The flavorings may be natural, artificial, or organic. It is named after AstroTurf, a brand of artificial grass. No significant difference in milk from cows treated with artificial growth hormones. It may be sweetened with sugar or artificial sweetener. Indoor climbing occurs in buildings on artificial rock structures. This was the first World Series played entirely on artificial turf. They are less likely to eat mixed materials containing some artificial fibers. The assessment of the height of artificial structures has been controversial. These methods are less precise than observations of artificial satellites. A study linked MRSA to the abrasions caused by artificial turf. The Aztecs further intensified agricultural production by constructing systems of artificial irrigation. The debate about the environmental impact of artificial trees is ongoing. There are different types of artificial vaginas. It is possible to find pages describing purely artificial problems. The techniques used to create artificial ribozymes involve directed evolution.