Half-wave potential-ph diagram for the parabenzoquinone system in n,n-dimethylformamide

Abstract

A half wave potential-pH diagram for the parabenzoquinone system has been obtained by the use of potentiometry, voltammetry and polarography in buffered N,N-dimethylformamide media. Acid-base and redox reactions are considered and the study is completed by the use of spectrophotometry.     

Phase Diagrams of Semicrystalline Polymer–Crystalline Substances: Polyolefins–1,2,4,5-Tetrachlorobenzene

The full phase diagrams of low-density polyethylene (LDPE), high-density polyethylene (HDPE), and isotactic polypropylene (i-PP) mixtures with 1,2,4,5-tetrachlorobenzene (TeCB), including the solubility curve of TeCB in a solid polymer, were constructed by an optical method. The diagrams contain a eutectic point that corresponds to the situation when the crystallization of TeCB out of its solution in a polyolefin is accompanied by the crystallization of monomer units of the macromolecules. As a result, the polymer acquires a gel structure with crystallites as crosslinks and amorphous regions saturated with TeCB. It is demonstrated that the eutectic point position on the phase diagram can be used for ranking polymers with respect to their thermodynamic affinity to a solvent. For the studied systems, the affinity to TeCB was decreased in the order i-PP, HDPE, and LDPE. Direct experimental evidence was obtained that TeCB crystals can be dissolved in a solid polymer via a vapor phase mechanism, which leads to the polymer amorphization.     

Influence of surface and bulk layers on the crossover features for interaction parameters of a ferroelectric thin film

The phase diagram of a ferroelectric thin film is studied by using the usual mean-field approximation. The crossover features, from the ferroelectric-dominant phase diagram to the paraelectric-dominant phase diagram, for the physical parameters of the thin film are discussed. Special attention is devoted to the investigation of surface and bulk layers, and how to influence the crossover values of exchange interactions and transverse fields.     

Hubbard模型中的相位弦效应与交互Chern-Simons理论

费米子符号在费米液体理论中至关重要. 然而, 在Mott绝缘体中, 很强的电子Coulomb相互作用抑制了体系的电荷涨落并消除了电子交换带来的费米子符号问题. 本文首先回顾二分晶格上Hubbard模型的相位弦理论, 从弱关联的费米液体到强关联的反铁磁Mott绝缘体的转变可以由此得到统一理解. 在任意Coulomb作用强度U下, 我们首先导出Hubbard模型的严格的符号结构. 在小U极限下, 它回到通常的费米子符号; 在大U极限下, 它给出了t-J模型的相位弦符号. 在半满情形下, 我们构造了一种电子分数化的表象, 其中, 电荷子与自旋子通过演生的交互Chern-Simons规范场相互耦合. 由此导出的基态波函数拟设与低能有效理论可以定性刻画Hubbard模型的基态相图. 在弱关联区域, 费米液体的准粒子由电荷子与自旋子的束缚态构成, 其长程相位相干性取决于背景自旋的关联性质. 体系的Mott转变可以通过电荷子打开能隙或是通过自旋子玻色凝聚来实现.     

Phase diagram of P3HT:PC70BM thin films based on variable-temperature spectroscopic ellipsometry

In this article, we present the research on the influence of the composition of thin films of a blend of poly (3-hexylthiophene −2,5-diyl) - P3HT with fullerene derivatives [6,6]-phenyl-C71-butyric acid methyl ester – PC70BM and [6,6]-phenyl-C61-butyric acid methyl ester – PC60BM on their thermal transitions. The influence of molar mass (Mw) of P3HT (Mw = 65.2; 54.2 and 34.1 kDa) and PCBM (PC60BM – Mw = 911 g/mol and PC70BM – Mw = 1031 g/mol) is examined in details. The article presents significantly expanded research compared to our previous work on thermal transitions in thin films of blend P3HT (Mw = 65.2 kDa) with PC60BM. For this reason, we also compare current results with previous ones. Here, we present for the first time a phase diagram of thin films of the P3HT(Mw = 65.2 kDa):PC70BM blend using variable-temperature ellipsometry. Our research reveals the presence of characteristic temperatures of pure phases in thin films of P3HT: PCBM blends. It turns out that the cold crystallization temperature of the P3HT phase in P3HT(Mw = 65.2 kDa):PC70BM blend films is lower than corresponding temperature in P3HT(Mw = 65.2 kDa):PC60BM blend films. At the same time, the cold crystallization temperature of the PC70BM phase behaves inversely. We demonstrate also that variable-temperature spectroscopic ellipsometry is a very sensitive technique for studying thermal transitions in these thin films. In addition, we show that the entire phase diagram can be determined based on the raw ellipsometric data analysis, e.g. using a delta angle at wavelength λ = 280 nm.     

浅论建筑结构分析中计算简图的建立

建筑结构的力学分析都是通过建立计算简图及计算模型进行的, 探讨了 建筑结构计算简图及计算模型的概念、建立计算简图的原则、对实际建筑结构进行简化的内 容, 并介绍了5种实际建筑结构简化的结果, 期望能帮助学生做好结构分析.     

Thompson＇s Group F and the Linear Group GL∞（Z）

The authors study the finite decomposition complexity of metric spaces of H, equipped with different metrics, where H is a subgroup of the linear group GL_∞(ℤ). It is proved that there is an injective Lipschitz map φ: (F, d _S ) → (H, d), where F is the Thompson’s group, dS the word-metric of F with respect to the finite generating set S and d a metric of H. But it is not a proper map. Meanwhile, it is proved that φ: (F, d _S ) → (H, d ₁) is not a Lipschitz map, where d ₁ is another metric of H.     

Phase transition and thermodynamic properties of Sr under high pressure

We have performed the first-principles and classical molecular dynamics simulations to investigate the phase diagram and thermodynamic properties of Sr under high pressure and temperature. The obtained solid phase diagram of Sr, based on the quasi-harmonic approximation (QHA), is greatly supported by the available experimental data under low pressure. From the coexistence-phase molecular dynamics simulations, we also obtained the high-pressure melting curve of Sr which shows good agreement with the experiment. While, the experimentally observed β-Sn structure of Sr-III was found to be mechanically unstable according to our phonon dispersion calculations and evolutionary algorithm structure searches. We find that α-U phase (space group Cmcm) is energetically favorable and is the good candidate of Sr-III.     

铁基超导体中的化学掺杂研究

目前已经发现的绝大部分铁基超导体都是通过化学掺杂而得到的。铁基超导体的母体一般在200K以下经历自旋密度波（SDW）转变：即其基态是一类巡游电子反铁磁不良导体。通过适当的元素替代可以在FeAs层产生额外的电子、空穴、巡游性或化学压力,从而有效地抑制SDW序,实现超导电性。本文侧重作者所在小组的相关研究结果,将铁基超导体中的元素替代研究分为FeAs层外和FeAs层内掺杂两大类,依次介绍和评述两年来国际上对4种主要铁基化合物中的化学掺杂研究进展。