1,720,956 research outputs found
Slope fans and aprons dominated by supercritical bedforms: topographic and feeding system controls (Southeastern Tyrrhenian Sea)
No full textIn the marine environment, turbidite supercritical bedforms have been widely reported from channel-axis and overbank wedges. On the contrary, their dominance in the make-up of fans and apron, apart from local areas such as channel mouths, is at present not recognized. However, since it has been postulated that turbidity currents reach the supercritical conditions for slope > 0.5°, submarine slopes should contain abundant supercritical flow deposits. Here, we provide a review of different types of slope fans and aprons dominated by supercritical bedforms, based on examples from the modern seafloor. We compare depositional elements located in different intraslope basins of the Tyrrhenian Sea, through high-resolution bathymetry, chirp subbottom section and, where available cores. The variable geological context results in axial and transvers slope fans with highly variable sizes (few to tens of kilometres) and geometries, dependent upon the erosive and/or depositional processes involved, as well as the seafloor topography of the area. In particular, we have recognized two types of lobe-shaped deposits characterized by supercritical bedforms: channel-attached fans and detached aprons. The first ones are connected to a canyon-channel system and develop on slope gradients of 0.5° to 1.2°, display small-scale bedforms (wavelength of about 150 m and height < 10 m), with upslope asymmetric or symmetric cross-sections, interpreted as cyclic steps and antidunes. According to the amplitude of the reflections, cores, and to the bedform aspect ratio, the channel-attached fans are interpreted to be composed of coarse-grained sediments. Our examples highlight that cyclic steps and antidunes dominate the channel-attached fans both in axial and lateral portion while scours mark topographic changes such as breaks in slope or laterally confined areas. Detached aprons develop from the un-incised shelf edge on steep slopes of about 1.2° to 3° and are composed by large-scale bedforms (wavelength of about 500 m and height of about 5 m) mainly upslope asymmetric, associated with cyclic steps. The low amplitude of the seismic reflections suggests the fine-grained nature of the aprons. This study shows that there are significant differences in the distribution and character of supercritical bedforms in slope settings according to the type of feeding system, the degree of flow confinement and the seafloor topography. The analysis of the downslope evolution of turbidity currents, and of the character of associated bedforms in deep-water systems can contribute new perspectives to refine our models of deep-sea depositions
Downslope evolution of supercritical bedforms in a confined deep-sea fan lobe, Amantea Fan, Paola Basin (Southeastern Tyrrhenian Sea)
Full text linkThe sedimentology of upper flow regime bedforms represents an important research topic at the present. Deposits interpreted as those of supercritical flows are widely recognized in modern fan systems, but their recovery is challenging. Most of the sedimentological information has come from channel thalwegs but supercritical bedforms are also frequently downslope from the channel mouths. Such an environment has been identified in the Paola basin, where erosive and depositional cyclic steps have been imaged and identified in a sandy submarine lobe of the Amantea Fan. High-resolution sub-bottom profiles provide insight into the bedform internal architecture and their relationships with a frontally-confining ridge. For the first time, supercritical bedforms in a submarine lobe have been interpreted in two distinct positions: in the scour of an erosional cyclic step and in the stoss side of a depositional cyclic step. Coarse to medium-grained massive sand with flame structures, indicating rapid sediment fall-out and frequently associated with the occurrence of hydraulic jumps, has been identified in the scour and at the toe of the ridge. The latter represents an example of topographically induced hydraulic jumps driven by a frontal confinement. Top-cut-out medium to fine sands with tractive structures have been interpreted as the deposits related to the stoss side of a cyclic step or small-scale antidune superimposed on the cyclic step surface. The presented data broaden the understanding of the range of processes that are driven by the interaction between turbidity currents and seafloor topography and the dip of the slope. The recognition that topography influences the density structure and the degree of criticality of the flow and, consequently, the morphodynamics and facies of the relative deposits may help to explain sediment distribution and improve depositional models of fan lobes in confined settings
Downslope evolution of supercritical bedforms in a confined deep-sea fan lobe, Amantea Fan, Paola Basin (Southeastern Tyrrhenian Sea)
No full textThe sedimentology of upper flow regime bedforms represents an important research topic at the present. Deposits interpreted as those of supercritical flows are widely recognized in modern fan systems, but their recovery is challenging. Most of the sedimentological information has come from channel thalwegs but supercritical bedforms are also frequently downslope from the channel mouths. Such an environment has been identified in the Paola basin, where erosive and depositional cyclic steps have been imaged and identified in a sandy submarine lobe of the Amantea Fan. High-resolution sub-bottom profiles provide insight into the bedform internal architecture and their relationships with a frontally-confining ridge. For the first time, supercritical bedforms in a submarine lobe have been interpreted in two distinct positions: in the scour of an erosional cyclic step and in the stoss side of a depositional cyclic step. Coarse to medium-grained massive sand with flame structures, indicating rapid sediment fall-out and frequently associated with the occurrence of hydraulic jumps, has been identified in the scour and at the toe of the ridge. The latter represents an example of topographically induced hydraulic jumps driven by a frontal confinement. Top-cut-out medium to fine sands with tractive structures have been interpreted as the deposits related to the stoss side of a cyclic step or small-scale antidune superimposed on the cyclic step surface. The presented data broaden the understanding of the range of processes that are driven by the interaction between turbidity currents and seafloor topography and the dip of the slope. The recognition that topography influences the density structure and the degree of criticality of the flow and, consequently, the morphodynamics and facies of the relative deposits may help to explain sediment distribution and improve depositional models of fan lobes in confined settings
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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