Browsing by Author "Rodrigues, Carla"
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- Activation of effector immune cells promotes tumor stochastic extinction: A homotopy analysis approachPublication . Sardanyés, Josep; Rodrigues, Carla; Januário, Cristina; Martins, Nuno; Gil-Gómez, Gabriel; Duarte, JorgeIn this article we provide homotopy solutions of a cancer nonlinear model describing the dynamics of tumor cells in interaction with healthy and effector immune cells. We apply a semi-analytic technique for solving strongly nonlinear systems – the Step Homotopy Analysis Method (SHAM). This algorithm, based on a modification of the standard homotopy analysis method (HAM), allows to obtain a one-parameter family of explicit series solutions. By using the homotopy solutions, we first investigate the dynamical effect of the activation of the effector immune cells in the deterministic dynamics, showing that an increased activation makes the system to enter into chaotic dynamics via a period-doubling bifurcation scenario. Then, by adding demographic stochasticity into the homotopy solutions, we show, as a difference from the deterministic dynamics, that an increased activation of the immune cells facilitates cancer clearance involving tumor cells extinction and healthy cells persistence. Our results highlight the importance of therapies activating the effector immune cells at early stages of cancer progression.
- How complex, probable, and predictable is genetically driven red queen chaos?Publication . Duarte, Jorge; Rodrigues, Carla; Januário, Cristina; Martins, Nuno; Sardanyés, JosepCoevolution between two antagonistic species has been widely studied theoretically for both ecologically- and genetically-driven Red Queen dynamics. A typical outcome of these systems is an oscillatory behavior causing an endless series of one species adaptation and others counter-adaptation. More recently, a mathematical model combining a three-species food chain system with an adaptive dynamics approach revealed genetically driven chaotic Red Queen coevolution. In the present article, we analyze this mathematical model mainly focusing on the impact of species rates of evolution (mutation rates) in the dynamics. Firstly, we analytically proof the boundedness of the trajectories of the chaotic attractor. The complexity of the coupling between the dynamical variables is quantified using observability indices. By using symbolic dynamics theory, we quantify the complexity of genetically driven Red Queen chaos computing the topological entropy of existing one-dimensional iterated maps using Markov partitions. Co-dimensional two bifurcation diagrams are also built from the period ordering of the orbits of the maps. Then, we study the predictability of the Red Queen chaos, found in narrow regions of mutation rates. To extend the previous analyses, we also computed the likeliness of finding chaos in a given region of the parameter space varying other model parameters simultaneously. Such analyses allowed us to compute a mean predictability measure for the system in the explored region of the parameter space. We found that genetically driven Red Queen chaos, although being restricted to small regions of the analyzed parameter space, might be highly unpredictable.
- Medicamentos genéricos e padrões de prescrição: conhecimentos e opiniões de médicos e farmacêuticosPublication . Rodrigues, Carla; Pimenta, R.; Fernandes, P.Poucos temas são tão controversos na área da saúde como a introdução de genéricos no mercado de medicamentos, contudo, estes podem desempenhar um papel fundamental na alocação eficiente de recursos financeiros na área do medicamento. Se os médicos, através da prescrição, são o factor decisivo para o aumento da quota de genéricos; os farmacêuticos enquanto dispensadores, assumem um papel preponderante na sensibilização dos utentes para a sua aceitação e adesão à terapêutica. Objectivo do estudo - Estudar os conhecimentos e opiniões de médicos e farmacêuticos sobre os medicamentos genéricos e a sua relação com a prescrição/dispensa de genéricos.
- Medication use for the management of professional performance: between invisibility and social normalisationPublication . Lopes, Noémia; Tavares, David; Pegado, Elsa; Raposo, Hélder António; Rodrigues, CarlaThis article aims to explore pharmaceuticalisation processes in professional work contexts. The approach focuses on identifying patterns of medicine and dietary supplement use for managing work performance, and on discussing the relationship between these consumption practices and work-related pressure factors. This analysis adapts the notions of 'normalisation' to understand the extent of cultural acceptability of these practices, and the notion of 'differentiated normalisation' to capture the tension between the trend towards normalisation of such consumption and its partial social (in)visibility within work settings. Empirical support for this analysis is based on a sociological study conducted in Portugal on professions under high performance pressures. The study involved three professional groups - nurses, journalists and police officers. A mixed methods approach was used, including focus groups, questionnaires and semi-structured interviews. Overall, the results show a trend towards the use of medicines and supplements for performance management, which reveals itself as a cultural response to work-related social pressures. Such consumption coexists with irregular patterns of either occasional or long-term use, as well as heterogeneous processes of 'normalisation' and 'hidden' consumption. Conclusions point to a social interconnection between the intensification of work pressures and the pharmaceuticalisation of work performance.
