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Results for “model predictive control”

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PubMedDate not supplied

Factors influencing the coping effort of mothers of hospitalized children.

The purpose of this study was to test a theoretical model predicting the relationships among four concepts: predictability of events, control, anxiety, and coping effort of mothers of children hospitalized with acute physical conditions. The sample consisted of 45 mothers of acutely ill, hospitalized children from 1-24 months of age. For each of the concepts, 16 events commonly associated with hospitalization of a child were proportionately ranked using magnitude estimation measurement technique. The psychometric properties of the instrument were estimated through reliability assessment and cross modality matching. Multiple regression analysis indicated that 97% of the dependent variable, coping effort, was explained by two of the three predictor variables--predictability of events and anxiety. Mothers who knew what events to expect experienced less anxiety and reported expending less effort to cope with the stressful events. Control was not a significant factor in predicting the mothers' coping effort.

Adaptation, Psychological↗

PubMed2002

Comparison of vaccination strategies for the control of dog rabies in Machakos District, Kenya.

Demographic and epidemiological field data were used in a deterministic model to describe dog rabies transmission in Machakos District, Kenya and to predict the impact of potential vaccination strategies for its control. The basic reproduction number (R0) was estimated to be 2.44 (1.52-3.36, 95% confidence limits). There were three key model predictions. The first was that a threshold dog density (K(T)) of 4.5 dogs km(-2) (3.8-5.2 dogs km(-2), 95% confidence limits) was required to maintain transmission. The second was that the estimated annual vaccination rate of 24% failed to decrease incidence and actually increased the stability of transmission and may be counter-productive. Thirdly, to control rabies, it was predicted that 59% (34%-70%, 95% confidence limits) of dogs should be vaccinated at any one time. This requires approximately 70% coverage for annual but only 60% coverage for semi-annual vaccination campaigns. Community-level vaccination trials are needed to test these predictions.

Animals↗

PubMed1984

Formation of the triple helix of type I procollagen in cellulo. Temperature-dependent kinetics support a model based on cis in equilibrium trans isomerization of peptide bonds.

The kinetics of triple-helix formation in type I procollagen at 37 degrees C in cellulo have been found to agree with predictions from the following model: triple-helix formation is initiated after completion of the synthesis of the procollagen polypeptide chains and after the chains associate to form interchain disulfide bonds within the C-propeptide; triple-helix formation propagates from this single nucleation site toward the N terminus of the molecule, interrupted by the random occurrence of peptide bonds in the cis configuration; cis-trans isomerization controls the rate of triple-helix formation. This model predicts that the activation energy of the rate-limiting process should be strongly positive. However, studies of triple-helix formation in vitro using thermally denatured material have shown only a low, or even negative, dependence of the rate on temperature in the physiological range. Here we report the temperature dependence of the rate of triple-helix formation in cellulo and a novel procedure for analyzing the resulting data to give an estimate of the Arrhenius activation energy of the rate-controlling process. It was found that this rate showed a strong, positive dependence on temperature, as expected, and that the activation energy was in satisfactory agreement with independent direct determinations of this parameter for cis-trans isomerizations. These findings lend further support to the model of triple-helix formation described above.

Animals↗

PubMed2003

Robustness of neuroprosthetic decoding algorithms.

