Temperature dependence of self-trapped exciton luminescence in nanostructured hafnia powder

The intrinsic optical properties and peculiarities of the energy structure of hafnium dioxide largely determine the prospects for applying the latter in new generation devices of optoelectronics and nanoelectronics. In this work, we have studied the diffuse reflectance spectra at room temperature for a nominally pure nanostructured $HfO_2$ powder with a monoclinic crystal structure and, as well its photoluminescence in the temperature range of 40 - 300 K. We have also estimated the bandgap $E_g$ under the assumption made for indirect (5.31 eV) and direct (5.61 eV) allowed transitions. We have detected emission with a 4.2 eV maximum at T < 200 K and conducted an analysis of the experimental dependencies to evaluate the activation energies of thermal quenching (140 meV) and enhancement (3 meV) processes. Accounting for both the temperature behavior of the spectral characteristics and the estimation of the Huang-Rhys factor S >> 1 has shown that radiative decay of self-trapped excitons forms the mechanism of the indicated emission. In this case, the localization is mainly due to the interaction of holes with active vibrational modes of oxygen atoms in non-equivalent ($O_{3f}$ and $O_{4f}$) crystal positions. Thorough study of the discussed excitonic effects can advance development of hafnia-based structures with a controlled optical response.Comment: 21 pages, 7 figures, 2 tables, 56 references. Keywords: hafnium dioxide, self-trapped exciton, F-center, thermal quenching of luminescence, luminescence enhacement, Huang-Rhys factor, effective phonon energy, bandgap widt

TREATMENT OF PATIENTS WITH DIABETIC FOOT SYNDROME

The article reviews modern approaches in complex treatment of patients with diabetic foot syndrome. Authors present their experience with the patients who arrived in planned and emergency order, the criteria of choice of the strategy of surgical treatment of diabetic foot syndrome. Direct and remote results of introduced scheme are studied and. its advantages and. disadvantages are revealed

Nitric Oxide Has a Concentration-Dependent Effect on the Cell Cycle Acting via EIN2 in Arabidopsis thaliana Cultured Cells

Ethylene is known to influence the cell cycle (CC) via poorly characterized roles whilst nitric oxide (NO) has well-established roles in the animal CC but analogous role(s) have not been reported for plants. As NO and ethylene signaling events often interact we examined their role in CC in cultured cells derived from Arabidopsis thaliana wild-type (Col-0) plants and from ethylene-insensitive mutant ein2-1 plants. Both NO and ethylene were produced mainly during the first 5 days of the sub-cultivation period corresponding to the period of active cell division. However, in ein2-1 cells, ethylene generation was significantly reduced while NO levels were increased. With application of a range of concentrations of the NO donor, sodium nitroprusside (SNP) (between 20 and 500 μM) ethylene production was significantly diminished in Col-0 but unchanged in ein2-1 cells. Flow cytometry assays showed that in Col-0 cells treatments with 5 and 10 μM SNP concentrations led to an increase in S-phase cell number indicating the stimulation of G1/S transition. However, at ≥20 μM SNP CC progression was restrained at G1/S transition. In the mutant ein2-1 strain, the index of S-phase cells was not altered at 5–10 μM SNP but decreased dramatically at higher SNP concentrations. Concomitantly, 5 μM SNP induced transcription of genes encoding CDKA;1 and CYCD3;1 in Col-0 cells whereas transcription of CDKs and CYCs were not significantly altered in ein2-1 cells at any SNP concentrations examined. Hence, it is appears that EIN2 is required for full responses at each SNP concentration. In ein2-1 cells, greater amounts of NO, reactive oxygen species, and the tyrosine-nitrating peroxynitrite radical were detected, possibly indicating NO-dependent post-translational protein modifications which could stop CC. Thus, we suggest that in Arabidopsis cultured cells NO affects CC progression as a concentration-dependent modulator with a dependency on EIN2 for both ethylene production and a NO/ethylene regulatory function

Increasing the efficiency of investments on survey of abundant land for their return to agricultural us

The "“State program for the effective involvement of abundant agricultural land in the use and the development of the reclamation complex of the Russian Federation” for 2021–2030" assumes the return of 12 million hectares out of 44 million hectares of all abandoned agricultural land (AAL) in the Russian Federation. The costs of 12 million hectares survey can be considered productive, while the costs of surveying the remaining 32 million hectares should be considered unproductive. The application of the new geoinformation database of “Soils of agricultural lands of the Russian Federation” (DB SALRU) developed by the Federal Research Centre “V.V Dokuchaev Soil Sience Institute” allows reduction of unproductive costs. By the example of the Vladimir region, a typical Russian region with AAL, the option of ranking AAL by their quality was demonstrated to determine the order of their return to agricultural use. The soil quality criteria are the bonitet and the normative yield of grain crops, which are part of the DB SALRU. It is proposed to consider the expenditures on the survey of AAL for the soils, which are first to be returned to agricultural use, as productive costs. These soils occupy 25% of the AAL of the region. The best quality soils are characterized by more than 40 points of bonitet and the standard yield of grain crops of more than 20 centners/ha. The cost of surveying the lands of the first order of returning to agricultural use is 10 million 80 thousand rubles. Survey of AAL soils of II–IV orders of involvement in agricultural use, with relatively poor quality compared to the soils of the first order, is proposed to be conducted in the case of expansion of the State program in the future. This would save the unproductive expenses for the survey of AAL for the Vladimir region by 30 million 165.5 thousand rubles. The application of the proposed GIS-approach makes it possible to reduce unproductive expenses for the survey of AAL in the Russian Federation nearly by 5.600 million rubles

