• Journal of Microbiology and Biotechnology
• /
• v.18 no.5
• /
• pp.901-907
• /
• 2008

Thermotoga neapolitana $\beta$-glucosidase (BglA) was subjected to site-directed mutagenesis in an effort to increase its ability to synthesize arbutin derivatives by transglycosylation. The transglycosylation reaction of the wild-type enzyme displays major ${\beta}(1,6)$ and minor ${\beta}(1,3)$ or ${\beta}(1,4)$ regioselectivity. The three mutants, N291T, F412S, and N291T/F412S, increased the ratio of transglycosylation/hydrolysis compared with the wild-type enzyme when pNPG and arbutin were used as a substrate and an acceptor, respectively. N291T and N219T/F412S had transglycosylation/hydrolysis ratios about 3- and 8-fold higher, respectively, than that of the wild-type enzyme. This is due to the decreased hydrolytic activity of the mutant rather than increased transglycosylation activity. Interestingly, N291T showed altered regioselectivity, as well as increased transglycosylation products. TLC analysis of the transglycosylation products indicated that N291T retained its ${\beta}(1,3)$ regioselectivity, but lost its ${\beta}(1,4)$ and ${\beta}(1,6)$ regioselectivity. The altered regioselectivity of N291T using two other acceptors, esculin and salicin, was also confirmed by TLC. The major transglycosylation products of the wild type and N291T mutant were clearly different. This result suggests that Asn-291 is highly involved in the catalytic mechanism by controlling the transglycosylation reaction.

• Journal of Surface Science and Engineering
• /
• v.34 no.5
• /
• pp.414-420
• /
• 2001

A 30-kV plasma immersion ion implantation setup (P $I^3$) has been equipped with a self-developed 6'-magnetron to perform hard coatings with enhanced adhesion by P $I^3$D(P $I^3$ assisted deposition) process. Using ICP source with immersed Ti antenna and reactive magnetron sputtering of Ti target in $N_2$/Ar ambient gas mixture, the TiN films were prepared on Si substrates at different pulse bias and ion-to-atom arrival ratio ( $J_{i}$ $J_{Me}$ ). Prior to TiN film formation the nitrogen implantation was performed followed by deposition of Ti buffer layer under A $r^{+}$ irradiation. Films grown at $J_{i}$ $J_{Me}$ =0.003 and $V_{pulse}$=-20kV showed columnar grain morphology and (200) preferred orientation while those prepared at $J_{i}$ $J_{Me}$ =0.08 and $V_{pulse}$=-5 kV had dense and eqiaxed structure with (111) and (220) main peaks. X-ray diffraction patterns revealed some amount of $Ti_{x}$ $N_{y}$ in the films. The maximum microhardness of $H_{v}$ =35 GN/ $M^2$ was at the pulse bias of -5 kV. The P $I^3$D technique was applied to enhance wear properties of commercial tools of HSS (SKH51) and WC-Co alloy (P30). The specimens were 25-kV PII nitrogen implanted to the dose 4.10$^{17}$ c $m^{-2}$ and then coated with 4-$\mu\textrm{m}$ TiN film on $Ti_{x}$ $N_{y}$ buffer layer. Wear resistance was compared by measuring weight loss under sliding test (6-mm $Al_2$ $O_3$ counter ball, 500-gf applied load). After 30000 cycles at 500 rpm the untreated P30 specimen lost 3.10$^{-4}$ g, and HSS specimens lost 9.10$^{-4}$ g after 40000 cycles while quite zero losses were demonstrated by TiN coated specimens.s.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.31 no.2
• /
• pp.259-266
• /
• 1998

A study on the biological and chemical characteristics in the middle last Sea of Korea was carried out at 31 stations in October $11\~18$, 1995 on board the R/V Tam-Yang. The chlorophyll a concentration, new and regenerated production, and the vertical diffusion of nitrate from the thermocline structure were investigated. From the vertical distribution of chlorophyll a, subsurface maxima were observed near the thermorline at most stations including the frontal zone, except at the southern stations where the maximum chloropyll a concentration occurred at the surface, The nanophytoplankton was the most dominant fraction comprising $83.5\%$ of total phytoplankton cell numbers, but netphytoplankton were common at the southern stations where the dominant species were Rhizosolenia sp. Nitrogenous new production and regenerated productions were measured using the stable isotope $^{15}N$ nitrate and ammonia uptake method. The vertically integrated nitrogen production varied between 8.470 and $72.945\;mg\;N\;m^{-2}\;d^{-1}$. The f-ratio, which is the traction of new production from primary production, waried between 0.03 and 0.72, indicating that $3\%$ to $72\%$ of primary production was supported by the input of nutrients from below the euphotic zone and the rest are supported by ammonia recycled within the euphotic layer. This range of f-ratio encompasses from extremely oligotrophic to eutrophic area characteristics. The differences in productivity and f-ratio among stations were related to frontal structure and the bottom topography. The values were high near the frontal zone and low outside of it, and the station near Ulleng Island showed the highest f-ratio. Vertical diffusion coefficients were calculated from both the water column stability (Kz-1) of King and Devol's equation (1979) and new nitrogen requirement (Kz-2). The values of Kz-2 ($0.11\~0.55\;cm^2/s$) were relatively low compared to the values reported previously.

