• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.552-556
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• 2000

The crystallization behavior and dc Conductivities of CuO-Nb$_2$O$_{5}$ -V$_2$O$_{5}$ glasses prepared by quenching on the copper plate were investigated. The conductivities of the glasses were range from 10$^{-4}$ s.$cm^{-1}$ / at room temperature, but the conductivities of the glass-ceramics were 10$^{-3}$ s.$cm^{-1}$ / increased by 10$^1$ order. The linear relationship between In($\sigma$T) and T$^{-1}$ suggested that the electrical conduction in the present glass system would be due to a small polaron hopping mechanism. The value of activation energy of glass-ceramics heat-treated at 30$0^{\circ}C$ for 12hrs was found to be 0.leV

• Journal of Mechanical Science and Technology
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• 제15권3호
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• pp.291-299
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• 2001

Recently, severe wear on the shutdown rod cladding of Ulchin Nuclear Power Plant #1, #2 were observed by the Eddy Current Test(E.C.T.). In particular, the wear at the sixth card location was up to 75%. The test results indicated that the Flow Induced Vibration(F.I.V.) might be the cause of the fretting wear resulting from the contact between Rod Cluster Control Assemblies(RCCAs) and their spacing cards(guide plates) arranged in the guide tube. From reviewing RCCAs fretting wear repots and analyzing the general characteristics of F.I.V. mechanism in the reactor, geometric layout and flow conditions around the control rod, it is concluded that the turbulence excitation is the most probable vibration mechanism of RCCA. To identify the governing mechanism of RCCA vibration, an experiment was performed for a representative rod position in which the most serious fretting wear experienced among the six rod positions. The experimental rig was designed and set up to satisfy the governing nondimensional numbers which are Reynolds number and mass damping parameter. The vibration amplitude measurement by the non-contact laser displacement sensor showed good agreements in the frequency and the maximum wearing(vibration) location with Ulchin E.C.T. results and Framatome report, respectively. The sudden increase in the vibration amplitude was sensed around the 6th guide plate with mass flow rate variation. Comparing the similitude rod behaviour with the idealized response of a cylinder in flow induced vibration, it was found that he dominant mechanism of vibration was transferred from turbulence excitation to periodic shedding at the mass flow ate 90ι/min. Also the critical velocity of the vibration in RCCAs was determined and the vibration can be prevented by reducing the bypass flow rate below the critical velocity.

• 약학회지
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• 제58권1호
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• pp.7-11
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• 2014

To study the resistance mechanism of E. faecalis to LCB01-0371, several resistant mutants to LCB01-0371 or linezolid were isolated by step-wise selection. The frequency of spontaneous mutations resistant to LCB01-0371 was lower than that of linezolid in E. faecalis. The genetic variations in resistant mutants were analyzed by DNA sequencing of domain V of 23S rRNA in each mutant. The first-step mutant to LCB01-0371 had a G2576T point mutation in V domain of 23S rRNA. However, no resistant mutant to LCB01-0371 was isolated in second-step mutant selection.

• 대한화학회지
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• 제28권4호
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• pp.251-258
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• 1984

색소를 흡착시킨 산화아연의 표면상태를 광기전력측정법을 이용하여 색소증감기구 및 바인더(binder)효과에 대한 연구를 수행하였다. 산화아연의 에너지트랩준위는 1.12eV이며, 색소흡착에 의해 0.99eV로 에너지준위가 낮아짐을 알았다. 바인더효과는 표면광기전력의 효율을 커지게 하나 에너지트랩준위에는 변화를 주지 않는다. 또한 색소증감기구로 흡착력이 강한 산형색소는 전자 이동(electron transfer)이며, 산화아연 고유흡수광에 減感작용이 있는 나트륨염형색소는 에너지이동(energy transfer)로써 추측된다. 근적외부인 1,100~1,350nm에 걸쳐 광기전력감도가 나타나므로 적외선에 의한 전자사진용 畵像材料로서 가능성을 제시하였다.

