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Feeding and growth variations affect δ 13C and δ 15N budgets during ontogeny in a lepidopteran larva
No full textA bstract Isotopes are widely used in ecology to study food webs and physiology. The fractionation observed between trophic levels in nitrogen and carbon isotopes, explained by isotopes biochemical selectivity, is subject to important within-trophic level variations, leading to imprecision in trophic levels estimation. Understanding the drivers of these variations is thus important to improve the study of food webs. In this study, we characterized this variation by submitting Spodoptera littoralis larvae to a gradient of starvation levels, a factor that we hypothesized would change the trophic fractionation between individuals. The various growth rates that resulted from these starvation levels resulted in a ∼2.5‰within-trophic level variation of the trophic fractionation in both carbon and nitrogen, which is substantial compared to the 3-4‰classically associated with between-trophic levels variations.Hence starved animal sampled in natura may be ranked at a higher trophic level than they really are if food availability is not estimated. We were able to gain an understanding of the effect of growth rate on isotopes fluxes between three easy-to-measure biological materials, food, organism and its wastes (frass), giving insight into physiological processes at play but also conveying helpful information to the sampling framework of field studies
On the planarity of benzyl cyanide
No full textInternational audienceThe microwave spectra of benzyl cyanide, C6H5CH2CN, were recorded using a molecular jet Fourier transform microwave spectrometer operating in the frequency range 2–26.5 GHz. Analyses of the 14N quadrupole hyperfine structures were performed simultaneously with the rotational frequencies. Rotational constants, centrifugal distortion constants, and nuclear quadrupole coupling constants χaa and χbb − χcc were all determined with very high accuracy in a fit containing 465 lines with standard deviation within the measurement accuracy. Results from quantum chemical calculations at many levels of theory employing the MP2 method indicate a non-planar heavy atom skeleton structure, where the CH2CN group is tilted up to 50° with respect to the phenyl ring. This conflicts with results from many calculations employing density functional theory methods and also with the conclusion of a previous microwave spectroscopic work (X.-Z. Liu, R.K. Bohn, S.A. Sorenson, N.S. True, J. Mol. Struct. 243 (1991) 325–339), stating that the CH2CN group and the phenyl ring are in-plane. By comparing the planar defect with those of several planar molecules reported in the literature, and with extensive support from quantum chemistry, we present for the first time evidence suggesting that the heavy atom structure of benzyl cyanide is probably not planar
Non-doped and transition metal-doped CuO nano-powders: structure-physical properties and anti-adhesion activity relationship
No full textInternational audienceBacterial contamination and biofilm formation generate severe problems in many fields
Caractérisation de matériaux composites à gradient fonctionnel bio-inspiré par ondes élastiques : mesures ultrasonores et modélisation mécanique
No full textEn ingénierie, lorsque deux matériaux de nature mécanique très dissemblable se rencontrent, ils présentent des déformations non-uniformes lors d’un chargement, conduisant à des concentrations de contraintes à leur interface, augmentant la probabilité de rupture. Pour relever les défis de conception et de fabrication associés, une stratégie innovante consiste à s’inspirer de l’une des interphases les plus extrêmes de la nature, au niveau de l'attache tendon-os. En effet, celle- ci remplit la tâche difficile de relier deux tissus fortement dissimilaires sur une région de taille submillimétrique. Bien que l'on ne sache pas exactement comment cette interphase biologique atteint de telles performances, les paramètres clés expliquant son efficacité mécanique exceptionnelle reposent sur une combinaison d'ingrédients mécanistiques limités, tels que des gradients fonctionnels de propriétés. Dans ce contexte, cette étude vise à comprendre l’interactions des ondes ultrasonores avec des échantillons obtenus par fabrication additive multi-matériaux, à l’image de l’interphase tendon-os. Un premier groupe est composé d’échantillons macroscopiquement homogènes obtenus en faisant varier la fraction volumique des deux constituants élémentaires, tandis qu’un second groupe est constitué d'échantillons hétérogènes présentant une interphase possédant un gradient fonctionnel de propriétés mécaniques. La caractérisation de l’ensemble de ces échantillons est réalisée en utilisant une méthode de mesure ultrasonore par ondes planes, qui repose sur l’emploi de sondes multiéléments pilotées par une électronique multivoies programmable. Afin d’extraire une information quantitative des signaux mesurés, un modèle de propagation d’ondes tenant compte de la variation spatiale des propriétés mécaniques, ainsi que de la nature viscoélastique du milieu, est développé. Les résultats préliminaires montrent un excellent accord entre les mesures et le modèle, ouvrant ainsi la voie à la caractérisation et à l'optimisation de systèmes multi-matériaux présentant des caractéristiques bio-inspirées complexes
