Seung Jae Baek

The Australian Society of Otolaryngology Head & Neck Surgery, Evans Head, New South Wales, Australia

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Publications (30)73.29 Total impact

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    ABSTRACT: Acute side effects of radiation such as oral mucositis are observed in most patients. Although several potential radioprotective agents have been proposed, no effective agent has yet been identified. In this study, we investigated the effectiveness of synthetic compound 3-amino-3-(4-fluoro-phenyl)-1H-quinoline-2,4-dione (KR22332) as a radioprotective agent.
    Yonsei medical journal. 07/2014; 55(4):886-94.
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    ABSTRACT: Recent advances in physics have made possible the use of non-thermal atmospheric pressure plasma (NTP) in cancer research. Although increasing evidence suggests that NTP induces death of various cancer cell types, thus offering a promising alternative treatment, the mechanism of its therapeutic effect is little understood. In this study, we report for the first time that NTP led to apoptotic cell death in oral cavity squamous cell carcinoma (OSCC). Interestingly, NTP induced a sub-G1 arrest in p53 wild-type OSCCs, but not in p53-mutated OSCCs. In addition, NTP increased the expression levels of ATM, p53 (Ser 15, 20 and 46), p21, and cyclin D1. A comet assay, Western blotting and immunocytochemistry of γH2AX suggested that NTP-induced apoptosis and sub-G1 arrest were associated with DNA damage and the ATM/p53 signaling pathway in SCC25 cells. Moreover, ATM knockdown using siRNA attenuated the effect of NTP on cell death, sub-G1 arrest and related signals. Taken together, these results indicate that NTP induced apoptotic cell death in p53 wild-type OSCCs through a novel mechanism involving DNA damage and triggering of sub-G1 arrest via the ATM/p53 pathway. These findings show the therapeutic potential of NTP in OSCC.
    Archives of Biochemistry and Biophysics 01/2014; · 3.37 Impact Factor
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    ABSTRACT: Recent advances in physics have made possible the use of non-thermal atmospheric pressure plasma (NTP) in cancer research. Although increasing evidence suggests that NTP induces death of various cancer cell types, thus offering a promising alternative treatment, the mechanism of its therapeutic effect is little understood. In this study, we report for the first time that NTP led to apoptotic cell death in oral cavity squamous cell carcinoma (OSCC). Interestingly, NTP induced a sub-G1 arrest in p53 wild-type OSCCs, but not in p53-mutated OSCCs. In addition, NTP increased the expression levels of ATM, p53 (Ser 15, 20 and 46), p21, and cyclin D1. A comet assay, Western blotting and immunocytochemistry of γH2AX suggested that NTP-induced apoptosis and sub-G1 arrest were associated with DNA damage and the ATM/p53 signaling pathway in SCC25 cells. Moreover, ATM knockdown using siRNA attenuated the effect of NTP on cell death, sub-G1 arrest and related signals. Taken together, these results indicate that NTP induced apoptotic cell death in p53 wild-type OSCCs through a novel mechanism involving DNA damage and triggering of sub-G1 arrest via the ATM/p53 pathway. These findings show the therapeutic potential of NTP in OSCC.
    Archives of Biochemistry and Biophysics 01/2014; · 3.37 Impact Factor
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    ABSTRACT: To investigate the electronic transport mechanisms in multi-layered graphene oxide (MGO), the temperature-dependent electrical conductivity (σ(T)) has been measured as a function of the annealing temperature (Ta). An individual MGO flake was gradually reduced by thermal annealing at Ta from 88 to 300 °C, with the reduction process confirmed at each stage by X-ray photoelectron spectroscopy. As Ta increases, the σ(T) of the MGO also increases. We found that the σ(T) is well interpreted by variable-range hopping in disordered regions in series through activated conduction across small barriers. We associate the localized states for hopping with the oxygen functional groups in GO, as well as the small activation barriers with the domain boundaries between the clustered oxygen functional groups and the graphitic region. Both the hopping and activation barrier resistances decrease systematically as the Ta increases.
    Synthetic Metals 01/2014; 191:1–5. · 2.11 Impact Factor
