1,721,227 research outputs found
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
Multiscale characterization of contaminations of trace elements in soils: spatial and vertical distribution, assessment of soil-plant-worm transfer and potential management by organic amendments
Full text linkHuman economic and technological development has a negative impact on the environment. The soil is not spared from this growing threat through its role in the environmental interface. Once degraded as a result of contamination, it can no longer fulfill its ecosystem functions such as the protection of ecosystems, food production or preservation of the quality of surface water and groundwater. The studies presented in the thesis are on soil contaminated by atmospheric fallouts enriched by trace elements. This type of contamination increases the natural levels of contaminants in soils and particularly in surface horizons to exceed the maximum levels set by legislation.
The first axe of research concerns the assessment of contamination at a landscape scale around a former zinc-lead ore-treatment plant. The spatial distribution of cadmium, lead and zinc in the topsoil (0-20 cm) was characterized using 247 samples taken in crop, grassland and forest on three major types of loam soils representative of the study area Sclaigneaux (Wallonia, Belgium). The distribution of contaminants is explained by the distance to the source of contamination, direction of dominant winds, land use and soil type. Subsequently, 22 soil profiles were sampled within the study area to estimate the vertical transfer of contaminants. Based on various indexes of contamination, no migration along the profiles has been demonstrated. Only some more clay horizons presented contaminant levels that increased relative to their upper horizons.
The second approach studied the soil-plant transfer and soil-plant-worm transfer of contaminants. First, a field study of the quality of grains of barley (Hordeum vulgare L.) harvested in the study area Sclaigneaux was performed. It appears that the concentration of cadmium in the grain meets quality standards for placing the cereals on the market. However, 78% and 94% of zinc and cadmium, respectively, concentrations measured in grains exceed the expected levels of a non-impacted environment by human activity. Secondly, a study on microcosms was conducted with soils of agricultural parcels around Sclaigneaux on which two crops (faba bean, Vicia faba L. and corn, Zea mays L.) were grown and where earthworms (Eisenia fetida (Savigny)) were introduced. The life traits of E. fetida such as mortality and adult weight were not affected by the levels of contaminants unlike the presence of plants which limit their reproduction (weight and number of cocoons). Moreover, the presence of E. fetida in microcosms influenced the mobility and bioavailability of contaminants.
The third approach deals with metal contaminations in vegetable gardens and their management using organic amendments. This method of stabilization aims to decrease the labile fraction of soil contaminants and further reduce their transfer to plants. To do so, two vegetables (spinach, Spinacia oleracea L. and lettuce, Lactuca sativa L.) were grown on contaminated garden soils enriched in various amendments sold in garden centers. The major finding of this study is that management by amendments does not allow a systematic decrease in the soluble fraction contaminants. This is mainly due to the direct intake of rapidly mobilized trace elements produced by the addition of some of the studied amendments.L’homme par son développement économique et technologique impacte sur son environnement. Le sol n’est pas épargné par cette menace croissante de par son rôle d’interface environnementale. Une fois dégradé à la suite de contaminations, il ne peut plus remplir ses fonctions écosystémiques telles que la protection des écosystèmes, la production alimentaire ou la préservation de la qualité des eaux de surface et souterraines. Les études présentées dans la thèse sont menées sur des sols contaminés par des retombées atmosphériques chargées en éléments traces. Ce type de contamination augmente les teneurs naturelles en contaminants dans les sols et plus particulièrement dans les horizons de surface jusqu’à dépasser les teneurs maximales définies par la législation.
Le premier axe de recherches a pour objet l’évaluation d’une contamination à l’échelle d’un paysage entourant une ancienne usine de traitement de minerai de zinc et plomb. La distribution spatiale des teneurs en cadmium, plomb et zinc dans l’horizon de surface (0-20 cm) a été caractérisée à l’aide de 247 échantillons prélevés en culture, prairie et forêt sur trois grands types de sols limoneux représentatifs de la zone d’étude de Sclaigneaux (Wallonie, Belgique). La répartition des contaminants est expliquée par la distance à la source de contamination, le sens des vents dominants, l’occupation du sol et le type de sol. Par la suite, 22 profils de sols ont été échantillonnés au sein de la zone d’étude afin d’estimer le transfert vertical en contaminants. Sur base de différents indices de contamination, aucune migration le long des profils n’a été mise en évidence. Seuls certains horizons plus argileux ont présenté des teneurs en contaminants qui augmentaient par rapport à leurs horizons supérieurs.
