High Oxygen Levels Research Articles

Exposure to hyperbaric O2 levels leads to blood-brain barrier breakdown in rodents

IntroductionHyperbaric oxygen has been used as a medical treatment tool in hyperbaric chambers and is an integral part of professional and combat divers’ activity. In extreme cases, exposure to hyperbaric oxygen can develop central nervous system oxygen toxicity (CNS-OT), which leads to seizures and eventually death. CNS-OT is caused by neuronal hyperactivity due to high oxygen levels, potentially damaging brain cells including the blood-brain barrier (BBB). However, the effect of hyperbaric oxygen levels on the healthy BBB has not been characterized directly yet.MethodsSix or three different groups of ~ eight rats or mice, respectively, were exposed to increasing levels of partial pressure of oxygen (0.21 to 5 ATA) in a hyperbaric chamber, followed by MRI scanning with gadolinium. Statistical significance (adjusted p-value ≤ 0.05) was assessed using linear regression and ordinary one-way (rats) or two-way (mice) ANOVA with correction of multiple comparison tests. In rats, the effect of 100% oxygen at 5 ATA was independently validated using FITC-Dextran (5 kDa). Statistical significance (p-value ≤ 0.05) was assessed using Welch’s t-test and effect size was calculated by Cohen’s D.ResultsIn rats, analyzed MRI scans showed a significant trend of increase in the % gadolinium in brain tissues as a result of hyperbaric oxygen pressures (p-value = 0.0079). The most significant increase was measured at 4 ATA compared to air (adjusted p-value = 0.0461). Significant increased FITC-Dextran levels were measured in the rats’ brains under 100% oxygen at 5 ATA versus air (p-value = 0.0327; Effect size = 2.0). In mice, a significant increase in gadolinium penetration into the hippocampus and frontal cortex was measured over time (adjusted p-value < 0.05) under 100% oxygen at 3 and 5 ATA versus air, and between the treatments (adjusted p-value < 0.0001).ConclusionsThe BBB is increasingly disrupted due to higher levels of hyperbaric oxygen in rodents, indicating a direct relation between hyperbaric oxygen and BBB dysregulation for the first time. We suggest considering this risk in different diving activities, and protocols using a hyperbaric chamber. On the other hand, this study highlights the potential therapeutic usage of hyperbaric oxygen for controlled drug delivery through the BBB into brain tissues in different brain-related diseases.

Considerations for implanting speech brain computer interfaces based on functional magnetic resonance imaging

Objective. Brain-computer interfaces (BCIs) have the potential to reinstate lost communication faculties. Results from speech decoding studies indicate that a usable speech BCI based on activity in the sensorimotor cortex (SMC) can be achieved using subdurally implanted electrodes. However, the optimal characteristics for a successful speech implant are largely unknown. We address this topic in a high field blood oxygenation level dependent functional magnetic resonance imaging (fMRI) study, by assessing the decodability of spoken words as a function of hemisphere, gyrus, sulcal depth, and position along the ventral/dorsal-axis. Approach. Twelve subjects conducted a 7T fMRI experiment in which they pronounced 6 different pseudo-words over 6 runs. We divided the SMC by hemisphere, gyrus, sulcal depth, and position along the ventral/dorsal axis. Classification was performed on in these SMC areas using multiclass support vector machine (SVM). Main results. Significant classification was possible from the SMC, but no preference for the left or right hemisphere, nor for the precentral or postcentral gyrus for optimal word classification was detected. Classification while using information from the cortical surface was slightly better than when using information from deep in the central sulcus and was highest within the ventral 50% of SMC. Confusion matrices where highly similar across the entire SMC. An SVM-searchlight analysis revealed significant classification in the superior temporal gyrus and left planum temporale in addition to the SMC. Significance. The current results support a unilateral implant using surface electrodes, covering the ventral 50% of the SMC. The added value of depth electrodes is unclear. We did not observe evidence for variations in the qualitative nature of information across SMC. The current results need to be confirmed in paralyzed patients performing attempted speech.

