Mössbauer investigations of three meteorites of the type SNC-achondrites are reported. The results are compared with Mössbauer spectra of other meteorites, and selected terrestrial and lunar rocks. Through the oxidation state of iron in the pyroxenes and magnetic oxides studied, the work confirms that the mantle of the Earth is highly oxidized compared with the mantle of asteroidal bodies and lunar basalts. The investigations show that at least one of the SNC meteorites (Nakhla) comes from a highly oxidized parent body, believed to be the planet Mars. Based on the results obtained, a somewhat general conclusion about the oxidation state of iron in planetary bodies is proposed.
Evaluation of drug precipitation is important in order to address challenges regarding low and variable bioavailability of poorly water-soluble drugs, to assess potential risk of patient safety with infusion therapy, and to explore injectable in situ suspension-forming drug delivery systems. Generally, drug precipitation is assessed in vitro through solution concentration analysis methods. Dual-wavelength UV-vis imaging is a novel imaging technique that may provide an opportunity for simultaneously monitoring changes in both solution and solid phases during precipitation. In the present study, a multimodal approach integrating UV-vis imaging, light microscopy, and Raman spectroscopy was developed for characterization of piroxicam supersaturation, precipitation, and dissolution in a flow-through setup. A solution of piroxicam dissolved in 1-methyl-2-pyrrolidinone was injected into a flowing aqueous environment (pH 7.4), causing piroxicam to precipitate. Imaging at 405 and 280 nm monitored piroxicam concentration distributions during precipitation and revealed different supersaturation levels dependent on the initial concentration of the piroxicam solution. The combination with imaging at 525 nm, light microscopy, and Raman spectroscopy measurements demonstrated concentration-dependent precipitation and the formation, growth, and dissolution of individual particles. Results emphasize the importance of the specific hydrodynamic conditions on the piroxicam precipitation. The approach used may facilitate comprehensive understanding of drug precipitation and dissolution processes and may be developed further into a basic tool for formulation screening and development.
It is generally believed that liquid water was once stable on the surface of Mars. In the rather thin and nearly oxygenfree atmosphere of Mars UV-radiation from the Sun reaches the martian surface, and in aqueous environment UV-light is a source of oxidation of Fe2+ (aq). As a Mars simulation experiment, we have studied the precipitates forming from the photochemical oxidation of Fe2+ (aq) in the laboratory by means of Mössbauer spectroscopy.Our results show that α-FeOOH (goethite) must have precipitated in martian aqueous environments as a result of photostimulated oxidation of Fe2+ (aq).
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