The neutron flux emitted from fusion devices induces many different nuclear reactions that can activate the vacuum chamber and irradiate operators. A γ-spectrometer was mounted inside the Plasma ...Focus (PF) PF-1000, the world’s largest plasma focus facility, after completing a campaign. Qualitative analysis was performed following a lengthy γ-spectrum acquisition period. Instrumental neutron activation analysis identified the elemental composition of the vacuum chamber for use by a Monte Carlo N-Particle simulation. In this way, the radioactivity accumulated inside the PF-1000 as the function of time was calculated.
Mass spectrometry provides an extremely sensitive method for the identification and quantification of modified nucleosides and hence for determining chemical modifications of nucleic acids. When mass ...spectrometry is used in conjunction with a new high-performance liquid chromatographic system capable of separating 15 methylated and naturally occurring nucleosides, this allows the quantification of products of in vitro DNA methylation. With synthetic (2H3)methyl-labeled methylnucleosides as internal references, the distribution of methylated products formed when calf thymus DNA was reacted with N-methyl-N-nitrosourea(MeNU) was determined. Five modified products, 1-methyldeoxyadenosine(m1dA), 3-methyldeoxycytidine(m3dC), 7-methyldeoxyguanosine(m7dG), 3-methylthymidine(m3T) and O4-methylthymidine(m4T) were detected and the relative distributions were measured. The ability of mass spectrometry/mass spectrometry (tandem mass spectrometry) to increase specificity and sensitivity in this determination is demonstrated and its application to in vivo studies is suggested.
