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PubMed1996

A formative model for student nurse development and evaluation--Part 1--Developing the model.

Preparing student nurses for the profession is a complex task for nurse educators; especially when dealing with the development of personal and interpersonal skills, qualities and values held in high esteem by the nursing profession and the community they serve. These researchers developed a model for formative evaluation of students by using the principles of inductive and deductive reasoning. This model was implemented in clinical practice situations and evaluated for its usefulness. It seems that the model enhanced the standards of nursing care because it had a positive effect on the behavior of students and they were better motivated; the model also improved interpersonal relationships and communication between practising nurses and students. The fact that students repeatedly use the model as a norm for self evaluation ensures that they are constantly reminded of the standards required of a professional nurse.

Clinical Competence↗

PubMed1992

A proposed health model: a step before model confirmation.

Health marketers have devoted extensive conceptual and empirical effort toward explaining and predicting individuals' health-related decisions. This paper proposes a health behavior model by combining the health belief model and the theory of planned behavior model. Recent modifications of the Fishbein and Ajzen (1975) model are discussed and an extension is introduced to better explain goal pursuit. These revisions (Bagozzi and Warshaw 1990) are incorporated in the proposed model.

Attitude to Health↗

PubMed1999

New experimental model to study the bone interface of endosseous implants: an in vitro three-dimensional model of cell culture.

To set up a three-dimensional culture model of endosseous implant material-osteoblast, titanium (Ti) discs were placed onto confluent cellular layers of human fetal osteoblasts that were cultured in calcifying conditions. Follow-up observations of living cells with phase-contrast microscopy and histological observations of the cell-Ti disc interface with ordinary microscopy and transmission electron microscopy were used to monitor and verify the formation of three-dimensional cellular structures at the osteoblast-Ti disc interface. These methods were further used to study osteoblast cell behavior during the early stage of bone healing in this three-dimensional cellular model. The follow-up observation showed that, upon the placement of the Ti disc, cells migrated from the cellular layer and attached to the rim of the disc, forming cell bridges. Cells continued to attach and orient throughout the culture time. A cellular multilayer at the osteoblast-Ti interface was formed, which resulted in the three-dimensional model. Furthermore, transmission electron microscopy observation showed that there was a mineralizing process at the osteoblast-Ti disc interface just like bone, which confirms the reality of this model. Histological observations with conventional microscopy demonstrated the interfacial relation between biomaterial and cells. If osteoblasts were replaced by other types of cells, this model could be used to study the other kinds of interfaces.

Cell Adhesion↗

PubMedDate not supplied

[Interactive determination of the parameters of mathematical models for planning radiotherapy of malignant tumors. I. Mathematical models for calculating dose tolerance, adequate doses and the likelihood of development of radiation complications in normal organs and tissues].

Mathematical models for calculating tolerance doses, adequate doses and the likelihood of radiation complications in the body's normal tissues are considered. To determine the parameters of these models that describe the outcomes of radiation exposure of complicated biological systems, a method of local adjustment of the parameters of the models has been developed, which will be described in parts 2 and 3 of the proposed paper. In part 1 (the present paper), particular emphasis is laid on the inclusion of an important parameter, such as a volume, into Ellis and LQ models. A mathematical model is presented for calculating the likelihood of a radiation complication in the tissue, which is the basis for deriving a formula to calculate an adequate uniform tissue radiation dose that is equivalent to the nonuniform tissue distribution of a dose in terms of the likelihood of radiation complications.

Humans↗

PubMed2000

Modeling alcohol's effects on organs in animal models.

Researchers have developed numerous animal models to investigate the development of various alcohol-related diseases. Such models have provided insights into the mechanism through which alcohol can induce liver damage. Animal models also have helped researchers explore the mechanisms by which both short-term (e.g., binge) and long-term drinking can interfere with the function of the heart, a condition referred to as alcoholic cardiomyopathy. Furthermore, animal models have provided substantial information on the causes of fetal alcohol syndrome. Such models have demonstrated that exposure to alcohol during gestation can lead to prenatal and postnatal growth retardation, characteristic facial malformations, immune system deficiencies, and alterations in the central nervous system.

Alcoholism↗

PubMed2001

River Water Quality Model no. 1 (RWQM1): I. Modelling approach.

