Elbert E N Macau

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Verified

Elbert verified their affiliation via an institutional email.

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• PhD in Electonic Engineering
• Professor (Full) at Federal University of São Paulo

Extreme events are rare, large-scale deviations from typical system behavior that can occur in nonlinear dynamical systems. In this study, we explore the emergence of extreme events within a network of identical stochastic Hodgkin-Huxley neurons with mean-field coupling. The neurons are exposed to uncorrelated noise, which introduces stochastic ele...

The severe acute respiratory syndrome of coronavirus 2 spread globally very quickly, causing great concern at the international level due to the severity of the associated respiratory disease, the so-called COVID-19. Considering Rio de Janeiro city (Brazil) as an example, the first diagnosis of this disease occurred in March 2020, but the exact mom...

We present a computational model of networked neurons developed to study the effect of temperature on neuronal synchronization in the brain in association with seizures. The network consists of a set of chaotic bursting neurons surrounding a core tonic neuron in a square lattice with periodic boundary conditions. Each neuron is reciprocally coupled...

Recurrence microstates are obtained from the cross recurrence of two sequences of values embedded in a time series, being the generalization of the concept of recurrence of a given state in phase space. The probability of occurrence of each microstate constitutes a recurrence quantifier. The set of probabilities of all microstates are capable of de...

Since the COVID-19 pandemic was first reported in 2019, it has rapidly spread around the world. Many countries implemented several measures to try to control the virus spreading. The healthcare system and consequently the general quality of life population in the cities have all been significantly impacted by the Coronavirus pandemic. The different...

Semiconductor lasers with optical feedback are well-known nonlinear dynamical systems. Under appropriate feedback conditions, these lasers emit optical pulses that resemble neural spikes. Influenced by feedback delay and various noise sources, including quantum spontaneous emission noise, the dynamics are highly stochastic. A good understanding of...

The Amazon Basin is the largest rainforest in the world, and studying the rainfall in this region is crucial for understanding the functioning of the entire rainforest ecosystem and its role in regulating the regional and global climate. This work is part of the application of complex networks, which refer to a network modeled by graphs and are cha...

Talk at the International Symposium on Spreading Dynamics

This article investigates the emergence of phase synchronization in a network of randomly connected neurons by chemical synapses. The study uses the classic Hodgkin–Huxley model to simulate the neuronal dynamics under the action of a train of Poissonian spikes. In such a scenario, we observed the emergence of irregular spikes for a specific range o...

COVID-19 outbreak, which resulted in further COVID-19 pandemics, was one of the toughest worldwide challenges in recent years. It clearly showed the necessity of the development of models allowing for simulation and reasonable prediction of epidemiologic processes. Traditional approach is based on compartment models, such as SIR model, firstly intr...

This article investigates the emergence of phase synchronization in a network of randomly connected neurons by chemical synapses. The study uses the classic Hodgkin-Huxley model to simulate the neuronal dynamics under the action of a train of Poissonian spikes. In such a scenario, we observed the emergence of irregular spikes for a specific range o...

The brain is formed by cortical regions that are associated with different cognitive functions. Neurons within the same region are more likely to connect than neurons in distinct regions, making the brain network to have characteristics of a network of subnetworks. The values of synaptic delays between neurons of different subnetworks are greater t...

We use ordinal analysis and spatial permutation entropy to distinguish between eyes-open and eyes-closed resting brain states. To do so, we analyze EEG data recorded with 64 electrodes from 109 healthy subjects, under two one-minute baseline runs: One with eyes open, and one with eyes closed. We use spatial ordinal analysis to distinguish between t...

Interconnected systems with critical infrastructures can be affected by small failures that may trigger a large-scale cascade of failures, such as blackouts in power grids. Vulnerability indices provide quantitative measures of a network resilience to component failures, assessing the break of information or energy flow in a system. Here, we focus...

Synaptic time delays and plasticity are intrinsic characteristics present in real neuronal networks, and the interplay between both can promote complex dynamics in the brain. In this work, we build connected plastic subnetworks of Hodgkin-Huxley neurons where the subnetworks are composed of excitatory neurons and the connectivity modifications foll...

The COVID-19 pandemic has given rise to a great demand for computational models capable of describing and inferring the evolution of an epidemic outbreak in the short term. In this sense, we introduce epidWaves, a package that provides a framework for fitting multi-wave epidemic models to data from actual outbreaks of COVID-19 and other infectious...

