High PO2 Research Articles

Myocardial oxygen handling and metabolic function of ex-situ perfused human hearts from circulatory death donors

BackgroundThis study investigated oxygen handling of human hearts donated after circulatory death (DCD) on normothermic ex-situ heart perfusion (ESHP) and evaluated oxygen handling markers as adjuncts to cardiac viability assessment. MethodsThis single-center retrospective study included human DCD heart transplantation procedures using ESHP. Lactate concentrations, blood gas, myocardial oxygen consumption (MVO2), delivery (MDO2) and extraction (MEO2), coronary blood flow (CBF), coronary vascular resistance (CVR), and adenosine infusion were reported over time. Correlation between parameters was assessed, and statistical testing compared patients who did and did not require extracorporeal membrane oxygenation (ECMO) support after transplantation. ResultsLactate concentrations decreased during ESHP in all transplanted hearts (n=25) and increased in 1 rejected heart. Arterial PO2 was 75.2±2.9 kPa, with an arteriovenous ΔPO2 of 44.8±10.4 kPa. Oxygen saturation was 100% in most arterial and venous samples. Average MVO2 was 2.7±0.6 mL·min-1·100·g-1 myocardium, MDO2 98.5±20.4 mL·min-1, and MEO2 8.6±1.8%. Average CVR was 0.025±0.006 mmHg∙min∙mL-1∙100 g-1 and increased over time. ΔPO2 correlated strongly with MVO2 (R=0.797, p<0.001) and lactate trend (R=0.799, p<0.001) in transplanted hearts, without differences compared to the rejected heart with increasing lactate. Adenosine infusion on ESHP was significantly higher in patients requiring ECMO post-transplantation versus non-ECMO cases (11.7 (4.5-21.0) vs. 2.2 (1.5-6.7) mL·h-1, p=0.039). ConclusionsHearts on normothermic ESHP receive excessive MDO2, due to high PO2 and CBF, while the MVO2 is relatively low. Thus, CBF and PO2 can potentially be lowered. Furthermore, ΔPO2 could serve as additional marker of metabolic function under these hyperoxic circumstances. The adenosine infusion rate might predict post-transplantation ECMO requirement.

Theoretical Understanding of Effects of Operating Modes on the Performance Durability of Solid Oxide Cells: A Comparison between Potentiostatic and Galvanostatic Operations

In solid oxide cells (SOCs), the choice between galvanostatic (constant current) and potentiostatic (constant voltage) modes does not significantly affect the performance of SOCs as long as the cell components remain unchanged and intact. However, the degradation of cell components, which leads to changes in electrochemical and physical properties of the cell, elevates the importance of the selected operating mode. This paper aims to investigate the effects of galvanostatic and potentiostatic operating modes on the evolving properties of SOCs and their subsequent influence on performance durability. Employing non-equilibrium thermodynamic analysis, a crucial approach for understanding the degradation phenomena within an active electrochemical system, this study aims to provide in-depth insights into how these operating modes affect the longevity and efficacy of SOCs. Key findings include: In cases where oxygen electrode (OE) degradation is accelerated by higher partial pressure of oxygen ( pO2 ), operating under constant voltage electrolysis can mitigate the high pO2 at the OE|electrolyte (OE|EL) interface. Conversely, if OE degradation occurs more rapidly under a lower pO2, constant current electrolysis is more effective in suppressing degradation by achieving a high pO2 at the OE|EL interface. For degradation of the fuel electrode (FE) due to higher pO2, constant current electrolysis is beneficial for more stable performance, which helps maintain low pO2 at the FE|EL interface. When FE degradation is accelerated by lower pO2, constant voltage electrolysis can avert low pO2 at the FE|EL interface. In practical scenarios, more complex degradation mechanisms come into play, especially when pO2 significantly deviates from initial conditions. Degradation in one electrode can influence pO2 in the other electrode, a phenomenon more pronounced in potentiostatic than in galvanostatic electrolysis.

