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  • 1
    ISSN: 1572-879X
    Keywords: gas-phase transesterification ; methyl phenyl carbonate (MPC) ; disproportionation ; diphenyl carbonate (DPC) ; TiO2/SiO2 catalyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The two-step synthesis of diphenyl carbonate (DPC) from dimethyl carbonate (DMC) and phenol has been compared in liquid phase and gas phase, both over heterogeneous catalysts. In the first step, equilibrium yields of methyl phenyl carbonate (MPC) in the transesterification of DMC and phenol were very low at low temperatures in the liquid phase although reaction rates were fast. This endothermic reaction was more favorable at high temperatures in the gas-phase reaction. Titanium oxide catalysts supported on SiO2 or activated carbon were found to be effective in a continuous gas flow reactor. In case of the second step, the disproportionation of MPC, selective formation of DPC was not feasible in the gas-phase reaction due to extensive side reactions. However, there was no by-product in the liquid-phase reaction over the TiO2/SiO2 catalyst. Therefore, our proposed two-step synthesis process consists of the gas-phase transesterification of DMC and phenol followed by the liquid-phase disproportionation of MPC to DPC, both over the TiO2/SiO2 catalyst.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of biomedical science 5 (1998), S. 267-273 
    ISSN: 1423-0127
    Keywords: Grave's disease ; Human foamy virus ; Korea ; Molecular epidemiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The possible association of human foamy virus (HFV) with human thyroid disorders such as Graves' disease (GD) has been a topic of controversy due to the inconsistent results reported by several groups of investigators. Here we report the investigation of the presence of HFV-related sequences in the Korean population. DNA was obtained from peripheral blood lymphocytes from 24 GD patients and 23 healthy blood donors and subjected to PCR amplification using three sets of nested primers derived fromgag, env, and LTR regions of the HFV genome. Contrary to previously reported studies, our analysis identified HFV-related sequences in the genomes of both healthy individuals and the GD patients. However, the nature of the HFV genome present in each group appeared to be different. We detected all 3 regions of HFV-related sequences in 29% of the HFV-positive GD patients, while no samples in the control group amplified all three regions. This suggests that the LTR may be used as a tool for screening for HFV in GD patients. Our data favor the hypothesis of a relationship between GD and the presence of HFV-related sequences, though in a complex way.
    Type of Medium: Electronic Resource
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