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Results for “Systems Theory”

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At least 217 records · Page 12Linked to original sources
PubMed1997

[Methodology of functional theory systems in the design of devices for controlling human physiological functions].

The paper describes a basically new approach to solving the most urgent sociomedical problem--timely medical aid delivery in emergency acute vital dysfunctions in human beings. Based on the theory of functional systems, a new concept of medical equipment building for human life and health protection has been developed. The original guarded signalling devices referring to information domestic microprocessor techniques intended for daily individual continuous control and notification of the first objective signs of physiological dysfunctions are described.

Electronics, Medical↗
PubMedDate not supplied

Nonlinear systems theory in medical care management.

Health care is provided to biological, not mechanical systems. The focus of attention is a human being, not an automobile or clock. Biological systems are highly complex and their behavior can be nonlinear. By understanding this difference, we can begin to answer the question of how can we deliver efficient and effective clinical care, while controlling spiraling costs. This article describes the behavior of complex systems and explores what has been learned about managing such systems in non health care fields. The author translates that learning into the health care setting and proposes a new model for the health care environment, based on the principles of complex adaptive systems. The approach advocated is to design models that can learn and adapt, and then to implement them with skill. Such models should include the elements of roadmaps, decision aids, and continuous improvement.

Decision Making, Organizational↗
PubMed2001

Propagation failure in discrete bistable reaction-diffusion systems: theory and experiments.

Wave front propagation failure is investigated in discrete bistable reaction-diffusion systems. We present a theoretical approach including dissipative effects and leading to an analytical expression of the critical coupling beyond which front propagation can occur as a function of the nonlinearity threshold parameter. Our theoretical predictions are confirmed by numerical simulations and experimental results on an equivalent electrical diffusive lattice.

Journal Article↗
PubMed1995

Estimating net joint torques from kinesiological data using optimal linear system theory.

Net joint torques (NJT) are frequently computed to provide insights into the motor control of dynamic biomechanical systems. An inverse dynamics approach is almost always used, whereby the NJT are computed from 1) kinematic measurements (e.g., position of the segments), 2) kinetic measurements (e.g., ground reaction forces) that are, in effect, constraints defining unmeasured kinematic quantities based on a dynamic segmental model, and 3) numerical differentiation of the measured kinematics to estimate velocities and accelerations that are, in effect, additional constraints. Due to errors in the measurements, the segmental model, and the differentiation process, estimated NJT rarely produce the observed movement in a forward simulation when the dynamics of the segmental system are inherently unstable (e.g., human walking). Forward dynamic simulations are, however, essential to studies of muscle coordination. We have developed an alternative approach, using the linear quadratic follower (LQF) algorithm, which computes the NJT such that a stable simulation of the observed movement is produced and the measurements are replicated as well as possible. The LQF algorithm does not employ constraints depending on explicit differentiation of the kinematic data, but rather employs those depending on specification of a cost function, based on quantitative assumptions about data confidence. We illustrate the usefulness of the LQF approach by using it to estimate NJT exerted by standing humans perturbed by support-surface movements. We show that unless the number of kinematic and force variables recorded is sufficiently high, the confidence that can be placed in the estimates of the NJT, obtained by any method (e.g., LQF, or the inverse dynamics approach), may be unsatisfactorily low.

Algorithms↗
PubMedDate not supplied

[Systems theory].

Explore the source record for details and available documents.

Communication↗
PubMed2006

Quantum chemical methods for the investigation of photoinitiated processes in biological systems: theory and applications.

With the advent of modern computers and advances in the development of efficient quantum chemical computer codes, the meaningful computation of large molecular systems at a quantum mechanical level became feasible. Recent experimental effort to understand photoinitiated processes in biological systems, for instance photosynthesis or vision, at a molecular level also triggered theoretical investigations in this field. In this Minireview, standard quantum chemical methods are presented that are applicable and recently used for the calculation of excited states of photoinitiated processes in biological molecular systems. These methods comprise configuration interaction singles, the complete active space self-consistent field method, and time-dependent density functional theory and its variants. Semiempirical approaches are also covered. Their basic theoretical concepts and mathematical equations are briefly outlined, and their properties and limitations are discussed. Recent successful applications of the methods to photoinitiated processes in biological systems are described and theoretical tools for the analysis of excited states are presented.

Biophysics↗
PubMed2006

Quantum open system theory: bipartite aspects.

We demonstrate in straightforward calculations that even under ideally weak noise the relaxation of bipartite open quantum systems contains elements not previously encountered in quantum noise physics. While additivity of decay rates is known to be generic for decoherence of a single system, we demonstrate that it breaks down for bipartite coherence of even the simplest composite systems.

Journal Article↗