1,721,055 research outputs found
Replication Data for Oblique aggradation: a novel explanation for sinuosity of low-energy streams in peat-filled valley systems
No full textLow-energy streams in peatlands often have a high sinuosity. However, it is unknown how this sinuous planform formed, since lateral migration of the channel is hindered by relatively erosion-resistant banks. We present a conceptual model of Holocene morphodynamic evolution of a stream in a peat-filled valley, based on a palaeohydrological reconstruction. Coring, ground-penetrating radar (GPR) data, and 14C and OSL dating were used for the reconstruction. We found that the stream planform is partly inherited from the Late-Glacial topography, reflecting stream morphology prior to peat growth in the valley. Most importantly, we show that aggrading streams in a peat-filled valley combine vertical aggradation with lateral displacement caused by attraction to the sandy valley sides, which are more erodible than the co-evally aggrading valley-fill. Owing to this oblique aggradation in combination with floodplain widening, the stream becomes stretched out as channel reaches may alternately aggrade along opposed valley sides, resulting in increased sinuosity over time. Hence, highly sinuous planforms can form in peat-filled valleys without the traditional morphodynamics of alluvial bed lateral migration. Improved understanding of the evolution of streams provides inspiration for stream restoration
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Potential of feldspar single-grain luminescence signal to enlight past and present landscape dynamics
No full textLa luminescence est basée sur la mesure de l'énergie qu'un minéral accumule par piégeage de charge électronique dans son réseau cristallin pendant une période d'enfouissement et qui est remise à zéro lorsque ce dernier est exposé à la lumière ou à la chaleur. Cette propriété est à l'origine d'une méthode robuste pour la datation des dépôts quaternaires. Ces dernières années, de nouvelles applications sont apparues, en particulier pour le traçage et la quantification des processus de surface dans les domaines fluviaux, en réponse au besoin actuel de méthodes pour quantifier ces processus à de nouvelles échelles de temps. Ce travail s'inscrit dans la lignée de ces développements récents et apporte de nouvelles idées sur la manière d'utiliser la luminescence pour répondre à ces besoins. La luminescence pourrait devenir un outil pour comprendre la dynamique de l'érosion, de l'incision et du transport de particules à la surface de la Terre. Dans cette thèse, la mesure mono-grain du signal de luminescence émis lors de la stimulation infrarouge (IR) de grains de feldspath (pIRIR) provenant de sédiments anciens et modernes de rivières de Nouvelle-Zélande (NZ) a été exploitée. Dans une première partie, l'accent a été mis sur l'applicabilité de ce signal pour le traçage des processus de surface, avec une étude de cas testée sur la rivière Rangitikei, qui a révélé deux choses. Premièrement, que ce signal peut être utilisé pour étudier l'évolution des taux d'érosion et d'incision dans un bassin versant en déséquilibre et deuxièmement, que la luminescence peut être utilisée pour tracer les sources de grains et étudier les variations de la contribution de ces sources dans le temps et dans l'espace en fonction des processus de transport. En particulier dans cette rivière, une période de fort apport de grains avec une signature spécifique a été identifiée, correspondant au bedrock érodé. Ces forts apports sont liés à une forte instabilité des parois du canyon, correspondant au passage d'un knickpoint. Dans une seconde partie, les processus de transport ont été étudié par analyse de l'évolution de la distribution du signal de luminescence dans les sédiments actuels de deux rivières en tresses des plaines de Canterbury, les rivières Waimakariri et Rakaia. Le signal de luminescence montre des tendances longitudinales similaires dans les deux rivières qui sont supposées résulter d'une remise à zéro progressive du signal de luminescence due à la combinaison du transport et du stockage dans la plaine d'inondation. Pour tester cette hypothèse, un modèle statistique simple permettant de simuler l'évolution longitudinale du signal de luminescence d'une population de grains en fonction de ces processus a été développé. Des simulations ont permis d'estimer les longueurs de transport caractéristiques, les temps de stockage et les vitesses virtuelles moyennes des grains dans les deux rivières étudiées. Enfin, pour approfondir la relation entre la luminescence et l'érosion, le signal de luminescence de sédiments