Surface tension of spherical drops from surface of tension.

The determination of surface tension of curved interfaces is a topic that raised many controversies during the last century. Explicit liquid-vapor interface modelling (ELVI) was unable up to now to reproduce interfacial behaviors in drops due to ambiguities in the mechanical definition of the surface tension. In this work, we propose a thermodynamic approach based on the location of surface of tension and its use in the Laplace equation to extract the surface tension of spherical interfaces from ELVI modelling.

Sulphide quinone reductase contributes to hydrogen sulphide metabolism in murine peripheral tissues but not in the CNS.

BACKGROUND AND PURPOSE: Hydrogen sulphide (H(2) S) is gaining acceptance as a gaseous signal molecule. However, mechanisms regarding signal termination are not understood. We used stigmatellin and antimycin A, inhibitors of sulphide quinone reductase (SQR), to test the hypothesis that the catabolism of H(2) S involves SQR. EXPERIMENTAL APPROACH: H(2) S production and consumption were determined in living and intact mouse brain, liver and colonic muscularis externa using gas chromatography and HPLC. Expressions of SQR, ethylmalonic encephalopathy 1 (Ethe1) and thiosulphate transferase (TST; rhodanese) were determined by RT-PCR and immunohistochemistry. KEY RESULTS: In the colonic muscularis externa, H(2) (35) S was catabolized to [(35) S]-thiosulphate and [(35) S]-sulphate, and stigmatellin reduced both the consumption of H(2) (35) S and formation of [(35) S]-thiosulphate. Stigmatellin also enhanced H(2) S release by the colonic muscularis externa. In the brain, catabolism of H(2) (35) S to [(35) S]-thiosulphate and [(35) S]-sulphate, which was stigmatellin-insensitive, partially accounted for H(2) (35) S consumption, while the remainder was captured as unidentified (35) S that was probably bound to proteins. Levels of mRNA encoding SQR were higher in the colonic muscularis externa and the liver than in the brain. CONCLUSIONS AND IMPLICATIONS: These data support the concept that termination of endogenous H(2) S signalling in the colonic muscularis externa occurs via catabolism to thiosulphate and sulphate partially via a mechanism involving SQR. In the brain, it appears that H(2) S signal termination occurs partially through protein sequestration and partially through catabolism not involving SQR. As H(2) S has beneficial effects in animal models of human disease, we suggest that selective inhibition of SQR is an attractive target for pharmaceutical development.

Experimental and theoretical assessment of the multi-domain flow behaviour in a waste body during leachate infiltration.

The optimisation of landfill operation is a key challenge for the upcoming years. A promising solution to improve municipal solid waste (MSW) management is the bioreactor technology. A meso-scale (around 1m(3)) experimental set-up was performed to study the effect of moisture control in low density conditions with different leachate injection operations and bioreactor monitoring including the use of a neutron probe. The moisture content distribution evolution demonstrates a multi-domain flow behaviour. A classic van Genuchten-Mualem description of the connected porosity proved insufficient to correctly describe the observed phenomena. A bimodal description of the connected porosity is proposed as solution and a connected/non-connected porosities numerical model was applied to the results. The model explains the experimental results reasonably well.

Thermal transport in isotopically disordered carbon nanotubes: a comparison between Green's functions and Boltzmann approaches.

We present a study of the phononic thermal conductivity of isotopically disordered carbon nanotubes. In particular, the behaviour of the thermal conductivity as a function of the system length is investigated, using Green's function techniques to compute the transmission across the system. The method is implemented using linear scaling algorithms, which allow us to reach systems of lengths up to L = 2.5 µm (with up to 200 000 atoms). As for 1D systems, it is observed that the conductivity diverges with the system size L. We also observe a dramatic decrease of the thermal conductance for systems of experimental sizes (roughly 80% at room temperature for L = 2.5 µm), when a large fraction of isotopic disorder is introduced. The results obtained with Green's function techniques are compared to results obtained with a Boltzmann description of thermal transport. There is a good agreement between both approaches for systems of experimental sizes, even in the presence of Anderson localization. This is particularly interesting since the computation of the transmission using Boltzmann's equation is much less computationally expensive, so that larger systems may be studied with this method.