Methano[10]annulene revisited: extended delocalization through conjugated polymers bearing larger Hückel aromatics

A comparative study of conjugated polymers derived from the two 10 pi electron circuits of naphthalene and methano[10]annulene is presented. The annulene pi topology allows for a greater degree of intrapolymer charge delocalization, a key structural parameter for enhancing the performance of organic semiconductors. Molecular design and synthesis based upon unusual aromatic cores will enable facile transport properties that would not ordinarily be realized under the 6 pi electron aromatic paradigm.     

泥沙输运模拟综述——现状及其发展趋势

随着流体力学中数值方法的飞速发展,计算模型已经成为研究流体运动,泥沙输运和不同环境(诸如河流,湖泊及沿海地区)中相应污染物归趋过程等方面非常有吸引力的工具,在过去的30多年里,发展了许多计算水动力学/泥沙输运模型.文章追溯当前具有代表性的(一维、二维、三维)模型的发展历程,描述他们各自的特点,优势及局限,力图作为对模型方面感兴趣读者的第一指南,同时也为大家讨论模型的局限性,未来的发展趋势和研究需求方面搭建一个平台.给出了模型的表达,时空特性,水动力学和沉积物的耦合方式,处理非恒定流,推移质和悬移质,泥沙交换过程,泥沙类型(粘性或非粘性)及非均匀泥沙输运的能力.总结了不同模型的应用实例,读者可以运用这些例子作为研究模型设置,模型率定及模型验证的参考.给出了选择泥沙输运模型应遵循的原则,模型输入及率定方面存在的问题及改进的途径.探讨了现有水动力学/泥沙输运模型在处理复杂湍流,泥沙携带,流动与输沙耦合,非均匀泥沙,离散和扩散系数,河岸来沙处理等方面的局限性及改进的方向.最后,对基于多相流思想的泥沙输运模型及其它一些交叉性问题作了评述与展望.     

EFFECT OF COMPOSITION AND PROCESSING CONDITION ON MICROSTRUCTURAL PROPERTIES AND DURABILITY OF FLUOROPOLYMER/ACRYLIC BLENDS

Fluoropolymer blends have been widely used as binders for exterior coatings because of their excellent resistance to ultra-violet (UV) radiation as well as to many corrosive chemical agents.It is known that the fluorinated component usually has a lower glass transition temperature and easily crystallizes in the final structure depending upon the blend composition and sample annealing condition.We investigated the effect of blend composition and annealing process (slow and fast cooling) on the surface mor...     

Decoherence via the dynamical casimir effect

We derive a master equation for a mirror interacting with the vacuum field via radiation pressure. The dynamical Casimir effect leads to decoherence of a superposition state in a time scale that depends on the degree of "macroscopicity" of the state components, and which may be much shorter than the relaxation time scale. Coherent states are selected by the interaction as pointer states.     

Spin squeezing and entanglement via hole-burning in atomic coherent states

We study the generation of spin squeezing via the hole burning of selected Dicke states out of an atomic coherent state prepared for a collection of N two-level atoms or ions. The atoms or ions of the atomic coherent state are not entangled, but the removal of one or more Dicke states generates entanglement, and spin squeezing occurs for some ranges of the relevant parameters. Spin squeezing in a collection of two-level atoms or ions is of importance for precision spectroscopy.     

Determination of endocrine-disrupting phenols, acidic pharmaceuticals, and personal-care products in sewage by solid-phase extraction and gas chromatography-mass spectrometry

The occurrence, fate, and effects of phenols with endocrine-disrupting properties as well as some pharmaceuticals and personal-care products in the environment have frequently been discussed in recent literature. In many cases, these compounds were determined by using individual methods which can be time-consuming if results for multiple parameters are required. Using a solid-phase extraction procedure with an anion exchanger in this work, we have developed and optimized a multi-residue method for the extraction of 21 phenols and acids in sewage influent and effluent. The phenols and acids were then selectively eluted in separate fractions and were converted into pentafluoropropionyl (PFP) and tert-butyldimethylsilyl (TBDMS) derivatives, respectively, for gas chromatography-mass spectrometric (GC/MS) determination. When applied to the sewage samples under study, the results for nonylphenol, bisphenol A (BPA), triclosan (TCS), 17ss-estradiol (E2), estrone (E1), salicylic acid, ibuprofen, naproxen, diclofenac, and a few other acidic drugs were consistent with those determined previously by individual methods. Using the same procedure, we also report, for the first time, the occurrence of 2-phenylphenol and parabens in those sewage samples.