Standard Gas Research Articles

Anthelmintic Potential of Vernonia amygdalina on Toxocara canis in Domesticated Dogs

Toxocariasis is a worldwide zoonotic parasitic infection and one route of preventing the disease in dogs and subsequent transmission to humans, especially children, is through treatment with anthelmintic. A study aimed at assessing the anthelmintic efficacy of Vernonia amygdalina leaves extract on Toxocara canis in domesticated dogs was carried out where the proximate and phytochemical components of the leaf extract were determined using the standard method and Gas Chromatography-Mass Spectrometry, the anthelmintic efficacy was assessed in vitro and in vivo respectively. The study revealed that this plant contained alkaloids, saponins, tannins, glycosides, flavonoids, terpenoids, phenol and steroids. Lethal concentration (LC50) of 14.83ml/mg at 12 hours and a percentage egg reduction of 84% after 2 weeks was recorded, which revealed that the plant leaves have anthelmintic potential and this could be attributed to the presence of flavonoids which are associated with the treatment of gastric infections and also n-Hexadecanoic acid which accounts for it anthelmintic (nematicidal) effect, alongside Octadecanoic acid which is an anti-inflammatory compound.

ON THE USE OF PSP TO DETERMINE THE RIM SEALING EFFECTIVENESS

Abstract The control of cavities sealing has been a challenging problem since early gas turbine development stages and several aspects regarding the flow physics and the modelling of rim seal flows still represent an open question. Fundamental test cases have been used in the open literature to characterize the level of ingestion by varying the main flow parameters and the geometrical features. In most of them, the effectiveness is measured by using taps connected to a gas analyzer used to sample the concentration of a foreign gas on the stator surface used to seed the purge flow. Consequently, the results are usually single point measurements, unsteady effects are inevitably neglected, the intrusiveness of the approach must be carefully checked and the application on the rotor side demands for complex slip-rings or telemetry. To overcome these limitations, the current work presents the application of the PSP technique to the study of hot gas ingestion phenomena on a single stage rotating cold rig. The 2D distributions of partial pressure of oxygen collected through the wide optical accesses present in the rig were then related to the seal effectiveness. The proposed methodology was firstly validated through a comparison with the data obtained from standard gas sampling and then applied as main experimental technique. The analysis of the results highlighted the capabilities of the PSP to fast collect data on both stator and rotor side, including the tip of the seal tooth where non uniform efficiency distributions in the circumferential direction have been detected.

Mechanisms and Application of Gas-Based Anticancer Therapies.

Cancer is still one of the major factors threatening public health, with morbidity and mortality rates at the forefront of the world. Clinical drawbacks, such as high toxicity and side effects of drug therapy, and easy recurrence after surgery affect its therapeutic effect. Gas signaling molecules are essential in maintaining biological homeostasis and physiological functions as specific chemical substances for biological information transfer. In recent years, the physiological regulatory functions of gas molecules in the cancer process have been gradually revealed and have shown broad application prospects in tumor therapy. In this paper, standard gas therapies are classified and introduced. Taking H2, CO2, NO, CO, H2S, and SO2 gases as examples, the research progress and application of gas therapies in malignant tumors are mainly introduced in terms of biological characteristics, anticancer mechanisms, and treatment strategies. Finally, the problems and prospects for developing gases as anticancer drugs are outlined.

A-387 Evaluation of the Analytical and Clinical Performance of epoc Point of Care Equipment Compared to Standard Blood Gas in Patients with Nephropathy

