Promoting mathematical proof from collective argumentation in primary school

The purpose of this research is to promote the construction of mathematical proof from argumentation at the primary level. To show this is a viable instructional strategy at the primary level, we use a teaching experiment methodology and a task related to geometric proof in this research study. To model and analyze the collective argumentation that took place in the classroom, we reconstructed the discussion using the extended Toulmin model. Collective argumentation at the primary level is a valuable opportunity for primary students and their teachers to generate mathematical proof through collaboration.     

Barium isotope fractionation during the experimental transformation of aragonite to witherite and of gypsum to barite,and the effect of ion (de)solvation

In this study, we present the experimental results for stable barium (Ba) isotope fractionation (¹³⁷Ba/¹³⁴Ba) during the transformation of aragonite (CaCO₃) and gypsum (CaSO₄·2H₂O) in Ba-bearing aqueous solution to witherite (BaCO₃) and barite (BaSO₄), respectively. The process was studied at three temperatures between 4 and 60?°C. In all cases, the transformation leads to a relative enrichment of the lighter ¹³⁴Ba isotope in the solid compared to the aqueous solution, with ^137/134Ba enrichment factors between –0.11 and ?0.17?‰ for BaCO₃, and –0.21 and –0.26?‰ for BaSO₄. The corresponding mass-dependent ^138/134Ba enrichment factors are ?0.15 to –0.23?‰ for BaCO₃, and –0.28 to –0.35?‰ for BaSO₄. The magnitude of isotope fractionation is within the range of recent reports for witherite and barite formation, as well as trace Ba incorporation into orthorhombic aragonite, and no substantial impact of temperature can be found between 4 and 80?°C. In previous studies, ion (de)solvation has been suggested to impact both the crystallization process of Ba-bearing solids and associated Ba isotope fractionation. Precipitation experiments of BaSO₄ and BaCO₃ using an methanol-containing aqueous solution indicate only a minor effect of ion and crystal surface (de)solvation on the overall Ba isotope fractionation process.     

狭义相对论百年风雨

介绍狭义相对论中某些争论并澄清一些看法．     

Mössbauer spectroscopic study on chemical changes of iron compounds with the aid of sulfate-reducing bacteria

⁵⁷Fe Mössbauer spectra were measured of reaction products formed during an incubation experiment with sulfate-reducing bacteria, which were isolated from estuarine sediments of the Tama River in Tokyo. The spectrum of the product incubated for several days showed some overlapping sextets. This product had a different chemical form from amorphous iron monosulfide produced by inorganic reaction between ferrous and sulfide ions. It was estimated that the structure of nearest neighbor of iron in this product was similar to that of pyrrhotite (Fe_1?x S). After several months of incubation, other singlet and doublet appeared successively on the spectrum, corresponding to mackinawite (FeS_1?x ) and new sulfide, respectively. Both values of isomer shift and quadrupole splitting of new sulfide increased with increasing incubation time and approached those of pyrite (FeS₂). Extended X-ray absorption fine structure (EXAFS) showed that iron atoms were coordinated by sulfur in the incubation product.     

献身演示实验室工作,提高物理课堂教学水平

作为演示实验室的教师 ,应结合教学内容 ,发挥积极性和创造精神 ,努力做好演示实验室的准备工作。同时 ,要利用现代化技术 ,不断研制和开发新的演示实验 ,本文介绍了几个新研制的实验。     

Search for massive rare particles with the MACRO track-etch detector at Gran Sasso

Searches for massive penetrating particles in the cosmic radiation have been performed with the MACRO nuclear track detector used as a “stand alone” detector. The complete experimental procedure is presented. In absence of candidates, updated estimates of the flux upper limits both for the CR-39 “stand alone” detector and for the global MACRO detector are presented for magnetic monopoles, nuclearites and charged Q-balls.     

研制开发大学物理实验CAI课件提高物理实验教学质量

本文结合实际介绍了CAI课件的开发与应用,并阐述了CAI课件在提高物理实验教学质量中所起到的作用。     

基于仿真软件的电磁场实验教学研究

应用电磁场的仿真软件COMSOL multiphysics对两个实验项目建模并仿真,得到三维立体解,形象直观地表现了电场或磁场的分布情况,同时验证了与理论计算结果的一致性,使学生对电磁场的理论从抽象的理解到感性认识,对工程实际问题产生形象思维。     

2种不同体系下镁碱沸石的水热合成及表征

介绍了研究型综合性实验--2种不同体系下镁碱沸石的水热合成及表征。该实验以传统水热晶化方法为基础,通过使用乙二胺和吡咯烷2种有机胺,在2种合成体系下分别制备了镁碱沸石FER,采用X射线粉末衍射仪(XRD)及固体核磁(MAS NMR)对产物的结构进行表征,产物的晶体形貌由扫描电子显微镜(SEM)进行表征,并使用氮气吸附/脱附测试对产物的性质进行表征。本文从实验教学的角度出发,整个实验步骤安排合理,内容丰富,可操作性强,充分体现了"制备合成-表征分析"的综合性科研思维模式,在让学生熟悉无机化学与材料化学科研中所使用的合成方法与表征手段的同时,也有助于学生了解科学研究工作的基本过程。