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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]

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]

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]

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.

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]

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.

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]

The gravity-driven flashing of superheated water, a non-equilibrium phase change phenomenon usually associated with geysers, has not been studied yet in the specific configuration of a pool heated from below. However, this vaporization mode is tightly linked with some of the safety issues of the Spent Fuel Pool (SFP) loss-of-cooling accident. In order to fill this gap, an experiment, presented in this article, was designed and provided first results that highlighted some relevant mechanisms behind this vaporization mode. By heating up 40 L of demineralized water at a constant reduced pressure of 25 mbar with a heating power of 1000 W , it was possible to reproduce the expected phenomenology of a SFP loss-of-cooling accident at the laboratory scale. Starting the test with an initially large supersaturation in dissolved gases within the liquid, the latter, once superheated, vaporized onto the air nuclei that resulted from the liquid degassing. When the dissolved gases content dropped below a threshold value, the nucleation vanished. The liquid continued to heat-up for a while until an energetic equilibrium was reached between the heat supply and the heat removal induced by the free surface evaporation. This equilibrium substantially limited the superheats reached within the liquid. • A first study of the gravity-driven flashing of water in a heated pool. • A novel similarity approach based on system's pressure distortion. • A vaporization mechanism strongly influenced by the dissolved gases. [ABSTRACT FROM AUTHOR]

[Display omitted] • Study of influence of dissolved gases on viscosity and surface tension of ionic liquids (ILs) at saturation conditions. • Combined surface light scattering and pendant-drop experiments including solubility measurements from 0.02 to 8 MPa. • Decrease in surface tension of [OMIM][PF 6 ] and [(mPEG 2) 2 Im]I with increasing pressure more pronounced for CO 2 than for Ar. • Viscosity of both ILs distinctly reduced with increasing CO 2 pressure, reaching a factor of 14 for [OMIM][PF 6 ] at 5 MPa. • Decrease or increase in viscosity of [OMIM][PF 6 ] or [(mPEG 2) 2 Im]I by Ar pressure due to fluidization or compression effect. The present study investigates the influence of dissolved gases on the viscosity and surface tension of ILs at saturation conditions. As model systems, the imidazolium-based ILs, namely, the hydrophobic 1-methyl-3-octylimidazolium hexafluorophosphate ([OMIM][PF 6 ]) and the hydrophilic 1,3-bis(2-(2-methoxyethoxy)ethyl)imidazolium iodide ([(mPEG 2) 2 IM]I), were studied in combination with argon (Ar) and carbon dioxide (CO 2) representing gases of relatively low and high solubility. By a combination of surface light scattering (SLS) and the pendant-drop (PD) method within one setup and sample cell, the surface tension determined by the PD method was used to access the saturated viscosity of the liquid bulk phase via SLS at temperatures of (303 and 323) K and pressures from (0.02 up to 8) MPa. At the same states and within the same setup, the gas solubility in the ILs was estimated on the basis of the evolution of the pressure during transient gas absorption. The addition of either gas causes a decrease in the surface tension of both ILs, which is more pronounced for CO 2 at a given pressure and for the lower temperature. This behavior seems to be related to the weakening of intermolecular interactions at the gas–liquid interface by adding gas, facilitated by possible surface enrichment effects of CO 2. The viscosity of both ILs is distinctly lowered with increasing CO 2 pressure, amounting to a factor of 14 for [OMIM][PF 6 ] at the largest pressure of 5 MPa. In the presence of Ar, the viscosity of [OMIM][PF 6 ] reduces with increasing pressure by 11% at 8 MPa, while that of [(mPEG 2) 2 IM]I increases by 7%. This behavior indicates that the fluidization effect on the liquid phase due to the solvation of Ar is dominant for the hydrophobic IL with higher Ar solubility, whereas it is outweighed by the competing compression effect of the gas for the hydrophobic IL. [ABSTRACT FROM AUTHOR]

Spatial and temporal patterns of primary productivity in the Arctic are expected to change with warming-associated changes in ice cover and stratification, yet productivity measurements are historically spatially and temporally limited. Over the last two decades, an approach that uses measurement of dissolved oxygen/argon ratios (O 2 /Ar) from a vessel's underway seawater system has emerged as an established method to assess net community production (NCP) rates with high spatial and/or temporal resolution. More recently, the measurement of oxygen/nitrogen ratios (O 2 /N 2) with a gas tension device (GTD) and optode have been piloted in underway settings to provide comparable NCP estimates. The GTD/optode approach has several advantages: instrumentation is small, inexpensive, and suitable for autonomous deployments; however, dissimilarity in solubility between O 2 and N 2 makes this tracer pair less accurate than O 2 /Ar. We conducted a side-by-side ship-based comparison of a GTD/optode and Equilibrator Inlet Mass Spectrometer (EIMS) in the Pacific Arctic during one of the North Pacific Research Board Integrated Ecosystem Research Program cruises in 2019. NCP from O 2 /Ar and O 2 /N 2 approaches were coherent throughout this cruise, with median mixed layer integrated NCP of 9.3 ± 2.8 and 7.9 ± 3.2 mmol O 2 m−2 day−1, respectively. The range of NCP was large, from less than zero to >100 mmol O 2 m−2 day−1, with some of the largest NCP estimates measured at well-established hotspots in the Pacific Arctic. While O 2 /Ar and O 2 /N 2 largely tracked each other, deviations were observed, principally in the Bering Sea where wind-induced bubbles were a primary driver, while a combination of temperature and wind drove differences over the majority of the cruise. The GTD/optode can be used to enhance spatial and temporal coverage of NCP measurements, yet the uncertainty makes this approach better-suited to regions with higher overall rates of NCP, while regions near-equilibrium may result in unacceptably high uncertainty. Additionally, the GTD/optode is reliant on well-calibrated oxygen observations, a potential challenge if autonomously deployed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthetic anaerobic effluents were prepared from binary gas mixtures of CH 4 /CO 2. • Dissolved CH 4 and CO 2 gases recovered by using two different PDMS membrane modules. • The presence of CO 2 had a negative impact on CH 4 recovery. • CH 4 recovery enhanced by increasing liquid flow rate and its share in gas mixture. • Higher CO 2 content and lower liquid flow rate favoured the CO 2 recovery. In this research, the recovery of dissolved biogas (CO 2 /CH 4) from synthetic anaerobic effluents was studied using non-porous, polydimethylsiloxane (PDMS), hollow-fibre gas–liquid membrane contactors towards the design of a reduced carbon-footprint integrated bioprocess. As a key parameter, the gas-to-liquid (G/L) ratio (employing argon as sweep gas) was systematically varied in the range of 0.5–2.0. The results showed on a 1 m2 PDMS module that increasing the liquid (effluent) flow rate favours the CH 4 transport, while a higher sweep gas flow rate is preferable for the CO 2 transport over CH 4. Depending on the actual biogas composition and the CO 2 content of the effluent, the methane recovery could be improved up to 63 % under steady-state conditions. In general, similar tendencies were observed when another PDMS membrane module with a smaller surface area (2 500 cm2) was applied hence, in this sense, the separation behaviour seems to be independent of the membrane size. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bromothymol blue's spectral properties were recorded in the presence of heavy water and of some selected electrolytes. • The removal of dissolved gases from the dye solution modifies its UV–vis absorption spectrum. • Re-admitted gases induce specific effects on the spectral features of the dye. The color of the pH indicator Bromothymol blue (BTB) changes from yellow to blue with increasing pH. The effect of some electrolytes (LiCl, NaCl, KCl, CsCl, KSCN and KClO 3) and of D 2 O on the spectral properties of dilute solutions of BTB is explored. The results are interpreted in terms of dimerization of the dye molecules and of the different hydration that D 2 O induces. The effects of dissolved gases on the spectral properties of BTB is studied. Complete removal of dissolved gas is achieved. Surprising effects on the UV–vis spectra emerged. After degassing solutions, gases were re-admitted via bubbling. The gases He, Ar, N 2 , CO 2 and CH 4.were studied. The effects can be explained by presence or absence of nano- and microbubbles of gas in the solution. These allow formation of dimers and multiple association via adsorption and so affect the spectral properties of the dye molecules. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ag n (n = 1–3) cluster doped PtO 2 monolayer is studied. • The electronic property of Ag n (n = 1–3)-PtO 2 monolayer upon the CH 4 , CO, C 2 H 2 , and C 2 H 4 are displayed and analyzed. • The sensing property and recovery time for gas detections are analyzed. The adsorption performance and sensing properties of Ag n (n = 1–3) cluster PtO 2 to four characteristic dissolved gases CH 4 , C 2 H 2 , C 2 H 4 , and CO in transformer oil was analyzed depend on DFT calculation. The adsorption structure, band structure, charge transfer, adsorption energy, density of states, work function, molecular orbital and recovery time were employed to explore the gas adsorption and sensing mechanism. The results exhibit Ag n (n = 1–3) cluster greatly enhance poor adsorption capacity and sensing property of pure PtO 2 for CH 4 , C 2 H 2 , C 2 H 4 , and CO. This paper provides the theoretical guidance to investigate a novel PtO 2 -based gas sensor. [ABSTRACT FROM AUTHOR]

This work presents the temporal evolution (April 2016 to June 2020) of the chemical and isotopic content of dissolved gas species (CO 2 , He, O 2 , N 2 and CH 4) present in groundwater at the Fuente del Valle (FV) and San Fernando (SF) galleries (Tenerife, Spain), and their relationship with the seismic activity observed on the island. CO 2 is the major dissolved gas species in the groundwater at both galleries, and the δ13C-CO 2 data show a clear endogenous origin as a result of interaction with deep fluids. A bubbling gas sample from Fuente del Valle revealed CO 2 rich gas with a considerable He component. The isotopic data of both components (δ13C-CO 2 and 3He/4He) in the bubbling gas support the sources inferred from the dissolved gas compositions, with the endogenous component affected by changes in volcanic-hydrothermal system activity. On October 2, 2016, a seismic swarm occurred, followed by an increase in seismic activity throughout Tenerife. After the event, geochemical variations were registered in the dissolved gas species, e.g., an increase in dissolved CO 2 and He content and CO 2 /O 2 , He/CO 2 , He/N 2 and CH 4 /CO 2 ratios. These changes suggest an injection of fluids into the Tenerife hydrothermal system during October 2016, confirming a connection between groundwater and the hydrothermal system. This investigation highlights the relevance of dissolved gases in groundwater as a tool for volcanic surveillance. • First extensive study of dissolved gases in groundwaters from Tenerife • Dissolved gas concentrations show changes coupled with a seismic swarm on Tenerife • Groundwaters have considerable dissolved He and CO 2 • Isotopic data provide important information about the endogenous origin of dissolved gases [ABSTRACT FROM AUTHOR]

In order to evaluate the running status of the transformer, through the detection of the dissolved gas in oil using highly sensitive gas sensor is proposed as an effective method. In this work, the adsorption characteristics of dissolved gases (H 2 , C 2 H 2 , CH 4) in transformer oil on Ni-doped GaN (Ni-GaN) were analyzed based on density functional theory, and the potential of the Ni-GaN as a gas sensor was explored. The results show that the Ni-GaN has the largest adsorption energy to C 2 H 2. On the other hand, the Ni-GaN has outstanding response to H 2 , C 2 H 2 and CH 4 , and its response are 6.88 × 103, 6.57, 39.38, respectively. According to the analysis of frontier molecular orbital theory, the band gap of the Ni-GaN will increase after adsorption of three kinds of gases. This also confirms the sensing behavior of the Ni-GaN to three kinds of gases. In addition, the Ni-GaN has excellent desorption behavior for CH 4. When the temperature is 398 K, the recovery time is only 8.90 s. Based on the working mechanism of the field effect transistor, by adjusting the strength of the applied electric field, it is found that the charge transfer in the adsorption process can be effectively adjusted. This work provides theoretical guidance for the development of the Ni-GaN gas sensitive sensor for detecting dissolved gas in transformer oil. [Display omitted] • The most stable site for Ni doping onto the GaN monolayer is analyzed. • The interaction mechanism of the dissolved gas in oil (H 2 , C 2 H 2 , CH 4) on the Ni-GaN surface is studied. • We have explored the potential of the Ni-GaN as a resistive sensor and a field effect transistor sensor. [ABSTRACT FROM AUTHOR]