Analysis of fumonisins B1 and B2 in spices and aromatic and medicinal herbs by HPLC-FLD with on-line post-column derivatization and positive confirmation by LC-MS/MS

Fumonisins are produced by the fungus Fusarium verticillioides, which are known to cause fatal diseases in some animals and humans. Here, we describe a sensitive, reproducible and reliable analytical method for the quantitative determination of fumonisins B(1) (FB(1)) and B(2) (FB(2)) in 112 spices and aromatic and medicinal herbs marketed in China. This method is based on high performance liquid chromatography and fluorescence detection (HPLC-FLD) coupled to a new on-line post-column derivatization using ortho-phthaldialdehyde with 2-mercaptoethanol and immunoaffinity column clean-up. Under the optimized experimental conditions, a complete separation of FB(1) and FB(2) was obtained using a Synergi C(18) column and a gradient elution at 0.8 mL min(-1) with methanol and 0.1 M phosphate buffer at pH 3.15. The limits of detection for FB(1) and FB(2) were both 40 μg kg(-1). Good recoveries were found for spiked samples with FB(1) and FB(2), ranging from 82.34% to 98.16% for FB(1) and from 72.58% to 97.10% for FB(2), with relative standard deviation (RSD) < 7.0%. 5 spices, 11 aromatic herbs and 96 medicinal herbs including 93 normal samples and 19 visibly moldy samples, which were spoiled artificially, were analyzed. The results showed that 8 (42.1%) visibly moldy samples and 8 (8.6%) normal samples were contaminated with FB(1) at mean contents of 129.0 and 165.9 μg kg(-1), and with FB(2) at 1745.0 and 256.8 μg kg(-1), respectively. Positive confirmation of detected samples was performed by liquid chromatography tandem electrospray ionization mass spectrometry (LC-ESI-MS/MS), using a triple quadrupole analyzer and operated in the multiple reaction monitoring mode.     

Direct detection of isoprene photooxidation products by using synchrotron radiation photoionization mass spectrometry

We report the combination of a vacuum ultraviolet photoionization mass spectrometer, operating on the basis of synchrotron radiation, with an environmental reaction smog chamber for the first time. The gas- and pseudo-particle-phase products of OH-initiated isoprene photooxidation reactions were measured on-line and off-line, respectively, by mass spectrometry. It was observed that aldehydes, methacrolein, methyl vinyl ketone, methelglyoxal, formic acid, and similar compounds are the predominant gas-phase photooxidation products, whereas some multifunctional carbonyls and acids mainly exist in the particle phase. This finding is reasonably consistent with results of studies conducted in other laboratories using different methods. The results indicate that synchrotron radiation photoionization mass spectrometry coupled with a smog chamber is a potentially powerful tool for the study of the mechanism of atmospheric oxidations and the formation of secondary organic aerosols.     

二维射影线性群与区传递4-(q+1,5,λ)设计

在组合设计的研究领域中,如何构造具有给定参数的t-设计是一个重要而且困难的问题.利用设计的自同构群来构造t-设计是这一问题有效的解决方法之一.在本文中,设D=(X,B)是一个4-(q+1,5,λ)设计,G≤Aut(D)区传递地作用在D上且X=GF(q)∪{∞},这里GF(q)是q元有限域.设PSL(2,q)(?)G≤PTL(2,q).利用Kramer和Mesner的关于构造区组设计的一个结果和二维射影线性群作用在X的5-子集的集合上的轨道,得到了如下结果:(1)G=PGL(2,17)并且D是一个4-(18,5,4)设计;或(2)G=PSL(2,32)并且D是一个4-(33,5,4)设计;或(3)G=PTL(2,32)并且D是4-(33,5,5)和4-(33,5,20)设计之一.     

One-step controlled precipitation to fabricate glucose-responsive microcapsules

Advanced multi-compartmental concanavalin A (Con A)/glycogen complex microcapsules incorporated with polymeric micelles were successfully fabricated by a facile, one-step controlled precipitation method. Dropwise addition of Con A solution into glycogen solution results in Con A/glycogen complex precipitates, which are captured by polyethyleneimine-modified CaCO₃ microparticles, forming a continuous shell structure. Removal of the carbonate cores yields hollow capsules of Con A/glycogen complex, which have variable sizes and wall thicknesses under different precipitation conditions. The capsules show molecular-recognizable response to glucose and dextran (M _w, 20 and 40 kDa), leading to breakdown of the capsule structure and release of the incorporated substances such as poly(styrene-b-acrylic acid) micelles.     

