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  • 1
    Electronic Resource
    Electronic Resource
    Determination of Senecio Alkaloids by thermospray liquid chromatography/mass spectrometry (1990)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 1-12 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of Senecio alkaloid and alkaloid N-oxide standards has been analyzed using positive and negative ion thermospray liquid chromatography/mass spectrometry (LC/MS) with an ammonium acetate-containing mobile phase. On-line separations of pyrrolizidine alkaloids from extracts of Senecio jacobaea (tansy ragwort) and Senecio vulgaris (common groundsel) were done using an ammonium hydroxide-containing mobile phase. All of the alkaloids known to be present in the extracts were detected by ammonium hydroxide thermospray LC/MS, as well as many other components which may be as-yet-unidentified alkaloids.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200190102
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of alkalies on suspension polymerization of vinyl acetate monomer, properties of poly(vinyl acetate) beads and poly(vinyl alcohols) (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 707-713 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The use of weak alkalies such as sodium carbonate (Na2CO3), sodium bicarbonate (NaHCO3) and their 1 : 1 molar mixture, and strong alkalies such as sodium hydroxide (NaOH) and sodium methoxide (NaOMe) as pH controllers in suspension polymerization of vinyl acetate monomer (VAM) has shown to have diverse effects on the yield of resulting poly(vinyl acetate) (PVAC) beads. Carbon dioxide as such or the carbonate seems to influence the yield. Further, these alkalies have a deep-seated effect not only on properties like viscosity, stereoregularity, glass transition temperature (Tg), and swelling coefficient (Q) of the PVAC beads but also on those of poly(vinyl alcohol) (PVA) obtained by alcoholysis of PVAC beads. The PVAC beads obtained using Na2CO3 showed higher viscosity, higher swelling coefficient (Q), and the PVA derived from these beads had higher Q, higher syndiotacticity/isotacticity ratio, and lower Tg.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070460417
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  • 3
    Electronic Resource
    Electronic Resource
    Reactivity of Monolithium Bis(trimethylsily)hydrazine towards carbon and tin halides (1991)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 605 (1991), S. 131-136 
    Details
    ISSN: 0044-2313
    Keywords: Monolithium bis(trimethylsily)hydrazine ; carbon and tin halides ; redox reactions ; substitution reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zur Reaktion von Lithium-bis(trimethylsilyl)hydrazin mit Halogen-Kohlenstoff- und -Zinn-VerbindungenLithium-bis(trimethylsilyl)hydrazin, LiHN2(SiMe3)2 (1) disproportioniert in THE. Mit CCl4 reagiert Verbindung 1 unter Bildung von Bis(trimethylsilyl)aminocarboimid-dichlorid, während CBr4 ausschließlich als Oxidans wirkt. Gegenüber Halogenkohlenwasserstoffen wie CHCl3, CHI3, CH2Cl2 und CH2I2 wirkt Verbindung 1 als starke Base. So reagiert 1 mit CHCl3 unter Bildung von N,N-bis(trimethylsilyl)chloroformylhydrazon und (Me3Si)2N2CH(Cl), während die Reaktion mit CH2I2 (Me3Si)2 N—N = CH2 ergibt. Me2SnCl2 reagiert mit 1 unter Bildung von und Me2Sn[HN—N(SiMe3)2]2.
