Impact of noise on a dynamical system: prediction and uncertainties from a swarm-optimized neural network

In this study, an artificial neural network (ANN) based on particle swarm optimization (PSO) was developed for the time series prediction. The hybrid ANN+PSO algorithm was applied on Mackey--Glass chaotic time series in the short-term $x(t+6)$. The performance prediction was evaluated and compared with another studies available in the literature. Also, we presented properties of the dynamical system via the study of chaotic behaviour obtained from the predicted time series. Next, the hybrid ANN+PSO algorithm was complemented with a Gaussian stochastic procedure (called {\it stochastic} hybrid ANN+PSO) in order to obtain a new estimator of the predictions, which also allowed us to compute uncertainties of predictions for noisy Mackey--Glass chaotic time series. Thus, we studied the impact of noise for several cases with a white noise level ($\sigma_{N}$) from 0.01 to 0.1.Comment: 11 pages, 8 figure

Medição simultânea de velocidade e concentração em meios líquidos

Este artigo descreve os procedimentos experimentais para medição simultânea de velocidade e concentração, utilizando Anemometria Laser Doppler e Fluorescência Induzida por Laser. Apesar da fluorescência induzida por laser ser uma técnica usual no âmbito da química analítica, a sua aplicação em Mecânica dos Fluidos não é comum. Efectuaram-se ensaios de maneira a caracterizar o comportamento experimental das soluções aquosas do traçador fluorescente (rodamina B) e desenvolveu-se um método experimental em que a Fluorescência Induzida por Laser podia ser utilizada juntamente com a Anemometria Laser Doppler

Two qubits entanglement dynamics in a symmetry-broken environment

We study the temporal evolution of entanglement pertaining to two qubits interacting with a thermal bath. In particular we consider the simplest nontrivial spin bath models where symmetry breaking occurs and treat them by mean field approximation. We analytically find decoherence free entangled states as well as entangled states with an exponential decay of the quantum correlation at finite temperature.Comment: 10 pages, 2 figure

Psychosocial and economic impacts of a charge in lightweight plastic carrier bags in Portugal: Keep calm and carry on?

Reducing plastic waste has become an urgent global challenge. To help fight this problem, European countries have undertaken the mission to reduce lightweight plastic bag consumption. In 2014, Portugal implemented a charge on lightweight plastic bags, calling for an adjustment from both consumers and firms. The present re- search aims to study the psychosocial and economic impacts of this tax measure, namely in terms of acceptability of the measure, potential attitude and behaviour changes, and impact on plastic bag markets. The psychosocial impacts were studied based on an online survey (N = 198) and on available datasets illustrating societal trends. Survey results showed that participants agreed with the charge and with widening it to all types of plastic bags. They attributed environmental motives to its implementation, developed reuse habits and mentioned a de- creased consumption of disposable plastics. In addition, individuals appear more concerned with the impacts of everyday plastic products in the environment, and more willing to pay higher taxes and prices to protect the environment. The economic impacts were studied using available data on the charge revenue and on the production and sales of plastic bags, among others. We illustrate that the implementation of the charge led to a sharp fall in the use of lightweight bags, generating a decrease in the production and sale of plastic bags overall, while avoiding significant impacts on the relevant economic sectors.info:eu-repo/semantics/acceptedVersio

