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Men sleep shorter and go to bed and get up later than women, thus they are later
chronotypes. This difference between the sexes is most pronounced between
puberty and menopause indicating the possibility that morningness is subject to
sexual dimorphism related to reproductive aspects. The objective of the study
was to compare the sleep-wake behavior of women with their actual partners and
with their preferred partners. As a hypothesis, we expect some assortment in
mating concerning chronotype (with the actual partner), but we also expect a
higher synchronization with a preferred ideal partner. 167 women were analyzed
in this study (mean age: 23.0 ± 2.57 (SD) years).
Mated women were earlier chronotypes than their partners (t
= –2.051, p = .042,
d = .34) but the difference was small (11:02 min
± 1:04 min). The results of the present study showed women preferring
a partner synchronized to their own sleep-wake-rhythm more than their actual
partners were. The above result was true either for single facets of the
sleep-wake rhythm (e.g. bed time, sleep onset) or for midpoint of sleep on free
days – an indicator of actual chronotype: women’s and
their partners’ correlation of midpoint of sleep was lower
(r = .513) than women’s and their ideal
partners’ correlation (r = .855). Amongst
various sleep-wake measures, women particularly preferred a partner going to bed
at the same time. Assortative mating according to sleep-wake rhythm exists, but
women for long-term pair-bonds would like their partners far more
Primitive meteorites contain small amounts of presolar minerals that formed in the winds of evolved stars or in the ejecta of stellar explosions. Silicon carbide is the best studied presolar mineral. Based on its isotopic compositions it was divided into distinct populations that have different origins: Most abundant are the mainstream grains which are believed to come from 1.5–3 M⊙ AGB stars of roughly solar metallicity. The rare Y and Z grains are likely to come from 1.5–3 M⊙ AGB stars as well, but with subsolar metallicities (0.3–0.5 times solar). Here we report on C and Si isotope and trace element (Zr, Ba) studies of individual, submicrometer-sized SiC grains. The most striking results are: (1) Zr and Ba concentrations are higher in Y and Z grains than in mainstream grains, with enrichments relative to Si and solar of up to 70 times (Zr) and 170 times (Ba), respectively; (2) For the Y and Z grains there is a positive correlation between Ba concentrations and amount of s-process Si. This correlation is well explained by predictions for 2–3 M⊙ AGB stars with metallicities of 0.3–0.5 times solar. This confirms low-metallicity stars as most likely stellar sources for the Y and Z grains.
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