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23 results on '"Davenport, J.W."'

3. Alternative function of the electron transport system in Azotobacter vinelandii: removal of excess reductant by the cytochrome d pathway

Author

Liu, J.-K., Lee, F.-T., Lin, C.-S., Yao, X.-T., Davenport, J.W., and Wong, T.-Y.

Subjects
Nitrogen-fixing microorganisms -- Research, Microbial respiration -- Physiological aspects, Cytochromes -- Research, Glycolysis -- Research, Oxygen -- Physiological transport, Electron transport -- Research, Biological sciences
Abstract

There is a mismatch between the effects of two respiratory mechanisms in the nitrogen-fixing bacterium Azotobacter vinelandii: electron transport system and glycolysis. More cytochrome d is synthesized to raise the oxygen uptake rate with increasing oxygen partial pressure. This ensures protection of nitrogenase from molecular oxygen. But the rate of glycolysis also goes high with exposure to excess of glucose. Except for the reinforced electron transport system under higher oxygen partial pressure, there is no system capable of converting the harmful extra glycolytic products.

Published
1995

6. Measuring the Hole-state Anisotropy in MgB2 by Electron Energy-loss Spectroscopy

Author

Klie, R.F., Su, Haibin, Zhu, Y., Davenport, J.W., Idrobo, J.-C., Browning, N.D., Nellist, P.D., Klie, R.F., Su, Haibin, Zhu, Y., Davenport, J.W., Idrobo, J.-C., Browning, N.D., and Nellist, P.D.

Abstract

We have examined polycrystalline MgB2 by electron energy-loss spectroscopy (EELS) and density of states calculations. In particular, we have studied two different crystal orientations, [110] and [001], with respect to the incident electron beam direction, and found significant changes in the near-edge fine structure of the B K-edge. Density-functional theory suggests that the pre-peak of the B K-edge core loss is composed of a mixture of pxy- and pz-hole states and we will show that these contributions can be distinguished only with an experimental energy resolution better than 0.5 eV. For conventional transmission electron microscope/scanning transmission electron microscope instruments with an energy resolution of ∼1.0 eV the pre-peak still contains valuable information about the local charge-carrier concentration that can be probed by core-loss EELS. By considering the scattering momentum transfer for different crystal orientations, it is possible to analytically separate pxy and pz components from the experimental spectra. With careful experiments and analysis, EELS can be a unique tool measuring the superconducting properties of MgB2, doped with various elements for improved transport properties on a subnanometer scale.

Published
2003

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