Search Results (29,698)

Cerebral venous thrombosis (CVT) is a rare and potentially critical cerebrovascular disease involving intracranial dural sinuses and veins. The diagnosis is a stepwise pathway starting from clinical suspicion and employing several neuroradiological techniques, mainly Computed Tomography (CT)-based and Magnetic Resonance Imaging (MRI)-based modalities. The neuroradiological findings, both in the diagnostic phase and in the follow-up phase, may provide some results at risk for misdiagnosis. Non-thrombotic filling defects of intracranial dural sinuses are among them, and the potential sources are artefactual and or anatomical (venous septa and arachnoid granulations). The misdiagnosis of these findings as CVT is potentially linked to dangerous consequences. A potential strategy to avoid this is to increase the knowledge about technical and anatomical reasons for non-thrombotic filling defects of intracranial dural sinuses and their imaging features. The main aim of this review is to address these issues, including the variability of the intracranial venous pathways, providing the solutions for overcoming the above-cited potential misdiagnosis of non-thrombotic filling defects as CVT. Full article

This study introduces a machine learning (ML)-driven approach to next-generation microwave filter design that enhances both accuracy and efficiency via repeated refinement. The approach includes generating a coupling matrix from filter specifications, followed by predicting physical parameters such as iris widths and resonator lengths using ML models, especially with the XGBoost algorithm. These predictions are validated and tuned via simulations and iterative adjustments to ensure meeting the performance criteria, such as center frequency, bandwidth, and return loss. For tuning, in this work, we used Simulated Annealing to extract a coupling matrix to reduce errors and hence allow accurate further optimization. The predicted values before optimization are more than 90 percent accurate compared to the optimized values, significantly reducing the optimization time and the number of iterations required. To demonstrate the procedure’s validity, third-, fourth-, and fifth-order filters are implemented, which shows significant improvements in design efficiency and accuracy. Full article

Background/Objectives: After open-wedge high tibial osteotomy (OWHTO), the patella is displaced distally, causing patellofemoral joint degeneration. The objective of this study was to ascertain whether the combination of OWHTO and lateral retinacular release (LRR) can prevent articular cartilage degeneration of the patellofemoral joint using magnetic resonance imaging T2 mapping. Methods: This study included 37 patients (37 knees) who underwent OWHTO alone (OWHTO group) and 37 patients (37 knees) who underwent OWHTO with LRR (OWHTO + LRR group) with a correction angle of <10° for varus knee osteoarthritis. MRI was performed on all knees prior to and 6 months after surgery to assess the patellar cartilage in sagittal images for T2 mapping. Three regions of interest, (the medial facet, patellar ridge, and lateral facet), were established for the articular cartilage on the patellar side. The T2 values were subsequently quantified. Lower limb alignment, patellar height, patellar tilt angle, and lateral shift ratio were evaluated pre-and post-surgery. Results: Mean T2 values at 6 months post-surgery of the medial facet and patellar ridge of the OWHTO group showed a significant increase after surgery; no significant changes were observed in either region in the OWHTO + LRR group. In both groups, a significant decrease in patellar tilt angle was observed postoperatively; no change was noted in the lateral shift ratio or congruence angle. The change in patellar tilt angle was significantly lower in the OWHTO + LRR group than in the OWHTO group. Conclusions: LRR combined with OWHTO prevented patellofemoral joint cartilage degeneration after surgery in cases of varus knee osteoarthritis. Full article

