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  • Springer  (43)
  • American Institute of Physics  (1)
  • American Physical Society (APS)  (1)
  • Blackwell Publishing Ltd  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The role of ethylene in the induction of amylase activity in wheat aleurone tissue (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 58 (1983), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: When wheat aleurone layers (Triticum aestivum L. var. Potam S-70) incubated in medium containing gibberellic acid were exposed to ethylene, the synthesis and release of amylase were enhanced relative to layers incubated in the presence of mercuric perchlorate. Exogenous ethylene stimulated gibberellic acid-induced amylase synthesis by approximately 2.2-fold. The ethylene-mediated stimulation of amylase formation was dependent upon the tissue being exposed to the gas during the lag phase of gibberellic acid action. Ethylene appeared to promote only quantitative changes in amylase synthesis and release, since the isoelectric focusing patterns of amylase is enzymes were not significantly altered by ethylene. Ethylene had no effect on the incorporation of [methyl-14C]choline into aleurone phospholipids, but stimulated the accumulation of [U-14C]adenine into poly(A) RNA of gibberellic acid-treated tissue by about 80%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1983.tb04187.x
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  • 2
    Electronic Resource
    Electronic Resource
    Pt-Sn/Al2O3 sol-gel catalysts: Metallic phase characterization (1993)
    Springer
    Catalysis letters 21 (1993), S. 309-320 
    Details
    ISSN: 1572-879X
    Keywords: Sol-gel catalysts ; platinum-tin catalysts ; platinum dispersion ; X-ray diffraction ; energy dispersive X-ray analysis ; EDX analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Highly dispersed platinum was found in Pt-Sn/Al2O3 catalysts prepared by the sol-gel method, i.e., cogelation of aluminum tri-sec-butoxide and tetrabutyltin and subsequent impregnation with hexachloroplatinic acid. X-ray diffraction studies showed that the cell parameter of pure platinum is not modified in bimetallic Pt-Sn samples. Moreover, energy dispersive X-ray analysis studies (EDX) showed that platinum, but not tin, was detected in the catalysts where tin was incorporated by the sol-gel coprecipitation of tin and aluminum. Incorporation of tin into the alumina network is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00769483
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  • 3
    Electronic Resource
    Electronic Resource
    Coke formation on an industrial reforming Pt–Sn/γ‐Al2O3 catalyst (2000)
    Springer
    Catalysis letters 65 (2000), S. 209-216 
    Details
    ISSN: 1572-879X
    Keywords: coke formation ; industrial reforming catalyst ; Pt–Sn/γ‐Al2O3 ; coke characterization ; coke burning off
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The characterization of the coke deposited on an industrial Pt–Sn/γ‐Al2O3 catalyst, used in a continuous reforming process, was performed with AFM, XRD, FTIR, EPR, NMR, TG‐DTG and DTA techniques. Composition, structure and location of the coke on the catalyst were investigated. The coke was predominantly deposited on the catalyst surface and in the interstices between the catalyst particles. Its content increased along the reactor from top to bottom. Coke was deposited in the form of uniform films and clusters of three‐dimensional disks with diameters between 0.12 and 0.18 μm. It had a pseudo‐graphite structure produced by the dehydrogenation and polymerization of the aromatic precursor compounds. The coked catalyst showed a good combustion behavior; it was regenerated below 550°C. These results are important to elucidate the coke formation mechanism, to generate new continuous reforming catalysts, and to optimize the reactor operation parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019042027077
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  • 4
    Electronic Resource
    Electronic Resource
    Dehydroxylation and the Crystalline Phases in Sol-Gel Zirconia (1998)
    Springer
    Journal of sol gel science and technology 11 (1998), S. 309-319 
    Details
    ISSN: 1573-4846
    Keywords: dehydroxilation in sol-gel ZrO2 ; paramagnetic point defects ; tetragonal zirconia stabilization ; nanocrystalline tetragonal ZrO2 ; nanocrystalline monoclinic ZrO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The formation and evolution with temperature of the crystalline phases in sol-gel ZrO2 was analyzed by using X-ray powder diffraction, refinement of the crystalline structures, ESR, and UV-Vis spectroscopy. The precursor phase of crystalline zirconia was amorphous Zr(OH)4 with the same local order as the tetragonal crystalline phase. This amorphous phase dehydroxylated with temperature, generating nanocrystalline tetragonal zirconia, and producing point defects that stabilized the tetragonal structure, generated a paramagetic ESR signal with g values like the free electron, and had a light absorption band at 310 nm. When the sample was annealed at higher temperatures, it continued dehydroxilating, and the point defects disappeared, causing the transformation of the nanocrystalline tetragonal phase into nanocrystalline monoclinic zirconia. The two crystalline nanophases coexisted since the beginning of crystallization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008666531404
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  • 5
    Electronic Resource
    Electronic Resource
    A Raman Scattering Study of PbTiO3 and TiO2 Obtained by Sol-Gel (1998)
    Springer
    Journal of sol gel science and technology 13 (1998), S. 849-853 
    Details
    ISSN: 1573-4846
