Q-exponential - Revision history

en>Quondum: italic 'q'

2014-05-01T00:11:30Z

italic 'q'

← Older revision		Revision as of 02:11, 1 May 2014
Line 1:		Line 1:
	~~{{Refimprove\|date=December 2009}}~~		Andrew Berryhill is what his wife loves to contact him and he totally digs that title. To climb is some thing I really enjoy performing. I've always cherished residing in Kentucky but now I'm contemplating other options. She works as a journey agent but soon she'll be on her own.<br><br>Here is my page :: [https://www.machlitim.org.il/subdomain/megila/end/node/12300 psychic phone readings]
	~~{{Infobox isotope\|~~

	~~\| background = #aaccee~~
	~~\| text_color =~~
	~~\| isotope_name = Oxygen-18~~
	~~\| isotope_filename =~~
	~~\| alternate_names =~~
	~~\| mass_number = 18~~
	~~\| symbol = O~~
	~~\| num_neutrons = 10~~
	~~\| num_protons = 8~~
	~~\| abundance = 0.2%~~
	~~\| halflife =~~
	~~\| error_halflife =~~
	~~\| decay_product =~~
	~~\| decay_mass =~~
	~~\| decay_symbol =~~
	~~\| mass =~~
	~~\| spin =0~~
	~~\| excess_energy =~~
	~~\| error1 =~~
	~~\| binding_energy =~~
	~~\| error2 =~~
	~~\| decay_mode1 =~~
	~~\| decay_energy1 =~~
	~~\| decay_mode2 =~~
	~~\| decay_energy2 =~~
	~~\| decay_mode3 =~~
	~~\| decay_energy3 =~~
	~~\| decay_mode4 =~~
	~~\| decay_energy4 =~~
	}}

	~~'''Oxygen-18''' ('''{{chem\|18\|O}}''')~~ is ~~a natural, [[Stable isotope\|stable]] [[isotope]] of [[oxygen]]~~ and ~~one of the [[environmental isotopes]].~~

	{{chem\|18\|O}} is an important precursor for the production of [[fluorodeoxyglucose]] (FDG) used in [[positron emission tomography]] (PET). Generally, in the [[radiopharmaceutical]] industry, enriched water ({{chem\|H\|2}}{{chem\|18\|O}}) is bombarded with hydrogen ions in either a [[cyclotron]] or [[linear particle accelerator\|linear accelerator]] creating [[fluorine-18]]. This is then synthesized into FDG and injected into a patient. It can also be used to make an extremely heavy version of water with the [[tritium]] isotope of hydrogen, {{chem\|3\|H\|2}}{{chem\|18\|O}}, or {{chem\|T\|2}}{{chem\|18\|O}}. This compound has a density almost 30% greater than natural water <ref>{{cite book \|last=Pauling \|first=Linus \|chapter=12-7. Heavy Water \|chapterurl=http://books.google.com.au/books?id=EpxSzteNvMYC&lpg=PP1&dq=isbn%3A0486656225&pg=PA438#v=onepage&q&f=false \|title~~=General Chemistry \|publisher=Dover \|year=1988 \|isbn=0-486-65622-5 \|page=438 \|edition=3rd}}</ref>~~

