• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.114-114
• /
• 2009

ZnO has received considerable attention due to its potential applicability to optoelectronic devices such as ultraviolet-light emitting diodes (UVLEDs) and laser diodes (LDs). As well known, however, polar ZnO with the growth direction along the c-axis has spontaneous and piezoelectric polarizations that will result in decreased quantum efficiency. Recently, nonpolar ZnO has been studied to avoid such a polarization effect. In order to realize applications of nonpoar ZnO-based films to LEDs, growth of high quality alloys for quantum well structures is one of the important tasks that should be solved. $Mg_xZn_{1-x}O$ and $Cd_xZn_{1-x}O$ is ones of most promising alloys for this application because the alloys of ZnO with MgO and CdO provide a wide range of band-gap engineering spanning from 2.4 to 7.8 eV. In this study, we investigated on $Mg_xZn_{1-x}O$ films grown with various Mg/Zn flux ratios The films were grown on R-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). we investigated on $Mg_xZn_{1-x}O$ films grown with various Mg/Zn flux ratios. The films were grown on R-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). With the relatively low Mg/Zn flux ratios, a typical striated anisotropic surface morphology which was generally observed from the nonpolar (11-20) ZnO film on r-plane sapphire substrates. By increasing the Mg/Zn flux ratio, however, additional islands were appeared on the surface and finally the surface morphology was entirely changed, which was generally observed for the (0001) polar ZnO films by losing the striated morphology. Investigations by X-ray $\Theta-2{\Theta}$ diffraction revealed that (0002) and (10-11) ZnO planes are appeared in $Mg_xZn_{1-x}O$ films by increasing the Mg/Zn flux ratio. Further detailed investigation by transmission electron microscopy (TEM) and photoluminescence (PL) will be discussed.

• Journal of Animal Science and Technology
• /
• v.62 no.5
• /
• pp.668-681
• /
• 2020

The purpose of this study was aimed to isolate a Salmonella Typhimurium-specific phage (KFS-ST) from washing water in a poultry processing facility and to investigate the feasibility of the KFS-ST as a novel bio-receptor for the magnetoelastic (ME) biosensor method. KFS-ST against S. Typhimurium was isolated, propagated, and purified using a CsCl-gradient ultracentrifugation. Morphological characteristics of KFS-ST were analyzed using transmission electron microscopy (TEM). Its specificity and efficiency of plating analysis were conducted against 39 foodborne pathogens. The temperature and pH stabilities of KFS-ST were investigated by the exposure of the phage to various temperatures (-70℃-70℃) and pHs (1-12) for 1 h. A one-step growth curve analysis was performed to determine the eclipse time, latent time and burst size of phage. The storage stability of KFS-ST was studied by exposing KFS-ST to various storage temperatures (-70℃, -20℃, 4℃, and 22℃) for 12 weeks. KFS-ST was isolated and purified with a high concentration of (11.47 ± 0.25) Log PFU/mL. It had an icosahedral head (56.91 ± 2.90 nm) and a non-contractile tail (225.49 ± 2.67 nm), which was classified into the family of Siphoviridae in the order of Caudovirales. KFS-ST exhibited an excellent specificity against only S. Typhimurium and S. Enteritidis, which are considered two of the most problematic Salmonella strains in the meat and poultry. However, KFS-ST did not exhibit any specificity against six other Salmonella and 27 non-Salmonella strains. KFS-ST was stable at temperature of 4℃ to 50℃ and at pH of 4 to 12. The eclipse time, latent time, and burst size of KFS-ST were determined to be 10 min, 25 min and 26 PFU/ infected cell, respectively. KFS-ST was relatively stable during the 12-week storage period at all tested temperatures. Therefore, this study demonstrated the feasibility of KFS-ST as a novel bio-receptor for the detection of S. Typhimurium and S. Enteritidis in meat and poultry products using the ME biosensor method.

• Economic and Environmental Geology
• /
• v.47 no.5
• /
• pp.497-505
• /
• 2014

This study is for discrimination between asbestiform and non-asbestiform based on size characteristics of tremolite-actinolite fibers in soils from a closed asbestos mine, Jecheon, Chungcheongbuk-do, Korea. Soils and tremolite asbestos rocks were collected from a closed asbestos mine area. The dimensions of fibers with minimum $5{\mu}m$ in length and 3:1 in aspect ratio were measured using transmission electron microscopy (TEM) and compared to the known tremolite populations ranging from asbestiform to non-asbestiform. The geometric means of width of soils, asbestos rocks and National Institute for Standard and Technology (NIST) and Health and Safety Laboratory (HSL) reference samples were $1.2{\mu}m$, $0.3-0.6{\mu}m$, $1.3{\mu}m$ and $0.2{\mu}m$, respectively. The geometric means of aspect ratio of soils, asbestos rocks and NIST and HSL reference samples were 7.3, 13.7-30.1, 7.2 and 37.8, respectively. The population of tremolite-actinolite fibers from soils compared to known asbestiform and non-asbestiform tremolite was lack of thin and high aspect ratio fibers. Upper results suggest that tremolite-actinolite fibers in soils cannot be classified into a commercial grade asbestos. The tremolite-actinolite fibers do not mainly appear to be the result of contamination from distance asbestos sources by wind. For the management and control of asbestos in soils, size distributions of amphiboles should be incorporated into asbestos survey results of soils.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.23 no.4
• /
• pp.167-172
• /
• 2013

