1,721,362 research outputs found
Les trois jeûnes du Manchot royal. Comparaison avec le jeûne de reproduction du Manchot empereur
No full textCherel Yves, Robin Jean-Patrice, Le Maho Yvon. Les trois jeûnes du Manchot royal. Comparaison avec le jeûne de reproduction du Manchot empereur. In: Revue d'Écologie (La Terre et La Vie), tome 43, n°4, 1988. pp. 367-374
Acoustic structuration of micronekton of the Southwest Indian Ocean oceanic ecosystem
No full textPour comprendre le fonctionnement d'un écosystème, il est essentiel de comprendre l'organisation du réseau trophique associé. Dans les eaux océaniques du sud-ouest de l'océan Indien (10-60°S, 35-90°E), si la répartition de la production primaire et la distribution des prédateurs supérieurs sont bien connues, un manque de connaissance demeure en ce qui concerne la distribution des différents organismes composant l'échelon trophique intermédiaire et ce, malgré leur importance écologique (pompe biologique et rôle trophique clé) et potentiellement économique (ambitions de pêche dans un futur proche). Pour combler ce manque, ce travail de thèse s'est concentré sur les distributions horizontale et verticale et la composition des organismes micronectoniques de cette région. La distribution du micronecton a donc été étudiée à méso- et large-échelle à partir d'enregistrements acoustiques (38 kHz). En termes de distribution verticale, une structuration en trois couches principales a été mise en évidence ; l'intensité et l'épaisseur de ces couches variant selon la période du jour (migrations nycthémérales) et les conditions océaniques (tourbillons océaniques à méso-échelle et fronts océaniques à large-échelle). En ce qui concerne la distribution horizontale, le sud-ouest de l'océan Indien a été caractérisé par des eaux (10 – 800 m) plus riches aux latitudes subtropicales, en été comme en hiver. Mais chaque type d'organisme ayant ses propres caractéristiques écologiques, il était important de pouvoir décrire les distributions propres à chaque groupe biologique composant ce micronecton. Une approche acoustique bifréquence (38 et 120 kHz) a permis de distinguer les crustacés micronectoniques des petits poissons mésopélagiques contenant une vessie natatoire gazeuse dans les eaux est de Kerguelen. En termes de distribution horizontale et de densité globale estimée, les crustacés micronectoniques dominaient les eaux océaniques à l'est de Kerguelen. Sur la verticale, deux types de structuration ont été mis en évidence : une structure agrégative et une structure en couches. Les crustacés micronectoniques ont été caractérisés par une structuration en couches, de jour comme de nuit, alors que les autres organismes sondés (les poissons ayant une vessie natatoire gazeuse notamment) présentaient une structuration mixte composée d'agrégats et de couches le jour et composée uniquement de couches la nuit. En résumé, l'approche acoustique utilisée dans ce travail a permis de décrire la distribution et la composition des organismes micronectoniques et fournit une base descriptive essentielle sur le micronecton du sud-ouest de l'océan Indien.To understand the functioning of an ecosystem, it is essential to understand the organization of its associated food web. While the distribution of primary production and top predators in the Southwest Indian Ocean's oceanic waters (10-60 ° S, 35-90 ° E) are well known, a lack of knowledge remains regarding the distribution of mid-trophic level organisms, despite their ecological (biological pump and key trophic role) and potentially economic (commercial fisheries in the near future) importance. To fill this gap, this work focused on the horizontal and vertical distribution and composition of micronektonic communities in this region. Micronekton comprises relatively small organisms (1 to 20 cm long) able to swim freely without being unduly affected by currents. Micronekton distributions have been studied at meso- and large-scale using acoustic recordings (38 kHz). A vertical structure in three layers has been identified ; the intensity and thickness of these layers vary depending on the considered time period (diel migration) and ocean conditions (meso-scale oceanic eddies and large-scale oceanic fronts). Horizontaly, the Southwestern Indian Ocean harbours the richest waters (10-800 m) in subtropical latitudes in summer and winter