Bacterial diversity of field-caught mosquitoes, Aedes albopictus and Aedes aegypti, from different geographic regions of Madagascar.

peer reviewedSymbiotic bacteria are known to play important roles in the biology of insects, but the current knowledge of bacterial communities associated with mosquitoes is very limited and consequently their contribution to host behaviors is mostly unknown. In this study, we explored the composition and diversity of mosquito-associated bacteria in relation with mosquitoes’ habitats. Wild Aedes albopictus and Aedes aegypti were collected in three different geographic regions of Madagascar. Culturing methods and denaturing gradient gel electrophoresis (DGGE) and sequencing of the rrs amplicons revealed that Proteobacteria and Firmicutes were the major phyla. Isolated bacterial genera were dominated by Bacillus, followed by Acinetobacter, Agrobacterium and Enterobacter. Common DGGE bands belonged to Acinetobacter, Asaia, Delftia, Pseudomonas, Enterobacteriaceae and an uncultured Gammaproteobacterium. Double infection by maternally inherited Wolbachia pipientis prevailed in 98% of males (n = 272) and 99% of females (n = 413); few individuals were found to be monoinfected withWolbachia wAlbB strain. Bacterial diversity (Shannon–Weaver and Simpson indices) differed significantly per habitat whereas evenness (Pielou index) was similar. Overall, the bacterial composition and diversity were influenced both by the sex of individuals and by the environment inhabited by the mosquitoes; the latter might be related to both the vegetation and the animal host populations that Aedes used as food sources.‘Arthropod Symbioses: from fundamental to pest disease management’

Interphase chemistry of Si electrodes used as anodes in Li-ion batteries

International audienceThe effect of the Si electrode morphology (amorphous hydrogenated silicon thin films - a-Si:H as a model electrode and Si nanowires - SiNWs electrode) on the interphase chemistry was thoroughly investigated by the surface science techniques: X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). XPS analysis shows a strong attenuation and positive shift of the Si 2p peaks after a complete charge/discharge performed in PC- and EC:DMC-based electrolytes for both electrodes (a-Si:H and SiNW), confirming a formation of a passive film (called solid electrolyte interphase - SEI layer). As evidenced from the XPS analysis performed on the model electrode, the thicker SEI layer was formed after cycling in PC-based electrolyte as compared to EC:DMC electrolyte. XPS and ToF-SIMS investigations reveal the presence of organic carbonate species on the outer surface and inorganic salt decomposition species in the inner part of the SEI layer. Significant modification of the surface morphol- ogy for the both electrodes and a full surface coverage by the SEI layer was confirmed by the scanning electron microscopy (SEM) analysis

Experimental and modeling study of the pyrolysis and combustion of 2-methyl-tetrahydrofuran

De Bruycker R, Tran L-S, Carstensen H-H, et al. Experimental and modeling study of the pyrolysis and combustion of 2-methyl-tetrahydrofuran. COMBUSTION AND FLAME. 2017;176:409-428.Saturated cyclic ethers are being proposed as next-generation bio-derived fuels. However, their pyrolysis and combustion chemistry has not been well established. In this work, the pyrolysis and combustion chemistry of 2-methyl-tetrahydrofuran (MTHF) was investigated through experiments and detailed kinetic modeling. Pyrolysis experiments were performed in a dedicated plug flow reactor at 170 kPa, temperatures between 900 and 1100 K and a N-2 (diluent) to MTHF molar ratio of 10. The combustion chemistry of MTHF was investigated by measuring mole fraction profiles of stable species in premixed flat flames at 6.7 kPa and equivalence ratios 0.7, 1.0 and 1.3 and by determining laminar burning velocities of MTHF/air flat flames with unburned gas temperatures of 298, 358 and 398 K and equivalence ratios between 0.6 and 1.6. Furthermore, a kinetic model for pyrolysis and combustion of MTHF was developed, which contains a detailed description of the reactions of MTHF and its derived radicals with the aid of new high-level theoretical calculations. Model calculated mole fraction profiles and laminar burning velocities are in relatively good agreement with the obtained experimental data. At the applied pyrolysis conditions, unimolecular decomposition of MTHF by scission of the methyl group and concerted ring opening to 4-penten-1-ol dominates over scission of the ring bonds; the latter reactions were significant in tetrahydrofuran pyrolysis. MTHF is mainly consumed by hydrogen abstraction reactions. Subsequent decomposition of the resulting radicals by beta-scission results in the observed product spectrum including small alkenes, formaldehyde, acetaldehyde and ketene. In the studied flames, unimolecular ring opening of MTHF is insignificant and consumption of MTHF through radical chemistry dominates. Recombination of 2-oxo-ethyl and 2-oxo-propyl, primary radicals in MTHF decomposition, with hydrogen atoms and carbon-centered radicals results in a wide range of oxygenated molecules. (C) 2016 The Combustion Institute. Published by Elsevier Inc. All rights reserved

