Kinetic Parameters Research Articles

Use of Population-Based Compartmental Modeling and Retinol Isotope Dilution to Study Vitamin A Kinetics and Total Body Stores among Ghanaian Women of Reproductive Age

BackgroundLimited data are available on vitamin A kinetics and total body stores (TBS) in women. Such information can be obtained using compartmental modeling and retinol isotope dilution (RID). ObjectivesObjectives were to apply population-based (“super-subject”) modeling to determine retinol kinetics in nonpregnant Ghanaian women of reproductive age and to use RID to predict TBS in the group and its individuals. MethodsWomen (n = 89) ingested a dose of [2H6]retinyl acetate and blood samples (3/woman) were collected from 6 h to 91 d, with all participants sampled at 14 d, about half at either 21 or 28 d, and each at other time. Composite data (plasma retinol fraction of dose; FDp) were analyzed using Simulation, Analysis and Modeling software to obtain kinetic parameters, TBS, and other state variables as well as model-derived values for the RID composite coefficient FaS. The latter were used in the RID equation TBS (μmol) = FaS × 1/SAp (where SAp is plasma retinol-specific activity) to predict TBS at various times. ResultsModel-predicted TBS was 973 μmol (n = 87). Geometric mean RID-predicted TBS was 965, 926, and 1006 μmol at 14, 21, and 28 d, respectively, with wide ranges [for example, 252–3848 μmol on day 14 (n = 86)]; TBS predictions were similar at later times. Participants had a mean 2 y of vitamin A in stores and estimated liver vitamin A concentrations in the normal range. Model-predicted vitamin A disposal rate was 1.3 μmol/d and plasma recycling number was 37. ConclusionsSuper-subject modeling provides an estimate of group mean TBS as well as group-specific values for the RID coefficient FaS; the latter can be used to confidently predict TBS by RID for individual participants in the group under study or in similar individuals at 14 d or more after isotope ingestion. Trial registration numberTrial is registered (NCT04632771) at https://clinicaltrials.gov.

Transport properties of canonical PIN-FORMED proteins from Arabidopsis and the role of the loop domain in auxin transport.

The phytohormone auxin is polarly transported in plants by PIN-FORMED (PIN) transporters and controls virtually all growth and developmental processes. Canonical PINs possess a long, largely disordered cytosolic loop. Auxin transport by canonical PINs is activated by loop phosphorylation by certain kinases. The structure of the PIN transmembrane domains was recently determined, their transport properties remained poorly characterized, and the role of the loop in the transport process was unclear. Here, we determined the quantitative kinetic parameters of auxin transport mediated by Arabidopsis PINs to mathematically model auxin distribution in roots and to test these predictions invivo. Using chimeras between transmembrane and loop domains of different PINs, we demonstrate a strong correlation between transport parameters and physiological output, indicating that the loop domain is not only required to activate PIN-mediated auxin transport, but it has an additional role in the transport process by a currently unknown mechanism.

Nanofibrous 3D scaffolds capable of individually controlled BMP and FGF release for the regulation of bone regeneration

The current clinical applications of bone morphogenetic proteins (BMPs) are limited to only a few specific indications. Locally controlled delivery of combinations of growth factors can be a promising strategy to improve BMP-based bone repair. However, the success of this approach requires the development of an effective release system and the correct choice of growth factors capable of enhancing BMP activity. Basic fibroblast growth factor (bFGF, also known as FGF-2) has shown promise in promoting bone repair, although conflicting results have been reported. Considering the complex biological activities of FGF-2, we hypothesized that FGF-2 can promote BMP-induced bone regeneration only if the dosage and kinetic parameters of the two factors are individually tailored. In this study, we conducted systematic in vitro studies on cell proliferation, differentiation, and mineralization in response to factor dose, delivery mode (sequential or simultaneous), and release rate. Subsequently, we designed individually controlled BMP-7 and FGF-2 release poly(lactide-co-glycolide) (PLGA) nanospheres attached to the poly(l-lactic acid) (PLLA) nanofibrous scaffolds. The data showed that BMP-7-induced bone formation was accelerated by a relatively higher FGF-2 dose (100 ng/scaffold) delivered at a faster release rate, or by a relatively lower FGF-2 dose (10 ng/scaffold) at a slower release rate in an in vivo bone regeneration model. In contrast, a very high dose of FGF-2 (1000 ng/scaffold) inhibited bone regeneration under all conditions. In vitro and in vivo data suggest that FGF-2 improved BMP-7-induced bone regeneration by coordinating FGF-2 dosage and release kinetics to enhance stem cell migration, proliferation, and angiogenesis. Statement of significanceBone morphogenetic proteins (BMPs) are the most potent growth/differentiation factors in bone development and regeneration. However, the clinical applications of BMPs have been limited to only a few specific indications due to the required supraphysiological dosages with the current BMP products and their side effects. Locally controlled delivery of BMPs and additional growth factors that can enhance their osteogenic potency are highly desired. However, different growth factors act with different mechanisms. Here we report a nanofibrous scaffold that mimics collagen in size and geometry and is immobilized with biodegradable nanospheres to achieve local and distinct release profiles of BMP7 and FGF2. Systematic studies demonstrated low dose BMP7 and FGF2 with different temporal release profiles can optimally enhance bone regeneration.

