Signaling pathways in hair aging.

Hair follicle (HF) homeostasis is regulated by various signaling pathways. Disruption of such homeostasis leads to HF disorders, such as alopecia, pigment loss, and hair aging, which is causing severe health problems and aesthetic concerns. Among these disorders, hair aging is characterized by hair graying, hair loss, hair follicle miniaturization (HFM), and structural changes to the hair shaft. Hair aging occurs under physiological conditions, while premature hair aging is often associated with certain pathological conditions. Numerous investigations have been made to determine the mechanisms and explore treatments to prevent hair aging. The most well-known hypotheses about hair aging include oxidative stress, hormonal disorders, inflammation, as well as DNA damage and repair defects. Ultimately, these factors pose threats to HF cells, especially stem cells such as hair follicle stem cells, melanocyte stem cells, and mesenchymal stem cells, which hamper hair regeneration and pigmentation. Here, we summarize previous studies investigating the above mechanisms and the existing therapeutic methods for hair aging. We also provide insights into hair aging research and discuss the limitations and outlook.

Risk assessment model and application of COVID-19 virus transmission in closed environments at sea.

This paper focuses on the risk assessment methods of novel coronavirus pneumonia virus (COVID-19) pneumonia virus spreading in closed marine environment. Firstly, the possibility of the spread of new coronavirus in closed environments at sea and the consequences of the harm caused by the epidemic are classified into five levels, and the corresponding risk assessment framework is constructed, and the risk assessment model of the spread of COVID-19 pneumonia virus in closed environment at sea is established taking the Japanese "Diamond Princess" as an example, the model is applied and its output is analysed. Finally, the proportion of the cumulative confirmed cases on the Diamond Princess is calculated, and the possibility of viral infection of Diamond Princess passengers in this COVID-19 pneumonia epidemic in four different risk transmission stages are assessed, and the corresponding risk assessment is undertaken. Through the calculation of risk assessment value, the five stages of the epidemic are established to assess the risk of the "Diamond Princess" outbreak. The research method in the present work helps to provide a risk assessment and analysis idea for the risk of spread of the COVID-19 epidemic in a closed environment at sea.