共查询到20条相似文献，搜索用时 31 毫秒
1.
This paper presents a quick, easy to implement and versatile way of using stochastic simulations to investigate the power and design of using single nucleotide polymorphism (SNP) arrays for genome-wide association studies in farm animals. It illustrates the methodology by discussing a small example where 6 experimental designs are considered to analyse the same resource consisting of 6006 animals with pedigree and phenotypic records: (1) genotyping the 30 most widely used sires in the population and all of their progeny (515 animals in total), (2) genotyping the 100 most widely used sires in the population and all of their progeny (1102 animals in total), genotyping respectively (3) 515 and (4) 1102 animals selected randomly or genotyping respectively (5) 515 and (6) 1102 animals from the tails of the phenotypic distribution. Given the resource at hand, designs where the extreme animals are genotyped perform the best, followed by designs selecting animals at random. Designs where sires and their progeny are genotyped perform the worst, as even genotyping the 100 most widely used sires and their progeny is not as powerful of genotyping 515 extreme animals. 相似文献
2.
Gregory P. Samsa 《Journal of Educational Measurement》1992,29(4):321-328
Regression to the mean (RTM) of individuals is the tendency for extreme individuals to become less extreme on remeasurement; RTM of group means describes this same tendency among group means. Under the classical test model, in pretest-posttest designs where subjects are selected on the basis of extreme values at the pretest, RTM of group means will always occur for the attribute used to select extreme subjects. For other attributes, however, RTM of group means requires a positive correlation between that attribute's measurement error and the measurement error of the attribute used in the selection. Thus, while all attributes will evidence RTM of individuals, extreme groups do not always regress to the mean. RTM depends most fundamentally on the magnitude of the pretest measurement error. 相似文献
3.
Analysis of Large-Scale Secondary Data in Higher Education Research: Potential Perils Associated with Complex Sampling Designs 总被引：1，自引：0，他引：1
Most large-scale secondary data sets used in higher education research (e.g., NPSAS or BPS) are constructed using complex survey sample designs where the population of interest is stratified on a number of dimensions and oversampled within certain of these strata. Moreover, these complex sample designs often cluster lower level units (e.g., students) within higher level units (e.g., colleges) to achieve efficiencies in the sampling process. Ignoring oversampling (unequal probability of selection) in complex survey designs presents problems when trying to make inferences—data from these designs are, in their raw form, admittedly nonrepresentative of the population to which they are designed to generalize. Ignoring the clustering of observations in these sampling designs presents a second set of problems when making inferences about variability in the population and testing hypotheses and usually leads to an increased likelihood of committing Type I errors (declaring something as an effect when in fact it is not). This article presents an extended example using complex sample survey data to demonstrate how researchers can address problems associated with oversampling and clustering of observations in these designs. 相似文献
4.
商周青铜器极好地做到了造型设计与装饰纹样的贯通勾连和交相辉映。不管是现实中真实的动物,还是想象中虚幻的神兽,往往都流传于神话传说当中,通过人们的理念构想反映于青铜器造型与纹样之中,反映出造物者相当浓厚的神话设计思想与理念色彩,从而使商周青铜器达成了从语言文字到视觉图像的文本转换。 相似文献
5.
Naoya Todo 《Structural equation modeling》2016,23(5):695-712
In longitudinal design, investigating interindividual differences of intraindividual changes enables researchers to better understand the potential variety of development and growth. Although latent growth curve mixture models have been widely used, unstructured finite mixture models (uFMMs) are also useful as a preliminary tool and are expected to be more robust in identifying classes under the influence of possible model misspecifications, which are very common in actual practice. In this study, large-scale simulations were performed in which various normal uFMMs and nonnormal uFMMs were fit to evaluate their utility and the performance of each model selection procedure for estimating the number of classes in longitudinal designs. Results show that normal uFMMs assuming invariance of variance–covariance structures among classes perform better on average. Among model selection procedures, the Calinski–Harabasz statistic, which has a nonparametric nature, performed better on average than information criteria, including the Bayesian information criterion. 相似文献
6.