We study the time delay in the synaptic conductance for suppression of spike synchronisation in a random network of Hodgkin–Huxley neurons coupled by means of chemical synapses. In the first part, we examine in detail how the time delay acts over the network during the synchronised and desynchronised neuronal activities. We observe a relation betwe...

Different algorithms for forecasting and tracking meteorological systems have been developed over the years. Many of them are used to study cloud propagation, precipitation and lightning for nowcasting. Therefore, it is necessary to define carefully the parameters (e.g., intensity thresholds and minimum size) that impact tracking of these variables...

Real-world networks show community structures – groups of nodes that are densely intra-connected and sparsely inter-connected to other groups. Nevertheless, Community Detection (CD) is non-trivial, since identifying these groups of nodes according to their local connectivity can hold many plausible solutions, leading to the creation of different me...

Programa CAPES-EPIDEMIAS COVID-19 - Acompanhamento populacional e controle da epidemia a partir de dados georreferenciados, telemedicina e padrões de comportamento social

We show that for the Kuramoto model (with identical phase oscillators equally coupled), its global statistics and size of the basins of attraction can be estimated through the eigenvalues of all stable (frequency) synchronized states. This result is somehow unexpected since, by doing that, one could just use a local analysis to obtain the global dy...

We study the time delay in the synaptic conductance for suppression of spike synchronisation in a random network of Hodgkin Huxley neurons coupled by means of chemical synapses. In the first part, we examine in detail how the time delay acts over the network during the synchronised and desynchronised neuronal activities. We observe a relation betwe...

Understanding the direct and indirect impact of the Pacific and Atlantic Oceans on precipitation in the region of Northeast Brazil (NEB) is crucial for monitoring unprecedented drought events. We propose nonlinear methods of phase coherence and generalized event synchronization analysis to understand the underlying mechanism. In particular, the rel...

The severe acute respiratory syndrome of coronavirus 2 spread globally very quickly, causing great concern at the international level due to the severity of the associated respiratory disease, the so-called COVID-19. Considering Rio de Janeiro city (Brazil) as an example, the first diagnosis of this disease occurred in March 2020, but the exact mom...

The severe acute respiratory syndrome of coronavirus 2 spread globally very quickly, causing great concern at the international level due to the severity of the associated respiratory disease, the so-called COVID-19. Considering Rio de Janeiro city (Brazil) as an example, the first diagnosis of this disease occurred in March 2020, but the exact mom...

The maturation of the autonomic nervous system (ANS) starts in the gestation period and it is completed after birth in a variable time, reaching its peak in adulthood. However, the development of ANS maturation is not entirely understood in newborns. Clinically, the ANS condition is evaluated with monitoring of gestational age, Apgar score, heart r...

The neuron dynamics is highly susceptible to variations in its current input. In this work, we study the dynamics of uncoupled and random coupled Hodgkin Huxley neurons under an external current with constant or pulsed amplitude. The profile of these pulse perturbations are considered as periodic, random, and a mix between these two types. For unco...

We show that for the Kuramoto model (with identical phase oscillators equally coupled) its global statistics and size of the basins of attraction can be estimated through the eigenvalues of all stable (frequency) synchronized states. This result is somehow unexpected since, by doing that, one could just use local analysis to obtain global dynamic p...

The maturation of the autonomic nervous system (ANS) starts in the gestation period and it is completed after birth in a variable time, reaching its peak in adulthood. However, the development of ANS maturation is not entirely understood in newborns. Clinically, the ANS condition is evaluated with monitoring of gestational age, Apgar score, heart r...

Due to technical problems this article has been published before corrections were implemented.

The paper reports on application of the Gompertz model to describe the growth dynamics of COVID-19 cases during the first wave of the pandemic in different countries. Modeling has been performed for 23 countries: Australia, Austria, Belgium, Brazil, Great Britain, Germany, Denmark, Ireland, Spain, Italy, Canada, China, the Netherlands, Norway, Serb...

In this work, we show that elementary changes in the topology of power grids, like the addition or removal of a single transmission line or the increase of its maximum transmission capacity can cause failures in the network. Also, we show that the probability of the occurrence of these failures can be related to the level of centralization of energ...

We analyze how the structure of complex networks of non-identical oscillators influences synchronization in the context of the Kuramoto model. The complex network metrics assortativity and clustering coefficient are used in order to generate network topologies of Erdös–Rényi, Watts–Strogatz, and Barabási–Albert types that present high, intermediate...

