Skeletally Dugundji spaces

We introduce and investigate the class of skeletally Dugundji spaces as a skeletal analogue of Dugundji space. The main result states that the following conditions are equivalent for a given space $X$: (i) $X$ is skeletally Dugundji; (ii) Every compactification of $X$ is co-absolute to a Dugundji space; (iii) Every $C^*$-embedding of the absolute $p(X)$ in another space is strongly $\pi$-regular; (iv) $X$ has a multiplicative lattice in the sense of Shchepin \cite{s76} consisting of skeletal maps

Very I-favorable spaces

AbstractWe prove that a Hausdorff space X is very I-favorable if and only if X is the almost limit space of a σ-complete inverse system consisting of (not necessarily Hausdorff) second countable spaces and surjective d-open bonding maps. It is also shown that the class of Tychonoff very I-favorable spaces with respect to the co-zero sets coincides with the d-openly generated spaces

Electrochemical activation of molecular nitrogen at the Ir/YSZ interface.

Nitrogen is often used as an inert background atmosphere in solid state studies of electrode and reaction kinetics, of solid state studies of transport phenomena, and in applications e.g. solid oxide fuel cells (SOFC), sensors and membranes. Thus, chemical and electrochemical reactions of oxides related to or with dinitrogen are not supposed and in general not considered. We demonstrate by a steady state electrochemical polarisation experiments complemented with in situphotoelectron spectroscopy (XPS) that at a temperature of 450 °C dinitrogen can be electrochemically activated at the three phase boundary between N2, a metal microelectrode and one of the most widely used solid oxide electrolytes—yttria stabilized zirconia (YSZ)—at potentials more negative than E = −1.25 V. The process is neither related to a reduction of the electrolyte nor to an adsorption process or a purely chemical reaction but is electrochemical in nature. Only at potentials more negative than E = −2 V did new components of Zr 3d and Y 3d signals with a lower formal charge appear, thus indicating electrochemical reduction of the electrolyte matrix. Theoretical model calculations suggest the presence of anionic intermediates with delocalized electrons at the electrode/electrolyte reaction interface. The ex situSIMS analysis confirmed that nitrogen is incorporated and migrates into the electrolyte beneath the electrode

On generalized VnV^n-continua

The notion of $V^n$-continua was introduced by Alexandroff \cite{ps} as a generalization of the concept of $n$-manifold. In this note we consider the cohomological analogue of $V^n$-continua and prove that any strongly locally homogeneous, generalized continuum $X$ with cohomological dimension $n$ is a generalized $V^n$-con\-ti\-nuum with respect to the cohomological dimension. In particular, every strongly locally homogeneous continuum of covering dimension $n$ is a $V^n$-continuum in the sense of Alexandroff. An analog of the Mazurkiewicz theorem that no subset of covering dimension $\le n-2$ cuts any region of the Euclidean $n$-space is also obtained for strongly locally homogeneous, generalized continua of cohomological dimension $n$.Comment: 7 page