Oxygen Environment Research Articles

Degradation behavior and ageing mechanism of E-glass fiber reinforced epoxy resin composite pipes under accelerated thermal ageing conditions

In this work, accelerated ageing experiments with circulating air and simulated oilfield water were carried out at 95 °C on aromatic amine-cured GFRP pipes used in oilfield environments, with effective ageing times of 5000 h and 3000 h respectively. The differences in ageing behavior and ageing mechanisms of the GFRP tubes at different times under the two conditions were then analyzed and discussed. The changes in the apparent morphology and microstructure of the samples after thermal ageing were first observed using optical microscopy and scanning electron microscopy, and the results demonstrated that the thermal oxygen environment triggered more drastic color changes and obvious oxidation layers. The resin matrix manifests a large number of nano-scale micropores and modest matrix shrinkage pores in the micron size range, this is accompanied by damage to the fiber cross-section. Hydrothermal ageing causes further dissolution of the surface resin and dissolution of the exposed fibers. ATR-FTIR analysis verifies the increase in CO bonding of the ester group during thermal oxidation and the decreasing strength of the C–O–C and C–H bonds, while the behavior of ageing water absorption and glass fiber hydrolysis is illustrated by changes in the intensity of the –OH and Si–O characteristic bands. NMR hydrogen spectroscopy verified the formation of amides, methyl ethers and carboxylic acids in the thermal oxidation products of epoxy resins. Furthermore, the decay pattern of the circumferential tensile strength indicates that the hydrothermal environment has a more significant effect on the mechanical properties of GFRP pipes, which is attributed to the physical dissolution of the surface resin, significant hydrolytic damage to the surface exposed fibers, and the combined damage to the resin-fiber interfacial bonding by chloride ions in simulated oilfield water.

Ischemia-induced alterations in the electrocardiogram of salmonid fish

Cardiovascular diseases such as coronary arteriosclerosis are widespread and constitute severe health and welfare problems for both farmed and wild salmonid fish. However, effective tools for rapid screening and analysing heart diseases in fish do not currently exist. Electrocardiogram (ECG) recordings are widely used for screening and diagnosing numerous cardiac pathologies in humans, but the use of ECG techniques to diagnose and characterize cardiac abnormalities in fish is still in its infancy. In this study, we induced myocardial ischemia in anaesthetized rainbow trout by surgical coronary artery ligation. Additionally, we experimentally manipulated the fish's heart rate and environmental oxygen availability by altering gill water flow and oxygen saturation (i.e., no flow, normoxic flow and hyperoxic flow), and analyzed changes in the ECG profile in detail. The main ECG abnormalities observed in fish with ligated coronaries in normoxia were atrioventricular blocks, prolonged QRS duration, reduced QRS amplitude and changes in the ST-segment such as the presence of early repolarization pattern. Furthermore, when gill water flow was stopped, fish exhibited pronounced hypoxic bradycardia, which alleviated all ECG abnormalities in coronary ligated fish. This is the first study to provide a detailed characterization of electrocardiographic markers of myocardial ischemia in fish. Our study shows that hypoxic bradycardia improves cardiac electrical conductivity, presumably by reducing mismatches in myocardial oxygen supply and demand. Yet, the importance of avoiding hypoxic bradycardia in experimental and biomedical studies on anaesthetized fish is highlighted as it can potentially lead to incorrect ECG interpretations.

Aerobic iron-oxidizing bacteria secrete metabolites that markedly impede abiotic iron oxidation.

