We report a new method for measuring particle size distribution (PSD) and refractive index of the top layer in a two-layer tissue phantom simulated epithelium tissue by varying the azimuth angle of incident linearly polarized light. The polarization gating technique is used to decouple the single and multiple scattering components in the returned signal. The theoretical model based on Mie theory is presented and a nonlinear inversion method - floating genetic algorithm - is applied to inverting the azimuth dependence of component of polarization light backscattered. The experiment results demonstrate that the size distribution and refractive index of the scatters of the top layer can be determined by measuring and analyzing the differential signal of the parallel and perpendicular components from a two-layer tissue phantom. The method implies to detect precancerous changes in human epithelial tissue.
Acousto-optic modulation of the femtosecond laser beam has wide potential in various fields such as microscopic imaging, micromachining and optical storage because of its rapidity, high accuracy and good repeatability. This paper reviews the latest research on acousto-optic modulation of femtosecond laser, describes the effects of spatial and temporal dispersion of such lasers after acousto-optic modulation, introduces the theoretical outcomes on pulse width evolution of the Gaussian laser pulses after acousto-optic modulation, discusses the characteristics of contemporary dispersion-compensating techniques for the acousto-optic modulation of femtosecond laser, and finally refers to the challenges of this technique.
在利用多电极阵列(multielectrode arrays,MEA)记录离体培养海马神经元网络的电生理研究中,发现电极附近神经元群体同步放电形成了局部场电位(local field potential,LFP),同时细胞外记录信号为跨膜电压信号的微分,这些因素使检测网络发放的锋电位遇到困难。为正确检测锋电位(spike),在综合比较多种检测方法的基础上,提出一种改进的峰值检测法,以0.6ms为判决阈值,有效解决了原峰值检测法因滑动窗分界导致的重复检测。通过该方法检测发育成熟的网络发放的锋电位,虚警率和漏报率分别为:5%±1%和2%±1%,效果优于传统的阈值检测法。上述结果表明,改进的方法适合于神经元网络电活动的研究。
