SI unit


Also found in: Dictionary, Thesaurus, Financial, Encyclopedia, Wikipedia.

unit

 [u´nit]
1. a single thing; one segment of a whole that is made up of identical or similar segments.
2. a specifically defined amount of anything subject to measurement, as of activity, dimension, velocity, volume, or the like.
3. a distinct part of a hospital, usually having a specific physical location and serving a defined function; see under names of specific units.
Ångström unit angstrom.
atomic mass unit (u) (amu) the unit of mass equal to ¹⁄₁₂ the mass of the nuclide of carbon 12. Called also dalton.
autonomous nursing unit a nursing unit under a decentralized administration system in which the staff is responsible for all aspects of unit functioning.
British thermal unit (BTU) a unit of heat formerly widely used, being the amount necessary to raise the temperature of 1 pound of water from 39° to 40°F., equal to approximately 252 calories.
CH50 unit the amount of complement that will lyse 50 per cent of a standard preparation of sheep red blood cells coated with antisheep erythrocyte antibody.
continuing education unit (CEU) a unit of credit for educational offerings given to professional persons, determined by a professional organization according to a mathematical formula after a thorough review of the program of study, the qualifications of the instructors, and the program objectives.
critical care unit intensive care unit.
electrostatic u's (esu) that system of units that is based on the fundamental definition of a unit charge as one that will repel a similar charge with a force of 1 dyne when the two charges are 1 cm apart in a vacuum.
environmental control unit a computerized system that allows the handicapped individual to operate several different appliances using a keyboard or other input device.
heat unit the amount of heat energy that is produced by one kVp (kilovolt peak) and one mA (milliampere) for one second with single phase, full wave rectified radiographic equipment.
Hounsfield unit an arbitrary unit of x-ray attenuation used for CT scans. Each voxel is assigned a value on a scale in which air has a value of −1000; water, 0; and compact bone, +1000.
intensive care unit see intensive care unit.
International unit (IU)
1. a unit of enzyme activity equal to the amount of enzyme that catalyzes the conversion of one micromole of substrate or coenzyme per minute under specified conditions (temperature, pH, and substrate concentration) of the assay method. Abbreviated U.
2. any of several arbitrary units that have been adopted by international bodies to express the quantities of certain vitamins (A, C, D, and thiamine hydrochloride), hormones (androgen, chorionic gonadotropin, estradiol benzoate, estrone, insulin, progesterone, and prolactin), and drugs (digitalis and penicillin).
Kienböck's unit a unit of x-ray exposure equal to 0.1 erythema dose; symbol X.
motor unit the unit of motor activity formed by a motor nerve cell and its many innervated muscle fibers.
postanesthesia care unit (PACU) a specialty unit in a hospital for giving postanesthesia care (care of patients recovering from anesthesia and intravenous sedation); formerly called recovery room.
radiologic u's units used to measure radiation, including roentgens, rads, rems, and curies.
u's of service (UOS)
1. the number of procedures done by a department.
2. individuals or groups of individuals who are the recipients of nursing care.
short procedures unit (short term care unit) a nursing unit where patients are briefly cared for following a medical or surgical procedure and are then discharged without spending the night.
SI unit any unit of the International System of units (the metric system); see also si units.
step-down unit a nursing unit designated to provide care for patients who are stable enough to be discharged from the intensive care unit but are not yet ready to be cared for on a medical-surgical unit.
Svedberg unit (S) a unit equal to 10−13 second used for expressing sedimentation coefficients of macromolecules.
Svedberg flotation unit (Sf) a unit equal to 10−13 second used for expressing negative sedimentation coefficients of macromolecules that float rather than sink in a centrifuge, e.g., lipoproteins.
terminal respiratory unit the functional unit of the lung, including a respiratory bronchiole, alveolar ducts and sacs, and alveoli; called also primary lobule of lung and primary respiratory lobule.
USP unit one used in the United States Pharmacopeia for expressing potency of drugs and other preparations.

SI unit 

Abbreviation of Système International d'unités (or International System of Units). It is derived from the metric system of physical units. There are seven base units, two supplementary units and many derived units. See candela per square metre; lumen; lux; micrometre (micron); nanometre.
Table S2 Base and supplementary SI units, and some derived units
physical quantitynamesymbol
base units
lengthmetrem
masskilogramkg
timeseconds
electric currentampereA
thermodynamic temperaturekelvinK
luminous intensitycandelacd
amount of substancemolemol
supplementary units
plane angleradianrad
solid anglesteradiansr
some derived units
areasquare metrem2
electric potential differencevoltV
electric resistanceohmΩ
energyjoule
forcenewtonN
frequencyhertzHz
illuminanceluxlx
luminancecandela per square metrecd/m2
luminous fluxlumenlm
powerwattW
velocitymetre per secondm/s
volumecubic metrem3
References in periodicals archive ?
While SI units are very similar to metric units, there are subtle differences.
x [10.sup.-34] when it is expressed in the SI unit [s.sup.-1] [m.sup.2] kg, which is equal to J s.
All tables and figures will also be presented in SI units. These tables and figures will be made available in online data supplements to published articles and letters.
This table presents a sample of reference numbers for SI units that an engineer may need on a job.
The SI subscript represents a quantity measured in SI units, while the EL subscript indicates a quantity measured in terms of the practical electrical units, represented by the Josephson and quantum Hall effects.
The updated DVE also offers a choice of scientific units for viscosity measurement including both cgs units: cP (centipoises) and P (Poise), and SI units: Pa-s (Pascal-seconds) and mPa-s (milliPascal-seconds).
According to my calculator and conversion data in "The use of SI units in IMechE publications", 100,000 lbf equates to 444.84kN.
Harnessing the bizarre workings of quantum mechanics is predicted to enable the development of compact atomic clocks, fast encryption, highly accurate sensors and a new set of SI units based on physical constants.
The best resource for SI units is the latest edition of the SI Brochure of the International Bureau of Weights and Measures (BIPM).
31 of 2006, which states in Article VIII that the SI units will be the exclusive basis of the legal units of measurement in the country.
The aim of this study was to apply 4 different IFCC and National Glycohemoglobin Standardization Program (NGSP) certified secondary reference measurement procedures (SRMPs) using different assay principles and calibrated in SI units (mmol/mol) and Diabetes Control and Complications Trial (DCCT) units (% Hb [A.sub.1c]) to see whether there were differences in the CVwp obtained.
They pay particular attention to determining physical constants that are directly involved in the anticipated new definitions of the SI units of measurement, which will be based on fixed values to be assigned to fundamental constants.