Sensitivity analysis of a branching process evolving on a network with application in epidemiology

We perform an analytical sensitivity analysis for a model of a continuous-time branching process evolving on a fixed network. This allows us to determine the relative importance of the model parameters to the growth of the population on the network. We then apply our results to the early stages of an influenza-like epidemic spreading among a set of cities connected by air routes in the United States. We also consider vaccination and analyze the sensitivity of the total size of the epidemic with respect to the fraction of vaccinated people. Our analysis shows that the epidemic growth is more sensitive with respect to transmission rates within cities than travel rates between cities. More generally, we highlight the fact that branching processes offer a powerful stochastic modeling tool with analytical formulas for sensitivity which are easy to use in practice.Comment: 17 pages (30 with SI), Journal of Complex Networks, Feb 201

Resonant metamaterial absorbers for infrared spectral filtering: quasimodal analysis, design, fabrication and characterization

We present a modal analysis of metal-insulator-metal (MIM) based metamaterials in the far infrared region. These structures can be used as resonant reflection bandcut spectral filters that are independent of the polarization and direction of incidence because of the excitation of quasimodes (modes associated with a complex frequency) leading to quasi-total absorption. We fabricated large area samples made of chromium nanorod gratings on top of Si/Cr layers deposited on silicon substrate and measurements by Fourier Transform spectrophotometry show good agreement with finite element simulations. A quasimodal expansion method is developed to obtain a reduced order model that fits very well full wave simulations and that highlights excitation conditions of the modes.Comment: 8 pages, 7 figure

Designing exploratory partnerships in Southeast Asia: The challenge of building a sustainable ecosystem to address chronic malnutrition

International audienceMalnutrition linked to under nutrition is a cause of 3.1 million child deaths annually. Stakeholders from all over the word, gathered within various organizations, from public to private sector, tend to work together to fight against this disease that affects very vulnerable people. However, these stakeholders are generally highly dependent on numerous geopolitical issues and form together a highly fragmented ecosystem, which appears to be not efficient enough to provide nutrition solutions to all affected children. At the same time, researchers have identified for decades that other forms of malnutrition, such as chronic malnutrition, could also result from dietary habits that are linked to specific sociocultural contexts, which require a radically different approach: instead of treating an easily diagnosable patient, the aim is to prevent and change nutritional habits, and the mass of affected children is much larger. Thus, innovative partnerships beyond NGOs, local actors and public agencies need to be explored, for instance with private actors, to consider new ways to structure such a sustainable ecosystem. And the shift in the understanding of how to treat the disease entails necessarily deep changes in the structuration of an appropriate ecosystem to deal with it, which also highlights the need for a collective capability for innovation.In this paper, we tackle the organizational issue of building a sustainable ecosystem, both robust and innovative, to prevent chronic malnutrition in Southeast Asia. In particular, we study the building of innovative partnerships that contribute to long-term nutrition transition in this area where there international funds alone are not sufficient to support the stunting prevention, and thus private and public actors must work to develop hybrids models

The three lipocalins of egg-white: only Ex-FABP inhibits siderophore-dependent iron sequestration by Salmonella Enteritidis

Salmonella Enteritidis is the most prevalent food-borne pathogen associated with egg-related outbreaks in the European Union. During egg colonization, S. Enteritidis must resist the powerful anti-bacterial activities of egg white (EW) and overcome ovotransferrin-imposed iron-restriction (the most important anti-bacterial mechanism of EW). Many pathogens respond to iron restriction by secreting iron-chelating chemicals called siderophores but EW contains a siderophore-sequestering “lipocalin” protein (Ex-FABP) that is predicted to limit the usefulness of siderophores in EW. S. Enteritidis produces two siderophores: enterobactin, which is strongly bound by Ex-FABP; and the di-glucosylated enterobactin-derivative, salmochelin (a so-called “stealth” siderophore), which is not recognized by Ex-FABP. Thus, production of salmochelin may allow S. Enteritidis to escape Ex-FABP-mediated growth inhibition under iron restriction although it is unclear whether its EW concentration is sufficient to inhibit pathogens. Further, two other lipocalins (Cal-γ and α-1-ovoglycoprotein) are found in EW but their siderophore sequestration potential remains unexplored. In addition, the effect of EW lipocalins on the major EW pathogen, S. Enteritidis, has yet to be reported. We overexpressed and purified the three lipocalins of EW and investigated their ability to interact with the siderophores of S. Enteritidis, as well as their EW concentrations. The results show that Ex-FABP is present in EW at concentrations (5.1 μM) sufficient to inhibit growth of a salmochelin-deficient S. Enteritidis mutant under iron restriction but has little impact on the salmochelin-producing wildtype. Neither Cal-γ nor α-1-ovoglycoprotein bind salmochelin or enterobactin, nor do they inhibit iron-restricted growth of S. Enteritidis. However, both are present in EW at significant concentrations (5.6 and 233 μM, respectively) indicating that α-1-ovoglycoprotein is the 4th most abundant protein in EW, with Cal-γ and Ex-FABP at 11th and 12th most abundant. Further, we confirm the preference (16-fold) of Ex-FABP for the ferrated form (Kd of 5.3 nM) of enterobactin over the iron-free form (Kd of 86.2 nM), and its lack of affinity for salmochelin. In conclusion, our findings show that salmochelin production by S. Enteritidis enables this key egg-associated pathogen to overcome the enterobactin-sequestration activity of Ex-FABP when this lipocalin is provided at levels found in EW

