Low PO2 Research Articles

Effects of fluid-induced oxidation on the composition of Fe–Ti oxides in the Eastern Gabbro, Coldwell Complex, Canada: implications for the application of Fe–Ti oxides to petrogenesis and mineral exploration

Magnetite (mag)–ilmenite (ilm) intergrowths are more common than mag–ulvospinel (usp) intergrowths in mafic–ultramafic Ni–Cu–PGE systems, yet the former has no known solid solution. The most accepted model for the formation of mag–ilm intergrowths in terrestrial environments is fluid-induced oxidation of mag–usp assemblages by oxygen in water. In this study, we re-examine this model in light of the fact that crustal fluids have very low pO2 and that mag–ilm intergrowths commonly occur in rocks that show little or no evidence of hydrothermal alteration. We also characterize the chemical changes that occurred during the formation of mag–ilm intergrowths and how they affect the use of Fe–Ti oxide chemistry for petrogenesis and mineral exploration. In the Eastern Gabbro, Coldwell Complex, a continuum of Fe–Ti oxide intergrowths occur ranging from cloth (mag–usp) to trellis (mag–ilm) types. Trellis-textured intergrowths have higher bulk Fe3+:Fe2+ ratios and are predominantly enriched not only in some multivalent (Ge, Mo, W, Sn) elements, but also in Cu and Ga, consistent with their formation via oxidation by a metal-rich fluid. These compositional changes are significant relative to typical elemental abundances in Fe–Ti oxides and could potentially lead to erroneous interpretations regarding primary magmatic processes if they are not taken into consideration. The irregular distribution of the intergrowths throughout the Eastern Gabbro suggests that different rock series and mineralized zones experienced variable degrees of fluid-induced oxidation. It is proposed that C in CO2 rather than O2 in water could potentially be an important oxidizing agent in mafic systems: $$ 9{\mathrm{Fe}}_2^{2+}\mathrm{Ti}{\mathrm{O}}_4+0.75{\mathrm{CO}}_2+1.5{\mathrm{H}}_2\mathrm{O}\leftrightharpoons 9{\mathrm{Fe}}^{2+}\mathrm{Ti}{\mathrm{O}}_3+3{\mathrm{Fe}}_2^{3+}{\mathrm{Fe}}^{2+}{\mathrm{O}}_4+0.75\mathrm{C}{\mathrm{H}}_4 $$ The applicability of this model is supported by the common occurrence of CO2 and CH4 in fluid inclusions in mafic rocks.

Muscle cooling modulates tissue oxidative and biochemical responses but not energy metabolism during exercise.

This study investigated whether muscle cooling and its associated effects on skeletal muscle oxidative responses, blood gases, and hormonal concentrations influenced energy metabolism during cycling. Twelve healthy participants (Males: seven; Females: five) performed two steady-state exercise sessions at 70% of ventilatory threshold on a cycle ergometer. Participants completed one session with pre-exercise leg cooling until muscle temperature (Tm) decreased by 6°C (LCO), and a separate session without cooling (CON). They exercised until Tm returned to baseline and for an additional 30min. Cardiovascular, respiratory, metabolic, hemodynamic variables, and skeletal muscle tissue oxidative responses were assessed continuously. Venous blood samples were collected to assess blood gases, and hormones. Heart rate, stroke volume, and cardiac output all increased across time but were not different between conditions. V̇O2 was greater in LCO when muscle temperature was restored until the end of exercise (p < 0.05). Cycling in the LCO condition induced lower oxygen availability, tissue oxygenation, blood pH, sO2%, and pO2 (p < 0.05). Insulin concentrations were also higher in LCO vs. CON (p < 0.05). Importantly, stoichiometric equations from respiratory gases indicated no differences in fat and CHO oxidation between conditions. The present study demonstrated that despite muscle cooling and the associated oxidative and biochemical changes, energy metabolism remained unaltered during cycling. Whether lower local and systemic oxygen availability is counteracted via a cold-induced activation of lipid metabolism pathways needs to be further investigated.

