• Food Science and Preservation
• /
• v.8 no.1
• /
• pp.109-117
• /
• 2001

Cordyceps militaris is a parasitic fungus that has been used as a Chinese medicine for the treatment of fatigue, debility, kidney disease, tuberculosis, asthma and cardiac insufficiency etc. This study was carried out to determine the antioxidative and antimutagenic effects of Cordyceps militaris using DPPH free radical donating method and Ames test, respectively. They were extracted with ethanol and then further fractionated to n-hexane, chloroform, ethyl acetate, butanol and water, stepwise. Among five fractions, the EtOAc and BuOH fractions showed the highest electron donating activities, about 2-fold higher than other fractions. In Ames test, most of the extracts had strong antimutagenic effects against the mutagenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine(MNNG), 4-nitroquinoline-1-oxide(4NQO), benzo($\alpha$)pyrene(B($\alpha$)P) and 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indol (Trp-P-1). The EtOH extracts of C. militaris (200 $\mu\textrm{g}$/plate) showed 62.8%, 74.4% and 67.2% inhibitory effects on the mutagenesis induced by 4NQO, B($\alpha$)P and Trp-P-1, respectively, against TA98 strain, whereas 78.1%, 78.6%, 78.6% and 82.7% inhibition were observed on the mutagenesis induced by MNNG, 4NQO, B($\alpha$)P and Trp-P-1, respectively, against TA100 strain. Especially, the BuOH fraction showed the highest antimutagenic effects against mutation induced by MNNG.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.55 no.7
• /
• pp.344-348
• /
• 2006

The effect of x on microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics for microwave components were investigated. All spcecimens prepared by the conventional mixed oxied method and sintered at $1450^{\circ}C$. Microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-xTiO_2$ ceramics were influenced by $MgTi_2O_5$ phase. Also the microwave dielectric properties of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics were dominated with an addition of $CaTiO_3\;and\;SrTiO_3$. The dielectric constant $(\varepsilon_r)$, quality factor $(Q{\times}f_r)$ and temperature coefficient of the resonant frequency $(TCRF,\;\tau_f)$ of the $(1-x)Mg_4Ta_2O_9-x(TiO_2,\;CaTiO_3,\;SrTiO_3)$ ceramics were $12.96\sim70.98,\;5,132\sim186,410GHZ$ and $-35.82\sim+75.96ppm/^{\circ}C$, respectively, and depend on x and addition materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.298-298
• /
• 2007

Influence of $TiO_2$ on the dielectric properties of the $Bi(Nb_{0.7}Ta_{0.3})O_4$ ceramic with 7 wt% zinc borosilicate(ZBS) glass was investigated as a function of the $TiO_2$ contents with a view to applying this system to LTCC technology. The $Bi(Nb_{0.7}Ta_{0.3})O_4$ ceramic addition of 7 wt% ZBS glass ensured successful sintering below $900^{\circ}C$. But, TCF of $Bi(Nb_{0.7}Ta_{0.3})O_4$ ceramic is large negative values, respectively, it is necessary to adjust to zero TCF for practical applications Therefore, the addition of materials having positive TCF, such as $TiO_2$, might be an effective method for the improvement. In general, increasing addition of $TiO_2$ increased dielectric constant and TCF but it decreased the sinterability and $Q{\tiems}f$ value significantly due to the dielectric property and high sintering temperature of $TiO_2$. $Bi(Nb_{0.7}Ta_{0.3})O_4$ ceramic with 7 wt% ZBS glass and then addition 0.5 wt% $TiO_2$ sintered at $900^{\circ}C$ demonstrated 42 in the dielectric constant(${\varepsilon}_r$), 1,000 GHz in the $Q{\times}f$ value, and $10{\pm}5\;ppm/^{\circ}C$ in the temperature coefficient of resonant frequency(${\tau}_f$).

