Brain delivery remains a challenge for the clinical translation of therapeutic nanomedicines, particularly in focal diseases with specific delivery needs, such as stroke. In this scenario, clinically relevant endovascular interventions are recently being proposed as strategies to enhance delivery into specific cerebral vascular territories. In this study, we assess the feasibility of endovascular delivery and magnetic retention of biocompatible magnetic nanocapsules (NCs) in cerebral circulation models that better predict human responses. More specifically, polymeric NCs synthesized with magnetic properties (superparamagnetic oxide nanoparticles, SPIONs) and fluorescent (Cy5) moieties were infused into pigs via a femoral microcatheter reaching the brain vasculature and showing greater efficacy in targeting the ipsilateral brain hemisphere with preferential accumulation in microvessels when compared to intravenous administration which resulted in very little accumulation. Transient adverse effects related to hemodynamic instability upon nanocapsule administration were observed in both administration groups related to acute complement activation. Successful endovascular brain NC delivery is further demonstrated in a 3D-vascular model of the human large arterial vessel brain supply, with successful NC accumulation in the target arterial segment (the proximal middle cerebral artery) with sensible enhancement when using local magnetic fields. This study demonstrates the feasibility of endovascular NC delivery for focal brain nanotargeting via clinically relevant and minimally invasive procedures and proves the advantages of using magnetized nanomaterials to improve local vascular NC retention. Further safety and efficacy studies, including drug nanocapsule formulations, are needed to establish the clinical relevance of the proposed approach.

The electro-optical behavior of and electric-field-induced structural changes in nematic liquid crystals (6CHBT and 5CB) doped with a low concentration (1 & times; 10-4) of Mn-doped zinc ferrite nanoparticles were investigated. Light transmission and surface acoustic wave attenuation techniques were employed to monitor structural responses under increasing and decreasing electric field modes, as well as after pulsed field application. The influence of nanoparticle morphology (rods, needles, and clusters) and particle size on the field-induced structural modifications was systematically evaluated. Shifts in the threshold electric field were observed. The results obtained from both experimental approaches were compared in terms of suspension stability and demonstrate the potential of these ferronematic systems for applications in sensors, smart materials, and information storage devices.

Magnetite particles as doping agents have been proposed to enhance the absorbing properties of materials when subjected to ultrasound waves. However, these can also affect the absorption of audible-range sounds when incorporated into textile materials, making them candidates for novel acoustic systems. Additionally, the same materials could serve as protective layers against electromagnetic radiation, making them double-functional. In this article, we present research conducted on nonwoven mats made of flax, hemp, and sheep wool fibers reinforced with jute mesh. The nonwovens were coated with multiple layers of water-based magnetite particle dispersion and tested for acoustic and electromagnetic absorption. The results indicated that magnetite particles could improve acoustic characteristics, with the degree of improvement depending on the internal structure and the type of fibers used. Simultaneously, electromagnetic shielding was achieved over specific frequency ranges. Therefore, natural textiles, when functionalized with magnetite particles, could be promising candidates for dual-adaptation materials for improved protection. (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

The design and development of functional self-assembled soft matter structures, particularly liquid crystals that adapt responsively to multiple stimuli, are essential for both fundamental scientific research and advanced technological applications. This work investigates how chiral dopant concentration governs the field-induced unwinding and hysteresis behavior of cholesteric liquid crystals (E7 liquid crystal mixture doped with CB15) confined in homeotropic cells. The study measures discrete pitch jumps and pronounced hysteresis loops as a function of dopant concentration in both voltage- and magnetic-field-driven unwinding, providing experimental insight into composition-controlled phase transitions in thin-layer geometries. A critical dopant concentration was identified below which the cholesteric helix does not form due to surface anchoring effects. The critical fields increase with the increase of dopant concentration, and a linear dependence of the magnetic threshold on concentration is demonstrated. Experimental observations are compared with theoretical models for infinite systems, with an emphasis on discrete switching phenomena and threshold behaviors. These results provide new guidelines for designing responsive cholesteric soft materials and electro- and magneto-optical devices that exhibit controllable, stepwise switching.

