Observation of a continuous interior crisis in the Hindmarsh-Rose neuron model.

Interior crises are understood as discontinuous changes of the size of a chaotic attractor that occur when an unstable periodic orbit collides with the chaotic attractor. We present here numerical evidence and theoretical reasoning which prove the existence of a chaos-chaos transition in which the change of the attractor size is sudden but continuous. This occurs in the Hindmarsh¿Rose model of a neuron, at the transition point between the bursting and spiking dynamics, which are two different dynamic behaviors that this system is able to present. Moreover, besides the change in attractor size, other significant properties of the system undergoing the transitions do change in a relevant qualitative way. The mechanism for such transition is understood in terms of a simple one-dimensional map whose dynamics undergoes a crossover between two different universal behavior

Considerations on the possible corrosion mechanisms of reinforced concrete structures and on the factors that control their kinetics

12 páginas, 11 figuras, 1 tabla.[ES] Resulta bien conocido que el acero permanece pasivo en el hormigón, en circunstancias normales, debido al pH fuertemente alcalino, y que la pasividad de las armaduras garantiza la durabilidad prácticamente ilimitada de las estructuras de hormigón armado (EHA). Sin embargo, existen cuestiones que siguen planteando, aún, activas controversias, con el riesgo de propiciar la aceptación de comportamientos o mecanismos que no son extensibles a todas las circunstancias, por ejemplo: a) que, descartada la carbonatación, el hormigón impone "siempre" un pH muy alcalino a los refuerzos, b) que, en las EHA que se corroen en estado activo, es "usual" un control catódico por difusión del oxígeno en la fase acuosa de la red de poros, c) que la influencia de los macropares galvánicos condiciona fuertemente el proceso de corrosión de las armaduras, d) que el recubrimiento de hormigón tiene "siempre" un efecto protector sobre las armaduras, e) que no importa el grado de corrosión inicial de las armaduras, porque la gran alcalinidad del hormigón garantiza su pasivación. En el trabajo presente se aportan resultados que demuestran que la respuesta de las EHA a las cuestiones anteriores es variada, a veces contradictoria, dependiendo del conjunto de condiciones experimentales.[EN] It is well known that in normal circumstances steel remains passive in concrete, due to the highly alkaline pH, and that the passivity of the rebars guarantees the practically unlimited durability of reinforced concrete structures (RCS). However, a number of matters continue to cause controversy, with the risk of promoting the acceptance of behaviours or mechanisms that cannot be extended to all circumstances; for instance: a) that when carbonation is ruled out, concrete "always" imposes a highly alkaline pH on rebars. b) that in RCSs corroding active state, cathodic control by oxygen diffusion in the aqueous phase of the pore network is "usual", c) that the influence of galvanic macrocouples strongly conditions the rebar corrosion process, d) that the concrete coating "always" has a protective effect on rebars. e) that the initial grade of corrosion of rebars does not matter, since the concrete's great alkalinity guarantees their passivation. This paper presents results which demonstrate that the response of RCSs in the above cases is variable, at times contradictory, depending on the set of experimental conditions.Peer reviewe

Temperature dependence of the magnetization processes in Co/Al oxide/Permalloy trilayers

The magnetization process of Co/Al oxide/Py trilayers and its evolution with the temperature have been analyzed. The particular behavior of the Co layers, including the shift of the hysteresis loops and a coercivity increase with the decrease of temperature, is related with the apparition of a CoO layer at the Co/Al-oxide interface

Goodness-of-fit test for point processes first-order intensity

Modelling the first-order intensity function is one of the main aims in point process theory. An appropriate model describes the first-order intensity as a nonparametric function of spatial covariates. A formal testing procedure is presented to assess the goodness-of-fit of this model, assuming an inhomogeneous Poisson point process. The test is based on a quadratic distance between two kernel intensity estimators. The asymptotic normality of the test statistic is proved and a bootstrap procedure to approximate its distribution is suggested. The proposal is illustrated with two applications to real data sets, and an extensive simulation study to evaluate its finitesample performance.Grant PID2020-116587GB-I00 funded by MCIN/AEI/10.13039/50110001103

