So a 74xx244 works at a commercial operating temperature, while a 54xx244 which is the same logic device [maybe the same pinout, and package] will continue to operate to the military operating temperature range [which is wider].
A distemper vaccine is more than a preventive against canine distemper virus. This vaccine, considered a core vaccine for all dogs in the United States, also protects against a host of other diseases you may not know your dog is susceptible to. These can include adenovirus, parvovirus, and others.
A vaccine is a diluted version of a disease such as distemper or parvovirus. A vaccine shows your dog's immune system what that disease looks like, so the immune system can create antibodies against it. In plain English, this means the immune system has a memory.. Indeed, the immune system contains memory cells.