梨膏的流变学特性及其影响因素

目的 考察人为加糖、加胶后梨膏触变性及黏度的变化。方法 以鸭梨为实验材料,通过真空浓缩方式制备鸭梨膏,采用HR-10型流变仪对其流体类型、黏度、触变性进行测定。结果 鸭梨膏属于非牛顿流体,具体细分为无限接近牛顿流体的假塑性流体,具有剪切稀化特性和正触变特性;损耗模量G″总是大于储能模量G’,表现出液体黏性性质;剪切速率与剪切力变化关系符合PowerLaw方程,拟合效果良好(r2>0.99);温度显著影响梨膏黏度,黏度随温度升高而降低,二者关系符合Arrhenius方程,拟合效果良好(r2>0.99);可溶性固形物含量(solublesolidscontent,SSC)对黏度的影响符合指数函数关系,模型拟合效果良好(r2>0.99);SSC以及人为加糖、加胶处理对梨膏触变性、黏度影响显著(P<0.05),黏度随SSC的升高而增强,人为加胶、加糖加胶会导致梨膏黏度显著升高(P<0.05);触变性随SSC的升高而增强,同时人为加糖、加胶、加糖加胶处理会导致梨膏触变性显著减弱(P<0.05)。结论 人为添加糖、胶会导致梨膏的流变学特性发生改变。本研究可为工业...     

Adaptive and blind watermarking scheme based on optimal SVD blocks selection

To protect the ownership of the digital products, a novel adaptive and blind watermarking scheme is designed. Firstly, the underlying reason of image quality degradation in singular value decomposition (SVD)-based watermarking scheme is analyzed and the potential scenario causing visible destroy is pointed out. Then the optimal SVD blocks selection strategy is proposed to improve the imperceptibility. Different from other block selection rules devised by subjective evaluation means, our selection rule aims to retain the image quality as much as possible from the source. Furthermore, information entropy is utilized to achieve the purpose of adaptive embedding. In the experiment, the proposed watermarking scheme is tested under several attacks, such as noise attack, JPEG compression, blurring, sharping, and etc. Finally, the proposed watermarking scheme is compared with other existing schemes, and the experimental results demonstrate the robustness, imperceptibility and superior of the proposed watermarking scheme.

     

Responses of phanerochaete chrysosporium to toxic pollutants: physiological flux, oxidative stress, and detoxification

The white-rot fungus Phanerochaete chrysosporium has been widely used for the treatment of waste streams containing heavy metals and toxic organic pollutants. The development of fungal-based treatment technologies requires detailed knowledge of the relationship between bulk water quality and the physiological responses of fungi. A noninvasive microtest technique was used to quantify real-time changes in proton, oxygen, and cadmium ion fluxes following the exposure of P. chrysosporium to environmental toxic (2,4-dichlorophenol and cadmium). Significant changes in H(+) and O(2) flux occurred after exposure to 10 mg/L 2,4-dichlorophenol and 0.1 mM cadmium. Cd(2+) flux decreased with time. Reactive oxygen species formation and antioxidant levels increased after cadmium treatment. Superoxide dismutase activity correlated well with malondialdehyde levels (r(2) = 0.964) at low cadmium concentrations. However, this correlation diminished and malondialdehyde levels significantly increased at the highest cadmium concentration tested. Real-time microscale signatures of H(+), O(2), and Cd(2+) fluxes coupled with oxidative stress analysis can improve our understanding of the physiological responses of P. chrysosporium to toxic pollutants and provide useful information for the development of fungal-based technologies to improve the treatment of wastes cocontaminated with heavy metals and organic pollutants.     

Synthesis and bio-activity evaluation of scutellarein as a potent agent for the therapy of ischemic cerebrovascular disease

Scutellarein, the main metabolite of scutellarin in vivo, has relatively better solubility, bioavailability and bio-activity than scutellarin. However, it is very difficult to obtain scutellarein in nature compared with scutellarin. Therefore, the present study focused on establishing an efficient route for the synthesis of scutellarein by hydrolyzing scutellarin. The in vitro antioxidant activities of scutellarein were evaluated by measuring its scavenging capacities toward DPPH, ABTS^+•, ^•OH free radicals and its protective effect on H₂O₂-induced cytotoxicity in PC12 cells using MTT assay method. The results showed that essential point to the synthesis was the implementation of H₂SO₄ in 90% ethanol in N₂ atmosphere; scutellarein had stronger antioxidant activity than scutellarin. The results have laid the foundation for further research and the development of scutellarein as a promising candidate for ischemic cerebrovascular disease.     

水产品中氯霉素残留检测方法研究进展

氯霉素是一类广泛用于水产养殖中的抗生素,杀菌广谱,但残留在水产品中会对人体健康造成严重损害。本文综述了氯霉素的检测方法,包括微生物法、免疫分析法、色谱分析法和其他方法,并对各种方法的特点进行了综述。微生物学法是根据氯霉素对微生物的生理机能、代谢的抑制作用,来定性和定量检测氯霉素,该方法灵敏度不高;酶联免疫法灵敏度高,重复性好,适合水产品中氯霉素筛选;高效液相色谱法检测水产品中氯霉素具有快速、准确、高效等特点;气相色谱法检测水产品中氯霉素灵敏度高、准确,适合水产品中氯霉素的检测;液相色谱-质谱串联法是水产品中氯霉素残留检测最主要的分析方法,具有分离度高、快速、准确的特点。最后对氯霉素药物残留检测方法发展趋势进行了展望。     

向家坝水电工程施工供水控制系统探析

介绍基于西门子自动化控制系统的向家坝水电工程施工供水系统架构,分析系统在使用中出现的问题,并提出有效的解决方法。     

高效液相色谱法检测罗非鱼中氯霉素的残留量

目的建立高效液相色谱法(high performance liquid chromatography,HPLC)测定罗非鱼中氯霉素残留量。方法样品采用乙酸乙酯为溶剂提取,无水硫酸钠脱水,提取液氮气吹干,以10%甲醇溶液溶解,冷冻除去脂肪,经C18固相萃取小柱净化,采用C18固相萃取柱分离,流动相甲醇-水,梯度洗脱,流速为1 m L/min,紫外检测波长280 nm。结果在0.1~5μg/m L范围内,氯霉素浓度和峰面积线性关系良好,精密度较好,相对标准偏差(relative standard deviation,RSD)在3.12%~7.53%之间,检测限为0.02μg/g,回收率80.5%~107.1%。结论该方法前处理方法简单、快捷,对实验员身体危害小,准确度较好,适用于罗非鱼中氯霉素含量的测定。