La seconde approche a étudié les transferts de contaminants du sol vers les plantes et/ou vers les vers de terre. Tout d’abord, une étude in situ de la qualité de grains d’orges (Hordeum vulgare L.) récoltés sur la zone d’étude de Sclaigneaux a été réalisée. Il ressort que les concentrations en cadmium dans le grain répondent à la qualité de mise sur le marché des céréales. Cependant, 78% et 94% des concentrations en cadmium et zinc mesurées dans les grains dépassent les teneurs attendues en milieu non impacté par des activités anthropiques industrielles. Dans un deuxième temps, une étude en microcosmes a été menée avec des sols de parcelles agricoles de Sclaigneaux sur lesquels deux plantes (la féverole, Vicia faba L. Tet le maïs, Zea mays L.) ont été cultivées et dans lesquels des vers (Eisenia fetida (Savigny)) ont été introduits. Les traits de vie d’E. fetida tels que la mortalité et le poids des adultes n’ont pas été impactés par les teneurs en contaminants ou la présence des plantes contrairement à leur reproduction (poids et nombre des cocons). Par ailleurs, la présence d’E. fetida dans les microcosmes a influencé la mobilité et la biodisponibilité des contaminants.
La troisième approche traite de contaminations métalliques en jardins potagers et de leur gestion à l’aide d’amendements organiques. Cette méthode de stabilisation a pour objectif de diminuer la fraction labile en contaminants du sol et par delà diminuer leur transfert vers les plantes. Pour se faire, deux légumes (l’épinard, Spinacia oleracea L. et la laitue, Lactuca sativa L.) ont été cultivés sur des sols de jardins potagers contaminés enrichis en divers amendements vendus en jardinerie. La conclusion majeure de cette étude est que la gestion sur base d’amendements du commerce ne permet pas une diminution systématique de la fraction soluble en contaminants. Ceci est principalement du à l’apport direct en éléments traces rapidement mobilisables réalisé par l’ajout de certains des amendements étudiés
Contribution à l’écologie de la restauration des écosystèmes cuprifères : Analyses des relations sols-communautés végétales de deux collines de cuivre du Katanga, RDC
No full textCopper-cobalt hills in Katanga (D.R. Congo) host singular plant communities. Those
are highly endangered by mining activities. The preservation of communities requires the
relations with the edaphic factors to be well understood. The study site is composed of two
copper outcrops – Fungurume V and Kavifwafwaulu I – situated within the Tenke Fungurume
mining claim. 84 and 43 quadrats were sampled for soils and plants covers were determined.
Pedological drills descriptions completed the field work. Collected data on vegetation and
soils analyzed for granulometry, pHs, bioavailables contents in Cu, Co, Zn, Mn, Fe, K, Mg,
Ca and P were subjected to statistical analysis to determine: (1) whether or not hills are
distinct; (2) soils groups and their edaphic characteristics; (3) plant communities, their
conservatory status and the edaphic factors influencing and (4) the aggregation between
communities and soils groups. The results from this study indicate that (i) soils and
communities are distinct from one hill to the other; (ii) five and four soils groups form
continuums within the hills for the edaphic parameters; (iii) seven and five communities are
split between steppe savannas and steppes/swards and are notably determined by
bioavailables Cu, Co and Mg and (iv) Fungurume V presents a good aggregation between
soils groups and plants communities while the situation is not as clear for Kavifwafwaulu I
were communities present a pronounced overlapping. Recommendations based on soils
groups are provided for the preservation of interesting plant communities.Les collines de cuivre-cobalt du Katanga (R. D. Congo) hébergent des communautés
végétales uniques grandement menacées par l’exploitation minière. La conservation des
communautés nécessite une compréhension fine des relations entretenues avec leur
environnement édaphique. Situées dans la concession de Tenke Fungurume les clairières de
Fungurume V et de Kavifwafwaulu I, sont l’objet d’une étude détaillée sur 84 et 43 quadrats.
