• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.5
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• pp.925-938
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• 2010

Depending on network conditions, a communication network could be overloaded when media are transmitted. Research has been carried out to lessen network overloading, such as by filtering, load distribution, frame dropping, and other methods. Among these methods, one of the most effective is frame dropping, which reduces specified video frames for bandwidth diminution. In frame dropping, B-frames are dropped and then I- and P-frames are dropped, based on the dependency among the frames. This paper proposes a scheme for protecting copyrights by encryption, when frame dropping is applied to reduce the bandwidth of media based on the MPEG-4 file format. We designed two kinds of frame dropping: the first stores and then sends the dropped files and the other drops frames in real time when transmitting. We designed three kinds of encryption methods using the DES algorithm to encrypt MPEG-4 data: macro block encryption in I-VOP, macro block and motion vector encryption in P-VOP, and macro block and motion vector encryption in I-, P-VOP. Based on these three methods, we implemented a digital rights management solution for MPEG-4 data streaming. We compared the results of dropping, encryption, decryption, and the quality of the video sequences to select an optimal method, and found that there was no noticeable difference between the video sequences recovered after frame dropping and the ones recovered without frame dropping. The best performance in the encryption and decryption of frames was obtained when we applied the macro block and motion vector encryption in I-, P-VOP.

• Korean Journal of Microbiology
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• v.28 no.1
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• pp.41-46
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• 1990

A bacterial isolate of DJ-12 capable of degrading 4-chlorobenzoic acid (4CBA) as well as 4-chlorobiphenyl (4CB) was used in this study. Its biodegradability of 4CBA was tested and the location of the genes coding for degradation of 4CBA was investigated by the nethod of in vivo cloning. The genes were found to be existed in the plasmid of pDJ121 which is about 65kb in size and which has 9, 11, 10, and 19 restriction sites for EcoRI, HindIII, SalI, and PstI, respectively. The hybrid plasmid of pDK450 was constructed by ligation of the EcoRI fragments of pDJ121 with pKT230 as a vector. In the recombinant cells selected through transformation of the hybrid vector into Pseudomonas putida KT2440, the 4CBA-degrading genes of DJ-12 were proved to be cloned and expressed in the Pseudomonas sp.

• Molecules and Cells
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• v.46 no.4
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• pp.209-218
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• 2023

In induced pluripotent stem cells (iPSCs), pluripotency is induced artificially by introducing the transcription factors Oct4, Sox2, Klf4, and c-Myc. When a transgene is introduced using a viral vector, the transgene may be integrated into the host genome and cause a mutation and cancer. No integration occurs when an episomal vector is used, but this method has a limitation in that remnants of the virus or vector remain in the cell, which limits the use of such iPSCs in therapeutic applications. Chemical reprogramming, which relies on treatment with small-molecule compounds to induce pluripotency, can overcome this problem. In this method, reprogramming is induced according to the gene expression pattern of extra-embryonic endoderm (XEN) cells, which are used as an intermediate stage in pluripotency induction. Therefore, iPSCs can be induced only from established XEN cells. We induced XEN cells using small molecules that modulate a signaling pathway and affect epigenetic modifications, and devised a culture method which can produce homogeneous XEN cells. At least 4 passages were required to establish morphologically homogeneous chemically induced XEN (CiXEN) cells, whose properties were similar to those of XEN cells, as revealed through cellular and molecular characterization. Chemically iPSCs derived from CiXEN cells showed characteristics similar to those of mouse embryonic stem cells. Our results show that the homogeneity of CiXEN cells is critical for the efficient induction of pluripotency by chemicals.

• Korean Journal of Microbiology
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• v.24 no.2
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• pp.86-90
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• 1986

The DNA methylated by Hpa II methylase was not cleaved by Sma, I, Ava I and Nae I endonucleases. This experimental data could be interpreted as strong evidences that Sma I, Ava I and Nae I methylases which yet to be isolated would methylate on the inmost cytosine nucleotide within their hexameric recognition sequences. The facts that Sma I, Ava I and Nae I endonucleases can not cleave the DNA methylated by Hpa II methylase are the valuable informations for protecting DNAs upon cleavage reactions by Sma I, Ava I and NAe I endonucleases especially for cDNA insertion experiments into vector DNAs using Sma I, Ava I and Nae I oligonucleotide linkers. In the case of Xma I endonuclease, partially cleaved DNA fragments were observed although the reaction rate was greatly decreased. This result implies that the methylation site of Xma I methylase which yet to be isolated would not be the same as that of Hpa II methylase in Xma I sequence.

