Most described Mesozoic ants belong to stem groups that existed only during the Cretaceous period.Previously,the earliest known crown ants were dated to the Turonian(Late Cretaceous,ca.94-90 million years ago(Ma))depo...Most described Mesozoic ants belong to stem groups that existed only during the Cretaceous period.Previously,the earliest known crown ants were dated to the Turonian(Late Cretaceous,ca.94-90 million years ago(Ma))deposits found in the USA,Kazakhstan,and Botswana.However,the recent discovery of an alate male ant in Kachin amber from the earliest Cenomanian(ca.99 Ma),representing a new genus and species,Antiquiformica alata,revises the narrative on ant diversification.Antiquiformica can be distinctly differentiated from all known male stem ants by its geniculate antennae with elongated scape,extending far beyond the occipital margin of the head and half the length of the funiculus,as well as its partly reduced forewing venation.Furthermore,the combination of a one-segmented waist with a well-developed node,elongated scape extending beyond the occipital margin,and reduced forewing venation,particularly the completely reduced m-cu and rs-m crossveins and absence of rm and mcu closed cells,firmly places the fossil within the extant subfamily Formicinae.Fourier transform infrared spectroscopy(FTIR)confirmed that the amber containing Antiquiformica alata originated from the Kachin mines in Myanmar.This discovery significantly revises our understanding of the early evolution of Formicinae.The presence of Antiquiformica in Cenomanian amber indicates that the subfamily Formicinae emerged at least by the start of the Late Cretaceous,with crown ants likely originating earlier during the earliest Cretaceous or possibly the Late Jurassic,although paleontological evidence is lacking to support the latter hypothesis.展开更多
Poly(aryl ether keton e)(PAEK) films with different crystallinities were obtained by controlling the cooling rate,which were subjected to the absorption and desorption of methylene chloride(CH_(2)Cl_(2)).We employed a...Poly(aryl ether keton e)(PAEK) films with different crystallinities were obtained by controlling the cooling rate,which were subjected to the absorption and desorption of methylene chloride(CH_(2)Cl_(2)).We employed attenuated total reflection Fourier transform infrared(ATR-FTIR)spectroscopy analyses to investigate the diffusion behavior of CH_(2)Cl_(2) in PAEK films with different crystallinities.According to the Fickian diffusion model,the calculated diffu sion coefficients of CH_(2)Cl_(2) in PAEK films were observed to decrease with increasing crystallinity.The effect of CH_(2)Cl_(2)absorption and desorption on the mechanical properties of PAEK films with different crystallinity was further analyzed using tensile tests.The tensile tests exhibited that CH_(2)Cl_(2) has two concurrent effects:plasticization and solvent-induced crystallization.Differential scanning calorimetry(DSC) and wide-angle X-ray diffraction(WXRD) techniques further confirmed solvent-induced crystallization behavior.The results would be beneficial to understand the solvent resistance of PAEK materials and consequently provide the practical application conditions of PAEK with a theoretical basis.展开更多
基金supported by the National Natural Science Foundation of China(32270467,32020103006)National Research Foundation of Ukraine(2020/02/0369 to A.G.R.)CONCYTEC through the PROCIENCIA“Interinstitutional Alliances for Doctorate Programs”(PE501084299-2023-PROCIENCIA-BM to M.S.E.)。
文摘Most described Mesozoic ants belong to stem groups that existed only during the Cretaceous period.Previously,the earliest known crown ants were dated to the Turonian(Late Cretaceous,ca.94-90 million years ago(Ma))deposits found in the USA,Kazakhstan,and Botswana.However,the recent discovery of an alate male ant in Kachin amber from the earliest Cenomanian(ca.99 Ma),representing a new genus and species,Antiquiformica alata,revises the narrative on ant diversification.Antiquiformica can be distinctly differentiated from all known male stem ants by its geniculate antennae with elongated scape,extending far beyond the occipital margin of the head and half the length of the funiculus,as well as its partly reduced forewing venation.Furthermore,the combination of a one-segmented waist with a well-developed node,elongated scape extending beyond the occipital margin,and reduced forewing venation,particularly the completely reduced m-cu and rs-m crossveins and absence of rm and mcu closed cells,firmly places the fossil within the extant subfamily Formicinae.Fourier transform infrared spectroscopy(FTIR)confirmed that the amber containing Antiquiformica alata originated from the Kachin mines in Myanmar.This discovery significantly revises our understanding of the early evolution of Formicinae.The presence of Antiquiformica in Cenomanian amber indicates that the subfamily Formicinae emerged at least by the start of the Late Cretaceous,with crown ants likely originating earlier during the earliest Cretaceous or possibly the Late Jurassic,although paleontological evidence is lacking to support the latter hypothesis.
基金financially supported by the National Key R&D Program of China (No.2022YFB3709402)。
文摘Poly(aryl ether keton e)(PAEK) films with different crystallinities were obtained by controlling the cooling rate,which were subjected to the absorption and desorption of methylene chloride(CH_(2)Cl_(2)).We employed attenuated total reflection Fourier transform infrared(ATR-FTIR)spectroscopy analyses to investigate the diffusion behavior of CH_(2)Cl_(2) in PAEK films with different crystallinities.According to the Fickian diffusion model,the calculated diffu sion coefficients of CH_(2)Cl_(2) in PAEK films were observed to decrease with increasing crystallinity.The effect of CH_(2)Cl_(2)absorption and desorption on the mechanical properties of PAEK films with different crystallinity was further analyzed using tensile tests.The tensile tests exhibited that CH_(2)Cl_(2) has two concurrent effects:plasticization and solvent-induced crystallization.Differential scanning calorimetry(DSC) and wide-angle X-ray diffraction(WXRD) techniques further confirmed solvent-induced crystallization behavior.The results would be beneficial to understand the solvent resistance of PAEK materials and consequently provide the practical application conditions of PAEK with a theoretical basis.
