40 research outputs found
Peculiarities of anisotropy and polarization as an indicator of noises in the CMB maps
We discuss some new problems of the modern cosmology which arose after the
BOOMERANG and MAXIMA-1 successful missions. Statistics of high peaks of the CMB
anisotropy is analyzed and we discuss possible inner structure of such peaks in
the observational data of future MAP and PLANCK missions. We have investigated
geometrical and statistical properties of the CMB polarization around such high
isolated peaks of anisotropy in the presence of a polarized pixel noise and
point sources. The structure of polarization fields in the vicinity of singular
points with zero polarization is very sensitive to the level of pixel noises
and point sources in the CMB maps.Comment: 9 pages, 2 figure
The Cosmological Gene Project: cluster analysis of the atmospheric fluctuations on arcmin-scale imaging of the Cosmic Microwave Background
We discuss some aspects of the Cosmological Gene Project started at the
Special Astrophysical Observatory (Russia) in 1999. The goal of the project is
to measure the anisotropy and polarization of the Cosmic Microwave Background
(CMB) and investigation of atmospheric fluctuations and foreground on
arcmin-scales using the radio-telescope RATAN-600. We develop the cluster
analysis of one-dimensional random fields for the application to the RATAN-600
scans. We analyze the specific properties of peak clusterisation in the
RATAN-600 scans which to separate the primordial CMB signal from noise.Comment: Submitted to Astronomy & Astrophysic
Electrochemical Reducing of Terbium and Holmium Ions in the Sodium and Potassium Chlorides Melt with Equimolar Composition
Interest to rare-earth metals (REM) and their alloys is due to the possibility of using them for the creation of new materials need for modern technology. For instance, REM as alloying components allows for preparation of material with special magnetic properties. A promising method for forming such coating is the surface treatment of metals. This process has an electrochemical character as such for the organization of technology the knowledge of kinetics and mechanism of these processes is important. Despite significant interest in rare-earth metals, these issues are not well described in the literature. In order to choose an adequate mathematical model for calculation of kinetic primers, preliminary experiments that allow evaluating the reversibility of the electrode process have been conducted. Based on that, it was concluded that cathodic reduction of terbium and holmium ions in equimolar NaCl-KCl melt is irreversible. By means of voltammetric analysis, kinetic parameters (transfer coefficients, heterogeneous constants of charge transfer rate) of terbium and holmium electroreduction in equimolar NaCl-KCl melt were determined. The experiment was conducted in a three-electrode cell under a purified argon atmosphere. A dependency of kinetic parameters on the concentration of terbium and holmium chlorides wt (%): 1, 3, 5, 7, 10, was determined. The experiment was conducted in 1073–1173K temperature range. Values of kinetic parameters increase with temperature but decrease with the increase of REM chloride. Based on obtained data, it was found that electroreduction of chloride complexes LnCl63– (Ln–Tb, Ho) in equimolar NaCl-KCl melt is irreversible in the studied range of temperatures and REM concentrations. In summary of experimental data, in range of temperature and rare-earth chloride concentration, and assumption was made that reduction of terbium and holmium ions occurs in two stages. The process includes the preceding stage of complex dissociation. A mechanism of LnCl63– complex reduction in the mentioned melt is proposed. The obtained results are in agreement with literate data for analogues systems
Determination Of Formation Regimes For Bilayer Cobalt Dysprosium Intermetalic Surface Alloy
High tech industrial fields on modern development stage are in need of construction materials with an optimal ratio of volume and surface properties, along with low cost of material itself. As evidenced by studies, in order to give a set complex of properties to a workpiece that operates under specific conditions, it is often sufficient to only modify its surface area. Over the course of studies, by means of gravimetric, influence of technological parameters (temperature and time samples are kept in the melt) on specific mass change of cobalt samples, that act as substrate, during electroless diffusive saturation with dysprosium in eutectic melt of lithium and potassium chlorides have been studied. A mathematical dependency was established for specific mass change of cobalt samples on time spent in melt for temperature range of 873–973 K. Composition of intermetallic coats obtained on surface of cobalt samples was studied means of EDX and SEM analyses. It was discovered, that for chosen temperature range, diffusion layers formed on surface of cobalt samples consists of two structural zones that correspond to Co-Dy and Cp2Dy phases
New multifunctional bromine-active polymers: synthesis, properties, and antimicrobial activity
: The increase in the frequency and scale of epidemics of infectious diseases gives extreme urgency to the development of new technologies for antiseptic and disinfectant treatment of various media, as well as materials/reagents for their implementation. Antimicrobial polymer materials of various chemical structures, including those containing halogen-active functional groups, are promising in this regard.This work is devoted to the synthesis and investigation of the properties of granular and fibrous polymer materials with immobilized N-bromosulfonamide groups of different structure. It is shown that copolymers of styrene with divinylbenzene and polypropylene can be used as a carrier polymer. A technique has been developed that allows obtaining polymers with a content of up to 23% of immobilized active bromine. The compliance of the synthesized materials with the declared structure has been proven by IR spectroscopy and a complex of chemical methods. A decrease in the strength of the obtained polymers compared to the original carriers has been observed, especially in the case of fibers. The stability of the synthesized polymers during storage is lower that of the previously described chlorine-active analogs. For the quantitative determination of active bromine in the target materials, a technique based on its rapid diffusion from the polymer into the taurine solution has been developed. Microbiological research has shown that the synthesized polymers have a pronounced antimicrobial activity, which is higher than that of immobilized N-chlorosulfonamides and is manifested even in the presence of a significant organic load.The set of investigated characteristics of synthesized polymers with immobilized N-bromosulfonamide groups suggests the prospect of their use as components of antiseptic dressing materials, antimicrobial filters, devices for obtaining antiseptic solutions, and other medical products
