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Phytochemicals and antioxidant activity in the kenaf plant (Hibiscus cannabinus L.)
Ryu, Jaihyunk,Kwon, Soon-Jae,Ahn, Joon-Woo,Jo, Yeong Deuk,Kim, Sang Hoon,Jeong, Sang Wook,Lee, Min Kyu,Kim, Jin-Baek,Kang, Si-Yong The Korean Society of Plant Biotechnology 2017 식물생명공학회지 Vol.26 No.4
Chemical compounds from four different tissues of the kenaf plant (Hibiscus cannabinus), a valuable medicinal crop originating from Africa, were examined to determine its potential for use as a new drug material. Leaves, bark, flowers, and seeds were harvested to identify phytochemical compounds and measure antioxidant activities. Gas chromatography mass spectrometry analyses identified 22 different phytocompounds in hexane extracts of the different parts of the kenaf plant. The most abundant volatile compounds were E-phytol (32.4%), linolenic acid (47.3%), trisiloxane-1,1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy] (16.4%), and linoleic acid (46.4%) in leaves, bark, flowers, and seeds, respectively. Ultra-high performance liquid chromatography identified the major compounds in the different parts of the kenaf plant as kaemperitrin, caffeic acid, myricetin glycoside, and p-hydroxybenzoic acid in leaves, bark, flowers, and seeds, respectively. Water extracts of flowers, leaves, and seeds exhibited the greatest DPPH radical scavenging activity and SOD activity. Our analyses suggest that water is the optimal solvent, as it extracted the greatest quantity of functional compounds with the highest levels of antioxidant activity. These results provide valuable information for the development of environmentally friendly natural products for the pharmaceutical industry.
A study of the human skin-whitening effects of resveratryl triacetate.
Ryu, Ja Hyun,Seok, Jin Kyung,An, Sang Mi,Baek, Ji Hwoon,Koh, Jae Sook,Boo, Yong Chool Springer-Verlag 2015 Archives of dermatological research Vol.307 No.3
<P>Resveratrol has a variety of bioactivities that include its anti-melanogenic effects, but its use in cosmetics has been challenging partly because of its chemical instability. Resveratryl triacetate (RTA) is a prodrug that can enhance stability. The purpose of this study was to examine the skin safety and whitening effects of RTA in human subjects. The primary skin irritation potentials of RTA and resveratrol were tested at 0.1 and 0.5 % on human subjects. Resveratrol at a concentration of 0.5 % induced weak skin irritation, whereas RTA did not induce any skin responses. The skin-whitening efficacy of a cosmetic formulation containing 0.4 % RTA was evaluated in two different test models. In the artificial tanning model, the test product and the control product were applied twice daily to the skin of the forearms of 22 human subjects after pigmentation induction by ultraviolet irradiation. Applying the test and the control products to the artificial tanning model for 8 weeks increased the individual topology angles (ITA) by 17.06 and 13.81 %, respectively, a difference that was statistically significant (p < 0.05). In the hyperpigmentation model, the test product and the control product were applied twice daily to the faces of 21 human subjects. The averaged intensity of the hyperpigmented spots decreased by 2.67 % in the test group and 1.46 % in the control group, a difference that was statistically significant (p < 0.05). Therefore, RTA incorporated into cosmetic formulations can whiten human skin without inducing skin irritation.</P>
Sang Wook Jeong,Jaihyunk Ryu,Seung Bin Im,Soon-Jae Kwon,Joon-Woo Ahn,Jin-Baek Kim,Sang Hoon Kim,Hee-Bong Lee,Si-Yong Kang 한국육종학회 2015 한국육종학회 심포지엄 Vol.2015 No.07
This study was carried out to determine the amount of lignin, cellulose, and hemicellulose in six kenaf cultivars during different harvesting stages. Three mutant cultivars (Jangdae, Jeokbong and Baekma), two original cultivars (Jinju, C14), and one Chinese cultivar (Auxu) were planted on May 14, 2013. Four harvesting times were made at intervals of 20 days from 15 July to 16 September, 2013. The overall growth characters of mutant cultivar ‘Jeokbong’ such as plant height, stem diameter, flowering time, and dry mass were similar with those of the original variety. The mutant cultivar ‘Baekma’ occurred 10-day late flowering in comparison with the original variety and also displayed higher dry mass than the original variety. Jinju, Auxu and Jangdae, mid-late maturing kenaf cultivars, had high dry weight compared to early maturing cultivars such as Jeokbong, Baekma and C14. In all cultivars, the lignin contents were increased by a late harvest. The Mid-late maturing kenaf cultivars showed high lignin content in comparison with those of the early maturity cultivars. There were no significant differences of cellulose, and hemicellulose content between the cultivars, however cellulose content in stems of these kenaf cultivars were significantly decreased by a late harvest. These results may provide valuable information to assist the parental selection of kenaf breeding.
