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  • 1940-1944  (10)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 5 (1940), S. 63-66 
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The greatest problem in creating organic molecular magnets seems to be to find systems in which there is a strong exchange interaction but which are also chemically and thermally stable. This paper discusses one possible solution to this problem, the use of ‘strain protection’, and the synthesis of stable strain-protected pi biradical, trioxytriangulene. This is the first representative of a new, unexplored family of pi biradicals, the non-Kekulé polynuclear aromatics.
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  • 3
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Carbazole modified polysiloxanes (CMPs) have been electrochemically cross-linked to form composite thin films containing oxidized carbazole dinners (bicarbazolyls) together with associated counter-ions. These materials have been found to undergo reversible switching between a coloured (oxidized) and clear (reduced) state. Investigations of the dynamic response reveal that the colouration step is rate-limited by charge transfer across the electrolyte-film interface essentially independent of counter-ion, while the bleaching effects are controlled by a double extraction mechanism dependent on counter-ion mobility.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The introduction of eight alkoxy or eight alkyl substituents onto the phthalocyanine (Pc) nucleus at the non-peripheral (1,4,8,11,15,18,22,25) positions produces derivatives which are soluble in a variety of organic solvents. However, other physico-chemical properties of the two series differ. Octa-alkyl derivatives, R8 Pcs, pack as more ordered molecular assemblies in the solid state and show thermotropic liquid crystal behaviour with transition temperatures dependent upon substituent chain length and the central metal atom. In contrast, octa-alkoxy materials, (RO)8 Pcs, melt directly into the isotropic liquid. The latter can be deposited as Langmuir-Blodgett films whereas the former cannot. Experiments with examples of the two series in which one or two of the chains are functionalized at the terminal positions with a hydrophilic moiety show that these amphiphilic analogues deposit well by the Langmuir-Blodgett method. A number of the films show a high degree of molecular ordering, as judged by X-ray reflectivity methods, transmission infrared, RAIRS and polarized optical spectroscopy. Results indicate that the type of ordering is controlled by the type of substituent and the length of the chain.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Azo-benzene chromophores with an oxygen donor and five different end-groups have been attached to octadecyl chains or to polysiloxane backbones via hexadecyl spacer groups. These were deposited by the Langmuir-Blodgett (LB) technique using our own design of diamond-barrier trough. The LB deposition properties of the polymers were superior to those of the low molecular mass materials, which did not show second harmonic generation (SHG) as deposited monolayers. The strength of SHG from the polymers correlated with acceptor strength, but the maximum signal was only about 10% of that of hemicyanine. Only one of the polymers gave thick films of very high quality; this had a hydroxyl end-group and showed no SHG except when deposited from an acid subphase. This was presumed to result from protonation of the azo group to create an acceptor. The quality of the deposited films may correlate with their phase behaviour; the best material showed only a presumed soft crystalline phase. The film-forming properties of that film were remarkable; loss figures of around 2.5 dB cm−1 have been recorded at 633 nm in films of 1.3 Μm thickness. Future work will seek to isolate and independently control the factors involved in good film formation and in high SHG.
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  • 6
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We have previously shown that a new class of quasi-one-dimensional p-type semiconductors can be created by dissolving small amounts of oxidising agents into the hydrocarbon chain matrix of discotic liquid crystals. This paper reports the elucidation of the mechanism of conduction in these new materials. In particular, the ac conductivity of 2,3,6,7,10,11 -hexahexyloxytriphenylene (HAT6) doped with the Lewis acid AlCl3, has been measured as a function of frequency (10−3–107 Hz), and temperature in its crystalline solid (K), hexagonal discotic liquid crystal (Dho) and isotropic liquid (I) phases. In macroscopically aligned K and Dho phases, the conductivity measured along the column axes is approximately 103 greater than that in the perpendicular direction. Both components of the conductivity are found to be independent of frequency at low frequencies, but show a power law dependence on frequency (Σ(Ω)∼Ωs, s∼0.8) at higher frequencies. This behaviour is characteristic of charge carrier transport by a hopping mechanism. The conductivity data have been analysed in terms of the Scher and Lax theory of hopping transport to obtain the parameters describing this process. The conduction along the columns is identified with a single charge transport process in which the carriers hop between localized states (radical cations) associated with counterions (perceived as AlCl4 −) linearly distributed off-axis along the columns.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 5 (1940), S. 89-93 
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The self-consistent polarization field (SCPF) and Fourier transform methods of calculating the polarization energy of excess charges are compared. The SCPF method is extended (i) to treat molecules as a set of submolecules rather than single points in the inner region around the charge, and (ii) to treat the outer region around the charge as an anisotropic dielectric continuum rather Ethan an isotropic one. The contribution to the polarization energy from the outer region depends on the average 〈ɛ −1〉, where ɛ is the dielectric tensor. These extensions allow the SCPF method to be used for elongated molecules, with potential applications to various systems lacking translational symmetry.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The adsorption of glutamate oxidase onto 25 Μm and 10 Μm platinum microelectrodes followed by immobilization in an electrochemically polymerized non-conducting polymer, poly(o-phenylenediamine), is described as a method of fabricating an enzyme electrode for the amperometric determination of glutamate. The response of the enzyme electrodes were found to be highly reproducible with a linear dynamic range upto approximately 15 mmol dm−3. The response of the 25 Μm and 10 Μm enzyme electrodes to glutamate were analysed using an established kinetic model and the potential application of the sensor for the study of neurotransmitter dynamics was investigated. The sensor was stable over a period of 30 days and the polymeric film was found to reduce interference from the electroactive compounds, uric acid and ascorbic acid.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Carbazolylalkyl-substituted polysiloxanes undergo anodic oxidation to give insoluble electrode supported cross-linked films containing dicarbazolyl groups. The electrochemistry of the immobilized dicarbazolyls can be addressed and the electrochemical switching between the coloured (oxidized) and colourless (reduced) states forms the basis of an electrochromic display. Cyclic voltammetry suggests a model in which virtually all of the pendant carbazole groups are converted into dicarbazolyls. The model is consistent with observation of a range of polymers, and analogous oligomers, and contrasts with earlier reports on the same type of material.
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  • 10
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Streptavidin and avidin were adsorbed onto graphite surfaces and images of their structures were obtained using a scanning tunnelling microscope. Individual protein molecules and their subunits were observed, and their sizes were found to agree closely with measurements from a subunit model based upon the crystal structure of streptavidin. The process of adsorption of streptavidin-FITC and avidin succinylfluorescein isothiocyanate onto the graphite surface was also investigated using fluorescence microscopy.
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