Abstract Backgroud Chronic kidney disease (CKD) is a public health problem, characterized by progressive loss of function of nephrons with consequent loss of ability to filter blood and maintain homeostasis. Due to the absence of symptoms, CKD usually receives a late diagnosis, which causes the patient to be immediately submitted to the hemodialysis procedure. Therefore, it is important that the patient has a fast and effective diagnosis, however it is necessary that it be done with clinical and analytical safety. Objective This study aimed to evaluate the performance of siemens Healthineers epoc® platform for the quantification of blood gas parameters, glucose, creatinine, ions, hemoglobin, hematocrit comparing this equipment with the reference methodology for blood gases in patients with CKD. Methods Eighty-five blood samples obtained from patients under clinical follow-up with nephrologists were collected and processed at epoc® and compared with the RapidPoint®500e Siemens Healthineers platform. Creatinine was compared with Abbott platform Architect®. Discrepancies related to clinical values and/or analyses were evaluated, considering the reference values determined for each method. For analytical verification, we analyzed the means of the results of each methodology, the percentage differences between the means of the results and Pearson's correlation coefficient. Results For clinical analysis considering the reference values for each method, all analyses were approved. Pearson's correlation coefficient was obtained for pH = 0.97, for pCO2 = 0.953 and pO2 = 0.9947. For glucose, the value of 0.9919 was obtained and for the ions, 0.887 for Na+ (sodium), 0.9727 K+ (potassium) and 0.9406 for Cl- (chloride). For Hb and Hct were 0.825 and 0.8231, respectively. For creatinine it was 0.9339. The analysis showed the differences in mean for Hb = 2.25%, Hct = 2.22%, ph = 0.1505%, pCO2 = 10%, pO2 = 6.28%, Na+ = 1.84%, Cl- = 3.93%, K+ = 1.77%, while glucose was 2.43% difference and creatinine 1.152%. The range analyzed for Hbt was 5.4–20.4, for ph of (7.133–7.475), for POC2 (29.8–115.8), for pO2 (15.1–118.4), for (Na+ 124.0–150.0), for (K+ 1.50–7.80), for (Cl- 92.0–121.0) and for K+ (1.50–7.80), for glucose (43.0–303.0). For creatinine it was (0.63–15.00) and (16.0–60.0) for hematocrit. In the accuracy evaluation, was obtained: Na+ (CVg = 2,4/DP = 3,29), K+ (CVg = 17,8/DP = 0,84), Cl-(CVg = 4,5/DP = 4,68), Glucose (CVg = 47,2/DP = 75,83), Creatinine (CVg = 32,6/DP = 3,10), ph (CVg = 0,883/DP = 0,065), pCO2 (CVg = 26,68/DP = 12,82), pO2 (CVg = 50,15/DP = 29,42), Hct (CVg = 24,43/DP = 9,0), Hbt (CVg = 24,43/DP = 3,08). Conclusion The study proved good results for the comparability between the epoc equipment® and the standard methodology. In addition, there was no difference in the clinical interpretation of patient studied, which is essential to ensure the safety in the use of these methodologies in the diagnosis and follow-up of CDK.

MATOQ: a Monte Carlo simulation of electron transport in environmental-friendly gas mixtures for Resistive Plate Chambers

The increasing interest in environmental-friendly gas mixtures for gaseous particle detectors, especially tetrafluoropropene-based gas mixtures for Resistive Plate Chambers (RPCs), has prompted in recent years the need for simulating electron transport coefficients and reaction rates in these mixtures. MATOQ is a Monte Carlo simulation program that calculates electron transport parameters, specifically designed for studying and optimizing environmental-friendly gas mixtures for RPCs. Unlike other existing codes, MATOQ allows for the simulation of electron avalanches by including the effect of space charge electric field, which can significantly impact the avalanche evolution in gaseous detectors such as RPCs. After the validation of the MATOQ simulation in the temporal and spatial growth configurations, we present the electron transport coefficients and the reaction rates in tetrafluoropropene-based gas mixtures, which may represent a valid alternative to the standard gas mixtures currently used for RPCs.