    Keywords: Raman ; TiO2 ; PbTiO3-nanocrystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The mechanisms that give rise to the broadening and the shifts of the Raman peaks of titanium dioxide and lead titanate nanocrystals prepared by sol-gel are discussed. Phonon confinement and oxygen deficiency are competitive mechanisms in TiO2 obtained by different sol-gel preparations whereas pressure effects on the nanocrystals predominate in ferroelectric PbTiO3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008602718987
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  • 6
    Electronic Resource
    Electronic Resource
    Preparation of Magnesia-Silica Oxides: Effect of Mg/Si Ratio and Sulfate on Acidity (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 321-325 
    Details
    ISSN: 1573-4846
    Keywords: magnesia-silica mixed oxides ; sol-gel magnesia-silica ; magnesia-silica acidity ; sulfated magnesia-silica ; isopropanol decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mg-Si binary oxides were prepared by the sol-gel method, using magnesium diethoxide and tetraethoxysilane as starting materials. Mg-Si mixed oxides were prepared at pH3 and 9 at nominal concentrations of 1.3, 4.0, and 6.7 mole% MgO. Density and strength of the acid sites were determined by pyridine thermal programmed desorption. Comparable Lewis acidity was found in pH3 and 9 preparations. However, when the samples were sulfated with sulfuric acid, strong Bronsted acidity was developed, reaching a maximum at 6.7 mole% MgO. The strong acidity of sulfated samples was corroborated using the isopropanol decomposition reaction as catalytic test. Similar conversions are obtained at 100°C on sulfated samples, whereas 260°C are required for non-sulfated ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026487018502
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal Stability of Sol-Gel Hydrotalcites (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 437-442 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel hydrotalcites ; X-ray diffraction ; aluminum precursors ; hydrotalcites Mg/Al ratio ; mixed metal hydroxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sol-Gel Hydrotalcites were synthesized using magnesium ethoxide and variable aluminum sources: aluminum acetilacetonate, aluminum chloride, aluminum nitrate and aluminum sulfate; in all cases, the gelation was done at pH 10. X-ray diffraction studies show that the crystallinity depends on the aluminum precursor used. The crystallinity was found in the order aluminum acetylcetonate 〉 aluminum chloride 〉 aluminum nitrate 〉 aluminum sulfate. The precursor determines the sintering behavior as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018309420745
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of Tin Precursor on the Catalytic Properties of Pt-Sn/Al2O3 Sol-Gel Prepared Catalysts (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 847-849 
    Details
    ISSN: 1573-4846
    Keywords: platinum-tin catalysts ; Pt-Sn sol-gel catalysts ; cyclohexane dehydrogenation ; n-hexane conversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Tin-alumina supports were prepared by cogelation of aluminum tri-sec-butoxide and tetrabutyltin or tin tetrachloride. Aqueous or acetone platinum solutions were used for impregnation. The results show that the specific surface area and the acidity of the catalysts were only slightly modified by the metal precursors used. On cyclohexane dehydrogenation and n-hexane conversion, high selectivity to olefins and low cracking products were detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018362813843
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  • 9
    Electronic Resource
    Electronic Resource
    Preparation of magnesia-silica oxides: Effect of Mg/Si ratio and sulfate on acidity (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 321-325 
    Details
    ISSN: 1573-4846
    Keywords: magnesia-silica mixed oxides ; sol-gel magnesia-silica ; magnesia-silica acidity ; sulfated magnesiasilica ; isopropanol decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mg−Si binary oxides were prepared by the sol-gel method, using magnesium diethoxide and tetraethoxysilane as starting materials. Mg−Si mixed oxides were prepared at pH3 and 9 at nominal concentrations of 1.3, 4.0, and 6.7 mole% MgO. Density and strength of the acid sites were determined by pyridine thermal programmed desorption. Comparable Lewis acidity was found in pH3 and 9 preparations. However, when the samples were sulfated with sulfuric acid, strong Bronsted acidity was developed, reaching a maximum at 6.7 mole% MgO. The strong acidity of sulfated samples was corroborated using the isopropanol decomposition reaction as catalytic test. Similar conversions are obtained at 100°C on sulfated samples, whereas 260°C are required for non-sulfated ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02436859
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal stability of sol-gel hydrotalcites (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 437-442 
    Details
    ISSN: 1573-4846
    Keywords: sol-gel hydrotalcites ; X-ray diffraction ; aluminum precursors ; hydrotalcites Mg/Al ratio ; mixed metal hydroxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sol-Gel Hydrotalcites were synthesized using magnesium ethoxide and variable aluminum sources: aluminum acetilacetonate, aluminum chloride, aluminum nitrate and aluminum sulfate; in all cases, the gelation was done at pH 10. X-ray diffraction studies show that the crystallinity depends on the aluminum precursor used. The crystallinity was found in the order aluminum acetylcetonate〉aluminum chloride〉aluminum nitrate〉aluminum sulfate. The precursor determines the sintering behavior as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02436879
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