• Proceedings of the KIEE Conference
• /
• 2001.11a
• /
• pp.100-102
• /
• 2001

In this paper, the piezoelectric and dielectric properties of $Pb(Zr_xTi_{1-x)O_3$ - $Pb(Co_{1/3}Nb_{1/3})O_3)$ piezoelectric ceramics have been investigated as a function of Zr/Ti mole ratio. From the results, when Zr/Ti mole ratio is 49/51, electromechanical coupling coefficient($k_p$), piezoelectric strain constant($d_{33}$) mechanical quality factor($Q_m$), and Permittivity(${{\varepsilon}_{33}}^T/{\varepsilon}_0$) is 64[%], 469[PC/N], 360 and 2000, respectively. Morphotropic Phase Boundary is Zr/Ti mole ratio(49/51) from XRD analysis. Also. From SEM observation, when sintering temperature is 1150[$^{\circ}C$], grain size is about $1{\sim}2[{\mu}m]$ and maximum sintering density is 7.85[$g/cm^3$].

• Korean Journal of Food Science and Technology
• /
• v.44 no.6
• /
• pp.779-784
• /
• 2012

Characteristic chemical compositions of jujube wine using different preparation methods including fermentation were investigated. Fermentation for jujube wine started using whole fruit (JW1), seed-removed fruit (JW2) and whole fruit heated at $100^{\circ}C$ for 2 h and then extracted (JW3). The free amino acids and flavors were analyzed quantitatively by HPLC and GC-MS. A total of 18 amino acids were identified in all samples. The amount of total free amino acids was detected from 141-210 ppm (JW1), 147-342 ppm (JW2), and 336-362 ppm (JW3). Large amounts of proline, aspartate, glutamate, arginine and alanine were detected in jujube wine. Thirteen kinds of volatile compounds including six alcoholic compounds (ethyl alcohol, iso-butyl alcohol, n-butyl alcohol, iso-amyl alcohol, n-amyl alcohol, and phenethyl alcohol), four ester (ethyl acetate, hexyl acetate, ethyl caprylate, and phenethyl acetate) and three aldehydes (diethylacetal, furfural, and benzaldehyde) were detected. Ethyl alcohol (30.50-33.95% peak area), benzaldehyde (2.55-15.97% ratio), furfural (0.07-15.28% ratio), iso-amyl alcohol (1.04-14.73% ratio), and phenethyl acetal (0.78-9.28% ratio) were abundant in jujube wine.

• Geomechanics and Engineering
• /
• v.35 no.4
• /
• pp.367-383
• /
• 2023

The present paper examines the natural frequency responses of the bi-directional (n_x-n_y, n_y-n_z and n_z-n_x) and multidirectional (n_x-n_y-n_z) functionally graded (FG) plate and curved structures with and without porosity. The even and uneven kind of porosity pattern are considered to observe the influence of porosity type and porosity index. The numerical findings have been obtained using a higher order shear deformation theory (HSDT) based isometric finite element (FE) approach generated in a MATLAB platform. According to the convergence and validation investigation, the proposed HSDT based FE model is adequate to predict free vibrational responses of multidirectional porous FG plates and curved structures. Further a parametric analysis is carried out by taking various design parameters into account. The free vibrational behavior of bidirectional (2D) and multidirectional (3D) perfect-imperfect FGM structure is examined against various power law index, support conditions, aspect, and thickness ratio, and for the curvature of curved structures. The results indicate that the maximum non-dimensional fundamental frequency (NFF) value is observed in perfect FGM plates and curved structures compared to porous FGM plates and curved structures and it is maximum for FGM plates and curved structures with uneven kind of porosity than even porosity.

