Junghoi Kim

Inhibitory Effects of 150 Plant Extracts on Elastase Activity, and Their Anti-inflammatory Effects

The inhibitory effects of 150 medicinal plants on elastase activity were investigated. Among the 150 plants, six plant extracts (final concentration 1 mg/ml in methanol) exhibited more than 65% of inhibition of elastase activity. The inhibitory effects of six active plants, including Areca catechu (IC50, 42.4 μg/ml), Cinnamonum cassia (IC50, 208.7 μg/ml), Myristica fragrans (IC50, 284.1 μg/ml), Curcuma longa (IC50, 398.4 μg/ml), Alpinia katsumadai (IC50, 465.7 μg/ml) and Dryopteris cassirrhizoma (IC50, 714.4 μg/ml) on the activity of human leukocyte elastase, hyaluronidase and lipid peroxidation were examined. In the lipid peroxidation assay, using the TBA method, three of the six plants, including Curcuma longa (IC50, 45.5 μg/ml), Areca catechu (IC50, 51.0 μg/ml) and Alpinia katsumadai (IC50, 116.3 μg/ml) exhibited more than 70% inhibition at the concentration of 1 μg/ml, but only one plant, Areca catechu (IC50, 563 μg/ml) showed high inhibitory effect on hyaluronidase activity. The results suggest that medicinal plants showing several biological activities may be potent inhibitors of the anti‐ageing process in skin. This property might be useful for application in cosmetics.

Optical properties of a photopolymer film for digital holographic storage

Tir- and mono functional monomers were dispersed in a solution of polysulfone in organic solvent containing a photo initiator and other additives. New photopolymer film was prepared by dispersing acrylic monomer in a polysulfone matrix. The Polysulfone was adopted as a binder since it affords transparent thick films with low dimensional changes during holographic recording. Optical property of the photopolymer showed high diffraction efficiency (>90%) under an optimized optical condition at 532nm laser. The angular selectivity for angular multiplexing page oriented holographic memories (POHMs), the maximum diffraction efficiency of the material during holographic recording, the diffraction efficiency of the films as a function of an incident angle of two beams, exposure energy for saturation of the holographic material and application for holographic data storage will be discussed.

Double side hologram reconstruction for digital holographic data storage using phase conjugated reference beam

We propose the fast accessible data storage system using the double side hologram reconstruction scheme which can simultaneously read out holograms using both the forward and phase conjugate reference beams. In this system, digital pages are recorded in the usual manner but are reconstructed in two CCD cameras by the double side hologram reconstruction. As a result, we achieved the speed of two times faster than the conventional readout and the estimated raw BER were 3.09×10-18 (left image) and 4.76×10-16 (right image), respectively.

Digital holographic smart card system using an organic-inorganic hybrid type photopolymer film

Organic-inorganic nanocomposite films were prepared by dispersing an aromatic methacrylic monomer and a photo-initiator in organic-inorganic hybrid sol-gel matrices. The film properties could be controlled by optimizing the content of an organically modified silica precursor (TSPEG) in the sol-gel matrices. The photopolymer film modified with the organic chain (TSPEG) showed high diffraction efficiency (>90%) under an optimized condition. In addition, we implement a digital holographic security system that combines the electrical biometrics technology with fully digital holographic storage using an organic-inorganic hybrid type photopolymer film.

Fabrication of apodized grating in photopolymer using SLM

Fabricating holographic apodized gratings is often impeded by nonlinear property of materials, which makes the resultant profile out of expectation. In this paper, the new scheme to fabricate Gaussian apodized grating is proposed. Instead of fixed Gaussian recording beams, recording beam profiles that can compensate the nonlinear sensitivity of the material at low recording intensities are created by a gray level spatial light modulator (SLM). DuPont’s HRF-150-38 photopolymer is chosen because of its stability and ease to use. As the first result of the experiment, a Gaussian grating of 2.7±0.02mm standard deviation is recorded at 0.3mW/cm2 recording intensity after exposure of 300 seconds.

Three-dimensional image display using the phase conjugation method of digital holographic data storage

We propose the double-side dual hologram reconstruction scheme which can simultaneously read out holograms using both the forward and phase conjugate reference beams, and demonstrate stereo image recording and playback by the holographic memory system. This system is composed of a stereoscopic camera obtained stereo image pairs, holographic data storage where stereo images are recorded in the usual manner but read out by double-side dual reconstruction, and a stereo monitor that use polarized light techniques. As a result, stereo digital pages, which are reconstructed by the proposed double-side dual reconstruction method, can be obtained with very low cross talk noise, and the estimated raw BER of retrieved holograms were approximately 3.59×10-4 (left image) and 5.0×10-4 (right image), respectively.

Analysis of thermal properties of the Dupont photopolymer for the digital holographic security card system

We analyze the thermal properties of the DuPont HRF150-38 photopolymer for digital holographic card manufacture. In case of recording after heating, the diffraction efficiency of the hologram is more than 70% at 100°C but is decreased exponentially at temperatures over 100°C. It is observed in the recording before heating that the diffraction efficiency of the hologram fixed by a UV light is increased to approximately 10% at 100°C, but the hologram are erased at temperatures over 120°C.

Digital hologram reconstruction using the dual-wavelength method

In this paper, to reduce the Bragg-mismatch problem of the dual-wavelength method, we record the hologram in the Duponts photopolymer of thickness L=38μm and use a digital image data which has 78×104 bit/page. Also, to compensate the image magnification problem, a pair of cylinder lens consisting of 4F system behind the F2 lens and proposed data matrix image processing technique is used. As a result, the raw BER through Gaussian fitting after extracting binary data is around 3.09×10-6.

Angular selectivity independent of the writing conditions in photorefractive grating

The independent characteristic of the angular selectivity for the writing conditions was presented in photorefractive grating. In general, the incident angle of writing beam and the interaction length determine the angular selectivity of the grating. When the focused probe beam is incident on the grating, we obtain a new relation that the angular selectivity of the photorefractive grating depends on the probe beam incident conditions and is independent of the writing conditions such as writing beam incident angle, wavelength, and interaction length. These characteristics are experimentally investigated as a function of the following parameters; writing beam incident angle, probe beam width and lens focal length. In the experimental results, it has demonstrated that the control parameters are not the incident angles of writing beam but the probe beam width and focal length of the convex lens. Another property of this configuration is to have same value within large angular range that is also determined by the readout conditions.

Holographic optical tunable filter using a liquid crystal spatial light modulator in a photorefractive crystal

We has described and demonstrated a new holographic optical tunable filter, which was tuned by the control of the windows in a LCD panel. This method can be a simple and effective way of photorefractive wavelength selective filter.