Pacheco-Vazquez F.,CINVESTAV |
Caballero-Robledo G.A.,CIMAV |
Solano-Altamirano J.M.,CINVESTAV |
Altshuler E.,University of Habana |
And 2 more authors.
Physical Review Letters | Year: 2011
An object falling in a fluid reaches a terminal velocity when the drag force and its weight are balanced. Contrastingly, an object impacting into a granular medium rapidly dissipates all its energy and comes to rest always at a shallow depth. Here we study, experimentally and theoretically, the penetration dynamics of a projectile in a very long silo filled with expanded polystyrene particles. We discovered that, above a critical mass, the projectile reaches a terminal velocity and, therefore, an endless penetration. © 2011 American Physical Society.
Hernandez Vera M.,CNRS Laboratory of Waves and Complex Media |
Hernandez Vera M.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas |
Lique F.,CNRS Laboratory of Waves and Complex Media |
Dumouchel F.,CNRS Laboratory of Waves and Complex Media |
And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013
Modelling molecular abundances in the interstellar medium (ISM) requires accurate moleculardata. Then, accurate determination of collisional rate coefficients is an essential stepin order to estimate the cyanide/isocyanide abundances in interstellar clouds. In addition,cyanides/isocyanides are the most common metal-containing molecules in circumstellar gas.In this work, we have carried out calculations of rate coefficients for the rotational excitationof aluminium cyanide (AlCN), aluminium isocyanide (AlNC), magnesium cyanide (MgCN)and magnesium isocyanide (MgNC) molecules in collision with He. The calculations arebased on new two-dimensional potential energy surfaces obtained from highly correlated abinitio calculations. Coupled states quantum approximation was used to obtain pure rotational(de-)excitation cross-sections of AlCN, AlNC, MgCN and MgNC by He. The fine structuresplitting of MgCN and MgNC was taken into account through a technique based on infiniteordersudden scaling relationship. Rate coefficients for transitions among the first 26 rotationallevels of AlCN and AlNC and among the first 41 fine structure levels ofMgCN andMgNCwerecalculated for the temperature range between 5 and 100 K. Significant differences betweenthe rate coefficients of both isomers were observed. These differences confirm that specificcalculations have to be performed for each isomer in order to obtain the necessary level ofdetail. The new rate coefficients should induce important consequences on the determinationof metal abundance in the ISM. In particular, our work confirms that the AlCN molecule issignificantly less abundant than AlNC in the ISM. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
Sanz A.S.,Institute Fisica Fundamental IFF CSIC |
Martinez-Casado R.,Imperial College London |
Martinez-Casado R.,Autonomous University of Madrid |
Penate-Rodriguez H.C.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas |
And 2 more authors.
Annals of Physics | Year: 2014
Classical viscid media are quite common in our everyday life. However, we are not used to find such media in quantum mechanics, and much less to analyze their effects on the dynamics of quantum systems. In this regard, the Caldirola-Kanai time-dependent Hamiltonian constitutes an appealing model, accounting for friction without including environmental fluctuations (as it happens, for example, with quantum Brownian motion). Here, a Bohmian analysis of the associated friction dynamics is provided in order to understand how a hypothetical, purely quantum viscid medium would act on a wave packet from a (quantum) hydrodynamic viewpoint. To this purpose, a series of paradigmatic contexts have been chosen, such as the free particle, the motion under the action of a linear potential, the harmonic oscillator, or the superposition of two coherent wave packets. Apart from their analyticity, these examples illustrate interesting emerging behaviors, such as localization by "quantum freezing" or a particular type of quantum-classical correspondence. The reliability of the results analytically determined has been checked by means of numerical simulations, which has served to investigate other problems lacking of such analyticity (e.g.,the coherent superpositions). © 2014 Elsevier Inc.
Gonzalez I.,University of Sao Paulo |
Gonzalez I.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas |
Guzman F.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas |
Deppman A.,University of Sao Paulo
Physical Review C - Nuclear Physics | Year: 2014
We present recent improvements in the crisp code for nuclear reaction simulation. The photoproduction of vector mesons was included in the code, which can evaluate also final state interaction of these mesons with the nucleus. Effects such as shadowing, subthreshold production, and Pauli blocking can be observed. The model is described in detail and some important quantities, such as cross section and nuclear transparency, are calculated as examples of the potential of our code. © 2014 American Physical Society.
Batista-Leyva A.J.,CINVESTAV |
Batista-Leyva A.J.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas |
Pacheco-Vazquez F.,CINVESTAV |
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2010
We investigate the dynamics of a disk shaped intruder sliding on a granular monolayer. The monolayer is on an inclined transparent plane, tilted at an angle much smaller than the angle of avalanche. A high speed camera allows us to measure the dynamics of both, the intruder (filming from top) and the grains (filming from below). We find a frictional force with a dependence on the speed of the intruder. Moreover, calculating a Reynolds-like number, it is possible to highlight the influence of the density of the beads that form the monolayer on the dynamics of the disk. We also find that the fluidization produced by the intruder's action reduces substantially the effective friction coefficient. © 2010 The American Physical Society.
