• Journal of Food Hygiene and Safety
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• v.37 no.5
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• pp.306-309
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• 2022

Probiotics are live microorganisms that confer health benefits onto the host when administered at adequate doses. Most widely used probiotics, such as lactobacilli and bifidobacteria, are known to be elements of healthy gut microflora and hence are not considered a threat to the host. However, probiotics may pose a risk in certain populations with compromised immune systems or defects in gut barrier functions. Herein, we evaluated the safety of Bifidobacterium breve BB077, according to the safety evaluation guidelines for probiotics produced by the National Institute of Food and Drug Safety Evaluation (NIFDS). The results show that B. breve BB077 is both non-hemolytic and non-cytolytic. In contrast, B. breve BB077 exhibited higher streptomycin and tetracycline resistance than the suggested NIFDS standard cut-off values. Hence, a genetic analysis of the streptomycin and tetracycline resistance genes was performed to determine the origin of antimicrobial resistance. Streptomycin and tetracycline resistance was shown have arisen from chromosomal mutations and considered intrinsic to the taxonomic group. In conclusion, the B. breve BB077 strain might be safe for human consumption.

• Biomolecules & Therapeutics
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• v.31 no.6
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• pp.640-647
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• 2023

The skin, the largest organ in the body, undergoes age-related changes influenced by both intrinsic and extrinsic factors. The primary external factor is photoaging which causes hyperpigmentation, uneven skin surface, deep wrinkles, and markedly enlarged capillaries. In the human dermis, it decreases fibroblast function, resulting in a lack of collagen structure and also decreases keratinocyte function, which compromises the strength of the protective barrier. In this study, we found that treatment with γ-aminobutyric acid (GABA) had no toxicity to skin fibroblasts and GABA enhanced their migration ability, which can accelerate skin wound healing. UVB radiation was found to significantly induce the production of matrix metalloproteinase 1 (MMP-1), but treatment with GABA resulted in the inhibition of MMP-1 production. We also investigated the enhancement of filaggrin and aquaporin 3 in keratinocytes after treatment with GABA, showing that GABA can effectively improve skin moisturization. In vivo experiments showed that oral administration of GABA significantly improved skin wrinkles and epidermal thickness. After the intake of GABA, there was a significant decrease observed in the increase of skin thickness measured by calipers and erythema. Additionally, the decrease in skin moisture and elasticity in hairless mice exposed to UVB radiation was also significantly restored. Overall, this study demonstrates the potential of GABA as functional food material for improving skin aging and moisturizing.

• Journal of Soil and Groundwater Environment
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• v.14 no.3
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• pp.40-46
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• 2009

The applicability of a well-type autotrophic sulfur-oxidizing reactive barrier (L $\times$ W $\times$ D = $3m\;{\times}\;4\;m\;{\times}\;2\;m$) as a long-term treatment option for nitrate removal in groundwater was evaluated. Pilot-scale (L $\times$ W $\times$ D = $8m\;{\times}\;4\;m\;{\times}\;2\;m$) flow-tank experiments were conducted to examine remedial efficacy of the well-type reactive barrier. A total of 80 kg sulfur granules as an electron donor and Thiobacillus denitrificans as an active bacterial species were prepared. Thiobacillus denitrificans was successfully colonized on the surface of the sulfur granules and the microflora transformed nitrate with removal efficiency of ~12% (0.07 mM) for 11 days, ~24% (1.3 mM) for 18 days, ~45% (2.4 mM) for 32 days, and ~52% (2.8 mM) for 60 days. Sulfur granules attached to Thiobacillus denitrificans were used to construct the well-type reactive barrier comprising three discrete barriers installed at 1-m interval downstream. Average initial nitrate concentrations were 181 mg/L for the first 28 days and 281 mg/L for the next 14 days. For the 181 mg/L (2.9 mM) plume, nitrate concentrations decreased by ~2% (0.06 mM), ~9% (0.27 mM), and ~15% (0.44 mM) after $1^{st}$, $2^{nd}$, and $3^{rd}$ barriers, respectively. For the 281 mg/L (4.5 mM) plume, nitrate concentrations decreased by ~1% (0.02 mM), ~6% (0.27 mM), and ~8% (0.37 mM) after $1^{st}$, $2^{nd}$, and $3^{rd}$ barriers, respectively. Nitrate plume was flowed through the flow-tank for 49 days by supplying $1.24\;m^3/d$ of nitrate solution. During nitrate treatment, flow velocity (0.44 m/d), pH (6.7 to 8.3), and DO (0.9~2.8 mg/L) showed little variations. Incomplete destruction of nitrate plume was attributed to the lack of retention time, rarely transverse dispersion, and inhibiting the activity of denitrification enzymes caused by relatively high DO concentrations. For field applications, it should be considered increments of retention time, modification of well placements, and intrinsic DO concentration.

