A new pivoting algorithm for the linear complementarity problem allowing for an arbitrary starting point

The linear complementarity problem is to find nonnegative vectors which are affinely related and complementary. In this paper we propose a new complementary pivoting algorithm for solving the linear complementarity problem as a more efficient alternative to the algorithms proposed by Lemke and by Talman and Van der Heyden. The algorithm can start at an arbitrary nonnegative vector and converges under the same conditions as Lemke's algorithm.This research is part of the VF-program Competition and Cooperation.     

Chirality and dendrimers; the issue of chiral recognition at the nanoscopic level

The synthesis and characterization of two chiral dendrimers, 1 and 2 , in their racemic form is presented. The chirality is based on the construction of four constitutionally different, but chemically resembling, branches to an achiral core. A multi-substituted pentaerythritol derivative is used as core and Fréchet's aromatic-ether dendritic wedges of different generation are used as branches. The synthetic approach makes use of the consecutive attachment of the four branches by selective deprotection of the core. Both chiral dendrimers of different size have been synthesized from the same precursor. ¹H-NMR Spectroscopy indicates an overall chiral shape for 1 , while for both 1 and 2 stratified structures are observed. Several attempts to resolve both dendrimers have not been successful so far, giving rise to a discussion on the degree of chirality in these dendrimers of nanometer dimensions.     

Plasmonic rod dimers as elementary planar chiral meta-atoms

We theoretically calculate the electromagnetic response of metallic rod dimers for the arbitrary planar arrangement of rods in the dimer. It is shown that dimers without an in-plane symmetry axis exhibit elliptical dichroism and act as "atoms" in planar chiral metamaterials. Because of a very simple geometry of the rod dimer, such planar metamaterials are much easier to fabricate than conventional split-ring or gammadion-type structures and lend themselves to a simple analytical treatment based on a coupled dipole model. Dependencies of the metamaterial's directional asymmetry on the dimer's geometry are established analytically and confirmed in numerical simulations.     

Optically active Babinet planar metamaterial film for terahertz polarization manipulation

A planar Babinet‐inverted dimer metamaterial possessing strong optical activity is proposed and characterized. An original fabrication method to produce large area (up to several cm²) freely suspended flexible metallic membranes is implemented to fabricate the metamaterial. Its optical properties are characterized by terahertz time‐domain spectroscopy, revealing anisotropic transmission with high optical activity. A simple coupled resonator model is applied to explain the principal optical features of the dimers, with predictive power of positions and number of resonances through a parametrical model. The model is validated for correct polarization‐dependent quantitative results on the optical activity in transmission spectra. The fabrication method presented in this work as well as the slit dimer design has great potential for exploitation in terahertz optics.     

Evolution of dislocations in perylene films with thickness and deposition rate

The growth of perylene films on an amorphous oxide bottom layer is investigated. The perylene films show clear spiral growth and formation of screw dislocations. As a function of deposition rate and film thickness the densities of screw dislocations, grains as well as the roughness and the lateral correlation length are determined from AFM images. The evolution of microstrain as calculated from an XRD peak profile analysis corresponds to the dislocation density. The simultaneous decrease of grain density and dislocation density with film thickness is explained by considering the overgrowth of grains due to loss of dislocations acting as growth spirals. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

     

Graphene-based nano-patch antenna for terahertz radiation

The scattering of terahertz radiation on a graphene-based nano-patch antenna is numerically analyzed. The extinction cross section of the nano-antenna supported by silicon and silicon dioxide substrates of different thickness are calculated. Scattering resonances in the terahertz band are identified as Fabry–Perot resonances of surface plasmon polaritons supported by the graphene film. A strong tunability of the antenna resonances via electrostatic bias is numerically demonstrated, opening perspectives to design tunable graphene-based nano-antennas. These antennas are envisaged to enable wireless communications at the nanoscale.     

Characterization of amorphous organic thin films, determination of precise model for spectroscopic ellipsometry measurements

The optical properties of tris(8-hydroxyquinoline) aluminum (Alq₃), N,N′-diphenyl-N,N′-bis(1-naphthyl)-1-1′biphenyl-4,4″diamine (α-NPD) and other amorphous organic materials for OLEDs application, e.g. 4,4-bis(2,2-diphenyl vinyl)-1,1-biphenyl (DPVBI) and Spiro-DPVBI have been studied by multi-angle spectroscopic ellipsometry (SE). The thin films of these materials have been deposited by organic vapor phase deposition (OVPD). The structural characterization has been performed using atomic force microscopy (AFM) and X-ray reflectometry (XRR). Comparison of the measurements using these different independent techniques enables the precise determination of the optical model for dielectric function of these thin films. The detail analyses on Alq₃ and α-NPD show that the Kim model with Gaussian broadening provides a significantly better fit to the ellipsometry data than the frequently used harmonic oscillator model. This conclusion is further proved by performing similar measurements on other amorphous organic samples for OLEDs application, e.g. DPVBI and Spiro-DPVBI. This result can be explained by the characteristic features of electronic states in organic molecules.     

KVI-AECR离子源的现状报告

In this paper the first results of the new ECR source at the KVI are presented.The source has been built following the design of Jyv(?)skyl(?) University,which is based on the AECR-U of LBNL.As the commissioning is going on,it seems that the extraction and analysing systems inherited from the old source are the limiting factors for the performance of the new source.Beam currents achieved with the source are at the moment a factor of 3 lower than the AECR source used at the Jyv(?)skyl(?) University.Further modifications to improve the source performance will be discussed.