Negative Oxygen Research Articles

Collision cross sections and transport coefficients of O−, O2−, O3− and O4− negative ions in O2, N2 and dry air for non-thermal plasmas modelling

The ions interaction data such as interaction potential parameters, elastic and inelastic collision cross sections and the transport coefficients (reduced mobility and diffusion coefficients) have been determined and analyzed in the case of the main negative oxygen ions (O−, O2−, O3− and O4−) present in low temperature plasma at atmospheric pressure when colliding O2, N2 and dry air. The ion transport has been determined from an optimized Monte Carlo simulation using calculated elastic and experimentally fitted inelastic collision cross sections. The elastic momentum transfer collision cross sections have been calculated from a semi-classical JWKB approximation based on a (n−4) rigid core interaction potential model. The cross sections sets involving elastic and inelastic processes were then validated using measured reduced mobility data and also diffusion coefficient whenever available in the literature. From the sets of elastic and inelastic collision cross sections thus obtained for the first time for O3−/O2, O2−/N2, O3−/N2, and O4−/N2 systems, the ion transport coefficients were calculated in pure gases and dry air over a wide range of the density reduced electric field E/N.

Influence of differential diagenesis on primary depositional signals in limestone-marl alternations: An example from Middle Permian marine successions, South China

The diagenetic alteration of rhythmic successions remains one of the main challenges in paleoclimatology and cyclostratigraphy. To address this very important problem, thin sections and geochemical data of the limestone-marl alternations from Middle Permian carbonate successions in South China are examined to identify differential diagenetic effects in the petrography, organic and inorganic compositions, strontium concentrations and stable isotopic compositions of limestone beds and marl interlayers. In the Lengshuixi outcrop and the JY66-1 drill core, the most conspicuous features are that the limestone beds exhibit dense cementation, high strontium concentrations, negative oxygen isotopic values and positive carbon isotopic values. In contrast, the marl interlayers contain talc and exhibit strongly deformed and oriented bioclasts, low strontium concentrations, positive oxygen isotopic values and negative carbon isotopic values.Although differential diagenesis has occurred, some paleoclimate proxies (e.g., computed gamma-ray values) still preserve their primary signals and thus are suitable for cyclostratigraphic research. Eccentricity rhythm and millennial-scale rhythm are obviously recorded in Middle Permian limestone-marl alternations in South China. The variations in the oxygen and carbon isotopic values of limestone-marl alternations from different basins represent responses to different processes of differential diagenesis. This knowledge assumes that differential diagenesis occurs in diagenetically closed systems under the deep sea-floor. However, this assumption may not be valid in diagenetically open systems, where exotic fluids may add unexpected disturbances. Hence, it is crucial to understand diagenetic systems by determining the variations in strontium concentrations, which are as important as variations in carbon and oxygen isotopic values.

Impact of Climate Comfort on Tourism in Putian City and Countermeasures

Putian is an emerging tourist city in Fujian Province. It not only has Weizhou Island, the birthplace of the world’s Mazu culture, but also the national 4A scenic spot, like Jiuyi Lake, Jiulong Valley, South Shaolin, etc., attracting thousands of tourists every year. This paper uses meteorological data of the Putian Municipal Meteorological Bureau from 1988 to 2017, negative oxygen ion data in the scenic spots of Weizhou Island, Jiuyi Lake and Jiulong Valley from 2014 to 2017 and monthly data of tourists from 2011 to 2017 provided by Putian City Tourism Bureau. Based on the Temperature and Humidity Index, the Wind Cold Index, the Index of Cloth Loading and the Air Comfort Index, this paper uses the analytic hierarchy process (AHP) to construct a new comprehensive climate comfort model. Using the new model, the climate comfort index of Putian is calculated, and the levels and time periods suitable for tourism are divided. The number of tourists in Putian City is increasing year by year and has obvious time distribution characteristics. There are two peak periods in which tourists are concentrated in each year, which are April to May and October to November, belonging to the spring-autumn type. This paper also uses Ordinary Least Square (OLS) regression method to analyze the climate comfort and tourist traffic. The results show that there is a clear correlation between the comfort index and the passenger flow. Accordingly, suggestions for improvement of tourism development in Putian are proposed.