HUBUNGAN JENIS PENGOBATAN ANTI TUBERKULOSIS TERHADAP KEPATUHAN MINUM OBAT ANTI TUBERKULOSIS

Pulmonary TB germs can infect various parts of the body and prefer parts of the body with high oxygen levels. The lungs are the main predilection site for pulmonary tuberculosis (TB) germs. Tuberculosis is an infectious disease caused by the bacteria Mycobacterium tuberculosis. Pulmonary Tuberculosis (Pulmonary TB) is an infectious disease caused by Mycobacterium Tuberculosis. The number of TB cases every year always increases with new cases and the success rate of treatment is still insufficient. Based on data from the World Health Organization (2018), there are 6.4 million people in the world infected with TB germs. In Indonesia, the number of TB cases is estimated to be 842,000 new TB cases per year (319 per 100,000 population) with 107,000 deaths per year (40 per 100,000 population). One factor that can be related to non-compliance with TB drug consumption is the type of TB treatment. The aim of the study was to identify the relationship between the type of anti-tuberculosis treatment and adherence to taking anti-tuberculosis medication. This research is a quantitative research study with a cross sectional approach. This research was carried out at the Deli Tua Community Health Center. The population of this study were pulmonary TB patients who were registered and receiving treatment at the Deli Tua Community Health Center, with a total of 68 respondents. The research results showed that there was no relationship between the type of treatment and compliance with taking anti-tuberculosis medication with a p value of 0.921. TB sufferers need to increase awareness of compliance with taking anti-tuberculosis medication.

Protective Effects of Resveratrol Against Airway Hyperreactivity, Oxidative Stress, and Lung Inflammation in a Rat Pup Model of Bronchopulmonary Dysplasia

Oxygen therapy provides an important treatment for preterm and low-birth-weight neonates, however, it has been shown that prolonged exposure to high levels of oxygen (hyperoxia) is one of the factors contributing to the development of bronchopulmonary dysplasia (BPD) by inducing lung injury and airway hyperreactivity. There is no effective therapy against the adverse effects of hyperoxia. Therefore, this study was undertaken to test the hypothesis that natural phytoalexin resveratrol will overcome hyperoxia-induced airway hyperreactivity, oxidative stress, and lung inflammation. Newborn rats were exposed to hyperoxia (fraction of inspired oxygen - FiO2&gt;95 % O2) or ambient air (AA) for seven days. Resveratrol was supplemented either in vivo (30 mg·kg-1·day-1) by intraperitoneal administration or in vitro to the tracheal preparations in an organ bath (100 μM). Contractile and relaxant responses were studied in tracheal smooth muscle (TSM) using the in vitro organ bath system. To explain the involvement of nitric oxide in the mechanisms of the protective effect of resveratrol against hyperoxia, a nitric oxide synthase inhibitor – Nω-nitro-L-arginine methyl ester (L-NAME), was administered in some sets of experiments. The superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities and the tumor necrosis factor-alpha (TNF-α) and interleukin-1β (IL-1β) levels in the lungs were determined. Resveratrol significantly reduced contraction and restored the impaired relaxation of hyperoxia-exposed TSM (p&lt;0.001). L-NAME reduced the inhibitory effect of resveratrol on TSM contractility, as well as its promotion relaxant effect (p&lt;0.01). Resveratrol preserved the SOD and GPx activities and decreased the expression of TNF-α and IL-1β in hyperoxic animals. The findings of this study demonstrate the protective effect of resveratrol against hyperoxia-induced airway hyperreactivity and lung damage and suggest that resveratrol might serve as a therapy to prevent the adverse effects of neonatal hyperoxia. Keywords: Bronchopulmonary dysplasia • Hyperoxia • Airway hyperreactivity • Resveratrol • Pro-inflammatory cytokines

Oxidative Metabolism in Brain Ischemia and Preconditioning: Two Sides of the Same Coin.

Brain ischemia is one of the major causes of chronic disability and death worldwide. It is related to insufficient blood supply to cerebral tissue, which induces irreversible or reversible intracellular effects depending on the time and intensity of the ischemic event. Indeed, neuronal function may be restored in some conditions, such as transient ischemic attack (TIA), which may be responsible for protecting against a subsequent lethal ischemic insult. It is well known that the brain requires high levels of oxygen and glucose to ensure cellular metabolism and energy production and that damage caused by oxygen impairment is tightly related to the brain's low antioxidant capacity. Oxygen is a key player in mitochondrial oxidative phosphorylation (OXPHOS), during which reactive oxygen species (ROS) synthesis can occur as a physiological side-product of the process. Indeed, besides producing adenosine triphosphate (ATP) under normal physiological conditions, mitochondria are the primary source of ROS within the cell. This is because, in 0.2-2% of cases, the escape of electrons from complex I (NADPH-dehydrogenase) and III of the electron transport chain occurring in mitochondria during ATP synthesis leads to the production of the superoxide radical anion (O2•-), which exerts detrimental intracellular effects owing to its high molecular instability. Along with ROS, reactive nitrosative species (RNS) also contribute to the production of free radicals. When the accumulation of ROS and RNS occurs, it can cause membrane lipid peroxidation and DNA damage. Here, we describe the intracellular pathways activated in brain tissue after a lethal/sub lethal ischemic event like stroke or ischemic tolerance, respectively, highlighting the important role played by oxidative stress and mitochondrial dysfunction in the onset of the two different ischemic conditions.

