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Results for “model predictive control”

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At least 631 records · Page 35Linked to original sources

PubMed2001

Risk adjustment alternatives in paying for behavioral health care under Medicaid.

OBJECTIVE: To compare the performance of various risk adjustment models in behavioral health applications such as setting mental health and substance abuse (MH/SA) capitation payments or overall capitation payments for populations including MH/SA users. DATA SOURCES/STUDY DESIGN: The 1991-93 administrative data from the Michigan Medicaid program were used. We compared mean absolute prediction error for several risk adjustment models and simulated the profits and losses that behavioral health care carve outs and integrated health plans would experience under risk adjustment if they enrolled beneficiaries with a history of MH/SA problems. Models included basic demographic adjustment, Adjusted Diagnostic Groups, Hierarchical Condition Categories, and specifications designed for behavioral health. PRINCIPAL FINDINGS: Differences in predictive ability among risk adjustment models were small and generally insignificant. Specifications based on relatively few MH/SA diagnostic categories did as well as or better than models controlling for additional variables such as medical diagnoses at predicting MH/SA expenditures among adults. Simulation analyses revealed that among both adults and minors considerable scope remained for behavioral health care carve outs to make profits or losses after risk adjustment based on differential enrollment of severely ill patients. Similarly, integrated health plans have strong financial incentives to avoid MH/SA users even after adjustment. CONCLUSIONS: Current risk adjustment methodologies do not eliminate the financial incentives for integrated health plans and behavioral health care carve-out plans to avoid high-utilizing patients with psychiatric disorders.

Adult↗

PubMed2006

Neural ensemble activity from multiple brain regions predicts kinematic and dynamic variables in a multiple force field reaching task.

In everyday life, we reach, grasp, and manipulate a variety of different objects all with their own dynamic properties. This degree of adaptability is essential for a brain-controlled prosthetic arm to work in the real world. In this study, rats were trained to make reaching movements while holding a torque manipulandum working against two distinct loads. Neural recordings obtained from arrays of 32 microelectrodes spanning the motor cortex were used to predict several movement related variables. In this paper, we demonstrate that a simple linear regression model can translate neural activity into endpoint position of a robotic manipulandum even while the animal controlling it works against different loads. A second regression model can predict, with 100% accuracy, which of the two loads is being manipulated by the animal. Finally, a third model predicts the work needed to move the manipulandum endpoint. This prediction is significantly better than that for position. In each case, the regression model uses a single set of weights. Thus, the neural ensemble is capable of providing the information necessary to compensate for at least two distinct load conditions.

Algorithms↗

PubMed1995

System issues for Controlled Ecological Life Support Systems.

There are several characteristics of a Controlled Ecological Life Support System that are distinct from commonly engineered systems. These are: 1) the uncertainty, due to limited data availability, and variability due to the heterogeneity of biological subsystems; 2) the closed, ecological nature of the system; and 3) the primary criterion of maximizing the probability of survival. Consequences of these features include: complex dynamics characterized by time scales ranging from milliseconds to months, posing difficult problems with respect to mathematical modeling and predictability; and the necessity for a unique controller design that can translate the high level requirement of survivability to low-level actuator tasks. Future research in the systems and control area should include an ecological perspective focusing on the unique dynamical characteristics of a Controlled Ecological Life Support System.

Ecological Systems, Closed↗

PubMed2001

An extended self-organizing map network for modeling and control of pulse jet fabric filters.

Pulse jet fabric filters (PJFFs) have become an attractive option of particulate collection utilities, because they can meet stringent particulate emission limits regardless of variation in operating conditions. Despite their wide applications, the present control algorithm for PJFFs can best be described as rudimentary. In this paper, a modeling and control strategy based on the local model network (LMN) is proposed. An extended self-organizing map (ESOM) network is developed to construct the LMN model of the filtration process using the filter's input-output data. Subsequently, these ESOM local models are incorporated into the design of local generalized predictive controllers (GPC), and the proposed controller design is obtained as the weighted sum of these local controllers. Simulation results show that the proposed controller design yields a better performance than both conventional GPC and proportional plus integral (PI) controllers yield.

Air Movements↗

PubMed2004

The effect of prenatal care on birthweight: a full-information maximum likelihood approach.

