Search Results (42)

Accurate absolute pressure measurement is of great importance in industrial control, environmental monitoring, and aerospace. Traditional fiber-optic Fabry–Perot (F-P) pressure sensors usually involve complex microfabrication and high-cost demodulation systems, while conventional diaphragm capsule sensors are limited in sensitivity and resolution. This work presents a low-cost, high-resolution fiber-optic F-P absolute pressure sensor. The sensor uses a vacuum capsule as one reflective surface and a partially reflective fiber collimator as the other, forming a low-finesse F-P interferometer. The cavity length is linearly modulated by the elastic deformation of the capsule under pressure, and high-precision demodulation is realized using frequency modulated continuous wave (FMCW) interferometry instead of conventional spectral methods. Static experiments from 10 to 110 kPa show that the sensor exhibits a high sensitivity of 15,105 nm/kPa and a resolution of 3.3 Pa. Furthermore, the sensor operates normally within the range of −20 °C to 70 °C, exhibiting a pressure–temperature cross-sensitivity of 0.081 kPa/°C and a cavity length drift of 496 nm/h. With the advantages of high performance, simple structure, low cost, and good scalability by selecting different capsules, the proposed sensor has promising potential for practical applications in pressure measurement fields. Full article

Both experimental and numerical studies were conducted to obtain the influence laws of complex cavitation flow structures around a Clark-Y hydrofoil cascade. The similarities and differences in cavitation flow characteristics between the cascade and single hydrofoil were compared to analyze the influence of the cascade configuration on the flow field structure. This study focuses on the correlations among cavity development, lift–drag characteristics, and flow field features of the hydrofoil cascade. The results indicate significant differences in the development degree and history of cavities at different positions within the cascade. The top layer of the cascade exhibits a cavitation pattern similar to a single hydrofoil; both generate large-scale shedding vortices at the trailing edge. In contrast, the cavitation phenomena in the middle and bottom layers are similar to each other. The suction side of the top-layer hydrofoil influences the middle and bottom layers. This interaction suppresses the formation of large-scale shedding bubbles and subsequently hinders re-entrant shocks. Furthermore, the cavities in the middle and bottom layers develop more rapidly, causing the dynamic characteristics of the cascade to reach their peak values earlier. At the cloud cavitation stage, the Strouhal numbers ($St$) for cavity collapse on the top and bottom hydrofoils are approximately 0.2 and 0.3, respectively. The $St$ for the middle hydrofoil exhibits an intermediate value that decreases from 0.3 to 0.2 as the cavitation number ($\sigma$) declines, reflecting a transitional characteristic modulated by the cascade structure. Compared to a single hydrofoil, the cascade is subject to the combined effects of the three-layer hydrofoils; consequently, its lift is approximately three times that of a single hydrofoil, though its drag also increases threefold. The lift variation pattern of the top-layer hydrofoil in the cascade is similar to that of a single hydrofoil. In contrast, the middle-layer hydrofoil exhibits a more complex lift evolution, as both its suction and pressure sides are significantly influenced by the surrounding cascade structure. For the bottom-layer hydrofoil, the lift remains relatively low because no cavities are generated on its surface. Lift fluctuation frequencies that aligned with cavity collapse were identified at 45 Hz, 70 Hz, and 50 Hz across the top, middle, and bottom cascade layers, respectively. Full article

Non-specific lipid transfer proteins (nsLTPs) play a crucial role in lipid transport across membranes, contributing to cellular integrity and structural stability. These proteins are characterized by the presence of eight conserved cysteine residues that form four disulfide bonds and a hydrophobic cavity that is essential for lipid binding and transport. Interactions of nsLTPs with diverse ligands enable them to participate in key biological processes, including signal transduction, protein folding, membrane stabilization, and cell wall organization. Additionally, these proteins are integral to plant responses to abiotic and biotic stresses and to developmental processes, including growth, germination, and flowering. The interaction between nsLTPs and plant signaling molecules activates regulatory networks that modulate stress-responsive gene expression, reinforcing plant resilience under adverse conditions. Despite their functional significance, the evolutionary trajectory, subcellular localization, and regulatory mechanisms governing nsLTP expression remain limited, as reflected in previous reviews on nsLTPs. This review provides a comprehensive analysis of nsLTP evolution, roles in plant defense and signaling, functional diversity, updated subcellular localization, and future research directions based on recent findings. Full article