We assessed the ability of two algorithms to predict hand kinematics from neural activity as a function of the amount of data used to determine the algorithm parameters. Using chronically implanted intracortical arrays, single- and multineuron discharge was recorded during trained step tracking and slow continuous tracking tasks in macaque monkeys. The effect of increasing the amount of data used to build a neural decoding model on the ability of that model to predict hand kinematics accurately was examined. We evaluated how well a maximum-likelihood model classified discrete reaching directions and how well a linear filter model reconstructed continuous hand positions over time within and across days. For each of these two models we asked two questions: (1) How does classification performance change as the amount of data the model is built upon increases? (2) How does varying the time interval between the data used to build the model and the data used to test the model affect reconstruction? Less than 1 min of data for the discrete task (8 to 13 neurons) and less than 3 min (8 to 18 neurons) for the continuous task were required to build optimal models. Optimal performance was defined by a cost function we derived that reflects both the ability of the model to predict kinematics accurately and the cost of taking more time to build such models. For both the maximum-likelihood classifier and the linear filter model, increasing the duration between the time of building and testing the model within a day did not cause any significant trend of degradation or improvement in performance. Linear filters built on one day and tested on neural data on a subsequent day generated error-measure distributions that were not significantly different from those generated when the linear filters were tested on neural data from the initial day (p<0.05, Kolmogorov-Smirnov test). These data show that only a small amount of data from a limited number of cortical neurons appears to be necessary to construct robust models to predict kinematic parameters for the subsequent hours. Motor-control signals derived from neurons in motor cortex can be reliably acquired for use in neural prosthetic devices. Adequate decoding models can be built rapidly from small numbers of cells and maintained with daily calibration sessions.

Action Potentials↗

PubMed1980

Cognitive processes and recovery from heart attack: a review and theoretical analysis.

A review of the literature on psychosocial aspects of recovery from heart attack is presented with emphasis on psychological responses experienced by the patient. Several theoretical models have previously been proposed to explain these data: a psychodynamic view stressing the importance of denial as a coping mechanism, and a second perspective emphasizing patients' beliefs about their health status. A third model is proposed based on cognitive appraisal processes (perceived control and predictability) shown experimentally to mediate reactions to stressors in a wide variety of situations. Viewing heart attack as a crisis situation, it is assumed that particular aspects of illness will generally have a less negative impact on physiological and behavioral health outcomes to the extent they are perceived to be predictable and/or controllable. Specific interventions to alter these perceptions are discussed, and mechanisms linking various recovery outcomes are proposed. The validity of this model is examined with reference to existing research and suggestions for future research are made.

Adaptation, Psychological↗

PubMed1984

Control of myometrial function in preterm versus term labor.

In this review I have attempted to briefly describe myogenic, neurogenic, and hormonal mechanisms which control myometrial function during term and preterm labor. The synthesis of myometrial gap junctions and receptors in response to hormonal changes appears to be a key element in the gradual evolution of contractility leading to labor. I suggest that the development of myometrial gap junctions is physiologically regulated and can be manipulated pharmacologically. Thus, this system provides a means of regulating myogenic control of smooth muscle. I have proposed a model, or working hypothesis, which may explain the indirect and direct interactions of various substances involved in the control of synthetic processes and stimulating or inhibiting myometrial contractility. The model predicts that term or preterm labor can be initiated at various steps. A more complete understanding of these interactions is necessary for a rational approach to the control of term or preterm labor.

Electrophysiology↗

PubMed1990

A nonlinear model of the arterial system incorporating a pressure-dependent compliance.

The three-element modified Windkessel model has been widely used to study the characteristics of the systemic arterial system. This model provides most of the features of the systemic input impedance, but does not describe the nonlinear effect of the pressure dependence of arterial compliance. The current investigation examines the hemodynamic consequences of such an inclusion. Simultaneous aortic pressure and flow during control and brief descending aortic occlusion were measured in open chest anesthetized experimental dogs. A numerical procedure was implemented to compute constant compliance linear and nonlinear compliance model-predicted pressure waveforms with flow as the input. Results show that the nonlinear compliance model in general can more accurately predict the measured pressure waveforms during control and during acute pressure loading. The difference between the predicted waveforms is more pronounced when blood pressure is high and when the pulse pressure is large.

Animals↗

PubMedDate not supplied

SOIL-SOILN simulations of water drainage and nitrate nitrogen transport from soil core lysimeters.

