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ABSTRACT: To evaluate the efficacy of photodynamic therapy (PDT) combined with intravitreal injection of anti-vascular-endothelial-growth-factor (anti-VEGF) antibody in patients with polypoidal choroidal vasculopathy (PCV).
Twenty-two eyes of 22 patients with PCV followed for 12 months after combination therapy with PDT and anti-VEGF were retrospectively reviewed. Patients received intravitreal anti-VEGF (1.25 mg bevacizumab or 0.5 mg ranibizumab) within 7 days after PDT. Retreatment with PDT and intravitreal anti-VEGF injections, or with intravitreal anti-VEGF alone, was performed when indicated. The main outcome measures were best-corrected visual acuity (BCVA) and central foveal thickness (CFT).
Mean logMAR BCVA was 0.43 at baseline and 0.45, 0.36, 0.30 and 0.28 at 1, 3, 6 and 12 months, respectively, after the initial combination therapy. Mean BCVA was significantly improved at 6 and 12 months after treatment (p < 0.05). Mean CFT was 269.4 μm at baseline and 180.1, 136.7, 127.5 and 139.6 μm at 1, 3, 6 and 12 months, respectively, after the initial combination therapy. CFT decreased significantly throughout the follow-up period. At 12 months, mean BCVA improved by 1.5 lines, and mean CFT decreased by 129.8 μm. Polypoidal lesions disappeared in 7 of the 13 eyes in which indocyanine green angiography was performed at 12 months. No changes in the branching vascular network were observed in any of these 13 eyes. Patients were treated with PDT a mean of 1.3 times and injected with intravitreal anti-VEGF a mean of 3.4 times over the 12-month period.
Combined PDT and intravitreal anti-VEGF may improve visual acuity and decrease CFT at 12 months. Large long-term prospective studies are needed to evaluate the efficacy and safety of combination therapy.
Ophthalmologica 01/2011; 225(3):169-75. · 1.42 Impact Factor
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ABSTRACT: We investigate the effects of a multigate-feeding structure on the gate resistance (R<sub>g</sub>) and RF characteristics of the high electron-mobility transistors (HEMTs). In this structure, the increase of R<sub>g</sub> with the gatewidth (W) is minimized; therefore, high maximum frequency of oscillation (f<sub>max</sub>) is achieved. Various numbers of gate feedings (N<sub>gf</sub>) using the air-bridge interconnections are adopted for fabricating the 0.1-mum depletion-mode metamorphic HEMTs. From these structures, we observe great reduction in R<sub>g</sub> with the increase of N<sub>gf</sub>, and their relationship is given by R<sub>g</sub>prop 1/[2middot(N<sub>gf</sub>-1)]<sup>2</sup>, where N<sub>gf</sub>=2,3,4,...; on the other hand, the effects of N<sub>gf</sub> on other small-signal parameters are negligible. Calculated cutoff frequency (f<sub>T</sub>) and f<sub>max</sub> from the extracted small-signal parameters all show good agreement with the measurement results. f<sub>T</sub> is slightly decreased with the increase of N<sub>gf</sub> due to the increase of gate-to-source capacitance. f<sub>max</sub> is, however, greatly increased with N<sub>gf</sub>, and this effect becomes greater at longer total gatewidth (W times number of gate fingers) . This is due to the smaller R<sub>g</sub> at greater N<sub>gf</sub> in the multigate-feeding structure. We propose that this gate-feeding structure provides a very effective way to suppress R<sub>g</sub> and maximize f<sub>max</sub> for the applications of the HEMTs with long W.
IEEE Transactions on Microwave Theory and Techniques 07/2009; · 1.85 Impact Factor
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ABSTRACT: We present a high-performance 94-GHz single-balanced monolithic millimeter-wave integrated-circuit (MMIC) mixer using the disk-shaped GaAs Schottky diodes grown on an n/n+ epitaxial structure. Due to the superior characteristics of the GaAs diodes with high diode-to-diode uniformity, the mixer shows a conversion loss of 5.5 dB at 94 GHz, a 1-dB compression point ( P <sub>1</sub> <sub>-dB</sub>) of 5 dBm, and high local-oscillator to radio-frequency isolation above 30 dB in an RF frequency range of 91-97 GHz. To our knowledge, the fabricated mixer shows the best performance in terms of conversion loss at 94 GHz and P <sub>1</sub> <sub>-dB</sub> among the W-band MMIC mixers without amplifier circuits.
