The origin of a 650 nm photoluminescence band in rubrene

Commonly observed variations in photoluminescence (PL) spectra of crystalline organic semiconductors, including the appearance or enhancement of certain PL bands, are shown to originate from a small amount of structural disorder (e.g., amorphous inclusions embedded in a crystal), rather than be necessarily related to chemical impurities or material oxidation. For instance, in rubrene, a minute amount of such disorder can lead to the appearance of a dominant PL band at 650 nm as a result of triplet excitons captured and fused at these sites, with a subsequent emission from the amorphous phase.     

Thermally activated singlet exciton fission observed in rubrene doped organic films

The magnetic field effects of photoluminescence (MPL) from rubrene doped organic films were recorded at different temperatures. The measured line shapes were attributed to the field modification on the rate constant of thermally activated singlet exciton fission which occurred between the doped rubrene molecules. And its amplitude exhibited a nonlinear dependence on the averaged intermolecular distance. Such an observation implies that the intermolecular coupling (IMC) which is modulated by changing the intermolecular distance is able to significantly affect the intensity of fission process. Therefore, investigating the variation of singlet fission with different strength of IMC could be an important means to study the dynamics of fission process. Our work reveals the importance of IMC factor which needs to be considered for the design of efficient singlet fission-sensitized organic photovoltaic devices.     

滑动轴承润滑油膜单气泡破裂扩散的仿真分析

滑动轴承在工作过程中由于供油压力不足、机械故障等原因,可能会因贫油而出现油膜气泡现象,导致承载力下降或油膜破裂。利用气液两相流的基础理论和数值模拟分析技术,针对滑动轴承润滑油膜中含有单个大气泡的现象,建立物理模型、数学模型及相应的初始和边界条件,利用VOF模型分析气泡的动力学行为,对于大气泡裂变的过程、破裂后子气泡的演变过程进行仿真。结果表明:轴承油膜中出现的大气泡,在工作过程中极易发生非对称性破裂,裂变成直径大小不等的子气泡;轴承工作过程中,在离心力的作用下气泡有向轴承外圈靠近的趋势,并且有些气泡黏附在轴承外壁上;轴承转速越高,气泡破裂得越快。     

Construction of diploid zygotes by interallelic complementation of ade6 in Schizosaccharomyces japonicus

The construction of diploid cells eases genetic analysis in haploid genetic systems because diploid cells allow for the characterization of essential genes. Here, we report the construction of diploid cells using ade6 point mutants that suppress each other via interallelic complementation in the fission yeast Schizosaccharomyces japonicus var japonicus (Sz. japonicus). We constructed an ade6-domK mutant in addition to the previously described ade6-domE. Phenotypes of both mutants exhibited adenine auxotrophy and red colonies. The mutations complemented the phenotypes in a mutually dependent manner. Diploid zygotes, in which the two mutations were introduced simultaneously into the same cells, were isolated by selecting for adenine independence. Such diploid cells are apparently larger in size than haploid cells, yet have a similar nuclear/cytoplasmic ratio, and thus the nuclear size control that has been reported in Sz. pombe is also present in Sz. japonicus.     

Role of phosphatidylinositol 3-phosphate in formation of forespore membrane in Schizosaccharomyces pombe

Phosphatidylinositol (PI) 3-kinase (encoded by the pik3(+) gene) in Schizosaccharomyces pombe has been identified as a homologue of VPS34p, a protein required for proper vesicular protein sorting. The clone defective in this protein carries enlarged vacuoles and exhibits sensitivity to high temperature or high ion concentration. The effect of disruption of pik3(+) on sporulation of Sz. pombe was examined. The diploid cells underwent G(1) arrest and meiosis. However, the spores formed by the deltapik3 cells were not viable. Electron-microscopic analysis revealed that the growth of the forespore membrane of deltapik3 cells was not correctly orientated, failing to engulf the nucleus or forming extremely small spores, as was confirmed by the use of Spo3p-GFP and GFP-Psy1p, which are markers of the forespore membrane. The coating materials found along the forespore membrane of the wild-type were greatly reduced in these cells. PI 3-P, the product of Pik3p, was detected on the forespore membrane, suggesting that PI 3-P-dependent vesicle transport may take place in formation of the forespore membrane. Misshaped forespore membrane, accumulation of vesicles, formation of small non-viable spores, and suppression by over expression of Psy1p were the phenotypes commonly seen in deltapik3 and deltaspo3 cells, suggesting a relationship between the functions of Pik3p and Spo3p in formation of the forespore membrane in Sz. pombe.     

利用高能缓发γ射线测定裂变数

利用裂变产额法得到短时间辐照²³⁵U样品的裂变总数,通过大体积NaI探测器测量3 MeV以上高能缓发γ射线总计数随时间的变化,从而得到一次裂变3 MeV以上高能缓发γ射线总发射率随时间的变化规律,并给出脉冲辐照下高能缓发γ射线的发射率。通过高能缓发γ射线测量了两块²³⁵U样品的裂变数,其相对不确定度小于4%。     

Enhancing Organic Semiconductor Molecular Packing Using Perovskite Interfaces to Improve Singlet Fission

Singlet fission, a process by which one singlet exciton is converted into two lower energy triplet excitons, is sensitive to the degree of electronic coupling within a molecular packing structure. Variations in molecular packing can be detrimental to triplet formation and triplet–triplet separation, ultimately affecting the harvesting of triplets for electricity in organic photovoltaic devices. Here, six phase-pure molecular packing structures of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) with varying optoelectronic properties are isolated using 2D lead halide perovskites as tunable, crystalline surfaces for crystallization. Transient absorption spectroscopy reveals that while triplet formation is fast (<100 fs) regardless of template structure, the increased ordering in perovskite-templated samples speeds up triplet–triplet separation and recombination, providing evidence that the benefits of phase-purity offset minor variations in molecular packing. Molecular dynamics modeling of the interface reveals that perovskite-templating allows for closer packing of TIPS-pentacene molecules for all perovskite templates. With an extensive number of organic molecule-perovskite pairings, this work provides a methodology to use ordered, periodic surfaces to elucidate structure–property relationships of small organic molecules in order to adjust structural or optoelectronic responses, such as molecular packing and singlet fission.