Pb-Mg-Al合金腐蚀机理的电子理论研究

为了了解Pb-Mg-Al合金腐蚀的物理本质, 本文采用基于第一性原理的赝势平面波方法系统地计算了Pb-Mg-Al合金中各物相的结合能、费米能级和局域态密度等电子结构参数, 分析了合金的电化学腐蚀机理. 计算结果表明：Pb-Mg-Al合金中各主要组成物相稳定性大小关系为 Mg₁₇Al₁₂>Mg₂Pb>Mg;Mg,Mg₂Pb和Mg₁₇Al₁₂的费米能级存在E_f(Mg)>E_f(Mg₂Pb)>E_f(Mg₁₇Al₁₂)的关系, 说明Mg最容易失去电子, Mg₂Pb次之, Mg₁₇Al₁₂最难;局域态密度表明, 在同样的外界条件下, 体系中Mg相和Mg₂Pb相对于Mg₁₇Al₁₂均处于不稳定的状态, 容易失去电子, 即容易发生腐蚀. Pb-Mg-Al合金体系中不同物相的费米能级差构成了电化学腐蚀的电动势, 导致电子从费米能级高的Mg相和Mg₂Pb相流向费米能级低的Mg₁₇Al₁₂相, 使Pb-Mg-Al合金发生腐蚀.     

氢、氟原子边缘修饰β-GeSe纳米带的第一性原理研究

采用第一性原理计算方法研究了二维β相GeSe的电子结构,通过对二维单层β-GeSe剪切得到一维β-GeSe扶手椅型纳米带.研究不同带宽(N=1-5)β-GeSe扶手椅型纳米带的几何结构和电子性质,发现不同带宽纳米带能带带隙不同,带隙总体上随着带宽减小,而纳米带直接带隙半导体性质不受带宽影响.通过使用H、F原子对GeSe扶手椅型纳米带边缘修饰,H原子修饰纳米带导致能带类型从直接带隙向间接带隙的转变.在费米能级附近处F原子各轨道对价带和导带贡献比H原子各轨道贡献多,在边缘修饰中纳米带对F原子更加敏感.未修饰和使用H原子修饰纳米带在可见光范围内没有吸收峰,用F原子修饰纳米带在可见光范围内出现吸收峰.研究表明可以通过边缘修饰调控纳米带光学特性.     

2.45GHz ECR 强流等离子体源核心部件设计与实验研究

电子回旋共振(Electron Cyclotron Resonance,ECR)等离子体源能产生高电荷态离子、高流强的单电荷态离子,提供稳定的束流和良好的重复性.核心部件的设计对ECR等离子体源是至关重要的,磁场对等离子体的生成和分布有直接影响,良好的磁场可以提高等离子体的性能和效率.采用有限元分析方法对ECR等离子体源磁场进行分析与设计,得到了满足设计需求与目标的磁场位形,通过高斯计对设计的永磁环轴向磁场精确测量,发现磁场仿真结果与实验结果吻合比较好,只是轴向磁场最大值及对应位置上有点偏差.通过集成实验,研究核心部件对离子源引出束流强度的影响,引出束流稳定且强度达到7 m A.     

Experimental study of the elastic scattering of ~(10)Be on ~(208)Pb at the energy of around three times the Coulomb barrier

Elastic scattering of 10Be on a 208Pb target was measured at ELab=127 MeV,which corresponds to three times the Coulomb barrier.The secondary 10Be beam was produced at the Radioactive Ion Beam Line in Lanzhou of the Heavy-Ion Research Facility in Lanzhou.The angular distribution of elastic scattering in the 10 Be+208Pb system shows a typical Fresnel diffraction peak.Optical model analysis of the angular distribution was performed using the Woods-Saxon,double-folding and global potentials.With the global potential,different density distributions were used.The results indicate that different density distributions for the projectile induce distinct effects in the angular distribution.     

