Development of High-Precision NO2 Gas Sensor Based on Non-Dispersive Infrared Technology.

Increasing concerns about air quality due to fossil fuel combustion, especially nitrogen oxides (NOx) from marine and diesel engines, necessitate advanced monitoring systems due to the significant health and environmental impacts of nitrogen dioxide (NO2). In this study, a gas detection system based on the principle of the non-dispersive infrared (NDIR) technique is proposed. Firstly, the pyroelectric detector was developed by employing an ultra-thin LiTaO3 (LT) layer as the sensitive element, integrated with nanoscale carbon material prepared by wafer-level graphics technology as the infrared absorption layer. Then, the sensor was hermetically sealed using inert gas through energy storage welding technology, exhibiting a high detectivity (D*) value of 4.19 × 108 cm·âˆšHz/W. Subsequently, a NO2 gas sensor was engineered based on the NDIR principle employing a Micro Electro Mechanical System (MEMS) infrared (IR) emitter, featuring a light path chamber length of 1.5 m, along with integrated signal processing and software calibration algorithms. This gas sensor was capable of detecting NO2 concentrations within the range of 0-500 ppm. Initial tests indicated that the gas sensor exhibited a full-scale relative error of less than 0.46%, a limit of 2.8 ppm, a linearity of -1.09%, a repeatability of 0.47% at a concentration of 500 ppm, and a stability of 2% at a concentration of 500 ppm. The developed gas sensor demonstrated significant potential for application in areas such as industrial monitoring and analytical instrumentation.

Direct Measurement of Dissolved Gas Using a Tapered Single-Mode Silica Fiber.

Dissolved gases in the aquatic environment are critical to understanding the population of aquatic organisms and the ocean. Currently, laser absorption techniques based on membrane separation technology have made great strides in dissolved gas detection. However, the prolonged water-gas separation time of permeable membranes remains a key obstacle to the efficiency of dissolved gas analysis. To mitigate these limitations, we demonstrated direct measurement of dissolved gas using the evanescent-wave absorption spectroscopy of a tapered silica micro-fiber. It enhanced the analysis efficiency of dissolved gases without water-gas separation or sample preparation. The feasibility of this sensor for direct measurement of dissolved gases was verified by taking the detection of dissolved ammonia as an example. With a sensing length of 5 mm and a consumption of ~50 µL, this sensor achieves a system response time of ~11 min and a minimum detection limit (MDL) of 0.015%. Possible strategies are discussed for further performance improvement in in-situ applications requiring fast and highly sensitive dissolved gas sensing.

Value of carotid corrected flow time or changes value of FTc could be more useful in predicting fluid responsiveness in patients undergoing robot-assisted gynecologic surgery: a prospective observational study.

Background: The aim of this study was to evaluate the ability of point-of-care Doppler ultrasound measurements of carotid corrected flow time and its changes induced by volume expansion to predict fluid responsiveness in patients undergoing robot-assisted gynecological surgery. Methods: In this prospective study, carotid corrected flow time was measured using Doppler images of the common carotid artery before and after volume expansion. The stroke volume index at each time point was recorded using noninvasive cardiac output monitoring with MostCare. Of the 52 patients enrolled, 26 responded. Results: The areas under the receiver operating characteristic curves of the carotid corrected flow time and changes in carotid corrected flow time induced by volume expansion were 0.82 and 0.67, respectively. Their optimal cut-off values were 357 and 19.5 ms, respectively. Conclusion: Carotid corrected flow time was superior to changes in carotid corrected flow time induced by volume expansion for predicting fluid responsiveness in this population.

Analysis of size-dependent optoelectronic properties of red AlGaInP micro-LEDs.

