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.
Cold fronts are the leading edge of cooler air masses, hence the name cold front. They have stronger temperature changes during the fall (autumn) and spring and during the middle of winter. Temperature changes associated with cold fronts can be as much as 50 Â°F (30 Â°C).