Halo white dwarfs and the evolution of the galaxy     

D. S. Wiebe  A. V. Moiseev  Ya. A. Tikhonov  A. V. Tutukov  B. M. Shustov 《Astronomy Reports》2006,50(1):23-30

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Separation of concentrated acid and salt solutions in nanoporous media as the basis for a new technology of processing of phosphorus-containing raw materials     

R. Kh. Khamizov  N. A. Tikhonov  A. N. Krachak  A. N. Gruzdeva  N. S. Vlasovskikh 《Geochemistry International》2016,54(13):1221-1235

The physical and mathematical models were used to study the method of acid retardation for separating acids from their salts in concentrated multicomponent solutions using nanoporous sorption materials. A combined mechanism of separation relies on the fact that in the sorption phase having a low dielectric permittivity, smaller-sized acid particles, namely, the molecules or strongly bound and weakly hydrated ion pairs, can penetrate the nanopores and are retained within these pores due to molecular sorption or competitive solvation forces. The dissolved salts presented by highly hydrated ions or weakly bound ion pairs can easily pass through the porous medium with a flow of concentrated solution, which is pumped through the column packed with the granulated bed of gel-type ion exchange resins or hypercrosslinked polymers. In conventional cyclic AR processes, purified acid is desorbed by water according to the mechanism of competitive solvation. However, such processes can be successfully used only when the salts separated from acids are highly soluble, as is the case with chloride and nitrate solutions free of components that may form compounds insoluble in neutral medium. At the separation in real sulfate and phosphate media, which normally contain alkaline earth metals and other components, conventional AR- based technologies proved to be unsuccessful. The new modified version of acid retardation is based on the previously discovered effect of stabilization of colloidal systems and supersaturated solutions in porous ion exchange media. A distinctive feature of the proposed technique is the use of weakly acidic aqueous solutions, instead of water, at the stages of acid displace in the cyclic AR processes. The proposed technique of WPA purification using strong-base gel-type ion exchangers in the phosphate form opens up the possibility of stable and feasible processes of acid separation and purification with simultaneous extraction of valuable components, e.g., REE concentrate.  相似文献   

Metallicity of Young and Old Stars in Irregular Galaxies     

N. A. Tikhonov 《Astrophysical Bulletin》2018,73(1):22-34

Based on archived images obtained with the Hubble Space Telescope, stellar photometry for 105 irregular galaxies has been conducted. We have shown the red supergiant and giant branches in the obtained Hertzsprung-Russel diagrams. Using the TRGB method, distances to galaxies and metallicity of red giants have been determined. The color index (V ? I) of the supergiant branch at the luminosity level M_I = ?7 was chosen as the metallicity index of red supergiants. For the galaxies under study, the diagrams have been built, in which the correlation can be seen between the luminosity of galaxies (M_B) and metallicity of red giants and supergiants. The main source of variance of the results in the obtained diagrams is, in our opinion, uncertainty inmeasurements of galaxy luminosities and star-forming outburst. The relation between metallicity of young and old stars shows that main enrichment of galaxies with metals has taken place in the remote past. Deviations of some galaxies in the obtained relation can possibly be explained with the fall of the intergalactic gas on them, although, this inconsiderably affects metallicities of the stellar content.  相似文献   

The irregular galaxy Cassiopeia 1 – a new member of the Local group     

N. Tikhonov 《Astronomische Nachrichten》1996,317(3):175-178

A photometry in the V, R, I (Cousins) system has been performed for stars in the galaxy Cassiopeia 1. The resulting colour-agnitude (CM) diagram of Cas 1 reveals the existence of blue stars and the absence of red ones. From an analysis of the CM diagram of the galaxy it is concluded that A_v = 4.0 mag, and the distance modulus (m – M)_o = 24.5 mag, corresponding to a distance of 790 kpc. The visual magnitude of the galaxy is V = 14^m.62 (M_v = −13^m.8) and the colour index (V – R) = 0.89 mag. From the distance determination the galaxy Cassiopeia 1 is a member of the Local group.  相似文献   

Palaeo-environmental and dietary analysis of intestinal contents of a mammoth calf (Yamal Peninsula,northwest Siberia)     

Bas van Geel  Daniel C. Fisher  Adam N. Rountrey  Jan van Arkel  Joost F. Duivenvoorden  Aline M. Nieman  Guido B.A. van Reenen  Alexei N. Tikhonov  Bernard Buigues  Barbara Gravendeel 《Quaternary Science Reviews》2011,30(27-28):3935-3946

