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Individual heterogeneity in diet and foraging behaviour is common in wild animal populations, and can be a strong determinant of how populations respond to environmental changes. Within populations, variation in foraging behaviour and the occurrence of individual tactics in relation to resources distribution can help explain differences in individual fitness, and ultimately identify important factors affecting population dynamics. We examined how foraging behaviour and habitat during the breeding period related to the physiological state of a long-ranging seabird adapted to sea ice, the Antarctic petrel Thalassoica antarctica. Firstly, using GPS tracking and state-switching movement modelling (hidden Markov models) on 124 individual birds, we tested for the occurrence of distinct foraging tactics within our study population. Our results highlight a large variation in the movement and foraging behaviour of a very mobile seabird, and delineate distinct foraging tactics along a gradient from foraging in dense pack ice to foraging in open water. Secondly, we investigated the effects of these foraging tactics on individual state at return from a foraging trip. We combined movement data with morphometric and physiological measurements of a suite of plasma metabolites that provided a general picture of a bird's individual state. Foraging in denser sea ice was associated with lower gain in body mass during brooding, as well as lower level of energy acquisition (plasma triacylglycerol) during both brooding and incubation. We found no clear relationship between the foraging tactic in relation to sea ice and the energetic stress (changes in plasma corticosterone), energetic balance (β-hydroxybutyrate) or trophic level (δ15N). However, a shorter foraging range was related to both the energetic balance (positively) and the trophic level (negatively). Our results highlight a diverse range of foraging tactics in relation to sea ice in Antarctic petrels. While the various foraging tactics do not seem to strongly alter energetic balance, they may affect other aspects of Antarctic petrels' physiology. Future changes in sea-ice habitats can thus be expected to have an impact on the individual state of seabirds such as Antarctic petrels, which could ultimately affect their population dynamics. Nonetheless, strong individual heterogeneity in the use of sea-ice habitats by a typical pagophilic species might strengthen its resilience to environmental changes and in particular to forecasted sea-ice loss. A free Plain Language Summary can be found within the Supporting Information of this article.

Polar Regions are experiencing environmental changes at unprecedented rates. These changes can spread throughout entire food webs from lower trophic levels to apex predators. As many top predators forage over large areas, these indirect effects may be associated with large-scale patterns of climate variability. Using global climate indices that are known to impact the Southern Ocean ecosystem (the El Niño Southern Oscillation and Antarctic Oscillation Indices) we assessed their efficacy to predict variation in the demographic parameters of Antarctic seabirds. First, we used a long-term dataset on adult survival (estimated from capture–mark–recapture data) and reproduction of Antarctic petrel Thalassoica antarctica, from the largest known breeding colony (Svarthamaren, Dronning Maud Land) and examined whether large-scale oceanographic fluctuations impact survival and reproduction. Second, we conducted an exhaustive literature review to determine whether the effects of large-scale environmental variability on Antarctic seabirds have a coherent fingerprint across the Antarctic continent and nearby islands. We found that most of the variation in both reproductive success, timing of hatching, and survival of Antarctic petrels can be accurately modeled using the two modes of large-scale climate variability in Antarctica. The literature review, combined with the results from our field study, suggests that while the anticipated trends in the global patterns of climatic variability will generally have detrimental effects on populations of top predators in the Southwest Atlantic, these conclusions cannot be extrapolated to all seabird populations in Antarctica without additional data.

Summary 1. Lipids are more depleted in 13 C than proteins. Variable lipid contents in tissues affect therefore the measurements of stable carbon isotope ratios. Model based (also called mathematical) normalization has been suggested to correct d 13 C values using the ratio of carbon to nitrogen (C ⁄ N) as a proxy for lipid content. This approach has not been thoroughly validated for terrestrial animals and it is not clear to what extent it is generally applicable or species ⁄ tissue specific. 2. Ratios of stable carbon isotopes (d 13 C) were obtained for muscle samples of 22 mainly terrestrial arctic mammal and bird species and for egg samples of 32 bird species from nine sites in the circumpolar Arctic. We used linear and nonlinear equations to model the difference in d 13 C between samples from which lipids had been extracted chemically and bulk tissue samples. Models were compared on the basis of a model selection criterion (AIC) and of prediction error as estimated by cross-validation. 3. For muscle samples, a linear and a nonlinear equation performed equally well. The observed values were also well predicted by a previously published general equation for aquatic organisms. For egg samples, a nonlinear equation fitted separately to waterfowl and non waterfowl bird species fitted the data best. Prediction errors were, however, larger than for muscle samples. 4. The generality of the inferred normalization equations was assessed by applying them to a second data set from a similar ecosystem, but produced in the frame of another study. The predicted lean d 13 Cv alues were within 0AE5& of the observed values for 73% of the muscle samples, but only for 27% of the egg samples. 5. Based on our results, we recommend model based normalization of d 13 Cv alues as an economic way to deal with varying lipid contents in muscle samples of mammals and birds. For egg samples, on the contrary, model based predictions had large errors. Therefore, we recommend chemical lipid extraction in order to estimate lipid-freed 13 C values for egg content.

