The good wear-resistance of state-of-the-art liquid lubricants is due to the formation of complex metal and organometallic films onto the friction surface, reducing the friction and wear. For this ...purpose, various additives of metal nanopowders are used, especially ones based on copper. The formation and growth of Cu nanoparticles, as well as the tribotechnical characteristics of lubricants, are mainly affected by the choice of stabilizer, because nanoparticles cannot resist the external conditions without protecting their surface. According to quantum chemical studies, the best stabilizer in the series of gelatin, ammonia, sodium borohydride, and sodium citrate is gelatin due to the very large amount of functional groups in its structure. The characterization of physicochemical properties via dynamic light scattering, atomic force microscopy, and electron microscopy, as well as the tribotechnical characteristics of liquid lubricants with stabilized Cu nanoparticles, are consistent with quantum chemical calculations, confirming that Cu nanoparticles stabilized in gelatin possess the better tribotechnical properties than other stabilizers.
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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
Close connection between autoimmune inflammation and proatherogenic lipid changes in rheumatoid arthritis has been well established, while for juvenile idiopathic arthritis (JIA) is under discussion. ...The aim of our work was to study the incidence and intensity of lipid disturbances in patients with different forms of JIA.90 children with JIA 6-18 years were examined using clinical, biochemical methods, ultrasonic duplex scanning of vessels, thin-layer chromatography, bioimpedance measurement. 49 children without chronic diseases made up the control group.Dyslipidaemia, was revealed in 48.9% of patients, mainly with systemic and polyarthritis Most often an increase in atherogenic coefficient (AC) was noted. Average AC value in JIA patients was higher than in control group (2.9 + 0.2 versus 2.0 + 0.1, p <0.05) and correlated with the disease activity index according to JADAS71 (r = 0.78), a doctor`s global assessment of the disease severity according to VAS (r = 0.61), the degree of joints dysfunction (r = 0.55), C-reactive protein (r = 0.53) and ESR (r = 0.68) level. An increase in the concentration of total cholesterol was observed in 28 (31.1%) children with JIA, commonly with a long-lasting disease, and in case of CS intake. In some JIA patients atherogenic changes were detected due to apolipoprotein A1 (ApoA1) deficiency (26.7%). Patients with JIA (maximum with polyarthritis) showed a decrease in the content of the main fractions of polar phospholipids and an increase in the phospholipid lysoforms and free fatty acids by 8.9% 21.4% and 9% compared with the control group. This leads to an increase erythrocytes membranes microviscosity. Dyslipidaemia was combined with body composition changes. In this patients IMCT was higher than in control group (0.73 + 0.03 versus 0.45 + 0.02, p <0.05).In high disease activity both systemic onset and polyarticular JIA proatherogenic lipid disturbances and vascular disorders took place.
Novel mechanism of antioxidant activity of buckminsterfullerene C60 based on protons absorbing and mild uncoupling of mitochondrial respiration and phosphorylation was postulated. In the present ...study we confirm this hypothesis using computer modeling based on Density Functional Theory. Fullerene's geroprotective activity is sufficiently higher than those of the most powerful reactive oxygen species scavengers. We propose here that C60 has an ability to acquire positive charge by absorbing inside several protons and this complex could penetrate into mitochondria. Such a process allows for mild uncoupling of respiration and phosphorylation. This, in turn, leads to the decrease in ROS production.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
In this paper, we calculate the geometry and band structure of iron sulfide (mackinawite) nanosheets. This material is one of the representatives of a new class of two-dimensional nanocatalysts for ...the hydrogen evolution reaction. Calculations show the absence of a band gap for model structures of crystalline and nanoscale mackinawite. In the model of oxidized nanoscale mackinawite, half of the sulfur atoms are replaced by oxygen atoms, and the band gap is 0.37 eV. The band-gap broadening can explain the appearance of catalytic activity in oxidized nanoscale mackinawite. The X-ray absorption spectra show a high sensitivity of the method to changes in the local atomic environment, especially in the first coordination sphere of iron atoms. The calculated model spectra allow determination of the features of the local atomic and electronic structure of the nanoscale mackinawite surface during the hydrogen evolution reaction.
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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
55.
Ti site occupancy in zircon Tailby, N.D.; Walker, A.M.; Berry, A.J. ...
