催化剂催化二氧化硫共聚的研究进展

目前有关二氧化硫(SO2)减排技术的研究成熟且较多,而SO2的高效利用却研究较少。SO2与烯烃、环氧化物及其他单体共聚制备含硫高分子是利用SO2的有效途径。探索和开发新型高效催化剂是提高其共聚反应效率及调控共聚物结构的根本手段和方法,因此,高效催化剂成为该领域的研究重点。文中分析比较了有机金属、过氧化物、Lewis酸、Lewis碱等催化剂对SO2与单体共聚制备含硫高分子的影响规律,希望对SO2催化共聚的研究和发展提供参考。

cDNA-AFLP analysis reveals altered gene expression profiles involved in juice sac granulation in pummelo(Citrus grandis)

Citrus fruits produced in China are often affected by granulation.Granulation is an altered physiological state of citrus fruits occurring usually before harvest but whose underlying mechanisms remain elusive.In this study,cDNA-AFLP technology enabled the identification of 116 granulation-associated genes in pummelo(C.grandis)juice sacs.Differentially expressed transcript-derived fragments(TDFs)were shown to be mainly involved in biological regulation and signal transduction,carbohydrate and energy metabolism,nucleic acid,protein metabolism,stress responses,and cell metabolism.Therefore,granulation in pummelo juice sacs seems to involve the following alterations:(1)changes in hormone levels;(2)activation of metabolic pathways related to ATP and sugar synthesis to produce more energy;(3)nucleic acid accumulation and increased protein degradation;(4)activation of stress-responsive metabolic pathways;(5)accelerated juice sac senescence.Our findings provide an overview of differential responses occurring at the transcriptional level in granulated juice sacs,thus revealing new insights into the adaptive mechanisms underlying this altered physiological state in‘Guanximiyou'pummelo(C.grandis)juice sacs.

Synergistic effect of vermiculite and submerged plants on lake sediments

The synergistic effect of vermiculite and the submerged macrophytes Vallisneria spiralis and Hydrilla verticillata on lake sediment was studied using diffusive gradients in thin films(DGT)technology.The dynamics of phosphorus(P)fractions in sediment,the labile-P and labile-S in the water-sediment continuum,and the microbial community in the rhizosphere were studied.Vermiculite effectively promoted reproduction of microorganisms in the sediments Microbial abundance in treatments containing V.spiralis with sediments containing 10%added vermiculite,and H.verticillata containing 50%added vermiculite being 1.7 and 3.5 times higher than the controls which contained no added vermiculite.Acidobacteria and Proteobacteria populations,which are both beneficial for the sediment microenvironment,were higher in treatment groups containing vermiculite.The bioavailable-P in treatment groups containing added vermiculite was lower at the sediment-water interface,with a correlating decrease of TP by between 63%and 91%in the overlying water.This suggests that vermiculite can affect the release of labile P and facilitate the assimilation of nutrients by macrophyte roots.Additionally,vermiculite can improve the Oxidation-Reduction potential and further reduce sulfide toxicity to plants.These results provide theoretical guidance and technical support for the application of vermiculite combined with submerged plants for the remediation of eutrophic lakes.

Effects of vermiculite on the growth process of submerged macrophyte Vallisneria spiralis and sediment microecological environment

Ecological restoration is one of the hot technologies for the reconstruction of eutrophic lake ecosystems in which the restoration and propagation of submerged plants is the key and difficult step. In this paper, the effect of vermiculite on the growth process of Vallisneria spiralis and sediment microenvironment were investigated, aiming to provide a theoretical basis for the application of vermiculite in aquatic ecological restoration. Results of growth indexes demonstrated that 5% and 10% vermiculite treatment groups statistically promote the growth of Vallisneria spiralis compared to the control. Meanwhile, the results of ecophysiological indexes showed that photosynthetic pigment, soluble sugar content, superoxide dismutase(SOD), and catalase(CAT) activity of 5% and 10% group were increased compared with the control while the malondialdehyde(MDA) content exhibited the opposite result(p < 0.05), which illustrated that vermiculite can improve the resistance of plants and delay the aging process of Vallisneria spiralis. In addition, result of PCA(Principal Component Analysis) demonstrated 5% and 10% group has improved the sediment physical conditions and create more ecological niche for microorganisms directly, and then promoted the growth of plants. The dissolution results showed that vermiculite can dissolve the constant and trace elements needed for plant growth. Furthermore, the addition of vermiculite increased the diversity of microorganisms in the sediments, and promoted the increase of plant growth-promoting bacteria and phosphorus-degrading bacteria. This study could provide a technique reference for the further application of vermiculite in the field of ecological restoration.