Navegando por Autor "Silva, Alcides Volpato Carneiro de Castro e"
Agora exibindo 1 - 18 de 18
Resultados por página
Opções de Ordenação
Item Analysis of chaotic behaviour in the population dynamics.(2001) Silva, Alcides Volpato Carneiro de Castro e; Bernardes, Américo TristãoRecently, we have shown that the Penna bitstring model for population senescence can be used to model cyclic or chaotic behaviours in population dynamics. In this paper, we analyse the attractor of the dynamics, through the calculation of the Lyapunov exponents. We obtained that the dynamics is characterized by the existence of some small exponents, which we relate to the existence of homeochaos, needed for the generation of stability and diversity in living systems.Item Arranjos produtivos locais e seus efeitos sobre o turismo.(2011) Flecha, Ângela Cabral; Fusco, José Paulo Alves; Silva, Alcides Volpato Carneiro de Castro eO presente artigo tem como objetivo apresentar um conjunto de indicadores de desempenho visando orientar os atores no sentido de aumentar sua coesão mútua e facilitar a busca de objetivos comuns. Tais indicadores foram definidos a partir da expertise dos autores na analise de redes de turismo, aliado a resultados obtidos na pesquisa em Ouro Preto. Dessa forma foi possível perceber, o grau de significância dos atores envolvidos em função dos critérios de escolha utilizados pelos visitantes para configurar seu caminho dentro da região turística analisada e assim reforçar os relacionamentos existentes.Item Astrobiologia : como modelar o crescimento de organismos na Terra e em exoplanetas.(2020) Velten, Hermano Endlich Schneider; Silva, Alcides Volpato Carneiro de Castro e; Pinheiro, Carlos Felipe SaraivaVamos discutir o chamado modelo de Eigen utilizado para modelar a evolução do código genético de microorganismo. Este modelo determina, em termos do tamanho da cadeia de informação e de sua probabilidade de erro ao se multiplicar, quais configurações genéticas sobrevivem a longo prazo. Mostramos algumas simulações deste modelo e discutimos como utilizar este tema no estudo da astrobiologia.Item Astrobiologia: como modelar o crescimento de organismos na Terra e em exoplanetas.(2020) Velten, Hermano Endlich Schneider; Silva, Alcides Volpato Carneiro de Castro e; Pinheiro, Carlos Felipe SaraivaVamos discutir o chamado modelo de Eigen utilizado para modelar a evolução do código genético de micro-organismo. Este modelo determina, em termos do tamanho da cadeia de informação e de sua probabilidade de erro ao se multiplicar, quais configurações genéticas sobrevivem a longo prazo. Mostramos algumas simulações deste modelo e discutimos como utilizar este tema no estudo da astrobiologia.Item From Spanish Flu to Syndemic COVID-19 : long- standing sanitarian vulnerability of Manaus, warnings from the Brazilian rainforest gateway.(2021) Ribeiro, Sérvio Pontes; Reis, Alexandre Barbosa; Cruz, Wesley Francisco Dáttilo da; Silva, Alcides Volpato Carneiro de Castro e; Barbosa, Eduardo Augusto Gonçalves; Vital, Wendel Coura; Góes Neto, Aristóteles; Azevedo, Vasco Ariston de Carvalho; Fernandes, Geraldo Wilson AfonsoA second deadlier wave of COVID-19 and the causes of the recent public health collapse of Manaus are compared with the Spanish fl u events in that city, and Brazil. Historic sanitarian problems, and its hub position in the Brazilian airway network are combined drivers of deadly events related to COVID-19. These drivers were amplifi ed by misleading governance, highly transmissible variants, and relaxation of social distancing. Several of these same factors may also have contributed to the dramatically severe outbreak of H1N1 in 1918, which caused the death of 10% of the population in seven months. We modelled Manaus parameters for the present pandemic and confi rmed that lack of a proper social distancing might select the most transmissible variants. We succeeded to reproduce a fi rst severe wave followed by a second stronger wave. The model also predicted that outbreaks may last for up to fi ve and half years, slowing down gradually before the disease disappear. We validated the model by adjusting it to the Spanish Flu data for the city, and confi rmed the pattern experienced by that time, of a fi rst stronger wave in October-November 1918, followed by a second less intense wave in February-March 1919.Item Gastrulation as a self-organized symmetry breaking process.(2005) Silva, Alcides Volpato Carneiro de Castro e; Bernardes, Américo TristãoAmong the stages a fertilized egg undergoes until reaching its final shape, gastrulation represents the first step in breaking its initial symmetry. This process is of enormous importance in development of the embryos sagittal symmetry plane or dorso-ventral axis. Gastrulation also results in the appearance of three regions, the germ layers, from which all of the organs and systems of the organism originate. In this paper, following the hypothesis which affirms that pattern formation at some stages of organism development are due to morphogens gradient, we introduce a model which mimics the early stages of gastrulation of many multicellular organisms. In this model, the cause of symmetry breaking is given by the intrinsic dynamics of the system.Item Mean-field and non-mean-field behaviors in scale-free networks with random boolean dynamics.