Repositório Institucional da Universidade de Aveiro
Not a member yet
41903 research outputs found
Sort by
Lipophilic profile of the edible halophyte Salicornia ramosissima
No full textSalicornia ramosissima J. Woods is considered, in the Iberian Peninsula and France, a gourmet product. Nevertheless, is one of the less studied Salicornia species. In this work, GC-MS was employed to, for the first time; fully characterise the lipophilic profile of S. ramosissima and to assess the effect of natural and extra irrigation in that profile. The obtained data showed esterified and free fatty acids, fatty alcohol, sterols, alkanes and aromatic acid derivatives, being palmitic acid, tetracosanol and octacosanol the most abundant compounds. The extra irrigation increases significantly (P < 0.001) the content of esterified lipophilic compounds. Stigmastanol, 24-ethyl-δ(22)-coprostenol, several secondary fatty alcohols and dicarboxylic acids were identified for the first time in Salicornia genus. Several of the detected compounds are known to have health benefits and our results suggest that S. ramosissima should be considered as an important dietary source of lipophilic phytochemicals
Molecular assessment of heterotrophy and prey digestion in zooxanthellate cnidarians
No full textZooxanthellate cnidarians are trophically complex, relying on both autotrophy and heterotrophy. Although several aspects of heterotrophy have been studied in these organisms, information linking prey capture with digestion is still missing. We used prey-specific PCR-based tools to assess feeding and prey digestion of two zooxanthellate cnidarians - the tropical sea anemone Aiptasia sp. and the scleractinian coral Oculina arbuscula. Prey DNA disappeared rapidly for the initial 1-3 days, whereas complete digestion of prey DNA required up to 10 days in O. arbuscula and 5 or 6 days in Aiptasia sp. depending on prey species. These digestion times are considerably longer than previously reported from microscopy-based examination of zooxanthellate cnidarians and prey DNA breakdown in other marine invertebrates, but similar to prey DNA breakdown reported from terrestrial invertebrates such as heteroptera and spiders. Deprivation of external prey induced increased digestion rates during the first days after feeding in O. arbuscula, but after 6 days of digestion, there were no differences in the remaining prey levels in fed and unfed corals. This study indicates that prey digestion by symbiotic corals may be slower than previously reported and varies with the type of prey, the cnidarian species and its feeding history. These observations have important implications for bioenergetic and trophodynamic studies on zooxanthellate cnidarians
Toxicity screening of soils from different mine areas-A contribution to track the sensitivity and variability of Arthrobacter globiformis assay
No full textThis study used the Arthrobacter globiformis solid-contact test for assessing the quality of soils collected in areas subjected to past and present mine activities in Europe (uranium mine, Portugal) and North Africa (phosphogypsum pile, Tunisia; iron mine, Morocco). As to discriminate the influence of soils natural variability from the effect of contaminants, toxicity thresholds were derived for this test, based on the dataset of each study area. Furthermore, the test sensitivity and variability was also evaluated. As a result, soils that inhibited A. globiformis dehydrogenase activity above 45% or 50% relatively to the control, were considered to be toxic. Despite the soil metal content determined, the properties of soils seemed to influence dehydrogenase activity. Overall, the contact test provided a coherent outcome comparing to other more time-consuming and effort-demanding ecotoxicological assays. Our results strengthened the feasibility and ecological relevance of this assay, which variability was quite reduced hence suggesting its potential integration within the test battery of tier 1 of soil risk assessment schemes
Morphodynamic evolution of a sand extraction excavation offshore Vale do Lobo, Algarve, Portugal
No full textOffshore sand and gravel extraction for aggregates and beach nourishment is an important economic activity and has been a common practice in various countries worldwide for many years. The evolution of a sandpit, in particular its migration and rate of replenishment, depends strongly on the type of sediments involved, and on the physical and hydrodynamic characteristics of the surrounding area. In order to fully assess the associated impacts on local ecosystems and on the neighboring coastline morphology it is essential to make accurate predictions of the excavation recovery times. For this purpose it is fundamental to investigate areas where there is an adequate observational control of the evolution of the sandpit, prior and after the excavation, to properly calibrate existing numerical models with observations and fully evaluate their prediction adequacy. The present work investigates the evolution of an offshore sandpit located off Vale do Lobo, Algarve, Portugal, within a time span of four years (2006-2010), based on 4 bathymetric surveys, prior to and after the dredging operations, complemented with the analysis of wave data and numerical modeling simulations. The bathymetric data were used to evaluate the morpho-sedimentary evolution and to calculate the sediment volume changes. The results show an infill of approximately 17% of the initial exploration pit in the first 4. years, with an overall smoothing of the initial excavation bottom topography. Observations combined with modeling results demonstrate that the pit evolution depends mainly on storm events, since it is essentially during these periods that there is a significant sediment movement at the site water depth. Based on (1) the predicted number of stormy days for the forthcoming years, assuming that (2) the yearly average of such events in the past 57. years is representative, and considering (3) a decrease of the sandpit recovery rate in time, predicted by models and observations, it was possible to estimate that the Vale do Lobo sandpit recovery period is of ca. 38. years for its full, or near full, replenishment
