Mineralogia dos filões aplito-pegmatíticos litiníferos da região de Segura

Publicação comemorativa do "Ano Internacional do Planeta Terra".Na região de Segura, os filões aplito-pegmatíticos litiníferos Variscos instruíram o Complexo Xisto-Grauváquico, Câmbrico. Os filões pegmatíticos são do tipo REL-Li e incluem-se na família dos pegmatitos LCT. A ocorrência de lepidolite, montebrasite, microlite, cassiterite e minerais do grupo da columbite primários sugerem um elevado grau de diferenciação nestes filões. A montebrasite primária é heterogénea e a lacroixite secundária ocorre nas suas zonas enriquecidas em Na. A cassiterite é zonada com alternância de zonas escuras e zonas claras e possui Mn > Fe, o que é raro. As zonas escuras são fortemente pleocroicas, com zonamento oscilatório, e possuem teores mais elevados de Nb e Ta do que as zonas claras. As inclusões de moscovite, apatite, ferrotapiolite, ixiolite e microlite foram encontradas em ambas as zonas da cassiterite, mas as exsoluções de ferrocolumbite, ferrocolumbite manganífera e manganocolumbite ocorrem nas zonas escuras

Asymptotic limits and stabilization for the 1D nonlinear Mindlin-Timoshenko system

This paper shows how the so called von Kármán model can be obtained as a singular limit of a modified Mindlin-Timoshenko system when the modulus of elasticity in shear k tends to infinity, provided a regularizing term through a fourth order dispersive operator is added. Introducing damping mechanisms, the authors also show that the energy of solutions for this modified Mindlin-Timoshenko system decays exponentially, uniformly with respect to the parameter k. As k → ∞, the authors obtain the damped von Kármán model with associated energy exponentially decaying to zero as well

Geoquímica do granito, filões de quartzo com scheelite e águas da mina abandonada de Fonte Santa (NE de Portugal)

Os filões de quartzo com scheelite da mina da Fonte Santa atravessam a formação do Quartzito Armoricano, do Ordovícico Inferior. A mineralização é de tipo “stockwork”, ocorre associada ao leucogranito sin-F3, da Fonte Santa, que aflora a 250 m a Sul do jazigo e relaciona-se com a zona de cisalhamento Moncorvo-Bemposta (Silva e Pereira, 2001). O leucogranito é de grão médio a fino, moscovítico, com foliação N80ºW, subvertical. Possui quartzo, microclina, albite, moscovite, turmalina, silimanite, zircão, apatite, e ilmenite. As amostras alteradas com microclinização e moscovitização intensa contêm clorite, columbite-tantalite, volframite, ixiolite rica em W e óxidos de ferro. É um granito peraluminoso, do tipo S, muito evoluído e estanífero com Sn > 44ppm (Silva, 2000). Alguns filões têm quartzo parcialmente recristalizado, por vezes brechóide, impregnado de sulfuretos preenchendo microfissuras e fracturas. A paragénese dos filões é constituída por quartzo, moscovite, clorite, turmalina, scheelite, pirrotite, pirite, esfalerite, calcopirite, galena, óxidos de ferro, sulfatos de Fe e fosfatos de Pb, Fe e Al. A mina da Fonte Santa foi explorada para W entre 1942 e 1982 (Triede, 2002). As águas associadas à mina da Fonte Santa, são pouco mineralizadas, com condutividade específica < 150 μS/cm, de tipo misto, bicarbonatadas ou sulfatadas. A maioria dos valores de pH (5.0 e 9.2) indicam que não há uma drenagem ácida significativa na região, tal como encontrado noutros locais (e.g., Antunes et al., 2002). Os valores mais ácidos (pH: 3.4-3.5) foram encontrados na lagoa da mina

Contaminação de águas associadas a mineralizações de W de Fonte Santa, NE Portugal

Na região da mina de Fonte Santa ocorrem filões de quartzo mineralizados em W, com scheelite, que cortam os quartzitos do Ordovícico Inferior e estão relacionados com a zona de cisalhamento de Moncorvo-Bemposta. Alguns filões com scheelite têm quartzo recristalizado e brechificado e sulfuretos, tendo sido explorados para W entre 1942 e 1982. As águas relacionadas com a mina da Fonte Santa são pouco mineralizadas, com condutividade eléctrica < 965 μ S/cm, e classificadas como de tipo misto. A maioria dos valores de pH (pH = 5.0 - 8.5) indicam que não há drenagem ácida significativa associada às actividades mineiras e os valores mais ácidos (pH = 3.4) foram obtidos numa lagoa da mina. Nas águas associadas com os filões mineralizados e antigas explorações foram encontradas concentrações elevadas de Fe e Mn que proíbem o seu consumo humano e utilização na agricultura

