The test may cause momentary gagging because the back of the throat is a sensitive area, but it should not be painful. The sample your doctor collects is taken to a laboratory, where it is put on a plate that allows any bacteria on it to grow. This process is called a culture.
Often these are called transition zones which represent the start and end of a specific region and can be large or small. For example, the transition zone between Sub-Saharan Africa and North Africa is rather large because there is a mixing between the two regions. Regional geographers study this zone as well as the distinct characteristics of Sub-Saharan Africa and North Africa.
The results of the study will help scientists understand Earth's water cycle, and how plate tectonics moves water between the surface of the planet and interior reservoirs, researchers say. The Earth's mantle is the hot, rocky layer between the planet's core and crust. Scientists have long suspected that the mantle's so-called transition zone, which sits between the upper and lower mantle layers 255 to 410 miles (410 to 660 kilometers) below Earth's surface, could contain water trapped in rare minerals. However, direct evidence for this water has been lacking, until now.