The synthesis and crystal structure of unsubstituted 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)

The fully unsubstituted 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) was synthesized for the first time by oxidation of dipyrromethane followed by treatment with boron trifluoride diethyl etherate in the presence of a base. The compound was fully characterized and its X-ray crystal structure is reported.     

The thermal degradation of perfluoropolypyridine

The thermal degradation of perfluoropolypyridine was studied in inert and oxidizing atmospheres by thermogravimetric techniques. Volatile products were analyzed mass-spectrometrically, and the yield of products giving rise to fluoride ion was also determined. The stability of the polymer on a weight loss basis is rather better than that of polytetrafluoroethylene in inert atmospheres, but rather worse in oxidizing atmospheres. The major breakdown route seems to involve removal of the fluorine from the heterocyclic nucleus by a mechanism as yet unknown.     

A study of dilatation and acoustic propagation in solidifying fats and oils: II. Experimental

Experimental evidence is presented to support the hypothesis that acoustic dilatation is linearly related to solid fat index dilation. This hypothesis is shown to be consistent with the measured temperature dependence of the dilation and ultrasonic velocity during solidification of palm oil, coconut oil, tristearin and a vegetable fat, all of which were diluted with triolein. The maximum solid content examined was 15%. The ultrasonic pulse echo method may provide a means of measuring the solid content of oils and of indicating the presence of phase transitions in the solid phase.     

Recognising Simple Behaviours Using Time-Delay RBF Networks

This paper presents experiments using a radial basis function variant of the time-delay neural network with image sequences of human faces. The network is shown to be able to learn simple behaviours based on y-axis head rotation and generalise on different data. The network model's suitability for future dynamic vision applications is discussed.     

Investigation of phase transitions in glyceride/paraffin oil mixtures using ultrasonic velocity measurements

A pulse echo technique has been used to measure the ultrasonic velocity of a number of 15% w/w glyceride/paraffin oil mixtures with increasing temperature (0–70 C). At the lower temperatures the glycerides are completely solid and there is a fairly steady decrease in velocity with temperature (ca. −3.8 ms⁻¹C⁻¹). As the temperature rises the glycerides become increasingly soluble in the paraffin oil and the velocity decreases more rapidly. Once the glyceride is completely soluble in the paraffin oil, a fairly steady decrease in velocity with temperature (ca. −3.3 ms⁻¹C⁻¹) resumes. The dependence of ultrasonic velocity on the amount of solid glyceride present means the technique can be used to investigate phase transitions in binary glyceride/oil mixtures.     

Poly-chlorinated biphenyls,poly-chlorinated naphthalenes and polynuclear aromatic hydrocarbons in severn estuary (U.K.) sediments

Sediments taken from the upper part of the Severn Estuary have been extracted by cyclic steam distillation into hexane. Analysis of the extract revealed a variety of organic pollutants including alkanes and several poly-nuclear aromatic hydrocarbons (PNA's). A PCB residue was detected and quantified using the technique of carbon-skeleton gas chromatography employing a 3% palladium catalyst and 2% RbCl salt column. The level of PCB in the sediments was found to be of the order of 1 ppm. No significant levels of poly-chlorinated napthalene (PCN) or DDT and related species were found.Organic contamination of one sediment (Arlingham) was found to be associated with the coal particles present in the sample. Levels of contamination at Arlingham were thus shown to be a function of sample composition rather than of the geographical location of the site.