Nicolas Valencia - Academia.edu (original) (raw)
Papers by Nicolas Valencia
<p>It is well accepted that convection in the Earth&#8217;s mantle provides... more <p>It is well accepted that convection in the Earth&#8217;s mantle provides the torques to drive vertical and horizontal plate motions. Yet the precise nature of the interaction between flow and plates remains incomplete, because the strength of plates allows them to integrate over a presumably complex flow field in the mantle beneath &#8211; making it difficult to get a glimpse even on the recent Cenozoic mantle flow. Over the past years a pressure driven, so-called Poiseuille, flow model for upper mantle flux in the asthenosphere has gained increasing geodynamic attention &#8211; for a number of fluid dynamic arguments. This elegantly simple model makes a powerful testable prediction: Poiseuille flow induce plate motion changes should coincide with regional scale mantle convection induced elevation changes.</p> <p>Here I will focus on Australia, which undergoes a profound directional change from westward to northward motion in the early Cenozoic. At the same time there is evidence for early Cenozoic high dynamic topography in the western part of the continent. Thus, suggesting a high-pressure source in the upper mantle to the west of Australia. Altogether these geological and geophysical observations indicate that the separation of Australia from Antarctica was largely driven by plume push torque from the Kerguelen plume.</p>
Mantle convection is a fundamental process responsible for shaping the tectonic evolution of the ... more Mantle convection is a fundamental process responsible for shaping the tectonic evolution of the Earth. It is commonly perceived that mantle convection is difficult to constrain directly. However, it affects the horizontal and vertical motion of the lithosphere. The former is observed in the spreading rates, while the latter leaves various imprints in the geological record. In particular, the positive surface deflections driven by mantle convection create erosional/non-depositional environments, which induce gaps (hiatus) in the stratigraphic record (i.e., an absence or thinning of a sedimentary layer). Modern digital geological maps allow us to map long-wavelength no-/hiatus surfaces at continental scale systematically.Here we compare our continent-scale hiatus mapping to plate motion variations in the Atlantic and Indo-Australian realms from the Upper Jurassic onward. In general, we find the datasets correlate except when plate boundary forces may play a significant role. There is...
&lt;p&gt;Natural fault system observations feature complexity that includes damag... more &lt;p&gt;Natural fault system observations feature complexity that includes damage variation from the outer damage zone to the fault core and associated rheological degradation (e.g. variation in the frictional strength and spatio-temporal slip localisation). In earthquake dynamic rupture simulations, faults are typically treated as infinitesimally thin interfaces with distinct on- versus off-fault rheologies. Commonly, such faults are explicitly represented in the discretisation of the computational domain.&lt;/p&gt;&lt;p&gt;Here we present a diffuse interface approach for dynamic rupture modelling. We introduce a 2D spectral element method (SEM) with an embedded smeared discontinuity representing volumetric fault slip. Our diffuse fault SEM is inspired by the stress-glut method of Andrews, 1999. In our approach, a subdomain in which the tangential stresses are limited by a critical shear strength and an empirical friction law is embedded in a purely elastic domain, resembling classical discrete fault representations. Our approach is implemented on a structured quadrilateral mesh within an SEM framework for elastic wave propagation, with PETSc (Balay et al. 2019) as a linear algebra back-end.&lt;/p&gt;&lt;p&gt;Our method collapses volumetric complexities onto a distribution within a compact support instead of the traditional interface approach, making it a flexible inelastic zone alternative for mesh-independent fault representation in dynamic rupture simulations. We conduct 2D numerical experiments, including a kinematically driven Kostrov-like crack and spontaneous dynamic rupture as defined in SCEC community benchmarks (Harris et al., 2018) of increasing complexity. We extract the spectral response from seismograms at different receivers normal and along the fault. We also analyse the capacity of flexible fault representation by including mesh-independent fault geometries.&amp;#160;&lt;/p&gt;&lt;p&gt;Our approach will allow us to incorporate volumetric failure rheologies in SEM dynamic rupture simulations and is part of the TEAR ERC project (www.tear-erc.eu).&lt;/p&gt;