- Medications, youth therapeutic cultures and performance consumptions: a sociological approachPublication . Lopes, Noémia; Clamote, Telmo; Raposo, Hélder António; Pegado, Elsa; Rodrigues, CarlaThis article analyses performance consumptions among young people. The theme is explored along two main axes. The first concerns the social heterogeneity in this field, considered on two levels: the different purposes for those investments - cognitive/mental and physical performance; and the different social contexts - university and work - where performance practices and dispositions may be fostered. The second axis explores the roles of pharmacological and natural consumptions, and their interrelationship, in the dissemination of these practices. The empirical data for this analysis were drawn from an ongoing research project on performance consumptions among young people (aged 18-29 years) in Portugal, including both university students and young workers without university education. The results correspond to the stage of extensive research, for which a questionnaire was organised at a national level, using non-proportional quota sampling. On the one hand, they show that (a) there is a hierarchy of acceptance of consumptions according to their purposes, with cognitive/mental performance showing higher acceptance and (b) both pharmaceuticals and natural products are consumed for every type of performance investment. On the other, the comparison between students and workers introduces a certain heterogeneity in this general backdrop, both in terms of the purposes for their consumptions and their opting for natural or pharmacological resources. These threads of heterogeneity will prompt a discussion of the dynamics of pharmaceuticalisation within the field of performance, in particular how therapeutic cultures may be changing in terms of the way individuals relate to medications, expanding their uses in social life.
- O natural e o farmacológico: padrões de consumo terapêutico na população portuguesaPublication . Lopes, Noémia; Clamote, Telmo; Raposo, Hélder António; Pegado, Elsa; Rodrigues, CarlaNeste artigo identificam-se os padrões de consumo terapêutico na população portuguesa, visando dar conta de um novo padrão emergente nas sociedades modernas, aqui designado de Pluralismo Terapêutico, noção com a qual se categoriza o uso conjugado ou alternado de recursos farmacológicos e naturais nas trajetórias terapêuticas dos indivíduos. O respetivo suporte empírico decorre de uma investigação, já concluída, que teve por base uma amostra nacional representativa. Os resultados mostram uma dualização dos consumos terapêuticos que é constituída por um padrão dominante de Farmacologismo – i.e., uso exclusivo de fármacos – coexistente com uma tendência crescente de pluralismo terapêutico. O efeito das fontes de informação terapêutica e dos seus usos leigos, bem como das perceções sociais de risco sobre o natural e o farmacológico, constitui neste estudo uma referência analítica central para a interpretação dos padrões encontrados. - ABSTRACT: In this article we identify patterns of therapeutic consumption, with the purpose of assessing an emerging pattern in modern societies, here designated as Therapeutic Pluralism, referring to the conjugated or alternated use of pharmacological and natural resources in the therapeutic trajectories of individuals. The empirical basis for this analysis stems from a concluded research on the topic, and is focused on a questionnaire administered to a representative sample of the Portuguese population. The results show a duality in therapeutic consumptions, expressed in the coexistence of a dominant pattern of Pharmacologism – that is, the exclusive therapeutic consumption of pharmaceuticals – and a growing trend towards therapeutic pluralism. The effects of information sources on health and its lay uses, as well as of the social perceptions of risk concerning the natural and the pharmacological, constitute key analytical references for this study’s interpretation of the identified patterns.
