Finite Element Based Comparative Analysis of Positive Streamers in Multi Dispersed Nanoparticle Based Transformer Oil

The dispersion of dissimilar nanoparticles (NPs) in transformer oil (TO) has a major impact on fast propagating positive streamers. This work investigates the positive streamer dynamics in TO modified by dispersing both Fe3O4 and Al2O3 NPs at a homogenous concentration. The hydrodynamic drift diffusion model of positive streamer evolution and propagation are solved using the commercial software package COMSOL Multiphysics. The impact of multiple NPs (MNPs) has been analysed for streamer propagation, electric field intensity, electron density, and space charge density of modified TO. MNPs successfully reduce streamer propagation velocity by 50%, 17%, and 37.5% comparing to pure oil, Fe3O4 based nanodielectric fluids (NDFs), and Al2O3 based NDFs, respectively. The spatial distribution of electron density reveals the loss of electrons from the ionization region until the saturation of NPs. A comparative study demonstrates that MNPs significantly alter the streamer dynamics and augment the dielectric strength of TO compared to individual NPs.

ELEMENTAL HOMEOSTASIS IN WISTAR RATS AS A MANIFESTATION OF ADAPTATION IN AN EXPERIMENT WITH METAL LOADING IN THE FORM OF MICRO- AND NANOPARTICLES

Relevance. In recent years, various methods have been widely used to determine the state of adaptation.One of the mechanisms providing adequate adaptation reactions and resistance of the organism to the action of hazardous environmental factors is an increase in the number of intra- and intersystem connections between the content of macronutrients and trace elements, as a means of reliable functioning of the organism. Objective. To reveal the typical stages of adaptation of the organism of rats in different conditions of the action of metals by studying the correlation dependences between the content of macronutrients and trace elements in various biological media and assessing the degree of adaptation of the elemental system. Materials and methods. Determination of the content of 14 chemical elements in whole blood and endocrine organs was performed using microwave mineralization of samples and was determined by the OES-ICP method on an Optima 2100 DV device. The assessment of their ratios and the analysis of correlations between the elements and the assessment of the degree of resistance of the organism by calculating the index - the degree of adaptation of the elemental system of the organism (A) according to the formula of R.M. Baevsky were carried out. Results. The degree of a, sti of experimental animals to the action of Al and Ag, Cr and Mn compounds was estimated according to the proposed by R. M. Baevsky et al. [4] the formula, taking into account the correlations between of macronutrients and trace elements in biological media (degree of adaptation - A). During intraperitoneal administration of metal salts, they were characterized by a stress stage for Al and Cr, the training stages corresponded to a change in the balance of elements under conditions of Mn salt administration. No significant violations of adaptation were found under the conditions of Ag action. Under the conditions of oral administration of metal salts, the degree of adaptation was higher for Ag and Al compounds, the stress stage was characterized by the effect of Mn and Cr salts on elemental homeostasis. Comparison of the action of NPs metal showed a greater adaptation to the action of NPs of Al and Ag oxides and worse to the action of NPs of Mn and Cr citrates. Sex differences in adaptation of animals to the action of metal salts were also revealed. Thus, in males exposed to Al, adaptation was characterized by a training stage, while in females the response to Ag action corresponded to the stress stage. The latter gives grounds to assert that the thyroid gland is more sensitive to Ag than in males. Correlation dependences between the content of metals and hormones in animals, exposed to compounds Ag, Al, Cr, Mn, showed a multidirectional effect of Ag and Al on the correlation between the content of metal and hormone I-TG If a direct correlation was found in the control between the content of metals in the blood and free T4 for animals of all groups, and in the experiment only under the condition of exposure to Al and Cr. For the hormone C-peptide (insulin precursor), a significant correlation was found. The bond was found only under the condition of exposure to Al and Mn. Conclusions. For the first time, an approach was applied to assessing the adaptation of an organism in terms of the balance of macronutrients and trace elements as an intermediate link in the adaptation process of the endocrine system in animal experiments. Comparison of the action of metal NPs showed a greater adaptation to the action of NPs of Al and Ag oxides and worse to the action of NPs of Mn and Cr citrates. Comparison of the effects of MC effect of metal nitrates and NPs of their oxides and hydrates according to the degree of adaptation of the elementary system indicates a higher toxicity of AgNO3, Al (NO3) 3, while the degree of adaptation under the action of NPs Mn-Ctr and Cr-Ct indicates their higher toxicity. Females were found to be more sensitive to Ag2O NPs than males, and the opposite effect was found under the conditions of Al2O3 NPs. The data obtained testify in favor of the existing ideas about the higher toxicity of metals in the form of nanoparticles compared to microparticles, that is, NPs of manganese and chromium citrates are more toxic.

