Empirical study on collaborative writing: What do coauthors do, use, and like

Abstrac

Venom toxins in the exploration of molecular, physiological and pathophysiological functions of acid-sensing ion channels

International audienceAcid-sensing ion channels (ASICs) are voltage-independent proton-gated cation channels that are largely expressed in the nervous system as well as in some non-neuronal tissues. In rodents, six different isoforms (ASIC1a, 1b, 2a, 2b, 3 and 4) can associate into homo-or hetero-trimers to form a functional channel. Specific polypeptide toxins targeting ASIC channels have been isolated from the venoms of spider (PcTx1), sea anemone (APETx2) and snakes (MitTx and mambalgins). They exhibit different and sometimes partially overlapping pharmacological profiles and are usually blockers of ASIC channels, except for MitTx, which is a potent activator. This review focuses on the use of these toxins to explore the structure-function relationships, the physiological and the pathophysiological roles of ASIC channels, illustrating at the same time the therapeutic potential of some of these natural compounds

Electron Paramagnetic Resonance Study of a Photosynthetic Microbial Mat and Comparison with Archean Cherts

International audienceOrganic radicals in artificially carbonized biomass dominated by oxygenic and non-oxygenic photosynthetic bacteria, Microcoleus chthonoplastes-like and Chloroflexus-like bacteria respectively, were studied by Electron Paramagnetic Resonance (EPR) spectroscopy. The two bacteria species were sampled in mats from a hypersaline lake. They underwent accelerated ageing by cumulative thermal treatments to induce progressive carbonization of the biological material, mimicking the natural maturation of carbonaceous material of Archean age. For thermal treatments at temperatures higher than 620 °C, a drastic increase in the EPR linewidth is observed in the carbonaceous matter from oxygenic photosynthetic bacteria and not anoxygenic photosynthetic bacteria. This selective EPR linewidth broadening reflects the presence of a catalytic element inducing formation of radical aggregates, without affecting the molecular structure or the microstructure of the organic matter, as shown by Raman spectroscopy and Transmission Electron Microscopy. For comparison, we carried out an EPR study of organic radicals in silicified carbonaceous rocks (cherts) from various localities, of different ages (0.42 to 3.5 Gyr) and having undergone various degrees of metamorphism, i.e. various degrees of natural carbonization. EPR linewidth dispersion for the most primitive samples was quite significant, pointing to a selective dipolar broadening similar to that observed for carbonized bacteria. This surprising result merits further evaluation in the light of its potential use as a marker of past bacterial metabolisms, in particular oxygenic photosynthesis, in Archean cherts

Interpreting human and avatar facial expressions

Abstract. This paper investigates the impact of contradictory emotional content on people's ability to identify the emotion expressed on avatar faces as compared to human faces. Participants saw emotional faces (human or avatar) coupled with emotional texts. The face and text could either display the same or different emotions. Participants were asked to identify the emotion on the face and in the text. While they correctly identified the emotion on human faces more often than on avatar faces, this difference was mostly due to the neutral avatar face. People were no better at identifying a facial expression when emotional information coming from two sources was the same than when it was different, regardless of whether the facial expression was displayed on a human face or on an avatar face. Finally, people were more sensitive to context when trying to identify the emotion in the accompanying text

Interspecific competition between entomopathogenic nematodes (Steinernema) is modified by their bacterial symbionts (Xenorhabdus)

BACKGROUND: Symbioses between invertebrates and prokaryotes are biological systems of particular interest in order to study the evolution of mutualism. The symbioses between the entomopathogenic nematodes Steinernema and their bacterial symbiont Xenorhabdus are very tractable model systems. Previous studies demonstrated (i) a highly specialized relationship between each strain of nematodes and its naturally associated bacterial strain and (ii) that mutualism plays a role in several important life history traits of each partner such as access to insect host resources, dispersal and protection against various biotic and abiotic factors. The goal of the present study was to address the question of the impact of Xenorhabdus symbionts on the progression and outcome of interspecific competition between individuals belonging to different Steinernema species. For this, we monitored experimental interspecific competition between (i) two nematode species: S. carpocapsae and S. scapterisci and (ii) their respective symbionts: X. nematophila and X. innexi within an experimental insect-host (Galleria mellonella). Three conditions of competition between nematodes were tested: (i) infection of insects with aposymbiotic IJs (i.e. without symbiont) of both species (ii) infection of insects with aposymbiotic IJs of both species in presence of variable proportion of their two Xenorhabdus symbionts and (iii) infection of insects with symbiotic IJs (i.e. naturally associated with their symbionts) of both species. RESULTS: We found that both the progression and the outcome of interspecific competition between entomopathogenic nematodes were influenced by their bacterial symbionts. Thus, the results obtained with aposymbiotic nematodes were totally opposite to those obtained with symbiotic nematodes. Moreover, the experimental introduction of different ratios of Xenorhabdus symbionts in the insect-host during competition between Steinernema modified the proportion of each species in the adults and in the global offspring. CONCLUSION: We showed that Xenorhabdus symbionts modified the competition between their Steinernema associates. This suggests that Xenorhabdus not only provides Steinernema with access to food sources but also furnishes new abilities to deal with biotic parameters such as competitors

Use of electrochemical techniques to study the corrosion of metals in model fluoride melts

