The geometry of the Barbour-Bertotti theories I. The reduction process

The dynamics of $N\geq 3$ interacting particles is investigated in the non-relativistic context of the Barbour-Bertotti theories. The reduction process on this constrained system yields a Lagrangian in the form of a Riemannian line element. The involved metric, degenerate in the flat configuration space, is the first fundamental form of the space of orbits of translations and rotations (the Leibniz group). The Riemann tensor and the scalar curvature are computed by a generalized Gauss formula in terms of the vorticity tensors of generators of the rotations. The curvature scalar is further given in terms of the principal moments of inertia of the system. Line configurations are singular for $N\neq 3$. A comparison with similar methods in molecular dynamics is traced.Comment: 15 pages, to appear in Classical and Quantum Gravit

Interactions between metal ions and DNA

84 years elapsed between the announcements of the periodic table and that of the DNA double helix in 1953, and the two have been combined in many ways since then. In this chapter an outline of the fundamentals of DNA structure leads into a range of examples showing how the natural magnesium and potassium ions found in nature can be substituted in a diversity of applications. The dynamic structures found in nature have been studied in the more controlled but artificial environment of the DNA crystal using examples from sodium to platinum and also in a range of DNA-binding metal complexes. While NMR is an essential technique for studying nucleic acid structure and conformation, most of our knowledge of metal ion binding has come from X-ray crystallography. These days the structures studied, and therefore also the diversity of metal binding, go beyond the double helix to triplexes, hairpin loops, junctions and quadruplexes, and the chapter describes briefly how these pieces fit into the DNA jigsaw. In a final section, the roles of metal cations in the crystallisation of new DNA structures are discussed, along with an introduction to the versatility of the periodic table of absorption edges for nucleic acid structure determination

Highly active binder free plasma sprayed non-noble metal electrodes for anion exchange membrane electrolysis at different reduced KOH concentrations

Alkaline anion exchange membrane water electrolysis (AEMWE) is considered to be an alternative to proton exchange membrane water electrolysis (PEMWE) and conventional alkaline water electrolysis (AWE), owing to the use of non-precious metal and avoiding high alkaline concentration electrolyte, respectively. Here, we report a highly efficient AEMWE design using the fabrication of membrane-electrode assembly (MEA) by simply sandwiching anion exchange membrane between electrodes developed by plasma spraying of NiMoAl for cathode and NiAl for anode in various low concentrated KOH solutions (0.1 to 1.0M). The first impression from the electrochemical characterization is that a higher KOH concentration has positive effects on the overall cell performance. However, this effect is limited at higher KOH concentration. The cell operated in 1.0M KOH exhibits the highest current density of 0.44 A/cm² at 1.80 V, which is very close the one, 0.5 A/cm² at 1.80 V, in 6.0M KOH achieved in AWE