• Korean Chemical Engineering Research
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• 제46권4호
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• pp.739-746
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• 2008

반응증류 공정은 전형적인 반응공정과 증류공정을 통합하여 증류탑에서 반응과 동시에 분리를 수행하는 공정이다. 반응증류 공정의 가장 큰 장점은 반응 전환율의 제약과 공비점으로 인한 제약을 효율적으로 극복할 수 있다는 데 있다. 본 연구에서는 에스테르화반응으로 얻어지는 대표적인 물질인 메틸 아세테이트를 합성, 생산하는 연속 반응증류 공정의 상세한 수학적 모델을 구성하여 동적 모사 및 동적 최적화를 수행하였다. 상평형을 가정한 평형단 모델에 반응속도 식을 적용하여 분리와 반응이 함께 일어나는 증류탑과 재비기 및 응축기를 수학적 모델로 구성하여 동적모사를 수행하여 실제 공정이 운전되는 시나리오대로 공정전체를 모사함으로써 공정 개시부터의 공정의 동적 특성을 살펴보았다. 이 동적 모델과 연계되어, 반응증류 공정으로 얻어지는 메틸 아세테이트의 순도를 목적함수로 하는 최적화 문제를 구성하여 그 결과로 최적의 원료주입 분율 및 재비기의 열량 및 환류비 등을 구할 수 있었다. 또한 여기서 얻어진 운전 변수의 값을 변화시킬 때 반응 전환율의 변화를 살펴봄으로써, 최적화 문제의 해로 구해진 운전 변수의 값의 타당성을 증명하였다.

• Bulletin of the Korean Chemical Society
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• 제28권10호
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• pp.1651-1655
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• 2007

Rod-like polymerizable LC molecules having two different reactive groups, i.e. acryl and diacetylene groups were prepared. 4-Hydroxyphenyldiacetylenes were synthesized by the coupling reaction of 1-bromoalkynes with 4-ethynylphenol and then reacted with 4-(6-acryloyloxyalkyloxy)benzoic acid to give polymerizable LC molecules 4a-d. The mesomorphic properties of compounds 4a-d were investigated by differential scanning calorimetry, polarized optical microscopy and X-ray diffractometry. Compounds 4a-c exhibited smectic and nematic phases, but compound 4d having a longest alkyl tail among the series formed only a smectic phase. Photopolymerizability of acryl and diacetylene groups was investigated by IR spectroscopy. An anisotropic polymer film could be prepared by selective polymerization of acryl groups with 365 nm UV light in the presence of a photoinitiator (2,2-dimethoxy-2-phenylacetophenone). The subsequent reaction of diacetylene groups with 254 nm UV light disrupted the anisotropic structure, suggesting that these LC molecules could be used for imaging on the film.

• IMMUNE NETWORK
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• 제5권1호
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• pp.30-35
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• 2005

Background: p38 and extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) signaling are thought to have critical role in lipopolysaccharide (LPS)-induced immune response but the molecular mechanism underlying the induction of these signaling are not clear. Methods: Specific inhibitors for p38, SB203580, and for ERK, PD98059 were used. Cells were stimulated by LPS with or without specific MAPK inhibitors. Results: LPS activated inducible nitric oxide synthase (iNOS), subsequent NO productions, and pro-inflammatory cytokine gene expressions (TNF-${\alpha}$, IL-$1{\beta}$, IL-6, and IL-12). Treatment of both SB203580 and PD98059 decreased LPS-induced NO productions. Concomitant decreases in the expression of iNOS mRNA and protein were detected. SB203580 and PD98059 decreased LPS-induced gene expression of IL-$1{\beta}$ and IL-6. SB203580 increased LPS-induced expression of TNF-${\alpha}$ and IL-12, and reactive oxygen species production, but PD98059 had no effect. Conclusion: These results indicate that both p38 and ERK pathways are involved in LPS-stimulated NO synthesis, and expression of IL-$1{\beta}$ and IL-6. p38 signaling pathways are involved in LPS-induced TNF-${\alpha}$ and IL-12, and reactive oxygen species plays an important role in these signaling in macrophage.

