Non-isothermal crystallization kinetics of V2O5-MoO3-Bi2O3 glasses

Characteristic temperatures, such as T _g (glass transition), T _x (crystallization temperature) and T _l (liquidus temperature) of glasses from the V₂O₅-MoO₃-Bi₂O₃ system were determined by means of differential thermal analysis (DTA). The higher content of MoO₃ improved the thermal stability of the glasses as well as the glass forming ability. The non-isothermal crystallization was investigated and following energies of the crystal growth were obtained: glass #1 (80V₂O₅·20Bi₂O₃) E _G=280 kJ mol^-1, glass #2 (40V₂O₅·30MoO₃·30Bi₂O₃) E _G=422 kJ mol^-1 and glass #3 (80MoO₃·10V₂O₅·10Bi₂O₃) E _G=305 kJ mol^-1. The crystallization mechanism of glass #1 (n=3) is bulk, of glass #3 (n=1) is surface. Bulk and surface crystallization was supposed in glass #2. The presence of high content of a vanadium oxide acts as a nucleation agent and facilitates bulk crystallization. This revised version was published online in August 2006 with corrections to the Cover Date.     

The potential antioxidant ability of hydroxytyrosol on Caenorhabditis elegans against oxidative damage via the insulin signaling pathway

Hydroxytyrosol (HY) deriving from olive leaves is a phenolic component which has been proven to possess a strong antioxidant ability. However, the underling mechanism is still unclear. To evaluate the antioxidant ability of HY comprehensively, assays in vitro and in vivo (Caenorhabditis elegans (C. elegans) was used as a model organism) were conducted. The results showed HY could scavenge 2,2-Diphenyl-1-picryl-hydrazyl (DPPH) radicals with a strong total reducing power. Pretreated with HY for 48 h, the cell viability of Chinese hamster ovary (CHO) cells was enhanced under oxidative stress by reducing the level of reactive oxygen species (ROS) and malondialdehyde (MDA). A suitable concentration of HY showed no side effects on the development, fertility, and movement of C. elegans. With the treatment of HY, the survival was enhanced by 15.79% under thermal stress. The ROS and MDA contents were also reduced, which might be associated with the increasing abilities of antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and the heat shock protein HSP-16.2. Nuclear localization of DAF-16 was greatly increased after treated with HY. More outcomes demonstrated HY exhibited an excellent antioxidant capacity via the insulin signaling pathway by upregulating daf-16 and sod-3 and downregulating the genes of age-1 and daf-2.     

基础有机化学教学与前沿科学研究的融合——共价有机骨架材料的成键方式

作为材料研究领域的明星,共价有机框架材料的研究是基于有机化学反应的成功选择和合成条件的不断优化。本文探讨将共价有机框架材料的成键方式引入有机化学教学课堂的途径,阐述有机化学反应在新型纳米材料设计合成中的应用。科教融合教学模式不仅能够培养学生掌握知识、运用知识解决实际复杂问题的能力;同时可以调动学生的学习兴趣、拓展科研视野、激发科研热情;更能在科研成果中增强学生的专业认同感、培养学生的创新意识和社会担当。科教融合是实现创新人才培养的一个重要环节。     

激光显微拉曼光谱仪在本科实验教学中的应用

拉曼光谱作为一种无损检测的指纹光谱是科研中的主要表征手段。激光显微拉曼光谱实验教学通过测试科研中的样品让学生了解拉曼测试的重要性以及科研的分析方法,构建科学研究和实验教学的桥梁。本实验课程同时安排创新探索实验,培养学生的自主学习兴趣和科研创新能力。通过本实验的学习,让学生们了解目前先进的分析手段和先进的大型仪器,有利于学生综合实验素质及科研能力的培养,为以后从事科学研究及相关工作所需综合能力的培养打下坚实的基础。     

以应用为导向的"材料制备与吸附性能"创新综合实验设计

基于应用型人才培养目标,通过创新实验教学内容和方法,将科研成果引入到实验教学内容中,设计出以实际应用为导向的磁性材料制备及吸附性能研究综合实验。该实验教学对材料的结构表征和性能测试进行补充和拓展,并融合较为前沿的科学问题,采用半开放式教学手段,鼓励学生自主设计、独立分析,构建科研反哺教学的协同机制。通过实践表明,该实验具备综合性特征,内容涵盖了材料化学、仪器分析、物理化学相关理论;经过系统训练,提升学生的专业操作技能,巩固理论知识,强化实践应用,有利于培养学生分析解决实际问题的能力和专业创新能力。     

