Well-balanced finite volume schemes for hydrodynamic equations with general free energy

Well balanced and free energy dissipative first- and second-order accurate finite volume schemes are proposed for a general class of hydrodynamic systems with linear and nonlinear damping. The natural Liapunov functional of the system, given by its free energy, allows for a characterization of the stationary states by its variation. An analog property at the discrete level enables us to preserve stationary states at machine precision while keeping the dissipation of the discrete free energy. These schemes allow for analysing accurately the stability properties of stationary states in challeging problems such as: phase transitions in collective behavior, generalized Euler-Poisson systems in chemotaxis and astrophysics, and models in dynamic density functional theories; having done a careful validation in a battery of relevant test cases.Comment: Videos from the simulations of this work are available at https://sergioperezresearch.wordpress.com/well-balance

Well-balanced finite volume schemes for hydrodynamic equations with general free energy

Well balanced and free energy dissipative first- and second-order accurate finite volume schemes are proposed for a general class of hydrodynamic systems with linear and nonlinear damping. The natural Liapunov functional of the system, given by its free energy, allows for a characterization of the stationary states by its variation. An analog property at the discrete level enables us to preserve stationary states at machine precision while keeping the dissipation of the discrete free energy. These schemes allow for analysing accurately the stability properties of stationary states in challeging problems such as: phase transitions in collective behavior, generalized Euler-Poisson systems in chemotaxis and astrophysics, and models in dynamic density functional theories; having done a careful validation in a battery of relevant test cases.Comment: Videos from the simulations of this work are available at https://sergioperezresearch.wordpress.com/well-balance

Microalgae as Contributors to Produce Biopolymers

Biopolymers are very favorable materials produced by living organisms, with interesting properties such as biodegradability, renewability, and biocompatibility. Biopolymers have been recently considered to compete with fossil-based polymeric materials, which rase several environmental concerns. Biobased plastics are receiving growing interest for many applications including electronics, medical devices, food packaging, and energy. Biopolymers can be produced from biological sources such as plants, animals, agricultural wastes, and microbes. Studies suggest that microalgae and cyanobacteria are two of the promising sources of polyhydroxyalkanoates (PHAs), cellulose, carbohydrates (particularly starch), and proteins, as the major components of microalgae (and of certain cyanobacteria) for producing bioplastics. This review aims to summarize the potential of microalgal PHAs, polysaccharides, and proteins for bioplastic production. The findings of this review give insight into current knowledge and future direction in microalgal-based bioplastic production considering a circular economy approach. The current review is divided into three main topics, namely (i) the analysis of the main types and properties of bioplastic monomers, blends, and composites; (ii) the cultivation process to optimize the microalgae growth and accumulation of important biobased compounds to produce bioplastics; and (iii) a critical analysis of the future perspectives on the field.publishe

Avaliação do Estado dos rios no Sul de Portugal: dos conceitos à prática

O aumento da população humana e o crescente desenvolvimento tecnológico tem conduzido a um excessivo consumo de água consequentemente associado à degradação dos ecossistemas aquáticos. Surge assim a necessidade de avaliar o estado dos ecossistemas aquáticos, através de programas de monitorização adaptados às diferentes realidades. Inicialmente, estes programas foram desenvolvidos tendo em consideração os diferentes usos da água, para os quais são definidos e legislados a nível de cada país valores máximos admissíveis e recomendados. Contudo, a consciencialização a nível global da progressiva contaminação dos ecossistemas aquáticos conduziu a um novo paradigma onde a água é considerada suporte das comunidades biológicas. Os ecossistemas aquáticos passam a ser avaliados numa perspectiva funcional, constituindo o objecto central da monitorização. Abandona-se uma perspectiva antropocêntrica (água considerada unicamente como recurso para as actividades humanas) em benefício de uma visão ecocêntrica, direccionada para a qualidade e preservação dos ecossistemas aquáticos. Nesta perspectiva, na Europa foi recentemente implementada a Directiva Quadro da Água (DQA - Directiva 2000/60/CE do Parlamento Europeu e do Conselho), segundo a qual os estados membros assumem o compromisso de alterar as estratégias tradicionais de utilização da água, facto que requer o desenvolvimento de uma nova concepção social e institucional sobre o valor da água. No âmbito da DQA, os estados membros deverão desenvolver Planos de Bacia Hidrográfica, onde se obriga à classificação do estado das massas de água (ecológico e químico) com vista à recuperação de todas as que se classificam abaixo de Bom. Neste contexto, as comunidades biológicas adquirem uma importância acrescida, uma vez que reflectem as contaminações físicas e químicas (pontual ou difusa) e as alterações morfológicas estruturais (caudais, vegetação ripícola, geomorfologia). No sul de Portugal (bacias hidrográficas do Sado/Mira e Guadiana), a avaliação do estado das massas de água rios efectuada nos anos de 2009 e 2010 no âmbito dos Planos de Bacia Hidrográfica, revelou que apenas 36% e 41% das massas de água rio apresentam Bom estado. Os principais elementos responsáveis pelas classificações indesejáveis foram os elementos biológicos (i.e diatomáceas e invertebrados bentónicos), o Fósforo Total e os níveis de Oxigénio Dissolvido. Consequentemente é necessário propor medidas para progressivamente reduzir a degradação, assim como propor medidas para prevenir a deterioração das massas de águas classificadas como Bom estado, sobretudo tendo em atenção que é objectivo da DQA que todas as massas de água atinjam o Bom estado até 2015

