排序方式: 共有51条查询结果,搜索用时 31 毫秒
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氨基糖苷类抗生素混合物对蛋白核小球藻的时间依赖性毒性 总被引:1,自引:0,他引:1
越来越多的研究表明,污染物在不同暴露时间具有不同的毒性变化规律。以4种氨基糖苷类抗生素,硫酸安普霉素(APR)、双氢链霉素(DIH)、硫酸新霉素(NEO)和硫酸链霉素(STS)为混合物组分,应用直接均分射线法和均匀射线法对4类抗生素设计出6组二元混合体系和4组三元混合体系,每个混合物体系设计5条射线共50条射线,采用时间毒性微板分析法(T-MAT)测定这些抗生素混合物射线在6个暴露时间点(即0、12、24、48、72和96 h)对蛋白核小球藻(C.pyrenoidosa)的生长抑制毒性。结果表明,抗生素二元和三元混合物系的50条射线对C.pyrenoidosa毒性均具有明显的时间依赖性,即混合物射线的毒性随着暴露时间的延长而增强;以半数效应浓度(EC50)的负对数p EC50为毒性指标,不同混合物体系的时间毒性变化规律不同,有的混合物从0 h开始,毒性随时间延长逐渐增强,有的从12 h或24h,甚至48 h后,毒性开始迅速增加;同一混合物体系中不同射线的毒性因组分浓度比的变化而变化,即混合物射线的毒性随毒性大的组分比例增加而增强。 相似文献
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微型化DNS法测定多糖水解液中还原糖的质量浓度 总被引:1,自引:0,他引:1
传统DNS比色法适用于常规还原糖含量的检测,但难以检测微量的样品以及快速检测大批量样品,故对传统DNS法进行改进,建立微型化DNS法测定多糖水解液中还原糖含量的方法.以DNS为显色剂,采用酶联免疫测定仪微盘比色测定多糖水解液中的还原糖含量,考察该方法的重复性和精确性,并与传统DNS法进行比较,结果表明:微型DNS法标准曲线线性良好,并且有良好的重复性和精密度,与传统DNS法相比,对样品的测定结果进行t检验,P=0.118 1(>0.05)表明两种方法检测到结果相一致.微型化DNS法在保证检测精确性的前提下有效减少了样品检测损耗量和提高了检测效率,有望扩大DNS比色法至微量化及批量化样品的还原糖含量检测领域. 相似文献
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Lydie Marešová Barbora Hošková Eva Urbánková Roman Chaloupka Hana Sychrová 《Yeast (Chichester, England)》2010,27(6):317-325
pHluorin is a pH‐sensitive variant of green fluorescent protein for measuring intracellular pH (pHin) in living cells. We constructed a new pHluorin plasmid with the dominant selection marker KanMX. This plasmid allows pH measurements in cells without auxotrophic mutations and/or grown in chemically indefinite media. We observed differing values of pHin for three prototrophic wild‐types. The new construct was also used to determine the pHin in strains differing in the activity of the plasma membrane Pma1 H+‐ATPase and the influence of glucose on pHin. We describe in detail pHluorin measurements performed in a microplate reader, which require much less hands‐on time and much lower cell culture volumes compared to standard cuvettes measurements. We also utilized pHluorin in a new method of measuring the buffering capacity of yeast cell cytosol in vivo, shown to be ca. 52 mM /pH for wild‐type yeast and moderately decreased in mutants with affected potassium transport. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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ABSTRACT: Single laboratory method performance parameters, including the calibration curve, accuracy, recovery, precision, limit of detection (LOD), and limit of quantification (LOQ), were evaluated for the analysis of total food folate by the trienzyme extraction and microplate assay with Lactobacillus casei subsp. rhamnosus . Standard Reference Material (SRM) 1546 (meat homogenate), SRM 2383 (baby food composite), SRM 1846 (infant formula), Certified Reference Material (CRM) 121 (wholemeal flour), and CRM 485 (mixed vegetables), representing a broad selection of food matrices, were used to evaluate the performance of the method. A generated 4-parameter logistic equation of the calibration curve was y = (0.0705 − 1.0396)/(1 + ( x /0.0165) 1.3072 ) + 1.0396 ( P < 0.0001). The test of parallelism demonstrated that matrix components in the food extracts did not affect the accuracy. Measured values of the SRMs and CRMs were within their certified or reference values. Recoveries for all reference materials met the requirements of the AOAC guidelines for single laboratory validation. Precision measured as repeatability, including simultaneous and consecutive replicates for each SRM and CRM, met the Horwitz criterion. LOD and LOQ values were 0.3 and 0.6 μg/100 g, respectively. The results showed that trienzyme digestion using α-amylase, PronaseR , and conjugase from chicken pancreas coupled with a 96-well microplate assay provided a highly accurate, reproducible, and sensitive method for the determination of folate in a variety of foods. 相似文献
