1,720,955 research outputs found
Rifting, methane release, global warming and anoxia: response of a Tethyan Jurassic carbonate platform
No full textThe response of two Tethyan carbonate platforms to the early Toarcian (Jurassic) oceanic anoxic event: environmental change and differential subsidence
No full textChemostratigraphic analyses (87Sr/86Sr, d13Ccarb) of limestones from twoJurassic platform-carbonate sequences in Italy (Trento and Campania–Lucania Platforms) illustrate previously established trends found in pelagicsediments and skeletal carbonates from biostratigraphically well-calibratedsections elsewhere in Europe. Chemostratigraphic correlations between theplatform-carbonate successions and appropriate intervals from well-datedreference sections allow the application of high-resolution stratigraphy tothese shallow-water peritidal carbonates and, furthermore, elucidate the faciesresponse to the Early Toarcian Oceanic Anoxic Event (OAE). Lower Jurassic(Toarcian) levels of the western Trento Platform (Southern Alps, NorthernItaly) contain spiculitic cherts that appear where rising carbon-isotope valuescharacterize the onset of the OAE: a palaeoceanographic phenomenoninterpreted as driven by increased nutrient levels in near-surface waters.There is a facies change to more clay-rich facies at the level of the abruptnegative carbon-isotope excursion, also characteristic of the OAE, higher in thesection. The Campania–Lucania Platform (Southern Apennines, SouthernItaly) records a change to more clay-rich facies where carbon-isotope valuesbegin to rise at the beginning of the OAE but the negative excursion, higher inthe section, occurs within oolitic facies. Although, in both examples, the EarlyToarcian OAE can be recognized by a change to more clay-rich lithologies, thisfacies development is diachronous and in neither case did the platform drown.Although the Trento Platform, in the south-west sector studied here, wasadversely affected by the OAE, it did not drown definitively until LateAalenian time; the Campania–Lucania Platform persisted throughout theJurassic and Cretaceous. Differential subsidence rates, which can be calculatedusing comparative chemostratigraphy, are identified as a crucial factor in thedivergent behaviour of these two carbonate platforms: relatively fast in the caseof the Trento Platform; relatively slow in the case of the Campania–LucaniaPlatform. It is proposed that where water depths remained as shallow as a fewmetres during the OAE (Campania–Lucania Platform), dissolved oxygen levelsremained high, nutrient levels relatively low and conditions for carbonatesecretion and precipitation remained relatively favourable, whereas morepoorly ventilated and/or more nutrient-rich waters (Trento Platform) adverselyinfluenced platform growth where depths were in the tens of metres range. Thestage was thus set for drowning on the more rapidly subsiding western marginof the Trento Plateau and a pulse of oolite deposition post-dating the OAE wasinsufficient to revitalize the carbonate factory
Stepwise extinction of larger foraminifers at the Cenomanian- Turonian boundary: A shallow-water perspective on nutrient fluctuations during Oceanic Anoxic Event 2 (Bonarelli Event)
No full textA two-step pattern in the extinction of larger foraminifers is recorded in the upper Cenomanian shallow-water carbonates of the southern Apennines (Italy). The fi rst step eliminated the alveolinids, the most extreme oligotrophs, and reduced dramatically the diversity of larger foraminifers. The second step wiped out the few survivors, seemingly able to tolerate mesotrophic conditions, leaving a disaster fauna dominated by small heterotrophs. This pattern of extinction parallels the ecological succession of shallow-water benthic foraminiferal assemblages along a gradient of increasing nutrient availability. High-resolution carbon isotope stratigraphy shows that the extinction of alveolinids was contemporaneous with the extinction of rotaliporid planktic foraminifers, the drowning of certain Tethyan carbonate platforms, and an episode of thermal instability recorded in sea-surface temperature in the open ocean. Ocean stratifi cation, during the fi rst phase of Oceanic Anoxic Event 2, would have promoted oligotrophic conditions in surface tropical waters and maximum diversity of larger foraminifers. Following this, ocean overturning caused by surface-water cooling is credited with delivering to shallow-water environments the excess nutrient loads previously stored at depth, triggering the environmental changes leading to stepwise extinction of larger foraminifers
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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