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61.
Photoelectric and absolute elements of the system RT Per have been determined inU, B, andV filters. It is suggested that the primary star may be surrounded by a gaseous disk. 相似文献
62.
The surface parameters are being evaluated using a methodology which considers the vertical temperature structure of MONTBLEX
’90. For this 30 metre micrometeorological tower data are utilised. In this process, a concept of isolated layers has been
introduced. The parameters have been evaluated following two successive iterative processes to give a consistent value both
in the flux-profile relation and the related similarity relation.
The heat flux obtained using the present methodology, is then utilised to examine its interplay with the synoptic as well
as mesoscale features. The existence of such an interplay is observed. 相似文献
63.
Wavelet and quadrant analyses were applied to turbulent velocity data in order to investigate the transition from the anisotropy of energy-containing eddies to the isotropy of the inertial subrange scales. The quadrant analysis of the wavelet coefficients of longitudinal and vertical velocity components allows the evaluation of the velocity structure functions and the momentum cospectrum as a function of the separation distance and of the quadrants. In an isotropic condition the contribution both of ejections and sweeps (even quadrants), and both of reflections and deflections (odd quadrants), has to be equal. The analysis has shown that in neutrally stratified conditions the transition to isotropy occurs in a frequency range (0.2 < r/z < 3) usually referred to as internal to the inertial subrange (r is separation distance, z is height). In the transition region, as in the isotropic region, the velocity structure functions still agree with the 1941 and 1962 Kolmogorov theories; but on the other hand the structure functions of the even and odd quadrants are fitted by power laws of different slopes in the transition region. The proposed analysis allows the investigation within the transition region of the different dynamical structure in the energy transfer from the energy-containing scales to the isotropic scales. 相似文献
64.
The present contribution gives an overview of current knowledge of a comprehensive and steadily growing research field. The first section deals with water pumping and particle retention mechanisms in ciliary and muscular filter feeders. The second section examines the biological filter pumps in order to assess adaptation to the environment. Filter-feeding benthic invertebrates have evolved filter pumps to solve common basic problems. This has led to a large degree of similarity between otherwise distant standing species, which makes comparative studies interesting and important. The present review of zoobenthic filter feeding aims at accentuating such recognition. 相似文献
65.
Late-Quaternary supply of terrigenous organic matter to the Congo deep-sea fan (ODP site 1075): implications for equatorial African paleoclimate 总被引:3,自引:1,他引:3
Late-Quaternary sections (about 1 Ma) from the Congo deep-sea fan (ODP Leg 175, site 1075) were used to reconstruct the terrigenous organic matter supply to the easternmost equatorial Atlantic Ocean. Variations in quantity and quality of the riverine organic matter reflect the interaction between the paleoclimatic development within the continental catchment area and the paleoceanographic conditions in the Congo river plume. To characterize the delivery of organic matter from terrigenous and marine sources, we used elemental and bulk carbon isotopic analyses, Rock-Eval pyrolysis, lignin chemistry, and organic petrology. High-amplitude fluctuations occurring about every 15-25 ka reveal a mainly precessional control on organic sedimentation. Results from Rock-Eval pyrolysis indicate a mixed kerogen type III/II, as would be anticipated in front of a major river. Fluctuations in Tmax from Rock-Eval pyrolysis demonstrate pronounced cyclic changes in the delivery of low- and high-mature organic matter. Contribution of the low-mature organic fraction was strongest during warm climates supporting enhanced marine production offshore of the Congo. Organic petrological observations confirm the existence of abundant terrigenous plant tissues, both non-oxidized (vitrinite) and oxidized (inertinite). Charcoal-like organic matter (fusinite) is attributed to periods of increased bush fires in the continental hinterland, and implies more arid climatic conditions. Results from ratios of specific phenolic lignin components suggest that terrigenous organic matter in Late-Quaternary sections of site 1075 mainly derives from non-woody angiosperm tissue, i.e., grasses and leaves. Correlation between the amount of specific lignin phenols and the bulk '13Corg signature fosters the conclusion that an appreciable amount of the terrigenous organic fraction derives from C4 plant matter. This may cause an underestimation of the terrigenous proportion of bulk organic matter when assessments are based on bulk carbon isotopic signatures alone. 相似文献
66.
Abstract Investigations aimed at obtaining knowledge about the environmental effects of mining aggregate from the sea bottom were carried out on the Stupsk Bank. Special attention was given to the magnitude and reach of changes of hydrologic conditions, in that to changes in concentration of matter suspended in sea water, and to dynamics of the sea bottom—change of bottom relief, resulting from both natural causes and from mining of the aggregate. 相似文献
67.
Jerry F. Payne L. Fancey J. Kiceniuk U. Williams Jim Osborne Anver Rahimtula 《Marine environmental research》1985,17(2-4)
The use of oil-based drilling muds has been discouraged in hydrocarbon exploration and production in the marine environment but these muds are presently being used to a considerable degree in the United Kingdom and Norwegian sectors of the North Sea. Field studies in the North Sea have demonstrated only localized impacts around individual drilling sites,1,2 even including those sites where ‘toxic’ diesel oils were employed as base fluids in drilling muds. Yet the question of disposal of cuttings contaminated with oil from drilling muds remains somewhat controversial. The induction of mixed-function oxygenases (MFO) has been validated on a number of occasions in the field as a sensitive index of low level hydrocarbon exposure (reviewed by Payne),3 including sites in the North Sea where diesel-based muds were used.4 The present study demonstrates that any potential for induction by hydrocarbon contaminated cuttings will probably be reduced by substitution of low-aromatic base oils for diesel in drilling mud formulations. 相似文献
68.
69.
Kinder A Sierts-Herrmann A Biselli S Heinzel N Hühnerfuss H Kammann U Reineke N Theobald N Steinhart H 《Marine environmental research》2007,63(5):506-515
Heat shock proteins 70 (hsp70) are known to be induced by a great variety of chemical stressors. The effects of different environmental contaminants, which were identified in sediments of the North Sea and the Baltic Sea as main contaminants or as contaminants of special toxicological interest, on the extent of expression of hsp70 in a permanent cell line Epithelioma papulosum cyprini (EPC) were investigated. Concentrations of the single contaminants leading to elevated hsp70 levels were compared to the respective concentrations of these contaminants encountered in the sediment extracts thus allowing an assessment of their contribution to the toxicity of these sediments. Analysis of hsp70 was performed using western blotting techniques with subsequent comparative quantification by densitometry. Eleven of thirteen contaminants have shown a dose-dependent increase in hsp70 levels. An expression of hsp70 was observed in most cases between 0.1 and 10 microg/mL test solution. Some of the investigated stressors led to extremely high hsp70 contents even at low concentrations. However, in most cases contaminant concentrations in sediments were too low to cause an effect. For this reason, effects of the tested sediments are attributed to other contaminants or rather to mixtures of stressors. 相似文献
70.
Abstract. The shell-boring gastropod Ocinebrina edwardsi (PAYR.) lives associated with Mytilus galloprovincialis LMK on which it preys. Predation is preferentially directed towards small (< 15 mm long) mussels. The predation rate (number of mussels eaten per gastropod per day) for medium sized mussels (16–25 mm long) during a year ranges from 0.03 to 0.11. The predation rate is directly influenced by the sea-water temperature. Predation follows a seasonal cycle reaching a maximum in July and a minimum in January. O. edwardsi drills selectively the median anterior region of the mussel valve, close to the dorsal edge. 相似文献