The responses of pepper plants to nitrogen form and dissolved oxygen concentration of nutrient solution in hydroponics

BackgroundThe presence of oxygen in the growth medium is absolutely essential for root development and the overall metabolic processes of plants. When plants do not have an adequate oxygen supply for respiration, they can experience a condition known as hypoxia. In order to investigate the impact of different nitrogen forms and varying oxygen levels in nutrient solutions on the growth, photosynthesis, and chlorophyll fluorescence parameters of bell pepper plants, a comprehensive study was conducted. The experiment was designed as a factorial experiment, considering two main factors: nitrogen forms (calcium nitrate and ammonium sulfate) with a fixed nitrogen concentration of 5 mM, and the oxygen levels of the nutrient solutions (ranging from 1.8 ± 0.2 to 5.3 ± 0.2 mg. L-1).ResultsThe study examined the effects of nitrogen (NH4+ and NO3−) application on various parameters of vegetative growth. The results demonstrated that the use of ammonium (NH4+) led to a reduction in the most measured parameters, including the fresh and dry mass of both the root and shoot, at low O2 concentrations of 1.8 ± 0.2; 2.6 ± 0.2 and 3.8 ± 0.2 mg. L-1. However, an interesting observation was made regarding the impact of oxygen levels on root growth in plants grown with nitrate (NO3−). Specifically, the highest levels of oxygen significantly increased root growth in NO3−-fed plants. Additionally, the application of NH4+ resulted in an increase in chlorophyll concentration in the leaves, particularly when combined with high oxygen levels in the nutrient solution. On the other hand, leaves of plants fed with NO3− exhibited higher photosynthetic rate (A), intrinsic water use efficiency (iWUE), and instantaneous carboxylation efficiency (A/Ci) compared to those fed with NH4+. Furthermore, it was found that NO3−-fed plants displayed the highest instantaneous carboxylation efficiency at oxygen levels of 3.8 and 5.3 mg. L-1, while the lowest efficiency was observed at oxygen levels of 1.8 and 2.6 mg. L-1. In contrast, NH4+-grown plants exhibited a higher maximal quantum yield of PSII photochemistry (Fv/Fm), as well as increased variable fluorescence (Fv) and maximum fluorescence (Fm), compared to NO3−-grown plants. Interestingly, the NO3−-fed plants showed an increase in Fv/Fm, Fv, and Fm with the elevation of oxygen concentration in the nutrient solution up to 5.3 mg. L-1.ConclusionThis study showed that, the growth and photosynthesis parameters in bell pepper plants are sensitive to oxygen stress in floating hydroponic culture. Therefore, the oxygen level in the nutrient solution must not be lower than 3.8 and 5.3 mg. L-1 in NH4+ and NO3− –supplied culture media or nutrient solutions, respectively.

Culture of Human Embryos at High and Low Oxygen Levels.

One of the parameters potentially affecting the in vitro growth of preimplantation embryos is the oxygen concentration in the culture environment. An increased oxygen concentration causes the generation of ROS which in turn can cause damage to the cells and seriously disrupt the embryonic development. Previous studies have assessed oxygen concentrations in the fallopian tubes of several mammals of between 5 and 8%, while the oxygen levels in the uterus were found to be even lower; similar measurements have been confirmed in humans. In addition, studies in mammalian embryos showed that low oxygen concentrations improve embryo development. Multiple studies on the effect of the oxygen concentration on human embryos have been conducted so far with diverse methodologies and objectives. Data from these have been included in three meta-analyses. All meta-analyses indicate the potential benefit in favor of a low oxygen concentration, though data are considered to be of a low methodological quality and further studies are considered necessary. However, based on the existing evidence, it is suggested that a low oxygen concentration should be adopted in the routine of the IVF laboratory, especially in the case of blastocyst culture.

