Free Metal Research Articles

Biomass-Derived Organonanomaterials as Contrast Agents for Efficient Magnetic Resonance Imaging.

Magnetic resonance imaging (MRI) is a popular imaging tool that is valuable for the early detection and monitoring of malignancies because it does not involve radiation and is noninvasive. Metal-based contrast agents (CAs) are commonly used in clinical settings despite concerns about the toxicity of free metals. Therefore, finding alternative nontoxic imaging probes is vital. In this work, we have synthesized and effectively utilized sustainable biomass lignin-based all-organic nanoconjugates linked with nitroxide radicals as MRI CAs. Lignin grafted with poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl) (LPGT) exhibits a longitudinal relaxivity of 0.54 mM-1 s-1. LPGT shows exceptional characteristics, including resistance to reduction and nontoxicity toward living organisms. LPGT displays enhanced MRI contrast in the BALB/c mouse model for a duration exceeding 4.35 h. Our primary goal is to design MRI agents that are exceptionally effective sustainable biomass-derived materials and do not require the use of metals. Nicely, LPGT offers adequate contrast enhancement at 5-fold lower (0.020 mmol/kg) than the standard dose (0.1 mmol/kg), easing worries about toxic metal buildup. Consequently, LPGT shows promise as a feasible CA for metal-free MRI.

A stable dual-function lanthanum MOF: Simultaneous CO2 capture and catalysis

Carbon dioxide (CO2) capture has become a hot topic in recent years because of global warming issues. However, most research has focused primarily on gas capture, with limited methods available for achieving both CO2 capture and conversion within a single material. Here, we synthesized FMU-101, a metal-organic framework (MOF) with metal-open sites, through the self-assembly of [1,1′-Biphenyl]-3,3′,5-tricarboxylic acid and lanthanide ions in a solvothermal environment. FMU-101 features hexagonal one-dimensional pores with a diameter of 1.4 nm. The presence of free dimethylamine cations and metal open sites in the channel contributes to its remarkable capability for selectively enriching CO2 from CO2/CH4 mixtures in dynamic breakthrough experiments. Furthermore, the metal-open sites in FMU-101 play a crucial role in CO2 fixation, serving as effective catalytic sites for converting the adsorbed CO2 into high-value chloropropylene carbonate, a versatile chemical intermediate. The segregation and conversion mechanisms were further elucidated through density-functional theory (DFT) calculations and Grand Canonical Monte Carlo (GCMC) simulations, which highlighted the critical role of metal-open sites in CO2 adsorption and transformation.

Green tea (Camellia sinensis L.) potential to liver of hyperuricemia rats (Rattus norvegicus) fed with high purine diet

Uric acid is produced in tissues containing xanthine oxidases, like the small intestine and liver, as involved in the purine metabolism of adenine and guanine. High uric acid levels cause damage to cell membranes due to the lipid peroxidase chain reaction. Foods containing high purines will activate the xanthine oxidase (XOD), causing an increase in free radicals. Free radicals attack polyunsaturated fatty acids (PUFA) by forming lipid peroxides. PUFA molecules contain multiple double bonds, which make them susceptible to oxidation by reactive oxygen species (ROS), such as free radicals. PUFA will be broken into simple compounds such as pentane, ethane, and aldehydes, leading to malondialdehyde (MDA) formation. High MDA levels illustrate the process of cell membrane oxidation leading to cell membrane damage. Hyperuricemia is often treated using synthetic drugs such as allopurinol; however, it can cause side effects. Some people will choose medicinal plants with minimal side effects. Green tea (Camellia sinensis L.) contains many polyphenol antioxidants, especially flavonoids, which also have a strong antioxidant effect by exerting multiple mechanisms such as inhibiting several enzymes, including antiphospholipid peroxidase, free radical scavengers, metal bonds, and xanthine oxidase (XOD). Statistical analysis results proved that green tea with a dose of 600 mg/kg BW could decrease the level of MDA in the liver by 84.87% (p 0.01) and reduce the activity of XOD by 35.36% (p 0.01). Taken together, green tea can improve liver histopathology.