Oxide ion conductivity in doped bismuth gallate mullite type oxide, Bi2Ga4O9

Mullite-phase bismuth gallate (Bi2Ga4O9) was successfully synthesized with partial substitution of bismuth with alkaline-earth cation, Mg2+, Ca2+, Sr2+, and Ba2+. The effect of this substitution on the electrical conductivity was investigated. In this study, substitution with Ca2+ of Bi site was further studied for increasing the ionic conductivity as well as the phase stability in reducing atmospheres. Substitution with Ca2+ was found to be the most effective and with 12.5 mol% of Ca2+ as the optimized doping amount. Conductivity and stability in reducing atmospheres was increased down to pO2 ≤ 10−19 atm while keeping the conductivity of σ = 2.6 × 10−2 S·cm−1 at 973 K largely independent of oxygen partial pressure. Oxygen permeation analysis estimates 76% of theoretical oxygen permeation rate at 973 K suggesting main charge carrier is oxide ion. Partial electronic conductivity was measured with the ion blocking method. Oxide ion conductivity is dominated over wide pO2 range excepting for hole conduction at high pO2. Density functional theory (DFT) analysis on oxide ion diffusion route suggests oxygen hoping through lattice vacancy is main pathway for oxide ion conductivity in this doped Bi2Ga4O9. Despite the low oxide ion conductivity in Mullite-phase oxide, it was found that Ca doped Bi2Ga4O9 shows good oxide ion conductivity over wide pO2 range.

Evaluation of a deuterated triarylmethyl spin probe for in vivo R2 ∗-based EPR oximetric imaging with enhanced dynamic range.

In this study, we compared two triarylmethyl (TAM) spin probes, Ox071 and Ox063 for their efficacy in measuring tissue oxygen levels under hypoxic and normoxic conditions by R2 *-based EPR oximetry. The R2 * dependencies on the spin probe concentration and oxygen level were calibrated using deoxygenated 1, 2, 5, and 10 mM standard solutions and 2 mM solutions saturated at 0%, 2%, 5%, 10%, and 21% of oxygen. For the hypoxic model, in vivo imaging of a MIA PaCa-2 tumor implanted in the hind leg of a mouse was performed on successive days by R2 *-based EPR oximetry using either Ox071 or Ox063. For the normoxic model, renal imaging of healthy athymic mice was performed using both spin probes. The 3D images were reconstructed by single point imaging and multi-gradient technique was used to determine R2 * maps. The signal intensities of Ox071 were approximately three times greater than that of Ox063 in the entire partial pressure of oxygen (pO2 ) range investigated. The histograms of the tumor pO2 images were skewed for both spin probes, and Ox071 showed more frequency counts at pO2 > 32 mm Hg. In the normoxic kidney model, there was a clear delineation between the high pO2 cortex and the low pO2 medulla regions. The histogram of high-resolution kidney oximetry image using Ox071 was nearly symmetrical and frequency counts were seen up to 55 mm Hg, which were missed in Ox063 imaging. As an oximetric probe, Ox071 has clear advantages over Ox063 in terms of sensitivity and the pO2 dynamic range.

High-Temperature Electromechanical Properties Single Crystalline Lithium Niobate-Lithium Tantalate Solid Solutions at Different Oxygen Partial Pressures

LiNbO3 (LN) is one of the most investigated electro-acoustic and electro-optical materials. Its high piezoelectric coefficients are a favorable condition for its use beyond optical applications, which includes, for example, high-temperature actuators. Compared for example to crystals of the langasite family, LN shows significantly higher piezoelectric coefficients but limited thermal stability. The latter is caused by evaporation of Li2O and related changes of e.g. electrical conductivity. As a consequence, long-term applications of LN are limited to temperatures of a few hundred degrees Celsius. A related material that offers improved thermal stability is LiNbO3 (LT). However, the Curie temperature is only about 600 °C. Furthermore, the piezoelectric coefficients are lower than for LN. The miscibility of LN and LT over the entire compositional range should allow, however, to tailor the crystal properties and, for example, to take advantage of the high piezoelectric coefficients of LT and the better thermal stability of LT. Therefore, the subject of this study are lithium niobate-lithium tantalate (LiNb1-xTaxO3, LNT) solid solutions with respect to their electroacoustic properties at temperatures between 400 and 900 °C. The objectives include the determination, understanding and correlation of defect structures, electronic and atomic transport and acoustic losses in LNT over a wide temperature range.The electromechanical properties of LNT crystals are determined as function of temperature and oxygen partial pressure (pO2) and compared with those of the congruent edge compounds LN and LT. Characterization methods include impedance spectroscopy, application of 6Li as tracer in combination with secondary ion mass spectrometry, resonant piezoelectric spectroscopy, noncontacting resonant ringdown spectroscopy and laser vibrometry. The latter reflects displacements of the sample surface even in the order of nanometers which enables the identification of the resonant modes.LNT crystals with different Nb-Ta compositions prepared by Czochralski growth and a µ-pulling down process are used to determine the overall electrical conductivity by electrical impedance spectroscopy. Further, Z- and Y-cut plates are applied as bulk acoustic wave resonators to measure the acoustic loss. When determined in air, the temperature-dependent electrical conductivity of LNT below about 600 °C is virtually independent of composition. In particular, for each sample a single activation energy is found from 400 to 600 °C which is the same for all samples within the error margins. Furthermore, the diffusive ion transport studied directly using 6Li tracers results in good agreement with the electrical conductivity when the diffusion coefficients are converted correspondingly using the Nernst-Einstein relation. Consequently lithium-ion migration can explain the overall electrical conductivity. Above about 600 °C the behavior depends on composition. At high Nb contents, a continuous increase of the slope of the electrical conductivity in an Arrhenius representation with temperature is observed, which is attributed to thermal instability.The pO2 dependent electrical conductivity shows constant values at high pO2. At sufficiently low pO2, a slope of -1/4 in a double logarithmic representation is found (see attached figure). This slope indicates electronic conduction which is caused by compensation of NbLi antisite defects. The behavior is already reported for LN by Smyth et al. (Ferroelectrics 50 (1983) 93). As the slope is independent of the composition x, it can be concluded that the same defect formation occurs in LNT. Important with respect to thermal stability is that, at a given temperature, the increase in conductivity for Ta-rich compositions starts at lower pO2 than for Nb-rich compositions.The acoustic loss is determined in a wide temperature range by the methods mentioned above. It shows some impact of the metal electrodes at low temperatures. In air and at temperatures above about 400 °C the acoustic loss is governed by the piezoelectric/carrier relaxation. It is caused by the motion of charge carriers in an oscillating piezoelectric field and, therefore, related to electrical conductivity. The finding is confirmed by modelling with independent materials data including electrical conductivity. Low pO2 result in additional loss contributions.In summary, the study leads to an understanding of the acoustic losses of LNT at high temperatures, which provides opportunities to reduce them. Furthermore, it becomes clear that Ta-rich compositions exhibit improved thermal stability. Figure 1

Wildfire activity and impacts on palaeoenvironments during the late Paleozoic Ice Age - New data from the North China Basin

The Late Paleozoic is widely recognized as a ‘high-fire’ world. However, the impact of wildfires on the vegetational change as well as the relationship between fire and low atmospheric pCO2 and high pO2 in the Late Paleozoic remains a matter of debate. New data on fossil charcoal and pyrogenic PAHs in coal deposits from the Yuzhou Coalfield, the southern part of the North China Basin, are integrated into previous studies to increase our current understanding of the role of wildfires on land and in marine environments during the late Carboniferous and early Permian. Analyses of bulk petrographic and organic geochemical data indicate that during deposition of the Taiyuan Formation (late Gzhelian and early Asselian Stage) wildfires were more prevalent and were characterized by a large proportion of crown fire. A previous plant macrofossil assemblage study of the Taiyuan and Shanxi formations, together with fire traits of ancient plant lineages, indicates that wildfire may likely be one of the major drivers of the thriving of the Cathaysian Flora during this period. Wildfire and post-wildfire processes might have acted as important controlling factors for organic carbon burial. Persistent organic carbon sequestration (as coals or charcoal) on land and increasing organic carbon burial in the ocean are coincident with the peak in pO2 during the apex of the Late Paleozoic Ice Age.

Ceramics with eutectic microstructure in the ZrO2–PrOx system

AbstractPraseodymium oxides present redox properties analogous to those of Ce‐based systems and have been proposed for catalytic applications in combination with CeO2, ZrO2, or both. However, uncertainties remain concerning the nature and redox behavior of Pr‐rich mixtures, especially with ZrO2. Here we study the eutectic composites of the ZrO2–PrOx system, focusing on the sensitivity of their microstructure, phase symmetry, and composition to variations of the processing atmosphere from oxidizing to reducing. Mixed oxides have been produced by a laser‐assisted directional solidification technique in O2, air, N2, or 5%H2(Ar) environment, and the resulting materials have been analyzed by scanning electron microscopy/energy‐dispersive X‐ray spectroscopy, X‐ray diffraction, Raman spectroscopy, and magnetic susceptibility. In air, N2, or 5%H2(Ar) atmosphere, a lamellar, eutectic‐like microstructure forms, the major phase being the one with less Pr content. Both the Pr concentration in each phase as the PrOx molar percentage of the eutectic composites decrease as the atmosphere becomes more reducing. Both eutectic phases are fluorite‐like when processing in air, whereas in N2 or 5%H2(Ar), the phase with high Pr content is of the A‐R2O3 type, and the phase with low Pr content can be described as a fluorite phase containing C‐R2O3‐like short‐range‐ordered regions. The results obtained for samples processed in O2 suggest that for high enough pO2 no eutectic forms, in analogy with the ZrO2–CeO2 system. The evolution of the phase composition and symmetry is discussed in terms of the limited stability of the phases found in the ZrO2–Pr2O3 system, namely, A‐ or C‐R2O3‐like, beyond a certain Pr oxidation degree and oxygen content.

Organic matter input, paleovegetation and paleoclimate of Upper Cretaceous lignite from Maiganga coalfield, Upper Benue Trough, Nigeria: Insights from biomarkers and stable isotopes

Upper Cretaceous Gombe Formation coals from Maiganga coalfield, Upper Benue Trough, Nigeria were investigated to evaluate the thermal maturity, organic matter input, paleovegetation, paleoclimate, and depositional environment using bulk and molecular geochemical techniques. Vitrinite reflectance (<0.40 %Ro) and biomarker maturity indicators (C31 homohopane 22S/(22S + 22R) < 0.3; 16(H) β/(β+α) phyllocladane <0.5; MPI-1 < 0.5; MPR <2.65) generally signify low thermal maturity. Source-related aliphatic and aromatic hydrocarbon ratios indicate that the coals are derived mainly from terrestrial organic matter but with considerable input from marine algal organic matter. The higher abundance of diterpenoids over triterpenoids and sesquiterpenoids suggests a prevailing contribution of gymnosperms to the Maiganga paleoflora. This is corroborated by the relatively heavier carbon isotopic composition (δ13C = −25.9‰ to −25.0‰) and low angiosperm/gymnosperm ratios. A new proxy, the polycyclic aromatic hydrocarbon ratio (PAHr) which is calculated from PAHr = (phenanthrene + pyrene + fluoranthene + perylene)/(phenanthrene + pyrene + fluoranthene + perylene + retene + cadalene), was proposed to evaluate the abundance and origin of combustion-derived polycyclic aromatic hydrocarbons (PAHs). The mostly high (>0.9) PAHr values for the coals are characteristic of a pyrogenic/combustion origin. Combustion-derived PAHs are abundant in the coals and their ratios indicate a mixed petrogenic/pyrogenic to dominantly pyrogenic origin. However, the high proportion of unburnt organic matter and low abundance of 7-ring PAHs such as coronene indicates limited, high-temperature wildfires. The coronene index values suggest burning temperature in the 700–1000 °C range, which is consistent with the estimated high pO2 of ∼26.5% in the Maastrichtian. n-Alkane proxies (Pwax, Paq, n-C23/n-C29, n-C27/n-C31, etc.) and hydrogen isotope ratios (−117‰ to −112‰) are suggestive of humid paleoclimate with frequent dry periods and lower paleopeat water levels. Moderately high pristane/phytane ratios (2.0–4.8) indicate deposition under sub-oxic to oxic freshwater settings. Additionally, low total sulphur content (0.29–0.90) and dibenzothiophene/phenanthrene ratios (0.05–0.17) imply peat accumulation in lacustrine-swamp to fluvial/deltaic depositional environments with minor post-depositional marine influence.

Effect of gas composition on the oxide scale growth mechanisms in a ferritic steel for solid oxide cell interconnects

The oxidation behavior of a ferritic steel Fe-23Cr-0.5Mn-0.6 Nb-0.1Ti (at%) considered for application in solid oxide cell (SOC) stack interconnects was studied at 800 °C. The oxidation kinetics and oxide scale microstructure formed in Ar-20%O2, Ar-4%H2-4%H2O and Ar-1%CO-1%CO2 atmospheres, simulating the SOC operation environments, were investigated by thermogravimetry (TG) in conjunction with electron microscopy (SEM/TEM) and atom probe tomography (APT). In all three environments multilayered oxide scales formed, consisting of Mn-Cr spinel on top of Cr2O3 and an additional Nb-rich oxide layer at the chromia-alloy interface. The initially faster oxidation in the low pO2 gases was attributed to formation of porous chromia scales compared to a dense scale formed in the high pO2 (Ar-O2) atmosphere. APT revealed segregation of minor alloying elements (Mn, Nb and Ti) to chromia grain boundaries in all three simulated SOC environments in quantitatively similar amounts, suggesting their similar effect on the ionic transport through the oxide scale. The findings indicate that oxygen activity in the test gas plays a dominating role in governing the oxidation kinetics and the oxide scale microstructure of the studied ferritic steel.

Clinical Accuracy of a Glucose Oxidase-Based Blood Glucose Test-Strip Across Extremes of Oxygen Partial Pressure.

Glucose oxidase (GOx)-based blood glucose monitors (BGMs) are influenced by the partial pressure of oxygen (Po2) within the applied sample. Limited in-clinic data exists regarding the quantitative effect of Po2 in unmanipulated capillary fingertip blood samples across physiologically representative glucose and Po2 ranges. Clinical accuracy data were collected as part of a BGM manufacturer's ongoing post-market surveillance program for a commercially available GOx-based BGM test-strip. The data set comprised 29 901 paired BGM-comparator readings and corresponding Po2 values from 5 428 blood samples from a panel of 975 subjects. A linear regression-calculated bias range of 5.22% (+0.72% [low Po2: 45 mm Hg] to -4.5% [high Po2: 105 mm Hg]); biases calculated as absolute at <100 mg/dL glucose was found. Below the nominal Po2 of 75 mm Hg, a linear regression bias of +3.14% was calculated at low Po2, while negligible impact on bias (regression slope: +0.002%) was observed at higher than nominal levels (>75 mm Hg). When evaluating BGM performance under corner conditions of low (<70 mg/dL) and high (>180 mg/dL) glucose, combined with low and high Po2, linear regression biases ranged from +1.52% to -5.32% within this small group of subjects and with no readings recorded at <70 mg/dL glucose at low and high Po2. Data from this large-scale clinical study, performed on unmanipulated fingertip capillary bloods from a diverse diabetes population, indicate Po2 sensitivity of the BGM to be markedly lower than published studies, which are mainly laboratory-based, requiring artificial manipulation of oxygen levels in aliquots of venous blood.