Predictors of Disease Severity in Patients Hospitalized with COVID-19 during the Omicron Surge of January 2022

Background: The surge of COVID-19 hospitalizations in January 2022, at the onset of the Omicron period and before widespread population immunity, was a window in which to study the impact of vaccination status and other factors on disease severity in Omicron infections. Methods: This was a case-control study of adults hospitalized with COVID-19 during January 2022 that evaluated risk factors for severe disease. Cases were patients with severe COVID-19, defined in three ways: (1) requiring supplemental oxygen &gt; 24 hours if not on home oxygen, (2) requiring high-level oxygen: either high flow of &gt; 15 L/min, noninvasive ventilation, or mechanical ventilation (MV), and (3) the composite of MV or hospital death. Controls were patients hospitalized with COVID-19 who did not meet the respective case definition. Results: Among the 379 patients not on home oxygen before admission, 133 required supplemental oxygen. Among all 393 patients meeting the study criteria, 58 required high-level oxygen, 22 required MV, and 28 died. Factors associated with all case definitions were (1) absence of full vaccination compared to booster vaccination: requiring oxygen, odds ratio [OR], 7.86 [95% CI, 3.78-16.4]; high-level oxygen, OR, 5.17 [95% CI, 2.01-13.3]; MV or hospital death, OR, 5.21 [ 95% CI, 1.63-16.6]; (2) immunocompromised status: requiring oxygen, OR, 2.79 [95% CI, 1.38-5.63]; high-level oxygen, OR, 3.79 [95% CI 1.66-8.67]; MV or hospital death, OR 4.63 [95% CI 1.72-12.5], and (3) age ≥ 75 years compared to 50 to 64 years: requiring oxygen, OR 2.85, [95% CI 1.43-6.07]; high-level oxygen, OR 4.02 [95% CI 1.47-11.0]; MV or hospital death, OR 5.68 [95% CI 1.49-21.7]. Other factors associated with requiring oxygen were obesity: body mass index (BMI) 35.0-39.9 kg/m2, OR, 2.4 [95% CI 1.09-5.26]; BMI ≥ 40.0 kg/m2, OR, 3.29 [95% CI 1.34-8.10] compared to BMI ≤ 24.9 kg/m2; and age 65-74 years compared to 50-64 years, OR, 2.13 [ 95% CI 1.03-4.38]. Factors associated with requiring high-level oxygen were cardiomyopathy, OR, 2.11 [95% CI 1.04-4.32], and male gender, OR 1.93 [95% CI 1.01-3.7]. Factors associated with MV or hospital death were cardiomyopathy, OR, 2.67 [ 95% CI 1.11-6.42], and chronic kidney disease, OR, 3.17 [95% CI 1.27-7.96]. Factors not associated with any case definitions were full vaccination without compared to with a booster: requiring oxygen, OR, 1.07 [95% CI 0.522-2.21], high-level oxygen, OR, 1.08 [0.415-2.81], MV or hospital death, OR 0.992 [0.328-3.0]; age 18-49 years compared to 50-64 years: requiring oxygen, OR, 1.04 [95% CI 0.495-2.2]; high-level oxygen, OR, 1.2 [95% CI 0.418-3.43]; MV or hospital death, OR, 0.355 [95% CI 0.034-3.75]; and other medical conditions. Conclusions: In patients hospitalized with COVID-19 during the Omicron surge of January 2022, factors associated with requiring oxygen were the absence of full vaccination, immunosuppression, age ≥ 65 years, and body mass index ≥ 35 kg/m2, but not the absence of a booster if fully vaccinated. This is further evidence that immune memory mitigates disease severity in Omicron infections.

Analysis of large-scale fires in Makkah’s King Khaled Road tunnel using non-gray radiation models

The present study validated a fire dynamic simulation approach for reducing costs and losses in tunnel fire tests. It analyzed various radiation models, including gray, non-gray, and non-gray sooting models. The central processing unit (CPU) run time of the last model was very long, and the model is of little value in practice. The non-gray model was found to be the most accurate and efficient. This model was used to study fire behavior in the King Khaled Road tunnel in Makkah. This was done because the tunnel is small, there aren't many ways to get out, and it's hard to get firefighting teams to a place like Makkah during the Hajj season when there are a lot of people. Results showed that gas temperature, radiation, CO and CO2 concentrations, and air velocity increased with heat release rate, oxygen concentration, and soot yield. The air velocity was overpredicted during the simulations, having consequences for most of the other quantities, and this led to a cooler gas temperature, higher oxygen levels, and lower CO and CO2 concentrations. In addition, it is established that gas temperature and radiation increased when the ambient temperature increased, and oxygen concentration and air velocity were mostly unaffected by changing ambient temperature.

