Adaptive, locally-linear models of complex dynamics

The dynamics of complex systems generally include high-dimensional, non-stationary and non-linear behavior, all of which pose fundamental challenges to quantitative understanding. To address these difficulties we detail a new approach based on local linear models within windows determined adaptively from the data. While the dynamics within each window are simple, consisting of exponential decay, growth and oscillations, the collection of local parameters across all windows provides a principled characterization of the full time series. To explore the resulting model space, we develop a novel likelihood-based hierarchical clustering and we examine the eigenvalues of the linear dynamics. We demonstrate our analysis with the Lorenz system undergoing stable spiral dynamics and in the standard chaotic regime. Applied to the posture dynamics of the nematode $C. elegans$ our approach identifies fine-grained behavioral states and model dynamics which fluctuate close to an instability boundary, and we detail a bifurcation in a transition from forward to backward crawling. Finally, we analyze whole-brain imaging in $C. elegans$ and show that the stability of global brain states changes with oxygen concentration.Comment: 25 pages, 16 figure

Digital Evolution: blockchain field research

Bernardino, C., Costa, C. J., & Aparicio, M. (2022). Digital Evolution: blockchain field research. In 2022 17th Iberian Conference on Information Systems and Technologies (CISTI): proceedings (pp. 1-6). (CISTI 2022. 17th Iberian Conference on Information Systems and Technologies, 22-25 June 2022, Madrid, Spain). IEEE. ISBN: 978-9-8933-3436-2. https://doi.org/10.23919/CISTI54924.2022.9820035Blockchain is a relatively new technology supported by a decentralized database that received special attention at the research level in the last years due to its fundamental characteristics. Numerous researchers have applied blockchain studies in many fields, but the scope is very large and there is no delimitation of new and emergent trends. The method used to better understand the evolution and impact of blockchain technology was a bibliometric analysis. A search was conducted at digital Elsevier’s database with a single keyword blockchain, and 23383 articles were collected. The study uses cluster analysis method, allowing to construct and visualize bibliometric networks and to build co-occurrences networks. The results indicate that there are positive correlations between countries, that China and the United States are part of the most influential cluster. Indicates also emerging developments in the areas of governance, industry, decision-making processes, management, internet of things, information security, and a new hot topic, energy.authorsversionpublishe

Applications of Data Science and Artificial Intelligence

Costa, C. J., & Aparicio, M. (2023). Applications of Data Science and Artificial Intelligence. Applied Sciences (Switzerland), 13(15), 1-3. [9015]. https://doi.org/10.3390/app13159015 --- The authors acknowledge financial support via ADVANCE-CSG from the Fundação para a Ciência and Tecnologia (FCT Portugal) through research grant number UIDB/04521/2020, and we gratefully acknowledge the financial support from FCT—Fundação para a Ciencia e Tecnologia, I.P., (Portugal), national funding through research grant UIDB/04152/2020—Centro de Investigação em Gestão de Informação (MagIC).Data science and artificial intelligence have emerged as pivotal disciplines in the era of big data and automation. With the ability to analyze massive datasets, uncover patterns, and predict outcomes, these technologies have found applications in numerous sectors, revolutionizing how we interact with information and make decisions. Here, we highlight some of the most significant applications of data science and AI and their impact on various industries.publishersversionpublishe

Desenvolvimento e uso de um jogo didático "Corrida da Química" e sua implementação no ensino da química no 8º ano de escolaridade

