A bit-level systolic array for digital contour smoothing

Linear operators for digital contour smoothing are described. These operators are defined by circulant Toeplitz matrices and allow to smooth digital contours in the least-squares sense. They minimize the undersampling, digitizing and quantizing error and allow to calculate invariants, such as curvature, which are not possible to calculate without smoothing. A bit-level systolic array which is capable of realizing the proposed operator is described. This array is easy to implement in VLSI, because the array cells involved are very simple. Furthermore, the array is completely pipelined on the bit-level, so that it operates with a high clock frequency achieving very high throughputs.     

Phase transitions and thermodynamic properties of dense assemblies of truncated nanocubes and cuboctahedra

Inspired by recent advances on the self-assembly of non-spherical nanoparticles, Monte Carlo simulations of the packing and thermodynamic properties of truncated nanocubes and cuboctahedra have been performed. The ergodicity problem was overcome by a modified Wang-Landau entropic sampling algorithm and equilibrium structural and thermodynamic properties were computed over a wide density range for both non-interacting and interacting particles. We found a structural transition from a simple cubic to a rhombohedral order when the degree of truncation exceeds a value of 0.9.     

Kondensation von Xylose mit Methylammoniumacetat

Zusammenfassung Erhitzt man Xylose mit Methylammoniumacetat in wäßriger Lösung, so entsteht ein komplexes Reaktionsgemisch, das niedermolekulare und höhermolekulare Verbindungen enthalt. Nach Oxydation mit Perjodat sind 1-Methyl-2,3,4- and 1-Methyl-2,3,5-tris-formylpyrrol (4 und 6) isolierbar. Zur Erklärung der Bildung wird angenommen, daß 2 Moleküle des Zuckers mit einem Molekül Methylamin kondensieren.

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Condensation of xylose with methylainmoniumacetate 6. Studies on Maillard reaction

Summary When xylose is heated with methylammoniumacetate in an aqueous solution, a complex mixture containing low molecular and high molecular compounds is formed. After oxidation with periodate, 1-methyl-2,3,4- and 1-methyl-2,3,5-tris-formyl-pyrrol (4 and 6) could be isolated. The formation is probably due to the condensation of two molecules of sugar and one molecule of methylamine.

     

Replication of single macromolecules with graphene

The electronic properties of graphenes depend sensitively on their deformation, and therefore strain engineered graphene electronics is envisioned. In order to deform graphenes locally, we have mechanically exfoliated single and few layer graphenes onto atomically flat mica surfaces covered with isolated double stranded plasmid DNA rings. Using scanning force microscopy in both contact and intermittent contact modes, we find that the graphenes replicate the topography of the underlying DNA with high precision. The availability of macromolecules of different topologies, e.g., programmable DNA patterns, render this approach promising for new graphene based device designs. On the other hand, the encapsulation of single macromolecules offers new prospects for analytical scanning probe microscopy techniques.     

Scattering of Electromagnetic Waves by a Semi-Infinite Carbon Nanotube

Scattering of electromagnetic cylindrical waves by an isolated, semi-infinite, open-ended, single-shell, zigzag carbon nanotube (CN) is considered in the optical regime. The CN is modeled as a smooth homogeneous cylindrical surface with impedance boundary conditions known from quantum-mechanical transport theory. An exact solution of the diffraction problem is obtained by the Wiener-Hopf technique. The differences between the scattering responses of metallic and semiconducting CNs are discussed.     

Data scattering in scanning tunneling spectroscopy

We investigated the scattering of current-voltage data obtained with scanning tunneling spectroscopy (STS) at room temperature at a solid-liquid interface on highly oriented pyrolytic graphite (HOPG) and in ultrahigh vacuum on HOPG and Au(111). For both experimental conditions, the data scattering can be described by a lognormal function for a moderate number of subsequent measurements. The lognormal distribution of the current can be explained by a normal distribution of the tip-surface distance. We give a simple empirical rule for STS data sorting.     

An apparatus for in situ spectroscopy of radiation damage of polymers by bombardment with high-energy heavy ions

A new target station providing Fourier transform infrared (FT-IR) spectroscopy and residual gas analysis (RGA) for in situ observation of ion-induced changes in polymers has been installed at the GSI Helmholtz Centre for Heavy Ion Research. The installations as well as first in situ measurements at room temperature are presented here. A foil of polyimide Kapton HN(?) was irradiated with 1.1 GeV Au ions. During irradiation several in situ FT-IR spectra were recorded. Simultaneously outgassing degradation products were detected with the RGA. In the IR spectra nearly all bands decrease due to the degradation of the molecular structure. In the region from 3000 to 2700 cm(-1) vibration bands of saturated hydrocarbons not reported in literature so far became visible. The outgassing experiments show a mixture of C(2)H(4), CO, and N(2) as the main outgassing components of polyimide. The ability to combine both analytical methods and the opportunity to measure a whole fluence series within a single experiment show the efficiency of the new setup.