Adsorption de PCB par des phases HDL organomodifiées

International audienceLes PCB sont des polluants persistants pour lesquels il faut encore chercher des solutions permettant de les retirer des sédiments. Le lavage par des tensioactifs offre de bons rendements de nettoyage. Il faut ensuite traiter les eaux du lessivage. Les Hydroxydes Doubles Lamellaires (HDL) ont montré des capacités intéressantes pour l'adsorption de polluants. L'insertion de tensioactifs lors de la synthèse de ces matériaux permet d'intercaler des polluants hydrophobes entre les feuillets brucitiques de ces argiles anioniques. Cette étude a pour objectif de tester la capacité de HDL à piéger un membre de la famille des PCB, le 4-chlorobiphényle (PCB 3). Les matériaux utilisés, à deux variantes du rapport MII/MIII, sont composés de zinc (Zn) et d'aluminium (Al) et intercalés avec du dodécylsulfate de sodium ou du dodécylbenzènesulfonate de sodium dès leur synthèse, ou encore des phases ZnAl-Chlore, mises en contact avec de l'acide humique après leur synthèse. Les HDL modifiés avec du tensioactifs montrent une forte capacité à la rétention du PCB 3, de l'ordre de 97% adsorbés, ainsi que les phases précipitées en présence du polluant. Les HDL sur lesquels est adsorbé l'acide humique montrent une capacité de dépollution de l'effluent bien inférieure, avec un maximum de 50% de PCB 3 adsorbés

Searching for a Stochastic Background of Gravitational Waves with LIGO

The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed the fourth science run, S4, with significantly improved interferometer sensitivities with respect to previous runs. Using data acquired during this science run, we place a limit on the amplitude of a stochastic background of gravitational waves. For a frequency independent spectrum, the new limit is $\Omega_{\rm GW} < 6.5 \times 10^{-5}$. This is currently the most sensitive result in the frequency range 51-150 Hz, with a factor of 13 improvement over the previous LIGO result. We discuss complementarity of the new result with other constraints on a stochastic background of gravitational waves, and we investigate implications of the new result for different models of this background.Comment: 37 pages, 16 figure

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Albiglutide and cardiovascular outcomes in patients with type 2 diabetes and cardiovascular disease (Harmony Outcomes): a double-blind, randomised placebo-controlled trial

Background: Glucagon-like peptide 1 receptor agonists differ in chemical structure, duration of action, and in their effects on clinical outcomes. The cardiovascular effects of once-weekly albiglutide in type 2 diabetes are unknown. We aimed to determine the safety and efficacy of albiglutide in preventing cardiovascular death, myocardial infarction, or stroke. Methods: We did a double-blind, randomised, placebo-controlled trial in 610 sites across 28 countries. We randomly assigned patients aged 40 years and older with type 2 diabetes and cardiovascular disease (at a 1:1 ratio) to groups that either received a subcutaneous injection of albiglutide (30–50 mg, based on glycaemic response and tolerability) or of a matched volume of placebo once a week, in addition to their standard care. Investigators used an interactive voice or web response system to obtain treatment assignment, and patients and all study investigators were masked to their treatment allocation. We hypothesised that albiglutide would be non-inferior to placebo for the primary outcome of the first occurrence of cardiovascular death, myocardial infarction, or stroke, which was assessed in the intention-to-treat population. If non-inferiority was confirmed by an upper limit of the 95% CI for a hazard ratio of less than 1·30, closed testing for superiority was prespecified. This study is registered with ClinicalTrials.gov, number NCT02465515. Findings: Patients were screened between July 1, 2015, and Nov 24, 2016. 10 793 patients were screened and 9463 participants were enrolled and randomly assigned to groups: 4731 patients were assigned to receive albiglutide and 4732 patients to receive placebo. On Nov 8, 2017, it was determined that 611 primary endpoints and a median follow-up of at least 1·5 years had accrued, and participants returned for a final visit and discontinuation from study treatment; the last patient visit was on March 12, 2018. These 9463 patients, the intention-to-treat population, were evaluated for a median duration of 1·6 years and were assessed for the primary outcome. The primary composite outcome occurred in 338 (7%) of 4731 patients at an incidence rate of 4·6 events per 100 person-years in the albiglutide group and in 428 (9%) of 4732 patients at an incidence rate of 5·9 events per 100 person-years in the placebo group (hazard ratio 0·78, 95% CI 0·68–0·90), which indicated that albiglutide was superior to placebo (p&lt;0·0001 for non-inferiority; p=0·0006 for superiority). The incidence of acute pancreatitis (ten patients in the albiglutide group and seven patients in the placebo group), pancreatic cancer (six patients in the albiglutide group and five patients in the placebo group), medullary thyroid carcinoma (zero patients in both groups), and other serious adverse events did not differ between the two groups. There were three (&lt;1%) deaths in the placebo group that were assessed by investigators, who were masked to study drug assignment, to be treatment-related and two (&lt;1%) deaths in the albiglutide group. Interpretation: In patients with type 2 diabetes and cardiovascular disease, albiglutide was superior to placebo with respect to major adverse cardiovascular events. Evidence-based glucagon-like peptide 1 receptor agonists should therefore be considered as part of a comprehensive strategy to reduce the risk of cardiovascular events in patients with type 2 diabetes. Funding: GlaxoSmithKline