Dynamiques développementales dans les interventions sur le travail : entre héritages et perspectives
No full textInternational audienceL’ouvrage aborde la façon dont des chercheurs et des praticiens prennent en compte les enjeux développementaux dans les interventions sur le travail. Le premier objectif de cet ouvrage est de proposer une mise en patrimoine des avancées sur cette question en évoquant des perspectives actuelles, mais aussi les héritages de travaux précurseurs de l’ergonomie ou de disciplines proches s’intéressant à l’activité humaine. Un deuxième objectif est d'éclairer la diversité des théories du développement qui sont aujourd’hui mises en mouvement dans des expériences concrètes d’intervention. Le troisième objectif est de mettre en lumière la façon dont la visée développementale interroge le positionnement de l’intervenant et des protagonistes de l’intervention. Cet ouvrage offre ainsi des possibilités d’enrichir ce patrimoine, de le faire vivre et de discuter la façon dont les liens entre développements et interventions sont et pourraient être traités
TTC12 loss-of-function mutations cause primary ciliary dyskinesia and unveil distinct dynein assemblymechanisms in motile cilia versus flagella
No full textInternational audienceCilia and flagella are evolutionarily conserved organelles whose motility relies on the outer and inner dynein arm complexes (ODAs/IDAs). Defects in ODAs/IDAs result in primary ciliary dyskinesia (PCD), a disease characterized by recurrent airway infections and male infertility. To date PCD mutations in assembly factors cause a combined ODA/IDA defect, affecting both cilia and flagella. We identified four loss-of-function mutations in TTC12, which encodes a cytoplasmic protein, in four independent families in which affected individuals displayed a peculiar PCD phenotype characterized by the absence of ODAs and IDAs in sperm flagella, contrasting with the sole absence of IDAs in respiratory cilia. We analysed both primary cells from individuals carrying TTC12 mutations and human differentiated airway cells invalidated for TTC12 by a CRISPR-Cas9 approach, as well as TTC12 depletion in the ciliated model, Paramecium tetraureli. Our results revealed an IDA defect restricted to a subset of single-headed IDAs different in flagella and cilia, while TTC12 depletion in Paramecium tetraurelia recapitulated the sperm phenotype. Overall, our study, which identifies TTC12 as a new gene involved in PCD, unveils distinct dynein assembly mechanisms in human motile cilia versus flagella
Nanoparticles on p-type Silicon as Catalysts for the Photoelectrochemical CO2 Conversion
No full textInternational audienc
Trunk spines of trees: a physical defence against bark removal and climbing by mammals?
No full textInternational audienceBackground and Aims The defensive role of spines has previously been related to leaves, young shoots and reproductive organs. However, some woody species harbour spines on their trunks where none of those organs are present. Several explanations are plausible: they could be (1) climbing aids, (2) remnants from defence of leaves or reproductive organs during an earlier development phase, or (3) an as-yet undescribed defence. Here we investigate whether they could play a role against either bark feeding or preventing climbing animals accessing food resources in the tree canopy.Methods We described 31 woody species with spines on their trunk, growing in a botanical garden, to test whether morphological strategies could be identified and suggest what could be their most likely function. As testing their function is difficult experimentally for large pools of species, we performed virtual experiments to evaluate the potential roles of trunk spines against bark removal and climbing animals of different sizes. We then compared for each species and their confamilial non-spiny species the nutritional profiles of leaf, bark and reproductive organs to test whether trunk spines were associated with a nutritious organ (more likely targeted by herbivores).Key Results We identified four morphological syndromes of trunk spines. Two corresponded to already known functions (anchorage for lianas and crown defence against large ground mammals), and two strategies are newly described trait syndromes with traits suggesting a defence against bark feeding and climbing mammals. By simulation, we show how each strategy could translate into defence against debarking and prevent herbivores from climbing.Conclusions We identified trunk spine strategies and the criteria to classify them, their most likely function and the likely feeding mode and size of animal against which different trunk spine strategies may be effective. We discuss further perspectives for testing their function and their ecological significance
