Sun-tae Jung

Electron-Transfer Mediator for a NAD-Glucose Dehydrogenase-Based Glucose Sensor

A new electron-transfer mediator, 5-[2,5-di (thiophen-2-yl)-1H-pyrrol-1-yl]-1,10-phenanthroline iron(III) chloride (FePhenTPy) oriented to the nicotinamide adenine dinucleotide-dependent-glucose dehydrogenase (NAD-GDH) system was synthesized through a Paal-Knorr condensation reaction. The structure of the mediator was confirmed by Fourier-transform infrared spectroscopy, proton and carbon nucler magnetic resonance spectroscopy, and mass spectroscopy, and its electron-transfer characteristic for a glucose sensor was investigated using voltammetry and impedance spectroscopy. A disposable amperometric glucose sensor with NAD-GDH was constructed with FePhenTPy as an electron-transfer mediator on a screen printed carbon electrode (SPCE) and its performance was evaluated, where the addition of reduces graphene oxide (RGO) to the mediator showed the enhanced sensor performance. The experimental parameters to affect the analytical performance and the stability of the proposed glucose sensor were optimized, and the sensor exhibited a dynamic range between 30 mg/dL and 600 mg/dL with the detection limit of 12.02 ± 0.6 mg/dL. In the real sample experiments, the interference effects by acetaminophen, ascorbic acid, dopamine, uric acid, caffeine, and other monosaccharides (fructose, lactose, mannose, and xylose) were completely avoided through coating the sensor surface with the Nafion film containing lead(IV) acetate. The reliability of proposed glucose sensor was evaluated by the determination of glucose in artificial blood and human whole blood samples.

Bragg grating-assisted WDM filter for integrated optical triplexer transceivers

We designed and experimentally demonstrated a Bragg grating-assisted wavelength-division-multiplexing filter for the three-wavelength multiplexing on a planar-lightwave-circuit platform. The 1310- and 1550-nm lights were designed to be separated after passing the directional coupler by a half-cycle and a full-cycle coupling actions with losses of 0.07 and 0.19 dB, respectively. The 1492-nm light was reflected back by a Bragg grating fabricated on the directional coupler and its loss was less than 2.0 dB. We also introduced and discussed the new concept of an integrated optical triplexer transceiver using this filter.

Formation of plasma induced surface damage in silica glass etching for optical waveguides

Ge, B, P-doped silica glass films are widely used as optical waveguides because of their low losses and inherent compatibility with silica optical fibers. These films were etched by ICP (inductively coupled plasma) with chrome etch masks, which were patterned by reactive ion etching (RIE) using chlorine-based gases. In some cases, the etched surfaces of silica glass were very rough (root-mean square roughness greater than 100 nm) and we call this phenomenon plasma induced surface damage (PISD). Rough surface cannot be used as a platform for hybrid integration because of difficulty in alignment and bonding of active devices. PISD reduces the etch rate of glass and it is very difficult to remove residues on a rough surface. The objective of this study is to elucidate the mechanism of PISD formation. To achieve this goal, PISD formation during different etching conditions of chrome etch mask and silica glass was investigated. In most cases, PISD sources are formed on a glass surface after chrome etching, and...

Thin film filter-embedded triplexing-filters based on directional couplers for FTTH networks

We designed and experimentally demonstrated a thin film filter (TFF)-embedded directional coupler-type triplexing-filter on the planar-lightwave-circuit platform. The triple-play multiplexing was significantly simplified by using one TFF. The 1.31- and 1.55-/spl mu/m lights were designed to be divided after passing the directional coupler by half-cycle and full-cycle coupling actions, respectively. The 1.49-/spl mu/m light was reflected by a TFF inserted in a trench on the directional coupler. The insertion losses of fabricated triplexing-filters were less than 2.0 dB with bandwidths of 20 nm. The newly proposed triplexing-filter provides a cost-effective high-performance solution for fiber-to-the-home networks.

