方差组分估计方法的研究

本文利用最大似然法、改进最大似然法与约束最大似然法估计了猪的出生重与二月龄体重的方差、协方差组分和遗传参数。配合的模型为多性状动物模型。典型变换的引入大大降低了计算量。     

绵羊生长性状母本效应方差组分、遗传参数估计的研究

本文利用公畜母畜模型和公畜外祖父模型估计了初生重、断奶重的直接加性遗传方差、母本遗传方差和遗传参数,得出初生重的直接加性遗传效应、母本遗传效应和总的加性遗传效应的遗传力分别为:0.164、0.101、0.103;断奶重相应的各遗传力为:0.076、0.108、0.081。初生重和断奶重二性状加性遗传效应和母本遗传效应间的遗传相关为:-0.57和-0.36。     

数量性状方差组分的估计方法

本文研究讨论了在单性状模型下几种方差组分估计方法,它们是:极大似然法(ML)、约束极大似然法(REML)、最小二乘无偏估计(MINQUE)、最小方差二乘无偏估计以及 Henderson 的第3法等。其中MINQUE和REML法的估计误差最小,但MINQUE的收敛速度高于REML。Henderson 第3法和ML对误差方差均为有偏估计,因此它们的估计误最大;MINQUE法实质上就是REML估计,因此在实际应用中多采用MINQUE和REML法。     

多性状模型方差组分估计方法

在家畜育种实践中,多性状模型估计方差组分会因为巨大的方程所带来的复杂计算而使应用受到极大的限制。但是在等结构矩阵和只有一个随机因子的线性模型中,通过典型转换使所有的相关性状都变为不相关的典范性状,分别对各个典范性状进行方差组分估计,然后再转换为原始性状的方差组分,这样就简化了计算步骤。近年来,不少学者提出了许多不同的具体计算方法,本文主要介绍和讨论K.Meyer所提出的REML算法,并举一个简单的例子来说明之。     

动物育种中的方差组分分析及统计软件包

方差组分估测是分析变异来源和预测育种值的基础,国内外对其进行了大量的研究,对动物育种中方差组分的估测方法及统计分析软件包作了一个简单的综述。     

动物育种中的方差组分分析及统计软件包

方差组分估测是分析变异来源和预测育种值的基础,国内外对其进行了大量的研究,对动物育种中方差组分的估测方法及统计分析软件包作了一个简单的综述.     

方差组分QTL定位分析商业家禽优势和亲缘影响

英国爱丁堡大学的科研人员最近采用方差组分QTL定位法分析了鸡第1、4、5号染色体上的3个候选区域的优势和亲缘影响。所有的数据来自于100只商业母鸡与46只公鸡配种获得的2708个母系后代连续40d的体重值和体型评分。他们采用线性模型评估多基因和QTL影响。他们采用似然比值检验对基因模型进行比较，从排列分析获得经验临界值。结果显示，对体重产生影响的主要QTL被发现位于第4号染色体，对体重和体型评分同时影响的QTL则出现在第5号染色体。     

数量性状方差组分的估计方法(续)

四、方差组分的其它估计方法除了极大似然法外,还有许多方法,如MIVQUE、MINQUE以及Henderson法等。下面我们将作一简单介绍。 (一)MINQUE法根据Henderson的算法,MINQUE估计方差组分的公式为:     

黑白花奶牛泌乳曲线参数的方差组份和遗传特性分析

本文根据北京黑白花奶牛８６０个有完整记录的泌乳期资料，利用Ｗｏｏｄ模型进行了泌乳曲线参数估计，并通过最小二乘法对估计结果进行了方差分析和相关性分析，估计了曲线参数的遗传力（ｈ＾２）、遗传相关（ｒＡ）、表型相关（ｒＰ）和环境相关（ｒＥ）。方差分析表明，父畜和胎次对产奶量（ＭＹ）、估计产奶量（ＥＭＹ）、ａ、ｃ、高峰月份（ＭＰＹ）和高峰月产奶量（ＰＹ）有极显著影响（Ｐ＜０．０１）；对持久力有显著影响（Ｐ     

A RADIOGRAPHIC TECHNIQUE FOR PELVIMETRY OF UNANAESTHESTISED EWES AND A COMPARISON OF THREE METHODS OF ESTIMATING THE AREA OF THE PELVIC INLET

SUMMARY A radiographic procedure is described which enables reliable estimation of the area of the pelvic inlet of up to 150 ewes per seven-hour day by combining use of a specialized radiographic table, immobilisation of the subject with a blindfold and 2 restraining belts, and a mobile condenser-discharge x-ray generator powered by a domestic electrical supply or a portable generator. Six pelvic dimensions, the distances between the medial ischiatic tuberosities, the lateral ischiatic tuberosities, the length of the pubic symphysis, the acetabular, transverse and conjugate diameters and the area of the pelvic inlet computed as the product of the transverse and conjugate diameters (pelvic axes), were estimated by three methods which allowed for magnification resulting from the dimensions of interest lying at varying heights above the film. The estimates were compared by linear regression analysis with their respective values obtained directly from the pelves dissected after slaughter, method A. Method B was isometric, using a perspex vaginal isometer with radiopaque calibrations. Methods C and D applied the theorem of similar triangles. Method C assumed that the dimensions of interest lay in a horizontal plane halfway through the dorso-ventral or lateral thickness of the subject when thickness was measured on a level with the femoral greater trochanters. Method D assumed that the dimensions of interest lay in the same horizontal plane as the height of the subject's anus above the table top when measured in sternal or lateral recumbency. The test subjects were groups of aged, non-pregnant Dorset Horn or Merino ewes. Method B estimated the pelvic axes unreliably in both breeds. Method D, although almost as reliable as method C in Dorset Horn ewes, was not used in merinos because it was cumbersome. Method C was preferred because the estimates were highly correlated with the exact values for both breeds and it was the easiest to apply since measuring body thickness was essential for calculating exposures. Using method C, R values in Dorset Horns for the transverse and conjugate diameters, and the area of the pelvic inlet, were 0.96, 0.78 and 0.81 respectively. For Merinos the corresponding values were 0.88, 0.80 and 0.84 respectively. As method C over-estimated the area of the pelvic inlet, a prediction equation was derived to minimise this tendency, resulting in revised estimates, accurate within 2.7% and 3.9% respectively, of the values obtained at the autopsy of the merino and Dorset Horn test subjects. All methods were unsatisfactory for estimating dimensions other than the transverse and conjugate diameters, and the area of the pelvic inlet. The procedure recommended has been used in several breeding flocks to determine the role of mature maternal pelvic size in feto-pelvic disproportion, birth injury to the fetal central nervous system and repeated maternal rearing failure.     

兔出血症三种快速诊断法比较研究

本试验对快速诊断兔出血症(RHD)的免疫酶染色法(IES),斑点酶联免疫吸附试验(Dot-ELISA)与间接荧光染色法(IFS)进行了比较。试验表明,三种快速诊断法对17份实验感染兔肝材料的检测结果与血凝试验(HA)的阳性符合率分别为88.2％、88.2％及93.3％,阴性符合率均为100％;对4份脏器材料检测结果证明,兔出血症病毒(RHDV)含量依次为;肝>脾>肾>肺>心肌。肝触片及快诊膜分别在4℃和室温放置1个月后,其检测结果不受影响。三种快速诊断对RHDV的检测具有很高的特异性、敏感性和稳定性。Dot-ELISA具有经济、简便、快速、敏感、准确的优点。     

DBL法与粪分析法测定鲤鱼饲料中有效赖氨酸含量的比较研究

以DBL法(染料结合法)和粪样分析法测定3种鲤鱼配合饲料的有效赖氨酸含量。结果表明,两种方法所测得的结果十分一致,相对误差在2％以下。以DBL法测定的赖氨酸对鲤是有效的。     

Employing a Monte Carlo algorithm in expectation maximization restricted maximum likelihood estimation of the linear mixed model

Multiple‐trait and random regression models have multiplied the number of equations needed for the estimation of variance components. To avoid inversion or decomposition of a large coefficient matrix, we propose estimation of variance components by Monte Carlo expectation maximization restricted maximum likelihood (MC EM REML) for multiple‐trait linear mixed models. Implementation is based on full‐model sampling for calculating the prediction error variances required for EM REML. Performance of the analytical and the MC EM REML algorithm was compared using a simulated and a field data set. For field data, results from both algorithms corresponded well even with one MC sample within an MC EM REML round. The magnitude of the standard errors of estimated prediction error variances depended on the formula used to calculate them and on the MC sample size within an MC EM REML round. Sampling variation in MC EM REML did not impair the convergence behaviour of the solutions compared with analytical EM REML analysis. A convergence criterion that takes into account the sampling variation was developed to monitor convergence for the MC EM REML algorithm. For the field data set, MC EM REML proved far superior to analytical EM REML both in computing time and in memory need.     

茶（Camellia sinensis）蜂花粉与蜂粮中花粉形态和营养成分的比较

采用扫描电子显微镜观察茶蜂花粉和不同酿制时间的蜂蜂中花粉粒外部形态和萌发沟,没有发现花粉的细胞壁和细胞结构被破坏的迹象,花粉粒在蜂粮酿制过程中外部形态保持不变。通过体外模拟消化试验和光学显微镜观察,发现蜂粮中花粉粒内含物外吐的数量比蜂花粉多,而且在蜂粮酿制过程中,随着时间的延长,其内含物外吐的花粉粒所占的比例增加,花粉内含物外吐使花粉更易于被破壁和消化。蜂花粉和蜂粮中营养成分测定结果表明,蜂粮配制初期,由于蜜蜂的添加物和乳酸发酵的作用,其蛋白质、总糖含量比蜂花粉高;随着配制时间的延长,蜂粮中营养成分有下降的趋势。     

就业弹性测算方法的选择及基于我国数据的实证分析

比较分析了各种计算GDP就业弹性的方法,认为采用双对数计量模型是测算就业弹性的最好方法.用双对数模型,按可比价格,测算了我国经济总量增长及按三次产业划分的经济增长对就业增加作用的弹性系数,指出其相关的政策含义.对估算方法的选择,以及模型严格的检验程序,是本文所注重的内容.