Influences des glaciaires-interglaciaires sur les ichtyofaunes des eaux douces européennes

Les ichtyofaunes continentales pléistocènes se composent d’espèces strictement d’eaux douces (sténohalines) et d’espèces pouvant s’adapter à des salures différentes (euryhalines) généralement migratrices à l’occasion de leur reproduction. Ces deux catégories de poissons sont caractérisées par des mobilités (possibilité de conquête de milieux) différentes, très limitées chez les sténohalines qui constituent la grande majorité des espèces nous intéressant, elles sont importantes chez les migrateurs. Les poissons sont des organismes fortement dépendants des températures, notamment en période de reproduction, et des compétences des milieux aquatiques. Ils devraient ainsi constituer d’excellents marqueurs des variations paléoclimatiques. L’étude des ichtyofaunes continentales sépare l’Europe en deux zones : 1) une Europe septentrionale fortement soumise aux glaciations dans laquelle seules les espèces « froides » ont survécu chez les sténohalines qui se limiteront à nous renseigner sur la compétence des rivières (Esox lucius). Dans cette aire géographique, les indications de variations de températures seront essentiellement le fait des migrateurs (Alosa alosa et Anguilla anguilla). 2) une Europe méridionale, moins soumise au froid, qui voit coexister « faune froide » et « faune chaude » dans laquelle des observations fines, fondées sur les « biozonations », sont théoriquement réalisables. Malheureusement les modifications climatiques y furent de faible ampleur. Le retour des espèces thermophiles en Europe septentrionale ne se fera, à partir de « zones refuges » d’Europe méridionale (en particulier la mer Noire et ses marges) qu’au Tardiglaciaire. Ce retour des espèces thermophiles s’est vraisemblablement réalisé en passant par les actuelles mers Baltique, du Nord et Manche.Continental ichthyofaunas are formed by species who lived strictly in fresh waters (stenohalines) and by species, which can adapt themselves to different salinities (euryhalines) and are generally migratory for the reproduction. These two fish categories are characterized by different mobilities (possibility to colonize new environment), limited for the stenohaline individuals that constitute the great majority of the species concerned by ichthyofaunas studies, they are important for the migrants. The fishes are very dependents on temperature, notably during the reproduction, and on the competence of the aquatic environments. So they should constitute excellent proxies of the environmental variations. In fact the composition of the Pleistocene ichthyofaunas divides Europe in two areas: 1) the North was under the influence of the glaciations: only the cold taxa have survived among the stenohaline, they will only provide information about competence of the aquatic environments (Esox lucius). In this geographic area, the indication of temperature variation will be obtained through the study of the migratory species (Alosa alosa and Anguilla anguilla). 2) in the South, cold and warm species have coexisted and close detailed observations, based on “biozonations”, are in theory possible. Unfortunately, climatic modifications are characterized by limited amplitudes. The come back of thermophilic species in Northern Europe will only happen during the Tardiglacial from “refuge zone” of the Southern Europe (particularly from the Black Sea and its margins). They have probably passed by the Baltic Sea, North Sea and the Channel

Формирование этапов выбора приоритетных стратегий развития порта

У статті розглянуті етапи процесу вибору пріоритетних стратегій розвитку порту. В умовах ринкової економіки обґрунтовано таку послідовність етапів: встановлення базового набору альтернативних стратегій, формування критеріїв оцінки альтернативних стратегій, обґрунтування шкали вимірювання переваг стратегій, вибір методу оцінки альтернативних стратегій, вибір пріоритетних стратегій. Визначено зміст кожного з етапів вибору пріоритетних стратегій розвитку порту.The stages of process of choice of priorities strategies of development of port are considered in the article. In the conditions of market economy the following sequence of stages is grounded: establishments of base set of alternative strategies, establishments of criteria of estimation of alternative strategies choice of scale of measuring of preference of strategies, choice of method of estimation of alternative strategies, choice of priorities strategies maintenance of each of stages of choice of priorities strategies of development of port is Certain

Towards integrated management of the pests and pathogens of cassava in Africa

Studies on pathogenic agents of cultivated plants are generally organised on a binomial basis with examination of a host plant and specific parasites or pests. As cassava in Africa has few important pests and they display a limited range of biological features and relations with the host, it was feasible for ORSTOM (L'Institut français de recherche scientifique pour le développement en coopératon) researchers to study each of them over a period of 25 years in Côte d'lvoire, Congo and Togo and such work is currently in progress in Benin and France. The diseases and pests concerned are African cassava mosaic disease and its whitefly vector (Bemisia tahaci), cassava bacterial blight caused by Xanthomonas campestris pv manihotis, cassava mealybug (Phenacoccus manihoti), and cassava green mite (Mononychelus progresivus). Research initially concerned only specific cassava-pathogen or cassava-pest combinations, without attention being paid to the system as a whole, despite obvious epidemic convergences resulting from a common environment, analogies between effects on the host plant and probable interactions between the various pests of the same crop. A biocenotic approach was developed to integrate the various research activities. It is aimed at analysis of the functioning of plant-pathogen and plant-pest systems and enables the design and evaluation of options for integrated management. 'Transversal' comparisons of cassava parasite models cover pathogenic agents (pests and diseases) and their variability, their biological cycles and the climatic factors affecting them, relations with the host (genetic variability, physiology and crop management), the effect of entomophagous species and entomopathogens on phytophagous pests and the integration potential of modelling. The ORSTOM studies show the complexity of the ecology of pathogenic agents and pests in the cassava biocenosis. The extent of the cassava cropping area and the variety of production situations, the variability of pests (phytophagous and entomophagous organisms) and diseases and the many interactions between the factors regulating epidemic mechanisms leads to a complex mosaic whose structure is described. The various sequences of analysis of a system of parasite constraints are shown in matrix form (variability of pathogenic agents, vectors and phytophagous organisms, host-parasite relation modes, epidemiology and population dynamics, modelling) for the various organisms investigated to date. The analysis reveals the fundamental achievements and gaps in knowledge and also the most appropriate areas for combining approaches. The body of knowledge assembled at different sites, during different periods and concerning a variety of organisms and the analysis of this knowledge show that it is not necessary at this stage to collect new information but to make a synthesis (modelling) that will open up original lines of research with combinations of approaches and solutions

