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The paper presents the results of a study of the rheological properties of agar-agar solutions prepared using water exposed to an electromagnetic field with a frequency of 30 to 170 MHz. The ...studies were carried out at three temperatures: 25, 35, and 45°С, the concentration varied from 0.1 to 0.7%, and the shear rate varied in the range of 100–1000 s
–1
. As a result of the study, a distinct influence of the electromagnetic field was found, and the quantitative response depends on the shear rate, solution concentration, temperature and frequency of the electromagnetic field. In the vast majority of cases, a decrease in the viscosity of solutions is observed as a result of exposure to an electromagnetic field. There is almost no quantitative correlation of viscosity changes with frequency. There is a complex picture of the mutual influence of the solution concentration, the frequency of the electromagnetic field, temperature and shear rate when measuring viscosity. The temperature dependence of viscosity for solutions to be subjected and not exposed to an electromagnetic field is multidirectional in nature and substantially depends on both the concentration of the solution, the frequency of the electromagnetic field, and the shear rate at which measurements were taken. An explanation of the observed dependences is proposed, which is based on the two-component agar-agar solutions, which leads to individualization of the changes in the rheological properties determined by agarose and agaropectin, respectively.
Determination of respiratory rate is a necessary task in assessing the state of health in humans. This review provides a description of modern devices used for recording and monitoring respiratory ...rate. The advantages and disadvantages of the principles of operation of these devices are discussed.
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•Reaction of F2 with TFE in hexafluoropropene (HFP) dimer and trimer matrices leads to C2F6 without explosions.•(HFP)2 and (HFP)3 moderate the chain branching fluorination of TFE by ...trapping F atoms in long-lived radicals.•High level composite correlated molecular orbital theory G3(MP2) calculations used to develop mechanism.•Equilibrium products of TFE direct fluorination e determined by gas phase Gibbs free energy minimization.•Approximate local temperature where reactions occur predicted.
Mechanisms for the processes of direct fluorination of tetrafluoroethylene (TFE) in matrices of TFE, hexafluoropropylene (HFP), and dimers and trimers of HFP ((HFP)2 and (HFP)3) from 77 K to 300 K have been developed. Electronic structure calculations at the composite correlated G3(MP2) and G4 molecular orbital theory levels of the energetics of a range of reactions involving TFE and fluorine are presented to aid in the development of these mechanisms. The equilibrium products of the direct fluorination of TFE in the gas phase at varied temperature and initial composition was determined by Gibbs free energy minimization. Spontaneous reactions (explosions) were observed for the fluorination of pure crystalline TFE and HFP. Fluorination of TFE can be performed without explosion in glassy matrixes of (HFP)2 or (HFP)3 at low temperatures. The explosive nature of the reaction decreases in the matrix order TFE > (HFP)2 > (HFP)3. The fluorination of TFE begins at the phase transition temperature of the matrix, i.e., after the transition of devitrified (HFP)2 and (HPF)3 into the supercooled liquid state at 110 K and 150 K, respectively. The experiments show that either the presence of a branched structure (C9F20, the saturated analog of (HFP)3) or the presence of unsaturated bonds (perfluorotoluene) separately cannot provide a medium for the safe fluorination of TFE as the direct fluorination of TFE in these matrices led to an explosion. HFP oligomers provide an effective environment for TFE fluorination because of the presence of double bonds surrounded by the branched perfluorinated groups. The unsaturated bonds of the HFP oligomers are an active participant in the chemical processes involved in the safe, direct fluorination of TFE.
The effect of a high-frequency discharge on the change in the topography of the surface of KU-1 optical quartz and transmission of visible light (400–1000 nm) is studied. The working gases of the ...discharge are D
2
and a D
2
/N
2
mixture, in which the fraction of N
2
is 25 mol %. The addition of nitrogen increases the rate of sputtering from 60 to 300 nm/h without changing the stoichiometry of the surface layers. After the exposure in plasma, the root-mean-square roughness of the surface decreases from 1.3 to 0.6 nm. The transparence of quartz remains unchanged. The analysis of the roughness and calculation of the diffuse light scattering with a wavelength of 400 nm after passing through quartz are executed using the power spectral density functions.
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•The heat capacity of crystalline monophosphate CsNiPO4 was performed between (6 and 650) K.•Phase transition was found at 382.8 K.•Crystal structure of CsNiPO4 was refined by ...Rietveld method at 298 K.•Thermal expansion of CsNiPO4 was investigated.•Thermodynamic functions were calculated over the range of T = (0 and 650) K.
The heat capacity function Cp,mo=fT of crystalline CsNiPO4 was measured between 6 K and 650 K. A heat capacity anomaly was found around 382.8 K due to a phase transition. The experimental data obtained were used to calculate the standard thermodynamic functions Cp,mo/R, Δ0THmo/RT, Δ0TSmo/R and Φmo/R in the range from T = (5 to 650) K, and the standard entropy of formation at 298.15 K. The fractal dimension of CsNiPO4 was calculated from experimental data on the low-temperature (6 ≤ T ≤ 50) K heat capacity and the topology of the phosphate structure was estimated. The crystal structure of caesium-nickel monophosphate was investigated. Thermal expansion parameters were determined with high-temperature X-ray diffraction measurements in the temperature range from T = (473 to 1073) K.
