The anatomy of a scientific rumor De Domenico, M; Lima, A; Mougel, P ...
Scientific reports,
10/2013, Volume:
3, Issue:
1
Journal Article
Peer reviewed
Open access
The announcement of the discovery of a Higgs boson-like particle at CERN will be remembered as one of the milestones of the scientific endeavor of the 21(st) century. In this paper we present a study ...of information spreading processes on Twitter before, during and after the announcement of the discovery of a new particle with the features of the elusive Higgs boson on 4(th) July 2012. We report evidence for non-trivial spatio-temporal patterns in user activities at individual and global level, such as tweeting, re-tweeting and replying to existing tweets. We provide a possible explanation for the observed time-varying dynamics of user activities during the spreading of this scientific "rumor". We model the information spreading in the corresponding network of individuals who posted a tweet related to the Higgs boson discovery. Finally, we show that we are able to reproduce the global behavior of about 500,000 individuals with remarkable accuracy.
Most networks, such as those generated from social media, tend to evolve gradually with frequent changes in the activity and the interactions of their participants. Furthermore, the communities ...inside the network can grow, shrink, merge, or split, and the entities can move from one community to another. The aim of community detection methods is precisely to detect the evolution of these communities. However, evaluating these algorithms requires tests on real or artificial networks with verifiable ground truth. Dynamic networks generators have been recently proposed for this task, but most of them consider only the structure of the network, disregarding the characteristics of the nodes. In this paper, we propose a new generator for dynamic attributed networks with community structure that follow the properties of real-world networks. The evolution of the network is performed using two kinds of operations: Micro-operations are applied on the edges and vertices, while macro-operations on the communities. Moreover, the properties of real-world networks such as preferential attachment or homophily are preserved during the evolution of the network, as confirmed by our experiments.
The announcement of the discovery of a Higgs boson-like particle at CERN will be remembered as one of the milestones of the scientific endeavor of the 21st century. In this paper we present a study ...of information spreading processes on Twitter before, during and after the announcement of the discovery of a new particle with the features of the elusive Higgs boson on 4th July 2012. We report evidence for non-trivial spatio-temporal patterns in user activities at individual and global level, such as tweeting, re-tweeting and replying to existing tweets. We provide a possible explanation for the observed time-varying dynamics of user activities during the spreading of this scientific "rumor". We model the information spreading in the corresponding network of individuals who posted a tweet related to the Higgs boson discovery. Finally, we show that we are able to reproduce the global behavior of about 500,000 individuals with remarkable accuracy.
Phenolic foams (PF) have a combination of properties that make them attractive for a number of engineering applications such as insulation, lightening, energy absorption and fire protection. Phenolic ...foams exhibit excellent fire-retardant behaviour but have insufficient mechanical properties (e.g. fatigue, flexural properties and friability) for different applications in comparison to other foam materials. Hence, numerous studies have tried to improve these mechanical properties without deteriorating its excellent fire-retardant behaviour. Different approaches have been investigated, such as the addition of fibres and particles or the chemical modification of the PF base resin. This work will first briefly present generalities from resin synthesis to foam production. The main part will review the existing papers dealing with the improvement of the compressive and flexural strength as well as the friability. Moreover, evolution of the cell size with these mechanical properties will be presented, although there is no well-defined link between them. Then, the influence of these modifications on the fire-retardant behaviour of PF will be discussed. Finally, the last part will present work to substitute phenol from petroleum sources to environmental friendly sources.
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•Density in relation with cell morphology is the key factor controlling the mechanical properties of phenolic foams.•Modification of phenolic foams by additive and/or reactive routes allows the improvement of their final properties.•Dicyandiamide is the most efficient additive for higher compressive strength and lower friability.•Aramide fiber addition induces the reduction of friability without impacting mechanical properties.•Phenolated lignins are very promising bio-based resins for production of sustainable phenolic foams.
Data management of National Veterinary Antipoison Center Lorgue, G. (Ecole Nationale Veterinaire de Lyon, Charbonnieres (France). Centre National d'Informations Toxicologiques Veterinaires); Mougel, P
Sciences Veterinaires Medecine Comparee (France),
(1988), Volume:
90, Issue:
1-2
Journal Article
Many industrial catalysts contain isolated metal sites on the surface of oxide supports. Although such catalysts have been used in a broad range of processes for more than 40 years, there is often a ...very limited understanding about the structure of the catalytically active sites. This Review discusses how surface organometallic chemistry (SOMC) engineers surface sites with well‐defined structures and provides insight into the nature of the active sites of industrial catalysts; the Review focuses in particular on olefin production and conversion processes.
