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Investigation of surface uniformity machined by ceramic brush
Kim, Youyoung,Kim, Jonghyun,Lee, Sun-Kyu Springer-Verlag 2018 INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TE Vol.94 No.5
<P>This paper investigates the issue of unevenness of machined surface using ceramic brush for aiming the automatic lapping of the large work surface. A numerical model and machining results with ceramic brush are presented. In the machined surface, the slight sloped surfaces between left and right sides along the feed direction were generated, and they were highly affected by the protrusion of fiber, the preload, the feed rate, and the overlapped machining. The numerical model for ceramic brush lapping is induced based on trajectory simulation of each brush fiber using the dynamic FEA result of contact pressure and deformation to understand the issues of surface uniformity. In the simulation part, A FEA model of brush lapping is proposed to investigate not only its elastic behavior during the machining process but also its effect on the machined surface. The lapping experiment is comprised of several steps using different preload, revolution speed, protrusion, feed rate, and overlapped machining pitch. For each step, it is shown that the trend of change in surface quality according to each machining parameter using the numerically controlled machine. Each machining condition plays an important role in lapping quality, which can determine the surface uniformity. Highly smooth surfaces were obtained by selecting the appropriate conditions without any unevenness issues on overlapped machining region. Also, the surface roughness comparison result with other surface finishing method presents similar quality even in worse initial surface roughness condition, which indicates the possibility of efficient automatic surface uniformity using ceramic brush lapping on milling surface of workpiece.</P>
Delineating Physical Organic Parameters in Site-Selective C–H Functionalization of Indoles
Kim, Youyoung,Park, Yoonsu,Chang, Sukbok American Chemical Society 2018 ACS central science Vol.4 No.6
<▼1><P/><P>Site-selective C–H functionalization is a great challenge in homogeneous transition-metal catalysis. Herein, we present a physical organic approach to delineate the origin of regioselective amidation of <I>N</I>-acylindoles through Ir(III) catalysis. Bulkiness of <I>N</I>-directing groups of indole substrates and electronics of carboxylate additives were identified as two major factors in controlling C2 and C7 selectivity, and their microscopic mechanisms were studied with DFT-based transition state analysis. Computational insights led us to interrogate a linear free energy relationship, and parametrization of molecular determinants enabled the establishment of an intuitive yet robust statistical model that correlates an extensive number of validation data points in high accuracy. This mechanistic investigation eventually allowed the development of a new C2 amidation and alkenylation protocol of indoles, which affords the exclusive functionalization at the C2 position with up to >70:1 selectivity.</P></▼1><▼2><P>Site-selective C−H functionalization is a great challenge in metal catalysis. Herein, we present a physical organic approach to delineate the origin of regioselective indole derivatizations.</P></▼2>
Kim, Youyoung,Park, Juhyeon,Chang, Sukbok American Chemical Society 2016 ORGANIC LETTERS Vol.18 No.8
<P>Ir(III)-catalyzed regioselective direct C-7 amidation of indoles in reaction with organic azides has been developed. While its efficiency was varied by the choice of N-directing groups, N-pivaloylindoles were most effective in undergoing the desired amidation at room temperature over a broad range of substrates. The reaction was scalable, and deprotection of the chelation group was also facile.</P>
Modification of the characteristics of silkworm powder by treatment with alkaline protease
( Sungkuk Kim ),( Youyoung Jo ),( Kwanggill Lee ),( Hyunbok Kim ),( Yongsoon Kim ),( Wantaek Ju ),( Daeun Jung ),( Haeyong Kweon ) 한국잠사학회 2015 International Journal of Industrial Entomology Vol.31 No.1
Enzymatic modification of proteins is often used to increase the biological activity of materials. Silkworm powder has been investigated as a functional food resource, but no study has been performed on its modification by commercial food enzyme. Therefore, this study aimed to determine the feasibility of such modification of silkworm powder by alkaline protease. The activity of the enzyme was confirmed using an azocasein assay. Subsequently the silkworm powder was hydrolyzed by enzymatic treatment. UV visible spectrometry showed that the supernatant of silkworm powder subjected to enzymatic treatment had a stronger absorption band than the untreated powder. SDS-PAGE electrophoresis showed that the molecular weight of silkworm powder decreased on enzymatic treatment. Thus the results indicate that commercial enzymes might be used to modify the characteristics of silkworm powder.