Impact of Solvents, Magnesium Oxide and Aluminium Oxide Nanoparticles on the Photophysical Properties of Acridine Orange Dye

Absorption and fluorescence spectroscopy techniques were applied to investigate the photophysical characteristics of acridine orange (AO) dye in solvents that included distilled water, dimethyl sulfoxide (DMSO), acetone and ethanol in various concentrations (1×10-4–1×10-6) M. All of the samples were served at room temperature. The relationships between various parameters describing the strength of optical transitions in atoms and molecules were reviewed. This study expresses various viewpoints by describing how concentration and solvent affect the dye's absorption and fluorescence spectra. The absorption spectra of AO exhibit a band at (490 nm), except for DMSO, which shifts more towards red by 5 nm. The fluorescence spectra show a blue shift in AO aqueous solution around 6 nm until (0.5×10-4) M, followed by a red shift at around 7 nm at (1×10-6) M. There is a blue shift in (1×10-5) M for DMSO at around 4 nm, then a 10 nm red shift in higher concentrations as well as a 9 nm red shift in acetone and 6 nm in ethanol. Adding magnesium oxide nanoparticles (MgO NPs) quenched AO in both absorption and fluorescence spectra, whereas maximum fluorescence and intensity increased when aluminium oxide nanoparticles (Al2O3 NPs) were added to the solution. KEYWORDS Laser dye, absorption spectrum, fluorescence spectrum, MgO NPs, Al2O3 NPs

Potential Use of Green Synthesized Al2O3 (Alumina) Nanoparticles from Guava Leaves (Psidium guajava) for the Removal of Methylene Blue from Wastewater

Recently non-harmful nanomaterials have acquired critical significant attention in wastewater treatment containing organic pollutants especially toxic and hazardous dyes. In this regard, a low cost and eco friendly method has been investigated for the green synthesis of alumina nanoparticles (Al2O3 NPs). The alumina nanoparticles were synthesized using an aqueous extract of Psidium guajava leaf as a potential stabilizing agent. The UV-visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) techniques were used to characterize the synthesized nanoparticles. The absorption at 281 nm confirmed the formation of alumina nanoparticles. The FTIR spectra and XRD analysis confirmed the presence of various functional groups and crystalline structures of Al2O3 NPs during the synthesis. The spectrum clearly indicates the organic moieties in Psidium guajava extract are responsible for the biosynthesis of Al2O3 NPs. The suface morphology of Al2O3 NPs was confirmed by SEM and EDS studies. Besides this, the removal of methylene blue through adsorption and kinetic study was also reported.

Green synthesis of nano-Al2O3, recent functionalization, and fabrication of synthetic or natural polymer nanocomposites: Various technological applications

Alumina nanoparticles (Al2O3 NPs) are one of the most extensively used nano-metallic oxides and nanofillers due to their fascinating properties in everyday applications. Furthermore, polymeric nanocomposites (PNCs) containing Al2O3 NPs...

Comprehensive numerical study of the effect of nanoparticle additives on the cutting transport performance in horizontal boreholes

The results of a numerical study of the effect of nanoparticle additives in the drilling fluid on the efficiency of cuttings removal from a horizontal well are presented. The rheological parameters of drilling fluids with nanoparticles (NPs) were set from the experiment. The SiO2 and Al2O3 NPs were used. The concentration of NPs in the drilling fluids varied from 0.25 to 2 wt%, while their average diameter ranged from 5 to 50 nm. The Eulerian granular media approach was used to simulate the cutting transport from the borehole. The numerical model was tested in detail on well-known experimental data on sand suspension flow in a round pipe. A good agreement with the experiment was obtained. A systematic computational study of the influence of several parameters on the efficiency of removing cuttings from the well was carried out. These parameters included the well's inclination angle from the vertical direction, the speed of rotation of the drill pipe, the flow rate of the drilling fluid, and the concentration, size, and composition of nanoparticles. It is shown that the 2 wt% concentration of nanoparticles in the drilling fluid results in a 2.7-fold increase in the cutting transport performance for horizontal boreholes. The positive effect of adding nanoparticles to the drilling fluid is enhanced with decreasing nanoparticle size.

Metal Oxide Nanoparticles Against Bacterial Biofilms: Perspectives and Limitations

At present, there is an urgent need in medicine and industry to develop new approaches to eliminate bacterial biofilms. Considering the low efficiency of classical approaches to biofilm eradication and the growing problem of antibiotic resistance, the introduction of nanomaterials may be a promising solution. Outstanding antimicrobial properties have been demonstrated by nanoparticles (NPs) of metal oxides and their nanocomposites. The review presents a comparative analysis of antibiofilm properties of various metal oxide NPs (primarily, CuO, Fe3O4, TiO2, ZnO, MgO, and Al2O3 NPs) and nanocomposites, as well as mechanisms of their effect on plankton bacteria cells and biofilms. The potential mutagenicity of metal oxide NPs and safety problems of their wide application are also discussed.