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【单选题】
关于密码子的描述哪一项是错误的A.
每种氨基酸只有一个密码子
B.
密码子无种属差异
C.
每一个密码子代表一种氨基酸或肽链合成起始、终止的信息
D.
有些密码子不为任何氨基酸编码
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举一反三
【简答题】绝缘栅双极型晶体管具有速度快、 ( ) 阻抗高,通态电压低、耐压高、电容量大的特点。
【多选题】Write down the approaches of determination of trace elements in environmental sample. What are their limitations? How to reduce or eliminate these problems?
A.
The main analytical techniques used for determination of trace elements in environmental samples include:
B.
Atomic absorption spectrometry (flame or electrothermal) (AAS, ET-AAS), atomic fluorescence spectrometry (AFS), inductively coupled plasma optical (or atomic) emission spectrometry (ICP-OES or ICP-AES), neutron activation analysis (NAA), X-ray fluorescence (XRF), proton-induced X-ray emission (PIXE), spark source or isotope dilution mass spectrometry (SSMS, IDMS), electrochemical (anodic stripping voltammetry and polarography) or inductively coupled plasma-mass spectrometry (ICP-MS).
C.
The main limitations for most of these analytical methods are sensitivity or precision problems due to interferences and sample matrix effects.
D.
In some cases these problems have been reduced or eliminated by the use of pre-analysis separation schemes, matrix-matching of reagent blanks, calibration standards and samples; the inclusion of instrument background correction (AAS) or the coupling of hydride generation (HG), electro thermal vaporization (ETV), cold vapor (CV), flow injection (FI), ultrasonic nebulisation (USN) or laser ablation (LA) devices to the trace element detector.
【判断题】Trace elements and vitamins are not necessary for the growth of bacteria.
A.
正确
B.
错误
【简答题】案例1:甲与乙有线电视台签订有线电视收视服务合同,按时交纳了收视、维护费。电视台播放《还珠格格》时,插播大量广告。据此,甲向法院起诉,要求电视台停止插播商业广告,并赔偿其在收看《还珠格格》剧期间受到侵害的费用每集20元,共960元。电视台辩称,其不存在合同违约,侵权亦不能成立,不同意甲的请求。 试问乙电视台的行为是否构成侵权行为?
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