1,721,126 research outputs found
Mass mortalities affecting populations of the yellow clam Amarilladesma mactroides along its geographic range
Full text linkThe yellow clam Amarilladesma mactroides (Deshayes, 1854) is considered a vulnerable species since the mid-1990s. Populations have experienced mass mortalities throughout their entire range of distribution (23–41°S) along exposed sandy beaches of Atlantic South America. Detrimental anthropogenic impacts have further contributed to failure of populations to make a recovery. To determine the factors involved in these events, density prior to a mortality event was calculated and live yellow clams encompassingmost of its geographic range distribution were analyzed histologically to describe parasites and pathologies. Moreover, moribund specimens were analyzed by molecular techniques to test for the presence of the virus OsHV-1. A mortality event was recorded after a maximum density of 127 clams/m2 was attained. No clear pattern was found between the prevalence and intensity of infection and localities, mortality events, or sampling season. Although OsHV-1 was not observed in any of the yellow clams tested, the possibility that another viral agent was implicated cannot be ruled out. The presence of bacteria of the genus Vibrio in combination with stress caused by a relatively high population density is suggested as the likely cause of these episodic mass mortalities.Fil: Vázquez, Nuria Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; ArgentinaFil: Fiori, Sandra Marcela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; ArgentinaFil: Arzul, Isabelle. Institut Francais de Recherche pour l'Exploitation de la Mer; FranciaFil: Carcedo, Maria Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Cremonte, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentin
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
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
Study of the ecology of Marteilia refringens and Bonamia ostreae, two protozoan parasites of the flat oyster, Ostrea edulis
No full textThe flat oyster Ostrea edulis is a bivalve mollusc native from European coasts. Since the end of the 20th century, this species has been struck by two epizootics diseases caused by the protozoan parasites Marteilia refringens and Bonamia ostreae. Today, although shellfish farmers are showing a renewed interest in this patrimonial species and conservation and restoration programs are developing in Europe, these parasitic diseases still put pressure on natural and farmed populations. Solutions to control these diseases are limited and require a good knowledge of parasite life cycles as well as their interactions with their hosts. Although the development of parasites in bivalves is relatively well described, questions remain about their behaviour in the environment. In this context, these PhD works have contributed to the development of eDNA / eRNA based approaches allowing the detection of parasites in seawater and benthos. These tools, combined with microscopical examination for M. refringens, were used to investigate experimentally parasite survival and release dynamics outside the flat oyster. These analytical approaches were also used in the context of a field study carried out in Rade of Brest on the environmental distribution and temporal dynamics of the parasites on a natural flat oyster bed. The developed approaches and obtained results not only bring new perspectives on the ecology of these non-cultivable microparasites but are also of interest for the surveillance and the evaluation of the health status of lasts flat oyster beds.L’huître plate Ostrea edulis est un mollusque bivalve natif des côtes européennes. Depuis la fin du XXème siècle, elle est frappée par deux épizooties dues aux parasites protozoaires Marteilia refringens et Bonamia ostreae. Aujourd’hui, alors que la profession manifeste un regain d’intérêt pour cette espèce patrimoniale et que des programmes de conservation et de restauration se développent en Europe, ces parasitoses exercent toujours un impact sur les populations naturelles et d’élevage. Les moyens de lutte contre ces parasites sont restreints et leur contrôle nécessite une bonne connaissance de leur cycle ainsi que de leurs interactions avec leurs hôtes. Si, le développement des parasites dans les bivalves est relativement bien décrit, des questions subsistent quant à leur distribution dans l’environnement. Dans ce contexte, ces travaux de thèse ont permis de développer des approches eDNA /eRNA permettant la détection des parasites dans l’eau de mer et le benthos. Ces outils, combinés à des observations en microscopie pour M. refringens ont été utilisés pour étudier expérimentalement la survie et la dynamique de libération des parasites en dehors de l’huître. Ces approches analytiques ont également été utilisées dans le cadre d’une étude in situ en Rade de Brest portant sur la distribution environnementale et la dynamique temporelle des parasites au niveau d’un gisement naturel d’huîtres plates. Les approches développées et les résultats obtenus apportent un éclairage sur l’écologie de ces microparasites non cultivables et présentent aussi un intérêt pour la surveillance et l’évaluation de l’état de santé des derniers gisements d’huîtres plates
REPAMO 2003. Bulletins de la surveillance. Juin à septembre 2003
No full textCe document compile l’ensemble des bulletins de la surveillance de la santé des mollusques marins émis au cours de l’année 2004 par le réseau REPAMO. Ces bulletins, édités à fréquence mensuelle ou en fonction du nombre d’événements, relatent les événements de mortalité notifiés au réseau ainsi que les résultats des analyses effectuées lors des prélèvements d’animaux réalisés sur les lieux des mortalités. Les bulletins sont diffusés aux instances professionnelles concernées (CRC, CNC, CDPMEM, CNPMEM, centres techniques), à la DGAL, à la DPMA, aux laboratoires d’analyses, à Ifremer ainsi que sur le site internet du REPAMO. Ils ont pour objectif de tenir les destinataires informés des épisodes de mortalités anormales de mollusques marins rencontrés sur le littoral français métropolitain et cors
Situation of European mollusc production regarding diseases
No full textThe production of marine molluscs is an important part of the European aquaculture. Its growth has unfortunately been hindered over the recent years by mortality events, linked to pathogen organisms. Surveillance of mollusc diseases in Europe includes active surveillance of regulated pathogens and non-regulated pathogens and passive surveillance based on mortality reports. However, mortality reporting relies on the good will of producers/fishermen and mostly concerns the Pacific cupped oyster Crassostrea gigas. Since these last years, implemented surveillance programmes have allowed for better defining of the geographic distribution of some mollusc pathogens. This is the case of Bonamia exitiosa, a protozoan parasite previously considered exotic to Europe and which has been detected in different European countries since 2008. Moreover, these different active and passive surveillance programmes have contributed to characterising new pathogens including the protozoan parasite Marteilia cochillia in cockles in Spain and parasites of the genus Mikrocytos in France, Spain, The Netherlands and United Kingdom. Transfer of animals and depuration centers seem to contribute to the spread of mollusc pathogens. However, the source of these apparently new pathogens is often difficult to identify
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