• Investigative Magnetic Resonance Imaging
• /
• v.4 no.2
• /
• pp.94-99
• /
• 2000

Purpose : With the use of localized, water-suppressed in vivo $^1H$ magnetic resonance spectroscopy (MRS), we evaluated the proton metabolic alterations in patients with chronic alcoholism and healthy normal controls. Material and Methods : Patients with chronic alcoholism (N = 10) and normal control subjects (N = 10) underwent MRS examinations using a stimulated echo acquisition mode (STEAM) pulse sequence with $2{\times}2{\times}2{\;}\textrm{cm}^3$ volume of interest (VOI) in the left cerebellum and basal ganglia. Proton metabolite ratios relative to creative (Cr) were obtained using a Marquart algorithm. Results : The specific feature in patients with chronic alcoholism was a significant decrease of N-acetylaspartate (NAA)/Cr ratio in the left cerebellum, compared with normal controls. No clear correlation of other metabolite ratios such as choline (Cho)/Cr and inositols (Ins)/Cr was established. Conclusion : Our preliminary study suggests that the reduction of NAA/Cr ratio may indicate neuronal loss in patients with chronic alcoholism. Thus, in vivo 1H MRS may be a useful modality in the clinical evaluation of patients with chronic alcoholism based on the proton metabolite ratios.

• Proceedings of the KSRS Conference
• /
• 2003.11a
• /
• pp.703-705
• /
• 2003

A comparison was made between the chlorophyll a and suspended solid (SS) retrievals from OSMI and SeaWiFS sensor to chlorophyll a and SS values determined with the standard method during the NFRDI's research cruises. The percentage of organic and inorganic materials from the SS was calculated to study the contribution of turbid water in the northern part of the East China Sea. The open sea waters in the Kuroshio regions of the East China Sea showed relatively higher concentration of volatile SS. However, towards the northwestern part of the East China Sea, the situation became much more optically different with the non-volatile SS from the Yangtze river and the sea bottom sources in the sea in winter and spring seasons. Furthermore, in order to indirectly detect low salinity water with high turbidity, which related to the Yangtze river using remote sensed data from the satellites, a comparison between the results of the band ratio(nLw 490nm/nLw 555nm) of SeaWiFS (OSMI) and the distribution of low salinity around the Jeju Island was presented.

• Preventive Nutrition and Food Science
• /
• v.9 no.3
• /
• pp.245-252
• /
• 2004

This study investigated the effects of an ethanol extract of Allium monanthum MAX. (AME) on ethanol-induced hepatotoxicity in rat liver. Sprague-Dawley rats weighing 100～150 g, were divided into 5 groups; normal group (NOR), AME 200 mg/kg treated group (S1), ethanol (35%, 10 mL/kg) treated group (S2), AME 200 mg/kg and ethanol (35%, 10 mL/kg) treated group (S3) and AME 400 mg/kg and alcohol (35%, 10 mL/kg) treated group (S4). AME was fractionated by the following solvents: n-hexane, chloroform, EtOAC and n-BuOH. Antioxidant index of the n-BuOH fraction was 600 ppm, highest among fractions. The growth rate and feed efficiency ratio were decreased by ethanol, but gradually increased to the corresponding level of the normal group by administering AME. The serum ALT activities that were elevated by ethanol were significantly decreased by AME administration. It was also observed that the hepatic activities of SOD, catalase, xanthine oxidase and GSH-Px that were increased by ethanol were also markedly decreased in the AME treated group with compared to ETB. These results suggest that ethanol extracts of Allium monanthum MAX. may have a protective effect on ethanol-induced hepatotoxicity in rat liver.

• Proceedings of the Polymer Society of Korea Conference
• /
• 2006.10a
• /
• pp.381-381
• /
• 2006

AcDP and AcAP were prepared by the reaction of acryloyl chloride (Ac) with 2,4,4' -trichloro-2' -hydroxydiphenyl ether (DP) and p-hydroxyacetophenone respectively in presence of triethylamine (TEA) in MEK at $0^{\circ}C$. The reaction was monitored by TLC and the prepared monomer was characterized by UV, IR, $1^H-NMR$ and GC-MS. Further, copolymers poly (AcDP-MMA-AcAP) were prepared in different feed ratio of monomers by free radical polymerization at $70^{\circ}C$, in which BPO as initiator and their molecular weight was determined by GPC. The AF activity of prepared polymers was investigated against representatives of marine microfoulers, shipfouling bacteria (B. macroides & P. aeruginosa) and microalgae (A.coffeaeformis & N. incerta). The antibacterial activity and diatom attachment assays showed significant AF potential of these polymers.