Search

Your search keyword '"Dias, Madalena M."' showing total 252 results
Start Over Author "Dias, Madalena M."
252 results on '"Dias, Madalena M."'

23. Chaos and mixing in NETmix.

Author

Matos, Joana, Santos, Ricardo J., Dias, Madalena M., and Lopes, José Carlos B.

Subjects
TOPOLOGICAL degree, FREQUENCIES of oscillating systems, HYDRODYNAMICS, TOPOLOGY, DIAMETER
Abstract

NETmix is a network of mixing chambers interconnected by channels, in which the most efficient mixing occurs under chaotic flow regimes. Chaos is highly influenced by the topology, particularly by the ratio chamber diameter/channel width, D/d. In this work, micromixing in NETmix is characterized through Lagrangian Mixing Simulation (LMS), which enables to establish the relation between the degree of mixing and the topology, D/d. The degree of mixing is then related with the Eulerian chaoticity from hydrodynamics and spectral analysis. The best mixing is obtained at D/d = 6.65 and is associated to a thin 8 shaped strange attractor. The spectral analysis shows a principal oscillation frequency at St = 0.13. Since the quasi‐periodic regime is alternated with chaotic behavior, NETmix has an intermittent bifurcation. For the NETmix system, orderly flows in the quasi‐periodic regime have higher mixing intensity than less orderly flows in the weak or strong chaotic regimes. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

35. Study of binary mixtures of Tribulus terrestris extract and Quillaja bark saponin as oil‐in‐water nanoemulsion emulsifiers.

Author

Schreiner, Tatiana B., Santamaria‐Echart, Arantzazu, Peres, António M., Dias, Madalena M., Pinho, Simão P., and Barreiro, Maria Filomena

Subjects
TRIBULUS terrestris, STABILIZING agents, BINARY mixtures, ZETA potential, EMULSIONS, EXPERIMENTAL design, STATISTICS
Abstract

Several industrial fields use emulsifiers in their products, with the ones of natural origin gaining increasing relevance. Identifying and using diversified sources for their extraction is a pertinent topic regarding sustainability principles, biodiversity preservation, or cost rationalization. This is the case of Quillaja bark saponin (QS), for which saponin‐rich extracts, for example, Tribulus terrestris (TT), are being highlighted as viable alternatives, even though constraints like performance are still on the table. In this context, an experimental design using binary emulsifier mixtures of TT with pure QS was carried out by changing their composition (50–90%wt. TT), content (1.5–4.5%wt.), and high‐pressure homogenization conditions (5–15 cycles). The emulsions were characterized by zeta potential, morphology, droplet size, and stability (expressed as the number of days without creaming formation). Moreover, the cream index for 30 days was determined to indicate the destabilization extent. The zeta potential showed stable emulsions (values below −41 mV); even still, creaming formed for samples using a low emulsifier and high TT contents. The emulsions' mean droplet diameter (D [3, 2]) was between 78 and 921 nm, with smaller sizes agreeing with higher stability. The statistical analysis indicated an optimum composition range comprising an emulsifier content between 3.9 and 4.5%wt. and TT content between 50 and 56%wt. to reach stable products. Overall, TT can provide an effective solution when combined with QS, decreasing the dependence on Quillaja bark. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

45. Corrigendum to “Chemical and organoleptic properties of bread enriched with Rosmarinus officinalis L.: The potential of natural extracts obtained through green extraction methodologies as food ingredients” [Food Chemistry 384 (2022) 132514]

Author

Kessler, Júlia C., primary, Vieira, Vanessa, additional, Martins, Isabel M., additional, Manrique, Yaidelin A., additional, Ferreira, Patrícia, additional, Calhelha, Ricardo C., additional, Afonso, Andreia, additional, Barros, Lillian, additional, Rodrigues, Alírio E., additional, and Dias, Madalena M., additional

Published
2022
Full Text
View/download PDF

46. Radiation Models for Computational Fluid Dynamics Simulations of Photocatalytic Reactors.

Author

Barbosa, Isabel S. O., Santos, Ricardo J., Dias, Madalena M., Faria, Joaquim L., and Silva, Cláudia G.

Subjects
COMPUTATIONAL fluid dynamics, CURTAIN walls, RADIATION, HEAT radiation & absorption
Abstract

The literature on computational fluid dynamics (CFD) simulations applied to photocatalytic systems is reviewed. CFD simulations referring to three models, namely, P‐1, discrete ordinates (DO), and Monte Carlo (MC) models, for simulating radiation distribution in annular photoreactors are addressed and previous works using these models are reviewed. The cases are a three‐dimensional (3D) annular photoreactor and a two‐dimensional (2D) rectangular enclosure with black walls and the results are compared with the literature. The DO model was selected to solve the radiation transfer equation (RTE) as the most reliable model to fit the radiation distribution inside the reactor. The setting‐up of mesh, angular discretization, and boundary conditions for CFD simulation of photocatalytic reactors are addressed. When correctly set, the CFD models show an excellent agreement with the literature results. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

48. Moringa oleifera L. Screening: SFE-CO 2 Optimisation and Chemical Composition of Seed, Leaf, and Root Extracts as Potential Cosmetic Ingredients.

Author

Kessler, Júlia C., Manrique, Yaidelin A., Martins, Isabel M., Rodrigues, Alírio E., Barreiro, Maria Filomena, and Dias, Madalena M.

Subjects
MORINGA oleifera, COMPOSITION of seeds, SUPERCRITICAL carbon dioxide, RESPONSE surfaces (Statistics), LINOLENIC acids, OLEIC acid
Abstract

Moringa oleifera L. tree (Mo) has emerged as a rich alternative source of bioactive compounds to design cosmetic formulations. Supercritical carbon dioxide fluid extraction (SFE-CO2) was successfully applied on the screening of Mo seed, leaf, and root extracts. The extraction yield was evaluated by response surface methodology (RSM), for pressure and temperature ranges of 117–273 bar and 41–60 °C, respectively, using a design of experiments (DOE). The pressure significantly affected the results ( α = 0.05 ), with the highest extraction efficiency obtained at conditions above 195 bar. The extracts' composition, evaluated by gas chromatography-mass spectrometer (GC-MS), revealed an increasing correlation between the pressure, total extract solubility, and mass of extract at a constant temperature, due to the higher extraction yield. Seed extracts presented more than 80% of oleic acid in relative composition (8.04 mgcompound∙gplantpart−1). Leaf extracts performed well for the obtainment of linolenic acid (>20%; 3.10 mg∙g−1), nonacosane (>22%; 0.46 mg∙g−1), and α-tocopherol (>20%; 0.21 mg∙g−1). Mo root resulted in higher relative composition for sterol molecules, despite its very low affinity with CO2. The most promising bioactive compounds, oleic acid and α-tocopherol, were more abundant when operating at 250 bar at 45 °C and 195 bar at 55 °C, for Mo seed and leaf SFE-CO2 extracts, respectively. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results