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  • 1
    Electronic Resource
    Electronic Resource
    Poly(p-phenylenevinylene) light-emitting diodes: Enhanced electroluminescent efficiency through charge carrier confinement (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2793-2795 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated light-emitting diodes with poly(p-phenylenevinylene) as the emissive layer, and with an electron-transporting layer formed from a solid state dispersion of 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole in poly(methyl methacrylate), placed between this and the negative electrode. These structures show typically a tenfold improvement in efficiency in the low-voltage regime and an eightfold improvement in the high-voltage regime over devices without the electron-transporting layer. Typical efficiencies are about 0.8% photons/electron. We consider that the role of the electron-transport layer is to confine holes to the emissive layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108094
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  • 2
    Electronic Resource
    Electronic Resource
    A RESEARCH NOTE SPICE INTERFERENCE WITH PHOSPHATASE ANALYSIS OF FOODS USING 2,6 DIBROMOQUINONE CHLORIMIDE FOR COLOR DEVELOPMENT (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of muscle foods 1 (1990), S. 0 
    Details
    ISSN: 1745-4573
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Estimating heat treatment of muscle foods by analysis of phosphatase enzyme activity using disodium phenyl phosphate (DSPP) as substrate and 2,6 dibromoquinone chlorimide (2,6 DBQ) for color development is subject to interference by some common spices. Both false high and false low results of the reactions have been demonstrated. Phenolics, which are common in spices and flavorings, may react with 2,6 DBQ to form the characteristic blue indophenol color indicating enzyme activity in samples with no phosphatase, or may interfere with indophenol formation in samples containing phosphatase, depending upon concentration. The possibility of false high or false low results, and therefore implied over or under processing, should be considered when using 2,6 DBQ in phosphatase enzyme analysis of foods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-4573.1990.tb00354.x
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  • 3
    Electronic Resource
    Electronic Resource
    Strained heterocyclic systems. 18. Structure of 1,2,3-methylidyne-2,3-dihydro-1H-cyclopenta[b]quinoxaline (1991)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 47 (1991), S. 587-590 
    Details
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108270190006850
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  • 4
    Electronic Resource
    Electronic Resource
    Chemical tuning of electroluminescent copolymers to improve emission efficiencies and allow patterning (1992)
    [s.l.] : Nature Publishing Group
    Nature 356 (1992), S. 47-49 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Much attention has recently been devoted to the development of efficient routes to conjugated polymers2"9. Because most organic materials with a high level of conjugation show poor solubility in common solvents, approaches to conjugated polymers have involved the preparation of a processible ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/356047a0
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  • 5
    Electronic Resource
    Electronic Resource
    Pyruvate – a novel substrate for growth and methane formation in Methanosarcina barkeri (1994)
    Springer
    Archives of microbiology 161 (1994), S. 33-46 
    Details
    ISSN: 1432-072X
    Keywords: Key words:Methanosarcina barkeri– Pyruvate-utilizing mutant – Methanogenesis – Archaea – Pyruvate fermentation – Acetate fermentation – Growth yields (YCH4) – Ferredoxin – Pyruvate: ferredoxin oxidoreductase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Methanosarcina barkeri strain Fusaro was found to grow on pyruvate as sole carbon and energy source after an incubation period of 10 – 12 weeks in the presence of high pyruvate concentrations (100 mM). Growth studies, cell suspension experiments and enzymatic investigations were performed with pyruvate-utilizing M. barkeri. For comparison acetate-adapted cells of M. barkeri were analyzed. 1. Pyruvate-utilizing M. barkeri grew on pyruvate (100 mM) with an initial doubling time of about 25 h (37 °C, pH 6.5) up to cell densities of about 0.8 g cell dry weight/l. The specific growth rate was linearily dependent on the pyruvate concentration up to 100 mM indicating that pyruvate was taken up by passive diffusion. Only CO2 and CH4 were detected as fermentation products. As calculated from fermentation balances pyruvate was converted to CH4 and CO2 according to following equation: Pyruvate−+H++0.5 H2O→1.25 CH4+1.75 CO2. The molar growth yield (YCH4) was about 14 g dry weight cells/mol CH4. In contrast the growth yield (YCH4) of M. barkeri during growth on acetate (Acetate−+H+→CH4+CO2) was about 3 g/mol CH4. 