Molecular Dynamics Simulation of Membrane Distillation for Different Salt Solutions in Nanopores.

Nanoporous membranes offer significant advantages in direct contact membrane distillation applications due to their high flux and strong resistance to wetting. This study employs molecular dynamics simulations to explore the performance of membrane distillation in a single nanopore, mainly focusing on wetting behavior, liquid entry pressure, and membrane flux variations across different concentrations and types of salt solutions. The findings indicate that increasing the NaCl concentration enhances the wetting of membrane pores, thereby decreasing the entry pressure of the solution. However, at the same salt concentration, the differences in wetting and liquid entry pressure among various salts, including CaCl2, KCl, NaCl, and LiCl, are minimal. The presence of hydrated ions significantly reduces membrane flux. As the concentration of NaCl solutions increases, the number of hydrated ions rises, thereby lowering the membrane flux of the salt solution. Furthermore, the type of salt has a pronounced effect on the structure of hydrated ions. Solutions with Ca2+ and Li+ exhibit the smallest first-layer radius of hydrated ions. Under the same salt concentration, KCl solutions demonstrate the highest membrane distillation flux, while CaCl2 solutions show the lowest flux.

Percutaneous endoscopic transforaminal decompression surgery for symptomatic double-level lumbar spinal stenosis with ossification.

This study aimed to explore the short-term effects of percutaneous endoscopic transforaminal decompression (PETD) for the treatment of symptomatic double-level lumbar spinal stenosis (LSS) with ossification. Twenty-eight patients diagnosed with double-level lumbar spinal stenosis who underwent double-level PETD surgery between January 2021 and January 2023 at our institution. General information, such as age, sex, disease duration, hospitalization time, and operation time, was recorded. Magnetic resonance imaging (MRI) dural sac cross-sectional area (DSCA) was recorded to assess the degree of spinal canal decompression. The White-Panjabi scoring system (WP) was used to assess preoperative and postoperative lumbar spine stability. Pre- and postoperative visual analog scale (VAS) and Oswestry Disability Index (ODI) scores were recorded to assess symptom improvement, and surgical efficacy was evaluated using the modified Macnab evaluation criteria at the 1-year postoperative follow-up. The types and risks of complications were also recorded. The patient's 1-year postoperative follow-up MRI showed that both L3/4 and L4/5 DSCA were significantly enlarged compared with preoperative values (P < .001). There was no significant difference in the WP scores at 3 months postoperatively compared with those preoperatively (P > .05). The VAS scores for hip and lower extremity pain at 3 days, 3 months, and 1 year postoperatively were significantly lower than those preoperatively (P < .001), and the ODI scores at 3 months and 1 year postoperatively were significantly lower than those preoperatively (P < .001). There were no significant differences in hip pain, lower extremity pain VAS scores, or ODI scores between the postoperative follow-up time points (P > .05). There was 1 case of lower limb numbness and 1 case of neuroedematous pain in the postoperative period, and all patients had no complications, such as dural sac tear, infection, or recurrence. The 1-year postoperative follow-up was assessed as excellent in 17 cases, good in 9 cases, and possible in 2 cases using the modified Macnab criteria, with an excellent rate of 92.9%. The efficacy of double-level PETD for symptomatic double-level LSS is clear, the local stability of the lumbar spine is less affected, and the risk is low, which can reduce the chances of reoperation in patients. Thus, it is a recommended surgical procedure.

A Complex Environmental Water-Level Detection Method Based on Improved YOLOv5m.

The existing methods for water-level recognition often suffer from inaccurate readings in complex environments, which limits their practicality and reliability. In this paper, we propose a novel approach that combines an improved version of the YOLOv5m model with contextual knowledge for water-level identification. We employ the adaptive threshold Canny operator and Hough transform for skew detection and correction of water-level images. The improved YOLOv5m model is employed to extract the water-level gauge from the input image, followed by refinement of the segmentation results using contextual priors. Additionally, we utilize a linear regression model to predict the water-level value based on the pixel height of the water-level gauge. Extensive experiments conducted in real-world environments encompassing daytime, nighttime, occlusion, and lighting variations demonstrate that our proposed method achieves an average error of less than 2 cm.

Construction of direct Z-scheme Co9S8/CdS with tubular heterostructure through the simultaneous immobilization and in-situ reduction strategy for enhanced photocatalytic Cr(VI) reduction under visible light.

