Search Results (151)

In neutrino and dark matter research, ²²²Rn and its progeny are among some of the main sources of radioactive backgrounds in underground laboratories. In areas with high ²³²Th backgrounds, the interference from ²²⁰Rn and its progeny must also be considered. This study presents a highly sensitive system for measuring ultra-low concentrations of ²²²Rn and ²²⁰Rn, utilizing the electrostatic collection method with a Si-PIN semiconductor detector. To achieve the required sensitivity, a cryogenic enrichment stage using activated carbon in an electrically cooled device (replacing conventional liquid-nitrogen cooling) is incorporated. The calibration factor for ²²²Rn is (67.93 ± 2.76) cph/(Bq·m⁻³), while for ²²⁰Rn, it is (46.08 ± 0.59) cph/(Bq·m⁻³). The detection limits of the complete system are 5.63 mBq·m⁻³ for ²²²Rn and 3.56 mBq·m⁻³ for ²²⁰Rn. The system was successfully applied to measure ²²²Rn contamination in commercial high-purity nitrogen cylinders, revealing that internal rusting of the cylinder walls is a dominant factor enhancing radon emanation. This electrically cooled, liquid-nitrogen-free design offers a practical and convenient solution for ultra-low-background radon measurements in underground physics experiments and industrial gas quality-control applications. Full article

High-purity SiC powder is an important feedstock for SiC crystal growth, but thermal-field regulation becomes difficult during large-batch synthesis. This study examined an α-SiC powder-synthesis furnace with upper and lower induction-coil groups through numerical simulations and 70 kg synthesis experiments. A representative two-dimensional axisymmetric model was used to compare eight cases with different coil-turn or numerical power allocations. Redistributing the coil turns changed $E_1$, $E_2$, volumetric Joule heat density, $Q$, and the resulting temperature and calculated gas-phase velocity-magnitude fields. From C01 to C04, the maximum calculated temperature decreased from 2501.10 to 2359.13 K, while $\Delta T$ decreased from 242.57 to 76.20 K. Increasing the upper-coil numerical power raised the temperature level while reducing $\Delta T$ to 152.41 K. Increasing the lower-coil numerical power also raised the temperature level, but increased $\Delta T$ to 292.26 K. Equal-total-power comparisons showed that axial power allocation affected $T_{\mathrm{m}\mathrm{a}\mathrm{x}}$ and $\Delta T$. XRD identified 6H-SiC as the detected crystalline phase in both analyzed middle-region specimens, although X-ray-amorphous carbon could not be excluded. The specimens also differed in macroscopic appearance, measured impurity concentrations, and local nitrogen concentration profiles. Because the experimental conditions were maintained nominally unchanged except for the upper-coil current, these specimen-level differences may be associated with altered internal thermal conditions. Such changes may affect local equilibrium, supersaturation, and species transport, providing a possible link to the observed material differences. The numerical results identify coil-turn allocation and axial power allocation as variables for regulating the calculated furnace fields. Full article

Lipases are important enzymes in the esterase family that hydrolyze ester bonds in triglycerides, producing simpler molecules. This property makes them valuable in biotechnology and environmental cleanup. In this study, lipase-producing bacteria were isolated and characterized from petroleum-contaminated soil to establish a cost-effective platform for enzyme production and bioremediation. Among the recovered isolates, Serratia liquefaciens AB1 exhibited the highest lipolytic activity and was therefore selected for further investigation. The influence of various inducer oils and agro-industrial residues on enzyme production was systematically assessed. In addition, fermentation parameters were optimized through the evaluation of different carbon and nitrogen sources to enhance lipase yield. Waste frying oil was identified as the most effective inducer, while glucose and yeast extract supported optimal enzyme production. The enzyme lipase AB1 was fully purified using CM-Sephadex C-50 chromatography, Sephadex G-100 and further characterized by SDS-PAGE, kinetic studies, and stability assays. Purification of the enzyme resulted in a specific activity of 610.92 U/mg, corresponding to a 9.42-fold increase in purity with an overall recovery of 76%. The enzyme exhibited an apparent molecular mass of approximately 64 kDa. It demonstrated optimal catalytic activity at 60 °C and pH 8 and retained substantial stability at this temperature for up to 120 min. Kinetic analysis revealed a low Km value of 30 µM, indicating strong substrate affinity, along with a Vmax of 23.89 U/mL, reflecting a high catalytic efficiency under the tested conditions. Enzyme activity was enhanced by Ca²⁺, Na⁺, and Ba²⁺, but inhibited by Mn²⁺ and Hg²⁺. These findings demonstrate the favorable biochemical properties of the purified lipase and provide a basis for future investigations into its potential application as a biocatalyst for bioremediation. Full article

