1,721,578 research outputs found
Fe (II) segregation at a specific crystallographic site of fibrous erionite: A first step toward the understanding of the mechanisms inducing its carcinogenicity
No full textTwo samples of fibrous erionite from different localities of Oregon, USA were suspended in FeCl2 solutions at different concentrations, at pH ca. 5, in anaerobic conditions. Comparison between released and acquired charges under the form of Fe confirms that erionite binds Fe (II) by ion exchange with the extra framework (EF) cations, mainly Na. The Fe (II) binding process exhibited by both studied samples here investigated indicates a direct correlation between the extent of the ion-exchange process and the Fe (II) concentration of the solution used for fibres incubation. In the sample from Rome no further Fe (II) acquisition was observed for concentrations exceeding 500 μM FeCl2. XPS investigation revealed that, when comparing surface and bulk composition of the samples, no Fe enrichment of the fibre surface was observed. Moreover, the location of Fe (II) within the erionite cage has been devised by combining chemical and structural data. Results highlight that, for both samples, Fe (II) is fixed at the Ca3 site being six-fold coordinated to water molecules. The occurrence of Fe (II) within the erionite cage causes a gradual migration of the other EF cations and in addition, induces a small rearrangement of the water molecules positions. It is worth mentioning that, in Fe-loaded zeolites at rather low Fe content, the Fe sites with very low nuclearity, located in well-defined crystallographic positions, represent the active sites for the formation of reactive oxygen species. Therefore, identification of segregation of Fe (II) at Ca3, which is coupled with the high surface area of erionite, provides very important information for the understanding of the molecular mechanism/s inducing its strong carcinogenicity. © 2015 Elsevier Inc
Piccolo scambio epistolare di argomento dantesco tra Bruno Nardi e Giovanni Galbiati
No full textIl contributo illustra uno scambio epistolare di argomento dantesco tra Bruno Nardi e Giovanni Galbiati
Antarctic snow: metals bound to high molecular weight dissolved organic matter
No full textIn this paper we studied some heavy metals (Cu, Zn, Cd, Pb, As, U) probably associated to high molecular weight organic compounds present in the Antarctic snow. Snow-pit samples were collected and analysed for high molecular weight fraction and heavy metals bound to them by means of ultrafiltration treatment. High molecular weight dissolved organic matter (HMW-DOM) recovered by ultrafiltration showed a dissolved organic carbon concentration (HMW-DOC) of about 18–83% of the total dissolved organic carbon measured in Antarctic snow. The characterisation of HMW-DOM fraction evidenced an ageing of organic compounds going from surface layers to the deepest ones with a shift from aliphatic compounds and proteins/amino sugars to more high unsaturated character and less nitrogen content. The heavy metals associated to HMW-DOM fraction follows the order: Zn > Cu > Pb >> Cd ∼ As ∼ U. The percentage fraction of metals bound to HMW-DOM respect to total metal content follows the order: Cu >> Pb > Zn, Cd in agreement with humic substance binding ability (Irwing-William series). Going down to depth of trench, all metals except arsenic, showed a high concentration peak corresponding to 2.0–2.5 m layer. This result was attributed to particular structural characteristic of organic matter able to form different type of complexes (1:1, 1:2, 1:n) with metals. © 2017 Elsevier Lt
Museums, New Technologies, Language. Cahiers de l’Ecole Doctorale Internationale “Culture Éducation, Comunication”.
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REALISTIC SUSY MODEL WITH FOUR FERMION FAMILIES, NATURAL R PARITY AND TAU-NEUTRINO IN THE EV RANGE
No full textThe mechanism of iron binding processes in erionite fibres
No full textFibrous erionite-Na from Rome (Oregon, USA) was K-exchanged and characterized from the structural point of view. In addition, the modifications experienced after contact with a Fe(II) source were investigated for evaluating if the large potassium ions, blocking off nearly all the erionite cavity openings, might prevent the Fe(II) binding process, which is currently assumed to be one of the reasons of the toxicity of erionite. The K-exchanged sample had a 95% reduction of the BET surface area indicating that it behaves as a mesoporous material. Exchanged K is segregated at K2 and at OW sites commonly occupied by H2O. The latter K cations provide a relevant contribution to the reduction of the surface area. Surprisingly, despite the collapse of its surface area the sample preserves the tendency to bind Fe(II). Therefore, yet in the case of a peculiar and potentially hostile structural environment the Fe(II) ion-exchange process has essentially the same kinetics observed in a typical erionite sample. This is a clear evidence of the very limited effect of the chemical composition of erionite on the Fe(II) binding process and reasonably it does not play a significant role in its toxicity. © 2017 The Author(s)
Escatologie medievali nell’Italia contemporanea.Tullio Gregory da Buonaiuti a Nardi e oltre
No full textProfilo degli interessi e degli studi di Tullio Gregory (1929-2019), limitatamente alle sue ricerche di storia dell'escatologia medievale, a partire dagli incontri giovanili con E. Buonaiuti e B. Nardi e dalla conoscenza della "nouvelle théologie". Genesi, prospettive e significati dei suoi conttributi sulle concezioni apocalittiche antiaristoteliche fra XIII e XIV secolo e su Giovanni Scoto Eriugen
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