Air Oxygen Research Articles

Dependence of carbonyl, sulphoxide and hydroxyl functional group formation on oxygen concentration during the oxidation of roading bitumen

The aim of this study was to provide insights into the chemical mechanism by which, over the course of its lifetime, bitumen in road surfacings reacts with oxygen in the atmosphere. Oxidation was measured at 50 °C (a realistic in-service temperature) to determine the effect of oxygen concentration on the formation of key oxidation products. Experiments were conducted on thin films of bitumen (<0.03 mm) so that the effect of oxygen diffusion on the rate was negligible. The films were oxidised under air (oxygen partial pressure 22.23 kPa) and pure oxygen (101.33 kPa).The rate of formation of carbonyl, sulphoxide and hydroxyl group containing reaction products was measured by infrared spectroscopy. The reactions were carried out over a time-frame sufficient to cover both the “fast” and “slow” (linear) reaction rate regions and the results discussed in terms of the reaction mechanism. It was observed that the rate of formation of all three functional groups was dependent on oxygen concentration. The apparent reaction order with respect to oxygen concentration was about 0.5 in each case and did not change significantly as the reaction moved from the fast and into the linear rate regions. The non-zero rate dependence observed despite the relatively high oxygen partial pressures used, is significant in that it is inconsistent with a conventional free radical autoxidation chain mechanism and suggests a parallel oxidation process is occurring.

Template-Assisted Synthesis of a Large-Area Ordered Perovskite Nanowire Array for a High-Performance Photodetector.

One-dimensional (1D) organic-inorganic hybrid perovskite nanowires (NWs) with well-defined structures possess superior optical and electrical properties for optoelectronic applications. However, most of the perovskite NWs are synthesized in air, which makes the NWs susceptible to water vapor, resulting in large amounts of grain boundaries or surface defects. Here, a template-assisted antisolvent crystallization (TAAC) method is designed to fabricate CH3NH3PbBr3 NWs and arrays. It is found that the as-synthesized NW array has designable shapes, low crystal defects, and ordered alignment, which is attributed to the sequestration of water and oxygen in air by the introduction of acetonitrile vapor. The photodetector based on the NWs exhibits an excellent response to light illumination. Under the illumination of a 532 nm laser with 0.1 μW and a bias of -1 V, the responsivity and detectivity of the device reach 1.55 A/W and 1.21 × 1012 Jones, respectively. The transient absorption spectrum (TAS) shows a distinct ground state bleaching signal only at 527 nm, which corresponds to the absorption peak induced by the interband transition of CH3NH3PbBr3. Narrow absorption peaks (a few nanometers) indicate that the energy-level structures of CH3NH3PbBr3 NWs only have a few impurity-level-induced transitions leading to additional optical loss. This work provides an effective and simple strategy to achieve high-quality CH3NH3PbBr3 NWs, which exhibit potential application in photodetection.

Environmentally adaptive lubrication enabled by gradient structure design of TiN-MoS2/Ti

Molybdenum disulfide (MoS2) films have been widely employed as lubricants for mechanical components but continue to face significant engineering challenges including their low hardness, high humidity sensitivity and weak adhesion to substrates. Although the co-deposition of MoS2 with additives provides enhanced functionality in some cases, the weak adhesion of MoS2 to the substrate is the key to the localized delamination or even early failure of the film. Herein, a novel MoS2-based film is designed and fabricated by magnetron sputtering deposition technique, which consists of Ti bonding layer, TiN load-carrying layer, TiN/Ti/MoS2 gradient layer, and top layer of Ti-doped MoS2 lubricating film. Results demonstrate that the rationally gradient design not only improves the adhesion strength between MoS2 and substrate, but also promotes the preferential growth of MoS2 along [001] zone axis perpendicular to the (002) crystal plane. The 3.2 at.% Ti-doped MoS2 film exhibits a low friction coefficient and wear rate before and after salt spray test, which is ascribed to the formation of a continuous and dense MoS2 tribofilm. Additionally, Ti additive can preferentially absorb oxygen in air, thereby preserving the self-lubricating ability of MoS2. This novel structure design provides an example for obtaining functional lubricants with good mechanical properties and environmental adaptability.

