Modeling the dynamics of a tracer particle in an elastic active gel.

The internal dynamics of active gels both in artificial (in vitro) model systems and inside the cytoskeleton of living cells has been extensively studied with experiments of recent years. These dynamics are probed using tracer particles embedded in the network of biopolymers together with molecular motors, and distinct nonthermal behavior is observed. We present a theoretical model of the dynamics of a trapped active particle, which allows us to quantify the deviations from equilibrium behavior, using both analytic and numerical calculations. We map the different regimes of dynamics in this system and highlight the different manifestations of activity: breakdown of the virial theorem and equipartition, different elasticity-dependent "effective temperatures," and distinct non-Gaussian distributions. Our results shed light on puzzling observations in active gel experiments and provide physical interpretation of existing observations, as well as predictions for future studies.

Energetics of active fluctuations in living cells.

The nonequilibrium activity taking place in a living cell can be monitored with a tracer embedded in the medium. While microrheology experiments based on optical manipulation of such probes have become increasingly standard, we put forward a number of experiments with alternative protocols that, we claim, will provide insight into the energetics of active fluctuations. These are based on either performing thermodynamiclike cycles in control-parameter space or determining response to external perturbations of the confining trap beyond simple translation. We illustrate our proposals on an active itinerant Brownian oscillator modeling the dynamics of a probe embedded in a living medium.

Fluctuation-response relations for nonequilibrium diffusions with memory.

Strong interaction with other particles or feedback from the medium on a Brownian particle entail memory effects in the effective dynamics. That motivates the extension of the fluctuation-dissipation theorem to nonequilibrium Langevin systems with memory. An important application is to the nonequilibrium modification of the Sutherland-Einstein relation between diffusion and mobility in the case of strong memory. Nonequilibrium corrections include the time correlation between the dynamical activity and the velocity of the particle, which in turn leads to information about the correlations between the driving force and the particle's displacement.

[Episiotomy: can its habitual use be defended? A study of 100 puerperae and a group of gynecologists and midwives]. / Episiotomia: l'utilizzazione abituale va difesa? Un'indagine su 100 puerpere, su un gruppo di ginecologi e di ostetriche.

METHODS: The authors studied vaginal delivery with and without episiotomy, during the period 1993-1994. The aim of this study was to examine 100 puerperal women and a group of gynecologists and midwives, to evaluate the benefits and risks of routinely used medical procedures, and to understand the rational of the procedure and put in evidence the indications on which decisions were based. RESULTS: This study does not indicate that episiotomy offers a clear benefit to primipara in terms of decreased numbers of risk factors, while it is indicated in laborious vaginal delivery. The opinion of sanitary operators about this procedure is favourable especially for primiparas, but however this does not necessarily mean that more routine episiotomy can be justified.

[Episiotomy: clinical, technical and psychological aspects]. / Considerazioni sull'episiotomia: aspetti clinici, tecnici e psicologici.

The authors investigate the validity of a selective and not on a basic episiotomy utilization. Recent retrospective reports proved episiotomy could have a protective effect on 1st and 2nd grade lacerations and a predisposing effect on 3rd and 4th grade ones. As far as prevention of genital prolapse is concerned, few reports now exist that can confirm or deny this role attributed to episotomy. Concerning episiotomy efficacy in preventing neurologic damage risks to the fetus during labour, no difference was found in Apgar scores and in mortality rates in newborns with or without episiotomy, both in preterm labours and at term born babies. On the contrary episiotomy possible complications are fairly well documented, particularly dispaurenia and sexual dysfunctions on intercourse resumption after delivery.