线粒体动力学在牙源性间充质干细胞中的研究现状

牙源性间充质干细胞(DMSC)是一种来源于哺乳动物牙齿相关组织的间充质干细胞,其具有自我更新、多向分化和免疫调节等功能,且容易获得,对组织工程学和再生医学具有重要的研究意义。线粒体是高度动态的细胞器,通过不断地分裂和融合来维持其形态,也称为线粒体动力学。研究表明,线粒体动力学是决定干细胞命运的关键因素。线粒体分裂和融合的协调对细胞功能和应激反应至关重要,而异常的分裂和融合导致干细胞功能障碍。近年来研究证实,DMSC在增殖、分化、凋亡和衰老过程中经历特定的线粒体动力学过程。本文就线粒体动力学分子调控的机制以及间充质干细胞线粒体的形态特征,线粒体动力学在生理和应激微环境下对DMSC行为的调控作用作一综述。

Sensitivity of on-line wavelength during retrieval of atmospheric CO2 vertical profile

Accurately measuring the differential molecular absorption cross section is the key to obtaining a high-precision concentration of atmospheric trace gases in a differential absorption lidar（DIAL） system. However, the CO2 absorption line is meticulous at 1.6 μm, easily translating and broadening because of the change of temperature and pressure. Hence, measuring the vertical profile of atmospheric temperature and pressure to calculate the vertical profile of the CO2 weight parameter is necessary. In general, measuring atmospheric temperature and pressure has a certain amount of uncertainty. Therefore, this study proposes the concept of a balanced on-line wavelength,where the differential molecular absorption cross section is larger and the CO2 weight parameter is insensitive to the uncertainty of atmospheric temperature and pressure. In this study, we analyzed the influence of uncertainty on the CO2 weight parameter at every preselected wavelength, as well as determined an appropriate wavelength near one of the absorption peaks. Our result shows that 1572.023 nm should be one of the appropriate balanced online wavelengths. The measurement errors of the mixing ratio of CO2 molecule in this wavelength are only 0.23%and 0.25% and are caused by 1 K temperature error and 1h Pa pressure error, respectively. This achievement of a balanced on-line wavelength will not only depress the requirement of the laser’s frequency stabilization but also the demand for measurement precision of the atmospheric temperature and pressure profile. Furthermore, this study can achieve the exact measurement of the vertical profile of atmospheric CO2 based on an independent differential absorption laser.

Wavelet modulus maxima method for on-line wavelength location of pulsed lidar in CO_2 differential absorption lidar detection

Differential absorption lidar(DIAL) is an excellent technology for atmospheric CO2 detection. However, the accuracy and stability of a transmitted on-line wavelength are strictly required in a DIAL system. The fluctuation of a tunable pulsed laser system is relatively more serious than that of other laser sources, and this condition leads to a large measurement error for the lidar signal. These concerns pose a significant challenge in on-line wavelength calibration. This study proposes an alternative method based on wavelet modulus maxima for the accurate on-line wavelength calibration of a pulsed laser. Because of the different propagation characteristics of the wavelet transform modulus maxima between signal and noise, the singularities of a signal can be obtained by detection of the local modulus maxima in the wavelet transform maximum at fine scales. Simulated analysis shows that the method is more accurate than the general method such as quintic polynomial fitting and can steadily maintain high calibration precision at different signal-to-noise ratios(SNRs). Last, 16 groups of real experiments were conducted to verify the simulated analysis, which shows that the proposed method is an alternative for accurately calibrating an on-line wavelength. In addition, the proposed method is able to suppress noises in the process of wavelength calibration, which gives it an advantage in accurate on-line wavelength calibration with a low SNR.