•Cobalt atoms have magnetic moment 0.5 µB at all values of x.•Alloys with 0 ≤ x ≤ 0.2 are paramagnets at T ≥ 2 K.•Alloys with 0.4 ≤ x ≤ 0.8 are anisotropic cluster ferromagnets.•Alloys with 1 ≤ x ≤ 2 ...are long range ordered ferromagnets.•Calculated magnetization curves satisfactorily agree with experimental ones.
The structure and magnetic properties of PrNi2−xCox alloys are investigated over the entire concentration range 0 ≤ x ≤ 2. It is shown that there is a continuous series of disordered solid solutions with a structure of the MgCu2 type. In all alloys, cobalt atoms have a magnetic moment μCo = 0.5 μB. The ground magnetic state of the alloys depends on the composition. In the range 0 ≤ x ≤ 0.2, alloys are paramagnetic at a temperature T = 2 K, in the alloys with 0.4 ≤ x ≤ 0.8, ferromagnetic order occurs in clusters of cobalt atoms due to the exchange interaction of Co – Co. Their magnetization in small magnetic fields is realized via turnabout, by 180°, of the magnetic moments of individual clusters. In the alloys with 1.0 ≤ x ≤ 2.0, the long-range ferromagnetic order is established. The processes of technical magnetization reversal in them are effected via the motion of domain walls and rotation of the vectors of spontaneous magnetization. In all alloys, magnetic saturation is not achieved at T = 5 K even in a magnetic field of 200 kOe, which is associated with a large splitting of the ground J multiple of Pr3+ ions by the crystal field. Numerical calculations of the magnetization curves are performed. In the approximation of the independence of the parameters of the crystal field on the concentration, a satisfactory agreement between the calculated and experimental curves was obtained.
Abstract
The sections of the coal-bearing strata of the Visean stage of the Kama coal basin in the territory of the Tatarstan republic are considered. It has been established that a coastal-marine ...terrigenous complex represents the coal-bearing strata. The complex is characterized by alternation of layers of coals, claystones, siltstones and sandstones. Coals lie at the base of the section, forming seams up to 10.0 m thick. Coals are allochthonous, formed due to the denudation erosion of peat deposits on land, the transfer of peat by water flows, and their sediment on the coastal part of the sea basin with normal salinity. The Visean caustobioliths can be classified as brown coals with a low degree of metamorphism. Their composition is dominated by the fusen component with scattered inclusions of liptinite and fusinite. In terms of material and petrographic composition, caustobioliths are classified as fusen varieties of gumite coals. In terms of the content of mineral impurities, the coals are low-medium ash, sulphurous.
The spin states of Co atoms in PrBaCo
2
O
5 + δ
with regard to the paramagnetic contribution of Pr
3+
ions have been determined from magnetic property studies for δ = 0.52 and 0.74. Results obtained ...without considering the paramagnetic contribution of Pr
3+
ions are inconsistent with available experimental data. With a decrease in temperature, the metal–insulator transition in PrBaCo
2
O
5.52
becomes sharper according to a sharp change in spin states (from HS/LS to LS/IS) of Co
3+
ions. In this case, Co
3+
ions occupying octahedra pass from the high-spin state (HS,
S
= 2) to the low-spin one (LS,
S
= 0) and those occupying pyramids pass from the LS-state to the intermediate spin state (IS,
S
= 1), as follows from the available structural data. In PrBaCo
2
O
5.74
, the metal–semiconductor transition occurs smoothly from HS/LS to the HS/IS state upon the smooth transition of the Co
3+
ion state from (LS,
S
= 0) to the (IS,
S
= 1) state in pyramides without change in the spin state of ions Co
3+
(HS,
S
= 2) and Co
4+
(LS,
S
= 1/2) in octahedrons.
To conduct a cross-sectional study on the structural and functional characteristics of various parts of skin microcirculation in working-age men with newly diagnosed hypertension (HTN).
The study ...included 118 male participants (ages 30 to 60) who were not regularly taking any medicine, had no medical complaints, and subjectively considered themselves healthy at the time of study. All participants underwent a cross-sectional comprehensive medical examination. The following tests were performed: complete blood count, biochemical blood tests, video capillaroscopy (VCS), laser Doppler flowmetry (LDF) and photoplethysmography (PPG) on the left hand fingers, determination of flow-mediated vasodilation of the brachial artery, echocardiography, ultrasound of extracranial and femoral arteries, 24-h ambulatory blood pressure monitoring (ABPM). According to ABPM data, the participants were divided into two equal groups called a control group(CG) and a hypertension group(HG). There were 59 participants with normal BP in CG, and 59 participants with newly diagnosed HTN in HG.
Nailfold VCS of the ring finger revealed no significant differences between the groups at the level of exchange microvessels. According to LDF data, there was no decrease in tissue perfusion and signs of an increase in the activity of endothelial, neurogenic, and myogenic regulation of the tone of precapillary arterioles in the HTN group. According to PPG of the index finger, in contrast to CG, HTN participants had significantly higher values of the following parameters: normalized augmentation index (Alp75) – 3.8 % and − 5.25 % (p < 0.005), stiffness index (SI) – 7.6 m/s and 7.35 m/s (p < 0.05), reflection index (RI) – 36.5 % and 28.4 % (p < 0.005), respectively.
