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21.
22.
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
23.
The excess vibrational entropy (ΔS
vibex) of several silicate solid solutions are found to be linearly correlated with the differences in end-member volumes (ΔV
i
) and end-member bulk moduli (Δκ
i
). If a substitution produces both, larger and elastically stiffer polyhedra, then the substituted ion will find itself in
a strong enlarged structure. The frequency of its vibration is decreased because of the increase in bond lengths. Lowering
of frequencies produces larger heat capacities, which give rise to positive excess vibrational entropies. If a substitution
produces larger but elastically softer polyhedra, then increase and decrease of mean bond lengths may be similar in magnitude
and their effect on the vibrational entropy tends to be compensated. The empirical relationship between ΔS
vibex, ΔV
i
and Δκ
i
, as described by ΔS
vibex = (ΔV
i
+ mΔκ
i
)f, was calibrated on six silicate solid solutions (analbite–sanidine, pyrope–grossular, forsterite–fayalite, analbite–anorthite,
anorthite–sanidine, CaTs–diopside) yielding m = 0.0246 and f = 2.926. It allows the prediction of ΔS
vibex behaviour of a solid solution based on its volume and bulk moduli end-member data. 相似文献
24.
This paper presents a new method which allows for the automatic extraction and tracking of the evolution of filaments in solar images. Series of Hα full-disk images are taken in regular time intervals to observe the changes of the solar disk features. In each picture, the solar chromosphere filaments are identified for further evolution examination. Two alternative preprocessing techniques converting grayscale images into black-and-white pictures with enhanced chromosphere granularity are examined: local thresholding based on median values and global thresholding with brightness and area normalization. The next step employs morphological closing operations with multi-directional linear structuring elements to extract elongated shapes in the image. After logical intersection of directional filtering results, remaining noise is removed from the final outcome using morphological dilation and erosion with a circular structuring element. Experimental results show that the developed technique can achieve excellent results in detecting large filaments and good detection rates for small filaments. 相似文献
25.
26.
Artur Chahud Setembrino Petri 《Proceedings of the Geologists' Association. Geologists' Association》2014
Three genera, known by dorsal finspine, are reported from conglomeratic sandstone at the base of the Lower Permian (Kungurian) Irati Formation (Paraná Basin) near Rio Claro, São Paulo State, Brazil, noteworthy for the great richness of vertebrate fossils. The fossils include: (1) the previously known Sphenacanthus with the species Sphenacanthus sanpauloensis and an indeterminate species; (2) the Permian – Carboniferous genus Amelacanthus; (3) a new indeterminate Chondrichthyes. These fossils are found together with: continental, fresh-water and salt-water vertebrates. The analysis of this assemblage allows inference about the origin of Paraná Basin Chondrichthyes as well as reconstruction of the paleoenvironment and the possible geographic isolation of these fishes during the Permian in Brazil. 相似文献
27.
Zdzisław M. Migaszewski Agnieszka Gałuszka Artur Michalik Sabina Dołęgowska Andrzej Migaszewski Stanisław Hałas Andrzej Trembaczowski 《Aquatic Geochemistry》2013,19(4):261-280
The paper presents the results of determinations of stable S and O isotopes of dissolved sulfates and O and H stable isotopes of waters from three ponds, that is, Marczakowe Do?y acid pond, Marczakowe Do?y fish pond and Podwi?niówka acid pit pond, located in the Holy Cross Mountains (south-central Poland). The δ34SV-CDT and δ18OV-SMOW of SO4 2? in waters of three ponds (n = 14) varied from ?16.2 to ?9.5 ‰ (mean of ?13.6 ‰) and from ?8.1 to ?3.2 ‰ (mean of ?4.8 ‰), respectively. The mean δ34S–SO4 2? values were closer to those of pyrite (mean of ?25.4 ‰) and efflorescent sulfate salts (mean of ?25.6 ‰), recorded previously in the Podwi?niówka quarry, than to sulfates derived from other anthropogenic or soil and bedrock sources. The SO4 2? ions formed by bacterially induced pyrite oxidation combined with bacterial (dissimilatory) dissolved sulfate reduction, and presumably with subordinate mineralization of carbon-bonded sulfur compounds, especially in both Marczakowe Do?y ponds. In addition, the comparison of δ18O–SO4 2? and δ18O–H2O values indicated that 75–100 % of sulfate oxygen was derived from water. Due to the largest size, the Podwi?niówka acid pit pond revealed distinct seasonal variations in both δ18O–H2O (?9.2 to ?1.6) and δD–H2O (?29.7 to ?71.3) values. The strong correlation coefficient (r 2 = 0.99) was noted between δ18O–H2O and δD–H2O values, which points to atmospheric precipitation as the only source of water. The sediments of both acid ponds display different mineral inventory: the Marczakowe Do?y acid pond sediment consists of schwertmannite and goethite, whereas Podwi?niówka acid pit pond sediment is composed of quartz, illite, chlorite and kaolinite with some admixture of jarosite reflecting a more acidic environment. Geochemical modeling of two acid ponds indicated that the saturation indices of schwertmannite and nanosized ε-Fe2O3 (Fe3+ oxide polymorph) were closest to thermodynamic equilibrium state with water, varying from ?1.44 to 3.05 and from ?3.42 to 6.04, respectively. This evidence matches well with the obtained mineralogical results. 相似文献
28.