Photosensitive Full-Swing Multi-Layer MoS<sub>2</sub> Inverters With Light Shielding Layers
Ryu, Jae Hyeon,Baek, Geun-Woo,Yu, Seung Jae,Seo, Seung Gi,Jin, Sung Hun IEEE 2017 IEEE electron device letters Vol.38 No.1
<P>Multi-layeredMoS(2) inverters with light shielding layers were fabricated and demonstrated for application in highly sensitive photodetectors, exploiting the particular advantages of an atomically thin layer and a sizable electrical bandgap. The photoleakage behaviors of the inverters under changing wavelengths of light were experimentally demonstrated to occur in a controlledmanner andwere analytically validated by load-line analysis. When the inverters were operated with a depletion load in the light of blue light emitting diodes, the low noise margin and transition width were significantly enhanced, by approximately 20% and 220%, respectively, as compared with those of the inverters in the dark.</P>
Ryu, Jae Hyeon,Baek, Geun-Woo,Kim, Seung Yeob,Kwon, Hyuck-In,Jin, Sung Hun Institute of Physics 2018 Semiconductor science and technology Vol.33 No.7
<P>In this letter, spray-coated single walled carbon nanotubes (SWNTs) as one of alternative electrodes in SnO thin-film transistors are demonstrated for emerging electronic applications. Herein, the device architecture of SnO TFTs with a polymer etch stop layer (SU-8) enables the selective etching of SWNTs in a desired region without the detrimental effects of SnO channel layers. Moreover, SnO TFTs with SWNT electrodes as substitutes successfully demonstrate decent width normalized electrical contact properties (∼1.49 kΩ cm), field effect mobility (∼0.69 cm<SUP>2</SUP> V<SUP>−1 </SUP>s<SUP>−1</SUP>), sub-threshold slope (∼0.4 V dec<SUP>−1</SUP>), and current on–off ratio (<I>I</I> <SUB>on</SUB>/<I>I</I> <SUB>off</SUB>?∼?3.5?×?10<SUP>3</SUP>). Systematic temperature dependency measurements elucidate that SnO channel transports with an activation energy within several tens of meV, together with decent contact resistance as compared to that of conventional Ni electrodes.</P>
Ryu, Sang Baek,Bae, Eun Kyung,Kim, Jinhyung,Hwang, Yong Sup,Im, Changkyun,Chang, Jin Woo,Shin, Hyung-Cheul,Kim, Kyung Hwan The Korean Society of Pharmacology 2013 The Korean Journal of Physiology & Pharmacology Vol.17 No.4
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been widely used as a treatment for the movement disturbances caused by Parkinson's disease (PD). Despite successful application of DBS, its mechanism of therapeutic effect is not clearly understood. Because PD results from the degeneration of dopamine neurons that affect the basal ganglia (BG) network, investigation of neuronal responses of BG neurons during STN DBS can provide informative insights for the understanding of the mechanism of therapeutic effect. However, it is difficult to observe neuronal activity during DBS because of large stimulation artifacts. Here, we report the observation of neuronal activities of the globus pallidus (GP) in normal and PD model rats during electrical stimulation of the STN. A custom artifact removal technique was devised to enable monitoring of neural activity during stimulation. We investigated how GP neurons responded to STN stimulation at various stimulation frequencies (10, 50, 90 and 130 Hz). It was observed that activities of GP neurons were modulated by stimulation frequency of the STN and significantly inhibited by high frequency stimulation above 50 Hz. These findings suggest that GP neuronal activity is effectively modulated by STN stimulation and strongly dependent on the frequency of stimulation.
Fast Automatic Frequency Calibrator Using an Adaptive Frequency Search Algorithm
Ryu, Hyuk,Sung, Eun-Taek,Park, Sangyong,Cho, Je-Kwang,Baek, Donghyun IEEE 2017 IEEE transactions on very large scale integration Vol.25 No.4
<P>A new adaptive frequency search algorithm (A-FSA) is presented for a fast automatic frequency calibrator in wideband phase-locked loops (PLLs). The proposed A-FSA optimizes the number of clock counts for each frequency comparison cycle, depending on the difference between the target frequency and the PLL output frequency, as opposed to a binary frequency search algorithm (B-FSA), where the frequency search time per cycle is fixed. This eliminates unnecessary clocking times during the frequency comparison process, and thus reduces the total PLL lock time. The additional circuitry needed for A-FSA is only a simple counter controller, thus minimizing hardware overhead. To verify the effectiveness of the proposed algorithm, two wideband PLLs are designed and simulated using a 65-nm CMOS technology: one with B-FSA, and the other with A-FSA. The latter achieves a lock time faster than the former by at least a factor of 2, even under worst case conditions.</P>
Acute and Subchronic Inhalation Toxicity of n-Octane in Rats
Sung, Jae-Hyuck,Choi, Byung-Gil,Kim, Hyeon-Yeong,Baek, Min-Won,Ryu, Hyun-Youl,Kim, Yong-Soon,Choi, Young-Kuk,Yu, Il-Je,Song, Kyung-Seuk Occupational Safety and Health Research Institute 2010 Safety and health at work Vol.1 No.2
Objectives: We have investigated the toxic effects of the inhalation of subchronic and acute levels of n-octane. Methods: The rats were exposed to n-octane of 0, 2.34, 11.68 and 23.36 mg/L (n = 5 rats/group/gender) in an acute inhalation test (Organization for Economic Co-operation and Development (OECD) TG 403), or to 0, 0.93, 2.62 and 7.48 mg/L (n = 10 rats/group/gender) for a subchronic inhalation test (OECE TG 413), to establish a national chemical management system consistent with the Globally Harmonized Classification System (GHS). Results: Acutely-exposed rats became lethargic but recovered following discontinuation of inhalation. Other clinical symptoms such as change of body weight and autopsy finds were absent. The LC50 for the acute inhalation toxicity of n-octane was determined to exceed 23.36 mg/L and the GHS category was 'not grouping'. Subchronically-treated rats displayed no significant clinical and histopathological differences from untreated controls; also, target organs were affected hematologically, biochemically and pathologically. Therefore, the no observable adverse effect level was indicated as exceeding 7.48 mg/L and the GHS category was 'not grouping' for the specific target organ toxicity upon repeated exposure. Conclusion: However, n-octane exposure should be controlled to be below the American Conference of Industrial Hygienists recommendation (300 ppm) to prevent inhalation-related adverse health effects of workers.