Fibrillation energy

Fig. 13 Influence of temperature on the fibrillation energy r of SAN in regimes I and II (after [54])...

Specific SAXS experiments of Paredes and Fischer (1979) showed that for PC the product of the fibril diameter D and the flow stress Oy (the tensile plastic resistance) remains constant, irrespective of temperature, as shown in Fig. 11.10, at a value of 0.54 J/m that was labeled as the fibrillation energy of the polymer by them and was later demonstrated to be the base surface energy of the polymer... 

For Regimes I and II it is possible to determine the fibrillation energy F from Fig. 12 using Eq. 10. The corresponding plot (Fig. 13) gives the surprising result that in the small stress regime (I) F is constant and amounts to 0.031 Jm", which is comparable to but smaller than the surface tension y of... 

The aim of the model is to find the relation between the energy dissipated in growing the crack tip craze, as that is the macroscopic toughness and the local force at the fibril closest to the crack tip which controls the molecular level failure... 

In recent years there has been a renewed appreciation of potential beneficial effects of roughness on a macroscale. For example Morris and Shanahan worked with sintered steel substrates bonded with a polyurethane adhesive [61]. They observed much higher fracture energy for joints with sintered steel compared with those with fully dense steel, and ascribed this to the mechanical interlocking of polymer within the pores. Extra energy was required to extend and break these polymer fibrils. 

The tensile stresses acting in the direction of converging stream lines can ellipsoidally deform the big particles, but not so much as to form fine fibrils from small particles (region B). The matrix are also elongated in the converging section. As they pass the die exit (region C), recoil of the matrix occurs to release the stored energy... 

The twist of these aggregates determines the resulting structure. When ribbons stack into fibrils, and fibrils into fibres, packing considerations cause these twisted aggregates to bend and modify their twist with an elastic energy penalty8eiast- For fibrils, it can be shown that the afibrii per peptide in a fibril is ... 

Figure 5.24 Model of hierarchical self-assembly of chiral rodlike monomers.109 (a) Local arrangements (c-f) and corresponding global equilibrium conformations (c -f) for hierarchical selfassembling structures formed in solutions of chiral molecules (a), which have complementary donor and acceptor groups, shown by arrows, via which they interact and align to form tapes (c). Black and the white surfaces of rod (a) are reflected in sides of helical tape (c), which is chosen to curl toward black side (c ). (b) Phase diagram of solution of twisted ribbons that form fibrils. Scaled variables relative helix pitch of isolated ribbons h hh /a. relative side-by-side attraction energy between fibrils eaur/e. Reprinted with permission from Ref. 109. Copyright 2001 by the National Academy of Sciences, U.S.A.

For an elastic fiber such as a muscle fibril at constant temperature, the internal energy C7 is a function of three variables the entropy S, the volume V, and the length L. With the aid of the laws of thermodynamics, it is possible to show that... 

Electrical cardioversion It may be desirable to reduce the dose of digoxin for 1 to 2 days prior to electrical cardioversion of atrial fibrillation to avoid the induction of ventricular arrhythmias, but physicians must consider the consequences of increasing the ventricular response if digoxin is withdrawn. If digitalis toxicity is suspected, delay elective cardioversion. If it is not prudent to delay cardioversion, select the lowest possible energy level to avoid provoking ventricular arrhythmias. Lab test abnormalities Periodically assess serum electrolytes and renal function (serum creatinine concentrations) the frequency of assessments will depend on the clinical setting. 

On swelling, an increase in surface energy of the fibril will result and equilibrium will obtain when this increase in surface energy... 

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