信息化课堂教学设计--以“刚体定轴转动的角动量及角动量守恒定律”为例

遵循“学生主体、教师主导”的教育教学理念,借助信息化教学工具,合理有效地设计好每一个教学环节.采用演示、体验、探究、问题导向和分组讨论等教学手段和方法,让学生在课堂中自主发现问题、分析问题并解决问题,实现“学生做中学、教师做中教”,大大提升教学效果.     

气体团簇离子束两步能量修形法的平坦化效应

本文提出采用气体团簇离子束的两步能量修形法来改善4H-SiC(1000)晶片表面形貌.先用15 keV的高能Ar团簇离子进行整体修形,再用5 keV的低能团簇离子优化表面.结果表明,在相同的团簇离子剂量下,与单一15 keV的高能团簇处理相比,两步法修形后的表面具有更低的均方根粗糙度,两者分别为1.05 nm和0.78 nm.本文还以原子级平坦表面为研究对象,揭示了载能团簇引起的半球形离子损伤(弧坑)与团簇能量的关系,及两步能量修形法在弧坑修复中的优势.在原子力显微镜表征的基础上,引入了二维功率谱密度函数,以直观全面地给出材料的表面形貌特征及其随波长(频率)的分布.结果表明,经任何能量的团簇离子轰击的表面,在0.05—0.20μm波长范围内,团簇轰击都能有效地降低粗糙度,而在0.02—0.05μm范围内,则出现了粗化效应,这是由于形成了半球形离子损伤,但第二步更低能量的团簇离子处理可以削弱这种粗化效应.     

p-TSA-catalyzed one-pot synthesis of novel 7-aryl-6H-benzo[h][1,3]dioxolo[4,5-b]xanthene-5,6(7H)-diones in ethanol

A one-pot, three-component reaction of aromatic aldehydes, 2-hydroxy-1,4-naphthoquinone, and 3,4-methylenedioxyphenol has been reported for the synthesis of novel 7-aryl-6H-benzo[h][1,3]dioxolo[4,5-b]xanthene-5,6(7H)-diones using environmentally benevolent para-toluene sulfonic acid (p-TSA) as the catalyst. This methodology provides a mild and fast route to diverse pyran derivatives in moderate to good yields.     

Metal-free and selective cleavage of unstrained carbon–carbon single bonds: Synthesis of β-ketosulfones from β-chlorohydrins and sodium sulfinates

A metal-free protocol for the selective cleavage of unstrained C–C single bonds was developed. Under the catalysis of KI and in the presence of NaHCO₃, the readily available α-chloro-β-hydroxy ketones underwent bond breaking and sulfonylation smoothly to afford β-ketosulfones with high efficiency and broad substrate scope. Mechanism investigations, both experimental and theoretical, showed that a retro-aldol cleavage/nucleophilic substitution sequence might be involved.     

基于杂交链式反应辅助多重信号放大的端粒酶灵敏检测

端粒酶是真核细胞维持端粒长度的关键逆转录酶,其生物活性的高低可以为多种癌症的临床诊断和预后治疗提供有价值的信息.本研究以人宫颈癌细胞(HeLa细胞)裂解液中的端粒酶为研究对象,通过借助杂交链式反应辅助多重信号放大策略,提出了一种新颖、灵敏的检测端粒酶电化学方法.首先将端粒酶的延伸引物自组装在金电极表面,当端粒酶存在时,端粒酶能够催化引物的延伸,产生与发卡环探针H1部分互补的序列,进而引发杂交链式反应,形成由两个发卡环探针(H1和H2)交替杂交而形成的DNA长链.由于H1和H2末端均修饰有生物素,加入链霉亲和素修饰辣根过氧化物酶后,辣根过氧化物酶被被连接到电极表面,催化邻苯二胺氧化生成2,3-二氨基吩嗪,产生显著的电化学信号.实验结果表明,本研究建立的端粒酶电化学检测方法高效、可行,线性范围宽,灵敏度高,可以检测每毫升10个HeLa细胞裂解液中的端粒酶.本方法具有较好的选择性,能有效区分端粒酶和对照蛋白.     

