Designing an experiment for parameter estimation involves two steps. The first one is qualitative, and consists in selecting a suitable configuration of the input/output ports so as to make, if possible, all the param...
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Designing an experiment for parameter estimation involves two steps. The first one is qualitative, and consists in selecting a suitable configuration of the input/output ports so as to make, if possible, all the parameters of interest identifiable. The second step is quantitative, and based on the optimization of a suitable criterion (with respect to the input shapes, sampling schedule,...) so as to get the maximum information from the data to be collected. When the model is nonlinear in the parameters, both steps present specific difficulties which are discussed in this paper. The practical importance of qualitative experiment design is illustrated by a very simple biological model. Various policies presented in the literature for quantitative experiment design are reviewed. Special emphasis is given to methods allowing uncertainty on the prior information to be taken into account.
A flexible system of nonlinear statistical models based on Gamma distributions of integer order has been developed to describe aspects of animal growth and development in quantitative terms. Models from this system ha...
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A flexible system of nonlinear statistical models based on Gamma distributions of integer order has been developed to describe aspects of animal growth and development in quantitative terms. Models from this system have been applied to data concerning the generation and growth of ovarian follicles in infant Wistar rats and shown to fit for a range of animals aged 8-24 days. The main work of this paper is to discuss the estimation of this global distribution. The effects of parametric redundancies and other computational issues are assessed in the context of the results obtained for the Wistar rat data. Clearly, the theory discussed is applicable generally to the estimation of population or reference values for developmental or growth parameters in humans or other animals.
This paper describes a knowledge based program for medical diagnosis, in an emergency context. The main characteristics of the proposed approach are a good robustness according unreliable data and a great explanation ...
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This paper describes a knowledge based program for medical diagnosis, in an emergency context. The main characteristics of the proposed approach are a good robustness according unreliable data and a great explanation power. The knowledge base consists in a set of concept descriptions, these concepts being divided in three classes: signs, processes and diagnoses. The data input is made using a standard fixed questionnaire. The inference mechanism contains two steps: during the first one, the best possible interpretation of the data set is built for each diagnosis, and the second one consists in a ranking of the interpretations, according to their level of consistency. The current application supported by this project is the diagnosis of the acute abdominal pains. The actual results are very encouraging, and this new approach appears well suited for diagnostic problems in noisy environment.
The application of parameter-bounding to classification of sparsely sampled responses from medical tolerance-testing is investigated. A four-parameter bounded-error model is used to yield parameter bounds. Two paramet...
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The application of parameter-bounding to classification of sparsely sampled responses from medical tolerance-testing is investigated. A four-parameter bounded-error model is used to yield parameter bounds. Two parameters less important for classification are tuned approximately then the non-linear bounds on the remaining parameters are examined. The problem of choosing which parameters to tune first is examined by reference to artificial records. A criterion for tuning is proposed and justified by estimation theory. Various bases for classification are discussed. Visual inspection of two-dimensional cross-sections of the feasible parameter region (the region within the parameter bounds) is found to be most satisfactory for the tolerance-test records. Classification by distance between centroids of the cross-sections is found not to work for these records.
The contractile component of muscle models represented by a 'black-box' which is always associated with the Hill's empirical force-velocity relation, is shown to be equivalent to a system composed of a con...
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The contractile component of muscle models represented by a 'black-box' which is always associated with the Hill's empirical force-velocity relation, is shown to be equivalent to a system composed of a contractor in series with a viscous damper, combining the contractile and viscous properties of heart muscle. The validity of the prosed model for the contractile element is studied in Maxwell's model, for isometric contractions by computer simulation technique, using the experimental results of Sonnenblick on cat papillary muscle. The model, although simple, faithfully reproduces the experimental force-velocity and force-time curves of isometric contractions. Effects of positive inotropic interventions on heart muscle performance are considered, and the model shown to accommodate the various states of contractility, by altering the contractile element parameters and the stiffness of the series elastic element in the model.
A speculative proposal that the physiological explication of the control of pulmonary ventilation in the mammal is made coherent and consistent with most physiological observation if the control conceptualization is f...
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A speculative proposal that the physiological explication of the control of pulmonary ventilation in the mammal is made coherent and consistent with most physiological observation if the control conceptualization is formulated around the notion that air flow is the real part of an analytic time varying signal. The instantaneous amplitude and phase of the signal correspond to depth and rate of breathing. The waveform treated as a hybrid modulated waveform is demodulated by a chemosensitive neuron functioning as a phase and amplitude detector by postulating electrochemical properties commonly attributed to excitable cells. The microscopic anatomy of a chemoreceptor also adds positive and negative feedback mechanisms such that there are at least three inner control loops active in addition to the overall ventilatory control loop. Isocapnic control may lie in this structure.
Models able to describe the events of cellular growth and division and the dynamics of cell populations are useful for the understanding of control mechanisms and for theoretical support for the automated analysis of ...
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Models able to describe the events of cellular growth and division and the dynamics of cell populations are useful for the understanding of control mechanisms and for theoretical support for the automated analysis of flow cytometric data and of cell volume distributions. This paper reports on models that have been developed by the authors with this aim, describing in a rather unitary frame the cell cycle of eukaryotic cells, like mammalian cells and yeast, and of prokaryotic cells. The model is based on the assumption that the progression of the nuclear division cycle is regulated by a sequential attainment of two threshold protein levels. It accounts for a number of features of cell growth and division in population of actively growing cells, it explains all the different patterns of cell cycle which are experimentally found and yields quantitative relations between timing of the cell cycle and macromolecular composition of the cells.
The simulation of a physiological system involves the construction of a model, generally in the form of mathematical equations, the manipulation of this model to obtain the solution of the equations, and finally the i...
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The simulation of a physiological system involves the construction of a model, generally in the form of mathematical equations, the manipulation of this model to obtain the solution of the equations, and finally the interpretation of the result. In a qualitative simulation, in a certain sense, we go directly from the real system to the interpretation without use of the mathematical model. This approach was introduced using artifical intelligence techniques, where we try to reproduce a human reasoning explaining the behavior of the physical system. The main goal of the work is to present a methodology, based on bond graphs, and the causal stroke algorithm (CASA) to obtain the antecedent and consequent of rules, model that explains the functioning of a physiological system. To illustrate the methodology, a qualitative dynamic compliance model of a ventricle is discussed.
Because of non-optimal glycemic control, many type I diabetic patients on non-feedback controlled insulin regimes are subject to life-threatening secondary complications. Therefore, to assist both closed-loop and open...
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Because of non-optimal glycemic control, many type I diabetic patients on non-feedback controlled insulin regimes are subject to life-threatening secondary complications. Therefore, to assist both closed-loop and open-loop (pumps, injections) insulin therapy, an appropriate computer-aided procedure was developed and verified. It comprises the following components: (1) a manageable and validated model of the glucose-insulin system, (2) a test procedure for identifying the metabolic situation of an individual patient in terms of the model, (3) a method of estimating (a) the pharmacokinetics of insulin on any route of application and (b) the absorption profiles of ingested glucose equivalents, and (4) computer-aided procedures of prospective simulation of glycemic profiles around the day under the influence of stipulated therapeutic regimes.
A review is given of our investigations and experiences with self-tuning control of blood pressure during surgery. Phenylephrine infusions were used for restoration and maintenance of normal arterial pressure during e...
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A review is given of our investigations and experiences with self-tuning control of blood pressure during surgery. Phenylephrine infusions were used for restoration and maintenance of normal arterial pressure during epidural analgesia in lower abdominal surgery. Sodium nitroprusside infusions or inspired concentrations of the volatile anaesthetic agent isoflurane were used for inducing hypotension during plastic, neuro or ENT surgery. The approach was based on the generalized minimum-variance self-tuning controller of D.W. Clarke and P.J. Gawthrop. Recursive least-squares type estimation of controller parameters was performed, latterly with a restricted exponential forgetting identification technique to provide a more adaptive algorithm.
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