• Journal of Welding and Joining
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• 제15권6호
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• pp.32-40
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• 1997

Solid state diffusion bonding is the joining process performed by creep and diffusion, which is accelerated by heating below melting temperature and proper pressing, in vacuum or shielding gas atmosphere. By this process we can obtain sufficient joint which can't be expected from the fusion welding. For Ti-6Al-4V alloy, the optimum solid state diffusion bonding condition and mechanical properties of the joint were found, and micro void morphology at bond interface was observed by SEM. The results of tensile test showed sufficient joint, whose mechanical properties are similar to that of base metal. 850$^{\circ}$C, 3MPa is considered as the optimum bonding condition. Void morphology at interface is long and flat at the initial stage. As the percentage of bonded area increases, however, small and round voids are found. Variation of void shape can be explained as follows. As for the void shrinkage mechanism, at the initial stage, power law creep is the dominant, but diffusion mechanism is dominant when the percentage of bonded area is increased.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1995년도 춘계학술대회
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• pp.80-80
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• 1995

T4 Endonuclease V (Mw 16,000) acts as a repair enzyme for UV induced pyrimidine dimers in DNA. Many researchers have studied the biochemical characteristics of the enzyme. However the precise action mechanism of T4 endo V has not fully elucidated yet. In our laboratory NMR spectroscopy technique is being used for the structural study of T4 endo V. Because of its low temperature stability and high content of ${\alpha}$-helix, the conventional $^1$H NMR technique was inapplicable. Therefore we utilized stable isotope labeling technique and so far prepared about 10 amino acid specific labeled proteins. The HSQC spectra of amino acid specific labeled proteins will help us to interpret the triple resonance 3D, 4D data which are under processing, We also studied the behaviors of specific amino acid residues whose roles might be critical. When the enzyme labeled by $\^$15/N-Thr was mixed with the substrate oligonucleotide (semispecific -TT- sequence), one crosspeak in its HSQC spectrum was completely desappeared, which means that one of seven Thr residues is in the binding site of the enzyme with DNA, This result is well consistent with previous report that implicated the Thr 2 residue in the activity of the enzyme. Similar studies were carried on the behaviors of Arg and Tyr residues.

• Biomolecules & Therapeutics
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• 제20권4호
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• pp.393-398
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• 2012

Recently, we reported that defective autophagy may contribute to the inhibition of the growth in response to PP2 (4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine), a selective SFK inhibitor, in multidrug-resistant v-Ha-ras-transformed NIH 3T3 cells (Ras-NIH 3T3/Mdr). In this study, we demonstrated that PP2 induces LC3 conversion via a mechanism that is uncoupled from autophagy and increases apoptosis in Ras-NIH 3T3/Mdr cells. PP2 preferentially induced autophagy in Ras-NIH 3T3 cells rather than in Ras-NIH 3T3/Mdr cells as determined by LC3-I to LC3-II conversion and GFP-LC3 fluorescence microscopy. Beclin 1 knockdown experiments showed that, regardless of drug resistance, PP2 induces autophagy via a Beclin 1-dependent mechanism. PP2 induced a conformational change in Beclin 1, resulting in the enhancement of the pro-autophagic activity of Beclin 1, in Ras-NIH 3T3 cells. Further, PI3K inhibition induced by wortmannin caused a significant increase in apoptosis in Ras-NIH 3T3 cells, as demonstrated by flow cytometric analysis of Annexin V staining, implying that autophagy inhibition through PI3K increases apoptosis in response to PP2 in Ras-NIH 3T3 cells. However, despite the fact that wortmannin abrogates PP2-induced GFP-LC3 punctae formation, some LC3 conversion remains in Ras-NIH 3T3/Mdr cells, suggesting that LC3 conversion may occur in an autophagy-independent manner. Taken together, these results suggest that PP2 induces LC3 conversion independent of PI3K, concomitant with the uncoupling of LC3 conversion from autophagy, in multidrug-resistant cells.

