1,311,445 research outputs found

    The role of UV in crab spider signals: effects on perception by prey and predators

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    Australian crab spiders Thomisus spectabilis sit on the petals of flowers and ambush prey such as honeybees. White-coloured T. spectabilis reflect in the UV (UV+ spiders) and previous research has shown that their presence, curiously, attracts honeybees to daisies. We applied an UV-absorber (Parsol®) to create UV-absorbing (UV–) spiders that did not reflect any light below 395 nm wavelength. These physical changes of visual signals generated by crab spiders caused honeybees to avoid flowers with UV– spiders on their petals. They also affected the perception of UV– spiders by honeybees and a potential avian predator (blue tits). Compared to UV+ spiders, UV– spiders produced less excitation of the UV-photoreceptors in honeybees and blue tits, which translated into a reduced UV-receptor contrast and a reduced overall colour contrast between UV– spiders and daisy petals. Our results reveal that a clean physical elimination of reflection in the UV range affects perception in predators and prey and ultimately changes the behaviour of prey.7 page(s

    Multiple roles for UV RESISTANCE LOCUS8 in regulating gene expression and metabolite accumulation in arabidopsis under solar ultraviolet radiation

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    Photomorphogenic responses triggered by low fluence rates of ultraviolet B radiation (UV-B; 280–315 nm) are mediated by the UV-B photoreceptor UV RESISTANCE LOCUS8 (UVR8). Beyond our understanding of the molecular mechanisms of UV-B perception by UVR8, there is still limited information on how the UVR8 pathway functions under natural sunlight. Here, wild-type Arabidopsis (Arabidopsis thaliana) and the uvr8-2 mutant were used in an experiment outdoors where UV-A (315–400 nm) and UV-B irradiances were attenuated using plastic films. Gene expression, PYRIDOXINE BIOSYNTHESIS1 (PDX1) accumulation, and leaf metabolite signatures were analyzed. The results show that UVR8 is required for transcript accumulation of genes involved in UV protection, oxidative stress, hormone signal transduction, and defense against herbivores under solar UV. Under natural UV-A irradiance, UVR8 is likely to interact with UV-A/blue light signaling pathways to moderate UV-B-driven transcript and PDX1 accumulation. UVR8 both positively and negatively affects UV-A-regulated gene expression and metabolite accumulation but is required for the UV-B induction of phenolics. Moreover, UVR8-dependent UV-B acclimation during the early stages of plant development may enhance normal growth under long-term exposure to solar UV

    Commercialisation de l'Heparin diagnostics par le biais d'une startup

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    Mon travail de bachelor m'a été proposé par un professeur de chimie analytique de l'université de Genève. Ce dossier a pour objectif de développer les différentes étapes d'un business plan afin d'aboutir à la commercialisation d'un dispositif médical breveté par M. Bakker et cela sous la forme d'une création d'entreprise. L'inventeur du dispositif a développé une technologie qui permet de mesurer en temps réel la concentration d'héparine dans le sang. L'héparine est un puissant anticoagulant utilisé lors d'opérations cardio-vasculaires. Actuellement, aucun autre dispositif ne permet une telle précision de mesures. C'est pourquoi nous pouvons considérer que ce dispositif représente une avancée majeure pour la médecine intensive. Le dispositif se place sur un marché peu exploité. Sa précision de mesures et sa diminution de complications lors des opérations offres des opportunités commerciales importantes. Le sondage effectué auprès des spécialistes et les résultats qu'offrent les différentes analyses de marché m'amène à recommander à M. Bakker de s'implanter sur le marché suisse. Les spécialistes ont montré un intérêt particulier au dispositif et sont prêts à l'essayer en interne. L'enthousiasme des utilisateurs relève d'une importance capitale pour Heparin diagnostics. Cibler les Hôpitaux universitaires sera donc la première étape pour la société. La réputation que se forgera la start-up en suisse permettra à cette dernière de s'étendre vers d'autres marchés. Les États-Unis subissent au fil des années un accroissement de l'obésité et une augmentation du taux de maladies cardio-vasculaires. C'est pourquoi le marché américain représente un marché attrayant pour l'entreprise. Dans ce travail, je me suis efforcée de recenser les éléments les plus pertinents afin que M. Bakker soit en mesure de démontrer aux investisseurs et aux utilisateurs les opportunités de Heparin diagnostic

    Removal of malathion from various waters by advanced oxidation processes

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    Summary: The degradation of malathion was investigated under various conditions, including ultrasound (US) irradiation, ultraviolet (UV) irradiation, and the combination of US/UV, UV/ZnO, UV/H2O2, and US/UV/ZnO/H2O2. In addition, the effect of the operational parameters, such as the initial concentration of the catalyst, the initial malathion concentration, the initial salt concentration (NaHCO3 and Na2SO4), and pH, were studied. Analyses were performed by a gas chromatography-mass spectroscopy instrument. The k values were in the following order: US/UV/H2O2/ZnO > US/UV > UV/ZnO > UV/H2O2 > UV > US. ZnO concentration of 100 mg/l, malathion initial concentration of 200 μg/l, H2O2 concentration of 30 mg/l, pH of 9, and irradiation time of 105 min were the optimum conditions for degrading malathion by the US/UV/H2O2/ZnO system. Additionally, the optimized parameters were also tested for the treatment of an actual water sample containing the pesticide. As a result, the efficiency of the US/UV/H2O2/ZnO system was higher in the distilled water sample than in the actual water sample. © 2015, Chemical Society of Pakistan. All rights reserved

    Star formation and dust extinction in nearby star forming and starburst galaxies

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    We study the star formation rate and dust extinction properties of a sample of nearby star forming galaxies as derived from Halpha and UV (2000 A) observations and we compare them to those of a sample of starburst galaxies. The dust extinction in Halpha is estimated from the Balmer decrement and the extinction in UV using the FIR to UV flux ratio or the attenuation law for starburst galaxies of Calzetti et al. The Halpha and UV emissions are strongly correlated with a very low scatter for the star forming objects and with a much higher scatter for the starburst galaxies. The Halpha to UV flux ratio is found larger by a factor ~ 2 for the starburst galaxies. We compare both samples with a purely UV selected sample of galaxies and we conclude that the mean Halpha and UV properties of nearby star forming galaxies are more representative of UV selected galaxies than starburst galaxies. We emphasize that the Halpha to UV flux ratio is strongly dependent on the dust extinction: the positive correlation found between F{Halpha}/F{UV}$ and F{FIR}/F{UV} vanishes when the Halpha and UV flux are corrected for dust extinction. The Halpha to UV flux ratios converted into star formation rate and combined with the Balmer decrement measurements are tentatively used to estimate the dust extinction in UV.Comment: accepted for publication in Astronomy & Astrophysic
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