• Current Optics and Photonics
• /
• v.6 no.3
• /
• pp.227-235
• /
• 2022

To investigate the aging-related physiological functions of organic light-emitting diodes (OLEDs), we examined mRNA expression changes in aging-related genes due to oxidative stress inhibition by 630-nm red light OLEDs. As a result of irradiating 630-nm OLED with an intensity of 5 mW/cm² for 15 min, the viability of dermal fibroblasts significantly increased by 1.3-fold. In addition, reactive oxygen species generated by H₂O₂ were significantly reduced about 4.9-fold by irradiation with 630-nm OLED. Quantitative reverse-transcription polymerase chain reaction results showed that 630-nm OLEDs altered aging-related gene mRNA expression levels through antioxidant activity. The mRNA expression levels of matrix metalloproteinase1 (MMP1) and MMP9 decreased significantly, by about 2.2- and 2.5-fold, compared to the control group, whereas those of collagen, type I, and alpha 1 increased significantly, by 4.9-fold. The mRNA expression levels of cancer suppression genes p16 and p53 in dermal fibroblasts were also significantly reduced by 630-nm OLED irradiation, by about 1.4- and three-fold, respectively, compared to the control. Overall, it was confirmed that 630-nm OLED irradiation lowered the level of ROS formation induced by H₂O₂ in dermal fibroblasts, and that this antioxidant effect could regulate the mRNA expression levels of aging- and tumor suppression-related genes. This study shows a link between 630-nm OLED irradiation and anti-aging physiological functions such as antioxidant function, and suggests the potential of OLEDs as a useful light source for skin care.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.45 no.2
• /
• pp.56-69
• /
• 2022

Silk is a unique natural biopolymer with outstanding biocompatibility, high mechanical strength, and superior optical transparency. Due to its excellent properties, silk has been widely reported as an ideal biomaterial for several biomedical applications. Recently, fluorescent silk protein, a variant of native silk, has been reported as a biophotonic material with the potential for bioimaging and biosensing. Despite the realization of fluorescent silk, the traditional degumming process of fluorescence silk is crude and often results in fluorescence loss. The loss of fluorescent properties is attributed to the sensitivity of silk fibroin to temperature and solvent concentration during degumming. However, there is no comprehensive information on the influence of these processing parameters on fluorescence evolution and decay during fluorescent silk processing. Therefore, we conducted a spectroscopic study on fluorescence decay as a function of temperature, concentration, and duration for fluorescent silk cocoon degumming. Sodium carbonate solution was tested for degumming the fluorescent silk cocoons with different concentrations and temperatures; also, sodium carbonate solution is combined with Alcalase enzyme and triton x-100 to find optimal degumming conditions. Additionally, we conducted a molecular dynamics study to investigate the fundamental effect of temperature on the stability of the fluorescent protein. We observed degumming temperature as the prime source of fluorescent intensity reduction. From the MD study, fluorescence degradation originated from the thermal agitation of fluorescent protein Cα atoms and fluctuations of amino acid residues located in the chromophore region. Overall, degumming fluorescent silk with sodium carbonate and Alcalase enzyme solution at 25 ℃ preserved fluorescence.

• Resources Recycling
• /
• v.31 no.6
• /
• pp.73-80
• /
• 2022

This study investigated the mineralogical characteristics and basic flotation properties of domestic molybdenum ores. The source mineral of molybdenum was identified as molybdenite, and the main gangue minerals in the raw ore were silicate minerals. Copper, lead, and zinc were also found in trace amounts. Based on the results of basic flotation properties, molybdenite's zeta potential showed negative charges in all pH ranges. The contact angle of molybdenite increased with pH, reaching a maximum of 74° at pH 9. In optimal conditions, the grade and recovery of the concentrate by unit flotation were MoS2 82.4% and 92.04%, respectively. Further investigation of the impurities in the concentrate revealed a sulfide mineral with surface characteristics similar to molybdenite and silicate minerals combined with molybdenite, which may degrade the quality of the concentrate. To improve the concentrate quality, we intend to control silicate minerals through regrinding and liberation and use column flotation to improve fine particle separation efficiency.

• Journal of Information Science Theory and Practice
• /
• v.10 no.spc
• /
• pp.56-65
• /
• 2022

