Search Results (608)

In order to satisfy the requirement for lightweight, highly reliable sprayable silicone rubber insulation material (SASI) in next-generation spacecraft, and to achieve a synergistic balance among the sprayability, mechanical properties and ablation resistance of SASI, this paper describes the preparation of nanostructured magnesium silicate (n-MS) via a hydrothermal method and systematically investigates its effects on the sprayability, mechanical properties and ablation resistance of sprayable SASI. The findings suggest that when the n-MS loading is set at 15 parts, the linear ablation rate and mass ablation rate of the SASI under oxy-acetylene conditions are as low as 0.10 mm/s and 0.07 g/s, respectively, representing reductions of 41.8% and 67.1% compared to the unmodified samples. Building upon this enhancement in ablation resistance, the tensile strength was also increased by 3.70 MPa, representing a 19.3% increase. It is crucial to note that during the spraying process, the viscosity of the silicone rubber system remained within a narrow range of 540–550 mPa·s following the addition of this filler. This finding indicates that the introduction of n-MS had no significant adverse effect on the spraying process. In summary, n-MS has been demonstrated to enhance the mechanical strength and ablation resistance of silicone rubber materials while maintaining adequate spray coating performance. In comparison with conventional filled silicone rubbers, the sprayable silicone rubber insulating material developed in this study provides a new material basis for the future lightweight and intelligent development of aerospace engines. Full article

The origin of life is commonly discussed within two competing conceptual frameworks: the metabolism-first and information-first hypotheses. While each emphasizes a different defining property of early life, modern biochemistry reveals a fundamental interdependence between metabolic processes and genetic information transfer, leading to a persistent chicken-and-egg problem. In this study, we investigate a prebiotically plausible reaction system that enables the concurrent formation of molecular precursors associated with both frameworks. Under simulated Hadean hydrothermal conditions, acetylene, ammonia, cyanide, and carbon monoxide were reacted in aqueous solution in the presence of transition metal sulfides. Using gas chromatography–mass spectrometry combined with stable isotope labeling, we demonstrate the simultaneous formation of the nucleobase uracil and the amino acids alanine and aspartic acid. Isotopic incorporation patterns allow reconstruction of the underlying reaction pathways and confirm the contribution of all starting materials to product formation. While amino acids are produced continuously over the observed period in significantly higher yields than uracil, uracil formation exhibits a pronounced time-dependent maximum after three days. Variations in pH, reaction time, and metal sulfide catalysts modulate product yields but do not prevent the parallel emergence of both molecular classes. These findings support a scenario in which proto-metabolic chemistry and molecular precursors of genetic information could have arisen simultaneously within a shared geochemical setting. The results provide experimental support for a coupled origin of metabolism and transcriptional building blocks, offering a potential resolution to the dichotomy between metabolism-first and information-first models of early life. Full article

Baby maize (Zea mays L.) is widely cultivated across Asia due to its short growth cycle and adaptability to diverse agroecological conditions. However, its production is frequently constrained by low soil fertility, leading to the excessive use of chemical fertilizers, which in turn contributes to environmental degradation. Endophytic bacteria with the ability to fix atmospheric nitrogen and solubilize inorganic phosphate represent a sustainable alternative for improving nutrient availability. This study aimed to isolate and characterize endophytic bacteria exhibiting dual nitrogen-fixing and phosphate-solubilizing capabilities from baby maize roots. A total of ten bacterial isolates were obtained and screened using nitrogen-free Burk medium and NBRIP medium. Among these, strain CMB2 demonstrated superior functional traits. Molecular identification based on 16S rRNA gene sequencing confirmed that the isolate belongs to Bacillus stercoris. In vitro assays revealed that B. stercoris CMB2 exhibited significant nitrogenase activity, as determined by the acetylene reduction assay, and strong phosphate-solubilizing ability, indicated by a clear halo zone and a high solubilization index. These findings suggest that B. stercoris CMB2 is a promising multifunctional endophytic bacterium for enhancing nutrient availability under controlled conditions. Further validation under greenhouse and field conditions is required to assess its potential for improving plant growth and nutrient uptake in baby maize. Full article

