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A good example of polar molecules can be understood when trying to make a cake. If water and oil are required, they will not mix together. If you put them into a measuring cup, the oil will rise to the top while the water remains on the bottom.
The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
Interferon was scarce and expensive until 1980, when the interferon gene was inserted into bacteria using recombinant DNA technology, allowing for mass cultivation and purification from bacterial cultures.
Amoebae are the simplest type of protozoans, and are characterized by a feeding and dividing trophozoite stage that moves by temporary extensions called pseudopodia or false feet.
As the western states of America were settled, pioneers often had to drink rancid water from ponds and other sources. This often resulted in chronic diarrhea, causing many cases of dehydration and death that could have been avoided if clean water had been available.