Ammonia (NH₃) is a compelling carbon-free hydrogen carrier. Its catalytic decomposition to produce a hydrogen/nitrogen (H₂/N₂) gas stream is central to the “NH₃-H₂” clean energy cycle, provided that residual NH₃ is removed to fuel-cell-grade purity downstream. This review integrates advances from the past five years across four major catalytic NH₃ decomposition pathways, encompassing conventional thermocatalysis, plasma-catalytic, photo(thermal), and electrically driven catalysis, within a unified mechanistic and practical framework, distinguishing it from existing single-pathway reviews. Noble metal catalysts, particularly Ru-based systems, achieve superior low-temperature activity through support engineering, promoter effects, and active-site construction. However, our analysis reveals that non-noble metal (Fe, Co, Ni) catalysts and their alloys, nitrides, and carbides have made substantial progress, with certain Co-based and bimetallic systems approaching Ru-level performance via interfacial oxygen vacancy engineering and electronic structure modulation. Emerging non-thermal routes effectively overcome thermodynamic barriers, enabling operation at temperatures 200–300 °C below conventional thermal requirements, though each faces distinct challenges in energy efficiency, stability, and scalability. Key challenges remaining across all pathways to practical implementation, including residual NH₃ removal and H₂ purification, catalyst deactivation and stability, heat management and energy efficiency, start-up/shut-down dynamics, as well as system integration and economics, are critically assessed. This review provides theoretical guidance and practical recommendations for developing scalable, low-temperature NH₃ decomposition technologies. Full article

Trace water is one of the most critical matrix contaminants in ultra-high-purity (UHP) process gases, like argon (Ar), nitrogen (N₂), and many others. Even trace amounts can severely degrade the quality of many products that are reliant on these gases. Despite its importance to advanced technology sectors, notably semiconductor manufacturing, it has proven quite difficult to realize preparative or analytical trace water metrology over the full amount fraction range needed or in the broad spectrum of industrially relevant matrix gases. Within the EU-funded PROMETH2O project consortium, this challenge has been addressed through the development or significant improvement of traceable measurement methods and standards spanning 5 nmol⋅mol⁻¹ to 5 µmol⋅mol⁻¹, tailored for use in UHP process gas production, such as Ar, N₂ and clean dry air (CDA). The measurement ranges were extended and the uncertainties were improved while being consistent with the current best practice at primary humidity standard laboratories. The developed standards provide combined standard uncertainties ranging from approximately 0.4 % to 1.5 % in water vapor amount fraction and from 0.03 °C to 0.07 °C in frost-point temperature, while the comb-assisted CRDS system achieves detection limits in the sub-ppb to ppt range. These capabilities were validated in applications that are relevant to process instrumentation and the gas industry. A distributed metrological infrastructure at various European national metrology institutes and partner sites now provides SI-traceable trace water measurements in UHP gases, strongly supporting and extending the calibration capabilities for the gas and semiconductor industries and the associated stakeholders. Full article

This paper reports new results on the synthesis and comparative characterization of cellulose nitrates (CNs) derived from Miscanthus × giganteus stems and from commercial microcrystalline cellulose (MCC). Miscanthus CNs synthesized by nitration with mixed sulfuric–nitric acids containing 16–20% water exhibit new functional properties: a high solubility in organic solvents (100% in acetone and 97–99% in alcohol–ether solvent) and a high viscosity (17–51 mPa·s), with a nitrogen content of 10.54–12.08 wt%. CNs from Miscanthus × giganteus are similar in nitrogen content and solubility to those from MCC (11.54% and 99%) but have a significantly greater viscosity (3 mPa·s), which is an undoubted advantage and considerably expands their potential application range. The solubility test of CNs synthesized from both sources demonstrated that Miscanthus CNs have a better film-forming ability. SEM analysis revealed a great difference in fiber length, despite the same cylindrical shape and observed aggregation: 1.0–2.0 mm for CNs from Miscanthus versus 40–60 μm for CNs from MCC. IR spectra of CNs from both sources showed the appearance of five new characteristic frequencies (1632–1633, 1273–1274, 823–826, 748, 677–686 cm^–1 for Miscanthus CNs and 1659, 1277, 832, 747, 691 cm^–1 for CNs from MCC), allowing the obtained compounds to be identified as nitric acid esters of cellulose. According to TGA/DTA analysis, the synthesized polymers have similarly high values of the onset temperature of both intense decomposition (197–198 °C) and narrow exothermic peaks (209–211 °C and 212 °C), respectively, indicating their high thermal stability. The combination of high solubility, viscosity, thermal stability and chemical purity of CNs derived from Miscanthus × giganteus stems suggests that strong thin films can be obtained and recommended for use in the manufacture of nitrocellulose membranes. Full article

