• 한국음향학회지
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• 제16권5호
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• pp.96-104
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• 1997

본 논문에서는 임펄스 잡음이 부가되는 환경 하에서 시지연 추정 및 시지연과 주파수 지연 목합 추정을 위한 새로운 강건 알고리즘들을 제안하였다. 제안된 방법은 ${\alpha}-stable$ 분포 이론을 바탕으로 하여 음의 분수 차수 모멘트(FNOM: fractional negative order moment)와 최소 산란(MD : minimum dispersion) 법을 이용한 강건 시지연 추정법들과 이를 응용한 시지연과 주파수 지연의 복합 추정법인 음의 분수 차수 모호함수법과 복합 최소 산란 법으로 구성되었다. 제안한 방법들을 평가하기 위하여 컴퓨터 모의 실험을 통해서 실제 응용 능력을 기존의 여러 방법들과 비교. 검토하였다. 실험 결과 2차 모멘트 이론을 바탕으로 한 관례적인 방법들은 가우시안 잡음 환경 (${\alpha}$=2인 $S{\alpha}S$ 잡음) 하에서만 시지연 추정이 가능하였고, 최근 제안된 Nikias[7]의 강건 시지연 추정법 들도 대부분이 제한된 임펄스 잡음 ($1<{\alpha}{\le}2$인 $S{\alpha}S$ 잡음)에 대해서만 그 성능이 입증된 반면, 본 연구에서 제안한 방법들은 가우시안 잡음 및 심한 임펄스 잡음 ($0<{\alpha}{\le}2$인 $S{\alpha}S$ 잡음) 하에서도 강건하게 시지연 추정이 가능함을 입증하였다.

• 한국환경과학회지
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• 제17권2호
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• pp.141-148
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• 2008

In order to investigate the effect of inflow of Yangze river on the distribution of chlorophyll-${\alpha}$, the results of serial oceanographic observation during 2000-2005 were used. The oceanographic conditions in the northern East China Sea is influenced by the Tsushima Warm Current and low saline water derived from the Yangze river. The distributions of these water masses vary significantly by the season in the northern East China Sea. The sea surface temperature and salinity were stable and concentrations of chlorophyll-${\alpha}$ were low in the eastern part of $126^{\circ}E$. On the contrary, the salinity was significantly influenced by the low saline water derived from Yangze river with the high concentrations of chlorophyll-${\alpha}$. It is suggested that the low saline water inflowed from the Yangze river affects high concentrations of chlorophyll-${\alpha}$ in the northern East China Sea in summer.

• 대한화학회지
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• 제29권4호
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• pp.397-405
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• 1985

금속킬레이트제로써 잘 알려진 몇가지 oxime 화합물들의 Amberlite XAD 수지들에 대한 흡착성을 분포계수값을 측정함으로써 상호 비교해 본 결과 킬레이트제로서는 분포계수값이 비교적 큰 salicylaldoxime (SAO)과 ${\alpha}$-benzoinoxime(${\alpha}$-BzO) 그리고 수지로서는 XAD-4 수지가 적합함을 알았다. SAO과 ${\alpha}$-BzO를 XAD-4 수지에 각각 침윤시킨 SAO-XAD-4 및 ${\alpha}$-BzO-XAD-4 침윤수지의 그 특성을 조사하였다. SAO와 ${\alpha}$-BzO의 XAD-4 수지에 대한 최적 흡착조건은 30% 메탄올, pH 1∼8(SAO) 및 pH 1~9 (${\alpha}$-BzO)였다. SAO 및 ${\alpha}$-BzO의 XAD-4 수지에 대한 흡착은 온도가 증가함에 따라 감소하였으며, 그 흡착메카니즘은 흡착엔탈피(-${\Delta}$H)를 구해본 결과 4.99 ~ 6.66 (Kcal/mol)인 것으로 보아 쌍극자-쌍극자 인력에 상응하는 분자 흡착임을 알 수 있었다. 한편 금속이온을 흡착시키는 매질용액과 흡착된 금속이온을 회수하는 염산수용액에서 침윤수지의 안정성을 조사한 결과, 전자는 pH 5∼10에서, 후자는 0.1~5M 염산수용액에서 비교적 큰 안정성을 보였다. 두 침윤수지에 의한 Mn(II), Co(II), Ni(II), Zn(II)등의 금속이온의 흡착몰비는 대략 1;2(금속이온:킬레이트제)이었으며 흡착된 금속이온은 3M-HCl 수용액 또는 3M-HCl/50%-MeOH 용리액으로 정량적으로 회수가 가능하였다.