Contemporary distribution transformers face modern technological and integration challenges due to modern electrification and load increase. Motivated by the need for improvement of transformer safety, lifetime, thermal and dielectric performance, we carry out research on transformer oil-based nanofluid with fullerene C60 nanoparticles as a potential replacement for conventional transformer oil. Unlike numerous studies based on numerical or experimental investigation of thermal or dielectric properties, we provide a comprehensive research on C60 nanofluid in academic laboratories and in industry, complemented by an analytical modeling. Large-scale nano-functionalization of transformer oil is performed unconventionally by dissolving C60 powder using an industrial oil treatment machine under controlled temperature and oil pumping conditions. The prepared nanofluid is applied in a three phase 250 kVA distribution transformer, on which temperature rise and high voltage tests are conducted. The nanofluid is subjected to experimental investigation of key physical properties, like density, viscosity, nanoparticle concentration, thermal conductivity, flash point, dielectric breakdown, dissipation factor and permittivity. An analytical model of a natural convection loop is employed to predict the effects of adding C60 nanoparticles into the oil on temperature and flow velocity within the distribution transformer. It is found that very small C60 concentration (0.004% w/V) determined by spectrophotometry has a low or negligible impact on viscosity, density and thermal conductivity, while significantly increases AC breakdown voltage (by 65%) and decreases flash point of the oil. The transformer filled with the C60 nanofluid met the requirements of the standard EN 60076-2:2011. Comparison of transformer temperature rise tests and analytical model predictions show a slight decrease in the transformer temperature due to enhanced coupling between the windings and cooling surfaces through improved oil circulation. The collected experimental, numerical and industrial results provide pros and cons of the large-scale C60 nanofluid preparation and future application in distribution transformers.

The rheological properties of nonpolar ferrofluids have been often studied under the action of an external magnetic or electric field. In this paper, we approach the problem conversely, and we aim to answer whether the ferrofluid shear flow affects the dielectric response. The ferrofluids are based on transformer oil and iron oxide nanoparticles stabilized with oleic acid. Basic physical characterization of the ferrofluids with three different nanoparticle concentrations is followed by experimental investigation of flow curves. Newtonian behavior of the ferrofluids is confirmed. The key experiment of this study consists of complex dielectric permittivity measurements in the frequency range from 20 Hz to 100 kHz at three different temperatures. In these measurements, the ferrofluids are sandwiched between two disk electrodes of a modular rheometer under the shear rates of 0, 10, 100, 500, and 1000s^{-1}. It is found that the low-frequency dielectric spectra of the ferrofluids exhibit a remarkable conductivity contribution leading to electrode polarization. Additional measurements of electrical conductivity and qualitative analysis of charge mobility in the ferrofluids are provided to understand the low-frequency dielectric relaxation. The results reveal that the slow dielectric relaxation is shear rate independent. The low-frequency dielectric spectra measured under the various shear rates exhibit constant behavior. The electric charge migrates across the shear flow velocity in the shear rate direction and the given rheological conditions do not affect its behavior. It is concluded that the electrical forces dominate the charge motion in the ferrofluids over the shear forces. The finding of the stable dielectric response of ferrofluids under the shear flow conditions supports the application of ferrofluids as dielectric media in electrical equipment with the presence of forced or natural convection.

Magnetic fluids based on non-polar liquids constitute attractive materials exhibiting magnetic field-sensitive dielectric relaxation processes. In this study, we focus on the dielectric response of three magnetic fluids with different bilayer stabilisation. The first stabilising layer is a fatty acid, while the second layer is polymeric. The dielectric spectra are studied on thin layers of magnetic fluids in the frequency range from 0.1 Hz to 200 kHz. The presence of the bilayer on the magnetic particle surfaces gives rise to two distinctive relaxation processes observable in permittivity and dissipation factor spectra. We show that the relaxation maxima are significantly sensitive to the acting direct current bias electric voltage (0-3 V). It is found that the bias electric field shifts the relaxation maxima towards higher frequencies and greater permittivity and dissipation factor values. The shift is similar to the effect of temperature, which is also documented in this study. The application of the Havriliak-Negami fitting functions on the studied dielectric spectra is employed in the analysis. The free charge and the resulting conductivity contribution are also taken into account. The direct current-sensitive dielectric response of magnetic fluids may find applications in multifunctional sensors that detect both electric and magnetic fields.

