Search Results (35,725)

This study designs a complementary split-ring resonator (CSRR)-based 5 GHz patch-type microwave resonant sensor for measuring the concentrations of glucose solutions under static and dynamic conditions. Circulating glucose solutions were used to simulate blood glucose, and the CSRR sensor was operated over a frequency range of 4.8–5.0 GHz. The planar microstrip configuration of the CSRR creates a highly confined electric field within the sensing area. When glucose solution covers or flows through the sensing region, the dielectric loading changes, altering the resonance condition and inducing perturbations. Identifiable measurement features can be extracted from data on the scattering parameter S₁₁. Glucose solutions with concentrations ranging from 5% to 65% were used to examine the response of the proposed sensor. The concentrations of these solutions were estimated on the basis of resonant frequency shifts, and variation in S₂₁ at the CSRR’s resonant frequency (or at a fixed frequency corresponding to the maximum slope) was also analyzed. Full article

Postural control is essential for daily function, and while stochastic resonance (SR) enhances balance in clinical populations, its efficacy in healthy young people remains underexplored. This study investigated (1) biomechanical effects of multisite plantar vibration on postural stability using center-of-pressure (CoP) parameters, and (2) short-term and sustained effects on balance performances. Phase 1 enrolled six participants to identify the optimal plantar stimulation configuration and to evaluate acute electromyographic responses under threshold-level vibration. Phase 2 evaluated long-term efficacy through an eight-week sham-controlled parallel-group randomized controlled trial. In this trial, eight participants received vibration combined with balance training, and another eight participants completed the same training protocol using sham insoles without vibration, analyzing CoP parameters (95% ellipse area, path length) and muscle activation (tibialis anterior, medial gastrocnemius, peroneus longus, extensor digitorum longus). Results showed full-site vibration reduced CoP area versus control (265.66 ± 188.6 mm² vs. 437.84 ± 190.95 mm², p < 0.05) without altering ankle muscle activation (all p > 0.05). Longitudinal analysis revealed CoP area reduction (−4.88 ± 10.42%) in the intervention group versus sham (p < 0.001), with maximum anterior displacement increasing by 25.03% during vibration (p < 0.05). Plantar white-noise vibration modulates CoP oscillations without neuromuscular activation changes, demonstrating that full-site stimulation acutely enhances postural stability while sustained intervention improves dynamic balance control. Full article

Perineural spread (PNS) from cutaneous squamous cell carcinoma (cSCC) to the skull base is increasingly recognised as a route of cancer spread. Management historically involved definitive radiotherapy to treat PNS at the skull base. In the endemic region with modern magnetic resonance neurogram (MRN) and skull base surgical expertise, the outcome has improved over the years. With the advent of immunotherapy, the outcome may be maintained while preserving critical organs in the head and neck region. We conducted a critical review of the literature to establish the treatment outcomes and pattern of failure as practice evolved. Furthermore, we described our skull base surgical and radiotherapy management guideline and outlined the emerging paradigm shift in the immunotherapy era. Full article

Tight oil reservoirs are characterized by poor petrophysical properties. After hydraulic fracturing, the low flowback rate of fracturing fluid readily leads to the formation of a water invasion zone in the near-wellbore region, which severely restricts the performance of Carbon dioxide (CO₂) huff-n-puff. To clarify the damage mechanism of the water invasion zone on CO₂ huff-n-puff in tight oil reservoirs and determine the key regulatory parameters, tight cores with a relative water invasion zone length Δδ = 0.3 were adopted as the research subject. Five groups of injection–soaking–production time combinations were designed, and single-factor analysis was implemented using the control variable method. Integrated with numerical simulation and nuclear magnetic resonance (NMR) testing, the influence of the water invasion zone, pore crude oil mobilization characteristics, and parameter regulation effects were systematically explored. The results demonstrate that the water invasion zone occupies effective pore throats to form a continuous water-phase barrier, hindering CO₂ seepage and mass transfer. After four huff-n-puff cycles, the cumulative recovery factor of the water-invaded model is 4.13 percentage points lower than that of the water-free model. After four huff-n-puff cycles, the cumulative recovery factor of the water-invaded model is 4.13 percentage points lower than that of the water-free model. The NMR T₂ spectra of cores with and without water invasion exhibit remarkable discrepancies: the water-free core presents a unimodal structure, while the water-invaded core features a distinctive bimodal structure, with obvious staged characteristics in crude oil mobilization. The recovery factor declines nonlinearly and sharply with the increase of Δδ, verifying that the water invasion zone length is the dominant controlling factor. The regulation effects of injection, soaking, and production time differ significantly: injection time serves as the pivotal parameter for enhancing oil recovery. Prolonging injection time can strengthen displacement intensity and dismantle the water-phase barrier, thereby elevating the recovery factor, whereas soaking time and production time have no significant improvement effect. The results can provide valuable references for the parameter optimization of CO₂ huff-n-puff in water-invaded tight oil reservoirs. Full article