Pengaruh Circuit Training dan Kadar Oksigen dalam Minuman Terhadap Nilai VO2MAX

This study aims to determine the effect of Circuit Training and oxygen levels in beverages on the VO2 MAX value of Rugby SME students. The sample used in this study amounted to 10 students of Rugby SMEs. The instrument in this study used the bleep test. The results of the analysis showed that there was a significant difference between the VO2 MAX value before and after the Circuit Training and the provision of beverages with high oxygen levels with data t-count value of 5.15 is greater than the T-table value of 1,833. This means that the difference in average VO2 MAX before and after exercise can be said to be significant with a significant level of 0.5%. The results of data analysis showed a significant effect between Circuit Training and the provision of drinks with high oxygen levels to the value of VO2 MAX Rugby UKM students. The conclusion of this study shows that Circuit Training exercises and oxygen levels in drinks have a positive and significant impact on increasing VO2 MAX Rugby UKM students, with a significant level of 0.5%. T-count values greater than T-table values prove the existence of strong evidence to state significant differences between VO2 MAX before and after exercise.

Phytochemical Screening and Antioxidant Activity Analysis of N-Hexane Extract of Sonneratia alba Mangrove Leaves

Mangrove plants have been widely used by people in various regions of Indonesia as traditional medicine for the treatment of wounds, fever, diarrhea, and others. Extreme habitat in coastal areas with high salinity and low oxygen level makes mangrove plants produce a variety of unique secondary metabolites and are rich in antioxidants. Although there have been studies on phytochemicals and antioxidant activity conducted, the study of mangroves in Bali, Indonesia, has not been widely explored. This study aims to determine the compounds contained in mangrove leaf extract and their antioxidant activity. The species to be studied is Sonneratia alba, which is commonly found in the Ngurah Rai Mangrove Forest, Bali, Indonesia. In this experimental study, compound extraction was carried out by maceration method using n-hexane solvent. Phytochemical screening using qualitative methods and GC-MS was carried out to determine the phytochemical compounds in the extract, while 1,1-diphenyl-2-picrylhydrazyl (DPPH) method was used to determine antioxidant activity. The result showed that the n-hexane S. alba mangrove leaves extract display strong antioxidant activity with IC50 value of 64.432 ± 7.675 ppm. The qualitative phytochemical tests showed that the extract contained phenol and steroid, which are known to have antioxidant properties. Moreover, GC-MS analysis showed that there are two compounds with the largest %area namely gamma-sitosterol and dl-alpha-tocopherol (52.88% and 7.77%, respectively), which have been reported to have antioxidant activities. To conclude, these findings demonstrate that n-hexane extract of S. alba mangrove leaves from Ngurah Rai Mangrove Forest, Bali, to have potential antioxidant activity.

P1229 The Role and Niche-Specific Adaptation of Malassezia in patients with Ulcerative colitis

Abstract Background Accumulating evidence has underscored the role of gut fungal microbiota (mycobiota) in the development of inflammatory bowel disease. We aimed to isolate a Malassezia strain directly from the human intestine mucosal surface from the patients with ulcerative colitis (UC) and investigated its genome and virulence in comparison with the same fungal species isolated from the human skin. Methods Mucosal lavage samples were collected separately from colonic areas with and without inflammation in patients with UC. Samples from healthy individuals (HT) were obtained in the same manner as from patients with UC at sigmoid or descending colon. Skin samples were taken from HT in our previous work. DNA was extracted from these lavage samples, and fungal isolation was conducted using PCR amplification with ITS4 and ITS5 primers. Comprehensive analysis and comparison of the genomes, transcriptomes, and virulence between M. globosa gut isolates and those of M. globosa strains isolated from the skin were performed. To determine the contribution of M. globosa gut isolates to exacerbating inflammation, 1107 fungal cells were orally gavaged to DSS-induced colitis mouse model for three days. Results Total 56 and 11 intestinal water-lavage samples from 29 UC patients and 11 HT were obtained respectively. The α- and b-diversities of mycobiota showed no significant differences between the groups, patients with UC vs. HT or the sites with inflammation vs. non-inflammation of the patient with UC. Malassezia was the fifth most frequently found fungal genus throughout the samples, and live fungal strains belong to 28 and 7 different species were isolated from the patients with UC and HT, respectively. The patients with UC tend to have higher frequency of M. globosa and M. restricta than HT in their gut mucosal surface with inflammation. Whole genome sequencing showed no specific genomic characteristics between gut-isolated M. globosa and skin-isolated M. globosa. However, gut-isolated M. globosa were suffered more from the higher oxygen levels than the skin isolates in different oxygen concentrations. In a mouse model, gut-isolated M. globosa exhibited a more pronounced exacerbation of DSS-induced colitis and elevated production of inflammatory cytokines, including TNF-a, IL-6, IL-12p40, IL-1b, and IL-18, while the skin isolates showed no difference compared to the negative control (Figure). Conclusion Our data shed new light on the pivotal role of M. globosa in the pathogenesis of UC, highlighting the potential influence of niche-specific adaptations on the virulence of this fungus. These findings provide critical insights into the complex interplay between the member of the gut mycobiota and host health.

