1,720,983 research outputs found
Periglacial landscapes on Svalbard: Terrestrial analogs for cold-climate landforms on Mars
No full textPeriglacial landforms on Earth reflect cold-climate conditions and are intimately related to processes due to the presence of ground ice and perennially frozen ground, permafrost. The overall objective of this thesis is to investigate the potential of Svalbard as an analogue to Mars cold-climate landforms, and explore past and present processes and surface conditions on Mars by inference from morphological counterparts in Svalbard. Svalbard has unique advantages that make it a very useful study area. Svalbard is easily accessible and offers a periglacial landscape where many different landforms can be encountered in close spatial proximity. These landforms include thermal contraction cracks, slope stripes, rock glaciers, gullies, debris flows, solifluction lobes, protalus ramparts, and pingos, all of which are close morphological analogues to landforms on Mars.
An approach of integrated landscape analysis, inferred from landform assemblages in Svalbard, is aimed to explore modeling landscape evolution on Mars. Key datasets include visual remote sensing data of similar resolution (20–25 cm/pxl) from Svalbard (High Resolution Stereo Camera–Airborne Extended [HRSC-AX]) and Mars (High Resolution Imaging Science Experiment [HiRISE]). Additional data are digital elevation models over both Svalbard and Mars and remote sensing data from Mars, such as Thermal Emission Imaging System (THEMIS) and Context Camera (CTX) images. Field work was done in combination with remote sensing to acquire ground-truth data.
In Svalbard, fluvial and debris-flow processes are evident in the formation of gullies, but the morphological characteristics clearly show that the transport and sedimentation of eroded material are predominated by debris flows. Most investigated gullies on Mars lack clear evidence for debris-flow processes. The Martian gully fan morphology is more consistent with the deposition of small overlapping fans by multiple fluvial flow events. Clear evidence for debris flows on Mars was only found in two new locations, in addition to a few previously published examples. Detailed studies on debris-flow deposits in a young mid-latitude crater on Mars suggest the action of liquid water after Mars’ last ice age (0.4–2.1 Ma ago). It may represent the most recent morphological indication of water induced mass wasting on Mars.
An investigation of small-scale lobes on Mars northern high-latitudes and their morphological counterparts in Svalbard (solifluction lobes) further suggests widespread thawing and the presence of transient liquid water in the recent past on Mars. Finally, different qualitative scenarios of landscape evolution on Mars to better understand the action of periglacial processes on Mars in the recent past are proposed.
The results show that field work is a suitable approach in analogue studies and facilitates acquisition of first-hand experience with permafrost environments. Based on the morphological ambiguity of certain landforms, it is concluded that Martian cold-climate landforms should not be investigated in isolation, but as part of a landscape system in a geological and spatial context. Analogous landforms in Svalbard occur in strikingly similar proximity as on Mars, which makes them useful to infer the spatial and chronological evolution of Martian cold-climate surface processes. The analysis of the morphological inventory of analogous landforms and landform systems in Svalbard and on Mars give substantial information to constrain the processes operating on the surface of Mar
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
Terrestrial gullies and debris-flow tracks on Svalbard as planetary analogs for Mars
No full textWe compared the morphology of gully sedimentary fans on Svalbard as possible analogs to gullies on Mars in order to constrain whether fl uvial and/or debris-fl ow processes are predominantly responsible for the formation of Martian gullies. Our analysis is based on high-resolution imagery (High Resolution Stereo Camera [HRSC-AX], ~20 cm/pixel) acquired through a fl ight campaign in summer 2008 and ground truth during two expeditions in the summers of 2008 and 2009 in Svalbard, compared to highresolution satellite imagery (High Resolution Imaging Science Experiment [HiRISE], ~25 cm/pixel) from Mars. On Svalbard, fluvial and debris-fl ow processes are evident in the formation of gullies, but the morphological characteristics clearly show that the transport and sedimentation of eroded material are predominated by debris flows. Most investigated gullies on Mars lack clear evidence for debris-flow processes. The Martian gully fan morphology is more consistent with the deposition of small overlapping fans by multiple fluvial flow events. Clear evidence for debris flows on Mars was only found in one new location, in addition to a few previously published examples. The occurrence of debris-flow processes in the formation of Martian gullies seems to be rare and locally limited. If predominantly fl uvial processes caused the formation of gullies on Mars, then large amounts of water would have been required for their formation because of the relatively low sediment supply in stream and/or hyperconcentrated fl ows. Repeated seasonal or episodic snow deposition and melting during periods of higher obliquity in the recent past on Mars can best explain the formation of the gullies
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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