Search Results (1,391)

Ammonia (NH₃) is a promising zero-carbon fuel to eliminate carbon footprint while the high autoignition temperature and low combustion rate of NH₃ remain challenging for practical implementation. Using dimethyl ether (DME) as pilot ignition fuel can substantially promote the reactivity of NH₃, thus paving the way for a widespread application of NH₃. In this study, the ignition process and nitrogen oxides (NO_x) emissions of the NH₃ liquid spray ignited by liquid DME spray were numerically investigated using Converge software. The ambient temperatures (T_amb) ranging from 900 K to 1100 K were used to mimic the in-cylinder temperature typically encountered in turbocharger engines. The effect of ammonia energy ratio (AER) and fuel injection timing was examined as well. It is found that only half of NH₃ is consumed at T_amb = 900 K while 97.4% of NH₃ is burned at T_amb = 1100 K. Nitric oxide (NO) and nitrogen dioxide (NO₂) formation also have strong correlation with T_amb and NO₂ is usually formed around the periphery of NO through these two channels HO₂ + NO = NO₂ + OH and NO + O(+M) = NO₂(+M). Extremely high nitrous oxide (N₂O, formed by NH + NO = H + N₂O) and carbon monoxide (CO) are produced with the presence of abundant unburned NH₃ at T_amb = 900 K. Additionally, increasing AER from 60% to 90% results in slightly declined combustion efficiency of NH₃ from 98.7% to 94%. NO emission has a non-monotonical relationship with AER owing to the ‘trade-off’ relationship between HNO concentration and radical pool at varying AERs. A higher AER of 95% leads to failed ignition of NH₃. Advancing DME injection not only increases combustion efficiency, but also reduces NO_x and CO emissions. Full article

Background: Chronic heart failure with reduced ejection fraction (HFrEF) is associated with high mortality, and renal dysfunction is common in these patients. Blood urea/creatinine ratio (UCR) has been identified as a potential prognostic marker, reflecting both renal function and neurohormonal activity. We assessed whether a UCR ≥ 95 at discharge from an outpatient service was associated with increased mortality. Methods: This retrospective study reviewed 337 patients (age 72.7 ± 14.3 years; 64.7% Male; Mean LVEF 33.2 ± 8.9%) with HFrEF referred to the Heart Failure Nurse Service at NHS Tayside for optimisation of heart failure medication. Cox proportional hazards models were used to assess the association between UCR and all-cause mortality. Results: Receiver operating characteristic (ROC) analysis identified a UCR threshold of 95 (area under the curve [AUC] 0.701) as predictive of mortality. Results demonstrated that a UCR ≥ 95 was independently associated with increased mortality (HR 1.85, 95% CI 1.09–3.14, p = 0.022). A high UCR was associated with increased mortality even in patients with preserved eGFR, a group typically considered at lower risk (HR 4.03, 95% CI 1.50–10.9, p = 0.006). Conclusions: These findings suggest that UCR could be a useful addition for identifying high-risk patients who may benefit from closer monitoring and more aggressive intervention following optimisation of heart failure medication. Full article

The increasing frequency of global extreme climate events has heightened the need to understand the mechanisms through which desert ecosystems respond to altered precipitation patterns. This includes elucidating how arbuscular mycorrhizal fungi (AMF) drive these responses by regulating key soil processes and shaping microbial community dynamics. We therefore conducted an in situ experiment involving increased precipitation and AMF suppression, and phospholipid fatty acid (PLFA) was employed to reveal the changes in soil microbial community. Results showed that increased precipitation significantly promoted the growth of soil AMF and Actinobacteria (Act). Increased precipitation significantly changed soil microbial community structure and promoted soil microbial community diversity, but it posed neutral effects on soil microbial community biomass. AMF suppression clearly inhibited AM fungal growth but increased the growth of Act and Gram-positive bacteria (G⁺) and posed limited effects on Gram-negative bacteria (G⁻), leading to an increased G⁺/G⁻ ratio. Notably, AMF suppression posed slight effects on the biomass, diversity, and structure of soil microbial community. Random forest analysis revealed that soil ammonium nitrogen (NH₄⁺-N), microbial biomass nitrogen (MBN), and soil organic carbon (SOC) were the main factors influencing different soil microbes, and soil Act and G⁺ were the main factors influencing plant community diversity, but AMF were the primary factor influencing plant community biomass. More importantly, structural equation modeling (SEM) results further confirmed that increased precipitation and AMF significantly altered plant community diversity by influencing soil AM fungi and increased plant community biomass by promoting soil AM fungal growth. In conclusion, our results demonstrate that increased precipitation enhances plant community productivity and diversity in desert ecosystems primarily by stimulating the growth of arbuscular mycorrhizal fungi, which function as a key biological pathway mediating the ecosystem’s response to climate change. Full article