Background and Objectives: Blood flow is critical for tissue oxygenation, and alterations in cerebrovascular and peripheral circulation have important health implications. This study aimed to examine the impact of distinct mechanisms for increasing intra-cavity pressure through the abdominal bracing (AB) and Valsalva maneuver (VM) on central and peripheral hemodynamics. Materials and Methods: A randomized crossover design was used, and thirty healthy young adults (age 21.9 ± 1.5 years; BMI 20.9 ± 1.8 kg/m²) performed AB and VM in a randomized order. All participants provided written informed consent, and the study protocol was approved by the Clinical Research Information Service (KCT0009742; registered on 30 August 2024). Hemodynamic responses were measured before and after each intervention, including heart rate, blood pressure, pulse wave velocity, carotid artery diameter, pulsatility index, resistive index, peripheral oxygen saturation, and cerebral oxygenation. Repeated-measures analysis of variance and paired t-tests were conducted on the datasets. Results: Both the VM and AB significantly increased heart rate (p < 0.001) and systolic blood pressure (VM: p = 0.015; AB: p < 0.001). Cerebral oxygen saturation decreased significantly (VM: p < 0.05; AB: p < 0.05), whereas oxyhemoglobin increased during both interventions, suggesting higher cerebral oxygen demand. The VM specifically increased the carotid pulsatility index (pre = 1.76 ± 0.28; post2 = 1.87 ± 0.33; p = 0.008), reflecting elevated central vascular resistance. In contrast, AB decreased peripheral oxygen saturation (pre = 98.43 ± 0.71; post1 = 97.49 ± 1.76; p < 0.001) and increased peripheral (heart–finger) pulse wave velocity (Lt: p = 0.026; Rt: p = 0.010), indicating greater stimulation of peripheral circulation. Conclusions: Distinct mechanisms that elevate intra-cavity pressure differentially influence central and peripheral hemodynamics. These findings suggest that intra-cavity pressure can selectively modulate hemodynamic responses, with potential applications in both clinical and exercise settings. Full article

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most aggressive and lethal human malignancies, with five-year survival rates showing only marginal improvement despite decades of intensive research. Its dismal prognosis reflects a combination of intrinsic biological aggressiveness, late clinical presentation, and marked resistance to standard therapies, underscoring the urgent need for innovative diagnostic and therapeutic approaches. Growing evidence indicates that the microbiome is a modifiable factor influencing the onset, progression, and treatment response of PDAC. Microbial communities originating from the gut, oral cavity, and even the tumor microenvironment can shape carcinogenic pathways, modulate immune activity, and alter the efficacy of chemotherapy and immunotherapy. In addition to bacteria, fungal and viral populations are emerging as relevant contributors within this complex ecosystem. This review provides a comprehensive overview of the current mechanistic and translational evidence linking the microbiome to PDAC biology and therapy. It further explores microbiota-targeted interventions—such as probiotics, postbiotics, engineered bacterial strains, bacteriophages, oncolytic viruses, and fecal microbiota transplantation—as promising adjuncts to conventional treatments. A deeper understanding of host–microbiome interactions could yield novel biomarkers and open innovative avenues for precision medicine in PDAC, ultimately improving patient outcomes and reshaping therapeutic paradigms. Integrating microbiome-based strategies into PDAC management may thus represent a crucial step toward more effective and personalized oncologic care. Full article

This paper presents a bistatic 60 GHz frequency-modulated continuous-wave (FMCW) radar system for non-contact heart rate monitoring, utilizing high-gain Fabry–Perot cavity (FPC) antennas at both the transmitter and receiver. Each FPC antenna integrates a partially reflective surface (PRS) and a metallic ground plane to form a resonant cavity. Compared to conventional patch arrays of the same aperture, the FPC antenna improves the antenna gain from 4.1 dBi to 8.1 dBi at the transmitter and from 3.9 dBi to 7.8 dBi at the receiver, resulting in an overall link budget enhancement of approximately 7.9 dB. This dual high-gain configuration theoretically increases the maximum detection range by a factor of 2.48. The proposed radar system was implemented and experimentally validated under indoor conditions using both calibration targets and human participants. Active measurement results confirm that the bistatic radar equipped with FPC antennas extends the reliable heart rate detection distance by approximately 2.27 times compared to a conventional system, closely matching the theoretical prediction. These results confirm the practicality and effectiveness of FPC antennas in extending both the range and reliability of millimeter-wave vital sign detection systems. Full article

This work studies the Purcell effect of two quasiperiodic multilayers of gold and titanium dioxide following the Thue–Morse and Fibonacci sequence, respectively. We systematically investigated the impacts of polarization direction, dipole height, and wavelength on the Purcell factor. Additionally, we compared the normalized field distribution profiles across all multilayer structures. Concurrently, under varying polarizations, we computed the radiative part of the Purcell factor, photoluminescence at the reflection and transmission side of multilayers, respectively. Our findings indicate that under near-field excitation conditions, the Purcell factor is predominantly governed by its non-radiative component rather than the radiative one. We attribute the observed discrepancies in the Purcell factor to variations in the intensity and spatial distribution of non-radiative losses within the metallic components of the multilayers. This mechanism provides a robust physical foundation for exploring and extending the applications of photonic quasicrystals in the modulation of nanoscale light–matter interactions. Furthermore, we examined cavities constructed from symmetric multilayers. Under z-polarization and long-wavelength conditions, the cavity effect was observed to enhance the radiative part of the Purcell factor, thereby further boosting spontaneous emission efficiency. This work offers novel insights into the design of semiconductor devices with improved quantum emission efficiency and photoluminescence. Full article

A methane (CH₄) sensor based on off-axis integrated cavity output spectroscopy (OA-ICOS) was developed, equipped with two measurement schemes: direct absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS). The sensor used an optical resonant cavity composed of two high reflection mirrors (reflectivity > 99%). With a cavity length of 7 cm, an effective optical path length of 10.8 m and a cavity volume of 8.9 mL were achieved. A distributed feedback laser was used to precisely target the CH₄ absorption line near 1.6537 µm. Compared with the original system, the cavity mode noise of the CH₄ sensor was further reduced by adding white noise perturbations. The white noise perturbations were generated by the broadband random noise from the signal generator. The special customized narrowband RF noise source was not required. The system complexity and cost could be reduced. In DAS mode, the signal-to-noise ratio (SNR) of the OA-ICOS was 16.2 and the minimum detection limit (MDL) was 2.2 ppm at 117 s. In WMS mode, the SNR of the OA-ICOS was 113.9 and the MDL was 1.2 ppm at 106 s. Compared with the results obtained from the WMS mode and DAS mode, the SNR and MDL was improved 7.0 times and 1.8 times, respectively. The proposed sensor system not only enabled high-accuracy trace gas measurement, but also demonstrated strong potential for applications due to its compact design and low cost. Full article

