Common Proper Motion Search for Faint Companions Around Early-Type Field Stars – Progress Report     

Valentin D. Ivanov  G. Chauvin  C. Foellmi  M. Hartung  N. Huélamo  C. Melo  D. Nürnberger  M. Sterzik 《Astrophysics and Space Science》2006,304(1-4):247-249

The multiplicity of early-type stars is still not well established. The derived binary fraction is different for individual star forming regions, suggesting a connection with the age and the environment conditions. The few studies that have investigated this connection do not provide conclusive results. To fill in this gap, we started the first detailed adaptive-optic-assisted imaging survey of early-type field stars to derive their multiplicity in a homogeneous way. The sample has been extracted from the Hipparcos Catalog and consists of 341 BA-type stars within ∼300 pc from the Sun. We report the current status of the survey and describe a Monte-Carlo simulation that estimates the completeness of our companion detection.  相似文献   

Non-local impact of large-scale engineering in harbors and gulfs on the environment     

Eduard  Svetlana  Valentin 《Ocean Engineering》2002,29(7):739-752

A system of numerical tools to predict the non-local long-term impact of large-scale constructions on the environment is described. The predictions have to be results of successive examination of free water oscillations, turbulent boundary layers on the sea bottom, and turbulent pulsation effects on sediment transport. Numerical results related to free water oscillations in diverse gulfs are shown, and non-local effects of the dam construction are found for an example of the Baltic Sea. Feasibility of suggested tools for turbulent flow is manifested.  相似文献   

Eocene paleomagnetism of the Caucasus (southwest Georgia): oroclinal bending in the Arabian syntaxis     

Mikhail L. Bazhenov  Valentin S. Burtman 《Tectonophysics》2002,344(3-4)

The Caucasus is very important for our understanding of tectonic evolution of the Alpine belt, but only a few reliable paleomagnetic results were reported from this region so far. We studied a collection of more than 300 samples of middle Eocene volcanics and volcano-sedimentary rocks from 10 localities in the Adjaro–Trialet tectonic zone (ATZ) in the western part of the Caucasus. Stepwise thermal demagnetization isolates a characteristic remanent magnetization (ChRM) in 19 sites out of 31 studied. ChRM reversed directions prevail, and a few vectors of normal polarity are antipodal to the reversed ones after tilt correction. The fold test is positive too, and we consider the ChRM primary. Analysis of Tertiary declinations and strikes of Alpine folds in the Adjaro–Trialet zone and the Pontides in Northern Turkey shows a large data scatter; Late Cretaceous data from the same region, however, reveal good correlation between paleomagnetic and structural data. Combining Late Cretaceous and Tertiary data indicates oroclinal bending of the Alpine structures which are locally complicated with different deformation. The overall mean Tertiary inclination is slightly shallower than the reference Eurasian inclination recalculated from one apparent polar wander path (APWP), but agrees with other. This finding is in accord with geological evidence on moderate post-Eocene shortening across the Caucasus. We did not find any indication of long-lived paleomagnetic anomalies, such as to Cenozoic anomalously shallow inclinations further to the east in Central Asia.  相似文献   

Numerical viscoelastic modelling by the spectral Laguerre method   总被引：1，自引：0，他引：1  

B.G. Mikhailenko  A.A. Mikhailov  G.V. Reshetova 《Geophysical Prospecting》2003,51(1):37-48

Seismic wave propagation in a viscoelastic media can be described by a system of integro-differential equations. The solution of such equations requires special methods when using finite-difference techniques in the time domain. In the frequency domain, the integral terms are represented by complex elastic parameters. This paper presents an efficient algorithm for viscoelastic modelling based on the integral Laguerre transform for the approximation of temporal derivatives and for the calculation of convolution integrals. For the calculation of spatial derivatives, it is possible to use various methods: finite-difference and finite-element techniques, spectral and pseudo-spectral methods. We then obtain a system of algebraic equations with a matrix independent of the parameter m , i.e. the degree of the Laguerre polynomials. In this case, only the right-hand side of the system has recurrent dependence on the parameter m , which is an analogue of the temporal frequency in the frequency domain. The obtained system with a large number of right-hand sides can be solved using fast methods, where the matrix is transformed only once, as opposed to the frequency-domain approach, when the matrix is transformed for each temporal frequency.  相似文献   

Natural and Human-Induced Variations in Water and Sediment Runoff in the Danube River Mouth     

Levashova  E. A.  Mikhailov  V. N.  Mikhailova  M. V.  Morozov  V. N. 《Water Resources》2004,31(3):235-246

Long-term natural and human-induced variations in water and sediment runoff in the Danube Delta head were studied on the basis of analysis of an extremely long series of observations (1840–2002). A considerable reduction of sediment runoff in the second half of the 20th century related to sediment accumulation in reservoirs was revealed. It was found that human activities had an insignificant impact on the water runoff variations and the period of 1961–2002 turned out to be abnormally water-abundant.  相似文献   

Conditions of pocket formation in the Oktyabrskaya tourmaline-rich gem pegmatite (the Malkhan field, Central Transbaikalia, Russia)     

Igor S. Peretyazhko  Victor Ye. Zagorsky  Sergey Z. Smirnov  Mikhail Y. Mikhailov 《Chemical Geology》2004,210(1-4):91-111