	~~==Paleoclimatology==~~
	~~In ice cores, mainly [[Arctic]] and [[Antarctic]], the ratio [[Δ18O\|O-18/O-16]] (δ{{chem\|18\|O}}) can be used to determine the temperature of precipitation through time~~. Assuming that atmospheric circulation and elevation has not changed significantly over the poles, the temperature of ice formation can be calculated as [[equilibrium fractionation]] between phases of water that is ~~known for different temperatures~~. ~~Water molecules are also subject to [[Rayleigh fractionation]]<ref>{{Cite book \| last1 = Kendall \| first1 = C. \| last2 = Caldwell \| first2 = E.A. \| chapter = Chapter 2: Fundamentals~~ in ~~Isotope Geochemistry \| chapterurl=http://wwwrcamnl.wr.usgs.gov/isoig/isopubs/itchch2.html \| title= Isotope Tracers in Catchment Hydrology \| publisher= Elsevier Science B.V., Amsterdam~~. ~~\| year = 1998}}</ref>~~ as atmospheric water moves from the equator poleward which results in progressive depletion of O-18, or lower δ{{chem\|18\|O}} values. In the 1950s, [[Harold Urey]] performed an experiment in which he mixed both normal water and water with oxygen-18 in a ~~barrel, and then partially froze the barrel~~'~~s contents~~.
	<br />
	The ratio O-18/O-16 (δ{{chem\|18\|O}}) can also be used to determine [[paleothermometry]] in certain types of fossils. The fossils in question have to show progressive growth in the animal or plant that the fossil represents. The fossil material used is generally [[calcite]] or [[aragonite]], however oxygen isotope paleothermometry has also been done of [[Phosphate\|phosphatic]] fossils using [[Sensitive high-resolution ion microprobe\|SHRIMP]].<ref>{{Cite journal \| last1 = Trotter \| first1 = J.A. \| last2 = Williams \| first2 = I.S. \| last3 = Barnes \| first3 = C.R. \| last4 = Lécuyer \| first4 = C. \| last5 = Nicoll \| first5 = R.S. \| title = Did Cooling Oceans Trigger Ordovician Biodiversification? Evidence from Conodont Thermometry \| journal = Science \| volume = 321 \| issue = 5888 \| pages = 550–4 \| year = 2008 \| doi = 10.1126/science.1155814\|bibcode = 2008Sci...321..550T \|pmid=18653889 \|url=http://www.sciencemag.org/cgi/pmidlookup?view=short&pmid=18653889}}</ref> For example, seasonal temperature variations may be determined from a single sea shell from a [[scallop]]. As the scallop grows, an extension is seen on the surface of the shell. Each growth band can be measured, and a calculation is used to determine the probable sea water temperature in comparison to each growth. The equation for this is:

	~~<math>T = A + B \cdot \left( \left( \delta {}^{18} \text{O} \right) \text{calcite} - \left( \delta {}^{18} \text{O} \right) \text{water} \right)</math>~~

	~~Where ''T'' is temperature in Celsius and ''A'' and ''B'' are constants.~~

	For determination of ocean temperatures over geologic time, multiple fossils of the same species in different [[Stratigraphy\|stratigraphic layers]] would be measured, and the difference between them would indicate long term changes.<ref>{{Cite book \| last1 = Kendall \| first1 = C. \| last2 = McDonnell \| first2 = J.J. \| title = Isotope Tracers in Catchment Hydrology \| publisher= Elsevier Science B.V., Amsterdam. \| year = 1998 \| url = http:~~//wwwrcamnl.wr.usgs.gov/isoig/isopubs/itchinfo.html}}</ref>~~

	~~==Plant physiology==~~

	In the study of plants [[photorespiration]], the labeling of atmosphere by oxygen-18 allows us to measure the oxygen uptake by the photorespiration pathway. Labeling by {{chem\|18\|O\|2}} gives the unidirectional flux of {{chem\|O\|2}} uptake, while there is a net photosynthetic {{chem\|16\|O\|2}} evolution. It was demonstrated that, under preindustrial atmosphere, most plants reabsorb, by photorespiration, half of the oxygen produced by [[photosynthesis]]. Then, the yield of photosynthesis was halved by the presence of oxygen in atmosphere.<ref>{{cite journal \|author=Gerbaud A, André M \|title=Photosynthesis and photorespiration in whole plants of wheat \|journal=Plant Physiol. \|volume=64 \|issue=5 \|pages=735–8 \|date=November 1979 \|pmid=16661044 \|pmc=543347 \|url=http://www.~~plantphysiol~~.org~~/cgi/pmidlookup?view=long&pmid=16661044}}</ref><ref>{{cite journal \|author=Canvin DT, Berry JA, Badger MR, Fock H, Osmond CB \|title=Oxygen exchange in leaves in the light \|journal=Plant Physiol~~. ~~\|volume=66 \|issue=2 \|pages=302–7 \|date=August 1980 \|pmid=16661426 \|pmc=440587 \|url=http:~~//~~www.plantphysiol.org~~/~~cgi~~/~~pmidlookup?view=long&pmid=16661426}}<~~/~~ref>~~