• 한국재료학회지
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• 제11권8호
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• pp.664-664
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• 2001

$\sigma$-VFe 금속간화합물에 대한 기계적 합금화(MA) 효과를 중성자 및 X선 회절법으로 조사하였다. MA 분말의 구조분석은 X선 회절(Cu-K$\alpha$) 린 중성자회절(HRPD, λ=1.835$\AA$)을 이용하여 행하였다. $\sigma$-VFe화합물의 MA시 큰 구조변화가 관찰되었으며, MA 60시간의 경우 Fe-Fe 훤자분포는 unit cell에 30개의 원자를 포함하고 있는 $\sigma$상의 tetragonal구조에서 $120^{\circ}C$이상에서 안정하게 존재하는 $\alpha$-(V,Fe) 고용체의 bcc 구조로 상변화함을 알 수 있었다. 또한 $\alpha$-VFe 화합물에 대한 중성자 및 X선 회절패턴의 비교분석을 행하였으며 그 결과 $\sigma$상이 가지는 화학적 규칙성에 기인하는 (101)과 (111) 회절 피크가 중성자 회절에서 뚜렷하게 관찰됨을 알 수 있었다.

• 한국미생물학회:학술대회논문집
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• 한국미생물학회 1991년도 춘계학술발표대회 논문집
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• pp.225-236
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• 1991

The genes encoding the thermostable $\alpha$-amylase and maltogenic amylase from Bacillus lichenciformis were cloned and expressed in E. coli. The recombinant plasmid pTA322 was found to contain a 3.1kb EcoRI genomic DNA fragment of the thermostable $\alpha$-amylase. The cloned $\alpha$-amylase was compared with the B. licheniformis native $\alpha$-amylase. Both $\alpha$-amylase have the same optimal temperature of $70^{\circ}C$ and are stable in the pH range of 6 and 9. The complete nucleotide sequences of the thermostable $\alpha$-amylase gene were determined. It was composed of one open reading rame of 1,536 bp. Start and stop codons are ATG and TAG. From the amino acid sequence deduced from the nucleotide sequence, the cloned thermostable $\alpha$-amylase is composed of 483 amino acid residues and its molecular weight is 55,200 daltons. The content of guanine and cytosine is $47.46mol\%$ and that of third base codon was $53_41mol\%$. The recombinant plasmid, pIJ322 encoding the maltogenic amylase contains a 3.5kb EcoRI-BamHI genomic DNA fragment. The optimal reaction temperature and pH of the maltogenci amylase were $50^{\circ}C$ and 7, respectively. The maltogenic amylase was capable of hydrolysing pullulan, starch and cyclodextrin to produce maltose from starch and panose from pullulan. The maltogenic amylase also showed the transferring activity. The maltogenic amylase gene is composed of one open reading frame of 1,734bp. Start and stop codons are ATG and ATG. At 2bp upstream from start codon, the nucleotide sequence AAAGGGGGAA seems to be the ribosome-binding site(RBS, Shine-Dalgarno sequence). A putative promoter(-35 and-10 regions) was found to be GTTAACA and TGATAAT. From deduced amino acid sequence from the nucleotide srquence, this enzyme was comosed of 578 amino acid residues and its molecular weight was 77,233 daltons. The content of guanine and cytosine was $48.1mol\%$. The new recombinant plasmid, pTMA322 constructed by inserting the thermostable $\alpha$-amylase gene in the EcoRI site of pIJ322 to produce both the thermostable $\alpha$-amylase and the maltogenic amylase were expressed in the E. coli. The two enzymes expressed from E. coli containing pTMA322 was reacted with the $15\%$ starch slurry at $40^{\circ}C$ for 24hours. The distribution of the branched oligosaccharides produced by the single-step process was of the ratio 50 : 50 between small oligosaccharide up DP3 and large oligosaccharide above DP3.

