First insights into the biodiversity and biogeography of the Southern Ocean deep sea

Shallow marine benthic communities around Antarctica show high levels of endemism, gigantism, slow growth, longevity and late maturity, as well as adaptive radiations that have generated considerable biodiversity in some taxa. The deeper parts of the Southern Ocean exhibit some unique environmental features, including a very deep continental shelf and a weakly stratified water column, and are the source for much of the deep water in the world ocean. These features suggest that deep-sea faunas around the Antarctic may be related both to adjacent shelf communities and to those in other oceans. Unlike shallow-water Antarctic benthic communities, however, little is known about life in this vast deep-sea region. Here, we report new data from recent sampling expeditions in the deep Weddell Sea and adjacent areas (748-6,348 m water depth) that reveal high levels of new biodiversity; for example, 674 isopods species, of which 585 were new to science. Bathymetric and biogeographic trends varied between taxa. In groups such as the isopods and polychaetes, slope assemblages included species that have invaded from the shelf. In other taxa, the shelf and slope assemblages were more distinct. Abyssal faunas tended to have stronger links to other oceans, particularly the Atlantic, but mainly in taxa with good dispersal capabilities, such as the Foraminifera. The isopods, ostracods and nematodes, which are poor dispersers, include many species currently known only from the Southern Ocean. Our findings challenge suggestions that deep-sea diversity is depressed in the Southern Ocean and provide a basis for exploring the evolutionary significance of the varied biogeographic patterns observed in this remote environment.     

Controls on tropical Pacific Ocean productivity revealed through nutrient stress diagnostics

In situ enrichment experiments have shown that the growth of bloom-forming diatoms in the major high-nitrate low-chlorophyll (HNLC) regions of the world's oceans is limited by the availability of iron. Yet even the largest of these manipulative experiments represents only a small fraction of an ocean basin, and the responses observed are strongly influenced by the proliferation of rare species rather than the growth of naturally dominant populations. Here we link unique fluorescence attributes of phytoplankton to specific physiological responses to nutrient stress, and use these relationships to evaluate the factors that constrain phytoplankton growth in the tropical Pacific Ocean on an unprecedented spatial scale. On the basis of fluorescence measurements taken over 12 years, we delineate three major ecophysiological regimes in this region. We find that iron has a key function in regulating phytoplankton growth in both HNLC and oligotrophic waters near the Equator and further south, whereas nitrogen and zooplankton grazing are the primary factors that regulate biomass production in the north. Application of our findings to the interpretation of satellite chlorophyll fields shows that productivity in the tropical Pacific basin may be 1.2-2.5 Pg C yr(-1) lower than previous estimates have suggested, a difference that is comparable to the global change in ocean production that accompanied the largest El Ni?o to La Ni?a transition on record.     

Oceanic Cd/P ratio and nutrient utilization in the glacial Southern Ocean

During glacial periods, low atmospheric carbon dioxide concentration has been associated with increased oceanic carbon uptake, particularly in the southern oceans. The mechanism involved remains unclear. Because ocean productivity is strongly influenced by nutrient levels, palaeo-oceanographic proxies have been applied to investigate nutrient utilization in surface water across glacial transitions. Here we show that present-day cadmium and phosphorus concentrations in the global oceans can be explained by a chemical fractionation during particle formation, whereby uptake of cadmium occurs in preference to uptake of phosphorus. This allows the reconstruction of past surface water phosphate concentrations from the cadmium/calcium ratio of planktonic foraminifera. Results from the Last Glacial Maximum show similar phosphate utilization in the subantarctic to that of today, but much smaller utilization in the polar Southern Ocean, in a model that is consistent with the expansion of glacial sea ice and which can reconcile all proxy records of polar nutrient utilization. By restricting communication between the ocean and atmosphere, sea ice expansion also provides a mechanism for reduced CO2 release by the Southern Ocean and lower glacial atmospheric CO2.     

Reduced North Atlantic Deep Water flux to the glacial Southern Ocean inferred from neodymium isotope ratios

The global circulation of the oceans and the atmosphere transports heat around the Earth. Broecker and Denton suggested that changes in the global ocean circulation might have triggered or enhanced the glacial-interglacial cycles. But proxy data for past circulation taken from sediment cores in the South Atlantic Ocean have yielded conflicting interpretations of ocean circulation in glacial times--delta13C variations in benthic foraminifera support the idea of a glacial weakening or shutdown of North Atlantic Deep Water production, whereas other proxies, such as Cd/Ca, Ba/Ca and 231Pa/230Th ratios, show little change from the Last Glacial Maximum to the Holocene epoch. Here we report neodymium isotope ratios from the dispersed Fe-Mn oxide component of two southeast Atlantic sediment cores. Both cores show variations that tend towards North Atlantic signatures during the warm marine isotope stages 1 and 3, whereas for the full glacial stages 2 and 4 they are closer to Pacific Ocean signatures. We conclude that the export of North Atlantic Deep Water to the Southern Ocean has resembled present-day conditions during the warm climate intervals, but was reduced during the cold stages. An increase in biological productivity may explain the various proxy data during the times of reduced North Atlantic Deep Water export.     

