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PubMed1976

Computer simulation of the effects of errors in birth registration on age-dependent anthropometric methods.

In developing countries birth registration is likely to be delayed, leading to official ages which systematically underestimate the true ages. A computer simulation showed that such official ages underestimate the incidence of malnutrition in a community and lead to misclassification of the nutritional status of many subjects. These errors are more marked below than above 2 years of age. Estimation of the mean delay and its addition to the official ages led to improvement of the results. Above 2 years such estimated ages gave acceptable results; below that age the results were still not acceptable. It is suggested that one method of improving age estimates in large scale anthropometric studies in areas where birth records exist might be to carry out a preliminary survey to estimate the"mean delay in registration. This mean dealy would be added to all official ages and results above 2 years would be accepted. Below 2 years the estimated birth date would be used as a starting point from which the true birth date can be obtained by careful questioning of the parents. Anthropometric results referred to the ages so obtained would give better results than those of uncorrected ages or age-independent anthropometric methods.

Age Factors↗
PubMed2005

A molecular dynamics computer simulation study of room-temperature ionic liquids. I. Equilibrium solvation structure and free energetics.

Solvation in 1-ethyl-3-methylmidazolium chloride and in 1-ethyl-3-methylimidazolium hexafluorophosphate near equilibrium is investigated via molecular dynamics computer simulations with diatomic and benzenelike molecules employed as probe solutes. It is found that electrostriction plays an important role in both solvation structure and free energetics. The angular and radial distributions of cations and anions become more structured and their densities near the solute become enhanced as the solute charge separation grows. Due to the enhancement in structural rigidity induced by electrostriction, the force constant associated with solvent configuration fluctuations relevant to charge shift and transfer processes is also found to increase. The effective polarity and reorganization free energies of these ionic liquids are analyzed and compared with those of highly polar acetonitrile. Their screening behavior of electric charges is also investigated.

Journal Article↗
PubMed1986

Evaluation of the effect of variability in the volume of distribution of theophylline on the predictability of the iterative and the Chiou methods using computer simulations.

The effect of variations in the volume of distribution on the precision of the ability of two methods--the Chiou and the iterative--to predict the total body clearance (TBC) of theophylline was evaluated utilizing computer simulations. Pharmacokinetic data [volume of distributions (V), elimination constants (k)] measured in a group of 55 adult bronchitic patients were utilized to conduct the simulations. An average V of 0.45 L/kg was utilized to calculate TBC with the Chiou and the iterative methods. Separate simulations were conducted utilizing initial (C1) serum concentrations of 2 and 10 micrograms/ml. At the C1 = 2 micrograms/ml condition, the iterative method was statistically significantly more precise (mean squared prediction error, 379.5 vs. 508.5). There were no differences when the initial serum concentration was 10 micrograms/ml under the simulated conditions. At the lower initial condition (C1 = 2) the mean prediction error was 62.3 and 54.9% for the Chiou and the iterative methods, respectively, and it ranged from 0 to 477%. It is recommended that caution be utilized when theophylline doses are individualized using these methods.

Adult↗
PubMed2006

Computer simulation and validation of the Archimedes Lever hypothesis as a mechanism for aortic isthmus disruption in a case of lateral impact motor vehicle crash: a Crash Injury Research Engineering Network (CIREN) study.

