Comparison of European hare (Lepus europaeus) population densities between an eco-farm and a conventional farm

European hare populations have not recovered from their shrinking over the past fifty years in Germany. Most hare habitas are agricultural regions which are farmed according to conventional farming standard. Organic farming is characterized by waiving of pesticides, growth regulators and arificial manure, by longer crop rotations and by wider seed seed-row spacings in some cereal crops. Thus, positive effects of eco-farming on hare populations in agricultural landscape may be assumed. However, eco-farming has not been studied in this regard up to now

Towards programmable friction: control of lubrication with ionic liquid mixtures by automated electrical regulation

For mechanical systems in relative motion it would be fascinating if a non-mechanical stimulus could be used to directly control friction conditions. Therefore, different combinations of lubricants and external triggers for tribological influence have already been investigated. We show that when two metallic friction partners are lubricated with ionic liquid mixtures (ILM), consisting of long-chain cation and two different high charge/mass ratio anion containing ILs, the application of an electric impulse induces a permanent change of the frictional response. Such mixtures are able to alter the coefficient of friction (COF) to a greater extent, more accurately and faster than the respective single-component ILs. This change in the frictional properties is presumably due to changes in the externally induced electrical polarization at the surface, which influences the molecular adsorption, the exchange of adsorbed ions and their molecular orientation. The correlation between surface charges and friction can be used to control friction. This is achieved by implementing an electric tribo-controller which can adjust preset friction values over time. Programming friction in this way is a first step towards tribosystems that automatically adapt to changing conditions

A Planar low-cost full-polymer Optical Humidity Sensor

AbstractWe present an all-polymer optical humidity sensor, based on a 1mm plastic optical fiber (POF) with a U-bend, cladded with poly(N,N-dimethylacrylamide) (PDMAA) in the sensing region. The cladding changes its scattering properties on absorption of environmental humidity, thus modulating the transmitted optical power through the sensor. We explain the working principle of the sensor and show experimental results regarding scattering behavior of the cladding material and sensitivity to sudden humidity changes. We also propose a planar layout suitable for application to a hot embossing or lamination process for large-scale fabrication

Manufacturing of embedded multimode waveguides by reactive lamination of cyclic olefin polymer and polymethylmethacrylate

We demonstrate the manufacturing of embedded multimode optical waveguides through linking of polymethylmethacrylate (PMMA) foils and cyclic olefin polymer (COP) filaments based on a lamination process. Since the two polymeric materials cannot be fused together through interdiffusion of polymer chains, we utilize a reactive lamination agent based on PMMA copolymers containing photoreactive 2-acryloyloxyanthraquinone units, which allows the creation of monolithic PMMA-COP substrates through C-H insertion reactions across the interface between the two materials. We elucidate the lamination process and evaluate the chemical link between filament and foils by carrying out extraction tests with a custom-built tensile testing machine. We also show attenuation measurements of the manufactured waveguides for different manufacturing parameters. The lamination process is in particular suited for large-scale and low-cost fabrication of board-level devices with optical waveguides or other micro-optical structures, e.g., optofluidic devices. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).DFG/SFB/TRR 12

The Structural and Mechanical Basis for Passive‐Hydraulic Pine Cone Actuation

The opening and closing of pine cones is based on the hygroscopic behavior of the individual seed scales around the cone axis, which bend passively in response to changes in environmental humidity. Although prior studies suggest a bilayer architecture consisting of lower actuating (swellable) sclereid and upper restrictive (non‐ or lesser swellable) sclerenchymatous fiber tissue layers to be the structural basis of this behavior, the exact mechanism of how humidity changes are translated into global movement are still unclear. Here, the mechanical and hydraulic properties of each structural component of the scale are investigated to get a holistic picture of their functional interplay. Measurements of the wetting behavior, water uptake, and mechanical measurements are used to analyze the influence of hydration on the different tissues of the cone scales. Furthermore, their dimensional changes during actuation are measured by comparative micro‐computed tomography (µ‐CT) investigations of dry and wet scales, which are corroborated and extended by 3D‐digital image correlation‐based displacement and strain analyses, biomechanical testing of actuation force, and finite element simulations. Altogether, a model allowing a detailed mechanistic understanding of pine cone actuation is developed, which is a prime concept generator for the development of biomimetic hygromorphic systems

Micro to nano: Surface size scale and superhydrophobicity

This work looks at the fundamental question of how the surface mobility of drops in the composite state is related to the size scale of the roughness features of the surface. To this end, relevant literature is first reviewed and the important terms are clarified. We then describe and discuss contact and roll-off angle measurements on a set of hydrophobicized silicon post surfaces for which all parameters except for the surface size scale were held constant. It was found that a critical transition from “sticky superhydrophobic” (composite state with large contact angle hysteresis) to “truly superhydrophobic” (composite state with low hysteresis) takes place as the size of the surface features reaches 1 μm

Scaling laws for the swelling of neutral and charged polymer brushes in good solvents

We compare the swelling of surface-attached neutral poly(4- vinylpyridine) (PVP) and charged poly(N-methyl-4- vinylpyridinium iodide) (MePVP) brushes under good solvent conditions using multiple-angle null ellipsometry. The polymer layers were prepared by the "grafting from" technique, where a low molecular mass initiator is self-assembled on the substrate and the polymer brush is grown in situ by free radical chain polymerization. The positively charged MePVP brush was generated from a neutral PVP brush by a polymer-analogous quaternization reaction. As predicted by mean-field theory, the thickness of the neutral swollen brush (PVP) increases with graft density whereas the thickness of the highly charged polyelectrolyte (MePVP) brush in pure water ("salt-free") is almost independent of the graft density