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A new methodology to classify European North-East Atlantic transitional waters into ecological types has been developed based on the most important hydrological and morphological features that are likely to determine the ecology of aquatic systems in transitional waters. Hydrological indicators help identifying if a transitional water area is dominated by fresh or sea water and/or by intertidal or subtidal areas, while morphological indicators allow an estimation of the complexity of the transitional water and the diversity of the habitats involved. Twelve transitional waters of the southern Bay of Biscay were classified using this methodology and the five hydro-morphological types obtained were validated with benthic macro-invertebrate data. Transitional waters with a complex morphology showed the highest values of species diversity, while those with a smaller tidal influence showed lower species diversity. The ‘Scrobicularia’ and ‘Abra’ assemblages, previously identified in the study area, were found to be related to different types of transitional waters. The ‘Abra’ assemblage only appeared in estuaries with a complex morphology and dominated by tidal influences, while the ‘Scrobicularia’ assemblage was detected in all the transitional waters except for a single coastal lagoon. This classification of transitional waters may therefore be useful to establish the biological reference conditions needed for European Directives. 相似文献
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从1株海绵内生真菌(Alternaria sp.)链格孢菌的发酵液中提取胞外多糖,对其进行Q Sepharose FF离子交换色谱分离纯化,得到2个组分JJY-W和JJY-S。运用各种化学方法及波谱方法对JJY-W和JJY-S的理化性质及结构进行分析,并对多糖清除自由基活性进行了评价。结果表明,JJY-W和JJY-S的分子量分别为1.4KD和1.8KD;JJY-W以半乳糖、葡萄糖为主,含有少量甘露糖,摩尔比为:甘露糖∶葡萄糖∶半乳糖=1∶2.5∶11。JJY-S以甘露糖、葡萄糖为主,含有少量半乳糖,摩尔比为:甘露糖∶葡萄糖∶半乳糖=3∶2∶1。JJY-W总糖含量为46.3%,未检测出糖醛酸,蛋白含量为2%。JJY-S总糖含量为52%,糖醛酸含量为6.1%,蛋白含量为14%。活性分析表明,2种多糖均具有一定的体外抗氧化活性,并随着浓度的增加清除自由基能力均增强,JJY-W清除DPPH自由基的活性要强于JJY-S,而JJY-S清除OH.自由基的活性要强于JJY-W。 相似文献
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蒙脱石红移、蓝移及水化特征的谱学分析 总被引:3,自引:0,他引:3
对提纯蒙脱石、钠化蒙脱石、有机插层蒙脱石进行紫外-可见光学吸收谱分析、红外光谱分析,发现蒙脱石随着粒度的变化产生红移和蓝移现象。1631插层样品较钠化样品红移20 nm以上,而提纯的胶体粒子样品较1631插层样品SM G-1631红移80 nm;由于提纯蒙脱石样品粒度变细羟基伸缩振动吸收峰向高波数移动了1.69 cm-1,即蓝移了1.69cm-1。蒙脱石水化性能的XRD分析表明,蒙脱石吸水后晶层发生膨胀、剥离,脱水时分散后的晶层发生凝聚作用,即面-面结合作用,形成蒙脱石“定向性层状集合体”衍射峰的d值产生了相应的变化,这种凝聚作用是蒙脱石分散剥离的逆作用,但凝聚后形成的凝聚蒙脱石的衍射谱特征与原始蒙脱石的大不相同。蒙脱石红移、蓝移及水化特征的谱学分析研究丰富了天然纳米蒙脱石矿物材料晶体化学研究的内容,具有重要的理论意义。 相似文献
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Macroscopic criteria for Green type porous materials with spheroidal voids: application to double porous materials
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Combined effects of matrix plastic compressibility and void shape are investigated for ductile porous materials. To this end, a spheroidal volume containing a confocal spheroidal (prolate or oblate) void subjected to uniform strain rate boundary conditions has been first studied. A Green type matrix is chosen as a prototype for investigating effects of plastic compressibility. This is carried out by using a kinematics limit analysis theory from which a closed‐form expression of the macroscopic criterion is established for the considered class of materials. These results are then extended to ductile porous materials made up of a green matrix containing randomly oriented spheroidal voids. In the framework of a two‐step homogenization procedure, the obtained results are implemented to describe the macroscopic behavior of double porous materials involving spherical voids at the microscale and randomly oriented and distributed spheroidal voids at the mesoscale. For validation purpose, the new derived criteria are assessed and validated by comparing their predictions to available upper bounds and numerical data from literature. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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Numerical analysis of the effect of natural microcracks on the supercritical CO2 fracturing crack network of shale rock based on bonded particle models
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The problem of predicting the geometric structure of induced fractures is highly complex and significant in the fracturing stimulation of rock reservoirs. In the traditional continuous fracturing models, the mechanical properties of reservoir rock are input as macroscopic quantities. These models neglect the microcracks and discontinuous characteristics of rock, which are important factors influencing the geometric structure of the induced fractures. In this paper, we simulate supercritical CO2 fracturing based on the bonded particle model to investigate the effect of original natural microcracks on the induced‐fracture network distribution. The microcracks are simulated explicitly as broken bonds that form and coalesce into macroscopic fractures in the supercritical CO2 fracturing process. A calculation method for the distribution uniformity index (DUI) is proposed. The influence of the total number and DUI of initial microcracks on the mechanical properties of the rock sample is studied. The DUI of the induced fractures of supercritical CO2 fracturing and hydraulic fracturing for different DUIs of initial microcracks are compared, holding other conditions constant. The sensitivity of the DUI of the induced fractures to that of initial natural microcracks under different horizontal stress ratios is also probed. The numerical results indicate that the distribution of induced fractures of supercritical CO2 fracturing is more uniform than that of common hydraulic fracturing when the horizontal stress ratio is small. 相似文献
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五矩二流太阳风等离子体特性的数值研究 总被引:4,自引:0,他引:4
本文数值求解了各向同性二流太阳风的五矩方程组,得出了1 Rs-2AU区域内太阳风密度、速度、电子和质子温度、它们的热流通量密度q以及非麦克斯韦分布尾部粒子过剩量ξ随日心距离的变化关系.文中比较了二流太阳风五矩模型、四矩模型(ξ=0)和低阶矩模型(不包括q和ξ二个矩方程)的等离子体特性,着重讨论了量ξ对质子温度及其热流通量的影响.结果表明,包括言的五矩方程可改善Te/Tp和qe/qp的计算值与观测值的符合程度. 相似文献