Caracterización térmica y química de fracciones de aceite de semilla de Syagrus romanzoffiana

The Jerivá (Syagrus romanzoffiana) kernel oil (JKO) has a pleasant coconut-like smell, with about 33% lauric acid and 28% oleic acid. The oil also contains bioactive compounds, such as phenolics, carotenoids, and tocopherols. JKO has a solid consistency at low temperatures, but has a low melting point and low solid content at room temperature. Thus, this work aimed to evaluate the thermal properties related to crystallization and fusion, as well as the chemical and oxidative characteristics of JKO fractions, olein and stearin, obtained from dry and solvent fractionation. In general, stearins had higher crystallization and melting temperatures, and higher solid fat content, unlike oleins, which may be associated with the concentration of high melting triglycerides in the stearins. No statistically significant difference was found for fatty acid profile or oxidative stability of the fractions. The type of fractionation influenced the chemical and thermal properties of JKO fractions. The solvent process promoted the most relevant differentiation of fractions. An olein was obtained with 7% less solid fat at 25 °C which remained visually liquid at 2 °C below the oil, as well as a stearin with 17% more solid fat at 25 °C which remained visually solid at 3 °C above the oil.El aceite de semilla de Jerivá (Syagrus romanzoffiana) (ASJ) tiene un agradable olor a coco, con aproximadamente un 33% de ácido láurico y un 28% de ácido oleico. Este aceite también contiene compuestos bioactivos, como fenólicos, carotenoides y tocoferoles. El ASJ tiene una consistencia sólida a baja temperatura, pero tiene un punto de fusión bajo y un contenido de sólidos bajo a temperatura ambiente. Este trabajo tuvo como objetivo evaluar las propiedades térmicas relacionadas con la cristalización y fusión, así como las características químicas y oxidativas de las fracciones de ASJ, oleína y estearina, obtenidas mediante fraccionamiento en seco y con solvente. En general, las estearinas tuvieron temperaturas de cristalización y fusión más altas y un mayor contenido de grasa sólida, a diferencia de las oleínas, esto puede estar asociado con la concentración de triglicéridos de alto punto de fusión en las estearinas. No se encontraron diferencias estadísticamente significativas para el perfil de ácidos grasos ni en la estabilidad oxidativa de las fracciones. El tipo de fraccionamiento influyó en las propiedades químicas y térmicas de las fracciones de ASJK. El proceso mediante solvente favoreció la diferenciación de fracciones más relevantes. Se obtuvo una oleína con 7% menos de grasa sólida a 25 °C que permaneció visualmente líquida a 2 °C por debajo del aceite, así como una estearina con 17% más de grasa sólida a 25 °C y que permaneció visualmente sólida a 3 °C por encima del aceite

Microalgas aplicadas à produção de biodiesel.

A fraca disponibilidade de recursos energéticos não renováveis reflecte-se na crescente procura e na maior relevância dos biocombustíveis, em particular do biodiesel, no panorama nacional. Esta fonte de energia de carácter biológico pode ser obtida a partir de várias matérias-primas de onde se destacam as oleaginosas e as microalgas. Embora sendo de etiologia diferente ambas possibilitam a utilização dos seus óleos que, após sofrerem transesterificação, originam a mistura de ésteres alquílicos designada por biodiesel. Com o objectivo de produzir biodiesel a partir de microalgas foram realizados seis crescimentos da microalga Chlorella protothecoides em reactores batch, em modo fotoautotrófico. A biomassa algal foi utilizada para a extracção dos lípidos e para a produção e análise do biodiesel. Realizou-se o controlo do crescimento da biomassa através de análises diárias. A alga foi colhida durante a fase estacionária de crescimento. A biomassa colhida foi sujeita a tratamentos de centrifugação, ultracongelação, liofilização e moagem, após os quais se procedeu à extracção dos lípidos. Obteve-se um rendimento de lípidos de 12,05%. Os lípidos extraídos foram transesterificados pelo método de Lepage e Roy com o objectivo de produzir biodiesel e simultaneamente derivatizar os ácidos gordos constituintes dos triglicéridos algais de modo a poderem ser analisados por cromatografia gasosa. Pela análise cromatográfica verificou-se que o biodiesel contém uma quantidade exagerada do ácido gordo linolénico 18:3Ω3 (≈ 56% relativamente ao total de ésteres metílicos) o que potencia uma estabilidade oxidativa baixa, incompatível com as exigências requeridas para o biodiesel comercial. No entanto, se o óleo das microalgas for misturado com outros óleos bastante saturados, o biodiesel final produzido a partir desta mistura tornar-se-á viável.info:eu-repo/semantics/publishedVersio

Water-use strategies in two co-occurring Mediterranean evergreen oaks: surviving the summer drought

In the Mediterranean evergreen oakwoodlands of southern Portugal, the main tree species are Quercus ilex ssp. rotundifolia Lam. (holm oak) and Quercus suber L. (cork oak). We studied a savannah-type woodland where these species coexist, with the aim of better understanding the mechanisms of tree adaptation to seasonal drought. In both species, seasonal variations in transpiration and predawn leaf water potential showed a maximum in spring followed by a decline through the rainless summer and a recovery with autumn rainfall. Although the observed decrease in predawn leaf water potential in summer indicates soil water depletion, trees maintained transpiration rates above 0.7 mm day–1 during the summer drought. By that time, more than 70% of the transpired water was being taken from groundwater sources. The daily fluctuations in soil water content suggest that some root uptake of groundwater was mediated through the upper soil layers by hydraulic lift. During the dry season, Q. ilex maintained higher predawn leaf water potentials, canopy conductances and transpiration rates than Q. suber. The higherwater status of Q. ilexwas likely associated with their deeper root systems compared with Q. suber. Whole-tree hydraulic conductance and minimum midday leaf water potential were lower in Q. ilex, indicating that Q. ilex was more tolerant to drought than Q. suber. Overall, Q. ilex seemed to have more effective drought avoidance and drought tolerance mechanisms than Q. suber

Spatiotemporal variability of hydrologic soil properties and the implications for overland flow and land management in a peri-urban Mediterranean catchment

Planning of semi-urban developments is often hindered by a lack of knowledge on how changes in landuse affect catchment hydrological response. The temporal and spatial patterns of overland flow source areas and their connectivity in the landscape, particularly in a seasonal climate, remain comparatively poorly understood. This study investigates seasonal variations in factors influencing runoff response to rainfall in a peri-urban catchment in Portugal characterized by a mosaic of landscape units and a humid Mediterranean climate. Variations in surface soil moisture, hydrophobicity and infiltration capacity were measured in six different landscape units (defined by land-use on either sandstone or limestone) in nine monitoring campaigns at key times over a one-year period. Spatiotemporal patterns in overland flow mechanisms were found. Infiltration-excess overland flow was generated in rainfalls during the dry summer season in woodland on both sandstone and limestone and on agricultural soils on limestone due probably in large part to soil hydrophobicity. In wet periods, saturation overland flow occurred on urban and agricultural soils located in valley bottoms and on shallow soils upslope. Topography, water table rise and soil depth determined the location and extent of saturated areas. Overland flow generated in upslope source areas potentially can infiltrate in other landscape units downslope where infiltration capacity exceeds rainfall intensity. Hydrophilic urban and agricultural-sandstone soils were characterized by increased infiltration capacity during dry periods, while forest soils provided potential sinks for overland flow when hydrophilic in the winter wet season. Identifying the spatial and temporal variability of overland flow sources and sinks is an important step in understanding and modeling flow connectivity and catchment hydrologic response. Such information is important for land managers in order to improve urban planning to minimize flood risk

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR