Comparaison de méthodes de décomposition de distributions polymodales de fréquences de longueurs en distributions unimodales successives (Normsep - Mix - Maximums successifs), application aux "bossus" (Pseudotolithus elongatus) du Congo

A partir des mensurations effectuées sur des échantillons de #Pseudotolithus elongatus$ au Congo dans les années 60 et des sous-échantillons récoltés pour l'estimation de l'âge par interprétation des otolithes, nous avons pu comparer les résultats obtenus dans la décomposition des distributions de fréquences de longueurs en distributions unimodales successives par différentes méthodes. La méthode des maximums successifs a donné des résultats pratiquement identiques à celle des "lectures d'âges". Les programmes NORMSEP et MIX ont donné pour leur part des résultats beaucoup plus difficiles à homologuer d'un point de vue biologique en dépit de leurs finesses mathématiques. Les distributions de fréquences de longueurs d'une cohorte étant souvent symétriques, l'application de la méthode des maximums successifs est fortement conseillée en l'absence de certitude sur la normalité. (Résumé d'auteur

Impurity conduction in phosphorus-doped buried-channel silicon-on-insulator field-effect transistors

We investigate transport in phosphorus-doped buried-channel metal-oxide-semiconductor field-effect transistors at temperatures between 10 and 295 K. In a range of doping concentration between around 2.1 and 8.7 x 1017 cm-3, we find that a clear peak emerges in the conductance versus gate-voltage curves at low temperature. In addition, temperature dependence measurements reveal that the conductance obeys a variable-range-hopping law up to an unexpectedly high temperature of over 100 K. The symmetric dual-gate configuration of the silicon-on-insulator we use allows us to fully characterize the vertical-bias dependence of the conductance. Comparison to computer simulation of the phosphorus impurity band depth-profile reveals how the spatial variation of the impurity-band energy determines the hopping conduction in transistor structures. We conclude that the emergence of the conductance peak and the high-temperature variable-range hopping originate from the band bending and its change by the gate bias. Moreover, the peak structure is found to be strongly related to the density of states (DOS) of the phosphorus impurity band, suggesting the possibility of performing a novel spectroscopy for the DOS of phosphorus, the dopant of paramount importance in Si technology, through transport experiments.Comment: 9 figure

Quantum coherent control of highly multipartite continuous-variable entangled states by tailoring parametric interactions

The generation of continuous-variable multipartite entangled states is important for several protocols of quantum information processing and communication, such as one-way quantum computation or controlled dense coding. In this article we theoretically show that multimode optical parametric oscillators can produce a great variety of such states by an appropriate control of the parametric interaction, what we accomplish by tailoring either the spatio-temporal shape of the pump, or the geometry of the nonlinear medium. Specific examples involving currently available optical parametric oscillators are given, hence showing that our ideas are within reach of present technology.Comment: 14 pages, 5 figure

Roles of the DYRK Kinase Pom2 in Cytokinesis, Mitochondrial Morphology, and Sporulation in Fission Yeast

Pom2 is predicted to be a dual-specificity tyrosine-phosphorylation regulated kinase (DYRK) related to Pom1 in Schizosaccharomyces pombe. DYRKs share a kinase domain capable of catalyzing autophosphorylation on tyrosine and exogenous phosphorylation on serine/threonine residues. Here we show that Pom2 is functionally different from the well-characterized Pom1, although they share 55% identity in the kinase domain and the Pom2 kinase domain functionally complements that of Pom1. Pom2 localizes to mitochondria throughout the cell cycle and to the contractile ring during late stages of cytokinesis. Overexpression but not deletion of pom2 results in severe defects in cytokinesis, indicating that Pom2 might share an overlapping function with other proteins in regulating cytokinesis. Gain and loss of function analyses reveal that Pom2 is required for maintaining mitochondrial morphology independently of microtubules. Intriguingly, most meiotic pom2Δ cells form aberrant asci with meiotic and/or forespore membrane formation defects. Taken together, Pom2 is a novel DYRK kinase involved in regulating cytokinesis, mitochondrial morphology, meiosis, and sporulation in fission yeast

Functional Interactions between Retinoblastoma and c-MYC in a Mouse Model of Hepatocellular Carcinoma