马尔可夫时滞网络控制系统的稳定性

针对同时具有马尔可夫(Markov)链跳变特性时滞和随机丢包现象的网络控制系统,建立了网络控制系统的离散模型,利用李亚普诺夫稳定性理论、线性矩阵不等式和自由权矩阵方法,分析了系统的均方稳定性和均方可镇定性,并基于线性不等式给出了系统均方稳定、镇定判据.该方法能判定具有马尔可夫时滞和丢包的网络控制系统的均方稳定性,并设计出同等条件下的均方可镇定时滞依赖控制器.与现有方法相比.能更准确地描述网络时滞特性,有效减小系统保守性,结果更具一般性.最后通过仿真实例证明了方法的有效性.     

Cellular peptide composition governed by major histocompatibility complex class I molecules

Major histocompatibility complex (MHC) class I molecules present peptides derived from cellular proteins to cytotoxic T lymphocytes (CTLs), which check these peptides for abnormal features. How such peptides arise in the cell is not known. Here we show that the MHC molecules themselves are substantially involved in determining which peptides occur intracellularly: normal mouse spleen cells identical at all genes but MHC class I express different patterns of peptides derived from cellular non-MHC proteins. We suggest several models to explain this influence of MHC class I molecules on cellular peptide composition.     

二阶差分方程边值问题的一个存在定理

运用拓扑度理论获得了如下边值问题Δ2 u(k) +g(k)f(u(k) ) =0 ,　k∈ [0 ,T]u(0 ) =0 =u(T+2 )的一个新的存在定理 ,其中T为固定的正整数     

一类二阶积微分受控系统的最优控制

研究了受控系统为受无界算子扰动的一类二阶非线性积微分方程的控制问题.对一类Lagrange问题(P),证明了最优控制的存在性.     

椭圆方程约束的最优边界控制问题的非重叠型区域分解迭代方法

研究了一类椭圆方程约束的最优边界控制问题的数值求解方法。为了避免运用传统数值方法所产生庞大的计算量,我们采用非重叠型区域分解迭代方法。即:将求解区域Ω分解成若干个非重叠子区域,把上述的最优边界控制问题分解成这些子区域上的局部问题,这些局部问题间的内边界条件采用Robin条件。建立了求解这些局部问题的迭代格式,推导证明了迭代格式的收敛性。最后,给出一个数值算例,验证了迭代格式的有效性。     

中等复杂程度全球热带海洋模式模拟的热带印度洋海表温度变率

利用一个中等复杂程度全球热带海洋模式模拟研究了表面强迫异常引起的热带印度洋海表温度(SST)变率．利用1958—1998年表面分析资料作为强迫场，积分海洋模式41年作为控制试验，并利用模式分别做动量(风应力)通量和热量通量无异常变化的平行试验，与控制试验作比较．通过3组试验模拟的上层海洋变率状况的比较，分析了动量和热量通量异常对热带印度洋SST变率的影响，并比较了其影响的相对重要性．结果表明，模拟的热带印度洋SST变率的主要模态表现为与热带太平洋ENSO相联系的海盆尺度的一致性增暖或变冷特征，次级模态为热带印度洋SST偶极子模态．通过3组试验结果的比较表明，动量通量和热量通量异常强迫对热带印度洋SST变率第一模态均有贡献，但热量通量异常强迫的影响比动量通量异常强迫的作用大．热带印度洋偶极子模态主要受动量(风应力)异常强迫影响，热量通量异常强迫主要起阻尼作用．     

种群服从Gompertz增长的数学生物经济模型的定性分析

对种群服从Gompertz增长的开放式生物资源建立了价格随供求而变化的捕获模型,并对其进行了详细分析。讨论了平衡点的存在性、稳定性及极限环的不存在性,从生态学和经济学的角度对所得到的结果做出了解释。探讨了关于生物资源开发的相关问题,为生物资源的实际开发与管理提供了必要的理论依据。     

受控系统为一类紧半群非线性发展方程的最优控制

研究无穷维空间中一类紧半群的非线性积微分方程及其对应的最优控制问题。首先，我们讨论对应的积分算子的紧性，给出此类积微分不等式相应Gronwall不等式。进而，证明了此类积微粉方程的温和解局部和全局存在性。最后，给出了相应的Lagrange型最优控制存在的充分条件。     

一类退化半线性椭圆方程支配系统的最优控制条件

研究了一类由退化半线性椭圆方程所支配的分布参数系统的最优控制问题.当退化点集的测度为零时,利用正则化方法和变分思想,得到了该分布参数系统最优控制所满足的必要条件.     

