Oxygen Ratio Research Articles

Clinical prediction for surgical versus nonsurgical interventions in patients with vertebral osteomyelitis and discitis.

Vertebral osteomyelitis and discitis (VOD), an infection of intervertebral discs, often requires spine surgical intervention and timely management to prevent adverse outcomes. Our study aims to develop a machine learning (ML) model to predict the indication for surgical intervention (during the same hospital stay) versus nonsurgical management in patients with VOD. This retrospective study included adult patients (≥18 years) with VOD (ICD-10 diagnosis codes M46.2,3,4,5) treated at a single institution between 01/01/2015 and 12/31/2019. The primary outcome studied was surgery. Candidate predictors were age, sex, race, Elixhauser comorbidity index, first-recorded lab values, first-recorded vital signs, and admit diagnosis. After splitting the dataset, XGBoost, logistic regression, and K-neighbor classifier algorithms were trained and tested for model development. A total of 1,111 patients were included in this study, among which 30% (n=339) of patients underwent surgical intervention. Age and sex did not significantly differ between the two groups; however, race did significantly differ (P<0.0001), with the surgical group having a higher percentage of white patients. The top ten model features for the best-performing model (XGBoost) were as follows (in descending order of importance): admit diagnosis of fever, negative culture, Staphylococcus aureus culture, partial pressure of arterial oxygen to fractional inspired oxygen ratio (PaO2:FiO2), admit diagnosis of intraspinal abscess and granuloma, admit diagnosis of sepsis, race, troponin I, acid-fast bacillus culture, and alveolar-arterial gradient (A-a gradient). XGBoost model metrics were as follows: accuracy =0.7534, sensitivity =0.7436, specificity =0.7586, and area under the curve (AUC) =0.8210. The XGBoost model reliably predicts the indication for surgical intervention based on several readily available patient demographic information and clinical features. The interpretability of a supervised ML model provides robust insight into patient outcomes. Furthermore, it paves the way for the development of an efficient hospital resource allocation instrument, designed to guide clinical suggestions.

Mother's own milk and bronchopulmonary dysplasia in appropriate for gestational age preterm infants.

To evaluate the association between mother's own milk (MOM) and bronchopulmonary dysplasia (BPD) in appropriate for gestational age (AGA) preterm infants <32 weeks. Clinical data of AGA preterm infants (24+0/7-31+6/7 weeks) were reviewed. Infants with ≥66% of cumulative prescribed enteral volumes as MOM from birth to 36 weeks were allocated to the high provision of MOM group (H-MOM), whereas those with <66% were assigned to the low provision of MOM group (L-MOM). Multiple regressions were used to assess the association of H-MOM with BPD and oxygen saturation to fraction inspired oxygen ratio (SFR) at 36 weeks. A total of 1041 infants met the inclusion criteria, with a median provision of cumulative enteral nutrition volumes of 5721 (IQR 2616) mL/kg. Among them, 517 (49.7%) were H-MOM and 524 (50.3%) L-MOM infants. H-MOM showed a reduction in the incidence of BPD to 31.6% compared to L-MOM infants. H-MOM had a lower risk of BPD than L-MOM infants after the adjustment for gestational age, sex, cesarean section, mean SFR at the first hours of life, surfactant administration, patent ductus arteriosus, sepsis, prolonged ventilatory supports/oxygen exposure, and cumulative energy intakes from birth to 36 weeks [aOR: 0.613, p = 0.047]. H-MOM was also associated with a lower risk of SFR in the first quartile at 36 weeks [aOR: 0.616, p = 0.028] than L-MOM. A high provision (≥66%) of enteral volume as MOM from birth to 36 weeks is associated with a reduced risk of both BPD and low SFR at 36 weeks in AGA preterm infants <32 weeks.

