Gas Chamber Research Articles

Breakdown of argon by a train of high-repetition long-wave-infrared pulses from a free-electron laser oscillator.

This study presents an experimental demonstration of laser-induced breakdown in argon, employing a free-electron laser with a wavelength of 10 μm and a repetition rate of 2.856 GHz. Despite the fluence of individual laser pulses being an order of magnitude smaller than the breakdown threshold, cascade ionization developed in the pulse train, leading to breakdown. The breakdown probability within a finite pulse train increases with gas pressure, and it was notably enhanced in a gas chamber with poor cleanliness. Numerical simulations of cascade ionization replicated the experimental results. The simulation revealed that breakdown phenomena are governed by the balance between avalanche multiplication of electrons within laser pulses and electron diffusion during pulse intervals.

First operation of a multi-channel Q-Pix prototype: measuring transverse electron diffusion in a gas time projection chamber

We report measurements of the transverse diffusion of electrons in P-10 gas (90% Ar, 10% CH4) in a laboratory-scale time projection chamber (TPC) utilizing a novel pixelated signal capture and digitization technique known as Q-Pix. The Q-Pix method incorporates a precision switched integrating transimpedance amplifier whose output is compared to a threshold voltage. Upon reaching the threshold, a comparator sends a 'reset' signal, initiating a discharge of the integrating capacitor. The time difference between successive resets is inversely proportional to the average current at the pixel in that time interval, and the number of resets is directly proportional to the total collected charge. We developed a 16-channel Q-Pix prototype fabricated from commercial off-the-shelf components and coupled them to 16 concentric annular anode electrodes to measure the spatial extent of the electron swarm that reaches the anode after drifting through the uniform field of the TPC. The swarm is produced at a gold photocathode using pulsed UV light. The measured transverse diffusion agrees with simulations in PyBoltz across a range of operating pressures (200–1500 Torr). These results demonstrate that a Q-Pix readout can successfully reconstruct the ionization topology in a TPC.

Core-level spectra of metallic lanthanides: Lanthanum (La)

The core-level aluminum excited spectra for lanthanum, the eponymous parent lanthanide metal, are presented together with exemplar spectra highlighting the metals reactivity from reaction with background chamber gases. Recommendations are given for the background integrations limits and form, together with comments on sensitivity factors.

Real-Time Monitoring of Toxic Gases using Artificial Neural Networks with SnO2-based Thick Film Gas Sensors

The present study aims to develop an advanced system for real-time identification and measurement of harmful gases using Pd-doped SnO2-based thick film gas sensors integrated with Artificial Neural Networks. These sensors, renowned for their exceptional sensitivity and selectivity, undergo testing in a meticulously controlled gas chamber environment. Here, gas concentrations, temperature, and humidity are meticulously controlled. The gas chamber setup allows for mixing gases like carbon monoxide, nitrogen dioxide, and sulfur dioxide with nitrogen gas to achieve desired concentrations ranging from to . Temperature is kept at and relative humidity is maintained between to . The sensitivity analysis of the sensor demonstrates its adeptness in detecting low concentrations of target gases, with sensitivity increasing as gas concentrations rise, also the selectivity assessments highlight their ability to accurately differentiate between target gases and common interferents, ensuring precise detection even in complex gas mixtures. Response time testing indicates rapid detection capabilities, crucial and useful for emergencies. The Artificial Neural Network model, trained via the backpropagation algorithm, demonstrates remarkable accuracy, precision, recall, and F1 scores in predicting gas concentrations. The findings indicate that this integrated system offers a reliable and efficient solution for toxic gas detection, with potential applications in industrial safety and environmental monitoring.