Hyun Sang Kim,Jun Sik Eom,Shin Ja Lee,Youyoung Choi,Seong Uk Jo,Sang Suk Lee,Eun Tae Kim,Sung Sill Lee Asian Australasian Association of Animal Productio 2023 Animal Bioscience Vol.36 No.8
Objective: The purpose of this study was to perform a comparative analysis of metabolite levels in serum and milk obtained from cows fed on different concentrate to forage feed ratios. Methods: Eight lactating Holstein cows were divided into two groups: a high forage ratio diet (HF; 80% Italian ryegrass and 20% concentrate of daily intake of dry matter) group and a high concentrate diet (HC; 20% Italian ryegrass and 80% concentrate) group. Blood was collected from the jugular vein, and milk was sampled using a milking machine. Metabolite levels in serum and milk were estimated using proton nuclear magnetic resonance and subjected to qualitative and quantitative analyses performed using Chenomx 8.4. For statistical analysis, Student's t-test and multivariate analysis were performed using Metaboanalyst 4.0. Results: In the principal component analysis, a clear distinction between the two groups regarding milk metabolites while serum metabolites were shown in similar. In serum, 95 metabolites were identified, and 13 metabolites (include leucine, lactulose, glucose, betaine, etc.) showed significant differences between the two groups. In milk, 122 metabolites were identified, and 20 metabolites (include urea, carnitine, acetate, butyrate, arabinitol, etc.) showed significant differences. Conclusion: Our results show that different concentrate to forage feed ratios impact the metabolite levels in the serum and milk of lactating Holstein cows. A higher number of metabolites in milk, including those associated with milk fat synthesis and the presence of Escherichia coli in the rumen, differed between the two groups compared to that in the serum. The results of this study provide a useful insight into the metabolites associated with different concentrate to forge feed ratios in cows and may aid in the search for potential biomarkers for subacute ruminal acidosis.
Young-Jung Kim,Wun-A Kook,Shi-Xun Ma,Bo-Ram Lee,Yong-Hyun Ko,Seon-Kyung Kim,Youyoung Lee,Jae-Gyeong Lee,Sooyeun Lee,Kyeong-Man Kim,Seok-Yong Lee,Choon-Gon Jang 대한약학회 2024 Archives of Pharmacal Research Vol.47 No.4
Novel psychoactive substances (NPSs) are new psychotropic drugs designed to evade substance regulatory policies. 25E-NBOMe (2-(4-ethyl-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethanamine) has recently been identifi ed as an NPS,and its recreational misuse has been reported to be rapidly increasing. However, the psychopharmacological eff ects andmechanisms of 25E-NBOMe have not been studied. We examined the abuse potential of 25E-NBOMe using the conditionedplace preference in male mice and self-administration paradigms in male rats. Additionally, immunoblot assay, enzymelinkedimmunosorbent assay, and microdialysis were used to determine the molecular eff ects of 25E-NBOMe in the nucleusaccumbens (NAc). Our data demonstrated that 25E-NBOMe induces conditioned place preference, and the dopaminergicsignaling in the NAc mediates these. Following 25E-NBOMe administration, expression of dopamine transporter and dopamineD1 receptor (D1DR) were enhanced in the NAc of male mice, and NAc dopamine levels were reduced in both male miceand rats. Induction of intracellular dopaminergic pathways, DARPP32, and phosphorylation of CREB in the NAc of malemice was also observed. Signifi cantly, pharmacological blockade of D1DR or chemogenetic inhibition of D1DR-expressingmedium spiny neurons in the NAc attenuated 25E-NBOMe-induced conditioned place preference in male mice. We alsoexamined the hallucinogenic properties of 25E-NBOMe using the head twitch response test in male mice and found that thisbehavior was mediated by serotonin 2A receptor activity. Our fi ndings demonstrate that D1DR signaling may govern theaddictive potential of 25E-NBOMe. Moreover, our study provides new insights into the potential mechanisms of substanceuse disorder and the improvement of controlled substance management.