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.122.1-122.1
• /
• 2015

The dependence of electronic properties and local structure of tantalum oxide thin film on oxygen deficiency have been investigated by means of X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and X-ray absorption spectroscopy (XAS). The XPS results showed that the oxygen flow rate change results in the appearance of features in the Ta 4f at the binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV whose peaks are attributed to Ta1+, Ta2+, Ta3+, Ta4+, and Ta5+, respectively. The presence of nonstoichiometric state from tantalum oxide (TaOx) thin films could be generated by the oxygen vacancies. The REELS spectra suggested the decrease of band gap for tantalum oxide thin films with increasing oxygen deficiency. In addition, XAS spectra manifested both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the decrease of oxygen deficiency.

• Journal of the Korean Society of Radiology
• /
• v.8 no.6
• /
• pp.287-292
• /
• 2014

In this study, the neutron capture cross section of $^{180}Ta$(natural existence ratio: 0.012 %) obtain by measuring has been compared with the evaluated data for the capture data. In generally, the neutron capture resonance is defined as Breit-Wigner formula. The formula consists of the resonance parameters such as neutron width, total width and neutron width. However in the case of $^{180}Ta$, these are very poor experimental neutron capture cross section data and resonance information in below 10 eV. Therefore, in the study, we analyzed the neutron resonance of $^{180}Ta$ with the measuring the prompt gamma-ray from the sample. And the resonance was compared with the evaluated data by Mughabghab, ENDF/B-VII, JEFF-3.1 and TENDL 2012. Neutron sources from photonuclear reaction with 46-MeV electron linear accelerator at Research Reactor Institute, Kyoto University used for cross section measurement of $^{180}Ta(n,{\gamma})^{181}Ta$ reaction. $BGO(Bi_4Ge_3O_{12})$ scintillation detectors used for measurement of the prompt gamma ray from the $^{180}Ta(n,{\gamma})^{181}Ta$ reaction. The BGO spectrometer was composed geometrically as total energy absorption detector.

• Environmental Analysis Health and Toxicology
• /
• v.21 no.4 s.55
• /
• pp.317-322
• /
• 2006

We have investigated the genotoxicity of 1,2,4-trimethylbenzene using Ames reverse mutation test. In Ames reverse mutation test, 1,2,4-trimethylbenzene treatment at the dose of 100, 50, 25, 12.5, $6.25{\mu}g/plate$ did not induce mutagenicity in Salmonella typhimurium TA98, TA100, TA1535, TA1537 and in Escherichia coli WP2uvrA with and without metabolic activation. These results indicate that 1,2,4-trimethylbenzene has no mutagenic potential under the rendition in this study.

• Korean Journal of Food Science and Technology
• /
• v.24 no.4
• /
• pp.341-346
• /
• 1992

The antimutagenic effects of enzymatic browning reaction products (MEBRPs) of polyphenol compounds (catechol, homocatechol, hydroxyhydroquinone, pyrogallol) by enzyme extracted from mushroom (Agaricus bisporus) were demonstrated through spore rec-assay using B. subtilis $H17(rec^+)$ and $M45(rec^-)$, Ames test using S. typhimurium TA98 and TA100 and SOS chromotest using E. coli PQ37/plasmid pKM101. In spore rec-assay, the MEBRPs showed antimutagenic effects by decreasing of the inhibition zone induced by MNNG. In Ames test with S-9mix in both TA98 and TA100, all of MEBRPs showed strong antimutagenic effects of about 21 to 99% against mutation by $B({\alpha})P$ and Trp-P-1, as adding $300\;{\mu}l$ of the MEBRPs. In SOS chromotest, MEBRPs showed antimutagenic effects by inhibiting the SOS-inducing function induced by 4NQO and MMC, as increasing in concentration of the MEBRPs. But they did not showed mutagenicity in these bacterial assays.

