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유체전단응력에 의하여 3T3-L1 지방세포가 받는 영향
이정근,이영훈,진희원,이서현,김지현,Lee, Jeongkun,Lee, Yeong Hun,Jin, Heewon,Lee, Seohyun,Kim, Chi Hyun 대한의용생체공학회 2018 의공학회지 Vol.39 No.4
Adipocytes affect obesity through the regulation of lipid metabolism. Physical loading is an important regulator of fat tissue. There are ongoing in vitro studies inducing mechanotransduction on 3T3-L1 preadipocytes with mechanical stimulus in order to treat obesity by inhibiting adipogenesis and provoking cell death. In this study, our goal was to suggest a new therapy for obesity by investigating whether fluid shear stress (FSS) changes transcription factors on 3T3-L1 related with adipogenesis and cell death. FSS loading was applied to 3T3-L1 preadipocytes at 1Pa and 1Hz. After loading, bright field images were taken and an immunofluorescence assay was conducted to observe actin stress fiber formation. Western blot analysis was conducted to identify the activation of the ERK pathway as well as the adipogenic factors, which including C/EBPs and $PPAR{\gamma}$. The expression of osteopontin, a protein related to inflammation in adipose tissue, and cell death related factors, Bax, Bcl-2, and Beclin, were also measured. Results showed that FSS stimulated the formation of actin stress fibers in 3T3-L1 and also that the activation of C/EBPs decreased significantly when compared with the control group. $PPAR{\gamma}$ activation in the 2 hour FSS group was lower than the 1 hour FSS group, which implied that the results were time dependent. Additionally, there were no differences in the expression of cell death factors after FSS loading. In summary, similar to other fibroblasts, the formation of actin stress fibers induced by mechanotransduction may affect the differentiation of 3T3-L1, leading to inhibition of adipogenesis and inflammation.
시변 자기 환경에 강한 자기왜곡 모델 내장형 헤딩 추정 필터
이정근,최미진,Lee, Jung Keun,Choi, Mi Jin 한국센서학회 2017 센서학회지 Vol.26 No.4
With regards to heading estimation using gyroscope and magnetometer signals, magnetic disturbance added in the magnetometer signals is a main degradation factor in the estimation accuracy. Although there are a number of existing mechanisms that may properly compensate for the magnetic disturbances, they are designed to react only to the magnetic disturbances, but not to the time derivative of disturbances. Note that the sensors may experience abrupt changes in the magnetic disturbances, particularly for ambulatory applications. This paper proposes a magnetic disturbance model-embedded heading estimation filter for time-varying magnetic environments. The proposed magnetic disturbance model is based on a first-order Markov chain with a conditional switching technique depending on the time derivative of disturbances. Once a high amount of derivative is detected, the corrupted magnetometer signals are discarded to protect the filter from them. In our experimental results, the averaged heading error of tests was $1.46^{\circ}$, while that of the original approach without switching was $5.75^{\circ}$.