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Adsorption of PCB 3 on organomodified LDHs

http://seesib.univ-bpclermont.fr/emec12/pages/fascicule.pdfInternational audience1200 million ton of Polychlorinated biphenyls (PCBs) have been produced worldwide and about 400 million tons are considered to be spread in the Environment. PCBs are persistent pollutants and highly immunotoxic toxic and carcinogenic. They may concentrate in river sediments and strongly affect ecosystems and biodiversity. Conventional cleaning processes are environmental non-friendly methods and there is still need to look for alternative ways of treating these contaminations. Washing sediments with surfactant solutions offers good results. Layered Double Hydroxides (LDH) are synthetic anionic clays that have proved to be good adsorbant for both surfactant and organic pollutants. Modification of LDH by anionic surfactant or polymer enhances their adsorption properties toward hydrophobic xenobiotics. This study aims to develop a new cleaning process based on the adsorption of PCBs by organically modified LDH. 4-chlorobiphenyl (PCB 3) was used as a model. ZnRAl LDH materials with variable anion exchange capacities, intercalated by sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (SDBS) or humic acid were tested as new sorbents. PCB 3 adsorptions were processed either by intercalation or direct coprecipitation (scheme). Surfactant modified LDH show a great ability to trap PCB 3, about 97% adsorbed, all the same by coprecipitation with pollutant. Humic acid adsorbed LDH are less efficient, with a maximum of 50% of adsorption

Macrodispersion of amorphous precipitated silica micropearls in an elastomer matrix: Role of silica intrinsic parameters

National audienceThe development of highly dispersible silica micropearls by Rhodia led to the introduction of silica as a reinforcing filler in Green tyres in 1992 by Michelin. However new environmental constraints imply to further improve the silica dispersion process. The objective of the present work was to investigate the role of silica intrinsic parameters on its dispersibility in order to determine key parameters to improve the silica dispersion. The behaviour of different silica grades was thus investigated: two classical silica micropearl grades for tyre applications different in their specific area (silica Z1165MP with a high specific area and silica Z1115MP with a lower specific area), the same grades chemically modified with a covering agent (silane), and pilot grades (same specific area, same aggregate structure as Z1165MP) synthesized by Rhodia where the physico-chemistry of the silica surface was modified during the silica process. The dispersion behaviour was characterized in model conditions: in air (impact on wall) and under shear in a SBR matrix (rheo-optical device). The direct observation of dispersion mechanism in a SBR matrix under shear showed that the Z1115MP dispersed via an efficient mechanism of disintegration with the sudden breakage of the micropearl into micron size fragments above a low critical stress whereas the Z1165MP ruptured into a few large fragments at a higher stress. The post-chemical modification of the silica surface using silane had no effect on the silica dispersion compared to raw materials. However the modification of the physico-chemistry of the silica surface during the silica process implied changes in the internal organisation of the micropearl and allowed to modify the dispersion mechanism

Mechanisms of dispersion in silica filled elastomers: Input of different approaches

International audiencePrecipitated silica is traditionally used as reinforcing filler in rubber applications. In pneumatic manufacture, it offers several advantages compared to carbon black. Indeed, in tyre treads, precipitated silica can yield a lower rolling resistance and better wet grip at equal wear resistance than carbon black.Filler dispersion can be characterized using different methods (. In the present work we use three different approaches to compare the dispersability of two grades of amorphous precipitated silica in the shape of micropearls, characterized by different specific areas. The three approaches are: the first approach is based on the analysis of the behaviour of silica micropearls under mechanical stress in air (fluidized bed and impact on wall) and in water (ultrasounds), dispersion kinetics of silica measured into air or water with the development of specific descriptors to follow dispersion kinetics, the second method is based on the characterization of dispersion mechanisms of silica micropearls into the elastomer matrix in the diluted regime via the use of a transparent counter-rotating plate-and-plate shear cell coupled with an optical microscope. In this case, the micropearl is subjected to hydrodynamic stresses due to the shear of the elastomer matrix, the last method is based on the analysis of dispersion during the mixing operation of silica and the elastomer in an internal mixer coupling information from rheology, bound rubber and SEM to follow the dispersion.We will show that the different approaches bring complementary information on the dispersion mechanisms but also on the intrinsic properties of silica