IEEE Electron Device Letters 04/2009; · 2.85 Impact Factor
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ABSTRACT: We present a gate-recess structure for
metamorphic high-electron-mobility transistors to enhance the maximum frequency of oscillation
. Among the established gate-recess structures, the narrow gate-recess structure shows a degraded
, despite superior dc characteristics due to a large gate-to-drain capacitance
caused by a small effective gate-to-drain spacing, while the wide gate-recess structure exhibits lower dc characteristics
due to the surface effects. To minimize
and maintain the dc characteristics of the narrow gate-recess structure, an additional gate-recess is performed for an electrical
isolation between the drain side cap layer and drain electrode. We obtain almost the same extrinsic transconductance of
from this, while we achieve
enhancement of
due to
reduction of
by the increase of effective gate-to-drain spacing compared to the narrow gate-recess structure.
Journal of The Electrochemical Society. 11/2008; 155(12):H987-H990.
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Min Han, Sung-Woon Moon,
Jung-Hun Oh,
Byeong-Ok Lim,
Tae Jong Baek,
Seok Gyu Choi,
Young Hyun BAEK,
Yeon-Sik Chae,
Hyun Chang Park,
Sam-Dong Kim,
Jin-Koo Rhee
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ABSTRACT: In this paper, millimeter-wave 94 GHz drive amplifiers based on metamorphic high electron mobility transistors (MHEMTs) were designed and fabricated. The fabricated 100 nm gate length MHEMT devices exhibit DC characteristics with a drain current density of 690 mA/mm and an extrinsic transconductance of 770mS/mm. The current gain cutoff frequency (f<sub>T</sub>) and the maximum oscillation frequency (f<sub>max</sub>) are 185 GHz and 230 GHz, respectively. The matching circuit of amplifier was designed using CPW (coplanar wave-guide) transmission line. The fabricated amplifier shows a good S<sub>21</sub> gain of 7.79 dB, an input return loss (S<sub>11</sub>) of -16.5 dB and an output return loss (S<sub>22</sub>) of-15.9 dB.
Millimeter Waves, 2008. GSMM 2008. Global Symposium on; 05/2008
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Dong Sik Ko,
Mun Kyo Lee,
Sang Jin Lee, Sung Woon Moon,
Du Hyun Ko,
Seok Ho Bang,
Yong Hyun Baek,
Min Han,
Seok Gyu Choi,
Tae Jong Baek,
Dong Chul Park,
Sam Dong Kim,
Jin Koo Rhee
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ABSTRACT: In this paper, we designed and fabricated waveguide voltage controlled oscillator (VCO), which have a center frequency of 94 GHz using the GaAs Gunn diode, varactor diode, and two bias posts with low pass filter (LPF). The cavity is designed for fundamental mode at 47 GHz and operated second harmonic VCO of 94 GHz center frequency. The fabricated VCO has 1.74 GHz bandwidth, 671 MHz linearity for 2.28% and 14 dBm output power. The highest output power is 15.58 dBm at 94.38 GHz.
Millimeter Waves, 2008. GSMM 2008. Global Symposium on; 05/2008
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Seok Ho Bang,
Sang Jin Lee,
Mun-Kyo Lee,
Dong Sik Ko, Sung-Woon Moon,
Yong Hyun Baek,
Min Han,
Seok Gyu Choi,
Tae Jong Baek,
Byoung-Chul Jun,
Dong Chul Park,
Sam-Dong Kim,
Jin-Koo Rhee
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ABSTRACT: In this paper, we designed a dot type GaAs Schottky diode for improvement of RF characteristics. The dot type GaAs Schottky diode shows that total resistance is 18.3 Omega, ideality factor is 1.41 at the room temperature and cut-off frequency is 435 GHz. The simulation result of designed single balanced mixer structure shows a good conversion loss of 6.28 dB.
