1,720,960 research outputs found
Innovative materials for heavy metals and hydrocarbons removal from wastewater of oil industry
Full text linkRecovery of wastewater is one of the most important challenges for our future due to the endemic scarcity of this resource in many parts of the world. Wastewaters derived from petrochemical activities represent a large share of water linked to human activities. This is due to the centrality of oil for the global economy and the great water consumption for all the linked activities, that goes from extraction to refinery. The adsorption technologies providing zeolite materials, both microporous and mesoporous, present a good choice for water remediation due to their simplicity, effectiveness, long term stability and adaptability. The development of new materials for adsorption technology is the main goal of this thesis. In particular, some microporous materials for heavy metals uptake and several mesoporous materials for hydrocarbons confinement have been characterized by structural and process point of view. Kinetic and thermodynamic (adsorption isotherms) behaviour of all material with different organic and inorganic pollutants is deeply investigated. Mathematical models to describe adsorption kinetics and isotherms have also been developed in order to obtain important parameter useful for the transaction from bench-scale to the next pilot scale. Structural characterization has been carried out to understand which changes occurred in material structure after adsorption of contaminants, the host-guest interactions and thermal stability of materials. This double characterization work was planned to screen a set of known materials and compare their performances to those of a new mesoporous amorphous material: the mesoporous silica-alumina or MSA. Indeed, the ultimate aim is to use MSA as multitalented material for simultaneous removal of heavy metals and hydrocarbons from wastewater derived from oil extraction, oil refining or oil contamination
Variazioni stagionali ed effetto della distanza da sorgenti industriali sulla distribuzione dimensionale di ioni ed elementi nel PM
No full textVariazioni stagionali nella concentrazione e nella solubilità di microelementi nel particolato atmosferico
No full textNel presente lavoro viene studiata la variabilità stagionale delle concentrazioni elementari nel particolato atmosferico (PM) nella Pianura Padana (periodo 2008-2012).
L'applicazione di un metodo di frazionamento chimico (frazioni estratta e residua) e dimensionale (frazioni fine e grossolana) ha permesso di suddividere la concentrazione totale di 20 elementi (As, Ba, Be, Cd, Co, Cu, Fe, Li, Mn, Pb, Ni, Rb, S, Sb, Se, Sn, Sr, Ti, Tl, V) in quattro diversi contributi, associati a diverse sorgenti emissive. Sono stati monitorati tre siti, posti a diversa distanza dall'area industriale di Ferrara e le variazioni estate-inverno di ciascun contributo sono state interpretate considerando le diverse condizioni di stabilità atmosferica e la presenza di sorgenti stagionali. In questo modo è stata ottenuta una descrizione piuttosto dettagliata del comportamento degli elementi come traccianti di sorgente.
Alcuni elementi tossici (Cd, As, V, Tl) sono presenti prevalentemente nella frazione fine e come specie chimiche solubili, più accessibili per l’ambiente e per l’uomo.
Le concentrazioni elementari ai tre siti sono risultate estremamente simili, indicando la grande omogeneità spaziale della composizione del PM e lo scarso contributo delle sorgenti locali, incluse quelle di tipo industriale. L'elevata stabilità atmosferica che caratterizza l'area di studio nei mesi invernali si conferma essere una delle cause principali del pronunciato aumento invernale delle concentrazioni elementari, anche se alcuni elementi, come Pb, Sn, Ni, Li e Rb, presentano contributi significativi da sorgenti a carattere stagionale. Le concentrazioni medie di alcuni elementi (Ti, Fe, Mn, S, V, Ni) sono influenzate dal trasporto a lungo raggio di masse d’aria provenienti dall'area sahariana (più frequenti nei mesi estivi) e dai paesi dell'est Europa (più frequenti nei mesi invernali)
Seasonal variations in the chemical composition of particulate matter: a case study in the Po Valley. Part II: concentration and solubility of micro- and trace-elements
No full textSize distribution (fine and coarse fraction) and solubility distribution (extracted and residual fraction) of 20 elements (As, Ba, Be, Cd, Co, Cu, Fe, Li, Mn, Pb, Ni, Rb, S, Sb, Se, Sn, Sr, Ti, Tl, V) in atmospheric particulate matter (PM) were determined during a 5-year field study carried out in the Po Valley (peri-urban area of Ferrara, in Northern Italy). By studying the contribution of the two size fractions and the two solubility fractions to the atmospheric concentration of each element, it was possible to obtain interesting information about the variability of PM sources, to assess the role played by atmospheric stability in determining pollution episodes, and to obtain an estimate of the bio-accessible fraction. Atmospheric stability is confirmed to be one of the main causes of atmospheric pollution in this area and is to be responsible for the pronounced winter increase in both PM and elemental concentration. Long-range transport of natural and polluted air masses caused temporary increases in PM and elemental concentration, while local industrial emission seemed to play a secondary role. Regulated elements were well below their concentration limit, but many toxic elements were in the form of fine particles and soluble chemical species, more accessible to the environment, and the human body
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
- …