The problem of accuracy in single-channel open probability measurements

The function of ion channels to mediate the flux of ions through membranes of living cells depends on their number, conductance, and open probability. The open probability, PO, characterizes gating of channels that is sensitive to experimental conditions and that can be determined in single-channel experiments. Individual experimental records and even whole series of single-channel activity measurements represent random samples of the stochastic gating continuous in time. The aim of this study was to understand the relationship between the accuracy (trueness and precision) of PO determination and the method of single-channel activity data collection. We used simulated single-channel experiments with variable settings of data collection for a range of open probability values. We found that at low PO, the trueness of PO determination depends on the average number of channel openings per record, while the precision of PO determination depends on the total number of channel openings in the whole dataset and on the distribution of open and closed times. We derived relationships that allow planning of single-channel experiments for the required accuracy of PO determination over a large span of open probabilities.

Role of oxygen atmosphere on fabrication and photovoltaic properties of amorphous Sn-I-O electron transport layer

Amorphous tin-indium-oxide (TIO) thin films as an electron transport layer (ETL) for perovskite solar cells (PSCs), were grown under controlled oxygen partial pressure (PO2). The effect of PO2 during TIO deposition on the photovoltaic response of TIO-ETL-based PSC was evaluated. A device of TiCl4 treated TIO-77 at.% deposited under lower PO2 shows improved shunt resistance and exhibited the best power conversion efficiency of 15%, which is greater than the devices deposited at high PO2. This work deciphers the importance of deposition atmosphere in fabricating ETLs for PSCs.

Nitric oxide mediates metabolic functions in the bivalve Arctica islandica under hypoxia.

The free radical nitric oxide (NO) is a powerful metabolic regulator in vertebrates and invertebrates. At cellular concentrations in the nanomolar range, and simultaneously reduced internal oxygen partial pressures (pO2), NO completely inhibits cytochrome-c-oxidase (CytOx) activity and hence mitochondrial- and whole-tissue respiration. The infaunal clam Arctica islandica regulates pO2 of hemolymph and mantle cavity water to mean values of <5 kPa, even in a completely oxygen-saturated environment of 21 kPa. These low internal pO2 values support a longer NO lifespan and NO accumulation in the body fluids and can thus trigger a depression of metabolic rate in the clams. Measurable amounts of NO formation were detected in hemocyte cells (~110 pmol NO 100−1 hemocytes h-1 at 6 kPa), which was not prevented in the presence of the NO synthase inhibitor L-NAME, and in the gill filaments of A. islandica. Adding a NO donor to intact gills and tissue homogenate significantly inhibited gill respiration and CytOx activity below 10 kPa. Meanwhile, the addition of the NO-oxidation product nitrite did not affect metabolic rates. The high nitrite levels found in the hemolymph of experimental mussels under anoxia do not indicate cellular NO production, but could be an indication of nitrate reduction by facultative anaerobic bacteria associated with tissue and/or hemolymph biofilms. Our results suggest that NO plays an important role in the initiation of metabolic depression during self-induced burrowing and shell closure of A. islandica. Furthermore, NO appears to reduce mitochondrial oxygen radical formation during surfacing and cellular reoxygenation after prolonged periods of hypoxia and anoxia.

Effect of high oxygen deficiency in nano-confined bismuth sesquioxide

Bismuth sesquioxide in its cubic form, i.e. δ-Bi2O3, is the fastest oxygen ionic conductor known which has important applications in energy technologies. However, the material is unstable as it undergoes high-density polymorphic transitions and degradation. In this work, we show that δ-Bi2O3 can be stabilized both at high and low temperatures (T < 775 °C) under low oxygen partial pressure (pO2 < 10−5 atm), where the material is nanostructured in multilayered thin film coherent heterostructures with yttrium stabilized zirconia. Density Functional Theory calculation confirms such a form of metastability, also showing that high oxygen defect concentration favors the cubic phase. Moreover, high oxygen deficiency in the nanoionics leads to an unexpected ‘two-regime’ conductivity with high values (σ > 1 S cm−1 at 600 °C) at high pO2 and lower ionic conductivity (σ ∼ 0.1 S cm−1 at 600 °C) at low pO2. Ionic conductivity at low pO2 occurs with high activation energy (Ea > 1.5 eV), suggesting a drastic decrease in mobility for high concentration of defects.

COVID-19 Epidemic in the Middle Province of Northern Italy: Impact, Logistics, and Strategy in the First Line Hospital.

The novel coronavirus (COVID-19) began in China in early December 2019 and rapidly has spread to many countries around the globe, with the number of confirmed cases increasing every day. An epidemic has been recorded since February 20 in a middle province in Northern Italy (Lodi province, in the low Po Valley). The first line hospital had to redesign its logistical and departmental structure to respond to the influx of COVID-19-positive patients who needed hospitalization. Logistical and structural strategies were guided by the crisis unit, managing in 8 days from the beginning of the epidemic to prepare the hospital to be ready to welcome more than 200 COVID-19-positive patients with different ventilatory requirements, keeping clean emergency access lines, and restoring surgical interventions and deferred urgent, routine activity.

Effect of mindfulness meditation protocol in subjects with various psychometric characteristics at high altitude.

IntroductionIncidence of high altitude‐related sickness is increasing due to more number of people visiting the areas of high altitude which may result in life‐threatening conditions including acute mountain sickness (AMS), high altitude pulmonary edema (HAPE), high altitude cerebral edema (HACE), and High‐altitude pulmonary hypertension (HAPH). We hypothesized that an advanced yoga regimen may be beneficial in dealing with the physiology of acclimatization.MethodsAnthropometric, Biochemical, and Psychological assessments were carried out in 48 participants before and after the advance meditation program (AMP) in the experimental group. Individuals with an age range of 20–65 years with no comorbidities were included in the study. Participants were exposed to AMP for 4 days. All assessments were carried out at the baseline and after the course. Prakriti was constituted for all participants using a standard questionnaire. The study was carried out after obtaining the written informed consent as per the guidelines outlined by the Institute Ethics Committee.ResultsPo2 and glucose levels were found significantly reduced along with changes in the Happiness index, anxiety, and mental well‐being. However, participants with lowered Po2, after 4 days of mindfulness intervention, showed a positive outcome measured by the established scales of anxiety, happiness, and information processing. Psychometric or Prakriti wise analysis revealed that subject with “Pitta” constitution exposed to high altitude and advance meditation showed changes in more parameters than “Vatta” or “Kapha” Constitution.ConclusionsAdvance meditation in the high altitude zone confers biochemical and neuro‐cognitive benefits. Molecular studies may require to understand the role of hypoxic condition in improving the disease state.

Investigation of the oxidation mechanism of an Al–Si–Al2O3 composite at 1100 °C and 1550 °C

An Al–Si–Al2O3 composite was prepared and sintered in air at 1100 °C and 1550 °C for 3 h to investigate the oxidation mechanism. The results show that the anti-oxidation performance of the Al–Si–Al2O3 composite is excellent, with anti-oxidation protection layers formed at both 1100 °C and 1550 °C, whereas the underlying oxidation mechanisms differ completely. At 1550 °C, Al(l), Si(l), and Al2O3(s) react with O2 directly to form a dense mullite solid solution at the surface of the sample, which seals all the diffusion channels of O2 into the sample, resulting in a rapid decrease in PO2 in the sample. At low PO2, Al(l), Si(l), and C(s) from the resin react with N2(g), and an AlN–SiC solid solution reinforcement is formed in the interior of the sample. At 1100 °C, the oxidation behaviour of Al(l), Si(s), and α-Al2O3(s) is different: Al(l) is oxidized to active α-Al2O3, and Si(s) particles are incompletely oxidized to Si@SiO2, accompanied by a volume expansion and a slow layer by layer decrease in PO2 in the sample. Then, the active oxidation of Al(l) occurs and a substantial amount of Al2O(g) is formed in the sample, which acts as a gas barrier to prevent O2 from penetrating into the sample, further lowering PO2. Then, the Al2O(g) and C(s) from the resin and the Al(l) in the interior react with N2(g) to form a whisker-like (Al2OC)1-x(AlN)x reinforcement in the sample. The Al–Si–Al2O3 composite shows the ability of self-healing at high temperatures in air atmosphere. The reaction model is established.

Local environmental variation obscures the interpretation of pyrite sulfur isotope records

Theoretically, within the long-term marine sulfur cycle, pyrite sulfur isotopes (δ34Spy) are determined by the degree of pyrite burial that is controlled by the marine redox conditions. Thus, the secular variation of δ34Spy records the history of marine and atmosphere redox evolution. As such, large magnitude change in δ34Spy in the Proterozoic has been attributed to widespread oceanic anoxia related to generally low atmospheric pO2 levels. However, noisy δ34Spy signals in the past 250 million years cannot be explained by the frequent oscillation of seawater redox, because the global ocean was already fully oxidized. Here, by developing a numerical model, we show that δ34Spy of syndepositional pyrite is significantly affected by local factors, such as organic matter content in sediment, sedimentation rate, and seafloor redox. Thus, the noisy δ34Spy records may reflect local environmental variations rather than the oscillation of global ocean redox. Our study also suggests that δ34Spy alone cannot provide a robust constraint on the global or local ocean redox condition. We suggest that, combining with the pyrite content data and δ34Spy can help quantify local/regional biogeochemical cycles.

Oxygen pumping characteristics of YBaCo4O7+δ for solar thermochemical cycles

A new medium-temperature oxygen sorbent material, YBaCo4O7+δ, was prepared and investigated for its potential applications as an oxygen pumping material to facilitate solar thermochemical fuel production using a two-step metal oxide redox cycle. The oxygen uptake and release attributes of YBaCo4O7+δ were studied by both thermogravimetric analysis and a small-scale vacuum test. The results reveal that the oxygen uptake capacity and kinetics of YBaCo4O7+δ depends on both the uptake temperature and partial pressure of oxygen (pO2), and can also be affected by the particle size. In the vacuum test, YBaCo4O7+δ could bring down the pO2 of a vacuum chamber from 21 kPa to 0.5 kPa, which accounted for over 97% of the oxygen in the system. It was also found that the major issue for applying YBaCo4O7+δ as pumping material came from the slow kinetics at the low pO2 level. The current study has proved that the particle size has a significant effect on the pumping behavior of YBaCo4O7+δ, especially for the uptake kinetics. Further research would be required for material development to make this application economically practical.

Effect of oxygen vacancies on electrical conductivity of La0.5Sr0.5FeO3−δ from first-principles calculations

Metal to semiconductor transition by hole compensation of excess electrons from VO and localized VO state in La0.5Sr0.5FeO3−δ under low PO2.

Biochemical and functional quality assessment of platelet concentrates

Background/Aim. Preparation of platelet concentrate (PC) from a unit of whole blood is a method dependent on a number of factors, which alone or together, can have a significant impact on the quality of the final product. Quality of PCs is determined with criteria defined in the Guide to the preparation, use and quality assurance of the Council of European Committee for Blood Transfusion. The aim of the study was to analyze the quality of PCs prepared from buffy coat (BC) and to allocate the factors of improvement and standardization of the quality of PCs. Methods. The study included a total of 80 PCs prepared from BC according to the standard procedure in the Blood Transfusion Institute Nis. The quality of PCs was determined according to the product volume and laboratory testing on the first (PC1), the third (PC3) and the fifth day (PC5) of the PC storage. The following parameters were determined: platelets, residual erythrocytes and leukocytes count, gas analysis [partial pressure of oxygen, carbon dioxide (pO2, pCO2)], pH, sterility and platelet aggregation triggered by using 3.2, 6.4 and 9.6 ?g collagen/mL (impedance aggregometry). Results. There were significantly lower platelet count, pO2, pCO2 and pH in the PC3 and PC5 samples (p &lt; 0.001). Except for the fulfillment of the criteria for platelet count, all the other quality parameters were in accordance with recommended criteria. Platelet aggregation for all the concentrations of collagen showed a decrease during the storage period, with statistically significant differences for PC3 and PC5 as compared to PC1 (p &lt; 0.01). There was statistically significant decrease in activity of PCs triggered with higher concentrations of collagen (6.4 and 9.6 ?g collagen/mL) in comparison with lower concentration of collagen (3.2 ?g collagen/mL). Conclusion. Platelet count, evaluated biochemical parameters and the platelet function were significantly changed during the storage period. In order to improve the quality of PCs it is important to store the products under proper conditions, change the type of plastic bag for PC storage and use platelet additive solutions (PAS) instead of plasma.

354: Does maternal anemia impact fetal oxygenation and risk of acidemia at term?

