Anion recognition by alpha-arylazo-N-confused calix[4]pyrroles

The first example of substitution reaction in the free alpha-position of N-confused calix[4]pyrroles is reported: azo-coupling with various arenediazonium salts. The obtained azocompounds were used for studies of their anion-binding properties by UV-Vis spectroscopy.     

Rod-climbing effect in Newtonian fluids

When a rotating rod is brought into a polymer melt or concentrated polymer solution, the meniscus climbs the rod. This spectacular rod climbing is due to the normal stresses present in the polymer fluid and is thus a purely non-Newtonian effect. A similar rod climbing of an interface between two fluids has therefore been taken as a signature that one of the fluids exhibits normal stress effects. We show here, however, that the effect can occur with simple Newtonian fluids: it occurs when a Taylor-Couette instability happens in the less viscous of the two liquids but not in the more viscous one.     

The German bakery waste incident; use of a combined approach of screening and confirmation for dioxins in feed and food

During the last six years several incidents have occurred with dioxins in feed, stressing the need for rapid screening methods for these compounds. The most recent incident was the contamination of bakery waste used for animal feed due to the use of waste wood for drying of the material. In addition to Germany, the material was also shipped to the Netherlands. Levels up to 12 ng TEQ/kg have been detected, being about 15 times over the current limit of 0.75 ng TEQ/kg. In the Netherlands a combined strategy of screening with the CALUX-bioassay and the HRGC/HRMS confirmatory method was used to rapidly control the incident. Pigs were contaminated by the incident but only to a very limited extent. Despite the rather low limits for pig meat, the CALUX bioassay showed excellent performance, once again confirming the value of this assay.     

Threshold vibrational excitation of CO2 by slow electrons

Threshold structures, reminiscent of those seen in the polar hydrogen halides, have recently been observed in the cross sections for electron impact excitation of certain vibrational levels of the nonpolar CO2 molecule. These structures occur at energies outside the range where shape resonances dominate the dynamics. We propose a virtual state model that describes the multidimensional nuclear dynamics during the collision and explains quantitatively the selectivity observed in the excitation of the Fermi dyad, as well as the pattern of threshold peaks and oscillations seen in the upper levels of the higher polyads.     

Nonlinear signal-processing model for signal generation in multilevel two-dimensional optical storage

A two-dimensional optical storage (TwoDOS) format with binary modulation is being developed in which channel bits are arranged on a two-dimensional hexagonal lattice [W. M. J. Coene, in Optical Data Storage, Vol. 88 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington, D.C., 2003), pp. 90-92]. The aim is to increase the capacity by a factor of 2 and the data rate by a factor of 10 over third-generation Blu-ray Disc technology. Following a route similar to that used in one-dimensional conventional optical storage [Jpn. J. Appl. Phys. 42, 1074 (2003)] could lead to a further increase in capacity by the addition of another dimension to writing data, such as the use of multiple levels instead of the two levels (pit and land) used in the binary TwoDOS disk format. We present a nonlinear signal-processing model for signal waveform generation as a function of the M-ary channel symbols, as well as simulated signal readouts for multilevel TwoDOS.     

Experimental implementation of an adiabatic quantum optimization algorithm

We report the realization of a nuclear magnetic resonance computer with three quantum bits that simulates an adiabatic quantum optimization algorithm. Adiabatic quantum algorithms offer new insight into how quantum resources can be used to solve hard problems. This experiment uses a particularly well-suited three quantum bit molecule and was made possible by introducing a technique that encodes general instances of the given optimization problem into an easily applicable Hamiltonian. Our results indicate an optimal run time of the adiabatic algorithm that agrees well with the prediction of a simple decoherence model.     

The Structure of the (Outer) Automorphism Group of a Bieberbach Group

Referring to Tits alternative, we develop a necessary and sufficient condition to decide whether the normalizer of a finite group of integral matrices is polycyclic-by-finite or is containing a non-Abelian free group. This result is of fundamental importance to conclude whether the (outer) automorphism group of a Bieberbach group is polycyclic-by-finite or has a non-cyclic free subgroup.