Objectives:We wished to compare the diagnostic performance of texture analysis (TA) against that of a visual qualitative assessment in identifying early sacroiliitis (nr-axSpA). Methods: A total of 92 participants were retrospectively included at our university hospital institution, comprising 30 controls and 62 patients with axSpA, including 32 with nr-axSpA and 30 with r-axSpA, who underwent MR examination of the sacroiliac joints. MRI at 3T of the lumbar spine and the sacroiliac joint was performed using oblique T1-weighted (W), fluid-sensitive, fat-saturated (Fs) T2WI images. The modified New York criteria for AS were used. Patients were classified into the nr-axSpA group if their digital radiography (DR) and/or CT results within 7 days from the MR examination showed a DR and/or CT grade <2 for the bilateral sacroiliac joints or a DR and/or CT grade <3 for the unilateral sacroiliac joint. Patients were classified into the r-axSpA group if their DR and/or CT grade was 2 to 3 for the bilateral sacroiliac joints or their DR and/or CT grade was 3 for the unilateral sacroiliac joint. Patients were considered to have a confirmed diagnosis if their DR or CT grade was 4 for the sacroiliac joints and were thereby excluded. A control group of healthy individuals matched in terms of age and sex to the patients was included in this study. First, two readers independently qualitatively scored the oblique coronal T1WI and FsT2WI non-enhanced sacroiliac joint images. The diagnostic efficacies of the two readers were judged and compared using an assigned Likert score, conducting a Kappa consistency test of the diagnostic results between two readers. Texture analysis models (the T1WI-TA model and the FsT2WI-TA model) were constructed through feature extraction and feature screening. The qualitative and quantitative results were evaluated for their diagnostic performance and compared against a clinical reference standard. Results: The qualitative scores of the two readers could significantly distinguish between the healthy controls and the nr-axSpA group and the nr-axSpA and r-axSpA groups (both p < 0.05). Both TA models could significantly distinguish between the healthy controls and the nr-axSpA group and the nr-axSpA group and the r-axSpA group (both p < 0.05). There was no significant difference in the differential diagnoses of the two TA models between the healthy controls and the nr-axSpA group (AUC: 0.934 vs. 0.976; p = 0.1838) and between the nr-axSpA and r-axSpA groups (AUC: 0.917 vs. 0.848; p = 0.2592). In terms of distinguishing between the healthy control and nr-axSpA groups, both the TA models were superior to the qualitative scores of the two readers (all p < 0.05). In terms of distinguishing between the nr-axSpA and r-axSpA groups, the T1WI-TA model was superior to the qualitative scores of the two readers (p = 0.023 and p = 0.007), whereas there was no significant difference between the fsT2WI-TA model and the qualitative scores of the two readers (p = 0.134 and p = 0.065). Conclusions: Based on MR imaging, the T1WI-TA and fsT2WI-TA models were highly effective for the early diagnosis of sacroiliac joint arthritis. The T1WI-TA model significantly improved the early diagnostic efficacy for sacroiliac arthritis compared to that of the qualitative scores of the readers, while the efficacy of the fsT2WI-TA model was comparable to that of the readers. Full article

This paper introduces a novel method for measuring the dielectric permittivity of materials within the microwave and millimeter wave frequency ranges. The proposed approach, classified as a guided wave transmission system, employs a periodic transmission line structure characterized by mirror/glide symmetry. The dielectric permittivity is deduced by measuring the transmission properties of such structure when presence of the dielectric material breaks the inherent symmetry of the structure and consequently introduce a stopband in propagation characteristic. To explore the influence of symmetry breaking on propagation properties, an analytical dispersion equation, for both symmetries, is formulated using the Rigorous Coupled Wave Analysis (RCWA) combined with the matrix transverse resonance condition. Based on the analytical equation, an optimization procedure and linearized model for a sensing structure is obtained, specifically for X-band characterization of FR4 substrates. The theoretical results of the model are validated with full wave simulations and experimentally. Full article

A review of natural materials that exhibit negative permittivity or permeability, including gaseous plasma, metals, superconductors, and ferromagnetic materials, is presented. It is shown that samples made of such materials can store large amount of the electric (magnetic) energy and create plasmonic resonators for certain values of permittivity, permeability, and dimensions. The electric and the magnetic plasmon resonances in spherical samples made of such materials are analyzed using rigorous electrodynamic methods, and the results of the analysis are compared to experimental data and to results obtained with other methods. The results of free oscillation and Mie scattering theories are compared. Similarities and differences between permittivity and permeability tensors for magnetized plasma and magnetized ferromagnetic materials are underlined. Several physical phenomena are explained on the grounds of rigorous electrodynamic analysis and experiments. These phenomena include unequal electric and magnetic energies stored in plasmonic resonators, the small influence of dielectric losses on the Q-factors of magnetic plasmon resonances, the role of radiation and dissipation losses on the properties of plasmonic resonators, and the theoretical possibility of the existence of lightning plasma balls. Full article

