Search results for "Magnesium"

Triple Isotope Fractionation Exponents of Elements Measured by MC-ICP-MS—An Example of Mg

2019

In most chemical reactions, stable isotopes are fractionated in a mass-dependent manner, yielding correlated isotope ratios in elements with three or more stable isotopes. The proportionality between isotope ratios is set by the triple isotope fractionation exponent θ that can be determined precisely for, e.g., sulfur and oxygen by IRMS, but not for metal(loid) elements due to the lower precision of MC-ICP-MS analysis and smaller isotopic variations. Here, using Mg as a test case, we compute a complete metrologically robust uncertainty budget for apparent θ values and, with reference to this, present a new measurement approach that reduces uncertainty on θ values by 30%. T…

Kinetic of growth and physico-chemical characterization of anodic films on magnesium

2008

Electrochemical Impedance Spectroscopy Study of the Behaviour of Lanthanide-Rich Films Formed on Aluminium-Magnesium Alloys

1998

The film covering formed on AA5083 aluminium-magnesium alloy by immersion treatments in solutions containing CeCl 3 has been characterized by means of electrochemical techniques. The measurement of linear polarization has enabled to establish that the treatments applied provide efficient protection against both uniform and pitting corrosion of alloy AA5083, used in shipbuilding, in solutions of NaCl. This study has been focused on the use of Electrochemical Impedance Spectroscopy as a characterization technique for these film coverings.

(Table 1) Geochemistry of ODP Site 160-963 sediments

2010

The Mediterranean Sea acts as a miniature ocean with the development of its own conveyor belt. It constitutes an ideal location to study and forecast how the marine environment responds to rapid climatic change. Here we present a palaeoenvironmental study carried out on the sediments of ODP Site 963, recovered in the Sicily Channel, the sill which divides the western from the eastern Mediterranean basin. We focused on the transition between the penultimate glacial (MIS 6) and the last interglacial (MIS 5), between approximately 130 and 115 kyr BP. A novel approach is proposed, taking into account centennial-scale geochemical data on major elements, selected trace elements, and yttrium and R…

(Table 1) Trace element/Ca ratios of Orbulina universa shells from late Neogene Mediterranean samples

2008

A Mediterranean composite sedimentary record was analyzed for Ba/Ca ratios on carbonate shells of Orbulina universa planktonic foraminifer (Ba/Ca)carb providing the opportunity to study and assess the extent of freshwater inputs on the basin and possible impacts on its dynamics during the Tortonian to Recent period. A number of scanning electron microscope analyses and auxiliary trace element measurements (Mn, Sr, and Mg), obtained from the same samples, exclude important diagenetic effects on the studied biogenic carbonates and corroborate the reliability of (Ba/Ca)carb ratios in foraminifera calcite as indicators of seawater source components during the studied interval. A long-term trend…

Heavy metal sorption in the lichen cationactive layer.

2007

Results of copper ion sorption in lichens owing to the ion exchange between the surroundings (aqueous solution) and the lichen cationactive layer have been presented. It indicates that the course of sorption of these ions, similarly as in the case of cations of other heavy metals, depends on the concentration and type of cations naturally found in lichen surroundings: H+, Na+, K+, Mg2+ and Ca2+. A determination method of heavy metal concentration in lichen surroundings has been proposed. It consists in exposure of transplanted lichens in the presence of salts that provide precisely determined, artificial salinity of precipitation with which the lichens are in contact. The studies were condu…

Photoaffinity Labeling and Photoaffinity Cross-Linking of Phosphofructokinase-1 from Saccharomyces cerevisiae by 8-Azidoadeninenucleotides

2001

Phosphofructokinase-1 from Saccharomyces cerevisiae is composed of four alpha- and four beta-subunits, each of them carrying catalytic and regulatory bindings sites for MgATP. In this paper, various photoaffinity labels, such as 8-azidoadenosine 5'-triphosphate, 8-azido-1,N6-ethenoadenosine 5'-triphosphate, and 8-N3-3'(2')-O-biotinyl-8-azidoadenosine 5'-triphosphate have been used to study their interaction with the enzyme in the dark and during irradiation. All nucleotidetriphosphates function as phosphate donor forming fructose 1,6-bisphosphate from fructose 6-phosphate. However, the kinetic analysis revealed distinctly differences between them. Photolabeling causes a decrease in enzyme a…

Water vapour pressure above saturated salt solutions at low temperatures

1999

Abstract The properties of water–salt systems in relation to their vapour pressure are studied especially at low temperature. The water vapour pressure of saturated salt solutions of strontium chloride, zinc chloride, nickel chloride, nickel nitrate, magnesium chloride, magnesium bromide, magnesium nitrate, calcium chloride, potassium nitrite, lithium chloride, lithium bromide, lithium iodide and sodium bromide are measured in a temperature range −40 to +10°C. The apparatus used in this study, is well adapted to measure very low pressure with an uncertainty of pressure measurement of 2% for a range between 10−3 and 10 mm Hg. The experimental values are fitted by Antoine equation with mean p…

Mixed complexes of alkaline earth uranyl cabonates: A laser-induced time-resolved fluorescence spectroscopic study

2008

The interaction of the alkaline earth ions Mg2+, Sr2+ and Ba2+ with the uranyl tricarbonate complex has been studied by time resolved laser-induced fluorescence spectroscopy. In contrast to the non-luminescent uranyl tricarbonate complex the formed products show slight luminescence properties. These have been used to determine the stoichiometry and complex stabilities of the formed compounds. As the alkaline earth elements are located in an outer shell of the complex the influence of the type of the alkaline earth element on the stability constant is not very drastic. Therefore all obtained data were averaged in order to derive an common stability constant for the described complexes. These…

Bioactivity Performance of Pure Mg after Plasma Electrolytic Oxidation in Silicate-Based Solutions

2021

The biodegradable metals, including magnesium (Mg), are a convenient alternative to permanent metals but fast uncontrolled corrosion limited wide clinical application. Formation of a barrier coating on Mg alloys could be a successful strategy for the production of a stable external layer that prevents fast corrosion. Our research was aimed to develop an Mg stable oxide coating using plasma electrolytic oxidation (PEO) in silicate-based solutions. 99.9% pure Mg alloy was anodized in electrolytes contained mixtures of sodium silicate and sodium fluoride, calcium hydroxide and sodium hydroxide. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), contact angle (CA), …