Levels of 3,3′,4,4′-tetrachloroazobenzene in herbicides and bulk reagents

The contamination levels of different commercial herbicides and bulk reagents with the carcinogen 3,3′,4,4′-tetrachloroazobenzene (TCAB) were determined by high resolution mass spectrometry. The concentrations vary from 0.00071 to 2.8 ug/g (ppm) for the herbicides and from 0.085 to 14 ug/g for the bulk reagents. They are thus lower than those of other reports.     

Glutathione status and glutathione reductase activity in spruce needles of healthy and damaged trees at two mountain sites

Levels of glutathione, in both reduced and oxidized form, and glutathione reductase activity were monitored in needles of healthy and damaged spruce trees (Picea abies (L.) Karst.) during the course of four vegetation periods at two natural sites. The glutathione content and glutathione reductase activity showed a pronounced annual rhythm in undamaged trees, whereas damaged spruce trees deviated significantly from this course. In comparison with undamaged trees, damaged trees showed markedly increased levels of glutathione during the test period of 1989-1991. However, glutathione reductase activity differed in damaged and undamaged trees, only in 1989-1990. The ratio of reduced to oxidized glutathione (GSH/GSSG ratio) was slightly higher in damaged trees, and the highest levels were found during the winter months. In the case of damaged trees, a correlation between GSH/GSSG ratio and current ozone levels at the sites could be clearly established. The present results indicate that damaged trees suffer from increased oxidative stress, especially in the period from June to October.     

Integrated assessment modeling of global climate change: Transparent rational tool for policy making or opaque screen hiding value‐laden assumptions?

One of the principal tools used in the integrated assessment (IA) of environmental science, technology and policy problems is integrated assessment models (IAMs). These models are often comprised of many sub‐models adopted from a wide range of disciplines. A multi‐disciplinary tool kit is presented, from which three decades of IA of global climatic change issues have tapped. A distinction between multi‐ and inter‐disciplinarity is suggested, hinging on the synergistic value added for the latter. Then, a hierarchy of five generations of IAMs are proposed, roughly paralleling the development of IAMs as they incorporated more components of the coupled physical, biological and social scientific disciplines needed to address a “real world” problem like climatic change impacts and policy responses. The need for validation protocols and exploration of predictability limits is also emphasized. The critical importance of making value‐laden assumptions highly transparent in both natural and social scientific components of IAMs is stressed, and it is suggested that incorporating decision‐makers and other citizens into the early design of IAMs can help with this process. The latter could also help IA modelers to offer a large range of value‐containing options via menu driven designs. Examples of specific topics which are often not well understood by potential users of IAMs are briefly surveyed, and it is argued that if the assumptions and values embedded in such topics are not made explicit to users, then IAMs, rather than helping to provide us with refined insights, could well hide value‐laden assumptions or conditions. In particular, issues of induced technological change, timing of carbon abatement, transients, surprises, adaptation, subjective probability assessment and the use of contemporary spatial variations as a substitute for time evolving changes (what I label “ergodic economics”) are given as examples of problematic issues that IA modelers need to explicitly address and make transparent if IAMs are to enlighten more than they conceal. A checklist of six practices which might help to increase transparency of IAMs is offered in the conclusions. Incorporation of decision‐makers into all stages of development and use of IAMs is re‐emphasized as one safeguard against misunderstanding or misrepresentation of IAM results by lay audiences.     

Wie überraschend treten Erdbeben auf?

The seismic focal process is controlled by two kinds of physical parameters: On the one hand, stable entities namely the tectonic-stress field, the dimensions of elastically reacting volumes, and the size and orientation of preexisting fractures; on the other hand, frictionlike processes which greatly influence the situation before an earthquake and the seismic dislocations. Because of the singular direction of fault movements the friction processes change in an irreversible manner. These continuously changing situations determine, however, the relationship between aseismic creep and seismic movements. The friction phenomena also determine the distribution of seismic dislocations on focal surfaces of different geometric area.