Microfibrous TiO2 supported photocatalysts prepared by metal-organic chemical vapor infiltration for indoor air and waste water purification

The photocatalytic degradation of gaseous (toluene) and aqueous (imazapyr, malic acid, orange G) pollutants over TiO2 supported photocatalysts is investigated using a batch reactor. A strong influence of the microstructural characteristics of TiO2 on the decomposition kinetics of the pollutants is found. Well crystallized, porous TiO2-anatase films grown under low pressure at 400–500 8C by MOCVD on glass plates and by MOCVI on glass micro-fibers are the best heterogeneous photocatalysts, showing the highest activity. We demonstrate a good control of these characteristics by choosing the deposition parameters. Achieving conformal coverage (i.e. good infiltration) of glass micro-fibers by the TiO2 thin films has also a strong influence on the photocatalytic activity. A correlation between optimal infiltration, film microstructure and photocatalytic activity is established. Strong similarities between optimal photocatalytic decomposition rate in gas and liquid phase were found with respect to the film microstructure and the photocatalyst mass. The total mineralization of the toluene was prevented because of the deactivation of the photocatalyst surface. However the reactivation of the photocatalyst was achieved by UV irradiation under oxygen stream. This allows a long-term use of the photocatalyst

Chromium carbide growth at low temperature by a highly efficient DLI-MOCVD process in effluent recycling mode

The effect of direct recycling of effluents on the quality of CrxCy coatings grown by MOCVD using direct liquid injection (DLI) of bis(ethylbenzene)chromium(0) in toluene was investigated. The results are compared with those obtained using non-recycled solutions of precursor. Both types of coatings exhibit the same features. They are amorphous in the temperature range 673–823 K. They exhibit a dense and glassy-like microstructure and a high hardness (> 23 GPa). Analyses at the nanoscale revealed a nanocomposite microstructure consisting of free-C domains embedded in an amorphous Cr7C3 matrix characterized by strong interfaces and leading to an overall composition slightly higher than Cr7C3. The stiffness and strength of these interfaces are mainly due to at least two types of chemical bonds between Cr atoms and free-C: (i) Cr intercalation between graphene sheets and(ii) hexahapto η6-Cr bonding on the external graphene sheets of the free-C domains. The density of these interactions was found increasing by decreasing the concentration of the injected solution, as this occurred using a recycled solution. As a result, “recycled” coatings exhibit a higher nanohardness (29 GPa) than “new” coatings (23 GPa). This work demonstrates that using bis(arene)M(0) precursors, direct recycling of effluents is an efficient route to improve the conversion yield of DLI-MOCVD process making it cost-effective and competitive to produce protective carbide coatings of transition metals which share the same metal zero chemistry

An integrated approach for prescribing fewer chest x-rays in the ICU

Chest x-rays (CXRs) are the main imaging tool in intensive care units (ICUs). CXRs also are associated with concerns inherent to their use, considering both healthcare organization and patient perspectives. In recent years, several studies have focussed on the feasibility of lowering the number of bedside CXRs performed in the ICU. Such a decrease may result from two independent and complementary processes: a raw reduction of CXRs due to the elimination of unnecessary investigations, and replacement of the CXR by an alternative technique. The goal of this review is to outline emblematic examples corresponding to these two processes. The first part of the review concerns the accumulation of evidence-based data for abandoning daily routine CXRs in mechanically ventilated patients and adopting an on-demand prescription strategy. The second part of the review addresses the use of alternative techniques to CXRs. This part begins with the presentation of ultrasonography or capnography combined with epigastric auscultation for ensuring the correct position of enteral feeding tubes. Ultrasonography is then also presented as an alternative to CXR for diagnosing and monitoring pneumothoraces, as well as a valuable post-procedural technique after central venous catheter insertion. The combination of the emblematic examples presented in this review supports an integrated global approach for decreasing the number of CXRs ordered in the ICU

