Phase transitions of K<Subscript>2</Subscript>TaF<Subscript>7</Subscript> within 680–800°C

Three thermal effects on heating/cooling of K₂TaF₇ in the temperature interval of 680–800°C were investigated by the DSC method. The values determined for the enthalpy change of the individual processes are: Δ_transIIH_m(K₂TaF₇; 703°C) = 1.7(2) kJ mol⁻¹, Δ_transIH_m(K₂TaF₇; 746°C) = 19(1) kJ mol⁻¹ and Δ_transIIIH_m(K₂TaF₇; 771°C) = 13(1) kJ mol⁻¹. The first thermal effect was attributed to a solid-solid phase transition; the second to the incongruent melting of K₂TaF₇ and the third to mixing of two liquids. These findings are supported by in situ neutron powder diffraction experiments performed in the temperature interval of 654–794°C.      

利用尺寸排阻色谱法研究蛋白质的变性

通过比较蛋白质变性时的色谱行为和生物物理特性，提出利用尺寸排阻色谱法研究蛋白质变性时的构象变化，根据色谱参数中保留时间，比较蛋白质变性时体积的相对变化，利用色谱峰数，确定形成变体的数目，根据峰形和峰数的变化，描述蛋白质的伸展程度，利用不同波长下峰高的变化，推断蛋白质变性芳香族基酸残基的暴露情况，利用建立的尺寸排阻色谱观察了液体和固液α－淀粉酶在低温下放置时的变性情况，讨论了变性时间和变性温度对蛋白     

舌尖上的化学之麻婆豆腐

民以食为天,麻婆豆腐作为一道有上百年历史、风靡世界的川菜美食,深受人们喜爱。以麻婆豆腐的制作步骤为线,介绍了4个重要烹饪阶段:肉臊炒制、底料炒制、红烧调色、勾芡收汁中发生的化学变化与消失或者新产生的风味化学物质,让学生进一步感受化学与生活的紧密联系,增强化学的学习兴趣。     

Comment on the paper “Comparison of the measured phase diagrams in the force-temperature plane for the unzipping of two different natural DNA sequences” by C.H. Lee, C. Danilowicz, V.W Coljee, and M. Prentiss

The paper by Lee et al. describes the experiments on the unzipping of λ DNA sequences as a function of force and temperature. This comment aims to stress that the unzipping takes place out of equilibrium due to high sequence-dependent free-energy barriers. The force at which a heterogeneous sequence is unzipped therefore depends on the experimental waiting time.     

《七录序》与阮孝绪的知识、思想世界

南朝时期,由于纸的普及,相比于使用简牍的时代,获取知识的途径已大为便捷。在这种背景下,私家藏书兴盛。家有文史、拥书万卷者,也不罕见。“知识下移”成为一种趋势。因此,带有“博”的词汇,如“渊博综广”等,常常被用来形容当时的知识人。阮孝绪阅读量惊人,号称“博极群书”。保留在《广弘明集》中的《七录序》就对阮孝绪的阅读过程、知识构成有所记录。从《七录序》可知,书籍总目《七录》因其穷“天下之遗书秘记”的性质,在某种程度上反映了梁武帝大同二年（536）以前,整个南朝的藏书规模。从私人阅读的角度来讲,《七录》是阮孝绪个人“阅读史”的总结,包含了他自身的“知识轮廓”。不过,阮孝绪博极群书,“阅读领域”几乎涉及了当时各个学术门类。因此,探讨阮孝绪私人阅读的历程以及《七录》的目录构成,也就具备了更大的意义。阮孝绪个人的“阅读史”与精神前进的历程,其实也是整个南朝学术文化、精神世界变化的缩影。     

Thermal expansion of amorphous Zr Al Cu Ni in the vicinity of the glass transition

The thermal expansion of non-crystalline Zr₆₅Al_7.5Cu_17.5 Ni₁₀ has been studied in the range of the glass transition and in the undercooled liquid using a dilatometric device. The measuring technique used permits reliable experimental results up to 40 K above the glass transition temperature. The linear thermal expansion coefficient obtained is almost constant in the glassy state with a value of . It discontinuously increases at the glass transition temperature yielding a value of in the undercooled liquid. The results are compared with specific heat measurements of the amorphous material in this temperature range and are interpreted in the framework of a cluster model. Received 5 March 1999 and received in final form 11 June 1999     

Regenerated silk fibroin nanofibers: water vapor-induced structural changes and their effects on the behavior of normal human cells

Nanofibrous non-woven matrices were prepared by electrospinning a regenerated silk fibroin (SF) solution, and the structural changes of SF nanofibers treated with water vapor were investigated using time-resolved IR and (13)C CP/MAS NMR spectroscopy. Conformational transitions of SF from random coil to beta-sheet structures were induced by water vapor treatment and were strongly dependent on the treatment time and temperature. Water vapor treatment provided a useful means of stabilizing the SF nanofiber matrices, resulting in the formation of matrices with a decreased solubility in water and increased mechanical strength. The adhesion and spreading of both normal human keratinocytes and fibroblasts onto the SF nanofiber matrices were also investigated, and the water vapor-treated SF nanofiber matrices showed good cellular compatibility, in comparison with traditional methanol-treated ones. This approach to controlling the conformational changes of SF nanofibers by water vapor treatment may be useful in the design and tailoring of novel materials for biomedical applications, including wound dressings and scaffolds for tissue engineering.     

Definite integral registers using infinitesimals

I propose a theoretical model of representation registers for definite integral notation. The two registers, adding up pieces (AUP) and multiplicatively-based summation (MBS), are developed from modes of interpreting integral notation identified by S. Jones (2015). In this model, the AUP register affords modeling with definite integral notation, while the MBS register affords sense-making with and evaluation of integrals. These registers are illustrated in the context of a Calculus I class that used an informal infinitesimals approach; in this class differentials such as dx directly represented infinitesimal quantities instead of serving as a reminder of a quantity that existed before a limit was taken. Theoretical implications of extending Duval’s register theory (2006) in this way are also explored.     

部分相干光经单缝衍射后的光谱变化

从几何成像规律和交叉谱密度函数的传输定律出发,从理论和实验两方面研究多色谢尔模型光束经单缝衍射后光场的光谱变化现象.理论研究结果表明:部分相干光谱经单缝衍射后,在衍射光场的某些点,光谱相对于光源的光谱往短波方向移动,即为蓝移;而在衍射光场的另一些点,光谱呈现红移.实验结果与理论结果符合得很好.