分子动力学模拟Ag-Pd 双金属团簇中不同位置Ag 原子偏析诱导的异常熔化

在双金属团簇中任意两种元素表面能的差别都会在团簇形成时产生偏析, 从而影响团簇的熔化、原子排布和结构. 因此双金属团簇中原子偏析行为的研究可以为新型纳米结构的可控制备提供理论基础. 本文用分子动力学结合嵌入原子方法研究了分布在团簇的核心层和亚表面层的Ag 原子偏析对(AgPd)₁₄₇ 团簇熔化的影响. 结果表明Ag 在Pd 团簇的不同位置时能量不同,在表面层时最稳定, 其次是核心层, 最后是亚表面层. 这造成了核心层的Ag 原子偏析到团簇的亚表面层时, 团簇原子能量随温度的增加而增大. 而亚表面层Ag 原子的偏析会使团簇原子能量随温度的增加而减小. 这种异常熔化的程度与偏析原子个数有关. 这为双金属团簇熔化行为的调节提供了有效途径.     

寄生植物和寄主植物间的物质分配

以寄生植物肉苁蓉和寄主植物梭梭为对象, 研究了寄生植物和寄主植物间的物质分配.结果显示, 肉苁蓉体内累积大量的可溶性碳水化合物, 其中可溶性总糖、淀粉以及总可溶性碳水化合物总量分别达到了5.56, 2.73, 8.29 g/株, 分别占梭梭肉苁蓉复合体的51.01%, 60.13%,53.73%; 肉苁蓉对K, P, Zn, Cu 的累积较多, 总量分别达到了348.15, 18.94, 0.24, 0.14 mg/株, 分别占复合体的18.46%, 16.36%, 7.27%, 5.67%. 本研究结果为寄生植物和寄主植物间的物质分配调节提供了初步的理论依据.     

CdTe/ZnS 量子点荧光可逆调控研究ctDNA 与吡柔比星的相互作用

水相合成了谷胱甘肽修饰的CdTe/ZnS 量子点(GSH-CdTe/ZnS QDs). 从原子力显微镜照片可以看出, 合成的核壳型GSH-CdTe/ZnS QDs 具有良好的分散性. 当吡柔比星与GSH-CdTe/ZnS QDs 相互作用时, 吡柔比星吸附在GSH-CdTe/ZnS QDs 的表面, 通过光诱导电子转移的方式猝灭GSH-CdTe/ZnS QDs 的荧光. 然后向GSH-CdTe/ZnS QDs-吡柔比星体系中加入ctDNA, 吡柔比星从GSH-CdTe/ZnS QDs 表面脱落后嵌入ctDNA 双螺旋结构中, 光诱导电子转移过程被阻断, GSH-CdTe/ZnS QDs 的荧光恢复. 根据GSH-CdTe/ZnSQDs 荧光的猝灭和恢复, 实现了量子点荧光的可逆调控. 结合共振瑞利散射和紫外吸收光谱, 讨论了GSH-CdTe/ZnS QDs 吡柔比星-ctDNA 的相互作用机理, 建立了一种研究蒽醌类抗癌药物与核酸相互作用的光谱方法.     

换热器内随温度变化的黏度对两流体(火积)的影响

以橄榄油为例来研究黏度固定和黏度为温度函数的情况下黏性热效应对顺流换热器内两流体相似文献   

有机半导体异质结电荷产生层及其在叠层有机发光二极管中的应用

叠层有机发光二极管因其具有更高的亮度、效率以及稳定性, 其研究备受关注.本文综述了叠层有机发光二极管的最新进展; 总结了作者研究小组基于有机半导体异质结的概念, 设计了由一种p 型有机半导体和一种n 型有机半导体层层组成的双层有机半导体异质结电荷产生层, 并用它们作为连接单元制备了叠层有机发光二极管, 器件的电压得到了降低, 功率效率得到了提高. 通过对电荷产生层的工作机制的深入剖析, 揭示了降低电压、提高功率效率的内在物理原因, 为进一步设计高性能有机电致发光器件提供了新的思路; 最后对叠层有机发光二极管的未来发展方向进行了展望.     

