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A 5-year climatology of cloud droplets chemical composition from puy de Dôme
No full textChemical and physical processes in the atmospheric multiphase systems significantly influence the transport, vertical redistribution, chemical transformation, and removal of chemical species from the atmosphere, and hence impact on the lifetime of both aerosols and gases. The chemical composition of cloud droplets is an important indicator of the oxidative properties of the atmospheric liquid phase. At present, most of the available knowledge in cloud chemical composition is derived from experimental field campaigns and, hence, only provides limited information on the temporal evolution
of cloud chemistry.
In this study, we compiled 5 years of measurements performed at the puy de Dôme atmospheric station (1465m a.s.l., Central France) and corresponding to more than 40 cloud events and 175 collected samples. Samples have been collected throughout the year for several seasons and at different time of nights and days. Because air masses reaching the sampling site have different origins (Marine/Atlantic Ocean, Continental, Saharan) and degree of anthropogenic influence, the data base offers a very complete
view of cloud composition variability. To our knowledge, this corresponds to one of the largest data base available from a free tropospheric site.
A set of parameters has been measured in each cloud sample and includes pH, conductivity, redox potential, dissolved organic carbon, cations and anions. In some cases, the measurements are completed by the determination of liquid phase concentrations
of Fe(II)/Fe(III), HCHO, H2O2 as well as of the cloud liquid water content (LWC).
In addition, the data base is completed by measurements performed in a continuous basis at the station, including reactive gases and aerosol physical, chemical and optical properties. Meteorological and radiative measurements are also available at the station. Back-trajectory analyses are regularly computed to establish a climatology of the different air masses advected to the sampling site.
Our results show no significant seasonal dependence of the cloud chemical composition that appears to be rather driven by the air mass origin. Clearly, we can distinguish a significant human impact on cloud chemical composition identified with very low pH and increased redox potential, DOC and NO−3 concentrations. On a climatological basis, the LWC does not appear to be driving the total ionic content (TIC) that is mostly controlled by the concentration of cloud condensation nuclei and soluble gas phase species concentrations
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
The sensitivity of natural cloud water to photochemical processes
No full textFormaldehyde and hydrogen peroxide are key constituents of atmospheric photochemical processes, in particular those involved in the HOx and NOx cycles. Direct photolysis of hydrogen peroxide is a source of radicals in both gas and aqueous phases and could therefore be used as an indicator of photochemical activity. Formaldehyde is both a primary pollutant and is produced by oxidation of organic compounds by reactions that can take place both in gas and liquid phases. As such, it can be considered
an indicator of organic matter state of oxidation. Quantifying the behaviour of these 2 species in clouds is therefore of importance to better constraining the relative importance of gaseous versus liquid phase processes and to check the validity of current cloud chemistry models.
In this study, we have used four years of cloud samples collected at the puy de Dôme atmospheric station to investigate the seasonal and diurnal dependence of both H2O2 and HCHO concentrations. A significant seasonal and diurnal dependence of H2O2 concentration in cloud droplets is found with maxima during summer time and round noon time. This shows that solar radiation is one of the most important factors that drive the cloud aqueous hydrogen peroxide concentration. On the contrary, the aqueous concentrations of HCHO do not appear to be linked to solar intensity. In addition, cloud samples collected at puy de Dôme have been used in laboratory experiments to better understand chemical phase processes. Both natural cloud samples and artificial cloud solutions were irradiated in a photo-reactor and the variations of pH, redox potential and key atmospheric substances (HCHO, H2O2, dissolved organic carbon (DOC), and carboxylic acids) were continuously monitored during the experiments. The behaviour of cloud samples differs significantly from that of artificial solutions. H2O2 concentration during the irradiations shows a decrease of about
15% h−1 while it usually increases for artificial solutions. DOC is not varying, while the behaviour of carboxylic acids and formaldehyde appears to depend on the cloud pH. These results lead to the conclusion that H2O2 in cloud is mainly produced by gas-to liquid
transfer and subsequently photo-chemically consumed in the cloud water. Instead, the processes controlling the concentration of HCHO are more complex and clearly change with cloud pH, and hence the degree of anthropogenic influence of the air mass
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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