Analytical Description of X-Ray Peaks: Application to L X-Ray Spectra Processing of Lanthanide Elements by Means of the Electron Probe Micro-Analyzer

The shape of Lα X-ray peaks analyzed by means of a LiF (200 plane) monochromator was described by a pseudo-Voigt function: P(λ) = 0.35 P1(λ)+ 0.65 P2(λ) where P1(λ) and P2(λ) are a Gaussian and a Lorentzian distribution centered at the same wavelength, with the same amplitude and half-width and in relative proportion 0.35 and 0.65 respectively. For peaks occurring at wavelength greater than ≃ 0.17 nm, a Gaussian offset was added in order to correct the asymmetry of peaks resulting from the monochromator mounting within the spectrometer. The effective wavelength resolution was obtained by quadrature addition of the instrumental resolution and the natural width of the X-ray peaks. It has been shown that the difference in peak width of the L emission peaks of the lanthanide elements resulted from their difference in their natural widths. For these elements, the Lβ2, Lγ1 and Lγ2 were found to be accompanied by non-diagram lines, Lβ14, Lγ9 and Lγ10 respectively. The wavelength separation distances Lβ14-Lβ2, Lγ9-Lγ1 and Lγ10-Lγ2 were found consistent with the distances derived from the plasmon theory

Structure and dynamics of Oxide Melts and Glasses : a view from multinuclear and high temperature NMR

Solid State Nuclear Magnetic Resonance (NMR) experiments allow characterizing the local structure and dynamics of oxide glasses and melts. Thanks to the development of new experiments, it now becomes possible to evidence not only the details of the coordination state of the network formers of glasses but also to characterize the nature of polyatomic molecular motifs extending over several chemical bonds. We present results involving 31P homonuclear experiments that allow description of groups of up to three phosphate units and 27Al/17O heteronuclear that allows evidencing μ3 oxygen bridges in aluminate glasses and rediscussion of the structure of high temperature melts.Comment: Journal of Non-Crystalline Solids (2007) in press; Also available online at: http://crmht.cnrs-orleans.fr/Intranet/Publications/?id=207

Seismic Response to Injection Well Stimulation in a High-Temperature, High-Permeability Reservoir

Fluid injection into the Earth's crust can induce seismic events that cause damage to local infrastructure but also offer valuable insight into seismogenesis. The factors that influence the magnitude, location, and number of induced events remain poorly understood but include injection flow rate and pressure as well as reservoir temperature and permeability. The relationship between injection parameters and injection-induced seismicity in high-temperature, high-permeability reservoirs has not been extensively studied. Here we focus on the Ngatamariki geothermal field in the central Taupō Volcanic Zone, New Zealand, where three stimulation/injection tests have occurred since 2012. We present a catalog of seismicity from 2012 to 2015 created using a matched-filter detection technique. We analyze the stress state in the reservoir during the injection tests from first motion-derived focal mechanisms, yielding an average direction of maximum horizontal compressive stress (SHmax) consistent with the regional NE-SW trend. However, there is significant variation in the direction of maximum compressive stress (σ1), which may reflect geological differences between wells. We use the ratio of injection flow rate to overpressure, referred to as injectivity index, as a proxy for near-well permeability and compare changes in injectivity index to spatiotemporal characteristics of seismicity accompanying each test. Observed increases in injectivity index are generally poorly correlated with seismicity, suggesting that the locations of microearthquakes are not coincident with the zone of stimulation (i.e., increased permeability). Our findings augment a growing body of work suggesting that aseismic opening or slip, rather than seismic shear, is the active process driving well stimulation in many environments

Isolation of bis-indole alkaloids with antileishmanial and antibacterial activities from Peschiera van heurkii (syn. Tabernaemontana van heurkii)

Des extraits de feuilles et d'écorces de tiges de #Peschiera van heurkii (Muell. Arg.) L. Allorge, (Syn. #Tabernaemontana van heurkii Muell. Arg.) ont montré une activité antileishmanienne et antibactérienne significative. Les activités étaient concentrées dans les fractions alcaloïdiques, desquelles ont été isolés et identifiés 20 alcaloïdes indoliques et bis-indoliques. La plus forte activité leishmanicide et antibactérienne fut observée avec les alcaloïdes dimères conodurine (1), N-démethyle - conodurine (=gabunine) et conoduramine. Les deux premiers composés se sont avérés faiblement toxiques vis-à-vis des cellules hôtes les macrophages, tout en présentant une forte toxicité pour les formes intracellulaires du parasite. #In vitro$, l'alcaloïde (1) s'est avéré moins actif que le médicament de référence, le glucantime (=N-methylglucamine antimonate). (Résumé d'auteur

Effects of regional and local stresses on fault slip tendency in the southern Taranaki Basin, New Zealand

© 2019 Elsevier Ltd Determining the potential for faults to slip is widely employed for evaluating fault slip potential and associated earthquake hazards, and characterising hydrocarbon seal integrity and reservoir properties. Here we use borehole and 3D seismic reflection data to estimate stress orientations and magnitudes, fault geometries and slip tendency in the southern Taranaki Basin, New Zealand. Late Cenozoic normal faults in the basin range in strike from E-W to NE-SW and are associated with stress changes from basin to borehole scales. The Maui and Maari-Manaia regions, part of the eastern mobile belt, show a strike-slip/normal stress regime (SHmax ≥ Sv > Shmin). The Tui region, part of the western stable platform, shows a normal stress regime (Sv > SHmax > Shmin). Both regions have a mean SHmax azimuth of ENE-WSW. Although the southern Taranaki basin is undergoing active deformation at plate tectonic scales, the stress magnitudes appear insufficiently high to reactivate the faults assuming a classic coefficient of friction. SHmax azimuths and SHmax:Sv magnitude ratios vary locally between boreholes and with depth. A borehole that intersects an inactive seismic-scale fault and borehole-scale faults over a 150-m interval shows SHmax to rotate by up to 30° proximal to the faults, which are favourably orientated for slip in both strike-slip and normal regimes. The small borehole-scale faults may, however, be active within the inactive seismic scale fault's damage zone. We highlight changes of slip tendency along faults resulting from local variations in the stress field and non-planar fault geometries that could not be resolved using only seismic reflection data and regional stress tensor. In the Taranaki Basin additional sub-seismic fault mapping, stress information and mechanical rock property testing are required to realise the potential of stress-based prediction of along-fault permeability and fluid migration

Self-healing capacity of nuclear glass observed by NMR spectroscopy

Safe management of high level nuclear waste is a worldwide significant issue for which vitrification has been selected by many countries. There exists a crucial need for improving our understanding of the ageing of the glass under irradiation. While external irradiation by ions provides a rapid simulation of damage induced by alpha decays, short lived actinide doping is more representative of the reality. Here, we report radiological NMR experiments to compare the damage in International Simplified Glass (ISG) when irradiated by these two methods. In the 0.1 mole percent 244Cm doped glass, accumulation of high alpha decay only shows small modifications of the local structure, in sharp contrast to heavy ion irradiation. These results reveal the ability of the alpha particle to partially repair the damage generated by the heavy recoil nuclei highlighting the radiation resistance of nuclear glass and the difficulty to accurately simulate its behaviour by single ion beam irradiations