集成微流控芯片

作为一种能够在微米级尺度操纵液体的新兴技术, 微流控芯片已经受到科学家们的广泛关注. 高密度集成的微流控芯片装置可以实现高通量并行化的实验以及多种操作单元的功能一体化, 作为一种新的方法学平台, 已经越来越多地应用于化学和生命科学的研究中. 本文着重介绍了集成化微流控芯片装置的基本概念、构建方法、及其在细胞生物学、分子生物学以及化学合成应用研究中的最新进展, 尤其强调了集成微流控芯片系统在传统方法难以达成或实现的单细胞和高通量的研究中的优势, 展望了集成化微流控芯片在化学以及生命科学中的应用前景.     

Reversing pathological neural activity using targeted plasticity

Brain changes in response to nerve damage or cochlear trauma can generate pathological neural activity that is believed to be responsible for many types of chronic pain and tinnitus. Several studies have reported that the severity of chronic pain and tinnitus is correlated with the degree of map reorganization in somatosensory and auditory cortex, respectively. Direct electrical or transcranial magnetic stimulation of sensory cortex can temporarily disrupt these phantom sensations. However, there is as yet no direct evidence for a causal role of plasticity in the generation of pain or tinnitus. Here we report evidence that reversing the brain changes responsible can eliminate the perceptual impairment in an animal model of noise-induced tinnitus. Exposure to intense noise degrades the frequency tuning of auditory cortex neurons and increases cortical synchronization. Repeatedly pairing tones with brief pulses of vagus nerve stimulation completely eliminated the physiological and behavioural correlates of tinnitus in noise-exposed rats. These improvements persisted for weeks after the end of therapy. This method for restoring neural activity to normal may be applicable to a variety of neurological disorders.     

The circadian molecular clock creates epidermal stem cell heterogeneity

Murine epidermal stem cells undergo alternate cycles of dormancy and activation, fuelling tissue renewal. However, only a subset of stem cells becomes active during each round of morphogenesis, indicating that stem cells coexist in heterogeneous responsive states. Using a circadian-clock reporter-mouse model, here we show that the dormant hair-follicle stem cell niche contains coexisting populations of cells at opposite phases of the clock, which are differentially predisposed to respond to homeostatic cues. The core clock protein Bmal1 modulates the expression of stem cell regulatory genes in an oscillatory manner, to create populations that are either predisposed, or less prone, to activation. Disrupting this clock equilibrium, through deletion of Bmal1 (also known as Arntl) or Per1/2, resulted in a progressive accumulation or depletion of dormant stem cells, respectively. Stem cell arrhythmia also led to premature epidermal ageing, and a reduction in the development of squamous tumours. Our results indicate that the circadian clock fine-tunes the temporal behaviour of epidermal stem cells, and that its perturbation affects homeostasis and the predisposition to tumorigenesis.     

Structural insight into brassinosteroid perception by BRI1

Brassinosteroids are essential phytohormones that have crucial roles in plant growth and development. Perception of brassinosteroids requires an active complex of BRASSINOSTEROID-INSENSITIVE 1 (BRI1) and BRI1-ASSOCIATED KINASE 1 (BAK1). Recognized by the extracellular leucine-rich repeat (LRR) domain of BRI1, brassinosteroids induce a phosphorylation-mediated cascade to regulate gene expression. Here we present the crystal structures of BRI1(LRR) in free and brassinolide-bound forms. BRI1(LRR) exists as a monomer in crystals and solution independent of brassinolide. It comprises a helical solenoid structure that accommodates a separate insertion domain at its concave surface. Sandwiched between them, brassinolide binds to a hydrophobicity-dominating surface groove on BRI1(LRR). Brassinolide recognition by BRI1(LRR) is through an induced-fit mechanism involving stabilization of two interdomain loops that creates a pronounced non-polar surface groove for the hormone binding. Together, our results define the molecular mechanisms by which BRI1 recognizes brassinosteroids and provide insight into brassinosteroid-induced BRI1 activation.