Elastic “pull” component

The concept of an apolar (hydrophobic)-polar (e.g., charge) repulsive free energy of hydration, AG,p, contributes to understanding the mechanism whereby ATPases function in three distinguishing respects. First and second, ATP binding, and particularly on hydrolysis with formation of ADP plus Pi, has the potential to effect both push and pull components of force. Third, release of Pi results in development of an elastic pull component of force that is most in evidence during isometric contractions. These three elements of force development are discussed immediately below. 

Development of an Elastic Pull Component of Force Resulting from an Apolar-Polar Repulsion on ATP Binding... 

Other elastomeric-type fibers iaclude the biconstituents, which usually combine a polyamide or polyester with a segmented polyurethane-based fiber. These two constituents ate melt-extmded simultaneously through the same spinneret hole and may be arranged either side by side or ia an eccentric sheath—cote configuration. As these fibers ate drawn, a differential shrinkage of the two components develops to produce a hehcal fiber configuration with elastic properties. An appHed tensile force pulls out the helix and is resisted by the elastomeric component. Kanebo Ltd. has iatroduced a nylon—spandex sheath—cote biconstituent fiber for hosiery with the trade name Sidetia (6). 

The NEB method recognized that the issues with the elastic band technique arose from specific components of the force. The issues with comer cutting arise from components of the force perpendicular to the path, which tend to pull images away from the path. Image sagging can be attributed to components of the tme force parallel to the path the spacing between images becomes uneven to balance out the net force. The simple solution to these issues is to minimize the elastic band with these force components projected out. The NEB force is... 

The two-component system—crystal lamellae or blocks alternating with amorphous layers which are reinforced by tie molecules— results in a mechanism of mechanical properties which is drastically different from that of low molecular weight solids. In the latter case it is based on crystal defects and grain boundaries. In the former case it depends primarily on the properties and defects of the supercrystalline lattice of lamellae alternating with amorphous surface layers (in spherulitic, transcrystalline or cylindritic structure) or of microfibrils in fibrous structure, and on the presence, number, conformation and spatial distribution of tie molecules. It matters how taut they are, how well they are fixed in the crystal core of the lamellae or in the crystalline blocks of the microfibrils and how easily they can be pulled out of them. In oriented material the orientation of the amorphous component (/,) is a good indicator of the amount of taut tie molecules present and hence an excellent parameter for the description of mechanical properties. In fibrous structure it directly measures the fraction and strength of microfibrils present and therefore turns out to be almost proportional to elastic modulus and strength in the fibre direction. 

Ultimately, fracture can only occur if all atomic bonds in an area are pulled apart and break. The stress necessary to break a bond (the theoretical strength) is between E/S and E/20, where E is the elastic modulus of the material [51]. Typical tensile stresses applied to highly loaded components are in the order of /1000 or even smaller, and yet fracture of components still occurs. To explain this discrepancy, it is necessary that certain strong local stress concentrations exist these are termed Jlaivs. The action of flaws can be discussed by using the simple example of an elliptical hole in a uniaxial tensile-loaded plate. At the tip of its major semi-axis (which is perpendicularly oriented to the stress direction), the stress concentration is [52] ... 

They provide a tool for analysing the results of pull-out tests, in order to resolve the bonding mechanisms and to determine the relative contributions of elastic and frictional shear stress transfer components. 

As discussed above, polymer chains tend to be disentangled and oriented under shear. One important result of the disentanglement and molecular orientation under shear is the decrease of viscosity with increasing shear rate. However, the flow of polymers is not pure viscous flow, and it has elastic component since the change of chain conformations is not completely irreversible. Upon the release of the shear, the polymer chains tend to recoil and be pulled back by the restraining force. Such elastic response has significant effect on the fiber formation processes. 

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