分类： 物理学 >> 核物理学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： We study in the framework of the Langevin model the influence of initial excitation energy (E*) of Hg compound nuclei (CNs) on the sensitivity of the excitation energy at scission (Esc*) to the nuclear friction strength (). It is shown that the sensitivity is enhanced substantially with increasing E*. Moreover, we find that the significant sensitivity of Esc* to at high E* is little affected by a marked difference in the neutron-to-proton ratio of a CN and in its size and fissility. Our findings suggest that, on the experimental side, a measurement of Esc* in energetic proton-induced spallation reactions can provide not only a sensitive but also a robust probe of nuclear dissipation in fission of highly excited nuclei. Further development of a suitable approach to spallation reaction is discussed.
分类： 生物学 >> 动物学 提交时间： 2021-11-26 合作期刊: 《古脊椎动物学报》
摘要： The Qaidam Basin is a key area for understanding the paleoenvironmental and faunal history of the Tibetan Plateau. The fossil schizothoracine fish, Hsianwenia wui, evolved extraordinarily thickened bones to adapt to the aridification of the Qaidam Basin during the Pliocene. However, the nature of the bone thickening itself remains elusive. To promote the further investigation of the physiological mechanism of the pachyostosis and the phylogenetic interrelationships of Hsianwenia and all relevant cyprinids, here we present a comprehensive morphological study of Hsianwenia. We have new information on the anterior part of the cranial cavity, a large supraneural 3 in the Weberian apparatus, numerous procurrent caudal fin rays supported by the preural centrum (Pu) 5, and a neural arch on Pu2. We also find the differentiated pattern of the bone-thickening: the pachyostosis exists in the endoskeleton but not in the dermal skeleton; it is more obvious in ventral bones than in dorsal ones, when the thickening is present in the dorsally and ventrally grouped endoskeletal bones (e.g., the epineural and epipleural intermuscular bones). Considering the integrity of musculoskeletal system manipulating the chewing activities, we suspect that the thickened pharyngeal jaws and the hard food processing might be associated with the unique hind protrusion (cleithral “humeral” process) of the dermal pectoral girdle of Hsianwenia.
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