| RF | radial fiber; radio frequency; receptive field; regurgitant fraction; Reitland-Franklin [unit]; rela... |
|---|---|
| RR | radiation reaction; radiation response; rate ratio; rational recovery [group]; recovery room; relati... |
| RCA | red cell agglutination; relative chemotactic activity; renal cell carcinoma; right carotid artery; r... |
| HBsAg/adr | hepatitis B surface antigen manifesting group-specific determinant a and subtype-specific determinan... |
| LSP | left sacroposterior [fetal position]; linguistic string project; liver-specific protein; lymphocyte-... |
| relative polycythemia | A relative increase in the number of red blood cells as a result of loss of the fluid portion of the blood. (05 Mar 2000) |
|---|---|
| relative refractory period | The period between the effective refractory period and the end of the refractory period; fibres then respond only to high intensity stimuli and the impulses conduct more slowly than normally. (05 Mar 2000) |
| relative risk | <epidemiology> The proportion of diseased people amongst those exposed to the relevant risk factor divided by the proportion of diseased people amongst those not exposed to the risk factor. This should be used in those cohort studies where those with and without disease are followed to observe which individuals become diseased. (05 Dec 1998) |
| relative scotoma | A scotoma in which there is visual depression but not complete loss of light perception. (05 Mar 2000) |
| relative sensitivity | The sensitivity of a medical screening test as determined by comparison with the same type of test; e.g., sensitivity of a new serological test relative to sensitivity of an established serological test. (05 Mar 2000) |
| relative specificity | The specificity of a medical screening test as determined by comparison with the same type of test (e.g., specificity of a new serological test relative to specificity of an established serological test). (05 Mar 2000) |
| relative value scales | Coded listings of physician or other professional services using units that indicate the relative value of the various services they perform. They take into account time, skill, and overhead cost required for each service, but generally do not consider the relative cost-effectiveness. Appropriate conversion factors can be used to translate the abstract units of the relative value scales into dollar fees for each service based on work expended, practice costs, and training costs. (12 Dec 1998) |
| relative viscosity | The ratio of the viscosity of a solution or dispersion to the viscosity of the solvent or continuous phase. (05 Mar 2000) |
| 5-year relative survival rate | <statistics> The likelihood that a patient will not die from causes associated with his or her cancer for at least 5 years after diagnosis. This is the standard many professionals use when determining someone a survivor of cancer. (16 Dec 1997) |
| activity | 1. The state of being active, the ability to produce some effect, the extent of some function or action. 2. <chemistry> A thermodynamic quantity that represents the effective concentration of a solute in a nonideal solution, if concentrations are replaced by activities, the equations for equilibrium constants, electrode potentials, osmotic pressure, boiling point elevation, freezing point depression and vapour pressures of volatile solutes are converted from approximations that hold only for dilute solutions to exact equations that hold for all concentrations. The activity is equal to the product of the concentration and the activity coefficient, a dimensionless number measuring deviation from nonideality. Symbol a. The potential or true thermodynamic activity of a substance, as opposed to its molar concentration. 3. <radiobiology> The number of nuclear transitions or disintegrations occurring in a given quantity of radioactive material per unit time. The SI unit of activity is s-1. The special name for the unit of activity is becquerel (Bq). The previously used special unit of activity, curie (Ci), is being replaced by the becquerel. 1 Bq = 2.7 x E-11 Ci. 1 Ci = 3.7 x E10 Bq. 4. Optical activity. (16 Dec 1997) |
| activity coefficient | <chemistry> The factor by which the value of a concentration of a solute must be multiplied to determine its true thermodynamic activity. (06 May 1997) |
| activity cycles | Bouts of physical irritability or movement alternating with periods of quiescence. It includes biochemical activity and hormonal activity which may be cellular. These cycles are shorter than 24 hours and include sleep-wakefulness cycles and the periodic activation of the digestive system. (12 Dec 1998) |
| activity, drug | A measure of the physiological response a drug produces in the body. A less active drug produces less response (and visa versa). (12 Dec 1998) |
| blocking activity | The repression or elimination of electrical activity in the brain by the arrival of a sensory stimulus. (05 Mar 2000) |
| blood bactericidal activity | Native bactericidal property of blood due to normally occurring antibacterial substances such as beta lysin, leukin, etc. (12 Dec 1998) |