Showing papers on "Oxygen published in 2008"
TL;DR: A catalyst that forms upon the oxidative polarization of an inert indium tin oxide electrode in phosphate-buffered water containing cobalt (II) ions is reported that not only forms in situ from earth-abundant materials but also operates in neutral water under ambient conditions.
Abstract: The utilization of solar energy on a large scale requires its storage. In natural photosynthesis, energy from sunlight is used to rearrange the bonds of water to oxygen and hydrogen equivalents. The realization of artificial systems that perform "water splitting" requires catalysts that produce oxygen from water without the need for excessive driving potentials. Here we report such a catalyst that forms upon the oxidative polarization of an inert indium tin oxide electrode in phosphate-buffered water containing cobalt (II) ions. A variety of analytical techniques indicates the presence of phosphate in an approximate 1:2 ratio with cobalt in this material. The pH dependence of the catalytic activity also implicates the hydrogen phosphate ion as the proton acceptor in the oxygen-producing reaction. This catalyst not only forms in situ from earth-abundant materials but also operates in neutral water under ambient conditions.
3,695 citations
TL;DR: In the last 30 years, research efforts by the scientific community intensified significantly, stemming from the pioneering work of Takahashi and co-workers, with the initial development of mixed ionic-electronic conducting (MIEC) oxides.
1,037 citations
TL;DR: In this article, the upper mantle oxygen fugacity at the top of the spinel peridotite rocks is shown to fall within 2 log units of the fayalite-magnetite-quartz (FMQ) oxygen buffer.
Abstract: Oxygen thermobarometry measurements on spinel peridotite rocks indicate that the oxygen fugacity at the top of the upper mantle falls within ±2 log units of the fayalite-magnetite-quartz (FMQ) oxygen buffer. Measurements on garnet peridotites from cratonic lithosphere reveal a general decrease in fo2 with depth, which appears to result principally from the effect of pressure on the controlling Fe3+/Fe2+ equilibria. Modeling of experimental data indicates that at approximately 8 GPa, mantle fo2 will be 5 log units below FMQ and at a level where Ni-Fe metal becomes stable. Fe-Ni alloy and an Fe2O3-garnet component will be formed as a result of the disproportionation of FeO, which is experimentally demonstrated through observations of high Fe3+/ΣFe ratios in minerals in equilibrium with metallic Fe. In the lower mantle, the favorable coupled substitution of Al and Fe3+ into (Fe,Mg)SiO3 perovskite results in very high perovskite Fe3+/ΣFe ratios in equilibrium with metallic Fe. As a result, the lower mantle sh...
887 citations
TL;DR: The transcriptional complex hypoxia-inducible factor has emerged as a key regulator of the molecular hypoxic response, mediating a wide range of physiological and cellular mechanisms necessary to adapt to reduced oxygen.
Abstract: The increase in body size of humans and other vertebrates requires a physiological infrastructure to provide adequate delivery of oxygen to tissues and cells to maintain oxygen homeostasis. The heart, lungs and the vasculature are all part of a highly regulated system that ensures the distribution of the precise amount of oxygen needed throughout the mammalian organism. Given its fundamental impact on physiology and pathology, it is no surprise that the response of cells to a lack of oxygen, termed hypoxia, has been the focus of many research groups worldwide for many decades now. The transcriptional complex hypoxia-inducible factor has emerged as a key regulator of the molecular hypoxic response, mediating a wide range of physiological and cellular mechanisms necessary to adapt to reduced oxygen.
761 citations
TL;DR: The bactericidal effect of nano-Fe0 was a unique property of nano -Fe0, which was not observed in other types of iron-based compounds, which may have caused the inactivation or enhanced the biocidal effects of dissolved iron.
Abstract: Zero-valent iron nanoparticles (nano-Fe0) in aqueous solution rapidly inactivated Escherichia coli. A strong bactericidal effect of nano-Fe0 was found under deaerated conditions, with a linear correlation between log inactivation and nano-Fe0 dose (0.82 log inactivation/mg/L nano-Fe0·h). The inactivation of E. coli under air saturation required much higher nano-Fe0 doses due to the corrosion and surface oxidation of nano-Fe0 by dissolved oxygen. Significant physical disruption of the cell membranes was observed in E. coli exposed to nano-Fe0, which may have caused the inactivation or enhanced the biocidal effects of dissolved iron. The reaction of Fe(II) with intracellular oxygen or hydrogen peroxide also may have induced oxidative stress by producing reactive oxygen species. The bactericidal effect of nano-Fe0 was a unique property of nano-Fe0, which was not observed in other types of iron-based compounds.
688 citations
TL;DR: In this article, a series of cerium modified MnOx/TiO2 catalysts were prepared by sol-gel method and used for low-temperature selective catalytic reduction (SCR) of NOx with ammonia.
538 citations
TL;DR: Solid state and solution evidence confirms the embedding of an adamantane-like, Ru4O6 fragment by the divacant, gamma-decatungstosilicate ligand in the resulting complex catalyzes water oxidation to oxygen with TON up to 500 and TOF > 450 h-1.
Abstract: Solid state and solution evidence confirms the embedding of an adamantane-like, Ru4O6 fragment by the divacant, γ-decatungstosilicate ligand. The resulting complex catalyzes water oxidation to oxygen with TON up to 500 and TOF > 450 h−1.
535 citations
TL;DR: In this article, a stable, cation-ordered oxides with layered lattice structures were obtained with medium-sized Ln 3+ ions over a wide range of oxygen partial pressures, a property essential for applications as oxygen separation membranes and solid oxide fuel cell cathodes.
446 citations
TL;DR: Clues from ancient rocks are helping to produce a coherent picture of how Earth's atmosphere changed from one that was almost devoid of oxygen to one that is one-fifth oxygen.
Abstract: Clues from ancient rocks are helping to produce a coherent picture of how Earth's atmosphere changed from one that was almost devoid of oxygen to one that is one-fifth oxygen.
442 citations
TL;DR: In this article, the photo-induced interfacial charge transfer from a semiconductor to an adsorbed molecular species and the catalytic multi-electron reduction of oxygen by Cu(I) ions were investigated.
441 citations
01 Jan 2008
TL;DR: In this article, the oxygen reduction reaction (ORR) is also the most important reaction in life processes such as biological respiration, and in energy converting systems such as fuel cells.
Abstract: Oxygen (O2) is the most abundant element in the Earth’s crust. The oxygen reduction reaction (ORR) is also the most important reaction in life processes such as biological respiration, and in energy converting systems such as fuel cells. ORR in aqueous solutions occurs mainly by two pathways: the direct 4-electron reduction pathway from O2 to H2O, and the 2-electron reduction pathway from O2 to hydrogen peroxide (H2O2). In non-aqueous aprotic solvents and/or in alkaline solutions, the 1-electron reduction pathway from O2 to superoxide (O2 -) can also occur.
TL;DR: In this article, the feasibility of using ilmenite as an oxygen carrier in chemical-looping combustion has been investigated, and it was found that the resulting oxygen is an attractive and inexpensive oxygen carrier.
Abstract: The feasibility of using ilmenite as oxygen carrier in chemical-looping combustion has been investigated. Itwas found that ilmenite is an attractive and inexpensive oxygen carrier for chemical-looping combustion.Alaboratory fluidizedbed reactor system, simulating chemical-looping combustion by exposing the sample to alternating reducing and oxidizing conditions,was used to investigate the reactivity. During the reducing phase, 15 g of ilmenite with a particle
size of 125–180μm was exposed to a flow of 450mLn/min of either methane or syngas (50% CO, 50% H2) and during the oxidizing phase to a flow of 1000mLn/min of 5% O2 in nitrogen. The ilmenite particles showed no decrease in reactivity in the laboratory experiments after 37 cycles of oxidation and reduction. Equilibrium calculations indicate that the reduced ilmenite is in the form FeTiO3 and the oxidized carrier is in the form Fe2TiO5 +TiO2. The theoretical oxygen transfer capacity between these oxidation states is 5%. The same oxygen transfer capacity was obtained in the laboratory experiments with syngas. Equilibrium calculations indicate that ilmenite should be able to give high conversion of the gases with the equilibrium ratios CO/(CO2 + CO) and H2/(H2O+H2) of 0.0006 and 0.0004, respectively. Laboratory experiments suggest a similar ratio for CO. The equilibrium calculations give a reaction enthalpy of the overall oxidation that is 11% higher than for the oxidation of methane per kmol of oxygen. Thus, the reduction from
Fe2TiO5 +TiO2 to FeTiO3 with methane is endothermic, but less endothermic compared to NiO/Ni and Fe2O3/Fe3O4, and almost similar to Mn3O4/MnO.
