A new study in the journal Nature has shown some hopeful results from an experimental gel that might protect women from H.I.V.

VOA: special.2009.03.16

When a particle moves in a circle, it has an acceleration towards the center of this size, v^2 over R.

当一个质点在圆周上运动时,它有一个指向圆心的加速度,v^2 / R

耶鲁公开课 - 基础物理课程节选

We'll get an expression in which there is no t; t has been banished in favor of v.

我们现在得到了一个不含t的表达式,t被v替换掉了

耶鲁公开课 - 基础物理课程节选

The event has not taken place here since nineteen ninety because of restrictions against visitors with H.I.V.

VOA: special.2009.12.02

Whenever you see a particle moving in a circle, even if it's at a constant speed, it has an acceleration, v square over r directed towards the center.

只要看到质点做圆周运动,即使是匀速圆周运动,也存在一个加速度,大小为 v^2 / r,方向指向圆心

耶鲁公开课 - 基础物理课程节选

South Africa has more than five million people infected with H.I.V., the largest number of any country.

VOA: special.2009.07.29

If it's going in a circle, you will say from now on, that it, indeed, has an acceleration, even though no one's stepping on the accelerator, of amount v^2 over R.

如果它在一个圆周上运动,你会说从现在起它其实有加速度,即使没有人去踩油门,加速度大小为 v^2 / R

耶鲁公开课 - 基础物理课程节选

Along with H.I.V., South Africa also has high rates of diabetes, high blood pressure and tuberculosis.

VOA: special.2010.04.28

In Eastern Europe, the number of new H.I.V.infections has leveled off.

VOA: special.2009.12.08

South Africa has the most people living with H.I.V.of any nation.

VOA: special.2010.04.28

EpiSurveyor has also been used in efforts to fight H.I.V.

VOA: special.2010.05.03

H.I.V.has slowed the progress in reducing maternal deaths.

VOA: special.2010.04.14