	~~==See also==~~
	* [[Willi Dansgaard]] — a [[paleoclimatology\|paleoclimatologist]]
	* [[Isotopes of oxygen]]
	* [[Paleothermometry]]
	* [[Pâté de Foie Gras (short story)]]
	* [[Δ18O]]

	~~==References==~~
	~~{{reflist}}~~

	~~{{Isotope\|element=oxygen~~
	~~\|lighter=[[oxygen-17]]~~
	~~\|heavier=[[oxygen-19]]~~
	~~\|before=[[nitrogen-18]], [[nitrogen-19]], [[fluorine-18]]~~
	~~\|after=stable~~
	}}

	~~[[Category:Environmental isotopes]]~~
	~~[[Category:Isotopes of oxygen]~~]

en>Mogism: /* References */Cleanup/Typo fixing, typo(s) fixed: , → , (2) using AWB

2013-10-24T17:25:29Z

References: Cleanup/Typo fixing, typo(s) fixed: , → , (2) using AWB

← Older revision		Revision as of 19:25, 24 October 2013
Line 1:		Line 1:
	~~The author~~'~~s name~~ is ~~Christy~~. ~~The preferred pastime~~ for ~~him~~ and ~~his children is~~ to ~~perform lacross and he would never give it up~~. ~~For years she's been working as~~ a ~~journey agent~~. ~~Her family life in Alaska but her [~~http://~~netwk~~.~~hannam~~.ac.kr/xe/~~data_2~~/~~85669 phone psychic readings~~] ~~husband wants them best psychic readings~~ ([http://~~cartoonkorea~~.~~com~~/~~ce002~~/~~1093612 mouse click~~ the ~~next webpage~~]) to ~~move~~.<br><br>~~Also visit my page email psychic readings~~ ([http://~~203~~.~~250~~.78.~~160~~/~~zbxe~~/~~?document_srl~~=~~1792908 Privacy~~ of ~~Data: This tool~~ is ~~built-with~~ and ~~functions-~~in ~~Client Side JavaScripting~~, ~~so only your computer will see or process your data input~~/~~output~~.a ~~cool way to improve~~])		{{Refimprove\|date=December 2009}}
			{{Infobox isotope\|

			\| background = #aaccee
			\| text_color =
			\| isotope_name = Oxygen-18
			\| isotope_filename =
			\| alternate_names =
			\| mass_number = 18
			\| symbol = O
			\| num_neutrons = 10
			\| num_protons = 8
			\| abundance = 0.2%
			\| halflife =
			\| error_halflife =
			\| decay_product =
			\| decay_mass =
			\| decay_symbol =
			\| mass =
			\| spin =0
			\| excess_energy =
			\| error1 =
			\| binding_energy =
			\| error2 =
			\| decay_mode1 =
			\| decay_energy1 =
			\| decay_mode2 =
			\| decay_energy2 =
			\| decay_mode3 =
			\| decay_energy3 =
			\| decay_mode4 =
			\| decay_energy4 =
			}}

			'''Oxygen-18''' ('''{{chem\|18\|O}}''') is a natural, [[Stable isotope\|stable]] [[isotope]] of [[oxygen]] and one of the [[environmental isotopes]].