Tubular Co9S8/CdS heterostructures have been successfully synthesized by in-situ growing CdS onto Co9S8 nanotubes through a simultaneous immobilization and in-situ reduction strategy. It turned out that the so-obtained heterostructure with Co9S8/CdS molar ratio of 1/10 can display a broad light absorption edge and especially much enhanced capacity for photocatalytic reduction of Cr(VI) under visible light. The characterization analysis and experimental results suggested that an interfacial electrostatic field between Co9S8 and CdS elements in the heterostructure could be constructed due to their different Fermi levels, allowing for more quantities of highly reductive electrons to participate in the photocatalytic reaction. Therefore, the so-obtained Co9S8/CdS (1/10) heterostructures could achieve the photocatalytic reduction efficiency of 100% within 20 min, which was more than two and four times larger than that of pristine CdS and Co9S8, respectively. Moreover, the possible photocatalytic reaction mechanism for reducing Cr(VI) was investigated and found to follow the direct Z-scheme charge transfer pathway. This novel fabrication route for composite photocatalysts with tubular heterostructures could lead to the widespread implementations for the elimination of various harmful pollutants in the process of environmental governance.

Investigating the role of membrane lipid composition differences on spray drying survival in Lactobacillus bulgaricus using non-targeted Lipidomics.

The cell membrane, consisting of a phospholipid bilayer, is an important defense system of lactic acid bacteria (LAB) against adverse conditions. However, this membrane gets damaged during the process of spray drying of LAB into powder. In this study, two strains of Lactobacillus bulgaricus L9-7 and L4-2-12 with significantly different survival rates of about 22.49% and 0.43% after spray drying were explored at the cell membrane level. A total of 65 significantly different lipid species were screened from the cell membranes of two strains, with cardiolipin (CL) 15:1_22:6_24:0_28:0 being the crucial lipid species affecting membrane resistance. Finally, the KEGG enrichment analysis revealed that glycerophospholipid metabolism was the most predominant pathway, and eleven lipid species were annotated, including CL. Overall, this paper provides valuable insights into enhancing the heat tolerance of LAB.

A salivary urea sensor based on a microsieve disposable gate AlGaN/GaN high electron mobility transistor.

The abundant bio-markers in saliva provide a new option for non-invasive testing. However, due to the presence of impurities in the saliva background, most of the existing saliva testing methods rely on pre-processing, which limits the application of saliva testing as a convenient means of testing in daily life. Herein, a disposable-gate AlGaN/GaN high electron mobility transistor (HEMT) biosensor integrated with a micro-sieve was introduced to solve the problem of signal interference caused by charged impurities in saliva for HEMT based biosensors, where the micro-sieve was utilized as a pre-treatment unit to remove large particles of impurities from saliva through the size effect and thus greatly improving the accuracy of detection. The experimental results showed that the HEMT based biosensor has excellent linearity (R2 = 0.9977) and a high sensitivity of 6.552 µA dec-1 for urea sensing from 1 fM to 100 mM in 0.1× PBS solution. When it comes to artificial saliva detection, compared to the HEMT sensor without the micro-sieve (sensitivity = 3.07432 µA dec-1), the sensitivity of the HEMT sensor integrated with the micro-sieve showed almost no change. Moreover, to verify that urea can be detected in actual saliva, urea is sensed directly in human saliva. The addition of the microsieve module provides a new way for biosensors to detect specific markers in saliva in real time, and the designed HEMT biosensor with the microsieve function has a wide range of application potential in rapid saliva detection.

An integrated electronic tag-based vertical flow assay (e-VFA) with micro-sieve and AlGaN/GaN HEMT sensors for multi-target detection in actual saliva.

Vertical flow assay (VFA) is an effective point-of-care (POC) diagnostic tool for widespread application. Nevertheless, the lack of multi-target detection and multi-signal readout capability still remains a challenge. Herein, a brand new VFA scheme for multi-target saliva detection based on electronic tags was proposed, where AlGaN/GaN HEMT sensors modified with different bio-receptors as electronic tags endowed the VFA with multi-target detection capability. In addition, the use of electronic tags instead of optical tags allowed the VFA to simultaneously carry out direct multi-target readouts, which ensure effective POC diagnostics for saliva analysis. Moreover, by integrating a hydrophilically optimized micro-sieve, impurities like sticky filaments, epidermal cells and other large-scale charged particles in saliva were effectively screened, which enabled the direct detection of saliva using AlGaN/GaN HEMT sensors. Glucose, urea, and cortisol were selected to verify the feasibility of the multi-target e-VFA scheme, and the results showed that the limit of detection (LOD) was as low as 100 aM. The linear response was demonstrated in the dynamic range of 100 aM to 100 µM, and the specificity, long-term stability and validity of the actual saliva test were also verified. These results demonstrated that the as-proposed e-VFA has potential for application in saliva detection for simultaneous multi-target detection, and it is expected to achieve the real-time detection of more biological targets in saliva.

