106 research outputs found
Photoprotective characteristics of natural antioxidant polyphenols
No full textFourteen natural polyphenols belonging to the classes of stilbenes, flavonoids and hydroxycinnamic acid derivatives, have been investigated in order to verify the combination of their photoprotective characteristics with their antioxidant properties.To this purpose, sun protection factor (SPF), UVA/UVB ratio and critical wavelengths (λc), have been considered to evaluate photoprotection capacity, while inhibition of lipid peroxidation has been adopted as a reliable measure of the antioxidant properties.The results obtained indicate that a large number of these natural phenol derivatives show both antioxidant activity and photoprotective characteristics and, as a consequence, they could be interesting components for pharma-photoprotection formulations. In fact, these compounds associate to a preventive function, linked to UV filtering properties, an effective action, correlated to antioxidant capacity of contrast towards UV-induced ROS injury. © 2014 Elsevier Inc
57Fe Mossbauer and NAA studies of Core ANTA91-8 from Ross Sea (Antartica)
No full textThe sedimentary core ANTA91-8, with geographic co-ordinates 70°47’ S 172°50’ E, was sampled in the Ross Sea at a water depth of 2,383 m. The core length of 511 cm covers the sedimentary hronology of the last three hundred kyears. Mossbauer data concerning the iron-bearing species present in 39 layers of ANTA91-8, and neutron activation analysis of 28 elements in 18 layers are reported and discussed
Evaluation of microwave-assisted acid extraction procedures for the determination of metal content and potential bioavailability in sediments
No full textAcid extractions represent a simple and effective tool for the assessment of metal contamination, origin and bioavailability in the aquatic environment. Optimized microwave-assisted procedures utilizing two extractions (8 M HNO3 and 1 M HCl) were developed. Particular attention was given to the evaluation of efficiency and selectivity of the developed procedures. This involved an examination of the sediment and the extraction residues by Mössbauer spectroscopy and X-ray diffractometry. These instrumental approaches were used to identify the geochemical phases associated with acid decomposition. Microwave digestion with 8 M HNO3 produced an efficient solubilization of the most important metal-bearing phases and left unaffected only the minerals (quartz, feldspars, muscovite) with a negligible metal content, thus providing a good estimate of the total metal concentrations. The 1 M HCl extraction, despite the limitation due to the incomplete solubilization of pyrite and to the partial dissolution of sheet silicates, represents a simple and effective technique for providing an estimate of the bioavailable metal fraction in sediments. The combined use of the two microwave-assisted acid extractions can provide a rapid and simple approach for the risk assessment of metal-polluted sediments
A Mossbauer study of some coloured marbles (cipollino mandolato, rosso antico and fior di pesco): implications on the nature of their colour.
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XRD, INAA and Mössbauer characterisation of some antartic soil cores from Wood bay
No full textMarine, lacustrine and terrestrial soil cores, sampled in a restricted area of Wood Bay in Antarctica, were characterised by X-ray diffraction, instrumental neutron activation analysis and 57Fe Móssbauer spectroscopy. The soils, formed from mechanical disgregation and weathering of rocks of volcanic origin from Mt. Melbourne, consist of alkaline feldspar, olivine, augitic clinopvroxene, and iron oxides such as haematite, goethite, and magnetite. Lacustrine and terrestrial soils are richer in clinopyroxene whereas marine soils are richer in olivine. This finding shows that the soils retain a content in olivine and clinopyroxene comparable to that found in the parent lava outcropping in the Mt. Melbourne volcano. The soils appeal' at the initial stage of weathering. Two main weathering effects are observed: 1) atmospheric oxygen determines the oxidation of the iron(Il) present in olivine and clinopyroxene and the neo-formed iron(III) is mainly retained in silicate sites as structural iron(lll). 2) A part of magnetite, present as a primary constituent of the volcanic rocks, is oxidised to bulk haematite and goethit
Characterisation of sediments of the Tarn flat lake (Antartica)
No full textXRD, INAA and 57Fe Mossbauer data for a sedimentary core of the small lake of Tam Flat in the region of Terra Nova Bay are reported and discussed. The lake sediments consist of quartz, muscovite, feldspars, calcite, fluorite and chlorite. Iron is present as Fe(II) in chlorite for about 16%, as Fe(III) up to 74% and in ferrihydrite for the remaining 10% of the total iron content.
The specimens from the border of the Tarn Flat lake contain amphiboles in addition to the silicates found in the sediment but less calcite and fluorite. Their iron chemistry differs from that of the sediment, in particular for the lower Fe(lII) content. The specimens from the borders of other lakes present in the region of Terra Nova do not contain calcite or fluorite and differ substantially for silicate composition.
The sediments of the Tam Flat lake derive from local materials, modified in silicate fraction and enriched in calcite and fluorite
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