Time-resolved multidistance near-infrared spectroscopy of the adult head: intracerebral and extracerebral absorption changes from moments of distribution of times of flight of photons

We report on multidistance time-resolved diffuse reflectance spectroscopy of the head of a healthy adult after intravenous administration of a bolus of indocyanine green. Intracerebral and extracerebral changes in absorption are deduced from moments (integral, mean time of flight, and variance) of the distributions of times of flight of photons (DTOFs), recorded simultaneously at four different source-detector separations. We calculate the sensitivity factors converting depth-dependent changes in absorption into changes of moments of DTOFs by Monte Carlo simulations by using a layered model of the head. We validate our method by analyzing moments of DTOFs simulated for the assumed changes in absorption in different layers of the head model.     

Where is urban food policy in Switzerland? A frame analysis

Food is increasingly included on the urban agenda in many countries, and comprehensive food policies have been developed in several cities, but the development of articulate urban food policies is still in its infancy in Switzerland. The goal of this paper is to explore the ways in which food is framed in official policies in Switzerland and thereby gain a better understanding of the potential for the development of urban food policies. The analysis is based on a case study approach focusing on the formal frames of food: reconstructed from official policy documents on agriculture, food, health, environment, and planning, at the federal and the local level. The results show that ‘urban food’ is not a major topic in most policy documents and that the dominant frame of food is economic. There is a clear distinction between the rural and the urban, and there were no frames integrating (rural) food production and (urban) consumption, across the city’s departments, or between the local and the federal level. We can conclude that there is not yet a comprehensive urban food policy in Switzerland. The analysis further allows the nomination of two possible pathways to guide the development of coherent and integrative urban food policies.     

Demand-driven image transmission with levels of detail and regions of interest

In this paper, we introduce a formal model which describes consistently levels of detail and regions of interest for the progressive transmission of raster images. This model serves as the foundation of a wavelet-based image communication framework which supports the progressive, redundancy-free transmission of multiple, possibly overlapping regions of interest in an image. To support demand-driven transmission, we introduce a method for interleaving control commands with the embedded bit stream. Since the dyadic wavelet decomposition allows the image resolutions in x and y direction to differ at most by a factor of two, we propose a new wavelet decomposition scheme which raises this number to a power of two for increased flexibility. We discuss some applications including the rectangular fish eye view, a focus and context display technique for raster images which efficiently uses this transmission method and saves screen real-estate.     

Thermo‐elasto‐hydrodynamic lubrication model for journal bearing including shear rate‐dependent viscosity

The simulation of the non‐stationary response of the journal bearings used in combustion engines plays a significant role in the bearing design process. Diverse simulation models contain various oil viscosity definitions taking pressure and temperature into consideration. However, viscosity dependence on the shear rate is often neglected. Within this paper, a bearing simulation model including the shear rate‐dependent viscosity is described. The modified Cross equation was used to describe shear rate influence on viscosity. Numerical modelling of the main crankshaft bearing of a modern four‐cylinder gasoline engine was performed. Selected calculation results were discussed and conclusions drawn. The modelling and calculation were carried out using the AVL software EXCITE (AVL LIST GmbH, Advanced Simulation Technology, Hans‐List‐Platz 1, Graz, Austria 8020). Copyright © 2007 John Wiley & Sons, Ltd.     

Charakterisierung von vernetzten Polymeren, 9a. Verfolgung der Nachvernetzung von Poly(styrol-co-divinylbenzol) zu feinporigen Adsorberpolymeren

The post-crosslinking of chloromethylated poly(styrene-co-divinylbenzene) to highly crosslinked, porous adsorbent polymers has been studied over a wide range of reaction temperature (50-80°C) and reaction time (up to 24.5 h). The crosslinked materials were characterized by nitrogen adsorption/desorption, mercury porosimetry, determination of the chlorine content, swelling measurements, pyrolysis gas chromatography, and Fourier transform infrared spectroscopy. Surface area, pore size distribution, pore volume, chlorine content, swelling degree, selected peak ratios in the pyrograms and in the FTIR spectrograms are shown to be clear functions of the post-crosslinking time. Therefore the post-crosslinking process can be monitored by physical as well as by chemical characterization methods. Moreover, information on the chemical homogeneity or inhomogeneity of the chloromethylated copolymers and the porous adsorbent polymers can be derived from the swelling and pyrolysis gas chromatographic results. Application of different solvents in the swelling experiments enables the construction of swelling diagrams. Based on these swelling diagrams, the anomalous swelling behaviour of adsorbent polymers during the post-crosslinking can be explained. The surface area and pore volume strongly increase with progressing post-crosslinking, and well-defined correlations between sample texture, pyrolysis and FTIR data are found. In general, changes of physical properties can be attributed to the chemical modification of the material due to the post-crosslinking.     

Investigations on the lubricating effectiveness of molybdenum disulfide

A scanning electron microscopical investigation of the lubricating mechanism of coarse and fine MoS₂ powder dry lubricants and suspensions of the powders has been carried out. The effective lubricating properties of dry MoS₂ is not due to sliding of MoS₂ lamellae but to the properties of the built up surface film; chemical reaction between MoS₂ and a sliding metallic surface can be a contributory factor.     

Automobile Transmission Gears as Tribological Systems

The influence of gear oils on the efficiency of automobile gears are explained. In order to analyze and evaluate this influence the transmission gear is considered as an tribotechnical system. The smallest energy transmission unit of a tribotechnical system is the tribological system. Therefore, the complex tribological system transmission gear is split into eight main tribological systems. Their technical functions and structures and the lubricant's influence on the function are described.