An Evaluation of Metal Binding Constants to Cell Surface Receptors in Freshwater Organisms, and Their Application in Biotic Ligand Models to Predict Metal Toxicity

Biotic ligand models (BLMs) predict the toxicity of metals in aquatic environments by accounting for metal interactions with cell surface receptors (biotic ligands) in organisms, including water chemistry (metal speciation) and competing cations. Metal binding constants (log KMBL values), which indicate the affinity of metals for cell surface receptors, are fundamental to BLMs, but have only been reported for a few commonly investigated metals and freshwater species. This review evaluated literature toxicity and uptake data for seven key metals (cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), uranium (U), and zinc (Zn)) and four key competing cations (protons (H), calcium (Ca), magnesium (Mg), and sodium (Na)), to derive average metal binding constants for freshwater organisms/taxa. These constants will improve current BLMs for Cd, Cu, Ni, Pb, and Zn, and aid in developing new BLMs for Co and U. The derived metal binding constants accurately predicted metal toxicity for a wide range of freshwater organisms (75–88% of data were within a factor of two and 88–98% of data were within a factor of three of the ideal 1:1 agreement line), when considering metal speciation, competing cations and the fraction of cell receptors ((fC)M50%) occupied by the metal at the median (50%) effect concentration (EC50). For many organisms, toxicity occurs when 50% of cell surface receptors are occupied by the metal, though this threshold can vary. Some organisms exhibit toxicity with less than 50% receptor occupancy, while others with protective mechanisms show reduced toxicity, even with similar log KMBL values. For Cu, U, and Pb, the toxic effect of the metal hydroxide (as MOH+) must be considered in addition to the free metal ion (M2+), as these metals hydrolyse in circumneutral freshwaters (pH 5.5 to 8.5), contributing to toxicity.

Non-consumable gamma-cyclodextrin additive constructing anti-solvation interphase realizing dendrites free and high-performance lithium metal batteries

Relying on surpassing high theoretical capacity (3,865 mAh/g) and the lowest relative electrode potential (0 V vs. metallic Li), lithium metal batteries (LMBs) have been regarded as the “holy grail” of next-generation energy storage technology. Whereases, the instability of pristine solid electrolyte interphase (SEI) layers and the disorderly growth of lithium dendrites are still significant challenges to the commercialisation of LMBs. In this study, a novel approach is introduced to homogenise Li deposition by incorporating an environmentally friendly electrolyte additive, gamma-cyclodextrin (γ-CD), in ether-based electrolytes. Through host-guest interactions, γ-CD additives not only form inclusion complexes to improve Li+ transference number to 0.86 but also encapsulate TFSI- anions and other solvent molecules within the “cavity effect” to relieve unfavourable solvent effect. Electrochemical characterisations demonstrate that introducing 1 wt% γ-CD elevates the oxidation decomposition voltage of ether electrolytes to 4.15 V, thereby inhibiting the decomposition of ether electrolytes and reducing the fracture of SEI layers. According to reduce the nucleate potential, the Li//Cu half battery exhibits improved stability for 100 cycles, with an improved average Coulombic efficiency (CE) maintained above 98.4 %. Even if applied at high current densities of 5.0 mA cm−2 for a capacity of 1.0 mAh cm−2, the Li//Li symmetric battery can cycle for over 800 h, and the Li//Li4Ti5O12 (LTO) full battery retains 98.8 % of the initial capacity after 1,400 cycles.

Antioxidant, antiacetylcholinesterase and apoptotic effects of essential oil of Isodon wightii (Bentham) H. Hara

Isodon wightii (Bentham) H. Hara is well known for aromatic essential oil. This is the first study aimed to evaluate antioxidant, antiacetylcholinesterase and apoptotic potential of I. wightii oil. DPPH scavenging, metal ion chelation and antiacetylcholinesterase activities were carried out for the extracted essential oil from the leaves of I. wightii. Cytotoxic effect on HeLa cells was studied by MTT assay and its apoptotic potential was determined by Acridine Orange/Ethidium Bromide and Hoechst33258 stains. A significant free radical scavenging and metal ion chelation were determined for oil. Acetylcholinesterase inhibition was recorded with IC50 value of 7.864 µg/mL. The cytotoxic effect of oil on HeLa cells was calculated with IC50 value of 13.264 µg/mL. High level of apoptosed cells were observed at 100 µg/mL oil treated cells. The results of the study emphasise the medicinal importance of I. wightii essential oil which could be a prominent plant based cancer therapeutic agent.

