 [L]- LABEL A marker, tag or indicator distinguishable by the observer but not by the system and used to identify a tracer.
- LABELED Made identifiable by a label.
- LABELING The act of incorporating a label into a chemical.
- LABELING, AUTOLOGOUS The radiolabeling of cells or plasma from a patient before re-administration to the same patient. J.
- LABELING, COLD Chemical or biochemical synthesis which incorporates a preformed label into a desired product.
- LABELING, CONJUGATION Labeling of a substance by conjugation with a labeled molecule.
- LABELING, END Procedure in which terminal phosphate groups of DNA are removed and enzymatically replaced with radiolabeled groups. J.
- LABELING, EXCHANGE Labeling of a substance by isotope exchange.
- LABELING, GENERAL Labeling in which compounds are nonuniformly labeled where the position of the radioactive atom in the molecule varies from one molecule to the other. Also called random labeling. NM.
- LABELING, ISOTOPIC Labeling in which the resulting product is only different from the initial one by its isotopic composition.
- LABELING, NON-ISOTOPIC Labeling in which the resulting product has a different chemical composition from the initial one.
- LABELING, RECOIL Labeling by a chemical reaction initiated by recoil.
- LABELING, (SITE) SPECIFIC Isotopic labeling at a definite location on a complex molecule. J, KE.
 LABELING, WILZBACH Labeling of a substance by exposing it to tritium gas.- LANTHANIDES An element which is any of the first series of f-block elements or inner transition elements commencing with lanthanum at atomic number 57 and ending with lutetium at atomic number 71.
- LANTHANOIDS See lanthanides.
- LASER OPTOACOUSTIC SPECTROSCOPY An optical spectroscopy technique in which an optoacoustic modulator is used to produce an equidistant series of sharp pulses in a laser beam.
- LATENCE TIME (OF A DETECTOR) See dead time.
- L-CAPTURE See L-electron capture.
- LEACH RATE The rate at which radioactivities are leached from solid waste aggregates by solubilization in water or aqueous liquid.
- LEAD CASTLE, CAVE OR HOUSING A structure, made of lead bricks, to enclose small radioactive sources. The structure may or may not contain viewing or handling facilities. NM.
- LEAD EQUIVALENT The thickness of lead, which, under specified conditions or irradiation, affords the same protection as the material under consideration. NM.
- LEAD GLASS Glass into which lead oxide is incorporated. M. Used for shielding purposes when limited visual observation is still necessary.
- LEAKAGE In reactors, the loss of neutrons to the surroundings. In general, all radiation except the useful beam.
- L-ELECTRON CAPTURE Radioactive decay of a nucleus by electron capture in which the electron captured by the nucleus was originally in the L-shell (2s or 2p atomic orbital).
- LEAST SQUARES TECHNIQUE A procedure for replacing the discrete set of results obtained from an experiment by a continuous function which best approximates the discrete results.
- LEPD Low-energy photon detector.
- LET Linear energy transfer.
- LETHARGY (OF A NEUTRON) A measure of the energy lost by neutrons in the slowing down due to multiple scatterings in the moderator. D.
- LEWIS EFFECT A peak in the thick target yield curves of narrow resonances near the resonance energy, due to the quantized character of charged-particle energy loss in penetrating matter. (Proc. of 3rd Int'l Conf on Chem. Analysis, Nucl. Inst. Meth. B66 11 [1992].)
- LIFETIME See average life.
- LIGAND A substance or part of a substance that binds to a specific receptor.
- LINAC A linear accelerator.
- LINEAR ANALYZER A position sensitive detector, used in radiochromatography imaging, in which there is no motion of detector relative to sample. J.
- LINEAR ACCELERATOR An accelerator in which the beam travels in a straight line during the entire acceleration process.
- LINEAR ELECTRON ACCELERATOR An evacuated metal tube in which electrons pass through a series of small gaps (usually in the form of cavity resonators in the high frequency range) so arranged and spaced that, at a specific excitation frequency, the stream of electrons on passing through successive gaps gains additional energy from the electric field in each gap.
- LINEAR ENERGY TRANSFER The average energy locally imparted to a medium by a charged particle of specified energy, per unit distance traversed.
- LINEAR PULSE AMPLIFIER See amplifier, linear pulse.
- LIQUID DROP MODEL A model of the nucleus in which the qualitative similarities to the cohesive forces of an ordinary liquid are recognized. The effects of volume energy and surface effects are supplemented by a variety of more subtle effects of both classical and quantal nature.
- LIQUID EMULSION Nuclear (photographic) emulsion manufactured in gel form so that after heating it can be poured to the desired shape at the desired time. NM.
- LIQUID ION-EXCHANGER See ion-exchanger, e.g., di-(2-ethylhexyl) phosphoric acid (HDEHP) is a liquid cation exchanger.
- LIQUID SCINTILLATION COUNTER A radiation counter utilizing a liquid scintillation detector.
- LIQUID SCINTILLATION DETECTOR See detector, liquid scintillation.
- LITHIUM-DRIFTED DETECTOR See germanium detector, Ge(Li).
- LIVE TIME For a measurement, the time during which a radiation measuring assembly is capable of processing events occurring in the radiation detector. It equals the clock time minus the integrated resolving or dead time.
- LIXIVIATION Extraction from a solid mixture by washing or percolation. M.
- LLOD Lower limit of detection; synonymous with limit of detection. CRC
- LOD Limit of detection. CRC
- LOGIT In competitive binding assays , the logit-log dose relationship, in which the response is defined by R=logit(y)=log[y/(1-y)] where y = b/bo with b = fraction of tracer bound and bo = value of b with no unlabeled ligand in the system. Logit transformed assay data frequently yield straight-line dose-response curves, amenable to statistical analysis.
- LOSS FREE COUNTING A scheme for correcting for dead time losses. It uses a pulser in conjunction with calculating the number of lost pulses during a dead period to augment the next spectral pulse artificially.
- LOW LEVEL COUNTING Any counting system in which special care is used to optimize the counting efficiency and reduce the background count rate. Such features as anticoincidence shielding and special materials are usually employed.
- LPO METHOD A radioiodination procedure employing the enzyme lactoperoxidase. KE.
- LUMINESCENCE A phenomenon in which the absorption of primary radiation by a substance gives rise to the emission of electromagnetic radiation characteristic for that substance.
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