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  • 1
    Electronic Resource
    Electronic Resource
    Fluorescence behaviour of polychlorinated dibenzofurans in organized molecular systems. Analytical applications (1995)
    Springer
    Microchimica acta 118 (1995), S. 185-196 
    Details
    ISSN: 1436-5073
    Keywords: spectrofluorimetry ; 2,3,7,8-tetrachlorodibenzofuran ; polyoxyethylene (10) lauryl ether ; C12E10 ; polychlorinated dibenzofurans ; micellar media ; sea water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Fluorescence characteristics of several polychlorinated dibenzofurans (PCDFs) of toxicological and environmental interest in the presence of cationic, anionic, neutral surfactants, α-cyclodextrin and β-cyclodextrin were examined. The fluorescence enhancement of 2,3,7,8-tetrachlorodibenzofuran (TTCDF) in the presence of polyoxyethylene(10) lauryl ether (C12E10) medium was utilized to establish a sensitive spectrofluorimetric method for determination of TTCDF. The optimization of variables as the concentration of surfactant, percentage of organic solvent and temperature, and effect of possible interferences from other PCDFs, polychlorinated dibenzo-p-dioxins (PCCDs), polychlorinated biphenyls (PCBs) and Arochlors were investigated. The method, which has a detection limit of 1.30 ng ml−1, has been applied to the determination of TTCDF in sea water with acceptable recoveries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244358
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  • 2
    Electronic Resource
    Electronic Resource
    On the Protection by Inorganic Phosphate of Calcium-Induced Membrane Permeability Transition (1997)
    Springer
    Journal of bioenergetics and biomembranes 29 (1997), S. 571-577 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondrial calcium ; inorganic phosphate ; membrane permeability transition ; calcium transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The role of inorganic phosphate as inhibitor of mitochondrial membrane permeability transition was studied. It is shown that in mitochondria containing a high phosphate concentration, i.e., 68 nmol/mg, Ca2+ did not activate the pore opening. Conversely, at lower levels of matrix phosphate, i.e., 38 nmol/mg, Ca2+ was able to induce subsequent pore opening. The inhibitory effect of phosphate was apparent in sucrose-based media, but it was not achieved in KCl media. The matrix free Ca2+ concentration and matrix pH were lowered by phosphate, but they were always higher in K+-media. In the absence of ADP, phosphate strengthened the inhibitory effect of cyclosporin A on carboxyatractyloside-induced Ca2+ efflux. Acetate was unable to replace phosphate in the induction of the aforementioned effects. It is concluded that phosphate preserves selective membrane permeability by diminishing the matrix free Ca2+ concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022483018482
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  • 3
    Electronic Resource
    Electronic Resource
    Interaction of SO2 with CeO2 and Cu/CeO2 catalysts: photoemission, XANES and TPD studies (1999)
    Springer
    Catalysis letters 62 (1999), S. 113-119 
    Details
    ISSN: 1572-879X
    Keywords: cerium oxides ; SO2 ; desulfurization ; copper ; X‐ray absorption spectroscopy ; photoemission and XPS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract CeO2 and Cu/CeO2 are effective catalysts/sorbents for the removal or destruction of SO2. Synchrotron‐based high‐resolution photoemission, X‐ray absorption near‐edge spectroscopy (XANES), and temperature‐programmed desorption (TPD) have been employed to study the reaction of SO2 with pure and reduced CeO2 powders, ceria films (CeO2, CeO2−x, Ce2O3+x) and model Cu/CeO2 catalysts. The results of XANES and photoemission provide evidence that SO4 was formed upon the adsorption of SO2 on pure powders or films of CeO2 at 300 K. The sulfate decomposed in the 390–670 K temperature range with mainly SO2 and some SO3 evolving into gas phase. At 670 K, there was still a significant amount of SO4 present on the CeO2 substrates. The introduction of O vacancies in the CeO2 powders or films favored the formation of SO3 instead of SO4. Ceria was able to fully dissociate SO2 to atomic S only if Ce atoms with a low oxidation state were available in the system. When Cu atoms were added to CeO2 new active sites for the destruction of SO2 were created improving the catalytic activity of the system. The surface chemistry of SO2 on the Cu‐promoted CeO2 was much richer than on pure CeO2. The behavior of ceria in several catalytic processes (oxidation of SO2 by O2, reduction of SO2 by CO, automobile exhaust converters) is discussed in light of these results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019007308054
