Structure of mass and momentum fields over a model aggregation of benthic filter feeders

International audienceThe structure of momentum and concentration boundary layers developing over a bed of Potamocorbula amurensis clam mimics was studied. Laser Doppler velocimetry (LDV) and laser-induced fluorescence (LIF) probes were used to quantify velocity and concentration profiles in a laboratory flume containing 3969 model clams. Model clams incorporated passive roughness, active siphon pumping, and the ability to filter a phytoplankton surrogate from the flow. Measurements were made for two crossflow velocities, four clam pumping rates, and two siphon heights. Simultaneous use of LDV and LIF probes permited direct calculation of scalar flux of phytoplankton to the bed. Results show that clam pumping rates have a pronounced effect on a wide range of turbulent quantities in the boundary layer. In particular, the vertical turbulent flux of scalar mass to the bed was approximately proportional to the rate of clam pumping

On the exchange of intersection and supremum of sigma-fields in filtering theory

We construct a stationary Markov process with trivial tail sigma-field and a nondegenerate observation process such that the corresponding nonlinear filtering process is not uniquely ergodic. This settles in the negative a conjecture of the author in the ergodic theory of nonlinear filters arising from an erroneous proof in the classic paper of H. Kunita (1971), wherein an exchange of intersection and supremum of sigma-fields is taken for granted.Comment: 20 page

Central Limit Theorem and Large Deviation Principle for Continuous Time Open Quantum Walks

International audienceOpen Quantum Walks (OQWs), originally introduced in [2], are quantum generalizations of classical Markov chains. Recently, natural continuous time models of OQW have been developed in [24]. These models, called Continuous Time Open Quantum Walks (CTOQWs), appear as natural continuous time limits of discrete time OQWs. In particular they are quantum extensions of continuous time Markov chains. This article is devoted to the study of homogeneous CTOQW on Z^d. We focus namely on their associated quantum trajectories which allow us to prove a Central Limit Theorem for the "position" of the walker as well as a Large Deviation Principle

Sperm motility and fertilisation success in an acidified and hypoxic environment

The distribution and function of many marine species is largely determined by the effect of abiotic drivers on their reproduction and early development, including those drivers associated with elevated CO2 and global climate change. A number of studies have therefore investigated the effects of elevated pCO2 on a range of reproductive parameters, including sperm motility and fertilisation success. To date, most of these studies have not examined the possible synergistic effects of other abiotic drivers, such as the increased frequency of hypoxic events that are also associated with climate change. The present study is therefore novel in assessing the impact that a hypoxic event could have on reproduction in a future high CO2 ocean. Specifically, this study assesses sperm motility and fertilisation success in the sea urchin Paracentrotus lividus exposed to elevated pCO2 for 6 months. Gametes extracted from these pre acclimated individuals were subjected to hypoxic conditions simulating an hypoxic event in a future high CO2 ocean. Sperm swimming speed increased under elevated pCO2 and decrease under hypoxic conditions resulting in the elevated pCO2 and hypoxic treatment being approximately equivalent to the control. There was also a combined negative effect of increased pCO2 and hypoxia on the percentage of motile sperm. There was a significant negative effect of elevated pCO2 on fertilisation success, and when combined with a simulated hypoxic event there was an even greater effect. This could potentially affect cohort recruitment and in turn reduce the density of this ecologically and economically important ecosystem engineer therefore potentially effecting biodiversity and ecosystem services

