Minimum Oxygen Concentration Research Articles

New Experimental Approaches for the Determination of Flammability Limits in Methane–Hydrogen Mixtures with CO2 Inertization Using the Spark Test Apparatus

This study presents a novel experimental method to determine the flammability limits and the minimum oxygen concentration in methane–hydrogen mixtures using the spark test apparatus (STA), by incorporating CO2 as an inert compound. The proposed methodology allows for the more accurate and efficient assessment of the safety of these flammable mixtures, which is crucial for industrial applications where hydrogen-enriched fuels are used. When comparing the literature data, the differences between methods are not significant, although the procedure, apparatus, and test conditions influence the results. Then, the proposed method is experimentally validated in the STA. Methane is enriched with hydrogen at different concentrations (10, 20, 30, and 50%). The results in the STA show good alignment with the literature data. Furthermore, literature data analysis allows for the generation of an empirical curve that shows the influence of hydrogen addition in methane–air mixtures. The theoretical flammability intervals are also presented as a result. Such representations, after method validation, are the base of the flammability interval test in the STA. The capability of the STA to define flammability ranges in ternary diagrams provides an innovative graphical approach to control explosive atmospheres and facilitates its application in the prevention of industrial accidents.

Combining the probabilistic finite element model and artificial neural network to study nutrient levels in the human intervertebral discs

BackgroundDiffusion distance and diffusivity are known to affect nutrient transport rates, but the probabilistic analysis of these two factors remains vacant. There is a lack of effective tools to evaluate disc nutrient levels. MethodsFive-hundred-disc samples with different combinations of morphological and water content parameters were generated, which were used to evaluate nutrient levels in unloaded and loaded states. Spearman correlation coefficients between inputs and responses were calculated. Artificial neural networks were trained to predict nutrient concentrations based on the dataset generated by the probabilistic finite element model. FindingsIn unloaded and loaded states, the minimum oxygen concentration of nucleus pulposus was negatively correlated with disc height (r = −0.83, p < 0.01 and r = −0.76, p < 0.01, respectively), and the minimum glucose concentration of annulus fibrosus was positively correlated with its water content (r = 0.68, p < 0.01 and r = 0.73, p < 0.01, respectively). The maximum lactate concentration of cartilage endplate was affected by endplate thickness (r = 0.94, p < 0.01 and r = 0.95, p < 0.01, respectively). For trained neural networks, nutrient concentrations could be well predicted, with coefficients of determination greater than 0.95 and mean absolute percentage errors less than 5 %. InterpretationThis study underscores the importance of disc height, annulus fibrosus water content, and endplate thickness in regulating nutrient levels, and precise control of these parameters should be prioritized in the design of tissue-engineered discs. Moreover, artificial neural networks might be a promising tool for evaluating nutrient levels.

Prevalence and impact of sleep-related breathing disorder in multiple system atrophy patients: a cross-sectional study and meta-analysis.