• Environmental Analysis Health and Toxicology
• /
• v.18 no.2
• /
• pp.121-129
• /
• 2003

The genotoxicity of pendimethalin [N-(l-ethylpropyl)-2, 6-dinitro-3, 4-xylidine, C$\_$13/H$\_$19/N$_3$O$_4$, M.W.=281.3, CAS No. 40487-42-1], one of selective herbicide, was evaluated in bacterial gene mutation system, chromosome aberration in mammalian cell system and in vivo micronucleus assay with rodent. In bacterial gene mutation assay, pendimethalin revealed dose-dependent mutagenic potential in 313 ∼ 5,000 ${\mu}$g/plate of Salmonella typhimurium TA 98 and TA 1537 both in the absence and presence of S-9 metabolic activation system, and TA 100 only in the absence of S-9 mixture. In the TA 1535, slight increase of revertant was also observed in the presence of S-9 metabolic activation system. No mutagenic potential was observed in the TA 1535 without metabolic activation system and TA l00 in the presence of S-9 mixture. In mammalian cell system using Chinese hamster lung (CHL) fibroblast, no clastogenicity of pendimethalin was observed both in the absence and presence of S-9 metabolic activation system in the concentration range of 2.32∼9.28 ${\mu}$g/ml. And also, in vivo bone marrow micronucleus assay, pendimethalin revealed no clastogenic potential in the dose range of 203∼810 mg/kg body weight after oral administration in mice. Consequently, in vitro chromosome aberration with mammalian cells and in vivo bone marrow micronucleus assay revealed no clastogenic potential of pendimethalin. However, pendimethalin revealed mutagenic potential in bacterial gene mutation assay.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.10 no.1
• /
• pp.17-22
• /
• 2000

A quaternary alloy film of $CoCr_{16.2}Pt_{10.8}Ta_4$was investigated for its magnetic properties and c-axis orientation with and without Ti underlayer. Additional elements such as Ta, Pt have been frequently introduced in CoCr alloy film for perpendicular recording as a means of improving magnetic performance. It has been reported that the addition of Pt and Ta in CoCr increase the coercivity and the magnetic isolation of columnar grains, respectively. However, CoCrPtTa perpendicular magnetic layer should be more increased its perpendicular magnetic anisotropy than at present for the application of ultrahigh recording density. The improvement of underlayers and substrate materials is one of the promised schemes to intensify the perpendicular magnetic anisotropy. In this study, the insertion of Ti underlayer shows the remarkable improvement of c-axis orientation compare with the direct deposition on the bare glass. The mechanism about this effect of Ti underlayer on CoCrPtTa is not to be clarified yet. Meanwhile, it is found that the magnetic domain of CoCrPtTa on 20 nm Ti underlayer has the continuous stripe pattern but the one of CoCrPtTa on 90 nm Ti underlayer shows the discrete mass type from the results of MFM investigation. This phenomenon is to be a distinct evidence that the improvement of perpendicular anisotropy by the adoption of Ti underlayer is originated from the reinforcement of the grain boundary segregation in CoCrPtTa alloy. Moreover, the transition of the M-H hysteresis pattern with the thickness of Ti underlayer indicates that the major contribution of Ti underlayer is not the magnetocrystalline anisotropy but the shape anisotropy due to the formation of uniform columnar grains by the nonmagnetic alloy segregation.

• Journal of the Semiconductor & Display Technology
• /
• v.2 no.2
• /
• pp.5-8
• /
• 2003

In this study, as Cu diffusion barrier, tantalum nitrides were successfully deposited on Si(100) substrate and $SiO_2$ by plasma assisted atomic layer deposition(PAALD) and thermal ALD, using pentakis (ethylmethlyamino) tantalum (PEMAT) and NH$_3$ as precursors. The TaN films were deposited at $250^{\circ}C$ by both method. The growth rates of TaN films were 0.8${\AA}$/cycle for PAALD and 0.75${\AA}$/cycle for thermal ALD. TaN films by PAALD showed good surface morphology and excellent step coverage for the trench with an aspect ratio of h/w -1.8:0.12 mm but TaN films by thermal ALD showed bad step coverage for the same trench. The density for PAALD TaN was 11g/cmand one for thermal ALD TaN was 8.3g/$cm^3$. TaN films had 3 atomic % carbon impurity and 4 atomic % oxygen impurity for PAALD and 12 atomic % carbon impurity and 9 atomic % oxygen impurity for thermal ALD. The barrier failure for Cu(200 nm)/TaN(10 nm)/$SiO_2$(85 nm)/ Si structure was shown at temperature above $700^{\circ}C$ by XRD, Cu etch pit analysis.