Population Genetics Identifies Challenges in Analyzing Rare Variants

Geneticists have, for years, understood the nature of genome‐wide association studies using common genomic variants. Recently, however, focus has shifted to the analysis of rare variants. This presents potential problems for researchers, as rare variants do not always behave in the same way common variants do, sometimes rendering decades of solid intuition moot. In this paper, we present examples of the differences between common and rare variants. We show why one must be significantly more careful about the origin of rare variants, and how failing to do so can lead to highly inflated type I error. We then explain how to best avoid such concerns with careful understanding and study design. Additionally, we demonstrate that a seemingly low error rate in next‐generation sequencing can dramatically impact the false‐positive rate for rare variants. This is due to the fact that rare variants are, by definition, seen infrequently, making it hard to distinguish between errors and real variants. Compounding this problem is the fact that the proportion of errors is likely to get worse, not better, with increasing sample size. One cannot simply scale their way up in order to solve this problem. Understanding these potential pitfalls is a key step in successfully identifying true associations between rare variants and diseases.     

精子冷冻环无保护剂玻璃化冷冻方法的初步研究

目的探讨精子冷冻环无保护剂玻璃化冷冻方法的可行性。方法正常精液标本上游处理后,进行常规冷冻和冷冻环无保护剂的玻璃化冷冻,复苏后分别从活力参数及电镜下超微结构等指标比较两种冷冻方法的效果。结果两种方法冷冻后精子存活率、活动率之间差异无显著性(48%∶48%;44.5%∶43.5%,P>0.05),但均较未冷冻的89%和88.5%明显下降(P<0.001)。超微结构亦较未冷冻时发生了一定的改变,但核结构基本保持完整。结论精子冷冻环无保护剂的玻璃化冷冻是一种简单、方便而行之有效的冷冻方法。     

Kindergarten children's representation and understanding of written number symbols

Two samples of kindergarten children's representation and understanding of written number symbols were examined in two time points in one academic year. About 85% of Chinese five year olds (mean = 5 years 10 months) were able to use conventional number symbols to represent the quantity of 30 or larger. At the end of the kindergarten year, 94% of Chinese six year olds (mean = 6 years 4 months) were able to use conventional number symbols to represent the quantity of 100 or larger. Some Chinese six year olds had problems in representing written addition and subtraction tasks. Children's ability to represent written number symbols, ability to represent written addition and subtraction formula and their performance on written addition and subtraction were closely related. The performance of children in a university-affiliated childcare center was better than that of the center serving working-class families in Time 1, but the performance reversed at the end of the kindergarten year.     

Measurement in clinical trials: A neglected issue for statisticians?

Biostatisticians have frequently uncritically accepted the measurements provided by their medical colleagues engaged in clinical research. Such measures often involve considerable loss of information. Particularly, unfortunate is the widespread use of the so‐called ‘responder analysis’, which may involve not only a loss of information through dichotomization, but also extravagant and unjustified causal inference regarding individual treatment effects at the patient level, and, increasingly, the use of the so‐called number needed to treat scale of measurement. Other problems involve inefficient use of baseline measurements, the use of covariates measured after the start of treatment, the interpretation of titrations and composite response measures. Many of these bad practices are becoming enshrined in the regulatory guidance to the pharmaceutical industry. We consider the losses involved in inappropriate measures and suggest that statisticians should pay more attention to this aspect of their work. Copyright © 2009 John Wiley & Sons, Ltd.     

Image processing in digital radiography

Image processing is a critical part of obtaining high-quality digital radiographs. Fortunately, the user of these systems does not need to understand image processing in detail, because the manufacturers provide good starting values. Because radiologists may have different preferences in image appearance, it is helpful to know that many aspects of image appearance can be changed by image processing, and a new preferred setting can be loaded into the computer and saved so that it can become the new standard processing method.Image processing allows one to change the overall optical density of an image and to change its contrast. Spatial frequency processing allows an image to be sharpened, improving its appearance. It also allows noise to be blurred so that it is less visible. Care is necessary to avoid the introduction of artifacts or the hiding of mediastinal tubes.     

高质量电镜影象幻灯片的简便制作方法

使用135单镜头反光照相机和近摄接圈,加置一个普通印相晒箱,即可对电镜底片直接成像,精确的曝光,配合标准程序冲洗,一步制成135幻灯片。其质量优良,且简便可靠、省工省时、节约材料,能大大提高工作效率。本文较为详细地介绍了具体操作方法及要点,并对其它常用制作方法亦做了分析讨论。     

天津市城区成年居民坐高身高指数的调查

目的：探讨成年人坐高身高指数的规律。方法：按中国体育科学会体育研究会规定的方法，测量男性321名，女性324名成人的坐高和身高，每5周岁为一个年龄组，男女各10个年龄组，结果：坐高身高指数均值曲线在男性21－30岁，女性21－35岁年龄组呈递增趋势，提示成年人QD在此年龄组躯干仍存在生长的可能性，在男性56－70岁，女性61－70岁年龄组呈递减趋势，提示成年人在此年龄组脊柱在逐渐缩短，男女两性的指数曲线在30岁左右形成一个交叉点，在此交叉点前女性低于男性，交叉点之后男性低于女性，成人坐高身高指数均值显示男女两性均属躯干均衡型，结论：成年人坐高身高指数具有阶段性递增，递减规律。     

脾脏切除对胸腺和淋巴结免疫功能的影响

报道脾脏切除（脾切）对动物胸腺和淋巴结免疫功能的影响，脾切后３ｗ大鼠胸腺细胞自发增殖及ＣｏｎＡ诱导增殖均无明显变化，ＣｏｎＡ诱导淋巴结细胞增殖脾切组明显高于假手术对照组，脾切后３ｗ再用ＳＲＢＣ免疫，５ｄ后小鼠腹腔淋巴结数量脾切明显高于对照组，用ＱＨＳ法测定淋巴结细胞对ＳＲＢＣ初次抗体产生脾切组则明显低于对照组。