TL;DR: In this paper, the authors show that the timing of these steps correlates with the amalgamation of Earth's land masses into supercontinents, leading to an explosion of algae and cyanobacteria, and a marked increase in photosynthesis, and the photosynthetic production of O2.
Abstract: Atmospheric oxygen concentrations in the Earth’s atmosphere rose from negligible levels in the Archaean Era to about 21% in the present day. This increase is thought to have occurred in six steps, 2.65, 2.45, 1.8, 0.6, 0.3 and 0.04 billion years ago, with a possible seventh event identified at 1.2 billion years ago. Here we show that the timing of these steps correlates with the amalgamation of Earth’s land masses into supercontinents. We suggest that the continent–continent collisions required to form supercontinents produced supermountains. In our scenario, these supermountains eroded quickly and released large amounts of nutrients such as iron and phosphorus into the oceans, leading to an explosion of algae and cyanobacteria, and thus a marked increase in photosynthesis, and the photosynthetic production of O2. Enhanced sedimentation during these periods promoted the burial of a high fraction of organic carbon and pyrite, thus preventing their reaction with free oxygen, and leading to sustained increases in atmospheric oxygen. Atmospheric oxygen levels on Earth rose in at least six distinct steps and an examination of the timing of the steps suggests that they coincided with the formation of supercontinents and supermountains. This leads to the hypothesis that increased erosion of these supermountains released large amounts of nutrients to the oceans, stimulating productivity and the release of oxygen to the atmosphere. The subsequent burial of organic carbon along with the mountain sediments would have sustained the increased oxygen levels.
TL;DR: In this paper, the authors have demonstrated the reasons why CeO2 becomes an active catalyst for diesel particulate (soot) abatement, which attracts recent worldwide attention in the development of clean diesel automobiles.
Abstract: The present work has demonstrated the reasons why CeO2 becomes an active catalyst for diesel particulate (soot) abatement, which attracts recent worldwide attention in the development of clean diesel automobiles. Four typical fluorite-type oxides, CeO2, ZrO2, Pr6O11, and a CeO2−ZrO2 solid solution have been studied as model catalysts for soot oxidation in conjunction with the redox property and the reactivity of solid oxygen species. It was found that the redox property measured in terms of oxygen storage/release capacity was not the sole determining factor for the observed catalytic activity decreasing in the order of CeO2 ≫ Pr6O11 ≈ CeO2−ZrO2 > ZrO2. The reactivity of oxygen species involved in the redox cycles would rather be important. The ESR measurement showed that admission of O2 to the pre-reduced CeO2 surface generated superoxide ions (O2−). Such reactive oxygen species were less abundant on CeO2−ZrO2 and were not detected on ZrO2 and Pr6O11. The labeled and unlabeled O2 pulse experiments demonst...
TL;DR: Delta18OP values of modern human teeth collected at 12 sites located at latitudes ranging from 4 degrees N to 70 degrees N together with the corresponding oxygen composition of tap waters from these areas were analyzed to investigate the impact of solid food consumption on the oxygen isotope composition of the total ingested water.
TL;DR: Two models of the role for mitochondria in oxygen sensing will be discussed and recent evidence will be presented which raises the possibility that these two models which implicate ROS (reactive oxygen species) and oxygen redistribution respectively may complement each other and facilitate rapid and dynamic activation of the HIF pathway in hypoxia.
Abstract: Mitochondrial respiration is responsible for more than 90% of oxygen consumption in humans. Cells utilize oxygen as the final electron acceptor in the aerobic metabolism of glucose to generate ATP which fuels most active cellular processes. Consequently, a drop in tissue oxygen levels to the point where oxygen demand exceeds supply (termed hypoxia) leads rapidly to metabolic crisis and represents a severe threat to ongoing physiological function and ultimately, viability. Because of the central role of oxygen in metabolism, it is perhaps not surprising that we have evolved an efficient and rapid molecular response system which senses hypoxia in cells, leading to the induction of an array of adaptive genes which facilitate increased oxygen supply and support anaerobic ATP generation. This response is governed by HIF (hypoxia-inducible factor). The oxygen sensitivity of this pathway is conferred by a family of hydroxylases which repress HIF activity in normoxia allowing its rapid activation in hypoxia. Because of its importance in a diverse range of disease states, the mechanism by which cells sense hypoxia and transduce a signal to the HIF pathway is an area of intense investigation. Inhibition of mitochondrial function reverses hypoxia-induced HIF leading to speculation of a role for mitochondria in cellular oxygen sensing. However, the nature of the signal between mitochondria and oxygen-sensing hydroxylase enzymes has remained controversial. In the present review, two models of the role for mitochondria in oxygen sensing will be discussed and recent evidence will be presented which raises the possibility that these two models which implicate ROS (reactive oxygen species) and oxygen redistribution respectively may complement each other and facilitate rapid and dynamic activation of the HIF pathway in hypoxia.
TL;DR: A carbon cathode open to the air is described, on which attached bacteria catalyzed oxygen reduction using electrons provided by the solid-phase cathode, and the strong decrease in activation losses indicates that bacteria function as true catalysts for oxygen reduction.
Abstract: Microbial fuel cells (MFCs) have the potential to combine wastewater treatment efficiency with energetic efficiency. One of the major impediments to MFC implementation is the operation of the cathode compartment, as it employs environmentally unfriendly catalysts such as platinum. As recently shown, bacteria can facilitate sustainable and cost-effective cathode catalysis for nitrate and also oxygen. Here we describe a carbon cathode open to the air, on which attached bacteria catalyzed oxygen reduction. The bacteria present were able to reduce oxygen as the ultimate electron acceptor using electrons provided by the solid-phase cathode. Current densities of up to 2.2 A m(-2) cathode projected surface were obtained (0.303 +/- 0.017 W m(-2), 15 W m(-3) total reactor volume). The cathodic microbial community was dominated by Sphingobacterium, Acinetobacter and Acidovorax sp., according to 16S rRNA gene clone library analysis. Isolates of Sphingobacterium sp. and Acinetobacter sp. were obtained using H-2/O-2 mixtures. Some of the pure culture isolates obtained from the cathode showed an increase in the power output of up to three-fold compared to a non-inoculated control, that is, from 0.015 +/- 0.001 to 0.049 +/- 0.025 W m(-2) cathode projected surface. The strong decrease in activation losses indicates that bacteria function as true catalysts for oxygen reduction. Owing to the high overpotential for non-catalyzed reduction, oxygen is only to a limited extent competitive toward the electron donor, that is, the cathode. Further research to refine the operational parameters and increase the current density by modifying the electrode surface and elucidating the bacterial metabolism is warranted.
TL;DR: In this paper, the surface modification of polyethyleneterephthalate (PET) polymer by plasma treatment was studied and the changes in surface morphology were observed by using atomic force microscopy (AFM).
Abstract: In this paper, we present a study on the surface modification of polyethyleneterephthalate (PET) polymer by plasma treatment. The samples were treated by nitrogen and oxygen plasma for different time periods between 3 and 90 s. The plasma was created by a radio frequency (RF) generator. The gas pressure was fixed at 75 Pa and the discharge power was set to 200 W. The samples were treated in the glow region, where the electrons temperature was about 4 eV, the positive ions density was about 2 × 1015 m−3, and the neutral atom density was about 4 × 1021 m−3 for oxygen and 1 × 1021 m−3 for nitrogen. The changes in surface morphology were observed by using atomic force microscopy (AFM). Surface wettability was determined by water contact angle measurements while the chemical composition of the surface was analyzed using XPS. The stability of functional groups on the polymer surface treated with plasma was monitored by XPS and wettability measurements in different time intervals. The oxygen-plasma-treated samples showed much more pronounced changes in the surface topography compared to those treated by nitrogen plasma. The contact angle of a water drop decreased from 75° for the untreated sample to 20° for oxygen and 25° for nitrogen-plasma-treated samples for 3 s. It kept decreasing with treatment time for both plasmas and reached about 10° for nitrogen plasma after 1 min of plasma treatment. For oxygen plasma, however, the contact angle kept decreasing even after a minute of plasma treatment and eventually fell below a few degrees. We found that the water contact angle increased linearly with the O/C ratio or N/C ratio in the case of oxygen or nitrogen plasma, respectively. Ageing effects of the plasma-treated surface were more pronounced in the first 3 days; however, the surface hydrophilicity was rather stable later. Copyright © 2008 John Wiley & Sons, Ltd.
TL;DR: Resuscitation with room air failed to achieve the authors' target oxygen saturation by 3 minutes of life, and it is recommended that it not be used for preterm neonates.
Abstract: OBJECTIVE. In this study of preterm neonates of 32 weeks, we prospectively compared the use of room air versus 100% oxygen as the initial resuscitation gas. METHODS. A 2-center, prospective, randomized, controlled trial of neonates with gestational ages of 23 to 32 weeks who required resuscitation was performed. The oxygen group was initially resuscitated with 100% oxygen, with decreases in the fraction of inspired oxygen after 5 minutes of life if pulse oxygen saturation was 95%. The room air group was initially resuscitated with 21% oxygen, which was increased to 100% oxygen if compressions were performed or if the heart rate was 100 beats per minute at 2 minutes of life. Oxygen was increased in 25% increments if pulse oxygen saturation was 70% at 3 minutes of life or 80% at 5 minutes of life. RESULTS. Twenty-three infants in the oxygen group (mean gestational age: 27.6 weeks; range: 24 –31 weeks; mean birth weight: 1013 g; range: 495–2309 g) and 18 in the room air group (mean gestational age: 28 weeks; range: 25–31 weeks; mean birth weight: 1091 g; range: 555–1840 g) were evaluated. Every resuscitated patient in the room air group met rescue criteria and received an increase in the fraction of inspired oxygen by 3 minutes of life, 6 patients directly to 100% and 12 with incremental increases. Pulse oxygen saturation was significantly lower in the room air group from 2 to 10 minutes (pulse oxygen saturation at 3 minutes: 55% in the room air group vs 87% in the oxygen group). Heart rates did not differ between groups in the first 10 minutes of life, and there were no differences in secondary outcomes. CONCLUSIONS. Resuscitation with room air failed to achieve our target oxygen saturation by 3 minutes of life, and we recommend that it not be used for preterm neonates. Pediatrics 2008;121:1083–1089
TL;DR: It was shown that even under aerobic conditions, alcohol fermentation plays an important role in the control of the level of pyruvate in the tissue, indicating that sensing the energy status is an important component of optimizing plant metabolism to changes in the oxygen availability.
Abstract: Plant internal oxygen concentrations can drop well below ambient even when the plant grows under optimal conditions. Using pea (Pisum sativum) roots, we show how amenable respiration adapts to hypoxia to save oxygen when the oxygen availability decreases. The data cannot simply be explained by oxygen being limiting as substrate but indicate the existence of a regulatory mechanism, because the oxygen concentration at which the adaptive response is initiated is independent of the actual respiratory rate. Two phases can be discerned during the adaptive reaction: an initial linear decline of respiration is followed by a nonlinear inhibition in which the respiratory rate decreased progressively faster upon decreasing oxygen availability. In contrast to the cytochrome c pathway, the inhibition of the alternative oxidase pathway shows only the linear component of the adaptive response. Feeding pyruvate to the roots led to an increase of the oxygen consumption rate, which ultimately led to anoxia. The importance of balancing the in vivo pyruvate availability in the tissue was further investigated. Using various alcohol dehydrogenase knockout lines of Arabidopsis (Arabidopsis thaliana), it was shown that even under aerobic conditions, alcohol fermentation plays an important role in the control of the level of pyruvate in the tissue. Interestingly, alcohol fermentation appeared to be primarily induced by a drop in the energy status of the tissue rather than by a low oxygen concentration, indicating that sensing the energy status is an important component of optimizing plant metabolism to changes in the oxygen availability.
TL;DR: In this article, surface area measurement, X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements were performed to study the surface and bulk oxygen mobility and to correlate it to the activity.
Abstract: Co 3 O 4 , CeO 2 and Co 3 O 4 –CeO 2 mixed oxides with Co/Ce nominal atomic ratio 0.1:5, prepared by co-precipitation method with sodium carbonate, were tested in the oxidation of propene under lean condition and the catalyst stability was checked by performing three consecutive heating–cooling cycles. Characterization of the textural properties were performed by surface area measurement BET, X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. Among the Co 3 O 4 –CeO 2 mixed oxides, Co 3 O 4 (30 wt%)–CeO 2 (70 wt%) gives the best activity attaining full propene conversion at 250 °C. This sample is characterized by the presence of Co 3 O 4 particles well dispersed and in good contact with ceria according to BET and XRD data and as evidenced by SEM micrographs. Oxygen temperature-programmed desorption (O 2 -TPD) and C 3 H 6 -temperature-programmed reduction (C 3 H 6 -TPR) experiments were carried out in order to study the surface and bulk oxygen mobility and to correlate it to the activity. At temperature around 200 °C, O 2 -TPD experiments showed the desorption of mobile surface oxygen species for the most active samples, Co 3 O 4 and Co 3 O 4 (30 wt%)–CeO 2 (70 wt%). C 3 H 6 -TPR experiments for both of the oxides also evidenced a high reactivity at low temperature, especially, for Co 3 O 4 (30 wt%)–CeO 2 (70 wt%) giving at 345 °C an intense peak of CO 2 formation. Conversely, the ceria sample showed by C 3 H 6 -TPR much less pronounced oxygen bulk mobility, starting to react with propene above 500 °C and forming only CO. In this case, the catalytic activity of ceria was explained in terms of formation of surface oxygen vacancies which are relevant to the propene oxidation in presence of gaseous oxygen.
TL;DR: High temperature fatigue of swimming sockeye salmon was not a result of a failure of either oxygen delivery to the gills or oxygen diffusion at the gill because oxygen partial pressure (PO2) and oxygen content (CO2) in arterial blood did not decrease with increasing temperature, as would be predicted for such limitations.
Abstract: The mechanism underlying the decrease in aerobic scope in fish at warm temperatures is not fully understood and is the focus of this research. Our study examined oxygen uptake and delivery in resting, swimming and recovering sockeye salmon while water temperature was acutely increased from 15 degrees C to 24 degrees C in 2 degrees C h(-1) increments. Fish swam at a constant speed during the temperature change. By simultaneously measuring oxygen consumption (M(O(2))), cardiac output (Q) and the blood oxygen status of arterial and venous blood, we were able to determine where in the oxygen cascade a limitation appeared when fish stopped sustained swimming as temperature increased. High temperature fatigue of swimming sockeye salmon was not a result of a failure of either oxygen delivery to the gills or oxygen diffusion at the gills because oxygen partial pressure (P(O(2))) and oxygen content (C(O(2))) in arterial blood did not decrease with increasing temperature, as would be predicted for such limitations. Instead, arterial oxygen delivery (Ta(O(2))) was initially hampered due to a failure to adequately increase Q with increasing temperature. Subsequently, lactate appeared in the blood and venous P(O(2)) remained constant.
TL;DR: In this article, the authors presented an overview of platinum-based catalysts as methanol-resistant oxygen reduction materials for direct DMFCs and proposed Pt alloyed with first-row transition elements as cathode material.
TL;DR: An optical dual sensor for oxygen and temperature is presented that is highly oxygen sensitive and covers a broad temperature range and is a key step forward in a number of scientifically or commercially important applications including food packaging, for monitoring of hyperthermophilic microorganisms, in space technology, and safety and security applications in terms of detection of oxygen leaks.
Abstract: An optical dual sensor for oxygen and temperature is presented that is highly oxygen sensitive and covers a broad temperature range. Dual sensing is based on luminescence lifetime measurements. The novel sensor contains two luminescent compounds incorporated into polymer films. The temperature-sensitive dye (ruthenium tris-1,10-phenanthroline) has a highly temperature-dependent luminescence and is incorporated in poly(acrylonitrile) to avoid cross-sensitivity to oxygen. Fullerene C70 was used as the oxygen-sensitive probe owing to its strong thermally activated delayed fluorescence at elevated temperatures that is extremely oxygen sensitive. The cross-sensitivity of C70 to temperature is accounted for by means of the temperature sensor. C70 is incorporated into a highly oxygen-permeable polymer, either ethyl cellulose or organosilica. The two luminescent probes have different emission spectra and decay times, and their emissions can be discriminated using both parameters. Spatially resolved sensing is ach...
TL;DR: In this article, Nanoporous gold (NPG) is used as a catalyst for the oxygen reduction reaction in both gas phase (in fuel cells) and aqueous environments (using rotating disk electrochemistry).
TL;DR: The results show that organisms at the sediment and water interface can stimulate P release from sediments, and their metabolism can alter the surrounding micro-environmental conditions, which aids the understanding of P biogeochemical cycling at the interface and its relationship with eutrophication in shallow lakes.
