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At least 433 records · Page 24Linked to original sources
PubMed2002

[Determination of major and minor components in standard talc samples by ICP-AES].

The standard talc sample was fused with Na2CO3 and Na2B4O7 and then the fused disc was dissolved with HCl solution. SiO2, MgO, Al2O3, Fe3O2 and CaO in talc samples were determined simultaneously by ICP-AES. The optimum analytical line with high sensitivity and low spectral interference were carefully chosen. The sources and properties of the interference were discussed. The recoveries for these elements were 98.8%-104.4%, with precision of 0.12%-2.4% RSD (n = 6). The results of major and minor components in talc samples by this method were in agreement with those provided by the standard method.

Aluminum Oxide↗
PubMed1998

Presolar corundum and spinel in ordinary chondrites: origins from AGB stars and a supernova.

On the basis of anomalous isotopic compositions of oxygen and magnesium, 14 oxide grains from two primitive meteorites (Bishunpur and Semarkona) have been identified as circumstellar condensates. One corundum grain has a high 18O/16O ratio and isotopic compositions of magnesium, calcium, and titanium that are compatible with a formation in ejecta of a type II supernova that was about 15 times the mass of the sun. The other grains have oxygen, magnesium, and titanium compositions that are consistent with a formation around asymptotic giant branch (AGB) stars with a range of mass and initial composition. The large range of aluminum/magnesium in circumstellar corundum and spinel is considered to reflect various stages of back-reaction between condensed corundum and gaseous magnesium in cooling stellar ejecta.

Aluminum↗
PubMedDate not supplied

Effect of magnesium administered during postischemic reperfusion on myocardial oxidative metabolism in isolated rat hearts.

To determine the effect of magnesium on myocardial function and oxidative metabolism after reperfusion, isolated rat hearts perfused retrogradely with erythrocyte-enriched medium (0.4 mM palmitate bound to 0.4 mM albumin, 11 mM glucose) were subjected to 60 minutes of no-flow ischemia followed by 60 minutes of reperfusion. Untreated postischemic hearts exhibited after 15 minutes of reperfusion recovery of myocardial oxygen consumption to 65% of the preischemic value despite persistent depression of left ventricular isovolumic pressure development to 21%. Magnesium (15 mM) administered during the initial 30 minutes of reperfusion reduced myocardial oxygen consumption of reperfuse myocardium by 35%. Oxidation of [1-14C]palmitate was slightly more reduced (-55%) than oxidation of [U-14C]glucose (-42%). Magnesium did not influence ultimate recovery of contractile function and cumulative myocardial release of creatine kinase. Thus, 15 mM magnesium administered during reperfusion elicited a reduction of oxidative metabolism. However, magnesium did not modify myocardial injury.

Animals↗
PubMed2000

Magnesium deficiency potentiates free radical production associated with myocardial infarction.

OBJECTIVE: Oxidative injury and magnesium deficiency may accompany cardiovascular disease states and the study was planned to find out whether magnesium deficiency promotes oxidative injury. METHODS: Serum malonaldehyde (MDA), magnesium, vitamin E and total glutathione levels (GSH) were estimated in 22 patients with acute myocardial infarction and 15 healthy controls. RESULTS: Low levels of Mg, GSH, vitamin E and elevated levels of MDA were observed in patients of acute myocardial infarction. Statistically significant correlations were observed between Mg and MDA, MDA and GSH, Mg and vitamin E. CONCLUSION: Our findings suggest that Mg deficiency can potentiate oxidative injury to post ischaemic myocardium and that antioxidants may have a role in protection against the prooxidant influence(s) of Mg deficiency.

Aged↗
PubMed1992

Peroxide-dependent amino acid oxidation and chemiluminescence catalysed by magnesium-pyridoxal phosphate-glutamate complex.

Magnesium-pyridoxal-5'-phosphate-glutamate (MPPG) has been shown to ameliorate atherosclerotic symptoms in rabbits. In vitro, MPPG in the presence of peroxides such as cholesterolhydroperoxide or cumene hydroperoxide and Mn2+ ions produces "excited states" measurable as chemiluminescence or ethylene release from 1-aminocyclopropane-1-carboxylic acid (ACC). The reactions are stimulated synergistically by unsaturated fatty acids. Pyridoxal phosphate exhibits similar properties, but can be differentiated from the activities of MPPG or the sum of the components present in MPPG.

Amino Acids↗
PubMed2004

Preparation and characterization of Eu(3+) doped powder spinel phosphors (MgAl(1.8)Y(0.2-x)O(4)).