Municipal wastewater treatment plants (WWTPs) are designed and operated with nitrogen removal as the primary constraint. Reliance on nitrification–denitrification-based treatment results in significant nitrous oxide (N₂O) emissions. We propose a paradigm shift in WWTP operation, in which nitrogen removal is transformed into an opportunity for resource recovery. Ammonium remaining in the treated effluent is subsequently recovered via ion exchange (IX) and converted into high-purity ammonium salts using a novel, closed-loop, high-pH, low-volume, controlled-regeneration process. Two IX materials are investigated for compliance with the method: zinc hexacyanoferrate composite beads and clinoptilolite-type zeolite. Operating WWTPs using this approach can achieve energy self-sufficiency while contributing to a circular nitrogen economy. Full article

The separation of synthesised ammonia from unreacted nitrogen and hydrogen is a crucial step in producing high-purity ammonia and enabling the efficient recycling of unreacted gases in the ammonia synthesis process. The separation of ammonia from nitrogen and hydrogen was studied using zeolite 13X. Experiments were performed using a custom-designed experimental apparatus developed specifically for this study. Adsorption isotherm data for ammonia, hydrogen, and nitrogen were obtained over a temperature range of 293–313 K and pressures up to 5 bar. The results show that the adsorption capacity of zeolite 13X for ammonia is significantly higher than for nitrogen and hydrogen. This indicates a substantially stronger affinity toward ammonia molecules, enabling highly selective adsorption. The experimental isotherm data were successfully fitted using the Sips model, which accurately described the adsorption behaviour of the gases and showed good agreement with the measured data. The adsorption performance of zeolite 13X was further evaluated through a series of dynamic breakthrough experiments under varying pressures and gas compositions. The results confirmed the high selectivity of zeolite 13X for ammonia, with negligible adsorption of nitrogen and hydrogen. Ammonia breakthrough time was found to increase with system pressure, reflecting enhanced adsorption capacity. These findings highlight zeolite 13X as an effective and reusable adsorbent for selective ammonia separation in multi-component gas streams, with promising potential for industrial applications. Full article

Carbon nano-onions (CNOs) were synthesized at ambient conditions using the wick-pyrolysis technique with ghee as a precursor. A high-purity copper substrate produced unique CNOs, differing from those obtained with other metals. To purify the nanoparticles, they underwent treatment with a solvent mixture of acetone and deionized water or were pyrolyzed at 1000 °C under nitrogen without a catalyst. Various characterization techniques, including X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), High-Resolution Transmission Electron Microscopy (HR-TEM), and Raman Spectroscopy, confirmed the successful formation of CNOs. Energy Dispersive Spectroscopy (EDS) and Elemental analysis (CHN) indicated the presence of oxygen in treated CNOs. X-ray photoelectron spectroscopy (XPS) revealed binding energies linked to C-O and C=O bonds. The average particle size was found to be 30–50 nm, with some agglomeration in pyrolyzed samples. A significant increase in surface area from 79.7 m²/g to 261.8 m²/g was observed, along with changes in pore radius and volume via Brunauer–Emmett–Teller (BET) analysis. Water contact angles on the CNO surface were measured at 125° and 138°, indicating hydrophobicity. Electrochemical tests on CNO-based composite electrodes yielded a specific capacitance of 109.7 F/g with 96% capacity retention over 5000 cycles. Full article

Magnesium oxide (MgO) nanoparticles, recognized for their versatile applications from catalysis to biomedicine, require synthesis methods that offer precise control over their properties while ensuring safety and scalability. This study explores a safer, industrially viable adaptation of the polyacrylamide gel synthesis route by utilizing magnesium sulfate (MgSO₄) instead of conventional nitrates to mitigate explosion risks during calcination. A systematic study was conducted to evaluate the influence of key synthesis parameters, such as crosslinker ratio, initiator concentration, precursor loading, calcination conditions (including temperature, time, and heating rate), pH, and the use of chelating agents (EDTA and citric acid), on the purity, morphology, size distribution, and colloidal stability of the synthesized MgO nanoparticles. Characterization via X-ray spectroscopy XRF and XRD, acoustic spectroscopy, nitrogen physisorption (BET), electronic microscopy SEM and TEM and dispersion stability analysis revealed that polymeric cell volume (controlled by crosslinker and initiator) significantly influences size distribution, while chelating agents in alkaline environments drastically reduce particle size to ~20 nm and alter morphology to platelets (EDTA) or polygonal shapes (citric acid). Crucially, a low heating rate (2.5 °C/min) was found to yield smaller particles (~30 nm) and higher purity. This work provides a comprehensive blueprint for the tailored, safe, and scalable synthesis of MgO nanoparticles with targeted properties for specific technological applications. Full article