Iron is one of the Earth's most abundant elements and is required for essentially all forms of life. Yet, iron's reactivity with oxygen and poor solubility in its oxidized form (Fe3+) mean that it is often a limiting nutrient in oxic, near-neutral pH environments like Earth's ocean. In addition to being a vital nutrient, there is a diversity of aerobic organisms that oxidize ferrous iron (Fe2+) to harness energy for growth and biosynthesis. Accordingly, these organisms rely on access to co-existing Fe2+ and O2 to survive. It is generally presumed that such aerobic iron-oxidizing bacteria (FeOB) are relegated to low-oxygen regimes where abiotic iron oxidation rates are slower, yet some FeOB live in higher oxygen environments where they cannot rely on lower oxygen concentrations to overcome abiotic competition. We hypothesized that FeOB chemically alter their environment to limit abiotic interactions between Fe2+ and O2. To test this, we incubated the secreted metabolites (collectively known as the exometabolome) of the deep-sea iron- and hydrogen-oxidizing bacterium Ghiorsea bivora TAG-1 with ferrous iron and oxygen. We found that this FeOB's iron-oxidizing exometabolome markedly impedes the abiotic oxidation of ferrous iron, increasing the half-life of Fe2+ 100-fold from ∼3 to ∼335 days in the presence of O2, while the exometabolome of TAG-1 grown on hydrogen had no effect. Moreover, the few precipitates that formed in the presence of TAG-1's iron-oxidizing exometabolome were poorly crystalline, compared with the abundant iron particles that mineralized in the absence of abiotic controls. We offer an initial exploration of TAG-1's iron-oxidizing exometabolome and discuss potential key contributors to this process. Overall, our findings demonstrate that the exometabolome as a whole leads to a sustained accumulation of ferrous iron in the presence of oxygen, consequently altering the redox equilibrium. This previously unknown adaptation likely enables these microorganisms to persist in an iron-oxidizing and iron-precipitating world and could have impacts on the bioavailability of iron to FeOB and other life in iron-limiting environments.

Oxygen Dependent Switchable Selectivity during Ruthenium Catalyzed Selective Synthesis of C3-Alkylated Indoles and Bis(indolyl)methanes.

Herein, we report a ligand-centered redox-controlled oxygen-dependent switchable selectivity during ruthenium-catalyzed selective synthesis of C3-alkylated indoles and bis(indolyl)methanes (BIMs). A wide variety of C3-alkylated indoles and BIMs were prepared selectively in moderate to good isolated yields by coupling a wide variety of indoles and alcohols, catalyzed by a well-defined, air-stable, and easy-to-prepare Ru(II)-catalyst (1a) bearing a redox-active tridentate pincer (L1a). Catalyst 1a efficiently catalyzed the C3-alkylation of indoles under an argon atmosphere while, under an oxygen environment, exclusively producing the BIMs. A few drug molecules containing BIMs were also synthesized efficiently. 1a exhibited excellent chemoselectivity with alcohols containing internal carbon-carbon double bonds. Mechanistic investigation revealed that the coordinated azo-aromatic ligand actively participates during the catalysis. During the dehydrogenation of alcohols, the azo-moiety of the ligand stores the hydrogen removed from the alcohols and subsequently transfers the hydrogen to the alkylideneindolenine intermediate, forming the C3-alkylated indoles. While under an oxygen environment, the transfer of hydrogen from the ligand scaffold to the molecular oxygen generates H2O2, leaving no scope for hydrogenation of the alkylideneindolenine intermediate, rather than it undergoing 1,4-Michael-type addition forming the BIMs.

Hydroxyurea's Impact on Erythropoiesis, Cell Death and HbF Expression in the Hudep-2 Model

