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  • 1
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Electron spin resonance (ESR) spectra and thermoluminescence (TL) curves and have been obtained for tricalciurn aluminate, Ca3Al2O6. The ESR spectra and one peak in the TL spectrum can be rationalized in arms of electron trapping at Fe(III), present as impurity, in all of the possible tetrahedral sites, with holes on non-bridging oxygen atoms. Manganese (II), which is also present as an impurity, probably replaces calcium in only two out of six possible sites.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Thermoluminescence and ESR in boron-stabilized β-dicalcium silicate have been studied before and after ultraviolet irradiation. Most of the results, apart from the electron spin resonance signals from impurity iron and manganese, can be explained on the basis of electron location on the substituent BO4 groups replacing silicate tetrahedra, with electron capture at this centre being responsible for the thermoluminescence.
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  • 3
    ISSN: 1572-9001
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A range of radicals, CH2(Mu) HX (1) and XCH(Mu)CR2 (2), where X is a second-row substituent, have been studied by transverse-fieldμ +SR spectroscopy. The reduced muon—electron hyperfine coupling constants (A′Mu) for class (1) were all close to 37.3 G, the value for the parent radical CH2(Mu)CH2. However, for class (2)A′ Mu values are greatly reduced, as is the case for the corresponding hydrogen derivatives, XCH2CR2, relative to CH3CH2. Nevertheless, the reduction in coupling for Mu in (2] is appreciably less that that for1H in XCH2CR2 radicals, suggesting significant competition between Mu and X for the out-of-plane site. In addition to theμ + SR studies, the ESR spectra for the radicals (MeO)3SiCHCH3 and (MeO)3SiCH2CH2 have been measured for comparative purposes.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Structural chemistry 2 (1991), S. (225)433 
    ISSN: 1572-9001
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The theory of hyperconjugation, orσ-π delocalization, which has been very successful in explaining the properties of carbocations, and the ESR parameters for a range of radicals, is invoked to explain two aspects of the results for muonated radicals. One is the commonly observed fact that the reduced muon hyperfine coupling constants in a range of radicals are greater by a factor of ca. 1.2 than the corresponding proton coupling constants. The other is the preference of C-Mu bonds in positionsβ to radical centers to occupy an eclipsed site which maximizesσ-π overlap. This theory, which has been largely dismissed by others, still seems to be an attractive and simple explanation of both phenomena. It is suggested that one alternative theory, which is termed the “zeropoint energy theory,” is closely linked to the hyper-conjugation theory proposed herein.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of solution chemistry 7 (1978), S. 571-586 
    ISSN: 1572-8927
    Keywords: Aqueous solutions ; dimethyl sulfoxide ; monosaccharides ; deuterium oxide ; glucose ; mannose ; galactose ; ribose ; sorbose ; fructose ; NMR chemical shifts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract At temperatures close to 0°C proton exchange between sugar hydroxyl groups and water is slow, and separate proton resonance peaks can be detected for the hydroxyl protons. All are shifted downfield of the water resonance, the anomeric hydroxyl proton shift being the greatest. Axial anomeric hydroxyl protons are shifted less than corresponding equatorial protons. Proton exchange with water is strongly acid and base catalyzed, but, at least in some cases, there seems to be an additional pH-independent mechanism involved. From the temperature effect on the shifts, and the effect of added dimethyl sulfoxide, we conclude that each hydroxyl group is bonded on average to two water molecules. This estimate of the hydration number for monosaccharides is far greater than those previously deduced from relaxation studies. It is suggested that the source of this difference lies in the residence times of the bound water molecules. Shifts of the hydroxyl proton resonances for sugars in methanol are compared with those for aqueous solutions and are found to be very similar. Hence it is concluded that these shifts do not reveal any special effects due to water structure. There are quite marked differences in the shifts for different sugars, and, in particular, the anomeric hydroxyl proton shifts for ketoses are smaller than those for aldoses.
