Thermal cutting processes that can be applied to dismantling nuclear power plants include oxygen cutting, plasma cutting, and laser cutting. According to the global trend, research projects are being carried out in various countries to upgrade laser cutting, and many studies are also being conducted in Korea with plans to apply laser cutting processes when dismantling nuclear power plants. However, with the current technology level of the laser cutting process, the maximum thickness that can be cut is limited to 250 mm. Therefore, in this study, a laser-oxygen hybrid cutting process was implemented by adding a laser heat source to the oxygen cutting process that can cut carbon steel with a thickness of 250 mm or more (RV, beam, column, beam, etc.) when dismantling the nuclear power plant. This has the advantage of improving the cutting speed and reducing the cutting width Kerf compared to conventional oxygen cutting. In this research, the laser-oxygen hybrid cutting process consisted of laser cutting to which Raycus’ 8 kW Fiber Laser power source was applied and oxygen cutting to which hydrogen was applied with Fuel Gas. The oxygen torch was placed perpendicular to the test piece, and the laser head was irradiated by tilting 35° to 70°. The effects of cutting directions on quality and performance were studied, and cutting paths were selected by comparing cutting results. Thereafter, it was confirmed that there is an optimal laser output power according to the cutting thickness by studying the effect on the cutting surface quality by changing only the laser output power under the same cutting conditions. The results of this study are expected to be helpful in the remote cutting process using laser-oxygen hybrid cutting when dismantling domestic nuclear power plants in the future.

As the decommissioning of domestic nuclear power plants (Gori Unit 1 and Wolseong Unit 1) becomes more visible, many research projects are being conducted to safely and economically decommissioning of domestic nuclear power plants (NPPs). After permanent shutdown, decommissioning of NNPs proceeds through decontamination, cutting of main equipment, waste disposal and site restoration stages. And various technologies are applied at each stage. In particular, remote cutting of neutron induced structures (RV, RVI, etc.) is a technology used in developed countries in the cutting stage, and remote cutting has been evaluated as a core technology for minimizing workers’ radiation exposure. Generally, remote cutting technologies are divided into mechanical/thermal/electrical cutting. Among various thermal cutting technologies, plasma arc cutting (PAC) is more economical and easily to remote control than other cutting technologies, and is also effective in cutting STS304 plates. PAC is a thermal cutting technology that melts the base material at the cutting area with a plasma arc heat source and removes melted material by blowing it out with cutting gas. The cutting quality depends on the stand-off distance and power (current), material thickness, cutting speed, etc., while double arcing will occur if the cutting conditions are not suitable. A monitoring system that can confirm double arcing during remote cutting is necessary because double arcing can reduce cutting quality, increase secondary waste (increase kerf and aerosol), and cause non-cutting. In this study, we used an ultrahigh-speed camera equipped with a band-pass filter to capture clear arc shapes, and measured voltage waveforms with a data acquisition system. We studied a monitoring method that can confirm the occurrence of double arcing by synchronizing the obtained arc shape and voltage waveform, and the effects of double arcing on the STS304 plates. The results of this study are expected to be helpful in the development of the remote cutting process using plasma arc cutting when decommissioning of domestic NPPs.

Histone H4 is a protein subunit of nucleosomes in eukaryotes and play crucial roles in DNA package and in regulation of gene expression by covalent modification. A viral histone H4 is encoded in a polydnavirus called Cotesia plutellae bracovirus (CpBV). The viral H4 (CpBV-H4) is highly homologous with other H4 proteins except 38 extended residues in N terminus. Its expression alters insect gene expression and suppresses immune and development. In this study, CpBV-H4 was expressed in a natural host, Plutella xylostella, and its suppressive activity on host gene expression was detected by suppressive subtractive hybridization (SSH) technique. SSH targets, of which expressions were down-regulated by CpBV-H4, were read by 454 pyrosequencing and annotated using the published P. xylostella whole genome. Resulting targets were assigned to most GO functional categories. Two chromatin remodeling factors were included in the SSH targets. Lysine demethylase (Px-KDM) of P. xylostella was highly expressed during entire larval period in all tested tissues. However, the suppression of Px-KDM expression by a specific RNA interference (RNAi) did not affect immune response, but significantly impaired the larval development. SWI/SNF of P. xylostella (Px-SWI/SNF) was expressed in all developmental stages. Its RNAi did not affect larval development, but led to significant alteration in adult metamorphosis. CpBV-H4 suppressed expressions of both Px-KDM and Px-SWI/SNF, but its truncated mutant lacking in the extended N-terminal tail did not. These results suggest that the developmental alteration in P. xylostella parasitized by C. plutellae can be caused by an epigenetic control of CpBV-H4 against chromatin remodeling factors.