• Journal of Microbiology and Biotechnology
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• 제18권8호
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• pp.1386-1392
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• 2008

A gene (sll0158) putatively encoding a glycogen branching enzyme (GBE, E.C. 2.4.1.18) was cloned from Synechocystis sp. PCC6803, and the recombinant protein expressed and characterized. The PCR-amplified putative GBE gene was ligated into a pET-21a plasmid vector harboring a T7 promoter, and the recombinant DNA transformed into a host cell, E. coli BL21(DE3). The IPTG-induced enzymes were then extracted and purified using Ni-NTA affinity chromatography. The putative GBE gene was found to be composed of 2,310 nucleotides and encoded 770 amino acids, corresponding to approx. 90.7 kDa, as confirmed by SDS-PAGE and MALDI-TOF-MS analyses. The optimal conditions for GBE activity were investigated by measuring the absorbance change in iodine affinity, and shown to be pH 8.0 and $30^{\circ}C$ in a 50 mM glycine-NaOH buffer. The action pattern of the GBE on amylose, an $\alpha$-(1,4)-linked linear glucan, was analyzed using high-performance anion-exchange chromatography (HPAEC) after isoamylolysis. As a result, the GBE displayed $\alpha$-glucosyl transferring activity by cleaving the $\alpha$-(1,4)-linkages and transferring the cleaved maltoglycosyl moiety to form new $\alpha$-(1,6)-branch linkages. A time-course study of the GBE reaction was carried out with biosynthetic amylose (BSAM; $M_p{\cong}$8,000), and the changes in the branch-chain length distribution were evaluated. When increasing the reaction time up to 48 h, the weight- and number-average DP ($DP_w$ and $DP_n$) decreased from 19.6 to 8.7 and from 17.6 to 7.8, respectively. The molecular size ($M_p$, peak $M_w{\cong}2.45-2.75{\times}10^5$) of the GBE-reacted product from BSAM reached the size of amylose (AM) in botanical starch, yet the product was highly soluble and stable in water, unlike AM molecules. Thus, GBE-generated products can provide new food and non-food applications, owing to their unique physical properties.

• 한국재료학회지
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• 제11권8호
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• pp.661-665
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• 2001

$\sigma$-VFe 금속간화합물에 대한 기계적 합금화(MA) 효과를 중성자 및 X선 회절법으로 조사하였다. MA 분말의 구조분석은 X선 회절(Cu-K$\alpha$) 린 중성자회절(HRPD, λ=1.835$\AA$)을 이용하여 행하였다. $\sigma$-VFe화합물의 MA시 큰 구조변화가 관찰되었으며, MA 60시간의 경우 Fe-Fe 훤자분포는 unit cell에 30개의 원자를 포함하고 있는 $\sigma$상의 tetragonal구조에서 $120^{\circ}C$이상에서 안정하게 존재하는 $\alpha$-(V,Fe) 고용체의 bcc 구조로 상변화함을 알 수 있었다. 또한 $\alpha$-VFe 화합물에 대한 중성자 및 X선 회절패턴의 비교분석을 행하였으며 그 결과 $\sigma$상이 가지는 화학적 규칙성에 기인하는 (101)과 (111) 회절 피크가 중성자 회절에서 뚜렷하게 관찰됨을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제18권6호
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• pp.644-648
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• 1997

Introduction of an alkyl substituent at the $C_{4\beta}$ position of antimalarial trioxanes has caused them to become more active in their antimalarial activity. We have designed a structurally simple 4β-phenyl substituted trioxane (3) as an active antimalarial since it can form a more stable carbon radical when reacting with ferrous bromide. The trioxane 3 has been prepared along with the corresponding isomer 4 according to the previously reported procedure. The synthesized trioxanes 3 and 4 were finally separated by using HPLC and assigned their stereochemistry by spectroscopy and X-ray crystallography. Their antimalarial activities were surprisingly low. The low activity was then rationalized based on the product distribution of the ferrous ion induced reaction of these trioxanes. These trioxanes with ferrous bromide did not produce any detectable amount of the corresponding $C_4$-hydroxylated product, consistent with the fact that neither $C_{4\beta}$-phenyl substituted nor $C_{4\alpha}$-phenyl substituted trioxane has any antimalarial activity. It implies that a $C_4$ substituent of antimalarial trioxanes has to stabilize an adjacent carbon-centered radical in a specific stability range in order to show a good antimalarial activity. This study, combined with related studies, could help develop more potent antimalarial trioxanes.