The photoluminescence (PL) studies of powder phosphors are under rigorous study in view of the applications they have in the field of technology. Different methods are available for the preparation of rare earth ions doped in different host environment of powder phosphors. In the present work, a novel route known as sol-gel technique is employed to prepare spinel phosphor MgAl(1.8)Y(0.2-x)O(4):Eu(x) (x = 2-6 mol%). Then the studies have been carried out to optimize the dopant concentration in the host lattice with the help of photoluminescence spectra. These phosphors have displayed bright red color under UV source. The emission intensities were determined and the relative fluorescence intensities have been estimated. The richness of the red color has been verified by determining their chromaticity coordinates (X, Y) from the CIE standard charts. With the help of XRD, electron spin resonance (ESR), and photo-acoustic (PA) spectra of the samples prepared are also used for the confirmity of the host and analyzing of the data.

Aluminum Oxide↗
PubMed2005

Relaxatory effect of magnesium on mesenteric vascular beds differs from normal and streptozotocin induced diabetic rats.

Magnesium deficiency has recently been proposed as a novel factor implicated in the pathogenesis of diabetes complications. Previous studies have shown that magnesium decreases basal tone in normal isolated aortic rings and reduces phenylephrine-induced contraction. The mechanism of this magnesium action is not very well known. The present study was designed to determine the role of endothelium and nitric oxide in magnesium sulfate-induced vasorelaxation in diabetic rat vessels. Diabetes was induced by a single tail injection of streptozotocin. Eight weeks later, superior mesenteric arteries of control and diabetic animals were isolated and perfused according to the McGregor method. Prepared vascular beds were constricted with phenylephrine to induce 70-75% of maximal constriction. Magnesium sulfate at concentrations of 0.001 M to 0.1 M was added into the medium and perfusion pressure was then recorded. Mesenteric bed baseline perfusion pressure in intact and denuded endothelium of diabetic groups was higher than controls. In all groups, relaxant response to magnesium in mesenteric bed was attenuated after endothelium removal, but a relaxatory effect appears at high concentration. In the presence of N (omega)-nitro-L-arginine methyl ester (L-NAME), magnesium-induced relaxation was significantly suppressed in intact mesenteric bed of control animals but in diabetics, the relaxant response was slightly inhibited. From the results of this study, it can be concluded that magnesium-induced endothelium dependent and endothelium independent vasorelaxation are mediated by nitric oxide in control rats while in diabetic animals other mechanisms may be involved.

Animals↗
PubMed2006

Bone-like apatite coating on Mg-PSZ/Al2O3 composites using bioactive systems.

A biomimetic method was used to promote bioactivity on zirconia/alumina composites. The composites were composed of 80 vol% Mg-PSZ and 20 vol% Al2O3. Samples of these bioinert materials were immersed in simulated body fluid (SBF) for 7 days on either a bed of wollastonite ceramics or bioactive glass. After those 7 days, the samples were immersed in a more concentrated solution (1.4 SBF) for 14 days. Experiments were also performed without using a bioactive system during the first stage of immersion. A bone-like apatite layer was formed on the surface of all the materials tested, using wollastonite the bioactive layer was thicker and its morphology was close to that observed on the existing bioactive systems. A thinner apatite layer consisting of small agglomerates was obtained using bioactive glass. The thickness of the ceramic layers was within the range of 15 to 30 microm.

Alloys↗
PubMed2005

Differential potentiometric titration: development of a methodology for determining the point of zero charge of metal (hydr)oxides by one titration curve.

A new methodology is presented, called differential potentiometric titration (DPT), which allows the determination of the point of zero charge (pzc) of metal (hydr)oxides using only one potentiometric curve. By performing extensive simulations of potentiometric titrations for various model (hydr)oxides, we found that an inflection point in a H+(cons,surf) versus pH potentiometric curve (H+(cons,surf): hydrogen ions consumed on the surface of the (hydr)oxide) and a peak in the corresponding differential curve, dH+(cons,surf)/dpH versus pH, appear at a pH equal to the pzc assumed for a model (hydr)oxide. This distinguishable peak appears at the same position irrespective of the surface ionization and the interfacial model adopted as well as the assumed ionic strength. It was found that the aforementioned peak also appears in the high-resolution differential potentiometric curves experimentally determined for four oxides (SiO2, TiO2, gamma-Al2O3, and MgO) that are widely used in various environmental and other technological applications. The application of DPT to the above-mentioned oxides provided practically the same pzc values as the corresponding ones achieved by using four different techniques as well as the corresponding isoelectric point (iep) values determined by microelectrophoresis. Differences between the pzc and iep values determined using various techniques in the case of MgO were attributed to the increasing dissolution of this oxide as pH decreases and the adsorption of cations (Mg2+, Na+) on the MgO/electrolytic solution interface.

Adsorption↗