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        검색결과 5

        1.
        2024.07 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Much effort has been carried out to calibrate and revise asteroseismic relations, given their importance of relations in asteroseismology in determining fundamental parameters of stars. In this study, we statistically explore asteroseismic relations with partial correlation coefficients to determine the most fundamental parameters, separately analyzing asteroseismic data based on the evolutionary status of stars from main sequence up to core helium-burning red-clump stars. We have found that regardless of the evolutionary status of the sampled stars the surface gravity and density of stars strongly influence the observed correlations. More importantly, it is found that indirect correlations derived considering the influence of confounding parameters are subject to the evolutionary status. For example, the observed correlation of the large frequency separation Δν with the central frequency νmax is influenced by the stellar mass, radius, and luminosity only for main sequence stars. The observed correlation of the width of the Gaussian envelope δνenv with νmax is influenced by the stellar mass, effective temperature, radius, and luminosity for main-sequence and subgiant stars. The observed relation between Δν and the small frequency separation δν02 is influenced by the stellar mass, radius, and luminosity for main-sequence and subgiant stars. In contrast, effective temperature, metallicity, and age do not seem to significantly affect the observed correlations. Finally, we conclude by discussing implication of our findings.
        4,000원
        2.
        2024.04 구독 인증기관·개인회원 무료
        Flower chafers (Coleoptera: Scarabaeidae: Cetoniinae) are globally distributed, comprising approximately 4,000 described species. They primarily feed on nectar and sap of deciduous trees. The larvae exhibit the unique characteristic of crawling on their backs, distinguishing them from other scarabs. Additionally, the majority of flower chafers fly with their elytra closed, unlike other scarabs that fly with fully opened wings. Šípek et al. (2016) conducted the first molecular phylogenetic study to investigate their phylogenetic relationships and characters of elytra related to the flight mode. Building upon this study, we infer the diversification times and rates of Cetoniinae and its subgroups, and reconstruct the evolutionary process of flight mode transformation. Furthermore, we discuss the current limitations and future directions of this topic.
        3.
        2015.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We investigate physical properties of the nearby (∼ 7.5 pc) astrometric binary μ Cas in the context of standard evolutionary theory. Based on the spectroscopically determined relative abundances ([ /Fe] & +0.4 dex, [Fe/H] ∼ −0.7 dex), all physical inputs such as opacities and equation of state are consistently generated. By combining recent spectroscopic analyses with the astrometric observations from the HIPPARCOS parallaxes and the CHARA array, the evolutionary model grids have been constructed. Through the statistical evaluation of the 2-minimization among alternative models, we find a reliable evolutionary solution (MA, MB, tage) = (0.74 M⊙, 0.19 M⊙, 11 Gyr) which excellently satisfies observational constraints. In particular, we find that the helium abundance of μ Cas is comparable with the primordial helium contents (Yp ∼ 0.245). On the basis of the well-defined stellar parameters of the primary star, the internal structure and the p-mode frequencies have been estimated. From our seismic computation, μ Cas is expected to have a first order spacing  ∼ 169 μHz. The ultimate goal of this study is to describe physical processes inside a low-mass star through a complete modelling from the spectroscopic observation to the evolutionary computation.
        4,200원
        4.
        2014.04 구독 인증기관·개인회원 무료
        Acetylcholinesterase (AChE) plays a pivotal role in the synaptic transmission in the cholinergic nervous system of most animals, including insects. Most insects possess two AChEs (i.e., AChE1 vs. AChE2), which are encoded by two paralogous loci originated from the duplication that occurred before the radiation of insects. The phylogenetic analysis suggested that the last common ancestor of ace1 and ace2 shared its origin with those of Platyhelminthes. In addition, ace1 lineage showed a lower evolutionary rate (d and dN/dS ratio) compared to ace2 lineage, suggesting that the ace1 lineage has maintained relatively more essential functions following duplication. Furthermore, structural modeling of AChEs revealed that consistent structural alteration in their active-site gorge topology was caused by amino acid substitution, likely leads to functional differentiation between two AChEs. The functional transition of ace in some hymenopteran insects appears to have occurred by only a few mutations resulting in dramatic alteration of AChE activity. Taken together, our findings provide basic information on when the ace duplication occurred and what structural features have been associated with the differentiation of two AChEs during evolution.