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《国际智能与纳米材料杂志》2013,4(3):179-198
The utilization of piezoelectric materials in MEMS devices under harsh environments has gained affordable appreciations due to its unique mechanical and electrical material properties. However, the reliability of MEMS devices triggered by fatigue damage remains elusive and needs to be further explored. Here, we present a continuum constitutive model for piezoelectric materials containing a substantive amount of randomly dispersed microcracks. The constitutive equation of the piezoelectric materials with microcracks is formulated via Helmholtz free energy by combining the Kachanvo damage evolution law and the Chaboche fatigue damage development to express the fatigue damage growth. A case of the fatigue damage analysis of the piezoelectric microplate with transverse matrix cracks in the status of plane stress is presented by adopting the von Karman’s plate theory. With numerical schemes employed, the effect of cyclic impulsive loadings and electrical loadings on the fatigue damage and fatigue life prediction of a piezoelectric microplate is investigated and discussed. The findings provide valuable insights into the fundamental mechanism of reliability in piezoelectric MEMS devices due to cyclic loadings, thereby offering new ways to exploit and fabricate the piezoelectric-based MEMS devices suitable for harsh conditions. 相似文献
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蒽酮比色法快速测定大麦叶片中可溶性糖含量的优化 总被引:2,自引:0,他引:2
ZHANG Shu-wei ZONG Ying-jie FANG Chun-yan HUANG Sai-hu LI Jing XU Jian-hu WANG Yi-fei LIU Cheng-hong 《食品研究与开发》2020,41(7):196-200
以大麦嫩苗鲜叶为试验材料,对经典蒽酮比色法反应体系中蒽酮及硫酸的用量、反应温度、反应时间、样品提取时间以及叶片取样部位等条件进行优化研究。结果表明,对蒽酮硫酸反应体系进行优化后的条件为:最佳蒽酮用量为100μL、浓硫酸为1 000μL;显色反应温度为100℃,最佳反应时间7 min;样品提取时间以沸水浴10 min为宜;大麦叶片取样部位以倒二叶顶部较为合适。该方法操作简单、快速、实用性强,可为植物样品可溶性糖指标快速筛选提供有效的参考价值。 相似文献
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比色法与HPLC法对比测定桑叶茶中γ-氨基丁酸的含量 总被引:3,自引:0,他引:3
应用酶标仪定量分析桑叶茶(下称桑茶)中的γ-氨基丁酸(γ-aminobutyric acid,GABA),经优化的显色体系在波长640 nm处有最大吸收波长,建立GABA质量浓度与吸光度的相关方程。比色法与高效液相色谱(high performance liquid chromatography,HPLC)法所测GABA在所需质量浓度范围内线性关系均良好(R2>0.99)。比色法的平均相对标准偏差为1.28%,平均回收率为98.46%;HPLC法的平均相对标准偏差为0.37%,平均回收率为100.10%。表明2?种检测方法均可准确定量测定GABA。经t检验比较分析,无统计学差异。采用比色法对桑叶与桑茶进行检测,结果表明不同加工方式会影响GABA含量。比色法方便快捷,更适合大量样品的检测。 相似文献
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A. A. Emami 《热应力杂志》2016,39(12):1499-1522
Based on Mindlin plate theory, thermoelastic damping (TED) analysis of functionally graded microplates are performed using strain gradient theory. System of governing differential equations coupled with thermal effects and the corresponding boundary conditions are derived using Hamiltonian’s principle. Afterward, temperature gradient is obtained by solving the heat conduction equation analytically. Then, the free vibration problem is analyzed to achieve the natural frequencies and quality factor due to TED. The results indicate that the effect of length-scale parameter on the TED of microplate is significant. 相似文献