In this study, we propose a novel approach to enhance upper stop-band attenuation in a split-ring resonator-based bandpass filter by partially inserting W-type hexaferrite films into a strategically placed mechanical hole. The hexaferrite exhibits a substantial increase in magnetic loss tangent in the desired band owing to ferromagnetic resonance, considerably improving attenuation in the upper stop-band while maintaining an acceptable insertion loss in the pass-band. The obtained results indicate that selectively placing the hexaferrite film enhances out-of-band rejection by up to 4 dB, with a slight degradation of 0.84 dB in pass-band insertion loss. Before inserting the hexaferrite film, the bandpass filter exhibited an insertion loss of 1.01 dB at 28 GHz and an attenuation of 20.04 dB at 32 GHz. By contrast, after inserting the hexaferrite film, the bandpass filter exhibited an insertion loss of 1.95 dB at 28 GHz and an attenuation of 24.45 dB at 32 GHz. Full article

Resonant transfer and excitation (RTE) is a correlated two-electron ion–atom collision process mediated by the two-center electron–electron interaction: a projectile electron is excited while a target electron is captured, forming doubly excited states. These states decay via X-ray (RTEX) or Auger (RTEA) emission. For sufficiently fast collisions with light targets, RTE becomes analogous to dielectronic capture (DC)—a key plasma process—and is successfully described by the impulse approximation (IA). Early (1983–1992) RTEX and more stringent, state-selective RTEA measurements provided essential indirect DC cross-section information before direct electron–ion measurements became available. A 1992 review by the first author,focusing on zero-degree Auger projectile spectroscopy (ZAPS) of state-selective KLL D states, validated the IA for low-$Z_p$ ($Z_p\le 9$) projectile ions, yet a puzzling systematic discrepancy remained: IA RTEA cross-sections were consistently larger than experimental, with the disagreement increasing as $Z_p$ decreased. The present article reviews RTEA progress since 1992, including new refinements to IA calculations, an exact analytic IA formulation, and instrumental ZAPS improvements. A methodical analysis demonstrates impressive agreement across measurements spanning both pre- and post-1992 eras, including new experimental results, effectively eliminating previous systematic discrepancies. IA validity is confirmed down to boron ions, with He${}^{+}$ and certain Li-like ions remaining the only notable exceptions. Recently, a rigorous quantum mechanical ion–atom collision treatment has emerged: nonperturbative close-coupling calculations of transfer excitation for He-like carbon ions colliding with He confirm the dominance of RTE via two-center electron–electron interactions at large impact parameters, yielding RTEA results in excellent agreement with experiments. Full article

Background: Dual-energy computed tomography (DECT) with virtual non-calcium (VNCa) reconstruction is emerging as an alternative method for identifying bone marrow edema (BME) in cases of inflammatory sacroiliitis, especially when magnetic resonance imaging (MRI) is contraindicated or unavailable. Objectives: The aim of this systematic review and meta-analysis is to evaluate the diagnostic performance of DECT with VNCa reconstruction for detecting BME in inflammatory sacroiliitis, using MRI as the reference standard. Methods: Following PRISMA-DTA guidelines and a pre-registered PROSPERO protocol (CRD420251103652), we searched PubMed, Web of Science, and the Cochrane Library up to June 2025. Seven studies comprising 358 patients and 591 sacroiliac joints were included. Quality assessment was performed using QUADAS-2. Pooled sensitivity and specificity were calculated using a bivariate random-effects regression model. Heterogeneity was evaluated using the I² statistic. Subgroup analyses were performed for anatomical site and slice thickness, along with a meta-regression according to anatomical site. Publication bias was assessed using Deeks’ test. Results: Quality assessment revealed a moderate risk of bias, primarily related to patient selection. The pooled sensitivity and specificity of DECT VNCa were 78% (95% CI: 65–88%) and 83% (95% CI: 71–91%), respectively. The area under the SROC curve was 0.91 (95% CI: 0.88–0.93), indicating good diagnostic accuracy. Heterogeneity was moderate for sensitivity (I² ≈ 68%) and high for specificity (I² ≈ 88%), largely driven by one outlier study. Sensitivity was lower for sacral BME than for iliac BME (69% vs 79%), although this difference did not reach statistical significance (p ≈ 0.07). Specificity tended to be higher with slice thickness ≥1 mm than with <1 mm (90% vs 84%), although the difference was not statistically significant (p ≈ 0.06). Exclusion of one outlier study (Deppe et al.) increased pooled specificity to 92% and reduced heterogeneity. Deeks’ test did not reveal significant publication bias. Conclusions: DECT VNCa has been shown to be highly accurate in the diagnosis of inflammatory sacroiliac BME. Its high specificity makes it suitable for confirming inflammatory activity when an MRI scan is not feasible. However, its sensitivity is moderate and variable, with a trend towards lower values for sacral lesions. This precludes its use as a standalone test to rule out active inflammatory sacroiliitis, especially in young patients. Standardization of acquisition protocols and site-specific diagnostic thresholds is recommended for optimal clinical implementation. Clinical Impact: Clarifying the diagnostic performance of VNCa of DECT to define its role as a complementary tool to MRI for assessing BME in inflammatory sacroiliitis. These results could guide appropriate patient selection and highlight the need for standardized protocols. Full article