modernes provenant de bassins versants répartis de part et d'autre de la ligne de partage des eaux des Alpes du Sud de NZ a été analysé conjointement avec les taux d'érosion déduits des isotopes cosmogénique (10Be). Cette approche a permis de documenter une variation spatiale des taux d'érosion et de d'observer une corrélation positive entre les taux d'érosion 10Be et le signal de luminescence des dépôts fluviaux. La nature du lien entre la luminescence et les taux d'érosion des reliefs est discutée dans ce travail, elle mériterait d'être étudiée plus en détail dans le futur. Cette thèse explore, teste et applique de nouvelles façons d'utiliser et d'interpréter les données de luminescence en mono-grain et révèle son fort potentiel pour étudier les processus de surface de la Terre. Des travaux complémentaires pourraient conduire la luminescence à devenir un outil important et approprié pour quantifier les dynamiques d'érosion et de transport.Luminescence is based on the measurement of the energy that a mineral accumulates by trapping electronic charge in its crystal lattice during a period of burial and which is reset when exposed to light or heat. This property has become a robust method for burial dating of Quaternary deposits. In the recent years, novel applications emerged, in particular for tracing and quantifying surface processes in fluvial domains as we currently lack of high-resolution method to quantify these processes at new time scales, bridging with other methods and applicable to past deposits. This work is in line with these recent developments and brought new ideas on how to use luminescence to meet these needs. In this thesis, the single-grain measurement of the luminescence signal emitted during infrared (IR) stimulation of feldspar grains (pIRIR method) from ancient and modern sediments of New Zealand (NZ) rivers was exploited. In a first part, the focus was placed on the applicability of this signal for tracing surface processes, with a case study test on the Rangitikei River, located on the North Island of NZ, that revealed two things. First, that this signal can be used to study evolution of erosion and incision rates in a catchment in disequilibrium and second, that luminescence can be used for tracing the sources of grains and to study variations in the sources contribution through time and space according to transport processes. In particular in this river, a period of high input of grains with a specific signature was identified, corresponding to bedrock. This was related to high instability of the canyon walls, related to the passage of a knickpoint in the Rangitikei. In a second part, the focal was moved on transport processes only. The idea was to study the evolution of the luminescence signal distribution in modern sediments of two braided rivers of the Canterbury Plains (NZ South Island), the Waimakariri and the Rakaia rivers. Luminescence signals show similar longitudinal trends in both rivers that are supposed to result from a progressive zeroing (bleaching) of the luminescence signal due to the combination of transport during flood and storage in the floodplain. To test this hypothesis, a simple statistical model that simulates the longitudinal evolution of the luminescence signal of a population of grains in relation to these processes was developed. These simulations have then been used to estimate the characteristic transport lengths, storage times and average virtual velocities of grains in the two investigated rivers. Finally, to further investigate the relationship between luminescence and erosion, the luminescence signal of modern sediments from catchments distributed on both sides of the Southern Alps of New Zealand divide was analyzed in conjunction with cosmogenic 10Be catchment-wide erosion rates. The approach allowed to document spatial variation in erosion rates characterized by an increase in erosion from NE to SW and from E to W in the central part of the South Island. Then a positive correlation between 10Be erosion rates and luminescence signal of fluvial deposits is demonstrated, for the first time. The nature of the link between feldspar luminescence signal and the erosion rates of landforms should deserve to be studied in detail in the future. This thesis explores, tests and applies new ways of using and interpreting single-grain luminescence dataset and revealed its strong potential to study Earth's surface processes. Further work could lead to luminescence becoming an important and appropriate tool to quantify erosion and transport dynamics
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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