In this paper, a design of vanadium dioxide for dynamic color gamut modulation based on Fano resonance is proposed. This approach facilitates color modulation by manipulating the phase transition state of vanadium dioxide. The device integrates both broadband and narrowband filters, featuring a structure consisting of a top silver mesh, a layer of vanadium dioxide, and a Fabry–Pérot cavity, which allows for effective modulation of the reflectance spectrum. Simulation results demonstrate that when vanadium dioxide is in its insulating state, the maximum reflectivity observed in the device spectrum, reaching 43.1%, appears at 475 nm. Conversely, when vanadium dioxide transitions to its metallic state, the peak wavelength shifts to 688 nm, accompanied by an increased reflectance peak of 59.3%. Analysis of electric field distributions reveals that the intensity caused by surface plasmonic resonance dominates over the excited Fano resonance while vanadium dioxide is in its insulating state, which is the opposite of when vanadium dioxide transitions to its metallic state. This behavior exhibits an excellent dynamic color-tuning capability. Specifically, the phase transition of vanadium dioxide results in a color difference ∆E₂₀₀₀ of up to 36.7, while maintaining good color saturation. This technique holds significant potential for applications such as dynamic color display and anti-counterfeit labeling. Full article

Metasurfaces are opening promising flexibilities to reshape the wavefront of electromagnetic waves. Notable optical phenomena are observed with the tailored surface plasmon, which is excited by metallic components in the visible spectrum. However, metamaterial or metasurface devices utilizing metallic materials encounter the challenge of low transmission efficiency, particularly within the visible spectrum. This study proposes a multilayer design strategy to enhance their transmission efficiency. By incorporating additional metal layers for improvements in the transmission efficiency and dielectric layers as spacers, cavities are formed along the propagation direction, enabling the modulation of transmittance and reflection through a process mimicking destructive interference. An analytical model simplified with the assumption of deep-subwavelength-thick metal layers is proposed to predict the structural parameters with optimized transmittance. Numerical studies employing the rigorous coupled wave analysis method confirmed that the additional metal layers significantly improve the transmittance. The introduction of the extra metal and dielectric layers enhances the transmission efficiency in specific spectral regions, maintaining a controllable passband and transmittance. The results indicate that the precise control over the layers’ thicknesses facilitates the modulation of peak-to-valley ratios and the creation of comb-like filters, which can be further refined through controlled random variation in the thickness. Furthermore, when the thickness of the silver layer followed an arithmetic sequence, a multilayer structure with a transmittance of approximately 80% covering the entire visible spectrum could be achieved. Significantly, the polarization extinction ratio and the phase delay of the incident beams could still be modulated by adjusting the geometrical structure and parameters of the multilayer metamaterial for diversified functionalities. Full article

Improving compactness is essential for high-power microwave (HPM) sources. In this paper, a novel reflective modulation cavity is proposed and investigated in a V-band relativistic coaxial transit-time oscillator (RCTTO). The cold cavity analyses and particle-in-cell simulations show that the reflective modulation cavity has larger reflection coefficients of TEM mode and stronger electron beam modulation capability when compared with a uniform modulation cavity. When the input diode voltage is 391 kV, the beam current is 4.91 kA, and when the guiding magnetic field is 0.6 T, the compact V-band RCTTO produces an output microwave power of 518 MW (conversion efficiency of 27.0%). Compared with the original RCTTO, the compact V-band RCTTO featuring a reflective modulation cavity exhibits a 24.8% increase in output power and a 5.4% improvement in efficiency, and the axial length of the magnetic field uniform region is reduced by 24.2%. The compact V-band RCTTO also demonstrates a broad operation voltage range, indicating potential for stable operation with voltage fluctuations in experiments. Furthermore, the reflective modulation cavity can be integrated into other high-frequency O-type HPM devices to enhance compactness, thereby diminishing the demands on the magnetic field region, which is advantageous for the future permanent packaging of HPM sources. Full article

