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A vacuum tube, electron tube, valve, or tube, is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.
The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to the lungs. In humans, the heart is approximately the size of a closed fist and is located between the lungs, in the middle compartment of the chest.
The Three Mile Island accident was a partial meltdown of the Three Mile Island, Unit 2 (TMI-2) reactor on the Susquehanna River in Londonderry Township, Pennsylvania, near the Pennsylvania capital of Harrisburg. It began at 4 a.m. on March 28, 1979. It is the most significant accident in U.S. commercial nuclear power plant history. On the seven-point International Nuclear Event Scale, it is rated Level 5 – Accident with Wider Consequences.
Aortic stenosis is the narrowing of the exit of the left ventricle of the heart, such that problems result. It may occur at the aortic valve as well as above and below this level. It typically gets worse over time. Symptoms often come on gradually with a decreased ability to exercise often occurring first. If heart failure, loss of consciousness, or heart related chest pain occur due to AS the outcomes are worse. Loss of consciousness typically occurs with standing or exercising. Signs of heart failure include shortness of breath especially when lying down, at night, or with exercise, and swelling of the legs. Thickening of the valve without narrowing is known as aortic sclerosis.
The Cavalier King Charles Spaniel is a British breed of toy dog of spaniel type. Four colours are recognised: Blenheim, tricolour (black/white/tan), black and tan, and ruby; the coat is smooth and silky. The lifespan is usually between eight and twelve years.
Mitral valve prolapse (MVP) is a valvular heart disease characterized by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. It is the primary form of myxomatous degeneration of the valve. There are various types of MVP, broadly classified as classic and nonclassic. In severe cases of classic MVP, complications include mitral regurgitation, infective endocarditis, congestive heart failure, and, in rare circumstances, cardiac arrest.
Mitral stenosis is a valvular heart disease characterized by the narrowing of the opening of the mitral valve of the heart. It is almost always caused by rheumatic valvular heart disease. Normally, the mitral valve is about 5 cm2 during diastole. Any decrease in area below 2 cm2 causes mitral stenosis. Early diagnosis of mitral stenosis in pregnancy is very important as the heart cannot tolerate increased cardiac output demand as in the case of exercise and pregnancy. Atrial fibrillation is a common complication of resulting left atrial enlargement, which can lead to systemic thromboembolic complications like stroke.
Aortic regurgitation (AR), also known as aortic insufficiency (AI), is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle. As a consequence, the cardiac muscle is forced to work harder than normal.
The J-2 is a liquid-fuel cryogenic rocket engine used on NASA's Saturn IB and Saturn V launch vehicles. Built in the U.S. by Rocketdyne, the J-2 burned cryogenic liquid hydrogen (LH2) and liquid oxygen (LOX) propellants, with each engine producing 1,033.1 kN (232,250 lbf) of thrust in vacuum. The engine's preliminary design dates back to recommendations of the 1959 Silverstein Committee. Rocketdyne won approval to develop the J-2 in June 1960 and the first flight, AS-201, occurred on 26 February 1966. The J-2 underwent several minor upgrades over its operational history to improve the engine's performance, with two major upgrade programs, the de Laval nozzle-type J-2S and aerospike-type J-2T, which were cancelled after the conclusion of the Apollo program.
Mitral regurgitation(MR), also known as mitral insufficiency or mitral incompetence, is a form of valvular heart disease in which the mitral valve is insufficient and does not close properly when the heart pumps out blood. It is the abnormal leaking of blood backwards – regurgitation from the left ventricle, through the mitral valve, into the left atrium, when the left ventricle contracts. Mitral regurgitation is the most common form of valvular heart disease.
Ebstein's anomaly is a congenital heart defect in which the septal and posterior leaflets of the tricuspid valve are displaced towards the apex of the right ventricle of the heart. It is classified as a critical congenital heart defect accounting for less than 1% of all congenital heart defects presenting in around 1 per 200,000 live births. Ebstein anomaly is the congenital heart lesion most commonly associated with supraventricular tachycardia.
Aortic valve replacement is a procedure whereby the failing aortic valve of a patient's heart is replaced with an artificial heart valve. The aortic valve may need to be replaced because:
Phentermine (phenyl-tertiary-butylamine), with several brand names including Ionamin and Sentis, is a medication used together with diet and exercise to treat obesity. It is taken by mouth for up to a few weeks at a time, after which the benefits subside. It is also available as the combination phentermine/topiramate.
The pressure-fed engine is a class of rocket engine designs. A separate gas supply, usually helium, pressurizes the propellant tanks to force fuel and oxidizer to the combustion chamber. To maintain adequate flow, the tank pressures must exceed the combustion chamber pressure.
Valvular heart disease is any cardiovascular disease process involving one or more of the four valves of the heart. These conditions occur largely as a consequence of aging, but may also be the result of congenital (inborn) abnormalities or specific disease or physiologic processes including rheumatic heart disease and pregnancy.
Cardiomegaly is a medical condition in which the heart becomes enlarged. It is more commonly referred to simply as "having an enlarged heart". It is usually the result of underlying conditions that make the heart work harder, such as obesity, heart valve disease, high blood pressure (hypertension), and coronary artery disease. Cardiomyopathy is also associated with cardiomegaly.
Brachiopods, phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection. Two major categories are traditionally recognized, articulate and inarticulate brachiopods. The word "articulate" is used to describe the tooth-and-groove structures of the valve-hinge which is present in the articulate group, and absent from the inarticulate group. This is the leading diagnostic skeletal feature, by which the two main groups can be readily distinguished as fossils. Articulate brachiopods have toothed hinges and simple, vertically-oriented opening and closing muscles. Conversely, inarticulate brachiopods have weak, untoothed hinges and a more complex system of vertical and oblique (diagonal) muscles used to keep the two valves aligned. In many brachiopods, a stalk-like pedicle projects from an opening near the hinge of one of the valves, known as the pedicle or ventral valve. The pedicle, when present, keeps the animal anchored to the seabed but clear of sediment which would obstruct the opening.
A split S2 is a finding upon auscultation of the S2 heart sound.
SteamOS is a Linux distribution developed by Valve. It is open source with some closed source components and is the primary operating system for Steam Machines and the Steam Deck.
References
- ↑ Zane Satterfield. Valve Exercising (Report). National Environment Services Center. CiteSeerX 10.1.1.432.2080 .
- ↑ William E. Forsthoffer (2021). Forsthoffer's Proven Guidelines for Rotating Machinery Excellence. Elsevier Science. p. 251. ISBN 9780323860192.
- ↑ Syam Babu Nayer; Larry R. Carson; Peter Olson Sr (1 August 2008). "Operation and Maintenance, Exercising Valves Boosts System Performance". Opflow. 34 (8): 14–16. doi:10.1002/j.1551-8701.2008.tb02941.x.
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