Photo-assisted Fenton degradation of tetracycline hydrochloride with magnetic Fe3S4/CuS composite

In recent years, semiconductor materials have gradually become popular through photodegradation of organic pollutants, and the semiconductor materials Fe3S4 and CuS have their own shortcomings. To make both materials useful, Fe3S4/CuS composites were prepared by hydrothermal method and degradation experiments were carried out using tetracycline hydrochloride (TCH) as a simulated pollutant. The effects of factors such as the mass ratio of Fe3S4 to CuS, temperature, pH changes, the consume of H2O2, and the amount of catalyst added on the degradation of TCH were explored. At room temperature, the Fe3S4/CuS composites exhibit good Fenton degradation efficiency. The F1C1.5 composite (mass ratio of Fe3S4 to CuS is 1:1.5) achieved 74.60 % at pH 4.0 within one hour. Subsequently, the free radical capture experiments and metal leaching experiments were conducted, and it was found that the active substance h+ played a major role. At the same time, the F1C1.5 composite shows stability, allowing for a lower concentration of iron leaching and having high catalytic activity after 5 cycles. These degradation properties, together with the ease of fabrication of the catalyst, will facilitate the practical application of this system in the continuous removal of TCH.

Transcriptome signature of juvenile Litopenaeus vannamei cultured under different salinity levels in response to Vibrio harveyi infection

Although the widely cultured Litopenaeus vannamei is highly tolerant to varying salinity levels, the rapid fluctuation of abiotic and biotic factors due to climatic changes may become stressors to the shrimp's physiology, resulting in impaired immunity and increased disease susceptibility. This study aimed to investigate the combined effects of both factors towards L. vannamei at transcriptomic level. L. vannamei were cultured at three different salinity levels (5 ppt, 20 ppt and 30 ppt) for 60 days and were challenged with Vibrio harveyi. RNA-seq analysis was conducted on the hepatopancreas to assess the differential expressed genes (DEGs) in both control and V. harveyi infected groups. Our results revealed 5,725 DEGs was observed in shrimp reared at 5 ppt, 3,643 DEGs at 20 ppt and 1,560 DEGs at 30 ppt. Most DEGs were identified to be associated with osmoregulation and transport activities, immune and stress regulation, nutrient metabolism, growth, chitin binding, gonadal development, and metal ion binding and toxicity. We identified that shrimp cultured at intermediate salinity of 20 ppt exhibits the greatest immunity level after infection by V. harveyi, given that low salinity (5 ppt) may augment the free ion metal toxicity, resulting in higher disease susceptibility. Both V. harveyi and salinity stress function together or separately to activate a wide range of immune and stress regulatory genes, which could be potential candidate markers for future RNAi and knockdown research in developing efficient prophylactic management strategies for L. vannamei.

N-doped polyacrylonitrile carbon fiber interlayer for uniform and dendrite free Zn metal battery

The aqueous zinc-ion battery’s (AZBs) inherent safety and inexpensive cost make it an attractive prospect for next-generation energy storage. Nevertheless, AZBs are presently troubled by the formation of Zn dendrites and unwanted side-reactions, which can lead to cycling instability and premature collapse. This study demonstrates the fabrication of an N-doped polyacrylonitrile (PAN) carbon fiber (PCF) network with ionic conductivity using the electrospinning of a PAN solution followed by thermal treatment. Zn plating and stripping behavior can be controlled by using a three-dimensional PCF with a polar functional group as an interlayer covering on the zinc anode. This allows for partially deposited zinc to be accommodated, which ultimately results in zinc dendrite-free deposition on the zinc anode. This phenomenon is initially proven in Zn@PCF symmetric cells, and then it is demonstrated further in Zn@PCF/MnO2 whole cells, where the dendritic Zn anode surfaces become completely smooth and devoid of any features. This results in a charging and discharging cycle that is far longer than one would normally experience. The findings of this study offer a viable path toward the development of dendrite-free AZBs with great performance.