Multivariate factorizable expectile regression with application to fMRI data

A multivariate expectile regression model is proposed to analyze the tail events of large cross-sectional and spatial data, where the tail events are linked by a latent factor structure. The computational advantage of the method is demonstrated, and the estimation risk is analyzed for every fixed number of iteration and fixed sample size, when the latent factors are either exactly or approximately sparse. The proposed method is applied on the functional magnetic resonance imaging (fMRI) data taken during an experiment of investment decisions making. It is shown that the negative extreme blood oxygenation level dependent (BOLD) responses may be relevant to the risk preferences.

Ga-doped ZnO films by magnetron sputtering at ultralow discharge voltages: Effects of defect annihilation

Preparation of high quality transparent conductive oxide (TCO) films by sputter deposition involves an intricate balance of defect generation by the highly energetic negative oxygen ions (depending on the discharge voltage) and the concomitant annihilation of these defects during film growth. Ga-doped ZnO films with a low Ga content (1.7at.%) were deposited to investigate the effects of defect annihilation on the microstructure evolutions as well as the optical and electrical properties. To achieve this aim, we prepared the GZO films by magnetron sputtering at ultralow discharge voltages (~70V) to minimize the defect generation, and varied the substrate temperature (from 130°C to 380°C) to adjust the annihilation rates. The microstructure was systematically characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Raman Spectroscopy. The electrical and optical properties were obtained by a Hall-effect measurement system and Spectroscopic Ellipsometry (SE), respectively. It was found that (i) even under the condition of highly controlled defect generation from the bombardment of negative oxygen ions, a sufficient annihilation of the defects cannot be realized without externally heating the substrate; and (ii) there existed a threshold temperature, above which both the structural quality and the electrical properties were improved with the increased temperature over the temperature range we examined. These results reveal that the growth temperature during the GZO film deposition has played an important role in effective annihilation of the irradiation-induced structural defects, which may be due to the higher diffusion barrier of Ga atoms in our GZO films.

The evolution of the metallicity gradient and the star formation efficiency in disc galaxies

We study the oxygen abundance profiles of the gas-phase components in hydrodynamical simulations of pre-prepared disc galaxies including major mergers, close encounters and isolated configurations. We analyse the evolution of the slope of oxygen abundance profiles and the specific star formation rate (sSFR) along their evolution. We find that galaxy-galaxy interactions could generate either positive and negative gas-phase oxygen profiles depending on the state of evolution. Along the interaction, galaxies are found to have metallicity gradients and sSFR consistent with observations, on average. Strong gas inflows produced during galaxy-galaxy interactions or as a result of strong local instabilities in gas-rich discs are able to produce both a quick dilution of the central gas-phase metallicity and a sudden increase of the sSFR. Our simulations show that, during these events, a correlation between the metallicity gradients and the sSFR can be set up if strong gas inflows are triggered in the central regions in short timescales. Simulated galaxies without experiencing strong disturbances evolve smoothly without modifying the metallicity gradients. Gas-rich systems show large dispersion along the correlation. The dispersion in the observed relation could be interpreted as produced by the combination of galaxies with different gas-richness and/or experiencing different types of interactions. Hence, our findings suggest that the observed relation might be the smoking gun of galaxies forming in a hierarchical clustering scenario.

