O2 Conditions Research Articles

The role of carbonic anhydrase-mediated tissue oxygen extraction in a marine teleost acclimated to hypoxia.

With the growing prevalence of hypoxia (O2 levels ≤2 mg l-1) in aquatic and marine ecosystems, there is increasing interest in the adaptive mechanisms fish may employ to better their performance in stressful environments. Here, we investigated the contribution of a proposed strategy for enhancing tissue O2 extraction - plasma-accessible carbonic anhydrase (CA-IV) - under hypoxia in a species of estuarine fish (red drum, Sciaenops ocellatus) that thrives in fluctuating habitats. We predicted that hypoxia-acclimated fish would increase the prevalence of CA-IV in aerobically demanding tissues to confer more efficient tissue O2 extraction. Furthermore, we predicted the phenotypic changes to tissue O2 extraction that occur with hypoxia acclimation may improve respiratory and swim performance under 100% O2 conditions (i.e. normoxia) when compared with performance in fish that have not been acclimated to hypoxia. Interestingly, there were no significant differences in relative CA-IV mRNA expression, protein abundance or enzyme activity between the two treatments, suggesting CA-IV function is maintained under hypoxia. Likewise, respiratory performance of hypoxia-acclimated fish was similar to that of control fish when tested in normoxia. Critical swim speed (Ucrit) was significantly higher in hypoxia-acclimated fish but translated to marginal ecological benefits with an increase of ∼0.3 body lengths per second. Instead, hypoxia-acclimated fish may have relied more heavily on anaerobic metabolism during their swim trials, utilizing burst swimming 1.5 times longer than control fish. While the maintenance of CA-IV may still be an important contributor for hypoxia tolerance, our evidence suggests hypoxia-acclimated red drum are using other mechanisms to cope in an O2-depleted environment.

The Mixing Character within Oxidation Reactor in Titanium Dioxide Production by Chloride Process

Chloride process is cost effective and environmental benefit, and the TiCl4 oxidation is the most important stage in this process. The structure of the jet ring has an obviously effect on the mixing of TiCl4 and O2 in the oxidation reactor, which is the key equipment in the production of titanium pigment. In this paper, the gas mixing condition with five jet rings of different structure was simulated and analyzed by computational fluid dynamics (CFD) simulation. The radial concentration distribution of TiCl4 and the non-uniformity of the mixture with different jet rings were obtained. The results showed the structure of the jet ring has great effect on the gas mixing. The mixing condition of the jet ring with combined opening orifice is better than that of the jet ring with uniform opening orifice， which is more effective in realizing fast and uniform mixing condition of TiCl4 and O2.

The Mixing Character within Oxidation Reactor in Titanium Dioxide Production by Chloride Process

Chloride process is cost effective and environmental benefit, and the TiCl4 oxidation is the most important stage in this process. The structure of the jet ring has an obviously effect on the mixing of TiCl4 and O2 in the oxidation reactor, which is the key equipment in the production of titanium pigment. In this paper, the gas mixing condition with five jet rings of different structure was simulated and analyzed by computational fluid dynamics (CFD) simulation. The radial concentration distribution of TiCl4 and the non-uniformity of the mixture with different jet rings were obtained. The results showed the structure of the jet ring has great effect on the gas mixing. The mixing condition of the jet ring with combined opening orifice is better than that of the jet ring with uniform opening orifice， which is more effective in realizing fast and uniform mixing condition of TiCl4 and O2.

Environmental oxygen affects ex vivo growth and proliferation of mesenchymal progenitors by modulating mitogen-activated protein kinase and mammalian target of rapamycin signaling

Background aimsStem and progenitor cells of hematopoietic and mesenchymal lineages reside in the bone marrow under low oxygen (O2) saturation. O2 levels used in ex vivo expansion of multipotent mesenchymal stromal cells (MSCs) affect proliferation, metabolism and differentiation. MethodsUsing cell-based assays and transcriptome and proteome data, the authors compared MSC cultures simultaneously grown under a conventional 19.95% O2 atmosphere or at 5% O2. ResultsIn 5% O2, MSCs showed better proliferation and higher self-renewal ability, most probably sustained by enhanced signaling activity of mitogen-activated protein kinase and mammalian target of rapamycin pathways. Non-oxidative glycolysis-based energy metabolism supported growth and proliferation in 5% O2 cultures, whereas MSCs grown under 19.95% O2 also utilized oxidative phosphorylation. Cytoprotection mechanisms used by cells under 5% O2 differed from 19.95% O2 suggesting differences in the triggers of cell stress between these two O2 conditions. ConclusionsBased on the potential benefits for the growth and metabolism of MSCs, the authors propose the use of 5% O2 for MSC culture.

