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21.
David A. Noever Helen C. Matsos Raymond J. Cronise Loren L. Looger Rachna A. Relwani Vladimir I. Nikora 《Climatic change》1994,27(3):299-320
Phytoplankton is considered a key component mediating the ocean-atmospheric exchange of carbon dioxide and oxygen. Lab simulations which model biological responses to atmospheric change are difficult to translate into natural settings owing in part to the vertical migration of phytoplankton. In the sea this vertical migration acts to regulate actual carbon dioxide consumption. To capture some critical properties of this vertical material transfer, we monitored the effects of atmospheric CO2 on dense suspensions of bioconvecting microorganisms. Bioconvection refers to the spontaneous patterns of circulation which arise among such upwardly swimming cells as alga, protozoa, zoospore and large bacteria. Gravity, phototaxis and chemotaxis have all been implicated as affecting pattern-forming ability. The ability of a biologically active suspension to detect atmospheric changes offers a unique method to quantify organism adjustment and vertical migration. With increasing CO2, bioconvection patterns in alga (P. parva) and protozoa (T. pyriformis) lose their robustness, and surface cell populations retreat from the highest CO2 regions. Cell movement (both percent motile and mean velocity) generally diminishes. A general program of image analysis yields statistically significant variations in macroscopic migration patterns; both fractal dimension and various crystallographic parameters correlate strongly with carbon dioxide content. 相似文献
22.
Boris P. Ilyashuk Andrei A. Andreev Anatoly A. Bobrov Vladimir E. Tumskoy Elena A. Ilyashuk 《Journal of Paleolimnology》2006,35(4):855-872
Chironomid, pollen, and rhizopod records from a permafrost sequence at Bol’shoy Lyakhovsky Island (New Siberian Archipelago)
document the development of a thermokarst palaeo-lake and environmental conditions in the region during the last Interglacial
(MIS 5e). Open Poaceae and Artemisia associations dominated vegetation at the beginning of the interglacial period. Rare shrub thickets (Salix, Betula nana, Alnus fruticosa) grew in more protected and wetter places as well. Saalian ice wedges started to melt during this time, resulting in the
formation of an initial thermokarst water body. The high percentage of semi-aquatic chironomids suggests that a peatland-pool
initially existed at the site. A distinct decrease in semi-aquatic chironomid taxa and an increase in lacustrine ones point
to a gradual pooling of water in the basin, which could in turn induce thermokarst and create a permanent pond during the
subsequent period. The highest relative abundance of Chironomus and Procladius reflects unfrozen water remaining under the ice throughout the ice-covered period during the later stage of palaeo-lake development.
The chironomid record points to three successive stages during the history of the lake: (1) a peatland pool; (2) a pond (i.e.,
shallower than the maximum ice-cover thickness); and (3) a shallow lake (i.e., deeper than the maximum ice-cover thickness).
The trend of palaeo-lake development indicates that intensive thermokarst processes occurred in the region during the last
Interglacial. Shrub tundra communities with Alnus fruticosa and Betula nana dominated the vegetation during the interglacial optimum. The climate was moister and warmer than present. The results of
this study suggest that quantitative chironomid-based temperature reconstructions from Arctic thermokarst ponds/lakes may
be problematic due to other key environmental factors, such as prolonged periods of winter anoxia and local hydrological/geomorphological
processes, controlling the chironomid assemblages. 相似文献
23.
