Diurnal rhythm of HMG CoA reductase activity in canine intestine is independent of luminal contents

Activity of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (EC 1.1.1.34) measured in isolated segments of canine intestinal mucosa showed a distinct diurnal rhythm. Total activity changed over a twofold range with a peak occurring during midday, shortly after feeding. Since the isolated segments had no contact with luminal contents, the rhythm was not directly related to food components or bile salts. Humoral or neural influences must mediate the rhythm. The diurnal rhythm persisted for at least 3–5 mo, but was lost by 10 mo following formation of the isolated segment, possibly because of mucosal involution.     

Einfluss der Temperatur auf das Fließverhalten von P92 Blechmaterial unter quasistatischer Zugbeanspruchung

Influence of temperature on the flow behaviour of P92 sheet metal under quasi static tensile loading The relatively new ferritic martensitic steel P92 (NF616) has been developed for the application in power plants. Because of its high creep resistance the material is used as pipe material, which means as thick‐walled part. Within the scope of the Collaborative Research Center 561 of Aachen University of Technology P92 is planed to use as sheet metal as a component of a sandwich structure for cooling thermal high loaded parts of a steam turbine. Single segments of this cooling structure were formed by die bending into the demanded shape. Therefore it is necessary to investigate the flow behaviour as a function of temperature for this material in combination with a mathematical model. In this work quasi static tensile tests in the temperature range between 293K and 973K were performed and the results were described as a function of temperature.     

Influence of Different Forming and Heat Treatment Stages on the Properties of P92‐Sheet

To improve the efficiency factor of combined cycle power plants from the state‐of‐the‐art 58% towards 65% in 2025, the steam turbine inlet temperature is to be increased up to approximately 700 °C at a steam inlet pressure of 300 bar. Modern ferritic steels like P92 however do not withstand such harsh operating conditions, necessitating the need for a cooling system. With the help of “grid sheet”, a sandwich material consisting of two face sheets and a core of woven wire mesh, the cooling is to be accomplished in the steam turbine. Since P92‐sheet needed for the face sheets of the grid sheet is not available in industry, the sheet was produced on laboratory scale. However, the used production process yielded partial inhomogeneous material properties, clarifying the need for the redevelopment of the former production process. In the new production process the cast round block was sawn to slices, which enabled a reduction of the number of required heatings above the austinitisation temperature. Using this new production process more homogeneous material properties were expected, which is evaluated using thickness measurements, chemical analyses among others. Furthermore, the effect of each process stage on the mechanical properties and microstructure were analysed.     

Asymptotic Bethe-Ansatz results for a Hubbard chain with 1/sinh-hopping

We investigate spin-1/2 electrons with local Hubbard interaction and variable range hopping amplitudes which decay like sinh()/sinh(r). Using Sutherland's Asymptotic Bethe Ansatz we derive the generalized Lieb-Wu integral equations from the two-particle phase shift. For half-filling we obtain a closed expression for the ground state energy density. Due to the nesting property there is a metal-to-insulator transition at U_c(> > 0) = 0⁺.In the singular limit = 0the charge gap opens when the interaction strength equals the bandwidth, U _c( = 0) =W.We would like to thank P. Nozières and A. Gogolin for stimulating discussions. F. G. thanks all his colleagues at the ILL Grenoble for their kind hospitality during a stay in 1993/94.     

Effects of mixed ETA and ETB-receptor antagonist (Ro-47-0203) on hepatic microcirculation after warm ischemia

There is evidence that endothelin (ET) is involved in disturbances of the hepatic microcirculation after warm ischemia. In this study we investigated the influence of a mixed ETA-, ETB-receptor antagonist (Bosentan) on ischemia-reperfusion damage of the liver by means of intravital fluorescence microscopy (IVM). Clamping of the left liver lobe (= warm ischemia) was performed in 16 male Wistar rats for 70 min. The treatment group (N = 8) received 15 mg/kg Bosentan (Ro-47-0203) 1 min prior to reperfusion. Controls (N = 8) received an equivalent amount of Ringer's solution. Between 20 and 90 min after reperfusion, leukocyte-endothelial cell interactions in sinusoids and postsinusoidal venules as well as perfusion of hepatic acini were studied. Application of Bosentan improved sinusoidal blood flow, attenuated manifestations of microvascular perfusion failure, and decreased the number of rolling leukocytes in postsinusoidal venules. Our results provide further evidence that ET is involved in postischemic impairment of hepatic microhemodynamics during reperfusion.