Oxygen-deficient Environment Research Articles

Sedimentological, Mineralogical and Geochemical Analysis of the Hyperthermal Latest Danian Event across the Galuconitic Marker Bed (Central Tunisia)

Field prospecting of the El-Haria Formation, which is Paleocene in age, leads to the discovery of the glauconitic marker bed in inner neritic to bathyal setting from Southern Tethyan realm. The recognition of this interval is based on lithological changes and an accurate stratigraphic proxy allows to distinguish of three main facies. The use of multivariate (cluster analysis and principal component analysis) and univariate (one-way Anova test) analysis confirm dissimilarities in composition between facies as testified by the significant differences. Sedimentological, geochemical and mineralogical analysis leads to assess paleo-environmental changes and to ascertain the variation of the lysocline and CCD across the glauconitic marker bed. Facies 1, particularly, rich in cobalt, sulfides and iron oxides reflects containment conditions affecting the surface and bottom water. These conditions lead to the extinction of the majority of benthic foraminifera and the disruption in planktonic foraminifers’ assemblage. In addition, the Facies 1 displays a brief shoaling of lysocline and CCD evidenced by the low calcite content, the bad preserved benthic foraminifera associated to the maximum fragmentation shells of planktonic foraminifera. In contrary, the rapid pattern of microfossil and the calcite recovery through the Facies 2 indicate suboxic to oxic conditions and a deepen lysocline and CCD. The cobalt lightly increases within the upper Facies, suggesting slightly oxygen deficient bottom water environment. The base of the glauconitic marker bed seems to be a lateral equivalent of the Latest Danian Event recorded throughout the Tethyan Realm (Spain and Egypt) and the Pacific Ocean.

Production of Syngas from Controlled Microwave-Assisted Pyrolysis of Crude Glycerol

Conversion of crude glycerol into synthesis gas was studied by using controlled microwave-assisted pyrolysis method. Pyrolysis of crude glycerol in the presence of carbonaceous catalyst was performed in a fixed bed reactor under oxygen-deficient environment using a domestic microwave. The effects of inert carrier gas flow rate and pyrolysis temperature on the product yield were investigated. Characterisation of the gaseous product showed that hydrogen, methane and carbon dioxide are the main components in the gaseous product. High temperature and low inert carrier gas flow rate are effective in pyrolysing crude glycerol due to sufficient energy and residence time for complete cracking of vapour into small gaseous molecules. Peak hydrogen yield of 35.2% by volume was obtained at the carrier gas flow rate of 100 mL/min and 600 °C.

Defect-dipole defined nanoscale ferroelectric polar-orders induced in Barium Zirconate

Nanoscale ferroelectric behaviour has been investigated in epitaxial BaZrO3 thin films grown in an oxygen deficient environment. Though centrosymmetric in nature, prominent ferroelectric polar states were observed via Piezo Force Microscopy (PFM), with polarization switching achieved when oppositely poled. Absence of intrinsic polar directions annul the conventional root causes for ferroelectricity like structural asymmetry and strain, rather attributes the nanoscale polar orders observed, to defect dipoles originated from oxygen vacancies introduced during the film growth. Electrostatic Force Microscopy (EFM) exhibiting inhomogeneous distribution of surface potential confirms the accumulation of oxygen vacancies contributing towards the measured polarizations.

Tunability of morphological properties of Nd-doped TiO2 thin films

In this work, an endeavor is made toward structural assessment and morphological variation of titanium dioxide (TiO2) thin films when doped with neodymium (Nd). The electron beam deposition technique was employed to fabricate Nd-based TiO2 thin films on n-Type Si substrates. Nd concentration was varied from 0.0 to 2.0 atomic percent (at.%) under identical growth environments. The films were deposited in an oxygen-deficient environment to cause the growth of rutile phases. Energy dispersive x-ray spectroscopy confirmed the presence and variation of Nd dopant in TiO2. X-ray diffraction analysis showed the transformation of amorphous structures of the as-grown samples to anatase polycrystalline after annealing at 500 °C, while atomic force microscopy exposed linearity in grain density in as-grown samples with doping until 1 at.%. Raman spectrums of as-grown and annealed samples revealed the growth of the anatase phase in the annealed samples. Based on these results it can be proposed that Nd doping has pronounced effects on the structural characteristics of TiO2 thin films.

Hypoxia induced the remodeling of pulmonary arterial smooth muscles and increased the pulmonary artery smooth muscle Krüppel-like zinc-finger transcription factor 5 expression

Objective: To study the effect of chronic hypoxia on pulmonary arterial remodeling and Krüppel-like zinc-finger transcription factor 5 (KLF5) protein expression in pulmonary artery smooth muscles in a hypoxia-induced pulmonary hypertension model. Methods: Totally 20 adult SD rats (200-250 g) were divided into a normoxia group and a chronic hypoxia group by the random number table. Rats in the chronic hypoxia group were put in an automatic hypoxia box for 21 days. After that, right ventricular systolic pressure (RVSP), mean right ventricular pressure (mRVP) and RV/(LV+ S) were measured. Lung tissue sections were made. The lumen area, ratio of wall thickness to radius of pulmonary artery were gauged by using the Image Pro Plus software. Primary PASMCs were cultured in oxygen-deficient environment (4% O2)or normal oxygen environment (21% O2)for 60 hours respectively, and then total protein or RNA were extracted for Western blotting and Q-PCR analysis.KLF5 protein expression in rat pulmonary arterial smooth muscle and pulmonary arterial smooth muscle cells was detected by Western blot. Results: Compared with the normoxia group(28.3±0.4), (11.3±1.0)mmHg (1 mmHg=0.133 kPa), the RVSP and mRVP in the chronic hypoxia group [(43.9±1.3), (26.5±2.3)mmHg] were significantly increased(P<0.05). The Rv/(LV+ S)of the chronic hypoxia group was(0.48±0.03), markedly higher than that of the normoxia group(0.27±0.01, P<0.05). The luminal area/total area of artery in the chronic hypoxia group decreased to (46.1±6.6)% compared with that in the normoxia group [(68.73±3.06)%, P<0.05]. The wall thickness/arterial radius(WT%)of the chronic hypoxia group increased up to (5.64±0.32)% as compared with (3.7±0.4)% of the normoxia group (P<0.05). The level of KLF5 protein in pulmonary arterial smooth muscles of the chronic hypoxia group was (21.6±7.2) times that of the normoxia group (P<0.05). Conclusion: Hypoxia induced the increase of RVSP, mRVP, RV/(LV+ S), accompanied with pulmonary arterial remodeling. The underlying mechanism of the artery change may be related to up-regulated expression of KLF5.

A NEW ASTROBIOLOGICAL MODEL OF THE ATMOSPHERE OF TITAN

ABSTRACT We present results of an investigation into the formation of nitrogen-bearing molecules in the atmosphere of Titan. We extend a previous model to cover the region below the tropopause, so the new model treats the atmosphere from Titan’s surface to an altitude of 1500 km. We consider the effects of condensation and sublimation using a continuous, numerically stable method. This is coupled with parameterized treatments of the sedimentation of the aerosols and their condensates, and the formation of haze particles. These processes affect the abundances of heavier species such as the nitrogen-bearing molecules, but have less effect on the abundances of lighter molecules. Removal of molecules to form aerosols also plays a role in determining the mixing ratios, particularly of HNC, HC3N, and HCN. We find good agreement with the recently detected mixing ratios of C2H5CN, with condensation playing an important role in determining the abundance of this molecule below 500 km. Of particular interest is the chemistry of acrylonitrile (C2H3CN) which has been suggested by Stevenson et al. as a molecule that could form biological membranes in an oxygen-deficient environment. With the inclusion of haze formation, we find good agreement of our model predictions of acrylonitrile with the available observations.

