Experimental evaluation of mode II fracture properties of Eucalyptus globulus L.

research projects BIA 2015-64491-P. UIDB/00667/2020 (UNIDEMI).Eucalyptus globulus Labill is a hardwood species of broad growth in temperate climates, which is receiving increasing interest for structural applications due to its high mechanical properties. Knowing the fracture behaviour is crucial to predict, through finite element models, the load carrying capacity of engineering designs with possibility of brittle failures such as elements with holes, notches, or certain types of joints. This behaviour can be adequately modelled on a macroscopic scale by the constitutive cohesive law. A direct identification of the cohesive law of Eucalyptus globulus L. in Mode II was performed by combining end-notched flexure (ENF) tests with digital image correlation (DIC) for radial-longitudinal crack propagation system. The critical strain energy release for this fracture mode, which represents the material toughness to crack-growth, was determined by applying the Compliance Based Beam Method (CBBM) as data reduction scheme and resulted in a mean value of 1.54 N/mm.publishersversionpublishe

Direct evaluation of mixed mode i+ii cohesive laws of wood by coupling mmb test with dic

grant number FCOMP-01-0124-287 FEDER-022692Governing cohesive laws in mixed mode I+II loading of Pinus pinaster Ait. are directly identified by coupling the mixed mode bending test with full-field displacements measured at the crack tip by Digital Image Correlation (DIC). A sequence of mixed mode ratios is studied. The proposed data reduction relies on: (i) the compliance-based beam method for evaluating strain energy release rate; (ii) the local measurement of displacements to compute the crack tip opening displacement; and (iii) an uncoupled approach for the reconstruction of the cohesive laws and its mode I and mode II components. Quantitative parameters are extracted from the set of cohesive laws components in function of the global phase angle. Linear functions were adjusted to reflect the observed trends and the pure modes (I and II) fracture parameters were estimated by extrapolation. Results show that the obtained assessments agree with previous experimental measurements addressing pure modes (I and II) loadings on this wood species, which reveals the appropriateness of the proposed methodology to evaluate the cohesive law under mixed mode loading and its components.publishersversionpublishe

Non-Newtonian fluid flow through three-dimensional disordered porous media

We investigate the flow of various non-Newtonian fluids through three-dimensional disordered porous media by direct numerical simulation of momentum transport and continuity equations. Remarkably, our results for power-law (PL) fluids indicate that the flow, when quantified in terms of a properly modified permeability-like index and Reynolds number, can be successfully described by a single (universal) curve over a broad range of Reynolds conditions and power-law exponents. We also study the flow behavior of Bingham fluids described in terms of the Herschel-Bulkley model. In this case, our simulations reveal that the interplay of ({\it i}) the disordered geometry of the pore space, ({\it ii}) the fluid rheological properties, and ({\it iii}) the inertial effects on the flow is responsible for a substantial enhancement of the macroscopic hydraulic conductance of the system at intermediate Reynolds conditions. This anomalous condition of ``enhanced transport'' represents a novel feature for flow in porous materials.Comment: 5 pages, 5 figures. This article appears also in Physical Review Letters 103 194502 (2009

Gellan-gum coated gold nanorods: a new tool for biomedical applications

Publicado em "Frontiers in Bioengineering and Biotechnology. Conference Abstract: 10th World Biomaterials Congress"Introduction: Gold nanorods (AuNRs) have been widely studied, in the scope of cancer research and biomedical applications [1]. Their optical properties, easy synthesis and high surface area make AuNRs an outstanding tool for a plethora of applications, such as drug delivery, imaging and tissue engineering [2]. However, before biomedical usage, it is necessary to modify AuNRs surface chemistry, to improve their biocompatibility and stability under biological conditions [3]. One possible approach is the use of biocompatible natural-based polymers that enhance AuNRs performance while allowing the controlled release of drugs/bioactive agents. Herein, we report the successful preparation of a core-shell nanostructure using low-acyl gellan gum (GG) [4], [5] for the coating of AuNRs. Methods: AuNRs were prepared following the seed-mediated growth method [6]. Then, particles were coated with a successive deposition of anionic and cationic polyelectrolytes (poly(acrylic acid) and poly(allylamine hydrochloride), respectively). The pre-coated nanorods were added to a low-acyl gellan gum (GG) solution, previously heated at 90ºC to allow dissolution, and the mixture was stirred overnight at room temperature. The GG-coated AuNRs (AuNR-GG) were characterized by UVvisible spectrometry, zeta potential measurements and transmission electron microscopy (TEM). AuNRs cytotoxicity was accessed in vitro after 1, 3, 7 and 14 days of SaOS-2 cell culture, using an MTS assay. Nanoparticles internalization was confirmed by TEM. In vivo biocompatibility tests were also performed by delivering a solution of AuNRs-GG via tail injection in mice. Results and Discussion: AuNRs were successfully synthesized and coated with a GG shell of approximately 7 nm, as shown in Figure 1. The presence of the GG around AuNRs clearly improved particles stability at different salt and pH conditions, as observed by UV-vis spectroscopy. The in vitro studies using SaOS-2 showed that AuNRs-GG are noncytotoxic. TEM analyses have confirmed that nanoparticles are uptaken by cells and aggregate within cytoplasmic vesicles as depicted in Figure 2. Additionally, in vivo tests suggest that AuNRs are harmless for mice after 24 hours. Conclusion: In this study, AuNRs were individually coated with a gellan gum (GG) shell, resulting in nanoparticles with enhanced stability under different salt concentrations and range of pH’s. Thence, one can conclude that the GG present around the nanoparticles acts as a stabilizer, improving AuNRs stability and biocompatibility. AuNRs-GG have shown noteworthy features and a high potential for further use on biomedical applications including intracellular drug delivery and imaging.QREN (ON.2 – NORTE-01-0124-FEDER-000018) co-financed by North Portugal Regional Operational Program (ON.2 – O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF)The Portuguese Foundation for Science and Technology (FCT) - SFRH/BD/102710/201

