患者，男，40岁，左下后牙遇冷不适，无自发疼．1年前患者曾一次补牙。检查：面树脂充填

有同学在讨论中国近代化的起步过程时，文中引述了这一时期每个阶段的历史人物，既可以引述相关的历史人物，又能正确说明中国近代化历程顺序的是 (    )

A．李鸿章、康有为、孙中山、陈独秀

B．严复、魏源、孙中山、胡适

C．梁启超、张之洞、鲁迅、孙中山

D．林则徐、谭嗣同、袁世凯、李大钊

( )，程序化系统的形成，它随着工程管理的集成而发展的。

A．70年代

B．80年代初

C．80年代中

D．90年代

如图所示，在光滑绝缘水平面上有直角坐标系xoy，将半径为R=0.4m，内径很小、内壁光滑、管壁极薄的圆弧形绝缘管AB水平固定在第二象限内，它的A端和圆心都在y轴上，B端在x轴上，与y轴负方向夹角θ=60º。在坐标系的第一、四象限不同区域内存在着四个垂直于水平面的匀强磁场， a、b、c为磁场的理想分界线，它们的直线方程分别为；在a、b所围的区域Ⅰ和b、c所围的区域Ⅱ内的磁感应强度分别为、，第一、四象限其它区域内磁感应强度均为。当一质量m =1.2×10^﹣5、电荷量q =1.0×10^﹣6C，直径略小于绝缘管内径的带正电小球，自绝缘管A端以v =2.0×10^{﹣2 m/s}的速度垂直y轴射入管中，在以后的运动过程中，小球能垂直通过c、a，并又能以垂直于y轴的速度进入绝缘管而做周期性运动。求：

（1）的大小和方向；

（2）、的大小和方向；

（3）在运动的一个周期内，小球在经过第一、四象限的过程中，在区域Ⅰ、Ⅱ内运动的时间与在区域Ⅰ、Ⅱ外运动的时间之比。 

《中国药典》2005年版规定肉桂油所测定的物理常数是

A．相对密度
B．折光率
C．熔点
D．沸点
E．旋光度

Space travel is definitely bad for astronauts’ bones, reducing their bone density after only a month of weightlessness, according to French research published on Friday.
Laurence Vico and his fellow workers at St Etienne University called for more research into the effects of microgravity, after their study of 15 astronauts from the Russian MIR station showed bone loss continued throughout space flights.
"Bone loss was especially striking in four astronauts, " the scientists reported in the Lancet Medical Journal.
They measured the Bone Mineral Density (BMD) of bones in the forearm and lower leg of the astronauts who had spent one to six months in space.
The BMD loss was significant in the tibia of the lower leg, a weight-bearing bone, but barely changed in the radius of the forearm. "Our results indicate the need to investigate not only different bones, but also different areas of the same bone since not all sites of the skeleton are similarly affected by space conditions, " they added.
Without gravity the body isn’t bearing any weight so there is no need for calcium which makes bones p, and it becomes empty into the bloodstream.
The research team suggested in future scientists should try to determine if the loss of bone density was only on weight-bearing bones on longer flights, also the possible recovery after returning to Earth.

Scientists have found that ______.

A. the BMD loss may cause serious illness to astronauts
B. the BMD loss may cause some change in astronauts’ bodies
C. astronauts shouldn’t care about the BMD loss
D. astronauts should take some calcium before space travel