Primary production and microbial activity in the euphotic zone of Lake Baikal (Southern Basin) during late winter     

V. Stra&#x;krbov  L.R. Izmest'yeva  E.A. Maksimova  S. Fietz  J. Nedoma  J. Borovec  G.I. Kobanova  E.V. Shchetinina  E.V. Pislegina 《Global and Planetary Change》2005,46(1-4):57

Three years of regular weekly/biweekly monitoring of seasonal changes in temperature, transparency, chlorophyll a (CHL) and bacteria [erythrosine-stained microscopic counts and cultivable colony forming units (CFUs)] at the vertical profile in the South basin of Lake Baikal (51°54′195″N, 105°04′235″E, depth 800 m) were evaluated. In more detail, the structure and function of phytoplankton and the microbial loop in the euphotic layer at the same site were investigated during the late-winter–early-spring period under the ice. The depth of euphotic zone (up to 1% of surface irradiation) was 35 to 40 m. Primary production was measured three times a week with the ¹⁴C method in 2, 10, 20, 30 and 40 m. Maximum production was found in 10 m, with lower values towards the surface (light inhibition) and towards the lower layers. The total production in cells larger than 1 μm in the column (0–40 m) was 204–240 mg C d⁻¹ m⁻², 30–40% of it being in cells 1–3 μm (mostly picocyanobacteria), which represented roughly 9% of the total chlorophyll a (estimated from pigment analyses). A major part of phytoplankton biomass was formed by diatoms (Synedra acus Hust., Asterionella formosa Hass. and Stephanodiscus meyerii Genkal & Popovskaya). Total production (including extracellular, dissolved organic matter) was 235–387 mg C day⁻¹ m⁻², and the exudates were readily used by bacteria (particles 0.2–1 μm). This part amounted to 1–5% of cellular production in 2 to 20 m and 11–77% of cellular production in 20–40 m, i.e., in light-limited layers. From 0 to 30 m, chlorophyll a concentration was 0.8 to 1.3 μg l⁻¹, wherefrom it decreased rapidly to 0.1 μg l⁻¹ towards the depth of 40 m. Bacteria (DAPI-stained microscopic counts) reached 0.5–1.4×10⁶ ml⁻¹; their cell volumes measured via image analysis were small (average 0.05 μm⁻³), often not well countable when erythrosine stain was used. Bacterial biomasses were in the range of 6–21 μg C l⁻¹. Numbers of colony forming units (CFUs) on nutrient fish-agar were c. 3–4 orders lower than DAPI counts. The amounts of heterotrophic protists were low, whereby flagellates reached 6 to 87 ml⁻¹ and ciliates, 0.2–1.2 ml⁻¹ (mostly Oligotrichida). Bacterial production was measured in the same depths as primary production using ³H-thymidine (Thy) and ¹⁴C-leucine (Leu) uptake. Consistently, bacterial abundances, biomasses, thymidine and leucine production were higher by 30–50% in layers 2, 10 and 20 m compared with that in the deeper 30 and 40 m, where cellular primary production was negligible. Leucine uptake in the deeper layers was even three times lower than in the upper ones. From the comparison of primary and bacterial production, bacteria roughly use 20–40% of primary production during 24 h in the layers 2 to 20 m.  相似文献   

Astrometric Observations of the Galilean Moons of Jupiter at the Pulkovo Normal Astrograph in 2016−2017     

N. V. Narizhnaya  M. Yu. Khovrichev  A. A. Apetyan  D. A. Bikulova  A. P. Ershova  I. A. Balyaev  A. M. Kulikova  K. I. Os’kina  L. A. Maksimova 《Solar System Research》2018,52(4):312-319

We present the results of observations of the Galilean moons of Jupiter carried out at the Normal Astrograph of the Pulkovo Observatory in 2016?2017. We obtained 761 positions of the Galilean moons of Jupiter in the system of the Gaia DR1 catalog (ICRF, J2000.0) and 854 differential coordinates of the satellites relative to each other. The mean errors in the satellites’ normal places and the corresponding root-mean-square deviations are ε_α = 0.0020′′, ε_δ = 0.0027′′, σ_α = 0.0546′′, and σ_δ = 0.0757′′. The equatorial coordinates of the moons are compared to the motion theories of planets and satellites. On average, the (O–C) residuals in the both coordinates relative to the motion theories are less than 0.031′′. The best agreement with observations is achieved by a combination of the EPM2015 and V. Lainey-V.2.0|V1.1 motion theories, which yields the average (O–C) residuals of approximately 0.02″. Peculiarities in the behavior of the (O–C) residuals and error values in Ganymede have been noticed.  相似文献   

Microfossils from the Arymas and Debengda formations, the Riphean of the Olenek Uplift: Age and presumable nature     