初中化学实验教学中探究程度与高阶思维的课堂研究

采用课堂观察的方法,从探究程度和高阶思维2个维度,对北京市顺义区27个初中化学实验教学案例的实施状况进行研究。结果显示,探究程度仍处于较低水平,学生提出问题的参与度尤其低;教师较多关注表面的完整的探究环节;高阶思维有不同程度体现,变量控制、证据推理和抽象概括思维得到有效发展,假设创造、模型认知和批判质疑思维仅在少数课例中体现。     

基于新工科内涵的环境化学课程建设*

为了提高环境类人才实践与创新能力,重构了符合新工科理念的环境化学“素养、能力、知识”一体化课程目标;基于科研反哺课程内容增补了新工科元素“环境计算化学——化学品构效关系;基于线上线下混合式构建了“三三三”教学模式,进行了多元化过程考核方式探索,教学设计强化了学生的能力培养与价值塑造。课程建设实践表明,学生的学习获得感与其课堂参与度呈现正相关,基于身边老师的科研反哺和前沿拓展,更能激发学生的应用挑战兴趣,促进提升实践能力和创新能力。环境化学课程实现了全方位新工科内涵式建设,以期为环境工程专业的新工科升级改造提供借鉴。     

培养“科学态度与责任”素养的初三化学复习*——化学与社会发展

分析了“化学与社会发展”的教学主题内容、教学现状,针对已有复习课教学设计中存在的问题提出了教学思想及创新点,以“北京冬奥会”为主线,将第9章涉及能源、材料和环境污染防治的内容有机串联,设计了“环保能源支撑‘绿色冬奥’、新型材料助力‘科技冬奥’、防污技术保障‘清洁冬奥’”等3个主要环节进行复习教学,促进学生完善知识体系,培养“科学态度与责任”学科核心素养,并对课堂教学进行了反思。     

Rapid geometrical equilibrium of palladium(II) complexes with tris[2-(diphenylphosphino)ethyl]phosphine disulfide and diselenide and their catalytic activity for Suzuki coupling reaction

Palladium(II) complexes with a tetradentate pseudo-tripodal ligand having two phosphino groups and two phosphine sulfide or selenide groups, pp₃X₂ (pp₃ = tris[2-(diphenylphosphino)ethyl]phosphine, X = S (1) or Se (2)), were prepared from [PdCl(pp₃)]Cl. Both of these phosphine chalcogenide complexes 1 and 2 showed rapid equilibrium between the five-coordinate [PdCl(pp₃X₂)]Cl with two bound phosphine chalcogenide groups and four-coordinate [PdCl₂(pp₃X₂)] with two dissociated pendant ones in chloroform. The thermodynamic parameters for the reaction, [PdCl(pp₃X₂)]⁺ + Cl⁻?[PdCl₂(pp₃X₂)], were obtained by low-temperature ³¹P NMR as follows: K²⁹⁸ = 3.7 × 10³ and 5.4 × 10² mol⁻¹, ΔH^° = 11.3 ± 0.3 and 13.4 ± 0.4 kJ mol⁻¹, and ΔS^° = 106 ± 2 and 97 ± 2 J mol⁻¹ K⁻¹ for 1 and 2, respectively. The rate for the geometrical change at 246.7 K for 1 was appreciably faster than that for 2. These thermodynamic and kinetic results indicate that the phosphine selenide Se atoms can stabilize the five-coordinate structure by effective π-back donation from Pd(II) compared with the phosphine sulfide S atoms. Difference in retention of the catalytic activity for Suzuki coupling, 2 > 1 > [PdCl(pp₃ or p₃)]Cl, was explained by difference in the π-accepting ability that stabilizes the catalytically active Pd(0) species. Considering the rapid dissociation-coordination equilibrium of the phosphine chalcogenide groups on Pd(II), it is probable that the oxidative addition and the subsequent transmetallation of the Pd(II) species are hardly blocked by the phosphine chalcogenide groups.     

Analysis of sodium adduct paeoniflorin, albiflorin and their derivatives by (+)ESI-MSn, DFT calculations and computer-aided mass spectrometry analysis program

In order to analyze paeoniflorin, albiflorin and their derivatives (PADs) in Paeonia Lactiflora rapidly and effectively, (+)ESI-MS(n) experiments were conducted, from which two diagnostic fragment patterns were acquired. Meanwhile, the dehydration ability of aglycones of PADs was obtained by calculating their activation energy using density functional theory, through which the unique dehydration phenomenon of benzoylalbiflorin, compared with benzoylpaeoniflorin, was interpreted. In addition, a computer-aided mass spectrometry analysis program was developed to facilitate the analysis of the unknown compound by suggesting the possible structure of the analyte.