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  • Korea  (7)
  • permeability  (7)
  • Arabidopsis thaliana  (5)
  • ion exchange  (5)
  • Springer  (24)
  • American Geophysical Union (AGU)
  • 1
    ISSN: 1572-879X
    Keywords: nickel ; Y-zeolite ; ion exchange ; hydrogenation of carbon dioxide ; methane ; hydrogen ; carbon monoxide ; acid strength ; electrostatic field
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Nickel metal introduced into Y-zeolite exhibited a high catalytic activity in the dehydro-genation of methane and in the hydrogenation of carbon dioxide with methane to obtain hydrogen and CO at about 850 K. The activity strongly depended on the nickel amount in NaY, and the catalytic properties were influenced by the kind of cations in the Y-zeolite. The higher CO2 conversion was obtained over Ni supported on non-acidic zeolites.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of biomedical science 5 (1998), S. 267-273 
    ISSN: 1423-0127
    Keywords: Grave's disease ; Human foamy virus ; Korea ; Molecular epidemiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The possible association of human foamy virus (HFV) with human thyroid disorders such as Graves' disease (GD) has been a topic of controversy due to the inconsistent results reported by several groups of investigators. Here we report the investigation of the presence of HFV-related sequences in the Korean population. DNA was obtained from peripheral blood lymphocytes from 24 GD patients and 23 healthy blood donors and subjected to PCR amplification using three sets of nested primers derived fromgag, env, and LTR regions of the HFV genome. Contrary to previously reported studies, our analysis identified HFV-related sequences in the genomes of both healthy individuals and the GD patients. However, the nature of the HFV genome present in each group appeared to be different. We detected all 3 regions of HFV-related sequences in 29% of the HFV-positive GD patients, while no samples in the control group amplified all three regions. This suggests that the LTR may be used as a tool for screening for HFV in GD patients. Our data favor the hypothesis of a relationship between GD and the presence of HFV-related sequences, though in a complex way.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 57 (1999), S. 139-143 
    ISSN: 1572-879X
    Keywords: MCM-41 ; chiral Mn(salen) ligand ; ion exchange ; asymmetric epoxidation ; styrene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract New tetradentate chelates of bis-Schiff bases were synthesized and then these chiral salen ligands were immobilized over mesoporous MCM-41 by using the ion-exchange method. The efficiency of the chiral catalyst was examined in the asymmetric epoxidation of styrene. Chiral Mn(salen) complexes immobilized onto mesoporous MCM-41 were stable during the reaction without any leaching and exhibited relatively high enantioselectivity for epoxidation as compared with homogeneous complexes.
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  • 4
    ISSN: 1573-904X
    Keywords: drug delivery systems ; skin alternatives ; transdermal drug delivery ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To test the barrier function of a bio-engineered human skin (BHS) using three model drugs (caffeine, hydrocortisone, and tamoxifen) in vitro. To investigate the lipid composition and microscopic structure of the BHS. Methods. The human skin substitute was composed of both epidermal and dermal layers, the latter having a bovine collagen matrix. The permeability of the BHS to three model drugs was compared to that obtained in other percutaneous testing models (human cadaver skin, hairless mouse skin, and EpiDerm™). Lipid analysis of the BHS was performed by high performance thin layered chromatrography. Histological evalulation of the BHS was performed using routine H&E staining. Results. The BHS mimicked human skin in terms of lipid composition, gross ultrastructure, and the formation of a stratum corneum. However, the permeability of the BHS to caffeine, hydrocortisone, and tamoxifen was 3-4 fold higher than that of human cadaver skin. Conclusions. In summary, the results indicate that the BHS may be an acceptable in vitro model for drug permeability testing.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Environmental geochemistry and health 17 (1995), S. 139-146 
    ISSN: 1573-2983
    Keywords: Metal contamination ; Seoul ; Korea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Medicine
    Notes: Abstract To investigate the dispersion patterns and the characteristics of heavy metal contamination due to urbanisation and industrialisation, soils and dusts collected from the Seoul area were analysed for Cu, Pb, Zn and Cd. The metal concentrations in most soils and dusts are higher than the world averages. The pollution index ((Σ Metal concentrations in soils/Permissible level for metal)÷(Number of metals)) of soils and dusts is 〉 1 in most of the Seoul area, a result that concurs with the industrialisation and urbanisation index of the Seoul area. The soils are contaminated with Cu, Zn, Cd and particularly Pb. This suggests that the contamination of the soils in the Seoul area are mainly caused by vehicular emissions. The pollution index of soil is the highest in the Kuro area where Cu and Zn contamination in soils are due to the indigenous brass and bronze factories. From the discriminant analysis, the Seoul area may be partitioned into control, traffic and industrialized areas by the metal concentrations in the order of Zn 〉 Cu 〉 Pb.
