分类: 物理学 >> 核物理学 提交时间: 2023-06-20
摘要: The stellar (n, ) cross section data for the mass numbers around A 160 are of key importance to nucleosynthesis in the main component of the slow neutron capture process, which occurs in the thermally pulsing asymptotic giant branch (TPAGB). The new measurement of (n, ) cross sections for 159Tb was performed using the C6D6 detector system at the back streaming white neutron beam line (Back-n) of the China spallation neutron source (CSNS) with neutron energies ranging from 1 eV to 1 MeV. Experimental resonance capture kernels are reported up to 1.2 keV neutron energy with this capture measurement. Maxwellian-averaged cross sections (MACS) are derived from the measured 159Tb (n, ) cross sections at kT = 5100 keV and are in good agreement with the recommended data of KADoNiS-v0.3 and JEFF-3.3, while KADoNiS-v1.0 and ENDF-VIII.0 signifificantly overestimate the present MACS up to 40% and 20%, respectively. A sensitive test of the s-process nucleosynthesis is also performed with the stellar evolution code MESA. Signifificant changes in abundances around A 160 are observed between the ENDF/B-VIII.0 and present measured rate of 159Tb(n, ) 160Tb in the MESA simulation.
分类: 生物学 >> 生态学 提交时间: 2017-11-17
摘要: We previously reported a highly potent DPP-IV inhibitor 6 with low in vivo efficacy. While trying to maintain consistent in vitro and in vivo biological activity, we initiated a pharmacokinetic property-driven optimization to improve the metabolic stability and permeability of inhibitor 6. A simple scaffold replacement of thienopyrimidine with pyrrolopyrimidine (21a) led to significantly improved metabolic stability (4% vs. 65% remaining). Further modification of the pyrrolopyrimidine scaffold to produce compound 21j resulted in much better oral bioavailability than 6. Importantly, compound 21j exhibits greater in vivo efficacy than does 6 and Alogliptin and is worthy of further development. (C) 2012 Elsevier Masson SAS. All rights reserved.