Biomedical subjects

János Tóth

Publications and source records attributed to János Tóth.

4 recordsLinked to original sources

PubMed2006

Polydispersed O/W emulsions in porous media: segregation at low-tension conditions.

The segregation of polydispersed oil was studied in theoretical models, sand packs, and plugs from consolidated cores at low tension and atmospheric conditions. The height of the oil belt formed at the top of the porous column and its change in time were measured. The analysis of the segregation curves indicates the subsequent appearance and rise of three pseudo-phases. The primary phase, which contains the dominant fraction of oil in the system, rises with a relatively high steady state velocity. Unsteady state and decreasing velocity characterize the transitional secondary phase which is a lean emulsion left behind. The ternary phase, which follows it with a semi-steady state low velocity, is a lean emulsion of the smallest oil blobs present in low concentration. The process terminates at the segregation of the mobile oil particles in the subsequent phases where a small fraction of the total oil content remains in the porous bed, mainly from the last stage of segregation due to the entrapment in suitable microstructures. According to the postulated mechanism, the decreasing probability of the repeated coalescence in pore bodies and dispersion at the connecting pore throats are responsible for the development of the mobile phases at the sufficiently low-tension conditions. The structure of the pore network, the size-distribution of the oil droplets, the density of their population, and the length of paths affect the mechanism, properties, and behaviour of the systems.

Journal Article↗

PubMed2005

[Primary prevention program of the Hungarian Spine Society--Part II. A prospective controlled study of exercises for the improvement of posture].

INTRODUCTION: The primary prevention program of the Hungarian Spine Society is set around 12 test exercises that assess performance of postural muscles and then develops their strength and flexibility. By this the scheme aims to make the biomechanically correct use of the spinal column spontaneous. SUBJECTS AND METHODS: The application of the scheme in the frame of physical education in a primary school was investigated in a prospective controlled study in the school-year of 2001/2002. Participating children were aged 6 to 14. The intervention group (n=200) regularly did the posture correction exercises with their teacher's direction in physical education classes, while the control group (n=213) did not. The 12 test exercises of the posture correction scheme of the Hungarian Spine Society were tested by an independent physiotherapist at the beginning and at the end of the school-year in both groups. Results were analyzed by paired and unpaired t-tests and by a chi-square test. RESULTS: At the end of the school-year the strength and flexibility of the postural muscles of the intervention group improved significantly compared both to their own performance (p<0.01) at the beginning of the school-year and to the control group. Test results of the control group were significantly (p<0.05) worse at the end of the school-year than their own results at beginning of the school-year, and were more significantly (p<0.01) worse than the test results of intervention group. CONCLUSION: The results of the controlled study confirm that regular use of the preventive exercises in physical education improves the strength and flexibility of postural muscles. In order to analyze the results concerning specific muscle groups or age groups a detailed study with age- and gender-matched controls will be necessary.

Adolescent↗

PubMed2005

Lumping in pharmacokinetics.

Pharmacokinetic (PK) models simplify biological complexity by dividing the body into interconnected compartments. The time course of the chemical's amount (or concentration) in each compartment is then expressed as a system of ordinary differential equations. The complexity of the resulting system of equations can rapidly increase if a precise description of the organism is needed. However, difficulties arise when the PK model contains more variables and parameters than comfortable for mathematical and computational treatment. To overcome such difficulties, mathematical lumping methods are new and powerful tools. Such methods aim at reducing a differential system by aggregating several variables into one. Typically, the lumped model is still a differential equation system, whose variables are interpretable in terms of variables of the original system. In practice, the reduced model is usually required to satisfy some constraints. For example, it may be necessary to keep state variables of interest for prediction unlumped. To accommodate such constraints, constrained lumping methods have are also available. After presenting the theory, we study, here, through practical examples, the potential of such methods in toxico/pharmacokinetics. As a tutorial, we first simplify a 2-compartment pharmacokinetic model by symbolic lumping. We then explore the reduction of a 6-compartment physiologically based pharmacokinetic model for 1,3-butadiene with numerical constrained lumping. The lumping methods presented here can be easily automated, and are applicable to first-order ordinary differential equation systems.

Algorithms↗

PubMedDate not supplied

Dynamic modeling of biochemical reactions with application to signal transduction: principles and tools using Mathematica.

Modeling of biochemical phenomena is based on formal reaction kinetics. This requires the translation of the original reaction systems into sets of differential equations expressing the effects of the various reaction steps. The temporal behavior of the system is obtained by solving the differential equations. We present the main concepts on which the formal approach of these two problems is based and we show how the amount of work needed to treat them can be significantly reduced by using a mathematical program package (Mathematica). Symbolic and numerical calculations can be performed with the programs presented and graphic presentations of the behavior of the system be obtained. The basic ideas are illustrated with three examples taken from the area of signal transduction and ion signaling.

Kinetics↗