Manifestaciones del síndrome de Down para su atención clínica odontológica

Introducción: El síndrome de Down es la aberración cromosómica más prevalente. En el 95% de los casos hay un cromosoma extra libre (trisomía 21). Los otros casos tienen el cromosoma adicional fijado a otro cromosoma (translocación). Existe una mayor incidencia de esta alteración a medida que aumenta la edad de la madre. Debido a que gran parte de las alteraciones clínicas del síndrome de Down se manifiestan en la región orofacial, el objetivo es concientizar al odontólogo acerca de la importancia de las manifestaciones clínicas, sistémicas y bucales que lo caracterizan. Dentro de las manifestaciones generales se destacan perfil facial plano, reflejo de moro disminuido, hipotonía, fisuras palpebrales oblicuas, anomalías del pabellón auricular, clinodactilia, pliegue palmar simiano, talla pequeña, retardo mental, alteraciones cardiacas congénitas .Las manifestaciones orales son variables. La boca se observa pequeña y entreabierta exteriorizando una macroglosia con depapilación y protrusión lingual. El prolapso lingual favorece la eversión del labio inferior, encontrándose agrietado. El labio superior se evidencia corto y la comisura labial descendida. Generalmente poseen respiración bucal que conduce a un inadecuado desarrollo del paladar, siendo motivo de sequedad en las mucosas, lo que da lugar a estomatitis y queilitis angular. El mayor riesgo de gingivitis implica que manifiesten con frecuencia enfermedad periodontal, incluso a edades tempranas de forma agresiva. Comúnmente presentan alteraciones dentarias tales como hipoplasia del esmalte, microdoncia, agenesia, retraso eruptivo y maloclusiones, pudiéndose encontrar mordida cruzada posterior, mordida abierta anterior. El conocimiento de las manifestaciones que estos pacientes presentan es muy relevante dado que hacen posible una adecuada atención integral, con el propósito de mejorar la salud bucal y aumentar la calidad de vida de estos niños.Facultad de Odontología (FOLP

Systemic importance of financial institutions: regulations, research, open issues, proposals

In the field of risk management, scholars began to bring together the quantitative methodologies with the banking management issues about 30 years ago, with a special focus on market, credit and operational risks. After the systemic effects of banks defaults during the recent financial crisis, and despite a huge amount of literature in the last years concerning the systemic risk, no standard methodologies have been set up to now. Even the new Basel 3 regulation has adopted a heuristic indicator-based approach, quite far from an effective quantitative tool. In this paper, we refer to the different pieces of the puzzle: definition of systemic risk, a set of coherent and useful measures, the computability of these measures, the data set structure. In this challenging field, we aim to build a comprehensive picture of the state of the art, to illustrate the open issues, and to outline some paths for a more successful future research. This work appropriately integrates other useful surveys and it is directed to both academic researchers and practitioners

Biología de la inflamación pulpar

La pulpa dental es un tejido conectivo localizado en la cavidad pulpar, conformando el complejo dentinopulpar, Presenta en la periferia una capa de odontoblastos los cuales se relacionan entre sí mediante uniones intercelulares especializadas. El cuerpo de dicha célula se localiza en la pulpa y su prolongación ocupa los conductillos dentinarios. Una zona pobre en células, integrada por capilares sanguíneos, fibras nerviosas amielínicas y prolongaciones citoplasmáticas de los fibroblastos. Una zona rica en células integrada por fibroblastos, macrófagos células dendríticas y células mesenquimatosas indiferenciadas.Facultad de Odontología (FOLP

Synaptic and circuit mechanisms promoting broadband transmission of olfactory stimulus dynamics

Sensory stimuli fluctuate on many timescales. However, short-term plasticity causes synapses to act as temporal filters, limiting the range of frequencies they can transmit. How synapses in vivo might transmit a range of frequencies in spite of short-term plasticity is poorly understood. The first synapse in the Drosophila olfactory system exhibits short-term depression, and yet can transmit broadband signals. Here we describe two mechanisms that broaden the frequency characteristics of this synapse. First, two distinct excitatory postsynaptic currents transmit signals on different timescales. Second, presynaptic inhibition dynamically updates synaptic properties to promote accurate transmission of signals across a wide range of frequencies. Inhibition is transient but grows slowly, and simulations show that these two features of inhibition promote broadband synaptic transmission. Dynamic inhibition is often thought to restrict the temporal patterns that a neuron responds to, but our results illustrate a different idea: inhibition can expand the bandwidth of neural coding