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  • 6
    ISSN: 1572-879X
    Keywords: MCM-41 ; zeolite ; ion exchange ; Pt cluster ; 129Xe NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mesoporous molecular sieve MCM-41 with a Si/Al ratio of 35 was obtained by hydrothermal synthesis using a gel mixture with a molar composition of 6 SiO2∶0.1 Al2O3∶1 hexadecyltrimethylammonium chloride∶ 0.25 dodecyltrimethylammonium bromide∶ 0.25 tetrapropylammonium bromide∶0.15 (NH4)2O∶1.5 Na2O∶300 H2O. The MCM-41 sample was calcined in O2 flow at 813 K and subsequently ion exchanged with Ca2+. A small Pt cluster has been supported on the MCM-41 sample following a procedure using ion exchange of Pt(NH3) 4 2+ . The Pt(NH3) 4 2+ ion supported on MCM-41 has been activated in O2 flow at 593 K and subsequently reduced with Fh flow at 573 K, in the same way used for the preparation of a Pt cluster entrapped inside the supercage of zeolite NaY. The resulting Pt cluster supported on the MCM-41 shows hydrogen chemisorption oftotal two H atoms per Pt at 296 K (based on the total amount of Pt) and high catalytic activity for hydrogenolysis of ethane. The chemical shift in129Xe NMR spectroscopy of adsorbed xenon indicates that the Pt cluster is located inside the mesoporous molecular sieve.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied composite materials 1 (1994), S. 351-371 
    ISSN: 1573-4897
    Keywords: commingled yarn ; impregnation ; consolidation ; thermoplastics ; processing ; permeability ; mechanical testing ; mathematical modelling ; compression moulding ; glass fibre bed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Impregnation mechanisms of different kinds of GF/PP commingled yarns have been studied. As the reinforcing fibres were always the same, a global description has been worked out. Two different mathematical approaches for fibre bed permeability (Kozeny-Carman and Gutowski) were compared. The constants of the applied mathematical models have to stay the same if the fibre reeinforcement and the fibre arrangement is the same. Neither the kind of matrix, nor the fibre volume content may change these constants. Differences in the degree of impregnation after the same process conditions can be only due to different sizes of fibre agglomerations, thus the initial distribution of reinforcing fibres and matrix. For an exact determination of impregnation times and conditions the exact distribution of fibres in the intermediate material and after processing has to be known. This distribution is determined by SEM microscopy and data given from the material supplier. The importance of different process parameters, such as temperature, pressure, processing time is weighted by determining the density and mechanical properties of the specimens.
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  • 8
    ISSN: 1573-5028
    Keywords: Arabidopsis thaliana ; cDNA ; gene expression ; starch biosynthesis ; starch branching enzyme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two starch branching enzyme (SBE) cDNAs were identified in an Arabidopsis seedling hypocotyl library using maize Sbe1 and Sbe2 cDNAs as probes. The two cDNAs have diverged 5′ and 3′ ends, but encode proteins which share 90% identity over an extensive region with 70% identity to maize SBE IIb [12]. Genomic Southern blots suggest that the two cDNAs are the products of single, independent genes, and that additional, more distantly related SBE genes may exist in the Arabidopsis genome. The two cDNAs hybridize to transcripts which show similar expression patterns in Arabidopsis vegetative and reproductive tissues, including seedlings, inflorescence rachis, mature leaves, and flowers. This is the first report of the identification of cDNAs encoding two closely related starch branching enzymes from the same species.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-904X
    Keywords: tracheal epithelial cells ; air-interfaced culture ; ion transport ; drug transport ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The objective of this study was to investigate how culture conditions would affect the morphological, functional, and permeability characteristics of rabbit tracheal epithelial cell layers being considered for drug transport studies. Methods. Rabbit tracheocytes were isolated by protease treatment and plated onto collagen-treated permeable supports at 1.3 × 106 cells/cm2. After 24 hr, cell layers were cultured either air-interfaced (AIC) on their apical surface or under conventional liquid covered conditions (LCC). Results. Scanning electron microscopy revealed mature cilia in AIC cell layers and ciliated cells denuded of cilia in LCC cell layers. Compared with LCC, AIC cell layers (n = 20) achieved a significantly higher peak equivalent short-circuit current (74.1 ± 6.5 vs. 51.6 ± 3.4 µA/cm2), a higher potential difference (70.9 ± 2.8 vs. 60.5 ± 3.0 mV), and a lower peak transepithelial electrical resistance (1.1 ± 0.03 vs. 1.5 ± 0.02 kohms,cm2). About 70% of the short-circuit current in AIC was amiloride-sensitive whereas 〈10% was furosemide-sensitive, similar to that found in native tissue. The corresponding values in LCC were 50% and 46%. The permeability of both AIC and LCC to lipophilic solutes (dexamethasone and propranolol) was similar, whereas the permeability of hydrophilic solutes (mannitol, sucrose, and albuterol) in AIC was only half that in LCC. Conclusions. Given the striking similarity in morphological and functional characteristics of the AIC to those in the in vivo situation, the AIC is favored as an in vitro model for future drug transport studies.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Asia Pacific financial markets 6 (1999), S. 221-233 
    ISSN: 1573-6946
    Keywords: book-to-market ; explanatory factors ; Korea ; stock returns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract This study examines relations between stock returns and potential explanatory factors in Korea, an important and segmented emerging market. Our results show that Korean stock returns in general and returns on stocks listed in Section 1 in particular are significantly positively related to book-to-market, sales-price, and debt-equity ratios, but not significantly related to market value of equity. Returns on stocks listed in Section 2 are, however, negatively related to market value of equity and not significantly related to the other three variables. Among the variables investigated by us, book-to-market ratio has the greatest explanatory power for stock returns and it indicates superior returns for value stocks. Our findings strengthen the international evidence of the role of book-to-market ratio in explaining stock returns by demonstrating its significance even in the segmented Korean market.
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