The answer is that the equatorial regions receive sun rays closest to the vertical (direct rays) because of their position relative to the equator where the tilting of the earth only mildly affects the climate. The climate along the equator changes very little through out the year and has summer like conditions for most of the year.
However the other regions may receive direct sun rays but for far more limited periods. In the months of July and August (summer months), the northern hemisphere is tilted towards the sun and receives the most direct rays. The opposite occurs in December and January when it is tilted away from the sun and thus winter sets in, whereas the southern hemisphere is at this time tilted toward the sun and receives the most direct sun rays.
<span>Unidirectional flow in the heart is ensured because the heart contains valves that prevent backflow.
These valves keep the flow of the heart going in one direction (hence the name "unidirectional").</span>
Sugar is sucrose and a carbohydrate. It's made up of 3 elements. 12 atoms of carbon, 22 atoms of hydrogen, and 11 atoms of oxygen. (C^12H^22O^11)