OBJECTIVES: Can aortic isthmus disruption occurring in a lateral motor vehicle crash (LMVC) be explained by the Archimedes Lever Hypothesis, where the intrathoracic aorta, super-pressurized by the thoracic impact force, functions as a rigid lever system? The long arm of this lever system is the proximal aorta-aortic arch, the short arm is the aortic isthmus fixed distally at the descending aorta, and the fulcrum is at the great vessels, especially the left subclavian artery. METHODS: The theory was tested by a simulation technique using a computer-based finite element numerical model system. This simulation model included the dynamics of the crashed vehicles, the direction of force impact, and the structure of the thorax and intrathoracic viscera, including the entire intrathoracic aorta. The specific patient whose data were entered into the model was chosen from a study of 34 LMCV aortic injuries (AIs). The model was constrained by patient and vehicle data from this surviving case. RESULTS: Three sequential lateral thoracic levels impacted by the vehicle side structures were selected. At each level, the maximum mean intra-aortic pressure was 50 to 100 ms after impact, the structure dynamics of the actual crash and the resultant vehicle deformation were simulated; only when the lateral impact was induced in a transverse plane including the first 4 ribs at the level of the aortic arch/isthmus system, with intra-aortic pressures from 200 to 500 mm Hg, were AI-compatible stresses and deformations in the aortic wall achieved at the isthmus. CONCLUSIONS: In LMVC AI, the simulation suggests that the aorta functions as an Archimedes Lever System in which the magnified force mediated by the long lever arm produces sufficient strain on the short lever arm to rupture the aorta at the isthmus.

Accidents, Traffic↗
PubMed1983

[Comparison of variability (STV and LTV) indices by computer-simulated data].

Many investigators have proposed their own formula for quantitative evaluation of STV (short term variability) and LTV (long term variability). There has even been confusion over the definition itself of STV. We compared those indices by using 'beat to beat interval' computer-simulated series and found that there is little difference between the STV indices. According to the definition of STV by the Japan Society of Obstetrics and Gynecology, it is the variance in beat to beat difference, which is determined by the variance in beat to beat intervals and the autocorrelation function of the same intervals. For all the 2,500 combinations of the variability and the autocorrelation, normal random interval series were generated by the computer and five indices (Dalton, Cabal, Yeh, Heilbron and de-Haan) were compared with calculated index values using these interval series. Assigning the variability and the autocorrelation to the X-axis and the Y-axis respectively, the Z-axis was used to indicate the value of the STV. Five curved surfaces thus formed have a similar shape, which shows us that these STV indices behave the same way in accordance with the change in STV. Further, the study of LTV indices with the same simulated data showed that Yeh's LTV index indicates only the variability but has no relation-ship with the autocorrelation and both de-Haan and Heilbron's LTV indices represent the variability and the autocorrelation. However, they increase as the autocorrelation increases unlike the STV indices.

Computers↗
PubMed1985

Computer simulation of the P31 NMR equations governing the creatine kinase reaction.

A method for solving the Bloch equations that govern magnetization transfer NMR experiments is presented. It requires the numerical evaluation of a matrix exponential and lends itself to computer simulation. It is a simple, versatile method for evaluating P31-NMR magnetization transfer experiments designed to measure biochemical exchange rates. We apply the method to the saturation and inversion transfer experiments and find that the "initial slope" method of determining flux is subject to at least two interpretations. This verifies the accepted concept that biochemical models representing compartmentation and competing reaction hypotheses cannot be reliably distinguished by simply selecting values for NMR and biochemical parameters that give a "best fit" to experimental data. However, our results do indicate that a controlled manipulation of biochemical exchange rate may distinguish between these two models.

Adenosine Triphosphate↗
PubMed2000

Acute response to precision, time pressure and mental demand during simulated computer work.

OBJECTIVES: The electromyographic (EMG) activity of shoulder and forearm muscles was recorded during a standardized computer task with different combinations of time pressure, precision demands, and mental demands to study the interaction of these factors and their effect on muscular response during simulated computer work. METHODS: The computer task lasted 5 minutes, and it was performed by 14 female computer-aided design (CAD) operators during 8 exposure combinations that differed with respect to time pressure, precision demand, and mental demand. Performance (number of produced drawings, mouse clicks, and errors) were recorded. The EMG activity was recorded from the trapezius, infraspinatus, deltoid, and extensor digitorum muscles. An electrogoniometer was used to measure wrist postures and movements. RESULTS: High time pressure (combined with low precision and low mental demands) resulted in higher EMG activity for all the muscles and in a small increase in the number of produced drawings. High precision demands caused a large reduction in the number of produced drawings, but not always a change in EMG activity. High precision demands and high mental demands led to no change or a reduction in muscle activity because the number of drawings was greatly reduced. CONCLUSIONS: The interaction between work pace and other exposure factors must be taken into account when the effects of changes in exposure demands on muscular response are predicted. Only then can it be predicted whether changing demands will constitute a risk of developing musculoskeletal disorders.

