The high-pressure properties of a new multiferroic of the langasite family Ba
3
TaFe
3
Si
2
O
14
were investigated in diamond-anvil cells (DAC) in the temperature range of 4.2–295 K by a new method ...of synchrotron Mössbauer spectroscopy. Strong enhancement of the Néel temperature
T
N
was observed at pressures above 20 GPa associated with the structural transformation. The highest value of
T
N
is about 130 K which is almost five times larger than the value at ambient pressure (about 27 K). It was suggested that the high value of
T
N
appears due to redistribution of Fe ions over 3
f
and 2
d
tetrahedral sites of the langasite structure. In this case, the short Fe-O distances and favorable Fe-O-Fe bond angles create conditions for strong superexchange interactions between iron ions, and effective two-dimensional (2D) magnetic ordering appears in the (
ab
) plane. The separation of the sample into two magnetic phases with different
T
N
values of about 50 and 130 K was revealed, which can be explained by the strong 2D magnetic ordering in the
ab
plane and 3D ordering involving inter-plane interaction.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Structural features of CB
x
films obtained by pulsed laser ablation of targets made of pressed diamond powder with boron-powder additions at B/C atomic ratio of
x
= 0.33 have been studied. The films ...were deposited on heated substrates, so that diffusion processes involving C and B atoms on the surface and in the volume of films were possible. Selected conditions of film deposition ensured their effective doping with boron (0.4 ≤
x
≤ 0.6). The incorporation of B atoms was accompanied by the formation of B–C chemical bonds, whereas the formation of
sp
2
graphite bonds and their ordering in clusters with laminar packing was suppressed. The films possessed very low resistivity (~1.4 mΩ cm) at room temperature and exhibited metallic type of conductance on decreasing the temperature to 77 K.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Experimental syntheses of two iron polyhydrides FeHx(I) and FeHx(II) have been carried out in diamond anvil cells by laser heating of metallic iron to temperatures of about 700 and 2000 K at ...pressures of 178 and 195 GPa, respectively. The initial sample is an iron plate enriched in the Fe-57 Mössbauer isotope placed in ammonia borane (BH3NH3). The electronic properties of FeHx compounds have been studied by measuring the electrical resistance R(T) at high pressures (180–216 GPa) in the temperature range of ~8–300 K. Based on the obtained R(T) data, two superconducting phases of FeHx compounds with the maximum critical transition temperatures Tc ≈ 25.0 and 27.7 K have been identified. It has been found that with increasing pressure, the temperature Tc in both hydrides increases linearly with the coefficients dTc/dP ~ 0.063 ± 0.001 K/GPa and 0.056 ± 0.003 K/GPa for the FeHx(I) and FeHx(II) phases, respectively. Superconductivity in iron hydrides revealed by the measured resistance R(T) has been confirmed by a number of additional methods.
Pulsed laser ablation of a MoS2 target causes enhanced splashing of the material. So, for MoSx films obtained by pulsed laser deposition (PLD) in the conventional normal incidence (NI) configuration, ...their typical morphology is characterized by an underlying granular structure with an overlayer of widely dis- persed spherical Mo and MoSx particles possessing micro-, sub-micro- and nanometer sizes. We investi- gated the possibility of using high surface roughness, which occurs due to particle deposition, as a support with a large exposed surface area for thin MoSx catalytic layers for the hydrogen evolution reac- tion (HER). For comparison, the HER performance ofMoSx layers formed by grazing incidence (GI) PLD was studied. During Gl-PLD, a substrate was placed along the direction of laser plume transport and few large particles loaded the substrate. The local structure and composition of thin MoSx layers formed by the deposition of the vapor component of the laser plume were varied by changing the pressure of the buffer gas (argon, Ar). In the case of Nl-PLD, an increase in Ar pressure caused the formation of quasi- amorphous MoSx (x ≥ = 2) films that possessed highly active catalytic sites on the edges of the layered MoS2 nanophase. At the same time, a decrease in the deposition rate of the MoSx film appeared due to the scattering of the vapor flux by Ar molecules during flux transport from the target to the substrate. This effect prevented uniform deposition of the MoSx catalytic film on the surface of most particles, whose deposition rate was independent of Ar pressure. The scattered vapor flux containing Mo and S atoms was a dominant source for MoSx film growth during GI-PLD. The thickness and composition distribution of the MoSx film on the substrate depended on both the pressure of the buffer gas and the distance from the target. For 1.0-2.5 cm from the target, the deposition rate was quite sufficient to form S-enriched quasi-amorphous MoSx (2.5 <x <6) catalytic films that consisted of densely packed 30-50 nm nanoparticles. The Gl-PLD films possessed a greater density of catalytically active sites with a distinct local atomic configuration including edge sites of the layered MoS2 nanophase and diverse S ligands in the amorphous phase, which contained Mo3-S clusters. At a modest loading of ~300 μg/cm2 on glassy carbon substrates and an overpotential of -140 my, these films activated H2 production with geometric current densities up to -10 mA/cm2.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
У статті проаналізовано досвід багаторічного використання металоостеосинтезу ребер за допомогою спиць та пластин для хірургічної стабілізації каркасу грудної клітки при травмі. Встановлено, що ...використання методу має ознаки комплексного підходу; основний термін застосування – відстрочений (89,1% випадків); використання даного методу дає змогу досягти добрих безпосередніх результатів у 91,9% випадків; частка післяопераційних ускладнень становить 6,8%. Стабілізація переломів ребер є абсолютно необхідною процедурою під час надання допомоги постраждалим з переломами ребер і груднини. Вибір методу хірургічної стабілізації залежить від стану хворого, досвіду клініки та/або хірурга, джерела фінансування.
An imaging-spectrometry method for measuring the spatial distributions of the temperature of microscopic objects with nonuniform spectral-emissivity distributions over their surfaces is described. An ...acousto-optic imaging spectrometer that allows measurements of the temperature distributions in the range of 500–5000 K with an error of ~1% and a spatial resolution of 500 × 500 elements over the surfaces of objects with dimensions of at most 5 mm was developed and manufactured. The efficiency of the instrument was demonstrated experimentally in measurements of the spatial distribution of the temperature of a laserheated tungsten plate.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
Thin-film precursors of BC
x
were formed by pulsed laser codeposition of boron and carbon. Targets made of pressed boron and carbon powders with an equal element content (B/C = 1/1) and an ...increased carbon content (B/C = 1/3) were used. The films were deposited on sapphire substrates at elevated temperature (700°C) which determined the initial properties of the precursor BC
x
films. Irradiation of the films was carried out by laser pulses of nanosecond duration with varying intensity. The films obtained by laser annealing of BC
x
(Q-BC
x
) were studied by scanning electron microscopy and micro-Raman spectroscopy. Irradiation under optimal conditions made allowed to realize pulsed melting of the films and partial preservation of their continuity on the substrate. The local structure of Q-BC
x
films and the nature of the changes in their electrophysical properties depended on the composition of the precursor films and the laser irradiation regimes.
By the method of interference correlations, it was directly proven for the first time that the pion-production volume in neutron-proton (
np
) interactions at primary momenta in the range 3.8–5.2 ...GeV/
c
is not constant. It was shown that the interference patterns for
np
and MgMg interactions are identical. It was established that the rate of expansion of the pion-production volume does not depend on the type of interacting particles (from
np
and
e
+
e
−
to PbPb collisions) or on their primary energy (from 3.4 to 200 GeV). It was found that the determination of dimensions is possible only for individual approximately stationary volume elements in their rest frame. A change in the kinematical properties of the subensemble under analysis leads to changes both in the size of the respective element and in its shape.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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