Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Systems Theory”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47Linked to original sources
PubMed2001

A dynamical systems investigation of lower extremity coordination during running over obstacles.

OBJECTIVE: To investigate intralimb coordination during running over a level surface and over obstacles of three different heights. DESIGN: The phasing relationships between the foot and leg motions in the frontal plane, and the shank and thigh motions in the sagittal plane were used to compare patterns of coordination. BACKGROUND: The coordinated actions of lower extremity segments are necessary to absorb the impact forces generated during running. The behavioral patterns of these segments can be studied under changing task demands using analysis techniques from the Dynamical Systems Theory. METHODS: Ten subjects ran at their self-selected pace under four conditions: over a level surface and over obstacles of different heights (5%, 10%, 15% of their standing height). A force platform was used to record impact forces during landing after obstacle clearance, while kinematics were collected using a two-camera system. RESULTS: The increases in obstacle height resulted in significant changes in impact forces (34% increase between the two extreme conditions) and more in-phase relationships between the segments during early stance. No changes were observed in the variability of the phasing relationships. CONCLUSIONS: The coordination changes observed might be compensatory strategies aimed to reduce forces and potential injury. However, since the impact forces still increased significantly, it is also possible that the observed changes might be at-risk movement patterns predisposing runners to injury.

Adult↗
PubMed2005

Isostructural solid-solid transitions in binary asymmetrical hard sphere system: based on solvent-mediated potential.

Size dependence is imparted onto a modified bridge functional, adopted for a recently proposed semi-analytical hard sphere reference system theory for calculation of solvent-mediated potential (SMP). The SMP for two large hard sphere particles immersed in a small hard sphere solvent bath predicted by the present improved version is in satisfactory agreement with the prediction from a theoretically based fitting formula. Isostructural solid-solid transitions in the binary asymmetrical hard sphere system are investigated based on a single-component macrofluid approximation combined with the improved version. It is found that the isostructural solid-solid transition appears when size asymmetry increases. The limiting asymmetry size ratio is near 1/8. As the size asymmetry increases, critical density for both large and small hard sphere components for the fcc isostructural solid-solid transition increases and decreases, respectively.

Journal Article↗
PubMed2004

Priming nonlinear searches for pathway identification.

BACKGROUND: Dense time series of metabolite concentrations or of the expression patterns of proteins may be available in the near future as a result of the rapid development of novel, high-throughput experimental techniques. Such time series implicitly contain valuable information about the connectivity and regulatory structure of the underlying metabolic or proteomic networks. The extraction of this information is a challenging task because it usually requires nonlinear estimation methods that involve iterative search algorithms. Priming these algorithms with high-quality initial guesses can greatly accelerate the search process. In this article, we propose to obtain such guesses by preprocessing the temporal profile data and fitting them preliminarily by multivariate linear regression. RESULTS: The results of a small-scale analysis indicate that the regression coefficients reflect the connectivity of the network quite well. Using the mathematical modeling framework of Biochemical Systems Theory (BST), we also show that the regression coefficients may be translated into constraints on the parameter values of the nonlinear BST model, thereby reducing the parameter search space considerably. CONCLUSION: The proposed method provides a good approach for obtaining a preliminary network structure from dense time series. This will be more valuable as the systems become larger, because preprocessing and effective priming can significantly limit the search space of parameters defining the network connectivity, thereby facilitating the nonlinear estimation task.

Models, Biological↗
PubMedDate not supplied

An approach to measuring change in muscular tissue contraction.

In this paper the authors consider a histological muscular component from the point of view of systems theory. Of the smooth and striated types of muscular fibres, the latter have a structural component that permits them to contract. Unlike the visceral striated and cardiac fibres, movements in the skeletal striated fibres are predominantly voluntary. An overlapping of certain fibre components--specifically a sliding movement of the filaments of which the fibre is composed--causes a variation in the overall size of the fibre and therefore of the muscle. The distances covered, whether in contraction or lengthening, vary according to the type of fibre from 1.8 to 3.8 microm, but depend only on the capacity of some filaments to slide over other filaments, with filament size itself remaining unchanged. Our objective is to obtain a metric of this system that will permit us to obtain some idea of the degree of variation in these distances. In future projects it will be possible to extend this theory to other involuntary muscular tissue movements (myocardial tissue, e.g.), in an endeavour to develop a mathematical approach to the study of myocardial processes damaged by electrical conduction problems.

