scholarly journals Исследование изменения лигандного состава хелата Eu-=SUP=-3+-=/SUP=- методами двухступенчатого лазерного возбуждения люминесценции и компьютерного моделирования кинетики

2019 ◽  
Vol 126 (2) ◽  
pp. 134
Author(s):  
И.В. Станишевский ◽  
Т.А. Павич ◽  
С.М. Арабей
Keyword(s):  
Dynamic Model ◽  
Rate Constants ◽  
Structural Rearrangement ◽  
Triphenylphosphine Oxide ◽  
Iterative Approximation ◽  
Reversible Processes ◽  
Experimental Kinetics ◽  
Nelder Mead Algorithm ◽  
Excitation Method ◽  
The Eu

AbstractThe europium(III)–tris(dibenzoylmethane)–triphenylphosphine oxide complex was studied in the polycrystalline state and in toluene at 298 K using the luminescence excitation method with two-stage rectangular pulses with decreasing intensity of stages. Experimental nonmonotonic kinetic curves were numerically simulated within the framework of a four-level dynamic model describing reversible processes in the complex, associated with its structural rearrangement. The maximum correspondence between the experimental and simulated curves was obtained using an iterative approximation performed using the Nelder–Mead algorithm. Based on the obtained numerical values of the rate constants and parameters of the model, experimental kinetics were interpreted, and it was concluded that they are a consequence of the processes associated with changes in the ligand composition of the Eu^3+ chelate.

scholarly journals ‘Voice’ or ‘exit’? From the streets of Syria to the borders of the EU

Geografie ◽  
2017 ◽  
Vol 122 (4) ◽  
pp. 429-448
Author(s):  
Franck Düvell
Keyword(s):  
Civil War ◽  
Dynamic Model ◽  
Host Country ◽  
Arab Spring ◽  
Arab World ◽  
Forced Migration ◽  
Main Host ◽  
The Arab Spring ◽  
The Eu

In 2011 and 2012, many citizens in the Arab world arose in what became known as the ‘Arab spring’. This led to a spiral of suppression and more protests, notably in Syria. These did not topple the regime but escalated into a long civil war. Several million people were forced to seek shelter in other countries. Turkey became the main host country of Syrian and other refugees as well as the main gateway into the EU. This article focuses on the interplay of protests and forced migration and analyses these events through the theoretical lens of Hirschman’s ‘voice, exit or loyalty’ model. Itargues for a revision of the original voice/exit model, notably for acknowledging the interaction of ‘voice and exit’ and thus suggests a much more complex and dynamic model.

Unusual Influence of the Temperature on the Standard Rate Constants of Charge Transfer for the Eu(III)/Eu(II) Redox Couple in Chloride-Bromide Melts

2007 ◽  
Vol 62 (7-8) ◽  
pp. 445-451 ◽  
Author(s):  
Sergey A. Kuznetsov ◽  
Marcelle Gaune-Escard
Keyword(s):  
Electron Transfer ◽  
Cyclic Voltammetry ◽  
Charge Transfer ◽  
Kinetic Parameters ◽  
Rate Constants ◽  
Redox Reaction ◽  
Electron Transfer Mechanism ◽  
Standard Rate ◽  
Standard Rate Constant ◽  
The Eu

The influence of bromide ions and temperature on the standard rate constants of the Eu(III)/Eu(II) redox reaction was determined. Cyclic voltammetry was used for the calculation of the kinetic parameters. It was shown that in NaCl-KCl (equimolar mixture)-NaBr (15 wt%)-EuCl3 melts increase of the temperature from 973 K up to 1023 K leads to a drastical decrease of the standard rate constant ks for the Eu(III)/Eu(II) redox reaction. This unusual influence of the temperature on the ks value was explained by a change of the electron transfer mechanism. It is suggested that at 1023 K another mechanism becomes dominant - the transfer of electrons through dissolved bromine in the melt. Bromine appeared in the melt due to the decomposition of chloride-bromide or bromide complexes of Eu(III), and the concentration of bromine in the melt increased with the growth of temperature.

scholarly journals Analysis of photoinduced reverse changes in bacterial reaction centers

2018 ◽  
Keyword(s):  
Electron Transfer ◽  
Rate Constants ◽  
Logarithmic Derivative ◽  
Reaction Centers ◽  
Main Reaction ◽  
Balance Equations ◽  
Electron Transfer Kinetics ◽  
Cyclic Electron Transfer ◽  
Experimental Kinetics ◽  
Kinetics Of

