1,720,975 research outputs found
Il metodo Rietveld nello studio della capacità deflocculante di tripolifosfati di sodio
No full textDermatoglifi digitali e palmari nei soggetti con sindromi dismorfiche e nei loro familiari. Presentazione dei dati
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Compositi biodegradabili rinforzati con idrossiapatite sintetizzata in situ per applicazioni in ingegneria tissutale
No full textIn questo lavoro si affronta la preparazione di compositi biodegradabili bioattivi a base policaprolattone (PCL) rinforzati con idrossiapatite (HA) sintetizzata in-situ tramite metodo sol-gel, potenzialmente sfruttabili come scaffold nella ricostruzione del tessuto osseo. Il metodo di sintesi proposto intende eliminare gli svantaggi connessi all’utilizzo dei componenti singoli del composito, permettendo di ottenere in un unico stadio di preparazione una fase inorganica rinforzante e porosa, costituita da HA pura, omogeneamente dispersa in una matrice polimerica. Lo scopo ultimo è quello di ottenere un biomateriale polimerico che, degradando in ambiente biologico, lasci scoperta la struttura di HA su cui possano attecchire le cellule per la ricostruzione del tessuto osseo. Inoltre, la matrice polimerica degradata lascia all’interno dello scaffold dei pori, i quali hanno dimensione adeguata al passaggio dei nutrienti e delle proteine, processi essenziali al processo biologico di ricostruzione del tessuto. Sono stati ottenuti compositi a diverso contenuto di HAP, ne è stata studiata la struttura cristallina e morfologica, ed è stata valutata la possibilità di stampare a compressione dei manufatti senza alterarne la struttura della fase inorganica
Enhanced reactivity of NiO/Pd(100) ultrathin films toward H2: Experimental and theoretical evidence for the role of polar borders
No full textNiO layers in the ultrathin regime exhibit an enhanced reactivity toward hydrogen with respect to the typical chemical inertness of bulk-like thicker samples. Such a behavior has been studied by means of photoemission (from both core and valence band levels) and quantum mechanical calculations. It is found that after H2 dosing in mild conditions (from PH2 = 6.5 × 10-7 Pa and T = 330 K) ultrathin films (thickness ≤6MLE, MLE = monolayer equivalent) quickly react forming metal nickel and water. The kinetic of the reaction has been followed in situ recording the intensity of the O 1s and Ni 2p photoemission spectra under different reaction conditions (PH2 ranging from 5 × 10-7 to 2 × 10-5 Pa and T from 330 up to 453 K), and a first-order dependence of the reaction rate on the PH2 and the activation energy of the rate determining step (0.16 ± 0.02 eV) have been determined. A 8 MLE thick film recovers the behavior of bulk-like NiO(100) surfaces, where more drastic reduction conditions are needed, and the kinetic implies an induction period followed by autocatalysis. The enhanced reactivity has been explained assuming the presence of NiO(100) islands exposing polar borders, whose existence was evidenced by previous scanning tunneling microscopy investigations. Such a scenario is confirmed by ab initio quantum mechanical calculations carried out employing polar and nonpolar terminated stepped surface epitaxially strained in order to account for the presence of the metal support which has not been explicitly included. Reported calculations indicate that the polar border can easily dissociate H2 without any activation barrier. The rate determining step of the reaction has been associated to the stage of the reaction where the previously formed hydroxyl groups react with a second hydrogen molecule (an Eley−Rideal-like mechanism) to form metal Ni islands and water, which readily desorbs
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
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