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  • 1995-1999  (747)
  • Industrial Chemistry and Chemical Engineering  (746)
  • Nuclear reactions
  • 101
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 243-251 
    ISSN: 0268-2605
    Keywords: arsenic ; speciation ; algae ; Fucus gardneri ; arsenosugar ; high-performance liquid chromatography (HPLC) ; inductively coupled plasma-mass spectrometry (ICP-MS) ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Arsenic speciation in a brown alga, Fucus gardneri, collected in Vancouver, B.C., Canada, was carried out by using high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). Hydride generation-atomic absorption spectrometry (HG-AAS) was used for total arsenic determination. The relative amounts of some arsenosugars 1 in growing tips are found to be different in comparison with the remainder of the plant. Fucus samples collected in summer contain 9 ppm of total arsenic. Most of the arsenic species are extractable. Fucus samples collected in winter contain relatively higher amounts of arsenic, 16-22 ppm, but only low amounts of this are extractable. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
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  • 102
    ISSN: 0268-2605
    Keywords: carbohydrate surfactants ; wetting behaviour ; siloxane ; silane ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The wetting behaviour of carbohydrate surfactants bearing siloxane, carbosilane, polysilane or silane moieties has been investigated. By static surface tension (γlv, σ) and wetting tension (γsv-γsl, α) measurements on a non-polar perfluorinated surface (FEP®), the contact angles of aqueous surfactant solutions above the critical micelle formation concentration (cmc) were determined. Surface tension and wetting tension react independently on defined changes in the chemical structure of the surfactant molecules. Siloxane surfactants reduce the surface tension most effectively, whereas for a neopentyl-substituted silane derivative the lowest solid/liquid interfacial tension was found. The data for isomeric siloxanes, carbosilanes and silanes suggest that donor-acceptor forces at solid interfaces have a maximum range of about 4.5 Å. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
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  • 103
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 299-299 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 104
    ISSN: 0268-2605
    Keywords: Nickel-σ-organyl complexes ; dispersed atomic Ni(0) ; Ni(I) ions ; silica ; EPR ; FMR ; spectrum calculation ; strain ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dispersed atomic nickel(0) is formed during the reaction of the nickel-σ-organyl complexes with silanol groups at temperatures below 373 K. That nickel is oxidized to Ni(I) by protons of the silanol groups in a consecutive step. The Ni(I) portion amounts to about 70% w/w of the Ni used. Six different Ni(I) species are detected by electron paramagnetic resonance. They are stabilized by interaction with the silica surface and the organic moieties; they act as anchor ions for the Ni(0) atoms. Ni(0) crystallites stabilized in this way are about 0.5 nm in diameter after a treatment at 373 K. The influence of the Ni(I) ions on the collective, magnetic properties of the clusters is revealed by calculation of ferromagnetic resonance (FMR) spectra using the independent-grain approach according to Schlömann and Kotyukov. A strain of about 10 GPa is brought about in the nickel crystallites by the interaction with Ni(I) ions. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 3 Ill.
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  • 105
    ISSN: 0268-2605
    Keywords: Metal-organic chemical vapor deposition (MOCVD) ; precursors ; titanium ; vanadium ; carbonitride ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ceramic thin films containing titanium, vanadium, carbon, oxygen and nitrogen were obtained on steel substrates at 873 K, under nitrogen and helium gases and at low pressure, by chemical vapor deposition (CVD) from two organometallic precursors, CpTiCl2N(SiMe3)2 and Cp2VMe2 (Cp, cyclopentadienyl). Independent TG-DTA-MS and CVD studies of the two precursors showed their ability to co-decompose within compatible temperature and pressure domains. The mechanism of the reactions occurring inside the CVD apparatus was also approached by GC-MS and NMR analyses of the condensed decomposition products. CVD conducted under He gas confirmed that the formation of nitride resulted from the nitrogen atoms of the precursor, but the nitrogen content in the films remained lower than approx. 5%. Higher nitrogen contents (up to 12%) were only obtained when using ammonia as a carrier gas. Both precursors being air- and moisture-sensitive, high-purity CVD equipment was used to reduce oxycarbide formation. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 14 Ill.
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  • 106
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 293-293 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 107
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 295-296 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 108
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 297-297 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 109
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 298-298 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 110
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 253-256 
    ISSN: 0268-2605
    Keywords: disilane ; gas source MBE ; synchrotron radiation ; silicon hydride ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Surface hydrogen and growth mechanisms are investigated for synchrotron radiation (SR)-assisted gas source molecular beam epitaxy (SR-GSMBE) using Si2H6 on the Si(100) surface in the low-temperature region. The surface silicon hydrides (deuterides) are monitored in situ during the epitaxial growth by means of infrared reflection absorption spectroscopy with a Si(100) substrate and a CoSi2 buried metal layer. It is concluded that the chemisorption of gas-phase reactive species such as SiHn and H generated by SR irradiation and the subsequent hydrogen desorption are the key mechanisms of SR-GSMBE at low substrate temperatures. © 1998 John Wiley & Sons, Ltd.
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  • 111
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 298-299 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 112
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 301-301 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 113
    ISSN: 0268-2605
    Keywords: fungicidal activity ; Ceratocystis ulmi ; triphenyltin(IV) ; tributyltin(IV) ; phenolic bridge ; carboxylate bridge ; polymers ; trigonal bipyramidal structures ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The methods of synthesis, elemental analysis, IR and NMR spectroscopic data and fungicidal activity against Ceratocystis ulmi are reported for a series of triorganotin esters of N-arylidene-ω-amino acids of general formula R3SnOCO(CH2)nN = CHAr (R = Ph, n-Bu; Ar = 2-HOC6H4, 2-HOC10H6; n = 1, 2, 3 and 5). The crystal structures for two of the compounds, tributyltin N-2-hydroxynaphthalidene glycinate (1) and tributyltin N-2-hydroxynaphthalidene-β-alaninate (2), have been determined. Although both of these compounds have a trans-R3SnO2 structure, in compound 1 the carboxylate group is monodentate and the fifth coordination position around the tin atom is taken up by a coordinated phenolic group, whereas in 2 the carboxylate group is bridging. These two examples thus correspond to the two different structures reported for trans-R3SnO2 complexes. Both compounds were found to be active against Ceratocystis ulmi, but there was no significant difference in their levels of biological activity against this particular fungus. Apart from compound 1, the other tributyltin compounds reported are believed to adopt the carboxylate bridging mode shown by compound (2).Crystal data: for 1, crystals monoclinic, space group P21/c, a = 12.9435(11) Å, b = 13.5769(10) Å, c = 15.7715(12) Å, β = 108.919(6)°, Z = 4, Rf = 0.046 and Rw = 0.058 for 1448 significant reflections; for 2, crystals monoclinic, space group C 2/c,a = 24.588(14) Å, b = 9.733(3) Å, c = 27.611(12) Å,β = 113.49(4)°, Z = 8, Rf = 0.053 and Rw = 0.069 for 3822 significant reflections. © 1998 John Wiley & Sons, Ltd.
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  • 114
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 115
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 327-335 
    ISSN: 0268-2605
    Keywords: zinc sulphide ; precipitation ; nanocrystallites ; nanopores ; optical transmission spectroscopy ; vibrational spectroscopy ; Raman spectroscopy ; X-ray diffraction ; transmission electron microscopy ; thermogravimetric analysis ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: During the synthesis of ZnS powders by wet chemical precipitation, the formation of nanoporous spheres is observed. The powders have been investigated using thermogravimetric analysis, X-ray diffraction and optical spectroscopies. Nanopore formation can be explained by several stages of growth. The formation of nanoparticles as primary particles is followed by their agglomeration forming secondary particles. These secondary particles are monodispersed spheres with a considerable porosity, because the agglomeration of the nanoparticles is unlikely to be volume-filling. The voids or nanopores formed by this agglomeration process in the secondary particles is estimated to comprise around 35% of the sphere volume. They are mainly filled with water and the residues of the chemical reagents. Water in the pores partially reacts with ZnS and forms hydrated sulphates. The chemical reagents used for the precipitation reactions are also found to be bound to the nanocrystallite's surfaces as ligands in some cases. Depending on the reaction conditions and reagents, the agglomeration of the nanoparticles can also be modified or hindered by the use of complexing agents acting as a sterically stabilizing surface layer on the nanocrystallites. The agglomeration of nanoparticles to larger units being a general phenomenon, this use of complexing agents to control pore formation and agglomerate size should be applicable to other nanocrystalline systems. © 1998 John Wiley & Sons, Ltd.
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  • 116
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 361-365 
    ISSN: 0268-2605
    Keywords: silicon nanoparticles ; optical properties ; CO2 laser ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Silicon nanoparticles have been synthesized by heating reactant gases with a 500 W CO2 laser. A technique based on scattering of He-Ne laser light by particulates in a reaction flame has been developed for probing the particle size evolution during the process, in order to scale down the particle diameter (under 10 nm). The optical and structural properties of laser-synthesized silicon nanopowders obtained in different runs are reported. © 1998 John Wiley & Sons, Ltd.
