Authors:Shi Xu, Sheng Li, Yun Wei, Li Zhang and Fei Xu
Titanium dioxide (TiO2), polythiophene and polythiophene/TiO2 were prepared by sol–gel and solid-state reaction methods. Water-free iron(III) chloride (FeCl3) was used as an oxidant. The phase composition, morphology and the spectral properties of the products were characterized by XRD, TEM, UV–Vis and FT-IR techniques. The photocatalytic activity of the products was evaluated by the degradation of methyl orange under sunlight irradiation. TEM results showed that the polythiophene/TiO2 composite particles were well dispersed, rod-like shaped with 20 × 80 nm dimensions. UV–Vis analysis indicated that the absorption edge of polythiophene/TiO2 was 605 nm. Compared with the unmodified TiO2 and bare polythiophene, polythiophene/TiO2 exhibited largely enhanced activity for the photocatalytic degradation of methyl orange under sunlight irradiation. A degradation efficiency of methyl orange of 85.6% could be obtained within 120 min. The sensitization mechanism of polythiophene for the TiO2 photocatalyst is discussed briefly.
Authors:Dongmei Li, Maoquan Xu, Guangshan Liu and Chao Li
Two marine sediment cores were collected from nearshore off Xinghua Bay mouth in Fujian, China and the 40K, 137Cs, 210Pb, 226Ra, 228Ra, 228Th and 238U in the cores were measured using γ-spectroscopy. For the core ZK6, the activities of 40K were vertically homogeneous within measured error in the whole core and 226Ra, 228Ra and 228Th showed large vertical variations with the same tendency. The sedimentation rates were 0.400 cm·y−1 above 50 cm and 0.737 cm·y−1 below depth of 50 cm. The change of sedimentation rates indicates the heterotaxy, which was justified by the absence of 137Cs in the zone of 25–50 cm. For core ZK6, the sedimentation rate was 0.179 cm·y−1. Vertical distributions of 40K, 226Ra, 228Ra, 228Th and 238U in the core ZK18 are similar to each other although there were significant large variations with depth. The large variations
of radioisotopes with depth in the cores mean that the sediment cores have been disturbed largely due to marine environment
change. The mean activities of radioisotopes in the core ZK6 are higher than ZK18 that may be ascribed to different hydrodynamic
Authors:X. Li, X. Xu, X. Li, X. Yang, W. Liu and L. Li
A reborn interest has occurred during the last decade toward wheat landraces for broadening genetic basis of modern wheat cultivars. The investigation of molecular traits within and between existing landraces of wheat can help scientists to develop appropriate strategies for their efficient maintenance and exploitation. The present study dealt with the gliadin characterization of forty-seven wheat landraces collected from wheat mainly planted areas of China, each of which was represented by a sample of at least 43 individuals. Twelve accessions selected on the basis of gliadin analysis were investigated further using 21 SSR markers. The results proved that landraces of wheat are a mixture of variable individuals genetically distinguishable from each other. Twelve of the analyzed 47 accessions were observed to be homogeneous, while 35 (74.5%) of them were heterogeneous in their gliadin composition. In total, 122 gliadin pattern were observed. On average, 10.1% (Gst) of the total variation arose from differentiation among regions, and 89.9% was attributed to within-region variation. Furthermore, nineteen of the 21 SSR markers were polymorphic across all the populations. The total number of the amplified DNA products was 110, with a mean of 6.11 alleles per locus. The values of genetic diversity within each landrace population varied from 0.006 to 0.351. Implications for the management of this valuable genetic resource are discussed.