Access to an ELM-suppressed X-point radiator regime in TCV snowflake minus configurations

TCV’s operating regime with an X-point radiator (XPR) has been broadened by changing the magnetic geometry. XPRs have properties that could make them an attractive power exhaust solution for fusion reactors. These include the conversion of a high fraction of exhaust power into radiation. TCV had previously accessed the XPR regime only with difficulties, as predicted for plasmas where radiative losses are dominated by carbon impurities, that are ubiquitous in TCV. Guided by this theoretical model of the XPR, recent experiments employed TCV’s configurational versatility to demonstrate that XPR access can be facilitated by introducing a second X-point in the vicinity of the separatrix. This configuration, which has a snowflake-minus topology, features a particularly long magnetic connection length from the region just above the X-point to the outer midplane together with a wide geometrical interface with the private flux region that reaches high neutral pressure. Transitioning to this configuration in a high-power H-mode leads to a shift in the radiating region across the separatrix from the divertor to a volume above the X-point, i.e. within the last closed flux surface (LCFS). This displacement of the radiating region is co-incident with the disappearance of edge localised modes (ELMs), while retaining H-mode confinement, a behaviour only, to date, observed in devices with metallic walls. In contrast to observations in these other devices, on TCV, the primary strike points in these configurations remain attached. Detailed measurements of the plasma kinetic parameters inside and outside of the separatrix now challenge the models for access and stability of the XPR and ELMs alike.

Kinetic analysis of coal oxidative pyrolysis before and after immersion effect

The oxidative pyrolysis kinetics of coal before and after immersion effect was studied by thermogravimetric experiments. Non-isothermal thermogravimetric analysis data were analyzed at four heating rates of 5, 10, 20 and 30 K/min. Furthermore, temperature-programmed experiments and Fourier-transform infrared (FTIR) spectroscopy were employed to understand the oxidation activity and chemical structure of raw coal and soaked coal. After coal immersion effect, the increase in the content of active functional groups, the increase in the concentration of gaseous products, and the decrease in crossing point temperature during oxidation process all indicate that soaked coal is easier to oxidize and spontaneously combust. Lastly, four model-free methods such as Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Friedman and Kissinger methods are employed to calculate the activation energy (Eα). Kinetic analysis reveals that Eα value obtained by the former three methods significantly depends on the conversion of coal oxidative pyrolysis process, and the average Eα value of soaked coal obtained by four methods is lower than that of raw coal. For the kinetic analysis of coal oxygen adsorption and combustion stages, it is more reliable to adopt the FWO and KAS methods in turn. This research helps to better understand the mechanism of enhanced oxidation activity of soaked coal and optimizes the calculation method of kinetic parameters in different oxidation stages of coal.

