A Two-Dimensional Hybrid Perovskite With Heat Switching Birefringence

Birefringent crystals that can switch light polarization have important applications in optoelectronics. In the last decades, birefringence is mostly optimized by chemical strategies. Recently, switching birefringence by physical means has attracted much attention. Here, this work reports the observation of heat switching birefringence in a 2D layered hybrid halide perovskite (C₂N₃H₄)₂PbCl₄ ((C₂N₃H₄)⁺=1,2,4-triazolium). This heat switching birefringence leads to a significant change in the interference color for the crystal plate under the illumination of orthogonal polarized light. Structure analyses reveal a heat dependent structure transition in (C₂N₃H₄)₂PbCl₄, whose birefringence is switched by the change in the distortion degree of PbCl₆ octahedron. This discovery may be beneficial to the further development of stimuli-responsive polarization optical devices.     

杆状病毒p35基因延缓昆虫细胞凋亡

构建了以新霉素抗性基因为筛选标记的带有ｐ３５基因的转移载体ｐ３５ＩＥ１Ｎｅｏ，以此载体转染Ｓｆ９细胞，经Ｇ４１８筛选得到染色体上稳定整合质粒ｐ３５ＩＥ１Ｎｅｏ的Ｓｆ９细胞，克隆化培养后取名为Ｓｆ９－３５．经细胞原位杂交实验证明，Ｓｆ９－３５细胞的染色体ＤＮＡ上含有ｐ３５基因；经放线菌素Ｄ处理后的细胞核酸电泳检测，证实Ｓｆ９－３５具有抗凋亡特性能够支持凋亡抑制基因缺失的ｖＡｃΔｐ３５病毒复制；发现ｐ３５基因在细胞内组成型表达只能延缓ｖＡｃΔｐ３５感染及放线菌素Ｄ处理诱发的细胞凋亡的过程，而不能完全阻止其诱发的细胞凋亡．     

Flocking dynamics for a multiagent system involving task strategy

Collective behavior sometimes requires forming a particular formation or reaching a certain velocity to accomplish a specific task, such as bird migration. In this paper, we investigate the collective migration model, which consists of two parts: Cucker–Smale type interaction and target velocity. Each agent has a strategy to allocate limited energy to group interaction and velocity tracking. In this case, if the system achieves monocluster flocking then the final velocity is equal to target velocity. When the strategy is invariant, we show that 1/2 is a critical threshold which is consistent with the classical Cucker–Smale model. When the strategy is time varying, we provide a time-varying strategy named threshold strategy to ensure that for any initial state the system achieves monocluster flocking and the final velocity reaches target velocity. In addition, the case of multiple target velocities is considered. According to the theory of bicluster flocking, we obtain a sufficient framework to guarantee that the system achieves bicluster flocking and two groups would reach their target velocities, respectively.