for a nonlinear image multiscale analysis is studied. Processing of an image is based on a solution of the strongly nonlinear parabolic partial differential equation, which can degenerate depending on values of the greylevel intensity function. The governing PDE is a generalization of the regularized (in the sense of Catté, Lions, Morel and Coll) Perona-Malik anisotropic diffusion equation. We present numerical techniques for solving the suggested initial-boundary value problem and also existence and convergence results. Numerical experiments are discussed. Received: 6 May 1998 / Accepted: 27 July 2000     

The convergence of graphics and vision

Computer graphics and computer vision are inverse problems. Traditional computer graphics starts with input geometric models and produces image sequences. Traditional computer vision starts with input image sequences and produces geometric models. Lately, there has been a meeting in the middle, and the center, the prize, is to create stunning images in real time. Vision researchers now work from images backward, just as far backward as necessary to create models that capture a scene without going to full geometric models. Graphics researchers now work with hybrid geometry and image models. Approaching similar problems from opposite directions, graphics and vision researchers are reaching a fertile middle ground. The goal is to find the best possible tools for the imagination. This overview describes cutting edge work, some of which will debut at Siggraph 98     

Synthesis and properties of corn zein/montmorillonite nanocomposite films

The objectives of this study were to apply fabrication techniques for the zein montmorillonite (MMT) nanocomposite films and characterize the obtained nanocomposite films. Zein MMT nanocomposite films were successfully produced from solvent casting and blown extrusion methods. The two methods could mix the zein MMT resulting in partially exfoliated nanocomposite structures according to X-ray diffraction and transmission electron microscopy. The thermal resistant of the zein nanocomposite films fabricated from both methods improved as the MMT content increased. However, the mechanical and barrier properties showed non-linear relationships with the MMT loadings. The impact of MMT on properties of zein films strongly depended on the preparation techniques. This can be the good starting point to further study in depth insight of the controllable MMT rearrangement in zein films which will remarkably improve zein film properties for packaging applications.     

Applications of fuzzy‐based linguistic patterns for the assessment of computer screen design quality

The main objective of this study was to develop a modeling framework which would unify different aspects of computer screen design and result in a quantitative criterion for an optimized computer screen format. The fuzzy set‐based linguistic design patterns were utilized as a tool to build this model. The linguistic patterns are based on categories of expressions related closely to natural language and truth values, which are close to a human designer's intuition. The proposed framework is capable of assessing the quality of computer screen design based on existing knowledge in human‐computer interface domain using the fuzzy‐based linguistic pattern approach. Exemplary patterns for an optimal screen density, information grouping, and some aspects of screen layout are presented, along with a sequence of calculations based on the exemplary screen format. This study showed that it is possible to achieve a rational and relatively easy to interpret assessment of different screen designs in the form of the degrees of truth. Such an evaluation criterion reflects the compatibility of a given screen design with the optimal one based on the current knowledge in the field. It is believed that the proposed methodological framework for computer screen design should significantly augment the efforts of human designers.     

A routine for measuring synergy in university–industry–government relations: mutual information as a Triple-Helix and Quadruple-Helix indicator

Mutual information in three (or more) dimensions can be considered as a Triple-Helix indicator of possible synergy in university–industry–government relations. An open-source routine th4.exe makes the computation of this indicator interactively available at the internet, and thus applicable to large sets of data. Th4.exe computes all probabilistic entropies and mutual information in two, three, and, if available in the data, four dimensions among, for example, classes such as geographical addresses (cities, regions), technological codes (e.g. OECD’s NACE codes), and size categories; or, alternatively, among institutional addresses (academic, industrial, public sector) in document sets. The relations between the Triple-Helix indicator—as an indicator of synergy—and the Triple-Helix model that specifies the possibility of feedback by an overlay of communications, are also discussed.