Effect of temperature on the creep behavior of a Ni–Cr–Fe–Al alloy: a comparison of the experimental data and a model

In order to characterise the mechanical behaviour of sandwich structures, which combine an interlayer of a woven wire mesh between two thin walled sheet metals, creep tests at 650, 680 and 750 °C were carried out on sheet metals made of the nickel based alloy Nicrofer 6025 HT (2.4633). In addition to the tests the creep behaviour was simulated by a model, which considers the creep rate as a function of the applied stress σ and the internal deformation resistance including an internal back stress σ_i and a particle resistance σ_P. The damage is included by a damage parameter D, which converges to “one” with increasing damage. A concluding comparison with the creep test results shows that the model is able to describe the creep behaviour of the investigated sheet metals.     

High precision processing of flexible P3HT/PCBM modules with geometric fill factor over 95%

Flexible OPV modules, based on P3HT:PCBM as absorber layer, were manufactured with a power conversion efficiency over 3% and for a total area of 3500 mm² consisting of 14 in series interconnected cells. The modules utilize the excellent mechanical and the outstanding optical properties of sputtered transparent ITO-Metal-ITO (IMI) electrodes deposited on the PET foil on the one hand, and the combination of large area slot-die coating with high resolution ultrafast laser patterning on the other hand. The manufacturing of modules with outstanding performance was found to be reproducible. The right combination of innovative electrodes and smart roll-to-roll compatible processing technologies demonstrates a viable path towards high efficient industrial module technology.     

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.     

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.     

Comparison of four motion correction techniques in SPECT imaging of the heart: a cardiac phantom study

The aim of this study was to evaluate the accuracy of four different motion correction techniques in SPECT imaging of the heart. METHODS: We evaluated three automated techniques: the cross-correlation (CC) method, diverging squares (DS) method and two-dimensional fit method and one manual shift technique (MS) using a cardiac phantom. The phantom was filled with organ concentrations of 99mTc closely matching those seen in patient studies. The phantom was placed on a small sliding platform connected to a computer-controlled stepping motor. Linear, random, sinusoidal and bounce motions of magnitude up to 2 cm in the axial direction were simulated. Both single- and dual-detector 90 degrees acquisitions were acquired using a dual 90 degrees detector system. Data were acquired over 180 degrees with 30 or 15 frames/detector (single-/dual-head) at 30 sec/frame in a 64x64 matrix. RESULTS: The simulated single-detector system, CC method, failed to accurately correct for any of the simulated motions. The DS technique overestimated the magnitude of phantom motion, particularly for images acquired between 45 degrees left anterior oblique and 45 degrees left posterior oblique. The two-dimensional and MS techniques accurately corrected for motion. The simulated dual 90 degrees detector system, CC method, only partially tracked random or bounce cardiac motion and failed to detect sinusoidal motion. The DS technique overestimated motion in the latter half of the study. Both the two-dimensional and MS techniques provided superior tracking, although no technique was able to accurately track the rapid changes in cardiac location simulated in the random motion study. Average absolute differences between true and calculated position of the heart on single- and dual 90 degrees -detectors were 1.7 mm and 1.5 mm for the two-dimensional and MS techniques, respectively. The corresponding values for the DS and CC techniques were 5.7 and 8.9 mm, respectively. CONCLUSION: Of the four techniques evaluated, manual correction by an experienced technologist proved to be the most accurate, although results were not significantly different from those observed with the two-dimensional method. Both techniques accurately determined cardiac location and permitted artifact-free reconstruction of the simulated cardiac studies.     

Length and torsion of the lower limb

Corrective osteotomies are often planned and performed on the basis of normal anatomical proportions. We have evaluated the length and torsion of the segments of the lower limb in normal individuals, to analyse the differences between left and right sides, and to provide tolerance figures for both length and torsion. We used CT on 355 adult patients and measured length and torsion by the Ulm method. We excluded all patients with evidence of trauma, infection, tumour or any congenital disorder. The mean length of 511 femora was 46.3 +/- 6.4 cm (+/-2SD) and of 513 tibiae 36.9 +/- 5.6 cm; the mean total length of 378 lower limbs was 83.2 +/- 11.4 cm with a tibiofemoral ratio of 1 to 1.26 +/- 0.1. The 99th percentile level for length difference in 178 paired femora was 1.2 cm, in 171 paired tibiae 1.0 cm and in 60 paired lower limbs 1.4 cm. In 505 femora the mean internal torsion was 24.1 +/- 17.4 degrees, and in 504 tibiae the mean external torsion was 34.9 +/- 15.9 degrees. For 352 lower limbs the mean external torsion was 9.8 +/- 11.4 degrees. The mean torsion angle of right and left femora in individuals did not differ significantly, but mean tibial torsion showed a significant difference between right (36.46 degrees of external torsion) and left sides (33.07 degrees of external torsion). For the whole legs torsion on the left was 7.5 +/- 18.2 degrees and 11.8 +/- 18.8 degrees, respectively (p < 0.001). There was a trend to greater internal torsion in femora in association with an increased external torsion in tibiae, but we found no correlation. The 99th percentile value for the difference in 172 paired femora was 13 degrees; in 176 pairs of tibiae it was 14.3 degrees and for 60 paired lower limbs 15.6 degrees. These results will help to plan corrective osteotomies in the lower limbs, and we have re-evaluated the mathematical limits of differences in length and torsion.     

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.