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1. 2-Hydroxyphenylacetic acid, a natural phenolic product found in the genus Astilbe, derives from the shikimic acid pathway via phenylpyruvic acid. The existence of two routes for the biosynthesis of 2-hydroxyphenylacetic acid could be demonstrated: a) A direct transformation of phenylpyruvic acid into 2-hydroxyphenylacetic acid involving a migration of the side chain. More than 95% of the tritium activity of 2-hydroxyphenylacetic acid was localized in position 5 when L-[4-³H]phenylalanine was fed. This complex oxidation is analogous to the known conversion of 4-hydroxyphenylpyruvic acid to homogentisic acid. b) A hydroxylation of [4-³H]phenylacetic acid to [4-³H]2-hydroxyphenylacetic acid was observed in vivo, and was also found to take place in vitro utilizing the system peroxidase- endiol-O2. 2. 2,3-Dihydroxyphenylacetic acid and 2-hydroxy-3-methoxyphenylacetic acid could be established as natural products occurring in higher plants. Their chemical synthesis is described. By feeding experiments the following metabolic pathway is suggested: 2-hydroxyphenylacetic acid → 2,3-dihydroxyphenylacetic acid → 2-hydroxy-3-methoxyphenylacetic acid. 3,4-Dihydroxyphenylacetic acid and 3-methoxy-4-hydioxyphenylacetic acid have been detected in extracts from various species of Astilbe and identified by paper chromatography. These two acids are metabolic products of 4-hydroxyphenylacetic acid. 3. Experiments with [U-14C]shikimic acid and DL-[α-14C]phenylalanine seem to indicate that the regulation of the biosynthesis of 2-hydroxyphenylacetic acid and 4-hydroxyphenylacetic acid takes place on the level of prephemc acid. 4. Preliminary results were obtained consistent with the hypothesis that in Astilbe chinensis the 2,3-dihydroxyphenylacetic acid, 3,4-dihydroxyphenylacetic acid and 2,5-dihydroryphenyl-acetic acid are further metabolized and can be degraded by ring cleavage. [ABSTRACT FROM AUTHOR]

Abstract: Due to the packaging constraints to which turbocharged engines are submitted in passenger cars, the inlet duct of the centrifugal compressor often requires a 90° bend. The compressor inlet perpendicular to its axis disturbs the flow and reduces the compressor performance. This paper presents an interesting solution based on a specifically designed inlet swirl-generator device (SGD) that palliates these negative effects. In addition, the SGD can be used to extend the surge margin of the compressor if the position of the SGD blades is modified in function of the reciprocating engine operation conditions. The paper describes how the swirl level and the pressure losses generated by the device have been characterized in a continuous flow test rig. After this the SGD plus a centrifugal compressor from a turbocharger unit have been tested in a specific turbocharger test bench. The results obtained show the influence of the SGD blades position on the compressor performance. In order to better understand the influence of the SGD on the turbocharger behaviour, the flow velocity triangles near the inducer have been reconstructed using an approach based on CFD calculations. [Copyright &y& Elsevier]