• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.1
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• pp.21-26
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• 2020

This article reports the result on the spectroscopic analysis of the three Lightbox CVD-grown diamonds. Lightbox Jewelry, a De Beers company, has begun selling CVD laboratory-grown diamonds since September 2018. Recently, we had the opportunity to examine three Lightbox's pendant necklaces. The 0.25 ct, 0.25 ct, and 0.26 ct round brilliant were graded as "H" near colorless, Fancy Vivid orangy pink, and Fancy Vivid blue with cut grades of excellent, respectively. The laser-inscribed Lightbox logo under the table, large enough to be easily visible with a microscope. Based on the spectroscopic techniques, for near colorless sample was not subjected to post-growth HPHT processing to improve its color. For pink sample, optical centers at H3, 3H, 594 nm, NV, and GR1 were recorded. It was speculated that the pink sample have been received irradiation and annealing. In addition, the blue CVD synthetic sample was concluded to be irradiated without annealing.

• The korean journal of orthodontics
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• v.22 no.2 s.37
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• pp.373-388
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• 1992

The purpose of this study was to clarify the histologic changes in the expansion of midpalatal suture by the tensile forces. 39 Sprague-Dawley rats were divided into a control group (3 rats) and three experimental groups (36 rats) -group 1, pressured with a light force(50-75 g), group 2, with a heavy force(250-300 g) and group 3, with a heavy force (250-300 g) plus laser irradiation. Autoradiographic and histopathologic observations were performed in 12, 24, 48 and 96 hours after force delivery. The results were as follows; 1. The anterior portion of midpalatal suture was more separated than the posterior portion in all experimental groups. Group 2 showed more separation than group 1 and no difference to group 3 2. Ligament tearing appeared intensively in 24 hours, but the sutural matrices increased with times. ; Group 2 showed more tearing than group 1, and active regeneration of sutural matrices was observed in group 3. 3. Vascular dilatation appeared intensively in 24 hours and decreased with times. ; The anterior portion of midpalatal suture showed more dilatation than the posterior portion, ; The changes was the greatest in group 3, group 2, group 1, in that order. 4. New bone formation and the new capillary prolieferation began to appear in 12 hours and increased with times, : Group 2 showed more changes than group 1 and no difference to group 3. 5. Infiltration of inflammatory cells was little observed and was the greatest in group 2, group 1, group 3, in that order 6. Positive reaction of cells to $[^3H]$ thymidine was the greatest in 24 hours, and decreased with times ; The reaction was the greatest in group 3, group 2, group 1, in that order.

• Journal of Periodontal and Implant Science
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• v.45 no.2
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• pp.38-45
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• 2015

Purpose: The purpose of this study was to evaluate the effect of photodynamic therapy (PDT) using erythrosine and a green light emitting diode (LED) light source on biofilms of Aggregatibacter actinomycetemcomitans attached to resorbable blasted media (RBM) and sandblasted, large-grit, acid-etched (SLA) titanium surfaces in vitro. Methods: RBM and SLA disks were subdivided into four groups, including one control group and three test groups (referred to as E0, E30, E60), in order to evaluate the effect of PDT on each surface. The E0 group was put into $500{\mu}L$ of $20{\mu}M$ erythrosine for 60 seconds without irradiation, the E30 group was put into erythrosine for 60 seconds and was then irradiated with a LED for 30 seconds, and the E60 group was put into erythrosine for 60 seconds and then irradiated with a LED for 60 seconds. After PDT, sonication was performed in order to detach the bacteria, the plates were incubated under anaerobic conditions on brucella blood agar plates for 72 hours at $37^{\circ}C$, and the number of colony-forming units (CFUs) was determined. Results: Significant differences were found between the control group and the E30 and E60 groups (P<0.05). A significantly lower quantity of CFU/mL was found in the E30 and E60 groups on both titanium disk surfaces. In confocal scanning laser microscopy images, increased bacterial death was observed when disks were irradiated for a longer period of time. Conclusions: These findings suggest that PDT using erythrosine and a green LED is effective in reducing the viability of A. actinomycetemcomitans attached to surface-modified titanium in vitro.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.3102-3102
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• 2001