Talk at UNIFESP

Complex network theory provides an important tool for the analysis of complex systems such as the Earth’s climate. In this context, functional climate networks can be constructed using a spatiotemporal climate dataset and a suitable time series distance function. The resulting coarse-grained view on climate variability consists of representing dist...

This special issue presents a series of 33 contributions in the area of dynamical networks and their applications. Part of the contributions is devoted to theoretical and methodological aspects of dynamical networks, such as collective dynamics of excitable systems, spreading processes, coarsening, synchronization, delayed interactions, and others....

In this work, we derive a model to study and simulate the dynamics of power grids that, after a few approximations, turns out to be the second-order Kuramoto model. We then use this model to perform some numerical simulations that relate to the vulnerability and stability of energy transmission networks. In relation to the stability, assuming the g...

Recurrence microstates can be used to analyze many properties of stationary states of stochastic and deterministic time series, including the level of correlation of stochastic signals. Here, we show how artificially inserted data (data that does not belong to a original stationary signal) may be detected using recurrence microstates statistics. We...

The mobile agents’ circular formation problem is driven by applications that require a desired spatial and temporal separation, such as data collection or satellite constellations. There are numerous strategies to assign the cluster number and spacing, the radius of the trajectory, communication network, and other parameters. In this numerical stud...

Force-directed algorithms are a class of methods widely used to solve problems modeled via physics laws and resolved by particle simulation. Visualization of general graphs is one of the research fields which uses such algorithms and provides a vast knowledge about their benefits and challenges. Taking advantage of the knowledge provided by graph v...

We investigate the synchronization of coupled electrochemical bursting oscillators using the electrodissolution of iron in sulfuric acid. The dynamics of a single oscillator consisted of slow chaotic oscillations interrupted by a burst of fast spiking, generating a multiple time-scale dynamical system. A wavelet analysis first decomposed the time s...

The Kepler-1647 is a binary system with two Sun-type stars (≈1.22 and ≈0.97 M⊙). It has the most massive circumbinary planet (≈1.52 MJup) with the longest orbital period (≈ 1,107.6 days) detected by the Kepler probe and is located within the habitable zone (HZ) of the system. In this work, we investigated the ability to form and house an Earth-size...

The Kepler-1647 is a binary system with two Sun-type stars (approximately 1.22 and 0.97 Solar mass). It has the most massive circumbinary planet (1.52 Jupiter mass) with the longest orbital period (1,107.6 days) detected by the Kepler probe and is located within the habitable zone (HZ) of the system. In this work, we investigated the ability to for...

Topological analysis and community detection in mobility complex networks have an essential role in many contexts, from economics to the environmental agenda. However, in many cases, the dynamic component of mobility data is not considered directly. In this paper, we study how topological indexes and community structure changes in a business day. F...

The self-organization of multiple autonomous mobile agents is a trending topic nowadays with applications in robotics, aerospace engineering, and satellite formations. We investigate a model of particles with coupled-oscillators dynamics focusing on the particular case of agents grouping in symmetric clusters while moving in concentric circular tra...

In this work, it is evaluated the conditions for the existence of a synchronization manifold in coupled systems. The objective is to enhance the comprehension of the possibilities and restrictions that are involved in the implementation of simultaneous bidirectional communication schemes. As a result, general conditions that rule the existence of t...

This work fo-cused in the problem of Urban mobility, which in an unplanned urban growth sce-nario might generate negative impacts, like traffic jams, air pollution and infras-tructure flaws. Based on real data for the city of São José dos Campos, the mobil-ity of a typical day was represented. These data consist of an Origin-Destinationsurvey: the...

The brain has the phenomenal ability to reorganise itself by forming new connections among neurons and by pruning others. The so-called neural or brain plasticity facilitates the modification of brain structure and function over different time scales. Plasticity might occur due to external stimuli received from the environment, during recovery from...

The study and comprehension of complex systems are crucial intellectual and scientific challenges of the 21st century. In this scenario, network science has emerged as a mathematical tool to support the study of such systems. Examples include environmental processes such as wildfires, which are known for their considerable impact on human life. How...

Chat groups are well-known for their capacity to promote viral political and marketing campaigns, spread fake news, and create rallies by hundreds of thousands on the streets. With the increasing public awareness regarding privacy and surveillance, many platforms have started to deploy end-to-end encrypted protocols. In this context, the group’s co...

