Topic
Valency
About: Valency is a research topic. Over the lifetime, 1632 publications have been published within this topic receiving 26141 citations.
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TL;DR: In this paper , a high-valency quadrangular prism (D4h) node with a connectivity of eight is proposed, based on which two isoreticular 3D imine-linked COFs can be created.
Abstract: The structural diversity of three-dimensional (3D) covalent organic frameworks (COFs) are limited as there are only a few choices of building units with multiple symmetrically distributed connection sites. To date, 4 and 6-connected stereoscopic nodes with Td, D3h, D3d and C3 symmetries have been mostly reported, delivering limited 3D topologies. We propose an efficient approach to expand the 3D COF repertoire by introducing a high-valency quadrangular prism (D4h) stereoscopic node with a connectivity of eight, based on which two isoreticular 3D imine-linked COFs can be created. Low-dose electron microscopy allows the direct visualization of their 2-fold interpenetrated bcu networks. These 3D COFs are endowed with unique pore architectures and strong molecular binding sites, and exhibit excellent performance in separating C2H2/CO2 and C2H2/CH4 gas pairs. The introduction of high-valency stereoscopic nodes would lead to an outburst of new topologies for 3D COFs.
4 citations
01 Aug 2015
TL;DR: It is shown that for Czech verbs from the Prague Dependency Treebank it holds “the greater the full valency of a verb, the more synonyms the verb has”.
Abstract: This paper investigates the relation between the number of full valency frames (we do not distinguish between complements and optional adjuncts, both are taken into account) of a verb and the number of its synonyms. It is shown that for Czech verbs from the Prague Dependency Treebank it holds “the greater the full valency of a verb, the more synonyms the verb has”.
4 citations
TL;DR: The Na content of the fast ionic conductor Na-β-alumina can be fully replaced by ion exchange with a wide variety of divalent ions as mentioned in this paper, and the structure and optical properties of the system are greatly affected by both composition and thermal treatment, which determine the balance between the configurational entropy, site preference and Coulombic repulsions of the cations in the conduction planes.
4 citations
TL;DR: The dependence of the catalytic activity on the method by which the catalyst has been prepared can be explained by the circumstance that in addition to the influence of other factors the origin of the catalyst had an effect on the interrelation of different types of free valencies on the catalyzing surface as mentioned in this paper.
Abstract: 1.
One must assume that on the surface of metals and ionic crystals there are free valencies of different types, which correspond to normal and excited valency states of the atoms of the adsorbent; different types of free valency represent active points with different activities.
2.
The dependence of the catalytic activity on the method by which the catalyst has been prepared can be explained by the circumstance that in addition to the influence of other factors the origin of the catalyst has an effect on the interrelation of different types of free valencies on the catalyzing surface.
3.
On the basis of the concept in regard to chemical correspondence between the reacting molecules and the catalyst and Pauling's theory of the metallic state, an explanation has been given to differences in the catalytic activity among metals of the IV period with respect to reactions which are slowed down by the chemisorption of nitrogen and reactions which involve chemisorption of hydrogen or deuterium.
4 citations
TL;DR: In this article, the anomalous variation of the magnetic susceptibility in liquid alloys of gold with polyvalent metals is discussed in terms of electron concentration and conventional pseudopotential theory.
Abstract: The anomalous variation of the magnetic susceptibility in liquid alloys of gold with polyvalent metals is discussed in terms of electron concentration and conventional pseudopotential theory. The characteristic minima of the susceptibility are shifted systematically towards the Au-rich side if the valency of the alloying element is increased, but considering the average electron concentration they all seem to occur at a critical electron to atom ratio of e/a≍1.6. They are obviously a manifestation of the electronic stabilization which gives rise to the formation of electron compounds in the critical range of composition. Theoretical calculations based on simple model potentials reproduce the typical shape of the observed susceptibility curves and also their systematic variations due to the change in valency. The results indicate that the susceptibility minima are primarily due to interactions between the ionic cores and the electrons which increase the diamagnetic contribution of the conduction e...
4 citations