Hunting of mammals by central chimpanzees (Pan troglodytes troglodytes) in the Loango National Park, Gabon

The predation and consumption of animals are common behaviours in chimpanzees across tropical Africa. To date, however, relatively little is known concerning the hunting behaviour of central chimpanzees (Pan troglodytes troglodytes). Here, we provide the first direct observations of hunting behaviour by individuals of the newly habituated Rekambo community in the Loango National Park, Gabon. Over a period of 23 months (May 2017 to March 2019), we observed a total of 61 predation attempts on eight mammal species, including four monkey species. The two most frequently hunted species were two monkey species (Cercocebus torquatus, Cercopithecus nictitans), which are not hunted at other long-term field sites. The majority of predation events observed involved parties of an average of eight individuals, mainly adult males, with hunting success being higher with increasing numbers of participants. Hunting occurred all year round, but hunting rates increased in the dry season, the period of high fruit availability in the Loango National Park. These results are in line with the nutrient surplus hypothesis which explains seasonal variation in hunting behaviour in several populations of eastern chimpanzees (Pan troglodytes schweinfurthii: e.g., Mahale, Tanzania; Ngogo, Uganda). Finally, with a hunting frequency of 2.65 hunts per month, the Rekambo community had higher hunting rates than other sites (Bossou, Republic of Guinea; Kahuzi-Biega, Democratic Republic of Congo; Budongo, Uganda) where red colobus monkeys are also absent. We discuss these results and compare them to patterns at other long-term sites

Décomposition empirique multimodale bidimensionnelle modifiée pour l'analyse d'images

Cet article présente une nouvelle approche d'analyse d'images par une décomposition empirique multimodale bidimensionnelle (BEMD). Cette décomposition, obtenue par un processus bidimensionnel dénommé « sifting process », permet d'extraire des structures à différentes échelles et fréquences spatiales, comportant des modulations en amplitude et en fréquence. Le « sifting process » est réalisé en utilisant d'une part la reconstruction morphologique pour analyser les fréquences, et d'autre part les fonctions radiales de base (RBF) pour l'interpolation de surfaces. Nous avons modifié l'algorithme original de « sifting process » pour permettre une pseudo décomposition passe-bande d'images par l'intermédiaire de critères d'échelle et de forme. Son efficacité est démontrée sur des images et en particulier des images de textures. De plus, la décomposition multimodale empirique bidimensionnelle, dans sa version classique et modifiée, ouvre une voie prometteuse pour la réduction de bruit et l'extraction de textures

Key Issues in Local Job Accessibility Measurement: Different Models Mean Different Results

International audienceThis methodological paper shows that using different local job accessibility models (LJAs) leads to significantly different empirical appreciations of job accessibility. Matching several exhaustive micro data sources on the Paris region municipalities, the paper benchmarks a representative set of LJA measurement models used in the recent literature and an original model where job availability is fully estimated according to a set of individual characteristics, job competition is fully modelled on the local labour market and frontier effects are controlled for. We show that the model-induced empirical differences are spatially differentiated across the Paris region municipalities, and that failing to fully estimate job availability may lead to overestimation of the job accessibility levels of underprivileged municipalities

Carboxylic acid derivatives via catalytic carboxylation of unsaturated hydrocarbons: whether the nature of a reductant may determine the mechanism of CO2 incorporation?

International audienceApplication of CO2 as a renewable feedstock and C1 building block for prodn. of commodity and fine chems. is a highly challenging but obvious industry-relevant task. Of particular interest is the catalytic coupling of CO2 with inexpensive unsatd. hydrocarbons (olefins, dienes, styrenes, alkynes), providing direct access to carboxylic acids and their derivs. Although not brand new for the scientific community, it is still a complete challenge, as no truly effective catalytic system has been reported to date. In this Perspective, we discuss the available exptl., theor. and mechanistic data for such homogeneously catalyzed carboxylation processes. A special focus is placed on the understanding of the key elementary steps and of some thermodn. and kinetic constraints

Estimation du flux optique sur une sequence d'images echocardiographiques

Nous présentons dans cet article une méthode fondée sur l'estimation du flux optique qui permet d'obtenir une cartographie des mouvements myocardiques. Une pré-segmentation des régions mobiles de l'image est tout d'abord réalisée au moyen d'un critère spatio-temporel. Ensuite un vecteur mouvement est estimé en chaque point des régions mobiles ainsi définies. Le calcul du flux optique est réalisé grâce à une méthode itérative initialisée par l'amplitude du mouvement dans la direction perpendiculaire aux contours myocardiques. La méthode proposée est générale pourvu que des hypothèses de stabilité de la luminance au cours du temps et de continuité de mouvement soient respectées

Reactivity of chromium(III) and cobalt(III) acetylacetonato complexes

A comparative study of the ligand reactivity at the 3-position in trisacetylacetonates of Cr(III) and Co(III), by means of nitration and Vilsmeier-Haack reactions, was attempted. The sequence Co > Cr in both reactions was found. Hückel calculations of reactivity indices were performed and theoretical reactivity results agreed with experiment

Optical activity of mixed complexes of copper(II) and amino acids in the visible region

Study of the visible absorption and circular dichroism spectra of mixed complexes formed by copper(II), an optically active amino acid anion and a phenanthroline or dipyridyl moiety, shows that although the absorption spectra are similar the Cotton effects differ. This behavior is analyzed in terms of the energy levels of the mixed complexes and their relationship with the sequence of levels of the corresponding bis-aminoacidates. An interpretation relating the variation of the circular dichroism bands with structural changes is proposed. © 1975