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Difference between revisions of "Count"

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{{MitoPedia
{{MitoPedia
|abbr=''N'' [x]
|abbr=''N'' [x]
|description=The '''number of entities''', ''N'', is different from a mere number. Whereas a number does not have a unit, a number of entities is composed of the numerical value and the countable entity, with the unit of a count [x]. Unfortunately, the dimensionless unit [x] is not explicitely considered by the SI and IUPAC (Mohr and Philipps 2015). This causes confusion, since then the unit [J] relates without discrimination to both: (1) exergy in the instrumental chamber (the system), and (2) exergy per countable entity (cells, particles, molecules, ions, electrons). The unit [Jāˆ™x<sup>-Ā­1</sup>] clearly indicates exergy per particle or object.
|description=The '''number of entities''', ''N'', is different from a mere number. Whereas a number does not have a unit, a number of entities is composed of the numerical value and the countable entity, with the unit of a count [x]. Unfortunately, the dimensionless unit [x] is not explicitely considered by the SI and IUPAC (Mohr and Philipps 2015). This causes confusion, since then the unit [J] relates without discrimination to both: (1) exergy in the instrumental chamber (the system), and (2) exergy per countable entity (cells, particles, molecules, ions, electrons). The unit [Jāˆ™x<sup>-Ā­1</sup>] clearly indicates exergy per particle or object. The unit [x] is a [[motive unit]].
|info=[[Gnaiger 2019 MitoPathways]]
|info=[[Gnaiger 2019 MitoPathways]]
}}
}}
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:::# Gnaiger E (2019) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed. Mitochondr Physiol Network 24.05. Oroboros MiPNet Publications, Innsbruck:112 pp. - [[Gnaiger 2019 MitoPathways |Ā»Bioblast linkĀ«]]
:::# Gnaiger E (2019) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed. Mitochondr Physiol Network 24.05. Oroboros MiPNet Publications, Innsbruck:112 pp. - [[Gnaiger 2019 MitoPathways |Ā»Bioblast linkĀ«]]
:::# Mohr PJ, Phillips WD (2015) Dimensionless units in the SI. Metrologia 52:40-7.
:::# Mohr PJ, Phillips WD (2015) Dimensionless units in the SI. Metrologia 52:40-7.
{{Keywords SI base units}}


{{MitoPedia concepts
{{MitoPedia concepts
|mitopedia concept=Ergodynamics
|mitopedia concept=Ergodynamics
}}
}}

Revision as of 09:14, 15 August 2019


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Count

Description

The number of entities, N, is different from a mere number. Whereas a number does not have a unit, a number of entities is composed of the numerical value and the countable entity, with the unit of a count [x]. Unfortunately, the dimensionless unit [x] is not explicitely considered by the SI and IUPAC (Mohr and Philipps 2015). This causes confusion, since then the unit [J] relates without discrimination to both: (1) exergy in the instrumental chamber (the system), and (2) exergy per countable entity (cells, particles, molecules, ions, electrons). The unit [Jāˆ™x-1] clearly indicates exergy per particle or object. The unit [x] is a motive unit.

Abbreviation: N [x]

Reference: Gnaiger 2019 MitoPathways

SI-units.png

Stating quantity values being pure numbers (p. 151)

There are also some quantities that cannot be described in terms of the seven base quantities of the SI, but have the nature of a count. Examples are a number of molecules, a number of cellular or biomolecular entities (for example copies of a particular nucleic acid sequence), or degeneracy in quantum mechanics. Counting quantities are also quantities with the associated unit one. The unit one is the neutral element of any system of units ā€“ necessary and present automatically. There is no requirement to introduce it formally by decision. Therefore, a formal traceability to the SI can be established through appropriate, validated measurement procedures (Section 2.3.3, p. 136).
As discussed in Section 2.3.3, values of quantities with unit one, are expressed simply as numbers. The unit symbol 1 or unit name ā€œoneā€ are not explicitly shown. SI prefix symbols can neither be attached to the symbol 1 nor to the name ā€œoneā€, therefore powers of 10 are used to express particularly large or small values.
Quantities that are ratios of quantities of the same kind (for example length ratios and amount fractions) have the option of being expressed with units (m/m, mol/mol) to aid the understanding of the quantity being expressed and also allow the use of SI prefixes, if this is desirable (Ī¼m/m, nmol/mol). Quantities relating to counting do not have this option, they are just numbers.
The internationally recognized symbol % (percent) may be used with the SI. When it is used, a space separates the number and the symbol %. The symbol % should be used rather than the name ā€œpercentā€. In written text, however, the symbol % generally takes the meaning of ā€œparts per hundredā€. Phrases such as ā€œpercentage by massā€, ā€œpercentage by volumeā€, or ā€œpercentage by amount of substanceā€ shall not be used; the extra information on the quantity should instead be conveyed in the description and symbol for the quantity.
The term ā€œppmā€, meaning 10-6 relative value, or 1 part in 106, or parts per million, is also used. This is analogous to the meaning of percent as parts per hundred. The terms ā€œparts per billionā€ and ā€œparts per trillionā€ and their respective abbreviations ā€œppbā€ and ā€œpptā€, are also used, but their meanings are language dependent. For this reason the abbreviations ppb and ppt should be avoided.
  • Reference: Bureau International des Poids et Mesures (2019) The International System of Units (SI). 9th edition:117-216 ISBN 978-92-822-2272-0. - Ā»Open Access pdfĀ«

References

  1. Bureau International des Poids et Mesures (2019) The International System of Units (SI). 9th edition:117-216 ISBN 978-92-822-2272-0. - Ā»Open Access pdfĀ«
  2. Gnaiger E (2019) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed. Mitochondr Physiol Network 24.05. Oroboros MiPNet Publications, Innsbruck:112 pp. - Ā»Bioblast linkĀ«
  3. Mohr PJ, Phillips WD (2015) Dimensionless units in the SI. Metrologia 52:40-7.

Template:Keywords SI base units


MitoPedia concepts: Ergodynamics