Indifferent Gender Preferences among Childless Beijing Citizens

Son preference, leading to skewed sex ratios at birth, is an important feature of contemporary Chinese demography, as well as being a critical policy issue. Using a 2006 representative survey, this article explores preferences for boys and girls among childless young adults in a district of Beijing who have a stated one child as their ideal number of children (though they may be eligible to bear more). The descriptive analysis finds no evidence of son-preference; rather an overall indifference to gender. A multivariate analysis provides some indicative evidence of indifference regarding predictors of desiring a girl, a boy or either. gs

Resolve negative cross section of quarkonium hadroproduction using soft gluon factorization

It was found that, using NRQCD factorization, the predicted $\chi_{cJ}$ hadroproduction cross section at large $p_T$ can be negative. The negative cross sections originate from terms proportional to plus function in ${^{3}\hspace{-0.6mm}P_{J}^{[1]}}$ channels, which are remnants of the infrared subtraction in matching the ${^{3}\hspace{-0.6mm}P_{J}^{[1]}}$ short-distance coefficients. In this article, we find that the above terms can be factorized into the nonperturbative ${^{3}\hspace{-0.6mm}S_{1}^{[8]}}$ soft gluon distribution function in the soft gluon factorization (SGF) framework. Therefore, the problem can be naturally resolved in SGF. With an appropriate choice of nonperturbative parameters, the SGF can indeed give positive predictions for $\chi_{cJ}$ production rates within the whole $p_T$ region. The production of $\psi(2S)$ is also discussed, and there is no negative cross section problem.Comment: 11 pages, 7 figure

Allopolyploid speciation and ongoing backcrossing between diploid progenitor and tetraploid progeny lineages in the Achillea millefolium species complex: analyses of single-copy nuclear genes and genomic AFLP

<p>Abstract</p> <p>Background</p> <p>In the flowering plants, many polyploid species complexes display evolutionary radiation. This could be facilitated by gene flow between otherwise separate evolutionary lineages in contact zones. <it>Achillea collina </it>is a widespread tetraploid species within the <it>Achillea millefolium </it>polyploid complex (Asteraceae-Anthemideae). It is morphologically intermediate between the relic diploids, <it>A. setacea</it>-2x in xeric and <it>A. asplenifolia</it>-2x in humid habitats, and often grows in close contact with either of them. By analyzing DNA sequences of two single-copy nuclear genes and the genomic AFLP data, we assess the allopolyploid origin of <it>A. collina</it>-4x from ancestors corresponding to <it>A. setacea</it>-2x and <it>A. asplenifolia</it>-2x, and the ongoing backcross introgression between these diploid progenitor and tetraploid progeny lineages.</p> <p>Results</p> <p>In both the ncp<it>GS </it>and the <it>PgiC </it>gene tree, haplotype sequences of the diploid <it>A. setacea</it>-2x and <it>A. asplenifolia</it>-2x group into two clades corresponding to the two species, though lineage sorting seems incomplete for the <it>PgiC </it>gene. In contrast, <it>A. collina</it>-4x and its suspected backcross plants show homeologous gene copies: sequences from the same tetraploid individual plant are placed in both diploid clades. Semi-congruent splits of an AFLP Neighbor Net link not only <it>A. collina</it>-4x to both diploid species, but some 4x individuals in a polymorphic population with mixed ploidy levels to <it>A. setacea</it>-2x on one hand and to <it>A. collina</it>-4x on the other, indicating allopolyploid speciation as well as hybridization across ploidal levels.</p> <p>Conclusions</p> <p>The findings of this study clearly demonstrate the hybrid origin of <it>Achillea collina</it>-4x, the ongoing backcrossing between the diploid progenitor and their tetraploid progeny lineages. Such repeated hybridizations are likely the cause of the great genetic and phenotypic variation and ecological differentiation of the polyploid taxa in <it>Achillea millefolium </it>agg.</p