1,721,819 research outputs found
RIGIDITY RESULTS FOR LICHNEROWICZ BAKRY-EMERY RICCI TENSORS
Full text linkWe investigate rigidity phenomena in the class of Riemannian manifolds with density. By a weighted manifold (or manifold with density) we mean a Riemannian manifold endowed with a weighted measure absolute continuous with respect to the Riemannian one. Associated to a weighted manifold there is also a natural divergence form second order diffusion operator: the f-Laplacian. Good choiches for the concept of curvature in this setting are those that reveal interplays with metric and topological properties of the space. We have focused on Lichnerowicz Bakry-Emery Ricci's tensors. When we impose the constancy of these tensors we are endowing the manifold of an additional structure, namely, a gradient Ricci soliton or a quasi-Einstein structure. The importance of Ricci solitons is due to Perelman's solution of Poincarè conjecture, while the importance of quasi-Einstein manifolds comes from the relationship they have with Einstein warped products. Actually in this thesis we also introduce an extension of the concept of gradient Ricci soliton, the Ricci almost soliton, allowing the soliton constant to be a generic smooth function on the weighted manifold. In view of the not necessarily constantness, one expects that a certain flexibility on the almost soliton structure is allowed and, consequently, the existence of almost solitons is easier to prove than in the classical situation. This feeling is confirmed by a number of diff erent examples of almost solitons. On the other hand we prove a rigidity result which indicates that almost solitons should reveal a reasonably
broad generalization of the fruitful concept of classical soliton. Considering elliptic equations and inequalities (naturally involving the f-Laplacian) for various geometric quantities and making use of analytical techniques coming from stochastic analysis such as stochastic completeness, in the form of the weak Omori-Yau maximum principle, parabolicity and Lp-Liouville type results, we prove rigidity in the form of metric rigidity (scalar curvature estimates, classification results, gap theorems for some geometric quantities) and in the form of triviality of the additional structure. Moreover we obtain also topological rigidity for these tensors (with consequences e.g. on the structure of the fundamental group)
Uptake and presentation of orally administered antigens
No full textThe mucosae of the gastrointestinal tract are continuously exposed to a myriad of antigens and microorganisms that the immune system has to discriminate between dangerous and harmless. Entry of pathogenic microorganisms occurs mainly via M cells that are concentrated in the follicle-associated epithelium overlying the Peyer's Patches (PPs). M cells are very selective and do not allow entry of all microorganisms. We have recently described an additional mechanism by which dendritic cells (DCs) can monitor the contents of the intestinal lumen. DCs send dendrites outside the epithelium, like periscopes. It is not clear whether this mechanism is constitutively active or is induced in response to signals from epithelial cells that have been in contact with pathogens or high numbers of non pathogenic bacteria in the lumen. Therefore, deciphering the signals that are released by epithelial cells after the encounter with mucosal antigens is of paramount importance to understand the ability of the DCs to respond to the different antigens and to mount immune or tolerogenic responses
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
Variations 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Some triviality results for quasi-Einstein manifolds and Einstein warped products
No full textIn this paper we prove a number of triviality results for Einstein warped products and quasi-Einstein manifolds using different techniques and under assumptions of various nature. In particular we obtain and exploit gradient estimates for solutions of weighted Poisson-type equations and adaptations to the weighted setting of some Liouville-type theorems
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