Numerical Implementation of Gradient Algorithms

A numerical method for computational implementation of gradient dynamical systems is presented. The method is based upon the development of geometric integration numerical methods, which aim at preserving the dynamical properties of the original ordinary differential equation under discretization. In particular, the proposed method belongs to the class of discrete gradients methods, which substitute the gradient of the continuous equation with a discrete gradient, leading to a map that possesses the same Lyapunov function of the dynamical system, thus preserving the qualitative properties regardless of the step size. In this work, we apply a discrete gradient method to the implementation of Hopfield neural networks. Contrary to most geometric integration methods, the proposed algorithm can be rewritten in explicit form, which considerably improves its performance and stability. Simulation results show that the preservation of the Lyapunov function leads to an improved performance, compared to the conventional discretization.Spanish Government project no. TIN2010-16556 Junta de Andalucía project no. P08-TIC-04026 Agencia Española de Cooperación Internacional para el Desarrollo project no. A2/038418/1

Valoración de las repercusiones cinemáticas en la extremidad inferior del antepié varo, en niños entre 7 y 10 años

El objetivo del estudio fue determinar las repercusiones cinemáticas del antepié varo (AV) en un grupo de niños de 7-10 años, tanto en estática como durante la marcha. Población: 30 niños con AV (9.3 ± 1.7 años; 6.1º ± 2.3º de AV), 21 niños control (GC) (9.2 ± 1.6 años). Se utilizaron los modelos “Oxford Foot” y “Plug-In-Gait” para analizar la cinemática, en estática y durante la marcha, en los 2 grupos (Sistema VICON, 6 cámaras). Para comparar todas las variables entre los dos grupos, se aplicó el t-test para muestras independientes, cuando los datos eran normales, y el test de Mann Whitney cuando no lo eran. En estática, el grupo AV presentó mayor eversión del retropié, descenso del arco longitudinal interno y una actitud en flexión de toda la extremidad inferior. Al caminar, este grupo presentó mayor eversión del retropié y aplanamiento del arco interno en todas las fases de la marcha analizadas; proximalmente, se observó mayor báscula anterior de la pelvis y flexión de las 3 grandes articulaciones de la extremidad inferior y mayor rotación externa de cadera. No existieron diferencias en la velocidad de la marcha, pero, para conseguir esta velocidad, el grupo AV necesitó mayor cadencia y una longitud y una duración de paso menor.The aim of this study was to determine the impact of the forefoot varus (FV) on the kinematics of the lower limb, in standing and during walking, in a group of children aged between 7 and 10 years. The Oxford Foot Model was used, simultaneously with a conventional lower limb model, to compare the kinematics of 10 forefoot varus children (9.3 ± 1.7 years; 6.1º ± 2.3º of FV) and 11 healthy controls (9.2 ± 1.6 years). Data acquisition was performed using a six-camera motion capture system. The independent t- test was used to compare normal data and the Mann-Whitney test to compare non-normal data. In standing, the FV group showed a higher hindfoot eversion, a lower height of the internal longitudinal arch and a higher flexion in the 3 main joints of the lower limb. During walking, this group presented a higher hindfoot eversion and a lower height of the internal longitudinal arch in all the studied phases; on the other hand, a higher pelvis anterior tilt, a higher flexion of the 3 main joints of the lower limb and a higher external rotation of the hip were found. There were no differences in the gait speed but, to achieve this speed, the FV group needed a higher cadence, due to a lower length and duration of the step.Peer Reviewe

Dual branes in topological sigma models over Lie groups. BF-theory and non-factorizable Lie bialgebras

We complete the study of the Poisson-Sigma model over Poisson-Lie groups. Firstly, we solve the models with targets $G$ and $G^*$ (the dual group of the Poisson-Lie group $G$) corresponding to a triangular $r$-matrix and show that the model over $G^*$ is always equivalent to BF-theory. Then, given an arbitrary $r$-matrix, we address the problem of finding D-branes preserving the duality between the models. We identify a broad class of dual branes which are subgroups of $G$ and $G^*$, but not necessarily Poisson-Lie subgroups. In particular, they are not coisotropic submanifolds in the general case and what is more, we show that by means of duality transformations one can go from coisotropic to non-coisotropic branes. This fact makes clear that non-coisotropic branes are natural boundary conditions for the Poisson-Sigma model.Comment: 24 pages; JHEP style; Final versio

Paleoseismological analysis of late Miocene lacustrine successions in the Prebetic Zone, SE Spain