Synthesis and antimicrobial properties of new polymeric materials with immobilized peroxyacid groups
A method has been developed for the modification of polymer materials of the FIBAN brand, which allows to
immobilize up to 5.5% of peroxyacid functional groups on them without significant changes in their physical and
mechanical properties. It has been shown that the concentration of active groups and the stability of the synthesized
materials depend strongly on the nature of the polymer carrier. Method for chemical analysis of the concentration of
immobilized peroxyacid groups have been proposed, and the features of the IR spectra of modified materials have been
described. It has been proved that all synthesized materials exhibit pronounced antimicrobial activity. Such materials can
be used for manufacturing goods with increased resistance to microbial colonization, including medical masks, respirator
filters, wound dressings, etc
Blue spectra and induced formation of primordial black holes
We investigate the statistical properties of primordial black hole (PBH)
formation in the very early Universe. We show that the high level of
inhomogeneity of the early Universe leads to the formation of the first
generation PBHs. %The existence of these PBHs This causes later the appearance
of a dust-like phase of the cosmological expansion. We discuss here a new
mechanism for the second generation of PBH formation during the dust-like
phase. This mechanism is based on the coagulation process. We demonstrate that
the blue power spectrum of initial adiabatic perturbations after inflation
leads to overproduction of primordial black holes with gg if the power index is .Comment: 16 pages, 2 figure
The comparison of velocity distribution between Adhesion approximation and the Euler-Jeans-Newton model
For the evolution of density fluctuation in nonlinear cosmological dynamics,
adhesion approximation (AA) is proposed as a phenomenological model, which is
especially useful for describing nonlinear evolution. However, the origin of
the artificial viscosity in AA is not clarified. Recently, Buchert and
Dom\'{\i}nguez report if the velocity dispersion of the dust fluid is regarded
as isotropic, it works on a principle similar to viscosity or effective
pressure, and they consider isotropic velocity dispersion as the origin of the
artificial viscosity in AA. They name their model the Euler-Jeans-Newton (EJN)
model. In this paper, we focus on the velocity distribution in AA and the EJN
model and examine the time evolution in both models. We find the behavior of AA
differs from that of the EJN model, i.e., although the peculiar velocity in the
EJN model oscillates, that in AA is monotonically decelerated due to viscosity
without oscillation. Therefore it is hard to regard viscosity in AA as
effective pressure in the EJN model.Comment: 11 pages, 5 figures; accepted for publication in Phys.Rev.
Caustics in growing Cold Dark Matter Haloes
We simulate the growth of isolated dark matter haloes from self-similar and
spherically symmetric initial conditions. Our N-body code integrates the
geodesic deviation equation in order to track the streams and caustics
associated with individual simulation particles. The radial orbit instability
causes our haloes to develop major-to-minor axis ratios approaching 10 to 1 in
their inner regions. They grow similarly in time and have similar density
profiles to the spherical similarity solution, but their detailed structure is
very different. The higher dimensionality of the orbits causes their stream and
caustic densities to drop much more rapidly than in the similarity solution.
This results in a corresponding increase in the number of streams at each
point. At 1% of the turnaround radius (corresponding roughly to the Sun's
position in the Milky Way) we find of order 10^6 streams in our simulations, as
compared to 10^2 in the similarity solution. The number of caustics in the
inner halo increases by a factor of several, because a typical orbit has six
turning points rather than one, but caustic densities drop by a much larger
factor. This reduces the caustic contribution to the annihilation radiation.
For the region between 1% and 50% of the turnaround radius, this is 4% of the
total in our simulated haloes, as compared to 6.5% in the similarity solution.
Caustics contribute much less at smaller radii. These numbers assume a 100 GeV
c^-2 neutralino with present-day velocity dispersion 0.03 cm s^-1, but reducing
the dispersion by ten orders of magnitude only doubles the caustic luminosity.
We conclude that caustics will be unobservable in the inner parts of haloes.
Only the outermost caustic might potentially be detectable.Comment: 12 pages, 17 figures, minor corrections, accepted by MNRA
Antiprotons from primordial black holes
Primordial black holes (PBHs) have motivated many studies since it was shown
that they should evaporate and produce all kinds of particles. Recent
experimental measurements of cosmic rays with great accuracy, theoretical
investigations on the possible formation mechanisms and detailed evaporation
processes have revived the interest in such astrophysical objects. This article
aims at using the latest developments on antiproton propagation models together
with new data from BESS, CAPRICE and AMS experiments to constrain the local
amount of PBH dark matter. Depending on the diffusion halo parameters and on
the details of emission mechanism, we derive an average upper limit of the
order of rho < 1.7E-33 g cm^-3.Comment: Accepted by A&A . Revision : clarification, results unchange