Search Results (164)

This paper proposes an energy-efficient current control strategy for drive modules of permanent magnetic actuators (PMAs) to reduce the cost and volume of DC-link capacitors. The drive module of the PMA does not receive the input power from an external power source during operation. Instead, the externally charged DC-link capacitors are used as internal backup power sources to guarantee the reliable operation even in the case of an emergency. Therefore, it is important to use the charged energy efficiently within the limited DC-link capacitors. However, conventional control strategies using a voltage open loop have trouble reducing the energy waste. This is because the drive module with the voltage open loop uses unnecessary energy even after the PMA mover has finished its movement. To figure it out, the proposed control strategy adopts a current control loop to save energy even if the displacement of the PMA mover is unknown. In addition, the proposed strategy can ensure the successful operation of the PMA by using the driving force analysis. The efficacy of the proposed strategy is verified through the experimental test. It would be expected that the proposed strategy can reduce the cost and volume of the PMA drive system. Full article

Dendrimers, 4-dimethylamino-1,8-naphthalimide (DAB) and its halogenated analog 3-bromo-4-dimethylamino-1,8-naphthalimide (DAB-Br), were evaluated on eukaryotic cells, human HFF-1 fibroblast cells, and five fungal species. Although both dendrimers have demonstrated antibacterial and antiviral potential, thus far, their effects on eukaryotic cells, particularly human and fungal cells, have not been investigated. For this purpose, their cytotoxicity, mechanisms of cellular entry, and antifungal activity were studied. Dynamic light scattering measurements revealed that both dendrimers exhibited positive surface charges (+28 to +35 mV), good colloidal stability, and nanoscale dimensions (117–234 nm), facilitating interactions with target cells. The MTT assay showed that DAB was more cytotoxic toward HFF-1 cells (IC₅₀ = 27 µg/mL) compared to DAB-Br (IC₅₀ = 68 µg/mL). In contrast, the resazurin-based antifungal assay demonstrated that DAB-Br had superior antifungal activity, achieving a lower minimum inhibitory concentration (0.148 µg/µL), compared to DAB (0.295 µg/µL). A trypan blue exclusion test revealed that both dendrimers entered cells through membrane permeabilization, either temporarily or permanently, depending on the concentration and exposure time. At concentrations above 30 µg/mL, irreversible permeabilization was observed within two hours of treatment, accompanied by a decrease in membrane lipid order, indicating altered membrane integrity and permeability. Conversely, at lower concentrations (7.5–15 µg/mL), dendrimers induced only temporary membrane permeabilization, with membranes remaining intact, suggesting a reversible interaction with the lipid bilayer. Conducting thorough and systematic research to fully explore their biological activities could provide valuable insight for future applications. Full article

This article considers a fluxgate magnetometer (FM) that operates based on a new physical principle. The authors analyze how the alternating electric charge potential of a cylindrical metal electrode impacts the structure of a cylindrical permanent magnet made of composite-conducting ferrite. They demonstrate that this impact and permanent magnet structure initiate the emergence of polarons with oscillating magnetism. This causes significant changes in the entropy of indirect exchange and the related sublattice magnetism fluctuations that ultimately result in the generation of circularly polarized spin waves at the spin wave resonance frequency that are channeled and evolve in dielectric ferrite waveguides of the FM. It is demonstrated that these moving spin waves have an electrodynamic impact on the measuring FM coils on the macro-level and perform parametric modulation of the magnetic permeability of the waveguide material. This results in the respective variations of the changeable magnetic field, which is also registered by the measuring FM coils. The authors considered a generalized flow of the physical processes in the FM to obtain a detailed representation of the operating functions of the FM. The presented experimental results for the proposed FM in the field meter mode confirm its operating parameters (±40 μT—measurement range, 0.5 nT—detection threshold). The usage of a cylindrical metal electrode as a source of exciting electrical change instead of a conventional multiturn excitation coil can significantly reduce temperature drift, simplify production technology, and reduce the unit weight and size. Full article

This study presents the design, optimization, and experimental validation of a large-air-gap voice coil motor (LAG-VCM) for high-precision magnetic levitation vibration isolation in vacuum environments. Key challenges arising from a large air gap, including pronounced leakage flux and a reduced flux density, were addressed by employing the equivalent magnetic charge method and the image method for the modeling of permanent magnets. Finite element analysis was applied to refine the motor geometry and obtain high thrust, low ripple, and strong linearity. To mitigate the severe thermal conditions of a vacuum, a heat pipe-based cooling strategy was introduced to efficiently dissipate heat from the coil windings. The experimental results demonstrate that the optimized LAG-VCM delivers a thrust of 277 N with low ripple while effectively maintaining coil temperatures below critical limits for prolonged operation. These findings confirm the suitability of the proposed LAG-VCM for vacuum applications with stringent requirements for both a large travel range and stable, high-force output. Full article