Algorithms↗
PubMed2004

Experimental observation of nonlinear traveling waves in turbulent pipe flow.

Transition to turbulence in pipe flow is one of the most fundamental and longest-standing problems in fluid dynamics. Stability theory suggests that the flow remains laminar for all flow rates, but in practice pipe flow becomes turbulent even at moderate speeds. This transition drastically affects the transport efficiency of mass, momentum, and heat. On the basis of the recent discovery of unstable traveling waves in computational studies of the Navier-Stokes equations and ideas from dynamical systems theory, a model for the transition process has been suggested. We report experimental observation of these traveling waves in pipe flow, confirming the proposed transition scenario and suggesting that the dynamics associated with these unstable states may indeed capture the nature of fluid turbulence.

Journal Article↗
PubMed2005

Challenges for the identification of biological systems from in vivo time series data.

Modern methods of high-throughput molecular biology render it possible to generate time series of metabolite concentrations and the expression of genes and proteins in vivo. These time profiles contain valuable information about the structure and dynamics of the underlying biological system. This information is implicit and its extraction is a challenging but ultimately very rewarding task for the mathematical modeler. Using a well-suited modeling framework, such as Biochemical Systems Theory (BST), it is possible to formulate the extraction of information as an inverse problem that in principle may be solved with a genetic algorithm or nonlinear regression. However, two types of issues associated with this inverse problem make the extraction task difficult. One type pertains to the algorithmic difficulties encountered in nonlinear regressions with moderate and large systems. The other type is of an entirely different nature. It is a consequence of assumptions that are often taken for granted in the design and analysis of mathematical models of biological systems and that need to be revisited in the context of inverse analyses. The article describes the extraction process and some of its challenges and proposes partial solutions.

Linear Models↗
PubMed1986

[Psychotherapy of patients with hearing impairment].

The need for psychotherapy with hearing impaired persons, and its necessity, are undisputed among professional workers. Yet, hardly any theory-based, field-tested experience exists so far concerning the procedures to be employed. The present contribution delineates both potential and limitations of psychotherapy with this population. Four schools of psychotherapeutic thinking are investigated as to their specific potential for contributing to psychotherapeutic work with hearing impaired clients. The aspect of "communication channel" is picked out from systems theory; from psychoanalysis, the concepts of therapeutic contract and transference appear significant; Humanistic Psychology, with its contributions concerning extraverbal expression and verbalization of feelings, has opened major routes of access to the hearing impaired individual; the broadest range of concepts and intervention strategies is presented by behavioural therapy. Behavioural approaches--cognitive conditioning, self-control techniques, thought-stopping, cognitive re-structuring--may be of greatest use in working with deaf clients. Given the cognitive and communicative characteristics of the target population, therapeutic work needs to be performed in an eclectic and synoptical manner. Its prime objective lies in uncovering the "deaf identity", in developing and protecting it.

Behavior Therapy↗
PubMedDate not supplied

Is dental hygiene a profession? A literature review.

From a literature review of theories of professionalism, the historical development of the attributes of a profession are discussed. This paper then discusses various theories of professionalism and specifically examines the extent to which the criteria developed by Greenwood are fulfilled by dental hygiene. Greenwood's model, which discusses certain attributes that a profession should possess, is selected to provide a broader model to analyze the current professional status of dental hygiene. Greenwood's model states that a profession has acquired: 1) systemic theory, 2) authority, 3) community sanction, 4) ethical codes, and 5) a culture. The author will conclude by suggesting possible steps the dental hygiene profession could continue to take to acquire these attributes and thereby recognition as a profession by other professions, governments and the public.

Canada↗
PubMed2001

Beyond enmeshment: evidence for the independence of intrusiveness and closeness-caregiving in married couples.

