检验检疫机构签发的证单一般以验讫日期作为签发日期。( )

为了探究影响电热的因素，小伟设计了如图所示电路，烧瓶中盛有质量、初温均相等的煤油，R_甲＞R_乙。

（1）为了在较短的时间内达到明显的实验效果，选用煤油而不是用水，主要是由于

_______________________________________________________________________。

（2）通电一段时间后，比较两烧瓶中温度计的示数，是为了探究电热与__________的关系。

（3）要利用此装置来探究电热与电流的关系，你还需要的操作是　　　　　　　　　　　

_______________________________________________________________________________。

（4）将此装置改装后可测量煤油的比热容，如图所示。测量时，分别向两个相同的烧瓶中加入初温均为t₀、质量相等的水和煤油，通电一段时间后，分别读出温度计的示数为t_水、t_煤油，请写出煤油比热容的表达式c_煤油=                                      

（已知水的比热容为c_水）。

Celebrate. Celebrate. Physicians are delighted with a Food and Drug Administration (FDA) advisory panel’s recommendation earlier this year that Vioxx and its cousins Bextra and Celebrex (all medicines known as Cox-2 inhibitors) should remain on the market, despite evidence they increase heart disease risk in some people. The panelists reached their decision after weighing all the data and concluding the benefits of these pain-relieving drugs outweighed the risks.
Specifically, these scientists acknowledged that, for some patients, these prescription drugs were uniquely effective in reducing pain from arthritis and other causes. For others—concerned about ulcers associated with aspirin and other OTC analgesics—the Cox-2 inhibitors offered the advantage of minimizing potentially serious effects of stomach irritation.
Now is an appropriate time for everyone to take a fresh look at the benefit-risk equation for Vioxx and the other Cox-2 inhibitors.
The risks-increased risk of heart disease in some who use the drugs—have been well publicized. Much less publicity has been given to a spectrum of real and potential benefits that go way beyond reduced risk of stomach irritation. These little-discussed benefits would have been lost, perhaps permanently-had Vioxx, Bextra and Celebrex been driven from shelves in pursuit of perfect safety, an unattainable goal.
For example, there is substantial evidence Cox-2 inhibitors can reduce development of colon polyps, which may become colon canceL Indeed. Celebrex is FDA-approved for those genetically prone to colon cancer. Ironically, the 2004 study that revealed the elevated heart attack risk of Vioxx was primarily designed to further establish the drug’s effectiveness in protecting against colon cancer. And while the results of that interrupted trial have not yet been published, there is good reason to believe they will confirm the protective effects against colon cancer established in research over the last 10 years.
At the time of its withdrawal from the market last fall, studies of Vioxx as well as the other Cox-2 drugs suggest that they had other anti-cancer properties as well, possibly reducing the risk of malignancies of a number of sites, including the lung and esophagus.
Had these drugs been dismissed, their untapped promise for prevention would have evaporated well before it was evaluated and applied to save lives. Fortunately, cooler and wiser heads prevailed.

When Cox-2 inhibitors were banned from sale, ______.

A．no research had been done about their effects

B．some studies demonstrated their usefulness

C．their risks were not well known to the public

D．some patients complained about the decision

航空运输中，危险品是由（）规定并公布的

A、中央军委

B、机长

C、民航主管部门

D、机场负责人

下列关于安全评估的描述中，错误的是（）

A．在大型网络中评估分析系统通常采用控制台和代理结合的结构

B．网络安全评估分析技术常被用来进行穿透实验和安全审计

C．X-Scanner可采用多线程方式对系统进行安全评估

D．ISS采用被动扫描方式对系统进行安全评估

在体育活动中，运动扭伤是比较常见的，如果你的同学不慎扭伤了踝关节，你应当为其做哪种应急处理（）

A.按摩

B.冷敷

C.热敷

D.贴膏药