Sleep-related breathing disorder (SRBD) is a prevalent non-motor symptom in multiple system atrophy (MSA). However, the reported prevalence of SRBD in MSA from different studies has shown inconsistency. Additionally, only one study has examined the impact of SRBD on both motor and non-motor symptoms in MSA. Cross-sectional study of 66 patients with probable MSA from China. SRBD was ascertained with polysomnography (PSG). All the MSA individuals were assessed using the Epworth Sleepiness Scale (ESS), Unified Multiple-System Atrophy Rating Scale (UMSARS), Hamilton Depression Scale (HAMD), Hamilton Anxiety Scale (HAMA), the Mini-mental State Examination (MMSE), Non-Motor Symptoms Scale (NMSS), and Pittsburgh Sleep Quality Index (PSQI). Moreover, a meta-analysis was conducted by searching studies related to MSA and SRBD in PubMed, Web of Science, Embase, and Cochrane databases. Data were pooled as necessary to calculate prevalence of SBRD with 95% confidence intervals (CI). Our study included 66 patients with MSA, 52 of whom had a diagnosis of SRBD (78.8%). There were no significant differences between the MSA with SRBD and without SRBD groups on the age, sex, disease onset, disease duration, UMSARS I, II, and IV, the NMSS, the HAMA, HAMD, the ESS the FSS, the MMSE, and the PSQI scales. However, MSA patients with SRBD having a significant higher obstructive apnea index and percentage of snoring during sleep than MSA patients without SRBD [10.0 (4.1-10.6) vs. 0.1 (0-0.3), and 8.3 (5.1-12.2) vs. 4.2 (0-7.5)]. Also, between the two groups, the mean and minimum oxygen concentrations during sleep were lower in MSA patients with SRBD than in those without SRBD [93.7 (93-95) vs. 95.5 (95.8-97), p = 0.001] and [83.9 (81.2-89.0) vs. 90.3 (89.8-93.3), p = 0.000]. The primary search strategy identified 701 articles, with 10 meeting the inclusion criteria. The overall prevalence of SRBD in a combined sample of 295 MSA patients was found to be 60.5% (95% CI, 43.2-76.5%). Further analysis revealed that the prevalence of SRBD in MSA patients in Asia was 79.2% (95% CI, 54.7-96.3%), which was higher than that in Europe (41.6, 95% CI, 32-51.5%). The study found a prevalence of 78.8% of SRBD in MSA patients, with a notably higher prevalence in Asia compared to Europe. The majority of SRBD cases in MSA were attributed to obstructive apnea. Furthermore, the presence of SRBD did not show a significant impact on the motor and non-motor symptoms of MSA patients.

Establishing mainstream partial nitrification in the membrane aerated biofilm reactor by limiting the oxygen concentration in the biofilm

The proliferation of nitrite oxidizing bacteria (NOB) still remains as a major challenge for nitrogen removal in mainstream wastewater treatment process based on partial nitrification (PN). This study investigated different operational conditions to establish mainstream PN for the fast start-up of membrane aerated biofilm reactor (MABR) systems. Different oxygen controlling strategies were adopted by employing different influent NH4+-N loads and oxygen supply strategies to inhibit NOB. We indicated the essential for NOB suppression was to reduce the oxygen concentration of the inner biofilm and the thickness of aerobic biofilm. A higher NH4+-N load (7.4 g-N/(m2·d)) induced higher oxygen utilization rate (14.4 g-O2/(m2·d)) and steeper gradient of oxygen concentration, which reduced the thickness of aerobic biofilm. Employing closed-end oxygen supply mode exhibited the minimum concentration of oxygen to realize PN, which was over 46% reduction of the normal open-end oxygen mode. Under the conditions of high NH4+-N load and closed-end oxygen supply mode, the microbial community exhibited a comparative advantage of ammonium oxidizing bacteria over NOB in the aerobic biofilm, with a relative abundance of Nitrosomonas of 30–40% and no detection of Nitrospira. The optimal fast start-up strategy was proposed with open-end aeration mode in the first 10 days and closed-end mode subsequently under high NH4+-N load. The results revealed the mechanism of NOB inhibition on the biofilm and provided strategies for a quick start-up and stable mainstream PN simultaneously, which poses great significance for the future application of MABR.

Evaluating the clinical and cost-effectiveness of a conservative approach to oxygen therapy for invasively ventilated adults in intensive care: Protocol for the UK-ROX trial.

In the United Kingdom, around 184,000 adults are admitted to an intensive care unit (ICU) each year with over 30% receiving mechanical ventilation. Oxygen is the commonest therapeutic intervention provided to these patients but it is unclear how much oxygen should be administered for the best clinical outcomes. The UK-ROX trial will evaluate the clinical and cost-effectiveness of conservative oxygen therapy (the minimum oxygen concentration required to maintain an oxygen saturation of 90% ± 2%) versus usual oxygen therapy in critically ill adults receiving supplemental oxygen when invasively mechanically ventilated in ICUs in England, Wales and Northern Ireland. The trial will recruit 16,500 patients from approximately 100 UK adult ICUs. Using a deferred consent model, enrolled participants will be randomly allocated (1:1) to conservative or usual oxygen therapy until ICU discharge or 90 days after randomisation. The primary clinical outcome is all cause mortality at 90 days following randomisation. The UK-ROX trial has received ethical approval from the South Central - Oxford C Research Ethics Committee (Reference: 20/SC/0423) and the Confidentiality Advisory Group (Reference: 22/CAG/0154). The trial commenced in May 2021 and, at the time of publication, 95 sites had opened to recruitment.

