타타늄의 열처리 조건에 따른 동전위 양극분극특성 및 표면 미세구조 변화

주동현,이용렬,정영화,양홍서,박상원,이도재,송호준,박영준 大韓齒科器材學會 2002 대한치과재료학회지 Vol.29 No.2

The corrosion resistance of metallic implants is essential for successful implant osseointegration. Moreover, the implant surface should have appropriate surface roughness for the attachment of the osteoblast and collagen fibrils. When titanium is exposed to air a thermodynamically very stable oxide film is formed at once. This oxide is very thin and yet it protects the metal from corrosion instantaneously. However, the oxide would not be ideal, and it would be supposed that the state of oxide film would be various by the different conditions when it is formed. The objective of this study was to evaluate the electrochemical properties and surface microstructural changes of titanium after passivation treatment or exposure to high heat (in vacuum or in air). ASTM grade 2 commercially pure titanium (Ti) disks of 10㎜ diameter were wet ground and polished with 240 and 600 grit SiC, and then ultrasonically cleaned with distilled water and ethanol. Cleansed as-received samples (As-R group) were passivated with 30% nitric acid solution at 50℃ for 15 minutes to make the Pas group. The Std-V samples were made by treating the Ti disks in vacuum quartz tube (10^-8 Torr) at 530℃ for 40 min for stress relieving, followed by annealing at 700℃ for 90 min, and then slow cooling to room temperature. The Std-A samples undergo identical procedure as the Std-V group except that it is done in air. For 530℃-V samples, Ti disks were heated at 530℃ for 40 minutes and slow cooled to room temperature. The 1000℃-V samples were produced by heating Std-V specimens again at 1000℃ for 2 hr, followed by cooling to room temperature. 530℃-A and 1000℃-A samples were also prepared. Potentiodynamic anodic polarization measurement, SEM, AFM and XRD analysis were performed to evaluate the effects of the various treatments. The difference in the mean values of E_corr between groups showed statistically significant difference (P<0.05), but that of I_corr did not show significance (P>0.05). When Ti surface was passivated there was a shift of corrosion potential (E_corr) in the noble direction and a lower corrosion current density (I_corr) value. Std-A samples showed most noble E_corr value among the tested groups. 530℃-V samples showed more noble E-corr than other tested groups except Std-A group. 1000℃-V samples showed more noble E-corr than those of Std-V sample. In the case of Std-, 530℃- and 1000℃-groups, -A sub-groups showed better corrosion resistant characteristics than -V sub-groups in regard to E-corr and I_corr values. In the SEM observations, the surfaces of the As-R samples showed only scratch line on smooth surface. In Pas samples, thick oxide layer covered the surface under high magnification observation. 530℃-A samples were covered by oxide granules, and Std-A samples had 25~50 nm-thick acicular oxides. The 1000℃-A samples were covered by coarse oxide crystals with a granule diameter of 0.1~0.6 μm having a gross appearance of milky white color, which was identified by XRD as a rutile. On the other hand, 1000℃-V samples showed an Widmansta¨tten structrue of which the orientation of the lattice is formed along crystallographic planes of the parent crystals. On the AFM observation, 530℃-A samples showed RMS roughness of 79.38 nm which is 5 times rougher than those of the As-R samples. Std-A sample had a roughness of 330.47 nm which is about 20-times rougher than that of the As-R sample. 1000℃-A samples were covered by coarse granular oxides and the roughness were about 0.56 μm. Vacuum sub-group samples showed a more smooth surface than air sub-group samples, and the oxide film was more dense. Due to variability of the surface treatment and heat treatment conditions, the process of the oxide formation seems to be affected thereby making the corrosion properties and surface micro-morphology different. However, more various electrochemical analysis together with surface analysis, and an investigation for the effects of those on the osteoblast cell adhesion and calcium phosphate apposition are needed for the improvement of the osseointegration rates of the titanium implants.

Verticillium sp.가 생산하는 cellulase의 정제 및 그 성질

유주현,홍대희,양융,진효상 연세대학교 산업기술연구소 1986 논문집 Vol.18 No.1

The cellulase of verticillium sp. was purified to investigate its some properties. The enzyme purification was carried out by ammonium sulfate fractionation, and column chromatography of Sephadex G-50, G-100 and DEAE Sephadex A-25, with its specific activity increased to 17 fold. The molecular weight was estimated to be 46,000 by gel filtration. The optimum pH and temperature were pH 7 and 50℃, respectively. The enzyme was stable over the range of pH5-7 at 50℃ for 1 hour. But half of its activity was lost after 2 hour. The km value was calculated to be 1.2mg of CMC/㎖.

