High Oxygen Partial Pressure Research Articles

Serum Cystatin C Level Monitoring for Intervention Opportunity of CBP in Children with Severe Sepsis.

Objective The aim of this study is to investigate the instruction value of the serum cystatin C (Cys C) level monitoring for intervention opportunity of continuous blood purification technology (CBP) in children with severe sepsis. Methods 67 children with severe sepsis in the pediatric intensive care unit (PICU) with CBP treatment were retrospectively selected from May 2016 to April 2020. According to the time intervals between the time point of serum Cys C level began to increase (>15 mg/L) and the time point of CBP began, all children were divided into group A (<24 h, 29 cases), group B (24–48 h, 22 cases), and group C (>48 h, 16 cases). The children's general characteristics, vital signs, biochemical parameters, acute physiology and chronic health evaluation (APACHE II), and sequential organ failure assessment (SOFA) scores were evaluated. The influence factors of prognosis of children with severe sepsis were analyzed by multivariate regression analysis. Results The intervals between the time point of PICU hospitalization and the time point of CBP began and the times of CBP in group A were significantly more than those in group B and C (P < 0.05). There was no statistically significant duration of CBP among three groups (P > 0.05). After follow-up of 28 d, there was no significant difference on the occurrence of coagulation disorders and hypovolemic shock induced by CBP among three groups (P > 0.05). However, the mortality of children in group A was lower than that in group C (P < 0.05). Children in group A had lower APACHE II scores, SOFA scores, serum K+, blood urea nitrogen (BUN), serum creatine (SCr), partial pressure of carbon dioxide (PCO2), and higher partial pressure of oxygen (PO2) than those of children in group C after CBP. (P < 0.05). SOFA scores ≥5 after CBP treatment and the time intervals between the time point of serum Cys C level began to increase (>15 mg/L) and the time point of CBP began ≥24 h were the independent influence factors on the prognosis by multivariate regression analysis. Conclusion There are significant evidences that continuous blood purification technology within 24 h of serum Cys C level may better control the condition of children with severe sepsis.

Reset First Resistive Switching in Ni1−xO Thin Films as Charge Transfer Insulator Deposited by Reactive RF Magnetron Sputtering

Reset-first resistive random access memory (RRAM) devices were demonstrated for off-stoichiometric Ni1−xO thin films deposited using reactive sputtering with a high oxygen partial pressure. The Ni1−xO based RRAM devices exhibited both unipolar and bipolar resistive switching characteristics without an electroforming step. Auger electron spectroscopy showed nickel deficiency in the Ni1−xO films, and X-ray photoemission spectroscopy showed that the Ni3+ valence state in the Ni1−xO films increased with increasing oxygen partial pressure. Conductive atomic force microscopy showed that the conductivity of the Ni1−xO films increased with increasing oxygen partial pressure during deposition, possibly contributing to the reset-first switching of the Ni1−xO films.

Changing the oxygen reaction mechanism in composite electrodes by the addition of ionic- or ambipolar-conducting phases: Series or parallel pathways

In this work, we conduct a systematic investigation of composite oxygen electrodes for Solid Oxide Cells (SOCs) based on the recently emerging misfit calcium cobaltite material, “Ca3Co4O9+δ” – C349. Its electrochemical performance is shown to be limited by its low intrinsic level of ionic conductivity, thus, requiring the addition of an ionic-conducting composite phase. In this respect, Ce0.8Gd0.2O2-δ (CGO) is the state-of-the-art choice due to its excellent ionic conductivity. Nonetheless, little attention has been given to the use of alternative ionic phases, such as Ce0.8Pr0.2O2-δ, which also offer minor levels of p-type conductivity. Therefore, we try to elucidate the influence of this minor electronic component in this phase, on the resultant oxygen reaction mechanism of the composite electrode. We demonstrate that a preferential series pathway for the oxygen reaction occurs in the CGO-based electrode, performing better at high temperatures and low oxygen partial pressures. Conversely, the CPO-based electrode presents superior performance under highly oxidising conditions and at low temperatures, related to an increasing importance of possible parallel reaction pathways. The results are supported by a detailed mechanistic study, based on a Distribution Function of Relaxation Times (DFRT) analysis, allowing clarification of potential mechanistic models for both electrodes.