We have theoretically investigated the size-dependent optoelectronic properties of InGaP/AlGaInP-based red micro-LEDs through an electro-optical-thermal coupling model. The model considers thermal effects due to current crowding near the electrodes, non-thermal efficiency droop due to electron leakage, and etch defects on the LED sidewall. Sidewall defects reduce the carrier concentration at the light-emitting surface's edge and exacerbate the current crowding effect. In addition, p-side electron leakage at high current densities is the leading cause of the efficiency droop of AlGaInP LEDs. In contrast, the effect of temperature on the overall efficiency degradation of LEDs is even more significant.

Surface Plasmon Field-Enhanced Raman Scattering Co-Excited by P-Polarized and S-Polarized Light Based on Waveguide-Coupled Surface Plasmon Resonance Configuration.

We constructed a waveguide-coupled surface plasmon resonance (WCSPR) structure to enhance Raman scattering. In this structure, P-polarized and S-polarized incident lasers can simultaneously coexcite the evanescent field, thereby further enhancing Raman scattering. This configuration is a five-phase Kretschmann resonance setup that consists of a SF10 prism/inner Ag film/SiO2 film/outer Ag film/water structure. The WCSPR configuration effectively concentrates and confines the evanescent field excited by the incident light. Ag nanoparticles assembled on the outer Ag film surface enhance the evanescent field further by means of surface plasmon resonance. By finely tuning the thickness of the Ag and SiO2 films, it is possible to achieve a coincidence between the SPR angle of P-polarized light and that of S-polarized light. At this angle, both P- and S-polarized light can jointly elevate the evanescent field intensity, leading to the simultaneous enhancement of the electric fields at the upper, lower, left, and right parts of the silver nanoparticles and generating maximum evanescent field enhancement. We achieved an electric field enhancement of up to 103 around the nanoparticles, leading to more SERS hotspots and comparable SERS enhancement capability to gap-type hotspots. Our WCSPR structure combined with the nanoparticles offers a feasible strategy for the SERS detection of large molecules that cannot be placed in traditional gap-type hotspots. It is highly convenient for SERS detection of large molecules.

Comparison of the carotid corrected flow time and tidal volume challenge for assessing fluid responsiveness in robot-assisted laparoscopic surgery.

We aimed to compare the ability of carotid corrected flow time assessed by ultrasound and the changes in dynamic preload indices induced by tidal volume challenge predicting fluid responsiveness in patients undergoing robot-assisted laparoscopic gynecological surgery in the modified head-down lithotomy position. This prospective single-center study included patients undergoing robot-assisted laparoscopic surgery in the modified head-down lithotomy position. Carotid Doppler parameters and hemodynamic data, including corrected flow time, pulse pressure variation, stroke volume variation, and stroke volume index at a tidal volume of 6 mL/kg predicted body weight and after increasing the tidal volume to 8 mL/kg predicted body weight (tidal volume challenge), respectively, were measured. Fluid responsiveness was defined as a stroke volume index ≥ 10% increase after volume expansion. Among the 52 patients included, 26 were classified as fluid responders and 26 as non-responders based on the stroke volume index. The area under the receiver operating characteristic curve measured to predict the fluid responsiveness to corrected flow time and changes in pulse pressure variation (ΔPPV6-8) after tidal volume challenge were 0.82 [95% confidence interval (CI) 0.71-0.94; P < 0.0001] and 0.85 (95% CI 0.74-0.96; P < 0.0001), respectively. The value for pulse pressure variation at a tidal volume of 8 mL/kg was 0.79 (95% CI 0.67-0.91; P = 0.0003). The optimal cut-off values for corrected flow time and ΔPPV6-8 were 357 ms and > 1%, respectively. Both the corrected flow time and Changes in pulse pressure variation after tidal volume challenge reliably predicted fluid responsiveness in patients undergoing robot-assisted laparoscopic gynecological surgery in the modified head-down lithotomy position. And pulse pressure variation at a tidal volume of 8 mL/kg maybe also a useful predictor.Trial registration: Chinese Clinical Trial Register (CHiCTR2200060573, Principal investigator: Hongliang Liu, Date of registration: 05/06/2022).