Studies on RPC detectors operated with environmentally friendly gas mixtures in LHC-like conditions

Resistive Plate Chambers (RPC) are gasesous detectors employed at CERN LHC experiments thanks to their trigger performance, timing capabilities and contained production costs. High Pressure Laminate RPCs are operated with a three-component gas mixture, made of 90–95% of C_2H_2F_4, around 5% of i-C_4H_{10} and 0.3% of SF_6. Due to the presence of leaks at detector level and to the greenhouse characteristics of C_2H_2F_4 and SF_6, RPCs in ATLAS and CMS were accounting for about 87% of CO_2 equivalent emissions during LHC Run 2. To address this, several alternative gases were studied, including R-1234ze as a possible substitute for R-134a. Furthermore, the addition of some amount of CO_2 into the RPCs gas mixture was explored as a possible short-to-medium term solution to lower the total greenhouse gas emissions and reduce the usage of C_2H_2F_4. A dedicated data taking campaign was performed at the Gamma Irradiation Facility at CERN, where RPCs detectors performance were studied with muon beam and gamma background. The detectors were operated with the addition of 30% and 40% and 50% of CO_2 to the standard gas mixture, together with an increased fraction of SF_6. Two different amounts of i-C4H10 were also evaluated to assess compatibility with the CMS and ATLAS requirements. Results from these beam tests with the above-mentioned gas mixtures are reported in this work.

Low-cost urban carbon monitoring network and implications for china: a comprehensive review.

The development and renewal of gas sensor technology have enabled more and more low-cost gas sensors to form a carbon monitoring network to meet the requirements of the city. In the context of China's commitment to achieving the "double carbon" target by 2060, this paper reviews the principles of four standard gas sensors and the application of several low-cost sensors in urban carbon monitoring networks, with the aim of providing a practical reference for the future deployment of carbon monitoring networks in Chinese cities. Moreover, the types, prices, and deployment of the sensors used in each project are summarized. Based on this review, non-dispersive infrared sensors have the best performance among the sensors and are commonly used in many cities. Lots of urban climate networks in cities were summarized by many reviews in the literature, but only a few sensors were studied, and they did not consider carbon dioxide (CO2) sensors. This review focuses on the dense CO2 urban monitoring network, and some case studies are also discussed, such as Seoul and San Francisco. To address the issue of how to better ensure the balance between cost and accuracy in the deployment of sensor networks, this paper proposes a method of simultaneously deploying medium-precision and high-precision fixed sensors and mobile sensors to form an urban carbon monitoring network. Finally, the prospects and recommendations, such as different ways to mitigate CO2 and develop an entire carbon monitoring system for future urban carbon monitoring in China, are also presented.

A multiline fitting method for measuring ethylene concentration based on WMS-2f/1f

Coal spontaneous combustion risk assessment is a global technical challenge for the sustainable development of deep mining technology, and C2H4 is a key indicator for early warning of coal spontaneous combustion. Tunable diode laser absorption spectroscopy (TDLAS) has the advantages of high selectivity, high sensitivity, high accuracy and real-time on-line measurement, and it can detect multiple gases simultaneously, so it has significant advantages in the accurate detection of coal spontaneous combustion indicator gases. To address the problem of cross-interference between the near-infrared absorption lines of CH4 and C2H4, which are the indicator gases of spontaneous combustion in coal, a multi-line fitting method was proposed in this study to calibrate the concentration of C2H4. The high-precision Environics2000 automatic standard gas dispenser from the United States, which has a built-in CPU computer control and data control and processing system, was used. Its gas concentration accuracy: ± 1.0%, gas flow accuracy: ± 1.0%, gas repeatability accuracy: ± 1.0%, flow linearity accuracy: ± 0.5%, and inlet operating pressure: minimum 10 psig (0.67 bar) ~ 75 psig (5.04 bar). The measured and simulated WMS-2f/1f signals were multilinearly fitted using a multilinear fitting algorithm and wavelength modulation spectroscopy (WMS), and the measurement of C2H4 concentration was achieved based on the extracted spectral line information. The results show that the maximum relative error of C2H4 concentration measurement is 2.40%, which is 54% lower than that of the conventional 2f peak measurement method, thus demonstrating the effectiveness of the multilinear fitting algorithm in the inversion of C2H4 concentration under the interference of absorption lines. In addition, this study has far-reaching implications for the application of TDLAS technology in the accurate detection of coal spontaneous combustion indicator gases.

