Anchor: A skateboarder slides down a handrail on his feet.
Entailed: A person sliding.
Contradiction: Nobody is sliding.
Contradiction: Slippers are required to be worn at all times.
Contradiction: Prusiner is trying to show that protein without nucleic acid can be infectious.
Contradiction: The mafia life is a booming industry. 
Contradiction: Wow, you're kidding me, I have never even heard of one.