• Journal of Microbiology and Biotechnology
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• 제19권3호
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• pp.299-306
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• 2009

Dissolved oxygen (DO) has a significant effect on the molecular weight of hyaluronic acid (HA) during the fermentation of Streptococcus zooepidemicus. Therefore, to further investigate the effect of DO on the yield and molecular weight of HA, this study compared the metabolic flux distribution of S. zooepidemicus under aerobic conditions at various DO levels. The metabolic flux analysis demonstrated that the HA synthesis pathway, considered a dependent network, was little affected by the DO level. In contrast, the fluxes of lactate and acetate were greatly influenced, and more ATP was generated concomitant with acetate at a high DO level. Furthermore, the has gene expression and HA synthase activity were both repressed under anaerobic conditions, yet not obviously affected under aerobic conditions at various DO levels. Therefore, it was concluded that the HA molecular weight would seem to depend on the concomitant effect of the generation of ATP and reactive oxygen species. It is expected that this work will contribute to a better understanding of the effect of the DO level on the mechanism of the elongation of HA chains.

• 한국분말재료학회지
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• 제4권4호
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• pp.283-290
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• 1997

$Ti_5Si_3$ intermetallics containing 0-6 wt% of Cu were made by reactive sintering (RS) under vacuum using elemental powder mixtures (Process 1), electro-pressure sintering (EPS) using RS'ed materials (Process2), and EPS using elemental powder mixtures (Process 3). Relatively low dense titanium silicides were gained by process 1, in which porosity decreased with increasing Cu content. For example, porosity changed from 42 to 19.4% with the increase in Cu content from 0 to 6 wt%, indicating that Cu is a useful sintering aid. The titanium silicides fabricated by Process 2 had a higher density than those by Process 1 at given composition, and porosity decreased with increasing Cu content. For example, porosity decreased from 38 to 6.8% with the change in Cu content from 0 to 6 wt%. A high dense titanium silicides were obtained by Process 3. In this Process, porosity decreased a little by Cu addition, and was almost insensitive to Cu content. Namely, about 9 or 7% of porosity was shown in 0 or 1-6 wt% Cu containing silicides, respectively. The hardeness increased by Cu addition, and was not changed markedly with Cu content for the silicides fabricated by Process 3. This tendency was considered to be resulted from porosity, hardening of grain interior by Cu addition, and softening of grain boundary by Cu-base segregates. All these results suggested that EPS using elemental powder mixtures (Process 3) is an effective processing method to achieve satisfactorily dense titanium silicides.

• 한국응용과학기술학회지
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• 제13권2호
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• pp.21-28
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• 1996

Diazotization of STA synthesized by the indirect diazotization method. The effect of catalyst and agitation (rpm) about STA and H-acid reaction were examined and the optimum conditions were investigated experimentally. The yields and characteristics of $1^{.st}$ coupling and diazotization synthesis were identified by HPLC and FT-IR analysis. $1^{.st}$ condensation of CNC and mPDSA were synthesized at $5^{\circ}C$ and pH=6.5. The conditions of alkaly coupling of H-acid were synthesized at $5^{\circ}C$ and pH=8. The condensation of products was identified by U. V. analysis. From this results, It was obtained to reactive dyestuffs of bi-functional reactivity with high fastness and high adsorption.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.1-2
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• 2003

