Pressure-Compensated Fiber-Optic Photoacoustic Sensors for Trace SO2 Analysis in Gas Insulation Equipment.

A high-sensitivity fiber-optic photoacoustic sensor with pressure compensation is proposed to analyze the decomposition component SO2 in high-pressure gas insulation equipment. The multiple influence mechanism of pressure on photoacoustic excitation and cantilever detection has been theoretically analyzed and verified. In the high-pressure environment, the excited photoacoustic signal is enhanced, which compensates for the loss of sensitivity of the cantilever. A fiber-optic F-P cantilever is utilized to simultaneously measure static pressure and dynamic photoacoustic wave, and a spectral demodulation method based on white light interference is applied to calculate the optical path difference of the F-P interferometer (FPI). The real-time pressure is judged through the linear relationship between the average optical path difference of FPI and the pressure, which gives the proposed fiber-optic photoacoustic sensor the inherent advantages of being uncharged and resistant to electromagnetic interference. The average optical path difference of FPI is positively related to pressure, with a responsivity of 0.6 µm/atm, which is based on changes in the refractive index of gas. In the range of 1-4 atm, the SO2 sensor has a higher detection sensitivity at high-pressure, which benefits from the pressure compensation effect. With the pressure environment of gas insulation equipment at 4 atm as the application background, the SO2 gas is tested. The detection limit is 20 ppb with an averaging time of 400 s.

Trends in population attributable fraction of modifiable risk factors for cardiovascular diseases across three decades.

AIM: To evaluate temporal trends, across three decades, in the population attributable fractions (PAFs) of modifiable risk factors for 5-year risk of cardiovascular diseases (CVDs). METHODS: Within population-based Rotterdam Study, we defined three time-groups of individuals without established CVD at 'baseline' with a mean age of 70 years, and followed for five years: Epoch 1990s (1989-1993, N=6195), Epoch 2000s (1997-2001, N=5572) and Epoch 2010s (2009-2014, N=5135). The prevalence of risk factors and related relative risks were combined to quantify PAFs. RESULTS: The PAF of the six risk factors combined for global CVD was 0.57 (95% confidence interval [CI] 0.47 to 0.65), 0.52 (0.39 to 0.62) and 0.39 (0.18 to 0.54) in three respective epochs. Hypertension contributed the highest PAF to global CVD in Epoch 1990s (0.37, 95% CI: 0.28 to 0.44) and 2000s (0.34, 95% CI: 0.22 to 0.43), while smoking was the largest contributor in Epoch 2010s (0.20, 95% CI: 0.06 to 0.32). Dyslipidemia changed population-level coronary heart disease risk over time. For stroke, hypertension became a less significant contributor over time, but smoking became a larger contributor. For heart failure, all risk factors showed non-significant PAFs in Epoch 2010s. PAFs related to individual risk factor varied among women and men. CONCLUSION: Six modifiable risk factors to population-level global CVD risk decreased over time, but still explained 39% of total CVD in the latest decade. PAFs changed considerably for hypertension, dyslipidemia, and smoking. Risk factors had different PAFs for different CVDs with pronounced sex differences.

The contribution of the individual cardiovascular risk factors to population CVD risk considerably changed over the past 3 decades, especially for hypertension, dyslipidemia, and smoking. Traditional modifiable risk factors exerted declining contributions to population burden of total CVD over the past three decades, suggesting good progress in CVD prevention. Nonetheless, in the latest decade, unfavorable risk factors accounted for 39% of total CVD burden. Sex differences in the contributions of abdominal obesity, diabetes and smoking to cardiovascular outcomes were observed.

Fiber-Optic Photoacoustic Gas Microsensor Dual Enhanced by Helmholtz Resonator and Interferometric Cantilever.

