Observational manifestations of the first protogalaxies in the 21 cm line

The absorption properties of the first low-mass protogalaxies (mini-halos) forming at high redshifts in the 21-cm line of neutral hydrogen are considered. The absorption properties of these protogalaxies depend strongly on both their mass and evolutionary status. The optical depths in the line reach ∼0.1–0.2 for small impact parameters of the line of sight. As a protogalaxy is compressed, the influence of gas accretion can be seen, manifest as a non-monotonic frequency dependence of the optical depth. The absorption characteristics in the 21-cm line are determined by the thermal and dynamical evolution of the gas in the protogalaxies. Since the theoretical line width in the observer’s rest frame is 1–6 kHz and the expected distance between lines 8.4 kHz, then the lines from low mass protogalaxies can be resolved using low frequency interferometers that exist or are being constructed.     

Evolution of the first supernovae in protogalaxies: Dynamics of mixing of heavy elements

The paper considers the evolution of the supernova envelopes produced by Population III stars with masses ofM _* ?? 25?C200M _?? located in non-rotating protogalaxies with masses of M ?? 10⁷ M _?? at redshifts z = 12, with dark-matter density profiles in the form of modified isothermal spheres. The supernova explosion occurs in the ionization zone formed by a single parent star. The properties of the distribution of heavy elements (metals) produced by the parent star are investigated, as well as the efficiency with which they are mixed with the primordial gas in the supernova envelope. In supernovae with high energies (E ? 5 × 10⁵² erg), an appreciable fraction of the gas can be ejected from the protogalaxy, but nearly all the heavy elements remain in the protogalaxy. In explosions with lower energies (E ? 3 × 10⁵² erg), essentially no gas and heavy elements are lost from the protogalaxy: during the first one to threemillion years, the gas and heavy elements are actively carried from the central region of the protogalaxy (r ?? 0.1r _v , where r _v is the virial radius of the protogalaxy), but an appreciable fraction of the mass of metals subsequently returns when the hot cavity cools and the envelope collapses. Supernovae with high energies (E ? 5 × 10⁵² erg) are characterized by a very low efficiency of mixing of metals; their heavy elements are located in the small volume occupied by the disrupted envelope (in a volume comparable with that of the entire envelope), with most of the metals remaining inside the hot, rarified cavity of the envelope. At the same time, the efficiency of mixing of heavy elements in less energetic supernovae (E ? 3 × 10⁵² erg) is appreciably higher. This comes about due to the disruption of the hot cavity during the collapse of the supernova envelope. However, even in this case, a clear spatial separation of regions enriched and not enriched in metals is visible. During the collapse of the supernova envelope, the metallicity of the gas is appreciably higher in the central region ([Z] ?? ?1 to 0) than at the periphery ([Z] ?? ?2 to ?4) of the protogalaxy; most of the enriched gas has metallicities [Z] ?? ?3.5 to ?2.5. The masses of enriched fragments of the supernova envelope remain appreciably lower than the Jeans mass, except in regions at the center of the protogalaxy upon which the surrounding enriched gas is efficiently accreted. Consequently, the birth of stars with metallicities close to those characteristic of present-day Galactic stars is very probable in the central region of the protogalaxy.     

Superbroad component in emission lines of SS 433

We have detected new components in stationary emission lines of SS 433; these are the superbroad components that are low-contrast substrates with a width of 2000–2500 km s^?1 in He I λ4922 and Hβ and 4000–5000 kms^?1 in He II λ4686. Based on 44 spectra taken during four years of observations from 2003 to 2007, we have found that these components in the He II and He I lines are eclipsed by the donor star; their behavior with precessional and orbital phases is regular and similar to the behavior of the optical brightness of SS 433. The same component in Hβ shows neither eclipses nor precessional variability. We conclude that the superbroad components in the helium and hydrogen lines are different in origin. Electron scattering is shown to reproduce well the superbroad component of Hβ at a gas temperature of 20–35 kK and an optical depth for Thomson scattering τ ≈ 0.25?0.35. The superbroad components of the helium lines are probably formed in the wind from the supercritical accretion disk. We have computed a wind model based on the concept of Shakura-Sunyaev supercritical disk accretion. The main patterns of the He II line profiles are well reproduced in this model: not only the appearance of the superbroad component but also the evolution of the central two-component part of the profile of this line during its eclipse by the donor star can be explained.     

Evolution of Comet Nucleus Rotation

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.     

Patterns and trends in the perception of seismic risk. Case study: Bucharest Municipality/Romania

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.     

Numerical Computation of Hansen-like Expansions

Fourier expansions of elliptic motion functions in multiples of the true, eccentric, elliptic and mean anomalies are computed numerically by means of the fast Fourier transform. Both Hansen-like coefficients and their derivatives with respect to eccentricity of the orbit are considered. General behavior of the coefficients and the efficiency (compactness) of the expansions are investigated for various values of eccentricity of the orbit. This revised version was published online in July 2006 with corrections to the Cover Date.     

The health state of the Romanian population during the transition period

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.     

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

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.     

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

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.     

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

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.