Radioactive contaminants in the subsurface: the influence of complexing ligands on trace metal speciation

Equilibrium thermodynamics is one of the pillars which support safety analyses of repositories for radioactive waste. The research summarized in this review deals with approaches to resolve the problems related to thermodynamic equilibrium constants and solubility of solid phases in the field of radioactive waste management. The results have been obtained at the Paul Scherrer Institut between 1995 and 2005 and comprise the scientific basis of the author's habilitation thesis in the field of nuclear environmental chemistry. The topics are grouped according to three different levels of problem solving strategies: (1) Critical and comprehensive reviews of the available literature, which are necessary in order to establish a reliable chemical thermodynamic database that fulfils the requirements for rigorous modeling of the behavior of the actinides and fission products in the environment. (2) In many case studies involving inorganic and simple organic ligands a serious lack of reliable thermodynamic data is encountered. There, a new modeling approach to estimate the effects of these missing data was applied. This so called "backdoor approach” begins with the question, "What total concentration of a ligand is necessary to significantly influence the speciation, and hence the solubility, of a given trace metal?” (3) In the field of natural organics, mainly humic and fulvic acids, we face an ill-defined problem concerning the molecular structure of the ligands. There, a pragmatic approach for performance assessment purposes was applied, the "conservative roof” approach, which does not aim to accurately model all experimental data, but allows estimates of maximum effects on metal complexation by humic substances to be calculate

Trace element complexation by humic substances: issues related to quality assurance

Despite the amount of data available and the effort that has been put into studying the binding of trace elements by humic substances, there is still a significant amount of uncertainty surrounding the validity and applicability of the existing values in solving particular problems in the environmental, toxicity and industrial fields. This paper discusses the problems associated with the characterisation of humic binding and proposes a general approach for quality assessing trace element-humic substances complexation data, which includes the normalisation of raw experimental data prior to any data treatment (modelling

Zinc Gluconate in the Treatment of Dysgeusia—a Randomized Clinical Trial

In the treatment of dysgeusia, the use of zinc has been frequently tried, with equivocal results. The aim of the present randomized clinical trial, which involved a sufficiently large sample, was therefore to determine the efficacy of zinc treatment. Fifty patients with idiopathic dysgeusia were carefully selected. Zinc gluconate (140 mg/day; n = 26) or placebo (lactose; n = 24) was randomly assigned to the patients. The patients on zinc improved in terms of gustatory function (p < 0.001) and rated the dysgeusia as being less severe (p < 0.05). Similarly, signs of depression in the zinc group were less severe (Beck Depression Inventory, p < 0.05; mood scale, p < 0.05). With the exception of the salivary calcium level, which was higher in the zinc patients (p < 0.05), no other significant group differences were found. In conclusion, zinc appears to improve general gustatory function and, consequently, general mood scores in dysgeusia patients

Die Medienkompetenz Jugendlicher im Umgang mit digitalen sozialen Netzwerken

Die Vielzahl, Vielfalt, Allgegenwart und permanente Präsenz sozialer Web 2.0-Angebote übt einen bedeutenden Einfluss auf das Aufwachsen, die Freizeitgestaltung, das schulische Lernen und die Identitätsbildung jugendlicher Nutzer aus. Der einstige Medienrezipient befindet sich nicht mehr nur in der Rolle des Lesers und passiven Konsumenten, sondern er ist gleichermaßen Akteur und Publizist [4, 22]. Der Umgang insbesondere jugendlicher Nutzer mit sozialen Netzwerken und deren Potentialen und Risiken ist daher seit einigen Jahren ein wichtiger Forschungsbereich [vgl. 3, 7, 8, 9, 10, 11]. In diesem Zusammenhang ist die Medienkompetenz von entscheidender Bedeutung [vgl. 4, 17, 22]. In diesem Beitrag wird die Medienkompetenz Jugendlicher speziell im Hinblick auf den Umgang mit sozialen Netzwerken thematisiert. Wie wird Medienkompetenz derzeit wissenschaftlich definiert? Finden die vielen speziellen Anforderungen an die Nutzer der „social network services“ (SNS) in den bestehenden Modellen ausreichend Berücksichtigung? Welche Teilkompetenzen sind für die Nutzung der digitalen sozialen Netzwerke durch Jugendliche notwendig? (...

Studie zur Verwendung von Kinderschutzsystemen

STUDIE ZUR VERWENDUNG VON KINDERSCHUTZSYSTEMEN Studie zur Verwendung von Kinderschutzsystemen / Müller, Gerd (Rights reserved) ( -