scholarly journals DYNAMICS OF NEUROMUSCULAR TRANSMISSION REPRODUCED BY CALCIUM-DEPENDENT SERIAL TRANSITIONS IN THE VESICLE FUSION COMPLEX

2021 ◽  
Author(s):  
Alejandro Martínez-Valencia ◽  
Guillermo Ramírez-Santiago ◽  
Francisco F. De-Miguel
Keyword(s):  
Experimental Data ◽  
Kinetic Model ◽  
Electrical Activity ◽  
Rate Constant ◽  
Rate Constants ◽  
Resting State ◽  
Neuromuscular Transmission ◽  
Spontaneous Release ◽  
Calcium Dependent ◽  
Vesicle Pool

Neuromuscular transmission, from spontaneous release to facilitation and depression was accurately reproduced by a mechanistic kinetic model of sequential maturation transitions in the molecular fusion complex. The model incorporates three predictions. First, sequential calcium-dependent forward transitions take vesicles from docked to pre-primed to primed states, followed by fusion. Second, pre-priming and priming are reversible. Third, fusion and recycling are unidirectional. The model was fed with experimental data from previous studies while the backward (β) and recycling (ρ) rate constant values were fitted. Classical experiments were successfully reproduced when every forward (α) rate constant had the same value, and both backward rate constants were 50-100 times larger. Such disproportion originated an abruptly decreasing gradient of resting vesicles from docked to primed states. Simulations also predict that: i. Spontaneous release reflects primed to fusion spontaneous transitions. ii. Calcium elevations synchronize the series of forward transitions that lead to fusion. iii Facilitation reflects a transient increase of priming following calcium-dependent transitions. iv. Backward transitions and recycling restore the resting state. v. Depression reflects backward transitions and slow recycling after intense release. Such finely-tuned kinetics offers a mechanism for collective non-linear transitional adaptations of a homogeneous vesicle pool to an ever-changing pattern of electrical activity.

The Rate-Constant for the Recombination of Methyl Radicals

1986 ◽  
Vol 39 (8) ◽  
pp. 1257 ◽  
Author(s):  
NL Arthur ◽  
JC Biordi
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Rate Constant ◽  
Rate Constants ◽  
The Other ◽  
Methyl Radicals ◽  
Experimental Conditions ◽  
Temperature Range ◽  
Best Value ◽  
Limiting Value

Rate constants for the recombination of CH3 radicals have been measured by means of the rotating sector technique in the temperature range 373- 463 K, and at a pressure of 30 Torr . CH3 radicals were produced by the photolysis of acetone, and the experimental data were fitted to sector curves generated from Shepp's theory. The results give kb = (2.81�0.22)×1013 cm3 mol-1 s-1, which, under the chosen experimental conditions, is close to its high-pressure limiting value. A comparison is made with the other values of the rate constant reported in the literature, and a best value is suggested.

scholarly journals Chamber simulation of photooxidation of dimethyl sulfide and isoprene in the presence of NO<sub>x</sub>

2012 ◽  
Vol 12 (21) ◽  
pp. 10257-10269 ◽  
Author(s):  
T. Chen ◽  
M. Jang
Keyword(s):  
Experimental Data ◽  
Kinetic Model ◽  
Rate Constants ◽  
Dimethyl Sulfide ◽  
Model Simulation ◽  
Methanesulfonic Acid ◽  
Oxidation Products ◽  
Chemical Mechanism ◽  
Gaseous Products ◽  
Dms Oxidation

Abstract. To improve the model prediction for the formation of H2SO4 and methanesulfonic acid (MSA), aerosol-phase reactions of gaseous dimethyl sulfide (DMS) oxidation products [e.g., dimethyl sulfoxide (DMSO)] in aerosol have been included in the DMS kinetic model with the recently reported gas-phase reactions and their rate constants. To determine the rate constants of aerosol-phase reactions of both DMSO and its major gaseous products [e.g., dimethyl sulfone (DMSO2) and methanesulfinic acid (MSIA)], DMSO was photooxidized in the presence of NOx using a 2 m3 Teflon film chamber. The rate constants tested in the DMSO kinetic mechanisms were then incorporated into the DMS photooxidation mechanism. The model simulation using the newly constructed DMS oxidation mechanims was compared to chamber data obtained from the phototoxiation of DMS in the presence of NOx. Within 120-min simulation, the predicted concentrations of MSA increase by 200–400% and those of H2SO4, by 50–200% due to aerosol-phase chemistry. This was well substantiated with experimental data. To study the effect of coexisting volatile organic compounds, the photooxidation of DMS in the presence of isoprene and NOx has been simulated using the newly constructed DMS kinetic model integrated with the Master Chemical Mechanism (MCM) for isoprene oxidation, and compared to chamber data. With the high concentrations of DMS (250 ppb) and isoprene (560–2248 ppb), both the model simulation and experimental data showed an increase in the yields of MSA and H2SO4 as the isoprene concentration increased.

