Kinetic Analysis Research Articles

Kinetic analysis of change of direction simulating a defensive action in soccer players with and without acute fatigue.

The objective of this study is to analyse the kinetic effects of acute fatigue during a 45° change of direction executed with the non-dominant limb, emulating a typical defensive action during pressing in soccer. Seventeen male professional soccer players (age: 21.7 ± 5.4 years) performed a 45° change of direction before and after a fatigue protocol. Participants were instructed to execute an approach run as quickly as possible, to change direction with their non-dominant foot on a force platform, and then continue running with the aim of stopping against an opponent. Times, forces, impulses, and force rates for different subphases during support were compared. Speeds remained consistent across pre-fatigue (4.53 ± 0.55 m s-1) and post-fatigue (4.58 ± 0.70 m s-1) trials. The results indicated a decrease in braking time (p = 0.01), impulse associated with the braking phase (p < 0.01), and impulse during body weight lifting (p = 0.01) under acute fatigue conditions. These changes suggest that, under acute fatigue, soccer players may not decelerate sufficiently in the initial direction of the run and may raise their body less in the first step after the change of direction. Maximum force values and force rates did not show significant changes; however, they were sufficiently high to suggest a potential injury risk in both conditions.

Trehalose-6-phosphate phosphatase expression and enzymatic properties of Fusariumgraminearum

This study presents an exhaustive characterization of the enzymatic attributes and structural properties of trehalose-6-phosphate phosphatase (TPP) derived from Fusarium graminearum. Enzyme activity was evaluated through a meticulously designed enzymatic assay. The findings indicate that the molecular weight of the enzyme is approximately 99.8 kDa, with an optimal reaction temperature and pH of 40 °C and 6.5, respectively. Magnesium ions (Mg2+) markedly enhance the enzymatic activity, resulting in a specific activity of 1.795 U/μg. Kinetic analysis revealed a Km value of 0.96 μmol/L and a Vmax of 15.79 μmol/L/min. Subsequent computational analysis elucidated the three-dimensional architecture of the enzyme and identified the binding site for the substrate trehalose-6-phosphate (T6P). T6P was found to form hydrogen bonds with TPP at residues Lys754, Arg720, His665, Glu758, and Asn756. Additionally, hydrophobic interactions were observed between T6P and residues Phe802, Ile610, Asp801, Pro752, and Gly753. The binding energy calculated for the T6P-TPP complex stood at −5.7 kcal/mol.

Effect of CO2 on the explosion limit parameters and kinetic characteristics of ammonia-hydrogen-air mixtures

To explore the effect of CO2 on the explosion limit parameters and kinetic characteristics of the NH3-H2-air mixtures, the standard combustible gases explosion limits device was utilized to test and analyze the explosion limit, critical oxygen concentration, and explosion triangle. Based on the CHEMKIN software, the suppression mechanism of CO2 on NH3-H2-air mixtures explosion with 0.4 R (hydrogen ratio) and a near-inerting critical concentration was simulated and analyzed. The results indicated that increasing F (volume fraction of CO2) led to a decrease in the upper explosion limit (UEL) of NH3-H2-air mixtures and an increase in the lower explosion limit (LEL). When F increased to 36%, the explosion of the NH3-H2-air mixtures with 0.4 R was completely suppressed. As R increased, the UEL and LEL decreased and increased linearly, respectively, the critical explosion-suppression concentration of CO2 increased, the critical oxygen concentration decreased, and the explosive zone area also increased. In addition, based on the analysis of the changing characteristics of the UEL and LEL, prediction models for the UEL and LEL of NH3-H2-air mixtures with different hydrogen ratios under the effect of CO2 were provided. Reaction kinetics analysis found that less CO2 had a more pronounced impact on ·H and ·OH. However, when F increased to 20-30%, the maximum mole fraction of ·O decreased the most. At this point, the sensitivity of·NH2 towards decreasing oxygen concentrations became comparable to that of ·H and ·OH. When F increased to a near-critical explosion-suppression concentration of 30%, ·H, ·OH, ·O, and ·NH2 were in a critical state of disappearing, and the chain initiation of the explosion was destroyed. Sensitivity analysis indicated that ·H+O2(+M)<=>HO2(+M) and ·NH2+·NH=N2H3 performed a more significant inerting effect on ·H and ·NH2, which ultimately led to the termination of the explosive chain reactions.