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    ABSTRACT: Graphene-based nanosheets (GNS) have been studied for use in electrochemical energy storage devices. A deeper understanding about the system is required for achieving enhanced power output and high energy storage. The effects of sulfur doping on the electrochemical properties of GNS are studied for their use as an anode material in lithium-ion batteries. Sulfur doping in GNS contributes to the high specific capacity by providing more lithium storage sites due to Faradaic reactions. In addition, superior rate performance of sulfur-doped GNS (S-GNS) is achieved through the improved electrical conductivity of S-GNS (1743 S m−1), which is two orders of magnitude higher than that of GNS (32 S m−1). In addition, good cyclic stability of S-GNS is maintained even after 500 cycles at a high current density of 1488 mA g−1 (4 C).
    Journal of Power Sources 01/2014; 262:79–85. · 5.26 Impact Factor
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    ABSTRACT: Step by step reduced graphene oxide(GO) thin film transistors were electrically characterized as a temperature and gate voltage. The GO transistors were prepared by thermally reduced using step by step method in same samples. The reduction temperature were subtracted from the inflection point of thermogravimetric analysis(TGA) plot and their points are 88, 158, 185, 215, 250, 300 degree Celsius. All GO condition at various reduction temperatures were defined using Raman spectroscopy and atomic force microscopy(AFM). Temperature dependence electrical measurements were carried out using two terminal technique and various temperatures up to unmeasurable condition. Our charge transport behaviors well fitted to 2 dimensional variable-range hopping(2D VRH) mechanism and fluctuation induced tunneling(FIT) model. Also the conductivity level of each step was increased more than 10{4 }times.
    03/2013;
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    ABSTRACT: We have measured magnetoresistance (MR) and twisted angle of twisted bilayer graphene, simultaneously. Twisted angle was measured by transmission electron microscopy (TEM) diffraction experiment on SiNx substrate. We performed Raman spectroscopy experiment and observed enhanced G mode which results from double resonance scattering process near van Hove singularity (vHs). MR shows superposition of two Shubnikov de Haas (SdH) oscillations and is analyzed by Landau fan diagram.
    03/2013;
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    ABSTRACT: We have demonstrated the structural modulation at the edge of MoS2 due to H2 exposure with spatially resolved Raman spectroscopy and the electrical characteristics of few-layer MoS2 with respect to H2 pressure from vacuum to 20 bars at 295 K T 350 K. Upon H2 exposure, the significant change of the edge in E2g mode was observed. The conductance increases and threshold voltage (Vth) shifts toward a negative gate voltage region, indicating n-type doping. These behaviors are enhanced by high temperature and long exposure time (t). The results reveal the creation of vacancy at the edge sites of MoS2 in H2 atmosphere causing the enhancement of n-type doping due to increase of metallic region.
    03/2013;
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    ABSTRACT: Novel carbon-based microporous nanoplates containing numerous heteroatoms (H-CMNs) are fabricated from regenerated silk fibroin by the carbonization and activation of KOH. The H-CMNs exhibit superior electrochemical performance, displaying a specific capacitance of 264 F/g in aqueous electrolytes, a specific energy of 133 Wh/kg, a specific power of 217 kW/kg, and a stable cycle life over 10000 cycles.
    Advanced Materials 02/2013; · 14.83 Impact Factor
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    ABSTRACT: OBJECTIVE: The aim of this study was to present the various strategies adopted in our center to improve and overcome problems with exposure of the operative field in 48 patients who underwent TORS for the treatment of laryngeal and hypopharyngeal cancer. METHODS: We present our operative and preoperative treatment protocols for patients undergoing TORS for laryngeal and hypopharyngeal cancer. In particular, we emphasize the role of preoperative exposure assessment and the usefulness of simple measures to overcome problems with exposure of the operative field. RESULTS: In 12 patients (25%), we experienced difficult laryngeal-hypopharyngeal exposure. However the correct positioning of the robotic arms, the proper use of the laryngeal and tongue blade and some simple maneuvers, such as the anterior traction of the tongue and the partial epiglottectomy, ensured the feasibility of TORS with negative margins in all patients. CONCLUSION: In TORS, the exposure of larynx and hypopharynx can be difficult, but the adoption of certain methods may make it possible in most patients. An accurate preoperative evaluation under general anesthesia is the primary strategy for reducing the number of cases terminated intraoperatively. Currently, TORS is not feasible in all patients, but in our opinion, reductions in the size of robotic equipment and development of new devices will extend the application of TORS to a larger number of patients.
