The Effect of Chemical Information on the Spatial Distribution of Fruit Flies: I Model Results

Animal aggregation is a general phenomenon in ecological systems. Aggregations are generally considered as an evolutionary advantageous state in which members derive the benefits of protection and mate choice, balanced by the costs of limiting resources and competition. In insects, chemical information conveyance plays an important role in finding conspecifics and forming aggregations. In this study, we describe a spatio-temporal simulation model designed to explore and quantify the effects of these infochemicals, i.e., food odors and an aggregation pheromone, on the spatial distribution of a fruit fly (Drosophila melanogaster) population, where the lower and upper limit of local population size are controlled by an Allee effect and competition. We found that during the spatial expansion and strong growth of the population, the use of infochemicals had a positive effect on population size. The positive effects of reduced mortality at low population numbers outweighed the negative effects of increased mortality due to competition. At low resource densities, attraction toward infochemicals also had a positive effect on population size during recolonization of an area after a local population crash, by decreasing the mortality due to the Allee effect. However, when the whole area was colonized and the population was large, the negative effects of competition on population size were larger than the positive effects of the reduction in mortality due to the Allee effect. The use of infochemicals thus has mainly positive effects on population size and population persistence when the population is small and during the colonization of an area

Effect of Adding a Third Metal to Carbon-Supported PtSn-Based Nanocatalysts for Direct Ethanol Fuel Cell in Acidic Medium

International audienc

Efeito do extrato etanólico bruto e das frações da Hyptidendron canum (Pohl ex Benth.) Harley em brânquias de Oreochromis niloticus L.

Alguns problemas relacionados à criação intensiva de peixes estão mais evidentes devido ao aumento da aquicultura em todo o mundo, destacando-se os distúrbios nutricionais e o aumento de doenças nos sistemas de produção. Com isso as pesquisas envolvendo produtos derivados de plantas vem ganhando espaço nessa área. A Hyptidendron canum é uma planta utilizada na medicina popular como antimalárica, anti-inflamatória, antiulcerativa e anti-hepatotóxica. Objetivou-se, neste trabalho, avaliar os efeitos celulares e teciduais do extrato etanólico bruto e das frações hexano, clorofórmio e acetato de etila da H. canum nas brânquias de Oreochromis niloticus L. Para isso, o extrato etanólico e as frações foram administrados no peixe através da ração. Após 24 horas da ingestão da ração, os peixes foram sacrificados e o segundo arco branquial de cada um foi processado histologicamente e corado com tricômico de Masson e Hematoxilina e Eosina (HE). Pela análise qualitativa das brânquias ao microscópio de luz, observou-se que o extrato bruto e as três frações promoveram, em diferentes intensidades nas lamelas, descamação e destacamento do epitélio respiratório, alteração da curvatura, desorganização do eixo, hiperplasia celular do tecido epitelial interlamelar e vasodilatação nas lamelas e no vaso central do filamento. Os resultados deste experimento mostraram que o extrato etanólico bruto e as três frações de H. canum promoveram processos inflamatórios e/ou lesões sistêmicas, dose dependente para O. niloticus

Identification of chemicals resulted in selective glycerol conversion as sustainable fuel on Pd-based anode nanocatalysts

International audiencePalladium-based nanoparticles were prepared using mild microwave-assisted heating. The activity of carbon supported PdM (M = Mn and Fe) toward glycerol oxidation in alkaline medium was studied by coupling electrochemical, analytical and in situ spectroscopic techniques. The complementary findings showed that glycerol was converted into oxalate, tartronate, glycerate, glycolate and formate. The ex situ analytical methods (liquid chromatography and mass spectrometry) were helpful to reveal glycerate as the major reaction product on PdM/C anodes, while from in situ infrared spectroscopy measurements no irreversible adsorbed poisoning species was detected in glycerol or intermediate oxidation to carbonate at the prepared electrodes. The correlation of the analytical and physicochemical (XRD, EDX and TEM) results concerned the shift of the onset potential toward lower values and the high Faradaic currents due to electronic structures provided by the Mn and Fe contents to the Pd based materials. Accordingly, glycerol is a sustainable raw material, which can be used in cogeneration processes for renewable energy sources and selective production of added-value molecules