Atomic structure of silver nanoparticles in soda-lime glass at T=10K before and after annealing was studied by Ag K-edge EXAFS. To overcome ambiguities in the structure determination by the ...Fourier-transform analysis of these spectra, caused by the presence of various species of the absorbing silver atoms in the sample, the refinements of the fitting technique of the Fourier transforms F(R) have been implemented. The F(R) of Ag K-edge EXAFS in as prepared and annealed glasses were analyzed in the extended range of interatomic distances (R) up to ~6.5Ǻ using Ag K-edge EXAFS in Ag-foil at the same temperature as the reference. The proposed technique of the fit enabled to go beyond the averaged description of silver nanoparticles structure in glass and to reveal the atomic structure of the core region of nanoparticles, the structural characteristics of their near-surface region, parameters of AgO bonds inside the glass matrix and the percentage of Ag atoms in each of these species before and after the annealing process. The mean size of silver nanoparticles in as prepared and annealed glasses was estimated and the mechanism of nanoparticles growth after the thermal treatment was suggested.
•Structural changes in Ag particles in glass due to annealing are studied by Ag EXAFS.•Refinements of the fitting technique of Fourier transforms of Ag EXAFS were suggested.•Proposed technique enabled to go beyond averaged description of particle structure•Structure of core, near-surface region of Ag particles, and AgO parameters were revealed.•Mechanism of Ag nanoparticles growth after the thermal treatment was suggested.
Bimetallic platinum-copper nanoparticles on carbon support are studied as a perspective electrochemical catalyst by anomalous small-angle X-ray scattering near the Pt absorption L3-edge. The ...simultaneous fitting of several diffraction patterns measured at different photon energies lead to a satisfactory agreement between experimental and model curves in the assumption of core-shell structure of the particles with Pt-rich shell and Cu-rich core. It is shown that the average size of as prepared nanoparticles is about 6 nm with distribution spread of about ±2 nm and with thickness of Pt-rich shell approximately 1.6 nm. After annealing at 350o C the average size of the particles increased by two times with additional enlargement of the Pt-rich shell thickness.
Abstract
This work presents the results of the investigation of the physiological state of the roach
Rutilus rutilus heckelii
breeders from the Sea of Azov stock during the spawning period. It has ...been established that, in the spring season of 2020 and 2021, the content of proteins and lipids in fish tissues, as well as hematological parameters in all investigated roach specimens from different water bodies were consistent with the average long-term values. The content of proteins in the muscles and liver of roach does not differ by sex. A higher protein content in the gonads of females is characteristic of the pre-spawning period due to the process of gonad maturation. The high content of lipids in the gonads of males apparently results from the lower energy consumption for maturation of the gonads and spawning. The average concentration of sodium and potassium ions decreased in comparison with the values obtained in 2020, while the concentration of chloride anions increased. It has been concluded that the physiological state of all investigated roach specimens was normal.
Using the model of hexagonal clusters we express the surface, curvature and Gauss curvature coefficients of the nuclear binding energy in terms of its bulk coefficient. Using the derived values of ...these coefficients and a single fitting parameter we are able to reasonably well describe the experimental binding energies of symmetric nuclei with more than 100 nucleons. To improve the description of lighter nuclei we introduce the same correction for all the coefficients. In this way we determine the apparent values of the surface, curvature and Gauss curvature coefficients which may be used for infinite nuclear matter equation of state. This simple model allows us to fix the temperature dependence of all these coefficients, if the temperature dependence for the bulk term is known. The found estimates for critical temperature are well consistent both with experimental and with theoretical findings.
The basic principles of operation of the sensors based on molecular-electronic transducers (METs) are described. The review of investigations of physical processes into MET and their operating ...characteristics are considered. Modern MET manufacturing technologies and the production methods and the new applications of planar microelectronic METs are discussed. An overview of devices and systems based on the METs is given.
Products of the catalytic hydrochlorination of deuterated acetylene over palladium chloride complexes supported on activated carbon are a mixture of vinyl chloride stereoisomers resulting from the
...syn
- and
anti
-addition of a hydrogen chloride molecule to the triple bond. The reaction is accompanied by the isomerization of the primary
trans
-vinyl chloride into its
cis
-stereoisomer; however, the characteristic isomerization times exceed significantly the duration of acetylene hydrochlorination. This fact allowed us to estimate the portion of products formed exclusively during the catalytic reaction, the difference in the effective activation energies of the
syn
- and
anti
-addition routes (~21 kJ/mol), and to demonstrate a monotonic increase in the part of the
syn
-addition product with increasing mass loading ω of the active metal, reaching saturation at ω > 2 wt %.
The 23Na Knight shift of NMR line which is highly correlated with the electron spin susceptibility and density of states at the Fermi level was studied for the sodium loaded opal. The measurements ...were carried out within a temperature range from 100 to 400 K for solid and melted confined sodium nanoparticles. The NMR line below 305 K was a singlet with the Knight shift reduced compared to that in bulk. Above this temperature the NMR line split reproducibly into two components with opposite trends in the Knight shift temperature dependences which evidenced a nanoconfinement-induced transformation and heterogeneity in the electron system. The findings were suggested to be related to changes in the topology of the Fermi surface.
This work is devoted to the problems of elaboration of the instrumental basis for low-frequency sensing of ambient noise of the ocean. The experimental data of testing of the technical parameters of ...a molecular-electronic hydrophone are given. The amplitude-frequency and noise parameters of prototypes have been studied. The operation of a hydrophone with a frequency range of 0.02–200 Hz and sensitivity of 0.75 mV/Pa is described. Ambient noise was measured with the use of correlation analysis.
The axial distribution of the ion mass-to-charge state in planar magnetron plasma has been studied. Copper is used as a target material, and argon was used as an operating gas. To study the ion ...mass-to-charge state, an upgraded quadrupole mass spectrometer was used. Measurements were carried out along the discharge system axis at a distance of 15 to 45 cm from the magnetron target. The operating pressure in a continuous mode was changed in the range from 1.2·10
–3
to 3·10
–3
Torr at discharge currents from 100 to 500 ma. It has been shown that at a distance of 15 cm from the magnetron, argon ions predominate in a fractional ratio. At the maximum distance, a significant copper ion fraction is observed. The fraction of argon ions decreases with increase in the discharge current and the operating pressure.
A technique for calculating the backscattering of ultrashort pulses of plane waves by an ideally conducting cylinder is described on the basis of the spectral representation. The Rayleigh solution in ...the Bessel function series representation is used to determine the scattering spectral components. The Gabor impulse reflection is investigated. A method for remote determination of the cylinder diameter from the shift of scattered field amplitude peaks is described.
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