A utilização de jogos didáticos no processo de ensino-aprendizagem da química é uma tendência recentemente proposta por vários autores. Esta abordagem pedagógica revela-se um útil instrumento para a promoção de aspectos relacionados com o desenvolvimento cognitivo, intelectual e criativo o que promove um acréscimo da motivação dos alunos para o processo de ensino. Consequentemente, considera-se que o uso destes instrumentos facilita a sociabilidade dos alunos, traduzindo-se num acréscimo das capacidades de interação pessoal, e contribui para promover o sucesso dos alunos na escola e na sociedade. Neste trabalho descrevem-se as etapas de construção de um jogo didático, intitulado “Corrida da Química” sendo este utilizado como suporte de aprendizagem da unidade didática “Reações Químicas". O processo de elaboração do jogo envolveu a construção dos vários componentes, nomeadamente: o tabuleiro do jogo (baseado na Tabela Periódica dos Elementos); os conjuntos de cartões; os modelos de equipamento de laboratório; modelos atómicos e peças de puzzle de modelos de iões. Serão apresentados os resultados da implementação de dois testes (teste inicial e teste final) que avaliaram o impacto do jogo no processo de aprendizagem permitindo concluir que este jogo contribuiu para uma melhoria do aproveitamento e uma participação mais ativa dos aluno

Modeling the ballistic-to-diffusive transition in nematode motility reveals variation in exploratory behavior across species

A quantitative understanding of organism-level behavior requires predictive models that can capture the richness of behavioral phenotypes, yet are simple enough to connect with underlying mechanistic processes. Here we investigate the motile behavior of nematodes at the level of their translational motion on surfaces driven by undulatory propulsion. We broadly sample the nematode behavioral repertoire by measuring motile trajectories of the canonical lab strain $C. elegans$ N2 as well as wild strains and distant species. We focus on trajectory dynamics over timescales spanning the transition from ballistic (straight) to diffusive (random) movement and find that salient features of the motility statistics are captured by a random walk model with independent dynamics in the speed, bearing and reversal events. We show that the model parameters vary among species in a correlated, low-dimensional manner suggestive of a common mode of behavioral control and a trade-off between exploration and exploitation. The distribution of phenotypes along this primary mode of variation reveals that not only the mean but also the variance varies considerably across strains, suggesting that these nematode lineages employ contrasting ``bet-hedging'' strategies for foraging.Comment: 46 pages, 18 figures, 6 table

CAN HEDGING AFFECT FIRM VALUE? AN OIL, GAS AND MINING PERSPECTIVE

Our paper investigates the impact of financial hedging on the firm value of a sample of mining, oil and gas companies that are publicly listed on the Toronto Stock Exchange. Employing a Tobin’s Q model for the sample of companies, the study finds that hedging does not significantly affect a firm’s valuation while other financial factors impact it in a statistically and economically significant manner. The results add further evidence to the current research literature that has reported contradictory empirical findings from prior research. Our observations are consistent with the school of thought that the firm valuation effect associated with hedging is insignificant. In these resource sectors, commodity price exposure is transparent and easy to hedge by investors, so there is no reason to expect that oil, gas and mining companies hedging their production price risk(s) should have higher firm values. &nbsp

Environmental risk assessment in a contaminated estuary: an integrated weight of evidence approach as a decision support tool

Environmental risk assessment of complex ecosystems such as estuaries is a challenge, where innovative and integrated approaches are needed. The present work aimed at developing an innovative integrative methodology to evaluate in an impacted estuary (the Sado, in Portugal, was taken as case study), the adverse effects onto both ecosystem and human health. For the purpose, new standardized lines of evidence based on multiple quantitative data were integrated into a weight of evidence according to a best expert judgment approach. The best professional judgment for a weight of evidence approach in the present study was based on the following lines of evidence: i) human contamination pathways; ii) human health effects: chronic disease; iii) human health effects: reproductive health; iv) human health effects: health care; v) human exposure through consumption of local agriculture produce; vi) exposure to contaminated of water wells and agriculture soils; vii) contamination of the estuarine sedimentary environment (metal and organic contaminants); viii) effects on benthic organisms with commercial value; and ix) genotoxic potential of sediments. Each line of evidence was then ordinally ranked by levels of ecological or human health risk, according to a tabular decision matrix and expert judgment. Fifteen experts scored two fishing areas of the Sado estuary and a control estuarine area, in a scale of increasing environmental risk and management actions to be taken. The integrated assessment allowed concluding that the estuary should not be regarded as impacted by a specific toxicant, such as metals and organic compounds hitherto measured, but by the cumulative risk of a complex mixture of contaminants. The proven adverse effects on species with commercial value may be used to witness the environmental quality of the estuarine ecosystem. This method argues in favor of expert judgment and qualitative assessment as a decision support tool to the integrative management of estuaries. Namely it allows communicating environmental risk and proposing mitigation measures to local authorities and population under a holistic perspective as an alternative to narrow single line of evidence approaches, which is mandatory to understand cause and effect relationships in complex areas like estuaries.info:eu-repo/semantics/publishedVersio