Detailed kinetic analysis of synthetic fuels containing ammonia

The imperative to adopt environmentally sustainable energy sources has propelled the exploration of zero-carbon alternatives, such as hydrogen and ammonia for energy supply. Integrating these species with methane is recognized as a viable short-term solution. However, a complete understanding of their chemical behaviour in a wide range of conditions remains elusive, especially in terms of safety parameters, limiting the applicability of this solution. To this aim, this work presents a detailed analysis of the overall reactivity, expressed either in terms of laminar burning velocity or flammability limits, of hydrogen-ammonia-containing fuels. Additional considerations were obtained by the analysis of the maximum pressure rise and maximum pressure obtained in adiabatic conditions. A spectrum of nitrogen/oxygen mixtures was scrutinized, and the influence of initial temperature within the range of 300–500 K was systematically investigated. The estimation quality of the adopted mechanism was evaluated by comparing numerical predictions with experimental measurements obtained by different systems, when available. A tendency in slightly more conservative results on the safe side was detected for the assessment of flammability limits and minimum oxygen concentration. This trend was attributed to the assumption of perfectly adiabatic conditions posed for the numerical analysis, which does not perfectly match the experimental conditions. Conversely, an excellent agreement between numerical and experimental laminar burning velocity was observed. Therefore, the collected data were used for the quantification of input parameters required by well-established correlations suitable for synthetic fuels.

Optimization of a Marker Gas for Analyzing and Predicting the Spontaneous Combustion Period of Coking Coal

The adequate assessment of the spontaneous combustion and oxidation characteristics of coking coal can help to reduce its spontaneous combustion potential. In this study, the natural ignition period of the Hex coking coal seam at Ping Coal was calculated based on the programmed-temperature-rise test and the thermal property parameters measured during the spontaneous combustion of the coal. Typical gas concentrations were measured at different oxygen concentrations and coal particle sizes to investigate the changes in the oxygen, carbon–oxygen, and hydrocarbon gas concentrations during the low-temperature oxidation of the coking coal and to determine the indicator gases at different oxidation stages. The following results were obtained: The minimum critical oxygen concentration required for spontaneous ignition was 8%, and fire prevention measures should be implemented below 200 °C. When the temperature of the coal sample reaches 50–60 °C, the rates of CO and CO2 production increase, and when the temperature of the coal sample reaches 100–120 °C, the spontaneous combustion and oxidation of the coal generates alkane gas, in which the coal particle size has a negligible effect on the concentration of each generated gas. CO and C2H4 were selected as the indicator gases for different coking coal oxidation stages, and C2H6 and the C2H4/C2H6 ratio were used as secondary indicators to assist in the analysis. Utilizing the enhanced mathematical model for the shortest spontaneous combustion period of coal seams, in conjunction with a programmed-temperature test device, experimental calculations were conducted to determine the adiabatic spontaneous combustion period. The results indicate that the natural ignition period for the Hex coking coal seam at Ping Coal is approximately 60 days, representing a brief timeframe, and the coal seam is characterized by a high risk of spontaneous combustion.

Influence of growth temperature on the properties of aluminum nitride thin films prepared by magnetron sputter epitaxy

High quality, uni-polar, epitaxial AlN with minimum oxygen content promises excellent surface acoustic wave and bulk acoustic wave resonator characteristics such as high electromechanical coupling coefficient and power handling capabilities, which is particularly useful for RF filter applications. By systematically varying the growth temperature, the study investigates its impact on the oxygen levels, defect states, and crystallographic texture of the AlN thin films using a combination of atomic force microscopy, X-ray diffraction, time-of-flight secondary ion mass spectrometry, spectroscopic ellipsometry, scanning transmission electron microscopy, as well as room temperature and temperature dependent I–V measurements. The research demonstrates that the films grown at a temperature of 700°C exhibit the most favorable results. These films exhibit the lowest oxygen levels, possess epitaxial growth, and display the highest crystalline quality (XRD AlN 0002 ω−FWHM=1.3°). Additionally, these films demonstrate a significant reduction in sub-bandgap absorption. By comparing the cathode current measured during deposition, we suggest that the presence of an impurity layer formed during idle time between depositions as a possible source of oxygen in the sputter chamber. In addition, the study presents a possible model to explain the mixed polarity observed in AlN and proposes various ways to achieve uni-polar AlN on silicon substrates.

