• Korean Membrane Journal
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• 제6권1호
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• pp.44-54
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• 2004

Organic-inorganic composite membranes based on sulfonated poly(phthalazinone ether sulfone) (sPPES)/silica hybrid were prepared using the sol-gel process under acidic conditions. The sulfonation of PPES with concentrated sulfuric acid as sulfonation agent was carried out to prepare proton exchange membrane material. The behaviors of the proton conductivity and methanol permeability are depended on the sulfonation time (5-100 hr). The hybrid membranes composed of highly sulfonated PPES (IEC value: 1.42 meq./g) and silica were fabricated from different silica content (5-20 wt%) in order to achieve desirable proton conductivity and methanol permeability demanded for fuel cell applications. The silica particles within membranes were used for the purpose of blocking excessive methanol cross-over and for forming the path way to transport of the proton due to absorbing water molecules with ≡SiOH on silica. The presence of silica particles in the organic polymer matrix results in hybrid membranes with reduced methanol permeability and improved proton conductivity.

• 대한화학회지
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• 제17권2호
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• pp.126-129
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• 1973

회전백금전극을 지시전극으로하고 수은-요오드화수은(II)을 기준전극으로하여 암모니아수용액에서 2.5-dimercapto-1,3,4-thiadiazole에 의한 은의 전류적정법을 연구하였다. 암모니아수용액에서 EDTA를 은폐제로 사용하여 여러 가지 이온들의 존재 하에 미량의 은을 직접 적정할 수가 있었으며 백금과 금 이온만이 방해하였다. 이 방법으로 미량의 은을 상대 오차 ${\pm}3{\%}$이내 정량할 수 있다.

• 한국재료학회지
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• 제3권5호
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• pp.529-537
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• 1993

TiC 입자를 강화재로 한 AI금속기지 복합재료를 액상교반법으로 제조하는데 따른 제조조건과 물성특성과의 관계를 조사하였다. TiC 입자는 중량비 10%를 첨가하였으며, 젖음성을 향상시키기 위하여 1.5wt%의 Mg을 첨가하였다. TiC입자 첨가에 의하여 내마모 특성, 인장강도, 경도 등이 증가 되었으나 과도한 교반은 기계적 특성을 저하시켰다. 본 실험조건에서 교반 속도의 최적조건은 500rpm이었다. Wetting agent로서 첨가한 Mg은 기지에 고루 분산하였다.

• 한국축산식품학회지
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• 제36권6호
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• pp.744-751
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• 2016

The objective of this study was to investigate the effects of partial beef fat replacement (0, 30, 50, 100%) with gelled emulsion (GE) prepared with olive oil on functional and quality properties of model system meat emulsion (MSME). GE consisted of inulin and gelatin as gelling agent and characteristics of gelled and model system meat emulsions were investigated. GE showed good initial stability against centrifugation forces and thermal stability at different temperatures. GE addition decreased the pH with respect to increase in GE concentration. Addition of GE increased lightness and yellowness but reduced redness compared to control samples. The results of the study showed that partial replacement of beef fat with GE could be used for improving cooking yield without negative effects on water holding capacity and emulsion stability compared to C samples when replacement level is up to 50%. The presence of GE significantly affected textural behaviors of samples (p<0.05). In conclusion, our study showed that GE have promising impacts on developing healthier meat product formulations besides improving technological characteristics.

• Journal of Pharmaceutical Investigation
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• 제36권5호
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• pp.315-320
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• 2006

Silymarin showed P-glycoprptein(P-gp) inhibitory activity as much as verapamil, a well-known P-gp inhibitor, by decreasing $IC_{50}$ value of daunomycin(DNM)($16.0{\pm}0.7{\mu}M$), increasing the DNM accumulation($224.9{\pm}3.2%$), and decreasing DNM efflux($58.5{\pm}6.7%$), concurrently. In this study, we clarified the mechanism of action of silymarin for P-gp inhibitory function. First, silymarin may bind to the ATP-binding site and thus, prevent ATP hydrolysis. Second, the P-gp inhibitory activity of silymarin is not related to changing the cellular P-gp level. Third, the cytotoxicity of silymarin was increased in the presence of verapamil, reflecting that silymarin is a competent P-gp substrate against verapamil in the P-gp-overexpressed adriamycin-resistant MCF-7 breast cancer(MCF-7/ADR) cells. Conclusively, silymarin had the P-gp inhibitory activity through the action of competent binding to the P-gp substrate-binding site. Therefore, silymarin can be a good candidate for safe and effective MDR reversing agent in clinical chemotherapy by administering concomitantly with anticancer drugs.

• The Korean Journal of Physiology and Pharmacology
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• 제19권5호
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• pp.413-420
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• 2015

Dexmedetomidine is a sedative and analgesic agent that exerts its effects by selectively agonizing ${\alpha}2$ adrenoceptor. Histamine is a pathophysiological amine that activates G protein-coupled receptors, to induce $Ca^{2+}$ release and subsequent mediate or progress inflammation. Dexmedetomidine has been reported to exert inhibitory effect on inflammation both in vitro and in vivo studies. However, it is unclear that dexmedetomidine modulates histamine-induced signaling and pro-inflammatory cytokine expression. This study was carried out to assess how dexmedetomidine modulates histamine-induced $Ca^{2+}$ signaling and regulates the expression of pro-inflammatory cytokine genes encoding interleukin (IL)-6 and -8. To elucidate the regulatory role of dexmedetomidine on histamine signaling, HeLa cells and human salivary gland cells which are endogenously expressed histamine 1 receptor were used. Dexmedetomidine itself did not trigger $Ca^{2+}$ peak or increase in the presence or absence of external $Ca^{2+}$. When cells were stimulated with histamine after pretreatment with various concentrations of dexmedetomidine, we observed inhibited histamine-induced $[Ca^{2+}]_i$ signal in both cell types. Histamine stimulated IL-6 mRNA expression not IL-8 mRNA within 2 hrs, however this effect was attenuated by dexmedetomidine. Collectively, these findings suggest that dexmedetomidine modulates histamine-induced $Ca^{2+}$ signaling and IL-6 expression and will be useful for understanding the antagonistic properties of dexmedetomidine on histamine-induced signaling beyond its sedative effect.

• Journal of Microbiology and Biotechnology
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• 제24권7호
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• pp.921-924
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• 2014

C31G is a potent antimicrobial agent and can disrupt the microbial membrane by the alkyl portion of the molecule. The objective of this study was to evaluate the virucidal effectiveness of C31G and mouthrinse containing C31G (Sense-Time) on seasonal influenza viruses. Evaluation of the virucidal activity against influenza viruses was performed with end-point titration in 10-day-old chicken embryos and Madin-Darby canine kidney cells. In vitro studies demonstrated that C31G and Sense-Time inhibited the growth of seasonal influenza viruses even in the presence of 5% organic material. Gargling with C31G or Sense-Time would enhance oropharyngeal hygiene, which would be helpful for reducing influenza transmission.

• Journal of Microbiology and Biotechnology
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• 제28권8호
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• pp.1299-1309
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• 2018

We previously reported on lactophoricin (LPcin), a cationic ${\alpha}-helical$ antimicrobial peptide derived from bovine milk, which has antimicrobial effects on Candida albicans as well as Gram-positive and Gram-negative bacteria. In this study, we designed the LPcin-YK3 peptide, a shorter analog of LPcin, and investigated its antimicrobial activity. This peptide, consisting of 15 amino acids with + 3 net charges, was an effective antimicrobial agent against the on the Gram-positive strain, Staphylococcus aureus (MIC: $0.62{\mu}g/ml$). In addition, the hemolytic activity assay revealed that the peptide was not toxic to mouse and human erythrocytes up to $40{\mu}g/ml$. We also used circular dichroism spectroscopy to confirm that peptide in the presence of lipid has ${\alpha}-helical$ structures and later provide an overview of the relationship between each structure and antimicrobial activity. This peptide is a member of a new class of antimicrobial agents that could potentially overcome the problem of bacterial resistance caused by overuse of conventional antibiotics. Therefore, it could be used as a therapeutic or natural additive, particularly in the cosmetics industry.

• 대한화학회지
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• 제34권6호
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• pp.534-538
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• 1990

H$_2$O을 용매로 하여 헤테로고리 염기인 이소퀴놀린과 CrO$_3$를 반응시켜 Cr(Ⅵ)화합물인 [$C_9H_7$NH]$_2Cr_2O_7$을 얻었다. 이 화합물은 비흡수성이면서 물에 잘 녹았다. 그리고 원소분석, 적외선 분광법으로 이 화합물의 구조가 [$C_9H_7$NH]$_2Cr_2O_7$임을 확인하였다. 또한, 이 화합물이 여러 가지 알코올을 알데히드나 케톤으로 전환시킬 수 있는 산화제로 작용하는가를 알아보기 위하여 알릴, 일차, 이차 알코올을 각각 산화반응에 이용한 결과 알코올들에 대해 효율적인 산화제로 작용하였다.

• Carbon letters
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• 제21권
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• pp.1-7
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• 2017

The effects of ammonia-treated graphene oxide (GO) on composites based on epoxy resin were investigated. Ammonia solutions of different concentrations (14-28%) were used to modify GO. Nitrogen functional groups were introduced on the GO surfaces without significant structural changes. The ammonia-treated GO-based epoxy composites exhibited interesting changes in their mechanical properties related to the presence of nitrogen functional groups, particularly amine ($C-NH_2$) groups on the GO surfaces. The highest tensile and impact strength values were 42.1 MPa and 12.3 J/m, respectively, which were observed in an epoxy composite prepared with GO treated with a 28% ammonia solution. This improved tensile strength was 2.2 and 1.3 times higher than those of the neat epoxy and the non-treated GO-based epoxy composite, respectively. The amine groups on the GO ensure its participation in the cross-linking reaction of the epoxy resin under amine curing agent condition and enhance its interfacial bonding with the epoxy resin.