Investigating the tolerance of plant reproductive systems to environmental changes has become a research priority under current climate change scenarios. Successful plant conservation requires ...knowledge of plant reproductive biology, particularly the meiotic characteristics of planted species. Meiosis, as part of microsporogenesis, is a critical plant developmental stage controlling future pollen quality. Meiosis in a Siberian fir (Abies sibirica) plantation, established in the Forest Arboretum of the Sukachev Institute, Russia, was studied from 2002 to 2004. The microsporogenesis pattern found for the Siberian fir appeared to be largely similar to that exhibited by other conifer species. Meiosis in the Siberian fir has the following characteristics: asynchrony, rapid progression of telophases I and II, and parallel and linear spindle arrangements at different meiosis II stages. General and specific meiosis irregularities were recorded at each stage. Some specific features of meiosis and the specific development of some irregularities were revealed. Pollen development analysis showed that irregular pollen grains made up less than 1% of all grains. The specific features of meiosis identified in fir trees growing in the Arboretum indicated low resistance of male reproductive structures to climatic changes and might account for high fir pollen sterility in this new environment.
Abstract
The work is devoted to the study of the porous structure formation of anodic alumina films at the initial stage of aluminium anodizing. SEM images of the surface morphology of the oxalic ...acid anodic films were analyzed. It was shown that at the initial stage, both major and minor pores are formed, the diameter ratio of which is about 1.16 and does not depend on the anodizing voltage. The results obtained indicate that the minor pores in the anodic films are located inside hexagonal cells composed of the major pores.
The resonant excitation of the
83
Kr first excited nuclear level (
E
= 9.4 keV) by solar axions whose fluxes depend on the axion–electron coupling constant
g
Ae
is sought. The γ- and X-ray photons ...and the conversion and Auger electrons from the excited-level relaxation are detected with a gas proportional counter of a low-background detector in the underground Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences). As a result, a new constraint
≤ 1.50 × 10
–17
(90% C.L.) has been obtained for the axion–electron and axion–nucleon coupling constants, which corresponds to new constraints on the axion mass
m
A
≤ 320 eV and
m
A
≤ 4.6 eV in the KSVZ and DFSZ axion models, respectively.
A comprehensive analysis of the current level of research in the development of intelligent hybrid nanosystems based on porous inorganic materials, in particular porous alumina, is carried out. The ...presented works show interesting opportunities for the development of intelligent, multifunctional optical devices with a microchip design.
Abstract
Currently, the study of the electric parameters of porous anodic alumina (PAA) layers is of interest for sensor applications (humidity, DNA, etc.). PAA layers are synthesized using ...electrochemical anodizing of aluminum foil in potentiostatic mode with an aqueous solution of sulfuric acid and glycerin as an electrolyte. The surface morphology of the layers was studied by atomic force microscopy. The electric characteristics were studied using impedance spectroscopy at room temperature and under heating. An increase in the impedance of the heat-treated PAA sample was found, as well as an increase in the impedance with an increase in the measurement temperature. The results are explained by the influence of adsorbed water molecules on the electric characteristics of porous layers.
The axio-electric effect in silicon atoms is sought for solar axions appearing owing to bremsstrahlung and the Compton process. Axions are detected using a Si(Li) detector placed in a low-background ...setup. As a result, a model-independent constraint on the axion-electron coupling constant |
g
Ae
| ≤ 2.2 × 10
−10
has been obtained, which leads to the bounds
m
A
≤ 7.9 eV and
m
A
≤ 1.4 eV (at 90% C.L.) for the mass of the axion in the DFSZ and KSVZ models, respectively.
A single-stage centrifugation method is used for the precipitation and crystallization of a solution of a hybrid halide perovskite compound of the CH
3
NH
3
PbI
3
composition. The perovskite films ...are annealed in the temperature range of 80–140°C, during which the excess of the
N
-methylpyrrolidone solvent was removed by evaporation. The X-ray phase analysis of the synthesized perovskite layer is carried out. The morphology of the surface of the layers after crystallization and the transmission spectra in the optical range are studied. The experiments and research results showed that the optimal temperature regime for the formation and crystallization of lead triiodide methylammonium perovskite films is 100–110°C. The perovskite layers obtained in these processing regimes have a surface morphology with a uniform granular crystal structure and are highly uniform. Moreover, in solar cells based on perovskite-like CH
3
NH
3
PbI
3
structures with an annealing temperature of 100–110°C, the short-circuit currents reached 16.0 mA/cm
2
. At the same time, at annealing temperatures of perovskite layers above 120°С, the maximum value of the short-circuit currents did not exceed 14.0 mA/cm
2
.
The results of karyological and cytogenetic studies of populations of conifer species from the families Pinaceae and Cupressaceae growing under extreme conditions have been summarized. A chromosomal ...variability has been revealed in coniferous plants growing at the southern and northern borders of their natural habitats, at ecological limits of distribution, in anthropogenically disturbed ecosystems, and under introduction conditions. A high frequency of changes in the number of chromosomes (mixoploidy, aneuploidy, and polyploidy) and their morphology has been observed. Different types of chromosomal anomalies (ring and polycentric chromosomes, chromosome fragments, and multiple chromosomal abnormalities), chromosome agglutination, mitotic and meiotic abnormalities, and the appearance of B chromosomes have been revealed. Using classical methods and fluorescent in situ hybridization (FISH), a polymorphism of nucleolar-forming regions of chromosomes has been studied and features of the 5S and 45S ribosomal DNA loci have been revealed.
A search for resonant absorption of solar axions by
169
Tm
nuclei was carried out. A newly developed approach involving low-background cryogenic bolometer based on
Tm
3
Al
5
O
12
crystal was used ...that allowed for significant improvement of sensitivity in comparison with previous
169
Tm
based experiments. The measurements performed with 8.18 g crystal during 6.6 days exposure yielded the following limits on axion couplings:
|
g
A
γ
(
g
AN
0
+
g
AN
3
)
≤
1.44
×
10
-
14
GeV
-
1
and
|
g
Ae
(
g
AN
0
+
g
AN
3
)
≤
2.81
×
10
-
16
.
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