This article addresses the challenges of the reduced efficiency in phase-shifted full-bridge series resonant converters (PSFB-SRCs) used within micro-inverters (MIs), especially under light load and high input voltage conditions. To enhance performance, first-order and second-order time-domain equivalent models that accurately predict the output gain across a wide range of operating conditions are developed. A novel control strategy is proposed, featuring turn-on time as a feedback variable, with phase shift angle and dead time as feedforward variables, enabling precise computation of frequency, duty cycle, and phase shift time for digital controllers. This ensures optimal efficiency, stability, and dynamic response, regardless of the load conditions. Experimental results from the prototype confirmed zero-voltage switching under heavy loads and efficient frequency limiting under light loads, achieving a peak efficiency of 97.8% at a 25 V input. Notably, the light load efficiency remained above 90% even at a 50 V input. These contributions significantly advance PSFB-SRC technology, providing robust solutions for high-efficiency MI applications in photovoltaic systems. Full article

With the ever-growing demand for high-speed optical communications, microwave photonics, and quantum key distribution systems, compact electro-optic (EO) modulators with high extinction ratios, large bandwidth, and high tuning efficiency are urgently pursued. However, most integrated lithium–niobate (LN) modulators cannot achieve these high performances simultaneously. In this paper, we propose an improved theoretical model of a chip-scale electro-optic (EO) microring modulator (EO-MRM) based on X-cut lithium–niobate-on-insulator (LNOI) with a hybrid architecture consisting of a 180-degree Euler bend in the coupling region, double-layer metal electrode structure, and ground–signal–signal–ground (G-S-S-G) electrode configuration, which can realize highly comprehensive performance and a compact footprint. After parameter optimization, the designed EO-MRM exhibited an extinction ratio of 38 dB. Compared to the structure without Euler bends, the increase was 35 dB. It also had a modulation bandwidth of 29 GHz and a tunability of 8.24 pm/V when the straight waveguide length was 100 μm. At the same time, the proposed device footprint was 1.92 × 10⁴ μm². The proposed MRM model provides an efficient solution to high-speed optical communication systems and microwave photonics, which is helpful for the fabrication of high-performance and multifunctional photonic integrated devices. Full article

In this work, we have proposed and optimized a large mode area segmented cladding fiber (SCF) with an unconventional low-index segment cladding. The low-refractive-index cladding proposed in this paper consists of three parts. There three geometric parameters chosen as design variables were the length and width of the first part and the leg length of the isosceles trapezoid in the second part. To investigate the properties of the proposed SCF, numerical modeling based on the finite element method (FEM) was performed. A high leakage loss ratio (>9000) between the high-order modes (HOMs) and the fundamental mode was achieved at a wavelength of 1310 nm, which is significantly higher than that of conventional SCFs. Additionally, the mode area of the proposed fiber reaches 890 µm² at a core radius of 20 µm. The bending effects on the SCF were also studied. When the bending radius is greater than 0.3 m, the mode area greater than 880 µm² and remains stable, and the leakage loss of the least high-order mode (LP11h) exceeds 30 dB/m. The new fiber design demonstrates significant potential for high-power fiber lasers Full article