Adult↗
PubMed2003

'Six-beam X-ray section topograph' images and computer-simulated images using the new n-beam dynamical theory based on the Takagi-Taupin equations.

A 'six-beam X-ray section topograph' experiment was performed whose images are in excellent agreement with the images computer-simulated using the theory derived by one of the authors [Okitsu (2003). Acta Cryst. A59, 235-244] based on the Takagi-Taupin dynamical theory. X-rays whose wavefront was limited to 0.1 x 0.1 mm were incident on a [1 1; 1]-oriented floating-zone silicon crystal with thickness of 9.911 mm so that a six-beam condition was satisfied. The six reflection indices were 000 (forward diffraction), 440, 484, 088, 4;48 and 4;04. The plane of incidence of the 088 reflection was adjusted so as to be perpendicular to the direction of the incident horizontal linear polarization of the synchrotron radiation, which was monochromated into 18.5 keV (0.670 A wavelength). While the simulations were performed under the assumptions that the incident X-rays were linearly polarized both horizontally and vertically, they were evidently different and only the simulated images under the assumption of horizontally polarized incident X-rays were in excellent agreement with the images obtained by the experiment.

Journal Article↗
PubMed1986

Computer simulation of mammalian gas-exchange.

Gas exchange efficiency is dependent upon the distribution of ventilation to perfusion throughout the lung, as well as the position and shape of the oxygen and carbon dioxide dissociation curves, and the composition of mixed venous blood. Computer simulation has allowed practical investigation of these relationships. A BASIC program suitable for small microcomputers is presented which calculates the arterial blood gases and gas transport corresponding to an arbitrary VA/Q distribution and mixed venous composition. The needed theory and equations are developed, the program is discussed, and an example is presented.

Carbon Dioxide↗
PubMedDate not supplied

Implementing computer simulations as a strategy for evaluating decision-making skills of nursing students.

This article describes the implementation of a computer assisted instruction clinical simulation, as an evaluation strategy for determining baccalaureate students' clinical decision-making skills. Students' reactions toward this strategy have been consistently positive. Similarly, faculty were satisfied with this method of assessment. Our experience has convinced us that computer simulation is an objective, efficacious, and pragmatic method for measuring students' clinical decision-making skills.

Clinical Competence↗
PubMed1988

Computer simulation of neuronal circuit models of rhythmic behavior in the electroencephalogram.

A computer program for modeling some features of the electroencephalogram (EEG) recorded by scalp electrodes in terms of the time- and space-dependent interactions of populations of neurons in different hypothetical brain configurations was developed. The input of the model consists of: (1) geometric and anatomic data characterizing the brain configuration; (2) physiologic features characterizing neurons; and (3) functions describing the time-dependent afferent impulses to the brain configuration under study. The output of the model consists of plots of selected intracellular and extracellular potentials as a function of time. In application of the model to various brain configurations, some configurations were sufficiently compact spatially that propagation times of action potentials between elements were either taken to be constant or were nearly independent of distance within the accuracy of the calculations. Other configurations represented cerebral cortex alone or a combined thalamocortical system in which many elements interacted via global interconnections. The basic requirement for rhythmic behavior is the existence of circuits containing inhibitory neurons. The characteristic frequencies of rhythmic oscillations are primarily determined by the local circuit parameters and are relatively independent of global circuit parameters.

Action Potentials↗
PubMed2002

Model intestinal microflora in computer simulation: a simulation and modeling package for host-microflora interactions.

