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51.
Rare-earth elements in a whole-rock sample and in major components of the Allende meteorite were investigated; for a few samples, abundances of Ba, Sr, Ca, and Al were also determined. Of the materials investigated in the present work, CaAl-rich inclusions G and O seem to be of the greatest significance. In spite of the minor difference in mineralogy between them, the apparent chondrite-normalized RE pattern is much different between these two inclusions. (Yb and Eu in inclusion G appear exceptionally irregular). This observation is inferred to reflect a rather subtle difference in condition of condensation. It is also worthwhile to note that, while two portions (pink and white) of the inclusion G show similar aspects in the abundances of lithophile trace elements investigated, they show a remarkable difference at the same time. The white portion (Gw) of inclusion G can be considered to be a mixture of chondritic material and highly fractionated material like the faintly pink portion (Gp) picked from the same inclusion. This would suggest the possibility that the Gp-like material was produced from chondritic dust.The “matrix” separated from Allende was found to be fractionated with respect to the RE abundances relative to representative chondrite. It has also a very high value for the Ba abundance. 相似文献
52.
A series of measurements of winds and wind-waves were carried out in wind-wave flumes. A data analysis based on the hypothesis
of local equilibrium yielded a new empirical formula on the controversial quantity of roughness heightz
0 over the water surface:
, where the nondimensional roughness height
is defined bygz
0/u
*
2 and the wave-wind parameterũ byω
p
u
*/g, g being the gravitational acceleration,u
* the friction velocity of air,ω
p
the peak frequency of wind-wave spectra. The obtained formula is compared with Charnock's (1955) and Toba's (1979) proposals;
is constant in the former and inversely proportional toũ in the latter. As in Toba's, this formula immediately leads to a practically important conclusion that the drag coefficientC
d
depends not merely on the usual variableU
10 (wind velocity at 10m height over the water surface), but also on the surface state represented by wind-waves. An explicit
expression is provided for the drag coefficient incorporating the wave-wind parameter; it covers the range ofC
d
calculated from most of the previous drag formulas, by varying the wave-wind parameter. 相似文献
53.
54.
Wind-wave spectra measured in a wind-flume are analyzed according to the hypothesis of local equilibrium. The gross relation between the wave height and the frequency is reexamined to yield the basic validity of the 3/2-power law of Toba orE~? in the range of 0.4≦?≦1, where? is the wave-wind parameter defined by?=ω p u */g; ω p denotes the peak frequency of the wind-wave spectra,u * the friction velocity andg the gravitational acceleration. Noticeable deviation is found, however, for?<0.4 or?>1. In particular, the data for large? suggest the existence of an upper limit of the wave nonlinearityE at about 5×10?2, whereE=Eω p 4 /g2 withE the total power of the wind wave spectrum. Then, the spectral form is investigated in detail. As? decreases, the normalized spectrum becomes more gradual as a whole, but its forward (low frequency) part tends to show a steeper profile. In the high frequency region ( \(\tilde \omega \) >2.6), the spectrum is found to have a functional form likeu * 2 ω ?3, which differs from the usualω-dependence asω ?5 orω ?4. It suggests weak dependence of the high-frequency spectra on the gravitational accelerationg and on the peak frequencyω p ; spectral density at high frequencies may be saturated, so that its magnitude may be dominated by the frequencyω, the friction velocityu *, the surface tension and the viscosity. 相似文献
55.
Abstract. A two-year ecological study in the Oliveri-Tindari (Messina) brackish water ponds evaluated the quantitative and qualitative distribution of Vibrio species in relation to the physicochemical conditions of the ponds.
The evaluation of 204 samples shows a general relationship between the halophilic vibrios and water temperature. In particular this relationship is stronger for the Vibrio fraction able to grow at 37°C, i. e. , those species related to human infections. On the other hand, the halophilic vibrios show no relation with the index of fecal contamination.
The ecology of V. parahaemolyticus is discussed in relation to the salinity of Marinello pond.
The distribution of V. cholerae non O1, isolated from all ponds, shows that this microorganism can be considered as autochthonous in coastal environments. 相似文献
The evaluation of 204 samples shows a general relationship between the halophilic vibrios and water temperature. In particular this relationship is stronger for the Vibrio fraction able to grow at 37°C, i. e. , those species related to human infections. On the other hand, the halophilic vibrios show no relation with the index of fecal contamination.
The ecology of V. parahaemolyticus is discussed in relation to the salinity of Marinello pond.
The distribution of V. cholerae non O1, isolated from all ponds, shows that this microorganism can be considered as autochthonous in coastal environments. 相似文献
56.
