High-pressure phase transitions of anorthosite crust in the Earth's deep mantle     

《地学前缘(英文版)》2018,9(6):1859-1870

We investigated phase relations, mineral chemistry, and density of lunar highland anorthosite at conditions up to 125 GPa and 2000 K. We used a multi-anvil apparatus and a laser-heated diamond-anvil cell for this purpose. In-situ X-ray diffraction measurements at high pressures and composition analysis of recovered samples using an analytical transmission electron microscope showed that anorthosite consists of garnet, CaAl₄Si₂O₁₁-rich phase (CAS phase), and SiO₂ phases in the upper mantle and the mantle transition zone. Under lower mantle conditions, these minerals transform to the assemblage of bridgmanite, Ca-perovskite, corundum, stishovite, and calcium ferrite-type aluminous phase through the decomposition of garnet and CAS phase at around 700 km depth. Anorthosite has a higher density than PREM and pyrolite in the upper mantle, while its density becomes comparable or lower under lower mantle conditions. Our results suggest that ancient anorthosite crust subducted down to the deep mantle was likely to have accumulated at 660–720 km in depth without coming back to the Earth's surface. Some portions of the anorthosite crust might have circulated continuously in the Earth's deep interior by mantle convection and potentially subducted to the bottom of the lower mantle when carried within layers of dense basaltic rocks.  相似文献   

水量统一调度以来黄河内蒙古河段耗水量分析   总被引：1，自引：0，他引：1  

金双彦  张遂业  马志瑾  张萍 《地理学报》2015,70(3)

黄河水量统一调度始于1999年3月,本次对1999-2011年黄河内蒙古河段引水和退水的年内、年际变化以及引排比关系进行了分析;利用遥感图片,核查了黄河干流石嘴山—头道拐河段的引退水口门;分别采用引退水法和水量平衡法计算了黄河内蒙古河段的引黄耗水量。结果表明:该研究时段内蒙古河套灌区退水量与引水量的比值平均为0.16,呈现逐年增大的趋势,引退水关系比较好,存在"大引大排"现象;引退水法年平均耗水量为75.44亿m3,年际变化相对比较平缓;水量平衡法年平均耗水量为56.72亿m3,年际变化非常明显;两种方法耗水量差别明显的原因之一是颁证引退水口门与实际引退水口门数量不相同。  相似文献   

热带季节雨林和次生林水源涵养服务价值变化过程研究     

裴厦  谢高地  张昌顺  刘春兰  陈龙 《地理与地理信息科学》2015,31(1)

为了掌握西双版纳热带季节雨林和次生林水源涵养服务价值的变化规律,基于西双版纳生态台站的定位观测数据,对比分析了两种林型水源涵养服务的构成及年内价值变化过程。结果表明,两种林型的水源涵养总量接近,分别为74 158m3/hm2和70 654m3/hm2,水调节量为主,占90%以上。热带季节雨林的水供给价值高于水调节价值,热带次生林的水调节价值和水供给价值大致相等,综合分析,热带季节雨林的年水源涵养服务价值(4 531元/hm2)比次生林(2 732元/hm2)高66%。两种林型的水源涵养服务变化过程相似:主要受水供给变化过程的影响,水源涵养服务变化曲线呈单峰态,月变异程度较大;热带季节雨林和次生林在雨季(5-10月)的水源涵养量分别占全年总量的54%和57%,水源涵养价值均占全年总价值的65%左右。  相似文献   

斜带石斑鱼(Epinephelus coioides)两种神经肽NPB的发现及表达分析     

李伟萍  胡哲  李玉  王翔  黄文  王宇  肖玲  李水生  张勇  林浩然 《海洋与湖沼》2015,46(4):879-886

神经肽B(Neuropeptide B,NPB)在生命体的许多生理活动中发挥着重要作用,如调节摄食行为、能量平衡、睡眠、神经内分泌功能和调节炎症性疼痛等。为了研究在石斑鱼中NPB与摄食调控的关系,本文对斜带石斑鱼(Epinephelus coioides)转录组数据比对分析后,在斜带石斑鱼中克隆得到了两种NPB(NPB1和NPB2)基因的c DNA序列,首次发现鱼类存在两种NPB基因。作者对NPB编码蛋白的信号肽及其成熟肽的结构进行了预测,发现与其它脊椎动物相一致。采用实时荧光定量PCR技术,研究了斜带石斑鱼不同组织中的m RNA的表达模式,结果发现NPB1和NPB2在脑组织中广泛表达,且在下丘脑中表达最为丰富;在其它的外周组织器官中也有相应的表达。饥饿试验的研究结果表明,在禁食3d和7d后,NPB1和NPB2的m RNA表达量都发生了显著的下调;复投喂后表达量恢复。由此可见NPB1和NPB2参与了斜带石斑鱼摄食行为的调节。  相似文献   

Estimation of the hydraulic conductivity of soils improved with vertical drains     

《Computers and Geotechnics》2015

In this study, some limitations associated with modeling the hydraulic conductivity of soil improved with vertical drains are discussed. In addition, some limitations of conventional methodologies for deducing the hydraulic conductivity from oedometer or Rowe cell tests are investigated. An alternative approach for estimating the hydraulic conductivity in soils improved by vertical drains is discussed. This methodology will allow for simpler finite element modeling of consolidation due to vertical drains. The effectiveness of this technique has been demonstrated using a field study.  相似文献   

In vitro acute cytotoxicity of neonicotinoid insecticide imidacloprid to gill cell line of flounder Paralichthy olivaceus     

