The Effect of Sulfonated Graphene on the Rheological Properties of Cement Paste.

With unique 2D nanostructures and excellent properties, graphene and its derivatives are a class of advanced nanosized reinforcements for cementitious materials. Sulfonated graphene (SG), one of the most important modified graphene materials, possesses sulfonate groups on the surface and significantly improves the mechanical and thermal properties of cement-based composites. It is important to investigate the influence of SG on cement-based materials as it is a prerequisite for practical applications. Herein, SG was prepared and introduced into cement paste to investigate its influence on the rheological properties of cement paste. With the increased addition of SG, a stable slurry was gradually obtained with low fluidity and high rheological parameters. The mechanism of the SG effect on the rheological properties of cement paste was also illustrated. Because of the high specific surface area and sulfonate groups of SG nanosheets, a large amount of flocculated structure was created by the complexing effect, chemical interaction, physical interaction and mechanical interlocking between SG and hydrated/unhydrated cement particles. Furthermore, polycarboxylate ether (PCE) superplasticizer was introduced to ensure fluidity and transportability in the practical application of SG. The results in this work lay a foundation for the practical application of modified graphene in cementitious materials.

[Isolation and Study on the Aflatoxin Genes of Aflatoxin-producing Fungi in Paprika Samples in Chengdu].

OBJECTIVE: To isolate aflatoxin-producing strains from paprika samples and to do a preliminarily study on the relationship between aflatoxin-producing ability and the genes aflR, omt-1 and ver-1. METHODS: Fungi were isolated by traditional culture method. Potential aflatoxin-producing strains were screened by phenotypic traits and multiplex PCR. After these potential aflatoxin-producing strains cultured in the toxigenic culture medium, the levels of aflatoxin B, (AFB1) of the cultures were tested with ELISA method. The phylogenetic tree of aflR, omt-1 and ver-1 was constructed to explore the relationship between these genes and the AFB1-producing capacity. RESULTS: 17 potential aflatoxin-producing fungi were isolated. The ratio of positive toxigenic strains is 64. 71%. 11 isolates were positive in AFB1 detection while existing high sequence homology with AS 3. 4408, 6 isolates were negative in AFB1 detection while existing high sequence homology with Aspergillus oryzae. CONCLUSION: Aspergillus flavus are potential candidates for aflatoxin control. Not all Aspergillus flavus have AFB1-producing capacity, aflR gene had a direct relation to AFB1-producing capacity, while ver-1 and omt-1 were related to the level of AFB1 producing.

[Non-modified magnetic beads coupled with multiple real-time PCR for detection and quantification of mycotoxigenic fungi in paprika samples].

OBJECTIVE: To establish a method for detecting 3 common toxigenic molds (Aspergillus, Penicillium, and Fusarium) based on non-modified magnetic beads coupled with multiple real-time PCR (NMB-multiple qPCR). METHODS: The primers and genus-specific probes were designed based on the rDNA sequences to develop a multiple real-time PCR using non-modified magnetic bead to enrichment of fungal spores. The sensitivity, specificity and repeatability of this assay were evaluated. RESULTS: The detection limit of this assay for spiked samples was 10(4) CFU/g, demonstrating a 10-fold greater detection sensitivity of this assay than that of real-time PCR. The NMB-multiple qPCR assay also showed good specificity and reproducibility and yielded comparable results with those by traditional colony counting method for spiked samples (P>0.05). CONCLUSION: NMB-multiple qPCR assay we established allows rapid and sensitive detection of common mycotoxigenic fungi in paprika.