1,216 research outputs found
Case study of sulphur compounds emissions characterization
International audienceIn order to manage the methane and sulphur compounds emissions of a landfill area with deposits of plasterworks, a flux measurements study was conducted with a mobile laboratory, portable analysers and different chambers. The static chamber was first used in order to locate the methane hot spots. The funnel and the Total Reduced Sulphur (TRS) analyser allow the comparison between emissions of methane and hydrogen sulphide which represent the predominant sulphur compound. In a second stage, the variability of the hydrogen sulphide emissions was monitored with two dynamic chambers and a period of several days. Hydrogen sulphide emissions by cap are much lower than those predicted by the methane flux and the concentration of hydrogen sulphide in landfill gas (LFG)
Introduction des trocas (Trochus niloticus, L.) à Lifou par transplantation de juvéniles produits en aquaculture
Une opĂ©ration d'introduction de trocas (#Trochus niloticus L.$) a Ă©tĂ© effectuĂ©e Ă Lifou (Iles LoyautĂ©) avec des juvĂ©niles produits en aquaculture. Cette opĂ©ration reprĂ©sente une tentative de constitution Ă moyen terme d'un stock de trocas exploitable par les pĂȘcheurs locaux. (RĂ©sumĂ© d'auteur
Synthetic Microfiber and Microbead Exposure and Retention Time in Model Aquatic Species Under Different Exposure Scenarios
Synthetic microfibers have been reported in most aquatic environments and represent a large proportion of environmental microplastics. However, they remain largely under-represented in microplastic ecotoxicity studies. The present study aims to investigate particle interaction with, and retention time in, aquatic organisms comparing microfibers, and microbeads. We used brine shrimp (Artemia sp.) and fish (Gasterosteus aculeatus) as invertebrate and vertebrate models, respectively. Organisms were exposed to a mixture of microbeads (polyethylene, 27â32 ÎŒm) and microfibers (dope dyed polyester; 500 ÎŒm-long) for 2 h, at high concentrations (100,000 part./L) in order to maximize organism-particles interaction. Artemia were exposed in the presence or absence of food. Fish were exposed either via the trophic route or directly via water, and water exposures were performed either in freshwater or seawater. In the absence of food, Artemia ingested high numbers of microbeads, retained in their digestive tract for up to 96 h. Microfiber ingestion was very limited, and its egestion was fast. In the presence of food, no microfiber was ingested, microbead ingestion was limited, and egestion was fast (48 h). Limited particle ingestion was observed in fish exposed via water, and particle retention time in gut did not exceed 48 h, both for direct and trophic exposure. However, water exposures resulted in a higher number of particles present in gills, and average retention time was higher in gills, compared to gut. This suggests that gills are organs susceptible to microplastic exposure and should be taken into account in fish exposure and effect studies. Our results show that particle ingestion and retention by organisms differ between microbeads and microfibers, suggesting particle selection based on size, shape, and/or color and species-specific selective feeding. We also showed that the presence of food results in limited particle ingestion and retention in Artemia and that microbeads are more likely to be transferred to organisms from upper trophic levels than microfibers. Finally, fish exposure to particles was not significantly different between freshwater and seawater conditions
Power-law scaling behaviour of impedance signal time series of healthy subjects at rest
International audienc
Topological phases for bound states moving in a finite volume
We show that bound states moving in a finite periodic volume have an energy
correction which is topological in origin and universal in character. The
topological volume corrections contain information about the number and mass of
the constituents of the bound states. These results have broad applications to
lattice calculations involving nucleons, nuclei, hadronic molecules, and cold
atoms. We illustrate and verify the analytical results with several numerical
lattice calculations.Comment: 4 pages, 1 figure, version to appear in Phys. Rev. D Rapid
Communication
Exact Solutions to the Sine-Gordon Equation
A systematic method is presented to provide various equivalent solution
formulas for exact solutions to the sine-Gordon equation. Such solutions are
analytic in the spatial variable and the temporal variable and they
are exponentially asymptotic to integer multiples of as
The solution formulas are expressed explicitly in terms of a real triplet of
constant matrices. The method presented is generalizable to other integrable
evolution equations where the inverse scattering transform is applied via the
use of a Marchenko integral equation. By expressing the kernel of that
Marchenko equation as a matrix exponential in terms of the matrix triplet and
by exploiting the separability of that kernel, an exact solution formula to the
Marchenko equation is derived, yielding various equivalent exact solution
formulas for the sine-Gordon equation.Comment: 43 page
Improving the sensitivity of future GW observatories in the 1-10 Hz band: Newtonian and seismic noise
The next generation gravitational wave interferometric detectors will likely be underground detectors to extend the GW detection frequency band to frequencies below the Newtonian noise limit. Newtonian noise originates from the continuous motion of the Earthâs crust driven by human activity, tidal stresses and seismic motion, and from mass density fluctuations in the atmosphere. It is calculated that on Earthâs surface, on a typical day, it will exceed the expected GW signals at frequencies below 10 Hz. The noise will decrease underground by an unknown amount. It is
important to investigate and to quantify this expected reduction and its effect on the sensitivity of future detectors, to plan for further improvement strategies. We report about some of these aspects. Analytical models can be used in the simplest scenarios to get a better qualitative and semi-quantitative understanding. As more complete modeling can be done numerically, we will discuss also some results obtained with a finite-element-based modeling tool. The method is verified by comparing its results with the results of analytic calculations for surface detectors. A key point about noise models is their initial parameters and conditions, which require detailed information about seismic motion in a real scenario. We will describe an effort to characterize the seismic activity at the Homestake mine which is currently in progress. This activity is specifically aimed to provide informations and to explore the site as a possible candidate for an underground observatory. Although the only compelling reason to put the interferometer underground is to reduce the Newtonian noise, we expect that the more stable underground environment will have a more general positive impact on the sensitivity.We will end this report with some considerations about seismic and suspension noise
Numerical analysis of seismic wave amplification in Nice (France) and comparisons with experiments
The analysis of site effects is very important since the amplification of
seismic motion in some specific areas can be very strong. In this paper, the
site considered is located in the centre of Nice on the French Riviera. Site
effects are investigated considering a numerical approach (Boundary Element
Method) and are compared to experimental results (weak motion and
microtremors). The investigation of seismic site effects through numerical
approaches is interesting because it shows the dependency of the amplification
level on such parameters as wave velocity in surface soil layers, velocity
contrast with deep layers, seismic wave type, incidence and damping. In this
specific area of Nice, a one-dimensional (1D) analytical analysis of
amplification does not give a satisfactory estimation of the maximum reached
levels. A boundary element model is then proposed considering different wave
types (SH, P, SV) as the seismic loading. The alluvial basin is successively
assumed as an isotropic linear elastic medium and an isotropic linear
viscoelastic solid (standard solid). The thickness of the surface layer, its
mechanical properties, its general shape as well as the seismic wave type
involved have a great influence on the maximum amplification and the frequency
for which it occurs. For real earthquakes, the numerical results are in very
good agreement with experimental measurements for each motion component.
Two-dimensional basin effects are found to be very strong and are well
reproduced numerically
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