watch by going online to foxnation.com to begin a free trial. all right, big concerns over the types of bombs russia may be dropping in ukraine. national security correspondent jennifer griffin is live from the pentagon. what can you tell us at this hour, jennifer? >> sandra, we talked to a senior u.s. official who did confirm they had seen evidence of thermobaric weapons, they have not seen they have been used, but they are known as vacuum bombs. more devastating and conventional explosives and they have a terrible impact on anyone caught in the blast radius. it consists of a fuel container with two separate explosive charges. they tend to cause very little primary fragmentation but the blast wave can be extremely powerful and generate high temperatures that can start