PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “computational modelling”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,117 records · Page 62Linked to original sources
PubMed1977

Model computation of the effect of arbitrary variations in aqueous inflow, outflow conductance, ocular rigidity and episcleral vein pressure on ocular pressure.

Model calculations of the time course of the intraocular pressure are performed in cases where the four determinants mentioned in the title vary, singly or simultaneously, according to specified time functions. Assumptions are 1) that the outflow of the aqueous humor is proportional to the driving pressure, and 2) that the intraocular pressure and volume are related to each other as described by Friedenwald. The mathematical solution if numerical and involves the repetition of the same calculatory step process. It is rendered probable that the maximal inhibitory effect of acetazolamide on the secretion of aqueous humour is reached in less than one minute after the drug has reached the receptors. A programmable calculator with 224 storage locations is used, the programs are given.

Acetazolamide↗
PubMed1989

Computer modeling of membrane-anchored cellular and viral proteins: organization and function.

1. Although secondary structure predictions are only 60% correct, the computer programs provide some idea as to peptide conformation. 2. The detection of hydrophobic domains in membrane-bound proteins allowed the identification of membrane insertional domains in the polypeptide. 3. A combination of computer analyses of protein conformation and the identification of functional domains in polypeptides must be substantiated by experimental data. 4. Computer analyses of membrane proteins may provide a theoretical approach to the selection and development of antibiotics capable of interfering with the insertion and function of viral proteins in cellular membranes.

Algorithms↗
PubMed2003

[Negative selection and computer models of the joint evolution of the patterns of polygenes, transposable elements, and origin identity labels].

Computer simulation of the population dynamics of the genomic patterns of polygenes, transposable elements (TEs), and origin identity labels (OILs) in the course of negative selection for an additive quantitative trait has been performed. It was demonstrated that active polygene alleles disappear very rapidly, whereas the patterns of TEs and OILs continue their evolution determined by strict selective inbreeding and gene drift. Dendrograms of the patterns of polygenes, TEs, and OILs were constructed for all generations. It was demonstrated that the final consensus pattern of OILs consists of the fragments of the original patterns, which contain neither active polygene alleles nor modifier or marker TEs. Neutral TE copies were present in the final pattern, as should be expected in the case of gene drift. Inbreeding coefficient increased steadily but by generation 100 reached values higher than 0.9. All other parameters and initial conditions being the same, the responses to negative and positive selections were asymmetric.

Animals↗
PubMed1994

Computer modelling of polymer decomposition by active interactions with enzyme molecules. A simulation of RNA digestion by ribonuclease.

A model of 200 polymer molecules each 70 units of length with randomly located susceptible and resistant links was elaborated. The production of mono-, di-, tri-unit and other fragments in repeating random interactions of polymer (P) with the polymer--cleaving enzyme (E) was calculated. Analysis of the calculations performed that the polymer molecules with an initial count of 70-units disappeared, imitating the first order kinetics with a half-life of about 0.37 x 10(3) P/E interactions. The production of fragments 30-69 units long was small and the life of those molecules was limited to a range from 0.5 x 10(3) to 5 x 10(3) P/E interactions. The mean polymer length decreases to one third at 10(3) P/E interactions. The production of single-unit fragments followed a sigmoidal relationship. The first reaction period, with increasing number of single-unit fragments per 10(3) P/E interactions, corresponded to a decrease in the mean polymer length to about 10 units. Then the production of one-unit fragments decreased and stopped at about 10(5) P/E interactions. This model could be used for analysis of RNA fragmentation processes by any number of RNA-ribonuclease interactions. Further development of this model would be of help in understanding the effect of various nucleotide sequences on the RNA digestion process.

Animals↗
PubMed1996

A computer model of the visual cortex.

A three-layered simulation of the visual cortex was constructed, receiving inputs from 252 retinal photoreceptors. Lateral geniculate body was taken as a simple relay station. In the cortical module afferent neurons with circular receptive fields, orientation selective simple cells, tuned complex cells, excentricity neurons and different kinds of inhibitory neurons were included. The model reproduces neuronal and network responses recorded in experiments and some sensory illusions, of which one is here demonstrated.

Afferent Pathways↗
PubMed2001

Computer modeling and simulation of human movement.

Recent interest in using modeling and simulation to study movement is driven by the belief that this approach can provide insight into how the nervous system and muscles interact to produce coordinated motion of the body parts. With the computational resources available today, large-scale models of the body can be used to produce realistic simulations of movement that are an order of magnitude more complex than those produced just 10 years ago. This chapter reviews how the structure of the neuromusculoskeletal system is commonly represented in a multijoint model of movement, how modeling may be combined with optimization theory to simulate the dynamics of a motor task, and how model output can be analyzed to describe and explain muscle function. Some results obtained from simulations of jumping, pedaling, and walking are also reviewed to illustrate the approach.

Bone and Bones↗
PubMed1986

Cox's regression model: computing a goodness of fit statistic.

A simple test for goodness of fit of the proportional hazards regression model has recently been proposed. This article indicates how a large number of programs in current use to fit this model can be easily adapted to incorporate this goodness of fit statistic.

Clinical Trials as Topic↗
PubMedDate not supplied

Anastomoses between bronchial and coronary circulation in a porcine model: computed tomographic and angiographic demonstration.

INTRODUCTION: Although the importance of the bronchial arteries is evident in modern day thoracic surgery, the significance of their communications with coronary arteries has yet to be appreciated, especially in cases of heart-lung transplantation and aortic aneurysm repair. We conducted a study to demonstrate the coronary-bronchial anastomotic routes in a porcine model using angiography and computed tomography. METHODS: Six young female white pigs were used. The heart and lungs were removed en bloc, including the lower trachea and oesophagus. Digital subtraction angiography of the bronchial circulation and spiral computed tomography scan were performed in a three-phase study before and after administration of contrast medium. This was achieved by infusion either into the cannulated bronchial artery or into the aortic root. Macroscopic evaluation was carried out using latex infusion into the bronchial or coronary circulation. RESULTS: We demonstrated communications between the bronchial and coronary systems in 5 of 6 subjects. This communication was located at the left atrial wall and the posterior and anterior wall of the left ventricle. In one case there were further anastomoses around the right atrial wall. CONCLUSIONS: There were communications between the left coronary arteries and the bronchial arteries in the majority of cases. Digital subtraction angiography and spiral computer tomography scan can demonstrate these communications directly and indirectly by measurements of contrast enhancement within the heart wall. Our study emphasises the importance of the bronchial arteries in cases of heart-lung transplantation and repair of thoracic aortic aneurysms.

Angiography, Digital Subtraction↗
PubMed1991

Computer modeling and functional evaluation of Venturi flow generators for use in ventilators.

A Venturi has been traditionally used for liquid and gas flow measurements based on Bernoulli and Venturi principles. Application of Venturi as a flow generator in a mechanical ventilator was limited to being a secondary source of flow or configured to compress flexible bags. The main reason for this level of utilization is the considerable flow deterioration of flow output under respiratory system load. A method was hence sought to probe into the possibility of using a Venturi device as the main flow generator with onload flow compensation. The Venturi was mathematically modeled to incorporate the three possible control variables which are controls of jet diameter, entrainment port size and the working pressure of the gas to be entrained. A set of experimental data were then quantitatively compared and evaluated with the results of computer simulation of the TUTSIM model of the system under equivalent conditions. The nature of the results can open up a range of different automatic control schemes and their practical implementation.

Computer Simulation↗