In situ velocity profiles in gassy sediments: Kiel Bay     

S. S. Fu  R. H. Wilkens  L. N. Frazer 《Geo-Marine Letters》1996,16(3):249-253

Acoustic behavior of gas-bearing sediments is significantly different from that of gas-free sediments. In situ velocity profiles and acoustic signal characteristics in gas-bearing sediments of the upper several meters of the sea floor in Kiel Bay are presented in this study. Observed velocities in gas-bearing sediments are both higher and lower than those of the gas-free sediments. Small amounts of gas appear to cause signal reverberation without much attenuation. whereas large amounts of gas cause substantial attenuation.  相似文献   

Seasonal distribution and growth of larval herring (Clupea harengus L.) in the Georges Bank-Gulf of Maine area from 1962 to 1970     

Boyar  H. C.; Marak  R. R.; Perkins  F. E.; Clifford  R. A. 《ICES Journal of Marine Science》1973,35(1):36-51

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Integrated coastal zone management in Kenya: initial experiences and progress     

E.N. Okemwa  R.K. Ruwa  B.A.J. Mwandotto 《Ocean & Coastal Management》1997,37(3):319-347

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Bedrock morphology and structures within overlying sediments,Start Bay,Southwest England,determined by continuous seismic profiling,side-scan sonar,and core sampling     

Nigel C. KellandJohn R. Hails 《Marine Geology》1972

The bedrock morphology of Start Bay, Southwest England, and the Structures within overlying sediments have been determined by a combined geophysical and geological survey. It has been established that the Skerries Bank consists of a drape of possibly coarse, unconsolidated material (bank deposits) overlying medium- to fine-grained silty sand (bay deposits). A break of slope in the bedrock surface, traced along the entire length of the Bay, and a step profile in the southern part of the Bay, may be either a legacy of submerged topography produced by vigorous tidal action, or alternatively the product of subaerial and marine processes. Other significant geological features in the Bay include infilled valleys, and “terraces” possibly pertaining to relict barrier beaches.  相似文献   

The effect of copper pollution on mitochondrial degeneration     

E. Aloj Totaro  F.A. Pisanti  P. Glees  A. Continillo 《Marine environmental research》1986,18(4)

The authors describe the effect of copper pollution on the mitochondria from various areas of the Torpedo marmorata central nervous system. A high percentage of swollen mitochondria has been observed in neurons from animals experimentally exposed to high level of copper (4 ppm). The correlation with age pigment granules is discussed.  相似文献   

积雪变化导致格陵兰冰盖高度变化     

J.R.McConnell 《海洋地质前沿》2001,17(1)

地面冰盖对气候变化的反应可能会对未 来的海平面变化产生重大的影响.近年来格 陵兰南部的卫星调查显示,较大高度的冰盖 总体高度变化甚小,但空间变化很大.当然 仅仅依靠卫星数据难以测定是什么地球物理 过程引起了这种高度变化以及近年的变化速 率是否超过了正常变化速率.我们利用雪粒 密度增大的物理模型和根据高海拔12个冰 心再造的年雪堆积记录,获取了1978～1988 年格陵兰南部冰盖高度的变化. 地中海的干涸及其产生的后果 К.Н. Несис 很久以来就知道,地史最后阶段最具戏 剧性的事件之一就是大约在6Ma前的中新 世末期地中海的被隔离和完全干涸.据西西 里岛墨西拿城附近该时期著名的沉积剖面, 这个事件被称之为墨西拿盐量转变. 马建华摘译自 , 2000, Vol.406,No.24 周立君校  相似文献   

A shipborne magnetic survey in Hudson Bay     

G. V. Haines  R. L. Coles 《Marine Geophysical Researches》1982,5(3):273-300

A marine magnetic total-field survey of Hudson Bay was conducted from 1975 to 1978. Approximately 62 000 line-km of data, or 35 000 five-minute averages, were acquired. The data were corrected for secular variation by means of a polynomial in latitude, longitude, and time, first fitted to annual mean differences from nine observatories and then integrated over time. The data were corrected for diurnal and transient variations by means of a linear interpolation, over geomagnetic latitude, of running hourly mean values from two neighbouring magnetic stations (numbering seven in all). Crossover differences are analysed in terms of a mixture of normal distributions resulting from the intermittent transient variations, and indicate the effectiveness of the corrections. The variance of the data is reduced, as a result of the corrections, by 87% during quiet periods and by 53% during disturbed periods, the weighted variance being reduced by 66%. Navigational accuracy is estimated, from a novel method utilizing crossover differences and field gradients, to be approximately 300 m. Anomalies are presented in profile form, and discussed briefly.Contribution from the Earth Physics Branch No. 973.  相似文献   

In situ tests for ice strength measurements     

H.R. Kivisild  S.H. Iyer 《Ocean Engineering》1976,3(5):329-342

Ice effects have caused extensive damage. Enormous forces have been recorded. On the other hand, ice has been used as a structural material under various situations. To use ice beneficially and to assess the danger of ice forces, it is necessary to know the mechanical properties of ice.Results from the large number of ice tests carried out in laboratories show the difficulties of sampling and testing procedures. Most of the tests have not reproduced faithfully enough the conditions existing in nature. To obtain adequate results, laborious and slow samplings and preparations of test specimens have been necessary. Recently, extensive use has been made of in situ tests in order to reduce the number of factors whixh can induce errors in measurements. Large scale tests have simulated actual structures. General ice properties have become available from small-scale in situ tests. Since these tests give rapid results, a large number are already available with a good coverage of field conditions.A theoretical basis has been devised for these in situ tests which measure essentially the unconfined and confined compressive strengths of ice, and practical devices have been developed to execute these tests. A correlation of measurements from laboratory tests and in situ tests has established a link between natural and artificial environments. Brittle elastic and clastic theories have been applied, to find the best correlations for ice tests. Test results have been related to the mechanical properties as used in engineering practice.A very summary conclusion of results is that cold sea ice and cold fresh water ice are both very strong. However, depending on the load rate, ice can be quite brittle, which mitigates dangerous effects from ice action against massive structures.  相似文献   

Remote determination of momentum-flux profiles in the lower atmospheric boundary layer     

R. D. Kouznetsov  V. F. Kramar  M. A. Kallistratova 《Izvestiya Atmospheric and Oceanic Physics》2006,42(6):696-703

An acoustic locator—a sodar—is a unique instrument for getting the objective characteristics of the current state of the atmospheric boundary layer (ABL) owing to a combination of such properties as remoteness, mobility, resolution, and information content. This study demonstrates the capabilities of a sodar to obtain data on the second moments of the field of wind-velocity fluctuations, in particular, the profiles of momentum flux in the lower ABL, which are very important in practical applications. A corresponding method is described, and the results of its experimental verification and some examples of its application under the conditions of different ABL stratification are presented.  相似文献   

Nitrate assimilation by zooxanthellae maintained in laboratory culture     

F. P. Wilkerson  R. K. Trench 《Marine Chemistry》1985,16(4):385-393

The ability of cultured zooxanthellae to use ammonium and nitrate was tested. The zooxanthellae were initially isolated from the anemone Aiptasia pulchella. The zooxanthellae were able to grow on media supplemented with either form of dissolved inorganic nitrogen (DIN) although ammonium was inhibitory above 300 μM. In accord with the intact symbiosis and freshly isolated algae, the cultured zooxanthellae took up ammonium. In contrast, the cultured algae demonstrated nitrate uptake and utilization. This was enhanced with DIN deprivation. Nitrate reductase was found in the algae and appeared to be inducible. Within the animal host, excretory ammonium may repress this induction.  相似文献