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1.
Chinese Journal of Stomatology ; (12): 387-389, 2003.
Article in Chinese | WPRIM | ID: wpr-263477

ABSTRACT

<p><b>OBJECTIVE</b>The aim of the study is to improve the anticorrosive property of the dental FeCrMo soft magnetic alloy covered with TiN film obtained by ion beam assisted deposition (IBAD) technology in oral environment.</p><p><b>METHODS</b>The magnetic force of the FECrMo soft magnetic alloy after TiN film treated were measured by Instron test machine. An advanced electro-chemical method was used to measure the electric potential of corrosion (Ecorr), passive potential (Ep), passive current density (Ip), current density of corrosion (Icorr), polarization resistance (Rp), of FeCrMo soft magnetic alloy in simulated oral environment before and after surface modification.</p><p><b>RESULTS</b>There were no statistic changes of the magnetic force in 4 groups after alloy with TiN film treated. Comparing with the alloy without surface modified, the Ecorr, Rp of FeCrMo soft magnetic alloy was obviously higher, and the Icorr, Ip and Ep were obviously lower.</p><p><b>CONCLUSIONS</b>The anticorrosive property of the dental FeCrMo soft magnetic alloy with TiN film is better than that without modified.</p>


Subject(s)
Humans , Chromium Alloys , Corrosion , Dental Alloys , Dental Prosthesis Retention , Magnetics , Molybdenum , Titanium , Pharmacology
2.
Chinese Journal of Biotechnology ; (12): 74-80, 2003.
Article in Chinese | WPRIM | ID: wpr-259191

ABSTRACT

Cis-1,2-dihydroxycyclohexa-3,5-diene (DHCD) can be used as a valuable chiral intermediates for applications in pharmaceuticals, aerospace, electrical and fine chemical industries. By on-line detection of toluene dioxygenase (TDO) activity in whole recombinant Escherichia coli JM109 (pKST11) cells that harbored TDO gene under a tac promoter, effects of IPTG and various benzene addition strategies on bioransformation of benzene to DHCD were investigated. When IPTG was used at the beginning of fermentation, the growth of cells was inhibited and TDO activity only maintained for 4 hours while same experiments with addition of IPTG at 6h or 8h generated TDO activity for 18 hours. Suitable induction time for IPTG was in the cell logarithmic growth phase and 0.5 mmol/L IPTG was sufficient for inducing maximum TDO activities. Benzene strongly inhibited the activity of TDO which catalyses the conversion of benzene to DHCD. It was found that both cell growth and TDO activity was remarkably inhibited by feeding of benzene vapor, only 7.5 g/L DHCD was obtained. While the benzene inhibition effect was ameliorated by two-liquid phase culture fermentation in which liquid paraffin was used as second phase in the broth. Using different initial ratios of paraffin to benzene in fed-batch culture, DHCD contents were increased to 22.6 g/L, which was 3-fold more compared with that in benzene vapor culture. A further improvement of DHCD production was achieved when the mixture of liquid paraffin and benzene was added continuously by peristaltic pump, the DHCD contents were increased to a final concentration of 36.8 g/L. It was proven that the key to improving DHCD production by recombinants is to prolong TDO activity in cells, which can be achieved by using suitable addition benzene strategies.


Subject(s)
Benzene , Metabolism , Cyclohexanols , Metabolism , Escherichia coli , Genetics , Metabolism , Fermentation , Physiology , Oxygenases , Genetics , Metabolism
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