Defective TiO2 with high photoconductive gain for efficient and stable planar heterojunction perovskite solar cells.

Formation of planar heterojunction perovskite solar cells exhibiting both high efficiency and stability under continuous operation remains a challenge. Here, we show this can be achieved by using a defective TiO2 thin film as the electron transport layer. TiO2 layers with native defects are deposited by electron beam evaporation in an oxygen-deficient environment. Deep-level hole traps are introduced in the TiO2 layers and contribute to a high photoconductive gain and reduced photocatalytic activity. The high photoconductivity of the TiO2 electron transport layer leads to improved efficiency for the fabricated planar devices. A maximum power conversion efficiency of 19.0% and an average PCE of 17.5% are achieved. In addition, the reduced photocatalytic activity of the TiO2 layer leads to enhanced long-term stability for the planar devices. Under continuous operation near the maximum power point, an efficiency of over 15.4% is demonstrated for 100 h.

Sedimentary characteristics of the Lower Cambrian Niutitang shale in the southeast margin of Sichuan Basin, China

The Lower Cambrian Niutitang formation shale in the Sichuan Basin is not only a source rock for the Sinian conventional gas reservoir but also a possible reservoir for shale gas. However, very limited work have been focused on the detailed sedimentary environment related to shale gas exploration. In this study, detailed field geological investigation, continuous sampling and analyses by SEM, EDS XRD, XRF and ICP-OES, were used to probe provenance and sedimentary environment of the Niutitang formation shale in the southeast margin of Sichuan Basin. Both field outcrop observation and laboratory experimental results indicate: 1) the presence of framboidal pyrite; 2) δU ≥ 1; and 3) a negative δCe index anomaly. The detrital mineral properties and major element analyses indicate that the geotectonic background of the sediment sources for the Niutitang formation shale can be linked to the neritic zone and slope zone. The horizontal bedding indicates that suspended sediments were involved in the sedimentation. The Ba minerals, REE characteristics and trace element index (U/Th) demonstrate that most of the study area was formed in a normal sedimentary environment, but several isolated zones were affected by submarine hydrothermal sedimentation. The sedimentation of the Niutitang shale most likely occurred in a weak hydrodynamic, deep water, oxygen-deficient reducing environment. The major sediment sources were continental margins, such as the neritic and continental slope zones.

Paleo-ocean redox environments of the Upper Ordovician Wufeng and the first member in lower Silurian Longmaxi formations in the Jiaoshiba area, Sichuan Basin

A study of paleo-ocean redox environments is important for understanding the deposition of black shale and has practical implications for shale gas exploration. Here, we selected a total of 52 shale samples from JY1 Well, the first shale gas well of commercial exploitation in China, to analyze the redox conditions of Upper Ordovician Wufeng (O3w) and the first member in lower Silurian Longmaxi shale (S1l1) in the Jiaoshiba area. Abundant pyrite framboids are observed in these units, with average framboid diameters ranging from 3.1 to 4.7 μm and maximum diameter about 10 μm. Analyses of redox-sensitive trace elements suggest the redox environment has evolved from an anoxic condition in the bottom of Member A to a dysoxic condition in the top of Member A, and to a dysoxic–oxic environment in Members B and C. Graptolite and radiolarian are discovered in these shale samples, indicating an oxygenated seafloor, which seems to be contradictory to the results from pyrite framboids and redox-sensitive trace elements. This contradiction is explained as follows: when the shale was deposited, the sedimentation was dominated by euxinic conditions; however, some oxygen may also occasionally migrate to the bottom water due to oxygen-deficient environment, deglaciation, and (or) strong upwelling of nutrient-enriched seawater, while the limited oxygen and anoxic environment is favorable for the preservation and accumulation of organic matter. Combined with the geological characteristics and redox conditions, Member A, especially the shales at the bottom of Member A, is expected to be the most favorable shale gas reservoir in the Jiaoshiba area.

