Transition, kinetics

All models described up to here belong to the class of equilibrium theories. They have the advantage of providing structural information on the material during the liquid-solid transition. Kinetic theories based on Smoluchowski s coagulation equation [45] have recently been applied more and more to describe the kinetics of gelation. The Smoluchowski equation describes the time evolution of the cluster size distribution N(k) ... 

Sawamoto T, Haruta S, Kurosaki Y, Higaki K, Kimura T (1997) Prediction of the plasma concentration profiles of orally administered drugs in rat on the basis of gastrointestinal transit kinetics and absorbability. J. Pharm. Pharmacol. 49 450-457. 

Polymeric micelles with selected chemistries and molecular architecture of block copolymers, such as PIPAAm-CigHgs, PIPAAm-PSt, PIPAAm-PBMA, and PIPAAm-PLA micelles, showed the same LCST and the same thermoreponsive phase transition kinetics as those for PIPAAm irrespective of the hydrophobic segment incorporation. This confirms two points (a) that hydroxyl groups or amino goups of PIPAAm termini completely react with the hydrophobic segment end groups and (b) that the block copolymers form core-shell micellar structures with hydrophobic iimer cores completely isolated from the aqueous phase. 

LIPID PHASE TRANSITION KINETICS LIPID PHASE TRANSITION KINETICS LIPID TRACER KINETICS Lipid transfer across membrane bilayers, PHOSPHOLIPID FLIP-FLOP Lipoamide,... 

LIPID PHASE TRANSITION KINETICS Membrane lipid asymmetry,... 

These studies led to the detailed assignment of voltammetric features of bromide adsorption to the respective structural properties, stability, and transition kinetics. 

Chauvin, R Brand, L. Roseman, S. Sugar transport by the bacterial phosphotransferase system. Characterization of the Escherichia coli enzyme I monomer/dimer transition kinetics by fluorescence anisotropy. J. Biol. Chem., 269, 20270-20274 (1994)... 

To model the interaction of two specifically interacting chains by a computer has been attempted120, UI. For studying the order-disorder transition kinetics in a system of two interacting macromolecules, the computer simulation on a simple cubic lattice was used. The following parameters of the model were applied. 1) the probability of breaking the contact between segments 2) the probability of formation of the first contact in the system 3) the initial number of contacts in the system. 

Previous investigations of helix-coil transition kinetics, which used a variety of fast relaxation methods (electric field jump, ultrasonic absorption, dielectric relaxation and temperature jump), encountered many difficulties (12). The systems studied were long homopolymers (>200 residues) that often had hydrolyzable side chains. Controversial results have been reported, depending on the experimental technique employed, because unwanted side chain reactions or molecular reorientation were often difficult to distinguish from the helix-coil conformational change. However, as observed here, a maximum in the relaxation times was detected for these experiments ranging from 15 ps to 20 ns and was attributed to the helix-coil transition. 

Extensive measurements of the kinetics to determine rate constants for the nanocrystal transition have been made only on the CdSe system (Chen et al. 1997, Jacobs et al. 2001). Both the forward and reverse transition directions have been studied in spherically shaped crystallites as a function of pressure and temperature. The time-dependence of the transition yields simple transition kinetics that is well described with simple exponential decays (see Fig. 5). This simple rate law describes the transformation process in the nanocrystals even after multiple transformation cycles, and is evidence of the single-domain behavior of the nanocrystal transition. Rate constants for the nanocrystal transition are obtained from the slope of the exponential fits. This is in contrast to the kinetics in the extended solid, which even in the first transformation exhibits complicated time-dependent decays that are usually fit to rate laws such as the Avrami equation. 

The measurements of activation volumes and activation energies in both transition directions reveal that the forward and reverse transition kinetics differs. (These... 

Most of the liquid crystalline main-chain polymers synthesized are polyesters. For the present study where isothermal phase transition kinetics studies should be performed, this was a less suitable alternative since they undergo thermally induced reactions, i. e. transesterifications, and for this reason instead polyethers were chosen. Polyethers also have other advantages like lower transition temperatures and higher solubilities. 

Polymer Synthesis. The polymers were made by a phase-transfer-catalyzed Williamson ether synthesis as described in the literature (15-201. and one reason for this choice of polyetherification method was that only electrophilic chain ends are produced (15.20-221. which gives the polymer a well-defined structure. This was important for die transition kinetics measurements presented later in this paper. 

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