Molten fluorides are appealing coolants for innovative nuclear systems but structural alloys may undergo corrosion at high temperature. Because corrosion primarily occurs via electrochemical reactions, electrochemical techniques are ideal for the study of corrosion thermochemistry and kinetics. Examples are given. An electrochemical series was established using voltammetry in LiF-NaF at 1173 K. Stability increases in the following order: Na, Cr, Fe, Ni, Mo/W, Ag, Au. Various alloys were also classified according to their oxidation resistance. A cathodic protection method was developed to curb the intergranular attack of some nickel alloys in molten LiF-CaF₂-MgF₂-ZrF₄ containing tellurium vapor at 953 K. Voltammetry and polarization resistance measurement were used to estimate the rate of chromium selective dissolution for nickel base alloys immersed in LiF-NaF at 1073 K and 1173 K

Atypical/Nor98 scrapie:properties of the agent, genetics, and epidemiology

Atypical/Nor98 scrapie cases in sheep were diagnosed for the first time in Norway in 1998. They are now identified in small ruminants in most European countries and represent an increasingly large proportion of the scrapie cases diagnosed in Europe. Atypical/Nor98 scrapie isolates have shown to be experimentally transmissible into transgenic mice and sheep but the properties of the TSE agent involved, like its biological and biochemical features, are so clearly distinct from the agent involved in classical scrapie that they have provided a challenging diagnostic for many years. No strain diversity has yet been identified among the atypical/Nor98 scrapie sample cases. The genetic predisposition of the sheep affected by atypical/Nor98 scrapie is almost inverted compared to classical scrapie, and the exact origin of this sporadic TSE strain is still speculative, but a spontaneous, non-contagious origin, like sporadic Creutzfeldt-Jakob disease in humans, can not be excluded. Further transmission and epidemiological studies are needed to better address this hypothesis

Zn1-xMgxO thin films deposited by original Infrared assisted Spray Chemical Vapor Deposition: evaluation of structural, optical and electrical properties with the aim of provide Cu(In,Ga)Se2 based photovoltaic devices

In this work, magnesium doped zinc oxide (Zn1-xMgxO) thin films were deposited using an original infrared assisted Spray Chemical Vapor Deposition (Spray-CVD) technique on borosilicate glass substrates. With a simple, safe and cost-effective apparatus, Zn1-xMgxO thin films was studied in a range of 0 to 40% in precursor mass ratio r = [Mg]/([Zn]+[Mg]). The optimal deposition temperature was 500°C. X-ray diffraction analysis confirmed the presence of magnesium in the hexagonal Wurtzite crystal lattice of zinc oxide for r values lower than 30%. The optical properties have been investigated by spectrophotometry and showed that the transparency is higher than 80% in the visible and infrared spectral domain for r values lower than 20%. The band gap energy increased from 3.28 to 3.94 eV (0 < r < 40%), and the resistivity of the samples increased from 4.16.10-2 to 7.09.10+3 Ω.cm (Hall effect measurement). Additional characterizations have been realized by X-ray fluorescence (XRF) and energy dispersive X-ray spectrometry (EDX). All results demonstrate that Zn1-xMgxO thin films with r = 20% obtained by our Spray-CVD method is an interesting candidate for buffer layer application in Cu(In,Ga)Se2 based solar cells

Canine oocyte maturation, fertilization and early embryonic development

Canine reproduction has several distinctive features. Firstly, folliculogenesis is unusual as numerous ovarian follicles contain several oocytes (polyovular follicles). Secondly, unlike in other mammalian species, oocytes at the time of ovulation are still at an immature stage (prophase I, germinal vesicle stage), and complete their maturation in the oviduct. This phenomenon is not easy to observe because the canine oocyte has a high lipid content and its DNA is difficult to visualise. Fertilization of immature oocytes has been observed in vitro, however in vivo, fertilization occurs in oocytes at the metaphase II stage, approximately 50 hours after ovulation. The 2-pronuclei stage is reached 72-124 hours after ovulation, and 2-cell embryos are present 96-168 hours after ovulation. The oviductal phase is long and embryos enter the uterine cavity at the morula or early blastocyst stage 10-12 days following ovulation. Implantation occurs 18 to 21 days after ovulation. In spite of all these specificities, studies on canine reproduction were so far mainly clinical. However, current research is focusing on fundamental knowledge, namely the mechanisms controlling oocyte maturation in vivo, in the hope to improve the yield of oocyte maturation in vitro, which is still very low.Plusieurs aspects de la reproduction sont particuliers à l'espèce canine. D'une part, la folliculogenèse est singulière car chez la chienne, de nombreux follicules ovariens contiennent plusieurs ovocytes (follicules poly-ovocytaires). D'autre part, contrairement à ce qui est observé chez les autres femelles de mammifères, au moment de l'ovulation, l'ovocyte est encore à un stade immature (prophase I, stade vésicule germinative ou VG) et la maturation ovocytaire se poursuit ensuite dans l'oviducte. L'observation de ce phénomène est rendue complexe par le fait que l'ovocyte canin est riche en lipides et que son ADN est donc difficile à visualiser. In vitro, la fécondation d'ovocytes immatures a été observée mais in vivo, elle a lieu au moment où les ovocytes ont atteint le stade métaphase II, environ 50 h après l'ovulation. Les premiers pronoyaux sont présents 72 à 124 h après l'ovulation et les premiers embryons au stade 2-cellules sont observés 96 à 168 h après l'ovulation. La période de transit dans l'oviducte est longue et les embryons n'atteignent l'utérus qu'au stade morula ou jeune blastocyste, 10 à 12 jours après l'ovulation et l'implantation a ensuite lieu vers 18 à 21 jours. Globalement, malgré toutes ces particularités, les recherches sur la reproduction dans l'espèce canine étaient jusqu'alors essentiellement cliniques. Les travaux visent maintenant à améliorer les connaissances fondamentales, notamment concernant les mécanismes contrôlant la maturation ovocytaire in vivo, pour pouvoir ensuite améliorer les rendements de la maturation in vitro, actuellement très faibles