Titanium dioxides nanoparticles coated aluminum oxide powders were fabricated by pulsed laser deposition (PLD) with Nd : YAG laser at 266 nm. The Pulse laser energy is 100 mJ/pulse. During the irradiation of the focused laser on the $TiO_2$ target, Ar gas is supplied into the chamber. The gas pressure is varied in a range of $1{\times}10^{-2}$ to 100 Pa. Titanium dioxides nanoparticles deposited aluminum oxide powders were characterized by using energy dispersive X-ray spectroscopy (EDX), high resolution transmission electron microscopy (HR-TEM), in order to understand the effect of Ar background gas on surface morphology and properties of the powders. The coated $TiO_2$ nanoparticles had nanosized spherical shape and the crystallite sizes of 10~30 nm. The morphology of coated $TiO_2$ nanoparticles is not affected by gas pressure. However, the particle size and crystallinity slightly increased with the increase of gas pressure. According to this technique, the size and crystallinity of nanoparticles can be easily controlled by controlling pressure during the laser irradiation.

• Korean Journal of Materials Research
• /
• v.4 no.1
• /
• pp.9-23
• /
• 1994

Epitaxial $CoSi_2$ layer has been grown on NaCl(100) substrate at low deposition temperature($200^{\circ}C$) by multitarget bias cosputter deposition(MBCD). The phase sequence and crystallinity of deposited silicide as a function of deposition temperature and substrate bias voltage were studied by X-ray diffraction(XRD) and transmission electron microscopy(TEM) analysis. Crystalline Si was grown at $200^{\circ}C$ by metal induced crystallization(M1C) and self bias effect. In addition to, the MIC was analyzed both theoretically and experimentally. The observed phase sequence was $Co_2Si \to CoSi \to Cosi_2$ and was in good agreement with that predicted by effective heat of formation rule. The phase sequence, the CoSi(l11) preferred orientation, and the crystallinity had stronger dependence on the substrate bias voltage than the deposition temperature due to the collisional cascade mixing, the in-situ cleaning, and the increase in the number of nucleation sites by ion bombardment of growing surface. Grain growth induced by ion bombardment was observed with increasing substrate bias voltage at $200^{\circ}C$ and was interpreted with ion bombardment dissociation model. The parameters of $E_{Ar}\;and \alpha(V_s)$ were chosen to properly quantify the ion bombardment effect on the variation in crystallinty at $200^{\circ}C$ with increasing substrate bias voltage using Langmuir probe.

• Polymer(Korea)
• /
• v.29 no.2
• /
• pp.190-197
• /
• 2005

Nanocomposites of three different polyesters with dodecyltriphenylphosphonium-montmorillonite $(C_{12}PPh-MMT)$ as an organoclay are compared with their thermal properties, mechanical properties, and morphologies. Poly (butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), and poly(trimethylene terephthalate) (PTT) were used as matrix polymers in the fabrication of polyester nanocomposite fibers. The variations of their properties with organoclay content in the polymer matrix and draw ratio (DR) are discussed. Transmission electron microscopy (TEM) micrographs show that some of the clay layers are dispersed homogeneously within the polymer matrix on the nano-scale, although some clay particles are agglomerated. We also found that the addition of only a small amount of organoclay is enough to improve the thermal stabilities and mechanical properties of the polyester nanocomposite fibers. Even polymers with low organoclay contents $(<5\;wt\%)$ were found to exhibit much higher strength and modulus values than pure polyester fibers. In the cases of all polyester hybrid fibers, the values of the tensile mechanical properties were found to decrease linearly with increasing DR. However, the initial tensile modulus of the PTT hybrid fibers were found to be independent of DR.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.6 no.6
• /
• pp.457-460
• /
• 2005

Nano-sized titanium oxide and zirconium oxide powders were synthesized by hydrolysis of titanium isopropoxide $[Ti(OC_3H7)_4]$ and zirconium tetrachloride ($ZrC1_4$) via a sol-gel technique. Lead titanate powders were prepared by mixing $TiO_2$ precursors with PbO slurry made with dilute $NH_4OH$. Lead zirconate titanate powders were, then, synthesized by mixing $PbTiO_3$ with $ZrO_2$ powders. The goal of this research was to obtain the $PbZrTiO_3(PZT)$ powders and sintering these powders at low temperature. The $PbTiO_3$ and PZT powders after firing were analyzed by X-ray diffraction(XRD) and transmission electron microscopy(TEM) was utilized to observe the shape and size of the synthesized nano-particles. In the XRD pattern, the well-crystallized PZT phase could be obtained in consequence of firing at $900^{\circ}C$. SEM micrographs also showed that grains of PZT were relatively well grown with the size of the range of $2{\~}4{\mu}m$. The densified perovskite structure of $PbZrTiO_3$ could be obtained by sintering at temperature as low as $900^{\circ}C$. Characterization of the samples showed improved piezoelectric properties.

