Search results for "magnesium"
showing 10 items of 490 documents
Identification of the crossing point at N=21 between normal and intruder configurations
2017
The β− decay of 34Mg was used to study the 34Al nucleus through γ spectroscopy at the Isotope Separator OnLine facility of CERN. Previous studies identified two β-decaying states in 34Al having spin-parity assignments J π = 4− dominated by the normal configuration π(d5/2) −1 ⊗ ν(f7/2) and J π = 1+ by the intruder configuration π(d5/2) −1 ⊗ ν(d3/2) −1(f7/2) 2. Their unknown ordering and relative energy have been the subject of debate for the placement of 34Al inside or outside the N = 20 “island of inversion.” We report here that the 1+ intruder lies only 46.6 keV above the 4− ground state. In addition, a new half-life of T1/2 = 44.9(4) ms, that is twice as long as the previously measured 20…
Effect of organic matrices on the determination of the trace element chemistry (Mg, Sr, Mg/Ca, Sr/Ca) of aragonitic bivalve shells (<i>Arctica …
2010
The element chemistry of biogenic carbonates can provide important data on past environments. However, the Sr/Ca and Mg/Ca ratios as well as the Mg and Sr concentrations of biological carbonates, especially aragonitic bivalves often depart from apparent thermodynamic equilibrium. When measured in situ by means of LA-ICP-MS, the Mg concentration is often substantially enriched (two- to threefold) near the organic-rich, annual growth lines. To test the hypothesis that some organic components exert a major influence on the skeletal metal content, the element chemistry of different shell components (insoluble organic matrix, IOM; dissolved CaCO3 and soluble organics, SOM) of Arctica islandica w…
CCDC 889025: Experimental Crystal Structure Determination
2015
Related Article: A. R. Popescu, I. Rojo, F. Teixidor, R. Sillanpää, C. Viñas|2015|Chem.-Eur.J.|21|8613|doi:10.1002/chem.201500307
Darstellung von poly-methylphenylenen nach grignard. Über methylsubstituierte polyphenylene. IV. Mitt.
1955
Die Einwirkung von 4,4′-Dijod-3,3′-dimethyldiphenyl bzw. von 2,5-Dibromtoluol auf Magnesium fuhrt zu methylsubstituierten Polyphenylenen. Die Reaktionsbedingungen der Grignardreaktionen wurden in mehrfacher Hinsicht variiert. Man erhalt keine linearen Makromolekule, wie dies fruher auch bei der Ullmannreaktion mit Kupferpulver festgestellt wurde. Die Grignardreaktion eignet sich trotz der milden Reaktionsbedingungen schlechter fur die Synthese linearer Polyphenylene als die Ullmannreaktion. The corresponding methyl-substituted polyphenylenes of 4,4′-diiodo-3,3′-dimethyldiphenyl or 2,5-dibromotoluene are obtained by treatment with magnesium. The conditions of the reactions were varied. No li…
Contents of free amino acids in needles of Norway Spruce trees in relation to novel forest decline. Studies on trees from a site in the northern Blac…
1993
The free amino acid content in needles of Norway spruce trees (about 45-year-old) was determined by means of HPLC. The studied trees have been growing at a forestry site in the Black Forest which is characterized by a high impact of ozone and magnesium deficiency. Measurements were carried out on visibly healthy and on damaged trees on several dates during two vegetation periods and during the course of a day. The amino acids occurring at the highest concentrations were glutamate, arginine, aspartate, and glutamine. The typical seasonal changes in the content of free amino acids, with their minimum during summer, were disturbed in the needles of the damaged trees. Particularly in summer and…
Complexes of Azelaic and Diethylenetrioxydiacetic Acids with Na+, Mg2+, and Ca2+ in NaCl Aqueous Solutions, at 25 °C
1999
Formation constants of Na + , Mg 2+ , and Ca 2+ complexes of azelaic and diethylenetrioxydiacetic acids have been determined by potentiometry (H + -glass electrode) at different ionic strengths (0 ≤ I ≤ 1 mol dm -3 ), at t = 25 °C. For all the systems the species ML and MHL have been found. The relative formation constants are reported together with the parameters for the dependence on ionic strength. Results are discussed in comparison with those for other carboxylic ligands. Speciation problems are considered also.
Microscale magnesium distribution in shell of the Mediterranean mussel Mytilus galloprovincialis: An example of multiple factors controlling Mg/Ca in…
2019
Abstract Since magnesium concentration (Mg/Ca) in biogenic calcite is considered to reflect water temperature during precipitation, the magnesium-to‑calcium ratio has been examined as a proxy for water temperature in paleoclimate research, although factors other than temperature may also influence Mg/Ca in biogenic calcite, thereby introducing a potential bias in the relationship between Mg/Ca and temperature observed in inorganic systems. To better understand factors controlling Mg incorporation into the calcitic shells of bivalves, the distribution of Mg in the Mediterranean mussel Mytilus galloprovincialis was studied, being compared with ambient sea surface temperature (SST), shell grow…
General and Theoretical Aspects of the Metal Enolates
2010
1 General Aspects 2 Structure of the Metal Enolates 3 Spectroscopy of the Metal Enolates 4 Reactivity of the Metal Enolates 5 Acknowledgments Keywords: general and theoretical aspects of metal enolates; metal enolate structure; calcium and magnesium enolates; spectroscopy of metal enolates - NMR spectroscopy; UV spectroscopy; enolate, applied to anionic structure with two carbon atoms bound through double bond; IR spectroscopy; generalized gradient approximation (GGA-DFT) for adsorption modes of acetone
ChemInform Abstract: General and Theoretical Aspects of the Metal Enolates
2010
1 General Aspects 2 Structure of the Metal Enolates 3 Spectroscopy of the Metal Enolates 4 Reactivity of the Metal Enolates 5 Acknowledgments Keywords: general and theoretical aspects of metal enolates; metal enolate structure; calcium and magnesium enolates; spectroscopy of metal enolates - NMR spectroscopy; UV spectroscopy; enolate, applied to anionic structure with two carbon atoms bound through double bond; IR spectroscopy; generalized gradient approximation (GGA-DFT) for adsorption modes of acetone
Isolation of a stable, acyclic, two-coordinate silylene.
2012
The synthesis and characterization of a stable, acyclic two-coordinate silylene, Si(SAr(Me(6)))(2) [Ar(Me(6)) = C(6)H(3)-2,6(C(6)H(2)-2,4,6-Me(3))(2)], by reduction of Br(2)Si(SAr(Me(6)))(2) with a magnesium(I) reductant is described. It features a V-shaped silicon coordination with a S-Si-S angle of 90.52(2)° and an average Si-S distance of 2.158(3) A. Although it reacts readily with an alkyl halide, it does not react with hydrogen under ambient conditions, probably as a result of the ca. 4.3 eV energy difference between the frontier silicon lone pair and 3p orbitals.