This article presents the results of the formation and evaluation of the surface morphology and investigation of the optical properties (in the near and middle infrared range) of Ta
2
O
5
nanocluster ...films obtained by thermal oxidation in the ambient air out of monodisperse cluster films of metallic tantalum created on Si(001) substrates by magnetron sputtering. Surface images were obtained by atomic force microscopy (in situ) and it is shown that Ta films have a porous densely packed structure consisting of individual spherical-shaped nanoparticles. The optical properties of the films are investigated using a near- and mid-IR spectrometer. It is shown that thin films (less than 100-nm thick) have a sharp boundary between the region of radiation transmission and the region of absorption and/or reflection, while for thicker films, this effect gradually disappears with increasing cluster film thickness and does not depend on the nanocluster size. The possibility of using these structures in thermophotoelectric generators in order to increase their efficiency is discussed.
The results of the scanning tunneling spectroscopy study of the electronic states of tantalum nanoclusters on a silicon substrate are presented. Nanoclusters are fabricated by cluster deposition from ...the gas phase using magnetron sputtering of a tantalum target. Clusters are formed using a Nanogen-50 cluster source (Mantis Deposition) with a quadrupole mass filter integrated into the preparation chamber of an Omicron Multiprobe MXPS VT AFM-25 ultrahigh vacuum system. It is established that the tunneling current differs significantly for spherical nanoclusters of different sizes, and the measured differential current–voltage characteristic of nanoclusters near the Fermi energy is nonmonotonic, which may indicate a change in the density of states near the Fermi energy. This change in the tunneling conductivity of nanoclusters depending on their size indicates the metal–nonmetal transition in metal nanoclusters on the semiconductor surface as the cluster size decreases.
The results of the formation and certification of the surface morphology and chemical composition and also the results of the study of radiation upon heating to high temperatures (600–800°C) of Ta
2
...O
5
nanocluster films obtained by sputtering a Ta target in an atmosphere of Ar and O
2
gases with subsequent filtering of the formed clusters according to the selected sizes and their deposition on a metal substrate (Ta) are presented. Surface images were obtained by atomic force microscopy (in situ), and it was shown that Ta films have a loose structure consisting of close-packed spherical nanoparticles. XPS analysis of the chemical composition showed that the resulting films are of high purity and are close to the compound Ta
2
O
5
. Using a spectrometer with a working range of 600–1700 nm, the emission spectra of films and substrates with natural tantalum oxide were obtained when heated to various temperatures. It is shown that films with small cluster sizes (2–3 nm) have a more stable emissivity at varying temperatures than films with large clusters (4–5 nm). In addition, when heated to the same temperature, small tantalum oxide clusters radiate more efficiently than a substrate with natural tantalum oxide film. The question is raised about the prospects of using the obtained structures as part of selective emitters to improve the efficiency of thermophotovoltaic systems.
We have considered procedure and results of the experimental study for spectral characteristics of self emission from laboratory models of electric thrusters with closed electron drift, with special ...reference to a thruster with an anode layer (TAL) and stationary plasma thruster (SPT), for a discharge power of 600, 800, and 1000 W, vertical and horizontal polarizations, and various propellants (krypton, xenon). The study allowed us to reveal a number of specific features of radio-frequency emission from thrusters with closed electron drift in the spectral domain. In particular, it was determined that the TAL has a broadband spectrum recorded in the frequency band from 1 to 4 GHz. Vertical polarization dominated in the studied modes, and the level of radio-frequency emission from TAL operating with krypton was 5–10 dB higher than in the case of its operation with xenon. In turn, the SPT has a broadband spectrum recorded in the frequency band from 1 to 3 GHz. Horizontal polarization slightly dominated in the studied modes. For the SPT, the maximum emission level excess in krypton operation compared to xenon was about 10 dB in the frequency range from 1 to 2 GHz for horizontal polarization. The results allow us to solve the problem of quantitative assessment for the effect of emission from thrusters with closed electron drift on the noise immunity of space communication systems.