Rooted in therapeutics: comprehensive analyses of Cannabis sativa root extracts reveals potent antioxidant, anti-inflammatory, and bactericidal properties.

Following the legalization of recreational Cannabis in Canada in 2018, the associated waste, including Cannabis roots, has significantly increased. Cannabis roots, comprising 30%-50% of the total plant, are often discarded despite their historical use in Ayurvedic medicine for treating inflammatory and infectious disorders. This study evaluates the phytochemical and therapeutic properties of Cannabis root extracts from a high tetrahydrocannabinolic acid, low cannabidiolic acid cultivar (variety Alien Gorilla Glue). We performed ultra high-performance liquid chromatography coupled with mass spectrometry (UPLC-QTOF-MS) to identify the chemical components of the Cannabis roots. Extracts using water, ethanol and acid-base solvents were tested for antioxidant activity through free radical scavenging, metal chelation, and lipoperoxidation inhibition assays. Mitochondrial membrane protection was assessed using flow cytometry with the MitoPerOx probe in THP-1 monocytic leukemia cells. Anti-inflammatory potential was evaluated by measuring interleukin-6 levels in lipopolysaccharide-stimulated THP-1 cells. Bactericidal/fungicidal efficacy against Escherichia coli, Staphylococcus aureus, and Candida albicans was determined using the p-iodonitrophenyltetrazolium assay. Additionally, we investigated the anticholinesterase activity of Cannabis root extracts, given the potential role of plant alkaloids in inhibiting cholinesterase, an enzyme targeted in Alzheimer's disease treatments. UPLC-QTOF-MS analysis suggested the presence of several phenolic compounds, cannabinoids, terpenoids, amino acids, and nitrogen-containing compounds. Our results indicated significant antioxidant, bactericidal, and anticholinesterase properties of Cannabis root extracts from both soil and hydroponic cultivation. Extracts showed strong antioxidant activity across multiple assays, protected mitochondrial membrane in THP-1 cells, and exhibited anti-inflammatory and bactericidal/fungicidal efficacy. Notably, soil-cultivated roots displayed superior anti-inflammatory effects. These findings demonstrate the remarkable antioxidant, anti-inflammatory, and anti-microbial activities of Cannabis roots, supporting their traditional uses and challenging their perception as mere waste. This study highlights the therapeutic potential of Cannabis roots extracts and suggests avenues for further research and application.

Polyoxometalate-Ionic Liquids for Mitigating the Effects of Iron Gall Ink Corrosion on Cellulosic Supports.

Iron gall ink (IGI), renowned for its indelibility, was the most important writing ink in the Western world from the 15th to the late 19th century. However, it is now known that IGIs induce acid-catalyzed hydrolysis and iron-catalyzed oxidation of the cellulose in historical paper documents. These mechanisms of deterioration cause significant damage to the writing support materials, including color alteration and burn-through appearance, and in the worst scenarios, physical disintegration of the supports. Minimally invasive, long-term effective conservation treatments that tackle the underlying mechanisms of IGI degradation and their corrosion effects are yet to be developed. This study introduces the deployment of hydrophobic and anticorrosive polyoxometalate-ionic liquids (POM-ILs) as colorless coatings to counteract IGI-corrosion of cellulosic supports. Model IGI-containing papers (mockups) were prepared, coated with POM-ILs, and artificially aged to assess the compatibility of POM-ILs with IGI-containing documents. Comprehensive monitoring using colorimetric and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM/EDS) analyses showed minimal interference with the aesthetic properties and morphology of the IGI mockups. In addition, polyoxometalates (POMs) with vacant metal atom sites in the cluster shell can be used to coordinate free transition metal ions. The ability of a monolacunary Keggin-type polyoxotungstate to coordinate free Fe(II) from IGI solution was demonstrated using UV-vis analysis. This led to the formation of a dimeric species, [(SiW11O39Fe)2O]K12·28H2O, which was characterized by single-crystal X-ray diffraction. Altogether, this study points to POM-ILs as promising protective coatings for effectively preserving historical IGI-written heritage.