Background and Objectives: Vascular dementia (VaD) and mixed dementia (MD) represent prevalent causes of cognitive decline in the elderly, as they share similar pathological pathways and clinical features. Distinguishing between these two conditions remains a challenge, due to their frequent clinical and neuroimaging overlap. Nevertheless, it is important from a prognostic perspective. Materials and Methods: The study comprised 114 participants, including patients with VaD (n = 33), MD (n = 26), Alzheimer’s disease (AD; n = 26), and 29 cognitively healthy controls (C). We evaluated routinely used cerebrospinal fluid (CSF) biomarkers (total tau, p-tau181, Aβ_1-42) and their ratios to assess inter-group differences, diagnostic accuracy, and correlations with cognitive score. Results: Patients with MD demonstrated significantly higher levels of t-tau and p-tau181, and lower levels of Aβ_1-42, compared to VaD (p < 0.004 for all analyses). With the exception of p-tau181/t-tau, all calculated ratios enabled differentiation between these groups. ROC analysis confirmed the high diagnostic accuracy of CSF Aβ_1-42 and t-tau (AUC 0.82 and 0.79 respectively) for detecting AD pathology in dementia patients. Furthermore, the t-tau/Aβ_1-42, p-tau181/Aβ_1-42 ratios were the most effective in differentiating AD-related from vascular pathologies (AUC 0.78 and 0.80 respectively), and in differentiating MD from VaD (AUC 0.79 and 0.77 respectively). A significant correlation was observed between CSF biomarkers (especially tau markers) and cognitive impairment severity. Conclusions: CSF biomarkers effectively differentiate mixed from vascular dementia by identifying underlying AD pathology independent of the clinical phenotype. This supports the use of CSF biomarkers in clinical practice to reveal the neurodegenerative component in patients with cerebrovascular disease, which is of fundamental importance for emerging disease-modifying treatment strategies in mixed neuropathologies. Full article

In high-frequency 400 V/48 V matrix planar LLC resonant converters for data center power supplies, enlarged interwinding parasitic capacitance can induce significant transformer-related common-mode (CM) displacement currents. However, the effects of secondary-side rectifier commutation and local winding position on the resulting CM spikes have not been sufficiently clarified. This paper establishes a unified analytical expression for the transformer-related CM current in a converter with a half-bridge primary and a full-bridge synchronous-rectifier (SR) secondary. The analysis shows that asynchronous SR commutation shifts the secondary reference potential and introduces additional excitation through the interwinding parasitic capacitances, thereby producing double-pulse CM current spikes. The unequal spike amplitudes among different secondary-side rectifier units are further explained by the combined effects of local winding position and distributed parasitic coupling. Based on these findings, a shielding-layer scheme was then proposed and verified on a 400 V/48 V, 300 kHz, 3 kW prototype. The experimental results show average reductions of about 15 dB over 150 kHz–800 kHz and 20 dB over 800 kHz–6.5 MHz in the CM voltage spectrum, whereas the prototype achieves a peak efficiency of 97.78%. Full article