The effects of polarisation on the performance of the Ba2Co9O14–Ce0.8Gd0.2O2- composite electrode for fuel cells and electrolysers

The potential of the [BaCoO3]n [BaCo8O11] family as a cathode for solid oxide fuel cells (SOFCs) or as an anode for solid oxide electrolyser cells (SOECs) is investigated via structural, microstructural and electrochemical characterisation. The crystallographic structure of the n = 1 member compound, Ba2Co9O14 (BCO), exhibits rhombohedral symmetry and presents a microstructure consisting of large platelets. Overall, the electrochemical performance of the Ba2Co9O14/Ce0.8Gd0.2O2-δ (BCO/CGO-20) composite electrode is found to be enhanced under cathodic polarisation, while becoming impaired under anodic polarisation. The latter behaviour may result from the high local oxygen partial pressures upon increasing the applied anodic polarisation that lead to a depletion of oxygen vacancies at the electrode/electrolyte interface, thus, decreasing the ionic conductivity as well as electrocatalytic activity of this interface. This work, therefore, provides the first electrochemical analysis of the performance of BCO-based electrodes under applied polarisation conditions for SOFC and SOEC applications, and highlights the higher potential of this compound as a cathode material for intermediate-temperature solid oxide fuel cells.

Hyperoxemia in postsurgical sepsis/septic shock patients is associated with reduced mortality

BackgroundDespite growing interest in treatment strategies that limit oxygen exposure in ICU patients, no studies have compared conservative oxygen with standard oxygen in postsurgical patients with sepsis/septic shock, although there are indications that it may improve outcomes. It has been proven that high partial pressure of oxygen in arterial blood (PaO2) reduces the rate of surgical-wound infections and mortality in patients under major surgery. The aim of this study is to examine whether PaO2 is associated with risk of death in adult patients with sepsis/septic shock after major surgery.MethodsWe performed a secondary analysis of a prospective observational study in 454 patients who underwent major surgery admitted into a single ICU. Patients were stratified in two groups whether they had hyperoxemia, defined as PaO2 > 100 mmHg (n = 216), or PaO2 ≤ 100 mmHg (n = 238) at the day of sepsis/septic shock onset according to SEPSIS-3 criteria maintained during 48 h. Primary end-point was 90-day mortality after diagnosis of sepsis. Secondary endpoints were ICU length of stay and time to extubation.ResultsIn patients with PaO2 ≤ 100 mmHg, we found prolonged mechanical ventilation (2 [8] vs. 1 [4] days, p < 0.001), higher ICU stay (8 [13] vs. 5 [9] days, p < 0.001), higher organ dysfunction as assessed by SOFA score (9 [3] vs. 7 [5], p < 0.001), higher prevalence of septic shock (200/238, 84.0% vs 145/216) 67.1%, p < 0.001), and higher 90-day mortality (37.0% [88] vs. 25.5% [55], p = 0.008). Hyperoxemia was associated with higher probability of 90-day survival in a multivariate analysis (OR 0.61, 95%CI: 0.39–0.95, p = 0.029), independent of age, chronic renal failure, procalcitonin levels, and APACHE II score > 19. These findings were confirmed when patients with severe hypoxemia at the time of study inclusion were excluded.ConclusionsOxygenation with a PaO2 above 100 mmHg was independently associated with lower 90-day mortality, shorter ICU stay and intubation time in critically ill postsurgical sepsis/septic shock patients. Our findings open a new venue for designing clinical trials to evaluate the boundaries of PaO2 in postsurgical patients with severe infections.

Effects of Oxygen Partial Pressure and Substrate Temperature on the Structure and Morphology of Sc and Y Co-Doped ZrO2 Solid Electrolyte Thin Films Prepared via Pulsed Laser Deposition.

Scandium (Sc) and yttrium (Y) co-doped ZrO2 (ScYSZ) thin films were prepared on a SiO2-Si substrate via pulsed laser deposition (PLD) method. In order to obtain good quality thin films with the desired microstructure, various oxygen partial pressures ( from 0.01 Pa to 10 Pa and substrate temperatures (Ts) from 25 °C to 800 °C were investigated. X-ray diffraction (XRD) patterns results showed that amorphous ScYSZ thin films were formed at room substrate temperature while cubic polycrystalline thin films were obtained at higher substrate temperatures (Ts = 200 °C, 400 °C, 600 °C, 800 °C). Raman spectra revealed a distinct Raman shift at around 600 cm−1 supporting a cubic phase. However, a transition from cubic to tetragonal phase can be observed with increasing oxygen partial pressure. Photoemission spectroscopy (PES) spectra suggested supporting analysis that more oxygen vacancies in the lattice can be observed for samples deposited at lower oxygen partial pressures resulting in a cubic structure with higher dopant cation binding energies as compared to the tetragonal structure observed at higher oxygen partial pressure. On the other hand, dense morphologies can be obtained at lower (0.01 Pa and 0.1 Pa) while more porous morphologies can be obtained at higher (1.0 Pa and 10 Pa).