High pO2 Flux Growth and Characterization of NdNiO3 Crystals

Single crystals of the perovskite nickelate NdNiO3 with dimensions of up to 50 μm on edge have been successfully grown using the flux method at a temperature of 400 °C and oxygen pressure of 200 bar. The crystals were investigated by a combination of techniques, including high-resolution synchrotron X-ray single-crystal and powder diffraction and physical property measurements such as magnetic susceptibility and resistivity. Resistivity measurements revealed a metal-insulator transition (MIT) at TMIT~180 K with apparent thermal hysteresis; however, no superlattice peaks or peak splitting below TMIT, which corresponds to a structural transition from Pbnm to P21/n, was observed. The successful growth of NdNiO3 crystals at relatively low temperatures and oxygen pressure provides an alternative approach for preparing single crystals of interesting perovskites such as RNiO3 (R = Sm-Lu) and parent phases of superconducting square planar nickelates.

Mo(AlxSi1−x)2 healing particles for high temperature ceramics and encapsulation by selective oxidation of aluminium

To prevent premature triggering of the healing reaction in Mo-Si containing self-healing thermal barrier coating system, an oxygen impenetrable shell (α-Al2O3) around the sacrificial healing particles (MoSi2) is desired. Here an encapsulation method is presented through selective oxidation of Al in Mo(AlxSi1-x)2 particles. Healing particles of Mo(AlxSi1-x)2 is designed in terms of alumina shell thickness, particle size and fraction Al dissolved. By replacing Si by Al in MoSi2 up to the maximum solubility (x = 0.65) a strong crack healing ability is maintained (relative volume expansion ≥ 40 %). The formed exclusive α-Al2O3, featuring a two-layered structure, results from a counter-diffusion process along the grain boundaries, and its oxidation kinetics fits well with the 3D diffusion-Jander model. After 16 h exposure in gaseous ambient with a pO2 of 5 × 10-10 atm. at 1100 °C, a closed and dense shell of α-Al2O3 is formed with a thickness of about 1.3 µm. The oxide shell produced under this condition provided healing particles with significantly improved stability upon exposure to high pO2 of 0.2 atm. at 1100 °C for 50 h. The particles after exposure feature an inner core of MoSi2 with Al completely consumed and an oxide shell of α-Al2O3.

Physiological Oxygen Levels Differentially Regulate Adipokine Production in Abdominal and Femoral Adipocytes from Individuals with Obesity Versus Normal Weight.

Adipose tissue (AT) inflammation may increase obesity-related cardiometabolic complications. Altered AT oxygen partial pressure (pO2) may impact the adipocyte inflammatory phenotype. Here, we investigated the effects of physiological pO2 levels on the inflammatory phenotype of abdominal (ABD) and femoral (FEM) adipocytes derived from postmenopausal women with normal weight (NW) or obesity (OB). Biopsies were collected from ABD and FEM subcutaneous AT in eighteen postmenopausal women (aged 50-65 years) with NW (BMI 18-25 kg/m2, n = 9) or OB (BMI 30-40 kg/m2, n = 9). We compared the effects of prolonged exposure to different physiological pO2 levels on adipokine expression and secretion in differentiated human multipotent adipose-derived stem cells. Low physiological pO2 (5% O2) significantly increased leptin gene expression/secretion in ABD and FEM adipocytes derived from individuals with NW and OB compared with high physiological pO2 (10% O2) and standard laboratory conditions (21% O2). Gene expression/secretion of IL-6, DPP-4, and MCP-1 was reduced in differentiated ABD and FEM adipocytes from individuals with OB but not NW following exposure to low compared with high physiological pO2 levels. Low physiological pO2 decreases gene expression and secretion of several proinflammatory factors in ABD and FEM adipocytes derived from individuals with OB but not NW.

Multifactor theoretical study on ionic transport numbers of mixed oxygen ionic-electronic conducting oxides determined by the electromotive force method

The electromotive force (EMF) method is widely applied to measure the ionic transport numbers (ti) of mixed oxygen-ionic and electronic conducting oxides. However, the results determined by the EMF method are the average/apparent ti (tiapp), subjected to a given gradient of oxygen partial pressure (PO2), rather than ti at a specific PO2, making it challenging to reveal the accurate properties of materials. In this study, to clarify the impact of this issue, a precise defect distribution model of Gd doped CeO2 (GDC), considering defect equilibrium and local charge neutrality, is built. A multifactor theoretical analysis is conducted to compare tiapp and ti of the membrane at different sides. The modeling results reveal that a thick membrane is recommended for avoiding the influence of membrane thickness on tiapp. When there is a large difference of PO2 between two sides of the GDC membrane (PO2highPO2PO2lowPO2>1025), tiapp is inclined to ti at the side of high PO2. Only when both sides of the GDC membrane are reducing atmosphere, tiapp of the modified EMF method is approximately the average of ti at both sides. The findings of this study are instructive for the rational application of EMF methods.

THE CLUE IS IN THE BLOOD GAS: A RARE MANIFESTATION OF LACTIC ACIDOSIS

THE CLUE IS IN THE BLOOD GAS: A RARE MANIFESTATION OF LACTIC ACIDOSIS

Positive feedback promotes terrestrial emergence behaviour in an amphibious fish.

Major ecological transitions such as the invasion of land by aquatic vertebrates may be facilitated by positive feedback between habitat choice and phenotypic plasticity. We used the amphibious fish Kryptolebias marmoratus to test the hypothesis that aquatic hypoxia, emergence behaviour and respiratory plasticity create this type of positive feedback loop that causes fish to spend increasing amounts of time on land. Terrestrially acclimated fish were more sensitive to aquatic hypoxia (emergence at higher PO2) and were less hypoxia tolerant (shorter time to loss of equilibrium) relative to water-acclimated fish, which are necessary conditions for positive feedback. Next, we tested the prediction that exposure to aquatic hypoxia causes fish to emerge frequently, reduce gill surface area, and become less hypoxia tolerant. Indeed, fish exposed to severe aquatic hypoxia spent almost 50% of the time out of water and coverage of the gill lamellae by an inter-lamellar cell mass almost doubled. Fish exposed to aquatic hypoxia that could emerge from water were also more sensitive to subsequent acute aquatic hypoxia and were less hypoxia tolerant than normoxia-exposed controls. These results are opposite those of fish that cannot escape from aquatic hypoxia and presumably arise owing to plastic changes that occur during air exposure. Together, these results indicate that emergence behaviour begets further emergence behaviour, driven by gill remodelling which reduces aquatic respiratory function. This type of positive feedback may explain how amphibious behaviour has repeatedly evolved in fishes that occupy hypoxic aquatic habitats despite the associated challenges of life on land.

Self-Assembled Multiphase Nanocomposite SrCo1–xFexO3-δ Thin Films with Voltage-Controlled Magnetism for Spintronic Applications

SrCo1–xFexO3-δ (SCFO) grown on SrTiO3 substrates using pulsed laser deposition forms either a single-phase film or a two-phase self-assembled nanocomposite film depending on the oxygen partial pressure, PO2. A high PO2 of 150 mTorr during growth promotes phase separation of SCFO into a nanocomposite comprising Co oxide pillars embedded epitaxially in a Fe-rich SCFO matrix made up of brownmillerite and oxygen-deficient perovskite, despite the average composition of Sr/(Co + Fe) = 1. The SCFO matrix in the nanocomposite consists of a brownmillerite structure at a high Co content and an oxygen vacancy ordered perovskite at a high Fe content. In contrast, single-phase SCFO films grow at 20 mTorr. Ionic liquid gating of the nanocomposites oxidizes brownmillerite into perovskite with interlayer defects and renders the matrix phase magnetic with a saturation magnetization of 200 emu cm–3 at 173 K when x = 0.30.