• 대한약리학회지
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• 제15권1_2호
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• pp.7-12
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• 1979

1. 두개내압상승(頭蓋內壓上昇)에 혈압상승(血壓上昇)이 중추(中樞)의 교감신경기능(交感神經機能)과의 관계(關係)가 있음을 확인(確認)하기 위하여, clonidine, phenoxybenzamine 및 phentolamine을 사용(使用)하여 이들 약물(藥物)이 두 개내압상승(頭蓋內壓上昇)에 따른 협압상승(血壓上昇)에 미치는 영향(影響)을 조사(調査)하였다. 2. 정맥내(靜脈內) clonidine은 측뇌실내(側腦室內) 주입시(注入時)와 같이 두개내압상승(頭蓋內壓上昇)에 따른 혈압상승(血壓上昇)을 억제(抑制)하였다. 3. Phenoxybenzamine 및 phentolamine의 정맥내주입후(靜脈內注後)에 두 개내압상승(頭蓋內壓上昇)에 따른 혈압상승(血壓上昇)은 현저히 약화(弱化)되었다. 4. 측뇌실내주입(側腦室內注入) phenoxybenzamine은 두개내압상승(頭蓋內壓上昇)에 따른 혈압상승(血壓上昇)에 영향(影響)을 미치지 않았다. 5. 측뇌실내(側腦室內)에 phenoxybenzamine을 주입후(注入後)에는 clonidine의 측뇌실내주입(側腦室內注入)이 두개내압상승(頭蓋內壓上昇)에 따른 혈압상승(血壓上昇)을 억제(抑制)치 못하였다. 6. 두개내압상승(頭蓋內壓上昇)에 따른 혈압상승(血壓上昇)에는 중추(中樞) 및 말초(末梢)의 교감신경기능(交感神經機能)이 관여(關與)함을 확인(確認)하였다.

• Bulletin of the Korean Chemical Society
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• 제25권5호
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• pp.721-725
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• 2004

Acetohydroxy acid synthase (AHAS) is one of several enzymes that require thiamine diphosphate and a divalent cation as essential cofactors. The active site contains several conserved ionizable groups and all of these appear to be important as judged by the fact that mutation diminishes or abolishes catalytic activity. Recently, we have shown [Yoon, M.-Y., Hwang, J.-H., Choi, M.-K., Baek, D.-K., Kim, J., Kim, Y.-T., Choi, J.-D. FEBS Letters 555 (2003), 185-191] that the activity is pH-dependent due to changes in $V_{max}$ and V/$K_m$. Data were consistent with a mechanism in which substrate was selectively catalyzed by the enzyme with an unprotonated base having a pK 6.48, and a protonated group having a pK of 8.25 for catalysis. Here, we have in detail studied the pH dependence of the kinetic parameters of the cofactors (ThDP, FAD, $Mg^{2+}$) in order to obtain information about the chemical mechanism in the active site. The $V_{max}$ of kinetic parameters for all cofactors was pH-dependent on the basic side. The pK of ThDP, FAD and $Mg^{2+}$ was 9.5, 9.3 and 10.1, respectively. The V/$K_m$ of kinetic parameters for all cofactors was pH-dependent on the acidic and on the basic side. The pK of ThDP, FAD and $Mg^{2+}$ was 6.2-6.4 on the acidic side and 9.0-9.1 on the basic side. The well-conserved histidine mutant (H392) did not affect the pH-dependence of the kinetic parameters. The data are discussed in terms of the acid-base chemical mechanism.

• 한국진공학회지
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• 제2권4호
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• pp.507-514
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• 1993

The solid state reaction of Mo/Si multilayer thin films produced by RF magnetron sputtering technique was examine dusing differential scanning calorimetry (DSC) and x-ray diffraction, and explained in view of two concepts, effective drivig force and effective heat of formation. In constant scanning rate DSC, there were two exothermic peks which corresponded to the formation of h-MoSi2 and t-MoSi2 , respectively. The activation energyfor theformation of h-MoSi2 was 1.5eV , and that of t-MoSi2 was 7.8eV. Nucleation wa stherate controlling mechanism for each of the silicide formation. Amorphous phase was not formed , which was consistent withtheprediction by the concept of effective driving force. h-MoSi2 the first crystalline phase, was considered to have lower interfacial free energy than t-MoSi2 and by increasing temperature it was transformed into more stable t-MoSi2.