Wang Yunfeng

Application of rotifer Brachionus plicatilis in detecting the toxicity of harmful algae

The toxicity of seven major HAB (harmful algal bloom) species/strains, Prorocentrum donghaiense, Phaeocystis globosa, Prorocentrum micans, Alexandrium tamarense (AT-6, non-PSP producer), Alexandrium lusitanicum, Alexandrum tamarense (ATHK) and Heterosigma akashiwo were studied against rotifer Brachionus plicatilis under laboratory conditions. The results show that P. donghaiense, P. globosa, P. micans, A. tamarense (AT-6), or A. lusitanicum could maintain the individual survival and reproduction, as well as the population increase of the rotifer, but the individual reproduction would decrease when exposed to these five algae at higher densities for nine days; H. akashiwo could decrease the individual survival and reproduction, as well as population increase of the rotifer, which is similar to that of the starvation group, indicating that starvation might be its one lethal factor except for the algal toxins; A. tamarense (ATHK) has strong lethal effect on the rotifer with 48h LC50 at 800 cells/mL. The experiment on ingestion ability indicated by gut pigment change shows that P. donghaiense, P. globosa, P. micans, A. tamarense (AT-6) and A. lusitanicum can be taken by the rotifers as food, but A. tamarense (ATHK) or H. akashiwo can be ingested by the rotifers. The results indicate that all the indexes of individual survival and reproduction, population increase, gut pigment change of the rotifers are good and convenient to be used to reflect the toxicities of HAB species. Therefore, rotifer is suggested as one of the toxicity testing organisms in detecting the toxicity of harmful algae.

Morphological and toxicity characteristics ofPseudo-nitzschia pungens strain PP0201-01 isolated from the East China Sea

The morphology and toxicity ofPseudo-nitzschia strain PP0201-01, isolated near the estuary of Changjiang (Yangtze) River in Year 2002 and tentatively identified asPseudo-nitzschia pungens, were studied. The strain was identified morphologically asP. pungens using scanning electronic microscope (SEM). The analytical results of LC-PDA (liquid chromatography with photodiode array detector), LC-MS (liquid chromatography with mass detector), and the toxicity data from mouse bioassay, showed that no domoic acid was produced by the strain. However, the mechanism of domoic acid production byPseudo-nitzschia species is complicated. More works are needed to assess the toxic species and to evaluate the potential risk of amnesic shellfish poisoning (ASP) in China.

The variational assimilation experiment of GPS bending angle

More and more new types of observational data provide many new opportunities for improving numerical weather forecasts. Among these, the GPS (Global Positioning System) bending angle is undoubtedly very important. There are many advantages of the GPS bending angle, such as high resolution, availability in all weather conditions, and global data coverage. Thus it is very valuable to assimilate GPS bending angle data into numerical weather models. This paper introduces how to obtain and assimilate the GPS bending angle. There are two methods of assimilation: the indirect method and direct method, and they are both introduced in this paper. During the minimizing process of variational assimilation, calculation efficiency is very important and the optimal step size greatly influences the algorithm efficiency. Based on the characteristics of the minimizing algorithm, we obtain an adaptive method for calculating the optimizing step suitable for all kinds of minimization algorithms through mathematical deduction. Finally, a numerical variational assimilation experiment is performed using the GPS bending angle data of 11 October 1995. The numerical results indicate the validity of the variational assimilation method and the adaptive method introduced here.More and more new types of observational data provide many new opportunities for improving numerical weather forecasts. Among these, the GPS (Global Positioning System) bending angle is undoubtedly very important. There are many advantages of the GPS bending angle, such as high resolution, availability in all weather conditions, and global data coverage. Thus it is very valuable to assimilate GPS bending angle data into numerical weather models. This paper introduces how to obtain and assimilate the GPS bending angle. There are two methods of assimilation: the indirect method and direct method, and they are both introduced in this paper. During the minimizing process of variational assimilation, calculation efficiency is very important and the optimal step size greatly influences the algorithm efficiency. Based on the characteristics of the minimizing algorithm, we obtain an adaptive method for calculating the optimizing step suitable for all kinds of minimization algorithms through mathematical deduction. Finally, a numerical variational assimilation experiment is performed using the GPS bending angle data of 11 October 1995. The numerical results indicate the validity of the variational assimilation method and the adaptive method introduced here.