• Clean Technology
• /
• v.17 no.1
• /
• pp.78-82
• /
• 2011

For effectively photochemical hydrogen production, P (negative semiconductor) and B (positive semiconductor) ions (0.1, 0.2, 0.5, and 1.0 mol%) incorporated $TiO_2$ (P- and B-$TiO_2$) nanometer sized particles were prepared using a solvothermal method as a photocatalyst. The characteristics of the synthesized P- and B-$TiO_2$ photocatalysts were analyzed by X-ray Diffraction (XRD), Transmission electron microscopy (TEM), W-visible spectroscopy (UV-Vis), and Photoluminescence spectra (PL). The evolution of $H_2$ from methanol/water (1:1) photo-splitting over B-$TiO_2$ photocatalysts was enhanced compared to those over pure $TiO_2$ and P-$TiO_2$ photocatalysts; 0.42 mL of $H_2$ gas was evolved after 10 h when 0.5 g of a 1.0 mol% B-$TiO_2$ catalyst was used.

• Asian Pacific Journal of Cancer Prevention
• /
• v.13 no.6
• /
• pp.2527-2532
• /
• 2012

Objectives: The aim of the present study was to explore mechanisms underlying the effects of down-regulating ${\beta}$-catenin expression on esophageal carcinoma (EC) cells. Methods: Cell cycle distribution and apoptosis were determined using flow cytometry and annexin V apoptosis assay, respectively. Transmission electron microscopy (TEM) was used to examine changes in ultrastructure, while expression of cyclin D1 protein and mRNA was detected by western blot and real-time PCR. Proliferating cell nuclear antigen (PCNA) and extracellular signal-regulated kinase (ERK) 1-2 were evaluated by Western blot analysis. PCNA labeling index (LI) was determined by immunocytochemistry. Results: Compared with pGen-3-con transfected and Eca-109 cells, the percentage of G0/G1-phase pGen-3-CTNNB1 transfected cells was obviously increased (P<0.05), with no significant difference among the three groups with regard to apoptosis (P>0.05). pGen-3-CTNNB1 transfected cells exhibited obvious decrease in cyclin D1 mRNA and protein expression (P<0.05) and the ultrastructure of Eca-109 cells underwent a significant change after being transfected with pGen-3-CTNNB1, suggesting that down-regulating ${\beta}$-catenin expression can promote the differentiation and maturation. The expression of PCNA and the ERKI/2 phosphorylation state were also down-regulated in pGen-3-CTNNB1 transfected cells (P<0.05). At the same time, the PCNA labeling index was decreased accordingly (P<0.05). Conclusion: Inhibition of EC Eca-109 cellproliferation by down-regulating ${\beta}$-catenin expression could improve cell ultrastructure by mediating blockade in G0/G1 through inhibiting cyclin D1, PCNA and the MAPK pathway (p-ERK1/2).

• Journal of Pharmacopuncture
• /
• v.15 no.3
• /
• pp.13-18
• /
• 2012

Objectives: The purpose of this study is to examine whether Hominis Placental pharmacopuncture solution (HPPS) combined with zinc-oxide nanoparticles (ZnO NP) activates RAW 264.7 cells. Methods: We soaked ZnO nanoparticles in the Hominis Placenta pharmacopuncture solution, thereby making a combined form (ZnO NP HPPS). The effect of ZnO NP HPPS on the intracellular reactive oxygen species (ROS) production was measured by 2', 7'-dichlorofluorescin diacetate (DCFH-DA) assay. The effect of ZnO NP HPPS on NF-${\kappa}B$ was measured by using a luciferase assay. The effect of ZnO NP HPPS on the cytokine expression was assessed by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR). The cellular uptake of ZnO NP HPPS was measured by using a flow cytometric analysis, and cellular structural alterations were analyzed by using transmission electron microscopy (TEM). Results: Neither the HPPS nor the ZnO NPs induced intracellular ROS production in RAW 264.7 cells. Neither of the materials activated NF-${\kappa}B$ or it's dependent genes, such as TNF-${\alpha}$, IL-1, and MCP-1. However, ZnO NP HPPS, the combined form of ZnO NPs and HPPS, did induce the intracellular ROS production, as well as prominently activating NF-${\kappa}B$ and it's dependent genes. Also, compared to ZnO NPs, it effectively increa-sed the uptake by RAW 264.7 cells. In addition, cellular structural alterations were observed in groups treated with ZnO NP HPPS. Conclusions: Neither ZnO NP nor HPPS activated RAW 264.7 cells, which is likely due to a low cellular uptake. The ZnO NP HPPS, however, significantly activated NF-${\kappa}B$ and up-regulated its dependent genes such as TNF-${\alpha}$, IL-1, and MCP-1. ZnO NP HPPS was also more easily taken into the RAW 264.7 cells than either ZnO NP or HPPS.