Flight trajectory analysis of CuSn-droplets generated by laser drop on demand jetting, using stereoscopic high-speed imaging.

Laser drop on demand jetting of Cu-base braze droplets was proven a suitable method for joining wires to electrode structures of electronic devices, particularly if the electrical contacts need to withstand high thermal loads. During joining, a braze preform of 600 µm diameter is placed inside a capillary, molten by a laser pulse and subsequently ejected from the capillary by inert gas overpressure similarly to conventional solder ball bumping processes. However, since the liquidus temperature of the used braze material of 990 °C is about 760 °C higher than of standard Sn-based solders used in electronics packaging, the system technology was modified significantly to enable jetting of CuSn alloys. In particular, the beam source emits a five times higher optical output power than standard machines designed for processing Sn-based solders. In addition, a modified capillary made from technical ceramic was machined, to withstand the significantly higher heating- and cooling rates during the process. In order to understand the influence of capillary geometry on droplet detachment, and flight trajectory, two capillary geometries were machined applying a picosecond laser ablation process. Subsequently, stereoscopic high speed videos of droplet detachment and flight phase were analyzed. Using this approach it is possible, to determine droplet flight trajectories, velocities and lateral positional deviations in dependency of relative inert gas overpressure inside the machining head, pulse power and capillary geometry. The findings indicate a significant influence of the capillary geometry and the applied overpressure on the droplet flight trajectory, whereas the role of the laser pulse power seems neglectable.

Linear stapled gastrojejunostomy results in fewer strictures compared to circular stapled gastrojejunostomy in laparoscopic gastric bypass surgery.

PURPOSE: Currently, there are two laparoscopic stapling techniques to perform the gastrojejunostomy in gastric bypass surgery: the linear stapling and circular stapling techniques. The aim of the study was to compare the two techniques regarding postoperative morbidity and weight loss at an accredited bariatric reference center in Switzerland. METHODS: We compared two consecutive cohorts at a single institution between November 2012 and June 2014 undergoing laparoscopic gastric bypass surgery. The frequency of complications and weight loss at 1 year was assessed in 109 patients with the 21-mm circular stapling technique (CSA) and 134 patients with the linear stapling technique (LSA). RESULTS: Postoperative complications were more frequent in the CSA group with 23.9 versus 4.5% in the LSA group (p = <0.0001). The main difference was the frequency of strictures, which occurred in 15.6% in the CSA group versus 0% in the LSA group. As a result, endoscopic dilation was required at least once in 15 patients. There was no statistically significant difference in percentage of excessive weight loss (EWL) in both groups; EWL was 74% in the CSA group and 73% in the LSA group (p = 0.68). CONCLUSION: Linear stapled laparoscopic gastric bypass had fewer stenotic strictures with similar weight loss at 1 year compared to circular stapling technique.

The role of calcium in acute pancreatitis.

Until recently, it was unclear whether calcium is more than a bystander in the development of acute pancreatitis. Now important evidence has been accumulated supporting a pivotal role of intracellular levels of calcium in the early pathogenesis of the disease. A sustained increase of cytosolic calcium concentrations, as observed in various models of acute pancreatitis, was identified as sabotaging crucial cellular defense mechanisms and initiating premature trypsinogen activation. These processes lead the acinar cell to necrosis, with spillage of activated proteases into the interstitial space, affecting surrounding acinar cells and initiating a vicious circle that ends in macroscopic acute pancreatitis and systemic inflammatory response syndrome. Comprehensive knowledge of the pathobiology of cytosolic calcium in the pancreatic acinar cell is leading to the understanding of coherent molecular pathways of early events in the pathogenesis of acute pancreatitis and is opening horizons for research into directly targeted therapeutic agents.