The results were announced on 12 April 1955, and Salk’s inactivated polio vaccine (IPV) was licensed on the same day. By 1957, annual cases dropped from 58 000 to 5600, and by 1961, only 161 cases remained.
Quote/cite this information
5 Matching Annotations
- Feb 2024
-
www.who.int www.who.int
-
-
incois.gov.in incois.gov.in
-
If a positive charge and a negative charge interact, their forces act in the same direction, from the positive to the negative charge. As a result opposite charges attract each other:
Two opposite charged are attracted to each other
-
-
chem.libretexts.org chem.libretexts.org
-
When an atom loses an electron it gains a positive charge and is called a cation.
Positive charge
-
Some atoms can gain additional electrons. When these atoms gain electrons, they acquire a negative charge because they now possess more electrons than protons. Negatively charged ions are called anions. Most nonmetals become anions when they make ionic compounds.
The gaining of electrons
-
-
www.khanacademy.org www.khanacademy.org
-
If there are more electrons than protons, then the net charge on the object is negative.
Definition of a negative charge
-