亚10飞秒脉冲的诊断与压缩

采用二次谐波-频谱分辨光闸法对克尔透镜锁模钛宝石激光器输出的飞秒脉冲的振幅和相位 进行诊断，测得其脉冲包络是双曲正割型的，而相位则近似为时间的三次幂形式. 通过对脉 冲频域相位的拟合，诊断出二阶群速度色散是造成脉冲啁啾、导致脉冲展宽的主要原因. 利 用棱镜对补偿二阶群速度色散，进一步将17 fs啁啾脉冲压缩至半高全宽为8.5 fs的近似转 换极限脉冲. 关键词： 飞秒脉冲 二次谐波-频谱分辨光闸法 群速度色散     

Characterization of electrokinetic gating valve in microfluidic channels

Electrokinetic gating, functioning as a micro-valve, has been widely employed in microfluidic chips for sample injection and flow switch. Investigating its valving performance is fundamentally vital for microfluidics and microfluidics-based chemical analysis. In this paper, electrokinetic gating valve in microchannels was evaluated using optical imaging technique. Microflow profiles at channels junction were examined, revealing that molecular diffusion played a significant role in the valving disable; which could cause analyte leakage in sample injection. Due to diffusion, the analyte crossed the interface of the analyte flow and gating flow, and then formed a cometic tail-like diffusion area at channels junction. From theoretical calculation and some experimental evidences, the size of the area was related to the diffusion coefficient and the velocity of analytes. Additionally, molecular diffusion was also believed to be another reason of sampling bias in gated injection.     

Imaging through flesh tissue using fs electronic holographic gating method

The experimental results of imaging through flesh tissue using fs electronic holographic gating method is reported. In the experiment, Ti: sapphire mode-locked laser is used as light source, of which the repetition rate is 100 MHz, central wavelength 800 nm, duration of pulse 20 fs, output power 80 mW. Tissue is a 7 mm thick chicken slice, and the imaged object is a metal wire with diameter of 0.5 mm. A general CCD is used to record holograms and a clear image of metal wire is obtained. Several relevant problems are discussed.     

机载脉冲多普勒雷达在测量数据丢失下的多目标跟踪

针对于多目标在机载多普勒盲区测量数据丢失下的跟踪问题,提出了一种鲁棒无偏转换自适应门限的CPHD(Robust Unbiased Converted Measurements-Adaptive Gating-Cardinalized Probability Hypothesis Density,RUCM-AG-CPHD)算法。该算法首先对目标测量信息进行无偏转换,并将无偏转换得到的噪声协方差矩阵做解耦;然后设计增益调节矩阵提高滤波器在目标量测数据丢失下的鲁棒性;最后采用自适应门限去除不相关的量测信息,同时保证检测到新出现的目标,从而有效地降低了算法的计算复杂度。仿真结果表明该算法的有效性和可行性,可以更加准确的估计出目标在盲区内测量信息丢失下的目标个数和状态,且计算量相对于传统的CPHD算法减少了8.6%。     

不同选通条件下对光谱烧孔孔深的研究

本文从理论上分析了低激发密度下，选通光分别为脉冲光和连续光时，孔深随时间的变化，得到可以通过脉冲光烧孔、连续光选通的方法缩短烧孔时间．应用ＢａＦＣｌ０．５Ｂｒ０．５：Ｓｍ２＋（２％）进行了实验，分析了单脉冲烧孔的孔深．     

MRI angiography of the carotid artery

Spin echo images of the carotid arteries in longitudinal view have been obtained by selection of oblique imaging planes. Blood flow within the lumen in the region of the carotid bifurcation has been visualized through the use of cardiac gating during end diastole. Using a surface coil placed about the mandible, high resolution images [(0.75 mm)² per pixel) were obtained with scan times typically equal to 9 min and image data matrix equal to 256 × 256. Images obtained with this technique of MRI carotid angiography demonstrate blood flow phenomenon as well as vascular anatomy.     

Trajectory correction for free-breathing radial cine MRI

Radial acquisitions can suffer from trajectory errors leading to reduced image quality. Here we present a new method of trajectory correction that uses all spokes of a radial acquisition and compare it to an existing method that uses a two-spoke pre-scan calibration. For both methods, estimates of the necessary shifts were made using magnitude or phase data and the performances were compared. The additional effect of B0 correction was considered in all cases. Mouse cardiac scans were used for the comparisons and we also compared the quality of navigator signals obtained from the radial data with each technique.     

Water wettability in nanoconfined environment

Water confined in nanoscale space behaves quite differently from that in the bulk.For example,in biological aquaporins and in carbon nanotubes,the traversing water molecules form a single file configuration.Water would stay in vapor state in extremely hydrophobic narrow nanopores owing to the physicochemical interactions between the water molecules and the surface of the nanopore.A spontaneous wet-dry transition has been identified in both biological and artificial nanopores.The nanopore is either fulfilled with liquid water or completely empty.Based on this mechanism,the wetting and dewetting processes inside nanopores have been further developed into highly efficient nanofluidic gates that can be switched by external stimuli,such as light irradiation,electric potential,temperature,and mechanical pressure.This review briefly covers the recent progress in the special wettability in nanoconfined environment,water transportation through biological or artificial nanochannels,as well as the smart nanofluidic gating system controlled by the water wettability.     

Pseudo Real-Time Method for Monitoring of the Limiting Anisotropy in Membranes

Data acquisition and analysis of the time-resolved fluorescence anisotropy is typically a time consuming process preventing usage of this experimental method for monitoring of time-dependent phenomena. We describe a method for pseudo real-time monitoring of the limiting fluorescence anisotropy r(infinity) allowing to track changes of the membrane order occurring on the time scale of minutes. Principle and performance of the method is demonstrated in the time domain with the time-correlated single photon counting detection. DMPC liposomes stained with 1,6-diphenyl-1,3,5-hexatriene (DPH) have been used to test influence of the diffusion membrane potential on the membrane order during the temperature-induced phase transition in DMPC membranes. It has been found that the transmembrane field of the order of -70 mV increases the phase transition temperature by about 1.5 degrees C-2 degrees C. It is proposed that the full advantage of the method can be utilized with a gated detection, which besides a faster data acquisition brings additional advantage of excitation light suppression. The method can be also used for imaging.