Oxygen Source Research Articles

Bioprinting of microalgae laden scaffold for tissue regeneration

Abstract In recent years, microalgae that can be a continuous source of oxygen for cells and rich in bioactive compounds, have been used as an innovative approach to prevent hypoxia after implantation of biomaterials. Oxygen can be provided photosynthetically by the polar microalga (Chlorella variabilis) in combination with human cells, even without an external oxygen source. In this study, 3D bioprinting of microalgae laden scaffolds was investigated and characterized before use in wound healing. Prepared bioink consisted of alginate and different ratios of collagen (5, 10 and 15%) and C. variabilis cells. Printing was carried out at 10 mm s−1 and the pressure was 50 kPa. Each sample had 0.6–0.7 mL volume and 6–7 × 105 cells. After the 3D bioprinting process, scaffolds were crosslinked with 100 mM calcium chloride for 10 min and incubated. It was observed that the microalgae grew well over 6 days in the scaffold. Also, an oxygen increase from 6 to 12 mg L−1 was determined. It was demonstrated that, development of microalgae-laden scaffolds is promising on the delivery of oxygen or bioactive compounds as therapeutic agents.

A Simplified Approach for Electrochemical Allylic Oxidation of Olefins

A simple method for the electrochemical allylic oxidation of olefins to enones based on peroxide‐mediated C–H activation is presented. t‐‍Butyl hydroperoxide serves a dual role as mediator and oxygen source, avoiding the utilization of expensive transition metal catalysts, potentially explosive supporting electrolytes such as perchlorates, or additional environmentally harmful mediators. This elegant methodology allows for an operationally simple and sustainable late‐stage transformation of delicate natural compounds such as terpenes or steroids into highly value‐added building blocks. Such an approach provides a greener alternative to conventional oxidation methods used for industrial applications. In total, 25 examples are demonstrated with isolated yields up to 80%. The robust scalability of the method was also demonstrated, and chromatography could be avoided in scale‐up simply by using recrystallization, which decreases the cost of downstream processing.

Identification of source and control of oxygen and nitrogen impurities in Kroll process for preparation of Ultra-soft titanium sponge

Identification of source and control of oxygen and nitrogen impurities in Kroll process for preparation of Ultra-soft titanium sponge

A review-chitosan nanoparticles towards enhancing nutrient use efficiency in crops.

A review-chitosan nanoparticles towards enhancing nutrient use efficiency in crops.

Silver Oxide Reduction Chemistry in an Alkane Environment.

The in situ reduction of silver oxide to metallic silver is of technological relevance for various applications, from conductive welding in electronics to silver (Ag) nanoparticle generation in reactive melt extrusion. This study revisits the redox reaction mechanisms involved in forming metallic silver particles through the reduction of silver(I) oxide (Ag2O) in an alkane and polymer melt environment and sheds light on the obtained particulate morphology. Liquid pentadecane was selected as a model alkane, and the observed redox chemistry and particle morphology were compared to the reactive melt extrusion in polyethylene. Unlike the well-studied reduction of metal salts in the presence of oxygen-containing organic materials, the reduction occurring in a pure alkane environment, namely the different particle morphology, is poorly understood. Our findings revealed that the primary byproducts of the reaction between Ag2O and pentadecane were CO2 and H2O, with minor products including alkenes and oxidized alkanes. The reduction process was not linear, with Ag2O acting both as a radical initiator and a source of oxygen. Gas chromatography detected CO2 formation at a rather low temperature, as low as 70 °C during the reaction between Ag2O and pentadecane, indicating a highly oxidative process resembling catalyzed combustion. Analytical techniques, including electron paramagnetic resonance (EPR) spectroscopy, confirmed that radicals were involved in the redox process via ROO• and HOO• radical species typically found in hydrocarbon oxidation under oxygen conditions. We hypothesize that the reaction is predominantly a complete oxidation, with only a small fraction of incomplete oxidation. Our observations also indicated that the metallic Ag formed directly on the surface of Ag2O in what appeared to be a solid-solid surface reaction, leading to a final Ag morphology resembling fused particles. While the resulting morphology may seem suboptimal regarding particle dispersion and homogeneity, it still offers a large contact area percolated structure that is advantageous for applications such as electronics welding. We thus conclude that in a pure alkane environment, the redox reactions are confined to the surface of the original particles.

Evaluation of Venturi Adapters for CPAP.

