Parse XML file with Simple XML and xpath

I'm trying to obtain the values of the nodes "/entry/comment[type="subcellular location"]/subcellularLocation/location" from this file http://ift.tt/1x7ww5o

I'm using SimpleXML and xpath but I can't access to this nodes with:

$var = "http://ift.tt/1x7ww5o"; $Unip_result= new SimpleXMLElement($var, NULL, TRUE);

$value=$Unip_result->xpath("/entry/comment[@type='subcellular location']");

The result is an empty array...