Microfluidic static droplet generated quantum dot arrays as color conversion layers for full-color micro-LED displays.

This paper presents an easy and intact process based on microfluidics static droplet array (SDA) technology to fabricate quantum dot (QD) arrays for full-color micro-LED displays. A minimal sub-pixel size of 20 µm was achieved, and the fluorescence-converted red and green arrays provide good light uniformity of 98.58% and 98.72%, respectively.

Effect of internal jugular vein catheterization on intracranial pressure and postoperative cognitive function in patients undergoing robot-assisted laparoscopic surgery.

Background: We aimed to evaluate the effects of internal jugular vein (IJV) catheterization on intracranial pressure (ICP) and postoperative delirium (POD) during robot-assisted laparoscopic surgery by measuring the optic nerve sheath diameter (ONSD). Methods: Data from a prospective single-center cohort study, conducted from October 2021 to February 2022, were used. Forty out of 80 patients scheduled for laparoscopic radical hysterectomy or prostatectomy were assigned to the group receiving IJV catheterization (Group I), and the other 40 only received peripheral venous cannulation (Group C) according to clinical need of patients. Ultrasonography of ONSDs, the proportion of regurgitation time in a cardiac cycle, and hemodynamic parameters were measured at four time points: immediately after induction of anesthesia in the supine position (T0), 30 min (T1), 60 min (T2) after orienting to the Trendelenburg position, and before returning to the supine position at the end of surgery (T3). Time to eye opening and emergence stay, POD, and QoR-15 were compared. Results: The ONSDs increase gradually as the surgery progressed. Group I showed a higher value of ONSD at T1 (4.72 ± 0.29 mm vs. 4.5 ± 0.33 mm, p = 0.0057) and T3 (5.65 ± 0.33 mm vs. 5.26 ± 0.31 mm, p < 0.0001). The proportions of the regurgitation time of IJVV were greater in Group I than those in Group C at T1 (14.95, 8.5%-18.9% vs. 9.6%, 0%-17.2%, p < 0.0001) and T3 (14.3, 10.6%-18.5% vs. 10.4%, 0%-16.5%, p = 0.0003). Group I had a delayed time to eye opening (10.7 ± 1.72 min vs. 13.3 ± 2.35 min, p < 0.0001) and emergence stay (32.2 ± 5.62 min vs. 39.9 ± 6.7 min, p < 0.0001). There were no significant differences in POD and QoR-15 between the two groups on day three. Conclusion: IJV cannulation may not be the preferred approach in robot-assisted laparoscopic surgery as it was risk factor for IJVV regurgitation, ICP elevation, emergence delayed.

Micro-Quartz Crystal Tuning Fork-Based Photodetector Array for Trace Gas Detection.

In this paper, a micro-quartz crystal tuning fork (M-QCTF) was first demonstrated for developing a low-cost, highly sensitive quartz tuning fork photodetector array for spectroscopic applications. A gas sensing system based on the M-QCTF photodetector and highly sensitive wavelength modulation spectroscopy was developed. Typically, an atmospheric greenhouse gas methane (CH4) molecule was selected as the target analyte for evaluating the M-QCTF and standard commercial QCTF detectivity. The results indicate that the M-QCTF photodetector exhibits ∼3.3 times sensitivity enhancement compared to the standard commercial QCTF. The long-term stability was evaluated by using the Allan deviation analysis method; a minimum detection limit of 1.2 ppm was achieved with an optimal integration time of 85 s, and the corresponding normalized noise equivalent absorption coefficient was calculated to be 4.45 × 10-10 cm-1 W/√Hz. Finally, a two-M-QCTF array detection scheme was experimentally demonstrated, and a signal-to-noise ratio enhancement factor of more than 1.7 times compared to that achieved using a single M-QCTF photodetector was realized, which proves a great potential for developing ultra-sensitive quartz tuning fork photodetector arrays for various applications.

