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Date: 27-4-2019
1555
Date: 21-3-2017
1758
Date: 25-7-2020
1139
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NMR active nuclei and isotopes as tracers of Group 17 elements
Although F, Cl, Br and I all possess spin active nuclei, in practice only 19F (100%, I = 1/2) is used routinely. Fluorine-19 NMR spectroscopy is a valuable tool in the elucidation of structures and reaction mechanisms of F-containing compounds.
Artificial isotopes of F include 18F (β+e mitter, t1/2= 1.83 h)and 20F (β- emitter, t1/2= 11.0 s). The former is the longest lived radioisotope of F and may be used as a radioactive tracer. The 20F isotope has application in F dating of bones and teeth; these usually contain apatite which is slowly converted to fluorapatite when the mineral is buried in the soil. By using the technique of neutron activation analysis, naturally occurring 19F is converted to 20F by neutron bombardment; the radioactive decay of the latter is then monitored, allowing the amount of 19F originally present in the sample to be determined.
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"الرعاية التلطيفية".. تحسين جودة حياة المرضى هي السر
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العلماء الروس يطورون طريقة جديدة لإعادة تدوير النفايات البلاستيكية
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اختتام المراسم التأبينية التي أهدي ثوابها إلى أرواح شهداء المق*ا*و*مة
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