To meet the requirements of flexibility and high performance for energy storage devices in flexible wearable electronic equipment, the MnO₂/acetylene black composite flexible cathodes is fabricated via 3D printing technology and the aqueous manganese-based zinc-ion flexible batteries are assembled. Based on bending and torsion mechanical tests, and the electrochemical tests, the optimal 3D printing electrode structure was determined. The micromorphology of the electrode after mechanical tests shows that when the printed lines of the upper and lower layers form a 30° angle, the electrode sheet exhibits the least damage. Electrochemical tests indicated that it had an ohmic resistance of 2.052 Ω, an interfacial charge transfer resistance of 141.1 Ω, a specific capacity of 103 mAh/g at 50 mA/g, and a specific capacity of 65 mAh/g at 500 mA/g. Compared with traditional coated electrodes, the 3D-printed electrode showed significantly improved diffusion coefficient, conductivity, and cycle stability. The assembled 3D-printed flexible battery could stably power a 1.5 V LED bulb under flat, bent, and twisted states. It provides a feasible solution for the development of high-performance flexible energy storage devices. Full article

Monoenoic fatty acids (MUFAs), defined by the presence of a single carbon–carbon double bond within a long aliphatic chain, constitute a structurally diverse and ecologically significant class of lipids widely distributed in aquatic organisms. In marine and freshwater environments, MUFAs are fundamental components of membrane phospholipids and storage lipids, where mono-unsaturation modulates melting point, lipid packing, and bilayer dynamics, enabling homeoviscous adaptation to fluctuations in temperature, pressure, salinity, and oxygen availability. Positional and geometric isomerism (e.g., cis-Δ5, Δ7, Δ9, Δ11, Δ13, and trans forms) further enhances biochemical diversity, providing sensitive chemotaxonomic markers and indicators of trophic transfer across food webs. In addition to common straight-chain monoenes, rare methyl-branched, cyclopropane-containing, and acetylenic derivatives occur in specialized aquatic taxa, reflecting evolutionary adaptation and ecological niche differentiation. Computational QSAR analyses suggest that monoenoic fatty acids and their unusual analogues occupy bioactivity spaces associated with lipid metabolism regulation, vascular and inflammatory modulation, antimicrobial defense, and membrane stabilization. This review integrates structural chemistry, biosynthesis, ecological distribution, trophic dynamics, and predicted biological activity of monoenoic fatty acids in aquatic systems, highlighting their dual role as adaptive membrane constituents and as biologically active mediators linking molecular lipid architecture to hydrobiological function and environmental change. Full article

Core–shell metal–organic framework (MOF) composites, owing to their unique structural advantages, have emerged as a prominent research focus in the field of chemistry, advanced materials and chemical engineering. By integrating MOFs with other functional components such as MOFs, covalent organic frameworks (COFs), metal oxides, carbon materials, ionic liquids or polymers into synergistic heterogeneous architectures, coreshell MOFs can markedly enhance physicochemical stability and enable diversified functional performances. This work provides a systematic overview of the major construction strategies for these materials, including in situ growth, self-templating, seed-mediated methods, one-pot synthesis and post-synthetic modification. It also summarizes recent applications in catalysis (thermal, electrocatalytic and photocatalytic processes) as well as gas adsorption and separation (such as CO₂ capture from flue gas, natural gas purification and acetylene separation). The final section discusses future research directions, including a deeper understanding of interfacial growth mechanisms, the development of green and scalable synthesis routes, the validation of engineering-oriented applications, and the integration of machine learning with high-throughput computation for structural prediction and accelerated materials screening, thereby providing important guidance for the development of high-performance core–shell MOFs. Full article

Different rhizobial strains can lead to distinct symbiotic phenotypes in alfalfa, yet molecular differences at the mature nodule stage remain unclear. Here, we analyzed 21-day post-inoculation (dpi) nodules induced by strains WE2 and WWL2. We measured nitrogenase activity (acetylene reduction assay, ARA) and performed dual RNA-seq to compare gene expression in both the alfalfa host and the rhizobia. On the host side, WE2-induced nodules showed higher expression of mature nodule marker genes (ENOD93 and leghemoglobin (Lb) genes) and higher expression of genes encoding SWEET transporters and amino acid and peptide transporters. Host differentially expressed genes were enriched in pathways related to transmembrane transport, redox and heme-related functions, and processes linked to maintaining microaerobic conditions. On the rhizobial side, WE2 nodules showed higher expression of genes involved in microaerobic respiration and nitrogen fixation (e.g., nif/fix and key respiratory chain genes), whereas WWL2 nodules showed higher expression of genes linked to transport, chemotaxis/motility, and environmental information processing. Together, these host and rhizobia expression patterns suggest coordinated differences between host pathways related to resource supply and microaerobic conditions and rhizobial expression programs for respiration and nitrogen fixation. Based on these associations, we propose a working model and provide candidate genes and pathways for functional validation and inoculant screening. Full article