Corrosion mechanism of magnesia-chrome and alumina-chrome refractories in E-scrap smelting

Pyrometallurgical processes have been widely recognised as the preferred technology for E-scrap recycling, and E-scrap smelting is usually accompanied by the formation of high-Al2O3-content slag. However, this slag can cause problems, such as refractory wear and even accelerated failure. Therefore, the corrosion mechanism of magnesia-chrome and alumina-chrome refractories in contact with FeOx-SiO2-CaO-Al2O3 smelting slag was experimentally studied in the range of 1300–1400 °C, in air (pO2 = 0.21 atm) and at pO2 = 10-7 atm. The results showed that refractory-component dissolution and new phases formation were the major causes of refractory degradation. The dissolution of the refractory components increased along with both increasing temperature and decreasing Al2O3 concentration in the initial slag. When decreasing the pO2, the dissolution of MgO and Al2O3 into the slag slowed down. New phases such as forsterite, anorthite, and spinel were detected at the interface between the slag and the bulk refractory. The formation of forsterite accelerated the refractory wear, whereas the newly formed (MgO,FeO)·(Cr2O3,Fe2O3,Al2O3) spinel phase acted as a protective layer against further corrosion. A lower Al2O3 concentration in the slag and a higher smelting temperature both densified the formed spinel layer. Additionally, a high oxygen partial pressure was beneficial to the formation of spinel in the magnesia-chrome refractory corrosion experiments. However, a low oxygen partial pressure was favourable for the formation of spinel on the surface of the alumina-chrome refractory materials. This study provides useful information for designing refractory materials and optimizing the processing parameters of E-scrap smelting.

Novel process for synthesizing fused mullite from titanium-rich medium/low grade or waste bauxite

This paper introduces a novel process to efficiently utilize medium-/low-grade or waste bauxite. The medium-/low-grade or waste bauxite is usually rich in iron oxide (total iron oxide content≥8%) or titanium dioxide (titanium dioxide content≥5%). In addition, both iron oxide and titanium dioxide have higher contents than typical bauxite (total iron oxide + titanium dioxide contents≥20%). It is difficult to obtain mullite with excellent properties using the process of beneficiation and sintering synthesis. Based on different reduction temperatures of K2O, Na2O, FeOx, SiO2 and TiO2, the reduction of K2O, Na2O and FeOx was set as the reduction end point. While SiO2 start to be reduced, TiO2 was unstable under high temperature and low oxygen partial pressure. The reason for the final formation of Ti2O3 in the TiO2→TiO2-x transformation process was analysed, and the morphology of the multiphase material obtained from the Ti2O3–3Al2O3·2SiO2 solid solution was characterized. The reaction model was established.

Li-Ion-Trapping-Induced Degradation Mechanism of Colored State in Tungsten Oxide Electrochromic Films

Aiming to investigate the degradation mechanism of their colored states, tungsten oxide films with different oxygen/tungsten ratio were prepared by direct current reactive magnetron sputtering through adjusting the oxygen partial pressure. After a long-term cycling test, the sample prepared under low oxygen partial pressure (LO#) showed an excellent cycle stability which its optical modulation amplitude remains stable at 23.6%, while the one prepared under high oxygen partial pressure (HO#) exhibited an obvious degradation process of the colored state, leading to the optical modulation amplitude decreased from 34.0% to 18.6% accompanied with a decay of ionic diffusion coefficient and electrode potential, but having an improved coloration efficiency. Combined with various structural characterizations, including SEM, LA-ICP-MS, Raman and XPS, we demonstrate such colored state degradation is attributed to the so-called shallow trap, which corresponds to the irreversible and non-coloring reaction with interstitial oxygen during the insertion of Li+ cations forming superoxides (e.g. LiO2). All these findings not only offer a new insight into the improvement of cyclic stability based on ion-exchange, but also provide a valued information to understanding the physicochemical mechanisms of degradation in electrochromic materials.

Expression of transport proteins in the rete mirabile of european silver and yellow eel

BackgroundIn physoclist fishes filling of the swimbladder requires acid secretion of gas gland cells to switch on the Root effect and subsequent countercurrent concentration of the initial gas partial pressure increase by back-diffusion of gas molecules in the rete mirabile. It is generally assumed that the rete mirabile functions as a passive exchanger, but a detailed analysis of lactate and water movements in the rete mirabile of the eel revealed that lactate is diffusing back in the rete. In the present study we therefore test the hypothesis that expression of transport proteins in rete capillaries allows for back-diffusion of ions and metabolites, which would support the countercurrent concentrating capacity of the rete mirabile. It is also assumed that in silver eels, the migratory stage of the eel, the expression of transport proteins would be enhanced.ResultsAnalysis of the transcriptome and of the proteome of rete mirabile tissue of the European eel revealed the expression of a large number of membrane ion and metabolite transport proteins, including monocarboxylate and glucose transport proteins. In addition, ion channel proteins, Ca2+-ATPase, Na+/K+-ATPase and also F1F0-ATP synthase were detected. In contrast to our expectation in silver eels the expression of these transport proteins was not elevated as compared to yellow eels. A remarkable number of enzymes degrading reactive oxygen species (ROS) was detected in rete capillaries.ConclusionsOur results reveal the expression of a large number of transport proteins in rete capillaries, so that the back diffusion of ions and metabolites, in particular lactate, may significantly enhance the countercurrent concentrating ability of the rete. Metabolic pathways allowing for aerobic generation of ATP supporting secondary active transport mechanisms are established. Rete tissue appears to be equipped with a high ROS defense capacity, preventing damage of the tissue due to the high oxygen partial pressures generated in the countercurrent system.

Thin-film chemical expansion of ceria based solid solutions: laser vibrometry study

Abstract The chemical expansion of Pr0.1Ce0.9O2–δ (PCO) and CeO2–δ thin films is investigated in the temperature range between 600 °C and 800 °C by laser Doppler vibrometry (LDV). It enables non-contact determination of nanometer scale changes in film thickness at high temperatures. The present study is the first systematic and detailed investigation of chemical expansion of doped and undoped ceria thin films at temperatures above 650 °C. The thin films were deposited on yttria stabilized zirconia substrates (YSZ), operated as an electrochemical oxygen pump, to periodically adjust the oxygen activity in the films, leading to reversible expansion and contraction of the film. This further leads to stresses in the underlying YSZ substrates, accompanied by bending of the overall devices. Film thickness changes and sample bending are found to reach up to 10 and several hundred nanometers, respectively, at excitation frequencies from 0.1 to 10 Hz and applied voltages from 0–0.75 V for PCO and 0–1 V for ceria. At low frequencies, equilibrium conditions are approached. As a consequence maximum thin-film expansion of PCO is expected due to full reduction of the Pr ions. The lower detection limit for displacements is found to be in the subnanometer range. At 800 °C and an excitation frequency of 1 Hz, the LDV shows a remarkable resolution of 0.3 nm which allows, for example, the characterization of materials with small levels of expansion, such as undoped ceria at high oxygen partial pressure. As the correlation between film expansion and sample bending is obtained through this study, a dimensional change of a free body consisting of the same material can be calculated using the high resolution characteristics of this system. A minimum detectable dimensional change of 5 pm is estimated even under challenging high-temperature conditions at 800 °C opening up opportunities to investigate electro-chemo-mechanical phenomena heretofore impossible to investigate. The expansion data are correlated with previous results on the oxygen nonstoichiometry of PCO thin films, and a defect model for bulk ceria solid solutions is adopted to calculate the cation and anion radii changes in the constrained films during chemical expansion. The constrained films exhibit anisotropic volume expansion with displacements perpendicular to the substrate plane nearly double that of bulk samples. The PCO films used here generate high total displacements of several 100 nm’s with high reproducibility. Consequently, PCO films are identified to be a potential core component of high-temperature actuators. They benefit not only from high displacements at temperatures where most piezoelectric materials no longer operate while exhibiting, low voltage operation and low energy consumption.

High-Speed Growth of Epitaxial Rutile GeO2 Thin Film on (001) TiO2 Under Highly Oxygen-Rich Condition and Its Structural Analysis

Recently, rutile germanium dioxide (r-GeO2) has been proposed as a novel ultra-wide bandgap (UWBG) semiconductor with ambipolar dopability, high carrier mobilities, and a higher thermal conductivity than Ga2O3, in addition to its wide bandgap (4.68 eV). These excellent properties indicate that r-GeO2 can be utilized as high-performance bipolar devices with high breakdown voltage. On the other hand, although r-GeO2 is most stable phase at the ambient condition, fabrication of its thin film is reported to be quite difficult, owing to the existence of energetically deep meta-stable phases, namely, amorphous and quartz phase, and high vapor pressure of r-GeO2. In this study, we accomplished fabrication of (001)-oriented r-GeO2 thin films on (001) rutile titanium dioxide (r-TiO2) substrate with high growth rate (≧1 mm/h) by mist chemical vapor deposition (mist CVD). Moreover, we investigated the structural properties of r-GeO2 film by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques.First of all, bis [2-carboxyethylgermanium (IV)] sesquioxide (C6H10Ge2O7) as a precursor. To analyze the decomposition process of C6H10Ge2O7 and optimize the growth conditions, Thermogravimetry-Differential Thermal Analysis (TG-DTA) was conducted in aqueous vapor. By the TG-DTA, GeO2 was found to be synthesized from C6H10Ge2O7 at 553-783 ℃ in aqueous vapor. Therefore, we determined the growth temperature of r-GeO2 thin film to be 550-850 ℃. As shown in XRD 2q/w scan profile (Fig. 1), (001)-oriented r-GeO2 thin film was grown on (001) r-TiO2 substrate at growth temperature (T g) of 700-775 ℃. The growth rates of all the r-GeO2 films were found to be 1.2-1.7 mm/h, which were much higher than those grown by molecular beam epitaxy (MBE) (10 nm/h). Moreover, XRD F scan revealed that r-GeO2 thin film was epitaxially grown without rotational domains.It is considered that the higher growth rate by mist CVD compared to that by MBE is attributed to the lower desorption rate of GeO in mist CVD due to its highly oxygen-rich condition. In Fig. 2, we show the schematics of GeO desorption from the surface in (a) MBE and (b) mist CVD, inspired by Wang et al. In mist CVD, oxygen partial pressure is much higher (~760 Torr) than that in MBE (1×10- 6 Torr), resulting lower vapor pressure of GeO and lower desorption rate in mist CVD system. Higher oxygen partial pressure also suppresses oxygen vacancies in the film. Moreover, in mist CVD, oxygen was continuously supplied by water in the reaction area. Therefore, such highly oxygen-rich condition as seen in mist CVD is considered to contribute to high temperature growth and high growth rate.Cross-sectional TEM image and Selected Area Electron Diffraction (SAED) patterns at r-TiO2 substrate and the r-GeO2/r-TiO2 interface viewed along the <110> zone axis are shown in Fig. 3 (a), (b), and (c), respectively. The r-GeO2 thin film for the TEM observation was grown at lower growth rate (50 nm/h) for higher crystallinity. In Fig. 3 (b), clear diffraction spots of r-TiO2 substrate were visible. On the other hand, in Fig. 3 (c), clear diffraction spots of r-GeO2 thin film were observed as well as those of r-TiO2 substrate at the interface. From the diffraction spots, we calculated lattice parameters of the r-GeO2 thin film to be a=4.5 Å and c=2.7 Å. This indicates that the film suffers from significant tensile stress along the in-plane direction, and in-plane strain value was ~2.3%. Thus, in order to release the strain and achieve higher crystalline quality, using a buffer layer or other substrates with less lattice mismatches to r-GeO2 may be needed.We believe that these results greatly contribute to the future development of r-GeO2 applied for power-electronics devices and exploration of novel materials that are difficult to synthesize under normal growth conditions.This work was supported, in part, by JSPS KAKENHI under Grant No. 21H01811. Figure 1

Effect of Micro-Patterned Membrane PEFC Dependent on Operating Current Density

1. IntroductionPolymer electrolyte fuel cells (PEFCs) have been widely recognized as a key technology for a future hydrogen-based society, because of their several practical applications such as in fuel cell vehicles, owing to their good operating capability at low temperatures.It is well known that the mass transport and the chemical reactions at the cathode side of PEFCs limit their performance. Heinzmann et al. used electrochemical impedance spectroscopy (EIS) and distribution of relaxation time (DRT) analysis [1] to show that the dominant processes that occur are cathode gas diffusion and oxygen reduction reaction (ORR).One method to improve the ORR is to increase the surface available for the chemical reaction. Jeon et al. fabricated a micropatterned membrane and applied it to a membrane electrode assembly (MEA) [2]. They confirmed that the use of a micropatterned membrane improved the performance of the PEFC.However, the mechanism of this improvement is yet to be clarified in detail. Micropatterns on the membrane should increase the active reaction area (Fig.1(a)). However, patterns on the membrane surface increase the length of the path from the top to the bottom of the catalyst layer, which should hamper oxygen diffusion (Fig.1(b)). We previously performed DRT analysis with micro-patterned MEA to investigate the mechanism of improvement in PEFC performance using a micro-patterned MEA [3]. In this study, a wider range of EIS was performed, and both the positive and negative effects of using a micro-patterned MEA are discussed herein.2. ExperimentA cathode micro-patterned MEA was fabricated, and EIS and DRT analyses were performed. The catalyst ink was prepared using Pt/C (TEC10V50E, Tanaka Kikinzoku Kogyo K.K.), isopropyl alcohol, water, and a 10% ionomer solution. This ink was sprayed onto a 5.0 mm line-patterned membrane (NRE-212, Sigma-Aldrich Co. LLC) to fabricate the MEA. The catalyst loading was adjusted to 0.4 mg/cm2. The cell was assembled using a commercial gas diffusion layer (Sigracet®︎ 29BC, SGL Carbon GmbH). The operation was carried out galvanostatically with a relative humidity of 80%, gas flow rate of 200 ccm, and oxygen partial pressure of 0.2. EIS was measured at 0.02 to 1.00 A, with frequency ranging between 0.1 Hz and 1 MHz. The acquired data were then subjected to DRT analysis using DRT tools by Wan et al. [4]. Noisy data points were excluded before application because of the high sensitivity of DRT analysis to noise.3.Results and discussionFig.2 shows the polarization curve results. Solid lines with circle markers and broken lines with ‘x’ markers indicate the patterned and flat samples, respectively. In the lower current region, where the ORR is dominant, the patterned sample outperforms the conventional flat sample. On the other hand, in the higher current region, where gas diffusion is dominant, the patterned sample suffers steep drops and the flat becomes relatively better.Fig.3 shows the DRT analysis graph. Fig.3(a) stands for patterned sample result and Fig3.(b) for flat sample. The peaks of DRT indicate the polarization resistance at its time dependency. In the high current density region, the peaks of the patterned and the flat samples are significantly different. In particular, at around 101 to102 Hz, an independent peak appears at 101 Hz for the patterned sample as the current density increases. This shows the polarization resistance of gas diffusion, which indicates that the gas diffusion in the patterned sample is significantly worse than that in the flat sample.The micro-patterned MEA has a negative effect on cell performance because of the longer oxygen diffusion path involved. It can be assumed that they might not perform as well as conventional flat MEA under certain conditions that favor good oxygen transportation, such as high current or low oxygen partial pressure operation. Therefore, it is important to consider the physical properties (catalyst layer porosity, ionomer content, etc.) and operating conditions in order to maximize the potential of the micro-patterned MEA.4. ConclusionWe performed a wide range of galvanostatic EIS and DRT analyses of the data from the operation of a cathode micro-patterned PEFC. The micro-patterned membrane is shown to have both a positive and a negative effect. Comprehensive optimization of parameters such as micropattern geometry, catalyst composition, and operating conditions, are required to take full advantage of the surface-patterning method.

Prereduction of Nchwaning Ore in CO/CO2/H2 Gas Mixtures

Prereduction of Nchwaning manganese ore was investigated by isothermal reduction between 600 and 800 °C to optimize the conditions for industrial pretreatment of manganese ores. Experiments were conducted in CO/CO2 gas mixtures with and without hydrogen at two different oxygen partial pressures. Ore in the size fraction 9.52–15 mm was reduced in a thermogravimetric furnace, and the O/Mn ratio from the chemical analysis was used to determine the extent of prereduction. The samples were investigated by X-ray diffraction to investigate the evolution of phases under the course of reduction. The X-ray diffraction revealed that bixbyite and braunite (I and II) were reduced to manganosite with no or limited formation of hausmannite. Reduction of iron oxides subsided with wüstite, which is stabilized by manganese in the monoxide phase, and hydrogen was seen to improve the reduction of iron oxides. Modeling revealed that the reduction rate increased 2.8-fold upon increasing the CO content from 30% to 70% in a CO/CO2 gas mixture. The addition of hydrogen improved the reduction rate with factors of 1.3 and 2.6 for the low and the high oxygen partial pressures, respectively. Hence, the optimal conditions for pretreatment can be achieved by keeping the oxygen partial pressure as low as possible while adding hydrogen to the reducing gas and ensuring a high reduction temperature. Successful pretreatment limits the extent of the Boudouard reaction in the submerged arc furnace, reducing the amount of CO produced and, thus, reducing the CO available for pretreatment. Hydrogen is a useful addition to the pretreatment unit since it lowers the oxygen partial pressure and improves the kinetics of prereduction.

