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PubMed2002

Interdisciplinary developments in hazardous environment research: a silent tribute to general systems theory?

PURPOSE: This paper draws attention to a welcome trend in certain areas of applied and experimental research that appears to endorse a General Systems Theory for the acquisition of knowledge. METHOD: By way of illustration it makes an appraisal of key studies of human/environmental interaction that were either derived from actual operational groups in naturalistic settings or contrived in the laboratory or the field to simulate extreme conditions. RESULTS: It urges more anthropologists, physicians, physiologists, psychologists, and sociologists to follow suit and make their disciplinary boundaries permeable. Were they to do that, it is argued that their research methods would be more appropriate for studying the dynamic integration of their subject matter than those derived from the conventional use of scientific method. CONCLUSIONS: It asserts that the solutions to complex problems of human adaptation to the environment are not to be found within the domain of any single academic discipline.

Adaptation, Physiological↗

PubMed1996

Living systems theory as a paradigm for organizational behavior: understanding humans, organizations, and social processes.

Living systems theories have been used to model human, organization, and communication processes. This paper attempts to describe these models and to highlight the isomorphisms among the models. Particular emphasis is given to self-regulating properties of humans as a subsystem of social systems. Attention is given to the advantages of generalizing across levels and phenomena and integrating the middle-range theories that dominate the field of organizational behavior. Three broad recommendations for future research are discussed.

Humans↗

PubMed1987

Integrating systems theory and attachment theory: the use of radio communication to modify attachments in a patient with psychogenic vomiting.

A case is presented that shows the usefulness of integrating systems theory and attachment theory in the formulation and treatment of a clinical problem. The 5 year old son of East Indian immigrants presented with persistent psychogenic vomiting associated with pathological family attachments. It was evident that the precarious family equilibrium was stabilized by the child's psychogenic vomiting. The therapeutic team suggested to the family that their problems might be more satisfactorily resolved if the mother and child maintained their link by two-way radio. Three weeks later the vomiting had ceased, the child no longer felt that he needed the radio and both parents had established new patterns of relating to their child, whose attendance and peer socialization at school showed marked improvement. To some extent the rapid resolution of the problems was facilitated by the cultural strengths of the family.

Acculturation↗

PubMed1984

[Systems theory of ultrasound pulse echo technic (1)].

The properties of diagnostic pulse echo systems, independent of instrument characteristics (ideal system) are analysed in Part 1 and it is shown in Part 2 how they are modified by "typical" instrument parameters. A simplified block diagram of an ideal system is analysed in the time and frequency domain by means of the one-dimensional system theory. The terms dynamic range, maximum penetration depth and amplitude resolution are explained.

Humans↗

PubMed2000

Utility of Biochemical Systems Theory for the analysis of metabolic effects from low-dose chemical exposure.

Adverse health outcomes from exposure to chemical agents are of increasing interest in human and ecological risk assessment and require the development of new analytical methods. Such methods must be able to capture the essence of integrated networks of biochemical pathways in a mathematically feasible fashion. Over the past three decades, Biochemical Systems Theory has been successfully applied to numerous biological systems. It is suggested here that S-system models derived from BST can provide the means for assessing chemical exposures and their effects at the metabolic level. This article briefly reviews essential concepts of S-systems and provides generic examples of chemical exposure scenarios. S-system models can be considered mechanistic, since their components are measurable quantities (e.g., concentrations, fluxes, enzyme activities, and rates). As dynamic models, they can be used to assess immediate and long-term metabolic responses to environmental stimuli. Direct mathematical analysis for low exposures leads to simple dose-response relationships, which have the form of power-law functions. Thus, if the S-system model yields an appropriate description of chemical exposure and its metabolic effects, the dose-response relationship for low exposures is linear in logarithmic coordinates. This result includes as a special case the standard linear relationship in Cartesian coordinates with zero intercept.

Dose-Response Relationship, Drug↗

PubMed1989

[Systems theory solution of the Bieri trilemma. Comments on the comments by E. G. Schmidt on my comments on the body-mind problem in psychosomatic medicine].

E. G. Schmidt criticizes my critique of the wholist-emergentist solution for the mind-body problem. Against my repudiation he proposes an emergentist system theory solution apparently solving the so-called Bieri trilemma. I contend that his solution falsely introduces "psychogenic" causality into the wholist-emergentistic theory.

Arousal↗

PubMed2004

On the role of general system theory for functional neuroimaging.

