Close coupling between phytoplankton growth and microzooplankton grazing in the western South China Sea

We conducted 28 dilution experiments during August-September 2007 to investigate the coupling of growth and microzooplankton grazing rates among ultraphytoplankton populations and the phytoplankton community and their responses to habitat variability (open-ocean oligotrophy, eddy-induced upwelling, and the Mekong River plume) in the western South China Sea. At the community level, standing stocks, growth, and grazing rates were strongly and positively correlated, and were related to the higher abundance of larger phytoplankton cells (diatoms) at stations with elevated chlorophyll concentration. Phytoplankton growth rates were highest (> 2 d(-1)) within an eastward offshore jet at 13 degrees N and at a station influenced by the river plume. Among ultraphytoplankton populations, Prochlorococcus dominated the more oceanic and oligotrophic stations characterized by generally lower biomass and phytoplankton community growth, whereas Synechococcus became more important in mesotrophic areas (eddies, offshore jet, and river plume). The shift to Synechococcus dominance reflected, in part, its higher growth rates (0.87 +/- 0.45 d(-1)) compared to Prochlorococcus (0.65 +/- 0.29 d(-1)) or picophytoeukaryotes (0.54 +/- 0.50 d(-1)). However, close coupling of microbial mortality rates via common predators is seen to play a major role in driving the dominance transition as a replacement of Prochlorococcus, rather than an overprinting of its steady-state standing stock.

Environmental changes reflected by sedimentary geochemistry in recent hundred years of Jiaozhou Bay, North China

Sediment geochemical technique was employed to assess how the sediment records reflect the environmental changes of Jiaozhou Bay, a semi-enclosed bay adjacent to Qingdao, China. In the past hundred years, Jiaozhou Bay has been greatly impacted by human interventions. A dated core sediment by Pb-210 chronology was analyzed for trace metals including Li, Cd, Cr, Pb, Cu, Ni, Co, Zn together with C, N, P and BSi. Based on the research, the development of Jiaozhou Bay environment in the past hundred years can be divided into three stages: (1) before the 1980s characterized by relatively low sedimentation rate, weak heavy metal pollution and scarce eutrophication; (2) from the 1980s to 2000, accelerating in the 1990s, during which high sedimentation rates, polluted by heavy metals and the frequent occurrence of red tide; (3) after 2000, the period of the improvement of environment, the whole system has been meliorated including the heavy metal pollution and hypernutrification. (c) 2006 Elsevier Ltd. All rights reserved.

Characteristics of nitrogen forms in the surface sediments of southwestern Nansha Trough, South China Sea

The area of the southwestern Nansha Trough is one of the most productive areas of the southern South China Sea. It is a typical semi-deep sea area of transition from shoal to abyssal zone. To understand distributions and roles of nitrogen forms involved in biogeochemical cycling in this area, contents of nitrogen in four extractable forms: nitrogen in ion exchangeable form (IEF-N), nitrogen in weak acid extractable form (WAEF-N), nitrogen in strong alkali extractable form (SAEF-N) and nitrogen in strong oxidation extractable form (SOEF-N), as well as in total nitrogen content (TN) in surface sediments were determined from samples collected from the cruise in April-May 1999. The study area was divided into three regions (A, B and C) in terms of clay sediment (< 4 mu m) content at < 40%, 40%-60% and > 60%, respectively. Generally, region C was the richest in the nitrogen of all forms and region A the poorest, indicating that the finer the grain size is, the richer the contents of various nitrogen are. The burial efficiency of total nitrogen in surface sediments was 28.79%, indicating that more than 70% of nitrogen had been released and participated in biogeochemical recycling through sediment-water interface.

Immunomodulation and antitumor activity of kappa-carrageenan oligosaccharides

The modulation of carrageenan oligosaccharides from Kappaphycus striatum on the immune system in S 180-bearing mice was investigated. The mice inoculated with S180 cell suspension were treated p.o. with carrageenan oligosaccharides (50, 100 and 200 mu g/g) for 14 days. The effects of carrageenan oligosaccharides on transplantable tumors and macrophage phagocytosis, quantitative hemolysis of sheep red blood cells (QHS),. lymphocyte proliferation, the activity of natural killer cells (NK), production of interleukin-2 (IL-2) and tumor necrosis factor-alpha (TNF-alpha) were studied. Carrageenan oligosaccharides could significantly inhibit the growth of transplantable sarcoma S180 and increase macrophage phagocytosis, the form of antibody secreted by spleen cells, spleen lymphocyte proliferation, NK cells activity, serumal IL-2 and TNF-alpha level in S 180-bearing mice. Considering all these results, it is suggested that carrageenan oligosaccharides exert their antitumor effect by promoting the immune system. (c) 2005 Elsevier Ireland Ltd. All rights reserved.

