Flexibility and coordination among acts of visualization and analysis in a pattern generalization activity

This study aims at exploring processes of flexibility and coordination among acts of visualization and analysis in students’ attempt to reach a general formula for a three-dimensional pattern generalizing task.The investigation draws on a case-study analysis of two 15-year-old girls working together on a task in which they are asked to calculate the number of blocks in a three-dimensional tower of different heights. The students’ activity was video- and audio-taped, fully transcribed and lasted for 50 min.The analysis discloses several instances of how the students were linking acts of visualization and analysis to reach a general formula. However, regarding flexibility, we found that it was more natural for the students to change visual format than to change analytical position and direction in their attempts to generalize the three-dimensional pattern of the task in a closed formula.     

Air-stability and bending properties of flexible organic field-effect transistors based on poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]

We have fabricated flexible field-effect transistors (FETs) using poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)], PCDTBT, as an active channel, poly(methyl methacrylate) (PMMA) as gate dielectric and biaxially oriented polyethyleneterephthalate (BOPET) as supporting substrate. The output and transfer characteristics of the devices were measured as a function of channel length. It has been observed that various OFET parameters viz. on–off ratio (∼10⁵), mobility (μ ∼ 10⁻⁴ cm² V⁻¹ s⁻¹), threshold voltage (V_th ∼ −14 V), switch-on voltage (V_so ∼ −6 V), subthreshold slope (S ∼ 7 V/decade) and trap density (N_it ∼ 10¹⁴ cm⁻² V⁻¹) are almost independent of the channel length, which suggested a very high uniformity of the PCDTBT active layer. These devices were highly stable under atmospheric conditions (temperature: 20–35 °C and relative humidity: 70–85%), as no change in mobility was observed on a continuous exposure for 70 days. The studies on the effect of strain on mobility revealed that devices are stable up to a compressive or tensile strain of 1.2%. These results indicate that PCDTBT is a very promising active layer for the air stable and flexible FETs.     

One Dimensional Iron Molybdophosphate Anionic Chains with Different Structural Arrangements Reflecting a Flexibility Character

Structural comparison of a new compound[(bpp)₃H₆]Fe₂^IIIFe₂^IIMo₂₄^V(H₂PO₄)₈(HPO₄)₄(PO₄)₄O₄₈(OH)₁₂· (H₂O)₄·2H₂O(1)[bpp=1,3-di(4-pyridyl)propane] with our previously reported two compounds[(bpy)₃Fe^II]₃· Fe₂^IIIFe₂^IIMo₂₄^V(H₂PO₄)₈(HPO₄)₄(PO₄)₄O₄₈(OH)₁₂(H₂O)₄·12H₂O(2) and[(bpy)₃Fe^II]₂Fe^IIFe^IIIMo₁₂^V(H₂PO₄)₂(H_2-xPO₄)·(H_1+xPO₄)(HPO₄)₂(PO₄)₂O₂₄(OH)₆(H₂O)₂·9H₂O(x=0―1)(3)(bpy=2,2'-bipyridine), which all exhibit one-dimensional mixed-valence iron molybdophosphate anionic chains constructed by alternating connection of Fe^III ions and magic[Fe^II(Mo₆P₄O₃₁)₂] units, reveals that the non-hydrogen atomic ratios of Mo:Fe:P:O within the polymeric anionic chains are the same for all the three compounds, while the polymeric anionic chains of the different compounds bear different numbers of negative charges. And therefore there exist different numbers of counter cations per {Fe₂^III[Fe₂^II(P₁₆Mo₂₄^VO₁₂₄)]} unit found in the titled compounds. It discloses that not only are the spatial assembling of counter cations and polymeric inorganic chains of three compounds quite different, but also the O―Fe^III―O bond angles and Fe^III―O bond lengths of the three different inorganic chains exhibit small differences. What is more important is that such small changes in bond length and bond angle in the assemblage of Fe^III―O bonds lead to the considerable fluctuations of inorganic chains in their structural conformation within the three compounds, reflecting an interesting phenomenon of “flexibility" in the pure inorganic one dimensional mixed-valence iron molybdophosphate chains.     

Studying the interdependence of contractual and operational flexibilities in the market of specialty chemicals

This paper focuses on the market of specialty chemicals and deals with the joint investigation and valuation of contractual and operational flexibilities from a manufacturers’ point of view. In this market, customized services related to research, development and manufacturing of chemicals, intermediates and active pharmaceutical ingredients are offered to a small number of customers. Traditionally, customers are granted a large degree of freedom with respect to demand quantity and time exposing the manufacturer to high uncertainty and financial risk. Using a model-based approach we quantify the effect of this contractual flexibility and relate it to the manufacturing flexibility concerning capacity allocation. Through the valuation of these flexibilities we provide first insights for the manufacturer on which customer requests to accept, how to set up the associated contracts with the customers and how to allocate capacity for a given portfolio of products.     

白光有机发光二极管的研究进展

由于白光有机发光二极管(WOLED)具有效率高、亮度高、功耗低、视角广、响应速度快、主动发光、超薄超轻以及可柔性化等优异性能, 并在显示和照明领域有广阔的应用前景, 受到学者和业界的广泛重视而成为研究热点. 本文首先介绍了实现WOLED的不同方法, 然后从发光材料种类的角度, 阐述了全荧光WOLED、全磷光WOLED、基于荧光/磷光杂化WOLED以及延迟荧光WOLED近年来的研究进展, 并结合我们研究团队最近的工作详细地介绍了不同高性能WOLED的器件结构、设计思想、工作原理、物理机制以及发光过程; 接着, 简单介绍了柔性WOLED最近研究进展; 最后探讨了WOLED目前存在的问题及其未来的发展趋势.     

