1,720,990 research outputs found
Ecologia del movimento e determinazione di habitat essenziali negli squali del Mar Mediterraneo
No full textNell'ultimo secolo è stato documentato un esaurimento complessivo delle risorse marine in molti oceani e in particolare nel Mar Mediterraneo. Questo esaurimento è stato determinato da molte attività antropiche, tra le quali le attività di pesca hanno uno degli impatti diretti più forti. Le specie elasmobranchi sono tra i più importanti predatori apicali e meso della catena alimentare, contribuendo all'equilibrio e al funzionamento degli ecosistemi marini. Il Mar Mediterraneo ospita un'ampia diversità di elasmobranchi che vivono in tutti gli ecosistemi marini. Tipicamente, il ciclo di vita degli elasmobranchi consiste in un tasso di crescita più lento rispetto ad altri organismi marini. Ciò implica anche che il tempo per raggiungere la maturità sessuale in cui un organismo può riprodursi per la prima volta richiede molto più tempo rispetto ad altre specie marine. All'interno del loro ciclo di vita, le specie di elasmobranchi richiedono spesso habitat specifici per completare le loro esigenze di riproduzione o di foraggiamento e la scelta non casuale porta a una specifica correttezza nell'uso dello spazio come ad esempio la filopatria, la fedeltà al sito e l'homing natale. La ricerca scientifica ha riportato come gli habitat essenziali, utilizzati in diverse fasi del loro ciclo di vita e attraverso le generazioni, possono essere soggetti a un'elevata pressione di pesca, in particolare le aree costiere di diversi sottobacini come il Mar Adriatico, dove si trova una delle pressioni di pesca più elevate. Come diretta conseguenza di un lungo periodo di pesca eccessiva, molte specie di elasmobranchi sono state minacciate di estinzione. L'attuale scenario nel Mar Mediterraneo richiede adeguate strategie di gestione e conservazione dirette alle specie di elasmobranchi commercialmente rilevanti e in via di estinzione. La conoscenza dell'uso dello spazio degli elasmobranchi durante tutto l'anno e tra le fasi della vita potrebbe contribuire notevolmente alla definizione di una gestione spazialmente esplicita che si è rivelata vincente in altri oceani per gestire in modo sostenibile la pesca degli elasmobranchi, arrestando o invertendo così lo scenario in declino . Con l'approccio multidisciplinare applicato per realizzare questa tesi di dottorato, i risultati raggiunti hanno fatto luce per definire periodi e luoghi critici in cui elasmobranchi commercialmente rilevanti come il palombo (Mustelus spp.) o grandi squali costieri in via di estinzione come lo squalo grigio (Carcharhinus plumbeus ) completare le fasi critiche del loro ciclo di vita come il parto, l'accoppiamento e la crescita utilizzando l'area del vivaio a fini di foraggiamento. Tale approccio multidisciplinare potrebbe essere fondamentale per fornire le informazioni mancanti sulle specie di elasmobranchi nel Mar Mediterraneo e supportare l'istituzione di una gestione su misura per la conservazione degli elasmobranchi.Over the last century, an overall depletion of the marine resources has been documented in many oceans and in particular in the Mediterranean Sea. This depletion has been driven by many anthropogenic activities among which fishing activities have one of the strongest direct impacts. The elasmobranch species are among the most important apex- and meso- predators in the food web, contributing to the balance and functioning of the marine ecosystems. The Mediterranean Sea hosts a wide diversity of elasmobranchs that live in all marine ecosystems. Typically, the elasmobranch life cycle consists in a slower growth rate compared to other marine organisms. This also implies that the time to reach sexual maturity at which an organism can reproduce for the first time takes much longer than other marine species. Within their life cycle, elasmobranch species often require specific habitats to complete their reproduction or foraging needs and no-random choice leads to a specific propriety in the use of space as for instance philopatry, site fidelity and natal homing. Scientific research has reported how essential habitats, used in different stages of their life cycle and across generations, can be subjected to high fishing pressure, especially the coastal areas of several subbasins like the Adriatic Sea where one of the highest fishing pressures is found. As the direct consequence of long period of overfishing, many elasmobranch species have been threatened by extinction. The current scenario in the Mediterranean Sea calls for appropriate management and conservation strategies directed to the commercially-relevant and endangered elasmobranch species. The knowledge of the use of space of elasmobranch throughout the year and among life stages could greatly contribute to the definition of a spatially explicit management which has resulted to be successful in other oceans to sustainably manage the elasmobranch fishery, thus halting or reversing the declining scenario. With the multidisciplinary approach applied to accomplish this PhD thesis, the achieved results have shed some light to define critical periods and locations in which commercially relevant elasmobranchs like the smooth hounds (Mustelus spp.) or endangered large coastal shark like the sandbar shark (Carcharhinus plumbeus) complete critical steps of their life cycle like birthing, mating and growing using nursery area for foraging purposes. Such multidisciplinary approach could be paramount to provide missing information of elasmobranch species in the Mediterranean Sea and support the establishment of tailored management towards elasmobranch conservation
Introduction:New Institutionalism and Greek History
No full textThis chapter introduces the themes and new institutionalist methodology of the volume Rediscovering Greek Institutions: New Institutionalist Approaches to Greek History
Introduction:New Institutionalism and Greek History
No full textThis chapter introduces the themes and new institutionalist methodology of the volume Rediscovering Greek Institutions: New Institutionalist Approaches to Greek History
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
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