•We study obtained reflectance spectra of six asteroids including two NEAs.•Spectral comparison of asteroids and their proper analog samples is made.•Intensity of an absorption band at 0.44-μm and ...Fe3+-content are strongly correlated.•Spectral signs of sublimation activity are found on Adeona, Interamnia, and Nina.•We discuss why weak absorption bands absent in reflectance spectra of NEAs.
Six asteroids including two NEAs, one of which is PHA, accessible for observation in September 2012 were investigated using a low-resolution (R≈100) spectrophotometry in the range 0.35–0.90μm with the aim to study features of their reflectance spectra. A high-altitude position of our Terskol Observatory (3150m above sea level) favorable for the near-UV and visible-range observations of celestial objects allowed us to probably detect some new spectral features of the asteroids. Two subtle absorption bands centered at 0.53 and 0.74μm were found in the reflectance spectra of S-type (32) Pomona and interpreted as signs of presence of pyroxenes in the asteroid surface matter and its different oxidation. Very similar absorption bands centered at 0.38, 0.44 and 0.67–0.71μm have been registered in the reflectance spectra of (145) Adeona, (704) Interamnia, and (779) Nina of primitive types. We performed laboratory investigations of ground samples of known carbonaceous chondrites, Orguel (CI), Mighei (CM2), Murchison (CM2), Boriskino (CM2), and seven samples of low-iron Mg serpentines as possible analogs of the primitive asteroids. In the course of this work, we discovered an intense absorption band (up to ∼25%) centered at 0.44μm in reflectance spectra of the low-Fe serpentine samples. As it turned out, the equivalent width of the band has a high correlation with content of Fe3+ (octahedral and tetrahedral) in the samples. It may be considered as a confirmation of the previously proposed mechanism of the absorption due to electronic transitions in exchange-coupled pairs (ECP) of Fe3+ neighboring cations. It means that the absorption feature can be used as an indicator of ferric iron in oxidized and hydrated low-Fe compounds on the surface of asteroids and other atmosphereless celestial bodies. Moreover, our measurements showed that the mechanism of light absorption is partially or completely blocked in the case of intermediate to high iron contents. Therefore, the method cannot probably be used for quantitative estimation of Fe3+ content on the bodies. Based on laboratory study of the analog samples, we conclude that spectral characteristics of Adeona, Interamnia, and Nina correspond to a mixture of CI–CM-chondrites and hydrated silicates, oxides and/or hydroxides. Spectral signs of sublimation activity on Adeona, Interamnia, and Nina at minimal heliocentric distances are likely discovered in the short-wavelength range (∼0.4–0.6μm). It is suggested that such cometary-like activity at the highest surface temperatures is a frequent phenomenon for C and close type asteroids including considerable amounts of ices beneath the surface. A usual way of origin of a temporal coma of ice particles around a primitive asteroid is excavated fresh ice at recent impact event(s).
The obtained reflectance spectra of two NEAs, (330825) 2008 XE3 and 2012 QG42, are predominantly featureless and could be attributed to S(C) and S(B)-type bodies, respectively. We discuss reasons why weak spectral features seen in reflectance spectra of the main-belt asteroids are not observed in those of NEAs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The aspects of design of reactance-less oscillators based on memristors are considered. The requirements on load elements in the circuits of such oscillators are formulated. The equations describing ...the dynamical behavioral of the memristor oscillators with the use of linear-drift models are presented. Examples of the analysis and synthesis of oscillators using such equations are presented. The possibility of generation in the circuits under consideration of periodic signals with a waveform close to harmonic oscillations is shown.
The genus
forms a deeply branching family in the class
and is currently represented by three physiologically diverse species of thermophilic prokaryotes. The type strain of the type species,
41
, is ...an obligate chemolithoautotroph growing exclusively by hydrogenogenic CO oxidation. Another strain, isolated from a hot spring at Uzon caldera, Kamchatka in the course of this work, is capable of coupling carboxydotrophy and dissimilatory reduction of Fe(III) from oxic and phyllosilicate minerals. The processes of carboxydotrophy and Fe(III) reduction appeared to be interdependent in this strain. The genomes of both isolates were sequenced, assembled into single chromosome sequences (for strain 41
a plasmid sequence was also assembled) and analyzed. Genome analysis revealed that each of the two strains possessed six genes encoding diverse Ni,Fe-containing CO dehydrogenases (maximum reported in complete prokaryotic genomes), indicating crucial role of carbon monoxide in
metabolism. Both strains possessed a set of 30 multiheme
-type cytochromes, but only the newly isolated Fe-reducing strain 019 had one extra gene of a 17-heme cytochrome, which is proposed to represent a novel determinant of dissimilatory iron reduction in prokaryotes. Mössbauer studies revealed that strain 019 induced reductive transformation of the abundant ferric/ferrous-mica mineral glauconite to siderite during carboxydotrophic growth. Reconstruction of the
strains energy metabolism is the first comprehensive genome analysis of a representative of the deep phylogenetic branch Clostridia Incertae Sedis, family V. Our data provide insights into energy metabolism of
with an emphasis on its ecological implications.
The existing ideas on the status of the Navier–Stokes equations are changed in taking into account the following facts: generally speaking, the terms of these equations neglected in the boundary ...layer equations are of the order of certain Burnett terms in the conservation equations; the Navier–Stokes equations cannot be used to describe slow nonisothermal gas flows since in this case it is necessary to take the Burnett temperature stresses into account; and in the transport relations the Burnett terms determine certain effects (for example, the mechanocaloric effect).
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The article presents the results of evaluating the applicability of various types of iron-containing nanoparticles in magnetic hyperthermia, as well as determining the degradation resistance of ...nanoparticles. The objects of study were iron-containing nanoparticles obtained by chemical precipitation and subsequent modification with gold, gadolinium, and neodymium. The main methods for studying the properties of the synthesized nanoparticles were transmission electron microscopy, X-ray phase analysis, and Mössbauer spectroscopy. Evaluation of the efficiency of the use of the synthesized nanoparticles in magnetic hyperthermia showed that Fe3O4@GdFeO3 nanoparticles, for which the specific absorption rate was more than 120 W/g, have the highest efficiency. An assessment of the resistance of the synthesized nanoparticles to corrosion in water at different temperatures showed that Fe2O3@NdFeO3 and Fe3O4@GdFeO3 nanoparticles have the highest resistance to degradation. It has been established that in the case of the initial Fe3O4 nanoparticles, the degradation processes are accompanied by partial destruction of the particles, followed by amorphization and destruction, while for Fe2O3@NdFeO3 and Fe3O4@GdFeO3 nanoparticles, the degradation processes proceed much more slowly, due to the presence of interfacial boundaries, which slow down the corrosion processes. The obtained results of corrosion tests in aqueous media make it possible to predict the area and time frame of applicability of iron-containing nanoparticles when using them in the biomedical direction, as well as to determine storage conditions.
The memristor pulse series oscillator based on the Schmitt trigger with a memristor and a capacitor at the input is discussed. It is shown that such circuit provides the generation of a pulse series ...the duration of which is determined by the amplitude of the input signal. The simulation results corroborate the wide functionality of the oscillator under discussion.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The paper presents the results of a study of iron oxide nanoparticles obtained by chemical coprecipitation, coated (Fe3O4@Au) and not coated (Fe3O4) with gold, which were subjected to thermal ...annealing. To characterize the nanoparticles under study, scanning and transmission electron microscopy, X-ray diffraction, and Mössbauer spectroscopy on 57Fe nuclei were used, the combination of which made it possible to establish a sequence of phase transformations, changes in morphological and structural characteristics, as well as parameters of hyperfine interactions. During the studies, it was found that thermal annealing of nanoparticles leads to phase transformation processes in the following sequence: nonstoichiometric magnetite (Fe3−γO4) → maghemite (γ-Fe2O3) → hematite (α-Fe2O3), followed by structural ordering and coarsening of nanoparticles. It is shown that nanoparticles of nonstoichiometric magnetite with and without gold coating are in the superparamagnetic state with a slow relaxation rate. The magnetic anisotropy energy of nonstoichiometric magnetite is determined as a function of the annealing temperature. An estimate was made of the average size of the region of magnetic ordering of Fe atoms in nonstoichiometric magnetite, which is in good agreement with the data on the average sizes of nanoparticles determined by scanning electron microscopy.