One of the most important goals of neuroscience is to establish precise structure-function relationships in the brain. Since the 19th century, a major scientific endeavour has been to associate structurally distinct cortical regions with specific cognitive functions. This was traditionally accomplished by correlating microstructurally defined areas with lesion sites found in patients with specific neuropsychological symptoms. Modern neuroimaging techniques with high spatial resolution have promised an alternative approach, enabling non-invasive measurements of regionally specific changes of brain activity that are correlated with certain components of a cognitive process. Reviewing classic approaches towards brain structure-function relationships that are based on correlational approaches, this article argues that these approaches are not sufficient to provide an understanding of the operational principles of a dynamic system such as the brain but must be complemented by models based on general system theory. These models reflect the connectional structure of the system under investigation and emphasize context-dependent couplings between the system elements in terms of effective connectivity. The usefulness of system models whose parameters are fitted to measured functional imaging data for testing hypotheses about structure-function relationships in the brain and their potential for clinical applications is demonstrated by several empirical examples.

Brain↗

PubMed1993

Beyond quality improvement teams: sociotechnical systems theory and self-directed work teams.

Increasingly, businesses are reporting successful implementation of self-directed work teams. In health care, team-based structures in both clinical and nonclinical areas are now rapidly emerging. This paper describes the linkage between the literature of sociotechnical systems theory and current applications of self-directed work teams, and outlines the organizational processes used to design and implement them. Several examples of self-directed work teams in industry and health care systems are provided. As much of the existing literature on self-directed work teams is from industry, there is a need for case reports and further research on their current applications in health care systems.

Decision Making, Organizational↗

PubMed1998

Bowen's family systems theory. A useful approach for a nurse administrator's practice.

Two concepts from Bowen's family systems theory are differentiation of self and triangles. These concepts are presented and recommended as useful tools for the nurse a administrator. By using the principles from differentiation of self, nurse administrators may improve the work environment by distinguishing between their own thoughts and feelings. Once a nursing administrator identifies and changes triangulation processes, healthy relationship patterns may occur and staff absenteeism and low morale may be improved.

Anxiety↗

PubMed1987

[Systems theory of the pulsed Doppler technic for blood flow measurement. II].

Following the discussion of the signal generation of an ideal pw Doppler system in the time and frequency domain using the means of the one-dimensional system theory in part 1 in this part 2 the main system parameters as resolution in space, and unambiguity ranges for space and velocity are explained and mathematical formula are derived for this.

Blood Flow Velocity↗

PubMed1979

A systems-theory approach to the analysis of multiexponential fluorescence decay.

A mathematical model of the fluorescence decay experiment based on linear systems theory is presented. The model suggests an experimental technique that increases the probability of correctly determining the decay constants of a multicomponent system. The use of moment methods for data analysis improves accuracy by combining information obtained from several discrete experiments. Examples are presented to show that the analysis of a three component system composed of known standards is improved as the number of experimental determinations is increased from one to four. The discrete measurements are made by changing the excitation and emission wavelengths.

Carbazoles↗

PubMed1989

Strategies for representing metabolic pathways within biochemical systems theory: reversible pathways.

The search for systematic methods to deal with the integrated behavior of complex biochemical systems has over the past two decades led to the proposal of several theories of biochemical systems. Among the most promising is biochemical systems theory (BST). Recent comparisons of this theory with several others that have recently been proposed have demonstrated that all are variants of BST and share a common underlying formalism. Hence, the different variants can be precisely related and ranked according to their completeness and operational utility. The original and most fruitful variant within BST is based on a particular representation, called an S-system (for synergistic and saturable systems), that exhibits many advantages not found among alternative representations. Even within the preferred S-system representation there are options, depending on the method of aggregating fluxes, that become especially apparent when one considers reversible pathways. In this paper we focus on the paradigm situation and clearly distinguish the two most common strategies for generating an S-system representation. The first is called the "reversible" strategy because it involves aggregating incoming fluxes separately from outgoing fluxes for each metabolite to define a net flux that can be positive, negative, or zero. The second is the "irreversible" strategy, which involves aggregating forward and reverse fluxes through each reaction to define a net flux that is always positive. This second strategy has been used almost exclusively in all variants of BST. The principal results of detailed analyses are the following: (1) All S-system representations predict the same changes in dependent concentrations for a given change in an independent concentration. (2) The reversible strategy is superior to the irreversible on the basis of several criteria, including accuracy in predicting steady-state flux, accuracy in predicting transient responses, and robustness of representation. (3) Only the reversible strategy yields a representation that is able to capture the characteristic feature of amphibolic pathways, namely, the reversal of nets flux under physiological conditions. Finally, the results document the wide range of variation over which the S-system representation can accurately predict the behavior of intact biochemical systems and confirm similar results of earlier studies [Voit and Savageau, Biochemistry 26: 6869-6880 (1987)].