Background : Sickle cell disease (SCD) is an inherited disorder caused by a mutation in the beta-globin gene, leading to the synthesis of sickle hemoglobin called HbS. Under deoxygenated conditions, HbS polymerizes and forms fibers that weakens red blood cells (RBC) resulting in hemolysis and vaso-occlusion. Recently, ineffective erythropoiesis in SCD has been reported, characterized by higher apoptosis levels during late erythropoiesis. Interestingly, fetal hemoglobin (HbF)-expressing erythroblasts during erythroid differentiation seem to be protected from the apoptosis. Hydroxyurea (HU) is the first major approved drug for SCD in US and Europe; its proven efficacy in decreasing SCD morbidity and mortality is mainly mediated by the induction of HbF expression that is well-known as a modulator of disease severity through its ability to interfere with HbS polymerization. Despite being used for decades, HU action mechanism still remains to be fully elucidated. More precisely, HU impact on RBC maturation process is poorly documented as well as its mode of action on gamma-globin gene expression. Aim : Our aim is to investigate the effect of HU on erythropoiesis kinetics, HbF induction and apoptosis. Methods : We used HUDEP-2 (Human Umbilical cord Derived Erythroid Progenitors-2) cell line as a model for erythropoiesis. Cells were differentiated in normoxia (20% oxygen) or hypoxia (5% oxygen) - to mimic bone marrow environment, and were treated or not with HU allowing the comparison of HU effect both in normoxia and hypoxia. Analysis was performed at day D1, D3, D6, D8 and D10 of differentiation using flow cytometry, microscopy (MGG staining) and High-Performance Liquid Chromatography (HPLC). Kinetics of differentiation were followed by microscopy with MGG coloration and by flow cytometry using GPA, CD49d, Band3 and HbF antibodies. Apoptosis was assessed using annexin V staining. Results : Wedid first assess HU effect on HbF expression during erythropoiesis by flow cytometry and HPLC. Both methods showed that HU induced HbF expression from D1 to D6 of differentiation and that this induction is higher when the cells are in hypoxic conditions. We also investigated the apoptotic rate during erythropoiesis. Interestingly, HU treatment does not induce apoptosis in differentiating erythroblast, but decreased proliferation rates by 2-fold change in normoxia. Hypoxic conditions also decreased proliferative rate similarly to HU in normoxia but interestingly, in hypoxic conditions, HU did not furthermore decrease cell proliferation. Then, we investigated HU effect on the differentiation kinetics. Based on the differential expression of CD49d and Band3 along the differentiation, the percentage of each stage of differentiation (proerythroblast, basophilic, polychromatic and orthochromatic) was estimated by flow cytometry in GPA + cells at D1, D3, D6, D8 and D10 of the differentiation. Figure 1 depicted flow cytometry representative results from our 4 culture conditions at D1. Our results did show that HU accelerates HUDEP-2 differentiation as soon as D1 of culture (normoxia D1 NT vs HU: ProE 53.3% vs 44%, Baso 29.9% vs 33.1%, Poly 15.2% vs 18% and Ortho 3.3% vs 3.8%) until the end of the differentiation (D8 and 10) in normoxia. This acceleration is accentuated in hypoxic conditions (Hypoxia D1 NT vs HU: ProE 34.7% vs 17.9%, Baso 42.2% vs 50.3%, Poly 17.7% vs 25.8% and Ortho 3.8% vs 4.7%) with a cumulative effect of hypoxia and HU. All the flow cytometry results were confirmed by MGG staining and quantification by microscopy. For the same day of differentiation, HU-treated HUDEP-2 are in later stages than HU-non treated cells. Conclusion : Our study is the first to investigate the impact of HU on RBC maturation - erythropoiesis. HU treatment increases HbF expression without impacting apoptosis. The treatment tends to promote erythroid differentiation by accelerating maturation processes with stronger effect in hypoxic conditions that mimic the in vivo low oxygen environment of the bone marrow, strongly suggesting that HU has other molecular targets than inducing HbF. All these results will be confirmed in CD34 + erythroid progenitors from patients with SCD. Our results give new insights on the effect of HU on erythropoiesis that would ultimately lead to a better understanding of its mechanism of action and to the identification of new therapeutical targets to counteract SCD ineffective erythropoiesis.

Characterization of biofilm bacterial communities in rural drainage system ancillary facilities

To investigate the differences in the bacterial communities of biofilms in the appurtenant facilities of rural sewage collection systems, a pilot research setup was constructed. A study was conducted using real sewage collected in a rural area, and the bacterial communities of biofilms in different appurtenant facilities were characterized using Illumina HiSeq high-throughput sequencing technology. The results showed that there were significant differences in biofilm bacterial communities among the different annexes. The biofilms from all four ancillary facilities (drop manhole, turning inspection well, mud trap, and direct inspection well) contained some amounts of denitrifying bacteria (relative abundance >6 %), but lacked ammonia- and nitrite-oxidizing bacteria (relative abundance <0.1 %). The relative abundance of sulfate-reducing bacteria was high (6.32 %), with Desulfobulbus being dominant (4.12 %) owing to the prolonged low dissolved oxygen environment in the sedimentation wells, which are at high risk of accumulating H2S relative to other ancillary facilities. All four ancillary facilities had high abundances of potential disease-causing bacteria (e.g., Acinetobacter and Arcobacter) in the biofilm and in the overwater. Therefore, the biosafety of the effluent should be taken into account in the collection process.

