Thermal and Mechanical Properties of Epoxy/Carbon Fiber Composites Reinforced with Multi-walled Carbon Nanotubes

Multi-scale hybrid composite laminates of epoxy/carbon fiber (CF) reinforced with multi-walled carbon nanotubes (MWCNTs) were fabricated in an autoclave. For laminate fabrication, 0.5 wt% of pristine MWCNTs or silane-functionalized MWNCTs (f-MWCNTs) were dispersed into a diglycidyl ether of bisphenol-A epoxy system and applied on the woven carbon fabric. The neat epoxy/CF composite and the MWCNTs-reinforced epoxy/CF hybrid composites were characterized by thermogravimetric analysis (TGA), thermomechanical analysis (TMA), tensile testing, and field emission scanning electron microscopy (FE-SEM). A significant improvement in initial decomposition temperature and glass transition temperature of epoxy/CF composite was observed when reinforced with 0.5 wt% of f-MWCNTs. The coefficient of thermal expansion (CTE), measured by TMA, diminished by 22% compared to the epoxy/CF composite, indicating an improvement in dimensional stability of the hybrid composite. No significant improvement in tensile properties of either MWCNTs/epoxy/CF composites was observed compared to those of the neat epoxy/CF composite.     

Reflexive Property of Rings

Mason introduced the reflexive property for ideals, and then this concept was generalized by Kim and Baik, defining idempotent reflexive right ideals and rings. In this article, we characterize aspects of the reflexive and one-sided idempotent reflexive properties, showing that the concept of idempotent reflexive ring is not left-right symmetric. It is proved that a (right idempotent) reflexive ring which is not semiprime (resp., reflexive), can always be constructed from any semiprime (resp., reflexive) ring. It is also proved that the reflexive condition is Morita invariant and that the right quotient ring of a reflexive ring is reflexive. It is shown that both the polynomial ring and the power series ring over a reflexive ring are idempotent reflexive. We obtain additionally that the semiprimeness, reflexive property and one-sided idempotent reflexive property of a ring coincide for right principally quasi-Baer rings.     

On Sums of Coefficients of Products of Polynomials

We study the nilpotency of the sums of all coefficients of some sorts of products of polynomials over reversible, IFP, and NI rings, and introduce an SCN ring as a generalization. We characterize SCN rings in relation with related ring properties, and also provide several useful properties and ring extensions of SCN rings.     

On minimal strongly prime ideals

In this paper we give some characterizations of a ring Rwhose unique maximal nil ideal N _r (R) coincides with the set of all its nilpotent elements N(R) by using its minimal strongly prime ideals.     

Syntheses,Photophysics, and Application of Iridium(III) Phosphorescent Emitters for Highly Efficient,Long‐Life Organic Light‐Emitting Diodes

Long live the OLED! Rational design and synthesis of Ir^III complexes bearing two cyclometalated ligands (C N) and one 2‐(diphenylphosphino)phenolate chelate (P O) as well as the corresponding Ir^III derivatives with only one (C N) ligand and two P O chelates are reported. According to the observed photophysical data, a P O ligand is found to be able to fine‐tune the light‐emitting electronic transition of these complexes.

     

一类多点边值问题的可解性

This paper deals with the existence of solutions for the problem
{（Фp（u′））′=f（t,u,u′）,t∈（0,1）,
u′（0）=0,u（1）=∑i=1^n-2aiu（ηi）,
where Фp（s）=｜s｜^p-2s,p〉1.0〈η1〈η2〈…〈ηn-2〈1,ai（i=1,2,…,n-2）are non-negative constants and ∑i=1^n-2ai=1.Some known results are improved under some sign and growth conditions. The proof is based on the Brouwer degree theory.     

Dissection of Environmental Changes at the Cytoplasmic Surface of Light‐activated Bacteriorhodopsin and Visual Rhodopsin: Sequence of Spectrally Silent Steps†

The physico‐chemical properties as well as the conformation of the cytoplasmic surface of the 7‐helix retinal proteins bacteriorhodopsin (bR) and visual rhodopsin change upon light activation. A recent study found evidence for a transient softening of bR in its key intermediate M [Pieper et al. (2008) Phys. Rev. Lett. 100 , 228103] as a direct proof for the functional significance of protein flexibility. In this report we compare environmental and flexibility changes at the cytoplasmic surface of light‐activated bR and rhodopsin detected by time‐resolved fluorescence spectroscopy. The changes in fluorescence of covalently bound fluorescent probes and protein real‐time dynamics were investigated. We found that in fluorescently labeled bR and rhodopsin the intensity of fluorescein and Atto647 increased upon formation of the key intermediates M and metarhodopsin‐II, respectively, suggesting different surface properties compared to the dark state. Furthermore, time‐resolved fluorescence anisotropy experiments reveal an increase in steric restriction of loop flexibility because of changes in the surrounding protein environment in both the M‐intermediate as well as the active metarhodopsin‐II state. The kinetics of the fluorescence changes at the rhodopsin surface uncover multiple transitions, suggesting metarhodopsin‐II substates with different surface properties. Proton uptake from the aqueous bulk phase correlates with the first transition, while late proton release seems to parallel the second transition. The last transition between states of different surface properties correlates with metarhodopsin‐II decay.     

烟酸二聚体的结构与性质

用密度泛函理论B3LYP方法选取6-311+G(d,p)基组对烟酸-烟酸复合物进行了量子化学计算研究, 通过在相同水平下的频率振动分析发现了势能面上存在7个极小值点, 其最稳定构型1对应一N…H—O型强氢键, 其结合能在消除基组重叠误差后为-48.3 kJ·mol-1. 通过自然键轨道(NBO)分析, 研究了电荷转移及轨道相互作用. 通过自洽反应场(SCRF)理论中的极化连续模型(PCM)在介电常数分别为1.0(真空)、2.247(苯)、10.36(二氯乙烷)、20.7(丙酮)、32.63(甲醇)、78.39(水)的不同溶剂环境下重新优化烟酸复合物势能面上最稳定构型1, 研究了溶剂对烟酸复合物几何构型及结合能的影响. 发现溶剂化作用增大了烟酸复合物分子间的结合能, 导致N…H距离减小. 当溶液介电常数在1.0-32.63范围时, 溶剂效应十分显著, 当介电常数大于32.63后, 溶剂化作用趋于稳定.     

Controllability of fractional-order impulsive neutral functional infinite delay integrodifferential systems in Banach spaces

In this work the controllability of fractional impulsive neutral functional integrodifferential systems in a Banach space has been addressed. Sufficient conditions for the controllability are established using fractional calculus, a semigroup of operators and Krasnoselskii’s fixed point theorem.