Derivatives of cyclam-1,8-diacetic acid: Synthesis and complexes with divalent transition metal ions

1,4,8,11-tetraazacyclotetradecane-1,8-diacetatic acid, H2te2a, and series of its derivative bearing two substituted N-benzyl groups were synthesized and their complexes were studied. Series of CoII and ZnII complexes was prepared in the solid-state and X-ray diffraction analysis showed that the metal ions are hexacoordinated by four nitrogen atoms of the macrocycle and two oxygen atoms of the carboxylate pendants. The two oxygen atoms were in cis and trans mutual position in the CoII and ZnII complexes, respectively. Potentiometric study of CoII, ZnII, CuII and NiII-H2te2a systems showed that the complexes are highly thermodynamically stable and the ligand is selective for CuII ions (logK = 27.5) over the other ions (logK = 21–22). UV-VIS and electrochemical data for the CoII-H2te2a system showed that complexation was rather slow (several hours at pH 4.5, 25 °C) and the complex undergoes slow oxidation with air oxygen.

Conducting Polymer‐Based e‐Refinery for Sustainable Hydrogen Peroxide Production

Electrocatalysis enables the industrial transition to sustainable production of chemicals using abundant precursors and electricity from renewable sources. De‐centralized production of hydrogen peroxide (H2O2) from water and oxygen of air is highly desirable for daily life and industry. We report an effective electrochemical refinery (e‐refinery) for H2O2 by means of electrocatalysis‐controlled comproportionation reaction (), feeding pure water and oxygen only. Mesoporous nickel (II) oxide (NiO) was used as electrocatalyst for oxygen evolution reaction (OER), producing oxygen at the anode. Conducting polymer poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) drove the oxygen reduction reaction (ORR), forming H2O2 on the cathode. The reactions were evaluated in both half‐cell and device configurations. The performance of the H2O2 e‐refinery, assembled on anion‐exchange solid electrolyte and fed with pure water, was limited by the unbalanced ionic transport. Optimization of the operation conditions allowed a conversion efficiency of 80%.

Pore network modeling of a microporous layer for polymer electrolyte fuel cells under wet conditions

The gas diffusion layers (GDLs) of polymer electrolyte fuel cells have been developed with applying microporous layers (MPLs) in their catalyst layer (CL) side to alleviate the accumulation of liquid water in the CL for oxygen transport to the cathode CL. A three-dimensional porous structure of our in-house hydrophobic MPL is numerically modeled with a pore network model (PNM). The convective air permeability and oxygen diffusivity, which depend on liquid saturation, are evaluated. To construct the PNM, focused ion beam scanning electron microscopy (FIB-SEM) is used to derive the pore size distribution (PSD). The model is ex-situ validated through air permeability and oxygen diffusivity tests with controlled saturation of non-volatile wetting liquid that is stable in the hydrophobic MPL. Oxygen diffusivity of the MPL is obtained by identifying the diffusion resistances of the concentration boundary layers and GDL substrate in the tests. The model predicts the effects of liquid water saturation in the MPL on the air and liquid water permeations, and the oxygen diffusion, and thus can be used to design optimal PSDs for practical cells.

Exurban and suburban forests have superior healthcare benefits beyond downtown forests