This paper uses a full-information maximum likelihood estimation procedure, the Discrete Factor Method, to estimate the relationship between birthweight and prenatal care. This technique controls for the potential biases surrounding both the sample selection of the pregnancy-resolution decision and the endogeneity of prenatal care. In addition, we use the actual number of prenatal care visits; other studies have normally measured prenatal care as the month care is initiated. We estimate a birthweight production function using 1993 data from the US state of Texas. The results underscore the importance of correcting for estimation problems. Specifically, a model that does not control for sample selection and endogeneity overestimates the benefit of an additional visit for women who have relatively few visits. This overestimation may indicate 'positive fetal selection,' i.e., women who did not abort may have healthier babies. Also, a model that does not control for self-selection and endogenity predicts that past 17 visits, an additional visit leads to lower birthweight, while a model that corrects for these estimation problems predicts a positive effect for additional visits. This result shows the effect of mothers with less healthy fetuses making more prenatal care visits, known as 'adverse selection' in prenatal care.

Birth Weight↗

PubMed2005

Models of foot-and-mouth disease.

During the 2001 foot-and-mouth disease outbreak in the UK, three very different models were used in an attempt to predict the disease dynamics and inform control measures. This was one of the first times that models had been used during an epidemic to support the decision-making process. It is probable that models will play a pivotal role in any future livestock epidemics, and it is therefore important that decision makers, veterinarians and farmers understand the uses and limitations of models. This review describes the utility of models in general before focusing on the three foot-and-mouth disease models used in 2001. Finally, the future of modelling is discussed, analysing the advances needed if models are to be successfully applied during any subsequent epidemics.

Animals↗

PubMed1988

The control of glomerular filtration rate and renal blood flow in chronically volume-expanded rats.

1. Chronic volume expansion by dietary salt loading practically abolishes tubuloglomerular feed-back (TGF) by means of a humoral inhibitor in tubular fluid. Elimination of the vasoconstrictor influence of feed-back does not, however, increase glomerular filtration rate (GFR) and renal blood flow (RBF), implying that chronic salt loading induces additional preglomerular vasoconstriction. This being so, the feed-back response which, although absent in free-flowing nephrons, can still be elicited by loop of Henle perfusion with Ringer solution, should be essentially normal, except that nephron GFR at any loop perfusion rate should be lower than in controls. Persistence of RBF, GFR and nephron GFR autoregulation would imply that autoregulation is achieved by a preglomerular resistance control system independent of feed-back. 2. These hypotheses were tested by clearance and micropuncture experiments in rats chronically fed a diet containing 40 g NaCl (kg food)-1. 3. RBF and GFR autoregulation indeed persisted, the former down to 90 mmHg compared with 105 mmHg in controls. In controls, nephron GFR measured distally was autoregulated down to 90 mmHg whereas that measured proximally was autoregulated only above 105 mmHg. In high-salt rats nephron GFR from both sites was autoregulated to 90 mmHg. 4. Loop of Henle perfusion with homologous tubular fluid in high-salt rats confirmed attenuation of feed-back. Loop perfusion with Ringer solution yielded a response comparable to that in controls (maximal reduction of nephron GFR to 57%, compared with 56% in controls). Absolute nephron GFR at any loop perfusion rate was lower in high-salt rats than in controls. 5. These observations confirm the initial hypotheses. Considering feed-back and autoregulation as independent, preglomerular resistance control mechanisms, together with elementary haemodynamic considerations, allows formulation of a renal haemodynamics model whose quantitative predictions regarding characteristics of RBF, GFR and feed-back control are remarkably consistent with the literature.

Animals↗

PubMed2005

Acute wrist trauma: value of a short dedicated extremity MR imaging examination in prediction of need for treatment.