Des échantillons composites de sols y ont été prélevés et les recouvrements spécifiques y ont
été déterminés. Ils sont accompagnés de descriptions de sondages pédologiques. Les données
collectées et analysées pour la granulométrie, les pH, les teneurs en C organique et N total, et
en Cu, Co, Zn, Mn, Fe, K, Mg, Ca et P biodisponibles sont soumises à des analyses
statistiques afin de déterminer : (1) si les collines sont distinctes, (2) les groupes de sols et
leurs caractéristiques édaphiques, (3) les communautés végétales présentes, leur intérêt
conservatoire et les paramètres édaphiques les influençant, et (4) l’organisation des
communautés sur les différents groupes de sols. Les résultats des analyses indiquent que (i)
les sols et communautés végétales sont différents d’une colline à l’autre, (ii) cinq et quatre
groupes de sols forment des continuums pour les valeurs des paramètres édaphiques, (iii) sept
et cinq communautés sont réparties entre savanes steppiques et steppes/pelouses et sont
discriminées pour les deux collines par le Cu, le Co et le Mg et (iv) Fungurume V présente
une bonne agrégation entre groupes de sols et communautés végétales tandis que le cas de
Kavifwafwaulu I est plus nuancé, la végétation s’y interpénétrant plus. Des recommandations
basées sur les groupes de sols sont apportées pour la préservation des communautés végétales
d’intérêt
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
Contribution to the mastery of metallic trace elements contaminations in vegetables
No full textThe set of problems resulting from metallic trace elements in vegetable gardens is increasingly
in the heart of the question, evidently as much as a concern for public health than in terms of
sustainable environmental management. Throughout this work, I aimed at studying particular
aspects of metallic trace contaminations, mainly their dispersal across the soil and soil-plant
transfers. Firstly, a toposequential study focused on the source of contamination was performed
in order to allow the description of the relation between the distance from the source of
contamination and the distribution of the metallic trace elements. It was observed that as far
the distance from the source of contaminations is as low the concentrations of traces elements
are. Secondly, two distinct experiments were performed to assess the soil-plant transfers. The
first one consisted in a culture on a range of contaminated soils of two vegetables varieties (i.e.
lettuce and endive). As a result, it was shown that the two varieties accumulated similarly the
trace elements. The aim of the second experiment was to study the relationship of different
organic matters on the phytoavailability of the traces elements. It was performed by culturing
Spinacia oleracea on three contaminated soils where three different organic amendments
(manure cow, manure cow-hen-horse, and compost) were added with four different
concentrations. Results based on soils and S. oleracea metallic trace elements concentrations
were compared to standards in application for the contaminations in trace elements in the soils
and to the foodstuff standards fixing the concentrations limits of cadmium and lead in the
vegetable-leafs. Finally, it was observed that it was the “manure of cow” amendment used at a
rate of 120g/kg of soil that represented best way to avoid large transfers of metallic trace
elements into the different parts of the plant susceptible to be eaten.La problématique des jardins potagers contaminés par les éléments traces métalliques (ETM) est
de plus en plus au cœur du débat tant pour des raisons évidentes de santé publique que dans le
cadre d’une gestion durable de l’environnement. Tout au long de ce travail, l’étude des
contaminations et de leur origine potentielle a été étudiée. Dans la première partie de ce
mémoire, une approche toposéquentielle centrée sur la source de contamination a permis la
mise en évidence de l’effet distance sur la répartition des éléments traces métalliques. En effet,
il a été constaté que plus on s’écartait de la source de contamination, plus les teneurs mesurées
dans les sols diminuaient. Ensuite, lors de la deuxième partie de ce mémoire, les transferts sols-
plantes des éléments traces métalliques ont été abordés à l’aide de deux expérimentations. La
première avait pour objectif d’étudier deux variétés de plantes potagères (laitue et scarole)
cultivées sur une gamme de sols potagers contaminés. Les résultats obtenus ont démontré que
les variétés accumulaient de manière similaire les éléments traces. La seconde expérience a
permis d’étudier l’influence de différents apports en matières organiques sur la
phytodisponibilité des éléments traces. Pour ce faire, une culture d’épinards (Spinacia oleracea) a