A high-sensitivity fiber-optic photoacoustic (PA) gas microsensor is demonstrated with dual enhancement based on acoustics and detection. Due to the characteristic of small size, a Helmholtz resonator is integrated into a miniature PA sensor. The acoustically amplified PA signal is detected by a high-sensitivity fiber Fabry-Perot (F-P) interferometric cantilever. The first-order resonant frequencies of the interferometric cantilever and Helmholtz resonator are matched by subtle adjustments. The weak PA signal is significantly enhanced in a volume of only 0.35 mL, which breaks the volume limitation of the resonance modes in traditional PA sensing systems. To improve the resolution of the microsensor, a white light interferometry (WLI)-based spectral demodulation algorithm is utilized. The experimental results indicate that the minimum detection limit of acetylene (C2H2) drops to about 15 ppb with an averaging time of 100 s, corresponding to the normalized noise equivalent absorption (NNEA) coefficient of 2.7 × 10-9 W·cm-1·Hz-1/2. The dual resonance enhanced fiber-optic PA gas microsensor has the merits of high sensitivity, intrinsic safety, and compact structure.

Rapid Photoacoustic Exhaust Gas Analyzer for Simultaneous Measurement of Nitrogen Dioxide and Sulfur Dioxide.

A rapid photoacoustic (PA) exhaust gas analyzer is presented for simultaneous measurements of nitrogen dioxide (NO2) and sulfur dioxide (SO2). A laser diode (LD) emitting at 450 nm and a light-emitting diode (LED) with a peak wavelength of 275 nm operated simultaneously, producing PA signals of NO2 and SO2, respectively. The LD and LED were modulated at different frequencies of 2568 and 2570 Hz, and their emission light beams were transmitted through two resonant tubes in a differential PA cell (DPAC), respectively. A self-made dual-channel digital lock-in amplifier was used to realize the simultaneous detection of dual-frequency PA signals. Cross interference between the PA signals at the two different frequencies was reduced to 0.02% by using a lock-in amplifier. In order to achieve a rapid dynamic measurement, gas sampling was accelerated by an air pump. The use of mufflers and the differential PA detection technique significantly reduced the gas sampling noise. When the gas flow rate was 1000 sccm, the response time of the PA dual-gas analyzer was 8 and 17 s for NO2 and SO2, respectively. The minimum detection limits of NO2 and SO2 were 1.7 and 26.1 ppb when the averaging time of the system was 10 s, respectively. Due to the wide spectral bandwidth of the LED, NO2 produced an interference to the detection of SO2. The interference was reduced by the precise detection of NO2. Since the radiations of the LD and LED passed through two different PA tubes, the impact of NO2 photochemical dissociation caused by UV LED luminescence on NO2 gas detection was negligible. The sharing of the PA cell, the gas lines, and the signal processing modules significantly reduced the size and cost of the PA dual-gas analyzer.

Fiber-Optic Photoacoustic CO Sensor for Gas Insulation Equipment Monitoring Based on Cantilever Differential Lock-In Amplification and Optical Excitation Enhancement.

A fiber-optic photoacoustic CO sensor for gas insulation equipment is proposed, which relies on F-P interferometric cantilever-based differential lock-in amplification and optical multipass excitation enhancement. The sensor has excellent characteristics of high sensitivity, antielectromagnetic interference, fast response, and long-distance detection. The photoacoustic pressure waves in the two resonators of the differential photoacoustic cell (DPAC) are simultaneously detected by two fiber-optic interferometric cantilevers and processed differentially; thereby, the gas flow noise is effectively suppressed. Based on the comprehensive analysis of the superposition of photoacoustic excitation and multipass absorption, the diameter of the resonator is determined to be 6 mm. The optical power emitted by the 1566.6 nm distributed feedback laser is increased to 500 mW by an erbium-doped fiber amplifier. The near-infrared light is reflected 30 times in the multipass cell, which improves the order of magnitude of optical effective excitation. Due to the low sound velocity of SF6 gas, the resonant frequency of the DPAC with a resonator length of 80 mm is 760 Hz. The response time to CO/SF6 gas is 93 s with a flow rate of 500 sccm. The detection limit of the CO sensor is 53 ppb, which realizes the accurate and timely perception of the SF6 decomposition derivative CO and provides technical support for trouble-free operation of gas insulation equipment.

Differential Cantilever Enhanced Fiber-Optic Photoacoustic Sensor for Diffusion Gas Detection.

