1) The President of the United States serves as the head of state and the head of government, responsible for leading the executive branch and representing the nation domestically and internationally.

2) The concept of proportional representation, used in some electoral systems, aims to ensure that political parties' representation in government aligns more closely with the proportion of votes they receive from the electorate.

3) Priyanka Chopra Jonas is an Indian actress, singer, and film producer who has made significant contributions to both Bollywood and Hollywood. She gained international fame through her role in the television series "Quantico" and has since starred in successful films.

4) The first commercially available digital camera, the Dycam Model 1, was introduced in 1990 and had a resolution of 376 x 240 pixels.