The behavior of the water wedge advancing along the interface between two homogeneous layers is investigated experimentally. The horizontally intruding wedge is strongly influenced by the detailed structure of the interface, even when the interface is sharp enough for its position to be visually determined. Within our experimental range, the intrusion velocity is very slow and depends on the thickness of the interface along which the water wedge intrudes. The wedge length is well described by the relation which is derived using an analogy to the linearly stratified case. The results could be useful for understanding the generation mechanism of the oceanic microstructure. 相似文献
57.
Akira Masuda 《Journal of Oceanography》1988,44(4):189-199
A Batchelor-modon eddy is a highly specialized nonlinear vortex pair, whose potential vorticity depends linearly on the stream function viewed from the coordinates moving with the translation velocity of the eddy. To generalize it, a skewed model is developed by introducing a cubic nonlinearity in addition to the linear term. A perturbation analysis shows that the eddy region is no longer a circle but is elongated longitudinally or transversely according as the sign of the cubic term. Moreover, the eddy is slightly flattened or steepened. The cubic term increases or decreases the translation velocity, if the average radius and the amplitude are fixed. A numerical experiment on anf-plane is carried out to show that these skewed eddies retain their initial forms even after they turn a corner of the basin; they are as stable as (first-mode) standard Batchelor-modon eddies. The present skewed model gives a reasonable qualitative interpretation of deformed eddies which result from merging of two eddies or from initially Gaussian eddies near the boundary. 相似文献
58.
A new version is adopted for the evaluation of the upwelling radiation from atmosphere bounded by the surface, where the surface is composed of two half semi-infinite Lambert surfaces and a stream is inserted between them. The contrast of the stream is discussed with respect to the atmospheric effect. The width of the stream is considered to be 0.5, 1, and 3km; The solar and observational direction is located in the normal plane to the stream. The observational site is located at altitude 30km. The horizontal distance of observational site to the stream is fixed to 6.28 . The atmosphere is assumed to be homogeneous, which is composed of aerosol and molecules, where the model aerosol is of the oceanic type.In the computational procedure, a probability of radiation interacting with respective half surfaces and the stream are calculated based on the assumption of single scattering in the atmosphere, where isotropic scattering is undertaken. By use of this probability, the emergent radiation at the top of the atmosphere is calculated approximately by considering the radiative interactions between atmosphere and surfaces up to twice. The numerical simulation exhibits the extraordinary effect near the stream. The contrast of the stream depends upon the albedo of the surrounding surfaces. It increases with the increase of the stream width and decreases with the optical thickness. 相似文献
59.
T. Kosugi K. Makishima T. Murakami T. Sakao T. Dotani M. Inda K. Kai S. Masuda H. Nakajima Y. Ogawara M. Sawa K. Shibasaki 《Solar physics》1991,136(1):17-36
The Hard X-ray Telescope (HXT) is a Fourier-synthesis imager; a set of spatially-modulated photon count data are taken from 64 independent subcollimators and are Fourier-transformed into an image by using procedures such as the maximum entropy method (MEM) or CLEAN. The HXT takes images of solar flares simultaneously in four energy bands, nominally 15 (or 19)–24, 24–35, 35–57, and 57–100 keV, with an ultimate angular resolution as fine as 5 arc sec and a time resolution 0.5 s. Each subcollimator has a field of view wider than the solar disk. The total effective area of the collimator/detector system reaches 70 cm2, about one order of magnitude larger than that of the HINOTORI hard X-ray imager. Thanks to these improvements, HXT will for the first time enable us to take images of flares at photon energies above 30 keV. These higher-energy images will be compared with lower-energy ones, giving clues to the understanding of nonthermal processes in solar flares, i.e., the acceleration and confinement of energetic electrons. It is of particular importance to specify the acceleration site with regard to the magnetic field figuration in a flaring region, which will be achieved by collaborative observations between HXT and the Soft X-ray Telescope on board the same mission.After the launch the name of SOLAR-A has been changed to YOHKOH. 相似文献
60.
Nitrate transport in the unsaturated zone of a riverbank filtration (RBF) system in Karany, Czech Republic, was studied. Previous study of the system estimated RBF recharge as 60% riverbank filtrate and 40% local groundwater contaminated by nitrates. Nitrate concentrations observed in RBF recently cannot be explained by simple groundwater contamination and a new conception of groundwater recharge is suggested. A two‐component model based on water 18O data modelled recharge of local groundwater. One component of groundwater recharge is rainfall and irrigation water moving through the unsaturated zone of the Quaternary sediments in piston flow. The second component is groundwater from the Cretaceous deposits with a free water table. Both the components of groundwater recharge have different nitrate concentrations, and resulting contamination of groundwater depends on the participation of water from Quaternary and Cretaceous deposits. Nitrates' origins and their mixing in the subsurface were traced by 15N data. Nitrate transport from the unsaturated zone is important and time variable source of groundwater contamination. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献