The Zeolitic Imidazolate Framework ZIF‐4 under Low Hydrostatic Pressures

The zeolitic imidazolate framework ZIF‐4 has recently been shown to exhibit large structural flexibility as a response to hydrostatic pressures, going from an open pore phase ( ZIF ‐ 4 ( Zn )‐ op ) to a closed pore phase ( ZIF ‐ 4 ( Zn )‐ cp ). The use of diamond anvil cell (DAC) setups has so far restricted thorough experimental insight into the evolution of lattice parameters at pressures below p < 0.1 GPa. Here we revisit the high‐pressure properties of ZIF‐4(Zn) by applying a new high‐pressure powder X‐ray diffraction setup that allows for tracking the evolution of lattice parameters in pressure increments as small as Δp = 0.005 GPa in the pressure range p = ambient – 0.4 GPa; a pressure resolution that cannot be achieved by using traditional DACs. We find ZIF‐4(Zn) has a bulk modulus of K( ZIF ‐ 4 ( Zn )‐ op ) = 2.01 ± 0.05 GPa and K( ZIF ‐ 4 ( Zn )‐ cp ) = 4.39 ± 0.20 GPa, clarifying and confirming some ambiguous results that have been reported previously.     

Flexible Electrochromic Poly(thiophene-furan) Film via Electrodeposition with High Stability

Flexible electrochromic(EC) materials have an urgent demand in the current electronic equipment market due to their technological interest and applications. However, at present, few flexible EC devices developed by industry exist due to some problems and challenges still to be solved such as flexibility. In this work, we have successfully synthesized a novel thiophene-furan(TFu) monomer via Stille coupling reaction,and facilely electrochemically polymerized in a neutral Bu_4 NPF_6-CH_2Cl2 electrolyte system to afford the corresponding poly(thiophene-furan)(PTFu) polymer film with good flexibility. The electrochemical and photoelectrochemical analyses of the as-prepared PTFu demonstrate that it has achieved the improved EC performance compared with pure polyfuran and polythiophene polymers, and as a result it possesses favorable EC parameters manifested as a reasonable ΔT(32.1%), faster response(1.38 s), excellent coloration efficiency(CE, 300.9 cm²·C^-1), and after a continuous redox process up to 2000 s, its optical stability can be maintained at 96%, and even after 3000 s, it can still be maintained at 80%. In addition, the successful assembly of the electrochromic device of PTFu film can easily realize the reversible conversion of the color from orange to gray. All these systematic studies suggest that the as-prepared flexible PTFu film is a promising candidate for EC materials and has great potential interest for versatile EC applications.     

分子动力学研究亚铁血红素激活蛋白转录激活机理

以3种亚铁血红素激活蛋白(Heme activator protein, HAP)-DNA 复合物(野生型HAP1-wt, Ser63/Arg63突变HAP1-18 和 Ser63/Gly63突变HAP1-PC7)为对象对亚铁血红素激活蛋白的转录激活机理进行了分子动力学研究. 对3个复合物分子动力学轨迹的比较性分析显示, 涉及到上游活化序列(Upstream activation sequences, UAS)识别的蛋白质-DNA 相互作用分布与实验观测到的3种蛋白转录活性一致. 进一步对3个复合物进行柔性分析显示, 3个DNA分子具有相似的柔性, 而又有所不同, 特别在涉及UAS识别的N-端和Zn2Cys6结构域前部有明显的柔性差异. 蛋白质柔性的差别导致不同的蛋白质-DNA相互作用. 因此亚铁血红素激活蛋白的N-端和Zn2Cys6结构域前部的柔性大小能够调节亚铁血红素激活蛋白转录激活功能.     

一种特种弹簧加工工艺的深入研究

通过对弹簧钢丝的热处理规范、弹簧钢丝强度、弹簧回弹量、芯轴直径与弹簧挠度之间的关系的深入研究,找到能满足弹簧挠度要求的钢丝强度"缝隙"、弹簧回弹量及芯轴直径的范围,以指导生产加工出挠度指标符合要求的特种弹簧.     

一种多孔配位聚合物的氢键协同客体响应

由硝酸锌、 吡唑-3,5-二羧酸（H₃pzdc）和2-氨基对苯二甲酸（H₂abdc）在溶剂热条件下反应得到一种多孔配位聚合物(Me₂NH₂)[Zn₂(pzdc)(abdc)]·H₂O·DMF(1·g), 其中Me₂NH₂⁺由溶剂N,N-二甲基甲酰胺（DMF）水解得到, 1可视为平行排列的平整带状{Zn₂(pzdc)}⁺链被abdc^2-柱子交错支撑而成的三维多孔框架. 通过脱附/吸附溶剂分子, 中心对称的配位聚合物1·g可以可逆转变成手性的(Me₂NH₂)[Zn₂(pzdc)(abdc)](1′). 单晶结构分析表明, 在客体响应过程中, 基于框架、 抗衡离子和客体分子之间的氢键协作与竞争, 抗衡离子发生了显著的移动 和转动, 导致{Zn₂(pzdc)}⁺链扭曲和转动, 伴随着超过10%的晶胞体积和孔洞率变化. 气体吸附测试表明, 化合物1'对N₂和CO₂存在不同的结构响应行为.