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Results for “Magnesium Compounds”

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At least 163 records · Page 9Linked to original sources
PubMed1985

Absence of genotoxic effects of nonasbestos mineral fibers.

The biological activity of natural and synthetic mineral fibers has been examined. Natural attapulgite [(Mg, Al)2Si4O10(OH).4H2O], synthetic xonotlite [Ca3Si3O8(OH)2] and natural sepiolite [Mg2Si3O8.2H2O] were selected. Genotoxic effects were investigated by means of a well established cellular model based upon the measurement of unscheduled DNA synthesis (UDS) in rat hepatocytes in primary culture. The intrinsic capacity of the fibers (1 and 10 micrograms/ml) to induce UDS was first tested. None of the fiber types showed detectable UDS-eliciting activity. Also, the possible modulation of the cellular response to genotoxic agents by the materials was examined by exposing the cells to mixtures of 2-acetylaminofluorene (AAF) (0.05 and 0.25 micrograms/ml) and fibers (1 and 10 micrograms/ml). In these experiments, the UDS response was significantly diminished in the presence of xonotlite. This phenomenon may reflect changes in the uptake and/or metabolism of AAF or may result from an inhibition of DNA repair processes, the latter suggesting a possible cocarcinogenic potential for this synthetic silicate. These results point to the immediate necessity of studying more extensively the biological effects of fibrous materials that can be used as substitutes for asbestos.

Animals↗
PubMedDate not supplied

Estimation of bioavailability of selected magnesium organic salts by means of molecular modelling.

In the present work the selected organic magnesium salts were characterised by means of molecular mechanics procedures. The most probable geometrical structures were determined by the optimisation of geometry and conformational research. The following QSAR parameters were determined: the molecular surface areas, volumes and log P. Parameters describing the geometrical structure were compared with the log P values in order to estimate the bioavailability of magnesium in the studied compounds. The magnesium ions better penetrate through biological membranes in form of chelates, where the ionic bonds are "hidden" in the interior of the reversibly formed intramolecular complexes. A correlation between the geometrical structure and the intensity of migration of studied magnesium salts was proposed with the aid of the mentioned QSAR parameters: the higher volume of the molecular form, the lower the penetration velocity. The penetrating molecules exhibit however a certain degree of polarity, both the too low and too high polarity can influence their penetration possibility.

Chemical Phenomena↗
PubMed1981

Theophylline magnesium salicylate, a new xanthine compound.

Interaction of 1 mole of magnesium salicylate and 2 moles of theophylline in water precipitated a crystalline compound, identified as theophylline magnesium salicylate pentahydrate from analytical and supportive physicochemical data. Similarly, barium salicylate and theophylline produced theophylline barium salicylate. No precipitates were formed with calcium salicylate or strontium salicylate under the same conditions. Theophylline magnesium salicylate is not a mixture of components and differs in composition from the known theophylline calcium salicylate dihydrate. Unlike the latter compound, it is not alkaline.

Animals↗
PubMed2005

Formation of microcrystals, micropuddles, and other spatial inhomogenieties in surface reactions under ambient conditions: an atomic force microscopy study of water and nitric acid adsorption on MgO(100) and CaCO3(104).

In this study, atomic force microscopy (AFM) is used to image freshly cleaved MgO(100) and CaCO3(104) as these surfaces undergo reaction with water and nitric acid under ambient conditions of temperature, pressure, and relative humidity. The reaction of water and nitric acid results in the formation of hydroxylated and nitrated surfaces, respectively. It is clear from the AFM images that there are spatial inhomogenieties and surface features that form on micrometer and nanometer length scales as these reactions proceed. These features, which include hillocks, patches, microcrystallites, and micropuddles, are due to surface and phase segregation as a result of facile ion mobility in the presence of adsorbed water. In addition, instabilities and oscillations in the AFM images provide an indication of liquid formation and the deliquescence (i.e., a solid to liquid-phase transition) of nitrate salts as a function of relative humidity.

Adsorption↗
PubMedDate not supplied

A strategy for controlling deposition of struvite in municipal wastewater treatment plants.

