Surfactant spreading on liquid films in the Stokes regime

Characterizing the spreading of surfactants on the surface of a liquid film is central to our understanding of natural and technological processes ranging from cell propulsion and drug delivery in pulmonary airways to cleaning food processing surfaces. In this work, we analyze the spreading dynamics of a drop of insoluble surfactants in a perfectly viscous (i.e., Stokes) regime. Using simple scaling arguments, we estimate that the size of a small surfactant drop grows as a power-law with time with an exponent of 1/3. The estimated scaling is then corroborated and better characterized using direct numerical simulations. Furthermore, the simulation results help establish the transition from the initial 1/3 scaling with time to the later 1/4 scaling that is expected when the spreading drop grows larger than the film thickness.Fil: Lu, Jiakai. Massachusetts Institute of Technology; Estados UnidosFil: Zhang, Qian. Purdue University; Estados UnidosFil: Ubal, Sebastian. Universidad Nacional de Entre Ríos. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática; ArgentinaFil: Corvalan, Carlos M.. Purdue University; Estados Unido

Coalescence of small bubbles with surfactants

Bubble coalescence is central to many important technological processes, such as separations, cleaning of oil spills, microfluidics, emulsification and foaming. It is well known that surfactants, which are frequently present as additives or contaminants, delay coalescence by slowing the drainage of the liquid film separating the approaching bubbles before they make contact. However, the coalescence and surfactant transport mechanisms developed after surfactant-laden bubbles make initial contact remain poorly understood. Here, we characterize these mechanisms using high-fidelity numerical simulations to predict the evolution of bubble interfaces, surfactant spreading, and induced Marangoni flows. Our results show that the surfactant initially accumulates on the tiny meniscus bridge formed between the coalescing bubbles due to the rapid and highly localized contraction of meniscus area. At the same time, a Marangoni-driven convective flow is generated at the interface, which drags the accumulated surfactant away from the joining meniscus and toward the back of the bubbles. Together, these transport mechanisms affect the rate bubble coalescence by dynamically modifying the local pull of surface tension on the bubble interfaces

Environmental health and inequalities : building indicators for sustainable development

O Brasil, mesmo com os avanços nos indicadores socioeconômicos ainda se apresenta desigual, situação fruto de um desenvolvimento historicamente excludente. Foi escolhido o Índice de Desenvolvimento Humano (IDH) e indicadores sociais, econômicos, ambientais e de saúde para exemplificar essa problemática. Foram selecionados os municípios que apresentavam mais baixos IDHs no ano de 2000 e comparada sua evolução temporal entre 2000 e 2010 por meio de indicadores relacionados aos pilares econômico, ambiental e social do desenvolvimento sustentável. Estes possuem um IDH classificado como baixo (<0.500) e correspondem a países como Laos, Iêmen, Haiti e Madagascar. No âmbito nacional, verificou-se, entre o início dos anos 2000 e o fim dessa década, uma importante melhora do indicador do pilar econômico (diminuição de 23,9% para 8,9% de pessoas vivendo com menos de 1/4 de salário mínimo), sendo que os indicadores referentes aos pilares social (aumento de 86,5% para 90,2% de mulheres alfabetizadas) e ambiental (aumento de 81% para 85% no acesso a rede geral de água), também apresentaram melhoria, embora em menor grau. Concluiu-se que para alcançar o desenvolvimento sustentável e com qualidade de vida, a melhora dos indicadores de saneamento e de educação deve ser uma prioridade para o Brasil. _______________________________________________________________________________________ ABSTRACTDespite its progress in terms of socioeconomic indicators, Brazil is still unequal, which is due to an unequal and exclusionary historical process. In this paper we selected the Human Development Index – HDI and other social, economic, environmental and health indicators to exemplify this situation. We selected the municipalities that had the lowest HDI in the country in 2000 comparing their evolution over time between 2000 and 2010 by means of indicators linked to the economic, environmental and social pillars of sustainable development. These municipalities have an HDI classified as low (<0.500), and correspond to countries such as Laos, Yemen, Haiti and Madagascar. At national level, data for the decade show a significant improvement in economic indicators (decrease from 23% to 8.9% of people living on less than a quarter of the minimum wage); social indicators (increase from 86.5% to 90.2% of literacy in women), and the environmental indicator associated with access to the water grid, which also improved to a lesser extent (increase from 81% to 85%). It was concluded that in order to achieve sustainable development with quality of life, the improvement of sanitation and education indicators should be a priority for Brazil

Diseases due to unhealthy environments: an updated estimate of the global burden of disease attributable to environmental determinants of health