Comparative Study on Macroscopic Parameters of Coal Spontaneous Combustion Under Different Test Methods

ABSTRACT The quantitative characterization and the accurate determination of the degree of danger of coal spontaneous combustion (CSC) characteristics are the hotspots and difficulties in the field of coal mine safety. This study compares the test results obtained from the Large-scale CSC experiment and the Kilogram-level CSC experiment and preliminarily determines the main macroscopic characterization parameters of CSC in Huangling No.2 well (including characteristic temperature, spontaneous combustion period, oxygen consumption rate and heat release intensity). At the same time, the various rules of the limit parameters of CSC (including the minimum float coal thickness, the minimum oxygen concentration and the maximum air leakage intensity) of the two experimental results are compared and analyzed. The results show that compared with the Large-scale CSC experiment, the Kilogram-level CSC experiment has the characteristics of rapid and accurate determination of macroscopic characterization parameters of CSC. Therefore, it can be used for the test, the accurate determination of characterization parameters and the determination of the tendency of the CSC process. It is of great significance to the prediction and the risk of CSC.

An investigation of the reaction of metallic uranium with oxygen/nitrogen gas mixtures

The effects of variations in oxygen content as a mixed oxygen/nitrogen gas on the exothermic reaction of uranium were investigated in this work. Samples of metallic uranium with various specific surface areas and masses were reacted in a thermogravimetric analysis system at temperatures ranging between 323 K and 1273 K using gas mixtures 10%, 5%, 1%, or 0.5% oxygen in nitrogen. From the results it was concluded that the minimum oxygen content necessary for the onset of ignition is correlated to the specific surface area of the metallic uranium. The higher the specific surface area, the lower the percentage of oxygen is needed to trigger an ignition event. Within the experimental parameters evaluated here, ignition does not appear to occur for any specific surface area investigated below 1% oxygen content.

Synthesis of Titanium Hydride Powder Via Magnesiothermic Reduction of TiCl4 in H2 gas Atmosphere

A novel method for the synthesis of titanium hydride powder from titanium tetrachloride via the magnesiothermic reduction in an hydrogen gas atmosphere was investigated. To examine the influence of temperature on the formation of titanium hydride, the reduction was conducted at 1023~1123 K under 1 atm of hydrogen gas atmosphere for approximately 30 min. Subsequently, the titanium hydride powder was sintered by maintaining the temperature for 0~120 min, and the decrease in the oxygen concentration of the powder was investigated. The experimental results showed that TiH1.924 was produced at 1023 K, whereas mixtures of TiH1.924 and TiH1.5 were produced at 1073 K and 1123 K. In addition, the hydrogen concentration in the powder decreased with increasing temperature. The concentration of oxygen in the powder decreased with increasing temperature and sintering time owing to the decrease in the specific surface area of the powder. The minimum concentration of oxygen was 0.246 mass% when the mixture of TiH1.924 and TiH1.5 was obtained at 1073 K and a sintering time of 120 min.