The ecology of the human intestinal microflora and its interaction with the host are poorly understood. Though more and more data are being acquired, in part using modern molecular methods, development of a quantitative theory has not kept pace with this increase in observing power. This is in part due to the complexity of the system and to the lack of simulation environments in which to test what the ecological effect of a hypothetical mechanism of interaction would be, before resorting to laboratory experiments. The MIMICS project attempts to address this through the development of a cellular automaton for simulation of the intestinal microflora. In this paper, the design and evaluation of this simulator is discussed.

Bacteria, Aerobic↗
PubMed1980

Computer simulation of ventilatory control by both neural and humoral CO2 signals.

A mathematical model portraying a humoral signal derived from time-dependent variations in arterial carbon dioxide tension (PaCO2) and a neural signal proportional to the metabolic CO2 production was tested by computer simulation. The signals were assumed to enter the central mechanism through afferent pathways connected in reciprocal inhibition. The central mechanism, previously described, contained proportional, gradient, and positive feedback components. The model simulates steady-state isocapnic hyperpnea under endogenous CO2 load and hyperpnea proportional to PaCO2 under exogenous CO2 load. This behavior is consistent whether the neural signal is present alone, the humoral signal is present alone, or both are present and synergistic. When the neural and humoral signals are opposed hypocapnia and hyperventilation ensue; the values being consistent with the isometabolic hyperbola. The model also portrays steady-state behavior when CO2 is inhaled during exercise. During hypometabolic states of rest the mechanism appears to become insensitive to PaCO2 levels.

Carbon Dioxide↗
PubMedDate not supplied

[Use of computer simulation in the study of the nurse's attention to the family].

The purpose of this work was to show the results attained with the application of computer-assisted simulation in the teaching of the subject Familial Nursing Care. The study was carried out at the Julio Trigo López Faculty of Medical Sciences during the second semester of the 1992-1993 school year. Work was based on 35 students of the fourth year of Nursing Degree. Six (6) computer-assisted simulations were elaborated and 2 instruments were created: Opinion Survey and Written Simulation. 82.4% of the students pointed out advantages in using the Simula software; 82,3% said that it improved their knowledge; and most students said that the Simula method was more useful for their final evaluation and had higher feedback.

Computer Simulation↗
PubMed2003

The computer simulation of wear behavior appearing in total hip prosthesis.

Computer algorithms are proposed for the estimation of wear appearing in artificial hip joints using finite element analysis based on the modified Archard's wear law, contact features and an analogue wear process. A pin-on-disk plate experiment is reconstructed to assess the efficiency and validity of the algorithms proposed here. Through the successful verification of wear depth and volume loss of the pin-on-disk plate as well as the artificial hip joint, the current algorithms provide significant agreement with experiments, clinical measurements and numerical calculations and are shown to be both valid and feasible. Further investigation into the effect of femoral heads with various sizes suggests that the larger femoral head may induce larger wear volume but gives a smaller wear depth and that wear depth and volume loss are apparently nonlinearly related to the femoral head diameter. It is shown that the current algorithms are useful and helpful in understanding wear behavior for alternative or new designs of artificial hip joints and even for other analogous structures.

Arthroplasty, Replacement, Hip↗
PubMed2003

Design and synthesis of S-(-)-2-[[4-(napht-1-yl)piperazin-1-yl]methyl]-1,4-dioxoperhydropyrrolo[1,2-a]pyrazine (CSP-2503) using computational simulation. A 5-HT1A receptor agonist.

Based on a computational model for 5-HT(1A)R-ligand interaction and QSAR studies, we have designed and synthesized a new series of arylpiperazines 2-8 which exhibit high 5-HT(1A)R affinity and selectivity over alpha(1)-adrenergic receptors. Among them, compound CSP-2503 (4) has been pharmacologically characterized as a 5-HT(1A)R agonist at somatodendritic and postsynaptic sites, endowed with anxiolytic properties.

Amino Acid Sequence↗