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871.
In January 1982, sediment microbial N transformations and inorganic N fluxes across the sediment/water interface were studied at nine sites off the South Island West Coast, New Zealand. The sediments showed a great variety in physical, chemical and biological properties. The sediment organic matter had a molar CN ratio of 5.9–10.9, and the total NP ratio was 1.2–4.0. The denitrification capacity in the top 7.5 cm of sediment was 0.1–77.2 mmol N m?2 day?1 and generally declined with increasing sediment depth. The in situ denitrification rate was 0.02–1.84 mmol N m?2 day?1 and highest activities were generally found in surface sediments and at 6–7.5 cm depth. Denitrification accounted for 82–100% of total nitrate reduction. Net N mineralization was indirectly estimated at 0.6–2.4 mmol N m?2 day?1, and the experimental determination of this N transformation gave 0.6–3.2 mmol N m?2 day?1. Denitrification accounted for 3–75% of net N mineralization. The diffusive flux of ammonium and nitrate across the sediment/water interface was 0.1–0.7 and 0.1–0.6 mmol N m?2 day?1, respectively.  相似文献   
872.
1974年10月11日耀斑的光谱分析表明,连续发射和微波爆发几乎同时达到极大。在连续辐射极大时刻出现了高项巴耳末发射线和微弱的巴耳末跳跃,所有这些说明这个耀斑是I型白光耀斑。我们发现,在这个耀斑连续发射的极大时刻,CaIIK线的K1处强度大大增强,约达到连续辐射强度的一半,对应的辐射温度达到5716K。这个反常增强的持续时间小于4分钟。现有的半经验模型似不能给出这样的结果。色球压缩区也不能给出解释  相似文献   
873.
本文讨论了第22太阳活动周的下列重要特点:1.呈现双峰,并在双峰期的槽中又突起孤立的单峰。2.黑子面积峰值滞后相对数峰值的仅占16.67%;黑子面积与相对数同步占58.33%;二者峰值不能对应占25%。3.1986年10月以后,纬度≥30°的有半影的黑子群共出现87群;延迟在峰年期间出现的有53群,占60.92%;对应有M级以上X射线爆发的活动区18个,占20.69%。这一现象与“蝴蝶图”规律不符。  相似文献   
874.
BOOK REVIEWS     
Books Reviewed in this article: Lob Trees in the Wilderness . Clifford and Isabel Ahlgren . Satellite Microwave Remote Sensing . T. D. Allan , ed. Sunbelt Cities: Politics and Growth Since World War II . Richard M. Bernard and Bradley R. Rice , eds. Legacy of Minneapolis: Preservation Amid Change . John R. Borchert , David Gebhard , David Lanegran , and Judith A. Martin . Bloomington, MN: Preparing a Historic Preservation Ordinance. Richard J. Roddewig . The Mountains of Northeastern Tasmania, A Study of Alpine Geomorphology . Nel Caine . Introductory Cartography . John Campbell . Englewood Cliffs, NJ: Changing Climate . Manual of Remote Sensing, Second Edition . 2 Vols. Robert N. Colwell , ed.-in-chief; David S. Simonett and John E. Estes , vol. eds. Remote Sensing in Meteorology, Oceanography and Hydrology . A. P. Cracknell , ed. Multidimensional Scaling . Mark L. Davison . Environmental Karst . Percy H. Dougherty , ed. The Urban Environment . Ian Douglas . Geomorphology of Europe . Clifford Embleton , ed. An Introduction to South Asia . B. H. Farmer . Great Geological Controversies . A. Hallam . Hazardous Waste Management: In Whose Backyard? Michalann Harthill , ed. Energy for Subsistence . Margaret Haswell . Perspective on Ratzel's Political Geography . James M. Hunter . Economic Deposits and their Tectonic Setting . Charles S. Hutchison . Energy Risk Assessment . Herbert Inhaber . Discovering the Vernacular Landscape . John Brinckerhoff Jackson . Climate and Energy Systems: A Review of Their Interactions . Jill Jäger . Dilemmas in Regional Policy . Antoni Kuklinski and J. G. Lambooy , eds. California Farmland: A History of Large Agricultural Landholdings . Ellen Liebman . The Spatial Organization of New Land Settlement in Latin America . Jacob O. Maos . Dark Continent: Africa as Seen by Americans . Michael McCarthy . Westport, CT: Climatology: An Introduction . John E. Oliver and John J. Hidore . Columbus, OH: The Geography of Warfare . Patrick O'Sullivan and Jesse W. Miller . The Expanding City. Essays in Honour of Professor Jean Gottmann . John Patten , ed. Scotland's Environment During the Last 30,000 Years . Robert J. Price . Integrated Urban Models . S. H. Putman . Development and the Environmental Crisis: Red or Green Alternatives? Michael Redclift .  相似文献   
875.