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  • 117
    ISSN: 0268-2605
    Keywords: α-Fe2O3 ; nanoparticles ; Morin transition ; antiferromagnetism ; weak ferromagnetism ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The magnetic properties of α-Fe2O3 nanoparticles of different shapes (spherical, rhombohedral and acicular), prepared as powders by a chemical route, have been investigated. The particle size effect on the Morin transition (TM = 263 K in the bulk system) have been studied by analyzing the temperature dependence of the zero-field-cooled (ZFC) and field-cooled (FC) magnetization. For spherical (average diameter between 10 and 50 nm) and rhombohedral (edge between 30 and 350 nm) particles, the Morin temperature was found to decrease with decreasing particle size and increasing magnetic field. On the other hand, acicular particles (major axis between 300 and 700 nm, minor axis between 70 and 100 nm) do not show the Morin transition, unless annealed. © 1998 John Wiley & Sons, Ltd.
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  • 118
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 303-303 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
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  • 119
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 435-438 
    ISSN: 0268-2605
    Keywords: tributyltin ; radiolabelling ; 113Sn ; synthesis ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method of synthesis of tributyl[113Sn]tin,­(n/C4H9)3113Sn(IV), from commercially avail-­able inorganic 113Sn(IV) is presented. Inorganic tin is first extracted in diethyl ether and reacted with C4H9MgCl to produce tetrabutyltin, (C4H9)4113Sn, which is then debutylated with HgCl2. The resulting tributyl[113Sn]tin chloride is isolated from the reaction mixture by successive extractions with hexane and aqueous Na2S2O3. The yield is 40-60% and the product obtained is 〉98% pure. It has the same specific activity as the starting 113Sn(IV), i.e. up to 550 MBq mg-1 Sn, making it suitable for use in environmental fate and toxicology studies at concentrations relevant of those found in the aquatic environment. © 1998 John Wiley & Sons, Ltd.
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  • 120
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 467-467 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 121
    ISSN: 0268-2605
    Keywords: density functional calculation ; binuclear metal carbonyl ; Cr2(CO)6+ ; laser ablation ; molecular beam ; optimized structures ; dissociation energy ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Density functional calculations have been made on a binuclear metal carbonyl ion Cr2(CO)6+ found in our laser ablation-molecular beam (LAMB) experiment. Optimized structures are calculated for three different conformations: T33 of D3d symmetry with three terminal carbonyl groups on each chromium atom, B2T22 of D2h symmetry with two bridging carbonyl groups and two terminal carbonyl groups on each chromium atom, and B4T11 of D4h symmetry with four bridging carbonyl groups and one terminal carbonyl group on each chromium atom. The most stable conformation is T33 which is 36.76 and 286.44 kJ mol-1 lower in energy than B2T22 and B4T11, respectively. The difference of conformation exerts a significant influence on the internuclear distance between chromium and the carbon of terminal CO, but hardly on the Cr-Cr bond length. For B2T22 and B4T11, longer C-O distances for bridging carbonyls compared with those for terminal ones indicate effective π*-back donation from the chromium atom to the bridging carbonyl groups. Furthermore, the relative abundance of Cr2(CO)n+ (n = 0-6) observed in our previous experimental study can be explained qualitatively by comparison of the excess energy produced in the formation of a Cr+-Cr bond with the CO dissociation energy of Cr2(CO)6+. © 1998 John Wiley & Sons, Ltd.
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  • 122
    ISSN: 0268-2605
    Keywords: metal clusters ; quantum-size effect ; nanostructures ; size effects ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Meta-cluster compounds can be exploited advantageously to study the evolution, with increasing size of the molecules of the physical properties of metal clusters from molecular to bulk-metal behavior. The metal-cluster molecules are well-defined, stoichiometric, chemical compounds. The molecules consist of a metal core of a variable number of atoms, surrounded by a shell of ligand atoms or molecules. Depending on the compound, the type of metal atom may be varied, whereas the core size can be changed from a few up to several thousands of atoms. Accordingly, these materials provide excellent model systems for monodisperse metal particles, embedded in a dielectric matrix, and can be investigated by the well-known experimental techniques of solid-state physics. © 1998 John Wiley & Sons, Ltd.
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  • 123
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 881-882 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
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  • 124
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 467-468 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 125
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 126
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 515-517 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 127
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 520-520 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 128
    ISSN: 0268-2605
    Keywords: methylmercury ; analysis ; HPLC- ICP MS ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel technique has been developed for the determination of trace amounts of methylmercury in various sample matrices. The newly developed HPLC method makes it possible to separate methylmercury and inorganic mercury with ultrasonic nebulization and detection by ICP MS for different mercury isotopic masses. The isotope-specific detection allows the application of the species-specific isotope addition method for the determination of methylmercury with a correction for artifact formation. The well-known water-vapour distillation method was used in combination with an enriched stable inorganic mercury isotope (200Hg2+) for the separation of methylmercury from various matrices. The subsequent determination of CH3 - 200Hg+ generated from 200Hg2+ was used in the correction for artifact formation during sample preparation. In comparison with a previously developed HPLC coupling technique with HPF-HHPN (high-performance flow/­hydraulic high-pressure nebulization), the stability of the detection procedure was improved considerably. The limit of detection (S/N = 3) for methylmercury was calculated to be about 0.015 μg kg-1. © 1998 John Wiley & Sons, Ltd.
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  • 129
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    Applied Organometallic Chemistry 12 (1998), S. 523-529 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No Abstract
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  • 130
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 541-549 
    ISSN: 0268-2605
    Keywords: organotin speciation ; analytical validation procedure ; organotin sediment extraction ; Grignard derivatization ; organotin extraction stability ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of several extraction variables such as acid concentration and strength (e.g. for HCl and HOAc), the presence of complexing agents (e.g. tropolone, sodium diethyldithiocarbamate) in the extracting mixture, solvent polarity (e.g. hexane, toluene) and sonication time for native butyl- and phenyl-tin compounds from sediment was evaluated. A toluene-HOAc mixture (10:4) yields the highest extraction efficiency for all the analytes and minimizes the degradation of trialkyl- and triaryl-tins during the extraction under sonication. In addition, losses of underivatized monobutyltin and monophenyltin were minimized in several steps of the analytical procedure. The analytical procedure developed was validated against existing CRMs for butyltin determination. © 1998 John Wiley & Sons, Ltd.
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  • 131
    ISSN: 0268-2605
    Keywords: methylmercury ; solid-phase microextraction ; gas chromatography-atomic fluorescence ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analytical method is described for methylmercury determination in fish and aqueous samples using solid-phase microextraction (SPME) followed by gas chromatography-atomic fluorescence spectrometry (GC-AFS). The procedure involves aqueous-phase derivatization of methylmercury species with sodium tetraethylborate in a sample vial and subsequent extraction with a silica fiber coated with poly-­(dimethylsiloxane). The mercury derivatives are desorbed in the splitless injection port of a gas chromatograph and subsequently analyzed by GC-AFS. The headspace SPME procedure is used and parameters affecting the extraction, adsorption and desorption are evaluated. Results for methylmercury analysis in standard reference material (DORM-2) and fish samples are presented. © 1998 John Wiley & Sons, Ltd.
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  • 132
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 577-584 
    ISSN: 0268-2605
    Keywords: organotin ; extraction ; analysis ; GC-FPD ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of: (1) the modifier type (methanol and formic, acetic and propionic acids), (2) complexing agents (diethylammonium diethyldithiocarbamate, ammonium pyrrolidinedithiocarbamate) either with or without acidic modifiers, (3) the extraction temperature (50-80 °C) and pressure (30-50 MPa), (4) the extraction procedure (static-dynamic or dynamic), and (5) the volume of static modifier, on the extraction efficiency of native butyl- and phenyl-tin compounds from sediment, were evaluated comprehensively. The highest extraction efficiency for butyl- and phenyl-tin compounds was obtained at 30 MPa and 50 °C by using CO2 modified with acetic acid (200 μl in the cell). Supercritical fluid extraction (SFE) extracts were hexylated and determined by GC-FPD using a 610 nm bandpass filter without any clean-up step. In summary, the developed analytical procedure is robust (no restrictor clogging; free from FPD interferences), it is low-cost (no complexing agents needed), it has a high sample throughput (〈3 h), it is independent of the matrix for the determination of butyltin compounds in sediment, and it provides the highest precision among the SFE procedures reported for organotin determination. © 1998 John Wiley & Sons, Ltd.
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  • 133
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    Applied Organometallic Chemistry 12 (1998), S. 585-590 
    ISSN: 0268-2605
    Keywords: butyltin ; estuarine microcosm ; environmental fate ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A radiotracer experiment was conducted in a controlled experimental ecosystem (microcosm) to determine the persistence and behavior of tributyltin (TBT) under conditions simulating a temperate, shallow estuarine ecosystem. Radiolabeled TBT was introduced to the estuarine microcosm, which contained estuarine water, sediment and fish. TBT and its degradation products were monitored for 40 days. TBT rapidly distributed among the compartments of the microcosm. The TBT half-life in the water column was 2.55 days for the first 11 days and then slowed to 13.4 days. More than 60% of the TBT and its metabolites were found in the sediment, indicating that the sediment was an important sink for butyltins. Higher concentrations of butyltins, relative to the water column concentrations, were found in the surface microlayer. TBT could be bioconcentrated by the fish to levels more than 200 times the exposure concentration, and underwent rapid degradation in the fish body, so that high concentrations of its metabolites were found in the fish. The concentrations of TBT adsorbed on the suspended particles were three orders of magnitude greater than that in dissolved form. © 1998 John Wiley & Sons, Ltd.