(2010) Silva, Alcides Volpato Carneiro de Castro e; Silva, Jafferson Kamphorst Leal daWe study two types of simplified Boolean dynamics in scale-free networks, both with synchronous update. Assigning only Boolean functions AND and XOR to the nodes with probability 1 − p and p, respectively, we are able to analyze the density of 1’s and the Hamming distance on the network by numerical simulations and by a mean-field approximation (annealed approximation). We show that the behavior is quite different if the node always enters in the dynamics as its own input (self-regulation) or not. The same conclusion holds for the Kauffman NK model. Moreover, the simulation results and the mean-field ones (i) agree well when there is no self-regulation, and (ii) disagree for small p when self-regulation is present in the model.Item Medidas de centralidade como parâmetros para se avaliar os atores da rede de turismo : o caso de Ouro Preto.(2011) Flecha, Ângela Cabral; Bernardes, Américo Tristão; Silva, Alcides Volpato Carneiro de Castro eNo turismo as medidas de centralidade são altamente justificadas pelo fato de gerarem dados precisos do comportamento quantitativo dos atores de uma rede. Desta forma, este artigo tem como objetivo mapear a rede de atores do turismo da cidade de Ouro Preto, identificar e descrever as medidas de centralidade desta rede como parâmetros para se avaliar o desempenho de seus atores. Foi utilizado o Ucinet 2.0 e os resultados apontam para a utilização destas medidas como fortes aliados às ações de marketing, tais como disseminação de informação, divulgação de novas ações, políticas e programas públicos e privados.Item New applications of an old individual-based model for biological dynamics.(2023) Ferreira, Fabíola Keesen; Silva, Alcides Volpato Carneiro de Castro e; Pinheiro, Carlos Felipe Saraiva; Arashiro, Everaldo; Ligeiro, Yan; Grelle, Carlos Eduardo de ViveirosA simplified representation or interpretation of reality using conceptual and mathematical models plays a role in understanding important phenomena, especially biological ones. Based on Medawar’s mutation accumulation theory, which predicts that the strength of natural selection decreases with age, favouring the accumulation of deleterious genes to be expressed at advanced ages, an individual-based model (IBM) published in 1995 was designed to demonstrate the biological ageing mechanism, with each individual being represented by a bitstring in a chronological manner. This model is called Penna Model (Penna, 1995) in honour of the creator, the physicist Thadeu Josino Pereira Penna. For this first time, this article carries out a systematic review of the use of Penna Model to assess its applicability in other phenomena and biological mechanisms. Our results indicate that the model was extensively explored and improved by researchers from different parts of the world, through small changes in the structure and base parameters of the model aimed at the biological phenomena of interest including Ecology, Evolutionary Ecology and Genetics issues. These changes have allowed the use of the model in other biological phenomena besides aging, with studies in systems of predation, competition, fragmentation, natural selection, speciation, genetics, immunology, epidemiology and others. The model is highlighted as a fairly flexible tool for applied biological dynamics of simple use, with the possibility of implementing different scales - temporal or spatial; and different languages - computational, logical or numerical; in addition to the possibility of inserting parameters that modify the individual and/or population that allow consistent results for decision-making.Item Recruitment and entropy decrease during trail formation by foraging ants.(2020) Lourenço, Giselle Martins; Ferreira, Fabíola Keesen; Fagundes, Roberth; Luna, P.; Silva, Alcides Volpato Carneiro de Castro e; Ribeiro, Sérvio Pontes; Arashiro, EveraldoSocial insects utilise a complex spatial orientation system mediated by chemical signals. This study investigated how the foraging behaviour of ants (Dorymyrmex thoracicus) varies depending on the quantity of an available resource using a feld experiment. Further, we demonstrated computationally that ant displacement is compatible with a model based on pheromone deposition. Our experiment tested how the resource size (large or small) and availability (one or two simultaneous patches) of resources ofered infuence the number of recruited ants (trafc fow) and the speed of trafc fow both moving towards a resource and returning to the colony. The results showed that the returning fow was higher than the going fow independent of resource. The trafc fow towards a single resource was higher than the fow for either of two simultaneous resources patches ofered; thus, multiple resources sources split the fow, regardless of the fact that resource size did not afect foraging choices. Our results indicated that the ants used an orientation mechanism that can be reproduced by a theoretical computer model. With our model, we showed that initially, the displacement of ants followed no clearly detectable pattern. However, with increasing levels of ant recruitment and consequent pheromone deposition on the most used trails, returning displacement revealed the formation of shorter and more organised trails. The model revealed key transition between periods of order and disorder that continued until the fow of information reached an organised state (Shannon entropy). This study highlights an exceptional mechanism of foraging optimisation in eusocial insects.Item Redes de empresas e seus efeitos sobre o turismo.