Steel passive state stability in activated fly ash mortars

[EN] The present study explores the behaviour of structural steel embedded in Portland cement (OPC) mortars and NaOH- and NaOH+waterglass-activated fly ash, in the presence and absence of 2% Cl- (CaCl2). Variations were determined in the corrosion potential (Ecorr), linear polarization resistance (Rp) and corrosion current density (icorr) under different environmental conditions (90 days at 95% relative humidity (RH), 30 days at ≈30 % RH, 760 days at ≈ 95% RH). In the absence of Cl-, fly ash mortars were able to passivate steel reinforcement, although the stability of the passive state in changing environmental conditions was found to depend heavily on the activating solution used. Steel corrosion in the presence of 2% Cl- was observed to be similar to the corrosion reported for the material in OPC mortars.[ES] En el presente trabajo se estudia el comportamiento del acero estructural embebido en morteros de cemento Pórtland (OPC) y de cenizas volantes activadas con NaOH y una mezcla de NaOH y waterglass, en ausencia y en presencia de un 2% de Cl- (CaCl2). Se determinó la evolución del potencial de corrosión (Ecorr), la resistencia de polarización lineal (Rp) y la intensidad de corrosión (icorr), variando las condiciones ambientales (90 días al 95% de humedad relativa(HR) -30 días a ≈ 30% HR- 760 días a ≈ 95% HR).En ausencia de Cl- los morteros de cenizas volantes activadas pueden pasivar los refuerzos de acero, si bien la estabilidad del estado pasivo ante cambios en las condiciones ambientales parece mostrar una fuerte dependencia de la solución activadora empleada. Enpresencia de un 2% de Cl- los aceros se corroen mostrando en comportamiento similar al observado en morteros en base OPC.Peer reviewe

Pain expressions and inhibitory control in patients with fibromyalgia: behavioral and neural correlates

Fibromyalgia (FM) is a generalized chronic pain condition associated with a variety of symptoms, including altered cognitive and emotional processing. It has been proposed that FM patients show a preferential allocation of attention to information related to the symptoms of the disease, particularly to pain cues. However, the existing literature does not provide conclusive evidence on the presence of this attentional bias, and its effect on cognitive functions such as inhibitory control. To clarify this issue, we recorded the electroencephalographic activity of 31 women diagnosed with FM and 28 healthy women, while performing an emotional Go/NoGo task with micro-videos of pain, happy, and neutral facial expressions. We analyzed behavioral data, performed EEG time-frequency analyses, and obtained the event-related potentials (ERPs) N2 and P3 components in NoGo trials. A series of self-reports was also administered to evaluate catastrophic thinking and the main symptoms of fibromyalgia. Pain expressions were associated with longer reaction times and more errors, as well as with higher theta and delta power, and P3 amplitude to NoGo stimuli. Thus, behavioral and psychophysiological data suggest that increased attention to pain expressions impairs the performance of an inhibitory task, although this effect was similar in FM patients and healthy controls. N2 amplitude was modulated by type of facial expression (larger to pain faces), but only for the control group. This finding suggests that the presentation of pain faces might represent a smaller conflict for the patients, more used to encounter pain stimuli. No main group effects were found significant for N2 or P3 amplitudes, nor for time-frequency data. Using stimuli with greater ecological validity than in previous studies, we could not confirm a greater effect of attentional bias toward negative stimuli over inhibitory performance in patients with FM. Studying these effects allow us to better understand the mechanisms that maintain pain and develop intervention strategies to modify them.Galician Government (Consellería de Cultura, Educación e Ordenación Universitaria; axudas para a consolidación e estruturación de unidades de investigación competitivas do Sistema Universitario de Galicia [grant number GPC2014/047] and funding from the Spanish Government (Ministerio de Economía y Competitividad) [grant number PSI2013-45818-R]. AG-V was supported by a grant from the Deputación da Coruña (Bolsas de investigación en ciencias da saúde 2017) and Xunta de Galici

Bandwidth selection for kernel density estimation with length-biased data

Length-biased data are a particular case of weighted data, which arise in many situations: biomedicine, quality control or epidemiology among others. In this paper we study the theoretical properties of kernel density estimation in the context of length-biased data, proposing two consistent bootstrap methods that we use for bandwidth selection. Apart from the bootstrap bandwidth selectors we suggest a rule-of-thumb. These bandwidth selection proposals are compared with a least-squares cross-validation method. A simulation study is accomplished to understand the behaviour of the procedures in finite samples

Technical-economic potential of PV systems on Colombian residential sector

Solar energy is the second most applied variable renewable source worldwide, after the wind. In 2014, its world installed capacity was around 177 GW. During the past years, the yearly new capacity of photovoltaic (PV) solar yearly new capacity has exceeded new wind projects, highlighting this new solar power trend. This study aims to estimate technical and economic potential of the solar PV in the Colombian residential sector taking into account characteristics such as socio-economic stratum, household electric power consumption, tariffs by utility and capital cost. Technical-economic simulation tools were integrated into a geographical information system (‘GIS’) to permit a spatial analysis. Results shows solar generation potential and its annual penetration potential for all socioeconomic strata within all Colombian municipalities up to 2030. The current technical potential is around 9.1 GWp (13.10 TWh/year), while the economic potential will be 3.2 GWp by 2030.The authors would like to express their gratitude to the Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (National Scientific and Technological Development Council – CNPQ), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior ((Brazilian Federal Agency for the Improvement of Higher Education-CAPES) and NETEP - European-Brazilian Network on Energy Planning, a project supported by a Marie Curie International Research Staff Exchange Scheme Fellowship within the 7th European Union Framework Programme (PIRSES-GA-2013-612263), for the essential support given for this work to be carried out