Browsing by Author "Yeh, Y. -J."

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Hepatic expression of MxA and OAS1 in an ex vivo liver slice assay independently predicts treatment outcomes in chronic hepatitis C
(2012-02-01)
Cheng, J. -C.
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Yeh, Y. -J.
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Huang, Y. -H.
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Liang, K. -H.
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Chang, M. -L.
. Antiviral effect of interferon is mediated by the expression of interferon-stimulated genes (ISGs). However, because of the difficulty in obtaining paired liver biopsies before and after interferon treatment, the key ISGs expressed in human hepatocytes and responsible for interferon-based antiviral activities in chronic hepatitis C remain illusive. Prior to a standard course of peginterferon plus ribavirin therapy, 104 patients underwent a liver biopsy. A small piece of the liver biopsy sample from each patient was submitted for ex vivo tissue culture in the presence or absence of interferon. Hepatic expression of 8 ISGs was detected by RT-PCR. The ISG expression patterns and clinicopathological variables were correlated with subsequent treatment outcomes. Multivariate logistic regression analysis showed that hepatic MxA expression (P = 0.008) and leucocyte count (P = 0.040) independently predicted the end of therapeutic virological response, while hepatic OAS1 expression (P = 0.003), genotype 1 (P = 0.002), HCV-RNA level (P = 0.007), AST/ALT ratio (P = 0.004) and leucocyte count (P = 0.034) independently predicted the sustained virological response. Immunohistochemistry analysis showed that interferon-induced OAS1 expression localized to the hepatocytes. In conclusion, hepatic MxA and OAS1 expression predicted, respectively, the end of therapeutic and sustained virological responses in interferon-based treatment of chronic hepatitis C.
Terahertz emission from Mg-doped a-plane InN
(2011)
Ahn, H.
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Yeh, Y. -J.
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Gwo, S.
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光電工程學系
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Department of Photonics
We report terahertz (THz) emission from magnesium doped a-plane indium nitride (a-InN:Mg) films with different background carrier density, relative to the Mg-doped InN films grown along the c-axis (c-InN: Mg). Due to its high electron affinity, as-grown InN film is typically n-type and it has extremely high background carrier density, which causes much weaker THz emission than that from other semiconductors, such as InAs. The background carrier density of Mg-doped InN can be widely changed by adjusting the Mg doping level. For c-InN: Mg, THz emission is dramatically enhanced (x500 than that of undoped c-InN) as the background carrier density decreases to a critical value of similar to 1x10(18) cm(-3), which is due to the reduced screening of the photo-Dember field at the lower carrier density. For a-InN, however, intense THz emission (x400 than that of undoped c-InN) is observed for both undoped and Mg-doped a-InN and the enhancement is weakly dependent on the background carrier density. The primary THz radiation mechanism of the a-plane InN film is found to be due to the acceleration of photoexcited carriers under the polarization-induced in-plane electric field perpendicular to the a-axis, which effectively enhances the geometrical coupling of the radiation out of semiconductor. The weak dependence of THz radiation on the background carrier density for a-InN shows that in-plane surface field induced-terahertz emission is not affected by the background carrier density. Small, but apparent azimuthal angle dependence of terahertz emission is also observed for a-InN, indicating the additional contribution of nonlinear optical processes on terahertz emission.
Terahertz emission mechanism of magnesium doped indium nitride
(2009-12-07)
Ahn, H.
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Yeh, Y. -J.
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Hong, Y. -L.
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Gwo, S.
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光電工程學系
We report carrier concentration-dependence of terahertz emission from magnesium doped indium nitride (InN:Mg) films. Near the critical concentration (n(c) similar to 1 x 10(18) cm(-3)), the competition between two emission mechanisms determines the polarity of terahertz emission. InN: Mg with n > n(c) exhibits enhanced positive polarity terahertz emission compared to the undoped InN, which is due to the reduced screening of the photo-Dember field. For InN: Mg with n < n(c), the polarity of terahertz signal changes to negative, indicating the dominant contribution of the surface electric field due to the large downward surface band bending within the surface layer extending over the optical absorption depth. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3270042]
Terahertz Emission of Magnesium doped Indiu
(2010)
Yeh, Y. -J.
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Ahn, H.
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Hong, Y. -L.
;
Gwo, Shangjr
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光電工程學系
Significant THz power enhancement and polarity reversal were observed from Mg-doped InN. The carrier concentration-dependent THz polarity reversal reflects the interplay between the surface-electric-field and the photo-Dember field for THz emission from InN:Mg. (C)2010 Optical Society of America
Terahertz Emission of Magnesium doped Indium Nitride
(2010)
Yeh, Y. -J.
;
Ahn, H.
;
Hong, Y. -L.
;
Gwo, Shangjr
;
光電工程學系
Significant THz power enhancement and polarity reversal were observed from Mg-doped InN. The carrier concentration-dependent THz polarity reversal reflects the interplay between the surface-electric-field and the photo-Dember field for THz emission from InN:Mg. (C)2010 Optical Society of America