汞扩散泵——镉捕集阱高真空系统

我们在二级玻璃汞扩散泵的真空系统上使用了室温的镉膜阱,证明镉膜阱能有效地捕集汞蒸气,使被抽容器达到气压力10^-5—10^-7毫米汞数量级的高真空。我们较系统地试验了镉膜的条件对于极限气压的影响,实验结果表明,新蒸发的镉膜效果最好;将镉膜在10^-2毫米汞的气压下搁置10小时后对于极限气压的影响不大;但若将其在大气下搁置10小时,则极限气压约升高一个数量级;进一步延长在大气中的暴露时间(达300天),对极限气压无更大的影响。初步的寿命试验表明,扩散泵工作140小时之后,极限气压才较显著地上升。降低镉膜阱的温度、增加镉膜阱的数目和被抽容器的高温烘烤都是提高真空度的有效途径;在实验中考虑了这些因素,我们曾获得了气压低达10^-9毫米汞数量级的超高真空。     

Cr~(4+): YAG被动调Q与激发态吸收饱和

运用速率方程计算了Ｃｒ４＋ＹＡＧ晶体的基态吸收、激发态吸收与入射脉冲的能量密度和强度的关系。在测量晶体透过率的实验中，发现Ｃｒ４＋ＹＡＧ晶体的激发态吸收趋于饱和。理论计算与实验数据拟合给出了包括基态吸收截面，激发态吸收截面和寿命等参数。在用Ｃｒ４＋ＹＡＧ对脉冲式ＮｄＹＡＧ激光器被动调Ｑ的实验中，得到脉宽５ｎｓ、能量９０ｍＪ的激光脉冲，并且发现这种调Ｑ与Ｃｒ４＋ＹＡＧ的激发态吸收饱和直接相关。     

新型电荷转移多金属氧酸盐的合成和红外光谱研究

以4种道森结构的杂多酸和3种芳香杂环化合物为原料合成了11种新型电荷转移多金属氧酸盐，研究了它们的红外光谱。结果表明：杂多酸形成电荷转移盐后，杂多阴离子的结构略有畸变但仍保持道森结构；有机给体和杂多阴离子之间存在电荷转移相互作用。     

一类亚解析函数的复合边值问题

本文研究了一类亚解析函数的复合边值问题.利用经典的消去法和对称扩张,得到了边值问题的可解条件和解的表达式.推广了解析函数的相应理论.     

Influence of a Second Cation (M = Ca2+, Mg2+) on the Phase Evolution of (BaxM1–x)F2 Starting from Amorphous Deposits

A second type of cation (Mg²⁺, Ca²⁺) was introduced into BaF₂ by low‐temperature atomic beam deposition. The structure evolution from low‐temperature (–150 °C) amorphous deposits to high‐temperature (< 1000 °C) annealed crystalline phases was studied by in‐situ transmission electron microscopy and X‐ray diffraction. Amorphous (Ba_0.5, Ca_0.5)F₂ crystallizes in a first step to metastable solid solution phase (fluorite‐type), which then decomposes into the pure phases of CaF₂ and BaF₂ at higher temperature. The crystallization behavior of amorphous (Ba_xMg_1–x)F₂ is completely different. When the Mg/Ba atomic ratio is around 1:1, the mixture transforms to the ternary compound BaMgF₄ at annealing, and no decomposition occurs by further heating up to 1000 °C. When the Ba concentration is below 15 % in atomic ratio (x < 0.15), the mixture forms a solid solution phase (rutile type) with the lattice expanded by +1 % compared to rutile type MgF₂. The difference between the phase evolutions of the two mixture systems is discussed.     

Synthesis,Computational Modeling,and Properties of Benzo‐Appended BODIPYs

A series of new functionalized mono‐ and dibenzo‐appended BODIPY dyes were synthesized from a common tetrahydroisoindole precursor following two different synthetic routes. Route A involved the assembly of the BODIPY core prior to aromatization, while in Route B the aromatization step was performed first. In general, Route A gave higher yields of the target dibenzo‐BODIPYs, due to the ease of aromatization of the BODIPYs compared with the corresponding dipyrromethenes, probably due to their higher stability under the oxidative conditions (2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone in refluxing toluene). However, due to the slow oxidation of highly electron‐deficient BODIPY 3 c bearing a meso‐C₆F₅ group, dibenzo‐BODIPY 4 c was obtained, in 35 % overall from dipyrromethane, only by Route B. Computational calculations performed at the 6‐31G(d,p) level are in agreement with the experimental results, showing similar relative energies for all reaction intermediates in both routes. In addition, BODIPY 3 c had the highest molecular electrostatic potential (MEPN), confirming its high electron deficiency and consequent resistance toward oxidation. X‐ray analyses of eight BODIPYs and several intermediates show that benzannulation further enhances the planarity of these systems. The π‐extended BODIPYs show strong red‐shifted absorptions and emissions, about 50–60 nm per benzoannulated ring, at 589–658 and 596–680 nm, respectively. In particular, db‐BODIPY 4 c bearing a meso‐C₆F₅ group showed the longest λ_max of absorption and emission, along with the lowest fluorescence quantum yield (0.31 in CH₂Cl₂); on the other hand monobenzo‐BODIPY 8 showed the highest quantum yield (0.99) of this series. Cellular investigations using human carcinoma HEp2 cells revealed high plasma membrane permeability for all dibenzo‐BODIPYs, low dark‐ and photo‐cytotoxicities and intracellular localization in the cell endoplasmic reticulum, in addition to other organelles. Our studies indicate that benzo‐appended BODIPYs, in particular the highly stable meso‐substituted BODIPYs, are promising fluorophores for bioimaging applications.     

HOPF BIFURCATION ANALYSIS OF A PREDATOR-PREY MODEL WITH TIME-DELAY

In this paper,a predator-prey model of three species is investigated.By introducing a delay as a bifurcation parameter,it is found that Hopf bifurcation occurs when τ crosses some critical values.     

Filling the in situ-generated vacancies with metal cations captured by C-N bonds of defect-rich 3D carbon nanosheet for bifunctional oxygen electrocatalysis

Nitrogen-doped carbon materials with vacancies/defects have been developed as highly efficient ORR electrocatalysts but with poor activity for OER,which limits ...     

Study on improving the toughness of rapidly curing epoxy resin composite materials with a biobased microcrystalline cellulose

Rapid solidification molding is one of the main low-cost forming methods for composite materials, and the reasonable selection of the solidification molding process is the key to achieving material performance. The curing system used in this paper is the widely used, inexpensive, and readily available epoxy resin (WSR618) and the transparent, colorless, and less toxic 593 curing agent, which cures at room temperature. Through the study of various temperature formulations, a rapid curing system was determined that has a 10-min cure at 80°C. The results showed that when the mass ratio of epoxy (EP) resin to curing agent was 5:1, the curing system was selected at 80°C for 10 min, and the bending strength could reach 100.19 MPa, and the impact strength could reach 12.82 kJ/m². However, the difficulty caused by quick solidification was a reduction in mechanical characteristics, which required modification. Microcrystalline cellulose is cheap and readily available and widely available, so microcrystalline cellulose (MCC) was chosen for modification in this study. The experimental results showed that the addition of MCC reduced the fracture brittleness of EP composite materials. When 0.75% MCC was added, the bending and tensile strengths reached 116.88 and 52.53 MPa, respectively, which were 16.66% and 18.74% higher than unmodified EP. The elongation at break reached 11.57%, which is 14.13% higher than unmodified.     

Comparative pharmacokinetic studies of Ephedra herba in common cold and nephrotic syndrome rat models

Ephedra herba is a conventional Chinese medicine to treat cold, fever, asthma, edema, and lung diseases in the clinic. At present, most pharmacokinetic studies focus on the pharmacokinetic process of alkaloids in normal animals. However, the non-alkaloid components are also active. In addition, the pharmacokinetic studies under pathological state make more sense for clarifying the material basis of efficacy. In this study, a sensitive and rapid ultra-high-performance–tandem mass spectrometry method was developed and applied to determine nine bioactive components (ephedrine, pseudoephedrine, methylephedrine, (+)-catechin, epicatechin, vitexin, vicenin-2, cinnamic acid, and ferulic acid) in normal, common cold and nephrotic syndrome rats after the oral administration of Ephedra herba. Compared to the normal group, except for ferulic acid, the exposure levels of the other eight components were significantly increased and the plasma clearance clearly declined in common cold rats. Similarly, the exposure levels of seven components other than cinnamic acid and ferulic acid were also significantly augmented and the plasma clearance decreased significantly in nephrotic syndrome rats. In brief, the pathological conditions of the common cold and nephrotic syndrome could lead to alterations in the pharmacokinetics profiles of the nine components, which provide a reference for further exploration of the pharmacodynamics basis of Ephedra herba.