Network Coding with Multimedia Transmission and Cognitive Networking: An Implementation based on Software-Defined Radio

Network coding (NC) is considered a breakthrough to improve throughput, robustness, and security of wireless networks. Although the theoretical aspects of NC have been extensively investigated, there have been only few experiments with pure NC schematics. This paper presents an implementation of NC under a two-way relay model and extends it to two\ua0non-straightforward scenarios: (i) multimedia transmission with layered coding and multiple-description coding, and (ii) cognitive radio with Vandermonde frequency division multiplexing (VFDM). The implementation is in real time and based on software-defined radio (SDR). The experimental results show that, by combining NC and source coding, we can control the quality of the received multimedia content in an on-demand manner. Whereas in the VFDM-based cognitive radio, the quality of the received content in the primary receiver is low (due to imperfect channel estimation) yet retrievable. Our implementation results serve as a proof for the practicability of network coding in relevant applications

Network Coding with Multimedia Transmission and Cognitive Networking: An Implementation based on Software-Defined Radio

Network coding (NC) is considered a breakthrough to improve throughput, robustness, and security of wireless networks. Although the theoretical aspects of NC have been extensively investigated, there have been only few experiments with pure NC schematics. This paper presents an implementation of NC under a two-way relay model and extends it to two non-straightforward scenarios: (i) multimedia transmission with layered coding and multiple-description coding, and (ii) cognitive radio with Vandermonde frequency division multiplexing (VFDM). The implementation is in real time and based on software-defined radio (SDR). The experimental results show that, by combining NC and source coding, we can control the quality of the received multimedia content in an on-demand manner. Whereas in the VFDM-based cognitive radio, the quality of the received content in the primary receiver is low (due to imperfect channel estimation) yet retrievable. Our implementation results serve as a proof for the practicability of network coding in relevant applications

Biogeography of the two major arbovirus mosquito vectors, Aedes aegypti and Aedes albopictus (Diptera, Culicidae), in Madagascar

Background: In the past ten years, the Indian Ocean region has been the theatre of severe epidemics of chikungunya and dengue. These outbreaks coincided with a high increase in populations of Aedes albopictus that outcompete its sister taxon Aedes aegypti in most islands sampled. The objective of this work was to update the entomological survey of the two Aedes species in the island of Madagascar which has to face these arboviroses. Methods: The sampling of Aedes mosquitoes was conducted during two years, from October 2007 to October 2009, in fifteen localities from eight regions of contrasting climates. Captured adults were identified immediately whereas immature stages were bred until adult stage for determination. Phylogenetic analysis was performed using two mtDNA genes, COI and ND5 and trees were constructed by the maximum likelihood (ML) method with the gene time reversible (GTR) model. Experimental infections with the chikungunya virus strain 06.21 at a titer of 107.5 pfu/mL were performed to evaluate the vector competence of field-collected mosquitoes. Disseminated infection rates were measured fourteen days after infection by immunofluorescence assay performed on head squashes. Results: The species Aedes aegypti was detected in only six sites in native forests and natural reserves. In contrast, the species Aedes albopictus was found in 13 out of the 15 sites sampled. Breeding sites were mostly found inman-made environments such as discarded containers, used tires, abandoned buckets, coconuts, and bamboo cuts. Linear regression models showed that the abundance of Ae. albopictus was significantly influenced by the sampling region (F = 62.00, p < 2.2 × 10-16) and period (F = 36.22, p = 2.548 × 10-13), that are associated with ecological and climate variations. Phylogenetic analysis of the invasive Ae. albopictus distinguished haplotypes from South Asia and South America from those of Madagascar, but the markers used were not discriminant enough to discern Malagasy populations. The experimental oral infection method showed that six Ae. albopictus populations exhibited high dissemination infection rates for chikungunya virus ranging from 98 to 100%. Conclusion: In Madagascar, Ae. albopictus has extended its geographical distribution whereas, Ae. aegypti has become rare, contrasting with what was previously observed. Changes are predominantly driven by human activities and the rainfall regime that provide suitable breeding sites for the highly anthropophilic mosquito Ae. albopictus. Moreover, these populations were found to be highly susceptible to chikungunya virus. In the light of this study, Ae. albopictus may have been involved in the recent outbreaks of chikungunya and dengue epidemics in Madagascar, and consequently, control measures should be promoted to limit its current expansion.Rôle des moustiques Culicidae, de leurs communautés microbiennes et des réservoirs vertébrés, dans la transmission des arbovirus à Madagasca

