Insights into the Retention Mechanisms on Perfluorohexylpropylsiloxane-Bonded (Fluophase-RP) and Octadecylsiloxane-Bonded (Betasil C18) Stationary Phases Based on the Same Silica Substrate in RP-LC

The solvation parameter model is used to elucidate the retention mechanism on a perfluorohexylpropylsiloxane-bonded (Fluophase RP) and octadecylsiloxane-bonded (Betasil C18) stationary phases based on the same silica substrate with acetonitrile–water and methanol–water mobile phase compositions. Dewetting affects the retention properties of Fluophase RP at mobile phase compositions containing less than 20% (v/v) acetonitrile or 40% (v/v) methanol. It results in a loss of retention due to an unfavorable change in the phase ratio as well as changes in specific intermolecular interactions. Steric repulsion reduces retention of bulky solutes on fully solvated Betasil C18 with methanol–water (but not acetonitrile–water) mobile phase compositions but is not important for Fluophase RP. The retention of weak bases is affected by ion-exchange interactions on Fluophase RP with acetonitrile–water, and to a lesser extent, methanol-water mobile phases but these are weak at best for Betasil C18. The system constants of the solvation parameter model and retention factor scatter plots are used to compare selectivity differences for Fluophase RP, Betasil C18 and a perfluorophenylpropylsiloxane-bonded silica stationary phase Discovery HS F5 for conditions where incomplete solvation, steric repulsion and ion-exchange do not significantly contribute to the retention mechanism. Lower retention on Fluophase RP results from weaker dispersion and/or higher cohesion moderated to different extents by polar interactions since solvated Fluophase RP is a stronger hydrogen-bond acid and more dipolar/polarizable than Betasil C18. Retention factors for acetonitrile–water mobile phases are highly correlated for Fluophase RP and Betasil C18 except for compounds with a large excess molar refraction and weak hydrogen-bonding capability. Selectivity differences are more significant for methanol–water mobile phases. Retention factors on Fluophase RP are strongly correlated with those on Discovery HSF5 for acetonitrile–water mobile phases while methanol–water mobile phases retention on Fluophase RP is a poor predictor of the retention order on Discovery HS F5.     

水分子团簇分子力场方法的比较研究

采用传统水分子力场模型(SPC, TIPnP(n=3-5))和极化模型(POL3, AMOEBA, SPC-FQ, TIP4P-FQ)对水分子二聚体团簇性质进行了比较和研究. 以从头计算和实验数据为依据, 分析水分子在外场作用下体系的静电极化, 电荷转移和分子结构变化. 通过水分子二聚体结合能和各分解能量项评价极化静电势能在双分子结合能中的地位和作用, 以及各水分子力场的适用性. 通过水分子团簇多体相互作用能的计算,展示不同极化水分子力场定量计算极化能量的实际能力. 通过对力场模型结果的对比和分析, 为进一步发展极化力场模型, 并应用到其他体系提供借鉴和依据.     

Scaling Function Between the Exponential-6 and the Generalized Lennard-Jones Potential Functions

The van der Waals forces for non-bonded interaction can be expressed either by the Exponential-6 or by the Lennard-Jones(m-n) potential functions, whereby m > n. Hitherto a relationship exists between the Exponential-6 and the Lennard-Jones(12-6) potential functions, with a scaling factor = 13.772 at or near the equilibrium and = 12.0 for long range interaction. This paper attempts to develop relationships between Exponential-6 and a more generalized Lennard-Jones(m-n). Analysis reveals that the relationship exists only when n = 6 and that two sets of scaling factors (as functions of index m) applies for the relationship between Exponential-6 and the Lennard-Jones(m-6), whereby m > 6.     

ELECTRON PARAMAGNETIC RESONANCE STUDIES OF SINGLE CRYSTAL SODIUM HEXAMOLYBDOCHROMATE (Ⅲ)Cr~(3+)/Na_3(AlMo_6O_(24)H_6)·8H_2O

An X-band EPR study on a Na_3(CrMo_6O_(24)H_6)·8H_2O single crystal diluted by its isomor-phic compound Na_3(AlMo_6O_(24)H_6)·8H_2O at room temperature is reported. Using the least squares-fitting method to simulate the EPR data for principal planes, the Hamiltonian parameterswere obtained. The principal values of the g tensors are g_(ZZ) = 1.904, g_(XX)= 1.973, g_(YY)=1.933. The zero field splitting tensor parameters are D = 0.275 cm~(-1), E = 0.05 cm~(-1). The fielddependence of Cr~(3+) energy levels with field at different angles from the principal axes whenthe field is along the principal planes is calculated based on these experimental parameters.The isofrequency plots of calculated field vs. angle are also shown. They agree well with theexperimental results.     

