In this immunohistomorphometric study, we have defined basic characteristics of the hair follicle (HF) immune system during follicle morphogenesis and cycling in C57BL/6 mice, in relation to the skin immune system. Langerhans cells and gammadelta T cell receptor immunoreactive lymphocytes were the predominant intraepithelial hematopoietic cells in neonatal mouse skin. After their numeric increase in the epidermis, these cells migrated into the HF, although only when follicle morphogenesis was almost completed. In contrast to Langerhans cells, gammadelta T cell receptor immunoreactive lymphocytes entered the HF only via the epidermis. Throughout HF morphogenesis and cycling, both cell types remained strikingly restricted to the distal outer root sheath. On extremely rare occasions, CD4+ or CD8+ alphabetaTC were detected within the HF epithelium or the sebaceous gland. Major histocompatibility complex class II+, MAC-1+ cells of macrophage phenotype and numerous mast cells appeared very early on during HF development in the perifollicular dermis, and the percentage of degranulated mast cells significantly increased during the initiation of synchronized HF cycling (first catagen). During both depilation- and cyclosporine A-induced HF cycling, the numbers of intrafollicular Langerhans cells, gammadelta T cell receptor immunoreactive lymphocytes, and perifollicular dermal macrophages fluctuated significantly. Yet, no numeric increase of perifollicular macrophages was detectable during HF regression, questioning their proposed role in catagen induction. In summary, the HF immune system is generated fairly late during follicle development, shows striking differences to the extrafollicular skin immune system, and undergoes substantial hair cycle-associated remodeling. In addition, synchronized HF cycling is accompanied by profound alterations of the skin immune system.
The electric power supply system is one of the most important research areas within sustainable and energy-efficient aviation for more-and especially all electric aircraft. This paper discusses the history in electrification, current trends with a broad overview of research activities, state of the art of electrification and an initial proposal for a short-range aircraft. It gives an overview of the mission profile, electrical sources, approaches for the electrical distribution system and the required electrical loads. Current research aspects and questions are discussed, including voltage levels, semiconductor technology, topologies and reliability. Because of the importance for safety possible circuit breakers for the proposed concept are also presented and compared, leading to a initial proposal. Additionally, a very broad review of literature and a state of the art discussion of the wiring harness is given, showing that this topic comes with a high number of aspects and requirements. Finally, the conclusion sums up the most important results and gives an outlook on important future research topics. INDEX TERMS Aviation, aerospace electronics, MEA, AEA, electric power supply systems, dc-dc power converters, power semiconductor devices, wide bandgap semiconductors, high voltage direct current (HVDC), circuit breaker, hybrid circuit breaker.
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