Wenjun?YongEmail author Edgar?Dachs Artur?Benisek Anthony?C.?Withers Richard?A.?Secco 《Physics and Chemistry of Minerals》2012,39(3):259-267
The heat capacity (C
p
) of dmitryivanovite synthesized with a cubic press was measured in the temperature range of 5–664 K using the heat capacity
option of a physical properties measurement system and a differential scanning calorimeter. The entropy of dmitryivanovite
at standard temperature and pressure (STP) was calculated to be 110.1 ± 1.6 J mol−1 K−1 from the measured C
p
data. With the help of new phase equilibrium experiments done at 1.5 GPa, the phase transition boundary between krotite and
dmitryivanovite was best represented by the equation: P (GPa) = −2.1825 + 0.0025 T (K). From the temperature intercept of this phase boundary and other available thermodynamic data
for krotite and dmitryivanovite, the enthalpy of formation and Gibbs free energy of formation of dmitryivanovite at STP were
calculated to be −2326.7 ± 2.1 and −2,208.1 ± 2.1 kJ mol−1, respectively. It is also inferred that dmitryivanovite is the stable CaAl2O4 phase at STP and has a wide stability field at high pressures whereas the stability field of krotite is located at high temperatures
and relatively low pressures. This conclusion is consistent with natural occurrences (in Ca–Al-rich inclusions) of dmitryivanovite
and krotite, where the former is interpreted as the shock metamorphic product of originally present krotite. 相似文献
29.
Wenjun?YongEmail author Edgar?Dachs Artur?Benisek Richard?A.?Secco 《Physics and Chemistry of Minerals》2012,39(2):153-162
The low-temperature heat capacity (C
P) of stishovite (SiO2) synthesized with a multi-anvil device was measured over the range of 5–303 K using the heat capacity option of a physical
properties measurement system (PPMS) and around ambient temperature using a differential scanning calorimeter (DSC). The entropy
of stishovite at standard temperature and pressure calculated from DSC-corrected PPMS data is 24.94 J mol−1 K−1, which is considerably smaller (by 2.86 J mol−1 K−1) than that determined from adiabatic calorimetry (Holm et al. in Geochimica et Cosmochimica Acta 31:2289–2307, 1967) and about 4% larger than the recently reported value (Akaogi et al. in Am Mineral 96:1325–1330, 2011). The coesite–stishovite phase transition boundary calculated using the newly determined entropy value of stishovite agrees
reasonably well with the previous experimental results by Zhang et al. (Phys Chem Miner 23:1–10, 1996). The calculated phase boundary of kyanite decomposition reaction is most comparable with the experimental study by Irifune
et al. (Earth Planet Sci Lett 77:245–256, 1995) at low temperatures around 1,400 K, and the calculated slope in this temperature range is mostly consistent with that determined
by in situ X-ray diffraction experiments (Ono et al. in Am Mineral 92:1624–1629, 2007). 相似文献
30.
On some aspects of peaks-over-threshold modeling of floods under nonstationarity using climate covariates 总被引:4,自引:3,他引:1
Artur Tiago Silva Mauro Naghettini Maria Manuela Portela 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(1):207-224
This paper discusses some aspects of flood frequency analysis using the peaks-over-threshold model with Poisson arrivals and generalized Pareto (GP) distributed peak magnitudes under nonstationarity, using climate covariates. The discussion topics were motivated by a case study on the influence of El Niño–Southern Oscillation on the flood regime in the Itajaí river basin, in Southern Brazil. The Niño3.4 (DJF) index is used as a covariate in nonstationary estimates of the Poisson and GP distributions scale parameters. Prior to the positing of parametric dependence functions, a preliminary data-driven analysis was carried out using nonparametric regression models to estimate the dependence of the parameters on the covariate. Model fits were evaluated using asymptotic likelihood ratio tests, AIC, and Q–Q plots. Results show statistically significant and complex dependence relationships with the covariate on both nonstationary parameters. The nonstationary flood hazard measure design life level (DLL) was used to compare the relative performances of stationary and nonstationary models in quantifying flood hazard over the period of records. Uncertainty analyses were carried out in every step of the application using the delta method. 相似文献