食品中痕量危害物分析过程污染的来源和控制

食品中危害物分析日趋痕量化,痕量化学分析因其敏感而易受外部环境的影响发生过程污染。通过对食品中痕量危害物检测过程污染实际案例的分析,发现污染的发生主要来自于实验环境、器具、试剂和过程控制等。探讨建立人员培训,方法学考查,实验环境和实验全过程控制等预防食品中痕量危害物化学分析过程污染的制度,并以此提高食品安全分析实验室检测过程预防污染的水平。     

In vitro growth and activity of chondrocytes on three dimensional polycaprolactone/chitosan scaffolds

Porous polycaprolactone/chitosan blend scaffolds with various compositional proportions were prepared using a particulate‐leaching method. The pore parameters of resultant scaffolds were found to be mainly modulated by porogen. The compressive mechanical properties and hydrophilicity of scaffolds were examined by measuring their compressive modulus and stress strength as well as swelling index. Selected chondrocytes isolated from articular cartilage of knee joints of rabbits were seeded on these scaffolds, and further in vitro cultured for various periods. The growth and activity of seeded cells were estimated by counting numbers of cells proliferated on scaffolds and measuring the amounts of proteoglycans and type II collagen synthesized by the seeded cells. It was found that some scaffolds composed of proper component ratios and having appropriate pore parameters exhibited promising characteristics for the adhesion and proliferation of seeded cells while maintaining the phenotype and activity of the cells. Copyright © 2010 John Wiley & Sons, Ltd.     

Capillary electrophoresis‐laser‐induced fluorescence detection of rat brain catecholamines with microwave‐assisted derivatization

In this study, a rapid and sensitive method is described for the catecholamines detection in rat brain. CE with LIF detection for the determination of FITC derivatized catecholamines (dopamine, epinephrine, and norepinephrine) was demonstrated. Conventional water bath and microwave‐assisted derivatization methods were employed and a significant reduction in the derivatization time from 2 h for the conventional water bath at room temperature (ca. 25°C) to 2 min for the microwave‐assisted derivatization was achieved. Online sample concentration of field‐amplified sample stacking (FASS) method was employed to achieve higher sensitivities (the detection limits obtained in the normal injection mode ranged from 2.6 to 4.5 ng L^?1 and in the FASS mode ranged from 22 to 34 pg L^?1). Furthermore, this microwave‐assisted derivatization CE–LIF method successfully determined catecholamines in rat brain with as low as 100 ng L^?1 (FASS mode) to 10 μg L^?1 (normal injection mode). This CE–LIF method provided better detection ability when compared to the best reports on catecholamines analyses.     

Combination of developed in-house method and application of Eichrom Sr resin to determine the radioactivity of <Superscript>90</Superscript>Sr in environmental sample

A method is described for the determination of ⁹⁰Sr in environmental samples using combination of developed in-house method, Eichrom Sr resin and Beta Counter. Strontium was efficiently, rapidly and simply separated from Ca and other interfering matrix components by Eichrom Sr resin. All the results in general showed good accuracy, high precision, reliable and in good agreement between these two measured and certified value of SRM (i.e. IAEA-375, IAEA-326, IAEA-152 and IAEA-414). As a whole, the procedure described in this work notably improves conventional methods in particular concerning the time needed, sample volume, safer and others. Thus, the introduced method was successfully performed and will be applied to actual sample for the determination of ⁹⁰Sr in different environmental materials such as soil, sediments, milk, biological sample, water etc.     

广义Ekeland变分原理的应用

研究了广义Ekeland变分原理在拟度量空间中的一些重要应用.利用广义Ekeland变分原理证明了函数f满足关于α的Takahashi ε-条件当且仅当f满足关于相同α的Hamel ε-条件.此外,利用关于α的Takahashi ε-条件得到了一些重要结论.     

Some results on metric n-Lie algebras

We study the structure of a metric n-Lie algebra G over the complex field C. Let G = SR be the Levi decomposition, where R is the radical of G and S is a strong semisimple subalgebra of G. Denote by m(G) the number of all minimal ideals of an indecomposable metric n-Lie algebra and R ⊥ the orthogonal complement of R. We obtain the following results. As S-modules, R ⊥ is isomorphic to the dual module of G/R. The dimension of the vector space spanned by all nondegenerate invariant symmetric bilinear forms on G is equal to that of the vector space of certain linear transformations on G; this dimension is greater than or equal to m(G) + 1. The centralizer of R in G is equal to the sum of all minimal ideals; it is the direct sum of R ⊥ and the center of G. Finally, G has no strong semisimple ideals if and only if R⊥■R.     

Generalized Hyers-Ulam stability of a general mixed additive-cubic functional equation in quasi-Banach spaces

In this paper, we establish a general solution and the generalized Hyers-Ulam-Rassias stability of the following general mixed additive-cubic functional equation

Ultimate boundedness and an attractor for stochastic Hopfield neural networks with time-varying delays

This paper investigates ultimate boundedness and a weak attractor for stochastic Hopfield neural networks (HNN) with time-varying delays. By employing the Lyapunov method and the matrix technique, some novel results and criteria on ultimate boundedness and an attractor for stochastic HNN with time-varying delays are derived. Finally, a numerical example is given to illustrate the correctness and effectiveness of our theoretical results.     

Influence of acute hyperglycemia on otoacoustic emissions and the medial olivocochlear reflex

Stimulus-frequency (SF) otoacoustic emission (OAE) amplitude and the amplitude of medial olivocochlear (MOC) inhibition of SF OAEs for ipsilateral, contralateral and bilateral MOC reflex elicitors were recorded in six subjects with type 2 diabetes during a glucose tolerance test (GTT). Five of the six subjects were tested twice for a total of 11 trials and three subjects were tested in a control experiment. During the GTT experiment, the subjects' blood glucose was elevated from a euglycemic level below 150 mg/dL to a hyperglycemic level above 160 mg/dL following the consumption of a bolus of 80 g of sugar. A subset of three subjects were tested in a control experiment during which SF OAE and MOC reflex measurements were made while blood sugar levels remained constant within the euglycemic region. Mean SF OAE amplitudes were elevated following glucose consumption. A statistically significant increase in MOC inhibition amplitude was observed during elevated sugar levels for the 11 GTT trials. Maximum inhibition occurred about an hour after glucose consumption when blood glucose levels peaked. Results indicate that acute hyperglycemia influences efferent control of the cochlea in people with type 2 diabetes.     

A density-functional theory investigation on desorption of O2 on Sn（111） and its comparison with initial oxidation on the X（111） （X=Si,Ge, Sn,Pb） surfaces

<正>The first-principles calculations are performed to investigate the adsorption of O₂ molecules on an Sn（111） 2×2 surface.The chemisorbed adsorption precursor states for O₂ are identified to be along the parallel and vertical channels, and the surface reconstructions of Sn（lll） induced by oxygen adsorption are studied.Based on this,the adsorption behaviours of O₂ on X（111）（X=Si,Ge,Sn,Pb） surfaces are analysed,and the most stable adsorption channels of O₂ on X（111）（X=Si,Ge,Sn,Pb） are identified.The surface reconstructions and electron distributions along the most stable adsorption channels are discussed and compared.The results show that the O₂ adsorption ability declines gradually and the amount of charge transferred decreases with the enhancement of metallicity.