Application of the Loo-Riegelman absorption method

The Loo-Riegelman absorption method provides the correct A/V₁ value and the correct rate constant k_a (if absorption is first order), whether metabolism occurs in compartment 1 only, compartment 2 only, or both compartments 1 and 2 of the two-compartment open model. In cases where there is metabolism in compartment 2, the disposition parameters estimated from intravenous data are only apparent and not the real values. The correct A/V₁ and k_a values are obtained, however, only under conditions not hithertofore specified. These conditions are that there must be essentially no bias in the disposition parameters k₁₂, k₂₁, and k_el. and in the C₀ value estimated from the intravenous data, and that in the oral study a large number of interpolated plasma concentrations, as well as the observed plasma concentrations, must be used, especially for drugs with long half-lives. It is shown that application of the Guggenheim method to the initial A₁ V₁, tvalues frequently provides a better method of estimating A/V₁ and k_a than the classical method. If biased disposition parameters are used in application of the Loo-Riegelman method to oral data, then essentially the correct value of k_a will be estimated, but the estimate of A/V₁ will be approximately equal to the true value of A/V₁ multiplied by the ratio of the biased C₀ value (obtained in fitting the intravenous data) to the true C₀ value of the intravenous data. The above indicates that intravenous data should be fitted by computer until there are no systematic deviations or trends and as small a sum of squared deviations as possible is obtained. The oral data should be fitted by spline or Akima methods, or similar procedures, to produce a function which passes through each observed plasma concentration and at the same time provides a large number of interpolated concentration data.Partly supported by Public Health Service Grant 5-P11-GM15559.     

Curve interpolation model for visualising disjointed neural elements

Neuron cell are built from a myriad of axon and dendrite structures. It transmits electrochemical signals between the brain and the nervous system. Three-dimensional visualization of neuron structure could help to facilitate deeper understanding of neuron and its models. An accurate neuron model could aid understanding of brain’s functionalities, diagnosis and knowledge of entire nervous system. Existing neuron models have been found to be defective in the aspect of realism. Whereas in the actual biological neuron, there is continuous growth as the soma extending to the axon and the dendrite; but, the current neuron visualization models present it as disjointed segments that has greatly mediated effective realism. In this research, a new reconstruction model comprising of the Bounding Cylinder, Curve Interpolation and Gouraud Shading is proposed to visualize neuron model in order to improve realism. The reconstructed model is used to design algorithms for generating neuron branching from neuron SWC data. The Bounding Cylinder and Curve Interpolation methods are used to improve the connected segments of the neuron model using a series of cascaded cylinders along the neuron’s connection path. Three control points are proposed between two adjacent neuron segments. Finally, the model is rendered with Gouraud Shading for smoothening of the model surface. This produce a near-perfection model of the natural neurons with attended realism. The model is validated by a group of bioinformatics analysts’ responses to a predefined survey. The result shows about 82% acceptance and satisfaction rate.     

A Kernel-Independent Treecode Based on Barycentric Lagrange Interpolation

A kernel-independent treecode (KITC) is presented for fast summation of particle interactions. The method employs barycentric Lagrange interpolation at Chebyshev points to approximate well-separated particle-cluster interactions. The KITC requires only kernel evaluations, is suitable for non-oscillatory kernels, and relies on the scale-invariance property of barycentric Lagrange interpolation. For a given level of accuracy, the treecode reduces the operation count for pairwise interactions from $\mathcal{O}$($N^2$) to $\mathcal{O}$($N$log$N$), where $N$ is the number of particles in the system. The algorithm is demonstrated for systems of regularized Stokeslets and rotlets in 3D, and numerical results show the treecode performance in terms of error, CPU time, and memory consumption. The KITC is a relatively simple algorithm with low memory consumption, and this enables a straightforward OpenMP parallelization.     

面向家庭健康监护的血压监护模块设计

目的:血压是反映人体循环系统机能的重要生理参数,血压的监测在临床和医疗保健中有着重要的地位。本文根据示波法测量人体血压的原理,研制出了一种面向家庭健康监护的血压监护系统。方法:系统采用s3c2440作为数据采集,传输及气动电路的控制核心,算法部分采用三次样条插值法来获取脉搏波包络线,最终通过幅度系数法求得舒张压和收缩压。结果:通过该系统对人体进行测试,并和柯氏音法进行了对比,得到了比较满意的结果。结论:实验结果显示本系统稳定,可靠,误差率小,可适用于家庭健康监护。     

Visual extrapolation of contour geometry

Computing the shapes of object boundaries from fragmentary image contours poses a formidable problem for the visual system. We investigated the extrapolation of contour shape by human vision. Measurements of extrapolation position and orientation were taken at six distances from the point of occlusion, thereby yielding a detailed representation of the extrapolated contours. Analyses of these measurements revealed that: (i) extrapolation curvature increases linearly with the curvature of the inducing contour, although there is individual bias in the slope; (ii) the precision with which an extrapolated contour is represented is roughly constant, in angular terms, with increasing distance from the point of occlusion; (iii) there is a substantial cost of curvature, in that the overall precision of an extrapolated contour decreases systematically with curvature; (iv) the shapes of visually extrapolated contours are characterized by a nonlinear decrease in curvature, asymptoting to zero; and (v) this decaying pattern of curvature is explained by a Bayesian model in which, with increasing distance from the point of occlusion, the prior tendency to minimize curvature gradually dominates the likelihood tendency to minimize variation in curvature.     

