Characterization of Mercury Contamination Surrounding a Chloralkali Production Facility in Tuzla,Bosnia and Herzegovina

Tuzla is among the most polluted cities of Bosnia and Herzegovina. The main source of pollution in the area is soil heavily contaminated by mercury released from a former chloralkali plant. This paper is focused on the characterization of mercury contaminated soil and air surrounding the chloralkali plant. In soil, the mobility and transformation of mercury were investigated by sequential extraction, while the methylation and reduction potentials were determined by the use of a radioactive tracer. Mercury emission from soil was determined by laboratory and by flux chamber measurements in the field. In addition, mercury concentrations in air were estimated by the analysis of air and the transplanted lichen Hypogymnia physodes. Mercury in soils in the vicinity of the chloralkali plant exceeded the background value by a factor of more than 3000. The fractionation of mercury in surface soil by sequential extraction showed that the mercury in soil was primarily bound to organic matter and a fraction containing elemental mercury and mercury (I) chloride is also significant. The obtained methylation and reduction potentials are low. The mercury flux from soil was estimated by two approaches. Fluxes of up to 8000?ng/m²/day were measured at the most polluted site; evaporation from soil was shown to be the primary source of elevated mercury in air. Air concentration mapping also revealed other sources of mercury; the most likely is the 715 MW coal power plant in the vicinity of former chloralkali facility.     

A study of entangled systems in the many‐body signed particle formulation of quantum mechanics

Recently a new formulation of quantum mechanics has been introduced, based on signed classical field‐less particles interacting with an external field by means of only creation and annihilation events. In this article, we extend this novel theory to the case of many‐body problems. We show that, when restricted to spatial finite domains and discrete momentum space, the proposed extended theory is equivalent to the time‐dependent many‐body Wigner Monte Carlo method. In this new picture, the treatment of entangled systems comes naturally and, therefore, we apply it to the study of quantum entangled systems. The latter is represented in terms of two Gaussian wave packets moving in opposite directions. We introduce the presence of a dissipative background and show how the entanglement is affected by different (controlled) configurations.     

Molecular and cellular approach in the study of antioxidant/pro-oxidant properties of Micromeria croatica (Pers.) Schott

Phytochemical composition and antioxidant activity of three wild populations of endemic Illyric-Balcanic species Micromeria croatica (Pers.) Schott have been evaluated with respect to plant organ and growing location. Multivariate analysis (principal component analysis) was performed to visualise (dis-)similarity among samples and identify the correlations between phytochemical variables that explain the most variability. The tested leaf extract from Ba?i? kuk locality exhibited protective effects against reactive oxygen species-induced damage of DNA and inhibition of lipid peroxidation, while it caused oxidative degradation of protein in the bovine serum albumin assay at higher concentrations. This extract also exhibited cytotoxic activity and facilitated the formation of reactive oxygen species in the HEp2 cell line, in a dose-dependent manner.     

Ultra‐small Palladium Nanoparticle Decorated Carbon Nanotubes: Conductivity and Reactivity

Carbon nanotubes decorated with ultra‐small metal nanoparticles are of great value in catalysis. We report that individual multiwalled carbon nanotubes decorated with ultra‐small palladium nanoparticles can be detected by using the nano‐impacts method. The high conductivity and reactivity of each decorated carbon nanotube is directly evidenced; this is achieved through studying the proton‐reduction reaction for the underpotential deposition of hydrogen onto the nanoparticles decorated on the carbon nanotube walls. The reductive spikes from current amplification are analyzed to estimate the approximate length of the decorated carbon nanotubes, revealing that the decorated carbon nanotubes are electroactive along its entire length of several micrometers.     

Facile Enzymatic Synthesis of Ketoses

Studies of rare ketoses have been hampered by a lack of efficient preparation methods. A convenient, efficient, and cost‐effective platform for the facile synthesis of ketoses is described. This method enables the preparation of difficult‐to‐access ketopentoses and ketohexoses from common and inexpensive starting materials with high yield and purity and without the need for a tedious isomer separation step.     

Über eine neue Bildungsart von Äthern des Glyzerins mit Phenolen

Ohne Zusammenfassung     

Reasoning and proof in geometry: effects of a learning environment based on heuristic worked-out examples

We analyze heuristic worked-out examples as a tool for learning argumentation and proof. Their use in the mathematics classroom was motivated by findings on traditional worked-out examples, which turned out to be efficient for learning algorithmic problem solving. The basic idea of heuristic worked-out examples is that they encourage explorative processes and thus reflect explicitly different phases while performing a proof. We tested the hypotheses that teaching with heuristic examples is more effective than usual classroom instruction in an experimental classroom study with 243 grade 8 students. The results suggest that heuristic worked-out examples were more effective than the usual mathematics instruction. In particular, students with an insufficient understanding of proof were able to benefit from this learning environment.     

Strategies to foster students’ competencies in constructing multi-steps geometric proofs: teaching experiments in Taiwan and Germany

In this article, we discuss the complexity of geometric proofs with respect to a theoretical analysis and empirical results from studies in Taiwan and Germany. Based on these findings in both countries, specific teachings experiments with junior high school students were developed, conducted, and evaluated. According to the different classroom and learning culture in East Asia and Western Europe, the interventions differed in their way of organizing the learning activities during regular mathematics lessons. The statistical analysis of the pre–post-test data indicated that both interventions were successful in fostering students’ proof competence.