1,720,967 research outputs found
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
L'induzione dei trasportatori per il glutamato EAAT da parte dei retinoidi: un approccio per la prevenzione del danno eccitotossico deglio oligodendrociti e dei loro precursori.
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
Shape-Related Toxicity of Titanium Dioxide Nanofibres
Full text linkTitanium dioxide (TiO2) nanofibres are a novel fibrous nanomaterial with increasing applications
in a variety of fields. While the biological effects of TiO2 nanoparticles have been
extensively studied, the toxicological characterization of TiO2 nanofibres is far from being
complete. In this study, we evaluated the toxicity of commercially available anatase TiO2
nanofibres using TiO2 nanoparticles (NP) and crocidolite asbestos as non-fibrous or fibrous
benchmark materials. The evaluated endpoints were cell viability, haemolysis, macrophage
activation, trans-epithelial electrical resistance (an indicator of the epithelial barrier competence),
ROS production and oxidative stress as well as the morphology of exposed cells.
The results showed that TiO2 nanofibres caused a cell-specific, dose-dependent decrease
of cell viability, with larger effects on alveolar epithelial cells than on macrophages. The
observed effects were comparable to those of crocidolite, while TiO2 NP did not decrease
cell viability. TiO2 nanofibres were also found endowed with a marked haemolytic activity, at
levels significantly higher than those observed with TiO2 nanoparticles or crocidolite. Moreover,
TiO2 nanofibres and crocidolite, but not TiO2 nanoparticles, caused a significant
decrease of the trans-epithelial electrical resistance of airway cell monolayers. SEM images
demonstrated that the interaction with nanofibres and crocidolite caused cell shape perturbation
with the longest fibres incompletely or not phagocytosed. The expression of several
pro-inflammatory markers, such as NO production and the induction of Nos2 and Ptgs2,
was significantly increased by TiO2 nanofibres, as well as by TiO2 nanoparticles and crocidolite.
This study indicates that TiO2 nanofibres had significant toxic effects and, for most
endpoints with the exception of pro-inflammatory changes, are more bio-active than TiO2
nanoparticles, showing the relevance of shape in determining the toxicity of nanomaterials.
Given that several toxic effects of TiO2 nanofibres appear comparable to those observed
with crocidolite, the possibility that they exert length dependent toxicity in vivo seems worthy
of further investigation
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
Determinanti di attività biologica dei nanomateriali in cellule dell'immunità innata: ruolo dell'aspect ratio, dei contaminanti ambientali e della protein corona
No full textAs defined by the European Union, “ ’Nanomaterial’ (NM) means a natural, incidental or manufactured material containing particles, in an unbound state or as an aggregate or agglomerate, where, for 50 % or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm-100 nm ” (2011/696/UE). Given their peculiar physico-chemical features, nanostructured materials are largely used in many industrial fields (e.g. cosmetics, electronics, agriculture, biomedical) and their applications have astonishingly increased in the last fifteen years.
Nanostructured materials are endowed with very large specific surface area that, besides making them very useful in many industrial processes, renders them very reactive towards the biological systems and, hence, potentially endowed with significant hazard for human health. For these reasons, in recent years, many studies have been focused on the identification of toxic properties of nanostructured materials, investigating, in particular, the mechanisms behind their toxic effects as well as their determinants of toxicity.
This thesis investigates two types of nanostructured TiO2 materials, TiO2 nanoparticles (NP), which are yearly produced in tonnage quantities, and TiO2 nanofibres (NF), a relatively novel nanomaterial. Moreover, several preparations of MultiWalled Carbon Nanotubes (MWCNT), another nanomaterial widely present in many products, are also investigated.-
Although many in vitro and in vivo studies have characterized the toxic properties of these materials, the identification of their determinants of toxicity is still incomplete. The aim of this thesis is to identify the structural determinants of toxicity, using several in vitro models. Specific fields of investigation have been a) the role of shape and the aspect ratio in the determination of biological effects of TiO2 nanofibres of different length; b) the synergistic effect of LPS and TiO2 NP on the expression of inflammatory markers and the role played therein by TLR-4; c) the role of functionalization and agglomeration in the biological effects of MWCNT.