• Asian Pacific Journal of Cancer Prevention
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• 제14권9호
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• pp.4983-4988
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• 2013

Objectives: To establish a taxol-resistant cell line of human ovarian carcinoma (A2780/Taxol) and investigate its biological features. Methods: The drug-resistant cell line (A2780/Taxol) was established by continuous stepwise selection with increasing concentrations of Taxol. Cell morphology was assessed by microscopy and growth curves were generated with in vitro and in vivo tumor xenograft models. With rhodamine123 (Rh123) assays, cell cycle distribution and the apoptotic rate were analyzed by flow cytometry (FCM). Drug resistance-related and signal associated proteins, including P-gp, MRPs, caveolin-1, PKC-${\alpha}$, Akt, ERK1/2, were detected by Western blotting. Results: A2780/Taxol cells were established with stable resistance to taxol. The drug resistance index (RI) was 430.7. Cross-resistance to other drugs was also shown, but there was no significant change to radioresistance. Compared with parental cells, A2780/Taxol cells were significantly heteromorphous, with a significant delay in population doubling time and reduced uptake of Rh123 (p<0.01). In vivo, tumor take by A2780 cells was 80%, and tumor volume increased gradually. In contrast, with A2780/Taxol cells in xenograft models there was no tumor development. FCM analysis revealed that A2780/Taxol cells had a higher percentage of G0/G1 and lower S phase, but no changes of G2 phase and the apoptosis rate. Expression of P-gp, MRP1, MRP2, BCRP, LRP, caveolin-1, PKC-${\alpha}$, Phospho-ERK1/2 and Phospho-JNK protein was significantly up-regulated, while Akt and p38 MARK protein expression was not changed in A2780/Taxol cells. Conclusion: The A2780/Taxol cell line is an ideal model to investigate the mechanism of muti-drug resistance related to overexpression of drug-resistance associated proteins and activation of the PKC-${\alpha}/ERK$ (JNK) signaling pathway.

• Journal of Microbiology and Biotechnology
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• 제2권2호
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• pp.85-91
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• 1992

The intestinal microflora of humans is an extraordinarily complex mixture of microorganisms, the majority of which are anaerobic microorganisms. The distribution of amylolytic microorganisms in the human large intestinal tract was investigated in various individuals of differing ages using anaerobic culture techniques. A large percentage of the amylolytic microorganisms present belonged to the Genus Bifidobacteria. The number of Bifidobacteria increased significantly at two years of age. Adults and children above 2 years old carried about $0.8{\times}10^9-2.0{\times}10^{10}$ colony forming units (CFU/gram) of amylolytic Bifidobacteria. Among these amylolytic Bifidobacteria, Int-57 was chosen for further studies. Between 65% and 85% of the amylase produced was secreted and the remaining amylase was bound to the cell wall facing the outside. Amylase production could be induced by starch in a stable form. When cells were grown on maltose or glucose, amylase production was much lower than on starch and amylase activity disappeared after 24 hours growth on these media. Partially purified enzymes showed optimum activity at a temperature of $50^{\circ}C$ and at an optimum pH of 5.5, respectively. Heat treatment at $70^{\circ}C$ for 30 minutes almost completely inactivated amylase. The hydrolysis products of starch were mainly maltose and maltotriose. Soluble starch, amylose, amylopectin, and $\gamma$-cyclodextrin($\gamma$-CD) were easily hydrolyzed. The rate of hydrolysis of $\alpha$-CD and $\beta$-CD was slower than that of $\gamma$-CD. Carboxymethyl cellulose, $\beta$-1, 3-glucan and inulin were not hydrolyzed.