Hydrologic and land use impacts on vegetation growth and NPP at the watershed scale in a semi-arid environment

Significant, adverse climatic change and drastically increased demographic pressure have strongly affected, in recent years, the hydrology and environment in the semi-arid Sahel region of West Africa. Marked rain deficits have coincided with increased water runoff, meaning less water availability for the vegetation. Conversely, changes in vegetation cover have had strong repercussions on the hydrologic cycle. To study these phenomena, the coupling of two explicit, process-based models, of catchment hydrology and of mixed vegetation cover, respectively, has been undertaken and applied to a 2 km² site in Niger. Some of the first significant results are presented herein. Some are consistent with intuitive judgments that can be made in the absence of a coupled model, others are much less so and show that representation through model coupling of hydrosphere/biosphere interactions is essential to produce more reliable analyses and projections. In particular, it is found that the relation of biomass productivity to rainfall under this dry, water-limited climate is not as straightforward as one would expect, more specifically, that its main control may not be the total season rainfall.     

Behavioural reactivation and subjective assessment of the state of vigilance--application to simulated car driving.

The frequency of some behaviour (such as self-centred gestures) increases during a task that leads to the occurrence of low-vigilance episodes. These gestures can be useful in stimulating oneself. A study carried out in 20 adults has enabled us to state that motor activity (recorded with an actimeter) increases with the duration of a monotonous driving task and sleep deprivation. The analysis of the scores recorded using the Karolinska Sleepiness Scale has shown that drivers can assess the deterioration of their state of vigilance according to the actual sleep preceding the driving test. Finally, the joint analysis of the subjective and objective data revealed a co-variation of these two types of indices. We discuss the stimulatory function of the motor activity in a task leading to the occurrence of low-vigilance episodes by investigating, among other things, the use, conscious or not, of this type of activity.     

Three Different Topics for Bioremediation Application on Soils and Waters Contaminated with Aromatic Compounds, by Using Immobilized Bacteria

Molecular techniques and modelling are presented as powerful tools required in the performance of efficient soil and water bioremediation systems. An Escherichia coli CC118-D strain was constructed by inserting the Klebsiella pneumoniae hpa B gene, coding for the unstable 3,4-dihydroxyphenylacetate 2,3-dioxygenase, into its chromosome. When the constructed strain was immobilized, both enzyme stability and viability increased along the studied period, in absence of antibiotic. We proposed this strategy as an approach to overcoming plasmid instability and to enhance enzyme activity and stability, avoiding antibiotic utilization. A model was developed to understand and predict the behaviour of bacteria and pollutants in a bioreactor system, considering: fluid dynamics, molecular/cellular scale processes and biofilm formation.     

Stage dependent susceptibility to lead in Bufo arenarum embryos

The stage dependent susceptibility to lead in amphibian development was studied by exposing Bufo arenarum embryos during neurulae, neuromuscular activity and gill circulation stages for twenty hours to 1 ppm Pb(2+). Survival, malformations and behavioral disorders were evaluated. The embryonic susceptibility to lead was markedly stage dependent. The survival at the neuromuscular activity stage was approximately half that of the other two periods; concerning malformations, the gill circulation stage was the least sensitive. The observed malformations consisted of failed closure of neural tube, hydropsy, small and cylindrical tails, reduced body size and incurvations in the body axis. Some alterations occurred in all experimental groups and therefore were considered non-dependent on the period of treatment. In all experimental embryos, neurological disorders such as trembles and loss of equilibrium were observed.     

Michoacán centre for science and technology education a summary of the project

Summary This paper looks at the problems of science and technology education in Mexico, and proposes ways in which the quality of education at every level can be improved. It advocates an interdisciplinary approach, and from that approach to science education, the development of environmental education.Prof. Gutiérrez-Vázquez received his training in microbiology and biochemistry in the National Polytechnic Institute in his native Mexico City, receiving his degree in 1954. He went from instructor to assistant professor (1950–1960), becoming a full professor, deputy dean and then dean of the Faculty of Biology in the same Institute (1961–1969); he published two books and some 20 papers dealing with the physiology of tubercle bacillus and other mycobacteria, as well as with other topics on microbiology. More recently (1970 to date), he became a full professor in the Center for Advanced Studies of the same Institute, where he has been head of the Department of Educational Research (1972–1981) and carried out research and development projects on science education for children and adolescents. During this period he has published some 20 more books and 30 odd papers, and written more than 80 science programmes for commercial television.     

Specialization of the entomopathogenic nematode Steinernema scapterisci with its mutualistic Xenorhabdus symbiont

The level of specialization of the entomopathogenic nematode Steinernema scapterisci with its native Xenorhabdus symbiont was investigated by testing (1) the influence of non-native bacterial strains on nematode fitness within an insect-host (Galleria mellonella) and (2) specificity of the association between the nematode infective juveniles and non-native bacteria. All non-native Xenorhabdus spp. or Photorhabdus spp. strains tested were mutualistically associated with other entomopathogenic nematodes in nature. We showed that most of the Xenorhabdus spp. strains tested led to an insignificant difference of the nematode's fitness compared to the one obtained with the native bacterium. Conversely, Photorhabdus spp. strains almost entirely abolished nematode reproduction. The phylogenetic analysis of bacterial strains tested, showed that there was a negative correlation between S. scapterisci's reproduction rate with a bacterial strain and the genetic distance of this bacterial strain from the native one. We also showed that the native bacterium was the only one which was transmitted by S. scapterisci's infective juveniles. All these results, suggested a specialization between S. scapterisci and its native Xenorhabdus. As the same phenomenon was already demonstrated in the association between S. carpocapsae and X. nematophila, specialization between partners would not be an exception in entomopathogenic nematode-bacteria interactions. Nevertheless, S. scapterisci showed a dramatically higher compatibility with non-native Xenorhabdus spp. strains than did S. carpocapsae, suggesting differences in the co-evolutionary processes between nematodes and bacteria in these two model systems.Table 1 List of the bacterial strains, native nematode species with their geographical origin, accession numbers of bacterial 16S rDNA partial sequences and number of combination experiments for each bacterium tested