Background: CPAP therapy has been shown to effectively reduce the risk of obstructive apnea and oxygen desaturation in procedural sedation. An economical approach to administering CPAP is through a Venturi adapter, which amplifies oxygen flows to produce pressures suitable for CPAP. The objective of this study was to evaluate the performance of four Venturi adapters across clinically relevant metrics including pressure-generation efficiency, inspired oxygen concentration (FiO2), dilution of the end-tidal carbon dioxide (EtCO2) sample for capnometry, and noise levels produced. Methods: A benchtop simulator was used to evaluate Venturi adapters. The simulator was composed of a test lung, corrugated tubing to simulate a trachea, a silicone-molded face, an air-cushioned mask strapped to the face, a high-pressure oxygen source, and several Venturi adapters. The oxygen flows required to produce specific airway pressures were measured to evaluate pressure-generation efficiency, and the noise levels produced by the Venturi adapters at these pressures were recorded. CO2 was infused into the test lung while the lung was ventilated, and the EtCO2 measured at the mask was compared with a reference measurement taken from the trachea. FiO2 was evaluated by ventilating the test lung and observing the steady-state oxygen concentration in the lung. Results: Each of the Venturi adapter designs provides their unique strengths and weaknesses. There appears to be a direct trade-off between high pressure-generation efficiency and high FiO2. There also appears to be a direct trade-off between high FiO2 and the extent of dilution in the EtCO2 sample. Some Venturi adapters produce high noise levels, which might result in patient discomfort and clinician unwillingness to use. Conclusion: Variations in Venturi adapter designs create different clinical benefits. Clinicians should choose the Venturi adapter to best suit their present clinical needs.

Insight into the High Hole Concentration of p-Type Ga2O3 via In Situ Nitrogen Doping.

The unclear p-type conduction mechanism and lack of reliable p-type Ga2O3 severely hinder Ga2O3-based high-voltage electronics. Here, we demonstrate in situ nitrogen (N) doping via metal-organic chemical vapor deposition homoepitaxy using N2O as oxygen source and acceptor dopant. Structural and compositional analyses confirm efficient N incorporation (favored by N-Ga bonding) compensating residual Si/H donors without compromising crystallinity. The Ga2O3:N epilayers achieve excellent p-type performance: 1.04 × 1018 cm-3 hole concentration, 0.47 cm2 V-1 s-1 mobility at room temperature, and 0.168 eV activation energy. A completely new insight into the p-type conduction mechanism in Ga2O3 is introduced, focusing on the crystallographic visualization of acceptors (N2-) and holes (O-), as well as the hole excitation process. It is suggested that careful suppression of the donor compensation effect and precise control of the N chemical potential, which leads to the fabrication of trace O- species solid-dissolved within Ga2O3, are essential for achieving high-hole-concentration p-type conduction in oxides.

Intramolecular Acyl-Migration for Acyloxyselenenylation of Alkenes Promoted by Oxone.

A novel green methodology for the Oxone-mediated oxidative addition of alkenes via intramolecular acyl migration has been developed. This transformation utilizes N-acyl-N-sulfonyl allylamines and diselenides as starting materials, with Oxone serving as the oxidant and water as a partial oxygen source. The protocol enables the synthesis of a series of β-acyloxy-γ-selenyl sulfonamides with high to excellent yields and demonstrates broad substrate scope. Notably, the excellent yield was maintained in gram-scale experiments, highlighting the scalability of this method. Through comprehensive control experiments, we have elucidated the reaction mechanism, which involves rapid radical generation, a predominant cationic pathway, and intramolecular acyl migration. This study presents an efficient and environmentally benign approach to the synthesis of valuable β-acyloxy-γ-selenyl sulfonamides.

Rhodium(II)‐Catalyzed Oxo‐Amination of Aryl Cyclopropanes

We describe a rhodium(II)‐catalyzed method for synthesizing β‐amino ketones from aryl cyclopropanes, utilizing water as an oxygen source and N‐fluorobis(benzenesulfonamide) (NFSI) as a commercially available nitrogen source. This approach offers good substrate tolerance under mild conditions, providing a novel and practical route for β‐amino ketone synthesis. Mechanistic studies reveal a sequential cascade pathway initiated by single electron transfer (SET) facilitated by the rhodium(II) catalyst, followed by hydrogen atom transfer (HAT) and radical polar crossover (RPC) steps. These insights underscore the potential of rhodium(II) in driving radical amination reactions, enhancing the synthesis of β‐amino ketones from simple precursors.