A. M. Stanevich  E. N. Maksimova  T. A. Kornilova  D. P. Gladkochub  A. M. Mazukabzov  T. V. Donskaya 《Stratigraphy and Geological Correlation》2009,17(1):20-35

Studied assemblages of diverse organic-walled microfossils separated from the Arymas and Debengda formations of the Olenek Uplift include several paleobiological groups of microorganisms. Sufficiently large morphotypes of the first group are identified with remains of cyanobacteria. Morphotypes of variable spiral structure, which dwelt in association or in symbiosis with cyanobionts, are attributed to the same bacterial community. The other group includes a series of different acritarch genera whose characters suggest their affinity with green algae of the order Desmidiales. It is very likely that this group coexisted on siliciclastic shoals with large ancestral forms of the present-day brown algae. Several microfossil taxa have been known before from the Neoproterozoic deposits only. With due regard for the relatively gradual accumulation of sedimentary succession lacking large hiatuses and for the regular series of K-Ar dates characterizing three Riphean formations of the Olenek Uplift, it is possible to suggest that there was the Arymas-Debengda-Khaipakh cycle of long-lasted, almost uninterrupted sedimentation within the time span of 1250–900 Ma. It is also admissible that age ranges of some Late Precambrian microfossils are much larger than their distribution intervals postulated formerly.  相似文献   

Mineralized biota from the neoproterozoic Uluntui Formation     

A. M. Stanevich  A. M. Mazukabzov  T. A. Kornilova  E. N. Maksimova 《Lithology and Mineral Resources》2012,47(1):89-97

First finds of microfossils from the silicified microphytolitic carbonates of the Uluntui Formation in the southwestern Baikal region are described. They are represented by remains of the cyanobacterial community that formed microphytolites. These microfossils are accompanied by acritarchs probably belonging to green algae. The silicified microfossils are sufficiently well preserved despite complete and repeated recrystallization of host primary carbonate rocks. Main phases of secondary mineralization are related to hydrothermal-metasomatic processes, which were likely provoked by collisional events on the southern flank of the Siberian Craton in the Silurian.  相似文献   

Evolution of a Viscous Protoplanetary Disk with Convectively Unstable Regions     

Ya. N. Pavlyuchenkov  A. V. Tutukov  L. A. Maksimova  E. I. Vorobyov 《Astronomy Reports》2020,64(1):1-14

The role of convection in the gas-dust accretion disk around a young star is studied. The evolution of a Keplerian disk is modeled using the Pringle equation, which describes the time variations of the surface density under the action of turbulent viscosity. The distributions of the density and temperature in the polar directions are computed simultaneously in the approximation that the disk is hydrostatically stable. The computations of the vertical structure of the disk take into account heating by stellar radiation, interstellar radiation, and viscous heating. The main factor governing evolution of the disk in this model is the dependence of the viscosity coefficient on the radius of the disk. The computations of this coefficient take into account the background viscosity providing the continuous accretion of the gas and the convective viscosity, which depends on the parameters of the convection at a given radius. The results of computations of the global evolution and morphology of the disk obtained in this approach are presented. It is shown that, in the adopted model, the accretion has burst-like character: after the inner part of the disk ($$R < 3$$ AU) is filled with matter, this material is transferred relatively rapidly onto the star, after which the process is repeated. Our results may be useful for explaining the activity of young FU Ori and EX Lup objects. It is concluded that convection may be one of the mechanisms responsible for the non-steady pattern of accretion in protostellar disks.  相似文献   

Correction to: Zeolite containing rocks of kudurs and reasons of geophagy within the territory of Sikhote-Alin Nature Zapovednik,Far East of Russia     

Panichev  Aleksander  Seryodkin  Ivan  Popov  Vladimir  Chekryzhov  Igor  Makarevich  Raisa  Lutsenko  Tatiana  Stolyarova  Tatiana  Sergievich  Aleksander  Khoroshikh  Pavel  Maksimova  Darya  Petrunenko  Yury 《Arabian Journal of Geosciences》2020,13(4):1-11

This paper establishes a mechanical model of the stress distribution in front of the driving face during coal roadway excavation. Theoretical research shows that the stress state in the plastic zone of the driving face is consistent with the limit equilibrium equation, and the elastic zone is in accordance with the equilibrium equation based on elasticity mechanics. Based on this improved mechanical state solution model, different coal material constitutive hypotheses are used for the analysis. The width of the plastic zone calculated under the brittle-perfectly elastic model can reach 2–5 times the height of the roadway, and the stress concentration coefficient can reach two or more times. 3DEC numerical simulation software was used to simulate the stress distribution of the heading face. The results of the simulation are similar to those of the theoretical analysis. Compared with the elastic-perfectly plastic model, the calculated results of the brittle-perfectly elastic model are more consistent with the numerical simulation results. The heading face coal during roadway excavation shows obvious damage, and the strength characteristics of the coal decrease.  相似文献   

