factors of Jhanas

Can any one explain me about the factors of Jhanas and how to eliminate them?

The factors of Jhanas

Applied Thought (vitakka)
Sustained Thought (vicara)
Rapture (piti)
Happiness (sukha)
One-pointedness (ekaggata)

The first Jhana contains all the five factors.
The second Jhana has not the first two applied thought (vitakka) and
sustained thought (vicara).
The third Jhana contains only happiness (sukha) and one-pointedness (ekaggata).
The forh Jhana contains only one-pointedness (ekaggata).

More: http://www.accesstoinsight.org/lib/authors/gunaratana/wheel351.html#ch4