高效液相色谱溶剂系统四面体优化法

改进了Ｇｌａｊｃｈ的三角形法,建立了适合于高效液相色谱（ＨＰＬＣ）的四面体优化法。将７个溶剂系统的实验结果输入计算机,由计算机模拟２３１个溶剂系统的色谱行为,优选出最佳溶剂系统。将此法用于１２种磺胺药物的分离,得到了满意的结果。     

利用TOCSY技术测定皂甙类化合物糖链连接顺序

探讨了利用HMBC及TOCSY相结合等二维核磁共振技术确定人参皂甙类化合物结构中糖链连接顺序的方法,并用该方法测定了胶股蓝皂甙ⅩⅦ(1)和西洋参皂甙L₃(2)中二个糖链的连接顺序,并通过化学方法得以确定.其结构分别为3-O-β-D-吡喃葡萄糖基20-O[β-D-吡喃葡萄糖基(1-6)-β-D-吡喃葡萄糖基]-20(S)-达玛-24-烯3,12,20三醇(1)和3-O-β-D-吡喃葡萄糖基-20-O-[β-D-吡喃木糖基(1-6)-β-D-吡喃葡萄糖基]-20(S)-达玛-23-烯-3,12,20,25-四醇(2).     

基于XFEM的混凝土纯弯曲梁的裂缝扩展模拟研究

选取纯弯曲梁进行裂缝扩展研究,在理论上符合Ⅰ型断裂模式．因此,本文利用扩展有限元法(XFEM)模拟了混凝土纯弯曲梁裂缝发展的全过程,结合线性叠加渐进假定,得到了不同初始缝高比的P-δ曲线、P-CMOD曲线以及临界有效裂缝扩展长度(a_c-a₀)/h与裂缝发展路经．对比试验数据和模拟结果表明：随着初始缝高比的增大,起裂荷载P_ini、最大荷载P_max、离散弗雷歇距离δ_dF与δ_{d F}^′,以及临界有效裂缝长度(a_c-a₀)/h均逐渐减小;试验与模拟的裂纹发展路径存在一定偏差,可知试验数据与模拟结果存在规律性差异．     

Open spaces and relaxation processes in the subsurface region of polypropylene probed by monoenergetic positron beams

Open spaces and relaxation processes in the subsurface region of isotactic polypropylene were investigated by monoenergetic positron beams. From measurements of the lifetime spectra of positrons, the size of the open spaces in the subsurface region (≤ 0.2 μm) was found to be larger than that in the bulk; their differences were estimated as 20% at 295 K and 10% at 395 K. From conventional positron annihilation experiments, the glass‐transition temperatures, T_{g (upper)}and T_g(lower) were determined as 306 K and 278 K, respectively. These transition temperatures were associated with the onset temperatures of the molecular motions under the constraint imposed by crystalline regions and those free from the constraint, respectively. In the subsurface region, although the onset temperatures of the molecular motions were close to those in the bulk, the molecular motions above T_{g (lower)} were found to be suppressed. The annihilation characteristics of positrons with different implantation energies were also discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 101–107, 2000     

Automated discovery of noncovalent inhibitors of SARS-CoV-2 main protease by consensus Deep Docking of 40 billion small molecules

Recent explosive growth of ‘make-on-demand’ chemical libraries brought unprecedented opportunities but also significant challenges to the field of computer-aided drug discovery. To address this expansion of the accessible chemical universe, molecular docking needs to accurately rank billions of chemical structures, calling for the development of automated hit-selecting protocols to minimize human intervention and error. Herein, we report the development of an artificial intelligence-driven virtual screening pipeline that utilizes Deep Docking with Autodock GPU, Glide SP, FRED, ICM and QuickVina2 programs to screen 40 billion molecules against SARS-CoV-2 main protease (Mpro). This campaign returned a significant number of experimentally confirmed inhibitors of Mpro enzyme, and also enabled to benchmark the performance of twenty-eight hit-selecting strategies of various degrees of stringency and automation. These findings provide new starting scaffolds for hit-to-lead optimization campaigns against Mpro and encourage the development of fully automated end-to-end drug discovery protocols integrating machine learning and human expertise.