稀土钙钛矿氧氮化物的研究进展

近年来,稀土钙钛矿氧氮化物因其出色的多功能性以及在光学、光催化、介电和磁性材料等领域的应用前景备受关注。本文介绍了稀土钙钛矿氧氮化物的结构稳定性计算方法,总结了其制备方法,最后阐述了其主要应用情况,并对其进一步研究和发展进行了展望。     

Analysis and evaluation of nucleosides,nucleobases, and amino acids in safflower from different regions based on ultra high performance liquid chromatography coupled with triple‐quadrupole linear ion‐trap tandem mass spectrometry

Safflower has both medicinal and edible values but research on its nutrient composition is still lacking. This study was established for the quantitative determination of 28 nucleosides, nucleobases, and amino acids based on the ultra‐performance liquid chromatography coupled with triple‐quadrupole linear ion‐trap tandem mass spectrometry. Analysis of 30 batches of safflower from different producing areas indicated that the contents of l ‐proline, l ‐asparagine, l (+)‐arginine, l ‐serine, l ‐histidine, uracil, guanosine, and uridine was high in safflower. Principle component analysis and cluster analysis found that samples from different regions could be distinguished well, and samples from the same area could be clustered into one class, different geographical environments may cause the differences of nucleosides, nucleobases, and amino acids in safflower. The analysis of principal component analysis, cluster analysis, and counter propagation artificial neural network show similar results. Then the content of nucleosides, nucleobases, and essential amino acids were compared, and found that the content in safflower from Gansu was higher than those from other regions, and there was a little difference between the samples from Xinjiang, Sichuan, and Yunnan. This research revealed the composition of nucleosides, nucleobases, and amino acids in safflower, and provided a theoretical basis for utilization of safflower.     

Preparation and Biological Evaluation of [99mTc]Tc-CNGU as a PSMA-Targeted Radiotracer for the Imaging of Prostate Cancer

Prostate-specific membrane antigen (PSMA) is a well-established biological target that is overexpressed on the surface of prostate cancer lesions. Radionuclide-labeled small-molecule PSMA inhibitors have been shown to be promising PSMA-specific agents for the diagnosis and therapy of prostate cancer. In this study, a glutamate-urea-based PSMA-targeted ligand containing an isonitrile (CNGU) was synthesized and labeled with ^99mTc to prepare [^99mTc]Tc-CNGU with a high radiochemical purity (RCP). The CNGU ligand showed a high affinity toward PSMA (K_i value is 8.79 nM) in LNCaP cells. The [^99mTc]Tc-CNGU exhibited a good stability in vitro and hydrophilicity (log P = −1.97 ± 0.03). In biodistribution studies, BALB/c nude mice bearing LNCaP xenografts showed that the complex had a high tumor uptake with 4.86 ± 1.19% ID/g, which decreased to 1.74 ± 0.90% ID/g after a pre-injection of the selective PSMA inhibitor ZJ-43, suggesting that it was a PSMA-specific agent. Micro-SPECT imaging demonstrated that the [^99mTc]Tc-CNGU had a tumor uptake and that the uptake was reduced in the image after blocking with ZJ-43, further confirming its PSMA specificity. All of the results in this work indicated that [^99mTc]Tc-CNGU is a promising PSMA-specific tracer for the imaging of prostate cancer.     

Adsorption Site Regulation to Guide Atomic Design of Ni–Ga Catalysts for Acetylene Semi-Hydrogenation

Atomic regulation of metal catalysts has emerged as an intriguing yet challenging strategy to boost product selectivity. Here, we report a density functional theory-guided atomic design strategy for the fabrication of a NiGa intermetallic catalyst with completely isolated Ni sites to optimize acetylene semi-hydrogenation processes. Such Ni sites show not only preferential acetylene π-adsorption, but also enhanced ethylene desorption. The characteristics of the Ni sites are confirmed by multiple characterization techniques, including aberration-corrected high-resolution scanning transmission electron microscopy and X-ray absorption spectrometry measurements. The superior performance is also confirmed experimentally against a Ni₅Ga₃ intermetallic catalyst with partially isolated Ni sites and against a Ni catalyst with multi-atomic ensemble Ni sites. Accordingly, the NiGa intermetallic catalyst with the completely isolated Ni sites shows significantly enhanced selectivity to ethylene and suppressed coke formation.     

Ruthenium [NNN] and [NCN]-type pincer complexes with phosphine coligands: synthesis,structures and catalytic applications

Transition Metal Chemistry - A series of ruthenium [NNN]- or [NCN]-type complexes (3–7) bearing PPh3 ancillary ligands have been synthesized from pyridine- or phenylene-bridged bis(triazoles)...     

Comparative study on properties of nanocellulose derived from sustainable biomass resources

Cellulose - Nanocellulose, a unique and promising nanosized cellulose fibers extracted from renewable biomass, has gained much attention from both the scientific and industrial communities due to...