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Search Results: 1 - 10 of 11694 matches for " Ho Ang Yoon "
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Polarization dependence of photocurrent in a metal-graphene-metal device
Minjung Kim,Ho Ang Yoon,Seungwoo Woo,Duhee Yoon,Sang Wook Lee,Hyeonsik Cheong
Physics , 2012, DOI: 10.1063/1.4745787
Abstract: The dependence of the photocurrent generated in a Pd/graphene/Ti junction device on the incident photon polarization is studied. Spatially resolved photocurrent images were obtained as the incident photon polarization is varied. The photocurrent is maximum when the polarization direction is perpendicular to the graphene channel direction and minimum when the two directions are parallel. This polarization dependence can be explained as being due to the anisotropic electron-photon interaction of Dirac electrons in graphene.
Photocurrent generation at ABA/ABC lateral junction in tri-layer graphene photodetector
Minjung Kim,Seon-Myeong Choi,Ho Ang Yoon,Sun Keun Choi,Jae-Ung Lee,Jungcheol Kim,Sang Wook Lee,Young-Woo Son,Hyeonsik Cheong
Physics , 2015, DOI: 10.1016/j.carbon.2015.09.095
Abstract: Metal-graphene-metal photodetectors utilize photocurrent generated near the graphene/metal junctions and have many advantages including high speed and broad-band operation. Here, we report on photocurrent generation at ABA/ABC stacking domain junctions in tri-layer graphene with a responsivity of 0.18 A/W. Unlike usual metal-graphene-metal devices, the photocurrent is generated in the middle of the graphene channel, not confined to the vicinity of the metal electrodes. The magnitude and the direction of the photocurrent depend on the back-gate bias. Theoretical calculations show that there is a built-in band offset between the two stacking domains, and the dominant mechanism of the photocurrent is the photo-thermoelectric effect due to the Seebeck coefficient difference.
Quantum interference with beamlike type-II spontaneous parametric down-conversion
Yoon-Ho Kim
Physics , 2003, DOI: 10.1103/PhysRevA.68.013804
Abstract: We implement experimentally a method to generate photon-number$-$path and polarization entangled photon pairs using ``beamlike'' type-II spontaneous parametric down-conversion (SPDC), in which the signal-idler photon pairs are emitted as two separate circular beams with small emission angles rather than as two diverging cones.
Two-photon interference without bunching two photons
Yoon-Ho Kim
Physics , 2003, DOI: 10.1016/S0375-9601(03)01114-9
Abstract: We report an interference experiment in which the two-photon entangled state interference cannot be pictured in terms of the overlap and bunching of two individual photons on a beamsplitter. We also demonstrate that two-photon interference, or photon bunching effect on a beamsplitter, does not occur if the two-photon Feynman amplitudes are distinguishable, even though individual photons do overlap on a beamsplitter. Therefore, two-photon interference cannot be viewed as interference of two individual photons, rather it should be viewed as two-photon or biphoton interfering with itself. The results may also be useful for studying decoherence management in entangled two-qubit systems as we observe near complete restoration of quantum interference after the qubit pairs, generated by a femtosecond laser pulse, went through certain birefringent elements.
Measurement of one-photon and two-photon wavepackets in spontaneous parametric down-conversion
Yoon-ho Kim
Physics , 2003, DOI: 10.1364/JOSAB.20.001959
Abstract: One-photon and two-photon wavepackets of entangled two-photon states in spontaneous parametric down-conversion (SPDC) fields are calculated and measured experimentally. For type-II SPDC, measured one-photon and two-photon wavepackets agree well with theory. For type-I SPDC, the measured one-photon wavepacket agree with the theory. However, the two-photon wavepacket is much bigger than the expected value and the visibility of interference is low. We identify the sources of this discrepancy as the spatial filtering of the two-photon bandwidth and non-pair detection events caused by the detector apertures and the tuning curve characteristics of the type-I SPDC.
Single-photon two-qubit "entangled'' states: preparation and measurement
Yoon-Ho Kim
Physics , 2003, DOI: 10.1103/PhysRevA.67.040301
Abstract: We implement experimentally a deterministic method to prepare and measure so called single-photon two-qubit entangled states or single-photon Bell-states, in which the polarization and the spatial modes of a single-photon each represent a quantum bit. All four single-photon Bell-states can be easily prepared and measured deterministically using linear optical elements alone. We also discuss how this method can be used for recently proposed single-photon two-qubit quantum cryptography protocol.