times. Since every organism has its own ecological characteristics, it was important to separatly describe the distribution of biological groups composing micronekton. A bi-frequency acoustic approach (38 and 120 kHz) allowed the distinction of micronektonic crustaceans from small mesopelagic gas-filled swimbladder fish in waters east of Kerguelen where micronektonic crustaceans where dominant in terms of overall acoustic density. Two distinct types of vertical structure were highlighted : an aggregative and a layer structure. Micronektonic crustaceans were characterized by layering, day and night, while other organisms (gas-filled swimbladder fish in particular) exhibited structure mixing aggregates and layers during the day, but only composed of layers during the night. In summary, the acoustic approach used in this work helped to describe the distribution and composition of micronektonic organisms and provides an essential knowledge base on the micronekton of the southwest Indian Ocean
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Ectreposebastes niger
No full textEctreposebastes niger (Fourmanoir, 1971) (Fig. 2) Pontinus niger Fourmanoir, 1971: 42, fig. 6. TYPE MATERIAL. — Holotype. Pacific Ocean • MNHN-IC-1970-0034, 122 mm SL, 09°56’S, 141°52’W; 0-1200 m depth; 12.IX.1969; CARIDE 5; R/V Coriolis. MATERIAL EXAMINED. — La Réunion • MNHN-IC-2019-0078; no sex data; 165 mm SL; Southwestern Indian Ocean; 19°45.84’S, 54°05.28’E- 19°41.43’S, 54°03.80’E; 18.IX.2016; Romanov, IRD LA PÉROUSE leg; R/V Antea. DISTRIBUTION. — Indo-West Pacific meso- and bathy-pelagic, mostly near continental/peri-insular slopes in tropical and temperate waters. DESCRIPTION Individual MNHN-IC-2019-0078 (165 mm SL) External morphology. Medium-sized, black-coloured scorpaeniform fish with black-yellowish eyes. Pinkish muscles visible through semi-transparent skin in scale pockets; scale pocket edges black. Body relatively high, slightly compressed laterally, flabby, lacking scales (most scales lost, except some pored LL scales) (Fig. 2). Most fin spines, some fin rays broken due to fragile, poorly-ossified nature. First pre-opercular spine weakly developed; others damaged. Lacrimal spines short, intact on the left side but damaged on right. Body proportions shown in Table 1. Otoliths. Thick and robust. Otolith shape triangular with pointed rostrum (Fig. 3); ventral rim convex; post-dorsal rim almost straight without depression; pre-dorsal rim forming angle close to 90° with post-dorsal rim. Otolith height almost equal to otolith length (ratio OH/OL 0.75-0.79 for right and left otoliths respectively). Sulcus acusticus: archaesulcoid, ostial, median. Ostium and cauda: undifferentiated, oval. Anterior region: double-peaked; rostrum broad, short, slightly pointed, antirostrum very short, rounded, broad; excisura wide with shallow notch. Posterior region: oblique to round or oblique to irregular. REMARK The morphology of our specimen corresponds well to the original description given by Fourmanoir (1971) and later by Mandrytsa (1990). Body measurements are close to the ranges presented in other studies. However, many proportions are close to or even outside of the lower end of reported ranges (Table 1). GENETIC ANALYSIS A 555 bp region of the mtDNA COI gene was isolated from the specimen and the sequence was deposited in the INSD (accession number: MN181524). The query sequence did not find 100% match to the mtDNA COI region of any other specimens. The nearest matches were non-identified specimens Ectreposebastes sp. (98.13% to 98.31% similarity) and Ectreposebastes imus (97.10% to 98.13% similarity). Neighbour joining tree analysis (Fig. 6) shows distinct clustering between E. imus, E. niger and Ectreposebastes sp. DNA signatures. The E. imus branch is separated from another branch that contains our E. niger specimen (MN181524) and Ectreposebastes sp. specimens (FOAE60706, FOAF803-07) collected from the Southwestern Pacific: Coral Sea (off Australian coast) and from over Lord Howe Rise. An ABGD analysis aimed at detecting genetic gaps between species (Puillandre et al. 2012) clustered Ectreposebastes sequences into three lineages, segregating E. imus, E. niger (MN181524) and Ectreposebastes sp.Published as part of Romanov, Evgeny V., Cherel, Yves & Marsac, Francis, 2021, New record of Ectreposebastes niger (Fourmanoir, 1971) (Setarchidae, Scorpaeniformes): a rare bathypelagic fish from La Pérouse Seamount, Western Indian Ocean, and distribution of Ectreposebastes Garman, 1899 in the Indian Ocean, pp. 283-296 in Zoosystema 43 (15) on pages 286-287, DOI: 10.5252/zoosystema2021v43a15, http://zenodo.org/record/490658
