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  • Electronic Resource  (8)
  • 1995-1999  (8)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of α-Si3N4 Particle Size on the Microstructural Evolution of Si3N4 Ceramics (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effects of initial particle size on the microstructure of silicon nitride ceramics produced by pressureless sintering have been investigated. The microstructures of the silicon nitride ceramics varied considerably with the size of the initial powder. With decreasing powder size, abnormal grain growth was enhanced, which resulted in significant bimodal distribution of grain size. The observed results are discussed in relation to the two-dimensional nucleation and growth theory for faceted crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb01828.x
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  • 2
    Electronic Resource
    Electronic Resource
    Size-dependent electronic level structure of InAs nanocrystal quantum dots: Test of multiband effective mass theory (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 2306-2309 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The size dependence of the electronic spectrum of InAs nanocrystals ranging in radius from 10–35 Å has been studied by size-selective spectroscopy. An eight-band effective mass theory of the quantum size levels has been developed which describes the observed absorption level structure and transition intensities very well down to smallest crystal size using bulk band parameters. This model generalizes the six-band model which works well in CdSe nanocrystals and should adequately describe most direct semiconductor nanocrystals with band edge at the Γ-point of the Brillouin zone. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476797
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  • 3
    Electronic Resource
    Electronic Resource
    Synaptic strengthening through activation of Ca 2+ -permeable AMPA receptors (1996)
    [s.l.] : Nature Publishing Group
    Nature 381 (1996), S. 793-796 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fast application of a hyperosmotic solution to dorsal horn neurons in culture caused a large increase in the probability of transmitter release, as indicated by an enhancement in the frequency of miniature excitatory postsynaptic currents (mEPSCs; Fig. la) and shown previously at several types of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/381793a0
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  • 4
    Electronic Resource
    Electronic Resource
    Semiochemistry of aposematic seed bugs (1997)
    Springer
    Entomologia experimentalis et applicata 84 (1997), S. 127-135 
    Details
    ISSN: 1570-7458
    Keywords: Hemiptera ; Heteroptera ; Lygaeidae ; Oncopeltus ; Tropidothorax ; Neacoryphus ; pheromone ; attractant ; aposematic ; Asclepiadaceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract (E)-2,7-Octadienyl acetate and (E) -2-octenyl acetate (1:10 by volume) were identified as a pheromone attractive to both sexes of the lygaeid bug, Tropidothorax cruciger. In a parallel investigation of Neacoryphus bicrucis (Lygaeidae), (E, E) -2,4-hexadienyl acetate and phenethyl acetate (≈9:1) were identified from males, and found attractive to both sexes of adults in the field plus a tachinid fly parasitoid of the bugs. In N. bicrucis, the pheromone was clearly shown to come from the tubular accessory glands of the metathoracic scent gland; this evidence, plus earlier literature reports for other species, indicate that male lygaeids are the pheromone emitters. In another lygaeid, Oncopeltus fasciatus, 2-isobutyl-3-methoxypyrazine was identified in the cardiac glycoside-laden fluid sequestered from milkweed hosts and expelled by these bugs when they are attacked. Alkyl methoxypyrazines are warning odorants associated with poisonous insect secretions, and their presence in O. fasciatus indicates that the plant-derived chemical defense of lygaeines is more elaborate than previously appreciated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003096317524
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  • 5
    Electronic Resource
    Electronic Resource
    Volatile, Potential Attractants from Ripe Coffee Fruit for Female Mediterranean Fruit Fly (1997)
    Springer
    Journal of chemical ecology 23 (1997), S. 1891-1900 
    Details
    ISSN: 1573-1561
    Keywords: Coffee fruit ; Coffea arabica ; host ; Mediterranean fruit fly ; Ceratitis capitata ; medfly ; analysis of volatiles ; attractant ; lure ; Diptera ; Tephritidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Twenty-eight volatile compounds from freshly crushed, ripe, dark red coffee fruit, Coffea arabica, were identified by dynamic headspace analysis techniques. Identifications were made on the basis of a comparison of Kovats indices and GC-MS spectra for unknowns and authentic samples. Of the compounds identified, 10 were alcohols, nine were aldehydes, five were ketones, and four were monoterpenes. The five most abundant volatiles in decreasing order were hexanal (21%), 2-(E)-hexenal (11%), 3-methyl-1-butanol (9.0%), 3-methyl-1-butanal (8.5%), and 1-hexanol (8.4%). The five least abundant volatiles of the 28 identified, in increasing order, were decanal (0.19%), methyl hexanoate (0.33%), pulegone (0.44%), α-isomenthone (0.45%), and 2-nonanone (0.55%). In preliminary tests, many of the identified volatiles attracted more female Mediterranean fruit flies than the control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/B:JOEC.0000006458.02342.61
