On the benefits of populations for noisy optimization

It is known that, in the absence of noise, no improvement in local performance can be gained from retaining candidate solutions other than the best one. Yet, it has been shown experimentally that, in the presence of noise, operating with a non-singular population of candidate solutions can have a marked and positive effect on the local performance of evolution strategies. So as to determine the reasons for the improved performance, we have studied the evolutionary dynamics of the (micro ,lambda)-ES in the presence of noise. Considering a simple, idealized environment, we have developed a moment-based approach that uses recent results involving concomitants of selected order statistics. This approach yields an intuitive explanation for the performance advantage of multi-parent strategies in the presence of noise. It is then shown that the idealized dynamic process considered does bear relevance to optimization problems in high-dimensional search spaces.     

Interaction of a stiffener with a crack in an anisotropic sheet

In this paper, the method of partitioning plan in plane problems of elasticity is combined with the generalized variational method and the stiffened problem for an anisotropic sheet with a crack is studied in detail. It is shown that the stiffening effect is rather sensitive to the ratio of β₂²/β₁² and the stiffness is less effective when the ratio increases.     

Photochemie von Aminoketonen. XV. Photochemische Acylgruppenwanderung in N-Tosyl-β-aminovinyl-phenyl-ketonen

Photochemistry of Aminoketones. XV. Photochemical Acyl Migration in N-Tosyl-β-aminovinyl-phenyl-ketones N-Tosyl-β-aminovinyl-phenyl-ketones 1a – i are prepared in good yields from β-chlorovinyl- phenyl-ketones by reaction with the sodium salts of tosyl amides in dry DMF at room temperature. In contrast to the relatively photostable N, N-dialkyl-β-aminovinyl-aryl-ketones the electronically excited 1 give irreversible chemical reactions within a few minutes. Among other not identified photoproducts the α-tosyl-β-aminovinyl-phenyl-ketones 2 were found. From the experimental results it is evident that the migration of the tosyl group prefers a radical-type two step reaction through an intermediate X / Y of a (1,5)-N→O-tosylrearrangement.     

Spektroskopische Untersuchungen zur Struktur von Silicium-Schwefel-Verbindungen mit mindestens einer Si-S-Bindung – ein Überblick

Spectroscopic Properties of Silicon-Sulfur-Compounds with at least one Si-S-bound – A Review Bond lenghts, bond angles and ²⁹Si-NMR data are tabulated. If possible this parameters are discussed on the bases of covalent radii, electronegativities and other general properties. Qualitative estimations of ²⁹Si-NMR shifts as a function of series of compounds, as a function of ring-size and by comparison with homologous Si-O compounds are suggested. Observations of contrarotating effects of ²⁹Si-NMR shifts in organosubstituted Si-O and Si-S molecules as compared to their hydrogensubstituted counterparts are discussed briefly.