This paper presents a comprehensive analytical framework for investigating loss mechanisms and thermal behavior in high-speed magnetic field-modulated motors for flywheel energy storage systems. Through systematic classification of electromagnetic, mechanical, and additional losses, we reveal that modulator components constitute approximately 45% of total system losses at rated speed. Finite element analysis demonstrates significant spatial non-uniformity in loss distribution, with peak loss densities of 5.5 × 10⁵ W/m³ occurring in the modulator region, while end-region losses exceed central-region values by 42% due to three-dimensional field effects. Our optimized design, implementing composite rotor structures, dual-material permanent magnets, and integrated thermal management solutions, achieves a 43.2% reduction in total electromagnetic losses, with permanent magnet eddy current losses decreasing by 68.7%. The maximum temperature hotspots decrease from 143 °C to 98 °C under identical operating conditions, with temperature gradients reduced by 58%. Peak efficiency increases from 92.3% to 95.8%, with the η > 90% region expanding by 42% in the speed–torque plane. Experimental validation confirms model accuracy with mean absolute percentage errors below 4.2%. The optimized design demonstrates 24.8% faster response times during charging transients while maintaining 41.7% smaller speed oscillations during sudden load changes. These quantitative improvements address critical limitations in existing systems, providing a viable pathway toward high-reliability, grid-scale energy storage solutions with extended operational lifetimes and improved round-trip efficiency. Full article

This study aimed to verify the possibility of stabilizing and focusing a plasma column generated by a plasma cutter. The simulation performed by the COMSOL Multiphysics software is based on the actual configuration and geometry of the burner. This article presented a universal computational method based on FEM simulations, focusing on the deflection of the current of electrically charged particles in a magnetic field within the context of a plasma cutting torch. The simulations estimate the optimal shape and positioning of a focused electron beam for various magnetic lens positions and plasma stream energies, revealing that higher initial electron energies lead to a more even beam focus. Among the configurations tested, positioning the cathode 3 mm above the ring-shaped permanent magnet proved most effective, maintaining beam linearity and minimizing electron scattering, making it suitable for practical implementations. Full article

Electric vehicles can serve as controllable loads, storing energy during off-peak periods and acting as generation units during peak periods or periods with high electricity prices. They function as distributed generation resources within distribution systems, requiring controlled charging and discharging of batteries. In this paper, we address the problem of the optimal allocation of parking lots within a distribution system to efficiently supply electric vehicle loads. The goal is to determine the best capacity and size of parking lots to meet peak hour demands while considering constraints on the permanent operation of the distribution system. Using the particle swarm optimization (PSO) algorithm, the study maximizes total benefits, taking into account network parameters, vehicle data, and market prices. Results show that installing parking lots could be economically profitable for distribution companies and could improve voltage profiles. Full article

Background: Complete heart block (CHB) is a cardiac conduction disorder that can be fatal if not treated promptly. Malnutrition has been shown to have a significant impact on various cardiac conditions. Aim: The objective was to determine if the nutritional status influences the outcomes in patients with CHB. Methods: A retrospective study was conducted using the United States Inpatient Sample database on patients admitted with complete heart block. Outcomes were compared between the patients with and without concomitant malnutrition. Results: The study included 37,480 patients with complete heart block, of whom 603 (1.61%) had malnutrition. Compared to patients without malnutrition, patients with malnutrition had higher adjusted in-hospital mortality rates (aOR 2.61; 95% CI 1.46–3.48), longer length of stay (LOS) (mean increase 2.23 days; p < 0.01), and higher hospital charges (mean increase USD 76,907.32; p < 0.01). The malnourished group also had significantly higher rates of cardiogenic shock (aOR 2.80; 95% CI 1.56–5.03; p < 0.01) and acute respiratory failure (aOR 2.65; 95% CI 1.67–4.22; p < 0.01). Patients with malnutrition had significantly lower rates of permanent pacemaker (aOR 0.57; 95% CI 0.38–0.86; p < 0.01) and longer delay to permanent pacemaker intervention (mean increase 1.38 days; p = 0.014). The impact on outcomes was worse in patients with severe malnutrition compared to those with mild to moderate malnutrition. Conclusions: Malnutrition is associated with significantly worse outcomes in CHB admissions, including higher mortality, resource utilization, complications, and lower and delayed pacemaker intervention. Individualized and timely nutritional interventions might potentially play a key role in improving outcomes in these patients. Full article