• Journal of Astronomy and Space Sciences
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• v.28 no.1
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• pp.17-26
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• 2011

Bow shock, formed by the interaction between the solar wind and a planet, is generated in different patterns depending on the conditions of the planet. In the case of the earth, its own strong magnetic field plays a critical role in determining the position of the bow shock. However, in the case of Mars of which has very a small intrinsic magnetic field, the bow shock is formed by the direct interaction between the solar wind and the Martian ionosphere. It is known that the position of the Martian bow shock is affected by the mass loading-effect by which the supersonic solar wind velocity becomes subsonic as the heavy ions originating from the planet are loaded on the solar wind. We simulated the Martian magnetosphere depending on the changes of the density and velocity of the solar wind by using the three-dimensional magnetohydrodynamic model built by modifying the comet code that includes the mass loading effect. The Martian exosphere model of was employed as the Martian atmosphere model, and only the photoionization by the solar radiation was considered in the ionization process of the neutral atmosphere. In the simulation result under the normal solar wind conditions, the Martian bow shock position in the subsolar point direction was consistent with the result of the previous studies. The three-dimensional simulation results produced by varying the solar wind density and velocity were all included in the range of the Martian bow shock position observed by Mariner 4, Mars 2, 3, 5, and Phobos 2. Additionally, the simulation result also showed that the change of the solar wind density had a greater effect on the Martian bow shock position than the change of the solar wind velocity. Our result may be useful in analyzing the future observation data by Martian probes.

• The Journal of Small Business Innovation
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• v.19 no.2
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• pp.53-68
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• 2016

Motivation and activities for technological learning, entrepreneurship, innovation, and creativity are driving forces of economic development in Asian countries. In the early stages of technological development, technological learning and entrepreneurship are efficient ways in which to catch up with advanced countries because firms can accumulate skills and knowledge quickly at relatively low risk. In the later stages of technological development, however, innovation and creativity become more important. This study aims to identify a) the factors (learning capabilities) that influence technological learning performance and b) barriers to enhancing innovation capabilities for the creative economy and organizations. The major part of this study is related to learning capabilities in the post-catch-up era. Based on a literature review and observations from Korean experiences, this study proposes a technological learning model composed of various influencing factors on technological learning. Three hypotheses are derived, and data are collected from Korean machine tool manufacturers. Intense interviews with CEOs and R&D directors are conducted using structured questionnaires. Statistical analysis, such as correlation and ANOVA are then carried out. Furthermore, this study addresses how to enhance innovation capabilities to move forward. Innovation enablers and barriers are identified by case studies and policy analysis. The results of the empirical study identify several levels of firms' learning capabilities and activities such as a) stock of technology, b) potential of technical labor, c) explicit technological efforts, d) readiness to learn, e) top management support, f) a formal technological learning system, g) high learning motivation, h) appropriate technology choice, and i) specific goal setting. These learning capabilities determine firms' learning performance, especially in the early stages of development. Furthermore, it is found that the critical factors for successful technological learning vary along the stages of technology development. Throughout the statistical and policy analyses, this study confirms that technological learning can be understood as an intrinsic principle of the technology development process. Firms perform proactive and creative learning in the late stages, while reactive and imitative learning prevails in the early stages. In addition, this study identifies the driving forces or facilitating factors enhancing innovation performance in the post catch-up era. The results of the preliminary case studies and policy analysis show some facilitating factors such as a) the strategic intent of the CEO and corporate culture, b) leadership and change agents, c) design principles and routines, d) ecosystem and collaboration with partners, and e) intensive R&D investment.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.292-292
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• 2016

