中国节节麦的细胞遗传学研究及有关问题探讨

应用染色体组分析法,对新疆节节麦、黄河流域节节麦、伊朗节节麦和中东节节麦的D染色体组进行了较系统的比较分析,结果表明:新疆节节麦与伊朗、中东两地节节麦在染色体组水平上无明显差异,其差异仅体现在染色体的细微结构组成上;臂内倒位是引起染色体结构组成上细微分化的主要原因。黄河流域节节麦与新疆节节麦的染色体组极为相近;其D组染色体无论在染色体组水平上,还是在染色体细微结构组成上均无差异。本文还就中国节节麦与中国特有六倍体普通小麦的起源演化,中国节节麦种质资源在现代小麦育种中的应用等问题进行了讨论。     

农业科技成果转化为现实生产力的对策

根据目前影响我国农业技术成果迅速转化为现实生产力的因素,提出了加速农业技术成果转化的对策。     

普通野生稻和药用野生稻种子休眠性的研究

对普通野生稻和药用野生稻种子休眠的原因进行了探讨,表明野生稻种的遗传特性、形态性状、颖壳的透性和种子的生理特性与种子休眠有关。研究结果为打破野生稻种子休眠、提高其发茅力提供了依据和适宜的方法。     

PES-C,(PP/Bis-T)PES的次级松驰与转变

描述了酚酞型聚芳醚砜(PES-C)的次级松驰和转变与其结构的关系.TBA和动态力学实验结果表明:PES-C及其共聚物(PP/Bis-T)PES分别在0～50℃和-100℃附近呈现出两个次级松驰峰;双酚T单元的引入导致了PES-C在0～50℃之间的次级松驰位置改变.证实了Cardo侧基的存在对-100℃的次级松驰有较大的贡献.     

由1971—2011年诺贝尔文学奖获奖情况反思中国文学

针对当前现状,以1971—2011年的诺贝尔文学奖四十年来的获奖情况为研究对象,从获奖作家所属的不同的国家分布、作家性别比例及和获奖作品风格与主旨这三个大的方面入手进行分析,探究诺贝尔文学奖的发展态势,概括和反思目前中国文学的发展状况,剖析中国作家莫言的获奖原因,由此提出对于中国作家要在诺贝尔文学奖中占有更多席位需要完善方面的建议和看法。     

Comparing two measures of creatinine clearance: an application of errors-in-variables and bootstrap techniques

Two indices of creatinine clearance (an index of kidney function) are compared on a group of cancer patients who underwent chemotherapy with a potentially nephrotoxic drug. The standard index, measured creatinine clearance MCC, is cumbersome to use, whereas the more convenient alternative, estimated creatinine clearance ECC, has not yet been conclusively evaluated on cancer patients. We conclude that under certain clinical conditions ECC and MCC are identically calibrated for males, but not for females, and we obtain estimated true and false positive rates for assessing the use of ECC instead of MCC as a diagnostic tool. We use a model that is formally equivalent to an errors-in-variables model with (unbalanced) repeated observations and correlated measurement errors. The bootstrap is used to obtain standard errors and confidence limits.     

The zero-inflated Poisson model and the decayed, missing and filled teeth index in dental epidemiology

For frequency counts, the situation of extra zeros often arises in biomedical applications. This is demonstrated with count data from a dental epidemiological study in Belo Horizonte (the Belo Horizonte caries prevention study) which evaluated various programmes for reducing caries. Extra zeros, however, violate the variance–mean relationship of the Poisson error structure. This extra-Poisson variation can easily be explained by a special mixture model, the zero-inflated Poisson (ZIP) model. On the basis of the ZIP model, a graphical device is presented which not only summarizes the mixing distribution but also provides visual information about the overall mean. This device can be exploited to evaluate and compare various groups. Ways are discussed to include covariates and to develop an extension of the conventional Poisson regression. Finally, a method to evaluate intervention effects on the basis of the ZIP regression model is described and applied to the data of the Belo Horizonte caries prevention study.     

Multiple roots of estimating functions

Estimating functions can have multiple roots. In such cases, the statistician must choose among the roots to estimate the parameter. Standard asymptotic theory shows that in a wide variety of cases, there exists a unique consistent root, and that this root will lie asymptotically close to other consistent (possibly inefficient) estimators for the parameter. For this reason, attention has largely focused on the problem of selecting this root and determining its approximate asymptotic distribution. In this paper, however, we concentrate on the exact distribution of the roots as a random set. In particular, we propose the use of higher-order root intensity functions as a tool for examining the properties of the roots and determining their most problematic features. The use of root intensity functions of first and second order is illustrated by application to the score function for the Cauchy location model.     

Error reduction in density estimation under shape restrictions

For the problems of nonparametric estimation of nonincreasing and symmetric unimodal density functions with bounded supports we determine the projections of estimates onto the convex families of possible parent densities with respect to the weighted integrated squared error. We also describe the method of approximating the analogous projections onto the respective density classes satisfying some general moment conditions. The method of projections reduces the estimation errors for all possible values of observations of a given finite sample size in a uniformly optimal way and provides estimates sharing the properties of the parent densities.     

球墨铸铁曲轴的气体软氮化

柴油机的珠墨铸铁曲轴系重要零件,气体软氮化应用到球墨铸铁领域还是一种新工艺,而且比中频淬火效果好,提高了曲轴的抗疲劳和抗磨损的能力。本文对气体软氮化的基本原理、设备、工艺参数的选择和催渗方法进行了探讨,对软氮化后曲轴的尺寸形状误差、光洁度和机械性能的提高等进行了较详细的试验、分析和比较,结果,经气体软氮化后的曲轴不但尺寸形站误差符合图纸要求外,而且抛去轻微氧化层后光洁度还略有提高,曲轴安全系数由1.3～1.6提高到1.70～1.77,并且一般不再发生疲劳断(?),使用寿命比原来寿命增加3.32倍以上。