Impact of hydrogen forming gas annealing on microwave properties of Ba(Zn1/3Ta2/3)O3 dielectric ceramics

The effect of H2forming gas annealing on the microwave properties of [Formula: see text] (BZT) dielectric ceramics has been studied. The structural, microwave, DC electrical and optical properties were analyzed by experiment results. With elevated temperature annealing, the microwave loss of BZT was increased. This trend correlated with high DC conductivity of annealed samples, as well as dampened phonons found in Raman spectra. These evidences, together, prove that the enhancement of oxygen vacancy defects induced by oxygen deficient sintering environment is one of the main extrinsic root causes for the high microwave loss in practical ceramic materials.

Enhancing the photoelectrochemical properties of titanium dioxide by thermal treatment in oxygen deficient environment

The effect of thermal treatment on TiO2 thin films under oxygen deficient environment (5% H2 in Ar) at partial pressure of 2×10−2Torr have been studied for photoelectrochemical (PEC) water splitting application. Thermal treatment in anatase TiO2 thin films exhibits a shift in optical absorption from UV to visible region and activates TiO2 for water splitting application under visible light. X-ray photoelectron spectroscopy results showed that the thermal treated thin films contain oxygen vacancies, which suggests improved charge transport. Optical absorption, X-ray spectroscopy (XPS) and Kelvin probe force microscope (KPFM) studies show reduction in band gap by 0.36eV, shift in valence band maximum by 0.49eV towards the Fermi level and work function values by 0.3eV towards the vacuum level. The pristine TiO2 thin films exhibit very less photoactivity in terms of photocurrent density, whereas thermally treated thin films displayed a markedly enhanced photocurrent density of ∼2.41mA/cm2 at 0.23V vs. Ag/AgCl. Higher values of photocurrent density in thermal treated TiO2 films have been explained in terms of change in the optical and electrical properties along with energy band diagram.

Sulfidation behavior of ZnFe2O4 roasted with pyrite: Sulfur inducing and sulfur-oxygen interface exchange mechanism

The sulfidation roasting behavior was analyzed in detail to reveal the reaction mechanism. Information about the sulfidation reaction, including phase transformation, ionic migration behavior and morphological change, were obtained by XRD, 57Fe Mossbauer spectroscopy, XPS and SEM analysis. The results showed that the sulfidation of zinc ferrite is a process of sulfur inducing and sulfur-oxygen interface exchange. This process can be divided into six stages: decomposition of FeS2, formation of the oxygen-deficient environment, migration of O2− induced by S2(g), formation of ZnFe2O4-δ, migration of Fe2+ accompanied by the precipitation of ZnO, and the sulfur-oxygen interface exchange reaction. The sulfidation products were zinc blende, wurtzite, magnetite and a fraction of zinc-bearing magnetite. These findings can provide theoretical support for controlling the process during which the recovery of Zn and Fe is achieved through the combined flotation-magnetic separation process.

Comprehensive study on critical role of surface oxygen vacancies for 2DEG formation and annihilation in LaAlO3/SrTiO3 heterointerfaces

Here we report comprehensive study of 2DEG at a-LAO/STO interfaces in comparison with 2DEG at crystalline LaAlO3 (c-LAO)/STO interfaces. We observe that the oxygen deficient environment during the deposition of LAO overlayer is essentially required to create 2DEG at LAO/STO interface regardless of growth temperature from 25°C to 700°C, indicating that the oxygen-poor condition in the system is more important than the crystallinity of LAO layer. The critical thickness (2.6 nm) of 2DEG formation at a-LAO/STO heterostructure is thicker than (1.6 nm) that at c-LAO/STO. Upon ex-situ annealing at 300°C under 300 mTorr of oxygen pressure, 2DEG at a-LAO/STO interface is annihilated, while that in c-LAO/STO interface is still maintained. With combing these findings and scanning transmission electron microscope (STEM) analysis, we suggest that oxygen vacancies at the LAO surface is attributed to the origin of 2DEG formation at the LAO/STO and the crystallinity of the LAO overlayer plays a critical role in the annihilation of 2DEG at a-LAO/STO interface rather than in the formation of 2DEG. This work provides a framework to understand the importance of prohibiting the LAO surface from being oxidized for achieving thermally stable 2DEG at a-LAO/STO interface.

