Variation Of Oxygen Content Research Articles

Templated N-Doped and O-Doped Carbons for Energy Storage and Conversion

Global energy demand has significantly increased in the last decades, and consequently, the environmental problems associated with the use of fossil fuels. More sustainable energy sources are required, and it is imperative to develop more efficient energy storage and conversion devices. In this context, batteries and fuel cells are promising options for stationary, portable, and transport applications.[1] Unfortunately, both polymer electrolyte membrane fuel cells (PEMFCs) and metal-air batteries are limited by the need for high Pt loadings in the cathode due to kinetic limitations imposed by the sluggish oxygen reduction reaction (ORR).[2] The conditions in the cathode can also result in the degradation of the carbon support (carbon corrosion) and Pt agglomeration, dislodgement, and dissolution.[3] Efforts aimed to solve these problems have intensified, principally the search for new catalysts materials to reduce or eliminate the need for Pt.[4] In the framework of these initiatives, heteroatoms-doped carbons obtained by carbonization of organic polymer gels (OPGs) are seen as attractive candidates for achieving some of these goals.[5] Even though resorcinol-formaldehyde polymers have been the most extensively studied, other precursors have been recently investigated for applications in batteries and supercapacitors.[6] In this study, high surface area mesoporous carbon materials with variable N and O contents were produced by carbonization of melamine-formaldehyde (MF) and resorcinol-formaldehyde (RF) polymer gels in the presence of SiO2 nanoparticles (20 to 200 nm) as hard-templates. Carbon products with up to 8 N-atom% and surface areas up to 500 m2/g were obtained by carbonization of nitrogen-rich melamine polymers (MF-C) depending on the annealing conditions (950°C or 1500°C). By adopting a similar approach, carbons with variable oxygen and nitrogen content were prepared by the combustion of resorcinol-formaldehyde (RF-C) and resorcinol-melamine-formaldehyde (RMF-C) polymers. The materials structure and chemical composition have been extensively investigated using a plethora of different techniques.Pt/MF-C and Pt/RF-C samples were prepared by an impregnation method to evaluate the stability of these catalysts under oxidizing and acidic conditions, as well as their catalytic activity toward the ORR. It was found that an increase in annealing temperature from 950 to 1500 oC resulted in a significant improvement in stability upon cycling the potential in accelerated ageing tests in acid media (0 to 1.4 V vs NHE) comparable or even better than the benchmark material Pt/Vulcan, and a preferential 4-electron reduction pathway for the ORR, as required for fuel cells and metal-air batteries applications. Preliminary data for the reduction of oxygen on Fe/MF-C and Fe/RF-C samples are underway, and preliminary results will also be presented.

Susceptibility of Neisseria gonorrhoeae to Resazomycins in Varying Oxygen Concentrations

Antibiotic resistance is a growing issue globally as many pathogenic bacterial species are becoming less susceptible to common antibiotic treatments. Antibiotic resistant pathogens are the cause of 23,000 deaths in the United States each year and increasing health care costs. It is imperative that new antibiotics be developed to combat this public health crisis. We recentlyidentified a novel family of resazurin-based compounds, resazomycins, to have antimicrobial activity in vitro against Neisseria gonorrhoeae, a human pathogen. Resazomycins are capable of killing N. gonorrhoeae in broth culture as well as within human endometrial cells, HEC-1-B. However, when different resazomycins were tested in a mouse model of gonorrhea, none of the compounds were able to completely clear the infection. The difference between in vitro and invivo antibacterial efficacy may be due to differences in oxygen concentration. Atmospheric oxygen levels are typically around 20% while the oxygen concentration of most mammalian tissues is around 3-5%. We hypothesize that the decreased oxygen concentration in vivo may affect the antimicrobial activity of resazomycins. To test this hypothesis, the susceptibility of different clinical isolates of N. gonorrhoeae to resazurin was measured under atmospheric (20%)and physiologic (2-3%) oxygen conditions. To date, certain strains of N. gonorrhoeae showed more growth following exposure to resazomycins under physiologic oxygen than atmospheric oxygen. This suggests N. gonorrhoeae is more resistant to resazomycins under low oxygen conditions. Further experimentation is needed to determine why certain N. gonorrhoeae strainsare showing less susceptibility to resazomycins under physiologic oxygen conditions.

Study of oxygen electrode reactions on symmetrical porous SrTi0.30Fe0.70O3-δ electrodes on Ce0.8Gd0.2O1.9 electrolyte at 800 °C–500 °C

Iron doped strontium titanates (SrTi1-xFexO3-δ) are an interesting mixed ionic-electronic conductor model used to study basic oxygen reduction/oxidation reactions. In this work, we performed an impedance spectroscopy study on symmetrical porous SrTi0.30Fe0.70O3-δ (STF70) electrodes on a ceria-based electrolyte. The sample was measured in varying oxygen concentration: from 0.3% to 100% in 800 °C–500 °C temperature range. Low polarisation resistance (e.g. <125 mΩ cm2 at 600 °C in the air) values were obtained, showing an overall high performance of the STF70 electrode. Impedance data analysis was assisted by the distribution of relaxation times method, which allowed an equivalent electrical circuit to be proposed comprising of two resistance/constant phase element sub-circuits connected in series. The medium frequency contribution, with a characteristic frequency of ∼2000 Hz at 800 °C in air, originates most probably from possible surface diffusion followed by charge transfer reaction limitation, whereas the lower frequency contribution (characteristic frequency <10 Hz) is due to gas-phase diffusion.

HISTORY OF PETER THE GREAT BAY DISCOVER AND OCEANOGRAPHIC SURVEYS IN THE JAPAN SEA TILL THE MIDDLE 20TH CENTURY

Peter the Great Bay (PGB) was not known to Europeans for a long time. The first European ship reached PGB in 1852. She was the French corvette Capricieuse commanded by captain G. de Rocquemaurel who was sent by his government for exploring the western coast of the Japan Sea; actually he had described the Posyet Bay only. Later the British HMS Winchester and Barracuda visited PGB in August, 1856. They discovered the Golden Horn Bay, them as Port May, and gave names to many other geographical locations. Large Russian expedition of 7 vessels was sent to Primorye coast under the leadership of N.N. Muravyov-Amursky, the Governor-General of Eastern Siberia, in the summer of 1859. They described thoroughly the entire PGB and changed many (not all) foreign geographical names to Russian ones. Scientific researches in the Japan Sea were started soon by L.I. Schrenk, who summarized the results of Russian observations in two books published in 1869 and 1874. Great success in understanding of oceanographic regime was the work of S.O. Makarov «The «Vitiaz» and the Pacific Ocean» (1894). S. Ogura created in 1927 the general chart of currents in the Japan Sea on the base of Japanese observations in 1900–1911 that was more detailed and comprehensive than the first chart of L.I. Shrenk. Moreover, S. Ogura plotted the water temperature and salinity distribution over the whole Japan Sea for February and August. Oceanographic studies in PGB were made in 1920s by K.A. Gomoyunov, the first professional oceanographer who lived constantly in the Russian Far East; he began from the Amur Bay survey in the summer of 1925. The USSR Hydrographic Office conducted the oceanographic survey in PGB and the Tatar Strait in 1926–1928, with measuring of temperature, salinity, dissolved oxygen content, pH, and water transparency, with the deepest measurements at the depth of 3500 m. In 1932, the Pacific Res. Inst. of Fisheries in Vladivostok together with the State Hydrographic Institute in Leningrad organized the large-scale Pacific expedition that covered all Far-Eastern Seas. In the framework of this expedition, the 5 cruises of RV Rossinante to the Japan Sea headed by N.I. Tarasov explored PGB, too, that allowed to analyze seasonal variations of temperature, salinity, oxygen content, and currents. Oceanographic researches in the Japan Sea became more active in the times of WWII, 4 small research vessels made observations at Primorye coast every month from April to October under general supervision of A.M. Batalin; in total, more than 100 exits to the sea were recorded in 1941–1946. The data collected in those years was the basis for the big atlas of the Japan Sea created under the leadership of A.I. Rumyantsev and published in 1951.

Characterization of sputtered MoOx thin films with different oxygen content and their application as back contact in CdTe solar cells

Transparent MoOx thin films with varied composition were successfully prepared by sputtering and the effects of oxygen contents on the composition stoichiometry, defect states, work functions, electrical and optical properties of MoOx films were systematically studied. These thin films were then utilized in cadmium telluride solar cells to act as back contact buffers. As compared with the CdTe solar cells with Au back contact, deteriorated performance was witnessed in those with MoOx buffers. The deterioration was demonstrated to be caused by the oxidation of CdTe surface, the large valence band offset and the insufficient work function. Finally, by optimizing the back contacts to form a CuCl/MoOx/ITO composite back contact, the efficiency was improved to 11.8%. This work demonstrates feasible approaches to prepare MoOx thin films with varied oxygen concentrations which could be easily applied to many other thin film solar cells and provide important indications in the preparation and optimization of the performance for bifacial devices.

Oxygen concentration variation in ullage influenced by dissolved oxygen evolution

To determine the oxygen concentration variation in ullage that results from dissolved oxygen evolution in an inert aircraft fuel tank, the CFD method with a mass transfer source is applied in the present study. An experimental system is also designed to evaluate the accuracy of the CFD simulations. The dissolved oxygen evolution is simulated under different conditions of fuel load and initial oxygen concentration in ullage of an inert fuel tank with stimulations of heating and pressure decrease. The increase in the oxygen concentration in ullage ranges from 0.82% to 5.92% upon stimulation of heating and from 0.735% to 12.36% upon stimulation of a pressure decrease for an inert ullage in the simulations. The heating accelerates the release of the dissolved oxygen from the fuel by increasing the mass transfer rate in the mass transfer source and decreasing the pressure, thereby accelerating the dissolved oxygen evolution by increasing the concentration difference between the gas and the fuel. The time constant that represents the oxygen evolution rate is independent of the initial oxygen concentration in ullage of an inert tank but depends closely on the fuel load, temperature and pressure. The time constant can be fitted using a polynomial equation relating the fuel load to temperature in the heating stimulation with an accuracy of 4.77%. Upon stimulation of a pressure decrease, the time constant can be expressed in terms of the fuel load and the pressure, with an accuracy of 5.02%.

Controlling inclusion evolution behavior by adjusting flow rate of shielding gas during direct energy deposition of AISI 316 L

To reveal the mechanism of oxidation and the effect of inclusion characteristics on the mechanical properties of additively-manufactured metal matrix, two groups of AISI 316 L stainless steel samples were fabricated under different flow rates of shielding gas (Ar) at two intensities of laser beam. As flow rates of shielding gas increased from 5 L/min to 25 L/min, the oxygen content in the melt pool decreased from 775 ppm to 375 ppm at low intensity of laser beam (73 W/m2), and from 677 ppm to 1470 ppm at high intensity of laser beam (725 W/m2). Variation in oxygen content affected melt pool shape, solidification texture, and the mechanical properties of the material. In each intensity of laser beam group, optimal flow rates of shielding gas condition for tensile property existed. As inclusion number density increased from 8866/mm2 to 45909/mm2, yield stress increased to 26 %. A rapid drop in ductility occurred at flow rate 5 L/min, because independently-nucleated spinel accelerated inclusion coalescence in the melt pool.

Study on Inclusions Distribution and Cyclic Fatigue Performance of Gear Steel 18CrNiMo7-6 Forging

The three-dimensional morphologies of inclusions in gear steel 18CrNiMo7-6 forging were investigated by a non-destructive extraction method, and the cleanliness of radial positions was analyzed, mainly including the variation of total oxygen content and the distribution of size and quantity of inclusions. In addition, fatigue performance was tested using an ultrasonic fatigue machine to investigate the fatigue characteristics of the steel. The results show that the quantity density of inclusions per unit volume in gear steel 18CrNiMo7-6 decreases exponentially with increasing size, oxide inclusions with a size less than 8 μm account for more than 90%, while sulfide inclusions account for more than 85%. The average value of the oxygen content can reflect the level of inclusions that were evenly distributed in the molten steel, and the accumulative total oxygen content increases significantly with increasing inclusion size. The fatigue specimen failed after the stress exceeded the critical value, and fatigue failure hardly occurred when the stress was below the critical value. Meanwhile, large-sized nondeformable inclusions such as Al2O3-CaO in gear steel 18CrNiMo7-6 are closely related to fatigue failure. It is recommended that the area from the center to the 1/2 radius with low cleanliness should be avoided, while the area from the 3/4 radius to the edge with high cleanliness should be selected during the machining of the gear.

Variability of dissolved oxygen in the Arabian Sea Oxygen Minimum Zone and its driving mechanisms

The Arabian Sea hosts one of the most intense, perennial Oxygen Minimum Zones (OMZ) in the world ocean. Observations along a meridional transect at 68°E extending from 8 to 21°N showed large seasonal as well as interannual changes in the dissolved oxygen and nitrite concentrations. Unlike previous studies that used observations from the periphery of the OMZ, our observations are from its core and also allow us demarcating the southern extent of the OMZ. The southern boundary of the OMZ extended up to ~9°N during the southwest monsoon but was restricted to ~11°N during the northeast monsoon. While previous studies report ventilation from the oxygenated Indian Central Water (ICW) at intermediate depths of the OMZ, none have so far discussed how this ventilation takes place or its variability. Our observations reveal intrusion of the ICW at intermediate depths (200–500 m) into the OMZ up to 16°N, in contrast to 11°N reported in earlier studies. The oxygen variations at the southern boundary of the OMZ are coherent with those in the sea level, associated with the westward propagating Rossby waves radiated off the west coast of India. Besides modulating the oxygen distribution in the surface layer and the upper boundary of the OMZ through upwelling or downwelling, these Rossby waves can potentially influence the oxygen at intermediate depths by controlling the isopycnal mixing of the ICW within the OMZ, leading to variations in oxygen and nitrogen concentrations. Further investigations are needed to better understand the potential influence of these Rossby waves on the OMZ variability and the associated nitrogen cycling.

AVALIAÇÃO QUÍMICA DE LENHOS CARBONIZADOS DE Araucaria columnaris SOB DIFERENTES CONCENTRAÇÕES DE OXIGÊNIO COMO COMPARATIVO DE ANÁLISE DE charcoal FÓSSIL

CHEMICAL EVALUATION OF Araucaria columnaris CARBONIZED WOODS UNDER DIVERSE OXYGEN CONCENTRATIONS AS COMPARATIVE ANALYSIS OF FOSSIL charcoal. In the face of environmental changes concerns, the study of climate change becomes essential to understand the life trajectory of planet earth. For this purpose, this work seeks to understand climate change and fluctuations in the amount of atmospheric oxygen across geological ages, carbonizing the Araucaria columnaris wood in varying oxygen concentrations, and comparing them to the fossil coal from Quiteria Outcrop. In this study, pyrolysis of Araucaria columnaris wood occurred with the use of TGA, under an atmosphere of 21% and 30% O2, analyzed in FTIR, distinguishing the constituent compounds of the wood. Multivariate analysis of the mains components (PCA) was applied, for data crossing. There is a distinction between carbonized wood and fossil charcoal, the charcoal burning temperature as well as the atmospheric oxygen composition being inconclusive. However, FTIR results indicate that the amount of oxygen has an influence on the degradation of the wood, and samples at 450 °C have greater similarities with fresh wood. Thus, it was observed that the temperature and the burning time are the main factors of the fires, being that the amount of oxygen available in the atmosphere influences the firing process.

Measurement of mitochondrial H2O2 production under varying O2 tensions.

Mitochondria-derived reactive oxygen species (ROS) play an important role in the development of several pathologies and are also involved in physiological signaling. Molecular oxygen is the direct substrate of complex IV of the respiratory chain, and at the same time, its partial reduction in mitochondria results in the formation of ROS, mainly H2O2. The accurate knowledge of the dependence of H2O2 production on oxygen concentration is vital for the studies of tissue ischemia/reperfusion, where the relationship between oxygen availability, respiration, and ROS production is critical. In this chapter, we describe a straightforward and reliable protocol for the assessment of H2O2 release by mitochondria at varying oxygen concentrations. This method can be used for any ROS-generating system where the effect of oxygen level on H2O2 production needs to be assessed.

Study on edge cracking of titanium cold rolled sheet

In this study, to understand oxygen effects on workability of titanium, edge cracking and microstructure changes with the oxygen content variations in the cold rolled sheets were observed carefully and discussed. The higher oxygen content of titanium sheet, the more the edge cracks occurred after cold rolling deformation. While the specimen containing low oxygen became fine grained structures after the cold rolling, the other high oxygen sheets consisted of relatively coarse and elongated grains. The fine-grained structures was assumed to come from an active twinning behavior, meanwhile the other’s elongated structures were due to the twinning suppression by increasing oxygen contents. In addition, distinct shear bands were appeared in the high oxygen sheets after cold rolling. The high oxygen contents may multiply dislocation density by suppression of twinning and promoting dislocation slips. The increased dislocations can also produce a concentration of strain, slip bands thus appears during the cold rolling deformation. These slip bands cause the edge cracking in the higher oxygen sheets.

Oxidation of a c-Tb2O3(111) thin film by the sequential formation of stoichiometric phases

We used temperature-programmed desorption (TPD), low energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS) to investigate the oxidation of a well-ordered c-Tb2O3(111) thin film supported on Pt(111) by gaseous oxygen atoms in ultrahigh vacuum. Our results provide evidence that the c-Tb2O3 film oxidizes through the sequential development of the stoichiometric ι-Tb7O12 and δ-Tb11O20 phases, followed by the formation of a variable oxygen concentration α-TbOx phase up to x = 2. The ι and δ-phases decompose to yield sharp O2 TPD peaks at about 780 and 640 K, while the α-phase evolves O2 between ~450 and 600 K during TPD. Quantitative analysis shows that changes in the XPS Tb 3d and 4d spectra caused by oxidation agree well with our estimates of the TbOx film stoichiometry determined from TPD. We observe a well-defined LEED pattern for ι-Tb7O12(111) after heating the oxidized film to ~700 K. In contrast, several observations, including incomplete ι → δ conversion, lack of an observable LEED pattern for the δ-Tb11O20 phase, and sensitivity of α-phase formation to thermal aging of the film, indicate that the δ and α-phases develop under kinetic control for the conditions studied, such that the phases decompose in UHV at temperatures lower than those needed for these phases to stabilize into more crystalline and uniform arrangements.

Description of 'Ca. Methylobacter oryzae' KRF1, a novel species from the environmentally important Methylobacter clade 2.

Members of the genus Methylobacter (Mtb) have been identified to be the most dominant methanotrophs in aquatic as well as terrestrial habitats. Methylobacter shows four species with validly published names and these are grouped in two clades based on phylogenetic and genomic comparisons. Mtb luteus and Mtb marinus (synonym: Mtb whittenburyi) belong to clade 1 Methylobacter. Clade 2 Methylobacter comprises of two species: Mtb tundripaludum and Mtb psychrophilus (type strain, no longer available). We isolated a yellow pigmented, rod-shaped methanotroph, strain (KRF1), from a tropical rice field in India, which might represent a putative novel species within Methylobacter clade 2. The cells are long, thick and motile rods. The strain grows under variable oxygen concentration (5-80% air) and also in nitrogen free media (5-50% air). The morphological, chemotaxonomic and genomic features of KRF1 were investigated in details. The digital DNA-DNA hybridization values and average nucleotide identity (ANI) comparisons with the members of its closest species, Mtb tundripaludum, were in the range of 20-26% and ~ 73-81%, respectively. The fatty acid methyl esters profile of KRF1 was different from the profile of Mtb tundripaludum SV96T. The major cell wall fatty acids of strain KRF1 are 16:1 ω7c/16:1 ω6c summed feature (55.4%) and 16:1 ω5c (28.6%). The draft genome of KRF1 is of 5.04 Mbp in size with a GC content of 49.3% and the whole genome shotgun sequencing project has the accession number RYFG00000000 (version: RYFG02000000). Due to the difficulties in the maintenance and cryopreservation of this culture, it could not be deposited in two international culture collections. We thereby propose KRF1 to be member of a Candidatus species, 'Candidatus Methylobacter oryzae' KRF1. The culture is maintained live in our laboratory and also in our institutional WDCM approved culture collection (MACS Collection of Microorganisms) as MCMB-1471.

The estimation of gross oxygen production and community respiration from autonomous time‐series measurements in the oligotrophic ocean

AbstractDiel variations in oxygen concentration have been extensively used to estimate rates of photosynthesis and respiration in productive freshwater and marine ecosystems. Recent improvements in optical oxygen sensors now enable us to use the same approach to estimate metabolic rates in the oligotrophic waters that cover most of the global ocean and for measurements collected by autonomous underwater vehicles. By building on previous methods, we propose a procedure to estimate photosynthesis and respiration from vertically resolved diel measurements of oxygen concentration. This procedure involves isolating the oxygen variation due to biological processes from the variation due to physical processes, and calculating metabolic rates from biogenic oxygen changes using linear least squares analysis. We tested our method on underwater glider observations from the surface layer of the North Pacific Subtropical Gyre where we estimated rates of gross oxygen production and community respiration both averaging 1.0 mmol O2 m−3 d−1, consistent with previous estimates from the same environment. Method uncertainty was computed as the standard deviation of the fitted parameters and averaged 0.6 and 0.5 mmol O2 m−3 d−1 for oxygen production and respiration, respectively. The variability of metabolic rates was larger than this uncertainty and we were able to discern covariation in the biological production and consumption of oxygen. The proposed method resolved variability on time scales of approximately 1 week. This resolution can be improved in several ways including by measuring turbulent mixing, increasing the number of measurements in the surface ocean, and adopting a Lagrangian approach during data collection.

Noninvasive and Wearable Optical Monitoring of Brain Death with Aid of a Protocol at Differentiated Fractions of Oxygen Inspired

Brain death is a permanent loss of all brain function [1]. Current clinical organ transplantations mostly depend on the organs from brain-dead patients [2]. And of note, a lot of blood deases are easy to cause cerebral haemorrhage, which is quite of danger and usually induce brain death if not detected and treated in time. Thus prompt evaluation of brain death is of great significance for saving medical resources and reducing economic burden of the patients' families. Current guide for diagnosing brain death required to perform a list of &gt;30 hours neurological examninations, some of which are even invasive, not in time and easily hampered by many confounding factors. An ideal ancillary test to assess brain death is highlighted to be noninvasive, sensitive, universally available, timely, and easy to perform at the bedside. Near infrared spectroscopy ( NIRS ) is capable of monitoring hemodynamics in response to brain activity noninvasively, conveniently, continually, and relatively inexpensively, evidented by a series of clinical cerebral studies recently. Weigl et al newly reported to use a time resolved NIRS to detect the fluorescence photons excited in the indocyanine green ( ICG ) for cerebral perfusion detection. It provided a novel optical ancillary tool to assess brain death, while its accuracy was only 69.2%, which did not reach the level of brain death confirmation. Plus, it was invasive, requiring injection of optical contrast agent. We attempted to assess brain death completely in nonivasive way with just a custom wearable NIRS device developed in our lab [3] ( fig.1 a ). We novelly incororate a protocol at markedly but safely varied fractions of oxygen respiration. Firstly, Monte Carlo modeling were carried out to test the difference in photon transport within human brain at different oxygen concentrations induced by varied fractions of oxygen respiration ( FIO2 ) [4]. 18 healthy subjects ( 41 ± 11 years old ) and 17 brain dead patients were recruited from the intensive care unit (ICU) in Sichuan Academy of Medical Sciences &amp; Sichuan Provincial People's Hospital. No significant difference in age was found between patients and healthy groups ( p &gt;0.413 ). These patients were finally clinically diagnosed by the international standards of brain death. Two protocols were used ( fig.1 b). One is consisted of 1 hour resting, 3-minute baseline measure, half-hour measurement at 60% FIO2 ( phase I, high oxygen ),a half hour measure at 40% FIO2 ( phase II, low oxygen ), and a half hour measure at 60% FIO2 ( phase III, high oxygen ). The other is low, high, and low. The Δ[Hb] and Δ[HbO2] time courses were recorded by NIRS in real time with related signal processing ( fig.1 c ). Statistical analysis were focus on the sensitivity and specificiy of our proposed methodology at combination of NIRS and above protocol, as well as which protocol act better. Fig.1 ( c right ) showed that the detected light signal profile dramatically differed among varied oxygen concentrations in human brain. Plus the hemodynamic responses varied clearly between two subject groups among varied FIO2 in both protocols ( fig1. d ). The ' II-III ' phase act more distinct in differing two groups than ' I-II ' phase. And the low-high-low protocol acted almost perfect in accessing brain death with highest sensitivity and specificity. Over all, the novel incorporation of NIRS and a low-high-low varied FIO2 protocol was shown to a be most sensitive, highly specific, noninvasive and real time way to assess brain death and promptly offer quality assured donor organs. [1] E. F. M. Wijdicks, P. N. Varelas, G. S. Gronseth, D. M. Greer, Evidence-based guideline update: Determining brain death in adults report of the quality standards subcommittee of the American Academy of Neurology, Neurology, vol. 74, no. 23, pp. 1911-1918, 2010 [2] K. Singbartl, R. Murugan, A. M. Kaynar, D. W. Crippen, S. A. Tisherman, K. Shutterly, S. A. Stuart, R. Simmons, Intensivist-led management of brain-dead donors is associated with an increase in organ recovery for transplantation, J. M. Darby, Am. J. Transplant., vol. 11, no. 7, pp. 1517-1521, 2011 [3] T. Li, M. Duan, Y. Zhao, G. Yu, Z. Ruan. Bedside monitoring of patients with shock using a portable spatially-resolved near-infrared spectroscopy. Biomed. Opt. Express, vol. 6, no. 9, pp. 3431-3436, 2015 [4] B. Pan, C. Huang, X. Fang, X. Huang, T. Li*, Noninvasive and Sensitive Optical Assessment of Brain Death, J. Biophotonics, vol. 12, no. 3, pp. e201800240, 2018 Disclosures No relevant conflicts of interest to declare.

Transcriptome analysis reveals new insights into immune response to hypoxia challenge of large yellow croaker (Larimichthys crocea)

Fish live in direct contact with aquatic environment, which exhibits much wider temporal and spatial variations in oxygen content. The molecular mechanisms underlying fish response to hypoxia have become a subject of great concern in recent years. In the present study, we performed transcriptome analysis of spleen and head kidney tissues from large yellow croaker (Larimichthys crocea) at 6 h, 24 h and 48 h after hypoxia challenge. A total of 2,499 and 3,685 differentially expressed genes (DEGs) were obtained in spleen and head kidney, respectively. The expression changes of 10 selected genes in each tissue were further validated by quantitative real-time PCR. Gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichments revealed that numerous DEGs were immune genes, involved in multiple immune-relevant pathways. In spleen, several pattern recognition receptors (PRRs), including Toll-like receptors (TLR1, TLR2-1, TLR2-2, TLR5 and TLR8), Fucolectins (FUCL1, FUCL4 and FUCL5) and macrophage mannose receptor (MRC1), were significantly down-regulated, suggesting that the immune processes mediated by these PRRs may be suppressed by hypoxia stress. However, some PRRs (FUCL4, FUCL5 and MRC1) and other innate immunity genes, such as C-type lectin domain gene family members, chemokines, chemokine receptors and complement components were up-regulated in head kidney, which may be due to the increases in phagocytosis and cytokine secretion by macrophages after hypoxic stimulus. The expression of genes involved in B cell receptor signaling pathway, Natural killer cell-mediated cytotoxicity and NF-κB signaling pathway decreased rapidly, but regained normal or increased over time, suggesting an early adjustment pattern of fish immune response to cope with hypoxia stress. Moreover, the anaerobic ATP-generating pathway was activated and energy consumption processes were repressed concurrently in both spleen and head kidney. These data provide valuable information for understanding the tissue-specific and temporal changes of immune gene expression in hypoxic large yellow croakers.