Comparison of Various Regional Analgesia Methods for Postoperative Analgesic Effects in Video-assisted Thoracoscopic Surgery: A Systematic Review and Network Meta-analysis.

BACKGROUND: The optimal analgesia for video-assisted thoracoscopic surgery (VATS) is still unknown. OBJECTIVES: Our aim was to conduct a network meta-analysis and systematic review to compare the efficacy of different analgesic strategies in VATS. STUDY DESIGN: Bayesian network meta-analysis. METHODS: We searched PubMed, Embase, Medline, Springer, Google Scholar, and Web of Science to evaluate all relevant randomized controlled trials that investigated the analgesic effects of different regional analgesia methods for VATS published through July 2021. After a comprehensive search of electronic databases, the following methods were identified: epidural analgesia (EA), local anesthetics (LA), superficial serratus anterior plane block (SSAPB), deep serratus anterior plane block (DSAPB), erector spinae plane block (ESPB), paravertebral block (PVB), and intercostal nerve block (ICNB). Primary outcomes were the visual analog scale score at rest, at 2 hours, 6 hours and 24 hours postoperatively. The secondary outcomes were postoperative analgesic consumption, incidence of nausea and emesis, and pruritus. RESULT: Overall, 35 trials met our inclusion criteria. EA and PVB were relatively more advantageous in terms of analgesic effect at 2 hours and 6 hours postoperatively; the EA group was superior to the DSAPB, ESPB, and ICNB groups at 24 hours postoperatively. EA was found to be superior to other analgesia techniques for 24 hour postoperative analgesic consumption., PVB showed advantages in reducing postoperative nausea, emesis, and pruritus. LIMITATIONS: Different concentrations and volumes of local anesthetics might affect the analgesic effects of the various analgesia techniques. CONCLUSION: EA and PVB have certain advantages in analgesia, but the incidence of postoperative pruritus after EA is higher. At the same time, considering the risk of coagulation and puncture complications, PVB may be a better choice.

Cold Laser Micro-Machining of PDMS as an Encapsulation Layer for Soft Implantable Neural Interface.

PDMS (polydimethylsiloxane) is an important soft biocompatible material, which has various applications such as an implantable neural interface, a microfluidic chip, a wearable brain-computer interface, etc. However, the selective removal of the PDMS encapsulation layer is still a big challenge due to its chemical inertness and soft mechanical properties. Here, we use an excimer laser as a cold micro-machining tool for the precise removal of the PDMS encapsulation layer which can expose the electrode sites in an implantable neural interface. This study investigated and optimized the effect of excimer laser cutting parameters on the electrochemical impedance of a neural electrode by using orthogonal experiment design. Electrochemical impedance at the representative frequencies is discussed, which helps to construct the equivalent circuit model. Furthermore, the parameters of the equivalent circuit model are fitted, which reveals details about the electrochemical property of neural electrode using PDMS as an encapsulation layer. Our experimental findings suggest the promising application of excimer lasers in the micro-machining of implantable neural interface.

Parylene C as an Insulating Polymer for Implantable Neural Interfaces: Acute Electrochemical Impedance Behaviors in Saline and Pig Brain In Vitro.

Parylene is used as encapsulating material for medical devices due to its excellent biocompatibility and insulativity. Its performance as the insulating polymer of implantable neural interfaces has been studied in electrolyte solutions and in vivo. Biological tissue in vitro, as a potential environment for characterization and application, is convenient to access in the fabrication lab of polymer and neural electrodes, but there has been little study investigating the behaviors of Parylene in the tissue in vitro. Here, we investigated the electrochemical impedance behaviors of Parylene C polymer coating both in normal saline and in a chilled pig brain in vitro by performing electrochemical impedance spectroscopy (EIS) measurements of platinum (Pt) wire neural electrodes. The electrochemical impedance at the representative frequencies is discussed, which helps to construct the equivalent circuit model. Statistical analysis of fitted parameters of the equivalent circuit model showed good reliability of Parylene C as an insulating polymer in both electrolyte models. The electrochemical impedance measured in pig brain in vitro shows marked differences from that of saline.

