Search Results (224)

With the introduction of advanced Fiber Bragg Grating (FBG) technology, Fabry–Pérot (FP) interferometers have become widely used in fiber-optic ultrasound detection. In these applications, the slope of the reflectance is a critical factor influencing detection results. Due to the intensity limitations of the laser source in fiber-optic ultrasound detection, the reflectance of the FBG is generally increased to enhance the signal-to-noise ratio (SNR). However, increasing reflectance can cause the reflectance curve to deviate from a sinusoidal shape, which in turn affects the slope of the reflectance and introduces greater errors. This paper first investigates the relationship between the transmission curve of the FP interferometer and reflectance, with a focus on the errors introduced by simplified assumptions. Further research shows that in sensors with asymmetric reflectance slopes, their transmittance curves deviate significantly from sinusoidal signals. This discrepancy highlights the importance of achieving symmetrical slopes to ensure consistent and accurate detection. To address this issue, this paper proposes an innovative method to adjust the rear-end reflectance of the FP interferometer by combining stress modulation, UV adhesive, and a high-reflectivity metal disk. Additionally, by adjusting the rear-end reflectance to ensure that the transmittance curve approximates a sinusoidal signal, the symmetry of the slope is maintained. Finally, through practical ultrasound testing, by adjusting the incident wavelength to the positions of slope extrema (or zero) at equal intervals, the expected ultrasound signals at extrema (or zero) can be detected. This method converts the problem of approximating a sinusoidal signal into a problem of the slope adjustment of the transmittance curve, making it easier and more direct to determine its impact on detection results. The proposed method not only improves the performance of fiber-optic ultrasound sensors but also reduces costs, paving the way for broader applications in medical diagnostics and structural health monitoring. Full article

Vector bending sensors can be utilized to detect the bending curvature and direction, which is essential for various applications such as structural health monitoring, mechanical deformation measurement, and shape sensing. In this work, we demonstrate a temperature-insensitive vector bending sensor via parallel Farby–Perot interferometers (FPIs) fabricated by etching and splicing a multicore fiber (MCF). The parallel FPIs made in this simple and effective way exhibit significant interferometric visibility with a fringe contrast over 20 dB in the reflection spectra, which is 6 dB larger than the previous MCF-based FPIs. And such a device exhibits a curvature sensitivity of 0.207 nm/m⁻¹ with strong bending-direction discrimination. The curvature magnitude and orientation angle can be reconstructed through the dip wavelength shifts in two off-diagonal outer-core FPIs. The reconstruction results of nine randomly selected pairs of bending magnitudes and directions show that the average relative error of magnitude is ~4.5%, and the average absolute error of orientation angle is less than 2.0°. Furthermore, the proposed bending sensor is temperature-insensitive, with temperature at a lower sensitivity than 10 pm/°C. The fabrication simplicity, high interferometric visibility, compactness, and temperature insensitivity of the device may accelerate MCF-based FPI applications. Full article

Background: In the United States, traumatic brain injury (TBI) contributes significantly to mortality and morbidity. Elovanoids (ELVs), a novel class of homeostatic lipid mediators we recently discovered and characterized, have demonstrated neuroprotection in experimental stroke models but have never been tested after TBI. Methods: A moderate fluid-percussion injury (FPI) model was used on male rats that were treated with ELVs by intravenous (IV) or intranasal (IN) delivery. In addition, using liquid chromatography-mass spectrometry (LC-MS/MS), we examined whether ELVs could be detected in brain tissue after IN delivery. Results: ELVs administered intravenously 1 h after FPI improved behavior on days 2, 3, 7, and 14 by 20, 23, 31, and 34%, respectively, and preserved hippocampal CA3 and dentate gyrus (DG) volume loss compared to the vehicle. Whole-brain tractography revealed that ELV-IV treatment increased corpus callosum white matter fibers at the injury site. In comparison to treatment with saline on days 2, 3, 7, and 14, ELVs administered intranasally at 1 h and 24 h after FPI showed improved neurological scores by 37, 45, 41, and 41%. T2-weighted imaging (T2WI) abnormalities, such as enlarged ventricles and cortical thinning, were reduced in rats treated by ELV-IN delivery compared to the vehicle. On day 3, ELVs were detected in the striatum and ipsilateral cortex of ELV-IN-treated rats. Conclusion: We have demonstrated that both ELV-IN and ELV-IV administration offer high-grade neuroprotection that can be selectively supplied to the brain. This discovery may lead to innovative therapeutic targets for secondary injury cascade prevention following TBI. Full article

