Assessing the joint effect of population stratification and sample selection in studies of gene-gene (environment) interactions

<p>Abstract</p> <p>Background</p> <p>It is well known that the presence of population stratification (PS) may cause the usual test in case-control studies to produce spurious gene-disease associations. However, the impact of the PS and sample selection (SS) is less known. In this paper, we provide a systematic study of the joint effect of PS and SS under a more general risk model containing genetic and environmental factors. We provide simulation results to show the magnitude of the bias and its impact on type I error rate of the usual chi-square test under a wide range of PS level and selection bias.</p> <p>Results</p> <p>The biases to the estimation of main and interaction effect are quantified and then their bounds derived. The estimated bounds can be used to compute conservative p-values for the association test. If the conservative p-value is smaller than the significance level, we can safely claim that the association test is significant regardless of the presence of PS or not, or if there is any selection bias. We also identify conditions for the null bias. The bias depends on the allele frequencies, exposure rates, gene-environment odds ratios and disease risks across subpopulations and the sampling of the cases and controls.</p> <p>Conclusion</p> <p>Our results show that the bias cannot be ignored even the case and control data were matched in ethnicity. A real example is given to illustrate application of the conservative p-value. These results are useful to the genetic association studies of main and interaction effects.</p

New medium teaching method for power electronics

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Treatment of a ruptured iliac aneurysm with an endoluminal stent graft.

The management of a 79-year-old man presenting with a ruptured common iliac aneurysm is described. The patient had multiple medical problems including hypertension, ischaemic heart disease, and atrial fibrillation, as well as a left hemispheric stroke 5 years previously. Traditional open surgery was judged unsuitable in this case because of the predicted poor outcome. The patient was subsequently treated successfully with endoluminal stent grafting.published_or_final_versio

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Author name used in this publication: X. D. XuePower Electronics Research Centre, Department of Electrical Engineering2002-2003 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

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Online torque estimator of switched reluctance motor running under hysteresis current control

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Trigonometry-based numerical method to compute nonlinear magnetic characteristics in switched reluctance motors

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Implementation of a voltage multiplier integrated HID ballast circuit with dimming control for automotive application

Author name used in this publication: K. W. E. ChengAuthor name used in this publication: D. H. WangPower Electronics Research Centre, Department of Electrical Engineering2009-2010 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe