Effet des variations d'énergie lumineuse associées à l'agitation verticale sur le bilan photosynthétique de cultures intensives d'algues en bassin

Une série d'expériences a été réalisée pour évaluer les effets de l'agitation sur le bilan photosynthétique de cultures d'algues en masse en bassins extérieurs. La méthode utilisée compare la production d'échantillons marqués au C14 disposés (1) selon un profil vertical classique, (2) sur un système rotatif faisant transiter un flacon entre la surface et le tond du bassin. Des mesures ont été effectuées périodiquement en milieu de journée sur un cycle annuel, et ont été complétées par 8 incubations réalisées entre le lever et le coucher du soleil pour un jour donné. Dans toutes les expériences réalisées durant la période estivale, la photosynthèse est supérieure dans le flacon mobile. Les effets des variations lumineuses (par le biais des mouvements de l'eau) sur te bilan photosynthétique de la colonne d'eau sont particulièrement notables au lever et au coucher du soleil; ce bilan peut être jusqu'à 2.5 fois plus important pour une colonne d'eau en mouvement. Le calcul d'un bilan journalier par extrapolation des profils de photosynthèse instantanés permet d'estimer le gain de production obtenu par agitation du milieu. Par contre pendant la période hivernale, la photosynthèse est supérieure dans le flacon immobile. Ces résultats ont des implications évidentes sur le monitoring de cultures d'algues en masse en bassins extérieurs.Experiments were carried out to define the effect of a particular mixing system (circular round a horizontal axis) upon the primary productivity of high-rate alga cultures. We know that mixing prevent algal cell sedimentation, gaseous and nutritional gradients, and variations in algae light reception. So, we wanted to quantity the effect of mixing on algal productivity with regard to flashing light (positive effect in comparison with continuous light).We used water from waste stabilization ponds (secondary pond output), with the native algae population dominated by Euglena and Chlorella (in Aveyron, South of France). The method used compares algal production of a water column with 14C-labelled samples i) in ten flasks placed along a classical vertical profile, ii) in a rotating system with a flask moving between the top and the bottom of the pond (0.5 m). The production is here considered as the mean of a mixed vertical profile. At the same time, physico-chemical and biological parameters were recorded (high load for N and P).Experiments were made periodically in the mid-afternoon over one year, and were completed by 8 incubations made between sunrise and sunset for on day (in August 1989). The aim was to evaluate the mixing affect with various environmental conditions. Physico-chemical parameters vary greatly over a day, and higher production values are measured in the mid-afternoon. Production observed for the stationary profile fitted the Steele model, and showed active photosynthetic from sunrise until sunset, with inhibition at high light intensities; maximal photosynthesis rates were measured between 4.00 and 5.00 PM.Results are compared to moving flask values : in all the summer experiments photosynthesis was higher in the moving flask. Light variation effects (through water movements) on the water column photosynthetic budget are particularly notable at sunrise and sunset bouts : this budget may be over 2,5 times that of homogeneous nonturbulent water. During winter however, photosynthesis is higher for the stationary profile. We compared production recorded with the two systems, and calculated the mathematical relationship between the two systems over one day (exponential) and over the year (linear relationship).By extrapolation of the instant photosynthesis profile to a 24-hour period, we can evaluate the production gain with culture mixing. We calculated the net production for various days over the year; around the end of April, the mixed system became more productive than the stationary one.Considering our results in environmental conditions, it is obvious that they are not representative of all mixing systems, particularly the techniques in which algae cell position shift continually with respect to the photic zone : the positive effect of mixing in our ponds may be linked to the flashing light effect. In the literature, we can see that photosynthetic activity increases with flash time duration. Our production figures for various hours along the day (or various flash durations) are in agreement with these results.During low photosynthetic activity periods, the flashing light effect can not act since light is available at all depths of pond. The most important factor acting, in our experiments, seems to be light, since the two systems are in similar conditions.These results have clear implications for monitoring intensive outdoor algal cultures

Experimental functional response and inter-individual variation in foraging rate of teal (Anas crecca)