The present study investigates whether social interaction moderates age-related deterioration of theory of mind (ToM) abilities. The study population consists of 65 Israeli adults aged 19–102 with varying degrees of self-reported social interaction. It is hypothesized that as age increases, success at ToM-related tasks will decrease. Second, it is hypothesized that the level of social interaction will predict success in ToM tasks only among the older population. Third, it is hypothesized that elderly people who have frequent social interactions within and outside the family environment will exhibit an advantage in maintaining ToM abilities as compared to their peers with limited social interaction. The results of the study support the first hypothesis: with increased age, success on the two ToM tasks measured decreases. The second hypothesis is also supported: social interaction predicts ToM abilities only in the older subpopulation (aged 65–102). The third hypothesis is partially supported: those in the older age group perform better on only one of the two ToM tasks measured. The results of the study are consistent with the theoretical position that social interaction moderates the impact of ageing on certain ToM abilities. Practical implications of the findings are discussed. 相似文献
7.
Population structure and linkage disequilibrium in elite barley breeding germplasm from the United States 总被引：2，自引：0，他引：2
Hao Zhou Gary Muehlbauer Brian Steffenson 《Journal of Zhejiang University. Science. B》2012,13(6):438-451
Cultivated barley is known to have a complex population structure and extensive linkage disequilibrium (LD). To conduct robust association mapping (AM) studies of economically important traits in US barley breeding germplasm, population structure and LD decay were examined in a complete panel of US barley breeding germplasm (3 840 lines) genotyped with 3 072 single nucleotide polymorphisms (SNPs). Nine subpopulations (sp1‒sp9) were identified by the program STRUCTURE and subsequently confirmed by principle component analysis (PCA). Out of the nine subpopulations, seven were very similar to the respective subpopulations identified by Hamblin et al. (2010) which were based on half of the germplasm and half of the SNP markers, but two subpopulations were found to be new. One subpopulation was dominated by six-rowed spring lines from Utah State University (UT) and the other was composed of six-rowed spring lines from multiple breeding programs (USDA-ARS Aberdeen (AB), Busch Agricultural Resources Inc. (BA), UT, and Washington State University (WA)). LD was found to decay across a range from 4.0 to 19.8 cM. This result indicates that the germplasm genotyped with 3 072 SNPs would be robust for mapping and possibly identifying the causal polymorphisms contributing to disease resistance and perhaps other traits. 相似文献
8.
魏丽 《江西教育学院学报》2008,29(4):81-84
小说《无限近似于透明的蓝》是日本当代著名作家村上龙三十多年前的一场青春实录。这部标志着日本文学进入亚文化化的小说．能够跨越时空和国界．至今依然受到人们普遍关注的一个重要原因就是：当“六十年代的年轻人”以一种极端颓废的生命哲学,试图向当时的日本社会发出反抗的声音时,这种行为本身恰恰在拥有了众多“全球亚文化”的表征形式之后,又直指独具特色的“日本亚文化”的表征核心。文章尝试从文本出发。以亚文化研究的角度,将这场发端于“全球化”语境中的研究,最终落实到“本土性”问题的探求上,并试图将小说的深意挖掘到每一个生命共同体都能共享精神资源的诗意空间。 相似文献
9.
Nest-site selection, an ecologically relevant behavior, was studied in the golden hamster in a model environment where the animals could choose between nestboxes differing in distance from resource or in structural features (size and illumination). Experiment 1 showed that hamsters can decrease foraging costs by setting their nests in the nestbox nearest to the food and/or nestmaterial sources, and that hoarding costs, as distinct from simple procurement costs, are taken into account in the choice process. Preferences for darker and larger nestboxes were obtained in Experiment 2. Experiment 3 revealed an internally coherent hierarchical pattern in preferences, with illumination being more important than size and resource distance, and size more important than resource distance. The results suggest that nest-site selection and foraging behaviors are parts of an integrated causal system. 相似文献
10.
11.
