Contribution à l'étude d'Andrographis paniculata (Nees.)

LYON1-BU Santé (693882101) / SudocSudocFranceF

Performances comparées de systèmes de culture destinés à l’alimentation animale en France et aux États-Unis

The combination of corn, peas and rapeseed, three crops well adapted to soil and climatic European conditions, can form the basis of balanced rations for pig farms. Despite production costs significantly higher, from the farm than those permitted by cropping systems based on corn and soybeans in the US, local supplies of protein-rich materials (PRM) is competitive economically, because of transportation costs and tariff protection on cereals in Europe. However, the supply of local origin PRM is far from meeting the needs of industry feed since nearly half of those needs is imported. This deficit ultimately returns to the question of the balance of French and European crop rotations, showing a surplus of grain and a protein déficit. Various case studies suggest that rebalancing rotations would be possible to improve the local supply and the economic and environmental performance of cropping systems corresponding. This would occur even in areas with already a large enough diversification of crops as Picardy and the Ile de France, analyzed in this article

Adsorption mechanisms of trivalent gold on iron- and aluminum-(oxy)hydroxides. Part 1: X-ray absorption and Raman scattering spectroscopic studies of Au(III) adsorbed on ferrihydrite, goethite, and boehmite

International audienceGold adsorption products on powdered ferrihydrite, goethite, and boehmite samples, prepared by reacting Au(III)-Cl solutions ([Au] = 4.2 x 10(-5)-9.0 x 10(-3) M; [Cl] = 0.017-0.6 M) with these adsorbents at pH Values of 4 to 9 and Au adsorption densities ranging from 0.046 to 1.53 mumol/m(2) were characterized using Au-L-III XAFS spectroscopy. The solutions (before and after uptake) were investigated by Raman scattering to determine speciation and by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) to determine solution composition. We present an analysis of several effects that are observed in the Au L-III-edge XAFS spectra, including X-ray beam.-induced photo-reduction, multi-electronic excitations, disorder effects. and multiple scattering, that would complicate interpretation of the spectra if not accounted for. A combination of methods (spectral deconvolution, principal component analysis, spectral inversion, and wavelet analysis) was used to identify and quantify these effects, to characterize the nature of mixed ligands around gold, and to distinguish between multiple-scattering features and features due to next-nearest neighbors in the XAFS spectra. Analysis of the Au-L-III XAFS spectra showed that Au(III) is present as square-planar Au(III)(O,Cl)(4) complexes in the aqueous solutions and on the surfaces of the Al/Fe-(oxy)hydroxide adsorption samples with dominantly 0 ligands at pH > 6 and mixed O/Cl ligands at lower pH values. The EXAFS-derived Au-O and Au-Cl distances are 2.00(2) and 2.28(2) Angstrom, respectively, and the magnitudes of the Debye-Waller factors and third cumulants from anharmonic analyses indicate very little thermal or positional disorder around Au(III) in the adsorption samples. Iron second neighbors are present around An in the Au(III)/ferrihydrite and Au(III)/ Goethite adsorption samples, with Au-Fe distances of 3.1(1) and 3.3(1) Angstrom. In boehmite, two sets of Au-Al distances were detected at 3.0(1) and 3.2(1) Angstrom. A reverse Monte Carlo study of the XAFS spectroscopic data suggests the presence of a continuum of edge-shared AuO4-FeO6 distances, which cannot be described correctly by a classical model of these data in which only a mean distance (although severely under-estimated) is derived. Copyright (C) 2004 Elsevier Ltd

Splitting of

FTIR spectra of the antisymmetric stretch $\nu_3$ and symmetric bending $\nu_2$ vibrational modes of isotopic species of CO2 trapped in argon matrix are recorded at 5 K with a resolution of $0.15 {\rm cm}^{-1}$. A splitting of the $\nu_2$ mode is observed for the different species in the trapping site termed unstable. Considering this splitting and the width of the $\nu_3$ line observed for this unstable site, one expects this site to be larger than the stable one. A theoretical model is elaborated to interpret this splitting. Calculations performed at harmonic level of approximation for vibrational modes in a single substitutional site (S1) and a double substitutional one (S2) in a fcc distorted argon lattice to minimize the free energy of the molecule-matrix system, show the splitting to occur in the larger site. The latter result leads us to invert former attribution of the sites: the stable site is a single substitutional one, whereas the unstable site is a double substitutional one

Crude oils as ore fluids: An experimental in-situ XAS study of gold partitioning between brine and organic fluid from 25 to 250°C

Organic matter can be associated with mineralization in hydrothermal ore deposits. One hypothesis is that this organic matter represents remnants of organic fluids (crude oils) that were competing with aqueous fluids for metal transport and contributed to metal endowment. We investigated the transport of gold (Au) in model oil compounds (S-free n-dodecane, CH3(CH2)10CH3, DD; and S-bearing 1-dodecanethiol, CH3(CH2)10CH2SH; DDT) from 25 °C to 250 °C using in-situ synchrotron X-ray absorption spectroscopy (XAS) experiments to determine the speciation and the structural properties of gold complexes in the aqueous- and oil-based fluids. For most experiments, DD or DDT were in contact with Au-bearing acidified water, or acidified water plus 10 wt% NaCl (pH25°C = 1.85 in both cases). Gold rapidly partitioned from the aqueous phase into DD and DDT. Below 125 °C, Au(III)Cl is dominant in the DD and the adjacent water with a refined coordination number (CN) of chloride of 4.0(3) and an AuCl bond length of 2.28 Å, consistent with the tetrachloroaurate complex (AuCl4−) being stable in both the aqueous and organic phases. In contrast, Au(III) is rapidly reduced in the presence of DDT and an Au(I) complex dominates in both water and adjacent DDT with a CN of sulfur ∼2.0, suggesting a [RS-Au-SR]− (RS = DDT with deprotonated thiol group) complex with AuS bond lengths ranging from 2.29(1) Å to 2.31(3) Å. In an open system of DDT in contact with water, of which the water and DDT were analyzed separately, AuCl4− was dominant in the water phase, and Au(RS)2− dominant in DDT, possibly due to different equilibration kinetics in the beaker and glassy carbon tube. Since sulfur and organothiol compounds are ubiquitous and abundant components in natural oils, this study demonstrates the potential of natural oils to scavenge and enrich gold from co-existing gold-bearing brines. In particular, Au(I) organothiol complexes may contribute to transport in low-temperature (<125 °C) ore fluids such as those in basinal environments – in both hydrothermal fluids and oils. At temperatures ≥125 °C, gold was reduced to metallic gold in all experiments, suggesting that organo-stabilized nanoparticles may be the major form of gold to be scavenged, concentrated or transported in crude oils at these conditions. The results imply that brine-oil interactions may enrich Au in oils, and that oils may be an effective ore fluid in sedimentary environments