No abstract available

[en] Elemental fluorine and acetyl hypofluorite, labelled with ¹⁸F, were added to eight simple aryl-tin derivatives. Both reagents gave good radiochemical yields of labelled aryl fluorides. Overall, acetyl hypofluorite gave more consistent yields (approximately 70 percent), while F₂ gave more variable yields (54 percent - > 95 percent)

[en] Direct fluorination of aromatic nuclei is difficult since the reaction is usually accompanied by unselective, partial, or total replacement of hydrogen. By attaching the tri-n-butyltin moiety to one position of the ring one can achieve an enhanced reactivity and site selectivity toward electrophilic fluorination. The intent of this study was to demonstrate the utility of the fluorodestannylation reaction for fluorine labelling of aromatic compounds and to compare F/sub 2/ and acetyl hypofluorite as the fluorinating agents. Thus, eight stannylated aromatic compounds (1-8) were synthesized via lithium halogen exchange of the bromo precursor and subsequent transmetallation using tri-n-butyltin chloride. The stannylated substrates were treated with F-18 F/sub 2/ and -78⁰C and CH/sub 3/COOF at room temperature. Both reagents gave good yields of labelled aryl fluorides. Overall, acetyl hypofluorite gave more consistent yields (≅70%), while F/sub 2/ gave more variable yields (54-95%). This method is currently being extended to label more complex systems such as L-Dopa with F-18 for brain studies with positron emission tomography. The authors have successfully stannylated Dopa on the ring and fluorination studies of this substrate are underway

[en] It is suggested that there are differences in the radiographic appearance of rheumatoid arthritis (RA) in men compared with women. Bone proliferation, cysts, and well-defined erosions are reported more frequently in men, whereas osteoporosis, nodules, and deformities are more frequent in women. The authors blindly evaluated hand and wrist radiographs in 32 males and 32 match females with RA. The mean age was 56.4 years and mean disease duration, 10.5 years. The two groups were similar in disease distribution, symmetry, and severity. Cystic changes and well-defined erosions were present in 12 of 64 male and six of 64 female hands. Bone proliferation was present in 13 of 64 male and 13 of 64 female hands and in women related to disease duration. Previously reported differences relate to inadequate matching

[en] The synthesis of 2-deoxy-2[¹⁸F]fluoro-D-glucose has been simplified by the use of C-18 SEP PAK cartridges. The fluorinated sugar produced from the reaction of acetyl hypofluorite and tri-acetyl glucal (TAG) was extracted from the neutralized reaction mixture with C-18 SEP PAK cartridges. The product was washed off the cartridge with diethyl ether and hydrolyzed by HCl. After hydrolysis the product was purified by passage through ion retardation resin, alumina and another C-18 cartridge. The radiochemical purity was 98% and the radiochemical yield was 28%, decay corrected to EOB, with a total synthesis time of 50 min from EOB. (author)

No abstract available

[en] The quasielastic (e,e[prime]p) reaction was studied on targets of deuterium, carbon, and iron up to a value of momentum transfer Q2 of 8.1 (GeV/c)2. A nuclear transparency was determined by comparing the data to calculations in the plane-wave impulse approximation. The dependence of the nuclear transparency on Q2 and the mass number A was investigated in a search for the onset of the color transparency phenomenon. We find no evidence for the onset of color transparency within our range of Q2. A fit to the world's nuclear transparency data reflects the energy dependence of the free-proton-nucleon cross section

[en] The first measurements of differential cross sections for deuteron photo-disintegration at photon energies up to 4 GeV were performed at the Thomas Jefferson National Accelerator Facility early in 1996. Cross section results for D(gamma,p)n at proton center of mass angle of 35^o, 53^o and 90^o will be presented. These results are in good agreement with previous measurements at low energy and extend to higher energies where data were previously unavailable. The 90^o degree data show behavior consistent with the constituent counting rules up to 4 GeV and are also in fair agreement with the asymptotic meson exchange model. The 37^o and 53^o data do not show clear signs of counting rule behavior, although a threshold in transverse momentum for the onset of scaling cannot be excluded