Long period grating cascaded to photonic crystal fiber modal interferometer for simultaneous measurement of temperature and refractive index

We propose and demonstrate a novel and simple dual-parameter measurement scheme based on a cascaded optical fiber device of long-period grating (LPG) and photonic crystal fiber (PCF) modal interferometer. The temperature and refractive index (RI) can be measured simultaneously by monitoring the spectral characteristics of the device. The implemented sensor shows distinctive spectral sensitivities of -30.82 nm/RIU (refractive index unit) and 47.4 pm/°C by the LPG, and 171.96 nm/RIU and 10.4 pm/°C by the PCF modal interferometer. The simultaneous measurement of the temperature and external RI is experimentally demonstrated by the sensor. The temperature shift and RI shift calculated by the sensor matrix agree well with the actual temperature and RI change in the experiment.     

Study on phenomenological curing model of epoxy resin for prediction of degree of cure

Curing course of Huntsman 1564/3486 epoxy resin system was studied under dynamic and isothermal curing conditions by differential scanning calorimetry technique. The autocatalytic cure kinetic model was established to describe the curing behaviour. A new modified phenomenological curing model based on the Olivier??s model was proposed to predict the relationship between the degree of cure and the couple of time and temperature. Then, the degree of cure was calculated by both the kinetic model and the modified Olivier??s model. A comparison of the results calculated with the experimental data show that the modified Olivier??s model is more accurate in the later stage of the curing course, especially at high temperatures. The modified Olivier??s model is simple and easy to use, could be applied to predict the degree of cure at isothermal temperatures well in engineering.     

Fabrication of Chitosan Single‐Component Microcapsules With a Micrometer‐Thick and Layered Wall Structure by Stepwise Core‐Mediated Precipitation

Incubation of CaCO₃ microparticles in chitosan (CS) solution at pH 5.2 and following with ethylenediaminetetraacetic acid disodium salt (EDTA) treatment resulted in CS single‐component microcapsules with an ultra‐thick wall structure. Repeating the incubation caused stepwise increase of wall thickness and finally resulted in CS microcapsules with a layered structure. This unique method is mediated by precipitation of CS on the CaCO₃ particles as a result of pH increase caused by the partial dissolution of CaCO₃. The obtained CS capsules are stable at neutral pH.     

Photoelectron spectroscopy and density functional calculations of CuSi(n)- (n = 4-18) clusters

We conducted a combined anion photoelectron spectroscopy and density functional theory study on the structural evolution of copper-doped silicon clusters, CuSi(n)(-) (n = 4-18). Based on the comparison between the experiments and theoretical calculations, CuSi(12)(-) is suggested to be the smallest fully endohedral cluster. The low-lying isomers of CuSi(n)(-) with n ≥ 12 are dominated by endohedral structures, those of CuSi(n)(-) with n < 12 are dominated by exohedral structures. The most stable structure of CuSi(12)(-) is a double-chair endohedral structure with the copper atom sandwiched between two chair-style Si(6) rings or, in another word, encapsulated in a distorted Si(12) hexagonal prism cage. CuSi(14)(-) has an interesting C(3h) symmetry structure, in which the Si(14) cage is composed by three four-membered rings and six five-membered rings.     

Nonlinear Cournot oligopoly games with isoelastic demand function: The effects of different behavior rules

The analysis of asymptotical convergence for the oligopoly game has always been important to characterize the firms’ long-term behavior. In the nonlinear oligopoly competition possibly involving chaotic fluctuations, non-convergent trajectories are particularly undesirable since the resulting behavior will become unpredictable. In this paper, consistent with a traditional assumption that the firms update their outputs simultaneously, we at first construct an adjustment process and discuss the convergence to the equilibrium for a nonlinear Cournot duopoly game with the isoelastic demand function. We indicate that the tendency to instability does rise with the number of firms and the adjustment speeds. In particular, we alter this assumption from simultaneous decisions to sequential decisions so that the latter firms are able to observe the former ones at every time periods. We finally arrive at a conclusion that the unique equilibrium is convergent as long as the adjustment speeds are less than a fixed threshold, no matter what the number of the firms. Our findings show that the firms with sequential decisions can achieve the equilibrium more easily.     

C60醛类衍生物非线性光学特性研究

研究了加合不同取代基团的C60醛类衍生物的光学非线性性质。利用简并四波混频（DFMW）方法获得了C60醛类各衍生物的三阶光学非线性超级化率γ^(3)及相应的三阶光学非线性系数χ^(3)值。同时也研究了它们各自的光限幅特性。结果表明：不同的取代基对C60醛类衍生物三阶光学非线性及光限幅特性的影响不同。