			{{chem\|18\|O}} is an important precursor for the production of [[fluorodeoxyglucose]] (FDG) used in [[positron emission tomography]] (PET). Generally, in the [[radiopharmaceutical]] industry, enriched water ({{chem\|H\|2}}{{chem\|18\|O}}) is bombarded with hydrogen ions in either a [[cyclotron]] or [[linear particle accelerator\|linear accelerator]] creating [[fluorine-18]]. This is then synthesized into FDG and injected into a patient. It can also be used to make an extremely heavy version of water with the [[tritium]] isotope of hydrogen, {{chem\|3\|H\|2}}{{chem\|18\|O}}, or {{chem\|T\|2}}{{chem\|18\|O}}. This compound has a density almost 30% greater than natural water <ref>{{cite book \|last=Pauling \|first=Linus \|chapter=12-7. Heavy Water \|chapterurl=http://books.google.com.au/books?id=EpxSzteNvMYC&lpg=PP1&dq=isbn%3A0486656225&pg=PA438#v=onepage&q&f=false \|title=General Chemistry \|publisher=Dover \|year=1988 \|isbn=0-486-65622-5 \|page=438 \|edition=3rd}}</ref>

			==Paleoclimatology==
			In ice cores, mainly [[Arctic]] and [[Antarctic]], the ratio [[Δ18O\|O-18/O-16]] (δ{{chem\|18\|O}}) can be used to determine the temperature of precipitation through time. Assuming that atmospheric circulation and elevation has not changed significantly over the poles, the temperature of ice formation can be calculated as [[equilibrium fractionation]] between phases of water that is known for different temperatures. Water molecules are also subject to [[Rayleigh fractionation]]<ref>{{Cite book \| last1 = Kendall \| first1 = C. \| last2 = Caldwell \| first2 = E.A. \| chapter = Chapter 2: Fundamentals in Isotope Geochemistry \| chapterurl=http://wwwrcamnl.wr.usgs.gov/isoig/isopubs/itchch2.html \| title= Isotope Tracers in Catchment Hydrology \| publisher= Elsevier Science B.V., Amsterdam. \| year = 1998}}</ref> as atmospheric water moves from the equator poleward which results in progressive depletion of O-18, or lower δ{{chem\|18\|O}} values. In the 1950s, [[Harold Urey]] performed an experiment in which he mixed both normal water and water with oxygen-18 in a barrel, and then partially froze the barrel's contents.
			<br />
			The ratio O-18/O-16 (δ{{chem\|18\|O}}) can also be used to determine [[paleothermometry]] in certain types of fossils. The fossils in question have to show progressive growth in the animal or plant that the fossil represents. The fossil material used is generally [[calcite]] or [[aragonite]], however oxygen isotope paleothermometry has also been done of [[Phosphate\|phosphatic]] fossils using [[Sensitive high-resolution ion microprobe\|SHRIMP]].<ref>{{Cite journal \| last1 = Trotter \| first1 = J.A. \| last2 = Williams \| first2 = I.S. \| last3 = Barnes \| first3 = C.R. \| last4 = Lécuyer \| first4 = C. \| last5 = Nicoll \| first5 = R.S. \| title = Did Cooling Oceans Trigger Ordovician Biodiversification? Evidence from Conodont Thermometry \| journal = Science \| volume = 321 \| issue = 5888 \| pages = 550–4 \| year = 2008 \| doi = 10.1126/science.1155814\|bibcode = 2008Sci...321..550T \|pmid=18653889 \|url=http://www.sciencemag.org/cgi/pmidlookup?view=short&pmid=18653889}}</ref> For example, seasonal temperature variations may be determined from a single sea shell from a [[scallop]]. As the scallop grows, an extension is seen on the surface of the shell. Each growth band can be measured, and a calculation is used to determine the probable sea water temperature in comparison to each growth. The equation for this is:

			<math>T = A + B \cdot \left( \left( \delta {}^{18} \text{O} \right) \text{calcite} - \left( \delta {}^{18} \text{O} \right) \text{water} \right)</math>

			Where ''T'' is temperature in Celsius and ''A'' and ''B'' are constants.