Inactivation of the RB tumor suppressor and activation of the MYC family of oncogenes are frequent events in a large spectrum of human cancers. Loss of RB function and MYC activation are thought to control both overlapping and distinct cellular processes during cell cycle progression. However, how these two major cancer genes functionally interact during tumorigenesis is still unclear. Here, we sought to test whether loss of RB function would affect cancer development in a mouse model of c-MYC-induced hepatocellular carcinoma (HCC), a deadly cancer type in which RB is frequently inactivated and c-MYC often activated. We found that RB inactivation has minimal effects on the cell cycle, cell death, and differentiation features of liver tumors driven by increased levels of c-MYC. However, combined loss of RB and activation of c-MYC led to an increase in polyploidy in mature hepatocytes before the development of tumors. There was a trend for decreased survival in double mutant animals compared to mice developing c-MYC-induced tumors. Thus, loss of RB function does not provide a proliferative advantage to c-MYC-expressing HCC cells but the RB and c-MYC pathways may cooperate to control the polyploidy of mature hepatocytes

E2F1 Mediated Apoptosis Induced by the DNA Damage Response Is Blocked by EBV Nuclear Antigen 3C in Lymphoblastoid Cells

EBV latent antigen EBNA3C is indispensible for in vitro B-cell immortalization resulting in continuously proliferating lymphoblastoid cell lines (LCLs). EBNA3C was previously shown to target pRb for ubiquitin-proteasome mediated degradation, which facilitates G1 to S transition controlled by the major transcriptional activator E2F1. E2F1 also plays a pivotal role in regulating DNA damage induced apoptosis through both p53-dependent and -independent pathways. In this study, we demonstrate that in response to DNA damage LCLs knocked down for EBNA3C undergo a drastic induction of apoptosis, as a possible consequence of both p53- and E2F1-mediated activities. Importantly, EBNA3C was previously shown to suppress p53-induced apoptosis. Now, we also show that EBNA3C efficiently blocks E2F1-mediated apoptosis, as well as its anti-proliferative effects in a p53-independent manner, in response to DNA damage. The N- and C-terminal domains of EBNA3C form a stable pRb independent complex with the N-terminal DNA-binding region of E2F1 responsible for inducing apoptosis. Mechanistically, we show that EBNA3C represses E2F1 transcriptional activity via blocking its DNA-binding activity at the responsive promoters of p73 and Apaf-1 apoptosis induced genes, and also facilitates E2F1 degradation in an ubiquitin-proteasome dependent fashion. Moreover, in response to DNA damage, E2F1 knockdown LCLs exhibited a significant reduction in apoptosis with higher cell-viability. In the presence of normal mitogenic stimuli the growth rate of LCLs knockdown for E2F1 was markedly impaired; indicating that E2F1 plays a dual role in EBV positive cells and that active engagement of the EBNA3C-E2F1 complex is crucial for inhibition of DNA damage induced E2F1-mediated apoptosis. This study offers novel insights into our current understanding of EBV biology and enhances the potential for development of effective therapies against EBV associated B-cell lymphomas

Tissus durs et âge individuel des vertébrés

Des écailles de bar ont été prélevées pour alimenter des études de dynamique des populations. Compte tenu de l'allocation proportionnelle utilisée, la composition en âge de l'échantillon pourrait être utilisée pour estimer celle de la population. Mais la structure démographique ainsi obtenue est biaisée dans le sens d'un rajeunissement du fait de la plus forte probabilité, chez les individus âgés, de rencontrer des écailles régénérées. Il devient alors nécessaire d'utiliser la composition en taille convertie en composition en âge au moyen d'une clé taille-âge. (Résumé d'auteur

Incidental mammal catches in pelagic trawl fisheries of the North east Atlantic

The marine mammals catch rate of pelagic trawling in the North-east Atlantic has not previously been assessed by direct observation. A study was funded by the European Commission to collect information on the catches of fish and mammals by several pelagic trawl fisheries from England, France, Ireland and Netherlands. This paper presents a summary of the results, as far as the by catch of marine mammals is concerned, between 1994-1995. It was not possible to carry out observations of all the pelagic trawl fisheries but a total of eleven fisheries were investigated in this study. In one fishery (Irish herring (Thunnus) trawling), four grey seals (Phoca vitulina) were caught in separate trawls during slightly more than 100 hours trawling. Cetaceans (dolphins) were incidentally caught in four pelagic fisheries (Dutch horsemackerel, (Trachurus trachurus) French tuna, (Thunnus) French hake, (Merluccius) French sea bass trawling Dicentrachus labrax). Eleven different trawls caught a total of eighteen dolphins (Stenella). These catches were observed during 1300 hours of deployment of the trawls. Visual inspection of pelagic trawl emptied using fish pumps was thought to be unreliable for the detection of cetacean bycatch. The extent of observation and number of observed bycatches is however too small to make a reliable assessment of overall by catch rates. In those fisheries where cetacean bycatch occurred rates were between 1.1 and 1.5 cetaceans per 100 hours of trawling