Kinetic Values Research Articles

Ionised AGN outflows in the Goldfish galaxy: The illuminating and interacting red quasar eFEDSJ091157.4+014327 at z ∼ 0.6

Context. Evolutionary models suggest that the initial growth phases of active galactic nuclei (AGN) and their central supermassive black holes (SMBHs) are dust-enshrouded and characterised by jet or wind outflows that should gradually clear the interstellar medium (ISM) in the host by heating and/or expelling the surrounding gas. eFEDSJ091157.4+014327 (z ∼ 0.6) was selected from X-ray samples of eROSITA (extended ROentgen Survey with an Imaging Telescope Array) for its characteristics: red colours, X-ray obscuration (NH = 2.7 × 1022 cm−2) and luminous (LX = 6.5 × 1044 erg s−1), similar to those expected in quasars with outflows. It hosts an ionised outflow as revealed by a broad [O III]λ5007 Å emission line in the SDSS integrated spectrum. For a proper characterisation of the outflow properties and their effects, we need spatially resolved information. Aims. We aim to explore the environment around the red quasar, morphology of the [O III] gas and characterise the kinematics, mass outflow rates and energetics within the system. Methods. We used spatially resolved spectroscopic data from Multi Unit Spectroscopic Explorer (MUSE) with an average seeing of 0.6″ to construct flux, velocity and velocity dispersion maps. Thanks to the spatially resolved [O III]λ5007 Å emission detected, we provide insights into the morphology and kinematics of the ionised gas and better estimates of the outflow properties. Results. We find that the quasar is embedded in an interacting and merging system with three other galaxies ∼50 kpc from its nucleus. Spatially resolved kinematics reveal that the quasar has extended ionised outflows of up to 9.2−0.4+1.2 kpc with positive and negative velocities up to 1000 km s−1 and −1200 km s−1, respectively. The velocity dispersion (W80) ranges from 600–1800 km s−1. We associate the presence of high-velocity components with the outflow. The total mass outflow rate is estimated to be ∼10 M⊙ yr−1, a factor of ∼3–7 higher than the previous findings for the same target and kinetic power of 2 × 1042 erg s−1. Considering different AGN bolometric luminosities, the kinetic coupling efficiencies range from 0.01%–0.03% and the momentum boosts are ∼0.2. Conclusions. The kinetic coupling efficiency values are low, which indicates that the ionised outflow is not energetically relevant. These values don’t align with the theoretical predictions of both radiation-pressure-driven outflows and energy-conserving mechanisms. However, note that our results are based only on the ionised phase while theoretical predictions are multi-phase. Moreover, the mass loading factor of ∼5 is an indication that these outflows are more likely AGN-driven than star formation-driven.

Mathematical Analysis of Nonlinear Differential Equations in Polymer Coated Microelectrodes

A theoretical analysis is conducted on the electrochemical behaviour of micro disk electrodes coated with thin coatings of electroactive polymers. The main focus of efforts to characterize the planar diffusion chemical reaction within polymer-modified ultra-microelectrodes is the creation of a theoretical model that explicitly takes into account the potential for the polymer film to cover the inlaid micro disc support surface. Approximate formulae for the steady-state amperometric response and formulation of the boundary value problem are given. The impact of substrate concentration, mediator concentration and current responsiveness in the solution besides the polymer film is also investigated. Akbari-Ganji method (AGM) and differential transformation method (DTM), two adequate and widely available analytical methods, were utilized to determine the steady-state non-linear diffusion equation. The approximate analytical solution for the substrate concentration and mediator concentration and the current for the small experimental kinetic values and diffusion coefficients are presented. We additionally determine the problem’s numerical solution using the MATLAB tool. A satisfactory agreement can be seen when the numerical outcomes verify with the analytical findings.

