• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.398-398
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• 2013

The electronic properties and the local structure of tantalum oxide thin film with variation of oxygen flow rate ranging from 9.5 to 16 sccm (standard cubic centimeters per minute) have been investigated by X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and X-ray absorption spectroscopy (XAS). The XPS results show that the Ta4f spectrum for all films consist of the strong spin-orbit doublet $Ta4f_{7/2}$ and $Ta4f_{5/2}$ with splitting of 1.9 eV. The oxygen flow rate of the film results in the appearance of new features in the Ta4f at binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV, these peaks attribute to $Ta^{1+}$, $Ta^{2+}$, $Ta^{4+}$/$Ta^{2+}$, and $Ta^{5+}$, respectively. Thus, the presence of non-stoichiometric state from tantalum oxide ($TaO_x$) thin films could be generated by the oxygen vacancies. The REELS spectra suggest the decrease of band gap for tantalum oxide thin films with increasing the oxygen flow rate. The absorption coefficient ${\mu}$ and its fine structure were extracted from the fluorescence mode of extended X-ray absorption fine structure (EXAFS) spectra. In addition, bond distances (r), coordination numbers (N) and Debye-Waller factors (${\sigma}^2$) each film were determined by a detailed of EXAFS data analysis. EXAFS spectrapresent both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the increase of oxygen flow rate.

• Journal of the Korean Chemical Society
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• v.38 no.5
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• pp.345-350
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• 1994

The $v_{a^+}$ Amide II combination band of thioacetamide has been used to evaluate thermodynamic parameters of the hydrogen bonding of thioacetamide(TA) with pyridine(Py), quinoline(Qu), and acridine(Ac) in $CHCl_3$ and $CCl_4$ over the temperature range from 5$^{\circ}C$ to 55$^{\circ}C$. This combination band was resolved into two Lorentzian-Gaussian product bands which have been identified withmonomeric TA and hydrogen bonded TA. The thermodynamic parameters for the hydrogen bonded TA were determined by computer analysis of concentration and temperature dependent spectra. The standard enthalpies for the 1 : 1 hydrogen bonded complex of TA to pyridine, quinoline, and acridine in $CHCl_3$ have been found to be -7.6 kJ/mol, -6.5 kJ/mol, and -5.4 kJ/mol, respectively. And the standard enthalpies for the 1: 1 hydrogen bonded complex of TA to pyridine and quinoline in $CCl_4$ have been found to be -13.3kJ/mol, and -12.0kJ/mol, respectively.

• Analytical Science and Technology
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• v.5 no.1
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• pp.111-114
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• 1992

Ordering phenomena were observed for Zn and Ta cations of $Ba(Zn_{1/3}Ta_{2/3})O_3$ under particular heat treatments, followed by a considerable lattice distortion. This lattice distortion was measured by X-ray powder diffraction with a precision of higher than 1/10,000. From this investigation, a significant lattice distortion occurred within 30 min. of sintering at $1350^{\circ}C$, and it was increased with sintering time.

• Transactions on Electrical and Electronic Materials
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• v.13 no.6
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• pp.287-291
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• 2012

We investigated the etching characteristics of TaN thin films in an $O_2/BCl_3/Cl_2/Ar$ gas using a high density plasma (HDP) system. A maximum etch rate of the TaN thin films and the selectivity of TaN to $SiO_2$ were obtained as 172.7 nm/min and 6.27 in the $O_2/BCl_3/Cl_2/Ar$ (3:2:18:10 sccm) gas mixture, respectively. At the same time, the etch rate was measured as a function of the etching parameters, such as the RF power, DC-bias voltage, and process pressure. The chemical states on the surface of the etched TaN thin films were investigated using X-ray photoelectron spectroscopy. Auger electron spectroscopy was used for elemental analysis on the surface of the etched TaN thin films. These surface analyses confirm that the surface of the etched TaN thin film is formed with the nonvolatile by-product.

• Bulletin of the Korean Chemical Society
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• v.21 no.7
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• pp.679-684
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• 2000

The Sr2Co0.5Nb(Ta)0.5O4 and Sr3CoNb(Ta)O7 compounds, both with Ruddlesden-Popper structures, have been synthesized by the ceramic method at $1150^{\circ}C$ under atmospheric pressure. The crystallographic structure of the compounds was assigned to the tetr agonal system with space group 14/mmm by X-ray diffraction(XRD) Rietveld refinement. The reduced lattice volume and lattice parameters increased as the Ta with 5d substitutes for the Nb with 4d in the compounds. The Co/Nb(Ta)O bond length has been determined by X-ray absorption spectroscopic(EXAFS/XANES) analysis and the XRD refinement. The CoO6,octahedra were tetragonally distorted by elongation of Co-O bond along the c-axis. The magnetic measurement shows the compounds Sr2Co0.5Nb(Ta)0.5O4 and Sr3CoNb(Ta)O7 have paramagnetic properties and the Co ions with intermediate spin sates between high and low spins in D4h symmetry. All the compounds showed semiconducting behavior whose electrical conductivity increased with temperature up to 1000 K. The electrical conductiviy increased and the activation energy for the conduction decreased as the number of perovskite layers increased in the compounds with chemical formula An+1BnO3n+1.