While aromatic polyimides and polyamides have found widespread use as high performance polymers, the present work addressed the need for organosoluble materials through the use of a hyperbranching scheme. The $AB_2$ monomers were prepared. The $AB_2$ monomers were then polymerized via aromatic fluoride-displacement and Yamazaki reactions to afford the corresponding hydroxyl-terminated hyperbranched polyimides (HT-PAEKI) and amine-terminated hyperbranched polyamides, respectively. HT-FAEKI was then functionalized with allyl and propargyl bromides as well as epichlorohydrin to afford allyl-terminated AT-PAEKI, propargyl-terminated PT-PAEKI, and epoxy (glycidyl)-terminated ET-PAEKI, in that order. All hyperbranched poly(ether-ketone-imide)s were soluble in common organic solvents. AT-PAEKI was blended with a bisphenol-A-based bismaleimide (BFA-BMI) in various weight ratios. Thermal, rheological, and mechanical properties of these blend systems were evaluated. Two characteristic hyperbranched polyamides, which the one has para-electron donating groups to the surface amine groups and the other has para-electron withdrawing groups to the surface amine groups, were selected to compare BMI curing behaviors. The electron rich polymer displayed ordinary Michael addition type exothermic reaction, while electron deficient polymer did display unusual curing behaviors. Based on analytical data, the later system provided the strong evidences to support room temperature curing of BMI by reactive intermediates instead of reactive primary amine groups on the macromolecule surface.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2375-2380
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• 2014

In the present investigation, a series of some novel 1,3-diaryl/heteroarylprop-2-en-1-one derivatives (3a-j) have been synthesized and evaluated for their in vitro cytotoxicity against three cancer cell lines, two hepatocarcinoma cell lines HUH-7, Hep-3b and one leukemia cancer cell line MOLT-4. Based on these results, structure-activity relationship (SAR) was studied on modification of $R^1$ and $R^2$ to identify the compound with maximum potency. Amongst the compounds, 3b and 3d strongly inhibited the growth of Hep-3b and MOLT-4 cells with $IC_{50}$ value of 3.39 and $3.63{\mu}M$ respectively. The results obtained from the inhibitory study had further been supported by the reactive oxygen species (ROS) measurement using flow cytometry in MOLT-4 cells. These observations collectively reveal that compounds comprising 1,3-diarylprop-2-en-1-one framework with pyrazole ring at position-3 and heteroaryl/aryl substituents at position-1 can be used as promising anticancer agents.

• 한국미생물·생명공학회지
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• 제47권1호
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• pp.43-53
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• 2019

The anticancer activity of guava (Psidium guajava L.) leaf extract (GLE) occurs via the induction of apoptosis in cancer cells. However, the mechanism behind GLE-induced apoptosis in the human hepatocellular carcinoma cell line HepG2 remains unclear. In the present study, we investigated the apoptotic effects and mechanism of action of GLE in cultured HepG2 cells. The results showed that GLE induced reactive oxygen species (ROS) synthesis and disrupted the mitochondrial membrane potential (${\Delta}{\Psi}m$). Moreover, GLE increased the expression of apoptotic pathway proteins, such as the cleaved forms of caspase-3, -8, and -9; the translocation of Bax and cytochrome c (cyt-c) from the mitochondria to the cytosol; and the downregulation of Bcl-2. In addition, p53 protein expression was increased upon GLE treatment. These observations indicate that the GLE-induced apoptosis in HepG2 cells is mediated by mitochondrial ROS generation, followed by caspase activation and cyt-c release, suggesting that GLE may be a promising candidate for the development of novel drugs for the treatment of liver cancers.

• 한국동물생명공학회지
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• 제36권1호
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• pp.2-8
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• 2021

Dimethachlor is a synthetic herbicide, belonging to the chloroacetanilide group, that inhibits the undesirable growth of weeds via the suppression of very long-chain fatty acid synthesis. Although dimethachlor has been shown to run off from agricultural fields into aquatic ecosystems, the toxicity of dimethachlor on aquatic invertebrates and vertebrates is unknown. In our study, we assessed the toxicity of dimethachlor on developing zebrafish embryos by analyzing viability, hatching ability, and phenotypic changes. Embryonic viability decreased from 48 h post-fertilization (hpf) at the highest concentration of dimethachlor. Decreased hatching ratio, shortened body length, and pathological changes in the eye, heart, and yolk sac were observed at sub-lethal concentrations. Additionally, dimethachlor increased the number of apoptotic cells and level of reactive oxygen species 120 hpf. Our results indicate that dimethachlor may act as an anti-developmental toxicant when accumulated in an aquatic environment.