Reaction kinetic modelling of tar cracking in a non-thermal plasma reactor: Model evaluation and reaction mechanism investigation

Gasification is a process that converts waste into syngas, offering various applications such as fuel, energy, hydrogen production, or further chemicals synthesis. However, tar formation hinders its application due to fouling, corrosion, and catalyst deactivation. Non-thermal plasma (NTP) has emerged as a promising method for tar reforming and cracking, demonstrated through surrogate compounds at the laboratory scale. The scope of this study is to investigate the reaction mechanisms in NTP tar cracking using a zero-dimensional (0D) plasma reactor model with Arrhenius kinetics, aiming to elucidate complex pathways, validate against experimental data, and contribute to the understanding of the reactions. The modelling work utilises a global model to represent NTP. This work collects various reaction kinetics and validates predictions against experimental data. The approach begins with heptane modelling, which is later expanded into (1) toluene in hydrogen gas and (2) a tar mixture (phenol, toluene, and naphthalene) in an oxygen-steam mixture. The model predicts external experimental results with good accuracy, especially at temperatures ranging from 600 to 800 K. The results reveal that radical collisions have a more significant impact on the process than electron impact reactions. Toluene and naphthalene ring-opening reactions occurred when a reactive functional group attacks aromatic double bonds. Finally, the model estimates tar cracking in syngas environment. The low oxygen environment results in secondary tar formation and an abundance of acetylene at the output. Lastly, the assumptions adopted in this study are verified by investigating the impact of plasma and electron temperatures, along with a comparative review of current methodologies in NTP chemistry modelling.

Exploring the potential of boron carbide in enhancing energy output of solid fuels for SFRJ and hybrid rocket propulsion systems

AbstractBoron carbide (B4C) is known for its exceptional hardness and high energy release during combustion, despite its ignition processes presents considerable challenges. This study focuses on exploring the potential of B4C as an enhancer for the energy output of solid fuels designed for hybrid rocket engines (HRE) or solid fuel ramjets (SFRJ). This study presents the successful incorporation of B4C and fluorinated PTFE (polytetrafluoroethylene) polymer into the HTPB (hydroxyl‐terminated polybutadiene) fuel matrix, aiming to enhance the ignition, combustion, and regression rate performance of solid fuel. Five different fuel compositions were formulated with varying mass ratios of B4C, and their post‐combustion products were characterized using XRD (X‐ray diffraction), HRSEM (high‐resolution scanning electron microscopy), and EDS (energy‐dispersive X‐ray spectroscopy) techniques. The HRSEM‐EDS analysis confirmed a uniform dispersion of B4C/PTFE additives throughout the HTPB matrix. To evaluate the combustion behavior of the B4C/PTFE additives, an opposite flow burner was employed with a gaseous oxygen oxidizer. The F4 fuel sample, loaded with B4C/PTFE (10/20), exhibited an average regression rate increase ranging from 0.61 to 1.15 mm/s when evaluated within the oxidizer flux range of 36–77 kg/m2s, in comparison to that of pure HTPB (0.4 mm/s to 0.76 mm/s). The ignition delay time was investigated as a key parameter affected by the B4C concentration in the solid fuel formulations. Furthermore, a comprehensive combustion mechanism is proposed and discussed for B4C/PTFE loaded in the HTPB matrix under an oxygen environment.

The impact of water and oxygen contents on the corrosion performance of yttrium silicate modified SiCf/SiC composites under high temperature conditions

SiCf/SiC composites have emerged as a prominent research area in the field of structural materials for engine hot-end applications. However, SiCf/SiC composites exhibit susceptibility to oxidation and corrosion when exposed to oxygen and water vapor. The yttrium silicate ceramic in the SiCf/SiC composite (SiCf/SiC-YS composite) serves as corrosion-resistant matrix. The corrosion behavior of SiCf/SiC-YS composites was assessed by examining the phase composition, microstructure, and bending strength after exposure to different water and oxygen environments. The results show that SiCf/SiC-YS composites exhibit excellent resistance to water and oxygen at temperatures below 1300 °C. Above 1300 °C, the decomposition of yttrium disilicate affects the internal structure and bending strength of the composites. Temperature- and water vapor concentration-dependent crystal transformation of yttrium silicate is a crucial factor that influences the microstructure and water-oxygen corrosion resistance of SiCf/SiC-YS composites.