Bacterial diversity on stainless steel surfaces of egg processing companies and potential of selected isolates to spoil liquid whole egg products

AimsTo assess the bacterial diversity in the French egg processing industry and to explore the adhesion and spoilage potential of selected bacteria.Methods and ResultsSterile stainless steel chips were suspended for 2 months inside the pipelines of seven egg processing companies, before and after the pasteurizer, at warm and cold seasons. After exposure, the bacterial diversity was assessed by 16S rDNA sequencing. The 231 collected isolates were mainly facultative anaerobic Gram positive bacteria, such as Streptococcus, Staphylococcus, Bacillus and Kocuria. Sixty‐five representative isolates were further characterized in vitro regarding the potential for adhesion and egg product spoilage. A high diversity was observed from one genus to another. Kocuria and Rothia isolates showed significantly higher adhesion than the isolates of the other genera. Only the isolates belonging to the genera Bacillus and Lysinibacillus, associated with high enzymatic activities on a solid egg‐based medium, were able to induce spoilage of liquid whole egg.ConclusionsBacteria collected on stainless steel surfaces placed in egg processing industries could be associated to liquid egg product spoilage.Significance and Impact of the StudyThis study provides new insights on the bacterial contamination in egg processing companies and represents a first step for the effective control of undesirable bacteria in liquid egg products

Influence of Lipid Profiles on the Risk of Hemorrhagic Transformation after Ischemic Stroke: Systematic Review

Background: It has been suggested that low cholesterol levels might be associated with an increased risk of hemorrhagic transformation (HT) in patients with acute cerebral ischemia. We systematically reviewed the literature to determine the influence of lipid profiles on the HT risk. Methods: We searched PubMed from 1966 and EMBASE from 1980 for studies that investigated the association between lipid profiles and HT. We performed a meta-analysis (weighted mean difference method) for the comparison between presence and absence of HT (all or symptomatic) for total, low-density-lipoprotein (LDL) and high-density-lipoprotein (HDL) cholesterol, and triglycerides. Results: Eight studies investigating 1,763 patients were eligible, but none was designed specifically to address this question. All studies recruited acute stroke patients selected on the presumed cause of cerebral ischemia or treatment received. The meta-analysis showed that: (i) patients with all HT had lower LDL cholesterol levels (p = 0.008) but no difference in HDL cholesterol levels (p = 0.066), total cholesterol (p = 0.129) and triglycerides (p = 0.900); (ii) patients with symptomatic HT had lower total cholesterol levels (p = 0.035) but did not differ in LDL (p = 0.056) and HDL cholesterol (p = 0.138) and triglyceride (p = 0.851) levels. Conclusion: HT is associated with baseline total and LDL cholesterol levels, but the mechanism of this association needs to be explored to identify preventive strategies

Étude paléodémographique et utilisation du feu à Hili N, une sépulture collective en fosse de la fin de l’âge du Bronze ancien aux Émirats Arabes Unis