Fertilization in flowering plants appears simple when compared to that in higher animals. In reality all pre-fertilization events involved in screening and selection of the partners, so familiar in animals, take place in a subtle way in flowering plants also. As plants lack mobility, they cannot perform, on their own, the most important and primary requirement of bringing the male (pollen grain) and the female (pistil) partners together. This process, termed pollination, is effectively outsourced largely to animal agents. Both plants and animals have evolved fascinating adaptations to do this, which is vital not only for their sustenance but also for crop productivity. 相似文献
12.
Copy number variants (CNVs) are pieces of genomic DNA of 1000 base pairs or longer which occur in a given genome at a different frequency than in a reference genome. Their importance as a source for phenotypic variability has been recognized only in the last couple of years. Chromosomal deletions can be seen as a special case of CNVs where stretches of DNA are missing in certain lines when compared to the reference genome of the mouse line C57BL/6, for example. Based upon more than 8 million single nucleotide polymorphisms (SNPs) in the fifteen inbred mouse lines which were determined in a whole genome chip based resequencing project by Perlegen Sciences, we detected 20166 such long chromosomal deletions. They cover altogether between 4.4 million and 8.8 million base pairs, depending on the mouse line. Thus, their extent is comparable to that of SNPs. The chromosomal deletions were found by searching for clusters of missing values in the genotyping data by applying bioinformatics and biostatistical methods. In contrast to isolated missing values, clusters are likely the consequence of missing DNA probe rather than of a failed hybridization or deficient oligos. We analyzed these deletion sites in various ways. Twenty-two percent of these deletion sites overlap with exons; they could therefore affect a gene's functioning. The corresponding genes seem to exist in alternative forms, a phenomenon that reminds of the alternative forms of mRNA generated during gene splicing. We furthermore detected statistically significant association between hundreds of deletion sites and fat weight at the age of eight weeks. 相似文献
13.
Tricia M. Benish 《Educational Psychology in Practice》2011,27(1):1-17
Social stories have been widely used for children with autism and developmental delays; however, little research has been conducted that examines their effectiveness with pre‐school children who have no developmental delays. The present study investigated this previously undocumented use of social stories. Social stories were used to decrease aggression and improve positive peer relations in a Head Start pre‐school setting. Participants included three four‐year‐old pre‐school students. A single‐subject, ABC multiple baseline design with counterbalanced treatment order was implemented where social stories were compared to a neutral book. Direct observations and pre‐ and post‐Behaviour Assessment System for Children‐2 (BASC‐2) Teacher Rating Scale (TRS) scores were examined. Results revealed some support for the usefulness of social stories in this setting and with this population. Limitations of the study are discussed and directions for future research are provided. 相似文献
14.
制造网格中资源管理系统研究 总被引：7，自引：0，他引：7
为实现制造业的资源共享和协同工作, 以开放网格服务架构(OGSA)为系统框架, 以GT3(Globus Toolkit 3.0)为开发工具, 提出了制造网格的概念. 然而, 由于制造资源的复杂性、多样性、特殊性和分散性, 制造网格中的资源管理问题明显比其他网格应用项目困难得多. 因此, 开发了制造网格信息服务(MGIS), 该服务通过有效集成检测查询服务(MDS)和各种类型的资源封装模板, 实现了制造资源的远程封装、注册、发现和监控. 同时, MGIS与GRAM(globus resource allocation manager)共同构建了制造网格的资源管理系统, 解决了制约制造网格应用的瓶颈问题. 最后, 给出了该系统的应用框架, 并通过制造网格试验床中的一个具体应用实例说明了其实际应用过程. 相似文献
15.
We tested the hypothesis that 4 - 5-year-old girls and boys in same-sex problem-solving groups would perform equally well when the group task required various cooperative and self-serving behaviors to obtain a resource. The hypothesis that girls and boys would employ different behaviors to obtain the resource was also tested. 20 same-sex, same-age groups of 4 children each (10 groups of girls and 10 groups of boys) were videotaped while solving a problem involving a cartoon movie as a resource. 1 child could view the movie provided 2 other children helped, 1 to turn a crank and 1 to push a light button; the fourth child was relegated to a bystander position. Results revealed that girls and boys were equally effective in achieving viewing time; gender variance in viewing time was significantly greater for girls than for boys; girls and boys did not differ in total behavioral output, but girls tended to use more verbal behavior than boys and boys engaged in significantly more physical behavior than girls; affect in boy groups was more positive than in girl groups; girls who achieved the most viewing time within their group differed behaviorally from girls who achieved the least viewing time, but did not differ behaviorally from boys; boys who achieved the most viewing time did not differ behaviorally from boys who achieved the least viewing time. 相似文献
16.
分析了机械学科本科毕业设计中引入现代设计方法的必要性,指出了机械学科本科毕业设计中常用的现代设计方法及其应用范围,举例介绍了现代设计方法的实际应用情况及应用效果,教学改革实践表明现代设计方法在机械学科本科毕业设计中应用可以极大地提高毕业设计的设计效率和设计水平。 相似文献
17.
Janice E. Williams 《Psychology in the schools》1994,31(3):232-237
This study investigated gender-related differences in the efficacy-expectation/performance discrepancies of high school students across four subject matter domains. Participants (N = 131) completed American College Testing (ACT) assessments in English, mathematics, reading, and science. Additionally, prior to each domain-specific test, students rated their perceived self-efficacy expectation for successful performance on that test. As anticipated, most students reporting greater efficacy expectation also tended to perform at higher levels, particularly in mathematics. Unexpectedly, the majority of student efficacy/performance discrepancy scores fell outside the congruent range in all content areas. Approximately equal numbers of male and female students inaccurately estimated their performance capabilities, with most noncongruent students tending to fall into either the extreme overestimation/underestimation categories. Implications are discussed regarding the application of these findings to refining educational methods, and enhancing self-motivation in educational settings. 相似文献
18.
Four-, 5-, and 6-year olds (N = 102) observed agents perform a reasoning task that required gathering hidden evidence. An agent who made sound inferences was contrasted with an agent who made either unsound inferences (UI; failed to base conclusion on gathered evidence) or guesses (failed to gather evidence). Four-year olds attributed knowledge to all agents and endorsed their conclusions widely. However, 5- and 6-year olds’ knowledge attributions were mitigated by UI, and 6-year olds neither attributed knowledge to a guesser nor endorsed his conclusions. Notably, parents’ tendency to make evaluativist epistemological judgments—which place value in evidence as a basis for belief—predicted children’s reluctance to learn from and credit knowledge to poor reasoners. Parents’ evaluativist judgments also predicted children’s selective learning about object functions. 相似文献
19.
Confidence intervals often are recommended as a means of communicating the extent to which individual test scores may be influenced by measurement error. However, test manuals and assessment texts vary widely in their recommendations about how confidence intervals should be constructed, and several contain misinterpretations of classical test theory. The most widely used procedure for constructing confidence intervals misrepresents the likely distribution of true scores, and confidence intervals constructed with it will be inaccurate, especially when extreme scores are involved. The various procedures for constructing confidence intervals that have been suggested in measurement texts are examined in relation to their approximation to the most accurate procedure that uses the estimated true score as the center of the confidence interval and the standard error of estimate to determine the width. In addition, the problems of applying these procedures to norm-referenced scores are discussed—an issue that has been largely ignored in the assessment literature and that leads to further misinterpretations of confidence intervals. 相似文献
20.
王军唐冰松 《福建工程学院学报》2020,(1):75-80
分析承揽合同当事方的激励问题,以当事方收益和社会收益两个角度阐述项目承揽的动力基础。工程项目承揽合同规模较大,执行时间长,多步交易模式合同在实际工程应用中最为广泛。多步交易强调当事方以分步的形式实现收益,进而实现各自权利义务。以履约关键节点视角审视合同当事方交易的过程,将当事方互动过程视为一系列关键节点实现的过程。在履约过程中,要进一步开放合同体系,通过合同履约关键节点的变更和接续的形式完善合同内容,使合同的治理机制更加适应实际项目治理的需要。 相似文献