An airplane had flown over the area where the birds were kept and spread a powerful chemical called DDT.

VOA: special.2010.03.14

When it reaches the brain, levodopa is changed into dopamine, the chemical that is lacking in people with the disease.

VOA: special.2009.04.07

And it can limit the need for chemical fertilizers by letting animal waste do the job of natural fertilizer.

VOA: special.2010.01.19

The students use the mixture to fertilize the soil instead of buying chemical fertilizers that could harm the environment.

VOA: special.2009.04.14

Plants naturally take in carbon dioxide they need for photosynthesis, the process of changing light energy to chemical energy.

VOA: special.2010.01.26

This medicine seems to work by governing the activity of a chemical involved in information processing, storage and memory.

VOA: special.2011.02.08

Last July,the Food and Drug Administration advised manufacturers to add what are called physical chemical identifiers to their medicines.

VOA: special.2010.03.01

But improved farming methods later increased their yields and, at the same time, made better use of chemical nitrogen fertilizer.

VOA: special.2009.07.28

They also will study chemical and physical properties of the soil samples with a method called infrared spectroscopy.

VOA: special.2009.01.20

Harvard's Nicholas Lange says the team looked instead at the chemical and electrical pathways that link the different parts of the brain.

VOA: special.2010.12.21

Chemical sprays like air fresheners, hair spray,cleaning products and even strong beauty aids can trigger an asthma attack.

VOA: special.2010.09.07

Scientists at the agroforestry center say the use of fertilizer trees can reduce the need for chemical nitrogen by up to three-fourths.

VOA: special.2009.09.01

She also shows how the chemical Luminol can reveal hidden blood stains that the eye alone cannot see.

VOA: special.2010.05.05

It asked more than one thousand women and minority members of the American Chemical Society about their experiences.

VOA: special.2010.04.01