Millimeter Waves, 2008. GSMM 2008. Global Symposium on; 05/2008
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Dong Sik Ko,
Mun-Kyo Lee,
Dan An,
Bok-Hyung Lee,
Byeong-Ok Lim,
Sang Jin Lee, Sung-Woon Moon,
Byoung-Chul Jun,
Seok Ho Bang,
Jung-Dong Park,
Wan Joo Kim,
Sam-Dong Kim,
Jin-Koo Rhee
[show abstract]
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ABSTRACT: In this paper, we present a high performance 94 GHz MMIC diode mixer using a 100-nm metamorphic high electron mobility transistor (MHEMT) diode and coplanar waveguide (CPW) 3-dB tandem coupler. A novel single-balanced structure of MHEMT diode mixer was proposed in this work, and 3-dB tandem coupler with the air-bridge structure was used for broadband LO-RF isolation. The fabricated mixer has LO-RF isolation, greater than 19 dB, in 15 GHz bandwidth of 82-97 GHz. The good conversion loss of 14.8 dB was measured at 94 GHz.
Microwave Conference, 2007. APMC 2007. Asia-Pacific; 01/2008
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ABSTRACT: We report on a high isolation 94 GHz MMIC single balanced cascode mixer using 0.1 mum metamorphic high electron mobility transistor (MHEMT) and CPW tandem couplers. Tandem couplers are introduced to overcome the limits of CPW based conventional directional couplers. Conversion loss of the single balanced cascode mixer was 9.8 dB at an LO power of 10.9 dBm. PldB (1 dB compression point) was -14.8 dBm at an input power of -4 dBm. The LO to RF isolation at 94 GHz and 100 GHz were -29.5 dB and -39.5 dB, respectively.
Microwave integrated circuit conference, 2007. eumic 2007. european; 11/2007
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ABSTRACT: To present a case of peripheral infiltrative keratitis mimicking infectious keratitis on the flap margin and limbus, which appeared on the first postoperative day after the laser in situ keratomileusis (LASIK).
A 36-year-old woman who underwent uneventful bilateral simultaneous LASIK developed multiple round infiltrate along the flap margin reaching to limbus from the 11 o'clock to 6 o'clock area in both eyes.
The flap was lifted and irrigation was performed with antibiotics. but infiltration seemed to appear again. The infiltrate was more concentrated at the periphery and was extended to the limbus. Direct smear and culture for bacteria and fungus were negative. Topical prednisolone acetate 1% eye drops was added, infiltrative condition was resolved.
LASIK induced peripheral infiltrative keratitis, in which infectious origin was ruled out, is reported.
Korean Journal of Ophthalmology 10/2007; 21(3):172-4.
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ABSTRACT: We investigate effects of the gate-recess structure on the high-frequency characteristics of the
depletion-mode metamorphic high electron mobility transistors (HEMTs). We characterize the dc and radio frequency performances
of two different gate-recess structures and perform a comparative study using the hydrodynamic device model simulation and
small-signal parameter analysis. The narrow gate-recess structure shows significantly higher dc performances than the wide
gate-recess structure, and this phenomenon is due to the presence of the negatively charged surface states on the
Schottky barrier layer surface in the wide gate-recess structure. Despite the superior dc characteristics, the narrow gate-recess
structure shows more degraded maximum frequency of oscillation
of
than that
of the wide gate-recess structure and almost the same cutoff frequency
of
. The degraded
of the narrow gate-recess structure is attributed to a
higher gate-to-drain capacitance
. The significant increase of
is caused by the reduction of effective gate-to-drain spacing due to the nonlinear electric potential distribution in the
gate-to-drain region.
Journal of The Electrochemical Society. 06/2007; 154(7):H541-H546.