Objective: Literature regarding osteochondral lesions in patients following elbow dislocation is scarce. The aim of this study was to examine osteochondral lesions on MRI in patients following simple elbow dislocations and evaluate inter-rater reliability between radiologists and orthopedic surgeons at different levels of experience. Methods: In this retrospective, single-center study, 72 MRIs of patients following simple elbow dislocations were evaluated. Ligamentous and osteochondral injuries were evaluated by a junior and senior radiologist and a junior and senior orthopedic surgeon. Osteochondral lesions were classified according to the Anderson classification, and their distribution was assessed. Inter-rater reliability was assessed using Cohen’s Kappa (95% CI) and Fleiss’ Kappa (95% CI). Results: The mean time from injury to MRI was 6.92 ± 4.3 days, and the mean patient age was 42.4 ± 16.0 years. A total of 84.5% of patients had a lateral collateral ligament tear, and 69.0% had a medial collateral ligament tear. Osteochondral lesions were found in 27.8% to 63.9% of cases. According to the senior orthopedic surgeon, 100% were first-grade lesions, whereas the senior radiologist classified 63.2% as first-grade, 26.3% as second-grade, and 5.3% as third- and fourth-grade lesions. Inter-rater reliability was fair to moderate for ligamentous injuries and fair for osteochondral lesions (Fleiss Kappa 0.25 [0.15–0.34]). Localization of the lesions differed depending on the examiner. For all examiners, osteochondral lesions of the lateral column (radial head and capitulum) were most common, with 57.8–66.7% of all lesions. Inter-rater reliability was moderate for lesions in the medial column (Fleiss Kappa 0.51 [0.41–0.6]) and fair for lesions in the lateral column (Fleiss Kappa 0.34 [0.24–0.43]). Conclusions: Osteochondral lesions following simple elbow dislocations are common; however, in contrast to the current literature, high-grade lesions seem to be relatively rare. Overall inter-rater reliability between radiologists and surgeons, as well as within surgeons, was only moderate to fair regarding ligament and osteochondral lesions. Full article

With the wide application of Residence Time Difference (RTD) fluxgate sensors in Unmanned Aerial Vehicle (UAV) aeromagnetic measurements, the requirements for their measurement accuracy are increasing. The core characteristics of the RTD fluxgate sensor limit its sensitivity; the high-permeability soft magnetic core is especially easily interfered with by the input noise. In this paper, based on the study of the excitation signal and input noise characteristics, the stochastic resonance is proposed to be realized by adding feedback by taking advantage of the high hysteresis loop rectangular ratio, low coercivity and bistability characteristics of the soft magnetic material core. Simulink is used to construct the sensor model of odd polynomial feedback control, and the Particle Swarm Optimization (PSO) algorithm is used to optimize the coefficients of the feedback function so that the sensor reaches a resonance state, thus reducing the noise interference and improving the sensitivity of the sensor. The simulation results show that optimizing the odd polynomial feedback coefficients with PSO enables the sensor to reach a resonance state, improving sensitivity by at least 23.5%, effectively enhancing sensor performance and laying a foundation for advancements in UAV aeromagnetic measurement technology. Full article

In the development of optical absorption technology, achieving ultra-wideband high absorption structures that span from the 200 nm ultraviolet C region to the 5800 nm mid-infrared range has been a significant challenge in materials science. Previous studies have shown that few optical absorbers can simultaneously achieve an absorption rate above 0.900 and cover such a vast spectral range. This study presents an innovative seven-layer composite structure that successfully addresses this long-standing technical issue. Through a carefully designed layered architecture, the researchers employed COMSOL Multiphysics (version 6.0) for detailed numerical simulations to verify the optical performance of the structure. The structural design features two key innovations. In the layered composition, the bottom (h1), h3, and h5 layers are made of metallic Fe, while the layers above them (h2, h4, and h6) use SiO₂. The top layer is composed of a discontinuous cylinder Ti matrix. The first innovation involves the use of an inwardly recessed square design on the metallic Fe planes of the h4 and h6 layers, achieving high absorption across the 600–5800 nm range. The second innovation involves the use of the discontinuous cylinder Ti matrix for the top layer, which successfully enhances absorption performance in the 200–600 nm wavelength range. This structure not only employs relatively low-cost metals and oxide materials but also demonstrates significant optical absorption potential. Through numerical simulations and precise structural design, this study provides new ideas and technological pathways for the development of ultra-wideband optical absorbers. Full article

