Chemical constituents of marine algal-derived endophytic fungus Exophiala oligosperma EN-21     

��P  ���  ������  ����� 《中国海洋湖沼学报》2011,29(1):63-67

Seven compounds (1–7) were identified from the cultivation of the endophytic fungus Exophiala oligosperma (EN-21) that was isolated from the inner tissue of the marine red alga Laurencia similis. Their structures were identified with spectroscopic and chemical methods as 2-phenoxynaphthalene (1), (2S, 3R, 4E, 8E)-1-O-β-D-glucopyranosyl-3-hydroxy-2-[(R)-2′-hydroxyoctadecanoyl] amino-9-methyl-4, 8-octadeca-diene (2), (22E,24R)-ergosta-7,22-dien-3β,5α,6β-triol (3), (22E, 24R)-3β, 5α, 9α-trihydroxy- ergosta-7, ...  相似文献   

云南省2009/2010年秋冬季罕见干旱诊断分析   总被引：1，自引：0，他引：1  

黄慧君  李庆红  高月忠  钟爱华  陈红玉  李建美 《热带地理》2011,31(1)

利用气候诊断方法,对云南省2009/2010年秋冬季干旱的成因进行初步分析。结果表明:云南出现严重干旱与西太平洋副高、西风带环流等大气环流系统出现异常有直接关系。副高出现明显异常,较常年同期偏强、偏西,700hPa流场上孟加拉湾长时间为东北气流控制,不利于将暖湿气流输送到云南;2009/2010年秋冬北半球500hPa极涡偏于西半球,强度偏弱,不利于冷空气向云南输送,由于冷空气和暖湿气流的输送都受到阻碍,冷暖空气难以在云南上空交汇;云南上空为较干燥的气流控制、云南及孟加拉的OLR值偏高,对流活动受到抑制,降水云系偏少等是云南降雨异常偏少,高温干旱的重要原因。  相似文献   

近6 ka以来科尔沁沙地东部气候变化记录   总被引：4，自引：3，他引：1  

刘冰  靳鹤龄  孙忠 《中国沙漠》2011,31(6):1398-1405

 根据科尔沁沙地东部TL剖面磁化率、有机质、化学元素等气候代用指标的变化特征和14C测年结果,分析和讨论了科尔沁沙地6 ka BP以来的气候变化过程。实验数据显示,高频磁化率、低频磁化率、有机质、Al2O3含量变化趋势基本一致,且峰值段对应古土壤层,谷值段对应风成砂层。依据气候代用指标的变化将6 ka BP以来科尔沁沙地气候变化分为3个阶段：Ⅰ.6.0～4.2 ka BP,气候暖湿,夏季风逐渐增强,并占主导,冬季风较弱,与全新世大暖期对应,但存在百年尺度的气候波动,其中：6.0～5.6 ka BP,5.6～5.4 ka BP,4.9～4.2 ka BP气候暖湿;5.6～5.5 ka BP,5.4～4.9 ka BP气候相对冷干。Ⅱ.4.2～1.3 ka BP,气候相对暖湿,与上一阶段相比夏季风有所减弱,但仍强于冬季风,其间也存在次一级波动,3.7～3.6 ka BP,3.4～1.3 ka BP,气候相对暖湿,4.2～3.7 ka BP,3.6～3.4 ka BP气候相对干冷。Ⅲ.1.3～0.65 ka BP以来,气候波动频繁,后期有向暖湿发展的趋势。总体而言,区域气候变化与全球具有较好的一致性。  相似文献   

东亚地区春季二氧化硫的输送与转化过程研究I.模式及其验证   总被引：5，自引：0，他引：5  

张美根  徐永福  Itsushi Uno  Hajime Akimoto 《大气科学》2004,28(3):321-329

结合新近评估的东亚地区污染源资料,作者利用一个耦合的区域化学输送模式系统以探讨东亚地区春季期间气象过程、气相与液相化学过程、非均相化学过程、气溶胶过程和干湿沉降过程对二氧化硫输送及转化过程的影响,并研究二氧化硫和硫酸盐气溶胶的空间分布及变化特征.模拟的二氧化硫和硫酸盐气溶胶的浓度值与2001年春季飞机和地面获取的观测值进行了比较.比较结果显示,模拟值与观测值具有很好的一致性,模式系统很好地反映了二氧化硫和硫酸盐气溶胶的分布特征和变化规律,再现了许多观测到的重要特征,为进一步分析模拟结果奠定了基础.  相似文献   

赤潮影响因素研究进展   总被引：13，自引：1，他引：12  

曾江宁  曾淦宁  黄韦艮  郑平  周青松  陈全震  高爱根 《海洋学研究》2004,22(2):40-47

通过对赤潮发生的生物、化学、物理等影响因素研究现状的分析,认为赤潮生物是引发赤潮的内在因素,化学因素是赤潮发生的物质基础,而物理因素则是提供赤潮发生的环境条件。在赤潮生物存在的前提下,化学和物理因素都可以限制赤潮的发生,所以,将生物学、化学与物理海洋学耦合仍旧是赤潮研究需要解决的问题。在分析了现有研究状况的基础上,从不同角度提出了赤潮的研究方向。  相似文献   

