The influence of the anion exchange membrane on mass-transport limiting phenomena in bipolar interface fuel cells with Fe–N/C based cathode catalyst layers

Water management is a very important issue in low temperature fuel cells such as proton exchange membrane fuel cells (PEMFCs) or anion exchange membrane fuel cells. Within bipolar interface fuel cells, water management inhibits an even more critical role. The earlier work on bipolar interface fuel cells (BPIFCs), employing Fe–N/C on the cathode side for the oxygen reduction reaction (ORR) in an alkaline environment, demonstrated increased stability of the catalyst compared to the acidic environment of the conventional PEMFCs. However, for the BPIFCs, severe mass transport limitations (MTL) dramatically reduced the power output of the cell within a few hours. In the present work water transport processes are identified as the source of the observed MTL, after evaluating the performance data of BPIFCs, where the amount of directly deposited anion exchange membrane (AEM) material was varied. It can be seen that the BPIFCs with lower AEM content show an earlier onset of MTL than the cells prepared with higher AEM content. It is shown that the AEM can be used as a tool to regulate the influx rate of product water from the bipolar interface into the CCL and that flooding of the porous layers is identified as the main source of the observed MTL. This work paves the way for further development of BPIFCs using Fe–N/C at the cathode electrode, as novel cell design strategies can now focus exclusively on avoiding flooding phenomena.

The AEM layer content in a bipolar interface fuel cell enables the opportunity to regulate the influx rate of water into the porous layer.     

Zeitschriften

Journal of Molecular Medicine -     

Zeitschriften

Journal of Molecular Medicine -     

Zeitschriften

Journal of Molecular Medicine -     

Zeitschriften

Journal of Molecular Medicine -     

Zeitschriften

Journal of Molecular Medicine -     

Zeitschriften

Ohne Zusammenfassung     

Load transfer in tilted implants with varying cantilever lengths in an all‐on‐four situation

Background: The aim of this study was to evaluate if tilting of the distal implant at different angulations (30° and 40°) with different cantilever lengths (4 mm and 12 mm) affects the stress and strain distribution in an ‘all‐on‐four’ situation. Methods: A completely edentulous mandible was modelled with four tapered implants placed within the interforaminal region to receive an all acrylic fixed prosthesis. The two posterior implants were tilted at an angle of 30° and 40°. The prosthesis cantilever was given two different variables of 4 mm and 12 mm. For all models, the equivalent von Mises stress and strain was analysed using three‐dimensional finite element analysis. Results: Statistical significance (p < 0.05) was seen when a comparison was made for the stress developed on the implant and cortical bone between the 30° and 40° distally tilted posterior implants in both situations. No significance was seen in the trabecular bone and on the strain developed in these situations. Conclusions: The study shows that increasing the tilt of the distal implants does not increase the stress significantly. It also shows that the architecture of the mandible plays a major role during treatment planning of a completely edentulous patient.     

Liver tissue engineering and cell sources: issues and challenges

Liver diseases are of major concern as they now account for millions of deaths annually. As a result of the increased incidence of liver disease, many patients die on the transplant waiting list, before a donor organ becomes available. To meet the huge demand for donor liver, alternative approaches using liver tissue engineering principles are being actively pursued. Even though adult hepatocytes, the primary cells of the liver are most preferred for tissue engineering of liver, their limited availability, isolation from diseased organs, lack of in vitro propagation and deterioration of function acts as a major drawback to their use. Various approaches have been taken to prevent the functional deterioration of hepatocytes including the provision of an adequate extracellular matrix and co‐culture with non‐parenchymal cells of liver. Great progress has also been made to differentiate human stem cells to hepatocytes and to use them for liver tissue engineering applications. This review provides an overview of recent challenges, issues and cell sources with regard to liver tissue engineering.     

Impact of pollution, climate, and sociodemographic factors on spatiotemporal dynamics of seasonal respiratory viruses

Seasonal viruses present a major cause of morbidity and mortality in temperate climates. Through major pandemics and smaller annual epidemics, viruses such as influenza, respiratory syncytial virus (RSV) and human rhinovirus (HRV) result in lost school and work days for most that are infected and more serious complications for the immunocompromised. The reasons for these viruses showing strict seasonality include but are not limited to the influence of cold weather and humidity on virus particles, human physiology, and human behavior. The relative importance of each is dependent on what geographic scale is being explored as well as the individual region and time period. Theoretical mathematics has also revealed that climatic changes are likely not the only reasons for strong seasonal cycles, but these are also based in periodic resonance with the natural cycles of immunity and antigenic variance, as well as nationwide synchrony through transportation networks. Investigations of seasonality will aid in understanding disease transmission, and thereby effective prevention strategies. The authors present a review of the literature on seasonal viruses, their annual diffusion through populations, and factors that reduce or enhance their seasonal spread. They also offer suggestions for targeted interventions to reduce the disease burden from seasonal viruses.