1,720,965 research outputs found
Étude des secteurs écologiques, du milieu physique et des caractéristiques de production de la steppe arborée à Acacia tortilis dans le parc national de Bouhedma (Tunisie méridionale)
No full textEcology, physical and production characteristics of the steppe with Acacia tortilis in the Bouhedma national park (Tunisia southernmost).
The present study was conducted in the Bouhedma national park and its surroundings, located in the arid area of Tunisia and considered a Biosphere reserve by UNESCO in 1977 ; it is a protected area with special ecological characteristics and an important dynamics of space occupation. The park contains the only wooded steppe with Acacia tortilis (Forsk.) Hayne subsp raddiana (Savi.) Brenan var. raddiana Brenan in Tunisia. With the aim of safeguarding and management of the park, a better knowledge of the distribution patterns and dynamics of the vegetation of this zone makes it possible to consider programmes of restoration and sustainable management of the natural environment. Based on the interpretation of remote sensing data and use of SIG, the study was devoted to the elaboration of charts relating to the ecological systems present in 2005, and to the distribution of the steppe with Acacia tortilis according to physical factors such as slope, altitude, type and depth of the soil. Also, the production of seeds was studied to explain the effect of physical factors on the regeneration of the species. The analysis of soil occupation dynamics translates into a good distribution (7056 ha) of steppe with Acacia tortilis. The study shows that Acacia tortilis is located on 6242 ha at an altitude of 20 m to 150 m and on 814 ha at an altitude from 150 to 250 m. This species grows on 5815 ha with a weak slope (0 to 3 %), on 928 ha with a slope of 3 to 5 % and only on 313 ha with a slope > 5 %. The results show that the Acacia tortilis is regenerated on the not very advanced soil of hydrous contribution with a surface of 3832 ha, on rendzina with 1280 ha, the isohumic soil with a surface of 986 ha. Acacia tortilis colonizes the far from deep soil with a surface of 2796 ha, the fairly deep soil with a surface of 2175, the very deep soil with a surface of 1970 ha, the not very deep soil with a surface of 75 ha and the deep soil with a surface of 40 ha.La présente étude a été effectuée dans le parc national de Bouhedma situé dans les zones arides tunisiennes et considéré comme une réserve de la biosphère de l’Unesco dès 1977. Le parc abrite l’unique steppe arborée à Acacia tortilis (Forsk.) Hayne subsp raddiana (Savi.) Brenan var. raddiana Brenan en Tunisie. L’étude a été consacrée, grâce à l’interprétation des données de la télédétection et l’utilisation des SIG, à l’élaboration des cartes relatives aux systèmes écologiques présents en 2005 et aux facteurs physiques du milieu (pente, altitude, type du sol, profondeur du sol). L’analyse du système écologique montre que la dynamique de l’occupation des sols se traduit par une bonne répartition de steppe arborée à Acacia tortilis avec une superficie de 7056 ha. L’étude montre qu’Acacia tortilis se localise sur 6242 ha à une altitude de 20 m à 150 m et sur 814 ha à une altitude de 150 à 250 m. Cette espèce pousse sur 5815 ha avec une faible pente (0 à 3 %), sur 928 ha avec une pente de 3 à 5 % mais seulement sur 313 ha avec une pente > 5 %. Les résultats montrent qu’Acacia tortilis se régénère fortement sur les sols peu évolués d’apport hydrique et sur les sols très peu profonds à profonds.Jaouadi Wahbi, Mechergui Kaouther, Gader Ghazi, Khouja Mohamed Larbi. Étude des secteurs écologiques, du milieu physique et des caractéristiques de production de la steppe arborée à Acacia tortilis dans le parc national de Bouhedma (Tunisie méridionale). In: Revue d'Écologie (La Terre et La Vie), tome 68, n°2, 2013. pp. 143-156
Effet des contraintes hydrique et saline sur la germination de trois espèces d’acacias en Tunisie
No full textEffect of water and salt stresses on germination of some acacia species in Tunisia.
This work has focused on the study of germination characteristics of seeds of Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan, a species native of Tunisia, and of two introduced species : Acacia salicina Lindl. and Acacia ampliceps Maslin, reforested in arid zones of Tunisia. Germination was followed under conditions of water and salt stresses. Pre-treatments designed to remove integumentary inhibitions were applied to seeds. The germination behaviour of acacias in osmotic stress conditions showed a treatment effect, concentration of PEG 6000, highly significant on germination rate and mean time of germination. We found that these species did not tolerate drought and we observed a complete inhibition of germination at -0.8 MPa. The study of the effect of salt stress on germination showed a better tolerance of Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan to salinity than the other two species as it germinated at high salt concentrations. Indeed, at 18 g/ l the germination rate reached 32 %. We didn’t find any relationship between seed germinative properties and ecology of the adult plant.Notre travail a porté sur l’étude des caractéristiques germinatives des semences d’Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan, espèce autochtone de la Tunisie et deux espèces introduites Acacia salicina Lindl. et Acacia ampliceps Maslin qui sont utilisées en reboisement dans les zones arides de la Tunisie. La germination a été suivie en conditions de stress hydrique et salin. Des prétraitements destinés à lever les inhibitions tégumentaires ont été appliqués aux semences. Le comportement germinatif des acacias en conditions de stress osmotique a mis en évidence un effet traitement hautement significatif concernant le taux de germination et le temps moyen de germination. Nous avons révélé que ces espèces ne tolèrent pas la sécheresse et nous avons observé une inhibition totale de germination à -0.8 MPa. L’étude de la contrainte saline sur la germination a révélé une meilleure tolérance à la salinité de l’Acacia tortilis (Forsk.) Hayne subsp. raddiana (Savi) Brenan par rapport au deux autres espèces puisqu’il a germé à des concentrations élevées de sel. En effet, à 18 g/ l le taux de germination atteint 32 %. Enfin nos travaux n’ont pas mis en évidence de relation entre les propriétés germinatives des semences et l’écologie de la plante au stade adulte.Jaouadi Wahbi, Mechergui Kaouther, Hamrouni Lamia, Hanana Mohsen, Khouja Mohamed Larbi. Effet des contraintes hydrique et saline sur la germination de trois espèces d’acacias en Tunisie. In: Revue d'Écologie (La Terre et La Vie), tome 68, n°2, 2013. pp. 133-141
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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