Metabolic reprogramming is closely linked to tumor proliferation, invasion, and immune escape. Despite its central role in amino acid metabolism, the regulatory mechanisms of asparagine metabolism in hepatocellular carcinoma (HCC) progression remain poorly characterized. Rather than focusing on canonical metabolic genes, prognostic markers were identified from co-expression modules associated with asparagine metabolism signatures. Using the TCGA database and asparagine metabolism-related gene sets, a prognostic risk-scoring model was developed through differential expression analysis, univariate Cox regression, and the LASSO algorithm and externally validated with the GEO dataset (GSE14620). Survival analysis, ROC curve evaluation, nomogram construction, scRNA-seq, GSEA, and drug sensitivity analysis were performed to systematically delineate the molecular mechanisms by which asparagine metabolism drives HCC progression. A three-gene signature comprising BOP1, SAC3D1, and PDE2A effectively stratified patients into high- and low-risk groups. High-risk patients exhibited markedly poorer overall survival, enrichment in tumor proliferation-associated pathways, increased tumor purity, reduced immune cell infiltration, and a substantially higher TP53 mutation rate (38% vs. 13%). In contrast, the low-risk group showed enrichment in pathways linked to hepatoblastoma suppression and liver function, alongside improved predicted response to immunotherapy. Single-cell analysis identified NK cells and endothelial cells as central mediators of asparagine metabolism-driven HCC progression, with BOP1, SAC3D1, and PDE2A displaying dynamic expression patterns during differentiation. Furthermore, the high-risk group was predicted to be more sensitive to chemotherapeutics such as cyclophosphamide and 5-fluorouracil. These findings highlight a potential interplay between nitrogen metabolism and asparagine metabolism in HCC and suggest mechanisms by which these pathways may influence NK cell and endothelial cell function to promote disease progression. This study establishes a novel prognostic model and identifies potential chemotherapeutic vulnerabilities in high-risk patients, warranting further experimental and clinical validation. Full article

This study investigates the synthesis and kinetic behavior of a magnetic biochar derived from avocado seed biomass for the removal of hexavalent chromium (Cr(VI)) from aqueous solutions. Magnetite (Fe₃O₄) was synthesized through different routes, including nitrogen-assisted coprecipitation, redox-controlled coprecipitation, polyol, sol–gel, and sonochemical methods, to evaluate their structural properties and iron incorporation efficiency. Based on compositional and crystallographic analyses, the coprecipitation under an inert atmosphere exhibited improved phase purity and higher Fe₃O₄ content, which was selected for in situ incorporation onto biochar produced by pyrolysis at 450 °C. The resulting magnetic material and composite were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS), confirming the suitability of the synthesis method and the successful deposition of magnetite onto the porous carbon matrix while preserving its structural integrity. Batch adsorption experiments were conducted at pH 2.0 to evaluate the effect of adsorbent dose and initial Cr(VI) concentration. The adsorption process reached equilibrium within 120 min and was better described by the pseudo-second-order kinetic model (R² ≥ 0.98), suggesting that chemisorption governs the rate-controlling step, with diffusion phenomena contributing but not dominating the overall mechanism. The maximum adsorption capacity predicted by the kinetic model reached 42.49 mg g⁻¹ at an initial concentration of 100 mg L⁻¹. The results demonstrate that avocado-seed-derived magnetic biochar represents a sustainable and effective material for chromium-contaminated water treatment, integrating agro-industrial waste valorization with enhanced adsorption performance and magnetic separability. Full article