High Verdet constant of Tb2O3-doped TiO-B2O3-Al2O3-Na2O magneto-optical glass.

Tb-doped magneto-optical (MO) glass is widely used in fiber optics, optical isolators, and modulators. However, only the paramagnetic Tb3+ ions exhibit significant MO effects, whereas the diamagnetism Tb4+ ions suppress the MO effects. Therefore, the valence state control of Tb ions is very critical to optimize MO performance. Here, a reduction strategy was introduced to adjust the Tb valence in glass to achieve the high MO effect. The TiO, which has low valence Ti2+ ions and good reducibility, was used to suppress the oxidation of Tb3+ to Tb4+ ions. In the TiO-B2O3-Al2O3-Na2O glass, 10 mol% TiO can increase the Verdet constant at 650 nm by 19%. With the further increase in Tb2O3 concentration, the Verdet constant reaches a high value of 117 rad/(T·m) at 650 nm, which is close to the Verdet constant of TGG crystal (121 rad/(T·m)). This work provides a new approach to increase the Verdet constant of MO glass.

MA-MIL: Sampling point-level abnormal ECG location method via weakly supervised learning.

BACKGROUND AND OBJECTIVE: Current automatic electrocardiogram (ECG) diagnostic systems could provide classification outcomes but often lack explanations for these results. This limitation hampers their application in clinical diagnoses. Previous supervised learning could not highlight abnormal segmentation output accurately enough for clinical application without manual labeling of large ECG datasets. METHOD: In this study, we present a multi-instance learning framework called MA-MIL, which has designed a multi-layer and multi-instance structure that is aggregated step by step at different scales. We evaluated our method using the public MIT-BIH dataset and our private dataset. RESULTS: The results show that our model performed well in both ECG classification output and heartbeat level, sub-heartbeat level abnormal segment detection, with accuracy and F1 scores of 0.987 and 0.986 for ECG classification and 0.968 and 0.949 for heartbeat level abnormal detection, respectively. Compared to visualization methods, the IoU values of MA-MIL improved by at least 17 % and at most 31 % across all categories. CONCLUSIONS: MA-MIL could accurately locate the abnormal ECG segment, offering more trustworthy results for clinical application.

Structurally Diverse Bisbenzylisoquinoline Alkaloids with Antiadipogenic Activity through PPARγ Downregulation from the Embryo of Nelumbo nucifera Seeds.

Six undescribed and six known bisbenzylisoquinoline alkaloids were isolated from the embryo of Nelumbo nucifera seeds. Their structures were fully characterized by a combination of 1H, 13C NMR, 2D NMR, and HRESIMS analyses, as well as ECD computational calculations. The antiadipogenic activity of 11 alkaloids was observed in a dose-responsive manner, leading to the suppression of lipid accumulation in 3T3-L1 cells. Luciferase assay and Western blot analysis showed that the active alkaloids downregulated peroxisome proliferator-activated receptor gamma (PPARγ, a key antiadipogenic receptor) expression in 3T3-L1 cells. Analysis of the structure-activity relationship unveiled that a 1R,1'S configuration in bisbenzylisoquinoline alkaloids led to a notable enhancement in antiadipogenic activity. The resistance level against lipid accumulation highlighted a consistent pattern with the suppressive effect on the PPARγ expression. These activity results indicate that alkaloids from the embryo of N. nucifera seeds have a potential of antiobesity effects through PPARγ downregulation.

Collectin-K1 Plays a Role in the Clearance of Streptococcus agalactiae in Nile Tilapia (Oreochromis niloticus).