Wheat silage is an underexplored forage in ruminant nutrition that offers potential benefits due to its high crude protein content and capacity to mitigate methane emissions. However, little is known about its interaction with feed additives. This study evaluated the effects of monensin (25 ppm) and narasin (13 ppm) on the in vitro ruminal fermentation of wheat silage using a randomized complete block design with three treatments and seven replicates per incubation. Gas production was recorded over 48 h, and fermentation parameters, including pH, in vitro organic matter digestibility (IVOMD), metabolizable energy (ME), ammonia nitrogen (NH₃-N), and volatile fatty acid (VFA) profiles, were determined. Both ionophores maintained a higher ruminal pH compared to the control (p < 0.01) and reduced total gas production, ME, and IVOMD (p < 0.01), without significant differences between monensin and narasin. No effects were observed on total VFA production, acetate-to-propionate ratio, or ammonia concentration, although isobutyrate was reduced (p < 0.01). Fermentation kinetics revealed decreased gas production and digestion rates in the slowly degradable fraction, particularly with monensin. In conclusion, ionophores modulated fermentation but did not improve digestibility or energy availability, suggesting limited nutritional benefits when wheat silage is used as the sole forage source. Full article

The existence of residual ammonium in weathered crust elution-deposited rare earth ore (WREO) tailings will cause serious environmental pollution, and it is necessary to remove it from the ore body. In this work, ferric chloride was applied as the eluent, and the effects of the ferric salt concentration, liquid/solid ratio, and the eluting temperature on the ammonium removal process were investigated. The results indicated that ferric chloride demonstrated a significant capability to eliminate residual ammonium (RA) from rare earth (RE) tailings. The optimal conditions identified for this process included a ferric salt concentration of 0.06 mol/L, a liquid/solid ratio of 2:1, and a temperature of 25 °C. Under optimal conditions, the removal efficiency of RA by ferric chloride was measured at 97.47%. The NH₄⁺ concentration in the final stage leachate was determined to be 1.85 mg/L, which satisfies the environmental standards. Kinetic analysis revealed an internal diffusion-controlled elution mechanism for RA in the RE ore tailings, with a reaction order of 0.28 and an activation energy of 13.36 kJ/mol. FT-IR characterization results showed that most of the RA salts were effectively removed. This study establishes a feasible approach to remove RA from RE ore tailings, thereby laying a theoretical foundation for this process. Full article

Biochar-based fertilizers have attracted increasing attention as sustainable soil amendments due to their potential to enhance nitrogen (N) retention and mitigate N losses. However, their effects on N dynamics in tea orchard soils remain inadequately understood. This study investigated the impact of biochar-based fertilizer (BF) on N migration and transformation into acidic tea orchard soils through controlled laboratory experiments comprising nine treatments, including sole urea (U) applications and various combinations of BF and U. The results showed that ammonia (NH₃) volatilization peaked within seven days after application. Compared with urea-only treatments, the application of BF at 15 t·ha⁻¹ combined with a low U application rate (0.72 t·ha⁻¹) significantly reduced NH₃ and total dissolved nitrogen losses by up to 22.33% and 33.56%, respectively, while higher BF rates increased these losses. BF applications markedly improved soil N sequestration, as evidenced by increases in total nitrogen, ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃⁻-N), and the NH₄⁺-N/NO₃⁻-N ratio. Additionally, soil organic carbon, urease activity, and pH were significantly enhanced. Random forest analysis identified soil pH and organic carbon as the primary predictors of NH₃ volatilization and soil N retention. Partial least squares path modeling revealed that the BF-to-urea ratio governed N dynamics by directly influencing N transformation and indirectly modifying soil physicochemical properties. BF applied at ≤15 t·ha⁻¹ with low U inputs exhibited potential for improving N use efficiency and sustainability, pending further field validation. Full article

This study compares MOVES5 emissions estimates for nitrogen oxides (NO, NO₂, and NO_x), ammonia (NH₃), and carbon monoxide (CO) to individual roadside emission measurements from heavy-duty (HD) diesel vehicles. Vehicle measurements were collected in Perry, Utah (winter 2020 and summer 2023) and Peralta, California (spring 2017), using the Fuel Efficiency Automobile Test (FEAT) remote sensing device. MOVES5 underestimated NO_x in the Utah winter campaign. MOVES5 underestimated mean NO emissions and overestimated mean NO₂ emissions across all campaigns, indicating potential deficiencies in the NO/NO_x and NO₂/NO_x ratios used by the model. NH₃ estimates were significantly higher than measurements, while CO estimates closely matched real-world measurements. Analysis by model year found that MOVES5 consistently underestimated emissions of the older model years and overestimated emissions from the newest model years for most pollutants. In the Utah winter campaign, MOVES5 underestimated NO_x by 47%, which, when applied to Utah’s emission inventory, suggests that HD diesel vehicles may contribute an additional ~1300 tons/year of unaccounted NO_x. Using a broader range of real-world measurements to update the MOVES model could improve its accuracy in estimating HD diesel vehicle emissions. Full article

This study investigates, for the first time, the relationship between carbon (δ¹³C) and nitrogen stable isotopic composition of Aspergillus niger mycelium, used as chitin and chitosan sources, and the fungus diet under controlled cultivation conditions. Four diets were tested, combining different carbon (C3- and C4-glucose) and nitrogen sources (KNO₃ and NH₄Cl). Results showed that carbon sources significantly influenced δ¹³C values of the mycelium: C4-glucose diets led to more negative Δ¹³C values (δ¹³C_MYCELIUM-δ¹³C_DIET) compared to C3-glucose diets. Nitrogen sources also affected isotopic fractionation, with KNO₃ leading to negative Δ¹⁵N (δ¹⁵N_MYCELIUM-δ¹⁵N_DIET) and NH₄Cl yielding positive Δ¹⁵N. Conversely, pH and temperature showed negligible effects on δ¹⁵N, while continuous aeration during growth significantly decreased δ¹⁵N, possibly due to partial assimilation of atmospheric nitrogen. These findings demonstrate that both nutrient and cultivation parameters can modulate the isotopic fractionation in A. niger, particularly for nitrogen. Although a direct correlation between diet composition and δ¹⁵N could not be established, this work provides the first experimental link between fungal metabolism and its isotopic fingerprint. The results offer a scientific foundation for applying stable isotope ratio analysis to authenticate and trace fungal-derived chitin and chitosan, with potential applications in food and winemaking industries. Full article

Managing eutrophic waterbodies produced large quantity of cyanobacterial sludge (CS), a biomass rich in nitrogen (N) that can be recycled through composting. However, how this management affects the compost fertility and ammonia (NH₃) volatilization is little known. This study used a chicken manure and wheat straw mixture with struvite, as the control composting treatment (CK). Subsequently, 10%, 20%, 30%, and 40% of the chicken manure was substituted with CS at the initiation of composting, which were named CS10%, CS20%, CS30%, and CS40%, respectively. The results showed that compost pH decreased by 0.2–0.5 units, while total N content significantly increased by 10.4–20.8% under all CS amended treatments compared to the CK. Furthermore, cumulative NH₃ volatilization in the CS amended treatments increased with higher CS substitution rates, showing a significant increase of 21.3–110.0%. In CS amended treatments, the initial contents of microcystin–RR and –LR were 82.0–328.0 μg kg⁻¹ and 48.0–192.0 μg kg⁻¹, respectively, which were degraded by 35.7–79.5% and 30.2–77.8%, peaking at 30% CS substitution. Notably, the CS40% treatment showed degradation rates dropping to 62.3% and 60.7%, accompanied by a significant increase in microcystin content. Meanwhile, the heavy metals (total arsenic, cadmium, chromium, mercury, and lead) contents of all composts complied with organic fertilizer standard (NY/T 525–2021) of China. Interestingly, the CS10% had significantly lower heavy metal concentrations compared to the CK, thus enhancing compost safety. In conclusion, 10% was an optimal CS incorporating ratio to improve the quality of compost derived from chicken manure, wheat straw and struvite, while reducing NH₃ emissions, which provided a feasible technical pathway for recycling the CS. Full article

