A general Markov chain approach for disease and rumour spreading in complex networks

Spreading processes are ubiquitous in natural and artificial systems. They can be studied via a plethora of models, depending on the specific details of the phenomena under study. Disease contagion and rumour spreading are among the most important of these processes due to their practical relevance. However, despite the similarities between them, current models address both spreading dynamics separately. In this article, we propose a general spreading model that is based on discrete time Markov chains. The model includes all the transitions that are plausible for both a disease contagion process and rumour propagation. We show that our model not only covers the traditional spreading schemes but that it also contains some features relevant in social dynamics, such as apathy, forgetting, and lost/recovering of interest. The model is evaluated analytically to obtain the spreading thresholds and the early time dynamical behaviour for the contact and reactive processes in several scenarios. Comparison with Monte Carlo simulations shows that the Markov chain formalism is highly accurate while it excels in computational efficiency. We round off our work by showing how the proposed framework can be applied to the study of spreading processes occurring on social networks

Urbanisation and asthma in low-income and middle-income countries: a systematic review of the urban-rural differences in asthma prevalence.

BACKGROUND: Urbanisation has been associated with temporal and geographical differences in asthma prevalence in low-income and middle-income countries (LMICs). However, little is known of the mechanisms by which urbanisation and asthma are associated, perhaps explained by the methodological approaches used to assess the urbanisation-asthma relationship. OBJECTIVE: This review evaluated how epidemiological studies have assessed the relationship between asthma and urbanisation in LMICs, and explored urban/rural differences in asthma prevalence. METHODS: Asthma studies comparing urban/rural areas, comparing cities and examining intraurban variation were assessed for eligibility. Included publications were evaluated for methodological quality and pooled OR were calculated to indicate the risk of asthma in urban over rural areas. RESULTS: Seventy articles were included in our analysis. Sixty-three compared asthma prevalence between urban and rural areas, five compared asthma prevalence between cities and two examined intraurban variation in asthma prevalence. Urban residence was associated with a higher prevalence of asthma, regardless of asthma definition: current-wheeze OR:1.46 (95% CI:1.22 to 1.74), doctor diagnosis OR:1.89 (95% CI:1.47 to 2.41), wheeze-ever OR:1.44 (95% CI:1.15 to 1.81), self-reported asthma OR:1.77 (95% CI:1.33 to 2.35), asthma questionnaire OR:1.52 (95% CI:1.06 to 2.16) and exercise challenge OR:1.96 (95% CI:1.32 to 2.91). CONCLUSIONS: Most evidence for the relationship between urbanisation and asthma in LMICs comes from studies comparing urban and rural areas. These studies tend to show a greater prevalence of asthma in urban compared to rural populations. However, these studies have been unable to identify which specific characteristics of the urbanisation process may be responsible. An approach to understand how different dimensions of urbanisation, using contextual household and individual indicators, is needed for a better understanding of how urbanisation affects asthma. PROSPERO REGISTRATION NUMBER: CRD42017064470

Longitudinal membrane function in functionally anuric patients treated with APD: Data from EAPOS on the effects of glucose and icodextrin prescription

Longitudinal membrane function in functionally anuric patients treated with APD: Data from EAPOS on the effects of glucose and icodextrin prescription. Background: Peritoneal dialysis is associated with changes in membrane function that can lead eventually to ultrafiltration (UF) failure. Factors driving these changes are thought to include hypertonic glucose exposure, but previously reported associations are confounded by the presence of residual renal function. Methods: Longitudinal membrane function (solute transport and UF capacity) were measured annually in a prospective cohort of 177 functionally anuric patients as part of the European Automated Peritoneal Dialysis Outcomes Study (EAPOS). Subgroup analysis was performed according to glucose exposure and icodextrin use at baseline. Results: The whole cohort experienced an increase in solute transport and reduction in UF capacity at 12 and 24 months that could not be explained by informative censoring. These changes were accelerated and more severe in patients using either 2.27% or 3.86% glucose, or those not using icodextrin at baseline. These differences could not be explained by age, comorbidity score, previous time spent on renal replacement, differential dropout from the study, peritonitis rates, or, by definition, residual renal function. Patients using icodextrin at baseline had worse membrane function and were more likely to be diabetic. There was an association between membrane function changes and achieved 24-hour ultrafiltration over the 2-year study period. Conclusion: Anuric automated peritoneal dialysis (APD) patients experience significant detrimental changes in membrane function over a relatively short time period. Glucose appears to enhance these changes independent of residual renal function. Icodextrin use in these circumstances is associated with less deterioration in membrane functio

La iniciación científica como posibilidad para aprender matemática en el colegio

El desempeño de los alumnos brasileros en las evaluaciones estatales (SARESP) e internacionales (PISA) indican las dificultades en relación al aprendizaje de la matemática. Delante de esa realidad, fue idealizado, en 2009, el proyecto de extensión “Iniciación Científica en el Colegio”, en el cual los alumnos del curso de licenciatura en matemática serían los orientadores de alumnos de las escuelas secundarias de la ciudad y/o región. Este proyecto tiene los siguientes objetivos: propiciar una interacción entre los alumnos del colegio y de la universidad; desarrollar la capacidad de elaboración y orientación de proyectos por parte de los alumnos de la licenciatura; despertar el interés de los alumnos del colegio por el estudio de la matemática y por la investigación científica; posibilitar al alumno de matemática el estudio de temas que, normalmente, no son abordados en el colegio. Así, los alumnos de la universidad tendrán la oportunidad de conocer el contexto escolar, y los alumnos del colegio de profundizar sus conocimientos matemáticos por medio de un estudio dirigido y con carácter de investigación

Efeito das proporções de colmo e panículas sobre as porcentagens de fibra em detergente neutro de três híbridos de sorgo em cinco diferentes estádios de maturação.