Production of Pyrolyzed Oil from Crude Glycerol using a Microwave Heating Technique

Crude glycerol, a by-product of biodiesel production created via transesterification was pyrolyzed using a microwave heating technique in an oxygen-deficient environment. Coconut shell-based activated carbon was used as a catalyst to assist in the heat transfer and the cracking of glycerol into gaseous and liquid products. Investigation into the product yield was conducted by varying the pyrolysis temperature between 300°C and 800°C. The result revealed that liquid and gaseous pyrolysis products yield fell in the range of 15−42% and 55−82% by mass, respectively. An analysis of the liquid product using gas chromatography mass spectrometry (GC-MS) shows that glycerin (C3H8O3), methanamine (CH5N), and cyclotrisiloxane (C6H18O3Si3) were among the highest derived compounds in the pyrolyzed liquid yield. The derived pyrolysis products can potentially be used as alternative fuels in combustion systems.

Empirical Kinetic Model of a Stone Dust Looping Carbonator for Ventilation Air Methane Abatement

A novel stone dust looping (SDL) process for mitigation of ventilation air methane (VAM) was investigated. The SDL process uses limestone as a sorbent to capture CO2 emissions, similar to a conventional calcium looping (CCL) process. However, unlike CCL where lime (CaO) is introduced directly to a flue gas from a thermal power plant with CO2 concentrations as high as 12–15% in an oxygen-deficient environment, the SDL process uses CaO to catalytically oxidize VAM, with concentrations of CH4 up to 0.1–1 vol % in air, and simultaneously capture CO2 produced. In the present study, kinetic parameters were derived from experiments in a single lab-scale fluidized bed reactor. A random pore model (RPM) was used to determine the rate-controlling steps for the SDL process, and kinetic parameters, such as activation energy (EaK) and pre-exponential factor (ks0), were obtained for a SDL process carbonator. Kinetic parameters were then used to derive an empirical model for a continuous SDL process and consisted of res...

Enhanced resistive switching and multilevel behavior in bilayered HfAlO/HfAlOx structures for non-volatile memory applications

In this work, hafnium aluminum oxide (HfAlO) thin films were deposited by ion beam sputtering deposition technique on Si substrate. The presence of oxygen vacancies in the HfAlOx layer deposited in oxygen deficient environment is evidenced from the photoluminescence spectra. Furthermore, HfAlO(oxygen rich)/HfAlOx(oxygen poor) bilayer structures exhibit multilevel resistive switching (RS), and the switching ratio becomes more prominent with increasing the HfAlO layer thickness. The bilayer structure with HfAlO/HfAlOx thickness of 30/40 nm displays the enhanced multilevel resistive switching characteristics, where the high resistance state/intermediate resistance state (IRS) and IRS/low resistance state resistance ratios are ≈102 and ≈5 × 105, respectively. The switching mechanisms in the bilayer structures were investigated by the temperature dependence of the three resistance states. This study revealed that the multilevel RS is attributed to the coupling of ionic conduction and the metallic conduction, being the first associated to the formation and rupture of conductive filaments related to oxygen vacancies and the second with the formation of a metallic filament. Moreover, the bilayer structures exhibit good endurance and stability in time.

Control of oxygen vacancies and their kinetic behaviours via reversible oxygen loss in BiFeO3 ceramics

Oxygen vacancies and their kinetic behaviours were systematically investigated in quenched BiFeO3 ceramics. Complex relaxation processes were observed and discussed based on the migration of , and the transition in between them, where , represent the oxygen vacancies with single and two positive charges, respectively. It is found that an oxygen-deficient environment promotes the transformation from to , while oxygen treatment can reverse such a transformation. This work provides a feasible alternative method to modulate oxygen vacancies and their migration in favour of the applications of BiFeO3.

