65 research outputs found

    Ace-1 duplication in Anopheles gambiae: a challenge for malaria control

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    <p>Abstract</p> <p>Background</p> <p>Insecticide resistance is a rapid and recent evolutionary phenomenon with serious economic and public health implications. In the mosquito <it>Anopheles gambiae s.s</it>., main vector of malaria, resistance to organophosphates and carbamates is mainly due to a single amino-acid substitution in acetylcholinesterase 1 (AChE1). This mutation entails a large fitness cost. However, a resistant duplicated allele of the gene encoding AChE1 (<it>ace-1</it>), potentially associated to a lower fitness cost, recently appeared in <it>An. gambiae</it>.</p> <p>Methods</p> <p>Using molecular phenotype data collected from natural populations from West Africa, the frequency of this duplicated allele was investigated by statistical inference. This method is based on the departure from Hardy-Weinberg phenotypic frequency equilibrium caused by the presence of this new allele.</p> <p>Results</p> <p>The duplicated allele, <it>Ag</it>-<it>ace-1</it><sup><it>D</it></sup>, reaches a frequency up to 0.65 in Ivory Coast and Burkina Faso, and is potentially present in Benin. A previous study showed that <it>Ag</it>-<it>ace-1</it><sup><it>D</it></sup>, present in both M and S molecular forms in different West Africa countries, was generated by a single genetic event. This single origin and its present distribution suggest that this new allele is currently spreading.</p> <p>Conclusion</p> <p>The spread of this less costly resistance allele could represent a major threat to public health, as it may impede <it>An. gambiae </it>control strategies, and thus increases the risk of malaria outbreaks.</p

    ANALYSIS OF SWITCHGRASS CHARACTERISTICS USING NEAR INFRARED SPECTROSCOPY

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    Switchgrass varieties grown under various environments were investi-gated by dispersive and Fourier Transform Near-Infrared (NIR) spectro-meters. The collected NIR spectra were analyzed using multivariate approaches. More specifically, principal component analysis (PCA) and projection to latent structures (PLS) regression techniques were employed to classify and predict characteristics of the switchgrass samples. The multivariate results were compared to reflectance indices that are commonly used to study the physiological performance of plants. From near infrared spectra, discrimination between the two growth locations was successfully achieved by PCA. Separation based on the ecotype and the rate of fertilizer applied to the field was also possible by the multivariable analysis of the spectral data. For the classification/ discrimination of the switchgrass samples, the near infrared spectra collected by the dispersive and the Fourier Transform spectrometers provided similar results. From the two near infrared data sets robust models were developed to predict non-structural carbohydrates content and the rate of nitrogen applied to the field. However, the spectra collected by the dispersive spectrometer resulted in more accurate models for these samples

    Sciadopitys verticillata Resin: Volatile Components and Impact on Plant Pathogenic and Foodborne Bacteria

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    Sciadopitys verticillata (Sv) produces a white, sticky, latex-like resin with antimicrobial properties. The aims of this research were to evaluate the effects of this resin (Sv resin) on bacterial populations and to determine the impact of its primary volatile components on bioactivity. The impact of sample treatment on chemical composition of Sv resin was analyzed using Fourier transform infrared spectroscopy (FTIR) coupled with principal component analysis. The presence and concentration of volatiles in lyophilized resin were determined using gas chromatography/mass spectrometry (GC/MS). Changes in bacterial population counts due to treatment with resin or its primary volatile components were monitored. Autoclaving of the samples did not affect the FTIR spectra of Sv resin; however, lyophilization altered spectra, mainly in the CH and C=O regions. Three primary bioactive compounds that constituted \u3e90% of volatiles (1R-α-pinene, tricyclene, and ÎČ-pinene) were identified in Sv resin. Autoclaved resin impacted bacterial growth. The resin was stimulatory for some plant and foodborne pathogens (Pseudomonas fluorescens, P. syringae, and Xanthomonas perforans) and antimicrobial for others (Escherichia coli, Bacillus cereus, Agrobacterium tumefaciens, and Erwinia amylovora). Treatment with either 1R-α-pinene or ÎČ-pinene reduced B. cereus population growth less than did autoclaved resin. The complex resin likely contains additional antimicrobial compounds that act synergistically to inhibit bacterial growth

    Lattice Matched Carbide–Phosphide Composites with Superior Electrocatalytic Activity and Stability

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    Composites of electrocatalytically active transition-metal compounds present an intriguing opportunity toward enhanced activity and stability. To identify potentially scalable pairs of a catalytically active family of compounds, we demonstrate that phosphides of iron, nickel, and cobalt can be deposited on molybdenum carbide to generate nanocrystalline heterostructures. Composites synthesized via solvothermal decomposition of metal acetylacetonate salts in the presence of highly dispersed carbide nanoparticles show hydrogen evolution activities comparable to those of state-of-the-art non-noble metal catalysts. Investigation of the spent catalyst using high resolution microscopy and elemental analysis reveals that formation of carbide−phosphide composite prevents catalyst dissolution in acid electrolyte. Lattice mismatch between the two constituent electrocatalysts can be used to rationally improve electrochemical stability. Among the composites of iron, nickel, and cobalt phosphide, iron phosphide displays the lowest degree of lattice mismatch with molybdenum carbide and shows optimal electrochemical stability. Turnover rates of the composites are higher than that of the carbide substrate and compare favorably to other electrocatalysts based on earth-abundant elements. Our findings will inspire further investigation into composite nanocrystalline electrocatalysts that use molybdenum carbide as a stable catalyst support

    Vivienda rural en Toconao : Proyecto de TĂ­tulo F.A.U. Universidad de Chile 1995

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    Rural housing in an agricultural community in the Atacama Desert's Oasis, at 2.415 mts. above sea level.Vivienda rural de una comunidad agrĂ­cola instalada en un oasis del desierto de Atacama, a 2.415 metros sobre el nivel del mar

    Vivienda rural en Toconao : Proyecto de TĂ­tulo F.A.U. Universidad de Chile 1995

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    Rural housing in an agricultural community in the Atacama Desert's Oasis, at 2.415 mts. above sea level.Vivienda rural de una comunidad agrĂ­cola instalada en un oasis del desierto de Atacama, a 2.415 metros sobre el nivel del mar

    Proyectos de arquitectura integrados al orden urbano

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    This is a design of a framework which is paralell to "Parque de los Reyes", working as an organizing pattern which allows for unity and diversity as well.Estudiantes diseñan trama espacial paralela al Parque de los Reyes, como patrón ordenador que permite a la vez unidad y diversidad
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