Authors:X. Li, X. Xu, X. Yang, X. Li, W. Liu, A. Gao and L. Li
Youzimai is a widespread wheat landrace and has been used extensively in breeding programs in China. In order to assess the genetic variation between and within Youzimai accessions, samples of 31 landrace accessions of wheat, all called ‘Youzimai’, were collected from 6 geographic regions in China and evaluated using morphological traits, seedling resistance to powdery mildew, gliadin and microsatellite markers. Typical differences among accessions were observed in morphological characteristics. Forty-five (58.4%) of 77 assayed SSR markers showed polymorphism over the entire collection and total 226 alleles were identified with an average of 5.02 alleles per locus. SSR data indicated that the accessions from Hebei province were the most diverse, as evidenced by greatest number of region-specific alleles and highest diversity index. These accessions, therefore, probably experienced the most substantial morphological and molecular evolution as a result of various natural and anthropomorphic influences. On the other hand, differentiation in gliadin phenotypes was found among seeds within 80.6% of total accessions and average 61.5% of entire collections showed heterogeneous and comprised resistant plants in reaction to powdery mildew, suggesting the presence of a wide diversity within the wheat landrace. By developing an intimate knowledge of the available wheat genotypes, appropriate selections can be made for commercial application in order to conserve and exploit the diversity of the wheat landraces.
Authors:Yigang Xu, Xiaolin Zong, Bing Han, Yijing Li and Lijie Tang
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. entericaCholeraesuis 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.
Authors:Diandou Xu, Zhi Zhang, Qiaolong Jiang, Yifan Li and Zhifang Chai
Passive air samplers (polyurethane foam disks) were deployed at 25 urban sites and 66 rural sites over the period of July
to October 2005, partly between October 2005 and January 2006 for about 120 days across China, and analyzed for extractable
organo-chlorine /-bromine /-iodine (EOCl/EOBr/EOI) and polychlorinated biphenyls (PCBs) using hybrid neutron activation analysis
(NAA) combined with gas chromatographymass spectrometry (GC-MS). The average concentration of EOCl, EOBr, EOI and ΣPCBs among
all the sites were 173.7, 3.5, 1.0 and 0.74 ng/d, respectively. Higher values of EOCl/Br/I and PCBs were detected in the areas
of high usage and high emission, which were linked to relatively high-income areas in China, while lower in the west ill-developed
region of China, which indicated that these pollutants mainly came from industrial pollution. Higher EOCl contents in traffic
areas stated that the exhaust emission from vehicle was another main source of organochlorines in the air. The relative proportions
of the known organochlorines (84 PCB congeners) to total EOCl were 0.02–3.0%, which implied that most of EOCl measured in
air were unknown.
Authors:Yaohui Li, Kaiming Liang, Bo Xu and JianWei Cao
Li2O–Al2O3–SiO2 glass-ceramics were prepared with Ta2O5 as nucleating agent, the crystallization mechanism and microstructure evolution were investigated by DTA, XRD, and SEM technologies.
With increasing amount of Ta2O5 from 2 to 6 mol%, the crystallization activation energy decreased from 297.73 to 218.66 kJ mol−1, while the crystallization index increased from 1.76 to 3.39. In addition, the cluster of dendritic crystals and lamellar
structure obtained in T-2 glass-ceramics indicated a typical two-dimensional crystallization mechanism, and the formation
of spherical β-quartz solid solution in T-4 specimens, with average size of 50–70 nm, was mainly due to bulk crystallization
mechanism. It was considered that Ta2O5 promoted the nucleation and crystallization of LAS glass by precipitating the crystalline precursor phase of Ta2O5, which acted as nuclei for the subsequent crystal growth. Eventually, the diffusion and crystallization process, microstructure
morphology, as well as the secondary grain growth were also investigated.
Effects of gaseous hydrogenation on crystallization behavior of melt-spun Mg63Pr15Ni22 amorphous ribbons have been investigated. The crystallization peak temperature Tp1 shifted to higher temperature with increasing heating rate for the un-hydrogenated Mg63Ni22Pr15 metallic glass, however, it is nearly unchanged for the hydrogenated sample. The present work indicates that the crystallization
is a nucleation-and-growth process for the un-hydrogenated Mg63Ni22Pr15 metallic glass. However, the crystallization of hydrogenated sample begins with nucleation and then diffusion-controlled
growth takes place.
Authors:Xiang Sun, Xiang Xu, Min Liu, Lin Li and De Sun
The enthalpies of dilution of matrine (MAT) in pure water and aqueous sodium chloride solutions were determined by isothermal
titration microcalorimetry at 298.15 K, and the corresponding homogeneous enthalpic interaction coefficients were calculated
according to the modified McMillan–Mayer model. The values of enthalpic pair-wise interaction coefficients, h2, are all positive and become more positive with increasing concentration of sodium chloride.