Compaction and mobility in randomly agitated granular assemblies

We study the compaction and mobility properties of a dense granular material under weak random vibration. By putting in direct contact millimetric glass beads with piezoelectric transducers we manage to inject energy to the system in a disordered manner with accelerations much smaller than gravity, resulting in a slow compaction dynamics and no convection. We characterize the mobility inside the medium by pulling through it an intruder grain at constant velocity. We present an extensive study of the relation between drag force and velocity for different vibration conditions and sizes of the intruder.Comment: 4 pages, 6 figures, to appear in the proceedings of Powders and Grains 200

Dynamic and instability of submarine avalanches

We perform a laboratory-scale experiment of submarine avalanches on a rough inclined plane. A sediment layer is prepared and thereafter tilted up to an angle lower than the spontaneous avalanche angle. The sediment is scrapped until an avalanche is triggered. Based on the stability diagram of the sediment layer, we investigate different structures for the avalanche front dynamics. First we see a straight front descending the slope, and then a transverse instability occurs. Eventually, a fingering instability shows up similar to rivulets appearing for a viscous fluid flowing down an incline. The mechanisms leading to this new instability and the wavelength selection are discussed.Comment: 4 pages, 6 figures, to appear in the proceedings of Powders and Grains 200

Reorganization of a dense granular assembly: the `unjamming response function'

We investigate the mechanical properties of a static dense granular assembly in response to a local forcing. To this end, a small cyclic displacement is applied on a grain in the bulk of a 2D disordered packing under gravity and the displacement fields are monitored. We evidence a dominant long range radial response in the upper half part above the sollicitation and after a large number of cycles the response is `quasi-reversible' with a remanent dissipation field exhibiting long range streams and vortex-like symmetry.Comment: 5 pages, 5 figures, accepted version for publication in Phys. Rev.

Unjamming a granular hopper by vibration

We present an experimental study of the outflow of a hopper continuously vibrated by a piezoelectric device. Outpouring of grains can be achieved for apertures much below the usual jamming limit observed for non vibrated hoppers. Granular flow persists down to the physical limit of one grain diameter, a limit reached for a finite vibration amplitude. For the smaller orifices, we observe an intermittent regime characterized by alternated periods of flow and blockage. Vibrations do not significantly modify the flow rates both in the continuous and the intermittent regime. The analysis of the statistical features of the flowing regime shows that the flow time significantly increases with the vibration amplitude. However, at low vibration amplitude and small orifice sizes, the jamming time distribution displays an anomalous statistics

Erosion waves: transverse instabilities and fingering

Two laboratory scale experiments of dry and under-water avalanches of non-cohesive granular materials are investigated. We trigger solitary waves and study the conditions under which the front is transversally stable. We show the existence of a linear instability followed by a coarsening dynamics and finally the onset of a fingering pattern. Due to the different operating conditions, both experiments strongly differ by the spatial and time scales involved. Nevertheless, the quantitative agreement between the stability diagram, the wavelengths selected and the avalanche morphology reveals a common scenario for an erosion/deposition process.Comment: 4 pages, 6 figures, submitted to PR

Erosion patterns in a sediment layer

We report here on a laboratory-scale experiment which reproduces a rich variety of natural patterns with few control parameters. In particular, we focus on intriguing rhomboid structures often found on sandy shores and flats. We show that the standard views based on water surface waves come short to explain the phenomenon and we evidence a new mechanism based on a mud avalanche instability.Comment: 4 pages, 4 figures, to appear as Phys. Rev. E rapid com

Neurexin Dysfunction in Adult Neurons Results in Autistic-like Behavior in Mice

Autism spectrum disorders (ASDs) comprise a group of clinical phenotypes characterized by repetitive behavior and social and communication deficits. Autism is generally viewed as a neurodevelopmental disorder where insults during embryonic or early postnatal periods result in aberrant wiring and function of neuronal circuits. Neurexins are synaptic proteins associated with autism. Here, we generated transgenic βNrx1δC mice in which neurexin function is selectively impaired during late postnatal stages. Whole-cell recordings in cortical neurons show an impairment of glutamatergic synaptic transmission in the βNrx1δC mice. Importantly, mutant mice exhibit autism-related symptoms, such as increased self-grooming, deficits in social interactions, and altered interaction for nonsocial olfactory cues. The autistic-like phenotype of βNrx1δC mice can be reversed after removing the mutant protein in aged animals. The defects resulting from disruption of neurexin function after the completion of embryonic and early postnatal development suggest that functional impairment of mature circuits can trigger autism-related phenotypes. © 2014 The Authors.Research at the F.G.S. lab was funded by grants from NEURON-ERANET (EUHF-AUTISM, PIM2010ERN-0070), Instituto de Salud Carlos III (PI111058), and Junta de Andalucía (P11-CVI-7599). We thank Dr. Leon Lagnado (University of Sussex) for the generous gift of the sypHy construct, Dr. Oscar Pintado for pronuclear injection, Dr. Angel Barco for helpful advice with bitransgenic mice, and Dr. Maria Luz Montesinos and Itziar Benito for assistance with some behavioral tests. Technical assistance during the generation of transgenic mice was provided by María Luisa Pecero. The authors wish to thank Drs. Rafael Fernández-Chacón and Amalia Martinez-Mir for support and critical reading of the manuscript. E.R-L received a fellowship from V Plan Propio de Investigación (Universidad de Sevilla), and J.L.N.-G is a recipient of a Juan de la Cierva MINECO contract. Part of the study was performed at CITIUS (Universidad de Sevilla).Peer Reviewe

