Search Results (955)

This article presents a comprehensive analytical, numerical, and experimental study of the amplification and detection of weak signals in magnetically coupled electromagnetic systems, using an architecture consisting of three magnetically coupled coils. A rigorous mathematical model of the system is developed, which includes the formulation of the mutual inductance matrix and a state-space representation that captures the dynamic interaction between the coils. It is important to note that the electromagnetic subsystem is linear and that the stochastic resonance effect is achieved by incorporating an external nonlinear bistable element. In this configuration, a weak periodic signal below a threshold is applied to the primary coil, while a controlled source of Gaussian white noise is injected into a secondary coil. A third coil functions as a sensing element, capturing the superimposed magnetic response resulting from coupling effects. The voltage induced in the sensor coil is subsequently processed by a bistable nonlinear element implemented via a Schmitt trigger, which provides the nonlinearity and bistability necessary to enable stochastic resonance and the detection of the weak periodic signal. The conditions of the SR are analyzed in terms of noise intensity, coupling coefficients, and system parameters, highlighting the existence of an optimal noise level that maximizes the signal-to-noise ratio (SNR) at the output. A detailed simulation framework has been developed in MATLAB/Simulink, enabling a systematic exploration of the parameter space and the validation of theoretical predictions. The simulation results are further supported by experimental measurements obtained from a physical prototype, which show agreement with the proposed model. The main contribution of this work lies in demonstrating that magnetically coupled electromagnetic structures can effectively interact with nonlinear bistable elements to exploit stochastic resonance in the detection of weak signals, even when the electromagnetic domain itself remains linear. The results demonstrate that magnetic coupling is an effective mechanism for mediating constructive interactions between noise and weak signals, thereby improving the detection of the latter. These results extend the applicability of stochastic resonance to hybrid electromagnetic systems and demonstrate its relevance in practical applications. Potential applications include ultra-sensitive magnetic detection, low-power signal detection, magnetic transducers, and robust signal recovery in noisy electromagnetic environments, particularly in contexts where conventional linear amplification fails. Full article

The development of cost-effective and resource-rich materials is crucial for the practical application of microwave absorbers. This study demonstrates the successful fabrication of core-shell Fe and TiC nanoparticles encapsulated within carbon shells using the arc discharge method. The samples are designated as Fe3Ti1 and Fe1Ti3, where the numbers indicate the Fe-to-Ti mass ratio in the precursor (e.g., Fe1Ti3 = 1:3 by mass). In the arc discharge synthesis mechanism, the mass ratio of Fe to Ti in the raw material was adjusted from 3:1 to 1:3 to optimize the Fe/TiC/C interfaces under a CH₄ forming gas atmosphere. TEM analysis reveals spherical and polyhedral nanoparticles with diameters of 30–50 nm and a uniform carbon shell thickness of 3–4 nm. Raman spectroscopy shows that the Fe1Ti3 sample has a higher defect density (I_D/I_G = 1.13) compared to Fe3Ti1 (0.87), indicating a more disordered carbon structure. Magnetic measurements yield saturation magnetization values of 87 emu/g for Fe3Ti1 and 50 emu/g for Fe1Ti3, with coercivities of 190.72 Oe and 203.65 Oe, respectively. When composited with paraffin at 50 wt% loading, the Fe1Ti3 sample exhibits superior microwave absorption performance, achieving a minimum reflection loss (RL) of −25.22 dB at 8.23 GHz and an effective absorption bandwidth (RL ≤ −10 dB) of 4 GHz (6.5–10.5 GHz) at a thickness of 2.5 mm. This enhanced performance is attributed to the synergistic effect of multiple loss mechanisms, including conduction loss within the three-dimensional core-shell architecture, interfacial polarization at the heterojunctions between the core and the carbon shell, and magnetic loss induced by ferromagnetic behavior associated with defects in both the shell and carbon atomic layers. The magnetic loss in the (Fe/TiC)@C nanocomposites primarily arises from the natural resonance (at ~6.5 GHz) and exchange resonance (at ~12 GHz) of the Fe cores. The dielectric loss is primarily attributed to dipole, interfacial, and space charge polarization from TiC and the carbon shell, as well as multiple scattering effects between nanoparticles. Furthermore, far-field radar cross-section simulations substantiate that the Fe/TiC@C nanocomposite demonstrates excellent radar wave attenuation capability. Further, first principles simulations reveal that introducing Fe at the C/TiC interface induces strong charge redistribution and orbital hybridization, transforming a localized dielectric interface into a highly conductive and electronically coupled C/Fe/TiC system. This interfacial modulation enhances both dielectric loss (via charge transport and polarization) and magnetic loss (via Fe-induced magnetic interactions), thereby enabling optimized dielectric-magnetic synergy for broadband microwave absorption in (Fe/TiC)@C nanocomposites. Full article

