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RISS 인기검색어
- 검색키워드
- 저자 : Overton, C.B. (검색결과 12 건)
- 무료
- 기관 내 무료
- 유료
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Overton, Kristen,Varma, Rick,Post, Jeffrey J. The Korean Academy of Tuberculosis and Respiratory 2018 Tuberculosis and Respiratory Diseases Vol.81 No.1
Background: It remains uncertain if $interferon-{\gamma}$ release assays (IGRAs) are superior to the tuberculin skin test (TST) for the diagnosis of active tuberculosis (TB) or latent tuberculosis infection (LTBI) in immunosuppressed populations including people with human immunodeficiency virus (HIV) infection. The purpose of this study was to systematically review the performance of IGRAs and the TST in people with HIV with active TB or LTBI in low and high prevalence TB countries. Methods: We searched the MEDLINE database from 1966 through to January 2017 for studies that compared results of the TST with either the commercial QuantiFERON-TB Gold in Tube (QFTGT) assay or previous assay versions, the T-SPOT.TB assay or in-house IGRAs. Data were summarized by TB prevalence. Tests for concordance and differences in proportions were undertaken as appropriate. The variation in study methodology was appraised. Results: Thirty-two studies including 4,856 HIV subjects met the search criteria. Fourteen studies compared the tests in subjects with LTBI in low TB prevalence settings. The QFTGT had a similar rate of reactivity to the TST, although the first-generation version of that assay was reactive more commonly. IGRAs were more frequently positive than the TST in HIV infected subjects with active TB. There was considerable study methodology and population heterogeneity, and generally low concordance between tests. Both the TST and IGRAs were affected by CD4 T-cell immunodeficiency. Conclusion: Our review of comparative data does not provide robust evidence to support the assertion that the IGRAs are superior to the TST when used in HIV infected subjects to diagnose either active TB or LTBI.
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( Kristen Overton ),( B. Sc. ),( M. B. B. S. ),( M. P. H. T. M. ),( Rick Varma ),( Mb. Ch. B. ),( M. R. C. P. (u. K. ) ),( F. A. Ch. S. H. M. ),( Dip. Hiv ),( Dip. Gum,D. T. M. &h. ),( D. F. F. P. ),( 대한결핵 및 호흡기학회 2018 Tuberculosis and Respiratory Diseases Vol.81 No.1
Background: It remains uncertain if interferon-γ release assays (IGRAs) are superior to the tuberculin skin test (TST) for the diagnosis of active tuberculosis (TB) or latent tuberculosis infection (LTBI) in immunosuppressed populations including people with human immunodeficiency virus (HIV) infection. The purpose of this study was to systematically review the performance of IGRAs and the TST in people with HIV with active TB or LTBI in low and high prevalence TB countries. Methods: We searched the MEDLINE database from 1966 through to January 2017 for studies that compared results of the TST with either the commercial QuantiFERON-TB Gold in Tube (QFTGT) assay or previous assay versions, the T-SPOT.TB assay or in-house IGRAs. Data were summarized by TB prevalence. Tests for concordance and differences in proportions were undertaken as appropriate. The variation in study methodology was appraised. Results: Thirty-two studies including 4,856 HIV subjects met the search criteria. Fourteen studies compared the tests in subjects with LTBI in low TB prevalence settings. The QFTGT had a similar rate of reactivity to the TST, although the first-generation version of that assay was reactive more commonly. IGRAs were more frequently positive than the TST in HIV infected subjects with active TB. There was considerable study methodology and population heterogeneity, and generally low concordance between tests. Both the TST and IGRAs were affected by CD4 T-cell immunodeficiency. Conclusion: Our review of comparative data does not provide robust evidence to support the assertion that the IGRAs are superior to the TST when used in HIV infected subjects to diagnose either active TB or LTBI.
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Chattopadhyay, S.N.,Overton, C.B.,Vetter, S.,Azadeh, M.,Olson, B.H.,Naga, N. El The Institute of Electronics and Information Engin 2010 Journal of semiconductor technology and science Vol.10 No.3
An optically controlled silicon MESFET (OPFET) was fabricated by diffusion process to enhance the quantum efficiency, which is the most important optoelectronic device performance usually affected by ion implantation process due to large number of process induced defects. The desired impurity distribution profile and the junction depth were obtained solely with diffusion, and etching processes monitored by atomic force microscope, spreading resistance profiling and C-V measurements. With this approach fabrication induced defects are reduced, leading to significantly improved performance. The fabricated OPFET devices showed proper I-V characteristics with desired pinch-off voltage and threshold voltage for normally-on devices. The peak photoresponsivity was obtained at 620 nm wavelength and the extracted external quantum efficiency from the photoresponse plot was found to be approximately 87.9%. This result is evidence of enhancement of device quantum efficiency fabricated by the diffusion process. It also supports the fact that the diffusion process is an extremely suitable process for fabrication of high performance optoelectronic devices. The maximum gain of OPFET at optical modulated signal was obtained at the frequency of 1 MHz with rise time and fall time approximately of 480 nS. The extracted transconductance shows the possible potential of device speed performance improvements for shorter gate length. The results support the use of a diffusion process for fabrication of high performance optoelectronic devices.