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of pure and sulfided NiMoO4 catalysts using synchrotron-based X-ray absorption spectroscopy (XAS) and temperature-programmed reduction (TPR) (1998)
    Springer
    Catalysis letters 51 (1998), S. 85-93 
    Details
    ISSN: 1572-879X
    Keywords: nickel molybdate ; HDS catalysts ; sulfur poisoning ; X-ray absorption spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This study aims at characterizing the properties of pure and sulfided NiMoO4 catalysts using synchrotron-based near-edge X-ray absorption fine structure (NEXAFS) and temperature-programmed reduction (TPR). Mo LII-edge and MIII-edge NEXAFS spectra indicate that on reaction with H2S, the Mo component of NiMoO4 gets partially reduced with the formation of MoS2 type species. For the β-phase of NiMoO4, the sulfidation of Mo is more extensive than for the α-phase, making the former a better precursor for catalysts of hydrodesulfurization (HDS) reactions. The Ni LII-edge features are relatively insensitive to the changes accompanying the partial sulfidation of NiMoO4. The sulfidation of the Ni component is confirmed by analysis of the Ni K-edge extended X-ray absorption fine structure (EXAFS) spectra which show the formation of Ni–S bonds (bond length ∼2.48 Å) and a NiMoSx phase. The S K-edge NEXAFS spectra show the presence of at least two types of sulfur species, one associated with a formal oxidation state of 2- and another associated with a formal oxidation state of 6+. We attribute the former to the presence of metal–sulfur bonds (MoSx and NiSy). The latter is associated with the formation of S–O bonds (SO 4 2- ). The formation of sulfates is also supported by the O K-edge NEXAFS spectra. The partially sulfided NiMoO4 catalysts (both α- and β-isomorphs) have a much lower thermal stability in a reducing environment than pure NiMoO4 and MoS2. The sulfided molybdates react with H2 in TPR producing H2O and H2S at temperatures above 400 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019089002041
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  • 5
    Electronic Resource
    Electronic Resource
    Cesium-catalyzed oxidation of zinc surfaces (1994)
    Springer
    Catalysis letters 26 (1994), S. 393-399 
    Details
    ISSN: 1572-879X
    Keywords: Zn oxidation ; Cs catalysis ; Cs/ZnO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract On zinc films, the adsorption probability of O2 is extremely low (10−3–10−2), and O2 exposures in the range of 103–104 langmuir are necessary to produce a significant transformation of metallic zinc into zinc oxide. The presence of submonolayer coverages of cesium enhances the oxidation rate of zinc by 2–3 orders of magnitude. The cesium adatoms interact with O2 molecules, producing a reservoir of reactive oxygen species that oxidize zinc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00810613
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  • 6
    Electronic Resource
    Electronic Resource
    The interaction of sulfur with Cu/Pt(111) and Zn/Pt(111) surfaces: copper-promoted sulfidation of platinum (1995)
    Springer
    Catalysis letters 32 (1995), S. 345-355 
    Details
    ISSN: 1572-879X
    Keywords: S poisoning ; Pt sulfidation ; Cu/Pt and Zn/Pt catalysts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The interaction of sulfur with Pt(111), Zn/Pt(111) and Cu/Pt(111) has been examined using X-ray photoelectron spectroscopy (XPS), X-ray excited Auger electron spectroscopy (XAES), and thermal desorption mass spectroscopy (TDS). At temperatures between 300 and 600 K, the exposure of Pt(111) to S2 gas produces a chemisorbed layer of sulfurwithout the formation of bulk sulfides. Exposure of S2 to a Zn/Pt(111) alloy, at room temperature, results in a breakdown of the alloy and formation of a zinc-sulfide film on Pt(111). Further S2 exposure at 550 K sulfidizes the remaining metallic zincwithout affecting platinum. For the Cu/Pt(111) surface alloy, on the other hand, exposure to S22 at 550 K leads to sulfidation of the platinum. Platinum can effectively compete for sulfur atoms bonded to copper but not for those bonded to zinc. The reaction of S2 gas with Cu/Pt(111) surfaces produces copper sulfides that promote the sulfidation of Pt by providing surface sites for the dissociation of S2, and by favoring the diffusion of S into the bulk of the system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00813229
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular and crystal structure of 1,4-diacethoxy naphthalene: Structural analysis of methyl substituted 1,4-diacethoxynaphthalenes (1989)
    Springer