PURPOSE: To assess predictive value of a short magnetic resonance (MR) imaging examination in addition to or instead of radiography in patients with acute wrist trauma to identify patients who require additional treatment versus those who do not and can be discharged without further follow-up. MATERIALS AND METHODS: Informed consent was obtained from all participating patients; the institutional review board approved the randomized controlled trial and use of data to create prediction models. Of 90 patients (37 female, 53 male; mean age, 40.0 years), 87 with acute wrist trauma were randomized to undergo radiography (n = 43) or radiography and a short MR imaging examination with low-field-strength dedicated extremity MR system (n = 44). Age, sex, trauma mechanism, presence of tenderness of the anatomic snuffbox, radiographic results, MR imaging results, and treatment data were collected. Univariable and multivariable logistic regression analysis was used to create four models for prediction of treatment need. RESULTS: Thirty-six patients had one or more fractures; one patient had a marked soft-tissue lesion. In univariable analysis, age (odds ratio, 1.02; 95% confidence interval: 1.00, 1.05), anatomic snuffbox tenderness (odds ratio, 2.31; 95% confidence interval: 0.90, 5.96), radiographic results (odds ratio, 31.2; 95% confidence interval: 8.90, 109), and positive MR imaging results versus MR imaging not performed (odds ratio, 1.86; 95% confidence interval: 0.57, 6.06) were significantly predictive of treatment need. In multivariable analysis, radiographic results (odds ratio, 24.7; 95% confidence interval: 6.59, 93.1) and positive MR imaging results (odds ratio, 6.28; 95% confidence interval: 1.27, 31.0) were significantly predictive of treatment need. Negative MR imaging results were not significantly predictive (odds ratio, 0.87; 95% confidence interval: 0.20, 3.82). CONCLUSION: A short MR imaging examination with a low-field-strength MR imaging system following radiography in initial evaluation of patients with acute wrist trauma has additional value in prediction of treatment need; it does not have value in identification of patients who can be discharged without further follow-up.

Adolescent↗

PubMed2004

Parent weight change as a predictor of child weight change in family-based behavioral obesity treatment.

BACKGROUND: Family-based behavioral weight control treatment involves the parent in the modification of child and parent eating and activity change. OBJECTIVE: To assess if parent standardized body mass index (z-BMI) change predicts child z-BMI change. DESIGN: Secondary data analysis based on parent and child z-BMI changes from 3 family-based, randomized, controlled weight control studies. Hierarchical regression models tested whether parent z-BMI change increased prediction of child z-BMI change through treatment and 24-month follow-up beyond other factors that influence child weight change, such as child age, sex, socioeconomic status, and baseline child and parent z-BMI. Differences in child z-BMI change as a function of quartiles of parental z-BMI change were tested using an analysis of covariance. SETTING: Pediatric obesity research clinic. PARTICIPANTS: Obese 8- to 12-year-old children and their parents from 142 families who participated in family-based weight control programs. MAIN OUTCOME MEASURES: Child and parent z-BMI changes over time. RESULTS: Parent z-BMI change significantly predicted child z-BMI change for the 0- to 6-month (P<.001) and 0- to 24-month (P <.009) time points. In hierarchical regression models, parent z-BMI change was a significant incremental predictor of child z-BMI change at 6 and 24 months, with the additional r(2) ranging from 11.6% at 6 months (P <.001) to 3.8% at 24 months (P =.02). Parents in the highest quartile of z-BMI change had children with significantly greater z-BMI change than that of children with parents in the other quartiles (P =.01). CONCLUSION: Parent z-BMI change is an independent predictor of obese child z-BMI change in family-based behavioral treatment, and youth benefit the most from parents who lose the most weight in family-based behavioral treatments.

Adult↗

PubMed2001

Modeling and closed-loop control of hypnosis by means of bispectral index (BIS) with isoflurane.

A model-based closed-loop control system is presented to regulate hypnosis with the volatile anesthetic isoflurane. Hypnosis is assessed by means of the bispectral index (BIS), a processed parameter derived from the electroencephalogram. Isoflurane is administered through a closed-circuit respiratory system. The model for control was identified on a population of 20 healthy volunteers. It consists of three parts: a model for the respiratory system, a pharmacokinetic model and a pharmacodynamic model to predict BIS at the effect compartment. A cascaded internal model controller is employed. The master controller compares the actual BIS and the reference value set by the anesthesiologist and provides expired isoflurane concentration references to the slave controller. The slave controller maneuvers the fresh gas anesthetic concentration entering the respiratory system. The controller is designed to adapt to different respiratory conditions. Anti-windup measures protect against performance degradation in the event of saturation of the input signal. Fault detection schemes in the controller cope with BIS and expired concentration measurement artifacts. The results of clinical studies on humans are presented.

Adult↗

PubMed1988

Computer simulation of management strategies for Psorophora columbiae in the rice agroecosystem.

