An efficient method for mapping the 12C+12C molecular resonances at low energies

The 12C+12C fusion reaction is famous because of its complication of molecular resonances,and it plays an important role in both nuclear structural research and astrophysics. It is extremely difficult to measure the cross sections of 12C+12C fusions at energies of astrophysical relevance because of the very low reaction yields. To measure the complicated resonant structure that exists in this important reaction, an efficient thick target method has been developed and applied for the first time at energies Ec.m.<5.3 MeV. A scan of the cross sections over a relatively wide range of energies can be carried out using only a single beam energy. The result of measurement at Ec.m.=4.1 MeV is compared with results from previous work.This method will be useful for searching for potentially existing resonances of 12C+12C in the energy range 1 MeV<Ec.m.<3 MeV.

Yield ratio of neutrons to protons in 12C（d,n）13N and 12C（d,p）13C from 0.6 to 3 MeV

The neutron yield in the12C(d,n)13N reaction and the proton yield in the12C(d,p)13C reaction have been measured using deuteron beams of energies 0.6-3 MeV.The deuteron beam is delivered from a 4-MeV electrostatic accelerator and bombarded on a thick carbon target.The neutrons are detected at 0°,24°,and 48°and the protons at135°in the laboratory frame.Further,the ratio of the neutron yield to the proton yield was calculated.This can be used to effectively recognize the resonances.The resonances are found at 1.4 MeV,1.7 MeV,and 2.5 MeV in the12C(d,p)13C reaction,and at 1.6 MeV and 2.7 MeV in the12C(d,n)13N reaction.The proposed method provides a way to reduce systematic uncertainty and helps confirm more resonances in compound nuclei.

Nuclear Astrophysics Experiments in Collaboration with Ruhr University

This paper reports on two nuclear astrophysics experiments performed in collabora- tion with Ruhr University. In a 12C＋2C fusion reaction, the 12C（12C, a）20e and 12C（12C, p）23Na reactions were studied in the energy range of E = 2.10 MeV to 4.75 MeV using -y-ray spectroscopy. The deduced astrophysical S（E）＊ factor exhibited a new, strong resonance at E -= 2.14 MeV, which lay at the high-energy tail of the Gamow peak. The resonance increased the reaction rate of the ^-channel by a factor of five near T = 8 ~ l0s K. The electron screening in d（d, p）t was stud- ied for a series of deuterated metal, insulator and semiconductor targets. Compared with the measurements performed with a gaseous D2 target, a large effect was observed in most metals, while a comparatively small effect was found in the insulators and semiconductors. Subsequently the temperature dependence of the electron screening in the d（d, p）t reaction was studied for the deuterated metals Pt and Co. Enhanced electron screening decreased with increasing tempera- ture. These data represent the first observations of the temperature dependence of a nuclear cross section.

Modified astrophysical S-factor of 12C+12C fusion reaction at sub-barrier energies

The 12C+12C fusion reaction plays a crucial role in stellar evolution and explosions.Its main open reaction channels includeα,p,n,and 8Be.Despite more than a half century of efforts,large differences remain among the experimental data of this reaction measured using various techniques.In this work,we analyze the existing data using a statistical model.Our calculation shows the following:1)the relative systematic uncertainties of the predicted branching ratios decrease as the predicted ratios increase;2)the total modified astrophysical S-factors(S^* factors)of the p andαchannels can be obtained by summing the S^* factors of their corresponding ground-state transitions and the characteristicγrays,while taking into account the contributions of the missing channels to the latter.After applying corrections based on branching ratios predicted by the statistical model,an agreement is achieved among the different data sets at Ecm>4 MeV,while some discrepancies remain at lower energies,suggesting the need for better measurements in the near future.We find that the S^* factor recently obtained from an indirect measurement is inconsistent with the direct measurement value at energies below 2.6 MeV.We recommend upper and lower limits for the 12C+12C S^* factor based on the existing models.A new 12C+12C reaction rate is also recommended.