Characterization of excavated plastic waste from an Indian dumpsite: Investigating extent of degradation and resource recovery potential.

In recent years, the concept of landfill mining has gained a lot of traction in India, and tonnes of plastic waste is being excavated. The present shift towards a circular economy necessitates to explore the use of excavated plastic waste as a source of valuable materials and energy. However, the physicochemical characteristics of plastic waste change due to the degradation and weathering process in landfills, making its valorization difficult. The current study investigates the change in physicochemical characteristics of plastic waste with age from an Indian dumpsite to identify the potential valorization options. In addition, a material and energy flow analysis was performed considering incineration treatment of plastic waste. The plastic waste ranged between 3.6 and 21% in the dumpsite and has almost doubled in recent decades, owing to the increase in plastic waste generation in India. Polyethylene (high- and low-density) accounted for approximately 66% of the excavated plastic waste and had a lot of adhered surface impurities. Mechanical pre-treatment using a shredder was effective in the removal of the adhered impurities with a recovery rate of 50-70% for polyethylene and a higher recovery of 70-90% for other types of plastic. Changes in the surface morphology of plastic waste with aging were observed through Scanning Electron Microscopy. The Fourier Transform Infrared Spectroscopy results confirmed low degradation levels for aged plastic waste, which is also confirmed through the high level of oxygen detected. The material and energy flow analysis revealed that incinerating one tonne of excavated plastic waste could produce approximately 1410 kWh of electricity.

Conducted Electrical Weapon Fire Risk in the Presence of Supplemental Oxygen.

Conducted electrical weapons (CEWs) are nonlethal weapons used in tactical environments. Tactical EMS (TEMS) operators provide patient care in environments where CEWs are present. CEWs may produce a spark that can be a source of ignition. When supplemental oxygen is in use by a TEMS operator, the flammability risk from the CEW is unknown. We measured oxygen levels over 20 minutes in an enclosed space with a supplemental oxygen source maximally flowing. Measurements were taken at various distances from the oxygen source to establish baseline concentrations. These concentrations were replicated within a plexiglass box where a CEW was activated to create a sparking arc between probes embedded in a fresh swine shoulder (with skin intact). Various flammable materials, typically found in a patient care setting were used as potential fuel sources. The highest oxygen levels were achieved directly at the source. At 15cm from the source, the maximum oxygen concentration was 31.5%. Within the box, ignition was only achieved at oxygen concentrations greater than 45% and only when human hair was present as fuel. No ignition was achieved at oxygen levels below this regardless of the tested fuel present. Ignition from a CEW is possible at supplemental oxygen levels greater than 45% when human hair is present. In an enclosed space, oxygen concentration levels of 45% are only present within 15cm of a flush rate oxygen source. The likelihood of CEW-caused ignition in such settings with supplemental oxygen in use is extremely low.

Influence of oxygen content on selective laser melting leading to the formation of spheroidization in additive manufacturing technology.

Selective laser melting (SLM) additive manufacturing technology with different oxygen contents leads to the appearance of spherical solids of different sizes on the surface of the part, which affects the mechanical properties of the part, surface roughness, etc. In this study, the SLM molding technique was applied using three different 316L metal powders with different oxygen contents. The spheroidization properties and morphology of the samples were observed using a Quanta 200 environmental scanning electron microscope (ESEM), and the samples were observed microscopically and subjected to EDX spectroscopy using metallographic microscopy, and the mechanical properties were investigated. The results of the study showed that when using gas atomized powders, no spheroidization occurred when the oxygen content of the powders was 5.44 ± 0.01% in all cases, whereas using water atomized powders produced spherical structures with larger dimensions. This observation was closely related to the shape and particle size of the powder. When 316L metal powder with an oxygen content of 4.52 ± 0.01% was used for molding, small spherical structures appeared on the surface of the samples. When metal powder with an oxygen content of 5.44 ± 0.01% was used for the molding, larger spherical structures appeared on the surface of the samples. When the powder with an oxygen content of 5.90 ± 0.01% was used for the molding, more small spherical structures and some large spherical structures appeared on the surface of the samples. This suggests that higher oxygen levels may inhibit the occurrence of spheroidization. EDX spectroscopic analysis revealed that the white matter on the surface of the samples without spheroidization was mainly composed of Fe and Cr, whereas the white matter on the surface of the large-sized spherical structures was mainly composed of Si and Mn, which may be related to the oxygenophilicity of the various substances.

