Extinction of Radiation in Sterically Interacting Systems of Monodisperse Spheres. Part 2: Experimental results

The Bouguer-Lambert-Beer law (BLBL), commonly used to describe the extinction of radiation in disperse systems, is known to be valid in the limit of low concentrations only. In Part [1] it was shown that steric particle-particle interactions lead to important effects in the range of high particle concentration and two versions of a more general extinction equation including steric interactions were derived for the regimes of fraunhofer diffraction and ray propagation in this part experimental evidence for the effects of steric interactions on the extinction of radiation in suspensions of monodisperse spherical particles is given. Various experiments on light extinction and on ultrasonic extinction are combined to cover a broad range of particle size parameters, mechanisms of particle-wave interaction and receiver apertures.     

Produkte endlicher einfacher Gruppen

Ohne Zusammenfassung     

Quantitative magnetic resonance imaging of vertebral bodies: a T1 and T2 study

Multiple point T1 and T2 values of 424 vertebral bodies were measured and analysed. The influence of several factors including age, sex, location in the spine and status of neighbouring discs on the measured relaxation times were evaluated. The results indicate limitations in the region of interest approach. Vertebral bodies of different age, sex and location in the spine could not be distinguished. For heterogeneous tissues a more advanced form of image analysis appears to be essential. Diurnal factors resulting from the stress of normal ambulatory activity caused increased variation in vertebral body relaxation time values.     

Fahnentransitive Ebenen gerader Ordnung

Ohne ZusammenfassungHerrn Günter Pickert zum 60. Geburtstag gewidmet     

A continuous liquid-liquid extraction system coupled on-line with capillary gas chromatography for environmental and ecotoxicological analysis

The applicability of a liquid-liquid extraction system which is coupled on-line with a capillary gas chromatograph was studied for environmental and ecotoxicological analyses. The optimized and automated system was used for the determination of apolar and rather non-volatile organic compounds in aqueous samples. Relevant aspects of sample introduction, phase separation and selection of extraction solvent are discussed. Three routine-tipe applications are described, viz. an improved method for the determination of hexachlorocyclohexanes in ground water and the determination of the so-called NCC-ether and ACC-ether in ecotoxicological studies. Depending on the application studied, the concentration levels varied from 0.1 to 6000 μg/I, using ECD and/or FID detection. Typical coefficients of variation obtained with the total extraction–GC procedure were 2–25%. The system was found to be rugged, it saves time compared with set-ups involving off-line liquid-liquid extraction and considerably reduces the manual work load.     

Zum chemischen Transport von Fe2O3 mit Tellurtetrachlorid

Chemical Transport of Fe₂O₃ by TeCl₄ The behaviour of the transport of Fe₂O₃ by TeCl₄ is calculated by the aid of the solubulities in the gas phase. TeOCl₂ existing in the gas phase is the essential species for the transport of oxygen. According to the calculations a reversion of the transport direction appears in the temperature range of about 800°C, which was confirmed experimentally. Stoichiometric single crystals of α-Fe₂O₃ were obtained showing in most cases rhombic plates of maximum dimensions 15° 10 · 1 mm.