Biochemical Phenomena↗

PubMed2004

Modeling panel detection frequencies by queuing system theory: an application in gas chromatography olfactometry.

In continuous vigilance tasks, the number of coincident panel responses to stimuli provides an index of stimulus detectability. To determine whether this number is due to chance, panel noise levels have been approximated by the maximum coincidence level obtained in stimulus-free conditions. This study proposes an alternative method by which to assess noise levels, derived from queuing system theory (QST). Instead of critical coincidence levels, QST modeling estimates the duration of coinciding responses in the absence of stimuli. The proposed method has the advantage over previous approaches that it yields more reliable noise estimates and allows for statistical testing. The method was applied in an olfactory detection experiment using 16 panelists in stimulus-present and stimulus-free conditions. We propose that QST may be used as an alternative to signal detection theory for analyzing data from continuous vigilance tasks.

Adult↗

PubMed1982

A systems theory model for foster home studies.

Systems and communications theories applied to the delicate task of matching children with families promise an objective method for understanding the complexities of family relationships. The author shows how one agency successfully incorporated sophisticated theoretical tools into a study process evaluating the suitability of foster family applicants.

Child↗

PubMed2001

Characterization of toxicokinetics and toxicodynamics with linear systems theory: application to lead-associated cognitive decline.

We present a theoretical approach to analysis of toxicokinetics and toxicodynamics using linear systems theory. In our approach, we define two impulse response functions that characterize the kinetic behavior of an environmental agent in the body and the dynamic time-course behavior of its effect on the body. This approach provides a formalism for understanding the relation among exposure, dose, and cumulative biologically effective dose and for understanding the implications of an effect time-course on cross-sectional and longitudinal data analyses. We use lead-associated cognitive decline as a specific example where the approach may be applied.

Cognition Disorders↗

PubMed1997

A phenomenological variant of ecological systems theory (PVEST): a self-organization perspective in context.

A framework that emphasizes and integrates individuals' intersubjective experiences with Bronfenbrenner's ecological systems theory (PVEST) is introduced and compared with self-organizational perspectives. Similarities, differences and advantages of each framework are described. In a demonstration of PVEST's utility, a subset of data from the 3rd year of a longitudinal study (14- to 16-year-old middle adolescent African-Americans) is used for examining an achievement variable: negative learning attitude. Explored separately by gender, a regression model that contained risk, stress, and a reactive coping variable for the prediction of negative learning attitudes was investigated. For boys, stress was an independent stressor across steps independent of the other variables entered; social support variable, perceived unpopularity with peers, that was a significant predictor of girls' negative learning attitude. Particularly for boys, the findings suggest critically important roles for teachers and peers in the negative learning attitude of midadolescent economically disadvantaged African-American students.

Adolescent↗

PubMed1981

An overview of a multifactor-system theory of personality and individual differences: III. Life span development and the heredity-environment issue.

In Part III of this three-part series on multifactor-system theory, multivariate, life-span development is approached from the standpoint of a quantitative and qualitative analysis of the ontogenesis of factors in each of the six systems. The pattern of quantitative development (described via the Gompertz equation and three developmental parameters) involves growth, stability, and decline, and qualitative development involves changes in the organization of factors (e.g., factor differentiation and convergence). Hereditary and environmental sources of variation are analyzed via the factor gene model and the concept of heredity-dominant factors, and the factor-learning model and environment-dominant factors. It is hypothesized that the sensory and motor systems are heredity dominant, that the style and value systems are environment dominant, and that the cognitive and affective systems are partially heredity dominant.

Genotype↗

PubMedDate not supplied

Classical Michaelis-Menten and system theory approach to modeling metabolite formation kinetics.

When single doses of drug are administered and kinetics are linear, techniques, which are based on the compartment approach and the linear system theory approach, in modeling the formation of the metabolite from the parent drug are proposed. Unlike the purpose-specific compartment approach, the methodical, conceptual and computational uniformity in modeling various linear biomedical systems is the dominant characteristic of the linear system approach technology. Saturation of the metabolic reaction results in nonlinear kinetics according to the Michaelis-Menten equation. The two compartment open model with Michaelis-Menten elimination kinetics is theorethicaly basic when single doses of drug are administered. To simulate data or to fit real data using this model, one must resort to numerical integration. A biomathematical model for multiple dosage regimen calculations of nonlinear metabolic systems in steady-state and a working example with phenytoin are presented. High correlation between phenytoin steady-state serum levels calculated from individual Km and Vmax values in the 15 adult epileptic outpatients and the observed levels at the third adjustment of phenytoin daily dose (r=0.961, p<0.01) were found.

Adult↗