Oil-Water Partitioning of a Synthetic Tetracarboxylic Acid as a Function of pH

The oil-water partitioning of a synthetic tetraacid acting as a model compound for indigenous C₈₀-C₈₂ ARN acids has been studied as a function of pH, ionic strength and type of monovalent counterion. Experimental data obtained with ultraviolet-visible and HPLC/UV analyses have been fitted to thermodynamic models based on one, two or four dissociation steps to obtain o/w partition coefficients (K _wo ) of the fully protonated acid between chloroform and aqueous solutions, and its apparent acidity constant(s), pK _a. As the study is conducted above the CMC of the tetraacid, in general high apparent acidity constants were obtained in the range from 6 to 8 resulting from micellization equilibria. K _wo values were obtained in the range from 10^?3 to 10^?4, and decreasing with increasing salinity. At 50 mM K⁺, no conclusions could be made regarding the number of distinguishable dissociation steps, while at higher ionic strength (184 mM and 452 mM K⁺) and at 184 mM Na⁺ a model with two dissociation steps provided good fits to the experimental data. The first step was found to be given by a pK _a ≈ 6.6–6.8 and the second dissociation step at pK _a values ≈ 7.8–8.3. The two-step mechanism supports previous results obtained by potentiometric titrations. No significant difference in the o/w behavior was observed when changing the counterion from potassium to sodium. The main partitioning of the tetraacid in the aqueous phase occurred above pH 8, where the fully deprotonated acid was formed.     

Isolation of Volatile Compounds with Repellent Properties against Aedes albopictus (Diptera: Culicidae) Using CPC Technology

The present work describes the use of Centrifugal Partition Chromatography (CPC) for the bio-guided isolation of repellent active volatile compounds from essential oils. Five essential oils (EOs) obtained from three Pinus and two Juniperus species were initially analyzed by gas chromatography–mass spectrometry (GC/MS) and evaluated for their repellent properties against Aedes albopictus. The essential oil from needles of P. pinea (PPI) presented the higher activity, showing 82.4% repellency at a dose of 0.2 μL/cm². The above EO, together with the EO from the fruits of J. oxycedrus subsp. deltoides (JOX), were further analyzed by CPC using the biphasic system n-Heptane/ACN/BuOH in ratio 1.6/1.6/0.2 (v/v/v). The analysis of PPI essential oil resulted in the recovery of (−)-limonene, guaiol and simple mixtures of (−)-limonene/β-pheladrene, while the fractionation of JOX EO led to the recovery of β-myrcene, germacrene-D, and mixtures of α-pinene/β-pinene (ratio 70/30) and α-pinene/germacrene D (ratio 65/45). All isolated compounds and recovered mixtures were tested for their repellent activity. From them, (−)-limonene, guaiol, germacrene-D as well the mixtures of (−)-limonene/β-pheladrene presented significant repellent activity (>97% repellency) against Ae. albopictus. The present methodology could be a valuable tool in the effort to develop potent mosquito repellents which are environmentally friendly.     

VxWorks平台内核态ARINC653分区实时调度算法设计与实现

集成模块化航空电子架构(Integrated Modular Avionic, IMA)已成为主流航空电子系统。ARINC 653作为航空电子设备IMA架构的标准应用接口,成为研究航空电子软件编程方法的入口。最新研究表明,VxWorks能够为航空电子分区管理提供最优化的平台。然而,基于VxWorks的ARINC 653高效分区调度算法依然是研究的“盲区”。由此,设计了VxWorks内核态分层ARINC 653分区实时调度算法,提高了分区调度效率,为VxWorks内核ARINC 653完整性的研究提供非常有价值的参考。实验数据说明,相较于传统用户态分区管理模型,该调度算法使分区释放开销和分区释放抖动两项指标均显著降低。     

保留时间两点校正反相高效液相色谱法测定持久性有机污染物的正辛醇-水分配系数

采用改进的反相高效液相色谱法(RP-HPLC)测定了持久性有机污染物(POPs)包括多环芳烃(PAHs)、多氯二苯并二恶英(PCDDs)、多氯二苯并呋喃(PCDFs)和十溴二苯乙烷(DBDPE)等的正辛醇-水分配系数(logKow)。采用保留时间双点校正法(DP-RTC)校正因色谱柱老化等引起的保留时间漂移。以37种有可靠logKow实验值的苯系物、PAHs、PCDD/Fs类似物为模型化合物,建立了logKow和外推至纯水相的保留因子logkw的定量结构-色谱保留关系(QSRR)模型,回归方程为logKow=(1.18±0.02)logkw+(0.36±0.11),其相关系数(R2)为0.985,交叉验证相关系数(R2cv)为0.983,标准偏差(SD)为0.16。进而,用4个已有可靠logKow实验值的验证化合物(联苯、芴、PCDD 1和PCDF 114)对模型进行了外部验证,表明RP-HPLC测得的logKow值与摇瓶法/慢搅法结果有很好的一致性,尤其是对疏水性强的化合物。采用该模型测定了29种特别受关注的POPs的logKow值,这些化合物的logKow实验值均未见报道。所建立的DP-RTC-HPLC是测定强疏水性POPs的logKow值的一种值得推荐的方法。     

正整数的一类三分拆的应用

利用正整数n的一类特殊的3分拆n=n1+n2+n3,n1>n2>n3≥1,且n2+n3>n1的Ferrers图将不定方程4x1+3x2+2x3=n(n≥9)的正整数解与这种分拆联系起来,从而得到了该不定方程的正整数解数公式;同时也给出了正整数n的一类4分拆的计数公式.此外,还给出了周长为n的整边三角形的计数公式的一个简单证明.     

在划分系统下集合对策值的结构

A set game, in which the worth of a coalition is expressed by a set instead of areal number, is a new type of cooperative game.A F-restricted set game is a set game restricted by partition system.The main theorems show the structures of IM-value,OIM-value,SCM-value and ICM-value respectively,and the equivalency of IM-value and the OIM-value for monotonicset games restricted by partition system as well.     

攒尖四坡屋面风致雪漂移的数值模拟

为获得攒尖四坡屋面的风致雪漂移规律,基于欧拉-欧拉方法和风雪单向耦合假定,运用计算流体动力学软件,选取Mixture模型分别对立方体周边和高低屋面上的风致雪漂移运动进行数值模拟,将模拟结果与两者的实地观测数据对比,探讨分析数值风洞的关键技术和参数设置,验证数值模拟方法的合理性与可靠性。依据攒尖四坡房屋的使用功能要求,设计分析模型与分析工况,在试算的基础上对屋面进行分区。以风速5 m/s,7 m/s,9 m/s,11 m/s,13 m/s和15 m/s,风向角0°,15°,30°和45°以及屋面坡度25°,30°,34°,40°和45°为分析参数,对攒尖四坡房屋的120种工况进行数值模拟,得到屋面各分区侵蚀沉积的基本规律,提出可用于抗雪设计的屋面积雪分布系数。研究表明,风向角的改变会使屋面积雪分布状态发生较大程度的变化,风速和屋面坡度的变化对屋面整体积雪量有较大影响。     

Evolution of Er^3＋ Distribution in the Oxyfluoride Glass Ceramics with Heating

The distribution characteristics of Er3+ ions doped in the oxyfluoride glass ceramics containing LaF3 nanocrystals heat-treated at 650 ℃ for different durations were investigated. The results of the integral absorption cross-section analysis demonstrated that the partition fraction of Er3+ in LaF3 nanocrystals increases with prolonging of heating time. The anomalous phenomena of Er3+ emissions in the up-and the down-conversion fluorescence spectra are well explained based on the calculated results.