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Quintas-Sanchez E.,InSTEC | Quintas-Sanchez E.,University of Bordeaux 1 | Quintas-Sanchez E.,French National Center for Scientific Research | Larregaray P.,University of Bordeaux 1 | And 3 more authors.
Journal of Physical Chemistry C | Year: 2014

Classical trajectory simulations, using potential energy surfaces of ab initio quality, are performed to investigate the influence of crystal symmetry on the Eley-Rideal abstraction dynamics of N atoms colliding, under normal incidence, N-preadsorbed tungsten (100) and (110) surfaces. Low-energy reactivity (<0.5 eV collision energy) results much higher for the (110) crystallographic plane. Such a feature stems from the topology of the interactions upon approach of the N-gas atom toward the N adsorbate: the strong lateral corrugation responsible for a significant threshold for recombination on the (100) surface is much smoother on the (110) plane, allowing low-energy incident atoms to react. Temperature is found to only slightly affect reactivity. © 2014 American Chemical Society. Source


Gonzalez J.A.,University of Santiago de Compostela | Hernandez-Garces A.,InSTEC | Rodriguez A.,University of Santiago de Compostela | Saavedra S.,University of Santiago de Compostela | And 4 more authors.
HARMO 2014 - 16th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes, Proceedings | Year: 2014

CALMET meteorological model is evaluated during a typical dry season period in a coastal domain at the Caribbean region, using four different CALMET input datasets. Evaluation was focused in terms of surface wind and temperature modeling performance. As input data, Weather Research and Forecast model (WRF) results are combined to meteorological measurements from different sites. CALMET results statistics (both relative and absolute) are calculated over sites not used as input data providers. Relative wind speed statistics values are high, due to the weak winds along the study period. However, absolute statistics are better. Also, a significant improvement in both wind speed and temperature statistics, both relative and absolute, is observed as more sites provide input data. © Crown Copyright 2014 Dstl. Source


Lopez Diaz A.,Hospital Hermanos Ameijeiras | Reynosa R.,InSTEC | Martin J.M.,Hospital Hermanos Ameijeiras | Castillo J.,Clinical Research Center | Torres L.A.,Clinical Research Center
IFMBE Proceedings | Year: 2015

Optimization and verification of Patient- Specific Treatment planning with unsealed I-131 sources is a desirable goal from medical and radiation protection point of view. To obtain a practical protocol to combine the estimation of the related parameters with patient’s specific treatment dose in hyperthyroidism diseases, four equipments were studied (Iodine Probe, a Philips Forte Camera with pin-hole collimators, a Mediso Nucline with HEGP for planar and SPECT techniques and a Mediso AnySan SPECT/CT). The linear behaviour on diagnostic and therapeutic activity range was verified, showing a linear correlation fitting factor R2 > 0.99. The differences between thyroid uptake determinations in all equipment were less than 6% for therapeutic activities and less than 1.1% in the diagnostic range. The combined protocol to calculate, with only one administration of I131, all the necessary parameters to the treatment dose estimation in 2D or 3D, was established and verified, avoiding wasting time with gamma cameras. Following this protocol the difference between apparent and calculated activities were less than 3%. © Springer International Publishing Switzerland 2015. Source


Quintas-Sanchez E.,InSTEC | Quintas-Sanchez E.,University of Bordeaux 1 | Crespos C.,University of Bordeaux 1 | Larregaray P.,University of Bordeaux 1 | And 2 more authors.
Journal of Chemical Physics | Year: 2013

Quasiclassical trajectories simulations are performed to study the influence of surface temperature on the dynamics of a N atom colliding a N-preadsorbed W(100) surface under normal incidence. A generalized Langevin surface oscillator scheme is used to allow energy transfer between the nitrogen atoms and the surface. The influence of the surface temperature on the N 2 formed molecules via Eley-Rideal recombination is analyzed at T = 300, 800, and 1500 K. Ro-vibrational distributions of the N2 molecules are only slightly affected by the presence of the thermal bath whereas kinetic energy is rather strongly decreased when going from a static surface model to a moving surface one. In terms of reactivity, the moving surface model leads to an increase of atomic trapping cross section yielding to an increase of the so-called hot atoms population and a decrease of the direct Eley-Rideal cross section. The energy exchange between the surface and the nitrogen atoms is semi-quantitatively interpreted by a simple binary collision model. © 2013 American Institute of Physics. Source


Quintas-Sanchez E.,InSTEC | Quintas-Sanchez E.,CNRS Institute of Molecular Sciences | Larregaray P.,CNRS Institute of Molecular Sciences | Crespos C.,CNRS Institute of Molecular Sciences | And 3 more authors.
Journal of Chemical Physics | Year: 2012

The scattering of atomic nitrogen over a N-pre-adsorbed W(100) surface is theoretically described in the case of normal incidence off a single adsorbate. Dynamical reaction mechanisms, in particular Eley-Rideal (ER) abstraction, are scrutinized in the 0.1-3.0 eV collision energy range and the influence of temperature on reactivity is considered between 300 and 1500 K. Dynamics simulations suggest that, though non-activated reaction pathways exist, the abstraction process exhibits a significant collision energy threshold (0.5 eV). Such a feature, which has not been reported so far in the literature, is the consequence of a repulsive interaction between the impinging and the pre-adsorbed nitrogens along with a strong attraction towards the tungsten atoms. Above threshold, the cross section for ER reaction is found one order of magnitude lower than the one for hot-atoms formation. The abstraction process involves the collision of the impinging atom with the surface prior to reaction but temperature effects, when modeled via a generalized Langevin oscillator model, do not affect significantly reactivity. © 2012 American Institute of Physics. Source

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