Varied effects exerted on sudden sensorineural hearing loss through HBO2 therapeutic pressure

This study aimed to compare the efficacy of two commonly used therapeutic pressures, 2.0 atmospheres absolute (ATA) versus 2.2 ATA, applied in hyperbaric oxygen (HBO2) therapy for sudden sensorineural hearing loss (SSNHL). We retrospectively reviewed the clinical records of 160 SSNHL patients treated by typical therapy or additional HBO2 therapy with pressure 2.0 or 2.2 ATA at Yijishan Hospital, the First Affiliated Hospital of Wannan Medical College, from February 2018 to May 2020. The pure-tone threshold audiometry results pre- and post-treatment were compared across three groups. In the range of frequencies 250-500 Hz, P2.0 (20.92±26.11 dB, p=0.047) and P2.2 group (20.47±21.54 dB, p=0.012) both acquired higher hearing gain compared to the control group (11.94±23.32 dB). While in the range of frequencies 1,000-2,000 Hz, only the P2.2 group showed significant improvement of the hearing gain compared to the control group (19.70±21.13 dB vs.10.56±25.24 dB, p=0.015). In the range of frequencies 4,000-8,000, both the P2.0 and P2.2 groups failed to reach the desired effect. Our results suggest that the therapeutic effect is associated with HBO2 therapeutic pressure when applying HBO2 treatment combined with standard medical therapy. Within the range of appropriate pressure, the higher pressure, which means higher partial pressure of oxygen, has better therapeutic efficacy for SSNHL.

Application of Copper as Stabiliser in Aluminium Assisted Transfer of Titanium in Submerged Arc Welding of Carbon Steel

The element transfer of Ti from molten flux to the weld metal is limited to less than 310 ppm Ti in the submerged arc welding of carbon steel. This limitation is due to the high oxygen partial pressure prevailing at the molten flux-weld pool interface. Our previous study illustrated that the use of Al powder in combination with Ti powder improves the transfer of Ti to the weld metal to 4% Ti, whilst maintaining 509 ppm O in the weld metal. The weld metal ppm O should be controlled at 200 to 500 ppm O to maintain weld metal toughness. In this study, the addition of Cu powder with Ti and Al powder is applied to illustrate the stabiliser effect of Cu in the weld pool. The role of Cu as weld pool stabiliser is due to its decrease of the temperature required to melt Ti into the weld pool, so increasing the quantity of metal powder melted into the weld pool. The weld metal composition improved to 5.1% Ti, 3.6% Cu, and 371 ppm O. Thus, the role of Al in controlling the partial oxygen pressure at the molten flux-weld pool interface is maintained in the presence of Cu powder.

High-flow nasal cannula therapy: A multicentred survey of the practices among physicians and respiratory therapists in Singapore

BackgroundUse of high-flow nasal cannula (HFNC) has become a regular intervention in the intensive care units especially in patients coming in with hypoxaemic respiratory failure. Clinical practices may differ from published literature. ObjectivesThe objective of this study was to determine the clinical practices of physicians and respiratory therapists (RTs) on the use of HFNC. MethodsA retrospective observational study looking at medical records on HFNC usage from January 2015 to September 2017 was performed and was followed by a series of questions related to HFNC practices. The survey involved physicians and RTs in intensive care units from multiple centres in Singapore from January to April 2018. Indications and thresholds for HFNC usage with titration and weaning practices were compared with the retrospective observational study data. ResultsOne hundred twenty-three recipients (69.9%) responded to the survey and reported postextubation (87.8%), pneumonia in nonimmunocompromised (65.9%), and pneumonia in immunocompromised (61.8%) patients as the top three indications for HFNC. Of all, 39.8% of respondents wanted to use HFNC for palliative intent. Similar practices were observed in the retrospective study with the large cohort of 63% patients (483 of the total 768 patients) where HFNC was used for acute hypoxaemic respiratory failure and 274 (35.7%) patients to facilitate extubation. The survey suggested that respondents would initiate HFNC at a lower fraction of inspired oxygen (FiO2), higher partial pressure of oxygen to FiO2 ratio, and higher oxygen saturation to FiO2 ratio for nonpneumonia patients than patients with pneumonia. RTs were less likely to start HFNC for patients suffering from pneumonia and interstitial lung disease than physicians. RTs also preferred adjustment of FiO2 to improve oxygen saturations and noninvasive ventilation for rescue. ConclusionsAmong the different intensive care units surveyed, the indications and thresholds for the initiation of HFNC differed in the clinical practices of physicians and RTs.