In a 1996 article on family theory, we (Green & Werner) proposed that family enmeshment should not be equated with high cohesion and that the construct of enmeshment fails to discriminate between two distinct relationship processes: Closeness-caregiving and intrusiveness. In this study, our model of these two independent dimensions of family connectedness was tested by assessing spouses from 264 couples, using the California Inventory for Family Assessment (CIFA). The CIFA scales showed acceptable reliability. Significant interspouse validity correlations also were obtained. As predicted by our theory, factor analyses distinguished dimensions of intrusiveness (blurring of boundaries) from dimensions of closeness-caregiving (such as warmth and nurturance). On all but two factors, behaviors of only one spouse (but not of both) had interpretable loadings. That is, in most areas, the two spouses' behaviors did not load together to form meaningful factors. The latter finding suggests that family systems theory--with its central notion of reciprocally contingent behaviors between family members--may be useful in understanding only a few dimensions of spouses' behavior (such as reciprocal aggression) whereas personality-in-context theories may be better for understanding most other dimensions (such as warmth and nurturance).

Adult↗
PubMed2004

Work conditions and employees' self-set goals: goal processes enhance prediction of psychological distress and well-being.

Although previous theory and research suggest that employee well-being should be predicted by work conditions (viz., Karasek and colleagues' job demands-control-social support [J-DCS] model), other factors are also likely to be important. In this study, the authors consider correlates of employee psychological distress and well-being using a goal-focused approach grounded in Ford's (1992) motivational systems theory. Specifically, work conditions and midlevel work goal processes (WGP) were examined in a questionnaire study of health care employees. Regarding predictions derived from the J-DCS model, the authors found full support for the iso-strain, partial support for the nonlinearity, and no support for the buffer hypothesis. Of importance, however, WGP (i.e., cognitions and emotions involved in the pursuit of self-set work goals) explained variance in job satisfaction, burnout, depression, and somatic complaints, over and above that of the J-DCS model. This suggests that investigation of WGP can enhance our understanding of employee psychological distress and well-being.

Adult↗
PubMed1990

The timer.

This article reviews the evidence that living systems at all levels, including cells, organs, organisms, groups, organizations, communities, societies, and supranational systems, have an information-processing system, the timer. The timer consists of one or more oscillators known as clocks or pacemakers, the phase of which can be reset. They measure duration or order in time or underlie rhythms of various sorts. The timer subsystem synchronizes internal processes of the system and coordinates the system with its environment. By 1965, 19 matter-energy and information processing subsystems were identified in living systems theory. Based on scientific evidence accumulated particularly in recent years, the timer is now recognized as an information processing subsystem, the 20th subsystem, which carries out an essential life process.

Animals↗
PubMed1995

Use of the multitrait multimethod (MTMM) to analyze family relational data.

In this article, the authors propose the logic of the multitrait multimethod (MTMM) approach for analysis of data as an alternative solution for examining family relational data. Application of the MTMM logic permits the assessment of common perspectives shared by all family members and of the unique perspectives of individuals. The advantages of using this approach in family research include the ability to (a) maintain consistency between systems theory views of family-as-a-unit, and (b) delineate patterns of agreement, disagreement, or both among family members.

Adult↗
PubMed1997

[Do clinical nurse practitioners affect the working environment and the quality of care?].

This correlational study examined the influence of a new kind of advanced nurse practitioner in Switzerland with the role of providing complex care, consulting with patients and families, fostering the growth of staff, enhancing team functioning and contributing to nursing knowledge through research. Based on systems theory the perception of staff about their work environment and their motivation to engage in continuing education as well as the patients' satisfaction with care and trust in the nurses were measured outcomes. Instruments were constructed for this study, tested and standardized. Data from three hospital units with an advanced practitioner were compared to three units without a practitioner similar in size, staffing, patient acuity and system of nursing care. Staff reported better guidelines for care, more frequent feedback and better professional advice on units with an advanced practitioner while the quality of communication, professional stimulation and support with difficult patients was comparable on all units. Motivation to further one's education was generally high. In units with an advanced practitioner, there was increased interest in psychosocial topics, and the availability of such literature was better. Patients were highly satisfied in all units, but there was a slight difference in patient trust. It was somewhat easier for patients on units with an advanced practitioner to ask the nurses questions. The study suggested that the advanced practitioner should contribute most by strengthening team cohesion through constructive feedback as well as enhancing a climate for continuing learning through better resources, guided case discussions and opportunities for shared problem solving.