Various control strategies were evaluated using a previously-described and validated (Focks et al. 1988a, 1988b) simulation model (PcSim) of the population dynamics of Psorophora columbiae breeding in the rice agroecosystem. As expected from field experience, focally-applied ground or aerial ULV aerosols of insecticides were seen to provide local control of peak populations. Similar control was predicted for larvicides when also used in and around urban and suburban areas. Both of these measures were predicted by simulation to provide only short term control of adults as a result of immigration of adults from surrounding, untreated provide only short term control of adults as a result of immigration of adults from surrounding, untreated areas. Evaluations of the effectiveness of diapause egg control or the elimination of early spring broods to provide lasting, season-long suppression were not encouraging if only conventional methods such as insecticides or tillage were used. This was primarily because the ability of Ps. columbiae to recolonize treated areas during the course of a breeding season would require the treatment of prohibitively large, parish- (i.e., county-) sized areas. Evaluations of host management (either removal or residual insecticide treatment of cattle) in and around urban and suburban areas were more encouraging. This technique, by providing continuing pressure on populations, has the potential to offset the impact of immigration and thereby afford long-term suppression in local areas. Finally, evaluations of the impact of modifications to irrigation practices indicated that this approach warrants consideration as a supplemental control technique. These results suggest that field evaluations of model predictions would be useful. They emphasize the need to better understand the movement and spatial distribution of Ps. columbiae. These factors would bear directly on the cost and therefore, the practicality of several of the long-term suppression strategies evaluated as they determine the size of the treatment area surrounding population centers needed to offset the impact of immigration from surrounding, untreated areas.

Agriculture↗

PubMed2000

A pre-admission program for underrepresented minority and disadvantaged students: application, acceptance, graduation rates and timeliness of graduating from medical school.

PURPOSE: To determine whether students' performances in a pre-admission program predicted whether participants would (1) apply to medical school, (2) get accepted, and (3) graduate. METHOD: Using prospectively collected data from participants in the University of North Carolina at Chapel Hill's Medical Education Development Program (MEDP) and data from the Association of American Colleges Student and Applicant Information Management System, the author identified 371 underrepresented minority (URM) students who were full-time participants and completed the program between 1984 and 1989, prior to their acceptance into medical school. Logistic regression analysis was used to determine whether MEDP performance significantly predicted (after statistically controlling for traditional predictors of these outcomes) the proportions of URM participants who applied to medical school and were accepted, the timeliness of graduating, and the proportion graduating. Odds ratios with 95% confidence intervals were calculated to determine the associations between the independent and outcome variables. RESULTS: In separate logistic regression models, MEDP performance predicted the study's outcomes after statistically controlling for traditional predictors with 95% confidence intervals. CONCLUSIONS: Pre-admission programs with similar outcomes can improve the diversity of the physician workforce and the access to health care for underrepresented minority and economically disadvantaged populations.

Cultural Deprivation↗

PubMed2006

Ecological determinants of distribution decline and risk of extinction in moths.

For successful conservation of species it is important to identify traits that predispose species to the risk of extinction. By identifying such traits conservation efforts can be directed toward species that are most at risk of becoming threatened. We used data derived from the literature to determine ecological traits that affect distribution, distribution change, and the risk of extinction in Finnish noctuid moths (Lepidoptera, Noctuidae). The ecological traits we examined included body size, larval specificity, length of the flight period, and overwintering stage. In addition, in monophagous species we examined the effects of resource distribution. Larval specificity, length of the flight period, and the overwintering stage each had an independent effect on the risk of extinction when the effects of other traits were controlled by entering all traits into the same regression model. Not a single trait predicted the risk of extinction when analysis was conducted without controlling for the other traits. This discrepancy among the results suggests that a single trait may not be enough to allow prediction of the risk of extinction. Instead, it seems that for successful, predictive conservation science data on several ecological characteristics are needed.

Animals↗

PubMed1975

[Control intensity of glycolytic enzymes in ultrasonic hemolysates of erythrocytes].

By addition of enzyme the control intensity was determined on the pacemaker enzymes hexokinase and phosphofructokinase, as well as on glyceraldehyde-3-phosphate-dehydrogenase and the pyruvate kinase with a control intensity of almost 0 in ultrasonic hemolysates from erythrocyte concentrate. This hemolysate approximately reflects the conditions existing in the intact cell with regard to glycolytic rate, ATP supply, and metabolite concentration. It is therefore suitable as a cell model, excluding the membrane, for studying inner control factors. For HK, PFK, GAPD, and PK predictions based on the linear glycolytic model about the significance of these enzymes for the regulation of the glycolytic rate could be confirmed.

Erythrocytes↗

PubMed1997

Modeling the paramyxovirus hemagglutinin-neuraminidase protein.

