Sulfur production from smelter off-gas using CO–H2 gas mixture as the reducing agent over modified Fe/γ-Al2O3 catalysts

A series of modifiedγ-Al_2O_3supported iron-based catalysts(M-Fe/γ-Al_2O_3)was developed to reduce SO_2in actual smelter off-gases using CO–H_2gas mixture as reducing agent for sulfur production.Used as modifiers,three metal additives—Ni,Co,and Ce were added to Fe/γ-Al_2O_3catalysts.Changes in catalyst structure and active phase were characterized with X-ray diffraction,XPS,SEM,and EDS.The reduction ability of catalysts was exhibited via CO-TPR.The prepared catalysts only need to be pre-reacted for a period of time,eliminating the need for presulfidation treatment.Reaction conditions were optimized in a fixed bed reactor to achieve high SO_2conversion and sulfur selectivity.XRD characterization was carried out to verify the resulting sulfur products.Combining in situ infrared characterization and catalyst evaluation of support and active component,the reaction mechanism was investigated and proposed.

哺乳动物纤毛/鞭毛内运输在精子形成中的作用及机制研究进展

纤毛/鞭毛是真核生物细胞表面伸出的进化保守的细胞器,独特的位置和特性使它们在细胞运动和信号传递等生命过程发挥重要作用。哺乳动物纤毛/鞭毛的组装和维持都依赖纤毛/鞭毛内运输(intraflagellar transport,IFT)。IFT是由IFT复合体A和复合体B在驱动蛋白或马达蛋白驱动下的双向运输系统。该过程可将货物蛋白在胞体的合成位点与纤毛/鞭毛尖端的装配位点之间进行运输。鞭毛是哺乳动物精子产生动力的特异性细胞器,其完整性对精子正常功能至关重要。近年来研究表明,IFT在哺乳动物精子鞭毛形成和雄性生殖能力方面必不可少。本文对参与IFT的蛋白在精子鞭毛形成中的作用和机制进行了综述,以探讨其在男性不育症中的发病机制,为不育症的诊断和治疗提供理论基础。

精子变形过程中组蛋白-鱼精蛋白替换调控机制

精子形成是精子发生的最后阶段,圆形精子细胞经历了一系列的形态变化和染色质凝聚,形成了具有物种特异性的成熟精子。组蛋白–鱼精蛋白替换是精子形成过程中的重要事件。在组蛋白–鱼精蛋白替换过程中,组蛋白首先被睾丸特异性的组蛋白变体所替代,随后过渡蛋白整合到细胞核中,最后过渡蛋白被鱼精蛋白取代。组蛋白–鱼精蛋白替换缺陷可能导致无精子症、少精子症或畸精症,从而导致男性不育。本文系统总结了组蛋白–鱼精蛋白替换过程中的调控机制研究进展,以期为男性不育症的诊断和治疗提供理论基础。

Catalytic activation of peroxodisulfate using shape-controlled cerium-manganese composite oxide for phenol degradation:Kinetics and degradation pathway investigation

Phenol-containing wastewater is typical organic wastewater,and its treatment is arduous.An advanced method to treat this type of wastewater is persulfate activation.Environmentally friendly ceriummanganese composite oxide materials were synthesized by hydrothermal method and applied to the phenol degradation process.Various ratios of cerium and manganese,as well as the amount of sodium hydroxide,were investigated.The solid solutions of cerium and manganese were formed and confirmed by X-ray diffraction(XRD) and transmission electron microscopy(TEM).H_(2)-temperature programmed reduction(H_(2)-TPR) and X-ray photoelectron spectroscopy(XPS) were utilized to analyze the synergistic effect of cerium and manganese.It is found that there is a transformation between Ce^(4+)/Ce^(3+) and Mn^(2+)/Mn^(3+),which makes the material more trivalent manganese and thereby increases the catalytic activity.The effect of materials in catalyzing phenol degradation by peroxodisulfate(PDS) under various preparation conditions is discussed and high-effciency removal of phenol can be achieved and the removal rate at 180 min is close to 100%.The kinetic of this process was investigated and activation energy of phenol degradation is 62,35 kJ/mol.The degradation pathway of phenol was studied and it is found that PDS can be activated by low metal ions and the OH and SO_(4·)^(-)radicals play crucial roles according to the quenching experiments.

杠杆增速、部门差异与金融危机——“结构性去杠杆”的实证分析与我国杠杆政策的讨论

本文通过1980-2017年42个经济体的分部门杠杆率数据,考察了杠杆增速与部门差异如何影响金融危机发生的概率。研究发现,杠杆增速比杠杆水平对金融危机的影响更为显著,且各部门的杠杆增速对宏观金融风险具有异质影响。相比于政府部门,私人部门(特别是居民部门)的相对杠杆增速越高,一国发生金融危机的概率越大。为有效缓释宏观金融风险,我国应以稳杠杆替代去杠杆,以结构性去杠杆为基本思路,对政府、企业、居民部门设置差异化的杠杆要求。

氧化酯化反应催化剂的研究进展

本工作综述了近年来醛或醇氧化酯化催化剂的研究进展,介绍了均相催化剂和非均相催化剂的研究情况,其中均相反应体系,催化剂不易分离且能耗较大,价格普遍偏高,适用于氧化酯化的均相反应体系难以工业化。非均相反应体系在工业化方面具有很大优势,催化剂分离简单易还原、可回收再利用等,但同样存在稳定性较差及收率较低的问题。分析了贵金属催化剂和非贵金属催化剂的合成、结构及催化醛氧化酯化性能,总结了部分催化剂催化醛氧化酯化的反应机理。通过各种制备方法调控催化剂的结构、形貌、比表面积,进而暴露大面积活性面及延长催化剂的使用寿命来提高催化剂的经济效益。展望了氧化酯化反应催化剂的研究方向,贵金属催化剂由于成本限制,非贵金属催化剂将是未来醛氧化酯化领域重点研究的方向。要点:(1)综述了醛与醇一步氧化酯化催化剂的研究进展。(2)重点介绍了均相催化剂与非均相催化剂的研究情况。(3)展望了氧化酯化反应催化剂的研究方向。