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.
In transitional areas where there is some air mass movement, cold or warm fronts can develop. Figure 7r-2 illustrates a vertical cross-section of a cold front. A cold front is the transition zone in the atmosphere where an advancing cold, dry stable air mass displaces a warm, moist unstable subtropical air mass. On a weather map, the cold front is drawn as a solid blue line with triangles.