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Results for “model predictive control”

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PubMed1994

Clarification and application of an ion parametric resonance model for magnetic field interactions with biological systems.

Theoretical models proposed to date have been unable to clearly predict biological results from exposure to low-intensity electric and magnetic fields (EMF). Recently a predictive ionic resonance model was proposed by Lednev, based on an earlier atomic spectroscopy theory described by Podgoretskii and Podgoretskii and Khrustalev. The ion parametric resonance (IPR) model developed in this paper corrects mathematical errors in the earlier Lednev model and extends that model to give explicit predictions of biological responses to parallel AC and DC magnetic fields caused by field-induced changes in combinations of ions within the biological system. Distinct response forms predicted by the IPR model depend explicitly on the experimentally controlled variables: magnetic flux densities of the AC and DC magnetic fields (Bac and Bdc, respectively); AC frequency (fac); and, implicitly, charge to mass ratio of target-ions. After clarifying the IPR model and extending it to combinations of different resonant ions, this paper proposes a basic set of experiments to test the IPR model directly which do not rely on the choice of a particular specimen or endpoint. While the fundamental bases of the model are supported by a variety of other studies, the IPR model is necessarily heuristic when applied to biological systems, because it is based on the premise that the magnitude and form of magnetic field interactions with unhydrated resonant ions in critical biological structures alter ion-associated biological activities that may in turn be correlated with observable effects in living systems.

Algorithms↗

PubMed2003

Actin-based motility: from molecules to movement.

Extensive progress has been made recently in understanding the mechanism by which cells move and extend protrusions using site-directed polymerization of actin in response to signalling. Insights into the molecular mechanism of production of force and movement by actin polymerization have been provided by a crosstalk between several disciplines, including biochemistry, biomimetic approaches and computational studies. This review focuses on the biochemical properties of the proteins involved in actin-based motility and shows how these properties are used to generate models of force production, how the predictions of different theoretical models are tested using a biochemically controlled reconstituted motility assay and how the changes in motility resulting from changes to the concentrations of components of the assay can help understand diverse aspects of the motile behavior of living cells.

Actin-Related Protein 2↗

PubMed2007

Neural network prediction of thermophilic (65 degrees C) sulfidogenic fluidized-bed reactor performance for the treatment of metal-containing wastewater.

The performance of a fluidized-bed reactor (FBR) based sulfate reducing bioprocess was predicted using artificial neural network (ANN). The FBR was operated at high (65 degrees C) temperature and it was fed with iron (40-90 mg/L) and sulfate (1,000-1,500 mg/L) containing acidic (pH = 3.5-6) synthetic wastewater. Ethanol was supplemented as carbon and electron source for sulfate reducing bacteria (SRB). The wastewater pH of 4.3-4.4 was neutralized by the alkalinity produced in acetate oxidation and the average effluent pH was 7.8 +/- 0.8. The oxidation of acetate is the rate-limiting step in the sulfidogenic ethanol oxidation by thermophilic SRB, which resulted in acetate accumulation. Sulfate reduction and acetate oxidation rates showed variation depending on the operational conditions with the maximum rates of 1 g/L/d (0.2 g/g volatile solids (VS)/d) and 0.3 g/L/d (0.06 g/g VS/d), respectively. This study presents an ANN model predicting the performance of the reactor and determining the optimal architecture of this model; such as best back-propagation (BP) algorithm and neuron numbers. The Levenberg-Marquardt algorithm was selected as the best of 12 BP algorithms and optimal neuron number was determined as 20. The developed ANN model predicted acetate (R=0.91), sulfate (R=0.95), sulfide (R=0.97), and alkalinity (R=0.94) in the FBR effluent. Hence, the ANN based model can be used to predict the FBR performance, to control the operational conditions for improved process performance.

Acetates↗

PubMed2005

Control-relevant modeling of the antitumor effects of 9-nitrocamptothecin in SCID mice bearing HT29 human colon xenografts.