An oxidative fumigant is potent to kill insect pests infesting stored grains. Its oxidative activity generates reactive oxygen species (ROS), which has been considered to be a main insecticidal factor. Furthermore, the oxidative fumigant has cytotoxic effect to insect cell lines, but the cytotoxicity is abrogated by antioxidant treatment. This study aimed to extend the usefulness of the oxidative fumigant in terms of medical purpose against cancer cells. Five cancer cell lines HCT 116 (human colorectal), Lovo (human colorectal), SW480 (human colorectal), MDA-MB-231 (human breast), and MCF-7 (human breast) were tested to determine their susceptibility to the oxidative fumigant with reference to two insect cell lines (Sf9 and Hi-Five). All cancer cell lines were highly susceptible to the oxidative fumigant, compared to the insect cell lines. Interestingly, basal ROS levels of the cancer cell lines were much higher than the insect cell lines. Furthermore, the oxidative fumigant significantly increased the ROS levels in the cancer cells. Treatment of vitamin E as an antioxidant mitigated the cytotoxicity of the oxidative fumigant. Thus, the high susceptibility of cancer cells to the oxidative fumigant may be induced by their high inducible ROS production. This study also investigated the antiviral activity of the oxidative fumigant against insect and plant viruses. The oxidative fumigant significantly inactivated a baculovirus (dsDNA virus) by inhibiting polyhedral production in Sf9 cells. It also inactivated tobacco mosaic virus (ssRNA virus) by suppressing phytopathogenicity. These results support a broad effect of the oxidative fumigant, which can be applied to agricultural and medical purposes.

Insect immunity is innate and consists of cellular and humoral immune responses. Cellular immune response usually requires hemocyte-spreading behavior, which is accompanied by cytoskeletal rearrangement. A glycolytic enzyme, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), catalyzes an oxidation reaction of glyceraldehyde-3-phosphate to 1,3-biphosphoglycerate in the cytosol. Another function of GAPDH in mammalian cell is to bind C-terminal α-tubulin to facilitate cytoskeletal arrangement. An immunoprecipitation (IP) of viral protein, CpBV-CrV1, against hemocyte protein lysate revealed that CpBV-CrV1 binds to GAPDH, identified by MALDI-TOF analysis. RNA interference (RNAi) of GAPDH significantly suppressed cellular immune response, but neither RNAi of hexokinase nor aldolase suppressed the cellular immune response. A common molecular motif of CpBV-CrV1 and a-tubulin at C-terminal region supported the IP analysis. To test the role of α-tubulin motif in CpBV-CrV1, point mutations of CpBV-CrV1 were applied and resulted in loss of the biological activity of CpBV-CrV1. Furthermore, an immunofluorescence assay indicates CpBV-CrV1 colocalized with a-tubulin in hemocytes collected from Plutella xylostella parasitized by Cotesia plutellae possessing C. plutellae bracovirus (CpBV). This result suggests that GAPDH plays a critical role in hemocyte-spreading behavior during immune challenge, and it is a molecular target of the pathogenic virus.

