1,720,963 research outputs found
Turbulent dispersion in the Ocean Surface Boundary Layer
Full text linkThe Ocean Surface Boundary Layer is where the atmosphere and the ocean interact and where the main exchanges of energy and matter take place. This layer is of considerable interest from an environmental point of view, as it is the area richest in flora and fauna, but in pollutants. In particular, among these, the study of the dispersion of plastic fragments with dimensions smaller than 5 mm defined as microplastics is crucial. In fact, in recent years, the growing consumption of single-use plastics, the low recycling rate and the improper disposal of waste have resulted in a serious threat to the marine ecosystem and to human health. Moreover, considering that there is a large mismatch between the estimates of the amount of plastic that enters the oceans and the total amount of plastic sampled at sea surface, for this particular pollutant, the study cannot be limited to the surface, but must also be extended to the entire water column. The study of microplastics dispersion in the mixed layer is tackled by the scientific community with numerical models, laboratory experiments and in situ measurement campaigns. Lagrangian models are very commonly used for this purpose, because they can explicitly take into account the different scales of turbulence and they are very often combined with parametric laws directly related to the travel time of the particles.
The aim of this work is to develop a methodology to deduce the marine turbulence, usable for calculating the dispersion of pollutants in the marine environment; in particular, an innovative parameterization of the vertical turbulent diffusivity have been developed with the aim to consider the sub-grid turbulence occurring in the mixed layer, which is not completely resolved by oceanographic models. This similarity law is based on characteristic scales calculated from meteorological and operational oceanographical models. This parametrization of the vertical turbulence has been implemented in a 3D Lagrangian dispersion model (Wiener3D v6). The model has been validated by comparison with microplastics sampling data deriving from marine monitoring campaigns. With this Lagrangian model, long-term simulations have been conducted in a domain comprising the Tyrrhenian Sea. The simulations allowed investigating the role of mean currents, sub-grid turbulence and, along the vertical direction, a rising/settling velocity in the microplastics displacements. Thus, the model allowed the analysis of the vertical distribution of microplastics along the water column as well as of beaches or seafloor zones subjected to accumulation. The results showed that vertical turbulent diffusivity is an essential factor for the vertical dispersion of microplastics within the mixed layer. Finally, it is observed that the settling/rising velocity assumes a key role in determining the accumulation of pollutants on the seafloor or on the surface, respectively
Modelling VOC Emissions from Building Materials for Healthy Building Design
Full text linkThe profound qualitative changes of indoor air and the progressive increase in the absolute number of pollutants, combined with the scientific awareness of the health impacts deriving from spending more than 90% of one’s time inside confined spaces, have increased the attention onto the needs of well-being, hygiene, and the health of users. This scientific attention has produced studies and analyses useful for evidence-based insights into building performance. Among the main pollutants in the indoor environment, Volatile Organic Compounds (VOCs) play a central role, and the use of box-models using the mass balance approach and Computational Fluid Dynamics (CFD) models are now consolidated to study their concentrations in an indoor environment. This paper presents the use of both types of modelling for the prediction of the VOC concentration in the indoor environment and the proposal of a guide value for the Indoor Air Quality (IAQ)-oriented building design, specifically related to the indoor VOC concentration due to building materials. Methodologically, the topic is addressed through environmental sampling, the definition of the parameters necessary for the numerical models, the simulations with the box-model and the CFD, and the comparison between the results. They show a good correspondence between the modelling tools used, highlighting the central role of ventilation and allowing a discussion of the relationship between regulatory limits of emissivity of materials and Indoor Air Guide Values for the concentration of pollutants
Microplastic detection and Lagrangian modelling in the Tyrrhenian Sea
No full textIn recent years the presence of microplastic (MP) in oceans is getting more and more attention due to its impacts on these environments. A major concern is represented by closed and densely populated basins, like the Mediterranean Sea. In this work, an assessment of MP concentrations in the Tyrrhenian Sea, a sub-basin of the Mediterranean Sea, is performed by means of numerical simulations. A Lagrangian stochastic model of dispersion, which requires hydrodynamic fields and MP sources as inputs, is employed. The hydrodynamic fields are supplied by the Copernicus Marine Environment Monitoring Service (CMEMS), while the MP sources are estimated by means of a novel method based on the population density. The results agree well with field data derived from Goletta Verde sampling campaign and highlight the importance of a correct estimation of the sources. Both the numerical results and field data show the presence of high polluted areas
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
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