Sperm penetration tests check to see whether a man's sperm can move through cervical mucus and the fallopian tubes to join with (fertilize) an egg. This test is usually done when a couple is having trouble becoming pregnant (infertility). There are different sperm penetration tests.
The idea that a boundary is shifting can be applied to different areas. A shifting frontier of science would be referring to the fact that science is always changing and growing, and always with new areas. In wartime, a shifting frontier would be an international border which is constantly being renegotiated.
Alaska: The Last Frontier is set on the Kilcher family's 600 acres of property located just out side of Homer, Alaska. The first of the family to settle the homestead was Yule Kilcher and his wife Ruth, around 80 years ago.