Determination of low molecular weight volatiles in Ficus carica using HS-SPME and GC/FID

Ficus carica L. is one of the earliest cultivated fruit trees, having an important consumption in Mediterranean countries. In this work, the volatile compound profiles of two characteristic Portuguese white varieties (‘‘Pingo de Mel” and ‘‘Branca Tradicional”) was determined by HS-SPME and GC/FID. Leaves, pulps and peels, submitted to freezing and lyophilisation treatments, were analysed. The two varieties presented a similar profile composed of eight volatile compounds: acetaldehyde, ethyl acetate, methanol, ethanol, hexanal, limonene, (E)-2-hexenal and octanal. The total volatile content was different among the vegetal materials, following the order leaves > peels > pulps. Methanol and ethanol are the major compounds in all samples. The developed procedure revealed to be rapid, sensitive, reproducible and accurate. The detection limit values were low, and the method precise. The recovery values for acetaldehyde, ethyl acetate, methanol and ethanol were generally high, suggesting that it will be most suitable for compounds with low molecular weight. Due to its rapidity and low cost, this technique can be useful in the quality control of fig fruit and leaves

Development and evaluation of an HPLC/DAD method for the analysis of phenolic compounds from olive fruits

A new HPLC/DAD methodology for separating nine phenolic compounds is described. This methodology is applied to the definition of qualitative and quantitative profiles of three Portuguese olive fruit cultivars (Cobrançosa, Madural and Verdeal). Two different extraction methods were needed for the complete definition of their profiles, one of them including a Sep-pack C18 cleaning step. The chromatographic separation was achieved using a Spherisorb ODS2 (25.0 × 0.46 cm; 5 μm, particle size) column. The solvent system used was a gradient of water-formic acid (19:1) and methanol, with a flow rate of 0.9 mL/min. The detection limit values for phenolic compounds were between 0.04 and 4.32 μg/mL and the method was precise. As a general rule, the recovery values were high. This technique can also be useful in the discrimination of Portuguese olive fruit cultivar

Phenolic profile of Cydonia oblonga Miller leaves

Cydonia oblonga Miller leaves phenolic compounds were analyzed by reversed-phase HPLC/DAD and HPLC/UV. Qualitative and quantitative analysis of phenolics were carried out in a total of 36 samples of quince leaves from three different geographical origins of Northern (Bragança and Carrazeda de Ansiães) and Central Portugal (Covilhã) and three collection months (June, August, and October of 2006). These leaves presented a common phenolic profile composed by nine compounds: 3-O-, 4-O- and 5-O-caffeoylquinic acids, 3,5-O-dicaffeoylquinic acid, quercetin-3-Ogalactoside, quercetin-3-O-rutinoside, kaempferol-3-O-glycoside, kaempferol-3-O-glucoside, and kaempferol-3-O-rutinoside. 5-O-caffeoylquinic acid was the major phenolic compound (36.2%), followed by quercetin 3-O-rutinoside (21.1%). Quince leaves are characterized by higher relative contents of kaempferol derivatives than fruits (pulps, peels, and seeds), especially in what concerns kaempferol-3-O-rutinoside (12.5%). C. oblonga leaves total phenolic content was very high, varying from 4.9 to 16.5 g/kg dry matter (mean value of 10.3 g/kg dry matter), indicating that these leaves can be used as a good and cheap source of bioactive constituents. Significantly differences were observed in 3-O-caffeoylquinic and 3,5-O-dicaffeoylquinic acids contents, according to geographical provenance and harvesting month, suggesting a possible use of these compounds as geographical origin and/or maturity markers

