Using dynamic explanations to enhance novice programmer instruction via the WWW

This paper describes how the World Wide Web (WWW)-delivered visual explanations of programming constructs have been developed and used to supplement the conventional instructional methods and materials traditionally employed in introductory programming courses. The explanations are constructed using inexpensive commercial software that supports the use of animation, graphics, color, and narrative to help students visualize a wide range of concepts and relationships. Initial student feedback suggests WWW-delivered visual explanations appear to be an effective means of addressing the individual learning needs of novice programmers.     

Einfluß der elektrochemischen Bedingungen auf die Wechselfestigkeit eines unlegierten Stahles

Dauerschwingversuche an Rundproben eines unlegierten Stahles mit 0,09% C unter Zug-Druck-Wechselbelastung (σ_m = 0, n = 2000/min) in wäßrigen Elektrolyten verschiedener pH-Werte ohne und mit äußerer Potentialvorgabe. Ermittlung der Zeit- und Wechselfestigkeit sowie metallographische Untersuchungen über die Ausbildung von Verformungsspuren und Rissen unter verschiedenen Korrosionsbedingungen. Verlauf von Stromdichte-Lastspielzahl-Kurven bei verschiedenen Prüfbedingungen. Erörterung und Deutung der Versuchsergebnisse.     

Preoperative biliary drainage, colonisation of bile and postoperative complications in patients with tumours of the pancreatic head: a retrospective analysis of 241 consecutive patients

OBJECTIVE: To analyse the outcome of preoperative biliary drainage in patients being operated on for a tumour in the pancreatic head. DESIGN: Retrospective study. SETTING: University hospital, The Netherlands. SUBJECTS: Consecutive series of 241 patients. MAIN OUTCOME MEASURES: Decline in bilirubin concentrations and bacterial contamination of bile as a result of preoperative drainage. Incidence of postoperative complications in patients who underwent preoperative drainage and those who did not. RESULTS: 184/241 patients underwent preoperative biliary drainage. Endoscopic drainage was the most effective, shown by a median reduction in bilirubin concentrations of 82%, 74%, and 50% after endoscopic drainage (n = 149), papillotomy (n = 25) and external drainage (n = 10), respectively. Bacterial contamination of bile was significantly more common when an endoprosthesis was used, but did not result in a higher rate of infective complications. 163 Whipple's resections, 33 total pancreatectomies, and 45 biliary-enteric bypasses were performed. 137/241 (57%) patients had postoperative complications. There was no significant difference in the incidence of postoperative complications between patients who had preoperative biliary drainage and those who did not (p = 0.4).     

Mode-locking external-cavity laser-diode sensor for displacement measurements of technical surfaces

A novel laser sensor for position measurements of technical solid-state surfaces is proposed. An external Fabry-Perot laser cavity is assembled by use of an antireflection-coated laser diode together with the technical surface. Mode locking results from pumping the laser diode synchronously to the mode spacing of the cavity. The laser cavity length, i.e., the distance to the measurement object, is determined by evaluation of the modulation transfer function of the cavity by means of a phase-locked loop. The mode-locking external-cavity laser sensor incorporates a resonance effect that results in highly resolving position and displacement measurements. More than a factor-of-10 higher resolution than with conventional nonresonant sensing principles is achieved. Results of the displacement measurements of various technical surfaces are reported. Experimental and theoretical investigations are in good agreement.