			For determination of ocean temperatures over geologic time, multiple fossils of the same species in different [[Stratigraphy\|stratigraphic layers]] would be measured, and the difference between them would indicate long term changes.<ref>{{Cite book \| last1 = Kendall \| first1 = C. \| last2 = McDonnell \| first2 = J.J. \| title = Isotope Tracers in Catchment Hydrology \| publisher= Elsevier Science B.V., Amsterdam. \| year = 1998 \| url = http://wwwrcamnl.wr.usgs.gov/isoig/isopubs/itchinfo.html}}</ref>

			==Plant physiology==

			In the study of plants [[photorespiration]], the labeling of atmosphere by oxygen-18 allows us to measure the oxygen uptake by the photorespiration pathway. Labeling by {{chem\|18\|O\|2}} gives the unidirectional flux of {{chem\|O\|2}} uptake, while there is a net photosynthetic {{chem\|16\|O\|2}} evolution. It was demonstrated that, under preindustrial atmosphere, most plants reabsorb, by photorespiration, half of the oxygen produced by [[photosynthesis]]. Then, the yield of photosynthesis was halved by the presence of oxygen in atmosphere.<ref>{{cite journal \|author=Gerbaud A, André M \|title=Photosynthesis and photorespiration in whole plants of wheat \|journal=Plant Physiol. \|volume=64 \|issue=5 \|pages=735–8 \|date=November 1979 \|pmid=16661044 \|pmc=543347 \|url=http://www.plantphysiol.org/cgi/pmidlookup?view=long&pmid=16661044}}</ref><ref>{{cite journal \|author=Canvin DT, Berry JA, Badger MR, Fock H, Osmond CB \|title=Oxygen exchange in leaves in the light \|journal=Plant Physiol. \|volume=66 \|issue=2 \|pages=302–7 \|date=August 1980 \|pmid=16661426 \|pmc=440587 \|url=http://www.plantphysiol.org/cgi/pmidlookup?view=long&pmid=16661426}}</ref>

			==See also==
			* [[Willi Dansgaard]] — a [[paleoclimatology\|paleoclimatologist]]
			* [[Isotopes of oxygen]]
			* [[Paleothermometry]]
			* [[Pâté de Foie Gras (short story)]]
			* [[Δ18O]]

			==References==
			{{reflist}}

			{{Isotope\|element=oxygen
			\|lighter=[[oxygen-17]]
			\|heavier=[[oxygen-19]]
			\|before=[[nitrogen-18]], [[nitrogen-19]], [[fluorine-18]]
			\|after=stable
			}}

			[[Category:Environmental isotopes]]
			[[Category:Isotopes of oxygen]]

en>Purple Post-its at 22:20, 27 June 2011

2011-06-27T22:20:54Z

New page

The author's name is Christy. The preferred pastime for him and his children is to perform lacross and he would never give it up. For years she's been working as a journey agent. Her family life in Alaska but her [http://netwk.hannam.ac.kr/xe/data_2/85669 phone psychic readings] husband wants them best psychic readings ([http://cartoonkorea.com/ce002/1093612 mouse click the next webpage]) to move.<br><br>Also visit my page email psychic readings ([http://203.250.78.160/zbxe/?document_srl=1792908 Privacy of Data: This tool is built-with and functions-in Client Side JavaScripting, so only your computer will see or process your data input/output.a cool way to improve])

← Older revision		Revision as of 02:11, 1 May 2014
Line 1:		Line 1:
	~~{{Refimprove\|date=December 2009}}~~		Andrew Berryhill is what his wife loves to contact him and he totally digs that title. To climb is some thing I really enjoy performing. I've always cherished residing in Kentucky but now I'm contemplating other options. She works as a journey agent but soon she'll be on her own.<br><br>Here is my page :: [https://www.machlitim.org.il/subdomain/megila/end/node/12300 psychic phone readings]
	~~{{Infobox isotope\|~~