This work contains the results of the research carried out on the framework of the design of the resonant power module of DAB. The peculiarity of this device is that it is supposed to be used as part of the basic element of a scalable power storage system, the load of which is an industrial three-phase network. The paper proposes a method of designing such devices based on preliminary analytical calculations and the development of numerical models. This method includes three stages. In the first iteration, the parameters of the resonant CLLC converter. In the second iteration, in the course of performing more accurate calculations and development of numerical models, the output parameters and the adjustment characteristic of the converter are determined, taking into account the specifics of the load. At the third stage, a numerical model of a high-frequency transformer is developed to determine the number of losses in the core and estimate the values of magnetic induction. Full article

Radiation of X-ray pulsars is powered by accretion on the neutron star surface from a binary companion under the influence of a strong magnetic field. We study the beaming of this radiation in the case of subcritical X-ray pulsars, where it is formed in the accretion channel close to the neutron star surface. We solve equations of the hydrodynamics and radiative transfer of two coupled polarization modes in the accretion channel numerically, taking into account resonant Compton scattering and vacuum polarization. The beaming patterns are obtained for different accretion rates, photon energies, and polarizations, as well as for different models of the neutron star surface radiation. The calculated beaming patterns are converted into light curves for both the intensity and polarization, taking into account the effects of General Relativity. These beaming patterns and light curves are found to be strongly affected by the resonant Compton scattering for photon energies comparable with the electron cyclotron energy. In particular, the angular redistribution of radiation near the cyclotron resonance may reduce the light-curve modulation amplitude, which is consistent with observational indications of a suppressed pulsed fraction at these energies. Full article

The synthesis of three novel, valuable bioconjugates obtained by coupling cholesterol bromoacetate with pyridine derivatives via an SN2 reaction was successfully carried out. Each of the products was fully characterized by magnetic nuclear resonance (¹H, ¹³C, APT, ¹H−¹H COSY, ¹H–¹³C HMBC, ¹H–¹³C HSQC), infrared spectroscopy (IR), and high-resolution mass spectrometry (HRMS). Full article

The purpose of this research is to determine which factors contribute to extending the read range of transponders equipped with different coupling-circuit topologies operating within selected RFID frequency bands. The analysis covered transponders that varied in both the configuration of their coupling circuits and their geometric dimensions. To accomplish this, transponder models were created using the EMCoS Studio electromagnetic simulation environment. Each model was subjected to simulations that yielded the mutual inductance and the voltage induced at the chip terminals. This study examines how the impedance of the embroidered antenna, the impedance of the chip’s coupling circuit, and the magnetic flux density affect the resulting chip voltage. In several of the investigated configurations, the peak chip voltage appeared outside the frequency range normally associated with RFID systems. The frequency at which this maximum occurred was dependent on the mutual inductance value. Understanding how individual parameters influence mutual inductance makes it possible to shift the voltage peak into a target operating band. Numerical simulation results, combined with the transponder’s mathematical model, enabled the calculation of the mutual inductance and the terminal voltage—quantities that directly determine the achievable read range. This study focuses on factors such as the resonant frequencies of the antenna and coupling circuit, their impedances, and the characteristics of the magnetic field. The findings show that tuning these parameters can affect not only the location of the voltage maximum, but also its amplitude. This effect introduces additional complexity in designing and selecting suitable transponder configurations. Full article

To address the issue of traditional bistable vibration energy harvesters (BVEHs) being prone to becoming trapped in a single potential well—which results in a narrowed energy harvesting bandwidth and reduced efficiency—this paper proposes a method that utilizes the nonlinear electromagnetic force generated during the induction process to modulate the kinematic behavior of the oscillator. The characteristics and influencing factors of the nonlinear force produced during electromagnetic induction are analyzed. A dual-cantilever beam structure is designed, with an iron-core coil and a magnet placed at the respective free ends. A mathematical model of a piezoelectric–electromagnetic coupled bimodal broadband vibration energy harvester is established and numerically simulated. Furthermore, a vertical vibration experimental platform is constructed to conduct frequency sweep tests. The experimental results demonstrate that the proposed piezoelectric–electromagnetic coupled bimodal broadband vibration energy harvester effectively improves energy harvesting efficiency. Within the frequency range of 5–20 Hz, the system exhibits two vibration modes, with resonant frequencies of approximately 7.7 Hz and 15.7 Hz. For a single-layer PVDF piezoelectric film, the maximum output power at the first and second resonance points is 8.9 μW and 9.7 μW, respectively. The electromagnetic module achieves maximum output powers of 0.39 W and 0.71 W. Moreover, within the frequency ranges of 6.3–9.8 Hz and 14–17.7 Hz (a total bandwidth of 7.2 Hz), the device maintains a stable power output. The effective bandwidth is broadened by approximately 80%, demonstrating excellent broadband performance. Full article