• International Journal of Oral Biology
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• v.44 no.2
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• pp.43-49
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• 2019

Tannic acid (TA) is a water-soluble polyphenol compound found in various herbal plants. We investigated the chemopreventive effects of TA on FaDu hypopharyngeal squamous carcinoma cells. In an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, TA showed dose-dependent cytotoxicity with a half maximal inhibitory concentration (IC50) of 50 ?M. Cell cycle analysis and immunofluorescence imaging demonstrated that under low-dose ($25{\mu}M$) treatment, FaDu cells were arrested in G2/M phase, and as the dose of TA was increased, apoptosis was induced with the increase of cell population at sub-G1 phase. The expressions of various cyclins, including cyclin D1 and cyclin-dependent kinases (CDK-1 and CDK-2), were down-regulated at low doses of TA, whereas apoptotic effectors such as cleaved caspase 3, cleaved caspase 7, and poly (ADP-ribose) polymerase (PARP) were expressed in a dose-dependent manner in Western blotting. In addition, TA-induced apoptosis of FaDu cells might be mediated by the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase pathway, with the upregulation of p-AKT/p-PKB (phosphorylated protein kinase B) and p-ERK. Overall, our data support the hypothesis that TA is a potential candidate agent for the treatment of hypopharyngeal cancer.

• Tribology and Lubricants
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• v.35 no.2
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• pp.106-113
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• 2019

We investigated the application of tetrahedral amorphous carbon (ta-C) coatings to fabricate a glass lens manufactured using a glass molding process (GMP). In this work, ta-C coatings with different thickness (50, 100, 150 and 200 nm) were deposited on a tungsten carbide (WC-Co) mold using the X-bend filter of a filtered cathode vacuum arc. The effects of thickness on mechanical and tribological properties of the coating were studied. These ta-C coatings were characterized by atomic force microscopy, scanning electron microscopy, nano-indentation measurements, Raman spectrometry, Rockwell-C tests, scratch tests and ball on disc tribometer tests. The nano-indentation measurements showed that hardness increased with an increase in coating thickness. In addition, the G-peak position in the Raman spectra analysis was right shifted from 1520 to $1586cm^{-1}$, indicating that the $sp^3$ content increased with increasing thickness of ta-C coatings. The scratch test showed that, compared to other coatings, the 100-nm-thick ta-C coating displayed excellent adhesion strength without delamination. The friction test was carried out in a nitrogen environment using a ball-on-disk tribometer. The 100-nm-thick ta-C coating showed a low friction coefficient of 0.078. When this coating was applied to a GMP, the life time, i.e., shot counts, dramatically increased up to 2,500 counts, in comparison with Ir-Re coating.

• Economic and Environmental Geology
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• v.46 no.5
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• pp.455-468
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• 2013

We performed reconnaissance survey on Dashinchilen Nb-Ta REE area and Sant Cu area which are located in southeastern part of Khangai rare metals mineralized belt. In Dashinchilen area, Nb and Ta have been found in pegmatitic granite that is largely distributed in the survey area and muscovite in pegmatite which is an intrusion in paleozoic sedimentary rocks which are mostly composed of sandstone. While grades of Nb and Ta are not high, an outcrop that has high Th and U contents (542 ppm of Th and 56.9 ppm of U) has been found. Average and maximum REE contents in the survey area is three times and seven times, respectively, larger than average REE contents in the crust of the Earth. In Sant area, copper oxides such as malachite has been found in quartzite in paleozoic sedimentary rocks. A sedimentary rock formation that has high grade of Mn (12.4-34.6 %) has been found in the survey area. This sedimentary rock formation is the same formation with that of Ugii Nuur Fe-Mn mineralization which is located about 200 km northwest of the survey area. Average and maximum REE contents in the survey area is two and half times and seven times, respectively, larger than average REE contents in the crust of the Earth. According to the factor analysis for the data of the geochemical analysis, Nb and Ta in Dashinchilen area are highly correlated with muscovite and Cu in Sant area is highly correlated with Mo, Sn, and Bi. Furthermore, the factor analysis results show that Fe in Sant area was deposited with rare earth elements.

• Environmental Analysis Health and Toxicology
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• v.7 no.3_4
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• pp.37-55
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• 1992

Effect of Synethrin on the Toxicity of Dichlorvos in Rats. Hematological, biological and enzymatic effects were investigated in rats treated with DDVP and synethrin. Mutagenicity was also examined. In serological analysis, LDH and ALP were more significantly increased in rats treated with the mixture of DDVP (10mg/kg) and synethrin (250mg/kg) than with either DDVP or synethrin. DDVP alone slightly increased cytochrome P-450 in the liver while synethrin or the mixture decreased it. Lipid peroxidation was significantly increased in the liver when rats were treated with both DDVP and the mixture. Cholinesterase activity was significantly decreased in the liver and serum when treated with DDVP as well as with the mixture. In mutagenicity test, DDVP was shown to be weakly positive to TA 97a, TA 100 and TA 102, but negative to TA 1537. Synethrin showed negative in all strains tested. These results suggest that the mixture of DDVP and synethrin increased the toxicities but not the mutagenicity.

• The Journal of the Korea Contents Association
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• v.7 no.5
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• pp.1-9
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• 2007

Topology information can be constructed hierarchically in the networks and the process of aggregating topology information is known as TA(Topology Aggregation). It is very important for scalability in networks. In paticular, routing and TA algorithm are very much elements on networks performance in private networks to networks interface. Therefore, in this paper, we designed and implemented routing simulator for TA in private networks to networks interface. And we evaluated and analyzed the existent TA algorithm using the implemented simulator. The implemented simulator can be used valuably to developing TA algorithm.