Kinetic study of magnesium dissolution using a magnesium oxide industrial by-product

Phosphorus recovery via struvite precipitation in wastewater treatment plants (WWTPs) is a key technology for nutrient recovery. This work investigates the dissolution kinetics of an industrial low-grade magnesium oxide (LG-MgO) by-product as an alternative to common magnesium sources for struvite precipitation. The main aims were to develop a parsimonious dissolution kinetic model capable of predicting the release of magnesium into the solution with accuracy and studying the influence of temperature on dissolution kinetics. The simultaneous fitting of all the experiments by non-linear regression rendered overall process values of the dissolution model’s frequency factor (498,606 L3.22 min−1 mmol−1.74), activation energy (37.51 kJ·mol−1), and reaction order (2.74). The goodness-of-fit for all experiments was evaluated by the total sum of squared residuals and R2 coefficients, being excellent under all conditions. The estimated kinetic coefficient values showed a temperature-dependent variation of the kinetic coefficient, increasing from 0.079 to 0.219 L3.22 min−1 mmol−1.74 when the temperature increased from 15 to 35 °C. The magnesium dissolution was fast in the first 5 min, where 40–78 % of magnesium dissolved with respect to the initial magnesium in the solid. Despite the assumptions made in the model derivation, the developed kinetic model provides a practical, reliable, and easy-to-use tool for WWTPs to estimate the LG-MgO dosage required to achieve targeted magnesium concentrations, thereby improving reagent use efficiency and phosphorus recovery.

Compaction quality assessment of highway using roller-integrated positive maximum kinetic energy increment detection technique

During conventional highway construction, quality control and acceptance (QC/QA) are based on limited spot tests of material density at random locations which may not comprehensively represent the entire compacted area and are vulnerable to potential biases. Based on roller-integrated positive maximum kinetic energy increment detection technique with real-time kinematic global positioning systems, this research adopted kinetic energy compaction value (KECV) as a real-time monitoring index for the highway compaction quality, and subsequently proposed an KECV-based assessment method to estimate the compaction quality of subgrade and pavement materials. Additionally, a global interpolation method (Green spline) was adopted to obtain estimates for both KECVs and compaction quality at any location on the work area, enabling the analysis of the passing rate of compaction quality for the entire work area. A case study on the Hengyong highway project in China indicates a highly linear correlation between the KECV and the compaction parameters, the compactness of LLL silt, and the relative density of cement-stabilized macadam; therefore, it can serve as a reliable index for monitoring compaction quality. Assessment of compaction quality on the entire work area can be fast and continuously achieved using the proposed method, which can effectively overcome the above limitation of conventional testing, timely feedback compaction information to avoid quality defects, and availably improve the construction quality of highways.

C-terminal Poly-histidine Tags Alter Escherichia coli Polyphosphate Kinase Activity and Susceptibility to Inhibition

In Escherichia coli, many environmental stressors trigger polyphosphate (polyP) synthesis by polyphosphate kinase (PPK1), including heat, nutrient restriction, toxic compounds, and osmotic imbalances. PPK1 is essential for virulence in many pathogens and has been the target of multiple screens for small molecule inhibitors that might serve as new anti-virulence drugs. However, the mechanisms by which PPK1 activity and polyP synthesis are regulated are poorly understood. Our previous attempts to uncover PPK1 regulatory elements resulted in the discovery of PPK1* mutants, which accumulate more polyP in vivo, but do not produce more in vitro. In attempting to further characterize these mutant enzymes, we discovered that the most commonly-used PPK1 purification method – Ni-affinity chromatography using a C-terminal poly-histidine tag – altered intrinsic aspects of the PPK1 enzyme, including specific activity, oligomeric state, and kinetic values. We developed an alternative purification strategy using a C-terminal C-tag which did not have these effects. Using this strategy, we were able to demonstrate major differences in the in vitro response of PPK1 to 5-aminosalicylic acid, a known PPK1 inhibitor, and observed several key differences between the wild-type and PPK1* enzymes, including changes in oligomeric distribution, increased enzymatic activity, and increased resistance to both product (ADP) and substrate (ATP) inhibition, that help to explain their in vivo effects. Importantly, our results indicate that the C-terminal poly-histidine tag is inappropriate for purification of PPK1, and that any in vitro studies or inhibitor screens performed with such tags need to be reconsidered in that light.