Iron ore reduction using agricultural waste biochar with different carbon to oxygen ratios

BackgroundDuring iron production ferric oxide is reduced to iron, with carbon used as the reducing agent. Traditionally, coke was used as the carbon component, which became a crucial raw material in the iron and steel industry after the industrial revolution. However, coke is the most significant contributor to CO2 emissions due to the source of heat and reducing agent. Thus, shifting to low carbon energy systems, such as those based on biomass, is challenging. Therefore, in this study, we employed the mushroom cultivation residue char (MCRC) as a reducing agent to investigate the feasibility of replacing coke in the production of metallic iron. MethodsAfter carbonization at different temperatures (500 °C, 700 °C and 900 °C), mushroom cultivation residue char (MCRC), were used as a reducing agent in the production of metallic iron. To create the composite pellets, the MCRCs were individually mixed with iron ore at different carbon to oxygen ratios (C/O) (0.7, 0.8 and 0.9) and 1 % of bentonite. The reduction process was undergoing in the electric muffle furnace at different high temperatures (1,000 °C, 1,200 °C and 1,300 °C) to investigate the biomass C/O ratios required for efficient iron production. Significant findingsThe results show that 0.8 was selected as the optimal C/O ratio for mushroom cultivation residue char (MCRC) to be used as a reducing agent. Its metallization rate can reach 31.99 %. The results also indicate that the carbon and volatiles in MCRC play a key role in iron making production using such biochar pellets. In conclusion, MCRC can be used as a reducing agent to increase the sustainability of iron production and reduce agricultural waste.

Improving electrochemical performances of LiNi0.5Mn1.5O4 by the strategy of oxygen vacancy doping

Despite the dazzling potential to be utilized as a high energy density lithium-ion battery cathode, the practical application of LiNi0.5Mn1.5O4 (LNMO) is hampered by the structural distortion related to Jahn-Teller effect of Mn3+ and the capacity degradation related to Mn2+ dissolution at high voltage. Herein, LNMO cathode materials doped with different contents of oxygen vacancies are synthesized by directly adjusting the oxygen ratio in the calcination atmosphere. Experimental and theoretical calculation results show that doping an appropriate amount of oxygen vacancies can regulate the electronic structure of Mn and Ni around oxygen vacancy, adjust the relative amount of Mn3+/Mn4+, increase the degree of disorder, and improve the electronic and ionic conductivity of LNMO, thereby enhancing its electrochemical performance. Especially, the modified LNMO exhibits a high capacity of 121.2 mAh g−1 at 0.5 C, a good capacity retention of 87.6 % after 100 cycles, and an excellent rate performance when the content of oxygen vacancies is about 20.60 %, corresponding to the oxygen ratio of 50 % in the calcination atmosphere. This study emphasizes the influence of doping oxygen vacancies on LNMO performance, enhancing its electrochemical properties without the introduction of additional elements. Moreover, these findings offer a fresh approach to enhancing the electrochemical performance of advanced batteries.

Plateau-Adapted Single-Pump, Single-Bed Vacuum Pressure Swing Adsorption Oxygen Generation Process Simulation and Optimization

To enhance the oxygen guarantee capacity in high altitude areas and address the challenges of traditional pressure swing adsorption oxygen generation fixed equipment with large volume and multiple device modules, a novel single-reversible-pump single-bed vacuum pressure swing adsorption (VPSA) oxygen generation process was proposed and simulated. This study investigated the effects of purge on oxygen productivity, purity, recovery, and energy consumption, determining that the optimum ratio of total oxygen in the purge gas to the total oxygen in the feed gas (P/F) was 0.176. A set of principle prototypes was developed and validated in plains. The process performance was then simulated and studied at altitudes of 3000 m, 4000 m, and 5000 m. Finally, the optimization was carried out by adjusting the product flow rate and feed flow rate, revealing that the best performance can be achieved when the oxygen purity exceeded 90% with lower energy consumption or larger productivity than the optimization goal. This study serves as a valuable reference for the optimization of the VPSA oxygen generation process in a plateau environment.

