Burning and Management Alternatives on Forage Accumulation and Floristic Composition of a Native Pasture

The forage accumulation and floristic composition of native pasture, submitted to burning and alternative management practices, was evaluated during one year. The experimental design was a completely randomized, with five treatments and three replications. The forage accumulation was evaluated in a grazing exclusion cage, and the floristic composition was estimated with Botanal method. The systems without burning were more productive and, among these, the forage accumulation was similar between the one without burning and without mowing and the improve treatments, and the annual accumulation was greater than 9,000 Kg/ha of green forage dry matter. The species Paspalum notatum, P. paniculatum and Desmodium incanum had greater contribution in the improved and mowed treatments. The biennial burning stimulated species of Andropogon and Schizachyrium genus and also opportunistic species. The alternative management showed to be more sustainable, promoted greater floristic diversity, and allowed increase of species with good nutritive value

Effect of Burning and Management Alternatives on Forage Litter Composition of a Native Pasture

The content and quantities of nutrients in forage and litter was evaluated in native pasture under grazing, submitted to burning and alternatives practices. The experimental design was a completely randomized, with three replications. The biennial burning has no effect in nutrients contents of the forage, but in the case of litter plus senescent material the concentration of Ca and Mg decreased as compared to the systems without burning. The sod-seeding treatment increased the nutrient contents in the alive and dead tissues. Nutrient accumulation on forage tissue and litter plus senescent material, was highest in the systems without burning

Atomistic simulations of self-trapped exciton formation in silicon nanostructures: The transition from quantum dots to nanowires

Using an approximate time-dependent density functional theory method, we calculate the absorption and luminescence spectra for hydrogen passivated silicon nanoscale structures with large aspect ratio. The effect of electron confinement in axial and radial directions is systematically investigated. Excited state relaxation leads to significant Stokes shifts for short nanorods with lengths less than 2 nm, but has little effect on the luminescence intensity. The formation of self-trapped excitons is likewise observed for short nanostructures only; longer wires exhibit fully delocalized excitons with neglible geometrical distortion at the excited state minimum.Comment: 10 pages, 4 figure

Improving the delivery and efficiency of fungus-impregnated cloths for control of adult Aedes aegypti using a synthetic attractive lure

Abstract Background Entomopathogenic fungi are highly promising agents for controlling Aedes aegypti mosquitoes. Deploying fungus-impregnated black cloths in PET traps efficiently reduced Ae. aegypti female survival rates under intra-domicile conditions. With the aim of further increasing the effectiveness of the traps, the addition of attractive lures to fungus-impregnated traps was evaluated. Methods Black cloths were suspended inside 2 l plastic bottles called “PET traps”. These traps were placed in rooms simulating human residences. The first experiments evaluated the attraction of mosquitoes to PET traps with black cloths covered in adhesive film with and without synthetic lures (AtrAedes™). Traps were left in the test rooms for either 24 or 48 h. The attractiveness of the lures over time was also evaluated. The efficiency of PET traps with fungus-impregnated black cloths associated with lures was compared to that of traps without lures. Results The highest percentage of captured mosquitoes (31 and 66%) were observed in PET traps with black cloths covered in adhesive film + attractive lure maintained in test rooms for 24 h and 48 h, respectively. Black cloths covered in adhesive film captured 17 or 36% of the mosquitoes at 24 h and 48 h, respectively. The attractiveness of the lures fell gradually over time, capturing 37% after 5 days on the bench and 22% of the mosquitoes after 30 days exposure to ambient conditions. Associating attractive synthetic lures with black cloths impregnated with M. anisopliae placed in test rooms for 120 h reduced mean survival to 32%, whilst black cloths impregnated with M. anisopliae without lures resulted in a 48% survival rate. Using Beauveria bassiana in the traps resulted in a 52% reduction in mosquito survival, whilst combining Beauveria and AtrAedes resulted in a 36% survival rate. PET traps impregnated with fungus + AtrAedes resulted in similar reductions in survival when left in the rooms for 24, 48, 72 or 120 h. Conclusions AtrAedes increased attractiveness of PET traps with black cloths under intra-domicile conditions and when associated with M. anisopliae or B. bassiana, significantly reduced Aedes survival. This strategy will reduce the number of PET traps necessary per household