A tunable diode laser absorption spectroscopy (TDLAS) sensor with a highly sensitive dual-component for methane (CH₄) and acetylene (C₂H₂) detection is reported in this paper for the first time. A multi-pass cell (MPC) design model was established employing a vector-based ray-tracing method. A dual-channel MPC with an interlaced dual hexagonal star pattern was designed to improve gas absorption and realize real-time synchronous detection of CH₄ and C₂H₂. During the simultaneous continuous monitoring of CH₄ and C₂H₂, the sensor exhibited an excellent linear response to concentration variations. The minimum detection limit (MDL) for CH₄ reached 132.08 ppb, improving to 77.32 ppb when the average time was increased to 300 s. In the case of C₂H₂, the MDL was measured at 20.19 ppb and further reduced to 3.50 ppb under the same extended average time. Full article

This review examines 14 volatile organic compounds (VOCs) across nine Taiwanese Photochemical Assessment Monitoring Station sites over nearly two decades from 2006 to 2024, categorised as aromatic compounds, alkanes, and alkenes. Aromatic compounds and alkenes declined significantly (47.2–82.2%), reflecting regulatory success, while alkanes showed variable trends, including a 2023 Tainan spike (ethane: 9.12 ppbC, propane: 9.10 ppbC). Urban sites (Wanhua and Tucheng) exhibited high VOC levels from traffic, industrial sites (Xiaogang, Qiaotou) showed petrochemical influences, and rural sites (Chaozhou, Puzi, Taixi) were more alkane-dominated. Winter peaks and rush-hour diurnal patterns were meteorologically driven, with isoprene peaking in summer due to biogenic emissions. Cluster analysis of raw and standardised data separated urban–industrial from rural sites and early (2006–2010) from later (2018–2024) years, revealing compositional shifts. Benzene posed cancer risks (range 2.2 × 10⁻⁶–7.8 × 10⁻⁶) across sites and periods; as an illustrative example, prior to 2010 the risk at industrial Xiaogang was 6.2 × 10⁻⁶, but since 2020 has halved to 3.2 × 10⁻⁶. Taken together, these long-term observations demonstrate how declining anthropogenic VOC emissions can coexist with compositional shifts and an increasing relative influence of biogenic compounds, while also highlighting the ongoing challenge of ozone. This shows the value of monitoring networks as tools for understanding evolving atmospheric chemical regimes, rather than solely for reporting trends. Full article

In this work, a carrier-free photoacoustic spectroscopy system is developed for the detection of trace acetylene gas in insulating oil. The photoacoustic cell was integrated with an oil–gas separator, allowing dissolved gases in oil to be introduced into the cell through free diffusion. The oil–gas separator is a custom-fabricated AF2400-coated ceramic membrane, and its spin-coating process was carefully designed to enable rapid oil–gas separation and achieve high film flatness. Using a resonant photoacoustic cell and a low-noise lock-in amplifier, the sensitivity of the system was improved to 6.90 mV/ppm, with a repeatability error less than 1.65%. Calibration experiments demonstrated that continuous detection of dissolved gas in oil could be achieved, with a response time T₉₀ of less than 72.5 min. Compared to traditional photoacoustic spectroscopy, the continuous measurement capability of this method is expected to enable earlier fault diagnosis, thus having greater potential in industrial fields. Full article

This study examines how both the nature of the carbon support and the palladium precursor influence catalytic performance in acetylene hydrogenation. Six Pd-based catalysts were prepared on four carbon materials—high-heat-treated fibers (HHTs), carbon nanotubes, activated carbon and high surface area graphite—using either sulfate or chloride precursors. Catalytic tests performed in a continuous fixed-bed reactor reveal that HHT-supported catalysts achieve the highest ethylene selectivity and long-term stability, while in general catalysts derived from sulfate precursors exhibit enhanced selectivity compared to their chloride-derived counterparts. These improvements are consistent with the formation of sulfur, which may be incorporated as sub-stoichiometric sulfide species (S²⁻) interacting with metallic Pd, as revealed by the XPS results, rather than to palladium dispersion alone. The role of the carbon support in stabilizing these sites was further assessed by complementary characterization techniques, including transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The combined results indicate that highly graphitic supports such as HHT fibers favor sulfur retention at the catalyst surface, thereby promoting the stability and catalytic performance of Pd–S active motifs during acetylene hydrogenation. Full article