The study and comprehension of complex systems are crucial intellectual and scientific challenges of the 21st century. In this scenario, network science has emerged as a mathematical tool to support the study of such systems. Examples include environmental processes such as the wildfires, which are known for their considerable impact on human life....

The number of spatiotemporal data sets has increased rapidly in the last years, which demands robust and fast methods to extract information from this kind of data. Here, we propose a network-based model, called Chronnet, for spatiotemporal data analysis. The network construction process consists of dividing a geometric space into grid cells repres...

The number of spatiotemporal data sets has increased rapidly in the last years, which demands robust and fast methods to extract information from this kind of data. Here, we propose a network-based model, called Chronnet, for spatiotemporal data analysis. The network construction process consists of dividing a geometric space into grid cells repres...

Power grids or energy transmission networks are among the biggest and more complex man made constructions ever made and are a typical example of a complex system. Its components need to be in a synchronous state in order to be fully functional and avoid cascade failures and blackouts. Power grids can be modeled as a complex network of oscillators,...

A methodology is presented based on wavelet techniques to approximate fast and slow dynamics present in time-series whose behavior is characterized by different local scales in time. These approximations are useful to understand the global dynamics of the original full systems, especially in experimental situations where all information is containe...

Two of the most remarkable phenomena in non-linear systems are multistability and remote synchronization. In the first one, depending on the initial conditions, the system may set in different states after the transient, while in the other, dynamical units that are not directly connected set in a synchronized state. In this work, we introduce a new...

Since 2012, the semiarid region of Northeast Brazil (NEB) has been experiencing a continuous dry condition imposing significant social impacts and economic losses. Characterizing the recent extreme drought events and uncovering the influence from the surrounding oceans remain to be big challenges. The physical mechanisms of extreme drought events i...

This special issue of the European Journal of Physics: Special Topics entitled Celestial Mechanics in the XXIst Century published a set of 15 papers aiming to put in perspective the main problems that are being addressed by the researchers in this area. Our goal is to draw attention to the challenges that they represent so that new approaches may b...

The recurrence analysis of dynamic systems has been studied since Poincaré’s seminal work. Since then, several approaches have been developed to study recurrence properties in nonlinear dynamical systems. In this work, we study the recently developed entropy of recurrence microstates. We propose a new quantifier, the maximum entropy (Smax). The new...

This work investigates the possibility of close binary (CB) star systems having Earth-size planets within their habitable zones (HZs). First, we selected all known CB systems with confirmed planets (totaling 22 systems) to calculate the boundaries of their respective HZs. However, only eight systems had all the data necessary for the computation of...

In this work is investigated the possibility of close-binary star systems having Earth-size planets within their habitable zones. First, we selected all known close-binary systems with confirmed planets (totaling 22 systems) to calculate the boundaries of their respective habitable zones (HZ). However, only eight systems had all the data necessary...

Object selection refers to the mechanism of extracting objects of interest while ignoring other objects and background in a given visual scene. It is a fundamental issue for many computer vision and image analysis techniques and it is still a challenging task to artificial visual systems. Chaotic phase synchronization takes place in cases involving...

The estimation of entropy from experimental data has a considerable bias when the discretization of the variable domain is comparable to the sample size. In this case, the source of the bias is the difference between the a priori distribution and the observed distribution from sampled data. In this paper, we estimate the entropy bias considering an...

Fire activity has a huge impact on human lives. Different models have been proposed to predict fire activity, which can be classified into global and regional ones. Global fire models focus on longer timescale simulations and can be very complex. Regional fire models concentrate on seasonal forecasting but usually require inputs that are not availa...

Bifurcation diagrams and Lyapunov exponents are the main tools for dynamical systems characterization. However, they are often computationally expensive and complex to calculate. We present two approaches for dynamical characterization of nonlinear systems via the generation of an undirected complex network that is built from their time series. Per...

The brain has the phenomenal ability to reorganize itself by forming new connections among neurons and by pruning others. The so-called neural or brain plasticity facilitates the modification of brain structure and function over different time scales. Plasticity might occur due to external stimuli received from the environment, during recovery from...

Abstract Urban mobility data are important to areas ranging from traffic engineering to the analysis of outbreaks and disasters. In this paper, we study mobility data from a major Brazilian city from a geographical viewpoint using a Complex Network approach. The case study is based on intra-urban mobility data from the Metropolitan area of Rio de J...

