Anisotropic singularities in modified gravity models

We show that the common singularities present in generic modified gravity models governed by actions of the type $S=\int d^4x \sqrt{-g}f(R,\phi,X)$, with $X= -{1/2}g^{ab}\partial_a\phi\partial_b\phi$, are essentially the same anisotropic instabilities associated to the hypersurface $F(\phi)=0$ in the case of a non-minimal coupling of the type $F(\phi)R$, enlightening the physical origin of such singularities that typically arise in rather complex and cumbersome inhomogeneous perturbation analyses. We show, moreover, that such anisotropic instabilities typically give rise to dynamically unavoidable singularities, precluding completely the possibility of having physically viable models for which the hypersurface $\frac{\partial f}{\partial R}=0$ exists. Some examples are explicitly discussed.Comment: 6 pages, final version to appear in PR

Miopatia necrosante paraneoplásica – relato de caso

Univ Fed Sao Paulo, UNIFESP, Div Med Interna, Sao Paulo, SP, BrazilUniversidade Federal de São Paulo (UNIFESP), Divisão de Medicina Interna, São Paulo, SP, BrazilWeb of Scienc

A Customer complaint from a telecommunication company: a Bayesian data analysis

This study considers a customer complaint dataset due to the technical services provided by a telecommunications company collected for 134 consecutive weeks from the first week of January 2018 up to the year 2019. The total count of weekly complaints is the sum of different causes, which characterizes compositional data. The data was analyzed assuming a Poisson regression model for the weekly total complaint count data in presence of a random factor and compositional models both under a Bayesian approach using existing MCMC (Monte Carlo Markov Chain) to get the posterior summaries of interest. The obtained results are of great importance to improve the service quality of the company

Contagion dynamics on higher-order networks

Understanding the dissemination of diseases, information, and behavior stands as a paramount research challenge in contemporary network and complex systems science. The COVID-19 pandemic and the proliferation of misinformation are relevant examples of the importance of these dynamic processes, which have recently gained more attention due to the potential of higher-order networks to unlock new avenues for their investigation. Despite being in its early stages, the examination of social contagion in higher-order networks has witnessed a surge of novel research and concepts, revealing different functional forms for the spreading dynamics and offering novel insights. This review presents a focused overview of this body of literature and proposes a unified formalism that covers most of these forms. The goal is to underscore the similarities and distinctions among various models, to motivate further research on the general and universal properties of such models. We also highlight that while the path for additional theoretical exploration appears clear, the empirical validation of these models through data or experiments remains scant, with an unsettled roadmap as of today. We therefore conclude with some perspectives aimed at providing possible research directions that could contribute to a better understanding of this class of dynamical processes, both from a theoretical and a data-oriented point of view.Comment: Review article. 17 pages and 5 figures. Submitted for publicatio

Data-driven contact structures: from homogeneous mixing to multilayer networks

The modeling of the spreading of communicable diseases has experienced significant advances in the last two decades or so. This has been possible due to the proliferation of data and the development of new methods to gather, mine and analyze it. A key role has also been played by the latest advances in new disciplines like network science. Nonetheless, current models still lack a faithful representation of all possible heterogeneities and features that can be extracted from data. Here, we bridge a current gap in the mathematical modeling of infectious diseases and develop a framework that allows to account simultaneously for both the connectivity of individuals and the age-structure of the population. We compare different scenarios, namely, i) the homogeneous mixing setting, ii) one in which only the social mixing is taken into account, iii) a setting that considers the connectivity of individuals alone, and finally, iv) a multilayer representation in which both the social mixing and the number of contacts are included in the model. We analytically show that the thresholds obtained for these four scenarios are different. In addition, we conduct extensive numerical simulations and conclude that heterogeneities in the contact network are important for a proper determination of the epidemic threshold, whereas the age-structure plays a bigger role beyond the onset of the outbreak. Altogether, when it comes to evaluate interventions such as vaccination, both sources of individual heterogeneity are important and should be concurrently considered. Our results also provide an indication of the errors incurred in situations in which one cannot access all needed information in terms of connectivity and age of the population.Comment: 11 pages, 4 figure

Logística do gerenciamento de contratos para pequenas e médias empresas

Orientador: Darli Rodrigues VieiraMonografia (Especialização) - Universidade Federal do Paraná, Setor de Ciências Sociais Aplicadas, Curso de Especialização em Gerência de Sistemas Logístico

O agronegócio no contexto internacional e no Brasil

This study deals with the expansion of modern agriculture in the post World War II period in the advanced capitalist countries. And how this agribusiness model was disseminated in several regions of the Brazilian countryside, particularly in the Northeast and in the savannahs of Bahia. To this end, it aims to analyze the new model of rural activities based on the pioneering concepts of the term agribusiness by John Davis and Ray Goldberg, elaborated in 1957. It is a quantitative and qualitative research using primary and secondary data and demonstrates the implications of the Green Revolution in the productive dynamics of savannahs in the West of Bahia.Este estudo trata da expansão da moderna agricultura no período pós Segunda Guerra Mundial nos países capitalistas avançados. E como este modelo de agronegócio se disseminou em várias regiões, em particular no Nordeste e nos cerrados da Bahia. Para tanto, tem como objetivo analisar o novo modelo das atividades rurais a partir das conceituações pioneiras do termo agronegócio de John Davis e Ray Goldberg, elaboradas em 1957. É uma pesquisa quantitativa e qualitativa utilizando-se de dados primários e secundários e demonstra as implicações da Revolução Verde na dinâmica produtiva dos cerrados do Oeste baiano

Vitamina D em pediatria

Vitamin D (VD) is one of the fat-soluble vitamins. Its main sources in nature are diet and exposure to sunlight. Recent findings have shown that organs other than the kidney and liver are also able to synthesize VD metabolically active (calcitriol). Vitamin D deficiency (VDD) has been described almost 2.000 years ago and is classically related to diseases of the musculoskeletal system (especially rickets and osteomalacia). However, in recent years, VDD has been linked to disorders that affect other systems in the body, such as asthma and diabetes. In addition, an increase in the prevalence of VDD worldwide has been observed, even in countries with good insolation conditions. The most appropriate way to prevent VDD is by vitamin supplementation since there are no safe limits to sun exposure. The treatment of the VDD is mainly based on the replacement of the vitamin and it is indicated in the symptomatic forms (osteo-muscular symptoms) of its deficiency. VD intoxication is rare and observed in infants and young children who take high doses of VD in an acute way. This review article approaches these and other questions about VD, with particular emphasis on the particularities related to children and adolescents

Understanding the Vegetable Oil Debate and Its Implications for Sustainability through Social Media

The global production and consumption of vegetable oils have sparked several discussions on sustainable development. This study analyzes over 20 million tweets related to vegetable oils to explore the key factors shaping public opinion. We found that coconut, olive, and palm oils dominate social media discourse despite their lower contribution to overall global vegetable production. The discussion about olive and palm oils remarkably correlates with Twitter's growth, while coconut increases more significantly with bursts of activity. Discussions around coconut and olive oils primarily focus on health, beauty, and food, while palm draws attention to pressing environmental concerns. Overall, virality is related to environmental issues and negative connotations. In the context of Sustainable Development Goals, this study highlights the multifaceted nature of the vegetable oil debate and its disconnection from scientific discussions. Our research sheds light on the power of social media in shaping public perception, providing insights into sustainable development strategies.Comment: 26 pages including figures and the S