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W-Y Luo,
Y-S Shih,
C-L Hung,
K-W Lo,
C-S Chiang,
W-H Lo,
S-F Huang,
S-C Wang, C-F Yu,
C-H Chien,
Y-C Hu
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ABSTRACT: Antiangiogenesis is an appealing anticancer approach but requires continued presence of the antiangiogenic agents, which can be remedied by gene therapy. Baculovirus is an emerging gene delivery vector but only mediates transient expression (<7 days); thus, this study primarily aimed to develop a hybrid baculovirus for sustained antiangiogenic gene expression and cancer therapy. We first constructed plasmids featuring adeno-associated virus inverted terminal repeats (AAV ITRs), oriP/Epstein-Barr virus-expressed nuclear antigen 1 (EBNA1) or Sleeping Beauty (SB) transposon and compared their efficacies in terms of persistent expression. In human embryonic kidney (HEK293) cells, AAV ITR failed to prolong the expression while oriP/EBNA1 moderately extended the expression to 35 days. In contrast, the SB system led to stable expression beyond 77 days even without antibiotic selection. Given this finding, we constructed a hybrid SB baculovirus expressing the SB transposase and harboring the transgene cassette flanked by inverted repeat/direct-repeat (IR/DR) elements recognizable by SB. The hybrid SB baculovirus efficiently transduced mammalian cells and mediated an expression duration longer than that by conventional baculoviruses, thanks to the transgene persistence and integration. The SB baculovirus (Bac-SB-T2hEA/w) expressing the antiangiogenic fusion protein comprising endostatin and angiostatin (hEA) also enabled prolonged hEA expression. With sustained hEA expression, Bac-SB-T2hEA/w repressed the angiogenesis in vivo, hindered the growth of two different tumors (prostate tumor allografts and human ovarian tumor xenografts) in mice and extended the life span of animals. These data altogether implicated the potential of the hybrid SB-baculovirus vector for prolonged hEA expression and for the treatment of multiple types of angiogenesis-dependent tumors.
Gene therapy 09/2011; 19(8):844-51. · 4.75 Impact Factor
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ABSTRACT: The gyrotron backward-wave oscillator (gyro-BWO) is a frequency tunable scheme at millimeter/terahertz regime. The continuous frequency tuning can be achieved by varying either the magnetic field or the beam voltage in a non-resonant structure. With a growing interest in terahertz-wave regime, gyro-BWO should be preferably operated with high-order mode due to the power-handling capability. Then the upcoming difficulty would be the terahertz interaction circuit as well as the severe transverse mode competition.
Infrared, Millimeter, and Terahertz Waves, 2009. IRMMW-THz 2009. 34th International Conference on; 10/2009
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ABSTRACT: This study proposes a mode-selective circuit to suppress the competing modes in a TE <sub>01</sub> gyrotron backward-wave oscillator (gyro-BWO). The circuit, also functioning as an interaction structure, comprises of several transverse slices. It eliminates the restrictions of the mode competitions and allows a longer interaction structure to optimize interacting efficiency. Mode-selective effect will be analyzed. Experimental results indicate that the Ka -band TE <sub>01</sub> fundamental harmonic gyro-BWO is capable of continuous tuning from 31.4 to 36.4 GHz with a peak efficiency of 23.7%, corresponding to 100 kW at I<sub>b</sub>=4.5 A and V<sub>b</sub>=93.6 kV .
Applied Physics Letters 04/2009; · 3.84 Impact Factor
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ABSTRACT: This work proposes an approach to generate circular TE <sub> mn </sub> modes at low terahertz region through sidewall couplings. With proper arrangement of the couplings on the circumference of the waveguide, they then jointly excite the desired mode. A model is developed to calculate the coupling strength and to analyze the mode purity. Accordingly, three mode converters TE <sub>21</sub> , TE <sub>01</sub> , and TE <sub>41</sub> , were designed, built, and tested at W -band. Back-to-back transmission measurements exhibit excellent agreement with the results of simulations. The measured optimal transmissions are 91%, 95%, and 89% with 3 dB bandwidths of 18.3, 24.0, and 20.2 GHz, respectively.
Applied Physics Letters 10/2008; · 3.84 Impact Factor
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ABSTRACT: Second harmonic gyrotron backward-wave oscillator (gyro-BWO) is a promising tunable source with only half the magnetic field requirement. But these merits have long been impeded by the transverse and axial modes competition as a result of lower efficiency. This study employs a slotted structure as a mode selector for suppressing the persistent low order transverse mode. In addition, an optimized two-step tapered structure is adopted to stabilize the high order transverse modes and axial modes. The interaction efficiency and the tuning bandwidth were greatly enhanced in the meanwhile. As a calculated result, a stable, ka-band, slotted second harmonic gyro-BWO is capable of producing an efficiency of 23% and a 3-dB tuning bandwidth of 9% at 5 A and 100 kV.