Crystallization Temperature Limit of (Ba,Sr)TiO<Subscript>3</Subscript> Thin Films Prepared by a Non Oxocarbonate Phase Forming CSD Route

A new chemical solution deposition (CSD) route for the fabrication of Ba_0.7Sr_0.3TiO₃ (BST) thin films has been developed which completely prevents the formation of an intermediate oxo-carbonate phase. The latter has been reported previously by several authors to be responsible for increased crystallization temperatures. Barium and strontium diaminoethoxides were synthesized starting from pure barium and strontium metal and aminoethanol. These alkoxides were found to be readily soluble in a wide range of solvents and thus were excellent candidates for the CSD process. To prepare a stable precursor solution the aminoalkoxides were dissolved in 2-butoxyethanol and then used for the deposition of BST thin films. We conclude that the minimum crystallization temperature of 600C to be independent of the formation of the oxo-carbonate phase. DTA-TGA were performed on the precursors and their solutions to study their decomposition behaviour. All films annealed at different temperatures were physically characterized by XRD, IR, and SEM. The films prepared by this route at 650C were found to have high dielectric constant and the leakage currents were comparable to BST films prepared by normal carboxylate based routes at 750C.     

室温固相反应一步合成N-亚水杨基-4-氨基安替比林

4-氨基安替比林与水杨酬醛通过室温固相反应合成N-亚水杨基-4-氨基安替比 林，反应无溶剂，15 min即可完成，产率达95%，用元素分析，IR，~1H NMR，X射 线粉末衍射和X射线单晶衍射对产物进行了表征。     

高温下淀粉的凝胶化作用

凝胶化作用是淀粉及改性产品生产过程中存在的一种现象。淀粉凝胶化作用的结果导致了在其产品中产生了只溶胀但不溶解的颗粒,从而影响了淀粉产品的整体性能。文章初步探讨了淀粉在高温成型过程中凝胶化作用的方式和起因。结果表明,淀粉浆料在高温成型过程中所产生的凝胶团粒是淀粉不完整的凝胶化作用的结果,足量的水分和高温是形成较多的凝胶化淀粉颗粒的原因。     

关于超高分子量聚丙烯超拉伸膜的结构性能的研究——Ⅱ.形态结构变化对力学性能的影响

用X-射线衍射、动态力学测定等手段研究了不同拉伸倍数的超高分子量聚丙烯薄膜的力学性能的变化.以X-射线衍射法并基于串联力学模型的假设得到的各样品的表观晶区模量E_c~(app)约为34-38GPa.样品模量E_b随拉伸倍数增加而逐渐增大,其变化趋势与非晶区取向因子的变化相类似,说明非晶区取向是左右样品模量的重要因素.室温下,69倍拉伸样品的模量为27GPa,约为表观结晶模量的3/4,且其值在-150-160℃的温度范围内没有急剧变化,说明超拉伸明显改善了材料的力学性能及热稳定性.在各拉伸样品中,考虑伸直链结晶生成的可能性,利用并串联力学模型对伸直链结晶的体积分数做了估算,并对X-射线衍射法所得表观结晶模量进行了修正,认为室温下聚丙烯的真正晶区模量约为47GPa.     

Conformation and internal mobility of 5H-dibenzo[a,d]cycloheptene derivatives in solution. Conformational analysis of highly flexible structures,part II

Summary The conformational possibilities of 5-(3-N,N-dimethylaminopropyl)-5H-dibenzo[a,d]cycloheptene (1), 5-(3-N,N-dimethylaminopropylidene)-10,11-dihydro-5H-dibenzo[a,d]cycloheptene (2), and 5-(3-N,N-dimethylaminopropyl)-10,11-dihydro-5H-dibenzo[a,d]cycloheptene (3) are analysed using empirical force field methods. Minimum energy conformations, interconversion pathways, interconversion graphs and interconversion energies are examined in view of the analysis of conformer equilibria of1,2, or3 in solution. In addition, some basic requirements of the analysis of fast interconverting conformers using the lanthanide induced shift method are discussed.

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Konformation und interne Beweglichkeit von 5H-Dibenzo[a,d]cyclohepten Derivaten in Lösung. Konformationsanalyse hochflexibler Strukturen, Teil 2

Zusammenfassung Die konformativen Möglichkeiten von 5-(3-N,N-dimethylaminopropyl)-5H-dibenzo[a,d]cyclohepten (1), 5-(3-N,N-dimethylaminopropylidene)-10,11-dihydro-5H-dibenzo[a,d]cyclohepten (2) und 5-(3-N,N-dimethylaminopropyl)-10,11-dihydro-5H-dibenzo[a,d]cyclohepten (3) wurden mit Hilfe empirischer Kraftfeldmethoden analysiert. Jene Konformationen, die einem energetischen Minimum entsprechen, sowie Interkonversionswege, Interkonversionsgraphen und Interkonversionsenergien wurden in Hinblick auf die Analyse der Konformerengleichgewichte von1,2 oder3 in Lösung untersucht. Weiters werden noch einige grundlegende Voraussetzungen für die Analyse von sich schnell ineinander umwandelnden Konformeren mittels der Lanthaniden-induzierten Verschiebungsmethode besprochen.

     

甲基丙烯酸—磷脂酰乙醇甲基丙烯酰胺共聚物LB膜的研究

制备了不同摩尔比的甲基丙烯酸-磷脂酰乙醇甲基丙烯酰胺共聚物,研究了这种共聚物在水面的表面压力(π)-分子面积(A)曲线、共聚物制成的MOS LB膜的电容(C)-电压(V)特性及此LB膜的相变温度。