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Objective Comparing the performance of the two nonparametric Bayesian methods for benchmark dose estimating under different dose response data,then comparing them with traditional parametric methods.Methods Introduce the basic principle of the nonparametric Bayesian method based on weighted process and stochastic process separately,then compared the estimations through simulate study and instance analysis.Results The simulate study shows that the posterior estimates were reasonably close to the target true BMD value for the two nonparametric methods,and NBP2 is more desirable compared to NPB1.The nine examples indicate that the BMD estimates from the nonparametric approaches generally fall into or very near the interval of those obtained from BMDS and nonparametric approaches tend to produce lower BMDLs than the parametric modeling approaches.Conclusion The posterior estimates were reasonably close to the target true BMD value for the two nonparametric methods,especially when standard parametric models fail to fit to the data adequately.The NPB2 method is slightly bet-ter than the NPB1 method in the aspect of estimation result and the software operation speed.
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Objective To explore postural stabilization of visual feedback to human body and its mechanisms. Methods Displacement of the center of pressure (COP) of 12 healthy young adult volunteers were investigated under upright posture with and without visual feedback conditions. The Brownian motion model was employed to compare the differences in diffusion coefficients, Hurst exponents, and critical points of the COP trajectories under the above two conditions, and one way repeated measures ANOVA was utilized to test the significance of these differences. ResultsUnder the visual feedback condition, in long-term time intervals, diffusion coefficients were reduced by about two thirds and Hurst exponents reduced by half; in short-term time intervals, no significant differences were found in diffusion coefficients in the medial-lateral (ML) direction and in Hurst exponents; in addition, the coordinates of the critical points presented no statistically significant differences in the time intervals except for the mean square displacement in the anterior posterior (AP) direction. ConclusionsVisual feedback enhances the closed-loop control mechanism of postural control, while it does not have great impact on the open-loop control mechanism and transitional characteristics of the two mechanisms; moreover, the effect of visual feedback on postural control in AP direction is more obvious than that in ML direction.