Aiming at the problem of the fiber-optic photoacoustic (PA) sensor being easily disturbed by external vibration and noise, a differential cantilever enhanced fiber-optic PA sensor is proposed for diffusion gas detection. The sensor comprises two PA tubes with the same structure and a pair of differential interferometric cantilevers. The two PA tubes are symmetrically distributed. The laser is incident on the PA tube as the signal channel to excite the PA pressure wave. Another tube without incident laser is used as the reference channel to suppress external disturbance. The external interference signals and PA signals superimposed with disturbance are detected by the differential cantilevers from the two channels. The signals are simultaneously restored by a single white-light interferometry demodulator, which multiplexed the spectral frequency domain of the superimposed interference spectrum. The experimental results show that the suppression effect of the differential cantilever enhanced PA sensor on ambient noise is improved by 80%, compared to the traditional single-cantilever sensor. The external cofrequency disturbance is suppressed by 20.9 dB. The minimum detection limit to acetylene (C2H2) downs to about 60 ppb with an integration time of 100 s. The sensor has excellent antivibration and electromagnetic interference ability.

Dense Multibutterfly Spots-Enhanced Miniaturized Optical Fiber Photoacoustic Gas Sensor.

A miniaturized optical fiber photoacoustic gas sensor enhanced by dense multibutterfly spots is reported for the first time. The principle of space light transmission of neglecting paraxial approximation is theoretically analyzed for designing a dense multibutterfly spots-based miniature multipass cell. In a multipass photoacoustic tube with a diameter of 16 mm, the light beam is reflected about a hundred times. The light spots on the mirror surfaces at both ends of the photoacoustic tube form a dense multibutterfly distribution. The volume of the micro multipass gas chamber is only 5.3 mL. An optical fiber cantilever based on F-P interference is utilized as a photoacoustic pressure detector. Compared with that of the single-pass structure, the gas detection ability of the photoacoustic system with dense multibutterfly spots is improved by about 50 times. The proposed miniaturized sensor realizes a detection limit of 3.4 ppb for C2H2 gas with an averaging time of 100 s. The recognized coefficients of minimum detectable absorption (αmin) and normalized noise equivalent absorption are 1.9 × 10-8 cm-1 and 8.4 × 10-10 W cm-1 Hz-1/2, respectively.

High-Precision Multipass Fiber-Optic Photoacoustic Gas Analyzer Based on 2f/1f Wavelength Modulation Spectroscopy.

A self-calibration fiber-optic photoacoustic (PA) gas analyzer based on 2f/1f wavelength modulation spectroscopy (WMS) is proposed, which utilizes gas and solid multipass absorption enhancement. The laser light is incident obliquely on the cell wall, and one end of the cell is equipped with a highly reflective mirror. The gas analyzer takes full advantage of the miniature multipass PA cell, which enhances the absorption of gas and solid simultaneously. As a result, the double absorption enhancement of 1f and 2f PA signals are realized. A dual-channel lock-in white-light interferometer based on fiber-optic PA demodulation is designed to simultaneously extract the 1f and 2f PA signals detected by the silicon cantilever. The experimental results of methane gas detection show that the minimum detection limit (MDL) of the PA gas analyzer is 20 ppb when the integration time is 60 s. Moreover, the detection error of gas concentration is within 3% when the laser power is reduced by half. The fiber-optic PA gas analyzer eliminates the influence of changes in the laser power and optical path loss, which can be used for the high-precision detection of trace gases.

High-Precision Photoacoustic Nitrogen Dioxide Gas Analyzer for Fast Dynamic Measurement.

A high-precision photoacoustic (PA) gas analyzer for fast dynamic measurement of ambient nitrogen dioxide (NO2) was developed. The PA analyzer used a differential PA cell combined with two mufflers to achieve rapid gas flow gas detection. A high-power laser diode (LD) with a center wavelength of 450 nm was used as the PA signal excitation source. To reduce the saturated absorption effect of NO2, ambient air was pumped into the analyzer at a flow rate of 900 sccm. Two mufflers were combined with the differential PA cell to reduce the noise caused by the airflow and pump. The parameters of the mufflers were optimized by using a finite element method. The experimental results showed that the gas flow noise was suppressed by 95%. The response time of the PAS analyzer was 34 s. The detection limits of the analyzer were 0.64 and 0.17 ppb when the integration times were 1 and 15 s, respectively. A 120 h continuous monitoring result was compared with the data from the National Environmental Monitoring Station to demonstrate the high reliability of the analyzer.

