Air filtration and radon daughter levels

The authors investigate the effect of filtration and aerosol loading of the air on the level of short-lived air-borne daughter products of radon. By the use of a combination of filtration and aerosol loading, it is possible to shift the partitioning of the radon daughters in the room between the states: airborne, plated-out on the walls, and trapped by filters; the airborne fraction will shift between being attached to aerosol particles and existing as molecular-sized clusters. When the air filtered the equilibrium factor decreases with increasing filtration rate. At high aerosol concentrations the decrease can be explained solely as an effect of the filter removing the daughter products from the air passing through it. As the aerosol production and concentration is lowered, the decrease in equilibrium factor becomes larger. This is caused by an increase in the unattached fraction of the airborne activity and hence in the wall-deposited fraction of the total activity. At a given radon concentration, the dose delivered to a certain portion of the respiratory tract depends not only upon the equilibrium factor but also upon the fraction of, especially, ₈₄²¹⁸Po in the unattached state. It is further demonstrated that, according to the dose model of Harley and Pasternak, the dose to the basal cells of the epithelium of the bronchii will in general decrease with increasing filtration rate and increase with decreasing aerosol concentration.     

Indicators of Biodiversity and Conservational Wildlife Quality on Danish Organic Farms for Use in Farm Management: A Multidisciplinary Approach to Indicator Development and Testing

Organic farming is expected to contribute to conserving national biodiversity on farms, especially remnant, old, and undisturbed small biotopes, forests, and permanent grassland. This objective cannot rely on the legislation of organic farming solely, and to succeed, farmers need to understand the goals behind it. A set of indicators with the purpose of facilitating dialogues between expert and farmer on wildlife quality has been developed and tested on eight organic farms. “Weed cover in cereal fields,” was used as an indicator of floral and faunal biodiversity in the cultivated land, and “uncultivated biotope area” on the farm was used as a general measure of wildlife habitats. Functional grouping of herbaceous plants (discriminating between “high conservation value” plant species and “competitive”/“ruderal” species) and low mobility butterflies were used as indicators of conservation value, especially focusing on the few sites left with considerable remnant conservation value. The dialog processes revealed that the organic farmers’ ideas and goals of conservation of wildlife quality were not necessarily the same as for biologists; the farmers expressed very different opinions on the biological rooted idea, that wildlife quality is related to the absence of agricultural impact. However, farmers also stated that the information given by the indicators and especially the dialogue with the biologist had influenced their perception and awareness of wildlife. We conclude that, combined with a dialogue process, using these indicators when mapping wildlife quality could be an important key component of a farm wildlife management advisory tool at farm level.     

Robustness in life history of the brown seaweed Ascophyllum nodosum (Fucales, Phaeophyceae) across large scales: effects of spatially and temporally induced variability on population growth

Understanding the demography and function of biotope-forming seaweed species is of great importance for the conservation of the target species itself, as well as its associated organisms. The brown seaweed Ascophyllum nodosum is fundamental for the functioning of coastal marine ecosystems in the North Atlantic. In this study, we use a data-based size-classified matrix model to investigate the temporal and spatial variability in demography, and the environment-specific stochastic sensitivity and elasticity, of two A. nodosum populations, one in western Sweden and one on the Isle of Man in the Irish Sea. A significant difference between the two populations was that the Swedish population had comparably low and more variable stochastic population growth rate (λ _s). This pattern was partly explained by the relatively high and varying mortality rates during extreme ice-years in Sweden, and by the lower survival of small individuals during all years. There were also fewer large individuals in Sweden due to lower transitions to the larger size-classes and higher probability of shrinkage. Sensitivities were analogous in the two populations, and showed a high selection pressure for increased individual growth. Elasticities were also similar, with the exception that survival of the smallest individuals (i.e., transition a _1,1), had a higher elasticity on the Isle of Man. Overall, the stochastic growth rate (λ _s) was most sensitive to proportional changes in loop- (i.e., survival within size-class) and, to some extent, growth-transitions in both study areas. These results show that structurally and demographically diverging A. nodosum populations may be similarly sensitive to changes in vital rates. This, in turn, indicates a plastic life history of A. nodosum that may cope with large environmental variability. The results further suggest that environmental change affecting the survival or growth of the larger, reproductive A. nodosum individuals could have severe and regional effects on the abundance and biomass of this species, with potential negative effects on the biodiversity of the associated communities.     

Network position: a key component in the characterization of social personality types

In recent years, animal social interactions have received much attention in terms of personality research (e.g. aggressive or cooperative interactions). However, other components of social behaviour such as those describing the intensity, frequency, directedness and individual repeatability of interactions in animal groups have largely been neglected. Network analysis offers a valuable opportunity to characterize individual consistency of traits in labile social groups and therein provide novel insights to personality research in ways previously not possible using traditional techniques. Should individual network positions be consistently different between individuals under changing conditions, they might reflect expressions of an individual's personality. Here, we discuss a conceptual framework for using network analyses to infer the presence of individual differences and present a statistical test based on randomization techniques for testing the consistency of network positions in individuals. The statistical tools presented are useful because if particular individuals consistently occupy key positions in social networks, then this is also likely to have consequences for their fitness as well as for that of others in the population. These consequences may be particularly significant since individual network position has been shown to be important for the transmission of diseases, socially learnt information and genetic material between individuals and populations.