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排序方式: 共有6793条查询结果,搜索用时 62 毫秒
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目的:在改变测量条件和标准条件的情况下进行测量,对比测量结果,检测QuickCheck的性能,为加速器的晨检及检测结果判读提供依据。方法:通过改变输出剂量、射野大小、SSD、准直器角度和机架角,评估QuickCheck的检测能力。QuickCheck检测的射野参数与三维水箱等测量进行对比。结果:输出剂量增大1 cGy或减小6 cGy,射野改变≥0.2 cm;SSD减小2 cm或增大1 cm,准直器旋转≥2 o,机架角旋转≥6 o,检测结果超过阈值。与三维水箱测量的结果相比,平坦度、对称性(G/T)和(L/R)及剂量率分别相差3.84%、0.67%、0.47%,1.2 MU/min。结论:QuickCheck在检测输出剂量、射野大小、准直器角度、平坦度、对称性及剂量率方面准确度很高,能够满足日常加速器质量保证的需要。在检测SSD、机架角偏差方面能力较弱。 相似文献
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《International journal of antimicrobial agents》2014,43(2):189-194
Apart from the BENCHMRK study, there are no large observational experiences describing the long-term efficacy and safety of rescue regimens for human immunodeficiency virus type 1 (HIV-1) infection. Antiretroviral-experienced patients with detectable viraemia starting a raltegravir (RAL)-based regimen between March 2007 and June 2009 were consecutively enrolled and followed for ≥4 years. Data were censored at Week 206 for homogeneity. Of 333 patients, 258 (77.5%) were still on RAL-based therapy at Week 206, and 241 had undetectable HIV-1 RNA (73% in intention-to-treat analysis). Of the 75 subjects who discontinued RAL therapy, 36 were lost to follow-up, 15 changed their regimen due to virological failure, 2 simplified their regimen stopping RAL, 9 stopped all antiretrovirals and 13 died. Overall, 100 subjects (30.0%) had at least one detectable viraemia, but only 32 (9.6%) had true viral failure. Seventeen patients continued their failing regimen. ‘Blips’ were experienced by 53 patients (15.9%), whilst 15 (4.5%) had confirmed viral rebound due to adherence issues and were re-suppressed upon treatment re-introduction. In a multivariate analysis of predictors of interruption or failure, each baseline HIV-1 RNA log10 increase was associated with an adjusted hazard ratio for failure of 1.6; having more than 13 previous treatment courses also emerged as a predictor. Overall, adverse events were rare (n = 64), with 13 deaths. Tumours were mainly early events, often fatal (7/15), mainly non-Hodgkin's lymphomas (8), followed by hepatocarcinoma (2). RAL proved effective and well tolerated in this cohort, and few patients experienced viral failure after 4 years. 相似文献
84.
《Journal of food composition and analysis》2014,34(2):216-219
The main goal of this paper is to discuss the problems associated with antioxidant profiling in complex samples using a high-throughput HPLC system coupled with post-column derivatisation reactor. Based on the experimental data reported in the literature, we demonstrated that improper optimisation of temperature and/or pH assay conditions performed using an on-line derivatisation reactor may substantially change the antioxidant peaks ratio of targeted phytochemical compounds. It has been found that despite the relatively high stability of flavonoids at high temperature and under binary mobile phase HPLC conditions, the reaction of target compounds with common ABTS, FCR and DPPH radicals at elevated regions (particularly above 100 °C) dramatically changes their antioxidant activity values expressed, for example, as TEAC (Trolox equivalent antioxidant capacity) parameters. In principle, separation and detection processes of antioxidant profiling assay must not significantly affect the antioxidant activity of target compounds. In the case of foods eaten by humans or animals, critical experimental parameters such as pH and temperature concerning interaction of target analytes with derivatisation reagent should be as close as possible to the real physiological values. 相似文献
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Polybrominated diphenyl esters are emerging environmental contaminants with few toxicological data, being a concern for the scientific community. This study evaluated the effects of BDE-47 on the health of Oreochromis niloticus fish. The animals were exposed to three doses of BDE-47 (0, 0.253, 2.53, 25.3 ng g−1) every 10 days, for 80 days. The BDE-47 affected the hepatosomatic and gonadosomatic index in female and the condition factor by intermediate dose in both sexes. The levels of estradiol decreased and the T4 are increased, but the vitellogenin production was not modulated in male individuals. Changes in AChE, GST, LPO and histopathology were observed while the integrated biomarker response index suggests that the lowest dose of BDE-47 compromised the activity of antioxidant enzymes. The oral exposure to BDE-47 in environmental concentrations is toxic to O. niloticus and the use of multiple biomarkers is an attribution in ecotoxicology studies and biomonitoring programs. 相似文献
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目的 采用GC-MS指纹图谱并结合多元统计等方法评价不同产地孜然质量。方法 采用气相色谱-四极杆飞行时间质谱(GC-Q-TOF/MS)技术对孜然挥发油进行定性和定量分析,建立20批不同产地孜然的指纹图谱;运用"中药色谱指纹图谱相似度评价系统软件(2012年版)"进行相似度评价,并进行聚类分析和主成分分析。结果 建立的指纹图谱确定了33个共有峰,相似度均>0.961,主要成分包括枯茗醛、γ-松油烯-7-醛、α-松油烯-7-醛、γ-松油烯、o-伞花烃、桧烯、枯茗醇、3-p-孟烯-7-醛等,其相对含量约占总含量的99.7%。通过聚类分析可将20批孜然分为5大类。主成分分析得到4个主成分的累积方差贡献率为88.946%,其结果显示S20号样品综合得分较高。主成分分析与聚类分析结果基本一致。结论 该方法特征性强,仪器精密度、重复性和稳定性良好,可用于孜然挥发油及其相关产品的质量控制和评价。 相似文献