Homogeneity analysis of square meter-sized electrodes for PEM electrolysis and PEM fuel cells

Electrodes for polymer electrolyte membrane electrolyzers and fuel cells are manufactured by coating a catalyst dispersion, consisting of precious metal, ionomer and solvents, onto a substrate that is subsequently dried. One target of current research is to produce square meter-sized electrodes, but so far the homogeneity that can be achieved in this scaling is unclear. To quantify the achievable homogeneity of an electrode, manufactured by means of slot die coating in a roll-to-roll pilot plant, this study focuses first on the selection of an appropriate substrate by investigating thickness, basis weight and surface free energy distribution at the square meter scale. Afterward, a dispersion is coated on the selected substrate, dried and investigated with respect to thickness and basis weight distribution. Among the investigated substrates, Kapton has the smallest scatter in terms of thickness and basis weight. The subsequent coating results in a precious metal loading of 1.10 mg cm\(^{-2}\), with a scattering of 5.5% that can be further reduced to 4.5% when edge effects can be prevented. These results are now available for further research in which it is necessary to investigate whether or not these fluctuations affect the achievable electrochemical efficiencies of electrodes.     

Influence of PCE kind and dosage on ettringite crystallization performed under terrestrial and microgravity conditions

Early ettringite crystallization in the presence of 2 chemically different polycarboxylate superplasticizers was studied by hydrating a commercial portland cement (CEM I 52.5 N) for 10 seconds. It was found that the presence of polycarboxylate superplasticizers leads to ettringite crystals which are longer, yet slimmer (higher aspect ratio), compared with the crystals obtained from neat cement paste. This finding suggests that the polycarboxylate (PCE) polymers predominantly adsorb on the lateral faces of the hexagonal‐prismatic crystals of ettringite. For the methacrylate‐based PCE, this effect increases with increasing superplasticizer dosage, whereas for the IPEG‐PCE, the effect achieved at a very low dosage (0.05%) is not altered when dosage increases. The behaviors of both PCE polymers can be explained by their different adsorption behavior, whereby the IPEG‐PCE reached the saturated adsorbed amount at much lower dosage than the MPEG‐PCE. Microgravity only has a minor effect on the growth of ettringite. There, generally smaller crystals are observed.     

Uncertainty‐conscious methodology for process performance assessment in biopharmaceutical drug product manufacturing

This work presents an uncertainty‐conscious methodology for the assessment of process performance—for example, run time—in the manufacturing of biopharmaceutical drug products. The methodology is presented as an activity model using the type 0 integrated definition (IDEF0) functional modeling method, which systematically interconnects information, tools, and activities. In executing the methodology, a hybrid stochastic–deterministic model that can reflect operational uncertainty in the assessment result is developed using Monte Carlo simulation. This model is used in a stochastic global sensitivity analysis to identify tasks that had large impacts on process performance under the existing operational uncertainty. Other factors are considered, such as the feasibility of process modification based on Good Manufacturing Practice, and tasks to be improved is identified as the overall output. In a case study on cleaning and sterilization processes, suggestions were produced that could reduce the mean total run time of the processes by up to 40%. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1272–1284, 2018     

ω‐Phthalimidoalkyl Aryl Ureas as Potent and Selective Inhibitors of Cholesterol Esterase

Cholesterol esterase (CEase), a serine hydrolase thought to be involved in atherogenesis and thus coronary heart disease, is considered as a target for inhibitor development. We investigated recombinant human and murine CEases with a new fluorometric assay in a structure–activity relationship study of a small library of ω‐phthalimidoalkyl aryl ureas. The urea motif with an attached 3,5‐bis(trifluoromethyl)phenyl group and the aromatic character of the ω‐phthalimide residue were most important for inhibitory activity. In addition, an alkyl chain composed of three or four methylene groups, connecting the urea and phthalimide moieties, was found to be an optimal spacer for inhibitors. The so‐optimized compounds 2 [1‐(3,5‐bis(trifluoromethyl)phenyl)‐3‐(3‐(1,3‐dioxoisoindolin‐2‐yl)propyl)urea] and 21 [1‐(3,5‐bis(trifluoromethyl)phenyl)‐3‐(4‐(1,3‐dioxoisoindolin‐2‐yl)butyl)urea] exhibited dissociation constants (K_i) of 1–19 μm on the two CEases and showed either a competitive ( 2 on the human enzyme and 21 on the murine enzyme) or a noncompetitive mode of inhibition. Two related serine hydrolases—monoacylglycerol lipase and fatty acid amide hydrolase—were inhibited by ω‐phthalimidoalkyl aryl ureas to a lesser extent.     

