1,720,992 research outputs found
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
50 years of woody vegetation dynamics in the Senegalese Sahel (Ferlo) : bases for a functional diversity approach
No full textSahelian woody vegetation has been the topic of many researches since the great drought that struck the Sahel in the 1970s-1980s. However, there is currently no consensus about the long-term trends of these savannas as observations sometimes seem contradictory according to the indicators used. Moreover, the observed trends often lack an understanding of the consequences on ecosystem functioning and subsequently on the provision of ecosystem services (ES), even if a decrease in ES is often assumed. As the inhabitants of the sylvo-pastoral zone of Senegal rely on these ES in their daily life, it is crucial to be able to predict the woody vegetation response to the current pressures acting on these ecosystems. In this research, we investigate the long-term trends of woody vegetation in order to discuss its persistence and its effects on two ecosystem functions (primary productivity and biogeochemical cycles) when facing three types of disturbances (drought, fire and grazing). This vegetation is examined from 1965 to 2018 using different indicators of the vegetation state and persistence, computed at several spatial scales and derived from multiple datasets (field inventory, remote sensing and literature). We first studied the spatial differentiation of the current woody vegetation according to the topography. Second, we evaluated changes since 1965 onward in terms of specific composition, density and woody cover. Third, we transposed the different indicators from the first two parts into a functional level of the woody communities, focusing on the vegetation response to pressure and effects on ecosystem. Based on this functional approach, we suggest some avenues for a potential management of this zone, in order to maintain the sylvo-pastoralism as land use.(AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 202
Cinquante ans de dynamique de la végétation ligneuse dans le Sahel sénégalais (Ferlo) : bases pour une approche de la diversité fonctionnelle
Get PDFAlthough the persistence of woody vegetation in the Sahel has been regularly studied since the great drought of the 1970s-1980s, given its influence on ecosystem functioning and services, understanding the response capacity of woody vegetation to different pressures (grazing, fire and drought) remains critical.
To understand how this vegetation copes with these pressures in the Sahelian sylvo-pastoral zone of Senegal, we undertook to apply a functional diversity approach. Based on several datasets (field inventories, remote sensing data and functional traits), we built indicators at different spatial scales. First, we studied community dynamics from 1965 to 2018. Secondly, we classified species into functional groups according to their effect traits linked to primary productivity and biogeochemical cycles. Changes since 1970 in the diversity of responses of these functional groups were investigated.
Remote sensing data show a decrease in the density of woody individuals until 2008, followed by stabilization (2008-2018). Historical inventories show changes in species composition, an increased ratio of bushes and a decline in the frequency of one quarter of species. Local topography strongly influences plant communities, which are dominated by a few minority species. Species and functional richness, adult and regeneration density and woody cover are all higher in lowland areas. Nevertheless, the lack of regeneration in many species is jeopardising their future.
The drought response in species whose abundance was stable from 1970 to 2015 differs from the response in declining species. The drought in the 1970s-1980s appears to have selected trait combinations that include a longer leafing period, vessels with a smaller area and shrub species. Furthermore, the diversity of responses in most of the functional groups has declined, indicating a loss of resilience of woody communities.
By cross-referencing data on species abundances with regeneration and the functional group they belong to, we determined a few key species to be protected to ensure the persistence of ecosystem functions provided by woody vegetation in the sylvo-pastoral system.
La persistencia de la vegetación leñosa saheliana se cuestiona regularmente desde la gran sequía de 1970-1980, dada su influencia en el funcionamiento del ecosistema y los servicios ecosistémicos. Sigue siendo crucial poder comprender la capacidad de respuesta de esta vegetación a diferentes presiones (pastoreo, fuego y sequía).