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  • 134
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    Applied Organometallic Chemistry 12 (1998), S. 651-656 
    ISSN: 0268-2605
    Keywords: butyltin ; TBT ; DBT ; MBT ; beluga whales ; St Lawrence River estuary ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fifty-two beluga whale samples (Six liver samples, and 46 blubber samples including ones from different depths of the fat layer) from the St Lawrence River, Canada, were analyzed for butyltin compounds (mono-, di-, and tri-butyltin) with a view to investigating the occurrence and contamination of butyltin in these animals. A special procedure was also developed for the determination of butyltin compounds in blubber samples with high lipid content (up to 95%). Total-butyltin concentrations in liver samples were found to be much higher than those in the blubber samples. The concentrations of butyltin compounds in blubber samples were observed to be related to their lipid content. Concentration levels of butyltin species in beluga whale were compared with those in other marine vertebrates in other parts of the world. The presence of butyltin compounds in liver and blubber samples suggests the accumulation of these toxicants by beluga whale. © 1998 John Wiley & Sons, Ltd.
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  • 135
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    Applied Organometallic Chemistry 12 (1998), S. 621-634 
    ISSN: 0268-2605
    Keywords: quality ; phenytins ; mussel ; Certified Reference Material ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organotin contamination of the marine environment can be considered one of the main environmental problems in the last 20 years. Starting from the ‘Arcachon case’, monitoring campaigns have been carried out worldwide in order to evaluate the concentration levels of these compounds in the marine environment. In 1987 the EC Standards, Measurements and Testing Programme (formerly BCR) started a ‘tin speciation’ project to assess and improve the quality of measurements in this field and to make available reference materials. Ten years of study within the framework of this project have produced results in the fields of method development and production of reference materials, particularly for butyltins. The quality of the phenyltin analytical results was lower than for butyltins and further efforts are still needed. To overcome this shortfall, the last certification campaign was aimed towards the certification of phenyltins, as well as butyltins, in a candidate mussel certified Reference Material. The results of the homogeneity and stability tests for phenyltins and of the certification campaign are presented here. The preparation of the material and the analytical methods used in the certification campaigns are also described. The certification of phenyltins was hindered by their lack of long-term stability; nevertheless, the exercise provided information about the state-of-the-art of phenyltin measurements in biological samples. © 1998 John Wiley & Sons, Ltd.
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  • 136
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    Applied Organometallic Chemistry 12 (1998), S. 643-650 
    ISSN: 0268-2605
    Keywords: tributyltin ; sediment ; degradation ; coastal British Columbia ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Butyltin concentrations in the sediments of two coastal areas of British Columbia, Canada, are reported. Two recent box cores from the deepest basin in the Strait of Georgia were sectioned and analyzed by GC-atomic emission spectrometry. No butyltin compounds were detected above 0.5 μgSn kg-1 (dry weight) in either core. These results are compared to those for a previous (1991) core from the same area. In that study, tributyltin (TBT) concentrations were in the range 1-2 μgSn kg-1 down the core and were higher than those of either of the degradation products, dibutyltin (DBT) and monobutyltin (MBT). Radioisotope dating (210Po-210Pb counting methods) was used to establish the rates of sedimentation of 0.25 and 2.6 cm y-1 at the two sites. Data suggest that a combination of rapid deposition of new, less-contaminated material and degradation of previously deposited butyltin compounds has resulted in the observed absence. Thirty-three surface sediments from the northern BC coastal harbor at Prince Rupert, collected in 1995, were analyzed for butyltin residues by GC-FPD. Concentrations of TBT, DBT and MBT were in the ranges from below the appropriate limit of detection (LOD) to 1262, to 109 and to 37 μgSn kg-1, respectively. TBT/DBT ratios ranged from 0.2 to 62 with most above unity, indicating that there is continuing fresh input of TBT. The sources are almost exclusively large ocean-going vessels that use the harbor for long-term anchorage. These findings are discussed with reference to the global TBT status. © 1998 John Wiley & Sons, Ltd.
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  • 137
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    Applied Organometallic Chemistry 12 (1998), S. 787-792 
    ISSN: 0268-2605
    Keywords: tetrakis(dimethylamino)titanium ; amminolysis ; precursor ; pyrolysis ; titanium nitride ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Precursors possessing Ti-N bonds were prepared by the reactions between Ti(NMe2)4 and each of three diamines H2NCH2CH2NH2, Me(H)NCH2CH2N(H)Me, HN(CH2CH2)2NH (Ti(NMe2)4:diamine = 1:2), and were converted into ceramics by pyrolysis. The reactions with H2NCH2CH2NH2 and HN(CH2CH2)2NH led to the formation of insoluble solids, whereas a soluble oil was obtained by the reaction with Me(H)NCH2CH2N(H)Me. The pyrolyses under argon gave carbon-rich Ti(N,C,O) phases,­but those under NH3- N2 resulted in the formation of Ti(N,C,O) phases with higher nitrogen contents. Despite the difference in precursor structures the pyrolysis behavior of three precursors under argon was rather similar, suggesting that the precursor obtained from Me(H)NCH2CH2N(H)Me was effectively cross-linked during pyrolysis. © 1998 John Wiley & Sons, Ltd.
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  • 138
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    Applied Organometallic Chemistry 12 (1998), S. 659-666 
    ISSN: 0268-2605
    Keywords: polymers ; polyphosphazenes ; synthesis ; surfaces ; surface reactions ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The macromolecular substitution approach for the synthesis of polyphosphazenes provides access to many different polymers. However, it precludes the use of reagents that contain two or more functional groups because such compounds would cause extensive crosslinking of the chains. This presents a problem because many of the uses for which polyphosphazenes seem ideally suited require the presence of -OH, -COOH, -NH2, -SO3H, -PR2 and other functional units in the side-chain structure. We have developed two approaches to introduce such active sites: (1) protection-deprotection reactions; and (2) direct reactions of active reagents with the organic side-groups of non-functional poly(organophosphazenes). These methods have been applied both at the molecular level and in the form of reactions carried out only at polymer surfaces. The resultant polymers have special properties that are valuable in the micro-encapsulation of sensitive biological agents; in the formation of hydrophobic, hydrophilic, or adhesive surfaces; in crosslinking reactions; and in the development of solid polymer electrolytes, bio-erodible polymers, pH-triggered hydrogels, polymer blends and interpenetrating polymer networks. Overall, more than 700 different polyphosphazenes are now known, and a large number of these are functional macromolecules targeted for specific property combinations and uses. © 1998 John Wiley & Sons, Ltd.
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  • 139
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    Applied Organometallic Chemistry 12 (1998), S. 749-753 
    ISSN: 0268-2605
    Keywords: polymer ; silicon ; gel ; films ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of organic-inorganic polymer hybrids consisting of carbon-carbon and siloxane chains was investigated by radical polymerization of 3-methacryloxypropyltrimethoxysilane (MAS) followed by acid-catalyzed hydrolytic polycondensation. The condensation of poly(3-methacryloxypropyltrimethoxysilane) (S-PMA) of various molecular weights Mn =830-12000 prepared by polyaddition provided transparent and flexible free-standing hybrid gel films. The mechanical properties of these films were highly dependent on the carbon-carbon chain length: with an increase in the carbon-carbon chain length, the elasticity of gel films increased, while the tensile strength and Young's modulus decreased. Hydrolyzability of S-PMA decreased with an increase in the carbon-carbon chain length, resulting in the formation of rubber-like films with flexibility. © 1998 John Wiley & Sons, Ltd.
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  • 140
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    Applied Organometallic Chemistry 12 (1998), S. 755-762 
    ISSN: 0268-2605
    Keywords: poly(vinyl alcohol) (PVA) ; sol-gel ; polymer hybrid ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homogeneous poly(vinyl alcohol) (PVA)-silica gel polymer hybrids were prepared by in-situ hydrolysis of poly(vinyl acetate) (PVAc) in a sol-gel reaction mixture with tetramethoxysilane (TMOS). The degree of hydrolysis was evaluated by FTIR and 13C CP/MAS NMR; it increased with an increase in the acid catalyst and reached 85% with 1.6 ml of 0.1 M HCl. The homogeneity of the polymer hybrids obtained was maintained when the reaction was performed at 60 °C. However, the polymer hybrid became turbid with an increase of the amount of catalyst present when the reaction was conducted at room temperature. The homogeneity of the polymer hybrids obtained was evaluated by nitrogen sorption porosimetry of a porous silica that was obtained by charring the PVA hybrid. The results confirmed the molecular-level dispersion of the PVA in the hybrid. © 1998 John Wiley & Sons, Ltd.
