scholarly journals Kinetics of chemical processes in the human brain. Modeling of the BOLD-signal at f-MRT research

2019 ◽  
Vol 488 (2) ◽  
pp. 157-161
Author(s):  
S. D. Varfolomeev ◽  
N. A. Semenova ◽  
V. I. Bykov ◽  
S. B. Tsybenova
Keyword(s):  
Experimental Data ◽  
Kinetic Model ◽  
Human Brain ◽  
Dynamic Behavior ◽  
Nervous Tissue ◽  
Chemical Processes ◽  
External Signal ◽  
Bold Signal ◽  
Brain Modeling ◽  
Kinetics Of

A kinetic model describing the impulse of increasing oxygen in the excited nervous tissue of the human brain in response to an external signal is presented. The model is based on biochemical data and describes experimental data on an impulsed hemodynamic response. The model predicts the dynamic behavior of the process participants, which preceding the oxygen impulse and determining the level of the BOLD-signal.

Kinetics of Chemical Processes in the Human Brain: Modeling of the BOLD fMRI Signal

2019 ◽  
Vol 488 (1) ◽  
pp. 125-128 ◽  
Author(s):  
S. D. Varfolomeev ◽  
N. A. Semenova ◽  
V. I. Bykov ◽  
S. B. Tsybenova
Keyword(s):  
Human Brain ◽  
Chemical Processes ◽  
Bold Fmri ◽  
Fmri Signal ◽  
Brain Modeling ◽  
Kinetics Of

Diffusion model for deposition of epitaxial GaAs layers prepared by the MOCVD method

1991 ◽  
Vol 56 (10) ◽  
pp. 2020-2029
Author(s):  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma ◽  
Rudolf Hladina
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Kinetic Model ◽  
Gas Phase ◽  
Substrate Surface ◽  
Deposition Process ◽  
Hydrogen Atmosphere ◽  
Epitaxial Gaas ◽  
Kinetics Of ◽  
Good Agreement

The authors proposed and treated quantitatively a kinetic model for deposition of epitaxial GaAs layers prepared by reaction of trimethylgallium with arsine in hydrogen atmosphere. The transport of gallium to the surface of the substrate is considered as the controlling process. The influence of the rate of chemical reactions in the gas phase and on the substrate surface on the kinetics of the deposition process is neglected. The calculated dependence of the growth rate of the layers on the conditions of the deposition is in a good agreement with experimental data in the temperature range from 600 to 800°C.

scholarly journals Kinetics of Transesterification of Safflower Oil to Obtain Biodiesel Using Heterogeneous Catalysis

2016 ◽  
Vol 14 (4) ◽  
pp. 929-938 ◽  
Author(s):  
Gabriel E. Galván Muciño ◽  
Rubi Romero ◽  
Armando Ramírez ◽  
María Jesús Ramos ◽  
Ramiro Baeza-Jiménez ◽  
...  
Keyword(s):  
Experimental Data ◽  
Statistical Analysis ◽  
Heterogeneous Catalysis ◽  
Kinetic Model ◽  
Methyl Esters ◽  
Molar Ratio ◽  
Safflower Oil ◽  
Estimated Parameters ◽  
Kinetics Of ◽  
Best Fit

Abstract The kinetics of the transesterification of safflower oil and methanol catalyzed by K2O/NaX was studied and modeled. The influence of the oil-methanol initial molar ratio and amount of catalyst were investigated to achieve a maximum triglycerides conversion (99 %) and a final methyl esters content of 94 % ±1. A kinetic model based on an Eley–Rideal mechanism was found to best fit the experimental data when assuming methanol adsorption as determining step. Other models derived from Langmuir – Hinshelwood – Hougen –Watson (LHHW) mechanisms were rejected based on statistical analysis, mechanistic considerations and physicochemical interpretation of the estimated parameters.

scholarly journals Kinetics of barite reduction from refractory barite-sulphide ore

10.30544/237 ◽  
2016 ◽  
Vol 22 (4) ◽  
pp. 261-268 ◽  
Author(s):  
Miroslav D Sokić ◽  
Vladislav Matković ◽  
Jovica Stojanović ◽  
Branislav Marković ◽  
Vaso Manojlović
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Kinetic Model ◽  
Copper Sulphide ◽  
Influence Of Temperature ◽  
Sulphide Ore ◽  
Lead Zinc ◽  
Complex Structural ◽  
Kinetics Of ◽  
Maximum Removal

Refractory sulphide–barite ore was reduced with carbon in order to release lead, zinc, and copper sulphide from barite-pyrite base. Mineralogical investigations showed that due to the complex structural-textural relationships of lead, copper and zinc minerals with gangue minerals, it is not possible to enrich the ore using the conventional methods of mineral processing. The influence of temperature and time was studied to optimize the conditions, and to determine the kinetics of the barite reduction. The maximum removal of barite from ore was 96.7% at 900oC after 180 min. Chemically controlled kinetic model showed the best compliance with the experimental data. An activation energy of 142 kJ/mol was found.