Exploration of microwave absorptivity and catalysis of CMF@Co-MoS2 for microwave-initiated depolymerization of lignin

Obtaining key platform chemicals from lignin is a sustainable refining concept of the non-petroleum route. Rapid pyrolysis is a potential refining technology, and microwave-assisted catalytic depolymerization with low energy consumption is preferred. Herein, we reported the strategy of microwave-initiated depolymerization using a self-designed dynamic vapor flow reaction system with a facilely prepared CMF@Co-MoS2-0.18 catalyst, achieving efficient conversion of lignin (Dealkalize) to monophenol. Under constant microwave irradiation (2.45 GHz), the CMF@Co-MoS2-0.18 catalyst had excellent dielectric properties (Dielectric loss factor: 0.56) and microwave heating properties (∼140 s rise to ∼ 600℃). Therefore, microwave-initiated depolymerization of lignin showed that the CMF@Co-MoS2-0.18 catalyst can improve the monophenol content (54.72 %) and phenol selectivity (35.84 %) under the synergistic effect of microwave absorptivity and catalysis. The reaction of the lignin model and kinetics analysis show that the CMF@Co-MoS2-0.18 catalyst increases the yield of monophenol by reducing depolymerization activation energy and selectively breaking the β-O-4 bond. The finite element analysis pointed out that under microwave irradiation, CMF@Co-MoS2-0.18 continuously conducted heat to lignin and the lignin vapor would have sufficient energy to collide with the catalyst active site at a high frequency, which led to an increase in the pre-exponential factor and initiated catalytic depolymerization lignin. In summary, we provide a potential pathway for the rapid conversion of lignin into key platform chemicals.

Polymeric Adsorbent for the Effective Removal of Toxic Dyes from Aqueous Solutions: Equilibrium, Kinetic, and Thermodynamic Modeling

AbstractThis study investigates the adsorption behavior of anionic (Congo red, Eosin yellow) and cationic (Malachite green) dyes on synthesized TD polymer particles, highlighting the material's potential as an effective adsorbent for industrial wastewater treatment. Key operational parameters, including initial solution's pH, contact time, initial dye concentration, and temperature, were systematically evaluated to determine their influence on adsorption efficiency. The experimental data demonstrated that the Langmuir isotherm provided the best fit for all three dyes, indicating monolayer adsorption with maximum adsorption capacities of 153.8 mg/g for Malachite green, 49.36 mg/g for Congo red, and 227.9 mg/g for Eosin yellow. Kinetic analysis revealed that the adsorption of Malachite green and Congo red followed pseudo‐second‐order kinetics, while Eosin yellow adsorption was better described by the intra‐particle diffusion model. Thermodynamic assessments, including Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°), confirmed the spontaneous and endothermic nature of the adsorption processes for Malachite green and Eosin yellow, contrasting with the exothermic behavior observed for Congo red. These findings underscore the versatility and effectiveness of TD polymer particles in removing both anionic and cationic dyes from aqueous solutions. Further research could explore material optimization and real‐world applications to broaden their utility in sustainable water treatment strategies.

Effect of Al2O3-SiO2 mass ratio and sintering temperature on the properties of water-soluble salt-based ceramic cores formed by binder jetting

Binder Jetting (BJ) technology, known for its cost-effectiveness and efficiency, is widely used for the rapid fabrication of complex ceramic cores. However, fabricating high-strength and water-soluble ceramic cores via BJ technology is particularly challenging due to the balance between mechanical properties and water solubility. In this work, BJ technology was employed to fabricate high-strength and water-soluble salt-based ceramic cores (SCC) regulated synergistically by Al2O3 and SiO2. The effects of the mass ratio of Al2O3 to SiO2 (A/S) and sintering temperature on the properties of Na2CO3-based samples were investigated, with detailed analyses of the regulation mechanism through thermodynamic, kinetic, and microstructural examinations. The results indicated that when A/S was 1:4, the bending strength of samples sintered at 760 °C for 60 min reached up to 62.38 MPa with good water collapsibility. Thermodynamic and kinetic analyses revealed that the formation of Na2SiO3 was prioritized over NaAlO2, and the content of Na2SiO3 as well as the proportion of liquid phase increased with the decrease of A/S and the increase of sintering temperature, resulting in the increase of sample density, as confirmed by microstructure analyses, which was the main strengthening mechanism of samples. Ultimately, complex-structure SCC samples were successfully fabricated. This study provides an insightful method for fabricating high-strength and water-soluble ceramic cores, with significant potential applications in the casting industry.

Influence of P and C co-alloying on soft magnetic properties and crystallization behavior of FeSiBPCCu nanocrystalline alloys

In this study, multicomponent synergistic effects were adopted to enhance the glass-forming ability (GFA), processing window (PW), thermal stability, and soft magnetic properties (SMPs) of FeCuSiB nanocrystalline alloys (NAs) with high Fe and Cu contents via P and C co-alloying. The co-addition of P and C is beneficial for enhancing the GFA, expanding the PW, and increasing the crystallization resistance of the compound phases in present FeCuSiBPC alloys. Consequently, the Fe81.5Cu1.7Si3.8B9P3C1 alloy exhibited a large optimum TA window of up to 100 °C and a large tA window of 40 min for nanocrystallization. Crystallization kinetic analysis showed that the co-addition of P and C led to a high-frequency factor (v) in the precipitation of α-Fe crystals, which was related to the high nanocrystal density (Nd) of α-Fe. This result may be attributed to the nucleation of α-Fe by Cu and CuP clusters. Additionally, the co-addition of P and C increased the growth active energy (Ep) of the α-Fe crystals because of their larger atomic diffusion resistance. The high Nd and Ep values led to the formation of fine nanostructures and excellent SMPs in FeCuSiBPC alloys. Therefore, the Fe81.5Cu1.7Si3.8B9P3C1 NA obtained by annealing at 420 °C for 30 min exhibited excellent SMPs with a Bs of up to 1.78 T, a low Hc of 7.5 A/m, and a high μe of 9863 (@1kHz). This study provides technical and theoretical guidance for optimizing the composition and processability of NAs with high Fe and Cu contents, paving the way for mass production of high-performance soft magnetic NAs.

Kinetic analysis of TCPP emission from fireproofed upholstered furniture under realistic indoor conditions

Kinetic analysis of TCPP emission from fireproofed upholstered furniture under realistic indoor conditions

Resolving NOX formation of ammonia-hydrogen flame utilizing PLIF technique collaborated with flame structures and chemical kinetics analysis

Carbon-free fuels such as ammonia and hydrogen have attracted much attention in response to tackling with climate problem of global warming, but their high NOX emissions limit practical applications unavoidably. Currently, very few studies have addressed the inter-relationship between flame structures and NOX formation. In addition, few previous studies have analyzed ammonia-hydrogen combustion with low hydrogen mixing ratio through in-depth NOX formation mechanisms. In this work, NOX formation of ammonia-hydrogen swirl flame with different equivalence ratios and hydrogen mixing ratios (<30 %) has been comprehensively investigated, and the connection between flame structures and NOX has been reflected based on PLIF technique. The analytical results showed that as equivalence ratio (Φ = 0.6–1.2) increased, NOX concentration increased firstly and then decreased subsequently, and peak NOX value was observed between Φ = 0.7–0.8. Besides, NOX increased as the hydrogen mixing ratio increased from 10 % to 25 %, being capable of reaching up to 2795 ppm. Furthermore with flame structure analysis, the flame structure could be classified into single-front flame, transition flame, and double-front flame, in which transition flame featured with the largest decomposition reaction region contributing to NH3 oxidation to form NOX (intensive OH radicals propagation); while double-front flame characterized by smallest decomposition reaction region inhibiting the NOX formation via OH suppression (weak OH radicals propagation). Based on systematically flame surface density and chemical kinetics analysis, lean combustion benefited the NOX pathway, whilst rich combustion favored the N2 pathway. In addition, as the hydrogen ratio increased, and the reducibility of NH/NH2 to NOX was weakened, which ultimately promoted the production of NOX. The findings achieved suggest that future combustion techniques by the ammonia-hydrogen dual fuel should avoid the occurrence of transition flame, and prone to the generation of double-front flame, which could thus implement effective suppression on NOX formation.