The study of the sorghum genetic diversity using the mul¬tiplex microsatellite analysis

This study is focused on evaluation of the genetic structure and diversity of the national sorghum collection. Analyzing the genetic diversity of crop species is of great importance for genetic resources management and food security of any country. Huge genetic diversity of sorghum provides a great opportunity to improve the agronomic characteristics of this crop. The efficiency of microsatellite  analysis has been demonstrated in many studies on the genetic diversity of different races and geographical groups of sorghum plants. Development of multiplex PCR analysis systems based on a set of polymorphic microsatellite loci will facilitate genetic tests on a large number of plant samples, thus making the research on sorghum diversity more efficient and comprehensive. A system of multiplex PCR analysis based on 12 polymorphic microsatellite loci was developed to perform single-stage high-throughput screening of cultivated and wild forms preserved in the sorghum germplasm collection. As a result of the microsatellite analysis of 200 sorghum plants, 229 alleles were detected. The studied loci showed high polymorphism. More than 17 alleles were identified in most loci, their polymorphic index content (PIC) ranging from 0.694 to 0.954. The value of the effective multiplex ratio (EMR) in the developed system was estimated at 0.833. The microsatellite analysis of sorghum accessions resulted in obtaining quantized gene expressions profiles, with a DNA profile for each accession, and revealed significant polymorphism among the plants of different sorghum varieties (races). The developed multiplex PCR system was shown to be efficient for evaluation of the genetic diversity and genetic relationships of sorghum plants from different races. The analysis of the obtained data using three bioinformatic techniques, NJ cluster analysis, PCoA, and the Bayesian model-based clustering, helped to classify the analyzed sorghum accessions into cluster groups according to their morphological and agronomic traits

Luminescence in anion-deficient hafnia nanotubes

Hafnia-based nanostructures and other high-k dielectrics are promising wide-gap materials for developing new opto- and nanoelectronics devices. They possess a unique combination of physical and chemical properties such as insensitivity to electrical and optical degradation, radiation damage stability, a high specific surface area, and an increased concentration of the appropriate active electron-hole centers. The present paper aims to investigate the structural, optical, and luminescent properties of anodized non-stoichiometric $HfO_2$ nanotubes. As-grown amorphous hafnia nanotubes and nanotubes annealed at 700{\deg}C with a monoclinic crystal lattice served as samples. It has been shown that the bandgap $E_g$ for direct allowed transitions amounts to $5.65\pm0.05$ eV for amorphous and $5.51\pm0.05$ eV for monoclinic nanotubes. For the first time, we have studied the features of the intrinsic cathodoluminescence and photoluminescence of the obtained nanotubular $HfO_2$ structures with an atomic deficiency in the anion sublattice at temperatures of 10 and 300 K. A broad emission band with a maximum of 2.3-2.4 eV has been revealed. We have also conducted an analysis of the kinetic dependencies of the observed photoluminescence for synthesized $HfO_2$ samples in the millisecond range at room temperature. It showed that there are several types of optically active capture and emission centers based on vacancy states in the $O_{3f}$ and $O_{4f}$ positions with different coordination numbers and a varied number of localized charge carriers ($V^0$, $V^-$, and $V^{2-}$). The uncovered regularities can be used to optimize the functional characteristics of developed-surface luminescent media based on nanotubular and nanoporous modifications of hafnia.Comment: 15 pages, 6 figures, 3 tables, 50 reference

Nonlinear electrochemical relaxation around conductors

We analyze the simplest problem of electrochemical relaxation in more than one dimension - the response of an uncharged, ideally polarizable metallic sphere (or cylinder) in a symmetric, binary electrolyte to a uniform electric field. In order to go beyond the circuit approximation for thin double layers, our analysis is based on the Poisson-Nernst-Planck (PNP) equations of dilute solution theory. Unlike most previous studies, however, we focus on the nonlinear regime, where the applied voltage across the conductor is larger than the thermal voltage. In such strong electric fields, the classical model predicts that the double layer adsorbs enough ions to produce bulk concentration gradients and surface conduction. Our analysis begins with a general derivation of surface conservation laws in the thin double-layer limit, which provide effective boundary conditions on the quasi-neutral bulk. We solve the resulting nonlinear partial differential equations numerically for strong fields and also perform a time-dependent asymptotic analysis for weaker fields, where bulk diffusion and surface conduction arise as first-order corrections. We also derive various dimensionless parameters comparing surface to bulk transport processes, which generalize the Bikerman-Dukhin number. Our results have basic relevance for double-layer charging dynamics and nonlinear electrokinetics in the ubiquitous PNP approximation.Comment: 25 pages, 17 figures, 4 table