Problem-Based Learning for Calculating Kinetic Parameters from Michaelis-Menten Equation

In “Advanced Enzymology” at the University of Barcelona, we teach various methods for identifying uni-uni irreversible reactions. Kinetic constants such as maximum velocity (Vmax) and Michaelis constant (Km) are calculated using non-linear regression with the Michaelis-Menten equation. However, if a computer is not available, students must calculate these kinetic parameters using linear regressions with Lineweaver-Burk, Eadie-Hofstee, and Hanes-Woolf plots. Michaelis-Menten equation: v = (Vmax [S]) / (Km + [S]), Lineweaver-Burk equation: 1/v = (Km/Vmax) (1/[S]) + 1/Vmax, Eadie-Hofstee equation: v = – Km (v/[S]) + Vmax, Hanes-Woolf equation: [S]/v = (1/Vmax) [S] + (Km/Vmax). The objective of this work was that students explore various methods for calculating kinetic constants and determine the most effective approach. A problem was prepared with data on substrate concentrations ([S]) and reaction rates (v). Data points with lower substrate concentration, and also with lower velocities had higher errors. The Michaelis-Menten plot provided only an approximate estimation of the kinetic constants, as it is not a linear graph. The Lineweaver-Burk plot generated maximum velocities that were too low due to the higher errors for low substrate concentrations, rendering impossible values of the kinetic parameters. The Eadie-Hofstee plot provided better results, as the values of v/[S] compensated their errors. Furthermore, kinetic constants were obtained directly from the slope and intersection of the line equation. The Hanes-Woolf plot also produced correct values for kinetic parameters, since high substrate concentrations were less erroneous than lower ones. After completing this computer class, students were very satisfied and learned the different methods for obtaining kinetic parameters. Non-linear regression is undoubtedly the most accurate method for obtaining kinetic parameters values. However, in the absence of computers, the Eadie-Hofstee plot is the best and most commonly used plot in kinetic papers.

Microstructure, martensitic transformation kinetics, and magnetic properties of (Ni50Mn40In10)100−xCox melt-spun ribbons

AbstractThe effect of Co-doping on the structure, microstructure, martensitic phase transformation kinetics, and magnetic properties of the melt-spun (Ni50Mn40In10)1−xCox (x = 1, 2, and 3) Heusler ribbons, named hereafter Co1 (x = 1), Co2 (x = 2), and Co3 (x = 3), was assessed using X-ray diffraction, scanning electron microscope, energy-dispersive spectroscopy, X-ray fluorescence, differential scanning calorimetry, and vibrating sample magnetometer. The XRD results reveal the formation of a 14M martensite structure alongside the face-centered-cubic (fcc) γ phase. The crystallite size ranges between 50 and 98 nm for the 14M martensite and from 9 to 16 nm for the γ phase. The mass fraction of the γ phase lies between 36.4 and 44.2%. Co-doping affects the lattice parameters and the characteristic temperatures (martensite start, martensite finish, austenite start, and austenite finish). The calculated activation energy values for the non-isothermal martensitic transformation kinetics are 257 kJ mol−1 and 135.6 kJ mol−1 for the Co1 and Co2, respectively. The produced ribbons show a paramagnetic behavior. The variation in the coercivity can be related to the crystallite size and mass fraction of the γ phase. The produced ribbons exhibit an exchange bias at room temperature that decreases with increasing the Co content.

Kinetic ITC of DNA Aptamers Binding for Small Molecules and Implications for Binding Assays and Biosensors.

The determination of kon and koff values through kinetic analysis is crucial for understanding the intricacies of aptamer-target binding interactions. By employing kinetic ITC, we systematically analyzed a range of ITC data of various aptamers. Upon plotting their kon and koff values as a function of their Kd values, a notable trend emerged. Across a range of Kd values spanning from 28 nM to 864 μM, the kon value decreased from 2×105 M-1 s-1 to 96 M-1 s-1, whereas the koff value increased from 1.03×10-3 s-1 to 0.012 s-1. Thus, both kon and koff contributed to the change of Kd in the same direction, although the range of kon change was larger. Since experiments are often run at close to the Kd value, this concentration effect also played an important role in the observed binding kinetics. The effect of these kinetic parameters on two common sensing mechanisms, including aptamer beacons and strand-displacement assays, are discussed. This work has provided the kinetic values of small molecule binding aptamers and offered insights into aptamer-based biosensors.

Comprehensive analysis on the combined effects of reaction kinetics and heat transfer on biomass pyrolysis

The current study links the heat transport phenomena and reaction kinetics when the pyrolysis was occurring of sugarcane bagasse (SCB) biomass. A thermogravimetric analyzer was used to conduct a kinetic research on the pyrolysis of biomass in a nitrogen atmosphere, covering a heating rate range of 10–40 °C/min. The thermogravimetric studies (TGA) allowed for the differentiation of three stages associated with the breakdown of hemicellulose, cellulose, and lignin. Using three first-order processes and the Arrhenius theory, the activation energy and pre-exponential factor were determined.Three important components of biomass—lignin, hemicellulose, and cellulose—were assumed to respond independently and in parallel in the kinetics model. Additionally, the transport characteristics of each component were assessed using their respective kinetic values and other thermo-physical characteristics. The regulating mechanism was then anticipated by the heat transfer map for three elements with different particle sizes. The transfer qualities were mainly influenced by particle size, at a crucial dimension dictating the shift in the system for several parts.

Raman spectra soft modeling of the biodiesel oxidation through evolving factor analysis & multivariate curve resolution

The oxidative stability of biodiesel is defined by its relative resistance to the action of oxygen at room temperature. Its determination is an essential reference to the quality of biofuel and a significant parameter to be determined. This parameter concerns the quality of the biodiesel to be supplied to the consumer, and its determination is fundamental to maintaining the engine's proper functioning. Raman spectroscopy allows the rapid obtaining of structural information regarding biodiesel quality and, when aided by multivariate analysis methods, allows a quantitative determination of specific properties. This work uses Raman spectroscopy, Multivariate Curve Resolution with Alternative Least Squares (MCR-ALS) method, and Evolving Factor Analysis (EFA) to study biodiesel's oxidation kinetics. Also, the vibrational modes C = C, CH2, and CH3 were identified as the main structural groups involved in this process, corroborating previous studies. The MCR-ALS & EFA combination allowed modeling of the degradation kinetics following an A → B → C mechanism, where A corresponds to the biodiesel (starting material), B is related to the hydroperoxide mixture, and C is the final product. The results also suggested that this process follows a first-order reaction, with kinetic constant values of k1 = 0.0056 min−1 and k2 = 0.0031 min−1.

Succinimide Derivatives as Acetylcholinesterase Inhibitors-In Silico and In Vitro Studies.

We studied the effect of succinimide derivatives on acetylcholinesterase activity due to the interest in compounds that influence this enzyme's activity, which could help treat memory issues more effectively. The following parameters were established for this purpose based on kinetic investigations of the enzyme in the presence of succinimide derivatives: the half-maximal inhibitory concentration, the maximum rate, the inhibition constant, and the Michaelis-Menten constant. Furthermore, computational analyses were performed to determine the energy required for succinimide derivatives to dock with the enzyme's active site. The outcomes acquired in this manner demonstrated that all compounds inhibited acetylcholinesterase in a competitive manner. The values of the docking energy parameters corroborated the kinetic parameter values, which indicated discernible, albeit slight, variations in the inhibitory intensity among the various derivatives.

Use of coenzyme Q-10 to improve the pregnancy rate in sheep

One of the factors responsible for less pregnancy rates is the use of frozen semen in sheep due to the oxidative stress created by the process. The aim of this experiment was to test the effects of adding coenzyme Q-10 (CoQ10) to the seminal extender on sperm quality and the pregnancy rate of sheep. In this study, ejaculates from eight Dorper rams of reproductive age were used and tested in four treatments: Control (pure BotuBov®), C1 (175 µM of CoQ10), C3 (350 µM of CoQ10), and C7 (700 µM of CoQ10). Samples were collected in triplicate from each animal, and sperm analysis was performed by CASA after thawing at 0 h and 2 h. The samples were also analyzed by flow cytometry for plasma and acrosomal membrane integrity, stability, lipid peroxidation, mitochondrial potential, and superoxide anion production. In total, 198 ewes were inseminated by laparoscopy and divided into two groups: control (n=98) and C7 (n=100). Pregnancy diagnosis was performed at 30 days. Coenzyme Q10 proved to be safe for semen cryopreservation, not altering sperm kinetic values between the groups post-thawing. In flow cytometry, the C1 and C7 groups achieved a better index of plasma membrane integrity and membrane stability (P<0.05). A increased pregnancy rate was observed in C7 (52 %) compared to the control (38 %). In conclusion, coenzyme Q10 assists in the cryopreservation process, protecting the sperm cell and improving pregnancy rates in ewes.

