Subjects: Physics >> Nuclear Physics submitted time 2023-05-30
Abstract： Thorium-229 possesses the lowest first nuclear excited state, with an energy of approximately 8 eV. The extremely narrow
linewidth of the first nuclear excited state, with an uncertainty of 53 THz, prevents direct laser excitation and realization of
the nuclear clock. We present a proposal using the Coulomb crystal of a linear chain formed by 229Th3+ ions, where the nuclei of 229Th3+ ions in the ion trap are excited by the electronic bridge (EB) process. The 7 P1∕2 state of the thorium-229 nuclear ground state is chosen for EB excitation. Using the two-level optical Bloch equation under experimental conditions, we calculate that 2 out of 36 prepared thorium ions in the Coulomb crystal can be excited to the first nuclear excited state, and it takes approximately 2 h to scan over an uncertainty of 0.22 eV. Taking advantage of the transition enhancement of EB and the long stability of the Coulomb crystal, the energy uncertainty of the first excited state can be limited to the order of 1 GHz
Subjects: Biology >> Biochemistry submitted time 2017-05-19
Abstract：Thirteen new pentacyclic triterpenoids, cleistocalyxic acids AK (1, 2, 4, 5, and 713) and cleistocalyxolides A (3) and B (6), and fifteen known analogues (1428), based on taraxastane, oleanane, ursane, multiflorane, and lupane skeletons, were isolated from the leaves of Cleistocalyx operculatus. The structures of 113 were elucidated by analysis of their spectroscopic data and ECD/TDDFT computations. Cleistocalyxolide A (3), presumed to be derived from the known taraxastane-type compound 14, has a rare rearranged triterpenoid backbone. Cleistocalyxic acid B (2) displayed cytotoxicity against HepG2, NCI-N87, and MCF-7 cancer cell lines with IC50 values ranging from 3.2 to 6.5 M and cleistocalyxic acid D (5) was active against HepG2 and NCI-N87 cells with the values around 5.0 M. The non-cytotoxic cleistocalyxic acid E (7) inhibited production of IL-6 by 68.1% and TNF- by 53.7% in LPS-induced RAW 264.7 macrophages at the concentration of 2 M.
Peer Review Status:
Awaiting Review
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