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Background
Rates of molecular evolution in different lineages can vary widely, and some of this variation might be predictable from aspects of species' biology. Investigating such predictable rate variation can help us to understand the causes of molecular evolution, and could also help to improve molecular dating methods. Here we present a comprehensive study of the life history correlates of substitution rate variation across the mammals, comparing results for mitochondrial and nuclear loci, and for synonymous and non-synonymous sites. We use phylogenetic comparative methods, refined to take into account the special nature of substitution rate data. Particular attention is paid to the widespread correlations between the components of mammalian life history, which can complicate the interpretation of results. 相似文献246.
Qiang Hu Liang Zhu Yanyan Liu Jianguo Sun Deo Kumar Srivastava Leslie L. Robison 《Biometrical journal. Biometrische Zeitschrift》2020,62(8):1909-1925
For the analysis of ultrahigh-dimensional data, the first step is often to perform screening and feature selection to effectively reduce the dimensionality while retaining all the active or relevant variables with high probability. For this, many methods have been developed under various frameworks but most of them only apply to complete data. In this paper, we consider an incomplete data situation, case II interval-censored failure time data, for which there seems to be no screening procedure. Basing on the idea of cumulative residual, a model-free or nonparametric method is developed and shown to have the sure independent screening property. In particular, the approach is shown to tend to rank the active variables above the inactive ones in terms of their association with the failure time of interest. A simulation study is conducted to demonstrate the usefulness of the proposed method and, in particular, indicates that it works well with general survival models and is capable of capturing the nonlinear covariates with interactions. Also the approach is applied to a childhood cancer survivor study that motivated this investigation. 相似文献
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A simple method to analyze media consumption and by-product build-up in high-cell-density perfusion cultures has been developed. This technique makes use of media replenishment strategy which can be used to decouple the two phenomena. Also, the replenished media method can be used to identify limitation by complex and undefined media components such as bovine serum. 相似文献
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Tiwari Vaibhav Tiwari Kavindra Nath Singh Brahma Deo 《Plant Cell, Tissue and Organ Culture》2001,66(1):9-16
A mass in vitro propagation system for Bacopa monniera (L.) Wettst. (Scrophulariaceae), a medicinally important plant, has been developed. A range of cytokinins have been investigated
for multiple shoot induction with node, internode and leaf explants. Of the four cytokinins (6-benzyladenine, thidiazuron,
kinetin and 2-isopentenyladenine) tested thidiazuron (6.8 μM) and 6-benzyladenine (8.9 μM) proved superior to other treatments. Optimum adventitious shoot buds induction occurred at 6.8 μM thidiazuron where an average of 93 shoot buds were produced in leaf explants after 7 weeks of incubation. However, subculture
of leaf explants on medium containing 2.2 μM benzyladenine yielded a higher number (129.1) of adventitious shoot buds by the end of third subculture. The percentage
shoot multiplication (100%) as well as the number of shoots per explant remained the high during the first 3 subculture cycles,
facilitating their simultaneous harvest for rooting. In vitro derived shoots were elongated on growth regulator-free MS medium and exhibited better rooting response on medium containing
4.9 μM IBA. After a hardening phase of 3 weeks, there was an almost 100% transplantation success in the field.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献