• Title/Summary/Keyword: TEM Journal

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Antibacterial Activity and Probiotic Potential of Lactobacillus plantarum HKN01: A New Insight into the Morphological Changes of Antibacterial Compound-Treated Escherichia coli by Electron Microscopy

  • Sharafi, Hakimeh;Maleki, Hadi;Ahmadian, Gholamreza;Zahiri, Hossein Shahbani;Sajedinejad, Neda;Houshmand, Behzad;Vali, Hojatollah;Noghabi, Kambiz Akbari
    • Journal of Microbiology and Biotechnology
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    • v.23 no.2
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    • pp.225-236
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    • 2013
  • Among several bacteria examined, an antibacterial-producing Lactobacillus strain with probiotic characteristics was selected and identified based on 16S rRNA gene sequencing. Subsequent purification and mode of action of the antibacterial compounds on target cells including E. coli were investigated. Maximum production of the antibacterial compound was recorded at 18 h incubation at $30^{\circ}C$. Interestingly, antibacterial activity remained unchanged after heating at $121^{\circ}C$ for 45 min, 24 h storage in temperature range of $70^{\circ}C$ to room temperature, and 15 min exposure to UV light, and it was stable in the pH of range 2-10. The active compounds were inactivated by proteolytic enzymes, indicating their proteinaceous nature, and, therefore, referred to as bacteriocin-like inhibitory substances. Isolation and partial purification of the effective agent was done by performing ammonium sulfate precipitation and gel filtration chromatography. The molecular mass of the GFC-purified active compound (~3 kDa) was determined by Tris-Tricine SDS-PAGE. To predict the mechanisms of action, transmission electron microscopy (TEM) analysis of ultrathin sections of E. coli before and after antibacterial treatment was carried out. TEM analysis of antibacterial compounds-treated E. coli demonstrated that the completely altered bacteria appear much darker compared with the less altered bacteria, suggesting a change in the cytoplasmic composition. There were also some membrane-bound convoluted structures visible within the completely altered bacteria, which could be attributed to the response of the E. coli to the treatment with the antibacterial compound. According to the in vivo experiments oral administration of L. plantarum HKN01 resulted in recovery of infected BALB/c mice with Salmonella enterica ser. Typhimurium.

Study on Formation Mechanism of Iron Oxide Nanoparticles (산화철 나노입자의 형성 메커니즘에 대한 연구)

  • Kim, Dong-Young;Yoon, Seok-Soo;Takahashi, Migaku
    • Journal of the Korean Magnetics Society
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    • v.22 no.5
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    • pp.167-172
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    • 2012
  • In order to analyze the formation mechanism of iron oxide nanoparticles, we measured the heat flow of $Fe(OL)_3$ precursor with temperature, and TEM images and AC susceptibility of aliquots samples sequentially taken from the reaction solution, respectively. The thermal decomposition of two OL-chain from $Fe(OL)_3$ produced the Fe-OL monomer, which were contributed to the formation of iron oxide nanoparticles. In the initial stage of nanoparticles formation, the small iron oxide nanoparticles had ${\gamma}-Fe_2O_3$ structure. However, as the iron oxide nanoparticles were rapidly growth, the iron oxide nanoparticles showed ${\gamma}-Fe_2O_3$-FeO core-shell structure which the FeO layer was formed on the surface of ${\gamma}-Fe_2O_3$ nanoparticles by insufficient oxygen supply from the reaction solution. These nanoparticles were transformed to $Fe_3O_4$ structure by oxidation during long aging time at high temperature. Finally, the $Fe_3O_4$ nanoparticles with high saturation magnetization and stable in the air could be easily synthesized by the thermal decomposition method.

Hyperthermia Properties of Fe3O4 Nanoparticle Synthesized by Hot-injection Polyol Process (Hot-injection Polyol 공정에 의해 제조된 Fe3O4 나노입자의 Hyperthermia 특성)

  • Lee, Seong Noh;Kouh, Taejoon;Shim, In-Bo;Shim, Hyun Ju
    • Journal of the Korean Magnetics Society
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    • v.24 no.2
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    • pp.51-55
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    • 2014
  • The $Fe_3O_4$ nanoparticle was synthesized by the hot-injection method while varying the injection time of the precursor solution. The crystal structure was determined to be cubic inverse spinel with space group of Fd-3m based on X-ray diffraction (XRD) measurements and the morphology of the prepared $Fe_3O_4$ nanoparticle was studied with a high-resolution transmission electron microscope (HR-TEM). When the precursor solution was injected for 0.5 min, the size of the $Fe_3O_4$ nanoparticle was 7.63 nm, while the size of the obtained particle was 21.27 nm with the injection time of 60 min. The magnetic properties of the prepared $Fe_3O_4$ nanoparticle were investigated by both vibrating sample magnetometer (VSM) and $^{57}Co$ M$\ddot{o}$ssbauer spectroscopy at various temperatures. From the hyperthermia measurement, we observed that the temperature of the $Fe_3O_4$ nanoparticle powder reached around $120^{\circ}C$ under 250 Oe at 50 kHz, when the injection time of the precursor solution was 60 min.

