1,721,094 research outputs found
The Role of Interfaces in Microfluidic Systems: Oscillating Sessile Droplets and Confined Bacterial Suspensions
Full text linkThis PhD thesis is focused on the role of interfaces that characterize microfluidic systems, such as
the free air/liquid interface of drops or the liquid/solid interface of fluids enclosed in microchannels.
This work has a twofold character: on one side, we studied the dynamics of sessile drops subject to oscillations of the substrate; on the other, we investigated the spatial concentration distribution of suspensions of motile bacteria, as a model system for active collids, tuned by geometrical confinement.
Dynamics of sessile drops. The first topic is related to the field of wetting phenomena and
open microfluidics, which deals with the behaviour of drops, typically in the nano-/microliter range,
deposited on open surfaces. At such length scale, these systems are dominated by capillarity and may give rise to unexpected effects, not commonly observed at the larger scale we are used to. Our studies aim to the achievement of an active control on the motion and shape of drops by means of vibration of the substrates, for chemical or biological applications.
In particular, the motion of liquid drops on an inclined substrate subject to vertical harmonic
oscillations have been considered. Typically, small droplets on inclined surfaces remain pinned because of contact angle hysteresis. When vertical oscillations are applied the droplets unpin and slide down. Surprisingly, for sufficiently large oscillation amplitude the droplets move upward against gravity. The systematical investigation of the response of drops on varying peak acceleration and frequency of oscillations, for fluids with different surface tensions and viscosity, allowed the control of the unidimensional motion along the substrate.
Then, we have studied the interfacial morphologies of water drops confined on the hydrophilic top
face of rectangular posts of width 0.5 mm and various length. For small volumes, the liquid film adopts the shape of a homogeneous filament with a uniform cross section close to a circular segment. For larger volumes, the water interface forms a central bulge, which grows with the volume. In the case of posts longer than a characteristic length, the transition between the two film shapes on varying the volume is discontinuous and exhibits the bistability of the two morphologic states associated with a hysteresis phenomenon. Vertically oscillating the post, with fixed water volume corresponding to the bistability, at certain frequencies induces an irreversible transition from the filament to the bulge state.
Self-propelled particles under geometrical confinement. The second topic deals with the
behaviour of active fluids, i.e. self-propelled colloid suspensions which are intrinsically out of equilibrium systems (Active Matter). In particular, in the presence of geometrical structures, such systems behave in a very different way with respect to equilibrium Browinan colloids. We have analyzed the role of different swimming patterns on the concentration distribution of bacterial suspensions confined between two flat walls, by considering wild-type E. coli and P. aeruginosa, which perform Run and Tumble and Run and Reverse patterns, respectively. The concentration profiles have been obtained by counting motile bacteria at different distances from the bottom wall. In agreement with previous studies, an accumulation of motile bacteria close to the walls was observed. Different fraction of motile bacteria and different wall separations, ranging from 100 μm to 250 μm, have been tested. The concentration profiles resulted to be independent on the walls separation and on the different kind of motility and to scale with the motile fraction. These results are confirmed by numerical simulations, based on a collection of self-propelled rod-like particles interacting only through steric interactions
La Bibbia e la Certosa. Letture dal De Tralatione Bibliae di Petrus Sutor (1525) sullo sfondo del contrasto tra Erasmo e i teologi di Parigi e Lovanio
No full textPrima parte: L'analisi del rapporto tra spiritualità certosina e devotio moderna consente di individuare il contesto in cui maturò ed ebbe fortuna il De tralatione Bibliae di Petrus Sutor, monaco certosino. La spiritualità certosina ebbe forte influsso sulla Congregazione di Montaigu, espressione estrema della devotio moderna, nella quale lo stesso Sutor fu massima autorità spirituale in qualità di priore della Certosa di Parigi. Alla Congregazione di Montaigu appartennero i principali oppositori di Erasmo nel campo della filologia biblica nell'area di Parigi e Lovanio. In essa ebbe fortuna l'opera di Sutor, anche se il mondo di Montaigu mostra due facce. Il mondo parigino di Montaigu risulta infatti più conservatore di quello lovaniense, che nelle figure di Iacobus Latomus e Frans Titelmans mostra una certa apertura all'umanesimo. Seconda parte e appendice: i contenuti del De tralatione Bibliae mostrano i rapporti di Sutor con altri oppositori erasmiani, Stunica in particolare. Emergono le fonti che stanno alla base delle informazioni storiche fornite da Sutor, tra cui emerge Petrus Comestor, e la risonanza del De tralatione Bibliae negli ambienti culturali inglesi, in particolare in John Fisher.First Part: In order to supply with due context Sutor's De tralatione Bibliae, it is necessary to rediscover the interplay between Carthusian spirituality and devotio moderna. The carthusian influence was particulary strong in the Congregation of Montaigu, which formed an extreme wing of devotio moderna. Sutor himself played a very important role in the Congregation of Montaigu having been his major authority for three years as Prior of the Parisian Charterhouse. The main critics of Erasmus in the field of biblical philology, who were active in Paris and Louvain theological units belonged to the Montaigu Congregation. There were differences between the Paris and Louvain Montaigu cultural and spiritual habits. Louvain shows a particular trend to moderation and acceptance of some fundamental humanistic issues, that we can trace in Iacobus Latomus and Francis Titelmans. Second Part and Appendix: The contents of Sutor's De tralatione Bibliae display the relationship between Sutor and other critics of Erasmus, in particular Stunica. Through the text we rediscover the different sources Sutor uses in order to supply the reader with historical information, especially Petrus Comestor, and we can identify some echoes of Sutor's works in John Fisher and the English cultural circles
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
Atmospheric Aerosol at the Svalbard Islands in Year 2010. A Preliminary Analysis of Multielemental Data from Size-Segregated Samples: (III) Crustal Elements and Minor Elements
No full textVariations 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
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