Synergy between Fe-Co oxide catalysts supported over HZSM-5 for direct conversion of methane to methanol

The direct conversion of methane to methanol over iron and cobalt oxide based composite catalysts supported over HZSM-5 was carried out in a fixed-bed micro reactor under changing process parameters and catalyst compositions. The prepared catalysts were well characterized by various techniques including N2 adsorption desorption, X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), pyridine FTIR, X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy and temperature programmed reduction (H2-TPR). The characterization results revealed the presence of various reducible iron and cobalt oxide species depending on the Fe/Co molar ratio and total metal oxide loading. Moreover, the XPS and UV–vis spectroscopic results also confirmed the variation of Fe2+/Fe3+ and Co2+/Co3+ species depending on the Fe-Co molar ratio which had strong influence on the performance of the composite catalysts. It was found that the cobalt species favours the formaldehyde formation whereas the iron species promotes the formic acid formation in their respective pure supported oxide catalysts. However, the synergistic effect of iron and cobalt oxide in equimolar ratio in composite catalysts appeared as effective for achieving highest yield of methanol. The methanol selectivity was also influenced by the alteration of various studied process parameters. The higher reaction temperature favoured the overoxidation of methanol to CO2 whereas the methanol selectivity increased with increasing the methane to oxygen ratio. The lattice to adsorbed oxygen ratio also had strong influence on the activity of composite catalysts and methanol selectivity. The highest methanol yield of 1.87% was achieved at the methane conversion of 42.81 % with the 20Fe1Co1Z catalyst at 873 K reaction temperature with CH4/O2 ratio of 2:1 and WHSV of 1030 ml hr−1 gcat−1.

Effects of methane to oxygen ratio on cell growth and polyhydroxybutyrate synthesis in high cell density cultivation of Methylocystis sp. MJC1.

Polyhydroxybutyrate (PHB) production through CH4 conversion by methanotrophs offers a solution for greenhouse gas emissions and plastic waste concerns. In this study, we aimed to achieve high cell density cultivation of Methylocystis sp. MJC1 for efficient PHB production. Cultivating MJC1 using CH4 and air (3:7, v/v) yielded a final cell density of 52.9 g/L with a 53.7% (28.4 g/L) PHB content after 210 h, showcasing PHB mass production potential. However, long-term cultivation led to a low volumetric productivity of 0.200g/L/h. To address this, we conducted cultivation at various O2/CH4 ratios using O2 instead of air, which significantly improved the PHB productivity. Under high O2 conditions (O2/CH4 ratio of 1.5), biomass productivity increased 1.51-fold compared to that under low O2 conditions in the same time frame; however, PHB accumulation was delayed. Using an equal ratio of CH4 and O2 induced active cell growth and selective PHB production, achieving the highest PHB productivity (0.365 g/L/h) with a final cell density of 55.9 g/L and PHB content of 61.7% (34.5 g/L) in 162 h. This study highlighted the significance of the O2/CH4 ratio in CH4 conversion and PHB production by M. sp. MJC1.

Thermodynamic and exergy assessment of a biomass oxy-fuel combustion with supercritical carbon dioxide cycle under various recycle flue gas conditions

The ongoing development of second-generation oxy-fuel combustion system with higher oxygen concentration have presented a potential pathway for efficient biomass utilization. It also signified the meticulous role of recycled flue gas in altering the combustion behaviour in the combustor. Accordingly, investigation into different recirculation modes focusing on recycle ratio, wet/dry conditions, and excess oxygen ratio are conducted with an indirect supercritical power cycle integrated biomass oxy-fuel combustion system. Energy and exergy analyses, as well as composition of flue gas produced are presented. Energy and exergy efficiencies increased with reducing recycle ratio, with respective highest efficiency of 31.33% and 44.37% obtained at excess oxygen ratio of 1.01 and recycle ratio of 0.5 under wet condition. Investigation of CO2 and H2O concentration in produced flue gas depicted a separated stage profile under dry recycle condition, different from the slight diverging profile observed under wet condition when the recycle ratio varied. Concentration of NOx and SOx increased with decreasing recycle ratio and are generally higher under dry condition. Selective exergy analyses of the proposed power cycle presented highest exergy loss in the combustor, followed by the air separation unit, heat exchanger, CO2 compression and purification unit, and turbine generator. Based on the obtained result, wet recycle flue gas enhanced the combustion performance in the combustor but slightly impaired the convective heat transfer in the heat exchanger. The performance of proposed biomass power cycle is optimized at low recycle ratio of 0.5 under wet recycle condition.

