Search results for "kinetics"
showing 10 items of 2224 documents
A Contribution Concerning the Unsettled Problem of Intrasplenic Microcirculation
1973
From morphological studies it is well known that the vascular bed of the spleen consists of at least two different compartments. Figure one schematically shows how the splenic microcirculation can be subdivided. One compartment corresponds to the white pulp (pathways number 1 and 2), the other compartment to the red pulp, for which the existance of either an open or a closed type of terminal vascular bed is discussed. Futhermore there are references that the microcirculation in the red pulp is not homogeneous but composed of both types, as illustrated by the pathways marked by number 3 and 4.
Differences in the glucose and fructose consumption profiles in diverse Saccharomyces wine species and their hybrids during grape juice fermentation
2009
7 pages, 4 figures, 5 tables.
Collective behaviours: from biochemical kinetics to electronic circuits
2013
In this work we aim to highlight a close analogy between cooperative behaviors in chemical kinetics and cybernetics; this is realized by using a common language for their description, that is mean-field statistical mechanics. First, we perform a one-to-one mapping between paradigmatic behaviors in chemical kinetics (i.e., non-cooperative, cooperative, ultra-sensitive, anti-cooperative) and in mean-field statistical mechanics (i.e., paramagnetic, high and low temperature ferromagnetic, anti-ferromagnetic). Interestingly, the statistical mechanics approach allows a unified, broad theory for all scenarios and, in particular, Michaelis-Menten, Hill and Adair equations are consistently recovered…
Novel synthesis of up-conversion phosphor based on rare-earth doped NaLaF4
2011
In this work Er3+ doped NaLaF4 material has been synthesized Along with the description of the synthesis route, luminescence spectra and decay kinetics of both traditional and up-conversion luminescence of Er3+ will be presented for different Er3+ doping levels. It will be shown that the main mechanisms involved in the creation of the up-conversion luminescence in NaLaF4:Er3+ under excitation at about 975 nm are excited state absorption and energy transfer. Relative impact of either of the mechanisms in NaLaF4:Er3+ depends on both the concentration of Er3+ and on the excitation wavelength: the increase of either the concentration or the excitation wavelength leads to the prevalence of energ…
Thermodynamics and Kinetics of Adsorption of Gaseous Single Cl/Br-VOCs of the Ethane Series onto Siliceous ZSM-5 at 25 °C. Prediction of the Adsorpti…
2001
This work deals with a thermodynamic and kinetic experimental study of adsorption of gaseous single Cl/Br-VOCs (1,2-dichloroethane, 1-bromo-2-chloroethane, and 1,2-dibromoethane) onto siliceous ZSM-5 at 25 °C. The adsorbed amounts, adsorption heats, and diffusivities were simultaneously obtained. The isotherms were of the type I and verified Henry's law in a very large domain of filling. The adsorption heats and the diffusivities of the brominated molecules displayed specific behaviors probably owing to a transport resistance. The comparison of the relative position of isotherms and the adsorption heats allowed us to predict that the competitive adsorption of their mixture would be similar …
Peak dispersion in gradient elution: An insight based on the plate model.
2020
Gradient elution in liquid chromatography reduces the analysis time, improves the efficiency and increases the peak capacity. The study of this chromatographic mode has been based mainly on kinetic dispersion models. The plate model has been applied to a lesser extent, despite being the basis for the concepts of plate height and chromatographic efficiency. In this work, a general equation describing peak dispersion in HPLC gradient elution is derived from the plate model. This equation is studied and validated for three types of gradients: (i) a reference gradient without ramp in which the retention factor varies with time identically throughout the column, (ii) a gradient of stationary pha…
Kinetics of zinc anodic dissolution from the EIS characteristic points
2003
A possible faradaic impedance function for the complex mechanism of metals electrodissolution across two consecutive electrotransferences has been developed in this work. The analysis of this function provides some characteristics points from which it is possible to calculate kinetic parameters of these processes. The dependence of these parameters on the potential has been studied in the case of Zn. These ones have been interpreted in terms of changes in the controlling stages of the overall rate of reaction. Keywords: EIS simulation, Zinc anodic dissolution, Kinetic constants and electron transfer
Up-Conversion Luminescence Processes in NaLaF4 Doped with Tm3+ and Yb3+ and Dependence on Tm3+ Concentration and Temperature
2021
In this work, luminescence processes in polycrystalline NaLaF4:Tm3+ and NaLaF4:Tm3+,Yb3+ materials were studied. Luminescence spectra and decay kinetics measurements were performed for NaLaF4 doped with various Tm3+ concentrations (0.01, 0.1, 0.5, 1, and 2 mol%) under direct excitation to 3P0, 1D2, 1G4, and 3H4 states. It was found that some of the Tm3+ excited states are more affected by Tm3+ concentration than other states. Under infrared excitation of Yb3+, energy transfer to Tm3+ occurred and intensive ultraviolet and blue up-conversion luminescence was observed. Possible up-conversion mechanisms are discussed. Spectroscopic measurements show that long-duration excitation radiation red…
Effect of mechanical stirring and temperature on dynamic hydrothermal synthesis of titanate nanotubes
2017
Abstract In the late century, it has been clearly demonstrated that titanate nanotubes (TNTs) are attractive nanomaterials with various potential applications due to their interesting properties. In this work, an essential reaction parameter, rarely considered in the literature, has been studied: stirring during hydrothermal synthesis. For this purpose, an intermittent mechanical stirring, ranging from 0 to 20 min/h, has been applied during the TNTs synthesis using a new dynamic hydrothermal reactor. It was proved that a long stirring cycle (more than 10 min/h) at 150 °C and an overall reaction time of 16 h promotes nanoribbons synthesis instead of nanotubes. In this context, a detailed mor…
Kinetics of block-copolymer aggregation in super critical CO2
2002
Small angle X-ray and neutron scattering (SAXS and SANS) are used to obtain structural information on the aggregation behavior of block-copolymers dissolved in supercritical CO2. The SANS technique is used to provide a detailed structural model for the micellar aggregates, which form below the critical micellization density (CMD), that we defined in our previous work. The SAXS technique (with a synchrotron source) is used to provide the first experimental information concerning the kinetic features of both formation and decomposition of such aggregates as soon as pressure jumps are applied to the solutions across the CMD. 2002 Elsevier Science B.V. All rights reserved.