Coexisting melt (MI), fluid-melt (FMI) and fluid (FI) inclusions in quartz from the Oktaybrskaya pegmatite, central Transbaikalia, have been studied and the thermodynamic modeling of PVTX-properties of aqueous orthoboric-acid fluids has been carried out to define the conditions of pocket formation. At room temperature, FMI in early pocket quartz and in quartz from the coarse-grained quartz–oligoclase host pegmatite contain crystalline aggregates and an orthoboric-acid fluid. The portion of FMI in inclusion assemblages decreases and the volume of fluid in inclusions increases from the early to the late growth zones in the pocket quartz. No FMI have been found in the late growth zones. Significant variations of solid/fluid ratios in the neighboring FMI result from heterogeneous entrapment of coexisting melts and fluids by a host mineral. Raman spectroscopy, SEM EDS and EMPA indicate that the crystalline aggregates in FMI are dominated by mica minerals of the boron-rich muscovite–nanpingite CsAl₂[AlSi₃O₁₀](OH,F)₂ series as well as lepidolite. Topaz, quartz, potassium feldspar and several unidentified minerals occur in much lower amounts. Fluid isolations in FMI and FI have similar total salinity (4–8 wt.% NaCl eq.) and H₃BO₃ contents (12–16 wt.%). The melt inclusions in host-pegmatite quartz homogenize at 570–600 °C. The silicate crystalline aggregates in large inclusions in pocket quartz completely melt at 615 °C. However, even after those inclusions were significantly overheated at 650±10 °C and 2.5 kbar during 24 h they remained non-homogeneous and displayed two types: (i) glass+unmelted crystals and (ii) fluid+glass. The FMI glasses contain 1.94–2.73 wt.% F, 2.51 wt.% B₂O₃, 3.64–5.20 wt.% Cs₂O, 0.54 wt.% Li₂O, 0.57 wt.% Ta₂O₅, 0.10 wt.% Nb₂O₅, 0.12 wt.% BeO. The H₂O content of the glass could exceed 12 wt.%. Such compositions suggest that the residual melts of the latest magmatic stage were strongly enriched in H₂O, B, F, Cs and contained elevated concentrations of Li, Be, Ta, and Nb. FMI microthermometry showed that those melts could have crystallized at 615–550 °C.

Crystallization of quartz–feldspar pegmatite matrix leads to the formation of H₂O-, B- and F-enriched residual melts and associated fluids (prototypes of pockets). Fluids of different compositions and residual melts of different liquidus–solidus P–T-conditions would form pockets with various internal fluid pressures. During crystallization, those melts release more aqueous fluids resulting in a further increase of the fluid pressure in pockets. A significant overpressure and a possible pressure gradient between the neighboring pockets would induce fracturing of pockets and “fluid explosions”. The fracturing commonly results in the crushing of pocket walls, formation of new fractures connecting adjacent pockets, heterogenization and mixing of pocket fluids. Such newly formed fluids would interact with a primary pegmatite matrix along the fractures and cause autometasomatic alteration, recrystallization, leaching and formation of “primary–secondary” pockets.  相似文献   

Subpollen Particles as Atmospheric Cloud Condensation Nuclei     

Mikhailov  E. F.  Ivanova  O. A.  Nebosko  E. Yu.  Vlasenko  S. S.  Ryshkevich  T. I. 《Izvestiya Atmospheric and Oceanic Physics》2019,55(4):357-364

Izvestiya, Atmospheric and Oceanic Physics - Bioparticles constitute a significant fraction of atmospheric aerosol. Their size range varies from nanometers (macromolecules) to hundreds of...  相似文献   

Some general relations of the development of complex molecular objects at early stages of biosphere formation as a consequence of the physical properties of condensed medium     

V. I. Baranov  L. A. Gribov  V. A. Dement’ev  I. V. Mikhailov 《Geochemistry International》2016,54(11):1011-1018

We analyzed the character of molecular transformations under conditions of condensed media, in which intermolecular interactions always occur. It was shown that, instead of discrete transfer of external energy into the molecule, the energy characteristics of the condensed medium (appearance of zones) could result in gradual accumulation of internal energy in reaction centers owing to sequential thermal collisions with particles of the medium initiating the chemical reaction. This does not require high temperatures. The established physical properties related to the energy characteristics of condensed media could play an important role in molecular transformations and, consequently, formation of complex molecular objects at early stages of biosphere formation.  相似文献   

Determination of the Spins of Supermassive Black Holes in FR I and FR II Radio Galaxies     

A. G. Mikhailov  Yu. N. Gnedin 《Astronomy Reports》2018,62(1):1-8

The spins of supermassive black holes in FR I and FR II radio galaxies are estimated using two models for the generation of the relativisitic jets, based on the Blandford–Znajek and Blandford–Payne mechanisms: the hybrid model of Meier and a flux-trapping model. The magnetic field at the event horizon is estimated assuming equipartition between the energy densities of the magnetic field and the accreting material. The magnetic field near the inner edge of the accretion disk is estimated assuming equipartition between the magnetic pressure and the radiation pressure, and also assuming proportionality between the magnetic field and the spin. In the case of FR I objects, both mechanisms for the generation of the jets (the hybrid model of Meier and a flux-trapping model) are efficient. For the FR II objects, equipartition between the energy densities of the magnetic field and the accretion flow facilitates stronger retrograde rotation of the supermassive black hole. Plots of spin versus mass suggest a predominantly chaotic character for the accretion in both types of radio galaxies.  相似文献   

Carbon costs and benefits of France’s biomass energy production targets     

Aude?ValadeEmail authorView author&#;s OrcID profile  Sebastiaan?Luyssaert  Patrick?Vallet  Sylvestre?Njakou Djomo  Ingride?Jesus Van Der Kellen  Valentin?Bellassen 《Carbon balance and management》2018,13(1):26

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