Twisted Class Field Theory
Seok Ho,Yoon
Mathematics , 2015,
Abstract: Neukirch has developed explicit and axiomatic class field theory, which applies to both local and global fields. One of the key ingredients in his theory is a $\hat{\mathbb{Z}}$-extension of the base field, and in the case of $\mathbb{Q}_p$, he uses the maximal unramified extension. However $\mathbb{Q}_p$ has another $\hat{\mathbb{Z}}$-extension, which we shall denote by $\hat{\mathbb{Q}}_p$. Thus, it is natural to ask if we could verify all the axioms required by taking $\hat{\mathbb{Q}}_p$ as the central object instead. We prove this is possible and the two reciprocity maps induced from the two distinct $\hat{\mathbb{Z}}$-extensions are the same.
A New Case of Turner Syndrome with Early Pubertal Development  [PDF]
Seok Ho Yoon, Dong Jun Lee, Son Moon Shin, So Young Yoon, Sung Won Park
International Journal of Clinical Medicine (IJCM) , 2016, DOI: 10.4236/ijcm.2016.75036
Abstract: Turner syndrome (TS) is a relatively common chromosomal disorder caused by complete or partial X monosomy. The most frequently observed karyotype, 45, X, arises more often by loss of the paternal X or Y chromosome in meiosis or in early embryogenesis than by loss of the maternal X chromosome. The main clinical features of TS are short stature, gonadal dysgenesis, and not to undergo pubertal development (e.g. primary amenorrhea). However, a few rare cases of TS have shown precocious puberty. Our case of a 9-year-old girl did not have any TS-specific clinical hallmarks, with the exception of short stature. She visited our clinic because of her pubertal development and short stature. In this report, we highlight the variability that can occur in patients with TS and emphasizes the need to carefully assess unusual growth patterns in any child, regardless of other underlying conditions.
Endogenous Endophthalmitis Associated with Facial Cellulitis After a Tongue Bite  [PDF]
Min Ho Kang, Mincheol Seong, Ju Hak Lee, Hee Yoon Cho
Open Journal of Ophthalmology (OJOph) , 2012, DOI: 10.4236/ojoph.2012.23018
Abstract: Endogenous endophthalmitis is an intraocular infection that results from hematogenous spread of organisms from a distant source of infection. Facial cellulitis is rarely reported as a focus of infection. We report a case of 51-year-old unconscious woman presenting with fever, facial swelling, and decreased visual acuity secondary to facial cellulitis, endogenous endophthalmitis and end-stage renal disease(ESRD). Generally systemic antibiotics in endophthalmitis have low efficacy because of the blood-ocular barrier. The management of endophthalmitis begins with intravitreal antibiotic injections and if the response is not favorable to do a vitrectomy. Twelve hours after the intravitreal antibiotic injection, vitrectomy was considered because of worsening of the vitreal cloudiness. However, the patient's general medical condition precluded vitrectomy. We experienced successful treatment with intravitreal antibiotic injection and continuous intravenous antibiotic administration because of the breakdown of the blood-ocular barrier due to ocular inflammation, especially in the setting of systemic vascular and fluid homeostatic changes.
HSF1-mediated oxidative stress response to menadione in Saccharomyces cerevisiae KNU5377Y3 by using proteomic approach  [PDF]
Il-Sup Kim, Hyun Kim, Young-Saeng Kim, Ingnyol Jin, Ho-Sung Yoon
Advances in Bioscience and Biotechnology (ABB) , 2013, DOI: 10.4236/abb.2013.41007
Abstract: The hat shock transcription factor HSF1 inthe yeast Saccharomyces cerevisiae regulates a wide range of genes and functions in diverse cellular reactions. To investigate the physiological response of HSF1 inthe presence of menadione (MD) in S. cerevisiae KNU 5377Y3, wild-type (k3wt) and isogenic hsf1 mutant (k3h1) cells were introduced. HSF1 was induced when k3wt cells were exposed to the superoxide-generating agent MD and k3h1 cells were hypersensitive to MD. Under MD stress, k3h1 cells down-regulated the expression of metabolic enzymes (Hxk, Fba1, Pgk1, Eno2, and Adh1), antioxidant enzymes (Trx2 and porin), and molecular chaperones and their cofactors (Hsp104, Ssb1, Hsp60, Hsp42, Hsp26, Hsp12, Cpr1, and Sti1). In addition, k3h1 cells increased cellular hydroperoxide levels and protein carbonylation under MD stress as compared to k3wt cells. However, there was a moderate difference in the wild-type (b3wt) and mutant (b3h1) cells derived from S. cerevisiae S288Cunder the same conditions. Thus, these results show that HSF1 is an important component of the stress response system, acting as an activator of cell rescue genes in S. cerevisiae KNU5377Y3, and its expression protects the cells from MD-induced oxidative damage by maintaining redox homeostasis and proteostasis in the presence of MD.
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