    Notes: Monolithium bis(trimethylsilyl)hydrazine LiHN2(SiMe3)2 (1) undergoes disproportionation in THF. Compound (1) reacts with CCl4 to provide bis(trimethylsily)aminocarbonimidic dichloride whereas CBr4 behaves exclusively as an oxidant. Compound (1) as a strong base towards haloalkanes like CHCl3, CHI3, CH2I2 and CH2Cl2. Also reaction of (1) with CHCl3 provides N,N-bis(trimethylsilyl)-chloroformylhydrazone and (Me3Si)2N2CH(Cl) whereas reaction with CH2I2 provides (Me3Si)2 N—N = CH2. Me2SnCl2 reacts with (1) to give two products and Me2Sn[HN-N(SiMe3)2]2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19916050115
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  • 4
    Electronic Resource
    Electronic Resource
    Ring Transformation Reactions, I. Conversion of 6-Aryl-4-(methylthio)-2-oxo-2H-pyran-3-carbonitriles to pyrazoles (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 1229-1231 
    Details
    ISSN: 0170-2041
    Keywords: Pyran-2-ones ; Pyrazoles ; Ring transformation ; Cyclocondensation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new ring transformation reaction has been studied by treating 6- or 5,6-disubstituted 4-(methylthio)-2-oxo-2H-pyran-3-carbonitriles 2 with hydrazine and methylhydrazine leading to polysubstituted pyrazoles 4, 5, 6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1991199101211
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  • 5
    Electronic Resource
    Electronic Resource
    Resonance Raman studies of the mechanism of photoreduction of iron protoporphyrin-IX dimethyl ester in the presence of axial ligands (1991)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 22 (1991), S. 427-434 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Resonance Raman studies of iron protoporphyrin-IX dimethyl ester chloride [FeIII(PPDME)Cl] in the presence of biologically relevant axial ligands such as 2-methylimidazole (2-MeIm) and 1,2-dimethylimidazole (1,2-Me2Im) revealed the occurrence of photoreduction even under aerobic conditions by excitation near the Soret absorption band. A comparison of the vibrational modes sensitive to the oxidation, spin and coordination states of the photoreduced and chemically reduced forms of FeIII(PPDME)Cl confirmed that the reduction of the central iron atom in the high-spin state takes place without any reduction of the porphyrin ring. No photoreduction is observed in pure dichloromethane solvent but trace amounts of alcohols and also some other polar solvents, which facilitate the separation of ion pairs, catalyse the process of photoreduction. From the exponential dependence of the fraction of sample reduced on the rate of photoreduction and illumination time, the rate constant for photoreduction, k-1R = 10 min, is obtained and the action spectrum of photoreduction shows a maximum coinciding with the Soret absorption band. The electron transfer from the axially ligated 2-MeIm to iron appears to be a primary step in photoreduction. From the dependence of photoreduction on the concentration of 2-MeIm, the ligand-free, intermediate spin FeII (PPDME) was identified as the intermediate species formed during photoreduction.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250220802
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  • 6
    Electronic Resource
    Electronic Resource
    Frequency-dependent alterations in enolase activity in Escherichia coli caused by exposure to electric and magnetic fields (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 15 (1994), S. 377-383 
    Details
    ISSN: 0197-8462
    Keywords: radiofrequency radiation ; amplitude modulation ; ELF ; 16 Hz ; 60 Hz ; modulation ; enolase activity ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Some neurochemical effects of low-intensity electric and magnetic fields have been shown to be nonlinear functions of exposure parameters. These effects occurred within narrow ranges of frequency and intensity. Previous studies on membrane-associated endpoints in cell culture preparations demonstrated changes in calcium efflux and in acetylcholinesterase activity following exposure to radiofrequency radiation, amplitude modulated (AM) at 16 and at 60 Hz, at a specific absorption rate of 0.05 W/kg. In this study, these modulation frequencies were tested for their influence on the activity of a cytoplasmic enzyme, enolase, which is being tested clinically for detection of neoplasia. Escherichia coli cultures containing a plasmid with a mammalian gene for enolase were exposed for 30 min, and cell extracts were assayed for enolase activity by measuring absorbance at 240 nm. The enolase activity in exposed cultures was compared to the activity in paired control cultures. Exposure to 147 MHz carrier waves at 0.05 W/kg, AM at 16 Hz showed enolase activity enhanced by 62%, and AM at 60 Hz showed enolase activity reduced by 28%. Similarly, exposure to 16 Hz fields alone, at 21.2 V/mrms (electric) and 97 nTrms (magnetic), showed enhancement in enolase activity by 59%, whereas exposure to 60 Hz fields alone, at 14.1 V/mrms (electric) and 65 nTrms (magnetic), showed reduction in activity by 24%. Sham exposures as well as exposure to continuous-wave 147 MHz radiation at 0.05 W/kg showed no change in enolase activity. Although the underlying basis for these field effects in the cytoplasmic compartment has not been established, differential sensitivities to 16 Hz and to 60 Hz signals provide a clear focus for additional research to determine the responsible mechanism. © 1994 Wiley-Liss, Inc.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250150502
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