    Journal of chemical crystallography 19 (1989), S. 307-316 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Methyl substituted 1,4-diacethoxynaphthalenes have been synthetized and analyzed by means of ultraviolet and1H-nmr. Positional effects of the methyl substitution on the spectroscopic parameters have been rationalized. 6,7-Dimethyl-1,4-diacethoxynaphthalene,V, has been analyzed by X-ray diffraction techniques. Crystals are monoclinic P21,a=8.816(1),b=26.676(7),c=6.189(1) Å,β=103.9 (2) ° and four molecules in the unit cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01194126
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular structure and reactivity of the 1,2-dihydrocarbazol-4(3H)-one: X-ray crystal structure of N-methyl and N-(p-methylbenzenesulfonyl) derivatives (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 249-257 
    Details
    ISSN: 1572-8854
    Keywords: Synthesis ; reactivity ; tetrahydrocarbazol-4-one
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Synthesis and reactivity analysis of the 1,2-dihydrocarbazol-4(3H)-one, and the N-methyl, N-tosyl and 2,2-dimethyl derivatives have been carried out. Molecular structures of the N-methyl and N-tosyl derivatives have been analyzed by X-ray diffraction. Crystals of the N-methyl derivative are monoclinic, space group P21/c,a=8.868(1),b=16.652(1),c=7.5440(4) Å, β=113.657(3). Crystals of the N-tosyl derivative are monoclinic, P21/c,a=12.0016(3),b=8.9178(2),c=16.0485(4) Å, β=104.372(2). An extended conjugation from the carbonyl group to the nitrogen atom and an envelope conformation for the common cyclohexenone fragment are evident in both cases. Oximation and Beckmann rearrangement, and etherification of the carbonyl group is reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665179
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  • 9
    Electronic Resource
    Electronic Resource
    Modulation of matrix Ca2+ content by the ADP/ATP carrier in brown adipose tissue mitochondria. Influence of membrane lipid composition (1996)
    Springer
    Journal of bioenergetics and biomembranes 28 (1996), S. 69-76 
    Details
    ISSN: 1573-6881
    Keywords: Matrix calcium ; BAT mitochondria ; membrane permeability transition ; adenine nucleotide translocase ; calcium transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The role of the adenine nucleotide translocase on Ca2+ homeostasis in mitochondria from brown adipose tissue was examined. It was found that in mitochondria incubated with 50 μM Ca2+, ADP was not needed to retain the cation, but it was required for strengthening the inhibitory effect of cyclosporin on membrane permeability transition as induced by menadione. In addition, carboxyatractyloside was unable to promote matrix Ca2+ release, even though it inhibits the ADP exchange reaction. However, when the Ca2+ concentration was increased to 150 μM, carboxyatractyloside did induce Ca2+ release, and ADP favored Ca2+ retention. Determination of cardiolipin content in the inner membrane vesicles showed a greater concentration in brown adipose tissue mitochondria than that found in kidney mitochondria. It is suggested that the failure of the adenine nucleotide translocase to influence membrane permeability transition depends on the lipid composition of the inner membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02109905
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  • 10
    Electronic Resource
    Electronic Resource
    Modulation of matrix Ca2+ content by the ADP/ATP carrier in brown adipose tissue mitochondria. Influence of membrane lipid composition (1996)
    Springer
    Journal of bioenergetics and biomembranes 28 (1996), S. 69-76 
    Details
    ISSN: 1573-6881
    Keywords: Matrix calcium ; BAT mitochondria ; membrane permeability transition ; adenine nucleotide translocase ; calcium transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The role of the adenine nucleotide translocase on Ca2+ homeostasis in mitochondria from brown adipose tissue was examined. It was found that in mitochondria incubated with 50 μM Ca2+, ADP was not needed to retain the cation, but it was required for strengthening the inhibitory effect of cyclosporin on membrane permeability transition as induced by menadione. In addition, carboxyatractyloside was unable to promote matrix Ca2+ release, even though it inhibits the ADP exchange reaction. However, when the Ca2+ concentration was increased to 150 μM, carboxyatractyloside did induce Ca2+ release, and ADP favored Ca2+ retention. Determination of cardiolipin content in the inner membrane vesicles showed a greater concentration in brown adipose tissue mitochondria than that found in kidney mitochondria. It is suggested that the failure of the adenine nucleotide translocase to influence membrane permeability transition depends on the lipid composition of the inner membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02150680
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