Deep learning-accelerated docking coupled with computational hit selection strategies enable the identification of inhibitors for the SARS-CoV-2 main protease from a chemical library of 40 billion small molecules.     

Predicting the wind noise from the pantograph cover of a train

Finite element and boundary element calculations are combined to predict the flow noise radiated from a 1/10th-scale model of an aerodynamic cover used around the pantograph on a train at 250 km h⁻¹. The solutions of the unsteady air flow over the cover and the resulting sound propagation are divided into two parts in order to keep the problem tractable. First the unsteady fluid flow is solved using large-eddy simulation (LES). The pressure histories on the cover are then used to predict the radiated sound, using a boundary element method to solve the Helmholtz equation. The result thus leans heavily on assumptions about the coupling of the two solutions, the propagation of sound in a disturbed medium and the efficacy of LES. The predicted sound pressure levels are compared with experimental measurements made in an anechoic wind tunnel. © 1997 John Wiley & Sons, Ltd.     

Analysis of serum from type II diabetes mellitus and diabetic complication using surface-enhanced Raman spectra (SERS)

In this paper, we show surface-enhanced Raman spectra (SERS) of serums from type II diabetes mellitus and diabetic complication (coronary disease, glaucoma and cerebral infarction), and analyze the SERS through the multivariate statistical methods of principal component analysis (PCA). In particular, we find that there exist many adenines in these serums, which maybe come from DNA (RNA) damage. The relative intensity of the band at 725±2 cm⁻¹ assigned to adenine is higher for patients than for the healthy volunteers; therefore, it can be used as an important ‘fingerprint’ in order to diagnose these diseases. It is also shown that serums from type II diabetes mellitus group, diabetic complication group and healthy volunteers group can be discriminated by PCA.     

Screening influence on the Stark effect of impurity states in strained wurtzite GaN/AlxGa1-xN heterojunctions under pressure

The screening effect of the random-phase-approximation on the states of shallow donor impurities in free strained wurtzite GaN/Al x Ga 1 x N heterojunctions under hydrostatic pressure and an external electric field is investigated by using a variational method and a simplified coherent potential approximation.The variations of Stark energy shift with electric field,impurity position,Al component and areal electron density are discussed.Our results show that the screening dramatically reduces both the blue and red shifts as well as the binding energies of impurity states.For a given impurity position,the change in binding energy is more sensitive to the increase in hydrostatic pressure in the presence of the screening effect than that in the absence of the screening effect.The weakening of the blue and red shifts,induced by the screening effect,strengthens gradually with the increase of electric field.Furthermore,the screening effect weakens the mixture crystal effect,thereby influencing the Stark effect.The screening effect strengthens the influence of energy band bending on binding energy due to the areal electron density.     

Geant4 Monte Carlo simulations for the LPCTrap setup

The LPCTrap setup at GANIL is fully operational since 2006. The first breakthrough was the detection of 100000 coincidences between the $ \beta$ particles and the recoil ions from the decay of ⁶He⁺ produced by the SPIRAL source. After preparation, the decaying nuclei are confined in a transparent Paul trap which is surrounded by a $ \beta$ -telescope made of a double-sided silicon strip detector followed by a scintillator, and by a micro-channel plate position-sensitive detector to record in coincidence the $ \beta$ particles and the recoil ions. Simulations of this system are needed in order to study possible systematic effects and extract with high accuracy the $ \beta$ - $ \nu$ angular-correlation coefficient. A code based on Geant4 is well suited for this purpose. In this contribution the results from the simulations compared with those from the experiment will be presented and discussed.     

平面Hamilton系统和时逆系统平衡点的稳定性

本文研究了拟周期平面Hamilton系统和时逆系统的平衡点的稳定性．在适当的条件下,证明了平衡点的稳定性以及在平衡点附近存在着大量的拟周期解．