Mesenchymal stem cells are widely cultivated in stirred tank bioreactors. Due to their adhesion properties, they are attached to small spherical spheres called microcarriers. To understand the hydromechanical stresses encountered by the cells, it is essential to characterize the flow using the PIV technique. However, the usual solid–liquid system used in cell cultures has poor optical properties. Thus, shifting to one with better optical properties, while respecting the physical characteristics, is mandatory to achieve a relevant representation. PMMA microparticles suspended with 61 wt% ammonium thiocyanate solution NH₄SCN were found to be a robust candidate. The refractive index (RI) of both sides is of the order of 1.491 with a density ratio of ${\rho }_f/{\rho }_p\approx$ 0.96, and particle size averaged around 168 μm. Using the RIM-PIV (refractive index matched particle image velocimetry) technique for a 0.7 L volume stirred tank equipped with an HTPG down-pumping axial impeller and operating at full homogeneous speed $N=150$ rpm, mean and turbulence quantities of the liquid phase were measured as a function of PMMA particle volume fractions ${\alpha }_p$, which ranged from 0.5 to 3 v%. This corresponds to a particle number density of $n=12$ particles/mm³, which is considered original and challenging for the PIV technique. At 3 v%, the addition of particles dampened the turbulent kinetic energy (TKE) of the liquid phase locally by 20% near the impeller. This impact became trivial (<10%) at the local-average level. The structure and direction of the recirculation loop also shifted. Full article

The chemical bath deposition of ZnO nanowires is of high interest for many functional devices, but the typical use of hexamethylenetetramine (HMTA) molecules forming formaldehyde as a harmful substance raises health, environment, and regulation issues. After a careful review of the multiple roles of HMTA molecules, we unambiguously show, using X-ray near-edge structure absorption spectroscopy with synchrotron radiation, that they do not form any complexes with the Zn(II) species, both in the low- and high-pH regions. In contrast and in agreement with thermodynamic computations, [Zn(H₂O)₆]²⁺ and Zn(NH₃)₄²⁺ ion complexes are revealed to be the predominant Zn(II) species in the low- and high-pH regions. The use of HMTA molecules is found to be critical to form ZnO nanowires with a high aspect ratio in the low-pH region. In contrast, HMTA molecules are shown to be fully substituted by ammonia in the high-pH region to form ZnO nanowires with a high structural and optical quality. The removal of HMTA molecules for the chemical bath deposition of ZnO nanowires in the high-pH region represents a significant step forward towards the development of a chemical synthesis fully compatible with green chemistry. Full article

Fine particulate matter (PM_2.5; aerodynamic diameter ≤ 2.5 µm) remains a challenging policy for industrialized coastal regions throughout East Asia. In this study, we present a multi-year chemical characterization of PM_2.5 and identify key factors contributing to extreme pollution events in Dangjin, a heavy-industry hub on Korea’s west coast. Between August 2020 and March 2024, 24-h gravimetric filters (up to n = 245; 127–280 valid analyses depending on constituent) were collected twice weekly in winter–spring and weekly in summer–autumn. Meteorological data and 48-h backward HYSPLIT trajectories guided source interpretation. The mean PM_2.5 concentration was 26.22 ± 15.29 µg/m³ (4.74–95.31 µg/m³). The mass was highest in winter (30.83 µg/m³). Secondary inorganic ions constituted 60.3% of the aerosol, with nitrate comprising 29.7%. A nitrate-to-sulfate ratio of 1.94 indicated a stronger influence from mobile NO_x emissions compared to that from coal combustion. The trajectory analysis showed north-easterly transport from Eastern China, followed by local stagnation, which promoted rapid ammonium-nitrate formation. Regional transport contributes to severe PM_2.5 episodes, with their magnitude increased by local NO_x and NH₃ emissions. Our findings suggest that effective mitigation strategies in coastal industrial corridors require coordinated control of long-range transport and domestic measures focused on vehicles and ammonia-rich industries. Full article

This study reports on the synthesis, structural characterization and gas sorption studies of a homometallic 2D Cd²⁺ MOF and two heterometallic 3D Cd²⁺/Ca²⁺ and Cd²⁺/Sr²⁺ -MOFs based on the angular tetracarboxylic ligand 3,3′,4,4′-sulfonyltetracarboxylic acid (H₄STBA). The homometallic 2D Cd²⁺ MOF with the formula [NH₂(CH₃)₂]⁺₂[Cd(STBA)]²⁻_n·nDMF·1.5nH₂O—(1)_n·nDMF·1.5nH₂O was synthesized from the reaction of CdCl₂·H₂O and 3,3′,4,4′-diphthalic sulfonyl dianhydride (3,3′,4,4′-DPSDA) with stoichiometric ratio of 1:1.3 in DMF/H₂O (5/2 mL) at 100 °C. The two heterometallic Cd²⁺/Ca²⁺ and Cd²⁺/Sr²⁺ compounds were prepared from analogous reactions to this afforded (1)_n·nDMF·1.5nH₂O with the difference that the reaction mixture also contained AE(NO₃)₂ (AE²⁺ = Ca²⁺ or Sr²⁺) and, in particular, from the reaction of AE(NO₃)₂, CdCl₂·H₂O and 3,3′,4,4′-DPSDA with stoichiometric ratio 1:1.1:1.4 in DMF/H₂O (5/2 mL) at 100 °C. Notably, compounds [CdCa(STBA)(H₂O)₂]_n·0.5nDMF—(2)_n·0.5nDMF and [CdSr(STBA)(H₂O)₂]_n·0.5nDMF—(3)_n·0.5nDMF are the first heterometallic compounds Mⁿ⁺/AE²⁺ (M = any metal ion) reported containing ligand H₄STBA. The structure of (1)_n·nDMF·1.5nH₂O comprises a 2D network based on helical 1D chain secondary building unit (SBU) [Cd²⁺(STBA)⁴⁻)]²⁻. The 2D sheets are linked through hydrogen bonding interactions, giving rise to a pseudo-3D structure. On the other hand, compounds (2)_n·1.5nH₂O and (3)_n·1.5nH₂O display 3D microporous structures consisting of a helical 1D chain SBU [Cd²⁺AE²⁺(STBA)⁴⁻)]. All three compounds contain rhombic channels along c axes. The three MOFs exhibit an appreciable thermal stability, up to 350–400 °C. Gas sorption measurements on activated materials (2)_n and (3)_n revealed moderate BET surface areas of 370 m²/g and 343 m²/g, respectively, along with CO₂ uptake capacity of 2.58 mmol/g at 273 K. Full article

Ammonia–coal co-combustion has emerged as a promising strategy for reducing carbon emissions from coal utilization, although its underlying reaction mechanisms remain insufficiently understood. The Chemkin simulation of zero-dimensional homogeneous reaction model and entrained flow reaction model was employed here, and the ROP (rate of production) and sensitivity analysis was performed for analyzing in-depth reaction mechanisms. The nitrogen conversion pathways were revealed, and the mechanisms were simplified. Based on simplified mechanisms, molecular-level reaction pathways and thermochemical conversion networks of nitrogen-containing precursors were established. The results indicate that NO emissions peak at a 30% co-firing ratio, while N₂O formation increases steadily. The NH radical facilitates NO reduction to N₂O, with NH + NO → N₂O + H identified as the dominant pathway. Enhancing NNH formation and suppressing NCO intermediates are key to improving nitrogen conversion to N₂. This paper quantifies the correlation between NO_x precursors such as HCN and NH₃ and intermediates such as NCO and NNH during ammonia–coal co-firing and emphasizes the important role of N₂O. These insights offer a molecular-level foundation for designing advanced ammonia–coal co-combustion systems aimed at minimizing NO_x emissions. Full article

The composting of organic waste is a sustainable strategy for waste management and soil fertility improvement. However, the composting process is often associated with greenhouse gas (GHG) emissions, having a negative impact on the environment. This study investigated the effects of BC pyrolysis temperature (300 °C, 600 °C) and application rate (5% and 10%) on GHG emissions during the thermophilic phase and compost quality. The experimental treatments were a control and four BC treatments varying in pyrolysis temperature (300 °C, 600 °C) and application rate (5%, 10%). As a result, BC pyrolyzed at 600 °C and added at 10% (T2R2) resulted in the highest thermophilic temperature (63.5 ± 0.5 °C). This treatment significantly achieved substantial reductions in NH₃, N₂O, CH₄, and CO₂ emissions by 55 ± 2.7%, 50 ± 2.7%, 88 ± 4.2%, and 23 ± 2.3%, respectively, relative to the control. Compost quality was enhanced notably, with dry matter increasing to 46.4 ± 0.11% (T2R1), organic matter reaching 30.9 ± 0.05% in T2R1, and total nitrogen peaking at 0.8 ± 0.001% (T1R2). The C:N ratio decreased from 27:1 in the control to 21:1 in the treatment of T1R2, indicating an accelerated composting process. The NH₄-N levels were the highest in T1R2 and T2R2 (659 ± 0.1 and 416 ± 0.2 mg kg⁻¹), while EC increased to 9.5 ± 0.006 ms/cm (T2R1), and bulk density decreased to 410 ± 0.08 kg/m³ (T1R1). These results demonstrate that high-temperature biochar, especially at a rate of 10%, is effective in reducing emissions and improving compost quality. Future research should explore long-term effects and microbial mechanisms to optimize biochar use in composting systems. Full article