2. Cell suspensions of pyruvate-grown M. barkeri catalyzed the conversion of pyruvate to CH4, CO2 and H2 (5 – 15 nmol pyruvate consumed/min×mg protein). At low cell concentrations (0.5 mg protein/ml) 1 mol pyruvate was converted to 1 mol CH4, 2 mol CO2 and 1 mol H2. At higher cell concentration less H2 and CO2 and more CH4 were formed due to CH4 formation from H2/CO2. The rate of pyruvate conversion was linearily dependent on the pyruvate concentration up to about 30 mM. Cell suspensions of acetate-grown M. barkeri also catalyzed the conversion of 1 mol pyruvate to 1 mol CH4, 2 mol CO2 and 1 mol H2 at similar rates and with similar affinity for pyruvate as pyruvate-grown cells. 3. Cell extracts of both pyruvate-grown and acetate-grown M. barkeri contained pyruvate: ferredoxin oxidoreductase. The specific activity in pyruvate-grown cells (0.8 U/mg) was 8-fold higher than in acetate-grown cells (0.1 U/mg). Coenzyme F420 was excluded as primary electron acceptor of pyruvate oxidoreductase. Cell extracts of pyruvate-grown M. barkeri contained carbon monoxide dehydrogenase activity and hydrogenase activity catalyzing the reduction by carbon monoxide and hydrogen of both methylviologen and ferredoxin (from Clostridium). This is the first report on growth of a methanogen on pyruvate as sole carbon and energy source, i.e. on a substrate more complex than acetate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248891
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  • 6
    Electronic Resource
    Electronic Resource
    Neutron activation analysis of the dissolution ofn-GaAs in 1M KOH (1994)
    Springer
    Journal of radioanalytical and nuclear chemistry 182 (1994), S. 257-265 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The dissolution ofn-GaAs in 1M KOH has been investigated using neutron activation analysis. For this purposen-GaAs electrodes were irradiated with thermal neutrons. Neutron irradiation induced defects were annihilated by annealing. The corrosion measurements were performed in the plateau region of the photocurrent in 1M KOH with and without Fe(CN) 6 4− and at rest potential in the dark (currentless) in the presence of Fe(CN) 6 3− . We could prove the hole injection of Fe(CN) 6 3− inton-GaAs and the lowering of the photocorrosion due to the presence of Fe(CN) 6 4− .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02037501
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal neutron irradiation induced defects in n-GaAs and their annihilation by annealing processes (1993)
    Springer
    Journal of radioanalytical and nuclear chemistry 174 (1993), S. 167-175 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Forperforming radiochemical photocorrosion measurements, n-GaAs samples were irradiated with thermal neutrons. The resulting changes in charge carrier concentration and mobility are determined by far IR reflectance measurements. A great part of the neutron irradiation induced defects could be annihilated by annealing at temperatures of up to 650°C. The neutron irradiation induced defects are responsible for essential changes in photoelectrochemical characteristics of n-GaAs electrodes in aqueous electrolytes. The photocurrent onset potential is shifted in positive direction and the maximum photocurrent is decreased. After annealing treatment the original photoelectrochemical behavior is restored.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02040344
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  • 8
    Electronic Resource
    Electronic Resource
    Novel method for studying the kinetics of surface reactions at submonolayer exposures: Decomposition of acetic acid on palladium foil (1992)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 19 (1992), S. 581-585 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The experimental set-up for relaxation spectroscopy with a newly constructed time-of-flight mass spectrometer (ToF-MS) is described. The response to single gas pulses is measured with the ToF-MS, which is equipped with a special storing ion source and an electrostatic ion reflector. The gas pulses, with rise and fall times of less than 2 ms, are generated by a solenoid valve in a differentially pumped system. Conventional ToF instruments with ionization by electron pulses detect only a small fraction of the incoming molecules. Therefore our instrument with the storing (integrating) ion source is more sensitive, typically by a factor of 1000. Pulses of deuterated acetic acid (AcOD) with a length of 20 ms are used to produce exposures of 1/1000 monolayer (ML) per pulse on a polycrystalline Pd foil. On clean Pd the formation of CO2 is observed. An activation energy of 0.78 eV and a preexponential factor of 3 × 108 s-1 are derived from the transients in the temperature range between 550 and 650 K. After a total dose of 1 ML of AcOD the CO2 signal ceases and the AcOD signal emerges, yielding an activation energy of 0.44 eV and a pre-exponential factor of 9 × 108 s-1. It is shown that even exposure to small doses of AcOD decreases the efficiency of CO2 formation. After a dose of 2 ML the CO2 formation is completely suppressed. To determine the energy and the pre-exponential factor for the investigated surface reaction, an exposure dose of less than 1/100 ML is sufficient.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.7401901108
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