Polyoxygenated ergostane-type sterols from the liquid culture of Ganoderma applanatum

A new polyoxygenated ergostane-type sterol, 3β,5α,6β,8β,14α-pentahydroxy-(22E,24R)-ergost-22-en-7-one (1), has been isolated from the liquid culture of the basidiomycete Ganoderma applanatum together with four known sterols, 3β,5α,9α-trihydroxy-(22E,24R)-ergosta-7,22-dien-6-one (2), ergosterol peroxide (3), 6-dehydrocerevisterol (4) and cerevisterol (5). Two of these sterols (2, 4) are reported to have been isolated from this species for the first time. The structures of these compounds were determined by chemical and spectroscopic analyses, including 1D- and 2D-NMR, as well as by comparison of their spectroscopic data with those reported in the literature.     

Folding-promoted TBACl-mediated chemo- and regioselective demethylations of methoxybenzene-based macrocyclic pentamers

Tetrabutylammonium chloride (TBACl) salt alone has not been shown previously to be capable of removing methoxy groups. It is demonstrated here that the use of TBACl achieves efficient folding-promoted chemo- and regioselective demethylations, eliminating up to two out of five methyl groups situated in similar macrocyclic chemical microenvironments.     

The minimum upper bound on the first ambiguous power of an irreducible, nonpowerful ray or sign pattern

Let A be an n×n irreducible ray or sign pattern matrix. If A is a sign pattern, it is shown that either A is powerful or else A^k has an ambiguous entry for some , and further, sign patterns based on the Wielandt graph show that this bound is the best possible. If A is a ray pattern, partial results for the same bound are given.     

Oxidative properties of a nonheme Ni(II)(O2) complex: Reactivity patterns for C-H activation, aromatic hydroxylation and heteroatom oxidation

Density functional theory calculations on the reactivity of a Ni(II)-superoxo complex in C-H bond activation, aromatic hydroxylation and heteroatom oxidation reactions have been explored; the Ni(II)-superoxo complex is able to react with substrates with weak C-H bonds and PPh(3).     

Transition from anodic titania nanotubes to nanowires: arising from nanotube growth to application in dye-sensitized solar cells

Anodic formation of titania nanowires has been interpreted using a bamboo-splitting model; however, a number of phenomena are difficult to explain with this model. Herein, transition from nanotubes to nanowires is investigated by varying the anodizing conditions. The results indicate that the transition requires a large number of hydrogen ions to reduce the passivated area of tube walls, and therefore can be observed only in an intermediate chemical dissolution environment. Accordingly, a model in terms of stretching and splitting is proposed to interpret the transition process. The model provides a basis to suppress the nanowires with surface treatments before anodization and to clear the nanowires with an ultrasonication process after anodization. The nanotube-nanowire transition also arises when the tubes are directly used in dye-sensitized solar cells. Treatment with titanium tetrachloride solution for about 10 h is found to be effective in suppressing the nanowires, and thus improving the photovoltaic properties of the solar cells.     

Γ-Convergence of 2D Ginzburg-Landau functionals with vortex concentration along curves

We study the variational convergence of a family of twodimensional Ginzburg-Landau functionals arising in the study of superfluidity or thin-film superconductivity as the Ginzburg-Landau parameter ε tends to 0. In this regime and for large enough applied rotations (for superfluids) or magnetic fields (for superconductors), the minimizers acquire quantized point singularities (vortices). We focus on situations in which an unbounded number of vortices accumulate along a prescribed Jordan curve or a simple arc in the domain. This is known to occur in a circular annulus under uniform rotation, or in a simply connected domain with an appropriately chosen rotational vector field. We prove that if suitably normalized, the energy functionals Γ-converge to a classical energy from potential theory. Applied to global minimizers, our results describe the limiting distribution of vortices along the curve in terms of Green equilibrium measures.     

Absolute fixed point sets for continuum-valued maps

The notion of an absolute fixed point set in the setting of continuum-valued maps will be defined and characterized.