Síntese e caracterização de um superplastificante para betão

A maior parte das estruturas da construção civil exigem um betão fresco com elevados níveis de trabalhabilidade. Estes níveis são conseguidos com a adição de uma quantidade de água várias vezes superior à teoricamente necessária, limitando as propriedades físicas do betão resultante. A solução para este problema consiste na adição, na mistura inicial, de substâncias fluidificantes, que proporcionem uma diminuição da quantidade de água. Estas substâncias são conhecidas por superplastificantes ou agentes redutores de água de alta gama. Estes aditivos são compostos químicos à base de polímeros orgânicos solúveis em água, que contêm grupos sulfito ligados às cadeias poliméricas em intervalos regulares. A maior parte das formulações comerciais pertencem às seguintes famílias: condensados de melamina-formaldeído sulfonados (SMF), condensados de naftaleno-formaldeído sulfonados (SNF) e linhosulfonatos modificados (MLS). Mais recentemente, surgiram no mercado produtos de natureza diferente conhecidos por polímeros de éter carboxílico (CE). Na prática, as partículas de cimento aderem umas às outras, delimitando água no seu interior. Deste modo, parte da superfície das partículas de cimento não fica disponível para a hidratação, nem mesmo a água que permanece no interior. Como consequência, a mistura toma-se muito viscosa e origina betões com baixas resistências mecânicas. Os superplastificantes vão provocar a dispersão dos aglomerados de partículas, reduzindo assim a viscosidade da pasta, aumentando a trabalhabilidade e as resistências mecânicas. No presente trabalho foram sintetizados condensados SMF em três etapas reaccionais consecutivas: metilolação, sulfonação e polimerização. O processo foi desenvolvido em meio aquoso, onde o pH do meio é o parâmetro operatório mais importante. Outras condições operatórias, nomeadamente a temperatura e a proporção de reagentes, têm também que ser tomadas em consideração. As condições processuais foram ajustadas por forma a melhorar as propriedades mecânicas do betão. Procedeu-se à caracterização do produto final por espectroscopia FTIR (Fourier Transform Infrared) e cromatografia GFC (Gel Filtration Chromatography). O mecanismo de actuação dos superplastificantes foi identificado e estudado recorrendo a técnicas de microscopia óptica

Effect of cinnamon powder addition to a Portuguese custard tart (Pastel de Nata) on healthy adults' postprandial glycemia

Background and Objective: Cinnamon is a spice used over the years in cooking to impart aromatic, flavor and taste properties to food and beverages. Moreover, cinnamon has been used for its medicinal properties due to its potential phenolic content, which can protect against cardio-metabolic diseases. Previous studies reported an improvement of postprandial glycemia after addition of cinnamon powder to a high-sugar meal. The study aims at investigating the effect of adding cinnamon powder to a Portuguese custard tart (Pastel de Nata) on the postprandial glycemic response in healthy subjects. Subjects and Methods: After review board and Ethic Committee of the State approval, thirty-two healthy human subjects were assigned in a controlled study and randomly allocated into 2 groups: 16 subjects ingested a custard tart with cinnamon powder (cinnamon group) and 16 subjects ingested a custard tart alone (control group). Blood glucose concentrations were measured before interventions and after 30, 60, 90 and 120 minutes. Chemical analysis was performed to quantify the total phenolic content and antioxidant activity. Results: The postprandial blood glucose (PBG) area under the curve (AUC) was significantly lower (p = 0.0005) in the cinnamon group (599.2 ± 9.1) compared to the AUC of the control group (645.7 ± 7.7). The administration of cinnamon powder to the custard tarts slightly decreased PBG mean values compared to custard tart without cinnamon powder, although it did not reach statistical significance (p = 0.273). Cinnamon addition to custard tart improved the total phenolic content (1278.7 ± 0.7 compared to 253.7 ± 22.8 mg/L gallic acid) and antioxidant properties, increasing 4.4 times the capacity of free-radical scavenger compared with custard tart without cinnamon (IC50). Conclusion: The addition of cinnamon powder to custard tart could be beneficial to glycemic control

Genetic diversity analysis of varronia curassavica Jacq. accessions using ISSR markers

Varronia curassavica Jacq. is a medicinal and aromatic plant from Brazil with significant economic importance. Studies on genetic diversity in active germplasm banks (AGB) are essential for conservation and breeding programs. The aim of this study was to analyze the genetic diversity of V. curassavica accessions of the AGB of Medicinal and Aromatic Plants of the Federal University of Sergipe (UFS), using inter-simple sequence repeat molecular markers. Twenty-four primers were tested, and 14 were polymorphic and informative, resulting in 149 bands with 97.98% polymorphism. The UPGMA dendrogram divided the accessions into Clusters I and II. Jaccard similarity coefficients for pair-wise comparisons of accessions ranged between 0.24 and 0.78. The pairs of accessions VCUR-001/VCUR-503, VCUR-001/VCUR-504, and VCUR-104/VCUR-501 showed relatively low similarity (0.24), and the pair of accessions VCUR-402/VCUR403 showed medium similarity (0.78). Twenty-eight accessions were divided into three distinct clusters, according to the STRUCTURE analysis. The genetic diversity of V. curassavica in the AGB of UFS is low to medium, and it requires expansion. Accession VCUR-802 is the most suitable for selection in breeding program of this species, since it clearly represents all of the diversity present in the AGB153CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFINANCIADORA DE ESTUDOS E PROJETOS - FINEPFUNDAÇÃO DE APOIO À PESQUISA E À INOVAÇÃO TECNOLÓGICA DO ESTADO DE SERGIPE - FAPITECnão temnão temnão temnão te

Guillain-Barré syndrome related to Zika virus infection: A systematic review and meta-analysis of the clinical and electrophysiological phenotype

BACKGROUND: The Zika virus (ZIKV) has been associated with Guillain-Barré syndrome (GBS) in epidemiological studies. Whether ZIKV-associated GBS is related to a specific clinical or electrophysiological phenotype has not been established. To this end, we performed a systematic review and meta-analysis of all published s

Results from On-The-Ground Efforts to Promote Sustainable Cattle Ranching in the Brazilian Amazon

Agriculture in Brazil is booming. Brazil has the world’s second largest cattle herd and is the second largest producer of soybeans, with the production of beef, soybeans, and bioethanol forecast to increase further. Questions remain, however, about how Brazil can reconcile increases in agricultural production with protection of its remaining natural vegetation. While high hopes have been placed on the potential for intensification of low-productivity cattle ranching to spare land for other agricultural uses, cattle productivity in the Amazon biome (29% of the Brazilian cattle herd) remains stubbornly low, and it is not clear how to realize theoretical productivity gains in practice. We provide results from six initiatives in the Brazilian Amazon, which are successfully improving cattle productivity in beef and dairy production on more than 500,000 hectares of pastureland, while supporting compliance with the Brazilian Forest Code. Spread across diverse geographies, and using a wide range of technologies, participating farms have improved productivity by 30–490%. High-productivity cattle ranching requires some initial investment (R$1300–6900/ha or US$410–2180/ha), with average pay-back times of 2.5–8.5 years. We conclude by reflecting on the challenges that must be overcome to scale up these young initiatives, avoid rebound increases in deforestation, and mainstream sustainable cattle ranching in the Amazon