보철물 절삭시 수종의 치과용 절삭기구와 냉각제의 효율성에 관한 연구

정은주,양홍서 전남대학교 치과대학 1996 전남치대논문집 Vol.8 No.1

The purpose of this study was to evaluate effects of dental cutting instruments and coolants to temperature changes of pulp chamber and to cutting weights. To evaluate effects of dental cutting instruments, the experimental groups were devided into 16. Four restorative materials (gold, base metal, resin, porcelain) were grinding with 4 cutting instruments(high speed diamond point, high speed fissure bur, low speed stone point, low speed rubber point). To evaluate effects of coolants, 16 groups were devided into 3 subgroups Group A : no use of coolant Group B : use of air coolant Group C : use of water-air spray coolant The results were as follows : 1. In kinds of coolants, temperature changes were shown in such order as group A, group B, group C. There was statistically significant difference between each group(p<0.05). Cutting weights were shown in such order as group C, group B, group A. There was statically significant difference between group C, B and A(p<0.05). 2. In kinds of cutting instruments, temperature change of diamond point as highest and temperature changes of high speed groups were higher than those of low speed groups. Cutting weights of fissure bur was highest and cutting weights of high speed groups were higher than those of low speed groups. 3. In kinds of materials of specimens, temperature change of base metal was highest and there were statistically significant difference between gold, base metal and resin, porcelain(p<0.05). Cutting weight of gold and base metal were higher than those of resin and porcelain. 4. The surface of specimen of group C, specially in use of high speed cutting instrument, showed less small particles than group A, B in SEM evaluation.

수종의 치과용 수복재료 및 시멘트의 radiopacity

정현주,강병철,오원만,양홍서 大韓口腔顎顔面 放射線學會 1994 Imaging Science in Dentistry Vol.24 No.1

The radiopacity of six composite resins, three resin luting cements and ten filling materials were studied. The purpose was to obtain an indication of radiopacity value of different brands within each of these groups of materials and to show differences in radiopacities of filling materials and natural tooth structures. On radiographs, the optimal densities of standardized samples were determined by computer imaging system and radiopacity values of the materials were expressed in millimeter equivalent aluminum. Within the groups of materials studied, there was considerable variation in radiopacity. The composite resins of P-50, Z100 and Prisma AP.H displayed much higher radiopacities than aluminum. Panavia resin cement was shown to be similarly radiopaque to aluminum. Generally, the radiopacity of base and filling materials appeared to be higher than that of the enamel and dentin. If materials with substantial difference in radiopacity are used in combined applications for restorative treatment of teeth, lower radiopacity can interfere with the diagnosis and detection of gaps near the restoration.

교잡종 찰옥수수에 대한 연구 III : Ⅲ. 국내 옥수수 유전자원 수집종에 대한 주요 특성 분포

서정은,주현민,최윤표,홍범용,조양희,주정일,지희정,이희봉 충남대학교 농업과학연구소 2007 농업과학연구 Vol.34 No.2

2006년 국내 각 지역으로부터 수집된 재래종옥수수 유전자원을 관행방법에 의해 파종하고 주요특성별로 분포도를 살펴본 결과는 다음과 같다. 1. 수집된 유전자원에 대한 발아율은 대부분 80∼100%이상의 분포를 보였으나, 일부 수집계통에는 30% 미만의 극히 저조한 발아율을 보였다. 2. 수집자원에 대한 초기생육을 살펴보면 극히 생육이 저조한 것이 40% 정도를 보였고, 극히 우수한 자원은 3%미만으로 나타났다. 3. 간장은 대부분이 150∼199cm범위에 55%가 분포하고 있었으나, l00cm이하가 5%, 250cm이상이 8%로 나타나 수집종간에 큰 차이를 보였다. 4. 주당 분얼수는 1개 미만이 40%의 분포를 보였으나, 일부 수집종에서 2 내지 3개의 분얼수를 보이는 계통이 확인되었다. 5. 개화소요일수는 61∼64일의 범위에서 40%, 57∼60일의 범위에서 30%의 분포를 보였으며, 특히 일부 수집종의 경우 55일 이하의 극조생종도 10% 정도의 분포를 보였다. 6. 이삭길이는 대부분 11∼15cm범위에 60%가 포함되어 있으나, 일부계통에서 5cm미만이 2%, 16∼20cm의 이삭길이도 10%가 분포하였다. Germination ratio on the 300 collected genetic resources showed 80 to 100 percentage, but those of some accessions were very low as below 30 percentage. Early growth phase of most of these lines were very poor while some collected lines were very vigor. Range of stem height showed from 150 to 199cm, but that of some accessions showed below 100cm as five percentage and some of them was over 250cm as eight percentage. Number of tillers per plant appeared less one but some collected lines have two to three tillers per plant. In days to tasseling, some accessions showed more four per plant. Ear length of these accession showed above 60 percentage as 11 to 15cm, while that of some collected lines showed over 10 percentage as 16 to 20cm.

