Oxygen Ratio Research Articles

Arterial blood gases in SCUBA divers at depth

BackgroundCurrent diving physiology postulates that SCUBA divers’ arterial blood gas (ABG) levels vary proportionally to environmental pressure, but, to date, ABGs have only been obtained during simulated dives. Also, recent evidence supports the use of the arterial/alveolar (a:A) partial pressures of oxygen (PO2) ratio to predict the arterial PO2 (PaO2) under hyperbaric conditions from measurements obtained at 1 atmosphere absolute (ATA). This work summarizes ABGs obtained in SCUBA divers in real underwater conditions and aims to validate the a:A ratio in predicting PaO2 in this subset of individuals at depth.MethodsThe study was approved by the local ethics committee. After cannulating the radial artery of the non-dominant limb, ABGs were sampled at the surface before the dive (A), at depth (15 meters of freshwater (mfw) or 42 mfw) before (B) and after (C) pedaling on a submersed bicycle for 10 minutes, and back at surface (D). After calculating the surface alveolar PO2 for each subject, the a:A ratio was obtained and used to predict PaO2 at depth. A linear regression between measured and predicted PaO2 was reported, along with the goodness-of-fit F test.ResultsSix subjects performed the dive at 15 mfw, and four others at 42 mfw. The PaO2 proportionally increased at both depths, remaining stable before and after pedaling. The a:A calculated from the baseline ABG obtained at rest, out of the water, adequately predicted the PaO2 at depth (R2 = 0.97, p<0.001), better at 15 mfw but losing accuracy at 42 mfw.ConclusionsThe ABGs confirmed the proportional rise of PaO2 in SCUBA divers underwater. The a:A ratio could be used to predict the magnitude of PaO2 rise at depth to limit exposure to hyperoxia, especially in repetitive recreational dives and professional divers.

PERFORMANCE OF FREE WATER SURFACE FLOW CONSTRUCTED WETLAND FOR LEAD AND CADMIUM IONS REMOVAL USING AZOLLA PINNATA PLANT

Phytoremediation is the ability of some plants to bio accumulate, decompose, or transformation of pollutants in soils, water, or air. In the current study, an effort is made to study the effectiveness of free-floating plants to treat simulated industrial wastewater polluted with Lead and Cadmium ions using Azolla Pinnata plant in a lab condition. Free water surface flow constructed wetland were fed with simulated Cd and Pb ions in different concentrations (5, 10 and 20) mgl-1. Different operating conditions were studied such as; pH, dissolved oxygen, electrical conductivity, temperature, and sodium adsorption ratio to find out the possibility of using treated wastewater for irrigation. Results showed that, Azolla plant had a higher removal efficiency to extract Lead ions (90.1%, 86.67%, and 81.3%) than Cadmium (79.3%, 78.4%, and 69.7%) when the initial concentration is (5, 10, 20) mgl-1 respectively, during 5 days. A slight reducing in pH (8.3 to 7.4) and dissolved oxygen (8.7 to 7.2) mgl-1 observed, all these values mentioned satisfied with the Iraqi standards and World Health Organization. From values of electrical conductivities (250- 750) (µScm-1) and the sodium adsorption ratios (0- 10) it was found that treated wastewater falls into class C2S1 which mean that water has good quality and can be used to irrigate moderately salt-tolerant crops on soils with good permeability.

Seasonal shifts in depth-to-water uptake by young thinned and overstocked lodgepole pine (Pinus contorta) forests under drought conditions in the Okanagan Valley, British Columbia, Canada

