Dynamically controlled asymmetric transmission of linearly polarized waves in VO2-integrated Dirac semimetal metamaterials

We numerically demonstrated a novel chiral metamaterial to achieve broadband asymmetric transmission (AT) of linearly polarized electromagnetic waves in terahertz (THz) band. The proposed metamaterial unit cell exhibits no rotational symmetry with vanadium dioxide (VO$_{2}$) inclusion embedded between Dirac semimetals (DSMs) pattern. The resonant frequency of AT can be dynamically tunable by varying the Fermi energy ($E_{\rm F}$) of the DSMs. The insulator-to-metal phase transition of VO$_{2}$ enables the amplitude of the AT to be dynamically tailored. The transmission coefficient $|T_{yx}|$ can be adjusted from 0.756 to nearly 0 by modifying the conductivity of VO$_{2}$. Meanwhile, the AT parameter intensity of linearly polarized incidence can be actively controlled from 0.55 to almost 0, leading to a switch for AT. When VO$_{2}$ is in its insulator state, the proposed device achieves broadband AT parameter greater than 0.5 from 1.21 THz to 1.80 THz with a bandwidth of 0.59 THz. When the incident wave propagates along the backward ($-z$) direction, the cross-polarized transmission $|T_{yx}|$ reaches a peak value 0.756 at 1.32 THz, whereas the value of $|T_{xy}|$ well below 0.157 in the concerned frequency. On the other hand, the co-polarized transmission $|T_{xx}|$ and $|T_{yy}|$ remained equal in the whole frequency range. This work provides a novel approach in developing broadband, tunable, as well as switchable AT electromagnetic devices.     

C-3-吡唑啉基取代的叶绿素类二氢卟吩衍生物的合成

以脱镁叶绿酸-a甲酯为起始原料,通过对E-环、3-位碳碳双键和20-位meso-氢的结构修饰,在二氢卟吩色基上构建和引进不同的官能团,并进一步利用其3-位乙烯基与重氮甲烷的1,3-偶极环加成反应,完成一系列C-3-吡唑啉基取代的叶绿素类二氢卟吩衍生物的合成.同时,讨论了叶绿素衍生物的1,3-偶极环加成反应的的区域选择性与立体选择性.所得新的叶绿素类二氢卟吩衍生物的化学结构均经UV,IR,1H NMR及元素分析得以证实.     

过渡金属离子置换钛酸纳米管的制备和光催化活性

TiO2纳米粉体和纳米膜材料在光催化降解大气和水中的污染物等方面具有广泛的应用[1]。近年来,以TiO2为原料与浓N aO H反应合成的钛酸纳米管具有比其原料TiO2更大的表面积和孔体积,且对丙烯有光催化氧化降解活性而备受关注[2]。以往在对TiO2纳米粉体和纳米膜材料在光催化研究中,人们发现由于光激发产生的电子与空穴的复合,导致光量子效率很低。为克服这个缺点,人们使用过渡金属离子掺杂等多种手段对TiO2进行改性[3]。但钛酸纳米管相类似的研究还未见报道。对钛酸纳米管的结构和组成的研究表明[4],此纳米管状物的组成是N axH2-xTi3O7,…     

顺（反）-2，4，7-三芳基5-氧代4H-5，6，7，8-四氢苯并吡喃衍生物的合成

在酸或碱怀条件下，5，5-二甲基-1，3-环已二酮和5-芳基-1，3-环已二酮与 查尔酮首先进行Michael加成反应，进而环合为7，7-二甲基-2，4-二芳基-5-氧代- 4H-5，6，7，8-四氢苯并吡喃衍生物和含有两个手性原子的顺和反-2，4，7-三芳 基-5-氧代-4H-5，6，7，8-四氢苯并吡喃衍生物。讨论了反应机理并且通过~1H NMR光谱和NOE差谱确定其产物构型。所合成新的多氢苯并吡喃衍生物的分子结构 均经红外光谱、核磁共振光谱和元素分析予以证实。     

Multiple Partial Attacks on Complex Networks

We numerically investigate the effect of four kinds of partial attacks of multiple targets on the Barabási Albert （BA） scale-free network and the Erdos-Rényi （ER） random network. Comparing with the effect of single target complete knockout we find that partial attacks of multiple targets may produce an effect higher than the complete knockout of a single target on both BA scale-free network and ER random network. We also find that the BA scale-free network seems to be more susceptible to multi-target partial attacks than the ER random network.     

第三代同步辐射光源储存环支撑组件振动控制研究

第三代同步辐射光源对束流轨道稳定性要求很高,上海光源是一台在建的第三代光源,束流位置稳定度要求达到微米乃至亚微米级.地基振动会使储存环磁聚焦结构中的各种元件发生机械振动引起随时间变化的束流闭合轨道畸变,影响束流轨道稳定性.上海光源场地振动幅值大,需要研究措施控制机械组件的振动.阻尼减振是一种有效的振动控制方法,针对上海光源储存环机械组件,作者设计了一种阻尼减振方案.试验结果表明,该方案能有效地控制机械组件的振动.这对于保证上海光源的束流稳定性要求有积极意义.     

Synthesis of Chlorin—enediyne Dyads by Palladium—catalyzed Coupling Reaction

Methyl 9-ethylenedioxpyropheophorbide-d was prepared from methyl pyropheophorbide-a by protection of cyclic ketone with ethylene glycol,and oxidation with OsO4 in vinyl group at 2-position.The terminal alkyne was introduced into chlorin chromophore by Grignard reaction,and the enediyne moiety was constructed by a palladium-catalyzed coupling reaction with (Z)-chloroenynes.     

“铜元素化合物”的高三线上主题式复习*

以高三复习课“铜元素化合物”的教学为例,基于主题教学思想,从“价类二维图”出发,引导学生从物质类别、氧化还原和化学平衡等多角度认识元素化合物间的相互转化,实现了主题内容的关联与进阶,促进了学生思维能力的提升和学科观念的建构。本节课是网络直播课,采用“腾讯课堂”平台,学生可以连麦回答问题,学生设计的实验方案发布在班级微信上,由教师共享屏幕,则所有学生可见。