A new tetranitrosyl binuclear iron complex, Fe
2
(SC
6
H
6
N)
2
(NO)
4
(1), has been synthesized by two methods. Molecular and crystalline structure of 1 were determined by X-ray analysis; the ...complex is binuclear of "μ-S" type with ~2.7052(4) Å between the irons. The compound crystallizes in monoclinic, space group P2
1
/n, Z = 2; parameters of the unit cell: a = 6.6257(2) Å, b = 7.9337(2) Å, c = 16.7858(4) Å, β = 96.742(2)°, V = 876.26(4) Å
3
. Parameters of Mössbauer spectrum for 1 are: isomer shift δ
Fe
= 0.096(1) mm/s, quadrupole splitting ΔE
Q
= 1.122(1) mm/s, line width 0.264(1) mm/s at 293 K. As follows from the electrochemical analysis of aqueous solutions of 1, it generates NO in protonic media without additional activation. NO amount and the rate of its activation are much higher in acidic solutions than in neutral and alkali ones. The constants of hydrolytic decomposition of 1 were calculated. The geometry and electronic structure of isolated 1 were studied using the density functional theory. Differential sensitivity of four lines of human tumor cells of various genesis to 1 has been determined (ovarian carcinoma (SCOV3), large intestine cancer (LS174T), mammary gland carcinoma (MCF7), and non-small cell carcinoma of lung (A549)); dependence of tumor cells amount on the complex concentration has been studied in order to use the complex as a promising antitumor agent for trials in vivo.
The variational principle of minimum total power and modern computational means are used to describe the deformation of metal in and to determine the power/force conditions for rolling rails and ...I-beams in universal beam passes. The results are engineering formulas for designing roll passes and calculating process parameters.
A survey is presented of the so-called program schemata technique for proving the decidability of propositional program logics. This method is based on the reduction to versions of the problem of ...relative totality for nondeterministic Yanov schemata.
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.
Tetragonal crystal structure of molybdenum oxytribromide, MoOBr3, consists of non-planar Mo2Br6 units joined by non-equidistant Mo-O-Mo bonds into infinite ladders, which are connected to each other ...by the van der Waals forces. Within unit cell, the apical Mo atoms in any given ladder are shifted along the c axis either above (+z) or below (−z) the basal ab plane of the Br atoms. Magnetic susceptibility taken at various frequencies χac(T) and magnetic fields χdc(T) as well as specific heat Cp(T) data evidence the formation of a long-range antiferromagnetic order at TN = 34 ± 1 K with largely reduced effective magnetic moments µeff = 1.3 ± 0.1 µB. First principles GGA+U calculations point to the predominance of intra-ladder ferromagnetic exchange interaction on both rungs Jrung = − 10 meV and legs Jleg = − 1 meV of the ladder, while much weaker inter-ladder antiferromagnetic exchange interaction Jinter = 0.2 meV couples the ladders. The anisotropic part of the exchange K = 0.6 meV in combination with Jinter allows estimating the spin-flop transition field µ0Hspin-flop ∼ 6 T in good correspondence with the magnetization M(H) data.
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•Space group P-421m of MoOBr3 was found through optimization of the crystal structure.•Magnetic structure of MoOBr3 is constituted by antialigned ferromagnetic spin ladders.•Order at TN = 34 K was established in measurements of magnetization and specific heat.
To evaluate the relationship between the severity of post-stroke cognitive impairment (PSCI) and coagulation parameters assessed using the dynamic thrombophotometry.
Thirty-five patients with ...hemispheric ischemic stroke (IS) with moderate neurological deficit at admission were included. All patients underwent a comprehensive clinical and instrumental assessment according to the current guidelines. On days 10-14, the cognitive status of patients was assessed using the Montreal Cognitive Assessment (MoCA). Coagulation parameters were assessed using the dynamic thrombophotometry at admission, on 6-8
days and 13-15
days from the onset of the disease. A database of laboratory studies of 30 apparently healthy volunteers was used as a comparison group.
Data analysis revealed that a number of spatial and temporal parameters were within the reference values, and there were no significant changes over time. Nevertheless, though the optical density of the fibrin clot (D) was within the reference values, it showed a steady increase from the admission by the end of the 1
week of the disease (
=0.007) and by 13-15
days (
=0.009). Correlation and multivariate linear regression, including baseline stroke symptom severity, showed significant associations (
<0.01 in all tests) between the higher optical density of the fibrin clot (D) on days 6-8 and 13-15 and lower MoCA score, confirming the negative effect of altered hemostatic parameters on cognitive function in IS patients.
The increase of optical density of the fibrin clot (D) by 6-8
and 13-15
days is a potential prognostic biomarker for the early development of PSCI.
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