Mass Production and Morphology of Brauna Brachiaria Under Different Nitrogen Rates in the Brazilian Savannah

Nitrogen is the nutrient that most contributes to increase forage productivity and quality. The objective was to evaluate Brauna brachiaria (Urochloa brizantha cv. Brauna) submitted to nitrogen doses in the Brazilian savannah through the total and green mass production, leaf:stem and brachiaria:weed ratio. Plots were established in a randomized block design, with four replications and four N doses 0, 50, 100 and 150 kg N/ha). After the uniformization cut, the data collect cycles occurred when the canopy reached 30 cm average height. Samples were taken until 15 cm from the ground in an area of 0.25 m2 . Fractions were separated according botanical (brachiaria and weeds) and morphological (leaf, stem, dead material and inflorescence) components. The maximum and minimum response points were calculated by derivative. Samples were weighed and dried and values were used to calculate components mass production and ratios. The highest value of dry matter production occurred at 100 kg N/ha dose (2,606 kg DM/ha). Below or above this value the mass production decreased. The highest value of relation green mass:dead material was 4.24 at 131 kg N/ha dose. Brauna was able to control the weeds, and the best performance (4.68) was observed at 86 kg N/ha dose. The highest accumulation rate occurred at 87.5 kg N/ha dose. Brauna had higher leaf:stem ratio with higher nitrogen doses but above 131 kg N/ha the dead mass can result in energy loss per respiration. Above 86 kg/N the mass accumulation rate decreases which means that the fertilization cost is not favorable over this dose

Clinical Forms of Chikungunya in Gabon, 2010

Chikungunya fever (CHIK) is a disease caused by a virus transmitted to humans by infected mosquitos. The virus is responsible for multiple outbreaks in tropical and temperate areas worldwide, and is now a global concern. Clinical and biological features of the disease are poorly described, especially in Africa, where the disease is neglected because it is considered benign. During a recent CHIK outbreak that occurred in southeast Gabon, we prospectively studied clinical and biological features of 270 virologically confirmed cases. Fever and arthralgias were the predominant symptoms. Furthermore, variable and distinct clinical pictures including pure febrile, pure arthralgic and unusual forms (neither fever nor arthralgias) were detected. No severe forms or deaths were reported. These findings suggest that, during CHIK epidemics, some patients may not have classical symptoms (fever and arthralgias). Local surveillance is needed to detect any changes in the pathogenicity of this virus

Andacollo copper-gold district, La Serena, Chile: Preliminary data from the porphyry copper and possible relationships between Cu and Au mineralization

The Andacollo mining district is located in the Coquimbo region of Chile at 30°14’ south, 71°06’ west, some 55 km southeast of La Serena, at a mean elevation of 1030 m within a semi-arid hilly landscape. Current mining activity in the district is concentrated on copper and gold. These metals are mined, respectively, from a porphyry copper deposit and epithermal, manto and vein gold deposits of adularia– sericite type. Other types of mineralization include mercury veins hosted by carbonate rocks. The gold veins are controlled by a northwest-trending set of normal faults, whereas the manto-type mineralization is strata-bound and largely confined to andesite breccias, dacites and sites of strong fracturing. The lateral and vertical continuity of the mantos is strongly controlled by rock type, faulting and intensity of fracturing. The gold deposits have been the focus of a recent study, but comparable information on the Andacollo porphyry has not become available. A brief, updated geological perception of the porphyry is now presented and possible relationships between the copper and gold deposits are analysed.Depto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEpu

Use of acidophilic bacteria of the genus Acidithiobacillus tobiosynthesize CdS fluorescent nanoparticles (quantum dots) withhigh tolerance to acidic pH

The use of bacterial cells to produce fluorescent semiconductor nanoparticles (quantum dots, QDs) rep-resents a green alternative with promising economic potential. In the present work, we report for thefirst time the biosynthesis of CdS QDs by acidophilic bacteria of the Acidithiobacillus genus. CdS QDs wereobtained by exposing A. ferrooxidans, A. thiooxidans and A. caldus cells to sublethal Cd2+concentrations inthe presence of cysteine and glutathione. The fluorescence of cadmium-exposed cells moves from greento red with incubation time, a characteristic property of QDs associated with nanocrystals growth. Biosyn-thesized nanoparticles (NPs) display an absorption peak at 360 nm and a broad emission spectra between450 and 650 nm when excited at 370 nm, both characteristic of CdS QDs. Average sizes of 6 and 10 nmwere determined for green and red NPs, respectively. The importance of cysteine and glutathione on QDsbiosynthesis in Acidithiobacillus was related with the generation of H2S. Interestingly, QDs produced byacidophilic bacteria display high tolerance to acidic pH. Absorbance and fluorescence properties of QDswas not affected at pH 2.0, a condition that totally inhibits the fluorescence of QDs produced chemicallyor biosynthesized by mesophilic bacteria (stable until pH 4.5–5.0). Results presented here constitute thefirst report of the generation of QDs with improved properties by using extremophile microorganisms