Different aprotinin applications influencing hemostatic chances in orthotopic liver transplantation

The effect of different aprotinin applications on hemmtatic changes and blood product requirements in orthotopic liver transplantation was investigated in a prospective, open, and randomized study. From November 1989 to June 1990, 13 patients received aprotinin as a bolus of 0.5 Mill, kallikrein inac-tivator units (KIU) on three occasions in the course of an OLT, whereas 10 other patients were treated with continuous aprotinin infusion of 0.1-0.4 Mill. KIU/hr. Before and after reperfusion of the graft liver, signs of hyperfibrinolysis, measured by thrombelastography, were significantly lower in the infusion group. Tissue-type plasminogen activator (t-PA) activity increased during the anhepatic phase but to a significantly lesser extent in the infusion group. Blood product requirements during OLT were tendentiously higher in the bolus group but not significantly so. However, the use of packed red blood cells was significantly lower in the postoperative period, whereas there was no significant difference in fresh frozen plasma requirements between the two groups. All 23 patients have survived, and only one woman of each group required retransplantation due to severe host-versus-graft reactions. Furthermore, we investigated the perfusate of the graft liver in both groups and detected signs of a decreased t-PA release in the infusion group. Our results demonstrate an advantage of aprotinin given as continuous infusion over bolus application in OLT

Static Friction between Elastic Solids due to Random Asperities

Several workers have established that the Larkin domains for two three dimensional nonmetallic elastic solids in contact with each other at a disordered interface are enormously large. This implies that there should be negligible static friction per unit area in the macroscopic solid limit. The present work argues that the fluctuations in the heights of the random asperities at the interface that occur in the Greenwood-Williamson model can account for static friction.Comment: Contains some improvements in the treatment of the subjec

Static and Dry Friction due to Multiscale Surface Roughness

It is shown on the basis of scaling arguments that a disordered interface between two elastic solids will quite generally exhibit static and "dry friction" (i.e., kinetic friction which does not vanish as the sliding velocity approaches zero), because of Tomlinson model instabilities that occur for small length scale asperities. This provides a possible explanation for why static and "dry" friction are virtually always observed, and superlubricity almost never occurs

Molecular Dynamics Simulations of the Roller Nanoimprint Process: Adhesion and Other Mechanical Characteristics

Molecular dynamics simulations using tight-binding many body potential are carried out to study the roller imprint process of a gold single crystal. The effect of the roller tooth’s taper angle, imprint depth, imprint temperature, and imprint direction on the imprint force, adhesion, stress distribution, and strain are investigated. A two-stage roller imprint process was obtained from an imprint force curve. The two-stage imprint process included the imprint forming with a rapid increase of imprint force and the unloading stage combined with the adhesion stage. The results show that the imprint force and adhesion rapidly increase with decreasing taper angle and increasing imprint depth. The magnitude of the maximum imprint force and the time at which this maximum occurs are proportional to the imprint depth, but independent of the taper angle. In a comparison of the imprint mechanisms with a vertical imprint case, while high stress and strain regions are concentrated below the mold for vertical imprint, they also occur around the mold in the case of roller imprint. The regions were only concentrated on the substrate atoms underneath the mold in vertical imprint. Plastic flow increased with increasing imprint temperature

Experimentelle Bestimmung biomechanischer Belastungen bei Skifahrer-Kollisionen

Background: Approximately 70’000 people sustain injury in accidents on Swiss slopes every year. High velocity of skiers and snowboarders increases the risk of severe injury of the head, back or knee in case of a fall or collision. To develop effective measures to prevent such injury, an understanding of the underlying injury mechanisms is mandatory. However, determining the necessary biomechanical data is difficult. Method: Collisions between two skiers were investigated experimentally. Crash test dummies were used to mimic a collision and to determine the biomechanical loading of different body regions during impact. Based on those recordings, injury criteria were calculated to estimate the injury risk of AIS 2+ injuries. The experiments were performed at 30 and 50 km/h. Results and discussion: The experimental set-up and the methodology chosen were suitable to measure the biomechanical loading of the dummy. The results indicate that a collision at 30 km/h can result in a significant head injury risk even if a helmet is worn. While at 30 km/h the primary impact causes the highest loading, the importance of the secondary impact (i.e. the impact on the ground) increases at higher collision speed. The data established in this study are an important basis for the development of effective prevention strategies

Reply to: Technical Comment on "Saccadic eye movement performance as an indicator of driving ability in elderly drivers"

ISSN:1424-7860ISSN:1424-399