1,721,203 research outputs found
Caratterizzazione morfo-funzionale e potenziali applicazioni di diatomee (Bacillariophyta) come nanodispositivi ottici naturali
No full textNegli ultimi decenni l’interesse nei confronti dei micro e nanodispositivi è profondamente cresciuto in ambito accademico ed industriale. In particolare l’utilizzo di nuovi nanomateriali basati sulla tecnologia del silicio poroso ha assunto una crescente importanza in molte applicazioni industriali, specialmente nella fabbricazione di filtri molecolari, catalizzatori e componenti per la sensoristica (1). Nella maggior parte dei casi tali nanomateriali silicei sono prodotti attraverso procedure che prevedono la caratterizzazione delle loro proprietà chimico-fisiche e la standardizzazione di approcci ingegneristici per la loro microlavorazione a livello industriale (1). Un differente approccio consiste nell’individuazione di nanostrutture ad elevata periodicità in organismi viventi(2).
Le microalghe rappresentano un classico esempio di organismi unicellulari nelle quali possono essere identificate complesse nanostrutture (3, 4). Fra queste le Bacillariophyta, comunemente note come diatomee, sono particolarmente interessanti a motivo delle loro pareti cellulari silicee consistenti in due unità indipendenti, definite valve, connesse in una struttura nota come frustulo. Le superfici valvari dei frustuli mostrano arrangiamenti regolari e specie-specifici di microcamere sviluppate nello spessore del frustulo, o areole, il cui significato funzionale è ancora ignoto(5).
Nel presente lavoro le proprietà ottiche dei frustuli di due specie di diatomee centriche, Coscinodiscus wailesii and Thalassiosira rotula, sono state investigare, mediante simulazioni numeriche e procedure sperimentali, nell’ ottica di individuare possibili applicazioni nanofotoniche.
Per entrambi le specie è stata effettuata una caratterizzazione morfometrica dell’ultrastruttura valvare e della relativa distribuzione geometrica delle areole mediante microscopia elettronica a scansione. Successivamente, T. rotula è stata testata come un microsensore di gas e vapori monitorando i suoi spettri di fotoluminescenza in differenti ambienti gassosi controllati. I pattern di areolae ad elevata periodicità delle valve di C. walesii sono stati invece testati come potenziali cristalli fotonici e fibre fotoniche naturali. I risultati ottenuti dimostrano che entrambi le specie si prestano alla realizzazione di innovativi materiali biologici per applicazioni micro e nanotecnologiche.
1) De Stefano, L., Rendina, I., Moretti, L. & Rossi, A.M. (2003). Sensor and Actuators, 104(2): 179-182.
2) Vukusic, P. & Sambles J. R. (2003). Nature, 424: 852-855.
3) De Stefano, M. & De Stefano, L. (2005). J. Nanosc. Nanotech., 5: 15-24.
4) Hamm, C. E. (2005). J. Nanosc. Nanotech., 5(1): 108-119.
5) Round, F. E., Crawford, R. M. & Mann, D. G. (1990). Cambridge University Press, Cambridge
The original (Greek text). Rethinking the Ereignis towards a new dwelling|L’οἰΚοΛοΓίΑ originaria. Ripensare l’Ereignis verso un nuovo abitare
No full text
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
Diatoms green nanotechnology for biosilica-based drug delivery systems
No full textDiatom microalgae are the most outstanding natural source of porous silica. The diatom cell is enclosed in a three-dimensional (3-D) ordered nanopatterned silica cell wall, called frustule. The unique properties of the diatom frustule, including high specific surface area, thermal stability, biocompatibility, and tailorable surface chemistry, make diatoms really promising for biomedical applications. Moreover, they are easy to cultivate in an artificial environment and there is a large availability of diatom frustules as fossil material (diatomite) in several areas of the world. For all these reasons, diatoms are an intriguing alternative to synthetic materials for the development of low-cost drug delivery systems. This review article focuses on the possible use of diatom-derived silica as drug carrier systems. The functionalization strategies of diatom micro/nanoparticles for improving their biophysical properties, such as cellular internalization and drug loading/release kinetics, are described. In addition, the realization of hybrid diatom-based devices with advanced properties for theranostics and targeted or augmented drug delivery applications is also discussed
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