• 천문학회보
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• 제40권1호
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• pp.66.1-66.1
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• 2015

We present the first observational detection of radial and azimuthal oscillations in full halo coronal mass ejections (HCMEs). We analyze nine HCMEs well-observed by LASCO from Feb 2011 to Jun 2011. Using the LASCO C3 running difference images, we estimated the instantaneous apparent speeds of the HCMEs in different radial directions from the solar disk center. We find that the development of all these HCMEs is accompanied with quasi-periodic variations of the instantaneous radial velocity with the periods ranging from 24 to 48 mins. The amplitudes of the instant speed variations reach about a half of the projected speeds. The amplitudes are found to anti-correlate with the periods and correlate with the HCME speed, indicating the nonlinear nature of the process. The oscillations have a clear azimuthal structure in the heliocentric polar coordinate system. The oscillations in seven events are found to be associated with distinct azimuthal wave modes with the azimuthal wave number m=1 for six events and m=2 for one event. The polarization of the oscillations in these seven HCMEs is broadly consistent with those of their position angles with the mean difference of $42.5^{\circ}$. The oscillations may be connected with natural oscillations of the plasmoids around a dynamical equilibrium, or self-oscillatory processes, e.g. the periodic shedding of Alfvenic vortices. Our results indicate the need for advanced theory of oscillatory processes in CMEs.

• 공업화학
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• 제8권5호
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• pp.872-879
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• 1997

암모니아와 금속염과의 기-고 반응을 이용한 화학열펌프에서 열전달 특성과 물질전달 특성을 개선하기 위하여 금속염을 팽창흑연에 반지름 방향으로 겉보기 밀도가 증가하도록 함침시켜 새로운 비균일 열전도성 반응블럭을 제조하였다. 이것은 겉보기 밀도가 반지름 방향으로 165, 222, 279, 337, $394(kg/m^3)$로 증가하도록 만든 것으로 균일 열전도성 반응블럭과 반응특성을 비교하였다. 실험결과 열전달특성은 비균일 열전도성 반응블럭이 훨씬 좋았고, 반응을 반복함에 따라 물질전달과 반응특성이 개선되었으며 반응의 재현성도 양호함을 알 수 있었다.

• 생명과학회지
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• 제16권3호
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• pp.375-381
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• 2006

Saccharomyces cerevisiae 로부터 알데히드 환원효소를 정제하였다. 정제된 알데히드 환원효소를 biocatalyst로 사용하여 치환기가 있는 카르보닐 화합물의 선택적 환원을 시도하였다. 효소를 이용한 환원반응의 생성물의 구조를 TLC, GC, Mass, NMR, FT-IR을 이용하여 확인하였으며 효소를 이용한 환원반응이 높은 선택성을 가지고 진행됨을 확인하였다. 또한 이 반응은 알데히드 환원효소의 억제제인 벤조산에 의해 크게 억제되었다. 치환기가 있는 카르보닐 화합물의 선택적 환원반응은 의약품 제조 분야에서 매우 중요한 반응이며 미생물에서 정제한 알데히드 환원효소가 biocatalyst 로서 선택적 환원반응에 이용될 수 있으리라 사료된다.

• 한국물환경학회지
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• 제36권3호
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• pp.185-193
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• 2020

Bimodal flocculation describes the aggregation and breakage processes of the flocculi (or primary particles) and the flocs in the water environment. Bimodal flocculation causes bimodal size distribution with the two separate peaks of the flocculi and the flocs. Extracellular polymeric substances and ionic species common in the water environment increase the occurrence of bimodal flocculation and flocculi-floc size distribution, under the flocculation mechanisms of electrostatic attraction and polymeric bridging. This study investigated bimodal flocculation and flocculi-floc size distribution, with respect to the extracellular polymeric substance concentration and ionic strength in the kaolinite-containing suspension. The batch flocculation tests comprising 0.12 g/L of kaolinite showed that the highest flocculation potential occurred at the lowest xanthan gum (as extracellular polymeric substances) concentration, under all the ionic strengths of 0.001, 0.01, and 0.1 M NaCl. Also, it was important to note that the higher ionic strength resulted in the higher flocculation potential, at all the xanthan gum concentrations. The bimodal flocculation and flocculi-floc size distribution became apparent in the experimental conditions, which had low and intermediate flocculation potential. Besides the polymeric bridging flocculation, steric stabilization increased the flocculi mass fraction against the floc mass fraction, thereby developing the bimodal size distribution.

• Journal of Microbiology and Biotechnology
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• 제16권1호
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• pp.57-63
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• 2006

We have cloned a xylanase gene (xynA) from Streptomyces thermocyaneoviolaceus. The deduced amino acid sequences of the XynA, including the active site sequences of glycosyl hydrolase family 10, showed high sequence homology with several xylanases assigned in this category. The XynA was overexpressed under an IPTG inducible T7 promoter control in E. coli BLR(DE3). The overproduced enzymes were excreted into culture supernatants and periplasmic space. The purified XynA had an apparent molecular mass of near 54 kDa, which corresponds to the molecular mass calculated from its gene. The optimum pH and temperature of the purified XynA were determined to be 5.0 and $65^{\circ}C$, respectively. The XynA retained over $90\%$ its activity after the heat treatment at $65^{\circ}C$ for 30 min. The XynA was highly efficient in producing xylose (X1), xylobiose (X2), xylotriose (X3), and xylotetraose (X4) from xylan.

