1,720,978 research outputs found
Editorial: Application of Photocatalysts in Environmental Chemistry
Full text linkThe removal of contaminants from wastewater, which are produced by human activities, and the development of new means of renewable energy production are the main issues that need to be addressed to solve environmental problems [...
Detailed Investigation of ROS arisen from Chlorophyll a/Chitosan based-biofilm
No full textThe aim of this work is to study the nature of reactive oxygen species, ROS, arisen from Chitosan/2-HP--Cyclodextrin/Chlorophyll a (CH/CD/Chla) blended biofilm under a photodynamic activity. Suitablemolecules, called primary acceptors, able to react selectively with ROS, in turn generated by the pho-tosensitizer (PS), herein Chla, are used to attempt this purpose. The changes of the absorption and theemission spectra of these acceptors after the irradiation of aqueous solution containing the active biofilmhave provided the specific nature of ROS and thus the main pathway of reaction followed by PS, in ourcondition. The1O2formation was unveiled using Uric Acid (UA) and 9,10-diphenilanthracene (DPA). Onthe other hand, 2,7- dichlorofluorescin and Ferricytochrome c (Cyt-c) were used to detect the formationof hydrogen peroxide and superoxide radical anion, respectively. Results suggest that among the possiblepathways of reaction, namely Type I and Type II, potentially followed by PSs, in our condition the hybridbiofilm CH/CD/Chla follows mainly Type II mechanism with the formation of1O2. However, the latter isinvolved in subsequent pathway of reaction involving Chla inducing, in addition, the formation of O2•−and H2O2
An interesting environmental friendly cleanup: the excellent potential of olive pomace for disperse blue adsorption/desorption from wastewater
Full text linkThe removal of Disperse Blue 73 from aqueous solutions, using olive pomace as adsorbent material, was investigated in a batch system with respect to contact time, pomace dosage, pH and temperature. SEM, FTIR-ATR, TG and XPS analyses appeared as powerful tools to characterize olive pomace, before and after the adsorption of dye, while UV–Visible analyses were used to quantify the amount of loaded dye on adsorbent material. The pseudo-second order kinetic model well fitted the experimental data and described the kinetic adsorption process. The dye desorption in glacial acetic acid was also obtained with the dye recovery enabling the recycle both of adsorbent material and dye itself. Five consecutive cycles of adsorption and desorption were performed and the absence of any degradation process affecting the dye after the adsorption/desorption cycles was observed. The recorded absorption spectrum, in acetic acid solution, before and after the desorption, confirmed such result. An environmentally friendly and a low cost material is thus presented, showing the excellent olive pomace potential both in disperse blue adsorption (with an efficiency of 100%) and desorption (with a mean value of 80% for each cycle). Additionally, an alternative environmental friendly use of olive oil solid residues is presented
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
Removal from wastewater and recycling of azo textile dyes by alginate-chitosan beads
Full text linkAlginate-chitosan beads were used as adsorbent to remove two azo anionic textile dyes, Direct Blue 78 and Direct Yellow 106, from aqueous solutions. Batch mode experiments of dyes adsorption were performed and the effects of various parameters such as contact time, adsorbent dosage, initial dye concentration, pH and temperature were examined. Successively, the dyes have been desorbed from the adsorbent and were recycled to dye a cotton fabric. The maximum efficiencies in dye removal, performed at pH 6, 298 K and with 0.5 g of adsorbent, were found to be about 97% for Direct Blue 78 and about 86% for Direct Yellow 106, respectively. The adsorption isotherms fitted the Freundlich’s model, the adsorption kinetics followed the pseudo-second order model and experimental data indicated an exothermic adsorption process. Moreover, the dyes desorption experiments from the alginatechitosan beads demonstrated that about 50% of dyes were released in distilled water at high temperature (368 K) and the colored solutions obtained were so reused in dyeing tests. The results demonstrated that the alginate-chitosan beads are very efficient systems able not only to remove dyes from wastewater, but also to recycle and reuse them in further dyeing processes
Interactions between 4-thiothymidine and water-soluble cyclodextrins: Evidence for supramolecular structures in aqueous solutions
Full text linkSince several years the inclusion of organic compounds (guests) within the hydrophobic cavity (host) of cyclodextrins (CDs) has
been the subject of many investigations. Interestingly, the formation of inclusion complexes could affect the properties of the guest
molecules and, for example, the influence of the delivery system can be a method to improve/change the photochemical behavior of
the guest. In particular, very recent studies have shown the protective role of CDs preventing the degradation of the encapsulated
guest. Starting from this consideration, in this work, only the structure and complexation mode of the inclusion complexes involving
4-thiothymidine (S4TdR, a known photosensitizer) and five CDs, namely 2-hydroxypropyl-α-cyclodextrin (2-HP-α-CD),
2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD), 2-hydroxypropyl-γ-cyclodextrin (2-HP-γ-CD), heptakis-(2,6-di-O-methyl)-β-cyclodextrin
(DIMEB CD) and heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB CD) were investigated by different spectroscopic
techniques (UV–vis, FTIR–ATR, 1H NMR) and cyclic voltammetry analysis (CV). This work is necessary for a prospective
research on the photoreactivity of S4TdR in aqueous environment and in the presence of CDs to prevent its degradation under irradiation.
UV–vis, FTIR–ATR and CV measurements suggested the formation of supramolecular structures involving the employed
CDs and mainly the pyrimidine ring of S4TdR. 1H NMR analyses confirmed such indication, unveiling the presence of inclusion
complexes. The strongest and deepest interactions were suggested when TRIMEB and DIMEB CDs were studied. The S4TdR
affinity towards CDs was also evaluated by using the Benesi–Hildebrand (B–H) equation at 25 °C employing CV and 1H NMR
methods. The stoichiometry of the interaction was also inferred and it appears to be 1:1 for all examined CDs
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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