Sources and sinks of bottom water oxygen in a seasonally hypoxic fjord

Deoxygenation of the ocean has been occurring over the last half century, particularly in poorly ventilated coastal waters. In coastal and estuarine environments, both the water column and sediments play key roles in controlling oxygen variability. In this study, we focus on controls of oxygen concentration in Bedford Basin (BB), a 70 m deep, seasonally hypoxic semi-enclosed fjord on the West Atlantic coast in Nova Scotia. The basin is connected to the Scotian Shelf via a narrow 20 m deep sill that restricts the resupply of bottom water. Hypoxia was recorded seasonally in 2018, 2019 and 2021 with minimum oxygen concentration of 5, 6.7 and 2.7 μM, respectively. Using a 1-D benthic-pelagic coupled model we investigate oxygen consumption and resupply processes during these years. The model was constrained with weekly water column measurements of temperature, salinity, chlorophyll-a fluorescence and dissolved oxygen from a monitoring station in the central basin together with seasonal measurements of benthic diffusive oxygen uptake. Our model suggested that 29-81%, and up to 36% of bottom water re-oxygenation occurred during the winter mixing period and through summer/fall intrusions of Scotian Shelf water, respectively. Occasional shelf water intrusions occurred rapidly, on a timescale of a few hours, and delivered equivalent amounts of oxygen as winter mixing and were sufficient to end bottom water hypoxia. Collectively, these mechanisms supplied the majority of the oxygen delivered to the bottom water. Oxygen supply to bottom waters during periods of water column stratification accounted for 19-36% of the annual flux. The mean benthic uptake was 12 ± 8 mmol m-2 d-1 and contributed ~20% of the total oxygen consumption below the sill depth. In 2021, sea surface temperature (SST) was unusually high and likely resulted in 50% less bottom water oxygenation compared to 2018 and 2019 due to increased stratification; SST in BB was found to be increasing at a rate of 0.11 ± 0.02 °C/year. Climate control on water column stratification are discussed and numerical experiments are used to compare the effects of different water column mixing scenarios on bottom water oxygenation.

Experimental Investigation of the Characteristics and Transformation Mechanism of Jimsar Oil Shale and Derived Shale Oil

An experimental investigation of the characteristics and transformation mechanism of Jimsar oil shale and derived shale oil was conducted using a solid-state nuclear magnetic resonance spectrometer (13C NMR), Fourier transform infrared spectroscopy (FT-IR), liquid 1H NMR, and gas chromatography-mass spectrometry (GC-MS) techniques. The carbon skeleton structure of Jimsar oil shale is mainly composed of aliphatic carbons (70.5%), mostly containing straight-chain methylene (CH2), and aromatic carbon (29.31%). Derived shale oil is primarily made of aliphatic compounds that are dominated by n-alkanes and alkenes (comprising more than 70%). The nature of the conversion of oil shale to shale oil is the decomposition of aliphatic groups dominated by methylene structures in organic matter. Additionally, as the heating rate is increased, the secondary cracking reactions in shale oil could increase the contents of short-chain alkanes and alkenes, which could then enhance the secondary polymerization reactions that increase the generation of cycloalkanes and aromatic compounds. Shale oil demonstrates a maximum yield value of 6.32%, the largest carbon, hydrogen, and nitrogen contents, and a minimum oxygen content at the pyrolysis heating rate of 5 °C/min.

Экологическая валентность северокаспийских моллюсков к кислороду

North Caspian molluscs are characterized by high frequency of occurrence and wide variability of quantitative indicators. In studies conducted in the period from 2013 to 2017 in the water area of the western part of the Northern Caspian the frequency of molluscs was 64%. The population was in the range of 10-8290 species/m2; biomass – 0.003-1162.066 g/m2. Molluscs lived at depths of 2.5-29.0 m, with an absolute oxygen content of 1.29-8.52 ml/l, and a relative oxygen content of 21-134%. Most abundant was Abra ovata (29%). Mytilaster lineatus occured with frequency 24%. According to the results of the research, there were determined the limits of tolerance to the oxygen content for all molluscs living in the Northern Caspian, as well as the optimum zone for the most frequent representatives of malacofauna. The minimum oxygen concentration registered in the bottom water of the western part of the Northern Caspian during the study period (1.29 ml/l) is not critical for species Mytilaster lineatus, Hypanis angusticostata and Didacna barbotdemarnyi. Oxygen concentration of less than 3 ml/l is resistant to species Cerastoderma lamarcki and Abra ovata, less than 4 ml/l – to Hypanis vitrea. Other species including those encountered in rare cases are found at concentrations above 4.06 ml/l. The oxyphilous species are Hypanis semipellucida and Didacna pyramidata. Mytilaster lineatus, Didacna barbotdemarnyi and Cerastoderma lamarcki have a wide environmental valence to oxygen. The absolute oxygen content within the range 5.78-9.08 ml/l is considered the most favorable for the of molluscs development, where all species of molluscs can be found. Most species demonstrated a quantitative increase with oxygen concentrations rising from 4 to 6 ml/l.