(Invited) Mapping Internal Polarization in YSZ Electrolytes Using Grain Size

Polarization development near the electrodes is important for the performance of YSZ devices. However, there are very difficult to measure experimentally. Embedded electrodes have been used to obtain a few readings across the electrolyte thickness, but so far there has been no report that provides a continuous mapping of the electrolyte polarization. Here we demonstrate that grain growth provides a means for such mapping. The method is based on the observation that cation mobility in YSZ (as well as other fluorite structured oxides) increases rapidly with decreasing oxygen potential. Placing YSZ under a large current in various atmospheres between electrodes of various configurations, we have created many grain size distributions that vary continuously or discontinuously between the cathode and anode. Aided by the correlation between grain boundary mobility and non-stoichiometry, the grain size map can be converted to a polarization map. Such mapping allows us to quantitatively assess the influence of electrode kinetics and atmosphere on internal polarization under large current conditions. Under the same conditions of enhanced grain growth, we have observed widespread cavitation throughout YSZ in nearly all the samples tested in a reducing atmosphere. This is surprising since the prevailing theory attributes cavitation to oxygen bubbles, and it predicts oxygen bubbles to form inside the YSZ electrolyte only under a large positive oxygen potential. Yet the large grain size in our cavitated samples clearly indicates a large negative oxygen potential. Therefore, we must rule out the oxygen bubble model. Instead, we propose that cavitation in these samples is in the form of voids, which come from condensation of supersaturated oxygen vacancies. These results further suggest strong electronic conduction in the electrolyte. Indeed, the observation of cavitation implies internal reactions between electronic defects and ionic defects, rendering the latter no longer fully ionized. These reactions have the effect of buffering the oxygen potential inside the electrolyte. The observed oxygen potential and grain size transition can only be successfully modeled by taking into account such internal reactions.

Ball lightning dynamics and stability at moderate ion densities

A general mechanism is presented for the dynamics and structure of ball lightning and for the maintenance of the ball lightning structure for several seconds. Results are obtained using a spherical geometry for air at atmospheric pressure, by solving the continuity equations for electrons, positive ions and negative ions coupled with Poisson’s equation. A lightning strike can generate conditions in the lightning channel with a majority of positive nitrogen ions, and a minority of negative oxygen ions and electrons. The calculations are initiated with electrons included; however, at the moderate ion densities chosen the electrons are rapidly lost to form negative ions, and after 1 µs their influence on the ion dynamics is negligible. Further development after 1 µs is followed using a simpler set of equations involving only positive ions and negative ions, but including ion diffusion. The space-charge electric field generated by the majority positive ions drives them from the centre of the distribution and drives the minority negative ions and electrons towards the centre of the distribution. In the central region the positive and negative ion distributions eventually overlap exactly and their space-charge fields cancel resulting in zero electric field, and the plasma ball formed is quite stable for a number of seconds. The formation of such plasma balls is not critically dependent on the initial diameter of the ion distributions, or the initial density of minority negative ions. The ion densities decrease relatively slowly due to mutual neutralization of positive and negative ions. The radiation from this neutralization process involving positive nitrogen ions and negative oxygen ions is not sufficient to account for the reported luminosity of ball lightning and some other source of luminosity is shown to be required; the plasma ball model used could readily incorporate other ions in order to account for the luminosity and range of colours reported for ball lightning. Additionally, ‘phantom plasma balls’ may well be generated and go unnoticed due to very low luminosity; luminous ball lightning may be the exception. Finally, the mechanism described here may also be active in the dynamics of bead lightning.

FeVI, FeV, and FeIV oxidation of cyanide: Elucidating the mechanism using density functional theory calculations

FeVIO42− (FeVI) is a promising oxidant/disinfectant and coagulant in treating water. FeVO43− (FeV) and FeIVO44− (FeIV) are intermediates in oxidations performed by FeVI and are highly effective in degrading recalcitrant contaminants. The performance of each ferrate requires a comprehensive understanding of the mechanism. This paper presents the use of density functional theory (DFT) to understand the oxidation of cyanide by FeVI, FeV, and FeIV. The sequence of steps in the oxidation process is the same for all three species. The electrostatic attraction of the positive H and C on HCN for two of the negative oxygen atoms on the ferrate is followed by the formation of a C-O bond with cleavage of an Fe-O bond. Subsequently, the formation of an H-O bond occurs with cleavage of the H-C bond, resulting in the formation of an NCO – ferrate complex. However, the energetics are different, with C-O bond formation being the rate determining step for FeVI while for FeV and FeIV it is the transfer of the H from C to O. Energy calculations describe the order of reactivity of ferrates with HCN as FeV>FeIV>FeVI, which agrees well with experimental results.

