Volatilization of organotin species from municipal waste deposits: novel species identification and modeling of atmospheric stability

Organotin compounds are used as pesticides and fungicides as well as additives in plastics. This study identifies the de novo generation of novel volatile organotins in municipal waste deposits and their release via landfill gas. Besides tetramethyltin (Me(4)Sn), a strong neurotoxin, and 5 previously reported organotins, 13 novel ethylated, propylated, and butylated tetraalkyltin compounds were identified. A concentration of 2-4 μg of Sn m(-3) landfill gas was estimated for two landfill sites in Scotland. The atmospheric stability of Me(4)Sn and methylated tin hydrides was determined empirically in a static atmosphere in the dark and under UV light to simulate night- and daytime conditions. Theoretical calculations were carried out to help predict the experimentally obtained stabilities and to estimate the relative stabilities of other alkylated species. Assuming first-order kinetics, the atmospheric half-life for Me(3)SnH was found to be 33 ± 16 and 1311 ± 111 h during day- and nighttime conditions, respectively. Polyalkylation and larger alkyl substitutes tend to reduce the atmospheric stability. These results show that substantial concentrations of neurotoxic organotin compounds can be released from landfill sites and are sufficiently stable in the atmosphere to travel over large distances in night- and daytime conditions to populated areas.     

Zur Elektrodenkinetik von Reinst – Eisen im Phosphatelektrolyten bei Feststoffeinschlag (Simulation von Erosionskorrosion)

Electrode kinetics of high purity iron in phosphate electrolytes under solid particle impact (Simulation of erosion corrosion) Erosion-corrosion of high purity iron was simulated by means of a vibration cell in a neutral phosphate electrolyte. The investigations were carried out to explain the initiation processes of this type of corrosion. The results confirm the general conception of the central role of reaction layer destruction in erosion-corrosion processes. Under these conditions a qualitative change in reaction layer formation occur. By solid impact the layers are destroyed locally and so conditions of pit nucleation exist. The destruction of the layers depends on the action of shear forces resulting from tensile or compressive strains.     

Modernisierung des Datenschutzes: Herausforderungen durch die Technik

Auf Einladung des Innenausschusses des Deutschen Bundestages fand am 5. M?rz 2007 eine ?ffentliche Anh?rung zum Thema der Modernisierung des Datenschutzes statt. Gegenstand waren Entschlie?ungsantr?ge der Fraktionen der FDP sowie von Bündnis90/Die Grünen zum Datenschutzaudit¹ sowie zum Scoring und zu Auskunftspflichten bei Datenschutzpannen.² Eingeladen war auch der Landesbeauftragte für den Datenschutz Mecklenburg Vorpommern, dessen schriftliche Analyse wir mit den Schwerpunkten der Herausforderungen durch die Technik und des Datenschutzaudits abdrucken.     

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.     

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).