The Tripartite Type III Secreton of Shigella flexneri Inserts Ipab and Ipac into Host Membranes

Bacterial type III secretion systems serve to translocate proteins into eukaryotic cells, requiring a secreton and a translocator for proteins to pass the bacterial and host membranes. We used the contact hemolytic activity of Shigella flexneri to investigate its putative translocator. Hemolysis was caused by formation of a 25-Å pore within the red blood cell (RBC) membrane. Of the five proteins secreted by Shigella upon activation of its type III secretion system, only the hydrophobic IpaB and IpaC were tightly associated with RBC membranes isolated after hemolysis. Ipa protein secretion and hemolysis were kinetically coupled processes. However, Ipa protein secretion in the immediate vicinity of RBCs was not sufficient to cause hemolysis in the absence of centrifugation. Centrifugation reduced the distance between bacterial and RBC membranes beyond a critical threshold. Electron microscopy analysis indicated that secretons were constitutively assembled at 37°C before any host contact. They were composed of three parts: (a) an external needle, (b) a neck domain, and (c) a large proximal bulb. Secreton morphology did not change upon activation of secretion. In mutants of some genes encoding the secretion machinery the organelle was absent, whereas ipaB and ipaC mutants displayed normal secretons

A mature cluster with X-ray emission at z=2.07

We report evidence of a fully established galaxy cluster at z=2.07, consisting of a ~20sigma overdensity of red, compact spheroidal galaxies spatially coinciding with extended X-ray emission detected with XMM-Newton. We use VLT VIMOS and FORS2 spectra and deep Subaru, VLT and Spitzer imaging to estimate the redshift of the structure from a prominent z=2.07 spectroscopic redshift spike of emission-line galaxies, concordant with the accurate 12-band photometric redshifts of the red galaxies. Using NICMOS and Keck AO observations, we find that the red galaxies have elliptical morphologies and compact cores. While they do not form a tight red sequence, their colours are consistent with that of a >1.3$~Gyr population observed at z~2.1. From an X-ray luminosity of .2*10^43 erg s^-1 and the stellar mass content of the red galaxy population, we estimate a halo mass of 5.3-8*10^13 Msun, comparable to the nearby Virgo cluster. These properties imply that this structure could be the most distant, mature cluster known to date and that X-ray luminous, elliptical-dominated clusters are already forming at substantially earlier epochs than previously known.Comment: 14 pages, 12 figures; accepted for publication in Astronomy & Astrophysic

Cannabinoid CB2 Receptor Potentiates Obesity-Associated Inflammation, Insulin Resistance and Hepatic Steatosis

BACKGROUND: Obesity-associated inflammation is of critical importance in the development of insulin resistance and non-alcoholic fatty liver disease. Since the cannabinoid receptor CB2 regulates innate immunity, the aim of the present study was to investigate its role in obesity-induced inflammation, insulin resistance and fatty liver. METHODOLOGY: Murine obesity models included genetically leptin-deficient ob/ob mice and wild type (WT) mice fed a high fat diet (HFD), that were compared to their lean counterparts. Animals were treated with pharmacological modulators of CB2 receptors. Experiments were also performed in mice knock-out for CB2 receptors (Cnr2 -/-). PRINCIPAL FINDINGS: In both HFD-fed WT mice and ob/ob mice, Cnr2 expression underwent a marked induction in the stromal vascular fraction of epididymal adipose tissue that correlated with increased fat inflammation. Treatment with the CB2 agonist JWH-133 potentiated adipose tissue inflammation in HFD-fed WT mice. Moreover, cultured fat pads isolated from ob/ob mice displayed increased Tnf and Ccl2 expression upon exposure to JWH-133. In keeping, genetic or pharmacological inactivation of CB2 receptors decreased adipose tissue macrophage infiltration associated with obesity, and reduced inductions of Tnf and Ccl2 expressions. In the liver of obese mice, Cnr2 mRNA was only weakly induced, and CB2 receptors moderately contributed to liver inflammation. HFD-induced insulin resistance increased in response to JWH-133 and reduced in Cnr2 -/- mice. Finally, HFD-induced hepatic steatosis was enhanced in WT mice treated with JWH-133 and blunted in Cnr2 -/- mice. CONCLUSION/SIGNIFICANCE: These data unravel a previously unrecognized contribution of CB2 receptors to obesity-associated inflammation, insulin resistance and non-alcoholic fatty liver disease, and suggest that CB2 receptor antagonists may open a new therapeutic approach for the management of obesity-associated metabolic disorder