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91.
The effect of salinity on Fucus ceranoides (Ochrophyta,Phaeophyceae) in the Mondego River (Portugal)
Algae(and their extracts) are increasingly important for pharmaceutical applications due to the diversity of useful compounds they contain. The genus Fucus contains one of the most studied species,Fucus vesiculosus. The species F. ceranoides differs from the others of the genus by presenting longitudinal air-vesicles and a capacity to survive at low salinities. It is an alga that inhabits the Mondego River estuary(Portugal), at the southern limit of its distribution, and can serve as a role model to understand the effect of a salt gradient on the production of bioactive compounds. We assessed the phenolic content and antioxidant activity of different F. ceranoides extracts(e.g. methanolic, aqueous and polysaccharide) prepared from samples harvested from two different zones to evaluate if the adaptation of F. ceranoides to different salinity levels influenced its chemical composition. The antioxidant activity of the extracts was determined using 1,2-diphenyl-picrylhydrazyl(DPPH) and 2.2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)(ABTS)radicals. These assays demonstrated that the methanolic extract of lyophilized F. ceranoides that grew at low salinities was the most bioactive, i.e. DPPH(IC_(50)=50.39 μg/mL) and ABTS(TEAC=2.42). The total phenolic content(Folin-Ciocalteu method) and the methanolic extract of the lyophilized F. ceranoides collected from a low salinity habitat exhibited the highest phenolic content(PGE=49.48 μg/mg of lyophilized extract)amongst those sampled. Thin layer chromatography(TLC) and Fourier transform infrared spectroscopy(FTIR) were used for the identification of compounds in the extracts. This characterization allowed confirmation that the various extracts contained almost the same compounds but with notable quantitative differences. Based on these results, we conclude that there were differences in the quantity of the compounds due to the effect of salinity. The drying methods used were also found to have influenced the quality of the extracted compounds. 相似文献
92.
Teresa Mineo Simone Lotti Silvano Molendi Simona Ghizzardi 《Experimental Astronomy》2017,44(3):287-296
Soft protons constitute an important source of background in focusing X-ray telescopes, as Chandra and XMM-Newton experience has shown. The optics in fact transmit them to the focal plane with efficiency similar to the X-ray photon one. This effect is a good opportunity to study the environment of the Earth magnetosphere crossed by the X-ray satellite orbits, provided that we can link the spectra detected by the instruments with the ones impacting on the optics. For X-ray photons this link has the form of the so-called response matrix that includes the optics effective area and the energy redistribution in the detectors. Here we present a first attempt to produce a proton response matrix exploiting ray-tracing and GEANT4 simulations with the final aim to be able to analyse XMM-Newton soft proton data and link them to the external environment. If the procedure is found to be reliable, it can be applied to any future X-ray missions to predict the soft particles spectra impacting on the focal plane instruments. 相似文献
93.
Leonardo Azevedo Rúben Nunes Amílcar Soares Guenther Schwedersky Neto Teresa S. Martins 《Geophysical Prospecting》2018,66(Z1):116-131
Seismic inversion plays an important role in reservoir modelling and characterisation due to its potential for assessing the spatial distribution of the sub‐surface petro‐elastic properties. Seismic amplitude‐versus‐angle inversion methodologies allow to retrieve P‐wave and S‐wave velocities and density individually allowing a better characterisation of existing litho‐fluid facies. We present an iterative geostatistical seismic amplitude‐versus‐angle inversion algorithm that inverts pre‐stack seismic data, sorted by angle gather, directly for: density; P‐wave; and S‐wave velocity models. The proposed iterative geostatistical inverse procedure is based on the use of stochastic sequential simulation and co‐simulation algorithms as the perturbation technique of the model parametre space; and the use of a genetic algorithm as a global optimiser to make the simulated elastic models converge from iteration to iteration. All the elastic models simulated during the iterative procedure honour the marginal prior distributions of P‐wave velocity, S‐wave velocity and density estimated from the available well‐log data, and the corresponding joint distributions between density versus P‐wave velocity and P‐wave versus S‐wave velocity. We successfully tested and implemented the proposed inversion procedure on a pre‐stack synthetic dataset, built from a real reservoir, and on a real pre‐stack seismic dataset acquired over a deep‐water gas reservoir. In both cases the results show a good convergence between real and synthetic seismic and reliable high‐resolution elastic sub‐surface Earth models. 相似文献
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95.
María Teresa Ramírez-Herrera 《地球表面变化过程与地形》1998,23(4):317-332
Spatial variations of Quaternary deformation and tectonic activity of faults along the Acambay graben are assessed using geomorphic and morphometric approaches. The Acambay graben is an east–west trending structure of apparent Quaternary age, located in the central part of the Mexican Volcanic Belt, which gives rise to pronounced scarps over a distance of about 80 km. Continuing tectonic activity in the Acambay graben is confirmed by recent well documented seismic episodes. The intensity of active tectonics has been interpreted through a detailed geomorphic study of the fault-generated mountain fronts and fluvial systems. The combined geomorphic and morphometric data provide evidence for relative variations in tectonic activity among the Acambay graben faults. Geomorphic indices suggest a relatively high degree of tectonic activity along the Venta de Bravo and the Acambay–Tixmadeje faults, followed, in order of decreasing activity, by the Pastores, Temascalcingo and Tepuxtepec faults. Spatial variations within faults have also been identified, suggesting a higher level of tectonic activity at the tips of the faults. This pattern of variation in the relative degree of tectonic activity is consistent with field evidence and seismic data for the Acambay graben. Geomorphic evaluation of the Acambay graben faults suggests that the Acambay–Tixmadeje and Venta de Bravo faults, and specifically the tips of these faults and a central segment near the town of Venta de Bravo, should be considered as areas of potentially high earthquake risk. © 1998 John Wiley & Sons, Ltd. 相似文献
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98.