Neutrophil-to-Lymphocyte Ratio as an Indicator of Opioid-Induced Immunosuppression After Thoracoscopic Surgery: A Randomized Controlled Trial.

Purpose: The neutrophil-to-lymphocyte ratio (NLR) is a useful prognostic marker for various diseases and surgery-induced immunosuppression. While opioids are important in general anesthesia, the association between immediate perioperative immune monitoring and opioid consumption for postoperative analgesia after video-assisted thoracoscopic surgery (VATS) is unknown. We aimed to investigate the effect of analgesic techniques on opioid-induced immune perturbation, and the feasibility of NLR as an indicator of opioid-induced immune changes. Patients and Methods: Patients were randomly assigned to two groups: Group P (n=40) or Group C (n=40). Patients in group P received ultrasound-guided paravertebral block (PVB) before surgery, and followed by sufentanil patient-controlled intravenous analgesia (PCIA) after surgery, and group C received sufentanil PCIA only. The total and differential white blood cell counts, including CD4+ T lymphocyte counts, CD8+ T lymphocyte were recorded before surgery and at 24 and 72 hours after surgery. NLR was determined using the frequencies of lymphocyte subpopulations. The cumulative dose of sufentanil were recorded at 24 and 24h after surgery while the 40-item quality of recovery questionnaire (QoR-40) score were assessed at 48h after the surgery. Results: At 24 and 48 hours after surgery, a lower sufentanil consumption, and higher QoR-40 recovery scores were found in group P than in group C (P<0.05). In biochemical analyses, the values of NLR were lower in group P compared to group C (p<0.0001) and ratio of CD4/CD8 were higher in group P compared to group C (p<0.05) on day three after surgery. NLR showed excellent predictive capability for immunosuppression, with an area under the curve (AUC) of 0.92 [95% confidence interval (CI), 0.86-0.98, P < 0.0001]. Conclusion: Opioid-sparing pain management strategies may affect postoperative immunosuppression and NLR could be a reliable indicator of opioid-related immunosuppression. Moreover, opioid-sparing pain management strategies could improve patient's satisfaction in VATS.

Micropore filling fabrication of high resolution patterned PQDs with a pixel size less than 5 µm.

PQDs are promising color converters for micro-LED applications. Here we report the micropore filling fabrication of high resolution patterned PQDs with a pixel size of 2 µm using a template with SU8 micropores.

Flexible Quantum-Dot Color-Conversion Layer Based on Microfluidics for Full-Color Micro-LEDs.

In this article, red and green perovskite quantum dots are incorporated into the pixels of a flexible color-conversion layer assembly using microfluidics. The flexible color-conversion layer is then integrated with a blue micro-LED to realize a full-color display with a pixel pitch of 200 µm. Perovskite quantum dots feature a high quantum yield, a tunable wavelength, and high stability. The flexible color-conversion layer using perovskite quantum dots shows good luminous and display performance under different bending conditions; is easy to manufacture, economical, and applicable; and has important potential applications in the development of flexible micro-displays.

MRI magnetic compatible electrical neural interface: From materials to application.

Neural electrical interfaces are important tools for local neural stimulation and recording, which potentially have wide application in the diagnosis and treatment of neural diseases, as well as in the transmission of neural activity for brain-computer interface (BCI) systems. At the same time, magnetic resonance imaging (MRI) is one of the effective and non-invasive techniques for recording whole-brain signals, providing details of brain structures and also activation pattern maps. Simultaneous recording of extracellular neural signals and MRI combines two expressions of the same neural activity and is believed to be of great importance for the understanding of brain function. However, this combination makes requests on the magnetic and electronic performance of neural interface devices. MRI-compatibility refers here to a technological approach to simultaneous MRI and electrode recording or stimulation without artifacts in imaging. Trade-offs between materials magnetic susceptibility selection and electrical function should be considered. Herein, prominent trends in selecting materials of suitable magnetic properties are analyzed and material design, function and application of neural interfaces are outlined together with the remaining challenge to fabricate MRI-compatible neural interface.