In the field of fiber-optic sensing, effectively reducing the noise of sensing spectra and achieving a high signal-to-noise ratio (SNR) has consistently been a focal point of research. This study proposes a deep-learning-based denoising method for fiber-optic sensors, which involves pre-processing the sensor spectrum into a 2D image and training with a cycle-consistent generative adversarial network (Cycle-GAN) model. The pre-trained algorithm demonstrates the ability to effectively denoise various spectrum types and noise profiles. This study evaluates the denoising performance of simulated spectra obtained from four different types of fiber-optic sensors: fiber Fabry–Perot interferometer (FPI), regular fiber Bragg grating (FBG), chirped FBG, and FBG pair. Compared to traditional denoising algorithms such as wavelet transform (WT) and empirical mode decomposition (EMD), the proposed method achieves an SNR improvement of up to $13.71 \mathrm{dB}$, an RMSE that is up to three times smaller, and a minimum correlation coefficient ($R^2$) of no less than 99.70% with the original high-SNR signals. Additionally, the proposed algorithm was tested for multimode noise reduction, demonstrating an excellent linearity in temperature response with a $R^2$ of 99.95% for its linear fitting and $99.74\%$ for the temperature response obtained from single-mode fiber sensors. The proposed denoising approach effectively reduces the impact of various noises from the sensing system, enhancing the practicality of fiber-optic sensing, especially for specialized fiber applications in research and industrial domains. Full article

The stable flight of drones relies on Global Navigation Satellite Systems (GNSS). However, in complex environments, GNSS signals are prone to interference, leading to flight instability. Inspired by cross-view machine learning, this paper introduces the VDUAV dataset and designs the VRLM network architecture, opening new avenues for cross-view geolocation. First, to address the limitations of traditional datasets with limited scenarios, we propose the VDUAV dataset. By leveraging the virtual–real mapping of latitude and longitude coordinates, we establish a digital twin platform that incorporates 3D models of real-world environments. This platform facilitates the creation of the VDUAV dataset for cross-view drone localization, significantly reducing the cost of dataset production. Second, we introduce a new baseline model for cross-view matching, the Virtual Reality Localization Method (VRLM). The model uses FocalNet as its backbone and extracts multi-scale features from both drone and satellite images through two separate branches. These features are then fused using a Similarity Computation and Feature Fusion (SCFF) module. By applying a weighted fusion of multi-scale features, the model preserves critical distinguishing features in the images, leading to substantial improvements in both processing speed and localization accuracy. Experimental results demonstrate that the VRLM model outperforms FPI on the VDUAV dataset, achieving an accuracy increase to 83.35% on the MA@20 metric and a precision of 74.13% on the RDS metric. Full article