Experimental and dynamic molecular study of zinc extraction from sphalerite concentrate in ternary deep eutectic solvent

The utilization of deep eutectic solvents (DESs) as a novel class of solvents in metal production offers a promising alternative to aqueous solutions due to their biocompatibility and non-aqueous nature. This study investigated the leaching of sphalerite concentrate using a ternary stable DES composed of choline chloride (ChCl), p-toluene sulfonic acid (PTSA), and ethylene glycol (EG) (at a molar ratio of 1:1:1). The effects of time, temperature, and milling time on zinc recovery were examined within specific ranges (20–1440 min, 40–100 °C, and 0–24 h, respectively). The study revealed the significant influence of time and temperature on zinc dissolution efficiency within ChCl:PTSA:EG. Higher temperatures and longer leaching times were found to improve efficiency substantially. The research emphasized the crucial role of milling time, demonstrating that longer durations enhanced zinc efficiency by introducing more defects on the sphalerite surface and reducing particle size. Under optimized conditions, including a temperature of 100 °C, 24 h of ball milling, and 1440 min of leaching, a zinc recovery of 99.7% was achieved. Infrared analysis confirmed the chemical stability of the solvents during the leaching process. The sphalerite leaching process involved the formation of zinc chloride ion complexes and evolution H2S gas. An unexpected finding is the presence of lead sulfate in the leach residue, which may be attributed to sulfide oxidation to sulfate species. The Avrami kinetic model provided an excellent fit with the sphalerite dissolution data in ChCl:PTSA:EG DES, indicating that the rate-controlling step was primarily influenced by the diffusion process. R2 values for kinetics fitting data were in the range of 0.87–0.97 for temperature of 40–100 °C. The molecular dynamic (MD) simulation findings indicated robust electrostatic interactions between the metal ions Zn2+ and Fe2+ and the Cl− ions of the ChCl molecules. Additionally, the MD calculations showed that the metal ions formed complexes with some O-S-O atoms within the PTSA molecule.

Oxygenolytic cleavage of 1,2-diols with dioxygen by a mononuclear nonheme iron complex: Mimicking the reaction of myo-inositol oxygenase

A mononuclear iron(II) complex, [(TpPh2)FeII(OTf)(CH3CN)] (1) (TpPh2 = hydrotris(3,5-diphenylpyrazol-1-yl)borate, OTf = triflate) has been isolated and its efficiency toward the aliphatic CC bond cleavage reaction of 1,2-diols with dioxygen has been investigated. Separate reactions between 1 and different 1,2-diolates form the corresponding iron(II)-diolate complexes in solution. While the iron(II) complex of the tetradentate TPA (tris(2-pyridylmethyl)amine) ligand is not efficient in affecting the CC cleavage of 1,2-diol with dioxygen, complex 1 displays catalytic activity to afford carboxylic acid and aldehyde. Isotope labeling studies with 18O2 reveal that one oxygen atom from dioxygen is incorporated into the carboxylic acid product. The oxygenative CC cleavage reactions occur on the 1,2-diols containing at least one α-H atom. The kinetic isotope effect value of 5.7 supports the abstraction of an α-H by an iron(III)-superoxo species to propagate the CC cleavage reactions. The oxidative cleavage of 1,2-diolates by the iron(II) complex mimics the reaction catalyzed by the nonheme diiron enzyme, myo-inositol oxygenase.

Statistical optimized production of Phytase from Hanseniaspora guilliermondii S1 and studies on purification, homology modelling and growth promotion effect

This investigation was performed to obtain a promising phytase enzyme producing yeast. In this regard, the PSM was used to isolate the phytase-producing Hanseniaspora guilliermondii S1 (MG663578) from sugarcane juice. The SSF optimum conditions for phytase generation were optimized using (OVAT) one-variable-at-a-time strategy using both Box-Behnken design and shake flask method (g/100 ml: 0.05 yeast extract, 0.15 Peptone, 0.05 malt extract 0.50 dextrose, pH 5.8 and 28ᵒC). The protein model developed was shown to be adequate for phytase production (91% accuracy), with the greatest phytase productivity in shake flask with substrate jack fruit seed powder being 395 ± 0.43 U/ml compared to 365U/ml for the BBD projected value. Crude Phytase was partially purified with a protein recovery of 43%, revealing a molecular weight of 120 kDa. It had an enzyme kinetic value of Km 3.3 mM and a Vmax of 19.1 mol/min. The 3D structure of PhyS1 amino acid sequences (PhyS1. B99990002) was simulated using Modeler 9.23, and the validated result revealed that 86.7% were in the favored region by Ramachandran plot. The SAVES server verified the 3D PDB file as satisfactory, and the model (in.pdb format) was uploaded in the PMDB database with the accession number ID: PM0082974. At the lab level, Hanseniaspora guilliermondii S1 (MG663578) producing phytase exhibited successful plant growth promotion activity in Ragi - CO 19 (Eleusine coracana L.) and Rice -Navarai - IR 64 (Oryza sativa L.). As a result, a phytase-based formulation for sustainable agriculture must be developed and tested on a large scale in diverse geographical areas of agricultural lands to determine its effect and potential on plant development.

Schiff base functionalized dialdehyde starch for enhanced removal of Cu (II): Preparation, performances, DFT calculations

Dialdehyde starch modified by 2-hydrazinopyridine (HYD-DAS) based on the reaction of dialdehyde starch (DAS) and 2-hydrazinopyridine was synthesized and characterized by FT-IR spectra, element analysis and SEM. HYD-DAS can efficiently adsorb Cu (II) ion to demonstrate visual color changes from yellow to dark brown in aqueous solutions. The influence on HYD-DAS to Cu (II) adsorption including pH value of solution, isotherm, kinetics, thermodynamics and possible mechanism had also been examined. Batch experiments indicate that HYD-DAS's to Cu (II) adsorption reaches equilibrium within 250 min, and its adsorption capacity and rate are 195.75 mg/g and 98.63 %, respectively. Moreover, HYD-DAS to Cu (II) adsorption remains robust and underscoring after five cycles to exhibit good selectivity and reusability. Kinetics studies suggest the absorption process follows a quasi-second-order with isotherms aligning to the Langmuir monolayer model, and thermodynamics reveals that it is a spontaneous endothermic nature of adsorption. Based on the analyses of XPS and DFT calculations, a possible mechanism for HYD-DAS to Cu (II) adsorption is that Cu (II) combined with nitrogen atoms from Schiff base and hydrazine pyridine ring in HYD-DAS.

One-step synthesis of magnetic biochar via co-pyrolysis of walnut shells and Fe-rich mine tails for adsorption capacity improvement of polystyrene sulfonate microplastics: Role of microplastic size

Microplastics made of polystyrene sulfonate microplastics (PSMPs) are highly mobile in aquatic ecosystems and can consequently lead to undesirable health effects in humans. Herein, the adsorption capacity of PSMPs was comprehensively analyzed using untreated biochar made from ground walnut shells (WSB) and iron (Fe) engineered WSB acquired from Fe-mining waste (Fe-WSB), to explore the changes in the adsorption potential and mechanisms by the co-pyrolysis of walnut shells and Fe-rich mine tailings. The adsorption of PSMPs for Fe-WSB (adsorption capacity (Qe) = 0.77–6.75 mg/g) was greater than that for WSB (Qe = 0.27–0.79 mg/g), particularly at lower pH levels, indicating that Fe integration and electrostatic interaction between Fe-WSB and PSMPs significantly affected the adsorption of PSMPs. The R2 values for adsorption kinetics and isotherms highlighted that chemisorption plays a fundamental role in PSMP adsorption using WSB and Fe-WSB in liquid solutions. Further, thermodynamic assessments indicated that PSMP210 (210 Da), PSMP10 K (10,000 Da), and PSMP32 K (32,000 Da) were adsorbed exothermically, with the adsorption efficiency decreasing as van der Waals forces became weaker at high temperatures. The results of X-ray photoelectron spectroscopy, which was conducted on WSB and Fe-WSB both before and after the adsorption of PSMPs, supported the notion that an enhancement in the primary adsorption mechanism (electrostatic interactions, pore-filling effects, π-π and H-bond interactions), following the integration of Fe-oxides onto the WSB surfaces, improved the adsorption of PSMPs in aqueous environments.