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ABSTRACT: We report the 94 GHz CPW branch-line bandpass filter for planar integrated millimeter- wave circuits. The basic idea is to use the branch-line coupler as a transversal filtering section by connecting the coupled ports to the open load stubs and taking the isolated port as the output node. The 94 GHz bandpass filter exhibits an insertion loss of 2.5 dB with an 11.7 % 3 dB relative bandwidth at a center frequency of 94 GHz and the return loss is better than -18 dB at a center frequency. The designed and fabricated 94 GHz bandpass filter shows the good performance for planar integrated millimeter-wave circuits.
Microwave Conference, 2006. APMC 2006. Asia-Pacific; 01/2007
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ABSTRACT: We present a uniplanar coplanar waveguide 3-dB tandem coupler operating at V-band frequencies. The uniplanar structure is monolithically fabricated by using two-section parallel-coupled lines and air-bridge crossovers replacing the conventional multilayer or the bonded structures. Due to an optimized tandem structure and nonbonded crossovers minimizing the parasitic components, a maximum coupling of 2.5dB is measured at 62GHz with a 2-dB bandwidth of 83%, while a high directivity factor of 33dB is simultaneously obtained at 58-62GHz. Over the entire design frequency range of 30-90GHz, we achieve good phase unbalance of 90±6.0°, return loss, and isolation lower than -23 and -16dB, respectively.
IEEE Microwave and Wireless Components Letters 05/2006; · 1.72 Impact Factor
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ABSTRACT: In this work, balanced medium power amplifiers for 60 GHz wireless LAN application were designed and fabricated. The single-ended and the balanced medium power amplifier on MIMIC technology were designed using 0.1μm Γ-gate GaAs PHEMT and CPW library. We compared the single-ended medium power amplifier on the balanced medium power amplifier of S-parameter and 1 dB gain compression point (P<sub>1dB</sub>). From measurement, the single-ended and the balanced medium power amplifiers show S<sub>21</sub> gains of 13.14 dB and 12.8 dB, respectively, at 60 GHz. Also, we obtain P<sub>1dB</sub> of 5.9 dBm and 7.5 dBm at 60 GHz, respectively. The balanced medium power amplifier has better return losses and P<sub>1dB</sub> than those of the single-ended medium power amplifier within V-band region.
Microwave Conference Proceedings, 2005. APMC 2005. Asia-Pacific Conference Proceedings; 01/2006
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Mun-Kyo Lee,
Jung-Dong Park,
Dan An,
Bok-Hyung Lee,
Sang-Jin Lee,
Tae-Jong Baek,
Jung-Hun Oh, Sung-Woon Moon,
Hyuk-Ja Kwon,
Wan-Joo Kim,
Yong-Hoh Kim,
Hyung-Moo Park,
Jin-Koo Rhee
[show abstract]
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ABSTRACT: For low LO power and broadband characteristics of the mixer, an antipodal fin-line to microstrip transition for operation in the 94 GHz frequency has been designed and characterized. Back to back transitions fabricated on soft substrates have been measured and simulated to verify their behavior. A single balanced fin-line mixer was designed and fabricated. In the mixer, a wideband fin-line to coplanar waveguide 180° balun and low pass filter were used. Conversion loss is less than 10 dB at LO power of 6 dBm.
Microwave Conference Proceedings, 2005. APMC 2005. Asia-Pacific Conference Proceedings; 01/2006
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ABSTRACT: To perform a comparative study, we experimented on two differential epitaxial structures, the conventional metamorphic high-electron-mobility-transistor (MHEMT) using the InAlAs/InGaAs/InAlAs structure and the InP-composite-channel MHEMT adopting the InAlAs/InGaAs/InP structure. Compared with the conventional MHEMT, the InP-composite-channel MHEMT shows improved breakdown performance; more than approximately 3.8 V. This increased breakdown voltage can be explained by the lower impact ionization coefficient of the InP-composite-channel MHEMT than that of the conventional MHEMT. The InP-composite-channel MHEMT also shows improved Radio Frequency characteristics of S 21 gain of approximately 4.35 dB at 50 GHz, and a cutoff frequency ( f T ) and a maximum frequency of oscillation ( f max ) of approximately 124 GHz and 240 GHz, respectively, were obtained. These are due to decreases in g o and g m