The paramyxovirus hemagglutinin-neuraminidase (HN) protein exhibits neuraminidase activity and has an active site functionally similar to that in influenza neuraminidases. Earlier work identified conserved amino acids among HN sequences and proposed similarity between HN and influenza neuraminidase sequences. In this work we identify the three-dimensional fold and develop a more detailed model for the HN protein, in the process we examine a variety of protein structure prediction methods. We use the known structures of viral and bacterial neuraminidases as controls in testing the success of protein structure prediction and modeling methods, including knowledge-based threading, discrete three-dimensional environmental profiles, hidden Markov models, neural network secondary structure prediction, pattern matching, and hydropathy plots. The results from threading show that the HN protein sequence has a 6 beta-sheet propellor fold and enable us to assign the locations of the individual beta-strands. The three-dimensional environmental profile and hidden Markov model methods were not successful in this work. The model developed in this work helps to understand better the biological function of the HN protein and design inhibitors of the enzyme and serves as an assessment of some protein structure prediction methods, especially after the x-ray crystallographic solution of its structure.

Amino Acid Sequence↗

PubMedDate not supplied

Coping behaviors at diagnosis and in adjustment one year later in children with diabetes.

The aim of this investigation was to determine the contributions of coping behaviors used at diagnosis to medical (metabolic control) and psychosocial adjustment (self-perceived competence; adjustment) 1 year later. A total of 89 children (8 to 14 years of age; 48% male; 59% White) received follow-up quarterly from diabetes diagnosis to 1 year later. Findings indicated that, in general, although metabolic control worsened over the first year, psychosocial status and coping behaviors were stable. Boys had worse metabolic control than girls. Multiple regression analysis indicated that self-worth at 1 year postdiagnosis was associated with less use of spirituality (beta = -.44), more use of humor (beta = .28), and more positive self-care (beta = .28); and self-care was less likely to be positive in older children (r = .32). These variables accounted for 47% of the variance (39% adjusted) in general self-worth when entry self-worth was controlled. Poorer overall adjustment at 1 year postdiagnosis was associated with more use of avoidance behaviors (beta = -.47) and poorer self-care (beta = -.71); and more use of avoidance was associated with older age. These variables accounted for 62% of the variance (58% adjusted) in adjustment when adjustment at diagnosis was controlled. Poorer metabolic control was associated with more use of avoidance (beta = .30) and female gender (beta = .39), and avoidance behaviors were more common in older children (beta = .12). This model predicted 33% of the variance (25% adjusted) in metabolic control 1 year after diagnosis.

Adaptation, Psychological↗

PubMed1986

Upstream operators enhance repression of the lac promoter.

To study regulation of transcription by distant elements, a wild-type lac operator was inserted upstream of a promoter-constitutive operator control region. The upstream operator is shown to aid in repression of transcription from the mutant control region. The effectiveness of the upstream operator as a function of its distance from the mutant control region parallels the length dependence observed for DNA cyclization. A quantitative model is proposed for action-at-a-distance of DNA control sites in which protein-protein and protein-DNA interactions are mediated by DNA looping. In this model, the effective concentrations of interacting proteins that are tethered by DNA are determined by the length of the intervening DNA and by its inherent bending and torsional stiffness. This model makes a number of predictions for both eukaryotic and prokaryotic control sequences located far from their sites of action.

Galactokinase↗

PubMed1990

Computer simulation of the hemodynamic determinants of myocardial oxygen supply and demand.

A computer program was developed that uses a mathematical model of the cardiovascular system to predict myocardial oxygen supply and demand as well as cardiac hemodynamics. This model combines the time-varying elastance model of the left ventricle, the modified Windkessel model of the arterial system, and the left ventricular pressure-volume area prediction of myocardial oxygen demand. The computer simulation permits independent control of variables, thus providing the opportunity to design "experiments" and to observe the results. The model predicts that tachycardia leads to reduced myocardial oxygen supply and increased demand. Hypertension caused by increased systemic vascular resistance increases supply more than it increases demand. On the other hand, increased contractility or left ventricular end-diastolic pressure increases demand more than supply, and may cause ischemia in the presence of coronary artery stenosis. The model is an aid in understanding how hemodynamic variables affect the balance between myocardial oxygen supply and demand. It can be used for education and to analyze study protocols prior to animal experimentation.

Animals↗