&lt;p&gt;&lt;span&gt;Mantle convection has profound effects on th... more &lt;p&gt;&lt;span&gt;Mantle convection has profound effects on the Earth&amp;#8217;s surface, such as inducing vertical motion, which is commonly termed dynamic topography. Sophisticated mantle convection models have been used to study current and past dynamic topography. But many input parameters, like complex rheologies and thermo-chemical flow properties remain poorly known, requiring ad-hoc model parameterization and long range extrapolation. This makes it attractive to explore simple analytic models of upper mantle flow. The existence of a weak asthenosphere allows one to explore upper mantle in the context of Poiseuille/Couette flow. The latter provides an geodynamically plausible link between flow properties and dynamic topography. Here we construct simple upper mantle flow models parameterized in terms of sources/sinks (plumes/slab) of Poiseuille/Couette flow. Our approach provides physical insight into the pattern of upper mantle flow, makes it easy to assess uncertainties of key model parameters, such as poorly resolved asthenospheric thickness and viscosity, and can be extended back in time, given first-order estimates of plume and subduction flux deduced from geological records. Importantly, it demands low computational cost relative to a time dependent geodynamic models. We present results for the Atlantic realm, and link our estimates of upper mantle flow history to Base Hiatus Surfaces (BHS) recently developed by Friedrich etal., (2018), Vibe etal., (2018), Carena etal., (2019), &amp;#160;Hayek metal., (2020) and Hayek metal., (2021). The latter serve as proxy for inferring past dynamic topography variations. We also relate our calculations to seismically inferred anisotropy, as a further proxy for upper mantle flow. Our results indicate that asthenospheric flow pattern can be explained through the concept of source to sink and that this flow type is testable against first order seismic and geologic observables.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;span&gt;References:&amp;#160;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Carena, S., Bunge, H. P., &amp; Friedrich, A. M. (2019). Analysis of geological hiatus surfaces across Africa in the Cenozoic and implications for the timescales of convectively-maintained topography.&amp;#160;Canadian Journal of Earth Sciences,&amp;#160;56(12), 1333-1346.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Friedrich, A. M., Bunge, H. P., Rieger, S. M., Colli, L., Ghelichkhan, S., &amp; Nerlich, R. (2018). Stratigraphic framework for the plume mode of mantle convection and the analysis of interregional unconformities on geological maps.&amp;#160;Gondwana Research,&amp;#160;53, 159-188.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Hayek, J. N., Vilac&amp;#237;s, B., Bunge, H. P., Friedrich, A. M., Carena, S., &amp; Vibe, Y. (2020). Continent-scale Hiatus Maps for the Atlantic Realm and Australia since the Upper Jurassic and links to mantle flow induced dynamic topography.&amp;#160;Proceedings of the Royal Society A,&amp;#160;476(2242), 20200390.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Hayek, J. N., Vilac&amp;#237;s, B., Bunge, H. P., Friedrich, A. M., Carena, S., &amp; Vibe, Y. (2021). Correction: Continent-scale Hiatus Maps for the Atlantic Realm and Australia since the Upper Jurassic and links to mantle flow-induced dynamic topography.&amp;#160;Proceedings of the Royal Society A,&amp;#160;477(2251), 20210437.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Vibe, Y., Friedrich, A. M., Bunge, H. P., &amp; Clark, S. R. (2018). Correlations of oceanic spreading rates and hiatus surface area in the North Atlantic realm.&amp;#160;Lithosphere,&amp;#160;10(5), 677-684.&lt;/span&gt;&lt;/p&gt;
XXVI Brazilian Congress on Biomedical Engineering, 2019
Down Syndrome (DS) is one of the most common genetic disorder worldwide and the most common cause... more Down Syndrome (DS) is one of the most common genetic disorder worldwide and the most common cause of intellectual disability, which generates problems regarding the functionality and independence to perform Activities of Daily Living (ADLs). This work proposes the development of a serious game-based system motivated by the results of a study concerning children with Down Syndrome (DS) and their laterality (left-right recognition) difficulty. This preliminary study was carried out using a system designed with the purpose to evaluate the children’s functional performance through data acquired using an RGB-D camera Kinect v2. This system uses a performance assessment protocol to analyze the laterality ability in children, providing a mirror-type visual feedback to the user. Thirteen participants (twelve with DS and one without DS) with ages between nine and ten years old were evaluated. In this evaluation, the children’s success percentage in distinguishing left from right was only 30.0%, confirming their laterality issue. Based on this preliminary validation, the serious game-based system was implemented as a proposal of an intelligent environment for the development of the right and left recognition. In general, children with DS are not able to pay attention for as much time as typical children. Thus, this game was designed to keep children interested and therefore focused on the task assigned, accelerating the learning. The game system acquires and processes parameters acquired by the Kinect and it aims to function as an intervention system that complements conventional therapies in helping the children to more efficiently develop their skills.
Machine vision is one of the most important tasks for the interaction between the robot and the e... more Machine vision is one of the most important tasks for the interaction between the robot and the environment, because it provides more information about the elements that exist there. The InMoov robot is the first life-size robot that can be produced by 3D printing and its design is open to the public. Between the following of the movement vector, the head control of this robot was implemented with the purpose of trackig the movement of an object. In the project the movement restrictions were taken corresponding to the range vision of the robot to develop the tracking and movement algorithms that will be aplied to the head movement of the robot under controlled conditions.
Anais do V Congresso Brasileiro de Eletromiografia e Cinesiologia e X Simpósio de Engenharia Biomédica, 2018
Resumo: O propósito deste estudo foi realizar um sistema de avaliação com realimentação visual do... more Resumo: O propósito deste estudo foi realizar um sistema de avaliação com realimentação visual do desempenho funcional em crianças com Síndrome de Down (SD) e compará-lo com o desempenho de uma criança sem SD. Foi também desenvolvido um método quantitativo exploratório para conformar uma base de dados. Foi implementado um Protocolo de Avaliação de Desempenho na atividade de alcance e encaixe de uma argola, utilizando um Sistema de imersão virtual com uma câmera RGB-D para medir os parâmetros cinemáticos do corpo. Foram avaliados treze participantes, 12 com SD e 1 sem SD, com idades entre 9 e 10 anos. Os perfis de desempenho funcional medidos foram identificados e analisados, verificando os movimentos de alcance e encaixe realizados pelas crianças com SD. Foi medida uma média máxima e mínima para cada amplitude angular do cotovelo. Os resultados demonstram a significância dos parâmetros obtidos com o sistema de imersão virtual. Os achados sugerem a importância de um sistema de intervenção que ajude a criança a desenvolver mais facilmente suas habilidades, bem como a importância de um sistema de medição permanente que forneça parâmetros objetivos de seu progresso.
&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp... more &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;span&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#160;Our results suggest that geologic maps yield geodynamically-relevant quantities, allowing one to constrain mantle-induced surface deflections of the lithosphere related to past dynamic topography.&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/span&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;
2016 XXI Symposium on Signal Processing, Images and Artificial Vision (STSIVA), 2016
Machine vision is one of the most important tasks for the interaction between the robot and the e... more Machine vision is one of the most important tasks for the interaction between the robot and the environment, because it provides more information about the elements that exist there. The InMoov robot is the first life-size robot that can be produced by 3D printing and its design is open to the public. Between the following of the movement vector, the head control of this robot was implemented with the purpose of trackig the movement of an object. In the project the movement restrictions were taken corresponding to the range vision of the robot to develop the tracking and movement algorithms that will be aplied to the head movement of the robot under controlled conditions.
Biosystems & Biorobotics, 2016
Stroke is a considerable cause of disability worldwide. A common motor recovery goal in physical ... more Stroke is a considerable cause of disability worldwide. A common motor recovery goal in physical therapy is to promote and enhance symmetry in motor patterns involved in daily functional tasks, aiming to prevent learned nonuse of the paretic side. The aim of this work is the development of a serious game for upper limbs training in stroke persons. This assistive technology is composed of a Kinect v2 combined with sEMG. We propose an integrated approach that includes three key factors: (a) fully immersive virtual environment with virtual body representation; (b) interaction with virtual objects; and (c) a biofeedback of arm movements of the patient through sEMG. The results show that the virtual reality environment here proposed is able to promote muscle activation in elbow flexion-extension movements, with average hit rate of 94.51 % (right arm), 93.1 % (left arm) and 85.67 % (both arms).
Review of Scientific Instruments, 2016
The lock-in amplifier is often used to study the enhancement of the magneto-optical Kerr effect (... more The lock-in amplifier is often used to study the enhancement of the magneto-optical Kerr effect (MOKE) in the presence of plasmon resonances. In the present work we show that it is possible to investigate such effect replacing the lock-in amplifier by a compensator, filter, and differential amplifier. This allows us to extract the full hysteresis loop in and out of the resonance without the need of a lock-in amplifier. Our results demonstrate these two setups are equivalent to study the enhancement of the transversal MOKE (T-MOKE) in magnetoplasmonic systems.