The end-Permian regression in the western Tethys: sedimentological and geochemical evidence from offshore the Persian Gulf, Iran

Detailed sedimentological and geochemical records across the Permian–Triassic boundary (PTB) in five offshore wells of the central Persian Gulf served to interpret the end-Permian sea-level change in this region. A decrease in sea level at the PTB was established by petrographical and geochemical study of the boundary. Thin sections showed that Upper Permian strata are composed of dolomite with minor anhydrite, changing into limestone in Lower Triassic sediments. Brine dilution toward the boundary supports sea-level fall in the Permian–Triassic transition, reflected by a decrease in anhydrite content and a shallowing-upward trend from lagoonal to peritidal facies. Isotopic changes at the boundary are in favor of sea-level fall. Changes in both carbon (from about 4 to –1‰) and oxygen (from 2 to –5‰) stable isotopes show negative excursions. The shift in carbon isotope values is a global phenomenon and is interpreted as resulting from carbonate sediment interaction with 12C-rich waters at the end-Permian sea-level fall. However, the oxygen isotope shift is attributed to the effect of meteoric waters with negative oxygen isotope values. The increase in strontium isotope ratios is also consistent with the high rate of terrestrial input at the boundary. The effect of meteoric conditions during diagenesis is evident from vuggy and moldic porosities below the PTB. The following transgression at the base of the Triassic is evident from the presence of reworked fossils and intraclasts resulting from deposition from agitated water.

A Synoptic Assessment of the Amazon River-Ocean Continuum during Boreal Autumn: From Physics to Plankton Communities and Carbon Flux.

The Amazon generates the world's largest offshore river plume, which covers extensive areas of the tropical Atlantic. The data and samples in this study were obtained during the oceanographic cruise Camadas Finas III in October 2012 along the Amazon River-Ocean Continuum (AROC). The cruise occurred during boreal autumn, when the river plume reaches its maximum eastward extent. In this study, we examine the links between physics, biogeochemistry and plankton community structure along the AROC. Hydrographic results showed very different conditions, ranging from shallow well-mixed coastal waters to offshore areas, where low salinity Amazonian waters mix with open ocean waters. Nutrients, mainly and , were highly depleted in coastal regions, and the magnitude of primary production was greater than that of respiration (negative apparent oxygen utilization). In terms of phytoplankton groups, diatoms dominated the region from the river mouth to the edge of the area affected by the North Brazil Current (NBC) retroflection (with chlorophyll a concentrations ranging from 0.02 to 0.94 mg m−3). The North Equatorial Counter Current (NECC) region, east of retroflection, is fully oligotrophic and the most representative groups are Cyanobacteria and dinoflagellates. Additionally, in this region, blooms of cyanophyte species were associated with diatoms and Mesozooplankton (copepods). A total of 178 zooplankton taxa were observed in this area, with Copepoda being the most diverse and abundant group. Two different zooplankton communities were identified: a low-diversity, high-abundance coastal community and a high-diversity, low-abundance oceanic community offshore. The CO2 fugacity (fCO2sw), calculated from total alkalinity (1,450 < TA < 2,394 μmol kg−1) and dissolved inorganic carbon (1,303 < DIC < 2,062 μmol kg−1) measurements, confirms that the Amazon River plume is a sink of atmospheric CO2 in areas with salinities <35 psu, whereas, in regions with salinities >35 and higher-intensity winds, the CO2 flux is reversed. Lower fCO2sw values were observed in the NECC area. The ΔfCO2 in this region was less than 5 μatm (−0.3 mmol m−2 d−1), while the ΔfCO2 in the coastal region was approximately 50 μatm (+3.7 mmol m−2 d−1). During the cruise, heterotrophic and autotrophic processes were observed and are indicative of the influences of terrestrial material and biological activity, respectively.

