1,720,963 research outputs found
Mécanique de l'écoulement dans des tubes liquides à confinement magnétique
No full textLa microfluidique joue un rôle très important dans le transport de bio-fluides, allant du diagnostic médical à la simulation d'organes biologiques. La mécanique de l'écoulement dans les microcanaux est très bien expliquée par l'équation de Navier-Stokes dans la limite de petits nombres de Reynolds. Cependant, malgré des décennies de recherche, un défi majeur reste à relever : surmonter l'importante traînée visqueuse ou perte de charge qui se produit lorsque la taille du canal d'écoulement diminue. Nous présentons une nouvelle approche en créant un canal d'écoulement liquide dans un autre liquide stable (tube liquide). Le canal liquide en écoulement est encapsulé par un liquide lubrifiant composé de ferrofluide maintenu en place par des forces magnétiques. Une réduction importante de la traînée atteignant 99% est obtenue, complétée expérimentalement par la démonstration d'une grande longueur de glissement record (à l’échelle du mm). Un profil de vitesses approchant celui d’un écoulement parfait est expliqué par un nombre de Reynolds modifié. Nous montrons que la fameuse instabilité de Plateau-Rayleigh est empêchée par la présence d’un interface liquide-liquide déformable. Dans ce contexte, nous étudions la stabilité et les déformations du tube liquide en identifiant l'échelle de longueur de la déformation, dont le contrôle peut ouvrir la voie à la réalisation de dispositifs microfluidiques ultra-souples. Les propriétés uniques du tube liquide, comme la résistance visqueuse réglable, les déformations réversibles induites par l'écoulement, le rendent approprié pour l'administration de médicaments, le transport de biomatériaux, la bio-impression et comme système modèle d’écoulement dans les artères, veines et d'autres interfaces complexes. Les nouvelles possibilités offertes par les écoulements lubrifiés stabilisés par des forces magnétiques permettent de repousser les limites actuelles de la microfluidique et ouvrent ainsi de nouvelles possibilités d’applications.Microfluidics plays a very important role in bio-fluid transport, ranging from medical diagnostics to the simulation of biological organs. The mechanics of flow in microchannels is very well explained by the Navier-Stokes equation in the small Reynolds number limit. However, despite decades of research, a major challenge remains to overcome the significant viscous drag or pressure drop that occurs as the size of the flow channel decreases. We present a new approach by creating a liquid flow channel in another stable liquid (liquid tube). The flowing liquid channel is encapsulated by a ferrofluid lubricant held in place by magnetic forces. A significant drag reduction of up to 99% is achieved, complemented experimentally by the demonstration of a record long slip length (on a mm scale). A velocity profile approaching that of a perfect flow is explained by a modified Reynolds number. We show that the famous Plateau-Rayleigh instability is prevented by the presence of a deformable liquid-liquid interface. In this context, we study the stability and deformations of the liquid tube by identifying the length scale of the deformation, the control of which may pave the way for the realisation of ultra-flexible microfluidic devices. The unique properties of the liquid tube, such as adjustable viscous resistance, reversible flow-induced deformations, make it suitable for drug delivery, biomaterial transport, bioprinting and as a model system for flow in arteries, veins and other complex interfaces. The new possibilities offered by lubricated flows stabilized by magnetic forces push the current limits of microfluidics and thus open up new application possibilities
Mécanique de l'écoulement dans des tubes liquides à confinement magnétique
No full textMicrofluidics plays a very important role in bio-fluid transport, ranging from medical diagnostics to the simulation of biological organs. The mechanics of flow in microchannels is very well explained by the Navier-Stokes equation in the small Reynolds number limit. However, despite decades of research, a major challenge remains to overcome the significant viscous drag or pressure drop that occurs as the size of the flow channel decreases. We present a new approach by creating a liquid flow channel in another stable liquid (liquid tube). The flowing liquid channel is encapsulated by a ferrofluid lubricant held in place by magnetic forces. A significant drag reduction of up to 99% is achieved, complemented experimentally by the demonstration of a record long slip length (on a mm scale). A velocity profile approaching that of a perfect flow is explained by a modified Reynolds number. We show that the famous Plateau-Rayleigh instability is prevented by the presence of a deformable liquid-liquid interface. In this context, we study the stability and deformations of the liquid tube by identifying the length scale of the deformation, the control of which may pave the way for the realisation of ultra-flexible microfluidic devices. The unique properties of the liquid tube, such as adjustable viscous resistance, reversible flow-induced deformations, make it suitable for drug delivery, biomaterial transport, bioprinting and as a model system for flow in arteries, veins and other complex interfaces. The new possibilities offered by lubricated flows stabilized by magnetic forces push the current limits of microfluidics and thus open up new application possibilities.La microfluidique joue un rôle très important dans le transport de bio-fluides, allant du diagnostic médical à la simulation d'organes biologiques. La mécanique de l'écoulement dans les microcanaux est très bien expliquée par l'équation de Navier-Stokes dans la limite de petits nombres de Reynolds. Cependant, malgré des décennies de recherche, un défi majeur reste à relever : surmonter l'importante traînée visqueuse ou perte de charge qui se produit lorsque la taille du canal d'écoulement diminue. Nous présentons une nouvelle approche en créant un canal d'écoulement liquide dans un autre liquide stable (tube liquide). Le canal liquide en écoulement est encapsulé par un liquide lubrifiant composé de ferrofluide maintenu en place par des forces magnétiques. Une réduction importante de la traînée atteignant 99% est obtenue, complétée expérimentalement par la démonstration d'une grande longueur de glissement record (à l’échelle du mm). Un profil de vitesses approchant celui d’un écoulement parfait est expliqué par un nombre de Reynolds modifié. Nous montrons que la fameuse instabilité de Plateau-Rayleigh est empêchée par la présence d’un interface liquide-liquide déformable. Dans ce contexte, nous étudions la stabilité et les déformations du tube liquide en identifiant l'échelle de longueur de la déformation, dont le contrôle peut ouvrir la voie à la réalisation de dispositifs microfluidiques ultra-souples. Les propriétés uniques du tube liquide, comme la résistance visqueuse réglable, les déformations réversibles induites par l'écoulement, le rendent approprié pour l'administration de médicaments, le transport de biomatériaux, la bio-impression et comme système modèle d’écoulement dans les artères, veines et d'autres interfaces complexes. Les nouvelles possibilités offertes par les écoulements lubrifiés stabilisés par des forces magnétiques permettent de repousser les limites actuelles de la microfluidique et ouvrent ainsi de nouvelles possibilités d’applications
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
Suppressing Interfacial Instability of Immiscible Liquid‐in‐Liquid Flow Using Magnetic Forces
No full textAbstract Interfacial instability prevents a liquid jet from flowing indefinitely within air or another liquid. An approach is presented here to suppress interfacial instability by means of a magnetic force applied by a ferrofluid envelope around the jet. The stability limits occurring within a large parameter window are experimentally investigated with length and time scales governed by the magnetic Bond number. Instabilities can be generated by modifying the magnetic force strength externally, with a remarkable return to stability when removing the external stimulus. The current system with soft and slippery interfaces enables investigations of flow systems beyond the limits of standard hydrodynamics allowing for exciting applications in flow chemistry, interface engineering and transport of biological materials.Ministerio de Ciencia e Innovación https://doi.org/10.13039/501100004837HORIZON EUROPE Marie Sklodowska-Curie Actions https://doi.org/10.13039/10001869
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