Sulfonylureas Compromise Microvascular Flow in Mouse Skeletal Muscle

Sulfonylureas are among the most prescribed oral anti-hyperglycaemics, particularly in low- and middle-income countries. Sulfonylureas are insulin secretagogues through blocking ATP-sensitive potassium channels (KATP) in β-cells of the pancreas. Despite wide usage, sulfonylureas are associated with increased cardiovascular disease morbidity and all-cause mortality, with ill-defined mechanisms. We tested the hypothesis that glyburide could block KATP channels in the microvasculature, thereby disrupting tissue oxygen demand-supply balance. We further investigated the contribution of other potassium channels to capillary-to-arteriole signalling. Experiments were conducted using an in-vivo anesthetized mouse skeletal muscle preparation (extensor digitorum longus, EDL); exteriorized and situated at in-situ length, overtop an oxygen-permeable membrane covering a gas chamber, and bathed in PlasmaLyte. C57BL/6 mice were employed (n=6-8). Brightfield images were captured at two wavelengths: oxygen-dependent and oxygen-independent, enabling the simultaneous determination of capillary hemodynamics and RBC oxygen content. Low oxygen challenges were achieved by dropping oxygen levels in the gas chamber from 7% to 2% for 3 minutes. Challenges were conducted before (control) and after drugs were added to bathing solution. Parameters were obtained before the challenge (baseline), during the challenge (2 regions) and after the challenge (recovery). Statistical significance was determined using a paired Student’s t-test. Target channels localization was investigated using immunofluorescence in formalin-fixed EDL. Oxygen challenges augmented EDL surface capillary hematocrit and RBC velocity and supply rate, while reducing RBC oxygen saturation. Incubation of the EDL with 10 μM glyburide decreased the baseline RBC supply rate (p<0.05 vs control) and blunted the magnitude of capillary responses to the oxygen challenge (p<0.05 vs control). Immunofluorescence confirmed the localization of KATP channels in EDL capillaries. Normal capillary responses were obtained when small and intermediate conductance or inward rectifier potassium channels were neutralized. This implies minimal or no contribution of these channels in oxygen signaling in the microvasculature. This data begins to elucidate the acute and direct effects of systemic KATP blockers on capillary-to-arteriole conducted signaling, which is likely key to optimal tissue oxygen regulation. Further experiments are warranted to confirm this conclusion. This work was supported by the Natural Science and Engineering Research Council of Canada (NSERC, RGPIN/04659-2017), an Ontario Graduate Scholarship (M.A.E) and a CIHR doctoral award (M.A.E). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Stability of Compressed Air Storage Underground Gas Storage Chamber and Steel Lining Structure Analysis

According to the address characteristics and structural characteristics of an underground artificial chamber gas storage, a structural model of an underground chamber including steel lining, flexible concrete, concrete lining, and surrounding rock is established, and two limit states of large slip and no contact between steel lining and flexible concrete are simulated respectively. The stability of the surrounding rock and lining structure are calculated and analyzed by using large finite element software FLAC3D and ANSYS respectively. The results show that the maximum deformation of the surrounding rock is 1.57cm, the maximum stress of steel lining is 262.08MPa, and the changes of plastic zone, displacement, and steel lining stress of surrounding rock can meet the design requirements of this project.

Impacts of High-Frequency Chicken Manure Biochar Application on N2O and CH4 Emissions from Vegetable Field in Subtropical China

Vegetable production in Subtropical China is distinguished by excessive nitrogen (N) fertilization, frequent irrigation, and multiple crop rotations in a single year. The aforementioned variables are closely related to soil nitrous oxide (N2O) and methane (CH4) emissions. Hence, we conducted a field trial to measure N2O and CH4 emissions using static chamber–gas chromatograph. Four treatments were used: control (CK) with no fertilizer, 100% chemical N fertilization (CN), the conventional 30% chicken manure N plus 70%CN (CMN + CN), and 30% chicken manure biochar N plus 70%CN (CMBN + CN). The annual cumulative N2O emissions reached 12.4, 63.5, 111.8, and 44.1 kg N2O-N ha−1 for the CK, CN, CMN + CN, and CMBN + CN treatments, respectively. Compared to the CN and CMN + CN treatments, the CMBN + CN treatment reduced N2O emissions by 35.9%–65.7%, while it simultaneously increased the total vegetable yield by 16.1% compared to the CN treatment. Seven seasons mean N2O emission factors are 1.3% for CN, 3.8% for CMN + CN, and 0.9% for CMBN + CN. The CH4 emission was negligible, ranging from 0.07 kg CH4-C ha−1 for the CK treatment to 0.8 kg CH4-C ha−1 for the CN treatment. N2O emissions peaked under the conditions of an interior chamber temperature of around 31.9 °C and the water-filled pore space (WFPS) of the soil being approximately 60%. Future climate change will intensify, triggering higher N2O emissions from subtropical vegetable fields. CMB can be one of the best substitutes for direct chicken manure application as a soil supplement because it has a beneficial effect on improving vegetable yield and reducing N2O emissions in Subtropical China.

Impact of urea fertilization rates on nitrogen losses, productivity and profitability in East African sugarcane plantations

AbstractFertilizer‐intensive sugarcane plantations are expanding in sub‐Saharan Africa (SSA) amidst increased groundwater pollution and carbon footprint concerns. Yet, the impact of nitrogen (N) levels on N losses, productivity and profitability in these plantations remains unclear. To address this gap, we conducted a completely randomized design experiment in a Ugandan sugarcane plantation using three N fertilization rates (low, standard and high) as treatments. N leaching under the different treatments was determined using the average drainage fluxes across a 1‐m‐layered profile which we estimated with a suite of pedotransfer functions (PTFs) and leachate N concentrations from suction cup lysimeters. Soil nitrous oxide fluxes were determined using static vented chamber bases and gas chromatography. Partial factor crop productivity was estimated from the average field fresh weight under each treatment and the amount of N fertilizer applied, while the return on investment was determined from the factory price of the field fresh weight and the market price of fertilizers. Our findings indicate that three out of five PTFs effectively estimated soil hydraulic properties at our test site, based on the close match between measured and predicted soil matric potential values. Notably, N leaching at low and standard N rates were comparable but significantly lower than at higher‐than‐standard N rates. Additionally, we measured comparable soil nitrous oxide emissions and field fresh weight but partial factor productivity and return on investment declined along the fertilizer intensification gradient. In conclusion, the study demonstrates the promising application of certain PTFs in N‐leaching modelling in the data‐scarce SSA. Furthermore, obtaining comparable field fresh weight with minimal N losses at lower‐than‐standard N rates presents an opportunity to mitigate groundwater pollution and greenhouse gas emissions. However, the potential impact of the switch from standard to low N rates on soil organic carbon stocks and sugarcane yields warrants further investigation.

Design and Performance Evaluation of a Deep Ultraviolet LED-Based Ozone Sensor for Semiconductor Industry Applications.

Ozone (O3) is a critical gas in various industrial applications, particularly in semiconductor manufacturing, where it is used for wafer cleaning and oxidation processes. Accurate and reliable detection of ozone concentration is essential for process control, ensuring product quality, and safeguarding workplace safety. By studying the UV absorption characteristics of O3 and combining the specific operational needs of semiconductor process gas analysis, a pressure-insensitive ozone gas sensor has been developed. In its optical structure, a straight-through design without corners was adopted, achieving a coupling efficiency of 52% in the gas chamber. This device can operate reliably in a temperature range from 0 °C to 50 °C, with only ±0.3% full-scale error across the entire temperature range. The sensor consists of a deep ultraviolet light-emitting diode in a narrow spectrum centered at 254 nm, a photodetector, and a gas chamber, with dimensions of 85 mm × 25 mm × 35 mm. The performance of the sensor has been meticulously evaluated through simulation and experimental analysis. The sensor's gas detection accuracy is 750 ppb, with a rapid response time (t90) of 7 s, and a limit of detection of 2.26 ppm. It has the potential to be applied in various fields for ozone monitoring, including the semiconductor industry, water treatment facilities, and environmental research.

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.

Carbon Release Characteristics at Soil–Air Interface under Litter Cover with Different Decomposition Degrees in the Arbor and Bamboo Forests of Pi River Basin

This study adopted the method of “exchanging space for time” and set up three experimental groups based on the shape, degree of damage, and degree of humification of the litter, namely the undecomposed layer, the semi-decomposed layer, and the decomposed layer. Using typical slopes of arbor and bamboo forests in the Pi River Basin as the research object, from October 2021 to December 2022, the soil carbon release flux was measured by using a closed static chamber gas chromatography method to reveal the carbon release law at the soil–air interface during the decomposition process of litter and quantitatively characterize the dynamic impact of the litter decomposition process on soil carbon release flux. Results showed that soil methane flux remained negative (sink) while soil carbon dioxide flux was positive (source) in both litter-covered and bare soil conditions. The methane and carbon dioxide release from soil was positively correlated with and significantly influenced by environmental factors such as soil moisture content and temperature. The methane release flux from soil showed a linear fitting relationship with soil moisture content and temperature, while the carbon dioxide release flux from soil was more in line with the exponential fitting relationship with soil moisture content and temperature. However, there were significant differences in the roles of various factors under different types of litter.

Has Extracorporeal Gas Exchange Performance Reached Its Peak?

Extracorporeal gas exchange therapies evolved considerably within the first three-four decades of their appearance, and have since reached a mature stage, where minor alterations and discrete fine-tuning might offer some incremental improvement. A different approach is introduced here, making use of modern, purely diffusive membrane materials, and taking advantage of the elevated concentration gradient ensuing from gas pressure buildup in the gas chamber of the oxygenator. An assortment of silicone membrane gas exchangers were tested in vitro as per a modified protocol in pursuance of assessing their gas exchange efficiency under both regular and high-pressure aeration conditions. The findings point to a stark performance gain when pressurization of the gas compartment is involved; a 40% rise above atmospheric pressure elevates oxygen transfer rate (OTR) by nearly 30%. Carbon dioxide transfer rate (CTR) does not benefit as much from this principle, yet it retains a competitive edge when higher gas flow/blood flow ratios are employed. Moreover, implementation of purely diffusive membranes warrants a bubble-free circulation. Further optimization of the introduced method ought to pave the way for in vivo animal trials, which in turn may potentially unveil new realms of gas exchange performance for therapies associated with extracorporeal circulation.

Interface fluid syndrome caused by the corneal perforation injury after small incision lenticule extraction: a case report

BackgroundTo report a case of interface fluid syndrome (IFS) following traumatic corneal perforation repair after small incision lenticule extraction (SMILE).Case presentationA 23-year-old woman, with a past history of SMILE, was struck in the left eye with a barbecue prod and subsequently underwent corneal perforation repair at local hospital. Primary wound repaired with a single 10 − 0 nylon suture at the area of leakage. After the surgery, her best corrected visual acuity (BCVA) was 20/30. Four days later, she presented at our hospital with blurred vision, and interface fluid syndrome (IFS) was diagnosed. Intraoperative optical coherence tomography (iOCT) was used to guide the resuturing of the corneal perforation in the left eye, followed by anterior chamber gas injection. At the first postoperative month, the BCVA was 20/25. The corneal cap adhered closely to the stroma, the surface became smooth.ConclusionsThis case illustrates that any corneal perforation following lamellar surgery, including SMILE, may lead to IFS. It is crucial to consider the depth of corneal perforation, and intraoperative optical coherence tomography (iOCT) plays a unique role in the repair procedure.

Highly sensitive detection of ammonia based on light-induced thermoelastic spectroscopy with hollow waveguide

In this paper, an ammonia (NH3) sensor based on light-induced thermoelastic spectroscopy (LITES) with hollow waveguide (HWG) is proposed for the first time. HWG has many advantages, such as small size, simple structure, high system stability and fast filling speed. The sensor used HWG with a length of 22 cm and an inner diameter of 4 mm as the light transmission medium and gas chamber. The interior of the HWG is covered with silver (Ag) and silver iodide (AgI). The reflectivity is increased and the transmission losses is reduced in the infrared region of the HWG. A diode laser with an output wavelength of 1.53 μm was employed, which can cover the two NH3 absorption lines of 6534.6 cm−1 and 6533.4 cm−1. The amplitude of the second harmonic signal (2f) showed a good linear response to the gas concentration. The experiments demonstrated that the NH3 sensor's minimum detection limit (MDL) under this system was 9.896 parts per million (ppm).

Design of an economic, portable, compact, and indigenous instrument setup for measuring sensing characteristics of thin film gas sensors.

Thin film gas sensor characterization is very demanding for various applications because of technical design trade-offs in commercially available gas sensors. For gas sensing characterization, a suitable gas-testing experimental setup is very much needed in this context. Various factors in the experimental setup can affect a thin film gas sensor's response beyond gas exposure. These factors include the test chamber's volume, relative humidity, uniform operating temperature, uniform pressure, uniform gas density, uniform gas distribution, uniform gas concentration in the gas chamber, and uniform relative gas flow velocity over the surface of the sensor. All these environmental parameters, not being so predictive in nature, induce an inherent design trade-off in the experimental setup design. Although all the commercially available gas testing experimental setups are equally good considering the dedicated purpose for which they are made. However, all of them are for generic applications but not for specific applications because of their inherent trade-offs in their usability features. Those trade-offs always provide an opportunity to introduce a new setup with its own unique advantages. Hence, in this article, we have presented a portable, compact, indigenous gas sensing experimental setup for studying the performance of gas sensors. We have characterized and tested the setup using a ZnO based thin film gas sensor when exposed to CO2 gas at concentrations ranging from 1445 to 4631 ppm. The proposed gas sensing setup's compact size offers unique advantages, including portability and compatibility for uniform environmental conditions.

Enhanced hydrogen gas sensing characteristics of CuO/ZnO heterojunction for thickness-dependence and its application

In this study, we experimentally verified the synthesis of ZnO and CuO thin films using a droplet-based hydrothermal method and their hydrogen sensing performance. The hydrogen gas detection performance of the fabricated heterostructured gas sensor was evaluated based on the results of an experiment conducted while controlling the temperature and hydrogen concentration in the gas chamber. According to the responses of single metal oxide sensors made of each ZnO and CuO and their heterojunction sensors, CuO deposited with 7 cycles on 5 cycles of ZnO had a resistance change rate of about 164 % and the change of the resistance took 3 s in the environment of 4 % hydrogen at 300 °C. This sensor showed the highest response rate and fastest reaction time out of all. CuO/ZnO showed the highest reaction at 300 °C, confirming its selective reaction to hydrogen. To solve the problem of metal oxide-based gas sensors with low selectivity, the operating principle of the heterojunction between metal oxide that has selective gas reactivity was analyzed and experimentally verified. Additionally, the fabricated sensor was confirmed to have selective responsiveness to different gases at various temperatures. Using these characteristics, it was confirmed that this heterostructure based sensor can be used as a sensor array for electronic nose that could classify unknown gases using the same sensor at various temperatures.

Fiber-optic trace gas sensing based on graphite excited photoacoustic wave

A fiber-optic trace gas sensing system based on photoacoustic (PA) effect of solids is reported. The modulated laser light absorbed by the gas is incident on a graphite sheet. The graphite sheet and cantilever are enclosed together to form an optical power detector based on PA effect of solids. This scheme is different from the traditional PA trace gas detection, achieving the separation of the gas chamber and the PA detector, thereby isolating the interference of airflow and environmental noise. In addition, due to the large size of the graphite sheet, the laser incident on the graphite sheet does not need to be converged through a lens, which makes it much easier to adjust the optical path. The PA pressure wave generated by the graphite sheet leads to the vibration of the optical interferometric cantilever. A fiber-optic white-light interferometer is used for high-resolution cantilever readout to detect the PA signal generated by solid excitations. The trace acetylene gas is used to verify the system performance. The experimental results indicate that when the averaging time is 100 s, the minimum detection limit (MDL) is 24 ppb. The normalized noise equivalent absorption (NNEA) coefficient of the designed PA system is 5.4×10−9 cm−1·W·Hz−1/2. This gas sensing system has the characteristics of intrinsic safety and high sensitivity, which can realize remote measurement of corrosive, flammable and explosive gases.

Enhancement of the thermoelectric performance of (BiSb)2Te3 films by single target sputtering

In this study, (BiSb)2Te3 thin films were deposited onto glass substrates at a temperature of 300 °C, utilizing radio frequency (RF) sputtering across a range of growth conditions. The primary focus of this investigation was to analyzse the effects of varying RF power, chamber gas pressure, and annealing temperature on the thermoelectric properties of the films, deposited by an exclusively-made single target.Notably, it was observed that increasing the annealing temperature significantly boosted both the deposition rate and grain size. Through carefully optimizsing growth conditions and subsequent annealing procedures, it was discerned that thin films cultivated at higher RF power levels exhibited markedly improved electrical conductivity, attributed to a discernible rise in carrier concentration. Furthermore, films generated under the RF power of 37.5 W showed a noteworthy augmentation in the Seebeck coefficient, recording approximately 147 μV/K. This enhancement in Seebeck coefficient correlated with the attainment of the highest power factor, reaching an impressive 220.57 μW/mK2.

Capillary oxygen regulates demand–supply coupling by triggering connexin40-mediated conduction: Rethinking the metabolic hypothesis

Coupling red blood cell (RBC) supply to O2 demand is an intricate process requiring O2 sensing, generation of a stimulus, and signal transduction that alters upstream arteriolar tone. Although actively debated, this process has been theorized to be induced by hypoxia and to involve activation of endothelial inwardly rectifying K+ channels (KIR) 2.1 by elevated extracellular K+ to trigger conducted hyperpolarization via connexin40 (Cx40) gap junctions to upstream resistors. This concept was tested in resting healthy skeletal muscle of Cx40-/- and endothelial KIR2.1-/- mice using state-of-the-art live animal imaging where the local tissue O2 environment was manipulated using a custom gas chamber. Second-by-second capillary RBC flow responses were recorded as O2 was altered. A stepwise drop in PO2 at the muscle surface increased RBC supply in capillaries of control animals while elevated O2 elicited the opposite response; capillaries were confirmed to express Cx40. The RBC flow responses were rapid and tightly coupled to O2; computer simulations did not support hypoxia as a driving factor. In contrast, RBC flow responses were significantly diminished in Cx40-/- mice. Endothelial KIR2.1-/- mice, on the other hand, reacted normally to O2 changes, even when the O2 challenge was targeted to a smaller area of tissue with fewer capillaries. Conclusively, microvascular O2 responses depend on coordinated electrical signaling via Cx40 gap junctions, and endothelial KIR2.1 channels do not initiate the event. These findings reconceptualize the paradigm of blood flow regulation in skeletal muscle and how O2 triggers this process in capillaries independent of extracellular K+.

Multiphysics Modeling for Combustion Instability in Paraffin-Fueled Hybrid Rocket Engines

The use of paraffin-based fuels is a promising approach to a low regression rate in hybrid rocket engines, and the capability to describe and predict combustion instability in the presence of liquefying fuels becomes an enabling step towards the application of hybrid rockets in a wide range of space transportation systems. In this work, a multiphysics model having this purpose is presented and discussed. The model is based on a network of submodels in which chamber gas dynamics is described by a quasi-1D Euler model for reacting flows while thermal diffusion in the grain is described by the 1D heat equation in the radial direction. An artificial neural network is introduced to reduce the computational cost required by the chemical submodel. A sensitivity analysis is performed to identify the key parameters, which have the largest influence on combustion instability and to evaluate the predictive capability of the model despite the uncertainty introduced with the necessary modeling simplifications. Results are presented considering two test cases with different oxidizers: hydrogen peroxide and gaseous oxygen. The procedure shows good agreement with the experimental results available in the literature.