A rotaxane mimic of the photoactive yellow protein chromophore environment: effects of hydrogen bonding and mechanical interlocking on a coumaric amide derivative

Hydrogen bonding in a [2]rotaxane is shown to stabilise the phenolate anion of a coumaric amide chromophore by almost 3 pKa units; however, the effect on the UV spectral shift in the anion is small and, significantly given the photochemistry of PYP, despite the hydrogen bonding olefin photoisomerisation in the anionic rotaxane remains heavily suppressed.     

Novel Industrial Application of Miniemulsion Polymerization – Use of Alkali Soluble Resin as Surfactant in Miniemulsion Polymerization

Nowadays, the great versatility of the miniemulsion polymerization technique to synthesize novel and high value added materials attracts great interest from both the academic and the industrial community. Recently, a novel process based on the use of alkali soluble resin (ASR) as sole surfactant in miniemulsion polymerization for high solids content latexes has been disclosed. This new technology opens a vast field for the production of high performance latexes for industrial applications, as well as an interesting topic for future academic research. This work presents the key factors influencing the use of ASR in aqueous polymer dispersions, highlighting the differences in terms of types and concentrations of ASR used in conventional and miniemulsion polymerization. The effects of type of initiator, ASR concentration and type, as well as solids content on the miniemulsion polymerization of styrene and acrylic monomers are presented.     

The Distance-Regular Graphs of Valency Four

Let W be a Coxeter group acting as a matrix group by way of the dual of the geometric representation. Let L be the lattice of intersections of all reflecting hyperplanes associated with the reflections in this representation. We show that L is isomorphic to the lattice consisting of all parabolic subgroups of W. We use this correspondence to find all W for which L is supersolvable. In particular, we show that the only infinite Coxeter group for which L is supersolvable is the infinite dihedral group. Also, we show how this isomorphism gives an embedding of L into the partition lattice whenever W is of type An, Bn or Dn. In addition, we give several results concerning non-broken circuit bases (NBC bases) when W is finite. We show that L is supersolvable if and only if all NBC bases are obtainable by a certain specific combinatorial procedure, and we use the lattice of parabolic subgroups to identify a natural subcollection of the collection of all NBC bases.     

How to statistically analyze nano exposure measurement results: using an ARIMA time series approach

Measurement strategies for exposure to nano-sized particles differ from traditional integrated sampling methods for exposure assessment by the use of real-time instruments. The resulting measurement series is a time series, where typically the sequential measurements are not independent from each other but show a pattern of autocorrelation. This article addresses the statistical difficulties when analyzing real-time measurements for exposure assessment to manufactured nano objects. To account for autocorrelation patterns, Autoregressive Integrated Moving Average (ARIMA) models are proposed. A simulation study shows the pitfalls of using a standard t-test and the application of ARIMA models is illustrated with three real-data examples. Some practical suggestions for the data analysis of real-time exposure measurements conclude this article.     

天目铁木愈伤组织和芽苗诱导技术

以天目铁木嫩茎尖为外植体,应用均匀设计法筛选其基部愈伤组织诱导和愈伤组织再分化芽苗的最适合培养基.结果表明,最适合的嫩茎尖基部愈伤组织诱导培养基为1/2DR+TDZ 2.30 mg·L^-1+2,4-D 0.55 mg·L^-1,诱导率为93.5%;愈伤组织芽苗再分化培养基为1/2DR+TDZ 3.30 mg·L^-1+KT 0.70 mg·L^-1,分化率达99.8%以上. 成功建立了天目铁木嫩茎尖离体诱导愈伤组织和芽苗再分化体系,且再生芽苗与野生植株染色体数目相同.     

交通产业链上企业工程项目成本控制的影响因素研究

一些企业以轨道交通产业为纽带形成了交通产业链,轨道交通产业链上的企业要注重对相关工程项目实施全过程中的成本控制.从产业链的视角出发,围绕财务指标、内部业务流程指标、客户指标、学习与成长能力指标这4个方面,构建了评价指标体系和成本控制指标体系.运用层次分析法和模糊综合评价法进行评价和分析,找出了影响轨道交通产业链上企业工程项目成本控制的主要因素.研究表明,有55%的人认为财务指标、内部业务流程指标、客户指标、学习与成长能力指标这4个因素对轨道交通工程项目成本控制的影响较大.     

强脉冲电磁场对金属凝固组织影响的研究

提出了用强脉冲磁场和电流细化金属凝固组织的新工艺.与未经磁场或电流处理的凝固样品相比,强脉冲电磁场能够显著地改善LY12铝合金的凝固组织,使晶粒明显细化、球化;电磁场的强度愈强,这种改善效果愈明显.对该新工艺的细化机理进行了理论分析,同时,指出了实验中的新现象和新问题. 关键词：     

Self-Organized Forest-Fires Near the Critical Time

We consider a forest-fire model which, somewhat informally, is described as follows: Each site (vertex) of the square lattice is either vacant or occupied by a tree. Vacant sites become occupied at rate 1. Further, each site is hit by lightning at rate λ. This lightning instantaneously destroys (makes vacant) the occupied cluster of the site.This model is closely related to the Drossel-Schwabl forest-fire model, which has received much attention in the physics literature. The most interesting behaviour seems to occur when the lightning rate goes to zero. In the physics literature it is believed that then the system has so-called self-organized critical behaviour.We let the system start with all sites vacant and study, for positive but small λ, the behaviour near the ‘critical time’ t _c , defined by the relation 1 − exp(− t _c ) = p _c , the critical probability for site percolation.Intuitively one might expect that if, for fixed t > t _c , we let simultaneously λ tend to 0 and m to ∞, the probability that some tree at distance smaller than m from O is burnt before time t goes to 1. However, we show that under a percolation-like assumption (which we can not prove but believe to be true) this intuition is false. We compare with the case where the square lattice is replaced by the directed binary tree, and pose some natural open problems.Part of vdB’s research is supported by BRICKS project AFM 2.2.     

N2O5 photolysis products investigated by fluorescence and optoacoustic techniques

Pulsed laser photolysis of N₂O₅ near 290 nm coupled with fluorescence detection (calibrated by NO₂ photolysis) showed that the O(³P) quantum yield is ≤0.1. A pulsed laser optoacoustic technique in a flow tube (ca. 6 torr of N₂) was tested by photolysis of NO₂ and then applied to N₂O₅. Nitric oxide was added to react with NO₃ free radical and the resulting increase in the optoacoustic signal confirmed the presence of NO₃ free radicals. Based on the relative optoacoustic signals observed for NO₂ and N₂O₅, the quantum yield for NO₃ production is 0.8 ± 0.2.     

Thermal isomerization of azulene to naphthalene in shock waves

The thermal isomerization of azulene was studied in shock waves over the range 1300–1900 K. Monitoring azulene and naphthalene light absorptions in the UV, a complete conversion azulene → naphthalene was observed. After correction for some falloff effects, a limiting high pressure rate constant k_x = 10^12.93 exp(?263 kJ mol^?1/RT) s^?1 was derived. Based on this k_x, specific rate constants k(E) for photoexcitation experiments were constructed.