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  • Author or Editor: Xiaolin Li x
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Abstract  

Neutron activation analysis after a nickel sulphide fire assay preconcentration for platinum group elements (PGE) has been established in our laboratory. In this work, the all PGE in DZ-2, a Chinese certified ultramafic rock standard reference material, are determined for testing the accuracy and precision of the method. The experimental conditions and the blank values from reagents and detection limits for the method are also presented.

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Abstract  

In determining the trace platinum group elements and gold in rocks and ores by the neutron activation analysis after a nickel sulphide fire assay preconcentration, there are interferences due to nuclides produced from second order nuclear reactions. This paper presents the degree of interference calculated over the ranges of long irradiation times and of reactor neutron flux from 1·1013 to 1·1015 n·cm–2·s–1. According to the results of these calculations, every one of the second order interfering reactions on the PGE+Au, except the197Au(n, )198Au(n, )199Au reaction, can be neglected under the long irradiation time or high reactor neutron flux. Special attention is given to the interference from gold in the determining platinum.

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In this study, Lactobacillus pentosus expressing porcine lactoferrin (pLF) was tested for in vitro antibacterial activity and for its ability to enhance immunity induced by an orally administered Aujeszky’s disease virus (ADV) vaccine. The cDNA encoding N-terminus of pLF was cloned into a Lactobacillus-specific plasmid to produce L. pentosus pLF expressing transformants (pPG612.1-pLFN/ L. pentosus). The antimicrobial activity of the recombinant pLF protein inhibited bacterial growth in vitro. The supernatant of pPG612.1-pLF-N/L. pentosus had an inhibitory effect on Staphylococcus aureus strain CVCC26003, Bacillus subtilis strain CVCC63501, Escherichia coli strain CVCC10141 and Salmonella enterica ssp. enterica Choleraesuis strain CVCC79102, while it did not inhibit the growth of Lactobacillus casei strain ATCC393. A mouse model was established to test the effectiveness of the orally administered probiotic L. pentosus recombinant strain in the gastrointestinal tract. Mice were immunised with an attenuated porcine Aujeszky’s disease virus (ADV) vaccine. Serum antibody levels determined using a mouse Aujeszky’s disease IgG ELISA showed that IgG levels were significantly higher in the pPG612.1-pLFN/L. pentosus group than in the PBS and Lactobacillus pentosus groups at days 7 and 21 (P < 0.01) and at day 14 (P < 0.05), indicating that this oral recombinant strain can improve the effectiveness of the vaccine and play a role in immune enhancement through humoral immunity. These results suggest that the recombinant Lactobacillus pentosus not only has the beneficial characteristics of lactic acid bacteria but also produces biologically functional lactoferrin.

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Abstract  

Adverse health effects of occupational exposures to metal-containing airborne particles have long been recognized. To reduce the adverse effects caused by metal-containing particles, it is important to make clear where they are from. SPM has been applied to the study of the sources of chromium, manganese, nickel and zinc in aerosol particles PM10. Micro-PIXE spectra of single particles were treated as fingerprints since each particle was characterized by its micro-PIXE spectrum. The sources of the metal-containing particles were identified using the fingerprints of single particles. The study shows that the major sources of the four kinds of metals in the air are metallurgic emission, vehicle exhaust, coal combustion and soil dust.

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Abstract  

This study is a one-year monitoring of the inhalable particulate matter (PM10) of Shanghai (from January 2006 to December 2006) to study PM10 pollution. Proton-induced X-ray emission (PIXE) was used to investigate the chemical elements in Shanghai PM10. The study finds seasonal variation in both mass concentration and of chemical elements in PM10. The results of the enrichment factor show that the chemical elements in the inhalable particles could be divided into two categories, soil elements from earth crust and anthropogenic pollution elements. The high enrichment factors suggest that anthropogenic activities were the dominant source for elements such as S, Cu, Cl, Zn, Pb and Br. Strong correlation of K, Ca, Fe and Ti, from factor analysis, indicates these elements coming from earth crust or soil, S, Zn and Pb from industrial pollution and/or traffic and Cl from coal combustion.

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A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method and ultrahigh-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS) were optimized and validated for 16 antibiotics belonging to three families (macrolides, quinolones, and sulfonamides) that were found in preserved eggs. Samples were extracted in 4 mL water and 10 mL acetonitrile with 1% acetic acid and subjected to a cleanup procedure using dispersive solid-phase extraction with C18 and primary secondary amine sorbents, prior to detection by UHPLC–MS/MS. Matrix-matched calibration was used for quantification to reduce the matrix effect with limits of quantification in the range of 0.3–3.0 μg/kg. Validation of the method was conducted by recovery and precision experiments. Recoveries of the spiked samples ranged from 73.8% to 127.4%, and the intra- and inter-day relative standard deviations were lower than 21.2% and 22.3%, respectively. This method was successfully applied to the analysis of antibiotics in preserved egg samples.

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