Red Amaranth (RA) Azo dye is a persistent pollutant in wastewater and stands as a toxicological risk, which has led to the development of effective methods for its removal and photocatalytic degradation. Therefore, CeO₂ nanoparticles were synthesized by a controlled precipitation method, and Ultraviolet-Visible (UV–Vis) analysis and Tauc plots yielded a band gap of ~3.24 eV. The CeO₂ nanoparticles showed the fluorite cubic phase, and nearly spherical particles with an average size of ~10 nm. Nitrogen physisorption revealed a type IV isotherm with a Brunauer–Emmett–Teller (BET) surface area of 85.27 m²·g⁻¹ and a total pore volume of 0.27 cm³·g⁻¹, indicating a mesoporous structure and high surface accessibility. The chemical behavior showed Ce and O, consistent with phase purity. Photocatalytic performance was evaluated in 20 ppm aqueous solution of RA under 365 nm UV irradiation (LED 100 W), with a temperature of ~20 °C and a 15 min dark adsorption step. Concentration decay was followed at λ_max = 520 nm by Lambert–Beer. The degradation efficiency η and pseudo-first-order kinetic were obtained from ln(C₀/C_t) vs. time. In addition, chemical oxygen demand (COD) tests were performed on RA solution before and after photodegradation, showing a COD reduction of ~85% (from 19.8 to 3 mg O₂·L⁻¹), which corroborates mineralization beyond chromophore bleaching. Under [C₀ = 20 mg·L⁻¹] and [m_cat = 1.0 g·L⁻¹], CeO₂ achieved [RA = 90% at 180 min, k = 0.0125 min⁻¹]. These results demonstrate that CeO₂ is an effective photocatalyst for RA degradation under UV-A irradiation, integrating adsorption, kinetic behavior, and mineralization performance into a coherent structure–property relationship. Full article

The valorization of agro-industrial residues represents a strategic approach to advancing sustainability and circular bioeconomy principles in the food sector. Although bacterial cellulose (BC) production from waste substrates has been widely explored, limited attention has been given to the role of nitrogen source modulation in complex fermentation systems. This study evaluated passion fruit peel hydrolysate (PFPH), a cellulose- and hemicellulose-rich by-product, as an alternative carbon source for BC production using a symbiotic culture of bacteria and yeast (SCOBY) under static conditions. Acid hydrolysis and detoxification were performed to obtain fermentable sugars while minimizing inhibitory compounds. Different nitrogen sources and purification strategies were comparatively assessed. The highest purified BC yield (81 g L⁻¹ of culture medium) was obtained using ammonium sulfate, whereas sodium nitrate promoted greater impurity removal (77.51% mass reduction). Structural and chemical analyses (FTIR, XPS, and XRD) confirmed effective delignification, enhanced surface purity, and increased crystallinity. SEM revealed a homogeneous nanofibrillar network, and thermogravimetric analysis indicated thermal stability up to approximately 300 °C. Soil burial assays showed 26% mass loss after 42 days, demonstrating controlled biodegradation consistent with food packaging requirements. Overall, PFPH proved to be an efficient and sustainable substrate for BC biosynthesis. The modulation of nitrogen source significantly influenced both production yield and structural properties, highlighting the potential of this system for developing environmentally responsible biopolymer materials for food packaging applications. Full article

This study presents a quantitative simulation analysis of hydrogen-enriched methane (HENG) storage with nitrogen as the cushion-gas in a depleted gas reservoir by varying three key operational parameters: the injection/withdrawal period, hydrogen blending ratio (5–20%), and injection depth. Ten injection–withdrawal cycles were modeled for each scenario, and performance was evaluated using cycle-averaged and cumulative hydrogen purity, recovery factors, and the mixing zone size. Extending the injection period increased hydrogen purity to 20.00–20.26% and reduced nitrogen to 0.001–0.003%, but recovery decreased from 65.63 to 53.83–41.09% due to enhanced dispersion and residual trapping. The blending ratio was the dominant control: 20% blending yielded 19.9–20.0% purity with nitrogen as low as 0.00–0.03%, whereas 5–10% blending produced lower purity but minimized nitrogen production to 0.97–1.08%. Injection depth affected nitrogen recovery more than purity, increasing from 0.72–1.20% (upper) to 1.46–1.61% (lower), along with thicker mixing zones. Final mixing zone size ranged from 3176 to 5546 blocks, with smaller zones consistently linked to higher purity and lower nitrogen breakthrough. The shut-in period further reduced nitrogen recovery from 6.49 to 1.33% and stabilized mixing behavior. Overall, minimizing late-cycle mixing zone thickness is essential for maintaining HENG storage performance. Although this study provides quantitative insights into HENG operational strategies, the use of a homogeneous grid and simplified fluid properties limits representation of geological heterogeneity and reactive processes. Future work will incorporate heterogeneity and reaction modeling into field-scale simulations to validate and refine these operating strategies for practical deployment. Full article