Water resources protection from nitrate nitrogen (NO3-N) contamination is an important public concern and a major national environmental issue. The abilities of the SOIL-SOILN model to simulate water drainage and nitrate N fluxes from orchardgrass (Dactylis glomerata L.) were evaluated using data from a 3-yr field experiment. The soil is classified as a Hagerstown silt loam soil (fine, mixed, semiactive, mesic Typic Hapludalf). Nitrate losses below the 1-m depth from N-fertilized grazed orchardgrass were measured with intact soil core lysimeters. Five N-fertilizer treatments consisted of a control, urine application in the spring, urine application in the summer, urine application in the fall, and feces application in the summer. The SOIL-SOILN models were evaluated using water drainage and nitrate flux data for 1993-1994, 1994-1995, and 1995-1996. The N rate constants from a similar experiment with inorganic fertilizer and manure treatments under corn (Zea mays L.) were used to evaluate the SOILN model under orchardgrass sod. Results indicated that the SOIL model accurately simulated water drainage for all three years. The SOILN model adequately predicted nitrate losses for three urine treatments in each year and a control treatment in 1994-1995. However, it failed to produce accurate simulations for two control treatments in 1993-1994 and 1995-1996, and feces treatments in all three years. The inaccuracy in the simulation results for the control and feces treatments seems to be related to an inadequate modeling of N transformation processes. In general, the results demonstrate the potential of the SOILN model to predict NO3-N fluxes under pasture conditions using N transformation rate constants determined through the calibration process from corn fields on similar soils.

Agriculture↗

PubMed2005

The effects of hypoxia on the theoretical modelling of tumour control probability.

Theoretical modelling of tumour response is increasingly used for the prediction of treatment result and has even been proposed as ranking criteria in some algorithms for treatment planning. Tumour response to radiation is greatly influenced by the details of tumour microenvironment, especially hypoxia, that unfortunately are not always taken into consideration for these simulations. This paper intends to investigate the effects of various assumptions regarding hypoxia distribution in tumours on the predictions of treatment outcome. A previously developed model for simulating theoretically the oxygenation in biologically relevant tissues, including results from oxygen diffusion, consumption and perfusion limitations in tumours, was used to investigate the effects of the different aspects of hypoxia on the predictions of treatment outcome. Thus, both the continuous distribution of values and the temporal variation of hypoxia patterns were taken into consideration and were compared with a 'black-and-white' simplification with a fully hypoxic compartment and a fully oxic one. It was found that the full distribution of oxygenation in the tissue is needed for accurate results. The 'black-and-white' simplification, while showing the same general trends for the predictions of radiation response, could lead to serious over-estimations of the tumour control probability. It was also found that the presence of some hypoxia for every treatment fraction leads to a decrease in the predicted local control, regardless of the change of the hypoxic pattern throughout the duration of the whole treatment. The results thus suggest that the assumptions regarding tumour hypoxia influence very much the predictions of treatment outcome and therefore they have to be very carefully incorporated into the theoretical modelling.

Cell Hypoxia↗

PubMed2005

An internally switched model of ocular tracking with prediction.

Ocular tracking of targets in biological systems involves switching between two strategies: slow pursuit and fast corrective saccades producing pursuit nystagmus. Here, a symmetric (bilateral) controller is used as a model for the oculomotor control system (OCS) to drive two cameras on a robotic head. It relies, as in biology, on internal switching in shared premotor circuits to alternate automatically between the two types of movements comprising nystagmus. The symmetric structural concept is gaining acceptance as evidence points to sharing of both fast phase and slow phase control in brainstem structures previously thought to be solely involved in one mode alone. This bilateral OCS model is a parsimonious design that is at once biomimetic and analytically simple. We extend prior results by incorporating more biological clues from floccular projections to establish rudimentary prediction mechanisms for both slow and fast phases; prediction is achieved by using retinal slip, which contains target velocity information. This provides a more accurate replication of the difference between fast phase and slow phase dynamics, and considers neural activity profiles in the superior colliculus to refine the controller performance. The resulting controller eliminates the need for saccades in steady state for low frequency inputs, and each saccade now has better accuracy, despite visual delays.

Animals↗

PubMed1993

Relationships among protein and albumin concentrations and oncotic pressure in nephrotic plasma.