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Mirage or Oasis? Assessing the Role of the United Nations Assistance Mission in Afghanistan
( Mahtab Shafiei ),( Kathryn Overton ) 서울대학교 통일평화연구원 2023 Asian Journal of Peacebuilding Vol.11 No.2
During a 20-year civil war, the United Nations Assistance Mission in Afghanistan (UNAMA) has served as a bastion of international support, democratic values, and humanitarian assistance. Highlighting democratization, security, economic assistance, and human rights, we employed over 20 years of United Nations (UN) archives to examine the effectiveness of its mission mandates, and found that UNAMA had reduced child labor and judicial corruption while increasing civil society and facilitating international humanitarian aid. However, UNAMA failed to improve security or establish an inclusive government, particularly with respect to human rights violations. After the US military withdrawal in 2021, the future of UNAMA is contingent upon political negotiations with the Taliban. Only time will tell whether contributions of the mission will persist into the post-conflict era.
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Simulation of 4H-SiC MESFET for High Power and High Frequency Response
Chattopadhyay, S.N.,Pandey, P.,Overton, C.B.,Krishnamoorthy, S.,Leong, S.K. The Institute of Electronics and Information Engin 2008 Journal of semiconductor technology and science Vol.8 No.3
In this paper, we report an analytical modeling and 2-D Synopsys Sentaurus TCAD simulation of ion implanted silicon carbide MESFETs. The model has been developed to obtain the threshold voltage, drain-source current, intrinsic parameters such as, gate capacitance, drain-source resistance and transconductance considering different fabrication parameters such as ion dose, ion energy, ion range and annealing effect parameters. The model is useful in determining the ion implantation fabrication parameters from the optimization of the active implanted channel thickness for different ion doses resulting in the desired pinch off voltage needed for high drain current and high breakdown voltage. The drain current of approximately 10 A obtained from the analytical model agrees well with that of the Synopsys Sentaurus TCAD simulation and the breakdown voltage approximately 85 V obtained from the TCAD simulation agrees well with published experimental results. The gate-to-source capacitance and gate-to-drain capacitance, drain-source resistance and trans-conductance were studied to understand the device frequency response. Cut off and maximum frequencies of approximately 10 GHz and 29 GHz respectively were obtained from Sentaurus TCAD and verified by the Smith's chart.
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S.N. Chattopadhyay,C. B. Overton,S. Vetter,M. Azadeh,B. H. Olson,N. El Naga 대한전자공학회 2010 Journal of semiconductor technology and science Vol.10 No.3
An optically controlled silicon MESFET (OPFET) was fabricated by diffusion process to enhance the quantum efficiency, which is the most important optoelectronic device performance usually affected by ion implantation process due to large number of process induced defects. The desired impurity distribution profile and the junction depth were obtained solely with diffusion, and etching processes monitored by atomic force microscope, spreading resistance profiling and C-V measurements. With this approach fabrication induced defects are reduced, leading to significantly improved performance. The fabricated OPFET devices showed proper I-V characteristics with desired pinch-off voltage and threshold voltage for normally-on devices. The peak photoresponsivity was obtained at 620 ㎚ wavelength and the extracted external quantum efficiency from the photoresponse plot was found to be approximately 87.9%. This result is evidence of enhancement of device quantum efficiency fabricated by the diffusion process. It also supports the fact that the diffusion process is an extremely suitable process for fabrication of high performance optoelectronic devices. The maximum gain of OPFET at optical modulated signal was obtained at the frequency of 1 MHz with rise time and fall time approximately of 480 nS. The extracted transconductance shows the possible potential of device speed performance improvements for shorter gate length. The results support the use of a diffusion process for fabrication of high performance optoelectronic devices.
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Simulation of 4H-SiC MESFET for High Power and High Frequency Response
S. N. Chattopadhyay,P. Pandey,C. B. Overton,S. Krishnamoorthy,S.K. Leong 대한전자공학회 2008 Journal of semiconductor technology and science Vol.8 No.3
In this paper, we report an analytical modeling and 2-D Synopsys Sentaurus TCAD simulation of ion implanted silicon carbide MESFETs. The model has been developed to obtain the threshold voltage, drain-source current, intrinsic parameters such as, gate capacitance, drain-source resistance and transconductance considering different fabrication parameters such as ion dose, ion energy, ion range and annealing effect parameters. The model is useful in determining the ion implantation fabrication parameters from the optimization of the active implanted channel thickness for different ion doses resulting in the desired pinch off voltage needed for high drain current and high breakdown voltage. The drain current of approximately 10 A obtained from the analytical model agrees well with that of the Synopsys Sentaurus TCAD simulation and the breakdown voltage approximately 85 V obtained from the TCAD simulation agrees well with published experimental results. The gate-to-source capacitance and gate-todrain capacitance, drain-source resistance and transconductance were studied to understand the device frequency response. Cut off and maximum frequencies of approximately 10 ㎓ and 29 ㎓ respectively were obtained from Sentaurus TCAD and verified by the Smith’s chart.
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