Korea Institute of Science and Technology Information (KISTI) is a Worldwide LHC Computing Grid (WLCG) Tier-1 center mandated to preserve raw data produced from A Large Ion Collider Experiment (ALICE) experiment using the world's largest particle accelerator, the Large Hadron Collider (LHC) at European Organization for Nuclear Research (CERN). Physical medium used widely for long-term data preservation is tape, thanks to its reliability and least price per capacity compared to other media such as optical disk, hard disk, and solid-state disk. However, decreasing numbers of manufacturers for both tape drives and cartridges, and patent disputes among them escalated risk of market. As alternative to tape-based data preservation strategy, we proposed disk-only erasure-coded archival storage system, Custodial Disk Storage (CDS), powered by Exascale Open Storage (EOS), an open-source storage management software developed by CERN. CDS system consists of 18 high density Just-Bunch-Of-Disks (JBOD) enclosures attached to 9 servers through 12 Gbps Serial Attached SCSI (SAS) Host Bus Adapter (HBA) interfaces via multiple paths for redundancy and multiplexing. For data protection, we introduced Reed-Solomon (RS) (16, 4) Erasure Coding (EC) layout, where the number of data and parity blocks are 12 and 4 respectively, which gives the annual data loss probability equivalent to 5×10^-14. In this paper, we discuss CDS system design based on JBOD products, performance limitations, and data protection strategy accommodating EOS EC implementation. We present CDS operations for ALICE experiment and long-term power consumption measurement.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.1
• /
• pp.55.2-56
• /
• 2021

The progenitor of Type Ia supernovae (SNe Ia) is mainly believed to be a close binary system of acarbon-oxygen white dwarf (CO WD) and non-degenerate companion (single degenerate) or another WD (double degenerate). However, it is unclear which system is more prevalent. Here, we present a high cadence optical/Near-IR light curve of normal but slightly faint type Ia SN 2019ein from IMSNG project. We fit the early light curve (t <+8.3 days from the first detection) with various models to find the shock-heated cooling emission from SN ejecta-companion interaction. No significant shock-heated cooling emission is found, from which we constrain the progenitor star size as the following. The upper limit (R_upper,*) of the companion size in R-band is ~0.2R_⊙ when forcing the first light time (t_fl) to have one value and ~0.9R_⊙ when using the mean value of tfl from the fitting in each band. Assuming the source of the I-band curve is almost powered from the radioactive decay, we obtained R_upper,*~1.2R_⊙. The early B-V color curve is in agreement with the model color curve of the 2M_⊙ main sequence companion. These results allow us to at least rule out large stars like red giants as a companion star of the binary progenitor system of this supernova. B-R and V-R color do not show any significant signs of a red bump, which shows a thin helium shell (MHe<0.1M_⊙) for the sub-Mch WD (double detonation model). In addition, we estimated the distance to NGC 5353 as 37.098±0.028Mpc.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.2
• /
• pp.64.2-64.2
• /
• 2019

HD 81817 is known as a hybrid star. Hybrid stars have both cool stellar wind properties and UV or even X-ray emission features of highly ionized atoms in their spectra. A white dwarf companion has been suggested as the source of UV or X-ray features. HD 81817 has been observed since 2004 as a part of our radial velocity (RV) survey program to search for exoplanets around K giant stars using the Bohyunsan Observatory Echelle Spectrograph (BOES) at the 1.8 m telescope of Bohyunsan Optical Astronomy Observatory (BOAO) in Korea. We obtained 84 RV measurements between 2004 and 2018 for HD 81817 and found two periodic RV variations. The obtained amplitudes of RV periods are around 200 m/s, which are significantly lower than that expected from a white dwarf companion. Furthermore, our re-analysis of the IUE spectra used by Reimers (1984) shows that the excess in UV emission can easily be explained by a pseudo-continuum of unresolved emission lines originating in the extended chromosphere of the star. We thus conclude that there are no companions of stellar mass to HD 81817. Meanwhile, we analyzed two periodicities in RV measurements and conclude that the period of 627.9 days is caused by intrinsic stellar activities based on H alpha equivalent width (EW) variations of a similar period. On the other hand, the period of 1047.8 days is likely to be caused by substellar companion which has a minimum mass of 27.6 M_JUP, a semi-major axis of 3.3 AU, and an eccentricity of 0.17 assuming the stellar mass of 4.3 M_⊙ for HD 81817. The inferred mass puts HD 81817 b in the brown dwarf desert.

• The Bulletin of The Korean Astronomical Society
• /
• v.45 no.1
• /
• pp.36.1-36.1
• /
• 2020

The progenitor of Type Ia supernovae (SNe Ia) is mainly believed to be a carbon/oxygen white dwarf (WD) with non-degenerate (single degenerate) or another WD companion (double degenerate). However, there is little observational evidence of their progenitor system. Recent studies suggest that shock-breakout cooling emission after the explosion can constrain the size of the progenitor system. To do so, we obtained a optical/Near-IR light curve of SN 2019ein, a normal but slightly sub-luminous type Ia supernova, from the very early phase using our high-cadence observation of Intensive Monitoring Survey of Nearby Galaxies (IMSNG). Assuming the expanding fireball model, the simple power-law fitting of the early part of the light curve gives power indices of 1.91 (B) and 2.09 (R) implying radioactive decay of 56Ni is the dominant energy source. By comparison with the expected light curve of the cooling emission, the early observation provides us an upper limit of the companion size of R∗≤1R⊙. This result suggests that we can exclude a large companion such as red giants, which is consistent with the previous study.

