PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “model predictive control”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 595 records · Page 33Linked to original sources
PubMed2002

The wall-thinning to transmitral flow-velocity relation: derivation with in vivo validation.

Motion of the endocardial surface in diastole is the resultant effect of wall thinning. Endocardial wall motion to transmitral flow (Doppler E-wave) relations that predict wall thinning are derived using conservation of myocardial volume, two simplified (spatiotemporally homogeneous) left ventricular (LV) geometric models and the constant-volume pump attribute of the heart. For validation, model-predicted vs. color M-mode recorded maximum rate of wall thinning was compared in (n = 15) normal controls. Excellent agreement for both models (r = 0.84, r = 0.86) was observed. For abnormal LV function (n = 15), model-predicted vs. M-mode recorded maximum rate of wall-thinning correlated poorly (r = -0.28, r = -0.22). We conclude that, in normal ventricles, the Doppler E-wave and wall thinning are related through the constant-volume attribute of the heart and its geometry. Pathologic cases are governed by the same principles, but the filling to wall-thinning relation is altered by spatiotemporal inhomogeneities in geometry and wall motion.

Adult↗
PubMedDate not supplied

Vector-borne infections in the tropics and health policy issues in the twenty-first century.

Over the past 2 decades scientific advances and evolving strategies have significantly contributed to improved tools for control of vector-borne infections. These are: diagnostics--rapid assessment methods, non-invasive or minimally so yet sensitive and specific; new chemotherapeutics; pyrethroid insecticides and biological insecticidal products; refined strategies, such as combination therapy, rotation of insecticides for resistance management, community-directed treatment, standardized monitoring and evaluation to define programme progress; better epidemiological knowledge through improved identification of parasites and vectors; GIS, remote sensing and climate models which provide tools for epidemic prediction, planning control programmes and permit effective policy analysis; greater involvement of NGDOs (non-governmental development organizations) and CSOs (civil society organizations) in control; advent of donation programmes which involve community-based or directed mass drug distribution. Future problems could be: (1) the over-emphasis on inflexible financing by the insistence of donors on SWAps (sector-wide investment), (2) the over-reliance on pyrethroid pesticides, (3) the over-expectation that basic research will provide new drugs and vaccines for resource-poor settings in the necessary time scales, and (4) the failure to recognize that biological processes have an inherent capacity for change which outstrips the capacity of health services to respond. Malaria is a paradigm of an 'emerging disease'. (5) The challenge of implementing a 'vertical' approach to disease control within national health programmes, in the face of significant donor opposition to such programmes is a challenge even when such approaches will secure a 'public good'.

Animals↗
PubMed1997

Family interaction and the course of schizophrenic illness. Results of a multivariate prospective study.

The aim of the present study was to assess the prognostic relevance of relatives' interactive behaviour towards the patient, as covered by the Münster Family Interview (MFI), to the further course of the schizophrenic illness. The MFI is a family interview (of the whole family, including the patient) designed to record the emotional family atmosphere based on the concept of expressed emotion (EE). The ratings take place directly after the interview on five scales (criticism, hostility, overinvolvement, resignation and warmth), the resignation scale being added to the 'classic' EE scales. Ninety-nine families of outpatients diagnosed with schizophrenia according to the DSM-III were examined with the MFI during a home visit. The patients were seen 1 and 2 years after the first examination. The target criteria selected for the prognostic significance of the interaction measurements were: rehospitalisation within 2 years; extent of symptoms after 1 year, and psychosocial skills after 1 year. The significance of the interaction dimensions was verified in regression models. The control variable used in the regression models was the Strauss-Carpenter scale. Regression models were produced for the total group and for a subgroup of moderately ill patients. All target criteria yielded serviceable prediction models. The most important variable for prediction was the control variable, the Strauss-Carpenter scale. However the interaction variables made additional contributions to the prognosis, especially in the subgroup of moderately ill patients. The best MFI scale for all the outcome criteria was resignation; criticism predicted only the symptomatology, and emotional overinvolvement the level of social functioning after 1 year. In conclusion, practical work with families of schizophrenic patients should emphasise the protective function of relatives towards patients more strongly.

Adolescent↗
PubMed1997

Model with distributed vectorial premotor bursters accounts for the component stretching of oblique saccades.

