1,721,138 research outputs found
The elusive 8.2 ka event in speleothems from southern France
No full textAbstract. The Holocene is generally considered a climatically stable period, yet a prominent perturbation occurred around 8.2 ka BP. Evidence of its impacts has been identified in many palaeoclimate archives across Europe. However, outside the Atlantic seaboard, no clear high-resolution signal for this event has emerged from southwestern Europe. Here, we investigate the potential impact of the 8.2 ka event in southern France through high-resolution multiproxy analyses of two speleothems from the Ardèche region. Variations in Mg / Ca and Sr / Ca of the speleothem calcite are mainly attributed to the prior calcite precipitation effect and indicate switches between drier and wetter conditions. The δ13C signal is likely influenced by soil development and biological activity, integrating both regional climate conditions and local geomorphology and hydrology. The pattern of speleothem δ18O changes do not correlate with regional palaeotemperature reconstructions and is therefore more likely related to hydrology, such as variations in the seasonality of karst recharge and/or the moisture source. During the 8.2 ka event, no distinct geochemical anomaly is recorded by the Ardèche speleothems, suggesting either a limited climatic impact in southern France or a lack of sensitivity of these speleothem proxies to respond to an event of this magnitude. While the muted δ18O response may be explained by its insensitivity to temperature changes and buffering by Mediterranean influences at the time, the absence of a clear hydrological response in Mg / Ca, Sr / Ca and δ13C remains unresolved. Therefore, despite a likely southward displacement of the mid-latitude westerlies induced by the 8.2 ka event, the Ardèche region may have remained under their influence, preventing a marked shift towards drier conditions. Consistent with other records from southern France, the lack of significant changes in our results that time challenges the spatial extent and uniformity of the impacts of the 8.2 ka event across western Europe
Ricostruzioni paleoclimatiche del Peri-Adriatico attraverso speleotemi: primi risultati
No full textNell’ambito di una tesi di dottorato presso l’Università di Bologna e l’Université de Savoie (Francia), ed in
collaborazione con l’Università di Melbourne (Australia), si sta portando avanti un ambizioso progetto di ricerca
con l’intento di individuare dei record paleoclimatici in speleotemi campionati in grotte d’Italia e del Carso
dinarico. In questa prima fase di campionamento, grazie al coinvolgimento degli speleologi locali, sono state
raccolte stalagmiti e colate già rotte in precedenza in grotte della Puglia, dell’Emilia Romagna, del Triestino,
della Slovenia, e della Bosnia Erzegovina. I campioni sono stati tagliati longitudinalmente lungo l’asse di
accrescimento e poi lucidati. Dei campioni più promettenti (con laminazione ben visibile, calcite primaria pulita,
senza evidenti segni di ricristalizzazione) sono stati datati bottom e top per il loro inquadramento cronologico. Il
successivo campionamento a microdrilling ha permesso di ricavare le polveri utili per le analisi degli isotopi
stabili dell’ossigeno e del carbonio, effettuate tramite spettrometria di massa. Tali studi permetteranno di
ricostruire il clima del passato delle aree di campionamento, fornendo un valido contributo allo studio
paleoclimatico del Mediterraneo centrale
L'objet emblématique Karst : Paysages, mémoires de l'environnement et des hommes, dix années de recherches au laboratoire EDYTEM.
No full textDelannoy Jean-Jacques, Boche Élisa, Cailhol Didier, Couchoud Isabelle, Chalmin Emilie, Drysdale Russell, Duval-Massaloux Mélanie, Dzikowski Marc, Gauchon Christophe, Hobléa Fabien, Jaillet Stéphane, Lignier Vincent, Malgat Charlotte, Nehme Carole, Perrette Yves, Poulenard Jerôme, Quiers Marine, Sadier Benjamin. L'objet emblématique Karst. Paysages, mémoires de l'environnement et des hommes, dix années de recherches au laboratoire EDYTEM. In: Collection EDYTEM. Cahiers de géographie, numéro 16, 2014. Environnements, dynamiques et territoires de la montagne : Dix ans de recherches au laboratoire EDYTEM. pp. 51-84
Ricostruzioni paleoclimatiche del Peri-Adriatico attraverso speleotemi: primi risultati
Full text linkNell’ambito di una tesi di dottorato presso l’Università di Bologna e l’Université de Savoie (Francia), ed in
collaborazione con l’Università di Melbourne (Australia), si sta portando avanti un ambizioso progetto di ricerca
con l’intento di individuare dei record paleoclimatici in speleotemi campionati in grotte d’Italia e del Carso
dinarico. In questa prima fase di campionamento, grazie al coinvolgimento degli speleologi locali, sono state
raccolte stalagmiti e colate già rotte in precedenza in grotte della Puglia, dell’Emilia Romagna, del Triestino,
della Slovenia, e della Bosnia Erzegovina. I campioni sono stati tagliati longitudinalmente lungo l’asse di
accrescimento e poi lucidati. Dei campioni più promettenti (con laminazione ben visibile, calcite primaria pulita,
senza evidenti segni di ricristalizzazione) sono stati datati bottom e top per il loro inquadramento cronologico. Il
successivo campionamento a microdrilling ha permesso di ricavare le polveri utili per le analisi degli isotopi
stabili dell’ossigeno e del carbonio, effettuate tramite spettrometria di massa. Tali studi permetteranno di
ricostruire il clima del passato delle aree di campionamento, fornendo un valido contributo allo studio
paleoclimatico del Mediterraneo centrale
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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