In this paper, a high-linear-sensitivity fiber curvature sensor based on the sphere-shaped misaligned structure (SSMS) with few-mode fiber (FMF) and single-mode fiber (SMF) was proposed and demonstrated. A spherical structure was prepared at one end of a few-mode fiber, which could effectively excite higher-order modes and generate interference in the misaligned cascade. When external environmental parameters changed, the resonance peaks formed by intermodal interference were displaced, and the shifts generated by different resonant peaks were also different. The experimental results show that the maximum curvature sensitivity was −2.220 nm/m⁻¹, and the linear fitting coefficient reached up to 0.991, which is an extremely high sensitivity among wavelength-modulated curvature sensors. Meanwhile, the strain sensitivity of the sensor was as low as 7.99 pm/με¯, and the temperature sensitivity was 3.958 pm/°C, which is a low temperature sensitivity and low strain sensitivity, and solves the cross-sensitivity problem. With advantages of simple manufacture, low cost, and favorable stability, the sensor is expected to be one of the best candidate instruments for measuring curvature and inclination. Full article

Background/Objectives: Acute ischemic stroke (AIS) is a leading cause of mortality and disability worldwide, with early and accurate diagnosis being critical for timely intervention and improved patient outcomes. This retrospective study aimed to assess the diagnostic performance of two advanced artificial intelligence (AI) models, Chat Generative Pre-trained Transformer (ChatGPT-4o) and Claude 3.5 Sonnet, in identifying AIS from diffusion-weighted imaging (DWI). Methods: The DWI images of a total of 110 cases (AIS group: n = 55, healthy controls: n = 55) were provided to the AI models via standardized prompts. The models’ responses were compared to radiologists’ gold-standard evaluations, and performance metrics such as sensitivity, specificity, and diagnostic accuracy were calculated. Results: Both models exhibited a high sensitivity for AIS detection (ChatGPT-4o: 100%, Claude 3.5 Sonnet: 94.5%). However, ChatGPT-4o demonstrated a significantly lower specificity (3.6%) compared to Claude 3.5 Sonnet (74.5%). The agreement with radiologists was poor for ChatGPT-4o (κ = 0.036; %95 CI: −0.013, 0.085) but good for Claude 3.5 Sonnet (κ = 0.691; %95 CI: 0.558, 0.824). In terms of the AIS hemispheric localization accuracy, Claude 3.5 Sonnet (67.2%) outperformed ChatGPT-4o (32.7%). Similarly, for specific AIS localization, Claude 3.5 Sonnet (30.9%) showed greater accuracy than ChatGPT-4o (7.3%), with these differences being statistically significant (p < 0.05). Conclusions: This study highlights the superior diagnostic performance of Claude 3.5 Sonnet compared to ChatGPT-4o in identifying AIS from DWI. Despite its advantages, both models demonstrated notable limitations in accuracy, emphasizing the need for further development before achieving full clinical applicability. These findings underline the potential of AI tools in radiological diagnostics while acknowledging their current limitations. Full article

In this experiment, the excellent coordination ability of sulfur-containing ligands was utilized. Diphenylacetyl disulfide and 3,3′-diaminodiphenyl sulfone were selected as ligands, and Cu(NO₃)₂·3H₂O, Ni(NO₃)₂·6H₂O and ZnCl₂ were reacted under one-pot conditions to synthesize three mononuclear complexes: [C₄H₁₈CuO₁₂S₂](I), [C₁₂H₁₈N₄NiO₁₁S](II) and [C₂₄H₂₄Cl₂N₄O₄S₂Zn](III). Complex (I) belongs to the orthorhombic crystal system with space group Pbca, while complexes (II) and (III) belong to the monoclinic crystal system with space groups P21/n and P2/n. The crystal structure of the complex was determined using X-ray diffraction (XRD). The structure of the complex was analyzed using infrared Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–Vis), nuclear magnetic resonance (NMR), and electrospray mass spectrometry (ESI-MS), and the thermal stability and composition of the complex were detected via thermogravimetry (TGA). In terms of application, the biological activity of complexes (I)–(III) in human cancer cell lines (lung cancer A549, liver cancer SMMC-7721, breast cancer MDA-MB-231, and colon cancer SW480) was tested using the MTS method. The results showed that complex (II) had a good inhibitory effect on breast cancer MDA-MB-231. Full article