scholarly journals Aromatization of light naphtha fractions on zeolites 1: Kinetic model

2003 ◽  
Vol 57 (9) ◽  
pp. 399-403 ◽  
Author(s):  
Svetlana Rovenskaja ◽  
Nikolaj Ostrovski
Keyword(s):  
Experimental Data ◽  
Kinetic Model ◽  
Rate Constants ◽  
Reaction Rate ◽  
Reaction Scheme ◽  
Activation Energies ◽  
Modeling And Optimization ◽  
Light Naphtha ◽  
Reaction Rate Constants

On the basis of analyzing kinetic experimental data performed in laboratory integral reactors a lumping kinetic model of the "Zeoforming" process was developed. A reaction scheme of the lumped components was proposed, that was adapted to the technological requirements. The reaction rate constants and activation energies were estimated, that are valid for certain feed compositions. The model is intended for further modeling and optimization of the process.

Kinetics of renin-antirenin reaction: micromethods for the assay of renin and antirenin

1975 ◽  
Vol 228 (4) ◽  
pp. 973-979 ◽  
Author(s):  
E Haas ◽  
H Goldblatt ◽  
RL Klick ◽  
L Lewis
Keyword(s):  
Experimental Data ◽  
Lower Limit ◽  
Rate Constant ◽  
Rate Constants ◽  
Data Accuracy ◽  
Michaelis Constant ◽  
Renin Substrate ◽  
Method Of Calculation ◽  
Human Renin ◽  
Kinetics Of

Indirect micromethods were designed for the assay of human renin (lower limit 0.25 times 10-4 U and of antirenin to human renin (lower limit 3 times 10-4 U), with the rat used for the bioassay of the angiotensin produced by the action of renin on renin substrate. This made possible the assay of unusually small amounts (0.01 mu1) of serum for antirenin. The Michaelis-Menten concept of a dissociating complex can be applied to the antireninrenin reaction: the rate constants for the formation and for the breakdown of the complex were k1 equal to 1.65 (ml/U antirenin per min) and k3 equal to 1.97 times 10-3 (U inactivated renin/U antirenin per min), respectively; the apparent Michaelis constant was 12 times 10-4 (U renin/ml). A second method of analysis was also applied by assuming the formation of a rather tight complex, with antirenin functioning as an irreversible inactivator of renin. Both methods of analysis yielded practically the same rate constant (k1 equal to 1.65 and k1 equal to 1.71), but the treatment according to the Michaelis-Menten equation affords a slightly better fit of the experimental data (accuracy equal to plus or minus 15.5 percent) than the second method of calculation (accuracy equal to plus or minus 21.6 percent).

Intramolekulare Excimere: Die Kinetik ihrer Bildung und Desaktivierung

1970 ◽  
Vol 25 (7) ◽  
pp. 1091-1096 ◽  
Author(s):  
Walter Klöpffer ◽  
Wolfgang Liptay
Keyword(s):  
Experimental Data ◽  
Rate Constant ◽  
Rate Constants ◽  
Kinetic Equations ◽  
High Rate ◽  
Excimer Fluorescence ◽  
Intramolecular Excimer ◽  
Excimer Formation

A set of kinetic equations has been developed which allows to calculate the rate parameters of intramolecular excimer formation, dissociation and of radiative and non-radiative desactivation processes. Experimental data necessary for evaluating the equations are monomer lifetime and relative fluorescence intensities of monomer and excimer fluorescence in solution with and without added quenching substance.Spectroscopical data of biscarbazolyl propane, diphenyl propane and derivatives are used in order to calculate the rate constants. It is shown that the stronger excimer fluorescence of diphenyl propane, as compared with biscarbazolyl propane, is due to the high rate constant of excimer formation in the former substance

scholarly journals Nitrogen Removal in a Horizontal Subsurface Flow Constructed Wetland Estimated Using the First-Order Kinetic Model

