Sulphur isotope evidence for an oxic Archaean atmosphere

The presence of mass-independently fractionated sulphur isotopes (MIF-S) in many sedimentary rocks older than approximately 2.4 billion years (Gyr), and the absence of MIF-S in younger rocks, has been considered the best evidence for a dramatic change from an anoxic to oxic atmosphere around 2.4 Gyr ago. This is because the only mechanism known to produce MIF-S has been ultraviolet photolysis of volcanic sulphur dioxide gas in an oxygen-poor atmosphere. Here we report the absence of MIF-S throughout approximately 100-m sections of 2.76-Gyr-old lake sediments and 2.92-Gyr-old marine shales in the Pilbara Craton, Western Australia. We propose three possible interpretations of the MIF-S geologic record: (1) the level of atmospheric oxygen fluctuated greatly during the Archaean era; (2) the atmosphere has remained oxic since approximately 3.8 Gyr ago, and MIF-S in sedimentary rocks represents times and regions of violent volcanic eruptions that ejected large volumes of sulphur dioxide into the stratosphere; or (3) MIF-S in rocks was mostly created by non-photochemical reactions during sediment diagenesis, and thus is not linked to atmospheric chemistry.     

Upper Palaeolithic infant burials

Decorations on the bodies of newborns indicate that they were probably important in their community. Several adult graves from the Stone Age (Upper Palaeolithic period) have been found but child burials seem to be rare, which has prompted discussion about whether this apparently different treatment of infants could be significant. Here we describe two recently discovered infant burials from this period at Krems-Wachtberg in Lower Austria, in which the bodies were covered with red ochre and decorated with ornaments and were therefore probably ritually buried. These findings indicate that even newborns were considered to be full members of these hunter-gatherer communities about 27,000 years ago.     

Boundary lubrication under water

Boundary lubrication, in which the rubbing surfaces are coated with molecular monolayers, has been studied extensively for over half a century. Such monolayers generally consist of amphiphilic surfactants anchored by their polar headgroups; sliding occurs at the interface between the layers, greatly reducing friction and especially wear of the underlying substrates. This process, widespread in engineering applications, is also predicted to occur in biological lubrication via phospholipid films, though few systematic studies on friction between surfactant layers in aqueous environments have been carried out. Here we show that the frictional stress between two sliding surfaces bearing surfactant monolayers may decrease, when immersed in water, to as little as one per cent or less of its value in air (or oil). We attribute this to the shift of the slip plane from between the surfactant layers, to the surfactant/substrate interface. The low friction would then be due to the fluid hydration layers surrounding the polar head groups attached to the substrate. These results may have implications for future technological and biomedical applications.     

Learning with participatory monitoring and evaluation in Dir district,northwest frontier province,Pakistan

This paper is concerned with the development of a monitoring and evaluation system for the second phase of a United Nations Drug Control Programme (UNDCP) in Pakistan and the manner in which participatory structures are developed and built on in a complex development context. Initially the paper introduces the context. The project is concerned with rural development issues as part of a structured programme to substitute opium poppy growing with a range of agricultural and social innovations. During the first phase of the project (up to 1993) the main focus of attention for the project was measured in terms of physical progress with road building, electricity supply, irrigation works and concentration on improved agricultural practices. Phase II has set out to build on this, most specifically in terms of gaining the greater participation of local people in the project activity. The paper describes the monitoring and evaluation (M&E) structure for the project and notes that it is intended that M&E further encourage participation and beneficiary analysis (analysis of project benefits by those who are intended to derive most from the project outputs). One of the primary means set out for achieving this was by inducing the professional staff working in the project to adopt new mind sets, adjusting their focus from being technical experts supplying undoubted technical improvements to being co-operative partners, bringing ideas to the area but equally being willing to work through these ideas and their implications and learn from the communities. The process for the development of the monitoring system is described, and the methodology ‘TeamUp’ discussed. Links are made to related areas of study—most specifically the literature of Rapid and Participatory Rural Development (RRA and PRA). Finally, the paper discusses the results of the research to date and the likely extension of the ideas to other projects.     

Book Review: Rational Analysis for a Problematic World Revisited: Problem Structuring Methods for Complexity,Uncertainty, and Conflict. Jonathan Rosenhead and John Mingers. Wiley,Chichester, United Kingdom. 2001, 365 pp., Chaps. 15, £22.50 (Amazon)

Systemic Practice and Action Research -     

Conditioned suppression: Dissociation of learning in baclofen treated rats

Summary In rats, baclofen induced a memory deficit related to a dissociation of learning. Baclofen given prior to training or prior to testing had no effect on the amnesia elicited by diazepam.     

Combining experts' opinions using a normal-wishart model

This paper examines how a Bayesian decision maker might update her distributions for continuous variables X_i, i=1, 2, …, upon hearing experts' forecasts expressed as quantiles. To utilize the relationship between the decision maker and experts, and to avoid problems associated with different scales and ranges of the variables, we assume that the decision maker transforms the experts' quantiles in terms of her own prior distribution for each X_i. A model using such a transformation is presented and its properties are examined.     

Electrochemical characterization of the Pt /PEDOT electrode in DMFC

Poly-(3, 4-ethylenedioxythiophene) (PEDOT) was applied in making electrodes and gas diffusion layer for direct methanol fuel cells (DMFC). Electrochemical characterizations of Pt/PEDOT electrodes, made by two different methods, were investigated by cyclic voltammetry, methanol oxidation tests and DMFC performance. The platinum particle structure in PEDOT/PSS (poly?styrene sulfonic acid) films was investigated by SEM and TEM. Our research work showed that PEDOT influenced the catalytic activity behavior in three different ways when it was applied to the anode, cathode and the gas diffusion layer. The DMFC performance agreed with the cyclic voltammetry and methanol oxidation test results.