IMPLEMENTATION OF THE K-EPSILON (K–Ε) MODEL FOR THE SIMULATION OF COAL GASIFIER /REACTOR

The objective of the present research is to use the standard turbulent kinetic energy and turbulent dissipation (k-e) model to do a numerical modelling and simulation of the gasification chamber or reactor which was used to gasifier Lafia-Obi bituminous coal. The numerical modelling and simulation were implemented with the aid of AutoCAD and Ansys softwares. The gasifier/reactor geometry was modelled using AutoCAD and then imported to Ansys workbench for simulation. Results show the modelled reactor geometry comprising a height of 0.9m, diameter of 0.5m and volume of 0.177m 3. Simulation results show mass fraction of producer gas components comprising of 16% carbon monoxide, 14% hydrogen, 2.7% methane and 18% carbon dioxide. The producer gas yield is in conformity with standard producer gas yield. Temperature profile around the modelled gasifier/reactor was displayed with a maximum of 960K.

Similarity evaluation method of single flow point energy consumption mapping based on Fréchet distance

Abstract Aiming at the problem of inaccurate measurement results caused by factors such as gas leakage during the calibration of the standard meter gas flow standard device of the same type and small diameter, this paper proposes a similarity assessment method of single flow point energy consumption mapping based on Fréchet distance (FD). First, through the statistical analysis of the historical energy consumption data of gas flow standard device, a discrete standard energy consumption mapping is formed. Next, the energy consumption mapping to be tested is standardized and the similarity of the energy consumption mapping is determined by the binary matrix accelerated search of the FD between the energy consumption mapping to be tested and the standard energy consumption mapping. Finally, the similarity threshold is calculated by combining the standard deviation of the FD and the reliability of the gas flowmeter calibration process is evaluated accordingly. The test shows that the method in this paper can effectively determine the reliability of the gas flowmeters calibration results.

Use of Sequential Organ Failure Assessment Among Intensive Care Unit Patients with Septic Shock

Purpose: Sepsis is a significant cause of mortality in modern intensive care units (ICUs). At Sharp Grossmont Hospital (SGH), sepsis cases increased the patient mortality rate in comparison to other Sharp facilities. Currently, no tools are utilized to identify septic patients at SGH. The study aimed to find out the impact of early consultation of advanced illness management (AIM) and goals of care conversations (GOCC) on reducing the length of stay (LOS) among septic shock patients.
 Methodology: Descriptive data were attained based on Electronic Medical Records (EMR) of 39 septic shock patients form which ICU nurses utilize to calculate Sequential Organ Failure Assessment (SOFA) on admission and daily for 2 days. 
 Findings: The education increased the ICU staff’s awareness of the high occurrence of septic shock among ICU patients. After the deployment of SOFA scores among 39 patients of septic shock, the average LOS was 3 days, compared to more than 5 days before implementing SOFA scores. Post-implementation, 33 % of patients received early AIM or GOCC intervention, with 84% of them receiving intervention from the first day of admission. These percentages are compared to pre-implementation, when early AIM or GOCC intervention was provided to 36.4 % of patients, with 41.3 % of them receiving AIM or GOCC from the first day of admission.
 Recommendations: In this study, the leader of change must be aware of standardized Arterial Blood Gas (ABG) orders for SOFA scores and measure the compliance of ICU nurses in documenting SOFA scores. Moreover, raise awareness among healthcare professionals about the high occurrence of septic shock mortality among ICU patients.

