Effect of the nucleating agents Cr2O3 and LiF on crystallizing phases and microstructures of glass-ceramics prepared by using some industrial wastes

Glass-ceramics in the system diopside-anorthite-orthoclase were prepared using the waste known as the by-pass cement dust in the amount of 36 % of the batch constituents. The effects of addition of the nucleating agents Cr2O3, LiF, and mixtures of them on the crystallizability, phase assemblages, and the resultant microstructures were investigated. Low concentration of Cr2O3 (0.5 wt%) causes volume crystallization and formation of fine-grained microstructures of microcline, anorthite and aluminous pyroxene. Higher concentrations of Cr2O3 favor formation of leucite and aluminous pyroxene and inhibit crystallization of anorthite. LiF causes the formation of microcline and its transformation into orthoclase. It also increases the crystallizability with the formation of nonuniform coarse-grained texture. Α mixture of 0.5 % Cr2O3 and 1.5 % LiF causes a synergistic effect, where fine-grained microstructure is formed (due to Cr2O3) with orthoclase formation (due to LiF) in addition to aluminous pyroxene and anorthite. The effects of various Cr2O3 concentrations were discussed on the bases of the increased viscosity and separation of Cr2O3 and/or chromiumspinel phases. The effects of LiF were attributed to the role of fluorine ions in reducing the viscosity of the glasses, consequently facilitating crystallization of the structurally more complex silicate in addition to favoring reaching thermodynamic equilibrium

Zur Polymorphie des Na2Si2O5

Ausgehend von Natronwasserglas wurden an verschiedenen Temperprodukten der Zusammensetzung Na2Si2O5 röntgenographisch bei Zimmertemperatur drei Modifikationen (α, β, γ) unterschieden. Bei diesen Formen wurden Umwandlungen stets nur in Richtung zur Hochtemperaturmodifikation α beobachtet. Bei der Differentialthermoanalyse zeigten die α-Form zwei und die γ-Form drei weitere reversible Umwandlungserscheinungen, die teilweise metastabil erfolgen. Durch Röntgenerhitzungsaufnahmen sind im Falle des α-Na2Si2O5 bei diesen Umwandlungseffekten auch strukturelle Veränderungen nachzuweisen

Topological properties and electronic structures of compounds with pyrite-type crystal structures

SiP2, FeS2, and AuSb2 crystallize with pyrite structure. The structural topologies of the three compounds are comparable, while their constituting elements belong to very different groups of the periodic system of the elements. This fact motivates our interest in finding some criteria for the stability of their atomic arrangements. We used density functional methods (LCAO-CO Ansatz) to characterize the topological properties of the electron density: in addition to the results from theoretically determined structural parameters, band structures, and the electron localization function, the electronic charges of the corresponding atoms are calculated on the basis of Bader's zero-flux surface approach. It is shown, that charge transfer between the constituting elements of the pyrite structure is a characteristic feature of the structural stability in the title compounds. The detailed results on the partial density of states for all studied compounds finally allow the explanation of the theoretically determined density topology on the atomic level

Properties of electronic spectra of antitumor-active dichlorobis(cycloalkylamine) platin(II) compounds

Complexes of PtCl₂(RNH₂)₂, with RNH, = cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, cycloheptylamine and cyclooctylamine, are investigated as powder samples and in solution applying different spectroscopic methods (absorption, excitation, emission, emission lifetime). It is concluded that the involved low energy states are mainly of metal d character. All these complexes exhibit a similar spectroscopic behavior despite the strongly different properties of the PtCl₂(RNH₂)₂ compounds in tests against a cancer cell line. Moreover, crystallographic unit cells of the compounds are determined from powder diffraction measurements

Arene-arene stacking in cis-bis[2-(2-thienyl)pyridine]platinum(II)

In the crystal structure of the title complex, [Pt(C₉H₆NS)₂], although the aromatic ligands are coordinated to a central heavy metal atom, T-shaped and shifted π-stacked arrangements of the aromatic moieties are preferred, leading to a sandwich herring-bone type of crystal-packing motif. The crystal structure is therefore consistent with the view that the arene-arene interactions are determined by electrostatics (multipole-multipole)

[1,2-Bis(2-hydroxyphenyl)ethylenediamine]dichloroplatinum(II), a new compound for the therapy of ovarian cancer. II. Synthesis and preliminary testing of the enantiomeric complexes

The enantiomeric [1,2-bis(2-hydroxyphenyl)-ethylenediamine]dichloroplatinum(II) complexes were synthesized and their configuration assessed. A preliminary test in the cisplatin-resistant human NIH:OVCAR-3 ovarian cancer cell line, which was previously characterized by its sensitivity against several therapeutically used drugs, showed that both enantiomers produce cytocidal effects in a concentration of 2.5 microM. A difference between the enantiomers became evident from the faster onset of cytocidal activity of the S,S-configurated compound

[1,2-Bis(2-hydroxyphenyl)ethylenediamine]dichloroplatinum(II), a new compound for the therapy of ovarian cancer. III. Detailed evaluation of the antitumor activity of the enantiomeric complexes on the human NIH:OVCAR-3 ovarian cancer cell line

The stereoisomeric [1,2-bis(2-hydroxyphenyl)ethylenediamine]dichloroplatinum(II) complexes were thoroughly tested on the cisplatin-resistant human NIH:OVCAR-3 ovarian cancer cell line. The racemate and its enantiomers produced cytocidal effects at a concentration of 2.5 microM (incubation time 256 h). The meso form, however, was merely cytostatically active. Differences between the enantiomers became evident after a short drug incubation time (1 h) followed by an incubation in drug-free medium (243 h). The S,S-configurated enantiomer (-)-3-PtCl2 proved to be the most active compound. To achieve cytocidal effects concentrations of 2.5-5.0 microM and incubation times of about 3 h were necessary for (-)-3-PtCl2. This compound is also sufficiently stable under test conditions as shown by the preincubation in cell-free medium for 3 h. These results and the augmentation of its antitumor activity by buthionine sulfoximine recommend the further preclinical development of (-)-3-PtCl2 for clinical use