Rizo O.D.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas |
Castillo F.E.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas |
Lopez J.O.A.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas |
Merlo M.H.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas
Bulletin of Environmental Contamination and Toxicology | Year: 2011
Concentrations of Co, Ni, Cu, Zn, Pb and Fe in the top-soils (0-10 cm) from urbanized and un-urbanized areas of Havana city were measured by X-ray fluorescence analysis. The mean Co, Ni, Cu, Zn and Pb contents in the urban topsoil samples (13.9 ± 4.1, 66 ± 26, 101 ± 51, 240 ± 132 and 101 ± 161 mg kg -1, respectively) were compared with mean concentrations for other cities around the world. The results revealed the highest concentrations of metals in topsoil samples from industrial sites. Lowest metal contents were determined in the un-urbanized areas. The comparison with Dutch soil quality guidelines showed a slight contamination with Co, Ni Cu and Zn in all studied sites and with Pb in industrial soils. On the other hand, the metal-to-iron normalisation using Earth crust contents as background showed that soils from urbanized areas in Havana city (industrial sites, parks and school grounds) are moderately enriched with zinc, moderately to severe enriched (city parks and school grounds) and severe enriched (industrial sites) with lead. The values of integrated pollution index (IPI) indicated that industrial soils are middle and high contaminated by heavy metals (1.19 ≤ IPI ≤ 7.54), but enrichment index values (EI) shows that metal concentrations on the studied locations are not above the permissible levels for urban agriculture, except soils from power and metallurgical plants surroundings. © 2011 Springer Science+Business Media, LLC.
Martinez-Mesa A.,University of Habana |
Zhechkov L.,Jacobs University Bremen |
Yurchenko S.N.,University College London |
Heine T.,Jacobs University Bremen |
And 2 more authors.
Journal of Physical Chemistry C | Year: 2012
We investigate the effect of the structural characteristics of idealized nanoporous environments on the adsorption of molecular hydrogen. The storage capacities of the (n,n) armchair and zigzag carbon foams (n = 2-5) are evaluated in a broad range of thermodynamic conditions. Our calculations are performed within an extension of the density functional theory of liquids to quantum fluids at finite temperature (QLDFT) of particles obeying Bose-Einstein statistics. The exchange-correlation (excess) functional is derived from the empirical equation of state of the homogeneous system. Graphitic foams are found to exhibit hydrogen uptakes similar to other carbonaceous materials, the largest gravimetric capacity being that of the (5,5) zigzag structure (∼4.5% at T = 77 K). The storage properties show a rather smooth dependence on the size of the pore. The effects of the H 2-H 2 interactions on adsorption isotherms are evaluated via the comparison of QLDFT results with calculations based on the ideal gas approximation. © 2012 American Chemical Society.
Perez-Gramatges A.,Dalhousie University |
Perez-Gramatges A.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas |
Chatt A.,Dalhousie University
Journal of Radioanalytical and Nuclear Chemistry | Year: 2012
A method for the preconcentration of Cu(II) by cloud point extraction (CPE) followed by its determination using neutron activation analysis (NAA) was developed. The method involves the use of a nonionic surfactant, namely PONPE-7.5, and a chelating agent 1-(2-pyridylazo)-2-naphthol (PAN). The phase diagram of the surfactant was constructed and the effects of different additives on the cloud point were investigated. Factors, such as the solution pH, ionic strength, temperature, and concentrations of chelating agent and surfactant, which can influence the extraction efficiency of the metal, were optimized. The copper(II) chelate was extracted into a surfactant-rich phase of small volume with a recovery of nearly 100% and a preconcentration factor of 60. The small volume of the surfactant-rich phase obtained complies with the green chemistry concept, allowing the design of extraction procedures having lower toxicity than those using organic solvents. The method was applied to tap water samples. © 2012 Akadémiai Kiadó, Budapest, Hungary.
Arbelo-Gonzalez W.,CNRS Institute of Molecular Sciences |
Arbelo-Gonzalez W.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas |
Bonnet L.,CNRS Institute of Molecular Sciences |
Garcia-Vela A.,Institute Fisica Fundamental
Physical Chemistry Chemical Physics | Year: 2013
The semiclassical Wigner treatment of Brown and Heller [J. Chem. Phys. 1981, 75, 186] is applied to direct triatomic (or triatomic-like polyatomic) photodissociations with the aim of accurately predicting final state distributions at relatively low computational cost, and having available a powerful interpretative tool. For the first time, the treatment takes rotational motions into account. The proposed formulation closely parallels the quantum description as far as possible. An approximate version is proposed, which is still accurate while numerically much more efficient. In addition to being weighted by usual vibrational Wigner distributions, final phase space states appear to be weighted by new rotational Wigner distributions. These densities have remarkable structures clearly showing that classical trajectories most contributing to rotational state j are those reaching the products with a rotational angular momentum close to [j(j + 1)]1/2 (in units). The previous methods involve running trajectories from the reagent molecule onto the products. The alternative backward approach [L. Bonnet, J. Chem. Phys., 2010, 133, 174108], in which trajectories are run in the reverse direction, is shown to strongly improve the numerical efficiency of the most rigorous method in addition to being state-selective, and thus, ideally suited to the description of state-correlated distributions measured in velocity imaging experiments. The results obtained by means of the previous methods are compared with rigorous quantum results in the case of Guo's triatomic-like model of methyl iodide photodissociation [J. Chem. Phys., 1992, 96, 6629] and close agreement is found. In comparison, the standard method of Goursaud et al. [J. Chem. Phys., 1976, 65, 5453] is only semi-quantitative. © 2013 the Owner Societies.
Rodriguez L.,University "Marta Abreu" of Las Villas |
Cardenas R.,University "Marta Abreu" of Las Villas |
Rodriguez O.,Instituto Superior Of Tecnologias Y Ciencias Aplicadas
International Journal of Astrobiology | Year: 2013
Abstract We modify a mathematical model of photosynthesis to quantify the perturbations that high energy muons could make on aquatic primary productivity. Then, we apply this in the context of the extragalactic shock model, according to which Earth receives an enhanced dose of high-energy cosmic rays when it is at the galactic north. We obtain considerable reduction in the photosynthesis rates, consistent with potential drops in biodiversity. Copyright © Cambridge University Press 2013Â.