943 research outputs found

    Порівняльний аналіз систем для ранжирування українських наукових періодичних видань та їхніх складових

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    Проаналізовано відомі бази даних наукових публікацій і рейтинги наукових публікацій, окремих науковців, наукових журналів та окремих галузей науки. Запропоновано інфологічну модель і бізнес-правила бази даних наукових публікацій. На її основі запропоновано метод розрахунку вебометричного рейтингу наукових публікацій, авторів, організацій, журналів.Проанализированы известные базы данных научных публикаций и рейтинги научных публикаций, отдельных ученых, научных журналов и отдельных направлений науки. Предложена инфологическая модель и бизнес-правила базы данных научных публикаций. На ее основе предложен метод расчета вебометрического рейтинга научных публикаций, авторов, организаций, журналов.The known databases of scientific publications and the rating of scientific publications, certain scientists, scientific journals and certain fields of science are analyzed. The infological model and the business rules of scientific publications database are proposed. The computing method of webometrics rating of scientific publications, authours, journals and organizations is proposed

    Diversification of myco-heterotrophic angiosperms: evidence from Burmanniaceae.

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    Background - Myco-heterotrophy evolved independently several times during angiosperm evolution. Although many species of myco-heterotrophic plants are highly endemic and long-distance dispersal seems unlikely, some genera are widely dispersed and have pantropical distributions, often with large disjunctions. Traditionally this has been interpreted as evidence for an old age of these taxa. However, due to their scarcity and highly reduced plastid genomes our understanding about the evolutionary histories of the angiosperm myco-heterotrophic groups is poor. Results - We provide a hypothesis for the diversification of the myco-heterotrophic family Burmanniaceae. Phylogenetic inference, combined with biogeographical analyses, molecular divergence time estimates, and diversification analyses suggest that Burmanniaceae originated in West Gondwana and started to diversify during the Late Cretaceous. Diversification and migration of the species-rich pantropical genera Burmannia and Gymnosiphon display congruent patterns. Diversification began during the Eocene, when global temperatures peaked and tropical forests occurred at low latitudes. Simultaneous migration from the New to the Old World in Burmannia and Gymnosiphon occurred via boreotropical migration routes. Subsequent Oligocene cooling and breakup of boreotropical flora ended New-Old World migration and caused a gradual decrease in diversification rate in Burmanniaceae. Conclusion - Our results indicate that extant diversity and pantropical distribution of myco-heterotrophic Burmanniaceae is the result of diversification and boreotropical migration during the Eocene when tropical rain forest expanded dramaticall
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