4-(1-硫杂-2亚氨基-3,4-二氮杂-1,4-亚丁基)-4-脱氧阿维菌素B1a的合成

以阿维菌素B1a为原料经选择性C-5羟基保护、氧化合成5-O-烯丙氧羰基-5-氧代-5-脱氧阿维菌素B1a (3), 然后与N-取代氨基硫脲偶联, 缩合产物经MnO2氧化关环、脱保护得到10个未见文献报道的4-(1-硫杂-2-亚氨基- 3,4-二氮杂-1,4-亚丁基)-4-脱氧阿维菌素B1a (7a～7j). 目标化合物结构经1H NMR, 13C NMR和MS确证.     

Concerted Rattling in CsAg5Te3 Leading to Ultralow Thermal Conductivity and High Thermoelectric Performance

Thermoelectric (TE) materials convert heat energy directly into electricity, and introducing new materials with high conversion efficiency is a great challenge because of the rare combination of interdependent electrical and thermal transport properties required to be present in a single material. The TE efficiency is defined by the figure of merit ZT=(S²σ) T/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the total thermal conductivity, and T is the absolute temperature. A new p‐type thermoelectric material, CsAg₅Te₃, is presented that exhibits ultralow lattice thermal conductivity (ca. 0.18 Wm^?1 K^?1) and a high figure of merit of about 1.5 at 727 K. The lattice thermal conductivity is the lowest among state‐of‐the‐art thermoelectrics; it is attributed to a previously unrecognized phonon scattering mechanism that involves the concerted rattling of a group of Ag ions that strongly raises the Grüneisen parameters of the material.     

Ultrasensitive electrochemiluminescent aptasensor for ochratoxin A detection with the loop-mediated isothermal amplification

In this study, we for the first time presented an efficient, accurate, rapid, simple and ultrasensitive detection system for small molecule ochratoxin A (OTA) by using the integration of loop-mediated isothermal amplification (LAMP) technique and subsequently direct readout of LAMP amplicons with a signal-on electrochemiluminescent (ECL) system. Firstly, the dsDNA composed by OTA aptamer and its capture DNA were immobilized on the electrode. After the target recognition, the OTA aptamer bond with target OTA and subsequently left off the electrode, which effectively decreased the immobilization amount of OTA aptamer on electrode. Then, the remaining OTA aptamers on the electrode served as inner primer to initiate the LAMP reaction. Interestingly, the LAMP amplification was detected by monitoring the intercalation of DNA-binding Ru(phen)₃²⁺ ECL indictors into newly formed amplicons with a set of integrated electrodes. The ECL indictor Ru(phen)₃²⁺ binding to amplicons caused the reduction of the ECL intensity due to the slow diffusion of Ru(phen)₃²⁺–amplicons complex to the electrode surface. Therefore, the presence of more OTA was expected to lead to the release of more OTA aptamer, which meant less OTA aptamer remained on electrode for producing LAMP amplicons, resulting in less Ru(phen)₃²⁺ interlaced into the formed amplicons within a fixed Ru(phen)₃²⁺ amount with an obviously increased ECL signal input. As a result, a detection limit as low as 10 fM for OTA was achieved. The aptasensor also has good reproducibility and stability.     

超声波对丰年虫卵孵化的影响

研究了固定频率和强度的超声波对饵料生物丰年虫卵（ｃｈｉｒｏｃｅｐｈａｌｕｓ）化的影响。实验结果表明,在适宜的超声波辐照下,丰年虫卵的孵化率比对照组提高８％,孵化时间提前２ｈ。     

爆炸载荷下双向梯度仿生夹芯圆板的力学行为

基于王莲仿生面内梯度芯层,通过引入面外梯度,设计了一种双向梯度仿生夹芯圆板。在此基础上,运用ABAQUS有限元软件,对不同排列方式的双向梯度夹芯圆板在不同爆炸载荷作用下的响应进行了数值仿真,着重分析了不同仿生夹芯圆板的前后面板挠度、芯层压缩量、变形模式和能量吸收等特性,得到了一种抗爆性能较好的芯层排列方式。结果表明:相较于单一的面外梯度夹芯圆板,合理设计的双向梯度仿生夹芯圆板可以有效降低后面板挠度,并提高芯层的能量吸收。     

周培源先生学术思想初探

周培源先生是蜚声海内外的著名理论物理学家、流体力学家、教育家和社会活动家,是我国力学事业的奠基人之一. 他在爱因斯坦广义相对论引力论和湍流理论领域攻坚70余年,取得了卓越的成就. 通过周培源先生的生平、学术成就及学术品格方面的重要事迹初步探索周培源先生的学术思想,以共享这宝贵的精神财富.     

Particle filter based visual tracking with multi-cue adaptive fusion

To improve the robustness of visual tracking in complex environments such as: cluttered backgrounds, partial occlusions, similar distraction and pose variations, a novel tracking method based on adaptive fusion and particle filter is proposed in this paper. In this method, the image color and shape cues are adaptively fused to represent the target observation; fuzzy logic is applied to dynamically adjust each cue weight according to its associated reliability in the past frame; particle filter is adopted to deal with non-linear and non-Gaussian problems in visual tracking. The method is demonstrated to be robust to illumination changes, pose variations, partial occlusions, cluttered backgrounds and camera motion for a test image sequence.     

Track before detect for point targets with particle filter in infrared image sequences

The problem of detecting and tracking point targets in a sequence of infrared images with very low signalto-noise ratio (SNR) is investigated in this paper. A track before detect algorithm for infrared (IR) point target is developed based on particle filter. The particle filter is used to estimate the state of the target in track stage. The unnormalized weights of the output of the filter are used to approximately construct the likelihood ratio for hypothesis test in detection stage. Experiment results with the real image sequences that SNR is about 2.0 show that the proposed algorithm can successfully detect and track point target.