| rodomontade | Vain boasting; empty bluster or vaunting; rant. "I could show that the rodomontades of Almanzor are neither so irrational nor impossible." (Dryden) Origin: F, fr. It. Rodomontana. See Rodomont. Source: Websters Dictionary (01 Mar 1998) |
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| rodonalgia | Synonym: erythromelalgia. Origin: G. Rhodon, rose, + algos, pain (05 Mar 2000) |
| rods (retina) | One of the two photoreceptor cell types of the vertebrate retina. In rods the photopigment is in stacks of membranous disks separate from the outer cell membrane. Rods are more sensitive to light than cones, but rod mediated vision has less spatial and temporal resolution than cone vision. (12 Dec 1998) |
| roe | <zoology> A roebuck. See Roebuck. The female of any species of deer. Origin: OE. Ro, AS. Rah; akin to D. Ree, G. Reh, Icel. Ra, SW. Ra. 1. <zoology> The ova or spawn of fishes and amphibians, especially when still inclosed in the ovarian membranes. Sometimes applied, loosely, to the sperm and the testes of the male. 2. A mottled appearance of light and shade in wood, especially in mahogany. Origin: For roan, OE. Rowne, akin to G. Rogen, OHG. Rogan, Icel. Hrogn, Dan. Rogn, ravn, Sw. Rom; of uncertain origin; cf. Gr. Pebble, Skr. Arkara gravel. Source: Websters Dictionary (01 Mar 1998) |
| roebuck | <zoology> A small European and Asiatic deer (Capreolus capraea) having erect, cylindrical, branched antlers, forked at the summit. This, the smallest European deer, is very nimble and graceful. It always prefers a mountainous country, or high grounds. Origin: 1st roe + buck. Source: Websters Dictionary (01 Mar 1998) |
| roed | <zoology> Filled with roe. Source: Websters Dictionary (01 Mar 1998) |
| roedeer | <zoology> The roebuck. Source: Websters Dictionary (01 Mar 1998) |
| Roentgen | <radiobiology, unit> The special unit of exposure, based on a quantity of ionisation (charge) produced by the absorption of X or gamma radiation energy in a specified mass of air under standard conditions. 1R = 2.58 x 10-4 C kg-1 or air. For radiation protection purposes, an exposure to 1 roentgen of x or gamma rays (air kerma of ~10-2 J kg-1) is generally assumed to produce an absorbed dose of 1 rad in water or soft tissue. Abbreviation: R (06 Aug 1998) |
| roentgen ray | <investigation> A type of irradiation used for imaging purposes that uses energy beams of very short wavelengths (0.1 to 1000 angstroms) that can penetrate most substances except heavy metals. This is the commonest form of imaging technique used in clinical practice everywhere in the world with the image captured on photographic film. An AP film is when the beams pass from front-to-back (anteroposterior) and is used for mobile film, particularly on the ward or in casualty. This is the oposite to a PA film (posteroanterior) in which the rays pass through the body from back-to-front. Most films taken in the main radiology department are PA. (20 Jun 2000) |
| Roentgen, Wilhelm | <person, radiobiology> German scientist who discovered X-rays in 1895. (13 Nov 1997) |
| roentgen-equivalent | <radiobiology> A unit of dose equivalent to that quantity of ionizing radiation of any type that produces in man the same biologic effect as one rad of X-rays or gamma rays; the number of rems is equal to the absorbed dose, measured in rads, multiplied by the quality factor of the radiation in question.100 rem = 1 Sv. (05 Mar 2000) |
| roentgen-equivalent physical | <radiobiology, unit> A roentgen equivalent physical is a unit of absorbed radiation approximately equivalent to a roentgen, an international unit of x- or gamma-radiation. An obsolete unit of measurement; that quantity of ionizing radiation of any kind which, upon absorption by living tissue, produces an energy gain per gram of tissue equivalent to that produced by 1 roentgen of X-rays or gamma-rays. Acronym: rep See: rad. (05 Mar 2000) |
| roentgenkymogram | <investigation> A record of the heart's movements taken with the roentgenkymograph. (05 Mar 2000) |
| roentgenkymograph | <apparatus> An apparatus for recording the movements of the heart and great vessels or of the diaphragm on a single film. It consists of a lead sheet called the grid in which are cut horizontal or vertical slits, typically less than 1 mm wide, spaced 1-2 cm apart. During an X-ray exposure lasting as long as several cardiac or respiratory cycles, the grid or the film is moved vertically to record cardiac motion or horizontally for diaphragm motion. (05 Mar 2000) |
| roentgenkymography | An obsolete technique involving the recording of movements of the heart by means of the roentgenkymograph. (05 Mar 2000) |