Applications of Nuclear Magnetic Resonance Imaging in Particle Technology

During the past decade, the application of Nuclear Magnetic Resonance (NMR) imaging techniques to problems of relevance to the process industries has been identified. In the context of particle technology, NMR imaging, in addition to the more routinely used techniques of Pulsed Gradient Spin Echo (PGSE) NMR and NMR spectroscopy, offer new methods of characterising pore structure, adsorption and diffusion processes within particles and packed beds of particles, as well as enabling time-resolved in-situ study of processes such as twophase flow, aggregation, polymerisation, crystallisation and phase separation phenomena. This paper reviews recent work in these areas, and also highlights the new insights NMR imaging can give us regarding the characterisation of porous materials, and the influence of the structure of the pore space on the transport processes occuring within a given porous solid.     

A spectrophotometric kinetic assay for acid phosphatases with aromatic phosphates

Acid phosphatases are measured by monitoring the rate of decomposition of various phenolic phosphates and/or production of the phenol at pH 4.8 (acetate buffer). All the substrates tested obey pseudo-first order kinetics; calibration plots are linear over wide ranges.     

Approaches to phenazine-derived N-isosteres of anthracyclinones

1-Hydroxyphenazine 5,10-dioxide showed antitumor properties against mouse leukemia P388. It also participated in biochemical mechanisms of quinoid antitumor agents, as indicated by inhibition of radiolabeled DNA-RNA precursors in cultured leukemia L1210 cells and by stimulation of oxygen consumption in mammalian microsomes. This suggests that the isosteric di-N-oxide system may be a biologically active substitute for 1,4-quinone, and that di-N-oxides of tetrahydrobenzo[b]phenazines can be explored as anthracyclinone N-isosteres. As potential synthetic intermediates, 7,8,9,10-tetrahydro-6,11-dihydroxybenzo[b]-phenazines have been prepared by 1) Diels-Alder addition of phenazine-1,4-quinone and 1-methoxy-3-(trimethylsilyloxy)-1,3-butadiene to give isolable but labile adducts and 2) condensation of 6,7-diamino-1,2,3,4-tetrahydro-2-hydroxy-5,8-dimethoxy-2-naphthoic acid with 3-methoxy-1,2-quinone. Attempts at N-oxidation gave instead oxidation of the 6,11-hydroquinone ring to quinone, regardless of hydroxyl protection. Despite previous literature indications, we have been unable to synthesize the 1,4-dihydroxyphenazine 5,10-dioxide system. We conclude that this hydroxyl substitution pattern (1,4) in an adjacent ring must be avoided in the redesign of anthracyclinone isosteres that have di N-oxide in place of quinone.     

Positron reemission brightness enhancement method

Numerical results are presented for a one-dimensional diffusion model for freely diffusing positrons in thin films with an initial exponential positron profile. The results are for two boundary conditions which are experimentally realizable. Since thermalized positrons generally obey this diffusion model, it should be possible to extract the bulk diffusion constant by fitting experimental measurements to the model's predictions. Recently, a scheme has been proposed for the brightness enhancement of slow positron beams. We discuss experimental methods for implementing this scheme and the various problems that may arise.Summer student at Brookhaven National Laboratory, 1980