Scientists have believed that S.I.V.did not cause a similar immune system problem for primates.

VOA: special.2009.09.08

Delta v is positive in this direction here, the work is negative. So work on the system is positive. Work done by the system is negative.

功是负的，总而言之,外界对系统做功的符号为正。

麻省理工公开课 - 热力学与动力学课程节选

So I can make a quantity that I'll call V bar, which is the molar volume, the volume of one mole of a component in my system, and that becomes an intensive quantity.

所以我可以定义，一个叫做一横的量，这是摩尔体积系统中,一摩尔某种组分的体积，它就变成了。

麻省理工公开课 - 热力学与动力学课程节选

It's the pressure the external world is applying on this poor system here.

V是气体初态和,末态的体积之差。

麻省理工公开课 - 热力学与动力学课程节选