The glycosylation process plays a crucial role in the structural integrity and biological activity of glycoproteins, where glycans are attached to a protein backbone. There are many kinds of glycans, the most common being N-glycans, which can be arranged into three classes, that is, complex, hybrid, and high mannoses, forming a structurally very diverse set of polar compounds that are difficult to detect and separate. Most commonly, N-glycans are labeled before separation by charged or fluorescence tags for better MS or fluorescence detection, respectively. This study examines the influence of ionic strength and organic modifier selection on the separation of fluorescently labeled dextran ladders in Hydrophilic Interaction Liquid Chromatography (HILIC). Using a Glycan BEH Amide column and varying the ammonium formate buffer concentration along with acetonitrile and methanol ratios, we investigated analyte retention, separation efficiency, and post-column conductivity changes. Our findings reveal that changes in the ionic strength of the mobile phase do not contribute to changes in selectivity, neither when acetonitrile nor methanol were used as organic modifiers to the mobile phase. However, the addition of methanol significantly changes the separation mechanism where two different prevailing separations mechanisms can be identified. It was assumed that the addition of methanol influences the folding pattern of dextrans around the permanent positive charge on the added tag, which influences the changes of separation selectivity. This work presents a systematic approach to altering mobile phase composition (buffer concentration, organic modifier type) to control retention and selectivity in complex glycan analysis. The discovery that methanol significantly alters separation behavior provides a potential new method for refining HILIC separations of polar compounds. Full article

The pacing pulse produced by implantable stimulators can be described as a truncated exponential decay from the starting peak amplitude, corresponding to the discharge of the output stage capacitance (reservoir and isolation capacitors, in series) along the application time. Pulse decay and charge balancing have relevant implications on the ideal setting of a pacing device, as demonstrated by mathematical predictions based on well-acknowledged theoretical statements. Successful stimulation is achieved with minimum energy expense at a pulse duration shorter than the chronaxie time, which represents the upper border of the advisable duration interval. With any start amplitude, the stimulation safety margin can be improved by a duration increase beyond the chronaxie only up to an absolute limit (longest useful duration), which depends on the chronaxie and the pulse time-constant. At the longest useful duration, the threshold start amplitude is at the minimum and cannot decrease any further, though it and the corresponding pulse mean amplitude largely exceed the rheobase. The overall pacing performance is affected, in addition, by the load resistance and the electrode capacitance. Pulse amplitude decay limits the effectiveness of extended duration in implantable stimulators, making short pulses preferable whenever possible. Proper pulse settings based on actual waveform properties can prevent energy waste and reduce pacing consumption, thus prolonging the service life of the stimulator. Full article

This paper addresses the author’s current understanding of the physics of interactions in polymers under a voltage field excitation. The effect of a voltage field coupled with temperature to induce space charges and dipolar activity in dielectric materials can be measured by very sensitive electrometers. The resulting characterization methods, thermally stimulated depolarization (TSD) and thermal-windowing deconvolution (TWD), provide a powerful way to study local and cooperative relaxations in the amorphous state of matter that are, arguably, essential to understanding the glass transition, molecular motions in the rubbery and molten states and even the processes leading to crystallization. Specifically, this paper describes and tries to explain ‘interactive coupling’ between molecular motions in polymers by their dielectric relaxation characteristics when polymeric samples have been submitted to thermally induced polarization by a voltage field followed by depolarization at a constant heating rate. Interactive coupling results from the modulation of the local interactions by the collective aspect of those interactions, a recursive process pursuant to the dynamics of the interplay between the free volume and the conformation of dual-conformers, two fundamental basic units of the macromolecules introduced by this author in the “dual-phase” model of interactions. This model reconsiders the fundamentals of the TSD and TWD results in a different way: the origin of the dipoles formation, induced or permanent dipoles; the origin of the Wagner space charges and the T_g,ρ transition; the origin of the T_LL manifestation; the origin of the Debye elementary relaxations’ compensation or parallelism in a relaxation map; and finally, the dual-phase origin of their super-compensations. In other words, this paper is an attempt to link the fundamentals of TSD and TWD activation and deactivation of dipoles that produce a current signal with the statistical parameters of the “dual-phase” model of interactions underlying the Grain-Field Statistics. Full article