Bluff-body MILD combustion regime for semicoke and bituminous coal mixtures with effect of oxidizer O2 concentration in O2/N2 and oxy-fuel (O2/CO2) atmospheres

The present study numerically investigates the effects of the O2 content (XO2) in the oxidizer on the MILD combustion behaviours of large-proportion semicoke mixtures, such as those involving temperature, MILD regime recognition, char surface consumption, homo/heterogeneous Damkhöler number, and NOx emission, under O2/N2 and O2/CO2 atmospheres. The results indicate that by increasing XO2 from 15 % to 30 %, the peak temperature increases significantly due to the increased char consumption rate, the high temperature region shrinks, and the axial length of the MILD regime region slightly increases from ∼1 to ∼1.4 m because of enhanced flue gas recirculation under O2/N2 or O2/CO2 atmosphere. The reduction effects of the char-O2 reaction proportions and the promoted effects of the char-CO2 reaction proportions due to the increased XO2 are both obviously weakened when N2 is substituted for CO2. A high O2 content and an O2/N2 atmosphere reduce the char burnout time. With increasing XO2, the maximum value of the turbulent Damkhöler number Dat increases from 6.79 to 10.16 under the O2/N2 atmosphere and from 3.99 to 10.6 under the O2/CO2 atmosphere, implying that a low O2 dilution and a CO2 environment promote the establishment of the homo-MILD regime. The maximum values of the surface Damkhöler number (Das-CO2 and Das-H2O) of the two gasification reactions (Char-CO2 and Char-H2O) have the same order of magnitude and are much lower than those of the surface Damkhöler number (Das-O2) of the Char-O2 oxidation reaction, i.e., Das-H2O < Das-CO2 ≪ Das-O2 < 1. The maximum values of the three surface Damkhöler numbers all increase with increasing XO2, while they decrease with the replacement of N2 by CO2, indicating that a high O2 content and an O2/N2 atmosphere could facilitate the establishment of an ideal hetero-MILD combustion regime to some extent. Low NOx emissions can be realized under moderate O2 and CO2 dilution conditions by regulating the oxy-MILD combustion regime of semicoke blends.

Caveolin-1 suppresses hippocampal neuron apoptosis via the regulation of HIF1α in hypoxia in naked mole-rats.

Naked mole-rats (NMRs) (Heterocephalus glaber) are highly social and subterranean rodents with large communal colonies in burrows containing low oxygen levels. The inhibition of severe hypoxic conditions is of particular interest to this study. To understand the mechanisms that facilitate neuronal preservation during hypoxia, we investigated the proteins regulating hypoxia tolerance in NMR hippocampal neurons. Caveolin-1 (Cav-1), a transmembrane scaffolding protein, confers prosurvival signalling in the central nervous system. The present study aimed to investigate the role of Cav-1 in hypoxia-induced neuronal injury. Western blotting analysis and immunocytochemistry showed that Cav-1 expression was significantly upregulated in NMR hippocampal neurons under 8% O2 conditions for 8 h. Cav-1 alleviates apoptotic neuronal death from hypoxia. Downregulation of Cav-1 by lentiviral vectors suggested damage to NMR hippocampal neurons under hypoxic conditions in vitro and in vivo. Overexpression of Cav-1 by LV-Cav-1 enhanced hypoxic tolerance of NMR hippocampal neurons in vitro and in vivo. Mechanistically, the levels of hypoxia inducible factor-1α (HIF-1α) are also increased under hypoxic conditions. After inhibiting the binding of HIF-1α to hypoxia response elements in the DNA by echinomycin, Cav-1 levels were downregulated significantly. Furthermore, chromatin immunoprecipitation assays showed the direct role of HIF1α in regulating the expression levels of Cav-1 in NMR hippocampal neurons under hypoxic conditions. These findings suggest that Cav-1 plays a critical role in modulating the apoptosis of NMR hippocampal neurons and warrant further studies targeting Cav-1 to treat hypoxia-associated brain diseases.