Structure and dimerization properties of the plant-specific copper chaperone CCH

Copper chaperones of the ATX1 family are found in a wide range of organisms where these essential soluble carriers strictly control the transport of monovalent copper across the cytoplasm to various targets in diverse cellular compartments thereby preventing detrimental radical formation catalyzed by the free metal ion. Notably, the ATX1 family in plants contains two distinct forms of the cellular copper carrier. In addition to ATX1 having orthologs in other species, they also contain the copper chaperone CCH. The latter features an extra C-terminal extension whose function is still unknown. The secondary structure of this extension was predicted to be disordered in previous studies, although this has not been experimentally confirmed. Solution NMR studies on purified CCH presented in this study disclose that this region is intrinsically disordered regardless of the chaperone’s copper loading state. Further biophysical analyses of the purified metallochaperone provide evidence that the C-terminal extension stabilizes chaperone dimerization in the copper-free and copper-bound states. A variant of CCH lacking the C-terminal extension, termed CCHΔ, shows weaker dimerization but similar copper binding. Computational studies further corroborate the stabilizing role of the C-terminal extension in chaperone dimerization and identify key residues that are vital to maintaining dimer stability.

Transition Metal Oxide/Sulfide on the Ni Foam for Electrocatalytic UOR & OER

Water electrolysis is an important technology related to the energy conservation, is a promising technology. Currently, one of the key efforts is to improve the efficiency and reduce the cost of water electrolysis, in particular, the anodic oxygen evolution reaction (OER). Nobel-metal free OER catalyst or alternative urea oxidation reaction (UOR) is thus favored. Due to the advantages of enhance charge transfer and desirable charge redistribution, we have investigated nobel-metal free transition metal oxide/sulfide heterostructure UOR electrocatalyst. Co-Ni based metal heterostructure is synthesized using a simple two-step hydrothermal method. The resulting samples are examined using X-ray diffractometer, Scanning electron microscopy, X-ray photoelectron spectroscopy and the Inductively coupled plasma will used as the material analysis. Electrochemical performance is evaluated using linear sweep voltammetry, electrochemical impedance spectroscopy, cyclic voltammetry, and electrochemical active surface area. Moreover, the electrocatalyst is also evaluated as OER catalysts. The relation between the material characteristics and the electrochemical performance is discussed.

Investigating the Effect of KOH Feed Concentration on a Stainless-Steel Anode Using a 3-Electrode Anion Exchange Water Electrolyser Cell Set-up

