Avalanche dynamics in fluid imbibition near the depinning transition

We study avalanche dynamics and local activity of forced-flow imbibition fronts in disordered media. We focus on the front dynamics as the mean velocity $\bar{v}$ of the interface is decreased and the pinning state is approached. Scaling arguments allow us to obtain the statistics of avalanche sizes and durations, which become power-law distributed due to the existence of a critical point at $\bar{v}= 0$. Results are compared with phase-field numerical simulations

Time dependent couplings and crossover length scales in non-equilibrium surface roughening

We show that time dependent couplings may lead to nontrivial scaling properties of the surface fluctuations of the asymptotic regime in non-equilibrium kinetic roughening models . Three typical situations are studied. In the case of a crossover between two different rough regimes, the time-dependent coupling may result in anomalous scaling for scales above the crossover length. In a different setting, for a crossover from a rough to either a flat or damping regime, the time dependent crossover length may conspire to produce a rough surface, despite the most relevant term tends to flatten the surface. In addition, our analysis sheds light into an existing debate in the problem of spontaneous imbibition, where time dependent couplings naturally arise in theoretical models and experiments.Comment: Accepted for publication in Physical Review E (Rapid Comm.

Vástagos cementados y no cementados en artroplastias totales de cadera por coxopatías mecánicas

En la controversia sobre la cementación o no del componente femoral se presenta el análisis clínico, radiológico y de supervivencia de los vástagos de una serie de 121 artoplastias totales de cadera (61 cementadas y 60 sin cementar). El estudio no evidencia diferencias significativas a los 5 años de seguimiento, aunque es destacable una mayor incidencia de dolor en el muslo entre los vástagos no cementados (35%) (p < 0,1) y una tasa de reabsorción ósea proximal más elevada (70%) que en los cementados (23%). Estos fenómenos son diseño dependientes. Un mayor número de cirugías de revisión por aflojamiento aséptico entre las prótesis cementadas nos hacen preferir la fijación sin cemento del componente femoral.We discuss the cemented or non-cement fixation of the femoral components in total hip arthroplasty on a serie of 121 femoral stem (61 cemented stem and 60 non-cemented stem). Survival analysis, clinical and radiographic data showed no significant differences between the two groups at 5 years follow-up. However the incidence of pain thigh phenomenon was higher for the non-cemented stem (35%) (p < 0.1). Stress schielding was evidently higher between the non-cemented implants (70%) too, as compared with cemented stem (23%). These findings are design-dependent. The cemented arthroplasties had a higher rate of revision procedures because of aseptic loosening (13%). In this way we prefer the non-cement fixation of the femoral implant

Spatial clustering of interacting bugs: Levy flights versus Gaussian jumps

A biological competition model where the individuals of the same species perform a two-dimensional Markovian continuous-time random walk and undergo reproduction and death is studied. The competition is introduced through the assumption that the reproduction rate depends on the crowding in the neighborhood. The spatial dynamics corresponds either to normal diffusion characterized by Gaussian jumps or to superdiffusion characterized by L\'evy flights. It is observed that in both cases periodic patterns occur for appropriate parameters of the model, indicating that the general macroscopic collective behavior of the system is more strongly influenced by the competition for the resources than by the type of spatial dynamics. However, some differences arise that are discussed.Comment: This version incorporates in the text the correction published as an Erratum in Europhysics Letters (EPL) 95, 69902 (2011) [doi: 10.1209/0295-5075/95/69902