Grazing impact of microzooplankton on phytoplankton in the Xiamen Bay using pigment-specific dilution technique

Phytoplankton group-specific growth and microzooplankton grazing were determined seasonally using the dilution technique with high-performance liquid chromatography （HPLC） in the Xiamen Bay, a subtropical bay in southeast China, between May 2003 and February 2004. The results showed that growth rates of phytoplankton ranged from 0.71 to 2.2 d^-1 with the highest value occurred in the inner bay in May. Mierozooplankton grazing rates ranged from 0.5 to 3.1 d^-1 with the highest value occurred in the inner bay in August. Microzooplankton grazing impact ranged from 39% to 95% on total phytoplankton Chl a biomass, and 65% to 181% on primary production. The growth and grazing rates of each phytoplankton group varied, the highest growth rate （up to 3.3 d^-1 ） was recorded for diatoms in August, while the maximum grazing rate （ up to 2.1 d ^-1 ） was recorded for chlorophytes in February in the inner bay. Among main phytoplankton groups, grazing pressure of microzooplankton ranged from 10% to 83% on Chl a biomass, and from 14% to 151% on primary production. The highest grazing pressure on biomass was observed for cryptophytes （83%） in August, while the maximum grazing pressure on primary production was observed for eyanobacteria （up to 151% ） in December in the inner bay. Net growth rates of larger phytoplanktons （diatoms and dinoflagellates） were higher than those of smaller groups （ prasinophytes, chlorophytes and cyanobacteria）. Relative preference index showed that microzooplankton grazed preferentially on prasinophytes and avoided to harvest diatoms in cold seasons （December and February）.

Validation of Microbial Limit Test Methods of Tongmai Tangyanming Capsule

[ Objectives] This study was conducted to establish a method for microbial limit test of Tongmai Tangyanming Capsule. [ Methods] According to the Chinese Pharmacopoei 2015 edition of the four general rules, the microbiological limits of non-sterile products were verified. [ Results] Tongmai Tangyanming Capsule has a strong inhibitory effect on Bacillus subtilis and Candida albicans. The antimicrobial activity was significantly eliminated after increasing the diluent （ 1 ： 20） ; and the recoveries were in the range of 0.5 -2 when the total quantities of aerobic microbes were determined by dilution method （1：20）. When the total quantities of mould and yeast were determined by dilution method （1：20）, the recoveries were from 0.5 to 2, and Escherichia coli, cholate-tolerant Gram-negative bacteria and Salmonella can be detected by the test solution dilution method. [ Condusions] With the plate method, the total quantities of aerobic bacteria and the quantities of mould and yeast were examined by increasing diluent, and conventional method was used for examination of control bacteria including E. coli, cholatetolerant Gram-negative bacteria and Salmonella. This method has been proved effective for microbial limit test of Tongmai Tangyanming Capsule, and can effectively control the quality of the preparation. The method is accurate and reliable.

Validation of Microbial Limit Test Methods of Compound Gangbangui Capsule

[Objectives] This study was conducted to establish a method for microbial limit test of Compound Gangbangui Capsule. [Methods] According to the Chinese Pharmacopoei 2015 edition of the four general rules,the microbiological limits of non-sterile products were verified. [Results]Compound Gangbangui Capsule has a strong inhibitory effect on S. aureus,and the antimicrobial activity was significantly eliminated after increasing the diluent（ 1∶ 20）; and the recoveries were in the range of 0. 5-2. 0 when the total quantities of aerobic microbes were determined by dilution method（ 1∶ 20）. When the total quantities of mould and yeast were determined by conventional method（ 1∶ 20）,the recoveries were from 0. 5 to 2. 0,and Escherichia coli can be detected in experimental groups by the test solution dilution method. [Conclusions]With the plate method,the total quantities of aerobic bacteria and the quantities of mould and yeast were examined by increasing diluent and conventional method,respectively,and control bacteria,E. coli was examined by conventional method. This method has been proved effective for microbial limit test of Compound Gangbangui Capsule,and can effectively control the quality of the preparation. The method is accurate and reliable.

ITSTUDIES ON THE EFFECT OF UREA ON THE COMPATIBILITY OF PMMA/PVC MIXTURES IN DMF BY A DILUTE- SOLUTION VISCOMETRY METHOD

The interaction between poly(methymethacrylate) (PMMA) and poly(vinyl chloride) (PVC) has been studied indilute urea solutions of dimethylformamide (DMF) at 28℃ using a dilute solution viscometry method. The results show thatthe polymer mixtures are compatible in DMF solution in the absence of urea. The influence of urea addition on the degree ofcompatibility of the polymer mixtures has been studied in terms of the compatibility parameters (△b_m and △[η]_m). It wasfound that the compatibility of the polymer mixtures is decreased with increasing urea addition, passing through a minimumat 0.5 M urea.

Estimating total nitrogen deposition in agroecosystems in northern China during the wheat cropping season

Atmospheric nitrogen (N) deposition has been poorly documented in northern China, an intensive agricultural and industrial region with large emissions of NHx and NOy. To quantify N deposition, total airborne N deposition was determined at three agricultural sites using a manual integrated total nitrogen input (ITNI) system during growth of winter wheat (Triticum aestivum L.) and Italian ryegrass (Lolium multiflorum Lam.) from September 2005 to May 2006. Total estimated N deposition averaged 54.9 and 43.2 kg N/hm2 across the three sites when wheat was grown to flowering and maturing, respectively. The average value was 50.2 kg N/hm2 when ryegrass was the indicator plant. Both indicator species gave similar total airborne N input results. The intermediate level of N supplied resulted in the highest N deposition, and the ratio of N acquired from deposition to total N content of the whole system decreased with increasing N supply to the roots. The contribution of atmospheric N to the total N content of the wheat and ryegrass sand culture systems ranged from 10% to 24%.

