Laser spectroscopy for QED tests in highly charged ions

An overview on laser spectroscopic work on highly charged ions (HCI) currently performed or in preparation at GSI is given. This includes laser spectroscopy on HCI in ion traps at the HITRAP facility and at the experimental storage ring (ESR).     

Determination of the effective elasticity tensor of a folded sandwich core

This document describes the homogenization of a folded sandwich core. By using a numerical homogenization concept the components of the elasticity tensor of the foldcore continuum are determined. The foldcore exhibits an effective orthotropic behaviour with the particularity that it can be auxetic. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural elucidation of biologically active neomycin N‐octyl derivatives in a regioisomeric mixture by means of liquid chromatography/ion trap time‐of‐flight mass spectrometry

Structural elucidation of six regioisomers of mono‐N‐octyl derivatized neomycin is achieved using MSⁿ (up to n = 4) on an ion trap time‐of‐flight (IT‐TOF) instrument equipped with electrospray ionization. The mixture of six derivatized neomycin analogues was generated by reductive amination in a shotgun synthetic approach. In parallel to the liquid chromatography/mass spectrometry (LC/MS) detection, the antibacterial activity of the neomycin regioisomers was tested by post‐column addition of buffer and bacterial inocula, subsequent microfractionation of the resulting mixture, incubation, and finally a chemiluminescence‐based bioactivity measurement based on the production of bacterial ATP. The MS‐based high‐resolution screening approach described can be applied in medicinal chemistry to help in designing and producing new antibiotic substances, which is particularly challenging due to the high functionality of most antibiotic substances, therefore requiring advanced (hyphenated) separation and detection techniques for compound mixtures. Copyright © 2010 John Wiley & Sons, Ltd.     

Neue Wege zu Polysilanen

Summary Disilane derivatives undergo disproportionation reactions to polysilanes. Investigated were 1,2-dimethyldisilane and 1,2-dimethyltetrachlorodisilane with catalysts like NH₄Cl, AgCN, and Nacyanamide. In case of 1,2-dimethyldisilane, with more than catalytic amounts of NH₄Cl, a nitrogen containing polysilane is formed. Two new compoundsMeSiH(NCO)₂ andMe ₂Si₂(NCO)₄ were synthesized and characterized. The last one leads to a polymer at heating. Additionally an electrochemical formation of polydimethylsilane is described.

     

Error linear complexity measures for multisequences

Complexity measures for sequences over finite fields, such as the linear complexity and the k-error linear complexity, play an important role in cryptology. Recent developments in stream ciphers point towards an interest in word-based stream ciphers, which require the study of the complexity of multisequences. We introduce various options for error linear complexity measures for multisequences. For finite multisequences as well as for periodic multisequences with prime period, we present formulas for the number of multisequences with given error linear complexity for several cases, and we present lower bounds for the expected error linear complexity.     

Some Notes on the Linear Complexity of Sidel’nikov-Lempel-Cohn-Eastman Sequences

We continue the study of the linear complexity of binary sequences, independently introduced by Sidel’nikov and Lempel, Cohn, and Eastman. These investigations were originated by Helleseth and Yang and extended by Kyureghyan and Pott. We determine the exact linear complexity of several families of these sequences using well-known results on cyclotomic numbers. Moreover, we prove a general lower bound on the linear complexity profile for all of these sequences.