Constituents of several .representative seaweeds, such as wakame Undaria pinnatifida; hijikia Hizikia fusifome; and kombu Laminaria japonica, were found to have fairly large reaction rates determined by quenching experiments of emission spectra in the near-infrared region (1max: 1270 nm) from singlet oxygen (102). Emission spectra of singlet oxygen generated from an aqueous solution of Rose Bengal under irradiation with a green laser (330 nm) were measured by a near-infrared (NIR) emission spectrometer constructed in our laboratory. The quenching experiments were as follows: Intensities of emission spectra were measured in the absence (I0) and in the presence of the seaweed constituents (I): Ratios of I0/I were plotted against every concentration of the quenchers (Stern-Volmer plots) which gives a straight line. The slope of each line gives a kqt value which gives a quenching constant kq value (an antioxidative constant against singlet oxygen) when the t value (half-life time of singlet oxygen in the solvent used) was given. The determined reaction rates are between 103-105 (g/l)-ls-1; the larger ones are as large as that of ascorbic acid, 8.4 ${\times}$ 104 (g/1)-ls-1. Most of these seaweed constituents also showed antioxidative activity against auto-oxidation and superoxide as well as their immunological enhancing activity. These results suggest a possibility that dietary fibers which are supposed to prevent the large-intestine cancer by their physical properties may prevent the cancer, at least in parts, by their chemical, antioxidative activity.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.53.1-53.1
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• 2011

Bioactive glass powders were synthesized by hydrothermal chemical route by the use of ultrasonic energy irradiation. We used sodalime, calcium nitrate tetra hydrate and di ammonium hydrogen phosphate as the precursor material to synthesize $SiO_2$ rich bio-active glass materials. The $SiO_2$ content was varied in the precursor mixture to 60, 52 and 45 mole%. Dense compacts were obtained by microwave sintering at $1,100^{\circ}C$. Mechanical properties were characterized for the fabricated dense bioactive glasses and were found to be comparable with conventional CaO-$SiO_2$-$Na_2O$-$P_2O_5$ bioactive glass. Detailed biocompatibility evaluation of the glass composition was investigated by in-vitro culture of MG-63 cell and mesenchyme stem cell. Cell adhesion behavior was investigated for both of the cell by one cell morphology for 30, 60 and 90 minutes. Cell proliferation behavior was investigated by culturing both of the cells for 1, 3 and 7 days and was found to be excellent. Both SEM and confocal laser scanning microscopy were used for the investigation. Western blot analysis was performed to evaluate the bimolecular level interaction and extent and rate of specific protein expression. The ability to form biological apatite in physiological condition was observed with simulated body fluid (SBF). In-vivo bone formation behavior was investigated after implanting the materials inside rabbit femur for 1 and 3 month. The bone formation behavior was excellent in all the bioglass compositions, specially the composition with 60% $SiO_2$ content showed most promising trend.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.658-658
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• 2013

Graphene is an attractive material for various device applications due to great electrical properties and chemical properties. However, lack of band gap is significant hurdle of graphene for future electrical device applications. In the past few years, several methods have been attempted to open and tune a band gap of graphene. For example, researchers try to fabricate graphene nanoribbon (GNR) using various templates or unzip the carbon nanotubes itself. However, these methods generate small driving currents or transconductances because of the large amount of scattering source at edge of GNRs. At 2009, Bai et al. introduced graphene nanomesh (GNM) structures which can open the band gap of large area graphene at room temperature with high current. However, this method is complex and only small area is possible. For practical applications, it needs more simple and large scale process. Herein, we introduce a photosensitive graphene device fabrication using CdSe QD coated nano-porous graphene (NPG). In our experiment, NPG was fabricated by thin film anodic aluminum oxide (AAO) film as an etching mask. First of all, we transfer the AAO on the graphene. And then, we etch the graphene using O2 reactive ion etching (RIE). Finally, we fabricate graphene device thorough photolithography process. We can control the length of NPG neckwidth from AAO pore widening time and RIE etching time. And we can increase size of NPG as large as 2 $cm^2$. Thin CdSe QD layer was deposited by spin coatingprocess. We carried out NPG structure by using field emission scanning electron microscopy (FE-SEM). And device measurements were done by Keithley 4200 SCS with 532 nm laser beam (5 mW) irradiation.

