1,721,021 research outputs found
Studio di biomateriali usati come scaffold per Tissue Engineering e loro caratterizzazione con tecniche spettroscopiche vibrazionali e di analisi termica
No full textThis research investigated someone of the main problems connected to the application of Tissue
Engineering in the prosthetic field, in particular about the characterization of the scaffolding
materials and biomimetic strategies adopted in order to promote the implant integration.
The spectroscopic and thermal analysis techniques were usefully applied to characterize the
chemico-physical properties of the materials such as
– crystallinity;
– relative composition in case of composite materials;
– Structure and conformation of polymeric and peptidic chains;
– mechanism and degradation rate;
– Intramolecular and intermolecular interactions (hydrogen bonds, aliphatic interactions).
This kind of information are of great importance in the comprehension of the interactions that
scaffold undergoes when it is in contact with biological tissues; this information are fundamental to
predict biodegradation mechanisms and to understand how chemico-physical properties change
during the degradation process. In order to fully characterize biomaterials, this findings must be
integrated by information relative to mechanical aspects and in vitro and in vivo behavior thanks to
collaborations with biomedical engineers and biologists.
This study was focussed on three different systems that correspond to three different strategies
adopted in Tissue Engineering: biomimetic replica of fibrous 3-D structure of extracellular matrix
(PCL-PLLA), incorporation of an apatitic phase similar to bone inorganic phase to promote
biomineralization (PCL-HA), surface modification with synthetic oligopeptides that elicit the
interaction with osteoblasts.
The characterization of the PCL-PLLA composite underlined that the degradation started along
PLLA fibres, which are more hydrophylic, and they serve as a guide for tissue regeneration.
Moreover it was found that some cellular lines are more active in the colonization of the scaffold.
In the PCL-HA composite, the weight ratio between the polymeric and the inorganic phase plays an
essential role both in the degradation process and in the biomineralization of the material.
The study of self-assembling peptides allowed to clarify the influence of primary structure on
intermolecular and intermolecular interactions, that lead to the formation of the secondary structure
and it was possible to find a new class of oligopeptides useful to functionalize materials surface.
Among the analytical techniques used in this study, Raman vibrational spectroscopy played a major
role, being non-destructive and non-invasive, two properties that make it suitable to degradation
studies and to morphological characterization. Also micro-IR spectroscopy was useful in the
comprehension of peptide structure on oxidized titanium: up to date this study was one of the first
to employ this relatively new technique in the biomedical field
Relazione su cinque campioni di intonaci parietali provenienti dal sito ex Vescovado di Rimini.
No full textQUALCHE CENNO SULLA SPETTROSCOPIA RAMAN.
II prodotto di un'indagine spettroscopica Raman consiste in un grafico (spettro) in cui il valore della frequenza (asse X) e dell'intensità relativa delle bande Raman (asse Y) è caratteristica della specie chimica esaminata e ne costituisce una specie di "impronta digitale". Dal valore della frequenza e dall'intensità delle bande è possibile risalire alla struttura molecolare del composto in esame e quindi alla sua formula chimica.
La spettroscopia Raman può, a ragione, essere considerato il mezzo ideale per l'analisi di pigmenti in quanto sensibile, non-distruttiva, selettiva e adatta all'applicazione in situ. Con l'uso poi della microscopia Raman è possibile analizzare anche regioni spaziali molto piccole del campione (circa l-2m se la lunghezza d'onda del laser utilizzato come sorgente è nel visibile ed abbinata ad un microscopio).
I vantaggi della spettroscopia Raman sono piuttosto importanti anche quando un reperto ha subito trattamenti conservativi successivi o quando un colore è formato da una mescolanza di pigmenti diversi.
RISULTATI DELLE ANALISI DEI CAMPIONI: RIMIMI EX VESCOVADO.
Tutte le misure sono state effettuate utilizzando uno spettrometro micro-Raman della Jasco abbinato ad un microscopio Olimpus (Obiettivo utilizzato 50 X); come sorgente eccitatrice è stata utilizzata la riga blu (488 nm) di un laser ad Argon della Coherent Radiation con potenza sul campione di circa 1mW; sistema di rivelazione CCD (Charge Coupled Device - 1100 X 300 pixel) della Princeton Instrument. Tali apparecchiature sono in dotazione del Centro di Studio sulla Spettroscopia Raman (CSSR) della Facoltà di Scienze dell'Università di Bologna, presso cui sono state svolte le analisi dei suddetti reperti.
L'identificazione dei campioni è stata effettuata per mezzo di una banca dati di spettri Raman di pigmenti e minerali realizzata negli ultimi anni presso il suddetto centro.
La percentuale è relativa all'abbondanza dei cristalli del rispettivo colore ed è fatta contando il numero di cristalli dello stesso colore che compaiono in cinque schermate scelte a caso sul campione. Tale valore è solo indicativo e serve per valutare l'abbondanza relativa dei costituenti.
CONCLUSIONI.
In buona sostanza sono stati rilevati solo tre pigmenti veri: Blu Egiziano, Goethite ed Ematite.
La calcite, trattandosi di affresco "deve" essere presente ovunque. Poteva comunque essere utilizzata anche per schiarire il colore.
Il quarzo può essere trovato assieme al blu egiziano in quanto entra nella preparazione del pigmento stesso, ma può anche derivare dall'uso di sabbie quarzifere nelle malte utilizzate per fare l'intonaco base.
Il rutilo lo si trova spesso e va considerato impurezza in quanto il suo uso come sbiancante risale solo al secolo scorso.
Il solfato di calcio è sicuramente una impurezza derivante dall'intonaco base.
Spettri Raman: a titolo di esempio si riportano nelle figure che seguono gli spettri Raman di alcuni dei campioni esaminati a confronto con quelli della banca dati
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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