Literature data on the promotional role of under‐rib convection for polymer electrolyte fuel cells (PEFCs) fueled by hydrogen and methanol are structured and analyzed, thus providing a guide to improving fuel cell performance through the optimization of flow field interaction. Data are presented for both physical and electrochemical performance showing reactant mass transport, electrochemical reaction, water behavior, and power density enhanced by under‐rib convection. Performance improvement studies ranging from single cell to stack are presented for measuring the performance of real operating conditions and large‐scale setups. The flow field optimization techniques by under‐rib convection are derived from the collected data over a wide range of experiments and modeling studies with a variety of components including both single cell and stack arrangements. Numerical models for PEFCs are presented with an emphasis on mass transfer and electrochemical reaction inside the fuel cell. The models are primarily used here as a tool in the parametric analysis of significant design features and to permit the design of the experiment. Enhanced flow field design that utilizes the promotional role of under‐rib convection can contribute to commercializing PEFCs.

Understanding the current density distributions in polymer electrolyte fuel cells (PEFCs) is crucial for designing cell components, such as the flow field of bipolar plates. A new serpentine flow field equipped with sub‐channels and by‐passes (SFFSB) was numerically and experimentally confirmed to enhance the reactant transport rates and liquid removal efficiency compared with a conventional advanced serpentine flow field (CASFF). Consequently, the maximum current and the power densities of the SFFSB were increased due to the promotion of under‐rib convection. In this study, current density distributions are measured under transient conditions to verify the PEFC performances enhanced by under‐rib convection. The current density distributions of the SFFSB are compared with those of the CASFF. The results show that the SFFSB has a higher local current density and a more uniform distribution than the CASFF, therefore, the PEFC performances with the new flow field of SFFSB is enhanced by the better current density distributions.

results from an acute coronary dissection of a nonatherosclerotic coronary artery. Eighty percent of spontaneous or primary coronary artery dissections occur in females with an age range between 25 and 60 years and most cases are sporadic. Most cases occur during pregnancy, pastpartum period, 6 or are related to oral contraceptive pills. 7 Although the exact pathophysiology of this rare condition remains unknown, it has been postulated that hormones, particularly progesterone, can cause weakening of the media. In addition, the stress of labour may lead to dissection of weakened vessels. 2,8 On the other hand, gender differences do exist. For example, the right coronary dissections are more common in men, while left coronary dissections are more common in females. 2,9 This leads to several reports suggesting a role for a cytokine-mediated action especially when an inflammatory cellular infiltrate is seen. But it remains uncertain whether these inflammatory changes are contributing to the dissection. 10 No inflammatory infiltrate was seen in our case.