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  • 6
    Electronic Resource
    Electronic Resource
    Low temperature suspension polymerization of vinyl acetate using 2,2′-azobis(2,4-dimethylvaleronitrile) for the preparation of high molecular weight poly(vinyl alcohol) with high yield (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 951-959 
    Details
    ISSN: 1435-1536
    Keywords: Key words High molecular weight ; PVAc ; high conversion ; PVA ; VAc ; low temperature ; ADMVN ; suspension polymerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  To obtain high molecular weight (HMW) poly(vinyl acetate) (PVAc) with high conversion and high linearity for a precursor of HMW poly(vinyl alcohol) (PVA), vinyl acetate (VAc) was suspension-poly-merized using a low-temperature initiator, 2,2′-azobis (2,4-dimethyl-valeronitrile) (ADMVN), and the effects of polymerization conditions on the polymerization behavior and molecular structures of PVAc and PVA prepared by saponifying PVAc were investigated. On the whole, the experimental results well corres-ponded to the theoretically predicted tendencies. Suspension polymerization was slightly inferior to bulk polymerization in increasing molecular weight of PVA. In contrast, the former was absolutely superior to the latter in increasing conversion of the polymer, which indicated that the suspension polymerization rate of VAc was faster than the bulk one. These effects could be explained by a kinetic order of ADMVN concentration calculated by initial-rate method and an activation energy difference of polymerization obtained from the Arrhenius plot. Suspension polymerization at 30 °C by adopting ADMVN proved to be successful in obtaining PVA of HMW (number-average degree of polymerization (P n)): (4200–5800) and of high yield (ultimate conversion of VAc into PVAc: 85–95%) with diminishing heat generated during polymerization. In the case of bulk polymerization of VAc at the same conditions, maximum P n and conversion of 5200–6200 and 20–30% was obtained, respectively. The P n, lightness, and syndiotacticity were higher with PVA prepared from PVAc polymerized at lower temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050333
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  • 7
    Electronic Resource
    Electronic Resource
    Rapid monitoring of gaseous fission products released from nuclear power stations (1998)
    Springer
    Journal of radioanalytical and nuclear chemistry 233 (1998), S. 281-284 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Rapid, in situ measurements were used for quantitative monitoring of gaseous fission products around the nuclear power stations in Taiwan. A portable high-resolution germanium detector with portable multichannel analyzer was used in the field monitoring work. The detecting unit was calibrated using activated Ar, Kr, and Xe isotopes dispersed in a large chamber to obtain absolute efficiency curve in terms of γ-counts per m3 versus gamma-ray energy. The calibrated detecting unit was brought to the nuclear power plants for in situ monitoring for both normal operation and nuclear accidental exercise. In a typical four-hour measurement, the detection limits for most Kr and Xe fission product isotopes were 0.0028%≈0.98% of the derived air concentration (DAC) imposed by the local authority. The dose rate caused by gaseous radioisotopes released from nuclear power stations and dispersed to the surroundings can be quantitatively monitored in a short period using this portable unit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02389684
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  • 8
    Electronic Resource
    Electronic Resource
    A study on the hydrated acrylic polymersPresented at ‘MacroAkron '94, 35th IUPAC Symposium on Macromolecules’, Akron, Ohio, 11-15 July 1994. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 37 (1995), S. 191-195 
    Details
    ISSN: 0959-8103
    Keywords: acrylonitrile ; copolymer ; methylacrylate ; hydration ; melting ; solid-state transition ; double melting transition ; double crystallization ; dipole-dipole interaction ; 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 effect of chemical composition of copolymers of acrylonitrile (AN) and methylacrylate (MA) on the hydration and thermal transition behaviour was investigated. An increase of the MA content considerably depressed both Tm and Tc of the hydrated polymers. A double melting and crystallization transition behaviour was observed when the hydrated polymer was reheated after cooling from the molten state. The separation between primary and secondary peaks was more notable in the second heating scan than in the first heating scan. A novel solid-state transition was observed in the dried acrylic polymers which had experienced hydration and melting in the wet state, followed by drying in the open state at 200°C.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210370307
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