Shadows Of Mapping Class Groups: Capturing Convex Cocompactness

We strengthen the analogy between convex cocompact Kleinian groups and convex cocompact subgroups of the mapping class group of a surface in the sense of B. Farb and L. Mosher. Received: August 2006, Accepted: January 2007, Revision: February 2007     

Molecular architecture via coordination: self-assembly of pseudohexagonal A2(3)X2(3)-macrocycles

[formula: see text] The interaction of two complementary ditopic building blocks, each incorporating 120 degrees angles between the active coordination sites, in methylene chloride at room temperature results in the spontaneous self-assembly of platinum-based assemblies of hexagonal shape.     

Kleinian groups with discrete length spectrum

We characterize finitely generated torsion-free Kleinian groupswhose real length spectrum (without multiplicities) is discrete.     

Novel Reactions of Phosphaalkynes in the Coordination Sphere of tert-Butylimido- vanadium(V) Complexes: A Simple Synthesis of 3-Aza-1,2,4,6-tetraphosphaquadricyclanes and 1,3,5-Triphosphabenzenes

A small variation in the vanadium reagent leads to a completely different product: The cyclooligomerization of phosphaalkynes 2 with tBuN=VCl₃⋅DME (DME=1,2-dimethoxyethane) proceeds with incorporation of the imido fragment to give the azatetraphosphaquadricyclanes 1 . In contrast, with the corresponding vanadium compound containing no Lewis base this fragment is not incorporated, and the 1,3,5-triphosphabenzenes 3 are obtained.     

Equivalent Curves in Surfaces

We consider various notions of equivalence for homotopy classes of curves on hyperbolic surfaces based on topological, algebraic, and geometric structures, and find the relationships between these equivalences.     

The total Position Spread in mixed‐valence compounds: A study on the model system

The behavior of the Total Position Spread (TPS) tensor, which is the second moment cumulant of the total position operator, is investigated in the case of a mixed‐valence model system. The system consists of two H₂ molecules placed at a distance D. If D is larger than about 4 bohr, the singly ionized system shows a mixed‐valence character. It is shown that the magnitude of the TPS has a strong peak in the region of the avoided crossing. We believe that the TPS can be a powerful tool to characterize the behavior of the electrons in realistic mixed‐valence compounds. © 2014 Wiley Periodicals, Inc.     

Electron affinities of the DNA and RNA bases.

Adiabatic electron affinities (AEAs) for the DNA and RNA bases are predicted by using a range of density functionals with a double-zeta plus polarization plus diffuse (DZP++) basis set in an effort to bracket the true EAs. Although the AEAs exhibit moderate fluctuations with respect to the choice of functional, systematic trends show that the covalent uracil (U) and thymine (T) anions are bound by 0.05-0.25 eV while the adenine (A) anion is clearly unbound. The computed AEAs for cytosine (C) and guanine (G) oscillate between small positive and negative values for the three most reliable functional combinations (BP86, B3LYP, and BLYP), and it remains unclear if either covalent anion is bound. AEAs with B3LYP/TZ2P++ single points are 0.19 (U), 0.16 (T), 0.07 (G), -0.02 (C), and -0.17 eV (A). Favorable comparisons are made to experimental estimates extrapolated from photoelectron spectra data for the complexes of the nucleobases with water. However, experimental values scaled from liquid-phase reduction potentials are shown to overestimate the AEAs by as much as 1.5 eV. Because the uracil and thymine covalent EAs are in energy ranges near those of their dipole-bound counterparts, preparation and precise experimental measurement of the thermodynamically stable covalent anions may prove challenging.     

Ground state of the quasi-1D correlated electronic system BaVS3

In this paper we review the salient features of the different instabilities exhibited by the quasi-1D system BaVS₃ and show that there is a subtle interplay between the different phases stabilized. The analysis of the Peierls instability shows that the mobile dz² electrons are more localized than calculated because of their strong correlation with the localized e(t_2g) electrons. The complex AF magnetic structure of BaVS₃ incorporates the magnetization of the e(t_2g) electrons with the Peierls pairing of the dz² electrons into magnetic singlets. Finally, we propose that the zig-zag disorder remaining after an incomplete orthorhombic phase transition could change the sign of the magnetic coupling and thus help to stabilize the canted ferromagnetism observed in non stoichiometric BaVS_3−δ and Sr and Ba substituted compounds.