A set of Sm-doped iron oxide magnetic nanoparticles (Fe x O y NPs) of different sizes as an example of ferromagnetic NPs at room temperature was synthesized by microware-assisted methods. Powder ...X-ray diffraction and transmission electron microscopy showed Fe x O y NPs with an inverse spinel structure. Mössbauer and X-ray absorption spectroscopy (XAS) were used to study the local atomic and electronic structure of iron in the NPs. Linear combination of XAS spectra of reference iron oxides failed in reproducing the spectra of Fe x O y NPs Piquer, C. ; J. Phys. Chem. C 2014, 118, 1332−1346 . We attribute this fact to the nonstoichiometric distribution of tetrahedral, Td 3+, and octahedral, Oh 3+ and Oh 2+, sites in NPs compared to bulk references. This distribution was successfully reproduced by linear combination of theoretical XAS spectra obtained for clusters where iron was in Td 3+, Oh 3+, and Oh 2+ defined oxidation and symmetry states. This approach allowed us to obtain the quantitative speciation of the fraction of Td 3+, Oh 3+, and Oh 2+ sites as a function of the different size of the Sm-doped Fe x O y NPs based on the XAS data. In contrast to the standard XAS reference compounds analysis where experimental spectra fits are limited to constant Td 3+/Oh 3+ and Td 3+/Oh 3+/Oh 2+ ratios and to Mössbauer spectroscopy that requires liquid helium temperatures, the proposed method opens a new possibility to quantitatively estimate the amount of each independent inequivalent iron site in terms of symmetry and oxidation state at room temperature.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Valence tautomer transition occurs mainly in 3d metalorganic complexes with redox-active ligands and makes them potential candidates for single-molecular switches. The transition occurs under ...temperature, pressure, or light-induced stimuli and is strongly affected by the intermolecular interactions. However single-crystal x-ray diffraction is not always applicable to such systems when crystal structure is destroyed upon transition or system is studied in the solution. Such an example is bis(o-semiquinonato) cobalt complex with TEMPO-functionalized iminopyridine ancillary ligand. In this work we apply two complementary techniques-ligand-sensitive Fourier transform infrared spectroscopy (FTIR) and metal sensitive Co K-edge x-ray absorption spectroscopy (XAS). In a solid state, a temperature hysteresis of magnetization larger than 40 K was observed upon cyclic cooling-heating. So, the temperature of phase transition upon cooling is about 40 K lower than that upon heating. In solution, the x-ray absorption spectra for high-temperature and low-temperature states were similar to that in the solid form, but the hysteresis was absent. Two methods are can probe valence tautomer transition, but XAS has an advantage for the liquid phase analysis and FTIR has larger sensitivity to the ligand related interactions in solid.
A quantitative measure of magnetic frustration is defined as a thermodynamically averaged relative number of excited pair interactions in the Hamiltonian of a system. The Metropolis algorithm has ...been upgraded to a hybrid multispin Monte Carlo method using a quasi-Markov chain of random events. The combination of canonical and multicanonical sampling of the Gibbs distribution in one computational scheme has made it possible to determine the temperature dependences of the increment in the number of excitations and the entropy increment of the hexagonal lattice of artificial spin ice and to calculate the configuration of the ground state. The temperature behavior of the frustration parameter of a geometrically frustrated hexagonal lattice of point dipoles is obtained numerically using the developed method. This method for calculating the quantitative measure of frustrations can be used to process experimental data.
Full text
Available for:
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
•Database of direct current magnetron sputtered TiN coatings was compiled.•Machine learning algorithms were trained to predict coating hardness.•Data filtering and imputing improved performance of ...machine learning algorithms.•The most important descriptors for predicting coating hardness were determined.•Trained algorithm was applied for the inverse problem of coating deposition.
