Effects of ultrasonic irradiation and direct heating on extraction of priority pesticides from marine sediments

Priority pesticides (alachlor, aldrin, γ-chlordane, chlorfenvinphos, chlorpyrifos, dieldrin, 4,4′-DDT, 4,4′-DDD, 4,4′-DDE, α-endosulfan, β-endosulfan, endosulfan sulphate, endrin, α-HCH, β-HCH, γ-HCH, δ-HCH, HCB, HCBD, heptachlor, heptachlor epoxide, isodrin, methoxychlor, mirex, quintozene, terbuthylazine and trifluralin) are a group of toxic substances that are known by their persistency in the aquatic environment. Their screening in marine sediments may provide information on the sources and distribution in the water mass of fresh-transitional and coastal waters. This work proposes a rapid and reliable method to extract multi-residues of priority pesticides by ultrasounds irradiation from marine sediments. Multiple variables have been optimised: ultrasound frequency, sonication intensity, signal operation mode, time of extraction and water bath temperature. After sample clean-up and pre-concentration of the pesticides by stir bar sorptive extraction, the compounds were analysed by gas chromatography-mass spectrometry (GC-MS) using the selective ion monitoring acquisition mode (SIM). Better performance was found for ultrasonic-assisted extractions (UAE) at frequency of 35 kHz and an output intensity of 60% in a sweep mode of operation. An increase of water bath temperature to 80°C had a significant effect on the extraction of pesticides with high octanol-water partitioning coefficients (K_ow). Under optimal conditions, method detection limits (MDLs) and method quantification limits (MQLs) ranged from 0.3 to 4.4 ng g^?1 and from 0.8 to 14 ng g^?1, respectively. Recoveries between 70 and 111%, at high precision levels, were found at different types of marine sediments with a single extraction cycle. Method performance was in good agreement with quality control guidelines.     

基于多频外差原理的相位解包裹方法

根据多频外差原理推导了三频光栅条纹解包裹的过程,获取了光栅条纹的绝对相位值。同时,为了减小误差,提高测量精度,提出了一种相位修正的方法,比较了相位修正前后的相位图,表明该方法能够非常有效地去除相位误差。通过将修正后的绝对相位值作为匹配的一个特征量,利用机器视觉中双目立体视觉的方法求取物体的三维特征。实验证实了该方法的可行性,并得到良好的测量结果。     

基于微波静磁波的并行磁光频谱分析研究

利用多个频率的微波静磁波同时与导波光的磁光作用可产生多级Bragg衍射光的原理可实现并行磁光频谱分析,即微波频率与衍射光在傅里叶透镜焦平面上的位置一一对应,而微波信号强度由多频静磁波对导波光的衍射效率确定。根据三频静磁波与导波光的磁光耦合方程,进行了仿真计算,结果表明,通过考虑多频磁光衍射中相位失配因素对衍射效率的影响可很好地恢复多频信号的相对强度。     

Recent advances in laser self-injection locking to high-Q microresonators

The stabilization and manipulation of laser frequency by means of an external cavity are nearly ubiquitously used in fundamental research and laser applications. While most of the laser light transmits through the cavity, in the presence of some back-scattered light from the cavity to the laser, the self-injection locking effect can take place, which locks the laser emission frequency to the cavity mode of similar frequency. The self-injection locking leads to dramatic reduction of laser linewidth and noise. Using this approach, a common semiconductor laser locked to an ultrahigh-Q microresonator can obtain sub-Hertz linewidth, on par with state-of-the-art fiber lasers. Therefore it paves the way to manufacture high-performance semiconductor lasers with reduced footprint and cost. Moreover, with high laser power, the optical nonlinearity of the microresonator drastically changes the laser dynamics, offering routes for simultaneous pulse and frequency comb generation in the same microresonator. Particularly, integrated photonics technology, enabling components fabricated via semiconductor CMOS process, has brought increasing and extending interest to laser manufacturing using this method. In this article, we present a comprehensive tutorial on analytical and numerical methods of laser self-injection locking, as well a review of most recent theoretical and experimental achievements.