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Double-compartment culture system for conditioning vascular grafts with different trans-wall oxygen levels
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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
Sviluppo di un sistema ex vivo bicompartimentale per la coltura di segmenti di vena safena umana in condizioni controllate di ossigenazione
Full text linkLAUREA MAGISTRAL
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
Development of tissue culture systems for biomechanical conditioning of small-caliber arterial vessels
Full text linkLe malattie cardiovascolari rappresentano la principale causa di morte nel mondo. Nello scenario delle malattie cardiovascolari, l’aterosclerosi rappresenta uno dei principali interpreti; essa infatti è responsabile di patologie come l’infarto del miocardio, l’ictus e altri disturbi vascolari. Si tratta di una complessa patologia multi-fattoriale delle arterie con origine infiammatoria. Tradizionalmente esistono due possibili approcci con cui sono stati studiati i meccanismi coinvolti nell’insorgenza e nello sviluppo dell’aterosclerosi e tramite i quali vengono valutate possibili terapie o dispositivi: modelli in vitro e modelli in vivo.
I modelli in vitro sono ormai di comune uso in laboratorio, sono facili da riprodurre e quantificare, relativamente economici e permettono di studiare stimoli isolati e controllati. Nonostante ciò, essi non garantiscono la riproduzione di un ambiente realistico complesso. Inoltre, spesso, il comportamento delle cellule in vitro è alterato rispetto al normale comportamento in vivo.
I modelli in vivo, invece, permettono di riprodurre il complesso ambiente biologico e di indurre condizioni patologiche più vicine a quelle che si riscontrano nell’organismo. Sono inoltre imprescindibili per testare trattamenti farmacologici e dispositivi. Nonostante ciò, la comunità scientifica è compatta nel richiedere a tutti gli interpreti della ricerca biomedica di ridurre l’uso dei modelli animali (regola delle 3R: reduce, replace, refine). Oltre alle forti implicazioni etiche, i test in vivo presentano svantaggi anche a livello economico e tecnico.
I modelli ex vivo si propongono come valido punto di incontro tra modelli in vitro e modelli in vivo. Essi permettono di isolare ed esaminare gli effetti di specifici stimoli, senza però rinunciare alla complessità dei tessuti biologici. Questo tipo di approccio non si erge assolutamente a sostituto degli altri due, ma può svolgere una fondamentale funzione di supporto e riduzione dei costi e dei tempi della ricerca.
L’obiettivo del presente lavoro di dottorato è proprio quello di proporre modelli ex vivo innovativi volti a indagare differenti aspetti relativi al processo aterosclerotico. In particolare, sono stati studiati tre modelli.
Il primo modello è un sistema per studiare i meccanismi coinvolti nello sviluppo della trombosi a livello cellulare e molecolare. Si tratta di una camera di coltura a piatti piani paralleli otticamente accessibile progettata per coltivare sezioni di arterie umane in condizioni emodinamiche controllate. Il sistema si è dimostrato compatibile con le procedure di laboratorio e con le tecniche microscopiche.
Un secondo modello è un sistema ex vivo che permette di trasferire ex vivo delle procedure per studiare la trombosi fino ad ora utilizzate solo in vivo. Si è fatto riferimento in particolare sulla trombosi indotta con cloruro ferrico. Il bioreattore è stato progettato e sviluppato per coltivare vasi interi espiantati di calibro e lunghezza diversa in condizioni fluidodinamiche controllate.
Infine, si è lavorato su un modello ingegnerizzato per studiare l’aterosclerosi. Infatti, I modelli basati sull’ingegneria dei tessuti vengono utilizzati grazie alla possibilità di mantenere la complessità delle strutture in vivo, ma controllando la composizione cellulare. A titolo esemplificativo, nel presente lavoro di tesi sono state coltivate cellule progenitrici avventiziali su scaffold elettrofilati di forma tubolare. I costrutti sono stati poi esposti a uno stimolo fluidodinamico controllato e in diverse condizioni di ossigeno, per studiare il potenziale angiogenico dell’ipossia. Il modello si è dimostrato adatto a questo tipo di considerazioni, ma, prima di poterne sfruttare appieno le potenzialità, devono essere risolte problematiche tecniche, dovute alla trasposizione di tecniche tradizioni di coltura e analisi a sistemi innovativi.Cardiovascular diseases (CVDs) are the leading cause of death in the world. Within the scenario of CVDs, atherosclerosis plays a key role, as it is responsible for myocardial infarction, stroke, and vascular diseases. Atherosclerosis is a complex multi-factorial inflammatory disease of the arteries. Traditionally, two approaches have been extensively used to study the mechanisms involved in atherosclerosis and to evaluate the effectiveness of therapies or devices: in vitro and in vivo models. In vitro methods are well-established, easy to perform and quantify, relatively not expensive and allow to study isolated and controlled stimuli. They lack, though, of biological realism. Moreover, the behaviour of cultured cells often can be very different from somatic cells in vivo.
In vivo models, instead, provide a complex environment and the possibility to induce more realistic pathological conditions. They are still unavoidable for testing hypothesis addressed by in vitro models and pharmacological treatments. Nevertheless, the scientific community insists on the reduce, replacement and refinement (3 Rs) in the use of animals for experiments. Besides strong ethical implications, animal models have also economical and technical drawbacks.
Ex vivo models can bridge the gap between in vitro and in vivo models, because they permit to isolate and investigate specific stimuli, but without loosing the complexity of the tissue. These approaches do not claim to substitute in vitro and in vivo models. But, instead, they yearn for supporting traditional approaches.
Therefore, the goal of this doctoral thesis was to design and develop innovative ex vivo models aiming at investigating different aspects related to the atherosclerotic process. In particular, three models were studied.
The first one, is an innovative model for studying the cellular and molecular mechanisms involved in the spreading of thrombosis. The culture system consisted in a parallel-plate optically accessible chamber for culturing human arterial slices exposed to a controlled blood flow. The system proved to be compliant with standard laboratory procedure and microscopy techniques, in particular with confocal microscopy.
The second model is an ex vivo culture system aimed at translating in ex vivo models procedures that have been employed to study thrombosis in vivo. In particular, we focused on the ferric chloride induced thrombosis, that, as far as we know, has been studied only with animal models. The versatile bioreactor was designed and developed to culture whole vessels with different diameters and lengths under fluid-dynamic controlled conditions.
Finaly, a tissue-engineered model for studying atherosclerosis was investigated. In fact, tissue-engineered inspired models have been used for their possibility to maintain the complexity of in vivo structures, but controlling cellular composition. As a proof of concept, we cultivated adventitial progenitor cells on tubular electrospun scaffolds under fluid-dynamic conditions to assess angiogenic effects of hypoxia. The model proved to be suitable for this kind of consideration, but, before exploiting its potentiality, technical problems must be solved. In fact, one main drawback of tissue-engineered models is related to the necessity to adapt traditional analysis protocols to these innovative approaches.DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIA32SIGNORINI, MARIA GABRIELLAALIVERTI, ANDRE
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
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