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11.
Macrofaunal assemblages with the prevalence of Bresiliidae shrimp and Mytilidae mussels are abundant in the hydrothermal vents
along the Mid-Atlantic Ridge. The mussels inhabit the zone of diffuse seeps of hydrothermal fluids with temperature abnormalities
up to several degrees. Shrimps inhabit an extreme biotope in the mixed interface between the seawater and the hydrothermal
fluid at a temperature up to 20–30°C. We studied the mussel and shrimp assemblages in three hydrothermal vent fields: the
Rainbow, Broken Spur, and Snake Pit. The species richness of the mussel assemblages in at least two regions (Broken Spur and
Snake Pit) is higher as compared with the shrimps of the same hydrothermal vent fields. The fauna inhibiting the shrimp swarms
lack almost any taxa specific for particular assemblages: almost all the taxa are also present in the mussel beds. The structure
of the shrimp assemblage is less homogeneous as compared with that of the mussel assemblage. The population prevalence of
one taxon (Copepoda) in the shrimp assemblage is most likely connected with the extreme and unstable conditions of the biotope
occupied by the shrimps in the hydrothermal field. The taxonomic similarity between the mussel and shrimp assemblages within
one hydrothermal vent field is higher as compared with the similarity between the mussel (or shrimp) assemblages from different
fields. 相似文献
12.
A. M. Anokhina V. I. Galkin K. V. Mandritskaya T. M. Roganova 《Astrophysics and Space Science》1993,209(1):19-38
A method for calculating average characteristics of Cerenkov light from very high energy (1–100 TeV) air showers is described. Simple approximation of lateral distribution of light is presented which might be useful for experiment as well as for simulations. 相似文献
13.
Anna Belehaki Ivan Kutiev Bodo Reinisch Norbert Jakowski Pencho Marinov Ivan Galkin Chris Mayer Ioanna Tsagouri Themistocles Herekakis 《Acta Geophysica》2010,58(3):432-452
The purpose of this paper is to evaluate the performance of the TSMP-assisted Digisonde (TaD) topside profiling technique.
We present systematic comparisons between electron density profiles and TEC parameters extracted from TaD model with (a) CHAMP-derived TEC parameters, (b) CHAMP reconstructed profiles, (c) ground based GPSderived TEC parameters, and (d) profiles reconstructed from RPI/IMAGE plasmagrams. In all cases, TaD follows the general trend of plasmaspheric
observations derived from the above datasets. Especially during storm cases, TaD shows remarkable agreement with the variations
of the ground based GPS-derived TEC parameters. Overall, the comparison results shows that TaD method can be adopted by EURIPOS to provide the electron density
distribution up to plasmaspheric heights in real-time. 相似文献
14.
Bottom fauna associated with mussel beds and alvinellid communities in the hydrothermal field at 9° N of the East Pacific Rise 总被引：1，自引：0，他引：1
Samples from mytilid mollusk and alvinellid polychaet communities and associated fauna were collected during cruise 49 of R/V Akademik Mstislav Keldysh at 9° N of the East Pacific Rise. The mytilids Bathymodiolus thermophylus occupied zones of diffuse releases of hydrothermal solutions with temperature anomalies a few degrees in amplitude. The alvinellid assemblages were located in the hottest parts of hydrothermal vents (～ 40°C) over sulfide mounds. The taxonomic compositions of these kinds of assemblages are different. The taxonomic richness of mytilid communities is almost twice higher. A comparison of the samples using Jaccard’s index showed a greater similarity among the alvinellid samples than that between the mytilid ones. With respect to the species number, polychaets formed the most diverse group, while gastropods were the second most diverse. The dominant species had greater proportions in alvinellid communities than in mytilid ones. This study showed great differences between the mytilid and alvinellid associations in their species composition and community structure. 相似文献
15.
The formation of annular features on Venus, the so-called coronae, is modeled. It is common practice to associate their formation with the uplift and relaxation of hot mantle diapirs. We managed to partially reproduce the topography and structural pattern of the initial stage of corona evolution, a radially fractured dome, by lifting and lowering a piston under a layer of sand with consistent oil or moist clay. We failed to model a dense radial fracturing, which is typical of the earliest stage of corona evolution. We were able to reproduce the necessary attribute of coronae, concentric structures, which are commonly assumed to be formed at the stage of dome relaxation. Their formation mechanism in our experiments can serve only as a partial analog of the processes that produce corona rims. There is an obvious need to use more accurate models. Nevertheless, our modeling shows that the brittle deformations manifest themselves more clearly than do the plastic ones in the formation of dome-shaped uplift during the generation of natural coronae. The modeling also shows that the pattern of deformation within the dome-shaped uplift depends to some extent on the relationship between the layer thickness and the cross-sectional piston sizes. The latter can be a model for the relationship between the lithosphere thickness and the cross-sectional sizes of the mantle diapir that form a corona. 相似文献
16.
S. V. Vysotskiy N. G. Galkin A. V. Barkar E. A. Chusovitin A. A. Karabtsov 《Russian Journal of Pacific Geology》2010,4(4):347-354
This paper reports the results of the study of hydrothermal precious opals. It was established that, in terms of their nanostructure
and formation conditions, the hydrothermal opals differ from exogenic precious opals. They are made up of small globules and
do not show any structuring of their nanoparticles on the basis of closest packing, which is typical of exogenic precious
opals. During their formation, these opals were subjected to pneumatolytic annealing—they experienced the impact of a high-temperature
vapor under elevated pressure. The influence of the thermal effect led to the formation of two-dimensional photonic band gaps
in the chaotic opal matrix. These bands are composed of sheets whose cells were formed owing to the thermal effects according
to the principle of “Benard cells.” Precisely these structured blocks and thin films are responsible for the spectral dispersion
of light and iridescence. 相似文献
17.
18.
The causes which prevent an increase in the accuracy of the refractive indices for high-precision electronic distance measurements
are described. It is shown that there is a large number of molecular resonances in the visible and IR spectrum which are due
to practically all atmospheric components and not just the trace gases. It is also shown that in such conditions the Rayleigh,
Lorentz-Lorenz and Sellmeier formulae need to be corrected. Methods for the correction and experimental testing are proposed.
Received: 16 July 1996 / Accepted: 27 March 1997 相似文献
19.
20.
The distributions of Fe, Mn, Zn, Cu, Ni, Co, Cr, Pb, As, Ag, Cd, Se, Sb, and Hg in 128 samples of tissues of the organisms that inhabit hydrothermal vent fields of the Mid-Atlantic Ridge (Menez Gwen, Snake Pit, and Rainbow) depending on the abiotic environmental parameters were studied. The majority of the elements studied showed direct correlations between their concentrations in the fluids released and in the tissues of hydrothermal organisms. A higher degree of bioaccumulation of metals was revealed in the Bathymodiolus mussels and Rimicaris shrimps from the Rainbow hydrothermal vent field as compared to their analogues from Menez Gwen and Snake Pit. This corresponds to the maximum concentrations of the majority of the metals studied in the Rainbow high-temperature hydrothermal fluids. The highest degree of bioaccumulation of heavy metals was found in gills of the symbiotrophic mussels Bathymodiolus and in maxillipeds of the ectosymbiotic shrimps Rimicaris, i.e., in the organs that function in dependence on chemosynthetic bacteria. Within the Rainbow vent field, the shrimps, which inhabit in biotopes with more high-temperature conditions and therefore are more strongly subjected to the influence of fluids, were found to contain higher metal contents than mollusks. The Fe-Mn hydroxide films that cover mussel shells might serve as important reservoirs of other metals related to Fe and Mn. 相似文献