Improved reference genome of Aedes aegypti informs arbovirus vector control

Female Aedes aegypti mosquitoes infect more than 400 million people each year with dangerous viral pathogens including dengue, yellow fever, Zika and chikungunya. Progress in understanding the biology of mosquitoes and developing the tools to fight them has been slowed by the lack of a high-quality genome assembly. Here we combine diverse technologies to produce the markedly improved, fully re-annotated AaegL5 genome assembly, and demonstrate how it accelerates mosquito science. We anchored physical and cytogenetic maps, doubled the number of known chemosensory ionotropic receptors that guide mosquitoes to human hosts and egg-laying sites, provided further insight into the size and composition of the sex-determining M locus, and revealed copy-number variation among glutathione S-transferase genes that are important for insecticide resistance. Using high-resolution quantitative trait locus and population genomic analyses, we mapped new candidates for dengue vector competence and insecticide resistance. AaegL5 will catalyse new biological insights and intervention strategies to fight this deadly disease vector

Reticulated vitreous carbon from polyurethane foam-clay composites

Reticulated vitreous carbon foams were prepared by carbonizing polyurethane precursor foams which were first infused with furfuryl alcohol. The cell size and the fraction of open cells of the precursor foam were controlled by the addition of clay in the polyurethane foam formulation. Addition of clay permitted control of the cell size of carbon foams. The higher open cell content in foams with clay permitted uniform infusion of furfuryl alcohol in the precursor, and thus more uniform carbon foams of higher density. These foams had a lower electrical resistance as compared to foams without clay.Department fo Science and Technology, Indi

Polyurethane foam-clay nanocomposites: Nanoclays as cell openers

Flexible and rigid polyurethane ( PU) foam nanocomposites were synthesized using unmodified and organically modified montmorillonite clays. X-ray diffraction and transmission electron microscopy studies showed that, while the unmodified clays were intercalated, the modified clays were exfoliated in the foams produced. The cell morphology of the foams was investigated by environmental scanning electron microscopy. The fraction of open cells ( defined as the cells in which the foam lamellae are all ruptured) in the foam is an important parameter governing many properties, such as the degree of softness in the case of flexible foams and dimensional stability for both rigid and flexible foams. The open cell content in PU-clay foamed nanocomposites was investigated. It was found that clays act as efficient cell openers in both rigid and flexible foams and a greater fraction of open cells was obtained with increasing clay concentration. Modified clays were found to be more efficient cell openers than the unmodified clay. The degree of softness of flexible foam was increased and the dimensional stability of both rigid and flexible foams was improved, with clay addition. The thermal conductivity and compressive strength of the rigid foams were not significantly affected by clay addition. The kinetics of the foaming process with different clays was investigated. The polymerization and the foaming reactions were found to be affected in different ways for the modified and unmodified clays. Comparison with chemical cell openers in the case of flexible foams indicated that clays could be a good alternative

Clay nanoplatelet induced morphological evolutions during polymeric foaming

Remarkable evolutionary changes in cell morphology during reactive polymer nanocomposite foaming are observed by controlled foaming of suspensions of montmorillonite clay in the oligomeric polyurethane component. Delaminated nanoplatelets, when present as a networked cluster in suspensions, are shown to have very high efficiency in generating gas embryos for bubble nucleation. In the post-nucleation foaming period, clay nanoplatelets show an additional de-wetting behavior. The packing fraction of clay platelets in suspension and the consequent suspension rheology affect the final foam morphology

Formation and characterization of polyurethane-vermiculite clay nanocomposite foams

Nanocomposites of rigid polyurethane foam with unmodified vermiculite clay are synthesized. The clay is dispersed either in polyol or isocyanate before blending. The viscosity of the polyol is found to increase slightly on the addition of clay up to 5 pphp (parts per hundred parts of polyol by weight). The gel time and rise time are significantly reduced by the addition of clay, indicating that the clay acts as a heterogeneous catalyst for the foaming and polymerization reactions. X-ray diffraction and transmission electron microscopy of the polyurethane composite foams indicate that the clay is partially exfoliated in the polymer matrix. The clay is found to induce gas bubble nucleation resulting in smaller cells with a narrower size distribution in the cured foam. The closed cell content of the clay nanocomposite foams increases slightly with clay concentration. The mechanical properties are found to be the best at 2.3 wt% of clay when the clay is dispersed in the isocyanate; the compressive strength and modulus normalized to a density of 40 kg/m(3) are 40% and 34% higher than the foam without clay, respectively. The thermal conductivity is found to be 10% lower than the foam without clay

Studies on poly(vinylidene fluoride)–clay nanocomposites: effect of different clay modifiers

Montmorillonite clay based poly(vinylidene fluoride) nanocomposites were prepared by melt-mixing. The clays used included unmodified clay, a commercially available ammonium based clay, and two organically modified clays prepared by cation exchange with hexadecylpyridinium chloride and with octadecyltriphenylphosphonium bromide. PVDF–clay nanocomposites were processed in a mini twin-screw extruder. The structure of nanocomposites, analyzed using WAXD and TEM, indicated different extents of the clay dispersion depending on the modifier. PVDF formed β-phase crystals in the presence of organically modified clay when crystallized from its melt; in contrast, α-crystals were formed in the absence of clay and with unmodified clay. SAXS analysis indicated that the long period and crystalline lamella thickness decreased with the addition of clay. The melting and crystallization temperatures increased around 10 and 13 °C, respectively, with 5 wt% of phosphonium modified clay, which was the highest among the clays used. Further, the clay served as a nucleating agent for PVDF matrix, as observed by hot-stage polarized optical microscopy. The average spherulitic radius, determined from small angle light scattering, decreased with clay content. The elongation at break increased around 200% with the addition of only 5 wt% of ammonium clay. The storage and loss moduli of the nanocomposites were significantly higher than those of PVDF throughout the temperature range. Dielectric measurements showed a maximum increase of about 8 units of dielectric constant at 1 Hz frequency with 5 wt% organoclay.© Elsevie

Tuning the dispersion of multiwall carbon nanotubes in co-continuous polymer blends: a generic approach

Melt-mixed blends of polyamide 6 and acrylonitrile-butadiene-styrene (PA6/ABS) with multiwall carbon nanotubes (MWNTs) were prepared with the intention to develop conducting composites. A generic strategy, namely specific interactions combined with reactive coupling, was adopted to facilitate and to retain the 'network-like' structure of MWNTs during melt-mixing. This was facilitated by the sodium salt of 6-amino hexanoic acid (Na-AHA) and certain phosphonium based modifiers, where it was envisaged that these modifiers would establish specific interactions (either 'cation-pi' or 'pi-pi') with the 'pi-electron' clouds of MWNTs, as well as restricting them in the PA6 phase of the blends via reactive coupling. This route eventually led to a remarkable increase in the electrical conductivity and dielectric constant in the blends with MWNTs. Raman, FTIR and TEM investigations further supported these observations