Geochemieal records of phosphorus in Jiaozhou Bay sediments - Implications for environmental changes in recent hundred years

Phosphorus is a key element and plays an important role in global biogeochemical cycles. The evolution of sedimentary environment is also influenced by phosphorus concentrations and fractions as well as phosphate sorption characteristics of the marine sediments. The geochemical characteristics of phosphorus and their environmental records were presented in Jiaozhou Bay sediments. Profiles of different forms of phosphorus were measured as well as the roles and vertical distributions of phosphorus forms in response to sedimentary environment changes were investigated. The results showed that inorganic phosphorus ( IP) was the major fraction of total phosphorus ( TP); phosphorus which is bound to calcium, iron and occluded phosphorus, as well as the exchangeable phosphorus were the main forms of IP, especially calcium-phosphorus, including detrital carbonate-bound phosphorus ( Det - P) and authigenic apatite-bound phosphorus ( ACa - P), are the uppermost constituent of IP in Jiaozhou Bay sediments. Moreover, the lead-210 chronology technology was employed to estimate how much phosphorus was buried ultimately in sediments. And the research showed that the impacts of human activities have increased remarkably in recent years especially between the 1980s and 2000. According to research, the development of Jiaozhou Bay environment in the past hundred years can be divided into three stages; (I) before the 1980s characterized by the relatively low sedimentation rate, weak land-derived phosphorus inputs and low anthropogenic impacts; (2) from the 1980s to around 2000, accelerating in the 1990s, during which high sedimentation rates, high phosphorus abundance and burial fluxes due to the severe: human activities impacted on the whole environmental system; (3) after 2000, the period of the improvement of environment, the whole system has been improved including the decreasing sedimentation rates, concentration and the burial fluxes of phosphonas.

Postnatal development of the retina in root vole Microtus oeconomus

Vision plays an important role in the living habits of animals, especially in feeding. We investigated the postnatal development of retina in root vole Microtus oeconornus. The result shows that the retina of the M. oeconornus is very primitive before postnatal day （PD） 3. The neuroblastic layer does not differentiate and makes up more than half of the retina layer. The outer plexiform layer （OPL） first comes into existence at PDS. At PD6, as the presence of the OPL becomes obvious, the outer nuclear layer （ONL） and inner nuclear layer （INL） are much clearer. At PD18, the retina is similar to an adult retina and each layer becomes distinct. The thickness and cell density of the ganglion cell layer （GCL） and ONL during different postnatal days were also examined. These results show that the thickness and density of ONL increase during ontogeny, while the thickness and density of GCL decrease. Compared with Rattus norvegicus, Apodemus agrarius , Cricetulus triton, Microtus mandarinus , Myospalax cansus , Spermophilus dauricus and Sciurotamias davidianus, the histological structure of the retina of M. oeconornus is between that of nocturnal and diurnal rodents.

基于CORBA的多agent供应链管理系统的研究

本文从现代供应链管理概念及要求出发 ,指出协调与合作在供应链管理中的重要作用 ,应用分布式人工智能理论及分析方法 ,提出了基于多 agent的供应链管理结构 ,定义了各功能agent的作用和职能 ,研究了基于多 agent的供应链管理协作内容、特点及解决方法 ,介绍了基于CORBA的分布式系统开发方法 ,提出了基于 CORBA规范及 KQML协议的支持供应链管理协作研究及开发的软件结构 .

自动导引车多Agent系统研究

多AGV系统的研究是移动机器人研究的一个重要方向，随着工厂自动化的不断发展及实际需求的推动，对多AGV系统的研究日益广泛和深入。多Agent理论是本文的核心指导理论，它来源于分布式人工智能（DAI）。分布式人工智能分为分布式问题求解（DPS）和多Agent系统（MAS）两个方向。由于MAS比DPS更能体现人类社会智能，具有更大的灵活性和适应性，更适合开放、动态的世界环境，因而越来越受到人们的重视。本文对Agent理论、Agent的基本结构、Agent的应用思想、多Agent系统的协调与协作等进行了详细地介绍。在总结了大量前人研究成果的基础上，本文认为有序是社会性的重要内涵，自主和有序是一个问题的两个方面，不能偏执一端，自主性体现了系统的灵活性，有序则体现了系统的效率。因此，我们提出了集中与分布相结合的控制机制，并成功地应用于多AGV系统的运行控制。其中涉及到了任务调度、路径规划、车辆的最优数量、通信机制、与生产系统的集成等AGES研究中的基本问题。