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 253 records · Page 14Linked to original sources
PubMed2002

Three-systems theory of human visual motion perception: review and update: comment.

This comment addresses two issues raised by Lu and Sperling [J. Opt. Soc. Am. A 18, 2331 (2001)]. These authors stated that stereomotion (movement of binocular disparity) is processed exclusively by a third-order motion system that involves feature tracking. This comment discusses evidence that clearly shows that stereomotion is processed by a low-level mechanism that does not track features. Lu and Sperling also claimed that motion signals from binocular rivalry have confounded many stereomotion experiments in the past. This comment discusses how stimuli employed in most previous studies of stereomotion processing would not produce rivalry.

Depth Perception↗
PubMed1987

Reversing the antilock braking system theory for suture removal.

A simple and extremely practical technique for removal of long subcuticular sutures is possible by simply interposing a rubber band between the suture and the traction source. We have likened the technique in a reverse manner to the pulsing application of brakes in the antilock braking system now commonly found in modern automobiles. We also suggest with this paper that Prolene at this time be tried as the suture of choice in pullout repairs of all types.

Proline↗
PubMed2005

Ericson fluctuations in an open deterministic quantum system: theory meets experiment.

We provide numerically exact photoexcitation cross sections of rubidium Rydberg states in crossed, static electric, and magnetic fields, in quantitative agreement with recent experimental results. Their spectral backbone underpins a clear transition towards the Ericson regime, associated with a universal, fluctuating behavior of the cross section of strongly coupled, fragmenting quantum systems.

Journal Article↗
PubMed1995

A cognitive-affective system theory of personality: reconceptualizing situations, dispositions, dynamics, and invariance in personality structure.

A theory was proposed to reconcile paradoxical findings on the invariance of personality and the variability of behavior across situations. For this purpose, individuals were assumed to differ in (a) the accessibility of cognitive-affective mediating units (such as encodings, expectancies and beliefs, affects, and goals) and (b) the organization of relationships through which these units interact with each other and with psychological features of situations. The theory accounts for individual differences in predictable patterns of variability across situations (e.g., if A then she X, but if B then she Y), as well as for overall average levels of behavior, as essential expressions or behavioral signatures of the same underlying personality system. Situations, personality dispositions, dynamics, and structure were reconceptualized from this perspective.

Affect↗
PubMed1992

Understanding corporate cultures: use of systems theory and situational analysis.

1. A company's culture is its heroes, values, myths, and symbols. In strong cultures, the lives and productivity of employees are shaped by where they work. 2. Understanding corporate cultures, generally, and the one in which one works, specifically, can help the occupational health nurse develop and implement intervention strategies specific to that company's culture. 3. A strong culture has a system of rules dictating employee behavior. In a less strong culture, the rules and definitions are less rigid, facilitating more flexibility and less predictability.

Humans↗
PubMed2006

The effects of sexual abuse as a child on the risk of mothers physically abusing their children: a path analysis using systems theory.

OBJECTIVE: The potential path from sexual abuse as a child to the current risk of physical abuse by mothers was assessed. Ontogenic variables including the experience of the parent's sexual abuse as a child and current depression or substance abuse were expected to have a greater impact on the risk of child abuse than microsystem and exosystem variables such as family functioning, domestic violence, income, community safety, and social support. METHOD: A path analysis using secondary data was conducted to examine these systemic impacts. The sample consisted of 265 women, the majority of whom were African-American with a high school education or GED. The majority of these women were employed, lower socio-economic status, and over 50% of the sample had never been married. RESULTS: Sexual abuse as a child was found to impact maternal depression. Maternal depression and locus of control impacted risk of physical abuse. These two variables accounted for 22% of the variance in the dependent variable. CONCLUSION: These findings indicate that it may not be the experience of sexual abuse itself that has an impact on a mother's risk of physical abuse, but rather whether she is able to resolve that trauma. Her locus of control appears to be important in this resolution. The majority of these women were low-income, urban African-American women; it may be important to focus on locus of control for this population.

Child↗
PubMed1996

Hepatobiliary kinetics of technetium-99m-IDA analogs: quantification by linear systems theory.

UNLABELLED: A compartmental model describing the extraction and disposition of 99mTc-acetanilidoiminodiacetic acid (IDA) compounds by the liver has been applied to 5 adult patients admitted for cholecystitis investigations and 29 jaundiced infants the majority of whom were clinically differentiable into neonatal hepatitic and biliary atretic groups. METHODS: In each case kinetic rate constants were calculated to describe hepatocyte extraction of 99mTc-IDA structural analogs from blood pool (k21) and subsequent elimination (k3) of this compound into biliary tract. Also modeled was the reverse-binding constant (k12) describing the return of such radiotracer to the systemic circulation and the blood fraction (f) which accounted for the composite vasculature forming a matrix in the liver. RESULTS: It was shown that these indices could be used to determine accurate compartmental mean residence times (MRT(c)s) for each patient by correlation with values obtained by deconvolutional analysis and independent measurement of leading edge parenchymal transit times. For the adult patients the following indices, typical of good hepatocyte function, were derived: k21 = 0.933 +/- 0.488 min-1, k12 = 0.0277 +/- 0.0340 min-1, k3 = 0.1610 +/- 0.0531 min-1, f = 0.3519 +/- 0.3048 and MRTc = 11.19 +/- 3.13 min. Analysis of the pediatric group revealed no significant differences in their respective MRT(c)s. However, significant differences in the extraction (p < 0.01) and excretion (p < 0.001) coefficients were prominent. CONCLUSION: This method can be applied to provide accurate and meaningful intercompartmental rate parameters and MRT(c)s for adults, nonobstructed and obstructed infants.

Aged↗
PubMed2005

Peculiarities of magnetic and spin effects in a biradical/stable radical complex (three-spin system). Theory and comparison with experiment.

The field dependencies of biradical recombination probability in the presence of paramagnetic species with spins S(3) = 1 and S(3) = (1)/(2) have been calculated in the framework of the density matrix formalism. To describe the effect of the "third" spin on the spin evolution in biradical, we have also considered the spin exchange interaction between the added spin and one of the paramagnetic biradical centers. A characteristic feature of the calculated field dependencies is the existence of several extrema with positions and magnitudes depending on the signs and values of the exchange integrals in the system. The method proposed can be used to describe the effect of spin catalysis. It is shown that for the system with the third spin S(3) = 1 spin catalysis manifests itself stronger than in the case of spin S(3) = (1)/(2). The dependence of spin catalysis efficiency on the exchange interaction with the third spin has an extremum with position independent of the value of the spin added.

Journal Article↗
PubMed1982

[Systems theory analysis of the chemical regulation of respiration with regard to its multidimensional character].

The chemical control of respiration provides for the maintenance of energy and substance equilibrium primarily and for the homoeostatic stability of the chemical blood parameters secondarily. Based on results having been obtained from an appropriate state space model some findings on respiration can be reproduced. In addition to the true qualitative reflecting the steady state at work performance, the contribute of separate chemical drives to the whole ventilation are represented correctly, suggesting the unneccisity of any additional specific work drives. Nervous influences of ventilation besides of its chemical control are not suitable to guarantee its controllability, they represent only disturbances mobilizing it. Coupled organ systems take part on transmitting primary afferent information about the chemical condition of the total metabolism, which proved to be necessary and sufficient for the chemical control activity.

Homeostasis↗
PubMed1997

The temporolimbic system theory of paranoid schizophrenia.

The hippocampus serves as a funnel for heavily processed sensory information that has converged at the entorhinal cortex. Lesions of the hippocampus do not alter incoming sensory or motor information but, rather, alter their integration with our baggage of emotional experiences and social values. According to Bogerts, such a lesion would be ideally situated to result in laboriously processed sensory information that is out of context to our outside environment. In this regard, Bogerts describes the pathological findings of a patient with a gross delusional disorder. The salient finding at autopsy was a developmental lesion in the left posterior parahippocampal gyrus. Although a number of lesions have been described in the brains of patients with schizophrenia, Bogerts believes that those in the limbic system appear critical to the expression of paranoid symptoms.

Adult↗
PubMed1996

Detection of seizures from small samples using nonlinear dynamic system theory.

The electroencephalogram (EEG), like many other biological phenomena, is quite likely governed by nonlinear dynamics. Certain characteristics of the underlying dynamics have recently been quantified by computing the correlation dimensions (D2) of EEG time series data. In this paper, D2 of the unbiased autocovariance function of the scalp EEG data was used to detect electrographic seizure activity. Digital EEG data were acquired at a sampling rate of 200 Hz per channel and organized in continuous frames (duration 2.56 s, 512 data points). To increase the reliability of D2 computations with short duration data, raw EEG data were initially simplified using unbiased autocovariance analysis to highlight the periodic activity that is present during seizures. The D2 computation was then performed from the unbiased autocovariance function of each channel using the Grassberger-Procaccia method with Theiler's box-assisted correlation algorithm. Even with short duration data, this preprocessing proved to be computationally robust and displayed no significant sensitivity to implementation details such as the choices of embedding dimension and box size. The system successfully identified various types of seizures in clinical studies.

Algorithms↗