Explore the vast range of titles available.

Thermal decomposition of solids often includes simultaneous occurrence of the overlapping processes with unequal contributions in a specific physical quantity variation during the overall reaction (e.g., the opposite effects of decomposition and evaporation on the caloric signal). Kinetic analysis for such reactions is not a straightforward, while the applicability of common kinetic calculation methods to the particular complex processes has to be justified. This study focused on the critical analysis of the available kinetic calculation methods applied to the mathematically simulated thermogravimetry (TG) and differential scanning calorimetry (DSC) data. Comparing the calculated kinetic parameters with true kinetic parameters (used to simulate the thermoanalytical curves), some caveats in the application of the Kissinger, isoconversional Friedman, Vyazovkin and Flynn–Wall–Ozawa methods, mathematical and kinetic deconvolution approaches and formal kinetic description were highlighted. The model-fitting approach using simultaneously TG and DSC data was found to be the most useful for the complex processes assumed in the study.

Amyloid formation involves the conversion of soluble protein species to an aggregated state. Amyloid fibrils of β-parvalbumin, a protein abundant in fish, act as an allergen but also inhibit the in vitro assembly of the Parkinson protein α-synuclein. However, the intrinsic aggregation mechanism of β-parvalbumin has not yet been elucidated. We performed biophysical experiments in combination with mathematical modeling of aggregation kinetics and discovered that the aggregation of β-parvalbumin is initiated by the formation of dimers stabilized by disulfide bonds and then proceeds via primary nucleation and fibril elongation processes. Dimer formation is accelerated by H₂O₂ and hindered by reducing agents, resulting in faster and slower aggregation rates, respectively. Purified β-parvalbumin dimers readily assemble into amyloid fibrils with similar morphology as those formed when starting from monomer solutions. Furthermore, addition of preformed dimers accelerates the aggregation reaction of monomers. Aggregation of purified β-parvalbumin dimers follows the same kinetic mechanism as that of monomers, implying that the rate-limiting primary nucleus is larger than a dimer and/or involves structural conversion. Our findings demonstrate a folded protein system in which spontaneously formed intermolecular disulfide bonds initiate amyloid fibril formation by recruitment of monomers. This dimer-induced aggregation mechanism may be of relevance for human amyloid diseases in which oxidative stress is often an associated hallmark.

The heat-discharging kinetics of an iron-substituted Mn2O3/Mn3O4 redox pair subjected to long-term thermal cycling tests using a temperature swing process at high temperatures was investigated for next-generation concentrated solar power plants equipped with thermochemical energy storage. The heat-discharge mode kinetics for long-term thermal-cycled samples have never been reported. Additionally, comparisons of the heat-discharge mode kinetics for both long-term thermal-cycled and as-prepared samples have never been discussed. In terms of the reproducibility and sustainability of thermochemical energy storage, kinetic evaluations of samples with thermally stable morphologies subjected to long-term thermal cycling at high temperatures are important for next-generation solar thermal power plants. For the long-term thermal-cycled sample, the A2 model based on the Avrami–Erofeev reaction describes the discharging mode behavior in a fractional conversion range of 0–0.24, the contracting area (R2) model best fits in a fractional conversion range of 0.24–0.50, and the third-order (F3) model matches in a fractional conversion range of 0.50–0.70. For the as-prepared sample, the power-law (P2) model describes the behavior of the first part of the discharging mode, whereas the Avrami–Erofeev (A4) model best fits the last half of the discharging mode. The predicted theoretical models for both samples were compared with previous kinetic data.

Composting is recognized as a sustainable waste management approach in which microorganisms treat and stabilize biodegradable waste under aerobic conditions to obtain compost as a final product. In this paper, composting of biowaste in a rotary drum composter (closed system) and an open container (open system) was compared. Temperature, pH, electrical conductivity, a carbon-to-nitrogen mass ratio (C/N ratio) and contents of moisture, carbon and dry and volatile matter, were measured during composting. Results showed decreasing profiles for moisture, volatile matter, and carbon contents, as well as for the C/N ratio, while increasing profiles for the dry matter content and electrical conductivity during composting in both systems. Leachates were formed only during the first three days of composting and were characterized with high organic loads, high ammonia concentrations, low pH, and high conductivity and turbidity. The organic matter content data during the composting process were analysed according to the first order kinetic model. Results suggested that there was a difference in the rate of organic matter decomposition, which was higher when composting in the open vessel than in the rotary drum composter.

Vascular interventional surgery is a typical method for diagnosing and treating cardio-cerebrovascular diseases. However, a surgeon is exposed to significant X-radiation exposure when the operation is conducted for a long period of time. A vascular intervention surgical robotic system for assisting the surgeon is a promising approach to address the aforementioned issue. When developing the robotic system, a high displacement accuracy is crucial, and this can aid in enhancing operating efficiency and safety. In this study, a novel kinetics analysis and active disturbance rejection control (ADRC)-based controller is proposed to provide high accuracy for a string-driven robotic system. In this controller, kinetics analysis is initially used to improve the accuracy affected by the inner factors of the slave manipulator. Then, the ADRC controller is used to further improve the operating accuracy of the robotic system. Finally, the proposed controller is evaluated by conducting experiments on a vascular model. The results indicate maximum steady errors of 0.45 mm and 6.67°. The experimental results demonstrate that the proposed controller can satisfy the safety requirements of the string-driven robotic system.

The aim of this work is to investigate the thermal behaviour of Malaysian poultry waste under oxidation and inert atmospheres. The poultry processing dewatered sludge (PPDS) derived from poultry waste was considered as a raw material. The study was conducted in the LABSYS Evo Setaram thermogravimetric analyser (TGA). The temperature was ramped from 30°C to 800°C in oxygen and nitrogen atmospheres at heating rates 5, 10, 15, and 20 K/min. The devolatilization process was more reactive in combustion than that in pyrolysis as evaluated from the derivative thermogravimetric (DTG) peak height and peak temperature at the second stage. In addition, a kinetic parameter called the activation energy of TGA combustion was consistently higher than pyrolysis at each conversion. The activation energy ranged from 127.32 to 245.47 kJ/mol and 88.86 to 133.13 kJ/mol for TGA under combustion and pyrolysis, respectively. The results of the TGA analysis indicate that the combustion and pyrolysis process significantly affect the degradation process of PPDS. The sample fuel properties and activation energy data obtained in this study may be beneficial for further development of thermochemical conversion (TCC) application of biomass through the computational fluid dynamics (CFDs) software.

Several successful examples—where physically sounded kinetic information was obtained from thermoanalytical data in different application fields, such as polymerization of thermosetting resins, biobased polymers and nanocomposites, crystallization and glass transition of semi-crystalline polymers and their nanocomposites—are here presented and discussed. It is explained how the kinetic parameters obtained from advanced isoconversional methods can be interpreted in terms of reaction mechanisms or changes in the rate-limiting step of the overall process, in the case of complex chemical reactions or complex physical transitions, and how these parameters can be used to extract model-fitting parameters.

Parkinson’s disease is a highly debilitating neurodegenerative condition whose pathological hallmark is the presence in nerve cells of proteinacious deposits, known as Lewy bodies, composed primarily of amyloid fibrils of α-synuclein. Several missense mutations in the gene encoding α-synuclein have been associated with familial variants of Parkinson’s disease and have been shown to affect the kinetics of the aggregation of the protein. Using a combination of experimental and theoretical approaches, we present a systematic in vitro study of the influence of disease-associated single-point mutations on the individual processes involved in α-synuclein aggregation into amyloid fibrils. We find that lipid-induced fibril production and surface catalyzed fibril amplification are the processes most strongly affected by these mutations and show that familial mutations can induce dramatic changes in the crucial processes thought to be associated with the initiation and spreading of the aggregation of α-synuclein.

DNA-encoded libraries (DEL)-based discovery platforms have recently been widely adopted in the pharmaceutical industry, mainly due to their powerful diversity and incredible number of molecules. In the two decades since their disclosure, great strides have been made to expand the toolbox of reaction modes that are compatible with the idiosyncratic aqueous, dilute, and DNA-sensitive parameters of this system. However, construction of highly important C(sp³)–C(sp³) linkages on DNA through cross-coupling remains unexplored. In this article, we describe a systematic approach to translating standard organic reactions to a DEL setting through the tactical combination of kinetic analysis and empirical screening with information captured from data mining. To exemplify this model, implementation of the Giese addition to forge high value C–C bonds on DNA was studied, which represents a radical-based synthesis in DEL.

Zeolitic imidazolate frameworks (ZIFs) are interesting materials for use in several aspects: energy storage material, gas sensing, and photocatalysis. The thermal stability and pyrolysis process are crucial in determining the active phase of the material. A deep understanding of the pyrolysis mechanism is in demand. Therefore, the thermodynamics and combustion process with different heating rates was examined, and the kinetic parameters were computed employing thermogravimetric tests. Based on the TG analysis of combustion, pyrolysis moves to the high-temperature region with an increase in heating rate. The decomposition process can be separated into the dehydration (300–503 K) and the pyrolysis reaction (703–1100 K). Three points of the decomposition process are performed by dynamical analysis owing to shifts of slopes, but the combustion process has only one stage. The Zeolitic imidazolate framework’s structure properties were examined using TDDFT-DFT/DMOl3 simulation techniques. Dynamical parameters, for instance, the possible mechanism, the pre-exponential factor, and the apparent activation energy are obtained through comparison using the Kissinger formula. The thermodynamics analysis of the Zn1-xCox-ZIF-8 materials is an effective way to explore the temperature influence on the process of pyrolysis, which can benefit several environment purifications, photocatalyst, and recent applications.