Cool... It definitely is a Phyllostachys, and it isn't a Ph. Nuda. If
the culms are particularly strong, it might be a Ph. Bambusoides. Or,
Ph. Bambusoides 'Holochrysa'.

Here is a pic of the latter of these two:
http://www.mulu.co.uk/images/holochrysa_med.jpg

Even though many pics you see of the non-holochysa variety of Ph.
bambusoides show it to be green, it also turns fairly yellow under the
right conditions.

Take all of this with a grain of salt though... There are a lot of
yellow forms of bamboo. I haven't seen a Ph. bambusoides shoot yet, so
can't compare it to your pictures. Hopefully someone who has one
shooting will chime in to confirm (or deny).