GC—MS分析不同方法提取的大黄挥发性成分

分别采用顶空进样法和超临界CO2萃取法提取大黄挥发性成分,采用GC-MS结合保留指数进行检测分析。顶空进样法分析鉴定出8种挥发性成分,超临界CO2萃取法鉴定出15种挥发性成分。两种提取方法分别侧重于不同类型的挥发性成分,利用GC-MS结合保留指数进行定性分析,更快速准确。     

高效液相色谱法检测食品接触材料中三聚氰酸的残留量

建立了一种用液相色谱技术检测分析食品接触材料中三聚氰酸残留量的方法。样品采用体积分数为10%的乙醇溶液作为提取溶液,超声提取。色谱分离采用氨基色谱柱,流动相为乙腈-磷酸盐缓冲溶液(体积比为75∶25),二极管阵列检测器检测。在优化条件下,三聚氰酸质量浓度在0.5～50 mg/L范围内与色谱峰面积线性关系良好,检出限(S/N=3)为0.1 mg/L。在0.1%的添加水平下,三聚氰酸的回收率在80%～93%之间,测定结果的相对标准偏差为1.36%～2.54%(n=6)。揭示了原料中三聚氰酸残留量与成型品的三聚氰酸迁移量的正相关关系。结果表明,该法简便、快速,可准确测定食品接触材料中三聚氰酸残留量。     

Investigation on catalyzed combustion of wheat straw by thermal analysis

Combustion of wheat straw incorporating TiO₂, CuO and MnO₂ was investigated by means of thermal analysis carried out at 20 °C/min in the temperature range from 50 °C to 900 °C. Combustion characteristic indexes had been put forward to describe wheat straw combustion characteristics. All the results showed that the catalysis of the catalysts to the wheat straw combustion had been embodied in facilitation of the volatile matters release from wheat straw, which reduced the temperature of the maximum combustion rate, and the relative active sequence of catalysts to the ignition characteristic could be improved remarkably. The catalysis of different catalysts to the Devolatilization Index could be described as follows: MnO₂ > TiO₂ > CuO, and the relative active sequence of catalysts to the Combustion Characteristic Index could be described as follows: CuO > TiO₂ > MnO₂.     

海地瓜多糖脱色工艺研究

比较了活性炭、H2O2及大孔树脂对海地瓜多糖的脱色效果。从脱色率及多糖保留率两方面进行考察,树脂D392处理优于活性炭和H2O2,对其脱色工艺进行优化,通过响应面实验建立了数学模型,并确定树脂D392脱色的最优工艺为时间:5h,pH 10,温度:60℃,此时,脱色率达(84.2±0.6)%,多糖保留率为(82.9±1.1)%。研究工作有利于海参多糖品质的提高,为海参多糖后续研究及应用奠定了基础。     

金属材料疲劳损伤检测的非线性声学方法*

金属材料的疲劳损伤有前期、后期两个阶段,前期疲劳损伤主要来源于位错,而随着疲劳程度的不断加深,位错密度也不断的增加,这将导致疲劳后期微裂纹的产生。这两个阶段产生声学非线性效应的机理不同,分别用位错模型、微裂纹模型对其产生非线性效应的机理进行了阐述,并对不同阶段的疲劳试样进行了相关实验研究。实验结果表明:对于材料早期疲劳损伤,随着疲劳程度的增加,其接收声波信号中的非线性谐波成分越来越显著,并且随着激励电压的增加,非线性效应更加明显,因此可用接收信号中的谐波激发情况来评估材料的早期疲劳损伤程度。而对于材料疲劳后期出现微裂纹后,其产生的非线性与早期疲劳损伤相比,谐波成分更加丰富,并且随激励电压的增加谐波幅度增加明显,可据此来判断材料中的疲劳损伤阶段。     