The update of the global burden of disease attributable to the environment is presented. The study focuses on modifiable risks to show the potential health impact from environmental interventions.; Systematic literature reviews on 133 diseases and injuries were performed. Comparative risk assessments were complemented by more limited epidemiological estimates, expert opinion and information on disease transmission pathways. Population attributable fractions were used to calculate global deaths and global disease burden from environmental risks.; Twenty-three percent (95% CI: 13-34%) of global deaths and 22% (95% CI: 13-32%) of global disability adjusted life years (DALYs) were attributable to environmental risks in 2012. Sixty-eight percent of deaths and 56% of DALYs could be estimated with comparative risk assessment methods. The global disease burden attributable to the environment is now dominated by noncommunicable diseases. Susceptible ages are children under five and adults between 50 and 75 years. Country level data are presented.; Nearly a quarter of global disease burden could be prevented by reducing environmental risks. This analysis confirms that eliminating hazards and reducing environmental risks will greatly benefit our health, will contribute to attaining the recently agreed Sustainable Development Goals and will systematically require intersectoral collaboration to be successful

Un método de muestreo para predecir la edad de ramas de primer orden

Se describe un método de muestreo de tipo destructivo para estimar la edad de ramas de primer orden con aplicación en cualquier especie que presente verdaderos anillos anuales de crecimiento en árboles vivos. Su implementación requiere estimar el desarrollo de altura total de los árboles, utilizando técnicas de análisis de tallo y de la medición de la altura y ángulo de inserción para una muestra de ramas de primer orden. El procedimiento permite estimar la edad y año de formación de las ramas, el período de mantención de ramas vivas y de persistencia de ramas muertas en la copa de los árboles. Es un método alternativo al de disección de ramas. La implementación de algoritmos requeridos se ilustra detalladamente para un individuo de Nothofagus obliqua (Mirb) Oerst. (Fagales: Nothofagaceae) de 48 años de edad

Un método de muestreo para predecir la edad de ramas de primer orden

A destructive sampling method to estimate the age of first-order branches is presented. The proposed method can be applied only to living tree species showing annual growth rings. The implementation requires an estimate of total tree height development applying stem analysis techniques and the measurement of stem height and insertion angle for a sample of first-order branches. The developed procedure allows estimating the age and year of branch formation, and the maintenance of branches within the death and live crown. It can be considered an alternative to branch dissection methods. The algorithms’ implementation is illustrated for a 48-year old Nothofagus obliqua (Mirb.) Oerst. tree.Se describe un método de muestreo de tipo destructivo para estimar la edad de ramas de primer orden con aplicación en cualquier especie que presente verdaderos anillos anuales de crecimiento en árboles vivos. Su implementación requiere estimar el desarrollo de altura total de los árboles, utilizando técnicas de análisis de tallo y de la medición de la altura y ángulo de inserción para una muestra de ramas de primer orden. El procedimiento permite estimar la edad y año de formación de las ramas, el período de mantención de ramas vivas y de persistencia de ramas muertas en la copa de los árboles. Es un método alternativo al de disección de ramas. La implementación de algoritmos requeridos se ilustra detalladamente para un individuo de Nothofagus obliqua (Mirb) Oerst. (Fagales: Nothofagaceae) de 48 años de edad

Climate services to improve public health.

A high level expert panel discussed how climate and health services could best collaborate to improve public health. This was on the agenda of the recent Third International Climate Services Conference, held in Montego Bay, Jamaica, 4-6 December 2013. Issues and challenges concerning a demand led approach to serve the health sector needs, were identified and analysed. Important recommendations emerged to ensure that innovative collaboration between climate and health services assist decision-making processes and the management of climate-sensitive health risk. Key recommendations included: a move from risk assessment towards risk management; the engagement of the public health community with both the climate sector and development sectors, whose decisions impact on health, particularly the most vulnerable; to increase operational research on the use of policy-relevant climate information to manage climate- sensitive health risks; and to develop in-country capacities to improve local knowledge (including collection of epidemiological, climate and socio-economic data), along with institutional interaction with policy makers

Consecuencias cognitivas del COVID-19: Resultados de un estudio de cohorte sudamericano

Antecedentes: Las manifestaciones neurológicas de la infección por SARS-CoV-2 han sido reportadas en la literatura científica. Sin embargo, los estudios cognitivos post COVID-19 en personas sin queja cognitiva previa son escasos. Objetivo: Nuestro objetivo es investigar el impacto cognitivo del COVID-19 en adultos sin quejas cognitivas previas a la infección y estudiar el desempeño cognitivo de acuerdo a la severidad de la enfermedad y a los factores de riesgo cognitivo. Métodos: Cuarenta y cinco pacientes post COVID-19 y cuarenta y cinco controles sanos apareados por edad, género y educación realizaron una evaluación neuropsicológica, que evalúa memoria, lenguaje, atención, funciones ejecutivas, habilidades visuoespaciales, incluyendo además escalas de sintomatología psiquiátrica, y la recopilación de datos sobre la severidad de la infección, la salud premórbida y la funcionalidad. Resultados: Se encontraron diferencias significativas entre los grupos en los compuestos cognitivos de memoria (p=0,016, d de Cohen= 0,73), atención (p<0,001, d de Cohen= 1,2), funciones ejecutivas (p<0,001, d de Cohen=1,4) y lenguaje (p=0,002, d de Cohen=0,87). El cambio del funcionamiento premórbido al funcionamiento posterior a la infección, fue significativamente diferente entre los grupos de gravedad (WHODAS; p=0,037). La ansiedad autoinformada se asoció con la presencia de disfunción cognitiva en los sujetos de COVID-19 (p=0,043). Conclusión: Nuestros resultados sugieren que los síntomas cognitivos en pacientes post COVID-19 pueden permanecer hasta tres meses después de la remisión de la enfermedad. Este estudio aboga a favor de incluir la evaluación cognitiva como una etapa protocolizada del examen post COVID-19. Es posible que las medidas de cribado no sean suficientes para detectar la disfunción cognitiva en los pacientes post COVID-19.Background: Neurological and psychiatric manifestations associated with SARS-CoV-2 infection have been reported throughout the scientific literature. However, studies on post-COVID cognitive impairment in people with no previous cognitive complaint are scarce. Objective: We aim to investigate the impact of COVID-19 on cognitive functions in adults without cognitive complaints before infection and to study cognitive dysfunction according to disease severity and cognitive risk factors. Methods: Forty-five post-COVID-19 patients and forty-five controls underwent extensive neuropsychological evaluation, which assessed cognitive domains such as memory, language, attention, executive functions, and visuospatial skills, including psychiatric symptomatology scales. Data were collected on the severity of infection, premorbid medical conditions, and functionality for activities of daily living before and after COVID-19. Results: Significant differences between groups were found in cognitive composites of memory (p=0.016, Cohen’s d= 0.73), attention (p<0.001, Cohen’s d=1.2), executive functions (p<0.001, Cohen’s d=1.4), and language (p=0.002, Cohen’s d=0.87). The change from premorbid to post-infection functioning was significantly different between severity groups (WHODAS, p=0.037). Self-reported anxiety was associated with the presence of cognitive dysfunction in COVID-19 subjects (p=0.043). Conclusion: Our results suggest that the presence of cognitive symptoms in post-COVID-19 patients may persist for months after disease remission and argue for the inclusion of cognitive assessment as a protocolized stage of the post-COVID examination. Screening measures may not be sufficient to detect cognitive dysfunction in post-COVID-19 patients.Fil: Crivelli, Lucía. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; ArgentinaFil: Calandri, Ismael. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; ArgentinaFil: Corvalan, Nicolás. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; ArgentinaFil: Carello, Maria Agostina. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; ArgentinaFil: Keller, Greta. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; ArgentinaFil: Martinez, Carlos. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; ArgentinaFil: Arruabarrena, Micaela. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; ArgentinaFil: Allegri, Ricardo Francisco. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia. Instituto de Neurociencias - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Neurociencias; Argentin

Coalescence of small bubbles with surfactants

Bubble coalescence is central to many important technological processes, such as separations, cleaning of oil spills, microfluidics, emulsification and foaming. It is well known that surfactants, which are frequently present as additives or contaminants, delay coalescence by slowing the drainage of the liquid film separating the approaching bubbles before they make contact. However, the coalescence and surfactant transport mechanisms developed after surfactant-laden bubbles make initial contact remain poorly understood. Here, we characterize these mechanisms using high-fidelity numerical simulations to predict the evolution of bubble interfaces, surfactant spreading, and induced Marangoni flows. Our results show that the surfactant initially accumulates on the tiny meniscus bridge formed between the coalescing bubbles due to the rapid and highly localized contraction of meniscus area. At the same time, a Marangoni-driven convective flow is generated at the interface, which drags the accumulated surfactant away from the joining meniscus and toward the back of the bubbles. Together, these transport mechanisms affect the rate bubble coalescence by dynamically modifying the local pull of surface tension on the bubble interfaces

Chile's 2014 sugar-sweetened beverage tax and changes in prices and purchases of sugarsweetened beverages :an observational study in an urban environment

This study examines changes in beverage prices and household beverage purchases following the implementation of tax reform in Chile (2014). Findings are consistent with previous evidence indicating that small increases in sugar-sweetened beverage (SSB) taxes are unlikely to promote large enough changes in SSB purchases to reduce obesity and noncommunicable diseases (NCDs).The Chilean government increased the tax rate from 13% to 18% on industrialized beverages with high levels of sugar (H-SSBs). Results of the tax modifications were small, and observed changes in prices and purchases of beverages after the tax were also small