| 1 | Configuration of nucleolar DNA in situ in nucleolus of Allium cepa cells显示文摘The location and configuration of nucleolar DNA have not been determined for a long time. In this paper, we have observed the nucleolar infrastructure and the character of nucleolar DNA in Allium cepa cells by conventional electron microscopy and the cytochemical NAMA-Ur DNA specific staining method. Furthermore, we have properly improved the NAMA-Ur method so as to analyze the location and configuration of nucleolar DNA in situ. Our results indicated that the nucleolar DNA in Allium cepa cells is mainly located at the border between fibrillar centers and dense fibribllar component, especially distributed in the configuration of encircling the fibrillar centers. | TAO Wei HE Jie JIAO Mingda HE Mengyuan HAO Shui | 2001 | Chinese Science Bulletin2001，46，1： | 1 |
| 2 | Conceptual design and analysis of legged landers with orientation capability显示文摘The lander with orientation capability is of fundamental importance for the“Returning”mission because its body can be the base with a suitable launching angle for the ascender lifting off.This paper proposes the conceptual design and verification of Landers with Orientation Capability(LOCs).Firstly,the topological composition of the lander is analyzed and expressed in the form of Lie group,which provides the fundamental principle for the type synthesis of LOCs.Then,the type synthesis approach for designing LOCs is proposed,which includes designing the Equivalent Parallel Mechanism(EPM)and the auxiliary limbs.Numerous mechanisms of LOCs with twodimensional rotational motions are obtained based on the type synthesis approach by developing and combining the EPMs and auxiliary limbs.Afterward,kinematics and Jacobian matrix of a typical legged lander are developed,the workspace is analyzed,singularity configurations are analyzed based on the wrench graph method,and finally,the orientation capability is analyzed.The pitch and yaw angle reach 17.5°,considering the permissible range of joints.The proposed types of LOCs offer potential candidate for the“Returning”mission of the exploration mission. | Rongfu LIN Weizhong GUO Changjie ZHAO Mingda HE | 2023 | Chinese Journal of Aeronautics2023，36，3： | 0 |
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