The size of plume heterogeneities constrained by Marquesas isotopic stripes

International audienceThe scale and geometry of chemical and isotopic heterogeneities in the source of plumes have important scientific implications on the nature, composition and origin of plumes and on the dynamics of mantle mixing over time. Here, we address these issues through the study of Marquesas Islands, one of the Archipelagoes in Polynesia. We present new Sr, Nd, Pb, Hf isotopes as well as trace element data on lavas from several Marquesas Islands and demonstrate that this archipelago consists of two adjacent and distinct rows of islands with significantly different isotopic compositions. For the entire 5.5 Ma construction period, the northern islands, hereafter called the Ua Huka group, has had systematically higher 87Sr/86Sr and lower 206Pb/204Pb ratios than the southern Fatu Hiva group at any given 143Nd/144Nd value. The shape and curvature of mixing arrays preclude the ambient depleted MORB mantle as one of the mixing end-members. We believe therefore that the entire isotopic heterogeneity originates in the plume itself. We suggest that the two Marquesas isotopic stripes originate from partial melting of two adjacent filaments contained in small plumes or "plumelets" that came from a large dome structure located deep in the mantle under Polynesia. Low-degree partial melting under Marquesas and other "weak" Polynesian hot spot chains (Pitcairn-Gambier, Austral-Cook, Society) sample small areas of the dome and preserve source heterogeneities. In contrast, more productive hot spots build up large islands such as Big Island in Hawaii or Réunion Island, and the higher degrees of melting blur the isotopic variability of the plume source

Vers des combustibles encore plus robustes en cas d’accident

La protection de l’intérieur et de l’extérieur des gaines de combustible de réacteurs nucléaires contre leur oxydation à haute température est nécessaire pour garantir leur intégrité en conditions accidentelles. Pour ce faire, le procédé DLI-MOCVD a été développé pour déposer en paroi interne de gaine des revêtements à base de chrome : chrome métallique, carbures de chrome amorphes CrCx et carbures mixtes de chrome CrSiyCx. L’optimisation du procédé de dépôt a été réalisée par le couplage d’expériences et de simulations. Il a aussi été montré que la solution de précurseur organométallique et de solvant utilisée pouvait être directement recyclée en sortie de réacteur, sans étapes de séparation et de purification couteuses, augmentant le potentiel d’industrialisation du procédé. Les propriétés physico-chimiques et structurales des revêtements déposés avec ce procédé ont été caractérisées. L’évaluation de leur résistance à l’oxydation à 1 200 °C a révélé les excellentes performances des revêtements CrCx, puisqu’ils retardent l’oxydation catastrophique des gaines de plus de deux heures pour une épaisseur de 10 μm, permettant ainsi des interventions en conditions accidentelles

Differing marine animal biomass shifts under 21st century climate change between Canada's three ocean

Identificadors digitals: Digital object identifier for the 'European Research Council' (http://dx.doi.org/10.13039/501100000781) and Digital object identifier for 'Horizon 2020' (http://dx.doi.org/10.13039/501100007601)Unidad de excelencia María de Maeztu CEX2019-000940-MUnder climate change, species composition and abundances in high-latitude waters are expected to substantially reconfigure with consequences for trophic relationships and ecosystem services. Outcomes are challenging to project at national scales, despite their importance for management decisions. Using an ensemble of six global marine ecosystem models we analyzed marine ecosystem responses to climate change from 1971 to 2099 in Canada's Exclusive Economic Zone (EEZ) under four standardized emissions scenarios. By 2099, under business-as-usual emissions (RCP8.5) projected marine animal biomass declined by an average of −7.7% (±29.5%) within the Canadian EEZ, dominated by declines in the Pacific (−24% ± 24.5%) and Atlantic (−25.5% ± 9.5%) areas; these were partially compensated by increases in the Canadian Arctic (+26.2% ± 38.4%). Lower emissions scenarios projected successively smaller biomass changes, highlighting the benefits of stronger mitigation targets. Individual model projections were most consistent in the Atlantic and Pacific, but highly variable in the Arctic due to model uncertainties in polar regions. Different trajectories of future marine biomass changes will require regional-specific responses in conservation and management strategies, such as adaptive planning of marine protected areas and species-specific management plans, to enhance resilience and rebuilding of Canada's marine ecosystems and commercial fish stocks