A new silicate fluoride,NaBa3 Si207 F,has been successfully synthesized by a high-temperature solution method.It crystallizes in the orthorhombic space group Cmcm(No.63).NaBa3 Si2 O7 F is the first barium-containing a...A new silicate fluoride,NaBa3 Si207 F,has been successfully synthesized by a high-temperature solution method.It crystallizes in the orthorhombic space group Cmcm(No.63).NaBa3 Si2 O7 F is the first barium-containing alkali metal silicate fluoride with the[NaO6]polyhedra,the[BaO8 F]polyhedra and isolated[Si2 O7]units.The optical characterizations indicate that NaBa3 Si2 O7 F possesses wide transparent window and available luminescence properties.To confirm the coordination surroundings of anionic groups and its thermostability,infrared spectroscopy and thermal behaviors were also analyzed,which proved the existence of tetrahedronly coordinated silicium atoms and the good stability of NaBa3 Si2 O7 F at high temperature.First-principles calculation was also implemented for better understanding the relationship between the structure of NaBa3 Si207 F and its property.Additionally,to further explore the structural novelty of NaBa3 Si2 O7 F,the comparison of the anionic structures was carried out in mixed alkali and alkaline-earth metal silicate fluorides.Interestingly,the result indicates the isolated[Si2 O7]dimer is rare among the above systems,which enriches the structural chemistry of silicate fluorides.展开更多
The term 'assortative mating' has been applied to describe two very different phenomena: (1) the tendency for indi- viduals to choose phenotypically similar mates from among conspecifics; or (2) the tendency to...The term 'assortative mating' has been applied to describe two very different phenomena: (1) the tendency for indi- viduals to choose phenotypically similar mates from among conspecifics; or (2) the tendency to prefer conspecific over hete- rospecific mates (behavioral reproductive isolation). Both forms of assortative mating are widespread in nature, but the relation- ship between these behaviors remains unclear. Namely, it is plausible that a preference for phenotypically similar conspecifics in cidentally reduces the probability of mating with phenotypically divergent heterospecifics. We present a model to calculate how the level of reproductive isolation depends on intraspecific assortative mating and the phenotypic divergence between species. For empirically reasonable levels of intraspecific assortment on a single trait axis, we show that strong reproductive isolation requires very substantial phenotypic divergence. We illustrate this point by applying our model to empirical data from threespine stickleback Gasterosteus aculeatus and Darwin's Finches (Geospiza spp). We conclude that typical levels of intraspecific assortment cannot generally be extrapolated to explain levels of interspecific reproductive isolation. Instead, reproductive isolation between species likely arises from different mate choice behaviors, or multivariate assortative mating [Current Zoology 58 (3): 484-492, 2012].展开更多
基金supported by the National Natural Science Foundation of China(U1703132,51872325 and 61835014)Tianshan Innovation Team Program(2018D14001)+5 种基金Xinjiang International Science&Technology Cooperation Program(2017E01014)the National Key Research Project(2016YFB0402104)the Science and Technology Project of Urumqi(P161010002)Xinjiang Key Research and Development Program(2016B02021)Major Program of Xinjiang Uygur Autonomous Region of China during the 13th Five-Year Plan Period(2016A02003)West Light Foundation of the Chinese Academy of Sciences(2016-YJRC-2)
文摘A new silicate fluoride,NaBa3 Si207 F,has been successfully synthesized by a high-temperature solution method.It crystallizes in the orthorhombic space group Cmcm(No.63).NaBa3 Si2 O7 F is the first barium-containing alkali metal silicate fluoride with the[NaO6]polyhedra,the[BaO8 F]polyhedra and isolated[Si2 O7]units.The optical characterizations indicate that NaBa3 Si2 O7 F possesses wide transparent window and available luminescence properties.To confirm the coordination surroundings of anionic groups and its thermostability,infrared spectroscopy and thermal behaviors were also analyzed,which proved the existence of tetrahedronly coordinated silicium atoms and the good stability of NaBa3 Si2 O7 F at high temperature.First-principles calculation was also implemented for better understanding the relationship between the structure of NaBa3 Si207 F and its property.Additionally,to further explore the structural novelty of NaBa3 Si2 O7 F,the comparison of the anionic structures was carried out in mixed alkali and alkaline-earth metal silicate fluorides.Interestingly,the result indicates the isolated[Si2 O7]dimer is rare among the above systems,which enriches the structural chemistry of silicate fluorides.
文摘The term 'assortative mating' has been applied to describe two very different phenomena: (1) the tendency for indi- viduals to choose phenotypically similar mates from among conspecifics; or (2) the tendency to prefer conspecific over hete- rospecific mates (behavioral reproductive isolation). Both forms of assortative mating are widespread in nature, but the relation- ship between these behaviors remains unclear. Namely, it is plausible that a preference for phenotypically similar conspecifics in cidentally reduces the probability of mating with phenotypically divergent heterospecifics. We present a model to calculate how the level of reproductive isolation depends on intraspecific assortative mating and the phenotypic divergence between species. For empirically reasonable levels of intraspecific assortment on a single trait axis, we show that strong reproductive isolation requires very substantial phenotypic divergence. We illustrate this point by applying our model to empirical data from threespine stickleback Gasterosteus aculeatus and Darwin's Finches (Geospiza spp). We conclude that typical levels of intraspecific assortment cannot generally be extrapolated to explain levels of interspecific reproductive isolation. Instead, reproductive isolation between species likely arises from different mate choice behaviors, or multivariate assortative mating [Current Zoology 58 (3): 484-492, 2012].