Comparative physical maps derived from BAC end sequences of tilapia (Oreochromis niloticus)

Background: The Nile tilapia is the second most important fish in aquaculture. It is an excellent laboratory model, and is closely related to the African lake cichlids famous for their rapid rates of speciation. A suite of genomic resources has been developed for this species, including genetic maps and ESTs. Here we analyze BAC endsequences to develop comparative physical maps, and estimate the number of genome rearrangements, between tilapia and other model fish species. Results: We obtained sequence from one or both ends of 106,259 tilapia BACs. BLAST analysis against the genome assemblies of stickleback, medaka and pufferfish allowed identification of homologies for approximately 25,000 BACs for each species. We calculate that rearrangement breakpoints between tilapia and these species occur about every 3 Mb across the genome. Analysis of 35,000 clones previously assembled into contigs by restriction fingerprints allowed identification of longer-range syntenies. Conclusions: Our data suggest that chromosomal evolution in recent teleosts is dominated by alternate loss of gene duplicates, and by intra-chromosomal rearrangements (~one per million years). These physical maps are a useful resource for comparative positional cloning of traits in cichlid fishes. The paired BAC end sequences from these clones will be an important resource for scaffolding forthcoming shotgun sequence assemblies of the tilapia genome. (Résumé d'auteur

Chromosome evolution in fishes: a new challenging proposal from Neotropical species

We present a database containing cytogenetic data of Neotropical actinopterygian fishes from Venezuela obtained in a single laboratory for the first time. The results of this study include 103 species belonging to 74 genera assigned to 45 families and 17 out of the 40 teleost orders. In the group of marine fishes, the modal diploid number was 2n=48 represented in 60% of the studied species, while in the freshwater fish group the modal diploid complement was 2n=54, represented in 21.21 % of the studied species. The average number of chromosomes and the mean FN were statistically higher in freshwater fish than in marine fish. The degree of diversification and karyotype variation was also higher in freshwater fish in contrast to a more conserved cytogenetic pattern in marine fish. In contrast to the assumption according to which 48 acrocentric chromosomes was basal chromosome number in fish, data here presented show that there is an obvious trend towards the reduction of the diploid number of chromosomes from values near 2n=60 with high number of biarmed chromosomes in more basal species to 2n=48 acrocentric elements in more derived Actinopterygi

Improved resistance to degradation of Ir nanoparticles supported onto antimony-doped tin dioxide monitored by identical-location transmission electron microscopy

SSCI-VIDE+ECI2D+LPIInternational audienceSupporting metal nanoparticles is a common approach in heterogeneous gas-phase catalysis to decrease the metal loading, prevent agglomeration and thus minimize the cost of a catalytic conversion. This approach proved particularly successful in proton-exchange membrane fuel cells (PEMFC) where the replacement of Pt-blacks (used in early PEMFCs) by carbon-supported Pt nanoparticles has significantly improved the Pt specific power density. Using the same material’s concepts in proton-exchange membrane water electrolysers (PEMWE) could minimize the noble metal loading especially at the anode where the oxygen evolution reaction (OER) takes place. However, high-surface area carbon supports are rapidly degraded in the operating conditions of a PEMWE anode (E > 1.6 V vs. the reversible hydrogen electrode, T = 80 °C) calling for alternative support materials. In this contribution, Ir nanoparticles have been deposited on different types of antimony doped tin dioxide (ATO) and on Vulcan XC72 as a reference support. Identical-location transmission electron microscopy (IL-TEM) experiments revealed improved stability of Ir nanoparticles supported onto ATO under simulated operating conditions of a PEMWE anode, therefore opening new possibilities for the rational design of highly-active, cost-efficient and stable OER catalysts

Improved resistance to degradation of Ir nanoparticles supported onto antimony-doped tin dioxide monitored by identical-location transmission electron microscopy

SSCI-VIDE+ECI2D+LPIInternational audienceSupporting metal nanoparticles is a common approach in heterogeneous gas-phase catalysis to decrease the metal loading, prevent agglomeration and thus minimize the cost of a catalytic conversion. This approach proved particularly successful in proton-exchange membrane fuel cells (PEMFC) where the replacement of Pt-blacks (used in early PEMFCs) by carbon-supported Pt nanoparticles has significantly improved the Pt specific power density. Using the same material’s concepts in proton-exchange membrane water electrolysers (PEMWE) could minimize the noble metal loading especially at the anode where the oxygen evolution reaction (OER) takes place. However, high-surface area carbon supports are rapidly degraded in the operating conditions of a PEMWE anode (E > 1.6 V vs. the reversible hydrogen electrode, T = 80 °C) calling for alternative support materials. In this contribution, Ir nanoparticles have been deposited on different types of antimony doped tin dioxide (ATO) and on Vulcan XC72 as a reference support. Identical-location transmission electron microscopy (IL-TEM) experiments revealed improved stability of Ir nanoparticles supported onto ATO under simulated operating conditions of a PEMWE anode, therefore opening new possibilities for the rational design of highly-active, cost-efficient and stable OER catalysts

Long-cycling of a water-soluble quinizarin derivative in redox flow batteries: Role of the cut-off voltage on the stability

International audienceTo improve the industrial applicability of aqueous organic redox flow batteries (AORFB), inexpensive redox compounds highly soluble in aqueous medium and stable during cycling are required. Thus, a water-soluble quinizarin derivative, 1,4-dihydroxy-2-carboxymethyl-9,10-anthraquinone (1,4-CDHAQ) prepared by a one-pot synthesis from relatively low-cost leucoquinizarin (widely used as intermediate in the dye industry) is evaluated in AORFB. It exhibits a good solubility in basic medium (> 0.4 M) and a low potential (-0.64 V vs Ag/AgCl) leading to a cell voltage of about 1 V when paired with ferri/ferrocyanide couple. Long-cycling AORFB of 2.5 months performed at a concentration of 0.4 M gives good performance in terms of energy efficiency and power density. The influence of the temperature on ASR values and so on the power density underlines the difficulty to obtain reproducible results at room temperature. A capacity fade rate of 0.008 %/cycle (0.28 %/day) is obtained after 2500 cycles, which is close to other values reported for anthraquinones in strong basic medium for long-cycling tests. Interestingly, the discharge cut-off voltage clearly affects the stability of the battery, leading to the formation of different degradation products as shown by 1H NMR. These results highlight the importance of the cycling conditions to improve the battery performance