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Results for “predictability of adaptation”

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At least 19 recordsLinked to original sources
PubMed1992

Multiple-model adaptive predictive control of mean arterial pressure and cardiac output.

A multiple-model adaptive predictive controller has been designed to simultaneously regulate mean arterial pressure and cardiac output in congestive heart failure subjects by adjusting the infusion rates of nitroprusside and dopamine. The algorithm is based on the multiple-model adaptive controller and utilizes model predictive controllers to provide reliable control in each model subspace. A total of 36 linear small-signal models were needed to span the entire space of anticipated responses. To reduce computation time, only the six models with the highest probabilities were used in the control calculations. The controller was evaluated on laboratory animals that were either surgically or pharmacologically altered to exhibit symptoms of congestive heart failure. During trials, the controller performance was robust with respect to excessive switching between models and nonconvergence to a single dominant model. A comparison is also made with a previous multiple-drug controller design.

Animals↗
PubMed1992

Predicting adaptive behaviour of severely and profoundly mentally retarded children with early cognitive measures.

A longitudinal study was conducted to determine the ability of the Uzgiris and Hunt scales to predict adaptive behaviour including, but not limited to, language. The Uzgiris and Hunt scales, six of the ABS domains and the Receptive-Expressive Emergent Language (REEL) scale were administered to 61 children who were severely or profoundly mentally retarded. The ABS domains and the REEL were readministered 4 years later. The findings generally supported earlier cross-sectional research and theory. However, this methodology permitted the finding that the earlier score on the ABS domain or REEL was by far the best single predictor of the later score on that same measure, an intuitively obvious, but nevertheless, important finding. The findings were interpreted regarding their implications for theory, practice and methodology.

Child↗
PubMed1978

An assessment of a property analyzer model in predicting adaptation patterns of simple and complex figures.

Selective adaptation patterns of simple contours and geometrical illusions under monocular stimulation were studied with five subjects. A strict property analyzer model predicted that adaptation patterns would mirror figural contours of both types of forms. The results supported this hypothesis: the geometrical illusions generated adaptation patterns reflecting their physical stimulus properties rather than the illusory percept resulting from contextual juxtaposition. The results are discussed with respect to a model of feature extraction which assumes that property analyzers possess a sensitivity bandwidth.

Form Perception↗
PubMed1987

Predictable adaptations by skeletal muscle mitochondria to different exercise training workloads.

1. Mitochondria were isolated according to their cellular location within the fibers of pooled gastrocnemius and plantaris muscle of the rat. This procedure yields two populations of mitochondria which display different biochemical properties. 2. The adaptive response of these mitochondria populations to the chronic exposure to different elevated energy demands (different modes of exercise training) was investigated. 3. The observed changes in mitochondrial protein content and cytochrome oxidase activity in the respective mitochondria population suggests that each population is capable of independent adaptations. 4. The adaptive response of each mitochondria population, furthermore, was predictable with respect to the metabolic energy demand of the exercise training workload.

Acclimatization↗
PubMedDate not supplied

Adaptive predictive coding with applications to radiographs.

Picture archiving and communications systems (PACS) require storage and transmission of vast amounts of data. For design/cost considerations, it is desirable to reduce the size of these data without sacrificing the integrity of the stored information. The major considerations in designing a data-compression scheme for a PACS system are discussed: fidelity of the reconstructed image, bit rate, hardware complexity, and processing time. The basic principles of conventional nonadaptive differential pulse-code modulation (DPCM) are reviewed and compared with adaptive techniques. The effect of adaptive quantization on radiographic images is examined. Special consideration is given to block-adaptive DPCM or the "switched quantizer," which greatly enhances the system performance as compared with nonadaptive techniques, and conservatively has a 5:1 compression ratio. Sample radiographs substantiate the results.

Bone and Bones↗
PubMed1987

Appraisals of control and predictability in adapting to a chronic disease.

In a sample of 92 patients with rheumatoid arthritis, we examined interrelations among various control appraisals, illness predictability, psychosocial adjustment, mood, and illness status. Perceiving greater personal control over the disease and symptoms and perceiving greater health-care-provider control over symptoms were associated with greater illness predictability. Patients reported more personal control over their symptoms than over the course of the disease and thought that their health care providers had more control over disease course than they did themselves. Multiple regression analyses showed that perceiving greater personal control over one's medical care and treatment was associated with positive mood and psychosocial adjustment. Negative mood was also associated with the belief that providers have greater control over the patient's daily symptoms. Patients who had a more severe disease and expressed greater personal control over its course reported greater mood disturbance and were rated as exhibiting less positive adjustment, but those who had more severe daily symptoms and expressed greater personal control over their symptoms reported less mood disturbance. These findings are discussed in terms of the possible benefits of patients' active participation in their care and the implications of perceiving personal and others' control over more or less controllable aspects of the illness, especially when the illness is more severe.

