Daniel J. Schneck

Feedback control and the concept of homeostasis

The maintenance of life requires a steady-state internal environment that must be held relatively constant within carefully prescribed limits. Feedback control mechanisms that provide this type of restraint work through homeostatic regulators that transmit information through a corresponding syntax that is uniquely their own. The language is coded into electromagnetic information that is of a reference nature (genetic, adaptive or conditioned), sensory (informative) or motor (causative), and which is transmitted as action potentials that have a functional dependence on the error signal and a parametric dependence on the disturbing signal. The analysis of homeostasis within the context of feedback control theory reduces seemingly complex, unrelated sequences of physiologic processes into more readily identifiable sets of common denominators that illucidate some basic principles of biologic function. Appropriate interpretation of these biologic principles may help us move closer to success in our efforts to improve the health, comfort and understanding of man. This is because the specific details of complex physiologic processes may be viewed as simply special cases (or different sets of boundary conditions) of a unified guiding theory.

Deductive physiologic analysis in the presence of “will” as an undefined variable

Abstract In physiological research, inductive reasoning has traditionally been the rule, rather than the exception. This is because mathematical formulations of human body function inevitably lead to indeterminate situations where there are more unknown quantities than there are equations to describe them. This paper discusses a deductive approach to the study of human body dynamics, where the indeterminateness is usually associated with the presence of “will” as an undefined variable. The point is made that “will” may be quantified by viewing musculoskeletal mechanics in terms of a minimum energy principle. Thus, variational and optimization methods may be employed to generate additional equations of motion which render the problem determinate in a deductive sense. Several examples illustrate the succesful use of variational methods in biodynamic modelling.

Biomechanical properties of human wrist ligaments

The Annals o f Biomedical Engineering has initiated a Ph.D. Abstracting Service under its section dedicated to Professional Technical Service. Current (no more than one or two years old) Ph.D. Thesis Abstracts will be published for the purpose of bringing to the attention of our readers timely and informative contributions to the literature. In order to make this service most effective, Ph.D. advisors, Department Chairmen, Program Directors, and other individuals who have access to such thesis abstracts are urged to send two copies of each to:

An Experimental Investigation of Pulsatile Laminar Flow Separation in Exponentially Diverging Tubes

Since the turn of the century, when Ludwig Prandtl formulated the theoretical concept of the boundary layer, the phenomenon of boundary layer or flow separation has been associated mostly with trouble, i.e., energy losses, reverse flow, vortex formation, wakes, stalling, increased drag, decreased lift, wall scouring effects, etc. One of the more serious problems with which flow separation has been associated in recent years is cardiovascular disease. There is an ever increasing abundance of evidence which suggests indirectly that the pathogenesis, localization and/or aggravation of certain forms of cardiovascular disease may be related to the incidence, persistence and consequences of internal, unsteady, laminar-flow separation. This very same evidence, because of its indirect speculative nature, has also brought to light an area of fluid mechanics that has hitherto been conspicuously neglected.

Music, the Body in Time, and Self-Similarity Concepts

It is shown in this paper that the structural configuration of music exactly parallels the structural configuration of the human body. Music and biological systems share time as a common denominator, since both derive from, and exist in the time dimension. Music and biological systems also share as a common denominator certain features of self-similarity that can be quantified by power-law formulations. Discussed herein is how further investigations into these two common features—selfsimilarity as an architectural property of both music and the human body, and space-time as common dimensions of perception—can provide some insights into specific mechanisms by which the six elements of music—rhythm, melody, harmony, timbre, dynamics, and form—succeed in eliciting profound physiological responses. Once these mechanisms are understood, they can be exploited to develop diagnostic protocols which, in turn, can provide a scientific basis for using music as a clinical intervention in a variety of diagnosed populations.

In viro simulation ofin vivo dynamic micromechanical failure of sructural composite biomaterials

The Annals o f Biomedical Engineering has initiated a Ph.D. Abstracting Service under its newly formed section dedicated to Professional Technical Service. Current (no more than one or two years old) Ph.D. Thesis Abstracts will be published for the purpose of bringing to the attention of our readers timely and informative contributions to the literature. In order to make this service most effective, Ph.D. advisors, department chairmen, program directors, and other individuals who have access to such thesis abstracts are urged to send two copies of each to:

Editorial: Software survey section

The purpose of the Software Survey Section in Annals of Biomedical Engineering is to encourage the open exchange of information on software programs unique to our professional field. With the rapid penetration of computers into academic and industrial institutions has come a parallel increase in the number of scientists and researchers designing their own software. The existence of much of this software remains unknown to even those of us who could most benefit from its use. We believe that it is of vital importance to our readers that such information be made available. We believe also that a professional journal is the best place to share such information. Your contribution would be most welcome.

Ischaemia in the Heart Due to Atherosclerotic Mechanisms, Flow Anomalies and Vascular Spasm

This paper addresses ischaemia in the heart due to atherosclerotic mechanisms that can be related back to endothelial injury. Furthermore, endothelial injury is examined from a fluid dynamic point of view.

A Fluid Mechanics Approach to the Problem of Sensory Feedback in Prosthetic Devices

Structural replacement of amputated limbs has been common for hundreds, even thousands, of years (1). However, the concept of restoring more than the lost structure and supporting musculature, for example, the lost sensory information, is relatively new. Even newer is the idea of using a fluid to transmit tactile information, rather than the more traditional transducers (e.g., strain gauges mounted on cables or various other parts of the terminal device). To use a fluid for this purpose increases the scope and potential for accessing sensory information. That is, the acquisition and transmission of such quantities as heat, prehensile slippage and/or prehensile forces (pressure and shear) is greatly simplified. On this basis, a new type of terminal device for an upper-extremity amputee has been designed and is described below. The device will allow fluids to act as the medium for the transmission of sensory feedback information to the prosthetic wearer. It also introduces a push/pull mode of operation which incorporates a versatile, previously unavailable, wrist mechanism.