En 1983, en bordure d’une tombe circulaire monumentale typique de la période Umm an-Nar (vers 2700-2000 av. J.-C.), une sépulture collective en fosse a été dégagée à Hili, aux abords de l’actuelle ville d’Al Ain (Émirat d’Abu Dhabi). L’objectif de la présente étude consiste à établir si cette structure originale datée de 2200-2000 av. J.-C., soit la fin de l’âge du Bronze ancien dans la région, est à mettre en relation avec un traitement ou un recrutement particulier de la population inhumée, et à tenter de définir de quelle manière le feu est intervenu durant l’utilisation de cette fosse funéraire. Nous avons pu démontrer que tous les défunts de plus d’un an pouvaient accéder à la tombe sans qu’il y ait de sélection d’âge ou de sexe qui soit perceptible. En revanche, une partie des bébés de moins de 12 mois a vraisemblablement été inhumée ailleurs.Le feu est présent sous la forme d’au moins quatre foyers, allumés durant les dernières phases d’utilisation de la fosse sépulcrale. Le sens de ces feux – idéologique, rituel ou utilitaire – nous échappe : nous pouvons seulement attester qu’ils ne visaient ni à brûler l’ensemble des os, ni à consumer un défunt particulier.In 1983, next to one of the monumental circular tombs considered to be diagnostic for the Umm an-Nar Period (ca 2700-2000 BC), a collective burial in a pit-grave was discovered. The first objective of the present study is to establish whether this structure, dated to 2200-2000 BC, i.e. the end of the Early Bronze Age in the region, is associated with a specific funerary practice or to a selection of the buried individuals. The second is to define the function of the fire in the pit. All the deceased aged more than one year were buried without any perceptible selection as to age or sex. However, some of the babies aged less than twelve months were probably buried elsewhere.At least four fires occurred during the last phases of use of the grave. The significance of these fires - ideology, ritual, utilitarian – is unknown. We can only confirm that these fires were not intended to burn all the bones, nor a particular individual

Toxigenic potential and antimicrobial susceptibility of Bacillus cereus group bacteria isolated from Tunisian foodstuffs

International audienceBackground: Despite the importance of the B. cereus group as major foodborne pathogens that may cause diarrheal and/or emetic syndrome(s), no study in Tunisia has been conducted in order to characterize the pathogenic potential of the B. cereus group. The aim of this study was to assess the sanitary potential risks of 174 B. cereus group strains isolated from different foodstuffs by detecting and profiling virulence genes (hblA, hblB, hblC, hblD, nheA, nheB, nheC, cytK, bceT and ces), testing the isolates cytotoxic activity on Caco-2 cells and antimicrobial susceptibility towards 11 antibiotics. Results: The entertoxin genes detected among B. cereus isolates were, in decreasing order, nheA (98.9%), nheC (97.7%) and nheB (86.8%) versus hblC (54.6%), hblD (54.6%), hblA (29.9%) and hblB (14.9%), respectively encoding for Non-hemolytic enterotoxin (NHE) and Hemolysin BL (HBL). The isolates are multi-toxigenic, harbouring at least one gene of each NHE and HBL complexes associated or not to bceT, cytK-2 and ces genes. Based on the incidence of virulence genes, the strains were separated into 12 toxigenic groups. Isolates positive for cytK (37,9%) harbored the cytK-2 variant. The detection rates of bceT and ces genes were 50.6 and 4%, respectively. When bacteria were incubated in BHI-YE at 30°C for 18 h and for 5 d, 70.7 and 35% of the strains were shown to be cytotoxic to Caco-2 cells, respectively. The cytotoxicity of B. cereus strains depended on the food source of isolation. The presence of virulence factors is not always consistent with cytotoxicity. However, different combinations of enterotoxin genetic determinants are significantly associated to the cytotoxic potential of the bacteria. All strains were fully sensitive to rifampicin, chloramphenicol, ciprofloxacin, and gentamycin. The majority of the isolates were susceptible to streptomycin, kanamycin, erythromycin, vancomycin and tetracycline but showed resistance to ampicillin and novobiocin. Conclusion: Our results contribute data that are primary to facilitate risk assessments in order to prevent food poisoning due to B. cereus group

Vélocimétrie dans les liquides conducteurs : sonde à distorsion magnétique

Nous proposons un nouveau type de sonde pour la mesure de vitesse dans les métaux liquides. Son principe repose sur la mesure du champ magnétique induit par un écoulement de fluide conducteur au voisinage d'un champ magnétique localisé. La méthode utilisée ici permet de mesurer à la fois la moyenne et les fluctuations. Celle-ci a été testé dans un écoulement laminaire et dans un écoulement turbulent de gallium liquide dit de Von Karman. Une excellente corrélation a été observé avec les signaux d'une sonde de potentiel prise comme référence