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  • Author or Editor: J. Xu x
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Abstract  

By introducing some parameters, we give new extensions of Hilbert inequality with best constant factors.

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Abstract  

The divalent oxidation state of californium (Cf) has been stabilized in crystalline SrB4O7. The ability to generate this less-stable oxidation state in an oxide matrix is significant. Factors promoting this stabilization have been determined. Access to this divalent state and those of many other lanthanide and actinide elements via a rather straightforward laboratory procedure now facilitates their study and characterization.

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Abstract  

The adsorption behavior of silica gel for Zr, Pu and fission products (Fe, Mo, Nd, etc.) in high-level liquid waste (HLLW) have been studied. The dynamic desorption for Zr and Pu are also investigated. Silica gel is found to have high selectivity for Zr to other elements in HLLW and its adsorption capacity can be enhanced by H2C2O4 elution and multiple reuse. However, the adsorption for Pu(IV) is also found. This may cause spent silica gel to be alpha waste. Further study should be carried out on the adsorption behavior for Pu(IV).

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Abstract  

We show that, in the classes of functions with values in a real or complex Banach space, the problem of Hyers-Ulam stability of a linear functional equation of higher order (with constant coefficients) can be reduced to the problem of stability of a first order linear functional equation. As a consequence we prove that (under some weak additional assumptions) the linear equation of higher order, with constant coefficients, is stable in the case where its characteristic equation has no complex roots of module one. We also derive some results concerning solutions of the equation.

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Abstract  

The isothermal crystallization and subsequent melting behavior of one propylene homopolymer and three propylene-1-decene copolymers with different comonomer contents prepared by metallocene catalyst were studied using differential scanning calorimetry (DSC). It is found that the Avrami exponent of the propylene copolymers decreases gradually with the increase of comonomer content, from 3.0 for the propylene homopolymer to 1.4 for the copolymer with 7.83 mol% 1-decene units. Higher comonomer content also weakens the dependence of crystallization rate constant and crystallization halftime on temperature. Double melting peaks, which correspond to α and γ crystal phases, respectively, are observed for all copolymers under isothermal crystallization. The result shows that higher crystallization temperature is favorable to the segregation of α and γ crystal phases, resulting in higher proportion of γ crystal phase.

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Summary

In the present paper, a simple and reliable high-performance liquid chromatography-diode array detection (HPLC-DAD) method was developed both for quantitative determination and fingerprint analysis of Agrimonia pilosa Ledeb for quality control. Under the optimized HPLC conditions, seven bioactive compounds including rutin, quercetin-3-rhamnoside, luteoloside, tiliroside, apigenin, kaempferol, and agrimonolide were determined simultaneously. For fingerprint analysis, 11 common peaks were selected as the characteristic peaks to evaluate the similarities of 16 different samples collected from different origins in China. Besides, hierarchical cluster analysis (HCA) was also performed to evaluate the variation of the raw materials. This is the first report of using a simple method for quality control of A. pilosa Ledeb through multi-component determination and chromatographic fingerprint analysis to the best of our knowledge.

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Abstract

High-performance liquid chromatography with a hydrophilic-interaction liquid chromatographic (HILIC) column has been successfully used to retain and separate the polar phosphonic herbicides glyphosate and glufosinate. Online electrospray tandem ion-trap mass spectrometric and DAD detection were used. The effects on the separation of mobile phase acetonitrile content, buffer concentration, and flow rate, and of column temperature, were investigated. With UV-visible detection at 195 nm, LOQ were <850 mg kg−1, showing the method is suitable for product quality control of these herbicides alone or in combination. Tandem mass spectrometric conditions were optimized for ion-trap detection. Quantification was by use of selected reaction monitoring transitions m/z 168 → 150 in negative-ion mode for glyphosate and m/z 182 → 136 in positive-ion mode for glufosinate. Limits of detection (LOD; S/N > 3) were 0.20 and 0.16 ng for glyphosate and glufosinate, respectively, and the respective limits of quantification (LOQ; S/N = 10) were 0.02 and 0.05 mg kg−1. Sample derivatization was not necessary to achieve low detection limits in residue analysis in this study. Recovery from watermelon, spinach, potato, tomato, radish-root, and water fortified with the herbicides ranged from 63.6 to 107.3% and relative standard deviations were <15.3%.

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Garlic is widely used as food flavouring, and China is the world's largest garlic producer and exporter. To develop a convenient technique for evaluation of garlic cultivars would be worthwhile, and it would have wide application in such a huge market. In this research, 3D front-face fluorescence data of 8 garlic cultivars were recorded, and independent component analysis was used to decompose the overall fluorescence spectra into six independent components. The first, second, and fourth independent components showed a big difference among the cultivars, and the chemical fluorophores behind these three components were specified as protein, vitamin B6, and ATP, respectively, as fluorescent markers for evaluation. The result showed that all 8 cultivars cluster separately. The cultivar “YNQJ” have the highest quality in terms of protein and vitamin B6, “NXYC” and “SDHB” have the highest content of ATP, while “SXXA” is the poorest in terms of protein and ATP, and “HNJZ” has the lowest content of vitamin B6. Therefore, rapid evaluation of garlic cultivars can be accomplished successfully by using only the proportion values of three properly selected fluorescent markers.

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Abstract  

Polyaniline/α-Al2O3 (PANI/α-Al2O3) composites were synthesized by in situ polymerization through ammonium persulfate ((NH4)2S2O8, APS) oxidized aniline using HCl as dopant. XRD and FTIR were used to characterize the PANI/α-Al2O3 composites. The thermal stabilities and glass transition temperature (T g) of PANI/α-Al2O3 composites were tested using thermogravimetric (TG) method and modulated differential scanning calorimetry (MDSC) technique. The results of TG showed that the thermal stability of PANI/α-Al2O3 composite increased and then decreased with the increase in α-Al2O3 content. The derivative thermogravimetry (DTG) curves showed one step degradation of PANI when the α-Al2O3 content was lower than 52.5 mass%, and exhibited two steps degradation when the α-Al2O3 content was higher than 63.6 mass%. The MDSC curves showed that the T g of PANI/α-Al2O3 composites increased and then decreased with the augment of α-Al2O3 for the interaction between PANI chains and the surface of α-Al2O3.

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