(2012) Flecha, Ângela Cabral; Silva, Alcides Volpato Carneiro de Castro e; Fusco, José Paulo Alves; Bernardes, Américo TristãoO presente artigo tem como objetivo propor um modelo de alinhamento competitivo para a rede de atores do turismo, visando aumentar sua coesão e facilitar a busca de objetivos comuns. Tal proposta foi definida com base na expertise dos autores na analise de redes de turismo, aliada a resultados obtidos na pesquisa em Ouro Preto (MG). Dessa forma, foi possível perceber o peso dos atores envolvidos em função dos critérios de escolha utilizados pelos visitantes para configurar seu caminho dentro da região turística analisada e, assim, reforçar os relacionamentos existentes.Item Roughness exponents to calculate multi-affine fractal exponents(1997) Silva, Alcides Volpato Carneiro de Castro e; Moreira, José Guilherme Martins AlvesWe propose a new method to determine the multi-affine fractal exponents based on a generalization of the roughness concept. For synthetic multi-attine fractal profiles with exactly known exponents, we show that the results obtained in this method are more accurate than the results obtained with the height-height correlation function method. Also in the present method, scaling is observed using profiles with a number of points more than one order of magnitude smaller.Item Scaling relations in food webs.(2006) Barbosa, Lauro Antônio; Silva, Alcides Volpato Carneiro de Castro e; Silva, Jafferson Kamphorst Leal daIn the last three decades, researchers have tried to identify universal patterns in the structure of food webs. It was recently proposed that the exponent _ characterizing the efficiency of the transport of energy in large and small food webs might have a universal value __ =1.13_. In this work we establish lower and upper bounds for this exponent in a general spanning tree with a fixed number of trophic species and levels. When the number of species is large, the lower and upper bounds are equal to 1, implying that the result _ =1.13 is due to finite-size effects and that the value of this exponent depends on the size of the web. We also evaluate analytically and numerically the exponent _ for hierarchical and random networks. In all cases the exponent _ depends on the number of trophic species K, and when K is large we have that _→1. Moreover, this result holds for any fixed number M of trophic levels.Item Severe airport sanitarian control could slow down the spreading of COVID-19 pandemics in Brazil.(2020) Ribeiro, Sérvio Pontes; Silva, Alcides Volpato Carneiro de Castro e; Cruz, Wesley Francisco Dáttilo da; Reis, Alexandre Barbosa; Góes Neto, Aristóteles; Alcantara, Luiz Carlos Junior; Giovanetti, Marta; Vital, Wendel Coura; Fernandes, Geraldo Wilson Afonso; Azevedo, Vasco Ariston de CarvalhoBackground: We investigated a likely scenario of COVID-19 spreading in Brazil through the complex airport network of the country, for the 90 days after the first national occurrence of the disease. After the confirmation of the first imported cases, the lack of a proper airport entrance control resulted in the infection spreading in a manner directly proportional to the amount of flights reaching each city, following the first occurrence of the virus coming from abroad. Methodology: We developed a Susceptible-Infected-Recovered model divided in a metapopulation structure, where cities with airports were demes connected by the number of flights. Subsequently, we further explored the role of the Manaus airport for a rapid entrance of the pandemic into indigenous territories situated in remote places of the Amazon region. Results: The expansion of the SARS-CoV-2 virus between cities was fast, directly proportional to the city closeness centrality within the Brazilian air transportation network. There was a clear pattern in the expansion of the pandemic, with a stiff exponential expansion of cases for all the cities. The more a city showed closeness centrality, the greater was its vulnerability to SARS-CoV-2. Conclusions: We discussed the weak pandemic control performance of Brazil in comparison with other tropical, developing countries, namely India and Nigeria. Finally, we proposed measures for containing virus spreading taking into consideration the scenario of high poverty.Item Simulations of populations of Sapajus robustus in a fragmentedlandscape.