Se determino la madurez, edad y se describio el crecimiento individual de Dosidicus gigas en la c... more Se determino la madurez, edad y se describio el crecimiento individual de Dosidicus gigas en la costa oeste de la region central del Golfo de California durante 2000 a 2002. Se muestrearon 3369 individuos con una proporcion de sexos de 1.8:1 (H-M). La LM50 en machos vario entre 46 a 56 cm, siendo menor a la que presentaron las hembras, entre 76 y 79 cm. Se analizo la edad en 251 calamares, y el crecimiento por sexos se describio ajustando, a los datos de edad-LM, los modelos de Gompertz y Logistico Integral minimizando la funcion negativa log–verosimilitud y se utilizo el criterio de informacion de Akaike para elegir el mejor ajuste. El modelo de Gompertz describio mejor el crecimiento del calamar gigante, y no se detectaron diferencias entre sexos (ARSS, F=0.73, p=0.54. Los parametros estimados para datos combinados fueron: LM
Revista médica de Chile, 2012
A new physiopathological classification of diabetic neuropathy Nowadays, Diabetic Neuropathy (DN)... more A new physiopathological classification of diabetic neuropathy Nowadays, Diabetic Neuropathy (DN) is considered the most common cause of peripheral neuropathy in clinical practice. It can affect sensitive, motor or autonomic nerve fibers, with symmetric, asymmetric, acute or chronic presentations. Due to this variability, with multiple physiopathologic mechanisms involved, a complex clinical classification has been used until recently. The aim of this review is to present a new classification of diabetic neuropathy, based on its physiopathology. It is divided in metabolic microvascular and hypoxic, autoimmune and inflammatory, compressive, secondary to complications of diabetes and related to treatment. It must be understood that DN is not just a functional disease, but a complication of diabetes with molecular and pathological substrates caused by hyperglycemia. Therefore, normalization of blood glucose is a fundamental step towards the successful prevention and treatment of DN.
Journal of Shellfish Research, 2013
ABSTRACT In this study, the statolith microstructure of the jumbo squid Dosidicus gigas was used ... more ABSTRACT In this study, the statolith microstructure of the jumbo squid Dosidicus gigas was used to determine age, individual growth, and changes in sexual maturity off the west coast of the central region of the Gulf of California during 2000 and 2002. The number of individuals sampled was 3,369 with a sex ratio of 1.8:1 (female to male). The size at first maturity (ML50%) in males varied between 46 cm and 56 cm, which was less than that seen in females (76-79 cm). The age of 251 squid was analyzed, and the growth of each sex was described by fitting the Gompertz and logistic models to the age-mantle length (ML) data. The Gompertz model best described the growth of the jumbo squid, and no significant differences were detected between sexes (ARSS, F = 0.73, P = 0.54). The parameters estimated for the combined data were ML infinity = 143.3 cm and g (growth coefficient at inflection point) = 0.004/y and t(0) (age at inflection point) = 259.5 days. From the hatch date frequency distribution, a permanent incorporation of small individuals (ML, < 55 cm) was identified in the fishing zone with 2 maximum values, one in May and another in November, suggesting that there are at least 2 cohorts in the population.
Journal of Obstetrics and Gynaecology Research, 2011
Good glycemic control in gestational diabetes mellitus (GDM) seems not to be enough to prevent ma... more Good glycemic control in gestational diabetes mellitus (GDM) seems not to be enough to prevent macrosomia (large-for-gestational-age newborns). In GDM pregnancies we studied the effects of glycemic control (as glycosylated hemoglobin [HbA1c]), pre-pregnancy body mass index (PP-BMI) and gestational weight gain per week (GWG-W) on the frequency of macrosomia. We studied 251 GDM pregnancies, divided into two groups: PP-BMI&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;25.0kg/m(2) (the non-overweight group; n=125), and PP-BMI≥25.0kg/m(2) (the overweight group; n=126). A newborn weight Z-score&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;1.28 was considered large-for-gestational-age. Statistical analysis was carried out using the Student&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s t-test and χ(2) -test, receiver-operator characteristic curves and linear and binary logistic regressions. Prevalence of macrosomia was 14.9% among GDM (n=202/251, 88.4%) with good glycemic control (mean HbA1c&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;6.0%), and 28.1% in those with mean HbA1c≥6.0% (n=49/251, P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.025). Macrosomia rates were 10.4% in the non-overweight group and 24.6% in the overweight group (P=0.00308), notwithstanding both having similar mean HbA1c (5.48±0.065 and 5.65±0.079%, P=0.269), and similar GWG-W (0.292±0.017 and 0.240±0.021kg/week, P=0.077). Binary logistic regressions showed that PP-BMI (P=0.012) and mean HbA1c (P=0.048), but not GWG-W (P=0.477), explained macrosomia. Good glycemic control in GDM patients was not enough to reduce macrosomia to acceptable limits (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;10% of newborns). PP-BMI and mean HbA1c (but not GWG-W) were significant predictors of macrosomia. Thus, without ceasing in our efforts to improve glycemic control during GDM pregnancies, patients with overweight/obesity need to be treated prior to becoming pregnant.
