Transposable elements （TEs） are self-replicating, mobile DNA sequences which constitute a significant fraction of eukaryotic genomes. They are generally considered selfish DNA, as their replication and random insert...Transposable elements （TEs） are self-replicating, mobile DNA sequences which constitute a significant fraction of eukaryotic genomes. They are generally considered selfish DNA, as their replication and random insertion may have deleterious effects on genome functionalities, although some beneficial effects and evolutionary potential have been recognized. Short interspersed elements （SINEs） are non-autonomous TEs with a modular structure： a small RNA-related head, a body, and a long interspersed element-related tail. Despite their high turnover rate and de novo emergence, the body may retain highly conserved domains （HCDs） shared among divergent SINE families： in metazoans, at least nine HCD-SINEs have been recognized. Data mining on public molecular databases allowed the retrieval of 16 new HCD-SINE families from cnidarian, molluscs, arthropods, and vertebrates. Tracking the ancestry of HCDs on the metazoan phylogeny revealed that some of them date back to the Radiata-Bilateria split. Moreover, phylogenetic and age versus divergence analyses of the most ancient HCDs suggested that long-term vertical inheritance is the rule, with few horizontal transfer events. We suggest that the evolutionary conservation of HCDs may be linked to their potential to serve as recombination hotspots. This indirectly affects host genomes by maintaining active and diverse SINE lineages, whose insertions may impact （either positively or negatively） on the evolution of the genome.展开更多
The design of compliant hinges has been extensively studied in the size and shape level in the literature.This paper presents a method for designing the single-axis flexure hinges in the topology level.Two kinds of hi...The design of compliant hinges has been extensively studied in the size and shape level in the literature.This paper presents a method for designing the single-axis flexure hinges in the topology level.Two kinds of hinges,that is,the translational hinge and the revolute hinge,are studied.The basic optimization models are developed for topology optimization of the translational hinge and the revolute hinge,respectively.The objective for topology optimization of flexure hinges is to maximize the compliance in the desired direction meanwhile minimizing the compliances in the other directions.The constraints for accomplishing the translational and revolute requirements are developed.The popular Solid Isotropic Material with Penalization method is used to find the optimal flexure hinge topology within a given design domain.Numerical results are performed to illustrate the validity of the proposed method.展开更多
文摘Transposable elements （TEs） are self-replicating, mobile DNA sequences which constitute a significant fraction of eukaryotic genomes. They are generally considered selfish DNA, as their replication and random insertion may have deleterious effects on genome functionalities, although some beneficial effects and evolutionary potential have been recognized. Short interspersed elements （SINEs） are non-autonomous TEs with a modular structure： a small RNA-related head, a body, and a long interspersed element-related tail. Despite their high turnover rate and de novo emergence, the body may retain highly conserved domains （HCDs） shared among divergent SINE families： in metazoans, at least nine HCD-SINEs have been recognized. Data mining on public molecular databases allowed the retrieval of 16 new HCD-SINE families from cnidarian, molluscs, arthropods, and vertebrates. Tracking the ancestry of HCDs on the metazoan phylogeny revealed that some of them date back to the Radiata-Bilateria split. Moreover, phylogenetic and age versus divergence analyses of the most ancient HCDs suggested that long-term vertical inheritance is the rule, with few horizontal transfer events. We suggest that the evolutionary conservation of HCDs may be linked to their potential to serve as recombination hotspots. This indirectly affects host genomes by maintaining active and diverse SINE lineages, whose insertions may impact （either positively or negatively） on the evolution of the genome.
基金supported by the National Natural Science Foundation of China(Grant No.91223201)the Natural Science Foundation of Guangdong Province(Grant No.S2013030013355),Project GDUPS(2010)the Fundamental Research Funds for the Central Universities(Grant No.2012ZP0004)
文摘The design of compliant hinges has been extensively studied in the size and shape level in the literature.This paper presents a method for designing the single-axis flexure hinges in the topology level.Two kinds of hinges,that is,the translational hinge and the revolute hinge,are studied.The basic optimization models are developed for topology optimization of the translational hinge and the revolute hinge,respectively.The objective for topology optimization of flexure hinges is to maximize the compliance in the desired direction meanwhile minimizing the compliances in the other directions.The constraints for accomplishing the translational and revolute requirements are developed.The popular Solid Isotropic Material with Penalization method is used to find the optimal flexure hinge topology within a given design domain.Numerical results are performed to illustrate the validity of the proposed method.