Activities of Daily Living↗
PubMed1991

Prediction of responses in milk constituents to changes in the nutrition of dairy cows.

Milk quotas, based on an average fat content, severely limit milk production on UK farms. Predictions of the time-course of lactation are incorporated into most computerized herd management programs but these models take no account of food inputs, body weight change or milk composition. Dynamic models are generally used to simulate metabolic pathways and, as such, have little direct relevance to commercial milk production. Dynamic models can be converted to an adaptive-predictive model that partitions food energy into milk and non-milk constituents. This paper reports the development of an adaptive-predictive model to partition food into milk and non-milk components. Additional functions further partition milk energy into the principal constituents, fat, protein and lactose.

Animal Feed↗
PubMed1991

Automatic tracking and digitization of multiple radiopaque myocardial markers.

An 80386 PC-based system was designed to track automatically multiple, miniature radiopaque markers implanted in the heart wall. This system eliminated the need for tedious, time-consuming manual digitization of marker coordinates. Use of a MATROX MVP-AT/NP image processing board incorporated advanced image processing and graphics features into the low-cost PC environment. Digital image enhancement and segmentation techniques (such as limiting analysis to predefined windows of interest, spatial band-pass and matched filtering, contrast stretching and clipping, linear adaptive prediction, intensity histogram analysis, adaptive binary thresholding, region growing, expanding region of analysis, and feature extraction) were incorporated into a user-friendly integrated marker processing software environment. Improved speed, accuracy, and reproducibility of the marker digitizing process were realized. These basic techniques have broad applications to other image processing needs in biomedical research.

Algorithms↗
PubMed1992

Coping and cognitive factors in adaptation to in vitro fertilization failure.

Characteristics were identified that predict adaptation following an unsuccessful attempt at in vitro fertilization (IVF). Forty-one women and their husbands were interviewed and administered questionnaires prior to IVF and 2 weeks after notice of a positive or negative pregnancy test. Of the 36 couples who failed to conceive as a result of IVF, 6 of the women studied developed clinical depressive symptoms. Those women who reported poorest adaptation to IVF failure were more likely to have reported depressive symptoms prior to IVF, were more likely to have reported feeling a general loss of control over their lives as a result of infertility, tended to use escape as a coping strategy, and reported having felt some responsibility for their IVF failure. Dispositional optimism, as well as a sense of being partially responsible for the infertility, was protective of distress following IVF failure.

Adaptation, Psychological↗
PubMedDate not supplied

Coping behavior and intelligence in the prediction of vocational rehabilitation of dialysis patients.

As part of an intensive psychiatric and psychological examination before starting hemodialysis, forty-seven patients with terminal renal failure, thirty-one men and sixteen women with an age range from the late teens to the mid fifties, had been administered with WBII and the Shanan Sentence Completion technique. The hypothesis was that coping style would predict adaptation to hemodialysis as assessed by vocational rehabilitation. Intelligence, level of education, and the tendency to perceive sources of conflict in the outer world rather than within oneself, were found predictive of subseuqent adaptations for the whole group. On all these variables, men and women showed different patterns of significant correlations between the different aspects of coping and vocational rehabilitation. Subsequent multiple step-wise regression showed women (percentage of explained variance: 75) to be more predictable than men (40%) with different variables contributing differentially to predictability. These findings, interpreted to support the general working hypothesis, are discussed in terms of their implications for treatment.

Adaptation, Psychological↗
PubMed1990

Lower-field myopia in birds: an adaptation that keeps the ground in focus.

In the lower visual field of pigeons, a myopia (near-sightedness) has been reported that progressively increases with the angle below the horizon. Previous data suggested that this lower-field myopia may be an adaptation that permits pigeons to keep the ground in focus while they forage, and simultaneously, to monitor the horizon and sky for predators. We report here a lower-field myopia in other species of birds that have a wide range of heights. A geometric model of this adaptation predicts that the amount of myopia should be systematically related to the distance from the pupil to the ground. The eyes of quail, chickens and cranes of various heights (7.0-104.1 cm) were refracted at 60 deg below the horizon. Their myopia was close to the predicted value at each height.