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Les oiseaux marins, bioindicateurs de la contamination passée et actuelle par le mercure : une approche globale
No full textLe mercure (Hg) est un métal toxique, qui constitue une menace majeure pour l’Homme et la biodiversité. Naturellement présent dans l’environnement, le Hg est aussi rejeté en quantité considérable par les activités humaines depuis la Révolution Industrielle et se dépose dans tous les écosystèmes, même les plus reculés. Les océans, qui recouvrent 70% de la surface de la Terre, sont très peu documentés dans les programmes internationaux de surveillance du Hg, notamment dans la région intertropicale et les régions polaires. Avec les changements climatiques, déterminer les tendances spatiales et temporelles de cette contamination dans ces régions inexplorées représente un enjeu capital. Les oiseaux marins constituent d’excellents bioindicateurs de la contamination des océans, à la fois à travers le temps et l’espace. En effet, ils reflètent la contamination du réseau trophique sur lequel ils reposent. Assimilé via l’alimentation, le Hg est majoritairement excrété lors de la mue et stocké dans leurs plumes de manière inerte. Ainsi, les plumes d’oiseaux marins représentent une archive précieuse, avec un potentiel de « machine à remonter le temps », grâce aux spécimens de musées. Dans ce contexte, ces travaux utilisent les oiseaux marins comme bioindicateurs des écosystèmes marins, dans trois grandes régions océaniques éloignées ‒ l’Océan Arctique, la région intertropicale (Océans Pacifique, Atlantique et Indien) et l’Océan Austral ‒ avec deux objectifs majeurs : (1) établir une cartographie contemporaine, à large échelle spatiale, de la contamination au Hg, et (2) déterminer rétrospectivement son évolution temporelle depuis le XIXème siècle, grâce aux spécimens de musée. Avec une couverture spatiale et temporelle uniques, ces travaux de thèse fournissent des données indispensables pour les programmes de surveillance internationaux, liés à la mise en application de la Convention de Minamata, qui vise à réguler les émissions anthropiques de Hg à échelle mondiale.Mercury (Hg) is a toxic metal, and its impacts on human and environmental health are a major concern. Globally, the amount of Hg released into the environment, through anthropogenic activities, has steadily increased since the Industrial Revolution. Both natural and anthropogenic Hg disperse globally and deposits in all ecosystems, including in remote oceans. Oceans, which cover 70% of the Earth’s surface, are poorly documented in international monitoring programs of Hg, particularly in intertropical and polar regions. In the current context of global climate, determining spatial and temporal trends in Hg contamination in these undocumented regions is crucial. Seabirds are excellent bioindicators of Hg contamination in the oceans, both across space and time, as they integrate and reflect Hg contamination of marine food webs on which they feed. After dietary assimilation, Hg is mainly excreted during moult and stored permanently in feathers. Therefore, seabird feathers represent valuable archives and act as a time-machine thanks to museum specimens. In this context, the present PhD thesis uses seabirds as bioindicators of Hg contamination in marine ecosystems, mainly from three remote oceanic regions ‒ the Arctic Ocean, the intertropical region (Pacific, Atlantic and Indian Oceans) and the Southern Ocean ‒ with two main objectives: (1) map contemporary Hg contamination at large spatial scale, and (2) document its temporal trends since the 19th century retrospectively, by using both museum-held and free-living seabirds. Thanks to unique spatial and temporal coverage, this work represents a valuable contribution to international monitoring programs that are fully involved in the implementation and effectiveness evaluation of the Minamata Convention, which aims to control and reduce anthropogenic Hg emissions at the global scale
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