The influence of varying levels of molecular oxygen on the functionality of azodicarbonamide and ascorbic acid during wheat bread making

Air, and thus also molecular oxygen (O2), is incorporated in wheat flour dough during mixing. O2 participates in several (enzymatic) reactions, including those resulting in the oxidation of free sulfhydryl groups, thereby increasing dough strength and bread volume. We here incorporated different O2 levels in dough by mixing dough samples for a fixed time under different modified atmospheres which led to significant changes in dough free sulfhydryl contents and bread volumes. Although altering the mixing time not only impacted how much O2 was incorporated in dough but also the mechanical input, the changes in dough and bread properties when using different mixing times, largely depended on differences in O2 uptake. When used in bread recipes, redox agents such as azodicarbonamide (ADA) and ascorbic acid (AH2) impact the dough sulfhydryl contents and bread volumes. The effect of different levels of O2 incorporation on dough samples which contained ADA or AH2 was studied by altering the mixing time or the O2 content in the mixing atmosphere. Lower ADA levels were needed when dough was mixed under an atmosphere enriched in O2. As AH2 requires O2 to be converted to dehydroascorbic acid (DHA) to exert its improver effect, it came as a surprise that when it was included in a dough which was prepared under O2 enriched conditions, no additional impact was obtained and that, even under reduced O2 conditions, its use still resulted in an increased bread volume. These findings suggest that AH2 oxidase very effectively uses O2 to form DHA.

Keep oxygen in check: An improved in-situ zymography approach for mapping anoxic hydrolytic enzyme activities in a paddy soil

Paddy soils regularly experience redox oscillations during the wetting and draining stages, yet the effects of short-term presence of oxygen (O2) on in-situ microbial hotspots and enzyme activities in anoxic ecosystems remain unclear. To fill this knowledge gap, we applied soil zymography to localize hotspots and activities of phosphomonoesterase (PME), β-glucosidase (BG), and leucine aminopeptidase (LAP) in three compartments of rice-planted rhizoboxes (top bulk, rooted, and bottom bulk paddy soil) under oxic (+O2) and anoxic (O2) conditions. Short-term (35 min) aeration decreased PME activity by 13–49 %, BG by 4–52 %, and LAP by 12–61 % as compared with O2 in three soil compartments. The percentage of hotspot area was higher by 3–110 % for PME, by 10–60 % for BG, and by 12–158 % for LAP under +O2 vs. O2 conditions depending on a rice growth stage. Irrespective of the aeration conditions, the rhizosphere extent of rice plants for three enzymes was generally greater under higher moisture conditions and at earlier growth stage. Higher O2 sensitivity for the tested enzymes at bottom bulk soil versus other compartments suggested that short-term aeration during conventional zymography may lead to underestimation of nutrient mobilization in subsoil compared to top bulk soil. The intolerance of anaerobic microorganisms against the toxicity of O2 in the cells and the shift of microbial metabolic pathways may explain such a short-term suppression by O2. Our findings, therefore, show that anoxic conditions and soil moisture should be kept during zymography and probably other in-situ soil imaging methods when studying anoxic systems.

High performance of ZnSnO thin-film transistors engineered by oxygen defect modulation

Thin film transistor (TFT) with low cost and high performance is significantly important for practical applications. In this work, In-free ZnSnO (ZTO) TFT with high performance is achieved by modulating the annealing atmosphere to manipulate the amount and charge state of oxygen defect, and then the effects of annealing atmosphere are systematically investigated by experiment and theoretical calculation. Results show that, O2 condition results in an inferior electron mobility although the formation of oxygen defect is suppressed. The oxygen vacancies created in N2 ambience are most probably dominated by neutral ones that limit the electron transport. The ZTO TFT dealt with vacuum condition exhibits the best performances, i.e. μlin, Vth, SS and Ion/Ioff are 19.80 cm2/Vs, 0.05 V, 0.46 V/dec and 108, respectively, which can be attributed to the cooperation of the decreased RC and RSH, the charge-state transition of oxygen defect. Further investigation indicates that, doubly charged oxygen vacancy not only results in the elevation of electron content and thus reduce the conduction barrier, but also shrinks the supercell volume to maintain the highly dispersed conduction band, which is crucially important for the electron transport. The findings may facilitate the ability to engineer other high performance AOS materials and devices.

Physical-chemical factors influencing the vertical distribution of phototrophic pico-nanoplankton in the Oxygen Minimum Zone (OMZ) off Northern Chile: The relative influence of low pH/low O2 conditions

The vertical distribution of phytoplankton is of fundamental importance in the structure, dynamic, and biogeochemical pathways in marine ecosystems. Nevertheless, what are the main factors determining this distribution remains as an open question. Here, we evaluated the relative influence of environmental factors that might control the coexistence and vertical distribution of pico-nanoplankton associated with the OMZ off northern Chile. Our results showed that in the upper layer Synechococcus-like cells were numerically important at all sampling stations. Pico-nano eukaryotes and phototrophic nanoflagellates (PNF) also showed high abundances in the upper layer decreasing in abundance down to the upper oxycline, while only Prochlorococcus showed high abundances under oxycline and within the oxygen-depleted layer. Statistical analyses evidenced that temperature, oxygen, and carbonate chemistry parameters (pH and dissolved inorganic carbon, DIC) influenced significantly the vertical distribution of phototrophic pico-nanoplankton. Additionally, we experimentally-evaluated the combined effect of low pH/low O2 conditions on a nanophytoplankton species, the haptophyte Imantonia sp. Under control conditions (pH = 8.1; O2 = 287.5 μM, light = 169.6 μEm−2s−1), Imantonia sp. in vivo fluorescence increased over fifty times, inducing supersaturated O2 conditions (900 μM) and an increasing pH (8.5), whereas upon an experimental treatment mimicking OMZ conditions (pH = 7.5; O2 = 55.6 μM; light = 169.6 μEm−2s−1), in vivo fluorescence declined dramatically, suggesting that Imantonia sp. did not survive. Although preliminary, our study provides evidence about the role of low pH/low O2 conditions on the vertical distribution of nanophytoplankton, which deserve future attention through both fieldwork and more extended experimental experiences.

Photocatalytic oxidation activity enhanced by iron-oxalate chelates for Fenton-like oxidation of As(III) in oxalate systems

This study investigated the Fenton-like oxidation of As(III) by three types of iron oxides in oxalate systems. The effects of pH, oxalate concentration and atmosphere on the oxidation of As(III) by iron oxide photocatalyst were studied. Firstly, hydrothermal carbon (HTC) was used as the carrier to load three kinds of iron oxides to prepare new composite materials, including α–FeOOH, αFe2O3 and Fe3O4, which can solve the dispersion problem of iron oxide by using a large number of rich functional groups on the HTC surface. The experiment results showed that under the conditions of O2, pH = 5.0 and oxalate concentration of 0.5 mmol·L1, As(III) was completely oxidized by α–FeOOH and α–Fe2O3 at 15 min and 20 min, respectively. Density functional theory (DFT) was used to study the surface adsorption energy of iron oxide and oxalate. The calculated results showed that the order of adsorption energy of three iron oxides for the oxalate is αFeOOH > αFe2O3 > Fe3O4. FeIII(C2O4)+, a mononuclear bidentate iron oxalate chelate with the strongest photosensitivity, was constructed in the Fe-Oxalate system containing only Fe(III), resulting in the photocatalytic efficiency of α–FeOOH and αFe2O3 was superior to that of Fe3O4. These findings contribute to arsenic remediation of water bodies by using iron materials and oxalate in the natural environment.

Study on Lifetimes of Plasma Etched Ru Lines

Copper (Cu) is a widely used interconnect material in ULSICs, large area TFT LCDs, and other electronics. However, as the dimensions shrinks, electronic scattering at grain boundaries and surfaces causes the large increase of line resistance and the RC delay [1]. Also, the barrier layer occupies a large fraction of the interconnect line, which is an issue in conductance and reliability [2]. An alternative interconnect material for Cu is necessary. Ruthenium (Ru) is a possible material for this purpose because of its low resistivity, high resistant to oxidation, good heat dissipation, low diffusion and good adhesion to dielectrics [3–6]. Furthermore, it was reported that Ru has a low resistivity scaling [7], which suggested that it can be more conductive than Cu lines in advanced technology nodes. In this study, the reliability of the plasma etched Ru line is studied using the electromigration (EM) stress method [8].The Ru film was sputter deposited on top of the SiO2 coated layer Si <100> wafer and covered with a sputter deposited SiO2 layer as a hard mask layer. After the sample was lithographically defined into a 4-point test pattern, the SiO2 hard mask layer was etched at CF4 10 sccm, 60 mTorr, and 600 W. Then, the Ru layer was etched under the condition of O2 40 sccm, 50 mTorr, and 600W. All etches were carried out in a parallel-plate plasma reactor (PlasmaTherm 700) under the RIE mode at room temperature. The remaining SiO2 hard mask on top of the Ru film was removed by dipping in a dilute HF solution. The electromigration (EM) test was done at room temperature on a probe station (Signatone S-1160). The EM stress was conducted under the constant current density (J) condition. Separately, in order to facilitate the breakdown of the Ru line, the sample was stresses at the constant voltage (V) with a power supply (Agilent E3645A).Figure 1(a) and (b) show the top views of an electric stressed Ru line under the (a) bright and (b) dark fields of an optical microscope. The surface of the line is smooth and has a small edge roughness. In the bright field mode, few voids, which are voids generated in the line, are barely visible. However, in the dark field, the light is diverged into a cone. Light is scattered through the voids, which shows as bright dots [9]. Figure 1(c) shows a broken line that was generated under a large constant voltage. The color change near the center of the line is the broken spot, which indicates the high local temperature in the process.Figure 2 shows the resistance-time (R-t) curves of a plasma-etched TiW/Cu line stressed at J = 6.00 105 A/cm2 and a Ru line stressed at J = 1.25 106 A/cm2. The Cu line was broken before 10,000 sec. However, the Ru line was not broken after 12,000 sec and the resistance remained the same through the stress period. Therefore, the Ru line is much resistant to the EM stress than the Cu line even under a larger current density condition. Although voids were observed in the stressed Ru line, they did not cause the line broken, i.e., through a series of voids growth, merge, and connection steps [10,11]. Although no barrier layer was used for the Ru line, no line peel off was observed before and after the stress. This can be another advantage over the Cu line.More detailed discussion on the plasma etching of the Ru line and the EM phenomenon will be presented.1. A. F. Mayadas, et al., Appl. Phys. Lett., 14, 345 (1969).2. C.-K. Hu, et al., Microelectron. Eng., 70, 406 (2003).3. L. G. Wen, et al., 2016 IITC/AMC, 34 (2016).4. S. Dutta, et al., 2017 IITC, 1 (2017).5. O. V. Pedreira, et al.,, 2017 IRPS, 6B-2 (2017).6. T. Zhan, et al., ACS Appl. Mater. Interfaces, 12, 22347 (2020).7. E. Milosevic, et al., J. Appl. Phys., 124, 165105 (2018).8. G. Liu and Y. Kuo, J. Electrochem. Soc., 156, H579 (2009).9. J. Q. Su and Y. Kuo, MRS Advances, 5, 2827 (2020).10. J. R. Black, IEEE T. Electron Dev., 16, 338 (1969).11. S. C. Hau-Riege, Microelectron. Reliab., 44, 195 (2004). Figure 1

Release Kinetics and In Vitro Characterization of Sodium Percarbonate and Calcium Peroxide to Oxygenate Bioprinted Tissue Models.

Oxygen-generating materials have been used in several tissue engineering applications; however, their application as in situ oxygen supply within bioprinted constructs has not been deeply studied. In this study, two oxygen-generating materials, sodium percarbonate (SPO) and calcium peroxide (CPO), were studied for their oxygen release kinetics under a 0.1% O2 condition. In addition, a novel cell-culture-insert setup was used to evaluate the effects of SPO and CPO on the viability of skeletal muscle cells under the same hypoxic condition. Results showed that SPO had a burst oxygen release, while CPO had a more stable oxygen release than SPO. Both SPO and CPO reduced cell viability when used alone. The addition of catalase in SPO and CPO increased the oxygen release rate, as well as improving the viability of skeletal muscle cells; however, CPO still showed cytotoxicity with catalase. Additionally, the utilization of 1 mg/mL SPO and 20 U catalase in a hydrogel for bioprinting significantly enhanced the cell viability under the hypoxic condition. Moreover, bioprinted muscle constructs could further differentiate into elongated myotubes when transferring back to the normoxic condition. This work provides an excellent in vitro model to test oxygen-generating materials and further discover their applications in bioprinting, where they represent promising avenues to overcome the challenge of oxygen shortage in bioprinted constructs before their complete vascularization.

Effects of acid pickling and nitrogen doping on the biochar–NO reaction performance of different biochars under high O2 conditions

Chinese fir (G type), elm (G-S type), and bamboo (G-S-H type) with different lignin types were used to prepare unmodified and modified biochars (modified by acid pickling, nitrogen doping, or both). Pore structures and functional group distributions of different biochars were characterized by Brunauer–Emmett–Teller analysis and Fourier transform infrared spectroscopy, and the key elements in biochar ash were semi-quantitatively determined by X-ray fluorescence spectroscopy and principal component analysis. Results showed that the different modification methods produce different NO removal performances. Both acid pickling and nitrogen doping improve the NO removal performance of elm-biochar—with its few defects—but not that of bamboo-biochar—with its high silicon content. In the case of Chinese-fir-biochar—with its high defect content, the improvement in NO removal performance is limited. The affinity of elements in biochar ash for oxygen atoms affects the nitrogen-doping as well as NO removal performance of biochar.

Temperature Sensitivity of Freshwater Denitrification and N2O Emission—A Meta‐Analysis

AbstractFreshwater denitrification removes a considerable amount of nitrogen from inland waters, which are under pressure from eutrophication and warming. However, incomplete denitrification can lead to the formation of N2O, a potent greenhouse gas, which can amplify climatic warming. Although temperature effects on denitrification are well studied in individual habitats and experiments, global patterns in temperature‐responses of denitrification and N2O emissions remain to be elucidated. Here, we investigated the temperature sensitivity (Q10) of denitrification and N2O emissions in freshwater ecosystems worldwide, using a meta‐analytic approach. To this end, Q10 values from in‐situ and temperature manipulation studies were related to environmental nutrient conditions, O2, pH, sediment organic matter (SOM), and geographic location. Temperature sensitivity of denitrification displayed a strong positive correlation with environmental nitrogen concentrations, pH and O2. Significant correlations with SOM and SOM:N ratios were observed as well, but the direction of the effect differed between in‐situ and temperature manipulation studies. Surprisingly, temperature sensitivity of N2O emissions did not correlate with pH, SOM, nutrient or O2 conditions. Temperature sensitivity of the ratio between N2O emission and NO3− concentration (adapted EF5 values) was 6.6 times higher in Australia and New Zealand compared to other geographic regions. As global temperatures and nitrogen deposition in freshwater ecosystems are expected to increase over the coming decades, our results suggest enhanced future denitrification, which may present a natural way to balance eutrophication. The observed temperature sensitivity of N2O emission factors, however, may indicate enhanced denitrification‐derived N2O emissions from freshwater ecosystems in a future warmer world.

Dirammox Is Widely Distributed and Dependently Evolved in Alcaligenes and Is Important to Nitrogen Cycle.