Anemia is a commonly diagnosed comorbidity in pregnancy. It decreases oxygen (O2) carrying capacity thereby increasing the risk of complications such as fetal growth restriction and preterm delivery. The effect of anemia on O2 delivery to the fetus is unknown. This study examines the relationship between maternal anemia and fetal oxygenation status as measured by umbilical cord pO2. This is a secondary analysis of a prospective cohort study of singleton term deliveries with universal admission CBC and cord gases between 2010 and 2014. Maternal anemia was defined as hemoglobin ≤10 g/dl on admission. The primary outcomes were umbilical artery (UA) and vein (UV) pO2; secondary outcomes were acidemia (UA pH< 7.1), low UA/UV pO2 (< 5th percentile), and high UA/UV pO2 (>90th percentile). Outcomes were compared between patients with and without anemia. Multivariable logistic regression was used to adjust for confounders. Of the 7,737 patients with an admission CBC and paired cord gases, 1,108 (14%) were anemic. Maternal anemia was associated with a significantly higher UA and UV pO2 [median (IQR): UA 20 (16,24) vs 19 (15,24) mmHg, p=0.01; UV 30 (25,36) vs 29 (23,34) mmHg, p< 0.01]. Compared to neonates of nonanemic mothers, neonates born to anemic mothers were more likely to have high UV pO2 >90% (15.9% vs 10.9%; aOR 1.51, 95% CI 1.26-1.82) and were less likely to have low UA pO2 < 5% (6.1% vs 7.7%, aOR 0.74, 95% CI 0.56-0.97). UV pO2 remained higher in anemic patients after stratifying by MCV. UA pO2 was higher only in patients with normocytic anemia. Proportions of UV pO2 < 5% and UA pO2 >90% were similar between groups. Although maternal anemia was associated with a significant difference in UA pH, there was no difference in neonatal acidemia (aOR 0.90, 95% CI 0.54-1.51). UA pCO2 and lactate were lower in the anemic group. Umbilical cord O2 content is higher in anemic mothers. Maternal anemia may lead to a compensatory rightward shift in the oxygen-hemoglobin dissociation curve, allowing for easier unloading of O2 to the placenta and increased O2 transfer to the fetus.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

37: Duration of maternal oxygen exposure and umbilical cord oxygen content

Maternal oxygen (O2) administration is a commonly performed intrauterine resuscitation technique. O2 is frequently administered for several minutes, sometimes hours, in order to maximize fetal oxygenation. We tested the hypothesis that a longer duration of O2 exposure is associated with higher umbilical cord pO2. This is a planned secondary analysis of a randomized noninferiority trial comparing O2 to room air (RA) in laboring patients. Patients were randomized to 10 L/min O2 or RA at any point in active labor when they developed Category II EFM. Interventions were generally continued until delivery. The primary outcome for this analysis was umbilical vein (UV) pO2. A secondary outcome was umbilical artery (UA) pO2. These were compared between patients with short and long durations of O2 exposure, defined as < 75th and ≥75th percentile of the duration of exposure in O2 arm, respectively. Outcomes were also compared between RA, short O2, and long O2 groups. Of the 114 randomized patients, 99 patients (48 O2 and 51 RA) had paired cord gases and were included in this analysis. Among O2 patients, the median duration of exposure was 96 minutes (IQR 47, 176). The 75th percentile for duration of exposure was 176 minutes. UV pO2 was lower in patients who received long durations (≥176 minutes) of O2 compared to those who received shorter durations (< 176 minutes) (median [IQR] 25.5 [21.5,33] vs 32.5 [26.5, 37.5] mm Hg, p=0.03) (Figure 1). There was no difference in UA pO2 between short and long duration O2 groups (Figure 2). There was no difference in UA or UV pO2 between RA, short duration O2, and long duration O2 groups (Table 1). Long durations of O2 exposure are not associated with higher cord pO2. In fact, patients with longer O2 exposure had lower UV pO2, suggesting impaired placental O2 transfer, possibly mediated by hyperoxia-induced placental vasoconstriction.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Influence of the hydrogen content on the optical properties of TiOx thin films

In this work, dark Ti(OxH)y films were obtained by DC magnetron reactive sputtering under different oxygen partial pressures (PO2) starting from a high base pressure chamber atmosphere (10−5 mbar) with the purpose of investigating the visible light absorption dependence of the hydrogen content and stoichiometry. The TiOx film compositions, thicknesses, and elemental depth profiles were measured by ion beam analysis (IBA) techniques in a self-consistent approach. The optical properties were investigated by visible and near-infrared spectrophotometry, and the crystallography was examined by small-angle X-ray diffraction. The films deposited at a low PO2 were dark, and as the partial oxygen pressure increases, they became transparent. The IBA showed that the hydrogen content exponentially decreased as the PO2 increased. The optical constants for the films, n and k, are dependent on oxygen and hydrogen ratio as well as the optical band gap that can be modulated from 0.40 to 3.25 eV, and thus a significant improved PEC activity. These modulations may be useful for optical or electronic devices as a variable semiconductor or dielectric layer.

The utility and determination of Pcrit in fishes.

The critical O2 tension (Pcrit) is the lowest PO2 at which an animal can maintain some benchmark rate of O2 uptake (ṀO2 ). This PO2 has long served as a comparator of hypoxia tolerance in fishes and aquatic invertebrates, but its usefulness in this role, particularly when applied to fishes, has recently been questioned. We believe that Pcrit remains a useful comparator of hypoxia tolerance provided it is determined using the proper methods and hypoxia tolerance is clearly defined. Here, we review the available methods for each of the three steps of Pcrit determination: (1) measuring the most appropriate benchmark ṀO2 state for Pcrit determination (ṀO2,std, the ṀO2 required to support standard metabolic rate); (2) reducing water PO2 ; and (3) calculating Pcrit from the ṀO2 versus PO2 curve. We make suggestions on best practices for each step and for how to report Pcrit results to maximize their comparative value. We also discuss the concept of hypoxia tolerance and how Pcrit relates to a fish's overall hypoxia tolerance. When appropriate methods are used, Pcrit provides useful comparative physiological and ecological information about the aerobic contributions to a fish's hypoxic survival. When paired with other hypoxia-related physiological measurements (e.g. lactate accumulation, calorimetry-based measurements of metabolic depression, loss-of-equilibrium experiments), Pcrit contributes to a comprehensive understanding of how a fish combines aerobic metabolism, anaerobic metabolism and metabolic depression in an overall strategy for hypoxia tolerance.

Rheological Effects of L-Glutamine in Patients with Sickle Cell Disease

Background: ENDARITM (oral pharmaceutical L-glutamine powder) received FDA approval in 2017 as a treatment for sickle cell disease (SCD). A pivotal phase 3 clinical study conducted by Emmaus Medical, Inc. showed that L-glutamine resulted in a lower incidence of vaso-occlusive crises (VOC) as well as a lower rate of hospitalizations and shorter hospital stays. No changes in standard clinical laboratory values were noted. The clinical improvements associated with sickle cell complications are believed to be due to an increase in the proportion of the reduced form of nicotinamide adenine dinucleotides in the red blood cells (RBC) of patients with SCD, reducing the oxidative stress. While the endpoints in the phase 3 study are clinically important, it is essential that we identify biomarkers or measurable laboratory changes that can serve as endpoints for future clinical trials assessing dose optimization and the efficacy and safety of L-glutamine in SCD individuals, including those with hepatic and renal dysfunction. RBC rheology is markedly abnormal in SCD; blood is more viscous for a given hematocrit than normal individuals, dense red blood cells (DRBC) are packed with HbS, potentiating sickling, and RBCs are less deformable than those of HbAA or HbAS individuals. High whole blood viscosity, high DRBCs, and poor RBC deformability are associated with higher rates of VOC. Given the demonstrated reduction in pain events, we hypothesized that L-glutamine might improve RBC rheology and sought to test this in vitro and in vivo using a battery of rheological tests. Methods: For the in vitro study, 6 mL of whole blood was drawn into an EDTA vacutainer from ten pediatric patients with sickle cell anemia (HbSS or HbSβ0) during routine clinical checkups under an IRB approved protocol. The cohort included 3 female and 7 male patients, ages 2-19 years old. All patients were on a steady dose of hydroxyurea and did not receive a transfusion within the 3 months prior to sample collection. A 200 mM stock solution of L-glutamine and water was mixed and filtered under light-protected conditions. Aliquots were stored at -20°C to avoid multiple freeze/thaw cycles. L-glutamine was added to 3 mL of whole blood for a final concentration of 1 mM (average in vivo L-glutamine plasma concentration in patients with SCD treated with L-glutamine); 3 mL of the same patient sample with water added served as a control. After a 24-hour incubation period at 4°C, whole blood viscosity was measured using a cone and plate viscometer at 37°C (DV3T Rheometer, AMETEK Brookfield, USA), %DRBCs were measured on an ADVIA 120 Hematology System (Siemens Healthcare Diagnostics, Inc., USA), and deformability measured using a Laser Optical Rotational Red Cell Analyzer (Lorrca®) (RR Mechatronics, the Netherlands) with the Oxygenscan module. The Oxygenscan measures RBC deformability at normoxia (Elmax), deformability upon deoxygenation (EImin), and point of sickling (PoS), the oxygen tension at which deformability begins to decline, reflecting the patient-specific pO2 at which sickling begins. Paired samples (with and without added L-glutamine) were analyzed using Student's t-test. For the in vivo study, rheological tests were performed on peripheral blood from one patient (18-year-old male on hydroxyurea) at baseline and treated with L-glutamine as part of his routine clinical care. Results and conclusions: Addition of L-glutamine in vitro significantly reduced the PoS, meaning RBCs incubated with L-glutamine could tolerate a lower pO2 before sickling compared to the control. RBCs incubated with L-glutamine also had significantly higher EImin, meaning deoxygenated RBCs were more flexible and deformable. Whole blood viscosity at 45s-1 and 225s-1 did not change significantly following incubation with L-glutamine; %DRBCs also did not change significantly (Table 1). The in vivo patient sample tested exhibited a similar improvement in PoS and EImin (Figure 1). We therefore propose to further test the performance of the PoS and EImin as possible biomarkers of response to L-glutamine in vivo. If validated, these biomarkers may also help further elucidate the mechanisms of action of L-glutamine in SCD. Disclosures No relevant conflicts of interest to declare.