Analysis of Lunar Terrain Altitudes and Correlation Links between the Terrain and Gravitational Field; Preliminary Conclusions on the Global Density Inhomogeneities of the Lunar Crust     

Chuikova  N. A.  Rodionova  Zh. F.  Maksimova  T. G.  Grishakina  E. A. 《Solar System Research》2019,53(3):161-171

The harmonic and statistical analysis of lunar terrain altitudes has been performed based on the procedure developed by the authors. The explanations for the displacements of the Moon's figure relative to the center of mass and for the shift of the major equatorial axis relative to the earthward direction have been given. The maps have been plotted for the density anomalies in the near-surface layers of the Moon that correspond to mascons (with negative correlation between the field and terrain mainly for N= 10, 11) and other variants of links between the gravitational field and terrain (with positive correlation between the field and terrain). It has been shown that the harmonics of the degree N= 5–9 mainly correspond to the isostatic compensation of the terrain in the near-surface layers of the crust; the low harmonics (N< 5) correspond to the isostatic compensation of the terrain in the deeper layers, while the harmonics of the degrees N > 11 may indicate the presence of tension in the crust generated by small structures of the terrain. Based on the maps, possible locations of deposits of volatile elements (mainly on the far side of the Moon and in the northern cir-cumpolar region) and other natural resources have been determined.

  相似文献   

Using the status of a world heritage site for the preservation of Lake Baikal     

I. I. Maksimova 《Geography and Natural Resources》2013,34(2):124-128

This paper is concerned with the implications of the status of World Natural Heritage Sites, the position of the Russian state on the issues related to observance of the provisions of the Convention Concerning the Protection of the World Cultural and Natural Heritage, and the authorities-civil society relationships on these problems. An analysis is made of the possibilities of effectively using the world heritage institute in Russia in the interests of preserving world values. A number of legal and organizational measures for their conservation are suggested.  相似文献   

Searching for Binary Systems Among Nearby Dwarfs Based on Pulkovo Observations and SDSS Data     

M.?Yu.?KhovrichevEmail author  A.?A.?Apetyan  E.?A.?Roshchina  I.?S.?Izmailov  D.?A.?Bikulova  A.?P.?Ershova  I.?A.?Balyaev  A.?M.?Kulikova  V.?V.?Petyur  A.?A.?Shumilov  K.?I.?Os’kina  L.?A.?Maksimova 《Astronomy Letters》2018,44(2):103-118

Our goal is to find previously unknown binary systems among low-mass dwarfs in the solar neighborhood and to test the search technique. The basic ideas are to reveal the images of stars with significant ellipticities and/or asymmetries compared to the background stars on CCD frames and to subsequently determine the spatial parameters of the binary system and the magnitude difference between its components. For its realization we have developed a method based on an image shapelet decomposition. All of the comparatively faint stars with large proper motions (V >13 ^m , μ > 300 mas yr^?1) for which the “duplicate source” flag in the Gaia DR1 catalogue is equal to one have been included in the list of objects for our study. As a result, we have selected 702 stars. To verify our results, we have performed additional observations of 65 stars from this list with the Pulkovo 1-m “Saturn” telescope (2016–2017). We have revealed a total of 138 binary candidates (nine of them from the “Saturn” telescope and SDSS data). Six program stars are known binaries. The images of the primaries of the comparatively wide pairs WDS 14519+5147, WDS 11371+6022, and WDS 15404+2500 are shown to be resolved into components; therefore, we can talk about the detection of triple systems. The angular separation ρ, position angle, and component magnitude difference Δm have been estimated for almost all of the revealed binary systems. For most stars 1.5′′ < ρ < 2.5′′, while Δm <1.5^m.  相似文献   

Uranium Distribution in Ore-Bearing Rocks of the Malinov Deposit: Evidence from Fission Radiography     

Kondrat'eva  I. A.  Maksimova  I. G.  Nad”yarnykh  G. I. 《Lithology and Mineral Resources》2004,39(4):333-344

Application of f-radiography for the study of ore-bearing rocks of the Malinov uranium deposit revealed the following specific features: (1) occurrence of uranium in both authigenic and terrigenous components; (2) important role of fine–dispersed (mineral-free) mode of uranium occurrence; and (3) participation of different-aged epigenetic processes in the ore formation. The sequence of ore formation and transformation in this deposit is similar to that in the Semizbai deposit. Therefore, they can be united into a single subtype of Mesozoic infiltration deposits in western Siberia.  相似文献