The influence of the cation of quaternized chitosans on antioxidant activity

Various quaternized chitosans (QCSs) were synthesized according to previous method. Their reducing power and antioxidant potency against hydroxyl radicals ((OH)-O-center dot) and hydrogen peroxide (H2O2) were explored by the established systems in vitro. The QCSs exhibited markedly antioxidant activity, especially TCEDMCS, whose IC50 on hydroxyl radicals was 0.235 mg/mL. They showed 65-80% scavenging effect on hydrogen peroxide at a dose of 0.5 mg/mL. Generally, the antioxidant activity decreased in the order TCEDMCS > TBEDMCS > EDMCS > PDMCS > IBDMCS > Chitosan. Furthermore, the order of their (OH)-O-center dot and H2O2 scavenging activity was consistent with the electronegativity of different substituted groups in the QCSs. The QCSs showed much stronger antioxidant activity than that of chitosan may be due to the positive charge density of the nitrogen atoms in QCSs strengthened by the substituted groups. (C) 2009 Elsevier Ltd. All rights reserved.

Effects of cell density, light intensity and mixing on Undaria pinnatifida gametophyte activity in a photobioreactor

An on-line controlled 7 1 sterilizable photobioreactor was used for the optimisation of a culture of gametophytes of Undaria pinnatifida. The gametophytes, which had been stored for three years in a culture cabinet at 16 degreesC, could rapidly grow in the photobioreactor under controlled conditions. The rate of increase of dissolved oxygen and pH were used to monitor the photosynthetic activity. Optimal gametophytes density changed varying the light intensity. The optimal cell densities were 3.24 and 3.45 g FW l(-1) when the cultures were exposed to 61.7 and 82.3 muE m(-2) s(-1), respectively. The optimal cell density was higher under a high photon flux density (PFD) than under low PFD. On the other hand, the optimal light intensities were different for different cell density cultures. The light saturation point was higher at high cell density cultures than at low cell density cultures. The optimal rotational speed was 150 rpm for high cell density culture in the photobioreactor. (C) 2003 Elsevier B.V. All rights reserved.

Coherence between solar activity and the East Asian winter monsoon variability in the past 8000 years from Yangtze River-derived mud in the East China Sea

AMS(14)C dating and grain-size analysis for Core PC-6, located in the middle of a mud area on the inner shelf of the East China Sea (ECS), were used to rebuild the Holocene history of the East Asian winter monsoon (EAWM). The 7.5-m core recorded the history of environmental changes during the postglacial transgression. The core's mud section (the upper 450 cm) has been formed mainly by suspended sediment delivered from the Yangtze River mouth by the ECS Winter Coastal Current (ECSWCC) since 7.6 kyr BP. Using a mathematical method called "grain size vs. standard deviatioW', we can divide the Core PC-6's grain-size distribution into two populations at about 28 mu m. The fine population (< 28 mu m) is considered to be transported by the ECSWCC as suspended loads. Content of the fine population changes little and represents a stable sedimentary environment in accord with the present situation. Thus, variation of mean grain-size from the fine population would reflect the strength of ECSWCC, which is mainly controlled by the East Asian winter monsoon. Abrupt increasing mean grain size in the mud section is inferred to be transported by sudden strengthened ECSWCC, which was caused by the strengthened EAWM. Thus, the high resolution mean grain-size variation might serve as a proxy for reconstruction of the EAWM. A good correlation between sunspot change and the mean grain-size of suspended fine population suggests that one of the primary controls on centennial- to decadal-scale changes of the EAWM in the past 8 ka is the variations of sun irradiance, i.e., the EAWM will increase in intensity when the number of sunspots decreases. Spectral analyses of the mean grain-size time series of Core PC-6 show statistically significant periodicities centering on 2463, 1368, 128, 106, 100, 88-91, 7678, and 70-72 years. The EAWM and the East Asian summer monsoon (EASM) agree with each other well on these cycles, and the East Asian Monsoon (EAM) and the Indian Monsoon also share in concurrent cycles in Holocene, which are in accord with the changes of the sun irradiance. (c) 2005 Elsevier B.V. All rights reserved.