Phytosociologic associations and Natura 2000 habitats of Portuguese coastal sand dunes

The Portuguese coastline is quite long and the littoral ecosystems are of the outmost importance in the context of the national flora and vegetation. The diversity of vegetation types and the endemicity of their flora justify the attention paid to coastal habitats in the implementation of the Natura 2000 network. In this paper we present a synatoxonomical revision of the phanerophytic, chamaephytic and hemicryptophytic communities occurring in the sandy coastal areas of Portugal, together with their correspondence to the “Natura 2000” natural habitat types. The production of synthetic tables with all available relevés has allowed the segregation of plant community types. We also include maps concerning the distribution of all validated vegetation types occurring in the Portuguese sandy coastal areas.info:eu-repo/semantics/publishedVersio

key determinants of e-commerce usage and repurchase intention

Aparicio, M., Costa, C. J., & Moises, R. (2021). Gamification and reputation: key determinants of e-commerce usage and repurchase intention. Heliyon, 7(3), [e06383]. https://doi.org/10.1016/j.heliyon.2021.e06383Nowadays, companies know that keeping customers engaged is essential to increase their loyalty. The main goal of this study is to understand the impact of gamification and reputation on the intention of repurchase in e-commerce. Gamification corresponds to the regular usage of game elements in non-game context. This study purposes a theoretical model indicating the determinants of repurchase intention. Here we present an empirical study (survey collected data) within a real e-commerce usage context. Data were analysed with SEM/PLS method. Results indicate a positive impact of trust on the intention to use of e-commerce, on buy frequency and on repurchase intention. Ease of use, usefulness of e-commerce platforms affect intension to use. We verified the impact of reputation on trust, as well as the impact of gamification on the effective use of the e-commerce platforms. Results indicate that gamified e-commerce websites determine usage and use positively influences repurchase intention in e-commerce context. Gamification, e-commerce, Repurchase intention, Information systems modelpublishersversionpublishe

A conceptual framework to implement gamification on online courses of computer programming learning: implementation

Piteira, M., Costa, C. J., & Aparicio, M. (2017). A conceptual framework to implement gamification on online courses of computer programming learning: implementation . In 10th International Conference of Education, Research and Innovation (ICERI2017) (pp. 7022-7031). (ICERI2015 Proceedings). IATED Academy.On the last years, gamification has studient in variuous contexts, such as marketing, health, sports and education. According to literature, gamification integrates "elements of game design in non-game context", with the objective of increasing users' engagement in certain activities. Therefore gamification integration on information systems should follow a formal and clear design process. However, these gamification design processes for specific contexts are not still defined. Thus, based on a literature review the authors proposed in a previously conducted study a framework for the implementation of gamification in online courses of computer programming learning. The framework is composed of the following dimensions: target audience, general goals, learning outcomes, topics, contents, gamification, cognitive absorption, flow, and personality. In the scope of this paper, authors present and describe the implementation of the conceptual framework. In order to achieve the objective, an online course of fundamentals of programming was designed and implemented, based on the previously proposed framework having then been launched a questionnaire to the students who attended the online course. The student's attitudes towards game elements have been identified.authorsversionpublishe