The effect of Mn-doped zinc ferrite nanoparticles at a low volume concentration (1 × 10−4) on structural changes in the nematic liquid crystals 6CHBT and 5CB, induced by weak magnetic fields, was investigated using surface acoustic wave (SAW) and light transmission (LT) techniques. Structural changes caused by the applied magnetic field, in both increasing and decreasing modes, as well as after pulsed changes, were examined by measuring the responses of SAW attenuation and LT using a linearly polarized laser beam. The influence of nanoparticle shape (rods, needles, and clusters) and temperature on the structural changes was investigated. A shift in the threshold field and the transition temperature was observed. In addition, the magnetic properties of the individual samples in powder form were examined using M–H curves, M–T curves, and XRD patterns. The results obtained from all measurements are compared, and the effectiveness of each technique, considering the influence of nanoparticle shape and suspension stability, was evaluated.

In the present paper, we formulate a thermodynamic model to describe the melting of inclusions with a boundary layer in nanopores. Within the scope of this task, we define the conditions for melting and describe how the temperature and heat of fusion of the inclusion are related to the size of the inclusion and its boundary layer. Experimental validation of the model is performed using silica gel matrices with different pore sizes containing inclusions of 1-octadecene and undecylenic acid. We report that both the melting point and the specific heat of fusion in such systems decrease with decreasing sizes of nanoinclusions. The results of the experiment agree well with the predictions of the model. The model described is then used to develop a method for determining the thickness of the inclusion's boundary layer based on experimental data of the inclusion's melting parameters. We apply this method to 1-octadecene and undecylenic acid and further use it to elucidate the process of inclusion formation for chain molecules in silica gel-based nanocomposites.

The possibility of determining the magnitude of neutral atom density in hydrogen plasma was investigated using Paschen-Back effect and resonant Faraday rotation of the polarization plane of light by residual neutral atoms in the plasma. In strong magnetic fields when the Zeeman shift is greater than the distance of the hyperfine structure energy levels the Paschen-Back effect is observed. In this case, it is no longer possible to speak about the independence of the splitting of each level of a given multiplet term.

The nematic 5CB liquid crystal composites with silica nanoparticles were studied using light transmission and surface acoustic wave (SAW) measurements. Several different kinds of hydrophobic aerosil were chosen as a source of silica nanoparticles. The synthesized colloidal systems exhibited a pronounced memory effect, as indicated by the hysteresis observed in both light transmission and surface acoustic wave (SAW) attenuation measurements within the nematic phase at ambient temperature. However, apparent influence of SiO2 surroundings following different aerosil sources for silica nanoparticles as dopants on the improvement of the memory effect was observed. Additional studies also showed on the influence of SiO2 surroundings on the threshold voltage as well as nematic-isotropic transition temperature. The potential application of appropriate composites could lead to the fabrication of electro-optical memory devices suitable for information storage applications. The nematic 5CB liquid crystal composites with silica nanoparticles were studied using light transmission and surface acoustic wave (SAW) measurements. Several different kinds of hydrophobic aerosil were chosen as a source of silica nanoparticles. The synthesized colloidal systems exhibited a pronounced memory effect, as indicated by the hysteresis observed in both light transmission and surface acoustic wave (SAW) attenuation measurements within the nematic phase at ambient temperature. However, apparent influence of SiO2 surroundings following different aerosil sources for silica nanoparticles as dopants on the improvement of the memory effect was observed. Additional studies showed also on the influence of SiO2 surroundings on the threshold voltage as well as nematic-isotropic transition temperature. The potential application of appropriate composites could lead to the fabrication of electro-optical memory devices suitable for information storage applications. Summarization of light transmission dependences on electric field for all investigated 5CB composites doped with silica nanoparticles including pure 5CB (a) and schematic illustration of arrangement between silica nanoparticles and liquid crystal (b)

High-frequency components such as microprocessors, transistors, antennas, voltage-controlled oscillators, and many others generate a large amount of heat. In the absence of satisfactory cooling, these components may suffer damage or even destruction. Therefore, it is important to find effective ways to cool these components. A possible solution is to use oil-based magnetic fluids. Magnetic fluids contain magnetic particles dispersed in oil, and their properties, including viscosity, affect their cooling capabilities. Viscosity can be changed by adding various additives or by adjusting the concentration of magnetic particles. The advantage of using oil-based magnetic fluids for cooling is that they allow for precise dosing and control of the amount of fluid applied to the component, reducing thermal losses and increasing cooling efficiency. In addition, oil-based magnetic fluids can also act as a dielectric, reducing electrical noise and increasing electromagnetic compatibility with the components. Analyzing the heating rate of magnetic fluids consisting of mineral oils in an alternating magnetic field with a frequency of 500 kHz, we have shown the capability of controlling thermal losses by adjusting the viscosity of the carrier liquid.