Enhancing the Production of Eco-Friendly Silk Fabrics through the Application of Nonthermal Plasma Wettability Techniques.

The combination of the effects of nonthermal plasma using atmospheric pressure of plasma jet and the photocatalytic effects of titanium dioxide nanoparticles was used to study the plasma flow modes, electrical characteristics, nonthermal characteristics, antimicrobial measurements, and surface modifications. Using different wettabilities of argon discharges in a laminar flow: (i) wet I, wettability with 2.4 slm argon mixture with oxygen ratio O2, equivalent to 15 mslm (Ar/O2), and (ii) wet II, wettability (Ar/O2) mixture combined with titanium dioxide, to accelerate the inactivation process on the nonwoven fabric surface. For wet 0, wet I, and wet II discharges, the average rate of heat transfer to the nonwoven silk fabric increased significantly. Specifically, it goes from 104.6 to 118.6 and then to 241.7 mW, respectively. The kinetic deactivation rate of Escherichia coli increases starting at 0.20, then going up to 0.32, and finally reaching 0.57 min-1. The increased wettability of the TiO2 photocatalyst results in an enhanced bactericidal rate, which is caused by both the heat impact from the nonthermal jet and potentially photocatalytic disinfection, leading to the generation of active species. The mechanical parameters owing to different wettabilities and plasma interactions with the fabric membrane were tested for the treated samples, such as stiffness, ultimate yield strength, tensile strength, strain, hardening, elongation, resilience, and toughness.

Emergency Department SpO2/FiO2 Ratios Correlate with Mechanical Ventilation and Intensive Care Unit Requirements in COVID-19 Patients.

Patients with coronavirus 2019 (COVID-19) are at high risk for respiratory dysfunction. The pulse oximetry/fraction of inspired oxygen (SpO2/FiO2) ratio is a non-invasive assessment of respiratory dysfunction substituted for the PaO2:FiO2 ratio in Sequential Organ Failure Assessment scoring. We hypothesized that emergency department (ED) SpO2/FiO2 ratios correlate with requirement for mechanical ventilation in COVID-19 patients. Our objective was to identify COVID-19 patients at greatest risk of requiring mechanical ventilation, using SpO2/FiO2 ratios. We performed a retrospective review of patients admitted with COVID-19 at two hospitals. Highest and lowest SpO2/FiO2 ratios (percent saturation/fraction of inspired O2) were calculated on admission. We performed chi-square, univariate, and multiple regression analysis to evaluate the relationship of admission SpO2/FiO2 ratios with requirement for mechanical ventilation and intensive care unit (ICU) care. A total of 539 patients (46% female; 84% White), with a mean age 67.6 ± 18.6years, met inclusion criteria. Patients who required mechanical ventilation during their hospital stay were statistically younger in age (P = 0.001), had a higher body mass index (P < .001), and there was a higher percentage of patients who were obese (P = 0.03) and morbidly obese (P < .001). Shortness of breath, cough, and fever were the most common presenting symptoms with a median temperature of 99°F. Average white blood count was higher in patients who required ventilation (P = <0.001). A highest obtained ED SpO2/FiO2 ratio of ≤300 was associated with a requirement for mechanical ventilation. A lowest obtained ED SpO2/FiO2 ratio of ≤300 was associated with a requirement for intensive care unit care. There was no statistically significant correlation between ED SpO2/FiO2 ratios >300 and mechanical ventilation or intensive care unit (ICU) requirement. The ED SpO2/FiO2 ratios correlated with mechanical ventilation and ICU requirements during hospitalization for COVID-19. These results support ED SpO2/FiO2 as a possible triage tool and predictor of hospital resource requirements for patients admitted with COVID-19. Further investigation is warranted.