Mitral valve prolapse represents the most common cause of primary mitral regurgitation in Western countries and has traditionally been viewed as a disorder driven by valvular incompetence and chronic volume overload. Within this paradigm, left ventricular enlargement was expected to correlate with regurgitant severity. However, patients with myxomatous bileaflet prolapse often exhibit left ventricular dilatation disproportionate to the degree of regurgitation, leading to the hypothesis of an intrinsic myocardial disease process. Cardiovascular magnetic resonance imaging has challenged this concept through the identification of doming volume, a previously unrecognized systolic blood compartment located between the mitral annular plane and the ventricular surface of prolapsing leaflets. This volume is mechanically coupled to ventricular contraction and contributes to total ventricular volume load independently of transvalvular regurgitation. Recognition of doming volume provides a physiological explanation for excessive ventricular remodeling observed in bileaflet prolapse and Barlow disease. Doming volume has important implications for imaging assessment. Its common exclusion from echocardiographic volumetric measurements may result in underestimation of left ventricular end-systolic volume, overestimation of ejection fraction, and underestimation of regurgitant burden, contributing to discordance between echocardiographic and cardiovascular magnetic resonance-derived measurements. Cardiovascular magnetic resonance enables comprehensive assessment, allowing accurate quantification of ventricular volumes, mitral regurgitation severity, doming volume, and myocardial tissue characteristics. Integration of doming volume into the evaluation of mitral valve prolapse improves physiological consistency between imaging findings and ventricular remodeling. However, further evidence is required before doming volume assessment can be incorporated into operative clinical indications or decision-making thresholds. Full article

Secondary plant metabolites such as polyphenols (flavonoids, phenolic acids, stilbenes, and lignans) are valued for their numerous benefits and commonly associated with antioxidants, anti-inflammatory, anticancer, neuroprotective, and antidiabetic effects. Comprehensive profiling facilitates their identification and quantification, with metabolomics emerging as an increasingly valuable tool. This current work provides an overview of recent application of metabolomics for investigating polyphenols with nutraceutical potential. It also highlights the influence of plant species and environmental stressors (both biotics and abiotic) inducing metabolic shifts that promote the production and accumulation of these bioactive compounds (BACs). While various analytical tools including mass spectrometry (MS) coupled with liquid chromatography (LC-MS) or gas chromatography (GC-MS), as well as nuclear magnetic resonance (NMR) spectroscopy have been utilized to identify the diverse group of polyphenol metabolites, LC-MS has been predominantly used due to its superior sensitivity and wider metabolite coverage, with flavonoids being the main compounds identified. The integration of bioinformatic tools and pathway enrichment analysis in metabolomics is providing expansive insight into the pool of polyphenols, and their bio-functional interpretation and metabolic variations beyond the narrow scope of chromatographic separation alone. This overview also identifies limitations of current methods and suggests directions for future research, aimed at facilitating the development of nutraceuticals. Full article