We determined oncotic pressure (pi) by membrane osmometry and assayed total protein (TP) and albumin (Alb) concentrations in plasma of 102 nephrotic subjects and 27 healthy controls. All three quantities were markedly depressed in the nephrotic group. When plasma was serially diluted and concentrated, nephrotic but not control plasma also exhibited a highly variable change point in the nonlinear relationship between TP or Alb and pi. Absent a unique change point, we developed quadratic models which incorporated TP, Alb, and (TP x Alb) to prospectively predict pi in unperturbed plasma. The ability of the most successful quadratic model to predict pi in afferent or efferent arteriolar plasma was limited; the prediction errors reached 10 mmHg in nephrotic and 6 mmHg in control subjects. The nephrotic model coefficients also differed significantly from control and pointed to an important influence of nonalbumin proteins on pi in nephrotic plasma. Investigation of the intrinsic membrane properties of diseased glomerular capillary walls requires precise knowledge of pi. For this purpose we recommend that pi be directly determined by membrane osmometry rather than calculated from protein concentration(s).

Adolescent↗

PubMed2004

Brain T1 in young children with sickle cell disease: evidence of early abnormalities in brain development.

Measurement of tissue spin lattice relaxation time (T(1)) has been used to characterize brain development in healthy children. Here we report the first study of brain T(1) in young children with sickle cell disease (SCD). The T(1) in 10 tissue samples was measured by established techniques; 46 SCD patients under the age of 4 years were compared to 267 controls, including 55 well children under the age of 4 years. A model was developed to predict the relationship between age and brain T(1) in controls, then we compared patient T(1) to healthy normal T(1). Most white matter and gray matter tissues in infant patients (<2 years old), had T(1) values significantly higher than normal. For example, 15.0% of patient caudate T(1) values were above the upper bound of the 95% confidence interval for controls, but only 2.5% of normal values are expected to be this high (p = 0.0003). Among infant patients, brain T(1) was significantly higher than normal in every tissue (p < 0.01) except cortical gray matter. However, patient T(1) values declined rapidly to values lower than normal by about age 4. Our findings imply that patients follow an abnormal developmental trajectory beginning early in infancy.

Anemia, Sickle Cell↗

PubMed2006

Mathematical models and the experimental analysis of behavior.

The use of mathematical models in the experimental analysis of behavior has increased over the years, and they offer several advantages. Mathematical models require theorists to be precise and unambiguous, often allowing comparisons of competing theories that sound similar when stated in words. Sometimes different mathematical models may make equally accurate predictions for a large body of data. In such cases, it is important to find and investigate situations for which the competing models make different predictions because, unless two models are actually mathematically equivalent, they are based on different assumptions about the psychological processes that underlie an observed behavior. Mathematical models developed in basic behavioral research have been used to predict and control behavior in applied settings, and they have guided research in other areas of psychology. A good mathematical model can provide a common framework for understanding what might otherwise appear to be diverse and unrelated behavioral phenomena. Because psychologists vary in their quantitative skills and in their tolerance for mathematical equations, it is important for those who develop mathematical models of behavior to find ways (such as verbal analogies, pictorial representations, or concrete examples) to communicate the key premises of their models to nonspecialists.

Humans↗

PubMed1991

Chance and necessity in ingestive behavior.

This paper begins with the paradox of invariants arising out of random events, and its title is based on the resolution of that paradox in Monod's book Chance and Necessity. In ingestive behavior this paradox arises particularly in the emergence of constancies in intakes from small bouts of behavior. I point out that one resolution of the paradox can be obtained by the use of averaging, eliminating the necessity to search for special detectors of variables whose values appear to be set by small modifications in a variety of control systems. The apparent regulation of body weight or food intake which remains relatively constant in the aggregate while components which enter into them fluctuate widely, is an illustration of the paradox and one possible resolution. I also describe four basic paradigms that could be taken as the main starting points for a comprehensive theory of ingestive behavior. They could be called regulation, learning, reward, and neural control. To some extent each is involved, and it is impossible at present to assign primacy. I conclude by suggesting that the basic tenet of ingestive behavior is that it occurs when there is an excess of excitation over inhibition in the neural systems that control it, and that the various factors which enter into such a calculation can best be represented by a computer model that incorporates all known controls that will make more accurate predictions than can be made with verbal theorizing. Such predictions can then be used to correct or confirm the model as data is collected. Finally, I provide some specific suggestions for activities of the Society for the Study of Ingestive Behavior.