Microfluidic-based spatiotemporal control of oxygen concentration in bacteria suspension culture from bulk to the single cells

Oxygen plays a crucial role in microbial growth and metabolism. However, the detailed bacterial responses and regulatory mechanisms toward the change of oxygen are still not completely understood partly due to the lack of real-time measurement and control of dissolved oxygen (DO). Here, we present a novel platform for spatiotemporal and real-time controls of oxygen concentrations by a simple microfluidic design in bacteria suspension culture on chip. The DO concentrations are precisely controlled or flexibly tuned in bioreactor arrays in nanoliter scale. Multiple bioreactor groups with diverse DO control strategies are integrated on a single chip. With our platform, adequate oxygen existed in the microfluidic culture channels and may be the critical factor for the fast growth during bacteria suspension culture. Notably, we extend our platform to mimic the DO oscillation environment and monitor the growth of bulk and single bacterium for many generations. This microfluidic platform exhibits the unique capability of spatiotemporal gas control and detection for microbial suspension culture in nanoliter scale, which can be applied for screening, studying, and culturing the industrial or niche-specific environmental microbiome, at bulk, single cell, or consortia level, responding to oxygen or other gas environment, such as carbon dioxide, ammonia, etc.

High-throughput quantification of red blood cell deformability and oxygen saturation to probe mechanisms of sickle cell disease.

The complex, systemic pathology of sickle cell disease is driven by multiple mechanisms including red blood cells (RBCs) stiffened by polymerized fibers of deoxygenated sickle hemoglobin. A critical step toward understanding the pathologic role of polymer-containing RBCs is quantifying the biophysical changes in these cells in physiologically relevant oxygen environments. We have developed a microfluidic platform capable of simultaneously measuring single RBC deformability and oxygen saturation under controlled oxygen and shear stress. We found that RBCs with detectable amounts of polymer have decreased oxygen affinity and decreased deformability. Surprisingly, the deformability of the polymer-containing cells is oxygen-independent, while the fraction of these cells increases as oxygen decreases. We also find that some fraction of these cells is present at most physiologic oxygen tensions, suggesting a role for these cells in the systemic pathologies. Additionally, the ability to measure these pathological cells should provide clearer targets for evaluating therapies.

Reduction of light output of plastic scintillator tiles during irradiation at cold temperatures and in low-oxygen environments

The advent of the silicon photomultiplier has allowed the development of highly segmented calorimeters using plastic scintillator as the active media, with photodetectors embedded in the calorimeter, in dimples in the plastic. To reduce the photodetector’s dark current and radiation damage, the high granularity calorimeter designed for the high luminosity upgrade of the CMS detector at CERN’s Large Hadron Collider will be operated at a temperature of about −30 °C. Due to flammability considerations, a low oxygen environment is being considered. However, the radiation damage to the plastic scintillator during irradiation in this operating environment needs to be considered. In this paper, we present measurements of the relative decrease of light output during irradiation of small plastic scintillator tiles read out by silicon photomultipliers. The irradiations were performed using a 60Co source both to produce the tiles’ light and as a source of ionizing irradiation at dose rates of 0.3, 1.3, and 1.6 Gy/h, temperatures of −30, −15, −5, and 0 °C, and with several different oxygen concentrations in the surrounding atmosphere. The effect of the material used to wrap the tile was also studied. Substantial temporary damage, which annealed when the sample was warmed, was seen during the low-temperature irradiations, regardless of the oxygen concentration and wrapping material. The relative light loss was largest with 3MTM Enhanced Specular Reflector Film wrapping and smallest with no wrapping, although due to the substantially higher light yield with wrapping, the final light output is largest with wrapping. The light loss was less at warmer temperatures. Damage with 3% oxygen was similar to that in standard atmosphere. Evidence of a plateau in the radical density was seen for the 0 °C data.

Confining monochromophore in dynamic polymer network for multi-stimuli responsive fluorescence-phosphorescence dual-emission

Organic fluorescence-phosphorescence dual-emission materials are attracting broad attention for their wide potential applications in information technology, display media, etc. Most reported organic systems rely on the combination of two or more luminogens that emit different-colored phosphorescence and fluorescence respectively. By contrast, the fluorescence-phosphorescence dual-emission from one single luminogen system are especially appealing, as they can offer many advantages such as improved luminescence stability, simplified fabrication process and excellent reproducibility. Nevertheless, it remains challenging to achieve stimuli-responsive fluorescence-phosphorescence dual-emission in monochromophore-based organic material. Herein, we specially designed one new bromine-substituted naphthalimide molecule and incorporated it into a dynamic carboxyl hydrogen-bonded polyacrylic acid (PAA) network to produce the robust multi-stimuli-responsive fluorescence-phosphorescence dual-emission materials. Detailed studies demonstrated that high-density carboxyl hydrogen-bonded crosslinks play important roles in the achievement of intense phosphorescence by providing a rigid environment and efficient oxygen barrier to stabilize the triplet-excited states. On this basis, responsive fluorescence-phosphorescence dual-emission characteristic was guaranteed to realize interesting luminescence color changes, because many environmental stimuli (e.g., temperature, humidity, or alcohol) were known to dissociate the carboxyl hydrogen-bonded crosslinks. This reported strategy is expected to be universal and promising for the future development of powerful organic fluorescence-phosphorescence dual-emission materials with versatile uses.

