Massless spinning particle model that interacts with electromagnetic and antisymmetric gauge fields in anti-de Sitter space-time is considered as a constrained Hamiltonian system.
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-dimensional ...anti-de Sitter space-time is realized as a real projective manifold parametrized by the homogeneous coordinates. Classical constraints that generate in the presence of interactions minimal world-line supersymmetry algebra extended by the dilatations of the ambient-space homogeneous coordinates are found. Various representations of the Lagrangian of the spinning particle are obtained. Dirac quantization is shown to produce first- and second-order equations for the wave function of the spinning particle that are presented in the homogeneous, inhomogeneous and intrinsic coordinates of
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Crystallite size values were determined by X-ray diffraction methods for 210 TiO
2 (anatase) nanocrystalline powders with crystallite size from 3 nm to 35 nm. Each X-ray diffraction pattern was ...processed using different free and commercial software. The crystallite size calculations were performed using Scherrer equation and Warren–Averbach method. Statistical treatment and comparative assessment of the obtained results were performed for the purpose of an ascertainment of statistical significance of the obtained differences. The average absolute divergence between results obtained with using Scherrer equation does not exceed 0.36 nm for the crystallites smaller than 10 nm, 0.54 nm for the range 10–15 nm and 2.4 nm for the range >
15 nm. We have also found that increasing the analysis time improves statistics, however does not affect the calculated crystallite sizes. The values of crystallite size determined from X-ray data were in good agreement with those obtained by imaging in a transmission electron microscope.
Abstract
A number of recent studies report enhancement of chemical reactions on water microdroplets or inside nanobubbles in water. This finding promises exciting applications, although the mechanism ...of the reaction acceleration is still not clear. Specifically, the spontaneous combustion of hydrogen and oxygen in nanobubbles opens the way to fabricate truly microscopic engines. An example is an electrochemical membrane actuator with all three dimensions in the micrometer range. The actuator is driven by short voltage pulses of alternating polarity, which generate only nanobubbles. The device operation is, however, restricted by a fast degradation of the electrodes related to a high current density. Here it is demonstrated that the actuator with ruthenium electrodes does not show signs of degradation in the long-term operation. It is the only material able to withstand the extreme conditions of the alternating polarity electrolysis. This property is due to combination of a high mechanical hardness and metallic conductivity of ruthenium oxide. The actuator combines two features considered impossible: on-water catalysis and combustion in a microscopic volume. It provides an exceptional opportunity to drive autonomous microdevices especially for medical or biological applications.
This Article covers the influence of the concentration of gold nanoparticles on laser-induced water decomposition. It was established that addition of gold nanoparticles intensifies laser-induced ...water decomposition by almost 2 orders of magnitude. The water decomposition rate was shown to be maximal at a nanoparticle concentration around 1010 NP/mL, whereas a decrease or increase of nanoparticle concentration leads to a decrease of water decomposition rate. It was demonstrated that, if the concentration of nanoparticles in water-based colloid was less than 1010 NP/mL, laser irradiation of the colloid caused formation of molecular hydrogen, hydrogen peroxide, and molecular oxygen. If the concentration of nanoparticles exceeded 1011 NP/mL, only two products, molecular hydrogen and hydrogen peroxide, were formed. Correlations between the water decomposition rate and the main optical and acoustic parameters of optical breakdown-generated plasma were investigated. Variants of laser-induced decomposition of colloidal solutions of nanoparticles based on organic solvents (ethanol, propanol-2, butanol-2, diethyl ether) were also analyzed.
An electrodynamic limitation on the characteristics of antennas with a semi-infinite range as the limiting case of ultra-wideband (UWB) antennas is found. This limitation relates the directivity, the ...input reflection coefficient, the lowest operating frequency, and the overall size of the antenna and takes into account its geometric shape. An expression for estimating the lowest operating frequency of antennas with a given size and shape is obtained. Expressions for estimating the minimum achievable size and lowest operating frequency of rectangular printed UWB antennas with linear polarization are derived.
