1,720,999 research outputs found
Applicazione di idrogel: Tensioattivi e polisaccaridi impiegati come costituenti altamente versatili
No full textHydrogels are unique materials composed of hydrophilic gelators linked together in a three-dimensional network capable of encapsulating large amounts of water. These materials are easily adaptable to different application areas i.e. biomedical areas, agriculture, removal of heavy metals from water or in food industry.
In this thesis, some eco-sustainable gelators have been selected as starting materials to develop hydrogels that possess characteristics related to the selected applications. For this purpose, zwitterionic amine oxide surfactants and polysaccharides, i.e. alginate and chitosan, were selected for their ability to form hydrogels by modulating their concentration or by adding crosslinking agents.
In Section B, several common techniques were selected to fully characterize the two polysaccharides in order to determine their structural features, which can affect the hydrogels properties.
In Section C, the hydrogels were prepared based on the selected application areas i.e. bioconversion, food packaging and cultural heritage.
The effect of surfactants structure and immobilization into hydrogel structure on the catalytic properties of Candida rugosa lipase (CRL) was investigated. The selected amine oxide surfactants exploited an improvement of the enzymatic activity as a function of the morphology of the micellar aggregates; in particular, by varying the headgroup size and the chain length, the micelles shift from spherical to rod-like leading to an increased hydrolytic activity. Furthermore, CRL was effectively entrapped in alginate hydrogel beads formed by ionotropic gelation induced by calcium ions. Different bead formulations were prepared and the effect of their morphology on the catalytic properties of CRL was assessed by studying two model reactions. The immobilized lipase showed noticeable recyclability and improved thermostability compared to the free enzyme.
Part of this study was addressed to the application of chitosan-based hydrogels to prepare membranes applicable as eco-friendly food packaging material. Chitosan-succinate films were prepared, starting by their hydrogel form, by solvent casting method using glycerol as plasticizer. The NaOH-neutralized membranes, compared to the non-neutralized ones, showed improved mechanical and physicochemical properties. The formation of amide bonds between chitosan and succinic acid, suggested by the FTIR analysis, was then confirmed by acid-base titration. The prepared membranes are currently under preliminary study as novel food packaging for pecorino cheese samples.
The last part of this thesis is included in a wider project focused on “Product and process innovation for maintenance, preservation and sustainable programmed restoration of cultural heritage” (Smart Cities and Communities and Social Innovation on Cultural Heritage project). It aimed at the improvement of the restoration and maintenance intervention on stone-based cultural heritages. For this purpose, novel approaches to reduce microbial colonization from stone materials were developed using classic oxidant biocidal agents supported in alginate hydrogels.
Novel ionically crosslinked alginate hydrogels, which contain oxidative biocides were developed and tested. All hydrogel formulations were able to eliminate biofilms from the stone surface, keeping the chromaticity and capillary properties of the cleaned stones unchanged. To assess the presence of residues, any type of surface alteration and to evaluate the hygroscopic behavior of the stone samples, microscopic techniques, colorimetry and 1H-NMR T2 relaxation measurements have been performed. They were applied both on a laboratory scale, using calcarenite specimens artificially colonized by filamentous cyanobacteria and green microalgae and “in situ” on stone artworks in rupestrian churches of “Sassi of Matera”
Advanced Modeling, Control and EMI Mitigation Techniques for Switching DC-DC Power Converters
Get PDFL'abstract è presente nell'allegato / the abstract is in the attachmen
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
La Giunta (paragrafi 5.4; 5.5; 5.6)
No full textIl contributo esamina, nell'ambito del tema generale trattato (La Giunta nel sistema istituzionale della Regione Puglia), le problematiche concernenti il numero dei componenti della Giunta regionale, la rappresentanza di genere e il voce-presidente della Giunta regiona
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
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