Preparation and characterization of Ga-doped TiO2 nanofibers by electrospinning (전기방사를 이용한 Ga이 첨가된 나노섬유의 제작 및 특성평가)

  • Song, Chan-Geun;Kang, Won Ho;Yoon, Jong-Won
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.22 no.6
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    • pp.274-278
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    • 2012
  • $TiO_2$ can be used optically and is applied on many areas such as gas sensor, solar cell and photocatalysis. Electrospun nanofibers have received great interest for development and utilization in some novel applications, such as chemical sensors, dye-sensitized solar cell and photo catalysis. In this study, pure $TiO_2$ and Ga-doped $TiO_2$ nanofibers synthesized by a modified electrospinning method. The Ga doped $TiO_2$ solution is prepared by mixing poly vinyl pyrrolidone, ethyl alcohol, and titanium (IV) isopropoxide. By electrospinning these sols, nanofibers were fabricated. These fibers are heat-treated at $800^{\circ}C$ in air. The prepared pure $TiO_2$ and Ga-doped $TiO_2$ nanofibers samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy.

Facile Synthesis of In2S3 Modified Ag3PO4 Nanocomposites with Improved Photoelectrochemical Properties and Stabilities

  • Zeng, Yi-Kai;Bo, Shenyu;Wang, Jun-hui;Cui, Bin;Gu, Hao;Zhu, Lei;Oh, Won-Chun
    • Korean Journal of Materials Research
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    • v.30 no.11
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    • pp.601-608
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    • 2020
  • In this work, Ag3PO4/In2S3 nanocomposites with low loading of In2S3 (5-15 wt %) are fabricated by two step chemical precipitation approach. The microstructure, composition and improved photoelectrochemical properties of the as-prepared composites are studied by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photocurrent density, EIS and amperometric i-t curve analysis. It is found that most of In2S3 nanoparticles are deposited on the surfaces of Ag3PO4. The as-prepared Ag3PO4/In2S3 composite (10 wt%) is selected and investigated by SEM and TEM, which exhibits special morphology consisting of lager size substrate (Ag3PO4), particles and some nanosheets (In2S3). The introduction of In2S3 is effective at improving the charge separation and transfer efficiency of Ag3PO4/In2S3, resulting in an enhancement of photoelectric behavior. The origin of the enhanced photoelectrochemical activity of the In2S3-modified Ag3PO4 may be due to the improved charge separation, photocurrent stability and oriented electrons transport pathways in environment and energy applications.

Preparation and characterization of Poly(2-methacryloyloxyethyl phosphorylcholine/fluorescein O-methacrylate)-coated iron oxide nanoparticles (Poly(2-methacryloyloxyethyl phosphorylcholine/fluorescein O-methacrylate)가 도입된 산화철 나노 입자의 제조 및 발열 특성 연구)

  • Ryu, Sunggon;Cheong, In Woo
    • Journal of Adhesion and Interface
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    • v.19 no.3
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    • pp.106-112
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    • 2018
  • Recently, the hyperthermia treatment of malignant tissues has gained great attention as a biocompatible and benign method that facilitates successful cancer therapy compared to radiation and chemotherapy. In this study, superparamagnetic ($Fe_3O_4$) iron oxide nanoparticles (IONP) coated with biocompatible polymer (IONP@P(MPC/FOM)) for the purpose of hyperthermia treatment were prepared and related characterization were performed. IONPs with having 15 nm diameter were first prepared by coprecipitation and followed by surface modification with 4-cyanopentanoic acid dithiobenzoate (CTP) for reversible addition-fragmentation chain transfer (RAFT) copolymerization by using 2-methacryloyloxyethyl phosphorylcholine (MPC) and fluorescein O-methacrylate (FOM) to form corona layer of P(MPC/FOM) on the surface of the IONP. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) confirmed the morphology and hydrodynamic size of the IONP@P(MPC/FOM) and thermogravimetric analysis (TGA) confirmed the formation of P(MPC/FOM) corona layer, respectively. Exposing IONP dispersion to alternating magnetic field suggests that the IONP@P(MPC/FOM) aqueous dispersion with 0.2 wt.% can be used for hyperthermia treatment.

Effects of the Precipitation of Carbides and Nitrides on the Texture Structures in Extra Low Carbon Steel Sheets containing B, Nb and Ti(ll) (B, Nb및 Ti를 함유한 극저탄소강에서 탄화물 및 질화물의 석출이 집합조직에 미치는 영향(ll))

  • Lee, Jong-Mu;Yun, Guk-Han;Lee, Do-Hyeong
    • Korean Journal of Materials Research
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    • v.3 no.2
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    • pp.131-139
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    • 1993
  • Abstract Alloying elements such as AI, Ti, Nb and B in the extra low carbon AI-killed steel precipitate as nitrides or carbides and change the recrystallization texture structure of the steel during heattreatment with the result of strong effects on the deep drawability of the steel sheet. In this study the effects of fine precipitates such as nitrides and carbides on the texture of extra low carbon steels into which Ti, Nb, B, P, Si and Mn were added as alloying elements were investigated by means of TEM, SEM and optical microscopic analyses. Fine N$b_2$C and T$i_2$AIN precipitates are mainly observed in the steel containing both Nb and Ti, while fine AIN and coarse BN precipitates are observed in the Nb~containing steel and coarse T${i_4}{N_3}$ and ${N_10}{N_22}$/T$i_68$ precipitates are observed in the Ti-containing steel. The grain size of the Ti containing steel is larger than that of the Nb containing steel and that of the one containing both Nb and Ti.

