GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Tracer diffusion measurement in polymer solutions near the glass transition by forced rayleigh scattering (1987)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 573-582 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Forced Rayleigh scattering, a relatively recently developed optical technique, is used to measure tracer diffusion coefficients in polymer-solvent mixtures near the system glass transition temperature, Tg. The technique has a wider range of potential application than has yet been realized, and so is presented in some detail. The objectives were to obtain data necessary to scrutinize free volume theory, and to understand so-called anomalous, non-Fickian diffusion effects observed by others in polymer-solvent mixtures near Tg. Data on dye tracer diffusion coefficients in the systems polyvinyl acetate-toluene, polystyrene-toluene, and polystyrene-tri-m-tolyl phosphate were obtained over a polymer concentration range from infinite dilution to 96 wt. %. Small molecule diffusion coefficients are seen to vary by as much as nine orders of magnitude (10-14 to 10-5 cm2/s) over this concentration range. The data are in reasonable accord with expectations based on the Duda-Vrentas version of free-volume theory.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690330406
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Probe diffusion in poly (vinyl acetate) / toluene solutions (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 2607-2627 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The technique of forced Rayleigh scattering has been used to examine the tracer diffusion of probe photochromic dyes, azobenzene and methyl red, in poly (vinyl acetate)/ toluene solutions, as a function of polymer concentration (0-96% by weight) and temperature (5-45°C). It is demonstrated that the dye diffusivity can be quantitatively scaled to the solvent diffusivity, thus permitting direct application of predictions for two-component systems. The results have been interpreted using the free volume theories of Fujita and Vrentas and Duda. While both approaches are able to describe the concentration dependence extremely well, the Vrentas-Duda expression has the virtue of being employed without any freely adjustable parameters. However, neither theory is particularly successful in predicting the observed temperature dependence.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090281310
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    facet.materialart.
    Unknown
    Autophagy Negatively Regulates Early Axon Growth in Cortical Neurons [Articles] (2013)
    The American Society for Microbiology (ASM)
    Details
    Publication Date: 2013-09-12
    Description: Neurite growth requires neurite extension and retraction, which are associated with protein degradation. Autophagy is a conserved bulk degradation pathway that regulates several cellular processes. However, little is known about autophagic regulation during early neurite growth. In this study, we investigated whether autophagy was involved in early neurite growth and how it regulated neurite growth in primary cortical neurons. Components of autophagy were expressed and autophagy was activated during early neurite growth. Interestingly, inhibition of autophagy by atg7 small interfering RNA (siRNA) caused elongation of axons, while activation of autophagy by rapamycin suppressed axon growth. Surprisingly, inhibition of autophagy reduced the protein level of RhoA. Moreover, expression of RhoA suppressed axon overelongation mediated by autophagy inhibition, whereas inhibition of the RhoA signaling pathway by Y-27632 recovered rapamycin-mediated suppression of axon growth. Interestingly, hnRNP-Q1, which negatively regulates RhoA, accumulated in autophagy-deficient neurons, while its protein level was reduced by autophagy activation. Overall, our study suggests that autophagy negatively regulates axon extension via the RhoA-ROCK pathway by regulating hnRNP-Q1 in primary cortical neurons. Therefore, autophagy might serve as a fine-tuning mechanism to regulate early axon extension.
    Print ISSN: 0270-7306
    Electronic ISSN: 1098-5549
    Topics: Biology , Medicine
    Published by The American Society for Microbiology (ASM)
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 4
    facet.materialart.
    Unknown
    FUV spectrum in the polar region during slightly disturbed geomagnetic conditions (2011)
    Wiley-Blackwell
    Details
    Publication Date: 2011-10-20
    Description: We present the results of simultaneous high resolution observations of far ultraviolet (FUV) spectra/images and precipitating electrons made for the polar region during a period of slightly disturbed geomagnetic conditions. The polar region was divided into five subregions: the dayside subauroral region, dayside auroral zone, polar cap, nightside auroral zone, and nightside subauroral region. Precipitation in the dayside subauroral region was dominated by soft electrons, and the intensity of the OI 135.6 nm line relative to the NI 149.3 nm line was significantly enhanced, while electrons of a few keV energies also existed. On the other hand, the nightside subauroral region showed the hardest electron spectrum among the five subregions, and the FUV intensity was the brightest there, with substantial increase in the long Lyman-Birge-Hopfield (LBH) band. The auroral zones showed series of inverted-V events with more energetic electrons in the nightside than in the dayside, and the corresponding FUV auroral features were also brighter and broader in the nightside. In the polar cap region, discrete polar arcs were seen, with corresponding electron beams of ∼keV, embedded in the diffuse low-intensity FUV background caused by polar rain. The relative intensity of OI 135.6 nm to the NI 149.3 nm line was evaluated for the five subregions and it was found to decrease with increasing electron characteristic energy when energy was smaller than ∼2 keV, and remained more or less the same above ∼2 keV, which was confirmed by simulations. On the other hand, the relative intensity of the long LBH band to the short LBH band increased with increasing characteristic energy over the entire energy range up to ∼4 keV. The OI 135.6 nm line and long LBH band intensities were compared with the energy flux of precipitating electrons, and they were found to have good correlations. When the energy flux was fitted as a function of the long LBH intensity by a power law, the power index was found to be 1.37 for the entire polar region with ∼75 km spatial bins, similar to the value obtained previously for inverted-V events with similar spatial averages.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 5
    facet.materialart.
    Unknown
    Effect of hot anisotropic He+ ions on the growth and damping of electromagnetic ion cyclotron waves in the inner magnetosphere (2017)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-19
    Description: Physics of electromagnetic ion cyclotron (EMIC) waves is complicated by inclusion of heavy ions. In particular, He + ions in the magnetosphere have long been considered to play important roles. Motivated by recent observations, we examine the effect of the inclusion of hot anisotropic He + ions in addition to the usual hot anisotropic protons. We solve the kinetic dispersion relation for this examination, and find the following results. First, inclusion of hot anisotropic He + ions leads to the growth of EMIC waves at frequencies below the He + gyro-frequency (He band) and a reduction of the EMIC wave growth rates (or damping of the waves) at frequencies between the proton and He + gyro-frequencies (H band). Second, this effect is more dramatic for higher temperatures of He + that would play a role in damping EMIC waves for both frequency bands and especially for cases without a He + temperature anisotropy. Lastly, the effect is more prominent for cold plasma dominant conditions such as the region inside the plasmasphere or plume than for hot proton dominant conditions such as the region outside the plasmasphere. We propose that this last effect can at least partially explain the satellite observations indicating the preferred (though not exclusive) occurrence of He band waves inside the plasmasphere for the times when hot anisotropic He + ions are supplied from the plasma sheet and ring current.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...