Utilización de la cestilla de Moss en el tratamiento de fracturas patológicas vertebrales

Las fracturas patológicas vertebrales pueden inducir radículo o mielopatía compresiva, inestabilidad y deformidad, de tal forma que el objetivo del tratamiento consistiría en restablecer lo más rápidamente posible la anatomía y función. En este sentido la utilización de una malla cilindrica de titanio como la «cestilla de Moss» consigue una estabilidad inmediata y permite la carga precoz. Presentamos un estudio retrospectivo de 6 pacientes afectos de fractura patológica vertebral intervenidos mediante abordaje anterior y estabilización instrumentada combinada con la «cestilla de Moss» rellena de injerto óseo o cemento acrílico. La valoración clínica se realiza subjetivamente por la presencia de dolor y neurológicamente según los grados de Frankel pre y postoperatorios. Radiológicamente se valora la corrección de la cifosis/lordosis/acuñamiento según el método de Cobb. La utilización de la «cestilla de Moss» en fracturas patológicas vertebrales consigue una estabilidad completa sin dependencia de la fusión ósea.Pathological spinal fractures could induce neurological deficit, instability and deformity. Therefore, the objective of the treatment consists of re-establishing the most quickly possible the anatomy and normal function. In this sense, the utilization of a cylindrical mesh of titanium, like the Moss's mesh, provide an immediate stability permiting early loading. We report a retrospective study of 6 patients with pathological spinal fracture operated by anterior decompression and spine stabilization using the Moss's mesh padded of bone graft acrylic cement. Clinical assessment was made subjectively for the presence of pain and neurologic ally according to pre and postoperatively Frankel's grades. The correction of the kyphosis, lordosis and vertebral collapse was assessed according to the Cobb's method. The utilization of the Moss's mesh in pathological spinal fractures provides a complete stability without dependence of the status of bone fusion

From sexual attraction to maternal aggression: When pheromones change their behavioural significance

This article is part of a Special Issue “Chemosignals and Reproduction”. This paper reviews the role of chemosignals in the socio-sexual interactions of female mice, and reports two experiments testing the role of pup-derived chemosignals and the male sexual pheromone darcin in inducing and promoting maternal aggression. Female mice are attracted to urine-borne male pheromones. Volatile and non-volatile urine fractions have been proposed to contain olfactory and vomeronasal pheromones. In particular, the male-specific major urinary protein (MUP) MUP20, darcin, has been shown to be rewarding and attractive to females. Non-urinary male chemosignals, such as the lacrimal protein ESP1, promote lordosis in female mice, but its attractive properties are still to be tested. There is evidence indicating that ESP1 and MUPs are detected by vomeronasal type 2 receptors (V2R). When a female mouse becomes pregnant, she undergoes dramatic changes in her physiology and behaviour. She builds a nest for her pups and takes care of them. Dams also defend the nest against conspecific intruders, attacking especially gonadally intact males. Maternal behaviour is dependent on a functional olfactory system, thus suggesting a role of chemosignals in the development of maternal behaviour. Our first experiment demonstrates, however, that pup chemosignals are not sufficient to induce maternal aggression in virgin females. In addition, it is known that vomeronasal stimuli are needed for maternal aggression. Since MUPs (and other molecules) are able to promote intermale aggression, in our second experiment we test if the attractive MUP darcin also promotes attacks on castrated male intruders by lactating dams. Our findings demonstrate that the same chemosignal, darcin, promotes attraction or aggression according to female reproductive stat

El síndrome facetar lumbar: Tratamiento mediante infiltraciones facetarias con fenol

Se presenta una serie de 125 pacientes afectos de cuadro de lumbociatalgia atípica, diagnosticados de síndrome facetario y tratados con infiltraciones de solución fenolada en las articulaciones interapofisarias posteriores afectadas, seguidas de un programa de rehabilitación protocolizado tras las infiltraciones. A propósito de los mismos y tras una análisis estadístico de los datos obtenidos del estudio, se establecen algunos criterios para el tratamiento de pacientes aquejados de este tipo de patología.The authors present a series of 125 patients afflicted with an atypical sciatic low-back pain, who were diagnosed of "facet joint syndrome" and treated with injections of phenol solution in the affected lumbar zygapophysial joints. The patients followed a protocolized rehabilitation program. After an statistical analysis of the data obtained from the study, some criteria are stabilized for the treatment of patients suffering this pathology