Nitrogen cycle is an essential process for environmental health. Dirammox (direct ammonia oxidation), encoded by the dnfT1RT2ABCD cluster, was a novel pathway for microbial N2 production defined in Alcaligenes ammonioxydans HO-1. Here, a copy of the cluster dnfT1RT2ABCD as a whole was proved to have existed and very conserved in all Alcaligenes genomes. Phylogenetic analyses based on 16S rRNA gene sequences and amino acid sequences of DnfAs, together with G + C content data, revealed that dnf cluster was evolved associated with the members of the genus Alcaligenes. Under 20% O2 conditions, 14 of 16 Alcaligenes strains showed Dirammox activity, which seemed likely taxon-related. However, the in vitro activities of DnfAs catalyzing the direct oxidation of hydroxylamine to N2 were not taxon-related but depended on the contents of Fe and Mn ions. The results indicated that DnfA is necessary but not sufficient for Dirammox activity. The fact that members of the genus Alcaligenes are widely distributed in various environments, including soil, water bodies (both freshwater and seawater), sediments, activated sludge, and animal–plant-associated environments, strongly suggests that Dirammox is important to the nitrogen cycle. In addition, Alcaligenes species are also commonly found in wastewater treatment plants, suggesting that they might be valuable resources for wastewater treatment.

Effect of oxygen vacancy on the dielectric relaxation characteristics of PMNT ceramics

The as-sintered 0.68 Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 ceramics were firstly prepared using the Columbite technique and then further annealed in specific atmosphere. The effect of annealing atmospheres, e.g. O2, N2 and air conditions, on the phase structure, microstructure and dielectric properties of ceramics were systematically discussed. The obtained results suggested that, compared to as-sintered sample, there is no obvious difference in phase structure and microstructure for ceramics annealed in O2 atmosphere, showing pure perovskite structure and higher density. While the appearance of second pyrochlore phase and porosity can be found as sample was annealed in nitrogen or air condition. It is worth noting that the dielectric properties of ceramics are very sensitive to the annealing atmosphere and there is a significant increase in dielectric constant and decrease in dielectric loss as the PMNT ceramic was treated in O2 atmosphere, while sample annealed in N2 or air condition would show the opposite trend.

Catalytic Coupling of Free Radical Oxidation and Electrophilic Chlorine Addition by Phase-Transfer Intermediates in Liquid Aerosols.

While examining the heterogeneous reaction of chlorine atoms with alkenes, in the presence of Cl2, we have observed an unexpectedly large enhancement of reactivity and the predominance of chlorinated reaction products even under high O2 conditions, where Cl atom recycling is expected to be minimal. These observations cannot be explained by known free radical oxidation or cycling mechanisms, but rather we find evidence for the multiphase catalytic coupling of free radical oxidation with electrophilic Cl2 addition. The mechanism entails the production of oxygenated reaction intermediates, which act as gas-liquid phase-transfer catalysts (gl-PTCs) by promoting the accommodation of gas-phase Cl2 by the aerosol, thereby enhancing electrophilic addition. Although the majority of PTCs typically couple chemistry between two immiscible liquid phases (aqueous/organic), there are few examples of PTCs that couple gas-liquid reactions. This work shows how multiphase reaction schemes of aerosols can be reimagined for understanding catalytic reaction mechanisms.

Clamping Skeletal Muscle PO2 Eliminates Hyperinsulinemic Microvascular Blood Flow Response

