98 research outputs found
Performance Analysis of Online Social Platforms
We introduce an original mathematical model to analyze the diffusion of posts
within a generic online social platform. Each user of such a platform has his
own Wall and Newsfeed, as well as his own self-posting and re-posting activity.
As a main result, using our developed model, we derive in closed form the
probabilities that posts originating from a given user are found on the Wall
and Newsfeed of any other. These probabilities are the solution of a linear
system of equations. Conditions of existence of the solution are provided, and
two ways of solving the system are proposed, one using matrix inversion and
another using fixed-point iteration. Comparisons with simulations show the
accuracy of our model and its robustness with respect to the modeling
assumptions. Hence, this article introduces a novel measure which allows to
rank users by their influence on the social platform, by taking into account
not only the social graph structure, but also the platform design, user
activity (self- and re-posting), as well as competition among posts.Comment: Preliminary version of accepted paper at INFOCOM 2019 (Paris, France
Ranking Online Social Users by their Influence
We introduce an original mathematical model to analyse the diffusion of posts
within a generic online social platform. The main novelty is that each user is
not simply considered as a node on the social graph, but is further equipped
with his/her own Wall and Newsfeed, and has his/her own individual self-posting
and re-posting activity. As a main result using our developed model, we derive
in closed form the probabilities that posts originating from a given user are
found on the Wall and Newsfeed of any other. These are the solution of a linear
system of equations, which can be resolved iteratively. In fact, our model is
very flexible with respect to the modelling assumptions. Using the
probabilities derived from the solution, we define a new measure of per-user
influence over the entire network, the -score, which combines the user
position on the graph with user (re-)posting activity. In the homogeneous case
where all users have the same activity rates, it is shown that a variant of the
-score is equal to PageRank. Furthermore, we compare the new model and
its -score against the empirical influence measured from very large data
traces (Twitter, Weibo). The results illustrate that these new tools can
accurately rank influencers with asymmetric (re-)posting activity for such real
world applications.Comment: 18 pages, 7 figures, journal publications. arXiv admin note: text
overlap with arXiv:1902.0718
Profiling substrate promiscuity of wild-type sugar kinases for multifluorinated monosaccharides
Fluorinated sugar-1-phosphates are of emerging importance as intermediates in the chemical and biocatalytic synthesis of modified oligosaccharides, as well as probes for chemical biology. Here we present a systematic study of the activity of a wide range of anomeric sugar kinases (galacto- and N-acetylhexosamine kinases) against a panel of fluorinated monosaccharides, leading to the first examples of polyfluorinated substrates accepted by this class of enzymes. We have discovered four new N-acetylhexosamine kinases with a different substrate scope, thus expanding the number of homologs available in this subclass of kinases. Lastly, we have solved the crystal structure of a galactokinase in complex with 2-deoxy-2-fluoro galactose, giving insight into changes in the active site that may account for the specificity of the enzyme towards certain substrate analogues
Experimental insights on the geometry and kinematics of fold-and-thrust belts above weak, viscous evaporitic décollement.: reply to comments by Hemin Koyi and James Cotton.
Experimental insights on the geometry and kinematics of fold-and-thrust belts above weak, viscous evaporitic décollement.
Champ de failles et tectonique en extension : modelisation experimentale
SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Mode d'entrée de la protéine Tat de HIV-1 dans les lymphocytes T CD4+
MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF
Foldbelts with early salt withdrawal and diapirism: Physical model and examples from the northern Gulf of Mexico and the Flinders Ranges, Australia
International audienc
Salt tectonics driven by sediment progradation: Part II – Radial spreading of sedimentary lobes prograding above salt
International audienc
Modélisation expérimentale des interactions entre déformations salifères et sédimentation turbiditique (une nouvelle approche expérimentale appliquée aux déformations des corps salifères allochtones)
Le long d une marge passive, la présence d'un niveau de sel mobile, ainsi que des apports sédimentaires détritiques importants peuvent déclencher une tectonique gravitaire déformant la couverture sédimentaire et le sel sous-jacent. Ces déformations sont contrôlées au niveau du glacis continental par la surcharge différentielle engendrée par le dépôt d'éventails turbiditiques (étalement gravitaire). Localement, lorsque la marge est mature, l'extrusion des évaporites forme des nappes de sel allochtone de quelques dizaines de kilomètres de longueur, pouvant être remobilisés et déformés par le dépôt de lobes/éventails turbiditiques. Deux styles structuraux se distinguent : Le premier (stepped counterregional) est dominé par la subsidence de la couverture sédimentaire et l extrusion du sel en aval du système. Le second (roho) est dominé par des mouvements de translation horizontaux accommodés par de nombreuses structures extensives.Nous avons développé un nouveau type de dispositif expérimental permettant d étudier les interactions entre sédimentation et tectonique salifère au sein des marges passives. Notre dispositif combine deux approches traditionnellement distinctes : l approche stratigraphique, s intéressant au transport et au dépôt sédimentaire, et l approche tectonique, se focalisant sur les déformations salifères. Le bassin tectono-stratigraphique conçu au cours de cette thèse permet donc de simuler les processus de transport et de dépôt turbiditique ainsi que les déformations gravitaires induites par une surcharge sédimentaire différentielle sur un niveau mobile salifère à l échelle régionale (étalement gravitaire) ou locale (remobilisation de nappe de sel allochtone).Salt-bearing passive margin with large clastic sediment supply are characterized by gravity-driven tectonics that deforms the sedimentary overburden and the underlying salt. These deformations are controlled along the continental rise by the differential loading generated by the deposition of turbidite fan (gravity spreading). Locally, along mature margin, extrusion of evaporites form allochthonous salt nappes (tens kilometres long) that are remobilized and deformed by the deposition of turbiditic lobes. Two end-members are recognized: the stepped counterregional structural style, which is dominated by subsidence of the sedimentary cover and distal salt extrusion. The roho structural style, which is dominated by lateral translation accommodated by several extensional structures.We designed a completely new kind of experimental apparatus for studying the interaction between sedimentation and salt tectonics along passive margin. Our device combines two approaches that are traditionally distinct: (1) the stratigraphic approach aiming to simulate sediment transport and deposition, and (2) the tectonic approach focusing on the deformation of the salt and its sedimentary cover. Thus, the tectono-stratigraphic basin built during this PhD work allows the modelling of turbiditic transport and deposition processes, as well as, salt-related deformations induced by differential loading of a mobile salt substratum at regional (gravity spreading) or local (allochthonous salt bodies remobilization).LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF
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