Is it all about awareness? The normalization of coastal risk

Coastal risk is already high in several parts of the world and is expected to be amplified by climate change, which makes it necessary to outline effective risk management strategies. Risk managers assume that increasing awareness of coastal risk is the key to public support and endorsement of risk management strategies – an assumption that underlies a common worldview on the public understanding of science, which has been named the deficit model. We argue that the effects of awareness are not as straightforward. In particular, awareness of coastal hazards might not lead to more technically accurate risk perceptions. Based on research on risk perception normalization, we explored the hypothesis that coastal risk awareness reduces coastal risk perception – in particular the perceived likelihood of occurrence of coastal hazards – through its effect on reliance on protective measures to prevent risk. Individuals can rely on protective measures, even when those are not effective, as a positive illusion to reduce risk perception. This effect might be stronger for higher probability hazards and for permanent residents of costal zones. Data from 410 individuals living in coastal zones corroborated most of our expectations. Global results demonstrated a risk normalization effect mediated by reliance on current measures. Additional analyses made clear that this effect occurred in 2 of the 5 high-probability hazards (flood and storm), and not in the low-probability hazard (tsunami). Normalization might be more likely among high-probability hazards which entail catastrophic and immediate impacts. This effect was also found among permanent residents, but not among temporary residents. Results imply that coastal risk management might benefit from (a) taking risk perception normalization effects into account, (b) tailoring strategies for permanent and temporary residents and (c) promoting a higher public engagement, which would facilitate a more adaptive and effective coping with coastal risk than the use of positive illusions.info:eu-repo/semantics/acceptedVersio

Mitophagy contributes to endothelial adaptation to simulated microgravity

Exposure to real or simulated microgravity is sensed as a stress by mammalian cells, which activate a complex adaptive response. In human primary endothelial cells, we have recently shown the sequential intervention of various stress proteins which are crucial to prevent apoptosis and maintain cell function. We here demonstrate that mitophagy contributes to endothelial adaptation to gravitational unloading. After 4 and 10 d of exposure to simulated microgravity in the rotating wall vessel, the amount of BCL2 interacting protein 3, a marker of mitophagy, is increased and, in parallel, mitochondrial content, oxygen consumption, and maximal respiratory capacity are reduced, suggesting the acquisition of a thrifty phenotype to meet the novel metabolic challenges generated by gravitational unloading. Moreover, we suggest that microgravity induced-disorganization of the actin cytoskeleton triggers mitophagy, thus creating a connection between cytoskeletal dynamics and mitochondrial content upon gravitational unloading

Collective Decoherence of Nuclear Spin Clusters

The problem of dipole-dipole decoherence of nuclear spins is considered for strongly entangled spin cluster. Our results show that its dynamics can be described as the decoherence due to interaction with a composite bath consisting of fully correlated and uncorrelated parts. The correlated term causes the slower decay of coherence at larger times. The decoherence rate scales up as a square root of the number of spins giving the linear scaling of the resulting error. Our theory is consistent with recent experiment reported in decoherence of correlated spin clusters.Comment: 4 pages, 4 figure

The complex TIE between macrophages and angiogenesis

Macrophages are primarily known as phagocytic immune cells, but they also play a role in diverse processes, such as morphogenesis, homeostasis and regeneration. In this review, we discuss the influence of macrophages on angiogenesis, the process of new blood vessel formation from the pre-existing vasculature. Macrophages play crucial roles at each step of the angiogenic cascade, starting from new blood vessel sprouting to the remodelling of the vascular plexus and vessel maturation. Macrophages form promising targets for both pro- and anti-angiogenic treatments. However, to target macrophages, we will first need to understand the mechanisms that control the functional plasticity of macrophages during each of the steps of the angiogenic cascade. Here, we review recent insights in this topic. Special attention will be given to the TIE2-expressing macrophage (TEM), which is a subtype of highly angiogenic macrophages that is able to influence angiogenesis via the angiopoietin-TIE pathway

Competition between electron pairing and phase coherence in superconducting interfaces

In LaAlO3/SrTiO3 heterostructures, a gate tunable superconducting electron gas is confined in a quantum well at the interface between two insulating oxides. Remarkably, the gas coexists with both magnetism and strong Rashba spin–orbit coupling. However, both the origin of superconductivity and the nature of the transition to the normal state over the whole doping range remain elusive. Here we use resonant microwave transport to extract the superfluid stiffness and the superconducting gap energy of the LaAlO3/SrTiO3 interface as a function of carrier density. We show that the superconducting phase diagram of this system is controlled by the competition between electron pairing and phase coherence. The analysis of the superfluid density reveals that only a very small fraction of the electrons condenses into the superconducting state. We propose that this corresponds to the weak filling of high- energy dxz/dyz bands in the quantum well, more apt to host superconductivity