미소결함의 형상인식을 위한 디지털 신호처리 적용에 관한 연구

김재열,홍석주,이규태,김병현,김훈조,김양중 韓國工作機械學會 2000 한국생산제조학회지 Vol.9 No.1

In this study, the classified researches the artificial and natural flaws in welding pails are performed using the pattern recognition technology. For this purpose the signal pattern recognition package including the user defined function was developed and the total procedure including the digital signal processing, feature extraction, feature selection and classifi-er selection is treated by bulk. Specially it is composed with and discussed using the statistical classifier such as the linear discriminant function the empirical Bayesian classifier. Also, the pattern recognition technology is applied to classifica-tion problem of natural flaw(i.e multiple classification problem - crack, lack of penetration, lack of fusion, porosity, and slag inclusion, the planar and volumetric flaw classification problem). According to this results, it is possible to acquire the recognition rate of 83% above even through it is different a little according to domain extracting the feature and the classifier.

나사형 임플란트 고정체의 길이, 직경, 플랫폼 형태에 따른 임플란트와 주위조직의 응력분포

강지은,정현주,양홍서 전남대학교 치의학연구소 2002 구강과학 Vol.14 No.1

Seven finite element models were constructed in mandible having single screw-type implant fixture connected to the second premolar-shaped superstructure, in order to evaluate how the length, diameter and platform shape of a screw-type fixture influence the stress in the supporting tissue around fixtures. The superstructure were made using UCLA abutment, and connected to the fixture with abutment screw. Each finite element model was varied in terms of length, diameter, and platform shape of the fixture according to the commercial fixture(3i Implant Innovations Inc, Palm Beach Gardens, FL33410, USA) while the superstructure and the mandible with a single fixture placed in it shared no difference in terms of appearance. In each model, 250N of vertical load was placed on the central pit of an occlusal plane and 250N of oblique load placed on the buccal cusp. The stress distribution in the supporting tissue and the other components was analysed using 2-dimensional Finite element analysis and the maximum stress in each reference area was compared. 1. Under lateral loading, the stress was larger in the larger in the abutment/fixture interface, and in the crestal bone, compared to the stress pattern under vertical loading. 2. The amount of stress at the superstructure was similar regardless of the length, diameter and platform shape of a fixture. 3. Around the longer fixture, the stress was decreased at the bone crest and subjacent cancellous bone and increased in the cancellous bone area apical to the fixture. 4. Around the wider fixture, the stress was decreased at the abutment/fixture interface, and the bone crest and increased in the cancellous bone area apical to the fixture. 5. Around the fixture having wider platform, less stress was resulted at the abutnent/fixture interface and the upper part of the cortical bone, compared to the fixture having standard platform. In short, the stress distribution of the supporting tissue was affected by length, diameter, and platform shape of a fixture, and the fixture which was larger in diameter and length could reduce the stress in the supporting tissues at the bone-fixture interface and bone crest area.