Infrared and Millimeter Waves, 2007 and the 2007 15th International Conference on Terahertz Electronics. IRMMW-THz. Joint 32nd International Conference on; 10/2007
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ABSTRACT: Second-harmonic gyrotron backward-wave oscillator gyro-BWO with a reduced magnetic field strength is a tunable source in the millimeter wave regime, but it has long been impeded by the severe mode competition as a result of low efficiency and narrow bandwidth. This study employs a slotted structure functioning as a mode selective circuit to suppress the lower order transverse modes. In addition, a two-step tapered waveguide is adopted to stabilize the higher-order transverse modes and axial modes. Some important characteristics of the slotted gyro-BWO will be analyzed and discussed. As a calculated result, the interaction efficiency is improved and the stable tuning range is broadened. A stable, Ka-band, slotted second-harmonic gyro-BWO is capable of producing an efficiency of 23% with a 3 dB tuning bandwidth of 9% at 5 A and 100 kV. © 2007 American Institute of Physics.
09/2007;
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ABSTRACT: Axial modes of the gyro-BWO are characterized by a discrete set of optimum transit angles separated by ~2pi. We show in theory that, during the rise and fall portions of the beam pulse, the frequency of a given axial mode varies in such a way that its transit angle remains at the characteristic value of the mode. Furthermore, in this transient period, axial mode competition is governed by the distinctive asymmetry of the mode profiles rather than by levels of the start-oscillation currents. A Ka-band gyro-BWO experiment has been carried out to examine the rise/fall time behavior. Time-frequency analyses of the output pulses show good agreement with theoretical predictions.
Infrared Millimeter Waves and 14th International Conference on Teraherz Electronics, 2006. IRMMW-THz 2006. Joint 31st International Conference on; 10/2006
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ABSTRACT: The axial modes of the gyrotron backward-wave oscillator (gyro-BWO) each exhibit a distinctive asymmetry in axial field profile. As a result, and in sharp contrast to the behavior of the familiar resonator-based gyrotron oscillator, particle simulations of the gyro-BWO reveal a radically different pattern of mode competition in which a fast-growing and well-established mode is subsequently suppressed by a later-starting mode with a more favorable field profile. This is verified in a Ka-band experiment and the interaction dynamics are elucidated with a time-frequency analysis.
Physical Review Letters 11/2005; 95(18):185101. · 7.37 Impact Factor
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ABSTRACT: The axial modes of the gyrotron backward-wave oscillator (gyro-BWO) each exhibit a distinctive asymmetry in axial field profile. As a result, particle simulations of the gyro-BWO reveal a radically different pattern of mode competition in which a fast-growing and well-established mode is subsequently suppressed by a later-starting mode with a more favorable field profile. This is verified in a Ka-band experiment and the interaction dynamics are elucidated with a time-frequency analysis.
Infrared and Millimeter Waves and 13th International Conference on Terahertz Electronics, 2005. IRMMW-THz 2005. The Joint 30th International Conference on; 10/2005
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ABSTRACT: Summary form only given. The dynamics of axial mode competition in the gyrotron backward-wave oscillator (gyro-BWO) has been investigated in theory and experiment. Because of the difference in field-shaping processes, the axial modes of the gyro-BWO each exhibit a distinctive asymmetry in field distribution along the axis. Multi-mode particle simulations reveal a consistent pattern of axial mode competition in which a fast-growing and well-established mode is subsequently suppressed by a slowly-growing mode with a favorable field profile. This is verified in a Ka-band gyro-BWO experiment. A detailed time-frequency analysis of both the simulation and experimental results further suggests that the competitiveness of a specific mode depends more on its field structure than on its initial growth rate. This perspective is expected to add a new basis for the understanding of mode competition phenomena in the gyro-BWO
Plasma Science, 2005. ICOPS '05. IEEE Conference Record - Abstracts. IEEE International Conference on; 07/2005
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ABSTRACT: We report the concept and development of a Ka-band mode and polarization converter that efficiently converts a TE10 rectangular waveguide mode into either a linearly or a circularly polarized TE21 cylindrical waveguide mode. The converter is composed of a power-dividing section, a mode-converting section, and a polarization-transitioning section. The converting process in each section is displayed and the working principles are discussed. A prototype has been built and tested. The measured results agree well with the numerical calculations for both linear and circular polarizations. The measured optimum back-to-back transmission is 94% with a 1-dB bandwidth of 4.1 GHz for the linear polarization. As for the circular polarization, the measured optimum transmission is 97%, but the corresponding bandwidth is indistinct due to some resonant dips. The reasons and impact for the dips are discussed. A bandwidth of 3.9 GHz is obtained for a single circular converter; meanwhile, an approach to eliminating these unwanted dips is presented in theory. For further diagnostics, the field pattern of either polarization is directly displayed on a temperature-sensitive liquid crystal display sheet, where the electric field strength can be discerned from the color spectrum. In addition to high conversion efficiency and broad bandwidth, this converter features easy construction, high mode purity, and polarization controllability.
Review of Scientific Instruments 06/2005; 76(7):074703-074703-6. · 1.37 Impact Factor