INVESTIGATION OF THE EFFECT OF OPERATING PARAMETERS ON NERNST VOLTAGE IN HYDROGEN-OXYGEN FUEL CELLS

In hydrogen-oxygen fuel cells, operating parameters have an influence on the maximum expected open circuit (Nernst) voltage. Even though fuel cells have been the subject of many research, none of them have theoretically investigated the impact of various operating parameters, particularly concerning Nernst voltage and maximum thermodynamic efficiency. In this study, a computer program was developed to theoretically determine the effect of various operating parameters on the Nernst voltage in hydrogen-oxygen fuel cells. This computer program was developed in MATLAB to mathematically examine the effects of hydrogen and oxygen mole ratios, anode and cathode pressures, and operating temperatures on the maximum expected open circuit voltage. When calculating Nernst voltages and maximum thermodynamic efficiency for fuel cell reactions containing water as a by-product, the effects of higher heating value (HHV) and lower heating value (LHV) are also considered in the solutions. As a result, it was also concluded that temperature increase reduces the fuel cell Nernst voltage and maximum thermodynamic efficiency. Therefore, it was observed from the figures that the best conditions for the Nernst voltage occur when HHV is assumed, the temperature is 353 K, the mole ratios of hydrogen and oxygen are 1.0, the anode and cathode pressures are 5 atm and 6 atm, respectively. In terms of thermodynamic efficiency, it was determined that there was a maximum increase of 92.2% in the LHV assumption compared to the HHV assumption at the temperature of 1000 K, provided that other operating parameters were kept constant.

The Synthetic Surfactant CHF5633 Restores Lung Function and Lung Architecture in Severe Acute Respiratory Distress Syndrome in Adult Rabbits

PurposeAcute respiratory distress syndrome (ARDS) is a major cause of hypoxemic respiratory failure in adults. In ARDS extensive inflammation and leakage of fluid into the alveoli lead to dysregulation of pulmonary surfactant metabolism and function. Altered surfactant synthesis, secretion, and breakdown contribute to the clinical features of decreased lung compliance and alveolar collapse. Lung function in ARDS could potentially be restored with surfactant replacement therapy, and synthetic surfactants with modified peptide analogues may better withstand inactivation in ARDS alveoli than natural surfactants.MethodsThis study aimed to investigate the activity in vitro and the bolus effect (200 mg phospholipids/kg) of synthetic surfactant CHF5633 with analogues of SP‐B and SP‐C, or natural surfactant Poractant alfa (Curosurf®, both preparations Chiesi Farmaceutici S.p.A.) in a severe ARDS model (the ratio of partial pressure arterial oxygen and fraction of inspired oxygen, P/F ratio ≤ 13.3 kPa) induced by hydrochloric acid instillation followed by injurious ventilation in adult New Zealand rabbits. The animals were ventilated for 4 h after surfactant treatment and the respiratory parameters, histological appearance of lung parenchyma and levels of inflammation, oxidative stress, surfactant dysfunction, and endothelial damage were evaluated.ResultsBoth surfactant preparations yielded comparable improvements in lung function parameters, reductions in lung injury score, pro-inflammatory cytokines levels, and lung edema formation compared to untreated controls.ConclusionsThis study indicates that surfactant replacement therapy with CHF5633 improves lung function and lung architecture, and attenuates inflammation in severe ARDS in adult rabbits similarly to Poractant alfa. Clinical trials have so far not yielded conclusive results, but exogenous surfactant may be a valid supportive treatment for patients with ARDS given its anti-inflammatory and lung-protective effects.

Sputtered Sn-doped Ga2O3 films under balance controlled of energy supply and ion bombardment for solar-blind detection application

The characteristics of amorphous Sn-doped Ga2O3 films deposited using radio frequency magnetron sputtering at room temperature under different sputter powers have been demonstrated. A balance mechanism of energy supply and ion bombardment controlled by sputter power has been found during the deposition. The increasing growth rate as power can be due to the increased yield sputtering species indicated by an in situ optical emission spectroscopy. As the power increases to 700 W, an obvious change from discrete nanoparticles to flat-continuous film can be observed because of sufficient energy supply for oxidation reaction, which leads to the maximum ratio of lattice oxygen and Sn4+ indicating the optimal film quality and conductive property. However, a non-negligible high energy ion bombardment presented at 900 W leads to the degraded film quality. The influence of sputtering power on Sn-doped Ga2O3 solar-blind photodetectors is demonstrated. It can obtain a good performance with an ultra-low dark current density of 2.2 × 10−11 A/cm2, a substantial light-dark current ratio of 1.08 × 103 and fast rise/decay time of 1.59 s/0.54 s at 700 W. The revelation of the role of sputtering power on the properties of Sn-doped Ga2O3 films may offer an interesting direction for low-cost and high-performance solar-blind photodetectors.