• Journal of Radiation Protection and Research
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• v.43 no.4
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• pp.160-169
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• 2018

Background: This study aims to develop an integrated optical system that can simultaneously or selectively measure the signals obtained from radioluminescence (RL), thermoluminescence (TL), and optically stimulated luminescence (OSL), which are luminescence phenomena of materials stimulated by radioactivity, heat, and light, respectively. The luminescence mechanism of various materials could be investigated using the glow curves of the luminescence materials. Materials and Methods: RL/TL/OSL integrated measuring system was equipped with a X-ray tube (50 kV, $200{\mu}A$) as an ionizing radiation source to irradiate the sample. The sample substrate was used as a heating source and was also designed to optically stimulate the sample material using various light sources, such as high luminous blue light emitting diode (LED) or laser. The system measured the luminescence intensity versus the amount of irradiation/stimulation on the sample for the purpose of measuring RL, TL and OSL sequentially or by selectively combining them. Optical filters were combined to minimize the interference of the stimulation light in the OSL signal. A long-pass filter (420 nm) was used for 470 nm LED, an ultraviolet-pass filter (260-390 nm) was used for detecting the luminescence of the sample by PM tube. Results and Discussion: The reliability of the system was evaluated using the RL/OSL characteristics of $Al_2O_3:C$ and the RL/TL characteristics of LiF:Mg,Cu,Si, which were used as dosimetry materials. The RL/OSL characteristics of $Al_2O_3:C$ showed relatively linear dose-response characteristics. The glow curve of LiF:Mg,Cu,Si also showed typical RL/OSL characteristics. Conclusion: The reliability of the proposed system was verified by sequentially measuring the RL characteristics of radiation as well as the TL and OSL characteristics by concurrent thermal and optical stimulations. In this study, we developed an integrated measurement system that measures the glow curves of RL/TL/OSL using universal USB-DAQs and the control program.

• Journal of Oral Medicine and Pain
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• v.24 no.4
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• pp.411-420
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• 1999

