Class A (type D) CpG ODNs (CpG-A ODNs) contain a central palindromic phosphodiester (PO) CpG sequence and a PS-modified 3â poly-G tail. The poly G tails form intermolecular tetrads that result in high molecular weight ordered structures.
Why does a tornado form when cold and hot air meet? The collision of warm and cold air is not the direct cause of a tornado, nor is it absolutely necessary. When a cold air mass pushes into a warm air mass (this is called a câ¦old front) the warmer, less dense air is forced upwards.
The National Weather Service defines a tornado as a violently rotating column of air in contact with the ground and pendant from a thunderstorm.. In other words, a thunderstorm is the first step in the creation of a tornado. Then, if other conditions are right, the thunderstorm could spin out one or more tornadoes. The three key conditions required for thunderstorms to form are: 1  Moisture in the lower to mid levels of the atmosphere. 2  Unstable air. 3  A lifting force.