Understanding the electrocatalytic activity of transition metal nanoparticles for solid oxide cell fuel electrodes

In this work, we utilized the concept of decoupling the electrocatalytic activity from the current conducting phase of solid oxide cell fuel electrodes to investigate the electrochemical performance of three different transition metals, namely Ni, Co, and Fe. It was found that the nickel and cobalt infiltrated cells had comparable performances in both 4% H2O/H2 and 50% H2O/H2. Furthermore, iron nanoparticles were found to be the better electrocatalyst at low pO2 values, however at higher pO2 values the iron infiltration became the inferior catalyst. Investigating the temperature dependence of the polarization resistance in terms of activation energy and pre-exponential factor showed interesting differences between the metal catalysts and a dependence on the gas atmosphere. The results were analyzed by developing a model based on the harmonic oscillator, the model allows for correlating changes in activation energy and pre-exponential factor with kinetic parameters of the electrode reaction. The model indicates that at higher pO2 values, iron nanoparticles experience a surface blockade, i.e. strong bonding of the reactants to the catalytic sites. For the nickel electrocatalyst, an increase in steam content according to the model leads to an increase in the turnover frequency, which is in good agreement with earlier reports in literature.

Structural Stabilization of Mullite Films Exposed to Oxygen Potential Gradients at High Temperatures

The oxygen shielding properties of polycrystalline Al4+2xSi2−2xO10−x (mullite) films applied as environmental barrier coatings (EBCs) on SiC fiber-reinforced SiC matrix composites (SiC/SiC) are determined by the grain boundary (GB) diffusion of oxide ions in the films, from the higher oxygen partial pressure (PO₂) surface to the lower PO₂ surface, with simultaneous GB diffusion of Al ions in the opposite direction. Herein, strategies to improve the oxygen shielding and phase stability of these films when applied to SiC/SiC substrates through bond coats are proposed, based on oxygen permeation data for mullite at high temperatures. The validity of these strategies is verified using experimental trials at 1673 K with bilayer specimens consisting of mullite films and bond coat substrates, serving as model EBCs. The data show that employing a bond coat made of β’-SiAlON rather than Si provides a source of Al for the overlying mullite film that greatly improves the phase stability of the film in the vicinity of the junction interface. Because the minimum equilibrium PO₂ values required to form SiO2 due to oxidation of the β’-SiAlON on a thermodynamic basis are significantly larger than those for oxidation of Si, the inward GB diffusion of oxide ions is effectively retarded, resulting in excellent oxygen shielding characteristics.