During oblique saccades, the durations of the horizontal and vertical components are stretched until they are approximately equal. Models of the saccadic system have been proposed that provide a mechanism for that stretching. However, they fail to simulate the pattern of activity recorded from premotor medium lead burst neurons (MLBNs) in the brain stem. A new model of the saccadic system is proposed that accounts for both the component stretching of oblique movements and the pattern of activity recorded in MLBNs. MLBNs that project to horizontal (or vertical) motoneurons actually have a wide span of on-directions (the direction associated with the largest discharge) around the cardinal direction. We infer from the wide span of their on-directions that, at the level of individual MLBNs, the vectorial signal present in spatially organized structures (e.g., the superior colliculus) is not decomposed into the separate horizontal and vertical components represented by the motoneurons. Nonetheless, all prior models of the saccadic system have decomposed the vectorial premotor command into horizontal and vertical commands at the level of the MLBNs. That decomposition was explicit, because individual MLBNs, with a sine- or cosine-shaped directional tuning curve, were used. We propose here that the decomposition into horizontal and vertical commands is carried out only at the level of the motoneurons. This decomposition is implicit, because no single MLBN encodes the horizontal or vertical command; the command only exists implicitly in the activity of the population of MLBNs. The new vectorial burster model correctly simulates the pattern of activity recorded in primate MLBNs, and the components of its oblique saccades are stretched. Two mechanisms contribute to this stretching: the distribution of MLBN tuning curves and the inhibition exerted by the contralateral population of MLBNs. In contrast, feedback control of the saccade contributes negligibly to the stretching. Even though the vectorial burster model predicts a component stretching, it is not constrained to produce perfectly straight oblique saccades because no trajectory control is implemented. The amount of curvature depends on the similarity of the horizontal and vertical systems (both neural and mechanical). In this model, stretching is interpreted simply as a side effect of the properties of the MLBNs' tuning curves. The distributed MLBNs of the vectorial burster model forces the general organization of the saccadic system to be reconsidered. We propose that a distributed architecture in which several different neural systems cooperate is needed.

Computer Simulation↗
PubMed1997

Body mass index and mortality in patients with severe alpha 1-antitrypsin deficiency.

It appears that patients with advanced stages of chronic obstructive pulmonary disease, and particularly emphysema, lose weight and have higher mortality even after controlling for lung function. In the present study, mortality of alpha 1-antitrypsin-deficiency patients PiZ as a function of body mass index (BMI) with control for FEV1, sex and smoking habits was studied. A total of 342 patients participated with a mean follow-up time of 7.6 yr. Ninety patients had BMI under 20 kg m-2, which was the cut-off defining underweight patients. The patients were divided into three groups according to their initial FEV1 % predicted: < 30%, 30-64% and > or = 65%. The underweight patients had significantly higher mortality in the two groups with the lowest FEV1 % predicted. A Cox regression model was applied to control for potential confounders. The risk ratio for the underweight patients was 1.6 (P = 0.03) after controlling for FEV1, age, sex and smoking habits. It is concluded that low body weight is an independent predictor of mortality, but the reason is still unclear.

Body Mass Index↗
PubMed2006

Nonlinear model predicts diverse respiratory patterns of birdsong.

A central aspect of the motor control of birdsong production is the capacity to generate diverse respiratory rhythms, which determine the coarse temporal pattern of song. The neural mechanisms that underlie this diversity of respiratory gestures and the resulting acoustic syllables are largely unknown. We show that the respiratory patterns of the highly complex and variable temporal organization of song in the canary (Serinus canaria) can be generated as solutions of a simple model describing the integration between song control and respiratory centers. This example suggests that subharmonic behavior can play an important role in providing a complex variety of responses with minimal neural substrate.

Animals↗
PubMed2006

The role of transmissible diseases in the Holling-Tanner predator-prey model.

Transmissible diseases are known to induce remarkable major behavioral changes in predator-prey systems. However, little attention has been paid to model such situations. The latter would allow to predict useful applications in both dynamics and control. Here the Holling-Tanner model is revisited to account for the influence of a transmissible disease, under the assumption that it spreads among the prey species only. We have found the equilibria and analyzed the behavior of the system around each one of them. A threshold result determining when the disease dies out has been identified. We also investigated the parametric space under which the system enters into Hopf and transcritical bifurcations, around the disease free equilibrium. The system is shown to experience neither saddle-node nor pitch-fork bifurcation. Global stability results are obtained by constructing suitable Lyapunov functions.

Animals↗
PubMed2002

The effect of services on the recurrence of child maltreatment.

