Coal-water fuel is a promising substitution of conventional fossil fuels for the countries, where clean energy sources like wind, solar, etc. cannot cover energy demand. However, this fuel has a lot ...of specifics for preparation, transportation, and combustion. Issues with coal-water fuel combustion can be solved with the use of fuel activation. The catalytic activation of the coal-water fuel produced from coal of different metamorphic stages with the help of titanium dioxide nanoparticles was experimentally studied. The research suggests that the addition of the titanium dioxide nanoparticles in 0.5–4% wt. increases the coal-water fuel thermal conductivity by 9–17% while the value of heat capacity decreases by 12–23%. Also, this addition decreases time delay before fuel ignition by 20–22% and a total time of the fuel droplet burning by 15%; increases maximum temperature of the volatiles combustion by 8–10%; and increases combustion completeness as well. For the first time, the optimal value of the nanoparticles additive content has been found.
The Cosmic Microwave Background (CMB) radiation is the only observable that allows studying the earliest stage of the Universe. Radioastronomy instruments for CMB investigation require low working ...temperatures around 100 mK to get the necessary sensitivity. On-chip electron cooling of receivers is a pathway for future space missions due to problems of dilution fridges at low gravity. Here, we demonstrate experimentally that in a Cold-Electron Bolometer (CEB) a theoretical limit of electron cooling down to 65 mK from phonon temperature of 300 mK can be reached. It is possible due to effective withdrawing of hot electrons from the tunnel barrier by double stock, special traps and suppression of Andreev Joule heating in hybrid Al/Fe normal nanoabsorber.
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•Brunogeierite was synthesized at 650 °C and 100 MPa by hydrothermal method.•Single crystal structure was refined by XRD.•Mössbauer spectrum corresponds to the octahedral position of ...iron ions VIFe2+.•Lattice dynamic calculations agree with experimental Raman data.•Brunogaierite Raman spectra are obtained as function of pressure up to 30 GPa.
We present complex spectroscopic data of the synthetic brunogeierite (Fe2+)2Ge4+O4 with space group Fd3¯m of spinel structure: a = 8.3783 (6) Å, V = 588.12 (13) Å3. Brunogeierite crystals up to 200 μm in size were crystallized by the interaction of a boric acid solution on a metal iron wire in the presence of germanium oxide (GeO2) at 600/650 °C and 100 MPa. Mössbauer spectrum of synthetic brunogeierite consists of the symmetric doublet with the parameters IS = 1.104(1) mm/s and QS = 2.845(1) mm/s, that corresponds to the octahedral position of iron ions (VIFe2+). The Raman spectra of Fe2GeO4 crystal consist of an intense main band at 756 cm−1 and four less intense bands at ∼644, 472, 302, and ∼205 cm−1 at ambient conditions. All five bands inherent in the spectrum of cubic spinel are present and gradual change in high pressure spectra up to 30 GPa. The color of the crystal changes from brown-orange to reddish at the center at 22.7 GPa and became opaque black up to 30.2 GPa. Herewith, in the high pressure spectra, we observed the splitting of some bands and the appearance of additional bands in a wide pressure range (from 1.6 to 30 GPa). The factor group analysis with the lattice dynamics calculation of potential crystal structure distortions shows the decreasing of the structure symmetry to tetragonal or rhombohedral in this pressure range.
Membrane nanotubes (NTs) and their networks play an important role in intracellular membrane transport and intercellular communications. The transport characteristics of the NT lumen resemble those ...of conventional solid-state nanopores. However, unlike the rigid pores, the soft membrane wall of the NT can be deformed by forces driving the transport through the NT lumen. This intrinsic coupling between the NT geometry and transport properties remains poorly explored. Using synchronized fluorescence microscopy and conductance measurements, we revealed that the NT shape was changed by both electric and hydrostatic forces driving the ionic and solute fluxes through the NT lumen. Far from the shape instability, the strength of the force effect is determined by the lateral membrane tension and is scaled with membrane elasticity so that the NT can be operated as a linear elastic sensor. Near shape instabilities, the transport forces triggered large-scale shape transformations, both stochastic and periodic. The periodic oscillations were coupled to a vesicle passage along the NT axis, resembling peristaltic transport. The oscillations were parametrically controlled by the electric field, making NT a highly nonlinear nanofluidic circuitry element with biological and technological implications.