The mathematical model structure selected to describe system behavior is at least partially dependent on the proposed use of the model. In this paper, a pharmacokinetic(PK)/pharmacodynamic (PD) model for use in drug delivery algorithm synthesis is developed. The antitumor agent 9-nitrocamptothecin (9NC) was administered orally to severe combined immunodeficient (SCID) mice bearing subcutaneously implanted HT29 human colon xenografts, and the effect of 9NC on those xenografts was characterized. Different PK model structures were considered in characterizing the dynamics of the drug concentration in the plasma. Akaike's Information Criterion (AIC) was used to select the model structure maximizing fit accuracy while simultaneously minimizing the number of model parameters. The resulting PK model was a set of coupled linear ordinary differential equations able to describe the nonlinear dynamic behavior (e.g. plateauing, etc.) of the drug concentrations observed in the plasma. Pharmacodynamics were modeled by characterizing tumor growth in both the untreated and drug-treated animals. The resulting PK/PD model related drug administration to effect, and this model has a structure that facilitates future control algorithm synthesis. Control algorithms in this context would directly utilize PK/PD model predictions. These predictions would be used to determine the amount and frequency of drug administration in order to reduce the tumor burden without violating clinically relevant constraints. This methodology could then be used to aid the clinician in selecting dose levels and schedules, and extension to patient tailored treatment may eventually be feasible with this approach.

Algorithms↗

PubMed1993

Mutations in the gene encoding the replication-initiation protein of plasmid RK2 produce elevated copy numbers of RK2 derivatives in Escherichia coli and distantly related bacteria.

Mini-replicons of the broad-host-range plasmid RK2 with increased copy number (cn) due to mutations in the gene encoding the essential replication initiation protein TrfA are described. The cn of these derivatives have been determined in Escherichia coli, Pseudomonas aeruginosa and Agrobacterium tumefaciens and were found to be elevated in all three bacterial hosts. One of the cn mutations was introduced into the intact 60-kb RK2 plasmid by homologous recombination in vivo, resulting in an approximately twofold cn increase. The expression of trfA from this mutant RK2 plasmid did not respond to the cn change as predicted by a simple transcription rate-limitation, replication control model. Implications for the model of RK2 replication control and the potential use of mutant RK2 mini-replicons as high-copy broad-host-range gene cloning vectors are discussed.

Bacterial Proteins↗

PubMed1996

Spatial selective attention in schizophrenic, affective disorder, and normal subjects.

Schizophrenic, affective disorder, and normal subjects performed tasks involving exogenous (automatic) and endogenous (voluntary) attention. In the exogenous attention task, schizophrenic subjects demonstrated a greater benefit in response time than did normal subjects. In the endogenous attention task, however, schizophrenic subjects showed a smaller benefit in response time than did normal subjects. These results are consistent with a model of schizophrenia that predicts a deficit in voluntary (endogenous) control, and a disinhibition and therefore enhancement of the automatic (exogenous) processes of spatial selective attention. Affective disorder subjects did not demonstrate a greater benefit in response time than normal subjects in the exogenous attention task, but did show a smaller benefit in response time than normal subjects in the endogenous attention task. The somewhat similar pattern of behavior of schizophrenic and affective disorder subjects suggests that abnormal spatial selective attentional processes may not be specific to schizophrenia.

Adult↗

PubMed2004

What causes scale errors in children?

A recent article by DeLoache et al. has documented an intriguing phenomenon in the development of action planning in young children. When children act on toy replicas of larger objects they make scale errors that are consistent with the full-sized object. Although the actions selected are inappropriate, their execution accurately takes into account the true size of the target. This phenomenon permits tests of the predictions of the perception-action and planning-control models of vision for action.

Brain↗

PubMed2001

Optical peroxide biosensor using the electrically controlled-release technique.