1. Stable isotopes of carbon and nitrogen are increasingly used in studies of animal diet reconstruction via mixing models. However, isotope ratios of both consumer and source tissues can be altered by various amounts of lipids, potentially leading to biased estimates of diet composition when they are not taken into account. 2. We investigated the consequences of lipid correction on the estimation of diet composition with mixing models. Using empirical data from three northern terrestrial trophic systems, we illustrated the direct effects of lipid extraction (LE) on the d13C and d15N of source and consumer tissues and its ultimate effects on the reconstruction of the consumer's diet. 3. In parallel, we developed a simulation tool in R, called fatsim, to assess sensitivity of mixing models to variation in isotopic ratios of samples from source or consumer tissues. This tool can be used to assess the effect of shifts in isotopic ratios caused by LE, or other sources of variation, in any trophic system and thus aid in decision making regarding lipid removal. 4. Using fatsim, we showed that the potential effects of LE on estimates of diet composition cannot be predicted without simulations, even in relatively simple systems. The sensitivity of a mixing model isotopic shift depends on the complexity of the system (number of sources) and on the relative positions of sources and consumers within the isotopic mixing space. 5. Our study confirms that the presence of lipids in tissues can bias the interpretation of diet reconstruction results. In a given trophic system, testing the sensitivity of a mixing model to LE can help decide whether lipid removal is required in order to avoid this bias.

The features of topically applied suncream films depend on the applied quantities and could be modified by water immersion and air drying. The aim of this study was to investigate the effects of the aforementioned factors on physical sunscreen films and to establish the correlation between the in vitro determined Sun Protection Factor (SPF) and the microstructure of the mineral coating. The assessments were conducted by using UV spectroscopy and electron microscopy on sunscreen films applied on both synthetic membranes and human skin. The results emphasize the paramount role played by the applied quantity to produce a continuous and protecting sunscreen film. The microscopic findings show that water immersion induces mainly a compactness of the sunscreen films, whereas no significant alterations were noted after air drying. Lastly, the SPF values, measured before and after water immersion, disclose the satisfactory water resistance of the broad-spectrum physical sunscreen considered.

International audience; The paper provides robust normative comparisons of 12 OECD countries based on their distributions of disposable income and access to two regional public goods: infant mortality and pupil-teacher ratios at public schools. Comparisons are performed using two and three-dimensional dominance criteria that coincide with the unanimity of utilitarian judgments taken over specific classes of utility functions. The criteria succeed in ranking conclusively about 30% of all possible comparisons in the two-dimensional case, compared with 67% for one-dimensional income-based comparisons and 6% for three-dimensional ones. Introducing local public goods seems to worsen the relative standing of Anglo-Saxon countries.

Cyclic voltammetry and linear sweep voltammetry were preliminarily used in order to evaluate the global antioxidant properties of dermocosmetic creams. Experiments were performed by introducing electrodes directly into the creams without any pretreatment of the samples. Current-potential curves showed significant anodic current depending on the antioxidant-containing cream studied. In comparison, little amperometric response was recorded with an antioxidant-free cream base. Aqueous solutions of the corresponding antioxidants showed analogous anodic waves and similar peak potentials. A correlation between the global anodic peak and the presence of the antioxidant species in the cream was made with eleven skin creams, attesting to the reliability of the method. Among the tested electrode materials, platinum gave the best results in terms of electrochemical kinetics and measurement precision (current peak standard deviation less than 5%). Exposure of a depilatory cream to oxidizing agents (e.g., hydrogen peroxide, air, or light) caused a decrease in peak current as expected. This methodology enabled us to evaluate the evolution of the total antioxidant capacity under oxidative stress and gives encouragement to further development of a voltammetric method to quantify cream antioxidant power.

One of the most critical steps in two-dimensional gel analysis is the comparison of spot lists. In this paper, we describe our approach to the matching problem. We propose a method based on syntactic pattern recognition techniques, which differs from previously used methods and offers a major improvement to cope with discontinuous geometric distortions. The method is based on non-metric considerations and describes the pattern observed on a given gel in a non-geometric way. This approach leads to the definition of finite automatons which can be used to automatically find the presence of a given pattern on a gel. The program uses a technique of clause generation related to artificial intelligence techniques. A set of rules is applied to the definition of homologousspots, and probability coefficients are computed to compare and to chose between different pairing hypotheses. Once matching has been achieved between a set of gels, the construction of a master gel which summarizes the information obtained is allowed. Two types of masters can be used. The first one summarizes the information between spots lists belonging to the same experiment and includes intensity considerations, while the second one summarizes the information resulting from different gels and does not include spot intensity and volume. Masters are written and known by the system as a spot list. This ability allows them to be handled just like spot lists and, using them, to perform all the actions available to the system. This approach is compared with a more classical one based on geometric corrections. The use of probability coefficients is also discussed and extended to their application to multiple matching and further utilization of masters.

We describe the application of a general method of comparing and sorting the patterns of protein expression obtained from two-dimensional (2-D) electrophoresis of a mixture of proteins. The method involved the use of two multidimensional classification programs and was applied, first, to the comparison of the protein patterns expressed at different stages during nymphal differentiation of imaginal wing discs in the insect Pieris brassicae. Comparison of these stages was based on the similarity of protein expression. The technique used allowed processing of all the information visible on a gel and took into account the variations in most of the spots labeled. Two qualitatively different stages of protein expression were found during the nymphal stage, and fine variations not revealed by any other method were shown to exist in genetic programing. Next, the method was applied to sorting the different polypeptides expressed; this was also done on the basis of their similarity of expression. We were able to characterize three groups of related peptides with common regulation features and apparently common physicochemical characteristics. The complete map of the most highly correlated peptides, which may constitute subunits of the same protein, was constructed by the programs, thus permitting fast rational analysis of protein expression. The clinical applications of these classification techniques are discussed.

International audience; A method derived from general computerized data analysis techniques is used here first to tabulate the characteristics of individual peptide spots observed by two-dimensional electrophoresis and to compare these characteristics among spots. Multivariate analysis of such data arrays then leads to the grouping of spots in an n-dimensional space, according to their expression characteristics. Such maps display zones which are characteristic of the tissue studied. These functional maps provide a powerful analytical tool for describing such functional interactions and also for predicting the function of unidentified peptides observed on the electrophoresis gels.