—
Four samples of natural Ti-bearing garnets from Odihincha, Maimecha-Kotui alkaline province, Krasnoyarsk Krai, Russia, were studied using electron microprobe analysis, X-ray powder diffraction ...(XRD), Fourier-transform infrared spectroscopy (FTIR), Raman and Mössbauer spectroscopy, and thermal analysis. The enthalpies of formation from elements were determined with a high-temperature heat-flux Tian–Calvet microcalorimeter by means of the melt solution calorimetry. The first ever values of
(298.15 K) were determined as follows: −5861.1 ± 11.3 kJ/mol for (Ca
3.00
Na
0.02
Fe
2+
0.01
) (
Al
0.21
Mg
0.04
)(Si
2.85
)O
11.92
(OH)
0.08
; −5915.2 ± 9.0 kJ/mol for Ca
3.01
(
Mg
0.05
)(Si
2.69
Al
0.16
)O
11.96
(OH)
0.04
; −5902.5 ± 9.1 kJ/mol for (Ca
2.97
)(
Mg
0.05
)(Si
2.64
Al
0.11
)O
11.96
(OH)
0.04
; and −5945.7 ± 10.2 kJ/mol for (Ca
2.90
Na
0.04
Mg
0.01
)(
Mg
0.13
Zr
0.08
) (Si
2.33
Al
0.07
)O
11.84
(OH)
0.16
. The standard Gibbs free energies of formation of these garnets were calculated using the values obtained for the formation enthalpies and estimated for the entropies. Also, the enthalpies of formation of the end-members of the isomorphic schorlomite–morimotoite series were derived. The thermodynamic constants were used in quantitative modeling of the stability fields of these minerals.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this paper, we present a numerical solution of the discrete control problem for the immune response in an infectious disease under conditions of uncertainty. This problem is described by a ...nonlinear system of ordinary differential equation with delay. Conditions of uncertainty mean that values of the parameters of the model are unknown and their estimates are corrected by new experimental data. We propose an algorithm that allows one, within the framework of the mathematical model of an infectious disease, to construct the control and to identify parameters. By using the algorithm proposed, we develop treatment programs based on immunotherapy. We show that immunotherapy is an effective treatment for all main forms of disease: acute, chronic, and lethal.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Hyperfine interactions of 57Fe nuclei in Fe100-xNix nanostructures synthesized in polymer ion-track membranes were studied by Mössbauer spectroscopy. The main part of obtained nanostructures was ...Fe100-xNix nanotubes with bcc structure for 0 ≤ x ≤ 40, and with fcc structure for 50 ≤ x ≤ 90. The length, outside diameter and wall thickness of nanotubes were 12 μm, 400 ± 10 nm and 120 ± 5 nm respectively. For the studied nanotubes a magnetic texture is observedalong their axis. The average value of the angle between the direction of the Fe atom magnetic moment and the nanotubes axis decreases with increasing of Ni concentration for nanotubes with bcc structure from ~50° to ~40°, and with fcc structure from ~55° to ~46°. The concentration dependences of the hyperfine parameters of nanotubes Mössbauer spectra are qualitatively consistent with the data for bulk polycrystalline samples. With Ni concentration increasing the average value of the hyperfine magnetic field increases from ~328 kOe to ~335 kOe for the bcc structure and drops to ~303 kOe in the transition to the fcc structure and then decreases to ~290 kOe at x = 90. Replacing the Fe atom with the Ni atom in the nearest environment of Fe atom within nanotubes with bcc structure lead to an increase in the hyperfine magnetic field by “6–9 kOe”, and in tubes with fcc structure—to a decrease in the hyperfine magnetic field by “11–16 kOe”. The changes of the quadrupole shift and hyperfine magnetic field are linearly correlated with the coefficient −(15 ± 5)·10−4 mm/s/kOe.
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