A novel capillary electrophoretic method for determining aliphatic aldehydes in food samples using 2-thiobarbituric acid derivatization

A novel electrophoretic method for sensitive determination of nine aldehydes, including formaldehyde (C1), acetaldehyde (C2), propanal (C3), butanal (C4), pentanal (C5), hexanal (C6), glutaradehyde (Gla), 2,3-butanedione (Bud) and methylgloxal (MGo) in food samples, has been developed based on CE with amperometric detection (CE-AD). After being derivatized with an electroactive compound, 2-thiobarbituric acid (TBA), these nine non-electroactive aldehydes were converted to electroactive adducts, and therefore detectable by CE-AD approach. Experimental conditions of derivatization and CE-AD detection were optimized. The proposed method was validated according to International Conference on Harmonization (ICH) requirements, with recovery results ranging from 82.8 to 123.8%. Calibration plots of aliphatic aldehydes were linear (r2 ≥ 0.9901) in the concentration range from 0.083 to 15.0 mg/L. The LODs were between 0.008 and 0.074 mg/L. The proposed CE-AD method provides a reliable and sensitive quantitative evaluation for non-electroactive low-molecular-mass monoaldehydes and dialdehydes in real sample matrices by employing relatively simple and inexpensive instrument.     

Titania-Doped Silica Fibers Prepared by Electrospinning and Sol-Gel Process

Titania-doped silica fibers were prepared by electrospinning of the sol of silica containing titania. The electrospun fibers had ribbon type morphology. The fibers had significant quantities of hydroxyl groups of Si—OH and Ti—OH. The fibers did not have crystalline structure. Diameters of the fibers were reduced by solvent evaporation and calcination. The hydroxyl groups on the fibers disappeared by calcination. The hydroxyl groups, M—OH (MSi, Ti) were changed to M—O—M by intermolecular and intramolecular condensation reactions.     

Silica based click amino stationary phase for ion chromatography and hydrophilic interaction liquid chromatography

A silica based amino stationary phase was prepared by immobilization of propargylamine on azide-silica via click chemistry. This readily prepared click amino stationary phase demonstrated good selectivity in separation of common inorganic anions under ion chromatography (IC) mode, and the triazole ring in combination with free amino group was observed to play a major role for separation of the anions examined. On the other hand, the stationary phase also showed good hydrophilic interaction liquid chromatography (HILIC) properties in the separation of polar compounds including nucleosides, organic acids and bases. The retention mechanism was found to match well the typical HILIC retention.     

Beam spreading of truncated Gaussian beams in Kolmogorov turbulence

Based on the extended Huygens-Fresnel principle and the hard-edge aperture function expanded as the sum of finite-term complex Gaussian function, analytical expression for average intensity of truncated Gaussian beam in Kolmogorov turbulence is derived, and some limiting cases are discussed. The influences of many factors, such as Fresnel number, wavelength, truncation parameter and structure constant on beam spreading are studied with the help of the average intensity formula. We found that the peak value of average intensity decreases and the beam spot spreads with the decrease of Fresnel number. The change of peak intensity against Fresnel number is slower with large aperture than that with small aperture. When Fresnel number is not small enough the influence of turbulence on intensity profiles is so small that can be neglected if structure constant is small.     

Interaction of electromagnetic waves with a magnetized nonuniform plasma slab

The absorption, reflection, and transmission of electromagnetic waves by a nonuniform plasma slab immersed in an ambient uniform magnetic field of various strengths are studied in this paper. The effects of the plasma parameters and magnetic field strength on the absorbed, reflected, and transmitted power are discussed. The magnetized nonuniform plasma slab is modeled by a series of magnetized uniform plasma subslabs. The calculation results show that the effects of the magnetic field strength and density gradient on the absorbed power, as well as the frequency band of resonant absorption, are significant. A complete analysis utilizing the scattering matrix method is also used to compare the above calculation results which neglect multiple reflections between subslab interfaces. Broadband absorption of electromagnetic waves can be achieved by changing the magnetic field strength and plasma density. More than 90% of the electromagnetic wave power can be absorbed in a magnetized nonuniform plasma slab with width of 12 cm and the absorption bandwidth can range from 1 to 20 GHz with different plasma parameters and external magnetic field strengths.     

Design and synthesis of pyromellitic diimide‐based donor–acceptor conjugated polymers for photovoltaic application

Three of conjugated polymers based on pyromellitic diimide (PMDI) as the acceptor unit and thienothiophene (TT) as the donor unit were successfully synthesized by Stille coupling. The effect of the side chain length and thiophene π‐bridge on the polymers' optical and electrochemical properties was investigated. Electrochemical characterization indicated that these polymers have deep highest occupied molecular orbital energy levels between ?5.7 and ?5.8 eV. Polymer solar cells were fabricated by using these PMDI‐based polymers as the donor and [6,6]‐phenyl‐C61‐butyric acid methyl ester as the acceptor. The polymer P1 whose PMDI unit was functionalized with 2‐ethylhexyl side chain shows the higher short‐circuit current (J_sc) and fill factor (FF) compared with that of P2 with a 2‐octyldodecyl side chain on the PMDI unit. The results also illustrate that the insertion of a thiophene π‐bridge between PMDI and TT (the polymer P3) leads to the broader absorption and better photovoltaic performance. The best performance was obtained from the cell based on the polymer P3 with a power conversion efficiency of 0.43% under the illumination of AM 1.5 G, 100 mW/cm². Copyright © 2014 John Wiley & Sons, Ltd.     

Inequalities for the Gaussian hypergeometric function

we study the monotonicity of certain combinations of the Gaussian hypergeometric functions F(-1/2,1/2;1;1- xc) and F(-1/2- δ,1/2 + δ;1;1- xd) on(0,1) for given 0 c 5d/6 ∞ andδ∈(-1/2,1/2),and find the largest value δ1 = δ1(c,d) such that inequality F(-1/2,1/2;1;1- xc) F(-1/2- δ,1/2 + δ;1;1- xd) holds for all x ∈(0,1). Besides,we also consider the Gaussian hypergeometric functions F(a- 1- δ,1- a + δ;1;1- x3) and F(a- 1,1- a;1;1- x2) for given a ∈ [1/29,1) and δ∈(a- 1,a),and obtain the analogous results.     

银莲花素晶体结构的精测

银莲花素,C₁₀H₈O₄,是无色透明晶体,属正交晶系,空间群D_2h¹⁵-P2₁/b2₁/c2₁/a,晶胞参数:a=11.063(4),b=11.633(4),c=13.873(4)Å,Z=8。实验结果表明化合物中两不饱和γ-内酯是以螺环形式与环丁烷相连,与光谱结果一致。     

Properties of proton-rich nuclei in a three-body model

Using a three-body model and realistic two-body potentials, we investigate the properties of the nuclei ¹⁸Ne and ²⁸S near the proton dripline. We figure out the two-proton separation energies, occupation of the valence protons, root-mean-square radii of matter and the valence protons. Besides, the spatial correlation densities are displayed to reflect the correlation between the two valence protons. The first excited 0⁺ state of ¹⁸Ne is most likely to be a halo state according to our calculation. Turning off the Coulomb interactions among the three-body systems, we get the two-neutron separation energies and configuration of the valence neutrons of their corresponding mirror nuclei. The results indicate that the three-body model is proper to describe some proton-rich nuclei and can be used to deduce reliable information.