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  • 141
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    Applied Organometallic Chemistry 12 (1998), S. 657-657 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 142
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    Applied Organometallic Chemistry 12 (1998), S. 781-785 
    ISSN: 0268-2605
    Keywords: phosphonium ; polymer ; monomer ; film ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(arylene ether) main-chain phosphonium ionomers were successfully synthesized and characterized. The reaction scheme involved first preparing the poly(arylene ether phosphine oxide) by a nucleophilic step or condensation polymerization of bisphenolates on activated aryl halides, wherein phenyl phosphine oxide was the activating group. High-molecular-weight, tough, film-forming polymers were produced with glass transition temperatures of 200°C or higher. The resulting materials were successfully reduced using phenylsilane in refluxing chlorobenzene. The derived phosphine or phosphine/phosphine oxide copolymer was reacted with alkyl halides to produce the phosphonium salts. The resulting materials showed enhanced hydrophilicity and in some cases could be successfully dispersed in water. In addition, chromophores such as Methyl Orange and Methyl Red were combined with the backbone ionomer to produce new film-forming, ionically linked species. The materials are of general interest for situations where water-dispersible intermediates, e.g. coatings, fiber sizings etc. are required. The phosphonium salts can be converted back to the phosphine oxide in fairly high yields by simple thermal methods and in quantitative yield by chemical methods (e.g. the Wittig reaction). © 1998 John Wiley & Sons, Ltd.
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  • 143
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    Chemical Engineering & Technology - CET 20 (1997), S. 144-148 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of the liquid phase hydrogenation of 4-tert-butylphenol to form cis- and trans- 4-tert-butylcyclohexanol at 1.0-10.0 MPa and 40°C in isopropanol over a Rh catalyst has been studied. The kinetic behavior of this parallel system is described by a proposed reaction network. Keto-enol tautomeric transformation of adsorbed 4-tert-butyltetrahydrophenol and 4-tert-butylcyclohexanone is thought to be a key step, which governs the stereoselectivity of the overall complex reaction of alkylphenol hydrogenation.
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  • 144
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    Chemical Engineering & Technology - CET 20 (1997), S. 138-143 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The gas-phase hydrogenation of buta-1,3-diene to but-1-ene, trans- and cis-but-2-ene and butane has been performed over 0.5% Pd/γ-Al2O3 catalyst. The reaction has been investigated at atmospheric pressure and 0°C over a wide range of conversions. The kinetic model based on the present day knowledge of reaction mechanism has been advanced. The parameters of the kinetic model have been estimated through statistical data fitting. The kinetic model provides a fairly good description of selectivity in the whole range of conversions.
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  • 145
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    Chemical Engineering & Technology - CET 20 (1997) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 146
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    Chemical Engineering & Technology - CET 20 (1997), S. 149-161 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The following article concerns emulsification reaction in a continuous screw loop reactor. The influence of hydrodynamics on the emulsification process as well as the influence of some specific substances were examined. We produced oil/water model emulsions under different test conditions and we determined the correlations between the mixing behavior of the reactor and the characteristic features of the obtained emulsion. Special consideration was given to the droplet size and its distribution. Variable operating conditions of the reactor are the residence time and the rotational speed of the screw, both of which have a decisive influence on the recycle factor and the number of passages through the rotor/stator system. In addition we determined the dependence of the obtained droplet size distribution on the viscosity of the continuous and dispersed phase, on the interfacial surface tension and on the phase proportions. The influence of the specific type of emulsifying agent and its concentration has been examined as well. The positive effect of the mixing and of the recirculation on the emulsification in the screw loop reactor was particularly evident with low emulsifier concentrations and with emulsifiers with slow adsorption kinetics. The established theories for emulsion formation (Kolmogoroff, Taylor) were used for a quantitative description of the experimental results. The screw loop reactor was compared to an agitated tank reactor and a toothed-ring dispersing machine (Ultra Turrax) based on the comminution energy which is produced per unit volume of emulsion. The agitated tank reactor produced only coarsely dispersed emulsions through the entire rotational speed range, wheras the screw loop reactor and the Ultra Turrax, particularly at high rotational speeds and, therefore, high power densities, showed a similar emulsification and produced much finer dispersed emulsions.
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  • 147
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    Chemical Engineering & Technology - CET 20 (1997), S. 162-170 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The performance of an upflow packed-bed biofilm reactor has been analyzed under multisubstrate limitation by considering simultaneous carbon oxidation and nitrification reactions. The fasting shock load of inlet methanol concentration has a much more pronounced effect on the response of the system compared to that of inlet NH4+ -nitrogen concentration. The exit concentration of NH4+ -nitrogen drops very close to zero, thereby showing essentially complete nitrification during methanol fasting condition. Further, the concentration profiles of oxygen within the biofilm show significant variation during methanol fasting and nonfasting conditions whereas during NH4+ -nitrogen fasting conditions the oxygen concentration profile in the biofilm remains essentially unaffected.
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  • 148
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    Chemical Engineering & Technology - CET 20 (1997), S. 182-191 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The uncatalyzed esterification of acetic acid is described in the literature as a typical example of reactive distillation. Many rigorous models were validated using this esterification as an example. Process proposals for the production of pure ethyl acetate from ethanol and acetic acid have been determined using short-cut methods with the assumption of chemical equilibrium only. In this publication, the limitations of this esterification are clarified, using a rigorous model that was developed. The reasons why reactive distillation appears to be unfavorable for this esterification are explained. It is, however, theoretically possible to obtain ethyl acetate in high purity with different variants of the process. Different process variants are examined in this work. Construction variables that are important for the design of reactive columns, such as the number of reactive separation stages and the holdup in the column, are analyzed. Furthermore, the influence of variables dependent on the component system, such as the phase equilibrium of the reactive system and the reaction kinetics on the conversion in the column, are described. It can be shown that the short-cut methods published so far for reactive distillation, which assume chemical equilibrium, are inadequate.
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  • 149
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    Chemical Engineering & Technology - CET 20 (1997), S. 192-198 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two devices were developed, mechanical and electrical, to measure the mechanical power relative to superficial gas velocity and stirring speed in a mechanically agitated reactor. Two bubble regimes were demonstrated. The study of gas holdup, obtained from the residence time distribution, and the bubble size, determined by interfacial area measurement, confirm these two regimes of flow. Our results show that the gas holdup, the interfacial area, and the liquid-side mass transfer coefficient are increasing functions of the energy dissipated in the solution.
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  • 150
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    Chemical Engineering & Technology - CET 20 (1997), S. 199-202 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An electrochemical technique which involved measuring the limiting current of the cathodic reduction of potassium ferricyanide was used to study the rate of mass transfer inside a cubical cavity machined in the wall of a vertical rectangular duct. Variables studied were side length, physical properties of the solution and flow rate of the solution. The mass transfer coefficient was found to decrease with increasing cavity size; in all cases, the mass transfer coefficient inside the cavity was less than that at the duct wall. Mass transfer data inside the cavity were correlated by the equation Shc = 0.525 (Sc Re de/L)0.33. Comparison of the present results with the results obtained using other cavity geometries shows that cavity geometry plays an important role in determining the rate of mass transfer inside the cavity.
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  • 151
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    Chemical Engineering & Technology - CET 20 (1997), S. 203-207 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Transient heat transfer in a mechanically agitated vessel is studied in the case of an anchor and an helical ribbon impeller using Newtonian and shear thinning fluids. Temperature stratification is found more pronounced with the anchor, making this impeller clearly inadequate for heat transfer. The impact of natural convection is evaluated first using the classical Gr/Re2 ratio. It is shown that the use of this criterion in viscous mixing is somewhat misleading. A new Grashof number is then proposed to assess the significance of the viscous and buoyancy effects in non-isothermal, non-Newtonian mixing applications. It is shown that the interpretation of this new number is strongly related to the concept of process viscosity.
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  • 152
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    Chemical Engineering & Technology - CET 20 (1997), S. 208-211 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The results of a process analysis and an experimental exploratory study of supercritical water oxidation (SCWO) show that elements of combustion technology are suitable to overcome the technical problems of SCWO. The Film Cooled Hydrothermal Burner (FCHB) which operates at 25 MPa up to 2000 K in the reaction zone keeping wall temperature under stress at 300 to 400 K shows further development potential of the Wallcooled Hydrothermal Burner (WHB) concept for SCWO, a still promising waste treatment process.
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  • 153
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    Chemical Engineering & Technology - CET 20 (1997), S. 212-219 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Subnetwork Corollary provides some sufficient conditions for which a complex reaction network could be determined to have capacity of admitting multiple positive steady-states, if it contains a subnetwork that also admit multiple positive steady-states. A family of reaction networks, involving catalytic reactions in an isothermal continuous flow stirred tank reactor (CFSTR), is determined to have the capacity to exhibit steady-state multiplicity by implementation of the Deficiency One Algorithm and the Subnetwork Corollary. A set of rate constants and two corresponding positive steady-states are constructed for several cases.
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  • 154
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    Chemical Engineering & Technology - CET 20 (1997) 
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    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 155
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    Chemical Engineering & Technology - CET 20 (1997), S. 221-229 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To review mass transfer trays from a process point of view, the dependence of efficiency on the loadings, the loading range and the maximum loadings with an acceptable tray efficiency have to be known. Comparing the results taken from experiments on Dualflex trays and from other types of trays which have been in industrial applications for many years and which are recognized as “industrial standard”, has been evaluated in this review.