Forests in urban areas provide great healthcare benefits to citizens, but it is less well known whether this benefit is related to different geographical spaces. We selected exurban forest, suburban forest, downtown forest, and urban control in Guangzhou, China to analyze the change characteristics of negative air ion concentration (NAIC), air oxygen content (AOC), and human comfort index (HCI). Based on Criteria Importance Through Intercriteria Correlation (CRITIC) method, the urban forest comprehensive healthcare index (UFCHI) was established. Finally, the evaluation criteria for UFCHI were identified by cluster analysis. The results demonstrated that (1) The NAIC in exurban forest (2,713 ± 1,573 ions/cm3) and suburban forest (2,147 ± 923 ions/cm3) was evidently better than downtown forest (1,130 ± 255 ions/cm3) and urban control (531 ± 162 ions/cm3). (2) The AOC was in the order of exurban forest (21.17 ± 0.38%) &amp;gt; suburban forest (21.13 ± 0.30%) &amp;gt; downtown forest (21.10 ± 0.16%) &amp;gt; urban control (20.98 ± 0.12%). (3) The HCI in urban control (5.56 ± 2.32) and downtown forest (5.15 ± 1.80) is higher than suburban forest (4.02 ± 1.53) and exurban forest (3.71 ± 1.48). (4) The UFCHI in exurban forest (1.000), suburban forest (0.790), and downtown forest (0.378) were beneficial to human health to some extent, while urban control (0.000) was at Level IV, having no healthcare benefit. Except in winter, the UFCHI in exurban forest and suburban forest were all at Level II and above; while downtown forest and urban control were all at Level III and below at all seasons. Overall, urban forests in the exurbs and suburbs have better healthcare benefits than those in the downtowns. Furthermore, it is recommended that urban residents visit exurban and suburban forests for forest therapy in spring, summer, and autumn.

Numerical Simulation of the HIsmelt Main Reactor for Optimizing Heat Transfer and Combustion at Different Hot Air Oxygen Contents and Daily Iron Production

ABSTRACT The HIsmelt process uses pulverized coal and iron ore as raw materials, eliminating the need for coking and iron ore lumping compared to traditional blast furnace ironmaking processes, and significantly reducing CO2 and other pollutants emissions. However, as a new ironmaking process, the flow field, heat transfer, and combustion influencing factors of the main reactor are not resolved. Therefore, in this study, based on the consideration of fluid mechanics, heat conduction, and combustion reaction, a two-dimensional mathematical model was developed for the upper space of SRV (smelting reduction vessel), the main reactor of the HIsmelt ironmaking process, based on actual production data. The effects of hot air oxygen content and daily iron production on the velocity field, temperature field, and CO2 content field inside the SRV were investigated. The results show that as the oxygen content of hot air increases, the central airflow in the furnace develops downward, the gas temperature rises gradually, and the CO2 mass fraction generally shows a rising trend. When the daily output of iron increases, the velocity of airflow in the furnace decreases significantly, the gyratory zone moves upward; the high-temperature distribution zone in the furnace contracts; and the CO2 mass fraction decreases.

Syngas production from municipal sewage sludge by gasification Process: Effects of fixed bed reactor types and gasification agents on syngas quality

In this experimental study, the results obtained from sewage sludge gasification carried out in two different fixed bed gasifiers, up draft and down draft, are presented. In addition, the effects of using three different heating temperatures (700, 800, 900 °C), two different gasification agents (dry air and pure oxygen), and their different flow rates (0.05, 0.1, 0.2, 0.4 L/min for dry air, 0.01 L/min for pure oxygen) on gasification efficiency are investigated. 75 g of sludge sample was used in each experimental study. The syngas composition produced from sludge gasification studies was measured by using online syngas analyzers. The maximum H2 content in syngas from updraft and downdraft gasifiers was achieved as 42 vol% and 46 vol% by using dry air as gasifying agent. H2 content for updraft and downdraft gasifiers was also obtained as 40 vol% and 45 vol%, respectively in the case of pure oxygen used as a gasifying agent. This paper presents a critical discussion identifying key points and contributing to a deeper understanding of its remarkable potential for sludge gasification by using different fixed bed gasifier configurations.

Identification of the Optimal Framework for Nitroxyl Radical/Hydroxylamine in Copper-Cocatalyzed Aerobic Alcohol Oxidation

8-Azabicyclo[3.2.1]octan-8-ol (ABOOL) and 7-azabicyclo[2.2.1]heptan-7-ol (ABHOL) are the main homologues of hydroxylamine 2-azaadamantan-2-ol (AZADOL) and 9-azabicyclo[3.3.1]nonan-9-ol. Both homologues feature a small bicyclic backbone and are known to be stable; however, to date, they have not been used as catalysts for alcohol oxidation. Herein, we report that these hydroxylamines can efficiently catalyze the oxidation of various secondary alcohols to their corresponding ketones using molecular oxygen in ambient air as the terminal oxidant and copper cocatalysts at room temperature. Furthermore, we show that ABOOL and ABHOL can be easily synthesized from commercially available materials.

