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The double neutron/proton ratio of nucleon emissions taken from two reaction systems using four isotopes of the same element, namely, the neutron/proton ratio in the neutron-rich system over that in the more symmetric system, has the advantage of reducing systematically the influence of the Coulomb force and the normally poor efficiencies of detecting low energy neutrons. The double ratio thus suffers less systematic errors. Within the IBUU04 transport model the double neutron/proton ratio is shown to have about the same sensitivity to the density dependence of nuclear symmetry energy as the single neutron/proton ratio in the neutron-rich system involved. The double neutron/proton ratio is therefore more useful for further constraining the symmetry energy of neutron-rich matter. 相似文献
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Qing-Zhong Li Wen-Ming Liu Ran Li Wen-Zuo Li Jian-Bo Cheng Bao-An Gong 《Structural chemistry》2013,24(1):25-31
The H2O···XCCNgF and H3N···XCCNgF (X = Cl and Br; Ng = Ar, Kr, and Xe) complexes have been studied with quantum chemical calculations at the MP2/aug-cc-pVTZ level. The results show that the inserted noble gas atom has an enhancing effect on the strength of halogen bond, and this enhancement is weakened with the increase of noble gas atomic number. The methyl and Li substituents in the electron donor strengthen the halogen bond. The interaction energy increases from ?3.75 kcal/mol in H3N–BrCCF complex to ?9.66 kcal/mol in H2LiN–BrCCArF complex. These complexes have been analyzed with atoms in molecules, natural bond orbital, molecular electrostatic potentials, and energy decomposition calculations. 相似文献
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α-取代氨基氟代苯基膦酸酯衍生物的合成、晶体结构与抗癌活性 总被引:4,自引:0,他引:4
利用席夫碱与亚磷酸酯反应, 合成了新型O,O'-二烷基-α-(6-甲氧苯并噻唑-2-基氨基)-4-氟苯基膦酸酯化合物, 结构经元素分析, IR, 1H NMR, 13C NMR和X单晶衍射确认. X单晶衍射测试结果表明: 化合物3d分子属于四面体晶系, 空间群I4(1)/a, a=2.1055(3) nm, b=2.1055(3) nm, c=2.0521(5) nm, α=90.00°, β=90.00°, γ=90.00°, V=0.9098(3) nm3,
Z=16, Dc=1.321 mg/m3, =0.250 mm-1, F(000)=3808. 化合物还存在着1个分子内氢键[N(2)—H(2)…O(1)]. 生物测定表明化合物3f在20 g/mL浓度下对PC3细胞的抑制率为84.3%. 相似文献
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In the present work we investigated a novel triplet ground-state germylenoid HB=GeLiF as well as its insertion reactions with RH(R = F,OH and NH2) using the DFT B3LYP and QCISD methods for the first time.Geometry optimization calculations show that the triplet HB=GeLiF has three equilibrium structures,in which the four-membered ring structure is the most stable with the lowest energy.All mechanisms of the three insertion reactions of germylenoid HB=GeLiF with RH(R = F,OH,and NH2) are identical to each other.Based on the calculated results,it is concluded that under the same conditions the insertion reactions should occur easily in the order of H-F > H-OH > H-NH2.In THF solvent the insertion reactions get more difficult than in the gas phase. 相似文献
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The ultimate goal of studying isospin physics via heavy-ion reactions with neutron-rich, stable and/or radioactive nuclei is to explore the isospin dependence of in-medium nuclear effective interactions and the equation of state of neutron-rich nuclear matter, particularly the isospin-dependent term in the equation of state, i.e., the density dependence of the symmetry energy. Because of its great importance for understanding many phenomena in both nuclear physics and astrophysics, the study of the density dependence of the nuclear symmetry energy has been the main focus of the intermediate-energy heavy-ion physics community during the last decade, and significant progress has been achieved both experimentally and theoretically. In particular, a number of phenomena or observables have been identified as sensitive probes to the density dependence of nuclear symmetry energy. Experimental studies have confirmed some of these interesting isospin-dependent effects and allowed us to constrain relatively stringently the symmetry energy at sub-saturation densities. The impact of this constrained density dependence of the symmetry energy on the properties of neutron stars have also been studied, and they were found to be very useful for the astrophysical community. With new opportunities provided by the various radioactive beam facilities being constructed around the world, the study of isospin physics is expected to remain one of the forefront research areas in nuclear physics. In this report, we review the major progress achieved during the last decade in isospin physics with heavy ion reactions and discuss future challenges to the most important issues in this field. 相似文献
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Gravitational radiation is a fundamental prediction of General Relativity. Elliptically deformed pulsars are among the possible sources emitting gravitational waves (GWs) with a strain-amplitude dependent upon the star's quadrupole moment, rotational frequency, and distance from the detector. We show that the gravitational wave strain amplitude h0 depends strongly on the equation of state of neutron-rich stellar matter. Applying an equation of state with symmetry energy constrained by recent nuclear laboratory data, we set an upper limit on the strain-amplitude of GWs produced by elliptically deformed pulsars. Depending on details of the EOS, for several millisecond pulsars at distances 0.18 kpc to 0.35 kpc from Earth, the maximal h0 is found to be in the range of ∼[0.4–1.5]×10−24. This prediction serves as the first direct nuclear constraint on the gravitational radiation. Its implications are discussed. 相似文献