Radon—Ein neuer analytischer Ansatz zur “In-situ-Bestimmung” der Gasleitf?higkeit von B?den

Vorliegende Arbeit beschreibt ein neuartiges Verfahren zur “In-situ-Bestimmung” der Gasleitf?higkeit von B?den. Es bedient sich des natürlich vorkommenden, radioaktiven Edelgases Radon. Hierbei wird in einer Me?kammer, die auf dem Boden aufsitzt, die H?he der Radonexhalation registriert. Sie ist u. a. direkt von der Gasleitf?higkeit des Bodens abh?ngig. Da das Verfahren zerst?rungsfrei arbeitet. er?ffnen sich eine Vielzahl von Applikationsm?glichkeiten, wie z. B. Beobachtungen befahrungsbedingter Strukturver?nderungen w?hrend und nach Holzerntema?nahmen sowie Untersuchungen zur Regeneration strukturell ver?nderter B?den. Dies kann beliebig oft und zu beliebigen Zeitpunkten am identischen Bodenausschnitt geschehen. The paper describes a new analytical tool for the “in situ” measurement of the gas permeability of soils. It uses on the exhalation of the redioactive rare gas radon. A chamber covering a certain surface area on the ground registers the amount of radon exhald. One of the factors, which directly controls the exhalation rate is the gas permeability. As this is a non-destructive method several possibilities for applications arise, as for example observation and analysis of changes in soil structure during and after regular timber harvesting, i.e. such caused by forest machines, as well as investigations about the regeneration of damaged sites. These investigations can be repeated as often as desired, at any time and, moreover, on the identical spot.     

Unusual osteochondral lesions of the talus in a horse

A 2-year-old Thoroughbred gelding was evaluated for a grade 3 out of 5 unilateral hind limb lameness. Flexion of the right hock and stifle joints (spavin test) exacerbated the lameness. Response to intra-articular and perineural anaesthesia isolated the source of lameness to the tarsocrural area, despite an absence of tarsocrural joint effusion. Routine radiographic examination of the hock did not reveal any significant abnormalities. Skeletal nuclear scintigraphic evaluation revealed a focal region of increased bone activity in the proximal medial trochlear ridge of the talus. Flexed lateromedial radiographic views identified three discrete semicircular lytic lesions at the proximal articular margin of the medial trochlear ridge of the talus. Conservative management of the lesions was associated with a successful return to racing. The location and appearance of the osteochondral lesions of this report have not been previously reported and may be a manifestation of developmental orthopaedic disease and abnormal endochondral ossification. Nuclear scintigraphy and flexed lateromedial radiographic views facilitated identification of the lesions. This radiographic view is recommended when lameness is isolated to the tarsocrural joint and standard radio-graphic projections fail to identify a cause.     

Metathesis of Alkanes Catalyzed by Silica-Supported Transition Metal Hydrides

The silica-supported transition metal hydrides (=Si-O-Si=)(=Si-O-)2Ta-H and (=Si-O-)xM-H (M, chromium or tungsten) catalyze the metathesis reaction of linear or branched alkanes into the next higher and lower alkanes at moderate temperature (25degrees to 200degreesC). With (=Si-O-Si=)(=Si-O-)2Ta-H, ethane was transformed at room temperature into an equimolar mixture of propane and methane. Higher and lower homologs were obtained from propane, butane, and pentane as well as from branched alkanes such as isobutane and isopentane. The mechanism of the step leading to carbon-carbon bond cleavage and formation likely involves a four-centered transition state between a tantalum-alkyl intermediate and a carbon-carbon final sigma-bond of a second molecule of alkane.     

Review: The strobilurin fungicides

The original article to which this Correction refers was published in Pest Management Science 58 (7): 649–662 (2002).Copyright © 2004 Society of Chemical Industry