Which trial do we need? Management of elderly, fragile, fully vaccinated patients hospitalized for SARS-CoV-2 infection

An 81-year-old male is admitted to the hospital because of progressive confusion. The family cannot precisely tell when symptoms started, possibly one week ago or a few days before. The patient has early Alzheimer's disease but has been independent in the activities of daily living until two days ago when the family reports increased confusion. The patient received four doses of the BNT162b2 mRNA SARS-CoV-2 vaccine, the last dose two months ago. He is afebrile. Room air oxygen saturation is 93%.

Propagation of an idealized infection in an airway tree, consequences of the inflammation on the oxygen transfer to blood

A mathematical model of infection, inflammation and immune response in an idealized bronchial tree is developed. This work is based on a model from the literature that is extended to account for the propagation dynamics of an infection between the airways. The inflammation affects the size of the airways, the air flows distribution in the airway tree, and, consequently, the oxygen transfers to blood. We test different infections outcomes and propagation speed. In the hypotheses of our model, the inflammation can reduce notably and sometimes drastically the oxygen flow to blood. Our model predicts how the air flows and oxygen exchanges reorganize in the tree during an infection. Our results highlight the links between the localization of the infection and the amplitude of the loss of oxygen flow to blood. We show that a compensation phenomena due to the reorganization of the flow exists, but that it remains marginal unless the power produced the ventilation muscles is increased. Our model forms a first step towards a better understanding of the dynamics of bronchial infections.

The Influence of Processing Conditions on Gas Transport and Thermal Properties of Graphite Foil Compressed from Exfoliated Graphite

Graphite foil (GF) compressed from exfoliated graphite (EG) is a sealing material, which is used in nuclear energy and the chemical industry. The preparation of graphite foil is a complex process, which includes the intercalation of graphite, water washing, thermal exfoliation and pressing of intermediate products. The preparation conditions significantly influence the structure of the material and its physicochemical properties. Thus, the aim of work was to reveal the correlation between GF processing conditions, its crystalline structure, porosity and gas permeability as well as thermal stability. Sealability of the material is connected with low value of gas permeability, while thermal stability allows use of the material in high-temperature processes. Optimization of these parameters allow for the obtaining of a reliable material and expanding of the areas of its application. Exfoliated graphite for GF was prepared at different temperatures of 600, 800 and 1000 °C from the H2SO4–graphite intercalation compound (GIC) of II, III, IV stages. The influence of the GF processing conditions (the GIC stage number and the EG preparation temperature) on the main properties (gas permeability and thermal oxidation stability) of the sealing materials was investigated. A decrease in GIC stage number leads to the formation of GF with lower macroporosity and lower nitrogen and hydrogen permeability. However, an increase in GF surface area leads to an increase in the rate of GF oxidation by air oxygen. An increase in the EG preparation temperature from 800 to 1000 oC results in the formation of EG with a developed micro- and mesoporosity and increasing GF gas permeability. A decrease in EG preparation temperature down to 600 °C promotes the formation of new transport macropores in GF. The change of the EG preparation temperature has little effect on GF oxidation stability.