Will harmful dinoflagellate Karenia mikimotoi grow phagotrophically

We studied the phagotrophic ability of dinoflagellate strain Karenia mikimotoi KM-Lü (isolated from the South China Sea), using fluorescent microspheres, bacteria isolated from the culture of K. mikimotoi and a marine microalgae Isochrysis galbana. We found that K. mikimotoi cultured under conditions of high light intensity could ingest fluorescent microspheres (diameters 0.5 and 2.0 μm) and fluorescence-labeled bacteria and microalgae. Under a low light intensity, however, only fluorescent microspheres (diameter 0.5 μm) and fluorescence-labeled microalgae were ingested. K. mikimotoi showed better growth by ingesting living marine bacteria or microalgae I. galbana than the controls, either in nutrient-depleted or nutrient-replete conditions. In nutrient-depleted conditions, the growth of K. mikimotoi was more significant with I. galbana as the prey item. In conclusion, the harmful dinoflagellate K. mikimotoi from the South China Sea has apparent phagotrophic ability, and some marine bacteria and microalgae may promote the growth of K. mikimotoi.

A binary-weighted 64-dB programmable gain amplifier with a DCOC and AB-class buffer

This paper designs a binary-weighted programmable gain amplifier (PGA) with a DC offset cancellation (DCOC) circuit and an AB-class output buffer. The PGA adopts the circuit topology of a differential amplifier with diode-connected loads. Simulation shows that the performance of the PGA is not sensitive to temperature and process variation. According to test results, controlled by a digital signal of six bits, the PGA can realize a dynamic gain of -2 to 61 dB, and a gain step of 1 dB with a step error within 0.38 dB. The minimum 3 dB bandwidth is 92 MHz. At low-gain mode, IIP3 is 17 dBm, and a 1 dB compression point can reach 5.7 dBm. The DCOC circuit enables the amplifier to be used in a direct-conversion receiver and the AB-class output buffer circuit reduces the overall static power consumption.

Variational data assimilation experiments of mei-yu front rainstorms in China

The numerical forecasts of mei-yu front rainstorms in China has been an important issue. The intensity and pattern of the frontal rainfall are greatly influenced by the initial fields of the numerical model. The 4-dimensional variational data assimilation technology (4DVAR) can effectively assimilate all kinds of observed data, including rainfall data at the observed stations, so that the initial fields and the precipitation forecast can both be greatly improved. The non-hydrostatic meso-scale model (MM5) and its adjoint model are used to study the development of the mei-yu front rainstorm from 1200 UTC 25 June to 0600 UTC 26 June 1999. By numerical simulation experiments and assimilation experiments, the T106 data and the observed 6-hour rainfall data are assimilated. The influences of many factors, such as the choice of the assimilated variables and the weighting coefficient, on the precipitation forecast results are studied. The numerical results show that 4DVAR is valuable and important to mei-yu front rainfall prediction.The numerical forecasts of mei-yu front rainstorms in China has been an important issue. The intensity and pattern of the frontal rainfall are greatly influenced by the initial fields of the numerical model. The 4-dimensional variational data assimilation technology (4DVAR) can effectively assimilate all kinds of observed data, including rainfall data at the observed stations, so that the initial fields and the precipitation forecast can both be greatly improved. The non-hydrostatic meso-scale model (MM5) and its adjoint model are used to study the development of the mei-yu front rainstorm from 1200 UTC 25 June to 0600 UTC 26 June 1999. By numerical simulation experiments and assimilation experiments, the T106 data and the observed 6-hour rainfall data are assimilated. The influences of many factors, such as the choice of the assimilated variables and the weighting coefficient, on the precipitation forecast results are studied. The numerical results show that 4DVAR is valuable and important to mei-yu front rainfall prediction.

A 6th order wideband active-RC LPF for LTE application

A low power, highly linear active-RC filter is presented. This filter is synthesized from a low pass 6 order Chebyshev RLC ladder, and exhibits a reconfigurable bandwidth (10 MHz, 50 MHz). In order to meet the high cutoff frequency (50 MHz) and strict adjacent channel rejection requirements, a novel operational amplifier based on a new compensation technique is used, which optimizes high frequency filter performance and minimizes current consumption. This filter is fabricated in a 0.18 m CMOS process, the measurement results indicate that the filter provides 10 MHz and 50 MHz selectable bandwidth, and excellent adjacent channel rejection: -15.3 dB at 12.5 MHz with 10 MHz cutoff frequency, -8.3 dB at 60 MHz with 50 MHz cutoff frequency, three times out-band rejection more than 60 dB while the in-band ripple is less than 1 dB.