日食电离层效应   总被引：7，自引：4，他引：7       下载免费PDF全文

何友文  龙其利 《地球物理学报》1990,33(4):373-383

本文分析了1987年9月23日日环食期间,我国14个电离层站和1988年3月18日日全食期间两个站的垂测仪和偏振仪记录,并综合50年代以来历次日食电离层效应的观测结果,证实:1.E层和F₁层光食效应明显,F₂层动力学效应显著;2.f₀F₂存在日食日值大于、小于或等于控制日值三种典型情况;3.TEC食变曲线有凹陷和不凹陷两种典型情况,甚至出现日食日值大于控制日值的异常现象. 本文对F₂层和外电离层的动力学特征作了定性讨论,认为:空间等离子体温度急剧下降和沿场扩散是F₂层和外电离层日食效应的最主要因素;而磁赤道上空等离子体的沿场扩散、“喷泉”效应,热层风和全（环）食带方位是影响位于磁赤道异常区各电离层站日食电离层效应的主要因素.  相似文献   

Climatic forcing of carbon-oxygen isotopic covariance in temperate-region marl lakes   总被引：1，自引：0，他引：1  

Drummond CN  Patterson WP  Walker JC 《Geology》1995,23(11):1031-1034

Carbon and oxygen stable isotopic compositions of lacustrine carbonate from a southeastern Michigan marl lake display linear covariance over a range of 4.0% Peedee belemnite (PDB) in oxygen and 3.9% (PDB) in carbon. Mechanisms of delta 13 C-delta 18 O coupling conventionally attributed to lake closure in arid-region basins are inapplicable to hydrologically open lake systems. Thus, an alternative explanation of isotopic covariance in temperate region dimictic marl lakes is required. We propose that isotopic covariance is a direct record of change in regional climate. In short-residence-time temperate-region lake basins, summer meteoric precipitation is enriched in 18O relative to winter values, and summer organic productivity enriches epilimnic dissolved inorganic carbon in 13C. Thus, climate change toward longer summers and/or shorter winters could result in greater proportions of warm-month meteoric precipitation, longer durations of warm-month productivity, and net long-term enrichment in carbonate 18O and 13C. Isotopic covariance observed in the Michigan marl lake cores is interpreted to reflect postglacial warming from 10 to 3 ka followed by cooler mean annual temperature, a shift toward greater proportions of seasonal summer precipitation, a shortening of the winter season, or some combination of these three factors.  相似文献   

固相萃取—高温裂解—气相色谱质谱法测定西台晶间卤水中溶解性有机质          下载免费PDF全文

黄孟丽  杨克利  张耀玲  钱桂敏  董亚萍  李武 《盐湖研究》2016,24(4):23-31

采用3种固相萃取材料(C18、XAD-8/4和PPL)分离富集西台吉乃尔盐湖卤水中的溶解性有机物(DOM),通过总有机碳/总氮分析(TOC/TN)、紫外—可见光谱分析、元素分析、傅里叶变换红外光谱分析(FTIR)、高温裂解—气相色谱质谱联用仪(Py-GC/MS)等对富集的有机物进行表征和分析方法比较。结果表明,西台吉乃尔盐湖卤水中的溶解性有机物主要有多糖类,芳香类、含氮类有机物,烷烃烯烃类化合物。PPL,C18和XAD-8/4的回收率分别为40±2%,7±2%和16±1%,虽然C18和XAD-8/4回收率较低,但3种吸附剂都有各自的特点,C18较易吸附烷烃烯烃类有机物,XAD-8/4较易吸附芳香类有机物,PPL较易吸附含N类有机物和多糖类有机物。  相似文献   

A cloud collision model for water maser excitation     

Tarter JC  Welch WJ 《The Astrophysical journal》1986,305(1):467-483

High-velocity collisions between small, dense, neutral clouds or between a dense cloud and a dense shell can provide the energy source required to excite H2O maser emission. The radiative precursor from the surface of the collisional shock front rapidly diffuses through the cloud, heating the dust grains but leaving the H2 molecules cool. Transient maser emission occurs as the conditions for the Goldreich and Kwan "hot-dust cold-gas" maser pump scheme are realized locally within the cloud. In time the local maser action quenches due to the heating of the H2 molecules by collisions against the grains. Although this model cannot explain the very long-lived steady maser features, it is quite successful in explaining a number of the observed properties of the high-velocity features in such sources as Orion, W51, and W49. In particular, it provides a natural explanation for the rapid time variations, the narrow line widths, juxtaposition of high- and low-velocity features, and the short lifetimes which are frequently observed for the so-called high-velocity maser "bullets" thought to be accelerated by strong stellar winds.  相似文献   

