Home About us Contact
|
Home About us Contact | ||
|
|
||
Oxide Precursor (oxide + precursor)
Selected AbstractsChemInform Abstract: The Synthesis of Metal Phosphides: Reduction of Oxide Precursors in a Hydrogen Plasma.CHEMINFORM, Issue 45 2008Anjie Wang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Glial-derived arginine, the nitric oxide precursor, protects neurons from NMDA-induced excitotoxicityEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2001Gilbert Grima Abstract Excitotoxic neuronal cell death is characterized by an overactivation of glutamate receptors, in particular of the NMDA subtype, and the stimulation of the neuronal nitric oxide synthase (nNOS), which catalyses the formation of nitric oxide (NO) from l -arginine (L-Arg). At low L-Arg concentrations, nNOS generates NO and superoxide (O2,,), favouring the production of the toxin peroxynitrite (ONOO,). Here we report that NMDA application for five minutes in the absence of added L-Arg induces neuronal cell death, and that the presence of L-Arg during NMDA application prevents cell loss by blocking O2,, and ONOO, formation and by inhibiting mitochondrial depolarization. Because L-Arg is transferred from glial cells to neurons upon activation of glial glutamate receptors, we hypothesized that glial cells play an important modulator role in excitotoxicity by releasing L-Arg. Indeed, as we further show, glial-derived L-Arg inhibits NMDA-induced toxic radical formation, mitochondrial dysfunction and cell death. Glial cells thus may protect neurons from excitotoxicity by supplying L-Arg. This potential neuroprotective mechanism may lead to an alternative approach for the treatment of neurodegenerative diseases involving excitotoxic processes, such as ischemia. [source] 3-Tocopherylisoxazolines by [2+3] CycloadditionEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2004Thomas Rosenau Abstract New isoxazoline derivatives of ,-tocopherol (1), the main component of vitamin E, were synthesized in a facile, two-step sequence consisting of nitration followed by 1,3-dipolar cycloaddition. 5-Nitromethyl-,-tocopheryl acetate (3), obtained from the cheap ,-tocopheryl acetate (2) by direct nitration in one step, acted as the nitrile oxide precursor in the reaction with various alkenes. The facile conversion proceeded in the presence of equimolar amounts of PhNCO and catalytic amounts of triethylamine. The NMR spectra of the product isoxazolines 5,13, showing strongly temperature-dependent resonances of the 4,,-CH, 4-CH2 and the acetyl group, are discussed, and the crystal structures of model compounds containing a methyl group instead of the isoprenoid side chain are presented. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] A Delivery System for Self-Healing Inorganic Films,ADVANCED FUNCTIONAL MATERIALS, Issue 22 2008Harvey A. Liu Abstract Multilayer composites that utilize polymeric and brittle inorganic films are essential components for extending the lifetimes and exploiting the flexibility of many electronic devices. However, crack formation within the brittle inorganic layers that arise from defects as well as the flexing of these multilayer composite materials allows the influx of atmospheric water, a major source of device degradation. Thus, a composite material that can initiate self-healing upon the influx of environmental water through defects or stress-induced cracks would find potential applications in multilayer composite materials for permeation barriers. In the present study, the reactive metal oxide precursor TiCl4 is encapsulated within the pores of a degradable polymer, poly(lactic acid) (PLA). Electrospun PLA fibers are found to be reactive to atmospheric water leading to the hydrolysis of the degradable polymer shell and subsequent release of the reactive metal oxide precursor. Release of the reactive TiCl4 from the pores results in hydrolysis of the metal oxide precursor, forming solid titanium oxides at the surface of the fibers. The efficacy of this self-healing delivery system is also demonstrated by the integration of these reactive fibers in the polymer planarization layer, poly(methyl methacrylate), of a multilayer film, upon which an alumina barrier layer is deposited. The introduction of nanocracks in the alumina barrier layer lead to the release of the metal oxide precursor from the pores of the fibers and the formation of titanium dioxide nanoparticles within the crack and upon the thin film surface. In this study the first delivery system that may find utility for the self-healing of multilayer barrier films through the site-specific delivery of metal oxide nanoparticles through smart reactive composite fibers is established. [source] Blue-shift of absorption edge in LaTiO2N by controlling the anion nonstoichiometryPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2006Toshihiro Moriga Abstract The perovskite-type oxynitride LaTiO2N was prepared by heating an oxide precursor at 950 °C for 5 hours under NH3 atmosphere at a flow rate of 1 dm3/min. The precursor was prepared by the polymerized complex method. The oxynitride obtained was almost stoichiometric, LaTi(O0.68N0.32)2.9, with a reddish orange color. The oxynitride was successively annealed at 950 °C for 3 hours under a NH3 atmosphere at flow rates of 50 cm3/min, 30 cm3/min and 10 cm3/min, respectively. The color and composition varied from yellow LaTi(O0.89N0.11)2.8 through green-yellow LaTi(O0.93N0.07)2.9 to light-blue LaTi(O0.98N0.02)2.9 in accordance with the decreased flow rate. The absorption edges varied from 2.28 eV for the reddish orange, 2.56 eV for the yellow, 3.17 eV for the green-yellow, to 3.44 eV for the light-blue oxynitrides. Annealing under NH3 is therefore effective in color tuning, mainly resulting in a blue-shift of the absorption edge. DV-X, calculations support the conclusion that the lower flow rate of NH3 led to a lower amount of nitrogen and higher oxygen levels in the oxynitrides. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Solution-Based Synthesis of Submicrometer ZrB2 and ZrB2,TaB2JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2008Yanli Xie Zirconium diboride and a zirconium diboride/tantalum diboride mixture were synthesized by solution-based processing. Zirconium n -propoxide was refluxed with 2,4-pentanedione to form zirconium diketonate. This compound hydrolyzed in a controllable fashion to form a zirconia precursor. Boria and carbon precursors were formed via solution additions of phenol,formaldehyde and boric acid, respectively. Tantalum oxide precursors were formed similarly as zirconia precursors, in which tantalum ethoxide was used. Solutions were concentrated, dried, pyrolyzed (800°,1100°C, 2 h, flowing argon), and exposed to carbothermal reduction heat treatments (1150°,1800°C, 2 h, flowing argon). Spherical particles of 200,600 nm for pure ZrB2 and ZrB2,TaB2 mixtures were formed. [source] | |||||||||||||