• Title, Summary, Keyword: uv-spectra

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A New Iron Emission Template for Active Galactic Nuclei

  • Park, Daeseong;Barth, Aaron J.;Ho, Luis C.;Laor, Ari
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.2
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    • pp.36.2-36.2
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    • 2019
  • Fe II emission is a prominent and ubiquitous feature in the spectra of broad-line Active Galactic Nuclei (AGN) by producing a pseudo-continuum from UV to optical with complex and strong blends of the numerous emission lines themselves, other emission lines, and continuum. Since theoretical modeling of such intricate Fe II emission is very difficult and still far from able to reproduce observed data in detail, an empirical iron emission template, derived from observations of a narrow-line Seyfert 1 galaxy, is an essential and practical tool to obtain accurate measurements of all the emission lines and continuum in AGN spectra. However, the existing iron templates, based on the single prototypical strong Fe II emitter I Zw 1, are suffering from inadequate S/N and non-simultaneous, inconsistent data with limited wavelength coverage, which consequently limit the accuracy of all the spectral measurements. To overcome the limitations and construct an improved iron template with wide spectral coverage, high-quality UV and optical spectra for the new and better identified template galaxy, Mrk 493, were successfully obtained from our HST STIS program (GO-14744). We will show the preliminary results for multicomponent spectral decomposition of the data and template construction with application tests to various AGN spectra and comparison with previous templates.

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A study of defect structures in $LiNbO_{3}$ single crystals by optical absorptions (광흡수에 의한 $LiNbO_{3}$ 단결정의 결함 구조 연구)

  • 김상수
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.6 no.3
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    • pp.327-340
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    • 1996
  • In this study, a series of $LiNbO_{3}$ crystals with different [Li]/[Nb] ratios, congruent $LiNbO_{3}$ crystals with doped Mg and with Mg and codoped with Mn were grown by the Czocharalski method. These were investigated by UV and IR spectrophotometry. Stoichiometry dependences of the UV absorption edge and the $OH^{-}$ absorption spectra were studied with different [Li]/[Nb] ratios. The position of the UV absorption edge adn the shape and peak point of the $OH^{-}$ absorption spectra changed monotonously upto a critical concentration of Mg ions. The mechanism of the incorporation of Mg ions changes at this concentration. The decomposition of the $OH^{-}$ absorption spectra using a Gaussian lineshape function showed that in Li-deficient crystals the absorption spectra consist of five components in contrast to more or less perfect stoichiometric crystals which reveal to three components. On the basis of these results, the intrinsic and the extrinsic defect structure models in $LiNbO_{3}$ crystals were examined. The behaviour of $\nu$ (OH) reflects the defect structure and supports the Li-site vacancy model as the intrinsic defect structure model and the corresponding extrinsic defect model. A brief discussion is also given of the behaviour of $\nu$ (OH) in $LiNbO_{3}$ crystals simultaneously doped with several kinds of impurity.

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EFFECT OF PHOTOCHEMICAL REACTIONS ON LUMINESCENCE OF CRYSTALLINE RDX

  • Kim, Hack-Jin;Kang, Tai-Jong
    • Journal of Photoscience
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    • v.2 no.2
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    • pp.83-87
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    • 1995
  • Luminscence spectra and decay of crystalline hexahydro-1,3,5-trinitro-1,3,5-s-tetrazine (RDX) are observed at 90 K and the effects of photochemical reaction on the luminescence of RDX are investigated. The uv light from high power Hg lamp is used for the photochemical reaction of RDX. While no significant changes are observed in the luminescence spectra after the photochemical reaction, the intensity profile of the spectra changes with the progress of chemical reactions. The biexponential decay of luminescence is modified by chemical reactions. Features of the electronic states of crystalline RDX are discussed in relation to the luminescence.

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Separation and Characteristics of Antioxidative Substances in Fermented Soybean Sauce (양조간장으로부터 항산화성 물질의 분리 및 그 특성)

  • Moon, Gab-Soon;Cheigh, Hong-Sik
    • Korean Journal of Food Science and Technology
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    • v.22 no.4
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    • pp.461-465
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    • 1990
  • Fermented soybean sauce was fractionated by gel filteration chromatography and the physico-chemical properties of each fraction were investigated for the study on the separation and characteristics of antioxidative substances in the soybean sauce. The brown coloured melanoidin fractions(MF-I) collected by Sephadex G-10 column were found to contain nitrogeneous compounds and to have strong antioxidative activity and reducing power. The freeze dried MF-I was further fractionated with Sephadex G-50 and G-100 successively and then MF-II and MF-III fractions were observed to be the most effective antioxidant and reducing power among the fractions. The UV-VIS and IR absorption spectra of the each fraction were also determined and discussed.

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Mechanism of Orientation of Liquid Crystal Molecules for Polarized UV-exposed Polyimide Alignment Layers (폴리애미드 배향막의 편광 자외선 조사에 따른 액정 배향 메카니즘)

  • 김일형;김욱수;하기룡
    • Polymer Korea
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    • v.26 no.2
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    • pp.209-217
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    • 2002
  • We studied the mechanism of orientation of polyimide molecules which were irradiated by polarized UU (PUV) using polarized Fourier transform infrared (FT-IR) spectroscopy and ultraviolet (UV) spectroscopy, According to the measured UV spectra, we found PI films mainly absorb UV light less than 350 nm wavelength, therefore, UV light less than 360 nm induces photochemical reaction of PI. PUV irradiation of PI films caused decrease of all peak intensities in the FT-IR spectra. except the newly formed broad peak at $3244 cm^{-1}$, due to degradation of the PI molecules. The remaining PI molecules after photo-degradation showed predominantly perpendicular molecular orientation to the irradiated PUV polarization direction, due to the preferential degradation of PI molecules parallel to irradiated PUV polarization direction. However the rubbing of PI films induced reorientation of the PI molecules parallel to the rubbing direction. We also investigated the alignment of the liquid crystal by rubbing or PUV irradiation. Liquid crystals align perpendicular to the PUV polarization direction and parallel to the rubbing direction.