Visible‐light‐induced and EDA Complex‐initiated Hydroxyselenization of α‐CF3 Alkenes: Access to α‐trifluoromethyl‐β‐selanyl tertiary Alcohols

AbstractA visible‐light‐induced and electron donor‐acceptor (EDA) complex‐initiated hydroxyselenization of α‐CF3 alkenes for the synthesis of valuable α‐trifluoromethyl‐β‐selanyl tertiary alcohols was first developed. The reaction uses ethanol as the green solvent, air (O2) as the ideal oxygen source, mild reaction conditions, simple operation and does not require the use of any transition metals and external photocatalysts. The synthetic value and practicality of this method has been demonstrated by the conversion of several substrates derived from drug molecules, efficient transformation under sunlight irradiation and gram‐scale reaction.

A rapid facility-level assessment of oxygen systems in 39 low-income and middle-income countries: a cross-sectional study.

A rapid facility-level assessment of oxygen systems in 39 low-income and middle-income countries: a cross-sectional study.

GreenMedChem-inspired light-air mediated C(sp3)-H bond oxidation: A new tool for isoquinolone synthesis.

GreenMedChem-inspired light-air mediated C(sp3)-H bond oxidation: A new tool for isoquinolone synthesis.

NaI-mediated α-keto-acylation of NH-sulfoximines with aryl methyl ketones.

A room-temperature NaI-mediated oxidative sulfoximidation of aryl methyl ketones to synthesize α-keto-N-acyl sulfoximines has been disclosed. This metal- and base-free NH-sulfoximidation is facilitated by tert-butyl hydroperoxide (TBHP) as the oxidant, affording α-ketoamides with good functional group tolerance, broad substrate scope, and scalability. Mechanistic investigations indicate the intermediacy of radicals and highlight molecular oxygen's significance as the oxygen source.

Carbon‐negative hydrogen from ethanol via catalytic oxidative reforming

AbstractThis study evaluated a commercial technology for producing low‐ or negative‐carbon hydrogen through ethanol catalytic oxidative reforming, focusing on the life cycle greenhouse gas emissions, or carbon intensity (CI). Various scenarios were analyzed: (a) comparing corn ethanol (first‐generation or Gen1 ethanol) and cellulosic ethanol (second‐generation or Gen2 ethanol) as feedstocks; (b) assessing carbon capture and sequestration (CCS) for CO2 from upstream fermentation; and (c) evaluating oxygen sourcing via air separation units vs. on‐site or off‐site water electrolysis using a proton exchange membrane. Findings indicate that the CI for hydrogen production using Gen2 ethanol from corn stover is lower than that of Gen1 corn ethanol. Additionally, using proton exchange membrane‐generated oxygen results in a lower CI than air separation unit‐generated oxygen, regardless of the sourcing method. Implementing CCS for the hydrogen production plant's evolved CO2 is essential for achieving a net‐negative CI for hydrogen from Gen1 ethanol. All examined scenarios, including both ethanol generations, oxygen sources, and CCS applications, demonstrated a net‐negative carbon intensity, surpassing the life cycle greenhouse gas emissions threshold of 0.45 kg CO2e/kg to enable policy credits as outlined in the Inflation Reduction Act §45V. In comparison, the CI for hydrogen from steam methane reforming stands at 3.4 kg CO2e/kg with CCS and 9.4 kg CO2e/kg without CCS.

Atomic Layer Deposition of Nickel Oxides as Electrocatalyst for Oxygen Evolution Reaction.

In this study, we present atomic layer deposition (ALD) of nickel oxides (NiOx) using a new nickel precursor, (methylcyclopentadienyl)(cyclopentadienyl)nickel (NiCp(MeCp)), and ozone (O3) as the oxygen source. The process features a relatively short saturation pulse of the precursor (NiCp(MeCp)) and a broad temperature window (150-250 °C) with a consistent growth rate of 0.39 Å per cycle. The NiOx film deposited at 250 °C primarily exhibits a polycrystalline cubic phase with minimal carbon contamination. Notably, the post-annealed ALD NiOx film demonstrates attractive electrocatalytic performance on the oxygen evolution reaction (OER) by providing a low overpotential of 320 mV at 10 mA cm-2, a low Tafel slope of 70.5 mV dec-1, and sufficient catalytic stability. These results highlight the potential of the ALD process using the NiCp(MeCp) precursor for the fabrication of high-activity catalysts.

Sustainable Sulfonylation and Sulfenylation of Indoles with Thiols through Hexamolybdate/H2O2-Mediated Oxidative Dehydrogenation Coupling.

