Fast ortho-para conversion of H2 adsorbed at copper surface step atoms

Ortho-para conversion of H2 adsorbed at the step atoms of a Cu(510) surface proceeds with a short conversion time constant around 1 s as observed in electron-energy-loss measurements of rotational populations. We suggest that this rapid conversion is related to the special character of the adsorption state, which involves a short H2-Cu bond length of 1.8 A. On the flat Cu(100) surface, conversion is found to occur at active sites, most likely step atoms.     

Constructive cooperative coevolution for large-scale global optimisation

This paper presents the Constructive Cooperative Coevolutionary (\(\mathrm {C}^3\)) algorithm, applied to continuous large-scale global optimisation problems. The novelty of \(\mathrm {C}^3\) is that it utilises a multi-start architecture and incorporates the Cooperative Coevolutionary algorithm. The considered optimisation problem is decomposed into subproblems. An embedded optimisation algorithm optimises the subproblems separately while exchanging information to co-adapt the solutions for the subproblems. Further, \(\mathrm {C}^3\) includes a novel constructive heuristic that generates different feasible solutions for the entire problem and thereby expedites the search. In this work, two different versions of \(\mathrm {C}^3\) are evaluated on high-dimensional benchmark problems, including the CEC’2013 test suite for large-scale global optimisation. \(\mathrm {C}^3\) is compared with several state-of-the-art algorithms, which shows that \(\mathrm {C}^3\) is among the most competitive algorithms. \(\mathrm {C}^3\) outperforms the other algorithms for most partially separable functions and overlapping functions. This shows that \(\mathrm {C}^3\) is an effective algorithm for large-scale global optimisation. This paper demonstrates the enhanced performance by using constructive heuristics for generating initial feasible solutions for Cooperative Coevolutionary algorithms in a multi-start framework.     

Ionic-charge dependence of the intermolecular coulombic decay time scale for aqueous ions probed by the core-hole clock

Auger electron spectroscopy combined with theoretical calculations has been applied to investigate the decay of the Ca 2p core hole of aqueous Ca(2+). Beyond the localized two-hole final states on the calcium ion, originating from a normal Auger process, we have further identified the final states delocalized between the calcium ion and its water surroundings and produced by core level intermolecular Coulombic decay (ICD) processes. By applying the core-hole clock method, the time scale of the core level ICD was determined to be 33 ± 1 fs for the 2p core hole of the aqueous Ca(2+). The comparison of this time constant to those associated with the aqueous K(+), Na(+), Mg(2+), and Al(3+) ions reveals differences of 1 and up to 2 orders of magnitude. Such large variations in the characteristic time scales of the core level ICD processes is qualitatively explained by different internal decay mechanisms in different ions as well as by different ion-solvent distances and interactions.     

Locked and unlocked nucleosides in functional nucleic acids

Nucleic acids are able to adopt a plethora of structures, many of which are of interest in therapeutics, bio- or nanotechnology. However, structural and biochemical stability is a major concern which has been addressed by incorporating a range of modifications and nucleoside derivatives. This review summarizes the use of locked nucleic acid (LNA) and un-locked nucleic acid (UNA) monomers in functional nucleic acids such as aptamers, ribozymes, and DNAzymes.     

Theoretical study of core ionized Cr(CO)6

The satellite structure of the C1s and O1s photoelectron spectra of chromium hexacarbonyl Cr(CO)₆ has been calculated by the INDO/CI method and compared with available high resolution core level photoelectron spectra. A reassignment of some of the lines is made. It is found that the satellite structure in both cases is dominated by excitations from metal-ligand bonding to metal-ligand antibonding Me(3d)-π^* orbitals, and that these shake-up excitations involve a significant charge transfer to the core ionized ligand from the rest of the molecule.     

Harmonic morphisms from the Grassmannians and their non-compact duals

In this paper we give a unified framework for the construction of complex valued harmonic morphisms from the real, complex and quaternionic Grassmannians and their non-compact duals. This gives a positive answer to the corresponding open existence problem in the real and quaternionic cases. Mathematics Subject Classifications (2000): 58E20, 53C43, 53C12The author is a member of EDGE, Research Training Network HPRN-CT-2000-00101     

Temperature dependence of the roton in liquid4He

In new neutron scattering measurements on⁴He at saturated vapour pressure (SVP), we have probed to within 0.0007 K of T_λ from below, revealing a dramatic increase in the damping rate of the momentum fluctuations and a marked softening of the roton frequency, with the changes occurring primarily very close to T_λ and being complete at T_λ. In contrast to 20 bars, the roton at SVP does not, however, go completely soft. Above T_λ, the modes are strongly damped and overlapping whereas at 20 bars they are overdamped (non-propagating).     

SCF and limited CI calculations for assignment of the Auger spectrum and of the satellites in the soft X-ray spectrum of H2O

SCF and limited CI calculations have been performed for a number of excited states of doubly ionized water. The calculations allowed an assignment of both the Auger spectrum and most of the satellites in the soft X-ray spectrum. The assignment for the two highest peaks in the Auger spectrum was ambiguous. SCF calculations of the K emission spectrum of H₂O were also performed. It was found that limited CI calculations were of importance for some states with two open shells in one symmetry. Such effects are caused by large off-diagonal lagrangian multiplies connecting the open shells in the reference configuration.