Exploring a surrogate of Pellet–Cladding interaction: Characterization and oxidation behavior

The present work analyzes the effect of different Zr contents on the microstructure and thermal behavior of non-irradiated UO2. A set of Zr-doped UO2 (0, 20, 40, 80, and 100 wt%) pellets was prepared via solid-state synthesis by mimicking the chemical bonding between ZrO2 and UO2. After sintering, the Zr-doped UO2 monoliths were characterized by scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. Oxidation of the Zr-doped UO2 samples has been monitored by thermogravimetric analysis. Results of thermal behavior under air and low oxygen partial pressure show a profound effect of delayed oxidation with the addition of Zr to UO2 and then an increased oxidation resistance of UO2 to U3O8 when compared to pure UO2 pellet.Graphical abstract

Alkaline Transition Metal‐Free Oxidative Coupling of Benzylic and Quasi Benzylic sp3 Bonds with O2

AbstractAn in‐situ strategy is reported for the transition‐metal‐free oxidation of a benzylic H‐pair to perform Csp3−Csp3 bond formation. This study used sixteen benzylic and quasi benzylic reactants of primary and secondary alkyl aryl compounds, e. g., toluene, pyridine, and quinoline derivatives, to perform an oxidative coupling reaction via convenient air oxygen (O2) and MeOH‐KOH solution with a yield of 0–98 %. We now report using an in‐situ green transition‐metal‐free oxidative coupling strategy for C−C bond formation. In other attempts, metal‐catalyzed oxidation of the benzylic sp3 C−H bond of the methylquinoline has been done to perform the sp3 functionalization reaction. The reaction of 2‐methylqunioline with phenylacetylene in the presence of CuCl catalyst completed to isoxazole linkage product.

Comparative Analysis of Peak Air Pressure and Oxygen Flow between Conventional and Modified Endotracheal Tube for Retromolar Intubation (PUNTUBE)- An In Vitro Study.

In conventional practice for retromolar intubation, endotracheal tube (ET) is bent. This leads to compression of the inner diameter of the tube which in turn reduces airflow. Furthermore, conventionally ETs are stabilised in position using inflated tracheal cuff. Elastic sticky tapes around the exit pose hindrance for surgical procedures on the face. Surgical manipulation and maxillomandibular fixation may lead to compression, damage or accidental extubation of ET. We have developed a modified ET dedicated to retromolar intubation with innovative means for tube stabilisation to solve these problems. To study the efficacy of the tube, a comparative in vitro study was done on mannequins. Null hypothesis of no change in air pressure and oxygen concentration in bent conventional ET versus modified ET was formulated. Comparison was done on the basis of the peak air pressure (PEP) and oxygen concentration, which was checked using air-gas monitor. The mean PEP was found to be 24.29 psi with standard deviation (SD) of 9.54 in sequentially bent conventional tube. This was found to be only 10.35 psi with SD of 3.22 in modified ET. Oxygen delivery was found to be 3.96 L/min in bent conventional tube, which was 5.22 L/min in modified tube. Both the findings were statistically significant. Modified retromolar tube (PUNTUBE) has been found to be efficient in maintaining low PEP while delivering more oxygen as compared to bent conventional tube. Novel mode of tube stabilisation in the form of PUNSTAB is an easy and effective way of tube stabilisation.

THE EXTINCTION OF THE IGNIS FATUUS

Ignis fatuus, a luminous phenomenon witnessed over the centuries by observers around the world, is no longer seen in modern times, suggesting that it is extinct. An explanation for this disappearance can be found in the description of ignis fatuus as a cool flame of methane. Unlike a conventional flame, which generates large amounts of heat, ignis fatuus is a flame that glows without heat through a chemiluminescence process. Its characteristic bluish color is due to the emission of excited formaldehyde, which is formed in the slow combustion of methane. It is generally accepted that the phenomenon is a spontaneous combustion of swamp gas in contact with the oxygen in air, but an analysis of the energies involved in the cool flame process indicates that the phenomenon is not spontaneous in nature. Experiments carried out in the 19th century show torches being used to ignite ignis fatuus. The abandonment of fire in favor of night lighting may hold the secret to this mystery of ignis fatuus’s extinction.