Spectral Analysis, Biocompounds, and Physiological Assessment of Cork Oak Leaves: Unveiling the Interaction with Phytophthora cinnamomi and Beyond

The cork oak tree (Quercus suber L.) symbolizes the Montado landscape in Portugal and is a central element in the country’s social and economic history. In recent decades, the loss of thousands of cork oaks has been reported, revealing the ongoing decline of these agroforestry ecosystems. This emblematic tree of the Mediterranean Basin is host to the soil-born root pathogen Phytophthora cinnamomi, an active cork oak decline driver. In this framework, the early diagnosis of trees infected by the oomycete by non-invasive methods should contribute to the sustainable management of cork oak ecosystems, which motivated this work. Gas exchange and visible/near-infrared (400–1100 nm) reflectance spectroscopy measurements were conducted on leaves of both control and P. cinnamomi inoculated plants. These measurements were taken at 63, 78, 91, 126, and 248 days after inoculation. Additionally, at the end of the experiment, biochemical assays of pigments, sugars, and starch were performed. The spectroscopic measurements proved effective in distinguishing between control and inoculated plants, while the standard gas exchange and biochemistry data did not exhibit clear differences between the groups. The spectral data were examined both daily and globally, utilizing the PARAFAC method applied to a three-way array of samples × wavelengths × days. The separation of the two plant groups was attributed to variations in water content (4v (O−H)); shifts in the spectra red edge; and structural modifications in the epidermal layer and leaves’ mesophyll. These spectral signatures can assist in the field identification of cork oaks that are interacting with P. cinnamomi.

Analysis of SF6 decomposed products by fibre‐enhanced Raman spectroscopy for gas‐insulated switchgear diagnosis

AbstractSulphur hexafluoride (SF6) decomposed products analysis is highly critical in the early‐stage fault diagnosis of gas‐insulated switchgear (GIS). Spectrum technology outperforms traditional methods on non‐invasiveness, no sample preparation, and no consumption. Here, the authors present an improved fibre‐enhanced Raman spectroscopy (FERS) as a comprehensive analytical tool to detect a suite of SF6 decomposed products (SO2F2, SOF2, SO2, H2S, CF4, OCS, CO2, and CO). The FERS approach is combined with two iris diaphragms for spatial filtering and a rear‐end reflector for additional Raman signal enhancement. Limits of detection down to 1 × 10−6–8 × 10−6 are achieved for different SF6 decompositions, and quantification of an undefined multigas, sampled from an 800 kV GIS in service, is realised utilising SF6 as the internal standard gas and with a maximum error of 5.5 %. The GIS is diagnosed according to the results and confirmed by an on‐site check. The authors foresee that this technique will provide a route for trace gas analysis in the power industry.

Development of quantitative detection method for mass spectrometry coupled to an infrared laser spectroscope (Picarro) to monitor in nitrogen matrix a complex gas mixture of H2 , He, CO, N2 , Ne, O2 , Ar, CO2 , H2 S, CH4 , C2 H4 , C2 H6 , C3 H6 , C3 H8 , i-C4 H10 , n-C4 H10 , and

The deep geological repository is considered the international reference for radioactive waste management. All gas exchanges must be understood in the context of the feasibility of such a repository. The technological challenge is to continuously monitor a wide range of gaseous molecules at low concentrations in confined spaces. A gas monitoring station, composed of two complementary analyzers, was developed: an electron impact quadrupole mass spectrometer (HPR-20 R&D Hiden Analytical) and an infrared laser spectroscope (Picarro). The spectrometer was calibrated using simple mixtures (i.e., C2 H6 in N2 ) and multiple mixtures (i.e., H2 , He, CO2 , CH4 , and O2 in N2 ) at different concentrations to correct interferences. A matrix calculation is proposed to calculate the relative concentrations. The method developed allows the measurement of gaseous species: light hydrocarbons, noble gases, sulfides, greenhouse gases, oxygen, hydrogen, and nitrogen in the same mixture. For each gas, the SDs and the limits of detection and quantification were calculated. The method was validated by comparing the concentrations of the measured gas species with the reference values of two standard gas cylinders. Calibration of a complex gas mixture remains a challenge because fragmentation of molecules, especially hydrocarbons, reduces the sensitivity of the method. The method developed is suitable for continuous gas monitoring in a confined environment and can be implemented to perform experiments in underground structures: galleries, microtunnels (cells), and boreholes.