Profiling transcriptomic response of Enchytraeus albidus to Cu and Ni: comparison with Cd and Zn
No full textMetals are among the most common contaminants in soils in Europe. Although their effects are relatively well known regarding survival and reproduction to soil invertebrates, their mode of action is poorly understood. Enchytraeus albidus is a model organism in ecotoxicology and with the development of a gene library for this species, transcriptomic studies are now possible. The main aim of this study is to understand the Cu and Ni mechanisms of response in E. albidus, in comparison with Cd and Zn (already studied). E. albidus were exposed to Cu and Ni for 4 days to the reproduction effect concentrations EC 50 and EC90. Results indicate that Cu and Ni have similar mechanisms of toxicity. When comparing four elements (hierarchical clustering) it was possible to observe a clear separation of Cd from all other metals. This separation correlates with the available information from other species regarding the toxicokinetics of the tested elements
Cradle-to-gate life cycle assessment of forest operations in Europe: environmental and energy profiles
No full textLife Cycle Assessment (LCA) has become a common and standardized methodology to evaluate the environmental profiles of forest systems. In this study twelve different European forest systems dedicated to wood production for industrial or energy uses (maritime pine, spruce, willow, poplar and Douglas-fir) were compared in detail from environmental and energy points of view considering a cradle-to-gate perspective. The scenarios included the silviculture of these tree species in Sweden, Germany, France, Italy and Portugal. A database with inventory data was constructed for each scenario. The scenarios considered were standardized using the same methodological life cycle assumptions in order to establish comparisons for an overall analysis. The results show a relatively wide range of variations in terms of biomass productivities as well as environmental and energy profiles. These variations depended on the tree species, management regime (different levels of fertilization, time of harvesting and intensity of forest operations) and the overall conditions of the location of the plantations. However, regardless of the scenario considered, operations related to logging such as harvesting and forwarding were identified as hotspots mainly due to the remarkable fuel requirement. Fertilization activities and fertilizer production (when required), thinning processes (when necessary) as well as weed control related processes reported also notable contributions to the categories under assessment. If these twelve scenarios are compared with other similar studies for the same tree species, significant differences can be found which are mainly linked to different forest management regimes and regional characteristics. The choice and the promotion of a specific forest biomass for industrial applications should not only depend on the biomass yield and the harvesting age but it should be also based on the intensity of forest practices since it considerably affects the environmental and energy profiles
Zinc oxide nanoparticles toxicity to Daphnia magna: size-dependent effects and dissolution
No full textAs the production of zinc oxide nanoparticles (ZnO-NPs) and other metal oxides is exponentially increasing, it is important to investigate potential environmental and health impacts of such nanoparticles. Nanoparticles' properties (e.g., size, dissolution rate) may change in different water media, and their characterization is essential to derive conclusions about toxicity results. Therefore, an aquatic model organism, Daphnia magna, was used to investigate the effect of ZnO-NPs with 2 different particle sizes (30 nm and 80-100 nm) and then compare these effects with ZnO microsized particles (>200 nm) and the ionic counterpart (in the form of ZnCl2 ) on immobilization, feeding inhibition, and reproduction endpoints. The 48-h median lethal concentration (LC50) for immobilization ranged between 0.76 mg Zn L(-1) for the ionic zinc and 1.32 mg Zn L(-1) for ZnO-NPs of 80 nm to 100 nm. For the chronic exposures, the reproduction output was impaired similarly among zinc exposures and possibly driven mainly by the zinc ionic form. The concentrations used showed a total dissolution after 48 h. On the other hand, feeding activity was more affected by the 30 nm ZnO-NPs than by the ionic zinc, showing that the particulate form was also playing an important role in the feeding inhibition of D. magna. Dissolution and particle size in the daphnia test media were found to be essential to derive conclusions on toxicity. Therefore, they can possibly be considered critical for evaluating nanoparticles' toxicity and fate