In recent decades, active research has been under way to find alternative sources of renewable raw materials for the production of valuable components. Microalgae, characterized by flexible ...metabolism, have great potential for organization of production of useful substances for various applications: pharmaceuticals, production of food additives, feed additives for animals and fish, materials, biofertilizers, and biofuels. Despite the large number of scientific publications dealing with separate stages of processes for the production of useful substances from microalgae, a systematic analysis of trends in the development of this sector of bioeconomics remains an important problem. The review presents an analysis of key stages in the production of useful substances from microalgae and the peculiarities of their implementation. Some problems concerning the improvement of performance of such productions using computer modeling tools were discussed.
Eight male volunteers aged 26 to 44 years were examined, who were in the “Arfa” hypomagnetic environment simulation facility for 4 h at a normal magnetic field level (background session), and twice ...within 24 h: one session during hypomagnetic environment simulation with an attenuation coefficient of 500, and one, in the conditions of the terrestrial magnetic field (placebo). Venous blood was collected at the end of each session. The values of 48 biochemical parameters reflecting the state of organs and tissues, as well as the main links of metabolism, were determined in plasma and serum. Psychological testing of the volunteers was carried out using the Assessment of Acute Physical Fatigue questionnaire by R. Kinsman and P. Weiser adapted by A.B. Leonova and Assessment of Acute Mental Fatigue by A.B. Leonova and N.N. Savicheva. The level of physical condition of the participants of the experiment was assessed according to the method of D.N. Davidenko. As a result of the first biochemical screening examination and psychological testing of volunteers who were in a simulated space-level hypomagnetic environment, it was established that the effect is stressful, accompanied by the activation of glycolysis, lipolytic processes, affects the acid–base balance of the body, the state of the vascular endothelium, and leads to changes in the hepato-biliary system. At the same time, the index of physical fatigue among the volunteers increases, and the level of physical condition significantly decreases. Subjectively, pronounced changes in the biochemical parameters of stressful orientation are not felt.
A comparative study of the supramolecular structure, physicochemical properties, and morphology of the powder celluloses (PCs) obtained from the waste paper of newsprint and cardboard, plant ...celluloses, and nonconventional raw materials was conducted using the methods of FT-IR spectroscopy, high-resolution solid-state
13
C NMR spectroscopy, wide-angle X-ray scattering, and scanning electron microscopy (SEM). According to the FT-IR and
13
C NMR spectroscopy results, the functional composition of the PCs is similar to that of the wood PCs and matches highly purified cellulose samples. The crystallographic structure of the powder samples corresponds to the structure of cellulose I. The crystallinity and the transverse dimensions of the crystallites are 39.4 and 40.2%, and 45 Å 110 and 54 Å 110, for the PCs from newsprint paper and cardboard, respectively. These values considerably exceed those for the initial waste paper samples. A comparative analysis of the SEM results showed a significant similarity among the PC fibers of different origin. The results of the study of the physicochemical properties of the PCs isolated from the waste paper allow predicting their competitive application in comparison with plant PCs.
The one-dimensional (1D) coordination polymer (dpp-bian)
−
Eu
2+
(4,4-bipy)
−
-(THF)
2
·4THF
n
(1)
(dpp-bian is 1,2-bis(2,6-diisopropylphenyl)iminoacenaphthene; 4,4′-bipy is 4,4′-bipyridine) was ...synthesized by the oxidation of the complex (dpp-bian)
2−
-Eu
2+
(THF)
4
with neutral 4,4′-bipy in tetrahydrofuran (THF). According to the single-crystal X-ray diffraction analysis, the coordination polymer chain in
1
consists of alternating europium(II) ions and 4,4′-bipyridine radical anions. Acenaphthene-1,2-diimine dpp-bian acts as a terminal chelating radical-anion ligand. The europium(II) atom is coordinated by four nitrogen atoms and two oxygen atoms of THF molecules. According to the thermogravimetric analysis, the thermal decomposition of
1
occurs in four steps. An increase in the magnetic moment of compound
1
in the range from 40 to 5 K is due to the ferromagnetic exchange interaction between the spins of dpp-bian (S = 1/2) and 4,4′-bipy radical anions (S = 1/2) and the spin of the Eu
2+
ion (S = 7/2).
The effect of biopreparations produced by carboxymethylation of plant raw materials on the growth and development of spring wheat has been studied. A presowing treatment of seeds with aqueous ...solutions of the tested preparations (150 g per 10 L per 1 ton of seeds) has provided some positive effect on the plant growth processes. Activation of the growth and development of wheat has been observed at the early developmental phases, from the germination phase (radicle appearance) to intense tillering phase. The studied preparations provide an increase in the yield of wheat by 30–43% (small-plot experiment), 15% (field experiment), and 21–32% (large-scale experiment). The yield increase in wheat caused by the use of growth regulators is not always accompanied by an increase in the protein and gluten content in grain. A decrease in the protein content in grain, which can be observed, for example, in the case of a nonfallow forecrop and a limited soil nitrogen, can be determined as a “growth dilution effect” caused by an increase in the yield volume per unit of area as well as by a productive tillering, which is of critical importance for the uniform grain ripening and grain quality.