Data mining approach identifies research priorities and data requirements for resolving the red algal tree of life

<p>Abstract</p> <p>Background</p> <p>The assembly of the tree of life has seen significant progress in recent years but algae and protists have been largely overlooked in this effort. Many groups of algae and protists have ancient roots and it is unclear how much data will be required to resolve their phylogenetic relationships for incorporation in the tree of life. The red algae, a group of primary photosynthetic eukaryotes of more than a billion years old, provide the earliest fossil evidence for eukaryotic multicellularity and sexual reproduction. Despite this evolutionary significance, their phylogenetic relationships are understudied. This study aims to infer a comprehensive red algal tree of life at the family level from a supermatrix containing data mined from GenBank. We aim to locate remaining regions of low support in the topology, evaluate their causes and estimate the amount of data required to resolve them.</p> <p>Results</p> <p>Phylogenetic analysis of a supermatrix of 14 loci and 98 red algal families yielded the most complete red algal tree of life to date. Visualization of statistical support showed the presence of five poorly supported regions. Causes for low support were identified with statistics about the age of the region, data availability and node density, showing that poor support has different origins in different parts of the tree. Parametric simulation experiments yielded optimistic estimates of how much data will be needed to resolve the poorly supported regions (ca. 10³to ca. 10⁴nucleotides for the different regions). Nonparametric simulations gave a markedly more pessimistic image, some regions requiring more than 2.8 10⁵nucleotides or not achieving the desired level of support at all. The discrepancies between parametric and nonparametric simulations are discussed in light of our dataset and known attributes of both approaches.</p> <p>Conclusions</p> <p>Our study takes the red algae one step closer to meaningful inclusion in the tree of life. In addition to the recovery of stable relationships, the recognition of five regions in need of further study is a significant outcome of this work. Based on our analyses of current availability and future requirements of data, we make clear recommendations for forthcoming research.</p

Arancou (Bourrouilla), Bilan scientifique 2005 du Service Régional de l'Archéologie Aquitaine

Bilan scientifique 2006 du Service Régional de l'Archéologie AquitaineBilan de la compagne de fouille à la grotte Bourrouilla à Arancou (64

Entire large solutions for semilinear elliptic equations

We analyze the semilinear elliptic equation $\Delta u=\rho(x) f(u)$, $u>0$ in ${\mathbf R}^D$ $(D\ge3)$, with a particular emphasis put on the qualitative study of entire large solutions, that is, solutions $u$ such that $\lim_{|x|\rightarrow +\infty}u(x)=+\infty$. Assuming that $f$ satisfies the Keller-Osserman growth assumption and that $\rho$ decays at infinity in a suitable sense, we prove the existence of entire large solutions. We then discuss the more delicate questions of asymptotic behavior at infinity, uniqueness and symmetry of solutions.Comment: Journal of Differential Equations 2012, 28 page

No distributed quantum advantage for approximate graph coloring

We give an almost complete characterization of the hardness of $c$-coloring $\chi$-chromatic graphs with distributed algorithms, for a wide range of models of distributed computing. In particular, we show that these problems do not admit any distributed quantum advantage. To do that: 1) We give a new distributed algorithm that finds a $c$-coloring in $\chi$-chromatic graphs in $\tilde{\mathcal{O}}(n^{\frac{1}{\alpha}})$ rounds, with $\alpha = \bigl\lfloor\frac{c-1}{\chi - 1}\bigr\rfloor$. 2) We prove that any distributed algorithm for this problem requires $\Omega(n^{\frac{1}{\alpha}})$ rounds. Our upper bound holds in the classical, deterministic LOCAL model, while the near-matching lower bound holds in the non-signaling model. This model, introduced by Arfaoui and Fraigniaud in 2014, captures all models of distributed graph algorithms that obey physical causality; this includes not only classical deterministic LOCAL and randomized LOCAL but also quantum-LOCAL, even with a pre-shared quantum state. We also show that similar arguments can be used to prove that, e.g., 3-coloring 2-dimensional grids or $c$-coloring trees remain hard problems even for the non-signaling model, and in particular do not admit any quantum advantage. Our lower-bound arguments are purely graph-theoretic at heart; no background on quantum information theory is needed to establish the proofs