Anisotropy of the mobility

In description of effects observed in extension of molten polymers, the determinant is the phenomenon of anisotropy of the mobility of macromolecules. In the Doi-Ed-vards reptation theory the anisotropy of the mobility of macromolecules is taken into account topologically by means of placing a macromolecule into a certain hypothetical tube. In this case large-scale movements are allowed only along the macromolecule and are totally inhibited in the lateral direction. This, indeed, is a limiting case of mobility anisotropy. 

The anisotropy of the electrical conductivity as a whole is determined by the anisotropy of the mobility of the charge carriers... 

To take the reptation of the macromolecule into account it is necessary to introduce the anisotropy of the mobility for every particle (bead) in the considered coarse-grained model of a macromolecule consisting of N subchains. We shall follow the work by Doi and Edwards [63] and Curtiss and Bird [47]. Although the original work by the latter authors deals with Kramers or rod-bead models, we shall consider a simplified version which will allow us to discuss the effect of reptation in a purified way. 

In an anisotropic liquid, the force of the resistance of the ball is a function of the direction of its movement, i.e., the anisotropy of the mobility of a body with an isotropic shape takes place. In movement of the ball parallel or perpendicular to 71, the usual Stokes law of resistance is valid ... 

The physical dimensions and dynamics of calmodulin have also been investigated by tyrosine fluorescence. To learn about the internal mobility of calmodulin, Lambooy et al 1 and Steiner et al measured the steady-state fluorescence anisotropy of the tyrosine. Since the average correlation... 

The argument for the formation of the double layer has proceeded simply. The existence of a boundary for the electrolyte necessarily implies a basic anisotropy in the forces operating on the particles in the intcrphase region. Owing to this anisotropy, there occurs a redistribution of the mobile charges and orientable dipoles (compared with their distribution in the bulk of the phases). This redistribution is the structural basis of the potential difference across the interface. 

The photoconductivity is highly anisotropic and its value along the macro-molecule chain is 103 times larger than in the perpendicular direction. The anisotropy is mainly due to the various values of the mobilities along and transverse to the chains. 

The second possibility (the direct magnetic effect of currents in Y) is shown to depend on the anisotropy of the magnetic susceptibility of Y. Quantitatively this shift is usually small, although it may account for the shift to high screening when some protons associate with an aromatic system, which has a large anisotropy due to the mobile electrons,... 

Steady-state measurements of the fluorescence anisotropy of fluorescein derivatives form the basis of a sensitive analytical technique also used to detect and quantitate proteins [36], steroids [37-39], therapeutic drugs, and narcotics [40-42], In a different approach, the anisotropy of the fluorescein conjugate is measured as a function of the medium viscosity to determine the segmental mobility of the chains that cover the binding site [43-45],... 

Reticulum ATPase [105,106], Owing to the long-lived nature of the triplet state, Eosin derivatives are suitable to study protein dynamics in the microsecond-millisecond range. Rotational correlation times are obtained by monitoring the time-dependent anisotropy of the probe s phosphorescence [107-112] and/or the recovery of the ground state absorption [113— 118] or fluorescence [119-122], The decay of the anisotropy allows determination of the mobility of the protein chain that cover the binding site and the rotational diffusion of the protein, the latter being a function of the size and shape of the protein, the viscosity of the medium, and the temperature. 

Several molecular properties can be measured using emission and excitation spectra. These include fluorescence lifetime, efficiency, anisotropy of the emitted light, mobility of chromophores, rates of quenching, and energy transfer to other chromophores. 

Abstract We use Nuclear Magnetic Resonance relaxometry (i.e. the frequency variation of the NMR relaxation rates) of quadrupolar nucleus ( Na) and H Pulsed Gradient Spin Echo NMR to determine the mobility of the counterions and the water molecules within aqueous dispersions of clays. The local ordering of isotropic dilute clay dispersions is investigated by NMR relaxometry. In contrast, the NMR spectra of the quadrupolar nucleus and the anisotropy of the water self-diffusion tensor clearly exhibit the occurrence of nematic ordering in dense aqueous dispersions. Multi-scale numerical models exploiting molecular orbital quantum calculations, Grand Canonical Monte Carlo simulations, Molecular and Brownian Dynamics are used to interpret the measured water mobility and the ionic quadrupolar relaxation measurements. 

Figure 3. Anisotropy of the water mo- Figure 4. Water transverse mobilities...

Abstract The discussion of relaxation and diffusion of macromolecules in very concentrated solutions and melts of polymers showed that the basic equations of macromolecular dynamics reflect the linear behaviour of a macromolecule among the other macromolecules, so that one can proceed further. Considering the non-linear effects of viscoelasticity, one have to take into account the local anisotropy of mobility of every particle of the chains, introduced in the basic dynamic equations of a macromolecule in Chapter 3, and induced anisotropy of the surrounding, which will be introduced in this chapter. In the spirit of mesoscopic theory we assume that the anisotropy is connected with the averaged orientation of segments of macromolecules, so that the equation of dynamics of the macromolecule retains its form. Eventually, the non-linear relaxation equations for two sets of internal variables are formulated. The first set of variables describes the form of the macromolecular coil - the conformational variables, the second one describes the internal stresses connected mainly with the orientation of segments. 

In such self-assembled structures the conductivity a as well as the charge carrier mobility n can be measured both parallel and perpendicular to the substrate. These studies nicely document how the structural organization of the chains increases both the anisotropy of the conductivity and of the charge-carrier mobility. 

In particular, the application of multi-exponential decay kinetics anticipated from models that assume distinct photophysical species within polymer chains may be inappropriate in some cases. The possibility of non-exponential fluorescence decay behaviour arising from energy migration and trapping (11) should also be considered. Additional studies of the mobilities of fluorescent probes incorporated in PMA using time-resolved fluorescence anisotropy measurements provide further support for a "connected cluster" model to describe the conformation of this polyelectrolyte in aqueous solution at low pH. 

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