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  • 1
    Electronic Resource
    Electronic Resource
    The aluminum–polyimide interface: An electron-induced vibrational spectroscopy approach (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3353-3362 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Clean polyimide films spin-coated onto gold substrate have been fully characterized by high resolution electron energy loss spectroscopy (HREELS): 19 electron-induced vibrational bands could be resolved and assigned by comparison with IR spectroscopy. The attribution of these peaks constitutes a firm and necessary basis for the detailed study of the incipient interface formation with aluminum at room temperature. The metal being evaporated at a low rate from a Knudsen effusion cell, its equivalent coverage on the polymer could be monitored very efficiently and allowed a clear distinction between three reaction steps: (i) at an Al coverage below 4×1014 Al atom/cm2, the aluminum atoms interact only with the C–O carbonyl in the polymer to form a C–O–metal complex; (ii) between 4 and 10×1014 atom/cm2, no further Al "reaction'' occurs, but the appearance of new CH and OH stretching bands is attributed to bond breaking in the polymer and diffusion of the residues towards the surface; (iii) after further metal evaporation, all the peaks reduce in intensity and the observation of a ν(Al–O) [or ν(Al–C) band] testifies the formation of an aluminum oxide (or carbide) at the surface. Although no dedicated theory can be invoked up to now for the interpretation of HREELS data collected with different electron impact energies and under different scattering geometries, the spectra measured from polyimide before and after aluminum condensation are consistent with a modification of the geometry of the polymer monomeric unit after bonding with the metallic atoms. The metallized polymer surface appears with an equal statistical spatial distribution of all the chemical groups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453930
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  • 2
    Electronic Resource
    Electronic Resource
    Electronic structure of polyimide (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 253-257 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a valence effective Hamiltonian (VEH) electronic structure calculation on the polyimide poly[N,N'-bis(phenoxyphenyl)-pyromellitimide], also called PMDA (pyromellitic dianhydride)–ODA (oxydianiline). The most important result is that the valence electronic bands are calculated to be very narrow, even though the calculation is performed on a perfectly stereoregular chain. For instance, the highest 35 occupied valence bands (i.e., the electronic bands with binding energies lower than 18 eV) have widths smaller than 0.25 eV. That result implies that even small disorder effects will tend to strongly localize the electronic processes in polyimide. From the band structure, we calculate the density of valence states and produce a theoretical simulation of the UPS spectrum. Good agreement with the recently published UPS experimental spectrum is obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452615
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  • 3
    Electronic Resource
    Electronic Resource
    Electron vibrational spectroscopy of thin polyimide films (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 6739-6749 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We describe high resolution electron energy loss (HREELS) and UV-photoemission (UPS) measurements performed to investigate the vibrational and electronic surface and interfacial properties of thin insulating polymer films. The measurements were performed in ultrahigh vacuum on PMDA–ODA films of thicknesses ∼30–50 and ∼1000 A(ring) which were spun onto silicon or onto metallic substrates and on thin PMMA films deposited on metallic substrates. The general characteristics of our HREELS spectra are weak, diffuse electron scattering and broad vibrational bands which we have assigned by comparison to infrared absorption data. Cooling the polymer films which were spun onto Si substrates to ∼100 K resulted in a uniform reduction of the overall spectral broadening. This additional inelastic scattering contributing to the broadening appears to originate at the PMDA–ODA/Si interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451405
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  • 4
    Electronic Resource
    Electronic Resource
    Low-cost pepsin-cellulase assays for prediction of digestibility of herbage (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 37 (1982), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Eight samples of perennial ryegrass-white clover herbage with in vivo dry matter digestibility (DMD) ranging from 0·279 to 0·264 were used to evaluate various cost-saving modifications to the two-stage pepsin–cellulase digestibility technique. The effect of sample size, cellulase quality, cellulase/sample ratio, digestion time and washing of residue following digestion were investigated. The loss of dry matter (DM) in the assay was correlated with in vivo DMD and each variation of the method was evaluated by comparing the s.d. between replicates and r.s.d. of the regression, as well as the convenience of the method for large-scale monitoring of digestibility of mixed ryegrass-clover herbage.It was found that the amount of cellulase used could be reduced by a factor of 25, compared with recently published methods, without increasing s.d. or r.s.d. appreciably. In addition stirring during digestion and washing of the residue could be omitted without any deleterious effects. Increasing digestion time did not reduce s.d. or r.s.d. and the low-grade cellulase proved to be slightly more economical.Increasing the sample size from 0·25 to 0·20 g improved the s.d. and r.s.d. but the residues from the larger samples were generally slower to filter, which made the assay unsuitable for routine use. Substantial reduction of digestion volume and use of a thermostatically controlled water bath instead of an incubator led to a considerable increase in efficiency and throughput of samples. Stirring the samples during digestion was found to be unnecessary, thus allowing more flexibility in the laboratory routine, for example using the weekend for digestion. Using the recommended method modification the repeatability between replicates and r.s.d. of the calibration regression was 0·204 and 0·215 respectively for samples ranging in DMD from 0·279 to 0·264.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.1982.tb01590.x
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  • 5
    Electronic Resource
    Electronic Resource
    THE USE OF OPTICAL TRIANGULATION FOR HIGH SPEED ACQUISITION OF CROSS SECTIONS OR PROFILES OF STRUCTURES (1990)
    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 13 (1990), S. 0 
    Details
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Optical triangulation is used in the human visual system and surveying tacheometers to estimate distance. This method is now used in systems with solid state sensors which enable fast measurement of distance with sufficiently high accuracy for many applications. City University has built on past experience to develop the optical triangulation technique to gather data appertaining to cross sections or profiles of structures in the range 0.2 m to 20 m radius from the measurement axis. Results obtained using three prototypes are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1477-9730.1990.tb00715.x
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  • 6
    Electronic Resource
    Electronic Resource
    BUILDING A DIGITAL CLOSE RANGE THREE DIMENSIONAL MEASURING SYSTEM FOR LESS THAN £5000 (1993)
    Oxford, UK : Blackwell Publishing Ltd
    The @photogrammetric record 14 (1993), S. 0 
    Details
    ISSN: 1477-9730
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying
    Notes: The use of CCD cameras for digital photogrammetry has only slowly been taken up by the photogrammetric community. However, the pace of change is quickening with better understanding and cheaper equipment. Recently a decision was made to start some research into close range three dimensional digital measurement. The overall objective was to develop a low cost system for the automated measurement of small industrial objects. This shorter contribution describes the initial stages of this work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1477-9730.1993.tb00777.x
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