Study on the characteristics parameters of magnesium dust explosion suppression by various inert gases

Alongside the extensive use of magnesium, dust explosion accidents have become increasingly frequent. Conducting research on suppressing magnesium dust explosions is of great significance for the healthy development of the magnesium industry. In this paper, the effects of four inert gases (CO2, N2, Ar, and He) on the explosion characteristics parameters of magnesium dust clouds with different concentrations were investigated using a closed explosion device. It was observed that at low volume fractions of inert gases in the explosion system, there were no significant differences in their effects on the explosion characteristics parameters and the combustion time of magnesium particles. In situations where there was a high level of oxygen, N2 was more effective than Ar in suppressing explosions. However, when the concentration of magnesium dust cloud was higher and the oxygen content was lower within the hybrids, N2 reacted with magnesium dust that was unable to react with oxygen. As a result, the explosion suppression effect gradually shifted from N2 being better than Ar to Ar being better than N2. Moreover, the differences in the effects of four inert gases on particle combustion time became increasingly prominent. However, in all operating conditions, CO2 demonstrated the most effective suppression of magnesium dust explosions, while He exhibited the least effective suppression effect. Furthermore, by employing a chemical reaction kinetics calculation model, it has been discovered that the content of inert gases significantly affected the combustion time and reaction mode of particle combustion, thereby causing variations in the propagation behavior of magnesium dust cloud flames.

Relief from Toxic Effects of Oxygen Using Succinates in Patients with COVID-19 Undergoing High-Flow Oxygen Therapy

Liberal oxygen therapy for COVID-19 causes hyperoxemia in most patients and reduces their survival rate. Even moderate hyperoxemia reduces oxygen delivery, and high levels of oxygen in central venous blood increase mortality in COVID-19 patients. These facts occur due to the manifestation of toxic effects of oxygen (vasoconstriction, bronchoconstriction) requiring the use of medications that reduce toxic effects. The aim of the study was to assess the ability of succinate preparations to eliminate the toxic effects of oxygen affecting central hemodynamics and blood oxygenation in patients with COVID-19. Material and methods. The effect of medicines containing succinates (Cytoflavin and Reamberin) in stopping the manifestations of hyperoxia in 51 surviving patients with the novel coronavirus infection who received high-flow oxygen therapy (HFOT) was analyzed in a retrospective study. Results. Monitoring of heart rate, respiratory rate, SpO₂, PaO₂ and PaO₂/FiO₂ during HFOT within 12 hours from the start of oxygen therapy showed an indirect, but statistically significant effect of stopping the toxic effects of oxygen. This was expressed in a decrease in tachycardia and tachypnea [to 86.7–115.0 (at P&lt;0.001) and 22–24 (P&lt;0.001), respectively] against the background of concomitantly administered succinate preparations, that provided effective oxygen absorption and contributed to the effective elimination of hypoxia and hypoxemia (an increase in PaO₂/FiO₂ to 196.0 [(184.2–249.0) at P&lt;0.001], which was confirmed by a dynamic decrease in the level of lactate (to 2.6±0.8 mmol/l at P&lt;0.001). Conclusion. The results obtained indirectly confirm the protective effect of succinates, which are more pronounced in Citoflavin, but require additional confirmation of the hypothesis of succinate effectiveness in stopping the toxic effects of oxygen in further studies.

Fire activities and their impacts on local ecosystems in the southern Ordos Basin during the Middle Jurassic: Evidence from pyrogenic PAHs and petrography of inertinite-rich coal

The high frequency of fires during the formation of some mire systems in the Jurassic is thought to have influenced how terrestrial ecosystems evolved. Ancient mires, now present as coal seams, contain high-resolution paleoenvironmental and paleoclimatic records. Thus, the analysis of coal beds provides valuable, insightful, and practical knowledge on the changes in paleoclimate and, in this case, fire prevalence. Using petrographic, carbon isotopic, mercury content, and polycyclic aromatic hydrocarbon (PAH) determinations, the Middle Jurassic No. 4 coal from the Binchang region in the Ordos Basin was examined in order to understand the nature of fire during the formation of the mires. The results show that the No. 4 coal exhibits a high content of inertinite (average content 70%). Notably, the correlation coefficient (r = 0.79) between the concentration of PAHs (with >3 rings) and the proportion of inertinite indicates that the high content of inertinite was predominantly the result of fire. The presence of natural char and coke in the coals further indicates the frequent incidence of fires during the Middle Jurassic in the southern Ordos Basin. High frequency of fires can be attributed to the availability of fuel (i.e., the buildup of organic material), high atmospheric oxygen levels, and intermittent dry climatic conditions. The random reflectance of inertinite (specifically, fusinite and semifusinite) in the No. 4 coal bed ranges from 1.25% to 2.45%, which, with the presence of pyrogenic PAHs, suggests that their formation may have been predominantly affected by low- and moderate-temperature fires. The high frequency of fires is thought to have significant impacts on terrestrial and hydrological ecosystems. These effects may have included the circulation of atmospheric mercury, as well as the possible occurrence of anoxic events in the lakes.

