Wikipedia-diskussion:AA-TaskForce/Ædelgasser/Xenon: Forskelle mellem versioner
Seekers (diskussion | bidrag) Hjælp til oversættelse... |
(Ingen forskel)
|
Versionen fra 27. jul. 2009, 01:39
Hjælp til oversættelse...
Er helt ude og.... her. Og jo mere jeg roder mig ud i oversættelsen af dette afsnit, jo mere forviret bliver jeg.
Hvad jeg har fået oversat (tror jeg):
Medicinsk billeddannelse
Gamma udledningen fra radioisotopen 133Xe kan for eksempel bruges til at scanne (og derved danne billeder) af hjerte, lunger og hjernen ved hjælp af Single Photon Emission Computed Tomography metoden. 133Xe er også blevet brugt til at måle blodgennemstrømning.[1][2][3]
Kernen af de to stabile isotoper af xenon, 129Xe og 131Xe, har et indre ikke-nul impulsmoment (nuklearspin). Når det blandes med et alkalie og nitrogen og derefter udsat for en laserstråle bestående af cirkulært polariseret lys som er indstillet til en spektrallinje inden for alkalie atomerne område,
Engelsk:
Medical imaging
Gamma emission from the radioisotope 133Xe of xenon can be used to image the heart, lungs, and brain, for example, by means of single photon emission computed tomography. 133Xe has also been used to measure blood flow.[4][5][6]
Nuclei of two of the stable isotopes of xenon, 129Xe and 131Xe, have non-zero intrinsic angular momenta (nuclear spins). When mixed with alkali vapor and nitrogen and exposed to a laser beam of circularly polarized light that is tuned to an absorption line of the alkali atoms, their nuclear spins can be aligned by a spin exchange process in which the alkali valence electrons are spin-polarized by the light and then transfer their polarization to the xenon nuclei via magnetic hyperfine coupling.[7] Typically, pure rubidium metal, heated above 100 °C, is used to produce the alkali vapor. The resulting spin polarization of xenon nuclei can surpass 50% of its maximum possible value, greatly exceeding the equilibrium value dictated by the Boltzmann distribution (typically 0.001% of the maximum value at room temperature, even in the strongest magnets). Such non-equilibrium alignment of spins is a temporary condition, and is called hyperpolarization.
Because a 129Xe nucleus has a spin of 1/2, and therefore a zero electric quadrupole moment, the 129Xe nucleus does not experience any quadrupolar interactions during collisions with other atoms, and thus its hyperpolarization can be maintained for long periods of time even after the laser beam has been turned off and the alkali vapor removed by condensation on a room-temperature surface. The time it takes for a collection of spins to return to their equilibrium (Boltzmann) polarization is called the T1 relaxation time. For 129Xe it can range from several seconds for xenon atoms dissolved in blood[8] to several hours in the gas phase[9] and several days in deeply frozen solid xenon.[10] In contrast, 131Xe has a nuclear spin value of 3/2 and a nonzero quadrupole moment, and has T1 relaxation times in the millisecond and second ranges.[11] Hyperpolarization renders 129Xe much more detectable via magnetic resonance imaging and has been used for studies of the lungs and other tissues. It can be used, for example, to trace the flow of gases within the lungs.[12][13]
--Seekers 27. jul 2009, 01:39 (CEST)
- ^ Van Der Wall, Ernst (1992). What's New in Cardiac Imaging?: SPECT, PET, and MRI. Springer. ISBN 0792316150.
- ^ Frank, John (1999). "Introduction to imaging: The chest". Student BMJ. 12: 1-44. Hentet 2008-06-04.
- ^ Chandak, Puneet K. (juli 20, 1995). "Brain SPECT: Xenon-133". Brigham RAD. Hentet 2008-06-04.
{{cite web}}: CS1-vedligeholdelse: Dato automatisk oversat (link) - ^ Van Der Wall, Ernst (1992). What's New in Cardiac Imaging?: SPECT, PET, and MRI. Springer. ISBN 0792316150.
- ^ Frank, John (1999). "Introduction to imaging: The chest". Student BMJ. 12: 1-44. Hentet 2008-06-04.
- ^ Chandak, Puneet K. (juli 20, 1995). "Brain SPECT: Xenon-133". Brigham RAD. Hentet 2008-06-04.
{{cite web}}: CS1-vedligeholdelse: Dato automatisk oversat (link) - ^ Otten, Ernst W. (2004). "Take a breath of polarized noble gas". Europhysics News. 35 (1): 16. doi:10.1051/epn:2004109.
{{cite journal}}:|access-date=kræver at|url=også er angivet (hjælp) - ^ Wolber, J. (2000). "On the oxygenation-dependent 129Xe T1 in blood". NMR in Biomedicine. 13 (4): 234-237. doi:10.1002/1099-1492(200006)13:4%3C234::AID-NBM632%3E3.0.CO;2-K.
{{cite journal}}: Ukendt parameter|coauthors=ignoreret (|author=foreslået) (hjælp); Ukendt parameter|doilabel=ignoreret (hjælp) - ^ Chann, B. (2002). "129Xe-Xe molecular spin relaxation". Physical Review Letters. 88 (11): 113-201. doi:10.1103/PhysRevLett.88.113201.
{{cite journal}}: Ukendt parameter|coauthors=ignoreret (|author=foreslået) (hjælp) - ^ von Schulthess, Gustav Konrad (1998). The Encyclopaedia of Medical Imaging. Taylor & Francis. s. 194. ISBN 1901865134.
{{cite book}}: Ukendt parameter|coauthors=ignoreret (|author=foreslået) (hjælp) - ^ Warren, W. W. (1966). "Nuclear Quadrupole Relaxation and Chemical Shift of Xe131 in Liquid and Solid Xenon". Physical Review. 148 (1): 402-412. doi:10.1103/PhysRev.148.402.
{{cite journal}}: Ukendt parameter|coauthors=ignoreret (|author=foreslået) (hjælp) - ^ Albert, M. S. (1998). "Development of hyperpolarized noble gas MRI". Nuclear Instruments and Methods in Physics Research A. 402: 441-453. doi:10.1016/S0168-9002(97)00888-7. Hentet 2007-10-01.
{{cite journal}}: Ukendt parameter|coauthors=ignoreret (|author=foreslået) (hjælp) - ^ Irion, Robert (marts 23, 1999). "Head Full of Xenon?". Science News. Hentet 2007-10-08.
{{cite news}}: CS1-vedligeholdelse: Dato automatisk oversat (link)