Giemsa versus acridine orange staining in the fish micronucleus assay and validation for use in water quality monitoring

This study concerns a comparative analysis of the acridineorange and Giemsastaining procedures for the fish erythrocyte micronucleusassay. The goal was to optimize the assay in the context of field watermonitoring. Fish (Carassius carassius) were exposed to a reference genotoxic agent, cyclophosphamide monohydrate 5 mg l−1 for 2, 4, and 6 days before testing. Slides from each individual were scored using the two procedures. The results show that the assay was more sensitive when acridineorange was used. When slides were Giemsa stained, the presence of ambiguous artefacts, leading to false positives and increasing random variance, reduced the contrast between exposed and control samples. AcridineOrangestaining was then applied in the context of waterqualitymonitoring. Fish were exposed for 4 days to water sampled in two hydrological contexts: basal flow and spring flood. The results show that exposure to spring flood water in an agricultural stream can induce mutagenicity

Practical Application of Matchmaking Problem : Trainee Allocation for Teachers

In this paper, we tackle a complex real-world problem: trainee allocation for primary school teachers in a French teaching Academy. In this real-world problem, the most difficult part consists of generating the preference lists according to the constraints, priorities and wishes in order to reduce this problem into the well-known Hospitals / Residents (HR) problem. Additionally, when we apply the existing algorithm for solving this problem we favorite one community or another. In this paper, we adapt the Swing method to the HR problem and we apply it to this real-world problem in order to balance the different objectives. In this way, the Swing method decreases the management cost of the operation

OH 1720 Megahertz Masers in Supernova Remnants: C-Shock Indicators

Recent observations show that the OH 1720 MHz maser is a powerful probe of the shocked region where a supernova remnant strikes a molecular cloud. We perform a thorough study of the pumping of this maser and find tight constraints on the physical conditions needed for its production. The presence of the maser implies moderate temperatures (50-125 K) and densities (~105 cm-3) and OH column densities of order 1016 cm-2. We show that these conditions can exist only if the shocks are of C-type. J-shocks fail by such a wide margin that the presence of this maser could become the most powerful indicator of C-shocks. These conditions also mean that the 1720 MHz maser will be inherently weak compared with the other ground-state OH masers. All the model predictions are in good agreement with the observations

Mutagenic impact on fish of runoff events in agricultural areas in south-west France

When heavy rainfall follows herbicide application, the intense surface runoff causes stream water contamination. Aquatic organisms are then briefly exposed to a complex mixture of contaminants. The aim of the present study is to investigate the genotoxic impact of such events on fish. A model fish, the Crucian carp (Carassius carassius) was exposed in controlled conditions, for 4 days, to water sampled daily in the Save River (France). The watershed of this stream is representative of agricultural areas in southwest France. Three hydrological conditions were compared: basal flow, winter flood, and spring flood. Chemical analysis of the water samples confirmed the higher contamination of the spring flood water,mainly explained by a peak of metolachlor. Genotoxicity was evaluated by micronucleus (MN) test and comet assay in peripheral erythrocytes. A significant increase in DNA breakdowns compared to controls was detected by the comet assay for all conditions. Exposure to spring flood water resulted in the highest damage induction. Moreover, induced chromosomal damage was only detected in this condition. In addition, fish were exposed, for 4 days, to an experimental mixture of 5 herbicides representative of the spring flood water contamination. Fish exhibited moderate DNA damage induction and no significant chromosomal damage. The mutagenicity induced by field-collected water is then suspected to be the result of numerous interactions between contaminants themselves and environmental factors, stressing the use of realistic exposure conditions. The results revealed a mutagenic impact of water contamination during the spring flood, emphasizing the need to consider these transient events in water quality monitoring programs

Nanotubes de carbone : quels risques pour l’environnement ?

Depuis le coup de projecteur sur les nanotubes de carbone au début des années 1990, les extraordinaires propriétés de ces nanoparticules ont déclenché un effort de recherche considérable qui s’est très rapidement traduit par la commercialisation de nombreux produits en contenant, comme souvent sans aucun recul quant à leur impact potentiel sur l’environnement

More competition in green products markets can help save the planet

To reach net-zero emissions, firms will depend on the relative cost of decarbonising their production lines. However, the abatement goods sector – the sector providing climate change mitigation goods – exhibits low competition and thus high prices. Eric Jondeau, Gregory Levieuge, Jean-Guillaume Sahuc, and Gauthier Vermandel argue that subsidies financed by a carbon tax are an efficient instrument to promote firm entry in the abatement goods sector, fostering competition and lowering the cost of abating carbon emissions. They estimate that such a subsidy would reduce the cost of the net-zero transition, saving $2.9 trillion in world GDP each year until 2060

Biocompatible polymer-assisted dispersion of multi walled carbon nanotubes in water, application to the investigation of their ecotoxicity using Xenopus laevis amphibian larvae

Carbon nanotubes (CNTs) tend to readily agglomerate and settle down in water, while the adsorption of compounds present in natural aquatic media could enhance their dispersion and stabilization in the water column. We designed a new exposure protocol to compare the biological responses of Xenopus laevis larvae exposed in semi-static conditions to size-reduced agglomerates of multi-walled carbon nanotubes (MWCNTs) in suspension in the water column and/or to larger agglomerates. Suspensions were prepared using a combination of a non-covalent functionalization with a non-toxic polymer (either carboxymethylcellulose, CMC, or gum arabic, GA) and mechanical dispersion methods (mainly ultrasonication). The ingestion of agglomerates which have settled down was incriminated in the disruption of the intestinal transit and the assimilation of nutrients, leading to acute and chronic toxicities at the highest tested concentrations. Rise in mortality, decrease in the growth rate and induction of genotoxicity from low concentrations (1 mg/L in the presence of CMC) were evidenced in presence of suspended MWCNTs in the water column. The biological responses seemed to be modulated when GA, a potential antioxidant, was used. We hypothesized that MWCNTs should interfere mainly at the surface of the gills, acting as a potential respiratory toxicant and generally inducing indirect effects