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Effect of Underlying Poly-Silicon on the Thermal Staability of the Ti-silicide Film (티타니움 실리사이드 박막의 열안정성에 미치는 기판 실리콘막의 영향)

  • Kim, Yeong-Uk;Lee, Nae-In;Go, Jong-U;Kim, Il-Gwon;An, Seong-Tae;Lee, Jong-Sik;Song, Se-An
    • Korean Journal of Materials Research
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    • v.3 no.2
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    • pp.158-165
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    • 1993
  • Abstract To investigate the effect of underlying Si on the thermal stability of the TiS$i_2$ film, TiS$i_2$ films obtained by the solid-state reaction of the Ti film on as-deposited or on heat-treated poly-silicon and amorphous-silicon were annealed at 90$0^{\circ}C$ for various times. The poly-Si film was evaluated by XRD, SEM and TEM. The thermal stability of the TiS$i_2$ film was evaluated by measuring the sheet resistance and microstructural evolution during furnace annealing. Agglomeration of the TiSi, film occurred more on amorphous-Si than on poly-Si. The thermal stability of the TiS$i_2$ film was improved by annealing poly-Si. The Si layer crystallized from amorphous-Si has an equiaxed structure with the (111) preferred orientation whereas for as-deposited poly-Si has a columnar structure with the (110) orientation. Better thermal stability of the TiS$i_2$ film can be obtained by the higher surface energy of underlying poly-Si.

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The Characteristics of the Wafer Bonding between InP Wafers and $\textrm{Si}_3\textrm{N}_4$/InP (Direct Wafer Bonding법에 의한 InP 기판과 $\textrm{Si}_3\textrm{N}_4$/InP의 접합특성)

  • Kim, Seon-Un;Sin, Dong-Seok;Lee, Jeong-Yong;Choe, In-Hun
    • Korean Journal of Materials Research
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    • v.8 no.10
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    • pp.890-897
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    • 1998
  • The direct wafer bonding between n-InP(001) wafer and the ${Si}_3N_4$(200 nm) film grown on the InP wafer by PECVD method was investigated. The surface states of InP wafer and ${Si}_3N_4$/InP which strongly depend upon the direct wafer bonding strength between them when they are brought into contact, were characterized by the contact angle measurement technique and atomic force microscopy. When InP wafer was etched by $50{\%}$ HF, contact angle was $5^{\circ}$ and RMS roughness was $1.54{\AA}$. When ${Si}_3N_4$ was etched by ammonia solution, RMS roughness was $3.11{\AA}$. The considerable amount of initial bonding strength between InP wafer and ${Si}_3N_4$/InP was observed when the two wafer was contacted after the etching process by $50{\%}$ HF and ammonia solution respectively. The bonded specimen was heat treated in $H^2$ or $N^2$, ambient at the temperature of $580^{\circ}C$-$680^{\circ}C$ for lhr. The bonding state was confirmed by SAT(Scannig Acoustic Tomography). The bonding strength was measured by shear force measurement of ${Si}_3N_4$/InP to InP wafer increased up to the same level of PECVD interface. The direct wafer bonding interface and ${Si}_3N_4$/InP PECVD interface were chracterized by TEM and AES.

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Comparison of Dry Reforming of Butane in Catalyst Process and Catalyst+Plasma Process over Ni/γ-Al2O3 Catalyst (뷰테인 건식 개질 반응을 위한 Ni/γ-Al2O3 촉매를 이용한 촉매 공정과 촉매+플라즈마 공정 비교)

  • Jo, Jin-Oh;Jwa, Eunjin;Mok, Young-Sun
    • Journal of the Korean Institute of Gas
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    • v.22 no.1
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    • pp.26-36
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    • 2018
  • Conventional nickel-based catalyst processes used for dry reforming reactions have high activation temperatures and problems such as carbon deposition and metal sintering on the active sites of the catalyst surface. In this study, the characteristics of butane dry reforming reaction were investigated by using DBD plasma combined with catalytic process and compared with existing catalyst alone process. The physical and chemical properties of the catalysts were investigated using a surface area & pore size analyzer, XRD, SEM and TEM. Using $10%Ni/{\gamma}-Al_2O_3$ at $580^{\circ}C$, in the case of the catalyst+plasma process, the conversion of carbon dioxide and butane were improved by about 30% than catalyst alone process. When the catalyst+plasma process, the conversion of carbon dioxide and butane and the hydrogen production concentration are enhanced by the influence of various active species generated by the plasma. In addition, it was found that the particle size of the catalyst is decreased by the plasma in the reaction process, and the degree of dispersion of the catalyst is increased to improve the efficiency.