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  • SPACE SCIENCES  (2)
  • Differential scanning calorimetry  (1)
  • Inaugural Articles  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Cure monitoring via different techniques: Isothermal cure of an epoxy-novolac molding compound (1994)
    Springer
    Journal of polymer research 1 (1994), S. 313-320 
    Details
    ISSN: 1572-8935
    Keywords: Isothermal cure ; Epoxy-novolac molding compound ; Differential scanning calorimetry ; Infrared spectroscopy ; Dielectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The isothermal cure of an epoxy-novolac molding compound was studied by means of Fourier-transform infrared spectroscopy (FTIR) and dielectrometry (DE). Results obtained were compared with previous differential scanning calorimetric (DSC) observations. The behavior of epoxide conversion (αFTIR) measured via FTIR was found similar to (but not exactly coinciding with) the extent of cure (αDSC) determined previously by means of DSC. As for the DE analysis, directly measurable properties such as permittivity (ɛ′) and loss factor (ɛ″) varied in a complicated manner during the course of cure, showing strong dependence on both temperature and frequency. Other dielectric parameters (such as ionic conductivity, relaxed permittivity, and characteristic relaxation time) previously suggested in the literature as suitable for cure monitoring purposes were found difficult to determine within the limited frequency range (100 to 104 Hz) here. With some arbitrariness, the relative drop in logɛ″ (at 100 Hz) was taken as an index (αDE) for the extent of cure. It was observed that αDE behaves in a manner similar to αFTIR and αDSC Comments on the application of these three techniques in the characterization of thermosetting systems were given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01374556
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Regulation of imprinted gene expression in Arabidopsis endosperm [Plant Biology] (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-02-02
    Description: Imprinted genes are expressed primarily or exclusively from either the maternal or paternal allele, a phenomenon that occurs in flowering plants and mammals. Flowering plant imprinted gene expression has been described primarily in endosperm, a terminal nutritive tissue consumed by the embryo during seed development or after germination. Imprinted expression in Arabidopsis thaliana endosperm is orchestrated by differences in cytosine DNA methylation between the paternal and maternal genomes as well as by Polycomb group proteins. Currently, only 11 imprinted A. thaliana genes are known. Here, we use extensive sequencing of cDNA libraries to identify 9 paternally expressed and 34 maternally expressed imprinted genes in A. thaliana endosperm that are regulated by the DNA-demethylating glycosylase DEMETER, the DNA methyltransferase MET1, and/or the core Polycomb group protein FIE. These genes encode transcription factors, proteins involved in hormone signaling, components of the ubiquitin protein degradation pathway, regulators of histone and DNA methylation, and small RNA pathway proteins. We also identify maternally expressed genes that may be regulated by unknown mechanisms or deposited from maternal tissues. We did not detect any imprinted genes in the embryo. Our results show that imprinted gene expression is an extensive mechanistically complex phenomenon that likely affects multiple aspects of seed development.
    Keywords: Inaugural Articles
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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    PAPER CURRENT
  • 3
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    Lunar ash flows - Isothermal approximation. (1972)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Suggestion of the ash flow mechanism as one of the major processes required to account for some features of lunar soil. First the observational background and the gardening hypothesis are reviewed, and the shortcomings of the gardening hypothesis are shown. Then a general description of the lunar ash flow is given, and a simple mathematical model of the isothermal lunar ash flow is worked out with numerical examples to show the differences between the lunar and the terrestrial ash flow. The important parameters of the ash flow process are isolated and analyzed. It appears that the lunar surface layer in the maria is not a residual mantle rock (regolith) but a series of ash flows due, at least in part, to great meteorite impacts. The possibility of a volcanic contribution is not excluded. Some further analytic research on lunar ash flows is recommended.
    Keywords: SPACE SCIENCES
    Type: Journal of Geophysical Research; 77; July 10
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Lunar ash flow with heat transfer. (1972)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The most important heat-transfer process in the ash flow under consideration is heat convection. Besides the four important nondimensional parameters of isothermal ash flow (Pai et al., 1972), we have three additional important nondimensional parameters: the ratio of the specific heat of the gas, the ratio of the specific heat of the solid particles to that of gas, and the Prandtl number. We reexamine the one dimensional steady ash flow discussed by Pai et al. (1972) by including the effects of heat transfer. Numerical results for the pressure, temperature, density of the gas, velocities of gas and solid particles, and volume fraction of solid particles as function of altitude for various values of the Jeffreys number, initial velocity ratio, and two different gas species (steam and hydrogen) are presented.
    Keywords: SPACE SCIENCES
    Type: Lunar Science Conference; Jan 10, 1972 - Jan 13, 1972; Houston, TX
    Format: text
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    NASA TECHNICAL REPORTS
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