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 112 (1990), S. 8614-8615 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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  • 7
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: ESR-Untersuchungen an γ-bestrahltem Polysulfon (aus 2.2′-Bis(4-hydroxyphenyl)-propan und 4.4′-Dichlorodiphenylsulfon) und an niedermolekularen Modellsubstanzen (Diphenylsulfon, 2.2′-Diphenylpropan, Diphenyläther) zeigen, daß die meisten erzeugten Radikale im Polymeren durch Reaktion mit den aus den Methylgruppen frei gemachten Wasserstoffatomen erzeugt werden. In großer Menge entstehen cyclohexadienylartige Radikale sowie Phenoxy- und ArṠO2-Radikale. Für diesen Mechanismus der Radikalerzeugung sprechen ferner die Ergebnisse von Untersuchungen, in denen das Polymere freien Wasserstoffatomen aus einer H2-Gasentladung ausgesetzt wurde.
    Notes: ESR studies of γ-irradiated polysulphone (prepared from 2.2′-bis(4-hydroxyphenyl)-propane and 4.4′-dichlorodiphenyl sulphone) and its model compounds (diphenyl sulphone, 2.2′-diphenyl propane, diphenyl ether), suggest that the majority of radicals produced in the polymer are formed by the subsequent reactions of hydrogen atoms released from the pendant methyl groups by the action of the γ-radiation. Cyclohexadienyl-type radicals are produced in quantity together with phenoxy and ArṠO2 radicals. Supporting evidence for the mechanism is obtained from studies of the hydrogen atom bombardment of the polymer.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The aim of this work has been to study various muonium containing radicals not previously studied by the μSR technique with a view to determining the effect of a bound muonium atom on the radical structures as compared with their hydrogen analogues. In the first group, muonium addition to the aromatic rings of styrene, phenylacetylene and allylbenzene are compared with the more important addition to the substituent double or triple bonds. In the second group, β-muonium substituted cyclopentyl and cycloheptyl radicals are compared with their protiated versions. In the third group, radicals obtained following muonium addition to trimethylsilylethene, tri (methoxysilyl)-ethene, and 1-chloro-2, 2-dimethylethene are discussed with respect to the competition between the β-muonium atom, and β-silicon or β-chlorine substituents for control of the conformation of the radical.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 19 (1984), S. 771-783 
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High energy muons induce radiation damage when they interact with molecules or ions. The chemical reactions expected to occur are summarised, and attention is then given to events likely to give rise to radicals exhibiting muon-electron hyperfine coupling. Addition of muonium atoms to double or treble bonds, which is one example of the way this can occur is considered, and, in particular, the resulting proton-muon hyperfine isotope effect is discussed. Finally, possible chemical models for paramagnetic muon centres in carbon and silicon are outlined.
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  • 10
    ISSN: 1572-8927
    Keywords: Water ; DMSO ; mixed solvents ; solvation ; enthalpy ; infrared ; spectroscopy ; non-electrolytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We report enthalpies of solution of formamide, N,N-dimethylformamide,N,N-dimethylacetamide, acetic acid, methyl acetate, and acetonitrile in water +dimethylsulfoxide mixed solvents. These, along with literature data for additional solutes,are analyzed in terms of the extended coordination model of solvation. We alsoanalyze infrared data for several of these solutes. These analyses show thatN,N-dimethylformamide and N,N-dimethylacetamide are preferentially hydrated,while the other solutes appear to be preferentially solvated by dimethylsulfoxide.In all cases, the extent of preferential solvation is relatively small. It is also foundthat the degrees of preferential solvation recovered from analyses of the enthalpydata correspond closely to those recovered from the infrared data, although thelatter refer only to the polar chromophores on the solute molecules. It is foundthat the extent to which the solutes disrupt the solvent-solvent interactions variessystematically with the area of the nonpolar surfaces of the solute molecules.
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