Introduction. Beta-blockers, also known as beta-adrenoceptor blocking agents, are medications used to treat conditions such as angina, heart failure and high blood pressure. They decrease the activity of the heart by blocking the action of hormones like adrenaline.
1 The concept of âdemographic changeâ describes a populationâs age structure adjusting to. changes in living conditions. Consequently, changes in thcomposition of a societyâe s age. structure are the result of social shifts. (. 2  cf. . 3  theory of first and second demographic transition.
U.S. Population Projections: 2005â2050. If current trends continue, the population of the United States will rise to 438 million in 2050, from 296 million in 2005, and 82% of the increase will be due to immigrants arriving from 2005 to 2050 and their U.S.-born descendants, according to new projections developed by the Pew Research Center.