Reactive HiPIMS deposition of Al-oxide thin films using W-alloyed Al targets

The outstanding oxidation resistance, thermo-mechanical stability, and chemical inertness of alumina, but also the synthesis of phase pure polymorphs attract particular attention in academia and industry. Especially, the difficulties regarding the synthesis of α- or γ-structured Al 2 O 3 by physical vapor deposition techniques are still strong limitations. Within this study, we investigated in detail the influence of 2 at.% tungsten in the Al-target on the process stability and phase formation during reactive DC magnetron sputtering as well as high power impulse magnetron sputtering (HiPIMS) of Al 2 O 3 -based coatings. The small addition of W to the Al target allows to increase the oxygen partial pressure by more than 200% while maintaining a stable deposition process. Ion mass spectroscopy measurements yield a promising high fraction of 16 O + and 32 O 2 + , when operating the W-containing target in the metal-to-poisoned transition mode. A significant increase of 16 O + is further provided by the target surface oxide in poisoned mode. Detailed time-of-flight ion mass spectroscopy investigations during one HiPIMS pulse show a clear temporal separation of the individual ions arriving at the substrate plane during the pulse on-time, allowing for controlled ion attraction by synchronizing the bias pulse to the discharge impulse. Equal amounts of 27 Al + and 32 O 2 + can be attracted using a bias on-time between 400 μs and 900 μs in the “off-time” (after glow) leading to a dense and nano-crystalline coating. Detailed electron microscopy investigations show the presence of metallic phase fractions for higher duty cycles (7.5%). Decreasing the duty cycle to 3.75% leads to amorphous coatings when operating the Al-target at the highest oxygen partial pressure in metallic mode. • R-HiPIMS deposition of W alloyed Al 2 O 3 coatings to control the poisoning behavior • W alloying increases the oxygen partial pressure by more than 200% before poisoning. • Despite of the target condition (poisoning mode) the Al + /O + ratio is still above 1.

Influence of Substrate Orientation and Oxygen Partial Pressure on the Morphology, Structure, and Electrical Property of Epitaxial Indium Tin Oxide Films

Indium tin oxide (ITO, tin-doped indium oxide) has been widely used in optoelectronic and other research fields because of its excellent electrical conductivity. However, there is a lack of systemic research on the influence of crystal orientation on the electrical properties of epitaxial ITO films. In this work, the epitaxial ITO films were deposited on low index planes of yttria-stabilized zirconia substrates by direct current magnetron sputtering at different oxygen partial pressures ranging from 0 to 3 Pa. The carrier concentration of the ITO film decreased with the increase of the oxygen partial pressure and further leading to the increase of overall resistivity. In addition, we also found that the Hall mobilities of ITO (100) films rapidly decreased with the oxygen partial pressure, while the Hall mobilities of ITO (111) films remained unchanged. The anisotropy of the carrier mobility was the main factor for the resistivity difference of ITO films with different orientations at high oxygen partial pressure.

Atomistic structure and three-dimensional spatial distribution of oxide clusters along voids in nitride metal/semiconductor superlattices

Epitaxial metal/semiconductor superlattices with atomically sharp interfaces and tunable Schottky barrier heights have attracted significant interest in recent years for thermionic emission-based high-temperature thermoelectric devices, optical hyperbolic metamaterials, hot-electron photocatalysis, and optoelectronic heterostructures for visible-to-terahertz frequency range applications. ZrN/ScN is a demonstration of such epitaxial metal/semiconductor superlattices and exhibits atomically sharp lattice-matched interfaces, albeit with the presence of threading dislocations on MgO substrates. Along with its influence on structural integrity and atomic diffusion, the presence of such defects significantly impacts electron and phonon transport in these metamaterials with carrier trapping, scattering, shunt path, etc. Therefore, an in-depth analysis of the atomistic structure and the composition of such defects is extremely necessary to design devices with improved efficiencies. In this paper, high-resolution scanning transmission electron microscopy and atom-probe tomography are employed to determine the structure and three-dimensional (3D) spatial distribution of oxide defect clusters along the voids in ZrN/ScN superlattices. $\mathrm{Sc}{\mathrm{O}}^{+}$ and $\mathrm{Sc}{\mathrm{O}}^{++}$ ions are found to cluster predominantly along such 3D interface defects with zirconium and scandium atoms surrounding them. Defect regions are also found to be depleted of nitrogen atoms and rich with a high concentration of oxygen. The oxygen content was found to be higher inside the ScN layers compared to ZrN. First-principles modeling analysis verified the clustering of oxygen at high oxygen partial pressure and demonstrated a higher affinity of scandium towards oxygen than for zirconium towards oxygen. These results mark significant progress in understanding the atomic structure and composition of defects in nitride superlattices.