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Conventional dogma suggests that decompression sickness (DCS) is caused by nitrogen bubble nucleation in the blood vessels and/or tissues; however, the abundance of bubbles does not correlate with DCS severity. Since immune cells respond to chemical and environmental cues, we hypothesized that the elevated partial pressures of dissolved gases drive aberrant immune cell phenotypes in the alveolar vasculature. To test this hypothesis, we measured immune responses within human lung‐on‐a‐chip devices established with primary alveolar cells and microvascular cells. Devices were pressurized to 1.0 or 3.5 atm and surrounded by normal alveolar air or oxygen‐reduced air. Phenotyping of neutrophils, monocytes, and dendritic cells as well as multiplexed ELISA revealed that immune responses occur within 1 h and that normal alveolar air (i.e., hyperbaric oxygen and nitrogen) confer greater immune activation. This work strongly suggests innate immune cell reactions initiated at elevated partial pressures contribute to the etiology of DCS. [ABSTRACT FROM AUTHOR]

The article is a publication of scientific and methodical character. The analysis of researches and publications has shown that it is urgent to continuously improve methods of determining the influence of acoustic cavitation on degradation of power oils in order to diagnose further the condition of these oils; develop measures to prevent such degradation or reduce its influence on the quality of power oils during their operation in oil-filled heat-mechanical equipment of a nuclear power plant. The paper deals with the results of improving the method for determining the degradation of energy oils under the influence of acoustic cavitation. The aim of the study is to improve the reliability of the results of determining the effect of acoustic cavitation on the degradation of energy oils. Subjects of research: turbine oils "Azmol TP-22с", "Agrinol TP-22", "TP- 30", "Reolube®OMTI" (based on trixylene phosphates), compressor oil "HF-12-16". The paper improves the schematic diagram of an installation for studying the effect of acoustic cavitation on the degradation of energy oils, which allows performing studies at an ultrasonic emitter power of 20 W with frequencies up to 125 kHz. During the study of the air (or hydrogen) content in turbine oils under the influence of ultrasonic cavitation in the presence of air (or hydrogen) above the surfaces of these turbine oils, it was shown that at a temperature of 20°C, these turbine oils contain air (or hydrogen) in the form of an emulsion with a total content of the corresponding gas (air or hydrogen) of no more than 15 % by volume. In the course of studying the effect of ultrasonic cavitation on the degradation of energy oils, it was found that under the influence of ultrasonic cavitation in energy oils: gases C2H6, C2H4, C2H2, CH4, H2, CO, CO2 are generated and dissolved in them; solid carbon particles are generated; the content of additives "Ionol", "B-15/41", "D-157" decreases. The presence of H2S or SO2 in gas flows over mineral turbine oils and the presence of PH3 in gas flows over fire-resistant synthetic turbine oil under the influence of ultrasonic cavitation on these turbine oils was established. For the studied energy oils in the temperature range of 10-100°C: an increase in temperature or ultrasonic irradiation leads to a decrease in the kinematic viscosity. The results of research can be used for reasonable choice or design: measuring equipment for subsequent determination of the nature of degradation of demulsifying, deactivating, anti-wear and anti-foam additives, combined additives and inhibitors of oxidation and corrosion in power oils under the influence of acoustic cavitation in the bearing units of hydrogencooled turbine generators equipped with turbine oil circulation systems; elements of systems for diagnostics of the state of these power generators; elements of systems for diagnostics of the state of these power oils. [ABSTRACT FROM AUTHOR]

Dissolved oxygen plays a central role for all organisms dwelling in water. However, the flux of oxygen by ebullition has not received much attention in environmental science. For a better quantitative understanding of the oxygen flux due to ebullition, we conducted a series of laboratory experiments, where we forced macrophytes to produce photosynthetic gas bubbles. Raising the CO2 concentration in the water greatly increased bubble formation. Depth was varied to compare the results with theoretically predicted composition of photosynthetic bubbles forming at minimum required gas pressure. Oxygen concentrations lay between this theoretical line as lower boundary (ca. 21% O2 at 0.3 m depth and 45% of O2 at 4.5 m) and 45% of oxygen as the purely empirical upper limit for all depths. As a consequence, no bubble formation was observed at depths below 4.5 m. Plain Language Summary: Under light, green plants produce oxygen, when they grow. Submerged plants can produce bubbles under these conditions. Some of these bubbles rise to the surface and hence transport oxygen out of the water into the atmosphere. We studied this process by measuring the composition of such bubbles in a laboratory experiment. Adding carbonic acid to the water boosted the bubble production a lot. Depending of depth, there is a minimum of gases required for bubble formation, which yields a theoretical minimum concentration for oxygen. In all experiments, the oxygen concentration of bubbles was above atmospheric percentage of 21%, but always below 45%. Key Points: Photosynthetic gas bubbles from submerged macrophytes contain other gases beyond oxygenThe depth‐dependent lower limit can be derived from minimum gas pressure consideration for the formation of bubblesEmpirically we find an upper limit of 45% of oxygen in the collected gas bubbles [ABSTRACT FROM AUTHOR]

Hot thermal fluids flow through the Earth's crust and carry valuable information about the deep subsurface. The monitoring of natural tracers transported in geothermal fluids, such as gases or ions, are relevant to better understand the geological processes in the Earth's subsurface and their relation to deep fluid dynamics. Recently developed technologies (e.g., portable gas-equilibrium membrane-inlet mass spectrometry) allow for the continuous monitoring of gas species at a much higher temporal resolution than the sampling procedures commonly used, based on a few individual samples. However, the monitoring of gas species from hot thermal fluids still poses experimental challenges tied to unwanted water vapor condensation in the headspace of the separation module, which irremediably leads to clogging (e.g., of the connecting capillaries) and failure of the detection device. In this contribution, we present two new experimental methods that provide suitable technical conditions to measure gases, even in high temperature geothermal fluids, using a portable gas analyzer. Two sites with different thermal water temperatures (first one ranging from 50 °C to 65 °C and second one close to boiling temperature) were selected. The first method was deployed on the thermal waters of Lavey-les-Bains (Vaud, Switzerland), for which we report results from October 2021. The second method was used in Beppu (Oita Prefecture, Japan), for which we report results from April 2018. Our results show that at both sites, our methods allow for continuous measurements of gas species (N2, Ar, O2, Kr, He, CH4, CO2 and H2) in thermal waters. Furthermore, they show that the variability of gas emanation from the two sites can only be adequately described by measurements with high temporal resolution, which both methods allow.

Dissolved gases in the effluent of anaerobic reactors, specifically dissolved methane (D-CH4) and sulphide (S2−), are a drawback for anaerobic-based sewage treatment plants (STPs). This article studied the simultaneous desorption/removal of both gases from anaerobic effluents with hollow fibre membrane contactors (HFMCs), evaluating two types of membrane materials (e.g. microporous and dense) at different operating conditions (atmospheric air as sweeping gas or vacuum, and different gas/liquid flows and vacuum pressures). The transfer of other gases, such as O2 and CO2, was studied as well. Desorption/removal efficiencies up to 99% for D-CH4 and 100% for S2− were obtained, with the higher efficiencies reported for the dense HFMC and with air as sweeping gas. It was found that the removal mechanism for S2− was oxidation with O2 from the air. In addition, the use of air as sweeping gas allowed the obtention of a nearly O2 saturated effluent, with more elevated dissolved oxygen concentrations in the microporous HFMC. Finally, it was found that the higher mass-transfer resistance in the dense membrane was compensated by a better performance in the liquid phase (lower mass-transfer resistance) in this unit, which allowed better D-CH4 desorption efficiencies. [ABSTRACT FROM AUTHOR]

In a transformer, the insulation materials will produce different dissolved gases due to various faults in the operation of the transformer, in which C2H2, CH4, and H2 are the main dissolved gases. In this study, the adsorption characteristics of the above three gases on the SnO2–GeSe monolayer surface were discussed and analyzed based on the density functional theory. The adsorption energy, transfer charge, geometric structure parameters, electronic density of states, electronic local function, charge difference density, and recovery time were calculated and compared to characterize the gas-sensing adsorption mechanism. The results showed that the SnO2–GeSe monolayer exhibited good adsorption capacity, selectivity, and repeatability for the three characteristic dissolved gases. After adsorbing CH4 gas molecules, the conductivity of the SnO2–GeSe monolayer decreased. After adsorbing C2H2 and H2 gas molecules, the conductivity of the SnO2–GeSe monolayer increased. Therefore, the SnO2–GeSe monolayer has great application potential in the real-time monitoring of dissolved gases in insulating materials, which may become a new type of resistive gas sensor. [ABSTRACT FROM AUTHOR]

In Underwater Acoustic Sensor Network (UASN), routing and propagation delay is affected in each node by various water column environmental factors such as temperature, salinity, depth, gases, divergent and rotational wind. High sound velocity increases the transmission rate of the packets and the high dissolved gases in the water increases the sound velocity. High dissolved gases and sound velocity environment in the water column provides high transmission rates among UASN nodes. In this paper, the Modified Mackenzie Sound equation calculates the sound velocity in each node for energy-efficient routing. Golden Ratio Optimization Method (GROM) and Gaussian Process Regression (GPR) predicts propagation delay of each node in UASN using temperature, salinity, depth, dissolved gases dataset. Dissolved gases, rotational and divergent winds, and stress plays a major problem in UASN, which increases propagation delay and energy consumption. Predicted values from GPR and GROM leads to node selection and Corona Virus Optimization Algorithm (CVOA) routing is performed on the selected nodes. The proposed GPR-CVOA and GROM-CVOA algorithm solves the problem of propagation delay and consumes less energy in nodes, based on appropriate tolerant delays in transmitting packets among nodes during high rotational and divergent winds. From simulation results, CVOA Algorithm performs better than traditional DF and LION algorithms. [ABSTRACT FROM AUTHOR]

When the transformer fails, the transformer oil will decompose and produce fault characteristic gases. Detecting dissolved gases in the oil is significant to maintaining the safety and stability of the transformers. This manuscript mainly studies six modified substrates of Cu n and Pd n (n=1–3) clusters modified WSe 2 , and applies them to detect three target gases (CO, CH 4 , C 2 H 2). By analyzing key parameters based on density functional theory, TM n clusters can effectively improve the electrical conductivity of WSe 2 and improve the detection ability of target gases. The order of adsorption effects of target gases on six modified substrates is as follow: TM 1 -WSe 2 is consistent with Cu 3 -WSe 2 (C 2 H 2 > CO > CH 4), and TM 2 -WSe 2 is the same with Pd 3 -WSe 2 (CO > C 2 H 2 > CH 4). The optimal recovery time for each gas is ultimately determined and these modifications are found to be effective in distinguishing and detecting the three gases. The research results show that WSe 2 can be used as a gas sensor material, which provides a theoretical basis for detecting the operating status of oil-immersed transformers. [Display omitted] • The electrical conductivity of the modified metal clusters are enhanced. • Adsorption energy, recovery time and sensitivity indicate that the metal clusters modified substrate have ideal adsorption and sensing properties for gas. • Analysis of state density and band structure elucidated the sensing mechanism and further proved the applicability of modified substrate to dissolved gas in oil. [ABSTRACT FROM AUTHOR]

The technique of physical modeling of macro processes of solidification of castings on transparent models and liquids has been developed. The model liquids may be water with different salt contents. Glass bottles can be used for transparent models. Thermal insulation of the top of the model is required. The developed technique allows to investigate the effect of dissolved gases on the microstructure of castings. It has been shown that gases dissolved in liquids have a direct effect on the solidification process and its kinetics. It has been shown that hot water containing less dissolved air than cold water solidifies in the freezer faster than cold water.

This review article discusses the operating conditions and key parameters of the sonohydrogen process, including the acoustic pressure amplitude, ultrasonic frequency and ambient bubble radius, which help achieve better sonochemical activity and higher hydrogen production rate. It also clarifies some discrepancies in the values of various operating conditions and state properties assumed and/or utilized in the literature studies. It further reviews the history of experiments available in the literature on different techniques to measure the bubble radius-versus time curve and discusses the parameters that govern the operation of the sonoreactor and the sonohydrogen process. The boundary conditions of the sonohydrogen process for the expected sonochemical activity and the acoustic bubble pressure and temperatures are comprehensively illustrated. The classifications of the acoustic cavitation bubbles are presented, followed by a discussion of the Blake cavitation threshold and its application to single bubble simulation and full sonoreactor geometries. Furthermore, a review of the predicted hot-spot temperature at different boundary conditions is demonstrated, tailed with the dependence of the sonochemical activity on the medium, including dissolved gases specific heat ratio, thermal conductivity, and thermal diffusivity. Moreover, the findings of this review emphasize the differences in the maximum bubble temperature (hot spot's temperature) for different dissolved gases. [Display omitted] • Hydrogen production through sonohydrogen process triggered by ultrasound waves. • Acoustic cavitation bubbles classification and discussion. • Discussion on Blake, rectified diffusion and transient cavitation thresholds. • Effects of bubble's hot spot, temperature and pressure on the sonohydrogen process. • Effects of dissolved gases, thermal conductivity, and thermal diffusivity on the performance. [ABSTRACT FROM AUTHOR]

Although most of researchers agree on the elementary reactions behind the sonolytic formation of molecular hydrogen (H2) from water, namely the radical attack of H2O and H2O2 and the free radicals recombination, several recent papers ignore the intervention of the dissolved gas molecules in the kinetic pathways of free radicals, and hence may wrongly assess the effect of dissolved gases on the sonochemical production of hydrogen. One may fairly ask to which extent is it acceptable to ignore the role of the dissolved gas and its eventual decomposition inside the acoustic cavitation bubble? The present opinion paper discusses numerically the ways in which the nature of dissolved gas, i.e., N2, O2, Ar and air, may influence the kinetics of sonochemical hydrogen formation. The model evaluates the extent of direct physical effects, i.e., dynamics of bubble oscillation and collapse events if any, against indirect chemical effects, i.e., the chemical reactions of free radicals formation and consequently hydrogen emergence, it demonstrates the improvement in the sonochemical hydrogen production under argon and sheds light on several misinterpretations reported in earlier works, due to wrong assumptions mainly related to initial conditions. The paper also highlights the role of dissolved gases in the nature of created cavitation and hence the eventual bubble population phenomena that may prevent the achievement of the sonochemical activity. This is particularly demonstrated experimentally using a 20 kHz Sinaptec transducer and a Photron SA 5 high speed camera, in the case of CO2-saturated water where degassing bubbles are formed instead of transient cavitation.

Dissolved gases, including noble gases, are versatile environmental tracers. Historically, the application of dissolved (noble) gases as tracers in hydrology used to be limited because their measurement required expensive, laboratory‐based instrumentation operated by highly trained personnel. Here, we highlight recent advances in mobile mass spectrometry (MS) methods for noble and other dissolved gases, which enable low cost, high‐throughput, real‐time measurements. We also present applications using mobile MS to quantify hydrological and biogeochemical processes in groundwater and surface waters and to assess hazards and risks to aquatic environments. Finally, we indicate potential future applications of these instruments to enhance hydrological research. Plain Language Summary: Measurements of hydrological tracers (i.e., specific chemicals or isotopes, whose abundance reflects the properties and history of the sampled water) are an established way to observe how water flows and how solutes might change at and below the Earth's surface over time. Dissolved gases, including noble (inert) gases such as helium, as well as reactive gases such as oxygen and nitrogen, are effective and versatile hydrological tracers. However, until recently, these measurements typically required large, expensive, laboratory‐based instrumentation operated by highly trained people, which has limited the use of these tracers. Here, we highlight recent advances in instrumentation for dissolved gas measurements that can be deployed in the field and are both less expensive and easier to operate than conventional lab‐based instruments. Thus, this new technology will enable more scientists to conduct dissolved gas measurements and to look at processes with a higher temporal and spatial resolution. We describe different applications where these new methods have helped to study the quantity and quality of water, as well as potential future applications of these methods. Key Points: New mobile mass spectrometry (MS) systems enable low‐cost, high‐resolution dissolved gas measurementsHigh‐resolution sampling of dissolved gas tracers can provide new insights into hydrologic processes and systemsCombining dissolved gas measurements with other experimental and numerical methods has the potential to further hydrological research [ABSTRACT FROM AUTHOR]

Abstract Past studies of noble gas concentrations in the deep ocean have revealed widespread, several percent undersaturation of Ar, Kr, and Xe. However, the physical explanation for these disequilibria remains unclear. To gain insight into undersaturation set by deep‐water formation, we measured heavy noble gas isotope and elemental ratios from the deep North Pacific using a new analytical technique. To our knowledge, these are the first high‐precision seawater profiles of 38Ar/36Ar and Kr and Xe isotope ratios. To interpret isotopic disequilibria, we carried out a suite of laboratory experiments to measure solubility fractionation factors in seawater. In the deep North Pacific, we find undersaturation of heavy‐to‐light Ar and Kr isotope ratios, suggesting an important role for rapid cooling‐driven, diffusive air‐to‐sea gas transport in setting the deep‐ocean undersaturation of heavy noble gases. These isotope ratios represent promising new constraints for quantifying physical air‐sea gas exchange processes, complementing noble gas concentration measurements.

Hydrogen is an important intermediate that is produced during carbohydrate fermentation to volatile fatty acid and utilized by methanogens to produce methane in the rumen. Ruminal volatile fatty acid and dissolved methane concentrations are more than 500 times greater than dissolved hydrogen concentration. Therefore, we hypothesized that dissolved hydrogen might have a higher sensitivity in response to dietary changes compared with volatile fatty acid and dissolved methane. Using goats, we investigated the effects of increasing dietary starch content (maize replaced with wheat bran) and supplementing with rhubarb rhizomes and roots on the relationships among dissolved hydrogen, dissolved methane and other fermentation end products. The study was conducted in a replicated 4×4 Latin square with a 2×2 factorial arrangement of four treatments: two starch levels (220 v. 320 g/kg dry matter (DM)), without and with rhubarb supplement (0% v. 2.8% of total mixed ration). Increased dietary starch and rhubarb supplementation did not alter volatile fatty acid concentrations or methane emissions in terms of g/day, g/g DM intake and g/g organic matter digested. However, goats fed the high-starch diet had greater dissolved hydrogen (P=0.005) and relative abundance of Selenomonas ruminantium (P

In a transformer, the insulation materials will produce different dissolved gases due to various faults in the operation of the transformer, in which C2H2, CH4, and H2 are the main dissolved gases. In this study, the adsorption characteristics of the above three gases on the SnO2–GeSe monolayer surface were discussed and analyzed based on the density functional theory. The adsorption energy, transfer charge, geometric structure parameters, electronic density of states, electronic local function, charge difference density, and recovery time were calculated and compared to characterize the gas-sensing adsorption mechanism. The results showed that the SnO2–GeSe monolayer exhibited good adsorption capacity, selectivity, and repeatability for the three characteristic dissolved gases. After adsorbing CH4 gas molecules, the conductivity of the SnO2–GeSe monolayer decreased. After adsorbing C2H2 and H2 gas molecules, the conductivity of the SnO2–GeSe monolayer increased. Therefore, the SnO2–GeSe monolayer has great application potential in the real-time monitoring of dissolved gases in insulating materials, which may become a new type of resistive gas sensor.

The flotation performance and flotation kinetics comparative experiments of the coal were performed in different deionized water (natural and degassed). Both the cumulative combustible recovery and the modified flotation rate constant in the natural water were greater than those in the degassed water, indicating that the dissolved gases were beneficial to promote the flotation process. In addition, six flotation kinetics models were adopted to fit the flotation tests data. It was found that the first-order model with rectangular distribution had the optimal fitting degree of the results for both the natural water and degassed water. The microscope tests results showed that the coal particles were more prone to agglomeration in the natural water, which was in favor of the flotation process and responsible for the greater flotation rate. [ABSTRACT FROM AUTHOR]

The process of removing corrosive gases from water at TPPs in packed columns of calciners and in columns of thermal deaerators with a storage tank in film mode is considered and a mathematical model is presented for calculating the efficiency of the desorption process. A cell model of the flow structure and an equation for calculating the mass transfer coefficient for a wave flow of a water film over the surface of a packing with artificial roughness are used. The value of the required height of the packing layer is obtained for the given density of irrigation with water and the efficiency of extracting gases dissolved in water. Formulas are given for calculating the parameters of a mathematical model: the coefficient of mass transfer in the wave film, the average velocity of water in the film, the dynamic retention of the liquid in the packing layer and the number of cells for complete mixing of the liquid phase. The possibility of using metal chaotic and regular packings is considered, and the results of calculations of the efficiency of mass transfer and the required height of the packing layer at various operating parameters of the desorption process are presented. The graphs of the required layer height for the given efficiency of mass transfer and the power spent on air supply to the desorber when using various nozzles of domestic and foreign production are presented. The article describes the operation of a thermal deaerator with a storage tank and outdated contact devices in a deaerator column at a TPP. The main mass transfer and hydraulic characteristics of modern nozzles for thermal deaerators are presented. Technical solutions have been developed that can be used when choosing a highly efficient metal chaotic packing with a rough surface, which provides an increase in the mass transfer coefficient in a liquid wave film and, accordingly, the efficiency of mass transfer. A variant for modernization of the deaeration column of the DSA-300 deaerator at the Kazan CHPP-3 by replacing outdated contact devices with a modern chaotic packing is shown. As a result of its application, compliance with the standards of water purification from dissolved oxygen is ensured at various loads on water and steam. [ABSTRACT FROM AUTHOR]

The paper investigates the effect of gases dissolved in water on the processes occurring during the laser breakdown of colloidal solutions of nanoparticles. The dynamics of the dependences of the plasma luminosity and acoustic signals on the concentration of nanoparticles under irradiation of colloids of nanoparticles saturated with air, argon, and molecular hydrogen has been studied. It is shown that irradiation of colloids saturated with molecular hydrogen and argon leads to an increase in the integral luminosity and integral acoustic signals in comparison with the control sample saturated with atmospheric gases, which indicates the obvious presence of the influence of gases dissolved in the liquid on the optical breakdown process. The most intense acoustic signals, as well as the brightest breakdowns, were observed when the colloidal solution was saturated with molecular hydrogen.

Experimental and ambient warming of Arctic tundra results in emissions of greenhouse gases to the atmosphere, contributing to a positive feedback to climate warming. Estimates of gas emissions from lakes and terrestrial tundra confirm the significance of aquatic fluxes in greenhouse gas budgets, whereas few estimates describe emissions from fluvial networks. We measured dissolved gas concentrations and estimated emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from water tracks, vegetated depressions that hydrologically connect hillslope soils to lakes and streams. Concentrations of trace gases generally increased as ground thaw deepened through the growing season, indicating active production of greenhouse gases in thawed soils. Wet antecedent conditions were correlated with a decline in CO2 and CH4 concentrations. Dissolved N2O in excess of atmospheric equilibrium occurred in drier water tracks, but on average water tracks took up N2O from the atmosphere at low rates. Estimated CO2 emission rates for water tracks were among the highest observed for Arctic aquatic ecosystems, whereas CH4 emissions were of similar magnitude to streams. Despite occupying less than 1% of total catchment area, surface waters within water tracks were an estimated source of up to 53–85% of total CH4 emissions from their catchments and offset the terrestrial C sink by 5–9% during the growing season. Water tracks are abundant features of tundra landscapes that contain warmer soils and incur deeper thaw than adjacent terrestrial ecosystems and as such might contribute to ongoing and accelerating release of greenhouse gases from permafrost soils to the atmosphere. Plain Language Summary: The Arctic is warming at least twice as rapidly as the rest of the Earth. Warming thaws permafrost, defined as ground that remains frozen for more than 2 years, and results in increased production and release of greenhouse gases by microbes. These gases, including carbon dioxide, methane, and nitrous oxide, trap heat in the atmosphere and contribute to further warming. Emissions of these gases have been extensively observed from soils and lakes in the Arctic, but fewer observations describe greenhouse gas emissions from stream networks. We estimated emissions of greenhouse gases from water flowing in vegetated depressions on Arctic hillslopes, called water tracks, which are tributaries of lakes and rivers. Water tracks may be conduits for gases from soils to the atmosphere. Compared to terrestrial tundra, water tracks emitted more carbon dioxide and methane than expected from their small areal coverage. Water tracks typically withdrew nitrous oxide from the atmosphere, though smaller water tracks supported higher concentrations and net emission of nitrous oxide. The abundance of water tracks combined with high rates of carbon dioxide and methane emission relative to adjacent ecosystems suggests that these features might contribute to increased release of greenhouse gases from Arctic landscapes as permafrost thaws. Key Points: Water tracks draining Arctic hillslopes are estimated to emit CO2 and CH4 to the atmosphere at greater rates than terrestrial tundraWater tracks produced and consumed N2O, resulting in low net emissions to the atmosphereDissolved gas concentrations varied among water tracks and over time and were related to precipitation, redox, and primary productivity [ABSTRACT FROM AUTHOR]

C2H6 and C2H4 gases are two typical decompositions produced by partial discharge of transformer oil. To fully evaluate the feasibility of MoS2-based materials for the detection of C2H6 and C2H4 gases, the adsorption of C2H6 and C2H4 molecules on intrinsic and Au-doped MoS2 monolayer have been studied in this paper by the First-principle of Density Functional Theory (DFT). The adsorption mechanism of MoS2-based monolayer were investigated carefully in terms of adsorption energy, adsorption distance, bandgap structure, charge transfer and density of states (DOS). The calculated results show that the adsorption structures of the C2H6 and C2H4 molecules on Au-doped MoS2 monolayer with larger adsorption energies were stable, and have shorter adsorption distance, higher charge transfer, and stronger orbital hybridization compared with the corresponding MoS2 monolayer adsorption structures. It is concluded that the doped-Au atom affects the electronic structure of MoS2 monolayer to enhance the adsorption capacity. From this aspect, the present research offers a theoretical guidance to the application of Au-doped MoS2 materials as the sensing material for C2H6 and C2H4 gases.

The surfaces of icy moons are covered by fractures, other tectonic features, and active or ancient remains of cryovolcanism. These observations suggest active or recent tectonics, but there is still much unknown about the specific conditions surrounding the formation of these features. One important process leading to the fracture of the ice shell is the freezing and consequent pressurization of its ocean, because water expands upon freezing. However, the influence of dissolved non‐condensable gases (herein referred to as volatiles) on the aforementioned dynamics remains poorly constrained. In this study, we present a new experimental investigation to explore the effect of dissolved volatiles in the internal pressure evolution of 10 cm diameter water spheres subjected to freezing temperatures between ~−60°C and ~−20°C. Our experiments reveal that spheres with a reduced initial amount of volatiles dissolved undergo an abrupt transition with dramatic increase of (a) the time between consecutive ice shell fractures and (b) the pressure required to break the shell. We show from a simple numerical model that this transition occurs when exsolution (i.e., nucleation and growth of bubbles) occurs and the fluid inside the shell becomes significantly more compressible. Exsolution is, in turn, triggered by the gradual thickening of the ice shell, which increases the concentration of dissolved volatiles and eventually leads to saturation. These results suggest that the content of volatiles of icy satellites plays a significant role in their geologic history and potential for habitability. Plain Language Summary: Icy moons have subsurface oceans which may be freezing. As water freezes, it expands. When a subsurface ocean on an icy moon freezes, this expansion of the ice shell increases the pressure in the ocean and can lead to the formation of water‐filled cracks in the icy surface of the moon. To understand how the amount of gas in the ocean water controls when the cracks form, we freeze small spheres of water with different amounts of air under controlled temperature. We find that at some point during the freezing and growth of the ice shell, there is a sharp change in how often cracks occur. This happens because dissolved gases remain in the liquid water during freezing and eventually there is enough gas in the water for bubbles to form. This is important because it tells us how the gas content in the oceans of icy moons might control some of the cracks we observe on the surface of icy moons. Key Points: The freezing of an ocean world is modeled experimentally by freezing spheres of waterIncreased dissolved volatiles in the water significantly influence the tectonic evolution of the body, leading to a lower frequency of fracture events and thinner ice shell at final failureThese results have implications for the geologic history and habitability of icy moons. Specifically, oceans become more volatile‐rich over time, which in turn decreases the frequency at which the ice shell fractures [ABSTRACT FROM AUTHOR]

Atmospheric gases that dissolve in groundwater at the time of recharge are valuable tracers of groundwater residence time, but corrections are sometimes required. Low‐solubility gases like SF6 are particularly susceptible to the effects of excess air, which is generally assumed to occur at the time of recharge. If after excess air correction SF6 is still elevated above the expected concentration for water in equilibrium with the atmosphere, this is often attributed to a terrigenic source. We propose that compressed air used during and after well installation is a potential source of excess air, which can sometimes explain elevated SF6 concentrations from wells drilled in the last few decades. This concept is demonstrated by correcting elevated SF6 and CFC‐12 measurements from 55 wells at field sites in the Pilbara region of Western Australia with up to 10 mL(STP)/kg of atmospheric air from the time of drilling (2006–2016). The resulting SF6 and CFC‐12 concentrations are consistent with recharge between 1950 and 1970 for most wells. Excess air in recharge from that period could not have contained enough SF6 to explain the measured concentrations. This decoupling of excess air from recharge is potentially also significant for other gaseous age tracers with limited solubility including SF5CF3, Halon 1301, 39Ar, 85Kr, and 81Kr. Key Points: Compressed air can be a source of excess dissolved gases in groundwaterExcess air from drilling might explain elevated SF6 in samples from wellsCorrections are sometimes possible using SF6‐CFC plots [ABSTRACT FROM AUTHOR]

The influence of a REM-containing Insteel 7 complex modifier on the structure and the contents of dissolved gases and sulfur in Fe–Al alloys with an increased aluminum content (11–15 wt %) melted in an open induction furnace is studied. [ABSTRACT FROM AUTHOR]

BACKGROUND: Carbon dioxide (CO2) is a gas that has a distinguished effect on the sonochemical process. Dissolving pure CO2 in solutions prevented sonochemical action in all laboratory‐scale experiments, reported until know. The mechanism underlying the pure‐CO2 nullifying sonochemical treatment is until now under debate. RESULTS: Herein, thanks to confronting detailed numerical simulation results for single bubble sonochemistry with literature experimental observations, the mechanism of pure CO2‐quenching sonochemical reaction was clarified. The acoustic generation of free radicals under CO2 atmosphere was simulated for different conditions of frequency (20−1100 kHz), acoustic power (0.5−1 W cm‐2), liquid temperature (20−50 °C) and external pressure (0.6−1.6 atm) and compared with that generated for air‐saturation, for the same conditions. Depending on the sonochemical parameters, it was found that CO2 may enhance, decrease or completely suppress the acoustic generation of hydroxyl radicals. The effect of CO2 was strongly operating conditions‐dependent. CONCLUSION: Given that CO2 nullified all sonolytic actions in aqueous solution, it was concluded that owing to its very high solubility in water (46‐fold much higher than that of air), CO2 could suppress the inertial cavitation bubbles responsible of all chemical actions. Gases of too higher solubility could favor the bubble–bubble coalescence rather than the production of inertial cavitation bubbles. The bubble–bubble coalescence in this case could be a suppressor of inertial cavitation. A high extent of bubbles coalescence could take place under CO2 saturation provoking total disappearance of the chemical activity. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Natural fluids with a pH (25 °C) up to 12.3 were collected from a sub-seafloor borehole observatory (Ocean Drilling Program (ODP) Hole 1200C) on South Chamorro Seamount, a serpentinite mud volcano in the Mariana forearc. We used systematic differences in the chemical compositions of pore waters from drilling operations during ODP Leg 195 and borehole fluids collected subsequently from Hole 1200C to define two endmember solutions, one of which was a sulfate-rich fluid with a methane concentration of 50 mM that ascends from the subduction channel and the other was a low-sulfate fluid. The sequence of sample collection and fluid compositions constrain subsurface hydrologic conditions. Deep-sourced, sulfate- and methane-rich, sterile fluids from the subduction channel can reach the seafloor unchanged within the central conduit, whereas other fluid pathways likely intersect the pelagic sediment that underlies the serpentinite mud volcano, providing potentially suitable conditions and inoculum for microbial anaerobic oxidation of methane (AOM). These AOM-affected, low-sulfate fluids also make it to the seafloor where they discharge. The source of the sulfate- and methane-rich fluid in the subduction channel is attributed to abiotic methane production fueled by hydrogen production from serpentinization and carbonate dissolution. This methane production includes a mechanism to raise the pH above values from serpentinization alone. Results from South Chamorro Seamount represent an end member along a transect defined by the distance from the trench. Results from this site are applied to other serpentinite mud volcanoes along this transect to speculate on likely chemical conditions within shallower and cooler portions of the subduction channel. [ABSTRACT FROM AUTHOR]

Submarine volcanic activity releases large amounts of gases and metals in the water column, affecting biogeochemical cycles and ecosystems at a regional and local scale. In 2018, Fani Maoré submarine volcano erupted 50 km offshore Mayotte Island (Comoros Archipelago, Indian Ocean). Active eruptive plumes were observed in May 2019 at and around the summit with acoustic plumes rising 2 km into the water column coupled to strong geochemical anomalies. Between May 2019 and October 2020, three research cruises monitored the eruptive activity. Here, we report spatial and temporal variability of water column chemistry above the volcano, focusing on dissolved gases, trace metal concentrations, and physico-chemical parameters. In May 2019, concentrations above 800 nM in CH 4 and H 2 were measured throughout the water column, with Total Dissolvable Mn and Total Dissolvable Fe concentrations above 500 nM, and CO 2 values of 265 μM. Strong water column acidification was measured (0.6 pH unit) compared to the regional background. From May 2019 to October 2020, we observed a general decrease in gas concentrations, and an evolution of the TDMn/TDFe ratios similar to previously reported values in other submarine volcanic contexts, and consistent with a decrease of the eruptive activity at the volcano. In October 2020, a rebound of high H 2 concentrations resulted from new lava flows, which were identified by seafloor observation using deep-towed camera, 5 km further than the volcano summit. During 2 years timespan of our observations (2019–2020), He, CO 2 and CH 4 concentrations correlate highlighting a magmatic origin of dissolved gases. δ13C-CH 4 values of −34‰ vs. vPDB might suggest magma/sediments interaction during the magma ascent, and potential thermal cracking of organic matter, although abiotic methane generation cannot be ruled out given the volcanic context. Weak correlations between H 2 and excess of 3He suggest complex processes of H 2 from magmatic degassing, lava/seawater interaction, and oxidation processes in the water column. Strong and correlated Fe, Mn and Si water column anomalies are also consistent with fluid-rock reactions induced by acidic fluids rich in magmatic volatiles. Water column acidification appears to be associated with the release of CO 2 -rich fluids. A year after the main eruptive event, the system seems to be back to steady-state highlighting the buffer capacity and resilience of the seawater column environment. • Massive gases released in the water column during the eruption. • Emitted gases respond in an uncoupled way due to original settings of the volcano. • Strong water column acidification due to the release of CO 2 -rich fluids. • Water column enrichments in iron and manganese by fluid-rock interactions. • Helium isotope signatures show evidence of a change in the magma path. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pt n (n = 1–3) cluster as the metal doping greatly improves the gas sensing of MoS 2 monolayer to three characteristic dissolved gases. • The adsorption and sensing property of Pt n (n = 1–3)-MoS 2 monolayer to CO 2 , CO, and H 2 are systematically analyzed and displayed. • Pt n (n = 1–3)-MoS 2 monolayer shows the outstanding and excellent gas sensing and selectivity to three dissolved gases. The adsorption performances and sensing properties of Pt n (n = 1–3) MoS 2 to three characteristic dissolved gases (CO 2 , CO, H 2) generated of partial discharges in converter transformer oil was analyzed using DFT. The adsorption structure, band structure, charge transfer, adsorption energy, density of states, sensitivity and recovery time were utilized to explore the gas adsorption and sensing mechanism. The results demonstrate Pt n (n = 1–3) cluster greatly enhance weak adsorption ability and sensing property of pure MoS 2 for CO 2 , CO, and H 2. This paper provides the theoretical possibility to investigate a novel MoS 2 -based gas sensor. [ABSTRACT FROM AUTHOR]