Fecha de publicación: 2011.
At present, approximately 1500 asteroids are known to evolve inside or sticked to the exterior 1:2 resonance with Mars at a ≃ 2.418 AU, being (142) Polana the largest member of this group. The effect of the forced secular modes superposed to the resonance gives rise to a complex dynamical evolution. Chaotic diffusion, collisions, close encounters with massive asteroids and mainly orbital migration due to the Yarkovsky effect generate continuous captures to and losses from the resonance, with a fraction of asteroids remaining captured over long time scales and generating a concentration in the semimajor axis distribution that exceeds by 20% the population of background asteroids. The Yarkovsky effect induces different dynamics according to the asteroid size, producing an excess of small asteroids inside the resonance. The evolution in the resonance generates a signature on the orbits, mainly in eccentricity, that depends on the time the asteroid remains captured inside the resonance and on the magnitude of the Yarkovsky effect. The greater the asteroids, the larger the time they remain captured in the resonance, allowing greater diffusion in eccentricity and inclination. The resonance generates a discontinuity and mixing in the space of proper elements producing misidentification of dynamical family members, mainly for Vesta and Nysa-Polana families. The half-life of resonant asteroids large enough for not being affected by the Yarkovsky effect is about 1 Gyr. From the point of view of taxonomic classes, the resonant population does not differ from the background population and the excess of small asteroids is confirmed.
Afiliación de los autores: Tabaré Gallardo, Carlos. Universidad de la República; Uruguay
Afiliación de los autores: Venturini, Julia. Universidad de la República; Uruguay
Afiliación de los autores: Roig, Fernando Virgilio. Ministério de Ciencia, Tecnologia e Innovacao. Observatorio Nacional; Brasil
Afiliación de los autores: Gil Hutton, Ricardo Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico "el Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico ; Argentina
Repositorio: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas
Fecha de publicación: 2010.
Molecular dynamics simulations have been carried out to investigate the structure and dynamics of liquid methanol confined in 3.3 nm diameter cylindrical silica pores. Three cavities differing in the characteristics of the functional groups at their walls have been examined: (i) smooth hydrophobic pores in which dispersive forces prevail, (ii) hydrophilic cavities with surfaces covered by polar silanol groups, and (iii) a much more rugged pore in which 60% of the previous interfacial hydroxyl groups were replaced by the bulkier trimethylsilyl ones. Confinement promotes a considerable structure at the vicinity of the pore walls which is enhanced in the case of hydroxylated surfaces. Moreover, in the presence of the trimethylsilyl groups, the propagation of this interface-induced spatial ordering extends down to the central region of the pore. Concerning the dynamical modes, we observed an overall slowdown in both the translational and rotational motions. An analysis of these mobilities from a local perspective shows that the largest retardations operate at the vicinity of the interfaces. The gross features of the rotational dynamics were analyzed in terms of contributions arising from bulk and surface states. Compared to the bulk dynamical behavior, the characteristic timescales associated with the rotational motions show the most dramatic increments. A dynamical analysis of hydrogen bond formation and breaking processes is also included. © 2010 American Institute of Physics.
Afiliación de los autores: Elola, M.D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Afiliación de los autores: Rodriguez, J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Afiliación de los autores: Laria, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Palabras claves: Breaking process; Dispersive forces; Dynamical analysis; Dynamical behaviors; Functionalized silica; Hydrogen-bond formation; Hydrophobic pore; Hydroxyl groups; Hydroxylated surfaces; Liquid methanol; Local perspective; Molecular dynamics simulations; Pore wall; Rotational dynamics; Rotational motion; Silanol groups; Silica pores; Spatial ordering; Structure and dynamics; Surface state; Time-scales; Trimethylsilyl; Trimethylsilyl groups; Dynamics; Functional groups; Hydrogen; Hydrogen bonds; Liquids; Methanol; Molecular dynamics; Rotational flow; Silica; Nanopores.
Repositorio: Biblioteca Digital (UBA-FCEN). Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales