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39 result(s) for "氧气"
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ATF4 regulates lipid metabolism and thermogenesis
Activating transcription factor 4 (ATF4) has been shown to play key roles in many physiological processes. There are no reports, however, demonstrating a direct link between ATF4 and lipid metabolism. We noticed that Atf4- deficient mice are lean, suggesting a possible role for ATF4 in regulating lipid metabolism. The goal of our current study is to investigate the involvement of ATF4 in lipid metabolism and elucidate the underlying mechanisms. Studies using Atf4-deficient mice revealed increased energy expenditure, as measured by oxygen consumption. These mice also showed increases in lipolysis, expression of uncoupling protein 2 (UCP2) and p-oxidation genes and decreases in expression of lipogenic genes in white adipose tissue (WAT), suggesting increased utilization and decreased synthesis of fatty acids, respectively. Expression of UCP1, 2 and 3 was also increased in brown adipose tissue (BAT), suggesting increased thermogenesis. The effect of ATF4 deletion on expression of UCPs in BAT suggests that increased thermogenesis may underlie increased energy expenditure. Thus, our study identifies a possible new function for ATF4 in regulating lipid metabolism and thermogenesis.
Medium oxygen enriched blast furnace with top gas recycling strategy
Top gas recycling oxygen blast furnace(TGR-OBF)process is a promising ironmaking process.The biggest challenge of the TGR-OBF in operation is the dramatic decrease of top gas volume(per ton hot metal),which once led to hanging-up and shutdowns in practice of the Toulachermet.In order to avoid this weakness,the strategy of medium oxygen blast furnace was presented.The maneuverable zone of the TGR-OBF was determined by the top gas volume,which should not be far from the data of the traditional blast furnace.The deviation of ±12.5% was used,and then the maneuverable blast oxygen content is from 0.30 to 0.47 according to the calculation.The flame temperature and the top gas volume have no much difference compared to those of the traditional blast furnace.The minimum carbon consumption of 357 kg per ton hot metal in the maneuverable zone occurs at the oxygen content of 0.30(fuel saving of 14%).In the unsteady evolution,the N2 accumulation could approach nearly zero after the recycling reached 6 times.Thus far,some TGR-OBF industrial trials have been carried out in different countries,but the method of medium oxygen enriched TGR-OBF has not been implemented,because the accumulation of N2 was worried about.The presented strategy of medium oxygen enriched TGR-OBF is applicable and the strategy with good operational performance is strongly suggested as a forerunner of the full oxygen blast furnace.
Oxygen-suppressed selective growth of monolayer hexagonal boron nitride on copper twin crystals
Controlled growth of hexagonal boron nitride (h-BN) with desired properties is essential for its wide range of applications. Here, we systematically carried out the chemical vapor deposition of monolayer h-BN on Cu twin crystals. It was found that h-BN nucleated and grew preferentially and simultaneously on the narrow twin crystal strips present in the Cu substrates. The density functional theory calculations revealed that the introduction of oxygen could effidently ~ne the selectivity. This is because of the reduction in the dehydrogenation barrier of the precursor molecules by the introduction of oxygen. Our findings throw light on the direct growth of functional h-BN nanoribbons on nano-twinned crystal strips and switching of the growth behavior of h-BN films by oxygen.
Oxygen Requirements for the Cambrian Explosion
Hypoxic tolerance experiments may be helpful to constrain the oxygen requirement for animal evolution. Based on literature review, available data demonstrate that fishes are more sensitive to hypoxia than crustaceans and echinoderms, which in turn are more sensitive than annelids, whilst mollusks are the least sensitive. Mortalities occur where O_2 concentrations are below 2.0 mg/L, equivalent to saturation with oxygen content about 25% PAL(present atmospheric level). Therefore, the minimal oxygen requirement for maintaining animal diversity since Cambrian is determined as 25% PAL. The traditional view is that a rise in atmospheric oxygen concentrations led to the oxygenation of the ocean, thus triggering the evolution of animals. Geological and geochemical studies suggest a constant increase of the oxygen level and a contraction of anoxic oceans during Ediacaran-Cambrian transition when the world oceans experienced a rapid diversification of metazoan lineages. However, fossil first appearances of animal phyla are obviously asynchronous and episodic, showing a sequence as: basal metazoans〉lophotrochozoans〉ecdysozoans and deuterostomes. According to hitherto known data of fossil record and hypoxic sensitivity of animals, the appearance sequence of different animals is broadly consistent with their hypoxic sensitivity: animals like molluscs and annelids that are less sensitive to hypoxia appeared earlier, while animals like echinoderms and fishes that are more sensitive to hypoxia came later. Therefore, it is very likely that the appearance order of animals is corresponding to the increasing oxygen level and/or the contraction of anoxic oceans during Ediacaran-Cambrian transition.
Numerical analysis of carbon saving potential in a top gas recycling oxygen blast furnace
Aiming at the current characteristics of blast furnace (BF) process, carbon saving potential of blast furnace was investigated from the perspective of the relationship between degree of direct reduction and carbon consumption. A new relationship chart between carbon consumption and degree of direct reduction, which can reflect more real situation of blast furnace operation, was established. Further- more, the carbon saving potential of hydrogen-rich oxygen blast furnace (OBF) process was ana- lyzed. Then, the policy implications based on this relationship chart established were suggested. On this basis, the method of improving the carbon saving potential of blast furnace was recycling the top gas with removal of CO2 and H2O or increasing hydrogen in BF gas and full oxygen blast. The results show that the carbon saving potential in traditional blast furnace (TBF) is only 38 56 kg · t ^-1 while that in OBF is 138 kg · t ^-1. Theoretically, the lowest carbon consumpt!on of OBF is 261 kg · t ^-1 and the corresponding degree of direct reduction is 0.04. In addition, the theoretical lowest carbon consumption of hydrogen-rich OBF is 257 kg · t ^-1. The modeling analysis can be used to estimate the carbon savings potential in new ironmaking process and its related CO2 emissions.
Oxygen as an oxidant in palladium/copper-cocatalyzed oxidative C-H/C-H cross-coupling between two heteroarenes
The palladium/copper-cocatalyzed oxidative C-H/C-H cross-coupling between two heteroarenes by using molecular oxygen as an oxidant instead of metal oxidants has been developed for the first time to construct biheteroaryl motifs. A relatively broad range of thiophenes, furans and indoles can smoothly couple with various N-heteroarenes in satisfactory yields. This catalytic system with O2 as the terminal oxidant offers clear advantages of economically feasible and eco-friendly processes.
Softening and Melting Behavior of Mixed Burden for Oxygen Blast Furnace
The behaviors of mixed burden in the cohesive zone of oxygen blast furnace were studied by softening and melting tests, and the influence of reducing gas and burden basicity on the softening and melting behaviors of mixed burden was also investigated. The results indicated that the softening range became wide, however, the melting range narrowed sharply in the atmosphere of oxygen blast furnace. The permeability of burden in the oxygen blast furnace was obviously improved comparing with the conventional blast furnace. In addition, the content of sulphur in the dripping iron of oxygen blast furnace was much lower than that of conventional blast furnace, however, the content of carbon increased. An optimum basicity of burden, which could lead to the appearance of the narrower melting range and better permeability of burden, was obtained in the atmosphere of oxygen blast furnace.
Selection of Oxygen Pressure in BOF Steelmaking
Based on the on-site investigation and the principle of compressible flow, the working oxygen pressure should be matched to the Mach-number at the nozzle in designing nozzle and oxygen supply schedule so that the higher penetration depth and the more blending energy can be obtained for reducing energy loss by shock wave in the ultrasonic oxygen jet in the normal BOF steelmaking. For some special BOF blowing technologies, such as steelmaking with high phosphorus hot metal, post combustion oxygen lance, hot metal pretreatment, etc, the difference between working oxygen pressure and designed diffusion pressure which is related to Mach-number is necessary, so that the velocity of the oxygen jet will be decreased because of shock wave for expected metallurgical results.
Oxygen vacancies effects on phase diagram of epitaxial La1-xSrxMnO3 thin films
We investigated the effects of oxygen vacancies on the structural, magnetic, and transport properties of Lal-xSrxMnO3 (x=0.1, 0.2, 0.33, 0.4, and 0.5) grown around a critical point (without/with oxygen vacancies) under low oxygen pressure (10 Pa) and high oxygen pressure (40 Pa). We found that all films exhibit ferromagnetic behavior below the magnetic critical temperature, and that the films grown under low oxygen pressures have degraded magnetic properties with lower Curie temperatures and smaller magnetic moments. These results show that in epitaxial La1-xSrxMnO3 thin films, the magnetic and transport properties are very sensitive to doping concentration and oxygen vacancies. Phase diagrams of the films based on the doping concentration and oxygen vacancies were plotted and discussed.
The oxygen sensor PHD3 limits glycolysis under hypoxia via direct binding to pyruvate kinase
Dear Editor, Oxygen levels are critical for cellular physiology. Under low oxygen (hypoxia), cells increase glycolysis while limiting mitochondrial oxidative metabolism. Such adaptation is largely mediated by the transcription factors HIF, which accumulate under hypoxia [ 1, 2]. Prolyl hydroxylase domain proteins (PHD) function as cellular oxygen sensors and target HIF for subsequent degradation under normoxia