Between the ceiling and the floor of the upstairs apartment and
mine; there is no insulation.

I had a similar problem that ended about 8 months ago when I moved
into a house. Until then, I'd had off and on problems with my
upstairs neighber, depending on who was living there at the time. My
research on the web and newgroups indicated that effective sound
insulation required 1) mass, and 2) layers. Not very practical in a
rental.

I learned to sleep wearing a sound insulating headset, like the one
you wear when shooting or using loud power tools. I stretched the
headband so that it didn't fit very tight; this was enough to mask the
sounds, while being confortable enough to sleep in.

However, I couldn't hear my alarm in the morning and had there ever
been a fire, I would have been burned alive. ;-)

For lighter sounds, I found that a pillow or folded towel on my head
works well.

I feel your pain.