Ultrahigh Sensitive Trace Gas Sensing System with Dual Fiber-Optic Cantilever Multiplexing-Based Differential Photoacoustic Detection.

An ultrahigh sensitive trace gas sensing system was presented with dual cantilever-based differential photoacoustic detection. By combining the double enhancement of multipass absorption and optical differential detection, the gas detection sensitivity was significantly improved. The dual-channel synchronous photoacoustic detection was realized by fiber-optic Fabry-Perot interference spectrum multiplexing. The photoacoustic signals detected by two fiber-optic cantilever microphones installed in a differential photoacoustic cell (DPAC) were out of phase, while the detected gas flow noises were in phase. The optical differential detection method achieved both highly sensitive optical interference measurement and differential noise suppression. In the multipass configuration, the interaction path between excitation light and target gas achieved 4.1 m, which improved the photoacoustic signal by an order of magnitude compared with a single reflection. The maximum gas flow allowed by the system based on the DPAC was 250 sccm, which realized the dynamic monitoring of H2S in the SF6 background. The detection limit for H2S in SF6 background was 5.1 ppb, which corresponds to the normalized noise equivalent absorption coefficient of 9 × 10-10 cm-1 W Hz-1/2.

Fiber-Optic Photoacoustic Gas Sensor with Multiplexed Fabry-Pérot Interferometric Cantilevers.

A fiber-optic photoacoustic (PA) gas sensor with multiplexed Fabry-Pérot (F-P) interferometric cantilevers is demonstrated. A compact cylindrical nonresonant PA tube with a volume of only 0.45 mL is designed. The PA signal is measured by two symmetrically installed fiber-optic interferometric cantilever microphones (FOICMs) to improve the signal-to-noise ratio (SNR). For multiplexing the two cantilevers by a single demodulation system, a dual cavity length synchronous measurement method based on total-phase demodulation algorithm with ultrahigh resolution is developed. The PA signal detection is realized by the second-harmonic wavelength modulation spectroscopy (2f-WMS) technique. The sensor performance is verified by conducting the detection of trace acetylene (C2H2). The normalized noise equivalent absorption (NNEA) coefficient is 2.5 × 10-9 cm-1·W·Hz-1/2, and the minimum detection limit (MDL) downs to about 0.2 ppm with an averaging time of 1 s. The fiber-optic PA gas sensor has characteristics of high resolution and immunity to electromagnetic and vibration interference. Furthermore, the technical scheme of the multiplexed cantilever demodulation shows great potential for remote multipoint monitoring of gases in harsh environments.

Integrated near-infrared fiber-optic photoacoustic sensing demodulator for ultra-high sensitivity gas detection.

An integrated near-infrared fiber-optic photoacoustic sensing demodulator was established for ultra-high sensitivity gas detection. The demodulator has capacities of interference spectrum acquisition and calculation, laser modulation control as well as digital lock-in amplification. FPGA was utilized to realize all the control and signal processing functions, which immensely improved the integration and stability of the system. The photoacoustic signal detection based on fiber-optic Fabry-Perot (F-P) acoustic sensor was realized by applying ultra-high resolution spectral demodulation technique. The detectable frequency of photoacoustic signal achieved 10 kHz. The system integrated lock-in amplification technology, which made the noise sound pressure and dynamic response range of sound pressure detection reached 3.7 µPa/√Hz @1 kHz and 142 dB, respectively. The trace C2H2 gas was tested with a multi-pass resonant photoacoustic cell. Ultra-high sensitivity gas detection was accomplished, which was based on high acoustic detection sensitivity and the matching digital lock-in amplification. The system detection limit and normalized noise equivalent absorption (NNEA) coefficient were reached 3.5 ppb and 6.7 × 10-10 cm-1WHz-1/2, respectively. The devised demodulator can be applied for long-distance gas measurement, which depends on the fact that both the near-infrared photoacoustic excitation light and the probe light employ optical fiber as transmission medium.

Arthroscopic versus Open Distal Hemitrapeziectomy without Interposition: 2-Year Results of a Randomized Controlled Trial.