Collectin-K1 (CL-K1) is a multifunctional C-type lectin that has been identified as playing a crucial role in innate immunity. It can bind to carbohydrates on pathogens, leading to direct neutralization, agglutination, and/or opsonization, thereby inhibiting pathogenic infection. In this study, we investigated a homolog of CL-K1 (OnCL-K1) in Nile tilapia (Oreochromis niloticus) and its role in promoting the clearance of the pathogen Streptococcus agalactiae (S. agalactiae) and enhancing the antibacterial ability of the fish. Our analysis of bacterial load displayed that OnCL-K1 substantially reduced the amount of S. agalactiae in tissues of the liver, spleen, anterior kidney, and brain in Nile tilapia. Furthermore, examination of tissue sections revealed that OnCL-K1 effectively alleviated tissue damage and inflammatory response in the liver, anterior kidney, spleen, and brain tissue of tilapia following S. agalactiae infection. Additionally, OnCL-K1 was found to decrease the expression of the pro-inflammatory factor IL-6 and migration inhibitor MIF, while increasing the expression of anti-inflammatory factor IL-10 and chemokine IL-8 in the spleen, anterior kidney, and brain tissues of tilapia. Moreover, statistical analysis of survival rates demonstrated that OnCL-K1 significantly improved the survival rate of tilapia after infection, with a survival rate of 90%. Collectively, our findings suggest that OnCL-K1 plays a vital role in the innate immune defense of resisting bacterial infection in Nile tilapia. It promotes the removal of bacterial pathogens from the host, inhibits pathogen proliferation in vivo, reduces damage to host tissues caused by pathogens, and improves the survival rate of the host.

Adoptive cell therapy for solid tumors beyond CAR-T: Current challenges and emerging therapeutic advances.

Adoptive cellular immunotherapy using immune cells expressing chimeric antigen receptors (CARs) is a highly specific anti-tumor immunotherapy that has shown promise in the treatment of hematological malignancies. However, there has been a slow progress toward the treatment of solid tumors owing to the complex tumor microenvironment that affects the localization and killing ability of the CAR cells. Solid tumors with a strong immunosuppressive microenvironment and complex vascular system are unaffected by CAR cell infiltration and attack. To improve their efficacy toward solid tumors, CAR cells have been modified and upgraded by "decorating" and "pruning". This review focuses on the structure and function of CARs, the immune cells that can be engineered by CARs and the transformation strategies to overcome solid tumors, with a view to broadening ideas for the better application of CAR cell therapy for the treatment of solid tumors.

Intraoperative Protection of Pharyngeal Autonomic Nerves: Preventing Dysphagia After Anterior Cervical Decompression and Fusion Surgery.

OBJECTIVE: The study aims to investigate whether intraoperative protection of the pharyngeal autonomic nerve can effectively reduce the incidence of postoperative dysphagia following anterior cervical decompression and fusion surgery (ACDF). METHODS: A retrospective analysis was conducted on 130 cases that underwent ACDF from January 2018 to June 2022 at our hospital. Divided into nonautonomic neuroprotection (NANP) group and autonomic neuroprotection group based on whether receive protective measures for the pharyngeal autonomic nerve during surgery. General data were recorded and compared between the 2 groups. Postoperative outcomes were evaluated using Neck Disability Index, Japanese Orthopaedics Association (JOA) score, and JOA improvement rate. The incidence and severity of postoperative dysphagia were assessed using Bazaz dysphagia assessment criteria and swallowing-quality of life questionnaire. RESULTS: There were no significant differences in general data (P > 0.05). The average operation time and intraoperative blood loss also showed no significant differences (P > 0.05). Both groups showed significant improvements in Neck Disability Index and JOA scores at all follow-up time points compared to preoperative scores (P < 0.01). The incidence of postoperative dysphagia in the autonomic neuroprotection group was significantly lower than that in the NANP group at all follow-up time points (P < 0.05). Both group showed a significant reduction in scores 3 days postoperatively compared to preoperative scores (P < 0.01), and the NANP group also showed significant reductions in scores at 3 month and 1 year postoperative follow-up time points compared to preoperative scores (P < 0.01). CONCLUSIONS: The adoption of pharyngeal autonomic nerve protective measures during ACDF can effectively lower the probability of postoperative dysphagia.

Hollow Copper Sulfide Photothermal Nanodelivery Platform Boosts Angiogenesis of Diabetic Wound by Scavenging Reactive Oxygen Species.