TL;DR: In this article, an inert indium tin oxide electrode in phosphate-buffered water containing cobalt (II) ions was used to produce oxygen from water without the need for excessive driving potentials.
Abstract: The utilization of solar energy on a large scale requires its storage. In natural photosynthesis, energy from sunlight is used to rearrange the bonds of water to oxygen and hydrogen equivalents. The realization of artificial systems that perform "water splitting" requires catalysts that produce oxygen from water without the need for excessive driving potentials. Here we report such a catalyst that forms upon the oxidative polarization of an inert indium tin oxide electrode in phosphate-buffered water containing cobalt (II) ions. A variety of analytical techniques indicates the presence of phosphate in an approximate 1:2 ratio with cobalt in this material. The pH dependence of the catalytic activity also implicates the hydrogen phosphate ion as the proton acceptor in the oxygen-producing reaction. This catalyst not only forms in situ from earth-abundant materials but also operates in neutral water under ambient conditions.
TL;DR: Resuscitation can be safely initiated for extremely low gestational age neonates with a low fraction of inspired oxygen (∼30%), which then should be adjusted to the infant's needs, reducing the oxygen load to the neonate.
Abstract: OBJECTIVE. Extremely low gestational age neonates have very low oxygen saturation in utero and an immature antioxidant defense system. Abrupt increases in oxygen saturation after birth may cause oxidative stress. We compared achievement of a targeted oxygen saturation of 85% at 10 minutes of life when resuscitation was initiated with low or high fractions of inspired oxygen and levels were adjusted according to preductal pulse oxygen saturation values. METHODS. A prospective, randomized, clinical trial was performed in 2 level III neonatal referral units. Patients of 28 weeks of gestation who required active resuscitation were randomly assigned to the low-oxygen group (fraction of inspired oxygen: 30%) or the high-oxygen group (fraction of inspired oxygen: 90%). Every 60 to 90 seconds, the fraction of inspired oxygen was increased in 10% steps if bradycardia occurred (100 beats per minute) or was decreased in similar steps if pulse oxygen saturation reached values of 85%. Preductal pulse oxygen saturation was continuously monitored. RESULTS. The fraction of inspired oxygen in the low-oxygen group was increased stepwise to 45% and that in the high-oxygen group was reduced to 45% to reach a stable pulse oxygen saturation of 85% at 5 to 7 minutes in both groups. No differences in oxygen saturation in minute-to-minute registers were found independent of the initial fraction of inspired oxygen used 4 minutes after cord clamping. No differences in mortality rates in the early neonatal period were detected. CONCLUSIONS. Resuscitation can be safely initiated for extremely low gestational age neonates with a low fraction of inspired oxygen (30%), which then should be adjusted to the infant’s needs, reducing the oxygen load to the neonate.
TL;DR: In this article, the isotope composition of the drinking water and food supplied to captive woodrats to quantify the relationships between drinking water (δdw), body water (βw), and tissue (γw) was used to study resource utilization and migration in animals and to reconstruct climate.
TL;DR: In this article, a series of Fe42Pt58 nanoparticles of different compositions (x = 63, 58, 54, 42, 15, and 0) were prepared and loaded onto a glassy carbon (GC) electrode where their catalytic activities in the electroreduction of oxygen were examined and compared.
Abstract: FexPt100-x nanoparticles of different compositions (x = 63, 58, 54, 42, 15, and 0) were prepared and loaded onto a glassy carbon (GC) electrode where their catalytic activities in the electroreduction of oxygen were examined and compared. Cyclic and rotating disk voltammetric studies of the resulting FexPt100-x/GC electrodes showed that the catalytic activity for oxygen reduction exhibited a peak-shape dependence on the particle composition (x). Among the series of nanocatalysts under study, Fe42Pt58 particles showed the maximum activity for O2 reduction in terms of the reduction overpotential and current density. This was accounted for by the effects of the Fe content on the electronic structures of the Pt active sites and the resulting Pt−O interactions. Kinetic analyses showed that direct four-electron reduction of adsorbed oxygen occurred on these catalyst surfaces. Additionally, the rate constant of O2 reduction increased with increasing Pt content in the alloy particles; yet, at x ≤ 42, the rate con...