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Biological oxidation of arsenite: batch reactor experiments in presence of kutnahorite and chabazite 总被引:1,自引:0,他引:1
Arsenic represents a threat to all living organisms due to its toxicity which depends on its speciation. This element is carcinogenic, teratogenic and is certainly one of the most important contaminants affecting millions of people around the world. Abiotic and biotic processes control its speciation and distribution in the environment. We have previously shown that a new bacterial strain named ULPAs1 performed oxidation of As(III) (1.33 mM) to As(V) in batch cultures. In order to develop new methods to remove arsenic from contaminated effluents or waste, by bacterial oxidation of As(III) to As(V) followed by its sorption, the conservation of oxidative properties of ULPAs1 was investigated when cultivated in batch reactors in the presence of two solid phases, chabazite and kutnahorite, already used as microorganisms immobilizing materials in biological remediation processes. In parallel, the retention efficiency of these solid phases toward arsenic ions and particularly arsenate was studied. Pure quartz sand was used as a reference material. Kutnahorite efficiently sorbed As(V), chabazite alone performed As(III) oxidation and pure quartz sand did not sorb arsenic at all. The arsenite oxidative properties of ULPAs1 were conserved when cultivated in the presence of quartz or chabazite. 相似文献
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Vincent Mirabet Pierre Fréon Christophe Lett 《Behavioral ecology and sociobiology》2008,63(2):159-171
There is evidence that individuals in animal groups benefit from the presence of knowledgeable group members in different
ways. Experiments and computer simulations have shown that a few individuals within a group can lead others, for a precise
task and at a specific moment. As a group travels, different individuals possessing a particular knowledge may act as temporary
leaders, so that the group will, as a whole, follow their behaviour. In this paper, we use a model to study different factors
influencing group response to temporary leadership. The model is based on four individual behaviours. Three of those, attraction,
repulsion, and alignment, are shared by all individuals. The last one, attraction toward the source of a stimulus, concerns
only a fraction of the group members. We explore the influence of group size, proportion of stimulated individuals, number
of influential neighbours, and intensity of the attraction to the source of the stimulus, on the proportion of the group reaching
this source. Special attention is given to the simulation of large group size, close to those observed in nature. Groups of
100, 400 and 900 individuals are currently simulated, and up to 8,000 in one experiment. We show that more stimulated individuals
and a larger group size both induce the arrival of a larger fraction of the group. The number of influential neighbours and
the intensity of the stimulus have a non-linear influence on the proportion of the group arrival, displaying first a positive
relationship and then, above a given threshold, a negative one. We conclude that an intermediate level of group cohesion provides
optimal transfer information from knowledgeable to naive individuals. 相似文献
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