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81.
In the Western Lake Baikal, recent Baikal Rift's tectonics control the topography, seismicity, climate, geomorphology, and economy. Scarps, facets, structural terraces, horsts and grabens, and trapezoid valleys can be clearly observed. They have been generated by the recent tectonic movements along the faults and represent a serious geologic hazard. The specific geological conditions predetermine a unique variety of landscapes. Thus, the main type of the economy is tourism. However, unorganized tourism leads to the degradation of the unique landscapes. It increases risk and requires disaster management. Three criteria has been used for risk assessment: (1) degree of geologic hazard; (2) degree of landscape degradation; and (3) degree of the economy's vitality. The high ecological significance and low stability to antropogeneous pressure are typical for landscapes of the Western Lake Baikal. Thus, some special activities of disaster management should be implemented based on our investigation. 相似文献
82.
Lyudmila V. Malakhova Viktor N. Egorov Tatiana V. Malakhova Sergey B. Gulin Yury G. Artemov 《Geo-Marine Letters》2010,30(3-4):391-398
Concentrations of dissolved methane in seawater and bottom sediments, as well as of methane emanating from gas seeps were measured at 18 stations including several small bays in the Sevastopol coastal area (Black Sea) during 2007–2008. Methane concentrations in surface waters ranged from 10 to 2,970 nmol l?1, and correlated well with values recorded for sediments. Methane concentrations in the water column were influenced by water depth, as well as by air and water temperatures. In the spring and summer of 2008, in situ CH4 saturation relative to air was in the range of 970–71,900%. Maximum saturation was in summer. CH4 fluxes to the atmosphere from the Sevastopol coastal area were estimated to vary from 190 to 1,550 μmol m?2 day?1. Gas bubbles escaping from the seepages contained about 57 vol% methane. Radiocarbon dating of the methane revealed an age not exceeding 150 years, implying a biogenic origin. 相似文献
83.
Sergey Bolotin 《Celestial Mechanics and Dynamical Astronomy》2005,93(1-4):343-371
We consider the plane restricted elliptic 3 body problem with small mass ratio and small eccentricity and prove the existence
of many periodic orbits shadowing chains of collision orbits of the Kepler problem. Such periodic orbits were first studied
by Poincaré for the non-restricted 3 body problem. Poincaré called them second species solutions. 相似文献
84.
Coupled hydrological and atmospheric modeling is an efficient method for snowmelt runoff forecast in large basins. We use short-range precipitation forecasts of mesoscale atmospheric Weather Research and Forecasting(WRF) model combining them with ground-based and satellite observations for modeling snow accumulation and snowmelt processes in the Votkinsk reservoir basin(184,319 km2). The method is tested during three winter seasons(2012–2015). The MODIS-based vegetation map and leaf area index data are used to calculate the snowmelt intensity and snow evaporation in the studied basin. The GIS-based snow accumulation and snowmelt modeling provides a reliable and highly detailed spatial distribution for snow water equivalent(SWE) and snow-covered areas(SCA). The modelling results are validated by comparing actual and estimated SWE and SCA data. The actual SCA results are derived from MODIS satellite data. The algorithm for assessing the SCA by MODIS data(ATBD-MOD 10) has been adapted to a forest zone. In general, the proposed method provides satisfactory results for maximum SWE calculations. The calculation accuracy is slightly degraded during snowmelt periods. The SCA data is simulated with a higher reliability than the SWE data. The differences between the simulated and actual SWE may be explained by the overestimation of the WRF-simulated total precipitation and the unrepresentativeness of the SWE measurements(snow survey). 相似文献
85.
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87.
Sergey Konovalov Anatoliy Samodurov Temel Oguz Leonid Ivanov 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):273
New and published data on the distribution and speciation of manganese and iron in seawater are analyzed to identify and parameterize major biogeochemical processes of their cycling within the suboxic (15.6σt16.2) and anoxic layers (σt16.2) of the Black Sea. A steady-state transport-reaction model is applied to reveal layering and parameterize kinetics of redox and dissolution/precipitation processes. Previously published data on speciation of these elements in seawater are used to specify the nature of the transformations. Two particulate species of iron (Fe(III) hydroxide and Fe(II) sulfide) are necessary to adequately parameterize the vertical profile of suspended iron, while three particulate species (hydrous Mn(IV) oxide, Mn(II) sulfide, and Mn(II) carbonate) are necessary to describe the profile of suspended manganese. In addition to such processes as mixing and advection, precipitation, sinking, and dissolution of manganese carbonate are found to be essential in maintaining the observed vertical distribution of dissolved Mn(II). These results are used to interpret the observed difference in the form of vertical distribution for dissolved Mn(II) and Fe(II). Redox transformations of iron and manganese are coupled via oxidation of dissolved iron by sinking suspended manganese at σt16.2±0.2 kg m−3. The particulate manganese, necessary for this reaction, is supplied through oxidation of dissolved Mn(II). The best agreement with observations is achieved when nitrate, rather than oxygen, is set to oxidize dissolved Mn(II) in the lower part of the suboxic layer (15.90σt16.2). The results support the idea that, after sulfides of these metals are formed, they sink with particulate organic matter. The sinking rates of the particles and specific rates of individual redox and dissolved-particulate transformations have been estimated by fitting the vertical profile of the net rate. 相似文献
88.
89.
Alexander Ruzmaikin Anvar Shukurov Dmitry Sokoloff Sergey Starchenko 《地球物理与天体物理流体动力学》2013,107(1-3):125-139
Abstract We propose a method of derivation of global asymptotic solutions of the hydromagnetic dynamo problem at large magnetic Reynolds number. The procedure reduces to matching the local asymptotic forms for the magnetic field generated near individual extrema of generation strength. The basis of the proposed method, named here the Maximally-Efficient-Generation Approach (MEGA), is the assertion that properties of global asymptotic solutions of the kinematic dynamo are determined by the distribution of the generation strength near its leading extrema and by the number and distribution of the extrema. The general method is illustrated by the global asymptotic solution of the α2-dynamo problem in a slab. The nature of oscillatory solutions revealed earlier in numerical simulations and the reasons for the dominance of even magnetic modes in slab geometry are clarified. Applicability of the asymptotic solutions at moderate values of the asymptotic parameter is also discussed. We confirm this applicability using comparisons with complementary asymptotic expansions and numerical simulations. In particular, this justifies application of the MEGA solutions to estimation of the generation threshold. 相似文献
90.
The latest data on holes in the spinous processes of the vertebrae of woolly mammoths, a rare pathology, are presented. This was identified at 19 sites of northern Eurasia. Such destructive changes are recorded ca. 34–12k 14C a bp , and only two sites dated to >50k and >41k 14C a bp. The main hypotheses about hole formation are: vertebral abnormalities; bone infections; genetic traits; and unfavourable geochemical environment. The pathology occurred in mammoths of all age groups, and could have arisen at the embryonic stage. There are two types: classic holes associated with osteolytic changes; and very rarely tumour-like lesions. The most likely cause of the lesions is alimentary osteodystrophy caused by chronic mineral starvation. The aetiology of this disease is usually associated with a deficiency or excess of macro- and microelements in the geochemical landscape, and through forage and water this leads to a severe metabolic disorder. Analysis of palaeopathological data shows two waves of geochemical stress in animals, ca. 26–18k and ca. 16–12k 14C a bp. Therefore, the woolly mammoth extinction can be viewed as a non-linear function, with two peaks of high mortality corresponding to the Last Glacial Maximum and the Lateglacial. 相似文献