X-ray, Mössbauer, and magnetic methods have been used to determine the structural-phase state of nanocomposites—carbide steels doped with chromium and nickel (Fe
0.90 –
x
Mn
0.10
Ni
x
)
83
C
17
, ...where
x
= 0.05 and 0.10, obtained by mechanosynthesis followed by annealings. The magnetic (para- or ferro-) states of the phases and their influence on the formation of magnetic hysteresis properties of carbide steels have been studied.
Formation of phases in nanocomposites of composition of carbide steels alloyed with chromium and nickel obtained as a result of mechanosynthesis in a planetary ball mill and further annealing was ...studied. It was shown that the structure mainly consisting of nickel-alloyed austenite and chromium-alloyed cementite is realized in composite (Fe
0.80
Cr
0.10
Ni
0.10
)
83
C
17
after annealing at temperatures of 700–800°C. The size of cementite grains is in the nanometer range.
The formation and doping of phases during mechanical synthesis followed by annealing in the (Fe
0.80
Cr
0.05
Ni
0.15
)
75
C
25
alloy are studied by the method of X-ray diffraction, Mössbauer ...spectroscopy, and magnetic measurements. It is shown that after mechanical synthesis, the nanocomposite contains mainly two phases (amorphous phase and cementite A). During annealing, as a result of crystallization of the amorphous phase, cementite B is formed, in which the nickel concentration is higher than in mechanically synthesized cementite A. Upon an increase in the annealing temperature, austenite with a nonuniform nickel concentration is formed. The Curie temperature of such austenite reaches 500°C. It is established that cementite in mechanically synthesized nanocomposite (Fe,Cr,Ni)
75
C
25
has a higher stability to temperature variations than mechanically synthesized composite (Fe,Ni)
75
C
25
.
Changes in the magnetic hysteresis properties of the (Fe
0.8
Cr
0.1
Ni
0.1
)
75
C
25
alloy during the formation of the phase composition at different stages of mechanosynthesis and subsequent ...annealing are studied by means of X-ray diffraction and Mössbauer spectroscopy.
The lead-lead isochron age of chondrules in the CR chondrite Acfer 059 is 4564.7 +/- 0.6 million years ago (Ma), whereas the lead isotopic age of calcium-aluminum-rich inclusions (CAIs) in the CV ...chondrite Efremovka is 4567.2 +/- 0.6 Ma. This gives an interval of 2.5 +/- 1.2 million years (My) between formation of the CV CAIs and the CR chondrules and indicates that CAI- and chondrule-forming events lasted for at least 1.3 My. This time interval is consistent with a 2- to 3-My age difference between CR CAIs and chondrules inferred from the differences in their initial 26Al/27Al ratios and supports the chronological significance of the 26Al-26Mg systematics.
We analyze nonlinear evolution of torsional Alfvén waves in a straight magnetic flux tube filled in with a low-β plasma, and surrounded with a plasma of lower density. Such magnetic tubes model, in ...particular, a segment of a coronal loop or a polar plume. The wavelength is taken comparable to the tube radius. We perform a numerical simulation of the wave propagation using ideal magnetohydrodynamics. We find that a torsional wave nonlinearly induces three kinds of compressive flows: the parallel flow at the Alfvén speed, which constitutes a bulk plasma motion along the magnetic field, the tube wave, and also transverse flows in the radial direction, associated with sausage fast magnetoacoustic modes. In addition, the nonlinear torsional wave steepens and its propagation speed increases. The latter effect leads to the progressive distortion of the torsional wave front, i.e., nonlinear phase mixing. Because of the intrinsic non-uniformity of the torsional wave amplitude across the tube radius, the nonlinear effects are more pronounced in regions with higher wave amplitudes. They are always absent at the axes of the flux tube. In the case of a linear radial profile of the wave amplitude, the nonlinear effects are localized in an annulus region near the tube boundary. Thus, the parallel compressive flows driven by torsional Alfvén waves in the solar and stellar coronae, are essentially non-uniform in the perpendicular direction. The presence of additional sinks for the wave energy reduces the efficiency of the nonlinear parallel cascade in torsional Alfvén waves.
We study the coronal mass ejection (CME) with a complex acceleration profile. The event occurred on 2009 April 23. It had an impulsive acceleration phase, an impulsive deceleration phase, and a ...second impulsive acceleration phase. During its evolution, the CME showed signatures of different acceleration mechanisms: kink instability, prominence drainage, flare reconnection, and a CME-CME collision. The special feature of the observations is the usage of the TESIS EUV telescope. The instrument could image the solar corona in the Fe 171 line up to a distance of 2 from the center of the Sun. This allows us to trace the CME up to the LASCO/C2 field of view without losing the CME from sight. The onset of the CME was caused by kink instability. The mass drainage occurred after the kink instability. The mass drainage played only an auxiliary role: it decreased the CME mass, which helped to accelerate the CME. The first impulsive acceleration phase was caused by the flare reconnection. We observed the two-ribbon flare and an increase of the soft X-ray flux during the first impulsive acceleration phase. The impulsive deceleration and the second impulsive acceleration phases were caused by the CME-CME collision. The studied event shows that CMEs are complex phenomena that cannot be explained with only one acceleration mechanism. We should seek a combination of different mechanisms that accelerate CMEs at different stages of their evolution.
Abstract
In the solar corona, magnetic reconnection occurs due to the finite resistivity of the plasma. At the same time, this resistivity leads to ohmic heating. Therefore, the reconnecting current ...sheet should heat the surrounding plasma. This paper presents experimental evidence of such plasma heating being caused by magnetic reconnection. We observed the effect during a C1.4 solar flare on 2003 February 16 at the active region NOAA 10278, near the solar limb. Thanks to such a location, we successfully identified all the principal elements of the flare: the flare arcade, the flux rope, and, most importantly, the presumed position of the current sheet. By analyzing the monochromatic X-ray images of the Sun obtained by the CORONAS-F/SPIRIT instrument in the Mg
xii
8.42 Å spectral line, we detected a high-temperature (
T
≥ 4 MK) emission at the predicted location of the current sheet. The high-temperature emission appeared during the CME’s impulsive acceleration phase. We believe that this additionally confirms that the plasma heating around the current sheet and the magnetic reconnection inside the current sheet are strongly connected.
The formation of phases in mechanically synthesized (Fe
0.90−
x
Mn
0.10
Ni
x
)
75
C
25
alloys, where
х
= 0.05 and 0.10, is studied via X-ray diffraction, Mössbauer spectroscopy, and magnetic ...measurements. It is shown that certain products form during the mechanosynthesis of the initial powders in a planetary ball mill: cementite doped mainly with manganese, ferrite, and an amorphous phase doped mainly with nickel. Annealing at 500°C and higher temperatures leads to the formation of a composite consisting of cementite and austenite doped mainly with nickel. Cementite regions with two different Curie temperatures form as the alloys cool after high-temperature (700°C) annealing, due to differences in the manganese doping of cementite in these regions.
The discovery of the ability of some mutations to stimulate haploidy during hybridization made it possible to create one of the most promising and sought-after trends in the f ield of reproductive ...biology. Haploid inducers created on their basis are capable of increasing the frequency of haploidy up to 15 %. The improvement of the existing haploid inducer lines and the search for new genes that contribute to a high frequency of haploidy are underway. Along with these studies, the f ield of application of haploid inducers in genetics and plant breeding is expanding. Haploid inducers carrying R1-nj genes for anthocyanin pigmentation of the seed and embryo are able not only to mark the hybrid embryo and identify haploid genotypes, but also to detect genes that suppress the anthocyanin color of the grain, like C1-I, C2-Idf, and In1-D. Depending on their quantity, the phenotypic manifestation of the gene in the seed varies. Haploidy is widely used for accelerating hybrid breeding and obtaining both new maize lines with improved traits and their sterile counterparts. By introducing certain genes into the genome of the improved line, breeders can use the doubled haploid (DH) breeding technology to accelerate the creation of pure lines carrying the desired gene. Haploid inducer maize lines and their tetraploid analogs are used in the selection of rediploid maize lines by their resynthesis from tetraploid genotypes. In 2019, Syngenta Company synthesized a haploid inducer maize line carrying a CRISPR/cas construct capable of simultaneously stimulating haploidy and editing the genome at a specif ied DNA site. Thanks to this technology, it became possible to improve haploid inducers by introducing various CRISPR/cas constructs into the haploid inducer genome for editing any DNA site. Maize haploid inducers are widely used in doubled haploid wheat breeding. The f irst experiments showed that the most effective haploid inducer for stimulating haploidy in wheat is maize pollen. Researchers are intensively searching for other ways of using maize haploid inducers in plant breeding.
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