This article describes a study on the synthesis and annealing processes of thin-film coatings of vanadium oxide on flat, parallel substrates made of quartz glass, sapphire, and silicon, as well as optical fibers using an organometallic precursor, triisopropoxy vanadium (V) oxide. For the first time, optical constants of nanomaterials were estimated in real time during synthesis and subsequent annealed using the lossy-mode resonance effect. The coatings produced in an inert atmosphere after deposition were amorphous, comprising a mixture of VO₂, V₂O₅, V₆O₁₃, and V₃O₅. This method allowed for accurate determination of the threshold temperature for the transformation of oxide mixtures into a monocomponent phase. Optimal conditions for synthesis and annealing were determined for the production of vanadium dioxide (VO₂) and pentoxide (V₂O₅). Morphological changes in coated surfaces were observed as a result of heat treatment. The composition and properties of these samples were studied using optical, terahertz and Raman spectroscopy, as well as temperature-dependent analysis of electrical resistance. The morphology of the coating surface was determined using a scanning electron microscope and an atomic force microscope. The reduction of VO_x to VO₂ was studied in an atmosphere of hydrogen and argon during annealing after deposition, with its effectiveness being compared. It was shown for the first time that the reduction of higher vanadium oxides is due to the presence of elemental carbon in the volume of the material formed from a metalorganic precursor during growth of vanadium oxide. Coatings obtained by annealing in hydrogen had a smaller hysteresis loop width (~5 °C) during phase transition compared to coatings obtained by argon annealing (~9 °C). Both types of coatings demonstrated a 50–60% increase in transmission at 1 THz frequency and in the IR region, accompanied by a 10³–10⁴-fold change in electrical resistance. Full article

Piezoelectric cantilever beam harvesters are widely considered for self-powered bridge monitoring, yet their performance is often constrained by resonance detuning under low-frequency ambient vibrations. This issue is particularly pronounced in bridge environments, where the dominant vibration frequencies are typically low and narrowly distributed. While several frequency tuning strategies have been proposed, their relative effectiveness under bridge-relevant conditions has not been systematically evaluated within a unified experimental framework. This study experimentally evaluated four tuning strategies for cantilever piezoelectric energy harvesters, i.e., spring tuning, magnetic tuning, tip mass adjustment, and beam length modification, to identify effective methods for matching the dominant frequency of bridge deck vibrations. A unified test platform using a common harvester configuration was established, and performance was quantified by resonant frequency alignment, maximum output voltage, and −3 dB bandwidth. Among the four methods, root-based spring tuning showed the best overall performance, achieving frequency matching while retaining strong electrical output, with a maximum voltage of 9.01 V and a bandwidth of approximately 1.5 Hz. Magnetic tuning also provided accurate frequency control, but reduced voltage by 15–25%. By contrast, tip mass and beam length tuning produced larger resonance shifts but caused voltage reductions of up to approximately 50%. Full article

Background: Liver histology remains the gold standard for assessing liver steatosis (LS); however, non-invasive methods are increasingly being explored in clinical practice. This study aimed to evaluate the agreement between magnetic resonance imaging (MRI) and liver histology in quantifying LS in patients with morbid obesity undergoing bariatric surgery (BS). Methods: This ancillary study is part of a prospective, double-blind, multicenter, randomized placebo-controlled trial investigating the effects of preoperative omega-3 polyunsaturated fatty acid supplementation on liver volume in morbidly obese patients undergoing BS. The parent trial yielded negative results, and randomization arm was retained as a covariate in all analyses. Patients underwent MRI within 2 days before surgery, followed by intraoperative wedge resection and TruCore needle liver biopsy. Agreement between MRI and histology was assessed using the intraclass correlation coefficient (ICC) and Cohen’s kappa coefficient (K) for both macro- and microvesicular steatosis. Results: Thirty-seven patients were enrolled; paired MRI and biopsy data were available for thirty-one (83.8%). Moderate and statistically significant agreement was observed between MRI and both TruCore (ICC: 0.52, p = 0.002; K: 0.42, p = 0.007) and wedge-resection (ICC: 0.53, p = 0.001; K: 0.29, p = 0.044) biopsies for macrovesicular steatosis. The MRI-derived values were systematically lower than histological estimates for macrovesicular steatosis (mean MRI: 23.4% vs. histology: 36.7–37.1%). No significant agreement was identified for microvesicular steatosis with either biopsy technique. Conclusions: In morbidly obese patients, MRI demonstrates only moderate agreement with liver histology for macrovesicular steatosis and is unreliable for microvesicular steatosis. The systematic underestimation of macrovesicular steatosis by MRI warrants caution when this modality is used as a standalone decision-making tool in this population. Further studies in larger and more heterogeneous cohorts are needed to better define the performance boundaries of MRI-derived fat-fraction measurement across the spectrum of obesity and metabolic liver disease. Full article