• Journal of Electrochemical Science and Technology
• /
• v.14 no.4
• /
• pp.388-396
• /
• 2023

Photoelectrochemical (PEC) water splitting is a vital source of clean and sustainable hydrogen energy. Moreover, the large-scale H₂ production is currently necessary, while long-term stability and high PEC activity still remain important issues. In this study, a GaN-based photoelectrode was modified by an additional NH₃ treatment (900℃ for 10 min) and its PEC behavior was monitored. The bare GaN exhibited a highly crystalline wurtzite structure with the (002) plane and the optical bandgap was approximately 3.2 eV. In comparison, the NH₃-treated GaN film exhibited slightly reduced crystallinity and a small improvement in light absorption, resulting from the lattice stress or cracks induced by the excessive N supply. The minor surface nanotexturing created more surface area, providing electroactive reacting sites. From the surface XPS analysis, the formation of an N-Ga-O phase on the surface region of the GaN film was confirmed, which suppressed the charge recombination process and the positive shift of E_FB. Therefore, these effects boosted the PEC activity of the NH₃-treated GaN film, with J values of approximately 0.35 and 0.78 mA·cm^-2 at 0.0 and 1.23 V_RHE, respectively, and an onset potential (V_on) of -0.24 V_RHE. In addition, there was an approximate 50% improvement in the J value within the highly applied potential region with a positive shift of V_on. This result could be explained by the increased nanotexturing on the surface structure, the newly formed defect/trap states correlated to the positive V_on shift, and the formation of a GaO_xN_1-x phase, which partially blocked the charge recombination reaction.

• Journal of Electrochemical Science and Technology
• /
• v.15 no.1
• /
• pp.67-95
• /
• 2024

Direct alcohol fuel cells (DAFCs) have gained much attention as promising energy conversion devices due to their ability to utilize alcohol as a fuel source. In this regard, Molybdenum-based electrocatalysts (Mo-ECs) have emerged as a substitution for expensive Pt and Ru-based co-catalyst electrode materials in DAFCs, owing to their unique electrochemical properties useful for alcohol oxidation. The catalytic activity of Mo-ECs displays an increase in alcohol oxidation current density by several folds to 1000-2000 mA mg_Pt^-1, compared to commercial Pt and PtRu catalysts of 10-100 mA mg_Pt^-1. In addition, the methanol oxidation peak and onset potential have been significantly reduced by 100-200 mV and 0.5-0.6 V, respectively. The performance of Mo-ECs in both acidic and alkaline media has shown the potential to significantly reduce the Pt loading. This review aims to provide a comprehensive overview of the bifunctional mechanism involved in the oxidation of alcohols and factors affecting the electrocatalytic oxidation of alcohol, such as synthesis method, structural properties, and catalytic support materials. Furthermore, the challenges and prospects of Mo-ECs for DAFCs anode materials are discussed. This in-depth review serves as valuable insight toward enhancing the performance and efficiency of DAFC by employing Mo-ECs.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.40 no.1
• /
• pp.110-117
• /
• 2012

This study was performed to determine light-adaptability under indoor lighting for Korean wild Daphniphyllum macropodum, and to provide an introduction plan for indoor spaces of landscape architecture. The experimental plants, Daphniphyllum macropodum were purchased from a farmhouse in Jejudo as anannualplant, and it was acclimatized in the glass-green house of the general farm of Gyeongnam National University of Science and Technology for40 days. The experiment was performed from February 15, 2010 to November 15, 2010. First, in the case of the fluorescent lamp, the growth and development condition was poor because the plants withered, or the leaves fell off under the 100lux to 500lux, but the condition under 1,000lux was good In the aspects of the number of leaves, form of the tree, photosynthesis rate in its body, and the value of sight, the best light intensity for the growth condition was under the 1,000lux. Second, in the case of the LED light, the growth and development condition was poor because the plants withered, or the leaves fell off under 100lux to 1,000lux, but the smooth growth and development was done under a more light intensity. The best intensity for the growth condition was under 2,000lux. Third, in the case of the three-wave light, the withering was serious by 1,000lux, and the growth and development was the worst amongst the four introduced lighting systems, therefore, growth under the three-wave light was incongruous. The best intensity for the growth condition was under 2,000lux. Fourth, in the case of the optical fiver, the withering did not existed under 100lux and growth was possible. The growth and development was the amongst in the four introduced lighting systems. Generally, in the more light intensity, more growth was observed, but the value of sight was higher under 1,000lux than under 2,000lux because the falling rate of leaves and the form of the tree was stable. The most effective light was under 1,000lux due to the high photosynthesis in its body. When Daphniphyllum macropodum is introduced into the indoor landscaping space considering the light, the optical fiber, fluorescent lamp, and LED light are suitable to introduce. The three-wave light is unfit. The most proper light intensity by the light source, in the case of the optical fiber, and fluorescent lamp, is 1,000lux, and, in the case of LED light, is 2,000lux. The wild Daphniphyllum macropodum is the species of tree to substitute the Schefflera actinophylla which is the introduced species, and it is expected to be use as the central tree in indoor spaces.