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A disposable enzymatic biofuel cell for glucose sensing via short-circuit current
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Fabrication and optimization of abiotic bioelectrodes for implantable glucose biofuel cell
No full textCe travail de thèse avait pour objectif d’optimiser la fabrication des biocathodes abiotiques pour biopiles à glucose implantables en utilisant différents procèdes d’impression. Le catalyseur mis en jeu est un catalyseur abiotique constitué de graphène dopé au fer et azote (Gr-N-Fe (2 %)).Des biocathodes en 2D ont été tout d’abord effectuées en utilisant deux méthodes de dépôt la pulvérisation ultrasonique et le dépôt par couchage. Les biocathodes réalisées par pulvérisation ultrasonique présentaient des très faibles performances électrochimiques dus aux faibles quantités de matière active déposées. De ce fait, la méthode de dépôt par couchage a été ainsi adoptée vu qu’elle permet de déposer des quantités de matière plus importante. Grâce à cette méthode, des densités de courant de l’ordre de 66 µA/cm2 avec une stabilité excédant les deux années ont été obtenues. Des tests préliminaires de culture cellulaire de la biocathode en présence de cellules fibroblastes issus de souris ont été validée. Fort de ces résultats, l’autorisation du comité d’éthique de Grenoble pour effectuer des implantations chez le rat a été obtenue. Les biocathodes flexibles ont ainsi fait l’objet d’une implantation dans le domaine intraabdominal d’un rat pour différentes périodes. Une absence de réaction inflammatoire est constatée après 5 mois d’implantation. Ceci met ainsi en évidence la biocompatibilité de cette dernière. De plus, ces biocathodes était électrochimiquement fonctionnelles même après une durée d’implantation de l’ordre de 5 mois.Dans la partie suivante de la thèse, des biocathodes en 3D ont été élaborées. Des biocathodes abiotiques imprimées en 3D ont été réalisées en premier lieu. L’utilisation de l’impression 3D avait pour but d’obtenir des électrodes en 3D ayant une macroporosité contrôlée facilitant ainsi la diffusion de l’électrolyte au sein de l’électrode en 3D. La fabrication de ces derniers était réalisée via deux méthodes : la première consistait à utiliser la matière active directement dans la formulation initiale tans dis que la deuxième consistait à créer les sites catalytiques plutôt in situ la forme en 3D. Une formulation à base de microfibrilles de cellulose, de chitosan en poudre, de catalyseur (ou précurseur) et de graphène commercial a été optimisée où un pourcentage massique total en graphène de 83.3 % été fixé. En effet, l’utilisation des microfibrilles de cellulose dans la formulation confère une meilleure microporosité aux bioélectrode comparé aux liants habituellement utilisés. Une optimisation des paramètres d’impression était par la suite effectuée. Un pourcentage théorique de remplissage a été fixé à 40 % où la meilleur macroporosité et homogénéité de distribution de pores ainsi que les meilleures performances électrochimiques sont obtenues. Des densités de courant de l’ordre de 400 µA/cm2 sous air sont apportées via la 1ére méthode. Quant à la 2éme méthode, une amélioration des performances électrochimiques d’un facteur de 1.5 est effectuée. Ceci est dû principalement à l’étape de pyrolyse qui apporte une amélioration de la conductivité ainsi que la porosité de la bioélectrode. Toutefois, ces améliorations se font au détriment de la tenue mécanique des biocathodes. En tenant compte de la tenue mécanique, les biocathodes réalisées via la 1ére méthodes ont été choisies pour effectuer des tests d’implantation de biopiles hybrides dans le domaine intraabdominal des rats. La densité de puissance de ces biopiles était de l’ordre de 80 µW avant implantation. Ces dernières restaient encore fonctionnelles même après une durée d’implantation de l’ordre de 3 mois. De plus, une quasi-absence de réaction inflammatoire au bout de 3 mois a été constatée, mettant en évidence la biocompatibilité de ces biocathodes.Finalement, une formulation à base de MFC à été aussi adopté afin de réaliser des anodes enzymatiques montrant une amélioration des performances électrochimiques d’un facteur de 1.5 comparé au chitosan.This thesis work aimed to optimize of abiotic biocathodes manufacturing for implantable glucose biofuel cells using different printing technics. The adopted catalyst is an abiotic catalyst consisting of graphene doped with iron and nitrogen (Gr-N-Fe (2 %)).2D biocathodes were firstly fabricated using two printing technics: ultrasonic spraying and doctor blade coating. Biocathodes produced by ultrasonic spraying exhibited poor electrochemical performances due to the small amounts of active material deposited. Using doctor blade printing technic, a current density of about 66 µA. cm2 was obtained with a high stability exceeding a period of two years. Preliminary cell culture tests of the biocathode’s compounds in the presence of fibroblast cells derived from mice have been validated. Based on these results, the authorization from the Grenoble ethics committee for electrode’s implantation in rats has been obtained. The flexible biocathodes were implanted in the intraabdominal domain of a rat for different periods. An absence of inflammatory reaction observed is after 5 months of implantation was noticed. This result highlights the biocompatibility of these flexible biocathodes. In addition, these biocathodes were electrochemically functional even after an implantation period of 5 months.In the next part of the thesis, 3D biocathodes were developed. 3D printed abiotic biocathodes were firstly fabricated. The use of 3D printing was on the purpose of obtaining 3D electrodes with controlled macroporosity. This configuration facilitate the electrolyte diffusion within the 3D electrodes. The 3D printed biocathode manufacturing was carried out via two methods: the first consisted of using the catalyst directly in the initial formulation, while the second consisted of creating the catalytic sites in situ the 3D shape. A formulation based on cellulose microfibrils, chitosan powder, catalyst (or precursor) and commercial graphene has been optimized where a total graphene mass percentage of 83.3% has been set. Indeed, the use of cellulose microfibrils in the formulation confers a better microporosity on the bioelectrodes compared to the binder usually used such as chitosan, PVA, PVDF etc. An optimization of the printing parameters was then carried out where a theoretical filling rate was set at 40 %. This rate demonstrated the best macroporosity and pore’s distribution homogeneity as well as the best electrochemical performances. Current densities of about of were provided via the 1st method. As for the second method, an improvement in electrochemical performance by a factor of 1.5 is achieved. This is mainly due to the pyrolysis step which improves the conductivity as well as the porosity of the bioelectrode. However, these improvements are made to the detriment of the biocathodes mechanical strength. This makes them more sensitive to the mechanical stresses induced during implantation. Taking into account the mechanical strength, the biocathodes produced using the 1st method were chosen to perform hybrid biofuel cell’s implantation in the rat’s intraabdominal part. The power density of these biofuel cells was of about 80 µW in vitro before implantation. This one remained functional even after an implantation period of around 3 months. In addition, a virtual absence of inflammatory reaction after 3 months has been observed, which highlights the biocompatibility of these biocathodes. This type of 3D printed electrodes for implantable glucose biofuel cells presented a new generation of electrodes produced for the first time in the literature. As a result, an invention about this work was made by our group.Given the improvement in the porosity provided by cellulose microfibrils, a comparative study between two enzymatic anodes made from glucose oxidase was carried out. This study has clearly demonstrated that by replacing chitosan with MFCs, an improvement in electrochemical performance by a factor of was obtained
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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