Early Plant Selection Effects on Crown Traits in Pensacola Bahiagrass with Selection Cycle

Crop Science ◽  
2003 ◽  
Vol 43 (6) ◽  
pp. 1996-1998 ◽  
Author(s):  
A. R. Blount ◽  
R. N. Gates ◽  
P. L. Pfahler ◽  
K. H. Quesenberry
2007 ◽  
Vol 7 (2) ◽  
pp. 125-132 ◽  
Author(s):  
J.R. Paiva ◽  
E.R. Cordeiro ◽  
M.C.M. Corrêa ◽  
M.D.V. Resende

1985 ◽  
Vol 24 (03) ◽  
pp. 120-130 ◽  
Author(s):  
E. Brunner ◽  
N. Neumann

SummaryThe mathematical basis of Zelen’s suggestion [4] of pre randomizing patients in a clinical trial and then asking them for their consent is investigated. The first problem is to estimate the therapy and selection effects. In the simple prerandomized design (PRD) this is possible without any problems. Similar observations have been made by Anbar [1] and McHugh [3]. However, for the double PRD additional assumptions are needed in order to render therapy and selection effects estimable. The second problem is to determine the distribution of the statistics. It has to be taken into consideration that the sample sizes are random variables in the PRDs. This is why the distribution of the statistics can only be determined asymptotically, even under the assumption of normal distribution. The behaviour of the statistics for small samples is investigated by means of simulations, where the statistics considered in the present paper are compared with the statistics suggested by Ihm [2]. It turns out that the statistics suggested in [2] may lead to anticonservative decisions, whereas the “canonical statistics” suggested by Zelen [4] and considered in the present paper keep the level quite well or may lead to slightly conservative decisions, if there are considerable selection effects.


Author(s):  
Wei‐Ping Zhang ◽  
Sai‐Nan Gao ◽  
Zhao‐Xin Li ◽  
Hua‐Sen Xu ◽  
Hao Yang ◽  
...  

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Adriano dos Santos ◽  
Erina Vitório Rodrigues ◽  
Bruno Galvêas Laviola ◽  
Larissa Pereira Ribeiro Teodoro ◽  
Paulo Eduardo Teodoro ◽  
...  

AbstractGenome-wide selection (GWS) has been becoming an essential tool in the genetic breeding of long-life species, as it increases the gain per time unit. This study had a hypothesis that GWS is a tool that can decrease the breeding cycle in Jatropha. Our objective was to compare GWS with phenotypic selection in terms of accuracy and efficiency over three harvests. Models were developed throughout the harvests to evaluate their applicability in predicting genetic values in later harvests. For this purpose, 386 individuals of the breeding population obtained from crossings between 42 parents were evaluated. The population was evaluated in random block design, with six replicates over three harvests. The genetic effects of markers were predicted in the population using 811 SNP's markers with call rate = 95% and minor allele frequency (MAF) > 4%. GWS enables gains of 108 to 346% over the phenotypic selection, with a 50% reduction in the selection cycle. This technique has potential for the Jatropha breeding since it allows the accurate obtaining of GEBV and higher efficiency compared to the phenotypic selection by reducing the time necessary to complete the selection cycle. In order to apply GWS in the first harvests, a large number of individuals in the breeding population are needed. In the case of few individuals in the population, it is recommended to perform a larger number of harvests.


2021 ◽  
pp. 019791832199478
Author(s):  
Wanli Nie ◽  
Pau Baizan

This article investigates the impact of international migration to the United States on the level and timing of Chinese migrants’ fertility. We compare Chinese women who did not leave the country (non-migrants) and were subject to restrictive family policies from 1974 to 2015 to those who moved to the United States (migrants) and were, thus, “emancipated” from these policies. We theoretically develop and empirically test the emancipation hypothesis that migrants should have a higher fertility than non-migrants, as well as an earlier timing of childbearing. This emancipation effect is hypothesized to decline across birth cohorts. We use data from the 2000 US census, the 2005 American Community Survey, the 2000 Chinese census, and the 2005 Chinese 1 percent Population Survey and discrete-time event history models to analyze first, second, and third births, and migration as joint processes, to account for selection effects. The results show that Chinese migrants to the United States had substantially higher childbearing probabilities after migration, compared with non-migrants in China, especially for second and third births. Moreover, our analyses indicate that the migration process is selective of migrants with lower fertility. Overall, the results show how international migration from China to the United States can lead to an increase in migrant women’s fertility, accounting for disruption, adaptation, and selection effects. The rapidly increased fertility after migration from China to the United States might have implications on other migration contexts where fertility in the origin country is dropping rapidly while that in the destination country is relatively stable.


