Effective boundary conditions for syncytial tissues

This study derives effective boundary conditions for potentials and currents on the interface between syncytial tissue and a surrounding volume conductor. The derivation is based on an idealized representation of the syncytium as a network of interconnected cells arranged periodically in space. The microscopic model of an interface assumes that the extracellular fluid is in direct contact with the outside volume conductor and that the inside of the cells is separated from the outside by the membrane. From this microscopic model, a homogenization process and boundary layer analysis derive effective boundary conditions applicable to macroscopic volume-averaged potentials. These effective boundary conditions call for the extracellular potential and current density to be continuous with the potential and current density in the volume conductor, and for the intracellular current to vanish. Hence, the long-debated appropriate boundary conditions for the bidomain model are established     

Determination of dynamic contact angles within microfluidic devices

Here, we report a single-point detection method for the determination of dynamic surface conditions inside microfluidic channels. The proposed method is based on monitoring fluorescence amplitude as a function of the convolution of a laser beam with segmented flow consisting of two immiscible liquids, one containing fluorescent dye. The fluorescence amplitude is determined by the flow rate and the droplet shape, which is affected by the channel surface properties. We modeled the interaction of a droplet and a laser beam via computer-aided design software, using the laser beam location in relation to the droplet shape as a parameter. The method was applied to fused silica capillaries with both unmodified and modified surfaces, with segmented flow exhibiting water contact angles of ≈?30° and ≈?100°, respectively. The method allows discrimination between hydrophillic and hydrophobic surfaces, as well as the quality of the treatment. The results were verified using fluorescence imaging of the droplets via a stroboscopic technique. We also applied this method to the analysis of microfabricated channels with non-circular cross sections. We demonstrated that the technique enables the determination of the hydrophobicity of channel surfaces, a crucial property required for the generation of segmented flow or emulsions for applications such as digital PCR.     

Sloughing and limited substrate conditions trigger filamentous growth in heterotrophic biofilms—Measurements in flow-through tube reactor

The aim of this study was to investigate the interaction between biofilm structure and sloughing in a flow-through tube reactor exposed to constant, limiting and non-limiting substrate conditions. Biofilm development and detachment were analysed by means of gravimetrical methods and confocal laser scanning microscopy (CLSM). This study revealed the impact of sloughing on biofilm structure. After six weeks of cultivation all biofilms were dominated by filamentous growth. In three out of four cultivations fungal networks developed after the first or second major sloughing event. In one biofilm, experiencing the highest substrate limitations, filamentous bacteria dominated the biofilm community prior to the first sloughing. Despite structural changes the overall biofilm substrate conversion rates remained rather constant. Several factors were identified, which possibly led to the first major sloughing event. For example, all biofilms had a density less than 40 kg m⁻³, a biofilm thickness above 80 μm, an increased surface roughness and presence of protozoa prior to sloughing. The observed fungal development may have several reasons: (1) small colonies dormant in the base biofilm adapted rapidly towards new conditions after sloughing, (2) spores attached after sloughing within the remaining base biofilm and (3) the absence of bacterial reseeding as a result of no recirculation of the bulk-fluid containing planktonic bacteria. Filamentous bacterial growth was due to the combination of limited substrate availability and high flow rates. These results can be significant for industrial systems where biofilm stability and sloughing as well as community composition are critical factors for process stability.     

A systematic literature review on state-of-the-art deep learning methods for process prediction

Artificial Intelligence Review - Process mining enables the reconstruction and evaluation of business processes based on digital traces in IT systems. An increasingly important technique in this...     

Stress‐Actuated Spiral Microelectrode for High‐Performance Lithium‐Ion Microbatteries

Miniaturization of batteries lags behind the success of modern electronic devices. Neither the device volume nor the energy density of microbatteries meets the requirement of microscale electronic devices. The main limitation for pushing the energy density of microbatteries arises from the low mass loading of active materials. However, merely pushing the mass loading through increased electrode thickness is accompanied by the long charge transfer pathway and inferior mechanical properties for long‐term operation. Here, a new spiral microelectrode upon stress‐actuation accomplishes high mass loading but short charge transfer pathways. At a small footprint area of around 1 mm², a 21‐fold increase of the mass loading is achieved while featuring fast charge transfer at the nanoscale. The spiral microelectrode delivers a maximum area capacity of 1053 µAh cm^?2 with a retention of 67% over 50 cycles. Moreover, the energy density of the cylinder microbattery using the spiral microelectrode as the anode reaches 12.6 mWh cm^?3 at an ultrasmall volume of 3 mm³. In terms of the device volume and energy density, the cylinder microbattery outperforms most of the current microbattery technologies, and hence provides a new strategy to develop high‐performance microbatteries that can be integrated with miniaturized electronic devices.     

Laser Structuring of Thin Metal Films of Compliant Electrodes on Dielectric Elastomers

Dielectric elastomer (DE) transducers are polymer-based devices consisting of an insulating elastomeric membrane with compliant electrodes on both sides, forming a flexible capacitor that can work as an actuator or sensor. In this report, a new direct and maskless method is presented to pattern-compliant metallic electrodes specially developed for DE applications. Highly conductive and stretchable nickel-based electrodes are first sputter deposited onto pre-stretched membranes, resulting in a wrinkled surface after relaxation. An arbitrary electrode design is directly patterned onto the double-sided coated DE membrane by means of an ultra-short pulse laser system with a wavelength of 355 nm. In this way, it is possible to achieve simultaneous ablation of both electrodes on the top and the bottom side of the silicone membrane, as well as a selective ablation of only the electrode facing the laser. With a minimal optical resolution of 20 µm, the laser structuring method opens the path toward the manufacturing of miniaturized DE transducers, such as micro-scale DE arrays with integrated conductive paths, as well as the integration of optical features like diffraction gratings into the DE electrodes.     

Selective degradation of ibuprofen and clofibric acid in two model river biofilm systems

A field survey indicated that the Elbe and Saale Rivers were contaminated with both clofibric acid and ibuprofen. In Elbe River water we could detect the metabolite hydroxy-ibuprofen. Analyses of the city of Saskatoon sewage effluent discharged to the South Saskatchewan river detected clofibric acid but neither ibuprofen nor any metabolite. Laboratory studies indicated that the pharmaceutical ibuprofen was readily degraded in a river biofilm reactor. Two metabolites were detected and identified as hydroxy- and carboxy-ibuprofen. Both metabolites were observed to degrade in the biofilm reactors. However, in human metabolism the metabolite carboxy-ibuprofen appears and degrades second whereas the opposite occurs in biofilm systems. In biofilms the pharmacologically inactive stereoisomere of ibuprofen is degraded predominantly. In contrast, clofibric acid was not biologically degraded during the experimental period of 21 days. Similar results were obtained using biofilms developed using waters from either the South Saskatchewan or Elbe River. In a sterile reactor no losses of ibuprofen were observed. These results suggested that abiotic losses and adsorption played only a minimal role in the fate of the pharmaceuticals in the river biofilm reactors.