• Korean Journal of Mathematics
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• v.18 no.4
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• pp.387-394
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• 2010

In this paper, we study the generalized Randers change $^*L(x,y)=L(x,y)+b_i(x,y)y^i$ from the Brewald metric L and the h-vector $b_i$. And in search for a non-Berwald Landsberg metric, we obtain the conditions on $b_i(x,y)$ under which $^*L$ is a Landsberg metric.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.80-82
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• 1988

This paper proposed a new equivalent circuit and parameter estimation for I.M, which is different from T type and L type equivalent circuits. By using this circuit, we can analyze the torque of I.M, such as seperately exited D.C Motor, further more, we think that this equivalent circuit is effective to the vector control system for I.M.

• Korean Journal of Microbiology
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• v.40 no.4
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• pp.359-363
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• 2004

I investigated an effective way to generate a metagenomic library from DNA prepared from environental samples. The sizes of DNA extracted from environmental samples were usually in the range of 10 to 100 kbp as estimated from $0.4\%$ agarose gel electrophoresis. Because of this small size, a fosmid, rather than BAC, was chosen as a vector. It was found that, for the successful generation of metagenomic library, the selection of DNA with the sized of about 40 kbp was critical and, therefore, a simple agarose gel electrophoresis system was developed to select this size of DNA. By the procedure described in this report, I obtained metagenomic libraries containing 25,000 fosmid clones, which corresponded to 1,000 Mb of metagenomic DNA.

• Journal of The Korean Society of Grassland and Forage Science
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• v.18 no.1
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• pp.69-76
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• 1998

This study was conducted to construct of the transgenic plants wliich are resistant to oxidative stresses including ozone with B. mpestris cytosolic glutathione reductase cDNA using the binary vector system of Agrobacterium tumefaciens. The 1.8kb B. campestris cytosolic GR cDNA was subcloned into the unique Sma I site of the plant transformation vector pBKSI- I, downstream of the constitutive CaMV 35s promoter and upstream of the nos termination sequence, in place of the uidA (GUS) reporter gene. The resulting plant transformation vector, pBKS-GRI, was introduced into A. tumefaciens LBA4404 by two cycles of tkeze-thaw method. The B. nqus cotyledonary petioles were transformed by the Agrubaferium harboring pBKS-GRI. Transformed shoots were induced and selected on regeneration medium supplemented with kanarnycin. The shoot formation was increased remarkably by addition of Ag$NO_3$, in MS media. The transgenic plants were analyzed for the presence of the B. campestris GR gene by Southern blot analysis and it was confirmed that a foregin gene was stably integrated into the genomes of B. nqus plants.

• Journal of Microbiology and Biotechnology
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• v.15 no.3
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• pp.544-550
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• 2005

To develop a highly efficient mammalian expression vector, a series of vectors were constructed based on the murine cytomegalovirus (MCMV) immediate-early (IE) promoter and human ${\beta}$-globin second intron. The resulting MCMV promoter was several-fold stronger than the HCMV promoter in various mammalian cell lines, such as the NIH3T3, Neuro-2a, 293T, and HT1080 cell lines, and was only slightly weaker than the HCMV promoter in HeLa and CHO cells. The inclusion of the human ${\beta}$-globin second intron behind the MCMV promoter or HCMV promoter markedly enhanced the promoter activity in various mammalian cell lines, and the resultant MCMV/Glo-I expression system was stronger than the HCMV promoter from 4.7- to 11.2-fold in every cell line tested. Also, the MCMV/Glo-I promoter induced a higher level of the VSV-G protein in a transiently transfected 293T cell line, which is useful for the production of recombinant retrovirus and lentivirus vectors.

• Korean Journal of Microbiology
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• v.36 no.2
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• pp.112-118
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• 2000

A new gene encoding an acidophilic TEX>$\alpha$-amylase of Bacillus cil-culans KCTC3004 was cloned into Eschericlzia coli using pUC19 as a vector. The gene localized in the 5.8 kb PstI DNA fragment was expressed independently of its orientation in the cloning vector showing enzyme activity about 40 times greater than that produced by the original B, circulans The optimum pH and temperature of the cloned enzyme were pH 3.6 and 45^{\circ}C.$ respectively. The enzyme hydrolyzed starch to produce maltotriose and maltooligosaccharides. The SDS-PAGE and zymopram of the enzyme produced in E coli(p.4L850) indicated a molecular weight of 55,000.