	~~\| background = #aaccee~~
	~~\| text_color =~~
	~~\| isotope_name = Oxygen-18~~
	~~\| isotope_filename =~~
	~~\| alternate_names =~~
	~~\| mass_number = 18~~
	~~\| symbol = O~~
	~~\| num_neutrons = 10~~
	~~\| num_protons = 8~~
	~~\| abundance = 0.2%~~
	~~\| halflife =~~
	~~\| error_halflife =~~
	~~\| decay_product =~~
	~~\| decay_mass =~~
	~~\| decay_symbol =~~
	~~\| mass =~~
	~~\| spin =0~~
	~~\| excess_energy =~~
	~~\| error1 =~~
	~~\| binding_energy =~~
	~~\| error2 =~~
	~~\| decay_mode1 =~~
	~~\| decay_energy1 =~~
	~~\| decay_mode2 =~~
	~~\| decay_energy2 =~~
	~~\| decay_mode3 =~~
	~~\| decay_energy3 =~~
	~~\| decay_mode4 =~~
	~~\| decay_energy4 =~~
	}}

	~~'''Oxygen-18''' ('''{{chem\|18\|O}}''')~~ is ~~a natural, [[Stable isotope\|stable]] [[isotope]] of [[oxygen]]~~ and ~~one of the [[environmental isotopes]].~~

	{{chem\|18\|O}} is an important precursor for the production of [[fluorodeoxyglucose]] (FDG) used in [[positron emission tomography]] (PET). Generally, in the [[radiopharmaceutical]] industry, enriched water ({{chem\|H\|2}}{{chem\|18\|O}}) is bombarded with hydrogen ions in either a [[cyclotron]] or [[linear particle accelerator\|linear accelerator]] creating [[fluorine-18]]. This is then synthesized into FDG and injected into a patient. It can also be used to make an extremely heavy version of water with the [[tritium]] isotope of hydrogen, {{chem\|3\|H\|2}}{{chem\|18\|O}}, or {{chem\|T\|2}}{{chem\|18\|O}}. This compound has a density almost 30% greater than natural water <ref>{{cite book \|last=Pauling \|first=Linus \|chapter=12-7. Heavy Water \|chapterurl=http://books.google.com.au/books?id=EpxSzteNvMYC&lpg=PP1&dq=isbn%3A0486656225&pg=PA438#v=onepage&q&f=false \|title~~=General Chemistry \|publisher=Dover \|year=1988 \|isbn=0-486-65622-5 \|page=438 \|edition=3rd}}</ref>~~

	~~==Paleoclimatology==~~
	~~In ice cores, mainly [[Arctic]] and [[Antarctic]], the ratio [[Δ18O\|O-18/O-16]] (δ{{chem\|18\|O}}) can be used to determine the temperature of precipitation through time~~. Assuming that atmospheric circulation and elevation has not changed significantly over the poles, the temperature of ice formation can be calculated as [[equilibrium fractionation]] between phases of water that is ~~known for different temperatures~~. ~~Water molecules are also subject to [[Rayleigh fractionation]]<ref>{{Cite book \| last1 = Kendall \| first1 = C. \| last2 = Caldwell \| first2 = E.A. \| chapter = Chapter 2: Fundamentals~~ in ~~Isotope Geochemistry \| chapterurl=http://wwwrcamnl.wr.usgs.gov/isoig/isopubs/itchch2.html \| title= Isotope Tracers in Catchment Hydrology \| publisher= Elsevier Science B.V., Amsterdam~~. ~~\| year = 1998}}</ref>~~ as atmospheric water moves from the equator poleward which results in progressive depletion of O-18, or lower δ{{chem\|18\|O}} values. In the 1950s, [[Harold Urey]] performed an experiment in which he mixed both normal water and water with oxygen-18 in a ~~barrel, and then partially froze the barrel~~'~~s contents~~.
	<br />
	The ratio O-18/O-16 (δ{{chem\|18\|O}}) can also be used to determine [[paleothermometry]] in certain types of fossils. The fossils in question have to show progressive growth in the animal or plant that the fossil represents. The fossil material used is generally [[calcite]] or [[aragonite]], however oxygen isotope paleothermometry has also been done of [[Phosphate\|phosphatic]] fossils using [[Sensitive high-resolution ion microprobe\|SHRIMP]].<ref>{{Cite journal \| last1 = Trotter \| first1 = J.A. \| last2 = Williams \| first2 = I.S. \| last3 = Barnes \| first3 = C.R. \| last4 = Lécuyer \| first4 = C. \| last5 = Nicoll \| first5 = R.S. \| title = Did Cooling Oceans Trigger Ordovician Biodiversification? Evidence from Conodont Thermometry \| journal = Science \| volume = 321 \| issue = 5888 \| pages = 550–4 \| year = 2008 \| doi = 10.1126/science.1155814\|bibcode = 2008Sci...321..550T \|pmid=18653889 \|url=http://www.sciencemag.org/cgi/pmidlookup?view=short&pmid=18653889}}</ref> For example, seasonal temperature variations may be determined from a single sea shell from a [[scallop]]. As the scallop grows, an extension is seen on the surface of the shell. Each growth band can be measured, and a calculation is used to determine the probable sea water temperature in comparison to each growth. The equation for this is:

	~~<math>T = A + B \cdot \left( \left( \delta {}^{18} \text{O} \right) \text{calcite} - \left( \delta {}^{18} \text{O} \right) \text{water} \right)</math>~~

	~~Where ''T'' is temperature in Celsius and ''A'' and ''B'' are constants.~~

	For determination of ocean temperatures over geologic time, multiple fossils of the same species in different [[Stratigraphy\|stratigraphic layers]] would be measured, and the difference between them would indicate long term changes.<ref>{{Cite book \| last1 = Kendall \| first1 = C. \| last2 = McDonnell \| first2 = J.J. \| title = Isotope Tracers in Catchment Hydrology \| publisher= Elsevier Science B.V., Amsterdam. \| year = 1998 \| url = http:~~//wwwrcamnl.wr.usgs.gov/isoig/isopubs/itchinfo.html}}</ref>~~

	~~==Plant physiology==~~

	In the study of plants [[photorespiration]], the labeling of atmosphere by oxygen-18 allows us to measure the oxygen uptake by the photorespiration pathway. Labeling by {{chem\|18\|O\|2}} gives the unidirectional flux of {{chem\|O\|2}} uptake, while there is a net photosynthetic {{chem\|16\|O\|2}} evolution. It was demonstrated that, under preindustrial atmosphere, most plants reabsorb, by photorespiration, half of the oxygen produced by [[photosynthesis]]. Then, the yield of photosynthesis was halved by the presence of oxygen in atmosphere.<ref>{{cite journal \|author=Gerbaud A, André M \|title=Photosynthesis and photorespiration in whole plants of wheat \|journal=Plant Physiol. \|volume=64 \|issue=5 \|pages=735–8 \|date=November 1979 \|pmid=16661044 \|pmc=543347 \|url=http://www.~~plantphysiol~~.org~~/cgi/pmidlookup?view=long&pmid=16661044}}</ref><ref>{{cite journal \|author=Canvin DT, Berry JA, Badger MR, Fock H, Osmond CB \|title=Oxygen exchange in leaves in the light \|journal=Plant Physiol~~. ~~\|volume=66 \|issue=2 \|pages=302–7 \|date=August 1980 \|pmid=16661426 \|pmc=440587 \|url=http:~~//~~www.plantphysiol.org~~/~~cgi~~/~~pmidlookup?view=long&pmid=16661426}}<~~/~~ref>~~

	~~==See also==~~
	* [[Willi Dansgaard]] — a [[paleoclimatology\|paleoclimatologist]]
	* [[Isotopes of oxygen]]
	* [[Paleothermometry]]
	* [[Pâté de Foie Gras (short story)]]
	* [[Δ18O]]

	~~==References==~~
	~~{{reflist}}~~

	~~{{Isotope\|element=oxygen~~
	~~\|lighter=[[oxygen-17]]~~
	~~\|heavier=[[oxygen-19]]~~
	~~\|before=[[nitrogen-18]], [[nitrogen-19]], [[fluorine-18]]~~
	~~\|after=stable~~
	}}

	~~[[Category:Environmental isotopes]]~~
	~~[[Category:Isotopes of oxygen]~~]