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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Fluvalinate residues ; Honey ; Gas chromatography-atomic emission detection (GC-AED) ; Gas chromatography-mass spectrometry (GC-MS) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two hyphenated techniques, gas chromatography-mass spectrometry and gas chromatography-atomic emission detection, have been used to identify the degradation products of the acaricide fluvalinate in a methanol solution of the commercially available formulation Mavrick, as well as in honey from beehives treated with this product. The major degradation products were 2-chloro-4-trifluoromethylaniline (I), methyl 2-[2-chloro-4-trifluoromethylaniline]-3-methylbutanoate (II), N-(2-chloro-4-trifluoromethyl-phenyl)valine (III), and 3-phenoxybenzaldehyde (IV). Fluvalinate in honey is gradually degraded, 3-phenoxybenzaldehyde being the most abundant residue.
    Additional Material: 5 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Advanced Materials 7 (1995), S. 130-136 
    ISSN: 0935-9648
    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
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Advanced Materials 7 (1995), S. 238-243 
    ISSN: 0935-9648
    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
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1071-1076 
    ISSN: 0947-6539
    Keywords: fullerenes ; endohedral helium complexes ; NMR spectroscopy ; ring currents ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis- to hexakisadducts of C60 (1-6) and mono- to tetrakisadducts of C70 (7-13) containing 3He atoms (endo-hedral helium complexes) were prepared and studied by 3He NMR spectroscopy to determine the influence of degree of functionalization and addition pattern on the chemical shift of the 3He atom. In the series of C60 derivatives, which included the previously measured 6-6 monoadduct 3He@C61H2, the 3He resonance was shifted considerably upfield relative to that of 3He@C60 (δ = -6.36) up to the bisadduct 1 (δ = -11.45). The resonances of the higher adducts 3-6, however, were shifted only slightly further up-field and all appeared in a rather narrow spectral range between δ = -11.84 and -12.26. The absence of further substantial upfield shifts was rationalized in terms of the compensation of deshielding due to the functionalization-induced decrease in the diamagnetic π-electron ring currents that extend around the fullerene sphere by the shielding that results from the weaker pentagonal-ring paramagnetic currents and the increased number of localized benzenoid substructures in 3-6. In contrast, all 3He resonances of the C70 adducts are shifted downfield relative to the signal of 3He@C70 (δ = -28.81). A monotonic relationship exists between the chemical shift and the degree of functionalization, whereby the 3He chemical shifts steadily decrease from monoadduct 7 (δ = -27.53) to the isomeric tetrakisadducts 12 (δ = -21.09) and 13 (δ = -20.68). This deshielding was explained by the reduction of the strong diamagnetic ring currents extending along the polar corannulene perimeters as a result of the functionalization at α- and β-type polar bonds in 7-13. In both series, the addition pattern was also found to have a distinct influence on the 3He chemical shift.
    Additional Material: 6 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: peptide folding ; NMR ; CD ; 310-helix ; gp120 ; CD4 binding domain ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A close association between the HIV surface protein gp120 and the CD4 T cell receptor initiates the viral multiplication cycle. A 15 amino acid peptide (LAV) within the CD4 binding domain of gp 120 has been shown to retain receptor binding ability. The structural behavior of the LAV peptide has been studied by CD and NMR methods in aqueous solution and upon addition of trifluoroethanol (TFE) to emulate the relatively apolar conditions at the membrane bound receptor. Previous work has shown that the LAV peptide folds into a β-pleated structure in more polar buffer/TFE mixtures, while a concerted structural change can be observed at a concentration of 60% TFE (v/v). This abrupt, cooperative refolding from a regular β-sheet to a helical secondary structure is known as “switch” behavior. Former CD experiments with LAV sequence variants have supported the assumption that four amino acids at the N-terminus (LPCR) are indispensable for the “switch.” The tetrad has a strong β-turn forming potential. The suggestion has been formulated that the tetrad can act as a nucleation site governing the refolding. The present NMR study of the LAV peptide in TFE gives evidence for a 310-helix suggesting that the tetrad adopts a type III β-turn and promotes the formation of a similar bend in the next overlapping tetrad until the sequence is restructured into a 310-helix at a critical polarity favoring intrachain hydrogen bonds. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron transfer reaction [(NH3)4COIII(μ-pzCO2)FeII(CN)5]- → [(NH3)4COII(μ-pzCO2)FeIII(CN)5]- has been studied in water-cosolvent mixtures at ionic strength of I = 0.5 mol dm-3 (NaClO4). A multiparameter regression coefficients have been compared to those obtained for the same reaction to a different ionic strength (I = 2.8 10-3 mol dm-3). The magnitude of these coefficients changes with the ionic strength. An explanation is given for this behavior. © 1996 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: This paper reports a new thermal programmed desorption-mass spectrometry (TPD-MS) method for determining the number and relative strength distribution of basic sites in solid catalysts using CO2 as titrant. The overall desorbed CO2 area is proportional to the total basicity, while the number of peaks and their maximum temperature (Tmax) are related to the particular type of basic site and its strength. The activation energy for CO2 desorption from various basic sites in each catalyst was calculated via TPD-MS experiments conducted at a variable heating rate for each catalyst, using the Kissinger equation. Diffuse reflectance infrared analysis of the bands at 2000-1000 cm-1 for CO2 adsorbed on various catalysts allows one to elucidate the nature of the chemical species involved, which depends on the particular type of site. The total basicity results obtained are compared with those provided by an existing spectrophotometric method using benzoic acid (pKa=4.19) as titrant.