Objective: To evaluate the morphofunctional alterations in the foot and their association with functionality, considering aspects such as disability, pain, and limitations in daily activities in patients with fibromyalgia syndrome (FMS). Methods: A case–control study was conducted in patients with FMS (case group) and without FMS (control group), matched by age and sex. Foot posture was assessed using the foot posture index (FPI), along with the presence of hallux valgus (HV), trigger points, hyperkeratosis, and dorsiflexion of the first metatarsophalangeal joint and ankle. Foot functionality was evaluated using the foot function index (FFI) questionnaire. Results: A total of 100 women with FMS and 100 women without FMS, with a mean age of 61.97 ± 9.26 years, were recruited. HV (p < 0.001), hyperkeratosis (p < 0.001), pronated and supinated foot (p < 0.001), as well as limitations in dorsiflexion of the first metatarsophalangeal joint (p < 0.001) and the ankle with the knee flexed (p < 0.001) and extended (p < 0.001), along with the activity of the flexor hallucis brevis (p = 0.006), adductor hallucis (p = 0.006), and dorsal interosseous (p = 0.002) muscles, were significantly associated with the FFI, being higher in individuals with FMS, indicating greater impairment of foot functionality in these patients. Multivariate analysis revealed a statistical association between FMS and low educational level (OR = 2.57, 95% CI 1.05–5.72), the presence of another rheumatic disease (OR = 5.07, 95% CI 2.34–11), and the presence of any active trigger point (OR = 11.15, 95% CI 3.97–31.31). Conclusions: The study highlights the relationship between morphofunctional foot alterations, specifically the presence of active myofascial trigger points, and functionality in patients with FMS. Full article

Background/Objectives: Traumatic brain injury (TBI) is a global healthcare concern affecting millions, with wide-ranging symptoms including sensory and behavioral changes that can persist long-term. Due to similarities with human brain cytoarchitecture and inflammation, minipig models are advantageous for translational TBI research. However, gaps in knowledge exist regarding their behavioral and sensory sequelae following injury. Methods: Therefore, in this study, we assessed changes in approachability using a forced human approach task (FHAT) and mechanical nociception using the von Frey test in adult male and female Yucatan minipigs for up to one week following a sham or central fluid percussion injury (cFPI). Specifically, the FHAT assessed each animal’s response to a forced interaction with either a known or unknown experimenter. To evaluate changes in nociceptive sensory sensitivity, von Frey monofilaments ranging from 0.008 to 300 g of force were applied to the pinna of the ear or base of the tail. Results: We found that forced approachability was affected by experimenter familiarity as well as cFPI in a sex-specific manner at subacute timepoints. We also found reductions in sensitivity following cFPI on the ear in male minipigs and on the tail in female minipigs. Conclusion: Overall, the current study demonstrates that cFPI produces both behavioral and sensory changes in minipigs up to one-week post-injury. Full article

According to the Centers for Disease Control and Prevention (CDC), the national public health agency of the United States, traumatic brain injury is among the leading causes of mortality and disability worldwide. The consequences of TBI include diffuse brain atrophy, local post-traumatic atrophy, arachnoiditis, pachymeningitis, meningocerebral cicatrices, cranial nerve lesions, and cranial defects. In 2019, the economic cost of injuries in the USA alone was USD 4.2 trillion, which included USD 327 billion for medical care, USD 69 billion for work loss, and USD 3.8 trillion for the value of statistical life and quality of life losses. More than half of this cost (USD 2.4 trillion) was among working-age adults (25–64 years old). Currently, the development of new diagnostic approaches and the improvement of treatment techniques require further experimental studies focused on modeling TBI of varying severity. Full article

