Nature of the ultramafite–mafite complex of the Guli Pluton (Polar Siberia)     

Yu. R. Vasiliev  M. P. Gora 《Doklady Earth Sciences》2017,476(2):1117-1119

Comparative analysis of the composition and formation conditions of the dunite–pyroxenite association of the Guli Pluton and ultramafic vulcanite (meimechite) showed the similarity of their initial melts and the same type of crystallization, demonstrating the cumulative origin of dunite.  相似文献   

Physicochemical Conditions of Crystallization of Rocks from Ultrabasic Massifs of the Siberian Platform     

V. A. Simonov  V. S. Prikhod’ko  Yu. R. Vasiliev  A. V. Kotlyarov 《Russian Journal of Pacific Geology》2017,11(6):447-468

A great volume of original information on the formation of the ultrabasic rocks of the Siberian Platform has been accumulated owing to the study of melt inclusions in Cr-spinels. The inclusions show the general tendencies in the behavior of the magmatic systems during the formation of the ultrabasic massifs of the Siberian Platform, tracing the main evolution trend of decreasing Mg number with SiO₂ increase in the melts with subsequent transition from picrites through picrobasalts to basalts. The compositions of the melt inclusions indicate that the crystallization conditions of the rocks of the concentrically zoned massifs (Konder, Inagli, Chad) sharply differ from those of the Guli massif. Numerical modeling using the PETROLOG and PLUTON softwares and data on the composition of inclusions in Cr-spinels yielded maximum crystallization temperatures of the olivines from the dunites of the Konder (1545–1430°C), Inagli (1530–1430°C), Chad (1460–1420°C), and Guli (1520–1420°C) massifs, and those of Cr-spinels from the Konder (1420–1380°C), Inagli (up to 1430°C), Chad (1430–1330°C), and Guli (1410–1370°C) massifs. Modeling of the Guli massif with the PLUTON software using the compositions of the melt inclusions revealed the possible formation of the alkaline rocks at the final reverse stage of the evolution of the picritic magmas (with decrease of SiO₂ and alkali accumulation) after termination of olivine crystallization with temperature decrease from 1240–1230°C to 1200–1090°C. Modeling with the PLUTON software showed that the dunites of the Guli massif coexisted with Fe-rich (with moderate TiO₂ contents) melts, the crystallization of which led (beginning from 1210°C) to the formation of pyroxenes between cumulate olivine. Further temperature decrease (from 1125°C) with decreasing FeO and TiO₂ contents provided the formation of clinopyroxenes of pyroxenites. For the Konder massif, modeling with the PLUTON software indicates the possible formation of kosvites from picrobasaltic magmas beginning from 1350°C and the formation of clinopyroxenites and olivine–diopside rocks from olivine basaltic melts from 1250°C.  相似文献   

Brown Carbon and Black Carbon in the Smoky Atmosphere during Boreal Forest Fires     

G. I. Gorchakov  A. V. Karpov  N. V. Pankratova  E. G. Semoutnikova  A. V. Vasiliev  I. A. Gorchakova 《Izvestiya Atmospheric and Oceanic Physics》2017,53(9):875-884

We have investigated the variability of smoke aerosol absorbing ability with variations in the content of brown carbon (BrC) and black carbon (BC). Using monitoring data on radiative characteristics of smoke aerosol at AERONET stations and the spatial distribution of aerosol optical depth (AOD) obtained by the MODIS spectrometer (Terra satellite), we have detected large-scale smokes during boreal forest fires in Russia and Canada (1995–2012). The spatial distribution (50°–70° N, 95°–125° W) and temporal variability (at AERONET station Fort McMurray) of AOD during the smoking of a part of Canada in July 2012 have been analyzed. AOD probability distributions for July 14–18, 2012, and an estimate of aerosol radiative forcing of smoke aerosol at the upper boundary of the atmosphere have been obtained. We have proposed a technique for the diagnostics of BrC and BC in smoke aerosol particles from the spectral dependence of the imaginary part of the refractive index. At a wavelength of 440 nm, the contributions of BrC and BC to the smokeaerosol absorbing abitity can be comparable in magnitude. In many cases, the absorption spectra of smoke aerosol can be adequately approximated by either power or exponential functions. The presence of BrC in smoke-aerosol particles highly extends the variety of observed absorption spectra in a smoky atmosphere and spectral dependences of single scattering albedo. In the spectral range of 440–1020 nm, the radiative characteristics of smoke aerosol are largely contributed by its fine mode.  相似文献   

The first <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar age data for trap intrusions of the western part of the Siberian Platform     

Yu. R. Vasiliev  M. P. Mazurov  S. N. Prusskaya  A. V. Travin 《Doklady Earth Sciences》2010,432(2):750-753

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Cooling and fragmentation of gas in rotating protogalaxies     

E. O. Vasiliev  E. I. Vorobyov  Yu. A. Shchekinov 《Astronomy Reports》2010,54(10):890-901

The dynamical, thermal, and chemical evolution of gas in protogalaxies with non-zero angular momentum is considered. It is shown that, in protogalaxies with a total mass (dark and baryonic) of M = 10⁷ M⊙ at redshifts z = 12 whose gas has rotational angular momentum (spin parameter λ ≳ 0.005), a disk-like structure forms during the initial collapse of the galaxy, in contrast to non-rotating protogalaxies, whose collapse is spherically symmetric. The existence of initial angular momentumfor gas in protogalaxies increases the cooling time of the gas, delaying the formation of the first stars. Increasing the rotational angular momentum of the gas leads to cooling of the gas to lower temperatures (T < 100 K), at which HD molecules dominate in the cooling, while the total mass of cool gas (T < 1000 K) is decreased. The stability of disk-like structures in the central regions of protogalaxies is analyzed. It is shown that the disk that is formed is gravitationally unstable, and multiple fragmentation at various distances from the center is possible when the initial rotational angular momentum of the protogalaxy is increased. The possible birth of several stars in the first protogalaxies is discussed.  相似文献   