An Analysis of Emission Exhaust Gas on 4-Stroke Engine Based on IOT Gas Analyzer

According to the Air Quality Live Index (AQLI), Indonesia's air quality has continued to deteriorate in the last two decades, so Indonesia is officially ranked 17th as the country with the worst air quality in the world. This is due to the population explosion in Indonesia causing industrial activity to also increase. The high levels of exhaust emissions in vehicles, of course, requires the need for technology to measure vehicle exhaust gases to reduce the impact of air pollution. However, the procurement of exhaust emission test equipment is still expensive, so only certain class workshops have this tool. In addition, the reading results of the vehicle's OBD (On Board Diagnostic) system are only able to display the condition or reading value of the Lambda sensor because other gas sensors readings such as CO2, HC, and CO cannot be displayed on the OBD reading results. The purpose of this study is to describe the design of the tool and the results of measuring CO and HC levels through the Blynk application. Research methods that use several gas sensors, such as MQ-7 and TGS-2602 (CO gas) and MQ-2 and TGS-2611 (HC gas), are then compared with the measurement results of a standard gas analyzer. The results showed that the MQ-7 value is close to the accuracy at 1000 rpm and 5000 rpm, namely 99.68% and 99.49%, while the level of accuracy at 3000 rpm is 99.37%. The TGS-2602 sensor at 1000 rpm only has the best accuracy and accuracy, namely 99.67% and 99.77%. The level of accuracy of the MQ-2 sensor has the best value at 1000 rpm rotation, which is 95.71% and the level of accuracy has the highest value at 7000 rpm rotation, which is 100%. For the level of accuracy of the TGS-2611 sensor, it has an accuracy level of 1000 rpm rotation of 94.65% and the level of accuracy of the sensor obtains very good values ​​at 1000 rpm, 7000 rpm, and 9000 rpm rotation of 100%.

Structure and Mechanical Behavior of Heat-Resistant Steel Manufactured by Multilayer Arc Deposition

The manuscript demonstrates the structure and the mechanical behavior of a material manufactured by multilayer arc deposition. Three-dimensional printing was performed using OK Autrod 13.14 wire on a substrate of heat-resistant 12Cr1MoV steel in the standard gas metal arc welding (GMAW) mode and in the coldArc mode with reduced heat input. The printed materials have 40–45% higher strength and 50–70% lower ductility compared to the substrate. The microhardness of the printed materials is higher than the substrate, but it is reduced at the transition regions between the deposited layers. These regions have been studied using optical microscopy and digital image correlation. Such layer boundaries are an additional factor in reducing the plasticity of the material. The increase in strength and decrease in ductility for printed materials compared to the ferrite–pearlitic substrate is associated with a high cooling rate and the formation of a mixture of acicular and allotriomorphic ferrite, which have higher hardness. The structure of the obtained layers along the height is non-uniform and undergoes changes during the deposition of new layers. The main difference between the 3D printing modes is the reduced heat input in the coldArc mode, which results in less heat accumulation and faster cooling of the wall. Thus, a more dispersed and solid structure was formed compared with GMAW. It was concluded that the cooling rate and the level of heat input are the main factors affecting the structure formation (martensitic, bainitic, or ferritic), the height and quality of the surface, and the mechanical properties of the printed wall.

Diagnostic accuracy of the peripheral venous pressure variation induced by an alveolar recruitment maneuver to predict fluid responsiveness during high-risk abdominal surgery

BackgroundIn patients undergoing high-risk surgery, it is recommended to titrate fluid administration using stroke volume or a dynamic variable of fluid responsiveness (FR). However, this strategy usually requires the use of a hemodynamic monitor and/or an arterial catheter. Recently, it has been shown that variations of central venous pressure (ΔCVP) during an alveolar recruitment maneuver (ARM) can predict FR and that there is a correlation between CVP and peripheral venous pressure (PVP). This prospective study tested the hypothesis that variations of PVP (ΔPVP) induced by an ARM could predict FR.MethodsWe studied 60 consecutive patients scheduled for high-risk abdominal surgery, excluding those with preoperative cardiac arrhythmias or right ventricular dysfunction. All patients had a peripheral venous catheter, a central venous catheter and a radial arterial catheter linked to a pulse contour monitoring device. PVP was always measured via an 18-gauge catheter inserted at the antecubital fossa. Then an ARM consisting of a standardized gas insufflation to reach a plateau of 30 cmH2O for 30 s was performed before skin incision. Invasive mean arterial pressure (MAP), pulse pressure, heart rate, CVP, PVP, pulse pressure variation (PPV), and stroke volume index (SVI) were recorded before ARM (T1), at the end of ARM (T2), before volume expansion (T3), and one minute after volume expansion (T4). Receiver-operating curves (ROC) analysis with the corresponding grey zone approach were performed to assess the ability of ∆PVP (index test) to predict FR, defined as an ≥ 10% increase in SVI following the administration of a 4 ml/kg balanced crystalloid solution over 5 min.Results∆PVP during ARM predicted FR with an area under the ROC curve of 0.76 (95%CI, 0.63 to 0.86). The optimal threshold determined by the Youden Index was a ∆PVP value of 5 mmHg (95%CI, 4 to 6) with a sensitivity of 66% (95%CI, 47 to 81) and a specificity of 82% (95%CI, 63 to 94). The AUC’s for predicting FR were not different between ΔPVP, ΔCVP, and PPV.ConclusionDuring high-risk abdominal surgery, ∆PVP induced by an ARM can moderately predict FR. Nevertheless, other hemodynamic variables did not perform better.

A mid‐infrared laser absorption sensor for calibration‐free measurement of nitric oxide in laminar premixed methane/ammonia cofired flames

AbstractAn interband cascade laser (ICL)‐based absorption sensor was developed for calibration‐free and high‐fidelity measurement of nitric oxide (NO) in laminar premixed methane/ammonia cofired flames using a combination of a micro‐probe and a low‐pressure, high‐temperature gas cell. The developed sensor, which has been shown to be particularly suitable for kinetic studies of ammonia combustion, used a tunable, continuous, narrow‐linewidth, free‐space ICL operating at ~5.2 μm to target the optimal NO transition centered at 1900.07 cm−1. A direct absorption spectroscopy technique with a reduced line model was implemented for calibration‐free measurements. Comprehensive experiments were first conducted to evaluate the sensor performance against the standard gas mixture at varied pressure from 20 to 101 kPa at 393 K, showing a relative difference of ≤2.5% and a measurement uncertainty of ≤2.0%. Such a sensor shows a minimum detection limit of ~2 ppm at the integration time of 1 s. The sensor was then applied for investigating the NO formation in ammonia‐methane cofiring flames with various ammonia blending ratios; the acquired experimental data was further used as benchmark data for evaluation of literature chemical mechanisms for ammonia combustion. The developed sensor system was demonstrated to be capable of providing quantitative and spatially resolved measurement of NO in ammonia‐methane cofired flames.

Characterising the methane gas and environmental response of the Figaro Taguchi Gas Sensor (TGS) 2611-E00

Abstract. In efforts to improve methane source characterisation, networks of cheap high-frequency in situ sensors are required, with parts-per-million-level methane mole fraction ([CH4]) precision. Low-cost semiconductor-based metal oxide sensors, such as the Figaro Taguchi Gas Sensor (TGS) 2611-E00, may satisfy this requirement. The resistance of these sensors decreases in response to the exposure of reducing gases, such as methane. In this study, we set out to characterise the Figaro TGS 2611-E00 in an effort to eventually yield [CH4] when deployed in the field. We found that different gas sources containing the same ambient 2 ppm [CH4] level yielded different resistance responses. For example, synthetically generated air containing 2 ppm [CH4] produced a lower sensor resistance than 2 ppm [CH4] found in natural ambient air due to possible interference from supplementary reducing gas species in ambient air, though the specific cause of this phenomenon is not clear. TGS 2611-E00 carbon monoxide response is small and incapable of causing this effect. For this reason, ambient laboratory air was selected as a testing gas standard to naturally incorporate such background effects into a reference resistance. Figaro TGS 2611-E00 resistance is sensitive to temperature and water vapour mole fraction ([H2O]). Therefore, a reference resistance using this ambient air gas standard was characterised for five sensors (each inside its own field logging enclosure) using a large environmental chamber, where logger enclosure temperature ranged between 8 and 38 ∘C and [H2O] ranged between 0.4 % and 1.9 %. [H2O] dominated resistance variability in the standard gas. A linear [H2O] and temperature model fit was derived, resulting in a root mean squared error (RMSE) between measured and modelled resistance in standard gas of between ±0.4 and ±1.0 kΩ for the five sensors, corresponding to a fractional resistance uncertainty of less than ±3 % at 25 ∘C and 1 % [H2O]. The TGS 2611-E00 loggers were deployed at a landfill site for 242 d before and 96 d after sensor testing. Yet the standard (i.e. ambient air) reference resistance model fit based on temperature and [H2O] could not replicate resistance measurements made in the field, where [CH4] was mostly expected to be close to the ambient background, with minor enhancements. This field disparity may have been due to variability in sensor cooling dynamics, a difference in ambient air composition during environmental chamber testing compared to the field or variability in natural sensor response, either spontaneously or environmentally driven. Despite difficulties in replicating a standard reference resistance in the field, we devised an excellent methane characterisation model up to 1000 ppm [CH4] by using the ratio between measured resistance with [CH4] enhancement and its corresponding reference resistance in standard gas. A bespoke power-type fit between resistance ratio and [CH4] resulted in an RMSE between the modelled and measured resistance ratio of no more than ±1 % Ω Ω−1 for the five sensors. This fit and its corresponding fit parameters were then inverted and the original resistance ratio values were used to derive [CH4], yielding an inverted model [CH4] RMSE of less than ±1 ppm, where [CH4] was limited to 28 ppm. Our methane response model allows other reducing gases to be included if necessary by characterising additional model coefficients. Our model shows that a 1 ppm [CH4] enhancement above the ambient background results in a resistance drop of between 1.4 % and 2.0 % for the five tested sensors. With future improvements in deriving a standard reference resistance, the TGS 2611-E00 offers great potential in measuring [CH4] with parts-per-million-level precision.

A two-staged adsorption/thermal desorption GC/MS online system for monitoring volatile organic compounds.

Real-time online monitoring of volatile organic compounds (VOCs) in ambient air is crucial for timely and effective human health protection. Here, we developed an innovative, automated two-staged adsorption/thermal desorption gas chromatography/mass spectrometry (GC/MS) system for real-time online monitoring of 117 regulated volatile organic compounds (VOCs). This system comprised a sampling unit, water management trap, two-staged adsorption/thermal desorption unit, thermoelectric coolers (TECs), and a commercial GC/MS system. By implementing a micro-purge-and-trap (MP & T) step and a two-staged adsorption/thermal desorption unit, the presence of interfering substances was effectively minimized. The utilization of a heart-cutting GC, combined with a single MS detector, facilitated the precise separation and detection of 117 C2-C12 VOCs, while circumventing the identification and coelution challenges commonly associated with traditional GC-FID or GC-FID/MS methods. The performance of our newly developed online system was meticulously optimized and evaluated using standard gas mixtures. Under optimal conditions, we achieved impressive results, with R2 values ≥ 0.9946 for the standard linear curves of all 117 VOCs, demonstrating a precision (RSD) ranging from 0.2% to 6.4%. When applied in the field monitoring, the concentration drifts for 10 ppbv standard gas mixtures were 0.01-5.64% within 24h. Our study developed a system for online monitoring of 117 atmospheric VOCs with relatively high accuracy and robustness.