Background: Right ventricular (RV) dysfunction is a key contributor to morbidity and mortality in systemic sclerosis (SSc), emerging from the combined effects of microvascular disease, myocardial fibrosis, interstitial lung involvement, and increasing pulmonary vascular load. Conventional echocardiography frequently fails to detect early RV impairment, prompting growing interest in deformation-based parameters such as RV free-wall longitudinal strain (RV-FWS), global longitudinal strain (RV-GLS), and RV–pulmonary artery (PA) coupling indices. Although natriuretic peptides reflect myocardial stress and are widely used in cardiopulmonary diseases, their integration with advanced RV imaging has been inconsistently reported in SSc. This systematic review synthesizes available evidence on RV strain, RV–PA coupling, and their relationship with clinical outcomes and biomarkers in SSc. Methods: A systematic search was conducted to identify clinical studies evaluating RV strain (RV-FWS, RV-GLS), right atrial strain, or RV–PA coupling indices in adult patients with SSc or SSc-associated pulmonary arterial hypertension (SSc-PAH). Eligible studies included those using speckle-tracking echocardiography or cardiac magnetic resonance feature-tracking. Study selection and data extraction were performed in accordance with PRISMA guidelines. Results: Seven studies met the eligibility criteria. Across unselected SSc cohorts, early disease without pulmonary hypertension (PH), and right-heart-catheterization-confirmed SSc-PAH, RV strain consistently detected myocardial impairment even when conventional echocardiographic indices remained normal. RV-FWS and RV-GLS were commonly reduced, and longitudinal data demonstrated progressive deterioration independent of standard measures. Strain-derived RV–PA coupling, particularly RV-FWS/PASP, significantly improved prognostic stratification when added to established PAH risk models. Two studies identified impaired RV deformation as a predictor of mortality, and CMR-derived right atrial strain provided additional prognostic value. Biomarker integration was limited, with only one study reporting an association between natriuretic peptide elevation (NT-proBNP) and impaired RV–PA coupling suggesting that biomarkers may reflect the hemodynamic load, although evidence remains limited captured by strain abnormalities. Conclusions: RV strain and RV–PA coupling indices are more sensitive than conventional echocardiography for detecting early RV dysfunction, monitoring disease progression, and predicting adverse outcomes in SSc. Although biomarker evidence remains limited, available data suggest that natriuretic peptides may provide complementary information to deformation-based assessment, although current evidence remains limited by reflecting combined myocardial and pulmonary vascular load. Standardized prospective studies including both strain imaging and biomarkers are needed to clarify the integrated diagnostic and prognostic value of advanced RV assessment in SSc. Full article

Biodegradable metals represent a paradigm shift in orthopedic fixation by providing temporary mechanical support synchronized with bone healing while eliminating long-term complications associated with permanent implants. Conventional bioinert alloys, including stainless steels, Ti-based alloys, and Co-Cr alloys, exhibit high elastic moduli that induce stress shielding and often require secondary removal surgeries. In response, resorbable metallic systems based on Mg, Zn, and Fe have emerged as promising alternatives. Among these, Fe-Mn-C alloys stand out for load-bearing applications due to their exceptional strength-ductility balance governed by twinning-induced plasticity mechanisms, tunable degradation behavior, and intrinsic magnetic resonance imaging compatibility through austenitic phase stabilization. Focusing on Fe-Mn-C alloys, this review critically examines the metallurgical design principles underlying stacking fault energy optimization, phase stability, and Mn-controlled electrochemical behavior. Processing innovations, such as additive manufacturing, are discussed as tools to architecture porosity, refine microstructure, and accelerate degradation by graded designs while preserving mechanical structural support during healing. Hybrid metallic-bioactive systems, surface functionalization strategies, and functionally graded porous architectures were evaluated as advanced approaches to enhance osteointegration and modulate degradability. Despite these advances, significant barriers remain for clinical translation. Persistent discrepancies between in vitro and in vivo degradation rates, often attributed to biological encapsulation and degradation product accumulation, complicate lifetime prediction. Localized corrosion at microstructural heterogeneities such as twin boundaries and phase interfaces can undermine structural reliability under load-bearing conditions. Moreover, predictive multi-physics modeling frameworks capable of coupling electrochemical kinetics, mechanical loading, microstructural evolution, and bone remodeling remain underdeveloped, limiting reliable safety-margin estimation. Regulatory progress is further hindered by the absence of standardized testing protocols specifically tailored to Fe-based biodegradable alloys, including harmonized degradation rate windows, validated corrosion-mechanics coupling methodologies, and clinically defined Mn ion release thresholds. This review aims to discuss whether Fe-based alloys, especially Fe-Mn-C alloys, can transition from promising laboratory materials to clinically viable next-generation orthopedic implants capable of delivering patient-specific, mechanically compatible, and biologically synchronized temporary fixation. Full article

Traditional cardiovascular assessment has historically focused on the isolated evaluation of either atrial or ventricular structure and function. However, the left atrioventricular coupling index (LACI) represents a paradigm shift by moving beyond single-chamber metrics to quantify the dynamic interaction between the left atrium and left ventricle. Defined as the ratio of left atrial end-diastolic volume to left ventricular end-diastolic volume, LACI integrates structural and functional aspects of cardiac performance. This comprehensive review examines the physiological basis of how the left atrium and ventricle operate as an integrated hemodynamic unit. We detail current measurement methodologies, including two- and three-dimensional echocardiography, cardiac computed tomography, and cardiac magnetic resonance imaging, which serves as the reference standard. Furthermore, the review explores the pathophysiological mechanisms driving atrioventricular uncoupling, specifically mechanical dysfunction, electromechanical desynchrony, and hemodynamic alterations. Extensive clinical evidence demonstrates LACI’s robust independent prognostic value across diverse cardiovascular conditions, such as heart failure, myocardial infarction, cardiomyopathies, and atrial fibrillation. Observational data suggest that LACI provides a promising prognostic value beyond established risk assessment tools by combining the assessment of both chambers’ interdependence. Finally, we outline future directions for clinical translation, highlighting the necessity for standardized measurement protocols, the integration of artificial intelligence, and the potential of LACI as a target for personalized therapeutic strategies. Full article

This paper presents the design, prototype realization, and experimental validation of an inductive wireless power transfer (WPT) platform for static charging of electric vehicles. The study integrates magnetic-coupler design, resonant power-stage realization, and occupied-area magnetic-field assessment within a prototype-oriented engineering framework. The realized Tx/Rx magnetic assembly has dimensions of approximately 700 × 800 × 60 mm per coil, an inductance of about 60 μH, a coupling factor of about 0.45, and estimated coil losses of around 2%. The proposed system belongs to the 35 kW class, while the realized prototype was experimentally validated at a nominal 30 kW operating level, with peak capability up to 45 kW for 1 min. Experimental evaluation was carried out for air gaps up to about 100 mm, with measured transfer efficiency in the range 80–92% and favorable operation around 30 kW and a vertical air gap of approximately 70 mm. Representative occupied-area magnetic-flux-density measurements remained below the adopted 27 μT reference level under the reported operating conditions. The results confirm the practical feasibility of the proposed static EV charging platform and support its engineering relevance for high-power inductive charging applications. Possible extension toward on-route charging is discussed only as future work. Full article

A graphene-based tunable broad-band terahertz (THz) metamaterial absorber is presented, exhibiting strong and stable absorption across a wide frequency range. The device employs an ultra-thin three-layer structure consisting of a metallic reflector, a dielectric spacer, and a patterned graphene metasurface with an asymmetric geometry. Through optimized structural parameters, the absorber achieves broad-band absorption exceeding 90% between 2.45 THz and 6.11 THz with a bandwidth of 3.66 THz, featuring three distinct resonant frequencies at 2.764 THz, 3.534 THz, and 5.41 THz, corresponding to peak absorption efficiencies of 97.26%, 96.96%, and 99.90%, respectively. Impedance matching and electric field analyses confirm that the enhanced absorption arises from the strong coupling of electric and magnetic resonances within the multilayer structure. Moreover, the absorber exhibits polarization-insensitive behavior under varying polarization angles and maintains high absorption stability for both TE and TM modes up to an incident angle of 60°, as verified by simulation results, and allows dynamic tunability through Fermi-level modulation. These characteristics highlight the absorber’s potential for advanced THz imaging, sensing, and stealth applications. Full article

Butyrate, a short-chain fatty acid produced by the fermentation of soluble dietary fiber by gut bacteria, also functions as a histone deacetylase inhibitor known to induce apoptosis and promote differentiation in colon tumor cells. During tumorigenesis, cancer cells undergo metabolic reprogramming to meet energetic and biosynthetic demands, increasing glycolytic metabolism and reducing oxidative metabolism—a phenomenon known as the Warburg effect. This study aimed to evaluate the impact of butyrate on the aggressiveness-related metabolic phenotype of three colon cancer cell lines (LS1034, C2BBe1, and WiDr). Butyrate’s effects were assessed through fluorine-18 fluorodeoxyglucose ([¹⁸F]FDG) uptake, flow cytometry analysis of cytoplasmic and membrane expression of glucose transporters (GLUT1, GLUT3, GLUT5, and GLUT12), lactate production, and analysis of Krebs cycle turnover and glycolysis–Krebs cycle coupling using nuclear magnetic resonance isotopomer profiling. [¹⁸F]FDG uptake decreased in C2BBe1 and WiDr cells, whereas an opposite response was observed in LS1034 cells, which also exhibited reduced GLUT5 expression. These uptake patterns were consistent with lactate production measurements, and an enhancement of oxidative metabolism was detected in C2BBe1 and WiDr cells. Although butyrate was consumed by all three cell lines, its metabolic handling appeared to differ in LS1034 cells, possibly reflecting cytotoxic stress and/or distinct metabolic regulation mechanisms. Overall, these findings indicate that butyrate exerts cell-line-dependent metabolic effects in colorectal cancer cells. In C2BBe1 and WiDr cells, butyrate exposure was broadly consistent with the attenuation of glycolytic/Warburg-associated features, whereas LS1034 cells displayed a divergent response and were interpreted separately. These data support further investigation of butyrate as a modulator of colorectal cancer cell metabolism, while highlighting the heterogeneity of metabolic responses across tumor models. Full article