Oxygen and electron transport in Ce0.1Sr0.9FeO3−δ

Ce0.1Sr0.9FeO3−δ was synthesized via a solid-state reaction in air and confirmed to be single-phase with the cubic perovskite structure (SG Pm3¯m). The oxygen content variation in the oxide was measured by a thermogravimetric technique in air from room temperature to 950 °С, and by a coulometric titration at 950 °С in the range of oxygen partial pressure (pO2) from 10−15 atm to 0.5 atm. Electrical conductivity (σ) was measured by a four-probe dc technique in the pO2 interval of 10−18–0.5 atm at 750–950 °С. Partial contributions to total conductivity from oxygen ions, electrons, and holes were separated, based on their different dependence on oxygen partial pressure. The obtained data were used to estimate oxygen flux density (jO2) through the oxide membrane. The obtained characteristics were compared with those of La0.5Sr0.5FeO3−δ as the most promising ferrite for an oxygen membrane material. While oxygen-ion and hole conductivity were higher in La0.5Sr0.5FeO3−δ, Ce0.1Sr0.9FeO3−δ had higher electron conductivity. Though oxygen flux density 8 ml·cm−2 min−1, calculated for a membrane of Ce0.1Sr0.9FeO3−δ under partial methane oxidation conditions was ~25% lower than that for La0.5Sr0.5FeO3−δ it characterized this oxide as a promising membrane material.

Phenolic and non-phenolic substrates oxidation by laccase at variable oxygen concentrations: Selection of bisubstrate kinetic models from polarographic data

Using laccase as a case study, an alternative methodology for discrimination of bisubstrate mechanism types, useful for Bi-Bi reactions when water is one of the products, is presented. A purified enzyme from fungal cultures of Ganoderma resinaceum and two reducing substrates: 2,2´-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and 2,6-dimethoxyphenol (DMP) are used. Kinetic assays of ABTS or DMP oxidation using variable initial concentrations of dioxygen are performed in a closed system and depletion rates of dioxygen are measured using polarography. Seven bisubstrate models based on Michaelis-Menten Bi-Bi mechanisms are applied to the experimental data. Akaike information criterion, a penalized likelihood analysis, and Akaike weights are used for model selection. Results show that the more likely bisubstrate models for ABTS and DMP oxidation are ping-pong and Theorell-Chance, respectively. However, the catalytic efficiency of oxygen reduction to water exhibits similar values, and is compatible with a process relatively independent of reducing substrates and the bisubstrate mechanism type. Finally, Michaelis-Menten constants towards dioxygen, 233 μM with ABTS and 700 μM with DMP, indicate that the soluble electron acceptor available for laccase-catalyzed reactions, is far removed from saturation.

Selective Sensors of Nitrogen Dioxide Based on Thin Tungsten Oxide Films under Optical Irradiation

It is shown that NO2 present in air, beginning at a concentration of 1 ppm, can be selectively detected by sensors based on Au/WO3:Au thin films activated by laser diode radiation with maximum intensity at 400 nm instead of constant heating. The radiation-activated photodesorption reduces the time of sensor response to NO2. A high humidity of air under conditions of room-temperature irradiation additionally increases the device sensitivity to NO2 due to the appearance of additional adsorption sites. The absence of a sensor response to reducing gases and varying oxygen concentration in the atmosphere is caused by the photodesorption of chemisorbed $${\text{O}}_{2}^{ - }$$ species during their interaction with holes generated in intrinsic optical transitions in the near-surface region of WO3 film.