Accumulation of Zn,Cu and Cd by crabs and barnacles     

P.S. Rainbow 《Estuarine, Coastal and Shelf Science》1985,21(5):669-686

The crab Carcinus maenas (L.) and the barnacle Elminius modestus Darwin were exposed to a range of dissolved concentrations of Zn, Cu and Cd for 21 days in artificial seawater. Accumulation of Zn and Cu by crabs has been interpreted in terms of the presence of a regulation mechanism to maintain constant body concentrations (83·2 ± 19·4 μg Zn g^?1 dry wt.; 39·8 ± 9·8 μg Cu g^?1 dry wt.) under varying external dissolved metal levels, until a threshold dissolved metal concentration (c. 400 μg Zn l^?1; c. 170 μg Cu l^?1) beyond which net accumulation of metal begins. Cadium appears to be accumulated by C. maenas at all exposures with no evidence for regulation of body cadmium concentrations. Exposure of E. modestus to Zn, Cu or Cd caused net accumulation of the respective metal in the bodies of the barnacles, with no evidence for regulation of body metal concentrations.  相似文献   

Asymmetrical breakwater gap wave diffraction using finite and infinite elements     

J.D. Pos 《Coastal Engineering》1985,9(2):101-123

An experimental technique and configuration has been developed by the author to simulate and measure (using short range photogrammetric techniques) the wave heights of waves diffracting into a model basin of infinite extent. The finite and infinite element program “WAVE” developed in the Department of Civil Engineering, University College of Swansea, Wales, has been modified to run on the UNIVAC 1100 at the University of Cape Town. The program is used to model the experimental configuration being tested mathematically. Two configurations, namely a symmetrical and an asymmetrical breakwater gap configuration, are analysed both experimentally and numerically. It is concluded that there is a good correlation between the finite element and experimental results and that the “WAVE” program is a very useful tool for the prediction of wave heights in large harbour basins.  相似文献   

The determination and analysis of the orbit of NIMBUS 1 ROCKET, 1964-52B: The semi-annual variation in air density from June 1968 to August 1974     

W.J. Boulton   《Planetary and Space Science》1985,33(12):1417-1431

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The transfer of polarized radiation in spectral lines: Formalism and solutions in simple cases     

Sean J. McKenna 《Astrophysics and Space Science》1985,108(1):31-66

A general treatment of the transfer of polarized radiation in spectral lines assuming a Rayleigh phase function and a general law of frequency redistribution is derived. It is shown how nine families of coupled integral equations for the moments of the radiation field arise which are necessary to fully describe the state of polarization of the emergent radiation from a plane-parallel, semi-infinite atmosphere. The special case of angle independent redistribution functions is derived from the general formalism, and it is shown how the nine families of integral equations reduce to the six linearly independent integral equations derived by Collins (1972). To serve as a test of the formulation, solutions for isothermal atmospheres are given.  相似文献   

The magnetic field of an infinite plane current sheet uniform except for two circular insertions of different uniform conductivities     

Attia A. Ashour 《Geophysical Journal International》1985,83(1):127-142

Summary. The electrical system of currents excited by a uniform electric field of arbitrary direction in an infinite plane sheet of uniform conductivity except for two non-overlapping circular areas is obtained analytically. Using the method introduced by Ashour, the magnetic field of the system is also obtained. The components of this additional field are expressed as line integrals which are suitable for computation. The results reduce, in the special case of one insertion, to those obtained earlier by Ashour & Chapman.
As an illustration, numerical results are obtained for the special case of two equal insertions of zero conductivity.
The analysis and results obtained are useful in estimating the modification of the currents flowing in an ocean and their magnetic field by two islands.  相似文献   

EVIDENCE OF HIGH COSMIC DUST CONCENTRATIONS IN LATE PLEISTOCENE POLAR ICE (20,000–14,000 YEARS BP)     

Paul A. LaViolette 《Meteoritics & planetary science》1985,20(3):545-558

Dust filtered from the lower portion of the Camp Century ice core (77°10'N, 61°08'W) has been analyzed for the presence of the cosmic dust indicators iridium and nickel using the neutron activation analysis technique. This study was carried out to test the hypothesis that the climatic change toward the end of the Last Ice Age was triggered by an incursion of nebular material into the Solar System. The analytical results are consistent with this hypothesis. Concentrations of Ir and Ni in the ice were one to two orders of magnitude higher during the latter portion of the Last Ice Age (19,700-14,200 years BP) as compared with current levels. Ir and Ni levels in 6 out of 8 samples suggest a total cosmic dust influx rate of about 0.5?3 times 10⁷ tons/yr to the Earth's surface as compared with about 1?7 x× 10⁵ tons/yr for the current influx. Elemental concentrations in 6 of the 8 dust samples ranged from 6? 96 ppb for Ir and < 60 to 3200 ppm for Ni. It is concluded that a major fraction of this invading dust would have been of submicron size in which case the concentration of light scattering particles would have been sufficient to significantly alter the light transmission properties of the Solar System and substantially affect the Earth's climate. These results mark the first time that cosmic dust deposition rates have been estimated for prehistoric times using the polar ice record.  相似文献   

Farey reprinted     

TREVOR D. FORD 《Geology Today》1992,8(5):174-175

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Discussion on: A mathematical model of permeability alteration around wells     

J. D. McKinley  M. D. Bolton 《国际地质力学数值与分析法杂志》1992,16(12):887-890

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Book review     

P. B. Attewell 《Geotechnical and Geological Engineering》1992,10(1):89-89

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CO₂ transfer between the upper mantle and the atmosphere: temporary storage in the lower continental crust     

J.LR. Touret 《地学学报》1992,4(1):87-98

The CO₂ atmospheric content has shown large variations over geological times. High contents (up to one order of magnitude more than present-day values) ultimately correspond to discrete episodes of mantle degassing, either juvenile, or subduction-related (carbon recycling). A number of arguments (e.g. the continuous volume increase of carbonate-bearing sediments with time) suggest that, throughout the Earth's history, juvenile CO₂ has formed a major contribution to the global carbon budget of the Earth.
The absence of a direct relationship between major volcanic episodes and the average CO₂ atmospheric content suggests that volcanoes might not be the only way by which mantle CO₂ is transported to the surface. It is proposed that large quantities of juvenile CO₂ could temporarily be stored in the lower continental crust during major episodes of granulite formation. These are primarily caused by magmatic underplating and they result in a vertical accretion of the crust by accumulation of CO₂-bearing, mantle-derived magmas. Most of the CO₂ migrates through the crust during post-metamorphic evolution and isostatic restoration of the normal continental thickness. However, large quantities of CO₂ can still be present in some areas, notably as high-density fluids enclosed in minerals.  相似文献