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.
This creates weather systems in both large regular systems of heat exchange and smaller systems where hot and cold air masses mix, producing chaotic processes difficult to predict with any accuracy. It is these latter, smaller systems which create tornadoes. A tornado occurs where hot and cold air masses mix. The hot, high-pressure air is attempting to rise. The cold, low-pressure air is attempting to sink. As these air masses pass each other, they form a vortex, a swirling maelstrom of air. If there is enough heat to drive this engine, this vortex can become temporarily stable -- a tornado. So long as there is heat to keep it going, the tornado will keep growing stronger until, eventually, the air masses have mixed sufficiently for the heat to dissipate.