Oxide Ion Conduction, Defect Chemistry, and the Conducting Mechanism in Ruddlesden–Popper La2–xMxBaIn2O7–0.5x (M = Ca, Sr, Ba)

Tetragonal La2BaIn2O7 belongs to the stoichiometric n = 2 members of the Ruddlesden–Popper (RP) structure, with La3+ and Ba2+ cations ordered in the rock salt and octahedral layers, respectively. Herein, a series of alkaline-earth-metal-doped materials La2–xMxBaIn2O7–0.5x (M = Ca, Sr, Ba) were prepared by the traditional solid-state reaction method. The results revealed that the substitutions of Ca/Sr/Ba for La introduced oxygen vacancies and led to good oxide ion conduction, e.g., ∼1.21 × 10–3–1.38 × 10–2 S/cm within 600–900 °C for the specimen La1.7Ba1.3In2O6.85, which was more than 2 orders of magnitude higher than the parent material. However, both the parent and acceptor-doped La2BaIn2O7 showed very limited proton conductions. The energetics of defect formation and oxygen vacancy migrations in La2BaIn2O7-based materials was studied through the static lattice and molecular dynamics (MD) atomistic simulations based on the interatomic potential approach. The defect formation energy calculations for the electrons and holes in La2BaIn2O7 rationalized the experimentally observed pure ionic conduction under low pO2 and mixed ionic and p-type electronic conductions under high pO2, respectively. The MD simulations indicated two-dimensional oxygen vacancy migration within the perovskite slab for the acceptor-doped La2BaIn2O7.

Association of Arterial Metabolic Content with Cerebral Blood Flow Regulation and Cerebral Energy Metabolism-A Multimodality Analysis in Aneurysmal Subarachnoid Hemorrhage.

BackgroundIn this study, the association of the arterial content of oxygen, carbon dioxide, glucose, and lactate with cerebral pressure reactivity, energy metabolism and clinical outcome after aneurysmal subarachnoid hemorrhage (aSAH) was investigated.MethodsIn this retrospective study, 60 patients with aSAH, treated at the neurointensive care (NIC), Uppsala University Hospital, Sweden, between 2016 and 2021 with arterial blood gas (ABG), intracranial pressure, and cerebral microdialysis (MD) monitoring were included. The first 10 days were divided into an early phase (day 1 to 3) and a vasospasm phase (day 4 to 10).ResultsHigher arterial lactate was independently associated with higher/worse pressure reactivity index (PRx) in the early phase (β = 0.32, P = .02), whereas higher pO2 had the opposite association in the vasospasm phase (β = −0.30, P = .04). Arterial glucose and pCO2 were not associated with PRx. Higher arterial lactate (β = 0.29, P = .05) was independently associated with higher MD-glucose in the vasospasm phase, whereas higher pO2 had the opposite association in the vasospasm phase (β = −0.33, P = .03). Arterial glucose and pCO2 were not associated with MD-glucose. Higher pCO2 in the early phase, lower arterial glucose in both phases, and lower arterial lactate in the vasospasm phase were associated (P < .05) with better clinical outcome.ConclusionsArterial variables associated with more vasoconstriction (higher pO2 and lower arterial lactate) were associated with better cerebral pressure reactivity, but worse energy metabolism. In severe aSAH, when cerebral large-vessel vasospasm with exhausted distal vasodilation is common, more vasoconstriction could increase distal vasodilatory reserve and pressure reactivity, but also reduce cerebral blood flow and metabolic supply. The MD may be useful to monitor the net effects on cerebral metabolism in PRx-targeted NIC.

Soft X-ray absorption study of sputtered tin oxide films

The bonding structure of tin oxide (SnOx) films grown by reactive DC magnetron sputtering has been studied by the combination of X-ray diffraction (XRD) and soft X-ray absorption near-edge structure (XANES). The oxygen incorporation in the films has been controlled by the O2 partial pressure (PO2) in the O2/Ar discharge mixture. In addition, the impact of substrate heating and post-deposition flash lamp annealing (FLA) on crystal growth has been studied. In general, it has been stablished a transition from SnO to SnO2 arrangements by increasing PO2, where XRD and XANES provide complementary results about the formation of single- and mixed-phase films. In samples produced at room temperature, XANES gives unique information about such structural evolution, as well as related to defects like the incorporation of O2 molecules at high PO2. FLA on samples grown at room temperature promotes crystal growth and the phase evolution follows the initial structural selectivity. Finally, the optical properties and surface morphology of the films have been correlated with the structural identification.