Organic acids composition of Cydonia oblonga Miller leaf

Organic acid profiles of 36 Cydonia oblonga Miller leaf samples, from three different geographical origins of northern (Bragança and Carrazeda de Ansiães) and central Portugal (Covilhã), harvested in three collection months (June, August and October of 2006), were determined by HPLC/UV (214 nm). Quince leaves presented a common organic acid profile, composed of six constituents: oxalic, citric, malic, quinic, shikimic and fumaric acids. C. oblonga leaves total organic acid content varied from 1.6 to 25.8 g/kg dry matter (mean value of 10.5 g/kg dry matter). Quinic acid was the major compound (72.2%), followed by citric acid (13.6%). Significant differences were found in malic and quinic acids relative abundances and total organic acid contents according to collection time, which indicates a possible use of these compounds as maturity markers. Between June and August seems to be the best period to harvest quince leaves for preparation of decoctions or infusions, since organic acids total content is higher in this season

Effect of the conservation procedure on the contents of phenolic compounds and organic acids in Chanterelle (Cantharellus cibarius) Mushroom

To check the influence of the conservation procedure in the chemical composition of chanterelle mushroom, phenolic compounds and organic acids of samples preserved under four different conditions (drying, freezing, conservation in olive oil and in vinegar) were determined. Phenolics and organic acids were analyzed by HPLC-DAD and HPLC-UV, respectively. The results showed that chanterelle is characterized by the presence of six phenolic compounds (3-, 4-, and 5-O-caffeoylquinic acid, caffeic acid, p-coumaric acid, and rutin) and five organic acids (citric, ascorbic, malic, shikimic, and fumaric acids). Samples preserved in olive oil also exhibited hydroxytyrosol, tyrosol, luteolin, and apigenin, whereas conservation in vinegar led to the detection of hydroxytyrosol, tyrosol, and tartaric acid in the analyzed samples. The conservation procedures to which chanterelle samples were subjected seem to affect the qualitative and quantitative phenolics and organic acids profiles

Nutritive value of Brachiaria decumbens and native pasture at various stages of maturity

Em cinco ensaios de digestibilidade, novilhos nelore (140-230 kg de peso vivo) foram alimentados com Brachiaria decumbens (BD) e pastagem nativa (PN), cortadas em vários estádios de crescimento e fornecidas sob a forma de feno; em um sexto experimento, o feno de pastagem nativa de baixa qualidade foi fornecido suplementado ou não com 0,5 kg de farelo de sementes de algodão por novilho por dia. Os dados de digestibilidade e consumo de BD foram, na maioria das vezes, significativamente superiores aos obtidos com PN, e as diferenças aumentaram com a maturidade das plantas. A suplementação de feno de PN de baixa qualidade com 0,5 kg de farelo de sementes de algodão/novilho/ dia resultou em aumento significativo no total de alimento consumido. Coeficientes de correlação significativos foram encontrados entre as digestibilidades de matéria seca e da matéria orgânica e os conteúdos de nitrogênio dos alimentos e das fezes; os valores de r, relacionando digestibilidade e consumo, variaram de 0,40 (PN) a 0,77 (BD) e, para nitrogênio fecal (NF) e matéria orgânica digestível (MOD), foram de 0,71 e 0,79 (BD, com e sem os dados da estação seca) e 0,66 para PN. Resultados similares foram obtidos quando se relacionou NF e consumo de matéria orgânica. Para BD, valores de r de 0,98 (para ambos os casos) foram encontrados quando a percentagem de folhas foi relacionada à digestibilidade e ao consumo de matéria orgânica.In five indoor digestion trials, Nellore steers (140-230 kg live-weight) were fed with Brachiaria decumbens (BD) and native pasture (NP), cut at different maturity stages and made into hay: in a sixth experiment poor quality native hay was given with and without 0.5 kg of cottonseed meal (CSM) per steer daily. Digestibility and intake of BD were for the most part significantly greater than NP and the differences increased with plant maturity. Supplementing poor quality native hay with 0.5 kg CSM per steer daily resulted in a significant increase in total feed intake. Significant correlation coefficients were found between digestibility of feed dry and organic matter and nitrogen content of feed and faeces; r values, relating digestibility to intake, ranged from 0.40 (NP) to 0.77 (BD) and for faecal nitrogen (FN) and digestible organic matter (DOM) were 0.71 or 0.79 (BD, with and without dry season herbage) and 0.66 for NP. Approximately similar figures were calculted for FN and organic matter intake. Within BD, r values of 0.98 (each case) were found between percentage of leaves and both digestibility and intake of organic matter