OBJECTIVE: Building on a previous model of recurrence, this study examined the relationship of services on the hazard of child maltreatment recurrence during CPS intervention for families who were provided continuing intervention following a confirmed index report of physical abuse or neglect. METHOD: This nonconcurrent prospective study selected 434 subject families who met study eligibility requirements from 1181 families randomly selected from the 2902 families who had experienced a substantiated report of child abuse or neglect during the sampling year. Data were collected and coded from archival sources for 5 years following the index report. Each record was coded by two research analysts to increase inter-rater reliability. Data were analyzed with the Cox Proportional Regression Model. RESULTS: Case characteristics that predicted recurrence were: child vulnerability, family stress, partner abuse, and social support deficits. After examining the potential effect of nine service-related variables only attendance at services predicted recurrence while controlling for other variables in the model. Families who were noted to attend the services identified in their service plans were 33% less likely to experience a recurrence of child maltreatment while their case was active with CPS. CONCLUSIONS: Implications of this and other research suggests that actively engaging families in a helping alliance and helping them accept and receive services may reduce the likelihood of future maltreatment.

Child↗
PubMed1997

Neuroscience nurses' intentions to care for persons with HIV/AIDS.

The purpose of this study, which was based on Ajzen's theory of planned behavior, was to determine the extent to which personal attitudes, subjective norms and perceptions of behavioral control influence the intentions of nurses to care for persons with HIV/AIDS. Questionnaires measuring the concepts of attitudes, subjective norms, perceived behavioral control and intention to care for persons with HIV/AIDS were completed by 368 members of a neuroscience nursing organization. Hierarchial regression analysis was used to determine if nurses' intentions were predicted by their attitudes and subjective norms, and if perceived behavioral control would add to the prediction. Attitudes accounted for a significant percent of variance when entered at the first step, and perceived behavioral control accounted for a significant increase in variance when entered at the second step. In the final model, only perceived behavioral control contributed significantly to the prediction of intention.

AIDS Dementia Complex↗
PubMed2005

The effect of ursodeoxycholic acid therapy on the natural course of primary biliary cirrhosis.

BACKGROUND AND AIMS: We used a multistate modeling approach to assess the effect of ursodeoxycholic acid (UDCA) therapy on the natural course of primary biliary cirrhosis (PBC), which remains controversial. METHODS: Our population included 262 patients with PBC who had received 13-15 mg/kg UDCA daily for a mean of 8 years (range, 1-22 years). Data were analyzed using a multistate Markov model, with histologic stage progression, death, and orthotopic liver transplantation (OLT) as main end points. Survival without OLT was compared with that predicted by the updated Mayo model and with the expected survival in the control population. RESULTS: Forty-five patients developed cirrhosis, 20 underwent OLT, and 16 died by the censor date. Ten deaths were due to liver disease. The overall survival rates were 92% at 10 years and 82% at 20 years. Survival rates without OLT were 84% and 66% at 10 and 20 years, respectively, which were slightly lower than the survival rate of an age- and sex-matched control population (relative risk [RR], 1.4; P = .1) but better than the spontaneous survival rate as predicted by the updated Mayo model (RR, .5; P < .01). The survival rate of patients in stage 1 and 2 was similar to that in the control population (RR, .8; P = .5), whereas the probability of death or OLT remained significantly increased in treated patients in late histologic stages (RR, 2.2; P < .05). CONCLUSIONS: Treatment with UDCA alone normalizes the survival rate of patients with PBC when given at early stages. However, there is a continued need for new therapeutic options in patients with advanced disease.

Adult↗
PubMed2005

Principles: mechanisms and modeling of synergism in cellular responses.

Cells can be considered as integrators of simultaneous stimuli, in which cross-talk between transduction pathways can eventually produce responses that are significantly different from simply additive responses. Synergism represents an efficient means of increasing the amplitude of cellular responses induced by low levels of stimulation. Recently, several kinetic and physicochemical models have been developed to describe and predict synergistic responses. In this article, the mechanisms that control the magnitude and timing of cellular synergism are discussed. We suggest that the analysis of theoretical models could enable a general prediction of synergism despite the presence of signal-specific synergistic responses. In addition, application of the proposed concepts should aid understanding of the wide occurrence of synergism induced by interacting transduction pathways in multi-drug clinical treatment.

Animals↗
PubMed1980

Mathematical model of steroidogenesis in rat and rabbit testes.

The purpose of this study was to develop a mathematical model of testicular steroidogenesis which could not only predict steroid secretion but also could be implemented to test the validity of assumptions used in studies of testicular testosterone biosynthesis in rats and rabbits. Since the two predominant fates of testicular steroids are metabolism and secretion, we hypothesized that the data for construction of the model could be observed testicular steroid secretions and that these data could then be used to elucidate intratesticular steroid conversions. Equations based on steroid secretion by testes perfused in vitro were developed to estimate transition probabilities corresponding to steroid secretion or conversion. The model was tested by comparing the predicted steroid secretion rates with those observed for control testes perfused in vitro. In addition, the transition probabilities determined by the model were used to indicate the predominant series of reactions for converting pregnenolone to testosterone. The results presented herein confirm the capability of the model to predict steroid secretion rates and to predict preferred pathways for testosterone biosynthesis in maximally stimulated testes perfused in vitro. Moreover, the model construction required only algebra and steady-state measurements.

