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Evolutionary dynamics of populations structured by dietary diversity and starvation: cross-diffusion systems
No full textIn questa tesi presentiamo alcuni progressi nell'analisi di problemi parabolici non lineari, derivanti dalla biologia e dall'ecologia. In particolare, studiamo l'esistenza, la regolarità e la stabilità delle soluzioni di equazioni alle derivate parziali (PDE), che descrivono l'evoluzione di due specie interagenti tra loro che si diffondono in un dominio spazialmente omogeneo. Le PDE considerate sono fortemente accoppiate, cioè accoppiate attraverso termini con derivata di secondo ordine, e danno luogo a sistemi che rientrano nella classe di sistemi di reazione-diffusione non lineari, chiamati sistemi di diffusione incrociata. Più precisamente, studiamo una classe di sistemi triangolari di diffusione incrociata, indotta dalla diversità alimentare delle popolazioni nell'ecosistema. Le tecniche usate nell'analisi riguardano metodi di entropia, stime a priori, argomenti di punto fisso e di compattezza. Inoltre, studiamo la stabilità lineare degli equilibri omogenei per analizzare l'instabilità di Turing e la conseguente formazione di motivi (pattern). Infine, completiamo l'analisi con simulazioni numeriche a supporto dei risultati teorici ottenuti.This thesis aims to present some recent results and advances in the analysis of nonlinear parabolic problems arising in biology and ecology. More precisely, we study the existence, regularity and stability of solutions of partial differential equations (PDEs), describing the evolution of two species that diffuse in a homogeneous environment and interact with each other. The PDEs we consider are strongly coupled and the system they give rise to belongs to a class of non-linear reaction-diffusion systems, called cross-diffusion systems. More precisely, we study a class of triangular starvation driven cross-diffusion systems arising in population dynamics. The tools employed are entropy methods, a priori estimates, fixed point and compactness arguments. Moreover, we analyze the linear stability of homogeneous equilibria to investigate Turing instability and pattern formation. Numerical simulations are performed to complement the theoretical results
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
Dynamique évolutive des populations structurées par la diversité alimentaire : systèmes de diffusion croisée
No full textCette thèse porte sur l’analyse des problèmes paraboliques non linéaires survenant dans la biologie et l’écologie. Plus précisément, nous étudions l’existence, la régularité et la stabilité des solutions d’une classe d’équations aux dérivées partielles (EDPs), décrivantes l’évolution de deux espèces qui diffusent dans un envi- ronnement homogène et interagissent les unes avec les autres. Les EDPs considérées sont fortement couplées et le système lui même appartient à une classe de systèmes de réaction-diffusion non linéaires, appelés systèmes de diffusion croisée. Plus précisément, nous étudions une classe de systèmes triangulaires avec diffusion croisée induits par la diversité alimentaire qui s’appliquent à la dynamique de population. Les outils utilisés sont les méthodes d’entropie, les estimations a priori, les arguments de point fixe et de compacité. De plus, nous analysons la stabilité linéaire des équilibres homogènes, afin d’étudier l’instabilité de Turing et la formation de motifs (pattern). Des simulations numériques sont réalisées pour compléter les résultats abstraits.This thesis aims to present some recent results and advances in the analysis of nonlinear parabolic problems arising in biology and ecology. More precisely, we study the existence, regularity and stability of solutions of partial differential equations (PDEs), describing the evolution of two species that diffuse in a homogeneous environment and interact with each other. The PDEs we consider are strongly coupled and the system they give rise to belongs to a class of non-linear reaction-diffusion systems, called cross-diffusion systems. More precisely, we study a class of triangular starvation driven cross-diffusion systems arising in population dynamics. The tools employed are entropy methods, a priori estimates, fixed point and compactness arguments. Moreover, we analyze the linear stability of homogeneous equilibria to investigate Turing instability and pattern formation. Numerical simulations are performed to complement the theoretical results
Dynamique évolutive des populations structurées par la diversité alimentaire : systèmes de diffusion croisée
No full textThis thesis aims to present some recent results and advances in the analysis of nonlinear parabolic problems arising in biology and ecology. More precisely, we study the existence, regularity and stability of solutions of partial differential equations (PDEs), describing the evolution of two species that diffuse in a homogeneous environment and interact with each other. The PDEs we consider are strongly coupled and the system they give rise to belongs to a class of non-linear reaction-diffusion systems, called cross-diffusion systems. More precisely, we study a class of triangular starvation driven cross-diffusion systems arising in population dynamics. The tools employed are entropy methods, a priori estimates, fixed point and compactness arguments. Moreover, we analyze the linear stability of homogeneous equilibria to investigate Turing instability and pattern formation. Numerical simulations are performed to complement the theoretical results.Cette thèse porte sur l’analyse des problèmes paraboliques non linéaires survenant dans la biologie et l’écologie. Plus précisément, nous étudions l’existence, la régularité et la stabilité des solutions d’une classe d’équations aux dérivées partielles (EDPs), décrivantes l’évolution de deux espèces qui diffusent dans un envi- ronnement homogène et interagissent les unes avec les autres. Les EDPs considérées sont fortement couplées et le système lui même appartient à une classe de systèmes de réaction-diffusion non linéaires, appelés systèmes de diffusion croisée. Plus précisément, nous étudions une classe de systèmes triangulaires avec diffusion croisée induits par la diversité alimentaire qui s’appliquent à la dynamique de population. Les outils utilisés sont les méthodes d’entropie, les estimations a priori, les arguments de point fixe et de compacité. De plus, nous analysons la stabilité linéaire des équilibres homogènes, afin d’étudier l’instabilité de Turing et la formation de motifs (pattern). Des simulations numériques sont réalisées pour compléter les résultats abstraits
Dynamique évolutive des populations structurées par la diversité alimentaire : systèmes de diffusion croisée
No full textThis thesis aims to present some recent results and advances in the analysis of nonlinear parabolic problems arising in biology and ecology. More precisely, we study the existence, regularity and stability of solutions of partial differential equations (PDEs), describing the evolution of two species that diffuse in a homogeneous environment and interact with each other. The PDEs we consider are strongly coupled and the system they give rise to belongs to a class of non-linear reaction-diffusion systems, called cross-diffusion systems. More precisely, we study a class of triangular starvation driven cross-diffusion systems arising in population dynamics. The tools employed are entropy methods, a priori estimates, fixed point and compactness arguments. Moreover, we analyze the linear stability of homogeneous equilibria to investigate Turing instability and pattern formation. Numerical simulations are performed to complement the theoretical results.Cette thèse porte sur l’analyse des problèmes paraboliques non linéaires survenant dans la biologie et l’écologie. Plus précisément, nous étudions l’existence, la régularité et la stabilité des solutions d’une classe d’équations aux dérivées partielles (EDPs), décrivantes l’évolution de deux espèces qui diffusent dans un envi- ronnement homogène et interagissent les unes avec les autres. Les EDPs considérées sont fortement couplées et le système lui même appartient à une classe de systèmes de réaction-diffusion non linéaires, appelés systèmes de diffusion croisée. Plus précisément, nous étudions une classe de systèmes triangulaires avec diffusion croisée induits par la diversité alimentaire qui s’appliquent à la dynamique de population. Les outils utilisés sont les méthodes d’entropie, les estimations a priori, les arguments de point fixe et de compacité. De plus, nous analysons la stabilité linéaire des équilibres homogènes, afin d’étudier l’instabilité de Turing et la formation de motifs (pattern). Des simulations numériques sont réalisées pour compléter les résultats abstraits
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
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