Field work focused on the Kuedinskie Kluchiki locality, Perm region, Urals, Russia, which contains a rich assemblage of diverse fossil organisms including higher plants(equisetophytes, pteridosperms, ginkgophytes, con...Field work focused on the Kuedinskie Kluchiki locality, Perm region, Urals, Russia, which contains a rich assemblage of diverse fossil organisms including higher plants(equisetophytes, pteridosperms, ginkgophytes, conifers, vojnovskyans) represented by stems, leaves and reproductive organs;invertebrates(mollusks, arthropods), and tetrapods(temnospondyl amphibians, seymouriamorphs, cotylosaurs, synapsids, diapsids), as well as bony fishes. General characteristics of the taxonomical composition of the Kuedinskie Kluchiki locality are given. A new peltaspermalean pteridosperm taxon, Compsopteris longipinnata sp. nov., and a voltzialean conifer Archaeovoltzia kuedensis sp. nov. are described. General considerations on the paleoecologic and paleogeographic conditions of the Kuedinskie Kluchiki locality origin are given.展开更多
Powder metallurgic Ti2 AlNb alloys with W addition are sintered at 900, 1000, 1070 °C,and 1150 °C(i.e., in the O + B2, a_2+ B2 + O, a_2+ B2, and single B2 phase regions, respectively)for 12 h, followed by wa...Powder metallurgic Ti2 AlNb alloys with W addition are sintered at 900, 1000, 1070 °C,and 1150 °C(i.e., in the O + B2, a_2+ B2 + O, a_2+ B2, and single B2 phase regions, respectively)for 12 h, followed by water quenching and furnace cooling. Comparisons of phase and microstructure between quenched and furnace-cooled W-modified alloys are carried out to illustrate the phase transformation and microstructure evolution during the cooling process. Furthermore, a comparison is also made between W-modified and W-free alloys, to reveal the function of the W alloying.W addition accelerates the solutions of a_2 and O phases during the high-temperature holding, and a Widmannsta¨tten B2 + O structure, which contributes to the properties, is induced by furnace cooling from all the phase regions. The Widmannsta¨tten structure includes a B2 matrix, primary O, and secondary O precipitates. However, W alloying refines the Widmannsta¨tten structure only when the alloys are solution-treated and then cooled from the single B2 phase. Although the hardness of the W-modified alloys is lower than that of the W-free alloys sintered in the same phase region, an enhancement of hardness, 489 ± 18 HV, is obtained in the alloy solution-treated in the single B2 phase region for only 0.5 h.展开更多
The top predators of arthropods,such as scorpions,spiders,and centipedes,are less commonly discovered in Mesozoic terrestrial Lagerst?tten.Scorpiones belong to the class Arachnida within Arthropoda,with relatively few...The top predators of arthropods,such as scorpions,spiders,and centipedes,are less commonly discovered in Mesozoic terrestrial Lagerst?tten.Scorpiones belong to the class Arachnida within Arthropoda,with relatively few fossil records[1].The earliest scorpions come from the mid Silurian,and at least some of them have been interpreted as transitional forms from sea to land[2].Despite being among the earliest terrestrial arthropods,fossil and living scorpions retain a largely conservative body plan[3].Mesozoic scorpions are mainly from mid-Cretaceous Burmese amber[4],whereas compression fossils of scorpions normally deposited in the strata are relatively rare except in the Late Triassic Keuper Sandstone Formation of England and the Early Cretaceous Crato Formation of Brazil[1].展开更多
文摘Field work focused on the Kuedinskie Kluchiki locality, Perm region, Urals, Russia, which contains a rich assemblage of diverse fossil organisms including higher plants(equisetophytes, pteridosperms, ginkgophytes, conifers, vojnovskyans) represented by stems, leaves and reproductive organs;invertebrates(mollusks, arthropods), and tetrapods(temnospondyl amphibians, seymouriamorphs, cotylosaurs, synapsids, diapsids), as well as bony fishes. General characteristics of the taxonomical composition of the Kuedinskie Kluchiki locality are given. A new peltaspermalean pteridosperm taxon, Compsopteris longipinnata sp. nov., and a voltzialean conifer Archaeovoltzia kuedensis sp. nov. are described. General considerations on the paleoecologic and paleogeographic conditions of the Kuedinskie Kluchiki locality origin are given.
基金the National Natural Science Foundation of China(Grant Nos.51474156 and U1660201)the National High Technology Research and Development Program(‘‘863" Program)of China(Grant No.2015AA042504)for financial support
文摘Powder metallurgic Ti2 AlNb alloys with W addition are sintered at 900, 1000, 1070 °C,and 1150 °C(i.e., in the O + B2, a_2+ B2 + O, a_2+ B2, and single B2 phase regions, respectively)for 12 h, followed by water quenching and furnace cooling. Comparisons of phase and microstructure between quenched and furnace-cooled W-modified alloys are carried out to illustrate the phase transformation and microstructure evolution during the cooling process. Furthermore, a comparison is also made between W-modified and W-free alloys, to reveal the function of the W alloying.W addition accelerates the solutions of a_2 and O phases during the high-temperature holding, and a Widmannsta¨tten B2 + O structure, which contributes to the properties, is induced by furnace cooling from all the phase regions. The Widmannsta¨tten structure includes a B2 matrix, primary O, and secondary O precipitates. However, W alloying refines the Widmannsta¨tten structure only when the alloys are solution-treated and then cooled from the single B2 phase. Although the hardness of the W-modified alloys is lower than that of the W-free alloys sintered in the same phase region, an enhancement of hardness, 489 ± 18 HV, is obtained in the alloy solution-treated in the single B2 phase region for only 0.5 h.
基金supported by the National Natural Science Foundation of China(41925008 and 42288201)。
文摘The top predators of arthropods,such as scorpions,spiders,and centipedes,are less commonly discovered in Mesozoic terrestrial Lagerst?tten.Scorpiones belong to the class Arachnida within Arthropoda,with relatively few fossil records[1].The earliest scorpions come from the mid Silurian,and at least some of them have been interpreted as transitional forms from sea to land[2].Despite being among the earliest terrestrial arthropods,fossil and living scorpions retain a largely conservative body plan[3].Mesozoic scorpions are mainly from mid-Cretaceous Burmese amber[4],whereas compression fossils of scorpions normally deposited in the strata are relatively rare except in the Late Triassic Keuper Sandstone Formation of England and the Early Cretaceous Crato Formation of Brazil[1].