ObjectiveTo determine if insulin mediated hyperemia is partially dependent on local muscle oxygen concentration.HypothesisThe blood flow responses to insulin are partially mediated by the local metabolic demand reflecting the increased oxygen consumption required to uptake and convert glucose into glycogen in skeletal muscle.Methods16 male Sprague Dawley rats (161g ‐ 204g) were anesthetized with sodium pentobarbital, the carotid artery and jugular vein were then cannulated for blood pressure monitoring and fluid resuscitation. Following cannulation, the extensor digitorum longus (EDL) was isolated and reflected onto an inverted microscope. Intravital video microscopy sequences of the EDL microcirculation were recorded during baseline and following hyperinsulinemic euglycemia or sham in all experiments. The muscle was reflected over a glass stage insert during Experiment 1a and 1b which allowed for direct observation of microvascular blood flow response to systemic insulin infusion in Experiment 1a. Experiment 1b consisted of a sham hyperinsulinemic euglycemic clamp which involved infusing saline at similar rates as insulin and glucose in standard clamp procedures. In Experiment 2, the EDL was reflected over a gas exchange chamber and microvascular capillary blood flow was recorded during sequential changes (7%‐12%‐2%‐7%) of oxygen concentration [O2] within the chamber during baseline and euglycemic conditions. The gas exchange chamber is fitted into the stage of an inverted microscope that interfaces directly with the EDL via a gas permeable polydimethylsiloxane membrane. By adjusting the concentration of gases flowing through the gas exchange chamber we have direct control of the [O2] within the overlying muscle. Hemodynamic measurements including capillary red blood cell (RBC) velocity, supply rate (SR), hematocrit, and oxygen saturation (SO2) were taken from in focus capillaries in the EDL during each experiment and analyzed offline using custom MATLAB software. All animal protocols were approved by Memorial University’s Institutional Animal Care Committee.ResultsIn Experiment 1a, the hyperinsulinemic euglycemic clamp caused a significant increase in SR from 8.9 ± 3.1 to 14.2 ± 4.9 cells/s at baseline to euglycemia (p = 0.01; N = 6, 677 capillaries at baseline and 552 at clamp), while no significant SR variation was detected after performing a sham clamp in Experiment 1b (11.0 ± 1.6 cells/sec at baseline and 11.4 ± 3.7 cells/sec at sham clamp; N = 6, 837 capillaries at baseline and 724 at sham clamp). In Experiment 2 using the gas exchange chamber, SR significantly decreased at 12% O2 (p = 0.01, p &lt; 0.03) and significantly increased at 2% O2 (p = 0.01, p &lt; 0.04), compared to baseline 7% O2, under both baseline and euglycemic conditions respectively (N = 6, 313 capillaries at baseline and 195 at clamp). SR responses to oxygen oscillations during euglycemia were not different to those at baseline for each O2 concentration (p &gt; 0.9). SO2 significantly increased at 12% O2 and significantly decreased at 2% O2 under both baseline and euglycemic conditions (p &lt; 0.05).ConclusionsOur saturation measurements demonstrate the effectiveness of using a gas exchange device to manipulate local oxygen concentrations in the muscle. Our SR results suggest the increase in blood flow observed in response to insulin is eliminated if the tissue oxygen microenvironment is fixed at a given [O2].

Hypoxic Signaling Is Modulated by Calcium Channel, CaV1.3, in Androgen-Resistant Prostate Cancer.

Androgen deprivation therapy (ADT) remains a key treatment for advance prostate cancer (PCa), but resistance leads to terminal castrate-resistant prostate cancer (CRPC). Its development is linked to the emergence of a hypoxic tumor microenvironment and associated hypoxia inducible factor (HIF) signaling, which is known to be modulated by intracellular calcium. ADT is also known to upregulate store-operated calcium entry (SOCE) through voltage-gated calcium channel, CaV1.3. Consequently, the role of CaV1.3 in supporting hypoxic signaling and CRPC biology was explored. Androgen-sensitive PCa LNCaP cells were cultured with and without ADT bicalutamide, alongside ADT-resistant CRPC cells (LNCaP-ABL), either in normal or low oxygen (O2) (1%) conditions. HIF-1α, CaV1.3, and androgen receptor (AR) gene expression was measured by qPCR and protein expression with Western blot in the presence or absence of siCaV1.3. SOCE was determined through Fura-2AM fluorescence measurement. Cell proliferation was quantified by WST-1 assay and survival by colony formation. CaV1.3 expression was increased during ADT but not hypoxia, correlating with an associated increase in SOCE. HIF-1α expression was upregulated by ADT under normal O2 conditions and increased during hypoxia across all cells but with a higher fold change in early ADT-resistant and CRPC cells. Under hypoxic conditions CaV1.3 small interfering RNA resulted in a significant reduction in HIF-1α expression for ADT-sensitive cells but increased in CRPC. A similar pattern was also observed for AR expression. Cell survival was found significantly reduced by siCaV1.3 under hypoxic conditions for all cells, with and without ADT. Whereas cell proliferation under the same conditions was reduced in CRPC only. This study highlights that CaV1.3 can modulated HIF signaling and impact on PCa tumor biology under hypoxia, but further investigation is required to ascertain if this mediated through SOCE or a noncanonical mechanism.