Vapor-phase oxidation of propylene glycol-methanol mixture to methyl lactate on CeO2/Al2O3 catalyst

The vapor-phase oxidation of mixtures of propylene glycol with methanol and ethanol to methyl and ethyl lactate, respectively, on supported CeO2/Al2O3 catalyst at 210-2500С was investigated. Air oxygen and a flow reactor with a fixed catalyst bed were used. A 20% solution of propylene glycol in alcohol was supplied to the reactor inlet. Oxidation of propylene glycol in the presence of methanol occurs according to the overall reaction CH3CHOHCH2OH +O2 + СН3OH = CH3CHOHCOOСН3 +2H2O. First, hydroxyacetone is formed, which is further oxidized to pyruvic aldehyde, which adds alcohol to form a hemiacetal. Next, this hemiacetal is rearranged according to Cannizzaro into methyl lactate. At 2200C and catalyst load &lt; 2 mmol PG/gcat/h, the selectivity for methyl lactate reached 70 wt.% at 100% propylene glycol conversion. In the presence of ethanol, the formation of a significant amount of acetaldehyde and its aldol condensation products, as well as the formation of diethoxyethane, was observed. Therefore, the selectivity for ethyl lactate at 100% propylene glycol conversion did not exceed 45%.

DETERMINATION OF PHENOLIC-TYPE ANTIOXIDANT ADDITIVES IN FRESH INSULATING OILS BY IR SPECTROMETRY ON A LIQUID EXPRESS ANALYZER ATTACHMENT

For more than 120 years, transformer oil, derived from oil, has been most widely used as an insulating and heat dissipating medium in oil-paper insulated electrical equipment. During operation, under the influence of such factors as elevated temperature of the windings, electric field, contact with air oxygen and metal parts of the equipment, the oil is oxidized resulting in the deterioration of its electrical insulation properties and creating the risk of failure of expensive electrical equipment. In order to slow down the oxidation process and extend the life of the oil, the inhibiting additive ionol is added. However, in previously published works we showed that the additive ionol itself also undergoes decomposition with the formation of other phenolic compounds, which presence acts as an additional indicator of intensive aging of the liquid dielectric. Therefore, it is advisable to control in fresh transformer oils not only the content of ionol itself but also the presence of its degradation products showing similar inhibitory properties. A method of quantitative determination of ionol (2,6-di-tret-butyl-4-methylphenol) as well as 2,6-di-tret-butylphenol is proposed in the present work. The method of analysis is based on the IR spectrometry using a liquid express analysis attachment. The proposed method has a number of advantages over other methods, including standardized methods, i.e. speed; simplicity; safety, since chemical reagents are not required; low cost of consumables.

Safety and pulmonary function impact of surgical mask usage in stable COPD patients during the COVID-19 pandemic

There are hesitations about the use of surgical face masks, which are the main tools in protection from the COVID-19 pandemic, one of the biggest disasters of our age, in chronic airway diseases. The purpose of the study was to examine how stable patients with chronic obstructive pulmonary disease (COPD) responded to short-term surgical mask use in terms of in-mask air quality, oxygen saturation, and pulmonary function. Forty-one patients with stable COPD, by clinical presentation and pulmonary function tests (PFTs), were included in a quasi-experimental study. Stable COPD patients' PFTs, in-mask air quality, and pollution measures were collected before and after wearing surgical masks for two hours at rest. The findings of simultaneous tests of peripheral-blood-oxygen saturation were also recorded. The mean age of participants was 67.1 years and 87.8% were male. The pre- and post-mask PFTs parameters for GOLD (A+B) group were FEV1 (ml), FEV1 (%), FVC (ml), FVC (%), FEV1/FVC (%) and DLCO (%) (p=0.067, p=0. 065, p=0.062, p=0.083, p=0.083, p=0.269, p=0.956, respectively), whereas in GOLD (C+D) group (p=0.340, p=0.538, p=0.728, p=0.044, p=0.105, p=0.054, respectively). In post-mask measurements, the respiratory function was not impaired in GOLD-2022 (A-B-C-D) COPD subgroups. Oxygen and carbon-monoxide concentrations in exhaled air and oxygen saturation decreased after surgical mask use. The difference was statistically significant, but the difference was unimportant in terms of clinical implications. Surgical masks don’t appear to have a negative effect on pulmonary function and clinical parameters in stable COPD. This study may help provide evidence-based data to overcome hesitations in use of surgical masks in chronic airway diseases.