Estimation and Tests for Departures from Rao-Structured Covariance Matrices

For linear models, a measure of departure of a variance-covariance matrix from Rao-structure (Rao, 1967) is proposed. Relevant estimation and testing problems are discussed. Illustrative examples are also presented.     

A Test of Equality of Survival Distributions for Two Sample Censored Grouped Survival Data

A common testing problem for a life table or survival data is to test the equality of two survival distributions when the data is both grouped and censored. Several tests have been proposed in the literature which require various assumptions about the censoring distributions. It is shown that if these conditions are relaxed then the tests may no longer have the stated properties. The maximum likelihood test of equality when no assumptions are made about the censoring marginal distributions is derived. The properties of the test are found and it is compared to the existing tests. The fact that no assumptions are required about the censoring distributions make the test a useful initial testing procedure.     

Robustness of statistical tests for multiplicative terms in the additive main effects and multiplicative interaction model for cultivar trials

The additive main effects multiplicative interaction model is frequently used in the analysis of multilocation trials. In the analysis of such data it is of interest to decide how many of the multiplicative interaction terms are significant. Several tests for this task are available, all of which assume that errors are normally distributed with a common variance. This paper investigates the robustness of several tests (Gollob, F _GH1, F_GH2, F_R)to departures from these assumptions. It is concluded that, because of its better robustness, the F _Rtest is preferable. If the other tests are to be used, preliminary tests for the validity of assumptions should be performed.     

Combining dependent tests for linkage or association across multiple phenotypic traits

A robust statistical method to detect linkage or association between a genetic marker and a set of distinct phenotypic traits is to combine univariate trait-specific test statistics for a more powerful overall test. This procedure does not need complex modeling assumptions, can easily handle the problem with partially missing trait values, and is applicable to the case with a mixture of qualitative and quantitative traits. In this note, we propose a simple test procedure along this line, and show its advantages over the standard combination tests for linkage or association in the literature through a data set from Genetic Analysis Workshop 12 (GAW12) and an extensive simulation study.     

加减止痉散配合推拿治疗腰椎间盘突出症的临床应用

目的：分析腰椎间盘突出症采用止痉散加减配合推拿治疗的临床应用效果。方法：将2013 年10 月～2014年10月我院中医 门诊收治的90 例腰椎间盘突出症患者,将其按随机数字表法分为对照组和治疗组(n=45)。对照组患者采用针刺、推拿及牵引疗 法,治疗组患者在此基础上给予中药止痉散加减进行治疗。对比两组患者的临床总有效率及直腿抬高试验结果。结果：治疗组的 临床总有效率(97.78%)明显高于对照组的临床总有效率(75.56%),差异具有统计学意义(P＜0.05);另外,治疗组直腿抬高试验＞ 70° 的比例(68.89%)明显高于对照组的(42.22%),差异具有统计学意义(P＜0.05)。结论：止痉散加减配合推拿治疗腰椎间盘突出症 具有较好的临床效果。     

Estimation and Tests of Mendelian Inheritance in Small Samples of Human Families

Estimation of parameters in human genetics is usually performed by Maximum Likelihood methods for large samples relying on asymptotic results. With the aim of evaluating the importance of the bias resulting from sample size, two sets of human family data have been analysed. The bias is not very important, but programs have been elaborated, giving better estimations. The tests of hypotheses from these estimations have also been considered.     

Microfluidic-based Electrotaxis for On-demand Quantitative Analysis of Caenorhabditis elegans' Locomotion

The nematode Caenorhabditis elegans is a versatile model organism for biomedical research because of its conservation of disease-related genes and pathways as well as its ease of cultivation. Several C. elegans disease models have been reported, including neurodegenerative disorders such as Parkinson''s disease (PD), which involves the degeneration of dopaminergic (DA) neurons ¹. Both transgenes and neurotoxic chemicals have been used to induce DA neurodegeneration and consequent movement defects in worms, allowing for investigations into the basis of neurodegeneration and screens for neuroprotective genes and compounds ^2,3.Screens in lower eukaryotes like C. elegans provide an efficient and economical means to identify compounds and genes affecting neuronal signaling. Conventional screens are typically performed manually and scored by visual inspection; consequently, they are time-consuming and prone to human errors. Additionally, most focus on cellular level analysis while ignoring locomotion, which is an especially important parameter for movement disorders.We have developed a novel microfluidic screening system (Figure 1) that controls and quantifies C. elegans'' locomotion using electric field stimuli inside microchannels. We have shown that a Direct Current (DC) field can robustly induce on-demand locomotion towards the cathode ("electrotaxis") ⁴. Reversing the field''s polarity causes the worm to quickly reverse its direction as well. We have also shown that defects in dopaminergic and other sensory neurons alter the swimming response ⁵. Therefore, abnormalities in neuronal signaling can be determined using locomotion as a read-out. The movement response can be accurately quantified using a range of parameters such as swimming speed, body bending frequency and reversal time.Our work has revealed that the electrotactic response varies with age. Specifically, young adults respond to a lower range of electric fields and move faster compared to larvae ⁴. These findings led us to design a new microfluidic device to passively sort worms by age and phenotype ⁶.We have also tested the response of worms to pulsed DC and Alternating Current (AC) electric fields. Pulsed DC fields of various duty cycles effectively generated electrotaxis in both C. elegans and its cousin C. briggsae ⁷. In another experiment, symmetrical AC fields with frequencies ranging from 1 Hz to 3 KHz immobilized worms inside the channel ⁸.Implementation of the electric field in a microfluidic environment enables rapid and automated execution of the electrotaxis assay. This approach promises to facilitate high-throughput genetic and chemical screens for factors affecting neuronal function and viability.