Study of the influence of different organic pollutants on Cu accumulation by Halimione portulacoides
C. Marisa R. Almeida A. Claúdia Dias Ana P. Mucha A.A. Bordalo M. Teresa S.D. Vasconcelos 《Estuarine, Coastal and Shelf Science》2009
The influence of each of four organic pollutants selected from among those commonly found in coastal areas, 1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene (DDE), monobutyltin (MBT), Triton X-100 and polycyclic aromatic hydrocarbons (PAHs), on Cu accumulation by Halimione portulacoides was investigated. Experiments were carried out in a laboratory setting, either in hydroponics (sediment elutriate) or in a salt marsh sediment (Cávado River, NW Portugal) soaked in elutriate. Groups of H. portulacoides were exposed to media for 6 days spiked with 10 mg/L Cu(II) and with one of the selected pollutants, at an environmentally realistic concentration. DDE and MBT did not cause any major change on Cu accumulation by H. portulacoides, whereas PAHs slightly increased accumulation only in hydroponics i.e. in the absence of sediment. On the other hand, the non-ionic surfactant Triton X-100 markedly favoured Cu accumulation on plant roots both in the presence and absence of sediment. The addition of DDE, MBT and Triton X-100 also favoured Cu solubility from sediments. Therefore, the simultaneous presence of pollutants from different nature (inorganic and organic) in the estuarine environment may result in a composition of water column, pore water, sediment or biota different of that expected considering the effect of each individual pollutant. 相似文献
99.
Claudia Spinetti Francesco Mazzarini Ruggero Casacchia Laura Colini Marco Neri Boris Behncke Rosamaria Salvatori Maria Fabrizia Buongiorno Maria Teresa Pareschi 《International Journal of Applied Earth Observation and Geoinformation》2009
Spectral properties of volcanic materials in the optical region (350–2500 nm) of the electromagnetic spectrum are analyzed. The goal is to characterize air-fall deposits, recent lava flows, and old lava flows based on their spectral reflectance properties and on the textural characteristics (grain size) of pyroclastic deposits at an active basaltic volcano. Data were acquired during a spectroradiometric field survey at Mt. Etna (Italy) in summer 2003 and combined with hyperspectral satellite (Hyperion) and airborne LiDAR (Light Detection and Ranging) data. In addition, air-fall deposits produced by the highly explosive 2002–2003 eruption have been sampled and spectrally characterized at different distances from the new vents. The spectral analysis shows that air-fall deposits are characterized by low reflectance values besides variations in grain size. This distinguishes them from other surface materials. Old lava flows show highest reflectance values due to weathering and vegetation cover. The spectral data set derived from the field survey has been compared to corrected satellite hyperspectral data in order to investigate the Hyperion capabilities to differentiate the surface cover using the reflectance properties. This has allowed us to identify the 2002–2003 air-fall deposits in a thematic image just few months after their emplacement. Moreover, the observed differences in the field spectra of volcanic surfaces have been compared with differences in the signal intensity detected by airborne LiDAR survey showing the possibility to include information on the texture of volcanic surfaces at Mt. Etna. The approach presented here may be particularly useful for remote and inaccessible volcanic areas and also represents a potentially powerful tool for the exploration of extraterrestrial volcanic surfaces. 相似文献
100.
Almeida CM Mucha AP Delgado MF Caçador MI Bordalo AA Vasconcelos MT 《Marine environmental research》2008,66(3):311-318
The presence of polycyclic aromatic hydrocarbons (PAHs) may change the mechanisms of metal uptake, thus influencing kinetics and extent of metal phytoextraction. Studies on the subject are scarce, particularly for salt marsh plants. The aim of this work was to investigate the effect of PAHs on the uptake of Cu by Halimione portulacoides, a plant commonly found in salt marshes. Experiments were carried out in the laboratory, either in hydroponics (sediment elutriate) or in sediment soaked in elutriate, which were prepared with sediment and water from a salt marsh of the Cavado river estuary (NW Portugal). Groups of H. portulacoides (grown in a greenhouse) were exposed to those media during six days. Cu(2+) (as Cu(NO(3))(2)), 10(2) and 10(4)mugl(-1), was added to the media as well as 1.6mugl(-1) of the sixteen EPA priority PAHs (0.1mugl(-1) of each PAHs). Cu was assayed in solutions, sediments and different plant tissues before and after experiments. After exposure, photosynthetic efficiency and levels of chlorophylls were also measured, indicating that plant stress indicators were identical in all plants independently of the media to which the plants were exposed. PAHs influenced both the soluble Cu fraction and Cu uptake by plants. The amounts of metal accumulated in both roots and stems were significantly higher when the 10(4)mugl(-1) of Cu enriched elutriate was amended with PAHs. Thus, results suggest that PAHs may modify Cu solubility, the Cu sorption by plants and/or the passive penetration of Cu into the root cells. Therefore, the combined effects of different types of pollutants should be taken in consideration when studying the remediation potential of plants, namely in terms of phytoextraction. 相似文献