Background/Objectives: Brain tumors are highly lethal cancers, with gliomas representing the most complex subtype. Magnetic resonance imaging (MRI) is the main non-invasive imaging modality. This review evaluates deep learning (DL) and artificial intelligence methods for brain tumor segmentation and classification. Methods: In this systematic review, PubMed and Scopus were searched for articles published from 2022 to March 2025. Authors independently identified eligible studies based on predefined inclusion criteria and extracted data. The study quality and risk of bias were assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) checklist. Results: Thirty-one studies met the inclusion criteria from 310 records, with eight addressing both segmentation and classification. Most segmentation studies used publicly available multiparametric MRI datasets. Performance varied by architecture and tumor region, with whole-tumor segmentation achieving the highest Dice Similarity Coefficient (DSC). Classical U-Nets reported DSC values ranging 80–87%, while models with residual or attention mechanisms exceeded 90%. Classification focused on tumor type and glioma grading, using features learned from multiparametric MRI. Reported accuracy ranged from 91.3% to 99.4%, with sensitivity and specificity often above 95%. However, variability across tumor subregions, limited external validation, reliance on public datasets, and heterogeneous preprocessing raise concerns about robustness and real-world generalizability. Evidence on the use of explainability methods for both tasks remains limited. Conclusions: DL models for glioma segmentation and classification demonstrate promising performance. However, standardized validation protocols, multi-center datasets, and the integration of explainable artificial intelligence techniques are needed to improve transparency, robustness, and clinical applicability. Full article

Background: The steady rise of prostate cancer in Saudi Arabia signals a critical public health shift that requires immediate investment in early detection and prevention to mitigate a future clinical crisis. Accurate diagnosis using multiparametric MRI and PI-RADS scoring remains challenging, as interpretations are highly experience-dependent and subspecialized radiologists are limited. Methods: To address this gap, this study introduces a novel Dual-Stream Attention Network designed to automate the classification of low-risk (PIRADS 2-3) versus high-risk (PIRADS 4-5) lesions from T2-weighted MRI. Leveraging a ResNet50 backbone, the architecture employs parallel streams for Local and Global Feature Processing, each enhanced by a Channel-Spatial Attention module to highlight diagnostically relevant regions. These features are integrated through a Cross-Stream Fusion mechanism and a gate-controlled Adaptive Feature Fusion module to optimize multi-scale information. The model was developed and validated on a regional dataset of 3850 images from Jazan Specialist Hospital and Prince Mohammed bin Naser Hospital. This research provides a standardized, high-precision diagnostic path tailored to the Saudi Arabian population, conducted under institutional review board approval (No. 25138). Results: The proposed dual-stream attention network achieved an accuracy of 97.8% on the validation set and 96.4% on the test set, demonstrating high performance and generalization capabilities in classifying prostate lesions from Saudi patient populations. Conclusions: The proposed dual-stream architecture with novel attention and fusion mechanisms demonstrates high effectiveness for prostate cancer classification from T2-weighted MRI in Saudi clinical settings. This represents the first deep learning model specifically trained and validated on Saudi Arabian prostate MRI data, with the potential to address the shortage of specialized expertise and improve diagnostic efficiency in the Kingdom. Full article

Background: Paramagnetic manganese (Mn(II)) has emerged as a promising alternative to gadolinium-based contrast agents (GBCAs) due to its favorable magnetic properties. Despite extensive research, no Mn-based agent has yet achieved clinical translation. Because free Mn(II) is toxic, macromolecular complexes incorporating stable macrocyclic DOTA chelators conjugated to polysaccharides may enhance coordination stability and improve the safety profile of Mn(II)-based contrast agents. Methods: Two chemical routes, maleimide- and ester-mediated, were evaluated for covalent coupling of DOTA-based macrocyclic ligands to the backbone of selected poly- and oligosaccharides. Subsequently, DOTA-modified carboxymethyldextran, aminodextran, and chitosan oligosaccharide were labeled with paramagnetic Mn(II) under mild conditions. ATR-FTIR confirmed the successful conjugation of DOTA chelators to the sugar backbone. The conjugates were further characterized by DLS, ICP-MS, and FPLC. In vitro relaxivity was measured at high field strength to evaluate MRI performance. In vivo contrast efficacy was first assessed using in ovo MRI in chicken embryos and subsequently evaluated by biodistribution studies in nude mice. Results: In vitro relaxivity studies demonstrated higher signal enhancement of the poly-/oligosaccharide-DOTA-Mn(II) conjugates compared with MnCl₂ and the clinical agent gadoteridol (ProHance^®). In ovo MRI showed persistent vascular enhancement up to 120 min, while in nude mice, contrast enhancement was observed in the liver, kidneys, and gallbladder 40 min post-injection. Conclusions: Mn(II)-tagged sugar-based imaging probes may offer a promising non-gadolinium alternative to GBCAs, with tunable biodistribution profiles depending on carrier molecular weight. Full article