Chronic rhinosinusitis (CRS) is a multifactorial infection of the nasal cavity and sinuses. In this study, nasal swabs from control donors (N = 128) and patients with CRS (N = 246) were analysed. Culture methods and metagenomics revealed no obvious differences in the composition of the bacterial communities between the two groups. However, at the functional level, several metabolic pathways were significantly enriched in the CRS group compared to the control group. Pathways such as carbohydrate transport metabolism, ATP synthesis, cofactors and vitamins, photosynthesis and transcription were highly enriched in CRS. In contrast, pathways related to lipid metabolism were more representative in the control microbiome. As S. aureus is one of the main species found in the nasal cavity, staphylococcal isolates from control and CRS samples were analysed by microarray and functional assays. Although no significant genetic differences were detected by microarray, S. aureus from CRS induced less cytotoxicity to lung cells and lower rates of glycolysis in host cells than control isolates. These results suggest the differential modulation of staphylococcal virulence by the environment created by other microorganisms and their interactions with host cells in control and CRS samples. These changes were reflected in the differential expression of cytokines and in the expression of Agr, the most important quorum-sensing regulator of virulence in S. aureus. In addition, the CRS isolates remained stable in their cytotoxicity, whereas the cytotoxic activity of S. aureus isolated from control subjects decreased over time during in vitro passage. These results suggest that host factors influence the virulence of S. aureus and promote its adaptation to the nasal environment during CRS. Full article

For uncooled infrared cameras based on microbolometers, silicon caps are often utilized to maintain a vacuum inside the packaged bolometer array. To reduce Fresnel reflection losses, anti-reflection coatings are typically applied on both sides of the silicon caps.This work investigates whether black silicon may be used as an alternative to conventional anti-reflective coatings. Reactive ion etching was used to etch the black silicon layer and deep cavities in silicon. The effects of the processed surfaces on optical transmission and image quality were investigated in detail by Fourier transform infrared spectroscopy and with modulated transfer function measurements. The results show that the etched surfaces enable similar transmission to the state-of-the-artanti-reflection coatings in the 8–12 µm range and possibly obtain wider bandwidth transmission up to 24 µm. No degradation in image quality was found when using the processed wafers as windows. These results show that black silicon can be used as an effective anti-reflection layer on silicon caps used in the vacuum packaging of microbolometer arrays. Full article

We proposed an active differential intensity (DI) fiber coupled plasmon waveguide resonance (CPWR) sensor based on the mode competition effect in the C-band, aiming to enhance the sensitivity. The sensing head is a fiber probe with a sensing layer of ITO/Au/ITO/TiO₂ film, enabling the excitation of CPWR in the C-band. The narrow CPWR spectrum allows DI interrogation by tracking the intensity of light at two wavelengths. The fiber probe is inserted into a dual-wavelength fiber laser to adjust the intra-cavity loss at the two lasing wavelengths. By using the differential modulation of the reflectivity from the refractive index variations, the mode competition effect is triggered. The powers at two lasing wavelengths change oppositely, enlarging the power difference and then resulting in enhanced sensitivity. The average sensitivity is up to 5702 dB/RIUs, which is 10 times higher than that of conventional DI interrogation. The sensitivity enhancement mechanism based on the mode competition effect provides a new technical approach for enhancing the sensitivity of DI SPR sensors. Full article

In order to reduce the pumping threshold and achieve a short-cavity single-mode transmission with a narrow-linewidth random fiber laser, we propose a tunable random fiber laser based on the combination of random grating and highly reflective fiber Bragg grating (FBG). Theoretical modeling of a random refractive index-modulated fiber grating was carried out. Random grating is regarded as a linear combination of uniform fiber gratings with different periods. Simulation calculations were performed using the transfer matrix method to determine the preparation parameters. Under the premise of satisfying light localization, a point-by-point method was used to write a random grating in a single-mode fiber using a femtosecond laser according to the simulated parameters. We constructed a random fiber laser with a linewidth of 1.68 kHz and a threshold of 29.2 mW using a random grating and a highly reflective FBG combined with an erbium-doped fiber. Due to the broad scattered wavelength range of the random grating, by changing the central wavelength of the high-reflection FBG, the tunable wavelength of the output laser was realized, and the tunable range was 0.847 nm (1549.110–1549.957 nm). Moreover, the laser’s central wavelength and output power are stable for a long time. Compared with other lasers, the proposed laser has the advantages of a lower threshold, shorter cavity length, narrower linewidth, and a relatively simple structure. Full article