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: In radiotherapy, the energy of the rays used could be larger than 10 MeV, which would potentially activate stable nucleus into a radioactive one. The induced reactions on some of the human essential elements are studied to show the probability of changes of nuclei. The Talys1.4 toolkit was adopted as the theoretical model for calculation. The reactions investigated include the (, n) and (, p) channels for the stable Na, Mg, Cl, K, Ca, and Fe isotopes, with the incident energy of ranging from 1 to 30 MeV. It was found that the cross sections for the reactions are very low, and the maximum cross section is no larger than 100 mb. By considering the threshold energy of the channel, the half-life time of the residue nucleus, and the percentage of the element accounting for the weight and its importance in the body, it is suggested to track the radioactive nuclei 22Na, 41Ca, and 42,43K after therapy. The results might be useful for medical diagnosis and disease treatment.
分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: In this paper, the growth curves of yeast cells exposed to X-rays were detected, and then fitted by Gompertz equation. The yeast cells treated with 50125 Gy showed an increased exponential growth rate, and lower total biomass at plateau. At doses 150 Gy, cells showed a decreased exponential growth rate and higher total biomass at plateau. DNA lesions were detected by comet assay. Meanwhile, intracellular accumulation of reactive oxygen species (ROS), reduction of mitochondrial membrane potential (m) and cell membrane integrity were evaluated. We conclude that X-ray irradiation results in DNA lesions, ROS accumulation and m decline in a dose-dependent manner, and that these changes may be one of causes of X-rays-induced apoptosis in yeast. Furthermore, yeast cell membrane integrity appeared compromised following irradiation, suggesting that membrane damage may also have a role in the biological effects of radiation.
分类: 物理学 >> 核物理学 提交时间: 2023-10-23
摘要: The pseudo-rapidity distributions of the charged particles produced in the asymmetric collision systems p+Al, p+Au and $^3$He+Au at $ sqrt{s_{NN}} = 200$ GeV are evaluated in the framework of a fireball model with Tsallis thermodynamics. The fireball model assumes that the experimentally measured particles are produced by fireballs following the Tsallis distribution and it can effectively describe the experimental data. Our results as well as previous results for d+Au collisions at $ sqrt{s_{NN}} = 200$ GeV and p+Pb collisions at $ sqrt{s_{NN}} = 5.02$ TeV validate that the fireball model based on Tsallis thermodynamics can provide a universal framework for pseudo-rapidity distribution of the charged particles produced in asymmetric collision systems. We predict the centrality dependence of the total charged particle multiplicity in the p+Al, p+Au and $^3$He+Au collisions. Additionally, the dependences of the fireball model parameters ($y_{0a}$, $y_{0A}$, $ sigma_{a}$ and $ sigma_{A}$) on the centrality and system size are studied.
分类: 天文学 >> 天文学 提交时间: 2024-05-10 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: Determining asteroid properties provides valuable physical insights but inverting them from photometric lightcurves remains computationally intensive. This paper presents a new approach that combines a simplified Cellinoid shape model with the Parallel Differential Evolution (PDE) algorithm to accelerate inversion. The PDE algorithm is more efficient than the Differential Evolution algorithm, achieving an extraordinary speedup of 37.983 with 64 workers on multicore CPUs. The PDE algorithm accurately derives period and pole values from simulated data. The analysis of real asteroid lightcurves validates the method's reliability: in comparison with results published elsewhere, the PDE algorithm accurately recovers the rotational periods and, given adequate viewing geometries, closely matches the pole orientations. The PDE approach converges to solutions within 20,000 iterations and under one hour, demonstrating its potential for large-scale data analysis. This work provides a promising new tool for unveiling asteroid physical properties by overcoming key computational bottlenecks.
分类: 化学 >> 物理化学 提交时间: 2017-11-05 合作期刊: 《结构化学》
摘要: A new iodiplumbate/organic hybrid constructed from asymmetric viologen and polyiodides, (PBPY-H2)2[PbI4(I3)2] (1, PBPY = N-(propionate)-4,4΄-bipyridinium), has been synthesized via solvothermal reaction and structurally determined by X-ray diffraction method. Compound 1 crystallizes in monoclinic system, space group P21/c with Mr = 1936.72, a = 11.622(2), b = 14.839(3), c = 13.372(2) Å, β = 109.447(3)°, V = 2174.6(7) Å3, Z = 2, Dc = 2.958 g/cm3, F(000) = 1712, μ(MoKα) = 11.011 mm–1, the final R = 0.0389 and wR = 0.0854 for 3866 observed reflections with I > 2σ(I). [PbI4(I3)2]4- mononuclear cluster of 1 features a seldom example of coordinated I3- donors for the lead center. Intermolecular hydrogen bonds between [PbI4(I3)2]4- clusters and (PBPY-H)24+ dimmers contribute to the formation of a 2-D layer. Its absorption spectrum was investigated, and lower energy band gap of 1.42 eV was explained by DFT calculation. Interestingly, 1 exhibits photocatalytic activity for the degradation of rhodamine B.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: The operation of the HIRFL accelerator has shown that the beam transmission efficiency of the sector focusing cyclotron (SFC) injector line is rather poor. Beam simulations have been performed to investigate the possible causes for this low transmission. It is predicted that the property of transversal coupling of the ion beam from electron cyclotron resonance (ECR) ion source can be an important factor to degrade the beam quality by increasing the beam emittance, resulting in a serious particle loss. An improved operation scheme for the SECRAL associated line has been proposed, and the corresponding experiment was carried out. This paper presents the test results.
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: A simulation approach is developed to obtain the linear energy transfer (LET) spectrum of all secondary ions and predict single event upset (SEU) occurrence induced by neutron in memory devices. Neutron reaction channels, secondary ion species and energy ranges, and LET calculation method are introduced respectively. Experimental results of neutron induced SEU effects on static random access memory (SRAM) and programmable read only memory (EEPROM) are presented to confirm the validity of the simulation results.
分类: 地球科学 >> 地质学 提交时间: 2017-10-09 合作期刊: 《古脊椎动物学报》
摘要: The traditional serial grinding method used to investigate the internal structure of fossils cannot be readily applied to valuable fossil specimens due to its destructive and time-consuming nature. Computed tomography (CT) is an ideal non-destructive technique for investigating the internal structure of fossils, in which thousands of serial images are obtained and used to produce an accurate reconstruction of the internal morphology. This paper reviews the design, development and applications of the first CT system in China dedicated exclusively to scanning fossils. The 225 kV three-dimensional (3D) fossil micro-CT (225-3D-μCT) is capable of high-resolution volumetric imaging, with a resolution up to 5 μm, and can accommodate specimens measuring up to 100 mm in diameter and 100 mm in length. The 450 kV ordinary fossil CT (450-TY-ICT) can produce high signal-to-noise ratio (SNR) images of specimens ranging up to 800 mm in diameter and 1000 mm in length, with a resolution up to 200 μm. Two paleontological CT facilities represent a high-performance platform offering the functional diversity needed to meet the demands of studying fossils at a variety of different scales. The two machines have become indispensable for paleontological research in China.