An optical biosensor using an electrically controlled-release system was developed for the measurement of peroxide concentration. The electrically controlled-release system consisted of a current-supplying system and a polymer complex by hydrogen bonding between the carboxylic and oxazoline group. The polymer complex was formed below pH 5.0 and was degraded above pH 5.4. The local pH change near the surface of the polymer complex could be controlled by applying the electric current to release an enzyme reaction reagent, 4-hydroxyphenylacetic acid (HPA), in the polymer complex. The releasing rate of HPA was proportional to the electric current applied to the polymer complex. The model of the controlled-release system was proposed to predict the degradation velocity of the polymer complex, which is equivalent to the releasing rate of HPA. The released HPA and analyte, peroxide, flowed into the reactor with the immobilized enzyme and then reacted with the enzyme. The peroxide concentration was measured based on the fluorescence detection of enzyme reaction product, 6,6'-dihydroxy (1,1'-biphenyl) 3,3'-diacetic acid (DBDA). The proposed biosensor had the linear analytical range of 0.025 approximately 1.0 mM with a response time of 20 min, good repeatability, and reproducibility.

Biosensing Techniques↗

PubMed2006

Latent variable analysis of coping, anxiety/depression, and somatic symptoms in adolescents with chronic pain.

Reports of adolescents' coping with recurrent pain, symptoms of anxiety/depression, and somatic complaints were obtained from a sample of 164 adolescents with recurrent abdominal pain and their parents. Confirmatory factor analysis revealed that coping consisted of 3 nonorthogonal factors: Primary Control Engagement Coping (problem solving, emotional expression, and emotional regulation), Secondary Control Engagement Coping (positive thinking, cognitive restructuring, acceptance, and distraction), and Disengagement Coping (denial, avoidance, and wishful thinking). Structural equation modeling using latent variables revealed that secondary control engagement coping predicted lower levels of anxiety/depression symptoms and somatic complaints, and disengagement coping was related to higher levels of anxiety/depression and somatic complaints. Implications for understanding child and adolescent coping with pain are highlighted.

Abdominal Pain↗

PubMed1996

Effects of maternal smoking on amniotic fluid volume and fetal urine output.

The purpose of this study was to assess the effects of maternal smoking on amniotic fluid volume and fetal urine output. Seventeen women (10 smokers and 7 non-smokers) were serially assessed through pregnancy. Smoking status was determined by self-report and carbon monoxide manometry. Amniotic fluid volume was assessed by sonographically measuring the maximum vertical pocket, the amniotic fluid index, and the two dimensions of the largest pockets. The coronal area formula was used to calculate bladder volume at 5-minute intervals for 20 minutes. Urine output was calculated from serial measurements of bladder volume. The mean gestational age of the first session was 26.8 (2.7) weeks, of the second session 32.4 (1.6) weeks, and of the last session 36.9 (2.1) weeks. In the univariate analysis there were no differences between smokers and non-smokers at any of the three visits for gestational age, fetal weight, maximum vertical pocket, amniotic fluid index, two-dimensional maximum pocket, and urine output. In the regression model, while controlling for gestational age, smoking status could not predict significant differences in any parameter. Maternal smoking does not appear to affect either amniotic fluid volume or fetal urine output.

Amniotic Fluid↗

PubMed2006

The diversification of Paleozoic fire systems and fluctuations in atmospheric oxygen concentration.