Protein kinase B/AKT phosphorylates hypoxia-inducible factor-3α1 in response to insulin, promoting cell growth and migration.

Hypoxia-inducible factors (HIFs) are best known for their roles in the adaptation to low oxygen environments. Besides hypoxia, HIF-1/2 α-subunits are also regulated by various non-hypoxic stimuli including insulin which can act via the PI3K/protein kinase B (PKB) signaling pathway. However, with respect to insulin little is known about HIF-3α. We aimed to investigate this relationship and found that insulin stimulates HIF-3α expression under both normal and low oxygen conditions. Blocking PKB activity reversed the effects of insulin, indicating that HIF-3α is a direct target of PKB. We identified serine 524, located in the oxygen-dependent degradation domain of HIF-3α, as a phosphorylation site of PKB. Mutating serine 524 impaired binding of PKB to HIF-3α and its ubiquitination, suggesting that PKB regulates HIF-3α stability through phosphorylation, thereby affecting important cellular processes such as cell viability and cell adhesion. Importantly, we discovered that this phosphorylation site also influenced insulin-dependent cell migration. These findings shed light on a novel mechanism by which insulin affects PKB-dependent HIF-3α expression and activity, with potential implications in metabolic diseases and cancer.

Co-combustion strategy of waste energetic materials with pine sawdust for efficient NOx emissions reduction

Excessive NOx emissions during incineration of waste energetic materials (EMs) is harmful to the environment. Co-combustion technologies with biomass have demonstrated remarkable advantages in reducing NOx emissions. Herein, the co-combustion characteristics and NOx emission behaviors of waste double-base propellant (DP) and pine sawdust (PS) were investigated via thermogravimetric (TG) and fixed-bed experiments firstly. Meanwhile, the general full factorial design (GFFD) was performed to explore the effects of different factors on the NOx emissions of co-combustion. The interaction mechanism between DP and PS was discussed as well. Moreover, the interaction of three other typical waste EMs (RDX, TNT, and triple-base propellant) co-combustion with PS in NOx emissions was studied utilizing orthogonal experiments. The kinetics under air atmosphere indicated that the mixing of PS slightly diminished the combustion reactivity of DP, conversely, the remaining residue of DP combustion promoted the combustion of PS. Oxygen concentration, temperature and mixing ratio all had significant effects on NOx emissions of co-combustion between DP and PS, the degree of effect decreased in turn. Overall, the mixing of PS all suppressed the NOx emissions with significant synergistic effects, optimal synergistic effect at 20 wt% of PS mixing. The synergistic effect in oxygen environment was lower than that in oxygen-free environment. Meanwhile, increasing temperature contributed to enlarging the synergistic effect. Additionally, there was synergistic effect of TNT and PS co-combustion, whereas RDX, TP exerted inhibition effect of co-combustion with PS. Therefore, the co-combustion strategy of waste EMs with PS provides reliable data support and guidance for the control of NOx emissions during the incineration of waste EMs.

One-step generating protect film resisting ozone and strong acid on conductive silicone adhesive with atmospheric pressure plasma-assisted

Enhancing the oxidation resistance of conductive silicone adhesive is crucial for long-term stability in rich oxygen and high-temperature environments. Coating thin film featuring low oxygen permeability on the adhesive has been considered a reliable solution. However, the current processes of coating film require extra precursor materials and post-treatment. Here we demonstrated a simple process with atmospheric pressure plasma-assisted to coat SiOxCy thin film on the conductive silicone adhesive within minutes. Our results indicated that the coated thin film has strong oxidation resistance that protects the conductive silicone adhesive from oxidation by 0.1 M HCl solution within 7 days and exposure to ozone for 20 min. The film presented a strong hydrophobic property with a contact angle of 120°. The film’s chemical structure was detected mainly with Si3+: –[Si(R)(-O-)-O–]– and Si4+: [Si(-O-)2–O–]–. The coating process is simple, requires no precursor material, and does not change the original conductivity of the conductive adhesive.