Abstract. As drought and prolonged water stress become more prevalent in dry regions under climate change, preserving water resources becomes a focal point for maintaining forest health. Forest regeneration after forest loss or disturbance can lead to overstocked juvenile stands with high water demands and low water-use efficiency. Forest thinning is a common practice with the goal of improving tree health, carbon storage, and water use while decreasing stand demands in arid and semi-arid regions. However, little is known about the impacts of stand density on seasonal variation in depth-to-water uptake or the magnitude of the effect of growing season drought conditions on water availability. Existing reports are highly variable by climatic region, species, and thinning intensity. In this study, stable isotope ratios of deuterium (δ2H) and oxygen (δ18O) in water collected from various soil depths and from branches of lodgepole pine (Pinus contorta) under different degrees of thinning (control: 27 000 stems per hectare; moderately thinned: 4500 stems per hectare; heavily thinned: 1100 stems per hectare) over the growing season were analyzed using the MixSIAR Bayesian mixing model to calculate the relative contributions of different water sources in the Okanagan Valley in the interior of British Columbia, Canada. We found that under drought conditions the lodgepole pine trees shifted their depth-to-water uptake through the growing season (June to October) to rely more heavily on older precipitation events that percolated through the soil profile when shallow soil water became less accessible. Decreased forest density subsequent to forest thinning did not cause a significant difference in the isotopic composition of branch water but did cause changes in the timing and relative proportion of water utilized from different depths. Thinned lodgepole pine stands were able to maintain water uptake from 35 cm below the soil profile, whereas the overstocked stands relied on a larger proportion of deep soil water and groundwater towards the end of the growing season. Our results support other findings by indicating that, although lodgepole pines are drought-tolerant and have dimorphic root systems, they do not shift back from deep water sources to shallow soil water when soil water availability increases following precipitation events at the end of the growing season.

Respiratory rate-oxygenation index on the 3rd day is the best predictor of treatment failure in COVID-19 patients.

Predictors of outcomes are essential to identifying severe COVID-19 cases and optimizing treatment and care settings. The respiratory rate-oxygenation (ROX) index, originally introduced for predicting the failure of non-invasive support in acute hypoxemic respiratory failure (AHRF), has not been extensively studied over time during hospitalization. This multicenter prospective observational study analyzed COVID-19-related AHRF patients admitted to eight Italian hospitals during the second pandemic wave. The study assessed the ROX index using receiver operator characteristic curves and areas under the curve with 95% confidence intervals to predict treatment failure, defined as endotracheal intubation (ETI) or death. A total of 227 patients (69.2% males) were enrolled, with a median arterial partial pressure of oxygen (PaO2)/fraction of inspired oxygen (FiO2) ratio at admission of 248 (interquartile range: 170-295). Nearly one-third (29.5%) required ETI or died during hospitalization. Those who experienced treatment failure were older (median age 70 versus 61 years, p<0.001), more likely to be current or former smokers (8.5% versus 6.4% and 42.4% versus 25.5%, p=0.039), had a higher prevalence of cardiovascular diseases (74.6% versus 46.3%, p<0.001), and had a lower PaO2/FiO2 ratio at presentation (median 229 versus 254, p=0.014). Gender, body mass index, and other comorbidities showed no significant differences. In patients who failed treatment, the ROX index was higher at presentation and worsened sharply by days 3 and 4. Conversely, in patients who survived without requiring ETI, the ROX index remained stable and reduced after 5-6 days. The ROX index's predictive ability improved notably by the third day of hospitalization, with the best cut-off value identified at 8.53 (sensitivity 75%, specificity 68%). Kaplan-Meier curves indicated that a ROX index of 8.53 or lower on days 1, 2, or 3 was associated with a higher risk of treatment failure. Thus, a single ROX index assessment on day 3 is more informative than its variability over time, with values of 8.53 or lower predicting non-invasive respiratory support failure in hospitalized COVID-19 patients.

The Study of Post-Harvest Processing and Handling of Residues From Plants Grown Primarily For Agronomics: Soybean Stalk, Corn Stover, Tomato Vine, Cucumber, Eggplant, and Summer Squash

Information on post-harvest handling of the crop is critical to the development of new or improved plant species and traits. This paper presents a comprehensive study of the grinding characteristics and handling properties of a number of crop residues under agronomic studies. We used a laboratory-scale knife mill connected to an in-line power meter to investigate the specific energy of size reduction for each crop. The summer squash sample yielded the smallest mean particle size upon grinding (P= 0.05). The results indicate a significant correlation between the Carbon to Oxygen (C/O) ratio and the Gross Calorific Value (GCV), ash, lignin content, and net specific grinding energy consumption (NSGEC) of the samples. Among agricultural residues, the soybean stalk sample, with the highest C/O ratio (0.96), exhibited the highest GCV (17.5 MJ/kg, db) and NSGEC (31.7 kWh/t), while the summer squash sample, with the lowest C/O ratio (0.46), showed the lowest GCV (13.6 MJ/kg, db) and NSGEC (5.1 kWh/t). The flowability of the ground biomass samples varied, with cucumber showing the best free flow properties. The results also showed that there is a significant positive correlation between the lignin content and NSGEC of all samples (p= 0.05).

Laser-induced plasma analysis of ammonia-oxygen and ammonia-oxygen-enriched-air flames at elevated pressures

This study employed Laser-induced breakdown spectroscopy (LIBS) to measure the fuel-oxidizer ratio (FOR) of ammonia combustion with oxygen-enriched air and pure oxygen flames at elevated pressures (100 - 300 kPa). The correlations between the spectral line intensity ratios of nitrogen (N), hydrogen (H), oxygen (O), and equivalence ratio were used to quantify the FOR of flames at various pressures. The effect of pressure on the stability and precision of the calibration profiles for the elemental intensity ratios in flames was investigated. It was observed that the H/O correlation decreases with pressure increase for both ammonia flames. N/O correlations decrease with elevated pressure for the ammonia-oxygen flame. Furthermore, the nitrogen (NII) spectral emission lines at 568 nm and 595 nm were used to estimate the plasma temperature, while the hydrogen (Hα) line at 656 nm was used for electron number density measurements.

Predicting Survival Status in COVID-19 Patients: Machine Learning Models Development with Ventilator-Related and Biochemical Parameters from Early Stages: A Pilot Study.

Objective: Coronavirus disease 2019 (COVID-19) can cause intubation and ventilatory support due to respiratory failure, and extubation failure increases mortality risk. This study, therefore, aimed to explore the feasibility of using specific biochemical and ventilator parameters to predict survival status among COVID-19 patients by using machine learning. Methods: This study included COVID-19 patients from Taipei Medical University-affiliated hospitals from May 2021 to May 2022. Sequential data on specific biochemical and ventilator parameters from days 0-2, 3-5, and 6-7 were analyzed to explore differences between the surviving (successfully weaned off the ventilator) and non-surviving groups. These data were further used to establish separate survival prediction models using random forest (RF). Results: The surviving group exhibited significantly lower mean C-reactive protein (CRP) levels and mean potential of hydrogen ions levels (pH) levels on days 0-2 compared to the non-surviving group (CRP: non-surviving group: 13.16 ± 5.15 ng/mL, surviving group: 10.23 ± 5.15 ng/mL; pH: non-surviving group: 7.32 ± 0.07, survival group: 7.37 ± 0.07). Regarding the survival prediction performanace, the RF model trained solely with data from days 0-2 outperformed models trained with data from days 3-5 and 6-7. Subsequently, CRP, the partial pressure of carbon dioxide in arterial blood (PaCO2), pH, and the arterial oxygen partial pressure to fractional inspired oxygen (P/F) ratio served as primary indicators in survival prediction in the day 0-2 model. Conclusions: The present developed models confirmed that early biochemical and ventilatory parameters-specifically, CRP levels, pH, PaCO2, and P/F ratio-were key predictors of survival for COVID-19 patients. Assessed during the initial two days, these indicators effectively predicted the likelihood of successful weaning of from ventilators, emphasizing their importance in early management and improved outcomes in COVID-19-related respiratory failure.

NO Emission Characteristics of Pulverized Coal Combustion in O2/N2 and O2/H2O Atmospheres in a Drop-Tube Furnace.