    Auris, nasus, larynx 10/2012; · 0.58 Impact Factor
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    ABSTRACT: We have investigated the transport properties of monolayer graphene doped with halogen molecules, iodine and bromine. For these doping, the charge neutrality point shifts to the hole carrier regime indicating p-type doping, and the carrier mobility is reduced. As compared to doping with other dopants, however, the reduction of the mobility is much weaker for doping with halogen molecules. Also, the minimum conductivities at the charge neutrality point are enhanced with subsequent doping for the monolayer graphene, in strong contrast to the cases with other dopants. When the graphene layer was doped selectively by covering its edge with a polymer layer, such unconventional behaviors were not observed any more. These observations can be understood that intercalated halogen molecules between the graphene layer and the underlying substrate leads to screening of charged impurities embedded in SiO2 substrate. Halogen molecules can be effective dopants for the graphene monolayer which changes the carrier concentration without significant degrading of the mobility.
    Synthetic Metals 10/2012; 162(s 17–18):1689–1693. · 2.11 Impact Factor
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    ABSTRACT: Reduced graphene oxide nanoribbon fibers were fabricated by using an electrophoretic self-assembly method without the use of any polymer or surfactant. We report electrical and field emission properties of the fibers as a function of reduction degree. In particular, the thermally annealed fiber showed superior field emission performance with a low potential for field emission (0.7 V µm(-1)) and a giant field emission current density (400 A cm(-2)). Moreover, the fiber maintains a high current level of 300 A cm(-2) corresponding to 1 mA during long-term operation.
    Nanotechnology 05/2012; 23(23):235601. · 3.84 Impact Factor
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    ABSTRACT: We have synthesized large scale bilayer graphene by using Chemical Vapor Deposition (CVD) in atmospheric pressure. Bilayer graphene was grown by using CH4, H2 and Ar gases. The growth temperature was 1050^o. Conventional FET measurement shows ambipolar transfer characteristics. Results of Raman spectroscopy, Atomic Force microscope (AFM) and Transmission Electron Microscope (TEM) indicate the film is bilayer graphene. Especially, adlayer structure which interrupt uniformity was reduced in low methane flow condition. Furthermore, large size CVD bilayer graphene film can be investigated to apply sensor devices. By using conventional photolithography process, we have fabricated device array structure and studied sensing behavior.
    02/2012;
  • Seung Jae Baek, Yung Woo Park
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    ABSTRACT: Thin layers of organic molecules, OTS and DMF, are coated on top of graphene which was extracted by the exfoliation. I-V characteristics of the organic molecules coated graphene were investigated at low temperature by varying the gate voltage. P-doping with slight enhancement of mobility was observed with the OTS coating. On the other hand, n-doping with relatively higher enhancement of mobility was obtained with the DMF coating. CNT is nested on top of the organic molecules coated graphene by dielectrophoresis and Coulomb blockade was observed in the sandwich device.
    02/2012;
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    ABSTRACT: Studies of the interaction between hydrogen and graphene have been increasingly required due to the indispensable modulation of the electronic structure of graphene for device applications and the possibility of using graphene as a hydrogen storage material. Here, we report on the behaviour of molecular hydrogen on graphene using the gate voltage-dependent resistance of single-, bi-, and multi-layer graphene sheets as a function of H(2) gas pressure up to 24 bar from 300 K to 345 K. Upon H(2) exposure, the charge neutrality point shifts toward the negative gate voltage region, indicating n-type doping, and distinct Raman signature changes, increases in the interlayer distance of multi-layer graphene, and a decrease in the d-spacing occur, as determined by TEM. These results demonstrate the occurrence of dissociative H(2) adsorption due to the existence of vacancy defects on graphene.
