Bayesian Inference for Gravitational Waves from Binary Neutron Star Mergers in Third Generation Observatories.

Third generation (3G) gravitational-wave detectors will observe thousands of coalescing neutron star binaries with unprecedented fidelity. Extracting the highest precision science from these signals is expected to be challenging owing to both high signal-to-noise ratios and long-duration signals. We demonstrate that current Bayesian inference paradigms can be extended to the analysis of binary neutron star signals without breaking the computational bank. We construct reduced-order models for ∼90-min-long gravitational-wave signals covering the observing band (5-2048 Hz), speeding up inference by a factor of ∼1.3×10^{4} compared to the calculation times without reduced-order models. The reduced-order models incorporate key physics including the effects of tidal deformability, amplitude modulation due to Earth's rotation, and spin-induced orbital precession. We show how reduced-order modeling can accelerate inference on data containing multiple overlapping gravitational-wave signals, and determine the speedup as a function of the number of overlapping signals. Thus, we conclude that Bayesian inference is computationally tractable for the long-lived, overlapping, high signal-to-noise-ratio events present in 3G observatories.

Stress profile in a two-dimensional silo: Effects induced by friction mobilization.

The effects of friction mobilization on the stress profile within a two-dimensional silo are investigated via simulations of discrete elements. Friction mobilization is driven by cyclic vertical displacement of the sidewalls. Two regimes have been observed for small filling height, with stress profiles identified as saturated (Janssen's profile) and exponentially growing. The transition between these regimes is denoted by an almost linear stress profile, similar to that of a hydrostatic system, with a significantly greater characteristic height compared to the height of the column of grains. For tall columns, the process of friction inversion is more complex. A partial inversion of friction mobilization is observed when the motion is reversed from upward to downward, which results in two coexisting zones of opposite mobilization. These zones are separated by a wide compaction front with a gradual upward progression sustained by the displacement of the walls. Conversely, if the motion is reversed, the two opposing friction mobilization zones retract, the transition zone becomes smooth, and the system rapidly transforms from two coexisting mobilization states to a Janssen-like regime. In both regimes, the general characteristics from the resulting stress profiles are depicted by generalizing Janssen's equation to include partial mobilization through the varying effective friction coefficient along the silo walls.

Effects of grain shape on the response of a two-dimensional granular material under constant shear rate.

We present a study on the effects of particle shape (disks, hexagons, and pentagons) on the macroscopic coefficient of friction of a two-dimensional, monodisperse, single-shaped, granular system, subjected to shear. We found that the mechanism of stress relaxation in disks is based on the sliding of adjacent planes parallel to the applied deformation direction. In hexagons, stress is relaxed through the creation of rigid pivots, which require hexagonal domains to nucleate and are responsible for the large fluctuations in the dilatancy and shear force. In pentagons the stress relaxation mechanism is through the rotation of individual pentagons, which is a consequence of their permanent misalignment, and are responsible for the small but relatively rapid fluctuations in the shear force. We observed that the friction coefficient is larger for polygonal particles than for the rounded ones. A maximum in the friction coefficient is observed in hexagon granulates with an initial width around 6.5 grains caused by the increased frequency in nucleation of rigid pivots. In mixtures of disks and hexagons we observed three different friction coefficient behaviors, which depended on the relative concentration of hexagons; in low concentrations of hexagons, <20%, the friction coefficient corresponds to that obtained in solely disks, at intermediate concentrations, <80%, the coefficient varies linearly with concentration, and at larger concentrations the friction coefficient corresponds to the values obtained for solely hexagons. On the contrary, mixtures of pentagons and hexagons showed two regimes; a low constant friction regime at concentrations lower than 60%, and an increased in friction observed with higher concentrations of hexagons.

Size segregation, convection, and arching effect.