High-frequency electromagnetic dynamics properties of THP1 cells using scanning microwave microscopy

Microwave measurements combined with scanning probe microscopy is a novel tool to explore high-localized mechanical and electrical properties of biological species. Complex permittivities and permeabilities are detected through slight variations of an incident microwave signal. Here we report the high-frequency dependence of the electromagnetic dynamic characteristics in human monocytic leukemia cells (THP1) through local measurements by scanning microwave microscopy (SMM). The amplitude and phase images were shown to depend on the applied resonance frequency. While the amplitude yields information about the resistivity determined by the water and the ionic strength, the phase information reflects the dielectric losses arising from the fluid density.     

Recent applications of particle image velocimetry in aerodynamic research

Particle image velocimetry (PIV) is increasingly used to investigate unsteady velocity fields instantaneously. For the first time the PIV technique allows the recording of a complete velocity field in a plane of the flow within a few microseconds. The PIV technique thereby provides information about unsteady flow fields which is difficult to obtain with other experimental techniques. The short acquisition times and fast availability of data reduce the operational time, and hence cost, in large scale wind tunnels and test facilities.

At DLR a variety of PIV systems for use in industrial wind tunnels has been developed in the past decade. The flexibility of these portable systems is illustrated by presenting several results of recent PIV applications. More recently the original photographic means of PIV image recording has been partially replaced by high resolution electronic imaging which can provide PIV data nearly on-line. Images recorded by either system use the same multiple-pass, cross-correlation analysis software, whose algorithms are briefly described. Several examples of actual applications are given: the flow issuing from a jet nozzle was imaged by a specially developed high-speed video camera at close proximity. A high resolution dual-frame digital camera was applied in the study of helicopter rotor aerodynamics and wake vortex measurements of an airplane model. Further, large image sequences exceeding 100 PIV recordings provided detailed information on the structure of a turbulent boundary layer.     

Supporting Cooperation through Customisation: The Tviews Approach

User interfaces for groupware systems rarely reflectthe different requirements for support of theirend-users. Here we present an approach to designingmulti-user interfaces for cooperative systems whichbuilds on previous work from the HCI community in thearea of end-user customisation. Using this approach wehave developed an approach and a system prototype basedon tailorable views, or Tviews, which allows end-usersengaged in group working to configure theircooperative system interfaces to support theirdifferent tasks, preferences and levels of expertise.Tviews are user interface components which can bedragged and dropped over representations ofapplication objects to customise presentation,interaction and event updating properties, and canthemselves be tailored using high-level, incrementalcustomisation techniques. We discuss the implicationsof this work for CSCW system development by referenceto studies of work carried out by the CSCW communitywhich point to a need for more flexible and tailorablesystem interfaces.     

Modelling of Complete Robot Dynamics Based on a Multi-Dimensional, RBF-like Neural Architecture

A neural network based identification approach of manipulator dynamics is presented. For a structured modelling, RBF-like static neural networks are used in order to represent and adapt all model parameters with their non-linear dependences on the joint positions. The neural architecture is hierarchically organised to reach optimal adjustment to structural apriori-knowledge about the identification problem. The model structure is substantially simplified by general system analysis independent of robot type. But also a lot of specific features of the utilised experimental robot are taken into account.A fixed, grid based neuron placement together with application of B-spline polynomial basis functions is utilised favourably for a very effective recursive implementation of the neural architecture. Thus, an online identification of a dynamic model is submitted for a complete 6 joint industrial robot.     

Tuning Fermi Levels in Intrinsic Antiferromagnetic Topological Insulators MnBi2Te4 and MnBi4Te7 by Defect Engineering and Chemical Doping

MnBi₂Te₄ and MnBi₄Te₇ are intrinsic antiferromagnetic topological insulators, offering a promising materials platform for realizing exotic topological quantum states. However, high densities of intrinsic defects in these materials not only cause bulk metallic conductivity, preventing the measurement of quantum transport in surface states, but may also affect magnetism and topological properties. In this paper, systematic density functional theory calculations reveal specific material chemistry and growth conditions that determine the defect formation and dopant incorporation in MnBi₂Te₄ and MnBi₄Te₇. The large strain induced by the internal heterostructure promotes the formation of large-size-mismatched antisite defects and substitutional dopants. The results here show that the abundance of antisite defects is responsible for the observed n-type metallic conductivity. A Te-rich growth condition is predicted to reduce the bulk free electron density, which is confirmed by experimental synthesis and transport measurements in MnBi₂Te₄. Furthermore, Na doping is proposed to be an effective acceptor dopant to pin the Fermi level within the bulk band gap to enable the observation of surface quantum transport. The defect engineering and doping strategies proposed here should stimulate further studies for improving synthesis and for manipulating magnetic and topological properties in MnBi₂Te₄, MnBi₄Te₇, and related magnetic topological insulators.