1,720,962 research outputs found
Effets de bas PH/PCO2 élevées sur les traits d'histoire de vie et la physiologie du premier stade de recrutement juvénile benthique du homard américain, homarus americanus
Full text linkRÉSUMÉ: Un cycle de vie complexe est un caractère commun chez la majorité des invertébrés marins, caractérisée par des mues énergétiquement couteuses, permettant le développement de la phase pélagique larvaire à la phase adulte benthique. Les conséquences du pH bas/ la pCO2 élevée en milieu marin sur le cycle de vie des crustacés sont peu connues, particulièrement pendant la phase post-larvaire qui précède la fixation benthique du recrutement juvénile. Chez les espèces d’intérêt, comme le homard Américain, Homarus americanus, il est important pour les industries de pêches de comprendre la sensibilité spécifique aux premiers stades de vie du développement dans un contexte de changements globaux. L’acidification des océans (AO) est la réduction progressive du pH marin causé par l’absorption de CO2 anthropique. D’autres incitateurs de l’augmentation de la pCO2 sont les fluctuations côtières naturelles et des fuites de systèmes de capture et de stockage de CO2 (CSC). Sachant que la pCO2 élevée peut affecter négativement les crustacés marins, cette étude a pour objectif d’identifier les impacts d’une augmentation de la pCO2 sur les traits d’histoire de vie et la physiologie de la première phase de recrutement juvénile (stade V) du homard Américain. Les juvéniles ont été soumis à sept différent pH (entre 8,1 et 7,12), représentatifs des conditions prédites d’AO, des fuites de CSC, et de fluctuations naturelles.
La survie, la durée du développement, les taux alimentaire et de respiration de tous les individus ont été examinés. Les résultats démontrent une réduction de la survie et du développement, et une variabilité du taux de l’alimentation lors d’une réduction du pH. Plus en détail, nous observons une demande énergétique qui augmente afin de maintenir l’homéostasie interne. Malgré une hausse de l’aérobie mitochondriale par mitohormésis, cette demande énergétique accrue n’est pas comblé parce que les mitochondries individuelles semblent être endommagées par ce qui pourrait être le stress oxydatif. Ceci contraint la capacité de continuer à travers les stades consécutifs de développement. Nos résultats démontrent les effets négatifs potentiels que pourrait avoir la pCO2 élevée sur les post-larves de homard, préfigurant une réduction du succès de recrutement benthique des stades V, ce qui pourrait avoir des incidences sur le futur de l’économie et les communautés de pêches du homard. -- Mot(s) clé(s) en français : Acidification des Océans, capture et stockage de carbone, fuites de CO2, pH bas, recrutement juvénile, épuisement, capacité aérobique, régulation acido-basique, fonction mitochondriale, pêche du homard américain. -- ABSTRACT: Complex life cycles are most common in marine benthic invertebrates. This developmental character includes frequent, energetically costly moults in order to progress discretely from the pelagic larval form to the benthic juvenile form. Low pH impacts on the resilience of crustaceans having a complex life cycle are virtually unknown, particularly during the settling post-larval phase that precedes benthic juvenile recruitment. For such species of economic importance, like the American lobster, Homarus americanus, it is important to understand and identify stage-specific vulnerabilities during early development in order to better understand recruitment variability and distribution in the context of global change for the lobster fisheries that drive a major part of coastal economies in Canada and the United States. Ocean acidification (OA) is the progressive decrease of oceanic pH / increased pCO2 caused by the uptake of excess atmospheric CO2. Other elevated pCO2 drivers are natural and anthropogenic coastal fluctuations and leakages from carbon capture storage systems (CCS). Knowing that such drivers of elevated pCO2 can negatively affect marine crustaceans, this study aims to identify the impacts of elevated seawater pCO2 on the life history and physiology of the first juvenile recruits (V) of the American lobster. Juvenile lobsters were held in one of seven pH levels (between 8.1 and 7.12), representative of predicted end-century ocean conditions and potential low pH extremes.