Mass Balance Method for Purity Assessment of Organic Reference Materials: for Thermolabile Materials with LC-UV Method

  • Lee, Joonhee;Kim, Byungjoo
    • Bulletin of the Korean Chemical Society
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    • v.35 no.11
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    • pp.3275-3279
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    • 2014
  • A mass balance method for purity assessment of thermolabile organic reference materials was established by combining several techniques, including liquid chromatography with UV/VIS detector (LC-UV), Karl-Fischer (K-F) Coulometry, and thermal gravimetric analysis (TGA). This method was applied to three fluoroquinolones like enrofloxacin, norfloxacin and ciprofloxacin. LC-UV was used to analyze structurally related organic impurities based on UV/VIS absorbance spectra obtained in combination with LC separation. For all three organic reference materials, the UV/VIS spectra of the separated impurities were similar to that of the major component of the corresponding materials. This indicates that the impurities are structurally related to the respective reference material sharing common chromophores. Impurities could be quantified by comparing their absorbances at the wavelength of maximum absorbance (${\lambda}_{max}$). The water contents of the reference materials were measured by K-F Coulometry by an oven-drying method. The total inorganic impurities contents were assayed from ash residues in TGA analysis with using air as a reagent gas. The final purities estimated from results of those analytical techniques were assigned as ($99.91{\pm}0.06$), ($97.09{\pm}0.17$) and ($91.85{\pm}0.17$)% (kg/kg) for enrofloxacin, norfloxacin and ciprofloxacin, respectively. The assigned final purities would be applied to the reference materials which will be used as calibrators for the certification of those compounds in matrix CRMs as starting points for the traceability of their certified values to SI units.

Studies on the Syntheses of Polymeric Dyes(III) -Composition and UV, VIS Spectrum- (고분자염료의 합성에 관한 연구(III) -Composition 및 UV, VIS Spectrum-)

  • 조경래;김경환
    • Textile Science and Engineering
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    • v.24 no.2
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    • pp.58-67
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    • 1987
  • Polymeric dyes were synthesized by the copolymerization of 4-(N-acrylamidomethyl)aminoazobenzene with styrene and vinyl acetate. Distributions of the monomers in a polymeric dyes were calculated by Harwood's method. The optical behavior of isomerizing side chain(aminoazo group) of polymeric dyes in several conditions were qualitatively studied from UV, VIS absorption spectra, especially the transcis isomerization process, and compared with those of p-aminoazobenzene and 4-(Nacrylamidomethyl)aminoazobenzene.

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PRELIMINARY STUDIES ON NATURAL PLANT EXTRACTS AS SUNSCREEN AGENTS

  • Lee, K.T.;Kim, J.H.
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.24 no.3
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    • pp.81-88
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    • 1998
  • The aim of this study is to evaluate several plant extracts with a view to developing UV sunscreen agents. In this study, 150 plant extracts were screened to elucidate their UV spectra using spectrophotometric method. Several plant extracts such as Phellodendron amurense, Morus alba, Rhododendron mucronulatum, Brassica alba have strong absorbency at UVA region (350nm), the suntanning wavelength. And Sophora flavescens, Caesalpinia sapper, Morus alba, Phellodendron amurense, showed absorption plateau value at UVB region (308nm), the erythema action wavelength. These extracts have a good absorbency property as synthetic filter and could be served as substitutes for synthetic UV sunscreen agents.

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Normalization and Search of the UV/VIS Spectra Measured from TLC/HPTLC (TLC/HPTLC에서 측정된 자외/가시부 스펙트럼의 표준화 및 검색)

  • Kang, Jong-Seong
    • YAKHAK HOEJI
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    • v.38 no.4
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    • pp.366-371
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    • 1994
  • To improve the identification power of TLC/HPTLC the in situ reflectance spectra obtained directly from plates with commercial scanner are used. The spectrum normalization should be carried out prior to comparing and searching the spectra from library for the identification of compounds. Because the reflectance does not obey the Lambert-Beer's law, there arise some problems in normalization. These problems could be solved to some extent by normalizing the spectra with regression methods. The spectra are manipulated with the regression function of a curve obtained from the correlation plot. When the parabola was used as the manipulating function, the spectra were identified with the accuracy of 97% and this result was better than that of conventionally used the point and area normalization method.

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Deterioration Mechanism of Paper According to Sizing and Beating (II) -Influences of Beating- (사이징과 고해에 따른 종이의 열화기구(제2보) -고해의 영향-)

  • 김봉용
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.31 no.2
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    • pp.58-63
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    • 1999
  • Three kinds of papers were prepared from different beating degree of pulps. Physical and optical properties were examined to elucidate the deterioration mechanism of paper according to beating degrees. Changes of double folds, elongation, water retention value, DP, K/S value and visible, UV region light absorption spectra of those papers treated by UV light were studied. Double folds and brightness were decreased more rapidly by UV treatment with increasing of beating degree. The light absorption rates of pulps in visible and UV region were also increased with change of beating level. The formation of new hydrogen bonds and higher light absorption rate of pulps according to beating induced to absorb and interact with much UV light. These phenomena maybe brought about to accelerate paper deteriortion by UV treatment both optical and physical properties.

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