Animals↗
PubMed2004

Analysis of disease progress as a basis for evaluating disease management practices.

The relationship between epidemiology and disease management is long-standing but sometimes tenuous. It may seem self-evident that improved understanding of epidemic processes will lead to more effective control practices but this remains a testable proposition rather than demonstrated reality. A wide range of models differing in mathematical sophistication and computational complexity has been proposed as a means of achieving a greater understanding of epidemiology and carrying this through to improved management. The potential exists to align these modeling approaches to evaluation of control practices and prediction of the consequent epidemic outcomes, but these have yet to make a major impact on practical disease management. For the immediate future simpler pragmatic approaches for analysis of disease progress, using nonlinear growth functions and/or integrated measures such as area under disease progress curves, will play a key role in informing tactical and strategic decisions on control treatments. These approaches have proved useful in describing control effectiveness and, in some cases, optimizing or changing control practices.

Agriculture↗
PubMed2004

Neural mechanisms for prediction: do insects have forward models?

'Forward models' are increasingly recognized as a crucial explanatory concept in vertebrate motor control. The essential idea is that an important function implemented by nervous systems is prediction of the sensory consequences of action. This is often associated with higher cognitive capabilities; however, many of the purposes forward models are thought to have analogues in insect behaviour, and the concept is closely connected to those of 'efference copy' and 'corollary discharge'. This article considers recent evidence from invertebrates that demonstrates the predictive modulation of sensory processes by motor output, and discusses to what extent this supports the conclusion that insect nervous systems also implement forward models. Several promising directions for further research are outlined.

Animals↗
PubMed2006

Comparison of different stomatal conductance algorithms for ozone flux modelling.

A multiplicative and a semi-mechanistic, BWB-type [Ball, J.T., Woodrow, I.E., Berry, J.A., 1987. A model predicting stomatal conductance and its contribution to the control of photosynthesis under different environmental conditions. In: Biggens, J. (Ed.), Progress in Photosynthesis Research, vol. IV. Martinus Nijhoff, Dordrecht, pp. 221-224.] algorithm for calculating stomatal conductance (g(s)) at the leaf level have been parameterised for two crop and two tree species to test their use in regional scale ozone deposition modelling. The algorithms were tested against measured, site-specific data for durum wheat, grapevine, beech and birch of different European provenances. A direct comparison of both algorithms showed a similar performance in predicting hourly means and daily time-courses of g(s), whereas the multiplicative algorithm outperformed the BWB-type algorithm in modelling seasonal time-courses due to the inclusion of a phenology function. The re-parameterisation of the algorithms for local conditions in order to validate ozone deposition modelling on a European scale reveals the higher input requirements of the BWB-type algorithm as compared to the multiplicative algorithm because of the need of the former to model net photosynthesis (A(n)).

Algorithms↗
PubMed2002

Cholesterol control, medication adherence and illness cognition.

OBJECTIVE: To examine the relation between illness cognitions and two measures of adherence in patients with hypercholesterolaemia, a disease marked by chronically high cholesterol. DESIGN: Cross-sectional. Based on the self-regulation model (Leventhal, Diefenbach, & Leventhal, 1992), patients' illness cognitions were predicted to be related to cholesterol control and medication adherence. Patients with illness cognitions consonant with an experts' mental model of hypercholesterolaemia were expected to show better control and adherence. METHOD: Hypercholesterolaemic patients (N = 169) were recruited at a university-based general medicine clinic. Patients completed a survey that assessed beliefs about hypercholesterolaemia and medication-taking behaviour. Cholesterol levels were obtained from patients' medical charts. RESULTS: Low-density lipoprotein (LDL) cholesterol control was related to believing that hypercholesterolaemia is a stable, asymptomatic disease with severe coronary consequences, and self-report of medication adherence was related to believing that the disease has severe coronary consequences (ps <.05). LDL cholesterol differences between groups low and high in various illness beliefs ranged between 0.04 and 0.24 mmol/l (2 and 9 mg/dl) which translated to between 1% and 18% lower LDL cholesterol levels. CONCLUSION: The present study shows several relations that have not been previously demonstrated between better LDL cholesterol control and illness cognition, cognitions that were similar to an expert or physician's mental model of hypercholesterolaemia. The magnitude of differences in patient cholesterol levels was small but may be clinically important.

Journal Article↗