Investigation and Optimization of a Line-Locked Quartz Enhanced Spectrophone for Rapid Carbon Dioxide Measurement.

We have developed a rapid quartz enhanced spectrophone for carbon dioxide (CO2) measurement, in which the laser wavelength was tightly locked to a CO2 absorption line and a custom quartz tuning fork (QTF) operating at 12.5 kHz was employed. The intrinsic QTF oscillation-limited response time, as well as the optimal feedback interval, was experimentally investigated. By tightly locking the laser to the R(16) transition of CO2, we obtained a stable laser operation with its center wavelength variation kept within 0.0002 cm-1, merely three times the laser linewidth. The reported CO2 sensor achieved a detection limit of 7 ppm, corresponding to a normalized noise equivalent absorption coefficient (NNEA) of 4.7 × 10-9 W·cm-1·Hz-1/2, at a response time of 0.5 s. The detection limit can be further improved to 0.45 ppm at an integration time of 270 s, illustrating a good system stability. This spectrophone enables the realization of compact and fast-response gas sensors for many scenarios, where CO2 concentration from sub-ppm to hundreds of thousands of ppm is expected.

An Image Study on Local Anesthetic Spread in Healthy Volunteers Receiving Subcostal Exterior Semilunaris Transversus Abdominis Plane (SE-TAP) Block.

BACKGROUND: Despite the popularity of the ultrasound-guided transversus abdominis plane (TAP) block and the diversity of advancing approaches, the extent of injectate spread limits its clinical benefits. This study used three-dimensional computed tomography (3D-CT) imaging and a cold stimulus to evaluate the spread of a local anesthetic injected through the subcostal exterior semilunaris to transversus abdominis plane (SE-TAP) block in healthy volunteers. METHODS: Eight healthy volunteers received a right-side ultrasound-guided SE-TAP block with 25 mL of 0.3% ropivacaine. The sensory block was assessed by a cold stimulus at 30 min, 2 h, 4 h, and 8 h following the SE-TAP block according to the 18-zone division method. A CT scan and 3D imaging were performed after the first sensory assessment. RESULTS: The injectate spread into the transversus abdominis space in all eight volunteers. 3D imaging confirmed that the injectate spread extensively along the costal margin in the plane of the transverse abdominis muscle and that it surpassed the semilunaris. Regarding the assessment using cold stimulus, five of six anterior zones and three of six lateral zones obtained successful rates of cutaneous sensory block higher than 75% 30 min after SE-TAP. Sensory block was achieved in the ventral dermatomes of all volunteers. CONCLUSION: Our study showed that the SE-TAP injectate, which was administered using simple anatomical landmarks to provide reliable analgesia for abdominal surgery, consistently spread along the costal margin and extensively blocked cutaneous sensitivity in the anterior and lateral abdominal walls.

2000 PPI silicon-based AlGaInP red micro-LED arrays fabricated via wafer bonding and epilayer lift-off.

In this article, 2000 PPI red silicon-based AlGaInP micro-LED arrays were fabricated and investigated. The AlGaInP epilayer was transferred onto the silicon substrate via the In-Ag bonding technique and an epilayer lift-off process. The silicon substrate with a high thermal conductivity could provide satisfactory heat dissipation, leading to micro-LED arrays that had a stable emission spectrum with increasing current density from 20 to 420 A/cm2 along with a red-shift of the peak position from 624.69 to 627.12 nm (Δλ = 2.43 nm). Additionally, increasing the injection current density had little effect on the CIE (x, y) of the micro-LED arrays. Further, the I-V characteristics and light output power of micro-LED arrays with different pixel sizes demonstrated that the AlGaInP red micro-LED array on a silicon substrate had excellent electrical stability and optical output.