<p>It is well accepted that convection in the Earth&#8217;s mantle provides... more <p>It is well accepted that convection in the Earth&#8217;s mantle provides the torques to drive vertical and horizontal plate motions. Yet the precise nature of the interaction between flow and plates remains incomplete, because the strength of plates allows them to integrate over a presumably complex flow field in the mantle beneath &#8211; making it difficult to get a glimpse even on the recent Cenozoic mantle flow. Over the past years a pressure driven, so-called Poiseuille, flow model for upper mantle flux in the asthenosphere has gained increasing geodynamic attention &#8211; for a number of fluid dynamic arguments. This elegantly simple model makes a powerful testable prediction: Poiseuille flow induce plate motion changes should coincide with regional scale mantle convection induced elevation changes.</p> <p>Here I will focus on Australia, which undergoes a profound directional change from westward to northward motion in the early Cenozoic. At the same time there is evidence for early Cenozoic high dynamic topography in the western part of the continent. Thus, suggesting a high-pressure source in the upper mantle to the west of Australia. Altogether these geological and geophysical observations indicate that the separation of Australia from Antarctica was largely driven by plume push torque from the Kerguelen plume.</p>
Mantle convection is a fundamental process responsible for shaping the tectonic evolution of the ... more Mantle convection is a fundamental process responsible for shaping the tectonic evolution of the Earth. It is commonly perceived that mantle convection is difficult to constrain directly. However, it affects the horizontal and vertical motion of the lithosphere. The former is observed in the spreading rates, while the latter leaves various imprints in the geological record. In particular, the positive surface deflections driven by mantle convection create erosional/non-depositional environments, which induce gaps (hiatus) in the stratigraphic record (i.e., an absence or thinning of a sedimentary layer). Modern digital geological maps allow us to map long-wavelength no-/hiatus surfaces at continental scale systematically.Here we compare our continent-scale hiatus mapping to plate motion variations in the Atlantic and Indo-Australian realms from the Upper Jurassic onward. In general, we find the datasets correlate except when plate boundary forces may play a significant role. There is...
&lt;p&gt;Natural fault system observations feature complexity that includes damag... more &lt;p&gt;Natural fault system observations feature complexity that includes damage variation from the outer damage zone to the fault core and associated rheological degradation (e.g. variation in the frictional strength and spatio-temporal slip localisation). In earthquake dynamic rupture simulations, faults are typically treated as infinitesimally thin interfaces with distinct on- versus off-fault rheologies. Commonly, such faults are explicitly represented in the discretisation of the computational domain.&lt;/p&gt;&lt;p&gt;Here we present a diffuse interface approach for dynamic rupture modelling. We introduce a 2D spectral element method (SEM) with an embedded smeared discontinuity representing volumetric fault slip. Our diffuse fault SEM is inspired by the stress-glut method of Andrews, 1999. In our approach, a subdomain in which the tangential stresses are limited by a critical shear strength and an empirical friction law is embedded in a purely elastic domain, resembling classical discrete fault representations. Our approach is implemented on a structured quadrilateral mesh within an SEM framework for elastic wave propagation, with PETSc (Balay et al. 2019) as a linear algebra back-end.&lt;/p&gt;&lt;p&gt;Our method collapses volumetric complexities onto a distribution within a compact support instead of the traditional interface approach, making it a flexible inelastic zone alternative for mesh-independent fault representation in dynamic rupture simulations. We conduct 2D numerical experiments, including a kinematically driven Kostrov-like crack and spontaneous dynamic rupture as defined in SCEC community benchmarks (Harris et al., 2018) of increasing complexity. We extract the spectral response from seismograms at different receivers normal and along the fault. We also analyse the capacity of flexible fault representation by including mesh-independent fault geometries.&amp;#160;&lt;/p&gt;&lt;p&gt;Our approach will allow us to incorporate volumetric failure rheologies in SEM dynamic rupture simulations and is part of the TEAR ERC project (www.tear-erc.eu).&lt;/p&gt;