뇌기저동맥 첨단부 폐쇄증후군 후 지연성 올리브 비대에 동반된 눈떨림

김영진,정주리,강성원,한선정,이성익,손일홍,양현덕 圓光大學校 醫科學硏究所 2008 圓光醫科學 Vol.23 No.2

눈입천장떨림(Oculopalatal tremor)은 치아핵, 적핵 및 올리브핵을 연결하는 신경로(dentatorubro-olivary pathway, Guillain-Mollaret triangle)의 손상 이후에 발생하는 비대성올리브핵 변성(hypertrophic inferior olivary degeneration)에 의한 지연성(delayed) 합병증이다. 다리 뇌출혈(pontine hemorrhage) 또는 뇌줄기경색(brainstem infarction)후 아래 올리브핵비대(inferior olivary hypertrophy)가 발생한 환자에서 입천장떨림(palatal tremor) 없이 눈떨림이 보고된 경우가 있으나, 뇌바닥동맥끝증후군(top of the basilar syndrome) 후 아래올리브핵비대가 발생한 환자에서 눈떨림이 보인 경우는 드물다. 뇌바닥동맥끝증후군 후에 아래올리브핵비대가 발생한 환자에서 지연성 수평 눈떨림 보고하고자 한다. 이것은 양측 소뇌다리의 손상 때문에 눈떨림의 수직 성분이 동반되지 않은 수평눈떨림을 보인 것으로 유추할 수 있다. Oculopalatal tremor(OPT) is a delayed complication of hypertrophic inferior olivary degeneration after the lesion in the dentato-rubro-olivary pathway, the Guillain-Mollaret triangle. Some cases of ocular tremor without palatal tremor associated with inferior olivary hypertrophy after pontine hemorrhage or brainstem infarction have been reported, but ocular tremor with inferior olivary hypertrophy after top of the basilar syndrome has rarely been described. We describe a patient showing delayed-onset horizontal ocular tremor with inferior olivary hypertrophy after top of the basilar syndrome. It can be postulated that the vertical component of ocular tremor could have not developed because of the lesions in bilateral cerebral peduncles.

Polyhydroxybutyrate Production in Halophilic Marine Bacteria, Vibrio proteolyticus, from the Korean Peninsula

Ju-Won HONG,Hun-Suk SONG,Yu-Mi MOON,Yoon-Gi HONG,Shashi Kant BHATIA,Hae Rim JUNG,Tae Rim CHOI,Su Yeon YANG,Hyung Yeon PARK,Yong-Keun CHOI,Yung-Hun YANG 한국생물공학회 2018 한국생물공학회 학술대회 Vol.2018 No.10

Production of glutaric acid from 5-aminovaleric acid using <i>Escherichia coli</i> whole cell bio-catalyst overexpressing GabTD from <i>Bacillus subtilis</i>

Hong, Yun-Gi,Moon, Yu-Mi,Hong, Ju-Won,No, So-Young,Choi, Tae-Rim,Jung, Hye-Rim,Yang, Soo-Yeon,Bhatia, Shashi Kant,Ahn, Jung-Oh,Park, Kyung-Moon,Yang, Yung-Hun Elsevier 2018 Enzyme and microbial technology Vol.118 No.-

<P><B>Abstract</B></P> <P>Glutaric acid is one of the promising C5 platform compounds in the biochemical industry. It can be produced chemically, through the ring-opening of butyrolactone followed by hydrolysis. Alternatively, glutaric acid can be produced via lysine degradation pathways by microorganisms. In microorganisms, the overexpression of enzymes involved in this pathway from <I>E. coli</I> and <I>C. glutamicum</I> has resulted in high accumulation of 5-aminovaleric acid. However, the conversion from 5-aminovaleric acid to glutaric acid has resulted in a relatively low conversion yield for unknown reasons. In this study, as a solution to improve the production of glutaric acid, we introduced <I>gabTD</I> genes from <I>B. subtilis</I> to <I>E. coli</I> for a whole cell biocatalytic approach. This approach enabled us to determine the effect of co-factors on reaction and to achieve a high conversion yield from 5-aminovaleric acid at the optimized reaction condition. Optimization of whole cell reaction by different plasmids, pH, temperature, substrate concentration, and cofactor concentration achieved full conversion with 100 mM of 5-aminovaleric acid to glutaric acid. Nicotinamide adenine dinucleotide phosphate (NAD(P)<SUP>+</SUP>) and α-ketoglutaric acid were found to be critical factors in the enhancement of conversion in selected conditions. Whole cell reaction with a higher concentration of substrates gave 141 mM of glutaric acid from 300 mM 5-aminovaleric acid, 150 mM α-ketoglutaric acid, and 60 mM NAD<SUP>+</SUP> at 30 °C, with a pH of 8.5 within 24 h (47.1% and 94.2% of conversion based on 5-aminovaleric acid and α-ketoglutaric acid, respectively). The whole cell biocatalyst was recycled 5 times with the addition of substrates; this enabled the accumulation of extra glutaric acid.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The first <I>E. coli</I> whole cell bioconversion from 5-aminovalerate to glutaric acid. </LI> <LI> Finding of critical factors for GabTD reaction. </LI> <LI> Achievement of high bioconversion rate over 90% based on α-ketoglutarate concentration. </LI> <LI> Repetitive use of whole cell biocatalyst to accumulate more glutaric acid. </LI> </UL> </P>