Oxy-steam combustion is a new oxy-fuel combustion technology. This paper focuses on the NO emission characteristics during the combustion of SF (Shen Fu) coal in O2/N2 and O2/H2O mixtures. Experiments were performed in a drop-tube furnace. Combustion tests were carried out in O2/N2 and O2/H2O atmospheres for various O2 concentrations (21%, 30%, 40%, and 60%) at different temperatures (1173 K, 1273 K, and 1373 K). In addition, combustion experiments at different excess oxygen ratios (λ) were conducted in O2/N2 and O2/H2O atmospheres. The influences of the atmosphere, oxygen concentration, temperature, and excess oxygen ratio on NO emissions were analyzed. The results show that the NO concentrations of SF coal combustion in the 21% O2/79% H2O atmosphere were much lower than those in the 21% O2/79% N2 atmosphere at the three temperatures considered. This was because a large amount of NO was decomposed during the SF coal combustion in the O2/H2O atmospheres. The reasons for the decomposition of NO include the selective non-catalytic reaction (SNCR) mechanism and char's important role as a catalyst for the destruction of NO, either directly or by reacting with CO or H2. In oxy-steam combustion, the NO concentrations significantly increased with the increase in the oxygen concentration from 21 vol.% to 60 vol.% and the temperature from 1173 K to 1373 K. The excess oxygen ratio (λ) slightly impacted the NO emissions in the O2/H2O atmosphere.

Splanchnic and cerebral oxygenation during cyclic phototherapy in preterm infants with hyperbilirubinemia

Cyclic phototherapy (cPT) can achieve a reduction in total serum bilirubin comparable to that achieved with standard continuous PT in preterm infants. Our aim was to assess the effect of cPT on splanchnic (rSO2S) and cerebral (rSO2C) oxygenation measured by near-infrared spectroscopy (NIRS). We prospectively studied 16 infants with a gestational age of 25–34 weeks with hyperbilirubinemia requiring PT. Splanchnic regional oxygenation (rSO2S), oxygen extraction fraction (FOES), and cerebro-splanchnic oxygenation ratio (CSOR) were recorded before, during, and after cPT discontinuation. We found that rSO2S, FOES, and CSOR did not change during the study period. The overall duration of single or multiple courses of PT was 6.5 (6.0–13.5) h, but by cycling PT, the actual exposure was 3.0 (1.5–4.9) h. Twelve patients (75%) required 15 min/h cPT, and four (25%) required prolonging cPT to 30 min/h. None of the patients developed enteral feeding intolerance.Conclusions: cPT treatment of hyperbilirubinemia in preterm infants does not affect splanchnic oxygenation or intestinal oxygen blood extraction, likely due to the short exposure to PT light, and it could contribute to decreasing the risk of feeding intolerance.What is Known:• The assumption that phototherapy (PT) is innocuous with no serious adverse effects has been questioned.• Cyclic phototherapy (cPT) can achieve a reduction in total serum bilirubin comparable to that achieved with standard continuous PT in preterm infants.What is New:• Splanchnic and cerebral oxygenation measured by near-infrared spectroscopy did not change during KMC.• cPT can contribute to decrease the risk of feeding intolerance likely due to the short exposure to PT light.

Serum β2-microglobulin as an independent risk factor for mortality in patients with acute respiratory distress syndrome caused by bacterial infection

Acute respiratory distress syndrome (ARDS) is a heterogeneous disease with extremely high mortality. We hypothesized that the serum β2-microglobulin (β2MG) level would be elevated and be an independent risk factor for 28-day mortality in patients with ARDS caused by bacterial infection. We retrospectively enrolled 257 patients with ARDS caused by bacterial infection from January 1, 2015 to February 28, 2021. Patients were followed for up to 28 days and were divided into a survival group and non-survival group according to their clinical outcomes. The serum β2MG levels and other clinical data were collected. The relationship between β2MG levels and 28-day mortality was explored by performing a Cox regression analysis adjusted for age, updated Charlson comorbidity index, disorders of consciousness, septic shock, albumin level, cardiac troponin I level, procalcitonin level, lactic acid level, prothrombin time, partial pressure of arterial oxygen/fraction of inspired oxygen ratio, estimated glomerular filtration rate and Sequential Organ Failure Assessment. In this cohort, 96 patients died in 28 days, yielding a 28-day mortality of 37.4%. The median level of serum β2MG for all enrolled patients was 4.7 (interquartile range [IQR]: 2.9–8.5) mg/L. Higher β2MG levels were significantly associated with 28-day mortality when the β2MG level was analysed as a continuous variable (hazard ratio [HR]: 1.053; 95% confidence interval [CI] 1.004–1.104; P = 0.032) and when it was categorized into tertiles (HR: 3.241; 95% CI 1.180–8.905; P = 0.023). The β2MG level exhibited a high diagnostic accuracy for predicting 28-day mortality (area under the curve [AUC] = 0.732; 95% CI 0.673–0.785; sensitivity: 74.0%; specificity: 64.0%; P < 0.001). The level of serum β2MG is elevated and is an independent risk factor of 28-day mortality in patients with ARDS caused by bacterial infection.

Stable isotope analysis of Late Pleistocene mammalian teeth from western, central, and north-central India and the associated Palaeolithic archaeology of the Indian Subcontinent

The oxygen (δ18O) and carbon (δ13C) ratios in bioapatite from dental tissues of fossil mammals are well-established proxies for climatic conditions and dietary patterns. In the present study, a total of 24 Late Pleistocene mammalian teeth belonging to Cervid, Bovid, Suid, Hippopotamid, Canid, Equid from Gopnath in Gujarat, ten separate localities from the Narmada Basin, and one in Son River Basin, India were analysed for δ13C and δ18O values to understand palaeoclimatic conditions and associated dietary habits between marine isotope stages (MIS) 5 and 3 as estimated from stratigraphic and archaeological record. The δ13C values in the samples of Gopnath, Narsinghpur and Doma range from −3.1 to 2.3 ‰, −3.2 to 1.3 ‰, and −2.0 ‰, respectively. The higher δ13C values in these specimens suggest a diet based predominantly on C4 plants. On the other hand, a relatively lower and large range of δ13C values from Nehlai (−11.1 to −3.5 ‰) suggests a predominately C3 to mixed C3-C4 diet. The δ18O values in Gopnath, Nehlai, Narsinghpur and Doma are −4.1 to −3.1 ‰, −4.7 to −2.1 ‰, −4.0 to −1.9 ‰ and −5.8 ‰, respectively. The relatively lower δ18O value points towards humid climatic conditions and the relatively higher δ18O values suggest relatively arid climatic conditions. The regional contexts are dominated by Late Pleistocene geological records predominantly associated with Middle Palaeolithic evidence, and the preliminary isotope results indicate that contemporary hominin groups occupied warm and semi-humid environments. This study attempts to examine the Late Pleistocene environments and hominin adaptations across western, central, and north-central India on a comprehensive scale.

Leg cycling efficiency is unaltered in healthy aging regardless of sex or training status.

Muscular efficiency during exercise has been used to interrogate aspects of human muscle energetics, including mitochondrial coupling and biomechanical efficiencies. Typically, assessments of muscular efficiency have involved graded exercises. Results of previous studies have been interpreted to indicate a decline in exercise efficiency with aging owing to decreased mitochondrial function. However, discrepancies in variables such as exercise stage duration, cycling cadence, and treadmill walking mechanics may have affected interpretations of results. Furthermore, recent data from our lab examining the ATP to oxygen ratio (P:O) in mitochondrial preparations isolated from NIA mouse skeletal muscle showed no change with aging. Thus, we hypothesized that delta efficiency (Δ€) during steady-rate cycling exercise would not be altered in older healthy subjects compared with young counterparts regardless of biological sex or training status. Young (21-35 yr) and older (60-80 yr) men (n = 21) and women (n = 20) underwent continual, progressive leg cycle ergometer tests pedaling at 60 RPM for three stages (35, 60, 85 W) lasting 4 min. Δ€was calculated as: (Δ work accomplished/Δ energy expended). Overall, cycling efficiencies were not significantly different in older compared with young subjects. Similarly, trained subjects did not exhibit significantly different exercise efficiencies compared to untrained. Moreover, there were no differences between men and women. Hence, our results obtained on healthy young and older subjects are interpreted to mean that previous reports of decreased efficiency in older individuals were attributable to metabolic or biomechanical comorbidities, not aging per se.NEW & NOTEWORTHY Muscular power is reduced, but the efficiency of movement is unaltered in healthy aging.

Risk factors for poor outcome in adult patients with respiratory syncytial virus infection evaluated at the emergency department.

Respiratory syncytial virus-associated acute respiratory infection (RSV-ARI) constitutes an emerging cause of morbidity in the adult population. The present retrospective study was aimed at identifying factors predictive of poor outcome that may be assessed at the first evaluation in the Emergency Department (ED). We included 275 adult patients with laboratory-confirmed RSV-ARI that required hospital admission from the ED between January 2018 and December 2019. Poor outcome (composite of progression to high-flow oxygen therapy, non-invasive or invasive mechanical ventilation, or intensive care unit admission, and/or 30-day all-cause mortality) occurred in 31 patients (11.2%). Immunosuppression was present in 59 patients (21.5%). Although bacterial co-infection was rare, antibiotic therapy was commonly initiated. Ribavirin was administered in 10 patients. Cognitive impairment (odds ratio [OR]: 2.452; 95% confidence interval [CI]: 0.990-6.072), concurrent oral anticoagulation (OR: 3.099; 95 CI: 1.287-7.464) and a pulse oximetry oxygen saturation to fraction of inspired oxygen ratio (SpO2/FiO2) ratio <382 at ED admission (OR: 3.013; 95 CI: 1.306-6.950) were independent risk factors for poor outcome, whereas influenza vaccination in the current season was protective (OR: 0.324; 95% CI: 0.138-0.763). Various factors easily available at the ED are useful for early risk stratification in adult patients with RSV-ARI.

Production of GeOx Films at Different Oxygen Flow Rates and Different Annealing Temperatures and Examination of Energy Band Gaps using Kubelka Munk Method

In this study, GeOx films were grown on silicon substrates using the Radio Frequency (RF) Magnetron Sputtering method at different oxygen flow rates and annealing temperatures. The films were produced at a substrate temperature of 250°C and a working pressure of 13 mTorr. Subsequently, the films were annealed at temperatures of 300°C, 500°C, 600°C, 700°C, 900°C, and 1000°C. Total and diffuse reflection measurements were performed to investigate the optical properties of the films. Energy band gaps were determined using diffuse reflection measurements and they were calculated using the Kubelka-Munk method. It was observed that the energy band gap increased with increasing oxygen ratio. Additionally, annealing temperatures were found to cause changes in the energy band gaps.

Goal-Directed Fluid Therapy Using Pulse Pressure Variation in Thoracic Surgery Requiring One-Lung Ventilation: A Randomized Controlled Trial.

Background: Intraoperative fluid management based on pulse pressure variation has shown potential to reduce postoperative pulmonary complications (PPCs) and improve clinical outcomes in various surgical settings. However, its efficacy and safety have not been assessed in patients undergoing thoracic surgery with one-lung ventilation. Methods: Patients scheduled for pulmonary lobectomy using uniportal video-assisted thoracic surgery approach were randomly assigned to two groups. In the PPV group, fluid administration was guided by the pulse pressure variation parameter, while in the near-zero group, it was guided by conventional hemodynamic parameters. The primary outcome was the partial pressure of oxygen (PaO2)/ fraction of inspired oxygen (FiO2) ratio 15 min after extubation. The secondary outcomes included extubation time, the incidence of postoperative pulmonary complications in the first three postoperative days, and the length of hospital stay. Results: The PaO2/FiO2 ratio did not differ between the two groups (364.48 ± 38.06 vs. 359.21 ± 36.95; p = 0.51), although patients in the PPV group (n = 44) received a larger amount of both crystalloids (1145 ± 470.21 vs. 890 ± 459.31, p = 0.01) and colloids (162.5 ± 278.31 vs 18.18 ± 94.68, p = 0.002) compared to the near-zero group (n = 44). No differences were found in extubation time, type and number of PPCs, and length of hospital stay. Conclusions: PPV-guided fluid management in thoracic surgery requiring one-lung ventilation does not improve pulmonary gas exchange as measured by the PaO2/FiO2 ratio and does not seem to offer clinical benefits. Additionally, it results in increased fluid administration compared to fluid management based on conventional hemodynamic parameters.