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  • 156
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    Chemical Engineering & Technology - CET 20 (1997), S. 230-239 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this contribution, a new method is proposed for determining effective macropore diffusion coefficients in porous media by digitized microphotographs of porous support materials and random walk simulations. The method introduced allows calculation of the effective diffusion coefficient as a function of the mean free path length over a wide variety of values. A versatile method for the preparation of porous substances for light microscopy is described.The frequently applied model of an active shell, which is used to model particle/solid collisions, was found to give incorrect results in conjunction with the application of the first passage time algorithm, which was applied to save computing time in the simulation of gas diffusion. It was possible to show that more realistic results are obtained if a Knudsen layer is used to model particle/solid collisions. Furthermore, in investigating diffusion in two- and three-dimensional representations of capillary tubes, it was found that results of simulations performed to calculate transport properties of fluids in porous media, based on two-dimensional model systems, cannot in any case be transferred to the corresponding three-dimensional systems.
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  • 157
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    Chemical Engineering & Technology - CET 20 (1997), S. 240-246 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rate of the homogenous exothermic hydrolysis reaction of acetic anhydride catalyzed by sulfric acid in solvent acetic acid was estimated from nonisothermal experimental batch reactor transient temperature data. Rate equations based on three different reaction mechanisms of hydrolysis published in the literature were fitted to the experimental rate data. The experimental results on runaway and limit cycle behavior obtained with this reaction were explained by using the mechanism-based rate equations for hydrolysis in the reactor dynamic models, and good agreement was obtained between the predicted and the experimental dynamic data.
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  • 158
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    Chemical Engineering & Technology - CET 20 (1997), S. 247-258 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: New uses of artificial selective membranes, particularly ion-exchange membranes, improve on traditional methods of treating liquid mixtures before, during or after chemical or biochemical reactions. With the correct choice of ion-exchange membrane in a membrane reactor, reactions can be performed in such a way that the main product is not contaminated by undesired byproducts. Recent examples, mainly in organic chemistry, are given for eight typical ion-exchange membrane reactors: electrodialysis (ED), electrometathesis (EMT), electro-ion substitution (EIS), electro-ion injection-extraction (EIIE), coupled counter-transport (CCT), electro-electrodialysis (EED), electrohydrolysis with bipolar membranes (EHBM), and catalysis with ion-exchange membrane (IEMC).
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  • 159
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    Chemical Engineering & Technology - CET 20 (1997), S. 259-267 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this study, a scale-down approach has been used for the simulation of the imperfect mixing on the growth processes by considering several configurations of continuous stirred tank reactor (CSTR, aerated) and plug flow tubular reactor (PFTR, not aerated). The steady-state concentrations of biomass and enzyme in a continuous culture were calculated as a function of dilution rate using modified Monod growth kinetics. A mathematical model for each combination of two bioreactors was developed to account for growth, substrate utilization (oxygen and glucose) and enzyme synthesis and decay. The model was then used to investigate biomass production and enzyme expression in relation to the volumetric fraction Uf = VPFTR/(VCSTR + VPFTR) and the recirculation ratio R = fr/(f + fr) of the fermentation system. These two mixing parameters were found to be significant factors in the biomass and enzyme production from the fermentation system. This model was also compared with some of the existing models.
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  • 160
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    Chemical Engineering & Technology - CET 20 (1997), S. 268-276 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: As an alternative to the existing bioheat transfer models a new system of two energy equations is proposed by considering the human body as a deformable porous medium. One equation is developed for the blood and the other for the peripheral skeletal tissue. It includes such significant factors as the vascular geometry and size, the blood flow and direction, thermal diffusion and the local thermal nonequilibrium between the blood and peripheral tissue. Discussion and application of both equations are given.
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  • 161
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    Chemical Engineering & Technology - CET 20 (1997), S. 282-284 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
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  • 162
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    Chemical Engineering & Technology - CET 20 (1997), S. 277-281 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new method for cleaning inner surfaces of pipes was studied both theoretically and experimentally. The method is based on the phenomenon of a sphere rotating in a pipe (levitation), when the translational movement of the sphere is restricted and the sphere is subjected to fluid flow in the pipe. The high rotation velocity causes a vibration process, which may be exploited for cleaning sediments or rust from the inner surfaces of pipes. A simplified theoretical model for the determination of the relationships among the dimensionless parameters governing the rotation phenomenon was developed. The model was validated with experimental data and found to be appropriate for engineering design of the system. Application of the cleaning method was demonstrated by cleaning the sediments and rust off the inner surface of a one-inch nominal diameter pipe.
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  • 163
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    Chemical Engineering & Technology - CET 20 (1997), S. 285-286 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An ortho-experiment design and the analysis method of mathematical statistics are adopted to study the conversion of gypsum and potassium chloride to potassium sulfate in the system of K+, Ca2+, NH4+ ‖ Cl-, SO42- in H2O. Optimal reaction parameters and engineering mean are acquired to attain a conversion yield of potassium chloride of 94.52%.
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  • 164
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    Chemical Engineering & Technology - CET 20 (1997), S. 414-418 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the present work, we employ a fuzzy logic controller (FLC) to control the unstable state of a nonlinear biological reaction. The state variable vectors consist of cell density and substrate concentration. The dilution rate is used as a manipulated variable to control the reaction dynamics. An analytic form of FLC employing Zadeh AND logic along with Center of Mass defuzzification method is considered. Simulations reveal that for servo response test, the FLC shows satisfactory performance for natural unsteady states for which a conventional PI controller is known to fail. Further simulations also show that the FLC gives satisfactory regulatory response and is relatively insensitive to the deviations in model parameters.
    Additional Material: 8 Ill.
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  • 165
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A ‘carbon source controlled shift technique’ was developed for fermentation medium optimization in continuous culture with the objective to maximize growth rate and growth-linked product formation of a biological system. An automatic culture medium preparation system was operated together with 2 parallel stirred tank reactors and a HPLC system for on-line analysis of the carbon source concentration in the reactors. A genetic algorithm was applied for experimental design. The concentrations of 7 medium components (mineral salts and vitamins) were optimized automatically within 40 continuous experiments to result in a maximum growth rate of the methylotrophic yeast Candida boidinii and growth-linked production of the formate dehydrogenase enzyme (FDH). The specific growth rate of Candida boidinii and the specific activity of the FDH enzyme at a set-point of 420 mM methanol in the reactor were, thus, improved by 19% to 0.16 h-1 and 26% to 164 U g-1, respectively, compared to the previously used medium, which has already been previously optimized in shake flask experiments. The results of the continuous medium optimization were evaluated with a full second order seven-dimensional polynomial model (regression coefficient 96.8%).
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  • 166
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    Chemical Engineering & Technology - CET 20 (1997), S. 419-423 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: By applying the macroscopic conservation laws to a simplified jet downstream from a sudden enlargement, a new correlation of the two-phase subcritical pressure recovery is obtained. Comparisons with the set of existing data (air-water and steam-water subcritical flows) show that the predictions obtained by means of this formula are more accurate than the ones given by available analytical models. The proposed correlation presents an important improvement of the pressure recovery predictions in the case of small mass velocities. However, it can not be applied in the conditions of quality too close to one.
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  • 167
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    Chemical Engineering & Technology - CET 20 (1997) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 168
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    Chemical Engineering & Technology - CET 20 (1997), S. 424-428 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In paper coating make-down, a poor dispersion of pigments in coating colors may lead to coater runnability problems. This is manifested by coat defects at the paper surface, excessive coater blade wear, and an over-consumption of pigments. For this reason, high shear impellers operated at high speed are used, yielding a high energy consumption. A new method to disperse high solids mix at low energy consumption is presented. This method based on the use of a rod impeller scraping the fluid surface in the vessel, is tested on a slurry composed of calcined and delaminated clays up to a solids content of 66.7 wt.% without dispersing aids.
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  • 169
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    Chemical Engineering & Technology - CET 20 (1997), S. 429-433 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When in contact with water, organoalkoxysilanes and other alkoxy metal compounds react to organofunctionalized polysiloxanes or heteropolysiloxanes. A new method for the continuous preparation of porous organopolysiloxane spheres was developed. Droplets of the precursor mixture are injected into the vertical reactor column. Movement of the gelating droplets is controlled by flow of the aqueous reaction medium. Advantages are adjustable residence time, minimized coalescence and low reactor height. An example shows typical product characteristics like narrow particle size distribution and macroporosity.
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  • 170
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    Chemical Engineering & Technology - CET 20 (1997), S. 435-444 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper describes how gain scheduling control is applied to a continuous stirred tank reactor model. The CSTR process, equipped with a cooling system, is modelled. Based on the resulting nonlinear model, a gain scheduling controller is designed. The gain scheduling follows a scheme denoted bias compensation. Compared to earlier reported gain scheduling schemes, the proposed scheme results in a controller that is less complex, which is advantageous in the controller implementation stage. Numerous simulations are performed, using the gain scheduling controller and two choices of control input to the reactor model. The simulation results indicate that a gain scheduling controller performs better than a linear controller. Simulations using different choices of control input to the reactor model indicate that proper process design is crucial for the controlled process performance.