Working-age men in the early stage of HTN have neither capillary rarefaction nor an increase in the tone of skin precapillary arterioles. The largest contribution to peripheral vascular resistance in the onset of HTN is most likely made by large muscular arterioles, in which the neurogenic regulation of vascular tone predominates.
•No capillary rarefaction and latent fluid retention in the skin interstitial space•No increase in the tone of precapillary arterioles and a decrease in skin perfusion•There is an increase in the tone of small muscular arteries and arterioles.
Abstract
The article discusses the structure of multilayer oil deposits of the Vereyian horizon in the territory of the Tatarstan Republic. It is shown that in the sections the reservoir rocks are ...different facies of limestones (mostly grainstone), sandstones and siltstones. The reservoir rocks were formed in the regressive stage of the development of the marine sedimentation basin. Oil deposits of the Vereyian horizon have experienced flooding processes with formation edgewater. The penetration of groundwater into reservoir rocks led to uneven oxidation of oils in oil-producing structures. With weak waterflooding, dolomite and pyrite were formed in the reservoir rocks, with strong waterflooding, anhydrite aggregates appear.
The synthesis and the structural and magnetic characteristics of ternary nonstoichiometric Fe
65 –
x
Al
35 –
y
M
x
,
y
(M
y
= Ga, B, Sn; M
x
= V, Mn;
x
= 3, 5, 10 at %) compounds are experimentally ...and theoretically studied. Quantum-mechanical calculations of the energy of formation and an electronic structure explain the characteristic features of the phase transformations that occur during the synthesis and describe the experimentally observed changes in the magnetic parameters for various impurity elements.
A transceiver is designed for the digital generation of a multibeam pattern of radiation. The transceiver consists of a transmitter and receiver, integrated into a single printed circuit board. The ...transceiver allows the formation of multiple beams in the far field of the radiation zone. The pattern of the multibeam radiation of a phased antenna array with digital pattern synthesis is measured experimentally.
Abstract
The structure of geological sections of the Visean stage of small oil fields in the Western Zakamya region of the Tatarstan Republic is considered. It has been established that potentially ...oil-bearing deposits are carbonate-terrigenous deposits of the Tulian-Bobrikian horizon and carbonate deposits of the Aleksininian horizon. In the Tulian-Bobrikian sediments, oil deposits are localized in fine-grained quartz sandstones, the cap rocks are dense claystones. Due to the small thickness of the layers of oil-saturated sandstones, their development is not very promising. In the deposits of the Aleksininian horizon, oil deposits are localized in cavernous limestones overlain by dense diagenetic dolomites. The thickness of the oil reservoirs is 2.0-2.5 m, which allows them to be considered as potential targets for development. The presence of sulfate mineralization in the pores of reservoir rocks suggests that the oil deposits of the Aleksininian horizon are at the initial stages of waterflooding..
The chromatographic properties and thermal stability are investigated for the polymeric stationary phase based on the norbornene polymer. It was shown that without additional cross-linking, ...poly(3-(tributoxysilyl)tricyclononene-7) demonstrates properties similar to liquid chromatographic stationary phases. It was also found to be more thermally stable than previously studied trimethylsilyl- and trimethoxysilyl- derivatives. The long-term heating at 170 °C resulted in an increase of mass transfer rate between stationary and mobile phases which could be observed as a decrease of parameter C of Van Deemter equation. This effect is rather unusual, as the polymeric stationary phases tend in decrease of the layer volume and porosity while ageing. Additionally, the values of thermodynamic parameters of sorption are calculated for the polymeric stationary phase: enthalpy of sorption varied −28 to −37 kJ/mol, entropy change was −41 to −51 J/mol K. The compensation curves were plotted for the alkanes, arenes, and alcohols, and the parameters of compensation plot were calculated, demonstrating the different sorption mechanisms both for hydrocarbons and oxygen-containing compounds, and different classes of organic compounds.
Abstract
High ice water content (IWC) regions in mesoscale convective systems (MCSs) are a potential threat to commercial aviation, as they are suspected to cause in-service engine power-loss events ...and air data probe malfunctions. To investigate this, the high-altitude ice crystals (HAIC)/high ice water content (HIWC) projects set up a first field campaign in Darwin (Australia) in 2014. The airborne instrumentation was selected to provide the most accurate measurements of both the bulk total water content (TWC), using a specially developed isokinetic evaporator, and the individual ice crystals properties, using particle imaging probes.
This study focuses on determining the size ranges of ice crystals responsible for the mass in high IWC regions, defined here as cloud regions with IWC greater than 1.5 g m
−3
. It is shown that for high IWC areas in most of the encountered MCSs, median mass diameters (MMDs) of ice crystals range from 250 to 500
μ
m and decrease with increasing TWC and decreasing temperature. At the same time, the mass contribution of the smallest crystals (below 100
μ
m) remains generally low (below 15%).
In contrast, data from two flight missions in a long-lasting quasi-stationary tropical storm reveal that high IWC values can also be associated with MMDs in the range 400–800
μ
m and peak values of up to 2 mm. Ice crystal images suggest a major growth contribution by vapor deposition (columns, capped columns) even for such larger MMD values.
PDF
