Narrow Results

This paper presents results on adaptive control strategies for a sensory system to identify (unknown) ground excitations which force the sensor and its seismic masses, so that acting forces can be measured and identified. The sensor system is modeled as a spring-mass-damper system within a rigid frame with two degrees-of-freedom. The seismic masses are under the load of internal control forces, which shall ensure stabilization of the mass point rest positions despite the continuing ground excitations. Using these (measured) resulting regulating forces, we are able to identify the excitation force. The control strategies are designed referring to the natural behavior of mechanoreceptors from biology. These are able to adapt their sensitivity to the environment, so that they filter the important information out of the flood of information. Mimicking this behavior, adaptive control strategies are used with time-varying controller gains. In this way, we are able to design controllers which are still sensitive while a constant stimuli affects. So new incoming information can be identified with a high quality. Further on, the sensor has to be universal and shall consume less energy as possible. Therefore, control strategies from literature are analyzed and modified, so that the most effective ones are used for the sensor system in this paper. Finally, the best working control strategies are tested for both their long-term behavior to an excitation which simulates different situations and for their response to different system parameters, chosen randomly.

Noxious thermal and/or mechanical stimuli applied to dentine can cause fluid flow in dentinal microtubules (DMTs). The fluid flow induces shear stress (SS) on intradental nerve endings and may excite pulpal mechanoreceptors to generate dental pain sensation. There exist numerous studies on dental thermal pain, but few are mathematical. For this, we developed a computational fluid dynamics (CFD) model of dentinal fluid flow (DFF) in innervated DMTs. Based on this model, we systematically investigated the effects of various parameters (e.g., biological structure, DFF velocity, and fluid properties) on the SS experienced by intradental nerve endings and thus provide a quantitative interpretation to the hydrodynamic theory. The dimensions of biological structures, odontoblastic process (OP) movement, dentinal fluid velocity, and viscosity were found to have significant influences on the SS while dentinal fluid density showed negligible influence under conditions studied. The results indicate that: (i) dental pain study of animal models may not be directly applied to human being and the results may even vary from one person to another and (ii) OP movement caused by DFF changes the dimension of the space for the fluid flow, affecting thus the SS on nerve endings. The present work enables better understanding of the mechanisms underlying dental pain sensation and quantification of dental pain intensity resulted from clinical procedures such as dentine sensitivity testing and dental restorative processes.

Background: The human hand is a specialised organ for fine motion and sensation and has a relatively large representation in the homunculus. The pathway of sensation starts from information sent by mechanoreceptors in the hand. This study reports the topography of the Pacinian corpuscle in the fingertips of a human cadaver.

Methods: All 10 digits from both hands of a fresh-frozen cadaver were examined. Glabrous skin distal to the distal interphalangeal joint was harvested superficial to the periosteum including fat and subcutaneous tissue. The glabrous skin were divided into 10 sections that included five distal and five proximal sections. Modified gold chloride staining was performed. Sectioned specimens were observed under a light microscope and the density of Pacinian corpuscles was determined in each segment. The density of the corpuscles was compared between the radial/ulnar and proximal/distal segments and also between digits from the right hand versus those from the left hand.

Results: Pacinian corpuscles were observed only in the subcutaneous tissue. There was no significant difference in density of the corpuscles between the distal and proximal segments or between the right and left hands. There was a statistically significant greater density of Pacinian corpuscles on the radial segments of all digits except the thumb.

Conclusions: There is a greater density of Pacinian corpuscles on the radial side of the human fingertip in all digits except the thumb.