Zur Farbigkeit der Pseudooxo-Krokonsäurebisamide

The colour of oxo- und pseudooxo croconic acid bisamides (1) in solution is due to two intense * transitions in the visible region. These transitions are related to those of the Klessinger-Lüttke basic indigo chromophore. The first band corresponds to the second absorption band of this basic chromophore red-shifted by the intramolecular charge transfer excitation between the molecular subsystems of1. The second band of1 is closely related to the colour band of the basic indigo chromophore. According to the results of various analysis and projection techniques the interpretation of the colour of1 in terms of the basic indigo chromophore is superior to any other one in terms of alternative chromophoric subsystems.

     

Atomic structure and stability of elliptical carbon onion

Elliptical carbon onions were produced from amorphous carbon by electron beam irradiation. Atomic structure and structural stability of the onion were investigated by high-resolution electron microscopy, molecular mechanics calculation and molecular orbital calculation, and a structure model of C₂₄@ C₈₄ was proposed at the center of the elliptical onion. Received 30 November 2000     

Independent particle model of spontaneous symmetry breaking in planar π-electron systems

The singlet stability of symmetry adapted (SA), restricted Hartree-Fock (RHF) solutions, and the implied symmetry breaking for several planar, π-electron systems, is investigated using the semiempirical Pariser-Parr-Pople Hamiltonian in the whole range of the coupling constant. We focus here on highly symmetric cyclic polyenes C₁₀H₁₀ and C₁₄H₁₄ and their various distorted analogues of lower symmetry, in particular on the perimeter models of naphthalene and anthracene (p-naphthalene and p-anthracene) modeling the so-called [n]-annulenes. Relying on earlier results for general systems with conjugated double-bonds, we explore the character and properties of both the SA and broken-symmetry (BS) RHF solutions for these systems and relate their behavior to those of highly symmetric cyclic polyenes and corresponding polyacenes. In this way we are able to provide a better understanding of the spontaneous symmetry breaking in these systems at the Hartree-Fock level of approximation.     

经腹联合经阴道彩超在评估凶险型前置胎盘合并胎盘植入中的应用价值

本文对经腹联合经阴道彩超在评估凶险型前置胎盘(PPP)合并胎盘植入中的应用价值进行了探讨。选取我院2017年6月~2019年6月PPP患者172例,所有患者均给予经腹彩超、经阴道彩超检查,以产后病理结果为对照,分析经腹彩超、经阴道彩超,以及二者联合,对PPP合并胎盘植入的评估价值。产后病理结果显示,172例PPP患者中,有合并胎盘植入患者120例(69.77%)、无合并胎盘植入患者52例(30.23%)。对PPP合并胎盘植入的敏感度、特异度、准确度进行评估,结果显示,经腹彩超其值分别为76.67%、73.08%、75.58%,经阴道彩超分别为83.33%、80.77%、82.56%,经腹联合经阴道彩超则分别为96.67%、96.15%、96.51%,二者联合明显高于经腹彩超、经阴道彩超,差异有统计学意义(P<0.05)。证实经腹、经阴道彩超是评估PPP合并胎盘植入的有效检查方法,且二者联合的评估价值更高,值得临床推广。     

PPP项目中国有企业与民营企业的融资效率对比研究

目前PPP模式的应用范围不断扩大,但投资者的融资效率普遍不高。投资者融资效率低下严重影响PPP项目绩效,制约PPP模式的可持续发展。本文以51家主营业务为PPP项目的国有企业与民营企业为样本,运用DEA模型分别从整体、不同领域和不同地区之间对比分析双方融资效率的异同。结果显示参与PPP项目投资者的规模效率普遍不足,主营成本与股权集中度是导致融资效率低下的主要因素,净资产收益率较低则是投资者不愿积极参与PPP项目的一个主要原因。对国企而言,优化企业对PPP项目的规模效率是提高融资效率的关键;而民企应注重优化和降低资产负债率,合理均衡地分配股权。因此,建议具有规模效率和纯技术效率优势的投资者通过组建联合体等方式参与PPP项目,实现优势互补,从而提高项目公司的整体效率。此外,也要针对不同领域和不同地区PPP项目的特点和对投资者的要求,有针对性地选择投资者,充分发挥国企资金实力雄厚和民企专业技术的优势,提高融资效率,助力PPP实践的可持续发展。     

有机试剂结构与性质的研究(X)——偶氮苯衍生物结构与吸收光谱的研究

本文应用PPP-SCF-CI法计算了偶氮苯衍生物的结构,发现偶氮苯衍生物波长最大的吸收峰(相应于电子从基态向第一激发态跃迁)是分子内荷移光谱,这些吸收峰的计算值与实验值完全一致.此外,还根据PPP计算结果研究了取代基对吸收光谱的影响.