On the origin of natural sapphire color

An attempt has been made to interpret natural sapphire optical absorption spectra with regard to the exchange-coupled pairs of iron impurities in their ferric and ferrous states. Level schemes have been calculated for Fe³⁺-Fe³⁺ and Fe²⁺-Fe²⁺ pairs of all the orders, their symmetry being observed. The selection rules are discussed. EPR and infrared spectroscopy information has been used to assist the optical spectroscopy data. The sapphire color has been interpreted as a function of Fe²⁺/Fe³⁺ ratios and of the presence of their pairs in the stone. The various types of charge compensation in Fe²⁺→Al³⁺ isomorphism are discussed.     

Palaeopascichnids from the Upper Vendian Chernyi Kamen Formation of the Middle Urals (Perm Region)

Doklady Earth Sciences - In 2020–2021 the palaeopascichnid fossils were found in the Krasnaya Gorka Site (Shirokovsky Reservoir, Kosva River area, Perm Region), a type Vendian fossil locality...     

The relationship between the neutral hydrogen and dark mass in the galaxies

Starting from Bosma (1981) paper, it was demonstrated by different authors that the observed shape of rotation curves of many spiral galaxies can be explained if to assume that the radial density distribution of the dark matter is correlated with the distribution of HI: the column densities of the dark matter and HI are proportional. We show that this correlation is obviously to be an artifact and can be explained by assuming that the gas surface density is approximately equal or in general proportional to the critical density for the local gravitational stability of gaseous layer.     

Thermal stability of wind near a hot star

We present computations of the ionization and thermal balance in the wind from WR and OB stars. The star’s radiation field is modeled using a Planck function with a temperature from 2 to 6 eV. We assume that the principal contribution from gas heating and cooling is from ions and atoms of hydrogen, carbon, nitrogen, oxygen, and neon. We take into account photoionization from the ground state and excited states, ionization by electron collisions, radiative and two-electron recombination, and excitation and de-excitation of discrete levels by the star’s dilute radiation and electron collisions. It is demonstrated that the thermal regime of gas in the conditions typical of the winds near WR and OB stars is stable.     

Distribution of the bacteria <Emphasis Type="Italic">Listeria monocytogenes</Emphasis> in the western part of the Sea of Okhotsk

The Amur River’s influence on the distribution of the opportunistic bacteria Listeria monocytogenes in the western part of the Sea of Okhotsk is discussed. The presence of Listeria in the seawater, sea ice, and sediments on the northeastern Sakhalin shelf and slope supports the idea of its connection with the Amur River discharge. The hypothesis of the allochtonic parentage of L. monocytogenes in the sea’s development is proved.     

A correlation between dark matter and neutral hydrogen in spiral galaxies

We test the hypothesis put forward by Bosma (1981) that the surface density of dark matter is proportional to the surface density of HI, using decompositions of the rotation curves of a number of galaxies according to the THINGS, along with data for the galaxy NGC 6822. The rotation curves of these galaxies can be explained by assuming the existence of a massive gaseous disk in the absence of a dark halo, although the proportionality factor ??_dark/??_HI between the surface densities of dark matter and HI is different for different galaxies. However, there emerges the problem of the gravitational stability of galaxies whose stellar-velocity dispersions have been estimated, if the thickness of the dark-matter disk is similar to or less than the thickness of the stellar disk. The proportionality between ?? _dark and ??_HI is probably due to the fact that the radial profiles of ??_HI for galaxies with flat rotational curves are close to the critical density of a gravitationally stable gaseous layer (??_HI ?? R ^?1), and ??_dark(R) for a pseudo-isothermal halo obeys the same law.     

The State of the Roshydromet Hydrological Observation Network in the Mouth Areas of RFAZ

Water Resources - Taking into account the entire mouth network in its current boundaries, the authors pioneered in representing the historical development of hydrological observations at the...