(2017) Ferreira, Fabíola Keesen; Silva, Alcides Volpato Carneiro de Castro e; Arashiro, Everaldo; Pinheiro, Carlos Felipe SaraivaThe study of populations subject to the phenomenon of loss and fragmentation of habitat, transformingcontinuous areas into small ones, usually surrounded by anthropogenic matrices, has been the focus ofmany researches within the scope of conservation. The objective of this study was to develop a com-puter model by introducing modifications to the renowned Penna model for biological aging, in order toevaluate the behavior of populations subjected to the effects of fragmented environments. As an objectof study, it was used biological data of the robust tufted capuchin (Sapajus robustus), an endangered pri-mate species whose geographical distribution within the Atlantic Rain Forest is part of the backdrop ofintense habitat fragmentation. The simulations showed the expected behavior based on the three mainaspects that affects populations under intense habitat fragmentation: the population density, area andconformation of the fragments and deleterious effects due the low genetic variability in small and isolatedpopulations. The model showed itself suitable to describe changes in viability and population dynamicsof the species crested capuchin considering critical levels of survival in a fragmented environment andalso, actions in order to preserve the species should be focused not only on increasing available area butalso in dispersion dynamicsItem A smooth path to plot hydrogen atom via Monte Carlo method.(2019) Lobo, Pedro Henrique Fernandes; Arashiro, Everaldo; Silva, Alcides Volpato Carneiro de Castro e; Pinheiro, Carlos Felipe SaraivaIn this paper, we show how to build a basic computer program using the Monte Carlo method to display the hydrogen atomic orbitals. For this, in a heuristic way, we applied a von Neumann acceptance-rejection method in simple problems of potential wells, and we end with the hydrogen orbitals representation. In this technique, we spread points uniformly on the 1D and 2D charts of probability density distributions, then we filtered points under these “curves or surfaces”, and we extended this logic to 3D cases. Throughout the work, we also made some comments to help beginner students better understand the term “wave function” present in the Schrödinger equation. Also, we made all source code available at a third-party platform, for any purpose under the MIT license. Keywords: hydrogen atom, quantum mechanics, Monte Carlo method, Neumann acceptance-rejection method.Item Social network analysis in disaster management.(2023) Flecha, Ângela Cabral; Bandeira, Renata Albergaria; Campos, Vania Barcellos Gouvêa; Silva, Alcides Volpato Carneiro de Castro e; Leiras, AdrianaPaper aims: This paper aims the use of Social Network Analysis (SNA) as an assessment tool to answer the following research questions: (i) Who are the actors in Humanitarian Operations Networks (HON)?; and (ii) Which actors exert influence on HON? Originality: This paper proposes the use of SNA in a different context, bringing new technics to the field of humanitarian logistics. Research method: Multiple methodological tools are used such as UCINET, Cytoscape, and EXCEL® to apply SNA in the Brazilian context of sudden-onset natural disaster-response operations. Main findings: This application validates the consistency of using SNA to assess HON, besides validating the stakeholder relationship model of the Public, Private, and People sectors in disaster-response operations. Implications for theory and practice: Results show strong participation of the public sector in disaster-response operations in Brazil, indicating the need for greater engagement from civil society. Besides, the proposed method can be adopted in the context of any other country.Item Worldwide COVID-19 spreading explained : traveling numbers as a primary driver for the pandemic.(2020) Ribeiro, Sérvio Pontes; Cruz, Wesley Francisco Dáttilo da; Barbosa, David Soeiro; Vital, Wendel Coura; Chagas, Igor Aparecido Santana das; Silva, Alcides Volpato Carneiro de Castro e; Morais, Maria Helena Franco; Góes Neto, Aristóteles; Azevedo, Vasco Ariston de Carvalho; Fernandes, Geraldo Wilson Afonso; Reis, Alexandre BarbosaThe spread of SARS-CoV-2 and the distribution of cases worldwide followed no clear biogeographic, climatic, or cultural trend. Conversely, the internationally busiest cities in all countries tended to be the hardest hit, suggesting a basic, mathematically neutral pattern of the new coronavirus early dissemination. We tested whether the number of flight passengers per time and the number of international frontiers could explain the number of cases of COVID-19 worldwide by a stepwise regression. Analysis were taken by 22 May 2020, a period when one would claim that early patterns of the pandemic establishment were still detectable, despite of community transmission in various places. The number of passengers arriving in a country and the number of international borders explained significantly 49% of the variance in the distribution of the number of cases of COVID-19, and number of passengers explained significantly 14.2% of data variance for cases per million inhabitants. Ecological neutral theory may explain a considerable part of the early distribution of SARS-CoV-2 and should be taken into consideration to define preventive international actions before a next pandemic.