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.
Tornadoes form in unusually violent thunderstorms when there is sufficient (1) instability and (2) wind shear present in the lower atmosphere. Instability refers to unusually warm and humid conditions in the lower atmosphere, and possibly cooler than usual conditions in the upper atmosphere. Wind shear in this case refers to the wind direction changing, and the wind speed increasing, with height.