Non-isothermal kinetic analysis of phase transformations in Fe-Co-V-Mo semi-hard magnetic alloy

In this study, the non-isothermal kinetics and phase transformations within the Fe-Co-V-Mo alloy were investigated. Four distinct transformations were identified: disorder → order (T1), first-stage polymorphic (T2), order → disorder (T3), and second-stage polymorphic (T4). The activation energy (E) for each transformation was determined using isoconversional methods. Fitting model were employed to calculate the kinetic triplets, confirming that all transformations follow the Avrami model. The Johnson-Mehl-Avrami (JMA) and Šesták-Berggren (SB) models were used to determine other kinetic parameters (n, M, and N). The findings suggest that the growth mechanisms for transformations T3 and T4 are interface-controlled, whereas transformation T2 is diffusion-controlled. Consequently, the A3/2 and A3 mechanisms were identified as predominant mechanisms for transformations T2 and T4, respectively. Additionally, transformation T3 follows the A3 mechanism at heating rates of 10 and 20 K/min, and the A2 mechanism at 30 K/min. Kinetic analysis revealed that the addition of Mo in Fe-Co-V alloys, acting as a ferrite (α) stabilizer, decreases the onset temperatures of transformations T1 and T3. Conversely, it increases those of transformations T2 and T4. Furthermore, Mo influences the reduction of E associated with transformation T3.

Oxidative pyrolysis for enhanced-CO2 adsorption capacity in biosolid-derived biochar

The study conducts the adsorption kinetic analysis of biosolid-derived biochar produced from pyrolysis and oxidative pyrolysis. The adsorption kinetic analysis is performed at three different temperatures. The characteristics of the adsorption and diffusion mechanisms are evaluated by applying adsorption kinetic models and diffusion mechanism models. The pseudo-first-order model (PFO) and the pseudo-second-order model (PSO) reveal that the CO2 adsorption process of the biosolid can be categorised as physisorption with activation energy below 40 kJ/mol. The CO2 adsorption capacities of the biochar produced at 700°C, 800°C, and 900°C are 6.3, 7.9, and 6.4 mg/g at 45°C, respectively. In contrast, the biochar produced from oxidative pyrolysis shows a CO2 adsorption capacity of 7.5 mg/g at 45°C. Film and intraparticle diffusions are primary rate-limiting factors of the adsorption process. The biochar samples maintain 84-85% of their adsorption capacities after five cyclic tests. The present study demonstrates the CO2 adsorption capacity of biosolid-derived biochar produced from different conditions of pyrolysis, providing an energy-efficient and sustainable solution to CO2 adsorption with solid adsorbents.

Structural characterization of noni (Morinda citrifolia L.) pectin and its inhibitory activity on pancreatic lipase

This study aimed to investigate the physicochemical properties and biological activities of noni pectin (NP) extracted using various solvents, three fractions of noni pectin were obtained using traditional chemical and deep eutectic solvents. NPs are composed of various ratios of galacturonic acid, arabinose, rhamnose, xylose, glucose, and galactose with different yields, molecular weights, esterification degrees (DE), and microstructures. Among the fractions, noni pectin extracted with Betaine-citric acid (BNP) exhibited higher molecular weight, degree for esterification and pancreatic lipase (PL) inhibitory activity than the other fractions. Enzyme kinetic analysis indicated that BNP inhibited PL via a noncompetitive mechanism. BNP significantly altered the secondary structure of PL and quenched PL fluorescence, suggesting a static quenching mechanism. Isothermal titration calorimetry (ITC) further demonstrated that the binding of BNP to PL was spontaneous and driven by enthalpy, primarily mediated by hydrogen bonding and van der Waals forces. Molecular docking simulations also confirmed strong noncovalent interactions (hydrogen bonding and van der Waals forces) between BNP and PL. This study validated the high efficiency of the deep eutectic solvent-extracted noni pectin fraction in pancreatic lipase inhibition.

Assessing the discrepant role of anions in the transformation of reactive oxygen species in H2O2 and PDS system: A comparative kinetic analysis

Clarifying reactive oxygen species (ROS) variation in the presence of co-existing anions is significant for understanding the catalytic effect of magnetite (Fe3O4)-induced advanced oxidation processes (AOPs) in natural environment, yet this remains controversial. Herein, we compare the specific impacts of NO3-, SO42-, and Cl- on ROS (•OH, SO4•-, O2•-, and 1O2) exposure concentration in H2O2 and peroxydisulfate (PDS) systems, as well as how these variations affect the catalytic efficiency by developing kinetic model. In both two systems, NO3- demonstrates no discernible effect on ROS, whereas SO42- inhibits the exposure of all ROS and thus micropollutants degradation. Through theoretical calculation, it is proposed that SO42- primarily exerts its influence through affecting the electronic structure over catalyst surface. Regarding Cl-, it affects ROS exposure mainly by reacting with ROS. It shows inhibitory effect on 1O2 in both systems, but its suppressive impact on •OH is markedly more pronounced in H2O2 system compared to PDS system, which may be related to its rapid reactivity with SO4•-. Besides, the chlorine radicals (mainly ClO•) generated through the reaction of Cl- may exert a selective influence on micropollutants degradation. This study can help to re-understand the influence behavior of co-existing anions during AOPs.

Biochemical and steady-state kinetic analyses of arsenate reductases from an arsenic-tolerant strain of Citrobacter youngae IITK SM2

Biochemical and steady-state kinetic analyses of arsenate reductases from an arsenic-tolerant strain of Citrobacter youngae IITK SM2

Is beudantite a stable host phase of arsenic and lead? New insights from molecular-scale kinetic analyses

Is beudantite a stable host phase of arsenic and lead? New insights from molecular-scale kinetic analyses

Comparative study of pre- and post-Cu modified calcium-based desulfurizers: experimental and theoretical insights into adsorption vs. catalysis

This study focused on the dry desulfurization of calcium-based materials, with the aim of conducting an in-depth investigation into the mechanistic differences in desulfurization between traditional commercial calcium-based materials and their Cu-modified counterparts, utilizing experiments, reaction kinetics, and density functional theory (DFT). Through a fixed-bed reactor, factors affecting desulfurization efficiency were investigated, with characterizations pre- and post-desulfurization. The experimental results showed that Cu significantly improved desulfurization performance of calcium-based materials, shifting the mechanism from adsorption- to catalysis-dominated. Among factors, temperature notably influenced calcium-based materials. Reaction kinetics analyses revealed that temperature boosted both rates of the surface chemical reaction-controlled stage and the internal diffusion process, explaining its significant impact. DFT simulations indicated Ca(OH)2(101) surfaces strongly adsorbed reactants but suffered from saturation and competitive adsorption, hindering efficiency. In contrast, Cu-modified surfaces, while exhibiting reduced adsorptive capacity, introduced new catalytic sites with low energy barriers, thereby enhancing desulfurization efficiency, particularly in the presence of water, which can directly participate in the subsequent formation of sulfate ions.

Nitrogen-doped hierarchically porous carbon derived from biomass for efficient capture of iodine

Effectively capturing radioactive iodine formed during nuclear energy utilization is crucial for environment protection and human health. Herein, we present a facile and effective strategy to synthesize a nitrogen-doped hierarchically porous carbon from corn stalks for iodine capture in gaseous and liquid environment. The as-prepared carbon material possesses a hierarchically micro/mesopore structure with highly developed mesopores, a large specific surface area (1892.99 m2 g−1), and suitable nitrogen-doping (2.32 at.%). As a result, the carbon material exhibits efficient iodine capture performance, showing a large capture capacity of 3.14 g g−1 at 80 °C for iodine vapor and a fast removal rate of ∼97 % within 5 min for iodine aqueous solution, outperforming most of carbon-based materials for iodine capture reported in literatures. Thermodynamic and kinetic analyses reveal that the adsorption of iodine vapor conforms to the Langmuir model and pseudo-second-order model, respectively. Density functional theory calculation results indicate that the doped-nitrogen heteroatoms strengthen the interaction between iodine molecules and carbon, which can enhance the affinity for iodine molecules by forming a donor–acceptor complex through the donation of lone-pair electrons, thereby facilitating effective capture of iodine. This work develops a biomass-based porous carbon with potential to efficiently capture radioactive iodine.