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Using of coal-water slurries as fuel for heat and power generation is interesting for researchers for a long time. Coal-water fuel (CWF) application has two major aspects of investigation: ...rheological properties to provide its transportation and atomization; and improvement of fuel combustion parameters. CWF combustion characteristics improvement can be achieved with the help of different physical and chemical methods. Influence of electromagnetic field on the structure and properties of hydrocarbon fuels is known. However, influence of electromagnetic treatment on the combustion parameters of coal-water fuel produced from coal of different metamorphic stages was not investigated before.
Experimental investigations of coal-water fuel combustion parameters: ignition time, time-temperature correlations, ignition temperature, maximal temperature of flame and others were performed. Fuels produced from coal of 6 basic metamorphic stages, which cover a wide range from Brown coal to Anthracite, were used for research. Investigations were carried out in two cases: without fuel pre-treatment with an electromagnetic field, and with it. It is shown in the article that electromagnetic pre-treatment of coal-water fuel improves fuel ignition and combustion stability, increases combustion process efficiency and reduces the total time of fuel burning.
•Water-coal fuel (CWF) combustion process is investigated.•4 stages of the process are showed and analyzed.•Electromagnetic pre-combustion treatment combustion is proposed.•Electromagnetic pre-activation improves CWF combustion efficiency.
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•Krieselite was synthesized at 600 °C and 100 MPa by hydrothermal method.•Single crystal structure was refined by XRD.•The assignment of Ag bands in non-polarized Raman spectra was ...carried out.•Lattice dynamic calculations agree with experimental Raman data.•Krieselite Raman spectra are obtained as function of pressure up to 30 GPa.
Spontaneous crystals of krieselite (Ge analogue of topaz) with the chemical formula Al2(Ge0.75Si0.25)O4(F1.63OH0.37) were synthesized using a thermo-gradient hydrothermal method at a temperature of 600/650 °C and pressure of 100 MPa. The unit cell parameters are: a = 8.9732(8) Å, b = 8.4823(7) Å, c = 4.7379(5) Å, V = 360.62(6) Å3, space group Pnma. The F-/OH– content of the samples was refined by FTIR spectroscopy method. Raman spectroscopy showed the main differences between the spectra of krieselite and topaz at the ambient conditions. The assignment of observed and calculated Ag bands (cm−1) for non-polarized Raman spectra was carried out. Using in situ Raman spectroscopy at high pressures, the dependence of the shift in the position of the main bands of the krieselite Raman spectrum on the pressure was established, and the corresponding paths of pressure induced distortion of crystal structure was assumed. According to the data of Raman spectroscopy, it was revealed that krieselite does not undergo the phase transitions up to 30 GPa. The probable way of crystal structure distortion within the space group Pnma was proposed based on simulation of high-pressure Raman spectra.
In the present work single-phase proton-conducting electrolyte CaZr0.95Sc0.05O3-δ (CZS) is synthesized by a conventional solid-state technique with different impurities content. Impurities are ...introduced by using different milling bodies during the synthesis. It is shown that milling by steel balls or grinding in a jasper mortar results in approximately 1 at.% of iron and silica respectively. Milling with ZrO2 balls does not lead to a noticeable increase in the level of impurities in CZS.
The influence of impurities on the bulk and grain boundary conductivity is studied by means of electrochemical impedance spectroscopy. The measurements are performed on symmetric cells with different electrodes: Pt|CZS|Pt, (Pt + PrO2)|CZS|(Pt + PrO2) and Ag|CZS|Ag. The data analyzed by the conventional equivalent circuit and distribution of relaxation times (DRT) techniques.