Attitude of Health Personnel↗
PubMed1997

The relationships among parent-adolescent differentiation, sex role orientation and identity development in late adolescence and early adulthood.

This study had three main objectives. The first was an attempt to clarify inconsistencies in research on family characteristics and identity formation. The second was to test a model that has been discussed over the past several years based on Bowen's intergenerational family systems theory. Finally, gender differences were explored within the models hypothesized. The models included family differentiation variables, sex role orientation and adolescent identity development. The path models that included mother/adolescent and father/adolescent differentiation, masculinity and femininity scales, and ideological and interpersonal identity achievement in separate analyses were tested using LISREL VII. The results suggested that interpersonal and ideological identity domains were differentially related to differentiation in the family system and sex role orientation. There were also gender differences. These results are discussed in relation to previous research evidence about family characteristics that best support identity achievement for males and females.

Achievement↗
PubMed2005

Wildfires, complexity, and highly optimized tolerance.

Recent, large fires in the western United States have rekindled debates about fire management and the role of natural fire regimes in the resilience of terrestrial ecosystems. This real-world experience parallels debates involving abstract models of forest fires, a central metaphor in complex systems theory. Both real and modeled fire-prone landscapes exhibit roughly power law statistics in fire size versus frequency. Here, we examine historical fire catalogs and a detailed fire simulation model; both are in agreement with a highly optimized tolerance model. Highly optimized tolerance suggests robustness tradeoffs underlie resilience in different fire-prone ecosystems. Understanding these mechanisms may provide new insights into the structure of ecological systems and be key in evaluating fire management strategies and sensitivities to climate change.

Computer Simulation↗
PubMed1984

Clinical applications of the Process Model of Family Functioning.

This paper discusses clinical applications of the Process Model of Family Functioning. It provides a framework for conducting and systematically recording a family assessment, and can help clinicians achieve and use improved control of clinical sessions to increase their diagnostic and therapeutic effectiveness. Ways of using FAM-III, a self-report test derived from the model, to confirm or amplify a clinical assessment and to assist or monitor therapeutic interventions are discussed. Viewing psychological and family systems theories as complementary, the model provides a rationale for integrating both sets of theories to achieve a more pluralistic view of pathogenesis and a more selective choice of therapies. An extended example illustrates the concurrent use of individual and family therapies. Other topics discussed include the role of family strengths, the derivation of therapeutic goals, moving from content to perceive underlying structure and process, making the conceptual shift from group-of-two to conceptualizing the family as a group (system) in equilibrium.

Adolescent↗
PubMed1985

Feminism and family therapy.

Feminism has had a profound effect on contemporary culture and on thinking in most academic fields, including psychoanalysis. Interestingly, until very recently it had made virtually no impact on the theory and practice of family therapy. This paper proposes an explanation for this peculiar phenomenon and argues that family therapy has been considerably handicapped by its insularity from the feminist critique. Utilizing feminist scholarship in psychoanalysis, history, and sociology, the paper analyzes the structural contradictions in family life that family therapists have essentially ignored and then outlines their clinical implications. Key points in the discussion include the argument that systems theory is an inadequate explanatory matrix from which to build a theory of the family, that the archetypal "family case" of the overinvolved mother and peripheral father is best understood, not as a clinical problem, but as the product of a historical process two hundred years in the making, and that power relations between men and women in families function in terms of paradoxical, incongruous hierarchies that reflect the complex interpenetration between the structure of family relations and the world of work. This conceptual model then provides the basis for an analysis and critique of sexual politics as they emerge in the prototypical clinical situation.

Adult↗
PubMed2004

Postural control in children: implications for pediatric practice.

Based on a systems theory of motor control, reactive postural control (RPA) and anticipatory postural control (APA) in children are reviewed from several perspectives in order to develop an evidence-based intervention strategy for improving postural control in children with limitations in motor function. Research on development of postural control, postural control in children with specific motor disabilities, and interventions to improve postural control is analyzed. A strategy for intervention to improve postural control systems at the impairment and functional activity levels based on a systems theoretical perspective is presented. Suggestions for research to improve evidence for best practice are provided.

Child↗