Geochimica et cosmochimica acta,
02/2011, Volume:
75, Issue:
3
Journal Article
Peer reviewed
Ti site occupancy in zircon (ZrSiO
4) is fundamental to thermobarometry because substitution mechanisms control Ti content–temperature relations. Here we describe the results of three independent ...methods used to demonstrate that Ti substitutes for Si and not Zr in zircon. Zircon grains were synthesized from oxide powders held in a Na
2WO
4 flux at 1
bar and 1300
°C. Zircon grains equilibrated with rutile
+
cristobalite show Ti contents (1201
ppm) nearly half that of zircon grains equilibrated with srilankite ((Ti,Zr)O
2)
+
tetragonal zirconia (2640
ppm). The lower Ti content of zircon grains produced at silica-saturated conditions indicates that Ti substitution predominately occurs on the Si site. Moreover, the higher Ti contents of silica-saturated experiments at 1
bar (1201
ppm), relative to those at 1
GPa (457
ppm,
Ferry and Watson, 2007), indicates a substantial pressure effect on Ti solubility in zircon. Measured Ti K-α edge X-ray Absorption Near Edge Structure (XANES) spectra of synthetic zircon grains show energies and normalized intensities akin to those seen among tetrahedrally coordinated Ti-bearing standard minerals, strongly suggesting that Ti occupies the Si site. Density functional theory (DFT) calculations confirm that Ti substitution is most likely to occur on the Si site and predict a Ti–O bond length of 1.797
Å (compared to an average of 2.160
Å for substitution on the Zr site), in excellent agreement with X-ray Absorption Fine Structure (EXAFS) spectra of experimentally grown zircon grains which indicate a value of 1.76(1)
Å. The software FEFF 8.4 was used to simulate XANES spectra from the defect structures determined by DFT for Ti substituting on both the Si and Zr sites. The predicted spectrum for Ti on the Si site reproduces all the key features of the experimental zircon spectra, whereas Ti on the Zr site is markedly different. All applied methods confirm that Ti substitutes for Si in zircon. Consequently, the Ti content of zircon at a given pressure is not only a function of temperature, but will increase with decreasing silica activity. Because elements that activate or quench cathodoluminescence (CL) in zircon are incorporated into the Zr site, a decoupling of CL from Ti contents – incorporated on the Si site in zircon is expected. This hypothesis has been verified by a systematic CL-trace element study of natural and experimental zircon.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The close match of stiffness between implant material and bone is critically important to avoid stress-shielding effect and ensure a fast healing of injured tissues. Here, we introduce liquid metal ...dealloying method for synthesis of robust open porous biomaterials possessing low Young's modulus. The remarkable advantage of the liquid metal dealloying method is a large flexibility in selecting chemical composition of a desired porous biomaterial together with unique tunable microstructure. To demonstrate the versatility of the method, a number of open porous TixZr100-x alloys with different chemical compositions and microstructural characteristics was developed by dealloying precursor (TixZr100-x)yCu100-y alloys in liquid magnesium. The effects of the processing conditions and the precursors' chemical composition on the microstructure of the porous TixZr100-x as well as their mechanical behavior were discussed in detail. In particular, the porous TixZr100-x distinguish themselves due to a low and tunable stiffness ranging from 3.2 to 15.1 GPa and a rather high strength reaching up to 480 MPa. This unique combination of mechanical properties of the new open porous TixZr100-x alloys becomes even more interesting in view of preliminary biological tests highlighting their excellent cytocompatibility. Overall, the liquid metal dealloying provides an opportunity for designing a new biomaterials platform with flexible tunable functionality.
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•Design and synthesis of open porous biomaterials by liquid metal dealloying•Chemical composition and microstructure of dealloying-based biomaterials are flexibly tunable.•Open porous TixZr100-x alloys with various compositions and microstructures were fabricated.•TixZr100-x exhibit low stiffness (3.2–15.1 GPa) and high strength (up to 480 MPa).•Liquid metal dealloying is a powerful tool for designing porous biomaterials.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We study spectral properties of fluorescent radiation from a two-level quantum system with broken inversion spatial symmetry, which can be implemented as a model of a one-electron two-level atom ...whose electric dipole moment operator has permanent unequal diagonal matrix elements. We consider the case of the excitation of this system by a bichromatic laser field consisting of a high-frequency resonance component with the frequency coinciding with the atomic transition frequency and a low-frequency component whose frequency coincides with the Rabi frequency of the high-frequency component. We show that by changing the intensity of the low-frequency component, we can efficiently control spectral properties of the fluorescent radiation of the system in the high-frequency range. We discuss possible methods for the experimental detection and practical use of the effects under study.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
—
The geometric and band structures of cobalt-metahydroxide nanosheets, which are related to a new class of two-dimensional nanocatalysts for the hydrogen-release reaction, are calculated. As a ...result of improving the procedure, the optimal exchange-correlation functionals, basis sets, and dimensions of the “frozen” core are chosen to calculate the atomic and electronic structures, the density of states, and the width of the forbidden band. The calculated results show a decrease in the forbidden band of the cobalt-metahydroxide nanosheets compared with the crystal phase. The X-ray absorption spectra show a high sensitivity of the method to changes in the local atomic environment, especially in the first coordination sphere of cobalt atoms. The calculated model structure makes it possible to determine the features of the local atomic and electronic structures on a cobalt-metahydrixide nanosheet surface during the hydrogen-release reaction.
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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
Experimental X-ray absorption spectra near the Fe
K
edge for as-synthesized MIL-88а metal–organic framework (MIL stands for Materials Institute Lavoisier) before and after activation have been ...obtained and analyzed for the first time. The theoretical analysis of experimental spectra has revealed changes in the local atomic structure of iron at the desorption of water from pores of the studied material in the process of activation.
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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
Here we present an original CMOS compatible fabrication method of a single-electron transistor structure with extremely small islands, formed by solitary phosphorus dopants in the silicon nanobridge. ...Its key feature is the controllable size reduction of the nanobridge in sequential cycles of low energy isotropic reactive ion etching that results in a decreased number of active charge centers (dopants) in the nanobridge from hundreds to a single one. Electron transport through the individual phosphorous dopants in the silicon lattice was studied. The final transistor structure demonstrates a Coulomb blockade voltage of ∼30 mV and nanobridge size estimated as 15 × 20 × 20 nm 3 . Analysis of current stability diagrams shows that electron transport in samples after the final etching stage had a single-electron nature and was carried through three phosphorus atoms. The fabrication method of the demonstrated structure allows it to be modified further by various impurities in additional etching and implantation cycles.
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