The Brazilian Colloquium on Orbital Dynamics (CBDO) is a scientific meeting that takes place every two years since 1982. Its main goal is to bring together researchers, professors, undergraduate and post graduate students who develop works on pure and applied Celestial Mechanics in the same lectures and discussions atmosphere, and thus to drive col...

Specific application of satellites require the building and maintenance of orbits with high altitude. In these cases, conventional orbital transfer methods may prove to be infeasible, especially with respect to fuel consumption. In this work we present an alternative strategy for an orbital transfer of a spacecraft from a low circular orbit to a hi...

Epileptic seizures are associated with excessively high synchronous activities of neocortex regions or other neural populations. Traub and Wong showed that synchronized bursts appear in epileptic seizures depend on the neural dynamics. Two suggested mechanisms responsible for the generation of partial epilepsy are the decrease of inhibition and inc...

Solar systems complexity, multiscale, and nonlinearity are governed by numerous and continuous changes where the sun magnetic fields can successfully represent many of these phenomena. Thus, nonlinear tools to study these challenging systems are required. The dynamic system recurrence approach has been successfully used to deal with this kind chall...

Epileptic seizures are associated with excessively high synchronous activities of neocortex regions or other neural populations. Traub and Wong showed that synchronized bursts that appear in epileptic seizures depend on neural dynamics. Two suggested mechanisms responsible for the generation of partial epilepsy are the decrease of inhibition and th...

Talk at PNLD 2019

Here we modeled and simulated disease spreading by means of a mechanistic stochastic model on metapopulations. Different network sizes, mobility rates and immunity duration for a susceptible–infected–recovered–susceptible (SIRS) like process are systematically explored. A transitory behavior was identified in the pathogen persistence where the mobi...

Network theory has established itself as an appropriate tool for complex systems analysis and pattern recognition. In the context of spatiotemporal data analysis, correlation networks are used in the vast majority of works. However, the Pearson correlation coefficient captures only linear relationships and does not correctly capture recurrent event...

In this paper, we divide the globe into a hexagonal grid and we extracted time series of daily fire counts from each cell to estimate and analyze worldwide fire season severity (FSS), here defined as the accumulated fire detections in a season. The central question here is evaluating the accuracy of time series forecasting methods to estimate short...

Nonlinear dynamics is about systems whose dynamics is ruled by nonlinear algebraic or nonlinear differential equations. In regard to their physical behavior, the relationships between changes in their inputs and the resultant behavior in their outputs are not proportional to one another. This behavior characterizes them as nonlinear systems. A nonl...

Network theory has established itself as an appropriate tool for complex systems analysis and pattern recognition. In the context of spatiotemporal data analysis, correlation networks are used in the vast majority of works. However, the Pearson correlation coefficient captures only linear relationships and does not correctly capture recurrent event...

In the context of networks of coupled oscillators, remote synchronization happens when phase difference between non-adjacent units become constant, even though there is no global phase-locking. We study such regime considering a star-like network of Stuart-Landau oscillators. As previous works, our setup comprises peripheral nodes with different bu...

Aerospace engineering is a relatively new topic in engineering. It deals with several aspects of activities related to space. It includes Astrodynamics, which is a field that studies the motion of spacecraft, like guidance and control, which studies different forms to guide the motion of a spacecraft, etc. All those fields started from the Celestia...

Excessively high, neural synchronisation has been associated with epileptic seizures, one of the most common brain diseases worldwide. A better understanding of neural synchronisation mechanisms can thus help control or even treat epilepsy. In this paper, we study neural synchronisation in a random network where nodes are neurons with excitatory an...

We extend a recently introduced prototypical stochastic model describing uniformly the search and return of objects looking for new food sources around a given home. The model describes the kinematic motion of the object with constant speed in two dimensions. The angular dynamics is driven by noise and describes a "pursuit" and "escape" behavior of...

We develop a prototypical stochastic model for a local search around a given home. The stochastic dynamic model is motivated by experimental findings of the motion of a fruit fly around a given spot of food but will generally describe the local search behavior. The local search consists of a sequence of two epochs. In the first the searcher explore...

In this work, we apply the spatial recurrence quantification analysis (RQA) to identify chaotic burst phase synchronisation in networks. We consider one neural network with small-world topology and another one composed of small-world subnetworks. The neuron dynamics is described by the Rulkov map, which is a two-dimensional map that has been used t...