    Scientific Reports 01/2012; 2:690. · 5.08 Impact Factor
  • Otolaryngology Head and Neck Surgery 10/2011; 146(5):865-7. · 1.73 Impact Factor
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    Dae Bo Shim, Ji-Sun Song, Seung Jae Baek
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    ABSTRACT: An ectopic hamartomatous thymoma is an extremely rare benign tumor of the lower neck that is the most common in middle-aged males. Pathologically, the tumor is characterized by a mixture of spindle cells, epithelial cells, mature adipose tissue, and lymphocytes. The histogenesis of this tumor is controversial. Recently, an origin from a remnant of the cervical sinus of His was proposed. Malignant lesions such as synovial sarcomas or malignant peripheral nerve sheath tumors can have similar clinical features and radiologic images. Thus, recognition of this tumor is important because it follows a benign clinical course and conservative surgical excision is the treatment of choice. Here, we report the case of a 34-year-old man with an ectopic hamartomatous thymoma in the left supraclavicular region and a review of the literature on this tumor.
    Auris, nasus, larynx 08/2011; 39(1):110-3. · 0.58 Impact Factor
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    ABSTRACT: Hepatocyte growth factor (HGF) can promote proliferation, invasion, and angiogenesis in various tumor cells. However, the prognosis according to expression of HGF/c-Met has not been reported in patients with squamous cell carcinoma of the oral tongue (SCCOT). Tumors from 61 patients with SCCOT were evaluated for the expression of HGF and c-Met by immunohistochemistry. For Western blot, we used fresh normal and cancer tissues from 3 patients with SCCOT. The positive rates of HGF and c-Met immunostaining in SCCOT were 57.3% and 54.1%, respectively. The c-Met staining was significantly correlated with lymph node metastasis (p = .005), tumor classification (p = .004), and recurrence (p = .018). Survival was significantly affected in patients with positive c-Met expression (p = .003). HGF and c-Met were strongly expressed in cancer tissues on Western blot. The c-Met expression may play an important role in the progression and the survival outcome of patients with SCCOT.
    Head & Neck 12/2010; 32(12):1655-64. · 2.83 Impact Factor
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    ABSTRACT: Human papilloma virus (HPV) infection is controversial as a causative factor in oral tongue cancer. This study aimed to clarify whether HPV directly affects the carcinogenesis and biological behaviour of oral tongue cancer by analyzing HPV prevalence, the physical status of the virus and clinicopathological parameters. Archival tissue was obtained from 36 patients diagnosed with T1 and T2 oral tongue cancer and 25 normal controls. HPV genotyping chip and real-time polymerase chain reaction were used to determine the prevalence, phenotype and physical status of HPV to clarify whether HPV directly affects oncogenesis. The results were also compared with clinicopathological parameters. HPV was detected in 36% (13/36) of oral tongue cancer patients, compared with 4% (1/25) of the control. In the HPV-positive group of oral tongue cancers, HPV-16 was the most common type and its prevalence rate was 85% (11/13). Of the HPV-16 infected oral tongue cancers, the integration rate of HPV-16 was 55% (6/11). The HPV-16 positive group showed shallower stromal invasion than the HPV-16 negative group (p=0.045). HPV-16 may be one of the causative factors in early squamous cell oral tongue carcinoma and be associated with its depth of invasion.
    International Journal of Oral and Maxillofacial Surgery 07/2010; 39(7):678-83. · 1.52 Impact Factor
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    Advanced Materials 04/2010; 22(14). · 14.83 Impact Factor

Publication Stats

59 Citations
73.29 Total Impact Points

Institutions

  • 2014
    • The Australian Society of Otolaryngology Head & Neck Surgery
      Evans Head, New South Wales, Australia
  • 2008–2014
    • Seoul National University
      • Department of Physics and Astronomy
      Sŏul, Seoul, South Korea
  • 2012
    • Ulsan National Institute of Science and Technology
      Urusan, Ulsan, South Korea
  • 2010–2011
    • Myongji Hospital
      Kōyō, Gyeonggi Province, South Korea
    • Kwandong University
      Gangneung, Gangwon, South Korea
  • 2006–2008
    • Yonsei University Hospital
      • Department of Internal Medicine
      Sŏul, Seoul, South Korea
  • 2005
    • Yonsei University
      Sŏul, Seoul, South Korea