Evolution of Comet Nucleus Rotation   总被引：1，自引：0，他引：1  

A.I. NeishtadtD.J. Scheeres  V.V. SidorenkoA.A. Vasiliev 《Icarus》2002,157(1):205-218

The secular evolution of comet nucleus rotation states subject to outgassing torques is studied. The dynamical model assumes that the nucleus inertia ellipsoid is axially symmetric. The outgassing torques acting on the surface are modeled using standard cometary activity formulae. The general rotational equations of motion are derived and separately averaged over the fast rotational dynamics terms and the comet orbit. Special cases where the averaging assumptions cannot be applied are evaluated separately. The modification of the comet orbit due to comet outgassing is neglected. Resulting from this analysis is a system of secular differential equations that describes the dynamics of the comet nucleus angular momentum and rotation state. We find that the qualitative secular evolution of the rotation state is controlled by a single parameter that combines parameters related to the comet orbit and parameters related to the nucleus surface geometry and activity. From this solution, we find qualitatively different evolutionary paths for comet nuclei whose entire surface is active, as compared to nuclei with only a single active region. For surface activity models between these extremes, we show that certain evolutionary paths are more likely than others. Additionally, our solution indicates that a comet nucleus' rotational angular momentum will tend to increase over time, potentially contributing to the observed phenomenon of comet nucleus splitting.  相似文献   

Patterns and trends in the perception of seismic risk. Case study: Bucharest Municipality/Romania   总被引：1，自引：1，他引：0  

Iuliana Armaş  Eugen Avram 《Natural Hazards》2008,44(1):147-161

This research looks at the very nature of perception of seismic risk, an issue that is not only academically important, but also it can save lives and reduce injury and community costs. The background idea is that citizens in big cities, vulnerable to seismic hazard are living with latent and permanent concerns about a possible earthquake. We were interested in revealing significant aspects of Bucharest citizens’ orientations and tendencies in relation to the possible seismic event. Bucharest, the capital of Romania, is exposed to the greatest seismic hazard compared with other European capitals. The dimensions of study were: the anticipations of seism occurrence, the behavior during the event, evaluations of consequences, support factors, and individual vulnerability. This article is an example of the low cost approach on a sample of 190 citizens, understood as an exercise in attempting to relate population characteristics to various aspects of risk perception. The methodology used was based on a field investigation, where the research agents’ applied one questionnaire containing free/post codified/fan answers concerning: demographic variables, the buildings’ features, and perceptions about the possible earthquake event. The findings of this study showed that the hazard perception significantly associates with aspects concerning the subjects’ orientation toward institutional factors/human relations/negativism, and toward financial/material/moral support in case of disaster etc. It is hoped that this issue will serve to inspire further investigations into this very important and socially sensitive field, due to the fact that hazard analysis and mitigation would be more effective when it takes into account the human dimension of disasters.  相似文献   

The health state of the Romanian population during the transition period     

Liliana Dumitrache  Iuliana Armas 《GeoJournal》1998,44(2):151-160

The paper attempts to make an assessment of the health state of the Romanian population during the transition period; the evolution of the health indicators, analyzed in the European context, shows the precarious health state of the Romanian population, in comparison both to Western countries and to the countries which are crossing a transition phase themselves. The values of the health indicators by region also show inequalities of health, the north-western and south-eastern areas of the country having to face serious problems. The reduction of living standard, the low quality health services, together with other factors associated with lifestyle seem to be responsible for the deterioration of the health state of the Romanian population. The introduction of adequate health and social policies in the following period could bring about an improvement of the situation. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Atmospheric transparency over central Yakutia from the sun photometer data in 2004—2014     

M. S. Vasiliev  S. V. Nikolashkin  R. N. Boroyev 《Russian Meteorology and Hydrology》2017,42(11):700-704

The transparency of the atmosphere over the central part of Yakutia is classified using ground-based observations of aerosol optical depth (AOD) for the period of 2004-2014. The annual variations in monthly mean values of AOD are compared with satellite monitoring data. It is revealed that every year the days with the values of AOD corresponding to the class III of atmospheric transparency (turbid atmosphere) made up 25-30% of the total number of AOD measurement days.  相似文献   

The influence of variations of elemental composition on the thermal properties of interstellar gas     

E. O. Vasiliev  Yu. A. Shchekinov 《Astronomy Reports》2016,60(10):924-938

The mixing of metals and redistribution of the relative abundances of chemical elements in the interstellar medium often takes place on a timescale that exceeds the characteristic timescales for many other processes, such as ionization and the establishment of thermal equilibrium. Under these conditions, different regions of interstellar gas can have different thermal, chemical, and spectral properties. The paper considers the ionization kinetics and thermal regime of interstellar gas with variations in the relative elemental abundances. The thermal properties and observational (spectral) characteristics are most sensitive to variations of the relative abundance of carbon, oxygen, neon, and iron. The dynamic consequences of such variations are considered.  相似文献