An analytical solution for geotextile-wrapped soil based on insights from DEM analysis

This paper presents a novel analytical solution for geotextile-wrapped soil based on a comprehensive numerical analysis conducted using the discrete element method (DEM). By examining the soil–geotextile interface friction, principal stress distribution, and stress–strain relations of the constituent soil and geotextile in the DEM analysis, a complete picture of the mechanical characterization of geotextile-wrapped soil under uniaxial compression is first provided. With these new insights, key assumptions are verified and developed for the proposed analytical solution. In the DEM analysis, a near-failure state line that predicts stress ratios relative to the maximums at failure with respect to deviatoric strain is uniquely identified; dilation rates are found to be related to stress ratios via a single linear correlation regardless of the tensile stiffness of the geotextile. From these new findings, the assumptions on the stress-state evolution and the stress–dilatancy relation are developed accordingly, and the wrapped granular soil can therefore be modeled as a Mohr–Coulomb elastoplastic solid with evolving stress ratio and dilation rate. The development of the proposed analytical model also demonstrates an innovative approach to take advantage of multiscale insights for the analytical modeling of complex geomaterials. The analytical model is validated with the DEM simulation results of geotextile-wrapped soil under uniaxial compression, considering a wide range of geotextile tensile stiffnesses. To further examine the predictive capacity of the analytical model, the stress–strain response under triaxial compression conditions is solved analytically, taking both different confining pressures and geotextile tensile stiffnesses into account. Good agreement is obtained between the analytical and DEM solutions, which suggests that the key assumptions developed in the uniaxial compression conditions also remain valid for triaxial compression conditions.     

Design of an Ultrafast G Protein Switch Based on a Mouse Melanopsin Variant

The primary goal of optogenetics is the light-controlled noninvasive and specific manipulation of various cellular processes. Herein, we present a hybrid strategy for targeted protein engineering combining computational techniques with electrophysiological and UV/visible spectroscopic experiments. We validated our concept for channelrhodopsin-2 and applied it to modify the less-well-studied vertebrate opsin melanopsin. Melanopsin is a promising optogenetic tool that functions as a selective molecular light switch for G protein-coupled receptor pathways. Thus, we constructed a model of the melanopsin G_q protein complex and predicted an absorption maximum shift of the Y211F variant. This variant displays a narrow blue-shifted action spectrum and twofold faster deactivation kinetics compared to wild-type melanopsin on G protein-coupled inward rectifying K⁺ (GIRK) channels in HEK293 cells. Furthermore, we verified the in vivo activity and optogenetic potential for the variant in mice. Thus, we propose that our developed concept will be generally applicable to designing optogenetic tools.     

Assessment of noise attenuating powertrain components

Forschung im Ingenieurwesen - Wind turbine noise used to be dominated by aerodynamic blade noise, effectively masking mechanical noise, originating from the drivetrain. Successful blade noise...     

Characterizing cerebral oxygen metabolism employing oxygen-17 MRI/MRS at high fields

This article provides a comprehensive overview of oxygen (¹⁷O) magnetic resonance spectroscopy and imaging, including the advantages and challenges offered by the different methods developed thus far. The physiological role and relevance of oxygen, and its participation in aerobic metabolism, are addressed to emphasize the importance of the investigations and the efforts related to these developments. Furthermore, a number of methods employed in the determination of the cerebral metabolic rate of oxygen in neural cells will be presented, focusing primarily on methodologies enabling absolute quantification.     

Simulating the emergence of norms in different scenarios

This paper deals with EMIL-S, a software tool box which was designed during the EMIL project for the simulation of processes during which norms emerged in an agent society. This tool box implements the cognitive architecture of normative agents which was designed during the EMIL project which is also discussed in other papers in this issue. This implementation is described in necessary detail, and two examples of its application to several different scenarios are given, namely a scenario in which persons involved in micro finance are simulated and learn how to sanction free riders and how to learn from these sanctions, and a scenario in which simulated persons move through a simulated airport where they more often than not have to wait in queues and learn how to behave properly in queues.     

Manufacturing of integrative membrane carriers by novel powder injection molding

Although offering distinctive economic benefits the mass fabrication of carrier devices incorporating membranes as quasi-monolithic devices reveals strong technological challenges. Powder injection molding would be an effective process for this purpose, however, manufacturing parts of considerable wall thickness variations and to meet strong precision demands remains problematic. To evaluate novel ways of process conducts as well as to determine influencing parameters a demonstrator design had been developed which enabled the generation of thin membranes by controlled piston movement. Suitable lay-out of the runner system had been determined with the help of simulation calculations. The combined injection + embossing process conduct enabled to reduce minimum membrane thickness to about a half. Investigation of parameter influence showed that embossing force and gap width before injection have an ameliorative effect on membrane quality whereas the embossing delay time had no significant impact.