été mise en place sur trois sols potagers contaminés auxquels différents amendements tels que le
fumier de vache, le fumier vache-poule-cheval et du compost ont été ajoutés en quatre
concentrations différentes. Les résultats de concentration en ETM ainsi obtenus pour les sols et
au sein des organes récoltés de S. oleracea ont été comparés aux normes en vigueur pour les
contaminations en éléments traces dans les sols et aux normes de commercialisation fixant les
concentrations en cadmium et en plomb dans les légumes-feuilles. Enfin, de l’analyse des
résultats concernant l’étude des différents apports en matières organiques et ceci, sous
différentes concentrations, il est ressorti que l’amendement « fumier de vache » appliqué en
concentration de 120 g de fumier/kg de sol est le traitement qui conduit à la meilleur
diminution des concentrations rencontrées dans les plantes
Valorization of the Digitalized Soil information for the modelling of pesticide lixiviation into groundwater
No full textIn Wallonia (southern Belgium), 81% of human drinking water is captured from groundwater tables. In spite of actions implemented under the European directives and thematic strategies, the required standard (0.1 µg L-1 by pesticide and 0.5 µg L-1 for all pesticides) for human drinking water is most often exceeded at some catchments. Tools such as mechanistic models are appropriate since they allow an a priori estimation of pesticide concentrations leached at the bottom of soil profile, which could reach the groundwater tables. However, simulations often lead to a degree of uncertainty due to the approximations noted in the models, or due to the reliability of available data.
The main objective of this thesis was to improve the usefulness of the Digital Soil Map of Wallonia (DSMW) and the associated soil analysis database named “Aardewerk” in the framework of the evaluation of the groundwater table contamination by pesticides, in order to reduce approximations associated with the GeoPEARL model and its meta-model MetaPEARL in the area of Condroz. In order to cover the broad spectrum of pesticides used in agriculture in Wallonia, nine theoretical pesticides have been defined.
The first research question is to measure the sensitivity of GeoPEARL to two soil data parameterization schemes at the regional scale, depending on whether we first aggregate soil data at a regional scale before application of the model (AC approach); or we first apply the model to soil profiles and aggregate simulated leached concentrations afterwards (CA approach). The results show a significant difference between the two approaches, compared on the basis of a spatial threshold (80th percentile) calculated by soil type. Moreover, this difference varies depending on pesticide type, and is more important when the simulated concentrations are very low. It is also clear from this analysis that only pesticides located in certain ranges of DT50 (30 and 67 days) and Kom (58 and 252 dm3 kg-1) give concentrations more often above water potability standard of 0.1 µg L-1.
The second research question is to calibrate MetaPEARL metamodel (simplified model) based on GeoPEARL simulated concentrations, from which it was derived by considering only the most sensitive parameters of GeoPEARL. The objective by developing a metamodel is to provide a simple tool, usable for a first evaluation of pesticides leaching in order to identify the most risk-prone areas, but also readily transposable for a global decision support system. In contrast to the approach of MetaPEARL calibration used until now, taking into account soil morphology through soil horizons (layers) types explains about 80% of the spatial variability of pesticide concentrations obtained from the complete original GeoPEARL model.
The third research question is to take into account the spatial variability of input variables within the same soil typological unit using stochastic simulations to assess the uncertainty associated with deterministic simulations (taking into account average values by soil type for the input variables at the regional scale) obtained from MetaPEARL. The random spread of soil characteristics variability leads to a very significant spreading of simulated pesticide concentrations. Moreover, we obtain values of 80th spatial probabilistic percentile higher than those obtained from the deterministic approach. Consequently, for a risk mapping designed to aid decision-making tools, the probabilistic approach should be used since it allows, by taking into account the spatial variability of the model input parameters, to obtain more realistic concentrations of leached pesticides
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
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