Adaptation, Physiological↗
PubMed1985

Auditory adaptation: notes on power and parabolic curve fitting across intensity: II.

The classic Simultaneous Dichotic Loudness Balance (SDLB) procedure for the study of auditory adaptation was used by Weiler and Hood (1977) in a successful test of a model for predicting adaptation in db at intensities above the initial baseline values, using a linear approximation across levels. When Balzer et al (Brit. J. Audiol., 1984, 18, 49-50) fitted curves for simple baseline adaptation data from four studies based on SDLB data, they reported good fits for the Gompertz technique and for a parabolic formula, but did not test the relative goodness of fit for the linear formula, nor for power approximations as Stevens (1975) might have proposed. The present study makes use of the data used by Balzer et al but examines a linear fit as well as two approximations to Stevens' power law. The present finding that the linear approximation is the least efficient examined would suggest that the Weiler and Hood model should be re-examined to determine the degree to which the model can be improved by use of a curvilinear baseline fit. In addition, it might be noted that the curvilinear formulae, of necessity, involve two or more stages. It is the the current effort of this laboratory to determine whether this reflects a multifactor basis to the classic SDLB adaptation, as well as results from other adaptation techniques.

Adaptation, Physiological↗
PubMed1985

The theory of homeoviscous adaptation of membranes applied to deep-sea animals.

Deep-sea organisms live at high pressure and low temperature. These two factors increase the order of the bilayer in cell membranes, and, on the basis of the homeoviscous theory of membrane adaptation, predictions are made of the fluidity and composition of deep-sea membranes. Some of the predictions have been tested using membranes from deep-sea fish and some of the results are consistent with the theory. The conclusion is that the theory receives general support from the deep sea and, conversely, adaptation of membranes to high pressure can be profitably investigated in a more detailed manner by testing further predictions based on the homeoviscous concept.

Adaptation, Physiological↗
PubMed1992

Prediction of bone adaptation in the ulnar-osteotomized sheep's forelimb using an anatomical finite element model.

A method for the prediction of the time-course of bone adaptation based on an alternative hypothesis of strength optimization has been previously investigated and developed by Prendergast and Taylor. This paper extends our work in the study of the effectiveness of this bone adaptation model in predicting similar bone remodelling to that observed in animal experiments. In particular the experimental work which has been modelled is that of Lanyon, Goodship, Pye and McFie. An anatomical finite element model of the sheep's forelimb has been generated for this purpose and is used to estimate stresses in the bone structure for the normal and osteotomized condition. The propensity for remodelling of the altered bone structure is predicted using the proposed remodelling law for the new stress field in the bone structure. The preliminary results indicate an initial bone adaptation pattern similar to that observed experimentally without the necessity to use arbitrarily different constants for the endosteal and periosteal surfaces. We therefore suggest that the remodelling law based on damage and repair gives a better predictive model of bone adaptation than previous models.

Adaptation, Physiological↗
PubMed1986

A molecular mechanism for sensory adaptation based on ligand-induced receptor modification.

Physiological responses mediated by cell-surface receptors frequently adapt or "desensitize" (i.e., terminate despite persistent occupancy of receptors by ligand). Binding of ligands to the external domains of a wide variety of surface receptors induces covalent modification of their cytoplasmic domains. A mechanism is presented in which the variety of receptor states generated by ligand binding and covalent modification act together to regulate physiological responsiveness. The development of the model is guided by observations of adaptation for chemotaxis in Escherichia coli and adenylate cyclase activation in Dictyostelium. The general features of the marked response and eventual exact adaptation predicted by the model match those observed in the experimental systems.

Adaptation, Physiological↗
PubMed1990

The minor events approach to stress: support for the use of daily hassles.

Everyday minor stressors (hassles) have been proposed as an alternative to major life-events as a measure of stress. This article examines three aspects of hassles as a stress measure: group contextual differences in hassles reported, the stability and consistency of hassles over time, and the effectiveness of hassles in predicting adaptational outcomes. Results showed that there are clear contextual differences in hassles. Groups report quite different patterns of hassles reflecting their particular social contexts. These patterns also appear to be stable across time, probably as a result of consistency in both group roles and situational factors. Finally, hassles are found to be substantially better than life-events in predicting psychological well-being and mental health dimensions. Taken together, these findings support the use of hassles as a valid and reliable measure of stress which has significant relationships to important adaptational outcomes.

Adaptation, Psychological↗