Background: The membrane protein-pigment complexes of photosynthetic isolated reaction centers (RC) Rhodobacter Sphaeroides are macromolecular systems for studying the physical mechanisms of electron and proton transport in biological structures, the role of molecular dynamics. The experimental kinetics of cyclic electron transfer in molecular complexes has a multiexponential character with negative values of decrements. For their description, a system of balance equations is used. Objective of the work is to determine the features of the kinetics of cyclic electron transfer in the RC using two models of electron transfer and the connection of such features with space-time motions in the RC. Materials and methods: Measurement of the absorption kinetics was performed at 865 nm using a two-channel diode spectrometer. The experimental kinetics of RC absorption (the main reaction of the system) was represented by the fitting method in the form of a sum of three exponential functions. In the first model with time-variable rate constants of the balance equations, the wavelet transform method of the logarithmic derivative of the electron transfer kinetics was used. In the second model, the equation of state and three differential equations with constant coefficients were used as the algebraic sum of the rate constants. To determine the values of the rate constants in the balance equation, an optimization problem was solved. The solution of the system of balance equations by the matrix method made it possible to determine the features of the kinetics of the population of substates of the RC. Results of calculations showed that the features of the wavelet spectrum of the logarithmic derivative of the electron transfer kinetics in the first model coincided with the features of the population kinetics of substates of the RC of the second RC model. These features were in the bands 1 s, 3 s, 60 s from the moment of switching on (off) the light and depend on the photoexcitation parameters. Conclusions: The features of the kinetics of the populations of substates in the RC both at the stage of illumination and at the relaxation stage are determined by changes in the structure of the RC in the form of effects of hidden parameters of the structural self-regulation of the RC (feedback through the RC structure).

Stochastic Dynamic Model for Estimation of Rate Constants and Their Variances from Noisy and Heterogeneous PET Measurements

2006 ◽  
Vol 69 (2) ◽  
pp. 585-604 ◽  
Author(s):  
Jari Niemi ◽  
Ulla Ruotsalainen ◽  
Antti Saarinen ◽  
Keijo Ruohonen
Keyword(s):  
Dynamic Model ◽  
Rate Constants ◽  
Stochastic Dynamic

Electron Microscopy and image reconstruction reveal the structural basis for spectrin's elastic properties

1992 ◽  
Vol 50 (1) ◽  
pp. 510-511
Author(s):  
Amy M. McGough ◽  
Robert Josephs
Keyword(s):  
Electron Microscopy ◽  
Elastic Properties ◽  
Conformational Changes ◽  
Quaternary Structure ◽  
Three Dimensional ◽  
Membrane Skeleton ◽  
Projection Algorithm ◽  
Structural Basis ◽  
Iterative Approximation ◽  
Membrane Skeletons

The remarkable deformability of the erythrocyte derives in large part from the elastic properties of spectrin, the major component of the membrane skeleton. It is generally accepted that spectrin's elasticity arises from marked conformational changes which include variations in its overall length (1). In this work the structure of spectrin in partially expanded membrane skeletons was studied by electron microscopy to determine the molecular basis for spectrin's elastic properties. Spectrin molecules were analysed with respect to three features: length, conformation, and quaternary structure. The results of these studies lead to a model of how spectrin mediates the elastic deformation of the erythrocyte.Membrane skeletons were isolated from erythrocyte membrane ghosts, negatively stained, and examined by transmission electron microscopy (2). Particle lengths and end-to-end distances were measured from enlarged prints using the computer program MACMEASURE. Spectrin conformation (straightness) was assessed by calculating the particles’ correlation length by iterative approximation (3). Digitised spectrin images were correlation averaged or Fourier filtered to improve their signal-to-noise ratios. Three-dimensional reconstructions were performed using a suite of programs which were based on the filtered back-projection algorithm and executed on a cluster of Microvax 3200 workstations (4).

Short-term volume and turgor regulation in yeast

2008 ◽  
Vol 45 ◽  
pp. 147-160 ◽  
Author(s):  
Jörg Schaber ◽  
Edda Klipp
Keyword(s):  
Dynamic Model ◽  
Volume Change ◽  
Volume Regulation ◽  
Time Course ◽  
Osmotic Shock ◽  
Intracellular Concentration ◽  
Short Term ◽  
Hydrodynamic Property ◽  
Turgor Regulation ◽  
Thermodynamic Framework

Volume is a highly regulated property of cells, because it critically affects intracellular concentration. In the present chapter, we focus on the short-term volume regulation in yeast as a consequence of a shift in extracellular osmotic conditions. We review a basic thermodynamic framework to model volume and solute flows. In addition, we try to select a model for turgor, which is an important hydrodynamic property, especially in walled cells. Finally, we demonstrate the validity of the presented approach by fitting the dynamic model to a time course of volume change upon osmotic shock in yeast.

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