Randomized Controlled Studies: This is a study in which 1) There are two groups, one treatment group and one control group. The treatment group receives the treatment under investigation, and the control group receives either no treatment (placebo) or standard treatment. 2) Patients are randomly assigned to all groups.
winds that blow in a steady direction can move a dune. such wind will consistently pick up sand from one side and deposit it to a other side. this causes the entire dune to s â¦ lowly move in the direction if the wind.
It is due to this reason that a snake becomes almost immobile on the smooth surface of glass. Snakes of sandy desert would have found themselves in a sad plight for another reason. Minute grains of desert sand constantly slip underneath so it is not possible for the snake to move forward by pressing its tail in sand. On the contrary, when lunging forward it will only succeed in making a furrow in the sand.