Successful river water quality modelling requires the specification of an appropriate model structure and process formulation. Both must be related to the compartment structure of running water ecosystems including their longitudinal, vertical, and lateral zonation patterns. Furthermore, the temporal variability of abiotic boundary conditions may be important and must be incorporated by an appropriate choice of model parameters. A six-step decision procedure is proposed to achieve these objectives. The steps address the determination of the following model features: (1) temporal representation (dynamic or steady-state); (2) model dimensionality; (3) mixing; (4) advection; (5) reaction terms; and (6) boundary conditions. Numerical criteria based on process time constants and length scales provide a basis for these decisions.

Decision Making↗

PubMed2001

Modelling of full-scale wastewater treatment plants with different treatment processes using the Activated Sludge Model no. 3.

In 1999 the Activated Sludge Model no. 3 (ASM 3) by the IWA task Group on Mathematical Modeling for Design and Operation of Biological Wastewater Treatment was presented. The model is used for simulation of nitrogen removal. On the basis of a new calibration of the ASM 3 with the easy degradable COD measured by respiration simulation runs of this paper have been done. In 2000 a biological phosphorus removal module by the EAWAG was added to the calibrated version of ASM 3 and is now serving the current requirements for modelling the enhanced biological P-removal. Only little experiences with different load situations of large-scale wastewater treatment plants were made with both new models so far. This article reports the experiences with the simulation and calibration of the biological parameters using ASM 3 and the EAWAG BioP Module. Three different large-scale wastewater treatment plants in Germany with different treatment systems will be discussed (Koblenz: pre-denitrification; Hildesheim: simultaneous denitrification with EBPR; Duderstadt: intermediate denitrification with EBPR). Informations regarding the choice of kinetic and stoichiometric parameters will be given.

Calibration↗

PubMed2002

Development of a Monte Carlo sampling shell for the pesticide root zone model and its application by the Federal Insecticide, Fungicide, and Rodenticide Act Environmental Modeling Validation Task Force.

A user interface to the U.S. Environmental Protection Agency pesticide root zone model (PRZM) was constructed to allow Monte Carlo sampling of input parameter distributions. The interface was constructed employing the Visual Basic for Applications development environment, along with the functionality of the Crystal Ball Professional forecasting and risk analysis package. The tool has been utilized by the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Environmental Model Validation Task Force to perform detailed statistical analyses of model input parameter uncertainty and the propagation of this uncertainty on the model outputs as well as comparisons of modeled and field-measured data.

Environment↗

PubMed1991

A Chinese female postnuptial leaving home model--a procedure for analyzing main parameters alpha and beta in the setting up, testing and estimation of the model.

"The first section of this article...sets up a model for leaving home after marriage that is suited to China's situation. The second section performs a statistical test and verification of the formulated model for leaving home after marriage. The third section...proposes a method for analyzing the main parameters...in the model...." The model is set up along the lines of the Brass-Gompertz relational fertility model.

Asia↗

PubMed2003

[Establishment of a mouse model of cyclophosphamide-induced thrombocytopenia and determination of platelet function in this model].

OBJECTIVE: To establish a mouse model of acute hematopoietic failure and explore the pathological basis of platelet changes in bone marrow suppression. METHODS: An initial large dose of cyclophosphamide (200 mg/kg) was injected through the tail veins of the mice, follow by daily intraperitoneal injection starting on the next day for 7 d. The number and morphology of the cells in the peripheral blood and bone marrow were observed by means of cell counting and smear, respectively, with the platelet aggregation determined using ADP. The coagulation time was measure by turbidimetry. RESULTS: The amount of platelets, erythrocytes, leukocytes and the nucleated cells in mice bone marrow was significantly lowered in the mouse models in comparison with the control mice, and the normal hematopoietic tissues were depressed. The blood platelets in the models were lowered by 49%, an amplitude of declination significantly greater than that occurring in the erythrocytes and leukocytes (by 28% and 25% respectively). Though the mean platelet volume and percent platelet aggregation underwent no obvious changes, the coagulation time was significantly shortened. CONCLUSION: The methods we described for establishing mouse models of hematopoietic failure induced by cyclophosphamide is rapid and highly efficient, and may facilitate ready preparation of mouse models of thrombocytopenia which respond strongly to cyclophosphamide without blood platelets function impairment.

Animals↗

PubMed2004

[The data management of 3D FE model reconstruction based on medical Images and the modeling for T10-T12 thoracic vertebrae].

