Determination of cyclodextrin inclusion constant for aromatic carbonyl compounds through spectrophotometric and electrochemical methods

α- and β-Cyclodextrins cavity inclusion constants (K_i) were determined for a series of benzaldehydes and acetophenones by using two different methods: Benesi-Hildebrand (BH) UV/vis spectroscopic method and electrochemical current (EC) method, determined by cyclic voltammetry. The values determined in the group of benzaldehydes varied from 322 ± 27 to 5688 ± 317 mol⁻¹ dm³ for UV/vis method, and 342 ± 19 to 7386 ± 142 mol⁻¹ dm³ for EC method. The values determined in the group of acetophenones varied from 2201 ± 88 to 9125 ± 251 mol⁻¹ dm³ for UV/vis method, and 1473 ± 33 to 7555 ± 187 mol⁻¹ dm³ for EC method. The equilibrium time estimated for UV/vis spectroscopic (BH) method was 240 min and for the cyclic voltammetry (EC) method was 310 min. Notably, despite their limitations, both methods were suitable and reliable for inclusion constant measurement, if the equilibrium time of the system is well established.     

In vitro and in vivo inhibition of Hass avocado polyphenol oxidase enzymatic browning by paeonol, β-cyclodextrin,and paeonol:β-cyclodextrin inclusion complex

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Investigation of the piroxicam/hydroxypropyl-β-cyclodextrin inclusion complexation by means of a supercritical solvent in the presence of auxiliary agents

The complexation of piroxicam and 2-hydroxypropyl-β-cyclodextrin by means of supercritical CO₂ has been investigated. The experiments were carried out by varying the temperature, pressure and contact time and introducing two different auxiliary agents: polyvinyl pyrrolidone or l-lysine.Cyclodextrins, which are widely used to solubilize a large variety of poorly soluble drugs, are often used in combination with some auxiliary agents to enhance the complexation efficiency of the conventional techniques. While many recent literature works report that supercritical carbon dioxide is a clean, non-toxic alternative to organic solvents, the use of auxiliary agents in the supercritical complexation process has been scarcely examined and still needs to be investigated.The inclusion complexes obtained in this work were analysed by means of the ‘differential solubility method’, differential scanning calorimetry and Fourier transform infrared spectroscopy. The results showed that the supercritical treatment could be successfully employed below 140-150 °C without incurring thermal degradation of the samples. While 66% inclusion efficiency could be obtained at 140 °C and 30 MPa for a mixture of piroxicam/2-hydroxypropyl-β-cyclodextrin (1:2 molar ratio), higher percentages of complexation (95% in the ternary samples with polyvinyl pyrrolidone and 89-91% in those with l-lysine) could be obtained at a lower temperature (130 °C) when auxiliary agents were employed.     

Dynamic crack propagation in matrix involving inclusions by a time-domain BEM

The dynamic crack propagation in composites with inclusions is analyzed by a time-domain boundary element method (BEM) in conjunction with the sub-region technique. The crack-growth direction and the crack-tip instantaneous velocity are determined by the maximum circumferential stress criterion. The instantaneous velocity is well smoothed by a bisection technique. New crack-tip elements of inconstant length are added to the active crack-tip to simulate the fast crack growth. Square root shape functions are adopted as to describe the proper asymptotic behavior in the vicinity of the crack-tips. The computation time for the dynamic fracture problems in composites with multiple inclusions is reduced by a numerical method. The influences of the inclusions on the shielding ratio, the crack growing path and the crack-tip instantaneous speed are well investigated.     

C–H···O hydrogen bonding in crystals

An overview is given on C–H···O hydrogen bonding in the solid state. Following a short survey of the early literature, the general properties of C–H···O bonding are discussed. The structural characteristics and some physical consequences of C–H···O bonds are described. A number of special systems are discussed in greater detail; these include water acceptors, inclusion complexes, and some biological structures.     

Some remarks on the lattice of fuzzy intervals

In this paper we study the connections between three related concepts which have appeared in the fuzzy literature: fuzzy intervals, fuzzy numbers and fuzzy interval numbers (FIN’s). We show that these three concepts are very closely related. We propose a new definition which encompasses the three previous ones and proceeds to study the properties ensuing from this definition. Given a reference lattice (X, ?), we define fuzzy intervals to be the fuzzy sets such that their p-cuts are closed intervals of (X, ?). We show that, given a complete lattice (X, ?), the collection of its fuzzy intervals is a complete lattice. Furthermore we show that, if (X, ?) is completely distributive, then the lattice of its fuzzy intervals is distributive. Finally we introduce a new inclusion measure, which can be used to quantify the degree in which a fuzzy interval is contained in another, an approach which is particularly valuable in engineering applications.     

评定主轴径向回转误差的最小区域环计算法

在深入研究主轴径向回转误差评定方法的基础上，根据对误差评定的判别法则，提出了一种新的评定主轴径向回转误差的计算方法──最小区域环计算法。在该方法的计算中不需要试探，可以直接确定出最小区域环圆心移动的最佳方向和步长，较之以往的传统计算方法具有运算速度快和计算精确的特点。     

Inclusion complexation of (11-ferrocenylundecyl)trimethylammonium bromide by β-cyclodextrin and its effects on electrochemical behavior of the surfactant

This report describes the influence of β-cyclodextrin complexation on thermodynamic and kinetic parameters of the electrode reaction of (11-ferrocenylundecyl)trimethylammonium bromide in aqueous media. The host attracted the reduced form having a less positive charge more strongly than the corresponding oxidized one. Thus, a hydrophobic interaction between the non-polar host cavity and the ferrocene moiety plays an important role in the inclusion complexation. Fast-scan voltammetric behavior of the amphiphilic ion suggested that inclusion-ejection processes practically attain equilibrium in the scan-rate range below 10 V s⁻¹, because of their fast rates. The relation between the peak current and peak potential leads to the conclusion that the enveloped guest exchanges no electrons directly with an electrode. The mean diffusion coefficient of the surfactant can be written as a linear combination of the contributions from a free monomolecular, a micelle-forming, and a host-bound surfactant. Since the binding affinity of the ferrocene moiety for the host cavity is much stronger than the aggregation force between the amphiphilic molecules in aqueous media, the host disrupts the micelles by incorporating the surfactant molecule into its cavity.     

重组融合蛋白TGFα－PE40的分离纯化和热稳定性研究

报告了重组融合蛋白ＴＧＦα－ＰＥ４０的分离纯化方法及稳定性研究。采用对原生质体进行超声破碎，抽得纯度为８０％的包涵体。包涵体用８Ｍ尿素变性后，再对ｐＨ９．０的缓冲液进行透析复性，最后经过ＭｏｎｏＱ柱及Ｓｕｐｅｒｄｅｘ－７５柱进行分离，可得到纯度为９８％的高活性ＴＧＦα－ＰＥ４０。经稳定性测试，纯化的ＴＧＦα－ＰＥ４０在４℃中可存放半年以上，并在５０℃以下活力稳定。     

汽轮机主油泵轴断裂分析

采用化学分析、力学性能测试和金相检验等手段，对某电站汽轮机主油泵轴的早期断裂进行了分析。结果表明，泵轴未经有效的热处理、边缘存在较大的夹杂物以及键槽未加工R角是导致泵轴断裂的主要原因。