- Optimal homotopy analysis of a chaotic HIV-1 model incorporating AIDS-related cancer cellsPublication . Duarte, Jorge; Januário, Cristina; Martins, Nuno; Ramos, Carlos; Rodrigues, Carla; Sardanyés, JosepThe studies of nonlinear models in epidemiology have generated a deep interest in gaining insight into the mechanisms that underlie AIDS-related cancers, providing us with a better understanding of cancer immunity and viral oncogenesis. In this article, we analyze an HIV-1 model incorporating the relations between three dynamical variables: cancer cells, healthy CD4 + T lymphocytes, and infected CD4 + T lymphocytes. Recent theoretical investigations indicate that these cells interactions lead to different dynamical outcomes, for instance to periodic or chaotic behavior. Firstly, we analytically prove the boundedness of the trajectories in the system’s attractor. The complexity of the coupling between the dynamical variables is quantified using observability indices. Our calculations reveal that the highest observable variable is the population of cancer cells, thus indicating that these cells could be monitored in future experiments in order to obtain time series for attractor’s reconstruction. We identify different dynamical behaviors of the system varying two biologically meaningful parameters: r 1, representing the uncontrolled proliferation rate of cancer cells, and k 1, denoting the immune system’s killing rate of cancer cells. The maximum Lyapunov exponent is computed to identify the chaotic regimes. Considering very recent developments in the literature related to the homotopy analysis method (HAM), we calculate the explicit series solutions of the cancer model and focus our analysis on the dynamical variable with the highest observability index. An optimal homotopy analysis approach is used to improve the computational efficiency of HAM by means of appropriate values for the convergence control parameter, which greatly accelerate the convergence of the series solution. The approximated analytical solutions are used to compute density plots, which allow us to discuss additional dynamical features of the model.
- The uses of coffee in highly demanding work contexts: managing rhythms, sleep, and performancePublication . Pegado, Elsa; Rodrigues, Carla; Raposo, Hélder António; Fernandes, Ana I.This paper presents a sociological approach to coffee consumption as a performance management strategy in work contexts, particularly in professions with intense work rhythms and highly responsive demands. Focusing on the daily work of three professional groups (nurses, police officers, and journalists), we analyze the social expression of coffee and how it is mobilized to deal with sleep problems, fatigue, concentration, or stress. For this purpose, three intertwined dimensions are explored: (1) the nature of these professionals’ work and the pressures for certain forms and levels of performance; (2) sleep problems as both a result of those work characteristics and a constraint on performance; and (3) the role of coffee in managing professional imperatives. The use of coffee appears as a legitimate practice in everyday working routines, due to its socializing markers, whereas additional benefits are attributed to the pharmacological properties of caffeine, given the perceived improvement in performance. The empirical data was derived from a study carried out in Portugal on the use of medicines and food supplements for performance management, following a mixed methods approach. In particular, data from a questionnaire survey in a sample of 539 workers and information collected through seven focus groups with a total of 33 participants were used.
- Topological Complexity and Predictability in the Dynamics of a Tumor Growth Model with Shilnikov's ChaosPublication . Duarte, Jorge; Januário, Cristina; Rodrigues, Carla; Sardanyes, JosepDynamical systems modeling tumor growth have been investigated to determine the dynamics between tumor and healthy cells. Recent theoretical investigations indicate that these interactions may lead to different dynamical outcomes, in particular to homoclinic chaos. In the present study, we analyze both topological and dynamical properties of a recently characterized chaotic attractor governing the dynamics of tumor cells interacting with healthy tissue cells and effector cells of the immune system. By using the theory of symbolic dynamics, we first characterize the topological entropy and the parameter space ordering of kneading sequences from one-dimensional iterated maps identified in the dynamics, focusing on the effects of inactivation interactions between both effector and tumor cells. The previous analyses are complemented with the computation of the spectrum of Lyapunov exponents, the fractal dimension and the predictability of the chaotic attractors. Our results show that the inactivation rate of effector cells by the tumor cells has an important effect on the dynamics of the system. The increase of effector cells inactivation involves an inverse Feigenbaum (i.e. period-halving bifurcation) scenario, which results in the stabilization of the dynamics and in an increase of dynamics predictability. Our analyses also reveal that, at low inactivation rates of effector cells, tumor cells undergo strong, chaotic fluctuations, with the dynamics being highly unpredictable. Our findings are discussed in the context of tumor cells potential viability.