Influence of alumina on the performance of Ag/ZnO based catalysts for carbon dioxide hydrogenation

We study silver-zinc oxide type catalysts with and without the addition of alumina and perform structural analysis and activity tests for the hydrogenation of carbon dioxide. Adding alumina has a dispersing effect on the zinc oxide without structurally altering the silver phase. An alumina-surface enriched ZnO/Al2O3 phase is observed with an increased surface reducibility. Ag/ZnO has a high selectivity towards carbon monoxide (63 ± 12 %) and methane (24 ± 3 %) and low selectivity towards methanol (13 ± 0.5 %). Operando infrared (SSITKA-FTIR) and mass spectrometric product detection indicate methane formation via an adsorbed carbon monoxide (COads) intermediate. The selectivity changes gradually with increasing alumina content, up to 80 ± 3 % toward methanol, and 20 ± 4 % carbon monoxide without methane detection, combined with a tripling of the space time yield to 0.65 ± 0.02mmolMeOH*gcat-1*h−1 at 250 °C and 30 bar. Kinetic analysis suggests that the selectivity change originates from hindering the CO-pathway, while the formate pathway leading to methanol remains active.

Directly Regenerating of Spent LiCoO2 with Gradient F-Doped Subsurface towards Ultra-Stable Storage Properties.

As great potential recycling strategy, the direct regeneration of spent LiCoO2 (LCO) is beneficial for lowering environmental pollutions and promoting global sustainability. However, owing to the using of binder and electrolyte, some fluorine impurities would be remained into spent materials. Considering the doping behaviors of F-elements, their suitable content introducing would facilitate the energy-storage abilities of regenerated LCO. Herein, through the tailored introduction of F-elements, spent LCO are successfully regenerated with physical-chemical evolutions. Benefitting from the existed oxygen vacancies, the diffusion energy-barrier of F-elements is reduced from 1.73 eV to 0.61 eV, facilitating the establishment of gradient F-doped subsurface, along with the formation of rigid CoO5F. Meanwhile, excess F-elements (1 wt %, as a threshold) lead to the formation of LiF passivation layer on the surface. Thus, the as-optimized sample displays a considerable capacity of 154.4 mAh g-1 even at 5.0 C, with retention rate (88.3 %) in 3.0-4.5 V. Supported by detailed electrochemical and kinetic analysis, the structural advantages are confirmed to boost the improved redox activity of Co-ions and the alleviating of irreversible oxygen-release. Give this, the work is anticipated to reveal the evolutions of regenerated LCO with the introduced F-elements, whilst providing the practical regeneration strategies toward excellent high-voltage properties.

Optimizing solvothermal synthesis of aluminum-loaded pomelo peel for enhanced fluoride adsorption using response surface methodology

Addressing fluoride contamination in water remains a critical challenge, particularly when seeking cost-effective solutions. In this study, we present a novel aluminum-loaded pomelo peel adsorbent (PPA-Al), synthesized via a one-step solvothermal method, with parameters optimized through response surface methodology. The ideal conditions were established at 2.96 g of pomelo peel, 2 g of NaAlO₂, a reaction temperature of 168.62 °C, and a duration of 140.78 minutes. Characterization of PPA-Al revealed an abundance of hydroxyl and carbon functional groups, enhancing its reactivity with coordination unsaturated aluminum sites. Adsorption isotherms conformed to both Langmuir and Freundlich models, achieving a maximum adsorption capacity of 88.81 mg·g⁻¹, outperforming many existing biomass-based adsorbents. Kinetic analysis indicated that fluoride adsorption followed a pseudo-second-order model, with thermodynamic evaluations suggesting that this process is a spontaneous endothermic reaction. Characterization techniques, including Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS), confirmed interactions between fluoride ions and -OH and -CH groups, as well as the formation of Al-F bonds. Notably, the use of PPA-Al reduces groundwater treatment costs by approximately 74.33∼83.24 % compared to activated alumina, and it can be reused multiple times without reagent regeneration. These findings highlight PPA-Al as a promising, efficient material for fluoride removal, while also demonstrating innovative applications for agricultural waste.