As far as biological effects elicited by TiO2 NF are concerned, the first part of the thesis demonstrates that long TiO2 nanofibres caused frustrated phagocytosis, cytotoxicity, hemolysis, oxidative stress and epithelial barrier perturbation. All these effects were mitigated by fibre shortening through ball-milling. However, short TiO2 NF exhibited enhanced ability to activate acute pro-inflammatory effects in macrophages, an effect dependent on phagocytosis. Therefore, aspect ratio reduction mitigated toxic effects, while enhanced macrophage activation, likely rendering the NF more prone to phagocytosis. These results suggest that, under in vivo conditions, short NF will be associated with acute inflammatory reaction, but will undergo a relatively rapid clearance, while long NF, although associated with a relatively smaller acute activation of innate immunity cells, are not expected to be removed efficiently and, therefore, may be associated to chronic inflammatory responses.
As far as the relationship between the effects of TiO2 NP and LPS, investigated in the second part of the thesis, are concerned, TiO2 NP markedly enhanced macrophage activation by LPS through a TLR-4-dependent intracellular pathway. The adsorption of LPS onto the surface of TiO2 NP led to the formation of a specific bio-corona, suggesting that, when bound to TiO2 NP, LPS exerts a much more powerful pro-inflammatory effect. These data suggest that the inflammatory changes observed upon exposure to TiO2 NP may be due, at least in part, to their capability to bind LPS and, possibly, other TLR agonists, thus enhancing their biological activities.
Finally, the last part of the thesis demonstrates that surface functionalization of MWCNT with amino or carboxylic groups mitigates the toxic effects of MWCNT in terms of macrophage activation and capability to perturb epithelial barriers. Interestingly, surface chemistry (in particular surface charge) influenced the protein adsorption onto the MWCNT surface, allowing to the formation of different protein coronae and the tendency to form agglomerates of different size. In particular functionalization a) changed the amount and the type of proteins adsorbed to MWCNT and b) enhanced the tendency of MWCNT to form large agglomerates. These data suggest that the different biological behavior of functionalized and pristine MWCNT may be due, at least in part, to the different tendency to form large agglomerates, which is significantly influenced by their different capability to interact with proteins contained in biological fluids.
All together, these data demonstrate that the interaction between physico-chemical properties of nanostructured materials and the environment (cells + biological fluids) in which these materials are present is of pivotal importance for the understanding of the biological effects of NM. In particular, bio-persistence and the capability to elicit an effective inflammatory response are attributable to the interaction between NM and macrophages. However, the interaction NM-cells is heavily influenced by the formation at the nano-bio interface of specific bio-coronae that confer a novel biological identity to the nanostructured materials, setting the basis for their specific biological activities.Come definito dall’Unione Europea, con il termine nanomateriale si intende “ un materiale di origine naturale, accidentale o industriale contenente particelle, in uno stato non aggregato, aggregato o agglomerato, in cui almeno il 50% delle particelle ha almeno una dimensione compresa tra 1 e 100 nm ” (2011/696/UE). I materiali nanostrutturati, date le loro peculiari caratteristiche fisico-chimiche, sono largamente impiegati in numerosi settori industriali (es. cosmetica, elettronica, agricoltura, campo biomedicale) e il loro utilizzo è cresciuto esponenzialmente negli ultimi quindici anni. I materiali nanostrutturati sono caratterizzati da una notevole area superficiale che, nonostante li renda molto utili in numerosi processi industriali, li rende estremamente reattivi nei confronti dei sistemi biologici e, quindi, potenzialmente pericolosi per la salute umana. Per questi motivi, negli ultimi anni, numerosi studi si sono focalizzati sull’identificazione delle proprietà tossiche dei materiali nanostrutturati, studiando in particolar modo i meccanismi alla base dei loro effetti tossici così come i loro determinanti strutturali di tossicità.
In questa tesi si studieranno due materiali nanostrutturati di TiO2, le nanoparticelle (TiO2 NP), la cui produzione consiste di decine di tonnellate ogni anno, e le nanofibre (TiO2 NF), un materiale relativamente nuovo. Inoltre saranno oggetto di studio anche diverse preparazioni di nanotubi di carbonio a parete multipla (MWCNT), un altro nanomateriale a larga diffusione. Nonostante le proprietà tossiche di questi materiali siano state caratterizzate in numerosi studi in vivo e in vitro, l’identificazione dei determinanti di tossicità dei NM risulta ancora incompleta. Lo scopo di questa tesi consiste nell’identificazione di determinanti strutturali di tossicità, utilizzando diversi modelli in vitro. Più nello specifico si è indagato a) il ruolo della morfologia e dell’aspect ratio nella determinazione degli effetti biologici prodotti da TiO2 NF di diversa lunghezza; b) l’effetto sinergico di LPS e TiO2 NP sull’espressione di marker infiammatori e il ruolo del TLR-4 in questo fenomeno; c) il ruolo della funzionalizzazione e dell’agglomerazione nella determinazione degli effetti biologici dei Nanotubi di Carbonio a Parete Multipla (MWCNT).