Para entender cómo esta vegetación resiste estas presiones en la zona silvopastoral saheliana del Senegal, adoptamos un enfoque de diversidad funcional. Utilizando varios conjuntos de datos (inventarios de campo, teledetección, rasgos funcionales), se construyeron indicadores a diferentes escalas espaciales. En un primer paso, estudiamos la evolución de las comunidades desde 1965 hasta 2018. A continuación, clasificamos las especies en grupos funcionales según sus rasgos de efecto relacionados con la productividad primaria y los ciclos biogeoquímicos. La evolución de la diversidad de respuestas de estos grupos ha sido analizada desde los años 70.
Los datos de teledetección muestran una disminución de la densidad leñosa hasta 2008, seguida de una estabilización (2008-2018). Los inventarios históricos muestran un cambio en la composición de las especies, un aumento de la proporción de arbustos y una disminución de la frecuencia para el 25 % de las especies. La topografía local influye mucho en las comunidades, que están dominadas por una minoría de especies. En efecto, la riqueza taxonómica y funcional, la densidad de adultos y de regeneraciones, así como la cobertura, son mayores en las depresiones. Sin embargo, la falta de regeneración de numerosas especies hace que su futuro sea incierto.
Las especies cuya abundancia se mantuvo estable entre 1970 y 2015 muestran una respuesta a la sequía diferente a la de las especies que están disminuyendo. La gran sequía seleccionó combinaciones de rasgos que incluyen un periodo de foliación más largo, vasos conductores de menor superficie y especies arbustivas. Además, la diversidad de respuestas de la mayoría de los grupos funcionales ha disminuido, lo que indica una pérdida de resiliencia de las comunidades.
Al cruzar los datos sobre la abundancia de las especies, su regeneración y su pertenencia a grupos funcionales, identificamos algunas especies clave que deben ser protegidas para garantizar la persistencia de las funciones ecosistémicas que proporciona la vegetación leñosa en el sistema silvopastoral.
La persistance de la végétation ligneuse sahélienne est régulièrement questionnée depuis la grande sécheresse de 1970-1980, vu son influence sur le fonctionnement de l’écosystème et les services écosystémiques. Il reste crucial de pouvoir appréhender la capacité de réponse de cette végétation face à différentes pressions (pâturage, feu et sécheresse).
Pour comprendre comment cette végétation résiste à ces pressions dans la zone sylvopastorale sahélienne du Sénégal, nous avons adopté une approche de diversité fonctionnelle. À partir de plusieurs jeux de données (inventaires de terrain, télédétection, traits fonctionnels), des indicateurs ont été construits à différentes échelles spatiales. Dans un premier temps, nous avons étudié l’évolution des communautés de 1965 à 2018. Nous avons ensuite classé les espèces en groupes fonctionnels selon leurs traits d’effets liés à la productivité primaire et aux cycles biogéochimiques. L’évolution de la diversité de réponse de ces groupes a été analysée depuis les années 1970.
Les données de télédétection montrent une diminution dans la densité des ligneux jusqu’en 2008, suivie d’une stabilisation (2008-2018). Les inventaires historiques révèlent un changement dans la composition spécifique, une augmentation de la proportion de buissons et une diminution de la fréquence pour 25 % des espèces. La topographie locale influence fortement les communautés, qui sont dominées par une minorité d’espèces. En effet, la richesse taxonomique et fonctionnelle, la densité des adultes et régénérations ainsi que le recouvrement sont plus élevés dans les dépressions. Néanmoins, l’absence de régénérations de nombreuses espèces rend leur futur incertain.
Les espèces présentant une abondance stable entre 1970 et 2015 montrent une réponse à la sécheresse différente de celles en diminution. La grande sécheresse a sélectionné des combinaisons de traits comprenant une plus longue période de feuillaison, des vaisseaux conducteurs de plus petite surface, et des espèces arbustives. En outre, la diversité de réponse de la majorité des groupes fonctionnels a diminué, indiquant une perte de résilience des communautés.
En croisant les données d’abondance des espèces, leur régénération et leur appartenance à un groupe fonctionnel, nous avons déterminé quelques espèces clés à protéger pour assurer la persistance des fonctions écosystémiques rendues par la végétation ligneuse dans le système sylvopastoral
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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