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21.
The day-to-day variations in ozone content at Uccle (51oN) during some stratospheric warming events are ex-amined. In particular, the attention is focused on the timing of commencement of ozone enhancement prior to peak day of warming and on the relationship in the ozone content between the upper and lower stratosphere. These two features are compared with the predictions of ozone transport models. There seems to be an agreement between mod-el predictions and observed features in some cases. 相似文献
22.
Marine sediment cores collected from several depths of water and distances from a California sewage outfall were tested to see if sediments influenced by sewage solids were a reservoir of enteric pathogens, and if concentrations of indicator bacteria were related to the presence of sewage solids. Vertical distributions of microorganisms in marine sediments were determined; there was a decrease of indicator bacteria with increasing sediment depth. Aeromonas was randomly isolated, but none of the enteric bacterial pathogens or viruses were detected. While classic indicator bacteria were of little value in predicting the presence of pathogens, or relative amounts of sewage solids, Clostridium perfringens may be a suitable indicator. Clostridium perfringens concentrations were not related to the presence of pathogens in sediments. 相似文献
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原子吸收光谱法(AAS)目前已广泛应用于地球化学分布和地球化学勘查研究中的元素测定。在地质样品分析中,AAS法之所以被普遍采用,在很大程度上是由于易于购得合适的商品仪器,这些仪器具有操作简单、可靠和高效的特点。方法对许多有地质意义的元素可达到10-6克(ppm)的检出灵敏度。 相似文献
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23.1 介绍 模拟与频率和方向相关的大洋波谱F(f,θ)的工作是极其困难的。唯一有点统一的理论(Hasselmann,1967)也还没有简化成一种实用形式。这篇研究中所探讨的是结合零散的,现有的理论,以达到这样一种目的:即发展一种与我们目前对风浪成长谱的了解相一致 ·95.的波谱模式。本章中我们将讨论一种离散的谱模式,这种模式采用了一种改进的能量传播的特征方法。数值方法最早是由Barnett等(1969)提出的。 相似文献
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Remotely sensed assessment of water quality levels in the Pearl River Estuary, China 总被引:3,自引:0,他引:3
In this paper, a method of assessing water quality from satellite data is introduced. The composite pollution index (CPI) was calculated from measured chemical oxygen demand (COD) and nutrient concentration. The relationships between CPI and 240 band combinations of SeaWiFS water-leaving radiance were analyzed and the optimal band combination for estimating CPI was chosen from the 240 band combinations. An algorithm for retrieval of CPI was developed using the optimal band combination, (L443 × L510)/(L412 + L490). The CPI was estimated from atmospherically corrected SeaWiFS data by employing the algorithm. Furthermore, the CPI value range for each water quality level was determined based on data obtained from 850 samples taken in the Pearl River Estuary. The remotely sensed CPIs were then transferred to water quality levels and appropriate maps were derived. The remotely sensed water quality level maps displayed a similar distribution of levels based on in situ investigation issued by the State Ocean Administration, China. This study demonstrates that remote sensing can play an important role in water quality assessment. 相似文献
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在固体地球中,破裂是一种普遍存在的自然现象,例如风化、爆炸、普撞、断层作用、地震等等。许多关于破裂的经验性研究已论证了破裂具有形如N(r)-r^-D的幂律关系,这提供了破裂是一个关于尺度分布的标度不变过程的证据。此处N(r)是尺度大于r的碎块的总数。因此,破裂能够从分形的观点加以描述。这一描述定量地得到了Gaudin-Schuhmann关系和Charles关系,并且足以包含尺度衰减的三种理论:Ri 相似文献
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Leitzinger M Odert P Kulikov YN Lammer H Wuchterl G Penz T Guarcello MG Micela G Khodachenko ML Weingrill J Hanslmeier A Biernat HK Schneider J 《Planetary and Space Science》2011,59(13):1472-1481
We present thermal mass loss calculations over evolutionary time scales for the investigation if the smallest transiting rocky exoplanets CoRoT-7b (∼1.68REarth) and Kepler-10b (∼1.416REarth) could be remnants of an initially more massive hydrogen-rich gas giant or a hot Neptune-class exoplanet. We apply a thermal mass loss formula which yields results that are comparable to hydrodynamic loss models. Our approach considers the effect of the Roche lobe, realistic heating efficiencies and a radius scaling law derived from observations of hot Jupiters. We study the influence of the mean planetary density on the thermal mass loss by placing hypothetical exoplanets with the characteristics of Jupiter, Saturn, Neptune, and Uranus to the orbital location of CoRoT-7b at 0.017 AU and Kepler-10b at 0.01684 AU and assuming that these planets orbit a K- or G-type host star. Our findings indicate that hydrogen-rich gas giants within the mass domain of Saturn or Jupiter cannot thermally lose such an amount of mass that CoRoT-7b and Kepler-10b would result in a rocky residue. Moreover, our calculations show that the present time mass of both rocky exoplanets can be neither a result of evaporation of a hydrogen envelope of a “Hot Neptune” nor a “Hot Uranus”-class object. Depending on the initial density and mass, these planets most likely were always rocky planets which could lose a thin hydrogen envelope, but not cores of thermally evaporated initially much more massive and larger objects. 相似文献