A framework for personalized Healthcare Service Recommendation

Development of the Internet enables numerous healthcare services to be available to many service consumers. As a result, many brokering web sites such as healthcare service portals and search engines are deployed to support userspsila choice. However, to provide better healthcare to the novice users, systems need more sophisticated mechanism for healthcare recommendation. In this paper, we propose healthcare service recommendation framework (HSRF) that considers health status and various contexts of each user. HSRF arranges healthcare services based on medical similarities between user and services. We successfully implemented the framework and confirmed its functionality and feasibility.

Reduction of insertion loss of thin film filters embedded in PLC platforms

We propose and experimentally demonstrate a method of reducing insertion loss of a thin-film-filter-embedded planar-lightwave-circuit platform for a triplexer transceiver module. Significant loss reduction was achieved by adding horn waveguide elements at the interfaces between the thin film filter and the output-port (transmission and reflection) waveguides.

Activation of pluripotency genes by a nanotube-mediated protein delivery system

The overexpression of cell reprogramming factors (Oct4, Sox2, Klf4, Nanog, and c‐Myc) allows differentiated cells to revertto an earlier developmental stage. Differentiated cells can also be reprogrammed by directly delivering reprogramming proteins tagged with cell‐penetrating peptides, which allow the proteins to pass through the cell membrane and into the cytoplasm–although this method has been an inefficient process. Here, we describe a novel technique for delivering reprogramming proteins into cells using titanium oxide (TiO2) nanotubes, which show no cytotoxic effects and do not affect cell proliferation. TiO2 nanotubes successfully transferred the above‐mentioned reprogramming factors into differentiated somatic cells. After 3 weeks of treatment with protein‐conjugated nanotubes, the somatic cells adopted an embryonic stem cell‐like morphology and expressed activated Oct4‐green fluorescent protein, a pluripotency biomarker. Our results indicate that TiO2 nanotubes can be used to directly deliver reprogramming factors into somatic cells to induce pluripotency. Mol. Reprod. Dev. 80: 1000–1008, 2013.

Development of compact and low-crosstalk PLC-WDM filters for hybrid-integrated bidirectional optical transceivers

This paper reports on the development of planar-lightwave-circuit wavelength-division-multiplexing (PLC-WDM) filters based on double polynomial curve directional couplers, which will be integrated into compact and low-cost bidirectional optical transceivers for FTTx systems. Silica-based PLC-WDM filters smaller than 5 mm/spl times/100 /spl mu/m for Ethernet passive optical network (E-PON) applications were designed and fabricated to have low bidirectional crosstalk (lower than -40 dB) as well as low insertion losses (lower than 1 dB) within the operating temperatures of -40 to 80/spl deg/C. Several features and design guides that can reduce the size of directional couplers and improve the level of bidirectional crosstalk are discussed.

Crosstalk enhancement of AWG fabricated by flame hydrolysis deposition method

The crosstalk of arrayed-waveguide grating (AWG) multi/demultiplexer has been reduced through the modification of the torch for flame hydrolysis deposition (FHD) process. The conventional type FHD torch was changed into a precursor-premixed type torch, which enhanced the AWG crosstalk level by 5-8 dB. The results were also compared with the characteristics of AWGs of which the core layers were fabricated by the plasma-enhanced chemical vapor deposition process.

A platform for personalized mobile u-health application design and development

In this paper, we propose an application platform and development environment to enable medical specialists such as doctor and therapist to design and develop personalized mobile u-healthcare applications based on patientpsilas health conditions and environmental situations. The personalized applications are specified in the form of application scenario using XML document which is downloaded and played on mobile phone. The platform provides models, functions, and facilities for medical specialists to design their own u-health applications. They design u-health application scenarios, and application scenario player of the platform executes the application scenario on the patientpsilas mobile phone. We confirmed that the suggested platform is useful and adequate in developing personalized mobile u-healthcare applications by implementing an actual stress application on the platform.