Influence of Oxygen and Nitrogen Flow Ratios on the Microstructure Evolution in AlCrTaTiZr High-Entropy Oxynitride Films

This study explores the influence of oxygen and nitrogen flow ratios on the microstructure and mechanical properties of AlCrTaTiZr high-entropy oxynitride films. Oxygen flow rates (0%–0.75%) were adjusted while maintaining a fixed nitrogen flow ratio (RN = 15%) to fabricate films with similar compositions. The results show that increasing oxygen flow enhanced hardness through solid solution strengthening and grain refinement, though excessive oxygen caused an amorphous structure and reduced hardness. After annealing at 900 °C, the hardness of all films was further increased. The film with a nitrogen flow ratio 40 times higher than oxygen exhibited the highest hardness of 21.8 GPa, along with superior mechanical performance. These findings highlight the potential of high-entropy oxynitride films for applications requiring high wear resistance and adhesion.

Reduced partition function ratios of iron, magnesium, oxygen, and silicon isotopes in olivine: A GGA and GGA + U study

Olivine, typically occurring as a forsterite-fayalite solid solution, is a major rock-forming mineral in mafic and ultramafic igneous rocks, and it is important for understanding the genesis, evolution, and alteration of its host rocks. In this study, both GGA and GGA + U methods were employed to calculate the reduced partition function ratios of Fe, Mg, O, and Si isotopes for the forsterite-fayalite solid solution, aiming to elucidate the impacts of Fe content and Hubbard U correction on the isotope fractionation signatures of Fe, Mg, O, and Si in olivine. On the whole, the βFe-factor, βMg-factor, βO-factor, and βSi-factor decrease with increasing Fe content. The linear correlations between β-factors and bond lengths obtained from GGA + U are better compared to those from GGA. The Hubbard U correction can increase the βFe-factor. When Fe/(Fe + Mg) ≤ 1/8, ≤ 1/2, and ≤ 1/2, the effect of Hubbard U correction on βMg-factor, βO-factor, and βSi-factor can be considered negligible, respectively, suggesting that the βMg-factor, βO-factor, and βSi-factor of Fe-bearing olivine calculated using GGA + U and those of Fe-free minerals calculated using GGA can be combined to derive 103lnα and trace geological processes. Furthermore, equilibrium fractionation of Fe, Mg, O, and Si isotopes between olivine and other minerals, including troilite, clinopyroxene, and garnet, were also calculated. Our results are helpful in interpreting the observed data regarding Fe, Mg, O, and Si isotopic compositions of olivine, leading to a comprehensive understanding of relevant geological processes.

Epidemiology of acute hypoxaemic respiratory failure in Australian and New Zealand intensive care units during 2005-2022. A binational, registry-based study.

