Network protocols that use aggressive retransmissions to compensate for packet loss due to congestion can increase congestion, even after the initial load has been reduced to a level that would not normally have induced network congestion. Such networks exhibit two stable states under the same level of load.
Beta blocker. Beta blocker, also written Î²-blocker, is a class of medications that are particularly used to manage cardiac arrhythmias, and to protect the heart from a second heart attack (myocardial infarction) after a first heart attack (secondary prevention).
Beta blockers differ in the type of beta receptors they block and, therefore, their effects. Non-selective beta blockers, for example, propranolol (Inderal), block Î²1 and Î²2 receptors and, therefore, affect the heart, blood vessels, and air passages. Selective beta blockers, for example, metoprolol (Lopressor, Toprol XL) primarily block Î²1 receptors and, therefore, mostly affect the heart and do not affect air passages.