A computer simulation study of cortical imaging from scalp potentials

In this paper, computer simulation studies were conducted to test the feasibility of imaging brain electrical activity from the scalp electroencephalograms. The inhomogeneous three-concentric-sphere head model was used to represent the head volume conductor. Closed spherical dipole layers, consisting of several thousand uniformly distributed dipoles, were used to reconstruct the cortical potential maps corresponding to neuronal sources located inside the brain. Simulation results indicate that the present procedure can image both cortical and deep sources, and for the cortical sources, a spatial resolution as high as 1.2 cm can be achieved.     

Implications of fertility patterns in the Republic of Korea: a study by computer simulation

Implications of various fertility patterns in the Republic of Korea (ROK) are studied by computer simulation. These patterns include the factors: age of marriage, sex preference, abortion (induced), contraception and sterilisation. As a result of studying a large number of combinations of these factors, the following tentative conclusions, among others, are reached. If future cohorts of women in the ROK become limiters after two live births and marry according to an observed high level marriage distribution, at least two of the methods of birth control--abortion, contraception, and sterilisation--will have to be used extensively to yield a mean number of live births (MNLB) in these cohorts of the order 2-2. However, if these women marry later than the observed high level marriage distribution and, in addition, accept effective methods of contraception more widely and use them more effectively, then the MNLB experienced by these cohorts could move below 2-5 wihtout the extensive utilisation of abortion and sterilisation.     

Role of back-diffusion studied by computer simulation

The solidification of Fe-Cr-C alloys was simulated with a program that allowed realistic treatment of diffusion in the liquid and the primary solid phase. It interacts with a thermodynamic databank and can evaluate the heat extraction continuously. Solidification under a constant rate of heat extraction can be simulated. In agreement with previous experience, diffusion of carbon in the fcc phase was found to be very effective, and it can be approximated by an infinitely fast diffusion. The same holds for carbon and chromium in the liquid. The back-diffusion of chromium in the fcc phase was examined in detail. Three different geometries were tested: the planar and cylindrical cases, as well as a new model based on two coupled cylinders. The simulation program allowed the effect of back-diffusion after the end of solidification to be included, and it was found to be important for the segregation ratio.     

A computer simulation of strength of metal matrix

The deformation and fracture behavior of metal matrix composites with a reaction layer at the fiber-matrix interface was studied by means of a computer simulation experiment, using a two-dimensional model, and the results of the simulation experiment were compared with the predictions based on the single fiber model, which has been proposed to describe the reduction of strength of composites due to a reaction layer. In the simulation experiment, the composite was regarded as an assembly of single fiber elements, in which, for each element, the reaction layer introduces a notch on the fiber surface when it is broken, which reduces the strength of the fiber if the thickness of the layer is thinner than a critical value, as has been studied by using the single fiber model. The strength of composites was reduced with increasing thickness of the reaction layer and the fracture mode became catastrophic. The strength values obtained by the simulation were equal to those based on the single fiber model only when the fracture of the fiber was caused by the extension of the notch having been introduced by premature fracture of the reaction layer. In other cases, the strength values of the simulation were lower than those predicted by the single fiber model, although the single fiber model gave approximate values.     

A computer simulation of jury decision making.

A computer simulation of jury decision making is described and evaluated in terms of its ability to account for findings in 2 empirical studies. The computer model is based on elementary assumptions about the effects of relative jury faction sizes and variability in juror resistance to persuasion. The model is used to simulate decision making in empirical studies based on a murder case and a rape case. In the simulation of the 1st study, the model's performance is compared to empirical results from 6- and 12-member juries using unanimous and nonunanimous decision rules. Criteria to evaluate the model's performance are distributions of verdicts, deliberation times, rates of juror vote changing, and reversals of 1st-ballot majorities. The evaluation results support the theory underlying the model. (61 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A computer simulation on tensile strength of surface-Damaged fibers

The strength of surface-damaged fibers was studied by means of a computer simulation experiment based on the Monte-Carlo method using a simple model which assumes that the surface flaws can be regarded as mode I notches on fiber surfaces, the strength of undamaged fibers obeys the Weibull distribution function, and the largest flaw determines the strength of damaged fibers. Normal and exponential distribution functions were taken as the flaw size distribution function. By employing the present simulation method, the effects of average flaw size, coefficient of variation of flaw size, density of flaws, and gage length on average strength and its coefficient of variation were studied. It was found that the surface-damaged fibers can retain their full strength only when the average flaw size is small, the coefficient of variation of flaw size is small, density of flaw size is low, and gage length is short. Otherwise the average strength of damaged fibers was reduced seriously. It was emphasized that the scatter of size of flaws and density of flaws strongly affect the strength of fibers as well as flaw size and gage length.     

High incidence of mutations of the p53 gene detected in ovarian tumours by the use of chemical mismatch cleavage

The susceptibility of complement-deficient individuals to various severe infections, and studies of the effector mechanisms involved in the destruction of infectious agents, demonstrate the importance of complement in providing an effective host defense system. It is also becoming increasingly apparent that complement not only plays a role in 'natural' defenses against infection and in enhancing the antibody-mediated effector mechanisms, but also influences adaptive immune responses directly.     

Affiliation structures in groups of young children: A computer simulation.

A computer program is described that simulates the emergence of affiliation networks in preschool groups and examines theoretical issues raised by the model, including general issues of validation. The simulation implies that triadic interactions, although observed in preschool groups, are not essential in the formation of affiliative structures (contra F. Strayer and J. Noel, 1986) and that, in this age range, therefore, polyadic friendship groupings can be understood as sets of dyadic relationships. The model also demonstrates how group structures can be generated without reference to group-level processes (contrast W. Hartup, 1983). It also focuses attention on the role played by preference formation in social isolation, by demonstrating that inhibition of preferences can give rise to isolation. The model also suggests that social outcomes are best described by nonlinear functions (cf. W. Roberts; see record 1987-03785-001). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Three-dimensional computer reconstruction of prostate cancer from radical prostatectomy specimens: evaluation of the model by core biopsy simulation

OBJECTIVES: A technique was developed for three-dimensional (3D) modeling of prostate cancer and transrectal biopsies. To test the model, the cancer yield of a simulated 10-biopsy protocol was compared with a simulated sextant protocol and with preoperative biopsies regarding cancer detection and correlation with tumor volume. METHODS: Transrectal ultrasound-guided core biopsies were taken from 81 men according to a standardized 10-biopsy protocol that included sextant biopsies. The patients underwent radical prostatectomy and specimens were step-sectioned and whole-mounted. Cancer and the prostate capsule were outlined on the slides and the regions transferred to a computer software program developed by our group. A 3D volume of each prostate was reconstructed from the sections. Virtual core biopsy needles imitating the positions of the real biopsies were inserted into the prostate and the cancer yield was calculated. Only the standardized positions were considered in this study (ie, additional biopsies from hypoechoic foci were not accounted for). RESULTS: Of the cancers detected with 10 standardized virtual biopsies, 24% would have remained undetected with sextant biopsies. The cancer yield of 10 virtual biopsies correlated with the preoperative biopsies (r = 0.64) and with the tumor volume (r = 0.56). A multiple regression analysis showed that the cancer yield of a simulation of 10 biopsies correlated better with tumor volume than did a simulation of sextant biopsies (P = 0.02). CONCLUSIONS: We conclude that computer-assisted 3D reconstruction of prostate cancer can be used as a model for evaluation and optimization of biopsy protocols.