宿烽  张士璀  李红岩  郭华荣 《中国海洋湖沼学报》2007,25(2):209-214

In vitro acute cytotoxicity of neonicotinoid insecticide imidacloprid (IMI) to the gill cell line of flounder (FG) that collected in the gill of Paralichthys olivaceus, was examined by 3 widely used endpoint bioassays: NR (neutral red), MTT (3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) and TCP (total cell protein). The result shows that the IMI increased at concentrations ≥0.5 μg/ml. The IC50 value of NR, MTT, and TCP was 41.86, 38.46, and 39.08 μg/ml, respectively. The ultrastructural observation revealed that the mitochondria of the cells exposed to 60 μg/ml IMI for 48 h were severely damaged, swollen or disrupted, while their nuclei and rough endoplasmic reticulum (RER) remained normal. This would suggest that the mitochondria are probably the primary target of IMI.  相似文献   

Flow and sediment regimes at tributary junctions on a regulated river: impact on sediment residence time and benthic macroinvertebrate communities     

Kristen M. Svendsen  Carl E. Renshaw  Francis J. Magilligan  Keith H. Nislow  James M. Kaste 《水文研究》2009,23(2):284-296

Tributaries may either ameliorate or exacerbate the geomorphic and ecologic impacts of flow regulation by altering the flux of water and sediment into the flow‐regulated mainstem. To capture the effects of tributary influences on a flow regulated river, long‐term discharge and cross‐sectional data are used to assess the geomorphic and hydrologic impacts of impoundment. In addition, the use of the short‐lived cosmogenic radioisotope ⁷Be (half‐life 53·4 days) to link sediment transport dynamics to benthic macroinvertebrate community structure is evaluated. It is found that the ⁷Be activity of transitional bed load sediment is highly seasonal and reflects both variations in activity of sediment sources and limited sediment residence time within the junction. Benthic communities also exhibit a strong seasonal variability. In the spring, neither the ⁷Be activity of the sediment, nor benthic communities exhibit clear relationships with sample site location. In contrast, during the late summer the ratio of Ephemeroptera (mayflies)/Trichoptera (caddisflies) decreased significantly below tributary junctions. This decrease in benthic community ratio was driven by increases in caddisfly abundance and was strongly correlated with the presence of recently ⁷Be tagged transitional bedload sediment. These observations are probably associated with the presence of coarse, stable, and unembedded substrate downstream of tributaries and the rapid turnover of sediment that may also be associated with a rapid flux in nutrients or seston. The results show that tributaries are impacting the flow‐regulated mainstem and that these impacts are reflected in the benthic community structure and in the ⁷Be activity of transitional bed load sediment. Moreover, the observed reduction in competence and capacity of the mainstem following flood control suggests that these spatial discontinuities may be a consequence of impoundment. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Effects of grid cell size and time step length on simulation results of the Limburg soil erosion model (LISEM)     

Rudi Hessel 《水文研究》2005,19(15):3037-3049

With increasing computer power, process‐based models that use grids to discretize space have become increasingly popular. For such models, the simulation results might depend on both grid cell size and, in the case of dynamic models, on the time step length used in the model. In this study, the dynamic Limburg soil erosion model (LISEM) was applied to a small catchment on the Chinese Loess Plateau. To study the effect of grid cell size and time step length, simulations were performed for grid cell sizes ranging from 5 to 100 m for a single time step length, and for time step lengths ranging from 2 to 120 s for a single grid cell size. The results show that the LISEM results vary considerably as a function of both grid cell size and time step length. For both increase in cell size and increasing time step length, the trend was a decrease in predicted discharge and predicted soil loss. For discharge, the most important causes are likely to be a decrease in slope with increasing grid cell size, rainfall averaging for longer time step lengths, and numerical dispersion of the kinematic wave solution. For soil loss, the cause is less clear, reflecting the complexity of soil loss prediction, which depends on available water, transport capacity and sediment redistribution, all of which change in time and space. These results show that a choice for a certain grid cell size and a certain time step length should be made before calibration of the model. Similar erosion models are likely to have similar dependencies on grid size and time step length. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Distribution and ultrastructure of pigment cells in the skins of normal and albino adult turbot, Scophthalmus Maximus     

郭华荣  黄冰  亓飞  张士璀 《中国海洋湖沼学报》2007,25(2):199-208

The distribution and ultrastructure of pigment cells in skins of normal and albino adult turbots were examined with transmission electron microscopy (TEM). Three types of pigment cells of melanophore, iridophore and xanthophore have been recognized in adult turbot skins. The skin color depends mainly on the amount and distribution of melanophore and iridophore, as xanthophore is quite rare. No pigment cells can be found in the epidermis of the skins. In the pigmented ocular skin of the turbot, melanophore and iridophore are usually co-localized in the dermis. This is quite different from the distribution in larvae skin. In albino and white blind skins of adult turbots, however, only iridophore monolayer still exists, while the melanophore monolayer disappears. This cytological evidence explains why the albino adult turbot, unlike its larvae, could never resume its body color no matter what environmental and nutritional conditions were provided. Endocytosis is quite active in the cellular membrane of the iridophore. This might be related to the formation of reflective platelet and stability of the iridophore.  相似文献   

认真学习<四川省防震减灾条例>提高依法治震水平     

余位清 《四川地震》2000,(3):5-11

从学习防震减灾法律法规的必要性,重要性和紧迫性;《四川省防震减灾条例》的产生过程及其意义;《四川省防震减灾条例》修改后的新内容和新特点;对依法行政,做好执法和执法监督工作等方面,阐述了认真学习《四川省防震灾条例》,努力提高依法治震水平的问题。  相似文献