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221.
Estimation of linear contrasts in experimental design, and testing their assumed values, is considered when the error distributions from block to block are not necessarily identical. The normal‐theory solutions are shown to have low efficiencies as compared to the solutions presented here. 相似文献
222.
Tamoor Hussain Zahid Akram Ghulam Shabbir Abdul Manaf Mukhtar Ahmed 《Saudi Journal of Biological Sciences》2021,28(12):6818-6828
Drought is a major and constantly increasing abiotic stress factor, thus limiting chickpea production. Like other crops, Kabuli Chickpea genotypes are screened for drought stress through Multi-environment trials (METs). Although, METs analysis is generally executed taking into account only one trait, which provides less significant reliability for the recommendation of genotypes as compared to multi trait-based analysis. Multi trait-based analysis could be used to recommend genotypes across diverse environments. Hence, current research was conducted for selection of superior genotypes through multi-trait stability index (MTSI) by using mixed and fixed effect models under six diverse environments. The genotypic stability was computed for all traits individually using the weighted average of absolute scores from the singular value decomposition of the matrix of best linear unbiased predictions for the genotype vs environment interaction (GEI) effects produced by a linear mixed-effect model index. A superiority index, WAASBY was measured to reflect the MPS (Mean performance and stability). The selection differential for the WAASBY index was 11.2%, 18.49% and 23.30% for grain yield (GY), primary branches per plant (PBP) and Stomatal Conductance (STOMA) respectively. Positive selection differential (0.80% ≤ selection differential ≤ 13.00%) were examined for traits averaged desired to be increased and negative (-0.57% ≤ selection differential ≤ -0.23%) for those traits desired to be reduced. The MTSI may be valuable to the plant breeders for the selection of genotypes based on many characters as being strong and simple selection process. Analysis of MTSI for multiple environments revealed that, the genotypes G20, G86, G31, G28, G116, G12, G105, G45, G50, G10, G30, G117, G81, G48, G85, G17, G32, G4, and G37 were the most stable and high yielding out of 120 chickpea genotypes, probably due to high MPS of selected traits under various environments. It is concluded that identified traits can be utilized as genitors in hybridization programs for the development of drought tolerant Kabuli Chickpea breeding material. 相似文献
223.
T. Foucart 《Biometrical journal. Biometrische Zeitschrift》1999,41(5):559-572
When the explanatory variables of a linear model are split into two groups, two notions of collinearity are defined: a collinearity between the variables of each group, of which the mean is called residual collinearity, and a collinearity between the two groups called explained collinearity. Canonical correlation analysis provides information about the collinearity: large canonical correlation coefficients correspond to some small eigenvalues and eigenvectors of the correlation matrix and characterise the explained collinearity. Other small eigenvalues of this matrix correspond to the residual collinearity. A selection of predictors can be performed from the canonical correlation variables, according to their partial correlation coefficient with the explained variable. In the proposed application, the results obtained by the selection of canonical variables are better than those given by classical regression and by principal component regression. 相似文献
224.
Taylor (1953) proposed a distance function in connection with the logit χ2 estimator. For product (associated) multinomial distributions, he showed that minimization of the distance function yields BAN estimators. Aithal (1986) and Rao (1989) considered a modified version of Taylor's distance function and showed that a member belonging to this class leads to a second order efficient estimator. In this paper we consider Taylor's distance function and show that a member belonging to this class produces a second order efficient estimator. In addition to the above two, the m.l. estimator is also second order efficient. In order to compare these three second order efficient estimators, the small sample variances of the estimators are estimated through a simulation study. The results indicate that the variance of the m.l. estimator is the smallest in most of the cases. 相似文献
225.
226.
雄性根田鼠的同胞竞争及其对同性个体的气味识别 总被引:6,自引:2,他引:4
采用两两互作实验并以尿标记来确定共居至成年的2雄性根田鼠同胞在行为竞争上的差异,之后在行为选择箱中分别观察它们对来自熟悉和陌生同性个体的新鲜尿气味的行为反应,以确定气味识别差异。结果表明:①雄性根田鼠两两互作时,尿标记的多少可以作为判断其社会等级的标准;②从属鼠对熟悉气味存在明显偏好,其对熟悉气味的访问时间、接近频次和自我修饰频次都显著高于陌生气味;③优势鼠则优先访问陌生气味,其对陌生气味的访问时间、嗅舔频次、嗅舔时间、自我修饰及反标记均显著高于熟悉气味;④对于陌生气味,优势鼠和从属鼠之间存在明显不同的行为反应模式。本实验结果提示,雄性根田鼠对同性尿气味识别的差异以及对陌生气味的行为反应,可能暗含着其领域防卫的信息。 相似文献
227.
Jon Olav Vik Christian N. Brinch Stan Boutin Nils Christian Stenseth 《Population Ecology》2008,50(3):267-274
The classic fur trade records on Canadian lynx (Lynx canadensis) have rarely been analysed in direct conjunction with data on its principal prey, the snowshoe hare (Lepus americanus). Comparable long-term data for hare exist only for a region south of Hudson Bay. We fitted a bivariate log-linear time-series
model to this hare and lynx data to disentangle the within- and between-population interactions of these species. To reduce
problems with fur returns being non-normal and non-linearly related to abundance, we transformed the fur returns to a normal
distribution based on sample quantiles. The estimated effect on next year’s lynx abundance of a 1% increase in current hare
abundance was a 0.23% (SE = 0.05) increase in lynx. Conversely, a 1% increase in current lynx abundance corresponded to a
0.46% (SE = 0.12) decrease in next year’s hare abundance. This contrasts with some earlier studies. However, these studies
mixed hare data from south of Hudson Bay with lynx totals for all of Canada. Despite this asymmetry of interaction strengths,
coefficients of determination were similar for hare versus lynx and lynx versus hare, because hare abundance varies more than
lynx. Both species showed clear intraspecific density-dependence of about equal strength. A 1% increase in current abundance
increased next year’s abundance by about 0.75%.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
228.
Spatial patterns of trees and juveniles in a laurel forest of Tenerife, Canary Islands 总被引:5,自引:0,他引:5
Spatial patterns are important characteristics of the forest and theycan reveal such things as successional status and ecological characteristics ofthe species. We tested the hypothesis that spatial distribution will bedifferent, depending on whether the species is intolerant or tolerant to shade.We assessed the spatial distribution of trees (> 4 cm dbh) andjuveniles in eight laurel forest plots. A univariate spatial analysis(performed with Ripley's K1) showed that all tree species havesignificantaggregation at short distances (2 m). Nevertheless, two groups ofspecies could be differentiated: Erica scoparia,Myrica faya and Ilex canariensisshowed a tendency for aggregation at large distances (larger than 6m)while L. azorica and Prunuslusitanicashowed aggregation only at shorter distances. Ripley's BivariateK1,2 analyses showed no significant differences in the spatialdistribution ofanalyzed species pairs from a null model. Only Laurusazoricahad a sufficient sample size for analysis of juvenile distribution. Aunivariateanalysis revealed thatL. azorica seedlings (stems < 50 cm high)were clumped in some plots up to 5 m, but this was not consistent.Saplings (stems > 50 cm high and < 4 cm dbh)didnot show strong clumping even at short distances. L.azoricasaplings had no significant aggregation with, nor repulsionfrom, adults of the same or different species. Spatial patterns of the speciesshould be considered in the development of restoration plans of the laurelforest 90%of which has disappeared or been intensively disturbed on Tenerife Island. 相似文献
229.
Summary . Spatial clustering is commonly modeled by a Bayesian method under the framework of generalized linear mixed effect models (GLMMs). Spatial clusters are commonly detected by a frequentist method through hypothesis testing. In this article, we provide a frequentist method for assessing spatial properties of GLMMs. We propose a strategy that detects spatial clusters through parameter estimates of spatial associations, and assesses spatial aspects of model improvement through iterated residuals. Simulations and a case study show that the proposed method is able to consistently and efficiently detect the locations and magnitudes of spatial clusters. 相似文献
230.
Maïlys Guillard Jolein Gloerich Hans J.C.T. Wessels Eva Morava Ron A. Wevers Dirk J. Lefeber 《Carbohydrate research》2009,344(12):1550-1557
The use of N-glycan mass spectrometry for clinical diagnostics requires the development of robust high-throughput profiling methods. Still, structural assignment of glycans requires additional information such as MS2 fragmentation or exoglycosidase digestions. We present a setting which combines a MALDI ionization source with a linear ion trap analyzer. This instrumentation allows automated measurement of samples thanks to the crystal positioning system, combined with MSn sequencing options. 2,5-Dihydroxybenzoic acid, commonly used for the analysis of glycans, failed to produce the required reproducibility due to its non-homogeneous crystallization properties. In contrast, α-cyano-4-hydroxycinnamic acid provided a homogeneous crystallization pattern and reproducibility of the measurements. Using serum N-glycans as a test sample, we focused on the automation of data collection by optimizing the instrument settings. Glycan structures were confirmed by MS2 analysis. Although sample processing still needs optimization, this method provides a reproducible and high-throughput approach for measurement of N-glycans using a MALDI–linear ion trap instrument. 相似文献