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).
During the past 30 years, Î²-blockers have been used to treat hypertension, prevent myocardial infarction, and treat arrhythmias. 29, 30 Treatment with Î²-blockers for heart failure has been controversial because of the negative chronotropic and inotropic actions of these drugs. Recent studies 3, 6â , 9 indicated that Î²-blockers improve signs and symptoms, exercise tolerance, and hemodynamics and reduce mortality in patients with heart failure.