Anion-exchange membrane water electrolysers (AEM-WE) have the potential to lower the capital cost of hydrogen production compared to proton-exchange membranes water electrolysers (PEM-WE). The alkaline conditions of AEM-WE result in: (i) a kinetically more favourable oxygen evolution reaction (OER), (ii) the ability to use platinum group metal (PGM)-free metal catalysts, and (iii) reduced cell component costs because of the less corrosive operating conditions. However, AEM-WE is held back from commercialisation by limited current density and durability.1 Compared to conventional alkaline water electrolysis, AEM-WEs have the advantage of lower ohmic resistance thanks to a solid polymer electrolyte which provides intrinsic ionic conductivity instead of relying on 6 M KOH and a porous separator. Most studies show, however, that a dilute KOH feed (< 1 M), rather than pure water, is critical to reaching a high current density in AEM-WE. Varying the concentration of KOH in the feed solution impacts catalyst activity and membrane resistance thereby making performance measurements in AEM-WE more complex. Moreover, the overpotential for the alkaline hydrogen evolution reaction (HER) is significant due to its sluggish kinetics. This means full-cell measurements are insufficient for understanding the behaviour of OER and HER catalysts in AEM-WE. It is therefore crucial to make half-cell measurements in AEM-WEs to decouple the effect of the anode and cathode electrocatalysts from the overall cell performance.In this context, our group recently demonstrated a 3-electrode, 5 cm2 membrane electrode assembly electrolyser cell2 that uses a reference electrode to decouple the anode and cathode contributions to the overall water splitting reaction. The technique was demonstrated for AEM-WEs and is soon to be published by Malone et al. (Figure 1A)3. In this study, we aimed to investigate the effect of KOH concentration in the feed solution on OER by using this 3-electrode cell setup. We used a stainless steel (SS)-felt at the anode as both catalyst and porous transport layer (PTL) in different concentrations of KOH feed while maintaining Pt/C as the cathode catalyst. We also repeated the tests with various anode catalyst layers (IrOx, NiFeOx) in combination with the SS PTL. For each test, full and half-cell polarisation curves and impedance spectroscopy were recorded before and after a sixteen-hour durability test at 1 A cm-2 at 40 °C. The results revealed the catalytic significance of the SS-felt in 1 M KOH as recently shown by Chen et al.4 Additionally, we demonstrated how the SS masks the performance of an IrOx catalyst layer in 1 M KOH. Reducing the KOH concentration to 0.18 M resulted in ≈ 7 % increase in the overall cell voltage at 1 A cm-2 (from 1.88 V to 2.00 V at 40 °C in Figure 1B). Aside from the ≈ 35 % increase in membrane resistance (e.g. 180 to 240 mΩ cm2 at 0.9 A cm-2) in 0.18 M KOH, the higher overpotential arose from the anode (Figure 1C), which could be attributed to the higher OER overpotential of SS-felt in a lower pH solution. Meanwhile, there was no appreciable change in cathode overpotential when the KOH concentration was reduced. These findings demonstrate the importance of 3-electrode cell measurements for understanding the impact of each component in an AEM-WE cell. Furthermore, the results reveal that both the choice of PTL material as well as the concentration of feed solution should be considered when testing different catalysts in AEM-WE.

BIODIVERSITY OF CELLULOLYTIC BACTERIA ISOLATED FROM FERMETODEGE FOR RUMINANTS

ARTICLE HIGLIGHTS- Fermetodege as a source of cellulolytic bacteria that degrade cellulosic materials.- Enhances ruminant feed by improving palatability and digestibility.- Utilizes water hyacinth, reducing invasive plant spread and supporting ecosystems.- Bioprospecting reveals new bacteria for effective fermentation starter development.ABSTRACTFermetodege is a name of fermented ruminant feed produced from free heavy metals water hyacinth, rice bran, and corn cobs. Its quality, as well as the fermentation process, are affected by numerous factors, such as the diversity, evenness, and dominance of indigenous cellulolytic bacterial species. A proper understanding of these influential factors is needed to improve the quality of the fermented feed. Therefore, this study aims to evaluate the diversity, evenness, and dominance of cellulolytic bacteria isolated from fermetodege. The cellulolytic activity of the isolates was tested by observing their growth on the carboxymethylcellulose (CMC) media. Isolates with cellulolytic activity formed a clear zone after the colonies were soaked with 0.1% Congo red and rinsed with 1 M NaCl. The Shannon-Weiner's diversity and evenness indexes, as well as Simpson's species dominance, were then calculated. The result showed that the Shannon-Weiner’s diversity index ranged from 0.6849 to 1.8173, and it was categorized as medium. The evenness index was between 0.7778 and 0.9983, which indicates a stable distribution of species. Meanwhile, the Simpson’s species dominance ranged from 0.1835 to 0.5082, which implies that none of the species was dominant. These results show that fermetodege is potentially a source of bacterial isolates and can be used as a fermentation consortium starter.

