Entwicklung einer schwach gekuehlten keramischen Leitschaufel der ersten Turbinenstufe. Teilprojekt 2.4.2.1 Abschlussbericht

The example of a highly loaded gas turbine guide blade is presented in order to outline the potential of optimisation of the available numerical methods in the field of ceramic materials. Starting from a structure-mechanical component analysis using the FE method, the temperature and stress distribution in the component is defined. The failure probability of a component can then be assessed in consideration of the calculated component stress using the fracture statistics processor CERITS, which was developed at the Department of Turbomachinery. Longer life of ceramic components necessitates the shaving of stress peaks, which in ceramic materials cannot be reduced by plastic deformation. Component stresses can be reduced by reducing the thermal stresses induced by temperature gradients. An analysis of the ceramic shell structure resulted in the following design guidelines for components under high thermal stress: (a) homogeneisation of the temperature distribution inside the component, (b) compensation of thermal stresses, (c) adaptation of stiffness. (orig./MM)Im Rahmen dieses Vorhabens soll, am Beispiel der hochbelasteten Gasturbinen-Leitschaufel aufgezeigt werden, welches Potential die durch derzeit verfuegbare numerische Verfahren gegebenen Optimierungsmoeglichkeiten fuer die Keramikanwendung darstellen. Ausgehend von einer strukturmechanischen Bauteilanalyse mit der FE-Methode kann eine Ermittlung und Bewertung der Temperatur- und Spannungsverteilung im Bauteil vorgenommen werden. Mit dem am Institut fuer Thermische Stroemungsmaschinen entwickelten Bruchstatistikprozessor CERITS kann unter Einbezug der zuvor berechneten Spannungsbelastung des Bauteils eine Bestimmung der Bauteilausfallwahrscheinlichkeit erfolgen. Das angestrebte Ziel einer keramischen Komponente mit einer ausreichenden Lebensdauer kann nur erreicht werden, wenn Spannungsspitzen, die von keramischen Werkstoffen nicht durch plastische Deformation reduziert werden koennen, vermieden werden. Eine Absenkung des Spannungsniveaus im Bauteil ist durch eine Verringerung der durch Temperaturgradienten induzierten Thermospannungen erreichbar. Die analytische Betrachtung der keramischen Schalenstruktur ergab folgende Gestaltungsrichtlinien fuer thermisch hochbelastete Bauteile:(a) Homogenisierung der Temperaturverteilung im Bauteil, (b) Kompensation der thermischen Dehnungen, (c) Anpassung der Steifigkeit. (orig./MM)Available from TIB Hannover: F97B2392+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Disposition of Caspofungin: Role of Distribution in Determining Pharmacokinetics in Plasma

The disposition of caspofungin, a parenteral antifungal drug, was investigated. Following a single, 1-h, intravenous infusion of 70 mg (200 μCi) of [(3)H]caspofungin to healthy men, plasma, urine, and feces were collected over 27 days in study A (n = 6) and plasma was collected over 26 weeks in study B (n = 7). Supportive data were obtained from a single-dose [(3)H]caspofungin tissue distribution study in rats (n = 3 animals/time point). Over 27 days in humans, 75.4% of radioactivity was recovered in urine (40.7%) and feces (34.4%). A long terminal phase (t(1/2) = 14.6 days) characterized much of the plasma drug profile of radioactivity, which remained quantifiable to 22.3 weeks. Mass balance calculations indicated that radioactivity in tissues peaked at 1.5 to 2 days at ∼92% of the dose, and the rate of radioactivity excretion peaked at 6 to 7 days. Metabolism and excretion of caspofungin were very slow processes, and very little excretion or biotransformation occurred in the first 24 to 30 h postdose. Most of the area under the concentration-time curve of caspofungin was accounted for during this period, consistent with distribution-controlled clearance. The apparent distribution volume during this period indicated that this distribution process is uptake into tissue cells. Radioactivity was widely distributed in rats, with the highest concentrations in liver, kidney, lung, and spleen. Liver exhibited an extended uptake phase, peaking at 24 h with 35% of total dose in liver. The plasma profile of caspofungin is determined primarily by the rate of distribution of caspofungin from plasma into tissues

Potential for Interactions between Caspofungin and Nelfinavir or Rifampin

The potential for interactions between caspofungin and nelfinavir or rifampin was evaluated in two parallel-panel studies. In study A, healthy subjects received a 14-day course of caspofungin alone (50 mg administered intravenously [IV] once daily) (n = 10) or with nelfinavir (1,250 mg administered orally twice daily) (n = 9) or rifampin (600 mg administered orally once daily) (n = 10). In study B, 14 subjects received a 28-day course of rifampin (600 mg administered orally once daily), with caspofungin (50 mg administered IV once daily) coadministered on the last 14 days, and 12 subjects received a 14-day course of caspofungin alone (50 mg administered IV once daily). The coadministration/administration alone geometric mean ratio for the caspofungin area under the time-concentration profile calculated for the 24-h period following dosing [AUC(0-24)] was as follows (values in parentheses are 90% confidence intervals [CIs]): 1.08 (0.93-1.26) for nelfinavir, 1.12 (0.97-1.30) for rifampin (study A), and 1.01 (0.91-1.11) for rifampin (study B). The shape of the caspofungin plasma profile was altered by rifampin, resulting in a 14 to 31% reduction in the trough concentration at 24 h after dosing (C(24h)), consistent with a net induction effect at steady state. Both the AUC and the C(24h) were elevated in the initial days of rifampin coadministration in study A (61 and 170% elevations, respectively, on day 1) but not in study B, consistent with transient net inhibition prior to full induction. The coadministration/administration alone geometric mean ratio for the rifampin AUC(0-24) on day 14 was 1.07 (90% CI, 0.83-1.38). Nelfinavir does not meaningfully alter caspofungin pharmacokinetics. Rifampin both inhibits and induces caspofungin disposition, resulting in a reduced C(24h) at steady state. An increase in the caspofungin dose to 70 mg, administered daily, should be considered when the drug is coadministered with rifampin

Dose response of rumen-protected conjugated linoleic acid supplementation to fattening bulls and heifers on growth, and carcass and meat quality

We investigated the influence of rumen-protected conjugated linoleic acid (rpCLA) on growth performances, and carcass and meat quality traits in beef. Twenty-four young bulls and 30 heifers obtained from double-muscled beef sires and dairy cows were fed a low-protein ration (110\ua0g/kg DM of crude protein) supplemented with 0, 8 or 80\ua0g/d of a commercial rpCLA product. The animals were monthly weighed and scored for body muscularity and fatness. Blood samples were collected after 140\ua0days on feed. Animals were slaughtered when they reached average in vivo fatness scores of around 2.5 (heifers) and 2.0 (bulls) points respectively. At slaughter, carcasses, various organs and parts of the gastrointestinal tract were weighed; the 5th rib was dissected and its tissue and muscle chemical composition was determined. The rpCLA had little influence on growth performance but decreased the blood urea content by 28% (p\ua0<\ua00.01). The rpCLA\ua0 7\ua0sex interactions for daily gain (p\ua0<\ua00.05), conformation scores (p\ua0<\ua00.01), and blood creatinine content (p\ua0<\ua00.05) suggest that males were more responsive to rpCLA than females when fed a low-protein ration, probably because of the metabolic protein-sparing effect of CLA. Only slight differences were observed in carcass weight and quality at slaughter. The results indicate that the response of beef cattle to rpCLA is dependent on sex or on their propensity for lean and fat accretion. It is also possible that counteracting feedback mechanisms compensate for the influence of rpCLA administration over the course of growth