By comparing Silurian through end Permian [approximately 250 million years (Myr)] charcoal abundance with contemporaneous macroecological changes in vegetation and climate we aim to demonstrate that long-term variations in fire occurrence and fire system diversification are related to fluctuations in Late Paleozoic atmospheric oxygen concentration. Charcoal, a proxy for fire, occurs in the fossil record from the Late Silurian (approximately 420 Myr) to the present. Its presence at any interval in the fossil record is already taken to constrain atmospheric oxygen within the range of 13% to 35% (the "fire window"). Herein, we observe that, as predicted, atmospheric oxygen levels rise from approximately 13% in the Late Devonian to approximately 30% in the Late Permian so, too, fires progressively occur in an increasing diversity of ecosystems. Sequentially, data of note include: the occurrence of charcoal in the Late Silurian/Early Devonian, indicating the burning of a diminutive, dominantly rhyniophytoid vegetation; an apparent paucity of charcoal in the Middle to Late Devonian that coincides with a predicted atmospheric oxygen low; and the subsequent diversification of fire systems throughout the remainder of the Late Paleozoic. First, fires become widespread during the Early Mississippian, they then become commonplace in mire systems in the Middle Mississippian; in the Pennsylvanian they are first recorded in upland settings and finally, based on coal petrology, become extremely important in many Permian mire settings. These trends conform well to changes in atmospheric oxygen concentration, as predicted by modeling, and indicate oxygen levels are a significant control on long-term fire occurrence.

Air↗

PubMed1998

Evaluation of clothing systems to determine heat strain.

This article describes the basic evaluation process and test methodology employed when temperature extremes for clothing systems must be considered as part of the U.S. Army's Health Hazard Assessment for material in the development and acquisition process. The goals of the evaluation are to select clothing systems that minimize the hazards of heat strain and to predict the heat strain for persons wearing such clothing. Clothing evaluations begin with biophysical assessments that determine the thermal characteristics (vapor permeability and insulation) for textiles via guarded hot plate tests and for clothing systems via thermal manikin tests. The results from biophysical tests can be used to select the textile and/or clothing with the best thermal characteristics. The data from manikin evaluations also can be used in prediction modeling. Human physiological testing is best done in a controlled laboratory environment, although for realism and user acceptability field trials may also be conducted. Proven test and measurement methods must be employed, and tests must control for confounding variables; subjects serve as their own controls, and test environment and procedures are consistent between trials. The process and test methodology described can be applied to the evaluation of civilian clothing systems as well as to the military systems for which they were developed.

Hot Temperature↗

PubMed1995

Antecedents and consequences of physical activity and exercise among older adults.

The antecedents and consequences of four markers of physical activity and exercise are examined for the 6,780 baseline self-respondents to the Longitudinal Study on Aging. These dichotomous markers reflect having a level of physical activity greater than one's peers (45.8%), getting as much exercise as needed (58.9%), having a regular exercise routine (28.4%), and walking a mile or more at least once a week (29.9%). The major factors associated with engaging in these behaviors are having fewer lower body limitations, better perceived health, more non-kin social supports, not worrying about one's health, and having a sense of control over one's health. When added to traditional models predicting subsequent (over the next 6 to 8 years) mortality, nursing home placement, hospital resource consumption, and changes in functional status, the four markers of physical activity and exercise have numerous statistically and substantively significant associations, all of which involve better health outcomes.

Aged↗

PubMed2000

A spatial statistical approach to malaria mapping.

BACKGROUND: Good maps of malaria risk have long been recognized as an important tool for malaria control. The production of such maps relies on modelling to predict the risk for most of the map, with actual observations of malaria prevalence usually only known at a limited number of specific locations. Estimation is complicated by the fact that there is often local variation of risk that cannot be accounted for by the known covariates and because data points of measured malaria prevalence are not evenly or randomly spread across the area to be mapped. METHOD: We describe, by way of an example, a simple two-stage procedure for producing maps of predicted risk: we use logistic regression modelling to determine approximate risk on a larger scale and we employ geo-statistical ('kriging') approaches to improve prediction at a local level. Malaria prevalence in children under 10 was modelled using climatic, population and topographic variables as potential predictors. After the regression analysis, spatial dependence of the model residuals was investigated. Kriging on the residuals was used to model local variation in malaria risk over and above that which is predicted by the regression model. RESULTS: The method is illustrated by a map showing the improvement of risk prediction brought about by the second stage. The advantages and shortcomings of this approach are discussed in the context of the need for further development of methodology and software.

Child↗

PubMed1991

Determinants and predictors of dengue infection in Mexico.

