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.
Although favorable conditions for tornadoes in the United States can occur at any time, they are most common in spring and least common in winter. Because spring is a transitional period for the climate, there are more chances of cooler air meeting with warmer air, resulting in more thunderstorms.he Midwestern states are very prone to tornado activity, as it is part of Tornado Alley.. States included in the area that are hit by tornadoes the most are Kansas, Missouri, Nebraska, Iowa, and South Dakota.