Methemoglobin reduction by NADH-cytochrome b(5) reductase in Propsilocerus akamusi larvae.

For oxygen respiration, a methemoglobin (metHb) reduction system is needed in the cell because metHb cannot bind oxygen. We examined the insect Propsilocerus akamusi larvae to elucidate the metHb reduction system in an organism that inhabits an oxygen-deficient environment. NADH-dependent reduction of metHb in coelomic fluid suggested the coexistence of cytochrome b5 reductase (b5R) and cytochrome b5 with hemoglobin in the fluid and that these proteins were involved in physiological metHb reduction in the larvae. The presence of b5R was revealed by purifying b5R to homogeneity from the midge larvae. Using purified components, we showed that larval metHb was reduced via the NADH-b5R (FAD)-cytochrome b5-metHb pathway, a finding consistent with that in aerobic vertebrates, specifically humans and rabbits, and b5R function between mammal and insect was conserved. b5R was identified as a monomeric FAD-containing enzyme; it had a molecular mass of 33.2 kDa in gel-filtration chromatography and approximately 37 kDa in SDS-PAGE analysis. The enzyme's optimal pH and temperature were 6.4 and 25 °C, respectively. The apparent Km and Vmax values were 345 μM and 160 μmol min(-1) mg(-1), respectively, for ferricyanide and 328 μM and 500 μmol min(-1) mg(-1), respectively, for 2,6-dichlorophenolindophenol. The enzyme reaction was inhibited by benzoate, p-hydroxymercuribenzoate, iodoacetamide, and iodoacetate, and was not inhibited by metal ions or EDTA.

Effects of post-lift-off annealing conditions on contact oxidation of Ti–Au top-contacts in In-Sn–Zn–O TFT

Thin film transistors (TFT) with an indium based mixed oxide semiconductor are investigated for titanium–gold top-contacts. It is noticed that upon post annealing, in order to remove chemical residuals from top-contact lift-off steps, oxidation of titanium occurs depending on the annealing conditions. Mobility of the TFT is strongly affected by contact oxidation arising from this post lift-off annealing process. Oxidation of the top-contact is facilitated by adsorbed surface oxygen or out-diffusing oxygen from the semiconductor depending on the post lift-off annealing conditions. A passivation layer that binds effectively to surface vacancies and removes adsorbed oxygen species from the semiconductor surface is demonstrated. The combinations of this passivation layer with relatively low temperature and short post lift-off annealing in an oxygen deficient environment result in significantly reduced contact oxidation and subsequently better transistor performance. Contact resistance as low as 90Ωcm and mobility as high as 5.3cm2/Vs are obtained for solution processed mixed metal oxide semiconductor in top-contact geometry.

A Transcending Insight into Disease Etiology and Life Sciences Enhancement of Oxygenation for Reestablishing Homeostasis Governing Life

Oxygen is the fundamental electron transport mechanism in the universe. Its the way through which the universe is monitoring, recording, maintaining internal stability, obtaining coordinated responses and is managing the ecology of life. All processes of integration and coordination of function in the ecology of life, whether mediated by nervous and hormonal systems comes under homeostatic regulation. The primary target and aim of every disease and disorder in the ecology of life is to impair oxygenation the outcome of which is the disruption of homeostatic regulation. An illness or disease thrives only in an oxygen deficient environment. The homeostatic regulation in the ecology of life is mediated through oxygen. Universe is an unquestionable natural truth that identifies itself and us as ‘unity’. In all of the mechanisms in the ecology of life, has only one object of maintaining constant conditions in the internal environment. A perfect homeostasis is the one and only requirement for healing of any disease or disorder in the ecology of life.