A variant to implement a spacecraft (SC) spatial attitude system with respect to the Sun is discussed. The sunward direction and the solar rotation axis are used as reference points. The system is based on measuring spectral line Doppler shift by scanning the solar image along the limb and is self-adjusting for relative spectral line shifts and instrument band shifts. The first harmonic of the signal serves as a basis for accurate adjustment of filter band. The second harmonic phase is used to measure the spacecraft attitude. The application of this method holds the greatest promise when the SO is stabilized by the sunward spinning because this ensures continuous monitoring of the spacecraft attitude.In addition, the method provides information on the precise coordinates of solar surface details during space-borne observations.  相似文献   
876.
色球压缩区是耀斑大气动力学过程的一个基本特征,是产生色球谱线红不对称性的基础。本文基于压缩区从大气高层向低层传播的理论公式,在二种不同情况下,计算得到了压缩区内物质运动速度随高度和时间的变化.结果表明,色球蒸发区压力增量Δp为常数时压缩区之寿命比压缩区波阵面后的压力p2为常数时要长得多,这就大大缓解了以往谱线不对称性的延续时间的理论值比观测值小的矛盾。形成高度不同的谱线具有不同程度的不对称性这一观测现象也同色球压缩区的传播特性相一致。  相似文献   
877.
We carried out one-dimensional hybrid simulations of resonant scattering of protons and He^2 ions by ion cyclotron waves in an initially homogeneous, collisionless and magnetized plasma. The initial ion cyclotron waves have a power spectrum and propagate both outward and inward. Due to the resonant interaction with the protons and He^2 ions, the wave power will be depleted in the resonance region. Both the protons and He^2 ions can be resonantly heated in the direction perpendicular to the ambient magnetic field and leading to anisotropic velocity distributions, with the anisotropy higher for the He^2 ions than for the protons. At the same time, the anisotropies of the protons and He^2 ions are inversely correlated with the plasma β‖p=8πnpkBT‖p/B0^2, consistent with the prediction of the quasilinear theory (QLT).  相似文献   
878.
利用紫台赣榆站太阳精细结构望远镜拍摄的色球和光球照片,研究了1990年11月6日至13日NOAA6361活动区的磁位形演化和耀斑产生区域,发现该活动区的活动主要集中在11日和12日两天还观测到新老活动区的碰撞耦合及耦合界面处小纤维(fibril)的快速变化,这些现象是由于前导黑子之一的p1黑子的连续几天的运动造成的.所有的活动也主要集中在P1黑子的周围.  相似文献   
879.
The modulation of cosmic rays (CRs) in the heliosphere is a dynamic and therefore a highly time-dependent process. Numerical models with only a time-dependent neutral sheet prove to be successful when moderate to low solar activity occurs but fail to describe large and discrete steps in modulated CRs when solar activity is high. To explain this feature of heliospheric modulation, the concept of global merged interaction regions (GMIRs) is required. The combination of gradient, curvature and neutral sheet drifts with these GMIRs has so far been the most successful approach in explaining the 11-year and 22-year cycles in the long-term modulation of CRs.  相似文献   
880.
太阳射电微波爆发及其精细结构研究进展   总被引:1,自引:0,他引:1  
太阳射电微波爆发携带着爆发源区的物理环境及辐射机制等诸多重要信息。其辐射频段较高,通常来自低日冕磁重联区,尤其是微波爆发的精细结构,持续时间短、变化快、结构复杂,可以反映重联过程复杂的磁场结构、高能粒子运动等许多特征。综述了太阳微波射电爆发分类研究的3个主要阶段,介绍了每一阶段的重要爆发类型、物理机制研究及相应的观测设备,讨论了进一步研究的方向。  相似文献   
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