&lt;p&gt;&lt;span&gt;Mantle convection has profound effects on th... more &lt;p&gt;&lt;span&gt;Mantle convection has profound effects on the Earth&amp;#8217;s surface, such as inducing vertical motion, which is commonly termed dynamic topography. Sophisticated mantle convection models have been used to study current and past dynamic topography. But many input parameters, like complex rheologies and thermo-chemical flow properties remain poorly known, requiring ad-hoc model parameterization and long range extrapolation. This makes it attractive to explore simple analytic models of upper mantle flow. The existence of a weak asthenosphere allows one to explore upper mantle in the context of Poiseuille/Couette flow. The latter provides an geodynamically plausible link between flow properties and dynamic topography. Here we construct simple upper mantle flow models parameterized in terms of sources/sinks (plumes/slab) of Poiseuille/Couette flow. Our approach provides physical insight into the pattern of upper mantle flow, makes it easy to assess uncertainties of key model parameters, such as poorly resolved asthenospheric thickness and viscosity, and can be extended back in time, given first-order estimates of plume and subduction flux deduced from geological records. Importantly, it demands low computational cost relative to a time dependent geodynamic models. We present results for the Atlantic realm, and link our estimates of upper mantle flow history to Base Hiatus Surfaces (BHS) recently developed by Friedrich etal., (2018), Vibe etal., (2018), Carena etal., (2019), &amp;#160;Hayek metal., (2020) and Hayek metal., (2021). The latter serve as proxy for inferring past dynamic topography variations. We also relate our calculations to seismically inferred anisotropy, as a further proxy for upper mantle flow. Our results indicate that asthenospheric flow pattern can be explained through the concept of source to sink and that this flow type is testable against first order seismic and geologic observables.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;span&gt;References:&amp;#160;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Carena, S., Bunge, H. P., &amp; Friedrich, A. M. (2019). Analysis of geological hiatus surfaces across Africa in the Cenozoic and implications for the timescales of convectively-maintained topography.&amp;#160;Canadian Journal of Earth Sciences,&amp;#160;56(12), 1333-1346.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Friedrich, A. M., Bunge, H. P., Rieger, S. M., Colli, L., Ghelichkhan, S., &amp; Nerlich, R. (2018). Stratigraphic framework for the plume mode of mantle convection and the analysis of interregional unconformities on geological maps.&amp;#160;Gondwana Research,&amp;#160;53, 159-188.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Hayek, J. N., Vilac&amp;#237;s, B., Bunge, H. P., Friedrich, A. M., Carena, S., &amp; Vibe, Y. (2020). Continent-scale Hiatus Maps for the Atlantic Realm and Australia since the Upper Jurassic and links to mantle flow induced dynamic topography.&amp;#160;Proceedings of the Royal Society A,&amp;#160;476(2242), 20200390.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Hayek, J. N., Vilac&amp;#237;s, B., Bunge, H. P., Friedrich, A. M., Carena, S., &amp; Vibe, Y. (2021). Correction: Continent-scale Hiatus Maps for the Atlantic Realm and Australia since the Upper Jurassic and links to mantle flow-induced dynamic topography.&amp;#160;Proceedings of the Royal Society A,&amp;#160;477(2251), 20210437.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Vibe, Y., Friedrich, A. M., Bunge, H. P., &amp; Clark, S. R. (2018). Correlations of oceanic spreading rates and hiatus surface area in the North Atlantic realm.&amp;#160;Lithosphere,&amp;#160;10(5), 677-684.&lt;/span&gt;&lt;/p&gt;
XXVI Brazilian Congress on Biomedical Engineering, 2019
Down Syndrome (DS) is one of the most common genetic disorder worldwide and the most common cause... more Down Syndrome (DS) is one of the most common genetic disorder worldwide and the most common cause of intellectual disability, which generates problems regarding the functionality and independence to perform Activities of Daily Living (ADLs). This work proposes the development of a serious game-based system motivated by the results of a study concerning children with Down Syndrome (DS) and their laterality (left-right recognition) difficulty. This preliminary study was carried out using a system designed with the purpose to evaluate the children’s functional performance through data acquired using an RGB-D camera Kinect v2. This system uses a performance assessment protocol to analyze the laterality ability in children, providing a mirror-type visual feedback to the user. Thirteen participants (twelve with DS and one without DS) with ages between nine and ten years old were evaluated. In this evaluation, the children’s success percentage in distinguishing left from right was only 30.0%, confirming their laterality issue. Based on this preliminary validation, the serious game-based system was implemented as a proposal of an intelligent environment for the development of the right and left recognition. In general, children with DS are not able to pay attention for as much time as typical children. Thus, this game was designed to keep children interested and therefore focused on the task assigned, accelerating the learning. The game system acquires and processes parameters acquired by the Kinect and it aims to function as an intervention system that complements conventional therapies in helping the children to more efficiently develop their skills.