A paleoseismological study of late Miocene lacustrine sediments was carried out in the Neogene basins of the Prebetic Zone in Albacete (Spain). We developed a multidisciplinary methodology which could be used to extrapolate the paleoseismic data to the present day. This multidisciplinary approach includes different disciplines, i.e. stratigraphy, structural analysis, seismological analysis and paleoseismology. Paleoseismological analysis was focussed on both shallow and deep lake deposits given that these sediments behave differently in different deformation fields. The seismites formed in shallow sediments were generated by liquefaction and include: sand dikes, pillow structures and intruded and fractured gr avels. The deep lake deposits show varied structures, such as loop bedding, disturbed varved lamination, mixed layers and pseudonodules. Seismites indicate paleoearthquake magnitude intervals. The trends of the seismites are usually oriented ve ry close to the stress field trends (from the late Miocene to the Present): NW-SE and NE-SW trends. This constitutes a link between tectonics and seismites. The va rved annual sedimentation evidenced by the deep lake facies was used as a relative dating method. Mixed layers were employed as paleoseismic indicators to calculate the earthquake recurrence interval. The mean recurrence interval is close to 130 years (9446 years of total record with 73 dated events), one maximum interval of 454 years and one minimum interval of 23 years and the mean estimated magnitude value is 5.1. The Gutenberg-Richter relationship shows similar "b" values close to 0.86 from paleoseismological and seismological data. This suggests that the seismic conditions have been similar since the late Miocene

Corneal Biomechanics After Intrastromal Ring Surgery: Optomechanical In Silico Assessment

Purpose: To provide a biomechanical framework to better understand the postsurgical optomechanical behavior of the cornea after ring implantation. Methods: Calibrated in silico models were used to determine the corneal shape and stresses after ring implantation. After mechanical simulations, geometric ray-tracing was used to determine the change in spherical equivalent. The effect of the surgical procedure, circadian variation of intraocular pressure, or the biomechanical weakening introduced by keratoconus (KC) were evaluated for each intrastromal ring. Results: Models predicted the postsurgical optomechanical response of the cornea at a population level. The localized mechanical effect of the additional intrastromal volume introduced by the implants (size and diameter) drives the postsurgical corneal response. However, central corneal stresses did not increase more than 50%, and thus implants did not strengthen the cornea globally. Because of the biomechanical weakening introduced by laser pocketing, continuous implants in a pocket resulted in higher refractive corrections and in the relaxation of the anterior stroma, which could slow down KC progression. Implants can move within the stroma, acting as a dynamic pivot point that modifies corneal kinematics and flattens the corneal center. Changes in stromal mechanical properties did not impact on refraction for normal or pathological corneas. Conclusions: Implants do not stiffen the cornea but create a local bulkening effect that regularizes the corneal shape by modifying corneal kinematics without canceling corneal motion. Translational Relevance: In silico models can help to understand corneal biomechanics, to plan patient-specific interventions, or to create biomechanically driven nomograms

Effect of pig slaughter weight on chemical and sensory characteristics of Teruel dry-cured ham

A preliminary study was carried out with 36 barrows to investigate the effect of slaughter weight (SW; 120, 130 and 140 kg) on chemical, instrumental and sensory characteristics of Teruel drycured ham. The intramuscular fat content tended to increase and salt, potassium nitrate and sodium nitrite contents decreased as SW increased. The panelists detected wider subcutaneous fat and lower cured colour, saltiness, hardness and fibrousness in hams from heavier pigs but no difference was observed on overall quality assessment. In conclusion, pig SW affected some chemical and sensory traits of dry-cured ham, which contributes to increase the heterogeneity

Continuous cell lines and immune ascitic fluid pools in arbovirus detection

Pour la recherche et l'isolement des arbovirus, des expérimentations successives nous ont amenés à utiliser, parmi les lignées de cellules en culture continue dont l'utilisation est préconisée par l'OMS, les deux systèmes cellulaires MOS61 (cellules de #Aedes pseudoscutellaris$) et Vero. La détection des virus dans les sytèmes cellulaires est réalisée à l'aide de 7 pools de 10 ascites hyperimmunes polyvalentes. Cette technique permet la mise en évidence de 70 sur 80 arbovirus transmis par les moustiques en Afrique, et permet de détecter très facilement les associations d'arbovirus grâce aux ascites immunes monospécifiques ou monoclonales (dengue-1-2-3-4 et fièvre jaune). (Résumé d'auteur

Sensibilidad a la colocación de los marcadores en el modelo convencional de análisis cinemático de la marcha

La correcta evaluación del movimiento articular a través de sistemas de análisis del movimiento depende, entre otros factores, de la correcta colocación de los marcadores reflectantes sobre los sujetos analizados. En el modelo convencional de marcha, de los 15 marcadores de miembro inferior, la mayoría se localizan en puntos anatómicos fáciles de localizar y que tienen poca posibilidad de error. Sin embargo, hay dificultad en otros, como el de la articulación de la rodilla y, sobre todo, en los del muslo y pierna. En el estudio, se empleó un sistema VICON 460, con el que se analizó la cinemática de miembro inferior de 5 sujetos adultos sanos (2 mujeres, 3 varones). Para evaluar los movimientos articulares se empleó el modelo convencional de marcha. Determinada la posición correcta de los marcadores en cada sujeto, se procedió a la variación por separado de los marcadores de la rodilla, el muslo y la pierna, moviendo cada uno 15 mm anterior y posteriormente con relación a la posición inicial. Estos pequeños desplazamientos producen importantes variaciones en los resultados cinemáticos obtenidos. Entre ellas en el varo-valgo de rodilla, parámetro que es de gran utilidad a la hora de detectar errores en la colocación de los marcadores