1,721,055 research outputs found
Homogenization, simple exclusion processes and random resistor networks on Delaunay triangulations
Full text linkThe aim of this PhD thesis is to prove some properties related to Delaunay triangulations on point processes with random conductances that allow to verify the validity of some assumptions in the theorems contained in [2,3,4]. As a consequence of these theorems, one can obtain the stochastic homogenization of the random walk on the Delaunay triangulation, the hydrodynamic limit of the simple exclusion process on the Delaunay triangulation and the scaling limit of the directional conductivity of the random resistor networks on Delaunay triangulation.
We start by introducing the random environment. According to [6], we introduce the Voronoi tessellation and we discuss some geometrical properties. We further give the definition of points in general quadratic position and we present a criterion that guarantees the boundedness of the Voronoi cells. We have that boundedness of Voronoi cells is a sufficient condition for Voronoi cells to be convex polytopes ([5]).
Then we give a brief introduction of the theory of point processes and simple point processes referring to [1]. First, we provide the basic definitions of random measures, counting measures (simple counting measures) and point processes (simple point processes). We present the stationary random measures and the properties related to the stationary point processes (stationary simple point processes). Then we provide the definition of Campbell measure and of local Palm distributions of a random measure. As a special case, we consider the local Palm distributions of a stationary random measures ξ with finite intensity. Called M the first moment measure of ξ, we obtain that the family of local Palm distributions coincides M −a.e. with the Palm distribution. Finally we discuss an ergodic theorem when ξ is a stationary ergodic point process with finite density.
Later, we argue sufficient conditions assuring that the points of a simple point process are in general position or in reinforced general position almost surely. The definition of points in reinforced general position, introduced in [8], coincides with that of points in general quadratic position. Following [8], we give a characterization of the simple point processes that are in general position, or general reinforced position, in terms of the reduced k−th moment measure. As an application of the previous results, we present the cases of Poisson point processes and Gibbsian point processes.
Afterwards, we present the exclusion process on Z^d. Following [7], we construct the exclusion process on Z^d and we discuss some of its properties. We also review the proof of the hydrodynamic limit of the symmetric exclusion process on Z^d.
Finally, we present the original contribution of the PhD work which was realised in collaboration with A.Faggionato. We consider the Voronoi tessellation associated to an ergodic and stationary point process on R^d. We introduce the Delaunay triangulation as the graph with vertex set given by the point process and with edges between vertexes whose Voronoi cells share a (d-1)-dimensional face. We also attach to each edge a random conductance. On the Delaunay triangulation we consider the random walk with random conductances, the simple exclusion process obtained by multiple random walks as above under hardcore interaction and the resistor network with random conductances. With the purpose of applying the general results obtained in [2,3,4] in the case of Delaunay triangulations, we investigate the validity of suitable moment bounds and we look for a bond percolation result for the existence of the simple exclusion process. We give specific criteria in our context assuring the validity of the assumptions made in [2,3,4]. As said at the beginning, as a byproduct between our results and [2,3,4], one can obtain the homogenization of the massive Poisson equation associated to the random walk, the hydrodynamic limit in path space of the simple exclusion process and the scaling limit of the directional conductivity of the resistor network.
[1] D.J. Daley, D. Vere-Jones; “An introduction to the theory of point processes.” New York, Springer Verlag, 1988.
[2] A. Faggionato; "Stochastic homogenization of random walks on point processes." Ann. Inst. H. Poincaré Probab. Statist. (to appear). arXiv:2009.08258 (2020).
[3] A. Faggionato; "Hydrodynamic limit of simple exclusion processes in symmetric random environments via duality and homogenization." arXiv:2011.11361 (2020).
[4] A. Faggionato; "Scaling limit of the conductivity of random resistor networks on simple point processes." arXiv:2108.11258 (2021).
[5] D. Hug, W. Weil; “Lectures on convex geometry.” Graduate Texts in Mathematics 286, Springer International Publishing, 2020.
[6] J. Møller; “Lectures on random Voronoi tessellation.” Lecture Notes in Statistics 87, Springer Verlag, New York, 1994.
[7] T. Seppäläinen; “Translation invariant exclusion processes.” Book in progress, https://people.math.wisc.edu/~seppalai/excl-book/ajo.pdf.
[8] H. Zessin; “Point processes in general position.” Izvestiya NAN Armenii Matematika 1, 75–82 (2008); preprinted in Journal of Contemporary Mathematical Analysis 43 (1), 59—65 (2008)
From natural products based research, n ew substances for the treatment of Candida sp infections: the case of spirulina platensis
No full textCastanea sativa Mill. barck extract: liver and intestinal protective effects in high-fat-diet rats
No full textHibiscus flowers and olive Leaves extracts-based formulation in neurodegeneration: a network-based approach
No full textNutraceuticals in Gastrointestinal ailments : an emerging paradigm
No full textInflammatory bowel disease (IBD) is a chronic gastrointestinal disorder, of multifactorial origin.
The pathogenetic mechanisms consist of immune dysregulation, altered intestinal microflora, oxidative stress, defects in the gastrointestinal mucosal barrier and increased permeability, altered intestinal motility, whose interplay leads to the onset of a state of chronic mucosal inflammation.1
The drugs for IBD treatment include corticosteroids, immunosuppressants, and anti-tumor necrosis factor (TNF)-α antibodies, and new therapeutic molecules, that increase the risk of opportunistic infections and malignancies. Furthermore, their efficacy decreases over time and highlights the need to identify new molecular targets for IBD therapy .1
Scientific Research aims at identifying tools able to affect several targets, with minimal side effects.
Nutraceutical identifies foods, or food phytochemicals, of animal or vegetal origin, with pharmaceutical properties.
Many vegetal extracts determine several effects towards the gastrointestinal tract, which may result in clinical benefits in subjects suffering from IBD.2
Castanea sativa Mill. bark extract (ENC), containing high amounts of hydrolizable tannins (Fig. 1), inhibits spasmodic contractions, induced by carbachol, histamine, potassium chloride, and barium chloride in guinea pig ileum and by carbachol or serotonin in guinea pig proximal colon.3 Furthermore, ENC increases gallbladder contraction and relaxes the sphincter of Oddi, suggesting its chronic administration may result not only in a restoration of gastrointestinal contractility, but also in the prevention of gallstone disease. 4
Also Acacia catechu Willd. extract (ACE) was investigated.5
ACE contains high amounts of catechins, such as (-)-Epicatechin and (+)-Catechin. This extract decreases, in a concentration-dependent manner, colon and ileum spontaneous contractility. In addition, ACE exerts a calcium antagonistic effect, more potent in proximal colon than in ileum. Furthermore, it exhibits antimicrobial effects against Campylobacter jejuni, Escherichia coli, and Salmonella spp., without inhibiting Bifido and Lactobacillus.
These data support the use of ENC and ACE as coadjuvant in the treatment of IBD
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
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