On-Chip All-Optical Passive 3.55 Gbit/s NRZ-to-PRZ Format Conversion Using a High-Q Silicon-Based Microring Resonator

We report the experimental result of all-optical passive 3.55 Gbit/s non-return-to-zero (NRZ) to pseudo-return-to-zero (PRZ) format conversion using a high-quality-factor (Q-factor) silicon-based microring resonator notch filter on chip. The silicon-based microring resonator has 23800 Q-factor and 22 dB extinction ratio (ER), and the PRZ signals has about 108 ps width and 4.98 dB ER.

40 Gbits/s all-optical clock recovery for degraded signals using an amplified feedback laser

All-optical clock recovery for the return-to-zero modulation format is demonstrated experimentally at 40 Gbits/s by using an amplified feedback laser. A 40 GHz optical clock with a root-mean-square (rms) timing jitter of 130 fs and a carrier-to-noise ratio of 42 dB is obtained. Also, a 40 GHz optical clock with timing jitter of 137 fs is directly recovered from pseudo-non-return-to-zero signals degraded by polarization-mode dispersion (PMD). No preprocessing stage to enhance the clock tone is used. The rms timing jitter of the recovered clock is investigated for different values of input power and for varying amounts of waveform distortion due to PMD.

Immune responses of the scallop Chlamys farreri after air exposure to different temperatures

The present study examined the influence of air exposure at different temperatures: a common perturbation associated with aquaculture handling practices, on immune responses in zhikong scallop Chlamys farreri. Scallops were exposed to air for 2 h, 6 h, 12 h and 24 h at 5 degrees C, 17 degrees C and 25 degrees C respectively. Thereafter, a recovery period of 24 h at 17 degrees C was applied. Haemocyte mortality, phagocytosis and reactive oxygen species (ROS) production of haemocytes, acid phosphatase (ACP) and superoxide dismutase (SOD) activity in haemocyte lysates were chosen as immumomarkers of anoxic stress. The results showed that an increase of haemocyte mortality and a decrease of phagocytosis and ACP activity were observed after 2 h of air exposure for all temperatures tested. Moreover, a significant increase of ROS production occurred following 2 h of air exposure at 25 degrees C and 24 h of air exposure at 17 degrees C. Significant differences were also observed in haemocyte mortality, percentage of phagocytic cells and ACP and SOD activity depending on the temperature of air exposure. Finally, after 24 h of recovery at 17 degrees C, percentage of phagocytic haemocytes and ACP activity did not return to initial values. ROS production was significantly higher than before the recovery period and initial values for scallops subjected to air exposure at 5 degrees C. In our study, scallops showed a relative low anoxia tolerance under a high temperature. All the scallops air exposed to 25 degrees C died after the 6 h sampling. In conclusion, air exposure associated to aquaculture practices was demonstrated to strongly affect functional immune activities of scallop haemocytes, and high temperature air exposure caused reduced survival of scallops. (c) 2007 Elsevier B.V. All rights reserved.

地震波谱元法数值模拟和偏移研究

With the development of both seismic theory and computer technology, numerical modeling technology of seismic wave has achieved great advancement during the past half century. The current methods under development include finite differentiation method (FDM), finite element method (FEM), pseudospectral method (PSM), integral equation method (IEM) and spectral element method (SEM). They exert their very important roles in every corner of seismology and seismic prospecting. Large quantity of researches towards spectral element method in the end of last century bring this method to a new era, which results in perfect solution of many difficult problems. However, parts of posterior works such as seismic migration and inversion which base on spectral element method have never been studied widely at least up to the present whereas are of importance to seismic imaging and seismic wave propagation. Based on previous work, this paper uses spectral element method to investigate the characteristics and laws of the seismic wave propagation in isotropic and anisotropic media. By thoroughly studying this high-accuracy method, we implement a kind of reverse-time pre- and post-stack migration based on SEM. In order to verify the validity of the SEM method, we have simulated the propagation of seismic wave in several different models. The simulation results show that: (1) spectral element method can be used to model any complex models and the computational results are comparable with the expected results and the analytic results; (2) the optimum accuracy can be achieved when the rank is between 4 and 9. When it is below 4, the dispersion may occur; and when it is above 9, the time step-length will be changed accordingly with the reducing space step-length in order to keep the computation stability. This will exponentially increase the computation time and at the same time the memory even if simulating the same media. This paper also applies explosive reflection surface imaging technology, time constancy principle of wave-filed extrapolation and least travetime raytracing technology of surface source to SEM pre- and post-stack migration of isotropic and anisotropic media. All imaging results derived by the above methods agree well with the real geological models and the position of interface and inflexions can also return to their right location well. This indicates that the method proposed in this paper is a kind of technology with high accuracy and robust stability. It can serve as an alternative method in real seismic data processing. All these work can boost the development of high-accuracy seismic imaging, and therefore have significant inference value.