Effects of the chemical structure of surfactants on the stability of naphthenic oil-based metalworking fluids

In this study,various nonionic surfactants(NS) with different ethylene oxide(EO) numbers and tail lengths and its binary blends with anionic surfactants(AS) were used as emulsifiers for naphthenic oil to form the microemulsion metalworking fluids(MWFs),and the effects of them on the stability of the emulsion system were investigated by formulation triangle method.The results indicated that binary complex surfactants of NS and AS as emulsifiers exhibited better emulsifying effect than that of single NS.NS with different EO numbers and tail lengths presented various emulsifying effects.NS(EO=10)exhibited the greatest number of stable formulations,especially the TX-10,but no linear relationship existed between the number of stable formulations and the tail length of NS.In addition,aromatic primary alcohol ethoxy late(APAE) series surfactants containing benzene groups similar to the cycloalkanes in the naphthenic oil so that presented the best emulsifying affect and the greatest number of stable formulations.The co-surfactant of sodium dodecyl benzene sulfonate(SDBS) binary blends with NS exerted the best synergistic effect,and the stable formulations numbers were ranged from 5 to 7,next sodium stearate(SS) comes last followed by sodium dodecyl sulfate(SDS-1) and sodium dodecyl sulfonate(SDS-2).     

Regularity condition on the anisotropy induced by gravitational decoupling in the framework of MGD

The European Physical Journal C - Previously, the Maxwell equal-area law has been used to discuss the conditions satisfied by the phase transition of charged AdS black holes with cloud of string...     

中国北方某河流水质现状调查及分析

为调查A河、B河下游水体的水质现状,于2014年丰水期（8月）和枯水期（12月）,选取A、B河下游各8个采样点,对水体的溶解氧、氨氮等6项理化指标,以及Hg、Pb等7项重金属指标进行检测,采用单项参数评价法和综合水质标识指数法对2条河流的水质现状进行分析及评价,并采用对数型幂函数普适指数公式对水体的富营养程度进行评价。结果发现,A、B河下游水质以劣V类为主,水体中各类重金属不超标,主要超标污染物为总氮、总磷、氨氮等。A河水质好于B河,2条河流丰水期水质好于枯水期。A、B河下游水体处于重富和极富营养化状态,应加强整治2条河流流域的农业面污染源,降低河流的富营养化风险。     

Self-interaction error in density functional theory: a mean-field correction for molecules and large systems

Corrections to the self-interaction error which is rooted in all standard exchange-correlation functionals in the density functional theory (DFT) have become the object of an increasing interest. After an introduction reminding the origin of the self-interaction error in the DFT formalism, and a brief review of the self-interaction free approximations, we present a simple, yet effective, self-consistent method to correct this error. The model is based on an average density self-interaction correction (ADSIC), where both exchange and Coulomb contributions are screened by a fraction of the electron density. The ansatz on which the method is built makes it particularly appealing, due to its simplicity and its favorable scaling with the size of the system. We have tested the ADSIC approach on one of the classical pathological problem for density functional theory: the direct estimation of the ionization potential from orbital eigenvalues. A large set of different chemical systems, ranging from simple atoms to large fullerenes, has been considered as test cases. Our results show that the ADSIC approach provides good numerical values for all the molecular systems, the agreement with the experimental values increasing, due to its average ansatz, with the size (conjugation) of the systems.     

Online separation and preconcentration of trace heavy metals with 2,6-dihydroxyphenyl-diazoaminoazobenzene impregnated amberlite XAD-4

A rapid and sensitive flow injection online preconcentration method was developed for determination of Cd, Co, Cu, and Zn in natural water samples by flame atomic absorption spectrometry. The procedure is based on the retention of analytes in the form of 2,6-dihydroxyphenyl-diazoaminoazobenzene (DHDAA) complexes on a microcolumn packed with XAD-4-DHDAA resin. Cd, Co, Cu, and Zn can be eluted from the microcolumn with 0.5 mol L⁻¹ HCl and pumped directly to the nebulizer-burner system of the flame atomic absorption spectrometer (FAAS). The enrichment factors are 42 (Cd), 33 (Co), 28 (Cu), and 31 (Zn), for a sample volume of 6.0 mL and 1 min preconcentration time relative to direct introduction of aqueous solutions into an atomic absorption spectrometer. The sampling frequency was 30 h⁻¹ with a 1 min loading. The proposed method allowed the determination of Cd, Co, Cu, and Zn with detection limits of 0.1, 0.5, 0.3, and 0.2 μg L⁻¹, respectively. The selectivity of the XAD-4-DHDAA resin for Cd, Co, Cu, and Zn over several electrolytes was also investigated. The method was validated by analysis of a standard reference material (GBW 08301) with the results agreement with those quoted by manufactures. The developed method was applied to the determination of trace Cd, Co, Cu, and Zn in tap water, ground water and river water samples with satisfactory results.     

基于小分子的铜离子与汞离子双识别荧光探针

铜离子在不同细胞生理过程中作为催化辅助因子起着很重要的作用,但是体内铜离子浓度出现异常也会导致疾病甚至死亡。与铜离子相比,汞离子是各种重金属污染物中最普遍、最危险的一种。因此,对它们高灵敏度、高选择性检测具有非常重要的意义。荧光探针法由于具有灵敏度高、快速便捷、可视化和原位无损检测等优点而成为Cu²⁺与Hg²⁺离子重要的检测手段之一。本文总结了近几年基于小分子Cu²⁺和Hg²⁺离子双识别荧光探针的设计合成、性能及其在分析方面的研究与最新进展,并展望了此类荧光探针未来的研究与发展方向。     

原子电性作用矢量用于Mannich碱红外光谱模拟

利用原子电性作用矢量(AEIV)对Mannich碱中C＝O与P＝O进行结构参数化表征,并通过多元线性回归(MLR)分析,建立了红外光谱振动频率定量结构光谱相关(QSSR)模型,继以留一法(LOO)交互检验(CV)对模型稳定性进行检验.对C＝O和P＝O键伸缩振动频率的建模相关系数(Rcum)和交互检验相关系数(RLOO)分别为0.9777,0.9973(C=O);0.9433,0.9911(P＝O).结果表明,AEIV与Mannich碱中C＝O与P＝O伸缩振动频率有很好的相关性.     

On Fisher Subgroups of Finite Groups

Ukrainian Mathematical Journal - Let ? be a Fitting set of a group G, let π be a nonempty set of primes, and let L ≤ G. In this case, ? is called a Fischer π-set of G if...     

Size dependence rectification performances induced by boron and nitrogen co-doping in rhombic graphene nanoribbons

Rectification performances of rhombic graphene nanoribbons coupled to gold electrodes through thiolate bonds with left and right vertical carbon atoms substituted by one nitrogen or boron atom are analyzed by performing theoretical calculations using a self-consistent ab initio approach that combines the density functional theory with the non-equilibrium Green's function formalism. Increasing the size of graphene nanoribbon markedly improves the rectification effect because of the asymmetric potential profile distribution in rhombic graphene for polarization near the boron and nitrogen atoms.