Kinetics of nanoparticle uptake into and distribution in human cells

The CeO2/CeO2−δ redox system occupies a unique position as an oxygen carrier in chemical looping processes for producing solar fuels, using concentrated solar energy. The two-step thermochemical ceria-based cycle for the production of synthesis gas from methane and solar energy, followed by CO2 splitting, was considered in this work. This topic concerns one of the emerging and most promising processes for the recycling and valorization of anthropogenic greenhouse gas emissions. The development of redox-active catalysts with enhanced efficiency for solar thermochemical fuel production and CO2 conversion is a highly demanding and challenging topic. The determination of redox reaction kinetics is crucial for process design and optimization. In this study, the solid-state redox kinetics of CeO2 in the two-step process with CH4 as the reducing agent and CO2 as the oxidizing agent was investigated in an original prototype solar thermogravimetric reactor equipped with a parabolic dish solar concentrator. In particular, the ceria reduction and re-oxidation reactions were carried out under isothermal conditions. Several solid-state kinetic models based on reaction order, nucleation, shrinking core, and diffusion were utilized for deducing the reaction mechanisms. It was observed that both ceria reduction with CH4 and re-oxidation with CO2 were best represented by a 2D nucleation and nuclei growth model under the applied conditions. The kinetic models exhibiting the best agreement with the experimental reaction data were used to estimate the kinetic parameters. The values of apparent activation energies (~80 kJ·mol−1 for reduction and ~10 kJ·mol−1 for re-oxidation) and pre-exponential factors (~2–9 s−1 for reduction and ~123–253 s−1 for re-oxidation) were obtained from the Arrhenius plots.

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Kinetics of Phenolic Compounds Modification during Maize Flour Fermentation

Molecules ◽

10.3390/molecules26216702 ◽

2021 ◽

Vol 26 (21) ◽

pp. 6702

Author(s):

Oluwafemi Ayodeji Adebo ◽

Ajibola Bamikole Oyedeji ◽

Janet Adeyinka Adebiyi ◽

Chiemela Enyinnaya Chinma ◽

Samson Adeoye Oyeyinka ◽

...

Keyword(s):

Phenolic Compounds ◽

Phenolic Acids ◽

Kinetic Models ◽

Titratable Acidity ◽

Second Order ◽

Soluble Solids ◽

Maize Flour ◽

First Order ◽

Compound Modification ◽

Kinetics Of

This study aimed to investigate the kinetics of phenolic compound modification during the fermentation of maize flour at different times. Maize was spontaneously fermented into sourdough at varying times (24, 48, 72, 96, and 120 h) and, at each point, the pH, titratable acidity (TTA), total soluble solids (TSS), phenolic compounds (flavonoids such as apigenin, kaempferol, luteolin, quercetin, and taxifolin) and phenolic acids (caffeic, gallic, ferulic, p-coumaric, sinapic, and vanillic acids) were investigated. Three kinetic models (zero-, first-, and second-order equations) were used to determine the kinetics of phenolic modification during the fermentation. Results obtained showed that fermentation significantly reduced pH, with a corresponding increase in TTA and TSS. All the investigated flavonoids were significantly reduced after fermentation, while phenolic acids gradually increased during fermentation. Among the kinetic models adopted, first-order (R2 = 0.45–0.96) and zero-order (R2 = 0.20–0.82) equations best described the time-dependent modifications of free and bound flavonoids, respectively. On the other hand, first-order (R2 = 0.46–0.69) and second-order (R2 = 0.005–0.28) equations were best suited to explain the degradation of bound and free phenolic acids, respectively. This study shows that the modification of phenolic compounds during fermentation is compound-specific and that their rates of change may be largely dependent on their forms of existence in the fermented products.

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Modeling of Phenoxy Acid Herbicide Mineralization and Growth of Microbial Degraders in 15 Soils Monitored by Quantitative Real-Time PCR of the FunctionaltfdAGene

Applied and Environmental Microbiology ◽

10.1128/aem.00990-12 ◽

2012 ◽

Vol 78 (15) ◽

pp. 5305-5312 ◽

Cited By ~ 17

Author(s):

Jacob Bælum ◽

Emmanuel Prestat ◽

Maude M. David ◽

Bjarne W. Strobel ◽

Carsten S. Jacobsen

Keyword(s):

Real Time ◽

Real Time Pcr ◽

Kinetic Models ◽

Exponential Model ◽

Dichlorophenoxyacetic Acid ◽

Order Kinetic ◽

Clear Trend ◽

Gene Copies ◽

2,4 Dichlorophenoxyacetic Acid ◽

Kinetics Of

ABSTRACTMineralization potentials, rates, and kinetics of the three phenoxy acid (PA) herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA), and 2-(4-chloro-2-methylphenoxy)propanoic acid (MCPP), were investigated and compared in 15 soils collected from five continents. The mineralization patterns were fitted by zero/linear or exponential growth forms of the three-half-order models and by logarithmic (log), first-order, or zero-order kinetic models. Prior and subsequent to the mineralization event,tfdAgenes were quantified using real-time PCR to estimate the genetic potential for degrading PA in the soils. In 25 of the 45 mineralization scenarios, ∼60% mineralization was observed within 118 days. Elevated concentrations oftfdAin the range 1 × 105to 5 × 107gene copies g−1of soil were observed in soils where mineralization could be described by using growth-linked kinetic models. A clear trend was observed that the mineralization rates of the three PAs occurred in the order 2,4-D > MCPA > MCPP, and a correlation was observed between rapid mineralization and soils exposed to PA previously. Finally, for 2,4-D mineralization, all seven mineralization patterns which were best fitted by the exponential model yielded a highertfdAgene potential after mineralization had occurred than the three mineralization patterns best fitted by the Lin model.

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Thermodynamics and Kinetics of Glycolytic Reactions. Part I: Kinetic Modeling Based on Irreversible Thermodynamics and Validation by Calorimetry

International Journal of Molecular Sciences ◽

10.3390/ijms21218341 ◽

2020 ◽

Vol 21 (21) ◽

pp. 8341

Author(s):

Kristina Vogel ◽

Thorsten Greinert ◽

Monique Reichard ◽

Christoph Held ◽

Hauke Harms ◽

...

Keyword(s):

Equilibrium State ◽

Kinetic Models ◽

Metabolic Pathways ◽

Irreversible Thermodynamics ◽

Titration Calorimetry ◽

Metabolic Network Analysis ◽

Arrhenius Relation ◽

Catalyzed Reactions ◽

Enzyme Catalyzed Reactions ◽

Kinetics Of

In systems biology, material balances, kinetic models, and thermodynamic boundary conditions are increasingly used for metabolic network analysis. It is remarkable that the reversibility of enzyme-catalyzed reactions and the influence of cytosolic conditions are often neglected in kinetic models. In fact, enzyme-catalyzed reactions in numerous metabolic pathways such as in glycolysis are often reversible, i.e., they only proceed until an equilibrium state is reached and not until the substrate is completely consumed. Here, we propose the use of irreversible thermodynamics to describe the kinetic approximation to the equilibrium state in a consistent way with very few adjustable parameters. Using a flux-force approach allowed describing the influence of cytosolic conditions on the kinetics by only one single parameter. The approach was applied to reaction steps 2 and 9 of glycolysis (i.e., the phosphoglucose isomerase reaction from glucose 6-phosphate to fructose 6-phosphate and the enolase-catalyzed reaction from 2-phosphoglycerate to phosphoenolpyruvate and water). The temperature dependence of the kinetic parameter fulfills the Arrhenius relation and the derived activation energies are plausible. All the data obtained in this work were measured efficiently and accurately by means of isothermal titration calorimetry (ITC). The combination of calorimetric monitoring with simple flux-force relations has the potential for adequate consideration of cytosolic conditions in a simple manner.

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Sorption Kinetics of Uranium-238, Neptunium-237, Caesium-134, and Strontium-85 on a Glacial Deposit

MRS Proceedings ◽

10.1557/proc-506-757 ◽

1997 ◽

Vol 506 ◽

Author(s):

L.N. Moyes ◽

D.J. Bunker ◽

J.T. Smith ◽

F.R. Livens ◽

C.R. Hughes ◽

...

Keyword(s):

Waste Disposal ◽

Kinetic Models ◽

Sorption Kinetics ◽

Kinetic Control ◽

Glacial Deposit ◽

Sorption Behaviour ◽

Low Level ◽

The Individual ◽

Kinetics Of ◽

Uptake Mechanisms

ABSTRACTBatch sorption experiments have been used to assess the sorption behaviour of four radionuclides, important in the context of low-level waste disposal, on a glacial substrate. Data for sorption of 238U, 237Np, 134Cs and 85Sr are compared and agree well with independent studies. A series of well-established kinetic models have been used to describe the individual uptake mechanisms and rate parameters reported. Sorption occurs via both equilibrium and kinetically controlled pathways, with neptunium sorption being under kinetic control to the greatest extent.

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