O2 Atmosphere Research Articles

Induced p-type semiconductivity in Mg-doped Nd2Zr2O7 pyrochlore system

Heterovalent B-site MgO substitution in the Nd2Zr2O7-system (Nd2Zr2−xMgxO7−x) has been explored. The pyrochlores were synthesized by a polymeric sol-gel method and characterized by X-ray diffraction (XRD), Raman spectroscopy and Scanning Electron Microscopy to determine structure, phase composition and microstructure. Impedance Spectroscopy (IS) was employed to study the electrical behavior of the ceramics over the ranges 200–800 °C and under pure N2 and O2. The XRD showed that the solid solution limit was x > 0.02 and all the materials show a cubic Fd3̅m structure. The Raman results confirm the structural disorder created by the introduction of Mg2+ and the subsequent generation of oxygen vacancies. The IS data shows a dramatical increase of the oxide-ion conductivity when doping and that the conductivity depends strongly on the atmosphere, leading to p-type semiconductivity under pure O2 atmosphere. The present study highlights the use of heterovalent dopants to drastically increase the oxide-ion conductivity of pyrochlore-like materials.

Pyrolysis and combustion kinetics of refuse derived fuel having different plastic ratio

This study reports the effect of plastic variation on the decomposition kinetics, and thermodynamic parameters of refuse-derived fuel (RDF) in the N2 and O2 atmospheres. Two simulated RDF compositions were analyzed: RDF-1 with 35 %-plastics, and RDF-2 with 5 %-plastics. Thermo-gravimetric analysis was conducted at multiple heating rates. The activation energy (E) and the pre-exponential factor (A) were determined using both Kissinger-Akahira-Sunnose, Flynn–Wall–Ozawa methods and the compensation factor method, respectively. In N2-atmosphere, increasing plastic fraction from 5 % to 35 %, increased both E, and A values from 169 to 259 kJ mol−1 and 1.6 × 1010 to 1.2 × 1023 s−1, respectively, due to higher energy requirement for plastic decomposition. However, an increase in plastic fraction reduces the fixed‑carbon content of RDF, which leads to a decrease in E and A values in the O2-atmosphere from 126 to 105 kJ mol−1 and 3.5 × 1016 to 1.6 × 106 s−1, respectively.

Sulfate triple-oxygen-isotope evidence confirming oceanic oxygenation 570 million years ago

The largest negative inorganic carbon isotope excursion in Earth’s history, namely the Ediacaran Shuram Excursion (SE), closely followed by early animal radiation, has been widely interpreted as a consequence of oceanic oxidation. However, the primary nature of the signature, source of oxidants, and tempo of the event remain contested. Here, we show that carbonate-associated sulfate (CAS) from three different paleocontinents all have conspicuous negative 17O anomalies (Δ′17OCAS values down to −0.53‰) during the SE. Furthermore, the Δ′17OCAS varies in correlation with its corresponding δ34SCAS and δ18OCAS as well as the carbonate δ13Ccarb, decreasing initially followed by a recovery over the ~7-Myr SE duration. In a box-model examination, we argue for a period of sustained water-column ventilation and consequently enhanced sulfur oxidation in the SE ocean. Our findings reveal a direct involvement of mass-anomalously 17O-depleted atmospheric O2 in marine sulfate formation and thus a primary global oceanic oxygenation event during the SE.

Effects of process atmosphere on additively manufactured FeCrAl oxide dispersion strengthened steel: Printability, microstructure and tensile properties

In this study, the effects of using a reactive process atmosphere (premixed Ar–O2 mixture and N2) on additively manufactured FeCrAl oxide dispersion strengthened (ODS) steel are evaluated by investigating the oxygen/nitrogen content of the as-built material, geometric characteristics and stability of the molten pool, microstructural feature, second phase formation and tensile properties. It was found that the use of reactive process gas within the building chamber allowed for in-situ alloying in the molten pool. With increasing oxygen content in the building chamber, more oxygen was dissolved by the molten pool allowing for more oxide formation. However, oxide agglomeration and coarsening were also seen to occur. When printing under the N2 process atmosphere, the nitrogen content in the as-built material increased, and the oxide agglomeration and coarsening were alleviated. A smaller depth-to-width ratio of the molten pool and a more uniform low-angle grain boundaries (LAGBs) distribution in the as-built material were realized when printing under Ar-1% O2 or N2 process atmosphere. Nitrogen, as low-cost gas, can be considered to replace traditional Ar as shielding gas for improved mechanical properties of as-built parts.

Friction behaviour and mechanism of a-C films in hydrogen, nitrogen, and oxygen atmospheres: Insights from reactive molecular dynamics

In this work, the friction mechanism of amorphous carbon (a-C) films in hydrogen (H2), nitrogen (N2), and oxygen (O2) atmospheres are investigated by using reactive molecular dynamics simulations. It is found that the a-C film has the highest friction in the H2 atmosphere and ultra-low friction in the O2 atmosphere. Further studies show that a-C films are difficult to passivated by H atoms. The violent diffusion of H atoms to a-C film under the action of high friction temperature leads to the increase of C atom density at the friction interface, resulting in high friction. In the O2 atmosphere, O atoms almost do not diffuse to the a-C film, mainly exist at the friction interface, weaken the density of C atoms, and form gas-dynamic lubrication to produce ultra-low friction. In addition, graphitization and passivation are not the key factors determining the low friction in the gas atmosphere.

Thermal oxidation of Ti-6Al-4V ELI with an ultrafine-grained surface at 500 °C: Oxidation kinetics, oxide characterization and corrosion performance

The oxidation behavior of Ti6Al4V ELI alloy subjected to surface severe plastic deformation (SSPDed) is compared to its solution annealed (SAed) counterpart in Ar + 20 % O2 atmosphere at 500 °C. Moreover, the corrosion performance of oxidized SAed and SSPDed samples is examined in the Ringer solution. The significantly increased presence of high-diffusivity paths, specifically dislocations and grain boundaries (GBs), on the surface of SSPDed sample facilitates the diffusion of oxygen anions and scale-forming elements toward the oxidation front. The SSPDed sample shows a superior oxidation performance due to the rapid formation of a three-layered oxide scale (consisting of an outer Al-rich, an intermediate Ti-rich, and an inner Al-rich oxide layer) on its surface. In contrast to the SAed sample, the SSPDed displays inner and outer Al-rich oxide layers that are more uniform and virtually continuous. The study proposes a physical model that attributes the improved high temperature oxidation and enhanced corrosion resistance of oxidized SSPDed samples to the latter Al-rich inner oxide layer.

Photogeneration of singlet oxygen catalyzed by hexafluoroisopropanol for selective degradation of dyes

Singlet oxygen (1O2) shows great potential for selective degradation of dyes in environmental remediation of wastewater. In this study, we showcased that 1O2 can be effectively generated from an anion complex composed of deprotonated hexafluoroisopropanol anion ([HFIP-H]‒) with hydroperoxyl radical (⋅HO2) via ultraviolet (UV) photodetachment. Electronic structure calculations and cryogenic negative ion photoelectron spectroscopy unveil critical proton transfer upon complex formation and electron ejection, effectively photoconverting prevalent triplet ground state 3O2 to long-lived excited 1O2, stabilized by nearby HFIP. Inspired by this spectroscopic study, a novel "photogeneration" strategy is proposed to produce 1O2 with the incorporation of atmospheric O2 and HFIP, acting as a catalyst. Conceptually, the designed catalytic cycle upon UV irradiation and electron injection is able to achieve different degradations of dye molecules in a controllable fashion from decolorization to complete mineralization, shedding new light on potential water purification.

Trace elements in sedimentary pyrite track redox and nutrient fluctuations in the Ediacaran/Cambrian Bambuí Group, Brazil

We apply trace element analysis of syn-sedimentary pyrite to track the redox and nutrient variations in the Ediacaran-Cambrian Bambuí Group of eastern Brazil. Sedimentary pyrite from black shales interleaved within the basal cap carbonate of the 635–600 Ma Pedro Leopoldo Member, deposited in an open marine setting connected to the global sea, preserve high Mo up to >200 ppm, erratic enrichment of micronutrients such as Cu, Ni, Ba, Zn and uniform enrichment of Se. This indicates the importance of oxidative continental weathering and development of an enhanced Redox Sensitive Elements (RSE) dissolved reservoir on the aftermath of the Marinoan glaciation, with atmospheric O2 levels, calculated from Se/Co ratios of pyrites, around 2.5–3.5 wt%. A shallow oxic layer over deep euxinic realms made possible by high concentrations of dissolved sulfate was probably maintained up to the late Ediacaran, during deposition of the Cloudina-bearing Lagoa Santa Member (585–540 Ma). Upsection, however, radical shifts to muted Mo concentrations and overall low micronutrient concentrations are recorded in the Serra de Santa Helena Formation, with O2 levels plunging below 1 wt%. This indicates the development of ferruginous bottom water conditions in a sulfate-poor setting, due to restriction of the basin by the encircling Brasiliano mountains that formed Gondwana. The restricted, oxygen-poor and nutrient-depleted conditions caused the demise of complex life forms and hampered the development of typical Ediacaran-Cambrian ecosystems. Basin re-connection might have occurred during deposition of the Lagoa do Jacaré Formation, with independent proxies such as local tidal facies indicating a return to more ventilated conditions in the upper Bambuí Group. Our results highlight the importance of basin restriction and connection over coupled redox-nutrients variations during the development of Ediacaran-Cambrian ecosystems.

Pearls and Pitfalls of Isolating Rat OPCs for In Vitro Culture with Different Methods

There are several in vitro models to study the biology of oligodendrocyte progenitor cells (OPCs). The use of models based on induced pluripotent stem cells or oligodendrocyte-like cell lines has many advantages but raises significant questions, such as inaccurate reproduction of neural tissue or genetic instability. Moreover, in a specific case of studying the biology of neonatal OPCs, it is particularly difficult to find good representative model, due to the unique metabolism and features of these cells, as well as neonatal brain tissue. The following study evaluates two methods of isolating OPCs from rat pups as a model for in vitro studies. The first protocol is a modification of the classical mixed glial culture with series of shakings applied to isolate the fraction of OPCs. The second protocol is based on direct cell sorting and uses magnetic microbeads that target the surface antigen of the oligodendrocyte progenitor cell—A2B5. We compared the performance of these methods and analyzed the purity of obtained cultures as well as oligodendrocyte differentiation. Although the yield of OPCs collected with these two methods is similar, both have their advantages and disadvantages. The OPCs obtained with both methods give rise to mature oligodendrocytes within a few days of culture in ITS-supplemented serum-free medium and a 5% O2 atmosphere (mimicking the endogenous oxygen conditions of the nervous tissue).Graphical Methods for isolating rat OPCs In the following study we compared methods for isolating neonatal rat oligodendrocyte progenitor cells, for the studies on the in vitro model of neonatal brain injuries. We evaluated the purity of obtained cell cultures and the ability to maturate in physiological normoxia and serum-free culture medium.

Waste eggshell to valuable Co3O4/eggshell material as an efficient catalyst for catalytic decomposition of N2O under simulated real tail gases

Co3O4 shows excellent catalytic activity for N2O decomposition, in which it is urgently needed to develop novel efficient catalysts/supports with cheap and environmentally-friendly properties. Herein, Co3O4 nanoparticles decorated eggshell catalysts (Co3O4/eggshell-GR, Co3O4/eggshell-IM, and Co3O4/eggshell-DP) were prepared using simple grinding, impregnation, and deposition-precipitation methods, where waste eggshells were used as an effective support and reaction-promoter. The results indicated that the preparation methods significantly influenced the catalytic activity of Co3O4/eggshell catalysts; the highest activity was obtained over the Co3O4/eggshell-DP. The activity of Co3O4/eggshell-DP was comparable to that of pure Co3O4. More importantly, its specific activity was about 7.3 times that of Co3O4 at 400 °C. The examined Co3O4/eggshell-DP also displayed outstanding stability and anti-poisoning property in NO, O2, and/or H2O-containing atmospheres. It was also verified that the excellent activity of Co3O4/eggshell-DP correlated with the unique structure of the eggshell and the close incorporation between CaCO3 and Co3O4. The Co3O4/eggshell-DP catalyst owned abundant Co3O4 nanoparticles, more Co3+ species, and excellent redox performance, promoting the conversion of N2O at a lower temperature. The presence of abundant surface basic sites and a larger amount of oxygen vacancies also facilitated the catalytic efficiency of Co3O4/eggshell-DP.

Effect of Oxygen Concentration on the Growth and Cathodoluminescence Properties of MgO Nanowires

MgO nanowires were grown by a thermal evaporation method at different N2/O2 gas ratios in order to investigate the effect of oxygen concentration on the growth and luminescence properties of the MgO nanowires. A thermal evaporation process was conducted at 1000oC and under a pressure of 500Torr. No nanowires were grown in a pure N2 gas atmosphere. Nanowires were formed at oxygen concentrations above 25% in a mixture of N2 and O2 gases. X-ray diffraction analysis showed that the MgO nanowires had a cubic crystal structure. Compared to the nanowires formed at high oxygen concentration, the nanowires grown at low oxygen concentration had larger diameters and rougher side surfaces. Nanowires with very smooth side surfaces were formed at high oxygen concentrations. The difference in surface roughness was supposed to be due to the change in the growth habit of nuclei. Two visible emissions were observed in the cathodoluminescence spectra of the MgO nanowires. One was an emission peak centered near 400 nm and the other was an emission peak with a central wavelength of 500 nm. As the oxygen concentration increased, the emission intensity of the 400 nm band decreased and the emission intensity of the 500 nm band increased. The maximum emission at 500 nm was observed from the nanowires formed in a pure O2 atmosphere. The full width at half maximum of the emission peak at 500 nm was narrower than that of the emission peak at 400 nm.

Strong positive fractionation of chromium isotopes in iron formation of the Jacadigo Group (Brazil) – A link to enhanced atmospheric oxygenation during the Late Neoproterozoic

Cr isotopes recorded in iron formations (IF) are considered to have the potential to reflect the isotope signatures in respective ambient surface seawater. The ∼600 Ma Fe and Mn deposits pertaining to the Banda Alta Formation (Urucum district, Mato Grosso do Sul, Brazil), comprise the world’s youngest and largest Neoproterozoic sedimentary Fe and Mn formations (MnF). Shale normalized Rare Earth Element and Yttrium (REY) patterns of drillcore samples show flat, positively sloped patterns with absent Europium anomalies and near- to supra-chondritic Yttrium-Holmium ratios with negative Cerium anomalies, which imply intermittent mixing of freshwater with seawater. Redox sensitive element enrichment factors (MoEF, UEF, CrEF) show positive correlation, indicating varying redox conditions across the Jacadigo Basin, with ephemeral euxinic conditions. The Cr isotope signatures across the Urucum IF (δ53Crauth at: Morraria Grande + 0.93 ± 0.34 ‰, 2σ, n = 28; Morro do Rabichão + 0.5 ± 0.4 ‰, 2σ, n = 3; and Morro do Urucum ca. + 0.64 ‰, n = 1) are statistically indistinguishable from previously published surface outcrop samples at Morro do Urucum. Our new data support: (1) a stable supply of oxidized Cr potentially from continental sources at the time of deposition, implying high atmospheric O2 levels in the Late Neoproterozoic; (2) insignificant alteration of the authigenic Cr isotope signals by tropical weathering despite surface iron up-concentration and leaching of carbonates, and (3) lack of isotope effects that would be associated with non-quantitative reduction processes and accompanying particulate transport to the chemical sediments in the Jacadigo Basin. The combined information from (isotope)geochemical data presented herein speak for a deposition of the Urucum IFs in restricted, periodically ice-covered and stratified sub-basins with partial connection to the open ocean, and for the presence of a sufficiently oxidative atmosphere which promoted a continuous supply of the surface waters with isotopically heavy Cr from the weathering landmasses at this time.

Influences of regeneration atmospheres on structural transformation and renderability of fluidized catalytic cracking catalyst

The regeneration of fluidized catalytic cracking (FCC) catalysts is an essential process in petroleum processing. The current study focused the regeneration reaction characteristics of spent fluidized catalytic cracking catalyst (SFCC) at different atmospheres with influences on pore evolution and activity, for a potential way to reduce emission, produce moderate chemical product (CO), and maintain catalyst activity. The results show that regeneration in air indicates a satisfaction on removing coke on the catalyst surface while giving a poor effect on eliminating the coke inside micropores. This is attributed that the combustion in air led to a higher temperature and further transformed kaolinite phase to silica-aluminum spinel crystals, which tended to collapse and block small pores or expand large pores, with similar results observed in pure O2 atmosphere. Nevertheless, catalysts regenerated in O2/CO2 diminished the combustion damage to the pore structure, of which the micro porosity after regeneration increased by 32.4% and the total acid volume rose to 27.1%. The regeneration in pure CO2 displayed low conversion rate due to the endothermic reaction and low reactivity. The coexistence of gasification and partial oxidation can promote regeneration and maintain the original structure and good reactivity. Finally, a mechanism of the regeneration reaction at different atmospheres was revealed.

Hydrocarbon Oxidation by a Porphyrin-π-Cation Radical Complex.

Heme and chlorin π-cation radical oxidants are widely implicated in biological and synthetic oxidation catalysis. Little insight into the role of π-cation radicals in proton coupled electron transfer (PCET) oxidation is available. We prepared a NiII-porphyrin-π-cation complex ([NiII(P•+)]) and found it to be capable of the oxidation of a variety of simple hydrocarbon substrates. Interestingly, some of the products were hydroxylated, with ([NiII(P•+)]) working in concert with atmospheric O2 to yield hydroxylated hydrocarbons. Kinetic data suggested that the porphyrin-π-cation radical species oxidised substrates via a concerted PCET mechanism, where the nickel porphyrin-π-cation radical accepted the electron, and the proton was transferred to a free anion. Our findings highlight the potential role of π-cation radicals as hydrocarbon activators, demonstrating that porphyrin ligand non-innocence could be a readily manipulated resource for oxidation catalyst development.

Hydrocarbon Oxidation by a Porphyrin‐π‐Cation Radical Complex

AbstractHeme and chlorin π‐cation radical oxidants are widely implicated in biological and synthetic oxidation catalysis. Little insight into the role of π‐cation radicals in proton coupled electron transfer (PCET) oxidation is available. We prepared a NiII‐porphyrin‐π‐cation complex ([NiII(P⋅+)]) and found it to be capable of the oxidation of a variety of simple hydrocarbon substrates. Interestingly, some of the products were hydroxylated, with ([NiII(P⋅+)]) working in concert with atmospheric O2 to yield hydroxylated hydrocarbons. Kinetic data suggested that the porphyrin‐π‐cation radical species oxidised substrates through a concerted PCET mechanism, where the porphyrin‐π‐cation radical accepted the electron, and the proton was transferred to a free anion. Our findings highlight the potential role of π‐cation radicals as hydrocarbon activators, demonstrating that porphyrin ligand non‐innocence could be a readily manipulated resource for oxidation catalyst development.

Co-thermal conversion, atmosphere, and blend type controls over heavy metals in biochars and bottom slags of textile dyeing sludge and durian shell

The co-thermal conversions of textile dyeing sludge ((TDS) with biomass may be turned into a feasible and green technology to valorize energy and products, but the transformation behavior of heavy metals remains unclear. This study aimed to quantify the migrations and distributions of HMs in biochars and bottom slags and their environmental risks in response to the co-pyrolysis and co-combustion of durian shell (DS) and TDS, atmosphere type, blend ratio, and temperature. The co-combustion interaction of DS and TDS raised the residual HM contents of the bottom slag. Co-pyrolysis reduces the environmental risks of HMs of the TDS, and the effect of CO2 atmosphere is better. In 80N220O2, Cr, Zn, and Cu in the TDS bottom slag had the highest leaching toxicity concentrations at 900 °C. At 800 °C, the leaching toxicity concentrations of HMs were Cr > Cu > Zn > Mn in TDS. The O2 concentration and atmosphere type did not significantly affect the HM morphology and transformation. K increased the temperature of converting solid-phase Ni to slag-phase NiO in DS sample and affected the transformation temperature and strength of Ni, Zn, and Pb in other sample at the high temperature. The combined results of all the three optimizations of HM contents, forms, and risks pointed to add 50 % DS in the N2 atmosphere and add 50 % DS in 50N250O2 and 80CO220O2 atmospheres as the optimal co-pyrolysis/combustion settings, respectively.

P-212 βhCG concentration in peripherical maternal blood after single embryo transfer, ongoing pregnancy rates and morphokinetics

Abstract Study question Is there a relationship between the concentration of the βhCG hormone in maternal blood, embryo morphokinetics and clinical outcome? Summary answer βhCG concentration is related to trophoectoderm quality, abortion rate and live birth rate, but not to embryo morphokinetics What is known already Measurement of βhCG has been widely used for early pregnancy detection after assisted reproduction treatments. Shortly after embryo implantation, trophoblastic βhCG is detectable in maternal blood, However, βhCG concentration in several women showed high variability, and embryo implantation also depends on endometrial receptivity, what means that in early stages, everything affecting endometrial receptivity, may affect βhCG concentration. Early high βhCG concentration has been related with higher pregnancy rate, but there are scarce information concerning relationship between βhCG early value and ongoing pregnancy rates Study design, size, duration Retrospective biomedical research of 508 patients having single embryo transfer of fresh embryos at IVIRMA VIGO clinic between 2017 and 2021 to analyse the relation between βhCG concentration, and embryo quality, embryo morphokinetics and ongoing pregnancy rate. Patients with recurrent miscarriage, advanced maternal age, uterine pathologies and severe male factor were excluded of the study. βhCG was measured in the peripherical maternal blood 13 days after embryo transfer Participants/materials, setting, methods All the embryos were generated by ICSI and were cultured in a time-lapse incubator under a 37ºC, 6% CO2 and 5% O2 atmosphere. T-Student and Youden test between embryo kinetics and βhCG values, Pearson correlation test to compare gestational successes with kinetic embryo data, and a linear regression model with βhCG like response variable and morphokinetic data like explanation variables were employed Main results and the role of chance βhCG concentration was greater in trophoectoderm A embryos compared to B and C (ASEBIR classification), 619.53 UI/ml, IC95% (483.16-755.90), 442.24 UI/ml, IC95% (350.18-534.31), 269.95 UI/ml, IC95%(88.88-451.01) (p = 0.038) respectively and there was a trend with Inner cell mass quality, being greater also in quality A vs B and C (p = 0.053) Patients who had a clinic abortion showed lower βhCG concentration compared to those with ongoing pregnancy and live birth, 385.37 UI/ml, IC95% (268.45-502.28) vs 987.53 IU/ml, IC95% (845.03-1130.03). T-student test linear regression analysis and Youden index, with βhCG cut-off points of 10 IU/ml and 100 IU/ml were employed, to analyze relationship between βhCG concentration and embryo morphokinetics, but it was not significant in any of the parameters analyzed Limitations, reasons for caution There is a limited sample size and data were obtained from a retrospective study. Patients and donor oocytes were analyzed in this study, although no differences were found when they compared Wider implications of the findings This study shows that a top quality trophoectoderm produces more βhCG, and that could be a predictive value for ongoing pregnancy Trial registration number 1712-VGO-122-EM

Quantitative assessment of aqueous sulfate contributions from Fe3+- and O2-driven oxidation pathways of hydrothermal sulfur using oxygen isotopes

Sulfate (SO42−) has been found in elevated concentrations in modern hydrothermal settings on Earth and linked to coupled ferric iron (Fe3+)- and molecular oxygen (O2)-driven oxidations of hydrothermal H2S and secondary sulfur (S) deposits enriched in elemental S and sulfide minerals. However, the relative proportions of SO42− from these two oxidation mechanisms in surface acidic hydrothermal systems are unclear. To address this uncertainty, we determined the aqueous SO42− contributions via Fe3+- and O2-driven oxidation pathways in acidic hot springs and mudpots of Iceland (Námafjall, Krýsuvík) and the United States (Valles Caldera, Lassen, Yellowstone). Approximately 40 water and 11 fumarole sediment samples were collected for oxygen isotope analyses (δ18O). The oxidation processes appear to be accompanied by large variation of the δ18O of SO42− (−8.8 to +5.5 ‰) similar to the δ18O of hot spring and mudpot water (−15.5 to +6.3 ‰), which is greatly controlled by inflow of meteoric water (e.g., runoff, groundwater) and surface evaporation. In the studied sites, the Fe3+-driven oxidation of hydrothermal elemental S and sulfide minerals appears to be an important source of SO42−, contributing ∼55 to 100% of SO42− when compared to contributions from O2-driven oxidation. Additionally, the distinctive high δ18O values of SO42− (up to +13.7 ‰) accompanied direct oxidation of H2S and/or hydrothermal S minerals by atmospheric O2 in dry (fumarolic) environments. This, in turn, is in agreement with previously determined O isotope fractionations (εsulfate-atm.oxygen ∼ 9.8 ‰) for low-temperature sulfide oxidation in the presence of O2. Our new quantitative measures of oxidation pathways signify the importance of Fe3+-driven oxidation of hydrothermal S to SO42− in the surface volcanic settings, which have significant implications for understanding widespread occurrences of SO42− found on the Fe-rich volcanic terrains of Mars.