Modern vacuum ion-plasma technology makes it possible to obtain coatings of various compositions and properties on the surface of metals. Titanium nitride ion-plasma coatings are the most widely used in industry and can significantly improve the mechanical and tribological characteristics of the tribocontacts. The synthesis of coating depends on many parameters and often an optimized set of parameters from a one coater cannot be directly transferred to another. In this work we have compiled a database of reactive direct current magnetron sputtered TiN coatings based on a wide range of reports available in literature. Machine learning algorithms were trained on the database entries from independent authors to establish a relationship between coating hardness and experimental deposition settings. We address the necessary steps for its training: filtration, imputing and feature selection. The algorithm was then applied to the coating inverse design problem and predicted optimal synthesis parameters for given hardness.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Results of the experimental studies of an acoustic tract by the shadow testing method are provided. An inhomogeneous distribution of acoustic rays is revealed within the testing zone. The principle ...of producing a tomogram under small–angle probing is demonstrated. As a result of studying the error in determining the coordinates of flaws in different parts of the testing zone, it has been established that the least error corresponds to the flaw position at the center of the testing zone.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The in vitro effect of cold shock on nucleated erythrocytes of the benthic scorpionfish
Scorpaena porcus
L. was studied. Blood samples were exposed to 22°C (control group) and 4°C (experimental ...group) for 3 h. Cold shock had no significant impact on vital characteristics of scorpionfish erythrocytes. The cells retained the integrity of cytoplasmic membranes, mitochondrial potential, and levels of oxidative processes, as evidenced by constant values of propidium iodide, rhodamine 123, and 2',7'-dichlorodihydrofluorescein diacetate fluorescence intensity. Main changes were concerned with erythrocyte shape and nucleus functional activity. While the red blood cells became more rounded, the nucleus size increased, leading to a higher nuclear–cytoplasmic ratio and a decrease in the fluorescence intensity of cells labeled with a nuclear dye SYBR Green I. Supposedly, this was due to cytoskeletal alterations and activation of transcriptional processes.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We present mathematical modeling of the process of determining the time coordinate of the moment of arrival of a pulse echo in the dual-frequency probing technique, as well as graphs of the involved ...measurement error versus the comparator’s discrimination threshold for different ratios of frequencies and distances and ratio of the frequencies of emitted pulses. Mathematical modeling has revealed limiting cases in which the measurement error increases and can reach 3–4%. Analysis of results has made it possible to identify additional requirements for the mathematical processing of received signals to keep the error within 1%.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This paper proposes adaptive microwave technologies for assessing the state of water systems. The expected results will allow the rapid assessment of temperature, salinity, disturbance of the water ...surface, the concentration of inorganic and organic substances, etc., by providing predictions of the distribution of anomalies of these parameters. To achieve this goal, experimental measurements from the monitoring of the aquatic environment in real time and the relevant analyses will be presented. The accuracy of the method used will be calculated from measurements at Kara-Bogaz-Gol Bay located in western Turkmenistan and elsewhere.
Full text
Available for:
CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The effect of moderate hypoxia on the processes of energy metabolism was studied in the tissues (gills, hepatopancreas) of the Mediterranean mussel
Mytilus galloprovincialis
(Lamarck, 1819). The ...mollusks was kept at 6.8–6.9 mg O
2
L
–1
(control group) or 1.9–2.0 mg O
2
L
–1
(experimental group). In both cases, water temperature was 22 ± 1°C, salinity 17–18‰, exposure time 72 h. Dissolved oxygen content in water was lowered by nitrogen bubbling for 4–5 h. Under moderately hypoxic conditions, a complex of biochemical reactions aimed at retaining the baseline energy status developed in the mussel tissues. While aerobic processes were clearly on the decline, as evidenced by a decrease in succinate dehydrogenase (SDH) activity, anaerobic glycolysis intensified. Aldolase and malate dehydrogenase (MDH) activities, as well as tissue pyruvate level, increased. Both lactate dehydrogenase (LDH) activity and lactate levels in mussel tissues remained unchanged. The state of the
M. galloprovincialis
adenylate system was comprehensively characterized. The tissue content of the ATP fraction remained at the level of control values, reflecting an adaptive trend in the reorganization of tissue metabolism. The ability of the hepatopancreas to accumulate ADP and AMP fractions from the circulatory systems under conditions of experimental hypoxic load was noted for the first time. Presumably, this may largely explain the increase in the pool of adenylates and the decrease in the adenylate energy charge in this organ. It was concluded that the reorganization of carbohydrate metabolism in
M. galloprovincialis
under moderately hypoxic conditions allows the mussel to retain the energy status of its tissues and, therefore, to populate challenging (hypoxic) waters.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
PDF
