Biosupramolecular nanowires from chlorophyll dyes with exceptional charge-transport properties

Conductive tubes: Self-assembled nanotubes of a bacteriochlorophyll derivative are reminiscent of natural chlorosomal light-harvesting assemblies. After deposition on a substrate that consists of a non-conductive silicon oxide surface (see picture, brown) and contacting the chlorin nanowires to a conductive polymer (yellow), they show exceptional charge-transport properties.     

Novel approach to biscarbazole alkaloids via Ullmann coupling - synthesis of murrastifoline-A and bismurrayafoline-A

Unprecedented Ullmann couplings of murrayafoline-A with either 6-bromo- or 4-bromocarbazole derivatives provide highly efficient synthetic routes to the biscarbazole alkaloids murrastifoline-A (6 steps, 66% overall yield) and bismurrayafoline-A (6 steps, 28% overall yield).     

Trace metal impurities in catalysis

Metal-catalysed transformations are a powerful tool in organic chemistry and the enormous progress, which has been made in the last few decades, was one more time honoured by the Nobel Prize in Chemistry in 2010. Many metal-containing compounds have been applied in carbon-carbon and carbon-heteroatom bond formations. However, not every component originally claimed as catalyst turned out to be the active ingredient in the end. Sometimes trace metal impurities were the actual catalytic species. In this tutorial review, we will highlight recent findings in transition metal-catalysed cross-coupling reactions and detail several reports from the past, which illustrate that "trace metal catalysis" is not a newly discovered phenomenon.     

Optimal frequencies for magnetic acceleration of cytochrome oxidase and Na,K-ATPase reactions

Low frequency magnetic fields increase the activity of the membrane enzymes, Na,K-ATPase and cytochrome oxidase, and the increased activity varies with frequency. Optimal frequencies for increases in the reaction rate constant of cytochrome oxidase and in the rate of splitting of ATP by Na,K-ATPase differ by an order of magnitude, and are in the ranges of the turnover numbers of the respective enzyme reactions. The two frequency dependence curves are similar in that the slope of the low frequency portion is about 10 times greater than the slope of the high frequency portion. The greater slope indicates greater ability to adjust quickly in the low frequency range, which may be significant for optimal biological control of activity.     

Pulsed Electron Spin Resonance Ex Situ Probe for Tooth Biodosimetry

An electron spin resonance (ESR) probe that includes a static field source and a microwave resonator for the measurement of paramagnetic defects in tooth enamel is presented. Such defects are known to be a good marker for quantifying the amount of ionizing radiation dose absorbed in the tooth. The probe can measure the tooth when it is positioned just above its outer surface, i.e., in ex situ geometry. It is operated in pulsed mode at a frequency of ~6.2 GHz that corresponds to the magnitude of the static magnetic field of its permanent magnet. A detailed design of the probe is provided, together with its specifications in terms of measurement volume and signal-to-noise-ratio for a typical sample. Experimental results that verify its sensitivity and capability to measure gamma-irradiated teeth are provided. The current minimal detected signal by the probe corresponds to a radiation dose of ~4 Gy.     

Optically induced mode conversion in graded-index fibers using ultra-short laser pulses

We propose the use of graded-index few-mode fibers for mode conversion by long-period gratings (LPG) transiently written by ultrashort laser pulses using the optical Kerr effect. The mode interaction is studied by numerically solving the multi-mode coupled nonlinear Schrödinger equations. We present highly efficient conversion of the LP₀₁- into the LP₁₁-mode preserving the pulse shape in contrast to previous results in step-index fibers. Furthermore, mode conversion using different wavelengths for inducing and probing the LPG is shown. Due to the flat phase-matching curve of the examined modes in the graded-index fiber, mode conversion can be observed for probe center wavelengths of 1,100 nm up to 1,800 nm with a write beam centered around 1,030 nm. Therefore, a complete separation of the probe from the write beam should be possible as well as the application of optically induced guided-mode conversion for all-optical modulation across a broad wavelength range.     

Optimal Actuator Placement for Dynamical Systems

Vibrations occur in many industrial areas and produce undesirable side effects. To avoid respectively suppress these effects actuators can be attached to the structure. Actuators can transfer forces into the structure, which can be used to control the system behavior of the structure in order to achieve, for example, vibration absorption, noise reduction and/or exact positioning. The appropriate positioning of actuators is of significant importance for the controllability of the structure. We present a method for determining the optimal actuator placement. We consider applications, where the dynamics of a system can be described by a finite dimensional, controllable and observable state-space model. The concept of controllability by Kálmán forms the basis for the definition of controllability measures. In this context, the controllability gramian plays an important role. In our approach actuators are placed in such a way that the selected controllability measure becomes maximal. This leads to an optimization problem with binary and continuous variables and linear matrix inequalities. The numerical results show the optimal actuator placement for a two dimensional flexible clamped plate. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)