The effects of moisture and physical ageing on the elastic behaviour of a structural epoxy

SUMMARY Three point bending tests indicate that elastic modulus diminishes linearly with moisture content, at a rate dependent of the ageing time. On the other hand, it seems that any curve modulus versus time of ageing for specific moisture content can be vertically shifted to coincide with other curves. A comparison of the DSC and bending tests data in the present work suggests that the ageing rate constants are not the same

Planting time for maximization of yield of vinegar plant calyx (Hibiscus sabdariffa L.)

Objetivou-se avaliar a produtividade de cálices de Hibiscus sabdariffa L., planta medicinal, em quatro épocas de plantio em Lavras M.G. Os tratamentos foram quatro épocas de plantio (18 de outubro; 15 de novembro; 18 de dezembro de 2001 e 15 de janeiro de 2002) e realizada uma colheita quando praticamente não existiam cálices em desenvolvimento, quase no final do ciclo da planta. Foram considerados os números de cálices por planta, as fitomassas frescas e secas dos cálices e a qualidade. Concluiu-se que a época de plantio influenciou o rendimento por planta e as fitomassas frescas e secas dos cálices, diferindo entre si pelo teste de Tukey a 5%. No plantio de outubro, houve maior rendimento (2.522 kg/ha), com produção de 5,24 vezes a mais em relação ao plantio do mês de janeiro (481 kg/ha). Os plantios nos meses de novembro e dezembro tiveram produções de 1.695 e 1.093 kg.ha-1 de cálices secos, respectivamente, e em relação ao mês de janeiro, a produção foi 3,52 e 2,27 vezes a mais.Deve-se realizar a colheita assim que os cálices estiverem maduros, a fim de preservar a qualidade

Características Sócio demográficas e Perfil Profissional da Mão de Obra da Construção Civil em Tucuruí/PA/Brasil

Nos últimos tempos, a construção civil brasileira teve mudanças devido à crise econômica, mercado consumidor mais exigente, demandas de materiais e técnicas mais sustentáveis, necessidade de controle e racionalização dos processos construtivos, por edificações mais eficientes sob o ponto de vista energético, exigências normativas de desempenho e durabilidade, implementação de certificações ambientais e de gestão e pelo aumento da competitividade entre as empresas. Assim, é fundamental a qualificação da mão de obra para uma melhor produtividade e eficiência no setor. É objetivo do presente artigo, identificar o perfil sócio econômico dos profissionais que atuam no interior do estado do Pará, por meio de um projeto e curso de extensão da UFPA, correlacionando esse perfil com os de outras cidades brasileiras. Especificamente, dados financeiros, de gênero, de faixa etária de idade, de grau de instrução, de estado civil, de vínculo empregatício e de interesse em qualificação foram obtidos. A metodologia empregada foi à abordagem quantitativa de dados, por meio de questionário de caracterização sócio demográfica aplicado no início do curso. Os resultados do perfil da mão de obra indicaram uma relação positiva de alto índice de escolaridade e interesse em participar de novos cursos. Foi notada também a presença feminina no público abordado. Esses resultados sugerem que a construção civil passa por processos de mudanças.Nos últimos tempos, a construção civil brasileira teve mudanças devido à crise econômica, mercado consumidor mais exigente, demandas de materiais e técnicas mais sustentáveis, necessidade de controle e racionalização dos processos construtivos, por edificações mais eficientes sob o ponto de vista energético, exigências normativas de desempenho e durabilidade, implementação de certificações ambientais e de gestão e pelo aumento da competitividade entre as empresas. Assim, é fundamental a qualificação da mão de obra para uma melhor produtividade e eficiência no setor. É objetivo do presente artigo, identificar o perfil sócio econômico dos profissionais que atuam no interior do estado do Pará, por meio de um projeto e curso de extensão da UFPA, correlacionando esse perfil com os de outras cidades brasileiras. Especificamente, dados financeiros, de gênero, de faixa etária de idade, de grau de instrução, de estado civil, de vínculo empregatício e de interesse em qualificação foram obtidos. A metodologia empregada foi à abordagem quantitativa de dados, por meio de questionário de caracterização sócio demográfica aplicado no início do curso. Os resultados do perfil da mão de obra indicaram uma relação positiva de alto índice de escolaridade e interesse em participar de novos cursos. Foi notada também a presença feminina no público abordado. Esses resultados sugerem que a construção civil passa por processos de mudanças