Sharply rising oxidative stress and ineffectual angiogenesis have imposed restrictions on diabetic wound healing. Here, a photothermal-responsive nanodelivery platform (HHC) was prepared by peroxidase (CAT)-loaded hollow copper sulfide dispersed in photocurable methacrylamide hyaluronan. The HHC could scavenge reactive oxygen species (ROS) and promote angiogenesis by photothermally driven CAT and Cu2+ release. Under near-infrared light irradiation, the HHC presented safe photothermal performance (<43 °C), efficient bacteriostatic ability against E. coli and S. aureus. It could rapidly release CAT into the external environment for decomposing H2O2 and oxygen generation to alleviate oxidative stress while promoting fibroblast migration and VEGF protein expression of endothelial cells by reducing intracellular ROS levels. The nanodelivery platform presented satisfactory therapeutic effects on murine diabetic wound healing by modulating tissue inflammation, promoting collagen deposition and increasing vascularization in the neodermis. This HHC provided a viable strategy for diabetic wound dressing design.

An integrated wearable sticker based on extended-gate AlGaN/GaN high electron mobility transistors for real-time cortisol detection in human sweat.

Cortisol hormone imbalances can be detected through non-invasive sweat monitoring using field-effect transistor (FET) biosensors, which provide rapid and sensitive detection. However, challenges like skin compatibility and integration with sweat collection have hindered FET biosensors as wearable sensing platforms. In this study, we present an integrated wearable sticker for real-time cortisol detection based on an extended-gate AlGaN/GaN high electron mobility transistor (HEMT) combined with a soft bottom substrate and flexible channel for sweat collection. The developed devices exhibit excellent linearity (R2 = 0.990) and a high sensitivity of 1.245 µA dec-1 for cortisol sensing from 1 nM to 100 µM in high-ionic-strength solution, with successful cortisol detection demonstrated using authentic human sweat samples. Additionally, the chip's microminiature design effectively reduces bending impact during the wearable process of traditional soft binding sweat sensors. The extendedgate structure design of the HEMT chip enhances both width-to-length ratio and active sensing area, resulting in an exceptionally low detection limit of 100 fM. Futhermore, due to GaN material's inherent stability, this device exhibits long-term stability with sustained performance within a certain attenuation range even after 60 days. These stickers possess small, lightweight, and portable features that enable real-time cortisol detection within 5 minutes through direct sweat collection. The application of this technology holds great potential in the field of personal health management, facilitating users to conveniently monitor their mental and physical conditions.

CL-K1 Promotes Complement Activation and Regulates Opsonophagocytosis of Macrophages with CD93 Interaction in a Primitive Vertebrate.

Collectin is a crucial component of the innate immune system and plays a vital role in the initial line of defense against pathogen infection. In mammals, collectin kidney 1 (CL-K1) is a soluble collectin that has recently been identified to have significant functions in host defense. However, the evolutionary origins of immune defense of CL-K1 and its mechanism in clearance of pathogenic microorganisms remain unclear, especially in early vertebrates. In this study, the Oreochromis niloticus CL-K1 (OnCL-K1) protein was purified and identified, which was capable of binding to two important pathogens of tilapia, Streptococcus agalactiae and Aeromonas hydrophila. Interestingly, OnCL-K1 exhibited direct bactericidal activity by binding to lipoteichoic acid or LPS on cell walls, disrupting the permeability and integrity of the bacterial membrane in vitro. Upon bacterial challenge, OnCL-K1 significantly inhibited the proliferation of pathogenic bacteria, reduced the inflammatory response, and improved the survival of tilapia. Further research revealed that OnCL-K1 could associate with OnMASPs to initiate and regulate the lectin complement pathway. Additionally, OnCD93 reduced the complement-mediated hemolysis by competing with OnMASPs for binding to OnCL-K1. More importantly, OnCL-K1 could facilitate phagocytosis by collaborating with cell surface CD93 in a lectin pathway-independent manner. Moreover, OnCL-K1 also promoted the formation of phagolysosomes, which degraded and killed ingested bacteria. Therefore, this study reveals the antibacterial response mechanism of CL-K1 in primitive vertebrates, including promoting complement activation, enhancing opsonophagocytosis, and killing of macrophages, as well as its internal links, all of which provide (to our knowledge) new insights into the understanding of the evolutionary origins and regulatory roles of the collectins in innate immunity.

ß-Glucans in particulate and solubilized forms elicit varied immunomodulatory and apoptosis effects in teleost macrophages in a dosedependent manner.

ß-Glucans are a group of heterogeneous glucose polymers that possess immunomodulatory activities. The complex nature of their structures, uncertainty regarding the doses, and variable immune effects pose a challenge to comprehensive understanding. In this study, we investigated the immune responses and apoptosis effects in Nile tilapia (Oreochromis niloticus) head kidney macrophages (MФ) upon exposure to two ß-Glucans (Paramylon and Laminarin) at low and high doses. Our results demonstrate that Paramylon elicits more robust immune responses than Laminarin, albeit with a dose-limiting effect. We also observed that the high-dose Paramylon induces apoptosis, whereas no such effect was detected in Laminarin treatment. Mechanistically, high-dose Paramylon activates the intrinsic apoptosis pathway, with significantly up-regulation of intrinsic apoptosis-related genes and impaired mitochondrial function. On the other hand, Laminarin triggers metabolic reprogramming in MФ, resulting in the enrichment of the metabolite α-Ketoglutarate, which protects the MФ from apoptosis. Overall, our findings highlight the importance of identifying the optimal dose range for ß-Glucans, based on sources or structures, to achieve maximal immunomodulatory effects. These results have important implications for the design and optimization of ß-Glucans-based drugs or adjuvants in immunotherapies.

Long-chain pentraxin 3 possesses agglutination activity and plays a role in host defense against bacterial infection in Oreochromis niloticus.

Pentraxin 3 (PTX3) is a soluble pattern recognition molecule in the innate immune system that has multiple functions. It is involved in resisting pathogen infection. However, the functions of PTX3 in teleost fish are not well understood. In this study, we identified and characterized PTX3 in Nile tilapia (Oreochromis niloticus) (OnPTX3). The open reading frame of OnPTX3 was found to be 1305 bp, encoding 434 aa. We conducted spatial mRNA expression analysis and found that the expression of OnPTX3 was significantly increased after infection with Streptococcus agalactiae and Aeromonas hydrophila, both in vivo and in vitro. We also observed that recombinant OnPTX3 protein could bind and agglutinate bacterial pathogen. Furthermore, OnPTX3 enhanced the phagocytosis of bacteria (S. agalactiae and A. hydrophila) by head kidney macrophages. Additionally, OnPTX3 was found to influence the expression of inflammatory cytokines, suggesting its involvement in the regulation of the inflammatory response. Moreover, OnPTX3 was shown to promote complement-mediated hemolysis and possess antibacterial activity. In conclusion, our research demonstrates that OnPTX3 has bacterial binding and agglutination activities, enhances phagocytosis, and regulates inflammation. It plays a crucial role in the defense of Nile tilapia against pathogenic bacteria, providing valuable insights for the prevention and control of aquatic diseases in the future.

Molecular Evolution of Antiparathion Nanobody with Enhanced Sensitivity and Specificity Based on Structural Analysis.

Nanobody (Nb) has gained significant attention in immunoassays owing to its numerous advantages, particularly its ease of molecular evolution. However, the limited understanding of how high sensitivity and specificity attained for antihapten Nbs hamper the development of high-performance Nbs. Herein, the antiparathion Nb (Nb9) we prepared previously was chosen as the model, and an approach based on X-ray crystallography, molecular docking, and rational site-directed saturation mutation for constructing a rapid and effective platform for nanobody evolution was described. Based on the structural analysis, two mutants, namely Nb-D5 (IC50 = 2.4 ± 0.2 ng/mL) and Nb-D12 (IC50 = 2.7 ± 0.1 ng/mL), were selected out from a six-sites directed saturation mutation library, 3.5-fold and 3.1-fold sensitivity enhancement over Nb9 to parathion, respectively. Besides, Nb-D12 exhibited improved sensitivity for quinalphos, triazophos, and coumaphos (5.4-35.4 ng/mL), indicating its broader detection potential. Overall, our study advances an effective strategy for the future rational evolution of Nbs with desirable performance.

Real-time free spectral range measurement based on a correlated resonance-tracking technology.

In this paper, we present a real-time measurement technology for the free spectral range (FSR) of an ultrahigh-aspect-ratio silicon nitride (Si3N4) waveguide ring resonator (WRR). Two different correlated resonant modes were tracked by two optical single-sideband frequency-shifted lights to eliminate interference noise in the Pound-Drever-Hall error signals. A relative precision of 0.1474 ppm was achieved for a 35 mm WRR with FSR = 1,844,944.5 kHz and finesse (F) = 13.2. Furthermore, a cross-correlation of 0.913 between FSR-calculated and thermistor-measured temperatures indicated a high correlation between the real-time FSR and room temperature. We believe this technology is currently the best way to realize low-finesse (F < 50) real-time FSR measurements in the GHz range.