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The proton exchange membrane fuel cell (PEMFC) is an efficient and clean power generation technology with the characteristics of fast reaction kinetics and low start-up temperature. The current rapidly development of PEMFC technology is expected to be widely popularized. A brief overview of the development of PEMFC was given in recent years, starting from the core components of PEMFC. The core components were classified from the perspective of key materials. The research status and technical features of proton exchange membranes (PEM), catalysts and gas diffusion layers (GDL) were introduced in detail. The research methods, improvement methods and progress of each component were summarized, and the research direction and development trend of PEMFC were prospected. Based on various advantages in high temperature environments, PEM with short side chains and low equivalent weight values will continue to be the focus of research under high temperature and low humidity environments. PEMFC will further develop towards the situation of low Pt or even no Pt, and achieve water balance under humidification-free. [ABSTRACT FROM AUTHOR]

The methodology of classroom-based researches is informed by anthropology, hermeneutics and phenomenology, so the researchers in this field are eager to understand what happens in classrooms and what is the rationale behind this. To achieve this end, the application of the method of thick description and interpretation has gradually gained widespread attention among them. The thick description is an in-depth description of detailed problematic experience, which can be classified into micro-thick description, scene-based thick description and interactive thick description. This method is supposed to be used to clarify the meaning of tendency and organizational behavior. In addition, the interpretation is a creative, context-dependent and generative process of interpreting and understanding the meaning, which can be divided into thick and light, internal and external, analytical and descriptive interpretations. Its significance lies in the due understanding of the issues concerned. Normally, descriptions and interpretations are often combined and integrated to be applied to the classroom-based researches, which can help researchers conduct detailed, focused and in-depth micro studies on what happens in classrooms. [ABSTRACT FROM AUTHOR]

Polymorphonuclear neutrophil leukocyte (PMN) is an important member of the human immune cells. Recentyears, the recognition of the PMN function and the relationship between PMN and periodontitis have been updated. Besidesthe pathogens killing and phagocytosis, PMN also play an important role in immunoregulation and proresolving. The maintaining of PMN homeostasis is an intricate process and the precondition of defense function, which involves activation, adhesion, recruitment, apoptosis and efferocytosis. The regulatory mechanism of PMN homeostasis called neutrophil rheostat, it works through several cytokines and cells. Any factors that break the homeostasis will result in the damage of host immunity,and may relate to the occurrence of periodontitis. Moreover, PMN dysfunction, because of host factors or microorganism factors, is closely related to periodontitis, especially those associated with systemic diseases and gene defect.