Background/Objectives: Bringing small interfering RNA (siRNA) into the cell cytosol to achieve specific gene silencing is an attractive but also very challenging option for improved therapies. The first step for successful siRNA delivery is the complexation with a permanent cationic or ionizable compound. This protects the negatively charged siRNA and enables transfection through the cell membrane. The current study explores the performance of the innovative, ionizable lipid 2-Tetradecylhexadecanoic acid-(2-bis{[2-(2,6-diamino-1-oxohexyl)amino]ethyl}aminoethyl)-amide (T14diLys), in combination with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), for siRNA delivery and the impact of the production method (sonication vs. extrusion) on the particle properties. Methods: Liposomes were produced either with sonication or extrusion and characterized. The extruded liposomes were combined with siRNA at different N/P ratios and investigated in terms of size zeta potential, encapsulation efficiency, lipoplex stability against RNase A, and knockdown efficiency using enhanced green fluorescent protein (eGFP)-marked colon adenocarcinoma cells. Results: The liposomes prepared by extrusion were smaller and had a narrower size distribution than the sonicated ones. The combination of siRNA and liposomes at a nitrogen-to-phosphate (N/P) ratio of 5 had optimal particle properties, high encapsulation efficiency, and lipoplex stability. Gene knockdown tests confirmed this assumption. Conclusions: Liposomes produced with extrusion were more reproducible and provided enhanced particle properties. The physicochemical characterization and in vitro experiments showed that an N/P ratio of 5 was the most promising ratio for siRNA delivery. Full article

This paper aims to describe and analyze a relativistic engine that uses a permanent magnet and an electrically charged device. This is a novel device that was not described before. According to Newton’s third law, every action is met with an equal and opposite reaction, meaning the total force in a system unaffected by external forces is zero. However, relativity principles state that signals cannot travel faster than the speed of light, so actions and reactions cannot occur simultaneously. As a result, the total force cannot be zero at any given moment. This implies that the system gains mechanical momentum and energy over a finite period. The question then arises about how to uphold the law of momentum and energy conservation. It has been shown that momentum is balanced by an equal and opposite momentum in the field, while the energy gained by the engine is offset by a reduction in the field’s energy. Previous analyses assumed that the bodies involved were macroscopically neutral, meaning the number of electrons and ions was equal in every volume element. This paper relaxes that assumption and examines charged bodies interacting with magnetic currents from permanent magnetic materials, exploring the implications for a charged relativistic engine based on a permanent magnet. Full article

The fundamental idea underlying the research presented in this paper was the desire to use less magnetically charged areas of the general construction of induction machines by increasing the active working surface by interposing a new internal stator armature. This results in a new air gap and foreshadows the advantage of increasing the torques developed by the motor considered, compared to the equivalent standard motor, at the same volume of iron. The following research-validation methods were followed: theoretical studies (analytical simulation and FEM), an experimental model (prototype), and testing on the experimental platform. We recall obtaining solid conclusions on the technological construction, functional and energy characteristics, as well as superior performances of over 50% regarding electromagnetic torques compared to the equivalent classic version. The prototype of this type of machine was surprising due to the ease with which the rotor can be rotated, highlighting the reduced inertia. In conclusion, concerning the problem addressed and the objectives pursued, the research had, in essence, an applied and experimental nature. The recent development of permanent-magnet synchronous motor constructions has led to the concept of creating such motors in the constructive configuration specified in the paper (two stators and two radial air gaps). Full article

In this work, the mechanical properties of hydrogels based on linear polyethyleneimine (PEI) chemically crosslinked with ethyleneglycoldiglycidyl ether (EGDE) were improved by the ionic crosslinking with sodium tripolyphosphate (TPP). To this end, the quaternization of the nitrogen atoms present in the PEI structure was conducted to render a network with a permanent positive charge to interact with the negative charges of TPP. The co-crosslinking process was studied by ¹H high-resolution magic angle spinning (¹H HRMAS) NMR and X-ray photoelectron spectroscopy (XPS) in combination with organic elemental analysis and inductively coupled plasma mass spectrometry (ICP-MS). In addition, the mobility and confinement of water molecules within the co-crosslinked hydrogels were studied by low-field ¹H NMR. The addition of small amounts of TPP, 0.03 to 0.26 mmoles of TPP per gram of material, to the PEI-EGDE hydrogel resulted in an increase in the deformation resistance from 320 to 1080%, respectively. Moreover, the adsorption capacity of the hydrogels towards various emerging contaminants remained high after the TPP crosslinking, with maximum loading capacities (q_max) of 77, 512, and 55 mg g⁻¹ at pH = 4 for penicillin V (antibiotic), methyl orange (azo-dye) and copper(II) ions (metal ion), respectively. A significant decrease in the adsorption capacity was observed at pH = 7 or 10, with q_max of 356 or 64 and 23 or 0.8 mg g⁻¹ for methyl orange and penicillin V, respectively. Full article