An original hybrid membrane-catalytic reactor (HMCR) was developed for the co-production of syngas and ultrapure hydrogen from fossil and renewable organic sources (methane and ethanol), as well as ...from synthetic feedstock (dimethyl ether) via dry and steam reforming. HMCR is a facility in which a porous ceramic catalytic converter prepared by self-propagating high-temperature synthesis (SHS) is integrated with a hydrogen-selective palladium-containing membrane. Due to separation of hydrogen from the reaction site and according to Le Chatelier-Brown principle it enables reforming to proceed effectively under milder temperature conditions as compared to a conventional reactor with a stationary bulk catalyst bed. On the basis of HMCR there can be developed mobile and small-size ultrapure hydrogen production units for fine processes of organic synthesis and electricity generation.
•Hybrid membrane-catalytic reactor was developed for syngas and H2 co-production.•H2 separation enables reforming to proceed effectively under milder conditions.•During DRM in HMCR hydrogen recovery reaches 83% at 5 atm and 700 °C.•Water content in the reaction medium affects negatively the hydrogen separation.
The problem of bacterial contamination through surfaces is important for the food industry. In this regard, there is a growing interest in new coatings based on nanoparticles that can provide a ...long-term antibacterial effect. Aluminum oxide nanoparticles are a good candidate for such coatings due to their availability and good biocompatibility. In this study, a coating containing aluminum oxide nanoparticles was produced using polytetrafluoroethylene as a polymer matrix—a polymer that exhibits excellent mechanical and physicochemical properties and it is not toxic. The obtained coatings based on “liquid Teflon” containing various concentrations of nanoparticles (0.001–0.1 wt%) prevented the bacterial growth, and they did not exhibit a cytotoxicity on animal cells in vitro. Such coatings are designed not only to provide an antibacterial surface effect, but also to eliminate micro damages on surfaces that inevitably occur in the process of food production.
Using different experimental techniques we visualize a cloud of gas in water that is produced electrochemically by the alternating polarity process. Liquid enriched with gas does not contain bubbles ...strongly scattering visible light but its refractive index changes significantly near the electrodes. The change of the refractive index is a collective effect of bulk nanobubbles with a diameter smaller than 200 nm. Any alternative explanation fails to explain the magnitude of the effect. Spatial structure of the cloud is investigated with the optical lever method. Its dynamics is visualised observing optical distortion of the electrode images or using differential interference contrast method. The cloud covers concentric electrodes, in a steady state it is roughly hemispherical with a size two times larger than the size of the electrode structure. When the electrical pulses are switched off the cloud disappears in less than one second. The total concentration of gases can reach very high value estimated as 3.5 × 1020 cm-3 that corresponds to an effective supersaturation of 500 and 150 for hydrogen and oxygen, respectively.
Based on a developed analytical model, a method is proposed for measuring the photonuclear cross section averaged over bremsstrahlung flux without application of additional target-monitor of photon ...flux. The method involves the use of a thin isotopic target, that completely overlaps the photon beam (a photonuclear converter), as well as an algorithm for processing the data on the yield of a reaction under study in such a target. The novel technique was validated on the reactions 100Mo(γ,n)99Mo and 58Ni(γ,n)57Ni in the range of photon end-point energy of 40.7–93.9 MeV. The photon flux-weighted average cross sections of the reactions measured experimentally are in good agreement with Monte Carlo simulations and TALYS predictions on their excitation functions.
•Effect of bremsstrahlung converter thickness on photon flux-weighted average (PFWA) cross section is shown.•Reference spectrum for above-threshold bremsstrahlung photons and its realization are proposed.•Weight function for bremsstrahlung photons integrable with reaction cross section in Lorentz form is derived.•Explicit relationship between Lorentz parameters of giant dipole resonance and PFWA cross section has been established.
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