Networks elastic

The net effect is that tackifiers raise the 7g of the blend, but because they are very low molecular weight, their only contribution to the modulus is to dilute the elastic network, thereby reducing the modulus. It is worth noting that if the rheological modifier had a 7g less than the elastomer (as for example, an added compatible oil), the blend would be plasticized, i.e. while the modulus would be reduced due to network dilution, the T also would be reduced and a PSA would not result. This general effect of tackification of an elastomer is shown in the modulus-temperature plot in Fig. 4, after the manner of Class and Chu. Chu [10] points out that the first step in formulating a PSA would be to use Eqs. 1 and 2 to formulate to a 7g/modulus window that approximates the desired PSA characteristics. Windows of 7g/modulus for a variety of PSA applications have been put forward by Carper [35]. 

Non-linear viscoelastic flow phenomena are one of the most characteristic features of polymeric liquids. A matter of very emphasised interest is the first normal stress difference. It is a well-accepted fact that the first normal stress difference Nj is similar to G, a measure of the amount of energy which can be stored reversibly in a viscoelastic fluid, whereas t12 is considered as the portion that is dissipated as viscous flow [49-51]. For concentrated solutions Lodge s theory [52] of an elastic network also predicts normal stresses, which should be associated with the entanglement density. 

Delarue, M. Sanejouand, Y.H., Simplified normal mode analysis of conformational transitions in DNA-dependent polymerases the elastic network model, J. Mol. Biol. 2002, 320, 1011-1024... 

ABA triblock copolymers of the styrene-diene type are well known, and owe their unique properties to their heterophase morphology. This arises from the incompatibility between the polystyrene A blocks and the polydiene B blocks, leading to the formation of a dispersion of very small polystyrene domains within the polydiene matrix. This type of elastic network, held together by the polystyrene "junctions", results in thermoplastic elastomer properties. 

In addition to actin and myosin, other proteins are found in the two sets of filaments. Tropomyosin and a complex of three subunits collectively called troponin are present in the thin filaments and play an important role in the regulation of muscle contraction. Although the proteins constituting the M and the Z bands have not been fully characterized, they include a-actinin and desmin as well as the enzyme creatine kinase, together with other proteins. A continuous elastic network of proteins, such as connectin, surround the actin and myosin filaments, providing muscle with a parallel passive elastic element. Actin forms the backbone of the thin filaments [4]. The thin... 

It can be assumed that the orientation of the amorphous regions is a result of the deformation of a rubber-elastic network. Therefore, it can be expected that crystallization during spinning occurs at the neck, where the deformation is maximal. The amorphous phase develops into a load-bearing factor which is related to its orientation, as expressed by Hermans orientation factor. 

Elastin-mimetic protein polymers have been fabricated into elastic networks primarily via y-radiation-induced, radical crosslinking of the material in the coacervate state [10]. Although effective, this method cannot produce polymers gels of defined molecular architecture, i.e., specific crosslink position and density, due to the lack of chemoselectivity in radical reactions. In addition, the ionizing radiation employed in this technique can cause material damage, and the reproducibility of specimen preparations may vary between different batches of material. In contrast, the e-amino groups of the lysine residues in polymers based on Lys-25 can be chemically crosslinked under controllable conditions into synthetic protein networks (vide infra). Elastic networks based on Lys-25 should contain crosslinks at well-defined position and density, determined by the sequence of the repeat, in the limit of complete substitution of the amino groups. 

Figure 7.4 Illustration of the Elastic Network Model for thymidylate kinase (cut-off = 8 Angstroms).

The molecular theory of elasticity of polymeric networks which leads to the equation of state, Eq. (28), rests on the following basic postulates Undeformed polymeric chains of elastic networks adopt random configurations or spatial arrangements in the bulk amorphous state. The stress resulting from the deformation of such networks originates within the elastically active chains and not from interactions between them. It means that the stress exhibited by a strained network is assumed to be entirely intramolecular in origin and intermolecular interactions play no role in deformations (at constant volume and composition). 

Zimmermann, D. R., Dours-Zimmermann, M., Schubert, M., and Bruckner-Tuderman, L. (1994). Versican is expressed in the proliferating zone in the epidermis and in association with the elastic network of the dermis./. Cell Biol. 124, 817-825. 

Zheng, W., and Doniach, S. (2003). A comparative study of motor-protein motions by using a simple elastic-network model. Proc. Natl. Acad. Sci. USA 100, 13253-13258. 

Atilgan AR, Durell SR, Jernigan RL et al (2001) Anisotropy of fluctuation dynamics of proteins with an elastic network model. Biophys J 80(1) 505-515... 

Chennubhotla, C., Reader, A.J., Yang, L.-W., and Bahar, I. "Elastic network model for understanding biomolecular machinery from enzymes to supramolecular assemblies". Phys. Biol. 2, S173-S180 (2005). 

Besides the formation of an elastic network, amylose gelation is also characterized by the development of opacity, which is generally attributed to chain aggregation.197,400 401 For a polydisperse amylose preparation (DP 3080, 2.4% solution, quenched to 32°C), the increase in turbidity slightly preceded the onset of G development.197 Crystallization, as detected by x-ray diffraction (intensity of the 100 diffraction peak),... 

The simplest of these approaches includes Gaussian Network Models (GNM) or Elastic Network Models (ENM) which assume that the native state represents the minimum energy configuration. A structure is represented as a network of beads connected by harmonic springs.12,13 One bead represents one residue and is usually centered on the position of the Ca carbon. Single parameter harmonic interactions are assigned to bead pairs which fall within a certain cutoff distance Rc. In case of proteins, Rc is usually around 8-10 A. The representation of the molecule in the... 

Wang Y, Rader AJ, Bahar I, Jernigan RL (2004) Global ribosome motions revealed with elastic network model. J. Struct. Biol. 147 302-314... 

Kurkcuoglu O, Jernigan RL, Doruker P (2004) Mixed levels of coarse-graining of large proteins using elastic network model succeeds in extracting the slowest motions. Polymer 45 649-657... 

Similarly, one can study the growth of the elastic constants (say the rigidity modulus) of a randomly formed elastic network, near the percolation point. The central force elastic problem (for networks formed out of linear springs only) belongs however to a different class of percolation problem, known as elastic percolation or central force percolation, and is discussed separately later (see Section 1.2.1(f)). 

Central force elastic percolation If one considers an elastic network of springs, which can provide only the central force, and not the bond-bending force considered earlier, then the elastic energy of such a random bond network can be expressed by the same energy function H in (1.11) with... 

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