University of the Littoral Opal Coast

About: University of the Littoral Opal Coast is a education organization based out in Dunkirk, France. It is known for research contribution in the topics: Catalysis & Dielectric. The organization has 1242 authors who have published 2383 publications receiving 46230 citations. The organization is also known as: ULCO.

Studies of the activation process over Pd perovskite-type oxides used for catalytic oxidation of toluene

Abstract: Calcined and reduced catalysts Pd/LaBO 3 (B = Co, Fe, Mn, Ni) were used for the total oxidation of toluene. Easiness of toluene destruction was found to follow the sequence based on the T 50 values (temperature at which 50% of toluene is converted): Pd/LaFeO 3 > Pd/LaMnO 3+ δ > Pd/LaCoO 3 > Pd/LaNiO 3 . In order to investigate the activation process (calcination and reduction) in detail, the reducibility of the samples was evaluated by H 2 -TPR on the calcined catalysts. Additionally, characterization of the Pd/LaBO 3 (B = Co, Fe) surface was carried out by X-ray photoelectron spectroscopy (XPS) at each stage of the global process, namely after calcination, reduction and under catalytic reaction at either 150 or 200 °C for Pd/LaFeO 3 and either 200 or 250 °C for LaCoO 3 . The different results showed that palladium oxidized entities were totally reduced after pre-reduction at 200 °C for 2 h (2 L/h, 1 °C/min). As LaFeO 3 was unaffected by such a treatment, for the other perovskites, the cations B are partially reduced as B 3+ (B = Mn) or B 2+ even to B 0 (B = Co, Ni). In the reactive stream (0.1% toluene in air), Pd 0 reoxidized partially, more rapidly over Co than Fe based catalysts, to give a Pd 2+ /Pd 4+ and Pd 0 /Pd 2+ /Pd 4+ surface redox states, respectively. Noticeably, reduced cobalt species are progressively oxidized on stream into Co 3+ in a distorted environment. By contrast, only the lines characteristic of the initial perovskite lattice were detected by XRD studies on the used catalysts. The higher activity performance of Pd/LaFeO 3 for the total oxidation of toluene was attributed here to a low temperature of calcination and to a remarkable high stability of the perovskite lattice whatever the nature of the stream which allowed to keep a same palladium dispersion at the different stages of the process and to resist to the oxidizing experimental conditions. On the contrary, phase transformations for the other perovskite lattices along the process were believed to increase the palladium particle size responsible of a lower activity.

The fate of biogenic iron during a phytoplankton bloom induced by natural fertilisation: Impact of copepod grazing

Abstract: The impact of copepod grazing on Fe regeneration was investigated in a naturally iron-fertilised area during Kerguelen Ocean and Plateau compared Study (KEOPS, Jan.–Feb. 2005). 55Fe-labelled natural plankton assemblages (

A Review of Signal Enhancement and Noise Reduction Techniques for Tunable Diode Laser Absorption Spectroscopy

Abstract: Tunable diode laser absorption spectroscopy (TDLAS), as a noninvasive spectroscopic method, permits high-resolution, high-sensitivity, fast, in situ absorption measurements of atomic and molecular species and narrow spectral features in gaseous, solid, and liquid phases. Advances in new diode laser sources and laser spectroscopic techniques generally have triggered an increasing application of TDLAS in various disciplines (for example, atmospheric environmental monitoring, chemical analysis, industrial process control, medical diagnostics and combustion monitoring, etc.) over the last four decades. This article reviews some important developments in TDLAS, from its basic principles as a spectroscopic tool to the demonstration of gas absorption measurements, emphasizing signal enhancement and noise reduction techniques developed for improving current TDLAS performance.

Shifts in bacterial community composition associated with increased carbon cycling in a mosaic of phytoplankton blooms.

Abstract: Marine microbes have a pivotal role in the marine biogeochemical cycle of carbon, because they regulate the turnover of dissolved organic matter (DOM), one of the largest carbon reservoirs on Earth. Microbial communities and DOM are both highly diverse components of the ocean system, yet the role of microbial diversity for carbon processing remains thus far poorly understood. We report here results from an exploration of a mosaic of phytoplankton blooms induced by large-scale natural iron fertilization in the Southern Ocean. We show that in this unique ecosystem where concentrations of DOM are lowest in the global ocean, a patchwork of blooms is associated with diverse and distinct bacterial communities. By using on-board continuous cultures, we identify preferences in the degradation of DOM of different reactivity for taxa associated with contrasting blooms. We used the spatial and temporal variability provided by this natural laboratory to demonstrate that the magnitude of bacterial production is linked to the extent of compositional changes. Our results suggest that partitioning of the DOM resource could be a mechanism that structures bacterial communities with a positive feedback on carbon cycling. Our study, focused on bacterial carbon processing, highlights the potential role of diversity as a driving force for the cycling of biogeochemical elements.

Are growth and density quantitative indicators of essential fish habitat quality? An application to the common sole Solea solea nursery grounds

Abstract: Bio-indicators were measured on juvenile fish to assess the quality of eight coastal and estuarine nursery grounds in the Eastern English Channel and in the Bay of Biscay during 3 years. Growth (size and otolith daily increment width), body condition (morphometric index) and abundance of juvenile common soles were analysed together with xenobiotic concentrations (heavy metals and organic contaminants). Condition indices displayed important variations and did not allow relevant estimation of environmental quality. On the contrary, growth and density indicators showed good steadiness above years but varied among sites. In spite of difficulties of interpreting these indicators on such a meso-scale approach, analyses highlighted the estuaries of Seine and Gironde. In these nursery areas, the levels of contamination were especially high, and the combination of fish growth performances and density was significantly lower than in other sites. The combination of these variables appears to provide reliable indicators of habitat quality and anthropogenic pressure on nursery grounds, especially highlighting contaminated areas. Such indicators may thus contribute to improve assessment of environmental quality of essential fish habitats with the aim of a sustainable management of fisheries resources. A study at a different scale, from this meso-scale nursery approach with more precise analyses, on local habitats, will nevertheless be necessary to optimize the relevance of these indicators for the assessment of essential fish habitat quality.