Hydrotreatment of Supercritical Carbon Dioxide Extracts of Hydrothermal Liquefaction Lignocellulosic Biocrude

Raw lignocellulosic biocrude produced by hydrothermal liquefaction and its supercritical carbon dioxide extract (SE) were hydrotreated at 350–405 °C and for 2–6 h utilizing commercial CoMo and NiMo catalysts. The hydrotreatment reduced the oxygen content of the SE down to 1.6 wt %, while the minimum oxygen content of the hydrotreated biocrude (HBC) was 3.1 wt %. No coke formation was observed in the hydrotreatment of the SE, while the yield of coke was 13 wt % when processing the raw biocrude. The hydrotreated SE (HSE) samples exhibited molecular weights 24–61% lower than that of the HBC samples, with larger low-boiling fractions (up to diesel). The better quality of the HSE and the absence of coke, together with the lower metal content of SE (0.2 g/kg) versus BC (8.5 g/kg), suggest that the implementation of hydrotreatment on SEs, instead of raw lignocellulosic biocrude, is a promising option.

Flame Retardant Nano-Structured Fillers from Huntite/Hydromagnesite Minerals.

In the current study, we propose a simple hydrothermal pathway to synthesize nano-structured Mg(OH)2 after application of thermal decomposition followed by hydration of commercial minerals based on hydromagnesite and huntite. The synthesis of nano-materials is performed without the use of any catalyst. The effect of decomposition temperature on the hydrothermal synthesis of Mg(OH)2 is extensively studied. It is shown that the morphology of resulting structures consists typically of particles ~200 nm in diameter and ~10 nm in thickness. Study of the structure at the molecular level designates the composition and supports the nano-sized characteristics of the produced materials. The associated thermal properties combined with the corresponding optical properties suggest that the material may be used as a flame retardant filler with enhanced transparency. In this concept, the flame retardancy of composite coatings containing the produced nano-sized Mg(OH)2 was examined in terms of limiting oxygen index (LOI), i.e., the minimum concentration of oxygen that just supports flaming combustion.

Improving oxygen conditions in periodically stagnant basins using sea-based measures - Illustrated by hypothetical applications to the By Fjord, Sweden

To improve the water quality of a habitat or to stop eutrophication driven by internal loading of phosphorus from anoxic bottoms, the deepwater in inshore and offshore sea basins may be oxygenated using sea-based measures. The minimum oxygen concentration DOmin in periodically stagnant basins is controlled by three factors, namely (i) the rate of oxygen depletion dDO/dt. (ii) The residence time Te of the stagnant water. (iii) The oxygen concentration DOstart in the basin water at the beginning of a stagnation period. A theoretical framework is presented, suitable for evaluation of sea-based measures to improve the oxygen conditions in periodically stagnant basins. Five different sea-based measures to improve the oxygen conditions are recognized and discussed. The application of sea-based measures might be particularly attractive for habitat improvements in basins with poor oxygen conditions despite land-based measures are fully implemented. The sea-based measures are illustrated by hypothetical applications to the By Fjord on the west coast of Sweden, a salt-stratified fjord with periodically stagnant anoxic basin water confined behind the shallow Sunninge Strait in the mouth. An interesting result of one of the hypothetical applications is that dredging of the Sunninge Strait in 1958 and 1976 reduced tidal currents by a factor of 4. This reduced the tidal power supply to vertical mixing in the basin water, which led to prolonged residence time Te, from 2-3 years to 3–5 years, and deteriorated oxygen conditions in the basin water.

