No abstract

Sticking together: The pore entrances of dye‐loaded green or red zeolite L crystals can be site‐specifically modified with either alkoxyamines or nitroxide radicals. Mild radical nitroxide exchange reactions of alkoxyamine‐terminated “green” zeolite crystals with nitroxide‐terminated “red” crystals leads to highly regular crystal chains that contain up to 15 covalently connected crystals with strictly alternating colors.

Systematic studies are presented demonstrating the complementarity of directed ortho metalation (DoM) and Ir-catalyzed strategies for the provision of borylated aromatics and their subsequent Suzuki-Miyaura coupling reactions. A new concept, the use of the TMS group, readily introduced by DoM, as a latent regiodirective moiety to overcome the otherwise problematic production of isomeric borylated product mixtures is presented. Additional electrophile-induced ipso-deborylation and DoM reactions of the Bpin products are described.

This article reports results of a theoretical analysis as well as a numerical study investigating the occurrence of flow instabilities in porous materials applied as volumetric solar receivers. After a short introduction into the technology of volumetric solar receivers, which are aimed to supply heat for a steam turbine process to generate electricity, the general requirements of materials applied as solar volumetric receivers are reviewed. Finally, the main methods and results of the two studies are reported. In the theoretical analysis it is shown that heat conductivity as well as permeability properties of the porous materials have significant influence on the probability of the occurrence of flow instabilities. The numerical study has been performed to investigate the occurrence of unstable flow in heated ceramic foam materials. In the simulations a constant heat flow of radiation, that is absorbed in a defined volume, and constant permeability coefficients are assumed. Boundary conditions similar to those of the 10 MW Solucar Solar project have been chosen. In a three dimensional, heterogeneous two phase heat transfer model it was possible to simulate local overheating of the porous structure. The parameters heat conductivity, turbulent permeability coefficient and radial dispersion coefficient have been varied systematically. Consequently, for a heat flux density of 1 MW/m 2 a parameter chart could be generated, showing the possible occurrence of ''unstable'' or ''stable'' thermal and fluid mechanical behaviour. These numerical results are beneficial for the design of optimized materials for volumetric receivers.

The combination of micro synthetic structures with bacterial flagella motors represents an actual trend for the construction of self-propelled micro-robots. The development of methods for fabrication of these bacteria-based robots is a first crucial step towards the realization of functional miniature and autonomous moving robots. We present a novel scheme based on optical trapping to fabricate living micro-robots. By using holographic optical tweezers that allow three-dimensional manipulation in real time, we are able to arrange the building blocks that constitute the micro-robot in a defined way. We demonstrate exemplarily that our method enables the controlled assembly of living micro-robots consisting of a rod-shaped prokaryotic bacterium and a single elongated zeolite L crystal, which are used as model of the biological and abiotic components, respectively. We present different proof-of-principle approaches for the site-selective attachment of the bacteria on the particle surface. The propulsion of the optically assembled micro-robot demonstrates the potential of the proposed method as a powerful strategy for the fabrication of bio-hybrid micro-robots.