• Journal of Microbiology and Biotechnology
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• 제24권2호
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• pp.236-244
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• 2014

The gene encoding ${\alpha}-\small{L}$-arabinofuranosidase (AFase) from Paenibacillus sp. DG-22 was cloned, sequenced, and expressed in Escherichia coli. The AFase gene (abfA) comprises a 1,509 bp open reading frame encoding 502 amino acids with a molecular mass of 56,520 daltons. The deduced amino acid sequence of the gene shows that AbfA is an enzyme consisting of only a catalytic domain, and that the enzyme has significant similarity to AFases classified into the family 51 of the glycosyl hydrolases. abfA was subcloned into the pQE60 expression vector to fuse it with a six-histidine tag and the recombinant AFase (rAbfA) was purified to homogeneity. The specific activity of the recombinant enzyme was 96.7 U/mg protein. Determination of the apparent molecular mass by gel-filtration chromatography indicated that AbfA has a tetrameric structure. The optimal pH and temperature of the enzyme were 6.0 and $60^{\circ}C$, respectively. The enzyme activity was completely inhibited by 1 mM $HgCl_2$. rAbfA was active only towards p-nitrophephenyl ${\alpha}-\small{L}$-arabinofuranoside and exhibited $K_m$ and $V_{max}$ values of 3.5 mM and 306.1 U/mg, respectively. rAbfA showed a synergistic effect in combination with endoxylanase on the degradation of oat spelt xylan and wheat arabinoxylan.

• Journal of Korean Neurosurgical Society
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• 제57권1호
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• pp.50-53
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• 2015

Usually fungal infections caused by opportunistic and pathogenic fungi had been an important cause of morbidity and mortality among immunocompromised patients. However clinical data and investigations for immunocompetent pathogenic fungal infections had been rare and neglected into clinical studies. Especially Cryptococcal brainstem abscess cases mimicking brain tumors were also much more rare. So we report this unusual case. This 47-year-old man presented with a history of progressively worsening headache and nausea for 1 month and several days of vomituritions before admission. Neurological and laboratory examinations performed demonstrated no abnormal findings. Previously he was healthy and did not have any significant medical illnesses. A CT and MRI scan revealed enhancing $1.8{\times}1.7{\times}2.0$ cm mass lesion in the left pons having central necrosis and peripheral edema compressing the fourth ventricle. And also positron emission tomogram scan demonstrated a hot uptake of fluoro-deoxy-glucose on the brainstem lesion without any evidences of systemic metastasis. Gross total mass resection was achieved with lateral suboccipital approach with neuronavigation system. Postoperatively he recovered without any neurological deficits. Pathologic report confirmed Cryptococcus neoformans and he was successively treated with antifungal medications. This is a previously unreported rare case of brainstem Cryptococcal abscess mimicking brain tumors in immunocompetent host without having any apparent typical meningeal symptoms and signs with resultant good neurosurgical recovery.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제31권4호
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• pp.349-352
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• 2009

Cementoblastoma is a benign ectomesenchymal odontogenic neoplasm that forms a mass of cementum or cementum-like tissue continuous with the tooth root. Cementoblastoma represents 1% to 6.2% of all odontogenic tumors, and occurs more than 75% arise in the mandible, with most cases arising in the molar and premolar regions. About 75% arises before the age of 30. Radiographically, it appears as a radiopaque mass with a thin radiolucent rim attached to the roots of a tooth. The recurrence rate is 37% in the current study and cortical expansion and perforation of the cortex are common findings in lesions that subsequently recurred. It is apparent that recurrence rate depends largely on the completeness of removal than any other factor. Here we present a 20 year old, female case of an unusual multiple recurrent cementoblastoma around a previous lesion which had been surgically excised 2 years ago.

• 천문학회보
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• 제42권2호
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• pp.62.2-62.2
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• 2017

We have made an investigation on the radial and azimuthal wave modes of full halo coronal mass ejections (HCMEs). For this, we consider 24 HCMEs which are simultaneously observed by SOHO and STEREO A & B from August 2010 to August 2012 when they were roughly in quadrature. Using the SOHO/LASCO C3 and STEREO COR2 A & B running difference images, we estimate the instantaneous apparent speeds of the HCMEs at 24 different position angles. Major results from this study are as follows. First, there are quasi-periodic variations of the instantaneous radial velocity with the periods ranging from 24 to 48 mins. Second, the amplitudes of instant speed variations are about a third of the projected speeds. Third, the amplitudes are found to have a weak anti-correlation with period. Our preliminary identification from SOHO observations shows that there are several distinct radial and azimuthal wave modes: m=0 (radial) for five events, m=1 for eleven events, m=2 for three events, and unclear for the other events. In addition, we are making a statistical investigation on the oscillation of 733 CMEs to understand their physical origins.

• 대한기계학회논문집A
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• 제21권5호
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• pp.735-745
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• 1997

In this study, the compressibility of resin was considered in filling analysis to account for the possible packing type flow. A numerical simulation program employing a hybrid finite element/finite difference scheme was developed to solve Hele-Shaw flow of the compressible viscous fluid at non-isothermal conditions. To advance the melt front, a control volume approach was adopted. Thin complex 3-D shapes of cavities, runners, and sprues were discretized by employing triangular, cylindrical and/or rectangular strip elements. Mass conservation was applied to each control volume to solve for the pressure distribution. Directly applying a constant mass flow rate at the inlet removes calculation of the apparent pressure boundary conditions, resulting in better simulation condition. The Cross model was used to model viscosity and the Tait equation was employed to represent density as a function of temperature and pressure. The validity of the developed program was verified through comparisons with available data in the literature and the effect of compressibility on the pressure distribution was discussed. To reduce computation time, 1-D and 2-D elements were used instead of applying triangular elements and the numerical results were compared to each other.