Assessment of quadriceps muscle inactivation with a new electrical stimulation paradigm

Introduction: In this study we evaluated the validity of garment‐based quadriceps stimulation (GQS) for assessment of muscle inactivation in comparison with femoral nerve stimulation (FNS). Methods: Inactivation estimates (superimposed doublet torque), self‐reported discomfort, and twitch and doublet contractile properties were compared between GQS and FNS in 15 healthy subjects. Results: Superimposed doublet torque was significantly lower for GQS than for FNS at 20% and 40% maximum voluntary contraction (MVC) (P < 0.01), but not at 60%, 80%, and 100% MVC. Discomfort scores were systematically lower for GQS than for FNS (P < 0.05). Resting twitch and doublet peak torque were lower for GQS, and time to peak torque was shorter for GQS than for FNS (P < 0.01). Conclusions: GQS can be used with confidence for straightforward evaluation of quadriceps muscle inactivation, whereas its validity for assessment of contractile properties remains to be determined. Muscle Nerve 51 : 117–124, 2015     

线性插值法在儿童保健工作质量综合评价中的应用

目的:探讨线性插值法在2012年广西14市儿童保健工作质量综合评价中的应用.方法:选取8个常用于评价儿童保健工作质量的指标,采用线性插值法对2012年广西14市儿童保健工作质量进行综合评价,利用RSR分档法对评价结果进行分档.结果:根据线性插值法计算结果排序及其分档,北海市的儿童保健工作质量综合评价结果最好,平均位次值为0.9468;梧州市的儿童保健工作质量综合评价结果最差,平均位次值为0.450 6;各地区儿童保健工作质量分档合理,有4个市处于质量好的档次,7个市处于质量中等的档次,其余地区处于质量差的档次,各档差异性有统计学意义(P＜0.01).结论:线性插值法结合RSR分档法具有一定的客观性和实用性,可综合评价儿童保健工作质量.     

Spline‐based procedures for dose‐finding studies with active control

In a dose‐finding study with an active control, several doses of a new drug are compared with an established drug (the so‐called active control). One goal of such studies is to characterize the dose–response relationship and to find the smallest target dose concentration d^*, which leads to the same efficacy as the active control. For this purpose, the intersection point of the mean dose–response function with the expected efficacy of the active control has to be estimated. The focus of this paper is a cubic spline‐based method for deriving an estimator of the target dose without assuming a specific dose–response function. Furthermore, the construction of a spline‐based bootstrap CI is described. Estimator and CI are compared with other flexible and parametric methods such as linear spline interpolation as well as maximum likelihood regression in simulation studies motivated by a real clinical trial. Also, design considerations for the cubic spline approach with focus on bias minimization are presented. Although the spline‐based point estimator can be biased, designs can be chosen to minimize and reasonably limit the maximum absolute bias. Furthermore, the coverage probability of the cubic spline approach is satisfactory, especially for bias minimal designs. © 2014 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd.     

Effects of aging and sex on voluntary activation and peak relaxation rate of human elbow flexors studied with motor cortical stimulation

Data are equivocal on whether voluntary activation is preserved or decreased in old compared to young adults. Further, data are scant on the effect of age on the rate of muscle relaxation when the muscle is contracting voluntarily. Assessment of both measures with transcranial magnetic stimulation (TMS) yields information which cannot be obtained with traditional peripheral nerve stimulation. Hence, voluntary activation and peak relaxation rate of the elbow flexors were assessed with TMS during repeated maximal efforts in 30 men and 28 women between the ages of 22–84 years. Voluntary activation was similar for the two sexes (P = 0.154) and was not affected by age in men (96.2 ± 2.7 %; P = 0.887) or women (95.1 ± 3.0 %; P = 0.546). Men had a significantly faster peak rate of relaxation than women in absolute units (−880.0 ± 223.2 vs. −360.2 ± 78.5 Nm/ s, respectively; P < 0.001) and when normalized to subject strength (−12.5 ± 2.1 vs. −8.7 ± 1.0 s⁻¹, respectively; P < 0.001). Absolute and normalized relaxation rates slowed with age in men (P = 0.002 and P = 0.006, respectively), but not women (P = 0.142 and P = 0.950, respectively). Across the age range studied, all subjects, regardless of age or sex, were able to achieve high voluntary activation scores for the elbow flexors (~95 %). In contrast, peak relaxation rate was markedly faster in men than women and slowed with age in men but not women. Normalization of relaxation rates to strength did not affect the influence of age or sex.