Case insensitive Xquery

[ambika_se]

Hi all
I want to make a Xquery which is like this

for $x in doc("file:///C:/Science.xml")//tva2:title
where $x//node()[contains(.,"Biological Science")]
return $x

Its working perfectly but if i try for( biological science) its not which is becoz XQUery is case sensetive.I can use lower -case or upper-case function but i want more than that I need to look for words Science not science or SCIENCE.
Can anybody plzz help me with it. If you know how to make query insensitive then it wud be great
Thanks