M

Marinelli beaker

in gamma-ray spectrometry, a source container having an overall cylindrical with an inverted well at the bottom designed to fit over the detector, intended to improve the detection efficiency by placing a large portion of the source near the detector

Mariscotti

M.A. Mariscotti, author of a 1967 article that described a statistical algorithm for recognizing spectral peaks in the presence of back­ground, often applied to gamma-ray spectra. The algorithm and its variants are sometimes called “Mariscotti peak search algorithms.”

MARLAP

Multi-Agency Radiological Laboratory Analytical Protocols Manual

mass attenuation coefficient (μ_m)

quotient of the linear attenuation coefficient of a material and its mass density

mass basis

solid form (wet, dry, or ash) on which the massic activity of a sample is based

mass defect

See mass excess

mass excess (Δ)

mass of an atom minus the product of the mass number and atomic mass constant [IUPAC]

According to some authorities, the mass excess is also called the mass defect.

massic

The adjective massic, when it modifies the name of a quantity, indicates the quotient of that quantity and its associated mass, as in massic activity (cf. volumic).

massic activity

quotient of the activity of a quantity of material and its mass (cf. volumic activity)

mass number

total number of protons and neutrons in an atomic nucleus — also called nucleon number

matrix

primary type of material of which a physical sample is composed

matrix spike (MS)

in analytical quality control, an aliquant of an ordinary sample to which a known amount of a standard or reference material is added before analysis, usually for the purpose of assessing the effect of the matrix on the performance of the meas­ure­ment process

matrix spike duplicate (MSD)

in analytical quality control, an aliquant of an ordinary sample to which a known amount of a standard or reference material is added, and which is then analyzed together with a matrix spike, usually for the purpose of assessing the effect of the matrix on the precision of the meas­ure­ment process

Md

atomic symbol for mendelevium

mean

See expectation (cf. arithmetic mean and average)

mean solar year

tropical year

(measurable) quantity

“attribute of a phenomenon, body or substance that may be distinguished qualitatively and determined quantitatively” [VIM] “The term quantity may refer to a quantity in a general sense…or to a particular quantity….”

Example: An example of a general quantity is massic activity. An example of a particular quantity is the massic activity of ¹³⁷Cs in a specified sample of soil.

measurand

“particular quantity subject to measurement” [VIM]

measurement

“set of operations having the object of determining a value of a quantity” [VIM]

Note: Measurement generally involves estimating the ratio of one particular quantity (the measurand) to a reference quantity of the same dimension (the unit of measurement). The estimated ratio is the numerical value of the result, and the uncertainty of the ratio is the numerical uncertainty of the result.

measurement function

in a mathematical model of measurement, the equation or equations used to calculate the value of the output quantity (measurand) from given values of the input quantities

(measurement) method

measurement procedure

Note: The term analytical method may be used when the measurement involves chemical or radiochemical analysis.

(measurement) procedure

1. “set of operations, described specifically, used in the performance of particular measurements according to a given method” [VIM]
2. standard operating procedure for per­form­ing a measurement

Note: The term analytical procedure may be used when the measurement involves chemical or radiochemical analysis.

measurement process

well-defined measurement procedure, implemented at a particular location with given personnel and measuring instruments, which has reached a state of statistical control

measurement quality objective (MQO)

statement of a requirement for the quality of a measurement, often expressed as a bound for some quantitative performance characteristic of the meas­ure­ment process, such as the minimum quantifiable value or the minimum detectable value

(measurement) standard

“material measure, measuring instrument, reference material or measuring system intended to define, realize, conserve or reproduce a unit or one or more values of a quantity to serve as a reference” [VIM]

Note: The French word for this concept is étalon. Since the term measurement standard is usually shortened to standard, which has more than one meaning in English, the VIM allows etalon as an English synonym for measurement standard, apparently in the hope that it will catch on.

median

0.5-quantile, or, equivalently, a 50^th percentile

metastable state

energy state of an atomic nucleus that is higher than the minimum-energy state for that atomic number and mass number, and which may persist for an extended period of time (cf. ground state)

meteorology

art of watching the weather and guessing what it will do next (cf. metrology)

method of measurement

“logical sequence of operations, described generically, used in the performance of measurements” [VIM]

method blank

artificial QC sample prepared to simu­late a normal sam­ple con­tain­ing little or none of the analyte, and analyzed with other samples to check for con­tamina­tion or low-level bias in the meas­ure­ment process

metrology

science of measurement (cf. meteorology)

Mg

atomic symbol for magnesium

minimum detectable value

estimate of the smallest true value of the measurand that ensures a specified high probability of detection

Note: A detection criterion must be defined (see critical value).

minimum quantifiable value

estimate of the smallest true value of the measurand that ensures a specified relative precision of measurement (usually 10 % relative standard deviation)

mixed waste

hazardous waste that is radioactive

Mn

atomic symbol for manganese

Mo

atomic symbol for molybdenum

mobile phase

phase in a chromatographic system that moves with respect to the stationary phase

mole (mol)

SI unit of amount of substance, defined as the number of elementary entities of a specified type equal to the number of atoms in 0.012 kg of ¹²C (see also Avogadro constant)

molecular weight

See relative molecular mass

moving phase

mobile phase

Mt

atomic symbol for meitnerium

Multi-Agency Radiological Laboratory Analytical Protocols Manual (MARLAP)

guidance document for radiochemistry laboratories and planners of projects involving radiochemical analyses, prepared by several federal agencies, including:

• Environmental Protection Agency (EPA)
• Nuclear Regulatory Commission (NRC)
• Department of Energy (DOE)
• Department of Defense (DoD)
• U.S. Geological Survey (USGS)
• Food and Drug Administration (FDA)
• Department of Homeland Security (DHS)
• National Institute of Standards and Technology (NIST)

MARLAP, which had been in progress since August 1995, was officially approved and released in December 2004.

multichannel analyzer (MCA)

digital electronic device for classifying and recording electrical pulses (e.g., produced in a radiation detector) according to strength in a sequence of data registers called channels

multiplet

in a spectrum, a combination of two or more peaks that are so close together that they partially or completely overlap