共沉淀法合成ZnMoO4粉体及其抗菌性能

以Zn(NO₃)₂·6H₂O、(NH₄)₆Mo₇O₂₄·4H₂O为主要原料,采用共沉淀法合成ZnMoO₄粉体。利用XRD、SEM等测试方法对合成样品的物相组成、微观结构进行表征。以培养的大肠杆菌为消杀对象,研究了不同热处理温度下的样品对大肠杆菌的抗菌性能。结果表明,前驱体主要为非晶态,含少量ZnMoO₄、Zn₂Mo₃O₈、Zn(OH)₂和MoO₃;前驱体经400~600 ℃、保温30 min热处理,其产物转化为ZnMoO₄,且随着热处理温度的升高,合成的ZnMoO₄晶型逐渐完善,抗菌性能增加,当热处理温度为600 ℃时,可以获得结晶良好的ZnMoO₄,其晶粒呈颗粒状和片状,平均粒径约为1.5 μm。不同热处理温度合成的ZnMoO₄均具有一定的抗菌性能,其中经600 ℃热处理得到的ZnMoO₄具有最佳抗菌性能,经过24 h抗菌检测,其抗菌率达到99.2%,在商用涂料料浆中外加5%的ZnMoO₄粉体,所制备涂层对大肠杆菌的抗菌率达到95.7%,表明ZnMoO₄及其涂料具有良好的应用前景。     

固体氧化物燃料电池运行初期电化学性能演变机制

固体氧化物燃料电池(solid oxide fuel cell,SOFC)是一种清洁高效的发电装置,其运行中的性能衰减受到众多因素的影响,如何分辨这些因素的贡献、并在此基础上确定衰减的主导因素,对于更有针对性地提升SOFC的运行寿命至关重要.广泛的测试结果表明,SOFC的电化学性能在运行初期(约前100 h)会发生最为...     

交联壳聚糖树脂与Zn2+的配位作用

研究了甲醛、环氧氯丙烷交联壳聚糖树脂(Chitosan crosslinked by aldehyde and epichlorohydrin,AECTS)吸附Zn2 后对树脂结构及性能所产生的影响.用FTIR、XRD、TG、DsC和SEM对吸附产物进行了结构表征,并深入分析了AECTS与Zn2 之间的作用机理.结果表明,Zn2 与AECTS中的氨基发生配位而被吸附;AECTS吸附Zn2 后,结晶度下降、总体上热稳定性变差:Zn2 对AECTS的主链分解具有明显的催化功能;Zn2 的配位使得AECTS的表面形态发生了改变.     

交联壳聚糖树脂与Zn2+的配位作用

研究了甲醛、环氧氯丙烷交联壳聚糖树脂(Chitosan crosslinked by aldehyde and epichlorohydrin,AECTS)吸附Zn2 后对树脂结构及性能所产生的影响.用FTIR、XRD、TG、DSC和SEM对吸附产物进行了结构表征,并分析了AECTS与Zn2 之间的作用机理.结果表明,Zn2 与AECTS中的氨基发生配位而被吸附;AECTS吸附Zn2 后,结晶度下降、总体上热稳定性变差;Zn2 对AECTS的主链分解具有明显的催化功能;Zn2 的配位使得AECTS的表面形态发生了改变.     

Wnt/β-catenin signaling stimulates the self-renewal of conjunctival stem cells and promotes corneal conjunctivalization

Limbal stem cell deficiency causes conjunctivalization characterized by the covering of the corneal surface with conjunctival epithelium. However, the driving force for the encroachment of these conjunctival cells is unclear. Conjunctival stem cells are bipotent stem cells that can proliferate and differentiate into conjunctival epithelial cells and goblet cells to maintain regeneration of the conjunctival epithelium. Here, we show a robust proliferative response of conjunctival stem cells and upregulation of Wnt2b and Wnt3a gene expression in the conjunctivae of mice with induced limbal stem cell deficiency. Topical application of the Wnt/β-catenin signaling activator CHIR resulted in increased proliferation of ΔNp63α-positive stem cells in the basal layers of the bulbar and forniceal conjunctivae and enhanced invasion of conjunctival epithelial and goblet cells into the corneal surface. We also found that in cultures of stem cells isolated from the human conjunctiva, Wnt/β-catenin pathway activation improved the expansion of the ΔNp63α/ABCG2 double-positive cell population by promoting the proliferation and preventing the differentiation of these cells. These expanded stem cells formed a stratified epithelium containing goblet cells under airlift culture conditions. Our data reveal that Wnt/β-catenin signaling contributes to the pathological process of limbal stem cell deficiency by promoting the self-renewal of conjunctival stem cells and suggest that these cells are a driving force in corneal conjunctivalization.Subject terms: Self-renewal, Stem-cell research, Experimental models of disease