Efficient removal and stepwise recovery of various heavy metals from water by using calcium carbonate with different activity

Heavy metals in wastewater have caused serious environmental contamination in the world. However, a key challenge with the most effective solution through chemical precipitation is the high pH of in the effluent by the use of lime. Herein, we propose a strategy using highly active calcium carbonate (HACC) for enhancing its slow-release activity, which efficiently removes heavy metal contamination while avoiding high pH of the effluent. The HACC demonstrate a removal of more than 99 % for Cd(II), Cu(II), Zn(II) and Pb(II) from the composite contaminated water within 50 min, while maintaining the pH of the effluent close to neutral. In addition, mechanistic analyses unveil that the free heavy metals in different solutions combine with OH– and CO32– released from HACC in different precipitation behaviors to form their respective precipitates, thereby discovering the mechanism of regulating the precipitation rates of different heavy metals by controlling the activity of calcium carbonate. Based on it, the stepwise recovery of heavy metals was realized by adjusting the calcium carbonates with different activity. The present work provides guidance for gentle and efficient removal of heavy metal pollution in water bodies and inspires the future development of recovery of heavy metals.

Effect of aluminum particles on the insulating properties of C4F7N/CO2 mixed gas

The C4F7N/CO2 mixed gas is most expected to replace SF6 in high-voltage power equipment, and the generation of free metal particles in gas-insulated equipment is unavoidable and highly susceptible to inducing insulation failures. In this paper, the effects of flaky, spherical, and mixed shape aluminum particle defects on the breakdown characteristics of C4F7N/CO2 mixed gas are investigated and compared to those of SF6 under the same conditions. The experimental results show that the effect of particle defects on the insulating properties of C4F7N/CO2 gas mixtures is visualized by the fact that particle defects reduce the breakdown voltage of C4F7N/CO2 gas mixtures, increase their stochasticity, and reduce the enhancement of the insulating properties of C4F7N/CO2 gas mixtures by increasing the air pressure. The greater the number of particles, the greater is the degree of influence. Comparison of the SF6 and C4F7N/CO2 gas mixtures reveals that, in the case of flake defects, increasing the air pressure improves the insulation performance of the SF6 gas better than that of the C4F7N/CO2 gas mixture. Under the condition of the same number of particles, the larger the proportion of spherical particles in the hybrid particles, the smaller is the influence of metal particles on the C4F7N/CO2 mixed gas and on SF6 gas.

Effect of cobalt on Microstructure and toughness properties of 9Cr-1.8W-0.4Ni-xCo weld metal

In this research, microstructural characterization and mechanical properties of 9%Cr, 0.4%Ni (including W and Mo) steel weld metal with alloyed cobalt were investigated. Due to their strong creep resistance, oxidation resistance, and low thermal expansion, 9%Cr steels are used in nuclear power plants, petrochemical industries, and fossil fuel-powered power plants that operate in high temperature conditions. In this context, weld metals comprising 0.5 %, 1 % and 1.5 % cobalt and cobalt-free weld metal were produced by SMAW (shielded metal arc welding) technique. Microstructure of the weld metals were characterized with optical microscope (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Also, XRD analysis was performed on the bulk samples and precipitated carbide/nitride phases extracted from the weld metals. In addition, differential scanning calorimetry (DSC) was used to determine the phase transformations. Thermo-Calc modeling study was also performed. Hardness, tensile and Charpy-V impact tests were carried out to determine the mechanical properties. The hardness did not change significantly when cobalt up to 1.5 % in the weld metal. However, with the increase of cobalt, the yield and tensile strength increased without affecting the elongation value too much. In the Charpy impact tests performed at different temperatures (−40 °C, −20 °C, +20 °C, +40 °C, +60 °C), the amount of cobalt increased toughness, especially at +40 and + 60oC temperatures. Ductile brittle transformation temperature (DBTT) of the weld metal with 1.5 % Co decreased from 29 °C to 15 °C compared to cobalt free weld metal. It is thought that this may be caused by the further separation of C, Cr and W from the matrix through forming precipitate by the cobalt effect. Besides the mechanical properties, microstructure was also affected by adding Co with inhibition of delta ferrite formation which decrease the toughness. Curie temperature increased with increasing cobalt content detected by DSC.

