Nuclear magnetic resonance imaging techniques as developed modestly within a university medical center environment: What can the small system contribute at this point?

This paper describes a geometrically small NMR imaging system which has been developed and assembled within a university medical center environment. Consideration is given to the technical specifications and basic economics for the magnet system, NMR spectrometer, and computer configuration. Initial research objectives for the system are outlined which include (1) the signal-to-noise improvement potential of rotational gradient imaging, and (2) ¹⁹F tracer imaging considerations with a detailed discussion concerning the feasibility of in vivo NMR imaging of ¹⁹F-fluorodeoxyglucose (2-FDG and 3-FDG). Finally, potentially significant areas for research within the constraints of a small NMR imaging system are described.     

Anionic polymerization of caprolactam. XLIII. Relationship between osmometric molecular weight,viscosity, and endgroups of a polymer

For unfractionated anionic polymers, the following relationship between the osmometric molecular weight and intrinsic viscosity is valid: M?_n = 13200[η]^1.115 (cresol), or M?_n = 13000[η]^1.021 (93.8% H₂SO₄). A comparison of the osmometric and viscometric data with the number of endgroups of a polymer confirmed the finding that under certain conditions, moderately branched molecules can be formed; the above parameters depend on the type of the activator used.     

Hydrocarbon detection using laser ion mobility spectrometry

A Laser Ion Mobility Spectrometer has been set up and trace detection experiments have been performed. We find that laser ionization almost selectively ionizes aromatic hydrocarbons. Aliphatic hydrocarbons are only laser-ionized in case these contain conjugated double bonds. As, in contrast to radioactive ion mobility spectrometry, background air constituents and air contaminants cannot be ionized, drift spectra are inherently simple and easily interpretable. We show that a laser ion mobility spectrometer can be operated in two basically different modes, either using tunable or fixed-frequency laser sources. In the tunable laser mode, aromatic hydrocarbons can be detected in the positive mode and distinguished from each other on account of their different excitation wavelengths and ion drift times. In the fixed-frequency mode, specially chosen and intentionally admitted aromatic hydrocarbons are laser ionized and the primary ionization is transferred to non-aromatic species by means of atmospheric pressure chemical ionization. In this latter mode of operation nitroglycerin and triacetone triperoxide, two non-aromatic high explosives, could be detected.