The United States of America (USA), commonly referred to as the United States (U.S.) or America, is a federal republic composed of 50 states, the federal district of Washington, D.C., five major territories, and various possessions. The 48 contiguous states and Washington, D.C., are in central North America between Canada and Mexico. The state of Alaska is in the northwestern part of North America and the state of Hawaii is an archipelago in the mid-Pacific. The territories are scattered about the Pacific Ocean and the Caribbean Sea. Major cities include New York, a global finance and culture center, and Washington, DC, the capital, both on the Atlantic Coast; Los Angeles, famed for filmmaking, on the Pacific Coast; and the Midwestern metropolis Chicago.
The land area of the contiguous United States is 2,959,064 square miles. Alaska, separated from the contiguous United States by Canada, is the largest state at 663,268 square miles. Hawaii, occupying an archipelago in the central Pacific, southwest of North America, is 10,931 square miles in area. The populated territories of Puerto Rico, American Samoa, Guam, Northern Mariana Islands, and U.S. Virgin Islands together cover 9,185 square miles. The United States is the world's third or fourth largest nation by total area (land and water), ranking behind Russia and Canada and just above or below China. The ranking varies depending on how two territories disputed by China and India are counted and how the total size of the United States is measured: calculations range from 3,676,486 square miles to 3,717,813 square miles to 3,794,101 square miles to 3,805,927 square miles. Measured by only land area, the United States is third in size behind Russia and China, just ahead of Canada.
The United States has a capitalist mixed economy which is fueled by abundant natural resources and high productivity. According to the International Monetary Fund, the U.S. GDP of $16.8 trillion constitutes 24% of the gross world product at market exchange rates and over 19% of the gross world product at purchasing power parity (PPP). The United States is the largest importer of goods and second largest exporter, though exports per capita are relatively low. In 2010, the total U.S. trade deficit was $635 billion. In 2009, the private sector was estimated to constitute 86.4% of the economy, with federal government activity accounting for 4.3% and state and local government activity (including federal transfers) the remaining 9.3%. The United States has been a leader in scientific research and technological innovation since the late 19th century. Methods for producing Interchangeable parts were developed by the U.S. War Department by the Federal Armories during the first half of the 19th century. This technology, along with the establishment of a machine tool industry, enabled the U.S. to have large scale manufacturing of sewing machines, bicycles and other items in the late 19th century and became known as the American system of manufacturing.
In Physiology or Medicine United States produced 100 Nobel laureates so far. There are number of medical research institutes in USA. A very famous National Institute of Diabetes and Digestive and Kidney Diseases is the leading institution in the field of diabetes research. Joslin Diabetes Center, Diabetes Research Institute are among such institutes which provides wide information on the diabetes. List of diabetes journal have been found from different universities and institutes. Many scientific journals related to the diabetes enhanced the knowledge of the disease in numerous manners.