Toxicity of rare earth elements (REEs) to marine organisms: Using species sensitivity distributions to establish water quality guidelines for protecting marine life

A lack of chronic rare earth element (REE) toxicity data for marine organisms has impeded the establishment of numerical REE water quality benchmarks (e.g., guidelines) to protect marine life and assess ecological risk. This study determined the chronic no (significant) effect concentrations (N(S)ECs) and median-effect concentrations (EC50s) of eight key REEs (yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), gadolinium (Gd), dysprosium (Dy) and lutetium (Lu)) for 30 coastal marine organisms (encompassing 22 phyla and five trophic levels from temperate and tropical habitats). Organisms with calcifying life stages were most vulnerable to REEs, which competitively inhibit calcium uptake. The most sensitive organism was a sea urchin, with N(S)ECs ranging from 0.64 μg/L for Y to 1.9 μg/L for La and Pr, and EC50s ranging from 4.3 μg/L for Y to 14.4 μg/L for Pr. Conversely, the least sensitive organism was a cyanobacterium, with N(S)ECs ranging from 121 μg/L for Y to 469 μg/L for Pr, and EC50s ranging from 889 μg/L for Y to 3000 μg/L for Pr. Median sensitivity varied 215-fold across all organisms. The two-fold difference in median toxicity (μmol/L EC50) among REEs (Y ∼ Gd > Lu ∼ Nd ∼ Dy ∼ Ce > La ∼ Pr) was attributed to offset differences in binding affinity (log K) to cell surface receptors and the percentage of free metal ion (REE3+) in the test waters. The toxicity (EC50) of the remaining REEs (samarium, europium, terbium, holmium, thulium and ytterbium) was predicted using a combination of physicochemical data and measured EC50s for the eight tested REEs, with good agreement between predicted and measured EC50s for selected organisms. Numerical REE water quality guidelines to protect marine life were established using species sensitivity distributions (e.g., for 95 % species protection, values ranged from 1.1 μg/L for Y to 3.0 μg/L for La, Pr or Lu).

Environmentally persistent free radicals and other paramagnetic species in wildland-urban interface fire ashes

Wildland-urban interface (WUI) fires consume fuels, such as vegetation and structural materials, leaving behind ash composed primarily of pyrogenic carbon and metal oxides. However, there is currently limited understanding of the role of WUI fire ash from different sources as a source of paramagnetic species such as environmentally persistent free radicals (EPFRs) and transition metals in the environment. Electron paramagnetic resonance (EPR) was used to detect and quantify paramagnetic species, including organic persistent free radicals and transition metal spins, in fifty-three fire ash and soil samples collected following the North Complex Fire and the Sonoma-Lake-Napa Unit (LNU) Lightning Complex Fire, California, 2020. High concentrations of organic EPFRs (e.g., 1.4 × 1014 to 1.9 × 1017 spins g−1) were detected in the studied WUI fire ash along with other paramagnetic species such as iron and manganese oxides, as well as Fe3+ and Mn2+ ions. The mean concentrations of EPFRs in various ash types decreased following the order: vegetation ash (1.1 × 1017 ± 1.1 × 1017 spins g−1) > structural ash (1.6 × 1016 ± 3.7 × 1016 spins g−1) > vehicle ash (6.4 × 1015 ± 8.6 × 1015 spins g−1) > soil (3.2 × 1015 ± 3.7 × 1015 spins g−1). The mean concentrations of EPFRs decreased with increased combustion completeness indicated by ash color; black (1.1 × 1017 ± 1.1 × 1017 spins g−1) > white (2.5 × 1016 ± 4.4 × 1016 spins g−1) > gray (1.8 × 1016 ± 2.4 × 1016 spins g−1). In contrast, the relative amounts of reduced Mn2+ ions increased with increased combustion completeness. Thus, WUI fire ash is an important global source of EPFRs and reduced metal species (e.g., Mn2+). Further research is needed to underpin the formation, transformation, and environmental and human health impacts of these paramagnetic species in light of the projected increased frequency, size, and severity of WUI fires.