We present a numerical study based on the contact dynamic procedure for the size segregation in a two-dimensional vibrating container. In agreement with previous studies, we find that the rising of the larger particle is accompanied by convection rolls. However, at low enough acceleration, rolls do not penetrate the entire cell and a local vault mechanism is observed, in which the larger particle moves up by steps. This mechanism, described in experiments by Duran and co-workers [Phys. Rev. E. 50, 5138 (1994)], occurs in a very narrow region of parameter space. Once the larger intruder reaches the exponential tail of convecting roll, its vertical motion becomes continuous and the corresponding rising speed is dramatically increased.

Experimental study of surface waves scattering by a single vortex and a vortex dipole.

Surface waves interacting with filamentary vortex offer an interesting tool to characterize static and dynamics of surface vorticity. An experimental study of the scattered wave by a single vortex as well as by a vortex dipole is reported. On a plane wave front, the vortex circulation introduces a spatial phase shift that gives rise to dislocated waves. Dislocations can be explained by the effect of the differential advection due to the vortex flow, on the propagating wave front. Both the Burgers vector of dislocations and the scattering cross section are measured in the deep water regime. The analogy between the wave-vortex interaction and the Aharonov-Bohm effect in quantum mechanics is explored by contrasting the Burgers vectors of dislocations as well as the form of the scattered wave in both cases. For the case of the hard core vortex, spiral waves are observed in agreement with theoretical works on both the Aharanov-Bohm effect and classical surface wave mechanics.

Bloqueo de los nervios iliohipogástrico e ilioinguinal para analgesia posquirúrgica en cesárea tipo Pfannenstiel realizada bajo anestesia general ¿Qué concentración del anestésico local usar? / Iliohypogastric ano ilioinguinal block for postsurgical analgesia after Pfannenstiel cesarean section performeo unoer general anaesthesia

El bloqueo bilateral de los nervios Iliohipogástrico e Ilioinguinal con bupivacaína al 0.5 por ciento puede proveer analgesia luego de cesárea con incisión de Pfannenstiel aunque la cantidad de droga usada está cerca de la dosis máxima segura. Diseñamos este estudio para comparar el efecto analgésico de la bupivacaína al 0.5 por ciento y diluida al 0.25 por ciento. Se incluyeron treinta pacientes aleatoriamente asignadas a un grupo de estudio (bupivacaína 0.25 por ciento, n= 15) y uno de control (bupivacaína 0.5 por ciento, n=15). Se evaluaron las pacientes con una Escala Visual Análoga (EVA) a las O, 4, 8, 12 y 24 horas posoperatorias por médicos que no sabían a qué grupo pertenecían y sólo en caso de necesidad se prescribió analgesia IM con Diclofenaco. Los puntajes de analgesia y los requerimientos de analgesia complementaria fueron notoriamente similares en ambos grupos y no hubo diferencias estadísticamente significativas. Concluimos que el bloqueo de estos nervios es una técnica analgésica efectiva (el dolor siempre estuvo en promedio por debajo de 4 en la EVA), que no es afectada por la dilución del anestésico y que además es segura pues no se presentaron complicaciones

The Iliohypogastric and Ilioinguinal bilate. ral block with 0.5% bupivacaine can provide analgesia after Pfannenstiel cesarean section although the required amount of the drug is near the maximum secure dose. We designed this study in order to compare the analgesic effect of 0.5% bupivacaine and diluted 0.25% bupivacaine. Thirty patients were included in the study and asigned in aleatory form to either a study (0.25% bupivacaine n=15) or a control group (0.5% bupivacaine n=15). They were evaluated with the Visual Analogue Scale (VAS) at 0,4,8,12,24 postoperative hours by physicians who did not know the group of the patient and prescribed intramuscular analgesia with Dicofenac only if required. The analgesia scores and the complementery analgesia requirements were similar in both groups and there were no significative differences. We conclude that this nerve block is an effective analgesic technique (pain was always under 4 in the VAS), unaffected by the anesthetic dilution and furthermore that it is a safe technique since there were no complications derived from the procedure.