    Additional Material: 8 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 2041-2048 
    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 thermal degradation of some plastisols [poly(vinyl chloride) and plasticizer mixtures] normally used in the toy industry was studied using a nonisothermal thermogravimetric technique. Some kinetic parameters such as activation energies are calculated according to some methods reported in the literature. A mathematical model based on considerations of the plasticizer amount was proposed to foresee the thermal degradation behavior of plastisols mostly used in the toy industry. Activation energies calculated according to the proposed model agree reasonably well with experimental results in a broad range of plastisol composition. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-6266
    Keywords: oriented fluoro-oligomers ; chemical vapor deposition ; ferroelectricity ; glass transition ; Brillouin spectroscopy ; x-ray diffraction ; vinylidene fluoride ; trifluoroethylene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The room temperature phase of the physical/chemical vapor-deposited statistical co-oligomer VDF/TrFE(70/30) has been characterized by different experimental methods such as small-angle x-ray scattering, wide-angle x-ray diffraction, size-exclusion chromatography, infrared absorption and optical refractometry. The characterization of the elastic properties was carried out using high-performance Brillouin spectroscopy in connection with special scattering geometries. The co-oligomer VDF/TrFE(70/30) was obtained by cracking the parent statistical copolymer and subsequently vapor depositing the shortened chains on highly oriented PTFE substrates (PIA-technique). The room temperature phase of the resulting oriented waxy crystal mats of VDF/TrFE(70/30) is predominantly ferroelectric. The physical properties are very different to those of similarly PIA-prepared n-alkanes, perfluoroalkanes, and blockfluoroalkanes. The microstructure of VDF/TrFE(70/30) is interpreted in terms of partially crystalline nano-sized structures giving rise to a marked freezing process below room temperature. © 1995 John wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 1434-1948
    Keywords: Ruthenium ; Chirality ; Cyclopentadienyl complexes ; Kinetics ; Asymmetric catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel, functionalized, chiral Cp-ligands with S- and P-donor atoms were designed. Together with known analogues containing ether side-chains they were complexed to ruthenium for use as chiral Lewis-acid catalysts. In the ether complexes [RuCl(η5-C5H4CH2CH2OR)(PPh3)2] {R = Me, (1S)-isobornyl, (1R)-menthyl, (1R)-fenchyl} the Cp-ligand is only η5-coordinated; all attempts to provoke a bidentate, Cp/O coordination were unsuccessful. The sulfide complex [Ru{η5:η1-C5H4CH2CH2S[(1R)-neomenthyl]}(PPh3)2][OTf] contains a bidentate Cp/S-coordinated ligand, but it is unstable. The stable phosphane complex [RuCl(η5:η1-C5H4CH2CH(Me)PPh2)(PPh3)] exists as a 77:23 mixture of diastereomers containing a strongly bidentate Cp/P ligand. The diastereomers interchange, with Ru-Cl bond cleavage as the rate-determining step.Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2005/1999/99126_s.pdf or from the author.
    Additional Material: 6 Ill.
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