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  • 171
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    Chemical Engineering & Technology - CET 20 (1997), S. 445-454 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two different layouts for the liquid-liquid extraction section of an industrial caprolactam process are evaluated. Laboratory mass transfer measurements on streams obtained from an industrial and a demonstration plant with different extraction sections are interpreted by a model describing the effect of surface contaminants on mass transfer coefficients. Indications of the impact of these layouts on the complexity of the extraction section, quality of products and efficiency of the extraction processes are given.
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  • 172
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    Chemical Engineering & Technology - CET 20 (1997), S. 455-461 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A time- and space-dependent model based on the piston-dispersion-exchange model for liquid flow was developed to analyze the performance of two-phase upflow and downflow fixed bed reactors and was applied to the catalytic SO2 oxidation. The hydrodynamic parameters were determined from residence time distribution measurements, using an imperfect pulse method for time-domain analysis of nonideal pulse tracer response. A transient diffusion model of the tracer in the porous particle coupled with the PDE model was used to interpret the obtained RTD curves. Gas-liquid mass transfer parameters were determined by a stationary method based on the least square fit of the calculated concentration profiles in gas phase to the experimental values. It is shown that two-phase downflow fixed bed reactor performs better at low liquid flow rates, while two-phase downflow fixed bed reactor performs better at low liquid flow rates, while two-phase upflow performs better at high liquid flow rates.
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  • 173
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    Chemical Engineering & Technology - CET 20 (1997), S. 462-468 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The autoxidation of aqueous sulfide solutions by dioxygen is studied at pH 9 and 14 and at initial sulfide concentrations between 1 and 100 mM. Disulfide as a primarary intermediate is proposed to enhance the sulfide oxidation by autocatalytically forming polysulfies. The postulate is supported by the observed acceleration of the process at increasing pH favoring the presence of disulfide rather than that of sulfur. The final reaction products thiosulfate and sulfate are proposed to result from the hydrolysis of the highly instable intermediate polythiosulfite in parallel parallel reaction pathways, assuming probabilities for breaking the sulfur chain at the α (sulfate) and β (thiosulfate) positions to be responsible for the selectivity. A reaction scheme is proposed, considering all experimental observations.
    Additional Material: 7 Ill.
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  • 174
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    Chemical Engineering & Technology - CET 20 (1997), S. 469-474 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bubble columns are commonly used in industry for polluted gas treatment. Based on the same principle, the droplet column which is not widely known in the literature, uses much higher gas velocities, up to 14 m/s. This study concerns the hydrodynamics and mass transfer in this apparatus, in presence or absence of solid particles. Our results have demonstrated the impact of dusts on mass transfer performance giving rise to an increase in the kL aL coefficient with decreasing particle size. However, no influence of dust on the hydrodynamics of the column has been demonstrated within the studied particle size range.A study of liquid holdups obtained by three different methods is also carried out. Our results are comparable, thus validating the methods used.
    Additional Material: 11 Ill.
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  • 175
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    Chemical Engineering & Technology - CET 20 (1997), S. 475-477 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple and new model for the prediction of drop velocity as a function of dispersed phase volume fraction has been proposed on the basis of experimental knowledge of onset time of complete separation between two phases as function of the initial hold-up.
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  • 176
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    Chemical Engineering & Technology - CET 20 (1997), S. 485-490 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic model of the liquid fluidized bed containing two or more solid particle species of different size and density is presented. The model incorporates the particle mass transport mechanisms of the convection and the dispersion. The movement of the upper interface of the bed subject to a change in the liquid velocity is specified using the mass balance constraint. The particle velocities and dispersion coefficients are evaluated using correlations. The model is capable of describing the bed expansion, concentration profiles of the individual particle species, the bulk density profile, and the occurrence of layer inversion.
    Additional Material: 7 Ill.
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  • 177
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    Chemical Engineering & Technology - CET 20 (1997), S. 491-494 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experiments were carried out in a conventional circulating fluidised bed to measure the axial pressure profile and total pressure drop, which covered a wide range of operating conditions. Material belonging to the Geldart A (fine material) as well as the Geldart B (course material) categories have been used in the present work. Slip velocity is determined from the total pressure drop and noticed that the slip velocity is much higher than the free fall velocity of single particle for Geldart A type material, while it is approximately equal to the free fall velocity of single particle for the Geldart B type materials.A model is developed for slip velocity taking into account all the hindrance effects: particle-particle, and particle-wall, and particle agglomeration. Predictions of the present model are validated with the data due to present study and the data reported in the literature.
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  • 178
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    Chemical Engineering & Technology - CET 20 (1997), S. 478-484 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two important structural factors that affect distillation efficiencies, the outlet weir heigh and the liquid flowpath length, are investigated. Performance and efficiency data of an industrial scale i-butane/n-butane distillation column equipped with two-pass trays are used as a basis for the calculations. A mathematical development for a new method for predicting the numbers of vapor and liquid phase transfer units is given. This method together with some other NTU calculation methods is used to assess the effect of the outlet weir height on efficiencies. The effect of outlet weir height on the Murphree tray efficiencies is investigated using the observed point efficiencies and different point efficiency to the Murphree tray efficiency relation methods. The effect of varying liquid flowpath lengths on efficiencies is studied by calculating the Murphree tray efficiencies for one-pass and two-pass trays. The results obtained using the NTU calculation method presented in this study show that a certain outlet weir height point efficiency reaches its maximum. Most of the other methods give opposite results giving a minimum for point efficiency at a certain outlet weir length. The results also show that the Murphree tray efficiencies for one-pass trays are higher than for two-pass trays. Obviously, this is caused by the longer liquid flowpath length of one-pass trays. The Murphree tray efficiencies are also calculated for an industrial-scale MTBE purification column. The column is equipped with two-pass trays in the stripping section and with one-pass trays in the rectifying section. The Murphree tray efficiencies of one-pass trays are considerably higher than the two-pass tray Murphree tray efficiencies.
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  • 179
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    Chemical Engineering & Technology - CET 20 (1997), S. 495-501 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An algorithm for the computation of design variables in layer crystallisation processes is presented, based on an algebraic solution of the moving boundary equation for heat transfer, as well as on an expression for the concentration profile. The algorithm was applied to the discontinuous crystallisation of a NaCl-H2O solution around the wall of an internally cooled cylindrical tube. Good agreement between simulation results and laboratory experiments was observed. After input of experimentally measurable values of the distribution coefficient, the algorithm enables the prediction of the following process variables along the crystallisation time: layer thickness, temperature, and composition profiles across the layer, as well as the end-values of solid and liquid mass and concentrations. Multistage processes can be studied by the series association of crystallisation cycles, enabling the determination of the optimal number of stages that meets a specific design criterion.
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  • 180
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    Chemical Engineering & Technology - CET 20 (1997) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 181
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    Chemical Engineering & Technology - CET 20 (1997), S. 502-509 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dust explosion hazard exists in plants and facilities wherever combustible dusts are hardled. Minimum explosible concentration of dust clouds is an important factor requiring special attention for hazard evaluation if any technological equipment is to be protected by inertisation. The mathematical models available for prediction of this parameter have been analysed for their application to organic dust clouds. Solution of the most general mode for determination of minimum explosible concentration of dust clouds proposed by Mitsui and Tanaka is presented, together with the comparison with experimental data. It has been found that the model is not successful in predicting the minimum explosible concentration for organic dusts. Recommendations on requirement of development of a new model for prediction of minimum explosible concentration of an organic dust such as polyethylen have been given.
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  • 182
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    Chemical Engineering & Technology - CET 20 (1997), S. 511-521 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When working with disperse solid matter systems, one uses the effect of vibration in numerous processes. Solid matter mixing with vibration has only occurred in very simple units up to now. By means of the 3D-vibrational mixer from the company Kuston, Kleve, the influence of vibration on bulk materials and new mixing techniques are demonstrated. The 3D-vibrational mixer is suitable for liquids and solids, does not require mixing tools that need to be cleaned, and does not carry out rotary motions which would hinder incoming lines. It is used for mixing small amounts, where the mixing tank can be used simultaneously as the transportation container, so that a transfer is unnecessary.With the aid of 4 linear motors, the vibrational amplitudes and the frequencies can be varied within wide boundaries in all three spatial directions. By analyzing the vibrational system by means of Lissajous figures, it can be demonstrated that the optimal mixing effect occurs in the case of small frequency differences between the three axes. For freeflowing bulk materials, the best possible mixing state, the uniform coincidence mixing, is achieved after 2 min.
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  • 183
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    Chemical Engineering & Technology - CET 20 (1997), S. 522-532 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The intermixing of fluidizing gas between the compartments of a compartmented circulating gas fluidized bed fitted with a V-valve and riser combination has been experimentally studied. The intermixing of fluidizing gas that flows co-current (cross flow) as well as counter-current (back flow) to the circulating solids has been investigated. At low aerations, gas cross flow increased proportionally with the increase in solid circulation rate. But at high aerations, gas cross flow increased with aeration even when solid circulation decreased. Studies on back flow of gas revealed some interesting observations. At high fluidizing bed height on upstream side back flow of V-valve, gas has been negligible. But at low upstream bed heights and low aeration in V-valve and riser back flow of V-valve, gas has been substantial.
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  • 184
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    Chemical Engineering & Technology - CET 20 (1997), S. 17-22 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mass transfer with chemical reaction by liquid/liquid phase tranfer catalysis (LLPTC) for an isothermal batch reactor was analyzed. The results for the phase transfer catalyzed reaction system can be generally described by a pseudo first-order hypothesis, whereas the reaction system can be controlled by simultaneous mass transfer of the catalysts between two liquid phases and chemical reaction in the organic phase. The mass transfer limitation is mainly from the mass transfer step of QX from the organic phase to the aqueous phase. The concept of catalyst-effectiveness vs. physically meaningful parameters in a liquid/liquid phase transfer catalyzed reaction is introduced. The catalyst effectiveness is increased as the mass transfer factors increase, the ratio of reaction rate coefficients of aqueous forward reaction to organic increases, and the equilibrium constant in the aqueous solution increases.
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  • 185
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    Chemical Engineering & Technology - CET 20 (1997), S. 171-181 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hydrodynamic parameters have been determined in common equipment, i.e., same column and liquid and gas distributors, for cocurrent and countercurrent two-phase flow through fixed beds. The piston/dispersion exchange model (PDE) with usual Danckwerts' boundary conditions (closed/closed system) has been used to describe the liquid flow. A new imperfect pulse method has been used to estimate the PDE model parameters directly from the experimentally nonideal input and output response. The transition between trickle flow and pulse flow, for two-phase downflow, and the occurrence of flooding, for countercurrent flow, has been investigated using a macroscopic model for the two-phase flow.
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  • 186
    ISSN: 0268-2605
    Keywords: sulphur ; alkyltin compounds ; GC-FPD interference ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Elemental sulphur, a common constituent of marine sediments, has been shown to give dialkyl sulphides with the Grignard reagents commonly used to derivatize alkyltin species before their determination by gas chromatography with flame photometric detection (GC-FPD). Further, it has been demonstrated that even with the red filter for 610 nm (normally used for organotin compounds) fitted to the detector, sulphur compounds do give rise to an emission signal, which may be mistaken for tin emission from a pentylated or propylated alkyltin compound, as the respective retention times are in some cases quite close. © 1997 by John Wiley & Sons, Ltd.
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  • 187
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    Applied Organometallic Chemistry 11 (1997), S. 67-67 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 188
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    Applied Organometallic Chemistry 11 (1997), S. 67-67 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 189
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    Applied Organometallic Chemistry 11 (1997), S. 153-161 
    ISSN: 0268-2605
    Keywords: polyimides ; solution polycondensation ; seven-membered cyclic polyimide intermediate ; polyimide-silica gel hybrids ; sol-gel reaction ; pyrolysis ; pore size ; surface area ; adsorption-desorption isotherms ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A facile preparation of polyimide-silica gel hybrids by the simultaneous in-situ formation of polyimides during the hydrolysis-condensation of tetramethoxysilane (TMOS) is reported here. The hydrolysis and condensation of TMOS was carried out in a solution of DMAc containing 5% LiCl, CaCl2 or ZnCl2 and the seven-membered cyclic polyimide intermediate. The seven-membered cyclic intermediates, precursors of polyimides, were derived from the low-temperature polycondensation of dianhydrides [benzophenonetetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), and 4,4-bis(hexafluoroisopropylidene)phthalic dianhydride (6FDA)] and di-isocyanates [isophorone di-isocyanate (IPDI), toluene di-isocyanate (TDI), hexamethylene di-isocyanate (HDI) and 4,4′-diphenylmethane di-isocyanate (MDI)]. These intermediates could readily be converted to the corresponding polyimides. Films were cast from the resulting mixtures and the solvent was gradually evaporated at 130 °C to result in the formation of clear, transparent, pale yellow or amber-colored hybrid films in which the salts were dispersed at the molecular level. Pyrolysis of polyimide-silica gel hybrids at 600 °C gave mesoporous silica. Silica gel obtained from hybrids HPI-8 (containing no salt) and HPI-11 (containing ZnCl2) had a pore radius (BJH method) of 2.9 nm, while that from hybrid HPI-9 (containing LiCl) had a pore radius of 11.4 nm. The surface areas (BET method) obtained were 203 m2 g-1, 19 m2 g-1 and 285 m2 g-1, while the pore volumes were 0.373 cm3 g-1, 0.158 cm3 g-1 and 0.387 cm3 g-1, respectively, for samples obtained from hybrids HPI-8, HPI-9 and HPI-11. © 1997 by John Wiley & Sons, Ltd.
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  • 190
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    Applied Organometallic Chemistry 11 (1997), S. 565-575 
    ISSN: 0268-2605
    Keywords: complexes of furan oximes ; IMP dehydrogenase ; purine inhibitors ; cytotoxicity ; nucleic acid inhibitors ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The copper complexes of furan oxime derivatives were found to be potent cytotoxic agents in both murine and human tissue cultured cell lines which were suspended as well as solid tumors. Mode of action studies in murine L1210 lymphoid leukemia cells showed that the compounds suppressed DNA, RNA and protein synthesis after 60 min at 100 μM. Inhibition of purine and pyrimidine de novo syntheses, as well as inhibition of ribonucleoside reductase and nucleoside kinase activities with DNA strand scission occurred. All of these effects of the drug probably added to its ability to cause cell death but most important was the inhibition of DNA topoisomerase II activity with IC50 values lower than those afforded by VP-16, the standard, which should cause apoptosis. © 1997 John Wiley & Sons, Ltd.
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  • 191
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    Applied Organometallic Chemistry 11 (1997), S. 591-600 
    ISSN: 0268-2605
    Keywords: organotin compounds ; lecithin liposome membrane ; Ca2+ and Pr3+ desorption ; 1H NMR ; radioactive tracer methods ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organometallic compounds and surfactants constitute a potential threat to the environment. For that reason we have embarked on a study of their joint action on membranes. Model lecithin liposome membranes were modified with the cationic surfactant trimethyldodecylammonium bromide or the anionic surfactant sodium dodecylsulfonate, and the effect of tripropyltin chloride on the process of calcium (Ca2+) and praseodymium (Pr3+) desorption from the liposome membrane was studied.Kinetic constants for the process of Ca2+ ion desorption from lecithin liposome membranes were determined using the radiotracer method. The percentage of Pr3+ ion desorption from liposome membranes was measured by the 1H NMR method.Trimethyltin, triethyltin and tripropyltin alone caused increased Ca2+ and Pr3+ desorption from liposome membranes with increasing concentration of the compounds and alkyl chain length. For both the processes studied, a cationic surfactant brought about a lower effectiveness of tripropyltin and an anionic surfactant resulted in a higher effectiveness.The effect observed can be explained by changes in the surface charge of the membrane, induced by the surfactant modifiers and by the concomitant change in the partition coefficient of the organotin. The results obtained indicate a protective or harmful joint action of the surfactants used with tripropyltin on membranes. © 1997 John Wiley & Sons, Ltd.
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  • 192
    ISSN: 0268-2605
    Keywords: triorganotin(IV) ; L-homocysteic acid ; infrared ; Mössbauer ; NMR ; sea urchin ; Paracentrotus lividus (Echinodermata) ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several new triorganotin(IV) derivatives of L-homocysteic acid (L-HCAH) with formula R3Sn(L-HCA) (R=Me, nBu, Ph) have been synthesized. Their solid-state configurations were determined by IR and Mössbauer spectroscopy. The tin(IV) atom is five-coordinated in all the complexes, with the L-homocysteic acid behaving as a monoanionic bidentate ligand coordinating the tin(IV) atom through a chelating or bridging carboxylate group. The sulfonate (SO3-) and NH3+ groups of L-homocysteic acid maintain their free acid configuration and hence do not participate to the coordination of the tin(IV) atom. Coordination hypotheses have been checked through the correlation between the Mössbauer parameter isomer shift, δ, and partial atomic charge on the tin atoms, QSn, performed, for all the new organotin(IV) compounds, on the basis of an equalization procedure applied to idealized trigonal-bipyramidal structures for R3Sn(L-HCA).1H and 13C NMR spectra of the complexes show that pentacoordination of the tin atom, with R groups in the equatorial plane of a trigonal bipyramid, is retained in DMSO solution. The NMR data confirm also that the uncoordinated NH3+ group of the ligand is still present in solution.Results gathered after exposure of two- to four-cell embryos of the sea urchin Paracentrotus lividus (Echinodermata) to the triorganotin(IV) L-homocysteate derivatives as well as to the parent triorganotin(IV) chlorides document cytotoxicity of the complexes, while free L-homocysteic acid exerts no significant toxic activity. The trimethyltin(IV) L-homocysteate derivative seems to exert a lower cytotoxicity than the tributyl- and triphenyl-tin(IV) ones. Different structural lesions have been identified by comparative analysis of mitotic chromosomes from untreated embryos (negative controls) and embryos treated with triorganotin(IV) L-homocysteate derivatives, such as (1) suppression of the stretch among sister chromatids at the beginning of anaphase stage; (2) deeply stained zones mainly located at the telomeric regions of chromosomes; (3) arm breakages; and (4) chromosome bridges among daughter chromosomes at anaphase stage. A colchicine-like effect of triorganotin(IV) L-homocysteate derivatives was observed. © 1997 John Wiley & Sons, Ltd.
