6,055 research outputs found
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
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 . 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
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