Geochemistry, petrogenesis, and tectonic setting of the Almogholagh batholith in the Sanandaj–Sirjan zone, Western Iran
No full textThe Almogholagh batholith in the northern Sanandaj-Sirjan magmaticemetamorphic zone comprises three intrusive bodies (gabbroic diorite, quartz syenite, and quartz monzonite) that were generated during the northeastward subduction of Neo-Tethys beneath the Iranian sector of the Eurasian plate. These bodies intruded at different time phases and are related to post-collision magmatism. The quartz syenite and quartz monzonite rocks with specifications of metaluminous, generally ferroan, alkalic to
alkali-calcic types, high content of Na2O þ K2O, Zr, Ce, Ga, Y, Nb, Ta, and rare earth elements, and depleted in Eu, Sr, and Ti show borderline characteristics between A1 and A2 types granitoids but with more affinity to A2 type. The gabbroic dioritic rocks show borderline specifications between A1 and I types rocks but with more affinity to I type. Distinctive spiked peak patterns in spider diagrams accompanied by (La/Yb)CN values equal to 2.44 to 6.11 and a Ba/La ratio >3 indicate the magmatism activity in the volcanic arc environment. The characteristics (Ba/Rb)PN < 1, (Ba/Th)PN < 1, and Th/Ta ratio from 3.18 to 8.42 suggest the magmatism activity of the continental margin setting. The specifications of post-collision magmatic
activities, 143Nd/144Nd > 0.512638 in some samples, εNdt > 0, εSrt > 0, and high content of Nb, Ta, and Zr (589 ppm) demonstrate the involvement of the mantle source, subducted slab fluids, high flux of mantle derived
halogen-rich volatiles, and contamination within the crust during the petrogenesis of intrusions. After the initial collision, the operation of minor subduction (with slab break-off) or foundering of the lithospheric mantle (delamination) occurred because of asthenospheric upwelling and heat flows in the mantle in the Sanandaj-Sirjan zone. Stretch and local disruptions were created by these heat flows; simultaneously, magma was formed and ascended upward
Geoquímica de litologias básicas e ultrabásicas da unidade de alóctone superior do maciço de Bragança
Get PDFThe Galicia - Tras-os-Montes Zone is composed of several exotic tectonic units emplaced upon the Central-Iberian autochthon. The upper allochthonous thrust complex crops out in the
Bragança Massif, where it is represented mainly by several lithologies of dominantly mafic and
ultramak compositions: evidences of granulite-facies and eclogite-facies metamorphism are
common. Four main rock tqpes were studied: 1) high-pressure granulites; 2) eclogites (enclosed by
paragneisses); 3) plutonic bodies, essentially composed of gabbroic rocks, 4) ultramafic rocks.
Previous works have shown that the first hvo lithotypes have passed through a complex
tectonometamorphic evolution, leading some authors to propose models considering polycyclical
tectonic models. However, the polycyclical hypothesis is apparently contradicted by the
geochronological information available until now, which usually correspond to ages related to the
Variscan cycle.
According to the geochemical data, the compositions of high-pressure granulites seem to
reflect fractionation processes under high-grade metamorphic conditions; redistribution of highly
incompatible trace elements (including some elements that are not easily transported by the most
common metamorphic fluids) would have occurred, at least locally. The trace element contents of
ditferent types of granulites (from mafic to felsic), when compared to the most basic compositions
amongst those that are proposed to represent the lower crust, display LREE-depleted patterns,
suggesting that, besides being reinobilize& the most incompatible elements have suEered removal, .
probably via a silicate liquid phase. Isotope Sm-Nd analyses were performed using one sample of
mafic granulite from the Tojal de Pereiros outcrop: a wr-mineral 1079*78 Ma isochron was obtained
The dated granulite has neither mineral relics nor texwral features hpthetically related to the
protolithi consequentl!: the geochronological datum marks Nd-isotope homogenization during a
metamorphic event. Therefore. high-pressure granulites represent fragments of Grenviilian basement
that were reactivated and eshumed during the Variscan orogeny.
Resunzo -Abstract I11
Three main compositional groups of eclogites were defined using hygromagmatophile trace
elements with essentially imrnobile behaviour in metamorphic processes: A) rocks of tholeiitic
composition, similar to N-MORB; B) subalkaline (tholeiitic to calc-alkaline) rocks displaying
geochemical signatures typical of supra-subduction settings; C) rocks related to alkaline basalt
protoliths. The diversity revealed by the eclogites together with the geochemical features of the
enclosing paragneisses (characteristic of sediments from basins related to volcanic arcs) suggest that
the protoliths of the metaigneous and metasedimentav rocks were formed in a back-arc marginal
basin. Isotope data from an eclogite sample reveals that the Sm-Nd system has been disturbed:
however, the wr-grt line indicates that the high-pressure metamorphic event is older than 508 Ma. A
389+10 Ma wr-mineral isochron was obtained using a sample of a metasomatic vein in granulitized
eclogite. The occurrence of the metasomatic event was determined by the penetration, in the
metabasites, of aqueous fluids generated by devolatilization reactions in-the enveloping paragneisses
during decompression. The Lower Devonian age clearly does not date the eclogitization; instead, it
corresponds to a later metamorphic episode.
