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C Sievert

Publications and source records attributed to C Sievert.

3 recordsLinked to original sources

[Automated determination of total nitrogen in milk by the Dumas method].

A nitrogen analyser based on the Dumas method (LECO FP-428) and equipped with a liquid injector has been tested. The intensive steam production during injection may result in poor nitrogen recoveries for volatile nitrogen compounds such as ethylene diamine. However, recoveries could be improved by slow injection and by filling the combustion tube with Cer(IV)-oxide. For the analysis of milk the instrument was calibrated with NaN3 solutions because their response was found to be less sensitive to burning conditions. Dumas-N and Kjeldahl-N of milk showed good correlation (r = 0.998). However, with the Dumas method about 6.7% (+ 0.035% N) higher nitrogen values were obtained. With a standard deviation of repeatability S(r) = 0.002% N (CVr = 0.33) and a between day reproducibility SD = 0.006% N (CVD = 1.1%) the precision of the Dumas method was similar to that reported for the Kjeldahl method. In order to avoid systematic errors the use of standard milk samples for calibration is recommended. It is concluded that modern instruments using the Dumas method allow precise measurements of nitrogen in milk with a high sample throughout.

Animals↗

A second forelimb motor area exists in rat frontal cortex.

Intracortical microstimulation of 40--50 points in the frontal cortex of ketamine-anesthetized rats using perpendicular penetrations has demonstrated a second forelimb area located rostrally near the frontal pole as well as confirming the existence of a more caudally located forelimb area just anterior to bregma. Cortex where neck and/or vibrissae movements were evoked separated the two forelimb areas. The rostral and caudal forelimb areas defined by microstimulation correspond with patches of corticospinal neurons labeled with HRP following injections of this tracer into the cervical enlargement. Digit movements were commonly evoked from the rostral forelimb area but were rarely elicited from the caudal forelimb area. The question of whether the rostral forelimb region is part of primary or supplementary motor cortex is not yet able to be answered.

Animals↗