Ra (redirected from right ascension)

Ra radium.

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RA, RAW airway resistance.

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Ra

The symbol for the element radium.

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RA

abbr.

rheumatoid arthritis

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Ra,

symbol for the element radium.

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RA,

1 abbreviation for rheumatoid arthritis.

2 abbreviation for right atrium.

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radium [ra´de-um]

a chemical element, atomic number 88, atomic weight, 226, symbol Ra. (See Appendix 6.) Radium is highly radioactive and is found in uranium minerals. Radium-226 has a half-life of 1622 years. It and its short-lived decay products emit alpha particles, beta particles, and gamma rays. One of the decay products, radon-222, is a radioactive gas. In clinical use, radium is contained in a metal container that stops alpha and beta particles and traps radon.



Radium is used in radiation therapy for malignant diseases, particularly those that are readily accessible, for example, tumors of the cervix uteri, mouth, or tongue. In the form of needles or pellets, it can be inserted in the tumorous tissue (interstitial implantation) and left in place until its rays penetrate and destroy malignant cells. It can also be used in the form of plaques applied to the diseased tissue. Large amounts of radium are used as a source of gamma rays, which are capable of deep penetration of matter. Radium rays have been used in the treatment of lupus erythematosus, eczema, psoriasis, xanthoma, mycosis fungoides, and other skin diseases; for the removal of papillomas, granulomas, and nevi; for palliative treatment in carcinoma and sarcoma; and in myelogenous and lymphatic leukemia.

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RA

see rheumatoid arthritis, ragocyte.

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Ra

chemical symbol, radium.

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RA

1 Refractory anemia 2 Renin activity 3 Retinoic acid 4 Rheumatoid arthritis, see there 5. Right atrium 6. Risk assessment