糖蜜发酵培养高铁营养酵母

采用生长周期短,易于工业化生产的酵母为菌株,以糖蜜为主要培养基,通过现代发酵工程技术,在3m^3发酵罐上进行中间试验,在12m^3发酵罐上试生产高铁营养酵母．其发酵产品高铁营养酵母铁的含量为1061mg／kg,高铁营养酵母的产率为2．54％,蛋白质的含量(质量分数)为51.90％.     

一类二阶积微分方程的控制问题

考虑了二阶非线性积微分方程的最优控制问题,其中系统中的主算子没有紧性,通过对控制变量附加条件,最后我们证明了Lagrange问题(P)最优控制的存在性.     

Interannual atmospheric variability forced by the deep equatorial Atlantic Ocean

Climate variability in the tropical Atlantic Ocean is determined by large-scale ocean-atmosphere interactions, which particularly affect deep atmospheric convection over the ocean and surrounding continents. Apart from influences from the Pacific El Ni?o/Southern Oscillation and the North Atlantic Oscillation, the tropical Atlantic variability is thought to be dominated by two distinct ocean-atmosphere coupled modes of variability that are characterized by meridional and zonal sea-surface-temperature gradients and are mainly active on decadal and interannual timescales, respectively. Here we report evidence that the intrinsic ocean dynamics of the deep equatorial Atlantic can also affect sea surface temperature, wind and rainfall in the tropical Atlantic region and constitutes a 4.5-yr climate cycle. Specifically, vertically alternating deep zonal jets of short vertical wavelength with a period of about 4.5?yr and amplitudes of more than 10?cm?s(-1) are observed, in the deep Atlantic, to propagate their energy upwards, towards the surface. They are linked, at the sea surface, to equatorial zonal current anomalies and eastern Atlantic temperature anomalies that have amplitudes of about 6?cm?s(-1) and 0.4?°C, respectively, and are associated with distinct wind and rainfall patterns. Although deep jets are also observed in the Pacific and Indian oceans, only the Atlantic deep jets seem to oscillate on interannual timescales. Our knowledge of the persistence and regularity of these jets is limited by the availability of high-quality data. Despite this caveat, the oscillatory behaviour can still be used to improve predictions of sea surface temperature in the tropical Atlantic. Deep-jet generation and upward energy transmission through the Equatorial Undercurrent warrant further theoretical study.     

煤炭海运总量的灰色预测

基于灰色数学理论,通过常规全数据GM(1,1)模型及等维新陈代谢GM(1,1)模型分别对煤炭海运总量进行建模并预测,并与传统的最小二乘曲线拟合所得结果进行比较,结果表明,运用灰色理论所建立的等维GM(1,1)进行预测是可行的,而且精度较传统方法高。     

High bacterivory by the smallest phytoplankton in the North Atlantic Ocean

Planktonic algae <5 m in size are major fixers of inorganic carbon in the ocean. They dominate phytoplankton biomass in post-bloom, stratified oceanic temperate waters. Traditionally, large and small algae are viewed as having a critical growth dependence on inorganic nutrients, which the latter can better acquire at lower ambient concentrations owing to their higher surface area to volume ratios. Nonetheless, recent phosphate tracer experiments in the oligotrophic ocean have suggested that small algae obtain inorganic phosphate indirectly, possibly through feeding on bacterioplankton. There have been numerous microscopy-based studies of algae feeding mixotrophically in the laboratory and field as well as mathematical modelling of the ecological importance of mixotrophy. However, because of methodological limitations there has not been a direct comparison of obligate heterotrophic and mixotrophic bacterivory. Here we present direct evidence that small algae carry out 40-95% of the bacterivory in the euphotic layer of the temperate North Atlantic Ocean in summer. A similar range of 37-70% was determined in the surface waters of the tropical North-East Atlantic Ocean, suggesting the global significance of mixotrophy. This finding reveals that even the smallest algae have less dependence on dissolved inorganic nutrients than previously thought, obtaining a quarter of their biomass from bacterivory. This has important implications for how we perceive nutrient acquisition and limitation of carbon-fixing protists as well as control of bacterioplankton in the ocean.     

网纹甜瓜营养液深液流栽培管理与环境调控

采用营养液深液流栽培方式,以网纹甜瓜为研究对象,根据作物生长发育不同时期对于温度、湿度、光照强度和营养液组分的不同要求,采用自主研制的温室环境测控系统,调节并控制网纹甜瓜生长的小气候环境和根际环境.一茬网纹甜瓜营养液深液流栽培实验证明,自主研制的营养液自动循环系统和基于CAN总线的温室环境测控系统能够完成预期的环境调控任务,作物生长快、产品无污染、品质优.