1,721,031 research outputs found
Isotopic and temperature data from northern Victoria Land ice wedges (East Antarctica)
No full textIce wedges, with tops located 27 to 55 cm below the ground surface, were studied over several summers
between 1998 and 2006 at three sites with differing elevations in northern Victoria Land, East Antarctica.
The thermal regime, based on data‐logger measurements over seven years, exhibits very low temperatures.
The inferred absence of snow and the high temperature gradients, between the ground surface and the top
of ice wedge, may trigger the cracking.
A co‐isotopic study of the wedge‐ice oxygen (d18O) and hydrogen (dD) isotopic values shows extremely
negative deuterium excess (d=dD‐8*d18O) values with a strong divergence from the expected precipitation.
These values suggest that water vapour condensation and sublimation processes play an important role
during the formation of these ground‐ice bodies, particularly at high‐elevation sites. Large temperature
gradients between the air/ground and permafrost, thin or absent snow cover, low humidity and open cracks
during winter are factors that may control the sublimation processes. In addition, strong katabatic winds
acting in the area may enhance sublimation. All these factors explain the less negative ice‐wedge d18O
values compared with the precipitation and very negative deuterium excess values found at the sites.
Observations of hoarfrost crystals in open fractures, even in summer, and frequent temperature inversions
between the air/ground interface and ice‐wedge top support the hypothesis that condensation and
sublimation are important processes in ice‐wedge formation. Moreover, sublimated snow may also
contribute to the formation process. Only isotopic values found at low‐elevation sites can be explained by
both melting‐refreezing and sublimation processes.Ice wedges, with tops located 27 to 55 cm below the ground surface, were studied over several summers
between 1998 and 2006 at three sites with differing elevations in northern Victoria Land, East Antarctica.
The thermal regime, based on data‐logger measurements over seven years, exhibits very low temperatures.
The inferred absence of snow and the high temperature gradients, between the ground surface and the top
of ice wedge, may trigger the cracking.
A co‐isotopic study of the wedge‐ice oxygen (d18O) and hydrogen (dD) isotopic values shows extremely
negative deuterium excess (d=dD‐8*d18O) values with a strong divergence from the expected precipitation.
These values suggest that water vapour condensation and sublimation processes play an important role
during the formation of these ground‐ice bodies, particularly at high‐elevation sites. Large temperature
gradients between the air/ground and permafrost, thin or absent snow cover, low humidity and open cracks
during winter a
Growth processes of an inland Antarctic ice wedge, Mesa Range, northern Victoria Land
No full textDuring the 16th Italian Antarctic Expedition (2000/01) a geomorphological survey of permafrost-related polygons was carried out in the Mesa Range area, upper Rennick Glacier. The investigated site is located in the uppermost reaches of Pain Mesa, which forms the northern sector of the Mesa Range. An ice wedge was found in a volcanic regolith at about 2200 m a.s.l. This altitude is below a well-defined erosional trimline, located at about 2380 m a.s.l. in this sector of Pain Mesa. The ice was sampled by inserting an ice screw, with an internal diameter of 14 mm, into the ice wedge in vertical sequences. Oriented block samples for thin sections were taken. A co-isotopic study was performed, measuring both oxygen (delta O-18) and hydrogen (delta D) isotope compositions. Tritium activity was measured, and major cations and anions were determined. The delta O-18 and delta D obtained showed a strong divergence from the snowfalls expected to occur at this elevation, with extremely negative d excess values. Sublimation processes were taken into account to define the origin of the ice forming the wedge. The tritium data obtained suggest that the growth process of the ice wedge might still be active today
“Variazioni dell’eccesso di deuterio nel corso degli ultimi 800.000 anni nella carota di EPICA Dome C (Antartide Orientale): implicazioni paleoclimatiche”
No full textCo-tutor: Dott.ssa Barbara Stenni – Dipartimento di Scienze Geologiche, Ambientali e Marine – Università di Triest
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
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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