Per quanto riguarda gli effetti biologici prodotti dalle TiO2 NF, nella prima parte della tesi si dimostra che TiO2 NF lunghe causano fagocitosi frustrata, citotossicità, emolisi, stress ossidativo e alterano l’integrità della barriera epiteliale. Tutti questi effetti erano mitigati dall’accorciamento delle fibre attraverso il processo di ball-milling. Al contrario, le TiO2 NF corte erano in grado di stimolare maggiormente l’espressione di marker infiammatori acuti nei macrofagi, un effetto dipendente dalla fagocitosi. La riduzione dell’aspect ratio, quindi, mitigava gli effetti tossici, mentre stimolava maggiormente l’attivazione dei macrofagi, fenomeno riconducibile ad un’aumentata fagcocitosi di queste fibre. Questi risultati suggeriscono che, in vivo, le NF corte potrebbero essere associate a una reazione infiammatoria acuta ma, parallelamente, essere soggette ad una clearance relativamente più rapida. Al contrario, le NF lunghe, stimolando in misura minore fenomeni di attivazione macrofagica, potrebbero essere rimosse in maniera meno efficiente e, quindi, essere associate a fenomeni infiammatori cronici.
Per quanto riguarda la relazione tra gli effetti delle TiO2 NP e del LPS, approfondite nella seconda parte della tesi, è stato dimostrato che le nanoparticelle potenziavano fortemente l’attivazione dei macrofagi indotta dal LPS mediante un pathway intracellulare mediato dal recettore TLR-4. L’adsorbimento del LPS sulla superficie delle TiO2 NP portava alla formazione di una specifica bio-corona, indicando che, quando legato alle TiO2 NP, il LPS induce effetti pro-infiammatori significativamente maggiori. Questi dati suggeriscono che i fenomeni infiammatori osservati in seguito all’esposizione alle TiO2 NP potrebbero essere dovuti, almeno parzialmente, alla loro capacità di legare il LPS e, probabilmente, altri agonisti dei TLR, aumentandone l’attività biologica.
E’ stato infine valutato il ruolo della funzionalizzazione e dell’agglomerazione negli effetti biologici di MWCNT, ed è stato dimostrato che la funzionalizzazione superficiale dei MWCNT con gruppi aminici o carbossilici mitigava gli effetti tossici dei MWCNT in termini di attivazione di macrofagi e di alterazione delle barriere epiteliali. La chimica di superficie (in particolare la carica superficiale) influenzava l’adsorbimento di proteine sulla superficie dei MWCNT, portando alla formazione di diverse bio-corone e influenzando la tendenza a formare agglomerati di differenti dimensioni. Questi risultati suggeriscono che il diverso comportamento biologico dei MWCNT pristini e funzionalizzati potrebbe essere associato, almeno in parte, alla differente tendenza a formare grandi agglomerati, che, a sua volta, sembrerebbe influenzata in maniera significativa dalla differente capacità di interagire con le proteine presenti nei fluidi biologici.
In conclusione, i dati presentati in questa tesi dimostrano che la comprensione degli effetti biologici dei nanomateriali richiede non solo la caratterizzazione delle loro proprietà fisico-chimiche ma, soprattutto, delle interazioni tra essi e l’ambiente biologico (cellule + fluidi biologici). In particolare, la biopersistenza e la capacità di determinare un’efficace risposta infiammatoria sono attribuibili all’interazione con i macrofagi. Inoltre, l’interazione tra cellule e materiali è notevolmente influenzata dalla formazione di specifiche bio-corone all’interfaccia bio-nano. La formazione della bio-corona conferisce una nuova identità biologica ai materiali nanostrutturati, costituendo così la base per specifiche attività biologiche
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