Animals↗

PubMed1997

Behavioral inhibition, sustained attention, and executive functions: constructing a unifying theory of ADHD.

Attention deficit hyperactivity disorder (ADHD) comprises a deficit in behavioral inhibition. A theoretical model is constructed that links inhibition to 4 executive neuropsychological functions that appear to depend on it for their effective execution: (a) working memory, (b) self-regulation of affect-motivation-arousal, (c) internalization of speech, and (d) reconstitution (behavioral analysis and synthesis). Extended to ADHD, the model predicts that ADHD should be associated with secondary impairments in these 4 executive abilities and the motor control they afford. The author reviews evidence for each of these domains of functioning and finds it to be strongest for deficits in behavioral inhibition, working memory, regulation of motivation, and motor control in those with ADHD. Although the model is promising as a potential theory of self-control and ADHD, far more research is required to evaluate its merits and the many predictions it makes about ADHD.

Affect↗

PubMed2001

Power consumption profiles in high-shear wet granulation. II: Predicting the overwetting point from a spreading energy.

Granulation is an important process in the pharmaceutical industry for the preparation of solid dosage forms. For high-shear wet granulation, the process endpoint is monitored using the device power consumption. However, granulation is very sensitive to variations in the feed product physicochemical properties and, in some cases, power consumption profiles can not be used for process control. In this paper, a model is proposed to predict the granulation overwetting point from the spreading energy of the liquid binder on the powder. This energy is independently calculated from measurements of the powder true surface area, liquid binder surface tension, and liquid contact angle on the powder surface.

Chemistry, Pharmaceutical↗

PubMed1978

Linkage of the endogenous avian leukosis virus genome of virus-producing chicken cells to inhibitory cellular DNA sequences.

The endogenous avian leukosis virus genome of uninfected virus-producing(V+) chicken embryo fibroblasts appears to be inefficiently transcribed and is noninfectious in transfection assays of high molecular weight DNA. We previously proposed that the endogenous virus genome was linked to a cis-acting control element which inhibited its transcription and, consequently, interfered with transfection by endogenous viral DNA. We now report that DNA of uninfected V+ cells is infectious at a low level when sheared to the approximate size of the virus genome. These results suggest that the endogenous virus genome of uninfected V+ chicken cells can be converted to an infectious form by separating it from adjacent cellular DNA sequences, as predicted by the cis-acting control element model.

Animals↗

PubMed2026

Advanced mitigation strategies for acrylamide formation in foods: Mechanistic insights, emerging innovations, and future perspectives.

Acrylamide is a heat-induced contaminant formed predominantly in carbohydrate-rich foods during high-temperature processing, posing significant concerns due to its potential carcinogenic, neurotoxic, and genotoxic effects. This review critically examines the mechanisms of acrylamide formation, emphasizing the role of the Maillard reaction and key precursors such as asparagine and reducing sugars, along with the influence of processing conditions including temperature, time, pH, and moisture. Various mitigation strategies are comprehensively discussed, ranging from raw material selection and genetic approaches to enzymatic treatments such as asparaginase and the application of natural and chemical inhibitors. Advances in processing technologies, including optimization of conventional thermal methods and emerging non-thermal techniques such as cold plasma and ultrasound, are evaluated for their effectiveness. The review also highlights the role of food additives, functional ingredients, and fermentation in reducing acrylamide formation. Furthermore, recent developments in analytical techniques, including chromatographic methods, biosensors, and artificial intelligence-based predictive models, are explored for improved detection and control. Risk assessment, toxicological implications, and global regulatory frameworks are also examined. Finally, future perspectives focusing on genetic engineering, personalized nutrition, and digital technologies such as AI and blockchain are discussed to support sustainable and industry-applicable mitigation strategies.

Acrylamide↗