分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-08
摘要： The gravitational collapse of a massless scalar field with a self-interaction term lambda phi(4) in anti-de Sitter space is investigated. We numerically investigate the effect of the self-interaction term on the critical amplitudes, forming time of apparent horizon, stable island, and energy transformation. The results show that a positive A suppresses the formation of black hole, while a negative A enhances the process. We define two susceptibilities to characterize the effect of the self-interaction on the black hole formation, and find that near the critical amplitude, there exists a universal scaling relation with the critical exponent alpha approximate to 0.74 for the time of black hole formation.
分类： 生物学 >> 植物学 >> 应用植物学 提交时间： 2018-10-26 合作期刊: 《广西植物》
摘要： Cladophora fracta, a filamentous green macroalgal epiphyte on rhodoliths, is described from five karst springs in North China. Although Cladophora species frequently appear in karst system, their genetic diversity, biogeographical affinities and physiological properties have not been well investigated in these environments. The specific objectives of this study were to: 1) describe the habitat of the Cladophora-like algae form the five karst springs; 2) identify the thallus to species level based on a combination of morphological characteristics and molecular sequence; and 3) explore the morphological influence of habitat. To elucidate the biogeographical patterns in Cladophora, both morphological and molecular evidence were compared of Cladophoraspecimens across five study sites. Analyses of partial small subunit (SSU) and large subunit (LSU) genes revealed that the studied 50 Cladophora specimens were genetically identical species and a total of 13 ribotypes were detected. The molecular sequencing results indicated that the examined species was highly homologous with Cladophora vagabunda, though they shared few morphological features. The genus didn't form a monophyletic clade but in three different clades both in SSU and LSU trees. The microscopic structure was more consistent with that of C. fracta. The Cladophora from the five karst springs did not show significant variation in cell dimensions. However, the species exhibited larger cell diameters than those reported from lakes. In addition, the rhizoid-like branches are only observed in two locations (XA and ST). Considering the morphological characteristics, we therefore hold our species as Cladophora fracta.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Zheng Yu
Ji Li
Bingqiu Chen
Yang Huang
Shuhua jia
Maosheng Xiang
Haibo Yuan
Jianrong Shi
Chun Wang
Xiaowei Liu
摘要： Using a sample of 96,201 primary red clump (RC) stars selected from the LAMOST and Gaia surveys, we investigate the stellar structure of the Galactic disk. The sample stars show two separated sequences of high-[{\alpha}/Fe] and low-[{\alpha}/Fe] in the [{\alpha}/Fe]-[Fe/H] plane. We divide the sample stars into five mono-abundance populations (MAPs) with different ranges of [{\alpha}/Fe] and [Fe/H], named as the high-[{\alpha}/Fe], high-[{\alpha}/Fe] & high-[Fe/H], low-[Fe/H], solar, high-[Fe/H] MAPs respectively. We present the stellar number density distributions in the R R Z plane, and the scale heights and scale lengths of the individual MAPs by fitting their vertical and radial density profiles. The vertical profiles, the variation trend of scale height with the Galactocentric radius, indicate that there is a clear disk flare in the outer disk both for the low-[{\alpha}/Fe] and the high-[{\alpha}/Fe] MAPs. While the radial surface density profiles show a peak radius of 7 kpc and 8 kpc for the high-[{\alpha}/Fe] and low-[{\alpha}/Fe] MAPs, respectively. We also investigate the correlation between the mean rotation velocity and metallicity of the individual MAPs, and find that the mean rotation velocities are well separated and show different trends between the high-[{\alpha}/Fe] and the low-[{\alpha}/Fe] MAPs. At last, we discuss the character of the high-[{\alpha}/Fe] & high-[Fe/H] MAP and find that it is more similar to the high-[{\alpha}/Fe] MAP either in the radial and vertical density profiles or in the rotation velocity.
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