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  • 193
    ISSN: 0268-2605
    Keywords: palladium ; platinum ; imidazoline ; DNA ; cyclometallated complexes ; cytotoxic activity ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper we describe the synthesis and chemical characterization of three new Pd(II)-imidazoline complexes: [PdCl2 (C6H5-CH2-C3H5N2)2] (2), [PdCl(SEt2) (C6H4-C3H5N2)] (5) and [Pd(C6H4-C3H5N2) (μ-Br)]2 (6). We have also analyzed the DNA modifications and in vitro antileukaemic activity of these compounds and of their previously reported analogs [Pd Cl2 (C6H5-C3H5N2)2] (1), [Pd (C6H4-C3H5N2) (μ-OAc)]2 (3), [Pd (C6H4-C3H5N2) (μ-Cl)]2 (4) and [Pt(C6H4-C3H5N2)(μ-Cl] (7). All these compounds modify the DNA secondary structure since they alter the melting temperature (Tm) of the DNA. Circular dichroism spectra indicated, moreover, that compounds 3, 5 and 6 induced higher modification on the double helix than compounds 1, 2 and 4. While compounds 1, 2 and 5 seem to induce slight changes in the electrophoretic mobility of the open and covalently closed circular forms of pUC8 DNA at high ri (input molar ratio of Pd or Pt to nucleotides), compounds 3, 6 and 7 do not modify at any ri the tertiary structure of the plasmid DNA. Antileukaemic tests suggest that compounds 1, 4 and 7 exhibit important cytotoxic activity since their IC50 values against HL-60 human leukaemic cells were below 10 μg ml-1. © 1997 John Wiley & Sons, Ltd.
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  • 194
    ISSN: 0268-2605
    Keywords: organotin compounds ; chemical speciation ; natural fluids ; biological fluids ; carboxylate complexes ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complex formation by (CH3)2Sn2+ with acetate (ac), malonate (mal), 1,2,3-propane-tricarboxylate (tricarballylate, tca) and 1,2,3,4-butanetetracarboxylate (btc) ligands in aqueous solution is reported. The study has been performed by potentiometry ([H+]-glass electrode) at T=25 °C, and in the 0≤I≤1 mol dm-3 ionic strength range. In order to evaluate the salt effects on the formation constants of the complex species, and to contribute to the definition of the chemical speciation of diorganotin(IV) compounds in natural waters where carboxylic ligands are naturally present, interactions of NaCl (which is the major component of all natural fluids), with the components of the systems under investigation have also been considered. A model for the ionic strength dependence of the formation constant was used in order to calculate the values of thermodynamic constants, at infinite dilution, for all the proposed species, by considering hydrolytic species too. A relationship between the charges on the different ligands considered and the stabilities of the complex species formed is also discussed. © 1997 John Wiley & Sons, Ltd.
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  • 195
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    Applied Organometallic Chemistry 11 (1997), S. 756-756 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 196
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    Applied Organometallic Chemistry 11 (1997), S. 743-749 
    ISSN: 0268-2605
    Keywords: methylarsonic acid ; dimethylarsinic acid ; trimethylarsine oxide ; mitotic arrest ; aneuploidy ; c-mitosis ; tetraploidy ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Inorganic arsenic is methylated in the mammalian body to methylarsonic acid (MMA), dimethylarsinic acid (DMA) and trimethylarsine oxide (TMA). To achieve a more precise understanding of arsenic carcinogenicity, we examined the genotoxic effects of organic arsenic compounds on human lymphocytes by assessing induction of mitotic arrest, sister chromatid exchange (SCE) and aneuploidy. MMA, DMA and TMA arrested mitosis, DMA induced hyperdiploid cells, and DMA and TMA induced tetraploid cells. Of the three arsenic metabolites tested, DMA had the strongest effects on cell mitosis and aneuploidy induction. DMA arrested mitosis and induced c-mitosis significantly. These results suggest that DMA arrests mitosis and induces aneuploidy through spindle disruptions similar to those observed with known spindle poisons, such as colchicine or vinblastine. Since aneuploidy has been thought to be associated with tumor induction or neoplastic transformation, induction of aneuploidy by organic metabolites of arsenic may play a major role in arsenic carcinogenesis in humans. © 1997 John Wiley & Sons, Ltd.
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  • 197
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    Applied Organometallic Chemistry 11 (1997), S. 805-811 
    ISSN: 0268-2605
    Keywords: [2+3] cycloaddition reaction ; silylisoxazolines ; silatrane ; pyridyl nitrile oxide ; vinylsilane ; vasodilating ; haemodynamic parameters ; antithrombotic properties ; acute toxicity ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-(2-Pyridyl)-5-phenyldimethylsilylisoxazoline, 3-(3-pyridyl)-5-phenyldimethylsilylisoxazoline and 3-(4-pyridyl)-5-phenyldimethylsilylisoxazoline were obtained by the [2+3] cycloaddition reaction of pyridyl nitrile oxides to phenyldimethylvinylsilane. The condensation of 3-pyridyl-substituted 5-triethoxysilylisoxazolines with triethanolamine afforded 3-(2-pyridyl) -5-silatranylisoxazoline, 3-(3-pyridyl)-5-silatranylisoxazoline and 3-(4-pyridyl)-5-silatranylisoxazoline (12). In experiments in vivo and in vitro the vasodilating, antiarrhythmic and antithrombotic properties of pyridyl-substituted silylisoxazolines, their influence on the haemodynamic parameters in anaesthetized animals and their acute toxicity have been studied. It has been found that pyridyl-substituted silylisoxazolines possess vasodilating and antithrombotic properties. In experiments on the noradrenaline-preconstricted isolated rabbit ear artery, 3-(2-pyridyl)- and 3-(4-pyridyl)-5-phenyldimethylsilylisoxazoline exhibited pronounced vasodilating activity. 3-(2-Pyridyl)- and 3-(3-pyridyl)-5-phenyldimethylsilylisoxazoline and 3-(2-pyridyl)-5-silatranylisoxazoline prolonged blood coagulation time. © 1997 John Wiley & Sons, Ltd.
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  • 198
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    Applied Organometallic Chemistry 11 (1997), S. 889-901 
    ISSN: 0268-2605
    Keywords: alkyl-lead ; atmosphere ; phase partitioning ; wet deposition ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurements of alkyl-lead compounds in air and rain at rural and urban sites in central England during 1996 are reported. Vapour, aerosol and rain concentrations of individual tetra-, tri- and di-alkyl-lead species have been determined simultaneously at both sites, along with inorganic lead aerosol. The results show the predominance of vapour-phase over particle-associated species, with tetramethyl-lead being the most prevalent vapour-phase compound, with concentrations of up to 5.8 ng Pb m-3. Theoretical phase-partitioning coefficients for individual alkyl-lead compounds have been calculated and compared with measured values. Washout ratios for alkyl-lead compunds were found to be smaller than for inorganic lead. Atmospheric concentrations of both organic and inorganic lead appear to be falling, broadly in line with recent reductions in the use of alkyl-lead in gasoline. © 1997 John Wiley & Sons, Ltd.
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  • 199
    ISSN: 0268-2605
    Keywords: laser ablation molecular beam ; binuclear metal carbonyls ; chromium carbonyl ; bond dissociation energies ; density functional calculations ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the laser ablation-molecular beam (LAMB) method, laser ablation of metal substrates in vacuum is utilized for the formation of novel organometallic and metal complex compounds containing monopositive metal ions. Mixed-metal binuclear carbonyl ions [MCr(CO)n]+, n=0-6, are prepared in the gas phase by the reaction of laser-ablated metal ions (M+) and Cr(CO)6 in the molecular beam injected nearby. The relative abundance of these ions, for M=transition metals, can essentially be explained by the M+-Cr bond dissociation energies. Results of density functional calculation show that this is essentially valid. © 1997 John Wiley & Sons, Ltd.
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  • 200
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    Applied Organometallic Chemistry 11 (1997), S. 919-927 
    ISSN: 0268-2605
    Keywords: double alkoxides ; precursors ; Group II metal aluminates ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Precursors to Group II metal aluminates (MAI2O4, M=Mg, Ca, Ba, Sr) are synthesized from inexpensive starting materials including Group II metal oxides/hydroxides, Al(OH)3, triethanolamine (TEA) and ethylene glycol, in a one-pot synthesis process. The precursors are soluble in common organic solvents and can be handled in moist air for a reasonable period of time. On pyrolysis in air to 1200 °C, all three precursors transform to the corresponding Group II metal aluminates. A termetallic double alkoxide, ‘ionomer-like’ structure is proposed, wherein the alkaline-earth metal is encapsulated by a TEA molecule bridging two alumatrane units. The precursors were characterized using TGA, NMR, mass spectroscopy and elemental analyses, and the pyrolysed precursors were briefly characterized using x-ray diffraction analysis. © 1997 John Wiley & Sons, Ltd.
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