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Health Risks of Ionizing Radiation: - Clark University

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204 Glossary<br />

Linear Energy Transfer (LET): The amount <strong>of</strong> energy deposited per unit <strong>of</strong> distance that the radiation<br />

travels in tissue.<br />

Least-Squares’ Model: Finds the line minimizing the sum <strong>of</strong> distances between observed points and the<br />

fitted line.<br />

Lens dose equivalent (LDE): applies to the external exposure <strong>of</strong> the lens <strong>of</strong> the eye and is taken as the<br />

dose equivalent at a tissue depth <strong>of</strong> 0.3 centimeter (300 mg/cm2).<br />

Life Span Study (LSS): Research conducted by the <strong>Radiation</strong> Effects Research Foundation to study<br />

whether the life span and causes <strong>of</strong> death among atomic-bomb survivors differ from those <strong>of</strong><br />

unexposed individuals. This research program includes both incidence and mortality studies based on<br />

vital-statistics surveys, death-certificate information, and other sources.<br />

Linear Model: A straight line with the formula: y = a + bx<br />

Linear Quadratic Model: Expresses the effect (e.g., mutation or cancer) as partly proportional to the<br />

dose (linear term) and partly proportional to the square <strong>of</strong> the dose (quadratic term). The linear term<br />

predominates at lower doses, the quadratic term at higher doses.<br />

Low-Dose <strong>Radiation</strong>: Low rates <strong>of</strong> radiation doses that are either less than 10 mSv received at high<br />

rates in single events, or dose rates less than 20 mSv per year received continuously.<br />

Lymphocyte: A white blood cell responsible for much <strong>of</strong> the body’s immune protection.<br />

Lymphoma: A malignant neoplasm originating from lymphocytes.<br />

Malformation: Deformity; abnormal shape or structure.<br />

Malignancy: A neoplasm or tumor that is cancerous as opposed to benign.<br />

Maximum Likelihood Model: Assigns a weight to each individual factor A, B, C instead <strong>of</strong> each<br />

combination <strong>of</strong> environments can be predicted accurately by assigning weights to each individual<br />

factor, then these factors can be said to operate independently, and the reduction <strong>of</strong> individual rules to<br />

a rule schema is justified.<br />

Mediastinal: Relating to the mediastinum.<br />

Mediastinum: A septum or cavity between two principal potions <strong>of</strong> an organ.<br />

Medullary Carcinoma: Carcinoma in which there is a predominance <strong>of</strong> cells and little fibrous tissue.<br />

Melatonin: A peptide hormone produced by the pineal gland that influences sleep-wake cycles and other<br />

circadian rhythms. It has a sedative effect and has been used to treat sleep disorders and jet lag, even<br />

though its impact on these conditions remains unclear.<br />

Meningioma: A slow-growing tumor that originates in the meninges.

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