Tests for a difference in timing of physiological response between two brain regions measured by using functional magnetic resonance imaging

Summary.  Functional magnetic resonance imaging (FMRI) measures the physiological response of the human brain to experimentally controlled stimulation. In a periodically designed experiment it is of interest to test for a difference in the timing (phase shift) of the response between two anatomically distinct brain regions. We suggest two tests for an interregional difference in phase shift: one based on asymptotic theory and one based on bootstrapping. Whilst the two procedures differ in some of their assumptions, both tests rely on employing the large number of voxels (three-dimensional pixels) in non-activated brain regions to take account of spatial autocorrelation between voxelwise phase shift observations within the activated regions of interest. As an example we apply both tests, and their counterparts assuming spatial independence, to FMRI phase shift data that were acquired from a normal young woman during performance of a periodically designed covert verbal fluency task. We conclude that it is necessary to take account of spatial autocovariance between voxelwise FMRI time series parameter estimates such as the phase shift, and that the most promising way of achieving this is by modelling the spatial autocorrelation structure from a suitably defined base region of the image slice.     

试论歌唱共鸣

歌唱的共鸣直接影响到歌唱的音色、音量和表现力,丰富的共鸣是歌唱技巧的基本问题,是声音训练的基础。     

电子回旋共振等离子体特性的数值模拟

以电子作为流体、离子作为粒子这一混合模型，研究了电子回旋共振（ＥＣＲ）等离子体微波放电的热现象及离子沿偏离轴向磁力线的输运．结果表明气压对ＥＣＲ等离子体影响很大．     

依文思蓝与硫酸依替米星和硫酸奈替米星相互作用的共振瑞利散射光谱及其分析应用

在酸性条件下,酸性双偶氮染料依文思蓝(EB)和药物硫酸依替米星(ETS)、硫酸奈替米星(NETS)各自的共振瑞利散射(RRS)强度十分微弱,但EB与ETS或NETS两者相互作用形成的离子缔合物能显著提高RRS强度并产生新的RRS光谱,EB-ETS和EB-NETS体系均在350—400,680—730 nm有两个强的散射带,最大散射峰位于713 nm处.RRS强度分别与0.2—8.0μg/mL的ETS和0.4—8.0μg/mL的NETS呈线性关系,据此建立了ETS和NETS的测定方法.该方法有较好的选择性,用于市售ETS和NETS注射液中药物含量和临床血药浓度的快速测定,结果满意.     

基于投影的fMRI时间序列图像配准方法研究

利用投影技术,针对功能磁共振时间序列图像,介绍了一种新的自动图像配准方法。该方法将序列图像二值化后沿着水平方向或垂直方向进行投影,根据投影向量元素的位置和大小,快速地计算出图像的旋转、平移运动的变化参数。仿真实验和实际的功能磁共振应用证实了该方法的有效性。     

Extrapolation designs and Φp-optimum designs for cubic regression on the q-ball

This paper continues earlier work of the authors in carrying out the program discussed in Kiefer (1975), of comparing the performance of designs under various optimality criteria. Designs for extrapolation problems are also obtained. The setting is that in which the controllable variable takes on values in the q-dimensional unit ball, and the regression is cubic. Thus, the ideas of comparison are tested for a model more complex than the quadratic models discussed previously. The E-optimum design performs well in terms of other criteria, as well as for extrapolation to larger balls. A method of simplifying the calculations to obtain approximately optimum designs, is illustrated.     

具有复合周期磁场的电子回旋脉塞

本文从降低回旋脉塞中直流磁场的角度出发,利用线性伏拉索夫——麦克斯韦方程组,对通过静态复合周期磁场的弱相对论电子注与缓变圆波导中沿纵向作任意缓变的TE_(mn)模式之间的互作用机理,在理论上进行了详细的分析和讨论,导出了色散方程并作了数值计算。分析和计算表明,由于采用了静态复合周期磁场,其电子注与波互作用的不稳定性产生在电子回旋共振条件下,从而可以在不同的电子回旋空间谐波上工作而大大地降低直流磁场。     

静电电子回旋脉塞的单粒子理论

本文用单粒子理论研究了静电电子回旋脉塞。通过对静电电子回旋脉塞中的电子运动的分析,导出了电子与波互作用的非线性摆方程。文中用二阶扰动方法求解非线性摆方程,得到了TE_(mn)和TM_(mn)两种工作模式的静电电子回旋脉塞不稳定性线性增益公式,进一步证实了静电电子回旋脉塞不稳定性是存在的。     

Two-Step Residual-Based Estimation of Error Variances for Generalized Least Squares in Split-Plot Experiments

In split-plot experiments, estimation of unknown parameters by generalized least squares (GLS), as opposed to ordinary least squares (OLS), is required, owing to the existence of whole- and subplot errors. However, estimating the error variances is often necessary for GLS. Restricted maximum likelihood (REML) is an established method for estimating the error variances, and its benefits have been highlighted in many previous studies. This article proposes a new two-step residual-based approach for estimating error variances. Results of numerical simulations indicate that the proposed method performs sufficiently well to be considered as a suitable alternative to REML.     

Computational schema on ridge analysis

The purpose of this paper is to revisit the response surface technique ridge analysis within the context of the “trust region” problem in numerical analysis. It is found that these two approaches inherently solve the same problem. We introduce the computational difficulty, termed the “hard case”, which originates in the trust region methods, also exists in ridge analysis but has never been formally discussed in response surface methodology (RSM). The dual response global optimization algorithm (DRSALG) based on the trust region method is applied (with a certain modification) to solving the ridge analysis problem. Some numerical comparisons against a general-purpose nonlinear optimization algorithm are illustrated in terms of examples appearing in the literature