应用动态顶空吸附-气相色谱-质谱法分析算盘子花气味的化学成分

花气味在维持大戟科(Phyllanthaceae)算盘子属(Glochidion)植物和头细蛾(Epicephala)专性传粉互利共生体系中发挥关键作用。本研究采用动态顶空吸附法(dynamic headspace adsorption)收集算盘子(Glochidion puberum)花气味,运用气相色谱-质谱(GC-MS)联用技术分离并鉴定其化学成分,用峰面积归一化法测得各组分的相对含量。结果表明:算盘子花气味中共鉴定出45种挥发物,主要包含单萜和倍半萜类物质;芳樟醇(38.06%)和β-榄香烯(23.84%)相对含量最高,占总相对含量的61.9%,为主要的气味成分,推测这两种物质可能是吸引传粉头细蛾的重要气味成分。本研究为进一步开展触角电生理检测和生物行为试验来筛选吸引传粉头细蛾的活性物质提供了理论依据。     

Structural and photoluminescence properties of SnO2:Ga films deposited on α-Al2O3 (0 0 0 1) by MOCVD

Gallium-doped tin oxide (SnO₂:Ga) films have been prepared on α-Al₂O₃ (0 0 0 1) substrates at 500 °C by the pulse mode metalorganic chemical vapor deposition (MOCVD) method. The relative amount of Ga (Ga/(Ga+Sn) atomic ratio) varied from 3% to 15%. Post-deposition annealing of the films was carried out at different temperatures for 1.5 h in ambient atmosphere . The structural, electrical, optical and photoluminescence (PL) properties of the films have been investigated as a function of annealing temperature. All the films have the rutile structure of pure SnO₂ with a strong (2 0 0) preferred orientation. A single ultraviolet (UV) PL peak near 337.83 nm was observed at room temperature for the 3% Ga-doped as-grown film and near 336 nm for the 15%-doped film, which can be ascribed to electron transition from the oxygen vacancy and interstitial Ga³⁺ donor levels to the acceptor level formed by the substitution of Ga³⁺ for the Sn site. After annealing, the luminescence spectra have changed a little bit, which is being discussed in detail.     

Activatable Small‐Molecule Photoacoustic Probes that Cross the Blood–Brain Barrier for Visualization of Copper(II) in Mice with Alzheimer's Disease

Copper enrichment in the brain is highly related to Alzheimer's disease (AD) pathogenesis, but in vivo tracing of Cu²⁺ in the brain by imaging techniques is still a great challenge. In this work, we developed a series of activatable photoacoustic (PA) probes with low molecular weights (less than 438 Da), RPS1 – RPS4 , which can specifically chelate with Cu²⁺ to form radicals with turn‐on PA signals in the near‐infrared (NIR) region. Introducing the electron‐donating group N,N‐dimethylaniline into the probe was found to significantly enhance the radical stability and PA intensity. The best probe in the series, RPS1 , showed a fast response (within seconds) to Cu²⁺ with high selectivity and a low PA detection limit of 90.9 nm . Owing to the low molecular weight and amphiphilic structure, RPS1 could effectively cross the blood–brain barrier (BBB) and thus allowed us, for the first time, to visualize Cu²⁺ in vivo via PA imaging in the brains of AD mice.     

Ca2+离子掺杂对γ-Ce2S3合成温度及热稳定性的影响

以CeCl₃·7H₂O、CaCl₂·2H₂O和C₂H₂O₄·2H₂O为原料,在制备钙铈氧化物前驱体基础上,再以Ar气为载气、CS₂为硫源对钙铈氧化物前驱体进行硫化合成Ca²⁺掺杂的γ-Ce₂S₃色料。 通过X射线衍射(XRD)、紫外-可见漫反射光谱(UV-Vis)及差热-热重分析(TG-DTA)等技术手段表征了色料的结构和性能。 结果表明,Ca²⁺掺杂能够明显降低γ-Ce₂S₃的合成温度,当n(Ca²⁺):n(Ce³⁺)≥0.16时,在900 ℃硫化150 min即可获得纯相的γ-Ce₂S₃,与不掺杂时合成γ-Ce₂S₃的温度相比降低了300 ℃左右。 同时,Ca²⁺掺杂能够提升γ-Ce₂S₃的抗氧化能力,当n(Ca²⁺):n(Ce³⁺)=0.64时,氧化放热峰的温度由不掺杂时的490.6 ℃提高至541.0 ℃。     

含双时间步法的化学非平衡流解耦算法

发展基于隐式双时间步法的化学非平衡流解耦型计算方法.采用算子分裂法对流动和反应进行解耦处理,流动方程组通过双时间步方法求解;源项方程组采用二阶梯形公式迭代求解;提出"源项消去"法,以消除化学反应源项对流动求解引入的误差,从而保证流动方程组求解的时间精度.理论分析和计算结果表明,方法既可以保证双时间步法的求解效率,又可以获得比较精确的非定常计算结果.     

