Dynamic-response feet

Prosthetic Feet. With the exception of partial foot amputees, the prostheses for all lower extremity amputees require a prosthetic foot. The prescription criteria for these feet take into consideration the amputation level, residual limb length, subject activity level, cosmetic needs, and the weight of the individual. Prosthetic feet range from the SACK (solid ankle cushioned heel) foot, which is relatively simple and inexpensive, to dynamic-response or energy-storing feet that are more complicated and considerably more costly. Note that prosthetic feet are often foot and ankle complexes. As such, prosthetic feet may replace plantarflexion/dorsiflexion, pronation/supination, and inversion/eversion. Prosthetic feet are typically categorized in terms of the function(s) they provide or replace and whether or not they are articulated. 

Spread footings are usually suitable for sites of rock and firm soUs. The stability of these foundations under seismic loads can be evaluated using a pseudostatic bearing capacity procedure. The applied loads for this analysis can be taken directly from the results of a global dynamic response analysis of the bridge with the soil-foundation-interaction effects represented in the structural model. 

The small-molecule-based machine conceived by von Delius, Geertsema, and Leigh [45] is a linear (for reviews, see [46], [100]) motor based on dynamic covalent chemistry [19-24] (forming, breaking, and reforming of dynamic covalent bonds with relatively fast equilibration in response to stimuli), namely on acyl-hydrazone and disulfide exchanges. The motor consists of a track that has four functional groups disposed alternately aldehyde-thiol-aldehyde-thiol which are the positions 1,2, 3, and 4 of the track, a walker NH2-NH-CO-(CH2)5-SH which has the feet A (hydrazide or acyl-hydrazine) and B (thiol), and a placeholder with a foot C of type thiol (Fig. 10). 

Analytic response theory, which represents a particular formulation of time-dependent perturbation theory, has constituted a core technology in much of the this development. Response functions provide a universal representation of the response of a system to perturbations, and are applicable to all computational models, density-functional as well as wave-function models, and to all kinds of perturbations, dynamic as well as static, internal as well as external perturbations. The analytical character of the theory with properties evaluated from analytically derived expressions at finite frequencies, makes it applicable for a large range of experimental conditions. The theory is also model transferable in that, once the computational model has been defined, all properties are obtained on an equal footing, without further approximations. 

To fully develop the photonic and material components of quantum-optical response invites the application of quantum electrodynamics (QED). The defining characteristic of this theory is that it addresses every optical interaction in terms of a closed dynamical system where light and matter are treated on an equal footing, each component addressed with full quantum-mechanical rigor. It is a theory whose predictions have been tested to a higher degree of precision... 

Unfortunately, the currently available prediction tools and definitions fail as soon as we subject the tissue and implant to dynamic mechanical stimulation. Let us consider the simplest case of a wood splinter in your foot. The normal tissue reaction you will receive is early inflammation, and if the splinter is deeply buried it will be encapsulated with coUagen in the process we call foreign body reaction or fibrotic capsule formation. There wiU, however, be a significant difference in the response depending on if you walk and put pressure on the tissue surrounding the splinter or if you completely unload this tissue. Excessive dynamic mechanical stimulation of the tissue will cause prolonged inflammation and also the formation of a thicker collagen capsule than would be the case if you completely rest the same splinter—tissue. 

The clue to this problem has already been alluded to it lies in the neglect of dynamic, inertial effects in the evaluation of the response of particles to the changes they experience in the interaction force. The fact that a kinematic description applies in some cases and not in others would therefore appear to relate to differences in the relative magnitude of dynamic to kinematic factors in different systems. These considerations are put on a quantitative footing in the following chapter. 

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