Trends of Pd3Au(111) Alloy Surface Segregation in Oxygen, Carbon, and Nitrogen Environments

Trends of Pd₃Au(111) Alloy Surface Segregation in Oxygen, Carbon, and Nitrogen Environments

Toward a Transportable Cell Culture Platform for Evaluating Radiotherapy Dose Modifying Factors

The current tools for validating dose delivery and optimizing new radiotherapy technologies in radiation therapy do not account for important dose modifying factors (DMFs), such as variations in cellular repair capability, tumor oxygenation, ultra-high dose rates and the type of ionizing radiation used. These factors play a crucial role in tumor control and normal tissue complications. To address this need, we explored the feasibility of developing a transportable cell culture platform (TCCP) to assess the relative biological effectiveness (RBE) of ionizing radiation. We measured cell recovery, clonogenic viability and metabolic viability of MDA-MB-231 cells over several days at room temperature in a range of concentrations of fetal bovine serum (FBS) in medium-supplemented gelatin, under both normoxic and hypoxic oxygen environments. Additionally, we measured the clonogenic viability of the cells to characterize how the duration of the TCCP at room temperature affected their radiosensitivity at doses up to 16 Gy. We found that (78±2)% of MDA-MB-231 cells were successfully recovered after being kept at room temperature for three days in 50% FBS in medium-supplemented gelatin at hypoxia (0.4±0.1)% pO2, while metabolic and clonogenic viabilities as measured by ATP luminescence and colony formation were found to be (58±5)% and (57±4)%, respectively. Additionally, irradiating a TCCP under normoxic and hypoxic conditions yielded a clonogenic oxygen enhancement ratio (OER) of 1.4±0.6 and a metabolic OER of 1.9±0.4. Our results demonstrate that the TCCP can be used to assess the RBE of a DMF and provides a feasible platform for assessing DMFs in radiation therapy applications.

The Identity of Nickel Peroxide as a Nickel Superoxyhydroxide for Enhanced Electrocatalysis.

Nickel peroxides are a class of stoichiometric oxidants that can selectively oxidize various organic compounds, but their molecular level structure remained elusive until now. Herein, we utilized structural prediction using the Stochastic Surface Walking method based on a neural network potential energy surface and advanced characterization using the as-synthesized nickel peroxide to unravel its chemical identity as the bridging superoxide containing nickel hydroxide, or nickel superoxyhydroxide. Superoxide incorporation tunes the local chemical environment of nickel and oxygen beyond the conventional Bode plot, offering a 6.4-fold increase in the electrocatalytic activity of urea oxidation. A volcanic dependence of the activity on the oxygen equivalents leads to the proposed active site of the Ni(OO)(OH)Ni five-membered ring. This work not only unveils the possible structures of nickel peroxides but also emphasizes the significance of tailoring the oxygen environment for advanced catalysis.

Impact of environmental oxygen on nanoparticle formation and agglomeration in aluminum laser ablation plumes.

The role of ambient oxygen gas (O2) on molecular and nanoparticle formation and agglomeration was studied in laser ablation plumes. As a lab-scale surrogate to a high explosion detonation event, nanosecond laser ablation of an aluminum alloy (AA6061) target was performed in atmospheric pressure conditions. Optical emission spectroscopy and two mass spectrometry techniques were used to monitor the early to late stages of plasma generation to track the evolution of atoms, molecules, clusters, nanoparticles, and agglomerates. The experiments were performed under atmospheric pressure air, atmospheric pressure nitrogen, and 20% and 5% O2 (balance N2), the latter specifically with in situ mass spectrometry. Electron microscopy was performed ex situ to identify crystal structure and elemental distributions in individual nanoparticles. We find that the presence of ≈20% O2 leads to strong AlO emission, whereas in a flowing N2 environment (with trace O2), AlN and strong, unreacted Al emissions are present. In situ mass spectrometry reveals that as O2 availability increases, Al oxide cluster size increases. Nanoparticle agglomerates formed in air are found to be larger than those formed under N2 gas. High-resolution transmission electron microscopy demonstrates that Al2O3 and AlN nanoparticle agglomerates are formed in both environments; indicating that the presence of trace O2 can lead to Al2O3 nanoparticle formation. The present results highlight that the availability of O2 in the ambient gas significantly impacts spectral signatures, cluster size, and nanoparticle agglomeration behavior. These results are relevant to understanding debris formation in an explosion event, and interpreting data from forensic investigations.