Machine vision is one of the most important tasks for the interaction between the robot and the e... more Machine vision is one of the most important tasks for the interaction between the robot and the environment, because it provides more information about the elements that exist there. The InMoov robot is the first life-size robot that can be produced by 3D printing and its design is open to the public. Between the following of the movement vector, the head control of this robot was implemented with the purpose of trackig the movement of an object. In the project the movement restrictions were taken corresponding to the range vision of the robot to develop the tracking and movement algorithms that will be aplied to the head movement of the robot under controlled conditions.
Anais do V Congresso Brasileiro de Eletromiografia e Cinesiologia e X Simpósio de Engenharia Biomédica, 2018
Resumo: O propósito deste estudo foi realizar um sistema de avaliação com realimentação visual do... more Resumo: O propósito deste estudo foi realizar um sistema de avaliação com realimentação visual do desempenho funcional em crianças com Síndrome de Down (SD) e compará-lo com o desempenho de uma criança sem SD. Foi também desenvolvido um método quantitativo exploratório para conformar uma base de dados. Foi implementado um Protocolo de Avaliação de Desempenho na atividade de alcance e encaixe de uma argola, utilizando um Sistema de imersão virtual com uma câmera RGB-D para medir os parâmetros cinemáticos do corpo. Foram avaliados treze participantes, 12 com SD e 1 sem SD, com idades entre 9 e 10 anos. Os perfis de desempenho funcional medidos foram identificados e analisados, verificando os movimentos de alcance e encaixe realizados pelas crianças com SD. Foi medida uma média máxima e mínima para cada amplitude angular do cotovelo. Os resultados demonstram a significância dos parâmetros obtidos com o sistema de imersão virtual. Os achados sugerem a importância de um sistema de intervenção que ajude a criança a desenvolver mais facilmente suas habilidades, bem como a importância de um sistema de medição permanente que forneça parâmetros objetivos de seu progresso.
&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp... more &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;span&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#160;Our results suggest that geologic maps yield geodynamically-relevant quantities, allowing one to constrain mantle-induced surface deflections of the lithosphere related to past dynamic topography.&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/span&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;/p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;
2016 XXI Symposium on Signal Processing, Images and Artificial Vision (STSIVA), 2016
Machine vision is one of the most important tasks for the interaction between the robot and the e... more Machine vision is one of the most important tasks for the interaction between the robot and the environment, because it provides more information about the elements that exist there. The InMoov robot is the first life-size robot that can be produced by 3D printing and its design is open to the public. Between the following of the movement vector, the head control of this robot was implemented with the purpose of trackig the movement of an object. In the project the movement restrictions were taken corresponding to the range vision of the robot to develop the tracking and movement algorithms that will be aplied to the head movement of the robot under controlled conditions.
Biosystems & Biorobotics, 2016
Stroke is a considerable cause of disability worldwide. A common motor recovery goal in physical ... more Stroke is a considerable cause of disability worldwide. A common motor recovery goal in physical therapy is to promote and enhance symmetry in motor patterns involved in daily functional tasks, aiming to prevent learned nonuse of the paretic side. The aim of this work is the development of a serious game for upper limbs training in stroke persons. This assistive technology is composed of a Kinect v2 combined with sEMG. We propose an integrated approach that includes three key factors: (a) fully immersive virtual environment with virtual body representation; (b) interaction with virtual objects; and (c) a biofeedback of arm movements of the patient through sEMG. The results show that the virtual reality environment here proposed is able to promote muscle activation in elbow flexion-extension movements, with average hit rate of 94.51 % (right arm), 93.1 % (left arm) and 85.67 % (both arms).
Review of Scientific Instruments, 2016
The lock-in amplifier is often used to study the enhancement of the magneto-optical Kerr effect (... more The lock-in amplifier is often used to study the enhancement of the magneto-optical Kerr effect (MOKE) in the presence of plasmon resonances. In the present work we show that it is possible to investigate such effect replacing the lock-in amplifier by a compensator, filter, and differential amplifier. This allows us to extract the full hysteresis loop in and out of the resonance without the need of a lock-in amplifier. Our results demonstrate these two setups are equivalent to study the enhancement of the transversal MOKE (T-MOKE) in magnetoplasmonic systems.