Optically transparent polyimide (PI) films with good atomic oxygen (AO) resistance have been paid extensive attention as thermal controls, optical substrates for solar cells or other components for low Earth orbit (LEO) space applications. However, for common PI films, it is usually quite difficult to achieve both high optical transparency and AO resistance and maintain the intrinsic thermal stability of the PI films at the same time. In the current work, we aimed to achieve the target by using the copolymerization methodology using the fluorinated dianhydride 9,9-bis(trifluoromethyl)xanthene-2,3,6,7-tetracarboxylic dianhydride (6FCDA), the fluorinated diamine 2,2-bis [4-(4-aminophenoxy)phenyl]hexafluoropropane (BDAF) and the polyhedral oligomeric silsesquioxane (POSS)-containing diamine N-[(heptaisobutyl-POSS)propyl]-3,5-diaminobenzamide (DABA-POSS) as the starting materials. The fluoro-containing monomers were used to endow the PI films with good optical and thermal properties, while the silicon-containing monomer was used to improve the AO resistance of the afforded PI films. Thus, the 6FCDA-based PI copolymers, including 6FCPI-1, 6FCPI-2 and 6FCPI-3, were prepared using a two-step chemical imidization procedure, respectively. For comparison, the analogous PIs, including 6FPI-1, 6FPI-2 and 6FPI-3, were correspondingly developed according to the same procedure except that 6FCDA was replaced by 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA). Two referenced PI homopolymers were prepared from BDAF and 6FDA (PI-ref1) and 6FCDA (PI-ref2), respectively. The experimental results indicated that a good balance among thermal stability, optical transparency, and AO resistance was achieved by the 6FCDA-PI films. For example, the 6FCDA-PI films exhibited good thermal stability with glass transition temperatures (T_g) up to 297.3 °C, good optical transparency with an optical transmittance at a wavelength of 450 nm (T₄₅₀) higher than 62% and good AO resistance with the erosion yield (E_y) as low as 1.7 × 10⁻²⁵ cm³/atom at an AO irradiation fluence of 5.0 × 10²⁰ atoms/cm². The developed 6FCDA-PI films might find various applications in aerospace as solar sails, thermal control blankets, optical components and other functional materials. Full article

Background: Foot morphology in children is a crucial factor influencing multiple aspects of their physical development. Between the ages of 5 and 10 years, the critical period of child development is when the movement and stability patterns are consolidated that can affect their long-term physical performance and quality of life. The aim of this study is to analyze how the type of foot influences different physical characteristics, laxity, strength, motor tests, and baropodometric variables in children aged 5 to 10 years. Methods: A cross-sectional study involving 196 children was conducted. Different physical characteristics, laxity, strength, motor tests, and baropodometric variables of the sample were analyzed for age and Foot Posture Index (FPI). Results: Differences in all variables were examined by age and FPI. Statistical analysis showed a moderate to high correlation (r > 0.6, p < 0.01) between FPI and the relaxed calcaneal stance position (RCSP) test. Some significant differences were also found in variables related to foot pronation and supination. These results provide valuable information for understanding differences in motor and functional development during childhood and pre-adolescence. Conclusions: The findings highlight the variability in physical and functional development between age and foot type groups, highlighting the importance of considering these differences in the assessment and management of foot-related conditions and biomechanics in childhood. Foot type significantly influences children’s growth and development. Full article

The purpose of this explanatory sequential mixed-methods study is to explain teacher–student relationships in preschool classrooms in terms of the child’s temperament and the pre-service preschool teachers’ personalities. The study was conducted using a sequential exploratory mixed-methods design. Since both quantitative and qualitative data were obtained, sampling was carried out in two stages: quantitative random stratified sampling, and qualitative purposive sampling. Quantitative data were obtained from 126 pre-service teachers. The qualitative study group consisted of 18 pre-service teachers. Quantitative data were collected using the Student–Teacher Relationship Scale-Short Form, the Short Temperament Scale for Children (STSC), and the Five Factor Personality Inventory (FPI). Qualitative data were obtained from interviews with 18 teachers. The findings revealed that the student–teacher relationship can be explained by adult and child characteristics. In addition, pre-service teachers’ perceptions of the student–teacher relationship are explained by adult characteristics much more than pre-service teachers’ perceptions. Full article

The majority of Fabry–Perot interferometer (FPI) tip refractive index (RI) sensors utilize silica optical fiber as the cavity material, with an RI of approximately 1.45. This restricts their applicability in measuring the RI of liquids with an RI of approximately 1.45. Here, we propose a fiber-optic FPI-tip RI sensor by bonding a flat, thin diamond film onto the apex of a single-mode optical fiber. The FPI cavity is constructed from a diamond with an RI of approximately 2.4, theoretically enabling the sensor to achieve an ultrawide RI measurement range of 1 to 2.4. A theoretical comparison of its measurement performance was conducted with that of an FPI-tip RI sensor whose cavity is formed by silica fiber. Additionally, an experimental examination of the device’s RI measurement performance was conducted. The results show that the sensor has visibility to the RI unit of −0.4362/RIU in the RI range of 1.33 to 1.40. Combined with other narrow-RI-ranged high-sensitivity sensors, our proposed RI sensor has the potential for use in a wide range of applications. Full article

