1,720,985 research outputs found
SF6 and CFC12 in the water column during POLARSTERN cruise PS106/2 (ARK-XXXI/1.2)
No full textDissolved gases that act as passive transient tracers have become increasingly popular in physical oceanography for determining the age of a water mass as well as its circulation. In particular, chlorofluorocarbon CFC12 and Sulfur Hexafluoride SF6 are most adapted for comparatively deep water masses that may be several decades old. We here present the full depth concentrations of CFC12 and SF6 from samples collected in June-July 2017 as part of the Polarstern expedition PS106.2 (ARK-XXXI/1.2) ”SiPCA” north of Svalbard, from the shelf to the Nansen abyssal plain. During selected casts, up to ten samples were collected from the Niskin (as first sample collected upon opening of the Niskin). All Niskin bottles had been cleaned with isopropanol beforehand. Samples were collected by connecting a 300 ml glass ampoule to the Niskin tap via an airtight stainless steel system. We let the ampoule fill three times for rinsing, screwed the system shut after the fourth filling, and immediately put the ampoule in icy cold water. These ampoules were flame sealed immediately after collection, one at a time, so that the last sample was sealed at worst a few hours after the cast. The samples were analysed on land in the months that followed the expedition, at the GEOMAR Helmholtz Zentrum für Ozeanforschung, according to the method described in Stöven (2011). These concentrations will now contribute both to local studies of the Svalbard shelf break and its ecosystem, but also to our understanding of the large scale circulation of deep water masses in the Arctic Ocean
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Ocean ventilation and anthropogenic carbon based on evaluated transient tracer applications
No full textThis thesis includes three manuscripts. The first describes the ventilation of the Mediterranean Sea in 2011 based on multiple transient tracer measurements. The second evaluates the application of different transient tracers and the IG-TTD model by using several data sets from the South Atlantic and Southern Ocean. The third manuscript intorduces a new theory about saturation states of transient tracers and provides a flux estimate of anthropogenic carbon through Fram Strait in 2012
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
Ventilation Processes of the Mediterranean Sea based on CFC-12 and SF6 measurements
No full textThe tracer data of CFC-12 and SF6 allow to determine a TTD ratio for most of the Eastern Mediterranean. The Ionian and Levantine Sea can be described by Δ/r ratios between 0:6-0:8. The Adriatic Sea has a high ratio of Δ/r = 1.2 for depths above 600m and a low ratio of Δ/r = 0.6 for the layers below. The tracer data of the Western Mediterranean as well as the Aegean and Cretan Sea does not fit into the 1D-TTD model. The reasons for the WMed are, that either the tracer couple does not fit into the 1D model or another TTD model must be chosen. The Δ/r ratio of the Aegean and Cretan Sea could not be determined due to the less significance of CFC-12 for young water masses. For all these sea areas a Δ/r ratio of 1.0 was set as mean ratio. Based on the tracer data, recent changes in the water column of the Mediterranean Sea were analyzed. The Eastern Mediterranean returns to a pre EMT (Eastern Mediterranean Transient) state with the Adriatic Sea as the major dense water source for the deep water of the Eastern Basin. The last dense water input from the Adriatic Sea can be verified in the bottom layer of the western Ionian Sea with CFC-12 concentrations > 230 ppt. The tracer minimum zone spreads out vertically and westwards with no intrusion of younger and denser water from the Aegean and Cretan Sea. The recent massive deep water formation of the Western Mediterranean (Western Mediterranean Transit) is shown by CFC-12 concentrations > 220 ppt. The exact spreading of the newly formed deep water could not be determined yet. Watermasses with characteristics of the Western Mediterranean deep water are entering the Tyrrhenian Sea via the channel between Sicily and Sardinia and are present at depths down to 2500m near the slope of Sicily. Based on the Δ/r ratios of the Eastern Mediterranean Sea, a new estimation of column inventories of anthropogenic carbon could be carried out. First calculations show that the column inventories have been underestimated by about 4.4% in comparison to Schneider et al. [2010]
Ozeanventilation und anthropogener Kohlenstoff basierend auf evaluierten Spurengasanwendungen
Get PDFThis thesis includes three manuscripts. The first describes the ventilation of the Mediterranean Sea in 2011 based on multiple transient tracer measurements. The second evaluates the application of different transient tracers and the IG-TTD model by using several data sets from the South Atlantic and Southern Ocean. The third manuscript intorduces a new theory about saturation states of transient tracers and provides a flux estimate of anthropogenic carbon through Fram Strait in 2012.Diese Dissertation besteht aus drei Manuskripten. Das erste Manuskript beschreibt die Ventilation des Mittelmeeres in 2011 basierend auf mehreren Spurengasmessungen. Das zweite Manuskript evaluiert die Anwendung von Spurengasen und dem IG-TTD Modell anahand diverser Datensätze aus dem Südatlantik und dem Südlichem Ozean, Das dritte Manuskript führt eine neue Theorie über Sättigungszustände der Spurengase ein und beeinhaltet eine Flussabschätzung von anthropogenem Kohlenstoff durch die Fram Straße in 2012
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