Numerical approach to an age-structured Lotka-Volterra model.

We study the impact of an age-dependent interaction in a structured predator-prey model. We present two approaches, the PDE (partial differential equation) and the renewal equation, highlighting the advantages of each one. We develop efficient numerical methods to compute the (un)stability of steady-states and the time-evolution of the interacting populations, in the form of oscillating orbits in the plane of prey birth-rate and predator population size. The asymptotic behavior when species interaction does not depend on age is completely determined through the age-profile and a predator-prey limit system of ODEs (ordinary differential equations). The appearance of a Hopf bifurcation is shown for a biologically meaningful age-dependent interaction, where the system transitions from a stable coexistence equilibrium to a collection of periodic orbits around it, and eventually to a stable limit cycle (isolated periodic orbit). Several explicit analytical solutions are used to test the accuracy of the proposed computational methods.

Towards a classification framework for patient safety incidents and adverse events for a mental health community-based model of service provision / Hacia un marco de clasificación de los incidentes y efectos adversos para un modelo de atención comunitaria de la salud mental

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New surgical approach to advanced Kienböck disease: lunate replacement with pedicled vascularized scaphoid graft and radioscaphoidal partial arthrodesis.

Reconstructive procedures such as proximal row carpectomy or partial arthrodesis have been commonly proposed for advanced Kienböck disease (Lichtmann IIIB to IV). The purpose of this study is to evaluate an alternative surgical technique to advanced Kienböck disease: lunate excision and replacement with pedicled vascularized scaphoid graft and partial radioscaphoidal arthrodesis. The main advantage of the proposed intervention is to preserve mobility while not jeopardizing prime clinical outcomes such as pain. By replacing the devitalized lunate we aim at maintaining midcarpal range of motion, and preventing disease progression with carpal collapse and osteoarthritis of the wrist. Between 2002 and 2008, 13 patients of mean age 41 years (range, 25 to 57 y) were operated using this technique. The surgical act included 3 key steps. First, we excised the lunate, then, filled the generated gap with the rotated scaphoid, using it as a pedicled vascularized autograft. Finally, we performed a partial radioscaphoid arthrodesis. At the final follow-up, none of the intervened patients had pain at rest, and 6 patients could perform nonrestricted daily activities. The average postoperative range of motion in flexion/extension was 70 degrees (range, 55 to 90 degrees), 44% (range, 38% to 54%) of what could be achieved by the contralateral arm, and only 16% (range, 14% to 19%) or 25 degrees (range, 18 to 30 degrees) less than the preoperative range of motion of the same wrist. Grip strength improved by more than 30% (range, 24% to 36%). At an average follow-up of 4 years after surgery, 12 of 13 patients had no radiographic evidence of osteoarthritis or collapse of subchondral bone at the level of the new scaphocapitate joint. At follow-up evaluation, the average DASH score was 14 points (range, 6 to 20). The patients experienced a significant improvement in their functional abilities, achieving good results compared with the conventional techniques. The absence of carpal collapse and good functional results are encouraging.

Biofilm formation at warming temperature: acceleration of microbial colonization and microbial interactive effects.

River biofilms that grow on wet benthic surface are mainly composed of bacteria, algae, cyanobacteria and protozoa embedded in a polysaccharide matrix. The effects of increased river water temperature on biofilm formation were investigated. A laboratory experiment was designed employing two temperatures (11.1-13.2°C, night-day; 14.7-16.0°C, night-day) and two nutrient levels (0.054 mg P l(-1), 0.75 mg N l(-1); 0.54 mg P l(-1), 7.5 mg N l(-1)). Biofilm formation at the higher temperature was faster, while the biomass of the mature biofilm was mainly determined by nutrient availability. The specific response of the three microbial groups that colonized the substrata (algae, bacteria and ciliates) was modulated by interactions between them. The greater bacterial growth rate and earlier bacterial colonization at the higher temperature and higher nutrient status was not translated into the accrual of higher bacterial biomass. This may result from ciliates grazing on the bacteria, as shown by an earlier increase in peritrichia at higher temperatures, and especially at high nutrient conditions. Temperature and ciliate grazing might determine the growth of a distinctive bacterial community under warming conditions. Warmer conditions also produced a thicker biofilm, while functional responses were much less evident (increases in the heterotrophic utilization of polysaccharides and peptides, but no increase in primary production and respiration). Increasing the temperature of river water might lead to faster biofilm recolonization after disturbances, with a distinct biofilm community structure that might affect the trophic web. Warming effects would be expected to be more relevant under eutrophic conditions.

Multifractal method for the instantaneous evaluation of the stream function in geophysical flows.

Multifractal or multiaffine analysis is a promising new branch of methods in nonlinear physics for the study of turbulent flows and turbulentlike systems. In this Letter we present a new method based on the multifractal singularity extraction technique, the maximum singular stream-function method (MSSM), which provides a first order approximation to the stream function from experimental data in 2D turbulent systems. The essence of MSSM relies in relating statistical properties associated with the energy cascade in flows with geometrical properties. MSSM is a valuable tool to process sparse collections of data and to obtain instant estimates of the velocity field. We show an application of MSSM to oceanography as a way to obtain the current field from sea surface temperature satellite images; we validate the result with independent dynamical information obtained from sea level measurements.

Rotura de la polea A2 en escalada libre / Injury to the A2 pulley in rock climbers

Se presenta un caso típico de lesión de la polea A 2 dando como resultado un efecto de cuerda de arco que se diagnosticó por ecografía. Esta lesión es bastante común en los escaladores (trepadores)

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