Previous authors have emphasized that the gabbroic plutonic bodies, compared to highpressure
granulites and eclogites, had a simpler tectonothermal evolution and that ihey postdate the
earliest defonnation phases recorded in the HP metamorphic rocks. Trace-element and isotope
compositions of gabbroic rocks indicate that they crystallized from continental tholeiitic magmas; the
%d VS. features reveal interaction with metamorphic rocks with long-term lower-crust residence.
Sm-Nd data suggest that igneous emplacement would have occurred during Upper Precambrian or
Cambrian times; an internal wr-mineral isochron shows that the closure of the Sm-Nd system after
partial granulitization (responsible for corona textures) has an Ordovician age; another internal Sm-
Nd isochron (obtained in a flasergabbro) may represent an early phase (Upper Silurian age) of
tectonic uplift. Isotope data, together with petrographic information collected in the gabbroic samples,
reveal that micro-domainal readjustments play a significant role in rocks that were affected by partial
mineralogical and textural transformations.
Ultramafic rocks - in part, at least - represent a portion of subcontinental lithospheric upper
mantle, located in an intraplate tectonic setting in the Lower Palaeozoic. Intimately associated
peridotite and pyroxenite layers are probably testimonies of the penetration of magmas (from which
pyroxenes were segregated) through rocks (of harzburgitic or similar compositions) previously
submitted to melt removal. Some pyroxenite bodies are well individualized and may contain garnet; .
this type of pyroxenites has traceelement patterns characteristic of their derivation from alka1'me
magmas; the ascent of strongly LREEenriched melts through upper mantle rocks, besides being
responsible for the generation of those bodies, could also have caused cryptic metasomatism
preferentially affecting the refractory lithologies. A garnet clinopyroxenite sample displayed a 485+17
Ma wr-mineral isochron (Sm-Nd system), implying that the presence of the alkaline magmas occurred
during the Lower Ordovician or earlier; therefore, this type of pyroxenites corresponds to deep
manifestations of the igneous phenomena that accompanied the extensional period marking the
beginning of the Variscan tectonic cycle.
The results of this work, together with other geological evidences previously presented, agree
with the polycyclical evolution hypothesis for the upper allochthonous thrust complex of NW Iberia.
The scarcity of geochronological results showing the occurrence of Precambrian metamorphic events
is probably due to the thermal effects of the very important Lower Palaeozoic magmatism and to the intense Variscan orogenic remobilization
Barreiras autoconcordantes e álgebras de Jordan em problemas combinatórios
No full textDoutoramento em MatemáticaApós a apresentação dos principais resultados sobre álgebras de Jordan,
nomeadamente sobre álgebras de Jordan euclidianas, analisam-se as
propriedades da barreira F=-detlog definida sobre um cone simétrico, com uma
abordagem puramente algébrica.
Apresenta-se uma nova demonstração da r-normalidade da barreira F, definida
sobre o cone dos quadrados de uma álgebra de Jordan euclidiana com
característica r, demonstra-se que o número de Caratheodory deste cone é
igual a r e deduzem-se as consequentes conclusões sobre o parâmetro óptimo
da barreira F.
Introduz-se a definição de barreira ν − euclidiana e, a partir das propriedades
dessa barreira, constrói-se um subgrupo de automorfismos sobre um cone
simétrico de um espaço vectorial euclidiano.
Descrevem-se as álgebras coerentes, nomeadamente as álgebras coerentes
homogéneas simétricas, as quais estão directamente relacionadas com grafos
fortemente regulares e, com base nelas, propõe-se um algoritmo para a
determinação de grafos fortemente regulares de ordem par, no pressuposto de
se conhecerem todos os quadrados latinos reduzidos simétricos unipotentes
da mesma ordem.
Finalmente, determinam-se famílias de álgebras de Jordan euclidianas que
incluem grafos regulares e fortemente regulares e deduzem-se as respectivas
tabelas de caracteres.After the main results on Jordan algebras, namely on Euclidean Jordan
algebras, the properties of the barrier F=-logdet defined on a symmetric cone
are analyzed in an algebraic way.
A new proof that the barrier F is r-ormal over the interior of the cone of squares
of a Euclidean Jordan algebra, with rank r, is presented. It is also established
that the Carathéodory number of that cone is equal to r. The consequences
about the optimal parameter of the barrier F are also deduced.
Based in the properties of a defined ν − Euclidian barrier, a subgroup of
automorphisms of a symmetric cone of a Euclidean vector space is
constructed.
A class of coherent algebras is described, namely the class of homogeneous
symmetric coherent algebras (which are directly related with strongly regular
graphs). An algorithm is then proposed for the determination of strongly
regular graphs of order even, supposing that all reduced symmetric unipotent
latin squares of the same order are known.
Finally, families of Euclidean Jordan algebras including regular and strongly
regular graphs are determined and their character tables are deduced