Se determino la madurez, edad y se describio el crecimiento individual de Dosidicus gigas en la c... more Se determino la madurez, edad y se describio el crecimiento individual de Dosidicus gigas en la costa oeste de la region central del Golfo de California durante 2000 a 2002. Se muestrearon 3369 individuos con una proporcion de sexos de 1.8:1 (H-M). La LM50 en machos vario entre 46 a 56 cm, siendo menor a la que presentaron las hembras, entre 76 y 79 cm. Se analizo la edad en 251 calamares, y el crecimiento por sexos se describio ajustando, a los datos de edad-LM, los modelos de Gompertz y Logistico Integral minimizando la funcion negativa log–verosimilitud y se utilizo el criterio de informacion de Akaike para elegir el mejor ajuste. El modelo de Gompertz describio mejor el crecimiento del calamar gigante, y no se detectaron diferencias entre sexos (ARSS, F=0.73, p=0.54. Los parametros estimados para datos combinados fueron: LM
Revista médica de Chile, 2012
A new physiopathological classification of diabetic neuropathy Nowadays, Diabetic Neuropathy (DN)... more A new physiopathological classification of diabetic neuropathy Nowadays, Diabetic Neuropathy (DN) is considered the most common cause of peripheral neuropathy in clinical practice. It can affect sensitive, motor or autonomic nerve fibers, with symmetric, asymmetric, acute or chronic presentations. Due to this variability, with multiple physiopathologic mechanisms involved, a complex clinical classification has been used until recently. The aim of this review is to present a new classification of diabetic neuropathy, based on its physiopathology. It is divided in metabolic microvascular and hypoxic, autoimmune and inflammatory, compressive, secondary to complications of diabetes and related to treatment. It must be understood that DN is not just a functional disease, but a complication of diabetes with molecular and pathological substrates caused by hyperglycemia. Therefore, normalization of blood glucose is a fundamental step towards the successful prevention and treatment of DN.
Journal of Shellfish Research, 2013
ABSTRACT In this study, the statolith microstructure of the jumbo squid Dosidicus gigas was used ... more ABSTRACT In this study, the statolith microstructure of the jumbo squid Dosidicus gigas was used to determine age, individual growth, and changes in sexual maturity off the west coast of the central region of the Gulf of California during 2000 and 2002. The number of individuals sampled was 3,369 with a sex ratio of 1.8:1 (female to male). The size at first maturity (ML50%) in males varied between 46 cm and 56 cm, which was less than that seen in females (76-79 cm). The age of 251 squid was analyzed, and the growth of each sex was described by fitting the Gompertz and logistic models to the age-mantle length (ML) data. The Gompertz model best described the growth of the jumbo squid, and no significant differences were detected between sexes (ARSS, F = 0.73, P = 0.54). The parameters estimated for the combined data were ML infinity = 143.3 cm and g (growth coefficient at inflection point) = 0.004/y and t(0) (age at inflection point) = 259.5 days. From the hatch date frequency distribution, a permanent incorporation of small individuals (ML, < 55 cm) was identified in the fishing zone with 2 maximum values, one in May and another in November, suggesting that there are at least 2 cohorts in the population.
Journal of Obstetrics and Gynaecology Research, 2011
Good glycemic control in gestational diabetes mellitus (GDM) seems not to be enough to prevent ma... more Good glycemic control in gestational diabetes mellitus (GDM) seems not to be enough to prevent macrosomia (large-for-gestational-age newborns). In GDM pregnancies we studied the effects of glycemic control (as glycosylated hemoglobin [HbA1c]), pre-pregnancy body mass index (PP-BMI) and gestational weight gain per week (GWG-W) on the frequency of macrosomia. We studied 251 GDM pregnancies, divided into two groups: PP-BMI&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;25.0kg/m(2) (the non-overweight group; n=125), and PP-BMI≥25.0kg/m(2) (the overweight group; n=126). A newborn weight Z-score&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;1.28 was considered large-for-gestational-age. Statistical analysis was carried out using the Student&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s t-test and χ(2) -test, receiver-operator characteristic curves and linear and binary logistic regressions. Prevalence of macrosomia was 14.9% among GDM (n=202/251, 88.4%) with good glycemic control (mean HbA1c&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;6.0%), and 28.1% in those with mean HbA1c≥6.0% (n=49/251, P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.025). Macrosomia rates were 10.4% in the non-overweight group and 24.6% in the overweight group (P=0.00308), notwithstanding both having similar mean HbA1c (5.48±0.065 and 5.65±0.079%, P=0.269), and similar GWG-W (0.292±0.017 and 0.240±0.021kg/week, P=0.077). Binary logistic regressions showed that PP-BMI (P=0.012) and mean HbA1c (P=0.048), but not GWG-W (P=0.477), explained macrosomia. Good glycemic control in GDM patients was not enough to reduce macrosomia to acceptable limits (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;10% of newborns). PP-BMI and mean HbA1c (but not GWG-W) were significant predictors of macrosomia. Thus, without ceasing in our efforts to improve glycemic control during GDM pregnancies, patients with overweight/obesity need to be treated prior to becoming pregnant.