1,720,963 research outputs found
Oxidative unhairing vs sulphide use. A critical comparison
No full textThe conventional unhairing process is one of the most pollutant steps in the leather tanning process, which usually involves great amounts of sulphides, lime and soda ash, generating high BOD and COD values in the wastewater. In this work, we have investigated different oxidative agents, combined or not with enzymes, as a possible replacement for sulphides in unhairing, focused on the possible industrial application of the method developed. Peroxymonocarbonate anion, persulfate anions (peroxymonosulfate and peroxydisulfate anion) and peroxynitrite anion have been chosen and the dehairing of bovine leather has been performed. The performance has been compared in terms of dehairing ability, time, suspended solids, pH, conductivity, COD and total nitrogen (Kjeldahl). All the tests were compared with a pilot test (hair-saving sulphide unhairing) and with a hydrogen peroxide dehairing. The results show the great ability of percarbonate, combined with enzymes, to give complete unhairing in 16 hours, no grain damage in absence of sulphides, and great homogeneity after dyeing tests. The results, also, showed a greater reduction of pollutants in the wastewater
An Overview on the Facile and Reversible Cations Intercalation in Nickel-Hexacyanoferrate Open Framework
Full text linkThe paper reports a detailed study about the influence of the electrolyte composition in nickel-
hexacyanoferrate (NiHCF) electrochemical behavior. Shapes and positions of the CV waves are
strongly related to the cation of the supporting electrolyte, which undergoes intercalation/de-
intercalation during the redox process. The electrochemical behavior of NiHCF has been characterized
in different electrolyte solutions containing either pure monovalent or trivalent metal nitrates. Nickel-
hexacyanoferrate permits the reversible insertion of a wide variety of monovalent, divalent and
trivalent ions in aqueous solution; the characteristic potential Ep of the cathodic process depends upon
the nature of the intercalated cation. Electrochemical measurements demonstrate the unprecedented
fast kinetics of trivalent ion insertion associated with this material. The reported findings represent the
first systematic step toward understanding the principles of multivalent charge screening and provide a
novel cation intercalation mechanism in NiHCF, assisted by both water molecules and ferrocyanide
vacancies. The synergistic mechanism can reduce the electrostatic repulsion and provide a preferential
path for the rapid cation intercalation
Development of a new method for the determination and quantification of residual specific glycol ethers in leather.
No full textI glicol eteri (GE) sono una famiglia di solventi, largamente usati nei rivestimenti di superficie, nelle vernici, negli inchiostri, nei liquidi per freni, nei pesticidi, nei detergenti domestici e industriali e negli additivi antighiaccio per i jet fuel. Sono divisi in due gruppi principali: Serie E, ottenuti a partire dall'etilene, e serie P, prodotta dal propilene. I GE sono studiati principalmente per la loro tossicità e i rischi derivanti dal loro uso e sono strettamente regolati e controllati. Otto composti sono limitati dal programma ZDHC (Zero Discharge of Hazardous Chemicals), a causa dei loro effetti tossici sull'uomo. I livelli di questi composti sono particolarmente controllati nel processo di produzione della pelle, in quanto i GE sono utilizzati come agenti impregnanti, stabilizzatori, solventi e veicoli per i coloranti. Lo scopo di questo studio è quello di sviluppare un nuovo metodo per la determinazione e la quantificazione di residui di glicol eteri specifici nella pelle mediante analisi GC-MS. DEGDME, EGEE, EGEEA, EGDME, EGME, EGMEA, 1PG2MEA e TEGDME sono gli 8 analiti studiati perché non dovrebbero essere presenti nei prodotti in pelle. Sono state studiate le condizioni di estrazione, valutando i diversi recuperi in seguito al cambiamento della temperatura, i solventi e il tipo di estrazione. L'acetone mostra il maggior recupero rispetto ad altri solventi come l'acetato di etile, il metanolo e l'esano, mentre il bagno ad ultrasuoni (59Hz) a 50°C per un'ora è stato più efficace dell'estrazione a temperatura ambiente nelle stesse condizioni. La quantificazione e gli studi dei recuperi degli analiti ricercati sono stati eseguiti mediante analisi GC-MS utilizzando una colonna capillare polare in modalità SIM. In conclusione, il metodo sviluppato ha dimostrato di essere rapido, selettivo, economico e può quindi essere utilizzato per ulteriori analisi e studi di altri glicoli/glicol eteri.
Glycol ethers (GE) are a family of solvents, largely used in surface coatings, paint, inks, brake fluids, pesticides, domestic and industrial cleaners, and jet fuel anti-icing additives. They are divided into two main groups: E-series, formed from ethylene, and P-series, formed from propylene. GE are mainly studied for their toxicity and the risks from their uses and are strictly regulated and controlled. Eight compounds are restricted by the ZDHC (Zero Discharge of Hazardous Chemicals) program, due to their toxic effects on humans. Levels of these compounds are particularly controlled in leather making process, as GE are used during its manufacturing process as impregnating agents, stabilizers, solvents, and vehicles for colorants. The purpose of this study is to develop a new method for the determination and quantification of residual specific glycol ethers in leather by GC-MS analysis. DEGDME, EGEE, EGEEA, EGDME, EGME, EGMEA, 1PG2MEA, and TEGDME are the 8 analytes investigate because they should not be present in leather products. Different extraction conditions were studied, evaluating the different recoveries when changing temperature, solvents, and type of extraction. Acetone shows the greatest recovery than other solvents like ethyl acetate, methanol, and hexane, while ultrasonic bath (59Hz) at 50°C for one hour has been more effective than extraction at room temperature in the same condition. The quantification and the studies of the recoveries of the searched analytes have been performed by GC-MS analysis using a polar capillary column in SIM mode. In conclusion, the developed method has proved to be rapid, selective, economic, and can therefore be used for further analysis and studies of other glycols/glycol ethers
Oxidative unhairing versus sulphide use – A critical comparison
No full textThe conventional unhairing process is one of the most pollutant steps in the leather tanning process,
which usually involves great amounts of sulphides, lime and soda ash, generating high BOD and COD
values in the wastewater.
In this work, we have investigated different oxidative agents, combined or not with enzymes, as a
possible replacement for sulphides in unhairing, focused on the possible industrial application of the
method developed. Peroxymonocarbonate anion, persulfate anions (peroxymonosulfate and
peroxydisulfate anion) and peroxynitrite anion have been chosen and the dehairing of bovine leather
has been performed. The performance has been compared in terms of dehairing ability, time,
suspended solids, pH, conductivity, COD and total nitrogen (Kjeldahl). All the tests were compared with
a pilot test (hair-saving sulphide unhairing) and with a hydrogen peroxide dehairing. The results show
the great ability of percarbonate, combined with enzymes, to give complete unhairing in 16 hours, no
grain damage in absence of sulphides, and great homogeneity after dyeing tests. The results, also,
showed a greater reduction of pollutants in the wastewater.Peer ReviewedPostprint (published version
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
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