青藏和伊朗高原热力异常与北疆夏季降水的关系   总被引：5，自引：1，他引：4  

赵勇  杨青  黄安宁  钱永甫 《气象学报》2013,71(4):660-667

青藏高原和伊朗高原热力异常对其周边地区天气气候有重要影响,已有研究多关注东部季风区,而对干旱区关注较少.针对这一不足,利用美国国家环境预测中心/美国国家大气研究中心(NCEP/NCAR)再分析月平均资料和北疆43站降水资料,分析了1961-2007年5月青藏高原和伊朗高原地表感热异常与北疆夏季降水的关系.奇异值分解(SVD)分析发现,5月青藏高原地表感热与北疆夏季降水呈负相关,伊朗高原为正相关.青藏高原和伊朗高原感热异常的大尺度对比,要比仅考虑单一高原的感热异常与北疆夏季降水有更密切的联系.定义了一个热力差异指数来表征这种地表感热异常的对比程度,相关分析发现,当5月伊朗高原地表感热偏强,青藏高原地表感热偏弱时,500hPa中亚上空和贝加尔湖上空分别为异常气旋和反气旋环流,在二者共同作用下,新疆上空盛行异常的偏南气流,有利于低纬度的暖湿气流北上,形成有利于降水的环流形势,同时越赤道索马里急流偏强,低纬度水汽被接力输送至中亚和新疆地区,为降水的发生提供了有利的水汽条件.进一步分析发现,青藏高原热力异常主要影响中高层大气环流,伊朗高原则主要影响水汽通量输送.  相似文献   

Manganese in runoff from upland catchments: temporal patterns and controls on mobilization / Teneur en manganèse de l'écoulement en bassins versants d'altitude: variations temporelles et contrôles de la mobilisation     

K. V. HEAL  P. E. KNEALE  A. T. McDONALD 《水文科学杂志》2013,58(5):769-780

Abstract

Knowledge of the hydrochemical dynamics of the trace metal manganese (Mn) in upland catchments is required for water quality management. Stream water Mn and other solutes and flow were monitored in two upland catchments in northern England with different soils: one dominated by peat (HS7), the other by mineral soils (HS4). Maximum Mn concentrations occurred at different times in the two catchments: in summer baseflow at HS4 and during late summer storm events at HS7. A two-component chemical mixing model was used to identify the hydrological processes controlling Mn concentrations in stream water. This approach was more successful for HS4 than HS7, probably because of different processes of Mn release in the two catchments and also difficulties in selecting conservative solutes. Factor analysis of the stream water chemistry data set for each catchment was more useful in identifying the controls on Mn release into runoff. The factors indicate that the main source of Mn at HS4 is the hydrological pathway supplying summer baseflow, whereas at HS7 Mn is released during the rewetting of dried peat soils. Manganese concentrations in stream water in upland catchments appear to depend on soil type and antecedent moisture conditions. This has implications for the design of sampling strategies in upland catchments and also for managing the quality of water supplies from such areas.  相似文献   

Effect of strong magnetic field on chemical potential and electron capture in magnetar     

高杰  罗志全  刘伟伟  李港 《海洋学报(英文版)》2010,29(9)

The chemical potential of electrons in a strong magnetic field is investigated. It is shown that the magnetic field has only a slight effect on electron chemical potential when B<10¹¹ T, but electron chemical potential will decrease greatly when B>10¹¹ T. The effects of a strong magnetic field on electron capture rates for ⁶⁰Fe are discussed, and the result shows that the electron capture sharply decreases because of the strong magnetic field.  相似文献   

连云港临洪河口水体中重金属的化学形态与分布特征研究   总被引：1，自引：0，他引：1  

李玉  李谷祺  冯志华 《海洋科学》2010,34(10):33-37

对连云港海域临洪河口水体中重金属元素Cu,Zn,Pb,Cd的主要存在形态及悬浮颗粒态重金属元素的赋存形态进行了分析。结果表明:悬浮态重金属Cu,Zn,Pb,Cd的含量在调查海域内空间分布基本均衡,Zn、Cu、Cd主要以溶解态形式存在,而Pb则主要以颗粒态形式存在。对悬浮态重金属元素的赋存形态分析表明,Cu主要富集在有机-硫化物态、Zn主要富集在残渣态、Pb主要富集在铁锰氧化物态和碳酸盐结合态、Cd主要富集在可交换态和碳酸盐结合态。  相似文献   

Seasonal controls on stream chemical export across diverse coastal watersheds in the USA     

Janet Barco  Stephanie Gunawan  Terri S. Hogue 《水文研究》2013,27(10):1440-1453

The current study focuses on understanding key factors controlling geochemical export in eight diverse coastal watersheds at seasonal and annual time scales. Geochemical, atmospheric and hydrologic data across a range of hydro‐climatic regimes and varying land uses were investigated and relationships analysed. A hyperbolic dilution model was fitted for each watershed system to evaluate discharge–concentration relationships. Nitrate concentration effects were observed in watersheds exposed to high atmospheric deposition rates as well as agricultural watersheds, whereas urban watersheds showed nitrate dilution effects. Dilution patterns were observed for calcium, magnesium and sulfate for almost all watersheds. Seasonal loads for almost all constituents were noted to be mainly driven by hydrologic seasonality, but are also dependent on inputs (atmospheric deposition and land use sources). Understanding the primary controls on hydro‐chemical interactions is critical for developing and refining predictive water quality models, especially in coastal watersheds where sensitive downstream ecosystems act as receiving waters for upstream pollutant loads. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献