Solid phase extraction with electrospun nanofibers for determination of retinol and α-tocopherol in plasma

A novel packed-fiber solid phase extraction procedure based on electrospun nanofibers for simultaneous determination of vitamins A (retinol) and E (α-tocopherol) in human plasma has been developed. Parameters affecting extraction efficiency were investigated in detail. The limit of detection is 0.01 μg mL^?1 for retinol, and 0.3 μg mL^?1 for α-tocopherol. The linear range is from 0.05 to 2.0 μg mL^?1 for retinol, and from 0.5 to 30 μg mL^?1 for α-tocopherol. The precision (RSD) is <6%, and the relative recovery >90%. The method was applied to analysis of retinol and α-tocopherol in human plasma with satisfactory results.     

Enhancement of Lovastatin Production by Supplementing Polyketide Antibiotics to the Submerged Culture of <Emphasis Type="Italic">Aspergillus terreus</Emphasis>

Feedback inhibition existed in lovastatin biosynthesis from Aspergillus terreus. Exogenous lovastatin and other different polyketide antibiotics biosynthesized by polyketide synthase were supplemented to the cultures of A. terreus to investigate their influences on lovastatin production. Supplementing exogenous lovastatin of 100 mg l⁻¹ at the early stage of fermentation and the fast stage of its biosynthesis resulted in decreases of 76.4% and 20% in final lovastatin production, respectively. However, the fungal cell growth was not affected; the growing cycle was only prolonged in the submerged cultivation. Separate supplementation of the five kinds of polyketide antibiotics such as tylosin, erythromycin, tetracycline, daunorobin, and rifamycin to the cultures resulted in increases of about 20~25% in the final lovastatin production. Especially, supplementing tylosin of 50 mg l⁻¹ at the beginning of lovastatin biosynthesis led to the final lovastatin production of 952.7 ± 24.3 mg l⁻¹, which was improved by 42% and 22% compared with that produced in the control and the original culture, respectively. These results are helpful to understand the regulations on lovastatin biosynthesis and improve the final desired metabolite contents in many antibiotics production.     

Phase-controlled preparation of iron (oxyhydr)oxide nanocrystallines for heavy metal removal

Obtaining cost-effective iron (oxyhydr)oxide nanocrystallines is the essential prerequisite for their future extensive applications in environmental remediation, such as the removal of heavy metals from contaminated waters. Here, various phases of iron (oxyhydr)oxide nanocrystallines were simply synthesized from the phase-controlled transformation of amorphous hydrous ferric- or ferrous-oxide in thermal solution with a certain ethanol/water ratio and with the presence of oleic acid. According to this method, goethite nanorods in diameter of 3–4 nm, hematite nanocubes sized 20–30 nm, and magnetite nanoparticles in diameter of 6–7 nm were successfully obtained. The final products of this transformation can be conveniently controlled by adjusting the reaction parameters, such as pH, temperature, and ethanol/water ratio. Due to the enhanced specific surface area and probably the modifications of the surface structure of nanocrystallines, the as-synthesized goethite nanorods and magnetite nanoparticles demonstrated extremely strong As(III) affinity, with 5.8 and 54 times of As(III) adsorption, respectively, higher than the micron-sized relatives. The cost-effective feature of as-synthesized nanocrystallines and their remarkably enhanced affinity toward arsenic made them potentially applicable for the removal of arsenic and such like heavy metals from the contaminated environment.     

Waterborne crackle decorative coatings and crack patterns

A preparation method of waterborne crackle decorative coatings was reported in this paper and the factors that influence crack patterns were investigated. The crackle coating consisted of a waterborne basecoat and a waterborne topcoat. The basecoat was made from two-component epoxy emulsion and the topcoat was made from fluorine-containing acrylic emulsion, silicone-acrylic emulsion or styrene-acrylic emulsion. Three junction types of crack patterns were prepared by the three top coatings, which were T-junction, Y-junction and mixed junction. T-junction type with long and straight cracks was prepared from styrene-acrylic emulsion 296DS. Y-junction type with curve and short cracks was prepared from fluorine-containing acrylic emulsion A603C and mixed junctions type was made from silicone-acrylic emulsion. Crack patterns with different spacing were prepared by controlling the thickness of topcoat, dryness of basecoat or conditions of film forming. The characterize methods of type and spacing for crack pattern were developed and properties of coating film including adhesion, water resistance, scrub resistance and so on were tested. The results showed that the crackle coatings possessed satisfactory properties for practical application.     

Extensions of the Borel–Cantelli lemma in general measure spaces

In this paper, an important bilateral inequality for a sequence of nonnegative measurable functions on a measure space \((S,\mathcal {B}_S,\mu )\) is obtained, and some sufficient conditions for \(\mu \left( \limsup \limits _{n\rightarrow \infty }A_n\right) =\mu (S)\) are given. In addition, a weighted version of the Borel–Cantelli Lemma on the measure space is obtained. Our results generalize the corresponding ones for bounded random sequences to the case of unbounded measurable functions.     

Breakdown-quenching characteristics and mechanisms for silicon photomultipliers

Some deviant breakdown-quenching characteristics of silicon photomultipliers are demonstrated and their physical mechanisms are explored. “Twice breakdown” phenomenon, “flat-topped” avalanche pulses and the determination method of the real breakdown voltage of the detector are analyzed. These characteristics are explained by the integration model in terms of avalanche threshold current based on the Haitz's equivalent circuit model. The reasoning results show that the maximum over-voltage for a normal operating silicon photomultiplier equals the product of the avalanche threshold current and the quenching resistor of the avalanche photo-diode (APD) pixel, approximately. Moreover, the model and results can be extended to other small avalanche junctions with quenching resistor.     

Multi-scales association modeling of membrane water resistance indexes

In order to quantify and predict the water resistance of membrane, a multi-scales association model was built up based on the Fick’s second law. Two water resistance indexes, balance time and seepage velocity, were put forward and calculated by the model for measuring the property of membrane water resistance. The association model linked macro-scale factors and micro-scale parameters together. The influence of macro-scale factors, environmental temperature and membrane thickness, and micro-scale parameters, water molecules diffusivity, membrane saturated water absorption rate and water escape concentration, were discussed. The properties of water resistances for two groups including 10 waterborne acrylate membranes samples were measured for validating the indexes calculated by the model. The well consistency between the results of calculations and experiments proved that the method of multi-scales association modeling for quantifying and predicting the membrane water resistance was feasible.     

单位球上F(p,q,s)空间到Bloch型空间的复合算子

该文分别给出了单位球B上空间F(p, q, s)到空间β^α之复合算子C_{varphi}为有界算子和紧算子的充要条件.同时作为推论获得了Bloch型空间的相应结果.     

螺旋管锅炉反应器管内汽液两相流压力降脉动研究

本又根据闭式循环热动力推进系统中锅炉反应器的各种可能的航行方向及运行参数，对螺旋管内汽液两相流压力降脉动特性进行了系统的试验研究，首次区分了两类不同特征的压力降脉动并得到了各主要因素的影响现律和发生脉动的界限准则。