28 research outputs found
Time-resolved Measurement of Quadrupole Wakefields in Corrugated Structures
Corrugated structures have recently been widely used for manipulating
electron beam longitudinal phase space and for producing THz radiation. Here we
report on time-resolved measurements of the quadrupole wakefields in planar
corrugated structures. It is shown that while the time- dependent quadrupole
wakefield produced by a planar corrugated structure causes significant growth
in beam transverse emittance, it can be effectively canceled with a second
corrugated structure with orthogonal orientation. The strengths of the
time-dependent quadrupole wakefields for various corrugated structure gaps are
also measured and found to be in good agreement with theories. Our work should
forward the applications of corrugated structures in many accelerator based
scientific facilities
Life cycle evolution in the trilobites Balangia and Duyunaspis from the Cambrian Series 2 (Stage 4) of South China
The evolution process can be reconstructed by tracking the changes in the dynamic characters of life cycles. A number of related trilobites from the Cambrian of South China provide additional information for the study of trilobite evolutionary patterns, which has been hampered by previous incomplete fossil record though. Here, Balangia and Duyunaspis represent related Cambrian oryctocephalid trilobites from South China, are comprehensively discussed over the ontogeny, and the results show that, from B. balangensis via D. duyunensis to D. jianheensis, their exoskeletal morphology shows a directional evolution. Based on the direction of evolutionary changes in the development of Balangia and Duyunaspis, we speculate that Duyunaspis likely evolved from Balangia instead of Balangia evolved from Duyunaspis, as was previously assumed. This inference is also supported by the phylogenetic tree. This research provides not only a better understanding of the mechanisms of evolution in trilobites, but also new insights for the relationship between developmental evolutionary changes and phylogeny in trilobites.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUENational Natural Science Foundation of ChinaGuizhou Bureau of Science and TechnologyPriority Research Program of Chinese Academy of Sciencespu