Helium Oxygen Research Articles

Effectiveness of ultra-/very-high-frequency oscillations combined with helium–oxygen gas mixture in a rabbit model

High-frequency oscillatory ventilation (HFOV) at frequencies of approximately 15 Hz is associated with optimal CO2 excretion. Higher frequencies using a nitrogen–oxygen gas mixture worsen CO2 excretion. An in vitro experiment using HFOV and a helium–oxygen gas mixture showed a significant increase in CO2 transport, which increased with increases in ventilation frequency. We hypothesised that in HFOV, the change in the arterial partial pressure of CO2 (PaCO2) would be greater at frequencies above 15 Hz when combined with helium–oxygen gas mixture administration. We tested this hypothesis in a hypoventilated healthy rabbit model by administering a helium–oxygen gas mixture at 15, 25, 35, and 45 Hz frequencies. One-way repeated measures ANOVA showed a significant decrease in PaCO2 among the four ventilation frequency groups. Post-hoc analysis showed significant differences between 15 and 35 Hz frequencies and between 15 and 45 Hz frequencies. The mean (standard error) decrease of PaCO2 was 10.8 (2.2), 14.1 (2.3), 21.3 (3.3), and 23.1 (2.5) mmHg at 15, 25, 35, and 45 Hz, respectively. Combination therapy of helium–oxygen gas mixture and high-frequency oscillation using ultra/very high frequencies (35–45 Hz) was associated with a greater PaCO2 decrease than that using the standard frequency (15 Hz).

Mathematical modeling of sound propagation through the respiratory tract in a modified gas environment

The aim of the work was to develop a mathematical model of sound propagation through the human respiratory tract when breathing certain respiratory gas mixtures. We based the model on an assembler model of branching of the respiratory tract. For calculations, we presented the human tracheobronchial tree in the form of an equivalent T-shaped cut section diagram, which includes parameters of the walls of the respiratory tract. We carried the simulation out in two main stages. At the first stage, we calculated the impedance of the flow from the small airways to the larger airways. At the second stage, we calculated the sound pressure caused by breathing. As a result, we obtained the curves of the impedance dependence on the frequency spectrum, as well as the sound power from the respiratory flow. We noted that when breathing air, the impedance value remains constant with increasing frequency. Moreover, we also noted that when exposed to a heavier gas than air, the impedance value constantly increases, and when exposed to lighter gases, after reaching a maximum, the impedance value decreases. We found that the highest sound pressure is typical for the oxygen-krypton mixture, and the lowest for the oxygen–helium mixture. We also found that in the case of modeling the laminar flow regime (with a critical Reynolds number equal to 1800), sound affects how many generations of bronchi more than in the case of modeling the transient flow regime (with a critical Reynolds number equal to 2700). Thus, we drew conclusions about the influence of the physical properties of gaseous media on the amount of sound pressure and the propagation of sound through the human respiratory tract.

A new insight into the oxygen reduction reaction of the Ca3Co4O9+δ/CGO composite air electrode

The calcium cobaltite Ca3Co4O9+δ (CCO) is an emerging electrode for Solid Oxide Fuel Cells or Solid Electrolyser Cells. Thanks to a thermal expansion coefficient which is in the same range of magnitude than the commonly used electrolytes, it should lead to improved durability. However, because the material suffers of a lack of oxide ion conductivity, it has to be used in composite with an ionic conductor. Displaying good compatability with ceria, first studies were carried out on composite with Ce0.9Gd0.1O1.95 (CGO). At 700 °C, an optimal Area Specific Resistance of 0.5 Ω cm2 was obtained for a 50/50 wt.% CCO/ CGO, 21 μm thick electrode, with CCO powder prepared by a solid-state route whose synthesis method led to large grains compared to the CGO powder. Here, to increase the density of triple-phase boundaries between the gas and the two materials, a CCO powder with smaller grain size was prepared using a citrate route. For screen printed 50/50 wt.% CCO (citrate)/CGO composite electrode deposited on symmetrical cell with a CGO electrolyte, an ASR of 0.35 Ω cm2 was achieved at 700 °C, under air. To go further in the understanding of the oxygen reduction reaction, the cell was then carefully studied at variable temperatures and under variable oxygen partial pressures, combining calculation of the distribution function of relaxation times (DFRT) and complex nonlinear least squares fitting (CNLS) of impedance spectra. At 700 °C, under air, it was shown that 55 % of the ASR was due to the oxygen molecule dissociation and diffusion of atomic oxygen species at the surface of the electrode materials. It was only 37 % at 600 °C. Experiment carried out under 21 % of oxygen in helium proved that gas diffusion was a limiting step at temperature higher that 650 °C whereas the redox of CCO was limiting at lower temperature. When deposited on a commercial anode supported 2R-Cell™ half cell, the maximum power density was improved by 284 %, reaching 532 mW/cm2 at 700 °C with a 50/50 wt.% CCO (citrate)/CGO composite air electrode against 187 mW/cm2 for a 50/50 wt.% CCO (solid-state)/CGO composite air electrode at the same temperature.

Determining N2O and N2 fluxes in relation to winter wheat and sugar beet growth and development using the improved 15N gas flux method on the field scale

AbstractThe objectives of this field trial were to collect reliable measurement data on N2 emissions and N2O/(N2O + N2) ratios in typical German crops in relation to crop development and to provide a dataset to test and improve biogeochemical models. N2O and N2 emissions in winter wheat (WW, Triticum aestivum L.) and sugar beet (SB, Beta vulgaris subsp. vulgaris) were measured using the improved 15N gas flux method with helium–oxygen flushing (80:20) to reduce the atmospheric N2 background to < 2%. To estimate total N2O and N2 production in soil, production-diffusion modelling was applied. Soil samples were taken in regular intervals and analyzed for mineral N (NO3− and NH4+) and water-extractable Corg content. In addition, we monitored soil moisture, crop development, plant N uptake, N transformation processes in soil, and N translocation to deeper soil layers. Our best estimates for cumulative N2O + N2 losses were 860.4 ± 220.9 mg N m−2 and 553.1 ± 96.3 mg N m−2 over the experimental period of 189 and 161 days with total N2O/(N2O + N2) ratios of 0.12 and 0.15 for WW and SB, respectively. Growing plants affected all controlling factors of denitrification, and dynamics clearly differed between crop species. Overall, N2O and N2 emissions were highest when plant N and water uptake were low, i.e., during early growth stages, ripening, and after harvest. We present the first dataset of a plot-scale field study employing the improved 15N gas flux method over a growing season showing that drivers for N2O and N2O + N2 fluxes differ between crop species and change throughout the growing season.

Impact of catalysis on n-butane oxidation in an RF atmospheric pressure plasma

The plasma catalytic oxidation of n-butane diluted in a helium oxygen RF plasma jet is used to study volatile organic compound removal to unravel plasma catalytic synergisms. The plasma conversion is tested for a stoichiometric n-butane oxygen mixture for varying plasma power and using a manganese oxide catalyst. It is shown that the interplay between plasma and catalyst is very complex. The catalyst enhances the power coupling, but also serves as a sink for oxygen atoms due to surface recombination. The surface processes are dominated by reactions of radicals and excited species from the plasma. The oxidation of n-butane at the catalyst surface is slightly enhanced. In total, however, n-butane oxidation without the catalyst is more efficient than with the catalyst, which constitutes an anti-synergism.

The Effect of Compression Induced Chorus Waves on 10–100 s eV Electron Precipitation

AbstractOn 7 January 2014, a solar storm erupted, which eventually compressed the Earth's magnetosphere leading to the generation of chorus waves. These waves enhanced local wave‐particle interactions and led to the precipitation of electrons from 10 s eV to 100 s keV. This paper shows observations of a low energy cutoff in the precipitation spectrum from Van Allen Probe B Helium Oxygen Proton Electron measurements. This low energy cutoff is well replicated by the predicted loss calculated from pitch angle diffusion coefficients from wave and plasma observations on Probe B. To our knowledge, this is the first time a single spacecraft has been used to demonstrate an accurate theoretical prediction for chorus wave‐induced precipitation and its low energy cutoff. The specific properties of the precipitating soft electron spectrum have implications for ionospheric activity, with the lowest energies mainly contributing to thermospheric and ionospheric upwelling, which influences satellite drag and ionospheric outflow.

A Helium Speech Unscrambling Algorithm Based on Deep Learning

Helium speech, the language spoken by divers in the deep sea who breathe a high-pressure helium–oxygen mixture, is almost unintelligible. To accurately unscramble helium speech, a neural network based on deep learning is proposed. First, an isolated helium speech corpus and a continuous helium speech corpus in a normal atmosphere are constructed, and an algorithm to automatically generate label files is proposed. Then, a convolution neural network (CNN), connectionist temporal classification (CTC) and a transformer are combined into a speech recognition network. Finally, an optimization algorithm is proposed to improve the recognition of continuous helium speech, which combines depth-wise separable convolution (DSC), a gated linear unit (GLU) and a feedforward neural network (FNN). The experimental results show that the accuracy of the algorithm, upon combining the CNN, CTC and the transformer, is 91.38%, and the optimization algorithm improves the accuracy of continuous helium speech recognition by 9.26%.

Modelling of Nonthermal Dielectric Barrier Discharge Plasma at Atmospheric Pressure and Role of Produced Reactive Species in Surface Polymer Microbial Purification

A nonthermal atmospheric plasma reactor was used to sterilize polymer surfaces and satisfy safety constraints in a biological medium. A 1D fluid model was developed using COMSOL Multiphysics software® 5.4 with a helium-oxygen mixture at low temperature for the decontamination of bacteria on polymer surfaces. An analysis of the evolution of the homogeneous dielectric barrier discharge (DBD) was carried out through studying the dynamic behavior of the discharge parameters including the discharge current, the consumed power, the gas gap voltage, and transport charges. In addition, the electrical characteristics of a homogeneous DBD under different operating conditions were studied. The results shown that increasing voltage or frequency caused higher ionization levels and maximum increase of metastable species' density and expanded the sterilization area. On the other hand, it was possible to operate plasma discharges at a low voltage and a high density of plasma using higher values of the secondary emission coefficient or permittivity of the dielectric barrier materials. When the discharge gas pressure increased, the current discharges declined, which indicated a lower sterilization efficiency under high pressure. A short gap width and the admixture of oxygen were needed for sufficient bio-decontamination. Plasma-based pollutant degradation devices could therefore benefit from these results.

Identifying High-Performance Metal–Organic Frameworks for Low-Temperature Oxygen Recovery from Helium by Computational Screening

Metal–organic frameworks (MOFs) are an important class of porous crystalline materials for applications ranging from gas adsorption and separation to catalysis. There are thousands of potential MOFs available for separation applications. We developed a computational approach to screen MOFs for the separation of oxygen–helium mixtures at low temperatures (100–200 K), conditions that were motivated by issues associated with propulsion in space-based settings. We used detailed molecular simulations for a small number of MOFs to develop screening methods that were then used to estimate the optimum temperatures for separations using pressure swing adsorption for 2932 MOFs from the CoRE MOF database and the swing capacity and oxygen–helium selectivity at these temperatures. We used the stability of the best-performing structures in the presence of moisture as a means to provide a short list of high-performance materials. In addition to identifying specific materials for oxygen–helium separations, this approach could prove useful for selecting adsorbents for other gas separations.

Evaluation of the Efficiency of Oxygen-Helium Therapy for Patients with Covid-19-Associated Pneumonia.

This article summarizes the experience of managing patients with COVID-19-associated pneumonia treated in one of the intensive care units of a multidisciplinary hospital with and without a heated oxygen-helium mixture. It has been shown that the use of a heated oxygen-helium mixture in the complex therapy of pneumonia caused by SARS-CoV-2 is effective. A comparative analysis of the clinical manifestations of the disease and the results of laboratory tests in the main and control groups of patients confirm with a high degree of reliability the improvement of blood oxygenation, the normalization of the acid-base balance and the positive dynamics of the main parameters, which ultimately increases the efficacy and reduces the time of treatment.

Sterilization mechanism of helium/helium–oxygen atmospheric-pressure pulsed dielectric barrier discharge on membrane surface

Pulsed dielectric barrier discharge (PDBD) exhibits several applications in different fields; however, the interaction of its components with substances remains a key issue. In this study, we employed experimental and numerical modeling to investigate the interactions between different PDBD components and substances in pure helium and a helium–oxygen mixture. A membrane comprising a Staphylococcus aureus strain was utilized as the treatment object to demonstrate the trace actions of the evolutions and distributions of certain components on the surface of the substance. The results revealed that the shapes and sizes of the discharging area and inhibition zone differed between groups. Under a pure helium condition, a discharge layer existed along the membrane surface, lying beside the main discharging channel within the electrode area. Further, an annulus inhibition zone was formed at the outer edge of the electrode in the pure helium group at 30 s and 1 min, and this zone extended to a solid circle at 2 min with a radius that was ∼50% larger than that of the electrode radius. Nevertheless, the discharging channel and inhibition zone in the helium–oxygen mixture were constrained inside the electrode area without forming any annulus. A 2D symmetrical model was developed with COMSOL to simulate the spatiotemporal distributions of different particles over the membrane surface, and the result demonstrated that the main components, which formed the annulus inhibition zone under the pure helium condition, contributed to the high concentration of the He+ annulus that was formed at the outer edge of the electrode. Moreover, O+ and were the main components that killed the bacteria under the helium–oxygen mixture conditions. These results reveal that the homogenization treatment on a material surface via PDBD is closely related to the treatment time and working gas.

The Effects of H2S and Recombinant Human Hsp70 on Inflammation Induced by SARS and Other Agents In Vitro and In Vivo.

The ongoing epidemic caused by SARS-CoV-2 infection led to the search for fundamentally new ways and means to combat inflammation and other pathologies caused by this virus. Using a cellular model of lipopolysaccharide (LPS)-induced sepsis (human promonocytes), we showed that both a hydrogen sulfide donor (sodium thiosulfate, STS) and a recombinant Heat shock protein 70 (rHsp70) effectively block all major inflammatory mediators when administrated before and after LPS challenge. The protective anti-inflammatory effect of rHsp70 and H2S was also confirmed in vivo using various animal models of pneumonia. Specifically, it was found that rHsp70 injections prevented the development of the acute respiratory distress syndrome in highly pathogenic pneumonia in mice, increased animal survival, and reduced the number of Programmed death-1 (PD-1)-positive T-lymphocytes in peripheral blood. Based on our model experiments we developed a combined two-phase therapeutic approach for the treatment of COVID-19 patients. This procedure includes the inhalation of hot helium–oxygen mixtures for induction of endogenous Hsp70 in the first phase and STS inhalation in the second phase. The use of this approach has yielded positive results in COVID-19 patients, reducing the area of lung lesions, restoring parameters of innate immunity and T-cell immune response against coronavirus infection, and preventing the development of pulmonary fibrosis and immune exhaustion syndrome.

Effect of gas flow on a helium/oxygen endoscopic plasma jet

This experimental study characterized the effect of carrier gas flow on an endoscopic plasma jet. This system generates and transports helium plasma in a tube over several meters, along with a separate channel transporting oxygen to enhance plasma reactivity on site. The resulting plasma plume exiting the tube allows treatment of tissue surfaces in an endoscopic setting with a view to perform therapeutic operations in the gastrointestinal tract. In a closed cavity simulating the tract, the carrier gas flow was studied by a combined approach investigating plasma plume chemistry, fluid dynamics, and plasma effects on the surface of a hydrogel tissue model reporting oxidation. These three aspects are shown to be closely inter-related. Plasma plume length, intensity, and shape strongly depend on helium content, velocity, turbulence, and environment. Optical emission spectroscopy was used to show that the helium gas flow rate increases the amount of helium and reactive oxygen species (ROS) in the plume. Schlieren imaging was used to visualize the transition of the fluid from buoyant to laminar and finally turbulent depending on flow rate, with a backflow in a closed cavity. Finally, the frontal and radial treatment of the cavity was assessed by measuring ROS delivery to a KI-starch agarose gel model. Helium flow rate had a noticeable effect on the treatment distribution profile and treatment intensity, with different maxima for frontal and radial treatments. This combined approach, in an accurate simulation of the target configuration (i.e. a closed, cylindrical cavity), is necessary to optimize treatment, as its outcome depends on a balance between ROS production, transport, and distribution.

Intraoperative Management of a Severely Kinked Endotracheal Tube and Difficult Airway.

This figure is a lateral cervical radiograph of a nasally intubated 16-yr-old patient with Crouzon syndrome obtained after completion of cranial fossa surgery for Chiari malformation and returning to supine from a prone position. The standard endotracheal tube was severely kinked in the nasopharynx, as shown in the image, and the location of the kinking is indicated with a red arrow. This was likely caused by the warming of the endotracheal tube and the patient’s unique pharyngeal anatomy. The tracheal intubation of the patient was difficult, requiring 11 attempts due to midface hypoplasia, obesity, macroglossia, and cervical spine instability. After the start of surgery, elevated airway pressures and the inability to pass a suction catheter suggested kinking of the endotracheal tube. Due to extremely difficult intubation, endotracheal tube replacement was not attempted. Because the severely kinked endotracheal tube limited inspiratory and expiratory airflow, adequate tidal volume was achieved by increasing peak inspiratory pressure.1 Intermittent measurement of plateau pressure with an expiratory hold yielded additional information about the pressure at the alveoli. Because expiration was passive, increasing the expiratory time facilitated exhalation and reduced the risk of breath stacking.2 A helium–oxygen mixture can also be used to improve ventilation by reducing gas density, increasing the likelihood of maintaining laminar flow across the point of obstruction, and improving bulk flow.3 If the patient can tolerate permissive hypercapnia, a reduction in minute ventilation is also an option to minimize turbulent flow. The use of a wire-reinforced tube is often recommended to prevent endotracheal tube kinking in such a patient.The authors declare no competing interests.

Helium in uranium dioxide: Computer simulation (Review Article)

Recent results of experimental studies, as well as computer modeling of the helium behavior in uranium-based nuclear fuels, are reviewed. Potential models of interaction of helium atoms, uranium and oxygen ions, results of application and perspectives of computer simulation methods in prediction of the most important properties of solid solutions of helium, such as its solubility and diffusion coefficients in stoichiometric and nonstoichiometric uranium dioxide, are discussed.

Combustion characteristics of hydrogen direct injection in a helium–oxygen compression ignition engine

The ignition of hydrogen in compression ignition (CI) engines by adding noble gas as a working gas can yield excellent thermal efficiency due to its high specific heat ratio. This paper emphasizes the potential of helium–oxygen atmosphere for hydrogen combustion in CI engines and provides data on the engine configuration. A simulation was conducted using Converge CFD software based on the Yanmar NF19SK engine parameters. Helium–oxygen atmosphere compression show promising hydrogen autoignition results with the in-cylinder temperature was significantly higher than that of air during the compression stroke. In a compression ignition engine with a low compression ratio (CR) and intake temperature, helium–oxygen atmosphere is recognized as the best working gas for hydrogen combustion. The ambient intake temperature was sufficient for hydrogen ignition in low CR with minimal heat flux effect. The best intake temperature for optimum engine efficiency in a low CR engine is 340 K and the engine compression ratio for optimum engine efficiency at ambient intake temperature is CR12 with an acceptable cylinder wall heat flux value. The helium–oxygen atmosphere as a working gas for hydrogen combustion in CI engines should be consider based on the parameter provided for clean energy transition with higher thermal efficiency.

Numerical study on peak current in pulse-modulated radio-frequency discharges with atmospheric helium–oxygen admixtures

Atmospheric pressure pulse-modulated radio-frequency (rf) plasmas have drawn growing attention due to their potential in applications. By selecting appropriate modulation parameters, the diffused and large-volume plasma can be generated in the pulse-modulated rf plasma with plenty of reactive oxygen species, which is essential for the biomedical application of helium–oxygen plasmas. In this paper, by means of a fluid model, the formation of the peak current in the first period (PCFP) in a pulse-modulated rf helium–oxygen discharge driven by a sinusoidal voltage is discussed, the existence of a reverse field near the anode caused by the negative and positive charges contributes greatly to the mechanism of PCFP. In the simulation, as oxygen admixture increases, the negative ions of O− and become dominative anions in the sheath region, which can’t be driven to the anode very quickly to build a reverse field, thus the PCFP eventually disappears. This study can effectively enhance the understanding of different transportation behavior of heavy negative ions and electrons, and further optimize pulse-modulated rf discharges with helium–oxygen mixtures in various applications.

A Statistical Study of Pancake Pitch Angle Distribution of Low‐Energy Protons and Their Correlation With Magnetosonic Waves

AbstractWe performed a statistical study of the proton pancake pitch angle distributions (PADs) at the energy from 10 to 300 eV with the Helium Oxygen Proton Electron instrument on board the Van Allen Probes. The occurrence rate of low energy proton pancake PADs and their dependence on the energy, L shell, magnetic local time (MLT) and AL* index are analyzed. The results indicate that: (a) the occurrence rate of pancake PADs decreases as the proton energy increases; (b) under active geomagnetic activities (AL* < −300 nT), pancake PADs preferentially occur in the dayside; (c) under weak geomagnetic activities (AL* > −100 nT), the occurrence rate of pancake PADs has little dependence on MLT. We further discuss the contribution of magnetosonic (MS) waves on the formation of proton pancake PADs at low energy. The strong correlation between the occurrence of pancake PADs and the appearance of MS waves indicates that MS waves contribute to the formation of low energy proton pancake PADs. Moreover, the proton diffusion coefficients caused by MS waves suggest that MS waves can cause the proton heating at low energies in high density regions.

Helium-oxygen in bronchiolitis-A systematic review and meta-analysis.

IntroductionBronchiolitis is common reason for infant hospitalization. The aim of our systematic review and meta‐analysis was to evaluate helium–oxygen (heliox) in bronchiolitis.MethodsWe screened 463 studies, assessed 22 of them, and included six randomized controlled trials. Primary outcomes were the need for continuous positive airway pressure (CPAP) or intubation, hospitalization duration, and change in the modified Woods Clinical Asthma Scale (M‐WCAS). We calculated mean differences with 95% confidence intervals (CIs) for continuous outcomes and risk ratios (RRs) for dichotomous outcomes.ResultsSix studies (five double‐ and one single‐blinded) with 560 infants were included. The risk of bias was high in one, moderate in four, and low in one. The RR for the need for CPAP (three studies) was 0.87 (CI: 0.56–1.35), and for intubation (four studies) was 1.39 (CI: 0.53–3.63), heliox compared to air–oxygen. The hospital stay (four studies) was 0.25 days longer (CI: −0.22 to 0.71) in the heliox group. The mean decrease in M‐WCAS from the baseline (three studies) was 1.90 points (CI: 1.46–2.34) greater in the heliox group.ConclusionWe found low‐quality evidence that heliox does not reduce the need for CPAP, intubation, or length of hospitalization for bronchiolitis. Based on the M‐WCAS scores, heliox seems to relieve respiratory distress symptoms rapidly after its initiation. The included studies had high heterogeneity in their methods and included relatively mild cases of bronchiolitis. A larger randomized controlled trial with more severe cases of bronchiolitis with enough power to analyze the need for intubation is needed in the future.

Statistical study of “trunk-like” heavy ion structures in the inner magnetosphere

We present a statistical study of “trunk-like” structures observed in He⁺ and O⁺ in the inner magnetosphere. The main characteristic of these structures is that the energy of the peak flux decreases earthward. Using observations from the Helium Oxygen Proton Electron (HOPE) instrument onboard Van Allen Probe A, we identify the trunks observed from November 2012 to June 2019 and obtain the universal time, <italic>L</italic> shell, magnetic local time (MLT), and energy information of each trunk’s root and tip. We then investigate the behavior of trunks in terms of their frequency of occurrence, temporal evolution, spatial and energy distribution, and trunk dependence on different geomagnetic indices. We find that (1) the trunks are always located at <italic>L</italic> = 1.5−4.0 and have a preferential location mainly concentrated at MLT = 18−24, (2) the sector within MLT = 14−16 is a forbidden zone without trunk roots, and (3) the energy of He⁺ trunks is the largest near dusk and gradually decreases in the counterclockwise direction, whereas the energy of O⁺ trunks is relatively evenly distributed with MLT and <italic>L</italic>. The differences between He⁺ and O⁺ trunks are probably due to the different charge exchange and Coulomb collision lifetime. The dependence on different geomagnetic indices indicates that the trunk structures occur more frequently during relatively quiet periods.