Study of Heavy Oil In-situ Combustion with Copper Biocatalysts: Kinetics and Thermodynamic Aspects of High-Temperature Oxidation Reactions

In-situ combustion is considered an efficient thermally enhanced oil recovery method. However, the combustion front stabilization remains a challenge for the scientific community. The present study examines the efficacy of copper tall oil (Cu-TO) and copper sunflower oil (Cu-SFO) on heavy oil high-temperature oxidation reactions, which are believed to solve this challenge. We applied non-isothermal differential scanning calorimetry (DSC) analyses combined with an isoconversional kinetic approach in order to calculate kinetic parameters, thermodynamic functions, and the effective rate constant of these reactions. The obtained results demonstrated that both catalysts are able to reduce the activation energies and shift oxidation regions to lower temperatures, with Cu-SFO showing superior performance. Kinetic predictions further supported these findings and revealed that the selected catalysts contributed significantly to decreasing oxidation times across all conversion ranges. Additionally, thermodynamic analyses indicated that Cu-SFO facilitated a more ordered and energetically favorable oxidation process, as demonstrated by increasingly negative entropy values and consistently lower Gibbs free energy. The research highlights the Cu-SFO catalyst exceptional ability to accelerate the transition from low-temperature to high-temperature oxidation while maintaining high catalytic activity. Taken together all these results, this research work contributes to provide comprehensive insights from the kinetic and thermodynamic analysis that reveal unique catalytic effects and reaction mechanisms, presenting an approach to stabilize combustion front and improve heavy oil recovery efficiency, addressing a critical challenge in the field of in-situ combustion.

Kinetic model of thermal decomposition of nitric acid solutions of hydrazine nitrate

The kinetic parameters of thermal decomposition of an aqueous solution containing 0.029 mass fractions of hydrazine nitrate and 0.44 mass fractions of nitric acid have been determined: onset temperature and specific thermal effect of exothermic reactions, activation energy, pre-exponential factor, reaction rate and order. Based on the data obtained, a mathematical model of thermal decomposition of nitric acid solutions of hydrazine nitrate has been proposed. It has been found that thermolysis of the solution has a multi-stage nature and can be described by a system of 5 equations of 1st and 2nd order. A comparison of two approaches to creating a mathematical model has been carried out: based on adiabatic calorimetry and differential scanning calorimetry data.

Influence of free and microencapsulated recombinant rabbit nerve growth factor with chitosan on rabbit sperm quality parameters.

β-nerve growth factor (βNGF) plays a crucial role in reproductive physiology and sperm quality. Enzymatic activity of seminal plasma and vaginal fluids reduces available βNGF and it has been demonstrated that chitosan microspheres could protect rrβNGF from degradation. This study examined the effects of microencapsulated rrbNGF with chitosan on rabbit sperm viability, motility and capacitation status. Results showed that 0.5 and 1 μg/mL of microencapsulated rrβNGF, as well as free rrβNGF or empty microspheres, did not adversely affect sperm viability or total motility after 2 h of incubation. However, the highest progressivity kinetic parameters were observed with 1 μg/mL free rrβNGF, while the highest curvilinear velocity (VCL) occurred with 0.5 μg/mL microencapsulated rrβNGF. Empty chitosan microspheres did not induce acrosome reaction (AR), but both concentrations of free and rrβNGFch favoured AR during invitro incubation. The study suggests that using chitosan spheres did not show any adverse effects on sperm traits, unlike free rβNGF and rrβNGFch promoted capacitation and AR. Further research is needed to explore the potential of rrβNGFch in modifying invitro capacitation and inducing ovulation during artificial insemination.

The influence of polyphenols on the hydrolysis and formation of volatile esters in wines during aging: An insight of kinetic equilibrium reaction

The evolution of volatile esters leads to changes in wine aroma during aging. In this study, polyphenol effect on ester equilibrium in wines was investigated through three aging experiments. Kinetic parameters of esters were calculated in four red wines. Results showed that the reaction rate constant (kobsd) was mainly determined by the molar concentration ratio of alcohols or acids to the corresponding esters. Phenolic matrix was more likely to influence the activation energy (Ea). Higher contents of total polyphenol led to the increase of Ea, resulting in the reactions less prone to happen but more susceptible to temperature changes. Combined with the practical wine aging and exogenous polyphenol addition experiments, the impact of polyphenol composition was revealed. Flavanols with higher polymerization degrees were found more beneficial for ester preservation than monomer flavanols or anthocyanins. This work could provide theoretical guidance in enhancing fruity aroma in wines via modulating phenolic matrix.

