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1	Measurements of the optical constants of magnesium oxide and calcium tungstate in the spectral region between 10 cm⁻¹ and 100 cm⁻¹ at 300̊K and 90̊K / Rowntree, Robert Fredric January 1963 (has links) No description available. Physics Magnesium oxide Calcium tungstate crystals
2	Příprava a charakterizace nanočástic pro in vitro buňečné studie / Preparation and characterization of nanoparticles for in vitro cell studies Hladík, Martin January 2015 (has links) This thesis deals with the preparation, characterization methods and in vitro imaging of nanoparticles with great potential for medical diagnostics. A key role in this work occupy nanoparticles comprising a core of calcium tungstate, CaWO4, covered by a natural polysaccharide together serve as a suitable model contrast agent for cell imaging techniques. CaWO4 natural properties such as the absorption of X-rays, natural fluorescence capabilities and capacities for doping fluorescently active lanthanides, makes from nanoparticles suitable candidates for the position of contrast agents for imaging in the diagnosis of oncological diseases. Moreover, by coverage of the inorganic core by natural polysaccharide nanoparticles reach the desired size and the possibility of active targeting to specific or nonspecific interactions with the cell membrane, which are key factors in in vitro cell studies. It was found the most suitable synthesis both doped and undoped core of this model reaching the formation of spherical particles of colloidal dimensions. Doping was realized by red fluorescent trivalent europium, Eu3+ , and green fluorescent trivalent terbium, Tb3+ , and neither of these dopants affected the original crystalline structure CaWO4. In the next stage, these fluorescent nuclei successfully dispersed...
3	Reactive replacement and addition of cations in bioclastic silica and calcite Allan, Shawn Michael 05 May 2005 (has links) Numerous organisms produce ornately detailed inorganic structures (often known as shells) with features on length scales from 50 nm to several centimeters. One class of such organisms are the diatoms; microscopic algae that form silica frustules. Another group of algae, the coccolithophorids, produce similar calcium carbonate structures. Over 100,000 species comprise these two classes of algae, every one of which is endowed with a unique cytoskeleton structure. Using various types of displacement reactions, the chemistry of the original structure can be modified to produce a new material. Magnesium vapor has been found to displace the silicon in diatom frustules to yield an MgO structure. The conversion has been reported at temperatures from 650°C to 900°C. In the current work, the conversion and processing of silica frustules to MgO was examined in depth. The effect of reaction temperature on grain size and extent of conversion was evaluated. With the goal of obtaining high purity MgO structures, various methods for removing the silicon products of reaction were investigated. Wet chemistry and high temperature vapor etches were evaluated. The MgO reaction served as an intermediate step in the production of magnesium tungstate diatoms, which were imbued with photoluminescent properties. Reactions were identified to allow the conversion of calcium carbonate (calcite) structures to alternative chemistries. Calcite sand-dollars were converted to calcium tungstate or calcium molybdate by aqueous solution chemistry. In this process, sand dollar tests (shells) and coccolithophore frustules were reacted with ammonium para-molybdate or ammonium para-tungstate. The reactions were evaluated for shape preservation, phase purity, and photoluminescence of the structures. Self-replication Phosphor Diatom Coccolithophore Shape-preserving reaction Magnesium tungstate Silicon etching Displacement reactions Calcium molybdate Calcium tungstate Magnesium Mangesium oxide Chlorine etching X-ray diffraction Bioclastic Fluorescence Bio mineral Scanning electron microscopy Calcite Cations Substitution reactions Silicates Calcium carbonate Nanostructured materials Synthesis Biotechnological microorganisms Diatoms Microstructure Ammonium Photoluminescence

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