Fabrication of Electrospun PVDF Nanofibers with Higher Content of Polar β Phase and Smaller Diameter by Adding a Small Amount of Dioctadecyl Dimethyl Ammonium Chloride

In this work,the effect of dioctadecyl dimethyl ammonium chloride(DDAC,a kind of alkyl ammonium salt) on polar β phase content and the diameter of electrospun PVDF nanofibers was investigated for the first time.Our experimental results show that the diameter of the electrospun PVDF nanofiber could be largely reduced and the content of polar β phase also become dominant immediately by just adding a little amount of DDAC.When the mass fraction of DDAC reached 4%,the content of polar β phase increased by about 39.1% compared with PVDF nanofibers without DDAC.Besides,the crystallinity of PVDF nanofibers also increased with the addition of DDAC.Based on the results,the possible mechanism of cooperative effect between electrospinning and DDAC on fiber diameter and formation of β phase in PVDF was discussed.     

Absorption,transportation and distribution of imidacloprid in maize

The neonicotinoid imidacloprid is a very important insecticide in maize cultivation in China. A laboratory experiment was conducted to investigate its absorption, transportation and distribution in maize plants. Plants were exposed to an aqueous solution of imidacloprid at five concentrations (10, 20, 50, 100 and 200 μg/mL). The residues of imidacloprid in different plant parts were determined by using a quick and effective method of high-performance liquid chromatography. Results showed that the average recoveries ranged from 85.16% to 102.23%, with relative standard deviations of 1.82–4.40% at three different spiking levels in each different matrix. The half-lives of imidacloprid in hydroponic maize water were from 5.33 to 11.55 days. The concentrations in roots, stems and leaves were from 5.61 to 7.48, 1.03 to 4.03 and 0 to 30.57 μg/mL after 6 h–7 days exposed in 10 μg/mL imidacloprid aqueous solutions, respectively. Our study showed that imidacloprid was strongly absorbed by roots and mainly accumulated in leaves. Quantity ratio and bioconcentration factors (BCFs) were also used to estimate the distribution and accumulation in maize. The values of quantity ratios were the highest in the leaves while lowest in the root after 7 days treatments, with the ranking of leaves > stem > root. The BCFs were 0.63–1.66, 0.52–0.92 and 3.20–6.78 in root, stem and leaves, respectively. These results demonstrated that the exposed time and imidacloprid application concentrations were also the main factors influencing the absorption. This study enhances our understandings of the uptake and distribution of imidacloprid in maize plants.     

Electromagnetoelastic behaviors of functionally graded piezoelectric

Analytical studies on electromagnetoelastic behaviors are presented for the functionally graded piezoelectric material (FGPM) solid cylinder and sphere placed in a uniform magnetic field and subjected to the external pressure and electric loading. When the mechanical, electric and magnetic properties of the material obey an identical power law in the radial direction, the exact displacements, stresses, electric potentials and perturbations of magnetic field vector in the FGPM solid cylinder and sphere are obtained by using the infinitesimal theory of electromagnetoelasticity. Numerical examples also show the significant influence of material inhomogeneity. It is interesting to note that selecting a specific value of inhomogeneity parameter can optimize the electromagnetoelastic responses, which will be of particular importance in modern engineering designs.     

具确定弱区域正交各向异性薄板的弹塑性屈曲分析

基于弹塑性力学和损伤理论,建立了一个与应力球张量有关的具损伤正交各向异性材料的混合硬化屈服准则,该准则无量纲化后与各向同性材料的Mises准则同构,在此基础上,建立了正交各向异性材料的增量型和全量型弹塑性损伤本构方程,并以具确定弱区域正交各向异性矩形薄板为例,根据屈曲时的能量准则和全量理论,以等效塑性应变为内变量,对其弹塑性屈曲问题进行了分析,讨论了几何参数和弱区域对正交各向异性薄板弹塑性屈曲临界应力的影响.     

COUPLED VARIATIONAL PRINCIPLES AND GENERALIZED COUPLED VARIATIONAL PRINCIPLES IN PHOTOELASTICITY

ＦｕＢａｏｌｉａｎ（付宝连）（ＲｅｃｅｉｖｅｄＮｏｖ．２２，１９９３；ＣｏｍｍｕｎｉｃａｔｅｄｂｙＣｈｉｅｎＷｅｉｚａｎｇ）ＣＯＵＰＬＥＤＶＡＲＩＡＴＩＯＮＡＬＰＲＩＮＣＩＰＬＥＳＡＮＤＧＥＮＥＲＡＬＩＺＥＤＣＯＵＰＬＥＤＶＡＲＩＡＴＩＯＮＡＬＰＲＩ...