Experimental and modeling studies on char combustion under pressurized O2/H2O conditions

The desorption kinetic parameters for pressurized combustion and gasification reactions were determined based on a C++ program coupled with the Langmuir-Hinshelwood (L-H) kinetic model developed and experimental data from pressurized char combustion, and the established L-H kinetic model for pressurized char-O2/H2O combustion was refined in the current paper. The activation energy for desorption in reactions involving pressurized char-O2 and char-H2O was determined to be 250.8 kJ/mol, accompanied by a pre-exponential factor of 5.42×1010 g/(m2 s). Using this foundation, the current research conducted simulations to investigate the impacts of temperature, pressure, and H2O concentration on the oxidation adsorption rate (Rads,oxi), desorption rate (Rdes), gasification adsorption rate (Rads,gas), and the competitive influences of kinetics and diffusion processes within the pressurized char-O2/H2O combustion. The simulation results indicate a gradual increase in Rdes and Rads,gas with char conversion to reach a peak, followed by a gradual decline. Conversely, the Rads,oxi varies smoothly throughout the char conversion process. At 1673 K/1.0 MPa, the char-O2/H2O reaction rate is primarily constrained by Rads,oxi and Rads,gas, with the adsorption reaction serving as the rate-controlling step. Moreover, it was noted that a rise in pressure resulted in a linear increase in Rads,oxi, Rdes, and Rads,gas. At elevated temperatures, the impact of pressure on them becomes more noticeable. However, the introduction of H2O mitigates this effect. Elevated temperature and pressure facilitate the competition on the kinetics of char-O2 combustion for O2 diffusion, resulting in the conversion of char being more susceptible to O2 diffusion rate limitation. With the addition of 20% H2O, the competition effect was weakened. In the case of pressurized combustion involving char and O2/H2O, the char conversion is primarily constrained by the O2 diffusion rate and is scarcely influenced by the H2O diffusion rate.

Use of magnetic fields to impact glass-transition and crystallization during manufacturing of ZBLAN optical fibers

ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) is the most stable glass among the Heavy Metal Fluoride (HMF) family and has a wide range of applications in medical industry, telecommunication, IR transmission, among others. But, due to crystal formation while manufacturing of ZBLAN fiber its theoretical minimum loss has not been achieved yet. Some techniques such as high cooling rate and microgravity conditions have been utilized to reduce the crystal formation but are challenging to implement during manufacturing of these fibers. Alternatively, magnetic field (MF), also a body force like gravity, is expected to influence the crystal formation mechanism and glass kinetics. In this work, ZBLAN glass is processed under magnetic fields of various intensities while simulating fiber drawing manufacturing process conditions. Then, the processed ZBLAN is analyzed using Differential Scanning Calorimetry (DSC) at varying scanning rates. Various glass kinetics parameters such as activation energy, fragility, and preferred crystallization mechanism in terms of Avrami parameter (n) have been analyzed. The glass transition temperature (Tg) increases for a given sample as scanning rate (β) increases. Samples processed under varying magnetic fields, at the same scanning rate, displayed higher glass transition temperatures. Also, when the magnetic field increases, the activation energy required for glass transition decreases, and the fragility index (m) decreases. There is also a preference for surface crystallization over volume crystallization. These results encourage application of magnetic fields for reducing crystal formation while processing ZBLAN glass.

Comparative Analysis of Kinetic Responses and Injury Risk During Landing from 45 cm Height: A Study of Barefoot vs. Sports Shoes Conditions

Jumping and landing biomechanics are closely related to the risk of acute injury due to prolonged exposure to high-ground reaction forces in basketball-like sports, which can lead to lower-limb musculoskeletal injuries in the hip, knee, and ankle. Footwear greatly impacts jumping mechanics, but going barefoot provides a unique perspective on how the human body interacts with the ground. This study aims to find out the kinetic responses during drop landing from 45 cm height with and without sports shoe conditions. Twenty-five healthy young adults were volunteers for this study. Kinetic parameters were recorded and processed by using Quattro Jump force plat and Mars Quarter performance analysis software. Data were presented as mean ± SD values and statistical analysis was performed using statistical software package SPSS-26. The drop landing data of with and without shoe shows scattered parameters with maximum forces of 4706.12N and 5393.04N at 45 cm height, indicating a 66% and 75% risk of metatarsal injury. The stabilization force was 632.64N and 623.64N at 45 cm, reached at 0.58s and 0.66s respectively. Time from Max Force to MFBS Regression analysis indicated a low R-squared value and a random fit plot. In barefoot (without shoe) conditions, the initial contact force, and maximum force were 85.71% and 13.60% higher (250N and 5393.04N respectively) compared to landing with shoes (100N and 4706.12N). However, the stabilization force was higher (632.64N) when landing with shoes compared to landing barefoot (623.64N). As a result, the risk of musculoskeletal injuries and joint stress was higher when landing barefoot due to the higher initial contact force and maximum force. On the other hand, landing with shoes enhances balance and stability due to the higher stabilization force.

An Investigation on the Thermal Degradation Kinetics of Wood-Polymer Composites Used in Interior Automobile Panels via Non-Isothermal Thermogravimetry

Wood plastic composites (WPCs) offer a promising alternative for various automotive components, combining the benefits of wood and polymers such as lightness, strength, and sustainability. However, determining decomposition kinetics is challenging due to the intricate composition of WPCs. Therefore, this research work focused to analyze the relationship between the thermal degradation of WPCs, the degradation atmosphere, and the kinetics. The kinetic parameters were evaluated by Coats and Redfern method based on a set of TGA experiments under variable atmospheres (inert and oxidative) using 10 ℃/min heating rate. Thermograms demonstrated significant differences in the thermal properties of WPC when subjected to oxidative and inert atmospheres, despite two conditions having the same number of thermal degradation zones. It has been suggested that the process of thermal decomposition of WPC contains three weight loss segments under inert and oxidative atmosphere according to the Gaussian multi-peak fitting function. The Coats-Redfern method showed multi-step chemical kinetics and more accurately characterizes the decomposition behavior of WPC, attributing to its multi-compositional properties. Proposed reaction schemes had regression coefficients higher than 0.9809 to obtain reaction order, activation energy and pre-exponential factor.

Experimental studies and pore-scale modeling of hydrate dissociation kinetics at different depressurization rates in a cubic hydrate simulator

Natural gas hydrate (NGH) is a promising energy resource that has triggered a race for scientific innovation in energy and environmental research. However, there still faces the challenges of low-efficiency hydrate dissociation and unstable gas production during the hydrate production. Clarifying the kinetic mechanism of hydrate dissociation is the key to improving the efficiency of “phase-transition to gas-supply” in hydrate-bearing sediment. This study successfully conducts hydrate dissociation experiments with different depressurization rates in the Cubic Hydrate Simulator (CHS). A novel dissociation kinetic model integrating the hydrate pore-scale morphology and its evolutions are established, and the sensitivities of the kinetic and thermal parameters are discussed in detail. The mathematical relationship between the hydrate saturation and reaction area is quantitatively analyzed for the hydrate formation and dissociation kinetics. The history matching simulation with the newly developed model achieves an excellent agreement with the experimental results. The full-lifecycle kinetic behaviors of the hydrate dissociation in the depressurization experiments are finely characterized. It is found that the evolutions of the hydrate saturation (SH) and temperature (T) spatial distributions exhibit strong heterogeneous characteristics in the vessel due to the phase transition and heat transfer effects. In addition, this reveals that the relatively high depressurization rate can lead to a more significant dissociation rate in the depressurization stage. This provides a new reliable and adaptable method for describing the hydrate dissociation kinetics in the porous media.

Automatization of theoretical kinetic data generation for tabulated TS models building - Part 1: Application to 1,3-H-shift reactions

