Polychlorinated biphenyl,DDT and dieldrin residues in grey seal (Halichoerus grypus) males,females and mother-foetus pairs sampled at the Farne Islands,England, during the breeding season

PCB, DDT, DDE, dieldrin and total non-polar organohalogen residues have been determined in the blubber-lipid of grey seals (Halichoerus grypus) sampled during the 1972 breeding season (November) at the Farne Islands off the north eastern coast of England. PCBs were analysed by gas-liquid chromatography linked to a chlorine- and carbon-selective microwave plasma detector and total organohalogen residues were determined by microcoulometry.Total organohalogen residues were negatively correlated with blubber thickness and positively correlated with age in males (aged 1 to 24 y) and females (aged 5 to 38 y). However, the correlation of blubber-lipid residue with age in males depended upon the inclusion of immature (aged < 6 y) animals, and in females reflected only a small residue increment. The mean blubber organohalogen concentration of the males was significantly greater than that of the females. PCB and DDT group residue concentrations were significantly correlated.PCB, DDT, DDE and dieldrin were detected in the liver of mother/foetus pairs demonstrating transplacental movement of these residues.The possibility of the condition of the seals at breeding time influencing residue levels and of these residues influencing the health of the population is discussed.     

Application of flow cytometry for examining phytoplankton succession in two eutrophic lakes

Flow cytometry has potential as a rapid assessment technique to evaluate phytoplankton biomass and species composition. It facilitates for multi-parameter analysis of individual cells on the basis of light scattering effects induced from cellular constituents, as well as auto-fluorescence. Fluorescence emission characteristics may be especially useful in classifying cyanobacteria as they contain phycoerythrin which emits light predominantly in the 550-600 nm waveband, chlorophyll-a (650-700 nm emission) and allophycocyanin (660 nm emission). The objective of our study was to assess the utility of flow cytometry for the rapid identification and sorting of freshwater algae and cyanobacteria species. Using a selection of laboratory-cultured freshwater algae and cyanobacteria species, this study demonstrated unique light scatter and fluorescent characteristics for each species examined, allowing for rapid species identification and sorting of mixed populations of laboratory cultures and samples from two lakes in the Rotorua region (New Zealand). Analysis of lake water samples collected over seven months demonstrated changes in abundance and community composition of phytoplankton in the two lakes and demonstrates that flow cytometry may be a useful technique for examining seasonal changes in phytoplankton composition.     

Theory of mind associations with other cognitive functions and brain imaging in normal aging.

The study investigated age-related differences in theory of mind and explored the relationship between this ability, other cognitive abilities, and structural brain measures. A cohort of 106 adults (ages 50–90 years) was recruited. Participants completed tests of theory of mind, verbal and performance intelligence, executive function, and information processing speed and underwent structural magnetic resonance imaging (measurement of whole brain volume, volume of white matter hyperintensities, and diffusion tensor imaging of white matter integrity). Theory of mind ability declined with increasing age, and the relationship between theory of mind and age was fully mediated by performance intelligence, executive function, and information processing speed and was partially mediated by verbal intelligence. Theory of mind performance correlated significantly with diffusion tensor imaging measures of white matter integrity but not with volume of white matter hyperintensities or whole-brain volume. Theory of mind age-related decline may not be independent of other cognitive functions; it may also be particularly susceptible to changes in white matter integrity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A thermal model of friction stir welding applied to Sc-modified Al–Zn–Mg–Cu alloy extrusions

A thermal model of friction stir welding is presented that proposes an energy-based formulation of the Johnson–Cook plasticity model in order to account for heat generation due to plastic deformation. The proposed formulation is derived from an empirical, linear relationship observed between the ratio of the maximum welding temperature to the solidus temperature of the alloy and the welding energy. The thermal model is applied to Sc-modified Al–Zn–Mg–Cu alloy extrusions joined by friction stir welding at 225, 250, 300 and 400 RPM (all other weld parameters held constant). With the incorporation of heat generation due to plastic deformation, the thermal model accurately predicts the maximum weld temperatures and temperature profiles at the higher energy weld conditions, i.e. 300 and 400 RPM. At the lower energy welds (i.e. 225 and 250 RPM) where plastic deformation contributes a larger portion to the total heat generation, the model under-predicts the maximum weld temperatures under the tool shoulder but shows good agreement with the remaining experimental temperature data.     

High mobility p-channel organic field effect transistors on flexible substrates using a polymer-small molecule blend

Organic field effect transistors have been fabricated on poly(ethylene terephthalate) film substrates with excellent operating characteristics and maximum mobilities of 1.1 cm²/(V s). The semiconductor was a solution processible blend of 6,13-bis(triisopropyl silylethynyl) pentacene and a poly(triaryl amine) used to combine the favourable properties of small molecules and polymers. We have demonstrated that such systems are a good candidate for flexible organic electronics and that the surface energy of the substrate plays a key role in controlling the morphology of the semiconductor film.     

Decentralised decision making in heterogeneous teams using anonymous optimisation

This paper considers the scenario where multiple autonomous agents must cooperate in making decisions to minimise a continuous and differentiable team cost function. A distributed and asynchronous optimisation algorithm is presented which allows each agent to incrementally refine their decisions while intermittently communicating with the rest of the team. A convergence analysis provides quantitative requirements on the frequency agents must communicate that is prescribed by the structure of the decision problem. In general the solution method will require every agent to communicate to and have a model of every other agent in the team. To overcome this, a specific subset of systems, called Partially Separable, is defined. These systems only require each agent to have a combined summary of the rest of the team and allows each agent to communicate locally over an acyclic communication network, greatly increasing the scalability of the system.     

Moving beyond ‘more crop per drop’: insights from two decades of research on agricultural water productivity

ABSTRACT

Concern over increasing water scarcity has led to the introduction of the concept of agricultural water productivity and an emphasis on interventions to achieve ‘more crop per drop’. Yet, a strong debate continues on how the concept is to be defined and used. Drawing largely from the irrigation literature, the origins of the concept and its methodological developments are reviewed, and its use in applied work over two decades is discussed. Based on this analysis of conceptual and applied research, key insights into the concept’s contributions and limitations are presented, as well as opportunities for further refinements.