BACKGROUND: Distal hemitrapeziectomy is suggested as an alternative for total trapeziectomy for carpometacarpal thumb joint osteoarthritis, when the scaphotrapeziotrapezoidal joint is unaffected. This can be performed as an arthroscopic or open procedure, with suggested advantages for the less invasive arthroscopic technique. To determine which technique has better outcome on subjective and objective measures, the authors performed a prospective, randomized, controlled trial. METHODS: The authors randomized 90 thumbs in the open ( n = 45) and arthroscopic ( n = 45) groups and evaluated results preoperatively and at 3-, 12- and 24-month follow-up. The primary outcome was the Patient-Rated Wrist and Hand Evaluation (PRWHE) to assess pain and function. Also, the authors evaluated pinch, grip, and range of motion, together with return to work, satisfaction, and complications. RESULTS: Full follow-up was obtained in 62 thumbs (open group, n = 32; arthroscopic group, n = 30). For both groups, the PRWHE improved from preoperatively to 12- and 24-month follow-up. Also, grip power, key pinch, and tip pinch improved at final follow-up for both groups. Between groups, there were no clinically important differences between PRWHE, power of grip or pinch, and range of motion. Operation time was shorter for the open group; also, return to work was slightly shorter after open surgery. Satisfaction was comparable between groups. CONCLUSIONS: This study shows good functional improvement and pain reduction obtained with a hemitrapeziectomy. No arthroscopic benefits could be substantiated in the results. Because of shorter operation time for the open procedure, and because of equal outcomes compared to the arthroscopic technique, we prefer open hemitrapeziectomy. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, I.

Risk factors for metastatic cutaneous squamous cell carcinoma: Refinement and replication based on 2 nationwide nested case-control studies.

BACKGROUND: Risk factors for cutaneous squamous cell carcinoma (cSCC) metastasis have been investigated only in relatively small data sets. OBJECTIVE: To analyze and replicate risk factors for metastatic cSCC. METHODS: From English and Dutch nationwide cancer registry cohorts, metastatic cases were selected and 1:1 matched to controls. The variables were extracted from pathology reports from the National Disease Registration Service in England. In the Netherlands, histopathologic slides from the Dutch Pathology Registry were revised by a dermatopathologist. Model building was performed in the English data set using backward conditional logistic regression, whereas replication was performed using the Dutch data set. RESULTS: In addition to diameter and thickness, the following variables were significant risk factors for metastatic cSCC in the English data set (n = 1774): poor differentiation (odds ratio [OR], 4.56; 95% CI, 2.99-6.94), invasion in (OR, 1.69; 95% CI, 1.05-2.71)/beyond (OR, 4.43; 95% CI, 1.98-9.90) subcutaneous fat, male sex (OR, 2.59; 95% CI, 1.70-3.96), perineural/lymphovascular invasion (OR, 2.12; 95% CI, 1.21-3.71), and facial localization (OR, 1.57; 95% CI, 1.02-2.41). Diameter and thickness showed significant nonlinear relationships with metastasis. Similar ORs were observed in the Dutch data set (n = 434 cSCCs). LIMITATIONS: Retrospective use of pathology reports in the English data set. CONCLUSION: cSCC staging systems can be improved by including differentiation, clinical characteristics such as sex and tumor location, and nonlinear relationships for diameter and thickness.

To screen or not to screen? The development of a prediction model for aorto-iliac stenosis in kidney transplant candidates.

Screening for aorto-iliac stenosis is important in kidney transplant candidates as its presence affects pre-transplantation decisions regarding side of implantation and the need for an additional vascular procedure. Reliable imaging techniques to identify this condition require contrast fluid, which can be harmful in these patients. To guide patient selection for these imaging techniques, we aimed to develop a prediction model for the presence of aorto-iliac stenosis. Patients with contrast-enhanced imaging available in the pre-transplant screening between January 1st, 2000 and December 31st, 2018 were included. A prediction model was developed using multivariable logistic regression analysis and internally validated using bootstrap resampling. Model performance was assessed with the concordance index and calibration slope. Three hundred and seventy-three patients were included, 90 patients (24.1%) had imaging-proven aorto-iliac stenosis. Our final model included age, smoking, peripheral arterial disease, coronary artery disease, a previous transplant, intermittent claudication and the presence of a femoral artery murmur. The model yielded excellent discrimination (optimism-corrected concordance index: 0.83) and calibration (optimism-corrected calibration slope: 0.91). In conclusion, this prediction model can guide the development of standardized protocols to decide which patients should receive vascular screening to identify aorto-iliac stenosis. External validation is needed before this model can be implemented in patient care.