Estimation of kinetic parameters is a key aspect of chemical combustion modeling and several approaches were developed to approximate unknown data. In this work, a code in Python was developed to build tables of transition state (TS) models automatically for intramolecular H-shift reactions in alkyl radicals. The code generates the kinetic rules for all the possible combinations of methyl-substituted reactions based on the structures of the minimal, non-substituted, reactant, TS, and product. The code is able to create and differentiate multiple transition state configurations, considering the axial and equatorial positions for the cyclic substituents and including all the possible pathways for the reactions, which is shown to be an important feature in performing accurate automatic kinetic calculations. Each structure is automatically submitted to geometry optimization and electronic energy calculations, as well as the relaxed scans of the torsional modes identified by the code. From the results of electronic calculations, the rate constants for each pathway are obtained automatically by the application of the transition state theory with tunneling corrections, in a defined temperature range. The kinetic coefficients, as well as the modified Arrhenius parameters, are then assembled and organized to create a final table that connects the kinetic data with TS structure characteristics. These tables can be directly applied as a kinetic data source for reaction mechanism development. The ability of the code to generate reliable rate constants was tested for 1,3-H-shift reactions and the results were compared with theoretical data manually produced, and showed a good agreement. In particular, the code was able to create all the transition state configurations, with an exhaustive description of all possible reaction pathways, using a rigorous and systematic counting based on symmetry, stereocenters, and diastereomers. The proposed method leads to more accurate results on these aspects, compared to repetitive hand calculations of dozens of rate constants.

Dynamic data-driven multiscale modeling for predicting the degradation of a 316L stainless steel nuclear cladding material

We have developed a long short-term memory stacked ensemble (LSTM-SE) surrogate modeling approach that can provide rapid predictions of microstructural evolution and the resultant mechanical properties of American Iron and Steel Institute (AISI) 316L series stainless steel (SS316L) fuel cladding under conditions of varying temperature and radiation dose rate. To acquire training data, we developed and implemented a kinetic Monte Carlo (KMC) model to simulate precipitation kinetics of M23C6, γ’, and G phases within SS316L cladding. Experimentally reported precipitation kinetics of SS316L in literature were linked to the kinetic parameters of the simulated precipitation in our KMC model. The model was then used to simulate microstructure evolution under synthetically generated treatments of varying temperature and radiation dose rate for periods of up to 3000 h. Changes in volume fraction, number density, and particle size of precipitates were recorded, and particle area fractions were correlated using statistical methods to develop the surrogate model. Simultaneously, the mechanical properties of the simulated microstructures were evaluated using microstructure-based finite element method (FEM) analysis to determine the elastic modulus, yield stress, ultimate tensile strength, and elongation to failure of the aged microstructures. Using this approach, our surrogate model can predict precipitation behavior within 0.25 % volume fraction and mechanical properties within 6 % relative error from the values predicted by the KMC and FEM models using 50 training simulations as input. The trained recurrent neural network-based model can return estimations of precipitation kinetics and mechanical properties ∼1000 times faster than the physics-based codes. This work demonstrates, as a proof of concept, that microstructural evolution under variable conditions can be predicted using a statistics-based model informed by a practicably obtainable dataset. The potential applications of this type of modeling framework are discussed.

Experimental Study on the Thermal Behavior Characteristics of the Oxidative Spontaneous Combustion Process of Fischer–Tropsch Wax Residue

Coal-to-liquid technology is a key technology to ensuring national energy security, with the Fischer–Tropsch synthesis process at its core. However, in actual production, Fischer–Tropsch wax residue exhibits the characteristics of spontaneous combustion due to heat accumulation, posing a fire hazard when exposed to air for extended periods. This significantly threatens the safe production operations of coal-to-liquid chemical enterprises. This study primarily focuses on the experimental investigation of the oxidative spontaneous combustion process of three typical types of wax residues produced during Fischer–Tropsch synthesis. Differential Scanning Calorimetry (DSC) was used to test the thermal flow curves of the three wax residue samples. Kinetic analysis was performed using the Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) methods to calculate their apparent activation energy. This study analyzed the thermal behavior characteristics, exothermic properties, and kinetic parameters of three typical wax residue samples, exploring the ease of reaction between wax residues and oxygen and their tendency for spontaneous combustion. The results indicate that Wax Residue 1 is rich in low-carbon chain alkanes and olefins, Wax Residue 2 contains relatively fewer low-carbon chain alkanes and olefins, while Wax Residue 3 primarily consists of high-carbon chain alkanes and olefins. This leads to different thermal behavior characteristics among the three typical wax residue samples, with Wax Residue 1 having the lowest heat release and average apparent activation energy and Wax Residue 3 having the highest heat release and average apparent activation energy. These findings suggest that Wax Residue 1 has a higher tendency for spontaneous combustion. This research provides a scientific basis for the safety management of the coal chemical industry, and further exploration into the storage and handling methods of wax residues could reduce fire risks in the future.

Thermogravimetric characteristics and predictive modelling of oil sand bitumen pyrolysis using artificial neural network

This study investigated the pyrolysis of oil sand bitumen as an alternative energy source in response to the global energy crisis. Thermogravimetric analysis was performed at different heating rates in a nitrogen atmosphere. Low moisture and ash content and high volatile matter content were found by proximate analysis, indicating the possibility for effective pyrolysis and ignition. Fourier-transform infrared spectroscopy identified functional groups, and X-ray diffraction confirmed the absence of problematic expandable clay minerals. The Friedman, Flynn–Wall–Ozawa, and Kissinger–Akahira–Sunose models were used to calculate the kinetic parameters. The activation energies of the models were primarily between 100 and 200 kJ/mol, with the Friedman model having higher values. It was discovered that the process was non-spontaneous and endothermic. An artificial neural network model demonstrated the potential for future energy applications by accurately predicting the behaviour of pyrolysis.

Evaluation of the reaction order and kinetic modeling of Domanic oil shale upgrading at supercritical water conditions

Two different kinetic models were developed for the kinetic study of Domanic oil shale conversion in the supercritical water. The oil shale reaction order was evaluated with a three-lump reaction scheme taking into account oil shale, gases, and synthetic oil. Contrary to the commonly reported first-order, it was found that a higher order (2.5) is more suitable for the conversion of oil shale at supercritical water conditions. The main reaction mechanism and predictions were obtained using a more detailed reaction network (five-lump model), which precisely estimates the experimental yield of all compounds contemplated. The statistical analysis suggested that the estimated kinetic parameters were suitably optimized, as well as the sensitivity analysis confirmed that these are the optimal values. The conversion of organic matter into gas and coke through free radical reactions exhibits larger rates using supercritical water. Low temperature (380 °C) and short reaction times favor the yield of synthetic oil because when these conditions are exceeded secondary cracking reactions provoke the generation of gases. Gas production is mainly carried out by the conversion of organic matter for brief reaction times and the transformation of carbonates for extended periods.

Differential impacts of body composition on oxygen kinetics and exercise tolerance of HFrEF and HFpEF patients

This study aims to (1) compare the kinetics of pulmonary oxygen uptake (VO2p), skeletal muscle deoxygenation ([HHb]), and microvascular O2 delivery (QO2mv) between heart failure (HF) patients with reduced ejection fraction (HFrEF) and those with preserved ejection fraction (HFpEF), and (2) explore the correlation between body composition, kinetic parameters, and exercise performance. Twenty-one patients (10 HFpEF and 11 HFrEF) underwent cardiopulmonary exercise testing to assess VO2 kinetics, with near-infrared spectroscopy (NIRS) employed to measure [HHb]. Microvascular O2 delivery (QO2mv) was calculated using the Fick principle. Dual-energy X-ray absorptiometry (DEXA) was performed to evaluate body composition. HFrEF patients exhibited significantly slower VO2 kinetics (time constant [t]: 63 ± 10.8 s vs. 45.4 ± 7.9 s; P < 0.05) and quicker [HHb] response (t: 12.4 ± 9.9 s vs. 25 ± 11.6 s; P < 0.05). Microvascular O2 delivery (QO2mv) was higher in HFrEF patients (3.6 ± 1.2 vs. 1.7 ± 0.8; P < 0.05), who also experienced shorter time to exercise intolerance (281.6 ± 84 s vs. 405.3 ± 96 s; P < 0.05). Correlation analyses revealed a significant negative relationship between time to exercise and both QO2mv (ρ= -0.51; P < 0.05) and VO2 kinetics (ρ= -0.63). Body adiposity was negatively correlated with [HHb] amplitude (ρ= -0.78) and peak VO2 (ρ= -0.54), while a positive correlation was observed between lean muscle percentage, [HHb] amplitude, and tau (ρ= 0.74 and 0.57; P < 0.05), respectively. HFrEF patients demonstrate more severely impaired VO2p kinetics, skeletal muscle deoxygenation, and microvascular O2 delivery compared to HFpEF patients, indicating compromised peripheral function. Additionally, increased adiposity and reduced lean mass are linked to decreased oxygen diffusion capacity and impaired oxygen uptake kinetics in HFrEF patients.