1,721,039 research outputs found
Effetto dell’invecchiamento idrotermico sulle proprietà termiche e meccaniche di resine epossidiche strutturali
No full textLe resine termoindurenti, utilizzate come matrici per materiali compositi rinforzati con fibre di carbonio, sono caratterizzate da un elevato grado di densità di reticolazione che conferisce loro una elevata fragilità e che allo stesso tempo le espone a significativi effetti di invecchiamento idrotermico durante il loro utilizzo [1]. In particolare si assiste alla diminuzione della temperatura di transizione vetrosa, per effetto di fenomeni di plasticizzazione e degradazione, e alla diminuzione di modulo elastico a flessione. Recentemente gli autori hanno proposto un metodo, Photoelastic Stress Analysis (PSA), molto efficace per monitorare le modifiche del materiale, in termini di swelling e tensioni residue, durante l’invecchiamento idrotermico [2]. In questo lavoro vengono presentati i risultati di due set di matrici epossidiche, sintetizzate in laboratorio, aventi diverse densità di reticolazione da cui si evincono differenti risposte in termini di resistenza termica e tenacità alla frattura in seguito ad invecchiamento termico accelerato dalla temperatura
Fracture toughness of synthesised high-performance epoxies subject to accelerated water aging
No full textThe effects of water uptake on the fracture toughness of epoxy systems with high glass-transition temperatures (Tgabove 170 °C) are investigated. Aging conditioning has been conducted in hot water, followed by a desorption conditioning in a room temperature dry-airborne. Water aging determines plasticisation effects and crosslink-density modifications, revealed by reductions of the Tg. It is less known how such modifications influence the material fracture toughness. In this study, Single Edge Notched Bending samples have been tested according to standards, to evaluate the KICfracture toughness at different stages of water absorption-desorption. The characterisation has been supported by Photoelastic Stress Analysis, allowing to evaluate stresses induced by swelling during aging. Results indicate that swelling stresses activate a crack closure mechanism that might contribute to the observed increase of the measured fracture toughness during water absorption, but are ineffective at saturation. Two epoxy systems, one based on DGEBA and the other on DGEBF, having different cross-link densities, have been studied. The plasticisation achieved at saturation translated into a significant increase of fracture toughness only in DGEBA, while fracture toughness measured at other conditioning stages was likely influenced by internal swelling stresses and sample pre-cracking strategy
Design, synthesis and characterization of a theranostic nanoplatform for tumor site-specific delivery of doxorubicin
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
Rare cell capture platforms based on antibody-conjugated electrospun nanofiber mats for noninvasive prenatal diagnostics
No full textThe chance of surviving to a disease often depends on early diagnosis and effective therapy. In the field of early prenatal diagnosis, micromanipulation is a reliable technique for manual selection and isolation of rare fetal cells in maternal biological fluids for molecular or cytogenetic analysis. This technique allows obtaining pure cell populations for analysis, but it is expensive and time consuming, as it requires qualified and experienced staff and specific equipment [1].
The aim of this study is to make the prenatal diagnosis more economical and reproducible in the hospital environment, by creating a device that allows selecting rare cells from biological samples in a semi-automated way. The device consists in electrospun nanofiber mats with surface functional groups conjugated to antibodies capable of selectively binding to the antigens present on the surface of target cells.
Nanofiber mats were produced from polymer mixtures of Nylon 6.6 and Polyacrylic Acid (PAA) in a suitable solvent, with or without the addition of a third polymer, synthetized in house, that should prevent non-specific cell binding. The first phase of the work was devoted to the determination of the operating parameters for electrospinning to optimize the morphology of the mats, their mechanical resistance and handling characteristics. Bioconjugation protocols, based on EDC/NHS (1-ethyl-3-(3- dimethylaminopropyl) carbodiimide hydrochloride)/(Sulfo-(N-hydroxysulfosuccinimide) chemistry were developed to provide the electrospun mats with specific cell capture abilities. In order to facilitate the recognition of the antibody by the receptors expressed by the target cells, the functional groups of the mat were previously reacted to a linker that acts as a spacer arm. Antibodies labelled with fluorescent probe were used to be able to assess the success of the conjugation reactions by fluorimetry and spectrofluorimetry analyses.
Protocols for cell capture tests on antibody-decorated mats were devised using different cell suspensions: fetal cells (CF), mesenchymal stem cells (MSC) and lymphocytes (WBCs, White Blood Cells). The results of the capture tests were obtained by observing the mats under the optical and electron microscopes (SEM)
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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