Description of the biogeochemical features of the subtropical southeastern Atlantic and the Southern Ocean south of South Africa during the austral summer of the International Polar Year

International audienceMeridional and vertical distributions of several biogeochemical parameters were studied along a section in the southeastern Atlantic and the Southern Ocean south of South Africa during the austral summer 2008 of the International Polar Year to characterize the biogeochemical provinces and to assess the seasonal net diatom production. Based on analyses of macro-nutrients, ammonium (NH4), chlorophyll a, (Chl a), phaeopigments, biogenic silica (BSi), particulate inorganic carbon (PIC), and particulate organic carbon and nitrogen (POC and PON, respectively), four biogeochemical domains were distinguished along the section: the subtropical Atlantic, the confluence zone of the subtropical and subantarctic domains, the Polar Frontal Zone (PFZ) in the Antarctic Circumpolar Current (ACC), and the north-eastern branch of the Weddell Gyre. The subtropical region displayed extremely low nutrient concentrations featuring oligotrophic conditions, and sub-surface maxima of Chl a and phaeopigments never exceeded 0.5 µg L−1 and 0.25 µg L−1, respectively. The anticyclonic and cyclonic eddies crossed in the Cape Basin were characterized by a deepening and a rise, respectively, of the nutrients isoclines. The confluence zone of the subtropical domain and the northern side of the ACC within the subantarctic domain displayed remnant nitrate and phosphate levels, whereas silicate concentrations kept to extremely low levels. In this area, Chl a level of 0.4-0.5 µg L−1 distributed homogenously within the mixed layer, and POC and PON accumulated to values up to 10 µM and 1.5 µM, respectively, indicative of biomass accumulation along the confluence zone during the late productive period. In the ACC domain, the Polar Frontal Zone was marked by a post-bloom of diatoms that extended beyond the Polar Front (PF) during this late summer condition, as primarily evidenced by the massive depletion of silicic acid in the surface waters. The accumulation of NH4 to values up to 1.25 µM at 100 m depth centred on the PF and the accumulation of BSi up to 0.5 µM in the surface waters of the central part of the PFZ also featured a late stage of the seasonal diatom bloom. The silica daily net production rate based on the seasonal depletion of silicic acid was estimated to be 11.9 ± 6.5 mmol m−2 d−1 in the domain of the vast diatom post-bloom, agreeing well with the previously recorded values in this province. The Weddell Gyre occasionally displayed relative surface depletion of silicic acid, suggesting a late stage of a relatively minor diatom bloom possibly driven by iceberg drifting releases of iron. In this domain the estimated range of silica daily net production rate (e.g. 21.1 ± 8.8 mmol m−2 d−1) is consistent with previous studies, but was not significantly higher than that in the Polar Front region

What causes the inverse relationship between primary production and export efficiency in the Southern Ocean?

The ocean contributes to regulating atmospheric CO2 levels, partly via variability in the fraction of primary production (PP) which is exported out of the surface layer (i.e. the e-ratio). Southern Ocean studies have found that, contrary to global scale analyses, an inverse relationship exists between e-ratio and PP. This relationship remains unexplained, with potential hypotheses being i) large export of dissolved organic carbon (DOC) in high PP areas, ii) strong surface microbial recycling in high PP regions and/ or iii) grazing mediated export varies inversely with PP. We find that the export of DOC has a limited influence in setting the negative e-ratio/PP relationship. However, we observed that at sites with low PP and high e-ratios, zooplankton mediated export is large and surface microbial abundance low suggesting that both are important drivers of the magnitude of the e-ratio in the Southern Ocean

From the Single- to the Triple-Decker Sandwich. Effect of Stacking on the Redox and UV-Visible Spectroscopic Properties of Lutetium(III) 1,2-Naphthalocyaninate Complexes

International audience(1,2-Naphthalocyaninato)lutetium(III), bis(1,2-naphthalocyaninato)lutetium(III), and tris(1,2-naphthalocyaninato)-dilutetium(III) have been synthesized in good yields. These complexes were characterized by UV-visible, 1H NMR, and mass spectroscopies and by electrochemical techniques. Bis(1,2-naphthalocyaninato)lutetium(III) is compared to bis(2,3-naphthalocyaninato)lutetium(III): the good correspondance between the experimental data and theoretical results obtained by others is emphasized in this work. Stacking one to three macrocyclic rings is possible in the series of the 1,2-naphthalocyanine sandwich-like complexes with lutetium(III); as shown by UV-visible spectroelectrochemistry and voltammetry, this influences greatly the π-conjugated systems, modifying spectacularly their spectroscopic and redox properties

An amphiphilic lutetium bisphthalocyanine: Lu[(PEO)4Pc] [(DodO)4Pc]

International audienceThe synthesis of an amphiphilic lutetium bisphthalocyanine is described. One phthalocyanine of the sandwich complex bears four hydrophobic chains (C12H25O = DodO), and the other bears four hydrophilic polyether groups (CH3(OCH2CH2)(n)O = PEO). The molecule has been characterized by 1H NMR and ESI mass spectrometry. The mean value for n, the number of polyethyleneoxy units in the starting PEOH, is 8 with a Gaussian distribution around that value; however, for the most abundant lutetium bisphthalocyanine, 4n = 26. On the spectrum, the peak corresponding to the adduct with two Na+ is higher than the one of the singly charged ion, a result of the affinity of polyethers for alkali ions

Grey scale memory in an optically addressed spatial light modulator with a Lu(Pc)2 doped layer

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New testing equipment for SMT PC boards

NUMBER OF PAGES: xxx+1005The device presented has been especially designed for testing surface-mounted components, and allows a resolution of 0.1 mm (4/1000 in). It is able to detect and identify opens and shorts in a few seconds, on both sides of the printed circuit board simultaneously (surface-mount technology allows boards to have components on both sides), with 4000 nonmultiplexed test points per side. The device is controlled by a simple PC or AT compatible, linked to the tester by a flat cable of 50 wires

Photogeneration of charges in poly(N-vinylcarbazole) doped with lutetium bisphthalocyanines and lutetium bisnaphthalocyanines

cited By 7International audienceLutetium bisphthalocyanines and bisnaphthalocyanines, sandwich complexes having interesting electronic properties were studied as electron-acceptors associated with the donor polyvinylcarbazole (PVCz) in single-layer photoconductors. It is known, from their redox properties, that these lanthanide complexes are potential electron-acceptors as well as electron-donors; moreover, they strongly absorb light from the near-UV to the near-IR. The xerographic spectra recorded between 400 and 900 nm show that the polymeric phases doped with the lutetium bisphthalocyanines are photoconductive. These new photoconducting phases are active in the near IR domain which is promising with regard to their potential applications. Copyright © 2003 Society of Porphyrins & Phthalocyanines

Photogeneration of charges in poly(N-vinylcarbazole) doped with lutetium bisphthalocyanines and lutetium bisnaphthalocyanines

cited By 7International audienceLutetium bisphthalocyanines and bisnaphthalocyanines, sandwich complexes having interesting electronic properties were studied as electron-acceptors associated with the donor polyvinylcarbazole (PVCz) in single-layer photoconductors. It is known, from their redox properties, that these lanthanide complexes are potential electron-acceptors as well as electron-donors; moreover, they strongly absorb light from the near-UV to the near-IR. The xerographic spectra recorded between 400 and 900 nm show that the polymeric phases doped with the lutetium bisphthalocyanines are photoconductive. These new photoconducting phases are active in the near IR domain which is promising with regard to their potential applications. Copyright © 2003 Society of Porphyrins & Phthalocyanines