Rate of elongation

Fig. 2. Typical stress—strain properties of staple fibers at 65% rh and 21°C. Rate of elongation is 50%/min. To convert N/tex to gf/den, multiply by 11.3.

The microtubule-associated proteins MAP2 and tau both have two separate functional regions (Lewis et al., 1989). One is the microtubule-binding site, which nucleates microtubule assembly and controls the rate of elongation (by slowing the rate of assembly). The second functional domain shared by MAP2 and tau is a short C-terminal a-helical sequence that can cross-link microtubules into bundles by self-interaction. This domain has some of the properties of a leucine zipper. Likely it is responsible for the organization of microtubules into dense stable parallel arrays in axons and dendrites (Lewis et al., 1989). 

Figure 3 Calculated stress-strain curves for monodisperse linear polyethylene (M = 475,000) at four different values of (Equation 2). T = 109°C and rate of elongation °e = 500%/min.

Viscoelastic properties have been discussed in relation to molar mass, concentration, solvent quality and shear rate. Considering the molecular models presented here, it is possible to describe the flow characteristics of dilute and semi-dilute solutions, as well as in simple shear flow, independent of the molar mass, concentration and thermodynamic quality of the solvent. The derivations can be extended to finite shear, i.e. it is possible to evaluate T) as a function of the shear rate. Furthermore it is now possible to approximate the critical conditions (critical shear rate, critical rate of elongation) at which the onset of mechanical degradation occurs. With these findings it is therefore possible to tune the flow features of a polymeric solution so that it exhibits the desired behaviour under the respective deposit conditions. 

We then see that the rate of elongation in the presence of a capping protein will be given by the following rate law ... 

This comprises a thermoplastic elastomer based on a polyolefin and a rubber. The polyolefin is a PP homo- or copolymer having a specified weight-average molec.wt. and elongational viscosity (measured at a temperature of 170C, a rate of elongation of 0.03 1/s and at a time of 10 s). 

The tensile strength test [Figure 3.1 (1)] (ASTM-638) employs samples of a specified shape, typically a dogbone, as depicted in Figure 3.2. The sample is clamped at one end and pulled at a constant rate of elongation until the center of the specimen fails. 

Elastic modulus was measured by a dynamic method at 160 °C. on samples with 2-inch bench marks elongated at a constant rate of 100% per minute. The stress at strains of 25, 50, 75, and 100% was used to calculate Youngs modulus. Elongation at rupture at 160°C. was measured at the same relative rate of elongation, the mean of four measure-... 

A rather complete survey of the entire field of viscometry, including the mathematical relationships applicable to various types of instruments, has been made by Philippoff (P4). The problem of slip at the walls of rotational viscometers has been discussed by Mooney (M15) and Reiner (R4). Mori and Ototake (M17) presented the equations for calculation of the physical constants of Bingham-plastic materials from the relationship between an applied force and the rate of elongation of a rod of such a fluid. ... 

DNA polymerase III in its holoen-zyme form is the major polymerase for DNA replication. It elongates the primer chains rapidly and pro-cessively leaving only very small gaps at the ends of single-stranded regions. The rate of elongation, which is 3 nucleotides / s for 8 kb... 

An analysis of the rate of elongation of a wire possessing a bamboo-type grain structure is given in Section 16.1.3. An essential aspect of the analysis is the assumption that the stress-induced atomic transport producing the elongation is diffusion-limited. Now, construct the main framework of a model for the same system in which the atomic transport is source-limited, as indicated below, and explain how the model works. 

Clearly, according to this model the rate of elongation increases with injection rate, with decreasing gap and increasing n. Because the shape of the front is not flat but, as shown in Fig. 13.16, bends backward and becomes tangent to the walls aty = H/2, the fluid elements that were oriented by the fountain flow in the y direction are deposited on the cold wall with an x-direction orientation. 

Transportation of a molten polymer through a converging channel, e.g. with extrusion, goes accompanied with elongational flow when the rate of elongation is high, next to the viscous deformation also a considerable elastic component may be present. After the polymer leaves the channel, the elastic deformation will spontaneously recover, which is apparent as an increase in diameter of the extrudate, the so-called die-swell. 

In perfused liver it also has effects on synthesis of most types of RNA and on amino acid uptake, and these may underlie much of the action on protein synthesis. For most effects on the liver there appears to be a delay of 15-60 min between the application of hormone and the first manifestation of the effect. Ribosomes from liver of hypophysectomized rats possess a lowered ability to carry out protein synthesis [86] and the defect can be reversed by administration of GH in vivo or in vitro. The effect may be at least partly on the rate of elongation of the growing polypeptide chain [85]. 

When the rate of elongation is increased, the tensile strength and the modulus also increase the elongation to break generally decreases (except in rubbers). Normally an increase of the speed of testing is similar to a decrease of the temperature of testing. To lightly cross-linked rubbers even the time-temperature equivalence principle can be applied. The rate dependence will not surprise in view of the viscoelastic nature and the influence of the Poisson ratio on the ultimate properties. 

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