Learning in concert: Some of the workhorse industrial catalysts used in a broad range of olefin production and conversion processes are based on ill‐defined metal sites isolated at the surface of oxide supports. The corresponding well‐defined surface species obtained by surface organometallic chemistry (SOMC) provide highly active catalysts and insight about the nature of the active sites in the industrial catalysts.
• The genetic structure of bacterial and fungal communities was characterized in the rhizosphere of Medicago truncatula Gaertn. cv. Jemalong line J5 at five developmental stages (three vegetative and ...two reproductive stages), and in three compartments (bulk soil, rhizosphere soil and root tissues). • The genetic structure of microbial communities was determined by cultivation-independent methods using directly extracted DNA that was characterized by automated ribosomal intergenic spacer analysis (ARISA). • Principal component analyses (PCA) indicate that, for all developmental stages, the genetic structure of microbial communities differed significantly by compartment, with a major shift in the community in root tissues corresponding to the most intimate compartment with the plant. • Differences were also recorded during plant development, the most significant being observed during the transition between vegetative and reproductive stages. Throughout this period, plants were shown to establish the highest level of symbiotic association (mycorrhization, nodulation) with arbuscular mycorrhizal fungi and Rhizobia. During the reproductive stages, the dynamics of the genetic structure differed between bacterial and fungal communities. At the last reproductive stage, the genetic structure of bacterial communities became close to that recorded during the first vegetative stages, suggesting a resilience phenomenon, whereas the genetic structure of fungal communities remained different from the vegetative stages and also from the early reproductive stages, suggesting a persistence of the rhizosphere effect.
The turnover of organic matter in soil depends on the activity of microbial decomposers. However, little is known about how modifications of the diversity of soil microbial communities induced by ...fresh organic matter (FOM) inputs can regulate carbon cycling. Here, we investigated the decomposition of two 13 C labeled crop residues (wheat and alfalfa) and the dynamics of the genetic structure and taxonomic composition of the soil bacterial communities decomposing 13 C labeled FOM and native unlabeled soil organic matter (SOM), respectively. It was achieved by combining the stable isotope probing method with molecular tools (DNA genotyping and pyrosequencing of 16S rDNA). Although a priming effect (PE) was always induced by residue addition, its intensity increased with the degradability of the plant residue. The input of both wheat and alfalfa residues induced a rapid dynamics of FOM-degrading communities, corresponding to the stimulation of bacterial phyla which have been previously described as copiotrophic organisms. However, the dynamics and the identity of the bacterial groups stimulated depended on the residue added, with Firmicutes dominating in the wheat treatment and Proteobacteria dominating in the alfalfa treatment after 3 days of incubation. In both treatments, SOM-degrading communities were dominated by Acidobacteria, Verrucomicrobia, and Gemmatimonadetes phyla which have been previously described as oligotrophic organisms. An early stimulation of SOM-degrading populations mainly belonging to Firmicutes and Bacteroidetes groups was observed in the alfalfa treatment whereas no change occurred in the wheat treatment. Our findings support the hypothesis that the succession of bacterial taxonomic groups occurring in SOM- and FOM-degrading communities during the degradation process may be an important driver of the PE, and consequently of carbon dynamics in soil.
This paper describes the characterization of gelatin–ceramic membranes grafted with laccase from Trametes versicolor for the degradation of pharmaceutical pollutants. Tetracycline was chosen as a ...model substrate to confirm the optimization of the grafting protocol using two kinds of microfiltration membranes with pore diameters equal to 0.2 and 1.4µm. The preparation of the enzymatic membranes was optimized by varying the concentrations of the enzyme and gelatin solutions used as well as by measurement of active support permeability. An immunogold labeling method coupled with scanning electron microscopy was applied for a first time to determine the spatial distribution of enzymes on the membranes. The amount and distribution of the grafted enzymes were then correlated with the tetracycline depletion observed with the enzymatic membranes.
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•Characterization of ceramic membranes grafted with laccases for micropollutants degradation.•Immunogold labeling for determination of spatial dispersion of the enzymes.•Amount and distribution of the enzyme grafted correlated with tetracycline depletion rate.•“Flow through membrane reactor concept” demonstrated with enzymatic membranes.
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