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Precision Engineering of 3D Fibrillar structures: Controlling Fiber Dimensions via Two-Photon Polymerization
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Microfabrication bi-photonique d’un modèle 3D de matrice extracellulaire à architecture et mécanique contrôlées
No full textNational audienceThe extracellular matrix (ECM) constitutes the immediate structural and functional environment of cells. Far more than a simple support, it forms a hierarchical fibrillar network that provides tissues with their mechanical strength and spatial organization, while regulating essential processes such as cell adhesion, migration, proliferation, and differentiation. The microarchitecture of the ECM (organization, fiber diameter, and pore distribution) defines local mechanical properties, the diffusion of biochemical signals, and cell dynamics. The ECM thus emerges as a key parameter in tissue behavior. Faithfully reproducing this architecture in vitro remains a major challenge. Conventional approaches, whether based on fibrillar hydrogels or structured biomaterials, can partially mimic the composition and topography of the ECM. However, they struggle to accurately replicate sub-micrometer scales, controlled organization, and reproducibility—factors necessary to isolate arch! itectural effects from biochemical background cues. This limitation hinders a detailed understanding of the relationships between mechano-architecture and cellular functions. Two-photon polymerization (2PP) therefore represents a privileged method for producing 3D culture scaffolds with architecture controlled at the subcellular scale. Its nanometric resolution and three-dimensional design freedom make it possible to engineer artificial fibrillar networks resembling those of the ECM, while independently modulating fiber diameter, alignment, density, and pore size. 2PP thus paves the way for highly controllable, reproducible, and customizable matrix models, providing a unique experimental framework to dissect the impact of architecture on cellular behavior. This thesis is developed within this perspective. It aims to establish a 2PP-based design strategy dedicated to the fabrication of in vitro fibrillar scaffolds inspired by collagen dimensions and ECM porosity. To achieve ! this, a systematic dimensional study of the spatial resolution of sub-micrometer fibers in a biocompatible acrylate resin was conducted in order to define a parametric space suited to scaffold design. In a second step, a mechanical characterization of the resulting porous structures was performed, enabling the identification of their constitutive laws and their potential applications in relation to the elasticity of in vivo tissues. The ultimate goal is to quantitatively link the architectural properties of the networks to cellular responses, in order to shed light on the role of the ECM in tissue organization.La matrice extracellulaire (MEC) constitue l’environnement structural et fonctionnel immédiat des cellules. Bien plus qu’un simple support, elle forme un réseau fibrillaire hiérarchisé qui confère aux tissus leur résistance mécanique, leur organisation spatiale et régule des processus essentiels tels que l’adhésion, la migration, la prolifération ou encore la différenciation cellulaires. La microarchitecture de la MEC (organisation, diamètre et distribution des pores) détermine les propriétés mécaniques locales, la diffusion des signaux biochimiques et la dynamique cellulaire. La MEC apparaît ainsi comme un paramètre clé du comportement tissulaire.Reproduire fidèlement cette architecture in vitro demeure un défi majeur. Les approches classiques, qu’elles reposent sur des hydrogels fibrillaires ou des biomatériaux structurés, permettent d’imiter partiellement la composition et la topographie de la MEC. Toutefois, elles peinent à restituer avec précision les échelles sub-micrométriques, l’organisation contrôlée et la reproductibilité nécessaires pour isoler l’effet architectural du fond biochimique. Cette limite freine la compréhension fine des relations entre mécano-architecture et fonctions cellulaires.L’impression biphotonique (2PP) constitue dès lors une méthode privilégiée pour produire des supports de culture 3D dont l’architecture est contrôlée à l’échelle subcellulaire. Sa résolution nanométrique et sa liberté géométrique tridimensionnelle permettent de concevoir des réseaux fibrillaires artificiels proches de ceux de la MEC, en modulant de manière indépendante le diamètre, l’alignement, la densité et la taille des pores. La 2PP ouvre ainsi la voie à des modèles de matrices hautement contrôlables, reproductibles et personnalisables, offrant un cadre expérimental unique pour disséquer l’impact de l’architecture sur les comportements cellulaires.Les travaux de cette thèse s’inscrivent dans cette perspective. Ils visent à établir une stratégie de conception par 2PP dédiée à la fabrication de matrices fibrillaires in vitro de type scaffold, inspirées des dimensions du collagène et de la porosité de la MEC. Pour ce faire, une étude dimensionnelle systématique de la résolution spatiale de fibres sub-micrométriques en résine acrylique biocompatible a été menée, afin de définir un espace paramétrique adapté à la conception de scaffolds. Dans un second temps, une caractérisation mécanique des structures poreuses obtenues a été réalisée, permettant d’identifier leurs lois de comportement et leur champ d’application au regard de l’élasticité des tissus in vivo. L’objectif ultime est de relier, de manière quantitative, les propriétés architecturales des réseaux aux réponses cellulaires, afin d’éclairer le rôle de la MEC dans l’organisation des tissus
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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