This paper presents strategies to reduce the risk of struvite deposition by controlling its location of formation. Two technical routes were investigated: (1) to fix the phosphate into the dewatered sludge cake, and (2) to remove phosphate from centrate or filtrate. Chemicals used include magnesium hydroxide [Mg(OH)2], both of reagent grade and reclaimed from a flue gas desulfurization system, magnesium chloride (MgCl2), calcium hydroxide [Ca(OH)2], ferric chloride (FeCl3) and aluminum sulfate [Al2(SO4)3]. Research results indicate that (1) for anaerobically well-digested sludge, Mg(OH)2 is effective in fixing phosphate into sludge cake and improving sludge dewaterability, and (2) adding Mg(OH)2 into a reactor, located between the sludge dewatering facilities and the centrate or filtrate discharge line, and using air for mixing and carbon dioxide stripping, proves feasible in reducing struvite deposition in centrate or filtrate discharge lines and can generate a potentially valuable plant fertilizer--struvite.

Alum Compounds↗
PubMed2004

Mineralogy at Meridiani Planum from the Mini-TES Experiment on the Opportunity Rover.

The Miniature Thermal Emission Spectrometer (Mini-TES) on Opportunity investigated the mineral abundances and compositions of outcrops, rocks, and soils at Meridiani Planum. Coarse crystalline hematite and olivine-rich basaltic sands were observed as predicted from orbital TES spectroscopy. Outcrops of aqueous origin are composed of 15 to 35% by volume magnesium and calcium sulfates [a high-silica component modeled as a combination of glass, feldspar, and sheet silicates (approximately 20 to 30%)], and hematite; only minor jarosite is identified in Mini-TES spectra. Mini-TES spectra show only a hematite signature in the millimeter-sized spherules. Basaltic materials have more plagioclase than pyroxene, contain olivine, and are similar in inferred mineral composition to basalt mapped from orbit. Bounce rock is dominated by clinopyroxene and is close in inferred mineral composition to the basaltic martian meteorites. Bright wind streak material matches global dust. Waterlain rocks covered by unaltered basaltic sands suggest a change from an aqueous environment to one dominated by physical weathering.

Calcium Sulfate↗
PubMed2001

Rapid removal of dilute lead from water by pyroaurite-like compound.

Rapid removal of dissolved dilute lead (Pb) by pyroaurite-like compound Mg(x)Fe(y)(OH)2(x+y) (CO3(2-))y/2 x mH2O; anionic clay: one of layered double hydroxides) from water was studied through batch and column experiments. The Pb-removal property of the compound was evaluated as a function of concentration of Pb in the treated solution, space velocity (Sv) of the solution in the column packed with the compound, pH of the solution and contaminated humic substance. The compound showed a highly effective Pb-removal property that was comparable to the other conventional adsorbents. The Pb was removed rapidly by the column packed with the compound over the wide range of the Sv. The buffering pH function of the compound contributed to the Pb removal producing weak-alkali atmosphere. The contamination of humic substance in the treated solution reduced the Pb removal largely depending on its amount. The effectiveness of the compound for the rapid Pb removal was confirmed through a series of experiments.

Charcoal↗
PubMed1997

Solid state NMR characterisation of the thermal transformation of Fuller's Earth.

Fuller's Earth, a dioctahedral calcium montmorillonite clay mineral of the smectite group, undergoes thermal transformation via a series of complex intermediate states that are highly structurally disordered. Fuller's Earth is a commercially significant material with considerable levels of paramagnetic iron (Fe3+) substitution into octahedrally coordinated metal sites. Despite the high iron-content (approximately 10% of the occupied octahedral metal sites) in these samples 29Si and 27Al magic angle spinning (MAS) NMR spectra of sufficient quality are obtained to reveal structural changes in samples that have been heated from room temperature to 1400 degrees C. Two major structural changes are clearly observed, initial dehydroxylation and then collapse of the layer structure into more highly connected silica-rich domains and an alumina-rich phase.

Aluminum↗
PubMed2002

Electronically conductive phospho-olivines as lithium storage electrodes.

Lithium transition metal phosphates have become of great interest as storage cathodes for rechargeable lithium batteries because of their high energy density, low raw materials cost, environmental friendliness and safety. Their key limitation has been extremely low electronic conductivity, until now believed to be intrinsic to this family of compounds. Here we show that controlled cation non-stoichiometry combined with solid-solution doping by metals supervalent to Li+ increases the electronic conductivity of LiFePO4 by a factor of approximately 10(8). The resulting materials show near-theoretical energy density at low charge/discharge rates, and retain significant capacity with little polarization at rates as high as 6,000 mA x g(-1). In a conventional cell design, they may allow development of lithium batteries with the highest power density yet.

Electric Capacitance↗