Algorithms and models for decision making in advanced technology systems

Environment Systems and Decisions -     

Study of the Degradation of Poly(ethyl glyoxylate): Biodegradation, Toxicity and Ecotoxicity Assays

Biodegradation of poly (ethyl glyoxylate) (PEtG), a functionalized polyacetal, was investigated over 6?month according to ASTM 5988-96 modified method and compared to micronized cellulose. More than 95?% of the polymer was converted into CO₂ over that period attesting the biodegradability of PEtG. The degradation by-products toxicity and ecotoxicity were evaluated. Toxicity was checked using an innovant non-mammalian toxicological model using the nematode Caenorhabditis elegans. Ecotoxicity was performed using a plant growth test with cress (Lepidium Sativum), and barley (Hordeum vulgare). In all cases, results concluded on the harmlessness of PEtG and relative by-products.     

Ancient Maya drained field agriculture: Its possible application today in the New River Floodplain,Belize C.A.

A drained field complex was identified in the New River near Lamanai, with evidence of Pre-Classic and Classic Mesoamerican occupation. X-ray diffraction analysis of alluvium indicated a dominance of gypsum and a natural sedimentary origin for the fields. Weathering by percolating solutions eliminates the gypsum leaving montmorillonite clay. Sediments deposited on the drained fields during flooding are in excess of 890 kg/ha/year, with an organic content of >50%. As water levels drop, exchangeable bases are leached. The presence of montmorillonite in Layers 1 and 3 and the high CEC of the clay fraction account for the low permeability and high potential productivity of these soils for agriculture. The indication of high levels of inorganic P in Layer 3 is taken as a sign that the layer was the ancient planting surface. By clearing the present forest cover, local farmers would have a nutrient-rich soil suitable for agriculture, that their ancestors also exploited for many centuries.     

Does a parthenogenesis-inducing <Emphasis Type="Italic">Wolbachia</Emphasis> induce vestigial cytoplasmic incompatibility?

Wolbachia is a maternally inherited bacterium that manipulates the reproduction of its host. Recent studies have shown that male-killing strains can induce cytoplasmic incompatibility (CI) when introgressed into a resistant host. Phylogenetic studies suggest that transitions between CI and other Wolbachia phenotypes have also occurred frequently, raising the possibility that latent CI may be widespread among Wolbachia. Here, we investigate whether a parthenogenesis-inducing Wolbachia strain can also induce CI. Parthenogenetic females of the parasitoid wasp Asobara japonica regularly produce a small number of males that may be either infected or not. Uninfected males were further obtained through removal of the Wolbachia using antibiotics and from a naturally uninfected strain. Uninfected females that had mated with infected males produced a slightly, but significantly more male-biased sex ratio than uninfected females that had mated with uninfected males. This effect was strongest in females that mated with males that had a relatively high Wolbachia titer. Quantitative PCR indicated that infected males did not show higher ratios of nuclear versus mitochondrial DNA content. Wolbachia therefore does not cause diploidization of cells in infected males. While these results are consistent with CI, other alternatives such as production of abnormal sperm by infected males cannot be completely ruled out. Overall, the effect was very small (9%), suggesting that if CI is involved it may have degenerated through the accumulation of mutations.     

Everyday vulnerabilities and “social dispositions” in the Malian Sahel,an indication for evaluating future adaptability to water crises?

Since the 1970s, precipitation in the Sahel has decreased and become very irregular, leading to widespread drought, whilst the human need for water has rapidly increased. A new “dispositions”-based approach was adapted in order to analyse human interactions with environmental hazards and applied to the case of Hombori village in north-eastern Mali. This article explores how the population and political stakeholders perceive, live with and respond to the increasing scarcity of water. It also explores how their current vulnerability and ability to cope with variations in available water resources indicate future adaptability to climate shocks. On the one hand, this research shows how the population copes with variations in water resource availability: the population’s socio-spatial organisation explains the inhabitants’ exposure to this problem and some of the factors affecting vulnerability, the elderly and women being the hardest hit. The water issue is generally managed on a “day-to-day” basis and considered a big problem only in the dry season, thus lowering any incentive for self-protection. The main two variables that could explain this kind of risk management are the conflicting local governance and current social rules. On the other hand, the discussion of results, based on a conceptual model of social responses, explains why these current “social dispositions” to cope with and even address the water scarcity issue do not guarantee future adaptability to climate change.