1,720,982 research outputs found
Resuspension of pollutants in urban conditions
No full textCe travail s’est intéressé à la remise en suspension de particules métalliques (PM2.5) dans un contexte de milieu urbain. Il s’est agi d’estimer la part de particules ré-entrainées dans l’air sous l’effet de paramètres météorologiques et pour des surfaces représentatives de milieux urbains. Dans ce but, des éprouvettes de surfaces de bâti (ardoise, enduit de façade, tuile, verre) ont été ensemencées en particules d’or avant d’être exposées au milieu extérieur. Les essais d'ensemencements ont été réalisés au sein de la chambre expérimentale conçue à cet effet. Les particules de l’étude avaient une distribution centrée sur 0,5 μm. Sept expérimentations de remise en suspension ont été réalisées. Des protocoles adaptés de récupération et de quantification des particules ont également été développés pour mesure par ICP-MS. La quantité de particules remises en suspension a été exprimée en fraction de remise en suspension (%) et par type de surface. Elle représentait le changement de concentration surfacique de particules avant et après les périodes d’expositions. La remise en suspension a pu être observée sur l’ensemble des surfaces pour des vitesses de vents comprises en moyenne entre 0,3 m.s-1 et 1,6 m.s-1. Nous avons également montré que les résultats indiquant une non remise en suspension pouvaient s’expliquer au travers de l’étude des incertitudes de mesures et par des effets de stockage de particules sur certaines surfaces. L’analyse en composantes principales des différents paramètres de l’étude a permis d’identifier la température, la durée d’exposition et l’humidité relative de l’air comme les variables les mieux explicatives des remises en suspensions observées.This work focused on the resuspension of metal particles (PM2.5) in an urban environment. The aim was to estimate the proportion of reentrained particles in the air under the effect of meteorological parameters and for representative surfaces of urban environments. For this purpose, test samples of building surfaces (slate, facade coating, tile, glass) were seeded with gold particles before being exposed to an outdoor environment. The seeding experiments were carried out in an experimental chamber designed for this purpose. The study particles had a distribution centered on 0,5 μm. Seven field campaigns for resuspension were carried out. Adapted protocols for particle recovery and quantification were also developed for measurement by ICPMS. The amount of resuspended particles was expressed as the resuspension fraction (%) and by type of surface. It represented the change in the surface concentration of particles before and after the exposure periods. Resuspension could be observed on all surfaces for wind speeds averaging between 0.3 m.s-1 and 1.6 m.s-1. We also showed that the results indicating non-suspension could be explained by the study of measurement uncertainties and by particle storage effects on some surfaces. The principal component analysis of the different parameters of the study identified temperature, exposure time and relative humidity as the best explanatory variables for the observed resuspensions
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
Etude des artefacts de prélèvement et de la<br />distribution gaz-particules des HAP
No full textAtmospheric polycyclic aromatic hydrocarbons (PAH) has been widely studied since several years because of their human health impact. Due to their physico-chemical properties, PAH in the atmosphere are present in particulate and gaseous phase. This gas-particle partitioning has a strong influence on PAH fate (degradation or deposition) and their health impact. So, for their study, a simultaneous samplig in the two atmospheric phases is necessary. In addition, the European Union (directive n°2004/107/CE) has recently decided that PAH should be monitored. Benzo(a)pyrene (BaP) has been chosen as tracer to represent this class of molecule. For both gas-particle partitioning study and for BaP monitoring, samplings are commonly carried out using high volume sampler. Unfortunately, several studies show that this kind of sampler induced sampling artefacts which could disturb the determination of the atmospheric concentrations in the two phases. The aim of this work is to improve the sampling procedure of PAH by the validation of a denuder sampler previously calibrated under laboratory conditions. In this goal several field campaigns were carried out to compare particulate phase sampling and gas-particle partioning with both conventional and denuder samplers. For concentrations in the particulate phase the results showed significant differences between the two samplers which could be important (up to a factor 10), especially for the most reactive PAH such as BaP. This could be the result of degradations occurring on the filter of the conventional sampler during sampling whereas the filter of the denuder sampler is protected from the oxidants by the denuder tube. The importance of the degradation artefact seems more linked to “the aged of particle” than to the concentrations of oxidant. On the other hand, no relevant differences were observed for the partition study of this kind of semi-volatil coumpounds between the two devices. Finally we conceived and realised an experimental device in order to study the reactivity of PAH occuring in the denuder tube during sampling. The study have been realised for naphthalene with ozone as oxidant.Les hydrocarbures aromatiques polycycliques (HAP) dans l'atmosphère sont largement étudiés depuis de nombreuses années, en raison de l'impact sanitaire de ces composés sur l'homme. Du fait de leurs propriétés physico-chimiques, les HAP se répartissent dans les phases gazeuses et particulaires. Cette partition gaz-particule influe sur leur devenir (transport et réactivité) et sur leur impact sanitaire. Ceci rend nécessaire le prélèvement simultané dans les deux phases. Par ailleurs le parlement européen (directive fille n°2004/107/CE) a récemment décidé qu'ils devaient faire l'objet d'une surveillance et le benzo(a)pyrène (BaP) a été choisi comme étant représentatif de cette classe de composés. Dans les cas d'une étude gaz-particule des HAP ou d'un suivi réglementaire (du B(a)P en phase particulaire) la mesure est généralement effectuée par préleveur conventionnel haut volume. Or, de nombreux auteurs ont montré que ce type de préleveur engendrait de multiples artefacts. Ce travail a pour objectif d'améliorer la mesure biphasique des HAP (et plus généralement des composés organiques semivolatils) en validant un tube dénudeur préalablement calibré en laboratoire. Pour cela nous avons réalisé plusieurs campagnes de terrain afin de comparer le préleveur dénudeur au préleveur conventionnel. Les résultats nous ont permis d'observer des différences parfois très importantes entre les préleveurs notamment pour les HAP les plus réactifs (dont le BaP). Ceci semble indiquer une dégradation des HAP particulaires sur le filtre du préleveur conventionnel tandis que le filtre du préleveur dénudeur est protégé des oxydants gazeux par le tube dénudeur. Néanmoins, l'ampleur de cette dégradation n'est pas une fonction linéaire de la quantité d'oxydants. Elle semble être influencé par d'autres paramètres, tels que l'état de "vieillissement" de la particule. Enfin nous avons conçu et réalisé un dispositif expérimental permettant d'étudier la dégradation potentielle des HAP à l'intérieur du tube durant le prélèvement. Cette étude a été réalisée pour le naphtalène avec l'ozone comme oxydant
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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