Declare your variable in the beginning of your script if you know you're gonna test it later. Don't give it a value at this point. A declared variable that has not been assigned a value will have the value 'null'. Use the === compare operator to check whether the variable is really boolean false. The == operator is not reliable as a value of 0 will also evaluate to false. (Basically, the === asks whether variable are of same value AND datatype!).
Nitrogen Fixation. Nitrogen fixation refers to the conversion of atmospheric nitrogen gas (N 2 ) into a form usable by plants and other organisms. Nitrogen fixation is conducted by a variety of bacteria, both as free-living organisms and in symbiotic association with plants. Because it is the principal source of the nitrogen in the soil, nitrogen that plants need to grow, nitrogen fixation is one of the most important biochemical processes on Earth.
Nitrogen has a number of important uses. It can be used to replace air and eliminate oxidation of materials. Its most important use is in creating ammonia, which in turn is used to make fertilizer and explosives. Liquid nitrogen is used as a refrigerant for very low temperatures.ses as inert gas. Nitrogen gas (N 2) is often used as a replacement for air where oxidation is undesirable. One area for use is to preserve the freshness of foods by packaging them in nitrogen. This greatly reduces the spoilage of the food, due to it getting rancid or suffering other forms of oxidative damage.