Efficient Electrosynthesis of Hydrogen Peroxide Using Oxygen-Doped Porous Carbon Catalysts at Industrial Current Densities.

Metal-free carbon catalysts (MFCCs) are one of the commonly used catalysts for electrocatalytic two-electron oxygen reduction (2e- ORR) synthesis of hydrogen peroxide (H2O2). Oxygen doping is an effective means to improve the performance of MFCCs, but the performance of oxygen-doped carbon catalysts is still not high enough, and the contribution of different oxygen functional groups (OFGs) to the catalytic performance is still inconclusive. In this paper, carbon-based catalysts with different oxygen contents and ratios of OFGs were prepared, and the high 2e- ORR activity of COOH + C-OH was demonstrated by combining the results of experiments and theoretical calculations. The prepared oxygen-doped carbon-based catalyst C-0.1M80 achieved an onset potential of 0.795 V (vs RHE), a selectivity of up to 98.2% (0.6 V vs RHE), and a H2O2 oxidation current of 1.33 mA cm-2 (0.5 V vs RHE) in a rotating ring-disk electrode test (0.1 M KOH solution), which was an outstanding performance in MFCCs. In a solid electrolyte flow cell, C-0.1M80 achieved a Faraday efficiency of 97.5% at 200 mA cm-2 with a corresponding H2O2 production rate of 123.7 mg cm-2 h-1. In addition, a flow cell stability test was performed at an industrial current density (100 mA cm-2) with an astounding 200 h of uninterrupted operation, also achieving an outstanding average Faradaic efficiency (95.8%).

Laminar burning velocity of NH3 + N2 + O2 and NH3 + Ar + O2 flames at ultra-lean and rich conditions

Ammonia (NH3) has received increasing attention as a carbon-free alternative fuel. The laminar burning velocities (SL) of NH3-containing flames have been extensively investigated, resulting in the development, updating, or optimization of many mechanisms. In this study, we aimed to test the validity of the available mechanisms by measuring the SL of ammonia flames at ultra-lean (ϕ = 0.3–0.6) and rich (ϕ = 1.5–1.8) conditions, which were not covered by literature experiments and thus outside the validation targets of the literature mechanisms. The measurements were conducted using the heat flux method at 1 atm and 298 K, with careful evaluation of uncertainties in laminar burning velocities, oxygen ratios, and equivalence ratios. In addition to NH3 + O2 + N2, we also tested NH3 + O2 + Ar flames to provide data at broader conditions. Simulations were carried out using eleven kinetic mechanisms that have been validated against the NH3 laminar burning velocities when first published, and none of them reproduces well the present experimental data with mixed behavior observed, indicating the necessity of SL measurements with different oxygen ratios and diluent types, as well as that there is still space for mechanism updating. A-factor reaction sensitivity analyses were also conducted using the eleven mechanisms, providing uncertainty ranges of rate constants based on their variations in the different mechanisms. Our analyses suggest that future mechanism updating should focus on especially on the temperature dependences of the sensitive reactions with large rate constant uncertainties. In addition, mechanism updating targeting fuel-rich side data will be more challenging than the lean side due to a larger number of large-uncertainty reactions.