In liquid crystals doped with aerosil nanoparticles, the state induced by applying voltage or a magnetic field stays remembered after removing the power. The ability to remember the induced state after removing the power is known as non-volatile memory effect. The present paper describes how the magnitude of voltage and magnetic field affects the memory effect in the nematic phase of liquid crystal 4-cyano-4′-pentylbiphenyl doped with aerosil nanoparticles and with a combination of aerosil and magnetic goethite nanoparticles. Capacitance measurements revealed increasing in memory when the magnitude of voltage and magnetic field is increased. Applying fields with various magnitudes provides the possibility of fabricatin a multilevel memory device based on the response to electric or magnetic field. The memory can be erased, and the initial state can be restored by heating the composites to the same temperature.

The polarization plane stimulated rotation angle of a probe signal in an intense laser field in plasma is calculated for arbitrary detunings of intense and weak laser waves compared with the resonant transition frequency of the medium. Estimates of the residual gas local density in a cesium plasma have been found based on the Faraday, Cotton-Mouton effects and on the effect of stimulated rotation of the polarization plane of the probe signal in an intense laser field. It is shown that the rotation in the medium has a complex structure consisting of the sum of only the influence of the magnetic field, only the influence of the intense laser field and the interfering part of the magnetic and intense laser fields.

A study of the role of diamond nanoparticles on 5CB liquid crystal composites with Fe3O4 nanoparticles is presented. Composite ferronematic systems based on the nematic liquid crystal 5CB doped with Fe3O4 magnetic nanoparticles and additionally bound to diamond nanoparticles (DNPs), of a volume concentration of 3.2 mg/mL, 1.6 mg/mL and 0.32 mg/mL, were investigated using both magneto-optical effect and surface acoustic waves (SAWs) to study the role of diamond nanoparticles on the structural properties of ferronematic liquid crystals. The responses of light transmission and SAW attenuation to an external magnetic field were investigated experimentally under a linearly increasing and decreasing magnetic field, respectively. Investigations of the phase transition temperature shift of individual composites were also performed. The experimental results highlighted a decrease in the threshold field in the ferronematic LC composites compared to the pure 5CB as well as its further decrease after mixing Fe3O4 with diamond powder. Concerning the transition temperature, its increase with an increase in the volume fraction of both kinds of nanoparticles was registered. The role of diamond nanoparticles in the structural changes and the large residual light transition and/or attenuation (memory effect) were also observed. The presented results confirmed the potential of diamond nanoparticles in nematic composites to modify their properties which could lead to final applications.

Ferrofluids based on mineral transformer oil have been intensively studied over two decades owing to their outstanding thermal and electrical insulating properties. However, current environmental demands on transformer operation give priority to the use of biodegradable transformer oils. Clearly, the differences in physical properties of biodegradable oils and those refined from crude oil determine the physical properties of ferrofluids based on the two types of oils. In this study, ferrofluids with various concentrations of iron oxide nanoparticles have been prepared on mineral transformer oil (M-oil) and biodegradable transformer oil based on gas-to-liquid technology (S-oil). The ferrofluids were subjected to experimental investigation of magnetization, AC magnetic susceptibility, thermal conductivity, viscosity and dielectric response. Based on zero-field-cooled and field-cooled magnetization curves, a lower temperature of a specific magnetization maximum associated with the melting of the oil (phase transition) was found for M-samples than for S-samples. The effect of carrier liquid on the onset of extrinsic superparamagnetism in addition to the intrinsic superparamagnetism is observed. Spectra of AC magnetic susceptibility of both types of ferrofluids exhibit quasi constant behaviour with a moderate decrease at high frequencies of a magnetic field. The viscosity of M-samples is slightly higher than that of S-samples. On the other hand, M-samples exhibit lower thermal conductivity than S-samples. In both cases, the thermal conductivity linearly decreases with temperature. Dielectric spectroscopy has revealed remarkable dielectric dispersion below 100 Hz in both ferrofluid types. The relaxation has been ascribed to interfacial polarization, which can be considered as a serious drawback from an electrical engineering application point of view. The measured physical properties of the ferrofluids are analyzed in regard to the density and viscosity of the base oils.