Cotesia plutellae, an endoparasitoids braconid wasp, possesses a polydnaviruses (PDVs) called Cotesia plutellae bracovirus (CpBV) that encodes viral histone H4 (= CpBV-H4). This viral histone H4 shares high sequence homology (82.5%) with host`s H4 of P.xylostella, except an extended N-terminal tail consisting of 38 amino acid residues with nine lysines. Its extended N-terminal tail has been postulated to play a crucial role in suppressing host immunity, growth and development-associated genes, presumably through an epigenetic control mechanism. A suppression subtractive hybridization (SSH) analysis was analyzed in transcriptome by short-read sequencing technology and provided several target and non-target genes of a viral histone H4. In this study, we analyzed the effect CpBV-H4 on the expression of two target genes: Lysine-specific demethylase (KDM) and Serine proteinase inhibitor (Serpins). Transient expression of CpBV-H4 into non parasitized P. xylostella was performed by microinjection of a recombinant expression vector, and showed the expression up to 70 h. Under this transient expression condition, we analyzed the effect of CpBV-H4 on the expression of target genes by RT-PCR at different time points. Interestingly, the CpBV-H4 significantly inhibited the expression of these target genes, while the truncated CpBV-H4 deleting the N-terminal tail did not show this inhibitory effect. This study also showed that the viral histone H4 suppresses expressions of lysine-specific demethylase and serine proteinase inhibitor (Serpin2) to inhibit host growth and development.

A novel oxidant fumigation (NOF) has been considered as alternative fumigant to replace methyl bromide that is a serious ozone depleter. Its high oxidative activity has been used as a bleaching or sanitary agent. Though some reports an insecticidal activity of NOF, its insecticidal action is yet to be understood. This study was conducted with an observation of an insecticidal activity of NOF against Plodia interpunctella, which is a stored grain insect pest. Cytotoxicity test was performed by using MTT assay, NOF gave a significant cytotoxicity on both Sf9 cells and HiFive insect cell lines. Sf9 cells were higher susceptible (IC50 = 43.2+ 3.5 ppm) to chloride dioxide than HiFive cells (IC50 = 174.6 + 5.9 ppm). To understand its cytotoxic effect on P. interpunctella, the larval hemocytes were incubated in vitro with different doses of NOF for 40 min at room temperature. In a dose-dependent manner, NOF gave a significant toxicity to the hemocytes. When NOF was injected to larvae of P. interpunctella, it significantly reduced total hemocyte counts compared to control. These results indicate that NOF has cytotoxic effect against hemocytes of P. interpunctella. This hemolytic activity of NOF can be regarded as a lethal factor to the stored grain insect pest.

Polydnavirus are well known to interfere with the host endocrine system, causing immune suppression and other physiological disorders. The Cotesia rubculla polydnavirus gene products, CrV1, are known to be a potent immunosuppressive agent. CrV1 protein express within 12 h after viral infection at oviposition during deposition of parasitoid eggs and are mainly secreted in to host hemocyte, where it functions like phagocytosis and cell spreading. This study identified its homolog in CpBV and analyzed its molecular characteristics motif called “coiled-coil. A point mutation of Alanine to Proline of CpBV-CrV1 could lose the coiled-coil motif from in silico assay. The coiled type CpBV-CrV1 could inhibit host cellular immunity, however, interestingly the mutant CpBV-CrV1 lacking in coiled-coil motif completely lost the immunosuppressive activity. This study suggests that the coiled-coil motif is functional to inhibit host cellular immune responses. RNA interference against CrV1 significantly loses the inhibitory activity and thus further supporting the immunosuppressive activity of CrV1. In this study we also have analyzed the localization of CrV1 by transient transfection in HiFive Cell lines by in situ hybridization.

A viral histone H4 (=CpBV-H4) is encoded in a polydnavirus, Cotesia plutellae bracovirus, and symbiotically associated with an endoparasitoid wasp, C. plutellae. It has an extended N-terminal tail consisting of 38 amino acid residues, compared to the host H4 and this extended N-terminal tail has been postulated to play a crucial role in an epigenetic control of gene expression. The (SSH) suppression subtractive hybridization analysis was analyzed in transcriptome by short-read sequencing technology. The SSH analysis provided several target and nontarget genes of a viral histone H4. In this study, we analyzed the effect CpBV-H4 on the expression of two target genes serpins and histone lysine N-methyl transferase. Transient expression of CpBV-H4 by microinjecting recombinant expression vector to non parasitized larvae of Plutella xylostella showed that it was expressed up to 70 h. Under this transient expression condition, we analyzed the effect of CpBV-H4 on the expression of target genes by RT-PCR at different time points. Interestingly, the CpBV-H4 significantly inhibited the expression of target genes after 44 h, while the truncated CpBV-H4 deleting the N-terminal tail did not show the inhibitory activity.