Redetermination of synthetic warwickite, Mg3TiO2(BO3)2

Single crystals of warwickite, trimagnesium titanium(IV) dioxide bis­(borate), Mg3TiO2(BO3)2, were prepared by slow cooling of the melt. The title compound is isotypic with Co3TiO2(BO3)2. In contrast to the previous refinement of warwickite [Moore & Araki (1974 ▶). Am. Mineral. 59, 985–1004], that reported only isotropic atomic displacement parameters for all atoms, anisotropic displacement parameters of all atoms were refined during the current redetermination. All atoms are situated on special positions (site symmetry .m.). One of the two Mg sites is statistically disordered with Ti atoms (ratio 1:1), while the other is fully occupied by Mg atoms. The occupancy ratio of the Mg and Ti atoms is similar to that reported in the previous study. Metal atoms (M) at the Ti/Mg and Mg sites are coordinated by six O atoms in form of distorted octa­hedra. Four edge-sharing MO6 octa­hedra form M 4O18 units, which are connected by common corners into layers parallel to (010). Adjacent layers are linked along [010] into a framework structure by sharing common edges. The B atoms are located in the triangular prismatic tunnels of the framework

Synthesis and crystal structure of novel nonstoichiometric suboxide solid solutions, Ti12−δGaxBi3−xO10

Single crystals of new Ti12−δGaxBi3−xO10 compounds (x = 1.42–1.74, δ = 0.77–0.62) were prepared at 900 °C with a Bi flux. Crystal structure analysis by X-ray diffraction (XRD) revealed that the solid solutions are isostructural with Ti12−δSn3O10 (cubic, space group Fm-3m).1) The δ and x values were determined by refinement of the occupancies for the Ti2 and Ti4 sites, and Ga site, respectively (Table 1). The cell parameter a decreases from 13.5616(3) Å to 13.5402(5) Å with increasing Ga content, x, while the total valence electron number of Ti12−δGaxBi3−xO10 was maintained at 117.1 by decreasing Ti defects, δ. Stella octangula is formed by sharing of the edges of four supertetrahedra composed of O-centered Ti tetrahedra and trigonal bipyramids (oxide part) (Figure 1). Another superpolyhedron is formed by sharing of the pyramidal planes of Ga/Bi-centered Ti mono-caped square antiprisms (intermetallic part). These two parts are incorporated in the structure. A polycrystalline bulk of a solid solution with x = 2.01, δ = 0.67 (a = 13.53772(13) Å) was synthesized by reaction sintering at 950 °C from the mixture of Ti, TiO2, Bi2O3, and Ga2O3. The resistivities measured for the bulk were 2.2–2.4×10−5 Ωm in the temperature range from 10 K to 300 K. Please click Additional Files below to see the full abstract

Superconductivity induced by doping holes in the nodal-line semimetal NaAlGe

The nodal-line semimetals NaAlSi and NaAlGe have significantly different ground states despite having similar electronic structures: NaAlSi exhibits superconductivity below 7 K, while NaAlGe exhibits semiconductive electrical conductivity at low temperatures, indicating the formation of a pseudogap at approximately 100 K. The origin of the pseudogap in NaAlGe is unknown but may be associated with excitonic instability. We investigated hole-doping effects on the ground state in the solid solution Na(Al1-xZnx)Ge and discovered that the pseudogap is suppressed continuously with increasing Zn content, followed by the appearance of a superconducting dome with the highest transition temperature of 2.8 K. This superconductivity most likely results from excitonic fluctuations.Comment: 7 pages, 9 figure

R-Ferrite-type barium cobalt stannate, BaCo2Sn4O11

BaCo2Sn4O11 is isotypic with R-ferrite, BaTi2Fe4O11. The Co atoms fully occupy trigonal–bipyramidal sites () and are disordered with Sn atoms in octa­hedral sites (.2/m symmetry), as represented in the formula BaCoSn2(Co0.34Sn0.66)4O11. Ba atoms are situated in a 12-fold coordinated site ( symmetry)

A ramsayite-type oxide, Ca2Sn2Al2O9

The title compound, dicalcium nonaoxidodistannate(IV)dialuminate, is the second example which crystallizes in the isotypic structure of a pyroxene silicate, Na2Ti2Si2O9 (ramsayite). ∞ 1[Sn2O8] chains and pyroxene-type ∞ 1[Al2O6] chains are formed along the b axis by sharing O atoms. The Ca atoms are situated in the resulting channels and exhibit a coordination number of 7

Gene expression profile and pathogenicity of biofilm-forming Prevotella intermedia strain 17

<p>Abstract</p> <p>Background</p> <p><it>Prevotella intermedia </it>(<it>P. intermedia</it>), a gram-negative, black-pigmented anaerobic rod, has been implicated in the development of chronic oral infection. <it>P. intermedia </it>strain 17 was isolated from a chronic periodontitis lesion in our laboratory and described as a viscous material producing strain. The stock cultures of this strain still maintain the ability to produce large amounts of viscous materials in the spent culture media and form biofilm-like structures. Chemical analyses of this viscous material showed that they were mainly composed of neutral sugars with mannose constituting 83% of the polysaccharides. To examine the biological effect of the extracellular viscous materials, we identified and obtained a naturally-occurring variant strain that lacked the ability to produce viscous materials <it>in vitro </it>from our stock culture collections of strain 17, designated as 17-2. We compared these two strains (strains 17 versus 17-2) in terms of their capacities to form biofilms and to induce abscess formation in mice as an indication of their pathogenicity. Further, gene expression profiles between these two strains in planktonic condition and gene expression patterns of strain 17 in solid and liquid cultures were also compared using microarray assays.</p> <p>Results</p> <p>Strain 17 induced greater abscess formation in mice as compared to that of the variant. Strain 17, but not 17-2 showed an ability to interfere with the phagocytic activity of human neutrophils. Expression of several genes which including those for heat shock proteins (DnaJ, DnaK, ClpB, GroEL and GroES) were up-regulated two to four-fold with statistical significance in biofilm-forming strain 17 as compared to the variant strain 17-2. Strain 17 in solid culture condition exhibited more than eight-fold up-regulated expression levels of several genes which including those for levanase, extracytoplasmic function-subfamily sigma factor (σ^E; putative) and polysialic acid transport protein (KpsD), as compared to those of strain 17 in liquid culture media.</p> <p>Conclusion</p> <p>These results demonstrate that the capacity to form biofilm in <it>P. intermedia </it>contribute to their resistance against host innate defence responses.</p