Eye-specific 3D modeling of factors influencing oxygen concentration in the lamina cribrosa

Our goal was to identify the factors with the strongest influence on the minimum lamina cribrosa (LC) oxygen concentration as potentially indicative of conditions increasing hypoxia risk. Because direct measurement of LC hemodynamics and oxygenation is not yet possible, we developed 3D eye-specific LC vasculature models. The vasculature of a normal monkey eye was perfusion-labeled post-mortem. Serial cryosections through the optic nerve head were imaged using fluorescence and polarized light microscopy to visualize the vasculature and collagen, respectively. The vasculature within a 450 μm-thick region containing the LC – identified from the collagen, was segmented, skeletonized, and meshed for simulations. Using Monte Carlo sampling, 200 vascular network models were generated with varying vessel diameter, neural tissue oxygen consumption rate, inflow hematocrit, and blood pressures (arteriole, venule, anterior boundary, and posterior boundary). Factors were varied over ranges of baseline ±20% with uniform probability. For each model we first obtained the blood flow, and from this the neural tissue oxygen concentration. ANOVA was used to identify the factors with the strongest influence on the minimum (10th percentile) oxygen concentration in the LC. The three most influential factors were, in ranked order, vessel diameter, neural tissue oxygen consumption rate, and arteriole pressure. There was a strong interaction between vessel diameter and arteriole pressure whereby the impact of one factor was larger when the other factor was small. Our results show that, for the eye analyzed, conditions that reduce vessel diameter, such as vessel compression due to elevated intraocular pressure or gaze-induced tissue deformation, may particularly contribute to decreased LC oxygen concentration. More eyes must be analyzed before generalizing.

Experimental study on propagation characteristics of rotating detonation wave with kerosene fuel-rich gas

In this study, kerosene fuel-rich gas produced by the combustion in the gas generator was used as the fuel and oxygen-rich air was used as the oxidant to investigate the propagation characteristics of the rotating detonation wave (RDW). The initiation of the kerosene fuel-rich gas and propagation process of the RDW were analyzed. The influences of the oxygen content in the oxidizer, kerosene mass flow rate of the gas generator, and temperature of the kerosene fuel-rich gas on the propagation process of the RDW were studied. The experimental results revealed that the propagation velocity of the RDW could be improved by increasing the three parameters mentioned above with the kerosene mass flow rate as the strongest factor. The minimum oxygen content that could successfully initiate and maintain the stable propagation of the RDW was 32%, achieving the RDW velocity of 1141.9 m/s. The RDW mainly propagated as two-counter rotating waves and a single wave when the equivalent ratios were 0.62–0.79 and 0.85–0.87, respectively. The highest RDW velocity of 1637.2 m/s was obtained when the kerosene mass flow rate, oxygen content, and equivalent ratio were 74.6 g/s, 44%, and 0.87, respectively.

Material evaluation for engineering a novel crucible setup for the growth of oxygen free Czochralski silicon crystals

For manufacturing of several high performance electronic devices, e.g. insulated-gate bipolar transistors (IGBT), single crystalline silicon crystals with high purity and minimum oxygen (in the range of 1015 at/cm3) concentration are required. Such silicon crystals are typically grown by the Floating Zone technique (Fz), as the more common and cheaper Czochralski technique (Cz) uses silica crucible, which leads always to a relatively high oxygen concentration in the silicon crystals (>1017 at/cm−3). Therefore, in this work potential materials were evaluated with respect to the development of a novel oxygen-free crucible system, which should enable a cost effective growth of oxygen free Cz silicon ingots. For that purpose different graphite materials as well as nitride bonded silicon nitride (NSN) were tested in contact with liquid silicon due to their infiltration behaviour and occurrence of crack formation. Functional silicon nitride (Si3N4) coatings were applied by powder based spray coating of reaction bonded silicon nitride (RBSN) and chemical vapour deposition (CVD) on graphite and NSN crucibles. Characterization of the crucible/coating systems before and after crystal growth experiments in a lab-scale casting furnace reveal information about morphology, infiltration behaviour and adhesion strength on the crucible. Further, investigations on the grown silicon crystals give information about impurity incorporation coming from the novel crucible systems. The results indicated, that especially graphite materials with low porosity and a high mechanical strength as well as NSN with polysilazane sealing in combination with a CVD Si3N4 coating have definitely a potential for application as crucible system in silicon growth processes.