Setting up the 3D finite element (FE) model on the basis of medical images is a necessary method of biomechanical analysis. The pretreatment, including data processing of images and mesh generation, becomes the bottleneck of FE analysis, and this is especially the case of the modeling for thoracic vertebrae, because the shapes and data are complicated. In this paper, on the basis of the data for building a 3D FE model of thoracic vertebrae, we present some structures and types of data which are essential for the reconstruction of CT medical image, analyze some methods for obtaining and processing the data from images, and then advance a theory for data management based on mesh generation by block with the software MSC. Marc. A 3D-FE Model of T10-T12 thoracic vertebrae is set up, which keeps the configuration of the true one, and satisfies the requirements of biomechanical analysis. We focus affention on the data obtainment and management during medical image processing and FE modeling, all of which are very important for the biomechanical analysis. It is helpful and instructive to reconstruct some similar tissues of human body on the basis of the medical images from CT, MRI, etc.

Biomechanical Phenomena↗

PubMedDate not supplied

Do black-box models of thermoregulation still have any research value? Contribution of system-theoretical models to the analysis of thermoregulation.

The aims and the usefulness of modelling the thermoregulatory system are outlined by demonstrating applications and results of simulation on different levels of complexity. It is shown that both very simple one-loop models and complex models based on spatially distributed parameters have contributed to a better understanding of the system, but that current issues primarily require the latter type. However, mathematical modelling must be performed in conjunction with experimental studies and must be adapted to the amount of basic physiological data. Future fields of modelling are the adaptive mechanisms and the interactions of systems.

Animals↗

PubMedDate not supplied

A pharmacokinetic model for enterohepatic recirculation in the rat: phenolphthalein, a model drug.

A classical compartmental pharmacokinetic model was developed to describe the systemic blood concentration-time profile of phenolphthalein and its glucuronide conjugate (total 3H) following a single intravenous bolus injection of [3H]phenolphthalein. The model incorporates a biliary transport system, including a finite lag time for the biliary phenophthalein glucuronide to be hydrolyzed in the intestine before absorption. Data obtained from bile duct-cannulated animals were fit to the same model excluding any component for intestinal absorption. Agreement between the rate constants obtained for both fits indicates that the model is internally consistent. The model was then used to simulate a 24-hour time-course of phenolphthalein-equivalent blood concentrations which indicates that the long apparent half-lives calculated during this period are artifacts of recirculation.

Animals↗

PubMed1985

The effect of hydrostatic gradient on solvent drag reflection coefficient in heteroporous membranes: differences between model-dependent and model-independent computations.

The accepted reason for apparent increase in solvent drag reflection coefficient (sigma f) with mean hydrostatic pressure gradient (delta p) across a heteroporous membrane is thought to be twofold. First, fractional volume flux traversing small pores (F) is thought to rise as delta p rises. Second, since it is believed that sigma f is directly related to F, then sigma f should rise with delta p to an asymptote. The first feature of a rise in F with delta p to an asymptote was shown to be true for two published two pore models. However, sigma f was closely correlated with F only if sigma f was computed from summation of known components of flux across each pore. If sigma f was computed by a model independent, purely thermodynamic method, then sigma f was not closely tied to F, and approached its asymptote at considerably lower values of delta p than the summation form of sigma f. It is concluded that although F rises with delta p above critical values of delta p, this alone cannot be the cause of a rising sigma f computed by model independent methods. Another explanation, such as anatomic change is required. In addition, model independent methods for computation of sigma f require fewer assumptions, less information and lower pressures than model dependent methods.

Animals↗

PubMed1985

Stochastic model of human granulocyte-macrophage progenitor cell proliferation and differentiation. II. Validation of the model.

In the accompanying paper we constructed a model for the proliferation and differentiation of granulocyte-macrophage progenitor cells in response to the specific proliferation/differentiation stimulus granulocyte-macrophage colony-stimulating activity (gm-CSA). Here we have tested the model without altering the model parameters, which were estimated on the basis of two types of experiment (clone number versus gm-CSA dose-response curves and clone size distributions with maximal gm-CSA) by using these parameters to simulate additional independent experiments. These included data from separation experiments in which progenitor cells were separated on a basis of their density and were then tested for their sensitivity to gm-CSA and their proliferative capacity. In addition, other sets of experimental data (e.g., mean clone size versus time and colony versus gm-CSA dose-response curves and colony-to-cluster ratios) were also examined to detect whether the mathematical model provides an adequate representation of the data. The model gave a successful simulation of all experimental data.