It is shown that impurities influence only the grain boundary conductivity which proves that the grain boundary segregation occurs. However, a large grain-boundary resistance could be an obstacle to determine the bulk resistance.
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•CaZr0.95Sc0.05O3-δ electrolytes with different impurities content were obtained.•Bulk and grain-boundary conductivities were distinguished using DRT technique.•The addition of Si decreases grain-boundary conductivity, while Fe – increases.
The complex niobium–rare earth pyrochlore–monazite–crandallite ores of the Tomtor deposit, located in the Siberian Arctic, should be considered as a new type of rare metal materials. The major ...valuable components of the ore are niobium (1.63–16.4%), rare earth elements (2.2–27.8%), yttrium (0.18–2.9%), and scandium (0.015–0.15%); associated components are titanium, vanadium, aluminum, and phosphorus. Because of the irregular distribution of the rare earth metals and niobium according to grain size, the extremely finely dispersed nature of the minerals and their close interpenetration to each other, ore processing by gravitation and flotation is not successful. The processes studied for the treatment of the Tomtor ores use direct alkaline-acid leaching to open the ore. A problem in the first stage of alkaline leaching is the high aluminum content, which decreases the activity of sodium hydroxide and alkaline-earth metals, which are bound to phosphorus. Ore processing using alkaline-nitrate and alkaline-chloride leaching was proposed and investigated. The first variant was used to obtain rare earth and scandium materials and a niobium–titanium concentrate, which can be a stock material for processors who use chlorination for the processing of ores and concentrates. The second variant is a complex advanced ore processing scheme with electrochemical regeneration of the waste chloride solutions obtaining sodium hydroxide, hydrochloric acid, and chloridizing agents. Moreover trisodium phosphate is used for purification of the waste mother liquors from metal cations. The complex salt, NaAlCl
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, is proposed as the chloridizing agent for the decomposition of the niobium–titanium concentrate. The recovery of rare earth metals in the second variant of processing is about 95%; while for niobium and titanium, this value is 92–94%.
The usage of coal-water fuel instead of dry coal for heat and power generation is a promising way to decrease harmful emissions during power generation. Improvement of the coal-water fuel ignition ...and combustion parameters is important due to the specifics of the fuel. The use of glycerol as a flammable additive to the coal-water fuel is environmentally friendly and leads to reducing the ignition time and threshold temperature of that composition fuel. Generally accepted approximation of the dependence of the main combustion parameters includes the ignition temperature and the time delay before ignition on the glycerol content of the fuel composition does not correspond to the physical nature of the process and does not reflect the real nature of the change. To approximate the experimental data in the case of complex two-component fuel based on the coal-water slurry and glycerol, a more suitable and physically correct inverse sigmoid function is proposed. The applicability of the proposed function has been confirmed by experimental studies.
In photodynamic therapy, light is absorbed by a therapy agent (photosensitizer) to generate reactive oxygen, which then locally kills diseased cells. Here, we report a new form of photodynamic ...therapy in which nonlinear optical interactions of near-infrared laser radiation with a biological medium in situ produce light that falls within the absorption band of the photosensitizer. The use of near-infrared radiation, followed by upconversion to visible or ultraviolet light, provides deep tissue penetration, thus overcoming a major hurdle in treatment. By modelling and experiment, we demonstrate activation of a known photosensitizer, chlorin e6, by in situ nonlinear optical upconversion of near-infrared laser radiation using second-harmonic generation in collagen and four-wave mixing, including coherent anti-Stokes Raman scattering, produced by cellular biomolecules. The introduction of coherent anti-Stokes Raman scattering/four-wave mixing to photodynamic therapy in vitro increases the efficiency by a factor of two compared to two-photon photodynamic therapy alone, while second-harmonic generation provides a fivefold increase.
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