Progress and prospect for high temperature single-phased magnetic ferroelectrics

Magnetic ferroelectrics are one of the most important functional materials. The present bottleneck limiting applications of them is lacking of high-temperature single-phased ferromagnetic-ferroelectric multiferroics with strong magnetoelectric coupling effect. Here, those progresses of the mechanism for coexistence of ferroelectric and magnetic order, experimental and theoretical studies on single-phased magnetic ferroelectrics, and the relationship between magnetic structure and crystal symmetry are summarized. With examples of BiFeO3, BiMnO3 and Bi2FeCrO6, the difficulties encountered in this field are analyzed. At last, some prospects to develop high-temperature single-phased ferromagnetic-ferroelectric multiferroics are also presented.     

二元Stancu-Kantorovic算子的保持性质

证明了二元Stancu-Kantorovic算子的两种保持性质。     

构建适用区域经济的有机化学实验教学体系

在地方高校高素质应用型人才培养模式要求下,以服务区域性地方经济建设为中心,构建具有"宽口径,因材施教;重技能,到岗即用"为特色的有机化学实验课程新体系,加强基础有机化学实验技能训练,培养创新意识,提高实验教学质量。     

基于ANSYS与Workbench的雨棚结构有限元分析

以某桥梁工程中的人行道雨棚为研究对象,利用有限元软件ANSYS建立了雨棚结构的整体有限元简化模型,对其同时承受风载和雪载的状态进行了静力学分析,得到了它的整体变形和应力分布结果,并提取其整体结构的轴向力和弯矩,作为分析其柱脚的载荷.在Pro/E中建立了柱脚的三维实体模型并将其导入到Workbench中,利用Workbench对其进行加载分析,得到柱脚的变形和应力分布情况.结果表明该雨棚的整体结构和柱脚设计均满足强度和刚度要求.     

Peptide bond formation destabilizes Shine-Dalgarno interaction on the ribosome

The ribosome is a molecular machine that translates the genetic code contained in the messenger RNA into an amino acid sequence through repetitive cycles of transfer RNA selection, peptide bond formation and translocation. Here we demonstrate an optical tweezer assay to measure the rupture force between a single ribosome complex and mRNA. The rupture force was compared between ribosome complexes assembled on an mRNA with and without a strong Shine-Dalgarno (SD) sequence-a sequence found just upstream of the coding region of bacterial mRNAs, involved in translation initiation. The removal of the SD sequence significantly reduced the rupture force in complexes carrying an aminoacyl tRNA, Phe-tRNA(Phe), in the A site, indicating that the SD interactions contribute significantly to the stability of the ribosomal complex on the mRNA before peptide bond formation. In contrast, the presence of a peptidyl tRNA analogue, N-acetyl-Phe-tRNA(Phe), in the A site, which mimicked the post-peptidyl transfer state, weakened the rupture force as compared to the complex with Phe-tRNA(Phe), and the resultant force was the same for both the SD-containing and SD-deficient mRNAs. These results suggest that formation of the first peptide bond destabilizes the SD interaction, resulting in the weakening of the force with which the ribosome grips an mRNA. This might be an important requirement to facilitate movement of the ribosome along mRNA during the first translocation step.     

明代中后期风化刑法的衰落

明代中后期随着商品经济迅速发展,社会风气日益腐化,放纵声色之风败坏了社会风化,对旨在纯正社会风气的风化刑法形成剧烈冲击。这在同时期的世情文学作品中得到穷形尽相的描写,犯奸者法不追究、嫁娶违律蔚然成风、男风与寡妇改嫁已然成俗。但是法不责众、律外原情等因素致使规制男女性事、迎亲嫁娶、妇女守节的风化刑法对此束手无策,有些条文甚至成了具文,统治者利用刑法维护风化的目的落空,衰落之相可见一斑。     

阳离子类型对混凝土中钢筋腐蚀临界氯离子浓度的影响

选用4种常见化冰盐KCl,NaCl,CaCl2和MgCl2,应用半电池电位法、电化学阻抗谱、电化学滴定与X射线衍射分析等方法,研究了阳离子类型对混凝土中钢筋腐蚀临界氯离子浓度的影响,利用半电池电位和腐蚀电流密度分别判定钢筋的起始腐蚀.结果表明:阳离子类型影响临界氯离子浓度,临界氯离子浓度的相对大小与其表征形式有关.以游离氯离子质量分数表征时,wf(MgCl2)＜wf(CaCl2)＜wf(NaCl)＜wf(KCl);以c(Cl-)/c(OH-)表征时,cKCl(Cl-)/cKCl(OH-)≈cNaCl(Cl-)/cNaCl(OH-)＜cCaCl2(Cl-)/cCaCl2(OH-)＜ cMgCl2(Cl-)/c MgCl2(OH-);以总氯离子质量分数表征时,wt(KCl)≈wt(NaCl)＜wt(MgCl2)＜wt(CaCl2).     

狭叶獐牙菜化学成分研究Ⅱ

目的:研究龙胆科(Gentianaceae)獐牙菜属狭叶獐牙菜(Swertia angustifolia Buch.)的化学成分。方法:采用硅胶柱层析和Sephadex LH-20柱层析分离纯化化合物,依据理化性质和现代波谱技术进行结构鉴定。结果:从乙酸乙酯部分分离鉴定了7个单体化合物,分别为香草酸(vanillic acid,1)、1,3,8-三羟基-5-甲氧基口山酮(1,3,8-trihydroxy-5-methoxy xanthone,2)、5,7,4′-三羟基二氢黄酮(5,7,4′-trihydroxy flavanone,3)、1-羟基-3,5,6-三甲氧基口山酮(1-Hydroxy-3,5,6-trimethoxy xanthone,4)、3,4-二羟基苯甲酸甲酯(methy-3,4-dihydroxy-benzoate,5)、邻苯二甲酸二异丁酯(diisobutyl phthalate,6)、1,8-二羟基-3,5-二甲氧基口山酮(methyl-bellidifolin,7)。结论:化合物1~7均为首次从狭叶獐牙菜中分离得到。     

基于自组装二氧化钛空穴阻挡层的高效钙钛矿太阳能电池

器件兼容功能层的自组装工艺是一种简单、可行和节能的策略。在介孔钙钛矿太阳能电池(perovskite solar cells, PSCs)中,致密的TiO₂膜起到空穴阻挡层的作用,而介孔的TiO₂膜起到电子传输层的作用。然而,这两层通常都要通过高温退火法获得。在此,我们通过室温自组装工艺沉积了致密的TiO₂薄膜,以作为PSCs有效的空穴阻挡层。通过沉积时间控制致密TiO₂薄膜的厚度。优化致密TiO₂薄膜的厚度(80 nm),有无空穴传输层的介孔PSCs的能量转化效率分别为17.95%和10.66%。值得注意的是,基于自组装TiO₂的全低温PSCs显示出16.41%的能量转化效率。