Kinetic Study of the Dehydrogenation of Isobutane over V-K-O /ZSM5 Catalyst

2013 ◽  
Vol 798-799 ◽  
pp. 174-177 ◽  
Author(s):  
Teng Teng Wu ◽  
Cheng Xue Wang
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Kinetic Model ◽  
Atmospheric Pressure ◽  
Contact Time ◽  
Model Parameters ◽  
Isobutane Dehydrogenation ◽  
Dehydrogenation Reaction ◽  
Reaction Pressure ◽  
Kinetics Of

The reaction kinetics of the dehydrogenation of isobutane over V-K-O /ZSM5 catalyst was investigated. The powerfunction model was established;The isobutane dehydrogenation reaction tests were carried out between 833-863K and reaction pressure to atmospheric pressure by changing the contact time(w/F=0.464-0.532gh/mol) ,through the experimental data the kinetics of model parameters were analyzed.The results show that the power-function kinetic model is reasonable,the apparent activation energy is 177.7492KJ/mol.

scholarly journals Anionic Polymerization of ε-Caprolactam under the Influence of Water: 2. Kinetic Model

2020 ◽  
Vol 4 (1) ◽  
pp. 8 ◽  
Author(s):  
Rainer Wendel ◽  
Philipp Rosenberg ◽  
Michael Wilhelm ◽  
Frank Henning
Keyword(s):  
Experimental Data ◽  
Kinetic Model ◽  
Reaction Kinetics ◽  
Water Content ◽  
Anionic Polymerization ◽  
Polyamide 6 ◽  
External Influences ◽  
Influence Of Water ◽  
Kinetics Of

The reaction kinetics of anionic polymerization for the production of anionic polyamide 6 (aPA6) are widely understood. It is also known that this reaction is very sensitive to external influences such as water. This paper analyzes and quantifies the influence of water on the reaction of ε-caprolactam to anionic polyamide 6. A kinetic model is developed in which the reactive molecules of the activator and catalyst are defined as variables and the concentrations of activator and catalyst as well as water content are considered. A model for the calculation of the reaction kinetics is established and validated with experimental data. The developed model can be used to predict the influence and compensation of water by addition of surplus activator and catalyst during the polymerization of ε-caprolactam.

scholarly journals Effect of Ethyl Acetate, Time and Particle Size on the Kinetics of the Oleoresin Extraction Process

2020 ◽  
Vol 7 (2) ◽  
pp. F15-F23
Author(s):  
M. S. Olakunle ◽  
A. O. Ameh ◽  
T. Oyegoke ◽  
H. U. Shehu
Keyword(s):  
Experimental Data ◽  
Particle Size ◽  
Kinetic Model ◽  
Ethyl Acetate ◽  
Extraction Process ◽  
Single Step ◽  
Particle Sizes ◽  
Order Model ◽  
First Order ◽  
Kinetics Of

The kinetics of the extraction of oleoresin from ginger using ethyl acetate as the solvent was studied in this work. The effects of particle size and extraction time on oleoresin’s solvent extraction were studied to obtain optimization data. The temperature of the process was kept constant at 40 °C. The Ginger particle sizes considered ranged between 1200-250 microns at extraction times ranging between 10–70 minutes. Experimental data generated were fitted into an empirical model to determine the kinetic parameters. The oleoresin yield increases with increasing extraction time up to an optimum time, after which the yield remains constant and yield also increases with decreasing particle size. The results obtained from the kinetics studies revealed that the introduction of the constant term accounting for the diffusion step separately (as an addition) into a single step first-order model (Patricelli’s first order model) raises the R-squared values from 87 % fitness of the model into becoming 99 % with the experimental data. This improved form of Patricelli’s first-order model was found to show a good agreement with Patricelli’s 2-step kinetic model. These findings confirmed that the oleoresin extraction process in the presence of ethyl acetate was found to be first-order kinetics involving two steps mechanism where the use of a single-step first-order model (Patricelli’s first-order kinetic model) and the choice of using ethyl acetate must have contributed to the strong resistance present in the first step of the extraction mechanism especially for the smaller particle size (250 microns). In getting the extraction yield improved, this study, therefore, recommends the use of small particle sizes (< 250 microns), higher temperatures (> 40 °C), and/or better alternative solvents like ethanol. Keywords: ethyl acetate, extraction, oleoresin, modeling.

scholarly journals Further study on kinetic modeling of sunflower oil methanolysis catalyzed by calcium-based catalysts

2016 ◽  
Vol 22 (2) ◽  
pp. 137-144 ◽  
Author(s):  
Marija Miladinovic ◽  
Marija Tasic ◽  
Olivera Stamenkovic ◽  
Vlada Veljkovic ◽  
Dejan Skala
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Kinetic Model ◽  
Sunflower Oil ◽  
Coefficient Of Determination ◽  
Reaction Conditions ◽  
High Coefficient ◽  
Relative Percentage ◽  
Kinetics Of ◽  
Good Agreement

The kinetic model, which was originally developed for sunflower oil methanolysis catalyzed by CaO.ZnO, was examined for several other calcium-based catalysts like neat CaO, quicklime and Ca(OH)2. This model including triacylglycerols mass transfer- and chemically-controlled regimes demonstrated a good agreement with the experimental data in terms of a high coefficient of determination (0.971?0.022) and acceptable mean relative percentage deviation (?15.9%). Hence, this model is recommended for modeling the kinetics of sunflower oil methanolysis over calcium-based catalysts under widely ranging reaction conditions.

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