Oikos ◽  
2003 ◽  
Vol 100 (3) ◽  
pp. 554-562 ◽  
Author(s):  
M. S. Singer ◽  
J. O. Stireman III

2004 ◽  
Vol 217 ◽  
pp. 252-257
Author(s):  
M. T. Murphy ◽  
S. J. Curran ◽  
J. K. Webb

The chemical abundances in damped Lyman-α systems (DLAs) show more than 2 orders of magnitude variation at a given epoch, possibly because DLAs arise in a wide variety of host galaxies. This could significantly bias estimates of chemical evolution. We explore the possibility that DLAs in which H2 absorption is detected may trace cosmological chemical evolution more reliably since they may comprise a narrower set of physical conditions. The 9 known H2 absorption systems support this hypothesis: metallicity exhibits a faster, more well-defined evolution with redshift than in the general DLA population. The dust-depletion factor and, particularly, H2 molecular fraction also show rapid increases with decreasing redshift. We comment on possible observational selection effects which may bias this evolution. Larger samples of H2-bearing DLAs are clearly required and may constrain evolution of the UV background and DLA galaxy host type with redshift.


1998 ◽  
Vol 11 (1) ◽  
pp. 570-570
Author(s):  
Johan Holmberg ◽  
Lennart Lindegren ◽  
Chris Flynn

We use the Hipparcos survey to derive an improved model of the local galactic structure. The availability of parallaxes for all the stars permits direct determination of stellar distributions, eliminating the basic indeterminacy of classical methods based on star counts. Hipparcos gives for the first time a truly three-dimensional view of the solar vicinity, and a complete, homogeneous and highly accurate set of magnitudes and colours. This means that new techniques can be applied in the treatment of the data which place strong constraints on a model that tries to describe the local Galactic structure. Here we investigate how well a static model of low complexitycan describe the Hipparcos observations. The interpretation of the Hipparcos data is complicated by various observational errors and selection effects that are hard to treat correctly. We do not try to correct the data, but instead use a model and subject this model to the same observational errors and selection effects. A model catalogue is created that can be compared with the observed catalogue directly in the observational domain, thereby eliminating the effects from various biases. Many features in the HR diagram are for the first time seen in field stars thanks to Hipparcos, such as the slanted red giant clump, previously seen in rich old open clusters such as Berkeley 18. This and other features ofthe observed HR diagram are well reproduced by the model thanks to the rather detailed modelling of the joint Mv/B — V distribution. Actually, separate distributions were derived for the three different components, disk, thick disk and halo, using the kinematic characteristics of the components to discriminate between them.


2021 ◽  
Vol 502 (4) ◽  
pp. 4669-4679
Author(s):  
Sofia Z Sheikh ◽  
Mariah G MacDonald

ABSTRACT Approximately 8 per cent of the ∼2800 known pulsars exhibit ‘nulling,’ a temporary broad-band cessation of normal pulsar emission. Nulling behaviour can be coarsely quantified by the nulling fraction, which describes the percentage of time a given pulsar will be found in a null state. In this paper, we perform the most thorough statistical analysis thus far of the properties of 141 known nulling pulsars. We find weak, non-linear correlations between nulling fraction and pulse width, as well as nulling fraction and spin period which could be attributed to selection effects. We also further investigate a recently hypothesized gap at 40 per cent nulling fraction. While a local minimum does exist in the distribution, we cannot confirm a consistent and unique break in the distribution when we investigate with univariate and multivariate clustering methods, nor can we prove the existence of two statistically distinct populations about this minimum. Using the same methods, we find that nulling pulsars are a statistically different population from normal, radio, non-nulling pulsars, which has never been quantitatively verified. In addition, we summarize the findings of the prior nulling pulsar statistics literature, which are notoriously contradictory. This study, in context, furthers the idea that nulling fraction alone does not contain enough information to describe the behaviour of a nulling pulsar and that other parameters such as null lengths and null randomness, in addition to a better understanding of selection effects, are required to fully understand this phenomenon.


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