Impaired enzymatic antioxidant defense in erythrocytes of rats with ammonia-induced encephalopathy: role NMDA receptors

Hepatic encephalopathy (HE), a medical term that deals with a neuropsychiatric disorder seen in patients with severe hepatic dysfunction, has been known for more than a century, however, pathogenetic mechanisms underlying cerebral dysfunction during conditions of liver disease are still not entirely understood. There is a consensus that an accumulation of ammonia in brain as a result of impaired detoxification capacity of the liver or the appearance of a portosystemic shunt is a primary cause of HE. Current evidence suggests that ammonia toxicity is mediated by hyperactivation of glutamate receptors, mainly N-methyl-D-aspartate receptors (NMDA-R) and affects many processes of aerobic metabolism that provides energy for a myriad of specific functions and viability of nerve cells. Recent reports on the presence of functional NMDA receptors in erythrocytes and deviations from normal ranges in many blood test parameters that was indicative of impaired hemodynamics and reduced carrying capacity for oxygen in erythrocytes in most patients with HE implicate the relationship between “erythrocyte damage” and cerebral dysfunction. In order to understand how, during hyperammonemia, disturbances in energy metabolism in brain that needs a constant supply of a high level of oxygen in the blood lead to encephalopathy, it is necessary to reveal ammonia-induced disorders in energy metabolism and antioxidant defense system of erythrocytes and explore the potential role of ammonia in reduced brain oxygenation. To detect the said missing link, the activities of erythrocyte antioxidant enzymes and concentrations of GSH, GSSG and H2O2 were measured in animals with hyperammonemia by using MK-801, a powerful noncompetitive NMDA receptor antagonist. It was found that the accumulation of ammonia in the blood of animals with hyperammonemia occurs within rat erythrocytes in large amounts and makes these cells which do not contain enzymes for the removal of ammonia, more susceptible to a prooxidant environment of ammonia created during oxidative stress that was completely or partially inhibited with the help of MK-801. Data obtained provide a support to identification of extra risk factors in cognitive disorders and in the prediction of unfavorable outcome with hypoperfusion in patients with elevated concentrations of ammonia in the blood.

Sleep‐mediated cognitive assessment and sleep architecture associations for real‐world diagnostic phenotyping of neurocognitive disorders

AbstractBackgroundSleep disorders precede cognitive deficits by an average of four years in Alzheimer’s disease, and disrupted sleep has been associated with worse cognitive performance. We examined the association of a novel sleep‐mediated cognitive assessment to sleep architecture in people with and without cognitive impairment, towards earlier diagnosis of cognitive impairment.MethodForty‐three participants from the Sleep &amp; Memory Center at the Neurological Institute of Athens cohort underwent a comprehensive evaluation that included polysomnography and pre‐ and post‐ sleep cognitive assessments of a novel short term verbal memory test as well as phonemic fluency testing. We examined the correlation of sleep‐mediated cognitive performance to sleep metrics of total sleep time, NREM/REM sleep, as well as respiratory metrics of Apnea‐Hypopnea Index and oxygen saturation during sleep.ResultSleep‐mediated spontaneous recall and phonemic fluency metrics were not associated to sleep architecture metrics. Instead, sleep‐mediated cued recall and recognition was positively associated to REM metrics of sleep time and relative REM/NREM ratio (R &gt; 0.39; p &lt; 0.039). On individual metrics, pre‐sleep verbal learning was positively associated to total sleep time (R &gt; 0.30; p&lt;0.05) as well as a larger REM/NREM ratio (R 0.52; p = 0.003). Finally, higher levels of oxygen during sleep, especially REM sleep, were associated with better pre‐sleep verbal learning (R &gt; 0.39; p &lt; 0.44).ConclusionOur results on people across a spectrum of cognitive abilities suggest that sleep‐mediated cognitive performance is significantly affected by shorter sleep times, and to a large extent these effects are dependent to the integrity of REM sleep. It is possible that both late evening learning abilities and sleep‐mediated memory reflects a person’s cholinergic capacity, as represented in subsequent REM sleep.