Heterofullerenes C_(48)N_(12) and C_(48)B_(12) with Rare T_h Symmetry: a DFT Study

The molecule with Th symmetry is rare. Two C60-1ike molecules C48N12 and C48B12 with rare Th symmetry have been reported here, which is an approach to seek for the molecule with rare Th symmetry. Their structural, electronic, vibrational, NMR, and thermodynamic properties have been calculated at the B3LYP/6-31G（d） level of theory. Vibrational modes have been assigned according to their symmetry. They all have 73 independent vibrational modes： 22 IR-active modes with Tu symmetry and 37 Raman-active modes with Ag, Eg and Tg symmetry, respectively. The heats of formation have been calculated using isodesmic reactions, and the values of C48N12 and C48B12 are 3812.0 and 3423.8 kJ mo1-1, respectively. According to the estimated band gaps for their fcc solid, they are all semiconducting materials, like C60, especially C48B12-based fcc solid.

Novel thick-target inverse kinematics method for the astrophysical ^(12)C+^(12)C fusion reaction

The ^(12)C+^(12)C fusion is one of the most important reactions in modern nuclear astrophysics.The trend and magnitude of the reaction rate within the Gamow window strongly influence various astrophysical processes.However,direct measurement of this reaction is extremely difficult,which makes it necessary to develop indirect methods.In this study,the ^(23)Na+p reaction system was used to study the compound nucleus ^(24)Mg.We employed a thick-target inverse kinematics method combined with the -charged-particle coincidence technique to measure the proton and exit channels of ^(24)Mg.Technical details of the ^(23)Na+p thick-target inverse kinematics experiment and analysis are presented herein.

USH2A mutation and specific driver mutation subtypes are associated with clinical efficacy of immune checkpoint inhibitors in lung cancer

This study aimed to identify subtypes of genomic variants associated with the efficacy of immune checkpoint inhibitors(ICIs)by conducting systematic literature search in electronic databases up to May 31,2021.The main outcomes including overall survival(OS),progression-free survival(PFS),objective response rate(ORR),and durable clinical benefit(DCB)were correlated with tumor genomic features.A total of 1546 lung cancer patients with available genomic variation data were included from 14 studies.The Kirsten rat sarcoma viral oncogene homolog G12C(KRAS^(G12C))mutation combined with tumor protein P53(TP53)mutation revealed the promising efficacy of ICI therapy in these patients.Furthermore,patients with epidermal growth factor receptor(EGFR)classical activating mutations(including EGFRL858Rand EGFRΔ19)exhibited worse outcomes to ICIs in OS(adjusted hazard ratio(HR),1.40;95%confidence interval(CI),1.01-1.95;P=0.0411)and PFS(adjusted HR,1.98;95%CI,1.49-2.63;P<0.0001),while classical activating mutations with EGFR^(T790)Mshowed no difference compared to classical activating mutations without EGFR^(T790)Min OS(adjusted HR,0.96;95%CI,0.48-1.94;P=0.9157)or PFS(adjusted HR,0.72;95%CI,0.39-1.35;P=0.3050).Of note,for patients harboring the Usher syndrome type-2A(USH2A)missense mutation,correspondingly better outcomes were observed in OS(adjusted HR,0.52;95%CI,0.32-0.82;P=0.0077),PFS(adjusted HR,0.51;95%CI,0.38-0.69;P<0.0001),DCB(adjusted odds ratio(OR),4.74;95%CI,2.75-8.17;P<0.0001),and ORR(adjusted OR,3.45;95%CI,1.88-6.33;P<0.0001).Our findings indicated that,USH2A missense mutations and the KRAS^(G12C)mutation combined with TP53 mutation were associated with better efficacy and survival outcomes,but EGFR classical mutations irrespective of combination with EGFR^(T790)Mshowed the opposite role in the ICI therapy among lung cancer patients.Our findings might guide the selection of precise targets for effective immunotherapy in the clinic.

低能^(12)C+^(12)C反应的测量

在鲁尔大学DTL实验室4MV串列加速器上利用12C束流轰击高纯度的C靶.通过γ谱学方法测量了Ec.m.=2.10-4.75MeV12C+12C熔合蒸发反应,并导出了12C(12C,α)20Ne和12C(12C,p)23Na反应的天体物理S(E)*因子.在Ec.m.≤3.0MeV时发现新的共振.特别是在Gamow峰的高能尾部Ec.m.=2.14MeV处出现强共振峰.当T=8×108K时,这些共振使得α链的反应率比无共振情况下提高了近5倍.