Self-balancing stresses

Residual (or inherent) stresses are self-balancing stresses that exist throughout the volume of a body in the absence of external forces. The appearance and growth of residual stresses in non-loaded articles are typical of materials prepared by the reactive processing. A general source... 

Recent research on the causes of disease and aging has increasingly supported the importance of stress [101]. One theory of the relationship between stress and disease is based on the concept of homeostasis [101]. Many researchers held that full, normal function of the self-regulating or homeostatic power of the body maintains the balanced, integrated condition we recognize as health. Failures in this capacity, such as those produced by frequent stressful experiences, can result in disease or death [101]. Walton and Pugh, in a review article, discussed both the fundamental elements of these theories and the current neuroendocrine research supporting their validity and immediate relevance [101]. 

A few years ago the concept considered was introduced also in the low-temperature chemistry of the solid.31 Benderskii et al. have employed the idea of self-activation of a matrix due to the feedback between the chemical reaction and the state of stress in the frozen sample to explain the so called explosion during cooling observed by them in the photolyzed MCH + Cl2 system. The model proposed in refs. 31,48,49 is unfortunately not quite concrete, because it includes an abstract quantity called by the authors the excess free energy of internal stresses. No means of measuring this quantity or estimating its numerical values are proposed. Neither do the authors discuss the connection between this characteristic and the imperfections of a solid matrix. Moreover, they have to introduce into the model a heat-balance equation to specify the feedback, although they proceed from the nonthermal mechanisms of selfactivation of reactants at low temperatures. Nevertheless, the essence of their concept is clear and can be formulated phenomenologically as follows the... 

The system has to stay far from equilibrium, or better the turnover of the major constituents is not at equilibrium, where formation and decomposition would be microscopically reversible and detailed balance would hold. This requires a metabolism sustained by a supply of energy-rich monomeric building blocks of the polymeric constituents. (It should be stressed that at equilibrium the first two conditions are not sufficient to cause selective evolutionary self-organization.) As a consequence of microscopic reversibility, all eigenvalues will always turn out to be real and negative. 

Surfactant self-assembly is a delicate balance between hydrophobic and hydrophilic interactions, and the interactions between the headgroups and the solvent are decisive both for the onset of self-assembly and for the curvature of the surfactant films and thus for aggregate shape and phase behavior. H, H, and NMR have been used successfully to study the hydration of surfactant aggregates. The three by far most used approaches are H (or H) self-diffusion, O quadrupole relaxation, and quadrupole splittings. We stress at the outset that a division into free and bound water molecules on which the concepts of hydration and hydration number are based is far from unambiguous, and furthermore this division is dependent on the physicochemical parameter monitored. 

An advantage of this process is that the amorphous tube crystallises rapidly during biaxial stretching. This increases the modulus and therefore also the stress at a faster rate than the thickness decreases. Hence, the balloon will obtain a diameter where the developed tensile stress just balances the internal pressure. This diameter will, of course, depend on several factors, such as temperature, wall thickness and on the stretch ratio in the machine direction, but not on the amount of air. If more air is introduced, the balloon will become only longer, not wider and, hence, the balloon is self-stabilising. 

Clinicians, like everyone else, vary in temperament, resilience and attitude to their own errors. Jenny Firth-Cozens (1997) has found that a tendency to self criticism is predictive of stress this tendency may be rooted in earher relationships, which in turn may find an echo in relationships with senior colleagues. For a highly self critical person, errors and mistakes will he particularly disturbing in serious cases the clinician may enter a vicious downward spiral of anxiety, shame and deteriorating performance. There is a fine balance to be struck between personal high standards and undue self criticism. The high personal standards of excellent clinicians may in fact make them particularly vulnerable to the impact of mistakes. 

Secondary stress is developed by self-constraint of the structure. Its basic characteristic is that it is self-limiting. That is, rotation and deformation or deflection take place until the forces and moments are balanced even though some permanent geometric changes may have taken place. 

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