1,721,054 research outputs found
Holocene climate variability derived from diatoms census counts. Preliminary data from the Ross area
No full textIn polar areas diatoms often represent the unique microfossil preserved in deep-sea sediments and, thus, a record of past environmental conditions and productivity. A detailed study of Late Quaternary and Holocene diatom assemblages in two marine cores from the north-western Ross Sea as part of HOLOCLIP (Holocene climate variability at high-southern latitudes: an integrated perspective) Project will document environmental condition changes in a little known region.
In the Joides Basin area, the Holocene is represented by a two-meter thick homogeneous biosiliceous mud. The strong occurrence of Chaetoceros Hyalochaete resting spores (CRS) at the base of the sequence highlights the beginning of the deglaciation. Up core, Fragilariopsis curta and F. kerguelensis become dominant, which abundance variations suggest changes in sea ice cover and sea-surface temperatures and track the Hypsithermal - Neoglacial transition.
In the coastal area of Cape Hallett, irregularly laminated biosiliceous mud characterizes the Late Holocene sedimentation. Over the last 5 ka, diatom assemblages are dominated by sea-ice related species, whereby F. curta is the most abundant diatom species with CRS, F. cylindrus and F. obliquecostata present as secondary species. Such diatom assemblages, evidenced in other coastal sectors of Antarctica, may indicate a well established sea ice yearly cycle which waning induced early spring water column stratification.
Integration of high-resolution diatom census counts in these cores, which represent a spatial coverage of paleoenvironmental changes during the Holocene, will allow to documenting sea ice yearly cycle variations at the centennial scale in relation to external forcing
Polar marine diatoms: key markers for Cenozoic environmental shifts. Sedimentary and paleo-environmental reports from Antarctic continental margin (Ross Sea, Wilkes Land and Prydz Bay)
No full textMarine diatoms are sensitive to water-mass distribution and their physical-chemical and biotic preferences affect their
biogeographical distribution. In sedimentary records, although altered by secondary processes such as dissolution, they
track the primary signal formed in surface water. This make them the major biostratigraphic and environmental markers
in the Southern Ocean as they record sea-surface temperatures, sea ice and other parameters usefull for
paleoceanographic and paleoclimatic reconstructions (Jordan et al. 2010; Leventer et al., 2010; Crosta, 2011; Escutia et
al., 2011). We present three case studies of diatom biostratigrapy and paleoceanographic reconstructions performed on
Antarctic sediments recovered from: 1) Pleistocene-Holocene sequences in the Ross Sea and Wilkes Lands, with
evidences of glacial/deglacial-interglacial phases (PNRA and IMAGES-CADO Projects in Atlantic and Australian
Sectors) (Caburlotto et al., 2010; Tolotti et al., 2013) and 2) Late Eocene-Early Miocene sequences in Prydz Bay, with
preliminary micropaleontological results and biostratigraphy related to the greenhouse/ice-house transition (ODP
Project in the Indian Sector) (Lagabrielle et al., 2009; Suto et al., 2012).
Jordan W.J. & Stikley C.E. 2010. Diatoms as indicators of paleoceanographic events. In: Smol J.P. & Stoermer E.F.
Eds., The Diatoms: Applications for the Environmental and Earth Sciences., II Edition., 424-452.
Escutia C., Brinkhuis H., Klaus A. & IODP Expedition 318 Scientists. 2011. IODP Expedition 318: From Greenhouse
to Icehouse at the Wilkes Land Antarctic Margin. Scientific Drilling, 12, 15-23.
Caburlotto A., Lucchi R.G., De Santis L., Macrì P. & Tolotti R. 2010. Sedimentary processes on the Wilkes Land
continental rise reflect changes in glacial dynamic and bottom water flow. International Journal of Earth Sciences,
99(4), 909 – 926.
Crosta X. 2011. Marine diatoms in polar and sub-polar environments and their application to Late Pleistocene
paleoclimate reconstruction. IOP Conf. Series: Earth and Environmental Science, 14, 1-18.
Leventer A., Crosta X. & Pike J. 2010. Holocene marine diatom records of environmental change. In: Smol J.P. and
Stoermer E. F. Eds., II Edition., 401-423.
Lagabrielle Y., Goddéris Y., Donnadieu Y., Malavieille J. & Suarez M. 2009. The tectonic history of Drake Passage
and its possible impacts on global climate. Earth and Planetary Science Letters, 279, 197–211.
Suto I., Kawamura K., Hagimoto S., Teraishi A. & Tanaka Y. 2012. Changes in upwelling mechanisms drove the
evolution of marine organisms. Palaeogeography, Palaeoclimatology, Palaeoecology, 339-341, 39–51.
Tolotti R., Salvi C., Salvi G. & Bonci M.C. 2013. Late Quaternary climate variability as recorded by
micropalaeontological diatom data and geochemical data in the western Ross Sea, Antarctica. Antarctic Science, 25(6),
804–820
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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