The survival, development rates, feeding rates, respiration rates of all individuals, as well as the carapace mineral content and mitochondrial enzyme function for selected individuals were recorded. As pCO2 increases, results suggest an increase in mortality and developmental rates and variable feeding responses. These patterns can apparently be explained by high pCO2 impacts on physiological traits. More specifically, we suggest that energetic demand increases in order to maintain internal homeostasis. However, this demand is not fully met despite increased aerobic mitochondrial capacity through mitohormesis, because individual mitochondria may be damaged by oxidative stress. This lack in energy reserves reduces the capacity to persevere through successive stages in development. Our results point to potential negative effects on the species recruits with elevated seawater pCO2, foreshadowing reduced recruitment success of stage V juveniles under future low pH scenarios, having potential economic and social repercussions on coastal lobster fisheries. -- Mot(s) clé(s) en anglais : Ocean acidification, Carbon Capture and Storage, CO2 leakages, low pH, juvenile recruitment, exhaustion, acid-base regulation, aerobic capacity, mitochondrial function, lobster fisheries
Seawater carbonate chemistry and energy metabolism and survival of the juvenile recruits of the American lobster (Homarus americanus)
No full textThe transition from the last pelagic larval stage to the first benthic juvenile stage in the complex life cycle of marine invertebrates, such as the American lobster Homarus americanus, a species of high economic importance, represents a delicate phase in these species development. Under future elevated pCO2 conditions, ocean acidification and other elevated pCO2 events can negatively affect crustaceans. This said their effects on the benthic settlement phase are virtually unknown. This study aimed to identify the effects of elevated seawater pCO2 on stage V American lobsters exposed to seven pCO2 levels. The survival, development time, metabolic and feeding rates, carapace composition, and mitochondrial function were investigated. Results suggested an increase in mortality, slower development and a reduction in aerobic capacity with increasing pCO2. Our study points to potential reduction in juvenile recruitment success as seawater pCO2 increases, thus foreshadowing important socio-economic repercussions for the lobster fisheries and industry
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
Seawater carbonate chemistry and stage survival and morphological measurements, mineral contents and resting metabolic rates of larvae and juvenile American Lobster
No full textBentho-pelagic life cycles are the dominant reproductive strategy in marine invertebrates, providing great dispersal ability, access to different resources, and the opportunity to settle in suitable habitats upon the trigger of environmental cues at key developmental moments. However, free-dispersing larvae can be highly sensitive to environmental changes. Among these, the magnitude and the occurrence of elevated carbon dioxide (CO2) concentrations in oceanic habitats is predicted to exacerbate over the next decades, particularly in coastal areas, reaching levels beyond those historically experienced by most marine organisms. Here, we aimed to determine the sensitivity to elevated pCO2 of successive life stages of a marine invertebrate species with a bentho-pelagic life cycle, exposed continuously during its early ontogeny, whilst providing in-depth insights on their metabolic responses. We selected, as an ideal study species, the American lobster Homarus americanus, and investigated life history traits, whole-organism physiology, and metabolomic fingerprints from larval stage I to juvenile stage V exposed to different pCO2 levels. Current and future ocean acidification scenarios were tested, as well as extreme high pCO2/low pH conditions that are predicted to occur in coastal benthic habitats and with leakages from underwater carbon capture storage (CCS) sites. Larvae demonstrated greater tolerance to elevated pCO2, showing no significant changes in survival, developmental time, morphology, and mineralisation, although they underwent intense metabolomic reprogramming. Conversely, juveniles showed the inverse pattern, with a reduction in survival and an increase in development time at the highest pCO2 levels tested, with no indication of metabolomic reprogramming. Metabolomic sensitivity to elevated pCO2 increased until metamorphosis (between larval and juvenile stages) and decreased afterward, suggesting this transition as a metabolic keystone for marine invertebrates with complex life cycles
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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