39 research outputs found

    Producing New Knowledge on Innovation Management

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    Effects of oxygen loss on carbon processing and heterotrophic prokaryotes from an estuarine ecosystem: results from stable isotope probing and cytometry analyses

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    Many aquatic ecosystems are experiencing a decline in their oxygen (O<sub>2</sub>) content and this is predicted to continue. Implications of this change on several properties of bacterioplankton (heterotrophic prokaryotes) remain however are poorly known. In this study, oxic samples (~170 µM O<sub>2</sub>?=?controls) from an oligohaline region of the Scheldt Estuary were purged with N<sub>2</sub> to yield low-O<sub>2</sub> samples (~69 µM O<sub>2</sub>?=?treatments); all were amended with <sup>13</sup>C-glucose and incubated in dark to examine carbon incorporation and cell size of heterotrophic prokaryotes, and relationships between organic matter (OM) degradation and phosphate (P) availability in waters following O<sub>2</sub> loss. Stable isotope (<sup>13</sup>C) probing of phospholipid fatty acids (PLFA) and flow cytometry were used. In samples that have experienced O<sub>2</sub> loss, PLFA biomass became higher, prokaryotic cells had significantly larger size and higher nucleic acid content, but P concentrations was lower, compared to controls. P concentration and OM degradation were positively related in controls, but uncoupled in low-O<sub>2</sub> samples. Moreover, the dominant PLFA 16:1<i>?</i>7c (likely mainly from Gram-negative bacteria) and the nucleic acid content of heterotrophic prokaryotic cells in low-O<sub>2</sub> samples explained (62–72 %) differences between controls and low-O<sub>2</sub> samples in P amounts. Shortly after incubations began, low-O<sub>2</sub> samples had consistently lower bacterial PLFA <sup>13</sup>C-enrichments, suggesting involvement of facultatively anaerobic metabolism in carbon incorporation, and supporting the view that this metabolic pathway is widespread among pelagic bacteria in coastal nutrient-rich ecosystems. Estimates based on <sup>13</sup>C-enrichment of PLFAs indicated that grazing by protozoa on some bacteria was stronger in low-O<sub>2</sub> samples than in controls, suggesting that the grazing pressure on some heterotrophic prokaryotes may increase at the onset of O<sub>2</sub> deficiency in nutrient-rich aquatic systems. These findings also suggest that physiological responses of heterotrophic prokaryotes to O<sub>2</sub> loss in such ecosystems include increases in cell activity, high carbon incorporation, and possibly phosphorus retention by cells that may contribute to reduce phosphate availability in waters

    YIG Thin Film Used to Miniaturize a Coplanar Junction Circulator

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    International audienceThe preparation of Yttrium Iron Garnet films (YIG) presenting controlled magnetic properties is of great interest for miniaturization of RF passive components. The present work deals with the integration of YIG ferrite sputtered films for coplanar circulators. These components must work at frequencies above 10GHz, and they must be compatible with mass-production and low-cost process. The YIG films (of thickness 15 μm) are deposited on an alumina substrate by RF magnetron sputtering. Their structural mechanical and magnetic properties in the millimetre wave range are optimised to enable the film's integration. A circulator is fabricated using such prepared film, and its properties in the microwave range are characterised using a network analyzer and a probing system

    Changes in micro-organism abundances in the organic matter released by <i>C</i>. <i>caespitosa</i> during a 96 h incubation.

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    <p>Prokaryote (black squares) and virus-like-particles (VLPs) abundances (grey circle) were plotted together for T15L40 (a) T15L200 (b) T22L200 (c) and T22L40 (d) condition. Data are mean (n = 9) ± s.e. of three incubations of three different set.</p

    Number of bands observed after PCR DGGE analysis of the bacterial (a) and archaeal (b) community, at 15°C (C15) and 22°C (C22), and in the 4 experimental conditions (T15L40, T15L200, T22L40 and T22L200) just after the mucus was released (black) and after 96 h of incubation (white).

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    <p>Number of bands observed after PCR DGGE analysis of the bacterial (a) and archaeal (b) community, at 15°C (C15) and 22°C (C22), and in the 4 experimental conditions (T15L40, T15L200, T22L40 and T22L200) just after the mucus was released (black) and after 96 h of incubation (white).</p
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