Numerical study on kinetics of tar production and mechanism of benzene formation during corn straw gasification

Tar production is a key factor hindering the industrialization of biomass gasification technology. Understanding the mechanisms of tar formation can help predict and reduce tar yield. A gasification model was proposed to investigate the effects of oxygen ratio (OR) and temperature on products formation. Its accuracy was validated using experimental data. The relative content of PAHs from corn straw gasification decreased from 95 % to 53 % with OR and temperature increasing, indicating PAHs relative content could be decreased by increasing OR and temperature. The concentrations of phenanthrene from cellulose and corn straw gasification at 900 °C were 0.85 and 378 ppm, separately. The concentrations of pyrene were 52 and 558 ppm, respectively. The content of PAHs from cellulose gasification was much less than that from corn straw gasification. However, the contribution of cellulose to PAHs formation increased with temperature increasing. Furthermore, the mechanism of benzene formation was analyzed qualitatively and quantitatively. C2H2, C3H3, and C4H6 were main precursors and exhibited a considerable role in benzene formation. H, OH, CH3, and C6H5 were the key radicals. The analysis results indicated that CH3→C2H2→C3H3→benzene and C2H3/C2H4→C4H6→n-C4H5→benzene were two main paths for benzene formation during corn straw gasification.

Sensitivity-Enhanced, Room-Temperature Detection of NH3 with Alkalized Ti3C2Tx MXene.

A layered Ti3C2Tx MXene structure was prepared by etching MAX-phase Ti3AlC2 with hydro-fluoric acid (HF), followed by alkalization in sodium hydroxide (NaOH) solutions of varying concentrations and for varying durations. Compared to sensors utilizing unalkalized Ti3C2Tx, those employing alkalized Ti3C2Tx MXene exhibited enhanced sensitivity for NH3 detection at room temperature and a relative humidity of 40%. Both the concentration of NaOH and duration of alkalization significantly influenced sensor performance. Among the tested conditions, Ti3C2Tx MXene alkalized with a 5 M NaOH solution for 12 h exhibited optimal performance, with high response values of 100.3% and a rapid response/recovery time of 73 s and 38 s, respectively. The improved sensitivity of NH3 detection can be attributed to the heightened NH3 adsorption capability of oxygen-rich terminals obtained through the alkalization treatment. This is consistent with the observed increase in the ratio of oxygen to fluorine atoms on the surface terminations of the alkalization-treated Ti3C2Tx. These findings suggest that the gas-sensing characteristics of Ti3C2Tx MXene can be finely tuned and optimized through a carefully tailored alkalization process, offering a viable approach to realizing high-performance Ti3C2Tx MXene gas sensors, particularly for NH3 sensing applications.

Energy and exergy analyses, and elemental distribution of microwave-assisted auger pyrolysis of textile dyeing sludge and furfural residue

Microwave-assisted pyrolysis has emerged as a promising treatment method for textile dyeing sludge (DS) and furfural residue (FR), demonstrating the potential to address environmental issues and harness their energy. In this study, microwave-assisted auger pyrolysis of DS and FR was conducted, and the mass balance, elements distribution, energy, exergy and sustainability analysis were investigated. The results indicated that the distribution ratios of carbon (46.14–76.29%), hydrogen (15.04–47.96%), and oxygen (3.62–36.55%) in chars decreased with increasing temperature. As the pyrolysis temperature increased during FR pyrolysis, there was a higher thermal energy loss and a decrease in energy efficiency, energy yield, and exergy efficiency. The pyrolysis temperature and the type of solid wastes are key factors in determining both energy efficiency and exergy efficiency. The energy/exergy utilization efficiencies for FR pyrolysis (57.03–82.24%/55.90–81.82%) surpassed those for DS pyrolysis (26.46–38.93%/23.35–36.65%). The highest energy and exergy efficiencies for DS (i.e. 38.93% and 36.65%) and FR (i.e. 82.24% and 81.82%) were achieved at 450 °C. FR pyrolysis had a lower environmental impact than DS pyrolysis. This study aimed to provide insights into the treatment and disposal of sludge and FR through microwave pyrolysis, considering both energy and exergy aspects.