Eric A. Jerde Lawrence A. Taylor Ghislaine Crozaz Nikolai V. Sobolev Vladimir N. Sobolev 《Contributions to Mineralogy and Petrology》1993,114(2):189-202
Major-element and REE compositions of 14 diamondiferous eclogites from the Udachnaya kimberlite in Yakutia, Siberia have been determined by electron microprobe and secondary ion mass spectrometer (SIMS). Based on previous clinopyroxene classification schemes (e.g., Taylor and Neal 1989), all of these eclogite xenoliths belong to Group B/C, although some of the garnet compositions and mineral REE abundances are inconsistent with the indicated groups. This demonstrates the inadequacy of the classification scheme based on African eclogites for application to Siberian samples. Because of the coarse grain size of the Udachnaya nodules, meaningful modal abundances could not be obtained. However, reconstructed REE compositions using various garnet: clinopyroxene ratios demonstrate relative insensitivity to changes in mode for common eclogitic assemblages. Many of these reconstructed REE compositions show LREE depletions. Some depletions are consistent with an origin (either directly or through partial melting) as normal or Type-I ocean floor basalt. Others, however, require material of eclogitic or pyroxenitic affinities to undergo partial melting; this facilitates the depletion of LREE while leaving the HREE at nearly original levels. Many of the eclogites of South Africa are consistent with a protolith of anomalous or Type II ocean floor basalt. This fundamental difference between the two regions is the likely cause of the inconsistencies with the chemicallybased classification. 相似文献
24.
Victor P. Yakushev Vladimir V. Karelin Vladimir M. Bure Elena M. Parilina 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(6):1671-1677
Problem of soil acidity regularization is modeled as stochastic adaptive control problem with a linear difference equation of the dynamics of a field pH level. Stochastic component in the equation represents an individual time variability of soil acidity of an elementary section. We use Bayesian approach to determine a posteriori probability density function of the unknown parameters of the stochastic transition process. The Kullback–Leibler information divergence is used as a measure of difference between true distribution and its estimation. Algorithm for the construction of an adaptive stabilizing control in such a linear control system is proposed in the paper. Numerical realization of the algorithm is represented for a problem of a field soil acidity control. 相似文献
25.
Wojciech Stopiński Gienadiy A. Sobolev Aleksandr W. Ponomaryov Vladimir Los 《Pure and Applied Geophysics》1991,136(1):49-58
Making measurements of electric resistivity at 16 s intervals, the authors noticed fast changes of this parameter prior to the occurrence of the main fracture. The changes are superposed on bay pulsations of increasing amplitude and decreasing period. This finding opens prospects for a wider use of an electric resistivity method and proves the high quality of automatic instruments, in particular their high resolution. It also gives evidence for the occurrence of short-period precursors in the fracture zone while the main fracture is being formed. 相似文献
26.
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28.
Vladimir Pletser 《Earth, Moon, and Planets》1988,41(3):295-300
The rings and satellites discovered by Voyager 2 in the Uranian system confirm the existence of small satellites and rings foreseen before their discoveries and close to the locations suggested by an exponential distance relation found by the method of comparison of magnitude order of successive distances ratios of the large Uranian satellites. A new exponential distance relation is deduced, fitting the distances of the large satellites and groups of rings and new small satellites with a spacing ratio of 1.456. Some characteristics of an hypothetical parent body for the new inner satellites are also deduced. 相似文献
29.
Determination of Porosity and Permeability out of Dispersion Analyses of Borehole Wall Displacements
Waves carried in the borehole can be measured by the use of controlled sources inside the borehole and receivers located in
the same borehole as well. This article gives the theoretical background and develops a new method to determine rock-physical
parameters out of such controlled measurements of waves carried inside the borehole. Theoretical dispersion curves of the
group velocities are matched to dispersion analyses of registrations obtained in the borehole. This inversion process intends
to determine the in situ porosity and permeability of the rock. 相似文献
30.
Grigory I. Dolgikh Mstislav N. Dubrov Stanislav G. Dolgikh Sergei N. Kovalev Vladimir V. Ovcharenko Egor A. Savvin Vladimir A. Chupin Vyacheslav A. Shvets Sergei V. Yakovenko 《Acta Geophysica》2006,54(2):187-197
The paper considers possibilities of applying laser strainmeters for the study of earthquake physics. One of laser strainmeters
is described. A high efficiency of using the laser strainmeters for the study of earthquakes and their precursors is shown.
In records of the spaced laser strainmeters, anomalous deformations propagating from the east to the west with the speed comparable
with that of migration of earthquakes were found. 相似文献