Symbiotic nitrogen fixation in black locust (Robinia pseudoacacia L.) seedlings from four seed sources

We conducted a greenhouse experiment to investigate the role of seed source in growth and symbiotic nitrogen fixation of black locust （Robinia pseudoacacia L）. Seeds from different sources were planted in the same environmental conditions and inoculated with a suspension of mixed Rhizobium. We used the modified ^15N isotope dilution method to estimate biological nitrogen fixation of Robinia trees. Different Robinia seed sources differed significantly in terms of tissue dry weight （50.6-80.1 g）, total N （1.31-2.16 g） and proportion of nitrogen derived from the atmosphere （ 0-51%）. A higher nitrogen fixation rate of Robinia trees was associated with higher dry weight. Moreover, the leaves of Robinia proved to adequately represent the nitrogen fixation capacity of entire plants. Our results confirmed that assessment of seed sources is a useful way to improve the nitrogen fixation capacity and therefore the growth rate of Robinia.

High-performance evanescently-coupled uni-traveling-carrier photodiodes

A new evanescently-coupled uni-traveling-carrier photodiode （EC-UTC PD） based on a multimode diluted waveguide （MDW） structure is fabricated, analysed and characterized. Optical and electrical characteristics of the device are investigated. The excellent characteristics are demonstrated such as a responsivity of 0.36 A/W, a bandwidth of 11.5 GHz and a small-signal 1-dB compression current greater than 18 mA at 10 GHz. The saturation current is significantly improved compared with those of similar evanescently-coupled pin photodiodes. The radio frequency （RF） bandwidth can be further improved by eliminating RF losses induced by the cables, the probe and the bias tee between the photodiode and the spectrum analyzer.

Experimental study using the dilution incubation method to assess water biostability

Water biostability is of particular concern to water supply as a major limiting factor for heterotrophic bacterial growth in water distribution systems. This study focused on bacterial growth dynamics in the series dilution of water samples with TOC（total organic carbon） values determined beforehand. The results showed that the specific growth rate of Pseudomonas fluorescens P17 varied dramatically and irregularly with TOC value when TOC concentrations were low enough during the initial periods of incubation under given conditions. According to this relationship between bacterial growth rate and TOC, a dilution incubation method was designed for the study of water biostability. With the method under a given condition, a turning-point TOC value was found at a relatively fixed point in the curve between bacterial growth rate and TOC of water sample, and the variation of growth rate had different characteristics below the turning-point TOC value relative to that over this value. A turning-point TOC value similarly existed in all experiments not only with tap water, but also with acetate and mixed solutions. And in the dilution incubation method study, the affections were analyzed by condition factors such as inoculum amount,incubation time and nature of the organic carbon source. In very low organic carbon water environments, the variation characteristics of bacterial growth rate will be useful to further understand the meaning of water biostability.

Antimicrobial activity of crude and semi-purified fractions of Warburgia ugandensis against some pathogens

Objective:To investigate in vitro antimicrobial activities of leaves and heartwood crude and semi-purified fractions of Warburgia ugandensis(Canellaceae)(W.ugandensis)on some pathogens.Methods:were prepared.Six bacteria[Klebsiella pneumoniae(K.pneumoniae),Escherichia coli(E.coli),Pseudomonas aeruginosa Crude and semi-purified fractions of the leaves and heartwood of W.ugandensis(P.aeruginosa),Shigella boydii(S.boydii),Staphylococcus aureus(S.aureus)and Streptococcus pneumonia]and one fungus(Candida albicans)were tested by agar well diffusion and broth dilution method to determine minimum inhibitory concentration(MIC).Results:S.boydii and S.aureus were found to be the most susceptible bacterial isolated in agar well diffusion and broth dilution method of both the crude and petroleum ether extracts,while K.pneumoniae was the most resistant bacterium isolated under the same condition except in chloroform fraction.K.pneumoniae had shown MIC value of 10 mg/mL in the leaves and heartwood in both the crude and petroleum ether extract.S.boydii and S.aureus had shown the MIC value of 1.0 mg/mL in the crude extract for the both leaves and heartwood;Whereas the petroleum ether semi-purified fraction had shown 0.5 mg/mL in the heartwood.In the crude extract,E.coli and P.aeruginosa exhibits similar MIC value of 1.75 mg/mL.In semi purified petroleum ether extract,E.coli had MIC value of 1.0 mg/mL;Whereas P.aeruginosa had shown no change in crude extract.Candida albicans revealed equal MIC value of 1.0 mg/mL for the both crude and semi-purified fractions of the leaves and heartwood.Conclusions:The crude and semi-purified fractions of W.ugandensis have considerable effect on pathogens.Semi-purified petroleum ether fraction has better antimicrobial activity in both agar well diffusion and broth dilution method.This study further shows the potential of W.ugandensis for further study in order to be use as a modern drug.