Cell Differentiation↗

PubMed1980

[Choice of the association model of rabbit muscle phosphofructokinase using mathematical modeling].

The sedimentation behaviour of the subform of rabbit muscle phosphofructokinase specifically eluted from DEAE cellulose by citrate was studied in different media by velocity experiments. The measured sedimentation coefficients of different components in the system can be classified into 12 groups, which is indicative of a complex multistep association process of the enzyme (with more than 3 oligomers). The concentration dependence of weight average sedimentation coefficient of phosphofructokinase was a studied. The choice of the probable association model of phosphofructokinase oligomers at low protein concentration was accomplished by means of computer simulation of the association process. Of 26 closed association models tested 14 models with 2 or 3 association constants are indistinguishable in view of Student's t-criterion of significance. All uniparametric association models studied significantly inferior approximate the experimental data. It is supposed that the dimer is not the structural unit of polymerization. Having this in mind and taking into account the demand for the multistep process, one may consider as most probable only 8 models of phosphofructokinase association, namely monomer-dimer-trimer-tetramer-monomer-dimer-tetramer-octamer (with 3 association constants) and linear polymerization up to the octamer with 2 association constants, where the "monomer" of association may be defined as trimer, tetramer or hexamer of subunits.

Animals↗

PubMed1982

Diffusion-controlled reactions of enzymes. A comparison between Chou's model and Alberty-Hammes-Eigen's model.

In the study of enzyme-catalysed mechanisms, it is often necessary to calculate the upper limit of enzyme reaction, which is usually used as an important criterion to identify whether an assumed enzyme-catalysed mechanism is reasonable or not. Basically, in the existing methods, there are two kinds of models, the Alberty-Hammes-Eigen model and the Chou model, for calculating the upper limit of enzyme reaction. In this paper, an analysis and comparison between these two models are made. It is pointed out that the magnitude of the van der Waals' binding energy between enzyme and substrate molecules will play a key role in deciding whether there is a significant difference or not for the results calculated from these two models. Through such a comparison, the role of the major protein outside the active site of an enzyme molecule also becomes obvious; if the van der Waals' binding energy is very small, the major protein will act like a 'wall', blocking the flow of some substrate molecules to the active site; while if the van der Waals' energy is greater than 3 kT (where k is the Boltzmann constant and T the absolute temperature), the major protein will behave like a 'accelerator', speeding up the flow of the substrate molecules to the active site around the enzyme molecule.

Diffusion↗

PubMed1978

Compartment model approach to the estimation of tumor incidence and growth: investigation of a model of cancer latency.

Consideration is made of the problems involved in determining the effects of a chronic disease process, such as stomach cancer, on the observed mortality of the U.S. population. Specifically, since the time of initiation of tumor growth is unknown and the tumor becomes clinically manifest only after reaching considerable size, the early rate and pattern of tumor growth is unobserved. As a possible solution to the analysis of such problems, it is proposed to use stochastic compartment modelling techniques which deal with the problems of estimating the transition probabilities of a partially observed stochastic process. Implementation of the stochastic compartment techniques in this case depends on the selection of certain mathematical expressions from theories of carcinogenesis, epidemiologic studies and animal studies which allow the calculation of transition probabilities to unobserved states by making them explicit functions of time or age. Though the selection of the specific functions might be subject to debate, the general strategy of explicitly selecting such functions, and thereby exposing them for review in terms of biologic reasonableness and consistency with the data, seems to be a valid and useful methodology. Furthermore, various ways of viewing the model results (say from its internal behavior, e.g., from implied distributions of waiting times in various disease states) yield different insights into the various factors in carcinogenesis. The model, with parameters representing tumor incidence, time to tumor death given onset, genetic susceptibility to tumor growth and the effects of competing forces of mortality, is fitted to data on deaths due to stomach cancer for male U.S. residents age 25 and over in 1969. Two basic forms of the model, one with a waiting time distribution for occupants of the latent state and another with a single latency time, achieved excellent fits to the data. Examination of parameter estimates and compartment waiting time distributions are consistent with theoretical expectations and intuition. It is concluded that such strategies, involving the integration of clinical, experimental and vital statistics data into a comprehensive model of population carcinogenesis, are potentially powerful tools for investigation of the temporal dimensions of disease development in a human population.

Adult↗