Ester-based nanofluids constitute an effective ecological alternative to petroleum-derived dielectric fluids for electrical engineering industry. Pulse induced dielectric breakdown is a key cause of power device failure. In this paper, we deal with the lightning impulse breakdown voltage (LI BDV) in natural and synthetic ester-based (NE and SE) nanofluids with various concentrations of magnetite (Fe3O4) and fullerene (C60) nanoparticles. The nanofluids show a decrement in positive polarity LI+ BDV as compared with the base ester. Negative polarity LI- BDV in the nanofluids is similar to that of base oils. Weibull statistical distributions are applied to analyse the results at different cumulative probabilities of 1%, 10%, and 50%. Natural ester with C60 nanoparticles shows higher positive LI+ BDV values at a low probability level, while the negative LI- BDV reaches higher values at higher probability levels. The decreased LI BDV in NE and SE due to the magnetite nanoparticles are attributed to the nanoparticle clustering and percolation. The tendency of C60 nanoparticles to enhance the LI BDV in NE but not in SE is interpreted in the view of the nanoparticle concentration and oil's viscosity effect on the streamer branching and propagation.

An important goal for the development of novel nanomaterials based on magnetic nanoparticles dispersed in liquid crystals is the improvement of the sensitivity to magnetic fields. Despite the continuous research of the magnetically-controlled properties of such hybrid composite materials, known as ferronematics, a persistent challenge lies in achieving consistent homogeneity and colloidal stability of the nanoparticles in liquid crystal media. Therefore, the design of the magnetic nanoparticles needs to be compatible with the liquid crystal matrix. Coating nanoparticles with (pro)mesogenic ligands has been shown to be a versatile way of stabilizing magnetic nanoparticles in liquid crystal matrices. Here, we report about the effect of dendrimer-functionalized cobalt ferrite nanoparticles (CoFe2O4@dend) on structure and magnetic sensitivity in the thermotropic liquid crystal 4-pentyl-4′-cyanobiphenyl (5CB) confirmed by small angle X-ray scattering (SAXS), magnetization and capacitance measurements. Our measurements reveal that for dendronized magnetic nanoparticles, the sensitivity to magnetic fields is improved. However, they exhibit a tendency to form clusters in the liquid crystal medium. These clusters induce a tilting of the overall ordering of the nematic director field due to magneto-nematic coupling.

The Klein-Gordon equation of motion in the transition layer of a free-electron laser of the relativistic strophotron type is studied. The condition of suddenly switching-on interaction is found: a smallness of the transition layer at the entrance compared to the distance traveled by the electron in longitudinal direction in one period of transverse oscillations in strophotron. The results are correspond to the results of classical description. It is shown, that in an electric strophotron, under the assumption of a suddenly switching-on interaction, the transverse energy of an electron at the moment t = 0 undergoes a jump. However, the total energy is conserved, because at the same moment t = 0, the longitudinal energy of the electron has the same jump with opposite sign.

З метою розвитку методiв нейтронної та рентґенiвської рефлектометрiї для дослiдження поверхневих шарiв рiдинних систем запропоновано метод збiльшення чутливостi рефлектометричного експерименту до появи та еволюцiї приповерхневих шарiв. У зв’язку з цим, проведено тестування багатошарових гетероструктур Ni/Ti щодо практичного застосування квазиоднорiдного пiдходу зi змiною ефективної густини довжини розсiяння рентґенiвського випромiнювання тонких (товщиною до 100 нм) металевих плiвок в рентґенiвських рефлектометричних експериментах на прикладi електрохiмiчних iнтерфейсiв. Структури з надзвичайно малою товщиною двошарової системи Ni/Ti та рiзним спiввiдношенням товщин пiдшарiв нiкелю та титану були синтезованi методом магнетронного напилення. Проаналiзовано дзеркальну вiдбивну здатнiсть рентґенiвського випромiнювання вiд поверхнi гетероструктур для визначення межi можливостi використання квазиоднорiдного наближення.