Nitrous oxide (N₂O) has attracted increasing attention as an oxidizer for space propulsion systems due to its non-toxic nature and favorable handling characteristics. Its relatively high vapor pressure allows self-pressurization, while its wide storage temperature range makes it attractive for a range of space applications. In parallel with broader efforts to identify alternatives to conventional toxic propellants, numerous studies have investigated liquid propulsion systems based on N₂O combined with hydrocarbon fuels, spanning both premixed fuel blends and non-premixed bipropellant configurations. This review summarizes experimental and system-level studies on N₂O–hydrocarbon propellant combinations, including ethylene, ethane, ethanol, propane, acetylene, methane, dimethyl ether, and propylene. Results reported by different research groups reveal clear differences among propellant combinations in terms of vapor pressure, thermal stability, chemical reactivity, and ignition delay. These differences have direct implications for injector design, mixing strategies, ignition mechanism, and system safety. By bringing together recent results from the literature, this paper aims to clarify the practical trade-offs associated with fuel selection in N₂O-based premixed and bipropellant systems and to provide a useful reference for the design and development of future space propulsion concepts. Full article

In this paper we provide the Group Contribution parameters for acetylenes and aromatic nitro compounds fitting with a recently developed Group Contribution method with chemical accuracy (1 kcal/mol) for the heat of formation of organics. These additional parameters widen the applicability of the Group Contribution method. We also provide further G4 quantum calculated values as reference when no experimental data are available and compare to previously reported G4 data. Full article

Nitrogen (N) fertilizers can promote soybean growth, nodulation, and nitrogen fixation to a certain extent. However, excessive nitrogen application inhibits the nitrogen fixation capacity of soybean nodules. In this study, three experimental materials were used to investigate the direct and indirect effects of localized exogenous nitrogen (Ammonium Nitrate, NH₄NO₃) on nodule nitrogen fixation in soybean. Three nitrogen supply methods were applied: bilateral nodulation dual-root soybeans, unilateral nodulation dual-root soybeans, and upper- and lower-layered soybeans. The root nitrogen accumulation of direct contact with exogenous nitrogen reached 72.61 mg/plant, 30.59 mg/plant, and 88.48 mg/plant, respectively, and its nitrogen accumulation ability was higher. Exogenous nitrogen inhibited nodule growth and nitrogen accumulation. Nodule development and nitrogenase activity were regulated both directly and indirectly by exogenous nitrogen, with a more pronounced inhibitory effect observed in the roots directly exposed to nitrogen. Experiment I demonstrated that the number and dry weight of nodules on the nitrogen supply side decreased by 35.04% and 40.00%, respectively, while the difference was not significant on the non-nitrogen supply side. Furthermore, the nodule system exhibited a substantial buffering effect on exogenous nitrogen. In Experiment I, no significant differences were observed in the number, dry weight, or nitrogenase activity of nodules on the non-nitrogen-supplying side. The number and dry weight of nodules in Experiment II decreased by 61.55% and 35.91%, respectively. The specific nitrogenase activity (SNA) and acetylene reduction assay (ARA) also decreased by 32.28% and 67.20%, respectively, showing significant differences. In Experiment III, the number and dry weight of nodules in the upper layers decreased by 23.70% and 15.12%, respectively. Furthermore, significant differences in nitrogenase activity were detected, indicating that the nodules exposed to exogenous nitrogen spontaneously initiated the nitrogen regulation mechanism. This partially offsets the inhibitory effect on the nitrogen fixation function of nodules on the indirectly exposed side. This study revealed that exogenous nitrogen supply significantly affected the growth efficiency and nodule nitrogen fixation function of soybean plants by regulating nitrogen absorption and resource allocation. The use of deep unilateral fertilization can ensure the nitrogen fixation capacity of nodules and nitrogen accumulation in soybean plants and provide theoretical support for improving nitrogen use efficiency and realizing scientific fertilization. Full article

Methylbutynol (MB) is a typical propargylic alcohol with both alkynyl and hydroxyl groups, featuring excellent modifiability and broad applications. Currently, it is produced through the reaction of alkaline metallic acetylides and acetone, requiring expensive raw material and harsh reaction conditions. Herein, a novel method was proposed by replacing the metallic acetylide with calcium carbide (CaC₂) as a low-cost industrial acetylide reagent. The effects of solvent, activator, and proton donor on the ball mill reaction, and the defoaming performance of the resultant MB and its oxidative coupling product (2,7-dimethyl-3,5-octadiyn-2,7-diol), were studied. Nucleophilic reactivity of CaC₂ with acetone can be regulated by the activating effect of the ball mill, an appropriate activator, and a proton donor. High yield of MB (~94%) was obtained under synergistic action of TBAF·3H₂O and acetylene, which represents a facile synthesis process of MB under mild conditions. MB exhibits good defoaming performance, and 2,7-dimethyl-3,5-octadiyn-2,7-diol is more promising, being an excellent non-ionic defoamer. The result is of great significance for exploring new chemical reactions of CaC₂ and its high-value utilizations. Full article