2016 ◽  
Author(s):  
Lijuan Cui ◽  
Wei Li ◽  
Yaqiong Zhang ◽  
Jiaming Wei ◽  
Yinru Lei ◽  
...  
Keyword(s):  
Kinetic Model ◽  
Rate Constant ◽  
Constructed Wetland ◽  
Rate Constants ◽  
Removal Rate ◽  
Order Kinetic ◽  
First Order ◽  
N Removal ◽  
Order Kinetic Model ◽  
Beijing China

We monitored the water quality and hydrological conditions of a horizontal subsurface constructed wetland (HSSF-CW) in Beijing, China, for 2 years. We simulated the area rate constant and the temperature coefficient with the first-order kinetic model. We examined the relationships between the nitrogen (N) removal rate, N load, seasonal variations in the N removal rate, and environmental factors, such as the area rate constant, temperature, and dissolved oxygen (DO). The effluent ammonia (NH4+-N) and nitrate (NO3&minus;-N) concentrations were significantly lower than the influent concentrations (p&lt;0.01, n=38). The NO3&minus;-N load was significantly correlated with the removal rate (R2=0.9566, p&lt;0.01), but the NH4+-N load was not correlated with the removal rate (R2=0.0187, p&gt;0.01). The area rate constants of NO3&minus;-N and NH4+-N at 20 &deg;C were 27.01&plusmn;26.49 and 16.63&plusmn;10.58 m∙yr&minus;1, respectively. The temperature coefficients for NO3&minus;-N and NH4+-N were estimated at 1.0042 and 0.9604, respectively. The area rate constants for NO3&minus;-N and NH4+-N were not correlated with temperature (p&gt;0.01). The NO3&minus;-N area rate constant was correlated with the corresponding load (R2=0.9625, p&lt;0.01). The NH4+-N area rate was correlated with DO (R2=0.6922, p&lt;0.01), suggesting that the factors that influenced the N removal rate in this wetland met Liebig's law of the minimum.

Lumping Kinetics of Asphaltene Hydrocracking over NiMo/γ-Al2O3

2011 ◽  
Vol 396-398 ◽  
pp. 806-810
Author(s):  
Ying Xian Zhao ◽  
Da Li ◽  
Xiao Lin
Keyword(s):  
Experimental Data ◽  
Kinetic Model ◽  
Rate Constant ◽  
Suggested Model ◽  
Reaction Paths ◽  
Kinetic Feature ◽  
Kinetics Of

Catalytic hydrocracking of asphaltene over Ni-Mo/γ-Al2O3 was conducted in a microbatch reactor at 693 K. A kinetic model with four lumps (asphaltene, liquid, gas and coke) containing five reaction paths was developed. The fitting of experimental data validated the suggested model and determined the rate constant of each individual reactions, to give the insight to the kinetic feature of asphaltene catalytic hydrocracking

Achieving Procedure of a Kinetic Model to Predict the Influence of the Process Global Temperature on a Technological Alcoholic Fermentation II. An Arrhenius type Kinetic Model

2008 ◽  
Vol 59 (4) ◽  
Author(s):  
Neculai Catalin Lungu ◽  
Maria Alexandroaei
Keyword(s):  
Experimental Data ◽  
Saccharomyces Cerevisiae ◽  
Kinetic Model ◽  
Economic Efficiency ◽  
Fermentation Process ◽  
Alcoholic Fermentation ◽  
Global Temperature ◽  
Medium Temperature ◽  
Biotechnological Process

The aim of the present work is to offer a practical methodology to realise an Arrhenius type kinetic model for a biotechnological process of alcoholic fermentation based on the Saccharomyces cerevisiae yeast. Using the experimental data we can correlate the medium temperature of fermentation with the time needed for a fermentation process under imposed conditions of economic efficiency.

Determination of rate constants of redox reactions of second order from current-less potential-time curves by a simplified graphical-numerical method

1983 ◽  
Vol 48 (5) ◽  
pp. 1358-1367 ◽  
Author(s):  
Antonín Tockstein ◽  
František Skopal
Keyword(s):  
Numerical Method ◽  
Explicit Form ◽  
Rate Constant ◽  
Optimization Algorithm ◽  
Rate Constants ◽  
Redox Reactions ◽  
Second Order ◽  
Wide Region ◽  
Recurrent Formula

A method for constructing curves is proposed that are linear in a wide region and from whose slopes it is possible to determine the rate constant, if a parameter, θ, is calculated numerically from a rapidly converging recurrent formula or from its explicit form. The values of rate constants and parameter θ thus simply found are compared with those found by an optimization algorithm on a computer; the deviations do not exceed ±10%.

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.

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