Interplay of the influence of oxygen partial pressure and rf power on the properties of rf-magnetron-sputtered AZO thin films

The complex interplay between the influence of oxygen partial pressure and that of rf power on the structural, electrical and optical properties of rf-magnetron-sputtered aluminium-doped zinc oxide, AZO, thin films is illustrated. The dependence of film electrical resistance and interplanar spacing of film crystallites on rf power seems to be different at higher oxygen partial pressure values than at lower ones. Film preparation was performed at room temperature (without extra heating) and low pressure p $$=$$ 0.5 mTorr, varying the rf power density between P $$=$$ 0.57 and 2.83 W $$\hbox {cm}^{-2}$$ at different relative oxygen partial pressure values. An explanation of film properties has been sought in terms of changes in the chemical properties of the films due to the bombardment of the films during film formation with negative oxygen ions.

Visible-light activate Ag/WO3 films based on wood with enhanced negative oxygen ions production properties

The Ag/WO3-wood was fabricated through a hydrothermal method and a silver mirror reaction. The system of visible-light activate Ag/WO3-wood was used to produce negative oxygen ions, and the effect of Ag nanoparticles on negative oxygen ions production was investigated. From the results of negative oxygen ions production tests, it can be observed that the sample doped with Ag nanoparticles, the concentration of negative oxygen ions is up to 1660 ions/cm3 after 60min visible light irradiation. Moreover, for the Ag/WO3-wood, even after 60min without irradiation, the concentration of negative oxygen ions could keep more than 1000 ions/cm3, which is up to the standard of the fresh air. Moreover, due to the porous structure of wood, the wood acted as substrate could promote the nucleation of nanoparticles, prevent the agglomeration of the particles, and thus lead the improvement of photocatalytic properties. And such wood-based functional materials with the property of negative oxygen ions production could be one of the most promising materials in the application of indoor decoration materials, which would meet people’s pursuit of healthy, environment-friendly life.

Planetary Nebulae and H ii Regions in the Starburst Irregular Galaxy NGC 4449 from LBT MODS Data

Abstract We present deep 3500–10000 Å spectra of H ii regions and planetary nebulae (PNe) in the starburst irregular galaxy NGC 4449, acquired with the Multi Object Double Spectrograph at the Large Binocular Telescope. Using the “direct” method, we derived the abundance of He, N, O, Ne, Ar, and S in six H ii regions and in four PNe in NGC 4449. This is the first case of PNe studied in a starburst irregular outside the Local Group. Our H ii region and PN sample extends over a galactocentric distance range of ≈2 kpc and spans ≈0.2 dex in oxygen abundance, with average values of and 8.3 ± 0.1 for H ii regions and PNe, respectively. PNe and H ii regions exhibit similar oxygen abundances in the galactocentric distance range of overlap, while PNe appear more than ∼1 dex enhanced in nitrogen with respect to H ii regions. The latter result is the natural consequence of N being mostly synthesized in intermediate-mass stars and brought to the stellar surface during dredge-up episodes. On the other hand, the similarity in O abundance between H ii regions and PNe suggests that NGC 4449’s interstellar medium has been poorly enriched in α-elements since the progenitors of the PNe were formed. Finally, our data reveal the presence of a negative oxygen gradient for both H ii regions and PNe, while nitrogen does not exhibit any significant radial trend. We ascribe the (unexpected) nitrogen behavior to local N enrichment by the conspicuous Wolf-Rayet population in NGC 4449.

Relationship between electronic properties of Fe3O4 substituted by Ca and Ba and their reactivity in chemical looping process: A first-principles study

Chemical looping process is a novel energy conversion scheme, in which the in-situ carbon capture and high energy conversion efficiency could be realized without energy penalty. Ferrite (Fe3O4) is one of many good oxygen carrier candidates, due to its unique lattice structure containing a number of empty tetrahedral and octahedral interstitial sites. We calculated electronic properties of the original Fe3O4 primary cell and its lattice substituted by Ca or Ba, focusing on the correlation of their electronic structures and redox activities. Differences in their electronic densities and atomic charges in Mulliken Populations reveal more negative oxygen ions appearing in the substituted cells. Electronic structure analysis demonstrates that the substitution of Ba makes Fe3O4 more electric conductive and its electron is prone to be exited, that is in consistent to the experimental fact that BaFe2O4 performed better in chemical looping reactions compared to ferrites substituted by other alkali earth elements.

