1,721,020 research outputs found
Il ruolo del substrato di rame nella sintesi di grafene cresciuto per deposizione chimica da fase vapore
Full text linkLa Chemical Vapor Deposition (CVD) permette la crescita di sottili strati di grafene con aree di decine di centimetri quadrati in maniera continua ed uniforme. Questa tecnica utilizza un substrato metallico, solitamente rame, riscaldato oltre i 1000 °C, sulla cui superficie il carbonio cristallizza sotto forma di grafene in un’atmosfera attiva di metano ed idrogeno. Durante la crescita, sulla superficie del rame si decompone il metano utilizzato come sorgente di carbonio. La morfologia e la composizione della superficie del rame diventano quindi elementi critici del processo
per garantire la sintesi di grafene di alta qualità e purezza.
In questo manoscritto si documenta l’attività sperimentale
svolta presso i laboratori dell’Istituto per la Microelettronica e i Microsistemi del CNR di Bologna sulla caratterizzazione
della superficie del substrato di rame utilizzato per la sintesi del
grafene per CVD. L’obiettivo di questa attività è stato la caratterizzazione della morfologia superficiale del foglio metallico con misure di rugosità e di dimensione dei grani cristallini, seguendo l’evoluzione di queste caratteristiche durante i passaggi del processo di sintesi. Le misure di rugosità sono state effettuate utilizzando tecniche di profilometria ottica interferometrica, che hanno permesso di misurare l’effetto di livellamento successivo all' introduzione di un etching chimico nel processo consolidato utilizzato presso i laboratori dell’IMM di Bologna. Nell'ultima parte di questo manoscritto si è invece studiato, con
tecniche di microscopia ottica ed elettronica a scansione, l’effetto di diverse concentrazioni di argon e idrogeno durante il
trattamento termico di annealing del rame sulla riorganizzazione dei suoi grani cristallini. L’analisi preliminare effettuata ha
permesso di individuare un intervallo ottimale dei parametri di
annealing e di crescita del grafene, suggerendo importanti direzioni per migliorare il processo di sintesi attualmente utilizzato
Linking protein-protein interactions to the diversity of amyloid-like aggregates
Full text linkProtein aggregation is often studied in the context of neurodegenerative diseases. Deposits of supramolecular aggregates, often appearing as ordered fibrils, are associated with the onset of devastating pathologies as Alzheimer´s and Parkinson´s diseases. Equally important is the impact that the formation of protein aggregates may have in the quality of a protein drug product. The presence of the so-called sub-visible particles (SVP) and visible particles in protein drug product is indeed considered one of the risk factors potentially inducing immune response in patients. Finally yet importantly, protein aggregates, and particularly amyloid fibrils, have unique structural, physico-chemical, mechanical and optical properties, making them appealing bio-inspired materials for several applications. Either one looks at protein aggregation in the context of diseases, drug development or biomaterials, understanding how protein-protein (PPIs) and protein-solvent interactions (PSI) determine aggregation kinetics and the morphology/structures of the final aggregates is a conditio sine qua non for unraveling the molecular mechanisms ruling the self-assembly reaction and for controlling it.
In our group, we have reported the possibility for a large group of proteins under specific destabilizing conditions to form a variety of protein aggregates, being it not limited to the formation of amyloid fibrils (Figure 1) [1]. In line with the scope of the conference, I will present our unique approach based on advanced fluorescence microscopy, small angle X-ray scattering and spectroscopy and aimed at identifying the key PPIs and PSIs responsible for such variability in structures and morphologies [2-6]. We use surfactants, salts, alcohols in bulk and microfluidic setups to finely tune the interactions between proteins and, consequently, control the self-assembly process. Our results show that subtle changes in the PPIs and PSI do not only affect the kinetics, but they may also have a dramatic effect on the 3D arrangement, microscopic structures, mechanical properties and stability of the final self-assembled structures. Our findings provide a scenario in which a pool of highly heterogeneous structures can be generated as a result of interconnected aggregation pathways, being this aspect of key relevance especially for protein drug product development and optimization.
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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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
The route to protein aggregate superstructures: Particulates and amyloid-like spherulites
No full textAbstractDepending on external conditions, native proteins may change their structure and undergo different association routes leading to a large scale polymorphism of the aggregates. This feature has been widely observed but is not fully understood yet. This review focuses on morphologies, physico-chemical properties and mechanisms of formation of amyloid structures and protein superstructures. In particular, the main focus will be on protein particulates and amyloid-like spherulites, briefly summarizing possible experimental methods of analysis. Moreover, we will highlight the role of protein conformational changes and dominant forces in driving association together with their connection with the final aggregate structure. Eventually, we will discuss future perspectives in this field and we will comment what is, in our opinion, urgently needed
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