1,721,038 research outputs found
Preservanti del legno: trattamenti innovativi a base di poliamidoamine e proposta di norma standard per termiti “del legno secco”
No full textIl legno è una risorsa rinnovabile ampiamente usata come materiale strutturale e per una varietà di manufatti, grazie alle proprietà meccaniche particolarmente vantaggiose ed alle caratteristiche estetiche. Tuttavia, a causa della sua natura organica, è soggetto a deterioramento fisico e biologico e in particolare all’attacco di insetti xilofagi come le termiti. È stato sviluppato e brevettato un trattamento innovativo del legno a base di poliamidoamine (PAA) funzionalizzate con silossani, che è stato testato su diversi agenti di biodeterioramento. A livello europeo e italiano, nell’ambito della tecnologia e dei prodotti per la protezione del legno, le norme standard esistenti riguardano test di efficacia e durabilità del legno nei confronti di diversi organismi, come i funghi lignivori, organismi marini perforanti (es. Teredini) e, tra gli insetti, i coleotteri xilofagi (Anobiidae, Lyctidae, Cerambycidae) e le termiti (Dictyoptera: Isoptera). Tuttavia, considerando in particolare le termiti, le uniche norme esistenti (UNI EN117, UNI EN118) riguardano esclusivamente le termiti sotterranee (Rhinotermitidae) come Reticulitermes spp. Le cosiddette termiti “del legno secco” (Kalotermitidae), rappresentate in Europa da Kalotermes flavicollis e Cryptotermes brevis, sempre più frequentemente si annoverano come pericolosi infestanti di manufatti lignei ed elementi strutturali per abitazioni/edifici. Queste termiti sono assai diverse da quelle sotterranee per caratteristiche biologiche ed etologiche, modalità di attacco e tipologia di danno sul legno e non è pertanto proponibile ne accettabile utilizzare le norme esistenti relative alle termiti sotterranee. Per sopperire all’assenza di norme internazionali ufficiali idonee, viene quindi proposto un protocollo specifico per verificare l’efficacia di trattamenti su legno contro specie di Kalotermitidi. Il presente lavoro era volto a testare l'efficacia di tre formulazioni di PAA (denominate A, B, C) come preservanti del legno, utilizzando per la termite sotterranea R. lucifugus lo standard EN 118, e per la termite del legno secco K. flavicollis il protocollo appositamente sviluppato. Dai risultati è emerso che tutte le formulazioni si sono rivelate efficaci come trattamenti preventivi nei confronti di R. lucifugus, facendo registrare un consumo di legno trascurabile ed una mortalità significativamente maggiore rispetto al controllo. Per quanto riguarda K. flavicollis, tutte le formulazioni di PAA hanno comportato una riduzione significativa del livello di attacco del legno e la formulazione B si è rivelata la più efficace anche nel ridurre la sopravvivenza delle termiti. Nel complesso, i trattamenti innovativi a base di PAA appaiono promettenti nella protezione del legno dagli attacchi delle termiti, risultando efficaci a basse concentrazioni, oltre ad avere un ridotto impatto ambientale e a dimostrare un buon fissaggio nel legno. Il protocollo proposto per la norma standard sulle termiti del legno secco si è rivelato valido ed efficace e potrebbe essere candidato tra le norme internazionali a questo scopo
Formation of an anchored copper(II) complex on a thiourea-functionalized silica gel by in situ modification of the tethered ligating function
No full textStructural motifs in heteroleptic copper and cadmium selenites
No full textCu(II) cations in the presence of diamine ligands such as tetramethylethylendiamine (TMEDA) react with Na2SeO3 to produce the heteroleptic selenite copper compound of formula [Cu3(TMEDA)3(SeO3)2(H2O)4](NO3)2. In the cationic moiety two copper atoms are linked by two selenite anions through the O-Se-O bridge. One of the two bridging selenite anion coordinates to a third copper atom through the third oxygen atom. Reaction of Cd(CH3COO)2·2H2O with Na2SeO3 in the presence of ligand with softer character such as thiourea [(NH2)2CS; tu] or selenourea [(NH2)2CSe; tu] in aqueous solution afforded the complex [(Cd(tu)2SeO3)2], whose structure has been elucidated by X-ray diffraction analysis. It is the first reported example of a molecular cadmium selenite complex. Two cadmium cations stabilized by the coordination of four ancillary thiourea soft ligands, are linked together by two bridging selenite ions through O and O-Se-O bridges. A comparison between the coordination mode of the selenite ion in those cadmium and copper complexes and in inorganic extended CdSeO3 and hydrated CuSeO3 phases is also reported
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
Olefin epoxidation over Molybdenum(VI) catalysts derived from dithiocarbamate complexes grafted onto silica
No full textVariations 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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