Changes in Carbon, Nitrogen, and Oxygen Stable Isotope Ratios and Mercury Concentrations in Killer Whales (Orcinus orca) during and after Lactation

The changes in the stable isotope ratios of carbon (δ13C), nitrogen (δ15N), oxygen (δ18O), and mercury (Hg) concentrations in muscle and liver tissues during and after lactation were studied in killer whales stranded along the coast of Hokkaido, in the northern area of Japan (n = 16). Calf muscles displayed δ13C- and δ15N-enriched peaks and a δ18O-depleted peak during lactation. The δ13C- and δ15N-enriched peaks appear to reflect the extensive nursing of 13C- and 15N-enriched milk and the onset of weaning, whereas the δ18O-depleted peak may be attributable to the extensive nursing of 18O-depleted milk and the onset of weaning. The δ13C and δ15N values tended to gradually increase after the weaning, whereas the δ18O values tended to decrease. The δ13C and δ15N levels in calves were similar between liver and muscle samples, whereas those in mature animals were higher in liver than in muscle samples. The isotopic turnover rates of C and N may be similar between the liver and muscle tissues in calves, which are rapidly growing animals. The Hg concentrations in muscle tissues were slightly higher in small calves than in large calves, probably due to the Hg transfer across placenta. The Hg concentrations in liver and muscle samples increased with increasing body length, and those in two liver samples from mature animals exceeded the high-risk threshold for marine mammal health effects (82 μg/wet g).

High-flow nasal oxygen in resource-constrained, non-intensive, high-care wards for COVID-19 acute hypoxaemic respiratory failure: Comparing outcomes of the first v. third waves at a tertiary centre in South Africa.

High-flow nasal oxygen (HFNO) is an accepted treatment for severe COVID-19-related acute hypoxaemic respiratory failure (AHRF). To determine whether treatment outcomes at Groote Schuur Hospital, Cape Town, South Africa, during the third COVID-19 wave would be affected by increased institutional experience and capacity for HNFO and more restrictive admission criteria for respiratory high-care wards and intensive care units. We included consecutive patients with COVID-19-related AHRF treated with HFNO during the first and third COVID-19 waves. The primary endpoint was comparison of HFNO failure (composite of the need for intubation or death while on HFNO) between waves. A total of 744 patients were included: 343 in the first COVID-19 wave and 401 in the third. Patients treated with HFNO in the first wave were older (median (interquartile range) age 53 (46 - 61) years v. 47 (40 - 56) years; p<0.001), and had higher prevalences of diabetes (46.9% v. 36.9%; p=0.006), hypertension (51.0% v. 35.2%; p<0.001), obesity (33.5% v. 26.2%; p=0.029) and HIV infection (12.5% v. 5.5%; p<0.001). The partial pressure of arterial oxygen to fraction of inspired oxygen (PaO2 /FiO2 ) ratio at HFNO initiation and the ratio of oxygen saturation/FiO2 to respiratory rate within 6 hours (ROX-6 score) after HFNO commencement were lower in the first wave compared with the third (median 57.9 (47.3 - 74.3) mmHg v. 64.3 (51.2 - 79.0) mmHg; p=0.005 and 3.19 (2.37 - 3.77) v. 3.43 (2.93 - 4.00); p<0.001, respectively). The likelihood of HFNO failure (57.1% v. 59.6%; p=0.498) and mortality (46.9% v. 52.1%; p=0.159) did not differ significantly between the first and third waves. Despite differences in patient characteristics, circulating viral variant and institutional experience with HFNO, treatment outcomes were very similar in the first and third COVID-19 waves. We conclude that once AHRF is established in COVID-19 pneumonia, the comorbidity profile and HFNO provider experience do not appear to affect outcome. What the study adds. This study adds to the body of evidence demonstrating the utility of high-flow nasal oxygen (HFNO) in avoiding invasive mechanical ventilation (IMV) in patients with severe COVID-19 hypoxaemic respiratory failure, and shows that this utility remained consistent across different waves of the COVID-19 pandemic.Implications of the study. In resource-constrained settings, HFNO is a feasible non-invasive alternative to IMV and can be employed with favourable and consistent outcomes outside traditional critical care wards. It also confirms that the degree of gas exchange abnormality, and not pre-existing patient-related factors, circulating wave variant or provider experience, is the main predictor of HFNO failure.