Acute hypoxaemic respiratory failure (AHRF) is a common reason for intensive care unit (ICU) admission. However, patient characteristics, outcomes, and trends over time are unclear. We describe the epidemiology and outcomes of patients with AHRF over time. In this binational, registry-based study from 2005 to 2022, we included all adults admitted to an Australian or New Zealand ICU with an arterial blood gas within the first 24h of ICU stay. AHRF was defined as a partial pressure of oxygen/inspired oxygen ratio (PaO2/FiO2) ≤ 300. The primary outcome was adjusted in-hospital mortality, categorised based on PaO2/FiO2 (mild: 200-300, moderate: 100-200, and severe < 100, and non-linearly). We investigated how adjusted mortality evolved based on temporal trends (by year of admission), sex, age, admission diagnosis and the receipt of mechanical ventilation. Of 1,560,221 patients, 826,106 (52.9%) were admitted with or developed AHRF within the first 24h of ICU stay. Of these 826,106 patients, 51.4% had mild, 39.3% had moderate, and 9.3% had severe AHRF. Compared to patients without AHRF (5.3%), patients with mild (8%), moderate (14.2%) and severe (29.9%) AHRF had higher in-hospital mortality rates. As PaO2/FiO2 ratio decreased, adjusted in-hospital mortality progressively increased, particularly below an inflection point at a PaO2/FiO2 ratio of 200. The adjusted in-hospital mortality for all patients decreased over time (13.3% in 2005 to 8.2% in 2022), and this trend was similar in patients with and without AHRF. The healthcare burden due to AHRF may be larger than expected, and mortality rates remain high in severe AHRF. Although mortality has decreased over time, this may reflect improvements in ICU care in general, rather than specifically in AHRF. More research is required to earlier identify AHRF and stratify these patients at risk of deterioration early, and to validate our findings.

Effects of Diethoxymethylsilane/Helium Flow Rate Ratio on Low-k Films Deposited by Plasma-Enhanced Chemical Vapor Deposition

As the semiconductor industry has continuously reduced the integrated circuit (IC) chip size, a resistance-capacitance (RC) delay emerged, causing deterioration of the chip performance. To reduce the RC delay, low dielectric constant (low-k) films with suitable mechanical strengths have been adopted as intermetal dielectrics (IMDs). In this study, low-k plasma-polymerized diethoxymethylsilane (ppDEMS) films were fabricated by plasma-enhanced chemical vapor deposition of the DEMS precursor with a flow rate ratio of the DEMS precursor to helium (He) carrier gas (DEMS/He FRR) as a key parameter. As the DEMS/He FRR increased, the refractive index was reduced from 1.401 to 1.386, and the k value decreased from 2.77 to 2.10. From high-resolution scans of C1s, O1s, and Si2p peaks of X-ray photoelectron spectroscopy, the carbon contents increased, and the oxygen contents decreased, along with a decrease in the film density. With the increased DEMS/He FRR, hardness decreased from 2.5 to 1.8 GPa, and elastic modulus decreased from 17.08 to 11.50 GPa. Leakage current densities for all the ppDEMS films were less than 10−7 A cm−2 at 1 MV cm−1. The ppDEMS films could be suggested as the IMDs according to their electrical and mechanical performance.

A tailored machine learning approach for mortality prediction in severe COVID-19 treated with glucocorticoids.

<sec><title>BACKGROUND</title>The impact of severe COVID-19 pneumonia on healthcare systems highlighted the need for accurate predictions to improve patient outcomes. Despite the established efficacy of glucocorticoids (GCs), variable patient responses are observed, and the existing clinical scores are limited in predicting non-responders. We propose a machine learning (ML) based approach to predict mortality in COVID-19 pneumonia treated with GCs.</sec><sec><title>METHODS</title>This is an ML-driven retrospective analysis involving 825 patients. We leveraged XGBoost to select the most appropriate features from the initial 52, including clinical and laboratory data. Six different ML techniques were compared. Shapley additive explanation (SHAP) values were used to describe the influence of each feature on classification. Internal validation was performed.</sec><sec><title>RESULTS</title>Nine key predictors of death were identified: increasing C-reactive protein (CRP), decreasing arterial partial pressure of oxygen to fraction of inspired oxygen ratio (PaO₂/FiO₂), age, coronary artery disease, invasive mechanical ventilation, acute renal failure, chronic heart failure, PaO₂/FiO₂ earliest value, and body mass index. Random forest achieved the highest test area under the receiver operating characteristic curve at 0.938 (95% CI 0.903-0.969). SHAP values highlighted age and PaO₂/FiO₂ improvement as the most influential features; the latter showed a higher impact than CRP reduction over time.</sec><sec><title>CONCLUSION</title>The proposed ML algorithm effectively predicts the risk of hospital death in COVID-19 pneumonia patients undergoing GCs. This approach can be adapted to datasets measuring similar clinical variables.</sec>.