The Effect of Riblets on the Aerodynamic Performance of NACA 0018 Airfoil

In this numerical study, riblets on the airfoil were utilized to enhance the aerodynamic performance of NACA0018 airfoil. Riblets of identical height and base length are strategically placed on the suction surface of the airfoil with varying spacing ratios along the flow direction (x) and chord length (c), specifically x/c = 0.3 and 0.7. Four distinct riblet airfoil models are subjected to computational fluid dynamics (CFD) analysis within an angle of attack range from 0° to 21° at a Reynolds number of Re=1×105. The obtained results are systematically compared with the performance of the plain airfoil. Numerical analyses reveal the significant influence of the spacing ratio on flow control and the overall aerodynamic performance of the airfoil, establishing a direct relationship with riblet spacing. The presence of riblet structures is observed to increase the lift coefficient, concurrently delaying the stall angle up to 19°. Notably, the ribbed structures effectively mitigate the interaction between the laminar separation bubble and trailing edge separation, leading to a reduction in turbulent kinetic energy values.

Higher Values of Force and Acceleration in Rear Cross Than Lead Jab: Differences in Technique Execution by Boxers

Background: Boxing, a globally popular combat sport, demands technical precision and powerful strikes at the same time. The kinetic assessment of straight punches, specifically the rear cross and lead jab, is crucial for understanding the biomechanical factors influencing punch effectiveness. This study aims to explore the kinetic properties of these punches in trained boxers, focusing on punch force, acceleration, and the concept of a proximal-to-distal pattern. Methods: Thirteen advanced-level male boxers (body weight 90.6 ± 19.2 kg, height 184.0 ± 7.4 cm, experience 9.5 ± 6.5 y) from local clubs participated in this study. Using a force plate and wireless IMU sensors, we recorded punch force and limb acceleration during the execution of rear-cross and lead-jab punches. Data analysis involved statistical tests to compare the kinetic differences (Mann–Whitney U-test) between the two punch types and assessment of the influence of body mass and training tenure on punch effectiveness (multiple regression analysis). Significant differences were observed between the rear cross and lead jab in terms of total ground reaction force (x¯ = 1709.28 N vs. x¯ = 1176.55 N), acceleration of the fist (x¯ = 94.33 m/s2 vs. x¯ = 66.07 m/s2), forearm (x¯ = 67.11 m/s2 vs. x¯ = 41.62 m/s2) and arm (x¯ = 88.40 m/s2 vs. x¯ = 81.36 m/s2), and target contact time (x¯ = 0.03 s vs. 0.02 s). The rear-cross punch exhibited higher kinetic values, indicating greater effectiveness. Additionally, body mass and training tenure were identified as significant factors influencing punch force (R2 score = 0.640). Conclusions: This study confirmed the biomechanical superiority of the rear cross over the lead jab in terms of generated force among trained boxers. The findings highlight the importance of coordination between each segment’s acceleration to generate a powerful strike. These insights are valuable for coaches and athletes in optimizing training strategies for boxing.

New laminar flame speed correlation for lean mixtures of hydrogen combustion with water addition under high pressure conditions

Hydrogen may become a substitute for liquid fossil fuels, contributing to greenhouse gas emissions reductions in internal combustion engines. Numerical simulations play a critical role in the advancement of these engines, with laminar flame speed being the main input. Experimental data of hydrogen flame speed at elevated pressures are scarce, due to the instability of the flames. Nonetheless, stable hydrogen flames can be predicted using chemical kinetics models. Moreover, the injection of water into the hydrogen fuelled engine could offer several benefits to engine combustion and emission performance, as it modulates the laminar flame speed within the combustion chamber and this effect has not been completely understood. Currently, no correlation exists to predict the laminar flame speed of hydrogen-air combustion with water addition under lean mixture engine operating conditions. In this study, we have extended the newly developed laminar flame speed correlation of hydrogen-air combustion to account for the effects of water addition under engine relevant conditions by using chemical kinetic laminar flame speed values. The laminar flame speed correlation was derived for pressures from 10 to 70 bar, temperatures from 400 to 800 K, equivalence ratios from 0.35 to 1 and water addition by mole from 0 to 20%. The hydrogen laminar flame speed correlation was expressed using polynomial forms with reduced order and number of terms with optimized values of coefficients. Additionally, a new exponential term was proposed to the power term α of the laminar flame speed correlation to capture the coupled effects of pressure and temperature on laminar flame speeds under engine-relevant lean burn water-diluted operating conditions.