There are many highly acclaimed researchers, scientists and doctors that doubt or deny that HIV is the cause of aids. Some of them even doubt the mere existence of HIV. If you have severe fear of aids, make sure to take a look at what these people have to say.
From Wikipedia, the free encyclopedia. The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions occurring in many animals that produces urea ((NH2)2CO) from ammonia (NH3). This cycle was the first metabolic cycle discovered (Hans Krebs and Kurt Henseleit, 1932), five years before the discovery of the TCA cycle. In mammals, the urea cycle takes place primarily in the liver, and to a lesser extent in the kidney.
The nitrogen cycle. The nitrogen cycle. The nitrogen cycle is one of the 'magical' cycles of nature in which essential nutrients for life, such as nitrogen, are cycled between atmosphere, soil and water without the elements vanishing. It enables components such as nitrogen to be used for one generation and recycled for future generations.