Background: Recurrences due to discontinuity in ablation lines are substantial after pulmonary vein isolation (PVI) with radiofrequency ablation for atrial fibrillation. Data are scarce regarding the durability predictors for very high-power short-duration (vHPSD, 90 W/4 s) ablation. Methods: A total of 20 patients were enrolled, who underwent 90 W PVI and a mandatory remapping procedure at 3 months. First-pass isolation (FPI) gaps, and acute pulmonary vein reconnection (PVR) sites were identified at the index procedure; and chronic PVR sites were identified at the repeated procedure. We analyzed parameters of ablation points (n = 1357), and evaluated their roles in predicting a composite endpoint of FPI gaps, acute and chronic PVR. Results: In total, 45 initial ablation points corresponding to gaps in the ablation lines were analyzed. Parameters associated with gaps were interlesion distance (ILD), baseline generator impedance, mean current, total charge, and loss of catheter–tissue contact. The optimal ILD cut-off for predicting gaps was 3.5 mm anteriorly, and 4 mm posteriorly. Conclusions: Biophysical characteristics dependent on generator impedance could affect the efficacy of vHPSD PVI. The use of smaller ILDs is required for effective and durable PVI with vHPSD compared to the consensus targets with lower power ablation, and lower ILDs for anterior applications seem necessary compared to posterior points. Full article

Conventional optical fiber temperature/strain sensors often have to make compromises between the resolution and the dynamic range. Here we present a new method that meets the measurement requirements for both high resolution and large dynamic range. A high-quality optical fiber Fabry-Perot Interferometer (FPI) constructed using a pair of chirped fiber Bragg gratings is employed as the sensor and a dual-mode direct spectrum interrogation method is proposed to identify the small drift of external temperature or strain. As a proof-of-concept illustration, a temperature resolution of 0.2 °C within 30–130 °C is demonstrated. For strain sensing, the resolution can be 10 µε within 0–1000 µε. The measurement resolution can be improved further by routinely increasing the reflectivity of the CFBG and the cavity length and the sensor can also be mass-produced. This new sensing schema not only resolves the conflict between the resolution and the dynamic range of fiber-optic temperature/strain sensors but can also be extended to other sensors and measurands. Full article

Polymers with a low dielectric constant (D_k) are promising materials for high-speed communication networks, which demand exceptional thermal stability, ultralow D_k and dissipation factor, and minimum moisture absorption. In this paper, we prepared a series of novel low-D_k polyimide films containing an MCM-41-type amino-functionalized mesoporous silica (AMS) via in situ polymerization and subsequent thermal imidization and investigated their morphologies, thermal properties, frequency-dependent dielectric behaviors, and water permeabilities. Incorporating 6 wt.% AMS reduced the D_k at 1 MHz from 2.91 of the pristine fluorinated polyimide (FPI) to 2.67 of the AMS-grafted FPI (FPI-g-AMS), attributed to the free volume and low polarizability of fluorine moieties in the backbone and the incorporation of air voids within the mesoporous AMS particles. The FPI-g-AMS films presented a stable dissipation factor across a wide frequency range. Introducing a silane coupling agent increased the hydrophobicity of AMS surfaces, which inhibited the approaching of the water molecules, avoiding the hydrolysis of Si–O–Si bonds of the AMS pore walls. The increased tortuosity caused by the AMS particles also reduced water permeability. All the FPI-g-AMS films displayed excellent thermooxidative/thermomechanical stability, including a high 5% weight loss temperature (>531 °C), char residue at 800 °C (>51%), and glass transition temperature (>300 °C). Full article