Ion implantation effects of negative oxygen on copper nanowires

Copper nanowires of diameter 80 nm were synthesized in polycarbonate membrane using template technique. Samples were then implanted with 160 keV O−1 ion beam with varying particle fluence of 1 × 1012, 5 × 1012 and 1 × 1013 ions/cm2. The SRIM (Stopping and range of ions in matter) software was used to study the processes involved. Compositional analysis confirms implantation of oxygen ions and the stoichiometry of Cu:O was found to be 6:1 by weight % when implanted at 1 × 1013 ions/cm2. Scanning electron microscopy reveals no changes in morphology of nanowires on implantation. X-ray diffraction analysis showed no shifting in the ‘2θ’ position of diffraction peaks however some new diffraction peaks of oxygen were seen. Implantation with oxygen ion led to the increased crystallite size and reduced strain. The conductivity of the nanowires was found to increase linearly with the ion fluence presenting constructive effect of negative ion implantation on copper nanowires.

Sensor Effect in Oxide Films with a Large Concentration of Conduction Electrons

This paper presents a joint experimental and theoretical investigation of sensor response of nanostructured In2O3 semiconductor thin films containing a large concentration of conduction electrons. The capture of the conduction electrons by oxygen adsorbates from air causes redistribution of the electrons inside the nanoparticles, resulting in reduction of the subsurface electron density, and the drop of the conductivity of nanoparticle thin films. When CO and H2 reduced gas analytes are introduced to the system, their reaction with previously adsorbed negative atomic oxygen ions O– releases electrons back to the nanoparticles, producing a noticeable increase of thin-film conductivity, which constitutes the sensor effect. This work presents a kinetic model of such processes, which allows us to a quantitative description of the sensor effect including dependence of sensor sensitivity on temperature. Concurrently, experiments are performed to quantify the sensor response by nanostructured In2O3 thin film as ...

Negative ion production in energetic O− and C− ions scattering on HOPG

In this work, we present negative-ion fractions as a function of exit velocity and angle after keV-energy negative oxygen and carbon ions scattering on a highly oriented pyrolytic graphite (HOPG) surface, at a scattering angle of 38°. The negative-ion fractions increase monotonously with the increase of exit velocity for specular scattering, while negative-ion fractions present a bell-shaped dependence on exit angle. In order to gain further insight into the nature of charge transfer on HOPG, a modified charge transfer model involving the contribution of positive ions has been proposed and roughly reproduced the velocity and angle dependences of negative-ion fractions.

Effect of space charge on the negative oxygen flux during reactive sputtering

Negative ions often play a distinctive role in the phase formation during reactive sputter deposition. The path of these high energetic ions is often assumed to be straight. In this paper, it is shown that in the context of reactive magnetron sputtering space charge effects are decisive for the energetic negative ion trajectories. To investigate the effect of space charge spreading, reactive magnetron sputter experiments were performed in compound mode with target materials that are expected to have a high secondary ion emission yield (MgO and CeO2). By the combination of energy flux measurements, and simulations, a quantitative value for the negative oxygen ion yield can be derived.

On the solubility of oxygen and xenon in n-hexane and n-perfluorohexane at room temperature

Experimental measurements have shown that, at room temperature, xenon has a good solubility in both n-hexane and n-perfluorohexane, whereas oxygen is poorly soluble in both liquids. However, oxygen proves to be more soluble in n-perfluorohexane than in n-hexane, in contrast with xenon behavior. This difference is investigated by calculating the reversible work of cavity creation in both liquids and estimating the solute–solvent attractive interactions. The magnitude of the reversible work of cavity creation in n-hexane is larger than in n-perfluorohexane, and also the strength of the solute–solvent dispersion attraction is larger in n-hexane. However, it emerges that the dispersion attractions between oxygen and n-perfluorohexane are stronger than expected due to specific interactions between partially negative fluorine atoms and oxygen molecules.