Search results for "CH4"

Structural, catalytic and electrical investigation on La1-xSrxCr1-yFeyO3- δ as anodes for IT-SOFCs

2012

The methane Raman spectrum from 1200 to 5500 cm(-1): A first step toward temperature diagnostic using methane as a probe molecule in combustion syste…

2005

International audience; We present a study of the spontaneous Raman spectra of (CH4)-C-12 from 1200 to 5500 cm(-1) at various temperatures. This study is of interest from a fundamental as well as from a practical point of view with regards to the temperature diagnostic in hydrocarbon combustion. The present investigation shows that the spontaneous (CH4)-C-12 Raman spectra are very sensitive to temperature and that the complexity of methane spectra is not an obstacle to use methane as a probe molecule in laser-diagnostic techniques. Our study consists in determining the polarisability parameters of methane (CH4)-C-12, unknown at the present time, from spontaneous Raman spectra recorded at pr…

Expression pattern of Notch1, 2 and 3 and Jagged1 and 2 in lymphoid and stromal thymus components: distinct ligand–receptor interactions in intrathym…

1999

The suggested role of Notch1 or its mutants in thymocyte differentiation and T cell tumorigenesis raises the question of how the different members of the Notch family influence distinct steps in T cell development and the role played by Notch ligands in the thymus. We report here that different Notch receptor-ligand partnerships may occur inside the thymus, as we observed differential expression of Notch1, 2 and 3 receptors, their ligands Jagged1 and 2, and downstream intracellular effectors hairy and Enhancer of Split homolog 1 (HES-1) and hairy and Enhancer of Split homolog 5 (HES-5), depending on ontogenetic stage and thymic cell populations. Indeed, while Jagged2 is expressed in both st…

Thermomineral waters of Greece: geochemical characterization

2020

Spectroscopic tools for remote sensing of greenhouse gases CH4, CF4 and SF6

2003

International audience; Highly symmetrical molecules such as CH4, CF4 or SF6 are known to be atmospheric pollutants and greenhouse gases. High-resolution spectroscopy in the infrared is particularly suitable for the monitoring of gas concentration and radiative transfers in the earth's atmosphere. This technique requires extensive theoretical studies for the modeling of the spectra of such molecules (positions, intensities and shapes of absorption lines). Here, we have developed powerful tools for the analysis and the simulation of absorption spectra of highly symmetrical molecules. These tools have been implemented in the spherical top data system (STDS) and highly-spherical top data syste…

Ecosystem carbon response of an Arctic peatland to simulated permafrost thaw

2019

Permafrost peatlands are biogeochemical hot spots in the Arctic as they store vast amounts of carbon. Permafrost thaw could release part of these long-term immobile carbon stocks as the greenhouse gases (GHGs) carbon dioxide (CO 2 ) and methane (CH 4 ) to the atmosphere, but how much, at which time-span and as which gaseous carbon species is still highly uncertain. Here we assess the effect of permafrost thaw on GHG dynamics under different moisture and vegetation scenarios in a permafrost peatland. A novel experimental approach using intact plant–soil systems (mesocosms) allowed us to simulate permafrost thaw under near-natural conditions. We monitored GHG flux dynamics via high-resolution…

In-situ analysis of the gas-emissions of the Eastern Carpathians (Romania) using the Multi-Gas instrument

2019

The Multi-Gas instrument is an important tool for the investigations and monitoring of volcanic systems world- wide, because it can be easily placed on a volcano and can provide real-time data on the compositional changes of the fluids that are released (Aiuppa et al., 2005, Shinohara et al., 2005). We used a specially designed Multi-Gas to gather in situ compositional information about low-temperature, CO2-rich gases, emerging from different manifestations like dry gas emissions (mofettes), bubbling pools and springs. The instrument is equipped with two IR sensors for CO2 (0-100%) and CH4 (0-7%) and one electrochemical sensor for H2S (0-200 ppm). The Multi-Gas was used during several field…

Simulations on the mechanism of CNT bundle growth upon smooth and nanostructured Ni as well as θ-Al2O3 catalysts

2011

Abstract In the current study, we have performed ab initio DFT calculations on the gradually growing 2D periodic models of capped single-wall carbon nanotubes (SW CNTs) upon their perpendicular junctions with the Ni(111) substrate, in order to understand the peculiarities of the initial stage of their growth on either smooth or nanostructured catalytic particles. Appearance of the adsorbed carbon atoms upon the substrate follows from the dissociation of CVD hydrocarbon molecules, e.g., CH4: (CH4)ads → (CH)ads+3Hads and (CH)ads → Cads+Hads. (Since the effective growth of CNTs upon Ni nanoparticles occur inside the nanopores of amorphous alumina, we have also simulated analogous surface react…

Experimental and theoretical study of line mixing in methane spectra. III. The Q branch of the Raman nu(1) band

2000

International audience; The shape of the nu(1) Raman Q branch of CH4 perturbed by Ar and He at room temperature has been studied. Stimulated Raman spectroscopy (SRS) experiments have been made in the 2915-2918 cm(-1) spectral region for total pressures from 0.4 to 70 atm and mixtures of approximate to 5% CH4 with He and Ar. Analysis of the spectra demonstrates that the shape of the Q branch is significantly influenced by line mixing and much narrower than what is predicted by the addition of individual line profiles. For the first time, a model is proposed for the calculation and analysis of the effects of collisions on the considered spectra. In this approach, the rotational part of the re…

Etude théorique de surfaces d'énergie potentielle, de moment dipolaire et de polarizabilité des complexes de van der Waals CH4-N2 et C2H4-C2H4

2010

In the present thesis both ab initio and analytical calculations were carried out for thepotential energy, dipole moment and polarizability surfaces of the weakly bound van der Waals complexes CH4-N2 and C2H4-C2H4 for a broad range of intermolecular separations and configurations in the approximation of the rigid interacting molecules. For ab initio calculations the CCSD(T), CCSD(T)-F12 and less computationally expensive methods such as MP2, MP2-F12, SAPT, DFT-SAPT were employed (for all methods the aug-cc-pVTZ basis set was used). The BSSE correction was taken into account during the calculations. The analytical calculations were performed in the framework of the classical long-range appro…