과거 수십년간 여러 가지 다른 레이저를 이용한 치아경조직에 대한 몇 가지의 생체외적 실험이 이루어졌다. 그러나 그 결과는 좋지 못하였다. 그러한 주 문제는 열작용이었다. 미국 식품의약국(FDA)에서 사용하도록 허가된 Er:YAG 레이저는 인간의 생체 치아를 삭제할 수 있는 최초의 레이저이다. 치아 삭제가 열작용의 원리에 의해 이루어지기는 하지만, 경조직의 미세폭발에 의하기 때문에 주변의 경조직과 연조직에 미치는 열작용은 거의 없다. 본 연구에서는 최근 국내에서 최초로 개발된 Er:YAG 레이저를 사용하여, 상아질과 법랑질에 일회 조사시 다양한 에너지 수준에 따른 삭제율을 연구하였다. 건조된 10개의 치아가 선택되었으며, 각각은 에폭시 레진에 포매되어 경화되었다. 그 후 다섯 개의 치아는 저속회전 다이아몬드 휠로써 교합면 삭제를 통해 상아질이 노출되었으며, 나머지 다섯 개의 치아는 협측 혹은 설측을 삭제하여 평평한 표면의 법랑질을 만들도록 하였다. 준비된 상아질과 법랑질 치아의 표면은 각각의 에너지 수준의 레이저를 조사할 6개의 구획으로 나누어 표본으로 삼았다. 상아질과 법랑질 표본은 에너지 수준에 따른 5개의 실험군(40 mJ, 80 mJ, 120 mJ, 160 mJ, 200 mJ)으로 나누어 그 삭제율을 분석하였다. 삭제된 부피는 삼차원 영상 표면분석기로 측정하였으며, 통계적으로 분석하였으며, 그 결과는 다음과 같다. 1. 상아질과 법랑질간의 삭제율의 차이는 통계적으로 유의한 차이가 있었다(p<0.0001). 2. 에너지 수준에 따른 삭제율의 차이는 통계적으로 유의한 차이가 있었다(p<0.0001). 3. 각각의 에너지 수준에서 상아질과 법랑질간의 삭제율의 차이는 통계적으로 유의한 차이가 있었으나(p<0.05), 40 mJ과 80 mJ에서는 유의한 차이를 보이지 않았다. 4. 상아질에서 각각의 에너지 수준 간의 삭제율이 유의한 차이를 보였으나(p<0.01), 160 mJ과 200 mJ간에는 삭제율의 유의한 차이가 없었으며, 법랑질에서도 각각의 에너지 수준 간의 삭제율이 유의한 차이를 보였으나(p<0.01), 120 mJ, 160 mJ, 200 mJ 간에 유의한 차이를 보이지 않았다. 본 연구에서는 건조된 치아에 다양한 에너지 수준의 Er:YAG 레이저를 적용했을 경우 상아질과 법랑질의 삭제 부피를 연구하여 정량화 및 통계적 분석을 하였다. 그 결과, Er:YAG 레이저는 치아경조직의 삭제에 매우 유용하였으며, 앞으로도 이를 임상적으로 널리 이용하기까지 좀더 다양하고 심화된 연구가 필요할 것으로 사료된다.

• Journal of the Korean Vacuum Society
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• v.21 no.5
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• pp.264-272
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• 2012

In this paper, we report THz generation and detection characteristics investigated by InGaAs semiconductor epilayers, as results of a basic study obtained from the InGaAs-based THz transmitter/receiver (Tx/Rx). High-temperature and low-temperature (LT) grown InGaAs epilayers were prepared by the molecular beam epitaxy technique for the characterization of THz generation and detection, respectively, and the surface emission based on the photo-Dember effect was tried for THz generation. THz wave was generated by irradiation of a Ti:Sapphire fs pulse laser (60 ps/83 MHz), and a LT-GaAs Rx was used for the THz detection. The frequency band shown in the spectral amplitudes Fourier-transformed from the measured current signals was ranging in 0.5~2 THz, and the signal currents were exponentially increased with the Tx beam power. The THz detection characteristics of LT-InGaAs were investigated by using an Rx with dipole (5/20 ${\mu}m$) antenna, and the cutoff frequency was ~2 THz.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.1
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• pp.70-77
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• 2020

The present study is aimed to assess the effect of antimicrobial photodynamic therapy (aPDT) on Streptococcus mutans biofilm through teeth whitening light emitting diode (LED). Planktonic and dynamic biofilm state cultures of S. mutans were used. Erythrosine 20 μM/L was used as the photosensitizer. Irradiation was performed by exposing cultures to clinic and homecare whitening LEDs for 15 minutes. The viability was measured through Colony Forming Unit counts and confocal laser scanning microscopy. aPDT using whitening LEDs and erythrosine significantly decreased the CFU count of S. mutans compared to that in the control group. Dynamic biofilm group showed more resistant features to aPDT compared with planktonic state. Clinic and homecare whitening LED device showed similar antimicrobial effect. The whitening LED, which could irradiate the entire oral arch, showed a significant photodynamic effect on cariogenic S. mutans biofilm. aPDT mediated by erythrosine and LEDs used for teeth whitening exhibited promising antimicrobial activity.