The functional response, i.e. the change in per capita food intake rate per time unit with changed food availability, is a widely used tool for understanding the ecology and behaviour of animals. However, waterfowl remain poorly explored in this context. In an aviary experiment we derived a functional response curve for teal (Anascrecca) foraging on rice (Oryzasativa) seeds. We found a linear relationship between intake rate and seed density, as expected for a filter-feeder. At high seed densities we found a threshold, above which intake rate still increased linearly but with a lower slope, possibly reflecting a switch from filter-feeding to a scooping foraging mode. The present study shows that food intake rate in teal is linearly related to food availability within the range of naturally occurring seed densities, a finding with major implications for management and conservation of wetland habitats.</p

Biologically Informed Individual-Based Network Model for Rift Valley Fever in the US and Evaluation of Mitigation Strategies

Citation: Scoglio, C. M., Bosca, C., Riad, M. H., Sahneh, F. D., Britch, S. C., Cohnstaedt, L. W., & Linthicum, K. J. (2016). Biologically Informed Individual-Based Network Model for Rift Valley Fever in the US and Evaluation of Mitigation Strategies. Plos One, 11(9), 26. doi:10.1371/journal.pone.0162759Rift Valley fever (RVF) is a zoonotic disease endemic in sub-Saharan Africa with periodic outbreaks in human and animal populations. Mosquitoes are the primary disease vectors; however, Rift Valley fever virus (RVFV) can also spread by direct contact with infected tissues. The transmission cycle is complex, involving humans, livestock, and multiple species of mosquitoes. The epidemiology of RVFV in endemic areas is strongly affected by climatic conditions and environmental variables. In this research, we adapt and use a network-based modeling framework to simulate the transmission of RVFV among hypothetical cattle operations in Kansas, US. Our model considers geo-located livestock populations at the individual level while incorporating the role of mosquito populations and the environment at a coarse resolution. Extensive simulations show the flexibility of our modeling framework when applied to specific scenarios to quantitatively evaluate the efficacy of mosquito control and livestock movement regulations in reducing the extent and intensity of RVF outbreaks in the United States

Average mass of seeds encountered by foraging dabbling ducks in Western Europe

Many dabbling ducks Anas spp. are largely granivorous, consuming a variety of seeds chiefly from aquatic plants. To assess the relative value and carrying capacity of wetlands for dabbling ducks, species-specific information about seed mass is needed, but it is still largely missing or scattered in the literature. By combining weights of seeds collected in the field with a literature review, we provide a reference table for seed mass of 200 western European plant taxa frequently encountered by foraging dabbling ducks. Seeds collected in the field were sampled in microhabitats and at depths at which ducks were observed to forage, and study sites represent wintering, staging as well as breeding areas within a flyway in western Europe. When combined with calorimetric data, the present reference table will aid managers and scientists in assessing the importance of seed food resources at different sites and during different parts of the annual cycle.</p

CHLOROPHYLLS: FROM EVANTABYPRODUCT TO NATURAL PORPHYRIN SOURCE

EnglishEvanta (Galipea longiflora) is a medicinal specie used as antiparasitic agent by the Tacana Amazonian community. The total alkaloids of this plant have showed interesting results in clinical studies for the treatment of cutaneous Leishmaniasis. During the alkaloids isolation and purification processes, chlorophylls, together with non-useful fractions, are eliminated. Chlorophylls represent an important natural source of porphyrins, which have huge potential applications in many fields (materials, catalysis, nanotechnology, diagnostic and photo- and sono-dynamic therapy). They also possess biological and pharmacological activity (antitumoral, antioxidant and antifungal properties). This work is aimed to isolate, purify and characterize chlorophylls contained in evanta leaves.Italiano L’evanta (Galipea longiflora) è una specie medicinale utilizzata come agente antiparassitario dalla comunità amazzonica tacana. Gli alcaloidi di questa pianta hanno mostrato risultati interessanti negli studi clinici per il trattamento della leishmaniosi cutanea. Durante i processi di isolamento e purificazione degli alcaloidi, le clorofille, insieme alle frazioni non utili, vengono eliminate. Le clorofille potrebbero costituire un'importante fonte naturale di porfirine, le quali hanno potenziali applicazioni in molti campi (materiali, catalisi, nanotecnologie, diagnostica e terapia foto- e sono-dinamica). Posseggono inoltre attività biologica e farmacologica (antitumorali, antiossidanti e antifungini). Questo lavoro è volto ad isolare, purificare e caratterizzare le clorofille presenti nelle foglie di evanta

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV