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In the present work, we report an update and extension of the previous ion-pair formation study of Hubers, M.M.; Los, J. Chem. Phys.1975, 10, 235-259, noting new fragment anions from time-of-flight mass spectrometry. The branching ratios obtained from the negative ions formed in K + SF6 collisions, in a wide energy range from 10.7 up to 213.1 eV in the centre-of-mass frame, show that the main anion is assigned to SF5- and contributing to more than 70% of the total ion yield, followed by the non-dissociated parent anion SF6- and F-. Other less intense anions amounting to

In the present work, we report an update and extension of the previous ion-pair formation study of Hubers, M.M.; Los, J. Chem. Phys. 1975, 10, 235–259, noting new fragment anions from time-of-flight mass spectrometry. The branching ratios obtained from the negative ions formed in K + SF6 collisions, in a wide energy range from 10.7 up to 213.1 eV in the centre-of-mass frame, show that the main anion is assigned to SF5− and contributing to more than 70% of the total ion yield, followed by the non-dissociated parent anion SF6− and F−. Other less intense anions amounting to <20% are assigned to SF3− and F2−, while a trace contribution at 32u is tentatively assigned to S− formation, although the rather complex intramolecular energy redistribution within the temporary negative ion is formed during the collision. An energy loss spectrum of potassium cation post-collision is recorded showing features that have been assigned with the help of theoretical calculations. Quantum chemical calculations for the lowest-lying unoccupied molecular orbitals in the presence of a potassium atom are performed to support the experimental findings. Apart from the role of the different resonances participating in the formation of different anions, the role of higher-lying electronic-excited states of Rydberg character are noted. [ABSTRACT FROM AUTHOR]

A semi-analytic method for quickly approximating the density-reduced critical electric field for arbitrary mixtures of gases is proposed and validated. Determination of this critical electric field is crucial for designing and testing alternatives to SF6 for insulating high voltage electrical equipment. We outline the theoretical basis of the approximation formula from electron fluid conservation equations, and demonstrate how for binary mixtures the critical electric field can be computed from the transport data of electrons in the pure gases. We demonstrate validity of the method in mixtures of N2 and O2, and SF6 and O2. We conclude with an application of the method to approximate the critical electric field for mixtures of SF6 and HFO1234ze(E), which is a high interest mixture being actively studied for high voltage insulation applications. [ABSTRACT FROM AUTHOR]

In this paper, we investigated Ni-doped WS2 (Ni@WS2) to detect the H2S, SO2, SOF2, and SO2F2 gases, which are also decomposition gases of SF6 (sulphur hexafluoride). Hence, Electron Difference density, adsorption length and energy, band structure (B.S.), charge transfer, and density of states (DOS) are detailed and studied in depth. The adsorption energy of SF6 decomposition gases i.e. H2S, SO2, SOF2, SO2F2 on Ni@WS2 are found to be −1.3, −1.46, −1.64, and −1.8 eV, respectively, which is superior as compared to other materials. It has been observed through the band structure analysis that after adsorption of SF6 decomposed gas on Ni modified WS2 bandgap reduces, and as a result, conductivity also changes. The dip in bandgap after adsorption of H2S, SO2, SOF2, and SO2F2 on Ni decorated WS2 can be arranged as Ni@WS2@SO2F2> Ni@WS2@SOF2> Ni@WS2@H2S > Ni@WS2@SO2. In brief, these investigations are very efficacious for detecting H2S, SO2, SOF2, and SO2F2 gases, by Ni-doped WS2 monolayer. [ABSTRACT FROM AUTHOR]

We present an optical sensor based on light-induced thermoelastic spectroscopy for the detection of hydrogen sulfide (H2S) in sulfur hexafluoride (SF6). The sensor incorporates a compact multi-pass cell measuring 6 cm × 4 cm × 4 cm and utilizes a quartz tuning fork (QTF) photodetector. A 1.58 µm near-infrared distributed feedback (DFB) laser with an optical power of 30 mW serves as the excitation source. The sensor achieved a minimum detection limit (MDL) of ∼300 ppb at an integration time of 300 ms, corresponding to a normalized noise equivalent absorption coefficient (NNEA) of 3.96 × 10−9 W·cm−1·Hz−1/2. By extending the integration time to 100 s, the MDL can be reduced to ∼25 ppb. The sensor exhibits a response time of ∼1 min for a gas flow rate of 70 sccm.

Agricultural soils are a major source of the potent greenhouse gas and ozone depleting substance, N2O. To implement management practices that minimize microbial N2O production and maximize its consumption (i.e., complete denitrification), we must understand the interplay between simultaneously occurring biological and physical processes, especially how this changes with soil depth. Meaningfully disentangling of these processes is challenging and typical N2O flux measurement techniques provide little insight into subsurface mechanisms. In addition, denitrification studies are often conducted on sieved soil in altered O2 environments which relate poorly to in situ field conditions. Here, we developed a novel incubation system with headspaces both above and below the soil cores and field‐relevant O2 concentrations to better represent in situ conditions. We incubated intact sandy clay loam textured agricultural topsoil (0–10 cm) and subsoil (50–60 cm) cores for 3–4 days at 50% and 70% water‐filled pore space, respectively. 15N‐N2O pool dilution and an SF6 tracer were injected below the cores to determine the relative diffusivity and the net N2O emission and gross N2O emission and consumption fluxes. The relationship between calculated fluxes from the below and above soil core headspaces confirmed that the system performed well. Relative diffusivity did not vary with depth, likely due to the preservation of preferential flow pathways in the intact cores. Gross N2O emission and uptake also did not differ with depth but were higher in the drier cores, contrary to expectation. We speculate this was due to aerobic denitrification being the primary N2O consuming process and simultaneously occurring denitrification and nitrification both producing N2O in the drier cores. We provide further evidence of substantial N2O consumption in drier soil but without net negative N2O emissions. The results from this study are important for the future application of the 15N‐N2O pool dilution method and N budgeting and modelling, as required for improving management to minimize N2O losses. [ABSTRACT FROM AUTHOR]

Introduction: We report a case and discuss the clinical characteristics and treatment of spontaneous Descemet membrane detachment (DMD). Case description: We describe a rare case of spontaneous DMD in a patient with prior anterior uveitis and provide a review of the current literature. A 20-year-old woman with a prior history of anterior uveitis presented with vision loss in the left eye. The slit-lamp examination showed corneal edema secondary to DMD, confirmed by anterior segment optical coherence tomography (AS-OCT). The patient underwent an intracameral injection of 20% sulphur hexafluoride (SF6) with complete resolution of the DMD. Although rare, several cases of spontaneous DMD have been reported in the literature, mostly occurring after intraocular surgery. We searched the Pubmed database (1949–2021) for peer-reviewed publications relevant to the topic of spontaneous DMD. Discussion: The pathogenesis of spontaneous DMD is complex and depends on several factors. It can occur due to anatomical anomalies, inflammatory disease, trauma, chemical injuries, and surgical or laser procedures. In most cases, early diagnosis and appropriate management led to resolution. [ABSTRACT FROM AUTHOR]

Livestock grazing plays a significant role in maintaining grasslands and promoting animal production globally. To understand the livestock performance in sown pasture (SP) vs native pasture (NP) is important to ensure more effective grassland-livestock interactions with minimal environmental impact. A 2 (treatment) * 2 (period) Latin Square design experiment was conducted with 10 growing Hu sheep ♂ × thin-tailed Han sheep ♀ rams grazed perennially SP vs NP in an inland arid region of China. The objectives were to evaluate the effects of grazing management on nutrient digestibility, nitrogen (N) and energy utilisation and methane (CH4) emission. The N intake, N retained and energy intake (gross energy (GE), and digestible and metabolisable energy) of sheep grazing in SP were significantly increased compared with those grazing in NP. There were significant linear relationships between DM intake (DMI) (g/kg BW or g/kg BW0.75) or CH4 (g/kg BW or g/kg BW0.75) emissions and forage nutrient and GE concentrations within each grassland type. The linear regression analysis indicated that forage CP or ether extract concentration was a good predictor for DMI (g/kg BW or g/kg BW0.75) (R2 = 0.756 or 0.752), and CH4 emission could be predicted using forage nutrient and GE concentrations (R2 = 0.381–0.503). These results suggest that DMI and CH4 emissions per unit metabolic BW were accurately predicted by multiple-factor combinations of forage nutrients, including ether extract and CP paired with GE. The present output could provide useful information for the development of sustainable sheep grazing systems in the inland arid regions of the world.

Viscosity, density, and interfacial tension of three binary systems (carbon dioxide–isopropanol, argon–isopropanol, and sulphur hexafluoride–isopropanol) were measured at temperatures of 313.15 K and 333.15 K and at pressures up to 100 bar for carbon dioxide, and for argon and sulphur hexafluoride up to 500 bar. A vibrating tube densimeter method has been used for density measurements and a variable-volume high-pressure optical view cell with some modifications for the other measurements. The results showed that pressure does not have a high impact on viscosity. Density is found to be a linear function of pressure and temperature and the densities of the investigated binary systems increase with pressure and decrease with temperature. Interfacial tension decreased with the elevated pressure at a constant temperature for all the investigated systems. Accurate prediction of thermodynamic and mass transfer data is fundamental in various engineering and industrial operations to design processes with a higher yield of targeted compounds. [ABSTRACT FROM AUTHOR]

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Aims: To evaluate the safety of the contrast enhanced voiding urosonography (ceVUS) and contrast enhanced ultrasound (CEUS) in children and adolescence and to receive data about parents' acceptance of intravesical and intravenous application of sulfur hexafluoride.Material and Methods: In this prospective, single centre study conducted over a 1 year study period, parents of 56 children (f/m=32/24; mean age 3.1 years; range 3 weeks - 15.9 years) with ceVUS and of 30 children (f/m=15/15; mean age 10.5 years; range 2 months - 17.7 years) with CEUS agreed to be included. A standardized telephone survey about the acceptance of the parents during and after the procedure as well as the adverse events (AE) were conducted within three days of the examination.Results: The parents would agree with the use of both ceVUS and CEUS as a diagnostic tool again in 96% (54/56) or 100% (30/30) of the cases, respectively and 92.9% (52/56) would prefer ceVUS to voiding cystourethrography (VCUG). In addition, 83.3% (25/30) would prefer CEUS to CT and 73.3% (22/30) would prefer CEUS to MRI. AE were reported in 3.6% after ceVUS (2/56; skin rash, mild fever) and in 3.3% after CEUS (1/30; vomiting). AE were subacute and self‑limited.Conclusions: The vast majority of parents prefer ceVUS and CEUS to VCUG, CT or MRI because of the safety profile of the contrast agent and diagnostic accuracy. [ABSTRACT FROM AUTHOR]

The objectives of this paper are to measure the resistance of insulation and contact, simultaneously the CB’s contact when opened/closed operations; and the quality of SF6 gas. Research of method, namely measure the resistance, simultaneously the CB’s contact, and quality of gas to be compared into the standard. Research results in the form of (a) insulation resistance is 97,000 MΩ and contact resistance was measured in ranging of 33 to 35 Ω, (b) simultaneously the CB’s contact was measured in ranging of 1.7 to 4.8 milliseconds, and (c) the quality of gas which includes several parameters, namely (i) gas pressure was measured 7.4 bar, (ii) impurity was measured in ranging of 98.4 to 98.9%, (iii) the dew point was measured in ranging of -41 to -45 0C and moisture content was measured in ranging of 80 to 104, and (iv) the value of products decomposition was measured in ranging of 33 to 100. Based on these results concluded, that the overall of part of circuit breaker with mediated by gas of SF6 is still a very viable when re-operated.

In this paper, some thermophysical properties at low pressure of sulphur hexafluoride ( SF 6 ) fluid are modelled and predicted. Also, by comparing the obtained results with experimental data, the correlation performance of virial coefficients to predict thermodynamic properties over a wide temperature range is evaluated. Studied properties consist of Joule–Thomson coefficient, enthalpy, deviation function, fugacity coefficient, thermal expansion, Boyle temperature and Boyle volume. The studied correlation function is the one suggested by Zarkova et al and compared with correlation of Meng et al. The obtained results show that the correlation equation presented has a good ability to predict the thermophysical properties of sulpur hexafluoride and its deviation from the ideal state over a wide range of temperatures. Average absolute deviations (AAD) of thermophysical properties of SF 6 calculated by this approach is mainly below 5 % . [ABSTRACT FROM AUTHOR]

Humidity has been considered as one of the main influencing factors that determine the conduction processes and electric strength of gas-insulated systems. Whereas in the past, various studies focused on the change in the partial discharge inception voltages, breakdown strength of homogeneous and inhomogeneous field arrangements, and insulator flashover voltage, recent studies have investigated the changes in ion currents measured through different gas gaps. In the framework of this contribution, a highly precise humidity control circuit has been developed to analyse the significance of humidity in the range from −25 to −5°C frost-point, which is fully applicable to operating gas-insulated devices. Using sulphur hexafluoride (SF(6)) as the insulation gas at 0.45 MPa, Al(2)O(3)-filled epoxy resin insulators, and technically rough electrodes, the humidity was found to significantly influence the intensity of microdischarges at interfaces. Charge generation from microdischarges at the interfaces substantially increased with increasing humidity. For an electric field of 5 kV/mm that were applicable to the dimensioning of gas-insulated devices, humidity strongly influences the charge provision from technically rough interfaces and potentially contributes to the surface-charge accumulation at insulator surfaces. On the other hand, for low-field conduction phenomena, no increase in the ion currents from natural ionisation or electrophoretic conduction was observed. For the investigated range of parameters, humidity is expected to be highly relevant for the design of gas-insulated devices.

Purpose: To evaluate the effectiveness of recombinant tissue plasminogen activator (rtPA) and sulphur hexafluoride gas (SF6) intravitreal injection for the displacement of large submacular haemorrhages (SMH) secondary to neovascular age-related macular degeneration and for guiding the selection of additional treatments or observations for choroidal neovascularization (CNV). Methods: The medical records of consecutive patients with recent-onset, large SMH, treated at Sacro Cuore Hospital from January 2004 to May 2016, were retrospectively analysed. All eyes underwent a 0.05-mL intravitreal injection of 50 μg rtPA, 0.3 mL of 100% SF6, and then face-down positioning. Afterwards, the eyes received additional treatments for CNV or observation, based on the severity and extent of the underlying pathology. The multimodal imaging features revealed after blood displacement were analysed and then correlated to the treatment selected as a second therapeutic option. Results: A total of 96 eyes met the inclusion criteria and was evaluated in this study. SMH was displaced from the fovea in the majority of the eyes (76%), allowing several diagnostic tools to evaluate the underlying macular features. In 19 cases (19.8%) exhibiting severe macular damage, no additional treatment was applied. In the remaining eyes, subsequent treatments included anti-vascular endothelial growth factor injections (44.8%), photodynamic therapy (n = 2), and submacular surgery (35.4%). Statistically significant correlations were found between the macular findings revealed after blood displacement and the additional treatments or observations selected for the underlying disease. The mean follow-up was 35 months. Improvements in visual acuity were statistically significant up to 3 years. Conclusion: Intravitreal rtPA and gas injection was found to be effective for the displacement of large SMH, allowing postoperative diagnostic testing, and thus guiding the opportunity to apply further treatments. The addition of subsequent individualized treatments may allow long-term visual gain in selected cases. [ABSTRACT FROM AUTHOR]

In recent years, many novel sensing nanomaterials were explored experimentally and theoretically as chemical gas sensors to detect sulphur hexafluoride (SF(6)) decomposed species with rapid response, high sensitivity and selectivity, as well as low cost, in order to estimate and guarantee the operation status of SF(6) insulation devices. However, there has been no systemic review yet to comprehensively understand their sensing mechanism and conclude their sensing application. Such kinds of nanomaterials include traditional carbon-based materials such as carbon nanotube and graphene, metal oxides such as SnO(2), ZnO and TiO(2), transition metal dichalcogenides such as MoS(2) monolayer and MoTe(2) monolayer as well as graphene-like InN monolayer. A systemic review would be significant to give a profound insight into the exploration of nanomaterial-based chemical gas sensors in the field of electrical engineering and to help youth scholars first stepping in this field rapidly master the progress inside. Thus, the authors attempt to complete this review here. They are hopeful that this review could provide some guidance to fulfil such purpose in the near future, and it would be full of perspective to explore more novel nanomaterials as defect indicators in SF(6) insulated devices. Furthermore, it is their hope that this review could broaden the sensing application of admirable nanomaterials in many fields such as environmental monitoring and pollutant scavenging.

Sulphur hexafluoride (SF6) gas owns remarkable properties as insulation medium and current interrupter, which make it being widely used in gas-insulated equipment up to now. However, SF6 gas has a drawback that gives adverse effect to the environment since it is a strong greenhouse gas. As the effort to minimize the SF6 usage, this study was conducted to investigate the AC breakdown behavior of SF6/N2 gas mixtures with 10/90 ratio at low pressure levels (i.e. 0.11 MPa to 0.15 MPa) under non-uniform field (i.e. R0.5-plane and R6-plane electrodes configurations). The results of the study indicate that the breakdown voltage of SF6/N2 gas mixtures in non-uniform field increases linearly with the increase of gas pressure and electrodes gap distance. As a function of gap distance, a higher increasing rate of breakdown voltage values were achieved at lowest pressure of 0.11 MPa compared to other pressure levels. In addition, it is also found that a higher breakdown voltage values was obtained under R6-plane configuration. But, the difference in breakdown voltage values between R0.5-plane and R6-plane configuration is less significant as the gap distance is increased. It is also observed that the field efficiency factor of R6-plane is higher than R0.5-plane which indicates a more uniform field exists between the electrodes. [ABSTRACT FROM AUTHOR]

Highlights • A CO photoacoustic sensor system is developed for SF 6 decomposition analysis. • A 10 W fiber-amplified near-infrared (NIR) diode laser was used as excitation source. • A photoacoustic module was designed to allow a high power laser beam and a large gas flow. • A theoretical model was established to describe the dynamic equilibrium processes of CO activation and deactivation. • Saturation-free ppb-level NIR CO detection was realized with the assistance of the gas flow. Abstract A photoacoustic sensor system for the ppb-level CO detection of sulphur hexafluoride (SF 6) decomposition was developed by use of a 10 W fiber-amplified near-infrared (NIR) diode laser. A photoacoustic detection module with symmetrical construction was designed to allow a high power laser beam and a large gas flow. A theoretical model was developed to describe the dynamic equilibrium processes of CO molecular activation and deactivation in the presence of gas flow. The 10 W optical excitation power effectively compensates the CO weak absorption line strength in the NIR spectral region and realizes a saturation-free CO detection with the assistance of the gas flow, resulting in a ppb-level CO detection sensitivity, which is comparable with the detection sensitivity obtained using a mid-infrared CO sensor. [ABSTRACT FROM AUTHOR]

Sulfur hexafluoride has been widely used in field studies and laboratory experiments to develop a relationship between gas transfer and wind speed. The interpretation of the data from such studies requires the diffusion coefficient of SF6 (D SF6), which has not previously been measured. In this study, D SF6 has been determined in pure water and in 35‰ NaCl over a temperature range of 5–25°C. The measurements were made using a continuous-flow diffusion cell where SF6 flows beneath an agar gel membrane while helium flows above the gel. The experimental data for pure water yielded the following equation: D SF6=0.029 exp (−19.3/RT, where R is the gas constant and T is temperature in kelvins). Measurements of D SF6 in 35‰ NaCl were not significantly different from the pure water values. On the basis of our data, we estimate the Schmidt numbers for seawater over the temperature range 5–25° C to be Sc=3016.1–172.00t+4.4996t 2−0.047965t 3, where t is temperature in degrees Celsius.

Globally, annual production of grape marc (GM), the residue of skins, seeds and stems remaining after making wine, has been estimated to be approximately nine million tonnes. No previous studies have compared effects on milk production and methane emissions when GM from either red or white grapes was fed to dairy cows. This experiment examines the effects of partial replacement of a perennial ryegrass (Lolium perenne L.) based diet with GM from either red or white grapes on yield and composition of milk and methane emissions. Thirty-two Holstein dairy cows in early lactation were offered either a control diet containing 15.0 kg dry matter (DM) of freshly harvested perennial ryegrass and 5.2 kg of a concentrate mix, or a diet similar to the control diet but with 5 kg DM of ryegrass replaced with 5 kg DM of GM from red grapes (RGM), or a diet similar to the RGM diet except the GM was from white grapes (WGM). Individual cow feed intakes, milk yields, and methane emissions were measured. Both diets containing GM decreased milk yields by approximately 10% and methane emissions by 15%. When fed to dairy cows, GM reduces methane emissions but at the cost of decreased milk production.

In ruminants, methane (CH4) is a by-product of digestion and contributes significantly to the greenhouse gas emissions attributed to agriculture. Grazed grass is a relatively cheap and nutritious feed but herbage species and nutritional quality vary between pastures, with management, land type and season all potentially impacting on animal performance and CH4 production. The objective of this study was to evaluate performance and compare CH4 emissions from cattle of dairy and beef origin grazing two grassland ecosystems: lowland improved grassland (LG) and upland semi-natural grassland (UG). Forty-eight spring-born beef cattle (24 Holstein–Friesian steers, 14 Charolais crossbred steers and 10 Charolais crossbred heifers of 407 (s.d. 29), 469 (s.d. 36) and 422 (s.d. 50) kg BW, respectively), were distributed across two balanced groups that grazed the UG and LG sites from 1 June to 29 September at stocking rates (number of animals per hectare) of 1.4 and 6.7, respectively. Methane emissions and feed dry matter (DM) intake were estimated by the SF6 tracer and n-alkane techniques, respectively, and BW was recorded across three experimental periods that reflected the progression of the grazing season. Overall, cattle grazed on UG had significantly lower (P0.05) in CH4 emissions per unit of feed intake when expressed either on a DM basis (20.7 and 21.6 g CH4 per kg DM intake for UG and LG, respectively) or as a percentage of the gross energy intake (6.0% v. 6.5% for UG and LG, respectively). However, cattle grazing UG had significantly (P

The results of investigations of MIG welding of S235JR steel with G4Si1 wire with the addition of gaseous sulphur hexafluoride SF6in the concentration of 1.6–6.4% to argon are presented. The aim of the investigations is to investigate the effect of sulphur hexafluoride SF6 on the parameters of droplet metal transfer and the formation of the welded joint in automatic MIG welding in argon. [ABSTRACT FROM AUTHOR]

The results of investigation of the process of MAG welding S235JR carbon steel with the addition of SF6gaseous sulphur hexafluoride with concentrations from 1.6 to 6.4% carbon dioxide are described. The aim of the investigations was to improve the droplet metal transfer and the formation of the welded joint in MAG CO2welding in carbon dioxide. The addition of the SF6sulphur hexafluoride to the carbon dioxide changes the process of melting of the electrodes, decreases the extent of splashing and shortens the short-circuiting time. The droplet transfer frequency increases by up to 1.6 times, the depth of penetration increases to 66% and the width of the welded joint decreases to 36%. The welding current increases in a wide range of the welding conditions, the arc voltage decreases, together with the amplitude of the deviation of the current and arc voltage [ABSTRACT FROM AUTHOR]

This study was carried out to investigate the effect of supplementation of three selected tanniniferous tropical tree leaves of Ficus benghalensis , Artocarpus heterophyllus and Azadirachta indica on enteric methane emission, rumen fermentation characteristics and protozoal population in 20 native Indian adult male sheep ( Mandya ). The experiment was conducted in randomized block design with four treatments of five animals each. The sheep in control group (CON) were fed on complete feed block (CFB) comprising finger millet straw and concentrate in the ratio of 60:40 (DM basis) without any inclusion of tropical tree leaves. Sheep in three test groups i.e. FIC, ART and AZA were also fed complete feed block prepared from finger millet straw and concentrate in the same ratio (60:40) as control, but wheat bran in concentrate mixture of test groups was partially replaced (10 parts w/w) with selected tanniniferous tropical tree leaves of Ficus benghalensis , Artocarpus heterophyllus and Azadirachta indica, respectively. The condensed tannin intake in sheep between 7.15 and 10.8 g/kg dry matter intake via selected tanniniferous tropical tree leaves did not influence dry matter and digestibility. About 20–26% reduction (p<0.05) in enteric methane emission is achievable simply through the supplementation of selected tree leaves in straw based diet. The reduction in protozoal numbers (p<0.05) due to selected tropical leaves supplementation appeared as primary cause for the reduction in enteric methane emission. The study confirmed that entodinimorphs protozoa are more vulnerable to the condensed tannin supplementation. The study established that significant reduction in methane emission is feasible without affecting feed fermentation characteristics. However, studies in large productive (growing, lactating) ruminants are warranted in order to explore the persistency of ameliorative effect in long term and improvement in productive performance thereof. [ABSTRACT FROM AUTHOR]

The parameters of runaway electrons produced in nanosecond high-voltage discharges in different gases (air, nitrogen, sulphur hexafluoride, krypton, argon, methane, neon, hydrogen, helium) at atmospheric and higher pressure were studied. An optical analysis was also performed to investigate the ionisation dynamics in diffuse discharges in nitrogen and nitrogen-containing mixtures. At breakdown of a point-to-plane gap by nanosecond (≃2 ns) high-voltage (≃200 kV) pulses of negative voltage polarity and gas pressure above 0.1 MPa, a supershort avalanche electron beam (SAEB) was detected by a collector behind the flat anode. For pressure >0.1 MPa of nitrogen and other gases it is shown that the maximum pressure for SAEB registration decreases with increasing the voltage pulse rise time. Therefore, to detect a SAEB at atmospheric and higher gas pressure, one should use voltage pulses with an amplitude of hundred kilovolts and rise time of ∼1 ns and shorter. The experimental research in the dynamics of optical radiation from the discharge plasma shows that the breakdown in which runaway electrons are produced develops as an ionisation wave.