Intestinal samples from the one-month-old Siberian mammoth calf ‘Lyuba’ were studied using light microscopy and ancient DNA to reconstruct its palaeo-environment and diet. The palynological record indicates a ‘mammoth steppe’. At least some pollen of arboreal taxa was reworked, and thus the presence of trees on the landscape is uncertain. In addition to visual comparison of 11 microfossil spectra, a PCA analysis contributed to diet reconstruction. This yielded two clusters: one of samples from the small intestine and the other of large-intestine samples, indicating compositional differences in food remains along the intestinal tract, possibly reflecting different episodes of ingestion. Based on observed morphological damage we conclude that the cyperaceous plant remains and some remains of dwarf willows were originally eaten by a mature mammoth, most likely Lyuba’s mother. The mammoth calf probably unintentionally swallowed well-preserved mosses and mineral particles while eating fecal material deposited on a soil surface covered with mosses. Coprophagy may have been a common habit for mammoths, and we therefore propose that fecal material should not be used to infer season of death of mammoths. DNA sequences of trnL and rbcL genes amplified from ancient DNA extracted from intestinal samples confirmed and supplemented plant identifications based on microfossils and macro-remains. Results from different extraction methods and barcoding markers complemented each other and show the value of longer protocols in addition to fast and commercially available extraction kits.  相似文献   

Correlation Properties of a Distribution of Objects from the PSCz Survey     

A. V. Tikhonov  A. I. Kopylov 《Astrophysics》2002,45(1):88-99

The properties of a sample of IR galaxies from the Point Source Catalog z (PSCz) Survey were investigated using the correlation gamma function [(r) and ^*(r)]. The results with different volume-limited subsamples indicate that the regions of strong correlations (a power-law decrease in density with distance with an exponent ₁ 1) are limited to a scale of 10-15 Mpc. A break is present at this scale in the dependences of log() on log(r) and of log(^*) on log(r). Such a break is also observed for various other samples of galaxies and clusters (at different scales). After the break the density dependence changes to another regime, corresponding to a fully uniform distribution for bright galaxies in the northern Galactic hemisphere. For some subsamples of the southern and northern hemispheres the latter regime corresponds to some decrease in density with distance. Indications of significant differences between the distributions of objects in the southern and northern hemispheres are obtained. It is shown that the section of the gamma function after the break, even when its extent is small, is a significant indicator of actual correlation properties of the distributions. The results of the analysis are in good agreement, on the whole, with preceding studies of the PSCz survey.  相似文献   

Red giants in the blue compact galaxy IZw18     

N. A. Tikhonov 《Astronomy Letters》2007,33(3):137-148

Archival Hubble Space Telescope (HST) data have been used for the photometry of stars in blue compact dwarf (BCD) galaxies of the IZw18 system. Applying the spatial selection of stars, we have detected red giants, stars older than 1–2 Gyr, in the galaxies. These red giants have allowed the distance to IZw18 to be reliably determined for the first time: D = 13.9 ± 1.2 Mpc. The presence of old stars in the galaxies of the IZw18 system refutes the hypothesis about the observed primary star formation in these galaxies.  相似文献   

Observations of the compact group of galaxies Shahbazian 130     

A. S. Amirkhanian  A. G. Eghkian  N. A. Tikhonov  R. K. Shahbazian 《Astrophysics》1991,35(1):288-292

Byurakan Astrophysical Observatory and Special Astrophysical Observatory, Academy of Sciences. Translated fromAstrofizika, Vol. 35, No. 1, pp. 67–75, July–August, 1991.  相似文献   

The “Quantochron 4-48” facility for registration of random fluxes of multidimensional signals     

V. L. Plokhotnichenko  A. V. Solin  A. G. Tikhonov 《Astrophysical Bulletin》2009,64(2):198-206

A facility for the registration of light fluxes meant for the study of their properties with high temporal resolution is described. The “Quantochron 4-48” acquisition facility measures the photon arrival times using periodic signals of three types-second-long period signals (pps), 10-kHz, and 30-MHz signals. The first two come from a GPS, whereas the latter signal comes from the PCI bus of the computer connected to the facility. These time scales are used to produce for each time instant a 28-bit time code supplemented by 48 bits bearing the information about the coordinates, energy, and polarization of the photon at the output of the detector. The sequence of complete 64-bit words is buffered in FIFO memory and sent to computer RAM. The device has as its base element a XILINX SPARTAN XCS40XL PQ240AKP0505 microchip incorporated into a PCI slot. The registration facility consists of two PC servers equipped with these boards and a control computer. The facility determines the photon arrival times to within 30 ns with a dead time of 30 ns and maximum lossless count rate of 10⁶ photons/s. The registration facility allows continuous recording of detector counts over 17 hours with a one microsecond World-Time (UT) calibration accuracy.  相似文献   

Optical monitoring of the z= 4.40 quasar Q 2203+292     

E. P. Ovcharov  P. L. Nedialkov  A. T. Valcheva  V. D. Ivanov  N. A. Tikhonov  I. S. Stanev  A. B. Kostov  Ts. B. Georgiev 《Monthly notices of the Royal Astronomical Society》2008,386(2):819-825

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