Arylsulfonylindole and arylsulfenylindole motifs stand as privileged scaffolds in drug discovery. Traditional methods for synthesizing these molecules have relied mainly on prefunctionalized precursors, involving multistep processes and generating a large amount of waste. In this study, we present a modular protocol for the preparation of 3-sulfonylindoles and 3-sulfenylindoles using indoles and thiols as starting materials via hexamolybdate/H2O2-mediated oxidative dehydrogenative C-S coupling. Notably, this method features a simple reaction setup and uses readily available thiols as a sulfide source, H2O2 as a green oxidant and oxygen source, alcohol as solvent, recyclable hexamolybdate as a catalyst, and water as the sole byproduct. These metrics are an acceptable green organic synthesis process.

Research Progress in Epoxidation of Light Small-Molecule Olefins.

Light olefins, as important bulk raw materials in the petrochemical industry, play an irreplaceable role in the development of the manufacturing industry and the economy. The epoxides of light olefins are important intermediates for the synthesis of polymers, drugs, and fine chemicals, and their green, efficient, and safe synthesis has attracted much attention. This review focuses on the research progress of light olefin epoxidation and elucidates traditional epoxidation methods, such as the chlorohydrin method. Although these processes have mature processes, they have drawbacks, including equipment corrosion, environmental pollution, poor safety, and high waste emissions. Special emphasis is placed on catalytic epoxidation systems using oxygen or organic peroxides as oxygen sources. For homogeneous catalytic systems, certain metal complexes exhibit high activity and selectivity yet are difficult to separate and recycle. Moreover, heterogeneous catalytic systems have become a research hotspot due to their advantages of easy separation and reusability, with supported metal catalysts being a prime example. Meanwhile, the effects of reaction temperature, pressure, solvent, etc., on epoxidation are explored. The specific reaction mechanisms are also studied and analyzed. Current research challenges, including enhancing catalyst stability and reducing costs, are summarized. In the future, developing highly efficient, green, and economically viable epoxidation technologies for large-scale industrial applications represents an important research direction in this field.

High Selectivity Hydroxylation and Other Functionalization of Quinoline-Directed Reactions under Cu(II)-Catalysis.

Despite progress in ortho C-H functionalization of aromatic rings directed by guiding groups, achieving highly selective hydroxylation in simple systems without the need for additional ligand assistance remains a significant challenge. Here, we report the direct hydroxylation of the ortho C-H bond of aromatic rings directed by quinoline under Cu(II) catalysis. Based on experimental analysis and DFT calculations, the main reason for the high selectivity of the quinoline-directed hydroxylation reaction is that the match between the new substrate and the method leads to an increased range of oxygen source incorporation. Isotope experiments and DFT calculations provide support for the origin of the oxygen source in the hydroxylation process and the rationale behind its observed distribution. Additionally, the introduction of various nucleophiles enabled the cyanation, nitration, and halogenation of ortho C-H bonds in the aryl group.

Ru3+-doped lead-free perovskite Cs3Bi2Br9 for photocatalytic selective oxidation of sulfides to sulfoxides using trace water as an oxygen source

Ru3+-doped lead-free perovskite Cs3Bi2Br9 for photocatalytic selective oxidation of sulfides to sulfoxides using trace water as an oxygen source

Economic improvement and fish farming based on Smart Aquaculture Automatized System in Segobang Village, Banyuwangi

The fisheries and marine sector in East Java has abundant potential, one of which is Banyuwangi district. Banyuwangi Regency has potential in freshwater aquaculture because it has 324 rivers with an area of 735 km2 and swamps and reservoirs of 60 hectares. One of the villages in Banyuwangi Regency is Segobang Village, which has the potential to have abundant water sources and continuous flow. This potential can be utilized by training and assisting fish nurseries in Segobang Village by utilizing continuously flowing water and Smart Aquaculture Automatized System (SAAS) technology by utilizing biofilters and running water and aeration as a source of oxygen. The stages carried out in this community service are as follows: initial assessment of the location, infrastructure and technology development, periodic training and mentoring, implementation and monitoring of the cultivation process, and continued marketing and sales. After the training, the Segobang Village community showed a significant increase in knowledge. The average pre-test scores ranged from 30 to 51, while the post-test scores increased to 79 to 87. This improvement shows that participants better understand the SAAS and its use in fish farming. Continued training and practice can help strengthen the adoption of this technology in the community.