Search results for "METAL"

Sintesi di un nuovo sensore fluorescente selettivo per Hg2++ contenente ossadiazoli fluorurati

2009

Chemical Cartography with APOGEE: Multi-element Abundance Ratios

2019

We map the trends of elemental abundance ratios across the Galactic disk, spanning R = 3-15 kpc and midplane distance |Z|= 0-2 kpc, for 15 elements in a sample of 20,485 stars measured by the SDSS/APOGEE survey (O, Na, Mg, Al, Si, P, S, K, Ca, V, Cr, Mn, Fe, Co, Ni). Adopting Mg rather than Fe as our reference element, and separating stars into two populations based on [Fe/Mg], we find that the median trends of [X/Mg] vs. [Mg/H] in each population are nearly independent of location in the Galaxy. The full multi-element cartography can be summarized by combining these nearly universal median sequences with our measured metallicity distribution functions and the relative proportions of the lo…

The Gaia-ESO Survey: impact of extra mixing on C and N abundances of giant stars

2018

The GES survey using FLAMES at the VLT has obtained high-resolution UVES spectra for a large number of giant stars, allowing a determination of the abundances of the key chemical elements C and N at their surface. The surface abundances of these chemical species are well-known to change in stars during their evolution on the red giant branch after the first dredge-up episod, as a result of extra-mixing phenomena. We investigate the effects of thermohaline mixing on C and N abundances using the first comparison between the GES [C/N] determinations with simulations of the observed fields using a model of stellar population synthesis. We explore the effects of thermohaline mixing on the chemic…

Temporal trends of heavy metals in sediment core from the gulf of Palermo (Sicily, Italy)

2009

The evaluation of long–term heavy metal concentrations in the Gulf of Palermo was carried out in this study. Measurements of Cr, Cu, Hg, Pb and Zn concentrations were performed by atomic absorption spectrophotometry (AAS) on dated fractions of a sediment core, dated by the 210Pbex method. They are found to cover a time period from 1951 to 2004. The constant sedimentation rate model was used for dating. Specific activities of 137Cs have also been measured in the sediment core sections as a check of the time scale derived by the 210Pbex method. A time-series analysis based on temporal decomposition was used in order to investigate the presence of heavy metal pollution trend. The additive comp…

Statistical analysis of the relation between metallic microstructures and mechanical properties

2020

This thesis aims at the development of physical relations between the intricate 3D features of metallic microstructures and the mechanical properties of the material. For understanding which are the microstructural determinants of the resultingmechanical behaviour of metals, a deep quantitative characterisation of the microstructure is needed. The main steps of quantitative characterisation of the microstructures are: identification of the phases distribution and their chemical composition, study of the microstructure morphology (geometrical arrangement of grains, grain boundaries, grain orientations, grain size and grain shape). An accurate description of the microstructure features enrich…

Steroidal supramolecular metallogels

2020

The review deals with an expanding number of steroidal compounds that are capable of forming a metallogel providing a multitude of novel materials rich in their properties. The future of steroidal metallogels holds a myriad of potential applications as new intelligent materials. Detection of potentially harmful compounds without expensive instrumentation, entrapment of environmentally hazardous substances, and sensitive and selective nanomaterials represent only a few of these potential applications. This article reviews the design, synthesis, characterization, and applications of steroidal metallogels. peerReviewed

Marine Invertebrates as Bioindicators of Heavy Metal Pollution

2015

The marine environment presents a range of anthropogenic contaminants. According to the World Health Organization, more than 100,000 chemicals are released into the global environment every year as a consequence of their production, use and disposal. The fate of a chemical substance depends on physical-chemical properties, in combination with the characteristics of the environment where it is released. Among the substances that accumulate in the sea, for anthropogenic activities, metals/metalloids have a leading position. Some of these have a biological role but their bioaccumulation is injurious. Chemical pollutants can cause effects on organisms, biodiversity and human health. Various eff…

UV Metal Semiconductor Metal Detectors. A Robust Choice for (Al,Ga)N Based Detectors

2004

UV detection is interesting for combustion optimization, air contamination control, fire and solar blind rocket launching detection. Most of these applications require that UV detectors have a huge dynamic response between UV and the visible, and a very low dark current in the range of the UV flux measured. (Al,Ga)N alloys present a large direct bandgap in this range and therefore can be used as an active region in such detectors. To take advantage of the large Schottky barrier, the good alloy quality, and to avoid any doping problems, we have developed MSM photodetectors. High quality material has been grown with MOCVD and MBE on sapphire substrates. Stress management is employed for alumi…

studio dei parametri dello stress ossidativo, delle metalloproteasi e delle determinanti emoreologiche nell'aterosclerosi preclinica

Metallothionein genes in the sea urchin Paracentrotus lividus

2014

Metallothioneins (MTs) constitute a heterogeneous superfamily of cysteine rich proteins, which coordinate divalent (Zn2+, Cd2+) or monovalent (Cu+) metal ions. Several functions have been proposed for these peptides, ranging from toxic metal protection to physiological metal homeostasis, free radical scavenging, oxidative stress protection, antiapoptotic defense, control of the redox status of the cell and also a role during development. Regarding the MT system in vertebrates’ nearest kin, little information is available at present. Recently MTs were also characterized in cephalochordates. Hence in order to shed some light on MT origin and functional differentiation through evolution, we st…