Transition metal dichalcogenides (TMDs) with a two-dimensional layered structure have been considered highly promising materials for next-generation flexible, wearable, stretchable and transparent devices due to their unique physical, electrical and optical properties. Recent studies on TMD devices have focused on developing a suitable doping technique because precise control of the threshold voltage ($V_{TH}$) and the number of tightly-bound trions are required to achieve high performance electronic and optoelectronic devices, respectively. In particular, it is critical to develop an ultra-low level doping technique for the proper design and optimization of TMD-based devices because high level doping (about $10^{12}cm^{-2}$) causes TMD to act as a near-metallic layer. However, it is difficult to apply an ion implantation technique to TMD materials due to crystal damage that occurs during the implantation process. Although safe doping techniques have recently been developed, most of the previous TMD doping techniques presented very high doping levels of ${\sim}10^{12}cm^{-2}$. Recently, low-level n- and p-doping of TMD materials was achieved using cesium carbonate ($Cs_2CO_3$), octadecyltrichlorosilane (OTS), and M-DNA, but further studies are needed to reduce the doping level down to an intrinsic level. Here, we propose a novel DNA-based doping method on $MoS_2$ and $WSe_2$ films, which enables ultra-low n- and p-doping control and allows for proper adjustments in device performance. This is achieved by selecting and/or combining different types of divalent metal and trivalent lanthanide (Ln) ions on DNA nanostructures. The available n-doping range (${\Delta}n$) on the $MoS_2$ by Ln-DNA (DNA functionalized by trivalent Ln ions) is between $6{\times}10^9cm^{-2}$ and $2.6{\times}10^{10}cm^{-2}$, which is even lower than that provided by pristine DNA (${\sim}6.4{\times}10^{10}cm^{-2}$). The p-doping change (${\Delta}p$) on $WSe_2$ by Ln-DNA is adjusted between $-1.0{\times}10^{10}cm^{-2}$ and $-2.4{\times}10^{10}cm^{-2}$. In the case of Co-DNA (DNA functionalized by both divalent metal and trivalent Ln ions) doping where $Eu^{3+}$ or $Gd^{3+}$ ions were incorporated, a light p-doping phenomenon is observed on $MoS_2$ and $WSe_2$ (respectively, negative ${\Delta}n$ below $-9{\times}10^9cm^{-2}$ and positive ${\Delta}p$ above $1.4{\times}10^{10}cm^{-2}$) because the added $Cu^{2+}$ ions probably reduce the strength of negative charges in Ln-DNA. However, a light n-doping phenomenon (positive ${\Delta}n$ above $10^{10}cm^{-2}$ and negative ${\Delta}p$ below $-1.1{\times}10^{10}cm^{-2}$) occurs in the TMD devices doped by Co-DNA with $Tb^{3+}$ or $Er^{3+}$ ions. A significant (factor of ~5) increase in field-effect mobility is also observed on the $MoS_2$ and $WSe_2$ devices, which are, respectively, doped by $Tb^{3+}$-based Co-DNA (n-doping) and $Gd^{3+}$-based Co-DNA (p-doping), due to the reduction of effective electron and hole barrier heights after the doping. In terms of optoelectronic device performance (photoresponsivity and detectivity), the $Tb^{3+}$ or $Er^{3+}$-Co-DNA (n-doping) and the $Eu^{3+}$ or $Gd^{3+}$-Co-DNA (p-doping) improve the $MoS_2$ and $WSe_2$ photodetectors, respectively.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.45 no.2
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• pp.175-184
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• 2019

The epidermal growth factor (EGF) has a intrinsic function of inducing growth and proliferation of cells through interacting with cell membrane receptors in human epidermis and dermis layer. These functions of EGF are used as a main ingredient for wound healing medicines and anti-aging cosmetics. As a cosmetic ingredient, the EGF has a problem in exhibiting its natural efficacy due to the lack of the ability to penetrate through the stratum corneum, which is known as the skin barrier. In this study, a recombinant human epidermal growth factor ($MTD_{151}-EGF$) fused with the macromolecule transduction domain $(MTD)_{151}$ with the skin penetration ability was developed to improve the skin penetration efficiency of the EGF. Expression of $MTD_{151}-EGF$ was performed in E. coli transformed with a vector encoding the $MTD_{151}-EGF$ gene and then purified. The purified $MTD_{151}-EGF$ was evaluated using cell proliferation assay, cytotoxicity test and skin penetration test by franz diffusion cell assay and artificial skin. Cell proliferation activity of $MTD_{151}-EGF$ purified to high purity of 99% or above was equivalent to the EGF or better, and cytotoxicity was not observed. In addition, the $MTD_{151}-EGF$ showed an excellent penetration efficiency compared to the EGF in the skin penetration test with EGF and $MTD_{151}-EGF$ labeled by FITC in an artificial skin penetration model. Based on the quantitative analysis of the penetrating substance using franz diffusion cell assay, the amount of penetration was about 16 times more than that of EGF. These results can be regarded as an effective alternative to improve the existing physical transdermal penetration method related to the use of various active ingredients for cosmetics.