Foram avaliados tres hibridos de sorgo de duplo proposito (BR 700, BR 701 e MASSA 03) para producao de silagem. Os hibridos foram cortados em cinco estadios de maturacao diferentes. Para avaliacao das proporcoes de colmos e paniculas utilizou-se delineamento estatistico em blocos ao acaso, em esquema fatorial 5x3x3, com tres repeticoes para cada tratamento. Nao foram observadas diferencas nas variaveis avaliadas entre os diferentes estadios de maturacao estudados, nem entre os hibridos avaliados. As porcentagens de fibra em detergente neutro (FDN) foram avaliadas nos materiais originais e respectivas silagens, nao sendo observado variacoes com o avanco do estadio de maturacao. para esta variavel utilizou-se delineamento estatistico inteiramente casualizado, em esquema fatorial 5x3x3x2. As medias foram comparadas pelo teste "SNK", com nivel de significancia de 5%

Teores de carboidratos solúveis e ácidos orgânicos de silagens de três genótipos de sorgo colhidos em cinco diferentes momentos de colheita.

Foram avaliados tres hibridos de sorgo de duplo proposito (BR 700, BR 701 e MASSA 03) para producao de silagem. Os hibridos foram cortados em cinco estadios de maturacao diferentes. O delineamento estatistico utilizado foi inteiramente casualizado, em esquema fatorial 5x3x3x2 para a analise de CHO's e de 5x3x3 para as analises realizadas apenas nas silagens (acidos organicos). As medias foram comparadas pelo teste "SNK", com nivel de significancia de 5%. No hibrido BR 700 observou-se reducao dos niveis de carboidratos soluveis entre as epocas dois e tres, no MASSA 03 a reducao ocorreu entre as epocas dois e tres, e quatro e cinco. Houve reducao significativa entre os teores de carboidratos soluveis doa materiais originais e das suas respectivas silagens. Os teores de acido acetico e butirico nao variaram com o avanco do estadio de maturacao. As porcentagens de acido latico reduziram entre a primeira e segunda epoca, no hibrido BR 700, e entre a segunda e terceira epoca nos outros dois, estabilizando a partir de entao

Avaliação agronômica de três híbridos de sorgo (BR 700, BR 701 e MASSA 03) colhidos em cinco diferentes estádios de maturação.

Foram avaliados tres hibridos de sorgo de duplo proposito (BR 700, BR 701 e MASSA 03) para producao de silagem. Os hibridos foram cortados em cinco estadios de maturacao diferentes. Foi utilizado delineamento estatistico em blocos ao acaso com tres repeticoes para cada tratamento. As medias foram comparadas pelo teste "SNK" (Student Newman Keuls), com nivel de significancia de 5%. os dados foram analisados pelo pacote estatistico SAEG (1997). Determinou-se a producao de materia seca/ha, altura das plantas e numero de plantas/ha. Nao foram observadas diferenças nas variaveis avaliadas entre os diferentes estadios de maturacao estudados, nem entre os hibridos avaliados dentro de uma mesma epoca

Local minimal energy landscapes in river networks

The existence and stability of the universality class associated to local minimal energy landscapes is investigated. Using extensive numerical simulations, we first study the dependence on a parameter $\gamma$ of a partial differential equation which was proposed to describe the evolution of a rugged landscape toward a local minimum of the dissipated energy. We then compare the results with those obtained by an evolution scheme based on a variational principle (the optimal channel networks). It is found that both models yield qualitatively similar river patterns and similar dependence on $\gamma$. The aggregation mechanism is however strongly dependent on the value of $\gamma$. A careful analysis suggests that scaling behaviors may weakly depend both on $\gamma$ and on initial condition, but in all cases it is within observational data predictions. Consequences of our resultsComment: 12 pages, 13 figures, revtex+epsfig style, to appear in Phys. Rev. E (Nov. 2000

Urbanisation is associated with prevalence of childhood asthma in diverse, small rural communities in Ecuador

BACKGROUND: Studies conducted in transitional communities from Africa and Asia have pointed to the process of urbanisation as being responsible for the increase in asthma prevalence in developing regions. In Latin America, there are few published data available on the potential impact of urbanisation on asthma prevalence. The aim of the present study was to explore how the process of urbanisation may explain differences in asthma prevalence in transitional communities in north-eastern Ecuador. METHODOLOGY/PRINCIPAL FINDINGS: An ecological study was conducted in 59 communities in Esmeraldas Province, Ecuador. Indicators of urbanisation were grouped into three indices representing the processes associated with urbanisation: socioeconomic, lifestyle and urban infrastructure. Categorical principal components analysis was used to generate scores for each index and a fourth index--a summary urbanisation index--was derived from the most representative variables in each of the three indices. The authors analysed the associations between community asthma prevalence and the indices, as well as with each indicator variable of every group. The overall prevalence of asthma was 10.1% (range 0-31.4% between communities). Three of the four indices presented significant associations with community asthma prevalence: socioeconomic (r = 0.295, p = 0.023), lifestyle (r = 0.342, p = 0.008) and summary urbanisation index (r = 0.355, p = 0.006). Variables reflecting better socioeconomic status and a more urban lifestyle were associated with greater asthma prevalence. CONCLUSIONS: These data provide evidence that the prevalence of asthma increases with increasing levels of urbanisation in transitional communities, and factors associated with greater socioeconomic level and changes towards a more urban lifestyle may be particularly important