A national serosurvey was conducted in Mexico from March to October 1986 to identify predictors of dengue transmission and target areas at high risk of severe annual epidemics. A total of 3,408 households in 70 localities with populations less than 50,000 were randomly sampled, and serology was obtained from one subject under age 25 years in each household. When comparing exposure and infection frequencies across the 70 communities, the authors found that median temperature during the rainy season was the strongest predictor of dengue infection, with an adjusted fourfold risk in the comparison of 30 degrees C with 17 degrees C. High temperatures increase vector efficiency by reducing the period of viral replication in mosquitoes. The proportion of houses in a community with larva on the premises was significantly associated with the community proportion infected (odds ratio (OR)adj = 1.9; 95% confidence interval (CI) 1.4-2.5), as was the proportion of households with uncovered water containers present (ORadj = 1.9; 95% CI 1.4-2.7). Because these factors have effects beyond the individual household and subjects infected from them create a risk for other subjects, both analyses of effects and organization of control efforts must be at the community level. A predictive model was constructed using the community level risk factors to classify communities as being at high, medium, or low risk of experiencing an epidemic; 57% of these communities were correctly classified using this model.

Adult↗

PubMed2006

On impact dynamics and contact events for biped robots via impact effects.

In this paper, impact dynamics of a five-link biped walking on level ground are studied, and the results are used to correlate the gait parameters with the contact event following impact. The conventional five-link biped kinematic model is improved such that, for the first time, the explicit solution for the external impulses is obtained in a detailed but compact form. Such a solution reveals that the direction of the swing tip velocity prior to impact is a key factor dictating the upcoming contact event and the slippage. The conventional conditions to warrant the types of impact are expanded to make them sufficient. The aforementioned results are used in the parametric analysis to predict the contact event after impact. Such a prediction is important for proper dynamic modeling, motion planning, and control of the upcoming supporting phase.

Gait↗

PubMed1990

Relation between small intestinal motor activity and transit in secretory diarrhea.

Our objective in this study was to correlate small intestinal motor activity with transit time in the fed state under normal conditions and in the secretory state induced by cholera toxin. In the control state, transit time was strongly and inversely correlated with the mean distance of propagation and to a lesser degree with frequency and total duration of all contractions. By contrast, transit time was not correlated with total amplitude and area of all contractions. When contractions were separated into propagating and nonpropagating contractions, there was a highly significant inverse correlation between transit time and all parameters of propagating contractions but no relation with any parameter of nonpropagating contractions. Similar results were obtained during the secretory state induced by cholera toxin. The control data were used to develop a mathematical model to predict transit time from contractile parameters and was validated using the data obtained in the secretory state. Our findings demonstrate that transit through the small intestine in the normal and secretory states is strongly related to the parameters of propagating contractions but not to parameters of nonpropagating contractions.

Animals↗

PubMed1980

Variable open-loop gain in the control of thermogenesis in cold-exposed rabbits.

We have previously demonstrated a multiplicative interaction between mean skin temperature (Tsk) and hypothalamic temperature (Thy) in the control of thermogenesis in cold exposed rabbits. Such a model predicts that open-loop gain will not be constant, but will vary according to the direction and degree of Thy displacements and to the prevailing level of Tsk when Thy is altered. Open-loop gain was calculated from steady-state displacements in body temperature induced by sustained step displacements in Thy. Hypothalamic temperature of rabbits was clamped at various levels ranging from 2 degrees C above to 3 degrees C below normal Thy and the resulting changes in rectal temperature attained at steady state were recorded. Experiments were conducted at ambient temperatures (Ta) of 2 degrees and 15 degrees C. Open-loop gain in response to hypothalamic heating was always greater than that obtained in response to equivalent levels of hypothalamic cooling. Furthermore, at lower levels of Tsk (Ta = 2 degrees C) open-loop gain was greater for all levels of Thy displacement when compared to that measured at higher levels of Tsk (Ta = 15 degrees C).

Animals↗