Spatial distribution of ciliates, copepod nauplii and eggs, Engraulis japonicus post-larvae and microzooplankton herbivorous activity in the Yellow Sea, China

The abundance of anchovy Engraulis japonicus larvae, >20 mum ciliates, copepod eggs and nauplii, and microzooplankton herbivorous activity were studied in the Yellow Sea in June 2000. Anchovy juveniles and larvae were found in only 6 of the 19 stations sampled. The ciliate communities were dominated by 2 species: Laboea strobila and Strombidium compressum. In the surface waters, the abundance of L. strobila ranged between 0 and 560 ind. l(-1). S. compressum only appeared at Stns 15 to 18 (20 to 3300 ind. l(-1)). L. strobila was found mainly in the top 20 m. The abundance of L. strobila was less than 50 ind, l(-1) in waters deeper than 25 m. S, compressum showed subsurface abundance peaks at the salinity abnormality. Tintinnids occurred occasionally with abundance lower than 100 ind. l(-1), The total ciliate abundance fell in the range of 40 to 3420 ind. l(-1). The ciliate biomass in the surface water and the water column ranged between 0,15 and 6.76 mug C l(-1) and 0.4 and 134.4 mg C m(-2), respectively, In the surface waters, the abundance of copepod eggs and nauplii ranged from 0,3 to 3.1 and 1,1 to 15.6 ind, l(-1), respectively. The average abundance of copepod eggs and nauplii in 4 depth (0, 5, 10 and 20 m) fell in the range of 0.2 to 2.8 and 1.0 to 29.4 ind. l(-1), respectively. As a food item of the E. japonicus post-larvae, the abundance of copepod nauplii and eggs appeared to be low. The abundance peaks of ciliate and E, japonicus post-larvae coincided. Although not found in the gut of E, japonicus post-larvae, aloricate ciliates might be ingested by first-feeding anchovy larvae, preventing initial starvation and prolonging the time to irreversible starvation. On the basis of dilution experiments with positive microzooplankton grazing rates, microzooplankton grazed at rates of 0 to 0.61 d(-1). Grazing pressure of microzooplankton on chlorophyll a standing stock (P-i) and potential chlorophyll a primary production (P-p) were 17 to 46% and 35 to 109% d(-1), respectively.

Effect of burrowing activity of root vole (Microtus oeconomus Pallas) on plant diversity in alpine meadow

Herbivory and burrowing activity of mammals may influence the species composition and diversity of plant communities. The effect of corridors and holes systems constructed by root vole (Microtus oeconomus Pallas) on the plant species diversity was studied in the habitat of high - mountain meadow (3250 in a.s.l in Qinghai-Tibet Plateau, China). By using grid method, these disturbances were studied on 16 plots (100 cm x 100 cm) distributed in 4 transects in studied area, in August 2000 and 2001. The disturbance intensity index, D, was calculated as the percent of the ground surface disturbed by voles in the study area. Plant species were identified and counted on the same plots. In total 46 plant species were identified - 39% of this number was considered as sensitive to the vole disturbances as their occurrence and/or abundance decreased along the disturbance intensity. Generally, a significantly negative correlation (r = - 0.911 P < 0.01) between vole aboveground disturbances and plant species diversity (H') was found. The results suggest that root vole ground disturbances, especially in the form of actively utilized holes and corridors have significantly negative influence on plant species diversity in high-mountain grassland habitat.

Enhanced activity of an In-Fe2O3/H-ZSM-5 catalyst for NO reduction with methane

Selective reduction of NO by CH4 on an In-Fe2O3/H-ZSM-5 catalyst was investigated in the presence of excess oxygen. Compared with In/H-ZSM-5, the In-Fe2O3/H-ZSM-5 catalyst with high Fe2O3 contents showed higher activity in a wide range of reaction temperatures. It was found that the addition of Fe2O3 yielded a promotion effect on CH4 activation. The influence of water vapor on NO conversion was also investigated. The activity of the In/H-ZSM-5 catalyst has been found to be strongly inhibited by water vapor, while the In-Fe2O3/H-ZSM-5 catalyst remained fairly active in the presence of 3.3% steam. (C) 2000 Elsevier Science B.V. All rights reserved.