2 μm单纵模激光频率短期不稳定度的测量

利用光纤延时自拍法对固体激光器输出激光频率的短期不稳定度进行了测量.Tm,Ho:YLF微片激光器具有毫瓦量级的单纵模、窄线宽的输出,实验测量了光纤延时长度为500 m下,积分时间为2 ms,4 ms,40 ms,100ms的拍频信号.利用自拍频法获得了光纤延时长度为100 m,200 m,300 m,400 m,500 m,对应的时间延时长度为0.5μs,1μs,1.5μs,2μs,2.5μs下的输出激光的自拍频信号,得出单频激光器的频率不稳定度为1.48 kHz/μs,最后对激光频率小稳定度与激光线宽的关系进行了讨论.     

Controlling the thermally activated delayed fluorescence of axially chiral organic emitters and their racemate for information encryption

A pair of axially chiral organic enantiomers were facilely prepared through a one-pot sequential synthesis. They exhibit circularly polarized luminescence activities and have thermally activated delayed fluorescence (TADF) and aggregation-induced emission enhancement properties. Meanwhile, these two enantiomers present remarkable and reversible thermochromism in the crystalline state, enabling dual-colour TADF switching between orange and red. However, when they form cocrystals, the resulting racemate shows opposite thermochromic behaviors. These intriguing results probably emanate from their different optical activities, leading to distinct molecular packing modes and molecular conformation variations. Moreover, information encryption based on thermochromism of organic enantiomers and their racemate has been presented for the first time. This work may expand the application scope of chiral organic luminogens and pave a new way to construct intelligent luminescent systems.

A pair of axially chiral organic enantiomers with circularly polarized thermally activated delayed fluorescence and aggregation-induced emission enhancement properties show opposite thermochromic behaviors to their racemate.     

SOME PROBLEMS IN THE TEACHING OF STRUCTURAL MECHANICS1)

结合结构力学的教学实践,给出了几何构造分析概念在求解静定结构内力、用机动法作梁的影响线、应用虚功原理求静定结构反力等方面的应用;分析了自由度、计算自由度、结构动力计算自由度、稳定性问题的自由度之间的区别与联系;汇总了力法、位移法等方法的特点及适用问题;介绍了部分结构力学内容应用多媒体、实验、数值仿真相结合的教学方法。将结构力学内容的内在联系、容易混淆的概念、各种方法的特点理清楚,从而提高教学效果。     

硅胶自环己烷中吸附含氧芳香化合物的研究

测定了15℃和30℃时硅胶自环己烷中吸附苯甲醇、苯甲醚、苯甲醛和苯甲酸的吸附等温线,这些等温线皆可用Langmuir公式表示。利用Langmuir常数n_m^s和b值计算了吸附过程的△G⁰、△H⁰和△S⁰;四种化合物的△S⁰皆为正值。测定了在较大复盖度时红外光谱图上硅胶表面自由羟基峰的移动值△v_OH。结果表明△H⁰和△v_OH及△v_OH^1/2间有线性关系。文中对所得结果做了初步的解释。     

硅胶自溶液中吸附胆固醇和卵磷脂

卵磷脂和胆固醇是细胞膜的主要组成,它们在不同界面上的定向排列方式对细胞膜的结构与功能起着重要的作用。用固体物质自非水溶剂中吸附类脂化合物形成类脂单层,再自水溶液中吸附蛋白质,可制成固体载体上的模拟生物膜。在固体表面上的类脂单层膜中类脂分子的定向方式与溶剂和固体表面性质有关。这些研究大多数是以非孔性物质为吸附剂(如aerosil,石墨化炭黑,carbochrom.等)自有机溶剂中吸附类脂化合物(主要是胆固醇和卵磷脂),根据单层饱和吸附时分子占据的面积推算单层中类脂化合物分子的取向。实际应用的吸附剂大多是孔性的,因此研究类脂化合物在孔性吸附剂(如,硅胶、活性炭等)上的吸附机理更有实际意义。