The evaluation of ecological status in a Large Portuguese River using Macroinvertebrates Assemblages

great variety of taxonomic and functional feeding groups, which provides them advantages as indicators of the ecological status of aquatic ecosystems. The implementation of the Water Framework Directive in Europe led to an extensive use of biomonitoring programs in order to access the water quality of streams and rivers. Still, the established Portuguese sampling protocol for aquatic macroinvertebrates does not differentiate small wadeable streams and large nonwadeable rivers. The development of better standardized sampling methods and the identification of more suitable metrics and indexes are extremely important to obtain an accurate ecological status of rivers. Given the importance of the correct evaluation of ecological status in aquatic ecosystems management, our main objectives are: (1) to identify the vulnerability of the established sampling protocol and selected metrics to our sampling sites and (2) to present a review of the different studies which have been carried out during the last years in large rivers and that could be applied on further bioassessment programs in Portuguese large rivers, both feasible and cost effective

Hydrodynamic Characterization of Phase Separation in Devices with Microfabricated Capillaries

Capillary microseparators have been gaining interest in downstream unit operations, especially for pharmaceutical, space, and nuclear applications, offering efficient separation of two-phase flows. In this work, a detailed analysis of the dynamics of gas–liquid separation at the single meniscus level helped to formulate a model to map the operability region of microseparation devices. A water–nitrogen segmented flow was separated in a microfabricated silicon-glass device, with a main channel (width, W = 600 μm; height, H = 120 μm) leading into an array of 276 capillaries (100 μm long; width = 5 μm facing the main channel and 25 μm facing the liquid outlet), on both sides of the channel. At optimal pressure differences, the wetting phase (water) flowed through the capillaries into the liquid outlet, whereas the nonwetting phase (nitrogen) flowed past the capillaries into the gas outlet. A high-speed imaging methodology aided by computational analysis was used to quantify the length of the liquid slugs and their positions in the separation zone. It was observed that during stable separation, the position of the leading edge of the liquid slugs (advancing meniscus), which became stationary in the separation zone, was dependent only on the outlet pressure difference. The trailing edge of the liquid slugs (receding meniscus) approached the advancing meniscus at a constant speed, thus leading to a linear decrease of the liquid slug length. Close to the liquid-to-gas breakthrough point, that is, when water exited through the gas outlet, the advancing meniscus was no longer stationary, and the slug lengths decreased exponentially. The rates of decrease of the liquid slug length during separation were accurately estimated by the model, and the calculated liquid-to-gas breakthrough pressures agreed with experimental measurements

South Portugal Reservoirs – Status and major concerns

In southern Portugal, the dry summers together with low precipitations and high temperatures highlight the importance of reservoirs, built mainly for water storage and to smoothing the interannual precipitation variability, in one of the driest regions in the country. According to the Water Framework Directive nº2000/60/CE, all states members are responsible for the classification of superficial water bodies using a system based on both ecological and chemical status. The Water Framework Directive set the aim of achieving the “Good” status for surface and groundwater by 2015. There are two reservoirs typologies in the south of Portugal, the main course and the south typologies. Data from the current River Basin Management Plans were used to identify the quality status of 28 reservoirs, 26 from south typology and 2 main course typology. General physical and chemical elements (total phosphorus, dissolved oxygen, oxygen saturation rate, nitrates, pH), biological elements (chlorophyll a), specific pollutants and priority substances were used to classify the reservoirs status in “Good” and “Less than Good” quality classes. Results showed that 20 reservoirs were rated as “Good” and only 8 reservoirs were below the “Good” status

The Infertility-Related Stress Scale: Validation of a Brazilian–Portuguese Version and Measurement Invariance Across Brazil and Italy

Infertility constitutes an essential source of stress in the individual and couple's life. The Infertility-Related Stress Scale (IRSS) is of clinical interest for exploring infertility-related stress affecting the intrapersonal and interpersonal domains of infertile individuals' lives. In the present study, the IRSS was translated into Brazilian-Portuguese, and its factor structure, reliability, and relations to sociodemographic and infertility-related characteristics and depression were examined. A sample of 553 Brazilian infertile individuals (54.2% female, mean aged 36 ± 6 years) completed the Brazilian-Portuguese IRSS (IRSS-BP), and a subsample of 222 participants also completed the BDI-II. A sample of 526 Italian infertile individuals (54.2% female, mean aged 38 ± 6 years) was used to test for the IRSS measurement invariance across Brazil and Italy. Results of exploratory structural equation modeling (ESEM) indicated that a bifactor solution best represented the structure underlying the IRSS-BP. Both the general and the two specific intrapersonal and interpersonal IRSS-BP factors showed satisfactory levels of composite reliability. The bifactor ESEM solution replicated well across countries. As evidence of relations to other variables, female gender, a longer duration of infertility, and higher depression were associated with higher scores in global and domain-specific infertility-related stress. The findings offer initial evidence of validity and reliability of the IRSS-BP, which could be used by fertility clinic staff to rapidly identify patients who need support to deal with the stressful impact of infertility in the intrapersonal and interpersonal life domains, as recommended by international guidelines for routine psychosocial care in infertility settings