Browsing by Author "Liu, H. C."

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Antioxidant nature of bovine milk beta-lactoglobulin
(2007-02-01)
Liu, H. C.
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Chen, W. L.
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Mao, S. J. T.
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生物科技學系
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Department of Biological Science and Technology
Heating is necessary for processing milk in the dairy industry, which evidently produces a conformational change in beta-lactoglobulin (beta-LG). beta-Lactoglobulin, a major protein that accounts for approximately 10 to 15% of total milk proteins, is a globular protein consisting of 162 AA with a relative molecular mass of 18.4 kDa. The purpose of the present study was to determine the antioxidant role of beta-LG in milk and the possible mechanism involved. We showed that beta-LG is a mild antioxidant whose potency is less than that of vitamin E and probucol (the latter being an antioxidant used for clinical therapy). The conversion of the beta-LG monomer to dimer was responsible, in part, for the mode of action in protecting low- density lipoproteins against copper-induced oxidation. Cross-linking the free thiol groups of beta-LG by heating (100 degrees C for 2 min), or chemically modifying the beta-LG by carboxymethylation to block the thiol groups resulted in a substantial loss of antioxidant activity. The data suggest that Cys-121 plays an essential role in the antioxidant nature of beta-LG. By using an anti-LG antibody affinity column to deplete the beta-LG from milk, we observed from the lost antioxidant activity that beta-LG contributes approximately 50% of the total activity. Because beta-LG is extremely sensitive to thermal denaturation, to maintain its antioxidant nature, dairy products consumed daily should not be overheated in order to maintain its antioxidant nature.
Copper-to-copper direct bonding using different (111) surface ratios of nanotwinned copper films
(2019-01-01)
Huang, J. W.
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Shie, K. C.
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Liu, H. C.
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Li, Y. J.
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Cheng, H. Y.
Copper-to-copper direct bonding emerges to be the most important technique for fine pitch packaging in microelectronic devices. Low temperature Cu-to-Cu direct bonding by using highly (111)-oriented nanotwinned Cu (nt-Cu) has been achieved because Cu (111) surface has higher surface diffusiyities. To investigate the bonding effect by using different surface ratio nt-Cu, electroplating under different conditions was performed. The results indicate that bonding with higher (111)-surface ratio copper films would obtain a higher bonding strength of 15% w hen bonding at 300 degrees C.
Reactant gas transport and cell performance of proton exchange membrane fuel cells with tapered flow field design
(2006-07-14)
Liu, H. C.
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Yan, W. M.
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Soong, C. Y.
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Chen, Falin
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Chu, H. S.
The objective of this work is to examine the reactant gas transport and the cell performance of a proton exchange membrane fuel cell (PEMFC) with a tapered flow channel design. It is expected that, with the reduction in the channel depth along the streamwise direction, the reactant fuel gas in the tapered channel can be accelerated as well as forced into the gas diffuser layer to enhance the electrochemical reaction and thus augment the cell performance. The effects of liquid water formation on the reactant gas transport are taken into account in the present study. Numerical predictions show that the cell performance can be enhanced with the fuel channel tapered, and the enhancement is more noticeable at a lower voltage. The results also reveal that the liquid water effect in general influences the cell performance and the effect becomes significant at lower voltages. (c) 2005 Elsevier B.V. All rights reserved.