P-391 Importance of oxygen tension in human ovarian tissue in vitro culture

Abstract Study question Is there any difference between 20% and 5% oxygen (O2) tension on the viability and quality of human follicles contained in cultured ovarian cortex? Summary answer 5% O2 yields higher follicle viability and quality than does 20% O2 tension after 6 days of in vitro culture (IVC). What is known already The primordial follicle (PMF) pool resides within the ovarian cortex, where in vivo O2 tension ranges between 2% and 8%. However, IVC is commonly performed at atmospheric O2 tension (20% O2), yielding low follicle survival rates. Elevated O2 tension or insufficient antioxidant protection can cause excessive reactive oxygen species (ROS) accumulation, leading to DNA lesions, such as oxidative stress damage and double-strand breaks (DSB). Study design, size, duration This prospective experimental study included frozen-thawed ovarian cortex from 6 adult patients (mean age: 28.5 years; age range: 26–31 years) undergoing laparoscopic surgery for non-ovarian diseases. Ovarian cortical fragments were cultured for 6 days at (i) 20% O2 with 5% CO2, and (ii) 5% O2 with 5% CO2. Non-cultured fragments served as controls. Participants/materials, setting, methods Cortical fragments were analyzed according to: hematoxylin and eosin (H&E) staining for follicle count and classification; cleaved caspase-3 immunostaining to identify follicle apoptosis; 8-hydroxy-2-deoxyguanosine (8-OHdG) and gamma-H2AX (γH2AX) immunolabeling to detect oxidative stress damage and DNA DSBs; and β-galactosidase staining to assess follicle senescence. Droplet digital PCR was also performed to further explore gene expression of superoxide dismutase 2 (SOD2) from the antioxidant defense system, and cyclin-dependent kinase inhibitors (p21 and p16) as senescence-related genes. Main results and the role of chance Apoptosis (p = 0.002) and follicle senescence (p = 0.03) rates were significantly lower in the 5% O2 than the 20% O2 group. Moreover, granulosa cells (GCs) in follicles in the 20% O2 group exhibited significantly (p < 0.001) higher oxidative stress damage rates than in the 5% O2 group. DNA DSB damage rates in GCs of follicles were also significantly higher (p = 0.001) in the 20% O2 than the 5% O2 group. SOD2 values were significantly greater in the 5% O2 group compared to the 20% O2 group (p = 0.04) and the non-cultured group (p = 0.002). Expression of p21 was significantly increased in 20% O2 (p = 0.03) and 5% O2 (p = 0.008) compared to no culture. Moreover, the 20% O2 group showed significantly greater p16 expression (p = 0.04) than the non-cultured group, while no significant variation was observed between 5% O2 and no culture. Limitations, reasons for caution This study focuses on improving follicle outcomes during the first step of ovarian tissue IVC, where follicles remain in situ within the tissue. The impact of O2 tension in further steps, such as secondary follicle isolation and maturation, was not investigated here. Wider implications of the findings Our findings suggest that 5% O2 tension culture is a promising step towards potentially solving the problem of poor follicle viability after IVC. Trial registration number N/A

Tuning charge transfer and magnetic properties in LaCoO3/LaMnO3/LaCoO3 trilayers by oxygen content

In this manuscript, perovskite oxide LaCoO3/LaMnO3/LaCoO3 (LLL) trilayers and the single-layer LaMnO3 (LMO) and LaCoO3 (LCO) films are epitaxially grown on (001)-oriented SrTiO3 substrates by polymer-assisted deposition combining with heat treating in Ar, air, and O2 atmospheres, respectively. The crystal structure and magnetic properties are investigated. It is found that the responses of LMO and LCO films to oxygen content are different, and the magnetic property of LMO is more sensitivity to oxygen content than that of LCO. The oxygen content can directly affect the structure and magnetic properties of LMO and LCO layers, which, in turn, modulate the interfacial magnetic properties of the LLL trilayers through interlayer coupling. By comparison with the magnetic properties of the single-layer films, an abnormal ferromagnetic (FM) transition is found in the LLL trilayers at around 216 K, besides two known FM transitions corresponding to those in the LCO and LMO layers, respectively. It is suggested that the abnormal FM transition is attributed to Mn4+–O–Co2+ FM super-exchange interaction, which is induced by the charge transfer from Mn3+ to Co3+ ions and the interlayer coupling between the LMO and LCO layers. The interlayer coupling of the trilayers, including the interfacial coupling and the diffusion-induced inlayer coupling, dominates the interface properties, which are tuned by oxygen content-dependent charge transfer. The cooperative function of the orbital/charge structure and the interlayer coupling dominates the magnetic properties of the LLL trilayer under the tensile strain. These findings provide new avenues to regulate the electronic and magnetic states of perovskite oxide multilayers and another way to the development of multifunctional electronic devices.