Implementation of donation after circulatory death kidney transplantation can safely enlarge the donor pool: A systematic review and meta-analysis.

BACKGROUND: Donation after circulatory death (DCD) kidney transplantation has been introduced to address organ shortage. However, DCD kidneys are not accepted worldwide due to concerns about inferior quality. To investigate whether these concerns are justified, we performed a systematic review and meta-analysis to investigate DCD graft outcomes compared to donation after brain death (DBD). MATERIALS AND METHODS: EMBASE, Medline, Cochrane, Web of Science and Google Scholar were searched from database inception until September 2020. Exclusion criteria were studies reporting on pediatric/dual kidney transplants, multi-organ transplants or studies including normothermic perfusion techniques. The primary outcome was graft survival. Secondary outcomes were primary non-function (PNF), delayed graft function (DGF), 3-months biopsy-proven acute rejection (BPAR), 1-year estimated Glomerular Filtration Rate (eGFR), patient survival, and urologic complications. A random-effects model was used for meta-analysis. Meta-regression analysis was performed in case of high between-study heterogeneity. RESULTS: Fifty-one studies were included, comprising 73,454 DCD and 518,229 DBD recipients. One-year graft loss was increased in DCD recipients (death-censored: risk ratio (RR) 1.10 (95%-confidence interval (CI) 1.04-1.16), all-cause: RR 1.13 (95%-CI 1.08-1.19)). Ten-year graft loss was similar to DBD (death-censored: RR 1.02 (95%-CI 0.92-1.13), all-cause: RR 1.03 (95%-CI 0.94-1.13)). DCD recipients had an increased risk of PNF (RR 1.43 (95%-CI 1.26-1.62)), DGF (RR 2.02 (95%-CI 1.88-2.16)), and 1-year mortality (RR 1.10 (95%-CI 1.01-1.21)). No differences were observed for 3-months BPAR, ureter stenosis/leakage, 1-year eGFR and 10-year mortality. CONCLUSION: Long-term DCD kidney transplant outcomes are similar to DBD despite a higher risk of PNF, DGF, and a 13% increased risk of graft loss in the first year after transplantation. These results should encourage implementation of DCD programs.

Added Value of Radiotherapy Following Neoadjuvant FOLFIRINOX for Resectable and Borderline Resectable Pancreatic Cancer: A Systematic Review and Meta-Analysis.

BACKGROUND: The added value of radiotherapy following neoadjuvant FOLFIRINOX chemotherapy in patients with resectable or borderline resectable pancreatic cancer ((B)RPC) is unclear. The objective of this meta-analysis was to compare outcomes of patients who received neoadjuvant FOLFIRINOX alone or combined with radiotherapy. METHODS: A systematic literature search was performed in Embase, Medline (ovidSP), Web of Science, Scopus, Cochrane, and Google Scholar. The primary endpoint was pooled median overall survival (OS). Secondary endpoints included resection rate, R0 resection rate, and other pathologic outcomes. RESULTS: We included 512 patients with (B)RPC from 15 studies, of which 7 were prospective nonrandomized studies. In total, 351 patients (68.6%) were treated with FOLFIRINOX alone (8 studies) and 161 patients (31.4%) were treated with FOLFIRINOX and radiotherapy (7 studies). The pooled estimated median OS was 21.6 months (range 18.4-34.0 months) for FOLFIRINOX alone and 22.4 months (range 11.0-37.7 months) for FOLFIRINOX with radiotherapy. The pooled resection rate was similar (71.9% vs. 63.1%, p = 0.43) and the pooled R0 resection rate was higher for FOLFIRINOX with radiotherapy (88.0% vs. 97.6%, p = 0.045). Other pathological outcomes (ypN0, pathologic complete response, perineural invasion) were comparable. CONCLUSIONS: In this meta-analysis, radiotherapy following neoadjuvant FOLFIRINOX was associated with an improved R0 resection rate as compared with neoadjuvant FOLFIRINOX alone, but a difference in survival could not be demonstrated. Randomized trials are needed to determine the added value of radiotherapy following neoadjuvant FOLFIRINOX in patients with (B)PRC.