使用威斯特波克射电望远镜对古代东方“客星”射电遗迹的探测     

G.G.C.帕伦博  P.斯基沃·卡姆波  G.K.迈利 《天文学报》1980,(4)

作者使用威斯特波克射电望远镜在610兆赫频率上对古代东方天文学家观测到的“客星”的七个视场区(1~o.5×1~o.5)进行了射电遗迹的巡天探测,结果没有发现弥漫射电辐射。本文给出了在这些视场区中的分立射电源的表,表中列出作者提出的这些射电源|b|<15°以內的光学证认。  相似文献   

Protein expression signatures: an application of proteomics   总被引：2，自引：0，他引：2  

Bradley BP  Shrader EA  Kimmel DG  Meiller JC 《Marine environmental research》2002,54(3-5):373-377

The methods of proteomics, the study of the protein complement of the genome, are applicable to environmental testing. Sets of proteins specific to different stressors can be isolated using computer imaging software. Individual proteins can be identified by mass spectrometry. The Protein Expression Signatures (PES) obtained have potential in diagnosing adverse factors in the environment. The challenge is to demonstrate their feasibility in complex environments. We have shown that PES for three endocrine disrupting compounds in trout (Onchorhynchus mykiss), can be detected in mixed sewage effluent. Other studies support these results. As protein databases expand, identification becomes routine, and capture molecules specific to each protein are developed, the possibility of simple field tests for multiple stressors becomes real.  相似文献   

马里亚纳群岛和约翰逊岛近海区锰结核的地球化学     

Chen  JC 潘秋霞 《海洋地质译丛》1996,(1):71-76

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南中国海越南南部近海九龙和南昆山盆地的地质演化     

GwangH．Lee  蓝利 《海洋地质》2003,(3):55-80

张裂和区域沉降是越南南部近海九龙和南昆山盆地的特色。初期的张裂开始于始新世-早渐新世。紧接着是晚渐新世地壳块体的上升和旋转。上升块体的侵蚀标志着九龙盆地从张裂到区域沉降的转变。第二阶段的张裂开始发生于南昆山盆地。并持续至晚中新世。南昆山盆地部分地区经历了中-晚中新世的倒转。九龙盆地中同生张裂和裂后单元分别由非海相沉和海陆交互相到浅海沉积组成。南昆山盆地中的同生张裂沉积分成早期同生断裂单元-相应于初期张裂阶段。和晚期同生张裂单元。在张裂的第二阶段沉积。早期同生和晚期同生张裂单元由非海相沉积和非海相到浅海沉积组成。后张裂单元由陆架、深海沉积组成。正式出版的报告资料显示九龙盆地以生油为主．油主要储集在破碎基岩高处。丽南昆山盆地通常含气，其气圈闭在中新世砂岩和晚中新世碳酸岩中。这些明显的特征可能随着南昆山盆地长期的张裂和倒转所造成的圈闭形成及圈闭整体破裂而出现差异。  相似文献   

中国浅海经济鱼类重金属的卫生质量状况   总被引：10，自引：0，他引：10  

甘居利  贾晓平 《海洋通报》1997,16(4):88-93

引用水产品卫生质量标准对我国浅海经济鱼类金属的卫生质量进行较全面的评价，结果表明总体卫生状况是良好的，食用是安全的，个别测站的少数品种单项超标，超标的重金属主要是镉，总汞，本世纪８０年代末９０年代初，上海，广东岸段鱼体重金属含量比８０年代初略有下降，福建岸段的则相反，广西岸段的保持较低水平。  相似文献   

广东沿海近江牡蛎氯代烃和石油烃含量分布与变化趋势   总被引：5，自引：0，他引：5  

甘居利  林钦  蔡文贵  贾晓平 《热带海洋学报》2006,25(1):47-50

根据历史调查资料和近年的观测数据,比较了广东沿海近江牡蛎Crassostrearivularis体中氯代烃和石油烃含量的地理分布与时间变化。2003年牡蛎体中六六六、滴滴涕、多氯联苯平均含量(湿重)分别为0.469、3.40和45.1ng·g-1,地理分布为粤东岸段>粤西岸段>珠江口。1989年以来六六六、多氯联苯含量呈持续下降趋势,滴滴涕含量在1989—1993年呈下降趋势,但在2003年明显反弹。牡蛎体中石油烃年平均含量1989年以来有一定的波动,2003年为4.75μg·g-1(湿重,大港原油当量),地理分布为珠江口>粤东岸段>粤西岸段。  相似文献